energy efficiency in the tanzanian industry: the cement...
TRANSCRIPT
Energy efficiency in the Tanzanian industry:
The cement industry as a case study
C. Samplonius Student of: International Technology Development Sciences Eindhoven University of technology The Netherlands
for: TPCC WazoHill Tanzania
Supervisors: Dr. ir. AM.C. Lemmens Ir. A Lamers Dr. P.E. Lapperre
Date: december 1994
Preface.
In most countries, at this moment, energy efficiency is an important item. This counts for Tanzania, too. Major reasons are the energy scarcity and the high prices of energy. And also environmental problems are significant reasons to safe energy.
This report will contribute in formulating and implementing an efficiency policy in the case of the Tanzanian Portland Cement Corporation (TPCC). The following elements are included: an assessment of the energy use and energy efficiency of TPCC, description of technica! options to save energy, discussion of a number of harriers which prevent TPCC to implement technica! options, and finally the description of policy options to save energy.
This study of the Tanzanian cement industry is the subject for my final project, being a compulsory subject for students in the stream" International Development Sciences" within the faculty of "Philosophy and Social Sciences" of the Eindhoven University of Technology. For this study, I have been three months in Tanzania, where I spend my time at TPCC.
First if all, I would like to thank Nsakula Makoba (production engineer), he bas helped me with explanation and information about many aspects of cement manufacturing, and Harry Mbekelu (operator of the kilns) whowas very friendly and contact me with many employees on the work floor. I am very grateful to the families of these men. They were very hospita! for my wife, little sun and me, during the period in Tanzania.
I am also thankful to the department ECN-Policy Studies, especially Frank van der Vleuten, who have helped me collecting useful information for my research.
Further, I would like to thank Lex Lemmens, my supervisor, whobas assist me to write this report and mr. Lamers, my technica! supervisor.
Last but not least, I wish to thank my wife Rosalie, who bas made is possible to do this study.
1
Contents.
Preface .................. .
Contents ...
Summery ...
1. Introduction.
1.1. Aim of the research. 1.2. Content of the report. . . . . . . 1.3. The cement industry in Tanzania. . . . . . . . . . . . . . .
2. Energy intensive industries in Tanzania.
2.1. Introduction. . . . . . . . . . . . 2.2. Energy intensive industries in Tanzania.
3. Cement production. . . . . . . . .
3.1. The cement production process.
3.1.1. Cement. ......... . 3.1.2. Main production process .
3.2. Cement production in Tanzania.
page.
• • 1.
• • • • 11.
Vlll.
1.
1. 1. 2.
6.
6. 6.
9.
9.
9. 9.
. 13.
3.2.1. Raw meal preparation. . . . . . . . . . . . . 13. 3.2.2. Raw meal grinding, drying and blending. . . . 15. 3.2.3. Pyroprocessing. . . . . . . . . . . . . . . . . . 17. 3.2.4. Clinker grinding. . . . . . . . . . . . : . . . . . . . . 18. 3.2.5. Cement storage. . . . . . . . . . . . . . . . . . . . . 19.
4. Energy information. 20.
4.1. Flowchart. . . 20. 4.2. Kiln heat balance. . . . . . . . . . . 24.
4.2.1. Calculation of the heat balance. . 26. 4.2.2. The heat balance. -· 36.
5. Energy conservation options. 38.
5.1. Energy management. . . . . . . . . . . . . . . . . 38.
5.1.1. Staff. . . . . . . . . . . . . . . . . . . . . . 38. 5.1.2. Reducing heat losses through reducing kiln interruptions. 39.
11
5.1.3. 5.1.4. 5.1.5. 5.1.6. 5.1.7. 5.1.8. 5.1.9.
Fuel cambustion system. . . . . . . . . . . . . . . . . . . . . . Reducing heat losses through advanced kiln controL . . . . . . . . Reducing heat content of exhaust gases. . . . . . . . . . . . . . Reducing heat losses by radiation and convection. . . . . . . . . . Dust insufflation. . . . . . . . . . . . . . . . . . . . . . . . . Uplining of the mills. . . . . . . . . . . . . . . . . . . . . . . Saving energy costs through replacing power meters. . . . . . 48.
. 41.
. 42. 44. 45. 47. 47.
5.2. Process changes. . . . . . . . . . . . . 50.
5.2.1. Precalciner. . . . . . . . . . . . 50. 5 .2.2. High pressure roller mills. . . . 52. 5.2.3. High efficient classifiers. . . . . . . . . . . . . 53.
5.3. Product changes. . . . . . . . . . . . . . . . . . . . . . . . . 55.
5.3.1. Portland natural pozzolan cement. . . . . . . . . . . . . . . . 55. 5.3.2. Changing of standards. . . . . . . . . . . . . . 55.
5.4. Energy conversion. . . . . . . . 57.
5.4.1. Conversion from oil to coal. 57. 5.4.2. Waste fuels. . . . . . . . . 59.
6. Economical picture. 60.
6.1. Introduction. . 60. 6.2. Savings. 61.
7. Barriers. . . 66.
7.1. General problems of public enterprises. . . . . . . . . . . . 67.
7.1.1. The Morrisonian model. ......... . 7.1.2. Public enterprises in Tanzania ....... . 7.1.3. Poor performance and management failures. 7.1.4. Consequences for TPCC. ........ .
7.2. Foreign exchange problems ........... .
67. 69. 71. 75.
77.
7.2.1. The foreign exchange constraint in Tanzania. . . . . . . . . . . 77. 7.2.2. Attempts made by the government to solve the foreign exchange crises. 77. _. _ 7.2.3. Effects of the foreign exchange shortage. . . . . . . . . . 78. 7.2.4. Effects for TPCC. . . . . . . . . . . . . . . 79.
7.3. Lack of competences. . . . . . . . . . . . . . . . 81.
7.3.1. Campetences in enterprises. . . . . . . . . . . 81. 7.3.2. Lack of campetences as a harrier to energy efficiency. . . . . . . . 82.
111
7.3.3. Training determinants ........... . 7.3.4. Contribution of training and development. .
7.4. Infrastructural problems ............ .
8. Policy options. . . . . . . . . . . . . . . . .
8.1. Starting an energy management project. . 8.2. Development and training. . . . . . . . . 8.3. Building incentive systems and motivation. 8.4. Privatization and reorganization. . . . . .
83. 84.
86.
87.
87. 88. 89. 90.
8.4.1. lntroduction. . . . . . . . . 90. 8.4.2. Limitations of privatisation. 91.
8.5. Conversion from oil to coal. . . . 92. 8.6. Guidelines for rational selection and adaption of technologies. . . . . . . 93.
9. Condusion and recommendations. 95.
9.1. Short term ad-hoc options. . 95. 9.2. Long term structural adjustment options. 96.
Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.
lV
List of Figures
Figure 1: Cement production 1966-1993. . . . . . . . . . . . . . . . . . . . . . 2. Figure 2: Capacity utilization 1966-1993 ...................... 3. Figure 3: Cement production process. . . . . . . . . . . . . . . . . . . . 12. Figure 4: Single impeller impact crusher. . . . . . . . . . . . . . . . . . 14. Figure 5: Drying and grinding in an air swept mill. . . . . . . . . . . . . 16. Figure 6: Flow chart of the Twiga plant. . . . . . . . . . . . . . . . . . . 23. Figure 7: Balance boundary. . . . . . . . . . . . . . . . . . . . . . . . 25. Figure 8: Enveloping cylinder. . . . . . . . . . . . . . . . . . . . . . . 33. Figure 9: Heat consumption of 4 stage cyclone preheaters for various size
depending upon the throughput capacity. . . . . . . . . . . . . . . 37. Figure 10: Total power consumption according TPCC and Tanesco. . . . . 49. Figure 11: Precalciner with combustion air through a tertiary air duet and through
the rotary kiln. . . . . . . . . . . . . . . . . . . . . . . . . 51. Figure 12: Specific energy use adjusted to standard operations. . 56. Figure 13: Energy consumption in the cement industry. 57. Figure 14: The foreign exchange vicious circle. 78. Figure 15: A model of individual competences. . . . . 81.
List of Tables
Table 1: Energy intensive industries. . . . . . . . . . . . . . . . . . . . . . . 7. Table 2: Clinker minerals. . . . . . . . . . . . . . . . . . . . . . 11. Table 3: Energy use in the different sectors. . . . . . . . . . . . . . 21. Table 4: Heat from fuel. . . . . . . 27. Table 5: Sensible heat raw meal. . . . . . . . . . . . 28. Table 6: Sensible heat water. . . . . . . . . . . . . . 28. Table 7: Sensible heat fuel. . . . . . . . . . . . . . . 29. Table 8: Sensible heat primary air ......................... 29. Table 9: Sensible heat exhaust gases and dust. . . . . . . . . . . . 31. Table 10: Radiation and convection losses kiln 1. 34. Table 11: Radiation and convection losses kiln 2. 34. Table 12: Radiation and convection losses kiln 3. 35. Table 13: Radiation and convection heat transfer. . . . . . . . . . . 35. Table 14: Heat balance. . . . . . . . . . . . . 36. Table 15: Number of unplanned stops. . . . . . . . . . . . . . . . . . . . 39. Table 16: Relation specific energy use and wear. . . . . . . . . . . . . . . 48. Table 17: Costs of TPCC 1992. . . . . . . . . . . . . . . . . . . . . . . . . 60-." -Table 18: Costs of the different departments. . . . . . . . . . . . . . . . . . 60. Table 19: Approximate rate of return on oil to coal conversions. . . . . . . . . . 65.
V
Appendices
Appendix 1: Cement production 1966-1993. . . . . . . . . . . . . . . . 102. Appendix 2: Analysis of the materials. . . . . . . . . . . . . . . . . 102. Appendix 3: Raw meal mills data. . . . . . . . . . . . . . . . . . . . 103. Appendix 4: kilns data. . . . . . . . . . . . . . . . . . . . . . . . . . 103. Appendix 5: Cement mills data. . . . . . . . . . . . . . . . . . . . . . 104. Appendix 6: The different zones and their respective refractory bricks. . . . . . 104. Appendix 7: production data 1993. . . . . . . . . . . . . . . . . . . . . . . 105. Appendix 8: kWh use in 1993 for the different units. . . . . . . . . . . . . . . 106. Appendix 9: Clustering of the kWh meters for the different sections. . . . . . . 107. Appendix 10: Radiation and convection heat transfer coefficient (total). . . . . . 108. Appendix 11: CP of gases. . . . . . . . . . . . . . . . . . . . . . . . 109. Appendix 12: CP of liquids and fuels. . . . . . . . . . . . . . . . . . . . 110. Appendix 13: CP of solids. . . . . . . . . . . . . . . . . . . . . . . . . . 111. Appendix 14: Personnet . . . . . . . . . . . . . . . . . . . . . . . . . 112. Appendix 15: Industries in Tanzania classified according ISIC (1988). . . . . . . 113. Appendix 16: The organisation structure of TPCC. . . . . . . . . . . . . . . . 116. Appendix 17: The structure of the decision making and policy formation in Tanzania. 117.
VI
Symbols and abbreviations
TPCC TCC
Tanzania Portland Cement Company Tanga Cement Company
MCC DANIDA SIDA TANESCO TSHS Blaine
Mbeya Cement Company Danish international development organisation Swedish international development organisation Tanzanian Electric Supply Company Tanzanian shilling fineness of cement (cm 2 / g)
MWh kWh tpd tpy cm g J kJ MJ GJ
A
~v D h
or L m
or or
m V
t Q a €
mega watt hour kilo watt hour ton per day ton per year centimeter gram joule kilo joule megajoule giga joule
[m2] area [kJ/kg°C] specific heat capacity [kJ/kg] calorific value [m] diameter [kJ/kg] heat content [kJ/kg cli] [m] length [kg/kg] specific mass [Nm/kg] specific gas quantity [kg] mass [kg/h] mass flow [m/s] velocity (cC] temperature [kW] heat flow (1 kW = 1 kJ/s) [W/m2 K] heat transfer coefficient [-] emissivity
VIl
Summery
The aim of the research is to ascertain for TPCC the exact energy use and energy efficiency in order to determine energy conservation options to come to a good policy with respect to energy efficiency.
TPCC is the biggest factory of the three cement factorles which Tanzania has. In 1993, the installed capacity amounts 520,000 tpy, and in 1993 the production amounts 387,000 tpy. The factory has three lime-stone crushers, two blending plants, three raw meal mills, three kilns, three cement mills and two packing plants. All the kilns use a dry system with a four stage preheater.
TPCC produces only one kind of cement, namely portland cement. Portland is not a brand name, but just a kind of cement. The production of portland cement at TPCC consist of the following stages; (1) extracting of the raw materials (limestone, red soil), (2) emshing the raw materials in the impact crushers, (3) milling the raw materialsin the raw meal mills, (4) blending the raw materialsin the blending plant, (5) burning of the raw materials in the kilns into clinker, (6) milling the clinker in the cement mills (adding 5% gypsum) into cement and (7) finally packaging of the cement.
In spite of the many defect control meters and kWh meters, a complete energy and material flow picture is tried to be made. In 1993, the energy use of TPCC is 39,590 ton fuel oil and 47,922,000 kWh. This means an average specific energy use of 0.102 ton oil and 124 kWh per ton cement. The burning process in the kilns is the most energy intensive and uses all the oil and a big part of the required power. The average heat consumption for producing one ton clinker is 4,334 kJ /kg clinker (1034 kcal/kg clinker). Modem kilns, which are often provided of a precalciner, use about 3,000 kJ /kg clinker. Besides the kilns, the raw meal mills and cement mills are the other important energy users. The reasons for the energy inefficiency are lack of preventive maintenance and lack of innovation.
Because of the high specific energy use, a saving of a few percent is already of great importance. In Western countries a lot of research is done in case of energy saving in the cement manufacturing. For this reason, a big number of energy conservation options are available, in the process of producing cement used at TPCC. In this report the energy conservation options are divided into four groups;
- Energy management: these measures do not require a major change of technology, and do not set high capital requirements. A few attractive options of energy management are; renewing defect kiln control meters, using new kind of insulation bricks, dust insufflation. Most of the energy management options involve preventive maintenance. - Process changes: they are more radical and require more investment capita!. Installing a precalciner is a process change which is very attractive if there is need for production enlarging, too. - Product changes: Making other kinds of cement and changing of standards are examples of product changes which could save energy.
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- Energy conversion: conversion from oil to coal is a possibility to reduce the energy costs. But the most important reason of conversion is saving foreign exchange.
Many harriers prevent the implementation of these technica! options. Generally, these harriers prevent TPCC acting rationally and in favour of the company. This involves not only energy efficiency, but also the efficiency of many other aspects, like production and employment efficiency. One of the most important harriers is the fact that TPCC is a public enterprise which works according to the Morrisoman model. In Tanzania, the government intervention and control in public enterprises causes weak market controls, administrative overburdening, power delegation without responsibility and a negative company culture. Other harriers are; lack of foreign exchange for purchasing equipment and spareparts, lack of campetences on the different levels of the compariy to run the plant effective, and lack of infrastructural support.
To overcome these harriers and implement technica! options in order to save energy, it is necessary to change the structure and culture of the company. Off course it is possible to implement direct some technica! improvements, but on the long run it is essential to reorganise the company, reducing the government intervention, start training of management and staff, building incentive systems. The policy options to achieve this are divided into two levels; government level and enterprise level.
IX
V
1. Introduction.
1.1. Aim of the research.
Cement is one of the most important matenals in the construction industry in the world, because of its main end use: concrete.
Cement manufacturing is also one of the most energy intensive of all industries. Cement is a typical commodity with sales depending primary on the energy price. The cast of energy camprises about 60 % of the direct manufacturing casts.
Any reductions in energy use during cement manufacturing would improve the competitive situation. Energy saving is not only important for the competitive situation of the Tanzanian Portland Cement Corporation (TPCC), but also for the Tanzanian govemment, because all fuel oil is imported. TPCC uses about 4 percent of the imported oil and uses 3.5 percent of the total power used in Tanzania. Energy saving means foreign exchange savings.
Aim of the research: to ascertain for TPCC the exact energy use and energy efficiency in order to determine energy conservation options to come to a good policy with respect to energy efficiency.
1.2. Content of the report.
Chapter one gives an introduction. Discussed are: aim of the research, content of the report apd cement in Tanzania generally.
In chapter two, a few of the most energy intensive industries in Tanzania are treated.
Chapter three is starting to give a short general survey about cement and the cement production process. After this a description of the production process of TPCC is made.
In chapter four, a general flow chart of the complete process is made. This flow chart illustrates the most important features (production flow, energy flow) of the complete production process. The flowchart is depicted on page 17. The flowchart is made on basis of data of the year 1993.
1
The same chapter continues with a heat balance for each of the three kilns, which are the main energy users. A heat balance on a kiln system can offer useful information on the thermal performance of the system.
In chapter five, technica! options to imprave energy efficiency are described. The measures are classified in the following groups:
- Energy management - Process changes - Product changes - Energy conversion
A short economical survey of TPCC and economical savings of the most attractive technica! options are discussed in chapter six.
Chapter seven describes the most important harriers, which prevent TPCC from an energy efficient policy. This chapter includes the following harriers:
- General problems of public enterprises - Foreign exchange problerns - Campetences - Infrastructural problerns
In chapter eight, policy options which are based on the technica! options to imprave energy efficiency and the harriers discussed in chapter 7, are described.
Chapter nine finished the report with conclusions and recornmendations.
1.3. The cement industry in Tanzania.
The dernand for cement in Tanzania increased from 13,000 tonnes per annum in 1946 to a production of 600,000 tonnes per year (in all three cernent factories). Befare 1959 Tanzania (then Tanganyika) imported all its cement requirements from abroad. In 1959 Tanzania Portland Cement Company Ltd. (TPCC) was registered, with the objective of importing bulk cement and bagging it at its Malindi Packing Plant. This plant was situated at the Dar es Salaam Harbour. The packing plant which started operation in 1960 was basically a distribution centre for the East Africa Portland Cement Company based in Mombasa, Kenya.
2
~ >< 'U
~ .. c ..
Total cement productTon 1966-1993
500 .-
400 I-
aoo 1--
li!OO I-
100 I-
0~·~~~~~~~~-69 69 70 72 74 7'9 79 eo e2 e4 ee ee 90 e2 e7 e9 71 73 7~ 77 79 e1 es a~ e7 ee 91 93
yo.ar
Fig. 1. Cement production 1966-1993
In 1962 the Tanzania government empowered TPCC to put up a cement plant in Tanzania. The first cement plant wasthen constructed at Wazo Hili some 20 km north of the city of Dar es Salaam. The production started in 1966.
The description of performance will be divided in three phases.
1966-1972
The installed capacity of the plant was 110,000 ton per year, producing only Ordinary Portland Cement. The cement production capacities rose from 45% (50,100 tpy) in the first year toa peak of 161% (177,503 tpy) by 1971 (Kimambo, R.H 1989 p.174, and Tanzania Portland Cement Co., Budget 1993). Figure 1 shows the total cement production and figure 2 show the capacity utilization.
These production and capacity utilization figures are strange and the production seems to high, because the rated capacity of kiln 1 is 350 ton clinker per day. This means, in the most favourable situation, without stops, 134,140 ton cement per day can be produced. The data is confirmed of two different sources, and gives no explanation of this phenomenon. The exceptionally good performance in the late sixties involved the management of only one kiln. It should be noted that the management of the plant was provided by the owners of the plant, Cementia Holding AG of Switzerland, who were competent and experienced cement experts.
3
CapacTty utl I rzatTon
:zee
1:50
g 1ee
:50
ll"'e.r
Fig. 2. Capacity utilization 1966-1993
They also received necessary back-up services from the long established sister plant at Bamburi, Mombasa in Kenya. Besides this, the economie environment within which the management operated was permissive. The foreign exchange was readily available, and in many cases spares could be picked off the shelves.
Furthermore, the management had a free hand in rewarding good workers and punishing bad ones. This combination of instant rewards and punishments plus annual payments of bonuses had the combined effect of high motivation of the work force.
1973-1979
On the basis of envisaged increasing demand for cement, the production capacity was increased, in 1972 to 270,000 tpy by adding a second kiln. In 1973 the government taak over complete ownership which was vested in the State Mining Corporation. The Cementia management experts at TPCC withdrew their services in 1973 and were replaced by Indian expatriate management in 1974. At the same time the international economie order started to change, affecting foreign exchange availability. As aresult it became harder to buy spareparts and consumables. The capacity utilization started to drop and by 1979 reached 76%
In 1979, a third kiln is added and the production capacity rises to 520,000 tpy.
4
1980-1993
The requirements of foreign exchange for capital replacement, spares and consumables were around US $2.5-3.0 million per year, while hardly 50% of this was available through Bank of Tanzania and DANIDA (Danish international development organisation) assistance.
In 1980, the performance dropped to about 55% of the rated capacity. In 1981 all expatriates left, and the management was totally localised. In that time, the general economie situation in the country was unfavourable, and the forex allocation was gradually declined in all sectors. In 1983 the production had dropped to 26% of the rated capacity. During the same period (early 1983) Kiln 3 developed a major breakdown after which it was found prudent to bring in once more an expatriate management team. This time Cementia International AB (nowadays Scancem) of Sweden were contracted for a period of five years with SIDA (Swedish international development organisation) forex support in 1984. After these five years the contract is continued until now.
Further in 1980, another cement plant was commissioned in Tanga, the Tanga Cement Company Ltd. (TCC), with a production capacity of 500,000 tonnes an annum. In 1983 the Mbeya Cement Company Ltd. (MCC) came into operation with a rated capacity of 250,000 tpy per annum.
The capacity utilization of these two factorles is very bad, because of the lack of a market Transport of cement is very expensive due to its heavy weight. TPCC bas no problems with the lack of a market, because it is close to Dar Es Salaam.
Per capita consumption of cement varies considerable from over 200 kg per year in places like Dar es Salaam to a few kg in distant places like Bukoba and Ngara in the nortb-western part of Tanzania.
5
2. Energy intensive industries in Tanzania.
2.1. Introduction.
One of the overall objectives of the National Energy Policy is the more efficient use of energy in the industry. Especially with regard to the use of petroleum derivatives because of the high cost of oil import. An other policy objective is the developing and utilizing of indigenous hydro-electric, coal and national gas resources and stepping up oil exploration with the goal to reduce the dependenee on imported oil through energy substitution.
In 1986, Tanzania consumed 855.000 tonnes of petroleum products. The transport sector accounted for nearly 51 percent of petroleum used in the country. The industry accounted for 26 percent and the household sector, 10 percent of consumption. The rest is accounted for by other factors. In 1988 the consumption was 1060 gigawatt hours (GWh) which corresponds with a per capita consumption of 46 kWh. The industry accounts forabout 30 percent of the use of electricity.
It may be clear that a substantial part of the energy is used in the industry and that in a policy of energy saving major attention should also be given to the industry.
2.2. Energy intensive industries in Tanzania.
The first step necessary to come to an healthy and suitable policy for energy efficiency, is to find industries or sectors which are high energy intensive and also have a considerable size. The best way to search for energy intensive industries is to collect data about the energy use in one year, for the different industries, and rank them from high to low. The industries which are using most of the energy deserve the fust priority. However, these data are not available. Therefor, the next procedure is used. First, a complete list of industries (according ISIC) in Tanzania is made. Second, for each industry, it is determined wether they are eligible for further energy research. The next parameters are used to judge this; size, energy intensitivity and the possibilities to save energy. The critenons for size is somewhat arbitrary. The industries are categorized in thréê classes; small (gross output of less than 500 million shilling a year), medium(500 million shilling to 1600 million shilling) and big (above 1600 million shilling).
When in the literature the industry is known as energy intensitivity, it is assumed that these industries are energy intensive in Tanzania, too. The industries are categorized in three classes; low, medium, high energy intensive.
6
This approach is by no means intended to be complete, it is just an indication of the most energy intensive industries in Tanzania, where probably savings can be obtained.
In appendices 15 a complete list of industries in Tanzania is given. This list includes the next parameters:
- Number of establishments - Number of persons engaged
Covers all employees, working proprietars and the unpaid workers. - Gross output total
It is computed by adding the total sales and services to the net balances of both finished and semi-finished products.
- Production costs These are made up of: costs of material consumed, cost of electricity fuel, lubricants and water, cost of re-sales, costs of services received, other cost of production.
- Net value added This represents the difference between gross output and production costs.
Table 1 shows the industries which are eligible for more research.
NI.Jilber NI.Jilber Gross Produc· Net ISIC·Code of of pers. output ti on value
establ. engaged total costs added (bil.shs) (bi l.shs) (bi l.shs)
341 Paper and paper products 10 2.713 1.570 1.218 352
3512 Fertilizers and pesticides 5 1.054 2.721 1.672 1.050
3610/3620 Pottery, china and earthenware 6 1.171 807 638 168 /3691 glass (prod.) and clay prod.
3692/3699 Cement, lime plasterand non· 13 3.179 2.194 1. 717 477 metallic products
Table 1. Energy intensive industries.
It is bebind the scope of this report to discuss every energy intensive industry, but in a few sentences the possibilities will be indicated.
