Combined cycle electric power plant having a control system which enables dry steam generator operation during gas turbine operation
First Claim
1. A method of operating a heat recovery steam generator of a combined cycle electric power plant, wherein said heat recovery steam generator is transferred from a first, steam generating mode of operation to a second, dry mode of operation, said combined cycle electric power plant comprising at least one gas turbine including an exit through which heated exhaust gases pass, said heat recovery steam generator being coupled to said gas turbine exit for transferring heat from the exhaust gases to a fluid passing through said heat recovery steam generator, a steam turbine coupled to receive superheated steam generated by said heat recovery steam generator, a first electric generator coupled to said gas turbine and driven thereby, a second electric generator coupled to said steam turbine and driven thereby, an afterburner for supplying additional heat to the exhaust gases passing from said gas turbine to said heat recovery steam generator, valve means for controlling the flow of fuel to said afterburner, condenser means for receiving and converting the spent steam from said steam turbine into condensate, first valve means for controlling the flow of condensate fluid to said heat recovery steam generator, second value means for controlling the flow of superheated steam to said steam turbine, said heat recovery steam generator comprising a low pressure storage tank, a first heat exchange tube, a boiler feedwater pump for supplying fluid from said low pressure storage tank to said first heat exchange tube, a main storage drum for receiving and storing water from said first heat exchange tube, a second heat exchange tube, and a high pressure pump for directing water from said main storage drum through said second heat exchange tube, said aforementioned elements of said heat recovery steam generator being interconnected to form a fluid flow path from said first to said second valve means, said method comprising the steps of:
- a. closing said first valve means to terminate the flow of condensate from said condenser to said heat recovery steam generator, while maintaining said second valve means open;
b. reducing the load demand signal applied to said gas turbine to a point sufficient so that the temperature of the exhaust gas turbine gases directed to said heat recovery steam generator does not exceed a predetermined maximum limit;
c. operating said heat recovery steam generator to generate steam therefrom as by the transfer of heat from the exhaust gas turbine gases to the fluid previously circulated thereto and directing the generated steam through said opened second valve means from said heat recovery steam generator, while extracting fluid from said low pressure storage tank, said main storage drum and said first and second heat exchange tubes; and
d. closing said second valve means, thus terminating the flow of superheated steam from said heat recovery steam generator, while containuing to operate said gas turbine at reduced load levels.
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Accused Products
Abstract
A combined cycle electric power plant includes gas and steam turbines and a steam generator for recovering the heat in the exhaust gases exited from the gas turbine and for using the recovered heat to produce and supply steam to the steam turbine. A condenser is associated with the steam turbine for converting the spent steam from the steam turbine into condensate to be supplied to the steam generator. The steam generator includes a low pressure storage tank, a first heat exchange tube, a boiler feedwater pump for directing fluid from the low pressure storage tank through the first heat exchange tube, a main storage drum, a second heat exchange tube, and a high pressure recirculation pump for directing water from the main storage drum through the second heat exchange tube. An afterburner further heats the exhaust gas turbine gases passed to the first and second heat exchange tubes. Method and apparatus are provided for controlling the transfer of the operation of the steam generator from a WET mode of operation to a DRY mode of operation. In particular, the heat supplied to the gas turbine exhaust gases is reduced, the fluid introduced into the steam generator is cut off, a blowdown valve for directing fluid from the steam generator is opened to further drain fluid therefrom, heat is continued to be supplied to the first and second heat exchange tubes whereby steam is continued to be generated within said generator and directed to the steam turbine, and finally the outlets associated with the steam generator are closed and the steam generator is filled with a suitable non-corrosive fluid such as nitrogen gas.
