improvements in sustainable energy and water practice...
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Improvements in Sustainable Energy and Water Practice In
the Food Processing Industry:
An in Depth Analysis of the Manufacture of Ghee at the
Butter Producers’ Co-operative Federation Limited,
Brisbane.
This thesis is submitted for the award of the degree of Master of
Engineering in the School of Engineering Systems,
Queensland University of Technology,
Brisbane.
July 2005
By Darryl Markwell
Student Number 04589947
Supervisor: Dr Richard Brown
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Acknowledgements
Many people have assisted in the preparation of the thesis; many more have been
involved in modifying the plant. The ideas for modifications have come from several
sources.
The person who started me on the journey for “Cleaner Production” would be Gerry
Hall who was the Chief Engineer at Sunny Queen Egg Farms’ factory. He was doing
this thirty years ago.
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Statement of Original Authorship
I hereby certify that the work contained in this thesis is all my own original work and has not been submitted for a higher degree to any other University or Institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made.
Signature:
Date:
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Abstract
This thesis is a documented energy audit and long term study of energy and water
reduction in a ghee factory. Global production of ghee exceeds 4 million tonnes
annually. The factory in this study refines dairy products by non-traditional
centrifugal separation and produces 99.9% pure, canned, crystallised Anhydrous
Milk Fat (Ghee). Ghee is traditionally made by batch processing methods. The
traditional method is less efficient, than centrifugal separation.
An in depth systematic investigation was conducted of each item of major equipment
including; ammonia refrigeration, a steam boiler, canning equipment, pumps, heat
exchangers and compressed air were all fine-tuned. Continuous monitoring of
electrical usage showed that not every initiative worked, others had pay back periods
of less than a year. In 1994-95 energy consumption was 6,582GJ and in 2003-04 it
was 5,552GJ down 16% for a similar output.
A significant reduction in water usage was achieved by reducing the airflow in the
refrigeration evaporative condensers to match the refrigeration load. Water usage
has fallen 68% from18ML in 1994-95 to 5.78ML in 2003-04.
The methods reported in this thesis could be applied to other industries, which have
similar equipment, and other ghee manufacturers.
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Flow chart of thesis
MethodologyChapter 3
Possible savingsChapter 8
AchievementsChapter 9
ConclusionChapter 10
Company historyChapter 1
Literature reviewChapter 6
Ghee descriptionChapter 4
Energy AuditChapter 7
ProjectChapter 2
Process descriptionChapter 5
Figure a: Flow chart of thesis
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Table of Contents
1 Butter Producers’ Co-operative Federation Ltd ________________________ 1 1.1 History _____________________________________________________ 1
1.2 Factory environmental impact ___________________________________ 2 1.2.1 Environmental Practices ___________________________________ 2 1.2.2 Discharges to Atmosphere __________________________________ 3 1.2.3 Discharges to trade waste and sewer __________________________ 4 1.2.4 Other waste (Contract waste removal) _________________________ 4
2 The project ______________________________________________________ 5 2.1 Project objectives _____________________________________________ 6
3 Methodology ____________________________________________________ 8 3.1 Assessment flow chart description ________________________________ 9
3.1.1 Performance Criteria ______________________________________ 9
3.2 Evaluation _________________________________________________ 12
3.3 Research for improvements ____________________________________ 13
3.4 Modification justification ______________________________________ 13
3.5 Implementation _____________________________________________ 14
3.6 Process assessment conclusion _________________________________ 14
3.7 Unsuccessful changes ________________________________________ 14
4 Ghee __________________________________________________________ 15 4.1 Ghee Description ____________________________________________ 15
4.2 Ghee specifications __________________________________________ 15
4.3 Ghee uses __________________________________________________ 16
4.4 Critical processing factors: ____________________________________ 16
4.5 Refining Process ____________________________________________ 17 4.5.1 Refining process equipment ________________________________ 17 4.5.2 Refining process operation ________________________________ 17 4.5.3 Processing overview _____________________________________ 19
5 Literature review ________________________________________________ 20 5.1 Literature review background __________________________________ 20
5.1.1 Reviewed resources ______________________________________ 21
5.2 Alternative sources of Milk Fat _________________________________ 21
5.3 Ghee properties crystallisation __________________________________ 24 5.3.1 Ghee colour ____________________________________________ 25
5.4 Processing and separation parameters ____________________________ 26 5.4.1 Refining process temperature ______________________________ 27 5.4.2 Temperature for vacuum drying ____________________________ 28
5.5 Energy Efficiency ___________________________________________ 29
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5.6 Conclusion _________________________________________________ 31
6 Energy and water audit ___________________________________________ 32 6.1 Building ___________________________________________________ 34
6.1.1 Air conditioning _________________________________________ 34 6.1.2 Lighting _______________________________________________ 36 6.1.3 Cold rooms _____________________________________________ 37 6.1.4 Lifts __________________________________________________ 37 6.1.5 Energy use proportions ___________________________________ 37
6.2 Storage ____________________________________________________ 39 6.2.1 Packing materials ________________________________________ 39 6.2.2 Butter and AMF _________________________________________ 39 6.2.3 Liquid storage __________________________________________ 39
6.3 Processing/refining __________________________________________ 40
6.4 Crystallisation ______________________________________________ 43
6.5 Canning plant _______________________________________________ 43
6.6 Dispatch ___________________________________________________ 44 6.6.1 Containerisation _________________________________________ 44
6.7 Services ___________________________________________________ 44 6.7.1 Boilers ________________________________________________ 44 6.7.2 Hot water ______________________________________________ 46 6.7.3 Ammonia refrigeration ____________________________________ 46 6.7.4 Compressed air__________________________________________ 48
6.8 Electricity usage _____________________________________________ 48 6.8.1 Waste streams __________________________________________ 54 6.8.2 Waste water ____________________________________________ 54
6.9 Benchmarking ______________________________________________ 54
6.10 Energy and Water Audit Conclusion _____________________________ 56
7 Future savings __________________________________________________ 57 7.1 Heat exchanger ______________________________________________ 57
7.2 Hot oil packing ______________________________________________ 58
7.3 Atmospheric cooling of hot oil _________________________________ 59
7.4 Improvement of refining process ________________________________ 60 7.4.1 Cream processing ________________________________________ 60
7.5 Processing temperature _______________________________________ 61 7.5.1 Solids removal. _________________________________________ 61 7.5.2 Pasteurisation. __________________________________________ 62 7.5.3 Water removal. __________________________________________ 62
7.6 Wastewater heat recovery _____________________________________ 62 7.6.1 Alternative in feed for refining _____________________________ 64
7.7 Air conditioning _____________________________________________ 66
7.8 Changing electricity tariff _____________________________________ 67 7.8.1 Electrical demand controls _________________________________ 67
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8 An overview of technical improvements ______________________________ 69 8.1 Crystallisation improvements __________________________________ 69
8.2 Refrigeration _______________________________________________ 72 8.2.1 Control of liquid ammonia _________________________________ 73 8.2.2 Timers for air conditioning ________________________________ 73 8.2.3 Cold room temperatures ___________________________________ 74 8.2.4 Heat exchanger for office air conditioning ____________________ 74 8.2.5 Compressor cooling water pump ____________________________ 74 8.2.6 Water usage reduction ____________________________________ 74 8.2.7 Water pumping__________________________________________ 76
8.3 Production improvements _____________________________________ 77 8.3.1 Ghee Supply ____________________________________________ 79 8.3.2 Filling machines _________________________________________ 80 8.3.3 Jacketed tube product transfer ______________________________ 83 8.3.4 Refining process control __________________________________ 84 8.3.5 Reducing the cooling load _________________________________ 85
9 Conclusion _____________________________________________________ 87 9.1 Water usage ________________________________________________ 88
9.2 Energy usage _______________________________________________ 88
9.3 The future __________________________________________________ 91
10 Bibliography _________________________________________________ 92
11 Appendices ___________________________________________________ 94 11.1 Appendix (a) Tetra-Pak schematic for cream processing _____________ 94
11.2 Appendix (b) Punrath cream processing __________________________ 95
11.3 Appendix (c) Polymorphic behaviour of Butter oil __________________ 96
11.4 Appendix (d) Centrifugal separator ______________________________ 97
11.5 Appendix (e) Old crystallising vat _______________________________ 98
11.6 Appendix (f) Air conditioning calculations ________________________ 99
11.7 Appendix (g) Compressed air usage table ________________________ 100
11.8 Appendix (h) Comparison of electricity charge rates _______________ 101
11.9 Appendix (i) Hot water usage _________________________________ 102
11.10 Appendix (j) Hot water heating ________________________________ 103
11.11 Appendix (k) Water bill comparison ____________________________ 104
11.12 Appendix (l) Electrical energy use _____________________________ 105
11.13 Appendix (m) Pump power efficiency ___________________________ 108
11.14 Appendix (n) Refining process throughput _______________________ 109
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Index of Figures Figure a: Flow chart of thesis…………………………………………………………v
Figure 1: Opened can of ghee. ...................................................................................... 1 Figure 2: Process assessment flow chart. ...................................................................... 8 Figure 3: Refining process schematic. ....................................................................... 19 Figure 4: Evidence of butter oil polymorphism. (BPCF, 1999) ................................. 27 Figure 5: Water and energy use 1994-2004. ............................................................... 33 Figure 6 energy and water used to produce 1 tonne 1995-2004 ................................. 33 Figure 7: The factory. ................................................................................................. 34 Figure 8: Pie chart of percentage of energy used 1994-95 ......................................... 38 Figure 9: Pie chart of percentage of energy used 2003-04. ....................................... 38 Figure 10: Production flow chart. ............................................................................... 41 Figure 11: Refining process flow chart. ...................................................................... 42 Figure 12: Seasonal energy usage profile, 2001-2002. ............................................... 49 Figure 13: After hours electrical load. ........................................................................ 50 Figure 14: Base electrical load. ................................................................................... 51 Figure 15: Production electrical load. ......................................................................... 52 Figure 16: Refining and cooling electrical load. ......................................................... 53 Figure 17: Wastewater heat recovery PINCH diagram. ............................................. 63 Figure 18: BPCF butter block rework machine. ......................................................... 64 Figure 19: Four t/hour butter rework machine. ........................................................... 65 Figure 20: Crystallisation vats. ................................................................................... 70 Figure 21: Reduction in crystallisation times after changes. ...................................... 70 Figure 22: New crystallisation vat. ............................................................................. 71 Figure 23: Comparison of refrigeration compressor run hours. ................................. 73 Figure 24: Photograph of old water pump in the foreground and the replacement on
the left. ................................................................................................................ 77 Figure 25: Typical can closing machine. .................................................................... 78 Figure 26: 4lb can filling machine. ............................................................................. 81 Figure 27: Refining process automatic controls. ........................................................ 84 Figure 28: Changed electrical load profile. ................................................................. 89
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Index of Tables Table 1: Process energy comparison. .......................................................................... 26 Table 2: Water boiling point at different vacua. ......................................................... 29 Table 3: Butter refining heating. ................................................................................. 45 Table 4: Refining energy usage comparison. .............................................................. 55 Table 5: Extract from Refrigeration Coefficient Of Performance table (Lommers,
2003). .................................................................................................................. 72 Table 6: Water usage. ................................................................................................. 75
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Abbreviations AIRAH The Australian Institute of Refrigeration Air conditioning and Heating
Inc.
AMF Anhydrous Milk Fat
ABO Anhydrous Butter oil
BOD Biological Oxygen Demand–used in wastewater to measure biological
activity
BPCF Butter Producers’ Co-operative Federation Limited
COP Coefficient of Performance. Mechanical power input compared to
refrigeration effect.
CT Current Transformer–used as a transducer for monitor electrical current
flow
EPA Environmental Protection Agency
in hg Inches of Mercury, which is an old measure of vacuum, i.e. the vacuum
supports a column of mercury x inches high.
KPI Key Performance Indicator
kW kilowatt
kWh kilowatt–hour–a unit of electrical energy
kWr kilowatt refrigeration
LPG Liquefied Petroleum Gas
L/s Litres/sec
MJ Mega Joule–a unit of energy (=3.6kWh)
PLC Programmable Logic Controller– used to control industrial process
RAC Refrigerated Air Conditioner–wall mounted air conditioner
ROI Return on investment–used in relation to capital expenditure
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t Metric tonne
TDS Totally Dissolved Solids–a measure of chemical impurities in water.
VSD Variable Speed Drive–used to electrically control motor speed by
altering the frequency
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1 Butter Producers’ Co-operative Federation Ltd
1.1 History1 The Co-operative was constituted on 29th February 1926 under The Primary
Producers Marketing Organisation Act of Queensland as the Queensland Butter
Board. Its purpose was, to market the commodity butter, produced in Queensland.
Its main function was price fixing for sales on the Queensland market.
It remained in an administrative capacity up until 1936. The State Government and
the Dairy Association then approved the establishment of a processing plant in
Brisbane to wrap and pat butter for distribution to the Brisbane Metropolitan area.
In 1946 the name of the organisation was changed to the Butter Marketing Board.
The operations of the Board were moved to the present site of operation at 489
Kingsford Smith Drive in 1955. The factory was built to pack butter and has evolved
into a Ghee canning plant.
The Board had another change of name in 1990 to its current name, Butter Producers'
Co-operative Federation Limited (BPCF).
BPCF was a world pioneer in manufacturing Ghee from butter (with centrifugal
separators2). During the Second World War the board (in conjunction with the
CSIRO) developed an Anhydrous Milk Fat
(AMF) product called Butter Concentrate.
Production of Ghee commenced soon after.
BPCF processing techniques produce the
traditional style Ghee that is packed in cans.
The BPCF business is now comprised of Ghee
manufacture mainly for export. Current
production of Ghee is approximately 3,500t/year.
Figure 1: Opened can of ghee.
1 Compiled from Board notes and “History of C.W. Coombs, M.B.E.” 2 Appendix (d) has an illustration and explanation of a centrifugal separator
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1.2 Factory environmental impact The BPCF has operated its factory with cleaner production techniques for many
years. The management is committed to continually improving our environmental
performance.
1.2.1 Environmental Practices
Dairy processing and packaging, by its nature, involves the efficient management of
liquids. This is the main focus of the BPCF’s practices. Production is seasonal and
BPCF makes to order.
The environmental impact of the company is very important and government bodies
monitor performance. The main bodies are:
• Environmental Protection Agency. The BPCF has an EPA license to operate at
the premises.
• National Pollutant Inventory requires annual reports on energy usage
• The National Packaging Covenant. The BPCF is a signatory to the national
packaging covenant.
• Workplace Health and Safety has the BPCF registered as a large dangerous
goods site.
All of these identities are interested in the environmental footprint from at least one
aspect of BPCF environmental initiatives
Recycling activities
• Raw material packaging (cartons or drums) is sold for reuse
• Waste cardboard (damaged cartons etc) is recycled
• All waste liquid from the refining process is centrifuged to remove fat from the
trade waste discharge. This results in no Biological Oxygen Demand (BOD)
surcharges on trade waste discharge
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• Waste lubricating oil is recycled
• Unusable waste butterfat is given to another company, for reuse as an animal
food supplement
• Empty can packaging (pallets and cardboard) is returned to can suppliers for
reuse
• Second-hand disposable pallets are used for product dispatch.
Reduction in packaging
• The can wall thickness was reduced by 20%. This may seem trivial, but 25t of
steel is used for cans annually.
• There is minimal excess packaging with product
• Can wastage is a Key Performance Indicator (KPI) for employee bonuses.
Wastage is running at 0.59%
• The volume and mass of waste have been reduced.
These practices have reduced running costs and selling used cartons returns
approximately $20,000 per year.
1.2.2 Discharges to Atmosphere
1.2.2.1 Condenser Discharges
The refrigeration system operates water-cooled evaporative condensers, which
discharge warm moist air. Rated3 discharges from evaporative condensers:
• Induced draught (600kWr) discharges 10.9m3/s of air.
• Induced draught (600kWr) discharges 10.9m3/s of air.
• Forced draught (800kWr) discharges 12.6m3/s of air.
3 Theoretical rating of the condensers at 35deg C
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The condensers are fitted with drift eliminators. The condenser water is treated with
chemicals for Legionella control. The wastewater with high Totally Dissolved
Solids (TDS) is bled off into the trade waste.
The towers are cleaned every three months and the basins refilled. There is
approximately 500L per basin.
1.2.2.2 Boiler flue gas and steam
Boiler No.14 (Maxitherm) is unattended natural gas fired of 1MW capacity. A
certified serviceman services it every five weeks.
The volume of flue gas emissions is approximately 66,644m3/month at
approximately 2000C. The wastewater with high TDS is bled off into the trade waste.
