FACULTY OF ENGINEERING AND SUSTAINABLE DEVELOPMENT Department of Building, Energy and Environmental Engineering

Energy Efficiency Opportunities in a Pulp Drying Machine

Gagandeep Mohey

Autumn 2016

Student thesis, Master degree (two years), 30 HE

Energy Systems

Master Programme in Energy Systems

Supervisor: Nawzad Mardaan, Håkan Persson

Examiner: Björn Karlsson

ABSTRACT

Global concerns about declining resources and climate change mean that industries must do their best to use energy as efficiently as possible. Energy is also an important component of a modern economy. The pulp and paper industry is one of the most energy-intensive industries round the world. In this study energy efficiency opportunities in pulp drying machines are identified and the saving potential is then quantified. The methodology followed was based on comparison of energy saving technologies and practices such as turbo vacuum blowers, shoe press, heat pump, use of low pressure steam etc. The data used for the calculations was taken from the mill data records. Six energy efficiency improvement projects were identified. The total proposed energy saving potential in the two pulp drying machines studied in the thesis is 10450 MWh. Installation of the shoe press shows the highest saving potential followed by the turbo vacuum blowers. Although the accuracy of the results is heavily dependent upon the accuracy of the data records from the case study mill. The proposed savings would act as a reference point and depending upon the estimated savings potential, would help the mill to identify areas, projects that need more detailed measurements for further action.

ACKNOWLEDGEMENT

I would like to express my sincere gratitude to my supervisor Nawzad Mardaan, Ph.D, Energy Systems Program Director, University of Gävle, Sweden for his generous guidance, valuable suggestions, continuous support and never ending encouragement during the entire thesis work. I am particularly grateful to Professor Björn Karlsson, Department of Building, Energy and Environmental Engineering for providing me with much useful input into the project

I extend my heartfelt gratitude to Mr. Håkan Persson (Manager - Energy Efficiency and Project Department, ABB AB, Sweden) who conceived the idea of this project, supervised it and gave me a wonderful opportunity to work on it and my career development. This is really appreciated.

I would like to appreciate Jonas Heikkinen for his helpful information/suggestions. On a personal note, I would like to express my profound gratitude to my brother, Amandeep Mohey without whose support my master studies in Sweden would have not been possible. He has been the source of my encouragement and guidance.

I cannot forget the contribution of my wife, Nistha Mishra and my son, Anay for providing me with unfailing support and continuous encouragement throughout my years of study here.

Last but not the least, thanks to my parents back in India, for their blessings and limitless support which put me in a position to take on such a study.

Table of Contents

Contents Page

1. Introduction 1

1.1 Description of problem 1

1.2 Aim of thesis 4

1.3 Methodology of study 5

1.4 Limitations of the thesis 6

1.5 Structure of thesis chapters 6

2. Energy efficiency 7

2.1 Concept of energy efficiency 7

2.2 What is energy efficiency 8

3. Energy in Sweden 8

3.1 The industrial sector 9

3.2 Energy use in Swedish pulp and paper industry 11

4. The case study pulp mill 14

5. Energy conservation opportunities

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5.1 Replace liquid ring vacuum pumps with turbo vacuum 16

blowers

5.2 Use shoe press in the press section 22

5.3 Use low pressure steam in the drying machines 26

5.4 Use heat pump to generate medium pressure steam 29

5.5 Replace V belts with flat belts 31

5.6 Replace metal halide lamps with LED lamps 33

6. Summary of energy conservation opportunities 34

7. Conclusions and discussions 36

8. References 37

List of tables

Title

Table: 3.1 Sector shares of fuel and electricity in relation to total Industrial energy use 2000 – 2008

Table: 5.1 Drying machine A vacuum pumps

Table: 5.2 Drying machine B vacuum pumps

Table: 5.3 Annual steam consumption in tons (year 2015)

Table: 5.4 Total medium pressure steam consumption in tons (year 2015)

Table: 5.5 Cost analysis of low pressure and medium pressure

Steam

Table: 5.6 List of motors identified with V belts in drying machine A

Table: 5.7 List of motors identified with V Belts in drying machine B

Table: 6.1 Summary of energy conservation opportunities

List of figures

Title

Figure: 3.1 Energy supply and use in Sweden 2013, TWh

Figure: 3.2 Final energy use in the industry, by energy carrier 1971 – 2013, TWh

Figure: 3.3 Final energy use in the industrial sector, by industry, percent

Figure: 4.1 Total electricity and steam consumption by drying machine A (Year 2015)

Figure: 4.2 Total electricity and steam consumption by drying machine B (Year 2015) Figure: 4.3 Total production in drying machine A (Year 2015)

Figure: 4.4 Total production in drying machine B (Year 2015)

Figure: 5.1 Water ring vacuum pump

Figure: 5.2 Turbo vacuum blower

Figure: 5.3 Difference between the pressure profile of a conventional roll press and that of a shoe press.

Figure: 5.4 Cross-section of a shoe press design

Figure: 5.5 Medium pressure (11bar) steam consumption (tons) in the drying machine A and B (year 2015).

1. Introduction

1.1 Description of the problem

The proper use of energy is essential for the functioning of the industrialized world and for the protection of the environment. Relevant factors of environment consist of food, water, energy, natural resources etc. Energy is one of the most important factors of environment and energy efficiency is critical to our future economic prosperity and environmental wellbeing. Pulp and paper production play a very important role in all areas of the human activity. We need it every day for widening the frontier of our knowledge. Paper is used for almost every writing and printing. It is also used for wrapping and packaging. The use of pulp and paper products has no limits.

Across the world, the Pulp and paper industry is one of the major manufacturing

industry providing not only a large number of product and services but also employment to a large number of people and also contributes to the economy of the nation.

The paper and pulp industry accounts for approximately 5% of the total industrial

final energy consumption and 2 % of direct carbon dioxide emissions from the industrial sectors in the world (Assessment of Emerging Energy Efficiency Technologies for Pulp and Paper industry-A technical review, Lingbo Kong, Ali Hasanbeigi, Lynn Price).

In Sweden, the pulp and paper industry accounts for almost half of the industrial

final energy use in percentage. This makes it all the more compelling for the industry to give energy efficiency high priority. Energy efficiency is an important element is sustainable development. (Energy Efficiency in German Pulp and Paper Industry, Tobias Fleiter).

A significant proportion of the total industrial energy is consumed by the drying

process and it is also a product quality defining step in most industrial processes such as pulp and paper etc (Improving Dryer energy efficiency J.C Atuonwu,G.van Straten, H.C van Deventer,A.J.B van Deboxtel ).

Drying is a process with a large energy consumption as compared to any other

production process. Statistics reveal that drying consumes 10 to 15 % of the total national industrial energy demand in Canada, USA, France and UK as well as 20 t0 25 % of the total national industrial energy demand for Denmark and Germany (Comparison of Energy Parameters in various Dryers, Ali Motevali, Saeid Minaei, Ahmad Banakar, Barat Ghobadian, Mohammad Hadi Khostaghaza).

