Title of Invention	COMBUSTION TURBINE INLET AIR COOLING SYSTEM USING AMMONIA ABSORPTION REFRIGERATION PLANT DRIVEN BY THE WASTE HEAT
Abstract	Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas at outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plat; single/two stage hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine.

Title of Invention

COMBUSTION TURBINE INLET AIR COOLING SYSTEM USING AMMONIA ABSORPTION REFRIGERATION PLANT DRIVEN BY THE WASTE HEAT

Abstract

Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas at outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plat; single/two stage hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine.

Full Text	FORM-2 THE PATENTS ACT, 1970 COMPLETE SPECIFICATION (Section 10) "LOW GRADE WASTE HEAT DRIVEN COMBUSTION TURBINE INLET AIR COOLING SYSTEM USING AMMONIA ABSORPTION REFRIGERATION PLANT' ASHOK DATTATRAYA ATRE 'Pushpa heights', 1st floor, Bibwewadi Corner, PUNE- 411 037, MAHARASHTRA STATE, INDIA Indian National The following specification particularly describes the nature of the invention and manner in which it is to be performed. 1 NATURE OF THE INVNETION: Present invention relates to low grade waste heat driven Combustion Turbine Inlet Air Cooling System. More particularly present invention is for improvement in efficiency as well as power output of Combustion Turbine based power plant using low grade waste heat available from the exhaust gases at the outlet of Heat Recovery Steam Generator (HRSG) provided in typical gas turbine combined cycle power plant. PRIOR ART: In prior art, the cooling of combustion air at inlet of combustion turbine is achieved by one of following methods or combination there of: 1. Cooling of gas turbine inlet air by indirect heat exchange with chilled water generated from Mechanical Vapour Compression Cycle Refrigeration Plant. 2. Cooling of gas turbine inlet air by indirect heat exchanger with chilled water generated from Vapour Absorption Refrigeration Plant driven by steam generated by burning fuel or the steam generated from existing heat recovery steam generator (HRSG) forming part of the power plant. 3. Evaporative cooling or mist cooling of gas turbine inlet air 4. Firing of fuel in the Exhaust gas Duct to provide energy required for running vapour absorption chillers for production of chilled water to be used for cooling the gas turbine inlet air. 5. Cooling of turbine inlet air by indirect heat exchanger with chilled water generated from Lithium Bromide based water Vapour Absorption chiller driven by hot water or steam. 2 Taking into consideration the above conventional methods of Combustion Turbine Inlet Air Cooling, following disadvantages exist in the prior art, a) In case of Mechanical Vapour Compression Cycle Refrigeration : 1) Refrigeration Plant needs electricity or motive power to produce refrigeration, which has higher running cost. 2) This either increases the running cost of the power plant or it reduces the net exportable power output from power plant. In either case, unit cost of power generation increases. b) In case of HRSG Steam driven Vapour Absorption Refrigeration : 1) A part of low pressure steam available from existing HRSG is used to drive the vapour absorption chillers. This reduces the power output from Steam Turbine due to reduction in steam supply to steam turbine. 2) Reduction in power generation from steam turbine reduces net exportable power output from power plant, which in turns increases, the unit cost of power generation. 3) The steam requirement of vapour absorption refrigeration plant can be achieved by enhancing the capacity of existing HRSG by auxiliary fuel firing at inlet of HRSG. However, it calls for additional fuel firing and its associated energy costs. 4) It also increases the unit cost of power generation from power plant. 5) In situation of shortage of make up water availability for cooling tower water, water cooled absorption chillers driven by evaporative cooled cooling water can not be used because eevaporatively cooled cooling tower need huge quantity of make up water. 3 6) Temperature limit for chilled water produced from typical Lithium Bromide Absorption chiller is 6 - 7 Deg C. Due to this the air can not be cooled upto 4.4 Deg. C. In case of Evaporative Cooling or Mist Cooling of inlet air : The lowest temperature of combustion turbine inlet air that can be theoretically achieved is equal to the wet bulb temperature at site, which is much higher (typically 25 to 28 Deg C) than the desired turbine inlet combustion air temperature of 15 Deg C or lower, particularly for power plants those are installed in coastal areas of tropical countries where humidity of air is very high. Hence, effectiveness of evaporative cooling is poor. Therefore this art can not be applied to power plants installed in coastal areas of tropical countries where ambient dry bulb temperature and humidity are very high. In case of duct fired system the fuel is fired in the exhaust gas entering or leaving Heat Recovery Steam Generator (HRSG) to generate additional heat which will generate steam or hot water. The steam or hot water generated is used to drive vapour absorption type chiller to generate chilled water. In this case additional fuel is required in duct firing which increases operating cost. In case of Lithium bromide- water vapour absorption chiller (Li-Br chiller), the vacuum has to be maintained in entire system due to which maintenance of the system becomes a critical issue. So this chiller has to be packaged unit. The system is highly susceptible to corrosion which limits the entire life span of this type of system not more than 15 years. Also Li-Br chillers can not reject heat through air cooled remote radiators especially if the ambient dry bulb temperatures are beyond 33 Deg C. In such situations, Li-Br chiller is 4 forced to reject heat through evaporatively cooled cooling towers typically operating at wet bulb temperatures of less than 30 Deg C. Make up water availability then becomes a critical issue for Li-Br chiller in such regions. Thus in areas where the make up water is not available or extremely costly, Li-Br chillers are not either technically feasible or not techno-economically cost effective and hence are not used. Use of Li-Br chillers also increases the power consumption because of additional chilled water circular pump, and cooling water circulation pump. Also in case of Li-Br chillers there is limit on the temperature of chilled water which is typically 6-7 Deg C. So air can not be cooled typically below 10 Deg C and certainly not upto 4.4 Deg C or lower. There are some systems in prior art which uses chilled water generated in Li-Br chiller in condenser of low temperature vapour compression system which is used in ice generation. This system requires additional power requirement to run the compressor required for low temperature refrigeration, f) Li-Br chiller cannot produce subzero temperatures in chilling, therefore, possibility of ice thermal storage is ruled out. Hence excess chilling whenever available or produced at the night times when ambient temperatures are lower and chilling demand is lower than availability can not be stored easily or such storage of chilled water is commercially uneconomical. Typical comparative statements between proposed combustion turbine inlet air cooling system using AARP (New Art) and vapour compression cycle based inlet air cooling system (Prior Art) (Comparative Statement 1), proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using heat input through duct fired hot water generator using vapour absorption chiller (Prior Art) (Comparative Statement 2), proposed combustion turbine inlet air cooling system using AARP ( New Art) and Combustion Turbine Inlet Air Cooling System operated on steam extracted from steam turbine and vapour absorption chilling 5 (Prior Art) (Comparative Statement 3) and proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using Li-Br vapour absorption chiller (Prior art) (Comparative Statement 4) are attached at the end to highlight the advantages of proposed system (New Art) over various Prior Arts. PRESENT SCENARIO AND NEED OF COMBUSTION TURBINE INLET AIR COOLING (CTIAC): In a combined cycle power plant (CCCP), combustion turbines typically burn gaseous fuels like natural gas, LPG or distillate liquid fuels like kerosene, high speed diesel, aviation fuels etc. to generate electric power. The waste heat in exhaust gas from combustion turbine is recovered in heat recovery steam generator (HRSG) to generate high pressure steam. The high pressure steam is expanded in steam turbine to produce additional electric power. Combustion turbines are rated at ISO conditions where ambient dry bulb temperature j considered is 15 Deg C. They are also capable of operating at inlet air temperatures as low as 4.4 Deg C and at such temperatures their output and efficiency is relatively higher when compared to those at higher inlet air temperature. Hence wherever and whenever techno-economically possible or feasible, the inlet air temperature should be brought down to 4.4 Deg C. or nearest value. Practically in coastal areas of tropical countries like India, Sri Lanka, Bangladesh, Malaysia, Indonesia, Brazil, West Indies islands, Panama etc. ambient dry bulb temperature is in the range of 25-35 Deg C (sometimes even higher) and these regions also have high humidity. To improve the performance of power plant, the desired inlet air temperature to combustion turbine therefore needs to be lowered. This signifies the necessity of cooling of combustion air to the inlet of combustion turbine system. 