In the paper and pulp industry, considerable energy savings will be feasible. Mean energy users in the paper industry are pulping (14%), paperrnaicing (36%), evaporation (9%) and bleaching (14%). With state-of-the-art processes about 10-40% energy saving is possible. New designs (heat integration) show energy savings of 15 to 90% and capita! saving to 25%. (H.J. Herzog, 1991, Energy managementand conservation in the pulpand paper industry, from the conference, energy and the environment in the 21st century).
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Further, the paper and pulp industry is an ideal candidate for cogeneration of electricity. In the US the cogeneration intensity in 1988 was 540 kWh/ ADMT( = Air Dried Metric Ton = 1000 kg).
In the fertilizer industry , the largest amounts of energy go into heat for chemica! furnaces and reactors and heat or refrigeration for distillation. Generally, the increased capita! investment required is often costly and often cast/benefit studies have favoured the higher operating costs using old equipment. Saving of 10-15% are possible with good housekeeping measures and energy programmes. (Industrial Energy U se Data Book, Oak Ridge Associated Universities, 1980) ·
In the subdivision pottery, china and earthenware, glass and clay products is the glass industry very energy intensive. In the glass industry, the average total energy costs of energy purchases are about 28% of the total purchases and 18% of the net output (UK). Probably, this percentage is higher in Tanzania. In developed countries, energy savings have been rather important in the seventies and the start of the eighties The energy use of flat glass is about 11 GJ /tonne and the energy use of container glass is about 7 GJ/tonne. (Neth. 1986) About 80% of the energy is used for the melting and fining process. In this process are the possibilities to save energy. Examples: Improved refractories, cogeneration, improver burner designs, etc. (V. Buskens, Energy use and energy saving options for different industrial sectors 1993).
Besides the cement industry, the lime plaster industry is energy intensive, too. The process of manufacturing of lime plaster is nearly the same process which is used in the cement industry. However, the specific energy use of manufacturing lime plaster is about 40-50% lower and often the production capacity is smaller. The possible energy savings in the plaster industry are less important than the energy saving in the cement industry, but they are still significant.
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3. Cement production.
This chapter contains two parts. The first part describes the general process to produce cement. The second part describes more specific the cement production at Twiga cement.
3.1. The cement production process.
3.1.1. Cement.
There are different kinds of cement, but the one mostly produced in the industry is portland cement. Portland cement is not a brand name, it is just a type of cement. Cement may be defined as an adhesive substance capable of uniting segments of masses of solid matters to a compact whole.
The main raw material for cement is calcareous rock (75-85%), principally limestone, which is mined from sedimentary formations of marine origin from virtually every geologie age. The second group raw materials are the argillaceous materials. For the production of portland cement at least five chemica! elements are needed:
-calcium carbonate (CaC03)
- silicium oxide (Si02)
- aluminium oxide (Al20 3)
-iron oxide (Fe20 3)
- calcium-sulphate (CaS04)
The four first mentioned materials are coming from the calcareous rock and the argillaceous materials. The last mentioned material is added during the grinding of the clinker, in the farm of gypsum and anhydride.
The amount of raw materials needed to produce one metric ton of cement ranges approximately between 1500 and 1800 kg. Finally, during the final grinding, it is possible to add different kinds of additives like fly ash, blast furniture slacks, pozzolan, etc to get different kinds of cement or to reduce the price of cement.
3.1.2. Main production process.
The process starts with the collection of raw material. Most rock is transported by dumper (truck) from the quarry to the plant. The rock is crushed in cone crushers or hammer mills to small pieces of about 2-3 cm.
9
Grinding
After crushing, the raw material is stored or straightly fed to the grinding mills for fine grinding and blending. The two main processes used in the cement manufacture are the wet and the dry process. In the wet process, the crushed raw materials are ground with water, thoroughly mixed and fed into the kiln in the form of slurry, which contains typically about 35 % moisture. The raw matenals are moisturized, because they can be mixed easier then. The wet process has important energetic disadvantages, because the water has to be evaporated again during the pyroprocessing. In the dry process the raw materials are ground, mixed and fed into the kiln in their dry state.
Two kinds of mills used in raw meal or clinker grinding are: the hall mill and the more modern high pressure roll.
The mills in a closed circuit system are provide from classifiers. Classifiers are installed in closed-circuit grinding systems to separate the fine, product-quality particles from the coarser oversize particles that are recycled for further grinding. The open circuit system, does not use a classifier, the material can only leave the mill when it is fine enough.
The purpose of raw grinding is to prepare a homogeneaus mixture of raw material in the proper chemica! proportions with a uniform finesse and with the proper partite size graduation to ensure the desired burning conditions in the kiln.
The raw grinding process significantly improves the chemica! uniformity of the raw mix, but in most cases not enough. Special silos are used for storing and further homogenization of the raw mix.
pyroprocessing
After grinding and blending the raw material is fed into the kiln to burn it to clinker. Cantrolling the burning of the mixed raw materials is the most important operation in manufacturing cement because:
- the fuel consumption is the major expense in the process - the capacity of a plant is determined by the kiln output - the strength and other properties of the cement depend on the
quality of clinker produced.
Two types of kilns are used in the industry: vertical or shaft kilns (accounting for only 5% of the world production) and rotary kilns. Vertical kilns, common in Europe and some developing countries, are generally only efficient at capacities up to 100,000 tonnes per year, whereas rotary kiln are efficient at capacities well beyond one million tonnes a year.
10
Rotary kilns are amenable to both wet and dry processes, whereas vertical kilns are limited to dry process only.
In clinker production the raw mix is gradually heated in the kiln until it reaches a temperature of about 1500°C.
In the first ( drying and preheating) zone, the raw mix is heated to 100-l20°C, to evaporate all moisture. After this the temperature increases to about 450°C to liberate more firmly bound water of hydration from the clay. In the second ( calcining) zone, the calcium carbonate (CaC03) is thermally decomposed in a temperature-range of 450-1100°C to form calcium oxide (CaO), accompanied by the liberation of carbon dioxide (C02). In this zone any present organic materials burned and present alkalies (Na and K) partially vaporize.
The dinkering process takes place at temperatures of 1100-1500°C. A series of reactions between the calcium oxide and the other raw material components, results in the formation in clinker.
The four main clinker minerals are: tetracalcium aluminoferrite (C4AF), tricalcium aluminate (~A), tricalcium silicate (~S), dieakiurn silicate (~S).
formula short l i mits functions name
3 CaO Si02 c3s 35-60 initial set and early strength 2 CaO Si02 c2s 20-45 long term strength 4 CaO Al 203 Fe203 C4AF 0-15 3 CaO Al 203 C3A 5-18 early strength
Table 2. Clinker minerals.
The characteristics of produced cement clinker depend on the relative concentrations of these different components. Produced clinker leaves the kiln in the form of dense solid modules which range in size from 10 to 75 mm. Coming out of the kiln it is led through a clinker cooler, which serves the dual purpose of lowering clinker temperature (from 1200-1500°C to 80-3000C) and rewinning clinker heat for reuse in combustion air inside the kiln.
For the dry process, it is possible to use a preheater or a precalciner.
A preheater is used to get an efficient heat exchange between the raw meal and the exhaust gases and is composed of a sequence of cyclones. The kiln can be shortened because the first heating is already done before the mixture is fed into the kiln. the hot kiln exit gases are simultaneous moving in the opposite direction and the highly turbulent mixing action between the feed and gases promote efficient heat exchange sufficient to induce 40-50% calcination in the raw material feed by the time it enters the rotary kiln.
11
~
=--~~-~ ~ ._.r.-quarry
Raw material collection
rotary drier
Raw material preparation
4-slage suspension preheater with precalciner
rotary kiln
Pyroprocessing
roller press ball mill with classifier
Clinker grinding
Fig. 3. Cement production process.
12
ball mill
cement silos
+
raw material blending silos
+ cllnker silos
I • i• • T,•'• •
A precalciner is a separate cambustion chamber between the rotary kiln and the preheater. A substantial portion (up to two-thirds) of the total fuel requirements is bumt in this chamber. Advantages of this system are that the kiln does nat have to be so big to get the same capacity, lower grade fuels can be used in the precalciner system and the dust emission is reduced.
Finish grinding
Mter the burning and cooling, the clinker is stared or is going straightly to the cement mills. The clinker is interground with 3-5% gypsum to produce finished cement. The gypsum is added to control the setting time of the cement when it is mixed with water. Grinding fineness is a very important factor in cement strength. Ordinary Portland cement has a fineness which is usually around 300m2 /kg. At this process stage also secondary constituents like blast fumace slag, fly ash and other pozzolans can be added. These secondary materials are interground with the clinker to produce blended cements.
Finally, the cement is shipped in bulk or in paper bags. Depending on the specific infrastructurallocation of the cement plant the finished cement is shipped by trucks, by train or by ship.
3.2. Cement production in Tanzania.
3.2.1. Raw material preparation.
The three major types of materials which are used for the production of Portland cement at TPCC are:
1. Limestone (Calcareous material)
2. Red soil (Argillaceous material)
3. Gypsum
The materials 1 & 2 are obtained from the campany's quarry which is nat far from the factory. The third material, which is added to the clinker befare milling is obtained from Makanya, Moshi ( 400 km). Appendix 2 shows an overview of chemica! elements in the raw materials.
13
The quarcy.
The quarry is an open bush site about 2-3 km from the production plant. After red soil is scrapped off, limestone in a form of solid rock is left behind. The rock is broken by blasting. Therefore it is necessary to drill blast holes. Drilling is done by drill wagons driven by air compressors (pneumatic type of drilling), Three blast holes can be made per hour. In order to get the right blasting results ~ extensive unit drilling pattem with three rows of staggered holes is used. After blasting, limestone is transported to the emshing unit.
For loading operation, wheelloaders and shovels are used. Transportation is done by Caterpillar, Koekurn and Terex dumper trucks. Transportation is one of the bottlenecks. The dumper trucks are often out of order, due to lack of maintenance and spare parts.
Crushing.
The factory employs two single impeller impact crusher (HAZEMAG Impact Crusher) for size reduction of limestone lumps. Limestone transported from the quarry is crushed to a size in the range of 30-40 mm. It is not necessary to crush the red soil.
The rated capacity of the two crushers is 200 ton per hour but due to technica! faults the real capacity is much smaller. Crusher 1 is build in 1966, crusher 2 is build in 1972
Fig. 4. Single impeller impact crusher.
14
There is also a third crusher, a gypsum crusher (SAP 4 HAZEMAG) with a rated capacity of 80 ton per hour, also this crusher is nearly worn out. This crusher is also build in 1966. Sometimes, emshing is a bottie neck. On this moment, TPCC bas ordered for buying a new crusher. A new crusher is very necessary, because all the crushers are very worn. Some times it is necessary to use the limestone crushers for emshing gypsum, what is dangerous, because when there is a little bit gypsum in the crushers left, there is a chance of cyclone blockage. This stops the whole production process of the kiln department
The crushed lime stone can either be fed directly to the hoppers of raw mill of scored in the crane hall. Transport of the material is effected through rubber belt conveyors.
3.2.2. Raw material grinding, drying and blending.
After emshing the raw materials limestone and red soil are fed into the mills. In paragraph 3.1.2. it is described that there are two main processes in cement manufacture: the wet and the dry process. In this plant the dry process is used, which means that there is no water added to the raw materials. However the raw material contains about 8-9% moisture. To dry the raw material, the waste gases of the kilns are utilized.
Raw meal mills.
There are three raw meal mills. All three mills are air swept mills. The advantage of the air swept-swept grinding mill is its suitability for utilizing great amounts of hot waste gases. Another advantage is the low investrnent cost cornpared to with a grinding circuit with a redreulating bucket elevator and air separator. However, the energy consumption for an air-swept mill grinding circuit is approximately 10-12% higher cornpared to the closed grinding circuit with a bucket elevator. Figure 5 shows the principle of an air swept mill.
Each mill is connected with one kiln which provides the waste gases for drying the raw materiaL Kiln 1 provides mill 1 of waste gases, kiln 2 provides mill 2, etc. Mill 3 is also connected with a hot gas generator, which is used if kiln 3 is out of order. In energetic respect, this hot gas generator is not very efficient. Appendix 3 shows specific inforrnation about the raw meal mills.
15
Every raw meal plant consists of:
-a mill - a feeder system -a cyclone - a separator - a control board - belt conveyors and elevators between the different units
The matenals are dozed by the feeders. Belt conveyors supply the matenals to the mill through a heat resistant device. This device protects the transport belt against hot air from the mill. After the mill the material is supplied to a gravity-type separator. In the separator the coarse material is separated and returned on belt conveyers to the mill. The fine material plus the gases move to the cyclone. Here the fine matenals are separated from the gases and sent to the blending plant through air slides and bucket elevators.
filter ~ t o .. 1 .. c toet .. u c .. 1 ==nr===========::::;cs;::::==:;=:[=:t~==~
hot oeses trom kr In
fan
I lmestone red soli
ballmlll
Fig. 5. Drying and grinding in an air swept mill.
After milling the raw meal bas to be blend.
cyclone
fine mate~rlal
For mill 1 and mill 2 together, there are 10 silosof which 4 silos for blending and 6 silos for storage. For mill 3, there are 4 silos of which 2 silos for blending and 2 silos for storage.
16
At the blending plant section, blending is done in batches. The blending silo is filled and then air is blown in by means of a compressor for two hours. The meal becomes fluidified and intensively mixed. Afterwards the contents is discharged into the starage silos for later use in the kiln.
3.2.3. Pyroprocessing.
These factory bas three rotary kilns and uses the dry process. The rated capacity of kiln 1 is 350 tpd, the rated capacity of kiln 2 is 500 tpd and the rated capacity of kiln 3 is 800 tpd. All of the three kilnare provided with a four stage preheater. See appendix four for additional information about the kilns.
The kilns.
One kiln plant consists of:
- the preheating cyclones - a rotary kiln - coolers - an impact impeller hammer - a transportation (feeder) system - a clinker transport system ( one belt conveyer for all kilns)
The purpose of preheating cyclones is to preheat the raw meal. Hot gases from the kiln which are sucked by the waste gas fan are used to preheat raw meal in the cyclones. The cyclone separates the hot waste gases from the raw meal through the principle of centrifuge. Exchange of heat is a counter-current process and takes place in the ducts between the cyclones. The preheating system bas four cyclones and it is called a four stage preheating cyclone.
The rotary kiln is a steel cylinder. Inside it is lined with refractory bricks of different strength depending on the temperature distribution inside. lt is mounted by riding rings running on supporting rollers. The kiln is inclined at an angle of about 3°, the kiln outlet being at low end. The lower end of the kiln is closed by a kiln bood with a burner pipe inserted.
Raw meal enters the kiln at the upper end and being transported it transfarms to clinker while it exchanges heat in a counter-current process with the hot gases. The heat in the kiln is supplied by the cambustion of fuel oil in the burning zone. The air blown with the primary air fan is called primary air. The primary air flow is about 12-13% of the total air flow. The secondary air flow is the flow which passes the cooler.
17
From kiln 1, the clinker formed drops to the horizontal fuller cooler where secondary air is blown in by fans to facilitate cooling of the clinker. Drag ebains transport clinker below the entire cooler.
For kiln 2 and 3, clinker formed enters into the planetary coolers consisting of lifters which raise the clinker and drop it through the air stream to improve the heat transfer.
Size reduction of clinker is effected by an impact impeller hammer to facilitate cement grinding.These crushers are in series with the cooler. The clinker with the smaller diameter by-pass the crusher, and the bigger is emsbed to a maximum size of 50 mm. Clinker then drops on the drag chain and then on conveyors and is transported to the crane hall for storage ready to be fed to the cement mill hoppers. Appendix 4 shows some additional information about the kilns.
3.2.4. Clinker grinding.
Finely, after burning the clinker, the clinker is fed into the cement mills, and ground with gypsum. This unit involves the highest electricity energy consumption in cement manufacture.
Cement mills.
The Wazo Hili plant bas three cement mills. Cement mill 1 & 2 are closed systems and mill 3 is an open system. Generally open systems use a few percent more energy. However, the investment costs for open systems are lower.
The total composition of one raw meal plant is:
-a mill - a feeder system -a cyclone - a separator ( only for mill 1 & 2) - a control board - belt conveyors between the different units
Clinker and 5% gypsum from the starage hall is fed into the respective cement mill hoppers using the overhead cranes. During grinding a large amount of energy is supplied to the mills. This energy is converted to heat inside of the mill. The heating is such that the temperatures of the mill feed increase.
18
Admixtures of clinker and gypsum during grinding are sensitive to these temperatures. If the temperature of the cement leaving the mill is to high, there is a possibility of a false set taking place when the cement is used. To prevent a false set, the mills are cooled by means of cooling water. See appendix 5 for additional information of the cement mills.
Cooling water is automatically injected through a nozzle into the mill when the temperature exceeds 115°C.
3.2.5. Cement storage.
Mter grinding in cement mills, cement is storedincement silos. Wazo Hili has four cement storage silos. Two of them have a capacity of 3360 ton each and the other two have a capacity of 3165 ton each.
The silos are equipped with filters. The daily stocks are measured by a metbod known as the "Dripping method". With help of a iron ball and a piece of rope, the height of cement can be measured inside the silo. Extraction of cement from the silos is effected by air slides. The bottorn of the storage silos are in a slant form with a hole at the centre for the discharge purposes.
To ease the discharge process, the bottorn of the silo is divided into 14 sectors. These sectors are covered by a membrane (canvas) and air is aerated through these canvas by means of a compressor. Aerated air into the silos pushes cement toward the centre hole and it drops into an air slide, into a bucket elevator and then into the packing plant.
There are three packing machines each with a capacity of 60 ton per hour in 50 kg paper bags. There are also two additional bulk filling units. About 90% of the cement is leaving the factory in bags.
19
4. Energy information.
4.1. A flowchart.
To realize a good policy with respect to energy efficiency it is important to know exact the present energy use and efficiency of every unit of the plant in order to determine energy conservation options.
A suitable marmer to show the results is a flow chart. A flowchart of the cement factory is depicted on the page 19. In these flowchart the most important features of the whole production process are shown. For every unit the specific energy use ( energy use for making one ton cement) is calculated
The collected information for this flow chart comes from the year 1993. In the factory are 40 kWh-meters. Every month the kWhrateis noted.Appendix 8 shows the kWh use for the different sections. A problem is the unreliability of the meters. It is not possible to determine defect meters if the deviation is little but the following meters are really defect: raw mill two only, cement mill two only. Maybe other meters are also defect but this was to difficult to find out. In the flow chart, the noted value of these meters are used in spite of their defect. A few meters are complete out of order: gypsum crusher, general office, weighbridge and packing plant 3. These meters are not included in the flow chart. The unreliability of the meters causes a deviation, for this reason it is not possible to determine the really kWh-use for every sectionor department
In the flowchart, most of the sections, have more than one kWh-meter to calculate the specific use. See appendix 9 for the clustering of the kWh meters.
Every month the production of raw meal, clinker and cement of every unit is also noted. This is done on basis of storage data.
For the raw meal mills the following calculation is made:
total use of kWh of one mill in 1993 specific energy use:-------------- * 1.62
total prod. of raw meal of that mill in 1993
The factor 1.62 is used because in this factory for making 1 ton cement, 1.62 ton raw meal is needed.
20
For the kilns the following calculation is made:
total use of k~ of one kiln in 1993 specific energy use: --------------- * 0.95
total prod. of clinker of that kiln in 1993
The factor 0.95 is used because in this factory for making 1 ton cement, 0.95 ton clinker is needed.
total energy use Cfuel) of one kiln in 1993 specific energy use Cfuel): ---------------
total prod. of clinker of that kiln in 1993
For the cement mills the following calculation is made:
total use of k~h of one mill in 1993 specific energy use: ---------------
total prod. of cement of that mill in 1993
For production data see appendix 7.
Camparing of the power use of different units:
unit 1 unit 2 unit 3
Ck~h/ton Ck~h/ton Ck~h/ton cement) cement) cement)
crushing 1.8 1.8 1.8 grinding 39 22 36 blending 1.5 1.5 1.5 burning 24 17 27 finish grinding 44 25 38 packing 1.6 1.6 1.6 overhead 1.4 1.4 1.4
Total 113.3 70.3 107.3
Table 3. Energy use in the different units.
It is noted, that there are big differences between the three units. Two important reasans for the difference are:
- The renewing of the mill internals of mills of unit 2, a few years ago - The unreliable meters which is probably the main reason.
The difference caused through mill internals is in the most favourable situation 10%.
21
The deviation of the kWh meters is more. According the meters, "raw meal mill 1 only" uses 1,330,660 kWh (for the production of 95,933 ton raw meal), "raw meal rnill 2 only" uses 290,110 kWh (for the production of 205,935 ton raw meal). A normal kWh use for this raw meal mill only is at least 2,000,000 kWh. This means a specific energy use of 34 kWh/ton cement.
For the cement mill 2 the same story counts. According the meters, "cement mill 2 only" uses 2,379,330 kWh (for the production of 62,147 ton cement), "cement mill 2 only" uses 1,943,110 kWh (for the production of 93,035 ton cement). A normal kWh use for this cement mill only is at least 3,000,000 kWh. This means a specific energy use of 38 kWh/ton cement.
22
A complete flow chart of the Twiga cement factory:
red soi l l imestone l imestone gypsl.ITI
prim. crushing prim. crush ing crushing 1.8 kWh- (primary 1.8 kWh - (primary (gypsl.ITI
crusher 1> crusher 2> crusher)
I I drying, drying, drying,
39 kWh - grinding 22 kWh - grinding 36 kWh- grinding (RH mill 1) (RH mill 2) (RH mill 3)
I 1.5 kWh blending
1, I 1.5 kWh blending I (blending plant (blending plant 2>
I 24 kW h- preheatins 17 kWh - preheatins 27 kWh - preheatins
burning burning burning 4,180 M J - cool ing 3,997 MJ - cool ing 4,142MJ- cool ing
(kiln 1) (kiln 2) (ki ln 3)
I
I finish grindins finish grinding finis grindins
44 kWh - (CM mill 1) 25 kWh - cool ing 38 kWh - cool ing (CM milt 2) (CM mill 3)
I I
packins packins packins bulk 1.6 kWh - ( packins 1.6 kWh - ( packins (packing
plant 1) plant 2) plant 3)
1 ton cement 1 ton cement 1 ton cement 1 ton c ement
Fig. 6. Flow chart of the Twiga plant.
23
4.2. Kiln heat balance.
The kiln department is using most of the energy. To search for possibilities for energy saving in this department it is important to make a heat balance of every kiln. Off course a heat balance is just a random indication, because the radiation and convection losses are strongly determined by the condition of the refractories. At TPCC these refractorles are replaced about every three months. However heat balances can offer useful information on the thermal performance of the system.
The heat balance which is made is a simplified heat balance. Because of the lack of measure equipment it is impossible and also irrelevant to make an exact heat balance.
The following meters which are important to make an heat balance are defect:
- raw meal feeder meter - primary air flow meter - gas analyzer of the end of the kiln - continue pyrometer - exhaust gas flow meter
Because of the lack of data from the defect meters is not possible to make a heat balance in a normal way. In absence of the defects mentioned, all the data could be collected during a 12 or 24 hours test. During this test the kiln must run at constant and steady conditions.
This heat balance differs from a normal heat balance in a few points:
The specific fuel use is calculated on a year basis. This means that the total use of fuel oil in 1993 is divided by the total production of clinker in 1993. The production of clinker is determined by using data on the stock.
The primary air flow is needed for the calculation of the sensible heat of the primary air ( cambustion air). The primary air is not measured, but calculated with help of the fuel use. First, the total needed air can be calculated with help of the fuel use. For the cambustion of 1 kg fuel about 14 kg air is needed. The required amount of primary air depends on the type of burner pipe. For the installed burner pipe about 11-13% of the total air needed is primary air. -~-
The exhaust gas flow, is calculated with help of the oxygen content in the exhaust gases. The amount of oxygen is measured at the end of the preheater. The oxygenvalue which is measured here, differs a little bit from the real amount of oxygen in the exhaust gases at the end of the kiln.
24
This is caused by leakage of the preheater. Normal, the difference between the oxygen measurements at the end of the preheater and at the end of the kiln gives an indication of the condition of the preheater. See paragraph 3.2.1. for the calculation.
The continues pyrometer is necessary to get a complete picture of the shell temperature. This pyrometer moves continue from one side of the kiln to the other side and back. Now, the measurements are done with a hand pyrometer. Every five or six meter ( dependent of which kiln) a measurement is made.
Balance boundary:
Basically, any shape of the boundary could theoretically be chosen. To give an extreme example: the boundary could even cut a rotary kiln at half a length. However, the boundary must be selected according to practical considerations. This means that the cutpoints which are generated must be:
- easily accessible for reliable measurements - of practical interest in the whole context
Each cutpoint means a certain item in the heat balance because it represents a heat flow either into or out of the system.
The balance boundaries for the heat balance in this report are depicted in the following picture:
Fig. 7. Balance boundary.
25
4.2.1 Calculation of the heat balance.
Energy inputs and the outputs are expressed in heat (kJ /kg cli). The following parts of the heat balance are calculated:
Inputs: - Heat from fuel
- fumace oil - bumabie components in the material
- Sensible heat: - primary air - raw material -water - fumace oil
Outputs:
- Heat of formation - Evaporation of water from raw meal - Exhaust gas sensible heat - Dust sensible heat - Incomplete cambustion - Losses due to radiation and convection - Clinker sensible heat - Cooler exhaust gases
Inputs:
Heat from fuel.
Fuel is introduced through:
- kiln firing - bumabie components in the material
The bumabie component in the material is unknown. This is not a problem because its share is very small compared to kiln firing.
The heat from fuel is:
h = m x CV
h = heat in fuel m = specific fuel consumption CV = calorific value
[kJ/kg cl i]
[kJ/kg cl il [kg fuel/kg clil [kJ/kg fuell
26
8,390,000 ton oil Example: h = ---------- x 40,740 kJ /kg cli = 4,396 kJ /kg cli
77,561,000 ton clinker
Heat from fuel in the three kilns is shown in table 4.
kiln 1 kiln 2 kiln 3
fuel used [ton]: 8,390 11,155 20,045 clinker produced [ton]: 77,561 107,755 186,860 CV fuel [kJ/kg fuell: 40,740 40,470 40,740
heat [kJ/kg cl i] 4,396 4,208 4,360
Table 4. Heat from fuel.
Sensible heat:
Materials which pass the system boundaries, contain a certain quantity of energy depending on heat capacity [cp] and temperature [°C] of the materiaL This quantity of energy is called sensible heat.
Generally sensible heat is calculated as follows:
h = m X CP X (t-20"C)
m = specific mass cP= average specific heat t = temperature
[kJ/kg cl i]
[kg/kg cl i] [kJ/kg •cJ ["Cl
Above formula uses a reference temperature of 20°C, i.e. sensible heats of material and gas flows at 20°C are zero. For the reference temperature of 20°C is chosen, because most heat balances have a reference temperature of 20°. It is therefore easier to campare different kilns. The value h (kJ /kg di) can either be positive (if t > 20°C) or negative (if t < 20°C).
For the following mass flows sensible heat is calculated:
- raw material -water - furnace oil - primary air
Sensible heat raw material
Because the raw meal feeder meter is out of order, it is assumed that 1 ton clinker can be made of 1.7 ton raw meal.
27
This is calculated by using data on the stock. The specific heat value is derived from the figure shown in appendix 13.
example: h = 1.7 kg/kg cli x 0.85 kJ/kg oe x (100-20te = 116 kJ/kg cli
Sensible heat in raw meal in the three kilns is shown below in table 5.
Sensible heat raw meal kiln 1 kiln 2 kiln 3
specific mass [kg/kg clil 1.7 1.7 1.7 specific heat [kJ/kg "Cl 0.85 0.85 0.85 t~rature [•C] 100 100 100
heat [kJ/kg cl il 116 116 116
Table 5. Sensible heat raw meal.
Sensible heat water
The raw meal contains about 0.3% water. For making 1 ton cement, 1.7 ton raw meal is needed. So the specific mass is 0.003 x 1. 7 = 0.005 kg/kg cli.
Specific heat value is derived from the figure shown in appendix 12.
example: h = 0.005 kg/kg cli x 4.2 kJ/kg oe x (100-20te = 2 kl/kg cli
Sensible heat in water is shown below in table 6 ..
Sensible heat water (0.3%) kiln 1 lei ln 2 ki ln 3
specific mass [kg/kg clil 0.005 0.005 0.005 specific heat [kJ/kg •c] 4.2 4.2 4.2 t~rature [•C] 80 80 80
heat [kJ/kg cl i] 2 2 2
Table 6. Sensible heat water.
Sensible heat fuel
Specific fuel used for a kiln is calculated as follows:
total fuel used in 1993 specific fuel use = ---------- = specific mass
total clinker produced in 1993
28
Table 4 shows the fuel used and dinker produced. The specific heat value is derived from the figure shown in appendix 12.
example: h = 0.108 kg/kg di x 2.15 kJ/kg oe x (110-20te = 21 kJ/kg di
Sensible heat in fuel is shown below in table 7.
Sensible heat fuel kiln 1 kiln 2 kiln 3
specific mass [kg/kg clil 0.108 0.104 0.107 specific heat [KJ/kg "Cl 2.15 2.15 2.15 tempersture ["Cl 110 110 110
heat [kJ/kg cl i] 21 20 21
Table 7. Sensible heat fuel.
Sensible heat primary air
Because the primary air flow meter is out of order, the primary air flow is calculated as follows: For the installed burner pipe about 11-13% (primary) air of the total airneededis used. The total air needed can be calculated with help of the fuel use. For the cambustion of 1 kg fuel about 14 kg air is needed. The needed fuel quantity is known.
Example primary air kiln 1: specific mass primary air: 0.12 (12% prim.air) x 14 (ratio prim.air/fuel) x 0.108 (spec.mass fuel) = 0.181
The specific heat value is derived from the figure shown in appendix 11.
example: h = 0.181 kg/kg cli x 1.3 kJ/kg oe x (40-20te = 5 kJ/kg di
Sensible heat in fuel is shown below in table 8.
Sensible heat primary air kiln kiln 2 kiln 3
ratio prim.air/total air 0.12 0.12 0.12 ratio primary air/fuel 14 14 14 specific mass [kg/kg clil 0.181 0.174 0.180 specific heat [kJ/kg "Cl 1.3 1.3 1.3 tempersture ["Cl 40 40 40
heat [kJ/kg cl il 5 5 5
Table 8. Sensible heat primary air.
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Outputs:
Heat of fonnation.
In most of the practical cases it is sufficient to assume a constant value of:
h = 1,750 kJ/kg cli
The heat of formation may naturally have some variations from one raw meal to other. But due to the narrow range which is specified for the cement clinker composition no major deviations of say more than ± 50 kJ /kg cli have to be expected in normal cases.
Eva po ration of water from raw meal
The raw meal contains about 0.3% water. For making 1 ton clinker, 1.7 ton raw meal is needed. So the specific mass is: 0.003 x 1.7 = 0.005 kg water/kg cli
If water evaporates the heat of evaporation is:
h = m x 2,450 [kJ/kg clil (evaporation heat of water)
m = evaporated water [kg/kg clil
For all three kilns:
h = 0.005 x 2,450 = 12 kJ /kg cli
Exhaust gas sensible heat and dust sensible heat
Because the exhaust gas flowmeter does not work the exhaust flow is calculated as follows:
Total input of raw meal per kg clinker is 1.7 kg. Total input of fuel per kg clinker is 0.104 kg. The ratio air/fuel is 14. Total air needed to bum fuel is (14 x 0.104 =) 1.4.7-kg. However more air is used, because there is still about 5 % oxygen in the exhaust air. Air contains about 20% oxygen, so 75% of the air is used. This means that the air input is (1.47 /0.75 =) 1.96 kg per kg clinker. Total input is 1.7 kg raw meal + 0.104 kg fuel + 1.96 kg air = 3.765 kg. Output is 1 kg clinker and 0.07 kg dust. So remains for the exhaust air 3.765 - 1.07 = 2.704 kg exhaust gas/kg cli.
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Exhaust gas temperatures of kiln 2 is 360°C and the ex.haust gas temperatures of kiln 3 is 370°C. These temperatures vary a little bit ( ± 10°C).
Dust in the ex.haust gases has the same temperature. Specific mass is 0.07 kg/kg cli.
The sensible heat is:
h = m x cP x (t-20•c> [kJ/kg cl il
cP of exhaust gases of cement kilns is 1.43 kJ/kg •c cP of dust is 0.95 kJ/kg •c
The specific heat value is derived from the figure shown in appendix 11 & 12. Sensible heat in exhaust gases and dust is shown below in table 9.
Sensible heat exhaust gases and dust kiln 2 ki ln 3
specific mass exhaust gases [kg/kg cl il 2.704 2.704 specific mass dust [kg/kg cl il 0.07 0.07 specific heat exhaust gases tKJ/kg •c1 1.43 1.43 specific heat dust tKJ/kg •c1 0,95 0,95 temperature r•cJ 355 370
heat exhaust gases [kJ/kg cl il 1295 1353 heat dust [kJ/kg cl il 23 23
Table 9. Sensible heat exhaust gases and dust.
This calculation counts only for kiln 2 & 3 because kiln 1 has a grate cooler and for this reason cooler exhaust gases. It is impossible to calculate these cooler ex.haust gas fu~ .
Incomplete cornbustion.
If unbumt gases such as CO, H2, CH4 occur in ex.haust gas an additional heat output occurs.
Loss can be calculated to:
h = m x (CO x 12,640 + H2 x 10,800 x CH4 x 35,840) [kJ/kg cl il
m = specific gas quantity [Nm /kg cl il CO, H2, CH4 = volume fractions in the exhaust
Contribution of H2 and CH4 is very little, so in most cases only CO is measured. But in all three kilns the oxygen level is very high, so CO content is almost zero.
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Clinker sensible heat.
Sensible heat is calculated as follows:
[kJ/kg di]
The temperature of the clinker leaving the cooler is for all three kilns approximate 100°C. The specific heat value is derived from the figure shown in appendix 12 and is 0.78.
Heat of clinker of all three kilns is:
h = 1 x 0.78 x (100°C - 20°C) = 62 kJ /kg cli
Cooler exhaust gases.
Only kiln 1, which have an horizontal grate fuller cooler, has exhaust gases. But without flow meters it is impossible to determine heat of the cooler exhaust gases.
Losses due to radiation and convection.
Radiation heat transfer depends on surface temperature and emissivity E.
All three kiln have a surface of rough oxidized steel. For a temperature of 100°C; the E = 1. Fora temperature of 400°C; the € = 0.9.
Convection heat transfer depends on the wind velocity v [m/s] and temperature. The velocity is not exact known, but a velocity of 3 m/s is used in the calculation. In practise it is quite convenient to treat bath, radiation and convection heat transfer together. Although the physicallaws of these two heat transfer phenomena are different they are usually given as a total.
atot = arad + aconv = total heat transfer coefficient.
Both, radiation heat transfer and convection heat transfer coefficient are dependent of the shell temperature. Kiln shell temperature depends very strong from zone and zype of refractory. Kiln shell temperature also depends very strong of the condition of refractory life. The kiln shell becomes much heater if refractory is worn. This calculation is clearly a random indication.
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For this calculation, the shell surface of every kiln is divided in 8 pieces which have different temperatures, and different radiation and convection coefficients.
For every piece is the heat flow calculated with help of the following formula:
Q = «tot X A X (t·t0 ) [\Jl
«tot = total heat transfer coefficient. A = surface [mzl t = shell temperature ["Cl t 0 = ambient temperature ["Cl
To determine heat transfer coefficient and surface of the planetary coolers, it is wrong to consider the total of the tube surfaces as radiation area. The radiating surfaces are not facing freely towards ambient. For kiln 2 and 3, which have planetary coolers, an outer enveloping cylinder area is taken as reference area. See figure 7.
This enveloping cylinder is divided into two parts. The same manner as above to calculate heat flow is used. Enveloping ki In
Fig. 7. Enveloping cylinder.
From heat flow Q the specific loss can be calculated:
h = (Q I m) x 3.6 [kJ/kg clil
m = clinker production [t/hl
For kiln 1, which have a grate cooler, it was not possible to calculate radiation and convection heat transfer.
Heat losses of the preheaters is also not calculated, because the temperature and the area are not known. Heat transfer of preheaters is not really big because temperature -" -is low. For kiln 2 and 3, heat losses of preheaters is classified under rest of the heat output.
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ki ln 1
Length Element Diameter Element surface a Q
position length area t~. total (m) (m) (m) <m') (•C) (IJ/m2 •C) (kiJ)
0 - 5 5 4.1 64.4 300 30 541 5 - 10 5 4.1 64.4 320 31 599
10 - 15 5 4.1 64.4 200 23 267 15 - 20 5 4.1 64.4 240 26 368 20 - 25 5 4.1 64.4 240 26 368 25 - 30 5 4.1 64.4 360 35 766 30 - 35 5 4.1 64.4 310 30 560 35 - 40 5 4.1 64.4 180 23 237
Tot al 40 515.2 3,706
Table 10. Radiation and convection losses kiln 1.
ki ln 2
Length Element Diameter Element Surface a Q
position length area t~. total (m) (m) (m) (m') <·c> (IJ/m2 •c> (W)
cooler 0 - 3 3 6.3 59.4 140 19 135 3 - 6 3 6.3 59.4 180 22 209
Total 6 118.8 344
kiln 0 - 6 6 4.5 84.8 270 27 570 6 - 12 6 4.5 84.8 340 33 895
12 - 18 6 4.5 84.8 200 23 349 18 - 24 6 4.5 84.8 250 26 507 24 - 30 6 4.5 84.8 240 25 466 30 - 36 6 4.5 84.8 330 32 841 36 - 42 6 4.5 84.8 270 27 570 42 - 48 6 4.5 84.8 190 23 330
Tot al 48 678.4 4,528
Table 11. Radiation and convection losses kiln 2.
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kiln 3
Length Element Diameter Element Surface a Q
position length area ten-p. total (m) (m) (m) (m') ("C) (W/m1 "C) (kW)
Cooler 0 - 4 4 7.3 91.7 140 19 209 4 - 8 4 7.3 91.7 190 22 342
Total 8 183.4 551
Kiln 0 - 6 6 4.9 92.3 310 30 803 6 - 14 8 4.9 123.2 340 32 1,262
14 - 22 8 4.9 123.2 180 22 434 22 - 30 8 4.9 123.2 260 26 769 30 - 38 8 4.9 123.2 250 26 737 38 - 46 8 4.9 123.2 350 34 1,422 46 - 54 8 4.9 123.2 300 30 1,034 54 - 60 6 4.9 92.3 170 21 291
Total 60 923.8 6,752
Table 12. Radiation and convection losses kiln 3.
kiln 1 ki ln 2 kiln 3
clinker produced [ton] 77,561 107,755 186,860 hour 5,202 5,971 5,838 ton per hour [t/h] 14.91 18.05 32.01 heat flow cooler [kWh] 344 551 heat flow kiln [kWh] 3,706 4,528 6,752
heat transfer cooler [kJ/kg cl il 65 62 heat transfer kiln [kJ/kg cl il 894 903 759
Table 13. Radiation and convection heat transfer.
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4.2.2. The heat balance
The kiln 4 which is used to campare is also a kiln with a four stage preheater and has a grate cooler. This heat balance is typical for a unit in the 2000-3000 tpd range. It is not really fair to campare TPCC kilns with kiln 4 because radiation and convection heat losses depends very strong of the kiln size. Figure 8 shows the specific heat consumption for four stage cyclone raw mix preheater of various sizes.
The kiln 5 which is used to campare is a kiln with a with a four stage preheater, a precalciner and a grate cooler. The capacity of these kiln amounts 2800 tpd.
kiln heat balance ki ln 1 ki ln 2 kiln 3 kiln 4 to kiln5to c~are c~are
kJ/kg cl i kJ/kg cl i kJ/kg cl i kJ/kg cli kJ/kg cl i
INPUT
fuel trom sensible heat 21 20 21 13 14 f rom combus ti on 41396 41208 41360 31150 31050
raw meal trom sensible heat 116 116 116 54 92 trom sensible heat of water 2 2 2 - -
combustion air trom sensible heat of all 5 5 5 6 8 air supplied (prim. air)
Total input 41540 41351 41504 31223 31164
OUTPUT
Heat of formation 11750 1,750 11750 11750 11789 Evaporation of water from raw meal 12 12 12 13 17 Exhaust gas sensible heat - 11295 11353 636 595 Dust sensible heat - 23 23 18 lnc~lete combustion - - - -Clinker sensible heat 62 62 62 63 Cooler exhaust gases - 0 0 423 520 Losses radiation & conv. kiln 862 903 759 297 243 Losses radiation & conv. cooler - 65 62 Losses rad. & conv. prehester - 241 483 Rest 23
Total output 41540 41351 41504 31223 31164
Table 14. Heat balance.
Remark: To calculate heat inputs and heat outputs, sametimes information is used which comes from data of stock and sametimes information is used which comes from a measurement.
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For example: to calculate specific fuel use, production data is used. To calculate radiation and convection heat transfer, information of a measurement is used. A few calculations are based of a mix, like radiation and convection heat transfer. Temperatures are measured in one moment and mass flows are calculated with information coming from data of the stock.
"' "" -ë u
.:<.
.t::. u
" E .D ~ .. > .. E ~
'0 3:
Fig. 9.
925 612,000
900 600,000
580,000
850 560.000
:0 ~ :J
540.000 CD
c 0
800 ä.
520.000 E
" "' c 0 u
500.000 ö 750 ..
490,000 :I:
725 0 3000 3500 LOOO t/24 h Klinker 0 6000 12000 18000 21000 24000 bbl/21. h clinker
Heat consumption of 4 stage cyclone preheaters for various size depending upon the throughput capacity.
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5. Energy conservation options.
Measures to imprave energy efficiency in producing cement can be divided into four groups.
- Energy management - Process changes - Product changes - Energy conversion
The first group includes measures that do nat require a major change of technology. Therefore these measures do nat set high capita! requirements and are mostly readily implementable. The second group of measures entails process technology changes. Most of these changes do set high capita! requirements and have consequently to be regarded as long term options. The third group contains measures which lead to product changes. Last but nat least there is also a possibility for fuel conversion. This might relieve expensive and scarce commercial energy supplies.
5.1. Energy management.
5.1.1. StalT.
Most measures which can be taken in energy management refer to methods, technology or materials. However one factor should nat be forgotten in energy savings programs and that is people. The staff in a plant all have a great influence on energy efficiency of the material used and on the technology applied. Every day the methods and actions of the staff in the plant determine whether the energy efficiency will be good or bad. Energy efficiency is therefore nat predetermined automatically and exclusively by environment (external influences), material or technology; it is also determined on a daily basis and to a crudal extent by staff. Three important rules come to the fore:
Staff should know the energy objectives. - Staff should know how they can achieve their objectives through practical actions. - Staff need motivation.
First, at the moment, most of the staff don't know why to save energy. They don't know which part of the production casts energy casts are.
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They don't know what the objectives (energy related and others) of the company are. A lot of purposes are secret. Staff need information to fulfil their job, not only instructions. They have to know their contribution of their job to the company. The management has to work to minimize the gab between management and the staff on the work floor, because it blocks the information stream in bath directions.
Second, staff don't know how to save energy. This problem can be solved through training. Especially, it is important to train the staff who operate the energy eating machines, like kilns and mills. Training of these staff is a main case to save energy.
Third, people need motivation. Without motivation of the staff 1t is difficult to save energy. Staff can be motivated through financial incentives, but they can also be motivated with appreciation and information. For example, by telling how many energy is saved and how many money is saved.
5.1.2. Reducing heat losses through reducing kiln interruptions.
An effective way of improving energy efficiency lies in reducing heat losses. The most significant heat losses occur in the pyroprocessing department These heat losses consist of heat content of exhaust gases leaving the system, radiation and conveedon losses, and heat content of the clinker when leaving the system. Most important for high efficiency cement production in rotary kilns is to obtain a stable, uninterrupted operation of the kiln department
Whenever the kiln has been shut down, heat is wasted when the system is started up again, because production will remain low until temperatures tbraughout the system are brought up to normaL It takes a long time to balance the system, ranging from 30 minutes to several hours. Therefore interruption causes considerable energy losses.
Factors which cause kiln interruption can be divided into internal and external. Internal factors which cause kiln interruptions are unplanned rnainterrance and lack of raw materials. For 1993, the most important reasans for unplanned stops except power interruption, are:
ki ln 1 kiln 2 kiln 3
toss of feed 8 7 8 cyclone blockage 6 8 5 waste gas fan tripped 3 8 4
Table 15. Number of unplanned interruptions.
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To reduce kiln interruption, all internal factors have to be identified and eliminated as far as possible.
For TPCC, the external factor which cause kiln interruption, (not only kiln interruption) is power distortions. TPCC gets its power from T ANESCO. These power interruptions affect not only energy efficiency but also production capacity. In 1993, the kilns were down for about 600 hours through power failure or power reduction. A possibility to become independent of this external factor is having an own power station. This could be a stand-by power station or a continue power station. At this moment there is a little stand-by power station ( 415 Volt/200 Amp) which provides power to kilns varying units avoiding kiln damage (e.g. primary air fans, to proteet burners) and also the packing plant, water pump and the weight bridge, to continue a smooth despatch of cement.
The following types of power generating plants may be considered:
- steam power stations - diesel power stations - gas-turbine power stations
Steam generating stations can be operated with the largest variety of fuels, i.e. solid, liquid and gaseous, offering the possibility of applying most economie fuels. In this country, there are big coal reserves. Maybe in the future, these coal reserves can be used for power generating or even as we see in a later on in this report also for burning the cement. Steam power station needs however big investments.
Diesel power offer the advantage of lower investments casts and shorter erection time. Diesel generators can also be used for covering peak demands if the public network is at times to weak. A diesel power station can be characterized by low specific heat consumption, low space consumption, low demand for cooling water, short starting time and high noise level. The prize of diesel is high, however, for a little power station of 15 MWh (which is needed for this factory) the specific heat consumption is about 2000 kcal/kWh and for a steam power station about 2800 kcal/kWh).
Gas turbines can be operated with fuel oil or natura! gas. Gas turbines of capacities between 2000 and 25000 kWh, showthebest efficiency. Gas turbines need the lowest_ investment. However the specific heat consumption is about 30% higher than that of a diesel unit of the same capacity. The starting reliability is very high. It may also be useful for covering peak demands. The exhaust gases of gas turbines in cement plants can be utilized in drying-grinding mills. Although, in this plant the drying-grinding mills are using the hot gases from the kilns.
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5.1.3. Fuel combustion system.
Fuel cambustion systems in the kilnare major contributors to energy inefficiency and refractory damage. Frequently encountered weaknesses in cement plants are reported including poorly adjusted firing, incomplete consuming of fuel with CO formation and cambustion with high excess air rates. This counts certainly for this plant.
Often, it is permitted to use lower primary air level and greater use of preheated secondary air from clinker cooler. Low primary air levels also mean that flame temperatures are high and conditions for cantrolling flame shape are most favourable.
Cambustion tests have indicated that reducing the kiln exit gas 0 2 level from 2 to 1% would result in about 4% energy savings (R. Venceswaren, The U.S. Cement industry). The reduction in efficiency with increased 0 2 level is caused by the requirement to heat the excess oxygen and nitrogen passing through the kiln to exit gas temperature. However, if excess air level is reduced below a certain level, CO is produced which also leads to an increase in fuel consumption due to incomplete cambustion of carbon.
Also the type of burner is very important. At this moment TPCC bas just installed a new burner for kiln 3. This is a Pillard Rotaflam burner. The current burner is in operation with an average of 12% primary air. The new burner required probably (according to manufacturers information) 5% of primary air.
Energy saved according to the manufacturer is 2.5 kcal/kg clinker per percent of primary air; according 7% (12%-5%) reduction of primary air this will save: 7 x 2.5 = 17.5 kcal/kg clinker.
Kiln 3 produced about 200,000 ton clinker a year. The energy saving is 200,000,000 x 17.5 = 3,500,000,000 kcal. Energy costs decreased by 3.500.000.000 kcal x 8 TSHS/1000 kcal = TSHS 28,000,000 ($ 56,000) a year.
None of the three kilns bas a gas analyzer at the end of the kiln which still works. They are out of order. For operators, it is impossible to regulate the kilnon a energy efficient way. Now, the oxygen level is 5-7%. There arealso more broken meters which are necessary to control the kiln on the right way. For this reason poor rnainterrance in this plant causes very big energy wasting, because of poorly adjusted firing and cambustion with high excess air rates.
In view of the extreme oxygen levels, about 10% energy saving are possible with good measureequipment. Especially the gas analyzer is of great importance.
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The second item which is important to operate consistently at an optimum 0 2 level of 1 to 2% and rnaintaio product qualities is training of the kiln operators (burners). Buroers have to know how to operate the kiln on the right manner in order to optimize the oxygen level.
5.1.4. Reducing heat losses through advanced kiln control.
Much heat losses occur because the kiln is operated suboptimally, and this is not only caused by broken meters. Operating the kiln in a stabie state is not easy because the chemica! reactions are complex, and abnormal phenomena such as poor dinkering conditions do occur, mainly caused by abrupt changes in raw material compositions. Kiln control should keep the burning process stabie and reeover quickly from upset conditions. Kiln operators tend to overburo clinker because control of a cement kiln is easier when it is hot. Th is increases both kiln and finish grinding energy use ( since the elioker produced less reactive) and reduces refractory life.
Each operator bas bis own knowledge and ideas about how to control a kiln. There are, therefore, wide variations in interpretations of operating conditions, resulting in operators making different control adjustment under similar circumstances.In actdition to these disadvantages of manual control there are considerations of costs associated with maintenance, downtime, refractory wear, risk of accidents and energy efficiency.
In the previous paragraph, we have seen that in this factory much heat losses occur through suboptimally operation, because a lot of meters and probes which are important to control the process are out of order.
Heat losses due to suboptimal operation might be reduced by installing a computer control in the kiln department The kiln control system should keep the burning process stabie and react quickly to changing conditions. This increases both kiln and finish grinding energy efficiency, because the operating temperature will be lower (and consequently the heat losses) and the produced clinker will be less reactive. Important is that these benefits can be obtained at relative low investment costs. At the moment a lot meters and probes are defect. It is expensive to repair or to replace these meters. Most of them are very old, they are not used any more in Western countries, so delivery time is almost long and the prices are high. This is again a reason to replace the old manual control system by a new computer. -control system.
A problem of a new computer control system could be lack of know-how to maintenance the system. To work with such a system, a great amount of theoretica! know how about the process is needed. Also specific skilis to write programs for the computer and make adjustments are required.
42
This problem can be solved through enough training, but this is very difficult and expatriates are expensive.
Most modern kiln control systems do not try to make a theoretica! model of the complicated process occurring inside the kiln, but rather use so-called "fuzzy-logic". The concept is that the control system is designed to imitate the thinking and actions of the best operators and hence it uses typical "rules of thumb" that operators use.
The program takes the general form:
IF ( condition), THEN ( control action)
Two main parameters are monitored by the fuzzy controller:
1. the level of nitric oxides in kiln exhaust gases. 2. the litre weight of clinker leaving the cooler.
The program determines whether the burning conditions are optimized based on a statistica! correlation between level of nitric oxide and litre weight of the clinker. Other parameters, such as temperature and the level of combustibles and oxygen in the preheater exhaust, are used as consistency checks. If the conditions are not optima!, adjustments are made either to the induce-draft fan speed to control kiln draft or to the fuel feed rate. Kiln speed and feed rate are held constant.
primary advantages of the kiln control system are:
- Savings in fuel consumption - Increase in refractory life - Reducing milling casts - Improving product quality - Reduction NOx level - Higher kiln running time
2.5- 5% up to 30% 7.5- 15%
Several companies worldwide have developed automatic control systems:
- Fl Smith: The LINKman - the WOKURS system by KHD Humboldt Wedag - SILTAC by Chichiba of Japan - OSCA LINKman system developed by Blue Circle Co. in the UK
and SIRA Ltd. (a modern version of UNKman).
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5.1.5. Reducing heat content of exhaust gases.
Exhaust gases include:
- cambustion gases from burning of fuel - carbon dioxide from calcination of raw materials - dust entrained in exhaust gases - dryer exit gases - vent air from the clinker cooler.
These heat losses will all diminish as the exhaust temperature is lowered. The exhaust temperature depends on the amount of primary cambustion air and on internal heat transfer efficiency. The amount of primary cambustion air may be reduced by adding more preheated secondary air (see paragraph 5.1.3. Fuel cambustion system).
Internal heat transfer efficiency of a rotary kiln is, in general, not good. Adding kiln length and increasing kiln speed will enhance internal heat transfer, but adding kiln length enlarges energy losses through radiation and convection. Also devices such as chains, trefoils and lifters will enhance internal heat transfer. The intent of these devices is to provide a large contact surface area between the hot cambustion gases and the kiln feed material in order to enhance heat transfer efficiency.
Chains:
Chains can be installed at the feed end of a kiln for two purposes. The ebains can absorb heat from the gas stream for transfer to the raw materials as the ebains move through the bed material, and they can enhance heat transfer by exposing more of the feed surface to the cambustion gases. Chains are used primarily in wet kilns to help with water evaporation, although they also can be used in dry kilns.
Trefoils:
Trefoil (trademark of the Harbison-Walker Refractories Group) systems consist of refractory arches constructed in the transition zone between the preheating and the calcining sections of the kiln. These arches divide the feed into separate streams an.c:i__ thereby enhance heat transfer in two ways. First, the arches provide more refractory surface area to absorb heat from cambustion gases an second, they expose more of the feed surface to the hot gases. Improvements in thermal efficiency from these systems have been difficult to measure.
44
Lifters:
Lifters or kiln tumbling ledges consist of rows of discontinuities installed as part of the refractory lining along the kiln axis. primary function of lifters is to increase the material angle of repose to assure that material turnbles rather than slides along the shell refractory lining. In kiln 2 and 3 which have bath a rotary cooler, are lifters used. In the kiln, the lifters will not significantly increase thermal efficiency.
5.1.6. Reducing heat losses by radiation and convection.
A considerable amount of heat is lost through the shell of a cement kiln particularly near the burning zone. The radiant heat losses combined with the leakage of ambient air into the firing end of the kiln can significantly lower the efficiency of fuel use. Shell heat losses can be reduced through the use of insulating refractories. Refractories resist the kiln shell against heat, abrasive action, thermal shock, and chemica! attack to extend life and efficiency. The kiln shell temperature and radiated heat quantity depend greatly on the thickness of the coating.
Normal refractory bricks have an average thermal conductivity (K factor, [W /m 2 K]) of about 0.75. One way to reduce heat losses is to insert a diatomaceous earth block brick (with thermal conductivity of about 0.18) bebind the refractories. Fora hot face temperature of 1100°C, this typically reduces the cold face temperature from 300°C to 166°C. The patented Johnson insulating system which uses a more insulating material called "Insblock" (with K factor of only 0.09), suggest that the kiln shell temperature can be reduced to l20°C.
A new high efficient insulating product ( designed as Lytherm 1535-GC) specifically designed for rotary kiln applications bas been developed by Lydall, Inc. The insulating material is made up of long, high purity ceramic fibres combined with a blend of binder materials to impart toughness and withstand the rotating kiln stresses. The material is finding increasing use as backup insulation to the hard refractory lining of rotary kilns.
The temperature curve of the kiln shell and the radiated and convected heat quantity depend greatly on the thickness of the refractory bricks. - ~ -Table 12 shows the temperature curve of kiln 3, but this is just a snapshot.
45
Suppose, the average kiln 3 shell temperature is 250°C. With an efficient insulating product, the kiln shell will be reduced to 200°C. The difference is 50°C.
The total surface of kiln 3 is:
60m x 4.9m x 3.14 = 924 m 2
The reduced radiation and convected quantity is:
0:101 = o:rad + o:conv = total heat transfer coefficient.
t0 = Ambient temperature (20°C)
h = Q / m x 3.6 = specific loss
The kiln shell is 250°C (average):
Q = 26 W jm2 C x 924m 2 x (250°C- 20°C) = 5526 kW.
h = 5526 kW I 32 t/h x 3.6 = 622 kJ/kg di
The kilnis shell 200°C (average):
Q = 23 W jm2 C x 924 m2 x (200°C - 20°C) = 3825 kW.
h = 3825 kW I 32 t/h x 3.6 = 430 kJ /kg di
The difference is 192 kJ /kg dinker. The total energy use of manufacturing 1 kg cement is about 4,500 kJ. An energy saving of 4% (192/4,500) is possible. However, probably the temperature difference is larger, so the energy saving is larger too.
It must be taken into consideration that a two layer lining has the inherent danger of mechanica! instability and has to be installed with a great deal of care. Furthermore, it must be ensured that the basic brick grade to be employed can withstand the greater severity of the service conditions (thermal, chemica!) due to the insulation.
46
5.1.7. Dost insuffiation.
At this moment a lot of dust of the kilns comes out of the exhaust pipes, because two of the three of the electrastatkal filters are out of order. Also the cooling tower ( only present at unit three) which is needed for an efficient working of the electra-filter, is out of order. For kiln 3, the emission of dust is estimated at about 2.2 ton per hour. For the other two kilns, the emission of dust is estimated at more than 1 ton per hour. For kiln 3, this value is calculated as follows:
For making 1 ton clinker, about 1.63 ton raw meal is needed. Three years ago, this is determined on bases of stock measurements when the filters were not out of order. Now, when the electra-filters are out of order, 1.7 ton raw meal is needed for making 1 ton clinker (this count for kiln 3). The difference is 1.7- 1.63 = 0.07 ton raw meal per 1 ton clinker.
In 1993, the average capacity of kiln 3 was 32 ton clinker per hour. So, 0.07 x 32 = 2.2 ton per hour dust goes into the air. Total production of kiln 3 in 1993 was about 187,000 ton clinker. There is about 187,000 x 0.07 = 13,090 ton spoiled.
The exact amount of emission is not known, but this little calculation shows how important it is, to repair the electrostatical filter, and the condition tower. However, the most important reason is to proteet the environment.
5.1.8. Uplining of the mill.
The configuration of the mill internals and the choice of correct matenals bas a significant effect on grinding mill performance. The mill is lined with plates, which serve to proteet the mill shell against wear and also to assist the lifting of the feed material/grinding media mixture. Grinding media and mill lining material are usually selected according to the wear characteristics of the material because these characteristics affect replacement casts.
The grinding media used in this factory consist of balls of Duncodar (hardalloys material), the same material is used for the liners. This material is a good wear-resistant materiaL However, the problem is that the mill -,internals are completely worn, especially in cement mill 1 and 3 and raw mill 1 and 3.
Wear that reduces the profiling of the liners will impair their lifting action and reduce the effectiveness of the grinding process. The effect of lining wear on power consumption is particularly dramatic in smaller diameter mills.
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For example, 5 centimetre of liner wear results in about a 14% increase in specific power consumption in an 2.5 meter diameter mill and about 6% increase in a 5 meter diameter mill (F. van der Vleuten, Cement in development, energy and environment).
The diameters and specific energy uses of the mills are:
diameter Energy estimate wear meter klolh/t.cem. eentimet re
Raw meal mill 1 2.9 39 4-5 Raw meal mill 2 3.6 22 0-1 Raw meal mill 3 3.8 36 5-6 Cement mill 1 2.7 44 4-5 Cement mill 2 2.8 25 0-1 Cement mi ll 3 3.2 38 5-6
Table 16. Relation specific energy use and wear.
Normal energy use of raw meal mills is about 20-30 kWh/ton cement. Depending of the kind of material and the mill size. The bigger the mill, the less the specific energy u se. Normal energy use of cement mills is about 25-35 kWh/ton cement depending of the diameter, kind of material and the used system (open or closed circuit).
In the above table, a conspicuous difference between the mills 2 on one hand, and the mills 1 and 3 on the other hand is makes clear that there is sarnething wrong. It is not only wear which causes this big difference. Cement mill 1 has problems with the feeder system which delivers to little clinker for the mill. Cement mill number 3 make use of an open system. Generally uses mills with an open system more energy than mills with a closed system. But most important is that the kWh meters of raw meal mill 2 and cement mill 2 are unreliable. See the following paragraph 5.1.9.
In spite of these reasans it is important in case of energy efficiency to replace timely the old internals (grinding media, Jiners and diaphrams) of the mills.
5.1.9. Saving energy costs through replacing power meters.
In the cement plant 37 kWh-meters are installed for the different sections and one main power meter for the whole factory, which is the property of TANESCO. Some sections have no kWh-meter or a broken kWh-meter, for example the gypsum crusher and weight bridge. Once a month, on the first day, the kWh meter stand is noted for accounting purposes. In 1993, the total energy use according these 37 kWh-meters amounts 39,605,920 kWh. TPCC purebasetheir power from TANESCO.
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According Tanesco the total energy use in 1993 amounts 47,922,000 kWh. The difference between TPCC measurements and T ANESCO measurements amounts 8,316,080 kWh. Most strange of this difference is that in some months the difference is very little, just a few percents, but there are months with a difference of more than 30 %. In figure 9 power consumption according TPCC and T ANESCO is reproduced.
Total power consumptlon 1993
month c TPCC .,.. Tan ... •co
Fig. 10. Total power consumption 1993 according TPCC and Tanesco.
It is impossible that the few energy consumers without meter are responsible for such a big difference. The weighbridge and gypsum crusher are small energy users. The Tanesco main meter is placed in 1966, when the plant is build, and is never calibrated or replaced. Without further investigation it is not possible to explain the really reason, because meters of TPCC are old and never calibrated too.
A second problem is that the energy information obtained cannot even be clearly assigned to individual departments and groups of machinery. The reason for this is the complicated entanglement of energy inputs and energy meters built up of the plant in three phases.
These inaccuracies of defect power meters and complicated entanglement makes it difficult to identify any existing potential for energy saving. To realize energy efficiency it is important to have accurate energy information of every section.
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5.2. Process changes.
5.2.1. Precalciner.
The development and adoption of precalciners bas been dominated by the Japanese ever since in 1971 Ishikawajima-Harima Heavy Industries installed the first precalciner system in Japan. Several major equipment manufactures have now developed their own version. Despite numerous alternatives and variations, these systems are reported to work well owing to the basic simplicity of the precalciner concept.
The essential factor of precalcining process is the actdition of a separate cambustion chamber to a conventional preheater. The main accomplishment of the precalciner design is to provide direct heat in the most effective manner possible where it is needed, in the calcining portion of the clinker production process where it is consumed by the rapid thermal demand of calcination. Precalciners are expected to be the prices of for the worldwide cement industry will into the future, until another superior revolutionary concept is developed.
In the simplest and most common case the cambustion air required for combustion of replacement fuels in the precalciner is passed with the kiln gas through the rotary kiln, which results in an increased excess of air for the primary firing system. On the other hand, in precalciner processes with tertiary air ducting the cambustion air bypasses the rotary kiln on the way to the calciner (see fig 11).
An advantage of using tertiary air is the significant lower gas temperature at the kiln inlet due to the lower capacity flow ratio. But for using tertiary air, a grate cooler is needed. Precalciners have a lot of benefits:
- Capacity increase of more than a factor of 2, so for example for kiln 3, which bas now capacity of 800 tpd should bas a capacity of more than 1600 tpd.
- lncreased refractory life in the burning zone, and also through this, improved kiln system availability of up to 10%
- About 50 % reduction in NOx formation because up to 60 % of the fuel is fired at reduced temperatures (about 820°C- 840°C) in the precalciner.
- Allowance for up to 60% use of waste fuels due to the low-temperature cambustion requirements in the precalciner (see also paragraph 3.2.2. Waste fuels).
- Reducing the heat loss from alkali bypasses, provided that the precalciner receives bis hot air from the clinker cooler rather than from the kiln. The alkalis are mostly volatilized in the rotary kiln instead of the preheater. Therefore a high amount of alkalis can be removed via the bypass. The additional fuel for calcining is introduce after the bypass port. ·
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,._ fuel
<=::=J air
<:===J exhaust gas
rotery kiln rotery kiln
Fig. 11. Precalciner with cambustion air through a tertiary air duet and through the rotary kiln.
- Improved potential for automation. - Improved rotary kiln operation stability because of its reduced thermal
requirements. - Lower capita! costs for comparable capacity. - About 5% impravement inthermal efficiency. - Lower specific heat consumption by about 10%.
An example of modifying an existing preheater system is the conversion of a 4-stage preheater to the V A-PASEC precalciner system in a cement factory in Turkey, in 1988. The capacity before the conversion was 1300 tones of clinker per day. The dimensions of the rotary tube kiln were 4.2 meter diameter x 60.0 meter. The system bas the registered tra de name V A-P ASEC, and this stand for Voest Alpine PArallel gas flow SErial material flow Calciner. The capacity after conversion was more then 3000 tones per day. The reduction in the specific heat consumption was from approximately 830 kcal/kg to 730 kcal/kg.
Largest problem to instaU a precalciner is the enormous investment costs. Because noi" -only an actdition of a separate cambustion chamber is needed, a lot of other adjustments are required, too:
- A bigger cooler. Preferabie a horizontal grate fuller cooler, because then it is possible to use tertiary air.
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- Enlargement of the capacity of the raw meal mills with a factor of more than 2. (see the next paragraph 5.2.2.)
- Enlargement of the capacity of the cement mills (see 5.2.2.) - Enlargement of the feeder system of the kilns - A bigger crusher or more crushers. - Enlargement of the clinker transport. - Enlargement of the raw meal transport.
It is also possible to shut down the energy wasting kiln 1 or even kiln 2. Then there is no need for more or bigger mills and bigger clinker transport. In this scenario the production of clinker is only done at one big energy saving kiln with calciner. The capacity of this kiln would at least more than 1600 tpd. For one kiln is also less maintenance and less spare-parts needed.
5.2.2. High pressure roller mills.
The introduetion of the high-pressure grinding roll onto the market in 1985 signalied a new era in the field of milling. With in a very short space of time the high-pressure grinding roll bas found acceptance in many sectors of industry using widely different methods of operation. While in farmer time the tube mill was the dominant grinding machine, it bas now been largely superseded by the roller mill and the high-pressure grinding roll. Tube mills are used less and less in raw material grinding, and in cement grinding they are being selected only for compound operation with a high-pressure grinding roll.
The most important modes of high-pressure grinding roll operation are:
Pregrinding:
Pregrinding increases the capacity of existing tube mills by up to 40 %, and cuts energy consumption up to 15%.
Hybrid grinding:
Hybrid grinding involves the recirculation of grits from the tube mill circuit to the - ~ _ high-pressure grinding roll. With hybrid grinding the capacity is raised by up to 80 % and the saving in energy is around 20%. Hybrid grinding is only possible with closed circuits.
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Combi grinding:
Combi grinding is the newest mode of operation and is used when the objective is to greatly increase of the capacity of existing systems. It involves pregrinding the clinker to a particular fineness and then finish grinding it in a downstream tube mill in either open or closed circuit. With combi grinding all the grids are recirculated to the high-pressure grinding roll via the separator (which is placed after the roller mill). combi grinding is better than hybrid grinding because the returned grit is coarser by the combi grinding, this makes the bed of material between the rolls more stable. The difference between returned grits and fresh material by hybrid grinding cause uneven intake of material into the grinding gap and leads to skewing of the roUs. Combi grinding increases capacity of existing tube mills by up to 200 %, and cuts energy consumption up to 20-30%.
Finish grinding:
Finish grinding systems incorporating high-pressure grinding rolls presently exist for raw material and granulated blast furnace slag. There are only a few reference system for cement. Finish grinding by roller mills saves about 5-15%. energy saving with roller mills depend on the grindability and moisture content of the feed materiaL For hard materials, roller mills can save 20 to 50% compared with hall mills.
For this factory it is only advisably to purebase these roller mills for capacity enlarging. Combi grinding is probably the most favourable. Another possibility is when cement mill 1 is worn, buying a new pregrinding unit for cement mill 3 to enlarge the capacity, instead of replacing mill internals.
5.2.3. High eflicient classifiers
Classifiers are installed in closed-circuit grinding systems to separate the fine, productquality particles from the coarser oversize particles that are recycled for further grinding.
Only cement mill three is an open-circuit grinding system, which means that there is no classifier. The material is classified in the mill self and is leaving the mill when the _ particles are fine enough. General, this system is less energy efficient than close-circuit systems.
Conventional turbo classifiers typically recycle as much as 60 % of the product-quality fines back to the mill, resulting in overgrinding and increased power use.
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Several companies have recently developed improved air classifications systems, especially for finish grinding systems.
The Mitsubishi Dual Separator (MDS) was developed, for the raw meal grinding systems. The MDS was developed for use in conjunction with a conventional centredischarge tube mill. The MDS is composed of a rotary-selector, vane-type centrifugal classifier placed upon a gravity classifier. Conventional centre-discharge mills (used by TPCC) use two kinds of separators in series connection: one to classify air swept meal and one to classify mechanically elevated meal. The MDS system separates both the air swept meal and the mechanically elevated meal. It controls the gas flow velocity in the classifying chamber with a fan that is independent of the classifier. The MDS is designed to avoid the formation of a gas circulating channel, which adversely affects the classifying efficiency by allowing the fine meal to become mixed with the coarse me al. Mitsubishi reports about a 10% reduction in energy use in the whole grinding process compared with a conventional mill. In addition, the investment casts is reported to be about 10% lower, and easier operation and maintenance are expected. Other equipment vendors also offer versions of high-efficiency separators (e.g., Fuller 0-SEP A, F.L.Smidth Sepax) for raw grinding circuits with claims of 15 to 50% increases in mill capacity, 12 to 25% power savings, and improved burnability of the raw mix.
For finishing grinding systems the high-efficiency classifier primarily include a new generation of vortex air classifiers. They use a horizontal air stream in the separation zone (the dominant air direction in classica! separator is vertical). These 'side-draft' classifiers provide for langer partiele residence time in the separation zone, thereby mitigating the entrapment of fine particles of coarse ones. In addition, the problem of fines bypassing is prevented without incurring high capital and power casts associated with the external fans used for this purpose in the earlier systems. Because the new classifiers are more compact than conventional classifiers, the capital casts may be lower.
Several companies are marketing high-efficiency side-draft classifiers:
- Onoda Cement Company, Japan: 0-SEPA - Sturtevant, Inc.,Boston, Massachusetts: SD-High-eff. Classifier - Polysius, Germany: CYCLOPOL - C-E Raymond: High-eff. Mechanica! Air Separator - Bauer, Springfield, Ohio: Centri-Sonic Classifier
Off coarse, replacement of the classifiers (for raw meal grinding systems or finish grinding systems) is only to justify if it is economical feasibility. It is a long term possibility, if the present equipment is write off or when there is a need to increase production.
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5.3. Product changes.
Changes in the manufactured end-product might lead to considerable energy saving. First, changes to products with at least the same quality as could be attained by substituting part of the Portland cement clinker in the end product by artificial or natura! pozzolanic materials or blast furnace slacks. Actding blast furnace slacks can be very attractive, however in Tanzania is no slacks available. Second, especially in the case of developing countries bas to be considered whether the high quality of Portland cement is necessary for the applications. In a large amount of applications lower quality cement, demanding less energy in manufacturing, will suffice.
5.3.1. Portland natural pozzolan cement.
The blending of portland cement with pozzolanic properties makes it possible to produce more cement from the same amount of clinker and as a result the energy consumption per ton of clinker will be reduced. Natura! pozzolans consist of glassy materials of volcanic origin. They contain essentially the same compounds as portland cement, only in different concentrations.
Experience in several countries learned that a considerable amount of natural pozzolans up to 40% can be added without changing the character of the cement as a general purpose cement. The rate of gaining strength is somewhat lower than for ordinary portland cement, but at later ages, beyond one year, the strength of the concrete containing pozzolan becomes generally higher than that of portland cement concrete.
The use of this cement reduces not only energy use but also emissions of dust, S02,
NOX and co2. Problem is to get pozzolan materials to Wazo hill. The nearest place to find pozzolan materials is at Iringa. Also at the Kilimanjaro are pozzolan materials. The distance is more than 400 km, so the transport difficult and the transport costs are high.
5.3.2. Changing of standards.
Tanzania has cement standard BS 12 1978. The 28 days strength is at least 4200 N /cm 2
• These standard de fine also specific surfaces required for obtaining a certain strength and durability.
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Cement standards affects energy consumption significantly. Tanzania have based their national cement standard on standard of United Kingdom. A major of applications in Tanzania doeshowever not require such high quality cement. For example, little houses, roads, plaster works, pavements. Lower quality cement can be produced with considerable less energy, and for less money.
Strength of cement depends largely of the fineness of the partieles. The partiele size fraction from 3 to 30 microns is conductive to the strength of cement. The partiele size fraction below 3 microns contributes to the initia! strength only. This partiele fraction hydrates fast and after one day results in the highest compressive and flexural strengths. The fraction above 60 microns hydrates slowly and contributes little to the strength of the cement. Partiele fraction from 3 to 30 microns should be represented as follows:
- in mass cements - in high strength cements - in super high strength cements
40-50% 55-65% above 70%
The values shown above are only orientation figures; the development of strength is dependent upon the partiele structure as well as the mineral composition of the cement. Higher partiele fineness (approximately 5000 cm2 /g Blaine) bas no influence upon the development of strength. Blaine is the specific surface (cm 2
/ g) of the cement and off course there is a direct relation between partiele size and Blaine.
The minimum fineness (Blaine) for the standard BS 12 1978 is 2250 cm2 /gram. Finer grinding requires about 5% more power per 100 cm2 /gram Blaine extra surface. (R. Venceswaren, The U.S. Cement industry). Often, the fineness of the cement produced in this plant is even much more than required according the standard. Also the variation (standard deviation) of the fineness of the produced cement is high.
Probable, energy can be saved through more equable grinding with less fineness.
Fig. 12. Specific energy use adjusted to standard operating values
Making different kinds of cement is technically easy to realize, but the biggest problem of using pozzolan cement or cement of less quality is that most people who are using cement, don't know how to work with other types of cement.
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Now, if they use the cement for construction which required little strength, they vary the ratio cement/sand. Sametimes the ratio cement/sand is up to 1 to 10.
To work with other types of cement needs education. It is imaginable that people use cement of low quality, where high quality is required.
5.4 Energy conversion.
5.4.1. Conversion from oil to coal.
During the early days of cement manufacture, coal was burned as a fuel in the cement kilns since it was so readily available in the industrialized countries. As the developing countries began to manufacture cement, they tended to use oil. which was easier to use, and at prices prevailing at the time, actually cheaper than imported coal. The energy shock of 1973 caused changes in the pattem of fuel use because of the manifold increase of oil prices. On a calorie basis, coal is now cheaper than oil, not only in the industrialized countries which in many cases have dornestic coal deposits, but also in many developing countries where imported coal can be landed at a reasonable costs. Consequently, ever since 1973 there bas been a worldwide move toward converting cement plants to coal usage. See figure 13.
