Title of Invention | A DUAL COOLING WATER SYSTEM ADAPTABLE TO POWER PLANTS |
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Abstract | A dual cooling water system adaptable to power plants having at least one generator air cooler for cooling hot air in the generator air cooler (1) with atmospheric air in winters and with water in summers, the system comprising a forced cooling water device imputed to the at least one generator air cooler (1), and having at least two forced cooling pumps (2), a first of the two forced cooling (2) pumps runs continuously, the second forced cooling pump automatically commences operation when the differential pressure between the suction and discharge of the generator falls below a specified value; a fin fan cooler (3) disposed in the cooling water circuit of the generator which transfers the heat from the hot water coming out of the at least one generator air cooler (1) to the atmosphere; atleast one plate-type heat exchanger (5) for cooling water being supplied from a cooling water sump (6); and two cooling water pumps (7) disposed in the circuit; characterized in that the forced cooling water device is configured to activate the second forced cooling pump to allow flow of water in the winter seasons via the fin fan cooler (3) and deactivate the second forced cooling pump and allow flow of water in the summer seasons being directed via the plate-type heat exchanger (5). |
Full Text | FIELD OF INVENTION The present invention generally relates to a cooling system for gas turbine generator in combined cycle Power Plants. More particularly, the invention relates to a dual cooling water system capable of additionally cooling hot air in the generator with atmospheric air in winters and with water in summers. BACKGROUND OF THE INVENTION Forced Cooling Water device is known to be used in the cooling of hot air in the gas turbine generators in Combined cycle power plants. The air inside the generator cools the windings on the rotor as well as those of the stator, the hot air being cooled with DM water which is supplied inside the generator coolers by several pumps. The DM water used for cooling the hot air is further cooled by at least one fin-fan cooler having the fins exposed to the atmosphere. In summers when the atmospheric temperature rises, and the difference between the water and the atmospheric temperature decreases the hot air is not effectively cooled inside the generator. As described hereinabove, the existing device for cooling i.e. Forced Cooling water device uses DM water as a coolant for cooling hot air and needs Fin fan Coolers for cooling the water for generation of power. The prior art device has limitations in summers as the ambient temperature rises and this restricts the power output of the generator thereby decreasing efficiency of the plant. The existing forced cooling water device however, fulfils the following requirements: Delivering cooling water to generator coolers. Transferring heat from water coolers to the air cooler system. Maintaining cooling water temperature and pressure within allowable values. The existing device is generally a closed cooling loop cycle type system. It consists of: Forced cooling water (circulating) pumps. DM water make-up pumps Fin-fan coolers Expansion tank -1 Expansion tank - 2 (with butyl rubber balloon) Carbon steel piping and valves The existing forced cooling device is operable during start-up, normal operation and blank start of the gas turbine. The operation and configuration of the prior art device includes: At least two forced cooling water pumps, the first pump running continuously and the second pump starts automatically upon the differential pressure between the discharge and suction falling below a specified value. A pressure switch provided at the suction end of the two pumps also calls for the pumps tripping on Now suction pressure'. Water is supplied through a header line to the generator coolers which after cooling the generator, caused to enter the fin-fan cooler located outside the GT where the hot water is cooled. Cooled water from the fin fan air cooler is returned back to the suction end of the cooling water pumps which makes the system closed. The cold water is again supplied to the generator coolers to repeat the cycle. An expansion tank-2 (with butyl rubber ballon) is disposed at the suction end of the cooling water pumps. The expansions tank-2 maintains the system pressure, and provides a volume control. The existing forced cooling water device is operated with demineralised water. Accordingly the expansion tank-1 is filled with demineralised water. To maintain the make-up pressure, DM make-up pumps are provided. The first of the two pumps continuously runs and a first constant pressure regulator is provided to maintain a constant pressure for make up. When the DM plant is operated, the make up is maintained in an expansion tank-1 by a float valve provided in the expansion tank- 1. A second constant pressure regulator maintains a constant pressure at the suction end of the forced cooling water pumps. In case, the pressure in the expansion tank drops, demineralised water is fed via a filling nozzle automatically. To avoid over pressure, a safety relief valve on the suction end of the forced cooling water pumps is provided. The pumps and the expansion tanks are located outside the Gas Turbine Building. The fin fan air coolers are located on the structure of the forced cooling water air cooler disposed outside