Fuel supply system control method, and fuel supply system control system

Abstract

To prevent a drain, which is generated in fuel flowing in a fuel supply line, from being frozen when starting activation of a gas turbine.SOLUTION: A fuel supply line 65 comprises: pressure reduction valves 74 and 75 provided at a downstream side of a confluent part 73 with a bypass line 70 at a downstream side of a heater 67, and a strainer 76 provided at a downstream side of the pressure reduction valves 74 and 75. In a first channel C1, a fuel F is supplied to a gas turbine via the heater 67. In a second channel C2, the fuel F is supplied to the gas turbine via the bypass line 70. In a first step of a fuel supply system control method, when starting activation of the gas turbine, a channel switching section 72 is controlled in such a manner that a channel of the fuel is the second channel C2. In a second step, supply of a heat exchange medium M is started to the heater 67. In a third step, in a case where the temperature of the heat exchange medium M in the exit part of the heater 67 becomes equal to or higher than a preset reference temperature, the channel switching section 72 is controlled in such a manner that the channel of the fuel F is switched from the second channel C2 to the first channel C1.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] There is known a gas turbine capable of driving the turbine using combustion gas generated by mixing and burning fuel with combustion air. In this type of gas turbine, fuel is supplied through a fuel supply line constituting a fuel supply system. For example, at the beginning of the start-up of the gas turbine, the fuel temperature is relatively low, and therefore the combustion state of the gas turbine may be affected by the fuel temperature. In order to reduce such an effect of the fuel temperature, a heater for heating the fuel may be installed in the fuel supply line. For example, Patent Document 1 discloses a technology for heating the fuel supplied to the gas turbine and removing mist contained in the fuel by installing a heater using an external heat source as a heater in the fuel supply line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 61-087926 Summary of the Invention [Problem to be solved by the invention]

[0004] Drain may be generated in the fuel flowing through the fuel supply line. The drain flows through the fuel supply line together with the fuel, but when the pressure is reduced as it passes through the flow control valve or pressure control valve installed in the fuel supply line, the temperature of the drain drops and it may freeze. Frozen drain may block the strainer installed in the fuel supply line to collect foreign matter contained in the fuel, thereby interfering with the fuel supply to the gas turbine.

[0005] As described above, a heater for heating the fuel may be installed in the fuel supply line, and in particular, in a heat exchange type heater capable of heating the fuel by heat exchange with a heat exchange medium, the fuel to be heated flows through fine tubes in order to improve the heat exchange efficiency. In such tubes, drainage from the air remaining in the tubes is likely to occur before the initial start-up of the gas turbine or during a long-term shutdown.

[0006] At least one embodiment of the present disclosure has been made in consideration of the above-described circumstances, and has an object to provide a fuel supply system control method and a fuel supply system control system that are capable of preventing drain generated in fuel flowing through a fuel supply line from freezing when a gas turbine begins to start up. [Means for solving the problem]

[0007] In order to solve the above problem, a fuel supply system control method according to at least one embodiment of the present disclosure includes: a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A fuel supply system control method for controlling a fuel supply system comprising: a first step of controlling the flow path switching unit so that the flow path of the fuel becomes the second flow path at the start of startup of the gas turbine; a second step of starting to supply the heat exchange medium to the at least one heater; a third step of controlling the flow path switching unit so that the flow path of the fuel is switched from the second flow path to the first flow path when a temperature of the heat exchange medium at an outlet of the at least one heater becomes equal to or higher than a preset reference temperature; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; has.

[0008] In order to solve the above problems, a fuel supply system control system according to at least one embodiment of the present disclosure includes: a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A control unit for controlling the flow path switching unit; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; having The control unit is At the start of startup of the gas turbine, the flow path switching unit is controlled so that the flow path of the fuel becomes the second flow path; After starting the supply of the heat exchange medium to the at least one heater, when the temperature of the heat exchange medium at the outlet of the at least one heater becomes equal to or higher than a predetermined reference temperature, the flow path switching unit is controlled so that the fuel flow path is switched from the second flow path to the first flow path. Effect of the Invention

[0009] According to at least one embodiment of the present disclosure, it is possible to provide a fuel supply system control method and a fuel supply system control system capable of preventing drain generated in fuel flowing through a fuel supply line from freezing when a gas turbine begins to start up. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a combined cycle plant according to an embodiment. FIG. [Diagram 2] FIG. 2 is an internal configuration diagram of the fuel supply system shown in FIG. [Diagram 3] FIG. 3 is a block diagram of the control device of FIG. 2. [Figure 4] 4 is a time chart showing changes in control parameters in each component of the combined cycle plant 1 when the startup sequence control is executed by the startup control section of FIG. 3. [Diagram 5] 4 is a flowchart showing a control method implemented by the control device of FIG. 3. [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 7] This is a modified example of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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.

