Gas Turbine Inlet Air Cooling System The 3rd Annual Australian Gas Turbine Conference 6th – 7th December 2001 Melbourne Australia Presented by
Bob Omidvar Manager, Power Engineering PB Power Australia PB Power
Heavy Duty GT - Effects of Ambient Temp 110% 105% 100% 95% 90% 85% 80% 75% 0
5
10
15
20
25
30
35
40
GT Inlet Temp (deg C) Heat rate kJ/kWh
PB Power
Power output MW
Exhaust flow t/h
Exhaust temperature °C
45
Aero-Derivative GT - Effects of Ambient Temp
120% 110% 100% 90% 80% 70% 60% 0
5
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40
GT Inlet Temp (deg C) Exhaust temperature C
PB Power
Heat rate kJ/kWh
Power output MW
Exhaust flow t/h
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Gas Turbine Performance Design Basis What Does ISO Condition Mean? !
Dry bulb 15°C
!
Relative humidity 60%
!
Wet bulb temperature 7.2°C
!
Atmospheric pressure 1 bar (sea level)
Most of the gas turbine installations are not in ISO standard locations, they are in the real world
PB Power
Ambient Air and Gas Turbine Performance 1. Air density is inversely related to the dry bulb temperature 2. Gas turbine output depends on mass flow and not the volume of air 3. Ambient temperature affects the following points drastically " Air flow " Output " Heat rate " Exhaust temperature
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Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Schematic of Evaporative Air Cooling shown with Optional Water Treatment Combustion Air
Water Tank Air Filter
Wetted Media
Water Treatment
Exhaust Gas
Fuel
Combustion Turbine
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Make Up
Blow down
Evaporative Cooler Applications: Areas where RH and wet bulb temperature is rather low
Advantage #
Lowest capital cost
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Lowest O&M cost
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Can operate on raw water
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Quick delivery and installation time
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Operates as an air washer and cleans the inlet air
PB Power
Disadvantage #
Limitation on capacity improvement
#
Highly influenced by the site wet bulb
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Schematic of Fog Inlet Air Cooling System Utilizing Demineralised Water Raw Water Demineralised Water Treatment Plant
Demineralised Water Tank
Combustion Air Air Filter
Exhaust Gas
Fuel
Combustion Turbine
PB Power
Fog Spray System
Fog Systems
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Demineralised Water Quality For Fog System Inlet Air Cooling Total dissolved solids
5 PPM maximum
pH
6-8
Na + K
0.1 PPM maximum
Silica (SiO2)
0.1 PPM maximum
Chlorides
0.5 PPM maximum
Sulphate
0.5 PPM maximum
PB Power
t/h
Fogging System Demin. Water Consumption Inlet air 36°C DB, 25°C WB Chilled air temp 25.5°C DB 25°C WB, 96%RH
10 9 8 7 6 5 4 3 2 1 0 0
25
50
75
100
125
150
175
Gas Turbine Output MW
PB Power
200
225
250
Fogging System Applications: Areas where RH and wet bulb temperature is rather low
Advantage #
Low capital cost
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Low O&M cost
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Can increase gas turbine performance better than evaporative cooling
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Quick delivery and installation time
PB Power
Disadvantage #
Limitation on capacity improvement
#
Highly influenced by the site wet bulb
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Schematic of a Direct System Using an Ammonia Refrigeration Machine Ammonia Suction Line
Mechanical Refrigeration Machine
Combustion Air Air Filter Condensate Drip Pan
Exhaust Gas
Fuel
Combustion Turbine
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Ammonia Liquid Line
Mechanical Refrigeration System (Direct Type) Applications: Areas where relative humidity is rather high
Advantage #
Can increase gas turbine performance better than evaporative cooling, and fog system
PB Power
Disadvantage #
High initial capital cost
#
High O&M cost
#
Longer delivery and installation time
#
Expertise is needed to operate and maintain the plant
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Schematic of an Indirect System Using a Mechanical Chiller
Combustion Air Mechanical Chiller Air Filter
Air Cooling Coil Condensate Drip Pan
Exhaust Gas
Fuel
Combustion Turbine
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Chilled Water Pump
Mechanical Refrigeration System (Indirect Type) Applications: Areas where relative humidity is rather high
Advantage #
#
Can increase gas turbine performance better than evaporative cooling, and fog system Not very sensitive to ambient air wet bulb temperature
Disadvantage # # # #
# # # PB Power
High initial capital cost High O&M cost Long delivery and installation time Expertise is needed to operate and maintain the plant Requires extra chilled water cooling circuit Higher parasitic load than direct type Higher energy input compared to direct type chiller
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Inlet Air Cooling With Ice Storage, Chilled Water Storage System Schematic
Combustion Air Mechanical Chiller/ Ice Maker
Air Filter
Condensate Drip Pan
Ice Storage Tank
Exhaust Gas
Fuel
Combustion Turbine