6 Conventionally in power plants, the combustion turbine inlet air is cooled either by mechanical refrigeration plant or by vapour absorption refrigeration plant run on steam generated by burning fuel. 1) Until very recent past, the conventional fuels like oil, gas were much cheaper. So the price of electricity was not high. Also the demand of electricity was not that as high as today. 2) In present scenario, the demand of electricity has increased significantly. The fuel prices are also increasing rapidly. So the only way to supply more electricity with minimum use of fuel is to increase the efficiency of the plant. Also, the need to conserve energy and need to recover maximum possible low grade heat is ever increasing. 3) Conventionally in combustion turbine which is used in combined cycle power plant, the performance greatly depends upon the inlet air temperature. If the temperature of combustion air is decreased the performance of the plant increases effectively due to increase in density of air. 4) Using cooled air at the inlet of combustion turbine, the more electricity can be generated at higher efficiency which will not only reduce the use of conventional fuels but also reduce quantity of flue gases per kW of power produced resulting in reduction of global warming. Thus there is a need to develop a combustion turbine inlet air cooling system such that a) It will use low grade heat from the exhaust gases at the outlet of heat recovery steam generator typically at 120-135 Deg C incorporating all or some of the following features: b) It will provide facility of ice thermal storage. c) If possible it can be air cooled directly or indirectly. It is capable of operating at dry bulb temperature (D. B. T.) of 30 Deg C and higher. 7 d) In certain situations and certain applications^ it will avoid chilled water circulation. e) Combustion turbine inlet air cooling system (new art) using vapour absorption chiller other than Lithium Bromide chiller has to be built for reasons given above and other reasons. SUMMARY OF THE PRESENT INVENTION: The object of present invention is to provide a low grade Waste Heat driven Combustion Turbine Inlet Air Cooling System which utilizes low grade heat available in the exhaust gas at outlet of Heat Recovery Steam Generator (HRSG). This heat is currently let out to atmosphere without any use. Typical temperature of this exhaust gas at outlet of HRSG is i about 110 Deg C to 120 Deg C or in some cases even higher than 120 Deg C. It is also the object of the present invention to improve the efficiency as well as power output of Combustion Turbine based power plant. It is also the object of the present invention to overcome the drawbacks and short falls of the prior arts. Increasing cost of energy (fuel) and user demand are now forcing power plant industry to increase the efficiency of energy utilization. Performance of combustion turbine (CT) greatly depends upon the temperature of the inlet air. Typical curve showing turbine power output v/s combustion turbine inlet air dry bulb temperature and heat rate v/s combustion turbine inlet air dry bulb temperature are shown in Figure 1 and Figure 2. Heat rate is quantity of heat input required to generate one unit of electrical power (1 kWh). Almost all makes of gas turbines follow almost the same or similar curves as shown in Figure 1 and Figure 2. The lower temperature of inlet air increases the power output very significantly and also improves efficiency and heat rate of turbine. Thus 8 objective of the present invention is to lower the temperature of inlet air thereby increasing overall efficiency of the combined cycle power plant (CCPP). According to this invention a waste heat recovery hot water generator will be installed on exhaust gas at the outlet of existing heat recovery steam generator of the power plant. The hot water generated from the said waste heat recovery hot water generator is used to generate hot water at temperature typically in the range of 68 Deg C to 130 Deg C. The hot water so generated is used to drive the Ammonia Absorption Refrigeration Plant (AARP). The ambient air rejects its heat directly to the liquid ammonia in evaporator of AARP before entering the combustion turbine and gets cooled down to required inlet temperature which is typically upto 12 Deg C. It can be cooled even lower to 4.4 Deg C. BRIEF DESCRIPTION OF THE SCHEMATIC DIAGRAM: I Figure 1 represents a graph of percentage output of gas turbine vs. combustion turbine i inlet air temperature. Figure 2 represents a graph of percentage heat rate of gas turbine vs. combustion turbine inlet air temperature. Figure 3 is a graph which is used for selection of AARP with single stage or AARP with two stages of desorption. The invention is described with respect to the accompanying Figure 4, simplified flow diagram of Waste Heat Driven Combustion Turbine Inlet Air Cooling System using single stage AARP to i i present the invention. Figure 5 presents the same system of AARP with two stages of desorption and single stage absorption. Figure 6 describes the option of ice generation facility which can be incorporated in single stage AARP. Figure 7 presents ice generation capacity which can be incorporated in AARP with two stages of desorption and single stage absorption. 9 DETAILED DESCRIPTION OF THE SCHEMATIC DIAGRAM: The system consists of following major components: • Exhaust Gas Heat Recovery Hot Water Generator to be installed on exhaust gas at outlet of existing HRSG of power plant. • Ammonia Absorption Refrigeration Plant. • Combustion Air Cooler (Also called liquid ammonia evaporator). • Ammonia Condenser. • Cooling Tower (When water cooling is considered). • Necessary accessories, ducting, piping etc. • Data logging and monitoring system. The electricity is generated in a gas turbine (marked as item no. 1) by combustion of fuel. The exhaust gas leaving the gas turbine drives a high pressure steam boiler (marked as item no. 2) and low pressure steam boiler (marked as item no. 3). The steam generated in the high pressure steam boiler and the low pressure steam boiler is used in a two stage steam turbine (marked as item no. 4) to generate additional electricity. The temperature of exhaust gas leaving low pressure steam boiler is typically 110 to 120 Deg C. These gases are then passed through waste heat recovery hot water generator (marked as item no. 5) to generate hot water in a closed loop. Water from expansion tank (marked as item no. 15) in a closed loop is pumped with the help of hot water circulation pump (marked as item no. 16) to hot water generator. The water enters hot water generator at minimum temperature of typically 68-80 Deg C. and is heated upto typically 100-130 Deg C. The hot water is supplied to the Ammonia Absorption Refrigeration Plant. Either of two types of AARP can be used depending upon the hot water temperature generated in waste heat recovery hot water generator. The types of AARP are single stage AARP or AARP with two stages of desorption. Figure 3 shows graph which helps in selection of single stage AARP or AARP with two stages of desorption and single stage of absorption. Depending 10 upon heat source temperature, cooling media temperature and liquid ammonia evaporation temperature, one of the AARP systems is selected. Notations for temperatures are given in Figure 3. In Figure 3, tH represents Typical Hot water temperature at the inlet of desorber of AARP. to represents Typical Evaporation temperature of ammonia in evaporator of AARP. Typical turbine inlet air temperature will be to + 2 Deg C or higher, tu is Typical