[0012] First, a configuration of a combined cycle plant 1 including a fuel supply system that is a control target of a fuel supply system control system 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 a 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 30 that can be driven by steam from the heat recovery boiler 20, a condenser 40 for converting the steam from the steam turbine 30 back into water, a feedwater pump 76 for sending the water in the condenser 40 to the heat recovery boiler 20, a generator 45, and a starter motor 49.

[0014] The gas turbine 10 includes a compressor 11 for compressing combustion air A, a combustor 14 for generating combustion gas by combusting fuel F supplied from a fuel supply system 50 together with the combustion air A compressed by the compressor 11, and a turbine 15 that can be driven by the combustion gas generated in the combustor 14. The compressor 11 has a compressor rotor 12 that rotates about an axis Ar, and a compressor casing 13 that covers the compressor rotor 12.

[0015] The turbine 15 has a turbine rotor 16 that is rotatable about an axis Ar, and a turbine casing 17 that covers the turbine rotor 16. The compressor rotor 12 and the turbine rotor 16 are connected to each other so as to be rotatable integrally about the same axis Ar, thereby constituting a gas turbine rotor 19. A fuel supply line 65 extending from a fuel supply system 50 is connected to the combustor 14.

[0016] The heat recovery boiler 20 includes an economizer 21 for heating water supplied from the condenser 40 by the feed water pump 76 with heat contained in the exhaust gas EG from the gas turbine 10, an evaporator 22 capable of generating steam by heating the water heated by the economizer 21 with the heat of the exhaust gas EG, and a superheater 23 capable of further superheating the steam with the heat of the exhaust gas EG. The economizer 21, the evaporator 22, and the superheater 23 all have heat transfer tubes through which water or steam passes and for exchanging heat between the water or steam and the exhaust gas EG. The evaporator 22 includes a drum 22a in addition to the heat transfer tubes. A portion of the water or steam stored in the drum 22a can be supplied to the condenser 40 via a boiler water discharge line 88. A boiler water discharge valve 89 is provided on the boiler water discharge line 88.

[0017] The steam superheated by the superheater 23 is supplied to the steam turbine 30 via a main steam line 81. A shutoff valve 78 and a control valve 79 are provided on the main steam line 81.

[0018] The steam turbine 30 has a steam turbine rotor 31 rotatable about an axis Ar, a steam turbine casing 34 covering the steam turbine rotor 31, and a shaft seal device 39. The steam turbine rotor 31 has a rotor shaft 32 rotatable about the axis Ar, and a plurality of moving blade rows 33 fixed to the rotor shaft 32. The plurality of moving blade rows 33 are arranged along the axial direction in which the axis Ar extends. A plurality of stator blade rows 36 are fixed to an inner circumferential surface of the steam turbine casing 34. The plurality of stator blade rows 36 are arranged along the direction in which the axial direction extends. Each of the plurality of stator blade rows 36 is disposed upstream of the steam flow with respect to any one of the plurality of moving blade rows 33.

[0019] Incidentally, the steam turbine 30 shown in FIG. 1 is a two-flow exhaust type steam turbine that divides the inflowing steam into two directions, but it may be a steam turbine that does not divide the inflowing steam.

[0020] The generator 45 has a generator rotor 46 that is rotatable about an axis Ar, and a generator casing 47 that covers the generator rotor 46. The generator 45 is electrically connected to an external system 63 by a connection line 60.

[0021] The gas turbine rotor 19, the steam turbine rotor 31, and the generator rotor 46 are located on the same axis Ar and are mechanically connected to one another. That is, the combined cycle plant 1 is a single-shaft combined cycle plant. The starter motor 49 can rotate these rotors about the axis Ar.

[0022] Fig. 2 is an internal configuration diagram of the fuel supply system 50 in Fig. 1. The fuel supply system 50 has a fuel supply line 65 for supplying fuel F to the combustor 14 of the gas turbine. One end of the fuel supply line 65 is connected to a fuel supply source (not shown), and the other end is connected to the combustor 14.

