Method of pressurizing fuel heating system

Abstract

To suitably pressurize various lines through which pressurized water exchanging heat with fuel by a fuel heater flows.SOLUTION: A fuel heating system comprises: a first fuel heater provided in a first water supply line to heat fuel to be supplied to a gas turbine; and a second fuel heater connected to a second water supply part and provided in a second water supply line merging with an upstream side of the first fuel heater to heat fuel at a downstream side of the first fuel heater. An upstream valve is provided between the second water supply part and the second fuel heater, and a first intermediate valve is provided between the second fuel heater and a merging part. A downstream valve is provided on the opposite side of the merging part when viewed from the first fuel heater in the first water supply line. The fuel heating system is pressurized by the following pressurizing method. The second water supply line is pressurized by second water supply at a position between the upstream valve and the first intermediate valve in a closed state of the upstream valve. Thereafter, the first intermediate valve is opened, and the second water supply line is pressurized on a position between the upstream valve and the downstream valve by first water supply in a closed state of the upstream valve and the downstream valve. Thereafter, the first intermediate valve is closed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for charging a fuel heating system. [Background technology]

[0002] There is a gas turbine that can drive the turbine with combustion gas generated by burning fuel. It is known that the operating state of a gas turbine is affected by the temperature of the fuel supplied to the gas turbine. For this reason, some fuel supply systems of gas turbines are equipped with a fuel heating system for heating the fuel as a means for adjusting the temperature of the fuel to a temperature suitable for the operation of the gas turbine.

[0003] For example, Patent Document 1 discloses a configuration in which a fuel heating system for heating fuel is provided in a fuel supply line for supplying fuel to a gas turbine. In this document, water heated by a boiler or the like is supplied to the fuel heating system, and the fuel can be heated by exchanging heat between the fuel and the heated feedwater. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-286864 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a fuel heating system capable of heating fuel by heat exchange with feedwater as in Patent Document 1, it is necessary to pressurize the various lines through which the feedwater passes in advance to correspond to the design pressure before heating the fuel. The process of pressurizing the various lines is performed in cooperation with the feedwater supply system and the opening and closing of the valves provided in the various lines through which the feedwater passes. However, depending on the order in which these valves are opened and closed, a large pressure difference may be applied to a specific valve, causing a feedwater leak. Such a feedwater leak may cause a malfunction, such as unintentionally activating a safety valve provided in the various lines.

[0006] At least one embodiment of the present disclosure has been developed in consideration of the above-mentioned circumstances, and aims to provide a method for pressurizing a fuel heating system that can appropriately pressurize each line through which feedwater passes when it is heat exchanged with fuel in the fuel heating system. [Means for solving the problem]

[0007] In order to solve the above problem, a method for charging a fuel heating system according to at least one embodiment of the present disclosure includes: A first water supply unit capable of supplying a first water supply; A second water supply unit capable of supplying a second water supply having a higher pressure than the first water supply; a first fuel heater provided in a first feedwater line connected to the first feedwater section for heating fuel flowing through a fuel supply line connected to a gas turbine; a second fuel heater connected to the second water supply section and provided in a second feedwater line that joins the first feedwater line upstream of the first fuel heater, for heating the fuel downstream of the first fuel heater with respect to the fuel supply line; an upstream valve provided in the second feedwater line between the second feedwater section and the second fuel heater; a first intermediate valve provided in the second feedwater line between the second fuel heater and the junction; a downstream valve provided on the first feedwater line on an opposite side of the junction as viewed from the first fuel heater; A method for charging a fuel heating system comprising: a high pressurization step of pressurizing the second water supply line between the upstream valve and the second water supply line with the second water supply from the second water supply section while the upstream valve is closed; a low pressure filling step of filling a space between the upstream valve and the downstream valve with the first supply water from the first water supply section while opening the first intermediate valve and closing the upstream valve and the downstream valve; a filling completion step of closing the first intermediate valve; Equipped with. Effect of the Invention

[0008] According to at least one embodiment of the present disclosure, it is possible to provide a method for pressurizing a fuel heating system that can appropriately pressurize various lines through which feedwater passes while being heat exchanged with fuel in a fuel heater. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a combined cycle plant according to an embodiment. FIG. [Diagram 2] FIG. 2 is a configuration diagram of the fuel heating system of FIG. [Diagram 3] FIG. 3 is a block diagram of the control device of FIG. 2. [Figure 4] FIG. 4 is an explanatory diagram of a pressure charging process of a fuel heating system according to a reference technology. [Diagram 5] 4 is a flowchart showing steps of a pressure charging process performed 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 6D] 6 is an explanatory diagram corresponding to each step in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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.

