Plant and plant control method

Abstract

This plant comprises: a gas turbine; an exhaust heat recovery boiler; a steam turbine; a carbon dioxide recovery device that uses an absorption liquid to recover carbon dioxide contained in exhaust gas that has been discharged from the exhaust heat recovery boiler; a steam supply system that supplies, to the steam turbine and the carbon dioxide recovery device, steam generated by the exhaust heat recovery boiler; a steam condenser that generates water from the steam discharged from the steam turbine; a steam condensate system that is provided downstream of the steam condenser and supplies the water generated by the steam condenser to the exhaust heat recovery boiler; and a first return system that supplies, to the steam condenser or a steam condensate tank for receiving and storing the water from the steam condenser, water generated by heat exchange between the absorption liquid and the steam in the carbon dioxide recovery device.

Description

Plant and plant control method

[0001] The present disclosure relates to a plant and a plant control method.

[0002] A gas turbine combined cycle power plant (hereinafter also referred to as "GTCC") is a highly efficient power generation facility that uses fossil fuels. In addition to generating electricity using a gas turbine, the GTCC utilizes the exhaust heat from the gas turbine to generate steam in a heat recovery steam generator (hereinafter also referred to as "HRSG"), which then uses the steam to generate electricity in a steam turbine, thereby achieving high power generation efficiency.

[0003] In a power plant equipped with a GTCC as described above, a carbon dioxide capture plant (hereinafter also referred to as "CCP") is sometimes installed, which captures carbon dioxide in the combustion exhaust gas from the gas turbine to reduce carbon dioxide emissions (see, for example, Patent Document 1). This CCP has a carbon dioxide absorption tower that absorbs carbon dioxide in the exhaust gas with an absorption liquid (e.g., an amine absorption liquid, etc.), and an absorption liquid regeneration tower that desorbs carbon dioxide from the absorption liquid that has absorbed the carbon dioxide. The absorption liquid regeneration tower of the CCP has a reboiler that heats the absorption liquid with steam to desorb carbon dioxide from the absorption liquid.

[0004] The absorbent regeneration tower uses steam to heat the absorbent that has absorbed carbon dioxide in the reboiler, thereby desorbing and releasing the carbon dioxide from the absorbent, recovering high-purity carbon dioxide, and regenerating the absorbent, which is then sent to the carbon dioxide absorption tower for recycling. Through this heating process, the steam supplied to the reboiler becomes condensed water.

[0005] Japanese Patent Application Laid-Open No. 2021-181786

[0006] In a power plant equipped with a GTCC and a CCP as described above, a configuration is being considered in which a portion of the steam generated in the heat recovery boiler of the GTCC is supplied to the reboiler of the CCP. In this configuration, how to treat the condensed water generated by heat exchange between the absorption liquid and the steam in the reboiler is an issue, and a configuration that allows efficient use of water throughout the plant is required.

[0007] The present disclosure has been made in view of the above, and aims to provide a plant and a plant control method that enable efficient use of water throughout the plant.

[0008] The plant according to the present disclosure includes a gas turbine, a heat recovery boiler that exchanges heat with exhaust gas from the gas turbine to generate steam, a steam turbine driven by the steam generated in the heat recovery boiler, a carbon dioxide recovery unit that recovers carbon dioxide contained in the exhaust gas discharged from the heat recovery boiler using an absorption liquid, a steam supply system that supplies the steam generated in the heat recovery boiler to the steam turbine and the carbon dioxide recovery unit, a condenser that generates water from the steam discharged from the steam turbine, a condensation system that is provided downstream of the condenser and supplies water generated in the condenser to the heat recovery boiler, and a first return system that supplies water generated in the carbon dioxide recovery unit by heat exchange between the absorption liquid and the steam to the condenser or to a condensate tank that receives and stores water from the condenser.

[0009] The plant control method according to the present disclosure is a plant control method for controlling the above-mentioned plant, which further includes a second return system that supplies water generated by heat exchange between the absorption liquid and the steam in the carbon dioxide capture device to the condensate system, and when no abnormality is detected in the steam supply system or the condensate system, water from the carbon dioxide capture device is supplied to the condensate system via the second return system, and when an abnormality is detected in the steam supply system or the condensate system, water from the carbon dioxide capture device is supplied to the condenser or the condensate tank via the first return system.

[0010] According to the present disclosure, it is possible to use water efficiently throughout the plant.