48 Citations
33 Claims
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1. A method of operating a heat recovery steam generator of a combined cycle electric power plant, wherein said heat recovery steam generator is transferred from a first, steam generating mode of operation to a second, dry mode of operation, said combined cycle electric power plant comprising at least one gas turbine including an exit through which heated exhaust gases pass, said heat recovery steam generator being coupled to said gas turbine exit for transferring heat from the exhaust gases to a fluid passing through said heat recovery steam generator, a steam turbine coupled to receive superheated steam generated by said heat recovery steam generator, a first electric generator coupled to said gas turbine and driven thereby, a second electric generator coupled to said steam turbine and driven thereby, an afterburner for supplying additional heat to the exhaust gases passing from said gas turbine to said heat recovery steam generator, valve means for controlling the flow of fuel to said afterburner, condenser means for receiving and converting the spent steam from said steam turbine into condensate, first valve means for controlling the flow of condensate fluid to said heat recovery steam generator, second value means for controlling the flow of superheated steam to said steam turbine, said heat recovery steam generator comprising a low pressure storage tank, a first heat exchange tube, a boiler feedwater pump for supplying fluid from said low pressure storage tank to said first heat exchange tube, a main storage drum for receiving and storing water from said first heat exchange tube, a second heat exchange tube, and a high pressure pump for directing water from said main storage drum through said second heat exchange tube, said aforementioned elements of said heat recovery steam generator being interconnected to form a fluid flow path from said first to said second valve means, said method comprising the steps of:
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a. closing said first valve means to terminate the flow of condensate from said condenser to said heat recovery steam generator, while maintaining said second valve means open; b. reducing the load demand signal applied to said gas turbine to a point sufficient so that the temperature of the exhaust gas turbine gases directed to said heat recovery steam generator does not exceed a predetermined maximum limit; c. operating said heat recovery steam generator to generate steam therefrom as by the transfer of heat from the exhaust gas turbine gases to the fluid previously circulated thereto and directing the generated steam through said opened second valve means from said heat recovery steam generator, while extracting fluid from said low pressure storage tank, said main storage drum and said first and second heat exchange tubes; and d. closing said second valve means, thus terminating the flow of superheated steam from said heat recovery steam generator, while containuing to operate said gas turbine at reduced load levels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of operating a combined cycle electric power plant comprising a heat recovery steam generator, wherein said heat recovery system generator is transferred from a first, steam generating mode of operation to a second, dry mode of operation, said combined cycle electric power plant further comprising at least one gas turbine including an exit through which heated exhaust gases pass to said heat recovery steam generator, a steam turbine coupled to said heat recovery steam generator and driven by the steam supply therefrom, means for generating electric power by the driving power of said turbines, said heat recovery steam generator having inlets for permitting the flow of fluid from said steam turbine thereto and outlets for permitting the flow of fluid to said steam turbine, said method comprising the steps of:
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a. reducing the heat supplied to the gas turbine exhaust gases as directed to said heat recovery steam generator; b. closing the fluid inlets to said heat recovery steam generator; c. continuing to supply heat to said gas turbine exhaust gases whereby steam is continued to be generated by said heat recovery steam generator; and d. closing said outlets of said heat recovery steam generator. - View Dependent Claims (22, 23)
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24. A control system for a combined cycle electric power plant comprising at least one gas turbine including an exit through which heated exhaust gases pass, means for generating steam coupled to said gas turbine exit for transferring heat from the exhaust gases to a fluid passing through said steam generating means, a steam turbine coupled to said steam generating means and driven by the steam supplied thereby, means for generating electric power by the driving power of said turbines, condenser means for receiving and converting the spent steam from said steam turbine into condensate, and said steam generating means comprising a low pressure storage tank, a first heat exchange tube, a boiler feedwater pump for directing fluid from said low pressure storage tank through said first heat exchange tube, a main storage drum, a second heat exchange tube, and a high pressure recirculation pump for directing fluid from said main storage pump through said second heat exchange tube, said control system comprising:
monitoring means for measuring the temperature of the exhaust gas turbine gases as directed to said steam generating means and responsive to such a temperature above a predetermined level, for deactuating said steam turbine. - View Dependent Claims (25, 26, 27, 28)
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29. A combined cycle electric power plant comprising:
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a. at least one gas turbine including an exit through which heated exhaust gases pass; b. means for generating steam coupled to said gas turbine exit for transferring heat from the exhaust gases to a fluid passing through said steam generating means; c. a steam turbine coupled to said steam generating means and driven by the steam supplied thereby; d. means for generating electric power by the driving power of said turbines; e. condenser means for receiving and converting the spent steam from said steam turbine into condensate; f. said steam generating means comprising a low pressure storage tank, a first heat exchange tube, a boiler feedwater pump for directing fluid from said low pressure storage tank through said first heat exchange tube, a main storage drum, a second heat exchange tube, and a high pressure recirculation pump for directing fluid from said main storage pump through said second heat exchange tube; and g. control means for transferring the operation of said steam generating means from a wet to a dry mode of operation, said transfer control means comprising means for measuring the temperature of the exhaust gas turbine gases as directed to said steam generating means and responsive to a temperature above a predetermined level, for deactuating said steam turbine. - View Dependent Claims (30, 31, 32, 33)
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Specification