1.2.3 Discharges to trade waste and sewer
Approximately 500kL of wastewater per month goes through grease traps before
discharge to trade waste. A contractor empties the solids from the grease traps as
required.
The fat is skimmed off and recycled off site by a waste removal contractor.
1.2.4 Other waste (Contract waste removal)
Sludge from butter refining, approximately 1,500L per week, is removed by a
contractor. The sludge contains neutralised fatty acids, non-fat milk solids, salt,
caustic soda and water.
A contractor removes dirty cartons and plastic as required.
4 Although Boiler No.2 (electric) is on the premises it is not used.
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2 The project The aim of the project was to investigate and document the reduction of energy and
water usage while fulfilling production, quality, safety and environmental
requirements.
Food-processing factories have many aspects. This thesis is specifically about
changes in a factory’s operations, which affect energy usage and water consumption.
An energy audit established consumption in various areas, such as air conditioning,
packing, boiler and refrigeration. It was found that approximately 80% of the energy
was used for heating and cooling mainly in the refining and crystallisation processes.
Continuous monitoring over the period would show if any measures were effective in
reducing electricity and water consumption. The audit identified waste streams such
product rework, heat energy, wastewater and general refuse.
The literature review determined Ghee qualities, potential alternative raw materials,
and critical process parameters. Worldwide many other companies produce Ghee
(2,000,000t/year each in India and Pakistan). Advanced work practices from other
factories and the energy audit (above) were used to determine the reduction strategy.
The body of published literature relating to Ghee manufacture is based on traditional
batch process Ghee manufacture. This requires heating the raw material to
temperatures greater than 1000C and holding for 30minutes, to precipitate solids and
dehydrate the oil. At various stages the oil is “washed” to remove some impurities.
Batch processing requires more energy and water than continuous processing. BPCF
continuous processing achieves traditional Ghee properties using centrifugal
separators, with a lower usage of resources. Before any changes were made, Ghee
quality characteristics were established.
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2.1 Project objectives
The diversity of the options makes planning decisions difficult. However most
feasible cost effective items would be undertaken first. Energy usage reduction is
the primary objective. This will be achieved by implementing the following
proposals:
1. The refining process.
• Improve the refining process control and tune the equipment
• Establish critical product processing parameters such as lowering the
process temperature would reduce the heating and cooling required.
• Assess alternative sources of milk fat such as cream
• Consider different methods of handling 25kg blocks of butter such as
Microwave heating
2. Pumping of fluids (either water or oil) around the factory have two major
issues.
• Temperature control of the fluid
• Energy required to pump the fluid
3. The crystallisation process has two major issues.
• Heat transfer from hot oil to the refrigerant
• Producing enough quality product for production needs
4. The refrigeration system effectiveness could be improved by:
• Lowering the refrigeration load by either better control (timers) or adjusting
temperatures.
• Increasing the Coefficient Of Performance (COP)
5. Boiler efficiency improvements can be either:
• Improving the energy usage efficiency i.e. steam available for energy input
• Reducing the boiler load
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6. Factory improvements
• Machine malfunctions in the packing process is a waste of energy and
materials
• Compressed air is an energy hungry resource. To be effective it needs
special measures and leak minimisation.
7. Water usage reduction generally does not have good ROI because it is low
cost. However if someone or something is using water, then other resources
are being used while the water is wasted. A reduction in water usage results
in other savings.
Enhancing existing equipment rather than expending capital on new equipment
improves the factory potential production capacity and lowers overheads.
It must be noted that low production volumes limit savings. Higher production
utilises the equipment better and justifies different proposals. Outside influences
affect energy consumption such as:
• Ambient air temperature affects air conditioning load
• Incoming butter temperature, frozen butter, reduces the refrigeration load but
increases the boiler load.
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3 Methodology
This flow chart5 (Figure 2) is the methodology behind changes. It is explained in detail
on the next pages.
Assess procedure/activity andestablish perfromance criteria
for current input, time orwaste.
Gather data.Box No.1
Research possibleimprovement and designs.
(Talk to operators)Box No. 3
implement improvement/training.
Box No. 5
ElvaluateIs it possibile to improve?
Box No.2
Is improvementjustifiable?Box No.4
Are improvementseffective?Box No.6
Yes
Yes
Yes No
No
Bad design?Box No.9
NoNo
Yes
Bad implementation/training?Box No.8
Yes
Maintain monitoring to observeif other factors influence
performance.Box No.7
The improvementoutcomes are the
new baseline
No
Figure 2: Process assessment flow chart.
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3.1 Assessment flow chart description
The chart illustrates the assessment process. It was adapted from a similar chart
(Barringer and Associates, 2002). The chart and assessment process have changed as
the project has progressed. Initially the emphasis was on reliability and fault
elimination.
As equipment became more dependable, productivity and energy considerations
assumed importance. Establishment of performance criteria is difficult because
everyone has his own perspective and priorities.
Safety is not mentioned because it is taken for granted that unsafe equipment or
practices are not condoned, in any circumstance.
The performance evaluation is critical. One of the performance criteria is electrical
energy usage. A selection of recorded electrical usage is shown section 11.12.
If a process is operating at optimum efficiency then it is low priority, because there is
always something else to do. If it is inefficient and evaluated as acceptable then
ineffectiveness is accepted.
3.1.1 Performance Criteria Figure 2: Process Assessment Flow chart. Box No.1
The performance criterion varies with the application. In this section the performance
criteria used over the last decade will be identified. The criteria show the
improvements in the performance of the plant. The three main criteria have been:
• Energy usage
• Water Usage
• Production.
These criteria have been used by (Sserunjogi et al., 1998) and (Punjrath, 1974) to
evaluate performance in their papers.
Based on flow chart from Barringer & Associates, 2002
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Measurement of Performance Criteria
Each performance criteria must be accurately measured to monitor changes over time.
Appropriate instrumentation for this measurement will now be described.
Energy
The two forms of energy used in the plant are electricity and gas. The energy supplier
meters each and monthly accounts have been recorded for the last decade. Such coarse
monitoring is useful for a historical macroscopic view of energy usage but is
insufficient for saving energy on a micro level. The latter includes items such as
electric motors, refrigeration, air compressors etc. Reading fixed instruments is used
for metering individual items. The data is then entered into a database and accessed as
required.
Electricity
Electricity is supplied to factory on three tariffs (shown section 11.8) through four
meters:
• Tariff 20 general supply has two meters. Fixed rate for 24-hour supply.
• Tariff 31 off peak supply used for hot water.
• Tariff 37 is used for the electric boiler, which is now decommissioned.
The supplier metering is insufficient for establishing time of use and load profiles.
BPCF use sub metering to identify usage of individual items. Once a pattern is
established, it is surprising how the trends can be predicted, unless there is an
improvement.
• There is independent on site metering and recording tariff 20 supply usage. It
has 600:1 CTs6 on incoming power lines. The CTs are connected power
meters, which are linked to a computer and consumption recorded
automatically every 10 minutes. Some of the recorded data is shown in
section 11.12
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• Refining process electricity supply is monitored in the same manner as tariff
20 metering
• Refrigeration compressor running hours are recorded every week to indicate the
refrigeration activity but not actual kWr load. It would have been better to
record kWh used. This was not done because there were limited resources.
• VSD have memories and displays. The memory records useful data, such as
kWh. There 35 VSDs through the factory. It is a very useful source of
information.
• Hand held devices such as tong testers7 are used for monitoring amperage
drawn by motors
• A lux meter was used for checking the lighting levels around the factory
• An anemometer and electronic physchrometer was used for tuning the air
conditioning
• Packing lines are fitted with hour meters, which are read and recorded daily.
All the recorded data is stored in an access database. The large files are sorted by
queries and either exported to Excel for graphs or printed as reports.
Water
Water is supplied by SEQ Water and billed quarterly (prior to 1998 bills were monthly
because of the large usage). In 1995-6 the water meter was read on a daily basis to
investigate usage by specific operations, which were using excess water. There is no
sub metering of water.
Production
Production is split into three areas:
• Refining
• Crystallisation
• Packing.
Refining
6 Current transformers (CTs) are used to detect electrical current flow in wires, without the current actually going through a meter.
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There is a flow meter and electricity metering for the refining process:
• The electricity usage is recorded automatically,
• The flow meter is used on the output from the refining process and the daily
throughput is recorded in an access database.
The production output can be directly compared against kWh used to provide
processing costs. In 1998 average output was 37.5t of refined oil per day. Currently
BPCF refine 47t/day.
Crystallisation
The temperatures of each vat in the crystallisation process are also recorded
automatically. The data is transferred to an access database. Graphs generated show
the crystallisation performance, see Figure 21.
Packing
All packing line outputs are recorded on run sheets. The data, which includes run
hours, is hand entered into an access database. During production the cans are check
weighed.
There is an enterprise agreement with the employees. They are paid a bonus on certain
Key Performance Indicators (KPI). The two relevant KPI are kg packed/ man-hour and
can wastage.
3.2 Evaluation Figure 2: Process Assessment Flow chart. Box No.2
There are many parameters to be considered in evaluating equipment and performance.
Evaluations are tailored to suit the circumstances of equipment or process. The first
thing to be evaluated is the data itself. Is the information accurate? Meters can fail.
Correlation of data from two sources is preferred.
7 Tong testers clamp onto electrical cables to show the current flow through that cable.
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Some evaluations are done over a period of time such as monitoring electricity usage.
Others are observation of displays or gauges. E.g. check a VSD display for amperage
drawn and confirm with a tong tester.
Temperatures are checked with infrared temperature sensor, which shows the surface
temperature of any item, process or liquid. It is a good way to check of performance
and operation.
There are many tools to assist the audit process. When there is a quantity of data e.g.
electricity usage readings, a spreadsheet is used to make charts for clear presentation.
Charts are a good method of evaluating trends and highlighting variations.
The evaluation outcome prioritises the next step, if there is no feasible change, then the
status quo is accepted. If there is a possible saving then research is undertaken into the
project.
3.3 Research for improvements Figure 2: Process Assessment Flow chart. Box No.3
When a potential improvement is identified, many times the solution is obvious.
Refinement of the solution to a workable outcome is the hardest part. Ideas are the key.
They can come from numerous sources.
When the information is gathered and organized the idea is put together. It is designed
in accordance with ergonomics, maintenance, simplicity and safety considerations.
3.4 Modification justification Figure 2: Process Assessment Flow chart. Box No.4
Justification is based on several criteria not just “Return on Investment” (ROI). Other
factors considered are safety, life cycle cost, reliability, maximum utilisation of plant,
easier operation and product quality. E.g. process improvement with the crystallisation
vats was not justified with a two-year payback period. The possibilities of product
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contamination with agitator gearbox lubricating oil or process-chilled water were
reasons for purchase. Other projects have pay back periods as short as six months.
3.5 Implementation Figure 2: Process Assessment Flow chart. Boxes Nos.5 and 6
The implementation of a new idea is critical, and usually difficult. Will the idea work?
What has been forgotten? Will employees embrace the idea or reject it e.g. employees
rejected the fitting of movement sensors on lights in storage areas. The employees
would not wait for the fluorescent lights to illuminate and claimed it was a safety issue.
Even though lights shining in unoccupied areas are wasteful.
Installation of new plant changes work practices and expectations. In the short term
implementation is a process of close supervision to see that predicted results occur. If it
is not working properly, then more modifications are necessary to ensure a successful
transition. In the long term supervision of successful modifications can be limited to a
regular casual inspection and monitoring performance criteria.
3.6 Process assessment conclusion Figure 2: Process Assessment Flow chart. Box No.7
There is no finish. Continuous assessment confirms that modifications are
improvements. The improved performance is the baseline for the next improvement.
Most times statistics can be determined by two methods to validate conclusions.
Constantly monitoring established performance criteria is a good assessment of how
the factory is performing. Most problems compound from a small anomaly to a major
malfunction if left unattended.
3.7 Unsuccessful changes Figure 2: Process Assessment Flow chart. Boxes Nos. 8 and 9
The ability to learn from mistakes and admit a failure cannot be underestimated. If an
unforeseen circumstance occurs or change does not work then the faults have to be
rectified.
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4 Ghee
The Koran refers to Ghee. It is commonly used in other cultures as a religious entity
and cooking medium. India and Pakistan make nearly 2,000,000t/year.
The name varies from culture to culture8 and in some countries it includes vegetable
oils. This project is only concerned with “Dairy Ghee”, even though the vegetable oils
have similar composition (triglyceride based).
BPCF packs all Ghee produced into steel cans. The purity and packaging ensures
product longevity and quality. Ghee packed in this manner is given a three-year use by
life.
4.1 Ghee Description
The most appropriate description for the BPCF Ghee is Anhydrous Butter Oil (ABO),
but generally it is called Anhydrous Milk Fat (AMF) (Dairy Consultant, 2002, pg. 6).
• “AMF must contain at least 99.8% Milk Fat and be made from fresh cream or butter.
No additives are allowed, e.g. for neutralisation of free fatty acids.
• ABO must contain at least 99.8% Milk Fat but can be made from cream or butter of
different ages. Use of alkali to neutralise free fatty acids is permitted.
• Butter oil must contain at least 99.3% milk. Raw material and processing
specifications are the same as for Anhydrous Butter oil”.
4.2 Ghee specifications
The BPCF product specifications are:
1. 99.9% pure Milk Fat and less than 0.1% water: Dairy Ghee is derived from
purified Milk Fat. Milk Fat consists of many types of triglycerides. The triglycerides
have different characteristics e.g. Melting temperature from 37-600C and varying
8 Roghan, Vasparci, Sapi are some names, each with variations in spelling
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densities. BPCF Ghee has lower water levels than ABO because impurities such as
high water levels reduce shelf life,
2. Peroxide value (milli-equivalents of O2/kg) less than 1: Used as indication of
oxidisation of unsaturated fatty acids. High oxidation levels indicate that the product
is rancid,
3. FFA level less than 0.3% (as oleic acid) High Free Fatty acid levels can be an
indicator the product is rancid,
4. Crystallisation: Visually evident crystalline structure is preferred. Consumers
(world wide) consider crystals a sign of purity. Crystals are formed during the
cooling of the pure hot oil. Depending on the crystallisation process large or small
crystals are formed,
5. Taste: Taste is variable according to location and background. Some users
prefer stronger flavours. Ghee produced by BPCF has a mild aroma and taste,
6. Colour: A yellow colour9 is also a sign of freshness in Dairy Ghee.
Overheated Ghee and Ghee made from buffalo milk is white,
7. PH: The pH of Ghee is slightly alkaline.
4.3 Ghee uses
• As a cooking medium, for frying, garnishing, or as food additive in pastries and
sweets.
• For religious events, a wick is placed in the Ghee and lit like a candle.
4.4 Critical processing factors:
Factors that can affect ghee characteristics during processing are:
o Stored bulk Ghee requires steady agitation to maintain a homogenous liquid.
If the Ghee is motionless, the various triglycerides settle into layers. This is
called fractionation. The layers have different characteristics.
Each can produced should have similar levels of high and low melting point fats,
9 Yellow colour caused by a high level of carotene
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o Ghee must not come into contact with brass or copper fittings. Copper causes
oxidation of the oil
o Ghee should not be stored at elevated temperatures for long periods.
Oxidisation rates are higher above 550C.
o After crystallisation the Ghee temperature should not be raised above 450C.
Crystal “memory10” could be lost.
o Ghee characteristics can be changed with inappropriate handling e.g. aeration
of Ghee.
4.5 Refining Process
4.5.1 Refining process equipment The refining process equipment is: • Three centrifugal separators
• Two butter shredders
• Variable speed controlled positive displacement lobe pumps
• A multi-stage water pump used to generate a vacuum
• Hot air extraction and cooling fans
• Air diaphragm pumps and centrifugal pumps.
4.5.2 Refining process operation The raw materials are 25kg cartons of butter, 1t palecons11 of AMF and 200kg drums
of AMF. Butter blocks are removed from the cartons and placed on the in feed
conveyor. At the other end of the conveyor a plastic wrapper is removed and the butter
blocks are shredded. AMF is liquefied and pumped to the melting tank.
The shredded butter falls into the melting tank and is heated by direct injection of dry
steam12. The melted butter (650C) is pumped through a filter to a neutralising vat where
an air diaphragm pump doses caustic soda. The caustic soda neutralises the Free Fatty
Acids (FFA) in the liquid butter. The operator adjusts the rate of dosing to suit the
particular type of raw material.