[0011] Fig. 1 is a schematic diagram showing an example of a plant according to this embodiment. Fig. 2 is a functional block diagram showing an example of a control system of a valve control unit. Fig. 3 is a flowchart showing an example of a plant control method according to this embodiment. Fig. 4 is a schematic diagram showing another example of a plant according to this embodiment. Fig. 5 is a schematic diagram showing another example of a plant according to this embodiment. Fig. 6 is a schematic diagram showing another example of a plant according to this embodiment.

[0012] Hereinafter, embodiments of a plant and a plant control method according to the present disclosure will be described with reference to the drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by a person skilled in the art, or those that are substantially identical.

[0013] 1 is a schematic diagram of a plant 100 according to this embodiment. In this embodiment, the plant 100 will be described as a power plant, but the plant 100 can be used for various purposes in which fuel is combusted to extract energy.

[0014] 1 , a plant 100 according to this embodiment includes a gas turbine 11, a heat recovery steam generator 13 that exchanges heat energy of combustion exhaust gas 12 from the gas turbine 11 in heat exchange sections 13A and 13B to generate steam S10, a steam turbine 16 driven by the steam S10 (S11, S12, S13) generated in the heat recovery steam generator 13, a steam supply line (steam supply system) L10 that supplies the steam generated in the heat recovery steam generator 13 to the steam turbine 16, a condenser 30 that generates water from the steam discharged from the steam turbine 16, and a condensate line (condensate system) L15 that is provided downstream of the condenser 30 and supplies condensate 31 generated in the condenser 30 to the heat recovery steam generator 13. The plant 100 constitutes a gas turbine combined cycle (GTCC) that generates power not only in the gas turbine 11 but also in the steam turbine 16 by utilizing the exhaust heat of the gas turbine 11 in the heat recovery steam generator 13 to generate power. The steam turbine 16 includes a high-pressure steam turbine 16H, an intermediate-pressure steam turbine 16I, and a low-pressure steam turbine 16L.

[0015] The gas turbine 11 includes an air compressor 11A, a combustor 11B, and a turbine section 11C. The air compressor 11A has rotating blades and stator vanes arranged alternately in multiple stages. The air compressor 11A compresses air A introduced from the outside and introduces the high-temperature, high-pressure compressed air into the combustor 11B. The combustor 11B injects fuel F into the high-temperature, high-pressure compressed air introduced from the air compressor 11A and combusts it to generate high-temperature combustion gas. The turbine section 11C has rotating blades and stator vanes arranged alternately in multiple stages. The combustion gas generated in the combustor 11B passes through the turbine section 11C. The energy of the combustion gas rotates the rotating blades as the combustion gas passes through the turbine section 11C. The turbine section 11C and the air compressor 11A are connected by a rotating shaft. The high-temperature, high-pressure combustion gas is supplied from the combustor 11B to the turbine section 11C, where the thermal energy of the high-temperature, high-pressure combustion gas is converted into rotational energy. This rotational energy drives an air compressor 11A arranged coaxially. A gas turbine generator G1 is connected to the rotating shaft of the gas turbine 11, and the rotational energy drives the gas turbine generator G1 to generate electricity. The combustion exhaust gas 12 that has driven the turbine section 11C is discharged to a heat recovery boiler 13. The heat recovery boiler 13 recovers the thermal energy of the combustion exhaust gas 12.

[0016] The heat recovery steam generator 13 has a heat exchange section 13A and a heat exchange section 13B. The steam supply line L10 has a first steam line L11, a second steam line L12, a third steam line L13, and a fourth steam line L14. The first steam line L11 connects the heat exchange section 13A of the heat recovery steam generator 13 to the high-pressure steam turbine 16H. The second steam line L12 connects the high-pressure steam turbine 16H to the heat exchange section 13B. The third steam line L13 connects the heat exchange section 13B to the intermediate-pressure steam turbine 16I. The fourth steam line L14 connects the intermediate-pressure steam turbine 16I to the low-pressure steam turbine 16L and introduces steam S13 to the low-pressure steam turbine 16L. The condensate line L15 connects the condenser 30 to the heat exchange section 13A and introduces condensate 31 to the heat exchange section 13A. The condensate pump 32 is installed in the condensate line L15 and pressurizes the condensate 31 generated by the condenser 30. A condensate tank 34 is connected to the condenser 30. The condensate tank 34 receives and stores water from the condenser 30. The condensate tank 34 can reduce the amount of stored water by releasing the stored water to the outside.

[0017] The heat exchange unit 13A exchanges heat between the condensate 31 supplied from the condenser 30 and the combustion exhaust gas 12. The condensate 31 exchanges heat with the combustion exhaust gas 12 to become steam (e.g., 550°C) S11. The steam S11 is sent to the high-pressure steam turbine 16H via a first steam line L11 and drives the high-pressure steam turbine 16H.

[0018] The heat exchanger 13B exchanges heat between the exhaust steam that has passed through the high-pressure steam turbine 16H and the combustion exhaust gas 12. The exhaust steam is introduced into the heat exchanger 13B of the heat recovery boiler 13 via the second steam line L12, where it exchanges heat with the combustion exhaust gas 12 to become steam (e.g., 550°C) S12. The steam S12 is sent to the intermediate-pressure steam turbine 16I via the third steam line L13 to drive the intermediate-pressure steam turbine 16I. The steam (e.g., 270°C) S13 that has passed through the intermediate-pressure steam turbine 16I is supplied to the low-pressure steam turbine 16L to drive the low-pressure steam turbine 16L. The exhaust steam that has passed through the low-pressure steam turbine 16L is returned to condensate (e.g., 40 to 50°C) 31 in the condenser 30.

[0019] The plant 100 has a fuel introduction line L1, an air introduction line L2, a combustion gas line L3, and a combustion exhaust gas discharge line L4. The fuel introduction line L1 introduces fuel F into the combustor 11B. The air introduction line L2 introduces air A into the air compressor 11A. The combustion gas line L3 introduces combustion gas into the turbine section 11C. The combustion exhaust gas discharge line L4 discharges combustion exhaust gas 12 from the turbine section 11C and introduces it into the heat recovery steam generator 13.

[0020] The plant 100 according to this embodiment also includes a carbon dioxide recovery unit 50 that recovers carbon dioxide contained in the combustion exhaust gas 12 discharged from the heat recovery boiler 13 using an absorption liquid, a steam supply line (steam supply system) L20 that supplies steam generated in the heat recovery boiler 13 to the carbon dioxide recovery unit 50, a first return line (first return system) L31 that supplies condensed water 56 generated by heat exchange between the absorption liquid and the steam in the carbon dioxide recovery unit 50 to the condenser 30, and a second return line (second return system) L32 that supplies the condensed water 56 generated by heat exchange between the absorption liquid and the steam in the carbon dioxide recovery unit 50 to the condensation system L15.

[0021] The carbon dioxide recovery unit 50 includes a carbon dioxide absorption tower 51, an absorption liquid regeneration tower 52, and a reboiler 55. The carbon dioxide absorption tower 51 absorbs carbon dioxide in the combustion exhaust gas 12A discharged from the heat recovery boiler 13 using an absorption liquid such as an amine absorption liquid. The absorption liquid regeneration tower 52 desorbs carbon dioxide from the absorption liquid that has absorbed carbon dioxide in the carbon dioxide absorption tower 51 using the reboiler 55. The reboiler 55 heats the absorption liquid using steam generated in the heat recovery boiler 13 to desorb carbon dioxide from the absorption liquid. The reboiler 55 is installed relative to the absorption liquid regeneration tower 52. The carbon dioxide recovery unit 50 heats the absorption liquid that has absorbed carbon dioxide in the absorption liquid regeneration tower 52, thereby stripping carbon dioxide from the absorption liquid, recovering high-purity carbon dioxide, and regenerating the absorption liquid.

[0022] The absorption liquid that has passed through the carbon dioxide absorption tower 51 and absorbed carbon dioxide is called a rich solution. The absorption liquid that has passed through the absorption liquid regeneration tower 52 and from which carbon dioxide has been separated is called a lean solution. The lean solution is sent to the carbon dioxide absorption tower 51 via a lean solution line L51, where it absorbs carbon dioxide again to become a rich solution. The rich solution is sent to the absorption liquid regeneration tower 52 via a rich solution line L52. The carbon dioxide recovery unit 50 circulates and reuses the absorption liquid within a closed system. The absorption liquid is not limited to an amine absorption liquid, and any liquid that has the property of absorbing and releasing carbon dioxide may be used, and the present invention is not limited thereto.

[0023] A reboiler line L25 equipped with a reboiler 55 for circulating a part of the lean solution is connected to the absorbent regenerator 52 near the bottom. A part of the lean solution regenerated in the absorbent regenerator 52 is heated by heat exchange with steam in the reboiler 55 installed in the reboiler line L25, and is circulated to the absorbent regenerator 52.

