Gas turbine fuel supply device, and method of controlling gas turbine fuel supply device

Abstract

To perform a stable operation by preventing misrecognition of a mixing ratio when starting a gas turbine.SOLUTION: The present application relates to a gas turbine fuel supply device capable of supplying first fuel and second fuel of a higher combustion rate relative to the first fuel to a combustor of a gas turbine. The device comprises a first fuel supply line and a second fuel supply line that merge together at a merging point and are connected to a combustor via a mixing line. The second fuel supply line comprises a first shut-off valve that becomes a control object when a mono-fuel combustion state is switched to a mixed combustion state, and a flow meter disposed upstream relative to the first shut-off valve. The flow meter is capable of outputting a detection value relating to the flow rate of the second fuel, for calculating the mixing ratio of the first fuel and the second fuel to monitor the operating condition of the gas turbine,.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fuel supply system for a gas turbine and a control method for a fuel supply system for a gas turbine. [Background technology]

[0002] For example, in thermal power plants, gas turbines that can be driven by combustion gases generated by burning fuel are used as turbines for driving generators. In recent thermal power plants, as a means for reducing emissions of carbon dioxide (CO2), which causes global warming, development is underway for gas turbines that use a hydrogen co-firing system, in which a second fuel (hydrogen) with a relatively high combustion speed is mixed with a first fuel such as natural gas as the fuel burned to generate the combustion gas, and the mixture is burned (co-firing), thereby reducing carbon dioxide emissions (e.g., Patent Document 1).

[0003] A fuel supply device for a gas turbine capable of co-firing a first fuel and a second fuel typically has a configuration in which a first fuel supply line for supplying the first fuel and a second fuel supply line for supplying the second fuel are joined together and connected to a combustor in which fuel is combusted. In this type of fuel supply device, since a considerable amount of the second fuel, which has high combustibility, is present in the second fuel supply gas line, it is desirable to discharge the second fuel remaining in the second fuel supply gas line to the outside when the gas turbine is stopped. For example, Patent Document 2 discloses a hydrogen combustion boiler that can burn hydrogen as fuel, rather than a gas turbine, and discloses a configuration in which hydrogen remaining in a hydrogen supply line for supplying hydrogen can be purged using an inert gas such as nitrogen, helium, or neon. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 149540 [Patent Document 2] JP 2018-200166 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a fuel supply device of a gas turbine capable of co-firing a first fuel and a second fuel, in order to remove the second fuel remaining in the second fuel supply line when the gas turbine is stopped, the second fuel is replaced with an inert gas as described in the above Patent Document 1. In this case, when the gas turbine is started, a sequence is adopted in which the inert gas in the second fuel supply line is replaced with the first fuel from the first fuel supply line and then the supply of the second fuel is started to start the co-firing operation of the gas turbine so that the inert gas replaced in the second fuel supply line is not supplied to the combustor.

[0006] In a gas turbine capable of co-firing a first fuel and a second fuel, a monitoring parameter such as a co-firing ratio is calculated using the flow rate of the second fuel measured by a flow meter arranged in the second fuel supply line, thereby monitoring the co-firing operation state of the gas turbine. The flow meter arranged in the second fuel supply line is typically a Coriolis flow meter capable of calculating the flow rate based on the volume of the fuel passing through. However, when the above-mentioned sequence is adopted, the second fuel supply line is replaced by the first fuel at the start of the gas turbine, so that the first fuel passes through the flow rate arranged in the second fuel supply line to a considerable extent. Since the density of the first fuel such as natural gas is larger than that of the second fuel such as hydrogen gas, when the first fuel passes through the flow meter which is a Coriolis flow meter, the error of the measurement value becomes large. As a result, when a monitoring parameter such as a co-firing ratio of the gas turbine is calculated based on such a flow measurement value, the operating state of the gas turbine may be erroneously recognized. For example, the mixed combustion ratio, which is one of the monitored parameters, is used for interlock control regarding the stopping of the supply of the second fuel. Therefore, if the error in this parameter becomes large, the interlock control will be activated even if the gas turbine is operating normally, causing problems in the operation of the gas turbine.

[0007] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and has an object to provide a fuel supply device for a gas turbine that enables stable operation by preventing erroneous recognition of a mixture ratio at the start-up of the gas turbine, and a control method for a fuel supply device for a gas turbine. [Means for solving the problem]

[0008] In order to solve the above problems, a fuel supply device for a gas turbine according to at least one embodiment of the present disclosure includes: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; Equipped with.

[0009] In order to solve the above problem, a control method for a fuel supply device of a gas turbine according to at least one embodiment of the present disclosure includes: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; an isolation valve provided in the second fuel supply line between the first shutoff valve and the junction; a vent line branching off from the second fuel supply line between the first shutoff valve and the isolation valve; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a second fuel supply line upstream of the isolation valve while the gas turbine is stopped and the isolation valve is closed; supplying the first fuel to a portion of the second fuel supply line downstream of the first shutoff valve by closing the first shutoff valve and opening the isolation valve; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; Equipped with.