10 The Ghee crystalline structure is retained even if the Ghee is melted to clear oil. Crystals reform as soon as the temperature falls. This reforming is called crystal memory. 11 Integrated container and pallet used for bulk shipment of liquid products. 12 Condensate is trapped and returned to the boiler feed water tank.
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Neutralised Milk Fat is pumped through a filter and plate heat exchanger to separator 13
No.1. The heat exchanger raises the product temperature to 850C. Separator No.1
output (95% Butter oil) is mixed with hot water and pumped to separator No.2. The
hot water forms droplets in the oil. Contaminants are attracted to the droplets, which
are removed by separator No.2.
Output from separator No.2 (99.5% pure butter oil) is pumped to vacuum deodorisers.
The water in oil emulsion is atomised in a vacuum at elevated temperature. The water
immediately boils and is drawn off. The output from deodorisers is better than 99.9%
pure butter oil at 850C.
Pumps transfer the oil to storage tanks, where it is stored until crystallisation.
Approximately 55t of raw material is processed in a day producing more than 47t of oil
at 850C.
All liquid waste removed from separators No.1 and No.2 is pumped to separator No.3.
It separates the waste into three streams: -
Sludge is pumped to a storage tank, for disposal offsite
Wastewater is discharged via a sump to trade waste (more than 25,000L/day)
Oil recovered by separator No.3 is returned to the melt vat for reprocessing.
While the principles of centrifugal separation are not unique to the BPCF process it has
evolved from a different source to other processes. The BPCF process has enough
subtle differences to warrant interest.
Butter is used in traditional processing. Some manufacturers use cream for Ghee
production. They generally use centrifugal separation, however most do not crystallise
their product even though it would be possible.
13 For separator operation see 12.4 Appendix (d)
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4.5.3 Processing overview The refining process converts Milk Fat based raw materials into 99.9% pure Butter
oil.
Figure 3: Refining process schematic.
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5 Literature review
5.1 Literature review background
The number of Ghee manufacturers in the western world is limited. No books
dedicated to Ghee manufacture were found. Generally, the information is restricted
to few chapters extracted from dairy processing books, published research, journal
articles and conference papers.
There are many excellent books on energy efficiency and process control.
Information has been obtained from a variety of sources tradeshows and trade
magazines e.g. “The Airah Journal” had an article on improving the efficiency of
water pumps by using VSDs. I acknowledge that this information has been used to
improve factory performance. However I cannot recall the origin of many ideas.
Most Ghee manufacturers are in the Middle East and Asia. There may be more texts
available in that region of the world, written in the local language.
The aim of the literature review is to gather knowledge relating to:
• Alternative sources of Milk Fat
• Ghee properties: crystallisation and colour
• Melting point of Milk Fat
• Processing parameters and alternative manufacturing processes
• Energy efficiency
• Any other relevant details on production.
The literature review includes discussion of some of the process parameters essential
to Ghee manufacture. It concentrates on properties of Ghee, its manufacture and
energy reduction. The review defines process parameters, which require less energy.
The information is used for purposes of comparison of the BPCF operation with that
of other plants. The comparisons in Table 1 confirm that the BPCF plant is much
more energy efficient than plants using traditional methods.
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5.1.1 Reviewed resources
There were a limited number of resources and texts specifically on Ghee. The
published articles are generic because specialised knowledge is the intellectual
property of dairy manufacturers. So the information has been obtained from a
variety of sources. These include:
• A dairy-processing handbook (Tetra-Pak, 1995)
• A submission for cream processing plant modification from a supplier (Tetra-
Pak, 1994)
• Books on the processing of milk fat to obtain butter (Bailey, 1950, Garti and
Sato, 1988, Varnam and Sutherland, 1994)
• An article obtained from a web site sponsored by a dairy consultant (Dairy
Consultant, 2002)
• Two of Indian conference papers (Sserunjogi et al., 1998, Punjrath, 1974)
• An environmental report on the Pakistani Ghee industry (ETPI., 1999)
• Journal articles on various subjects (Campos et al., 2002)
• A local dairy consultant, who has intimate knowledge of the BPCF plant,
offered very useful advice (Parodi, 2003)
• A book written about energy saving (Easthop and Croft, 1990)
• Refrigeration efficiency is described in an AIRAH handbook (Lommers, 2003).
• The Australian standard for conducting energy audits AS/NZS 3598:2000
• A document from an American University on conducting energy audits.
• Other information was obtained from industry sources.
This is not the biggest research knowledge base and sometimes the facts quoted
conflict. However BPCF has the advantage of being able to run trials e.g. one paper
(Aneja et al, 2002, pg. 188) advises quiescent conditions for crystallisation and another
vigorous agitation. Both were tried and vigorous agitation is superior prior to packing
in BPCF operations. However tests have shown that changes do occur in the can after
packing
5.2 Alternative sources of Milk Fat Cream is an obvious alternative raw material because it is 40% Milk Fat. There are
many articles (Dairy Consultant, 2002), (Tetra-Pak, 1994), (ETPI., 1999), (Early,
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1992), (Aneja et al., 2002) relating to the direct processing of cream into AMF. It is
also available from a range of suppliers. It has to be considered because there is
advantages with heat transfer between two liquids the incoming raw material and the
finished processed oil.
One of the articles reviewed (Tetra-Pak, 1995) has a diagram, reproduced section 11.1
showing the extra equipment required for cream processing. The equipment is another
separator to remove excess water and a homogeniser for phase inversion.
Processing fresh cream may cause a problem with crystallisation. “During this
ripening phase, crystallisation processes take place in the fat globules… This results
in the formation of different crystalline structures within the fat globules, and induces
destabilisation process by damaging the fat globule membrane.” (Garti & Sato, 1988,
pg. 306).
(Garti & Sato, 1988, pg. 306) explains phase inversion as: “Before churning, water
represents the continuous and fats the disperse phase in cream, whereas the inverse
applies to butter.” “ Mechanical agitation in the butter making machine causes
destabilisation of the previously stable emulsion cream, which is reflected by the
clumping of the fat to the butter grain. A continuous butter –oil phase is finally
obtained.”
It was said (Dairy Consultant, 2002, pg. 5) “Either the Clarifixator11 or the
Centrifixator14 is used for mechanically liberating the fat and thus allowing for the
phase inversion”.
The previous paragraphs raised a concern regarding the crystallization of refined
fresh cream, which had to be allayed. A local dairy expert (Parodi, 2003) was asked
for his opinion and he made three points:
14 Variations of centrifugal separators
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• The aging of cream does affect the structure. Opinions differ on whether the
changed structure of the cream would survive the BPCF refining process
850C.
• Raising the temperature of aged cream to lower temperatures, probably about
600C, would not damage the structure
• Because BPCF "seed" the hot oil with crystals, the oil would probably
crystallize.
But the cream processing document (Tetra-Pak, 1994) ignores the possibility that the
oil produced would not crystallise, without cream aging or souring. Cream can be aged
or soured by varying temperature (6-250C) over 12 hrs (Dairy Consultant, 2002, pg 2).
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5.3 Ghee properties crystallisation
Ghee production is a commercial process. Customers’ requirements are part of the
process outcome. It is perceived by customers that the visible presence of crystals in
Ghee is a sign of a quality product. Therefore adherence to established characteristics
of ghee quality is essential. BPCF ghee is a quality product.
The statement that “Grain formation is one of the critical attributes affecting consumer
acceptance of ghee” (Aneja et al., 2002, pg. 188) was echoed in other literature. The
perception that the presence of crystals is a sign of purity can be explained by “Impure
oil does not crystallise because impurities absorb onto the nucleus surface and poison
growth sites” (Garti and Sato, 1988, pg. 202)
There are some relevant factors about Ghee production and crystallisation;
• “The emulsion of fresh butter seems to be more difficult to split” (Tetra-Pak,
1995, pg. 282)
• “The slow nature of cooling the Ghee results in the formation of large fat
crystals dispersed in liquid Milk Fat” (Early, 1992, pg. 135)
• The specific heat of Ghee is 1.7kJ kg-1K-1 (Early, 1992, pg. 127)
• The heat conductivity of Ghee 1.7x 10-4 kJ m-1 s -1 K-1 (Early, 1992, pg. 127)
• Cooling is required, at a measured rate. If cooling is constant the rate of
temperature drop varies with phases of liquid. The heat convection required is
increased by agitation. This has the advantage of creating turbulent flow over
the cooling surface. (Parodi, 2003)
• “ The formation of crystals is hastened by stirring to bring the first crystals in
contact with more of the liquid” (Bailey, 1950, pg. 39)
• “….seeding the liquid with a small proportion of crystals from an extraneous
source” is recommended (Bailey, 1950, pg. 36)
• “For nucleation to occur, the molecules of the mother phase must form
embryos that develop further into nuclei and crystals.” (Garti and Sato, 1988,
pg. 194)
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• “Secondary nuclei form whenever tiny crystallites are removed from the
surface (of existing crystals)”. “….vigorous agitation will cause this.” (Garti
and Sato, 1988, pg. 204)
Two factors emerge:
1. Crystal formation will occur as pure aged Milk Fat is cooled
2. Crystallisation may be enhanced by seeding and vigorous agitation.
Seeding is mixing preformed crystals with cool oil (less than 450C). The crystals grow
and propagate.
One article (Tetra-Pak, 1995, pg. 283) also shows hot packing at more than 350C. This
may be common practice and explains why BPCF crystals are different to competitors.
5.3.1 Ghee colour
Fresh Ghee is yellow when cooled. When it used for cooking or after prolonged
exposure to heat, Ghee turns white when cooled. This behaviour is explained by
“Carotenes are coloured yellow because they absorb in the visible region of the
spectrum (about 450nm) as the molecules contain long chains”. The long chains are
broken with oxidation and “then the absorbance frequency is shifted to the ultraviolet,
becoming invisible to the human eye” (Early, 1992, pg. 126). The colour change
occurs because the yellow carotene chains are no longer whole.
The oxidation reaction rate increases with temperature, and can more than double with
every 100C rise depending on the composition of the oil. “Product temperatures
should be kept to a minimum preferably no higher than 550C, to minimise oxidation”
(Early, 1992, pg. 119).
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5.4 Processing and separation parameters
The refining of butter oil is an intricate process. Butter oil can be damaged or wasted
by incorrect techniques so proven technology is essential. The knowledge for process
change will specifically consider maintaining quality when improving the process or
altering the raw materials to reduce energy requirements.
Melting by direct heating (steam injection) leads as a rule to the formation of a new
type of emulsion15 (Tetra-Pak, 1995, pg. 283) needs to be clarified because BPCF
directly inject dry steam as part of the process, without any adverse effects. BPCF have
found wet steam can change the emulsion.
Various articles confirm that centrifugal separators are the most energy efficient
method of purification. The comparison below lists information from two sources:
• Batch processing16–(ETPI., 1999)
• Centrifugal processing–(Punjrath, 1974)
For 1t of oil Batch processing Centrifugal processing
Steam 1.4-3.4t 350kg
Electrical energy 45kWh 4.5kWh
Table 1: Process energy comparison.
The plant layout for different centrifugal separations is similar, see sections 11.1 and
11.2. “To produce 100kg of Ghee, the plant utilizes 32kg of steam and 4.5kWh of
electrical energy” (Punjrath, 1974). This is surprising because the figure is
significantly less than 12kWh quoted in another text (ETPI., 1999, pg. 17).
Both Indian and Pakistani manufacturers also make soap17 as a by-product. It is not
known at this time whether they have more waste or bigger production. BPCF
produces approximately 0.75t/day of potential soap.
15 Superheated dry steam does not change the emulsion, wet steam can. The subtle difference alters the whole process. 16 “In India,….the most common method of producing ghee is by batch process, whereby butter or cream is commonly heated in steam jacketed stainless steel vessels of 500-1,00kg capacity” (Sserunjogi et al, 1998). Batch processing removes the water by heating the oil above 1000C several times. The centrifugal process is typically performed at less than 850C. 17 Neutralised free fatty acids, which are produced during the refining process, are the base of soap.
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5.4.1 Refining process temperature
The energy requirements could be reduced if the refining occurred at temperatures less
than 850C. The review explores whether it is possible to process at a lower
temperature. To establish the melting point of the Milk Fat the composition has to be
identified. “Milk Fat composition depends on the route from which it was derived”
(Early, 1992, pg. 26).
Milk Fat does not have easily defined attributes. A good description is: “Milk Fat is
comprised mostly of triglycerides, with small amounts of mono- and diglycerides,
phospholipids, glycolipids, and lipoproteins” (Dairy Consultant, 2002, pg. 2).
The heterogeneous mix of triglycerides in Milk Fat causes this. There are three main
types Alpha, Beta and Beta Prime18” (Garti and Sato, 1988).
Figure 4: Evidence of butter oil polymorphism. (BPCF, 1999)
18 The triglyceride molecules are different sizes, which impart different characteristics e.g. melting points. These molecules are named Alpha, Beta etc.
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BPCF records were checked for evidence of polymorphism. The steeper lines on the
left (Figure 4) are typical of sensible heat change, with a plateau around 300C. This
cooling chart shows a second plateau at 550C. The cooling is constant and the
temperature plateaus when the latent heat of either solidification or crystallisation is
removed.
There are liquid solid phase diagrams in section 11.3, which show % liquid of the
various triglycerides at various temperatures (Bailey, 1950, pg. 215)
“The melting point for milk fat is 370C” (Dairy Consultant, 2002, pg. 6). “Complete
or almost complete melting at …350C” (Bailey, 1950, pg.312)
It is now common to separate at 50-550C. “In the manufacture of AMF directly from
cream, treated cream at a temperature of 55-600C with a fat content of about 40% is fed
to the cream concentrator which is a self-desludging19 centrifugal separator” (Early,
1992, pg. 130).
“Before the final concentration starts the temperature of the melted butter should have
reached 600C”20 (Tetra-Pak, 1995, pg. 283).
It is possible that centrifugal separation would be successful at 600C21, down from the
current refining temperature of 850C. A lower processing temperature would require
less heating energy.
5.4.2 Temperature for vacuum drying This is a description of vacuum drying (Tetra Pak, 1994, pg. 7.10). It is heated to 90-
950C then most of the remaining moisture is flashed off through treatment in a vacuum
chamber.
19 Solids and heavy materials build up as sludge in the separator bowl. At specified intervals, apertures in the bowl open and release the sludge. 20 If the oil is not fully melted then during refining, the solids have a significantly different specific gravity and would be separated from the hot oil and discarded. 21 This could not be tried with saleable product. Further laboratory testing is required.
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The water boiling point changes with pressure, the lower the pressure, the lower the
temperature. A chart showing the highest temperature to which water can be raised
under different vacua is reproduced below (Murray Deodorisers, 1954, pg. 27).
BPCF vacuum is more than 25inches (0.1m) of mercury.
Vacuum Boiling point
in hg kPa 0f 0C
21.5 72 155 68
22 74 152 67
22.5 76 150 66
23 78 147 64
23.5 80 144 62
24 81 141 61
24.5 83 137 58
Table 2: Water boiling point at different vacua.
From Table 2 it could be concluded that with vacuum available, the processing
temperature could be lowered to less than 650C.
5.5 Energy Efficiency The number of documents available on energy savings and auditing is overwhelming.
The Australian standard was used as the basis of the audit. Additional information
came from the AGO and the Queensland Government Eco-Efficiency initiative.
A guide to improving general factory energy efficiency was studied (Easthop and
Croft, 1990). It has a reasoned approach to reduction of energy use and advises on the
evaluation of costs associated with energy usage, which are:
a) Capital investment
b) Fuel costs
c) Other operating costs e.g. maintenance and labour etc
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They also suggest money expended should be converted to cash in real terms such as
Net Present Value (NPV).
The depth of understanding displayed encompasses many diverse subjects, such as the
text on the limits of heat recovery from boiler flue gas22 to identifying waste streams.
They also describe lesser-known technology. Vapour absorption cooling is one
instance.
They (Easthop & Croft, 1990, pgs, 203-246) have some interesting theories on
calculating possible heat recovery, with pinch technology. This knowledge is relevant
to many processes.
Where their work can be compared with other references, it can be shown to be
accurate. For example, they say the Coefficient of Performance for refrigerants was
similar. A check of the “Refrigerant Selection Guide 2003” (Lommers, 2003)
promoted by AIRAH shows that there is less than 10% variation on commonly used
refrigerants.
The information was detailed on how to conduct an energy audit and evaluate losses
with air conditioning and lighting. Of particular interest was the section on the storage
of hot and cold energy to reduce peak demand.
The PINCH technology section was used to estimate potential saving from the hot
wastewater, as shown in Figure 17.
22 If the temperature of the gas is below 1500C (the dew point for sulphuric acid) then heavy corrosion in the flue will result.
