JP2015068314A - Fuel gas heating facility and combined cycle power generation plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve plant efficiency without lowering plant output when a double pressure type exhaust heat recovery boiler is employed.SOLUTION: Fuel gas heating facilities includes: a water extraction line L1 which extracts heating water from a heating water outlet of an intermediate-pressure fuel economizer 19 installed at an exhaust heat recovery boiler 4; a low-temperature fuel heating device 33 which heats a fuel gas to be used by a gas turbine plant 2 using the heating water extracted through the water extraction line L1; a water extraction line L2 which extracts heating water from a heating water outlet of a high-pressure secondary fuel economizer 14 located in an exhaust gas flow passage upstream from the intermediate-pressure fuel economizer 19 installed at the exhaust heat recovery boiler 4; a high-temperature fuel heating device 31 which further heats the fuel gas having been heated by the low-temperature fuel heating device 33 using the heating water extracted through the water extraction line L2; and a heating water return line L3 which returns the heating water after the heating of the fuel gas by the high-temperature fuel heating device 31 to the heating water outlet of the intermediate-pressure fuel economizer 19.

Description

  Embodiments of the present invention relate to a fuel gas heating facility applied to a combined cycle power plant that combines a gas turbine plant, a steam turbine plant, and an exhaust heat recovery boiler.

  In a combined cycle power plant, there is a technique for improving plant efficiency by heating fuel gas (for example, Patent Document 1). A basic configuration for realizing this is shown in FIG.

  The combined cycle power plant 40 is configured by combining a gas turbine plant 41, a steam turbine plant 42, and an exhaust heat recovery boiler 43.

  The gas turbine plant 41 includes an air compressor 44, a gas turbine combustor 45, a gas turbine 46, and a fuel heating device 57, and the atmosphere sucked by the air compressor 44 is increased in pressure, and the high-pressure air is supplied from the fuel heating device 57. The heated fuel gas is added to generate a combustion gas in the gas turbine combustor 45, and the gas turbine 46 is driven using the combustion gas as a driving gas.

  The steam turbine plant 42 includes a steam turbine 53 directly connected to the generator 52, a condenser 54, a condensate pump 55, and a feed water pump 56, and turbine-driven steam supplied from the exhaust heat recovery boiler 43 is converted by the steam turbine 53. The expansion work is performed and the generator 52 is rotationally driven with the rotational torque generated during the expansion work to obtain an electrical output, while the turbine exhaust that has finished the expansion work is condensed in the condenser 54 to be condensed water, The condensate is pressurized by the condensate pump 55 and the feed water pump 56 and supplied to the exhaust heat recovery boiler 43.

  The exhaust heat recovery boiler 43 includes a superheater 47 arranged from the upstream side to the downstream side along the flow of exhaust gas from the gas turbine 46, an evaporator 49 communicating with the steam drum 48, and a economizer 50. Housed in a casing 58, water supplied from the steam turbine plant 42 is preheated by the economizer 50 and guided to the steam drum 48 through the control valve 51, where the heated water is naturally used by the evaporator 49 using the specific gravity. The saturated steam is circulated to be saturated, and the saturated steam is heated again by the superheater 47 to generate superheated steam, and the superheated steam is supplied to the steam turbine plant 42 as turbine drive steam.

  In this prior art, paying attention to the temperature of the feed water heated by the economizer 50 of the exhaust heat recovery boiler 43, skillfully utilizing the heat energy of the heating water that has little thermal effect even if there is a load fluctuation, The plant thermal efficiency is improved. That is, efforts are made to improve plant efficiency by increasing the calorific value of the fuel gas introduced into the gas turbine combustor 45. More specifically, a fuel heating device 57 is provided in the gas turbine plant 41, and the heating water at the outlet side of the economizer 50 of the exhaust heat recovery boiler 43 that is less affected by load fluctuations is used as a heating source for the fuel heating device 57. The fuel gas is heated, the latent heat required when the water vapor contained in the fuel gas evaporates is removed, and as a result, the calorific value is increased. We are striving to improve.

  When applying the above technique to a double pressure exhaust heat recovery boiler, a configuration in which heated water is extracted from the outlet side of the medium pressure economizer is widely used.