cooling media Temperature in condenser and absorber for heat rejection. Cooling Media could be air, water or other liquids like thermic fluids etc. In case of water cooled condenser with remote radiators, tu is Dry Bulb Temperature of ambient air+ 5 Deg C. For Evaporatively cooled condenser, tu is Wet Bulb Temperature of ambient air + 2 Deg C. In case of directly air cooled condenser, tu is Dry Bulb Temperature of ambient air + 3 Deg C. i DETAILED DESCRIPTION OF SINGLE STAGE AARP: Single stage AARP is used when the hot water temperature is high enough to generate required refrigeration effect. Typical single stage Ammonia Absorption Refrigeration Plant consists of Ammonia evaporator, absorber,: desorber, rectifying column, ammonia condenser and subcooler. ' Evaporator (marked as item no. 11) of AARP is placed in the air flow path. It is placed in the air flow path such that the liquid ammonia flowing through the tubes flows across direction with respect to air flow direction. It acts as air cooler which supplies cooled air ; j to the inlet of combustion turbine. Liquid ammonia entering the evaporator gets evaporated in the tubes by directly absorbing heat from the ambient air. The tubes of evaporator (heat exchanger) through which the liquid ammonia flows can be of falling film design or rising film design. The vapours leaving the evaporator are passed through sub-cooler (marked as item no. 10). In sub-cooler, the liquid ammonia entering evaporator gets subcooled with ammonia vapours coming out from evaporator. The i ammonia vapours from sub-cooler are absorbed in absorber (marked as item no. 12) in 11 the spray of weak ammonia-water solution in water. The heat of solution is removed with the help of air cooed condenser or cooling water. The strong ammonia solution formed after absorption is pumped to the desorber (marked as item no. 6). Solution heat exchanger (marked as item no. 14) is provided! to preheat the strong solution before entering the desorber and to cool the weak solution before entering the absorber. Heat is supplied in the desorber to boil off ammonia from strong solution. The heat source used in the desorber is the hot water generated in the above said waste heat recovery hot water generator. The hot water enters the desorber typically at 100 - 130 Deg C or even lower. and leaves typically at 68-80 Deg C. The ammonia vapours formed in the desorber contain some water vapours due to affinity between ammonia and water. The rectifying column (marked as item no. 7) is provided to remove the water vapours from the vapour mixture. The pure ammonia vapours generated in rectifying column are condensed in condenser (marked as item no. 8). This condenser can be of air cooled or water cooled type depending upon the water availability at the site. Liquid ammonia formed thus gets i accumulated in receiver (marked as item no. 9). The receiver supplies liquid ammonia to the evaporator where it gets evaporated with the help of heat rejected by the ambient air which is to be supplied to the inlet of combustion turbine. The water condensate formed due to moisture condensation during air cooling is collected in condensate tank (marked as item no. 17). Thus the ambient air gets directly cooled with the liquid ammonia to the required temperature before entering the combustion turbine. The said condenser (marked as item no. 8) can be water cooled or directly air cooled or indirectly air cooled or evaporatively cooled. It depends upon the availability of make up water at the site. Similarly, the said absorber (marked as item no. 12) can be water cooled with heat rejection in evaporatively cooled cooling tower or closed water circulation with heat rejection to air cooled remote radiators. In this case also, assessment of availability of make up water becomes a critical issue for selection of types of cooling system. 12 DETAILED DESCRIPTION OF AARP WITH TWO STAGES OF DESORPTION AND SINGLE STAGE OF ABSORPTION: Two stages of desorption and single stage of absorption in AARP are used when the hot water temperature is not high enough to generate required refrigeration effect in single stage AARP. Typical AARP with two stages of desorption consists of evaporator, two desorbers, two absorbers (one intermediate and other for absorbing ammonia vapours generated by evaporation of liquid ammonia in the turbine inlet air cooling heat exchanger i.e. air cooler), two solution heat exchangers, rectifying column, condenser, receiver, and subcooler. Liquid ammonia from receiver (marked as item no. 9) gets evaporated in air cooler (marked as item no. 11) by absorbing heat from the combustion inlet air entering the gas turbine. Ammonia vapours get absorbed by weak ammonia solution coming from low pressure desorber in low pressure absorber (marked as item no. 12). The strong ammonia solution from low pressure absorber is desorbed in low pressure desorber (marked as item no. 18). Weak ammonia solution returns to low pressure absorber. Ammonia vapours formed in low pressure desorber are absorbed in high pressure absorber (marked as item no. 19) by weak solution returning from high pressure desorber (marked as item no. 6). Hot water generated in waste heat recovery hot water generator (marked as item no. 5) is used as heat source in both desorbers. Rectifying column (marked as item no. 7) removes water vapours from ammonia vapours. Pure ammonia vapours get condensed in condenser. The condenser can be evaporatively cooled, water cooled, directly air cooled or indirectly air cooled with remote radiators. , The advantages of the new system are as under: 1. The proposed CTIACS uses waste heat from exhaust gases available at outlet of existing power plant. Hence the running cost is lowest. There is no consumption 13 of steam from existing HRSG for operation of the same CTIACS. Hence no reduction in power output of steam turbine. 2. Also the proposed CTIACS needs no additional fuel consumption for power plant to increase power output from existing plant, 3. There is substantial increase in Gas Turbine power output due to 'Combustion Turbine inlet air cooling' down to 12 Deg C or even lower. The output of steam turbine would also increase due to increase in flue gas quantity and subsequent increase in steam output from HRSG. 4. Internal electrical power consumption reduces considerably due to absence of chilled water circulation pump and vacuum pump, since the air gets cooled directly by liquid ammonia in the said evaporator as compared to Li-Br chiller. 5. Since the AARP unit is not required to be packaged, absorber, sub-cooler and evaporator can be placed near the combustion turbine and desorber / desorbers (in case of two stages AARP), rectifying column, condenser and ammonia receiver can be placed near the heat source. 6. Completely air cooled AARP plant is possible where there is a shortage of make up water. 7. Since AARP works under pressure, no special care is needed for maintenance of vacuum. 8. Corrosion is negligible in AARP so the life span of the plant is more than 25 years. 9. The system is fully automatic in operation1 with continuous automatic modulation of major operating parameters and online data logging of the working parameters is possible. 14 VARIATIONS POSSIBLE TO BE COVERED AND PROVIDED WITHIN THE INVENTION OF THIS NEW CTIACS: 1. The temperature of the hot water generated in the Waste Heat Recovery Hot Water Generator is dependent on the exhaust gas temperature at the outlet of HRSG. The waste heat recovery hot water generator could be of finned tube or bare tube construction having countercurrent or co-current flow of heat exchanging medium depending upon the above parameters. Finns of finned tube of waste heat recovery hot water generator can be of extruded aluminium type or carbon steel Ljtype fins or welded fins or spiral fins. 2. Single or two stage AARP can be selected and its selection will be dependent upon the temperature of hot water available as well as other operating parameters and cooling media temperatures. 3. Condenser or absorber can be cooled using air cooled condenser where there is a shortage of make up water for cooling tower. 4. Fins of air cooler i.e. evaporator of AARP can be of extruded aluminium type or carbon steel L type fins or welded fins or spiral fins. 5. Condenser can be of direct air cooled type, water cooled type or evaporatively cooled or indirectly air cooled with remote radiators depending upon the make up water available. 6. Absorber can be water cooled with heat rejection in evaporatively cooled cooling tower or closed water circulation with heat rejection in air cooled remote radiators. 