Fuel gas heating device and combined cycle plant

Abstract

The present application relates to a fuel gas heating device for heating a fuel gas supplied to a gas turbine. This device is provided with a hydrocarbon gas heater and a hydrogen-containing gas heater for heating, respectively, a hydrocarbon gas supplied as a fuel gas and a hydrogen-containing gas. The hydrocarbon gas heater heats a hydrocarbon gas by heat exchange with a first heat medium supplied from a first heat medium supply line. The hydrogen-containing gas heater heats a hydrogen-containing gas by heat exchange with a second heat medium supplied from a second heat medium supply line that branches from the first heat medium supply line.

Description

Fuel gas heating equipment and combined cycle plants

[0001] This application claims priority to Japanese Patent Application No. 2023-185162, filed with the Japan Patent Office on October 30, 2023, the contents of which are incorporated herein by reference.

[0002] 2. Description of the Related Art Gas turbines are known that can drive a turbine using combustion gas produced by burning fuel. Conventionally, examples of fuel gas used in gas turbines include hydrocarbon gases such as natural gas.

[0003] Here, the fuel gas supplied to the gas turbine is sometimes preheated to optimize plant performance. For example, Patent Document 1 discloses a configuration in which a fuel gas heating unit is provided in a fuel gas supply line to heat the fuel supplied to the gas turbine. In this document, the fuel gas heating unit heats the fuel gas flowing through the fuel gas supply line by exchanging heat with a high-temperature heat medium.

[0004] Japanese Patent Application Laid-Open No. 2018-178821

[0005] In recent years, in gas turbines, in addition to conventional hydrocarbon gases such as natural gas, the use of hydrogen-containing gases, which have a higher combustion rate, as fuel gas has been considered. Therefore, when adopting a configuration in which the fuel gas is heated by heat exchange with a heat transfer medium, as in Patent Document 1, it is necessary to design the system taking into account hydrogen embrittlement and erosion. For example, when using a hydrocarbon gas such as natural gas as the fuel gas, as in the past, the tubes through which the heat transfer medium flows are made of stainless steel, while the shell outside the tubes is made of carbon steel, thereby reducing costs. However, the joints between different materials, such as stainless steel and carbon steel, are vulnerable to hydrogen embrittlement and erosion. Therefore, in order to use hydrogen-containing gas as the fuel gas, the entire system must be redesigned using stainless steel, which significantly increases costs.

[0006] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a fuel gas heating device and a combined cycle plant that can suitably heat both fuels while keeping costs down when handling hydrocarbon gas and hydrogen-containing gas as fuel gas supplied to a gas turbine.

[0007] In order to solve the above-mentioned problems, at least one embodiment of the fuel gas heating device according to the present disclosure provides a fuel gas heating device for heating fuel gas to be supplied to a gas turbine, the fuel gas heating device comprising: a first fuel supply line for supplying a hydrocarbon gas to the gas turbine as the fuel gas; a second fuel supply line that merges with the first fuel supply line and is for supplying a hydrogen-containing gas to the gas turbine as the fuel; a hydrocarbon gas heater that is provided on the first fuel supply line upstream of a junction with the second fuel supply line and is for heating the hydrocarbon gas; a hydrogen-containing gas heater that is provided on the second fuel supply line upstream of the junction and is for heating the hydrogen-containing gas; a first heat medium supply line that supplies a first heat medium for heat exchange with the hydrocarbon gas to the hydrocarbon gas heater; and a second heat medium supply line that branches off from the first heat medium supply line and is for supplying at least a portion of the first heat medium to the hydrogen-containing gas heater as a second heat medium for heat exchange with the hydrogen-containing gas.

[0008] In order to solve the above problem, a combined cycle plant according to at least one embodiment of the present disclosure includes the gas turbine to which the fuel heated by the fuel gas heating device according to at least one embodiment of the present disclosure is supplied.

[0009] According to at least one embodiment of the present disclosure, when handling hydrocarbon gas and hydrogen-containing gas as fuel gas supplied to a gas turbine, a fuel gas heating device and a combined cycle plant can be provided that can heat both fuels suitably while keeping costs down.

[0010] It is a schematic configuration diagram of a combined cycle plant according to one embodiment. It is a schematic diagram showing the internal configuration of the fuel gas heating device of Figure 1. It is a perspective transparent view schematically showing the hydrocarbon gas heater of Figure 2. It is a perspective transparent view schematically showing the hydrogen-containing gas heater of Figure 2.

