Intake air heating system, operation method of intake air heating system, and gas turbine system

Abstract

This intake air heating system is configured so as to heat external air flowing in an intake air flow path communicated with a compressor of a gas turbine, the intake air heating system comprising: a first heating unit that includes a return flow path for returning some compressed air discharged from the compressor to the intake air flow path; a second heating unit that includes a heater configured so as to utilize a heat source differing from the compressed air to heat the external air; and a control device that is configured so as to control the second heating unit such that the external air is heated by the heater in a high load segment where the gas turbine load is higher than a first stipulated load.

Description

[Technical Field]

[0001] The present disclosure relates to an intake air heating system, a method of operating an intake air heating system, and a gas turbine system. This application claims priority based on Japanese Patent Application No. 2022-127617, filed with the Japan Patent Office on August 10, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Conventionally, an intake air heating system that heats external air supplied to a compressor of a gas turbine is known. For example, a heating unit of a gas turbine disclosed in Patent Document 1 is configured to heat external air using compressed air as a heat source. The heating unit includes a return line for returning a portion of the compressed air discharged from the compressor to an intake duct. The compressed air flowing through the return line mixes with external air flowing through the intake duct, heating the external air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-097046 Summary of the Invention [Problem to be solved by the invention]

[0004] In the gas turbine described above, when the heating unit performs heating, the operating efficiency of the gas turbine may decrease, partly because a portion of the compressed air discharged from the compressor is returned to the intake duct, thereby reducing the flow rate of the combustion gas supplied to the turbine.

[0005] An object of the present disclosure is to provide an intake air heating system, an operating method for an intake air heating system, and a gas turbine system that improve the operating efficiency of a gas turbine. [Means for solving the problem]

[0006] In at least one embodiment of the present disclosure, the intake air heating system comprises: 1. An intake air heating system configured to heat external air flowing through an intake air flowpath communicating with a compressor of a gas turbine, the system comprising: a first heating unit including a return flow path for returning a portion of the compressed air discharged from the compressor to the intake flow path; a second heating unit including a heater configured to heat the external air using a heat source different from the compressed air; and a control device configured to control the second heating unit so that the external air is heated by the heater in a high load section in which the gas turbine load is higher than a first specified load.

[0007] A method of operating an intake air heating system according to at least one embodiment of the present disclosure includes: 1. A method of operating an intake air heating system configured to heat external air flowing through an intake air flowpath communicating with a compressor of a gas turbine, comprising: The intake air heating system includes: a first heating unit including a return flow path for returning a portion of the compressed air discharged from the compressor to the intake flow path; a second heating unit including a heater configured to heat the external air using a heat source different from the compressed air; Including, The method includes a second heating unit control step of controlling the second heating unit so that the external air is heated by the heater in a high load section in which the gas turbine load is higher than a first specified load.

[0008] A gas turbine system according to at least one embodiment of the present disclosure includes: The intake air heating system; The gas turbine. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an intake-air heating system, an operating method for an intake-air heating system, and a gas turbine system that improve the operating efficiency of a gas turbine. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a gas turbine system according to an embodiment; [Figure 2] 10 is a schematic graph showing a load section of a heating operation of a second heating unit according to one embodiment. [Figure 3] 10 is a schematic graph showing a load section of a heating operation of a first heating unit according to one embodiment. [Figure 4] FIG. 4 is a schematic view showing a second heating unit according to one embodiment. [Figure 5] 4 is a schematic graph showing the heating ratio of a first heating unit and a second heating unit according to an embodiment. [Figure 6] FIG. 1 is a schematic diagram illustrating details of a gas turbine according to an embodiment. [Figure 7] 3 is a flowchart illustrating an operation method of an intake air heating system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0012] <Outline of Gas Turbine System 1> FIG. 1 is a schematic diagram of a gas turbine system 1 according to an embodiment of the present disclosure. A gas turbine 3 constituting the gas turbine system 1 includes a compressor 7, a combustor 8 that generates a mixture of compressed air produced by the compressor 7 and fuel, and a turbine 30 that is driven by combustion gas discharged from the combustor 8. The compressor 7 is configured to start rotation by a starter 4. The fuel supplied to the combustor 8 is, for example, gas fuel, but may also be liquid fuel. The turbine 30 in this example is configured to drive a generator 6 using the combustion gas discharged from the combustor 8 as a power source. Exhaust gas discharged from the turbine 30 flows through an exhaust duct 39.