7. When the remote radiators are used as condenser, the cooling media flowing through remote radiators can be water, other liquids like thermic fluids etc. 8. Option of incorporating Ice Thermal Storage is also possible if heat source temperature is high enough so as to drive Ammonia Absorption Refrigeration Plant at refrigeration temperatures at subzero temperature (i.e. lower than 0 Deg 15 C). This is particularly possible in night when the ambient dry bulb temperatures are low. In such conditions, the AARP can be utilized for ice generation. Using low temperature AARP (below 0 Deg C.) the ice can be generated in ice bank tanks (marked as item no. 23). The flow of refrigerant liquid ammonia can be controlled using flow control valves for ice production (marked as item no. 24 & 25). Thus when inlet air cooling is not required the AARP can be utilized to generate ice. The inlet air to the combustion turbine can be further cooled till 4.4 Deg C by placing chilled water coil (marked as item no. 22). Through this coil, chilled water of 0 Deg. C is circulated using chilled water circulation pump (marked as item no. 26). Chilled water transfers its heat to the above said ice bank tank. The ice thermal storage can be used in air cooling system to reduce temperature further below 15 Deg C to reach minimum at 4.4 Deg C. Thus AARP is run almost continuously at its rated capacity and for much higher time during the day the temperature of 4.4 Deg C can be achieved and maximum power output can be obtained. Same ice bank tank can be incorporated in case of AARP with two stages of desorption. Thus following options can be considered for the use of ice thermal storage. a) There are cases where ice can be formed using AARP in the night and can be stored in ice thermal storage. Thermal ice storage can be used alongwith the use of AARP during day time to cool the gas turbine inlet air below 15 Deg C and nearer to 4.4 Deg C depending upon the capacity of the ice thermal storage. i b) There are cases where during night time the temperature of gas turbine inlet air can be reached upto 4.4 Deg C. But it is not possible to reach 4.4 Deg C. during day time. The system can be made such that it reaches the minimum Dossible temperature during day time using ice thermal storage. 16 c) There are cases where it is not possible to reach the temperature of 15 Deg C. even during day time. Ice thermal storage, which can be run during night time, can be used in such case to reach possible minimum temperature. Completely air cooled Ammonia Absorption Refrigeration plant can be also used wherever make up water is not available for cooling tower. The invention is applicable to all above possible variations and hence the invention is versatile, flexible and has wide application range. 17 Comparative Statement No. 1 Typical Comparison between proposed combustion turbine inlet air cooling system using AARP (New Art) and vapour compression cycle based inlet air cooling system (Prior Art) Mechanical refrigeration Proposed System 1 Ambient air temperature DegC 35.00 35.00 2 Inlet air temperature to gas turbine DegC 4.4 4.4 3 Tons of Refrigeration , ! TR 6200 6200 4 Power Output MW 132.04 132.04 5 Power output from steam turbine MW 66.02 66.02 6 Power output from CCPP MW 198.06 198.06 7 Captive power consumption MW 7.50 2.00 8 Net Exportable power \| MW 190.557 196.06 9 Net additional exportable power due to CTIAC MW NA 5.50 10 Existing unit cost of power Rs/kWh 2.26 11 Savings/earning per hour 12430.00 12 Savings per annum Rs. In Crorei NA 9.94 13 Savings in 20 years ' Rs. In Crore NA 198.88 18 Comparative Statement No. 2 Typical Comparison between proposed combustion turbine inlet air cooling system using AARP(New Art) and Combustion Turbine Inlet Air Cooling System using heat input through duct firedhot water generator using vapour absorption chiller (Prior Art) Duct fired Proposed System 1 i Ambient air temperature ' DegC 35.00 35.00 2 Inlet air temperature to gas turbine DegC 4.4 4.4 3 Tons of Refrigeration TR 6200 6200 4 Power Output from Gas Turbine MW 132.04 131.90 5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 66.02 65.95 6 Power Output from CCPP MW 198.06 197.85 8 Captive Power consumption for CTIACS System MW 2.00 2.50 9 Net exportable power output from CCPP after accounting for captive power consumption MW 196.06 195.35 10 Net additional exportable power due to CTIACS MW 071 11 Existing unit cost of power j Rs./kWh 2.26 - 12 Savings / Earnings per hour Rs./hr 1600.00 - 13 Additional Fuel consumption for Duct firing cu.m/hr 2305.88 NA 14 Additonal cost of fuel per hour (Expenditure) Rs./hr 16141.18 NA 15 Net Savings per annum Rs./hr - 14541.18 16 Savings per annum Rs. In Crore NA 11.63 17 Savings in 20 years Rs. In Crore NA 174.49 19 Comparative Statement No. 3 Typical Comparison between proposed combustion turbine inlet air cooling system usingAARP (New Art) and Combustion Turbine Inlet Air Cooling System operated on steamextracted from steam turbine and vapour absorption chilling (Prior Art) Steam Extraction Proposed System 1 Ambient air temperature DegC 35.00 35.00 2 Inlet air temperature to gas turbine DegC 4.4 4.4 3 Tons of Refrigeration TR 6200 6200 4 Power Output from Gas Turbine MW 132.04 131.90 5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 66.02 65.95 6 Power Output from CCPP MW 198.06 197.85 7 Reduction in power output due to steam extraction MW 2.50 NA 8 Captive Power consumption for CTIACS System MW 1.50 2.50 9 Net exportable power output from CCPP after accounting for captive power consumption MW 194.06 197.85 10 Net additional exportable power due to CTIACS MW NA 3.79 11 Existing unit cost of power Rs./kWh 2.26 - 12 Savings / Earnings per hour j Rs./hr - 8570.00 13 Net Savings per annuhi ' Rs./hr NA 8570.00 14 Savings per annum Rs. In Crore NA 6.86 15 Savings in 20 years Rs.ln Crore NA 137.12 20 Comparative Statement No. 4 Typical Comparison between proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using Li-Br vapourabsorption chiller (Prior Art) LiBr Chiller Proposed System 1 Ambient air temperature DegC 35.00 35.00 2 i Inlet air temperature td gas turbine DegC 15 15 3 Tons of Refrigeration TR 3410 3410 4 Power Output from Gas Turbine MW 123.27 123.27 5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 61.64 61.64 6 Power Output from CCPP MW 184.91 184.91 7 Captive Power consumption for CTIACS System MW 0.8 0.55 8 Net exportable power output from CCPP after accounting for captive power consumption MW 184.06 184.36 9 Net additional exportable power due to AARP CTIACS .MW 0.30 10 Existing unit cost of power Rs./kWh 2.26 - 11 Savings / Earnings per hour Rs./hr - 678.00 12 Net Savings per annum Rs./hr NA 678.00 13 Savings per annum Rs.ln Crore NA 0.54 14 Savings in 20 years Rs.ln Crore NA 10.85 21 1. Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plant; hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine. 2. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in claim no. 1 wherein the single or two desorption stage Ammonia Absorption Refrigeration plant is installed. 3. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in claims no. 1 & 2 wherein inlet air to the combustion turbine is directly cooled bi liquid ammonia in the evaporator (i.e. combustion air cooler) of ammonia absorption refrigeration plant. 4. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in claims no. 1, 2 & 3 wherein no additional fuel is required to increase power output of power plant. j i j 5. Waste heat driven bombustion turbine inlet air cooling system claimed in claims no. 1, 2, 3 & 4 wherein the said waste heat recovery hot water generator consists of finned tubes. 6. Waste heat driven combustion turbine inlet air cooling system as claimed in claims no. 1, 2, 3 , 4 & 5 wherein directly, air cooled or indirectly air cooled with remote radiators or evaporatively cooled or water cooled ammonia condenser and ammonia absorbers are provided. 7. Waste heat driven combustion turbine inlet air cooling system plant as claimed in claims no. 1, 2, 3, 4, 5 & 6 wherein condensate tank is provided to collect condensate formed in air cooler. 22 8. Waste heat driven combustion turbine inlet air cooling system as claimed in claims no. 1,2, 3,4, 5, 6 & 7 above and herein described with respect to drawings of the accompanying specification. M. S. Khadilkar (Agent for applicant) Dated this 28th day of March 2006 23 ABSTRACT Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas at outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plant; single / two stage hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine. 24