Trend towards coal
y•ar c eoel + 011 o •lect.r-tef"t.y .o. ne.~. oo.a
Fig. 13. Energy consumption in the cement industry.
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Using coal:
Coal is ground and simultaneously dried in special mills to a certain minimum fineness prior to being blown into the kiln. There are two basic grinding systems: direct fired and indirect fired coal firing systems and two variants: semi-direct and semi-indirect. In the direct fired system, the finely ground coal is blown into the kiln directly from the coal mill. In the indirect fired system, the ground coal is separated from the coal mill exhaust gases and stared in a silo and the ground coal is then metered into the primary air at a controlled rate as required by the pyroprocess. The relative capital casts of the system are: direct (100%), semi-indirect (150%), and indirect (190%). Direct fired systems have lower capita! casts (typical $2 million to $4 million, depending of plant size ), but slightly higher fuel consumption.
Indirect fired systems (capita! casts typically between $2.5 million to $6 million) are generally preferred in cases of large plants with several production lines where a centralized grinding system will result in lower operation casts.
Converting to the use of coal requires many more installations than just the coal mil!. Coal exhibits considerable variations in calorific value, moisture content and ash content, and by installing suitable stockpilling/reclaiming facilities such variations can be evened out through homogenization prior to use in the kiln. Special facilities are required for transportation, handling, storing and reclaiming of coal prior to its use in the pyroprocess.
Tanzania have big coal reserves, but they are not yet on a large scale exploited. Exploitation a these mines is expensive and needs investment. Exploitation of the mines are not the only casts. The coal mines are situated at the Mbeya (Kiwira). The distance is more than 900 km. The transport of coal is expensive and required a sufficient developed infrastructure. Additional investments in supporting infrastructure for transportation is necessary. This increase capita! casts dramatically. For a cement plant is it important that the fuel delivering is reliable.
In Mbeya is also a cement factory. This plant uses coal to burn cement. For this cement factory in Mbeya it is more attractive because transports casts are significant lower. To transport coal it is maybe possible to make use of the Tazara railway. This railway. -starts in Dar Es Salaam and goes straight to Mbeya. Using the train to transport coal provides also employment.
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5.4.2. Waste fuels.
The high kiln temperature, long residence time in the buming zone, and the scrubbing action of the material in the kiln allow the cement manufacturing process to use a wide range of fuels. Although alternative fuels do not offer energy savings in terms of reducing the energy required to produce a ton of clinker, they offer two opportunities:
- To make productive use of materials that might be otherwise be wasted - To provide lower-grade heat without using high-grade fuels.
Alternative fuels can also offer significant costs savings to the cement plant. Waste fuels that have been used in various cement plants include: municipal wastes (e.g. United Kingdom, French and Germany), rice hulls (e.g. in Uruguay, California), wood wastes, rubber products/tires, hazardous wastes, waste oil, spent pot liners, sewage sludge, petroleum cokes, coconuts shells, peanut shells (e.g. in Niger), agricultural refuse and animal waste (e.g. in India). For this company it would be possible to use for example rice hulls, wood wastes, coconut shells and covers of coffee beans.
The primary energy saving potential of burning waste materials is a function of the amount that is substituted. In some cement plants about 15-30% of the primary fuel has been substituted by car tires and waste rubber, dried sewage sludge. With a precalciner higher rates are possible. Cambustion of wastes in cement kilns might be one of the best op ti ons for disposal of wast es. No combustion residu es have to be disposed of as they are all absorbed in the clinker in the sintering zone . Organic toxic components are completely burned. The normal emission from the cement is unchanged.
The biggest problem is how to collect the waste fuels and how to transport them. It is a prerequisite for using for such supplementary fuels to develop an efficient and economie coneetion and transport system.
In Tanzania, transport costs are relative high. Roads are scarcely and the existing roads are overburden. The place where waste fuel is produced is considerable far away from the cement plant. Other problems are storage of waste fuel, purebase of a waste fuel mill and the purebase of new burners. These new equipment requires large investment.
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6. Economical overview.
6.1. Introduction.
Energy saving is not a final goal. The main reason for the cement industry is to save currency and especially foreign currency. In table 17, it can be seen how significant the energy cast are. About 46% of the total casts are energy casts.
Costs of TPCC 1992 (X 1,000,000 TSHS)
Persennel (incl. soc. costs, meals etc) 1,180 10.3% Electricity 2,020 17.6% Fuel oi l 3,050 26.6% Diesel, petrol, lubricants 260 2.2% Paper bags 780 6.8% Gypsum 480 4.2% Maintenance 500 4.4% Interest 100 0.9% Local freight 860 7.5% Export freight 470 4.1% Fees 610 5.3% Other 1,150 10.0%
Total 11,460
Table 17. Casts of TPCC 1992.
Other important casts, besides power and fuel casts, are personnel, paper bags, gypsum, maintenance, freight and fees. The direct personnel casts are about 400 million shilling, but the personnel casts include also pension, housing, meals, overtime and medica! casts. The remairring casts include storage, insurance, bank charges, communication, environment, residential houses, incentives, safari expenses, etc.
mines raw mill kiln cement packing total mill plant
Administration costs 1,410
Business division 1,560
Production costs 805 1,240 4,040 1,320 1,085 8,490
fixed costs 530 280 455 265 260 1,790 variable costs 275 960 3,585 1,055 825 6,700
energy costs 175 920 3,430 550 45 5,120 other 100 40 155 505 780 1,580
Table 18. Casts of the different departments.
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Table 18 shows that the direct manufacturing costs of 1992 amounts to 8,490 million TSHS. A distinction is made between variabie and flxed costs. The fixed costs amount to 1,790 million TSHS, and the variabie costs amount to 6700 million TSHS. The variabie costs consist for the largest part of energy costs, namely 76%. The main production costs come from the kiln division and consist for the Iargest part of fuel costs. From above it proves that a small energy saving of a few percent is already of great importance. It is therefore important to look at interventions which could save on energy. In the next paragraph technica! interventions and their potential for reduction of energy use are looked at.
6.2. Savings trough teehoical intervention.
It is not the intension of this paragraph to discuss every technica! option. Only affordable options, easy to realize, with a short pay back time and some important other, mostly long term, options are discussed. Important to note is, that the amounts which could be saved mentioned beiow are only indications.
Own power station.
To reduce unplanned kiln interruptions, it is almost required to have an own power station. It is not necessary to have a power station which can provide the whole factory, but the power station needs only to provide the kilns. As can be seen in paragraph 4.1.2. diesel power is favourable. The advantages are; low investment costs, possibility to use it partly, short starting time. The calculation given below is an attempt to find out if an own power station is financial feasible.
There are two reasons why TPCC looses money through power interruptions; decreased production and decreased energy efficiency.
First, the losses caused by decreased production can be calculated as follows:
decreased production x (selling price - variabie costs)
In paragraph 5.1.2. it is indicated that about 600 hour are lost through power interruption. With an assumed utilization of 80% and an average production capacity of the three kilns of 500 tonnes clinker per day, the decreased production are:
0.8 x 600 hour x 500 tpd / 24 hour x 1.05 = 10,500 ton cement
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The factor 1.05 is used because with 1 kg clinker, 1.05 kg cement can be made.
At this moment the selling price of one ton cement is average on 32,000 TSHS for one ton cement. The variabie costs per ton cement are:
6,700 million TSHS / 390,000 ton cement = 17,180 TSHS/ton cement
The losses caused by decreased production are: 10,500 ton x (32000 TSHS/ton- 17180 TSHS/ton) = 155 million TSHS
Second, the losses caused by decreased efficiency can be calculated as follows:
decreased efficiency x costs of oil
In the heat balance, depicted in paragraph 4.2.2., it can be seen that a considerable part of the heat losses is lost through convection and radiation. Every time when there is an interruption of the kilns, the convection and radiation losses go on, without production of clinker. A rough estimate (taking into account the number of interruptions and the time involved with these interruptions), is an energy efficient improvement of at least 4%. Table 16 shows that the oil costs in 1992 amounts to 3,050 million TSHS" The saving in one year is:
0.04 x 3,050 million TSHS = 122 million TSHS 1 Total extra cash flow is: 155 million TSHS + 122 million TSHS = 277 million TSHS.
On the other side, there are also investment costs. The costs for 1 Kwh installed power amounts $500 (about 250,000 TSHS) At least an power plant of 6 MWh is needed to provide the kiln plants of power:
6,000 kWh x 250,000 TSHS/kWh = 1,500 million TSHS
The erection costs are estimated to be in the same order.
In this calculation, the pay-back time which is more than 5 year, is too long to be attractive. However, TPCC pays a reasonable large kWh price (42 TSHS / $0.084 for 1 kWh), and it is possible that the costs for the production of 1 kWh with an own diesel power station are lower. In this case the pay back time becomes smaller. In actdition of the large pay back time, it is probably, in view of the poor maintenanç~ _ situation of the cement plant, that there arise rnainterrance problems with an own power plant, resulting in power interruptions, too.
All advantages and disadvantage taken into account, an own power plant is probably financial feasible, but not really financial attractive. However, a more detailed study is needed to do definitive recommendations about investments of an own power plant.
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New measurement systems for the kiln.
Fuel cambustion systems in the kiln are major contributors to energy inefficiency and refractory damage. At this moment, all three kiln have defect meters in their measurement system. The most important meters of the kilns, the gas analyzers which are essential to control the kiln, are out of order, toa. In view of the high specific energy use in camparing with other kilns and the oxygen level in the exhaust gases which is much toa high, about 10% energy saving is possible with good measuring equipment.
The total use of fuel oil in 1992 was about 40,000 ton. A saving of 10 % is 4,000 ton. This 4,000 ton casts 4,000 ton x 80,000 TSHS/ton oil = 320,000,000 TSHS ($ 640,000) a year. This is a multitude of the casts of good measuring equipment.
Reduction radiation and convection losses.
Paragraph 5.1.6. describes the immense losses through radiation and convection. Also the heat balance in paragraph 4.2.2. shows the importance of these losses. Remarkable is the enormous difference between the kilns of TPCC and the kilns which are used as a comparison. A possibility to reduce the radiation and convection losses is using insulation bricks. The output of the simplified calculation in paragraph 5.1.6. is that a saving of at least 4% feasible is.
Table 16 shows that the oil casts in 1992 amounts to 3,050 million TSHS. The saving in one year is: 0.04 x 3,050 million TSHS = 122 million TSHS However the price of insulation bricks ( about 80,000,000 TSHS) and the extra work to place the insulation bricks bas taken into account.
Dust insuffiation
At this moment a lot of dust of the kilns comes out of the exhaust pipes, because two of the three of the electrostatical filters are out of order. Also the cooling tower ( only present at unit three) which is needed for an efficient working of the electra-filter, is out of order. For kiln 3, the emission of dust is estimated at about 2.2 ton per hour. For the other two kilns, the emission of dust is estimated at more than 1 ton per hour.
It is difficult to ascertain the price of dust, because it is no raw meal or clinker. But it .. has a already a value, because it is carried, crushed, milled and partly burned. To make an assessment, it is assumed that dust has the same price as raw meal The variabie casts per ton raw meal are:
1,235 million TSHS / 620,000 ton clinker = 2,000 TSHS/ton raw meal
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The deserved income is at least 13,090 x 2,000 = 26,000,000 shilling ( = about $ 52,000) for only kiln 3. Properly the deserved income is bigger, because of the lost chance to produce more cement.
Precalciner
Calculating the financial benefits of a precalciner becomes very difficult. There is not only an addition of a separate cambustion chamber needed, but a lot of other adjustments, mostly enlargements of other units of the plant, are required, because of the capacity increase with factor 2. These additional adjustment are a multiple of the casts of only an extra cambustion chamber. Further study is needed to produce a financial overview of all casts involved with the increasing of the capacity.
The expectation is that a precalciner is financial viable. The demand of cement is much bigger than TPCC can supply. The advantages of increased capacity can be very important, because cement is an important building material, which is needed for development of the country. If the difference between the demand of cement and the supply of cement remains equal, the decision purchasing a precalciner is the most obvious choice to enlarge the capacity.
Conversion to coal
Conversion from oil to coal is a long term option. Without interference of the Tanzanian government, it not possible to change the fuel used because the investments required are very large. The investment casts include; casts for the conversion of the plant of TPCC, investments in infrastructure, development casts of the coal mines, etc.
The following table 19 shows the alternative rates of return obtainable for a range of price differentials between coal and oil by converting from an oil fired to an indirect coal fired system. The table is based of an oil price of$ 200/ton oil (about 100,000 TSHS/ton oil), which is the oil price for TPCC at the end of 1993. Further, in this table 19, it is assumed that no significant additions to infrastructure are involved and that no investments are dorre in exploitation coal mines. Where substantial infrastructure investments and exploitation investments are involved, the rates of return can be drastically affected. Three kiln sizes are considered: 750 tpd, 1500 tpd, 3000 tpd, with an average energy consumption of 4,200 kJ /kg clinker.
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kiln size Oil/Coal eest differential (in $/ton oil)
30 40 50 60 70 80 90 100 110 120
750 tpd 8 14 18 23 27 32 36 40 44 48 1,500 tpd 20 28 35 43 50 57 64 72 79 86 3,000 tpd 33 45 57 69 81 93 105 117 129 141
Table 19. Approximate rate of return on oil to coal conversions.
The kiln size of 1500 tpd approximates most the situation of TPCC. However the rates of returns are probably a little bit lower because TPCC has three kilns, and need more investment for replacing the fuel cambustion systems. The number of kilns has no influence on the number of coal mills. One coal mill is needed for all three kilns, in case of the indirect fire system, the most obvious system for TPCC. The rates of return becomes higher, when TPCC increase their capacity.
Besides rates of return, the increased independency of oil and the creation of employment are other subjects which can play a role in the choice for conversion.
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7. Barriers.
In the previous chapter, a complete list of technica! options to save energy is given, which in many cases prove or promise to be economically attractive. Important is to find out why such measures to save energy are not realized.
This chapter wants to examine the following harriers:
- General problems of public enterprises - Foreign exchange problems - Lack of campetences - Infrastructural problems
The first harrier is a management problem. TPCC is a subsidiary of the Saruji Company which is a public enterprise. In Tanzania, the power structure of public enterprises, their relationship with the government and the lack of market control cause many problems which are discussed in paragraph 7.1. The second harrier is the deficiency of foreign exchange resulting in lack of spare parts and purchasing possibilities for new equipment. Lack of campetences is the third harrier. Competence development has been assigned great significanee in relation to important organizational matters such as efficiency, competitiveness, and potential for economie growth. Last but not least lack of infrastructural support, Iike an adequate power supply, adequate transport facilities etc.
All these harriers lead to a bad condition of plant, overdue rnainterrance and lack of innovation. In chapter four many examples of inefficiency which can improved through normal rnainterrance are mentioned: reducing kiln interruptions, fuel cambustion systems, dust insufflation, uplining the mills, replacing power meters. Reasans for overdue maintenance are generally the same reasans which cause economie inefficiency; lack of foreign exchange, lack of incentives, poor management, inadequate power structure etc.
Important to note is that energy efficiency has no priority for the management of TPCC. Cement is a very important product for the development of Tanzania. It involves building and public works. Producing cement as much as possible has the first priority.
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7.1. General problems of public enterprises (1).
Between 1972 and 1986 public enterprises in Tanzania contributed 40 per cent of the country's GDP, and at the end of 1986 they employed about 32% of the totallabeur force. During the same period they absorbed an annual average of 75% of gaveroment funds. These enterprises became a significant feature in the Tanzanian economy.
7.1.1. The Morrisonian model.
Herhert Morrisonian (Transport minister in the UK from 1929 to 1932), developed the idea of an autonomous, self-contained public corporation, operating with its own corporate personality, perpetual succession, the right to sue and be sued, full control over its movable and immovable assets and accountable to ParHament only through the minister in charge. Most of the public corporations in the world have been based on this model. Also the parastatal corporations in Tanzania are working according to the Morrisonian model. The Morrisonian corporatien could attract experienced experts who were expected to run the corporatien efficiently. The model assumes that managerial autonomy is necessary to provide room for creativity and innovation. It was also the intension to introduce some unspecified quantity of market control into the running of public enterprises while retaining accountability to parliament.
Morrisoman public corporations became very popular during the period of demands for more decentralized government. The argument was that decentralization would increase efficiency. For the same reason, Tanzania chose for the Morrisoman model.
This model is overly optimistic. The model removed market controls like in the usual public enterprise structures. But the alternative direct control by parHament is removed in this model, too. The only control left is a indirect control by parliament. This proves to be insufficient in the case of the cement industry in Tanzania.
Market controls
Market usually imposes several controls on enterprises. Competition is usually the most effective control because it farces enterprises of all kinds, to struggle in order to capture a share of the market
(1) This paragraph makes use of the following literature: - H. Horrisonian, Government and parliament, 1959. - P. Hihyo, Non-market control and the accountability of public enterprises, 1994, chapter 1,2 and 3 - A. Coulson, Tanzania, A political economy, 1982.
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Quality control, innovation, product differentiation, adequate service and other means to satisfy consumers always arise from the urge either to retain or to attain a fair share of the consumer market Price mechanics are also very important in shaping the behaviour of the producers. Where an enterprise bas a monopoly of the market, it is not forced by price fluctuation of price differentials to sell more or to produce more or better quality products. Financial markets also may impose controls, including credit conditions and credit controls. Where credit is easily obtainable, the use of credit may not be determined by financial market pressures. There are several reasans that public enterprises are prevented from control of the market An important reason is that it is difficult for the judiciary in many countries to exercise controls over public enterprises, including
// the enforcement of public and consumer rights. ,P 'c."c n
In many cases public enterprises are used to bring structural transformation and to generate employment They have been called upon to perfarm functions which otherwise would be performed by the government, which in turn bas justified their claim of a share in the functions, immunities and privileges of the state. As government proxies, they have been given wide powers to interfere with the existing rights of the public. In order to justify this, the concept of "common good" bas been invoked. An other concept is the idea of "inevitable nuisance". The ground bebind these concepts was that the failure of the market to provide adequate utilities created a duty on the part of the public to undertake measures in order to the public good and to tolerate nuisance arising from such measures.
Control by parHament
The indirect accountability structure of the Morrisonian model creates the conditions for struggles between memhers of parHament (policy makers) as controllers and managers as experts. First, the principle of operational autonomy, which in theory separates politics from commerce, is more aften than not used to block certain kinds of polities. Second, communication bottlenecks can cause struggle. The enterprise cannot be questioned directly, only through the government. But because these enterprises perfarm commercial functions of a highly specialized nature, which government cannot undertake given the limitations of its human resources, the government is expected to leave them to operate without undue interference. However, government continues to exercise various controls over the operational activities of public enterprises.
Beside these problems, the advantages of indirect accountability for both public enterprise management and government are financial. Indirect accountability requires self contained finances. This implies that once funds have been transferred from government to a public enterprise, they become divareed from the national budget, even if the government retains control over the financial operations of these enterprises. The public loses it rights to demand an account of such funds in the context of governments accounts.The independenee of finances is meant to create confidence among lenders that their money is not destined for government coffers.
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In the past the Tanzanian state could not adequately funds its public investments projects, and sought most of its funds from private financial markets. Fora while, this succeeded, but the combination of non-market, bureaucratie controls, the abysmal performance of such enterprises, and constant politica! interference in their activities destroyed lenders' confidence. The Morrisoman model in essence claims to emulate private sector enterprise. In order to attract both skilied human resources and creditors, public corporations are projected as private enterprises with public funding. It was seen as a dynamic innovation which would show that in a dynamic society, public enterprise could best operate on the basis of non-governmental intervention. But the publiefprivate analogy was as mistaken as it was unfortunate. Firstly, the managerial autonomy was more assumed than real; secondly the objectives of the model were to increase control without increasing accountability.
7.1.2. Public enterprises in Tanzania.
Characteristics of the publk enterprises.
Tanzania copied the Morrisonian model of public enterprise not only because of its colonial history, but also because this model is almost universally accepted as the most rational model of public enterprises. Hence the most of the immunities and protective clauses found in British public enterprise legislation have been reproduced in Tanzania legislation. In Tanzania, as in many other developing countries, the state is looked upon as an instrument of development. This, in turn, justifies wide and unfettered executive powers to intervene in the economy.
Second, the role of the state in public enterprises was made more obvious by the fact that the state relied upon these enterprises to operate where the market had failed. This also provided the ideological basis for the dismissal of market controls as factors in the management of public enterprises. Public enterprises as organs of policy were visible instruments of state power. In order to harness them politica! needs and aspirations, they were given an ideological role. In addition to being used to control information, broadcasting, education and culture, they became the primary testing grounds for new politica! and other programmes. Examples are participatory management through the formation of workers' councils, enterprise management committees (beginning 1970) and developing militia (beginning 1973).
The third characteristic of the Tanzanian system is government dependenee on public enterprises for revenues, services and credit. Between 1969 and 1979 numerous public enterprises were formed in all sectors.
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They were given monopoly powers over distribution services. This created a special dependenee between all consumers and the public sector. Government, as a consumer, awarded itself priority, using its position as the controller of public enterprises to get the best services and the right of first treatment in allocation of scarce resources. The structure of dependendes which emerged from the over-reliance of government in these enterprises required that the government keep a close watch on their management. This non-market control further weakened the reliance of public enterprise managers on commercial principles, which in turn encouraged the government to keep enterprise boards very weak.
These general characteristics of public enterprises counts for TPCC, too. The most important decisions and the future plans are made by government. Further, cement is indeed a sought-after product for building big houses by government officials.
Lack of market controls over the public enterprises.
Pricing is one of the market controls which could have helped to enforce market discipline in public enterprises. But, in Tanzania, neither producers nor consumers have influence on pricing mechanisms. In 1973, the Price Commission is formed to regulate the prices. The cammission is formed during a period of economie crises. The industrial output in Tanzania was dwindling. It became an institution for increasing prices in order to increase the profit margins of the producers, and so increasing the tax revenues. In this way, earning more and producing less, public enterprises remain securely from the pressure of the market. The price controls inhibits innovation and do not encouraged the retention of good managers and efficient technologies because there is no reason to produce more efficient.
A next lack of market control is that of consumer protection. Consumers influence the behaviour of producers either by refusing to buy defective goods or by enforcing their collective rights. Between 1970 and 1985, choice as a regulating factor was notgenerally available to consumers. However, consumer-oriented legislation existed. Examples are the Food Quality Act of 1978 and the Weights an Measures Act of 1982. Other consumer mechanisms failed mainly as a result of the systematic vialation of consumer proteetion laws by public enterprises. For example, TPCC was accused of selling bags of cement weighing 40 kg at the 50 kg price. Other examples are; Sale of underfilled botties of beer, distributing of cassava which was condemned as being unfit for human consumption. The courts, which could have played an important role, were also apathetic towards price hikes and other consumer problems. Courts began relaxing their interpretation of laws and explaining boarding and over-pricing as ills which could not be cured by court action.
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In any case, public enterprises were never charged, and both the courts and the public knew that, as part of the state system, public enterprises enjoyed special protection. The absence of effective pressure groups has also contributed to the ineffectiveness of consumer law. Public awareness of consumer rights exists only when private and public voluntary organizations popularize consumer law and support the enforcement of consumer rights and remedies. In 1965 Tanzania adopted a party state corporist power structure under which lawful politica! activity can only be organized through the ruling party and its government. The state can also intervene in the various activities of religieus bodies. This leaves no space for independent pressure groups to develop.
Some of these problems are inherent in the Morrisonian model and others are peculiar to Tanzania. Together, the power structure of the Morrisoman model and the need of the Tanzanian state have undermined the function of market mechanisms in cantrolling public enterprises.
TPCC experience little market controls, too. The relative high price of cement is determined by the Price Commission. Further, the supply of cement is small and the demand is big. A stronger monopoly position is not possible.
7.1.3. Poor performance and management failures.
General causes of poor performance
After 1975 the performance levels of most public enterprises either stagnated or declined. An important reason of this, is the neglect of the agriculture in the general industrialization strategy, in spite of the policy of Ujamaa socialism which was based on transforming small peasant producers into a dynamic economie and politica! force. No significant investments in infrastructure or other necessary factors were made. This was destructive because, agriculture was the main souree of foreign exchange, which is necessary for foreign skills, spare parts, new technology and repayment of loans. The neglect of the agriculture and the over-emphasis on industry set into motion vicious circle of dependency, stagnation inflation and decline in growth in all sectors.
Further, the deliberate neglect of and the attempt to suppress the private sector caused much uncertainty in investment policy and put the sector on the defensive. As a result, the private sector withdrew from major investment areas. This is a government's failure to diversify sourees of tax revenue. Another long-term effect of the neglect of the private sector is that the Tanzanian government became dependent on the private sectors of other countries, because the public enterprises produces not all kind of goods which were produced through the own private sector.
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Other politica! factors include the war with Uganda, and Tanzania's contribution to the liberation wars in Southern Africa. The cost of these wars were immense.