[0013] The compressor 7 is in communication with an intake air flow path 9. External air flowing through the intake air flow path 9 is sent to the compressor 7 to generate compressed air. The gas turbine system 1 of the present disclosure includes an intake air heating system 5 configured to heat the external air flowing through the intake air flow path 9, and the intake air heating system 5 includes a first heating unit 10 and a second heating unit 20. The first heating unit 10 is configured to heat the external air using the compressed air discharged from the compressor 7 as a heat source. More specifically, the first heating unit 10 includes a return flow path 15 for returning a portion of the compressed air discharged from the compressor 7 to the intake air flow path 9. The compressed air returned from the return flow path 15 to the intake air flow path 9 mixes with the external air, heating the external air.

[0014] The intake passage 9 illustrated in the figure includes a suction chamber 90 and an intake duct 95 that connects the suction chamber 90 to the compressor 7, and the return passage 15 connects to a discharge pipe 99 housed in the suction chamber 90. Compressed air flowing from the return passage 15 into the discharge pipe 99 is injected into the suction chamber 90 from a nozzle provided in the discharge pipe 99. In this example, the discharge pipe 99 is located between an intake filter 94 housed in the suction chamber 90 and an outlet 93 of the suction chamber 90.

[0015] The second heating unit 20 includes a heater 24 configured to heat the external air using a heat source different from the compressor 7. The heat source of the heater 24 may be heat recovered from the exhaust gas discharged from the turbine 30 (details will be described later), or may be heat obtained from a heating element that generates heat by supplying electric power. The heater 24 illustrated in FIG. 1 is housed in the suction chamber 90, and more specifically, is disposed between the intake filter 94 and the inlet 92 of the suction chamber 90. The heater 24 may also be disposed between the intake filter 94 and the outlet 93.

[0016] The heating control of the second heating unit 20 is performed by a control device 80, which is a component of the intake air heating system 5. The control device 80 controls the second heating unit 20 so that the heater 24 heats the external air in a high load section where the gas turbine load is higher than a first specified load. The heating control of the second heating unit 20 by the control device 80 may be performed only in the high load section. Alternatively, the second heating unit 20 may perform a heating operation also in sections other than the high load section (see FIG. 2).

[0017] FIG. 2 is a schematic graph showing the intervals of the heating operation of the second heating unit 20 according to one embodiment. The horizontal axis of the graph represents the gas turbine load, with G1 corresponding to the first specified load (similarly shown in FIGS. 3 and 5). The first specified load is a load lower than the rated load of the gas turbine system 1, e.g., an arbitrary gas turbine load greater than 75% and less than 95% of the rated load. The heating amount in the operating interval of the second heating unit 20 shown in the graph is not necessarily constant. For example, the heating amount in the high load interval may be feedback-controlled according to the temperature of the exhaust gas discharged from the turbine 30, or the heating amount in the high load interval may be constant regardless of the exhaust gas temperature. In this example, feedback control is performed only when the gas turbine load exceeds a high specified load (the gas turbine load indicated by G3 in FIG. 3) that is greater than the first specified load. Feedback control is not performed when the gas turbine load is equal to or less than the high specified load. The feedback control of the second heating unit 20 may be P control, PI control, or PID control, but PI control is used in this example. Furthermore, the gas turbine system 1 according to one embodiment may always be operated at a partial load. In this case, an upper limit specified load (gas turbine load indicated by symbol U), which is the maximum gas turbine load in the high load section, is lower than the rated load of the gas turbine system 1, and operation in a load section higher than the upper limit specified load is not performed. The upper limit specified load is, for example, any gas turbine load that is equal to or greater than 80% and less than 100% of the rated load. The upper limit specified load is a gas turbine load that is greater than the high specified load.

[0018] As illustrated in FIG. 2, the second heating unit 20 performs heating operation not only in the high load section but also in the medium load section. The medium load section is a gas turbine load section in which the gas turbine load is equal to or greater than a second specified load that is lower than the first specified load, and equal to or less than the first specified load. G2 in the graph corresponds to the second specified load (the same applies to FIGS. 3 and 5). As an example, in the medium load section, feedback control of the heating amount by the second heating unit 20 is not performed. As a more detailed example, in the medium load section, the opening of the second flow control valve 22 (described below) of the second heating unit 20 is maintained constant. The second specified load is an arbitrary gas turbine load that is equal to or greater than 30% and less than 60% of the rated load of the gas turbine system 1.

[0019] According to the above configuration, in the high load section, the external air is heated by a heat source other than the compressed air. This makes it possible to reduce the flow rate of the compressed air flowing through the return flow path 15 as a heat source for heating the external air, and to suppress a decrease in the flow rate of the combustion gas supplied to the turbine 30 in the high load section. This realizes an intake air heating system 5 that improves the operating efficiency of the gas turbine 3.