Full Text

FORM-2 THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (Section 10)
"LOW GRADE WASTE HEAT DRIVEN COMBUSTION TURBINE INLET AIR COOLING SYSTEM USING AMMONIA ABSORPTION REFRIGERATION PLANT'
ASHOK DATTATRAYA ATRE
'Pushpa heights', 1st floor,
Bibwewadi Corner,
PUNE- 411 037, MAHARASHTRA STATE, INDIA
Indian National
The following specification particularly describes the nature of the invention and manner in which it is to be performed.
1

NATURE OF THE INVNETION:
Present invention relates to low grade waste heat driven Combustion Turbine Inlet Air Cooling System. More particularly present invention is for improvement in efficiency as well as power output of Combustion Turbine based power plant using low grade waste heat available from the exhaust gases at the outlet of Heat Recovery Steam Generator (HRSG) provided in typical gas turbine combined cycle power plant.
PRIOR ART:
In prior art, the cooling of combustion air at inlet of combustion turbine is achieved by one of following methods or combination there of:
1. Cooling of gas turbine inlet air by indirect heat exchange with chilled water generated from Mechanical Vapour Compression Cycle Refrigeration Plant.
2. Cooling of gas turbine inlet air by indirect heat exchanger with chilled water generated from Vapour Absorption Refrigeration Plant driven by steam generated by burning fuel or the steam generated from existing heat recovery steam generator (HRSG) forming part of the power plant.
3. Evaporative cooling or mist cooling of gas turbine inlet air
4. Firing of fuel in the Exhaust gas Duct to provide energy required for running vapour absorption chillers for production of chilled water to be used for cooling the gas turbine inlet air.
5. Cooling of turbine inlet air by indirect heat exchanger with chilled water generated from Lithium Bromide based water Vapour Absorption chiller driven by hot water or steam.
2

Taking into consideration the above conventional methods of Combustion Turbine Inlet Air Cooling, following disadvantages exist in the prior art,
a) In case of Mechanical Vapour Compression Cycle Refrigeration :
1) Refrigeration Plant needs electricity or motive power to produce refrigeration, which has higher running cost.
2) This either increases the running cost of the power plant or it reduces the net exportable power output from power plant. In either case, unit cost of power generation increases.
b) In case of HRSG Steam driven Vapour Absorption Refrigeration :
1) A part of low pressure steam available from existing HRSG is used to drive the vapour absorption chillers. This reduces the power output from Steam Turbine due to reduction in steam supply to steam turbine.
2) Reduction in power generation from steam turbine reduces net exportable power output from power plant, which in turns increases, the unit cost of power generation.
3) The steam requirement of vapour absorption refrigeration plant can be achieved by enhancing the capacity of existing HRSG by auxiliary fuel firing at inlet of HRSG. However, it calls for additional fuel firing and its associated energy costs.
4) It also increases the unit cost of power generation from power plant.
5) In situation of shortage of make up water availability for cooling tower water, water cooled absorption chillers driven by evaporative cooled cooling water can not be used because eevaporatively cooled cooling tower need huge quantity of make up water.
3

6) Temperature limit for chilled water produced from typical Lithium Bromide Absorption chiller is 6 - 7 Deg C. Due to this the air can not be cooled upto 4.4 Deg. C.
In case of Evaporative Cooling or Mist Cooling of inlet air : The lowest temperature of combustion turbine inlet air that can be theoretically achieved is equal to the wet bulb temperature at site, which is much higher (typically 25 to 28 Deg C) than the desired turbine inlet combustion air temperature of 15 Deg C or lower, particularly for power plants those are installed in coastal areas of tropical countries where humidity of air is very high. Hence, effectiveness of evaporative cooling is poor. Therefore this art can not be applied to power plants installed in coastal areas of tropical countries where ambient dry bulb temperature and humidity are very high.
In case of duct fired system the fuel is fired in the exhaust gas entering or leaving Heat Recovery Steam Generator (HRSG) to generate additional heat which will generate steam or hot water. The steam or hot water generated is used to drive vapour absorption type chiller to generate chilled water. In this case additional fuel is required in duct firing which increases operating cost.
In case of Lithium bromide- water vapour absorption chiller (Li-Br chiller), the vacuum has to be maintained in entire system due to which maintenance of the system becomes a critical issue. So this chiller has to be packaged unit. The system is highly susceptible to corrosion which limits the entire life span of this type of system not more than 15 years. Also Li-Br chillers can not reject heat through air cooled remote radiators especially if the ambient dry bulb temperatures are beyond 33 Deg C. In such situations, Li-Br chiller is
4

forced to reject heat through evaporatively cooled cooling towers typically operating at wet bulb temperatures of less than 30 Deg C. Make up water availability then becomes a critical issue for Li-Br chiller in such regions. Thus in areas where the make up water is not available or extremely costly, Li-Br chillers are not either technically feasible or not techno-economically cost effective and hence are not used. Use of Li-Br chillers also increases the power consumption because of additional chilled water circular pump, and cooling water circulation pump. Also in case of Li-Br chillers there is limit on the temperature of chilled water which is typically 6-7 Deg C. So air can not be cooled typically below 10 Deg C and certainly not upto 4.4 Deg C or lower. There are some systems in prior art which uses chilled water generated in Li-Br chiller in condenser of low temperature vapour compression system which is used in ice generation. This system requires additional power requirement to run the compressor required for low temperature refrigeration, f) Li-Br chiller cannot produce subzero temperatures in chilling, therefore, possibility of ice thermal storage is ruled out. Hence excess chilling whenever available or produced at the night times when ambient temperatures are lower and chilling demand is lower than availability can not be stored easily or such storage of chilled water is commercially uneconomical.
Typical comparative statements between proposed combustion turbine inlet air cooling system using AARP (New Art) and vapour compression cycle based inlet air cooling system (Prior Art) (Comparative Statement 1), proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using heat input through duct fired hot water generator using vapour absorption chiller (Prior Art) (Comparative Statement 2), proposed combustion turbine inlet air cooling system using AARP ( New Art) and Combustion Turbine Inlet Air Cooling System operated on steam extracted from steam turbine and vapour absorption chilling
5

(Prior Art) (Comparative Statement 3) and proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using Li-Br vapour absorption chiller (Prior art) (Comparative Statement 4) are attached at the end to highlight the advantages of proposed system (New Art) over various Prior Arts.
PRESENT SCENARIO AND NEED OF COMBUSTION TURBINE INLET AIR COOLING (CTIAC):
In a combined cycle power plant (CCCP), combustion turbines typically burn gaseous fuels like natural gas, LPG or distillate liquid fuels like kerosene, high speed diesel, aviation fuels etc. to generate electric power. The waste heat in exhaust gas from combustion turbine is recovered in heat recovery steam generator (HRSG) to generate high pressure steam. The high pressure steam is expanded in steam turbine to produce additional electric power.
Combustion turbines are rated at ISO conditions where ambient dry bulb temperature
j
considered is 15 Deg C. They are also capable of operating at inlet air temperatures as low as 4.4 Deg C and at such temperatures their output and efficiency is relatively higher when compared to those at higher inlet air temperature. Hence wherever and whenever techno-economically possible or feasible, the inlet air temperature should be brought down to 4.4 Deg C. or nearest value. Practically in coastal areas of tropical countries like India, Sri Lanka, Bangladesh, Malaysia, Indonesia, Brazil, West Indies islands, Panama etc. ambient dry bulb temperature is in the range of 25-35 Deg C (sometimes even higher) and these regions also have high humidity. To improve the performance of power plant, the desired inlet air temperature to combustion turbine therefore needs to be lowered. This signifies the necessity of cooling of combustion air to the inlet of combustion turbine system.
6