Japanese Patent Laid-Open No. 02-283803

  As described above, in the double pressure exhaust heat recovery boiler, in order to increase the fuel gas temperature in order to improve the plant efficiency, there is a wide range of methods for increasing the fuel gas temperature using the extraction water from the outlet side of the medium pressure economizer as a heat source. It is used.

  However, in a multi-pressure type exhaust heat recovery boiler, when the fuel gas temperature is raised by using the extraction water from the outlet side of the medium pressure economizer as the heat source, the fuel gas temperature can only be increased up to about 200 ° C. There are limits to improving plant efficiency. On the other hand, it is possible to raise the fuel gas temperature to 200 ° C. or more by using extracted water from the outlet side of the high pressure economizer of the exhaust heat recovery boiler as a heat source. Since the work of the turbine and the low-pressure turbine will be reduced, the plant output will be lower than when extracting water from the outlet side of the medium-pressure economizer (in this case, the work of the medium-pressure turbine and low-pressure turbine will be reduced). This is not usually done.

  The present invention has been made in view of such circumstances, and a fuel gas heating facility and a combined apparatus capable of improving plant efficiency without reducing plant output when adopting a double pressure exhaust heat recovery boiler. An object is to provide a cycle power plant.

  The fuel gas heating facility of the embodiment is a fuel gas heating facility applied to a combined cycle power plant in which a steam turbine plant and an exhaust heat recovery boiler are combined with a gas turbine plant, and is installed in the exhaust heat recovery boiler. Fuel gas used in the gas turbine plant is heated using a first extraction line that extracts heating water from a heating water outlet of the first economizer and heated water extracted through the first extraction line. A first fuel heating device and a first water heater for extracting heated water from a heated water outlet of a second economizer located upstream of the first economizer installed in the exhaust heat recovery boiler. 2 and a second fuel addition unit for further heating the fuel gas heated by the first fuel heating device using heated water extracted through the second extraction line. A device comprises a second heated water after the fuel gas heating in the fuel heating system return first heating water returning to the heating water outlet of the first economizer line.

  According to the embodiment, when adopting a double pressure exhaust heat recovery boiler, plant efficiency can be improved without reducing plant output.

1 is a schematic system diagram showing a configuration of a combined cycle power plant according to a first embodiment. The schematic system diagram which shows the structure of the combined cycle power plant concerning 2nd Embodiment. The schematic system diagram which shows the structure of the conventional combined cycle power plant.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
First, a first embodiment will be described with reference to FIG.

  FIG. 1 is a schematic system diagram showing the configuration of the combined cycle power plant according to the first embodiment.

  The combined cycle power plant 1 is configured by combining a gas turbine plant 2, a steam turbine plant 3, and an exhaust heat recovery boiler 4.

  The gas turbine plant 2 includes an air compressor 5, a gas turbine combustor 6, a gas turbine 7, a high temperature fuel heating device 31, and a low temperature fuel heating device 33. The heated fuel gas from the high temperature fuel heating device 31 and the low temperature fuel heating device 33 is added to the gas turbine, the combustion gas is generated in the gas turbine combustor 6, and the gas turbine 7 is driven using the combustion gas as a driving gas.

  The steam turbine plant 3 includes a steam turbine 28 directly connected to the generator 27, a condenser 29, and a low-pressure feed water pump 30, and causes the steam-driven steam supplied from the exhaust heat recovery boiler 4 to perform expansion work in the steam turbine 28. The generator 27 is rotationally driven with the rotational torque generated during the expansion work to obtain an electrical output, while the turbine exhaust that has finished the expansion work is condensed in the condenser 29 to be condensed into condensate. The pressure is increased by the low-pressure feed water pump 30 and the water is supplied to the exhaust heat recovery boiler 4 through the feed water line L0.