[0011] First, a configuration of a combined cycle plant 1 including a fuel heating system 80 according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of the combined cycle plant 1 according to one embodiment, and Fig. 2 is a configuration diagram of the fuel heating system 80 in Fig. 1.

[0012] The combined cycle plant 1 includes a gas turbine 10, a heat recovery boiler 20 for generating steam using exhaust gas EG from the gas turbine 10, a steam turbine 60 that can be driven by steam from the heat recovery boiler 20, and a condenser 40 for converting the steam from the steam turbine 60 back into water.

[0013] The gas turbine 10 includes a compressor 11 for compressing combustion air, and a turbine 15 driven by combustion gas generated by mixing and burning the combustion air compressed by the compressor 11 with fuel supplied from a fuel supply system. The rotors of the compressor 11 and the turbine 15 are connected to each other to form a gas turbine rotor 19.

[0014] The steam turbine 60 includes a high-pressure steam turbine HP, an intermediate-pressure steam turbine IP, and a low-pressure steam turbine LP. The high-pressure steam turbine HP, the intermediate-pressure steam turbine IP, and the low-pressure steam turbine LP have their respective rotating shafts connected to one another to form a steam turbine rotor 61. The steam turbine rotor 61 is integrally connected to the gas turbine rotor 19 described above. The steam that has completed its work in the steam turbine 60 is returned to condensation in the condenser 40.

[0015] The condensate from the condenser 40 can be supplied to the heat recovery boiler 20 via a condensate supply line 62. A low-pressure feed water pump 63 is provided in the condensate supply line 62, making it possible to adjust the amount of condensate supplied to the heat recovery boiler 20. In addition, a superheater 64 is provided on the condensate supply line 62 downstream of the low-pressure feed water pump 63, making it possible to adjust the temperature of the water supplied to the heat recovery boiler 20.

[0016] A make-up water tank 42 is connected to the condenser 40 via a make-up water supply line 41. A make-up water supply pump 43 is installed in the make-up water supply line 41, so that make-up water can be supplied from the make-up water tank 42 when the condenser 40 runs short of condensed water.

[0017] The heat recovery boiler 20 has a configuration for recovering and effectively utilizing heat (exhaust heat) contained in the exhaust gas EG from the gas turbine 10. The heat recovery boiler 20 includes a low-pressure economizer 21, a low-pressure evaporator 22, a high-pressure primary economizer 23, an intermediate-pressure economizer 24, an intermediate-pressure evaporator 25, a low-pressure superheater 26, a high-pressure secondary economizer 27, an intermediate-pressure superheater 28, a high-pressure evaporator 29, a high-pressure primary superheater 30, a primary reheater 31, a secondary reheater 32, and a high-pressure secondary superheater 33 as components for utilizing the heat recovered from the exhaust gas EG.

[0018] The exhaust gas from which heat has been recovered in the heat recovery steam generator 20 is discharged to the outside through a chimney 34.

[0019] In the heat recovery boiler 20, the feed water (condensate) from the condenser 40 is first heated by the low-pressure economizer 21. At least a portion of the feed water heated by the low-pressure economizer 21 is stored in the low-pressure drum 44. The low-pressure evaporator 22 is connected to the low-pressure drum 44, and steam can be generated from at least a portion of the water stored in the low-pressure drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure drum 44.

[0020] Furthermore, the feedwater heated by the low-pressure economizer 21 is supplied to a high-pressure feedwater pump 45 and a medium-pressure feedwater pump 46. The medium-pressure feedwater pump 46 pressurizes the feedwater to a first pressure P1, and the high-pressure feedwater pump 45 pressurizes the feedwater to a second pressure P2 (>first pressure P1). The feedwater pressurized to the second pressure P2 by the high-pressure feedwater pump 45 is heated by the high-pressure primary economizer 23 and the high-pressure secondary economizer 27, and then supplied to the high-pressure drum 47. The feedwater pressurized to the first pressure P1 by the medium-pressure feedwater pump 46 is heated by the medium-pressure economizer 24, and then supplied to the medium-pressure drum 48. The high pressure water supply pump 45 and the medium pressure water supply pump 46 may be integrally constructed.

[0021] The high-pressure evaporator 29 is connected to the high-pressure drum 47, and steam can be generated from at least a portion of the water stored in the high-pressure drum 47. The steam generated in the high-pressure evaporator 29 is returned to the high-pressure drum 47. The steam extracted from the high-pressure drum 47 is superheated by the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, and supplied to the high-pressure steam turbine HP. A attenuator 49a is provided between the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, and by controlling the amount of attenuation in the attenuator 49a, the steam temperature supplied to the high-pressure steam turbine HP can be appropriately adjusted.

