Heat Pump Integration in a Cheese Factory Helen Becker 1 , Aurélie Vuillermoz 2 , François Maréchal 1 1 Industrial Energy Systems Laboratory (LENI) Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland 2 EDF R&D, Eco-efficiency and Industrial Process Department Centre de Renardières, 77818 Moret sur Loing, France PRES’11: 14th International Conference on Process Integration, Modeling and Optimization for Energy Saving and Pollution Reduction
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Heat Pump Integration in a Cheese Factory
Helen Becker1, Aurélie Vuillermoz2, François Maréchal1
1 Industrial Energy Systems Laboratory (LENI)Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
2 EDF R&D, Eco-efficiency and Industrial Process DepartmentCentre de Renardières, 77818 Moret sur Loing, France
PRES’11: 14th International Conference on Process Integration, Modeling and Optimization for Energy Saving and Pollution Reduction
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Outline
• Introduction
• Process integration / heat pump integration
• Example of a cheese factory
• Methodology - Heat pump integration
• Option 1: without process modifications
• Option 2: with process modifications
• Results
• Conclusion
2
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Process integration: Optimize the energy efficiency
3
Rawmaterials Products
By-Products
EnergyServices
EnergyWater Air Inert GasFuelElectricity
Support
Heat losses WaterSolids GaseousWaste
Representation of industrial processes
Reducing energy consumption and operating costs
Energy conversion and utility Units(e.g. heat pumps, steam boiler, cooling water, ...)
Process operation Units
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Heat pump integration
• Heat pump integration potential
• Heat pump integration options
• No process modifications - heat exchange restrictions between process units and heat pumps --> integration of intermediate heat transfer units
• MILP problem with additional constraints (*)
• Process modifications - no heat exchange restrictions
• Conventional heat cascade model (MILP problem)
4
* Becker H., Girardin L. and Maréchal F., 2010, Energy integration of industrial sites withheat exchange restrictions, European Symposium on Computer Aided Process Engineering- ESCAPE 20, 1141–1146.
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Example of a cheese factory
5
Rawmaterials(milk)
Products (cheese)By-Products (concentrated whey)
Energy Services
EnergyWater Air Inert GasFuelElectricity
Support
Heat losses WaterSolidsWaste
Energy conversion and utility Units(e.g. heat pumps, steam boiler, cooling water, ...)
Gaseous
Curdling
Evaporation
Prepasteu-
rization
Air-conditioningHot WaterCleaning
Pasteu-
rization
Forming Refining
Pasteurization
Packaging
Cream
Whey
Pasteurization
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Process heat requirement definition
6
• Process operation units
• Definition of process streams for heat integration
Evaporation unit is modeled considering the existing thermal vapour
Figure 2: Grand composite curve of the process and integrated composite curve of the utilitysystem using Carnot scale.
3.1 Heat pump integration option 1: No process modifications allowedHeat pumps are used to valorize waste heat from the process below the pinch point bydriving it above the pinch point with the help of mechanical power, reducing thereforehot and cold utility requirements. In the first approach, the process can not be modified.Thus, the direct heat exchange between a potential heat pump and the process is not al-lowed. The approach from Becker et al. (2010) is applied: two sub-systems (in this casethe process and the heat pump) cannot exchange heat directly. A closed cycle heat pumpusing the refrigerant R245fa is considered. By analyzing the shape of the grand compositecurve, appropriate operating conditions for the heat pump and the intermediate networkcan be estimated. Then, simultaneously the interdependent flow rates of the utility units,heat pumps and the heat distribution fluids are defined, in order to minimize the operatingcosts. The potential of a closed cycle heat pump without direct heat exchange is illustrated
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Energy Integration
0 500 1000 1500 2000 2500 3000 3500 4000 45000.2
0.1
0
0.1
0.2
0.3
0.4
0.5
Heat Load [kWh/tprod]
Ca
rno
t F
acto
r 1
- T
a/T
[-]
Cold streamsHot streams
MER hot = 2146.3 kWh/tprod
MER cold = 892.4 kWh/tprod
7
!1000 !500 0 500 1000 1500250
300
350
400
450
500
Heat Load [kWh/tprod]
Tem
pera
ture
[K
]
All streams
MER hot = 2146.3 kWh/tprod
MER cold = 892.4 kWh/tprod
Hot and cold composite curves Grand composite curve
Waste heat at 44°CHeat pump integration ?