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Dewatering is a major operation done during the drying process in the final pulp

making process involving a diluted solution of pulp suspension with more than one percentage concentration of solid fibre. Forming section, Press section and dryer section are the three major section of a pulp machine.

The fibres which are present in the pulp and water slurry form a web due to

drainage by gravity and applied suction underneath, in the forming section. Mechanical pressure, through the use of nips of a series of presses or rotating rolls helps in the removal of additional water and resulting in the consolidation of the wet web in the Press section. In the dryer section, the remaining water is evaporated through a series of steam heated cylinders resulting in the binding amongst the inter fibres. This is a highly critical step in the development of pulp. Drying involves large equipment size, capital and operation costs. [Ghosh and Oxley, 2007]

The amount of water removed per kg of pulp in a machine is; Dryer section between 1.0 and 1.3 kg, forming section 200 kg and press section 2.6 kg respectively. As compared to any other section of the machine, it costs more to remove the water in the dryer section (Reese, 1988). The relative costs of dewatering are: forming section 10%; press section 12% and dryer section 78%. The dryer section is by far the largest consumer of electricity and steam. It is responsible for almost 60% of the paper machines total energy consumption. The largest heat consumer in the pulp and paper is the dryer and recovery from this area is necessary (The case study of Energy Flow analysis and strategy in Pulp and Paper Industry Hua-Wei Chen, Chung – Hsuan Hsu, Gui Bing Hong).

Inspite of its key role and relatively high operational costs, it is noticed that not

much attention is given towards improving the efficiency of the drying machine in the mills. This leads to consumption of unnecessary large amounts of electricity, steam and also adds to the cost of operation. A large number of studies have been carried out regarding the pulp and paper sector energy use. Many of which concentrate on comparing mills to each other or try to define the gap between current and theoretical minimum energy consumption (Pulp and Paper Industry Energy Bandwidth Study; Department of Energy’s Industrial Technologies Program, Atlanta 2006). A lot of research has also been done to improve the energy efficiency of a particular mill (Kilponen, L.; Ahtila, P.; Parpala, J.; Pihko, M).

The historical trends of the Indian pulp and paper industry were analyzed by

Schumacher and Sathaye and they found that actual energy intensity had grown as the industry was more focused in saving the capital investments and labour (Schumacher, K.; Sathaye, J, USA 1999).

Specific electricity and heat consumptions and the development in the global pulp and paper industry energy use till 2030 was studies by Szabó et al. based upon specific electricity, heat consumptions for each product grade and assumed energy efficiency improvements (Szabó, L.; Soria, A.; Forsström, J.; Keränen, J.T.; Hytönen, E, 2009).

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The aim of this study is to identify energy saving opportunities in a pulp Drying Machine. It is extremely important to have a focused approach towards energy efficiency improvement of the Pulp Drying Machines, not only because the relative cost of dewatering is the highest but also as it would lead to improvement in the product quality and monetary savings (Ghosh, A.K).

At the mill studied in the thesis lacked resources regarding the identification of

energy saving opportunities and the estimation of the energy saving potential. A set of possible reasons were identified which were then categorized into four sub problems:

(a) Sub Problem 1 – Lack of knowledge

The lack of knowledge about drying section of the machine also exists in the mills. The drying process is very intricate as it involves a number of complex sub processes which are heat transfer, evaporation and water removal. Steam pressure, vacuum system cylinder surface temperature, and condensate removal also play an important role. There are many possible reasons for it. The first and foremost could be wrong information about its little or no effect on the quality of the product. Another possible reason could be the intricate nature of the drying process where a number of sub process are involved.

These include the transfer of heat, evaporation and removal of water with a key

role being played by steam pressure, temperature of the cylinder surface, hood balance and condensate removal. These components help in finalizing the drying capacity and final product quality.

(b) Sub Problem 2 Lack of training based on energy efficiency to the manager and operating, maintenance staff

It has been noticed that the main focus of the operating or the production team is to achieve the production target similarly for the maintenance team it is to address to the machine fault and its removal. Little or no attention is paid to provide them technical training based on the energy conservation and efficient machine operation. This results in focus only becoming production targets or reduction of the breakdown time whereas no scope is left for energy efficiency.

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(c) Sub problem - 3 Lack of comprehensive strategy on energy efficiency

Lack of comprehensive strategy on energy efficiency leads to energy efficiency becoming a low priority in the mill. It then leads to increased energy costs, no focus on investments based on energy efficiency. Although energy efficiency may not be a core business activity for the mill due to its lack of generating income but the lack of the strategy leads to the loss of savings and reduced productivity. (Thollander and Ottosson 2010).

(d) Sub problem 4 Lack of sub-metering in the mill

For proper management of energy, it is very important that it should be measured. Lack of sub-metering about where, when and how much energy is being used takes away very crucial information.

This information in hand, the mill team becomes better equipped to take

important decisions that could improve efficiency and also save energy. Since energy efficiency for a pulp mill is a very comprehensive study, it may not

be possible to consider each aspect of it. In order to limit my study Sub Problem 1 are considered for the thesis.

1.2 Aim of the thesis

Principal aim - The aim of the thesis is to improve the Energy efficiency of the Pulp drying machine installed at the mill considered for the thesis.

In order to achieve the above aim it has been sub divided into three research questions, which are

1. Supplementary aim – 1 What is Energy use in the Pulp and Paper

Industry in Sweden and the world and identify latest energy saving practices and technologies,

2. Supplementary aim - 2 What is the installed capacity, present steam and electricity consumption of the drying machine installed at the mill considered in the thesis,

3. Supplementary aim - 3 Quantification of the identified energy saving opportunities; based on a comparison between the latest energy saving technologies available with the drying machines and those installed at the mill.

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1.3 Methodology of the study

The research methodology of the thesis consisted of the following steps:

1. Literature survey - In order to make the framework of the research on improvement of energy efficiency of the pulp dryer machine, a detailed literature survey on the subject was carried out. This was done with the help of books on the subject, technical journals and websites of the companies which are either making the drying machines or its components. It helped to make a list and also understand the latest energy efficient technologies available for the drying machines in the pulp and paper industry.

2. Data collection – Secondary data collected from the plant records were

used in the thesis. It included installed capacity of the machine and other machine details, monthly steam consumption, monthly electrical consumption, vacuum pump design details, press system etc. This data helped in understanding the present technology, equipment type, process details in the mill.

3. Quantified electricity and steam conservation opportunities

The quantification of electricity and steam based upon various opportunities to improve the energy efficiency of the drying machine were then identified by making a comparison between the latest energy saving technologies available and best practices in the pulp drying machine (made available through literature survey) with respect to the present machine installed at the mill studied in the thesis (made available through the secondary data).

The above method was chosen as it assisted in making a preliminary survey for the identification and quantification of energy efficient technologies for the pulp drying machines. In cases where on site actual measurements of electricity, steam, pressure etc. are not permitted to be carried out (like in this study), this method is quite helpful as it uses the existing, easily obtained data from the plant, and estimate the scope for savings. The results obtained here would set a reference point and depending upon the estimated savings potential, would encourage the mill to identify areas, projects that need more detailed measurements before further action.