[0010] In order to solve the above problem, a control method for a fuel supply device of a gas turbine according to at least one embodiment of the present disclosure includes: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; a vent line branching off from the second fuel supply line between the first shutoff valve and the flow meter; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a side of the second fuel supply line upstream of the first shutoff valve while the gas turbine is stopped and the first shutoff valve is closed; supplying the first fuel to a downstream side of the first shutoff valve in the second fuel supply line; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; Equipped with. Effect of the Invention

[0011] According to at least one embodiment of the present disclosure, it is possible to provide a fuel supply device for a gas turbine that can operate stably by preventing erroneous recognition of the mixture ratio at the start-up of the gas turbine, and a control method for a fuel supply device for a gas turbine. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a schematic configuration diagram of a gas turbine according to a first embodiment. [Diagram 2] 4 is a flowchart showing a control method for the fuel supply system according to the first embodiment. [Figure 3A] 3 is an explanatory diagram corresponding to each step in FIG. 2. [Figure 3B] 3 is an explanatory diagram corresponding to each step in FIG. 2. [Figure 3C] 3 is an explanatory diagram corresponding to each step in FIG. 2. [Figure 3D] 3 is an explanatory diagram corresponding to each step in FIG. 2. [Figure 3E] 3 is an explanatory diagram corresponding to each step in FIG. 2. [Figure 4] FIG. 5 is a schematic configuration diagram of a gas turbine according to a second embodiment. [Diagram 5] 7 is a flowchart showing a control method for the fuel supply system according to the second embodiment. [Figure 6A] 6 is an explanatory diagram corresponding to each step in FIG. 5. [Figure 6B] 6 is an explanatory diagram corresponding to each step in FIG. 5. [Figure 6C] 6 is an explanatory diagram corresponding to each step in FIG. 5. [Figure 6D] 6 is an explanatory diagram corresponding to each step in FIG. 5. [Figure 6E] 6 is an explanatory diagram corresponding to each step in FIG. 5. [Figure 7] This is a modified example of FIG. [Figure 8] FIG. 11 is a schematic configuration diagram of a gas turbine according to a third embodiment. [Figure 9] FIG. 1 is a schematic configuration diagram of a gas turbine according to a reference technology. [Figure 10] 10 is a flowchart showing a control method for the fuel supply device of FIG. [Figure 11A] 11A to 11C are explanatory diagrams corresponding to the steps in FIG. 10. [Figure 11B] 11A to 11C are explanatory diagrams corresponding to the steps in FIG. 10. [Figure 11C] 11A to 11C are explanatory diagrams corresponding to the steps in FIG. 10. [Figure 11D] 11A to 11C are explanatory diagrams corresponding to the steps in FIG. 10. [Figure 11E] 11A to 11C are explanatory diagrams corresponding to the steps in FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, some 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.

[0014] FIG. 1 is a schematic diagram of a gas turbine 1 according to a first embodiment. The gas turbine 1 includes a compressor 3 for generating compressed air, a combustor 2 for generating combustion gas by mixing and burning the compressed air generated by the compressor 3 with fuel, a fuel supply device 4 for supplying fuel to the combustor 2, and a turbine 6 driven by the combustion gas. The compressor 3 and the turbine 6 are connected to one shaft. In the gas turbine 1 having such a configuration, the compressed air compressed by the compressor 3 and the fuel supplied from the fuel supply system 4 are supplied to the combustor 2, and these are mixed and burned to generate combustion gas. This combustion gas flows into the turbine 6 and functions as power for driving the turbine 6.

[0015] The fuel supply device 4 handles a mixed fuel obtained by mixing a first fuel F1 and a second fuel F2 as the fuel to be supplied to the combustor 2. The second fuel F2 is a fuel having a higher combustion speed than the first fuel F1. In addition, the second fuel F2 is a fuel having a lower calorific value per unit volume than the first fuel F1. In this embodiment, the first fuel F1 is liquefied natural gas (LNG), and the second fuel F2 is hydrogen gas.

[0016] The first fuel F1 can be supplied via a first fuel supply line 8 connected to a first fuel supply source 7. A first flow meter 10 for detecting the flow rate of the first fuel F1 is provided in the first fuel supply line 8. The first flow meter 10 may be an orifice flow meter like a second flow meter 15 described later, or may be a Coriolis flow meter.

[0017] The second fuel F2 can be supplied via a second fuel supply line 16 connected to a second fuel supply source 14. The second fuel supply line 16 is provided with a second flowmeter 15, which is an orifice flowmeter for detecting the flow rate of the second fuel F2, a flow rate adjustment valve 18 for adjusting the flow rate of the second fuel F2, a first shutoff valve 20a, and a second shutoff valve 20b. The second shutoff valve 20b is provided upstream of the first shutoff valve 20a in the second fuel supply line 16. The first shutoff valve 20a and the second shutoff valve 20b can be controlled to be closed to stop the supply of the second fuel F2 to the junction 25.

[0018] Further, an isolation valve 13 is provided in the second fuel supply line 16 between the first shutoff valve 20a and the junction 25. The isolation valve 13 is a manual valve that can be opened and closed by an operator, and in this embodiment, in particular, the isolation valve 13 is provided in a position in the second fuel supply line 16 that is closer to the junction 25 than to the first shutoff valve 20a. When the isolation valve 13 is in an open state, the second fuel supply line 16 communicates with the junction 25, so that the second fuel F2 supplied from the second fuel supply line 16 is mixed with the first fuel F1 supplied from the first fuel supply line 8 and is supplied to the combustor 2 as a mixed fuel Fm, thereby enabling the gas turbine 1 to perform a multi-fuel operation. On the other hand, when the isolation valve 13 is in a closed state, the second fuel supply line 16 is isolated from the junction 25, so that the supply of the second fuel F2 from the second fuel supply line 16 is stopped.