the gas turbine building. A NaOH-dosing unit is provided for feeding dilute NaOH liquid into the system for control of water pH value, so as to avoid corrosion to carbon steel piping system. OBJECTS OF THE INVENTION It is therefore an object of the present invention to propose a dual cooling water system capable of cooling hot air in the generator with atmospheric air in winters and with water in summers which provides enhanced output. Another object of the present invention is to propose a dual cooling water system capable of cooling hot air in the generator with atmospheric air in winters and with water in summers which increases the efficiency of the generator vis-a-vis the plant. SUMMARY OF THE INVENTION Accordingly, there is provided a dual cooling water system adaptable to power plants having at least one generator air cooler, for cooling hot air in the generator air cooler with atmospheric air in winters and with water in summers, the system comprising; a forced cooling water device imputed to the at least one generator air cooler and having at least two forced cooling pumps, a first of the two pumps runs continuously, the second forced cooling water pump automatically commences operation, when the differential pressure between the suction and the discharge of the generator falls below a specified value; A fin fan cooler disposed in the cooling water circuit of the generator which transfers the heat from the hot water coming out of the at least one generator air cooler to the atmosphere; atleast one plate-type heat exchanger for cooling water supplied from a cooling water sump; and two cooling water being pumps disposed in the circuit; characterized in that the system is configured to : activate the second forced cooling pump to allow flow of water in the winter seasons via the fin-fan cooler, and deactivate the second forced cooling pump to allow flow of water in the summer seasons being directed via the plate-type heat exchanger. According to the invention, the air to be cooled is passed through the generator air coolers where it is cooled sufficiently with DM water (about a temperature of 40 - 45°C). The DM water is then cooled with Fin Fan Coolers having fins exposed to the atmosphere. In summers when the differential temperature between the ambient and that of the DM water reduces the air inside the generator cannot be effectively cooled thereby the windings of the stator of the generator is not properly cooled. This phenomenon restricts the maximum output from the generator. The inventive system uses plate type heat exchangers and water from the Cooling water Sump for efficient cooling of the DM water even at lower differentials which enhances the output from the machine because of sufficient heat absorption from the air inside the generator. Alternatively, the hot air can be cooled with DM water with the help of Fin fan Coolers. Accordingly, the inventive cooling system adapts plate type heat exchangers for cooling water in case of low temperature differential, and fin coolers in case of high temperature differential to improve efficiency of the machine. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.l - a single line diagram of a forced cooling water device for gas turbine generator in a combined cycle power plant according to prior art. Fig.2 - a single line diagram of a dual cooling water system according to the invention. DETAILED DESCRIPTION OF A PREFERED EMBODIMENT OF THE PRESENT INVENTION. As shown in figure 1, a forced cooling device, comprises two forced cooling pumps (2), one of the two pumps runs continuously, the second pump automatically starts when the differential pressure between the suction and discharge of the generator falls below a specified value. Firstly, forced cooling water is pumped into generator air cooler (1). After cooling the generator air, the water is passed through a fin-fan cooler (3). The fin fan cooler (3) transfers heat from hot water to the atmosphere. The forced cooling water pumps are operated with demineralised (DM) water for which a DM-plant with 'make-up' pumps are provided. Further, at least two expansion tanks are provided for the DM-plant (not shown). Associated controls and piping are provided to operate the system. The dual cooling water system of the invention as shown in Fig. -2, is enabled to adapt a forced water cooling device of Fig. -1. The system is generally operable when the ambient temperature rises in summers, so as to limit the temperature where, the temperature differential between the ambient and the cooled water starts decreasing. The system comprises apart from the forced cooling water device, atleast one plate type heat exchanger (5) which cools the water from the cooling water sump (6) of the main power station. Two cooling water pumps (7) having foot-valves are disposed in the cooling water circuit. A self-cleaning strainer (8) is disposed between the cooling water pumps (7) and the heat exchanger (5). The dual cooling water system works on the principle of heat transfer from Hot air inside the generator to DM water flowing in the tubes of the generator air Coolers (1). The forced cooling water is pumped to the generator air coolers (1) and the Fin Fan Coolers (3). The fin fan coolers (3) transfer heat from the hot water to the atmosphere. In summers, when the ambient temperature is at its peak, the differential between the hot water from the generator air coolers (1) and the atmosphere is less and thus the cooling is not