In most of the industries substantial amount of energy is consumed in generating hot water and refrigeration effect. If these process operations of heating and chilling are made more efficient, then significant amount of energy consumption can be reduced. Thermax Ltd with the aim of providing energy efficient and environment friendly solution for such applications has come up with a Heat Pump using its Vapour absorption technology.
As the name suggests, a Heat Pump is an equipment which pumps heat from a lower temperature heat source to a comparatively higher temperature heat sink. As the direction of the heat flow is against the natural course, external work has to be supplied to achieve the required pumping
Heat Pumps are available in both Vapour Absorption cycle as well as Vapour Compression cycle. The Vapour Compression systems are mostly electrically driven whereas the Vapour Absorption cycle is thermally driven. Thus, the Vapour Absorption based Heat Pump essentially operates with three utilities:
1. Low temperature Heat source – from which Heat is absorbed
2. Driving Heat source – which supplies work for the pumping
3. Product Hot water stream – to which Heat is added in the Heat pump
2. Driving Heat source – which supplies work for the pumping
3. Product Hot water stream – to which Heat is added in the Heat pump
Vapour Absorption CYCLE Based Heat Pump
The heat balance across the Heat pump remains the same as that of a vapour absorption based chiller i.e., heat is absorbed in the Evaporator and Generator and the absorbed heat is then rejected in the Absorber and Condenser. Depending on the relative temperatures of the Low Temperature Heat Source, Driving Heat Source and Desired Hot water temperatures, the Heat Pump is operated using different cycles to cater to the altered requirement.
Thus, Heat Pump can be classified into:
1. Heat Pump Type I
2. Heat Pump Type II (Heat Transformer)
1. Heat Pump Type I
2. Heat Pump Type II (Heat Transformer)
Heat Pump Type I
• In Type I heat pump, a Low-Grade Heat Source (40oC - 35oC), typically cooling water is circulated in the Evaporator.
• A High-Grade Driving Heat Source (180oC - 160oC) is utilised in the Generator by means of which heat rejection is done to a medium grade heat medium (60oC - 90oC).
• That is, the heat absorbed in the Evaporator from the Low-Grade Heat Source & the heat absorbed in the Generator from a High-Grade Driving Heat Source is rejected to medium grade heat medium circulated in the Absorber and Condenser.
• TYPICAL HEAT BALANCE:
– Heat Balance equation:
Q1 + Q3 = Q2
– Co-efficient of performance,
COP =Heat output / Heat Input
= Q2 / Q3
= 1.7
• That is, For every 1.7 kcal of heat added to the hot water by Heat Pump, 0.7 Kcal is absorbed from the low temperature Heat source (waste heat source), and hence, Fuel consumption for a given Heating requirement reduces by 40%.
• As 0.7 kcal Heat is absorbed from the Cooling water, the Cooling tower Heat duty is also reduced.
• Correspondingly, evaporative losses in the tower also reduce.
• In Type I heat pump, a Low-Grade Heat Source (40oC - 35oC), typically cooling water is circulated in the Evaporator.
• A High-Grade Driving Heat Source (180oC - 160oC) is utilised in the Generator by means of which heat rejection is done to a medium grade heat medium (60oC - 90oC).
• That is, the heat absorbed in the Evaporator from the Low-Grade Heat Source & the heat absorbed in the Generator from a High-Grade Driving Heat Source is rejected to medium grade heat medium circulated in the Absorber and Condenser.
• TYPICAL HEAT BALANCE:
– Heat Balance equation:
Q1 + Q3 = Q2
– Co-efficient of performance,
COP =Heat output / Heat Input
= Q2 / Q3
= 1.7
• That is, For every 1.7 kcal of heat added to the hot water by Heat Pump, 0.7 Kcal is absorbed from the low temperature Heat source (waste heat source), and hence, Fuel consumption for a given Heating requirement reduces by 40%.
• As 0.7 kcal Heat is absorbed from the Cooling water, the Cooling tower Heat duty is also reduced.
• Correspondingly, evaporative losses in the tower also reduce.