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5.6 Conclusion
The literature review has determined that the best course of action would be to retain
the existing process. Traditional processing techniques were not as energy efficient as
the BPCF process. Researchers in other countries were trying to emulate the BPCF
process. Regardless of the process the natural properties of Ghee are:
1. The crystalline structure of Ghee is a sign of purity.
2. Yellow colour is an indicator of freshness.
In theory the current operations could be made more energy efficient if the refining
process temperature was lowered to 650C and natural cooling of the refined oil was
used below 550C. This would reduce the refrigeration load.
An alternative source of butterfat could be cream. The processing of cream appeals
because of improvement of heat transfer between the incoming raw material and the
leaving refined oil and low labour requirements. The negative effect is the low fat
yield (40%). A 100kL storage silo would be needed, for a day’s production. The
process of cream ageing takes 16hours. A second silo would be needed for a week’s
production. The capital cost of two silos, an extra separator and a homogeniser would
rule out this option.
A new energy audit could determine the effectiveness of the existing equipment and
identify waste streams. Theoretical efficiencies would then become the benchmark.
The course of action would then be to achieve the theoretical efficiencies.
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6 Energy and water audit
“You cannot manage what you cannot measure”23
The BPCF energy audit follows the same principles as AS/NZS 3598:2000 level
3 audit. “An energy audit establishes both where and how energy is being used,
and the potential for energy savings”(AS/NZS 3598, 2000). The water audit is
less comprehensive. It relied on service provider metering.
The history of BPCF auditing is:
• An external energy audit was commissioned (1995)
• A database of all equipment and electrical requirements was compiled. The
results were compared to usage.
• A cursory audit was conducted (in collaboration with another QUT student)
2002.
Continuous auditing checks the energy usage in all areas.
• An electrical use monitoring system records electrical use every ten minutes
• Various meters are read and usage recorded on a regular basis. Samples of the
results are shown section 11.12.
• Service provider bills (since 1995) for energy and water are scrutinized and
variations investigated
• Waste bins are inspected because discarded materials indicate how equipment
is performing e.g. damaged cans in the bin are lost production
• Visual and auditory inspections are conducted regularly
The energy auditing shows actual usage. Conclusions were drawn about potential
energy savings. While savings are possible, whether they are economically viable has
to be ascertained.
The trend of energy and water use is evident from Figure 5. The financial year 97-98
shows low use because overseas contract packing was used and the volume packed
on site was down 16%. The year 2003-04 shows high use because production was up
by 10%.
23 Commonly used, original source unknown.
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4500
5000
5500
6000
6500
7000
94-9
5
95-9
6
96-9
7
97-9
8
98-9
9
99-0
0
00-0
1
01-0
2
02-0
3
03-0
4
Year
Ener
gy (G
J)
3000
5000
7000
9000
11000
13000
15000
17000
19000
Wat
er (k
L)
GJ-energy
Water
Figure 5: Water and energy use 1994-2004.
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
95-9
6
96-9
7
97-9
8
98-9
9
99-0
0
00-0
1
01-0
2
02-0
3
03-0
4
Year
GJ
of e
nerg
y pe
r ton
ne
1.000
1.250
1.500
1.750
2.000
2.250
kL W
ater
per
tonn
e
GJ/tonne
kL/tonne
Figure 6 energy and water used to produce 1 tonne 1995-2004
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6.1 Building
The four level building is cavity brick (Figure 7). There are windows on the eastern,
southern and northern ends. The galvanised iron roof is insulated and painted white.
Figure 7: The factory.
6.1.1 Air conditioning
Production, Laboratory and Office areas are air-conditioned. Doors are fitted with
self-closers.
Building materials and insulation reduce the influence of external environmental
loads, with the exception of the Laboratory, which has tinted windows on the eastern
sides, which allow solar heat loads, during summer mornings.
Most air conditioning units are fan coil units cooled by chilled water. The Office,
Laboratory and Product Packing areas are fitted with thermostats, water control
valves and timers. Only the office air conditioning has heating coils. Other units in
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the factory have no form of temperature control. RACs24 are used in remote
locations.
Air conditioning loads were calculated using a “Trane25” handbook and an AIRAH26
handbook. The loads were compared with loads calculated from anemometer and
psychrometric sling readings. Theoretical and actual results concur when compared
on a spreadsheet.
The air conditioning load was estimated using two methods, as shown in Appendix (f).
Heat loads were calculated using details of wall orientation (north, east, south and
west) insulation, ceiling insulation, lighting, personnel, window sizes etc.
Both calculations suggested a load of within 10% of 92kW for production areas. This
was then compared with airflow and temperature from the various air registers, which
was calculated to give the cooling effect, which was taking place on a day with 350C
ambient temperature.
The air conditioning units are supplied with 140C chilled water. The water temperature
increases to 160C, when the air is cooled. An air conditioning load of 92kW and water
temp increase of 20C provides enough information to calculate the water flow rate. The
energy required to raise the temperature of one litre of water is 4.181kJ/kg.K-1.
Flow rate =Cooling required kW/((water out-water in temp) x 4.181) L/s Equation 1
=92/((16-14) x4.181)L/s
=92/8.362L/s
=11.2L/s
The power required to pump 11.2L/s (1Litre~1kg) of water with indicated discharge
gauge pressure of 250kPa can also be calculated.
• Gravity @ 9.81m/s2.
24 Refrigerated Air Conditioning unit 25 Air conditioning supplier. 26 Australian Institute of Refrigeration And Heating. AIRAH
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• Assuming 64% efficiency, based on 80% motor efficiency and 80% pump
efficiency.
• The head pressure of a metre column of water is ~10kPa. Therefore 250kPa is
equivalent to a 25m column. This pressure is caused not by head, but by pipe
restrictions e.g. valves, pipe fittings and heat exchangers.
Power = (height x gravity x mass/sec)/efficiency Equation 2
= (25 x 9.81 x 11.2)/ (64x1000)kW
= 4.2kW
Because this is a simple way to work out pump power, the error is high, plus or minus
about 20%27. The motor fitted to the air conditioning water pump was 18kW, which is
on the large side. Testing28 showed the motor was drawing 11kW of electricity. This
may be a common problem in factories, when the duty of the original pump changes
and it is pumping more water than required see section 11.13.
A variable speed drive was fitted and tuned. The pump power required to achieve
room temperatures of 230C was found to be 5.6-6kW. The pump and motor were
replaced with a smaller unit.
6.1.2 Lighting
Light levels were measured in various areas with a lux meter29. Levels were altered
to comply with appropriate standard (AS1680.1, 1990).
Natural light is used in office and workshop. In several areas twin tube fluorescent
fittings have been fitted with a single triphosphor tube, because it produces sufficient
illumination.
It is recommended by this study that skylights should be installed in the change
rooms and the toilets.
27 This method does not consider heat gain from water flow through the pipe or other inefficiencies. 28 A device was attached to the electricity supply wire. This device (Tong Tester) measures the amps flowing through the cable. Then a table was consulted which linked the number of amps to motor kW. 29 A lux meter is an electronic device, which measures light intensity.
Thesis 18/05/2009
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6.1.3 Cold rooms
Cold rooms have concrete render over cork insulation (200mm thick) and cavity
brick walls. The doors are fitted with rubber seals.
6.1.4 Lifts
There is a goods lift for elevating packing materials from the basement to the
packing areas. Two employees are required to operate the lift. Pallets of materials are
loaded in the basement and unloaded on the required floor. Empty pallets are
returned to the ground floor. A return journey takes ten minutes and requires about
2kWh. There can be 20 return journeys in a day.
The preferred option would be the addition of an annex on the eastern side of the
existing building, see Figure 7. The annex floor would be the same height as a semi
trailer tray, so that cans could be unloaded onto roller conveyors. The roller
conveyors would be connected to two full size can depalletisers.
The can depalletisers on the ground floor would feed cans to individual packing lines
as required. This would save on lift operating costs (energy and labour).
The cost of approximately $750,000 rules out this option.
6.1.5 Energy use proportions
Electricity and gas are the primary sources of energy, see Figure 9 for usage.
• Electricity is used for refrigeration and powering equipment
• Gas is used exclusively for steam production (approximately 560MJ30 per
tonne). Steam is used for heating in the refining process.
• A small amount of LPG is used as fuel for forklifts.
On site activities are divided into storage, refining of Milk Fat, crystallisation of
Ghee, canning/packing and dispatch.
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6582GJ
26% Boiler
20% Hot Water
54% other
Figure 8: Pie chart of percentage of energy used 1994-95
5552GJ
41% Boiler13% Refrigeration
3% Refining11% Crystallisation
20% Hot Water
12% Packing
Figure 9: Pie chart of percentage of energy used 2003-04.
30 Converting the cooling load of 38.9kWh per ton to the theoretical MJ by multiplying the conversion factor 1kWh =3.6MJ and refrigeration Coefficient of performance 4.7 gives 658MJ of cooling.
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6.2 Storage
6.2.1 Packing materials
Packing materials are dry stored in the basement. The basement is accessed by a
ramp up to ground level. As required the materials are transported by a lift to the 1st
floor (packing).
6.2.2 Butter and AMF
To maintain butter freshness, it is stored in five cold rooms at temperatures from plus
40C to plus 120C. The colder temperatures allow for longer storage periods but
require more refrigeration input and more heating to achieve the refining
temperature.
The cold rooms are on the ground floor adjacent to a loading dock and have a storage
capacity of 1,000t.
AMF is also dry stored around the building in drums and palecons (~2,000t
capacity).
6.2.3 Liquid storage
After processing the hot pure oil is pumped to storage vessels located on the first floor
and an external silo.
Hot oil will crystallise with natural cooling. However time and storage constraints
require refrigerated cooling. The process is carefully controlled to promote crystalline
growth.
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After crystallisation, the Ghee is pumped to a 65t storage silo. The silo is fitted with a
specially designed agitator, which prevents fractionation31 of the Ghee. The dimple
plate walls incorporate voids for cooling/heating liquids to maintain Ghee temperature
(220C). Ghee is pumped through a jacketed stainless steel tube32 to individual packing
lines.
A heating/cooling liquid (water) is counter flowed through the tube jacket. This
maintains product supply at a constant temperature. Ghee is supplied to any of the
packing lines as required. The pump speed is controlled by a VSD33 working on
product pressure in the supply pipe. Flow varies from 9 to 150L/minute.
6.3 Processing/refining
Milk Fat is heated to 850C, neutralised, refined to remove impurities and dehydrated.
The flow chart shown in Figure 8 illustrates the refining process in detail.
Output from the refining process is transferred to storage tanks. For heat recovery the
hot processed oil is cooled by counter flowed town water. The heated water is mixed
with steam condensate then pumped around the boiler flue. The resulting hot water is
added to the hot water storage.
Approximately 17kL of hot water are used on a refining day. 10kL of water is
removed from the raw materials. This water is a potential source of recoverable heat.
The low-grade heat cannot currently be used in the refining process.
31 Ghee is not a homogenous liquid, if left the constituents separate into layers. The layers have different densities and characteristics. Each can packed should contain a mixture of hard and soft fats. 32 The inner tube is 50mm polished 316SS with 1.6mm wall. The outer tube is 65mm polished 316SS 1.6mm with wall. The tubes are concentric and a 5mm SS rod is spirally wound around the inner tube to hold the tubes apart and promote turbulent flow. 33 Variable speed drive used to electronically control electric motor speed.
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Incoming butterTemperature varies
40C & 120Ccapacity for 1000t
Incoming reseals,cans & cartons
Dry storage
Packing area
Hot oil Storage80kl
Incoming drums &and paleconsDry storageapprox 600t
Refining
Crystallisation42t
fork
lift
pipe
pipe
pipe
Pal
let s
of
carto
ns a
nd re
seal
s
Crystallised gheeStorage@220C
70klpipe
pipe
waste water
pipe
Incoming drums &and paleconsheating rooms
forklift
Palletisation
Containerisation
fork
lift &
truck
conveyor
Depalletisation forcans
fork
lift
Con
veyo
rs fo
r can
s
Figure 10: Production flow chart.
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Incoming buttercapacity for 1000
tonnes40C& 120C
Neutralising vatscaustic soda dosed
Butter melting vat @ 650C
Heat exchangertemperature
raised to 850C
Shredders pump
pum
p
pump
Separator No.1most water removed
and someneutralised Fatty
acids
pumpSeparator No.2hot water added
for polishing
Incoming drums &and palecons from
heating room
heat reclaimed intransfer pipe
Separator No.3waste from No.1&2
cleaned before goingto waste
Deodoriser "B"
Deodoriser "C"
Deodoriser "A"
Deodoriser "D"
pum
p
pum
p
pum
p
Hot
oil
pump
pump
Figure 11: Refining process flow chart.
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6.4 Crystallisation
Crystallisation is located on the second floor. The hot oil is pumped through
distribution piping to any of the 18-cooling/crystallisation tanks. The total
crystallisation capacity is 42t.
The oil is cooled to 18.50C in the water-cooled tanks. Automatic controls are
programmed to regulate the circulated chilled water. The chilled water is supplied by a
heat exchanger in the engine room.
Crystallised Ghee consistency is very important, as all fillers are volumetric and
variations in density alter filling weights. This either over fills the cans or causes under
weight cans. Either condition wastes materials or product.
Once crystallised the Ghee is transferred to a temperature controlled storage silo.
6.5 Canning plant
Ghee is produced 7:00am-4:00pm, 9 days/fortnight. All Ghee is packed into cans or
drums. The packing/canning section is located on the first floor. There are dedicated
packing lines for each size34, consisting of:
• A depalletiser
• A can closing and a filling machine
• An inkjet printer
• A check weighing machine
• A carton packing machine (air operated, PLC controlled)
• Can and box conveyors (motors are 0.55kW or less).
The can closers and fillers are fitted with VSDs (Danfoss model 3000VLT) on 4kW
motors. Machine speed variations enable the line speed to be matched to requirements
and conditions.
34 The sizes are 150g, 250g, 1lb, 500g, 2lb, 1kg, 4lb, 2kg, 10kg and 18kg. Similar sizes utilise common packers and depalletisers.
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Packing materials suppliers are required to supply consistent packaging. Management
actively encourages employees to reduce wastage of cans and Ghee. This is seen as a
waste reduction activity.
The cartons are palletised by hand, in an adjacent room. The pallets of cartons are
stored until the order is completed. Then a hydraulic lift transports the pallets to the
ground floor.
The pallets are trucked to the off site containerisation area where they are loaded into
containers for shipment to customers
6.6 Dispatch
6.6.1 Containerisation LPG is used here for shrink-wrapping of pallets and forklift fuel. The forklifts are
tuned every three months for emission control.
6.7 Services
6.7.1 Boilers
One 1MW gas fired, water tube boiler is used exclusively for heating in the refining
process (1-2 days/week). The boiler flue is used for heating water transferred to the hot
water storage from the process heat recovery equipment.
Water condition is monitored daily and an automatic TDS35 controller is fitted.
The burner is tuned every five weeks. Flue loss (A.I.E., 2004) of input energy would be
~17%. Therefore a boiler heating efficiency of 80% is expected. However there are
heat losses through insulation and normal boiler operation such as air purge cycles
during start up. This is confirmed by calculations in Table 3.
35 High levels of Totally Dissolved Solids (TDS) are an indication of water being contaminated with impurities.
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Energy required for elevating butter temperature Butter Properties Latent heat of fusion 90kJ/kg Specific heat at 400C 2.1kJ/kg.K Butter temperature in 140C Process temperature 800C ΔT 660C Latent heat of fusion/tonne 90MJ =m*Cf Energy required to raise temperature 138MJ =m*C*ΔT Total 229MJ If heat efficiency is 80% 286MJ/t required Boiler output is (allowing for heat lost through insulation and burner start up air purge cycles) 70% 408MJ/t required Comparison of heating energy/t produced by the refining process. The improvement was achieved by changing the refining process controls, section 8.3.4. Natural gas for 2002-03 44t produced /day 2,024GJ of gas used 3,519t of oil produced 575MJ/t Natural gas for 18-05…13-09-2004 47 t produced /day 713GJ of gas used 1,412t of oil produced 505MJ/t Percentage improvement36 =575-505/575 12%
Table 3: Butter refining heating.
Boiler efficiency is as good as can be expected. The only reductions possible are
lowering the process temperature or increasing incoming butter temperature. Butter has
to be stored at less than 140C to maintain freshness.
36 Achieved by increasing efficiency of the refining process, section 8.3.4
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6.7.2 Hot water
22kL electrically heated (2x100kW elements) storage system has a set point of 750C.