[0023] At least one heater 67 for heating the fuel F is provided in the fuel supply line 65. The heater 67 is capable of heating the fuel F by supplying heat to the fuel F flowing through the fuel supply line 65. Although the heating method of the heater 67 is not limited, in this embodiment, a heat exchange type heater capable of heating the fuel F by heat exchange with the heat exchange medium M is exemplified.

[0024] The heater 67 uses a part of the feedwater flowing through the water supply line 59 downstream of the economizer 21 as the heat exchange medium M. As shown in Fig. 1, a branch line 68 for extracting the feedwater as the heat exchange medium M branches off from the middle of the water supply line 59. The branch line 68 is led to the heater 67, and is configured so that heat exchange can be performed inside the heater 67 between the heat exchange medium M flowing through the branch line 68 and the fuel F flowing through the fuel supply line 65. In addition, the branch line 68 is provided with a valve 69 for adjusting the flow rate of the heat exchange medium M introduced into the heater 67.

[0025] A temperature sensor 77 for detecting the temperature T of the heat exchange medium M is provided at the outlet of the heater 67 in the branch line 68. In the heater 67, heat exchange between the fuel F and the heat exchange medium M occurs, so that the temperature of the heat exchange medium M at the outlet of the heater 67 decreases compared to the inlet side of the heater 67. The temperature sensor 77 can detect the temperature of the heat exchange medium M after heat exchange with the fuel F in the heater 67.

[0026] In addition, a bypass line 70 is connected to the fuel supply line 65 so as to bypass the heater 67. The bypass line 70 branches off from the fuel supply line 65 at an upstream branching portion 71 and merges with the fuel supply line 65 at a downstream junction 73. The heater 67 described above is provided in the fuel supply line 65 between the upstream branching portion 71 and the downstream junction 73.

[0027] Further, on the fuel supply line 65, downstream of the downstream junction 73, a pressure regulating valve 74, a flow rate regulating valve 75, and a strainer 76 are provided in this order from the upstream side. The pressure regulating valve 74 and the flow rate regulating valve 75 are valve mechanisms for regulating the pressure and flow rate, respectively, of the fuel F supplied to the combustor 14 via the fuel supply line 65, and also function as a pressure reducing valve for reducing the pressure when the fuel F passes through. The strainer 76 is a component for collecting foreign matter contained in the fuel F supplied to the combustor 14, and is formed of, for example, a fine mesh.

[0028] The upstream branching section 71 is provided with a flow path switching section for switching the flow path of the fuel F. In the present embodiment, the upstream branching section 71 is provided with a three-way valve 72 as an example of the flow path switching section. The three-way valve 72 can switch between a first flow path C1 and a second flow path C1 as the flow path of the fuel F in the fuel supply system 50. The first flow path C1 is a flow path in which the fuel F supplied from a fuel supply source (not shown) on the upstream side flows from the upstream branching point 71 along the fuel supply line 65, through the heater 67, and through the downstream junction 73 to the combustor 14. The second flow path C2 is a flow path in which the fuel F supplied from a fuel supply source (not shown) on the upstream side flows from the upstream branching point 71 along the fuel supply line 65, through the bypass line 70, and through the downstream junction 73 to the combustor 14 (i.e., in the second flow path C2, the heater 67 is bypassed). Such flow path switching is realized by opening and closing the three-way valve 72 in response to a control signal from the control device 100.

[0029] Next, a description will be given of a control device 100 for controlling the combined cycle plant 1 having the above configuration.

[0030] The control device 100 is composed of, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads the program into the RAM or the like and executes information processing and arithmetic processing to realize various functions. The program may be installed in a ROM or other storage medium in advance, may be provided in a state stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication means. The computer-readable storage medium may be a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

[0031] As shown in FIG. 3, the control device 100 includes a start-up control unit 102, a temperature detection unit 104, a heater control unit 106, and a flow path switching control unit .

[0032] The startup control unit 102 is configured to start up the combined cycle plant 1. The operation at the time of startup of the combined cycle plant 1 is stored in a storage medium as a sequence program, and a preset startup sequence control is performed by executing the sequence program.

[0033] FIG. 4 is a time chart showing changes in control parameters in each component of the combined cycle plant 1 when the startup sequence control is executed by the startup control unit 102 in FIG.

[0034] In the startup sequence control, first, at time t1, the gas turbine 10 in a cold state is started up. The gas turbine 10 is started up by rotating the gas turbine rotor 19 together with the steam turbine rotor 31 and the generator rotor 46 by the start-up motor 49.