Conventionally in power plants, the combustion turbine inlet air is cooled either by mechanical refrigeration plant or by vapour absorption refrigeration plant run on steam generated by burning fuel.
1) Until very recent past, the conventional fuels like oil, gas were much cheaper. So the price of electricity was not high. Also the demand of electricity was not that as high as today.
2) In present scenario, the demand of electricity has increased significantly. The fuel prices are also increasing rapidly. So the only way to supply more electricity with minimum use of fuel is to increase the efficiency of the plant. Also, the need to conserve energy and need to recover maximum possible low grade heat is ever increasing.
3) Conventionally in combustion turbine which is used in combined cycle power plant, the performance greatly depends upon the inlet air temperature. If the temperature of combustion air is decreased the performance of the plant increases effectively due to increase in density of air.
4) Using cooled air at the inlet of combustion turbine, the more electricity can be generated at higher efficiency which will not only reduce the use of conventional fuels but also reduce quantity of flue gases per kW of power produced resulting in reduction of global warming.
Thus there is a need to develop a combustion turbine inlet air cooling system such that
a) It will use low grade heat from the exhaust gases at the outlet of heat recovery steam generator typically at 120-135 Deg C incorporating all or some of the following features:
b) It will provide facility of ice thermal storage.
c) If possible it can be air cooled directly or indirectly. It is capable of operating at dry bulb temperature (D. B. T.) of 30 Deg C and higher.
7

d) In certain situations and certain applications^ it will avoid chilled water circulation.
e) Combustion turbine inlet air cooling system (new art) using vapour absorption chiller other than Lithium Bromide chiller has to be built for reasons given above and other reasons.
SUMMARY OF THE PRESENT INVENTION:
The object of present invention is to provide a low grade Waste Heat driven Combustion Turbine Inlet Air Cooling System which utilizes low grade heat available in the exhaust gas at outlet of Heat Recovery Steam Generator (HRSG). This heat is currently let out to atmosphere without any use. Typical temperature of this exhaust gas at outlet of HRSG is
i
about 110 Deg C to 120 Deg C or in some cases even higher than 120 Deg C.
It is also the object of the present invention to improve the efficiency as well as power output of Combustion Turbine based power plant.
It is also the object of the present invention to overcome the drawbacks and short falls of the prior arts.
Increasing cost of energy (fuel) and user demand are now forcing power plant industry to
increase the efficiency of energy utilization. Performance of combustion turbine (CT)
greatly depends upon the temperature of the inlet air. Typical curve showing turbine
power output v/s combustion turbine inlet air dry bulb temperature and heat rate v/s
combustion turbine inlet air dry bulb temperature are shown in Figure 1 and Figure 2.
Heat rate is quantity of heat input required to generate one unit of electrical power (1
kWh). Almost all makes of gas turbines follow almost the same or similar curves as
shown in Figure 1 and Figure 2. The lower temperature of inlet air increases the power
output very significantly and also improves efficiency and heat rate of turbine. Thus
8

objective of the present invention is to lower the temperature of inlet air thereby increasing overall efficiency of the combined cycle power plant (CCPP).
According to this invention a waste heat recovery hot water generator will be installed on exhaust gas at the outlet of existing heat recovery steam generator of the power plant. The hot water generated from the said waste heat recovery hot water generator is used to generate hot water at temperature typically in the range of 68 Deg C to 130 Deg C.
The hot water so generated is used to drive the Ammonia Absorption Refrigeration Plant (AARP). The ambient air rejects its heat directly to the liquid ammonia in evaporator of AARP before entering the combustion turbine and gets cooled down to required inlet temperature which is typically upto 12 Deg C. It can be cooled even lower to 4.4 Deg C.
BRIEF DESCRIPTION OF THE SCHEMATIC DIAGRAM:
I
Figure 1 represents a graph of percentage output of gas turbine vs. combustion turbine
i
inlet air temperature. Figure 2 represents a graph of percentage heat rate of gas turbine vs.
combustion turbine inlet air temperature. Figure 3 is a graph which is used for selection
of AARP with single stage or AARP with two stages of desorption. The invention is
described with respect to the accompanying Figure 4, simplified flow diagram of Waste
Heat Driven Combustion Turbine Inlet Air Cooling System using single stage AARP to
i i
present the invention. Figure 5 presents the same system of AARP with two stages of
desorption and single stage absorption. Figure 6 describes the option of ice generation
facility which can be incorporated in single stage AARP. Figure 7 presents ice generation
capacity which can be incorporated in AARP with two stages of desorption and single
stage absorption.
9

DETAILED DESCRIPTION OF THE SCHEMATIC DIAGRAM:
The system consists of following major components:
• Exhaust Gas Heat Recovery Hot Water Generator to be installed on exhaust gas at outlet of existing HRSG of power plant.
• Ammonia Absorption Refrigeration Plant.
• Combustion Air Cooler (Also called liquid ammonia evaporator).
• Ammonia Condenser.
• Cooling Tower (When water cooling is considered).
• Necessary accessories, ducting, piping etc.
• Data logging and monitoring system.
The electricity is generated in a gas turbine (marked as item no. 1) by combustion of fuel. The exhaust gas leaving the gas turbine drives a high pressure steam boiler (marked as item no. 2) and low pressure steam boiler (marked as item no. 3). The steam generated in the high pressure steam boiler and the low pressure steam boiler is used in a two stage steam turbine (marked as item no. 4) to generate additional electricity. The temperature of exhaust gas leaving low pressure steam boiler is typically 110 to 120 Deg C. These gases are then passed through waste heat recovery hot water generator (marked as item no. 5) to generate hot water in a closed loop. Water from expansion tank (marked as item no. 15) in a closed loop is pumped with the help of hot water circulation pump (marked as item no. 16) to hot water generator. The water enters hot water generator at minimum temperature of typically 68-80 Deg C. and is heated upto typically 100-130 Deg C. The hot water is supplied to the Ammonia Absorption Refrigeration Plant. Either of two types of AARP can be used depending upon the hot water temperature generated in waste heat recovery hot water generator. The types of AARP are single stage AARP or AARP with two stages of desorption. Figure 3 shows graph which helps in selection of single stage AARP or AARP with two stages of desorption and single stage of absorption. Depending
10

upon heat source temperature, cooling media temperature and liquid ammonia evaporation temperature, one of the AARP systems is selected. Notations for temperatures are given in Figure 3. In Figure 3, tH represents Typical Hot water temperature at the inlet of desorber of AARP. to represents Typical Evaporation temperature of ammonia in evaporator of AARP. Typical turbine inlet air temperature will be to + 2 Deg C or higher, tu is Typical cooling media Temperature in condenser and absorber for heat rejection. Cooling Media could be air, water or other liquids like thermic fluids etc. In case of water cooled condenser with remote radiators, tu is Dry Bulb Temperature of ambient air+ 5 Deg C. For Evaporatively cooled condenser, tu is Wet Bulb Temperature of ambient air + 2 Deg C. In case of directly air cooled condenser,
tu is Dry Bulb Temperature of ambient air + 3 Deg C.
i
DETAILED DESCRIPTION OF SINGLE STAGE AARP:
Single stage AARP is used when the hot water temperature is high enough to generate
required refrigeration effect. Typical single stage Ammonia Absorption Refrigeration
Plant consists of Ammonia evaporator, absorber,: desorber, rectifying column, ammonia
condenser and subcooler. '
Evaporator (marked as item no. 11) of AARP is placed in the air flow path. It is placed in the air flow path such that the liquid ammonia flowing through the tubes flows across direction with respect to air flow direction. It acts as air cooler which supplies cooled air
; j
to the inlet of combustion turbine. Liquid ammonia entering the evaporator gets evaporated in the tubes by directly absorbing heat from the ambient air. The tubes of evaporator (heat exchanger) through which the liquid ammonia flows can be of falling film design or rising film design. The vapours leaving the evaporator are passed through sub-cooler (marked as item no. 10). In sub-cooler, the liquid ammonia entering
evaporator gets subcooled with ammonia vapours coming out from evaporator. The
i
ammonia vapours from sub-cooler are absorbed in absorber (marked as item no. 12) in
11