The hot water is circulated through the building by either of two multistage impellor
pumps. The approximate volumes of water used per day are:
• 10kL on refining days for rinse water
• 3kL for washing equipment and warm up.
• 4kL for boiler feed water. Some boiler feed water comes from town supply
because the water softener operating temperature is restricted 400C37 water.
• 1kL on a normal day for cleaning factory.
A large insulated stainless steel tank stores recovered heat and uses off peak electricity
for heating. When the heating energy used is compared to heating energy input there is
a considerable amount of energy lost. This energy is dissipated through the insulation,
see section 11.10.
The refining wash water could be made in a calorifier as required. It would be heated
by direct steam injection and could use excess boiler capacity.
6.7.3 Ammonia refrigeration
The ammonia refrigeration is an unattended 1,500kWr single stage liquid circulation
system. Electronic controls start the equipment and load the compressors to maintain
temperatures in cold rooms, air conditioning and chilled water.
6.7.3.1 Refrigeration Compressors
Four reciprocating compressors are available. Suction set point is varied automatically
to suit the loading 250–370kPa.
In 1998 May-June-July the compressors averaged 17 hours/day and for the same period
2004, the compressors ran 10 hours/day, see Figure 23.
37 The water softener is fibreglass. Elevated temperatures reduce the service life.
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6.7.3.2 Loads
The refrigeration loads are:
• Cold rooms, two at 40C and two at 120C
• A shell and tube heat exchanger cooling glycol brine, which is used to cool a
10kL tank of chilled water to 140C. The chilled water is used for air
conditioning and cooling crystallisation vats.
• A welded plate heat exchanger cools glycol brine, which is used for air
conditioning cooling in the office and laboratory.
6.7.3.3 Evaporative Condensers
There are two condensers in use for the refrigeration system. They are:
• One Auscon 600kWr induced draft evaporative condenser
• One BAC 800kWr forced draft evaporative condenser.
The condensers are controlled automatically. The lead condenser fan and all pumps
start when any compressor starts. A pressure switch set at 1,000kPa controls the
second condenser fan.
Condenser water treatment is maintained to reduce calcification on the refrigerant
tubes and kill bacteria. The TDS of the water are maintained below 1,500
microsiemens.
It is important to have clean heat transfer surfaces (tubes) in condensers. Calcium
builds up on tubes and reduces the amount of heat transferred from the refrigerant.
This can result in higher condensing pressures and consequently higher compressor
loads.
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6.7.4 Compressed air
A leaflet (AMEI, 2004) on efficient usage of compressed air was used as a guide for
best practice. The guide recommended several items, which were already common
practice.
• The airlines sized for the flow
• Water traps and filters are fitted at each machine
• Cold inlet air is ducted from outside the building
• Maintenance employees check and repair audible air leaks when the factory is
not operating
• Air tools are not used
• Cleaning by blowing compressed air is not common practice.
The air usage was analysed by recording all air operated factory equipment in a
spreadsheet and calculating air usage, see section 11.7. It was found that in theory the
two fastest filling lines would use all compressor capacity. This was found to be the
case, after air leaks were eliminated.
Fitting solenoid valves on the compressed air lines to isolate from supply when not in
use reduced small air leaks on various packing lines.
6.8 Electricity usage
Electricity is used throughout the factory by various items of equipment. The
equipment is automatically and manually controlled. The best way to identify usage is
24 hour/day metering at many points. Cost constraints limited the number of meters to
two. A spreadsheet section 11.12 shows consumption by various areas.
The data recorded by the meters is best presented in graphical form. The following
charts show trends quite clearly, as in Figure 12. The data was also used to monitor
that plant modifications were successful. Figure 14 shows improved heat transfer from
crystallisation to refrigeration because there is more energy used constantly.
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Subsequent charts show daily usage profiles and weekend usage, administration
usage, canning operation usage, refining usage and crystallisation usage.
Accounts from energy providers were used as the basis for Figure 12. The BPCF
meters confirmed that service provider bills were accurate.
0
50
100
150
200
250
300
350
Jul
Aug
Sep
Oct
Nov
Dec Jan
Feb
Mar
Apr
May Jun
Month
Ener
gy (G
J)
Electricity GJ
Boiler gas GJ
Figure 12: Seasonal energy usage profile, 2001-2002.
Production fluctuates with orders, which vary with Muslim religious festivals. May-
November can be as high as 450t/ month. December production is generally 150-200t.
Figure 12 shows that December energy consumption is less than any other month. The
production load drops off when the factory closes over the Christmas period.
Only the office and cold rooms operate as per normal. All unnecessary items38 are
turned off.
38 Refrigerators in lunchrooms, factory air conditioning, process chilled water and water coolers etc.
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24hours electrical usage (weekend)
0
10
20
30
40
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
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11:0
0
12:0
0
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19:0
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20:0
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21:0
0
22:0
0
23:0
0
Time (10 minute intervals)
Elec
tric
ity (k
Wh)
10/08/20027/08/2004
Figure 13: After hours electrical load.
10-Aug-02 & 07-Aug-04 were Saturdays. Daily non-workday usage has been
lowered from 580kWh to ~460kWh/day. The new 5kWh peak shows that the load is
low. Items turned on are:
• Refrigerated cold rooms
• Silo cooling and agitation (some extra cooling is required in summer)
• Lunchroom facilities
• Computer network servers
• Exit lights
• Security lights are on timers at night.
Turning off the refrigeration compressor cooling water pump when it was not
required lowered consumption.
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24hours electrical usage (base load)
0
10
20
30
40
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:0
011
:00
12:0
013
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14:0
015
:00
16:0
017
:00
18:0
019
:00
20:0
021
:00
22:0
023
:00
Time (10 minute intervals)
Elec
tric
ity (k
Wh)
9/08/20026/08/2004
Figure 14: Base electrical load.
Every second Friday the factory closes for a day off. 09-Aug-02 and 06-Aug-04 were
rostered off Fridays. The load profile is the base load and includes:
• Six people
• Six computers
• Office lighting
• Cleaners’ activities
• Office air conditioning
• Charging forklift batteries.
The consumption for these days was 800kWh, which is used as the base load for
operating days.
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Figure 15: Production electrical load.
8-Aug-02 and 28-Jul-04 are a normal production days without crystallisation. Total
usage was 1,400kWh. Packing equipment used 600kWh (1,400-800). Equipment
used that day was:
• Base load
• Air compressors
• Can fillers and closers
• Carton packers
• Ghee supply pump
• Conveyors
• Factory air conditioning.
Usage is similar regardless of which lines are used. The profile shows peaks at
morning and lunch start-ups. In addition, there are smaller peaks after tea breaks.
24hour electricity usage (packing)
0
10
20
30
40
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:0
011
:00
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013
:00
14:0
015
:00
16:0
017
:00
18:0
019
:00
20:0
021
:00
22:0
023
:00
Time (10 minute intervals)
Elec
tric
ity (k
Wh)
8/8/02
28/07/04
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24hours electricity usage (refining and cooling)
0
10
20
30
40
50
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:0
011
:00
12:0
013
:00
14:0
015
:00
16:0
017
:00
18:0
019
:00
20:0
021
:00
22:0
023
:00
Time (10 minute intervals)
Elec
tric
ity (k
Wh)
6/08/20029/09/2003
Figure 16: Refining and cooling electrical load.
These profiles show electrical energy used for refining and hot oil cooling on two
days 06-Aug-02 and 09-Sep-03. This profile illustrates the highest usage of all days.
Total general consumption was 2,400kWh. The equipment used was:
• Base load
• 450kWh for refining process (independently monitored)
• The air compressors
• Multistage impellor water pump
• Product cooling.
The profile shows the peak loads of processing followed by the cooling after hours.
The after hours plateau 09-Sep-03 shows that heat from the cooling tanks is
transferred to the refrigeration more effectively. This is better because the product is
cooled quicker.
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6.8.1 Waste streams
The waste streams identified are:
• 10kL of wastewater removed from the butter and 15kL added during processing is
separated and diverted to the drains. There is potential for heat recovery from the
800C wastewater.
• Waste heat from hot oil to be cooled. Heat is already recovered from the hot oil for
water heating. About 50MJ/t is recovered. 530MJ/t is refrigeration load.
• Waste heat from refrigeration condensers
• Wrapping materials and packaging from inputs and production rejects.
6.8.2 Waste water
Estimates of hot water use were made from a pressure gauge (9.81kPa/m) located in
the base of the hot water system.
Other wastewater volumes are estimated by subtracting the yield of butter oil from
the input butter.
Town Water
Brisbane City Council supply meters are used to check the water usage. Water costs
69c/kL or with trade waste costs approximately $1.70/kL.
6.9 Benchmarking
Comparison with a similar process is not easy, as the documentation on processing is
not commonly published. The only references found applied to vegetable oil
processing:
1. Electricity;
Processing; Batch processing uses 45-130kWh/t (possibly including cooling and
packing). Refining using centrifugal separators uses 12kWh/t.
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BPCF uses 430-450kWh for 47t ~ 9.8kWh/t plus hot water.
Crystallisation The electricity used depends on the starting temperature.
Currently the temperature is less than 550C. Cooling uses 38.9kWh/t, see section
11.12.
2. Water: Traditional methods use 12-45m3 water per tonne compared with 25m3
per 44t at BPCF
3. The BPCF use 205kg(steam)/t (oil). Batch processing uses 1.4-3.4t (steam)/t
(ETPI., 1999)
Energy/process Units per
ton of oil
Batch
Processing
Centrifugal
Processing
BPCF Other
Refining steam t/t 1.4-3.4 320 205 Not given
Refining electricity kWh/t 45-130 4.5 9.8 12
Crystallisation kWh/t Not given Not given 35 Not given
Water m3/t 12-45 Not given 0.6 Not given
Table 4: Refining energy usage comparison.
Sources:
Batch processing (ETPI., 1999)
Centrifugal process (Punjrath, 1974) and (Aneja et al., 2002)
BPCF BPCF production and energy use records
Other (ETPI., 1999)
The figures in Table 4 relate only to Ghee manufacture. Energy used for auxiliary
equipment such as administration air conditioning is not included.
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6.10 Energy and Water Audit Conclusion The energy audit was directed by a number of documents:
• The Australian Standard
• Websites such as the Australian Greenhouse Office
• Queensland Government Eco-Efficiency initiatives.
The audit showed which areas were using energy and water. The research revealed
how to reduce the usage.
The oil processing heating uses 40% of the total energy used, see Figure 9. Lowering
the process temperature would reduce heating and cooling loads. If this is not
possible then recovering waste heat from the waste streams, by changing input
materials or processing methods, could be done. Improving the refining process
control has also reduced waste, energy and water costs.
The refrigeration system should not be neglected; improving heat transfer from
ammonia refrigeration to the process chilled water would lower energy requirements.
When this has been done, the load profiles will be lower which will allow BPCF to
take advantage of cheaper electricity tariffs.
The energy audit has raised some questions on alternative raw materials and process.
The questions can only be answered by conducting a literature review, which has
determined some alternatives. They are defined in Section 8.
While savings are always possible, practicalities of time and budgetary constraints
rule out many. Efforts are concentrated on the best returns on investment.
The water audit is less comprehensive. The usage is collated in Table 6, which shows
how the usage has dropped. Extracts from two water bills section 11.11 illustrate that
water usage dropped considerably. This was mainly caused by:
• Altering refrigeration condenser controls
• Reducing boiler requirements
• Better housekeeping.
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7 Future savings
The literature review has offered alternatives. The most energy efficient production
would be to pump the cream from tankers directly to storage where it would be
prepared for processing by souring. Then refine the cream at 650C. Cooling to 450C
and seeding would be done simultaneously in a scraped surface heat exchanger. The oil
would be packed hot. Crystallisation would occur in the can as the oil cooled.
Unfortunately this is not possible, because of capital cost. The lowering of the refining
process temperature and the raising the packing temperature would lower the energy
requirements.
The following potential savings require further investigation:
7.1 Heat exchanger………………………………….………Audit
7.2 Hot oil packing…………………………………………Literature review
7.3 Atmospheric cooling……………………………………Audit
8.4 Improvement of refining process…………..……….….Audit
7.5 Processing temperature.……….……………………….Literature review
7.6 Wastewater heat recovery……….……………………..Audit
7.7 Air conditioning……………....……………………….. Audit
7.8 Changing electricity tariff………………………………Audit
7.1 Heat exchanger
The audit showed more energy used in cooling the product compared with heating.
Energy losses in the cooling system or external loads are the likely causes for this
result. A likely explanation would be the heat exchange between the refrigerant to the
chilled water could be improved.
The chilled-water (used for crystallization and air-conditioning) is cooled in the engine
room. The current secondary heat exchanger is a series of tubes immersed in a tank of
water. Glycol at -40C is pumped through the tubes. The water flows over the tubes.
Heat transfer is a combination of conduction and convection. A plate exchanger is
more efficient as it promotes turbulent flow for good heat transfer (both sides).
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Heat exchangers are used to transfer heat energy between two fluids, without actually
mixing the fluids. The fluids flow either side of an impermeable barrier and the heat is
transferred through the wall (usually thin metal).
The refrigeration compressors work harder to cool the water than necessary. A plate
heat exchanger would allow a higher refrigeration set point. This would lower energy
use by reducing compressor duty and raising the theoretical (Table 5) coefficient of
performance from 4.7:1 to 7:1. It must be noted that theoretical improvements are not
always achieved in practice.
A direct heat exchange is allowed with double wall welded plate heat exchangers.
Sales brochures indicate that plate heat exchangers can have a six times better heat
transfer coefficient. Electricity savings of $5.00/hour for 40 hours/week would result
from installation.
There would also be better temperature control for crystallisation.
7.2 Hot oil packing
The cream-processing article (Tetra-Pak, 1994) suggested packing the butter oil at
temperatures above 550C. BPCF currently pack at 200C. No crystallising would be
required. Energy usage would be reduced by 20%.
The reasons for not filling hot oil are:
• Filling equipment would have to be replaced. Current filling machines are
designed for a cold viscous liquid, warmer liquids change cylinder –piston
clearance and pistons seize after prolonged hot running. Changing materials used
for pistons could overcome this.
• The main perceived problem is hot oil is less viscous and there is a filling time of
less than 1.5 seconds per can. The liquid has to be forced through an orifice
(filling valve); this results in high flow rates. The oil is deposited into a stationary
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can; the liquid flow is decelerated quickly. Splashing of oil over the can sides
would result from current equipment39.
Cans would have to be cleaned, possibly by washing with water, which would
then have to be dried before packing.
7.3 Atmospheric cooling of hot oil
The option of atmospheric cooling of the hot oil (by dissipating the heat through the
storage vessel walls) was tried. Existing 100t storage had enough capacity to hold the
oil for a few days. Tests showed that it took three days40 for the oil temperature to
drop from 650C to 550C in the insulated storage tanks.
Purified hot oil oxidises if the temperature is above 550C (Early, 1992) for any long
period of time.
Crystallisation was achieved with the natural dissipation of heat. Additional
refrigerated cooling was required to obtain the 200C packing temperature.
This option also reduced refrigeration load of cold rooms and improved flexibility of
production:
• Butter previously stored in refrigerated cold rooms was stored as hot oil
• There was sufficient purified oil on hand to meet packing demands (50t/day).
The consequence was that the oil started oxidising because of lengthy time at
elevated temperatures.
This needs more testing now that heat recovery has lowered the refined oil
temperature.
39 There are machines available. They have more sophisticated methods of filling e.g. bottom fill to overcome the splashing problem. Consequently, they are expensive. 40 This was tried with the addition of an antioxidant. The Peroxide Value (PV) level was elevated but within limits.
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7.4 Improvement of refining process
The Milk Fat refining process uses at least 40%41 of the total energy consumption.
Lowering the processing temperature as discussed in section 5.4 would make a
significant reduction in consumption, possibly as high as 40%. This depends on the
amount of heat recovered from processed oil.
7.4.1 Cream processing
Cream processing requires extra equipment and has low yields, approximately 4 t/hour.
Extra processing days would be needed to meet production requirements. The
additional equipment required would be:
• A temperature controlled storage silo new cost $80,000
• A centrifugal separator new cost $150,000
• A homogeniser (phase inverter) new cost $150,000
This could not be justified on energy savings alone. The labour savings of seven
employees involved in manual handling of raw butter must be also considered. The fact
that these employees are only required on refining days (1.5 days per week) reduces
the savings.
There is only 40% Milk Fat in cream. The 60% water has to be removed. It would be
treated as wastewater and dumped down the drain. This liquid would incur trade waste
BOD charges42.
If cream were the only input it would limit the availability of cheaper material.