  The exhaust heat recovery boiler 4 is a multi-pressure exhaust heat recovery boiler having a high pressure, a medium pressure, and a low pressure, and is a high pressure disposed from the upstream side to the downstream side along the flow of exhaust gas from the gas turbine 7. A superheater 8, a reheater 9, a high-pressure evaporator 11 that communicates with the high-pressure steam drum 10, a high-pressure tertiary economizer 12, an intermediate-pressure superheater 13, a high-pressure secondary economizer 14, and a low-pressure that communicates with the intermediate-pressure steam drum 15. An evaporator 16, a low-pressure superheater 17, a high-pressure primary economizer 18, an intermediate-pressure economizer 19, a low-pressure evaporator 21 and a low-pressure economizer 22 communicating with the low-pressure steam drum 20 are accommodated in a casing 37, and a steam turbine plant 3 is preheated by the low-pressure economizer 22 and guided to the low-pressure steam drum 20 through the control valve 23. Here, a part of the heated water is naturally circulated in the low-pressure evaporator 21 by using the specific gravity. To saturated steam It was heated at pressure superheater 17 by generating superheated steam supplied to the steam turbine plant 3 the superheated steam as a turbine driving steam. Further, a part of the remaining heating water is further transferred to the intermediate pressure superheater 13 via the high and medium pressure feed water pump 24, the intermediate pressure economizer 19, the control valve 25, and the intermediate pressure steam drum 15. Are continuously supplied to the high pressure superheater 8 through the high and medium pressure feed water pump 24, the high pressure primary economizer 18, the high pressure secondary economizer 14, the high pressure tertiary economizer 12, the control valve 26, and the high pressure steam drum 10. . Further, in each of the high-pressure steam drum 10 and the intermediate-pressure steam drum 15, using the specific gravity of the heated water, the high-pressure evaporator 11 and the intermediate-pressure evaporator 16 are each naturally circulated into saturated steam, and the saturated steam is again high-pressure. The superheater 8 and the medium pressure superheater 13 are respectively heated to generate superheated steam, and the superheated steam is supplied to the steam turbine plant 3 as turbine drive steam.

  The high-temperature fuel heating device 31 heats the fuel gas using hot water extracted through the extraction line L2 from the connecting pipe connecting the high-pressure secondary economizer 14 and the high-pressure tertiary economizer 12 as a heating source. The heated water obtained by heating the fuel gas with the high-temperature fuel heating device 31 is sent to the heated water return line L3. The heating water return line L3 includes a branch point 35 and a middle side economizer outlet 36 to the extraction water line L1 leading to the low temperature fuel heating device 33 among the communication lines from the intermediate pressure economizer 19 to the intermediate pressure steam drum 15. Connected to the section between.

  The fuel gas temperature is controlled by the high-temperature fuel heating device outlet temperature control valve 32 at the heating water outlet of the high temperature fuel heating device 31 by an operation signal from the control device 100 or manually. At this time, for example, the temperature of the heating water outlet of the high temperature fuel heating device 31 and the temperature of the medium pressure economizer outlet 36 are measured by a temperature detector (not shown), and the high temperature fuel heating device outlet temperature control valve 32 measures the temperature of the high temperature fuel heating device 31. The temperature of the heated water outlet is adjusted to be equal to the temperature of the medium pressure economizer outlet 36 so that the heat balance is not changed.

  The low-temperature fuel heating device 33 heats the hot water extracted from the connecting pipe connecting the intermediate pressure economizer 19 and the intermediate pressure steam drum 15 through the extraction line L1 as a heating source. The heated water obtained by heating the fuel gas with the low temperature fuel heating device 33 is sent to the heated water return line L4. The heating water return line L4 is connected so as to return to the feed water line L0 leading from the low pressure feed pump 30 to the low pressure economizer 22.

  The fuel gas temperature is controlled by the low temperature fuel heating device outlet temperature control valve 34 at the heating water outlet of the low temperature fuel heating device 33 by an operation signal from the control device 100 or manually. At this time, for example, the temperature of the heating water outlet of the low temperature fuel heating device 33 and the temperature of the feed water line L0 leading to the low pressure economizer 22 are measured by a temperature detector (not shown), and the low temperature fuel heating device outlet temperature control valve 34 measures the low temperature fuel. The temperature is adjusted so that the temperature of the heating water outlet of the heating device 33 is equal to the temperature of the water supply line L0 leading to the low-pressure economizer 22, so that the heat balance is not changed.