[0035] Next, the startup control unit 102 controls the rotation speed Rg of the gas turbine 10 so as to increase it to a preset reference rotation speed Rref (e.g., rated rotation speed). Fig. 4 shows how the rotation speed Rg of the gas turbine 10 reaches the preset reference rotation speed Rref (e.g., rated rotation speed) from time t1 to time t2. During this time, the combined cycle plant 1 is in an unloaded state.

[0036] When the rotation speed Rg of the gas turbine 10 reaches the reference rotation speed Rref at time t2, the start-up control unit 102 inputs a preset load G0 to the combined cycle plant 1. When a predetermined time has elapsed after the load G0 is reached and a steam supply start condition is satisfied at time t3, steam supply to the steam turbine 30 is started. The steam supply start condition includes, for example, that the temperature difference between the temperature of the steam turbine rotor 31 and the supply steam temperature is lower than a preset value.

[0037] When the supply of steam to the steam turbine is started, the rotation speed Rs of the steam turbine 30 gradually increases. When the rotation speed Rs of the steam turbine 30 reaches the reference rotation speed Rref at time t4, the load G is further increased.

[0038] 3, the temperature detection unit 104 is configured to detect the temperature T of the heat exchange medium M supplied to the heater 67. In this embodiment, the temperature detection unit 104 detects the temperature T of the heat exchange medium M after heat exchange in the heater 67 by the temperature sensor 77 provided at the outlet of the heater 67.

[0039] The heater control unit 106 is configured to control the heater 67. The operation of the heater 67 can be controlled based on the flow rate of the heat exchange medium M supplied to the heater 67. The flow rate of the heat exchange medium M can be adjusted by opening and closing a valve 69 provided on the branch line 68. The flow rate of the heat exchange medium M adjusted by opening and closing the valve 69 may be variable based on the temperature of the heat exchange medium M.

[0040] The flow rate switching control unit 108 is configured to switch the flow path of the fuel F in the fuel supply system 50 to the first flow path C1 or the second flow path C2 by controlling the open / close state of the three-way valve 72, which is a flow path switching mechanism. As will be described later, the flow path switching by the flow path switching control unit 108 is performed based on the temperature of the heat exchange medium M detected by the temperature detection unit 104.

[0041] Next, a control method performed by the control device 100 having the above configuration at the start-up of the combined cycle plant 1 will be described. Fig. 5 is a flowchart showing the control method performed by the control device 100 of Fig. 3, and Figs. 6A to 6C are explanatory diagrams corresponding to each step of Fig. 5.

[0042] First, the start-up control unit 102 of the control device 100 starts the start-up sequence control of the combined cycle plant 1 (step S100). In the start-up sequence control, various controls described above with reference to FIG. 4 are sequentially performed. At a relatively early stage before the rotation speed Rg of the gas turbine 10 reaches the reference rotation speed Rref at time t2, the flow path switching control unit 108 switches the three-way valve 72 so that the flow path of the fuel F becomes the second flow path C2 as the initial flow path of the fuel supply system 50 (step S101). In the second flow path C2 switched in step S101, as shown in FIG. 6A, the fuel F from the upstream fuel supply source (not shown) flows so as to bypass the heater 67 by passing through the bypass line 70 via the fuel supply line 65 and the upstream branch portion. At this time, since the combined cycle plant 1 has just been started, the temperature T of the heat exchange medium M has not risen sufficiently, and the heater 67 cannot perform a sufficient heating function.

[0043] Next, the control device 100 determines whether the rotation speed of the gas turbine 10 reaches the reference rotation speed Rref in the combined cycle plant 1 being started by the start-up sequence control (step S102). In the example of FIG. 4, the rotation speed Rg of the gas turbine 10 is controlled to gradually increase from time t1 to time 2, and at time t2, the rotation speed Rg of the gas turbine 10 reaches the reference rotation speed Rref, causing the gas turbine 10 to enter a full speed no load (FSNL) state. When the rotation speed Rg of the gas turbine 10 reaches the reference rotation speed Rref in this way (step S102: YES), the heater control unit 104 starts supplying the heat exchange medium M to the heater 67 as shown in FIG. 6B (step S103). At this time, the flow path of the fuel F remains the second flow path C2.