PB Power
Air Cooling Coil
Chilled Water Pump
Inlet Air Cooling With Chilled Water Storage System Schematic
Chilled Water Storage Tank
Mech. Chiller
Combustion Air Air Filter
Air Cooling Coil Condensate Drip Pan
Exhaust Gas
Fuel
Combustion Turbine
PB Power
Chilled Water Pump
Mechanical Refrigeration System With Ice Storage Applications: Areas where RH is rather high,plus a wide variation in electricity tariff between peak and non peak hours
Advantage #
#
#
Can increase gas turbine performance better than evaporative cooling, and fog system Not very sensitive to ambient air wet bulb temperature Can utilise low night time tariff to produce and store ice for peak hours operation PB Power
Disadvantage #
High initial capital cost
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High O&M cost
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Longer delivery and installation time
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Higher expertise is needed to operate and maintain the plant
Chiller Electrical Load MW 36°C DB, 25°C WB, 10°C Chilled Air Temp
Chiller Electrical Load MW
6 5 4 3 2 1 0 0
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50
75
100
125
150
175
Gas Turbine Output MW
PB Power
200
225
250
275
300
Gas Turbine Inlet Air Cooling Available Technologies 1. Evaporative cooler 2. Fogging system 3. Mechanical refrigeration system (direct type) 4. Mechanical refrigeration system (indirect type) 5. Mechanical refrigeration with ice storage 6. Mechanical refrigeration system with chilled water storage 7. Single stage Lithium Bromide Absorption chiller 8. Two stage Lithium Bromide Absorption chiller
PB Power
Absorption Chiller Inlet Air Cooling System Schematic
Combustion Air Absorption Chiller
Air Cooling Coil
Exhaust Gas
LP Steam
Return Condensate
Air Filter
Condensate Drip Pan
Chilled Water Pump
Fuel
Heat Recovery Steam Generator Combustion Turbine
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Flow Diagram Pressure approx. 60 Torr 60 mm Hg 80 mbar 8 kPa
Condenser
tc 45°C
37°C
Tower Water Out
Generator Steam or Hot Water
70 °C
Heat Medium In
95 °C
Heat Medium Out
Pressure approx. 6,2 Torr 6,2 mm Hg 8,2 mbar 0,83 kPa
to 4°C 6°C
Evaporator
12°C
Chilled Water
Absorber 32,5°C 27°C
Tower Water In
ta 35°C Chilled Water Tower Water Concentrated Solution (LiBr) Diluted Solution (LiBr) Steam or Hot Water Refrigerant (Water)
70°C
50°C
PB Power
Picture courtesy of York International
Absorption Chiller Steam Consumption 36°C DB, 25°C WB, 10°C Chilled Air Temp 80
Steam Consumption t/h
70 60 50 40 30 20 10 0
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125
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175
200
Gas Turbine Output MW
225
250
275
300 Single Stage Two Stage
PB Power
Single Stage Lithium Bromide Absorption Chiller Applications: Areas where relative humidity is rather high, and the plant is going to operate in a combined cycle or cogeneration mode and has access to low pressure steam
Advantage #
Can increase gas turbine performance better than evaporative cooling, and fog system
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Not very sensitive to ambient air wet bulb temperature
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Low electrical parasitic load
PB Power
Disadvantage #
High initial capital cost
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High O&M cost
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Longer delivery and installation time
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High expertise is needed to operate and maintain the plant
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In case of a steam operated chiller, cannot be applied in an open cycle gas turbine plant
Two Stage Lithium Bromide Absorption Chiller Applications: Areas where relative humidity is rather high, and the plant is going to operate in a combined cycle or cogeneration mode and has access to low pressure steam
Advantage #
Can increase gas turbine performance better than evaporative cooling, and fog system
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Not very sensitive to ambient air wet bulb temperature
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Low electrical parasitic load
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Requires less steam per unit of refrigeration than single stage chiller PB Power
Disadvantage #
High initial capital cost
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High O&M cost
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Longer delivery and installation time
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High expertise is needed to operate and maintain the plant
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In case of a steam operated chiller, cannot be applied in an open cycle gas turbine plant
Condensate Formation t/h
Condensate Formation on the Chilled Water Coil t/h Based on 36°C DB, 25°C WB, 10°C Chilled Inlet Air Temperature 20 15 10 5 0
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35
45
55
65
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85
95
105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255 265
Gas Turbine Output MW
PB Power
Performance Evaluation Of Different Inlet Air Cooling Systems Base Condition ! ! !
35°C Dry bulb 25°C Dry bulb 44.7% Relative humidity
Real world condition
Increase in power output Percent Change Gas turbine output before inlet air cooling
108.23 MW (net)
0%
Gas turbine output with mechanical refrigeration system and inlet air temperature of 10°C
124.8 MW (net including chiller electrical load)
15.3%
114.8 MW (net)
6%
116.65 MW (net)
7.69%
Gas turbine with evaporative cooler running at 85% RH Gas turbine with fog system running at 100% RH PB Power
Capital Cost Comparisons of Inlet Cooling Systems Options Evaporative cooler Fog system (excluding water treatment plant) Single stage LiBr absorption chiller Two stage LiBr absorption chiller Ammonia mechanical refrigeration system PB Power
Relative Costs 1 2 8 10 9.5
Major Contributors To The O&M Costs Options Evaporative cooler Fog system (excluding water treatment plant)
O&M Costs # # # # # #
Single stage LiBr absorption chiller
# # # #
Two stage LiBr absorption chiller
# # # #
Ammonia mechanical refrigeration system
# #
PB Power
Make up water Water treatment (if applicable) Make up water Demineralised water treatment Injection pump power consumption Steam Cooling tower chemical treatment Chiller maintenance Electric power consumption Steam Cooling tower chemical treatment and make up water Chiller maintenance Electric power consumption Electric power consumption Cooling tower chemical treatment and make up water Chiller maintenance
Heavy Duty Gas Turbine NOx Emission kg/MWh GT with Dry Low NOx burner
NOx Emission kg/MWh
0.470 0.460 0.450 0.440 0.430 0.420 0.410 0
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10
15
20
25
Ambient Temperature deg C
PB Power
30
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Heavy Duty Gas Turbine CO2 Emission kg/MWh
CO2 Emission kg/MWh
590 580 570 560 550 540 530 520 0
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25
30
Ambient Temperature deg C
PB Power
35
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Aero-Derivative Gas Turbine NOx Emission kg/MWh GT with Dry Low NOx burner
NOx Emission kg/MWh
0.43 0.42 0.41 0.4 0.39 0.38 0.37
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20
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Ambient Temperature deg C
PB Power
30
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Aero-Derivative Gas Turbine CO2 Emission kg/MWh
CO2 Emission kg/MWh
550 540 530 520 510 500 490 480 470 0
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20
25
30
Ambient Temperature deg C
PB Power
35
40
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In Selecting Inlet Air Cooling As A Retrofit To An Existing Plant Points to watch: !
Check the generator capacity in order not to overload the generator
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Quality of raw water for the evaporative cooler
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When using an existing demineralised water treatment plant, be careful about the capacity and quality of available demineralised water
!
With an existing heat recovery steam generator, inlet air cooling will change the behaviour of the existing HRSG, leading to a drop in steam production at high pressure and increase in intermediate and low pressure steam PB Power