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1.4 Limitation of the thesis

There were certain limitations in carrying out the direct power, steam and the measurement of other parameters in the mill studied in the thesis. Hence secondary data made available by the plant team has been used to carry out the efficiency analysis.

1.5 Structure of the thesis chapters

The thesis has been presented in seven chapters with bibliography at the end. In the first chapter, which is the present one, an introduction and a brief about the problem handled in the thesis has been given. Also the purpose of the thesis, methodology adopted, limitations of the study and schemes of the various chapters are presented. Chapter two provides an overview of energy efficiency and the need

of energy efficiency. In chapter three the energy use in Sweden has been discussed. It also provides and overview about the industrial sector and the energy use in Swedish pulp and paper sector.

In chapter four details regarding the total annual production and total annual electricity and steam energy consumption in the two drying machines studied in the case study mill have been provided. In chapter five the energy analysis has been carried out by using the secondary data. Based on analysis, energy conservation opportunities have been identified and proposed for implementation. In chapter six the results have been provided. In chapter seven the results of the thesis have been discussed and concluded.

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2. Energy Efficiency

2.1 Concept of energy efficiency

2.1.1 Introduction

Energy efficiency refers to achieving equal amount of output or services by utilizing a lower energy input. Energy is not only required as an input in industrial processes but is also needed in the domestic circles to provide a quality life to the mankind. The oil crisis in 1970’s in the United States of America led to the development of the concept of energy efficiency (Nilsson L, Larson E, Gilbreath K and Gupta A, 1996).

. This further promoted the interest in finding energy efficient solutions and energy

savings for supply security and economy. Another important driving force for the energy efficiency solutions are the significant challenges to both sustainable economic growth and environmental protection posed by the climate change and global warming. Industrial Energy Efficiency can be improved by various means, including management, technology, policy and regulatory strategies (Abdelaziz, Saidur, & Mekhilef, 2011).

Environment is directly affected by the energy use through the extraction and consumption of natural resources for fuel and climate changes due to burning of fossil fuels. Almost thirty - three percent of the global energy use is consumed by the manufacturing industries (International Energy Agency (IEA)). The cost effective path to reduce consumption of energy and green - house gas emissions is the energy efficiency in the industry (Siitonen, S, 2010).

10 Use of certain indicators, activity level, sector structure and energy efficiency

(Phylipsen, D. Energy Efficiency Comparisons among Countries) provide and idea about the consumption of energy and about the level of energy efficiency that exists in the industry. They could play a big role for the evaluation of energy efficiency policies and also for the identification of savings potential.

Comparing the of two same sector industries on the basis of their energy performances can lead to the identification of energy savings potential in the production processes (Asia-Pacific Economic Cooperation (APEC), Energy Efficiency Indicators). This could then further be made on an international basis which would then help in making of energy policies either for the whole economy or any specific sector. Classification of the potential energy savings can be made on the basis of three main points - technical, economic and market potential. Commonly used indictor for the energy efficiency which is used in the industry is the SEC (Specific Energy Consumption).

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It shows the energy consumed per tonne of production. It is a good indicator for

the industries that consume large amounts of energy and could be a little difficult to identify the SEC where the production processes are highly integrated (Vakkilainen, E.; Kivistö, A. Energy Consumption Trends and Energy Consumption in Modern Mills in Forest Industry Production).

2.2 What is energy efficiency?

It is defined as a way of managing and restraining the growth in energy consumption. An equipment is more efficient in energy use if it delivers more output for the same energy input or the same services for a less energy input (International Energy Agency). Another comprehensive definition is “the percentage of the total energy input to a machine or equipment that is consumed in useful work and not wasted as useless heat” (Business Dictionary).

3. Energy is Sweden

Sweden is a country with one of the highest per capita energy usage in the world (IEA, 2007). A large part of its energy system is dependent on the imports of the nuclear fuel for the generation of electricity in the nuclear reactors and also oil, natural gas which is used in its transport system. A part of its energy system is also based on renewable energy such as wind, bio fuel and water. It is the fifth most electricity consuming country per capita in the world (SEA, 2005). Its electricity production is mainly based upon hydel and nuclear but it is now slowly expanding in the field of wind energy and use of biofuel to generate electricity and heat production. The countries that have higher electricity consumption per capita are Iceland, Norway, Finland and Canada. The prices of electricity in Sweden are low as the major chunk of the electricity generation is done through hydro and nuclear power. Hence there is a little incentive for saving of electricity (Trygg, 2006; Nord-Ågren and Moshfegh, 2003).

The energy use in Sweden can be divided into three user sectors namely the industrial sector, transportation sector and the residential sector. Biofuel and electricity are primarily used in the industrial sector. This sector contributes to a very high energy usage due to existence of energy intensive industries such as paper – pulp and steel industry (SEA, 2005). The transportation sector uses energy in the form of fuels and electricity.

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Fuels are mainly oil products such as petrol, diesel and aviation fuel. District heating, electricity, oil or biofuels are mainly used in the residential service sector. The cold climate through a great part of the year increases the heating demand for buildings. The details about the supply and use of energy in Sweden is shown in Figure 3.1 below,

3.1 The industrial sector

Figure: 3.1 Energy Supply and use in Sweden 2013, TWh

(Swedish Energy Agency and Statistics Sweden, 2013)

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Heavy Industries including pulp and paper as well as basic metal production formed the basic of the Swedish industrialization from the 1890s and onwards, This is turn implied an energy and pollution intensive sector in Sweden. Today the manufacturing industry accounts for 40 percent of the total domestic energy use. In year (Energy transition in the Swedish Pulp and paper industry, Magnus Lindmark, Ann Kristin Bergquist , Lars Fredrik Andersson ). In 2013 a small percentage (around 1%) reduction in the energy usage was observed as compared to year 2012. This accounts for close to 40% final energy use by the industry in Sweden (Trygg L, 2006). From the Figure 3.2 which shows the final energy use by the energy carrier it is clear that electricity and biomass are the main energy carriers in the industries in Sweden. Electricity constituted around 35 percent whereas biomass constituted around 38%. Oil products, coal and natural constituted for around 23 percent and the remaining 3 percent was accounted for District heating in the Swedish Industry in 2013.

Figure: 3.2 Final Energy Use in the Industry, by Energy Carrier 1971 – 2013, TWh

(Swedish Energy Agency and Statistics Sweden, 2013)

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After the oil crisis of the 1970s, efforts were made to decrease the use of oil in the

industrial sector. In 2013, oil products accounted for 7 percent as compared to 48 percent in the year 1971 of the total energy use. Out of the total industrial energy use the proportion of electricity has jumped from 21 percent in 1970 to 35 percent in 2013. The use of biomass has also increased from 21 percent to 38 percent of the total energy used by the industry.

Biomass is mainly used to large extent in the pulp, paper and wood products industry.

3.2 Energy use in swedish pulp and paper industry

Pulp and paper, the iron, steel and chemical industry account for around 66 percent of the total energy use in the industry in Sweden. The percentage of the total energy use by the various industrial sectors is shown in Figure 3.3 below.