[0011] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0012] First, a configuration of a combined cycle plant 1 including a fuel gas heating device 100 according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of the combined cycle plant 1 according to one embodiment.

[0013] The combined cycle plant 1 includes a gas turbine 10, a heat recovery boiler 20 for generating steam using exhaust gas EG from the gas turbine 10, a steam turbine 60 that can be driven by steam from the heat recovery boiler 20, and a condenser 40 for converting the steam from the steam turbine 60 back into water.

[0014] The gas turbine 10 includes a compressor 11 for compressing combustion air, and a turbine 15 driven by combustion gas produced by mixing and burning the combustion air compressed by the compressor 11 with fuel gas supplied from a fuel supply system 70. The rotors of the compressor 11 and the turbine 15 are connected to each other to form a gas turbine rotor 19.

[0015] The steam turbine 60 includes a high-pressure steam turbine HP, an intermediate-pressure steam turbine IP, and a low-pressure steam turbine LP. The high-pressure steam turbine HP, the intermediate-pressure steam turbine IP, and the low-pressure steam turbine LP have their respective rotating shafts connected to one another to form a steam turbine rotor 61. The steam turbine rotor 61 is integrally connected to the gas turbine rotor 19 described above. The steam that has completed its work in the steam turbine 60 is returned to condensation in the condenser 40.

[0016] The condensate from the condenser 40 can be supplied to the heat recovery boiler 20 via a condensate supply line 62. A low-pressure feedwater pump 63 is provided in the condensate supply line 62, which makes it possible to adjust the amount of condensate supplied to the heat recovery boiler 20. In addition, a superheater 64 is provided in the condensate supply line 62 downstream of the low-pressure feedwater pump 63, which makes it possible to adjust the temperature of the water supplied to the heat recovery boiler 20.

[0017] A makeup water tank 42 is connected to the condenser 40 via a makeup water supply line 41. A makeup water supply pump 43 is installed on the makeup water supply line 41, and makeup water can be supplied from the makeup water tank 42 when the condenser 40 runs short of condensed water.

[0018] The heat recovery steam generator 20 has a configuration for recovering and effectively utilizing heat (exhaust heat) contained in the exhaust gas EG from the gas turbine 10. The heat recovery steam generator 20 includes a low-pressure economizer 21, a low-pressure evaporator 22, a high-pressure primary economizer 23, an intermediate-pressure economizer 24, an intermediate-pressure evaporator 25, a low-pressure superheater 26, a high-pressure secondary economizer 27, an intermediate-pressure superheater 28, a high-pressure evaporator 29, a high-pressure primary superheater 30, a primary reheater 31, a secondary reheater 32, and a high-pressure secondary superheater 33 as components for utilizing the heat recovered from the exhaust gas EG.

[0019] The exhaust gas from which heat has been recovered in the heat recovery boiler 20 is discharged to the outside through a chimney 34 .

[0020] In the heat recovery steam generator 20, the feedwater (condensate) from the condenser 40 is first heated by the low-pressure economizer 21. At least a portion of the feedwater heated by the low-pressure economizer 21 is stored in the low-pressure drum 44. The low-pressure drum 44 is connected to the low-pressure evaporator 22, and steam can be generated from at least a portion of the water stored in the low-pressure drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure drum 44.

[0021] Furthermore, the feedwater heated by the low-pressure economizer 21 is supplied to a high-pressure feedwater pump 45 and a medium-pressure feedwater pump 46. The medium-pressure feedwater pump 46 pressurizes the feedwater to a first pressure P1, and the high-pressure feedwater pump 45 pressurizes the feedwater to a second pressure P2 (>first pressure P1). The feedwater pressurized to the second pressure P2 by the high-pressure feedwater pump 45 is heated by the high-pressure primary economizer 23 and the high-pressure secondary economizer 27, and then supplied to a high-pressure drum 47. The feedwater pressurized to the first pressure P1 by the medium-pressure feedwater pump 46 is heated by the medium-pressure economizer 24, and then supplied to a medium-pressure drum 48. The high-pressure feedwater pump 45 and the medium-pressure feedwater pump 46 may be integrally configured.

[0022] The high-pressure evaporator 29 is connected to the high-pressure drum 47, and is capable of generating steam from at least a portion of the water stored in the high-pressure drum 47. The steam generated in the high-pressure evaporator 29 is returned to the high-pressure drum 47. The steam extracted from the high-pressure drum 47 is superheated by the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, and is supplied to the high-pressure steam turbine HP. A superheater 49 a is provided between the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, and by controlling the amount of superheat reduction in the superheater 49 a, the temperature of the steam supplied to the high-pressure steam turbine HP can be appropriately adjusted.

[0023] The steam that has completed its work in the high-pressure steam turbine HP is heated by a primary reheater 31 and a secondary reheater 32, and then supplied to the intermediate-pressure steam turbine IP. A superheater 49b is provided between the primary reheater 31 and the secondary reheater 32, and by controlling the amount of superheat in the superheater 49b, the temperature of the steam supplied to the intermediate-pressure steam turbine IP can be appropriately adjusted.

[0024] The intermediate-pressure evaporator 25 is connected to the intermediate-pressure drum 48, and is capable of generating steam from at least a portion of the water stored in the intermediate-pressure drum 48. The steam generated in the intermediate-pressure evaporator 25 is returned to the intermediate-pressure drum 48. A portion of the steam extracted from the intermediate-pressure drum 48 is heated by the intermediate-pressure superheater 28, supplied to an outlet flow path of the high-pressure steam turbine HP, and supplied to the intermediate-pressure steam turbine IP via the primary reheater 31 and secondary reheater 32.

[0025] The low-pressure evaporator 22 is connected to the low-pressure drum 44, and is capable of generating steam from at least a portion of the water stored in the low-pressure drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure drum 44. A portion of the steam extracted from the low-pressure drum 44 is heated by the low-pressure superheater 26 and supplied to an outlet flow path of the intermediate-pressure steam turbine IP, and then supplied to the low-pressure steam turbine LP. The steam that has completed its work in the low-pressure steam turbine LP is returned to the condenser 40.

[0026] The combined cycle plant 1 having the above configuration includes a fuel supply system 70 for supplying hydrocarbon gas Gc and hydrogen-containing gas Gh as fuel gas F to the combustor 12 of the gas turbine 10. The fuel supply system 70 supplies the fuel gas F to the combustor 12, where the combustor 12 mixes the fuel gas F with combustion air compressed by the compressor 11 and combusts the mixture to generate combustion gas for driving the gas turbine 10 (in FIG. 1 , for ease of illustration, the combustor 12 is shown positioned away from the gas turbine 10).

[0027] The fuel supply system 70 includes a first fuel supply source 72a for supplying a hydrocarbon gas Gc and a second fuel supply source 72b for supplying a hydrogen-containing gas Gh. The hydrocarbon gas Gc is natural gas, and the hydrogen-containing gas Gh has a hydrogen content of 50 mol% or more. Here, the hydrocarbon gas Gc is a fuel gas having a lower hydrogen content than the hydrogen-containing gas Gh, and the hydrogen content may be 0%. Furthermore, the hydrogen-containing gas Gh is a fuel gas having a hydrogen content at least higher than that of the hydrocarbon gas Gc, and preferably has a hydrogen content of 50 mol% or more.

[0028] The hydrocarbon gas Gc is supplied from a first fuel supply source 72a to the combustor 12 of the gas turbine via a first fuel gas supply line 74a. The hydrogen-containing gas Gh is supplied from a second fuel supply source 72b to the combustor 12 of the gas turbine via a second fuel gas supply line 74b. As shown in FIG. 2 , the first fuel gas supply line 74a and the second fuel gas supply line 74b join together inside the fuel gas heating device 100 and are connected to the combustor 12 of the gas turbine 10 via a fuel gas supply line 74c. The hydrocarbon gas Gc flowing through the first fuel gas supply line 74a and the hydrogen-containing gas Gh flowing through the second fuel gas supply line 74b are each heated by the fuel gas heating device 100.

[0029] The internal configuration of the fuel gas heating device 100 will now be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the internal configuration of the fuel gas heating device 100 of Fig. 1.

[0030] The first fuel gas supply line 74a is provided with a hydrocarbon gas heater 76 for heating the hydrocarbon gas Gc. A shutoff valve 78 for shutting off the hydrocarbon gas Gc in the first fuel gas supply line 74a and a flow rate adjustment valve 79 for adjusting the flow rate of the hydrocarbon gas Gc in the first fuel gas supply line 74a are provided on the first fuel gas supply line 74a between the hydrocarbon gas heater 76 and a junction 75 with the second fuel gas supply line 74b.

[0031] The hydrocarbon gas heater 76 is configured to heat the hydrocarbon gas Gc flowing through the first fuel gas supply line 74a by heat exchange with a first heat medium M1. The first heat medium M1 is supplied via a first heat medium supply line 80. In the present embodiment, the first heat medium supply line 80 includes a high-pressure water feed line 80a branching off from a steam line connecting the medium-pressure economizer 24 and the medium-pressure drum 48 of the heat recovery boiler 20, and a medium-pressure water feed line 80b branching off from a steam line connecting the high-pressure secondary economizer 27 and the high-pressure drum 47 of the heat recovery boiler 20.

[0032] High-temperature heated water M1a (supply water from the high-pressure water supply pump 45) having a first pressure P1 is supplied from the high-pressure water supply line 80a as the first heat medium M1. High-temperature heated water M1b (supply water from the medium-pressure water supply pump 46) having a second pressure P2 lower than the first pressure P1 is supplied from the medium-pressure water supply line 80b as the first heat medium M1. The high-pressure water supply line 80a merges with the medium-pressure water supply line 80b at a junction 81 on the downstream side.

[0033] The hydrocarbon gas heater 76 includes a first heater 76a for heating the hydrocarbon gas Gc by heat exchange with a first heat medium M1a flowing through the high-pressure water feed line 80a, and a second heater 76b for heating the hydrocarbon gas Gc by heat exchange with a first heat medium M1b flowing through the medium-pressure water feed line 80b. As a result, the hydrocarbon gas Gc flowing through the first fuel gas supply line 74a is heated in the first heater 76a by heat exchange with the first heat medium M flowing through the high-pressure water feed line 80a, and is further heated in the second heater 76b by heat exchange with the first heat medium M1b flowing through the medium-pressure water feed line 80b, thereby effectively raising the temperature.

[0034] A flow control valve 82 for adjusting the flow rate of the first heat medium M1a is provided in the high-pressure water supply line 80a upstream of the first heater 76a. A shutoff valve 83 for shutting off the first heat medium M1a flowing in that section and a flow control valve 84 for adjusting the flow rate of the first heat medium M1a flowing in that section are provided in the high-pressure water supply line 80a between the first heater 76a and the junction 81. A flow control valve 85 for adjusting the flow rate of the first heat medium M1b flowing in that section is provided in the medium-pressure water supply line 80b between the junction 81 and the second heater 76b. A shutoff valve 86 for shutting off the first heat medium M1b flowing in that section and a flow control valve 87 for adjusting the flow rate of the first heat medium M1b flowing in that section are provided in the medium-pressure water supply line 80b either upstream or downstream of the first heater 76b.

[0035] Here, Fig. 3A is a perspective view schematically showing the hydrocarbon gas heater 76 of Fig. 2. The hydrocarbon gas heater 76 is a heat exchanger having a shell-and-tube structure including a shell 77 and a heat transfer tube 79.

[0036] The shell 77 has a hollow structure, into which the hydrocarbon gas Gc to be heated is introduced from the first fuel gas supply line 74a. The heat transfer tubes 79 penetrate the shell 77 and are housed inside, and a first heat medium M1 is introduced from the first heat medium supply line 80, thereby heating the hydrocarbon gas Gc through heat exchange inside the shell 77. In the hydrocarbon gas heater 76 having such a configuration, the heat transfer tubes 79, through which the first heat medium M1 flows, are made of stainless steel, while the shell 77 outside the heat transfer tubes 79 is made of relatively inexpensive carbon steel, thereby enabling cost reduction (i.e., the hydrocarbon gas heater 76 includes the shell 77 including stainless steel and the heat transfer tubes 79 including carbon steel, and therefore has a joint 73 where different materials are joined together).

[0037] The hydrogen-containing gas heater 88 is configured to heat the hydrogen-containing gas Gh flowing through the second fuel gas supply line 74b by heat exchange with the second heat medium M2. The second heat medium M2 is supplied via a second heat medium supply line 89 branched from the first heat medium supply line 80. In this embodiment, the second heat medium supply line 89 branches off from the high-pressure water supply line 80a of the first heat medium supply line 80 (particularly, from a branch point 92 provided between the flow rate adjustment valve 82 and the first heater 76a), so that a portion of the high-pressure first heat medium M1a (supply water from the high-pressure water pump 45) is used as the second heat medium M2.

[0038] The second fuel gas supply line 74b is provided with a shutoff valve 90 for shutting off the hydrogen-containing gas Gh and a flow rate control valve 91 for adjusting the flow rate of the hydrogen-containing gas Gh. A flow rate control valve 93 for adjusting the flow rate of the second heat medium M2 in the compartment is provided in the second heat medium supply line 89 between the branch point 92 and the hydrogen-containing gas heater 88. A shutoff valve 94 for shutting off the second heat medium M2 in the compartment is provided in the second heat medium supply line 89 either upstream or downstream of the hydrogen-containing gas heater 88, and a flow rate control valve 95 for adjusting the flow rate of the second heat medium M2 in the compartment is provided.

[0039] Furthermore, the second heat medium supply line 89 merges with the first heat medium supply line 80 (medium-pressure water supply line 90b) downstream, so that the first heat medium M1 and the second heat medium M2 after heat exchange are returned to the condensate supply line 62 (see Figure 1).

[0040] Here, Fig. 3B is a perspective view schematically showing the hydrogen-containing gas heater 88 of Fig. 2. The hydrogen-containing gas heater 88 is a heat exchanger that includes a shell 96 and a heat transfer tube 97 and has a shell-and-tube structure similar to the hydrocarbon gas heater 76 described above.

[0041] The shell 96 has a hollow structure, into which the hydrogen-containing gas Gh to be heated is introduced from the second fuel gas supply line 74b. The heat transfer tubes 97 penetrate the shell 96 and are housed inside, and the second heat medium M2 is introduced from the second heat medium supply line 89, thereby heating the hydrogen-containing gas Gh by heat exchange inside the shell 96. In the hydrogen-containing gas heater 88 having such a configuration, both the heat transfer tubes 97, through which the second heat medium M2 flows, and the shell 96 located outside the heat transfer tubes 97 are made of stainless steel. As a result, the joints 98 between the shell 96 and the heat transfer tubes 97 are made of the same material, which provides excellent resistance to hydrogen embrittlement and corrosion.

[0042] As described above, in the above embodiment, the hydrocarbon gas Gc and the hydrogen-containing gas Ch are supplied to the combustor 12 of the gas turbine 10 via the first fuel supply line 74a and the second fuel supply line 74b as the fuel gas F. The first fuel supply line 74a and the second fuel supply line 74b are respectively provided with the hydrocarbon gas heater 76 and the hydrogen-containing gas heater 88 for heating the hydrocarbon gas Gc and the hydrogen-containing gas Gh, so that the hydrocarbon gas Gc and the hydrogen-containing gas Gh can be heated by heat exchange with the heat medium.

[0043] In this way, by separately configuring the configuration for heating the hydrogen-containing gas Gh and the configuration for heating the hydrocarbon gas Gc, it is possible to reduce costs overall compared to when the entire device is designed taking hydrogen embrittlement and corrosion into consideration. In particular, as shown in Figures 3A and 3B, the hydrocarbon gas heater 76, which does not require resistance to hydrogen embrittlement and corrosion, is at least partially configured to include a relatively inexpensive carbon steel material, thereby reducing costs, while the hydrogen-containing gas heater 88, which handles the hydrogen-containing gas, is entirely configured from a stainless steel material, thereby achieving good resistance to hydrogen embrittlement and corrosion.

[0044] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0045] The contents described in each of the above embodiments can be understood, for example, as follows.

[0046] (1) A fuel gas heating device according to one aspect is a fuel gas heating device for heating fuel gas to be supplied to a gas turbine, comprising: a first fuel supply line for supplying a hydrocarbon gas as the fuel gas to the gas turbine; a second fuel supply line that merges with the first fuel supply line and is for supplying a hydrogen-containing gas as the fuel to the gas turbine; a hydrocarbon gas heater that is provided on the first fuel supply line upstream of a junction with the second fuel supply line and is for heating the hydrocarbon gas; a hydrogen-containing gas heater that is provided on the second fuel supply line upstream of the junction and is for heating the hydrogen-containing gas; a first heat medium supply line that supplies a first heat medium for heat exchange with the hydrocarbon gas to the hydrocarbon gas heater; and a second heat medium supply line that branches off from the first heat medium supply line and is for supplying at least a portion of the first heat medium to the hydrogen-containing gas heater as a second heat medium for heat exchange with the hydrogen-containing gas.

[0047] According to the above aspect (1), a hydrocarbon gas and a hydrogen-containing gas are supplied as fuel gas to the gas turbine via a first fuel supply line and the second fuel supply line. The first fuel supply line and the second fuel supply line are each provided with a heater for heating the hydrocarbon gas and the hydrogen-containing gas, so that the hydrocarbon gas and the hydrogen-containing gas can be heated by heat exchange with a heat medium. By providing a configuration for heating the hydrogen-containing gas separately from a configuration for heating the hydrocarbon gas in this way, it is not necessary to redesign the entire device in consideration of hydrogen embrittlement and corrosion. As a result, a fuel gas heating device can be provided that can heat the hydrocarbon gas and the hydrogen-containing gas in separate lines while keeping costs down.

[0048] (2) In another aspect, in the aspect (1), the hydrogen-containing gas heater and the second fuel supply line are made of stainless steel.

[0049] According to the above aspect (2), the hydrogen-containing gas heater for heating the hydrogen-containing gas is made of stainless steel together with the second fuel supply line, thereby preventing the joints between different materials, which would be weakened from the viewpoint of hydrogen embrittlement and corrosion, from being exposed to the hydrogen-containing gas.

[0050] (3) In another aspect, in the above aspect (1) or (2), the first heat medium supply line includes: a high-pressure line for supplying the first heat medium having a first pressure; and an intermediate-pressure line for supplying the first heat medium having a second pressure lower than the first pressure; and the second heat medium supply line branches off from the high-pressure line of the first heat medium supply line.

[0051] According to the above aspect (3), the hydrogen-containing gas is heated using the first heat medium supplied from the high-pressure line having a relatively high pressure. Since the hydrogen-containing gas has a larger specific heat than the hydrocarbon gas, the hydrogen-containing gas can be efficiently heated by heat exchange with the first heat medium supplied from the high-pressure line having a higher temperature and pressure.

[0052] (4) In another aspect, in the aspect (3) above, the hydrocarbon gas heater includes: a first heater for heating the hydrocarbon gas by heat exchange with the first heat medium flowing through the high-pressure line; and a second heater for heating the hydrocarbon gas by heat exchange with the first heat medium flowing through the medium-pressure line.

[0053] According to the above aspect (4), the hydrocarbon gas among the fuel gases can be effectively heated by being heated in multiple stages by a first heater capable of heat exchange with a first heat medium flowing through the high-pressure line and a second heater capable of heat exchange with the first heat medium flowing through the medium-pressure line.

[0054] (5) In another aspect, in any one of the above aspects (1) to (4), the first fuel supply line and the second fuel supply line branch off from each other from a fuel supply line located upstream, and a switching valve is provided in the fuel supply line to switch between the hydrocarbon gas and the hydrogen-containing gas as the fuel gas.

[0055] According to the above aspect (5), either a hydrocarbon gas or a hydrogen-containing gas is supplied to the gas turbine as a fuel gas depending on the switching state of a switching valve (for example, the shutoff valve 78 or the shutoff valve 90 in the above embodiment). In this configuration, the hydrocarbon gas or the hydrogen-containing gas supplied to the gas turbine in this manner can be effectively heated with a configuration that reduces costs.

[0056] (6) In another aspect, in any one of the above aspects (1) to (5), the first heat medium and the second heat medium are heated water heated by exhaust heat recovered from the gas turbine.

[0057] According to the above aspect (6), heated water generated using exhaust heat recovered from the gas turbine (for example, heat recovered from the exhaust gas of the gas turbine by a heat recovery boiler) is used as a heat medium for heating each fuel gas. By effectively utilizing the thermal energy recovered in this way within the system, good energy efficiency can be achieved.

[0058] (7) In another aspect, in any one of the above aspects (1) to (6), the hydrocarbon gas is natural gas, and the hydrogen-containing gas has a hydrogen content of 50 mol % or more.

[0059] According to the above aspect (7), in a gas turbine that uses natural gas as the hydrocarbon gas and hydrogen gas having a hydrogen content of 50 mol% or more as the hydrogen-containing gas, the fuel supplied to the gas turbine can be suitably heated. Note that natural gas is a fuel gas having a lower hydrogen content than the hydrogen-containing gas, and the hydrogen content may be 0%. Furthermore, the hydrogen-containing gas is a fuel gas having a hydrogen content at least higher than that of natural gas, and preferably has a hydrogen content of 50 mol% or more.