effective. However, with the plate type heat exchangers (5) installed, the hot water from the generator air coolers (1) is passed through these heat exchangers (5) and effective cooling is achieved even at low differential between the primary and secondary cooling water of the heat exchangers (5). The device is dual in the sense that it gives two options for cooling the hot water, the first being by the atmosphere through the fin fan coolers (3) and the second through the plate type heat exchangers (5). The flow of the water is controlled with necessary valves and fittings. In winters the first option of cooling through the fin fan coolers (3) can be employed. This can be done by auto cut-in and auto-cut-out with the cold air temperature in the generator. WE CLAIM 1. A dual cooling water system adaptable to power plants having at least one generator air cooler for cooling hot air in the generator air cooler (1) with atmospheric air in winters and with water in summers, the system comprising : a forced cooling water device imputed to the at least one generator air cooler (1), and having at least two forced cooling pumps (2), a first of the two forced cooling (2) pumps runs continuously, the second forced cooling pump automatically commences operation when the differential pressure between the suction and discharge of the generator falls below a specified value; a fin fan cooler (3) disposed in the cooling water circuit of the generator which transfers the heat from the hot water coming out of the at least one generator air cooler (1) to the atmosphere; atleast one plate-type heat exchanger (5) for cooling water being supplied from a cooling water sump (6); and two cooling water pumps (7) disposed in the circuit; characterized in that the forced cooling water device is configured to :- activate the second forced cooling pump to allow flow of water in the winter seasons via the fin fan cooler (3) and deactivate the second forced cooling pump and allow flow of water in the summer seasons being directed via the plate-type heat exchanger (5). 2. The system as claimed in claim 1, comprising a self-cleaning strainer (8) disposed between the cooling water pumps (7) and the heat exchanger (5). 3. The system as claimed in claim 1, wherein the forced cooling water device is operated with demineralised water (DM-water) for which at least one DM make up-plant with expansion tanks including associated controls are provided. 4. A dual cooling water system adaptable to power plants having at least one generator air cooler for cooling hot air in the generator air cooler with atmospheric air in winters and with water in summers as substantially described herein with reference to the accompanying drawings. A dual cooling water system adaptable to power plants having at least one generator air cooler for cooling hot air in the generator air cooler (1) with atmospheric air in winters and with water in summers, the system comprising a forced cooling water device imputed to the at least one generator air cooler (1), and having at least two forced cooling pumps (2), a first of the two forced cooling (2) pumps runs continuously, the second forced cooling pump automatically commences operation when the differential pressure between the suction and discharge of the generator falls below a specified value; a fin fan cooler (3) disposed in the cooling water circuit of the generator which transfers the heat from the hot water coming out of the at least one generator air cooler (1) to the atmosphere; atleast one plate-type heat exchanger (5) for cooling water being supplied from a cooling water sump (6); and two cooling water pumps (7) disposed in the circuit; characterized in that the forced cooling water device is configured to activate the second forced cooling pump to allow flow of water in the winter seasons via the fin fan cooler (3) and deactivate the second forced cooling pump and allow flow of water in the summer seasons being directed via the plate-type heat exchanger (5). |
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00074-kol-2006-description complete.pdf
74-kol-2006-correspondence.pdf
74-kol-2006-correspondence1.1.pdf
74-kol-2006-description (complete).pdf
74-kol-2006-examination report reply recieved.pdf
74-kol-2006-examination report.pdf
74-kol-2006-granted-abstract.pdf
74-kol-2006-granted-claims.pdf
74-kol-2006-granted-description (complete).pdf
74-kol-2006-granted-drawings.pdf
74-kol-2006-granted-form 1.pdf
74-kol-2006-granted-form 2.pdf
74-kol-2006-granted-specification.pdf
74-kol-2006-reply to examination report.pdf
Patent Number | 249435 | ||||||||||||||||||
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Indian Patent Application Number | 74/KOL/2006 | ||||||||||||||||||
PG Journal Number | 42/2011 | ||||||||||||||||||
Publication Date | 21-Oct-2011 | ||||||||||||||||||
Grant Date | 19-Oct-2011 | ||||||||||||||||||
Date of Filing | 24-Jan-2006 | ||||||||||||||||||
Name of Patentee | BHARAT HEAVY ELECTRICALS LIMITED | ||||||||||||||||||
Applicant Address | REIGIONAL OFFICES AT REGIONAL OPERATIONS DIVITION (ROD), PLOT NO : 9/1, DJBLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY , KOLKATA-700091, REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA | ||||||||||||||||||
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PCT International Classification Number | F01D 25/12 | ||||||||||||||||||
PCT International Application Number | N/A | ||||||||||||||||||
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