Figure: 3.3 Final Energy Use in the Industrial sector, by industry, percent

(Swedish Energy Agency and Statistics Sweden, 2015)

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Sweden ranked third in terms of export of paper products and fourth with regard

to pulp. It is estimated that the export of pulp and paper was as high as 80 percent in the year 2005 (SFI 2005). Pulp and paper industry in Sweden is very energy intensive and process optimization is considered as prerequisite to compete with similar industries across the world. The contribution of the Swedish Pulp and Paper Industry to Sweden’s GDP is around 6 %. More than 85 % of the pulp and paper products produced in Sweden are exported around the world. The pulp and paper industry of Sweden is ranked third in Europe, after Germany and Finland. ( The Swedish Forest Industries Federation, 2010a). Table 3.1 below shows the sector shares of total consumption of fuel and electricity.14 Industrial sectors have been considered. Pulp / paper account for a large part of the total energy consumption in the Swedish Industry; 30.6 % Fuel and 49.5 electricity (Svensson et al., 2012).

Table: 3.1 Sector shares of fuel and electricity in relation to total industrial energy

use 2000 – 2008

(Industrial energy demand and energy efficiency – Evidence from Sweden,

Tommy Lundgrena, Per-Olov Marklunda and Shanshan Zhanga)

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The Swedish industry consists of around 60 mills and employs around 27,500 workforces. It also accounts for around 6 percent of the Swedish aggregated production value and 50 percent of the aggregated domestic industrial energy use (Swedish Forest Industries Federation 2005 and Swedish Energy Agency 2006). The magnitude of energy savings may vary from mill to mill. Research in pulp and paper industry in Finland has shown the economic saving potential of around 10 – 15 percent in case of fuels and between 1 to 4 percent in case of electricity, the average payback period of around 2 years (Hietaniemi and Ahtila P2007). It can be noted from above that the potential in heat savings is much higher as compared to savings in electricity.

The Swedish pulp and paper industry is dominated by a very small number of mills. It is to be noticed that around 12 largest paper mills produce 70% of the total paper capacity and 6 largest pulp mills account for 65% of the pulp capacity (Swedish Forest Industries Federation, 2010b).

There are three basic means of producing pulp: mechanical, chemical and chemical–mechanical. While the chemical pulp process mainly uses biomass as the primary energy source, the mechanical pulp process uses more electricity. The pulp and paper industry of Sweden uses around 50TWh of biomass, 22.9 TWh of electricity and 7.3 TWh of fossil fuels. The dependency of fossils fuels has been gradually reduced since the 1970’s. The chemical pulp mills also generate about 5 TWh of electricity through the use of back pressure turbines (Swedish Forest Industries Federation, 2007). One of the reasons could be due to energy efficiency improvements, as the Swedish pulp and paper industry has the reputation of being one of the most energy efficient industries in the world (Nilsson et al. 1996), constant reduction in the use of fossils fuels and increase in the use of electricity (SEA 2007).

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4. The case study mill

The case mill studied in this thesis is a typical Swedish pulp mill. The mill produces bleached pulp in a few different qualities that demands a little bit different amount of energy among them. It has an annual capacity of 540,000 tons and employs around 330 people.

Total electricity and steam consumption by the drying machine A and drying

machine B in the year 2015 is shown in Figure 4.1 and Figure 4.2 respectively

Figure: 4.1 Total electricity and steam consumption by drying machine A

(Plant data, 2015)

Figure: 4.2 Total electricity and steam consumption by drying machine B

(Plant Data, 2015)

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The yearly total production in drying machine A and drying machine B is shown below. Air dry tons (Adt) is a weight measurement for the selling of pulp. The plant aims to have 90%fibres and 10% moisture.

Figure: 4.3 Total production in drying machine A (Year 2015) – 170128 Adt (Plant data, 2015)

Figure: 4.4 Total production in drying machine B – 124806 Adt (Plant data, 2105)

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5. Energy conservation opportunities

5. 1. Replace liquid ring vacuum pumps with turbo vacuum blowers

The vacuum System of the drying machine A and drying machine B was studied for energy saving possibility.

Present Status

Pulp making requires large volumes of water and dewatering is a crucial part of the process. Assisted traditionally by a liquid ring pump system, the vacuum system is in fact the second largest consumer of energy after the drying machine. In a vacuum system run by a frequency converter-high speed motor combination, vacuums and dewatering can be monitored and controlled accurately and reliably, and the vacuum levels required by the process can be achieved without losses in air flow or valve pressure. The result is improved control over the wet end of the process. Optimized solutions contribute to higher pulp quality and substantial savings in the costs of energy and water. They also reduce the impact on the environment. It was observed that the currently liquid ring vacuum pumps are being used to generate the vacuum which is used to remove the moisture from the pulp.

Figure 5.1 shows a water ring vacuum pump below

Figure:5.1 Water ring vacuum pump

(water ring vacuum pumps.com)

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The details and working of the liquid ring vacuum pump is as follows. A liquid

ring vacuum pump consists of a cylindrical body and a sealant fluid. This sealant fluid under the influence of the centrifugal force forms a ring against the inside of the concentric casing. This force is created by a multi-bladed impeller whose shaft is mounted in such a way so as to be eccentric to the liquid ring. This arrangement, results in suction to continuously draw out the gas from the vessel being evacuated as the pockets bounded by the impeller blades which are next to each other and the increase in size of the ring on the pump inlet side. The rotation of the blades towards the discharge side of the pump results in reduction of the size of the pockets and hence the evacuated gas is compressed leading to its discharge.

The water ring not only acts as a seal but also helps to absorb the heat of

compression, friction and condensation. Any liquid may act as a ring but it should not vaporize at the process conditions. Liquids such as water, ethylene glycol, mineral oil and organic solvents are used in the liquid ring vacuum pumps.

These liquid ring pumps (water) has the following limitations:

a) They have poor power efficiency, especially with low vacuums

b) The control range is limited as the water ring could break or collapse after

a certain point

c) These pumps require large amount of water use and also cooling towers.

d) Need for bacteria control

e) The method used to control the capacity is bleed valve vacuum control,

which highly un economical.

f) The wear and tear of these pumps results in drop of its efficiency

g) Heavy investment on building and foundation; heavy construction with low

frequencies (Runtech Info Centre News)

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Turbo vacuum blower system shown in Figure 5.2 below, is specially developed for paper sheet dewatering and felt conditioning on paper, board, tissue and pulp machines. The ecological and economic advantages offered by them effectively enhance the competitiveness of the production processes.

Figure: 5.2 Turbo vacuum blower

(Ecopump Turbo System)

Turbo vacuum blowers are aimed at not only controlling and adjusting capacity,

but also on other areas such as water saving, light foundation, compact size, light

weight, easy and fast maintenance, etc.

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The advantages of the turbo vacuum blowers are given below

1. Power savings:

It is basically a combination of modern high-speed electric drive and high efficiency turbo blower. Speed control from zero to maximum without any limitations in the operating range can be achieved with the help of a frequency converter. It should be noted that even small saving in the vacuum capacity would lead to significant savings in the electric power. Vacuum capacity can be efficiently controlled through speed adjustments.

The estimated power savings with the turbo blower vacuum system, compared with a liquid ring pump system, gives an estimated savings of about 60% of the power consumed earlier. Savings of this extent are made possible by both improved pumping efficiency and the speed control provided by the AC drives.

2. Water savings: They also help to reduce the annual water consumption. It is due to the fact

that the new system does not require any sealing water. In addition to the savings in water consumption, improvements in electrical and mechanical performance and process quality have also met expectations. Furthermore, changes in the wet end of the process due to the new system have also resulted in increased production volumes.

3. Savings in space:

Use of turbo vacuum blowers also leads to saving of space. The turbo impellers are directly mounted on the motor shaft, which makes the system very compact and mechanically reliable. No gearbox or couplings are needed. The solid shaft AC motor is robust and has no resonance frequencies within the operating range. Cast titanium or our latest carbon composite impellers are mechanically and chemically very stable. As the water separators also operate as collectors, the minimum amount of piping is used

4. Improving the system reliability and maintenance:

The system is made compact and mechanically stable due to the direct mounting of the turbo impellers on the motor shaft. Oil lubricated ceramic ball bearings and lightweight parts make the system easy to handle from maintenance point of view. Hence the system is also easy to handle from the maintenance point of view. Turbo blower and separator are close each other, hence there is no condensing problem in inlet piping of turbo.

5. Heat recovery potential:

Recovering the energy used for pumping air, makes the energy balance superior. Entire power which is used to generate vacuum is transformed into process air heat in a Turbo air vacuum blower, whereas in water ring pump, this heat is transferred to seal water (Reese, J.R).

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This makes it important to cool the water which requires additional cost. This

heat could be recovered: especially in high vacuum positions this results to high temperature air, which makes recovery very feasible. This hot air could be taken into an exchanger, to heat process water or to heat the hood supply air (Turb air vacuum systems for pulp and paper industry)

Table 5.1 and Table 5.2 below shows the list of the Liquid Ring vacuum pumps which were identified in the Drying Machine A and Drying Machine B respectively. It is proposed to replace them with Turbo Vacuum Blowers with speed control drives.

Table: 5.1 Drying machine A vacuum pumps

Sno Vacuum Pump Rated Savings (kW)

Number kW

1 1 75 37.5

2 2 75 37.5

3 3 55 27.5

4 4 66 33

5 8 132 66

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Table: 5.2 Drying machine B vacuum pumps

Sno Vacuum Pump Rated kW Savings (kW)

Number

1 1 75 37.5

2 3 132 66

3 4 90 45

4 5 110 55

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5.2 Use shoe press in the press section

The press section of the drying machine A and drying machine B were also studied for energy saving possibility. It was observed that currently the mill is using pre dryers for the drying machine A and drying machine B.

The pressing technology of paper machines is presently progressing very rapidly. New types of presses are being developed and introduced in the industry.

We can classify them into three types: high-impulse presses that have

wider roll diameters and thus higher loads; shoe presses where the lower roll is replaced by a shoe that follows the exact shape of the upper roll. They have much wider nip and much higher loads and hot presses where the web is pressed against a moderately heated central roll (Wedel, G. 1993)

.

Shoe press technology is an exemplary technology as it improves the dewatering capacity. It does so by extending the time that the pulp sheet remains in the press nip. This time is referred to as the nip residence time (Wahlstrom, B. 1991). The quantity of water removed in the pressing section is proportional to the magnitude and the duration of the pressure applied to the sheet. ‘Press Impulse’ is referred to as the product of pressure and nip residence time [MacGregor, 1989; Pikulik, 1999].

In the shoe press, the nip consists of a stationary shoe, which is loaded against a press roll whereas in a roll press it is a conventional bottom roll. Felts are required for transporting the water from the press. A belt or sleeve forms the shell that runs between the mechanical press and the bottom felt. On the inside of the belt oil is supplied which acts as a load transfer medium and also provides lubrication between the stationary shoe and the moving belt.

The higher the dry content of the pulp web after leaving the press section,

the less energy has to be expended in subsequent drying. A high initial wet strength of the moist pulp web after leaving the press also leads to a lower number of breaks, especially in the first dryer groups. This is essential for good runnability of the entire production facility. Along with its main task, namely dewatering the paper, the press also has a big influence on the quality characteristics. It decisively influences thickness and volume, as well as the surface characteristics (Pikulik, I.I. (1999).

Difference between the pressure profile of a conventional roll press and that of a shoe press is shown in Figure 5.3 below. The areas under the curves are the press impulse (1 psi = 6.9 kN/m2).

22

Figure: 5.3 Difference between the pressure profile of a conventional roll

press and that of a shoe press. (Schiel, 1992)

The difference in the cross-section design of a roll press and a shoe press is shown in Figure 5.4. It can be seen that the shoe press on the far left has an open loop belt. The other three designs have a closed belt or sleeve. Figure: 5.4 Cross-section of a conventional roll press nip and various shoe press

designs (Schiel, 1992)

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Higher dryness achieved at the exit of the press section is the major advantage of the shoe press. As compared to the rolling press, the increase is about 5 to 10 %, depending upon the grade produced. This results in a better runnability [Wedel, 1993]. Runnability is defined as how smoothly paper runs through a paper or board machine or printing press without breaking the sheet [CEPI, 2000].

The increased dryness levels also lead to an increase in the production

capacity around 10 to 20 %. It is when the shoe press is put on an existing (dryer limited) pulp, paper or board machine (Lange, D.V. 1996). The capital expenditure is reduced due to the shortening of the drying, when the shoe press is implemented on a new pulp or paper machine.

Another advantage is the reduction in the steam demand in the drying

section. This leads to an improvement in the energy efficiency in spite of a minor or no increase in the electricity consumption (Optimizing the Energy Efficiency of conventional multi cylinder dryers in paper industry Jobien Laurijssen, Frans J De Gram, Ernst Worrell, Andre Faaij).

Among papermakers there is a rule of thumb: "an increase by 1% dryness after the press, will result in thermal energy savings of roughly 4%". This rule holds for constant production, that is unchanged machine speed (Establishing The Scientific Base for Energy Efficiency in Emerging Drying and Pressing Technologies - C. Bermond). Or in terms of kWh/tonne, an increase by 1% dryness after the press will roughly give you thermal energy savings of 60kWh/tonne. A shoe press may give you an increased dryness after the press of up to 4%, whereby the savings in thermal energy are correspondingly higher.

Shoe press also provides improvement in the production characteristics (Mirsberger, P. 1992a). Since most physical and surface characteristics of the pulp are in a way related to the density of the sheet, the pressing section is very important for the properties of the pulp.

Pressing causes densification [Lange, 1996; Mirsberger, 1992a]. However,

the effect of a shoe press on the properties may differ according to the grades produced. It also causes a favorable increase in the strength properties. This the results in saving in refining, the use of fewer strength additives, and the application of cheaper furnishes. With the installation of a shoe press increased dryness levels can be achieved without reducing the thickness of the sheet [Wahlstrom, 1991; Mirsberger, 1992a]. This results in cost savings by reducing the amount of fiber needed [Lange, 1996].

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Table 5.3 shows the low pressure steam (3 bar) and medium pressure steam

(11 bar) consumed by drying machine A and drying machine B in the year 2015.

Table: 5.3 Annual steam consumption in tons (year 2015)

DM A DM B

3 bar 72990 155199

11 bar 165185 20351

Total 238175 175550

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5.3 Use low pressure steam in the drying machines

During the analysis it was observed that the mill is using medium pressure steam (11 bar) at the dryers of drying machine A and drying machine B. Use of medium pressure steam is not recommended in the dryers as it adds to the cost of operation of the dryers due to its high generation cost.

Steam at low pressure (3 bar) which is available in the mill should be instead

used to run the dryers. This would not only improve the performance of the dryers but would also reduce the cost of operation of the dryers due to the low cost of generating low pressure steam as compared to medium pressure steam. This is the trend for all new machines and major rebuilds where there is low pressure steam available. (Pulp and Paper Energy Best Practices by Tappi).

Use of low pressure steam eliminates venting excess steam to the atmosphere; and facilitates reducing main high pressure boiler operation. The plant has installed steam ejectors which allows the use of both medium pressure and low pressure steam.

The total monthly steam consumed by the drying machine A and drying machine B is given in the table 5.4 below (Plant data,2015)

Table: 5.4 Total medium pressure steam consumption in tons (Plant data,2015)

11 bar

Drying Machine A 165185

Drying Machine B 20351

185536

26

Figure 5.5 shows the monthly medium pressure steam (11 bar) consumption in tons by the drying machine A and drying machine B in the year 2015 respectively.

Ste

am

( T

on

s)

25000

20000

15000

10000

5000

0

Jan Feb M ar Apr May Jun Jul Aug Sep Oct N ov Dec

Months

DM

A

DM B

Figure: 5.5 Medium pressure (11bar) steam consumption (tons) in the drying machine A and B (Plant data, 2015).

27

A cost analysis was then performed to evaluate the generation cost of medium pressure and low pressure steam. This cost analysis is shown in the Table 5.5. From the above analysis in the table it is concluded that the difference in the cost of generation of medium pressure and low pressure steam is 0.015 SEK / kg of steam. Another advantage of low pressure steam is that it can generate more electricity than medium pressure steam.

Table: 5.5 Cost analysis of low pressure and medium pressure steam

Cost in SEK/MWh

Heat Content Cost

LP Steam

6.02euro/ MWh

57 SEK/MWh 77 x 10-5 MWh /kg

0.044 SEK/kg

MP Steam

7.63euro/ MWh

73 SEK/MWh 81 x 10-5 MWh /kg

0.059 SEK/kg

Calculation details

1. The cost of low pressure steam (LP steam) = 6.02 euro / MWh and medium pressure steam (MP Steam) = 7.63 euro / MWh has been taken from the plant data,

2. The cost in euro/MWh was then converted to cost in Swedish Kroner (SEK)/ MWh by using the currency exchange rate (1 euro = 9.57 SEK)

3. Heat content is defined as the amount of energy in it, which is capable of

doing work. The heat content of low pressure is 670kcal/kg and of medium pressure steam is 700kcal/kg.

4. The value in kcal / kg is then converted to MWh/kg by using the conversion

1 kcal = 11 x 10 -7 MWh, which gives the heat content in MWh/kg,

5. The cost of steam (in SEK/MWh) is then multiplied by the heat content (in MWh/kg) to get the final cost of steam in SEK/kg.

6. From this we can then find out that the difference in the cost of generation of

medium pressure steam as compared to low pressure steam is 0.015 SEK/kg

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5.4 Use heat pump to generate medium pressure steam

A heat pump is a device that is capable of increasing the temperature of a waste heat source to a temperature where the waste heat turns useful. This then benefits by replacing the purchased energy with the waste heat and thus reduces energy costs. Heat pumps use waste heat which would otherwise have been rejected to the atmosphere. They deliver heat for less money than the cost of the fuel. They operate on a thermodynamic principle of Carnot Cycle. (Industrial heat pumps for Steam and fuel savings, U.S department of Energy Efficiency and Renewable Energy). Functions of a heat Pump

1. Receives heat from a waste heat source,

2. Increase the temperature of the waste heat and

3. Deliver useful heat at higher temperature

4. Use electricity

The work required to deliver a heat pump depends upon the increase in temperature of the waste heat. Heat pumps consume energy to increase the temperature of the waste heat and result in reduction in the use of purchased steam or fuel. Working of a Heat Pump

Waste heat is delivered to the evaporator of the heat pump resulting in the vaporization of the working fluid in it. The compressor then increases the pressure of the working fluid that results in increase of the condensing temperature. The working fluid then condenses in the condenser and delivers high temperature heat to the process steam that is being heated (Industrial heat pumps for Steam and fuel savings, U.S department of Energy Efficiency and Renewable Energy).

(Opportunities for integration of Absorption heat pumps in pulp and paper process, Bahador Bakhtiari, Louis Fradette, Robert Legros, Jean Paris )

COP of heat pump = The coefficient of performance or COP (sometimes CP) of a heat pump is a ratio of heating or cooling provided to work required. Higher COPs equate to lower operating costs. The maximum COP is given by:

COPmax= Thigh / (Thigh-Tlow).

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From the temperature taken from the plant, Thigh = 403.15 K and Tlow = 333.15 K. The COPmax is around 5.7. This is theoretical COPmax. The actual COP would be around 3.

The plant uses boiler which run on black liquor and bark as fuel to generate steam. Steam is then used in the various processes and a part of it is also used to generate electricity from the turbine installed in the plant. Since the mechanical heat pump runs on electricity and delivers heat, its use could prove costly if the electricity bought from the grid is used to run it. But if the electricity which is generated in the plant by the use of the turbine, it could give benefit. Since the electricity consumption would depend upon a number of factors including design details, number of stages of the mechanical heat pump so this could be further investigated by the plant team and a decision could be made in this regard. It was observed that the case study mill is currently using medium pressure steam for pulp drying in the drying machine A and B. This medium pressure steam is being generated from the boiler installed in the plant.

The individual monthly and total consumption of the medium pressure steam (11 bar) in the drying machine A and drying machine B is shown in Figure 5.5 (refer to page 27) and Table 5.4 (refer to page 26).

Waste heat was lost from the pulp mill through the ventilation air of the drying section. A part of this waste heat can be recovered by the use of a compression heat pump. This will not only save 10 % on the present steam usage but will also generate steam for the drying process. Heat pumps also require minimum maintenance.

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5.5 Replace V belts with flat belts for the motor power transmission in the drying machines

It was observed that the mill is currently using V Belts for power transmission from their motors in the pulp drying machines. V belts are energy in-efficient as they have frictional engagement between the lateral wedge surfaces of the belt profile, large bending cross section, large mass and different effective diameter and different speeds of individual belts. They also cause bearing damage due to vibrations, fluttering as the tensions in the belt is uneven due to different effective diameter.

Use flat belts in place of V belts. Flat belts are energy efficient, longer life – 2.5 to 3 times higher than conventional V Belts and gives energy savings of around 4 to 5 % (Habasit AG). The efficiency of the flat belt, typically peaking at over 98%, is not only higher but the efficiency gap widens for light loads.

As flat belts are engaged on the outer pulley diameter and not on the lateral

surface as the V belt, less wear and tear is caused on the belt surface and the pulley hence have a better life.

A flat belt also has the following advantages 1. For the same load, flat belts are much thinner than V-belts, leading to much

lower hysteresis losses;

2. Frictional Engagement on the outer pulley diameter

3. Small bending cross section area, small mass

4. Precisely defined effective diameters across the belt width

5. Exact speeds (Technology Assessment – Energy Efficient Belt Transmissions, Anibal De Almeida, Steve Greenberg)

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The list of motors identified with V belts in the drying machine A and drying machine B is shown in Table 5.6 and Table 5.7. It also shows the rated power of these motors.

Table: 5.6 List of motors with V Belts in drying machine A (Plant data, 2016)

Sno Area Name Rated kW

1 Motor 1 150

2 Motor 2 150

3 Motor 3 32

4 Motor 4 30

Table: 5.7 List of motors with V Belts in drying machine B (Plant data, 2016)

Sno Area Name Rated kW

1 Motor 1 2 x 18

2 Motor 2 18

3 Motor 3 132

4 Motor 4 132

5 Motor 5 160

6 Motor 6 160

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5.6 Replace metal halide lamps with LED lamps

It was observed that the plant was using around 64 numbers of 400 W metal halide lamps in the drying machine A and drying machine B area.

At the start metal halide lamps have fairly high lumen output, but lumen

output depreciates very fast. Lumens (denoted by lm) are a measure of the total

amount of visible light (to the human eye) from a lamp or light source. The higher the lumen rating the “brighter” the lamp will appear. It is observed that the lighting output starts to decline just as soon as the power is turned on to the new bulb. When the metal halide lamp reaches to 40% of its rated life, it has lost around 30-40% of light output, and as low as 40% of its initial lumens by the end of lamp life.

Light emitting diodes are semiconductor devices filled with gases and coated with different phosphor materials. On the contrary a light emitting diode lamp fades very slowly. Well-designed LED lamp fixtures are able to retain 70% of their initial output up to 100,000 hours (Analysis of the performance of domestic lighting lamps – M.M Aman, G.B Jasmon, H. Mokhlis, A.H.A Bakar).

This depends upon operating conditions and other factors. At 24 hours per

day of continuous use, such fixtures can deliver useful light for eleven years or longer — five times as long as metal halide sources (Alb Energy Solutions). Lamps and ballasts experience losses when operating together as a system. This is called as the fixture loss. There are also no lumen fixture losses in LEDs as compared to upto 30 % in metal halides.

These 400 W metal halide lamps can be easily replaced with 200 W light emitting diode lamps (165 W Bulb + 35 W Ballast). It gives 20,000 initial lumens and has an estimated life of 50,000 hours. Lasts 2.5 times more as compared to an HID lamp.

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6. Summary of energy conservation opportunities

The main aim of the study was to identify the opportunities to improve the energy efficiency of the drying machine in the mill. In order to work on it we further sub divided it to 3 supplementary aims, which were,

1. To know the energy use in pulp and paper Industry is Sweden and identify the energy efficiency opportunities in the drying machines,

2. What is the present Installed capacity, steam and electricity consumption of the drying machines

3. Quantification of the energy saving potential based upon a comparison of the technologies.

The summary of savings projected is shown in Table 6.1.

Sno. Energy Conservation Savings per Annum

Opportunities

Drying Drying

Machine A Machine B

1 Replace Liquid Ring Vacuum 1700 MWh 1750 MWh

Pumps with Turbo Vacuum

Blowers

2 Use Shoe Press in the Press 4400 MWh 550 MWh

Section

3 Use Low Pressure Steam in the 350 MWh 40 MWh

Drying Machines

4 Use Heat Pump to generate 1200 MWh 140 MWh

Medium Pressure Steam

5 Replace V belts with Flat Belts

120 MWh 200 MWh

for the motor power

transmission in the plant

6 Replace Metal Halide Lamps 50 MWh

with LED Lamps

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From the table we can see that the identified opportunities promote the need to use energy efficient technology. Use of turbo vacuum pumps, shoe press in the press section, low pressure steam in the drying machines, heat pump to generate medium pressure steam, use of flat belts and light emitting diode lamps would help in saving a considerable amount of energy.

This study undertaken has been successful in getting answers to the research

questions energy use in Sweden pulp and paper Industry has been mentioned in Figure 3.3 and Table 3.1. The steam and electricity consumption of the two drying machines is presented in Figure 4.1 and Figure 4.2. Six energy efficiency opportunities were identified during the study on the drying machine A and drying machine B. Lastly, six energy efficiency opportunities identified. The details of which are presented in point 5 of the contents.

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7. Conclusions and discussions

A study for the identification of energy saving opportunities in the pulp drying machines to improve the energy efficiency was undertaken in a case study pulp mill in Sweden. It was subdivided into three further research questions.

The thesis also demonstrates that significant energy savings potential is

available through the identified six energy efficient improvements in the two studied drying machines of a pulp mill. The total proposed energy saving potential in the drying machine A and drying machine B is 10450 MWh. The benchmarking of energy intensity index for the two drying machine shows that drying machine A has the high energy saving potential as compared to drying machine B. In the drying machine A saving potential is 7770 MWh and the proposed saving potential in drying machine B is 2680 MWh.

Of the six energy-efficiency improvement opportunities identified on the basis of

the latest energy saving opportunities and calculation of energy savings in the pulp case study mill studied in Sweden were use of shoe press in the press section and replacing liquid ring vacuum pumps with turbo vacuum blowers. These measures should be taken up on a first priority basis. The main decision however remains with the case study mill team. The installation of the heat pump is based upon a number of factors including design, efficiency, electricity consumption etc. This can be further analyzed in the future work or by the plant team. Installation of Shoe press would give highest energy saving potential in drying machine A and replacement of liquid ring vacuum pumps with turbo vacuum blowers in drying machine B. The other measures also save a considerable amount of energy and can be taken on a second priority basis.

The Specific steam consumption per production for drying machine A is 830 kWh / Ton of sales production and for drying machine B is 1003 kWh/ Ton of sales production. The difference is because both the drying machines manufacture different grades of pulp.

The methodology which was followed to carry out this study has been very

helpful in making a preliminary survey for the identification and quantification of energy efficient technologies for the pulp drying machines. This method is quite helpful as it uses the existing, easily obtained data from the plant, and estimate the scope for savings. This is best possible solution in case where actual on site measurements of various parameters could not be done, either due to legislations or due to non-availability of measuring instruments. In this thesis work actual measurements were not allowed on the site and the data from the records was provided by the mill were used. So the accuracy of the results is heavily dependent upon the accuracy of the data obtained from the mill. As a conclusion the results obtained here would set a reference point and depending upon the estimated savings potential, would help the mill to identify areas, projects that need more detailed measurements for further action.