Heat Pump Type I APPLICATIONS
Heat Pump For Paint Booth Heating Application
– Heating Capacity :2.34 MW
– Heat pumped from Waste heat source (cooling water) = 0.965 MW
= Fuel consumption reduced by 89 kg/h of HSD
= 40% Savings
– Cooling tower Heat duty reduced by = 0.965 MW
OPERATING PARAMETERS
Heat Pump For Paint Booth Heating Application
– Heating Capacity :2.34 MW
– Heat pumped from Waste heat source (cooling water) = 0.965 MW
= Fuel consumption reduced by 89 kg/h of HSD
= 40% Savings
– Cooling tower Heat duty reduced by = 0.965 MW
OPERATING PARAMETERS
Heat Pump For Wort Heating Application
– Heating Capacity : 458 kW
– Heat pumped from Waste heat source (cooling water) = 181 kW
= Steam consumption reduced by 272 kg/h
= 40% Savings
– Cooling tower Heat duty reduced by = 181 kW
– Heating Capacity : 458 kW
– Heat pumped from Waste heat source (cooling water) = 181 kW
= Steam consumption reduced by 272 kg/h
= 40% Savings
– Cooling tower Heat duty reduced by = 181 kW
OPERATING PARAMETERS
Heat Pump For Hot Air
– Heating Capacity : 8 MW
– Heat pumped from Waste heat source (cooling water) = 3.1 M
= Steam consumption reduced by 4700kg/h
= 39 % Savings
– Cooling tower Heat duty reduced by = 3.1 MW
OPERATING PARAMETERS
– Heating Capacity : 8 MW
– Heat pumped from Waste heat source (cooling water) = 3.1 M
= Steam consumption reduced by 4700kg/h
= 39 % Savings
– Cooling tower Heat duty reduced by = 3.1 MW
OPERATING PARAMETERS
Heat Pump For District Heating Application
– Heating Capacity: 8 MW
– Heat pumped from Waste Heat source (Exhaust Gas) = 3.29 MW
= Steam consumption reduced by 5050 kg/h
= 40% Savings
OPERATING PARAMETERS
– Heating Capacity: 8 MW
– Heat pumped from Waste Heat source (Exhaust Gas) = 3.29 MW
= Steam consumption reduced by 5050 kg/h
= 40% Savings
OPERATING PARAMETERS
• Here, the 16.3°C Water leaving the Evaporator is made to exchange Heat with Gas turbine exhaust so as to cool the Exhaust to temperatures as low as 70-80°C to increase the recovery. Due to the absorbed heat, the same water returns to the Heat pump at 26.1°C.
Heat Pump Type II
Heat Pump Type II is better known as Heat Transformer. This type of Heat Pump transforms a waste heat source to a more useful heat source by raising its temperature. A medium grade heat source(110°C - 100°C) is circulated in Evaporator as well as Generator, where Heat is absorbed into the Heat pump. Part of this absorbed heat is rejected to a higher-grade heat medium(150°C - 160°C) in the Absorber which is the actual output of the heat pump, and the remaining heat is rejected to cooling water (30°C) circulated in the condenser. That is, Medium grade Waste heat is added to High-grade heat utilising Medium grade Waste heat source.
TYPICAL HEAT BALANCE
– Heat Balance equation:
Q1 = Q2 + Q3
– Co-efficient of performance,
COP = Q2/Q1
= 0.45
– That is, 45% of waste heat that was initially rejected to atmosphere can be pumped to a useful heat source (Product Hot water/steam), thus enhancing overall process efficiency greatly.
– The Heat pump output will always be hot water, which can be flashed in a flash tank to provide steam as per the desired pressure, thus, when steam is required as an output, heat pump – flash tank circuit and related accessories will become a part of the solution offered.
Heat Pump Type II is better known as Heat Transformer. This type of Heat Pump transforms a waste heat source to a more useful heat source by raising its temperature. A medium grade heat source(110°C - 100°C) is circulated in Evaporator as well as Generator, where Heat is absorbed into the Heat pump. Part of this absorbed heat is rejected to a higher-grade heat medium(150°C - 160°C) in the Absorber which is the actual output of the heat pump, and the remaining heat is rejected to cooling water (30°C) circulated in the condenser. That is, Medium grade Waste heat is added to High-grade heat utilising Medium grade Waste heat source.
TYPICAL HEAT BALANCE
– Heat Balance equation:
Q1 = Q2 + Q3
– Co-efficient of performance,
COP = Q2/Q1
= 0.45
– That is, 45% of waste heat that was initially rejected to atmosphere can be pumped to a useful heat source (Product Hot water/steam), thus enhancing overall process efficiency greatly.
