Steam supply system

Abstract

The steam supply system is provided with a steam flow path for supplying steam to the steam turbine, and an evaporator and a plurality of superheaters or reheaters on the downstream side of the evaporator are arranged on the steam flow path. A steam bypass flow path branched from the downstream side of the evaporator and the upstream side of the plurality of superheaters or reheaters in the steam flow path is configured so as to merge among the plurality of superheaters or reheaters in the steam flow path. The temperature of the steam supplied to the steam turbine is controlled by adjusting the flow rate of the steam in the steam bypass flow path.

Description

Technical Field

[0001] This invention relates to a steam supply system.

[0002] This application claims priority based on Japanese Patent Application No. 2023-184366 filed with the Japan Patent Office on October 27, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] A steam supply system is known for supplying steam to steam turbines in power plant equipment. The steam supply system is configured, for example, to supply steam generated in a boiler such as a conventional boiler or a waste heat recovery boiler to the steam turbine via piping. Generally, higher steam temperatures result in higher power plant efficiency; therefore, steam generated in the boiler is supplied to the steam turbine after being heated by a high-pressure superheater or reheater.

[0004] However, high-pressure superheaters or reheaters are designed assuming the power plant is at its maximum load. Therefore, at low loads with reduced steam flow, the steam is overheated, potentially exceeding the maximum operating temperature (specification limit) of the structures exposed to the steam (boiler, steam turbine, piping, etc.). Consequently, some steam supply systems include devices for controlling the steam temperature below the maximum operating temperature. For example, Patent Document 1 discloses a device with a desuperheater that adjusts the steam temperature by spraying water onto the main steam supplied to the steam turbine.

[0005] Previous technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-125760 Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] In steam temperature regulation using a desuperheater employing the spray method described in Patent Document 1, low-temperature spray water is injected into the high-temperature steam. Generally, while the heat exchange between media with large temperature differences exhibits good temperature regulation responsiveness, the reduced heat exchange efficiency (the effective heat transfer temperature difference as a whole power plant) leads to decreased power plant efficiency. In recent years, there has been an increasing demand in power plants to improve efficiency during low-load operation, with a desire to reduce this efficiency reduction caused by desuperheaters that accompany the spray water.

[0010] At least one embodiment of the present invention was made in view of the above circumstances, and its object is to provide a steam supply system capable of temperature regulation of steam supplied to a steam turbine with good heat exchange efficiency.

[0011] means for solving technical problems

[0012] To address the aforementioned issues, at least one embodiment of the steam supply system according to the present invention includes:

[0013] Steam flow path, used to supply steam to the steam turbine;

[0014] An evaporator, disposed in the steam flow path, is used to generate the steam;

[0015] Multiple superheaters or reheaters are located in the steam flow path at a position further downstream than the evaporator;

[0016] A steam bypass path branches off from the downstream side of the evaporator and the upstream side of the plurality of superheaters or reheaters in the steam path, and is configured to converge among the plurality of superheaters or reheaters in the steam path; and

[0017] A steam temperature control unit is used to control the steam temperature supplied to the steam turbine by adjusting the steam flow rate in the steam bypass path.

[0018] Invention Effects

[0019] According to at least one embodiment of the present invention, a steam supply system capable of temperature regulation of steam supplied to a steam turbine with good heat exchange efficiency can be provided. Attached Figure Description

[0020] Figure 1 This is a schematic structural diagram of a combined cycle power plant involved in one implementation method.

[0021] Figure 2 This is a schematic diagram of a steam supply system involved in one implementation method.

[0022] Figure 3 It is shown Figure 2 The control flow diagram of the internal structure of the control device.

[0023] Figure 4 It is shown Figure 3 A graph of an example of the function FX2.

[0024] Figure 5 This is a schematic diagram of a steam supply system according to another embodiment.

[0025] Figure 6 It is shown Figure 5 The control flow diagram of the internal structure of the control device.

[0026] Figure 7 It is shown Figure 6 A diagram of an example of the function FX4. Detailed Implementation

[0027] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the structures described or shown in the drawings as embodiments are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0028] First, refer to Figure 1 The structure of a combined cycle power plant 1, which is an example of a power plant equipment having steam supply systems 80A and 80B according to several embodiments, will be described. Figure 1 This is a schematic structural diagram of a combined cycle power plant 1 according to one implementation method.

[0029] The combined cycle power plant 1 includes a gas turbine 10, a waste heat recovery boiler 20 for generating steam from the exhaust gas EG from the gas turbine 10, a steam turbine 60 that can be driven by steam from the waste heat recovery boiler 20, and a condenser 40 for reducing the steam from the steam turbine 60 into water.

[0030] 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.

[0031] The steam turbine 60 comprises a high-pressure steam turbine HP, a medium-pressure steam turbine IP, and a low-pressure steam turbine LP. The high-pressure steam turbine HP, the medium-pressure steam turbine IP, and the low-pressure steam turbine LP are interconnected via their respective rotating shafts, forming a steam turbine rotor 61. The steam turbine rotor 61 is integrally connected to the aforementioned gas turbine rotor 19. The steam that has performed work in the steam turbine 60 is reduced to condensate in the condenser 40.

[0032] The condensate from the condenser 40 can be supplied to the waste heat recovery boiler 20 via the condensate supply line 62. A low-pressure water supply pump 63 is installed on the condensate supply line 62 to adjust the condensate supply to the waste heat recovery boiler 20. Furthermore, a desuperheater 64 is installed downstream of the low-pressure water supply pump 63 in the condensate supply line 62 to adjust the water supply temperature to the waste heat recovery boiler 20.

[0033] Additionally, a makeup water tank 42 is connected to the condenser 40 via a makeup water supply line 41. A makeup water supply pump 43 is installed on the makeup water supply line 41, which can supply makeup water from the makeup water tank 42 when the condensate in the condenser 40 is insufficient.

[0034] The waste heat recovery boiler 20 has a structure for recovering and effectively utilizing the heat (waste heat) contained in the exhaust gas EG from the gas turbine 10. The waste heat recovery boiler 20 includes a low-pressure economizer 21, a low-pressure evaporator 22, a high-pressure primary economizer 23, a medium-pressure economizer 24, a medium-pressure evaporator 25, a low-pressure superheater 26, a high-pressure secondary economizer 27, a medium-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 structures for utilizing the heat recovered from the exhaust gas EG.

[0035] In addition, this embodiment shows an example of a system in which two high-pressure superheaters and two reheaters are provided, but it is not limited to this, and the number of high-pressure superheaters and reheaters may be three or more.

[0036] In addition, the exhaust gas after the heat is recovered in the waste heat recovery boiler 20 is discharged to the outside through the chimney 34.

[0037] In the waste heat recovery boiler 20, the feed water (condensate) from the condenser 40 is first heated by a low-pressure economizer 21. At least a portion of the feed water heated by the low-pressure economizer 21 is stored in a low-pressure steam drum 44. A low-pressure evaporator 22 is connected to the low-pressure steam drum 44, which is capable of generating steam from at least a portion of the water stored in the low-pressure steam drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure steam drum 44.

[0038] Furthermore, the water heated by the low-pressure economizer 21 is supplied to the high-pressure water supply pump 45 and the medium-pressure water supply pump 46. The medium-pressure water supply pump 46 pressurizes the water to a first pressure P1, and the high-pressure water supply pump 45 pressurizes the water to a second pressure P2 (> the first pressure P1). The water pressurized to the second pressure P2 by the high-pressure water supply pump 45 is heated by the high-pressure primary economizer 23 and the high-pressure secondary economizer 27 before being supplied to the high-pressure steam drum 47. The water pressurized to the first pressure P1 by the medium-pressure water supply pump 46 is heated by the medium-pressure economizer 24 before being supplied to the medium-pressure steam drum 48.

[0039] In addition, the high-pressure water supply pump 45 and the medium-pressure water supply pump 46 can be integrated into one unit.

[0040] A high-pressure evaporator 29 is connected to the high-pressure steam drum 47, capable of generating steam from at least a portion of the water stored in the high-pressure steam drum 47. The steam generated in the high-pressure evaporator 29 is returned to the high-pressure steam drum 47. The steam drawn from the high-pressure steam drum 47 is superheated by a high-pressure primary superheater 30 and a high-pressure secondary superheater 33, and then supplied to the high-pressure steam turbine HP. A first desuperheater 49a is provided between the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, and by controlling the amount of desuperheating in the first desuperheater 49a, the temperature of the steam supplied to the high-pressure steam turbine HP can be appropriately adjusted.

[0041] After performing work in the high-pressure steam turbine HP, the steam is heated by the primary reheater 31 and the secondary reheater 32 before being supplied to the intermediate-pressure steam turbine IP. A second desuperheater 49b is provided between the primary reheater 31 and the secondary reheater 32. By controlling the desuperheating amount in the second desuperheater 49b, the temperature of the steam supplied to the intermediate-pressure steam turbine IP can be appropriately adjusted.

[0042] An intermediate-pressure evaporator 25 is connected to the intermediate-pressure steam drum 48, capable of generating steam from at least a portion of the water stored in the intermediate-pressure steam drum 48. The steam generated in the intermediate-pressure evaporator 25 is returned to the intermediate-pressure steam drum 48. A portion of the steam extracted from the intermediate-pressure steam drum 48 is heated by the intermediate-pressure superheater 28 and supplied to the outlet flow path of the high-pressure steam turbine HP, and then supplied to the intermediate-pressure steam turbine IP via the primary reheater 31 and the secondary reheater 32.

[0043] A low-pressure evaporator 22 is connected to the low-pressure steam drum 44, capable of generating steam from at least a portion of the water stored in the low-pressure steam drum 44. The steam generated in the low-pressure evaporator 22 is returned to the low-pressure steam drum 44. A portion of the steam extracted from the low-pressure steam drum 44 is heated by the low-pressure superheater 26 and then supplied to the outlet flow path of the intermediate-pressure steam turbine IP, and finally to the low-pressure steam turbine LP. The steam that has performed work in the low-pressure steam turbine LP is returned to the condenser 40.

[0044] Next, the steam supply system 80A of the combined cycle power plant 1 with the above structure will be described. Figure 2 This is a schematic diagram of a steam supply system 80A according to one embodiment.

[0045] The steam supply system 80A is integrated with the aforementioned combined cycle power plant 1 and is configured as a system for supplying steam from the high-pressure steam drum 47 to the high-pressure steam turbine HP. The steam supply system 80A has a steam flow path 81 extending downstream from the high-pressure steam drum 47 to the high-pressure steam turbine HP. A high-pressure primary superheater 30 and a high-pressure secondary superheater 33 are disposed on this steam flow path 81 for heating the steam flowing in this flow path (hereinafter, appropriately referred to as "main steam MS1"). The main steam MS1 is superheated by the high-pressure primary superheater 30 and the high-pressure secondary superheater 33 to become superheated steam, and is supplied to the high-pressure steam turbine HP (reference) located downstream. Figure 1 ).

[0046] A branch 83 is provided between the high-pressure steam drum 47 and the high-pressure primary superheater 30 in the steam flow path 81 (downstream of the high-pressure steam drum 47 and upstream of the high-pressure primary superheater 30), from which the steam bypass flow path 82 branches off. The steam bypass flow path 82 rejoins the steam flow path 81 at a confluence 84 located between the high-pressure primary superheater 30 and the high-pressure secondary superheater 33 in the steam flow path 81 on its downstream side. That is, the steam bypass flow path 82 is configured to connect the branch 83 and the confluence 84. A blocking valve 85 for blocking the steam flowing in the steam bypass flow path 82 (hereinafter appropriately referred to as "bypass steam BS1") and a flow regulating valve 86 for adjusting the flow rate of the bypass steam BS1 are provided on the steam bypass flow path 82. The flow rate of the bypass steam BS1 can be adjusted by controlling the opening of the blocking valve 85 and the flow regulating valve 86 respectively by the control device 100A described later.

[0047] The main steam MS1 from the high-pressure steam drum 47 is superheated by the high-pressure primary superheater 30 and the high-pressure secondary superheater 33, but a portion of the main steam MS1 is guided to the steam bypass path 82 as bypass steam BS1, thus avoiding superheating by the high-pressure primary superheater 30. Therefore, compared to the main steam MS1 that has passed through the high-pressure primary superheater 30, the bypass steam BS1 is at a lower temperature. By merging with the main steam MS1 at the confluence point 84, it de-cools the main steam MS1 supplied to the high-pressure steam turbine HP. In this temperature adjustment of the main steam MS1, the bypass steam BS1 is at a higher temperature than the spray water injected in the first desuperheater 49a, resulting in a small temperature difference with the main steam MS1 and thus a good heat exchange rate (the effective heat transfer temperature difference as a whole power plant).

[0048] Furthermore, when adjusting steam temperature within a power plant through heat exchange with a heat medium, using a relatively low-temperature heat medium such as spray water can achieve good responsive cooling due to the large temperature difference, but on the other hand, it leads to a decrease in heat exchange efficiency. Therefore, it can be said that bypass steam BS1, with its high-grade energy, can suppress the reduction in power plant efficiency compared to spray water, which has low-grade energy, and can appropriately adjust the steam temperature supplied to the high-pressure steam turbine HP.

[0049] Furthermore, the aforementioned first desuperheater 49a is provided between the high-pressure primary superheater 30 and the high-pressure secondary superheater 33 in the steam flow path 81. This first desuperheater 49a is located further downstream than the confluence portion 84. The first desuperheater 49a can adjust the steam temperature supplied to the high-pressure steam turbine HP by spraying water SW1 from the high-pressure water supply pump 45 as spray water onto the main steam MS1. As described later, this control of the first desuperheater 49a is coordinated with the supply control of bypass steam BS1 via the steam bypass flow path 82, thereby appropriately adjusting the steam temperature supplied to the high-pressure steam turbine HP.

[0050] Furthermore, a desuperheater outlet steam temperature sensor 87 is provided between the first desuperheater 49a and the high-pressure secondary superheater 33 in the steam flow path 81 to detect the steam temperature (hereinafter appropriately referred to as "desuperheater outlet steam temperature T1") of the main steam MS1 passing through the first desuperheater 49a. Also, a superheater outlet steam temperature sensor 88 is provided downstream of the high-pressure secondary superheater 33 in the steam flow path 81 to detect the steam temperature (hereinafter appropriately referred to as "superheater outlet steam temperature T2") supplied to the high-pressure steam turbine HP.

[0051] The steam supply system 80A includes a control device 100A as a control unit. The control device 100A comprises, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. Furthermore, as an example, a series of processes for implementing various functions are stored in the storage medium in the form of a program. The CPU reads this program into RAM and performs information processing / analysis to achieve various functions. Alternatively, the program can be pre-installed in ROM or other storage media, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication units. Computer-readable storage media include magnetic disks, optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

[0052] Here, Figure 3 It is shown Figure 2The control flow diagram of the internal structure of the control device 100A is shown below. The control device 100A receives the following inputs: power plant output L (or power plant load), the opening degree D of the flow regulating valve 86, the desuperheater outlet steam temperature T1 detected by the desuperheater outlet steam temperature sensor 87, the superheater outlet steam temperature T2 detected by the superheater outlet steam temperature sensor 88, and the superheater outlet steam target temperature T2g corresponding to the superheater outlet steam temperature T2. The superheater outlet steam target temperature T2g is, for example, preset to correspond to the highest operating temperature specified by specifications for the high-pressure steam turbine HP, which is the destination of the steam supply, or for the piping constituting the steam flow path 81 connected to the high-pressure steam turbine HP.

[0053] In control device 100A, the power plant output L is first input into function FX1. Function FX1 is a function that defines the relationship between the facility output L and the target opening value Dg of the flow regulating valve 86, and is prepared in advance. Function FX1 outputs the target opening value Dg of the flow regulating valve 86 corresponding to the input power plant output L. The difference ΔD between the opening D of the flow regulating valve 86 and the target opening value Dg obtained by function FX1 is input into PI controller 101a. PI controller 101a outputs the opening command value S1a corresponding to the difference ΔD. The opening command value S1a is the command used to control the opening of the flow regulating valve 86.

[0054] Furthermore, in the control device 100A, the difference ΔT2 between the superheater outlet steam temperature T2 and the superheater outlet steam target temperature T2g is input to the PI controller 102a. The PI controller 102a outputs the operating quantity x (0-100%) corresponding to the difference ΔT2. The operating quantity x is a parameter used to determine (output) the desuperheater outlet steam target temperature T1g through the proportional function FX2 (the parameter used to operate the proportional function), and the desuperheater outlet steam target temperature T1g is output by inputting it into the function FX2.

[0055] Here, Figure 4 It is shown Figure 3 The graph shows an example of the function FX2. Function FX2 specifies the relationship between the operating amount x and the target steam temperature T1g at the desuperheater outlet. In this example, it is specified that when the operating amount x is 0%, the target steam temperature T1g at the desuperheater outlet is x1 [°C], and when the operating amount x is 100%, the target steam temperature T1g at the desuperheater outlet is x2 [°C].

[0056] Return to Figure 3The difference ΔT1 between the target steam temperature T1g at the desuperheater outlet and the steam temperature T1 at the desuperheater outlet, calculated using function FX2, is input into the PI controller 103a. The PI controller 103a outputs a desuperheater command S2a corresponding to the difference ΔT1. The spray volume of the sprayed water in the first desuperheater 49a is controlled by sending the desuperheater command S2a to the first desuperheater 49a.

[0057] Thus, in the control device 100A, by coordinating the flow rate of bypass steam BS1 in the steam bypass flow path 82 and the spray volume of spray water in the first desuperheater 49a, the spray volume of spray water in the first desuperheater 49a can be suppressed, and the steam temperature supplied to the high-pressure steam turbine HP can be appropriately controlled so that it does not exceed the maximum operating temperature. Therefore, by suppressing the amount of spray water used in the first desuperheater 49a, the decrease in heat exchange efficiency caused by the consumption of low-grade energy can be suppressed, thereby improving the power plant efficiency.

[0058] Furthermore, in the flow control of the bypass steam BS1, the opening of the flow regulating valve 86 is controlled to achieve the target opening value Dg determined by the power plant output L using a feedforward method, as described above. Therefore, for example, when the power plant output L changes drastically, the steam temperature control with good responsiveness can be achieved by having the target opening value Dg change in accordance with the power plant output L.

[0059] As described above, the spray water used in a first desuperheater 49a has lower energy grade than the bypass steam BS1, but the spray water injection quantity control can achieve high-precision steam temperature control compared to the flow control of the bypass steam BS1. Specifically, the flow rate of the bypass steam BS1 depends on the pressure loss of the main steam MS1 flowing in the high-pressure primary superheater 30 and the high-pressure secondary superheater 33. Furthermore, to reduce the pressure loss of the steam bypass flow path 82, the pressure loss of each device installed in the steam bypass flow path 82 (shut-off valve 85, flow regulating valve 86, and piping, etc.) needs to be as low as possible. Therefore, these devices installed in the steam bypass flow path 82 become large, making them unsuitable for fine control, and their accuracy is easily reduced compared to the spray water injection quantity control in the first desuperheater 49a. Therefore, by combining this with the aforementioned bypass steam BS1 flow control, good control accuracy can be ensured, and power plant efficiency can be improved.

[0060] Next, the steam supply system 80B of the combined cycle power plant 1 with the above structure will be described. Figure 5 This is a schematic diagram of a steam supply system 80B according to another embodiment.

[0061] Steam supply system 80B has a high-pressure steam turbine HP (reference) Figure 1 A steam flow path 91 extends downstream to the intermediate-pressure steam turbine IP. A primary reheater 31 and a secondary reheater 32 are disposed on this steam flow path 91 for heating the steam flowing in this flow path (hereinafter, appropriately referred to as "main steam MS2"). The main steam MS2 becomes reheated steam after being heated by the primary reheater 31 and the secondary reheater 32, and is supplied to the intermediate-pressure steam turbine IP located downstream (see reference 31). Figure 1 ).

[0062] A branch 93 is provided upstream of the primary reheater 31 in the steam flow path 91, from which the steam bypass flow path 92 branches off. The steam bypass flow path 92 rejoins the steam flow path 91 downstream at a junction 94 located between the primary reheater 31 and the secondary reheater 32 within the steam flow path 91. In other words, the steam bypass flow path 92 is configured to connect the branch 93 and the junction 94. The steam bypass flow path 92 is equipped with a shut-off valve 95 for blocking the steam flowing in the steam bypass flow path 92 (hereinafter appropriately referred to as "bypass steam BS2") and a flow regulating valve 96 for adjusting the flow rate of the bypass steam BS2. The flow rate of the bypass steam BS2 can be adjusted by controlling the opening of the shut-off valve 95 and the flow regulating valve 96, respectively, using the control device 100B described later.

[0063] The main steam MS2 from the high-pressure steam turbine HP is heated by the primary reheater 31 and the secondary reheater 32, but a portion of the main steam MS2 is guided as bypass steam BS2 to the steam bypass path 92, thus avoiding heating by the primary reheater 31. Therefore, the bypass steam BS2 is at a lower temperature than the main steam MS2 and merges with the main steam MS2 that has passed through the primary reheater 31 in the confluence section 94, thereby de-cooling the main steam MS2 supplied to the intermediate-pressure steam turbine IP. In this temperature adjustment of the main steam MS2, the bypass steam BS2 is at a higher temperature than the spray water injected in the second desuperheater 49b, resulting in a small temperature difference with the main steam MS2 and thus a good heat exchange rate (the effective heat transfer temperature difference as a whole power plant).

[0064] Furthermore, when adjusting steam temperature within a power plant through heat exchange with a heat medium, using a relatively low-temperature heat medium such as spray water can achieve good responsive cooling due to the large temperature difference, but on the other hand, it leads to a decrease in heat exchange efficiency. Therefore, it can be said that bypass steam BS2 has high-quality energy, which, compared to spray water with low-quality energy, can suppress the reduction in power plant efficiency and can appropriately adjust the steam temperature supplied to the intermediate-pressure steam turbine IP.

[0065] Furthermore, the aforementioned second desuperheater 49b is provided between the primary reheater 31 and the secondary reheater 32 in the steam flow path 91. This second desuperheater 49b is located further downstream than the confluence portion 94. The second desuperheater 49b can adjust the steam temperature supplied to the intermediate-pressure steam turbine IP by spraying the supply water SW2 from the intermediate-pressure water pump 46 as a spray water onto the main steam MS2. As described later, this control of the second desuperheater 49b is coordinated with the supply control of the bypass steam BS2 via the steam bypass flow path 92, thereby appropriately adjusting the steam temperature supplied to the intermediate-pressure steam turbine IP.

[0066] Furthermore, a desuperheater outlet steam temperature sensor 97 is provided between the second desuperheater 49b and the secondary reheater 32 in the steam flow path 91 to detect the steam temperature (hereinafter appropriately referred to as "desuperheater outlet steam temperature T3") of the main steam MS2 passing through the second desuperheater 49b. Also, a reheater outlet steam temperature sensor 98 is provided downstream of the secondary reheater 32 in the steam flow path 91 to detect the steam temperature (hereinafter appropriately referred to as "reheater outlet steam temperature T4") supplied to the intermediate-pressure steam turbine IP.

[0067] The steam supply system 80B includes a control device 100B as a control unit. The control device 100B comprises, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. Furthermore, as an example, a series of processes for implementing various functions are stored in the storage medium in the form of a program. The CPU reads this program into RAM and performs information processing / analysis to achieve various functions. Alternatively, the program can be pre-installed in ROM or other storage media, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication units. Computer-readable storage media include magnetic disks, optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

[0068] Here, Figure 6 It is shown Figure 5The control flow diagram of the internal structure of the control device 100B is shown below. The control device 100B receives the following inputs: power plant output L (or power plant load), the opening degree D of the flow regulating valve 96, the desuperheater outlet steam temperature T3 detected by the desuperheater outlet steam temperature sensor 97, the reheater outlet steam temperature T4 detected by the reheater outlet steam temperature sensor 98, and the reheater outlet steam target temperature T4g corresponding to the reheater outlet steam temperature T4. The reheater outlet steam target temperature T4g is, for example, preset to correspond to the highest operating temperature specified by specifications for the intermediate-pressure steam turbine IP, which is the destination of the steam supply, or for the piping constituting the steam flow path 91 connected to the intermediate-pressure steam turbine IP.

[0069] In control device 100B, the power plant output L is first input into function FX3. Function FX3 is a function that defines the relationship between the facility output L and the target opening value Dg of the flow regulating valve 96, and is prepared in advance. Function FX3 outputs the target opening value Dg of the flow regulating valve 96 corresponding to the input power plant output L. The difference ΔD between the opening D of the flow regulating valve 96 and the target opening value Dg obtained by function FX3 is input into PI controller 101b. PI controller 101b outputs the opening command value S1b corresponding to the difference ΔD. The opening command value S1b is the command used to control the opening of the flow regulating valve 96.

[0070] Furthermore, in the control device 100B, the difference ΔT4 between the reheater outlet steam temperature T4 and the reheater outlet steam target temperature T4g is input to the PI controller 102b. The PI controller 102b outputs the operating quantity x (0-100%) corresponding to the difference ΔT4. The desuperheater outlet steam target temperature T3g is output by inputting the operating quantity x into the function FX4.

[0071] Here, Figure 7 It is shown Figure 6 The graph shows an example of the function FX4. Function FX4 is a function that specifies the relationship between the operating amount x and the target steam temperature T3g at the desuperheater outlet. In this example, it is specified that when the operating amount x is 0%, the target steam temperature T3g at the desuperheater outlet is x1 [°C], and when the operating amount x is 100%, the target steam temperature T3g at the desuperheater outlet is x2 [°C].

[0072] Return to Figure 6 The difference ΔT3 between the target steam temperature T3g at the desuperheater outlet, calculated using function FX4, and the steam temperature T3 at the desuperheater outlet is input into the PI controller 103b. The PI controller 103b outputs a desuperheater command S2b corresponding to the difference ΔT3. The spray volume of the sprayed water in the second desuperheater 49b is controlled by sending the desuperheater command S2b to the second desuperheater 49b.

[0073] Thus, in the control device 100B, by coordinating the flow rate of bypass steam BS2 in the steam bypass path 92 and the spray volume of spray water in the second desuperheater 49b, the spray volume of spray water in the second desuperheater 49b can be suppressed, and the steam temperature supplied to the intermediate-pressure steam turbine IP can be appropriately controlled so that it does not exceed the maximum operating temperature. Therefore, by suppressing the amount of spray water used in the second desuperheater 49b, the decrease in heat exchange efficiency caused by the consumption of low-grade energy can be suppressed, thereby improving the power plant efficiency.

[0074] Furthermore, in the flow control of bypass steam BS2, the opening degree of flow regulating valve 96 is controlled to achieve the target opening value Dg determined by the power plant output L using a feedforward method, as described above. Therefore, for example, when the power plant output L changes drastically, by having the target opening value Dg change accordingly with the power plant output L, it is also possible to achieve responsive steam temperature control through the flow control of bypass steam BS2.

