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Application of Solar Thermal for Boosting Waste Heat in LowTemperaturePinch Processes: A Dairy Indus

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Milk Pasteurisation. NERI Conference 2007 ... Over 50 % of milk is processed into powder ... Andersson, E., Harvey, S., Berntsson, T., 2006. ... – PowerPoint PPT presentation

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Title: Application of Solar Thermal for Boosting Waste Heat in LowTemperaturePinch Processes: A Dairy Indus


1
Application of Solar Thermal for Boosting Waste
Heat in Low-Temperature-Pinch Processes A
Dairy Industry Application
  • Andrew Morrison, Martin Atkins, Michael Walmsley
  • Energy Research Group
  • School of Science and Engineering
  • The University of Waikato

2
Improving Energy Efficiency
  • Dairy processes in NZ contain
  • Large quantities of low grade waste heat
  • A pinch point of approximately 50 ºC
  • . . . and are faced with
  • Increasing energy costs
  • Threat of carbon tax implementation
  • Push towards renewable forms of energy

3
Improving Energy Efficiency
  • Need to explore possible ways of improving energy
    efficiency!!
  • Pinch Analysis to examine the overall process
  • Application of heat pumps for utilising waste
    heat
  • Potential for solar thermal systems to boost
    waste heat
  • Dairy case-study

4
Pinch Analysis
  • Process integration tool developed 1970s
  • Significant savings in a broad range of
    industries
  • Systematic process analysis for minimum utility
    usage
  • Correct placement and sizing of heat pumps
  • Batch processes and mass integration

5
Pinch Analysis
Hot Water for CIP
Milk Pasteurisation
6
Pinch Analysis
Combined Cold Stream
7
Pinch Analysis
HOT UTILITY 750 kW
Composite Curves
PINCH 145 ºC
COLD UTILITY 1000 kW
8
Pinch Analysis
Grand Composite Curve
Direct heat exchange
120ºC
Quantify energy at each temperature level
9
Heat Pumps
A heat pump absorbs low-temperature heat and
upgrades it to a higher temperature to provide
process heat.
W
10
Heat Pumps
QHmin W
QHP W
W
QHP
QCmin
ABOVE PINCH
Unlikely to be feasible
11
Heat Pumps
QHmin
QHP W
W
QHP
QCmin W
BELOW PINCH
Definitely not feasible
12
Heat Pumps
QHmin (QHP W)
QHP W
W
QHP
QCmin QHP
ACROSS PINCH
Energy Savings!!!
13
Heat Pumps
  • Higher COPHP
  • Improved economics
  • Greater amount of useful energy
  • Lower temperature rise
  • gt 25 ºC is unlikely to be feasible (Most heat
    pumps operate with a much lower temperature lift)

25 ºC
167 kW
14
Solar Thermal
  • Application of Solar Thermal Systems
  • Able to operate with a temperature rise gt 40 ºC
  • Work input has no direct cost
  • Utilise a renewable source of energy
  • Rising energy costs will lead to economic
    feasibility
  • Correct process design is essential

15
Solar Thermal
16
Dairy Case-Study
  • Typical New Zealand Milk Powder Plant
  • Over 30 large-scale powder plants in NZ
  • Over 50 of milk is processed into powder
  • Powder production uses a significant quantity of
    thermal energy due to the removal of water
  • Focused on the wet-side of the process (prior to
    the dryer)

17
Dairy Case-Study
Centrifugal Separator
Steam and make-up water
Cleaning-in-Place System
18
Dairy Case-Study
19
Dairy Case-Study
Hot Utility
Pinch Temperature 46 ºC
40 ºC
Cold Utility
20
Dairy Case-Study
21
Dairy Case-Study
22
Dairy Case-Study
23
Dairy Case-Study
Design 1
24
Dairy Case-Study
Cost-Benefit Analysis Duty of solar system
279kW Solar collector area required
1883m2 Total cost of solar collectors
300,000 Volume of steam saved 2340
tonnes Total value of steam savings 70,000
Payback on cost of solar collectors 4.4
years Not yet economically feasible!!
25
Dairy Case-Study
26
Dairy Case-Study
27
Dairy Case-Study
Cold Utility
28
Dairy Case-Study
29
Dairy Case-Study
Design 1
30
Dairy Case-Study
Design 2
31
Dairy Case-Study
Design 3
32
Dairy Case-Study
Design 1 Total steam reduction 279 kW 279 kW
generated by Solar system Design 2 Total
steam reduction 418 kW 279 kW generated by
Solar system 139 kW recovered from Cow water
cooling Design 3 Total steam reduction Up to
1666 kW 279 kW generated by Solar system Up
to 1387 kW recovered from Cow water cooling
33
Dairy Case-Study
  • Summary
  • Solar thermal has the potential to utilise waste
    energy
  • Reduce overall energy use and CO2 emissions
  • Increase the use of renewable sources of energy

Specific industrial design is essential to
optimise the system
34
Acknowledgements
  • Energy Research Group, University of Waikato
  • Final Year Design Group
  • David Aston, Karl Jamieson, Nathan Johnson,
    Christina Kelly, Kirstin Stephens

References
Andersson, E., Harvey, S., Berntsson, T., 2006.
Energy efficient upgrading of biofuel integrated
with a pulp mill. Energy 31, 1384-1394. Kalogirou,
S., 2003. The potential of solar industrial
process heat applications. Applied Energy 76,
337-361. Kalogirou, S., 2004. Solar thermal
collectors and applications. Progress in Energy
and Combustion Science 30, 231-295. Kemp, I.C.,
2005. Reducing dryer energy use by process
integration and pinch analysis. Drying Technology
23, 2089-2104. Schnitzer, H., Brunner, C.,
Gwehenberger, G., 2007. Minimizing greenhouse gas
emissions through the application of solar
thermal energy in industrial processes. Journal
of Cleaner Production 15, 1271-1286. Smith, R.,
2005. Chemical process design and integration.
John Wiley Sons Ltd, England.
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