Currently raw materials include rejected production from Australian dairy factories
such as out of date butter and inferior first grade butter.
41 7% of the electricity plus 100% of natural gas consumption 42 The Brisbane City Council monitors trade waste. BOD levels are an indicator of treatment required by the council before they can discharge the effluent to the river. Industrial users pay a surcharge based on monitored BOD levels.
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Cream may be suitable as a secondary input to butter if a scraped surface heat
exchanger can do the phase change.
7.5 Processing temperature
The main factor influencing centrifugal separation is the specific gravity of the fluid
and the impurities. Therefore to obtain maximum output all of the butter must be
melted. Triglycerides have different melting points. This is indicated the fact that all
three physical phases are present at the same temperature during the filling of the
crystallising vats with liquid hot oil 500C. Oil vapour can be seen rising from the vat.
This is definitely a vapour, not just evaporation. There is often a layer of solidified
crystals adhering to the wall.
The crystals remain despite the wash from the vat agitator throwing the oil onto the
walls. It is not hot enough to melt the crystals. Therefore the processing temperature
must be higher than 550C.
In regards to processing temperature, a dairy industry consultant (Parodi43, 2003) was
asked about oil processing. Why does BPCF process the oil at 850C?
The literature read so far has given three reasons (in italics):
7.5.1 Solids removal.
The solids in the butter would only precipitate at high temperatures. The separators
would still work at lower temperatures (Parodi, 2003), if the butter were liquid. The
lowest process temperature required for separation was not stated, but assumed to be in
excess of 450C (butter oil fully in liquid phase). For separation: Parodi said that the oil
would separate at lower temperatures. No specific temperature was given, possibly less
than 450C.
43 Dr Parodi is a recognised authority on dairy products. He was also employed by BPCF and is familiar the process.
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7.5.2 Pasteurisation.
The oil would need to be held at 850C for more than one minute for pasteurization. If
the oil were pure (less than 0.01% moisture) pasteurization would not be required
(Parodi, 2003). To pasteurize the oil: He said pasteurization was not important if the
moisture was removed.
7.5.3 Water removal.
Water is removed from the oil in sealed vacuum vessels (deodorizers). Water removal
is improved if it is vaporised by initiating a phase change i.e. boiling. This is achieved
at lower temperatures by reducing the internal vessel pressure and increasing the
surface area of the water by atomisation. Improved water removal rates allow increased
flow rates and higher daily production.
In the past the equipment could not reliably achieve a vacuum less than -80kPa in the
deodorizers (Parodi, 2003). So processing at more than 800C was important. Parodi
would recommend lowering processing temperature, if the vacuum were sufficient44.
The vacuum is generated by pumping water at high speed through are series of
venturis. The installation of a new pump and pipes achieves less than -80kPa pressure
in the deodorizers. The deodorizer’s manufacturers booklet indicates that a process
temperature of 60-650C would still provide a safety margin for operation.
Lowering the process temperature would save heating/cooling energy.
7.6 Wastewater heat recovery
Heat recovery from wastewater (more than 25kL/day at 800C) could be used to heat 50t
of incoming butter at 120C.
The distance from the boiler precludes using the heat for preheating combustion gases.
44 A table in the literature review shows water-boiling temperature at various vacua.
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The water contains 3-5% solids, which would make a heat exchanger a high
maintenance item. The heat could be recovered from the copper drain by either
jacketing the pipe or wrapping a copper tube around the drain and counter flowing a
secondary coolant.
The main problem is transferring the low-grade heat to the butter45. Butter has poor
heat transfer and the raw material is 25kg blocks. A method of mechanically deforming
the butter to increase the surface area would have to be used, see section 7.6.1.1.
If achieved it would reduce boiler load. The amount of potentially recoverable heat was
calculated using PINCH technology (Easthop and Croft, 1990). The red line is heat
flow required for heating the butter. The blue line the heat in the wastewater. The
crossover point of the two plots is the resulting temperature of the fluids after heat
recovery (PINCH point).
The amount of recoverable heat is the number of kilowatts at this point.
Temperature heat load butter oil and waste water
0
10
20
30
40
50
60
70
80
90
5 10 15 20 25 50 75 100
125
150
175
200
225
Energy (kW)
Tem
pera
ture
(0 C)
Waste waterButter oil
Figure 17: Wastewater heat recovery PINCH diagram.
45 This is why steam is directly injected into shredded butter in the current process.
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7.6.1 Alternative in feed for refining
Butter has some characteristics, which make it difficult to process. These are:
• Poor heat transfer in solid and liquid phase
• Tendency to bridge across the inlets of pumps
• Unless the faces of screws are wiped, butter clogs augers. This is why butter
reworking equipment has two screws working together.
7.6.1.1 Screw feeder
Figure 18: BPCF butter block rework machine.
The butter block rework machine (Figure 18) would mechanically deform 25kg blocks
of butter. This device would turn 250mm x 250mm x 400mm butter blocks into a pump
able fluid.
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Two screws (left and right hand scrolls) rotate in the lower housing. They mesh and the
flights work a wiping action on each face to prevent a build-up on the screws. The
design may be easier to understand if the photographs of a butter reworker are seen, in
Figure 19.
Figure 19: Four t/hour butter rework machine.
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An alternative in feed for the processing of butter blocks may allow better recovery
from the wastewater. The machine would have to mechanically deform the blocks so
that the surface area was increased and the butter was malleable enough to pump. It
would have the capacity of 11t or 440 blocks of butter per hour. That is seven blocks
per minute (less than 10 seconds for each block).
7.6.1.2 Microwave heating
The sales literature indicates that energy usage is half that of natural gas for heating.
How ever the indicated capital cost would be $150,000. Return on investment based on
these energy savings would eliminate microwave heating as an option.
This option may be possible if another saving can be found i.e. a reduction in labour
cost.
7.7 Air conditioning
Air conditioning could be further improved, because there is no form of temperature
control on the air-handling units, some areas are too cool. Fitting thermostats and
control valves on fan coil units would reduce the air conditioning load, by reducing
unneeded cooling requirements
The pumps and pipes were altered, see section 8.2.7. and a variable speed drive fitted
to the supply pump. This would be reflected in further energy savings and a
reduction in the refrigeration load.
Cost
Thermostat and valve at $ 800 each five required $4,000
This could not be justified using a two-year payback period.
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7.8 Changing electricity tariff
7.8.1 Electrical demand controls
Changing the electrical tariff requires the following changes:
• The four electricity meters would be replaced by one (each metering point costs
$1,000)
• The hot water system electrical supply would have to be rerouted ($17,000)
• A peak demand controller would be required. ($10,000).
The predicted maximum demand would be around 250kW. The peak demand
controller would turn off non-essential equipment when the peak was approached, as
the cold rooms have thermal inertia (because of the mass of stored butter). If one were
turned off for half an hour, there would not be any adverse effect.
The equipment, which would be controlled, would be:
• Cold rooms
• Air conditioning (limited off time)
• Refrigeration compressors
• Battery chargers
• Some of the building lighting
• Crystallisation.
Electricity suppliers46 offer different methods of charging to encourage larger
consumers to use electricity when it suits the generator e.g. off peak water heating. The
four main types are:
• Flat charge of 12.68c/kWh for all electricity used
• Off-peak where the suppliers control supply and turn on equipment, when the
suppliers have excess capacity. Currently charged at 5.63c/kWh
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• Peak demand where electricity costs 4.59c/kWh, but there is additional charge
of $21.71 for the number of kilowatts used in any half hour
• Charges for electricity vary on the time of use. Electricity used between
9:00pm and 7:00am (off-Peak) is charged at 6.33c/kWh otherwise at 17.91 or
14.61c/kWh
Section 11.8 compares the various tariffs applied the 2003 calendar year. The cheapest
costs are the current tariffs 20 and 31.
46 Suppliers do this because they want to have constant demand, which makes their equipment operate better.
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8 An overview of technical improvements
Many of the improvements were only small. The sum of the savings is significant.
Many of the ideas can be used in different applications. An example is that a company
was overdosing the chemical treatment to the wastewater. The problem was that the
electronic controller response to high chemical levels was too slow for the dose rate,
which was controlled by a solenoid valve. A timer was installed on the solenoid control
circuit to pulse the valve on and off. The control of chemical dosing was more precise
and accurate levels resulted in savings on chemical costs. BPCF use the same principal
in a totally different application for the refrigeration plant, see section 8.2.1.
The items below reduced energy and water usage in some way.
8.1 Crystallisation improvements
There are eighteen crystallisation vats. The vats are used to cool and crystallise hot oil.
The old crystallising vats were not very efficient because the oil agitation was poor.
The oil congealed on the inside wall and insulated the oil from the cooling effect. This
meant extra cooling time with extra heat from the water pump. This was wasted
energy.
The old vat design is shown in section 11.5. New crystallisation tanks (shown in
Figure 22 and Figure 20) were designed and installed.
The features of the new tanks are:
• Dimple plate47 walls certified to a 1,000kPa, which improved heat transfer from
the oil to the cooling water.
• A gate type agitator, which improved the product agitation.
47 Dimple plate is two parallel steel plates. One is flat. The other has a series of dimples pressed into the surface the two plates are welded together. A cooling fluid is pumped through the cavity formed by the dimples between the two plates.
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Figure 20: Crystallisation vats.
The impact of new vats and heat recovery on starting temperature and crystallisation time.
15
25
35
45
55
65
75
1 6 11 16 21 26 31 36 41 46 51 56
15 minute intervals
Tem
pera
ture
(deg
rees
C)
Vat 14 29-11-99 (old vat)
Vat 12 07-08-03 (new vat and heat recovery)
Vat 7 19-07-04 (new vat and improved heat recovery)
Figure 21: Reduction in crystallisation times after changes.
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Figure 22: New crystallisation vat.
The new tank addresses both heat transfer and Ghee agitation. The improved heat
transfer reduced the cooling/crystallisation times, see Figure 21.
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8.2 Refrigeration
Background
The refrigeration plant was designed for a much larger load. The load has been
reduced, which has necessitated changing the controls and allowed the refrigeration
pressure set point to be raised. This improved the Coefficient Of Performance (COP),
see Table 5. Improved COP means less electrical input is required to refrigerate
loads.
Table 5: Extract from Refrigeration Coefficient Of Performance table (Lommers, 2003).
To trend the changes in the refrigeration load, the readings of hour meters on the refrigeration compressors were recorded weekly. Figure 23 charts the results. Production demands affect the affect the refrigeration activity. However it is evident that effect of many changes reduced the refrigeration load and resulted in less refrigeration compressor run hours. The dip in December is the Christmas closure. Product stored in the main silo needed cooling in 02-03 and 03-04.
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Refrigeration compressors run hours 96-97 and 03-04
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
Jul
Aug Sep OctNov Dec Ja
nFeb Mar Apr
May jun
Month
Ave
rage
runn
ing
time
(hou
rs/d
ay)
96-97
02-03
03-04
Figure 23: Comparison of refrigeration compressor run hours.
8.2.1 Control of liquid ammonia
The refrigeration plant circulates ammonia to achieve refrigeration effect. Altering the
pressure of the ammonia to change from the liquid phase to the vapour phase and back
does this. During this process liquid ammonia at 1,000kPa was transferred to a vessel
which was at suction pressure approximately 250kPa. Because the vessel was too big,
the solenoid valve was open for too long and the suction pressure was increased. This
added to the refrigeration load.
A timer was installed to pulse the control circuit of the valve. This limited the valve to
two minutes open and five minutes off. The flow liquid ammonia from the receiver to
the accumulator was sufficient to maintain levels, but the compressor run hours per
week were reduced.
8.2.2 Timers for air conditioning
Air conditioning and pumps were turned on and off manually in various areas. These
items were not always turned off at night. Multifunction timers were installed to
control the operations.
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This enables air conditioning to be turned on and areas cooled before work commences
and turned off when not overnight or after hours. This reduces electrical loads.
8.2.3 Cold room temperatures
The cold room temperatures were found to be too low for requirements (minus 150C).
Obviously the colder the room the more energy required for cooling. This room
temperature was raised to 40C, which suited production requirements.
Faulty door seals were replaced which reduced the refrigeration load.
8.2.4 Heat exchanger for office air conditioning
The office air-conditioning unit was designed to use 60C-chilled water for office
cooling. The heat exchanger used to cool the water was not able to achieve this without
excessive refrigeration input, because heat transfer in the heat exchanger was
inadequate.
A welded plate heat exchanger, which has excellent, heat transfer, was installed for the
application. This lowered the refrigeration load. It also allowed the room temperature
to be maintained and increased comfort for employees.
8.2.5 Compressor cooling water pump
The refrigeration compressors are water-cooled. The cooling water pump was running
24 hours/day. The controls were changed so that the pump runs only when a
compressor is operating.
The pump has a 4kW motor and the compressors only run approximately 10 hrs/day
saving 14 hours/day i.e. 4kW for 14hours.
8.2.6 Water usage reduction
Refrigeration evaporative condensers use 600L of water per hour. BPCF had three
condensers. One was decommissioned. The control of the condensers was altered
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(Jan-96) so that all water pumps start when a compressor starts and as the condensing
pressure increases the fans start. Previously the fan and water pump started
simultaneously as the condensing pressure increased.
The modification stopped calcium carbonate build up on the condenser tubes and
reduced the water consumption. Now the water usage (Table 6) has stabilised and the
major water consumption is oil washing in the refining process and boiler feedwater.
kL 94-95 95-96 96-97 97-98 98-99 99-00 00-01 01-02 02-03 03-04
July 1,842 1,170 421
Not enough
Bills keptto be
accurate
1,306 976August 1,519 1,021 765 1,611 September 1,431 1,037 490 2,566 2,038 October 1,387 1,010 627 1,522 1,427 1,866 1,,739November 1,413 1,010 696 December 1,348 1,186 618 1,562January 1,682 892 247 1,278 February 1,588 648 640 1,919 1,485 March 1,502 464 691 3,669 2,819 April 1,435 687 538 1,144 1,358May 1,519 615 422 1,331 June 1,325 580 422 1,141 Total 17,991 10,320 6,577 5,191 5,385 5,098 5,854 5,594 5,635
Table 6: Water usage.
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8.2.7 Water pumping
There are two circulated water circuits. Both had impellor pumps fitted with 18kW
electric motors. The water was pumped from a water storage pit through the factory
and back to the pit. This was used for:
• Factory air conditioning
• The crystallisation tanks.
Both water circuits had the same problems:
• Calculations (Equations 1 and 2) showed that the motors were oversized
• The supply pipe work to the crystallisation vats was undersized and had too
many bends
• The return water pipes were open at the top floor, which meant the energy
(gravity) of the return water was wasted.
When the new crystallisation tanks were installed the pipe work was fixed. VSDs were
installed on the chilled process water pumps and the air conditioning water pump.
Each VSD has a display, which can show motor power, amps, kilowatt-hours or input
values (kPa) from pressure transducers. The motor speed was reduced until
temperatures increased or the rate of cooling was too slow and then the motor speed
was increased until temperatures stabilised.
Process water pump
The motor power on the display is now 8.5kW, instead of the existing 18kW. The
cooling rate is still the same; just the power consumed is less.
Air conditioning pump
The air conditioning pump was too big. After initial tuning it was found that a 5.5kW
motor was sufficient, instead of the existing 18kW motor. The pump and motor were
replaced.
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Figure 24: Photograph of old water pump in the foreground and the replacement on the left.
Figure 24 clearly shows the size difference in pump motors. Checks have shown that
temperatures are acceptable to employees, which is the basic criteria for performance.
A bonus is that the power factor has improved since these two motors were tuned. It
now averages around 0.76 up from 0.69. The extra power was used to increase the
pressure in the pipes, which increased frictional losses. This ended up as extra
refrigeration load.
Not only was the electrical power required for pumping reduced but also the
refrigeration power was reduced.
8.3 Production improvements
There were many improvements; some are explained in detail, the bullet points below
give a brief description:
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• Packing line controls were simplified. Variable speed drives were fitted to each
packing line so that machine speeds could be altered to match conditions
• Can closing machines were overhauled to reduce damaged cans
• Automated packing equipment and depalletisers were installed on each filling
line
Figure 25: Typical can closing machine.
• The compressed air system was changed e.g. supply lines were improved and
leaks reduced
• Employees were rotated every hour during the shift so that they did all of the
tasks associated with operating a packing line. E.g. the filling machine operator
moved to depalletiser operation, that person moved onto the packing machine.
This had many positive aspects:
1) They all had a chance to see the process from someone else’s point of view.
It made the production more harmonious.
2) Employee rotation maintained interest and stopped repetition.