Economie and social factors
An important factor which caused inefficiency is the overburdening. The firms have, statutorily and administratively, been saddled with a multiplicity of objectives. They are required by law and politically expected to pursue socio-economie goals. The combination of economie and social objectives means that they are supposed to operate with some degree of profit motive while contributing to the public interest, especially in their allocative and distributive function.
Issues of income distribution, employment generation, social and politica! stability, regional balance and equity compel them to address allocative issues, but in doing so they are not expected to sacrifice technica! or productive efficiency. Often the day to day activities of public enterprises have been over-determined by development needs as defined by ministries, holding corporations or other control agencies, with the diversity and multiplicity of objectives in Tanzania's public enterprise systems resulting from the lack of uniform policy on how to establish and shape public enterprises.
These overburdening is clear present at TPCC. A few examples are: taking care of education of the children of the employers, running a dispensary, having a militia of at least 60 persons, having twice much as employees as necessary to boost employment opportunities, taking care of transport of their staff, etc.
Because the enterprises have assigned social policy objectives or tasks, the tendency bas been to give monopoly rights to these enterprises in order to reduce competition. with the hope that lack of competition will allow the successful combination of economie and social objectives. For example, private accumulation is regarded as wrong (leads to a class society). In such a situation, the objective of state enterprise monopoly is to enable the enterprise to perform well on the economie and social fronts, but to proteet the power structure desired by the groups presently in power. This may be done by keeping production out of the hands of groups such as the elite, the middle class, private entrepreneurs and so on, which are politically unacceptable because they tend to accumulate capita!.
Overprotection, through immunities against legal actions, diminished liability for negligence or break of contract, affects the behaviour of management towards customers and the public. The right to withhold information on grounds of national security also must have some impact on the way public enterprises have conducted their business. Statutory limitations on the compensation that can be paid for break of contract or mistake may also encourage careless behaviour by management.
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A management team aware that its enterprise is unlikely to bear any substantial costs resulting from break of contract or the careless performance of its duty is likely to operate without fear of loss of employment as a consequence of its acts or mistakes. Overprotection and monopoly have combined to reduced management efficiency.
Management performance may also have been affected by the size of the corporations. Most public enterprises were formed under the Public Corporations Act of 1969. The Act did not spell out clear procedures to be foliowed or the criteria to be used. This mistake encourage unplanned growth in the number of public corporations. Related to this was the lack of guidelines on the extend to which corporations could change their organizational structures. So, many corporations expanded by forming subsidiaries or specialized units, although their capita! structures remained unchanged. This increased not only the demand for finances, but also employment rosters and the bureaucracy. Efficiency bas been further undermined by the multiple roles imposed on some corporations. Some functions performed by the so-called independent units as cleaning, maintenance, accounting, and so forth, can often be better performed at a lower cost and with less delay by sub-contractors.
The lack of consumer organizations able to act as watchdogs and prevent enterprises from vialating quality standards, weight requirements and prices, bas also provided liberty to corporations to produce and serve as they found convenient in their circumstances. Although the 1989 reintroduction of competition and liberalization of trade have increased consumer choice, consumer consciousness is still low.
Performance related factors
Performed related factors fall into two categories, one within the relationship between management and public enterprise control agencies, and the other relating to mechanisms for ensuring optimum performance of obligations and duties by public enterprises with respect to the customer.
It is now commonly accepted that the relationship between management and enterprise is that of agent and principal. It includes the duty to make decisions which are in the interest of the owners of enterprise. In order to do this, there must be a high level of commitment of the management to make decisions which maximize benefits for the enterprise. Private sector enterprises rely on the share markets to attain such commitment. Managerial efficiency is normally measured by the extend to _ ~ _ which the managers maintain the value of enterprise stock and the amount of capital they raise for tbe company on the share market. Prospects for insolvency, a fall in value of shares or threat of take-overs by other companies are taken as signs of bad performance. The managers job is then in danger. This provides little guidance in the public sector, where capital structures are seldom open for contribution by the public. Managerial commitment.
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Therefore, bas to be based on loyalty and thrust, which can be attained only if managers are given adequate incentives (aften high dividend). But, where organizations find that adequate incentives to management are too expensive, they avoid such casts. They rely instead of mechanisms such as patronage, proteetion or ideology, or they make management insecure by removing tenure.
Until 1988, Tanzanian public policy was directed away from paying high dividends for loyalty and trust to public enterprise managers and employees. Economie privileges and social status to high trust and loyalty positions was taboo. The taboo was based on the ideology of a classless society, which wisbed to raise sacrifice, heroism and politica! acceptability above salaries, allowance and bonuses. Consequently, the public sector attracted managers who keep up appearance with respect to organizational goals while at the same time engaging in corruption, social parasitism (using enterprise facilities and timefortheir own activities) and management by neglect. Management by neglect was illustrated by the way in which most managers avoided tackling difficult issues such as low Iabour productivity, low energy efficiency, waste of materials and low morale.
Partly the management of TPCC is coming from Sweden. The salaries they get is high enough to expect loyalty and commitment. But besides these Swedish managers by far the biggest part of the management consist of local managers which salaries are low.
The performance of corporations could have been better if they were less protected from the consequences of their activities. If the duties performed are of a general nature and are performed for the general public, the absence of a customer relationship bas the potential for undermining efficiency. Such corporation can quickly become paternalistic and bureaueratic and can easily treat their service as a privilege. Once people know that their salades and job security depend on their services, they tend to respect both their job and their customers.
Political factors
Public enterprises share to a large extent in the administrate functions of the state, such as licensing, administering development projects, resetding population and providing public utilities. All of these tasks put public enterprises in a position where they participate in the politica! process. In Tanzania, this politica! role is strengthened by the use of public enterprises as -" -instruments of ideological reproduction. They have been burdened with politica! tasks such as providing financial support for the peoples' militia, politica! education, housing, the local casts of the state politica! party, trade unions and other branches of mass organizations, as well the duty to provide services to top government and party officials at low rates or on credit or in some cases gratuitously.
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In addition, public corporations are expected to provide preferential treatment to government departments and officials in the allocation of resources they produce, distribute or controL These factors have combined to make public enterprises more political than commercial or economie. Govemment hires and evaluate managers more on the basis of political considerations than on managerial competence.
Legal culture
Legal mechanisms can strengthen managerial performance if an enterprise system permits this. Mortgages, debentures, charges, securities and other legal instruments can take care of discipline into spending pattem of enterprises. Absence of such instruments leads to problems. For example, in Tanzania most public enterprise loans have been obtained from or through govemment as a guarantor. Govemment funding or intermediation in funding activities is likely to act as a disincentive for the efficient use of such loans.
Another legal issue; there are inconsistencies in the system of appointing enterprise officials. The president influences this system of appointing. Presidential involvement in the running of enterprises (as chancellor or chairperson or through the appointment of ministers and principal secretades to enterprise boards) undermines the ability of the government to control these enterprises objectively. Also important persons from public enterprises bas influence on this system of appointing. Ministers can not be held responsible for the activities of their subordinates, if they notare entitled to appoint and to remove them. It is important to clarify the chain of authority linking: president, ministers and enterprises.
7.1.4. Consequences for TPCC.
A first consequence is that actions and decisions taken by management of TPCC under authority of the govemment or not under authority of the govemment, are not always in favour of the company. The managers have the chance to exploit their position. For example giving friends and family priority for jobs. Sametimes they do things which give them status, for example the purchasing expensive computer systems which are superfluous. Or perhaps they create structures and procedures which proteet them from power losses. The consequence of these structures is that sametimes important information do not reach the right person.
A second consequence is that the absence of a motivated management bas direct negative influence on the company culture of TPCC and in this manner on the energy and production efficiency.
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With an unmotivated management arises the present negative company culture where corruption, low work ethic and uninterested staff are normaL In this situation, commitment with the company lacks, staff has no loyalty with their employer and are happy when there are work interruptions. In addition, this negative company culture has bad influence on the decision making, speed of decision making, innovation, production efficiency and the energy efficiency ofTPCC. The current power structure prevents hardworking mentality because promotion, rewards, perquisites, etc depends not of campetences of the employee but on conneedons which the employee has.
To imprave this company culture, it is important that managers set an example to the staff and struggle against corruption and the apathetic mentality of employees. In order to do this they need possibilities to give employees bonuses and incentives when they are motivated, hard working and show initiatives. On the other hand they need possibilities to punish people who are inactive or who are corrupt.
An other problem is the low degree of participation of the employees at TPCC. They get no, or little information about plans and purposes and have no voice in decision making. This also involves mentality and sense of responsibility with respect to the company. Integration of the staff of TPCC is a precondition for efficiency. A person whose apinion is not respected and whose work is not appreciated, becomes unmotivated and has no feeling of solidarity with other units and cannot identify himself with the organization as a whole. If creative persons are put under tight control, the innovatiness and technica! enthusiasm may easily wither and their competence steadily depreciate.
A next problem resulting from a negative culture and low degree of participation is the speed of decision making. The speed of decision making is important for efficiency because it involves the performance of maintenance and innovation. At TPCC, almost all decisions are taken on a level which is higher than necessary. To increase the speed of decision making, it is necessary that the decisions are taken on the lowest level which is possible.
Information, incentives, integration, responsibility for every one on every level, control of delivered work and control of realized purposes are necessary to imprave the culture of a company.
The current form of management and administration and the resulting negative company culture is one of the main reasans of the poor maintenance situation at TPCC and the resulting energy inefficiency. To increase energy efficiency and production efficiency a reorganisation is probably inevitable.
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7.2. Foreign exchange problems (1).
7.2.1. The foreign exchange constraint in Tanzania.
The quadrupling of oil prices in January (following the Arab-lsrael War of october 1973), ushered in an era of chronic foreign exchange crises for many non-oil producing developing countries. The oil price increase was foliowed by a general world recession (1974/75) leading, inter alia, to a slow down in external demand for exports from developing countries. The second oil price rise between 1978 and 1979 further strained the economies of these countries.
As an agrarian non-oil producing country, Tanzania absorbed the full impact of these oil price rises. Internally, the prolonged periods of drought (1975,1979), and economie polides emphasizing industrialization, considerably reduced the output of both food and export crops. Declining production of food and export crops necessitated importation of food grains while the fall in the output of export crops meant reduced export earnings. Other factors include bad agriculture policy, inflexibility with respect to economie policy and exchange rate adjustment and poor institutional performance.
The disintegration of the East African Community in 1977 caused Tanzania loss of an export market, loss of cheap sourees of imported consumer goods and strained the meagre foreign exchange reserves as Tanzania bas since then been impelled to divert some of the investment into off-setting the dislocation in Transport and communication systems caused by the disintegration of the community.
The increasing over-valuation of the Tanzanian shilling naturally contributed to the stagnation of exports and the increasing demand for imports.
Other factors which have contributed to the deterioration of the external balance include a fast growing service sector, problems with administration and decision making, debt service increase and initia! laxity in cantrolling imports.
7.2.2. Attempts made by the government to solve the foreign exchange crises.
In 1971, following a mini foreign exchange crisis in 1979, Tanzania introduced administrative allocation of foreign exchange, with the aim of balancing the supply of,.~ . and demand for foreign exchange. Foreign exchange control in Tanzania is a part of the "Control Operations" of the Bank of Tanzania. The allocation is a direct metbod of cantrolling imports, and is administered by an "Advisory Committee", with the Bank Gavernor as its Chairman.
(1) This paragraph make use of the following literature: · A. Mbelle, Foreign exchange and industrial development: a study of Tanzania, 1988.
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To retain flexibility, the issuing of import Heences is done on a six month basis, and is determined by the "expected" availability of foreign exchange. As a second attempt to solve the exchange crises the country bas actively sought loans, both bilateral and multilateral in an attempt to break the vicious circle.
Third, control of monetary and credit expansion was aimed at reducing expenditures which do not increase the level of production in the economy.
The different programmes made by the government towards solving the balance of payments crisis include:
The National Economie Survival Programme (1981-1982): the policy was adopted in 1981, with the primary aim of reviving exports and increasing industrial output from current capacities. The Structural Adjustment Programma (SAP), (1982-1985): the thrust of the SAP was rehabilitation of the economy and restructuring of economie activity. The Economie Recovery Programma (ERP), 1986-1989): the ERP represents a continuation of the structural adjustment efforts aimed at achieving sustairred growth in real incames and welfare improvements.
7.2.3. Effects of the foreign exchange shortage.
The shortage of foreign exchange shortage bas both direct and indirect effects. The direct effects will take a vicious circle sequence as shown in figure 14.
J Less foreign exchange -, I
11
Less exports of Limited importsof agricultural and essential inputs and industrial goods services to sectors
Low production of incentive goods, less agricultural r-and industrial production
Fig. 14. The foreign exchange vicious circle.
The situation described in figure 14 bas persisted in Tanzania for more than a decade. In order to raise the output of agriculture and industrial sectors foreign exchange is required.
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Given this vicious circle, the policy issue is to try and break it. To this end, Tanzania has made a number of attempts to arrest the situation which are described in the previous paragraph.
The indirect effects of the foreign exchange shortage take different farms depending on the sectoral dependencies. Lack of foreign exchange leads to less imparts and less manufactured consumer goods. This in turn leads to reductions in import duty and sales tax revenue, which results into an increase in budget deficits. The government is driven into borrowing from banking system. An inflationary spiral results with all the accompanying effects.
Depletion of foreign reserves reduces the ability to pay for imported factors of production necessary for economie development. Sectors of the economy that are heavily dependent on imparts of capita! and intermediate inputs, like the cement sector become greatly constrained by the acute foreign exchange shortage.
7.2.3. Effects for TPCC.
The agriculture gat most of the problems because of the little amount of exchange allocated, but most of the industries also have a shortage of exchange. This shortage results directly in a acute spare part problem. As most of the industries in Tanzania, TPCC depends very heavily on foreign spare parts and to a lesser degree on foreign consultancy and engineering.
TPCC consumes a lot of foreign exchange. The heavy fuel oil is the major expenditure of TPCC, but TPCC pays for fuel oil with local currency. The same counts for petrol, diesel, lubricants, air conditioners, transport equipment etc., which also come from other countries, but can be paid with local currency.
The inflow of foreign exchange of TPCC in 1993 is about 7 million dollar. Most of this amount is corning from sales to the neighbour countries. Another important amount of foreign exchange (for major capita! investments) is corning from the Joint Venture Funds. Probably, the Joint Venture Funds is initiated by TPCC and SIDA, because the top management of TPCC is Swedish and has connections with SIDA,
The outflow of foreign exchange in 1993 includes investment casts (about 1.5 rnillion dollar), operational casts (3 million dollar), export freight and management fees. The operational casts consists for the largest part of spare parts. Other important operational casts are refractories, grinding media, explosives and paper bags. Spare parts are needed to maintain the cement plant. Same spare parts are indispensable for the bare running of the plant. Other spare parts are less important, but are meaningful for energy efficiency, improving the work situation, production efficiency etc.
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In case of scarcity of foreign exchange off course, the preferenee is for the first mentioned group. Lack of spare parts influence energy efficiency directly. Example: In paragraph 5.1.2. it is noted how important uninterrupted kiln operation is for energy efficiency. The causes of kiln interruptions were divided into two factors; internal and external. The internat factors are due to lack of normal preventive maintenance which is difficult to realize without necessary spare parts. Other important examples of energy inefficiency due to lack of spare parts are the defect of the electrostatical filters and the lack of measurement equipment which are necessary to run the kilns and other machinery in a efficient way. Spare parts are not in stock and are just ordered when it is too late, often when the plant already bas a break down. Additional problem, is the very long delivery time for the spare parts, particularly since most of the spare parts are not of the common type.
Investments can be used for energy efficiency. But as known, the priority of the management of TPCC is production. So the scarce foreign exchange is used for investments which enlarges the production.
It is difficult to determine how important the role of foreign exchange exact is with relation to ·lack of spare parts and poor previous maintenance. It is sure that it is not the only harrier, but it cannot be denied that foreign exchange is important to run the factory in an efficient way.
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7.3. Lack of Competences (1).
7.3.1. Competences in enterprises.
Competence development bas been assigned great significanee in relation to important organizational matters such as efficiency, competitiveness, and potential for economie growth. Investments in competencies, through personnel training and learning in work, are regarded as being increasingly important for the success in firms or other organizations as well for future economie development on a national level. In western countries the most important achievement of modern economie growth is undoubtedly increase of human capita!.
It is important to distinguish between physical and intellectual competence on the one hand and work motivation and commitment on the other. The two farmer element tagether constitute the individual employee's basic capacity toperfarm tasks; what the person is technically or potentially able to do on the job. The two latter elements of human capita! influence the actual performance of work by reflecting what the individual employee, given his/her competences, is willing to do on the job. Together, the ability and the willingness to perfarm define the individual employee's capability in work. Both, the ability and the willingness of the employee depends to a great degree on the managementand the company culture but depend also on education and the country culture.
In figure 15 the relations between work-related competence and human knowledge, skilis and aptitudes are reproduced.
I Knowledge ~
1
~: lndividual worlc-related J.,.... l competence
Aptitude
Fig. 15 A model of individual competences.
-.I -I
(1) This paragraph malces use of the following literature: - 0 Nordhaug, Human Capital in Organizations, 1992.
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Sleilts
I
J
The concept of employee competence bas been assigned highly different meanings and is among the most diffuse in the organizationalliterature. A general accepted definition is; work-related competence are the composite of human knowledge, skilis and aptitudes that may serve productive purposes in organizations. It does not include attitude, motivation and commitment. This is not to say that such factors are unimportant, but they are more intermediary variables in relation to the causal conneetion between competence and work performance.
Knowledge is defined as specific information about a subject or a field. Skill is defined as a special ability to perfarm work-related tasks. Aptitudes encompass natural talents that can be applied in work and form a basis for the development of knowledge and skills. Furthermore, knowledge is a necessary prerequisite for the possession of skills.
7.3.2. Lack of competences as a harrier to energy efficiency.
A large organisation like TPCC needs a great diversity of competences, to perfarm its tasks well. Purchasing of spare parts, selling of cement, marketing, cleaning and maintenance of the plant, administration, performing social tasks are just a few examples of issues which require competences. In this paragraph some examples of the relation between energy efficiency and campetences are discussed. It is by no means intended to be complete.
First, operating the kilns and mills require specific competences. As written in paragraph 5.1.3. and 5.1.4., energy efficiency depends strongly on the competence and experience of the concerned operator. Most of the operators didn't know how to save energy, in such a way that there is no danger for instability of the kiln. The kiln is more stable, and control is easier when the temperature is bigger. These higher temperatures cause energy inefficiency of the burning process, higher energy use at the finish grinding process, and reduced refractory life. Training of these operators can imprave efficiency.
Second, an important reason of energy inefficiency is overdue maintenance. In chapter 4, many situations of inefficiency are described. Most of them can be improved through normal maintenance (reducing kiln interruptions, fuel cambustion systems, dust insufflation, uplining the mills, replacing power meters). Maintenance and especially preventive maintenance require adequate competences. Maintenance has_. _ many aspects; repairing, control and lubricating of machinery, development of maintenance schedules, timely ordering for spare parts, judgement of the conditioning of equipment, etc. A considerable lack of the needed competence of most of these aspects causes the poor maintenance situation at TPCC.
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The technica! information about the plant and its condition is little and insufficient. The repairing of the equipment, if dorre at all, is aften inadequate and a lot of spare parts are nat available.
Third, in western countries, the energy crises in 1973 and the current environment problems have initiated a trend to develop processes and equipment which are more energy efficient and more environment-minded. Often, new equipment and processes are high-tech. Adaption and assimilation of these new technologies demands specific knowledge, high educated and up to date trained staff. An mustration of a high tech option for reducing energy use is the advanced kiln control system. The lack of knowledge and trained staff is the bottie neck to implement this option.
Fourth, management campetences are essential to run the whole organisation. The important role of the management is already discussed in paragraph 7.1. In this paragraph 7.1. especially commitment and willingness come up to the fore, but at least of the same importance is the campeterree of the managers to manage the company proficient, and to take the right decisions in with respect to of energy efficiency
7.3.3. Training determinants.
It is camman knowledge that some companies invest heavily in developing their campetences through training, whereas other companies do nat. However, it is nat exact known what the factors determining the training and investment in training are. An small attempt is made to find out a few of these determinants why TPCC invest little in developing campeterree of their staff through training.
First, the slogan "knowledge is power" still counts. When the staff of TPCC are more trained and well informed ,they become also more mature and aware of their situation. The management bas take their subordinates more into account. But some of the current rulers do nat have interest in losing their power and have little motivation to promate the training activities.
Second, the lack of competition does nat stimulate the training activities of TPCC. Generally, competition farces firms to make sustairred efforts in training their employees because when other firms have a better pricejquality ratio or have more product differentiation the market share of these firms will decrease.
Third, development of campetences through training outside of the company is difficult. In Tanzania, consultants, training firms, business associations, etc are scarce.
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7.3.4. Contri bution of training and development.
In the following, the purpose is to discuss possible contribution of development and training. A distinction is made of how training and development may contribute to human capita! provision and in which training and development may produce effects that facilitate the transformation of human capital into work performance.
Provision of human capital.
This section describes how training and development may contribute to human capital provision.
Qualification: Transmission of knowledge and skilis that are directly significant for employee's work performance is the most recognized function of employee training and development. The purpose is to increase labour productivity by continually adjusting the qualifications of the workforce to fit new tasks and new technology which are often necessary from increasing production and reducing energy use. It may partly be a matter of training people to master new jobs and partly of updating knowledge related to new technology. It must not be forgotten that the development of general campetences ( communication skills, ability to cooperate with colleagues, analytica! capacities, problem solving skills, ability to cope with change, etc.) important is, especially when there is a process of restructuring and strategie reorientation, for example privatisation. The stock of individual campetences in the organisation may be seen as an aggregate intangible asset, a potential that can be utilized to imprave organizational performance.
Screening capacity: Participation in and individual outcomes from persounel training may be used as criteria for selection and promotion, thus improving the internal screening capacity. First, as the employee by pursuing training demonstrates motivation and interest in professional development of job performance. Second, the degree of participation is easily observable and may thereby serve as a supplement to other objective selection or screening criteria. Third, individual outcomes from training in the form of increased or altered campetences may be subject to tests or other evaluations.
Decision making capacity: Decentralisation of organisation structures is currently common both within private· • -business and the public sector. Successful decentralization of decisions, which is needed to increase the overall capacity of decision-making at TPCC, requires that the relevant campetences are present also on lower levels in the organisation. Training is a central means to attain this, and especially training that disseminates information about relations between local decisions and strategie goals.
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Consequently, courses directed at increasing the decision-making capacity must convey knowledge about economie prospects, technology, and organizational structure , which can stimulate employee involvement and participation.
Transformation of human capital.
This section describes in which training and development may produce effects that facilitate the transformation of human capita! into work performance.
Socialization and legitimization: In addition to developing purely task-oriented competences, training and development also transmit, values, attitudes, and norms. The clearest examples can be found in introduetion courses for new employees. Through these courses, the management in most cases wants to present and promate the firm's philosophy, goals, and strategies. Training activities support socialization within companies. It is a form of social control that contributes to making employees' behaviours more predictabie and thereby reduces uncertainty. The object of socialization is to gain support and enthusiasm for goals like reducing energy use and policy of the company and to generate a certain level of internal homogeneity and consensus. In this way the need for direct supervision and evaluation of the employees's job performance is reduced. In addition, training and development may contribute to legitimate the related goals, strategies, compensation systems and decisions.
Social integration: Training and development may also strengthen the social integration. Courses that include employees from different parts of the company are probably particularly important. Employees are given the opportunity to exchange experience from their activities, which in turn may lead to an increased understanding of problems and working methods in other parts of the company. For example the mining division of TPCC can understand the importance of the quality and homogeneity of extracting raw materials which is necessary for a stabie burning process. The employees thus obtain a braader and more holistic perspective of the organisation. Moreover, intra firm social networks are extended. As a consequence, informal communication across forma! unit boundaries is likely to become more frequent. This may reduce the information load on forma! communication channels.
Organizational adaptability: The de mand for continuous adaption and new technologies is multifaceted. N ew ( energy sa ving) technologies must be identified and implemented. Also new products ( other kinds of cement) have to be developed. Training and development enlarge the adaptability of organizational change and a changing external environment. The generation of change-relevant individual competences, such as the capacity to cope with uncertainty, adjust new situations and adjust new technology, is paramount.
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7.4. lnfrastructural problems.
Infrastructure, broadly defined as electric power, irrigation, transport, telecommunications, water supply and sanitation will play a key role in stimulating economie growth and efficiency in organisations. An enterprise Iike TPCC depends to a great degree on infrastructural services, especially transport, power supply, water supply and telecommunication, for efficient producing.
Producing cement requires a reliable power supply. This is important in relation to energy efficiency, because every interruption of power means production and energy losses. In paragraph 5.1.2. it is written how important a constant power supply is for process stability of the kilns. At least a few times a week TPCC has trouble with the power supply. Sametimes the power interruptions takes a few minutes, but sametimes hours or even days. Besides interruptions, decreased power availability and power fluctuations cause problems, too. In Tanzania, TANESCO is the national power supplier. When TANESCO has troubles with the supply of power and therefor has a decreased power availability ,companies like TPCC have no preferenee to obtain power.