[0044] Next, the temperature detection unit 104 detects the temperature T of the heat exchange medium M (step S104), and it is determined whether or not the temperature T is equal to or higher than the reference temperature Tref (step S105). At this time, since a certain amount of time has passed since the start-up sequence control was started in step S100, the temperature of the heat exchange medium M gradually rises as the warm-up progresses. In order for the heater 67 to be in a state where it can heat the fuel F, in addition to the temperature of the heat exchange medium M being sufficiently raised, it is also necessary for the heater 67 to be warmed up (i.e., a warm-up time considering the heat capacity of the heater 67 itself is required). In step S105, the temperature T of the heat exchange medium M flowing out from the heater 67 is compared with a preset reference temperature Tref by the temperature sensor 77 provided at the outlet of the heater 67, and it is determined whether the heater 67 has been sufficiently warmed up to a state suitable for heating the fuel F.

[0045] The reference temperature Tref is set so that the temperature of the fuel F in the first flow path C1 between the pressure regulating valve 74 or the flow rate regulating valve 75 and the strainer 76 is equal to or higher than the melting point of the drain. As a result, switching from the second flow path C2 to the first flow path C1 is performed at a timing when the heating function of the heater 67 can be fully exerted, and by heating the fuel F by the heater 67, it is possible to suitably prevent freezing of the drain downstream.

[0046] When the temperature T becomes equal to or higher than the reference temperature Tref (step S105: YES), the flow path switching control unit 108 switches the three-way valve 72 so that the flow path of the fuel F is changed from the second flow path C2 to the first flow path C1 (step S106). In the first flow path C1, as shown in FIG. 6C, the fuel F flowing through the fuel supply line 65 passes through the heater 67, and is heated by heat exchange with the heat exchange medium M flowing through the branch line 68. Drain may be generated in the fuel F flowing through the fuel supply line 65, and the drain may freeze due to the pressure of the fuel F being reduced when passing through the pressure regulating valve 74 or the flow rate regulating valve 75 on the downstream side, and may cause the strainer 76 to be clogged. In particular, in a heat exchange method such as the heater 67, the fuel F flows through fine tubes to improve the heat exchange efficiency between the fuel F and the heat exchange medium M. In such fine tubes, drain is likely to be generated from the air remaining in the tubes during the shutdown when the plant is restarted.

[0047] In this embodiment, the flow path of the fuel F is switched from the second flow path C2 to the first flow path C1 when the heater 67 is sufficiently able to heat the fuel F. Therefore, since the fuel F that has passed through the heater 67 is sufficiently heated, the drain contained in the fuel F does not freeze even if the fuel F is decompressed when passing through the pressure regulating valve 74 or the flow rate regulating valve 75 on the downstream side. As a result, clogging of the strainer 76 can be suitably prevented.

[0048] Thereafter, the control device 100 determines whether the startup sequence control is completed (step S107). When the startup of the combined cycle plant 1 is confirmed by the completion of the startup sequence control (step S107: YES), the control device 100 transitions to normal operation (step S108).

[0049] FIG. 7 is a modified example of FIG. 2. In this modified example, a plurality of heaters (a first heater 67a and a second heater 67b) are arranged in the fuel supply line 65 instead of the heater 67 in FIG. 2. Both the first heater 67a and the second heater 67b can heat the fuel F flowing through the fuel supply line 65 by heat exchange with the heat exchange medium M, similar to the heater 67 described above. The second heater 67b is arranged downstream of the first heater 67a with respect to the flow of the fuel F. Also, the first heater 67a is arranged downstream of the second heater 67b with respect to the flow of the heat exchange medium M. That is, the plurality of heaters provided in the modified example are arranged such that the heater (the first heater 67a) through which the fuel F passes first is different from the heater (the second heater 67b) through which the heat exchange medium M passes first. In the fuel supply system 50 having such a configuration, when the second flow path C2 is selected as the flow path of the fuel F, the fuel F flowing through the fuel supply line 65 can be heated by the first heater 67a and then further heated in multiple stages by the second heater 67b.

[0050] In the fuel supply system 50 thus including a plurality of heaters, the temperature sensor 77 is provided at the outlet of the heater that is located furthest downstream of the plurality of heaters with respect to the flow of the heat exchange medium M. In this modification, the temperature sensor 77 is provided at the outlet of the second heater 67b that is located downstream of the first heater 67a.

[0051] In this manner, when multiple heaters are provided, the flow path of the fuel F is switched based on the temperature T of the heat exchange medium M at the outlet of the heater located furthest downstream with respect to the flow of the heat exchange medium M. As a result, similar to the above-described embodiment, the fuel F can be supplied to the multiple heaters to heat them at the timing when it is confirmed that the multiple heaters have been warmed up to a degree that allows them to heat the fuel F based on the temperature T. As a result, in a state in which the first flow path C1 is selected as the flow path of the fuel F, it is possible to effectively prevent the drain contained in the fuel F from freezing downstream.

[0052] 7, for ease of explanation, a case where the number of heaters installed in the fuel supply line 65 is two is illustrated, but three or more heaters may be provided in the fuel supply line 65. In this case as well, by installing a temperature sensor 77 at the outlet of the heater located at the most downstream side with respect to the flow of the heat exchange medium M, the flow path switching mechanism can be controlled based on the temperature T detected by the temperature sensor 77, and the same action and effect can be obtained.

[0053] As described above, according to each of the above embodiments, when the temperature T of the heat exchange medium M at the outlet of the heater 67 becomes equal to or higher than the reference temperature Tref, flow path switching from the second flow path C2 to the first flow path C1 is performed at a timing when heating by the heater 67 becomes sufficiently possible. As a result, even if drainage occurs in the fuel F when the fuel F flows through the first flow path C1, the drainage is preferably prevented from freezing downstream due to heating by the heater 67.

[0054] 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.

[0055] The contents described in each of the above embodiments can be understood, for example, as follows.

[0056] (1) A fuel supply system control method according to one aspect includes: a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A fuel supply system control method for controlling a fuel supply system comprising: a first step of controlling the flow path switching unit so that the flow path of the fuel becomes the second flow path at the start of startup of the gas turbine; a second step of starting to supply the heat exchange medium to the at least one heater; a third step of controlling the flow path switching unit so that the flow path of the fuel is switched from the second flow path to the first flow path when a temperature of the heat exchange medium at an outlet of the at least one heater becomes equal to or higher than a preset reference temperature; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; has.

[0057] According to the above aspect (1), when the gas turbine starts up, first, fuel is supplied to the gas turbine via the first flow path. In the first flow path, the fuel passes through the bypass line, thereby bypassing the heater to which the supply of the heat exchange medium has not started. Thereafter (for example, after a predetermined period of time has elapsed since the completion of the first step), the supply of the heat exchange medium to the heater is started. Thereafter, the flow path is switched from the second flow path to the first flow path at a timing when the temperature of the heat exchange medium at the outlet of the heater becomes equal to or higher than a reference temperature, thereby making it possible for the heater to perform heating sufficiently. As a result, even if drainage occurs in the fuel when the fuel flows through the first flow path, the drainage is preferably prevented from freezing downstream due to heating by the heater. In addition, a pressure reducing valve and a strainer are disposed downstream of the junction of the fuel supply line with the bypass line downstream of the heater. When the first flow path is selected as the fuel flow path, the temperature of the fuel passing through the bypass line is reduced by the pressure reducing valve, but as described above, the fuel is sufficiently heated by the heater to prevent the drain contained in the fuel from freezing. This makes it possible to preferably prevent the frozen drain from clogging the strainer.

[0058] Incidentally, the outlet of the heater may be not only a location immediately adjacent to the heater in the system connected downstream of the heater, but also any location where the temperature of the heat exchange medium exiting the heater can be measured. Furthermore, the switching of the fuel flow path from the second flow path to the first flow path in the third step may be performed instantly or gradually. In the latter case, in the third step, the flow paths are switched so that the flow rate of the fuel flowing through the second flow path gradually decreases and the flow rate of the fuel flowing through the first flow path gradually increases. In this case, when the third step is performed, the flow paths are switched so that the fuel flow rate in the first flow path does not immediately become zero, but gradually decreases as the fuel flow rate in the second flow path increases. Such flow path switching can be realized, for example, by using a three-way valve as in the above-mentioned embodiment, but may also be realized by combining it with a normal valve that can be opened and closed.

[0059] (2) In another embodiment, in the above embodiment (1), The reference temperature is set so that the temperature of the fuel in the first flow passage between the pressure reducing valve and the strainer is equal to or higher than the melting point of the drain.

[0060] According to the above aspect (2), the reference temperature, which is the threshold value when the fuel flow path is switched from the second flow path to the first flow path, is set as the temperature of the heat exchange medium on the outlet side of the heater at which the fuel temperature between the pressure reducing valve and the strainer in the first flow path becomes equal to or higher than the melting point of the drain. As a result, the second flow path is switched to the first flow path at a timing when the heating function of the heater can be fully exerted, and by heating the fuel with the heater, freezing of the drain on the downstream side can be suitably prevented.