[0019] The second fuel supply line 16 includes a first vent line 19 branching off from a branch point 26 provided between the first shutoff valve 20a and the isolation valve 13. The first vent line 19 is configured to communicate with the outside from the branch point 26, and is provided with a first vent valve 21 that can be opened and closed. The second fuel supply line 16 also includes a second vent line 27 branching off from a branch point 29 provided upstream of the second shutoff valve 20b. The second vent line 27 is configured to communicate with the outside from the branch point 29, and is provided with a second vent valve 28 that can be opened and closed. The second fuel supply line 16 also includes a third vent line 30 branching off from a branch point 32 provided between the second shutoff valve 20b and the flow rate control valve 18. The third vent line 30 is configured to communicate with the outside from the branch point 32, and is provided with a third vent valve 31 that can be opened and closed. Incidentally, a branch point 26 of the first vent line 19 from the second fuel supply line 16 is provided at a position closer to the junction 25 than to the first shutoff valve 20a.

[0020] The first fuel supply line 8 and the second fuel supply line 16 join each other downstream and are connected to a mixing line 22. When the first fuel F1 and the second fuel F2 are both supplied, the first fuel F1 and the second fuel F2 are mixed by joining each other at a joining point 25 of the first fuel supply line 8 and the second fuel supply line 16, and are sent to the combustor 2 via the mixing line 22 as mixed fuel Fm, thereby enabling a mixed combustion operation of the gas turbine 1. When the supply of the second fuel F2 is stopped, the mixing line 22 supplies only the first fuel F1 to the combustor 2, thereby enabling a single-fuel operation of the gas turbine 1. In addition, the mixing line 22 is provided with a third shutoff valve 20c capable of shutting off the fuel flowing through the mixing line 22.

[0021] Although detailed illustration is omitted, the downstream side of the mixing line 22 branches off and is connected to a plurality of fuel injection nozzles provided in the combustor 2. These fuel injection nozzles are premixed fuel injection nozzles that can premix the fuel supplied from the mixing line 22 with the combustion air supplied from the compressor 3 and inject the premixed fuel into the combustion chamber of the combustor 2 to form a flame.

[0022] Among the above components, the flow rate control valve 18, the first shutoff valve 20a, the second shutoff valve 20b, the third shutoff valve 20c, the first vent valve 21, the second vent valve 28, and the third vent valve 31 are control valves that can be automatically opened and closed based on control signals from a control device, which is a control unit (not shown). The control device is configured as an electronic calculation device such as a computer device that can perform various controls required for the operation of the gas turbine 1 by executing a control program installed in advance.

[0023] Next, a method for controlling the fuel supply device 4 having the above configuration will be described. Fig. 2 is a flowchart showing the method for controlling the fuel supply device 4 according to the first embodiment, and Figs. 3A to 3E are explanatory diagrams corresponding to the respective steps in Fig. 2.

[0024] First, as an initial state in which this control method is carried out, as shown in Fig. 3A, the gas turbine 1 is in a stopped state, and the isolation valve 13, the third shutoff valve 20c, the first vent valve 21, the second vent valve 27, and the third vent valve 31 are in a closed state (the other valves are in an open state). From such an initial state, while temporarily opening the first vent valve 21, nitrogen gas is supplied from the outside to the second fuel gas supply line 16 via the first vent line 19, thereby replacing the upstream side of the isolation valve 13 in the second fuel gas supply line 16 with nitrogen gas (step S100). As a result, highly combustible hydrogen gas remaining in the second fuel supply line 16 from the previous operation is discharged to the outside, and the safety of the gas turbine 1 is ensured while the gas turbine 1 is kept stopped.

[0025] After the replacement with nitrogen gas is completed in step S100, the first vent valve 21 may be closed. In step S100, the first fuel F1 flows from the first fuel supply line 8 into the second fuel supply line 16 on the downstream side of the isolation valve 13 (i.e., the junction 25 side).

[0026] 3B, hydrogen gas is supplied from the second fuel supply source 14 to the second fuel gas supply line 16, thereby replacing the second fuel gas supply line 16 upstream of the isolation valve 13 with hydrogen gas (step S101). At this time, the isolation valve 13 in a closed state is provided at a position in the second fuel supply line 16 closer to the junction 25 than to the first shutoff valve 20a. In other words, the isolation valve 13 is provided near the junction 25 in the second fuel supply line 16. As a result, the gas turbine 1 before start-up can be put into standby by filling a wide range of the second fuel supply line 16 with the second fuel F2.

[0027] In addition, if the gas turbine 1 is tripped (emergency stopped) for some reason during the mixed combustion operation of the gas turbine 1, the third shutoff valve 20c arranged in the mixing line 22 and the first shutoff valve 20a or the second shutoff valve 20b arranged in the second fuel supply line 16 are switched to a closed state to stop the fuel supply to the combustor 2. In this situation, if an openable / closable valve is not arranged near the junction 25, the second fuel F2 remaining in the second fuel supply line 16 will be directly supplied to the combustor 2 when the gas turbine 1 is restarted the next time the exclusive combustion operation is performed using the first fuel F1. In this embodiment, the isolation valve 13 is arranged near the junction 25 in the second fuel supply line 16, so that the second fuel F2 supplied to the combustor 2 when the gas turbine 1 is restarted in this manner can be reduced.

[0028] 3C, the first shutoff valve 20a is closed and the isolation valve 13 is opened to take in the first fuel F1 from the first fuel supply line 8 (step S102). At this time, since the first shutoff valve 20a is in a closed state, the first fuel F1 from the first fuel supply line 8 is filled into the range of the second fuel supply line 16 downstream of the first shutoff valve 20a (i.e., the junction 25 side). In step S102, the flow rate adjustment valve 18 is controlled to be in a closed state, as shown in FIG. 3C.

[0029] 3D, the flow rate control valve 18 is controlled to be slightly opened to a predetermined opening degree (step S103), and the third shutoff valve 20c is controlled to be opened, thereby starting the gas turbine 1 in a mono-fuel combustion state (step S104). As a result, the pressure upstream of the first shutoff valve 20a gradually increases.

[0030] Next, in the second fuel gas supply line 16, it is determined whether the upstream pressure P1 of the first shutoff valve 20a becomes higher than the downstream pressure P2 (step S105). If the upstream pressure P1 becomes higher than the downstream pressure P2 (step S105: YES), the first shutoff valve 20a is controlled to be open (step S106). As a result, as shown in Fig. 3E, the first fuel F1 present on the upstream side of the first shutoff valve 20a passes through the downstream side of the first shutoff valve 20a and is supplied to the junction 25, thereby starting a multi-fuel operation of the gas turbine 1 (step S107).

[0031] Here, the configuration and control of a gas turbine 1' according to a reference technique will be described. Fig. 9 is a schematic configuration diagram of a gas turbine 1' according to a reference technique, Fig. 10 is a flowchart showing a control method of the fuel supply device 4 in Fig. 9, and Figs. 11A to 11E are explanatory diagrams corresponding to each step in Fig. 10.

[0032] The configuration of the gas turbine 1 according to the reference technique is different from the fuel supply device 4 in the first embodiment shown in FIG. In the following description, components corresponding to those in the first embodiment described above are given the same reference numerals, and duplicate descriptions will be omitted as appropriate unless otherwise specified.

[0033] First, as shown in Fig. 11A, in an initial state in which this control method is carried out, the gas turbine 1 is in a stopped state, and the third shutoff valve 20c, the first vent valve 21, the second vent valve 27, and the third vent valve 31 are in a closed state (the other valves are in an open state). From this initial state, while temporarily opening the first vent valve 21, nitrogen gas is supplied from the outside to the second fuel gas supply line 16, thereby replacing the second fuel gas supply line 16 with nitrogen gas (step S300). As a result, highly combustible hydrogen gas remaining in the second fuel supply line 16 from the previous operation is discharged to the outside, and the safety of the gas turbine 1 is ensured while the gas turbine 1 is kept stopped.

[0034] Next, prior to starting up the gas turbine 1, as shown in FIG. 11B, the first fuel F1 is supplied to the second fuel gas supply line 16 from the first fuel gas supply line 8 via the junction 25, thereby replacing the second fuel gas supply line 16 with the first fuel F1 (step S301).

[0035] Next, the third shutoff valve 20c is opened, the gas turbine 1 is started in a mono-fuel combustion state (step S302), and the first shutoff valve 20b is closed (step S303) as shown in Fig. 11C. Then, as shown in Fig. 11D, the flow rate control valve 18 is controlled to be slightly opened to a predetermined opening degree (step S304). This causes the pressure on the upstream side of the first shutoff valve 20a to gradually increase.

[0036] Next, in the second fuel gas supply line 16, it is determined whether the upstream pressure P1 of the first shutoff valve 20a becomes higher than the downstream pressure P2 (step S305). If the upstream pressure P1 becomes higher than the downstream pressure P2 (step S305: YES), the first shutoff valve 20a is controlled to be open (step S306). As a result, as shown in Fig. 11E, the first fuel F1 present on the upstream side of the first shutoff valve 20a passes through the downstream side of the first shutoff valve 20a and is supplied to the junction 25, thereby starting a multi-fuel operation of the gas turbine 1 (step S307).

[0037] In a series of control sequences in the reference technology, as shown in Fig. 11B and Fig. 11C, the second flowmeter 15 is included in the charging range of the first fuel F1 before the start of the gas turbine 1'. Therefore, when the gas turbine 1' is started, the first fuel F1 having a higher density than the second fuel F2 temporarily flows through the second flowmeter 15. Therefore, when a Coriolis flowmeter is used as the second flowmeter 15, there is a risk of erroneously recognizing the flow rate based on the density difference between the first fuel F1 and the second fuel F2. Since the flow rate detection value detected by the second flowmeter 15 is used, for example, to calculate the mixture ratio, which is a monitoring parameter during the multi-fuel operation of the gas turbine 1', it is necessary to avoid such erroneous recognition.

[0038] The problems in the reference technology can be suitably solved by the above-mentioned first embodiment. In a series of control sequences in the first embodiment, the first fuel F1 does not reach the second flowmeter 15. If the second flowmeter 15 is a Coriolis flowmeter and the first fuel F1 reaches the second flowmeter 15 in the second fuel supply line 16, the first fuel F1, which has a density different from that of the second fuel F2, flows through the second flowmeter 15 at the start of the gas turbine 1, and the flow rate may be erroneously recognized. In particular, since the densities of the first fuel F1, which is natural gas, and the second fuel F2, which is hydrogen gas, are significantly different, if a Coriolis flowmeter is used as the second flowmeter 15, the flow rate cannot be accurately measured. Since the measured value of the second flowmeter 15 is used, for example, for calculating the mixed combustion ratio, which is an important control parameter during the mixed combustion operation of the gas turbine 1, such erroneous recognition must be avoided. In contrast, in the present embodiment, as described above, the first fuel F1 does not reach the second flow meter 15, and therefore such erroneous recognition by the second flow meter 15 can be suitably avoided.

[0039] Fig. 4 is a schematic configuration diagram of a gas turbine 1 according to the second embodiment. The second embodiment is different from the fuel supply device 4 in the first embodiment shown in Fig. 1 in that the second embodiment does not have the isolation valve 13, but instead has a first shutoff valve 20a arranged at the position of the isolation valve 13. In the following description, components corresponding to those in the first embodiment described above are given the same reference numerals, and duplicate descriptions will be omitted as appropriate unless otherwise specified.

[0040] Next, a description will be given of a method for controlling the fuel supply device 4 having the configuration shown in Fig. 4. Fig. 5 is a flowchart showing a method for controlling the fuel supply device 4 according to the second embodiment, and Figs. 6A to 6E are explanatory diagrams corresponding to the steps in Fig. 5.

[0041] First, as an initial state in which this control method is carried out, as shown in Fig. 6A, the gas turbine 1 is in a stopped state, and the first shutoff valve 20a, the first vent valve 21, the second vent valve 27, and the third vent valve 31 are in a closed state (the other valves are in an open state). From this initial state, while temporarily opening the first vent valve 21, nitrogen gas is supplied from the outside to the second fuel gas supply line 16 via the first vent line 19, thereby replacing the upstream side of the first shutoff valve 20a of the second fuel gas supply line 16 with nitrogen gas (step S200). As a result, highly combustible hydrogen gas remaining in the second fuel supply line 16 from the previous operation is discharged to the outside, and the safety of the gas turbine 1 is ensured while the gas turbine 1 is kept stopped.

[0042] After the replacement with nitrogen gas is completed in step S200, the first vent valve 21 may be closed. In step S200, the first fuel F1 flows from the first fuel supply line 8 into the second fuel supply line 16 on the downstream side of the first shutoff valve 20a (i.e., the junction 25 side).

[0043] 6B, hydrogen gas is supplied from the second fuel supply source 14 to the second fuel gas supply line 16 via the first vent line 19, thereby replacing the second fuel gas supply line 16 upstream of the second shutoff valve 20a with hydrogen gas (step S201). At this time, the first shutoff valve 20a in a closed state is provided at a position in the second fuel supply line 16 closer to the junction 25 than to the second flow meter 15. That is, the first shutoff valve 20a is provided near the junction 25 in the second fuel supply line 16. As a result, the gas turbine 1 before start-up can be put into standby by filling a wide range of the second fuel supply line 16 with the second fuel F2.

[0044] Next, as shown in Fig. 6C, the flow rate control valve 18 is controlled to be in a closed state (step S202). Then, as shown in Fig. 6D, the flow rate control valve 18 is controlled to be slightly opened to a predetermined opening degree (step S203), and the gas turbine 1 is started in a mono-fuel combustion state (step S204). As a result, the pressure upstream of the first shutoff valve 20a gradually increases.

[0045] Next, in the second fuel gas supply line 16, it is determined whether the upstream pressure P1 of the first shutoff valve 20a becomes higher than the downstream pressure P2 (step S205). If the upstream pressure P1 becomes higher than the downstream pressure P2 (step S205: YES), the first shutoff valve 20a is controlled to be open (step S206). As a result, as shown in Fig. 6E, the first fuel F1 present on the upstream side of the first shutoff valve 20a passes through the downstream side of the first shutoff valve 20a and is supplied to the junction 25, thereby starting a multi-fuel operation of the gas turbine 1 (step S207).

[0046] In the second embodiment described above, since the isolation valve 13 is not provided as compared with the first embodiment, the fuel supply device 4 can be realized with a simpler configuration. Even in a series of control sequences in the second embodiment having such a configuration, the first fuel F1 does not reach the second flowmeter 15. If the second flowmeter 15 is a Coriolis flowmeter and the first fuel F1 reaches the second flowmeter 15 in the second fuel supply line 16, the first fuel F1, which has a different density from the second fuel F2, flows through the second flowmeter 15 at the start of the gas turbine 1, and the flow rate may be erroneously recognized. In particular, since the densities of the first fuel F1, which is natural gas, and the second fuel F2, which is hydrogen gas, are significantly different, if a Coriolis flowmeter is used as the second flowmeter 15, the flow rate cannot be accurately measured. Since the measured value of the second flowmeter 15 is used, for example, for calculating the mixed combustion ratio, which is an important control parameter during the mixed combustion operation of the gas turbine 1, such erroneous recognition must be avoided. In contrast, in the present embodiment, as described above, the first fuel F1 does not reach the second flow meter 15, and therefore such erroneous recognition by the second flow meter 15 can be suitably avoided.

[0047] In the gas turbine 1 having the above configuration, when switching from a mono-fuel operation using the first fuel F1 to a mixed-fuel operation using the first fuel and the second fuel F2, during mono-fuel operation using the first fuel F1, the first shutoff valve 20a and the second shutoff valve 20b are closed, and the second vent valve 28 and the third vent valve 31 provided therebetween are opened, so that the flow control valve 18 is opened to a specified opening degree for pressure equalization. At this time, if the distance between the first shutoff valve 20a and the second shutoff valve 20b is large, a relatively large volume of the second fuel F2 located therebetween is discharged to the outside from the second vent valve 28 and the third vent valve 31 when mono-fuel combustion of the first fuel F1 is performed, resulting in a lot of waste. In the first embodiment, the distance between the first shutoff valve 20a and the second shutoff valve 20b is shorter than in the second embodiment, so that the amount of the second fuel F2 discharged to the outside from the second vent valve 28 and the third vent valve 31 is small, and efficient operation is possible.

[0048] Fig. 7 is a modified example of Fig. 4. In this modified example, the second fuel supply line 16 is configured to be shorter between the second flow meter 15 and the branch point 26 than in the configuration shown in Fig. 4. Therefore, in a series of sequences, by reducing the volume of the first fuel F1 and the second fuel F2 passing through the second fuel supply line 16, more efficient operation can be expected and the device configuration can be made compact. In addition, in this modified example, the distance between the first shutoff valve 20a and the second shutoff valve 20b is also shorter than in the second embodiment, so that less second fuel F2 is discharged to the outside from the second vent valve 28 and the third vent valve 31, and therefore efficient operation is possible.

[0049] Fig. 8 is a schematic diagram of a gas turbine 1 according to the third embodiment. In the third embodiment, compared to the first embodiment shown in Fig. 1, the gas turbine 1 has an existing section 4a capable of mono-fuel operation using the first fuel F1 by having a configuration centered around the first fuel supply line 8, and a first additional equipment 4b1 and a second additional equipment 4b2 for supplying the second fuel F2 are retrofitted to the existing configuration 4a. As a result, by adding these additional equipments to the existing section 4a capable of mono-fuel operation using the first fuel F1, it is possible to easily improve the configuration to one capable of mixed-fuel operation.

[0050] The first additional equipment 4b1 includes a second shutoff valve 20b and a flow rate adjustment valve 18. The second additional equipment 4b2 includes a first shutoff valve 20a and a second flow meter 15. The first additional equipment 4b1 and the second additional equipment 4b2 are connected in turn between the second fuel supply unit 14 and the junction 25. The second additional equipment 4b2 and the junction 25 are connected via an extension line 16a constituting the second fuel supply line 16. The extension line 16a is provided over a length of, for example, several tens of meters depending on the position of the second fuel supply unit 14.

[0051] In this configuration, the first additional equipment 4b1 and the second additional equipment 4b2 can be attached to the existing section 4a, which is capable of single-fuel combustion with the first fuel F1, to improve the system so that it can perform mixed combustion of the first fuel F1 and the second fuel F2. In particular, the first additional equipment 4b1 and the second additional connection section 4b2 can be manufactured elsewhere. The first additional equipment 4b1 and the second additional equipment 4b2 manufactured elsewhere can be transported to the site where the gas turbine 1 is to be installed and attached to the existing section 4a at the site via the extension line 16a, thereby reducing the amount of work at the site and enabling efficient additional construction work.

[0052] As described above, according to each of the above embodiments, in a series of controls at the start of mixed combustion in the gas turbine 1, only the second fuel F2 passes through the second flow meter 15 arranged in the second fuel supply line 16. Therefore, the first fuel F1, which has a different density, passes through the second flow meter 15, and the detection value of the second flow meter 15 is used to prevent misidentification of the mixed combustion ratio, which is a parameter for monitoring the operating state of the gas turbine 1, and stable operation of the gas turbine 1 can be achieved.

[0053] 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.

[0054] The contents described in each of the above embodiments can be understood, for example, as follows.

[0055] (1) A fuel supply device for a gas turbine according to one aspect includes: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; Equipped with.

[0056] According to the above aspect (1), the second fuel supply line is provided with a first shutoff valve that is to be controlled when the operating state of the gas turbine is switched from the mono-fuel combustion state to the multi-fuel combustion state. In addition, a flowmeter capable of outputting a detection value of the flow rate of the second fuel is provided on the upstream side of the first shutoff valve in the second fuel supply line in order to calculate the mixture ratio, which is one of the monitoring parameters of the operating state of the gas turbine. In the fuel supply device for the gas turbine having such a configuration, when the operating state of the gas turbine is switched from the mono-fuel combustion state to the multi-fuel combustion state, the second fuel is supplied from the upstream side of the second fuel supply line in a state where the first shutoff valve is closed, thereby filling the upstream side of the first shutoff valve in the second fuel supply line with the second fuel. Then, when the upstream pressure of the first shutoff valve becomes larger than the downstream pressure, the first shutoff valve is opened to supply the second fuel from the second fuel supply line to the junction, thereby starting the multi-fuel combustion of the gas turbine. In such a series of controls at the start of mixed combustion in a gas turbine, only the second fuel passes through the flow meter arranged in the second fuel supply line, so that the flow of the first fuel, which has a different density, can be prevented from misinterpreting the mixed combustion ratio, which is a parameter for monitoring the operating state of the gas turbine, using the detection value of the flow meter, thereby realizing stable operation of the gas turbine.

[0057] (2) In another embodiment, in the above embodiment (1), The second fuel supply line includes an isolation valve provided between the first shutoff valve and the junction.

[0058] According to the above aspect (2), an isolation valve is provided between the first shutoff valve and the junction. This isolation valve is closed before switching the operating state of the gas turbine from the mono-fuel combustion state to the multi-fuel combustion state, thereby restricting the filling range of the first fuel in the second fuel supply line so that the first fuel entering the second fuel supply line from the junction does not reach the flow meter. As a result, when the gas turbine starts multi-fuel combustion, the first fuel does not pass through the flow meter arranged in the second fuel supply line. The passage of the first fuel with a different density prevents the mixed-fuel ratio, which is a parameter for monitoring the operating state of the gas turbine, from being misidentified using the detection value of the flow meter, thereby realizing stable operation of the gas turbine.

[0059] (3) In another embodiment, in the above embodiment (2), The isolation valve is provided at a position on the second fuel supply line that is closer to the junction than to the first shutoff valve.

[0060] According to the above aspect (3), an isolation valve is disposed in the second fuel supply line near the junction. As described above, this isolation valve has a function of restricting the filling range of the first fuel that enters the second fuel supply line from the junction before the gas turbine starts co-firing. Therefore, by disposing the isolation valve near the junction, the filling range can be kept small. If the gas turbine is tripped (emergency stopped) for some reason during the mixed combustion operation of the gas turbine, the fuel supply to the combustor is stopped by switching to a closed state a shutoff valve (a valve capable of shutting off the entire fuel supplied to the combustor downstream of the junction) arranged in the mixed combustion line and a first shutoff valve arranged in the second fuel supply line. In this situation, if an openable / closable valve is not arranged near the junction, the second fuel remaining in the second fuel supply line will be supplied to the combustor as it is when the gas turbine is next restarted and the first fuel is used for the mono-fuel operation. In this embodiment, by arranging an isolation valve in the second fuel supply line near the junction, the second fuel supplied to the combustor when the gas turbine is restarted in this manner can be reduced.