the spray of weak ammonia-water solution in water. The heat of solution is removed with
the help of air cooed condenser or cooling water. The strong ammonia solution formed
after absorption is pumped to the desorber (marked as item no. 6). Solution heat
exchanger (marked as item no. 14) is provided! to preheat the strong solution before
entering the desorber and to cool the weak solution before entering the absorber. Heat is
supplied in the desorber to boil off ammonia from strong solution. The heat source used
in the desorber is the hot water generated in the above said waste heat recovery hot water
generator. The hot water enters the desorber typically at 100 - 130 Deg C or even lower.
and leaves typically at 68-80 Deg C. The ammonia vapours formed in the desorber
contain some water vapours due to affinity between ammonia and water. The rectifying
column (marked as item no. 7) is provided to remove the water vapours from the vapour
mixture. The pure ammonia vapours generated in rectifying column are condensed in
condenser (marked as item no. 8). This condenser can be of air cooled or water cooled
type depending upon the water availability at the site. Liquid ammonia formed thus gets
i accumulated in receiver (marked as item no. 9). The receiver supplies liquid ammonia to
the evaporator where it gets evaporated with the help of heat rejected by the ambient air
which is to be supplied to the inlet of combustion turbine. The water condensate formed
due to moisture condensation during air cooling is collected in condensate tank (marked
as item no. 17). Thus the ambient air gets directly cooled with the liquid ammonia to the
required temperature before entering the combustion turbine.
The said condenser (marked as item no. 8) can be water cooled or directly air cooled or indirectly air cooled or evaporatively cooled. It depends upon the availability of make up water at the site. Similarly, the said absorber (marked as item no. 12) can be water cooled with heat rejection in evaporatively cooled cooling tower or closed water circulation with heat rejection to air cooled remote radiators. In this case also, assessment of availability of make up water becomes a critical issue for selection of types of cooling system.
12

DETAILED DESCRIPTION OF AARP WITH TWO STAGES OF DESORPTION AND SINGLE STAGE OF ABSORPTION:
Two stages of desorption and single stage of absorption in AARP are used when the hot water temperature is not high enough to generate required refrigeration effect in single stage AARP. Typical AARP with two stages of desorption consists of evaporator, two desorbers, two absorbers (one intermediate and other for absorbing ammonia vapours generated by evaporation of liquid ammonia in the turbine inlet air cooling heat exchanger i.e. air cooler), two solution heat exchangers, rectifying column, condenser, receiver, and subcooler.
Liquid ammonia from receiver (marked as item no. 9) gets evaporated in air cooler (marked as item no. 11) by absorbing heat from the combustion inlet air entering the gas turbine. Ammonia vapours get absorbed by weak ammonia solution coming from low pressure desorber in low pressure absorber (marked as item no. 12). The strong ammonia solution from low pressure absorber is desorbed in low pressure desorber (marked as item no. 18). Weak ammonia solution returns to low pressure absorber. Ammonia vapours formed in low pressure desorber are absorbed in high pressure absorber (marked as item no. 19) by weak solution returning from high pressure desorber (marked as item no. 6). Hot water generated in waste heat recovery hot water generator (marked as item no. 5) is used as heat source in both desorbers. Rectifying column (marked as item no. 7) removes water vapours from ammonia vapours. Pure ammonia vapours get condensed in condenser. The condenser can be evaporatively cooled, water cooled, directly air cooled or indirectly air cooled with remote radiators. ,
The advantages of the new system are as under:
1. The proposed CTIACS uses waste heat from exhaust gases available at outlet of existing power plant. Hence the running cost is lowest. There is no consumption
13

of steam from existing HRSG for operation of the same CTIACS. Hence no reduction in power output of steam turbine.
2. Also the proposed CTIACS needs no additional fuel consumption for power plant to increase power output from existing plant,
3. There is substantial increase in Gas Turbine power output due to 'Combustion Turbine inlet air cooling' down to 12 Deg C or even lower. The output of steam turbine would also increase due to increase in flue gas quantity and subsequent increase in steam output from HRSG.
4. Internal electrical power consumption reduces considerably due to absence of chilled water circulation pump and vacuum pump, since the air gets cooled directly by liquid ammonia in the said evaporator as compared to Li-Br chiller.
5. Since the AARP unit is not required to be packaged, absorber, sub-cooler and evaporator can be placed near the combustion turbine and desorber / desorbers (in case of two stages AARP), rectifying column, condenser and ammonia receiver can be placed near the heat source.
6. Completely air cooled AARP plant is possible where there is a shortage of make up water.
7. Since AARP works under pressure, no special care is needed for maintenance of vacuum.
8. Corrosion is negligible in AARP so the life span of the plant is more than 25 years.
9. The system is fully automatic in operation1 with continuous automatic modulation of major operating parameters and online data logging of the working parameters is possible.
14

VARIATIONS POSSIBLE TO BE COVERED AND PROVIDED WITHIN THE INVENTION OF THIS NEW CTIACS:
1. The temperature of the hot water generated in the Waste Heat Recovery Hot
Water Generator is dependent on the exhaust gas temperature at the outlet of
HRSG.
The waste heat recovery hot water generator could be of finned tube or bare tube construction having countercurrent or co-current flow of heat exchanging medium depending upon the above parameters.
Finns of finned tube of waste heat recovery hot water generator can be of extruded aluminium type or carbon steel Ljtype fins or welded fins or spiral fins.
2. Single or two stage AARP can be selected and its selection will be dependent upon the temperature of hot water available as well as other operating parameters and cooling media temperatures.
3. Condenser or absorber can be cooled using air cooled condenser where there is a shortage of make up water for cooling tower.
4. Fins of air cooler i.e. evaporator of AARP can be of extruded aluminium type or carbon steel L type fins or welded fins or spiral fins.
5. Condenser can be of direct air cooled type, water cooled type or evaporatively cooled or indirectly air cooled with remote radiators depending upon the make up water available.
6. Absorber can be water cooled with heat rejection in evaporatively cooled cooling tower or closed water circulation with heat rejection in air cooled remote radiators.
7. When the remote radiators are used as condenser, the cooling media flowing through remote radiators can be water, other liquids like thermic fluids etc.
8. Option of incorporating Ice Thermal Storage is also possible if heat source temperature is high enough so as to drive Ammonia Absorption Refrigeration Plant at refrigeration temperatures at subzero temperature (i.e. lower than 0 Deg
15

C). This is particularly possible in night when the ambient dry bulb temperatures are low. In such conditions, the AARP can be utilized for ice generation. Using low temperature AARP (below 0 Deg C.) the ice can be generated in ice bank tanks (marked as item no. 23). The flow of refrigerant liquid ammonia can be controlled using flow control valves for ice production (marked as item no. 24 & 25). Thus when inlet air cooling is not required the AARP can be utilized to generate ice. The inlet air to the combustion turbine can be further cooled till 4.4 Deg C by placing chilled water coil (marked as item no. 22). Through this coil, chilled water of 0 Deg. C is circulated using chilled water circulation pump (marked as item no. 26). Chilled water transfers its heat to the above said ice bank tank. The ice thermal storage can be used in air cooling system to reduce temperature further below 15 Deg C to reach minimum at 4.4 Deg C. Thus AARP is run almost continuously at its rated capacity and for much higher time during the day the temperature of 4.4 Deg C can be achieved and maximum power output can be obtained. Same ice bank tank can be incorporated in case of AARP with two stages of desorption.
Thus following options can be considered for the use of ice thermal storage.
a) There are cases where ice can be formed using AARP in the night and can
be stored in ice thermal storage. Thermal ice storage can be used
alongwith the use of AARP during day time to cool the gas turbine inlet
air below 15 Deg C and nearer to 4.4 Deg C depending upon the capacity
of the ice thermal storage.
i
b) There are cases where during night time the temperature of gas turbine
inlet air can be reached upto 4.4 Deg C. But it is not possible to reach 4.4 Deg C. during day time. The system can be made such that it reaches the minimum Dossible temperature during day time using ice thermal storage.
16

c) There are cases where it is not possible to reach the temperature of 15 Deg C. even during day time. Ice thermal storage, which can be run during night time, can be used in such case to reach possible minimum temperature.
Completely air cooled Ammonia Absorption Refrigeration plant can be also used
wherever make up water is not available for cooling tower.
The invention is applicable to all above possible variations and hence the
invention is versatile, flexible and has wide application range.
17