[0022] The steam that has completed its work in the high-pressure steam turbine HP is heated by the primary reheater 31 and the secondary reheater 32, and is then supplied to the intermediate-pressure steam turbine IP. A desuperheater 49b is provided between the primary reheater 31 and the secondary reheater 32, and by controlling the amount of desuperheat in the desuperheater 49b, the steam temperature supplied to the intermediate-pressure steam turbine IP can be appropriately adjusted.

[0023] The intermediate-pressure evaporator 25 is connected to the intermediate-pressure drum 48, and is capable of generating steam from at least a portion of the water stored in the intermediate-pressure drum 48. The steam generated in the intermediate-pressure evaporator 25 is returned to the intermediate-pressure drum 48. A portion of the steam extracted from the intermediate-pressure drum 48 is heated by the intermediate-pressure superheater 28, and supplied to an outlet flow passage of the high-pressure steam turbine HP, and then supplied to the intermediate-pressure steam turbine IP.

[0024] The low-pressure evaporator 22 is connected to the low-pressure drum 44, and steam can be generated from at least a portion of the water stored in the low-pressure drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure drum 44. A portion of the steam extracted from the low-pressure drum 44 is heated by the low-pressure superheater 26 and supplied to an outlet flow passage of the intermediate-pressure steam turbine IP, and then supplied to the low-pressure steam turbine LP. The steam that has completed work in the low-pressure steam turbine LP is returned to the condenser 40.

[0025] The combined cycle plant 1 having the above configuration includes a fuel supply system 70 for supplying fuel F from a fuel supply source 72 to the gas turbine 10. The gas turbine 10 has a combustor 12 capable of generating combustion gas for driving the gas turbine 10 by mixing the fuel F supplied from the fuel supply system 70 with combustion air compressed by a compressor 11 and combusting the fuel (in FIG. 1, the combustor 12 is shown at a position away from the gas turbine 10 for ease of illustration). FIG. 1 shows a fuel supply line 71 through which the fuel F supplied to the combustor 12 of the fuel supply system 70 flows. The fuel supply line 71 may be provided with a flow rate adjustment valve for adjusting the flow rate of the fuel F supplied to the combustor 12 and a shutoff valve for shutting off the fuel F.

[0026] The fuel supply system 70 includes a fuel heating system 80 for heating the fuel F flowing through the fuel supply line 71. As shown in Fig. 1 and Fig. 2, the fuel heating system 80 includes a first water supply section 81, a second water supply section 82, a first fuel heater 83, and a second fuel heater 84.

[0027] The first feedwater section 81 is configured to supply first feedwater HW1 to the fuel heating system 80. In this embodiment, the first feedwater section 81 can supply the first feedwater HW1 having a first pressure P1 to the first fuel heater 83 via a first feedwater line 85 branching off from a steam line connecting the medium-pressure economizer 24 and the medium-pressure drum 48 of the heat recovery boiler 20. The first feedwater line 85 is connected to merge with the condensate supply line 62 downstream of the first fuel heater 83.

[0028] The second feedwater section 82 is configured to supply second feedwater HW2 to the fuel heating system 80. In this embodiment, the second feedwater section 82 can supply the second feedwater HW2 having a second pressure P2 (>first pressure P1) to the second fuel heater 84 via a second feedwater line 86 branching off from a steam line connecting the high-pressure secondary economizer 27 and the high-pressure drum 47 of the heat recovery boiler 20. The second feedwater line 86 is connected to join at a joining section 87 provided midway through the first feedwater line 85.

[0029] The first fuel heater 83 and the second fuel heater 84 are components for heating the fuel F flowing through the fuel supply line 71. The first fuel heater 83 is provided in the first feedwater line 85, and can heat the fuel F flowing through the fuel supply line 71 by heat exchange with the first feedwater HW1 flowing through the first feedwater line 85 and / or the second feedwater HW2 that merges with the first feedwater line 85 from the second feedwater line 86. The second fuel heater 84 is provided in the second feedwater line 86, and can heat the fuel F flowing through the fuel supply line 71 by heat exchange with the second feedwater HW2 flowing through the second feedwater line 86. The second fuel heater 84 is provided downstream of the first fuel heater 83 with respect to the fuel F flowing through the fuel supply line 71, and is thereby able to further heat the fuel F heated by the first fuel heater 83.

[0030] A first valve V1, which is an upstream valve, is provided in the second feedwater line 86 between the second feedwater section 82 and the second fuel heater 84. A second valve V2 and a third valve V3, which are first intermediate valves, are provided in the second feedwater line 86 between the second fuel heater 84 and the junction 87. A fourth valve V4, which is a second intermediate valve, is provided in the first feedwater line 85 between the junction 87 and the first fuel heater 83. This fourth valve V4 includes a main valve V4a and an auxiliary valve V4b provided in parallel with each other. A fifth valve V5 and a sixth valve V6, which are downstream valves, are provided in the first feedwater line 85 on the opposite side of the junction 87 from the first fuel heater 83. Furthermore, as shown in FIG. 1, the second feed water line 86 downstream of the sixth valve V6 is merged with the condensate supply line 62, so that the heated water after heat exchange with the fuel F in the fuel heating system 80 is returned to the condensate supply line 62.

[0031] In the fuel heating system 80 having the above configuration, the first feedwater line 85 has a first pressure design value PS1 corresponding to the first pressure P1 of the first feedwater HW1 supplied from the first feedwater section 81. The first pressure design value PS1 is set to include a sufficient margin with respect to the first pressure P1, thereby preventing malfunctions such as breakage and damage during operation.

[0032] Further, the second supply water line 86 has a second pressure design value PS2 corresponding to the second pressure P2 of the second supply water HW2 supplied from the second supply water section 82. The second pressure design value PS2 is set with a sufficient margin with respect to the second pressure P2, thereby preventing malfunctions such as breakage and damage during operation. As described above, since the second pressure P2 is greater than the first pressure P1, the second pressure design value PS2 is also set greater than the first pressure design value PS1.

[0033] In the fuel heating system 80 having the above configuration, at a stage where the waste heat of the exhaust gas EG from the gas turbine 10 becomes available, the first feedwater HW1 heated by the waste heat of the gas turbine 10 or the second feedwater HW2 heated by the waste heat of the gas turbine 10 is supplied from the first feedwater section 81 and the second feedwater section 82 to the first feedwater line 85 and the second feedwater line 86, respectively, to heat the fuel F. In the fuel heating system 80, as a preliminary preparation for carrying out such a heating operation, it is necessary to carry out a pressurizing process in which the first feedwater line 85 and the second feedwater line 86 are brought to a predetermined pressure by supplying water. Note that the pressurizing process may be carried out before the start-up of the gas turbine 10, and it is not necessarily necessary that the waste heat of the gas turbine 10 is available. In other words, in the pressurizing process, the first feedwater HW1 and the second feedwater HW1 do not have to be heated in the high-pressure primary economizer 23, the high-pressure secondary economizer 27, or the intermediate pressure economizer 24. However, even before the gas turbine 10 is started, the first water supply section 81 is capable of supplying feedwater pressurized to the second pressure P2 by the high-pressure feedwater pump 45, and the second water supply section 82 is capable of supplying feedwater pressurized to the first pressure P1 by the medium-pressure feedwater pump 46.

[0034] Such a charging process is performed by the control device 100 by controlling the fuel heating system 80. 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. In this embodiment, the case where the operation of the fuel heating system 80 is automatically controlled by the control device 100 is illustrated, but the same operation may be performed manually by an operator or the like.

[0035] Fig. 3 is a block diagram of the control device 100 of Fig. 2. The control device 100 includes a valve control unit 102, a first water supply control unit 104, and a second water supply control unit 106.

[0036] The valve control unit 102 is configured to control the open / closed state of each valve (the above-mentioned first valve V1 to sixth valve V6) provided in the fuel heating system 80. The first feedwater control unit 104 is configured to control the supply state of the first feedwater HW1 from the first feedwater section 81. The second feedwater control unit 106 is configured to control the supply state of the second feedwater HW2 from the second feedwater section 82. The control device 100 is capable of carrying out the pressurization process by controlling each of these components in cooperation with each other.

[0037] Next, a description will be given of a charging process performed by the control device 100 having the above configuration. First, a reference technique for the charging process performed by the control device 100 will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram of the charging process of a fuel heating system 80 according to the reference technique.

[0038] In the reference technology, a high pressure charging step and a low pressure charging step are respectively performed by the control device 100 before start-up of the gas turbine 10. These steps are performed by cooperation between the opening and closing operations of each valve by the valve control unit 102 and the supply operations of the first feedwater HW1 and the second feedwater HW2 by the first feedwater control unit 104 and the second feedwater control unit 106.

[0039] Specifically, in the pressurization process of the reference technology, the third valve V3 is first closed. In this state, the second water supply control unit 106 supplies the second water supply HW2 from the second water supply unit 82, thereby carrying out a high pressurization step. At this time, since the first valve V1 and the second valve V2 are open, the second water supply HW2 supplied from the second water supply unit 82 pressurizes the second water supply line 86 between the second water supply unit and the third valve V3 (high pressurization range RH) to the second pressure P2 (in FIG. 4, the high pressurization range RH is indicated by a thick line).

[0040] Next, the sixth valve V6 is closed. In this state, the first water supply HW1 is supplied from the first water supply section 81, thereby carrying out a low pressure charging step. At this time, since the fourth valve V4 and the fifth valve V5 are open, the first water supply HW1 supplied from the first water supply section 81 charges the first water supply line 85 between the first water supply section 81 and the sixth valve V6, and the second water supply line 86 between the third valve V3 and the junction section 87 (low pressure charging range RL) to the first pressure P1 (<second pressure P2) (in FIG. 4, the low pressure charging range RL is indicated by a dashed line).

[0041] In this way, when the charging process is completed in the reference technology, a high charging range RH and a low charging range RL are formed as shown in Fig. 4. At this time, the high charging range RH and the low charging range RL are formed with the third valve V3 as the boundary, so a large pressure difference is applied to the third valve V3, and there is a risk of leakage. If leakage occurs in the third valve V3, heated water flows from the high charging range RH to the low charging range RL. For example, if there is a safety valve in the low charging range RL, this may cause a malfunction such as the safety valve being unintentionally activated. Such a problem can be suitably solved by the control method according to the present embodiment described below.

[0042] Next, the charging process performed by the control device 100 according to this embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a flow chart showing each step of the charging process performed by the control device 100 of Fig. 3, and Figs. 6A to 6D are explanatory diagrams corresponding to each step of Fig. 5.

[0043] When the filling process is carried out, the fuel heating system 80 is filled with water as a preliminary preparation. The filling process is a process for distributing the feed water supplied through at least one of the first water supply section 81 or the second water supply section 82 to the first water supply line 85 and the second water supply line 86. However, since the filling process is carried out before the filling process, the pressure of the feed water supplied through the first water supply line 85 and the second water supply line 86 may be lower than the pressure of the first water supply HW1 and the second water supply HW2. In the following description, the state in which such filling has been carried out in advance is described as the initial state.

[0044] 6A, in the fuel heating system 80, the first valve V1 to the fifth valve V5 are closed, and the sixth valve V6 is controlled to a minimum opening (step S100). Then, the fifth valve V5 is opened, and the high-pressure feedwater pump 45 and the medium-pressure feedwater pump 46 are started (step S101). This causes the first feedwater section 81 and the second feedwater section 82 to start supplying the first feedwater HW1 and the second feedwater HW2, respectively.

[0045] At this time, second supply water HW2 is supplied from the second supply water section 82 to the second supply water line 86 between the second supply water section 82 and the first valve V1, which is the upstream valve (high charging range RH). Such supply of the second supply water HW2 is performed so that the pressure in the high charging range RH becomes the high charging target value Pt2 set corresponding to the second pressure design value PS2. The pressure in the high charging range RH can be detected by a pressure sensor (not shown) installed in that range.

[0046] Next, as shown in Fig. 6B, the sixth valve V6 is closed and the auxiliary valve V4b of the fourth valve V4 is opened (step S102). As a result, the area (preliminary charging range RS) between the third valve V6, which is the first intermediate valve, and the sixth valve V6, which is the downstream valve, is preliminarily charged by the first water supply HW1 from the first water supply section 81 (the preliminary sub-pressure range RS is shown by a dashed line in Fig. 6B). Such preliminary charging by the first water supply HW1 is performed so that the pressure in the preliminary charging range RS becomes the preliminary charging target value Pt3. The preliminary charging target value Pt3 is set lower than the low charging target value Pt1 (< the high charging target value Pt2) set corresponding to the first pressure design value PS1. As a result, the pressure in the preliminary charging range RS at the completion of the preliminary charging step is lower than that at the completion of the low charging step described below. The pressure in the preliminary charging range RS can be detected by a pressure sensor (not shown) installed in that range.

[0047] Next, when the pressure in the preliminary charging range RS reaches the preliminary charging target value Pt3 (step S103: YES), as shown in FIG. 6C, the second valve V2 and the third valve V3, which are intermediate valves, and the main valve V4a of the fourth valve, which is the second intermediate valve, are opened (step S104). As a result, the area (low charging range RL) between the first valve V1, which is the upstream valve, and the sixth valve V6, which is the downstream valve, is low-pressurized by the first water supply HW1 from the first water supply unit 81 (the low charging range RL is shown by a broken line in FIG. 6C). Such low charging by the first water supply HW1 continues until the pressure in the low charging range RL reaches the low charging target value Pt1 (< the high charging target value Pt2). The low charging target value Pt1 is set corresponding to the first pressure design value PS1, and is set to be larger than the preliminary charging target value Pt3 and smaller than the high charging target value Pt2. The pressure in the low charging range RL can be detected by a pressure sensor (not shown) installed in that range.