[0061] (4) In another embodiment, in the above embodiment (2) or (3), a vent line branching off from the second fuel supply line between the first shutoff valve and the isolation valve; The system further includes a vent valve disposed in the vent line.

[0062] According to the above aspect (4), a vent line having a vent valve is provided so as to branch off from the second fuel supply line. With this, before the start of mixed combustion in the gas turbine, the second fuel can be supplied while opening the vent valve with the isolation valve closed, thereby filling the second fuel in the range of the second fuel supply line up to the isolation valve.

[0063] (5) In another embodiment, in the above embodiment (4), A branch point of the vent line from the second fuel supply line is provided at a position closer to the junction than to the first shutoff valve.

[0064] According to the above aspect (5), the branch point of the vent line to the second fuel supply line is provided near the junction, which ensures a wide filling range when the first fuel is filled into the second fuel supply line before the gas turbine starts mixed combustion.

[0065] (6) In another embodiment, in any one of the above (1) to (5), The fuel supply system further includes a second shutoff valve provided in the second fuel supply line upstream of the flow meter.

[0066] According to the above aspect (6), the second fuel supply line is provided with a second shutoff valve upstream of the flow meter. Thus, when an abnormality occurs in the operation of the gas turbine, the supply of the second fuel, which has a higher combustion speed, can be stopped reliably by closing the second shutoff valve together with the first shutoff valve.

[0067] (7) In another embodiment, in any one of the above (1) to (6), The mixing line further includes a third shutoff valve.

[0068] According to the above aspect (7), a third shutoff valve is provided in the mixing line downstream of the junction. Thus, in the event of an abnormality in the operation of the gas turbine, the fuel supply to the combustor can be stopped appropriately by closing the third shutoff valve.

[0069] (8) In another embodiment, in the above embodiment (1), The first shutoff valve is provided at a position on the second fuel supply line where the distance to the junction is shorter than the distance to the flow meter.

[0070] According to the above aspect (8), the position of the first shutoff valve provided in the second fuel supply line is set to be closer to the junction than the flow meter. This allows the first shutoff valve to also function as the isolation valve described above, and therefore the configuration of the fuel supply device can be simplified by omitting the isolation valve.

[0071] (9) In another embodiment, in any one of the above (1) to (8), The first shutoff valve and the flow meter are integrally configured as an additional unit.

[0072] According to the above aspect (9), the first shutoff valve and the flow meter, which are the main components provided in the second fuel supply line, may be integrally configured as an additional unit. In this case, for example, by retrofitting an additional unit to a fuel supply device of an existing gas turbine capable of mono-fuel combustion of the first fuel, it is possible to easily improve the gas turbine to one capable of mixed combustion.

[0073] (10) In another embodiment, in any one of the above (1) to (9), the first fuel comprises natural gas; The second fuel includes hydrogen gas.

[0074] According to the above aspect (10), in a fuel supply device for supplying fuel to a gas turbine capable of co-firing fuels including natural gas and hydrogen gas as a first fuel and a second fuel, it is possible to prevent misinterpretation of the co-firing ratio, which is a parameter for monitoring the operating state of the gas turbine, and to realize stable operation of the gas turbine.

[0075] (11) A method for controlling a fuel supply device of a gas turbine according to one aspect includes the steps of: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; an isolation valve provided in the second fuel supply line between the first shutoff valve and the junction; a vent line branching off from the second fuel supply line between the first shutoff valve and the isolation valve; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a second fuel supply line upstream of the isolation valve while the gas turbine is stopped and the isolation valve is closed; supplying the first fuel to a portion of the second fuel supply line downstream of the first shutoff valve by closing the first shutoff valve and opening the isolation valve; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; Equipped with.

[0076] According to the above aspect (11), the second fuel supply line is provided with a first shutoff valve that is to be controlled when the operating state of the gas turbine is switched from the mono-fuel state to the multi-fuel state. In addition, a flow meter capable of outputting a detection value of the flow rate of the second fuel is provided on the upstream side of the first shutoff valve in the second fuel supply line in order to calculate the mixture ratio, which is one of the monitoring parameters of the operating state of the gas turbine. In the fuel supply device for the gas turbine having such a configuration, when the operating state of the gas turbine is switched from the mono-fuel state to the multi-fuel state, the second fuel is supplied from the upstream side of the second fuel supply line in a state where the first shutoff valve is closed, so that the upstream side of the first shutoff valve in the second fuel supply line can be filled with the second fuel. Then, when the upstream pressure of the first shutoff valve becomes larger than the downstream pressure, the first shutoff valve is opened to supply the second fuel from the second fuel supply line to the junction, and multi-fuel combustion of the gas turbine can be started. In such a series of controls at the start of mixed combustion in a gas turbine, only the second fuel passes through the flow meter arranged in the second fuel supply line, so that the flow of the first fuel, which has a different density, can be prevented from misinterpreting the mixed combustion ratio, which is a parameter for monitoring the operating state of the gas turbine, using the detection value of the flow meter, thereby realizing stable operation of the gas turbine.

[0077] (12) A method for controlling a fuel supply device of a gas turbine according to one aspect includes the steps of: A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a junction of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; a vent line branching off from the second fuel supply line between the first shutoff valve and the flow meter; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a side of the second fuel supply line upstream of the first shutoff valve while the gas turbine is stopped and the first shutoff valve is closed; supplying the first fuel to a downstream side of the first shutoff valve in the second fuel supply line; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; Equipped with.