[0061] (3) In another embodiment, in the above embodiment (1) or (2), the at least one heater includes a plurality of heaters arranged in series with respect to a flow path of the heat exchange medium; The temperature is detected by a temperature sensor provided at the outlet of the heater that is located furthest downstream with respect to the flow of the heat exchange medium among the plurality of heaters.

[0062] According to the above aspect (3), the fuel in the first flow path can be heated by a plurality of heaters arranged in series with respect to the flow path of the heat exchange medium. In this case, the flow path can be switched based on the temperature detected by a temperature sensor installed at the outlet of the heater that is the most downstream of the plurality of heaters with respect to the flow of the heat exchange medium. The outlet of the heater located at the most downstream side may be not only the location immediately adjacent to the heater in the system connected further downstream of the heater located at the most downstream side, but also any location where the temperature of the heat exchange medium exiting the heater can be measured.

[0063] (4) In another embodiment, in any one of the above (1) to (3), the at least one heater includes a plurality of heaters arranged in series with respect to a flow path of the heat exchange medium; The plurality of heaters are arranged such that a heater through which the fuel first passes is different from a heater through which the heat exchange medium first passes.

[0064] According to the above aspect (4), the heaters capable of heating the fuel by heat exchange between the fuel and the heat exchange medium are arranged such that the heater through which the fuel passes first is different from the heater through which the heat exchange medium passes first, thereby making it possible to heat the fuel by the heat exchange medium with good heat exchange efficiency.

[0065] (5) In another embodiment, in any one of the above (1) to (4), The flow path switching mechanism is a three-way valve that is installed in the fuel supply line and is capable of switching between the first flow path and the second flow path.

[0066] According to the above aspect (5), by configuring the flow path switching mechanism using a three-way valve, it is possible to suitably switch between the first flow path and the second flow path while preventing the configuration from becoming complicated.

[0067] (6) In another embodiment, in any one of the above (1) to (5), The heat exchange medium is water supplied from a steam turbine which, together with the gas turbine, constitutes a combined cycle.

[0068] According to the above aspect (6), water supplied from a steam turbine constituting a combined cycle together with a gas turbine can be used as the heat exchange medium supplied to the heater capable of heating the fuel in the first flow passage.

[0069] (7) A fuel supply system control system according to one aspect includes: a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A control unit for controlling the flow path switching unit; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; having The control unit is At the start of startup of the gas turbine, the flow path switching unit is controlled so that the flow path of the fuel becomes the second flow path; After starting the supply of the heat exchange medium to the at least one heater, when the temperature of the heat exchange medium at the outlet of the at least one heater becomes equal to or higher than a predetermined reference temperature, the flow path switching unit is controlled so that the fuel flow path is switched from the second flow path to the first flow path.

[0070] According to the above aspect (7), when the gas turbine starts up, first, fuel is supplied to the gas turbine via the first flow path. In the first flow path, the fuel passes through the bypass line, thereby bypassing the heater to which the supply of the heat exchange medium has not started. Thereafter (for example, after a predetermined period of time has elapsed since the completion of the first step), the supply of the heat exchange medium to the heater is started. Thereafter, the flow path is switched from the second flow path to the first flow path at a timing when the temperature of the heat exchange medium at the outlet of the heater becomes equal to or higher than a reference temperature, thereby making it possible for the heater to perform heating sufficiently. As a result, even if drainage occurs in the fuel when the fuel flows through the first flow path, the drainage is preferably prevented from freezing downstream due to heating by the heater. In addition, a pressure reducing valve and a strainer are disposed downstream of the junction of the fuel supply line with the bypass line downstream of the heater. When the first flow path is selected as the fuel flow path, the temperature of the fuel passing through the bypass line is reduced by the pressure reducing valve, but as described above, the fuel is sufficiently heated by the heater to prevent the drain contained in the fuel from freezing. This makes it possible to preferably prevent the frozen drain from clogging the strainer.