[0048] In the above-mentioned preliminary filling step, only the sub-valve V4b of the fourth valve V4 is opened to fill the tank to a relatively low preliminary filling target value Pt3, but in the low filling step performed thereafter, the main valve V4a is also opened. In this manner, by changing the flow rate of the heated water passing through the fourth valve V4 so as to increase stepwise, low filling to a low filling target value Pt1 that is larger than the preliminary filling target value Pt3 can be suitably performed.

[0049] In this way, before the low filling step of filling to the low filling range RL, a preliminary filling step of preliminary filling to a preliminary filling range RS, which is a part of the low filling range RL, is performed. This makes it possible to perform high-quality filling with the first water supply HW1, for example, by preventing a situation in which the first water supply HW1 does not reach a part of the range when the low filling step is performed after the preliminary filling step.

[0050] In this embodiment, the range from the third valve V3 to the sixth valve V6 is used as the preliminary charging range RS, but other ranges may be used. The preliminary charging range RS is not limited to a part of the low charging range RL, and may be, for example, the preliminary charging range RS may be a range from the first valve V1 to the fourth valve V4, which is the second intermediate valve. In this case, during the preliminary charging step, the first water supply HW1 is supplied from the first water supply section 82 with the first valve V1 and the fourth valve V4 (main valve 4a and sub-valve 4b) closed, thereby performing preliminary charging.

[0051] Next, when the low charging range RL reaches the low charging target value Pt1 (step S105: YES), after a predetermined period of time has elapsed (step S106), the second valve V2 and the third valve V3, which are the first intermediate valves, are closed (step S107) as shown in Fig. 6D. This completes a series of charging processes.

[0052] When this series of steps is completed, the upstream valve, the first valve V1, is filled with the first feed water HW1 and the second feed water HW2, respectively. Therefore, the first valve V1 is subjected to the differential pressure between the first feed water HW1 and the second feed water HW2, and even if a leak occurs in the first valve V1 based on this differential pressure, the first intermediate valves, the second valve V2 and the third valve V3, are in a closed state, so that the effect of the leak extends downstream of the second valve V2 and the third valve V3, effectively preventing malfunctions such as the operation of a safety valve installed in that range.

[0053] Furthermore, such a process of filling the heated water with pressure may be performed before fuel F is supplied to first fuel heater 83 and second fuel heater 84. In other words, at the stage of filling each pressurized water supply line of fuel heating system 80, fuel F is not supplied to fuel supply line 71 heating system. At the stage of supplying fuel F to fuel supply line 71, each pressurized water supply line of the fuel heating system is pressurized. Therefore, even if fuel F leaks from fuel supply line 71, the leaked fuel F can be prevented from entering the various supply lines through which feed water flows.

[0054] As described above, according to each of the above embodiments, it is possible to appropriately pressurize various lines through which the heated water that exchanges heat with the fuel F in the fuel heating system 80 passes.

[0055] At a first timing during or after the start-up of the gas turbine 10, the fourth valve V4, the fifth valve V5, and the sixth valve V5 are opened, and the heated first feedwater HW1 is supplied to the first fuel heater 83 to heat the fuel F. At a second timing during or after the start-up of the gas turbine 10 (which may be different from or the same as the first timing), the first valve V1, the second valve V2, and the third valve V3 are opened, and the heated second feedwater HW2 is supplied to the second fuel heater 84 to heat the fuel F. As described above, since the charging process is performed in advance, it is possible to flow the feedwater at an appropriate flow rate and flow velocity when each valve is opened, and the risk of valve damage, failure, and the like can be suppressed.

[0056] 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.

[0057] The contents described in each of the above embodiments can be understood, for example, as follows.

[0058] (1) In one aspect, a method of operating a fuel heating system includes: A first water supply unit capable of supplying a first water supply; A second water supply unit capable of supplying a second water supply having a higher pressure than the first water supply; a first fuel heater provided in a first feedwater line connected to the first feedwater section for heating fuel flowing through a fuel supply line connected to a gas turbine; a second fuel heater connected to the second water supply section and provided in a second feedwater line that joins the first feedwater line upstream of the first fuel heater, for heating the fuel downstream of the first fuel heater with respect to the fuel supply line; an upstream valve provided in the second feedwater line between the second feedwater section and the second fuel heater; a first intermediate valve provided in the second feedwater line between the second fuel heater and the junction; a downstream valve provided on the first feedwater line on an opposite side of the junction as viewed from the first fuel heater; A method for charging a fuel heating system comprising: a high pressurization step of pressurizing the second water supply line between the upstream valve and the second water supply line with the second water supply from the second water supply section while the upstream valve is closed; a low pressure filling step of filling a space between the upstream valve and the downstream valve with the first supply water from the first water supply section while opening the first intermediate valve and closing the upstream valve and the downstream valve; a filling completion step of closing the first intermediate valve; Equipped with.