Comparative Statement No. 1

Typical Comparison between proposed combustion turbine inlet air cooling system using AARP (New Art) and vapour compression cycle based inlet air cooling system (Prior Art)
Mechanical refrigeration Proposed System
1 Ambient air temperature DegC 35.00 35.00
2 Inlet air temperature to gas turbine DegC 4.4 4.4
3 Tons of Refrigeration , ! TR 6200 6200
4 Power Output MW 132.04 132.04
5 Power output from steam turbine MW 66.02 66.02
6 Power output from CCPP MW 198.06 198.06
7 Captive power consumption MW 7.50 2.00
8 Net Exportable power | MW 190.557 196.06
9 Net additional exportable power due to CTIAC MW NA 5.50
10 Existing unit cost of power Rs/kWh 2.26
11 Savings/earning per hour 12430.00
12 Savings per annum Rs. In Crorei NA 9.94
13 Savings in 20 years ' Rs. In Crore NA 198.88
18

Comparative Statement No. 2

Typical Comparison between proposed combustion turbine inlet air cooling system using AARP(New Art) and Combustion Turbine Inlet Air Cooling System using heat input through duct firedhot water generator using vapour absorption chiller (Prior Art)
Duct fired Proposed System
1 i Ambient air temperature ' DegC 35.00 35.00
2 Inlet air temperature to gas turbine DegC 4.4 4.4
3 Tons of Refrigeration TR 6200 6200
4 Power Output from Gas Turbine MW 132.04 131.90
5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 66.02 65.95
6 Power Output from CCPP MW 198.06 197.85
8 Captive Power consumption for CTIACS System MW 2.00 2.50
9 Net exportable power output from CCPP after accounting for captive power consumption MW 196.06 195.35
10 Net additional exportable power due to CTIACS MW 071
11 Existing unit cost of power j Rs./kWh 2.26 -
12 Savings / Earnings per hour Rs./hr 1600.00 -
13 Additional Fuel consumption for Duct firing cu.m/hr 2305.88 NA
14 Additonal cost of fuel per hour (Expenditure) Rs./hr 16141.18 NA
15 Net Savings per annum Rs./hr - 14541.18
16 Savings per annum Rs. In Crore NA 11.63
17 Savings in 20 years Rs. In Crore NA 174.49
19

Comparative Statement No. 3

Typical Comparison between proposed combustion turbine inlet air cooling system usingAARP (New Art) and Combustion Turbine Inlet Air Cooling System operated on steamextracted from steam turbine and vapour absorption chilling (Prior Art)
Steam Extraction Proposed System
1 Ambient air temperature DegC 35.00 35.00
2 Inlet air temperature to gas turbine DegC 4.4 4.4
3 Tons of Refrigeration TR 6200 6200
4 Power Output from Gas Turbine MW 132.04 131.90
5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 66.02 65.95
6 Power Output from CCPP MW 198.06 197.85
7 Reduction in power output due to steam extraction MW 2.50 NA
8 Captive Power consumption for CTIACS System MW 1.50 2.50
9 Net exportable power output from CCPP after accounting for captive power consumption MW 194.06 197.85
10 Net additional exportable power due to CTIACS MW NA 3.79
11 Existing unit cost of power Rs./kWh 2.26 -
12 Savings / Earnings per hour j Rs./hr - 8570.00
13 Net Savings per annuhi ' Rs./hr NA 8570.00
14 Savings per annum Rs. In Crore NA 6.86
15 Savings in 20 years Rs.ln Crore NA 137.12
20

Comparative Statement No. 4

Typical Comparison between proposed combustion turbine inlet air cooling system using AARP (New Art) and Combustion Turbine Inlet Air Cooling System using Li-Br vapourabsorption chiller (Prior Art)
LiBr Chiller Proposed System
1 Ambient air temperature DegC 35.00 35.00
2 i Inlet air temperature td gas turbine DegC 15 15
3 Tons of Refrigeration TR 3410 3410
4 Power Output from Gas Turbine MW 123.27 123.27
5 Power Output from Steam turbine (considered as 50% of Turbine output) MW 61.64 61.64
6 Power Output from CCPP MW 184.91 184.91
7 Captive Power consumption for CTIACS System MW 0.8 0.55
8 Net exportable power output from CCPP after accounting for captive power consumption MW 184.06 184.36
9 Net additional exportable power due to AARP CTIACS .MW 0.30
10 Existing unit cost of power Rs./kWh 2.26 -
11 Savings / Earnings per hour Rs./hr - 678.00
12 Net Savings per annum Rs./hr NA 678.00
13 Savings per annum Rs.ln Crore NA 0.54
14 Savings in 20 years Rs.ln Crore NA 10.85
21

1. Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plant; hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine.
2. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in claim no. 1 wherein the single or two desorption stage Ammonia Absorption Refrigeration plant is installed.
3. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in
claims no. 1 & 2 wherein inlet air to the combustion turbine is directly cooled bi liquid ammonia in the evaporator (i.e. combustion air cooler) of ammonia
absorption refrigeration plant.
4. Waste Heat Driven Combustion Turbine Inlet Air Cooling System as claimed in
claims no. 1, 2 & 3 wherein no additional fuel is required to increase power
output of power plant. j
i j
5. Waste heat driven bombustion turbine inlet air cooling system claimed in claims no. 1, 2, 3 & 4 wherein the said waste heat recovery hot water generator consists of finned tubes.
6. Waste heat driven combustion turbine inlet air cooling system as claimed in claims no. 1, 2, 3 , 4 & 5 wherein directly, air cooled or indirectly air cooled with remote radiators or evaporatively cooled or water cooled ammonia condenser and ammonia absorbers are provided.
7. Waste heat driven combustion turbine inlet air cooling system plant as claimed in claims no. 1, 2, 3, 4, 5 & 6 wherein condensate tank is provided to collect condensate formed in air cooler.
22

8. Waste heat driven combustion turbine inlet air cooling system as claimed in claims no. 1,2, 3,4, 5, 6 & 7 above and herein described with respect to drawings of the accompanying specification.

M. S. Khadilkar (Agent for applicant)
Dated this 28th day of March 2006
23

ABSTRACT
Waste Heat Driven Combustion Turbine Inlet Air Cooling System comprising of hot water generator, generating hot water using heat from the flue gases, the said hot water generator installed on exhaust gas at outlet of last stage of HRSG (Heat Recovery Steam Generator) of power plant; single / two stage hot water driven Ammonia Absorption Refrigeration Plant which directly reduces the temperature of ambient air to 15 Deg C or below which is supplied to existing gas turbine.
24

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=Pmec7yg28dpChrEBq8i8RA==&loc=vsnutRQWHdTHa1EUofPtPQ==

« Previous Patent

Next Patent »

Patent Number

269927

Indian Patent Application Number

483/MUM/2006

PG Journal Number

47/2015

Publication Date

20-Nov-2015

Grant Date

18-Nov-2015

Date of Filing

29-Mar-2006

Name of Patentee

TRANSPARENT ENERGY SYSTEMS PRIVATE LIMITED

Applicant Address

PUSHPA HEIGHTS,1st FLOOR, BIBWEWADI CORNER, PUNE-411 037,MAHARASHTRA,INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	ATRE ASHOK DATTATRAYA	PUSHPA HEIGHTS 1ST FLOOR BIBWEWADI CORNER PUNE 411 037

PCT International Classification Number

F01K19/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA