Steam supply system and steam supply method

Abstract

To provide a control method for compensating a supply amount of vapor from a GTCC to a CO2 recovery device when a plant is stopped in the plant in which the GTCC and the CO2 recovery device are combined.SOLUTION: A plant including a power plant including a gas turbine, a heat recovery steam generator, and a steam turbine, a CO2 recovery device, a low-pressure system for extracting low-pressure steam from a low-pressure system that supplies low-pressure steam to the steam turbine from the heat recovery steam generator and supplying the extracted low-pressure steam to the CO2 recovery device, a second system for extracting intermediate-pressure steam from an intermediate-pressure system that supplies intermediate-pressure steam to the CO2 recovery device and supplying the extracted intermediate-pressure steam to the second system, a low-pressure steam control valve on an upstream side of a connection position of the first system in the low-pressure system, an intermediate-pressure steam control valve in the intermediate-pressure system, and a steam back-up valve in the second system. In a vapor supplying method for supplying vapor generated by an exhaust heat recovery boiler to a CO2 recovery device, a low-pressure vapor control valve and a medium-pressure vapor control valve are closed and a vapor backup value is opened based on an operation state of a power plant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a steam supply system and a steam supply method for supplying steam to a CO2 recovery device. [Background technology]

[0002] There is a plant that combines a gas turbine combined cycle (GTCC) with a CO2 capture device. Patent Document 1 discloses a plant that combines a GTCC with a CO2 capture device, which has a medium-pressure steam supply system that supplies medium-pressure steam generated in a heat recovery boiler to the CO2 capture device, and a low-pressure steam supply system that extracts a portion of the low-pressure steam from a low-pressure system that supplies low-pressure steam from the heat recovery boiler to a steam turbine and supplies the extracted low-pressure steam to the CO2 capture device. In such a plant, by supplying steam through the medium-pressure steam supply system at the time of plant startup, it is possible to compensate for the steam supply to the CO2 capture device, which tends to be insufficient at the time of plant startup. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-256870 Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to plant startup, in situations such as when the plant is shut down, load is rejected, or the steam turbine trips, the steam control valve installed in the low-pressure steam supply system may be closed, making it impossible to supply low-pressure steam to the CO2 capture device, which may result in a decrease in the CO2 capture rate.

[0005] The present disclosure provides a steam supply system and a steam supply method that can solve the above problems. [Means for solving the problem]

[0006] A steam supply system according to the present disclosure is a steam supply system that supplies steam generated in a heat recovery boiler to a CO2 recovery device that recovers CO2 from exhaust gas discharged from a power plant including a gas turbine, a heat recovery boiler, and a steam turbine, the steam supply system comprising: a low-pressure system that supplies low-pressure steam from the heat recovery boiler to the steam turbine; a first system that is connected to the low-pressure system and extracts the low-pressure steam from the low-pressure system and supplies it to the CO2 recovery device; and a second system that is connected to the low-pressure system upstream of a connection position of the first system in the low-pressure system. a low-pressure steam control valve provided on the side of the first system, an intermediate-pressure system that supplies intermediate-pressure steam from the heat recovery boiler to the steam turbine, a second system that is connected to the intermediate-pressure system and extracts the intermediate-pressure steam from the intermediate-pressure system and supplies it to the first system, an intermediate-pressure steam control valve provided in the intermediate-pressure system, a steam backup valve provided in the second system, and a control device, wherein the control device closes the low-pressure steam control valve and the intermediate-pressure steam control valve and opens the steam backup valve based on the operating state of the power plant.

[0007] a low-pressure steam control valve provided in the low-pressure system upstream of a connection position with the first system; a medium-pressure steam control valve provided in the medium-pressure system; and a steam backup valve provided in the second system. The steam supply method of the present disclosure is a steam supply method for supplying steam generated by the heat recovery boiler to the CO2 recovery system in a plant including: a power plant including a gas turbine, a heat recovery boiler, and a steam turbine; a CO2 recovery device that recovers CO2 from exhaust gas of the power plant; a first system that extracts low-pressure steam from a low-pressure system that supplies the low-pressure steam from the heat recovery boiler to the steam turbine and supplies the low-pressure steam to the CO2 recovery system; a second system that extracts medium-pressure steam from a medium-pressure system that supplies medium-pressure steam from the heat recovery boiler to the steam turbine and supplies the medium-pressure steam to the first system; [Effects of the Invention]

[0008] According to the steam supply system and steam supply method described above, in a plant that combines a GTCC and a CO2 capture device, when the amount of steam supplied from the heat recovery steam generator to the CO2 capture device decreases in situations such as when the plant is shut down, load is rejected, or the steam turbine trips, the amount of steam supplied to the CO2 capture device can be supplemented, and the CO2 capture rate can be maintained. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a plant according to each embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a main part of a plant configuration according to each embodiment. [Figure 3] 4 is a flowchart illustrating an example of control according to the first embodiment. [Figure 4] 10 is a flowchart illustrating an example of control according to the second embodiment. [Figure 5] 10 is a flowchart illustrating an example of control according to the third embodiment. [Figure 6] 10 is a flowchart showing an example of control according to the fourth embodiment. [Figure 7] 13 is a flowchart showing an example of control according to the fifth embodiment. [Figure 8] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (overview) Hereinafter, the steam supply control to the CO2 recovery device according to the present disclosure will be described with reference to FIGS. FIG. 1 shows the schematic configuration of a plant that combines a GTCC (combined cycle power plant) and a CO2 capture system. The plant 100 includes a gas turbine 10, a heat recovery steam generator (HRSG) 20, a steam turbine 30, a CO2 capture system 40, generators G1 and G2, and a control device 50. The gas turbine 10 is connected to and drives the generator G1. The steam turbine 30 is connected to and drives the generator G2. Exhaust gas discharged from the gas turbine 10 is sent to the HRSG 20, where it is used before being sent to the CO2 capture system 40. The HRSG 20 recovers heat from the exhaust gas, generates high-pressure steam, intermediate-pressure steam, and low-pressure steam, and supplies these to the steam turbine 30. The HRSG 20 supplies a portion of the low-pressure steam extracted from a system that supplies low-pressure steam to the connected steam turbine to a regenerator 42 of the CO2 capture system 40. Furthermore, the HRSG 20 sends the exhaust gas after heat recovery to a CO2 recovery unit 40. The CO2 recovery unit 40 includes an absorber 41 and a regenerator 42, and extracts CO2 from the exhaust gas sent from the HRSG 20 by circulating an absorbing solution between the absorber 41 and the regenerator 42. Steam is required as a heat source to extract CO2, and in the plant 100, low-pressure steam supplied from the HRSG 20 is used as the heat source. The low-pressure steam used in the CO2 extraction process is condensed into low-pressure hot water, and the generated low-pressure hot water is supplied from the CO2 recovery unit 40 to the HRSG 20. In this configuration, steam cannot be supplied to the CO2 recovery unit 40 after the GTCC starts up until a sufficient amount of low-pressure steam is generated in the HRSG 20. Therefore, a medium-pressure extraction system L10 is provided that extracts a portion of the medium-pressure steam from the HRSG 20 and supplies it to the CO2 capture unit 40, and the control device 50 controls switching between the system that supplies low-pressure steam to the CO2 capture unit 40 and the medium-pressure extraction system L10.When the GTCC is started up, a portion of the medium-pressure steam, which generates a sufficient amount of steam earlier than the low-pressure steam, is supplied to the CO2 capture unit 40 through the medium-pressure extraction system L10, making it possible to supply sufficient steam to the CO2 capture unit 40 even when the GTCC is started up.In addition, not only during plant startup, but also during plant shutdown, load rejection, and tripping of the steam turbine 30, the steam control valves (V2, V5, and V7 in Figure 2) are closed, preventing low-pressure steam from being supplied to the CO2 capture device 40. However, in this embodiment, even under these circumstances, steam is supplied to the CO2 capture device 40 through the medium-pressure extraction system L10 to make up for the shortage of low-pressure steam.

[0011] 2 is a diagram showing an example of a main part of a plant configuration according to each embodiment. The HRSG 20 provided downstream of the gas turbine 10 includes a low-pressure economizer 21L, an intermediate-pressure economizer 21I, a high-pressure economizer 21H, a low-pressure evaporator 22L, an intermediate-pressure evaporator 22I, a high-pressure evaporator 22H, a low-pressure superheater 23L, an intermediate-pressure superheater 23I, a high-pressure superheater 23H, a reheater 24, a low-pressure drum 25L, an intermediate-pressure drum 25I, and a high-pressure drum 25H. The steam turbine 30 includes a high-pressure turbine 31, an intermediate-pressure turbine 32, and a low-pressure turbine 33. Low-pressure steam is supplied from the low-pressure superheater 23L to the low-pressure turbine 33 via lines L1 and L9. Line L9 is connected to line L2, which leads to the CO2 capture system 40. A portion of the low-pressure steam supplied from the low-pressure superheater 23L branches off and is supplied to the CO2 capture system 40 (regenerator 42) through line L2. Furthermore, line L3, which branches off from line L1, is provided upstream of the connection point between line L1 and line L9 (upstream in the steam flow direction, hereinafter simply referred to as the upstream side and downstream side). Line L3 is provided with a low-pressure turbine bypass valve V1. During periods of low-pressure steam generation during plant startup, the low-pressure turbine bypass valve V1 is opened, and the low-pressure steam bypasses the low-pressure turbine 33 and is sent to a condenser (not shown) through line L3. A low-pressure steam control valve V2 (CCP indicates a CO2 capture system) is provided upstream of the connection point between line L1 and line L9 and downstream of the branch point between line L1 and line L3. Line L2 also has a low-pressure steam extraction valve V3. In addition, downstream of the low-pressure steam extraction valve V3, there is a temperature control spray SP1 for adjusting (cooling) the low-pressure steam temperature to an appropriate temperature, and a temperature control spray valve SPV1 for adjusting the flow rate of the mist water sprayed from the temperature control spray SP1.

[0012] High-pressure steam is supplied from the high-pressure superheater 23H to the high-pressure turbine 31 via line L4. Line L4 is provided with a high-pressure steam control valve V5 that adjusts the flow rate of the high-pressure steam. Line L6' is connected to line L4, and line L6' is provided with a high-pressure turbine bypass valve V6. When the high-pressure turbine bypass valve V6 is opened, the high-pressure steam bypasses the high-pressure turbine 31 and flows to the reheater 24 via line L6' and line L6. The high-pressure steam supplied to the high-pressure turbine 31 is returned to the reheater 24 via line L5 and line L6. Line L6 is joined with line L5 and line L11 and line L6' on the outlet side of the intermediate-pressure superheater 23I.

[0013] Intermediate-pressure steam is supplied from the reheater 24 to the intermediate-pressure turbine 32 via line L7 and line L7'. Line L7' is provided with an intermediate-pressure steam control valve V7 that adjusts the flow rate of the intermediate-pressure steam. Line L7 is connected to line L8, which is provided with an intermediate-pressure turbine bypass valve V8. When the intermediate-pressure turbine bypass valve V8 is opened, the intermediate-pressure steam bypasses the intermediate-pressure turbine 32 and flows to a condenser (not shown) via line L8. A pressure gauge P1 is provided upstream of the intermediate-pressure turbine bypass valve V8 in line L8. The intermediate-pressure steam supplied to the intermediate-pressure turbine 32 is supplied to the low-pressure turbine 33 and the CO2 capture device 40 via line L9. Line L7 is connected to an intermediate-pressure extraction system L10 that leads to line L2, which is a steam supply system to the CO2 capture device 40. The medium-pressure extraction system L10 is provided with a medium-pressure backup steam pressure regulating valve V4. The medium-pressure extraction system L10 is provided to supply medium-pressure steam to the CO2 capture device 40 during GTCC startup, plant shutdown sequence, load rejection, steam turbine trip, and other such events. A pressure gauge P2 is provided downstream of the medium-pressure backup steam pressure regulating valve V4 in the medium-pressure extraction system L10. Near (e.g., downstream of) the position of the pressure gauge P2, a temperature control spray SP2 for adjusting (cooling) the temperature of the medium-pressure steam to an appropriate temperature and a temperature control spray valve SPV2 for adjusting the flow rate of atomized water sprayed from the temperature control spray SP2 are provided. A thermometer T1 for measuring the temperature of the steam flowing through the medium-pressure extraction system L10 is provided downstream of the temperature control spray SP2 in the medium-pressure extraction system L10. The medium-pressure extraction system L10 is connected to the system L2, for example, downstream of the temperature control spray SP1. The low-pressure or medium-pressure steam generated by the HRSG 20 is supplied to the CO2 recovery unit 40 via a line L2.

[0014] The control device 50 controls the apertures of the low-pressure turbine bypass valve V1, low-pressure steam control valve V2, low-pressure steam extraction valve V3, intermediate-pressure backup steam pressure control valve V4, high-pressure steam control valve V5, high-pressure turbine bypass valve V6, intermediate-pressure steam control valve V7, intermediate-pressure turbine bypass valve V8, temperature control spray valve SPV1, and temperature control spray valve SPV2. For example, the control device 50 controls the aperture of the intermediate-pressure turbine bypass valve V8 based on the measurement value of a pressure gauge P1, controls the aperture of the intermediate-pressure backup steam pressure control valve V4 based on the measurement value of a pressure gauge P2, and controls the aperture of the temperature control spray valve SPV1 based on the measurement value of a thermometer T1.

[0015] First Embodiment When the plant 100 is shut down, the steam turbine 30 is shut down, and then the gas turbine 10 is shut down. To shut down the steam turbine 30, the control device 50 controls the low-pressure steam control valve V2, the intermediate-pressure steam control valve V7, and the high-pressure steam control valve V5 to close. This reduces the amount of steam in the piping of the system L2, which extracts low-pressure steam for the CO2 capture device 40, resulting in a shortage of steam, the heat source used by the CO2 capture device 40 to capture CO2. The plant shutdown sequence is assumed to first close the steam control valve V2 and other valves, then shut off fuel to the gas turbine 10 and end combustion. Therefore, even after the shortage of low-pressure steam, there is a period of time during which exhaust gas continues to be emitted from the gas turbine 10 due to combustion. Therefore, in this embodiment, the intermediate-pressure backup steam pressure control valve V4 is opened when the plant is shut down or the steam control valve V2 is closed. There is a surplus of steam in the intermediate-pressure system because the intermediate-pressure steam control valve V7 is closed. By opening the medium-pressure backup steam pressure regulating valve V4, the excess steam is supplied to the CO2 capture device 40 through the medium-pressure extraction system L10. This makes up for the shortage of low-pressure steam, making it possible to maintain the CO2 capture rate from the exhaust gas of the gas turbine 10.

[0016] At this time, the opening of the intermediate-pressure backup steam pressure regulating valve V4 may be fixed based on a predetermined set value, or feedback controlled so that the pressure measured by the pressure gauge P2 provided downstream of the intermediate-pressure backup steam pressure regulating valve V4 coincides with the target value, or a combination of these controls may be used. Note that the intermediate-pressure steam control valve V7 is closed, and the intermediate-pressure turbine bypass valve V8 is controlled so that the pressure measured by the pressure gauge P1 provided upstream thereof maintains the target value.

[0017] (operation) Next, the control flow when shutting down the plant 100 will be described with reference to FIG. FIG. 3 is a flowchart showing an example of control according to the first embodiment. First, the control device 50 receives a plant shutdown signal indicating that the plant 100 is to be shut down (step S1). This signal may be input to the control device 50 by an operator, received from another device, or generated by the control device 50 itself. Upon receiving the plant shutdown signal, the control device 50 closes the low-pressure steam control valve V2, the medium-pressure steam control valve V7, and the high-pressure steam control valve V5 (step S2). Next, the control device 50 opens the closed medium-pressure backup steam pressure control valve V4 (step S3). The control device 50 may feedback-control the aperture of the medium-pressure backup steam pressure control valve V4 so that the pressure measured by the pressure gauge P2 reaches a predetermined target value (a target pressure value that can achieve the required amount of steam supply). Alternatively, the control device 50 may open the medium-pressure backup steam pressure control valve V4 at a predetermined aperture (a fixed value of aperture that can achieve the required amount of steam supply). Alternatively, feedback control and control to open the medium-pressure backup steam pressure control valve V4 at a predetermined aperture may be combined. This allows the CO2 capture device 40 to stably and continuously supply the amount of steam required.

[0018] In the processing flow of FIG. 3, steps S1, S2, and S3 are performed in this order, but steps S2 and S3 may be performed simultaneously, or the order of steps S2 and S3 may be reversed.

[0019] (effect) As described above, in the first embodiment, when the plant is shut down, the steam control valves V2, V5, and V7 are closed and the medium-pressure backup steam pressure regulating valve V4 is opened, thereby supplying the amount of steam necessary for CO2 capture to the CO2 capture device 40. As a result, even during a time period when the plant is shut down and there is concern about a shortage of steam supplied to the CO2 capture device 40, steam can be continuously supplied, and the CO2 capture rate can be maintained while the gas turbine 10 is burning.

[0020] Second Embodiment In the first embodiment, control for compensating for a shortage of steam supply when the plant 100 is shut down was described. In the second embodiment, control during load rejection (when the plant 100 is isolated from the power grid and continues to operate without load) will be described. When the plant 100 performs load rejection, the steam control valves V2, V5, and V7 are closed to shut down the steam turbine 30, instantly cutting off the supply of steam. This reduces the amount of low-pressure steam supplied to the CO2 capture device 40, but because the gas turbine 10 continues to operate without load even after load rejection, CO2 continues to be generated by combustion. In the second embodiment, to continue capturing CO2 even after load rejection, the intermediate-pressure backup steam pressure control valve V4 is opened when load rejection occurs or the steam control valve is closed. There is a surplus of steam in the intermediate-pressure system because the intermediate-pressure steam control valve V7 is closed. The surplus steam is supplied to the CO2 recovery device 40 through the intermediate pressure extraction system L10 by opening the intermediate pressure backup steam pressure regulating valve V4, thereby recovering CO2 from the exhaust gas of the gas turbine 10.

[0021] The intermediate-pressure backup steam pressure regulating valve V4 may be opened at a fixed opening based on a predetermined set value, or may be feedback-controlled so that the opening matches the measurement value of the pressure gauge P2 to the target pressure, or a combination of these controls may be used.The intermediate-pressure turbine bypass valve V8 is controlled so that the pressure measured by the pressure gauge P1 installed upstream maintains the target value.

[0022] (operation) Next, the flow of control during load shedding of the plant 100 will be described with reference to FIG. FIG. 4 is a flowchart showing an example of control according to the second embodiment. First, the control device 50 acquires a load shedding signal indicating that the plant 100 is to be subjected to load shedding (step S1a). This signal may be input to the control device 50 by an operator, may be received from another device, or may be generated by the control device 50 itself. Upon acquiring the load shedding signal, the control device 50 closes the low-pressure steam control valve V2, the medium-pressure steam control valve V7, and the high-pressure steam control valve V5 (step S2). Next, the control device 50 changes the medium-pressure backup steam pressure control valve V4 from closed to open (step S3). The control device 50 may feedback-control the aperture of the medium-pressure backup steam pressure control valve V4 so that the pressure measured by the pressure gauge P2 reaches a predetermined target value, or may open the medium-pressure backup steam pressure control valve V4 at a predetermined aperture (fixed value). Alternatively, the control device 50 may combine feedback control and control to open the medium-pressure backup steam pressure control valve V4 at a predetermined fixed aperture, such as by the method exemplified in the first embodiment.

[0023] In the processing flow of FIG. 4, steps S1a, S2, and S3 are performed in this order, but steps S2 and S3 may be performed simultaneously, or the order of steps S2 and S3 may be reversed.

[0024] (effect) As described above, in the second embodiment, the steam control valves V2, V5, and V7 are closed and the intermediate-pressure backup steam pressure regulating valve V4 is opened during load rejection, thereby supplying steam necessary for CO2 capture to the CO2 capture device 40. This makes it possible to capture CO2 from the exhaust gas of the gas turbine 10 during load rejection. In other words, even during a time period after load rejection when there is concern about a shortage of steam supplied to the CO2 capture device 40, steam can be continuously supplied, and the CO2 capture rate can be maintained while the gas turbine 10 is operating without load.

[0025] Third Embodiment In the third embodiment, control will be described for when the steam turbine 30 trips (hereinafter referred to as an ST trip) (when the steam turbine 30 is stopped due to the occurrence of some abnormality or the like, and the gas turbine 10 continues to operate). When an ST trip occurs, the steam control valves V2, V5, and V7 are closed to instantly shut off the supply steam to stop the steam turbine 30. This reduces the amount of low-pressure steam supplied to the CO2 capture device 40, but the gas turbine 10 may continue to operate after the ST trip. CO2 continues to be generated by combustion while the gas turbine 10 is operating. In the third embodiment, to continue capturing CO2 even after an ST trip, the intermediate-pressure backup steam pressure control valve V4 is opened in response to the occurrence of an ST trip or the closure of the steam control valve. As a result, excess steam created by closing the intermediate-pressure steam control valve V7 is supplied to the CO2 capture device 40 via the intermediate-pressure extraction system L10, and the process of capturing CO2 from the exhaust gas of the gas turbine 10 continues.

[0026] The intermediate-pressure backup steam pressure regulating valve V4 may be opened at a fixed opening based on a predetermined set value, or the opening of the intermediate-pressure backup steam pressure regulating valve V4 may be feedback-controlled so that the measurement value of the pressure gauge P2 becomes the target value, or these types of control may be combined. The intermediate-pressure turbine bypass valve V8 is controlled so that the pressure measured by the pressure gauge P1 provided in the upstream stage is maintained at the target value.

[0027] (operation) Next, the flow of control when the ST trips will be described with reference to FIG. FIG. 5 is a flowchart showing an example of control according to the third embodiment. First, the control device 50 acquires an ST trip signal indicating the occurrence of an ST trip (step S1b). This signal may be input to the control device 50 by an operator, may be received from another device, or may be generated by the control device 50 itself. Upon acquiring the ST trip signal, the control device 50 closes the low-pressure steam control valve V2, the medium-pressure steam control valve V7, and the high-pressure steam control valve V5 (step S2). Next, the control device 50 changes the medium-pressure backup steam pressure control valve V4 from closed to open (step S3). The control device 50 may feedback-control the opening of the medium-pressure backup steam pressure control valve V4 so that the pressure measured by the pressure gauge P2 reaches a predetermined target value, or may open the medium-pressure backup steam pressure control valve V4 at a predetermined opening (fixed value).

[0028] In the processing flow of FIG. 5, steps S1b, S2, and S3 are performed in this order, but steps S2 and S3 may be performed simultaneously, or the order of steps S2 and S3 may be reversed.

[0029] (effect) As described above, in the third embodiment, the steam control valves V2, V5, and V7 are closed and the medium-pressure backup steam pressure regulating valve V4 is opened during an ST trip, thereby supplying the steam necessary for CO2 capture to the CO2 capture device 40. As a result, even during a time period after an ST trip occurs when there is concern about a shortage of steam supplied to the CO2 capture device 40, steam can be continuously supplied, and the CO2 capture rate can be maintained while the gas turbine 10 is operating.

[0030] <Fourth embodiment> In the first to third embodiments, the control has been described in which the medium-pressure backup steam pressure regulating valve V4 is opened when the low-pressure steam control valve V2 and the like are closed, and medium-pressure steam is supplied to the CO2 capture device 40. Because steam in the medium-pressure system is relatively hot, there is a possibility that equipment damage or deterioration may occur if the steam is supplied to the CO2 capture device 40 while still at a high temperature. Therefore, in the fourth embodiment, a control is added in which the temperature control spray valve SPV2 is opened to spray atomized water onto the medium-pressure steam, thereby reducing the temperature of the medium-pressure steam. For example, the temperature control spray valve SPV2 is opened simultaneously with the opening operation of the medium-pressure backup steam pressure regulating valve V4, and temperature control is started.

[0031] The temperature control spray valve SPV2 may be opened at a fixed opening based on a predetermined set value, or may be feedback controlled so that the temperature measured by a thermometer T1 provided downstream of the temperature control spray valve SPV2 coincides with a target value. Alternatively, feedback control and control to open at a predetermined opening may be combined.

[0032] (operation) Next, the flow of control when the ST trips will be described with reference to FIG. FIG. 6 is a flowchart showing an example of control according to the fourth embodiment. First, the control device 50 acquires a plant shutdown signal, a load rejection signal, or an ST trip signal (step S1c). Upon acquiring these signals, the control device 50 closes the low-pressure steam control valve V2, the medium-pressure steam control valve V7, and the high-pressure steam control valve V5 (step S2). Next, the control device 50 changes the medium-pressure backup steam pressure control valve V4 from closed to open, and simultaneously changes the temperature control spray valve SPV2 from closed to open (step S3c). The control device 50 may feedback-control the opening of the temperature control spray valve SPV2 so that the temperature measured by the thermometer T1 reaches a predetermined target value, or may open the temperature control spray valve SPV2 at a predetermined fixed opening. Alternatively, the temperature control spray valve SPV2 may be opened by combining feedback control and control to open at a predetermined fixed opening.

[0033] In the processing flow of FIG. 6, steps S1c, S2, and S3c are performed in this order, but steps S2 and S3c may be performed simultaneously, or the order of steps S2 and S3c may be reversed.

[0034] (effect) As described above, in the fourth embodiment, the temperature control spray valve SPV2 is opened simultaneously with the medium-pressure backup steam pressure regulating valve V4, which prevents excessive heat input to the CO2 recovery device 40 due to a sudden increase in relatively high-temperature medium-pressure steam, which can cause damage or deterioration of the equipment.

[0035] Fifth Embodiment In the first to fourth embodiments, the control of supplying medium-pressure steam to the CO2 capture system 40 by opening the medium-pressure backup steam pressure regulating valve V4 has been described in a situation where the amount of steam supplied to the CO2 capture system 40 is reduced by closing the low-pressure steam control valve V2 or the like. On the other hand, if the medium-pressure backup steam pressure regulating valve V4 is left open, medium-pressure steam continues to be supplied to the CO2 capture system 40. After the gas turbine 10 is shut down (after fuel is shut off), the amount of heat retained by the steam in the HRSG 20 decreases due to the lack of heat input. If the amount of heat retained in the HRSG 20 decreases too much, the HRSG 20 will need to be heated again the next time the plant 100 is started up, which may increase the start-up time of the plant 100 and the required fuel flow rate of the gas turbine 10. Furthermore, after fuel is shut off to the gas turbine 10, no CO2 is generated by combustion, so the amount of steam required in the CO2 capture system 40 is zero or very small, and no steam supply is required. Therefore, in the fifth embodiment, the intermediate pressure backup steam pressure regulating valve V4 is closed at the same time as the fuel supply to the gas turbine 10 is shut off, thereby preventing the heat from leaking out of the HRSG 20 system.

[0036] (operation) Next, with reference to FIG. 7, the flow of control in this embodiment when the plant is shut down, when a load is rejected, or when a steam turbine is tripped will be described. FIG. 7 is a flowchart showing an example of control according to the fifth embodiment. It is assumed that the medium-pressure backup steam pressure regulating valve V4 is open due to the control of the first to fourth embodiments. First, the control device 50 acquires a fuel cutoff signal indicating that fuel is to be cut off to the gas turbine 10 (step S11). Upon acquiring the fuel cutoff signal, the control device 50 closes the medium-pressure backup steam pressure regulating valve V4 (step S12). When combined with the fourth embodiment, in addition to the medium-pressure backup steam pressure regulating valve V4, the temperature control spray valve SPV2 is also closed.

[0037] (effect) According to the fifth embodiment, it is possible to prevent the supply of more steam than necessary from the GTCC to the CO2 recovery device 40, which would otherwise cause the stored heat to flow out of the HRSG 20, and to keep the inside of the HRSG 20 warm in preparation for the next startup of the GTCC.

[0038] As described above, according to the first to fifth embodiments, in a plant that combines a GTCC and a CO2 capture system, sufficient steam can be supplied to the CO2 capture system even in situations where there is concern about a decrease in the amount of steam supplied to the CO2 capture system, such as when the plant is shut down, load is rejected, or a steam turbine trips.

[0039] FIG. 8 is a diagram showing an example of the hardware configuration of a control device according to each embodiment. A computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input / output interface 904, and a communication interface 905. The control device 50 described above is implemented in the computer 900. The functions described above are stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from the auxiliary storage device 903, loads it into the main storage device 902, and executes the above processing in accordance with the program. The CPU 901 also allocates a storage area in the main storage device 902 in accordance with the program. The CPU 901 also allocates a storage area in the auxiliary storage device 903 for storing data being processed in accordance with the program.

[0040] A program for implementing all or part of the functions of the control device 50 may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, if a WWW system is used, the term "computer system" also includes the homepage provision environment (or display environment). Furthermore, the term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. Furthermore, if the program is distributed to the computer 900 via a communication line, the computer 900 that receives the program may load the program into the main storage device 902 and execute the above-described processing. Furthermore, the program may be for implementing part of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system.

[0041] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0042] <Additional Notes> The vapor supply system and the vapor supply method described in each embodiment can be understood, for example, as follows.

[0043] (1) A steam supply system according to a first aspect is a steam supply system that supplies steam generated in a heat recovery boiler (20) to a CO2 recovery device (40) that recovers CO2 from exhaust gas discharged from a power plant including a gas turbine (10), a heat recovery boiler (20), and a steam turbine (30). The steam supply system includes: a low-pressure system (L1, L9) that supplies low-pressure steam from the heat recovery boiler (20) to the steam turbine (30); a first system (L2) connected to the low-pressure system and extracting the low-pressure steam from the low-pressure system and supplying the low-pressure steam to the CO2 recovery device; and a second system (L3) that is positioned closer to the low-pressure system than a connection position of the first system in the low-pressure system. The power plant includes a low-pressure steam control valve (V2) provided upstream, an intermediate-pressure system (L7, L7') that supplies intermediate-pressure steam from the heat recovery boiler to the steam turbine, a second system (L10) that is connected to the intermediate-pressure system and extracts the intermediate-pressure steam from the intermediate-pressure system and supplies it to the first system, an intermediate-pressure steam control valve (V7) provided in the intermediate-pressure system, a steam backup valve (V4) provided in the second system, and a control device (50), and the control device closes the low-pressure steam control valve (V2) and the intermediate-pressure steam control valve (V7) and opens the steam backup valve (V4) based on the operating state of the power plant. This means that in a plant that combines a GTCC and a CO2 capture unit, even when the GTCC is operating in a state where the amount of low-pressure steam supplied to the CO2 capture unit is reduced, the amount of steam supplied to the CO2 capture unit can be supplemented, and the CO2 capture rate can be maintained.

[0044] (2) A steam supply system according to a second aspect is the steam supply system of (1), wherein the second system is provided with a temperature control spray (SP2) for reducing the temperature of the medium-pressure steam and a temperature control spray valve (SPV2) for adjusting the amount of water sprayed from the temperature control spray, and when the control device opens the steam backup valve (V4), it opens the steam backup valve (V4) and also opens the temperature control spray valve. This prevents damage to equipment caused by relatively high-temperature medium-pressure steam being supplied to the CO2 capture device.

[0045] (3) A steam supply system according to a third aspect is the steam supply system of (1) to (2), wherein the control device closes the steam backup valve (V4) when the supply of fuel to the gas turbine is cut off after opening the steam backup valve (V4). This allows the HRSG to be kept warm.

[0046] (4) A steam supply system according to a fourth aspect is a steam supply system according to any one of (1) to (3), wherein the control device closes the low-pressure steam control valve and opens the steam backup valve when the power plant is stopped. This means that even in situations where there is concern about a shortage of steam supply when the power plant is shut down, steam can be continuously supplied to the CO2 capture device, maintaining the CO2 capture rate.

[0047] (5) A steam supply system according to a fifth aspect is a steam supply system according to any one of (1) to (4), wherein the control device closes the low-pressure steam control valve and opens the steam backup valve when the power plant performs load rejection. This means that even in situations where there is concern about a shortage of steam supply when the power plant experiences load shedding, steam can be continuously supplied to the CO2 capture device, making it possible to maintain the CO2 capture rate.

[0048] (6) A steam supply system according to a sixth aspect is a steam supply system according to any one of (1) to (5), wherein the control device closes the low-pressure steam control valve and opens the steam backup valve when the steam turbine trips. This means that even in situations where there is concern about a shortage of steam supply during a steam turbine trip, steam can be continuously supplied to the CO2 capture device, maintaining the CO2 capture rate.

[0049] (7) A steam supply system according to a seventh aspect is a steam supply system according to any one of (1) to (6), wherein the control device closes the low-pressure steam control valve and opens the steam backup valve when the steam turbine stops and the gas turbine continues to operate during operation of the power plant. As a result, even if the steam supply to the steam turbine is cut off, as long as the gas turbine is running, steam can continue to be supplied to the CO2 capture device, thereby maintaining the CO2 capture rate.

[0050] (8) A steam supply system according to an eighth aspect is a steam supply system according to any one of (1) to (7), wherein, when the steam backup valve is opened, the control device feedback controls the opening degree of the steam backup valve so that the pressure downstream of the steam backup valve reaches a target value. This allows steam to be supplied to the CO2 capture device in a stable and continuous manner.

[0051] (9) A steam supply system according to a ninth aspect is a steam supply system according to any one of (1) to (8), wherein the control device, when opening the steam backup valve, opens the steam backup valve at a predetermined opening degree when the power plant is in a transient state, and otherwise feedback controls the opening degree of the steam backup valve so that the pressure downstream of the steam backup valve reaches a target value. This allows steam to be supplied to the CO2 capture device in a stable and continuous manner.

[0052] (10) A steam supply system according to a tenth aspect is a steam supply system according to any one of (2) to (9), wherein when the temperature control spray valve is opened, the control device feedback controls the opening degree of the temperature control spray valve so that the temperature of the medium-pressure steam downstream of the temperature control spray valve becomes a target value. This allows the temperature of the steam supplied to the CO2 capture device to be controlled to an appropriate temperature.

[0053] (11) A steam supply system according to an eleventh aspect is a steam supply system according to any one of (2) to (9), wherein the control device, when opening the temperature control spray valve, opens the temperature control spray valve at a predetermined opening degree when the power generation plant is in a transient state, and otherwise feedback controls the opening degree of the temperature control spray valve so that the temperature of the medium-pressure steam downstream of the temperature control spray valve reaches a target value. This allows the temperature of the steam supplied to the CO2 capture device to be controlled to an appropriate temperature.

[0054] (12) A steam supply method according to a twelfth aspect is a steam supply method for a plant including a power plant including a gas turbine, a heat recovery boiler, and a steam turbine, a CO2 recovery device that recovers CO2 from exhaust gas of the power plant, a first system that extracts low-pressure steam from a low-pressure system that supplies low-pressure steam from the heat recovery boiler to the steam turbine and supplies the low-pressure steam to the CO2 recovery device, a second system that extracts medium-pressure steam from a medium-pressure system that supplies medium-pressure steam from the heat recovery boiler to the steam turbine and supplies the medium-pressure steam to the first system, a low-pressure steam control valve provided in the low-pressure system upstream of a connection position with the first system, a medium-pressure steam control valve provided in the medium-pressure system, and a steam backup valve provided in the second system, the method comprising: closing the low-pressure steam control valve and the medium-pressure steam control valve and opening the steam backup valve based on an operating state of the power plant. [Explanation of symbols]