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3) It reduced the “them and us” mentality. This was a significant step in
production improvement.
• Key Performance Indicators (KPI) were set in 2000 as part of the enterprise
bargaining agreement with production employees. One of the KPIs was
kilograms packed per man-hour worked (kg/Mh). This KPI has risen steadily
from 116kg/Mh in 1999-2000, to 155kg/Mh in 2003-04. The increased output
was bought about by changing work practices, employee culture, and
equipment.
• The crystallisation process was automated by stopping the cooling water when
a certain temperature was achieved. If no vats required cooling, the process
water pump also stopped.
The combination of these things has increased productivity. Increased output is useless
if wastage is not reduced. The improved efficiency has reduced wastage.
This reduced the electrical energy consumption because fewer cans had to be reworked
or thrown away. Of the equipment cannot produce saleable product then energy is
wasted, or water is wasted washing down dirty machinery.
8.3.1 Ghee Supply
Background
Ghee was supplied to the filling machines directly from the crystallising vats. This
required many pumps and complicated pipe work. When a vat was emptied another
was used for supply. There were delays during vat changing and Ghee specific gravity
varied from vat to vat. This necessitated weight adjustments on the filling machines for
each vat change.
The vats hold approximately 2t and if 40t per day were packed, then there would be 20
changes. This was totally impractical in many ways.
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Solution
A 65kL storage silo was installed. Ghee was pumped by either of two positive
displacement pumps through a single supply line. The pump speed was controlled by
VSD and a pressure transducer mounted in the supply. Rate of supply varies from 9-
150L/minute.
The advantages are:
• Homogenous liquid with a constant specific gravity and temperature. This
improves packing efficiencies.
• Crystallisation and packing can occur simultaneously. This utilises the plant
more effectively.
• Packing capacity per day is now in excess of 50t. Previously it was limited to
the crystallisation capacity of 42t. This means fewer days are required to pack
the same amount, which saves on overheads such as lights and air conditioning.
Also a jacketed tube supply line was installed. The old pipe had many fittings and was
not hygienically welded. The pressure set point for the variable speed drive dropped
from 5bar to 2.5bar, which reduced the energy used by the pump.
8.3.2 Filling machines
Background
Each packing line has a volumetric filling machine (mechanically driven piston in a
cylinder). Typically the filling machine has a number of vertical filling heads, which
rotate around the vertical axis. If a can is positioned under the filling valve, it is filled.
Each filling machine had similar problems. The 4lb filler modification is described in
more detail. The 4lb line was filling at 42 cans per minute. There are nine filling heads,
which gives only 12 seconds for the filling head to discharge and refill. The two main
problems were:
• Weight variations, under and over filling are both undesirable
• Splashing of ghee onto the can exterior. Customers do not like dirty cans.
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The were two problems, with the 4lb filling machine (Figure 26);
1. Air was being sucked past the piston seals into the filling cylinder during
the head recharging cycle. The air formed bubbles in the Ghee. When the
Ghee was ejected from the cylinder into the can. The air bubbles burst and
splashed ghee out of the can. This caused weight variations, which had to
be compensated for with overfilling
2. The stream of ghee from the filling valve was hitting the base of the can
flowing back up the inside of the can walls and over the top, which resulted
in more splashing.
Figure 26: 4lb can filling machine.
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Once the ghee had splashed outside the can it coated parts the machine, which were in
contact with the cans, and several cans were soiled.
Air in the filling cylinder/head
The filling machine was designed so that the can filling and the cylinder refilling each
had 1800 of filling machine rotation i.e. six seconds to complete the cycle. It was noted
that can filling took less time and refilling improved (less air sucked in) if given more
time.
The controls were altered. Now the line operates at 52 cans per minute. The can filling
takes approximately 1.5 seconds. The cylinder refilling takes approximately 8.5
seconds.
This extra time allowed the piston to travel at a slower speed and suck ghee into the
cylinder instead of air. Weight variations were reduced.
Modifying filling head discharge
The discharge from the filling valve was a 30mm solid stream. When the can filling
time was reduced the problem was exacerbated. How to put 1.8kg into a can in 1.5
seconds without splashing? It was decided to change the flow pattern. The outlet of the
valve was modified so the discharge was conical. This served two purposes. The
impact surface area was increased and the cone was aimed above the bottom corner of
the can, which reduced the tendency of the ghee to flow up the walls.
There was a problem with air trapped inside the cone of ghee. This was overcome by
inserting a device to break the ghee stream in part of the cone. This allowed the air to
escape and stopped the bubbling. The photograph (Figure 26) of the 4lb-filling
machine shows that there is no ghee splashed on the clear guards and that the can
filling is completed by 450 rotation of the filling machine.
This may seem unrelated to energy efficiency, however the electricity meter is still
running while the equipment is cleaned because ghee has splashed everywhere.
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8.3.3 Jacketed tube product transfer
After refining, all oil transfer is by pump through stainless steel tube. There are about
200m of product tubing. When the tube cools the oil sets and cannot be pumped. The
tube has to be heated. It was heated by steam trace.
Steam trace heating is typically 6mm copper tube wound around the outside of the
stainless steel tube. When heating is required a valve is opened and steam warms the
tube.
This was replaced with two concentric stainless tubes. Product is pumped through the
centre tube. The heating medium was pumped through the void. This has a few
advantages:
• The boiler was not required every day
• The product temperature can be controlled precisely, plus or minus 10C
• The system is automated: tube warming occurs before starting time and packing
can commence immediately.
This type of tubing is used extensively throughout the building. After a few months it
was decided to try the jacketed tube to recover heat from the refining process output.
This was successful and has been further refined. Savings from the jacketed tube are
hard to define because there are so many. Here are some:
• No lost production time in the morning with start up. This lost time is also
wasted energy because machines are running but there is no production.
• Boiler fuel: The boiler requires half an hour to heat up in the morning. This
cycle uses about 700MJ just to heat the boiler up. Boiler energy used in 1995-
1996 was 2,735GJ compared to 2,220GJ in 2003-2004
• Heat recovery from the hot oil of 50MJ/t was used to preheat the make up
water for the hot water system.
• The hot oil temperature just prior to crystallisation was lowered by heat
recovery. This in turn lowered the refrigeration load.
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8.3.4 Refining process control The refining process controls were complicated. Errors in processing caused poor
product (sometimes requiring reprocessing) and low output.
Figure 27: Refining process automatic controls.
Automation (control cabinet shown in Figure 27) of the oil refining solved control
issues and increased the throughput:
1. The rate of processing was improved from 7.5t/hour to 8t/hour. Lost time
during start up was reduced. Improved throughput requires less processing days
to achieve the same production. A start up costs about $100 (gas and
electricity), so less refining days saves energy
2. Oil leaving processing was at 650C after heat recovery. Improved control
allowed the water flow to be increased when required and shut off when not
needed. This coupled with diverting oil to a different storage tank improved
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heat recovery. The better performance lowered hot water energy requirements
and the refrigeration load.
The automatic controls illustrated in Figure 27 are:
1. A PLC, which is located in the top left hand corner of the cabinet. The PLC is
linked to a touch screen for operator interface, many inputs and various outputs
2. Seven VSDs (top of Figure 27), which regulate pump speeds to match the
levels sensed in the various process vessels. A potentiometer controls the in
feed pump speed and the rest of the pumps follow. The operator can start the
whole process with the touch of one button.
The labour issues of increased input of raw material (done by hand) were resolved.
Eventually automation of the input should be considered. A potential design is shown
in Figure 18
8.3.5 Reducing the cooling load
Background
The refined oil leaves the process at 850C. Most of the crystallisation of the refined oil
occurs at temperatures less than 350C. The oil could be cooled quickly to 350C before
reaching the cooling tanks without affecting crystal development. If energy
consumption were the only criteria, then atmospheric cooling would be preferred to
refrigerated cooling, but the cooling time is too long and hot oil oxidises which leads to
quality problems.
Solution
The hot refined oil is pumped to storage and then cooling/crystallisation. Jacketed pipe
was installed was installed for product transfer to facilitate start up. Hot water was
flowed through the jacket to melt any residue.
Then the idea to cool the oil with town water was implemented. Initially oil
temperatures were approximately 550C. As the refining throughput increased so did
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the oil temperature. The oil temperature was approximately 650C, when the refining
process 44t/day.
To improve the heat recovery it was decided to change a work practice and fill a
different storage vessel. The delivery pipe was longer and the last section was plain
straight tube. The tube was changed to the “jacketed” type and additional heat
recovery achieved.
In addition the improved refining controls allowed higher flow rates of cooling
water. The heat recovery now reduces the oil temperature to less than 580C. This is
shown in the crystallisation time chart, in Figure 21.
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9 Conclusion
The aim of the project was to investigate and document the reduction of energy and
water usage while fulfilling production, quality, safety and environmental
requirements.
This study shows that energy, water, waste and labour reductions were attained. The
factory was fine-tuned and various systems were integrated to enhance performance.
The equipment was set up and maintained to perform at consistently higher levels.
Changing workplace culture and work practices was also important.
Achievable reductions change as technology improves and the process of continuous
improvement is vital to any manufacturing facility or it will not be competitive in a
changing world market. The participation of the labour force cannot be emphasised
enough-the whole business has to function as a team, not individuals.
Most of the equipment is unchanged since July 1995. However the control systems,
utilisation and operation have been altered. Technological advancements make more
changes viable. The following two examples highlight the impact of new technology:
• The installation of the water pump VSDs was not economically viable 15 years
ago. VSD technology has only become widespread in the workplace in the last
ten years.
• Electronic process controls such temperature controllers can regulate to closer
tolerances than was previously possible, with mechanical devices. Precise
temperature control eliminates heating and cooling energy wastage. PLCs have
more functions and are cheaper to purchase. More automation of the plant is
inevitable.
A successful factory is more than some machines in a building and few people going
there every day. The equipment is worth nothing without the skill and knowledge of
the trained employees. The skills base of the employees is also changing. They operate
the equipment to achieve production.
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However the factory now produces a consistently high quality product with less waste
and lower labour costs. Energy and water costs are stable at approximately $33 per
tonne, down from $35 per tonne in 1998, despite inflation and GST.
In addition maintenance costs such water treatment chemicals and replacement parts
have been reduced. Some of the results have been convincing. The impact of
crystallisation changes and heat recovery is shown in Figure 21.
9.1 Water usage
Water consumption was reduced 1,500kL per month to 1,399kL shown by the water
bills section 11.11. This was mainly achieved by altering the evaporative condenser fan
controls. Other measures were the fitting of nozzles on wash down hoses and reducing
the boiler usage.
9.2 Energy usage
There has been some effort, thought and risk in the factory development. Both
electricity and gas consumption has been reduced. More effort has been put into
reducing electricity because that was identified as an area with the most potential for
savings. A number of steps achieved the energy reductions. These were:
• Reducing the boiler duty
• Increasing the efficiency of pumping systems
• Increasing the efficiency of the refining process
• Reducing the refrigeration load and hence refrigeration activity
• Controlling the after hours activity with timers and automation
• Improving the packing process to increase output and reduce waste
Correct interpretation of data is also important. For example Figure 28 is an electrical
load profile. It shows two similar production days/crystallisation loads. It illustrates
the changes bought on by the installation of new crystallisation vats.
The operator turned on the cooling at 15:00hrs 9-Sep-03 resulting in high electrical
demand. The flat line from 17:00 hrs 9-Sep-03 is different to 6-Aug-02. It shows that
the crystallisation vats transfer the heat from refined oil more effectively to the
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refrigeration system. Initial indications are that the refrigeration load has been
increased and therefore more energy is required.
However the results are a shorter crystallisation time and less running time for the
water pumps and agitators. Ultimately there was a reduction in energy used.
24 hour Electricity usage
0
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25
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35
40
45
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Time (10 minute intervals)
Elec
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Wh)
6/08/20029/09/2003
Figure 28: Changed electrical load profile.
The following six items are the ones where most energy was saved in the plant:
1) Reducing the boiler duty Boiler duty was reduced when an alternative form heating product transfer pipes was
installed. This meant that the boiler was only fired on refining days. Increased
refining throughput also reduced the number of refining days.
Boiler energy usage dropped by 19% from 1995-1996 compared to 2003-2004. 2) Increasing the efficiency of pumping systems The exercise of changing air conditioning water pumps was very rewarding section
8.2.7. Installing a variable speed drive and a smaller new pump reduced electricity
usage, improved the power factor and still meet supply demands.
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3) Increasing the efficiency of the refining process The refining process was automated which reduced wastage and increased the daily
output as shown in section 11.14 which compares 1998 output with 2004. The
increased output is beneficial because it means less refining days are required for the
same throughput. This results in lower labour and energy costs.
4) Reducing refrigeration activity There really are too many refrigeration modifications to list. Here are some items that
reduced the refrigeration activity:
• Improving the heat transfer from air conditioning water and the factory chilled
water
• Running the cold rooms at higher temperatures and replacing the door seals
• Controlling load run times with timers
• Modulating the feed of liquid ammonia from the receiver by limiting the
solenoid opening to five minutes.
Individually these seem insignificant but together they have caused a reduction in
refrigeration compressors’ run hours see Figure 23 and a reduction in energy used.
5) Controlling the after hours activity with timers and automation The importance of controlling air conditioning and other utilities with timers cannot
be overlooked. Often air conditioning and lighting is left on for extended periods
when not required.
When there large areas involved the loads are considerable. Generally enough energy
is wasted to justify expenditure on simple timers.
6) Improving the packing process to increase output and reduce waste Fixing small machine problems often reduces downtime and wastage. Downtime has
two sides the actual time stopped and the time to restart. The time to restart is often
longer than the stoppage.
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Marginal increases in production rates are worthwhile. Over time an extra 5 cans per
minute turns into 300 cans per hour and 2,400 cans per day. It is the same with
producing defective product. Rework costs money in lost packaging, lost production
and reprocessing costs.
It is better to stop and fix something than run all day and produce rubbish.
9.3 The future The effort expended has been rewarded with favourable results. This project is not
completed. Section 7 Future savings shows that improvements are possible with
further research into:
• Lower the refining temperature to reduce energy requirements by 40%.
• Packing hot refined oil without the cooling process, which may save 20%.
Implementation of either would reduce energy requirements. It is not possible
currently because the product has a three-year shelf life. Modifications may affect
product characteristics. Further research would establish if either was possible.
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10 Bibliography A.I.E. Services flue loss, Useful energy data, Toukley. The Australian Institute of
Energy. http://www.aie.org.au/facts_index.htm (reviewed 11/11/2004, 2004). AMEI. Efficient compressed air systems. Air and Mine Equipment Institute of
Australia. 2004. Aneja, R. P., et al. Technology of Indian milk products. Delhi. Dairy India. 2002. Australian Greenhouse Office http://www.greenhouse.gov.au/ (reviewed 2004) AS1680.1. Interior lighting-General principles and recommendations. Standards
Australia. 1990. AS/NZS 3598. Energy audits. Standards Australia. 2000. Bailey, A. E. Melting and solidification of fats. New York & London. Interscience
Publishers. 1950. Barringer and Associates. Life cycle cost issues. Barringer and Associates Inc.
http://www.barringer1.com/lcc.htm (reviewed 2004, 18-11-04). Butter Producers' Co-operative Federation records. 1994-2005 Campos, R., et al. Effect of cooling rate on the structure and mechanical properties of
milk fat and lard. Guelph, Canada. University of Guelph. 2002. In Food Research International
Dairy Consultant. Buttermaking/AMF/Butteroil.
http://www.dairyconsultant.co.uk/pages/buttermaking (reviewed 23/12/2002, 2002).
Early, R. The technology of dairy products. Glasgow & London. Blackie. 1992. Easthop & Croft. Energy efficiency: for engineers and technologists. New York.
Wiley. 1990. ETPI. The Edible Oil and Ghee Sector. Environmental report (draft) 1999. In Int.
Dairy Journal, ed. Elsevier Science Ltd. Garti, N. & K. Sato. Crystallization and polymorphism of fats and fatty acids. New
York. Marcel Dekker Inc. 1988. Lommers, C. A. Air conditioning and refrigeration industry selection guide-2003.
Melbourne. The Australian Institute of Refrigeration Air conditioning and Heating Inc. 2003.
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Murray Deodorisers. Vacreator, vacuum pasteuriser. Fifth ed. Murray Deodorisers.
1954. Parodi, P. Personal communication2003. ed. Manager Punjrath, J. S. New developments in ghee making. Indian Dairyman (26). 1974. 275. Sserunjogi, M. L., et al. A Review Paper: Current knowledge of ghee and related
products. International Dairy Journal, 8 (8). 1998. 677-688. Tetra-Pak. Cream processing at the Butter Producers' premises. Brisbane. Tetra-Pak.