[0024] The carbon dioxide recovery unit 50 has a first gas discharge line L6, a second gas discharge line L7, and a discharge line L8. The first gas discharge line L6 discharges the treated gas 12B from which carbon dioxide has been removed to the outside from the top of the carbon dioxide absorption tower 51. The second gas discharge line L7 introduces carbon dioxide 53 discharged from the top of the absorbent regeneration tower 52 to the carbon dioxide compressor 57. The discharge line L8 discharges compressed carbon dioxide 58 compressed by the carbon dioxide compressor 57.

[0025] The steam supply line L20 connects the fourth steam line L14, which supplies steam S13 from the exhaust of the intermediate-pressure steam turbine 16I to the low-pressure steam turbine 16L, to the reboiler 55. The steam supply line L20 extracts a portion of the steam S13 from the fourth steam line L14 and supplies it to the reboiler 55 as steam S20.

[0026] The steam S20 supplied to the reboiler 55 from the steam supply line L20 described above reaches a temperature (e.g., 130 to 140°C) required for regenerating the absorbing liquid in the reboiler 55. In the reboiler 55, the steam S20 is condensed by heat exchange with the absorbing liquid to become condensed water 56. The temperature of the condensed water 56 produced in the reboiler 55 drops to approximately 100°C.

[0027] The condensed water line L30 is connected to the reboiler 55. The condensed water line L30 returns condensed water 56 generated in the reboiler 55 to the GTCC side. The condensed water line L30 branches into a first return line L31 and a second return line L32.

[0028] The first return line L31 is connected to the condenser 30. The first return line L31 supplies the condensed water 56 from the reboiler 55 and the condensed water line L30 to the condenser 30. A first control valve V1 is provided in the first return line L31. The first control valve V1 is, for example, a solenoid valve or the like, and opens and closes the first return line L31. When the first control valve V1 is open, the condensed water 56 from the condensed water line L30 is supplied to the condenser 30 via the first return line L31. On the other hand, when the first control valve V1 is closed, the condensed water 56 from the condensed water line L30 is not supplied to the condenser 30. The opening and closing of the first control valve V1 is controlled by the valve control unit 60.

[0029] The second return line L32 is connected to a portion of the condensate line L15 downstream of the condensate pump 32. The second return line L32 supplies condensed water 56 from the reboiler 55 and the condensate line L30 to the condensate line L15 downstream of the condensate pump 32 (hereinafter referred to as the pump downstream side). A second control valve V2 is provided in the second return line L32. The second control valve V2 is, for example, an electromagnetic valve, and opens and closes the second return line L32. When the second control valve V2 is open, the condensed water 56 from the condensate line L30 is supplied to the condensate line L15 downstream of the pump via the second return line L32. On the other hand, when the second control valve V2 is closed, the condensed water 56 from the condensate line L30 is not supplied to the condensate line L15 downstream of the pump.

[0030] The valve control unit 60 controls the opening and closing operations of the first control valve V1 and the second control valve V2. In this embodiment, the plant 100 is provided with a system abnormality detection unit 61 that detects an abnormality in at least one of the steam supply lines L10, L20 and the condensate line L15. The valve control unit 60 may control the opening and closing operations of the first control valve V1 and the second control valve V2 based on, for example, a detection result of the system abnormality detection unit 61.

[0031] 2 is a functional block diagram showing an example of a control system of the valve control unit 60. As shown in FIG. 2, the valve control unit 60 includes a communication unit 62, a processing unit 63, and a storage unit 64.

[0032] The communication unit 62 performs wired or wireless communication with external devices and includes an interface such as a network interface card.

[0033] The processing unit 63 performs various types of information processing and includes a processor such as a CPU (Central Processing Unit) and memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0034] The processing unit 63 may control the opening and closing operations of the first control valve V1 and the second control valve V2 based on the detection result of the system abnormality detection unit 61. The processing of the processing unit 63 will be described in detail later.

[0035] The storage unit 64 stores information such as various programs and data for controlling the opening and closing operations of the first control valve V1 and the second control valve V2 in the processing unit 63. The storage unit 64 includes storage devices such as a hard disk drive (HDD) and a solid state drive (SSD).

[0036] In the control unit 60, the processor in the processing unit 63 reads out various programs and loads them into memory, thereby executing information processing corresponding to the functions of the above-mentioned units. Examples of the various programs include programs received by the communication unit 62, programs stored in the storage unit 64, and programs recorded on an external recording medium. The control unit 60 functions as an information processing device (computer) that executes various information processes. Note that the various programs may be executed by an information processing device other than the control unit 60, or the control unit 60 and the other information processing device may cooperate to execute the various programs.