[0078] According to the above aspect (12), the second fuel supply line is provided with a first shutoff valve that is to be controlled when the operating state of the gas turbine is switched from the mono-fuel combustion state to the multi-fuel combustion state. In addition, a flow meter capable of outputting a detection value of the flow rate of the second fuel is provided on the upstream side of the first shutoff valve in the second fuel supply line in order to calculate the mixture ratio, which is one of the monitoring parameters of the operating state of the gas turbine. In the fuel supply device for the gas turbine having such a configuration, when the operating state of the gas turbine is switched from the mono-fuel combustion state to the multi-fuel combustion state, the second fuel is supplied from the upstream side of the second fuel supply line in a state where the first shutoff valve is closed, thereby filling the upstream side of the first shutoff valve in the second fuel supply line with the second fuel. Then, when the upstream pressure of the first shutoff valve becomes larger than the downstream pressure, the first shutoff valve is opened to supply the second fuel from the second fuel supply line to the junction, thereby starting the multi-fuel combustion of the gas turbine. In such a series of controls at the start of mixed combustion in a gas turbine, only the second fuel passes through the flow meter arranged in the second fuel supply line, so that the flow of the first fuel, which has a different density, can be prevented from misinterpreting the mixed combustion ratio, which is a parameter for monitoring the operating state of the gas turbine, using the detection value of the flow meter, thereby realizing stable operation of the gas turbine. [Explanation of symbols]

[0079] 1. Gas turbine 2. Combustor 3. Compressor 4 Fuel supply device 4b1 1st additional equipment 4b2 2nd additional equipment 6. Turbine 7 First fuel source 8. First fuel supply line 10 1st flow meter 13 Isolation valve 14 Secondary fuel source 15 2nd flow meter 16 Second fuel supply line 16a Extension Line 18 Flow control valve 19 First Vent Line 20a First shutoff valve 20b Second shutoff valve 20c Third shutoff valve 21 First vent valve 22 Mixed Line 25 Confluence 26 First Turning Point 27 Second Vent Line 28 Second vent valve 29 Second Branch Point 30 Third Vent Line 31 Third vent valve 32 The third turning point

Claims

1. A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a joining portion of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve, and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; A fuel supply device for a gas turbine comprising:

2. 2 . The fuel supply system for a gas turbine according to claim 1 , further comprising an isolation valve provided in the second fuel supply line between the first shutoff valve and the junction.

3. 3. The fuel supply device for a gas turbine according to claim 2, wherein the isolation valve is provided at a position in the second fuel supply line closer to the junction than to the first shutoff valve.

4. a vent line branching off from the second fuel supply line between the first shutoff valve and the isolation valve; 3. The fuel supply system for a gas turbine according to claim 2, further comprising a vent valve provided in the vent line.

5. 5. The fuel supply device for a gas turbine according to claim 4, wherein a branch point of the vent line from the second fuel supply line is provided at a position closer to the junction than to the first shutoff valve.

6. 3. The fuel supply device for a gas turbine according to claim 1, further comprising a second shutoff valve provided in the second fuel supply line upstream of the flow meter.

7. 3. The fuel supply system for a gas turbine according to claim 1, further comprising a third shutoff valve provided in the mixing line.

8. 2 . The fuel supply device for a gas turbine according to claim 1 , wherein the first shutoff valve is provided at a position on the second fuel supply line that is closer to the junction than to the flow meter.

9. 3. The fuel supply system for a gas turbine according to claim 1, wherein the first shutoff valve and the flow meter are integrally configured as an additional unit.

10. the first fuel comprises natural gas; The fuel supply system for a gas turbine according to claim 1 or 2, wherein the second fuel includes hydrogen gas.

11. A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a joining portion of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve, and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; an isolation valve provided in the second fuel supply line between the first shutoff valve and the junction; a vent line branching off from the second fuel supply line between the first shutoff valve and the isolation valve; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a second fuel supply line upstream of the isolation valve while the gas turbine is stopped and the isolation valve is closed; supplying the first fuel to a portion of the second fuel supply line downstream of the first shutoff valve by closing the first shutoff valve and opening the isolation valve; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; A method for controlling a fuel supply system of a gas turbine, comprising:

12. A fuel supply device for a gas turbine capable of supplying a first fuel and a second fuel having a combustion speed higher than that of the first fuel to a combustor of the gas turbine, a first fuel supply line for supplying the first fuel; a second fuel supply line for supplying the second fuel; a mixing line connecting a joining portion of the first fuel supply line and the second fuel supply line to the combustor; a first shutoff valve that is provided in the second fuel supply line and that is to be controlled when an operating state of the gas turbine is switched from a mono-fuel state in which only a first fuel is supplied to the combustor to a multi-fuel state in which a mixed fuel of the first fuel and the second fuel is supplied to the combustor; a flow meter that is provided in the second fuel supply line upstream of the first shutoff valve, and that is capable of outputting a detection value of a flow rate of the second fuel in order to calculate a mixing ratio of the first fuel and the second fuel for monitoring an operating state of the gas turbine; a vent line branching off from the second fuel supply line between the first shutoff valve and the flow meter; a vent valve provided in the vent line; A method for controlling a fuel supply system of a gas turbine, comprising: supplying a second fuel to a side of the second fuel supply line upstream of the first shutoff valve while the gas turbine is stopped and the first shutoff valve is closed; supplying the first fuel to a downstream side of the first shutoff valve in the second fuel supply line; opening the first shutoff valve when an upstream pressure of the first shutoff valve becomes greater than a downstream pressure in the second fuel supply line while the gas turbine is started; A method for controlling a fuel supply system of a gas turbine, comprising:

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