[0075] On the other hand, compared to the bypass steam BS2, the spray water used in the second desuperheater 49b has lower energy grade, but the spray water injection quantity control can achieve high-precision steam temperature control compared to the flow control of the bypass steam BS2. Specifically, the flow rate of the bypass steam BS2 depends on the pressure loss of the main steam MS2 flowing in the primary reheater 31 and secondary reheater 32. Furthermore, to reduce the pressure loss of the steam bypass flow path 92, the pressure loss of each device installed in the steam bypass flow path 92 (shut-off valve 95, flow regulating valve 96, and piping, etc.) needs to be as low as possible. Therefore, these devices installed in the steam bypass flow path 92 become large, making them unsuitable for fine control, and their accuracy is easily reduced compared to the spray water injection quantity control in the second desuperheater 49b. Therefore, by combining this with the aforementioned bypass steam BS2 flow control, good control accuracy can be ensured, and power plant efficiency can be improved.

[0076] Furthermore, the constituent elements in the above embodiments can be appropriately replaced with well-known constituent elements without departing from the spirit of the present invention, and the above embodiments can be appropriately combined.

[0077] The contents described in the above embodiments can be understood as follows, for example.

[0078] (1) The steam supply system involved in one method has:

[0079] Steam flow path, used to supply the steam generated in the evaporator to the steam turbine;

[0080] Multiple superheaters or reheaters are located in the steam flow path at a position further downstream than the evaporator;

[0081] A steam bypass path branches off from the downstream side of the evaporator and the upstream side of the plurality of superheaters or reheaters in the steam path, and is configured to converge among the plurality of superheaters or reheaters in the steam path; and

[0082] The steam temperature control unit controls the steam temperature supplied to the steam turbine by adjusting the steam flow rate in the steam bypass path.

[0083] According to the method described in (1) above, the steam generated in the evaporator is supplied to the steam turbine via a steam flow path equipped with multiple superheaters or reheaters. A portion of the steam flowing in the steam flow path merges between the multiple superheaters or reheaters in the steam flow path via a steam bypass flow path branching from the downstream side of the evaporator and the upstream side of the multiple superheaters or reheaters. Thus, by supplying relatively low-temperature steam bypassing the multiple superheaters or reheaters to the steam heated by the multiple superheaters or reheaters, the steam temperature supplied to the steam turbine can be adjusted. For example, compared to the spray water injected in conventional desuperheaters, the temperature of this steam bypassing the multiple superheaters or reheaters is higher, resulting in a smaller temperature difference with the steam heated by the multiple superheaters or reheaters, and a better heat exchange rate (effective heat transfer temperature difference as a whole power plant). Therefore, it is possible to suppress the decrease in power plant efficiency and adjust the steam temperature.

[0084] (2) In another manner, in the manner described in (1) above, it also possesses:

[0085] A desuperheater is used to deheat the steam by injecting water supplied for generating the steam in the evaporator between the plurality of superheaters or reheaters in the steam flow path.

[0086] The steam temperature control unit controls the steam temperature by adjusting the steam flow rate in the steam bypass path and the water injection rate in the desuperheater.

[0087] According to the method described in (2) above, a desuperheater is also provided that can de-temperature the steam by injecting water (spray water) into the steam supplied to the steam turbine. Thus, as described above, by coordinating and adjusting the steam flow rate in the steam bypass path and the amount of water injected into the desuperheater, the steam temperature supplied to the steam turbine can be appropriately controlled.

[0088] (3) In another manner, in the manner described in (2) above,

[0089] The desuperheater is located downstream of the confluence of the steam bypass flow path in the steam flow path.

[0090] According to the method described in (3) above, water is sprayed into the steam flow path downstream of the confluence of the steam bypass flow path via a desuperheater. As a result, the steam temperature supplied to the steam turbine can be appropriately controlled over a wide range of piping with steam flow downstream of the confluence in the steam flow path, so as not to exceed the maximum operating temperature set according to the specifications.

[0091] (4) In another manner, in the manner described in (2) above,

[0092] The steam temperature control unit controls the flow rate of steam in the steam bypass path according to the operating status of the power plant equipped with the steam turbine.

[0093] According to the method described in (4) above, the steam flow rate in the steam bypass path is controlled based on the operating state (e.g., load or output) of the power plant, which has a steam turbine as a component. For example, this control is performed in a feedforward manner based on the operating state of the power plant, so that when the operating state of the power plant changes, the steam temperature supplied to the steam turbine can be appropriately controlled by changing the steam flow rate in the steam bypass path.

[0094] (5) In another manner, in the manner described in (4) above,

[0095] The steam temperature control unit adjusts the amount of water injected into the desuperheater in such a way that the temperature of the steam passing through the desuperheater reaches the target temperature.

[0096] According to the above (5), by adjusting the amount of water injected into the desuperheater, the temperature of the steam passing through the desuperheater can be controlled with high precision so that the temperature becomes the target temperature.