[0037] An example of control by the valve control unit 60 will be described in detail. FIG. 3 is a flowchart illustrating an example of a plant control method according to this embodiment. FIG. 3 illustrates an example of control by the valve control unit 60 as plant control. As shown in FIG. 3, the processing unit 63 determines whether the system abnormality detection unit 61 has detected an abnormality (step S10). If the system abnormality detection unit 61 determines that an abnormality has not been detected (No in step S10), the processing unit 63 performs control to close the first control valve V1 and open the second control valve V2 (step S20). If the system abnormality detection unit 61 detects an abnormality (Yes in step S10), the processing unit 63 performs control to open the first control valve V1 and close the second control valve V2 (step S30).

[0038] By this control, when no abnormality occurs in the steam supply lines L10, L20 and the condensate line L15, the first control valve V1 is closed and the second control valve V2 is opened, so that condensed water 56 from the reboiler 55 is supplied from the condensate line L30 through the second return line L32 to the downstream side of the pump of the condensate line L15. In this case, when normal operation is being performed on the GTCC side, it is possible to prevent the condensed water 56 from being supplied to the condenser 30, and therefore it is possible to prevent a deterioration in the degree of vacuum of the condenser 30.

[0039] Furthermore, if an abnormality occurs in the steam supply lines L10, L20 and the condensate line L15, the steam supply lines L10, L20 and the condensate line L15 are closed on the GTCC side. In such a case, the first control valve V1 is opened and the second control valve V2 is closed, so that condensed water 56 from the reboiler 55 is supplied to the condenser 30 from the condensed water line L30 via the first return line L31. This ensures a supply destination for the condensed water 56, allowing efficient use of water throughout the plant.

[0040] Fig. 4 is a schematic diagram showing another example of a plant according to this embodiment. A plant 100A shown in Fig. 4 differs from the plant 100 described above in that a first return line L31A is connected from the condensed water line L30 to the condensate tank 34. The other configurations are the same as those of the plant 100 described above.

[0041] When the first control valve V1 is opened, the first return line L31A supplies the condensed water 56 from the reboiler 55 and the condensed water line L30 to the condensate tank 34. In this way, the condensed water 56 from the reboiler 55 and the condensed water line L30 may be configured to be able to be supplied to the condensate tank 34. This ensures a supply destination for the condensed water 56, allowing efficient use of water throughout the plant. Note that when the first control valve V1 is closed, the first return line L31A does not supply the condensed water 56 from the reboiler 55 and the condensed water line L30 to the condensate tank 34.

[0042] Fig. 5 is a schematic diagram showing another example of a plant according to this embodiment. A plant 100B shown in Fig. 5 differs from the plant 100 described above in that the second return line L32 and the second control valve V2 are not provided. In addition, a valve control unit 60 controls the first control valve V1. The other configurations are the same as those of the plant 100 described above. Note that the first return line L31 may be connected from the condensed water line L30 to the condensate tank 34.

[0043] When the first control valve V1 is opened by the valve control unit 60, the first return line L31 supplies condensed water 56 from the reboiler 55 and the condensed water line L30 to the condenser 30. In this way, the condensed water 56 generated in the reboiler 55 is not discharged outside the system but is supplied from the condensed water line L30 to the condenser 30 via the first return line L31 and reused as condensate. This enables efficient use of water throughout the plant 100B. The valve control unit 60 may control the opening and closing operation of the first control valve V1 based on the detection result of the system abnormality detection unit 61. Alternatively, the valve control unit 60 may independently control the opening and closing operation of the first control valve V1 regardless of the detection result of the system abnormality detection unit 61. In this case, the system abnormality detection unit 61 may not be provided.

[0044] Fig. 6 is a schematic diagram showing another example of a plant according to this embodiment. A plant 100C shown in Fig. 6 differs from the plant 100 described above in that the steam supply line L20 connects the second steam line L12, which supplies exhaust steam that has passed through the high-pressure steam turbine 16H to the heat recovery steam generator 13, with the reboiler 55. The plant 100C also differs from the plant 100 described above in that a cooler 59 is disposed upstream of the reboiler 55 in the steam supply line L20. The other configurations are the same as those of the plant 100 described above.