[0059] According to the above aspect (1), in the high pressurization step, the second feedwater is supplied from the second water supply section with the upstream valve closed. As a result, the second feedwater line between the second water supply section and the upstream valve is pressurized with the second feedwater having a relatively high pressure. In the subsequent low pressurization step, the first intermediate valve is opened and the upstream valve and downstream valve are closed with the first feedwater being supplied from the first water supply section. As a result, the area between the upstream valve and the downstream valve is pressurized with the first feedwater having a relatively low pressure. When the high pressurization step and the low pressurization step are completed in this manner, the first intermediate valve is closed.

[0060] When each of these steps is completed, the upstream valve is pressurized with the first feedwater and the second feedwater, respectively, so that the upstream valve is subjected to the differential pressure between the first feedwater and the second feedwater, but even if a leak occurs in the upstream valve, the first intermediate valve is in a closed state, so that the effect of the leak extends downstream of the first intermediate valve, effectively preventing problems such as the operation of a safety valve installed in that range. In this way, each line for supplying heated water to the fuel heating system can be suitably pressurized.

[0061] (2) In another embodiment, in the above embodiment (1), The method further includes a pre-pressurization step of closing the first intermediate valve and closing the downstream valve before the low pressurization step, and filling a pre-pressurization range between the first intermediate valve and the downstream valve with the first water supply from the first water supply section while keeping the first intermediate valve and the downstream valve closed.

[0062] According to the above aspect (2), a preliminary filling step is performed before the low filling step. In the preliminary filling step, the first intermediate valve is closed and the downstream valve is closed, and the first feed water is supplied from the first water supply section. As a result, the preliminary filling range between the first intermediate valve and the downstream valve is pre-pressurized by the first feed water. In this manner, in the preliminary filling step, a part of the range that is filled by the first feed water in the low filling step is pre-pressurized. As a result, when the low filling step is performed after the preliminary filling step, it is possible to perform high-quality filling by the first feed water, for example, to prevent a situation in which the first feed water does not reach a part of the range.

[0063] (3) In another embodiment, in the above embodiment (2), The pressure in the pre-charging range at the completion of the pre-charging step is lower than that at the completion of the low-charging step.

[0064] According to the above aspect (3), in the preliminary filling step, filling with the first water supply is performed so that the pressure in the preliminary filling range is lower than that in the low filling step. By performing the preliminary filling step before the low filling step in this manner, filling with the first water supply in the low filling step can be performed with good quality.

[0065] (4) In another embodiment, in the above embodiment (2) or (3), the fuel heating system further includes a second intermediate valve provided in the first feedwater line between the junction and the first fuel heater, The second intermediate valve includes a main valve and a sub-valve that are provided in parallel with each other on the first water supply line, The preliminary charging step is performed in a state where the main valve is closed and the sub-valve is opened, The low pressure charging step is performed with the main valve and the sub-valve open.

[0066] According to the above aspect (4), in the preliminary filling step, preliminary filling is performed at a relatively low pressure by the first water supply from the first water supply section by opening only the sub-valve constituting the second intermediate valve. In the subsequent low pressure filling step, filling can be performed at a pressure higher than that of the preliminary filling by opening both the main valve and the sub-valve constituting the second intermediate valve.

[0067] (5) In another embodiment, in any one of the above (1) to (4), The high and low pressure charging steps are performed before the fuel is supplied to the first and second fuel heaters.

[0068] According to the above aspect (5), the high pressure filling step and the low pressure filling step are performed before the fuel to be heated is supplied to each fuel heater. As a result, at the stage of pressurizing each line of the fuel heating system, fuel is not supplied to the fuel heating system. Even if fuel leakage occurs in these fuel heaters, the leaking fuel can be prevented from entering the various lines through which heated water flows.

[0069] (6) In another embodiment, in any one of the above (1) to (5), The first water supply unit includes a first water supply pump for pressurizing the water supply, The second water supply section is A second feed water pump for pressurizing the feed water to a higher pressure than the first feed water pump. Equipped with.

[0070] According to the above aspect (6), the first feedwater supplied by the first feedwater supply unit is pressurized by the first feedwater pump. The second feedwater supplied by the second feedwater supply unit is pressurized by the second feedwater pump to a higher pressure than that of the first feedwater pump.