[0071] Incidentally, the outlet of the heater may be not only a location immediately adjacent to the heater in the system connected downstream of the heater, but also any location where the temperature of the heat exchange medium exiting the heater can be measured. Furthermore, the switching of the fuel flow path from the second flow path to the first flow path may be performed instantly or gradually. In the latter case, in the third step, the flow paths are switched so that the flow rate of the fuel flowing through the second flow path gradually decreases and the flow rate of the fuel flowing through the first flow path gradually increases. In this case, when the third step is performed, the flow paths are switched so that the fuel flow rate in the first flow path does not immediately become zero, but gradually decreases as the fuel flow rate in the second flow path increases. Such flow path switching can be realized, for example, by using a three-way valve as in the above-mentioned embodiment, but may also be realized by combining it with a normal valve that can be opened and closed. [Explanation of symbols]

[0072] 1. Combined cycle plant 10. Gas Turbine 11 Compressor 12 Compressor rotor 13 Compressor casing 14 Combustor 15 Turbine 16 Turbine rotor 19 Gas turbine rotor 20. Waste heat recovery boiler 21 Economizer 22 Evaporator 22a Drum 23 Superheater 30 Steam Turbine 31 Steam turbine rotor 32 Rotor shaft 33 Moving blade row 34 Turbine casing 36 Stator blade row 40 Condenser 45 Generator 46 Generator rotor 47 Generator casing 49 Starting motor 50 Fuel supply system 60 Connection Line 63 External system 65 Fuel supply line 67 Heater 68 Branch Line 69 Pump 70 Bypass Line 71 Upstream branch 72 Three-way valve 73 Downstream confluence 74 Pressure Regulating Valve 75 Flow control valve 76 Strainer 76 Water Pump 77 Temperature Sensor 78 Shut-off valve 79 Regulating valve 81 Main Steam Line 88 Boiler water discharge line 89 Exhaust valve 100 Control device 102 Start control section 104 Temperature detection unit 106 Heater control unit 108 Flow path switching control unit

Claims

1. a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A fuel supply system control method for controlling a fuel supply system comprising: a first step of controlling the flow path switching unit at the start of startup of the gas turbine so that a flow path of the fuel becomes the second flow path; a second step of starting to supply the heat exchange medium to the at least one heater; a third step of controlling the flow path switching unit so that a flow path of the fuel is switched from the second flow path to the first flow path when a temperature of the heat exchange medium at an outlet of the at least one heater becomes equal to or higher than a preset reference temperature; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; A fuel supply system control method comprising the steps of:

2. 2. The fuel supply system control method according to claim 1, wherein the reference temperature is set so that a temperature of the fuel in the first passage between the pressure reducing valve and the strainer is equal to or higher than a melting point of the drain.

3. the at least one heater includes a plurality of heaters arranged in series with respect to a flow path of the heat exchange medium; 3. The fuel supply system control method according to claim 1, wherein the temperature is detected by a temperature sensor provided at an outlet of a heater that is located furthest downstream with respect to a flow of the heat exchange medium among the plurality of heaters.

4. the at least one heater includes a plurality of heaters arranged in series with respect to a flow path of the heat exchange medium; 3. The fuel supply system control method according to claim 1, wherein the plurality of heaters are arranged such that a heater through which the fuel passes first is different from a heater through which the heat exchange medium passes first.

5. 3. The fuel supply system control method according to claim 1, wherein the flow path switching mechanism is a three-way valve that is installed in the fuel supply line and is capable of switching between the first flow path and the second flow path.

6. 3. The fuel supply system control method according to claim 1, wherein the heat exchange medium is water supplied from a steam turbine which constitutes a combined cycle together with the gas turbine.

7. a fuel supply line for supplying fuel to the gas turbine; at least one heater in the fuel supply line for heating the fuel by heat exchange with a heat exchange medium; a bypass line connected to the fuel supply line to bypass the at least one heater; a flow path switching unit for switching between a first flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the at least one heater and a second flow path in which the fuel flowing through the fuel supply line is supplied to the gas turbine via the bypass line; A control unit for controlling the flow path switching unit; Equipped with The fuel supply line includes: a pressure reducing valve provided downstream of a junction with the bypass line downstream of the at least one heater; A strainer provided downstream of the pressure reducing valve; having The control unit is At the start of startup of the gas turbine, the flow path switching unit is controlled so that the flow path of the fuel becomes the second flow path; a flow path switching unit that controls the flow path switching unit so that the fuel flow path is switched from the second flow path to the first flow path when a temperature of the heat exchange medium at an outlet of the at least one heater becomes equal to or higher than a predetermined reference temperature after starting the supply of the heat exchange medium to the at least one heater.

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