A next mustration of dependency of infrastructure is transport. Transport of cement is very expensive, because it is a heavy materiaL Often, if the distance is more than a few hundred kilometres around the producing plant, the transport casts are higher than the producing casts. In table 16 it is written, that freight amounts about 1,330 million TSHS. Besides direct transport casts, indirect transports casts for transport of oil and transport of gypsum (gypsum price includes transport casts). This is a substantial part of the total casts. The Tanzanian raad network is small and the quality is poor which causes higher transport casts for TPCC. Because of these insufficient raad network it becomes probiernatie to change from oil to coal, as fuel for the kilns (see paragraph 8.5.). The distance between the coal mines and TPCC amounts about 900 km.
A complete other aspect of infrastructure is the lack of contractors, consultancy bureaus and engineering bureaus. In Western countries, most enterprises have many subcontractors for most various matters. Maintenance, cleaning, management, training of personnel, transport, building new plant parts, etc. are potential possibilities to subcontract. The reason for this phenomena is that these subcontractors are highly - ~ -specialized and very flexible, and can aften fix the activities and problems better and cheaper than the enterprise self. Enterprises in Tanzania don't have these possibilities. They have to do most of their activities by themselves. For specialized issues they have to subcontract Western companies, which are aften very expensive.
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8. Policy options.
The policy options can be divide into two levels; one on enterprise level and the other on government level. Paragraph 8.1. to 8.3. describes policy options on enterprise level. Paragraph 8.4. to 8.6. describes policy options on government level.
8.1. Starting an energy management project.
Until now there is no adequate energy bookkeeping. The exact energy use of the different departments is unknown. Once a month, on the first day, the kWh meter stand of the different departments are noted, but in paragraph 5.1.9. it became clear that the meters are unreliable.
In 1993, the difference between TPCC measurements and T ANESCO (power supplier) measurements amounted 8,316,080 kWh. Most strange in this difference is that in some months the difference is very little, just a few percents, but there are months with a difference of more than 30 %.
A second strange issue is the monthly difference between the calculated efficiencies of the mills and the kilns. Variations of 25% are no exception. The causes forthese variations are in the first place careless bookkeeping and in the second place unreliable meters. Also power interruptions are responsible for part of the variation. Not only the kWh meters are unreliable but also other meters which are important for calculating energy efficiency. Most of the material flowmeters are out of order.
A next problem is that the energy data obtained cannot even be clearly assigned to individual departments and groups of machinery. The reason for this is the build-up complicated entanglement of energy inputs and energy meters because of the built up of the plant in three phases.
These inaccuracies of defect power meters and complicated entanglement makes it difficult to identify the existing potential for energy saving To realize energy efficiency it is important to have accurate energy information for every section. Besides energy data, for every production unit (raw material preparation, raw mills, etc) a criteria list of process data which have a certain influence on energy consumption is needed. Examples of criteria are; fineness degree of cement or raw meal, percent of limestone in raw meal, temperature of the kilns, and off course material flow. Having an adequate system to collect data about energy use, material flow and other important information is necessary to search potential for energy saving.
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Experience in other organizations bas shown that data and information collected will not work without the backing of an adequate organization. It is required to develop and implement a system that the energy information will be translated into energy saving actions. People of all hierarchical levels have to be involved. Suitable operating procedures have to be developed, so that energy management functions are integrated within daily operating routines.
A possibility to collect data, is the use of a computerized system. For example HEMS ('Holderbank' energy management system) which is successfully introduced in a cement plant in Portugal. These large cement plant (5,500 tpd) saved about $660.000 a year. The HEMS is composed of three parts;
- The PROPLAN (production planning) utilizes linear optimization software to identify the most energy cast efficient production plan, given the plant operation parameters, the sales requirements, and the terms of the power supply contract.
- The ELCON ( electric laad contra!) keeps track of usage 'online' and indicates where and when corrective measures are necessary.
- The EDI (Energy Data & Information) provides constant feedback on the complete energy picture.
8.2. Development and training.
At TPCC, most of the staff are in a more or less degree trained. However, aften they have got their training a long time ago, when they started their job at TPCC. A large part of the staff has more than 10 or 20 years on the same job. Off course this does not improve effectivity and flexibility of the staff. Campetences of the staff decrease and goes out of date. The employees have no challenge any more in their jobs. Beside this, the training activities they have got are only focused for the job they are going to fulfil. A burner is only trained for burning the kilns and do know nothing about other things in the plant. The consequences of these limitations are extensive described in paragraph 7.3 ..
In the same chapter, the importance of training and development is discussed. It appears that there is no doubt that people are the keystone in an organisation and that the campetences of the staff and management and their commitment and willingness determine the vitality, strength, competitive position, effectiveness and theefficient use of inputs, like energy, of the organisation. Training and development may contributed to increase human capita! and the transformation of the acquired human capita! into work performance.
To come to an vigorous and useful development and training policy the first step is to determine the training requirements.
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Training requirements are the difference between the required campetences and the present competences. There are different possibilities to determine the training requirements:
- In the 'discussion of progress', on different levels, it is possible to discuss the gabs between required campetences and the present competences, and the resulting training requirements.
- In a conversatien on the shop-floor between the executives and the staff. - Starting a research in order to find the training requirements.
Training requirements can have relations with individuals and groups, functions and formations, etc. Probably one of the results of the search of training requirements is, that there is a demand of regular returning training activities for core function like mechanics or administrative personnel.
A second step is to specify these training requirements. Some specifications are
- training targets . - expectations of the managers and participants - extent of the group - the contents (programm) - the design or style ( educative approach, prepara ti on, evaluation, supervision, etc.) - the performance (when, duration, casts, etc.)
The last step is to choose where the training takes place, inside or outside the company. TPCC bas little choice, because the possibilities to subcontract training institutes is small. This lack of choice is a handicap, because the development of courses and realizing of training programmes in order to increase human capita! require experience and certain competences. ·
8.3. Building incentive systems and motivation.
In the previous paragraph 8.2. we have seen the importance of competent people. But the utilization of competence depends on the employees' motivation to work, defined as a drive toward attaining the best possible job performance. In cognitive motivation theory, incentives and rewards are of central importance and are considered to be one of the main determinants of individual work motivation.
An important distinction bas been drawn between intrinsic and extrinsic rewards or motivation. The farmer have to do with the individual 's own feeling of having succeeded or failed in sarnething he/she wishes to do. Improved mastery of work, increased personnel competence, greater self-confidence, self realization, and a feeling of solidarity with others are common intrinsic rewards.
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Extrinsic rewards are stimuli located outside the individual that are most often controlled by others and that include rewards such as wages, perquisites, promotion, status and recognition for one's work from colleagues and managers.
Intrinsic rewards are indirectly influenced by the firm. Job design, the learning environment, opportunities for participation in decision-making and the social environment in the workplace may influence intrinsic rewards. In this perspective, a considerable proportion of personnel-related work acts as an indirect part of the incentive system in a company.
Extrinsic rewards have, however, a decisive influence on the -utilization of competence. If employees feel that they are not sufficiently valued in terms of salary and status, the incentive to utilize their knowledge and skilis will diminish.
One aspect of the incentive system which often seems to be overlooked is the extent to which managers are rewarded for stimulating their subordinates to develop and utilize their competence. Many companies have found that it is fruitless to invest resources in redesigning jobs or in training supervisors to facilitate employee development if supervisors are not rewarded and supported for these activities.
8.4. Privatization and reorganization.
8.4.1. Introduction.
Privatization and reorganization is a national and politica! affair. Privatisation, strictly speaking, is the juridical transfer of ownership of assets and liabilities from the public to the private sector. But often privatisation is more than only the juridical transfer of ownership, it involves a politica! process of reorganizing public enterprises as forms of privatization. Accountability of the enterprises and power structures in the enterprises, but also in the Tanzanian government, will be changed. There are different reasons for a government to start privatisation. First, there can be an ideological reason. The philosophical assumption of privatisation polides are that the public sector is inferior to the private one, that competition is the key to efficiency, that efficiency cannot be achieved by relying on the public enterprises, and that reducing public ownership and increasing private ownership inevitable entails increases in personal freedom, personal choice and democracy. Second, privatisationcan also have financial objectives. For example, in Britain, privatisation became an indirect way of reducing the proportion of GDP absorbed by public spending.
But both of these arguments ignores partly the history of public enterprises. Public enterprises are initiated for diverse reasons. In paragraph 7.1. is told that public enterprises fill gaps in the least favoured sectors, and that some inefficiencies are
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inherent to the nature of their activities. In addition, it is nat always a fact that private enterprises are more efficient than public one. For these reasons, it is important to identify enterprises which are eligible for privatisation and enterprises which are nat eligible. Generally, enterprises which needs the pressure market controls to increase efficiency are suitable for privatisation.
A cement factory fill no gaps in a least favoured sector, and inefficiency is nat inherent of cement manufacturing. However, TPCC bas some characteristics of a natura! monopoly, TPCC could be a normal commercial enterprise, without a direct interlering government. Off course some regulations and agreements between TPCC and the gaveroment remain necessary.
However, generally in Tanzania, privatisation of public enterprises gives many problems. Possibility of privatisation of public enterprises bas to be assessed in the context of existing conditions and limitations.
8.4.2. Limitations of privatisation.
In this paragraph an attempt is made to describe some of problems and limitations of privatisation.
First, the monopoly of TPCC will continue, when privatised, because there is a big demand of cement, and there is no competing cement factory in the neighbourhood. Transport of cement is only economical for a small distance.
Second, Tanzania bas a long tradition of bureaueratic decision making, state intervention and development of Tanzania from the top. Modernization, bolstered by ujamaa socialism was introduced from above. Neither the worker or peasants, nor the entrepreneurs were given a chance to debate , enrich or augment its policies. Modernization policy was introduced and implemented in a very technica! and bureaucratie way. Cooperations were created, reorganized and further reorganized without the memhers being consulted on the farms of the cooperations they wanted. Public corporatien were established without parliamentary debate. This top-down style was a continuatien of the colonial tradition. Again the current restructuring strategies have no interference of the organisations and people concerned, but are a product of a long policy dialogue between international donors and the Tanzanian government. This is nat improving the possibility to come to a healthy company culture. People will be lacking a competition. ~ _ spirit and enterprise capability.
Third, Tanzanian people are used toa a strongly invalving government. In Tanzania, the state is the largest employer, and uses the public sector as a mechanism for stability. The state is also the supplier of health and education services, and the public sector bas had exclusive control of the banking, insurance and social security systems.
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Tanzania bas public enterprises formed to carry out special ideological or politica! programmes. This tradition of gaveroment interference in the daily live of Tanzanian people is deeply rooted. Privatisations will take quite some time and their social implications will be far-reaching. For example employment guaranty, basic facilities and other social securities will be more insecure.
Fourth, it is not easily to find buyers for the public enterprises of Tanzania. Capital markets are thin and the gaveroment is not able to give sufficient guarantees and support. This is further complicated by the fact that the little capita! available is concentrated in the hand of a few ethnic groups. People of Asian origin and a few business groups have a better chance of benefiting from privatisation, because they are well organized at family, regional and ethnic level. State monopoly is likely to be converted into ethnic and regional monopoly of a private nature. Additional to this problem is the fear of loosing national sovereignty and control of important enterprises by having the ownership of these enterprises slipped back into foreign hands as befare the early nationalization. Privatisation is a really long term process, with many obstacles. The long tradition of socialism has created a inflexible society, which restraints a smoothly transition from public enterprises to private enterprises, within a short period.
8.5. Conversion from oil to coal
Tanzania has proven coal reserves of 304 million tonnes and inferred reserves of about 1,200 million ton. But still in a great number of Tanzanian plants, also the TPCC cement plant, oil is the main energy supplier. It will be clear that if TPCC wants to change from oil to coal it is not possible without conceroing the Tanzania government because a first prerequisite for TPCC is the reliable supply of coal.
There are two main reasans for the present under utilizing coal; the first reason is that only a small part of the coalfields are exploited. The production of sellable coal at Kiwira and Ilima coal fields was about 27,000 tonnes in 1989. At this moment, 1994, TPCC needs for his cement production at least about 55,000 tonnes coal a year. From the production of 27,000 tonnes, about 17,000 tonnes of coal was sold to their main customers Mbeya cement and the Southero Paper Mills. The demand for coal of the two firms was far greater than the coal delivered so they had to import coal from Zambia instead. Major obstacles for the delivery of coal from Kiwira to Mbeya cement factory and the Southero Paper Mills are mainly lack of transporting trucks . ~ . and coalloading facility at the Uyole (T AZARA) railway station. Lack of sufficient developed infrastructure which is required to transport the coal from the mines to the user is the second reason. The distance between the Kiwara coal mines and TPCC is 900 km. To bridge this distance, enormous investments in infrastructure are required.
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Exploitations of the coal mines, development of the required infrastructure, investments for conversion at TPCC, are long term projects. In the Tanzanian, the energymaster plan and programme (1990-2005) bas already noted of coal development, but the attention for this is very small. Attention is only given to the impravement of the quality of coal (not necessary for using coal in the cement industry), transport facilities to provide the Mbeya cement factory and the Southem Paper Mills more adequate and a coal utilization project in order to use coal for cooking in households and institutions.
Coal development is necessary for the development of the Tanzanian economy and for becoming less dependent of foreign exchange.
Further research of the following two issue is essential; coal utilization and infrastructure development. Research of coal utilization is important because TPCC is probably not the only enterprise which can converse from oil to coal. The more enterprises which can changing from oil to coal, the more profitable coal development and infrastructure impravement is. Research of infrastructure development is important to get insight in possibilities of coal transport to provide Dar Es Salaam with minimum casts.
8.6. Guidelines for rational selection and adaption of technologies.
Some problems of technica! options described in chapter 5 and the acquisition of techniques are related to the question of industrial information. Industrial information includes information on the manufacture and the technique (plans, diagrams, instructions for use, maintenance and experiments carried out in the countries where the technique is applied) and on resources for financing and management methods. When TPCC wants to purebase new equipment, aften they are dependent of the information of the manufacturer of these equipment. Off course this is not in the favour of TPCC.
Thus, to import new technologies it is important to have industrial information. Industrial information enables the importing enterprises like TPCC to determine needs for production and energy efficiency and to formulate a specific strategy during the negotiations with the exporting firms. In addition, it helps in determining the applicability of techniques and in evaluating the casts and economie and social advantages of a project, and particularly its effect on the environment. Precise and detailed information would in some measure limit failures of transfer, because in many cases, information from the manufacturer on caphal goods remains inadequate. Patents reveal only fragmentary data. If the technica! description and instruction for use of the machinery are correctly prepared, the problems (maintenance and operating problems) which may arise with the machines are decreased.
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More over, the information is often one-sided. Most of it is focused on large-scale technologies, while information on small- and medium-scale technologies is virtually non-existent. Small scale cement factories had been very interesting for a big country like Tanzania. The other two cement factories, which are situated on the other side of the country, have a big overcapacity and transport at long distance is expensive. The withholding of information on certain technologies has had the effect of diminishing the range of choice. The Iack of such information has led to over inflation of investment costs as well as a high rate of industrial failure.
Off course, not only TPCC or the other cement factories have this problem, also other companies whoimport Western technologies. For this reason it is in the interests of Tanzania, to establishing industrial information services. In this conneetion it is essential to establish relations with the organisations spedalizing in industrial information:
- The Development Sciences Information System (DEVSIS-AFRICA) at Addis Ababa in Ethiopia.
- The International Referral System for Sourees of Environmental Information (IRS) at Nairobi in Kenya.
- The Industrial and Technological Information Bank (INTIB). - The Technological Information Exchange System (TIES) at Vienna in Austria. - The Socially Appropriate Technology Information System (SATIS-GRET).
These organisations can provide substantial assistance in establishing these services.
In addition, it is important to train industrial documentation personnel which is responsible for research and verification of data on techniques and the procedures for technology imports. Also for TPCC, it can be very useful, to have personnel who collect industrial information and who follow new trends about modern technologies related with cement manufacturing.
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9. Condusion and recommendations.
The potential to save energy in this factory, is large. The kiln heat balance shows a difference of more than 25% between the kilns in this plantand the other ki1ns with a small energy use. Because the cost of energy comprises about 60% of the direct manufacturing costs, a saving of a few percent is already of great importance.
The main reasons of inefficiency are the poor maintenance condition of the factory and the lack of innovation. In western countries, the energy crises in 1973 and the current énvironment problems have initiated a trend to develop processes and equipment which are more energy efficient. For this reason many technica! options in order to save energy are available. A great number of these options are not implemented or utilized at TPCC.
The reasons for lack of maintenance and implementation of technica! options are various, and are both internal and external. Often these reasons are the same as the reasons for general inefficiency of public enterprises. One important reason is the power structure of public enterprises and the resulting company culture.
It is possible and also recommendable to implement technica! options in order to save energy or energy costs. But, trying to create a company structure and culture where technica! options are implemented when they are financial attractive is more important.
In this last chapter, recommendations will be done on the basis of all findings of this whole report. The recommendations are split up into 2 groups; ad-hoc options which are often short term on one side and structural adjustment options which are often long term on the other side. Ad-hoc options includes mainly technica! options which often can be implemented without structural adjustments of the organisation structure and management. Structural adjustment options includes mainly policy options which are necessary to come to an healthy company culture. When structural options are implemented, the company will handle more rational, the technica! options to save energy will be enforced when they are financial attractive, and the energy use will be decreased.
9.1. Ad-hoc options.
A measure, which is easy to realize on short term, but very meaningful is, is to check and repair all meters which are important to control the clinker burning, especially the gas analyses of the end of the kilns.
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In combination with this, it is necessary to train the burners, and explain them, why saving energy.
An alternative for repairing the meters of the kiln is to replace the old measure equipment for an actvaneed kiln control system. The advantages of this kiln control system are manifold; savings in the fuel consumption, increase in the refractory life, etc. After checking and repairing or replacing of all meters of the whole plant, it can be very effective and financial attractive to start an energy management project. Developing a system and procedures to collect data and translate them into energy saving actions is the core of an energy management project.
The heat balance shows the enormous losses by radiation and convection, which are only partly caused through the relative small kilns. Reducing these heat losses is possible through the use of insulating refractories, which decreases significant the kiln shell temperature. Some additional inquiry is necessary to knpw the exact type of refractory can be used.
Another important measure which is easy to realize on short term, is dust insufflation. Repairing the electra filter and cooling tower does not only mean energy saving but environmental saving, too.
At this moment, the demand of cement is larger than the supply. With further development in the construction industry, the demand of cement will become larger. This enhanced the need of enlargement of the cement production capacity. A precalciner is the only option, as it will involve relative little investment in installation. It enlarges the capacity with more than 100% and a energy saving of 10% is feasible. It increases also the possibilities to use alternative fuels.
A long term option, is to use an alternative souree of energy i.e. from oil to coal. Tanzania has own coal reserves. Disadvantages of coal usage is the big investment involved, especially in infrastructure and transport facilities, also the coal mill plant, starage and the burner. But to become less dependent of oil imparts and foreign exchange, on the longer term, conversion is inevitable. Implementing this option is not possible without supporting of the government.
9.2. Structural adjustment options.
Privatisation or reorganisation of TPCC is a long term option, which involves many problems, uncertainties and unforeseen affairs. Off course, reorganisation is a subject of the Tanzanian government.
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Reasans of privatisation are improving the company culture, increasing the rationality of the management, addition of some market controls, etc. which are essential to imprave production and energy efficiency. Many obstacles have to be overcome, and the Tanzanian government bas to develop a long term strategy, to minimize the problems caused by privatisation and reorganisation.
People determine the vitality, strength and potency of the organisation. Training of bath staff and management are crudal for improving management competences, increasing the decisiveness in the whole organisation, strengthen of the competitive position, enlarging of the commitment, improving the organizational adaptability, facilitating reorganisation and off course to increase energy efficiency and for many other important cases. In addition of training, building a system of incentives and punishments is essential, too.
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Reference
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2. Blanck, M. (1991) NEW WAYS IN ENERGY MANAGEMENT FOR INCREASING ENERGY PRODUCTIVITY IN THE PLANT Zement-Kalk-Gips nr. 11/1991 p. 565-570
3. Broek, van den R. (1993) RURAL ELECTRIFICATION PROJECT APPRAISAL TANZANIA AS A CASE STUDY Technische universiteit Eindhoven.
4. Dekkiche, E.A (1991) ADV ANCED KILN CONTROL SYSTEM Zement-kalk-gips Nr 6/1993, p 286-290
5. Duda, W.H. (1985) CEMENT DATA BOOK Volume 1 & 2 International process engineering in the cement industry (3 rd edition) Wiesbaden: Eauverlag GmbH
6. ENCI (1992) BASIC CEMENT COURSE Maastricht: ENCI
7. Ertug, S., Altenhofer, F. {1991) CONVERSION OF A4-STAGE CYCLONE PREREATER TO THE VA-PASEC PRECALCINER SYSTEM Zement-Kalk-Gips nr. 1/1991 p.16-20
8. Fog, M.H., Nadkarni, K.L. (1983) ENERGY EFFICIENCY AND FUEL SUBSTITUTION IN THE CEMENT INDUSTRY WITH EMPHASIS ON DEYBLOPING COUNTRIES Washington: The World Bank
9. Gardeik, H.O. {1991) OPTIMIZATION OF ROTATING KILNS IN THE CEMENT INDUSTRY WITH RESPECT TO PRODUCT QUALITY, ENERGY USAGE AND EMISSION OF POLLUTANTS Zement-Kalk-Gips nr. 5/1991 p.105-109
10. Gerger, W., Liebl, P. (1991) THERMISCHE VERWERTUNG VON SEKUNDARBRENNSTOFFEN BEI DEN GMUNDNERZEMENTWERKEN Zement-Kalk-Gips NR. 9/1992, p. 457-462
98
11. Kimambo, R.H. (1989) DEVELOPMENT OF THE NON-METALLIC MINERALS AND THE SILICATE INDUSTRY IN TANZANIA Eastem Africa Publications Itd., Dar Es Salaam.
12. Kimmenaede, AJ.M. van (1976) WARMTELEER VOOR TECHNICI Educaboek-Stam Techniche Boeken, Cuturnborg ISBN 90-11-394046
13. Kirch,J. (1991) UMWELTRNTLASTUNG DURCH VERWERTUNG VON SEKUNDARBRENNSTOFFEN Zement-Kalk-Gips nr. 12/1992, p. 605-610
14. Kupper, D., Knobloch, 0. (1991) FINISH GRINDING OF CEMENT WITH POLYCOM HIGH PRESSURE GRINDING ROLLS Zement-Kalk-Gips nr. 1/1991, p. 21-27
15. Labahn 0., Kohlhaas B. (1982) RATGEBER FUR ZEMENTINGENIEURE Wiesbaden; Berlin: Eauverlag ISBN 3-7625-2020-8
16. Mehrotra, V.N., Screenivasan, P., Hartmann, R. (1991) BETRIEBSERFAHRUNGEN MIT 5- UND 6 STUFIGENZYKLONVORWARMERANLAGEN IM ZEMENTWERK DAMOH/INDIEN Zement-Kalk-Gips nr. 12-1991 p. 611-616
17. PBNA (1983) POLYTECHNISCH ZAKBOEKJE 40e druk ISBN 90-6228-015-3
18. Patzelt, N. (1992) HIGH PRESSURE GRINDING ROLLS. A SURVEY OF EXPERIENCE 34th IEEE Cement Technology Technica! Conference 1992
19. Patzelt, N., Lohnherr, L. (1992) OPTIMIERUNGSMOGLICHKEITEN AN ROLLENMUHLEN Zement-Kalk-Gips 1/1992, p. 14-20
20. Scheuer, A, Ellerbrock, H.G. (1992) MOGLICHKEITEN DER ENERGIEEINSPARUNG BEI DER ZEMENTHERSTELLUNG Zement-Kalk-Gips nr. 5/1992 p. 222-230
99
21. Shane, K (1990) MODIFYING AN EXISTING PREREATER SYSTEM FOR IMPROVED PRODUCTIVITY AND EFFICIENCY 32th IEEE Cement Industry Technica! Conference 373-405
22. Tanzania Portland Cement Co.Ltd. BUDGET 1993
23. Tanzania Portland Cement Co.Ltd. Monthly operations report 1991, 1992, 1993.
24. Tresouthick, S.W., Mishulovich, A. (1991) ENERGY AND ENVIRONMENTAL CONSIDERATIONS FOR THE CEMENT INDUSTRY In: Tester, J.W.,et al.:Energy and the environment in the 21 st century. Cambridge: MIT Press
25. Tripathy, S.C., Roy, M.C., Balasubramanian, R. (1992) ENERGY AUDITING KIT FOR CEMENT INDUSTRIES Energy conversion Mgmt, vol. 33 no. 12, p.1073-1078
26. Vencateswaren, S.R., Lowitt, H.E. (1988) THE U.S. CEMENT INDUSTRY: AN ENERGY PERSPECTIVE Columbia: Brrergetics Inc. report: DOE/RL/01830-T58
27. Vleuten, F. van der, (1994) CEMENT IN DEVELOPMENT, ENERGY AND ENVIRONMENT ECN NOP /MLK project: Strategies and instruments to promate energy efficiency in developing countries.