[0071] (7) In another embodiment, in any one of the above (1) to (6), The second supply water line has a design pressure higher than that of the first intermediate valve on the upstream side thereof and than that of the first supply water line and that of the second supply water line on the downstream side thereof.

[0072] According to the above aspect (7), the first feedwater line and the second feedwater line of the fuel heating system are designed to have different design pressures with the first intermediate valve as a boundary. In the fuel heating system having such a configuration, by carrying out each of the above-mentioned steps, each line through which the heated water flows can be suitably pressurized. [Explanation of symbols]

[0073] 1. Combined cycle plant 10. Gas Turbines 11 Compressor 12 Combustor 15 Turbine 19 Gas turbine rotor 20. Waste heat recovery boiler 21 Low-pressure economizer 22 Low pressure evaporator 23 High-pressure primary economizer 24 Medium pressure economizer 25 Medium pressure evaporator 26 Low pressure superheater 27 High pressure secondary economizer 28 Intermediate pressure superheater 29 High-pressure evaporator 30 High pressure primary superheater 31 Primary reheater 32 Secondary reheater 33 High pressure secondary superheater 34 Chimney 40 Condenser 41 Make-up water supply line 42 Water Supply Tank 43 Make-up water supply pump 44 Low Pressure Drum 47 High Pressure Drum 48 Medium Pressure Drum 49a, 49b desuperheater 60 Steam Turbine 61 Steam turbine rotor 62 Condensate supply line 63 Low pressure water supply pump 64 Desuperheater 70 Fuel supply system 80 Fuel Heating System 81 1st water supply section 82 2nd water supply section 83 1st fuel heater 84 Second fuel heater 85 First Water Supply Line 86 Second Water Supply Line 87 Junction 100 Control device 102 Valve control section 104 First water supply control section 106 Second water supply control section HP High Pressure Steam Turbine IP Intermediate Pressure Steam Turbine LP Low Pressure Steam Turbine F fuel HW1 1st water supply HW2 Second water supply V1 First valve V2 Second valve V3 3rd valve V4 4th valve V4a Main valve V4b sub valve V5 Fifth valve V6 6th valve

Claims

1. A first water supply unit capable of supplying a first water supply; A second water supply unit capable of supplying a second water supply having a higher pressure than the first water supply; a first fuel heater provided in a first supply line connected to the first water supply section for heating fuel flowing through a fuel supply line connected to the gas turbine; a second fuel heater connected to the second water supply section and provided in a second supply line that joins the first supply line upstream of the first fuel heater, for heating the fuel downstream of the first fuel heater with respect to the fuel supply line; an upstream valve provided in the second supply line between the second water supply section and the second fuel heater; a first intermediate valve provided in the second feedwater line between the second fuel heater and the junction; a downstream valve provided on the first feedwater line on an opposite side to the junction as viewed from the first fuel heater; A method for charging a fuel heating system comprising: a high pressurization step of pressurizing the second water supply line between the upstream valve and the second water supply line with the second water supply from the second water supply section while the upstream valve is closed; a low pressure filling step of filling a space between the upstream valve and the downstream valve with the first supply water from the first water supply section while opening the first intermediate valve and closing the upstream valve and the downstream valve; a charging completion step of closing the first intermediate valve; A method for charging a fuel heating system comprising:

2. 2. The method for filling a fuel heating system as described in claim 1, further comprising a pre-filling step of, before the low pressurization step, closing the first intermediate valve and closing the downstream valve, and filling a pre-pressurization range between the first intermediate valve and the downstream valve with the first water supply from the first water supply section.

3. The method of claim 2 , wherein the pressure in the pre-filling range at the completion of the pre-filling step is lower than at the completion of the low-filling step.

4. the fuel heating system further includes a second intermediate valve provided in the first feedwater line between the junction and the first fuel heater, The second intermediate valve includes a main valve and a sub-valve that are provided in parallel with each other on the first water supply line, The preliminary charging step is performed in a state where the main valve is closed and the sub-valve is opened, The method for charging a fuel heating system according to claim 2 , wherein the low charging step is performed with the main valve and the sub-valve open.

5. 3. The method of claim 1, wherein the high pressure charging step and the low pressure charging step are performed before the fuel is supplied to the first fuel heater and the second fuel heater.

6. The first water supply unit includes a first water supply pump for pressurizing the water supply, The second water supply section is a second feed water pump for pressurizing the feed water to a higher pressure than the first feed water pump; 3. A method for charging a fuel heating system according to claim 1 or 2, comprising:

7. 3. A method for filling a fuel heating system as described in claim 1 or 2, wherein the design pressure of the second feed water line upstream of the first intermediate valve is higher than the design pressure of the first feed water line and the second feed water line downstream of the first intermediate valve.

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