[0020] <Details of the first heating unit 10> Returning to FIG. 1 , the first heating unit 10 further includes a first flow rate adjustment valve 12 disposed in the return flow path 15. The heating operation of the first heating unit 10 is controlled by a control device 80. More specifically, the control device 80 sends a control signal to the first flow rate adjustment valve 12, thereby controlling the flow rate of the compressed air flowing through the return flow path 15 and controlling the amount of heat applied to the external air by the first heating unit 10.

[0021] In one embodiment, the first heating unit 10 performs a heating operation in a low load section where the gas turbine load is lower than a second specified load. That is, the control device 80 controls the first heating unit 10 so that the first flow rate control valve 12 opens the return flow path 15 in the low load section. Note that opening the first flow rate control valve 12 does not necessarily mean that the first flow rate control valve 12 is fully open. If the opening degree of the first flow rate control valve 12 exceeds 0%, it is understood that the first flow rate control valve 12 is open (the same applies to the second flow rate control valve 22 described below). Furthermore, the heating control of the first heating unit 10 by the control device 80 may be performed only in the low load section, or may be performed in sections other than the low load section (see FIG. 3 ).

[0022] FIG. 3 is a schematic graph showing the intervals of the heating operation of the first heating unit 10 according to one embodiment. The horizontal axis of the graph represents the gas turbine load. The heating amount in the operation interval of the first heating unit 10 shown in the graph is not necessarily constant. For example, the heating amount in the low load interval may be feedback controlled according to the gas turbine load, or the heating amount in the low load interval may be constant regardless of the gas turbine load. In this example, the heating amount of the first heating unit 10 is feedback controlled in the low load interval. The feedback control of the first heating unit 10 may be P control, PI control, or PID control, but in this example, PI control is used.

[0023] As illustrated in FIG. 3, the first heating unit 10 performs a heating operation not only in the low load section but also in the medium load section. As a more detailed example, in the medium load section, feedback control of the heating amount of the second heating unit 20 is performed. More specifically, in the medium load section, the opening degree of the first flow rate adjustment valve 12 of the first heating unit 10 is feedback controlled in accordance with the exhaust temperature. Also, in the example of the same figure, in the high load section, the heating operation by the second heating unit 20 is not performed. In other words, in the high load section, the control device 80 controls the first heating unit 10 so that the first flow rate adjustment valve 12 closes the return flow path 15.

[0024] According to the above configuration, when the first flow control valve 12 is opened in the low load section, compressed air discharged from the compressor 7 is extracted, and the extracted compressed air heats the external air. As a result, the flow rate of compressed air flowing into the combustor 8 decreases, and the flow rate of combustion gas for driving the turbine 30 decreases. In this case, the amount of fuel supplied to the combustor 8 is increased to maintain the output of the gas turbine system 1. This increases the combustion temperature in the combustor 8, thereby suppressing the amount of CO (carbon monoxide) generated. As a result, CO generation is suppressed in the low load section, and the operating efficiency of the gas turbine 3 can be improved in the high load section. Furthermore, according to the above configuration, the first flow control valve 12 closes the return flow path 15 in the high load section. As a result, the first heating unit 10 does not operate in the high load section, thereby further improving the operating efficiency of the gas turbine 3.

[0025] <Details of the second heating unit 20> FIG. 4 is a schematic diagram showing a second heating unit 20 according to an embodiment of the present disclosure. The heat source of the second heating unit 20 illustrated in the figure is exhaust gas discharged from the turbine 30 (see FIG. 1). The heat source of the exhaust gas is recovered by a heat recovery steam generator 19, which is a component of the gas turbine system 1, and used as the heat source of the second heating unit 20. The heat recovery steam generator 19 is configured to generate a heating medium from boiler feedwater using the exhaust gas supplied from an exhaust duct 39 as a heat source. The heating medium is hot water or steam (superheated steam). For example, superheated steam is generated by heating the boiler feedwater with high-temperature exhaust gas that has flowed into the heat recovery steam generator 19 relatively soon thereafter. This superheated steam may be supplied to other equipment constituting the gas turbine system 1, such as a steam turbine. On the other hand, the low-temperature exhaust gas flowing near the outlet of the heat recovery boiler 19 heats the boiler feedwater, producing hot water (this hot water may flow further within the heat recovery boiler 19 and be converted into superheated steam by heat exchange with the high-temperature exhaust gas).