[0045] In the plant 100C, a portion of the exhaust steam that has passed through the high-pressure steam turbine 16H is extracted from the second steam line L12 to the steam supply line L20 as steam S20. The exhaust steam that has passed through the high-pressure steam turbine 16H is reheated in the heat recovery boiler 13, and then supplied to the intermediate-pressure turbine 16I for reuse. Therefore, even if a portion of the exhaust steam from the high-pressure steam turbine 16H that flows through the second steam line L12 is extracted to the steam supply line L20, the efficiency of the steam turbine 16H is not affected.

[0046] The steam S20 extracted to the steam supply line L20 is supplied from the steam supply line L20 to a cooler 59, cooled by the cooler 59, and supplied to the reboiler 55. In Fig. 6, the cooler 59 is shown as an example of a configuration in which it is provided as part of the carbon dioxide recovery unit 50, but the configuration is not limited to this and the cooler 59 may be provided as a configuration separate from the carbon dioxide recovery unit 50. By being cooled by the cooler 59, the steam S20 is supplied to the reboiler 55 in a state in which the steam temperature is appropriately set to a temperature for efficiently operating the reboiler 55. Therefore, the operating efficiency of the reboiler 55 can be improved.

[0047] 6 illustrates an example of a configuration in which the steam supply line L20 connects the second steam line L12 and the reboiler 55 to the plant 100, and a cooler 59 is disposed on the steam supply line L20 upstream of the reboiler 55; however, the present invention is not limited to this. For example, the plant 100A illustrated in FIG. 4 and the plant 100B illustrated in FIG. 5 may have a configuration in which the steam supply line L20 connects the second steam line L12 and the reboiler 55 to the plant 100A, and a cooler 59 is disposed on the steam supply line L20 upstream of the reboiler 55. Furthermore, in any of the above configurations, the cooler 59 may not be provided.

[0048] As described above, according to the first aspect of the present disclosure, there is provided a gas turbine 11, a heat recovery boiler 13 that exchanges heat with exhaust gas from the gas turbine 11 to generate steam, a steam turbine 16 that is driven by the steam generated in the heat recovery boiler, a carbon dioxide recovery unit 50 that recovers carbon dioxide contained in the exhaust gas discharged from the heat recovery boiler 13 using an absorption liquid, and steam supply lines L10, L20 that supply the steam generated in the heat recovery boiler 13 to the steam turbine 16 and the carbon dioxide recovery unit 50. There is provided a plant 100, a plant 100A, or a plant 100B including a condenser 30 that generates condensate 31 from steam discharged from a steam turbine 16, a condensate line L15 that is provided downstream of the condenser 30 and supplies the condensate 31 generated in the condenser 30 to a heat recovery boiler 13, and a first return line L31 that supplies condensed water 56 generated by heat exchange between an absorption liquid and steam in a carbon dioxide recovery device 50 to the condenser 30 or a condensate tank 34 that receives and stores water from the condenser 30.

[0049] According to this configuration, the condensed water 56 generated in the reboiler 55 is not discharged as wastewater but is supplied from the condensed water line L30 to the condenser 30 via the first return line L31 and is reused as condensed water. This allows efficient use of water throughout the plant 100, plant 100A, or plant 100B.

[0050] According to a second aspect of the present disclosure, the first aspect further includes a second return line L32 that supplies condensed water 56 generated by heat exchange between the absorption liquid and steam in the carbon dioxide recovery unit 50 to the condensate line L15.

[0051] According to this configuration, first return lines L31, L31A are provided to return the condensed water 56 from the carbon dioxide capture unit 50 to the condenser 30 or the condensate tank 34, and a second return line L32 is provided to return the condensed water 56 to the condensate line L15. Therefore, for example, when normal operation is being performed on the GTCC side, the condensed water 56 can be returned from the second return line L32 to the condensate line L15, thereby preventing the condensed water 56 from being supplied to the condenser 30 and preventing a deterioration in the degree of vacuum of the condenser 30. Furthermore, for example, when the steam supply lines L10, L20 and the condensate line L15 are blocked on the GTCC side, the condensed water 56 can be returned from the first return line L31 to the condenser 30, thereby ensuring a supply destination for the condensed water 56.

[0052] According to the third aspect of the present disclosure, in the second aspect, the condensate line L15 has a condensate pump 32 that pressurizes the condensate 31 generated in the condenser 30, and the second return line L32 supplies condensed water 56 from the carbon dioxide recovery unit 50 to the portion of the condensate line L15 downstream of the condensate pump 32.