– The Heat pump output will always be hot water, which can be flashed in a flash tank to provide steam as per the desired pressure, thus, when steam is required as an output, heat pump – flash tank circuit and related accessories will become a part of the solution offered.
Heat Pump Type II APPLICATIONS
Heat Pump Used In Poly Film Manufacturing Company
• The plant manufactures poly film for photovoltaic cells
• The manufacturing process requires 100°C water
• During the process this water temperature increases to 110°C
• For reutilisation, the 110°C water leaving the process was cooled to 100°C in a dry cooler where the heat was simply rejected to the atmosphere
• Using Heat pump Type II, the available heat was utilised for generation of 4 barg steam, which finds use within the manufacturing process.
OPERATING PARAMETERS
Heat Pump Used In Poly Film Manufacturing Company
• The plant manufactures poly film for photovoltaic cells
• The manufacturing process requires 100°C water
• During the process this water temperature increases to 110°C
• For reutilisation, the 110°C water leaving the process was cooled to 100°C in a dry cooler where the heat was simply rejected to the atmosphere
• Using Heat pump Type II, the available heat was utilised for generation of 4 barg steam, which finds use within the manufacturing process.
OPERATING PARAMETERS
• As can be seen, addition of Type II Heat pump not only reduces the boiler load by 6.5 TPH but also reduces the power requirement of the dry cooler, as the heat rejection to atmosphere is reduced to half and is done in a cooling tower, which consumes substantially less power as compared to a dry cooler.
Heat Pump Used In Food Industry
• In this application, Gas engine’s jacket water is cooled in the Type II heat pump.
• Using the 93°C jacket water as heat source, hot water of 125°C is heated to 135°C.
• This hot water of 135°C is then used in a pasta manufacturing process.
• In this application, Gas engine’s jacket water is cooled in the Type II heat pump.
• Using the 93°C jacket water as heat source, hot water of 125°C is heated to 135°C.
• This hot water of 135°C is then used in a pasta manufacturing process.
Operating Parameters
Heat Pump Used In Refineries and Petrochemicals
• The product streams of many processes in refineries are at elevated temperatures, these have to cooled before taking to filling & storing on account of high volatilities to avoid evaporation losses.
• Also, high temperature heat sources i.e. steam @ 4-8 bar are required in substantial quantities for innumerable processes.
• Here, Heat pump Type II can be used to pump heat from the medium temperature streams to higher temperature, to provide steam @ desired pressure.
• This will not only reduce steam costs but also reduce the costs incurred for product cooling which may include use of dry coolers or any other such indirect heat exchangers where effectively the heat is rejected to the atmosphere.
Advantages Of Heat Pumps:
• 40% savings can be attained in external heat source consumption for generating hot water as compared to conventional hot water generator.
• If the cooling water is being used as a low temperature heat source, the heat rejections in the cooling tower will reduce correspondingly by 40%. Thus, the evaporating losses will also reduce.
• There is reduction in Carbon Dioxide (CO2 emissions due to lower fuel consumption.
The report elucidates the concept and technology of Thermax’s Heat Pump Type I and Heat pump Type-II.
• The product streams of many processes in refineries are at elevated temperatures, these have to cooled before taking to filling & storing on account of high volatilities to avoid evaporation losses.
• Also, high temperature heat sources i.e. steam @ 4-8 bar are required in substantial quantities for innumerable processes.
• Here, Heat pump Type II can be used to pump heat from the medium temperature streams to higher temperature, to provide steam @ desired pressure.
• This will not only reduce steam costs but also reduce the costs incurred for product cooling which may include use of dry coolers or any other such indirect heat exchangers where effectively the heat is rejected to the atmosphere.
Advantages Of Heat Pumps:
• 40% savings can be attained in external heat source consumption for generating hot water as compared to conventional hot water generator.
• If the cooling water is being used as a low temperature heat source, the heat rejections in the cooling tower will reduce correspondingly by 40%. Thus, the evaporating losses will also reduce.
• There is reduction in Carbon Dioxide (CO2 emissions due to lower fuel consumption.
The report elucidates the concept and technology of Thermax’s Heat Pump Type I and Heat pump Type-II.
AUTHOR CREDIT AND PHOTOGRAPH
P Babu
Head - Innovations
Thermax Ltd.
Pune
Head - Innovations
Thermax Ltd.
Pune
Vikas Tripathi
Head - Marketing
Thermax Ltd.
Pune
Head - Marketing
Thermax Ltd.
Pune
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