  The high temperature fuel heating device outlet temperature control valve 32 and the low temperature fuel heating device outlet temperature control valve 34 are not necessarily required to be installed. As long as the same temperature control can be performed, another one may be adopted. Further, if the desired temperature can be continuously obtained without adjusting the temperature, the installation of these temperature control valves can be omitted.

  As described above, the low-temperature fuel heating device 33 and the high-temperature fuel heating device 31 are provided as heating devices having different heating temperatures for heating the fuel gas in stages, and the medium pressure economizer 19 is used as a heating source for heating the fuel gas. By using warm water extracted through the extraction lines L1 and L2 from the outlet side and the outlet side of the high-pressure secondary economizer 14, the fuel gas can be heated up to about 300 ° C. in addition to high temperature fuel. The heated water after heating the fuel gas in the heating device 31 and the low-temperature fuel heating device 33 is returned to the outlet side of the medium pressure economizer 19 and the feed water line L0 through the heating water return lines L3 and L4, respectively, and after each fuel gas is heated By adjusting the temperature so that the temperature of the heated water becomes equal to the temperature of the warm water of the return destination, it is possible to prevent the heat balance from being lost. That is, while suppressing a decrease in plant output, the fuel gas temperature can be efficiently increased to about 300 ° C., the heat balance of the plant can be maintained, and the plant efficiency can be increased.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the element which is common in 1st Embodiment, and the overlapping description is abbreviate | omitted.

  FIG. 2 is a schematic system diagram showing the configuration of the combined cycle power plant according to the second embodiment.

  In the second embodiment, a bypass line L5 is provided that connects the extraction line L2 on the heating water inlet side of the high temperature fuel heating device 31 and the heating water return line L3 on the heating water outlet side without passing through the high temperature fuel heating device 31. The three-way valve 38 is provided at the junction of the heating water return line L3 and the bypass line L5. Instead of providing the three-way valve 38 at the junction of the heating water return line L3 and the bypass line L5, the three-way valve 38 may be provided at the branch point of the extraction line L2 and the bypass line L5.

  Further, a bypass line L6 that connects the extraction line L1 on the heating water inlet side of the low temperature fuel heating apparatus 33 and the heating water return line L4 on the heating water outlet side of the low temperature fuel heating apparatus 33 without using the low temperature fuel heating apparatus 33 is provided. A three-way valve 39 is provided at the junction of L4 and bypass line L6. Instead of providing the three-way valve 39 at the junction of the heated water return line L4 and the bypass line L6, the three-way valve 39 may be provided at the branch point between the extraction line L1 and the bypass line L6.

  The three-way valves 38 and 39 bypass part of the heating water flowing into the high temperature fuel heating device 31 and the low temperature fuel heating device 33, respectively, and the flow rate of each heating water is constant by an operation signal from the control device 100 or manually. Adjust so that

  The high / medium-pressure feed water pump 24 supplies heated water to the high-temperature fuel heating device 31 and the low-temperature fuel heating device 33 and also supplies heated water to the high / medium-pressure system in the exhaust heat recovery boiler 4. By making the water flow rate constant, the flow rate fluctuation factor in the water supply system is reduced, and the plant efficiency can be improved and the stability of the system can be improved.