28. Mbelle, A. (1988) FOREIGN EXCHANGE AND INDUSTRIAL DEVELOPMENT, A STUDY OF TANZANIA Sweden: Kompendietryckeriet-Kallered ISBN 91-7900-510-1
29. Mihyo, P. (1994) NON MARKET CONTROLS AND THE ACCOUNTABIUTY OF PUBUC ENTERPRISES IN TANZANIA Great Brittain: Ipswich Book Co. Ltd. ISBN 0-333-59352-9
30. Ministry of water, energy and minerals Ganuari, 1991) ENERGY MASTER PLAN AND PROGRAMME (1990-2005) The United Republic of Tanzania
100
31. Ministry of water, energy and minerals (april, 1992) 1HE ENERGY POLICY OF TANZANIA The United Republic of Tanzania
32. Bureau de statistics, industrial statistics section, president office, planning commission (1988) SURVEY OF INDUSTRIAL PRODUCTION The United Republic of Tanzania
33. Bureau de statistics, industrial statistics section, president office, planning commission (1992) INDUSTRIAL COMMODffiES; QUARTERLY REPORT 1992:2 The United Republic of Tanzania
34. Nordhaug, 0. (December 1992) HUMAN CAPITAL IN ORGANIZATIONS Competence, Training and Learning Norway: Scandinavian University Press ISBN: 82-00-21807-4
35. Jefferson, W. (March 1990) ENERGY AND 1HE ENVIRONMENT IN 1HE 21st CENTURY England, London, The MIT Press ISBN: 0-262-20078-3
36. Carroll, L. (1980) INDUSTRIAL ENERGY USE DATA BOOK Oak Ridge Associated Universities US, New York, Garland STPM Press ISBN: 0-8240-7273-1
37. Vijselaar, H. (1991) HUMAN RESOURCES Samson Bedrijfsinformatie ISBN: 90-14-04492-5
101
Appendix 1: Cement production 1966-1993
year production rated capacity capacity utilization
(ton per year) (ton per year) (%)
1966 50,100 110,000 45 1967 146,917 110,000 133 1968 157,339 110,000 142 1969 168,634 110,000 154 1970 167,296 110,000 152 1971 177,503 110,000 161 19n 236,956 270,000 125 1973 314,002 270,000 116 1974 296,400 270,000 110 1975 266,000 270,000 99 1976 244,400 270,000 91 1977 244,880 270,000 91 1978 250,685 270,000 93 1979 298,841 520,000 76 1980 286,414 520,000 55 1981 252,994 520,000 49 1982 214,712 520,000 41 1983 126,022 520,000 24 1984 171,767 520,000 33 1985 180,555 520,000 35 1986 232,300 520,000 45 1987 280,000 520,000 54 1988 301,000 520,000 58 1989 380,000 520,000 73 1990 300,000 520,000 58 1991 410,000 520,000 79 1992 410,000 520,000 79 1993 387,011 520,000 74
Appendix 2: Analysis of the materials
raw meal cl inker cement (%) (%) (%)
Loss of ignition - 0.4-0.7 1.5-2.5 Insoluble residue - 0.2-0.6 19-21 Si02 22-24 20-22 1.5-2.5 Al 303
6-7 6-7 5.9-6.5 Fe203
2.6-3.0 2-3 2.5-3.0 cao 66-69 67-69 63-65 MgO 0.2-0.35 0.1-0.5 0.1-0.5 so3
- 0.2-0.5 2-4
102
Appendix 3: Raw meal mills data
mi ll 1 mill 2 mi ll 3
Type Drun mill, Tirax unidan, Tirax unidan air swept mill, air mill, air (Hunboldt) swept swept
(FLS) (FLS)
Internat diameter 2.90 3.60 3.84 (meter)
useful length 4.96 6.20 5.80+3.80 (meter)
grinding media 39 58 72 (ton)
grinding media 33% 33% 33% fi ll ing ratio
rated capaci ty 38 52 72 (ton)
capacity on this 35 47 75 moment (ton)
Rotatien speed 17 16 16.5 Crpm)
Power available 605 850 1255 CkiJ)
Power used 600 800 900 CkiJ)
first start june january march 1966 1972 1979
Appendix 4: kilns data
kill 1 kill 2 kill 3
Hanufacturer Hunboldt FLS FLS
Type of cooler Horizontal planetary planetary grate fuller unax unax cooler cooler cooler
diameter 3.16 3.60 3.95 (meter)
useful length 41.8 49.8 61 (meter)
rated capaci ty 350 500 800 (ton per day)
capac ity on th is 360 430 no - ~ -moment Ctpd)
Rot at i on speed 2 2 2 Crpm)
first start june january march 1966 1972 1979
103
Appendix 5: Cement mills data
mi ll 1 mi ll 2 mi ll 3
Type Unidan milt Unidan (KRUPP) (FLS) (FLS)
Process closed closed open ei rcui t circuit circuit
Internat diameter 2.70 2.80 3.20 (meter)
useful length first chanber 3.03 2.90 3.46 second chanber 5.30 6.20 1.39 third chanber - - 6.45 (meter)
grindins media first chanber 23 23 37 second chanber 40 47 14 third chanber . . 69 (ton)
grindins media 33% 33% 33% fitting ratio (every chamber)
rated capscity 22 30 46 (ton)
capscity on this 19 23 40 moment (ton)
Rotation speed 18 18.7 17 (rpm)
Power available 1020 1020 1580 (kW)
Power used 900 900 1480 (kW)
first start june january march 1966 1972 1979
Appendix 6: The different zones and their respective refractory bricks.
zone Tempersture Type of refractory range ("C) bricks
Preheatins 800·1000 Low all.lllinl.lll
Calcining 1000·1200 Low all.lllinl.lll
Transition zone 1200·1250 High all.lllinl.lll
Burning 1300-1500 Magnet i te
Cooling zone 900-1500 High all.lllinl.lll
Cooler Low all.lllinllll/ fire bricks
104
Appendix 7: Production data 1993
Total production of raw meal Total production of clinker Total production of cement
Total use of oil Total use of power
production of raw meal eperating Chours) output per hour kWh used kiJh per ton raw meal kiJh per ton cement Cx1.62)
standard eperating kiln eperation Chours) util i zation (%) production of clinker (ton) oil used (ton) Calorie value oil (kJ/kg) Heat consumption (kcal/kgcli) Heat consumption CkJ/kgcli) kiJh used kiJh per ton clinker kiJh per ton cement (x0.95)
production of cement operatien (hours) output (ton/hour) kiJh used kiJh per ton cement
621,153 ton 372,176 ton 387,715 ton
39,590 ton 47,922,000 kiJh
RH mill 1 RH mill 2
95,933 205,935 2,730 4,192
35 49 2,365,440 2,748,510
25 13 40 22
kiln 1 kiln 2
8,760 8,760 5,202 5,971
59 68 77,561 107,755 8,390 11,155
40,740 40,740 1,049 1,004 4,396 4,208
2,142,890 1,965,940 28 18 26 17
CM mi ll 1 CM mill 2
62,147 93,035 3,374 4,059
18 23 2,734,200 2,574,650
44 28
105
RH mill 3
320,513 4,327
74 7,233,630
23 37
ki ln 3
8,760 5,838
67 186,860 20,045 40,740
1,041 4,360
5,299,410 28 27
CM mill 3
231,829 5,863
40 8,838,520
38
Appendix 8: kWh use in 1993 for the different units
kiJh
Crusher 1: 293,690 Crusher 2: 383,030 Gypsl.lll crusher: defect Crane 1 and 2: 295,070 Raw mi ll 1 onl y: 1,330,660 Raw mill plant: 1,034,780 Raw mill 2 only: 290,110 Raw mill blower 2: 1,555,300 Raw mill plant 2: 903,100 Raw mill 3 onl y: 4,076,030 Raw mill blower 3: 2,271,010 Raw mill plant 3: 886,590 Blending plant 2: 26,389 Raw meal transport: 109,260 Raw meal circulation: 147,110 Blending plant 1: 241,530 Kiln plant 1: 2,142,890 Kiln plant 2: 322,300 Kiln 2 waste gas blower: 998,700 Kiln 2 oil heater: 644,940
.Kiln 3 waste gas blower: 2,531,830 Kiln 3 feed: 747,940 Kiln 3 drive: 247,710 Kiln 3 outlet: 530,680 Kiln 3 inlet: 1,241,250 Clinker transport: 192,468 Cement mill 1 only: 2,379,330 Cement mill plant 1: 354,870 Cement mill 2 only: 1, 943,000 Cement mill plant 2: 631,650 Cement mill 3 only: 8,239,240 Cement mill plant 3: 599,280 Packing plant 1: 132,700 Packing plant 2: 462,860 Packing plant 3: defect General office: defect Weighbridge: defect Lighting transformer: 378,890 Water: 954,849 Workshop/stores: 287,510
Total: 39,859,460
Total Tanesco: 47,922,000
Di fference: 8,072,540
106
Appendix 9: Clustering of the kWh meters for the different sections
RM mill 1 Raw mill 1 only Raw mill plant
RM mill 2 Raw mill 2 only Raw mill blower 2 Raw mill plant 2
RM mill 3 Raw mi ll 3 only Raw mill blower 3 Raw mill plant 3
Ki ln 1 Ki ln plant 1
Ki ln 2 Ki ln plant 2 Kiln 2 waste gas blower Kiln 2 oil heater
Ki ln 3 Kiln 3 waste gas blower Ki ln 3 feed Ki ln 3 drive Ki ln 3 outlet Ki ln 3 inlet
CM mill 1 Cement mill 1 only Cement mill plant 1
CM milt 2 Cement mill 2 only Cement mill plant 2
CM mill 3 Cement mill 3 only Cement mill plant 3
107
Appendix 1 O: Radiation and convection heat transfer coefficient (total)
\1'1 <D
0 <D
L ~ft
0 \1'1
\1'1 ....
0 ....
0 n
I I I
/~ .w I l I I
i ~~ ~ VJ! , ~ .
I I
i I ~~~~ w j/ (\~v ~~~~ ~ f
I
!'' ·.~~~~~~~~ . .
I 1 . . '
·i~VV::~ 1 ,o /~/:V .0 :/1 ~~ ,~''f I ,'t
~~
~~' . cf' I ~-~ I 1 __ -~v ~~ >-..'wl _,
ç:.;' I
I ' I ~~~, /r / ~ 1/ --- ' ~
I VVt?~o I/ L~V /( ~ ,/r 1
s = jo .9
r ö loc Ambient
N
0
V/ ---r I
l ' . . . I I . ' ' 0
o 1 co 200 Joe •co soa soa T-T0 CCl
108
- I
Appendix 11: CP of gases.
1\ I i I I I I I I I 1 I I~ I · ! ~ I I I i I I i I ; L I I i I
\I I I ! I I I I I 1\ I ~.I I i~ I \I 1\ \ I I I I I ~ \ i I I I I I I I I\ l-i1 I ~ I ~ '\\I I I I I L ~ ! .. I 11
1\ I I I I I I I I I 1 I ~ 1 I ~\~ ;\ I \ \1 I I I I ~ I \1 I i I I I I I I I\ Eii I l§\·~ 1\ i \\ I I I I I ~~~ , I81:E ~ . . r
I \ I i I I I I I I I 1\ I ~ I I 'I I \ 1 \1\ I I I i t
0 ::> .. 0 ::> '
I \ i \I I I I I I I I I I \I ~I I I\ I \ I I \ I I I I ~ 0 ::> ..,
0 I ~ ~ I I I I 11 I I I ~ I \8 I I ', I 11 1\ I l I I I f '
. . .
I I !\ I \I I I I I I I I I I \1 f. I I ',/ I I I \1 I I I ~ ~ ::> I -
I I i \ ~ I I I I I I I I I ~ I~ I I, !\ I \\ i I ! t I I 1\ I ~ I I I I I I I I i \J ~ I I \ i \ l ~~\ I I i ~ ! ! I\ I\ I I I I I I I ~ r8 I \l \1 ~~ ~ I I r 0
0
1111\11\ I 1.1 I I 'I\ I \I I I I I I \ i\ [\
I \~I \ I I \
Cf) 1\ w
I I Cf)
~~ < (!) u
~
111111~ ~ ~I ~~èi 1\\
I I I I 1\ r8 I \ I\ I I I I I I I ~i I~~\ ~ \
I I I I 1\ ç:\J ~ ~ 11 \
; I I I I \ ~ I\ I\ \ ~ 111111~.
I \
I I ~ "'
0
"' -I I ~ 0
0 .. I I I I
0 0 ...
0 0 . 0 0 ..,
I Lt.. ] 1\ a
"I ~1111\1~ , I I 0 0 ...
a_ C::t
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. . . . . . . . . . '
0 0
0
o~·~ ot·~ oz·z OI'Z oo·z 06'1 oa·1 oc1 o~·1 oç·t Ot't oc·1 a~·, o C:.<N ;rll
109
Appendix 12: CP of liquids and fuels
I I· I I ïemo. I c of liquid water I I I p
I I ,., I I O"C 4.22 kJ/kg c I I c:oo ... I I .., l. 4.18 kJ/kg c I I
1 00°C . I
I 4.22 kJ/kg c I I I
C? OF FUELS 0 ,._ ~,
0 I Ref. ...., ~,
ol ,.., ~,
~I ~,
ol "' -
0 ,._
-(.)
(.!) ::.::o
111 ........ ....,-::.::
0 ,., . -0 -. -0 Qt
0
0 ... I
0 0 so 100 lSO 200 TEMP CCJ
110
Appendix 13: CP of solids
en 0 ··-......J 0 en l..L 0
CL (.)
\ \ i\
\
1\
u 0 N -~
\
1\ '
\ '
c ro c
~ ~ I I I
I\ I I
I I I
I \
\ . :\
\ !I I \ I l""'l ,4' l '""" ' \<...: V
\ B ,V\ I
I \ ~\ I
'1\\ I~~ I\~~' \~
\ \\\\ \ ~ \
~~~~\\ Î\ ·\ Cá ~ \ ~ I~
\ \ -c:
f\ ~ ~I\ 1\ \ I)~\ 1\ ~ ~~ ~ '§b:
" ~ ~ """'
~ ' t I 1 I
I
I I I
I
I
~ \ V
~ '
~ ~ ~ f-
~ ~ I I
~ ~ ~
0 0 ".,
0 0 ....
0 0 n
0 0
""
0 0
0 0 0
0 0 <:>
0 0 :ll
,..., O<..l c._, ......
a.. :::
ol.LJ o>-
"'
~· 0 0 :t'l
0 0 ....
f-
1-
1-
1-
'
0 0 n
0 0
""
0 0
0
Oto"l Ot"l OZ'l Ol"l OO"l 05"0 oa·o OL"O 09"0 o ~>~ ;r:.~
111
-. -
Appendix 14: Persennel
Persennel complement of the company at 1·01·1993
1. corporate management 13
2. eperation management 19 production 185 mines 91 concrete products 20 quality control 27
3. maintenance management 5 engineering 247 project 26
4. business management 5 plant sales 13 depots 25 export 7 research 2
5. finance accounting 42 computer 7 materials 37
6. manpower & administation administration 30 welfare 91 training & militia 61
112
Appendix 15: Industries in Tanzania classified according ISIC (1988).
Nunber Nunber Gross Produc· Net energy si ze ISIC·code of of pers. output ti on value inten·
establ. engaged tot al costs added sive bi l.shs bil.shs bil.shs
TOT AL 771 126.321 57.563 42.908 14.654
2 Hining and carrying 37 5.785 1.070 729 341
210!290 Coal mining and other mining 37 5.785 1.070 729 341
2100/2901 Coal mining, stone quarrying 20 1.213 226 107 118 Low Smalt 2902/2903 Phosphate and Salt mining 12 1.722 175 103 72 Low Smalt 2909 Hining and quarrying n.e.c. 5 2.850 669 519 149 Low Hed.
3 Hanufacturing 11 114.163 51.758 40.401 . 11.357
31 Hanufacturing of Food, 65 41.914 13.604 10.178 3.425 Beversges and Tobacco
311!312 Food manufacturing 45 32.430 7.403 6.000 1.403
3111/3112 Heat and Diary products 12 1.007 568 544 24 Hed. Hed. 3113 Fruit and vegetable canning 4 267 103 84 19 Hed. Smalt
and preserving 3115 Vegetable oils and fats 30 2.061 1.278 1.219 59 Hed. Hed. 3116 Grain milling products 13 1.496 1.508 1.461 46 Hed. Hed. 3117 Bakery products 24 582 319 283 36 Hed. Smalt 3118 Sugar factories and refineries 18 16.229 1.431 956 474 Hed. Hed. 3119 Confectionery products 5 104 13 9 4 Low Smalt 3121/3122 Food products and prepared 39 10.684 2.180 1.441 739 Low Big
animal feeds n.e.c.
313 Beverage industry 17 4.424 2.197 1.422 775
3131/3132 Distilled sprits, wine ind. 5 3.223 1.328 821 507 Hed. Hed. /3133 and malt l iquor
3134 Soft drinks 12 1.201 870 601 269 Hed. Hed.
314 Tobacco manufactures 3 5.060 4.003 2.757 1.246
3140 Tobacco manufactures 3 5.060 4.003 2.757 1.246 Low Big
32 Textile, ~earing Apparel and 63 39.846 12.118 10.063 2.055 leather Industries
321 Hanufacture of textiles 85 32.617 10.638 8.863 1.775
3211 Spinning, weaving etc. 53 23.945 7.293 6.334 959 Hed. Big 3212 Made-up textiles except apparel 11 3.849 1.335 1.034 301 Hed. Hed. 3213 Knitting mills,carpets and rugs 12 3.059 539 403 136 Hed. Hed. 3215/3219 Cordage,ropes,twine and textiles 9 1.764 1.470 1.091 379 Hed. Hed.
322 Hanuf. of wearing apparel 50 2.443 448 371 77
3220 ~earing apparel except footwear 50 2.443 448 371 77 Hed. Smalt
323 Hanuf. of teather and products 14 1.465 421 327 94 of l., l. subst. and fur
3231 Tanneries and teather finishins 7 1.130 302 255 47 Low Smalt 3233 Lesther products and subsitutes 7 335 119 72 47 Low Small
324 Hanuf. of footwear, except vulc. 14 3.321 611 502 109 rubber or plastic footwear
3240 Footwear·leather 14 3.321 611 502 109 Lów Hed.
113
Nl.lli:ler Nl.lli:ler Gross Produc· Net energy si ze ISIC·code of of pers. output ti on value inten·
establ. engaged total costs added sive bi l.shs bi l.shs bi l.shs
33 Manuf. of \Jood ancl \.loodproducts, 122 5.312 1.184 825 359 including Furniture
331 Manufacture of \Jood ancl \Jood 65 3.525 786 512 274 ancl corkproducts
3311/3312 \Jood ancl \Jood products 65 3.525 786 512 274 Low Med. /3319
332 Manuf. of furniture ancl fixtures 57 1.787 399 313 85
3320 Manuf. of furniture ancl fixtures 57 1.787 399 313 85 Low Small
34 Manufacture of Paper ancl Paper 62 5.607 2.881 2.234 647 prod., Printins ancl Publishing
341 Paper ancl paper products 10 2.713 1.570 1.218 352
3412 Containers, boxes of paper 4 971 601 468 134 High Med. ancl paper-board
3411/3419 Pulp, paperboard ancl Pulp ancl 6 1. 742 968 751 218 High Med. paper articles n.e.c.
342 Printing, publ. anclallied incl. 52 2.894 1.311 1.016 295
3420 Printins and publishing 52 2.894 1.311 1.016 295 Low Med.
35 Manuf. of Chem., Petr., Coal, 67 6.540 9.088 6.601 2.487 Rubber ancl Plastic Products
351 Manuf. of inclustrial chemieals 10 1.628 3.523 1.948 1.575
3511 Basic incl. chemical except fert. 5 574 802 276 525 High Med. 3512 Fertilizers and pesticides 5 1.054 2.721 1.672 1.050 High Big
352/353 Manuf. of ether chemical prod. 43 3.488 3.355 2.716 639 ancl petroleum refineries
3521 Paints, varnishes ancl lacquers 5 253 236 183 53 Med. Med. 3522/3523 Drugs ancl medicines, soaps, 29 1.630 1.972 1.760 213 Med. Big
perfumes cosmetics ancl ether cleanins preparations
3529/3530 Manuf. of ether chemical prod. 9 1.605 1.146 m 373 High Med. ancl petroleum refineries
355 Manufacture of rubber products 9 920 1.897 1.758 139
3551 Tyres ancl tubes 8 830 1.874 1.738 136 High Big 3559 Rubber products n.e.c. 1 90 23 20 3 High Small
356 Manuf. of plastic prod. not 5 504 313 179 134 elswere classified
3560 Plastic products 5 504 313 179 134 High Small
36 Manuf. of Non-metalie Mineral 19 4.350 3.000 2.355 645 Products
361/362 Manuf. of pottery ancl Glass 19 4.350 3.000 2.355 645 /369 glassprod. ancl non-metallic prod.
3610/3620 Pottery, china ancl eerthenware 6 1.171 807 638 168 High Med. /3691 glass (prod.) ancl clay prod.
3692/3699 Cement, lime plaster ancl non· 13 3.179 2.194 1. 717 4n High Big metallic products
114
NUlDer NUlDer Gross Produc- Net energy si ze I SIC-code of of pers. output ti on value int en-
establ. engaged total costs added sive bi L.shs bil .shs bil .shs
37 Basic Metal Industries 6 1.150 4.024 3.629 394
371!3n Iron, steel and non-ferrous 6 1.150 4.024 3.629 394 basic industries
3710J3no Iron, steel and non-ferr. metals 6 1.150 4.024 3.629 394 Med. Big
38 Manuf. of Fabricate Metal Proef. 96 8.488 5.688 4.373 1.315 Machinery and Equipment
381 Manuf. of Fabricate Metal Proef. 49 3.849 1.665 1.136 529
3811 Cutlery, hand tools and hardware 6 1.029 442 289 153 low Smal l 3812 Furniture and fixtures of metal 4 289 60 27 32 Low Small 3813 Structural metal products 10 625 236 153 83 Low Small 3819 Fabricated metal products n.e.c. 29 1.906 928 666 261 Low Med.
382 Manuf. of mach. exc. electrical 12 1.016 280 185 95
3823 Metal, wood working machinery 4 255 165 120 45 Med. Small 3829 Machinery and equipment 8 761 115 65 50 Med. Small
383 Manuf. of electrical machinery 11 1.500 711 581 130 apparatus and supplies
3831/3832 Electrical machinery, apparatus 11 1.500 711 581 130 Med. Med. 3833/3839 and supplies
384 Manuf. of transport equipment 23 2.106 3.022 2.464 558 Med. Big
3843 Motor veh i cl es 23 2.106 3.022 2.464 558
385 Manuf. of professional, scient., 1 17 9 7 2 measuring and cantrolling equipm. photographic and optical goods
3853 Watch assemling 1 17 9 7 2 Low Smal l
39 Other Manufacturing Industries 11 956 1n 142 30
3901 Jewellery and related articles 6 684 136 114 22 Low Small 3909 Other industries 5 2n 36 28 8 Low Small
4 Electric gas water 23 6.373 4.734 1.n8 2.956
4101 Electricity 23 6.373 4.734 1.n8 2.956 Big
115
Appendix 16: The organisation structure of TPCC.
I board of di rectors I I workers council
I general manager I internat auditor I operational I
adviser to gm I technical assistant
I I I I I manpower and finance eperation maintenance business aàninistration di vision division division division division
H administr. department I ~ materials
department I ~ product i ons
department H engineering I
department H depots
department
r- medical - stores - process - electrical '- mwanze rnaintensnee
r- security - pur eh as i ng, - production r- mechani cal r- doeloma loc al rnaintensnee
1- tranport - purchasing, - packing plant 1- prevent i ve '- new dar foreighn wazo rnaintensnee
- estate - material - packing plant I- workshop - ubungo eontrol mal indi
I I r- garage
~ welfare ~ c~ter H mines ~ sales department department department civil department
1- pregrammer 1- quarry 1- process
'- administr. '- crusher and '- customer cleaning
training accounting I ~ quality con. projects
I H experts I department department department department department
'- management L works chemist accounting
1- finance accounting - concrete '- marketing,
.__ sales products research anc:l accounting department intell igence
- safety sectien
- shift management
116
Appendix 17: The structure of the decision making and policy formation in Tanznia.
Ruling party
National executive committee
Central committee
I Planning Committeel
I Economie
I sub-committee
I I I
r - - - - J l - - - - 1
I-- Cab i net President's office
Economie Committeel President of the cabinet Economie affairs unit [
Parl iament
Vice Parastatal president's Organisation
office Committee
Planning
I Commission
Prime minister's
I I I office
ministry I lministry I lmi~i~try of I f1mance
I l I
I Holding Corporatien
Independent Independent parastatal I Subsidiary parastatal organisation Corporatien organisation
(Source: Mihyo, P. Non-market controls and the accountablity of public enterprises in Tanzania (1994))
117