Current hot utility 2345 kWh/tprod
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Methodology - indirect and direct heat pump integration
• Indirect heat pump integration
• Heat pump cannot exchange directly with the process
• Closed cycle heat pump
• Process modifications are not allowed
• Transfering heat via intermediate heat transfer units
• Direct heat pump integration
• Heat pump can exchange directly with process
• Open cycle heat pump / mechanical vapour compression
• Process modifications are allowed
• Modifying layout of evaporation unit
8
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Indirect heat pump integration
9
Sub-system
1
Sub-system
2
Sub-system
3
Heat transfer system (HTS)
No direct heat exchange possible
Direct heat exchange possible
General
units (GU)
Heat transfer
units (HTU)
Energy Support
Electricity Fuel Water Air Inert Gas
Heat losses Solids Water GasWaste
Raw
materials
Energy
servicesProductsByproducts
• Introduction of subsystems with restricted matches *
• Introduction of intermediate heat transfer units (two water loops)
* Becker H., Girardin L. and Maréchal F., 2010, Energy integration of industrial sites withheat exchange restrictions, European Symposium on Computer Aided Process Engineering- ESCAPE 20, 1141–1146.
r245fa heat pump
Cheese process
Intermediate water loop high temperature
Waste heatheats water
HP coldsource
HP hotsource
Satisfieshot process
demand
Intermediate water looplow temperature
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Indirect heat pump integration
• Advantages
• No process modifications --> no supplementary investment costs
• Safety and product quality
• Disadvantages
• High temperature lift --> small COP
• Considering storage problem --> supplementary costs
10
!1000 !500 0 500 1000 1500!0.2
!0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Heat Load [kWh/tprod]
Carn
ot F
acto
r 1!
Ta/T
[!]
othersutility
Natural gas consumption: 2157 kWh/tprodCurrent natural gas consumption: 2895 kWh/tprod
Saving potential 25 %
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Direct heat pump integration - Analyzing evaporation unit
11
Waste heat producer for heat pump
Optimizing evaporation unit ?
Replacing thermal vapour compression with a MVR unit ?
Milk inlet
Effect 1
T1
P1
Effect 3
T3
P3
Effect 2
T2
P2
steam
product
steam
condensates
To thermal vapour compression
....
To effect 4 and 5 ...
PH PH PH PH
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Direct heat pump integration - Process modifications
• Keep evaporation layout
• CASE A : Thermal vapour compression is replaced with mechanical vapour compression (MVR)
• Modify pressure of effects
• CASE B: Realizing all effects in parallel & integration of a MVR unit
• CASE C: Optimizing layout of evaporation & integration of 3 MVR units
• Constant area of each evaporator
12
Qi = Ui · Ai · (Tvap ! Tprod)
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Direct heat pump integration
• Advantages
• Better energy efficiency
• No storage problem
• Disadvantages
• Process modifications may give higher investment costs
• MVR is in direct contact with the product
13
H. Becker, A. Vuillermoz, F. Maréchal
Introduction Methodology Results Conclusion
Comparison of scenarios
14
Heat recovery
r245faHP
AMVR
BMVR
CMVR
• Current consumption: 2895 kWh/tprod of natural gas, 194 kWh/tprod of electricity
5 AcknowledgementsThe authors wish to thank ECLEER for supporting this research and collaborating in itsrealization.
ReferencesBecker H., Girardin L. and Maréchal F., 2010, Energy integration of industrial sites with
heat exchange restrictions, European Symposium on Computer Aided Process Engi-neering - ESCAPE 20, 1141–1146.
Becker H., Maréchal F. and Vuillermoz A., 2011, Process integration and opportunity forheat pumps in industrial processes, International Journal of Thermodynamics, ECOS2009 special issue, accepted.
Kapustenko P. O., Ulyev L. M., Boldyryev S. A. and Garev A. O., 2008, Integration of aheat pump into the heat supply system of a cheese production plant, Energy 33, 882–889.
Linnhoff B. and Townsend D., 1983, Heat and power networks in process design. part1: Criteria for placement of heat engines and heat pumps in process networks, AIChEJournal 29 (5), 742–748.
Pavlas M., Stehlík P., Oral J., Kleme! J., Kim J. and Firth B., 2010, Heat integrated heatpumping for biomass gasification processing, Applied Thermal Engineering 30, 30–35.
Wallin E. and Berntsson T., 1994, Integration of heat pumps in industrial processes, HeatRecovery Systems & CHP 14 (3), 287–296.
r245faHP
AMVR
BMVR
CMVR
• Used equation
• Heat pump size for r245fa heat pump
• max: peak power of the heat source
• mean: heat source is stored and progressively upgraded