  As described above in detail, according to each embodiment, when adopting a multi-pressure type exhaust heat recovery boiler, plant efficiency can be improved without reducing plant output.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Combined cycle power plant, 2 ... Gas turbine plant, 3 ... Steam turbine plant, 4 ... Waste heat recovery boiler, 5 ... Air compressor, 6 ... Gas turbine combustor, 7 ... Gas turbine, 8 ... High pressure superheater, DESCRIPTION OF SYMBOLS 9 ... Reheater, 10 ... High pressure steam drum, 11 ... High pressure evaporator, 12 ... High pressure tertiary economizer, 13 ... Medium pressure superheater, 14 ... High pressure secondary economizer, 15 ... Medium pressure steam drum, 16 ... Medium pressure evaporator, 17 ... Low pressure superheater, 18 ... High pressure primary economizer, 19 ... Medium pressure economizer, 20 ... Low pressure evaporator drum, 21 ... Low pressure evaporator, 22 ... Low pressure economizer, 23 ... Control valve , 24 ... High and medium pressure feed water pumps, 25 and 26 ... Control valves, 27 ... Generators, 28 ... Steam turbines, 29 ... Condensers, 30 ... Low pressure feed water pumps, 31 ... High temperature fuel heating devices, 32 ... High temperature fuel heating devices Outlet temperature control valve, 33 ... low temperature fuel heating device 34 ... Low temperature fuel heating device outlet temperature control valve, 35 ... Medium pressure steam drum connecting pipe Low temperature fuel heating device heating water extraction point, 36 ... Middle side economizer outlet, 37 ... Casing, 38, 39 ... Three-way valve, 40 ... Combined cycle power plant, 41 ... gas turbine plant, 42 ... steam turbine plant, 43 ... exhaust heat recovery boiler, 44 ... air compressor, 45 ... gas turbine combustor, 46 ... gas turbine, 47 ... superheater, 48 ... steam Drum, 49 ... evaporator, 50 ... economizer, 51 ... control valve, 52 ... generator, 53 ... steam turbine, 54 ... condenser, 55 ... condensate pump, 56 ... feed pump, 57 ... fuel heating device 58 ... Casing, 100 ... Control device, L1, L2 ... Extraction line, L3, L4 ... Heated water return line, L5, L6 ... Bypass line.

Claims (9)

A fuel gas heating facility applied to a combined cycle power plant combining a gas turbine plant with a steam turbine plant and an exhaust heat recovery boiler,
A first extraction line for extracting heated water from a heated water outlet of a first economizer installed in the exhaust heat recovery boiler;
A first fuel heating device that heats fuel gas used in the gas turbine plant using heated water extracted through the first extraction line;
A second extraction line for extracting heated water from a heating water outlet of a second economizer located upstream of the first economizer installed in the exhaust heat recovery boiler;
A second fuel heating device for further heating the fuel gas heated by the first fuel heating device using heated water extracted through the second extraction line;
A fuel gas heating facility comprising: a first heating water return line that returns the heated water after heating the fuel gas in the second fuel heating device to the heated water outlet of the first economizer.   Provided on the first heated water return line, the temperature of the heated water at the heated water outlet of the second fuel heating device is equal to the temperature of the heated water at the heated water outlet of the first economizer The fuel gas heating facility according to claim 1, further comprising a temperature control valve that adjusts the temperature as described above. A first bypass line connecting a heating water inlet and a heating water outlet of the second fuel heating device without going through the second fuel heating device;
A three-way valve for joining the first bypass line on the first heated water return line, wherein the three-way valve adjusts the flow rate of the heated water passing through the second fuel heating device to be constant. The fuel gas heating facility according to claim 1, further comprising: A first bypass line connecting a heating water inlet and a heating water outlet of the second fuel heating device without going through the second fuel heating device;
A three-way valve for branching the first bypass line on the second extraction line, wherein the three-way valve adjusts the flow rate of the heated water passing through the second fuel heating device to be constant. The fuel gas heating facility according to claim 1, further comprising:   2. A second heating water return line for returning the heated water after heating the fuel gas in the first fuel heating device to a feed water line for feeding water to the exhaust heat recovery boiler is further provided. 5. The fuel gas heating facility according to any one of 4 above.   A temperature control valve provided on the second heating water return line and for adjusting the temperature of the heating water at the heating water outlet of the first fuel heating device to be equal to the temperature of the water supply in the water supply line; The fuel gas heating facility according to claim 5, further comprising: A second bypass line connecting a heating water inlet and a heating water outlet of the first fuel heating device without going through the first fuel heating device;
A three-way valve that joins the second bypass line on the second heated water return line and that adjusts the flow rate of the heated water passing through the first fuel heating device to be constant. The fuel gas heating facility according to claim 5, further comprising: A second bypass line connecting a heating water inlet and a heating water outlet of the first fuel heating device without going through the first fuel heating device;
A three-way valve for branching the second bypass line on the first extraction line, wherein the three-way valve adjusts the flow rate of the heated water passing through the first fuel heating device to be constant. The fuel gas heating facility according to claim 5, further comprising:   A combined cycle power plant comprising the fuel gas heating facility according to any one of claims 1 to 8.

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