[0053] According to this configuration, the condensed water 56 is supplied to the downstream portion of the condensate line L15 that has been pressurized by the condensate pump 32, thereby reducing the burden on the condensate pump 32.

[0054] According to the fourth aspect of the present disclosure, in the second or third aspect, the first return line L31 supplies condensed water 56 from the carbon dioxide recovery device 50 to the condenser 30, and further includes a condensate tank 34 that receives and stores water from the condenser 30.

[0055] According to this configuration, the condensed water 56 supplied to the condenser 30 can be stored in the condensate tank 34. By using the condensate tank 34 as a buffer in this manner, the volume of water that can be stored in the condenser 30 can be ensured.

[0056] According to a fifth aspect of the present disclosure, in any of the second to fourth aspects, the system further includes a system abnormality detection unit 61 that detects an abnormality in at least one of the steam supply lines L10, L20 and the condensate line L15, a first control valve V1 provided in the first return line L31, a second control valve V2 provided in the second return line L32, and a valve control unit 60 that controls the first control valve V1 and the second control valve V2 based on the detection result of the system abnormality detection unit 61, and when no abnormality is detected, the valve control unit 60 controls to close the first control valve V1 and open the second control valve V2, and when an abnormality is detected, controls to open the first control valve V1 and close the second control valve V2.

[0057] According to this configuration, when no abnormality is detected in the steam supply lines L10, L20 and the condensate line L15, the first control valve V1 and the second control valve V2 are controlled so as to return the condensate 56 from the second return line L32 to the condensate line L15, and when an abnormality is detected in at least one of the steam supply lines L10, L20 and the condensate line L15, the first control valve V1 and the second control valve V2 are controlled so as to return the condensate 56 from the first return line L31 to the condenser 30. Therefore, the return destination of the condensate 56 can be appropriately switched.

[0058] According to a sixth aspect of the present disclosure, in any of the second to fifth aspects, the steam turbine 16 has a high-pressure steam turbine, an intermediate-pressure steam turbine, and a low-pressure steam turbine, and the steam supply lines L10, L20 extract a portion of steam from a system that supplies steam from the intermediate-pressure steam turbine to the low-pressure steam turbine and supply it to the carbon dioxide capture unit 50.

[0059] According to this configuration, it is possible to supply to the carbon dioxide recovery unit 50 steam containing an appropriate amount of thermal energy for heat exchange with the absorbing liquid.

[0060] According to a seventh aspect of the present disclosure, in any of the first to sixth aspects, the steam turbine 16 has a high-pressure steam turbine 16H, the carbon dioxide recovery unit 50 has a reboiler 55, and the steam supply lines L10 and L20 extract a portion of steam from a system that supplies steam from the high-pressure steam turbine 16H to the heat recovery boiler 13 and supply the extracted steam to the reboiler 55 of the carbon dioxide recovery unit 50.

[0061] In this configuration, the exhaust steam that has passed through the high-pressure steam turbine 16H is reheated in the heat recovery boiler 13 and then reused. Therefore, even if a portion of the exhaust steam from the high-pressure steam turbine 16H is extracted and supplied to the reboiler 55, it does not affect the efficiency of the steam turbine 16. Therefore, the steam generated in the heat recovery boiler 13 can be supplied to the carbon dioxide recovery unit 50 without affecting the efficiency of the steam turbine 16.

[0062] According to the eighth aspect of the present disclosure, in the seventh aspect, a cooler 59 is arranged upstream of the reboiler 55 in the steam supply line L20.

[0063] According to this configuration, the cooler 59 is disposed upstream of the reboiler 55 in the steam supply line L20, so that the steam temperature can be appropriately set to operate the reboiler 55 efficiently.

[0064] According to a ninth aspect of the present disclosure, there is provided a plant control method for controlling a plant 100, 100A relating to any of the second to sixth aspects, wherein, when no abnormality is detected in the steam supply line L10, L20 or the condensate line L15, water from the carbon dioxide recoverer 50 is supplied to the condensate line L15 via the second return line L32, and when an abnormality is detected in the steam supply line L10, L20 or the condensate line L15, water from the carbon dioxide recoverer 50 is supplied to the condenser 30 or the condensate tank 34 via the first return line L31.

[0065] The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the steam supply line L20 is connected from the fourth steam line L14 to the reboiler 55, but the present invention is not limited to this configuration. The steam supply line L20 may be connected to the reboiler 55 from another portion of the steam supply line L10.