[0060] (8) A combined cycle plant according to one aspect includes the gas turbine supplied with the fuel gas heated by the fuel gas heating device according to any one of the above aspects (1) to (7).

[0061] According to the above aspect (8), when hydrocarbon gas and hydrogen-containing gas are used as fuel gas to be supplied to a gas turbine equipped in a combined cycle plant, the fuel gas can be suitably heated by the fuel gas heating device according to each of the above aspects.

[0062] REFERENCE SIGNS LIST 1 combined cycle plant 10 gas turbine 11 compressor 12 combustor 15 turbine 19 gas turbine rotor 20 heat recovery boiler 21 low-pressure economizer 22 low-pressure evaporator 23 high-pressure primary economizer 24 intermediate-pressure economizer 25 intermediate-pressure evaporator 26 low-pressure superheater 27 high-pressure secondary economizer 28 intermediate-pressure superheater 29 high-pressure evaporator 30 high-pressure primary superheater 31 primary reheater 32 secondary reheater 33 high-pressure secondary superheater 34 chimney 40 condenser 41 makeup water supply line 42 makeup water tank 43 makeup water supply pump 44 low-pressure drum 47 high-pressure drum 48 intermediate-pressure drum 49a, 49b attemperator 60 steam turbine 61 steam turbine rotor 62 condensate supply line 63 Low-pressure water supply pump 64 Desuperheater 70 Fuel supply system 72a First fuel supply source 72b Second fuel supply source 74a First fuel gas supply line 74b Second fuel gas supply line 74c Fuel gas supply line 75 Junction 80 First heat medium supply line 80a High-pressure water supply line 80b Medium-pressure water supply line 76 Hydrocarbon gas heater 76a First heater 76b Second heater 88 Hydrogen-containing gas heater 89 Second heat medium supply line 92 Branch point 100 Fuel gas heating device Gc Hydrocarbon gas Gh Hydrogen-containing gas F Fuel gas

Claims

1. A fuel gas heating device for heating a fuel gas to be supplied to a gas turbine, comprising: a first fuel supply line for supplying a hydrocarbon gas to the gas turbine as the fuel gas; a second fuel supply line merging with the first fuel supply line for supplying a hydrogen-containing gas to the gas turbine as the fuel; a hydrocarbon gas heater provided on the first fuel supply line upstream of a junction with the second fuel supply line for heating the hydrocarbon gas; a hydrogen-containing gas heater provided on the second fuel supply line upstream of the junction for heating the hydrogen-containing gas; a first heat medium supply line for supplying a first heat medium for heat exchange with the hydrocarbon gas to the hydrocarbon gas heater; and a second heat medium supply line branching off from the first heat medium supply line for supplying at least a portion of the first heat medium to the hydrogen-containing gas heater as a second heat medium for heat exchange with the hydrogen-containing gas.

2. The fuel gas heating device according to claim 1, wherein the hydrogen-containing gas heater and the second fuel supply line are made of stainless steel.

3. A fuel gas heating device as described in claim 1 or 2, wherein the first heat medium supply line includes: a high-pressure line for supplying the first heat medium having a first pressure; and a medium-pressure line for supplying the first heat medium having a second pressure lower than the first pressure; and the second heat medium supply line branches off from the high-pressure line of the first heat medium supply line.

4. A fuel gas heating device as described in claim 3, wherein the hydrocarbon gas heater includes: a first heater for heating the hydrocarbon gas by heat exchange with the first heat medium flowing through the high pressure line; and a second heater for heating the hydrocarbon gas by heat exchange with the first heat medium flowing through the medium pressure line.

5. A fuel gas heating device as described in claim 1 or 2, wherein the first fuel supply line and the second fuel supply line branch off from each other from a fuel supply line located upstream, and the fuel supply line is provided with a switching valve for switching between the hydrocarbon gas and the hydrogen-containing gas as the fuel gas.

6. A fuel gas heating device according to claim 1 or 2, wherein the first heat medium and the second heat medium are heated water heated by exhaust heat recovered from the gas turbine.

7. The fuel gas heating device according to claim 1 or 2, wherein the hydrocarbon gas is natural gas, and the hydrogen-containing gas has a hydrogen content of 50 mol % or more.

8. A combined cycle plant comprising the gas turbine to which the fuel gas heated by the fuel gas heating device according to claim 1 or 2 is supplied.

Images