[0055] 100···Plant, 10···Gas turbine, 20···HRSG, 21L···Low-pressure economizer, 21I···Intermediate-pressure economizer, 21H···High-pressure economizer, 22L···Low-pressure evaporator, 22I···Intermediate-pressure evaporator, 22H···High-pressure evaporator, 23L···Low-pressure superheater, 23I···Intermediate-pressure superheater, 23H···High-pressure superheater, 24···Reheater, 25L···Low-pressure drum, 25I···Intermediate-pressure drum, 25H···High-pressure drum, 30···Steam turbine, 31···High-pressure turbine, 32···Intermediate-pressure turbine, 33···Low-pressure turbine, 40···CO2 capture unit, 50···Control device, G1, G2···Generator, P 1 to P2: Pressure gauge, T1: Thermometer, SP1 to SP2: Temperature control spray, SPV1 to SPV2: Temperature control spray valve, V1: Low-pressure turbine bypass valve, V2: Low-pressure steam control valve, V3: Low-pressure steam extraction valve, V4: Medium-pressure backup steam pressure control valve, V5: High-pressure steam control valve, V6: High-pressure turbine bypass valve, V7: Medium-pressure steam control valve, V8: Medium-pressure turbine bypass valve, L1 to L11: System, 900: Computer, 901: CPU, 902: Main memory device, 903: Auxiliary memory device, 904: Input / output interface, 905: Communication interface

Claims

1. A method for extracting CO from exhaust gas emitted from a power plant including a gas turbine, a heat recovery boiler, and a steam turbine. ２ CO2 recovery ２ A steam supply system for supplying steam generated in the heat recovery boiler to a recovery device, a low-pressure system for supplying low-pressure steam from the heat recovery steam generator to the steam turbine; A gas turbine engine is connected to the low-pressure system, and extracts the low-pressure steam from the low-pressure system to generate the CO ２ a first system that supplies the recovery device; a low-pressure steam control valve provided in the low-pressure system upstream of a connection position with the first system; an intermediate pressure system for supplying intermediate pressure steam from the heat recovery steam generator to the steam turbine; a second system connected to the intermediate pressure system, extracting the intermediate pressure steam from the intermediate pressure system and supplying the extracted medium pressure steam to the first system; an intermediate pressure steam control valve provided in the intermediate pressure system; a steam backup valve provided in the second system; a control device; Equipped with the control device closes the low-pressure steam control valve and the intermediate-pressure steam control valve and opens the steam backup valve based on an operating state of the power plant. Steam supply system.

2. The second system is provided with a temperature control spray for reducing the temperature of the medium-pressure steam and a temperature control spray valve for adjusting the amount of water sprayed from the temperature control spray, When the control device opens the steam backup valve, the control device opens the steam backup valve and also opens the temperature control spray valve. The steam supply system of claim 1 .

3. when the supply of fuel to the gas turbine is cut off after the control device opens the steam backup valve, the control device closes the steam backup valve. The steam supply system according to claim 1 or 2.

4. When the power plant is stopped, the control device closes the low-pressure steam control valve and opens the steam backup valve. The steam supply system according to claim 1 or 2.

5. the control device closes the low-pressure steam control valve and opens the steam backup valve when the power plant performs load rejection. The steam supply system according to claim 1 or 2.

6. When the steam turbine trips, the control device closes the low-pressure steam control valve and opens the steam backup valve. The steam supply system according to claim 1 or 2.

7. the control device closes the low-pressure steam control valve and opens the steam backup valve when the steam turbine stops and the gas turbine continues to operate during operation of the power plant. The steam supply system according to claim 1 or 2.

8. When the control device opens the steam backup valve, the control device feedback controls the opening degree of the steam backup valve so that the pressure at the downstream side of the steam backup valve reaches a target value. The steam supply system according to claim 1 or 2.

9. When the control device opens the steam backup valve, the control device opens the steam backup valve at a predetermined opening degree when the power plant is in a transient state, and otherwise feedback controls the opening degree of the steam backup valve so that the pressure in the downstream stage of the steam backup valve reaches a target value. The steam supply system according to claim 1 or 2.

10. When the temperature control spray valve is opened, the control device feedback controls the opening degree of the temperature control spray valve so that the temperature of the medium-pressure steam in a downstream stage of the temperature control spray valve becomes a target value. The steam supply system of claim 2 .

11. When the temperature control spray valve is opened, the control device opens the temperature control spray valve at a predetermined opening degree when the power plant is in a transient state, and otherwise feedback controls the opening degree of the temperature control spray valve so that the temperature of the medium-pressure steam in a downstream stage of the temperature control spray valve becomes a target value. The steam supply system of claim 2 .

12. A power plant including a gas turbine, a heat recovery boiler, and a steam turbine, and a method for extracting CO from exhaust gas of the power plant. ２ CO2 recovery ２ a recovery device for recovering the CO ２ a second system that extracts medium-pressure steam from an intermediate-pressure system that supplies medium-pressure steam from the exhaust heat recovery boiler to the steam turbine and supplies the extracted medium-pressure steam to the first system; a low-pressure steam control valve provided in the low-pressure system upstream of a connection position with the first system; an intermediate-pressure steam control valve provided in the intermediate-pressure system; and a steam backup valve provided in the second system, ２ A method for supplying steam to a recovery device, comprising: based on the operating state of the power plant, the low-pressure steam control valve and the intermediate-pressure steam control valve are closed, and the steam backup valve is opened. Steam supply method.

Images