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8. References Assessment of Emerging Energy Efficiency Technologies for Pulp and Paper industry -A technical review, Lingbo Kong, Ali Hasanbeigi, Lynn Price (Journal of cleaner production 122 (2016) 5 - 28) The case study of Energy Flow analysis and strategy in Pulp and Paper Industry Hua-Wei Chen, Chung – Hsuan Hsu, Gui Bing Hong (Energy Policy 43 (2012) 448 – 445) Strategic energy management in energy-intensive enterprises: a quantitative analysis of relevant factors in the Austrian paper and pulp industry – Alfred Posch, Thomas Brudermann, Nina Braschel, Magdalena Gabriel (Journal of Cleaner Production 90 (2015) 291 – 299. Improving Dryer energy efficiency and controllability simultaneously by process modification, J.C Atuonwu,G.van Straten, H.C van Deventer,A.J.B van Deboxtel (Computers and Chemical Engineering 59 (2013) 138 – 144) Energy transition, carbon dioxide reduction and output growth in the Swedish Pulp and paper industry 1973 to 2006 , Magnus Lindmark, Ann Kristin Bergquist , Lars Fredrik Andersson (Energy Policy 39 (2011) 5449 – 5456) The case study of energy flow analysis and strategy in pulp and paper industry, Hua Wei Chen, Chung Hsuan Hsu, Gui Bing Hong Energy Efficiency in German Pulp and Paper Industry / A model based assessment of saving potentials, Tobias Fleiter, Daniel Fehrebach, Ernst Worrell, Wolfgang Eichhammer. (Energy 40 (2012) 84 - 99) Establishing The Scientific Base For Energy Efficiency In Emerging Drying And Pressing Technologies - C. Bermond (Centre Technique du Paper, Domaine Universitaire, BP 251, 38044, Grenoble, cedex 9, France) Comparison of Energy Parameters in various Dryers, Ali Motevali, Saeid Minaei, Ahmad Banakar, Barat Ghobadian, Mohammad Hadi Khostaghaza (Energy conversion and management 87 (2014) 711 - 725) Optimizing the Energy Efficiency of conventional multi cylinder dryers in paper industry Jobien Laurijssen, Frans J De Gram, Ernst Worrell, Andre Faaij (Energy 35 (2010) 3738 – 3750) Opportunities for integration of Absorption heat pumps in pulp and paper process, Bahador Bakhtiari, Louis Fradette, Robert Legros, Jean Paris (Energy 35 (2010) 4600 – 4606)

37

Technology Assessment – Energy Efficient Belt Transmissions, Anibal De Almeida, Steve Greenberg (Energy and Buildings 22 (1995) 245 - 253) Analysis of the performance of domestic lighting lamps – M.M Aman, G.B Jasmon, H. Mokhlis, A.H.A Bakar (Energy Policy 52 (2013) 482 - 500)

Pressing – the state of the art and future possibilities, in: Paper Technology, February 1991, pp. 18-27, Wahlstrom, B. (1991)

Shoe pressing of paper grades, in: Proceedings 1996 TAPPI Papermakers Conference, pp. 435-438, Lange, D.V. (1996), Shoe press concept can meet quality needs for graphic paper applications, in: Pulp and Paper, April 1992, pp. 87-89, Mirsberger, P. (1992a),

Optimization of paper machine dryer section. Proceedings of 7th International Conference on Pulp, Paper and Conversion Industry, New Delhi (2005), Ghosh, A.K. Habasit AG http://www.habasit.com/en/belt-design.htm accessed on 6 May 2016. Pulp and Paper Energy Best Practice Guidebook, Tappi May 2006 Energy conservation agreements within Finnish pulp and paper industry – methods and results. Available at: http://www.motiva.fi/, last accessed April 8, 2016 Hietaniemi and Ahtila P2007 Advances in pressing and drying, in: Paper, February 1993, pp. 31, Wedel, G. (1993) TurbAirVacuum Systems http://turbomachinery.man.eu/docs/librariesprovider4/Turbomachinery_doc/turbair- vacuum-systems.pdf?sfvrsn=4 accessed on 10 April 2016

Effects of shoe pressing on fine paper properties, in: TAPPI Journal, vol. 82, no. 11, pp. 88-92, Pikulik, I.I. (1999)

Energy efficiency and the pulp and paper industry. Report number IE962. Washington (DC): American Council for an Energy-Efficient Economy; 1996. Nilsson L, Larson E, Gilbreath K and Gupta A, 1996

High humidity hoods conserve energy and improve runnability, Tappi Engineering Conference, p653 (1988), Reese, J.R. A review on energy saving strategies in industrial sector. Renewable and Sustainable Energy Reviews, 15(1), 150-168, Abdelaziz, E. A., Saidur, R., & Mekhilef, S. (2011).

38

Energy management practices in Swedish energy-intensive industries. Journal of Cleaner Production 18(12): 1125-1133, Thollander P, Ottosson M, 2010.

International Energy Agency (IEA). World Energy Outlook 2011; IEA: Paris, France, 2011.

Implications of Energy Efficiency Improvement for CO2 Emissions in Energy-Intensive Industry. Ph.D. Thesis, Aalto University, Helsinki, Finland, 2010, Siitonen, S.

Energy Efficiency Comparisons among Countries. In Encyclopedia of Physical Science and Technology, 3rd ed.; Meyers, R.A., Ed.; Academy Press: New York, NY, USA, 2003; pp. 433–440, Phylipsen, D

Asia-Pacific Economic Cooperation (APEC). Energy Efficiency Indicators: A Study of Energy Efficiency Indicators for Industry in APEC Economies; APEC: Tokyo, Japan, 2000.

Energy Consumption Trends and Energy Consumption in Modern Mills in Forest Industry Production; Technical Report LUT/Energy-RR—10; LUT Energy: Lappeenranta, Finland, 2010, Vakkilainen, E.; Kivistö,A

International Energy Agency http://www.iea.org/topics/energyefficiency/ (accessed on 10 February 2016)

Business Dictionary http://www.businessdictionary.com/definition/energy- efficiency.html (accessed on 10 February 2016)

IEA (International Energy Agency), 2007. Key World Energy Statics. OECD/IEA, France

SEA (Swedish Energy Agency), 2005. The Swedish Energy Market. Eskilstuna, Sweden Swedish industrial and energy supply measures in a European system perspective. Linköping Studies in Science and Technology, Dissertation No.1049, Linköping University, Linköping, Sweden, Trygg L, 2006.

Electricity use and connected CO2- emissions for cooker manufacturing in Denmark, England and Sweden – A benchmarking study,In Proc. of ACEEE Summer Study in Energy Efficiency for Industry, New York, USA., Nord-Ågren E and Moshfegh B, 2003.

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