[0097] (6) In another manner, in the manner described in (5) above,

[0098] The target temperature can be variably set in such a way that the outlet temperature of the plurality of superheaters or reheaters becomes a preset target outlet temperature.

[0099] According to the method described in (6) above, the target temperature corresponding to the steam temperature passing through the desuperheater can be variably set so that the outlet temperature of multiple superheaters or reheaters becomes a preset target outlet temperature. Therefore, the steam temperature supplied to the steam turbine can be appropriately controlled so that it does not exceed the maximum operating temperature set according to specifications.

[0100] (7) In another manner, in the manner described in (2) above,

[0101] The water is condensate generated from the steam after it has done work in the steam turbine.

[0102] According to the above (7), in the desuperheater, by spraying the condensate generated from the steam after it has done work in the steam turbine as spray water, the temperature of the steam supplied to the steam turbine can be appropriately adjusted.

[0103] (8) In another manner, in any of the manners (1) to (7) above,

[0104] The plurality of superheaters or reheaters are heat exchangers capable of exchanging heat with the waste heat of the gas turbine that together with the steam turbine forms a combined cycle power plant.

[0105] According to the above (8), in a combined cycle power plant, multiple superheaters or reheaters heat the steam generated by heat exchange with the waste heat of the gas turbine and supply it to the steam turbine, thereby enabling appropriate control of the steam temperature supplied to the steam turbine.

[0106] Symbol Explanation

[0107] 1-Combined cycle power plant, 10-Gas turbine, 11-Compressor, 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-Medium-pressure superheater, 29-High-pressure evaporator, 30-High-pressure primary superheater, 31-Primary reheater, 32-Secondary reheater, 33-High-pressure secondary superheater, 34-Chimney, 40-Condenser, 41-Makeup water supply pipeline, 42-Makeup water tank, 43-Makeup water supply pump, 44-Low-pressure steam drum, 47-High-pressure steam drum, 48-Medium-pressure steam drum, 49a-First reducing... 49b-Second desuperheater, 60-Steam turbine, 61-Steam turbine rotor, 62-Condensate supply line, 63-Low-pressure water supply pump, 64-Desuperheater, 80A, 80B-Steam supply system, 81-Steam flow path, 82-Steam bypass flow path, 83-Branch, 84-Merging point, 85-Block valve, 86-Flow regulating valve, 87-Desuperheater outlet steam temperature sensor, 88-Superheater outlet steam temperature sensor, 91-Steam flow path, 92-Steam bypass flow path, 93-Branch, 94-Merging point, 95-Block valve, 96-Flow regulating valve, 97-Desuperheater outlet steam temperature sensor, 98-Reheater outlet steam temperature sensor, 100A, 100B-Control device.

Claims

1. A steam supply system comprising: Steam flow path, used to supply steam to the steam turbine; An evaporator, disposed in the steam flow path, is used to generate the steam; Multiple superheaters or reheaters are located in the steam flow path at a position further downstream than the evaporator; A steam bypass path branches off from the downstream side of the evaporator and the upstream side of the plurality of superheaters or reheaters in the steam path, and is configured to converge among the plurality of superheaters or reheaters in the steam path; and The steam temperature control unit controls the steam temperature supplied to the steam turbine by adjusting the steam flow rate in the steam bypass path.

2. The steam supply system according to claim 1, further comprising: A desuperheater is used to deheat the steam by injecting water supplied for generating the steam in the evaporator between the plurality of superheaters or reheaters in the steam flow path. The steam temperature control unit controls the steam temperature by adjusting the steam flow rate in the steam bypass path and the water injection rate in the desuperheater.

3. The steam supply system according to claim 2, wherein, The desuperheater is located downstream of the confluence of the steam bypass flow path in the steam flow path.

4. The steam supply system according to claim 2, wherein, The steam temperature control unit controls the flow rate of steam in the steam bypass path according to the operating status of the power plant equipped with the steam turbine.

5. The steam supply system according to claim 4, wherein, The steam temperature control unit adjusts the amount of water injected into the desuperheater in such a way that the temperature of the steam passing through the desuperheater reaches the target temperature.

6. The steam supply system according to claim 5, wherein, The target temperature can be variably set in such a way that the outlet temperature of the plurality of superheaters or reheaters becomes a preset target outlet temperature.

7. The steam supply system according to claim 2, wherein, The water is condensate generated from the steam after it has done work in the steam turbine.

8. The steam supply system according to claim 1 or 2, wherein, The plurality of superheaters or reheaters are heat exchangers capable of exchanging heat with the waste heat of the gas turbine that together with the steam turbine forms a combined cycle power plant.

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