1994. ed. Manager Tetra-Pak. Dairy Handbook. Sweden. Tetra-Pak. 1995. Varnam, A. H. & Sutherland J. P. Milk and milk products: technology, chemistry and
microbiology. London & New York. Chapman & Hall. 1994.
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11 Appendices
11.1 Appendix (a) Tetra-Pak schematic for cream processing (Tetra-Pak 1995)
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11.2 Appendix (b) Punrath cream processing (Punrath 1974)
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11.3 Appendix (c) Polymorphic behaviour of Butter oil (Bailey, 1950)
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11.4 Appendix (d) Centrifugal separator Alfa Laval website (2004)
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11.5 Appendix (e) Old crystallising vat Drawing sourced from BPCF archives
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11.6 Appendix (f) Air conditioning calculations
Office air conditioning Predicted peak load
20 kW Note this is at ambient 350C.
The load is less in the morning. Hours of operation 10.5 Hrs
Usage for time when air con operates
457 kWh Friday (When there was only office air conditioning and base load)
Base electrical load for period
320 kWh Saturday (Average usage on a weekend day at this time)
Difference 137 kWh Associated equipment kW Pumps and condensers do not run continuously Air conditioning fan 4 42 kWh Air conditioning water pump
3.5 18 kWh
Condensers 4 21 kWh Compressor cooling 2 11 kWh Remaining 45 kWh Compressor efficiency 64%29 kW Coefficient of performance 4.7 136 kWr Predicted peak load is 20kW48
48 Note this is only one room and only part of the air conditioning load. The total air conditioning load was approximately 250kWr.
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11.7 Appendix (g) Compressed air usage table
Atlas Copco GA410 70.0 L/s
Champion econopak F10 20.0 L/s90.0 L/s
Pressure 1 100 kPa Pressure 2 800 kPaVolume 1 90.0 L Volume 2 ?? L
Temperature 1 293 0K Temperatu 302 0K
12 L/s of compressed air
4lb filling line air consumptionCans/min 52Cans /ctn 6
Rams Op/mi L/stroke L/s length Dia shaft Depalletiser Layer remover 1 0.5 17.7 0.1473 2 0.075 rodles
Row remover 1 10.4 0.785 0.1361 0.2 0.05 0.01Filler Fill valve 1 1.0 0.098 0.0016 0.025 0.05 rodles
Filling cyl ram 1 52.0 2.121 1.8378 0.24 0.075 0.03Check weigher Reject ram 1 0.196 0.0000 0.2 0.025 0.01Reseal applicator Lid blower air jet 1Carton erector Box holder ram 2 8.7 0.094 0.0136 0.15 0.02 0.01
Carton infeed 1 8.7 0.010 0.0014 0.01 0.025 rodlesCarton opener 1 8.7 2.513 0.3630 1 0.04 0.01Vacuum 4 8.7 1Carton pusher 1 8.7 2.513 0.3630 1 0.04 0.02Carton fold push 1 8.7 1.257 0.1815 0.5 0.04 0.02Flaps 3 8.7 0.049 0.0071 0.05 0.025 rodles
Packer Infeed stop 1 26.0 0.049 0.0213 0.05 0.025 0.01Can push 1 26 0.754 0.3267 0.3 0.04 0.02Row pusher 1 8.7 1.005 0.1452 0.4 0.04 0.02Lift/lower 1 8.7 1.005 0.1452 0.4 0.04 0.02Flaps 2 8.7 0.098 0.0142 0.1 0.025 0.01Box stop 2 8.7 0.031 0.0045 0.05 0.02 0.01Vacuum 6 8.7 15.0 1
Tape machine Flap folder 1 8.7 0.046 0.0066 0.06 0.022 0.08
Cylinder dimensions
Compressed air is supplied by two compressors
This quoted output is free air delivered, which means the volume of air at atmospheric pressure.The volume of compressed air is less.
"=Pressure 1 x Volume1 xTemperature 2/(Temperature 1 xPressure 2)volume of compressed air
(measured by infrared
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11.8 Appendix (h) Comparison of electricity charge rates This compares electricity tariff charges Electricity tariffs in 2000
General supply Tariff 20 For 1st 10,000 12.2 c/kWh remainder @ 10.65 c/kWh Hot water Tariff 31 4.36 c/kWh Boiler Tariff 37 Day charge rate 6.2 c/kWh Peak demand tariff Rate 3.81 c/kWh Peak demand $17.95 kW
Plus rental for electricity meters $1,200 each Electricity tariffs in 2004 General supply Tariff 20 For 1st 10,000 14.4 c/kWh Remainder @ 12.78 c/kWh Hot water Tariff 31 5.31 c/kWh Boiler No longer used Peak demand tariff Rate 4.59 c/kWh Peak demand $21.71 kW
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11.9 Appendix (i) Hot water usage
QBB hot water storage losses Specific heat water 4.184 kJ/kg K
1kWh= 3.6 MJ Hot water storage vessel
Diameter 2.2 mHeight 5.7 m
Volume of water 21.7 kL
Water temperature set point 75 0C Heat loss exercise-Heating turned off for 24hrs and water temperature checked after 24hours
Temperature after 24 hrs 65 0C Difference to set point 10 0C
"=specific heat of water*Temperature change*volume of water/1000 907 MJ of heat lost in 24hrs Converted to kWh (/3.6MJ) 252 kWh/day Expected efficiency of the electric heating 80% Electrical energy lost per day 315 kWh/day Average days per month 30.5 Electrical energy lost per month 9,575 kWh Water heating average monthly usage 2003-2004 20,875 kWh Percentage of total heat lost 46%
Hot water usage
Average production per year 3,600 t Average production per month 300 t
Production per day 47 t Number of refining days 6.4 days/month
Hot water usage per refining day Separator preheat & cleaning 3,000 L/day
Boiler processing & water 14,000 L/day 17,000 L/day 109 kL/year
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11.10 Appendix (j) Hot water heating
1997 2004
Average production per refining day 39 t 47 t Average annual electrical consumption 345,407 kWh 250,472 kWh
Average electrical monthly usage 28,784 kWh 20,873 kWh
Number of refining days per month 7.7 days 6.4 days
Number of other work days/ month 12 days 13 days Volume of town water to be heated/normal day 1 kL 1 kL Volume of water to be heated/month for factory 12 kL 13 kL
Normal temperature 75 0C Incoming water temperature 17 0C 17 0C
Difference 58 58 Heat energy required 5,430 MJ 5,567 MJ
1,508 kWh/month 1,546 kWh/month
Volume of town water to be heated 17 kL 7 kL Incoming water temperature 17 0C 17 0C
Difference 58 58 Heat energy required 7,501 MJ 3,089 MJ
Volume of water (recovered heat) 10 kL
Incoming water temperature 65 0C Difference 10 0C
761 MJ Total 3,849 MJ/day
1,927 kW/day
Heating water 57,698 MJ/month 24,570 MJ/month 16,027 kWh/month 6,825 kWh/month
Heating losses 10,813 kWh/month 10,813 kWh/month Total 28,349 kWh/month 19,185 kWh/month
Heat recovery Specific heat of butter 2.1 kJ/kg K Recovered energy 50 MJ/t Volume of recovered heat 15,000 MJ/t Energy recovered 4,167 kWh Average monthly drop is 5,000 kWh
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11.11 Appendix (k) Water bill comparison There are two BPCF water bills below. The top one from 1995 shows 1,502kL of water used in 1 month. The second bill shows 1,358kL was used for three months in 2004.
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11.12 Appendix (l) Electrical energy use
To ascertain performance and consumption averages have to be taken over a period of
time. The results of this study show that refining uses 9.8kWh/t and crystallisation uses
38.9kWh/t.
The median electrical usage for a non–workday is now 460kWh. There is very little air
conditioning load during this period.
DATE Total kWh Packing
kWhSat-Sun-
HolidayRefining
kWhCrystal
kWh Output tThursday-1-Apr-04 3,010 460 424 2,126 44.05
Friday-2-Apr-04 1,110 650 460 Saturday-3-Apr-04 850 850
Sunday-4-Apr-04 930 930 Monday-5-Apr-04 3,200 460 432 2,308 46.30
Tuesday-6-Apr-04 2,640 460 160 2,020 12.51Wednesday-7-Apr-04 2,100 1,640 460
Thursday-8-Apr-04 1,950 1,490 460 Friday-9-Apr-04 600 600
Saturday-10-Apr-04 540 540 Sunday-11-Apr-04 550 550 Monday-12-Apr-04 620 620
Tuesday-13-Apr-04 2,000 1,540 460 Wednesday-14-Apr-04 2,130 1,670 460
Thursday-15-Apr-04 2,140 1,680 460 Friday-16-Apr-04 860 860
Saturday-17-Apr-04 530 530 Sunday-18-Apr-04 580 580 Monday-19-Apr-04 2,740 460 419 1,861 42.94
Tuesday-20-Apr-04 2,760 460 244 2,056 25.46Wednesday-21-Apr-04 2,460 2,000 460
Thursday-22-Apr-04 1,960 1,500 460 Friday-23-Apr-04 1,610 1,150 460
Saturday-24-Apr-04 350 350 Sunday-25-Apr-04 400 400 Monday-26-Apr-04 460 460
Tuesday-27-Apr-04 2,490 460 424 1,606 44.61Wednesday-28-Apr-04 2,160 1,700 460
Thursday-29-Apr-04 1,440 980 460 Friday-30-Apr-04 660 660
Saturday-1-May-04 430 430 Sunday-2-May-04 380 380 Monday-3-May-04 460 460
Tuesday-4-May-04 2,360 460 401 1,499 42.07Wednesday-5-May-04 1,800 1,340 460
Thursday-6-May-04 1,370 910 460 Friday-7-May-04 1,370 910 460
Saturday-8-May-04 330 330 Sunday-9-May-04 320 320
Monday-10-May-04 2,360 460 409 1,491 41.57Tuesday-11-May-04 2,589 460 150 1,979 9.00
Wednesday-12-May-04 1,050 460 308 282 31.12
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Thursday-13-May-04 1,970 1,510 460 Friday-14-May-04 680 680
Saturday-15-May-04 410 410 Sunday-16-May-04 480 480 Monday-17-May-04 1,360 900 460
Tuesday-18-May-04 2,290 460 413 1,417 43.27Wednesday-19-May-04 1,660 1,200 460
Thursday-20-May-04 1,410 950 460 Friday-21-May-04 2,270 460 398 1,412 40.42
Saturday-22-May-04 320 320 Sunday-23-May-04 330 330 Monday-24-May-04 1,760 1,300 460
Tuesday-25-May-04 1,740 1,280 460 Wednesday-26-May-04 2,160 460 434 1,266 42.81
Thursday-27-May-04 1970 460 425 1,085 44.54Friday-28-May-04 650 650
Saturday-29-May-04 490 490 Sunday-30-May-04 640 640 Monday-31-May-04 1,530 1,070 460 40.96Tuesday-1-Jun-04 1,394 934 460 19.53
Wednesday-2-Jun-04 1,404 944 460 Thursday-3-Jun-04 1,176 716 460
Friday-4-Jun-04 1,149 689 460 Saturday-5-Jun-04 348 348
Sunday-6-Jun-04 342 342 Monday-7-Jun-04 2,079 460 415 1,204Tuesday-8-Jun-04 1,812 460 216 1,136
Wednesday-9-Jun-04 1,660 1,200 460 Thursday-10-Jun-04 1,559 1,099 460
Friday-11-Jun-04 514 514 Saturday-12-Jun-04 394 394
Sunday-13-Jun-04 389 389 Monday-14-Jun-04 411 411 Tuesday-15-Jun-04 2,227 460 408 1,359 41.16
Wednesday-16-Jun-04 2,450 460 361 1,629 33.73Thursday-17-Jun-04 1,607 1,147 460
Friday-18-Jun-04 1,398 938 460 Saturday-19-Jun-04 371 371
Sunday-20-Jun-04 350 350 Monday-21-Jun-04 2,192 460 447 1,285 44.62Tuesday-22-Jun-04 2,293 460 239 1,594 21.95
Wednesday-23-Jun-04 1,498 1,038 460 Thursday-24-Jun-04 1,218 758 460
Friday-25-Jun-04 597 597 Saturday-26-Jun-04 394 394
Sunday-27-Jun-04 426 426 Monday-28-Jun-04 2,297 460 437 1,400 46.97Tuesday-29-Jun-04 1,803 1,343 460
Wednesday-30-Jun-04 2,503 460 409 1,634 38.90Thursday-1-Jul-04 2,301 460 249 1,592 26.01
Friday-2-Jul-04 1,906 1,446 460 Saturday-3-Jul-04 807 807
Sunday-4-Jul-04 818 818 Monday-5-Jul-04 2,533 460 437 1,636 48.18
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Tuesday-6-Jul-04 2,071 1,611 460 Wednesday-7-Jul-04 1,594 1,134 460
Thursday-8-Jul-04 1,725 460 420 845 42.75Friday-9-Jul-04 672 672
Saturday-10-Jul-04 444 444 Sunday-11-Jul-04 426 426 Monday-12-Jul-04 2,040 1,580 460 Tuesday-13-Jul-04 2,377 460 431 1,486 44.60
Wednesday-14-Jul-04 1,915 460 260 1,195 27.68Thursday-15-Jul-04 2,055 1,595 460
Friday-16-Jul-04 1,494 1,034 460 Saturday-17-Jul-04 441 441
Sunday-18-Jul-04 341 341 Monday-19-Jul-04 2,258 460 449 1,349 44.94Tuesday-20-Jul-04 2,178 1,718 460
Wednesday-21-Jul-04 2,055 460 445 1,150 49.22Thursday-22-Jul-04 1,785 1,325 460
Friday-23-Jul-04 562 562 Saturday-24-Jul-04 402 402
Sunday-25-Jul-04 486 486 Monday-26-Jul-04 2,485 460 464 1,561 48.00Tuesday-27-Jul-04 2,543 460 474 1609 51.79
Wednesday-28-Jul-04 1,767 1,307 460 Thursday-29-Jul-04 1,979 1,519 460
Friday-30-Jul-04 2,568 460 430 1,678 45.76Saturday-31-Jul-04 626 626
Total t 1,227kWh 170,678 52,445 58,451 12,032 47,750 MJ (electricity) 614,441 188,802 210,424 43,315 171,900 MJ (electric hot water) 319,255 MJ (gas) 645,939 Percentage of total49 41% 12% 13% 3% 11% Number of days 122 43 122 32 32 Average kWh 1,249 479 417 Median kWh 1,240 460 kWh/t 42.7 9.8 38.9
49 Shown in Figure 9
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11.13 Appendix (m) Pump power efficiency (Fantech, Dec 2004)
The explanation of fan efficiency is applicable to pump power when there are pipe
restrictions.
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11.14 Appendix (n) Refining process throughput
Date Output (t) Date Output 01-Jul-98 40.68 5-Jul-04 48.18 06-Jul-98 38.28 8-Jul-04 42.75 21-Jul-98 33.41 13-Jul-04 44.6 29-Jul-98 24.20 19-Jul-04 44.94 30-Jul-98 30.36 21-Jul-04 49.22
06-Aug-98 31.56 26-Jul-04 48 13-Aug-98 40.42 27-Jul-04 51.79 17-Aug-98 42.40 30-Jul-04 45.76 24-Aug-98 30.99 3-Aug-04 46.88 24-Aug-98 39.31 9-Aug-04 49.38 31-Aug-98 39.84 12-Aug-04 46.47 01-Sep-98 39.94 16-Aug-04 46.77 08-Sep-98 35.44 18-Aug-04 44.2 15-Sep-98 42.88 23-Aug-04 50.11 17-Sep-98 39.36 25-Aug-04 50.09 21-Sep-98 38.74 31-Aug-04 43.27 22-Sep-98 40.99 6-Sep-04 49.97 25-Sep-98 31.62 7-Sep-04 48.48 28-Sep-98 38.68 13-Sep-04 49.14 29-Sep-98 39.15 20-Sep-04 48.83 06-Oct-98 37.11 21-Sep-04 42.76 07-Oct-98 37.90 28-Sep-04 40.02 12-Oct-98 39.08 4-Oct-04 49.73 15-Oct-98 38.09 11-Oct-04 49.11 19-Oct-98 37.99 18-Oct-04 41.38 21-Oct-98 41.64 19-Oct-04 47.23 22-Oct-98 39.62 26-Oct-04 47.07 27-Oct-98 41.29 3-Nov-04 47.91
Daily Average 37.5t/day 46.93t/day