[0066] DESCRIPTION OF SYMBOLS 11 Gas turbine 11A Air compressor 11B Combustor 11C Turbine section 12, 12A Combustion exhaust gas 12B Treated gas 13 Waste heat recovery boiler 13A, 13B Heat exchange section 16 Steam turbine 16H High-pressure steam turbine 16I Medium-pressure steam turbine 16L Low-pressure steam turbine 30 Condenser 31 Condensate 32 Condensate pump 34 Condensate tank 50 Carbon dioxide recovery unit 51 Carbon dioxide absorption tower 52 Absorbent regeneration tower 53 Carbon dioxide 55 Reboiler 56 Condensed water 57 Carbon dioxide compressor 58 Compressed carbon dioxide 60 Valve control unit, control unit 61 Detection unit 62 Communication unit 63 Processing unit 64 Memory unit 100, 100A, 100B, 100C Plant A Air F Fuel G1 Gas turbine generator G2 Steam turbine generator L1 Fuel introduction line L2 Air introduction line L3 Combustion gas line L4, L5 Combustion exhaust gas discharge line L6 First gas discharge line L7 Second gas discharge line L8 Discharge line L11 First steam line L12 Second steam line L13 Third steam line L10, L20 Steam supply line L14 Fourth steam line L15 Condensate line, condensate system L25 Reboiler line L30 Condensate line L31, L31A First return line L32 Second return line L51 Lean solution line L52 Rich solution line S10 Steam V1 First control valve V2 Second control valve

Claims

1. A plant comprising: a gas turbine; a heat recovery boiler that exchanges heat with exhaust gas from the gas turbine to generate steam; a steam turbine driven by the steam generated in the heat recovery boiler; a carbon dioxide recovery unit that recovers carbon dioxide contained in the exhaust gas discharged from the heat recovery boiler using an absorption liquid; a steam supply system that supplies the steam generated in the heat recovery boiler to the steam turbine and the carbon dioxide recovery unit; a condenser that generates water from the steam discharged from the steam turbine; a condensation system that is provided downstream of the condenser and supplies water generated in the condenser to the heat recovery boiler; and a first return system that supplies water generated in the carbon dioxide recovery unit by heat exchange between the absorption liquid and the steam to the condenser or to a condensate tank that receives and stores water from the condenser.

2. The plant according to claim 1, further comprising a second return line that supplies water generated by heat exchange between the absorption liquid and the steam in the carbon dioxide recovery unit to the condensate line.

3. The plant according to claim 2, wherein the condensate system has a condensate pump that pressurizes the water produced in the condenser, and the second return system supplies water from the carbon dioxide recovery unit to a portion of the condensate system downstream of the condensate pump.

4. The plant according to claim 2, wherein the first return system supplies water from the carbon dioxide recovery unit to the condenser, and further comprises a condensate tank that receives and stores water from the condenser.

5. The plant according to claim 2, further comprising: a system abnormality detection unit that detects an abnormality in at least one of the steam supply system and the condensate system; a first control valve provided in the first return system; a second control valve provided in the second return system; and a valve control unit that controls the first control valve and the second control valve based on the detection result of the system abnormality detection unit, wherein the valve control unit controls to close the first control valve and open the second control valve when no abnormality is detected, and controls to open the first control valve and close the second control valve when an abnormality is detected.

6. The plant according to claim 2, wherein the steam turbine has a high-pressure steam turbine, an intermediate-pressure steam turbine, and a low-pressure steam turbine, and the steam supply system extracts a portion of the steam from a system that supplies the steam from the intermediate-pressure steam turbine to the low-pressure steam turbine and supplies the extracted steam to the carbon dioxide recovery unit.

7. The plant according to claim 1, wherein the steam turbine has a high-pressure steam turbine, the carbon dioxide recovery unit has a reboiler, and the steam supply system extracts a portion of the steam from a system that supplies the steam from the high-pressure steam turbine to the heat recovery boiler and supplies the extracted steam to the reboiler of the carbon dioxide recovery unit.

8. The plant according to claim 7, wherein a cooler is disposed upstream of the reboiler in the steam supply system.

9. A plant control method for controlling a plant as described in claim 2, wherein, when no abnormality is detected in the steam supply system or the condensate system, water from the carbon dioxide recovery unit is supplied to the condensate system via the second return system, and when an abnormality is detected in the steam supply system or the condensate system, water from the carbon dioxide recovery unit is supplied to the condenser or the condensate tank via the first return system.

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