[0026] The description of the second heating unit 20 continues. The second heating unit 20 according to one embodiment includes a heating medium flow path 29 for guiding the heating medium generated by the heat recovery steam generator 19 to the suction chamber 90 of the intake air flow path 9, a second flow control valve 22 provided in the heating medium flow path 29, and a piping section 25 that is a heater 24 arranged in the intake air flow path 9. As described above, the second heating unit 20 is controlled by the control device 80. In this example, when the second flow control valve 22 is opened in response to a control signal sent from the control device 80 to the second flow control valve 22, the heating medium is supplied from the heat recovery steam generator 19 to the piping section 25 via the heating medium flow path 29. Furthermore, by controlling the opening degree of the second flow control valve 22, the flow rate of the heating medium flowing through the piping section 25 is controlled. This controls the amount of heat applied to the outside air by the second heating unit 20. 2 as an example, in the medium load section, as the gas turbine load increases, the opening degree of the second flow control valve 22 increases, and in the high load section, the opening degree of the second flow control valve 22 remains approximately constant. Note that the heating medium flowing through the heating medium flow path 29 illustrated in FIG. 4 is hot water, and the hot water has a higher temperature than the boiler feedwater before flowing into the heat recovery boiler 19.

[0027] The control device 80 according to one embodiment controls the second heating unit 20 so that the second flow control valve 22 closes the heating medium flow path 29 during the low load section. Therefore, the second heating unit 20 does not heat the external air during the low load section. According to the above configuration, during the low load section, the flow rate of the compressed air flowing through the return flow path 15 can be increased by the amount that the second heating unit 20 does not heat the external air. Therefore, during the low load section, the generation of CO can be further suppressed.

[0028] <Example of Heating Control of First Heating Unit 10 and Second Heating Unit 20> FIG. 5 is a schematic graph showing the heating ratio of the first heating unit 10 and the second heating unit 20 according to one embodiment. The horizontal axis of the graph represents the gas turbine load, and the vertical axis represents the ratio of the heating amount of the first heating unit 10 to the heating amount of the second heating unit 20. For example, the first heating unit 10 is responsible for all heating of the external air in the low load section, and the second heating unit 20 is responsible for all heating in the high load section. Note that the vertical axis of FIG. 5 merely represents the ratio of the heating amount of the first heating unit 10 to the heating amount of the second heating unit 20. Therefore, the heating amount of the external air is not necessarily constant throughout the low load section, the medium load section, and the high load section.

[0029] In the intermediate load section illustrated in Figure 5, both the first heating unit 10 and the second heating unit 20 are responsible for heating. As a more specific example, the control device 80 controls the first heating unit 10 and the second heating unit 20 so that the first flow control valve 12 opens the return flow path 15 and the second flow control valve 22 opens the heating medium flow path 29. In the intermediate load section illustrated in Figure 5, as the gas turbine load increases, the heating rate of the first heating unit 10 decreases and the heating rate of the second heating unit 20 increases. The reason for this is as follows.

[0030] In the feedback control of the first flow control valve 12 in the medium load section, for example, the aperture of the first flow control valve 12 is controlled based on a target value and an actual measured value of the exhaust temperature of the exhaust gas from the turbine 30. At this time, the amount of fuel supplied to the combustor 8 is relatively high in order to increase the gas turbine load, and the exhaust temperature rises as the gas turbine load increases. As a result, feedback control is executed to decrease the aperture of the first flow control valve 12, and the heating amount of the first heating unit 10 decreases. On the other hand, in the medium load section, control is executed so that the heating amount of the second heating unit 20 increases as the gas turbine load increases. As a more specific example, the aperture of the second flow control valve 22 increases as the gas turbine load increases. Therefore, as the gas turbine load increases in the medium load section, the heating rate of the first heating unit 10 decreases and the heating rate of the second heating unit 20 increases.

[0031] According to the above configuration, the heating operation of the external air in the intermediate load section is performed by the first heating unit 10 and the second heating unit 20. This makes it possible to operate the gas turbine system 1 while achieving a balance between suppressing CO generation and improving the operating efficiency of the gas turbine 3.

[0032] <Details of Gas Turbine 3> 6 is a schematic diagram showing details of a gas turbine 3 according to an embodiment of the present disclosure. The gas turbine 3 in the figure is a two-shaft gas turbine. More specifically, the gas turbine 3 includes a compressor 7, a high-pressure turbine 33 having a first shaft 31 connected to the rotating shaft of the compressor 7, and a low-pressure turbine 34 having a second shaft 32 different from the first shaft 31. The high-pressure turbine 33 rotates integrally with the compressor 7. The low-pressure turbine 34 is configured to receive exhaust gas from the high-pressure turbine 33 and to rotate using this exhaust gas as a power source. The exhaust gas discharged from the low-pressure turbine 34 flows into an exhaust duct 39.

[0033] An inlet guide vane is provided at the inlet of the compressor 7, and the intake air volume of the compressor 7 is controlled by adjusting the opening of the inlet guide vane. In a two-shaft gas turbine, the opening of the inlet guide vane of the compressor 7 is controlled to maintain a balance between the output of the high-pressure turbine 33 and the power of the compressor 7. Therefore, when the turbine inlet temperature decreases due to, for example, a decrease in the amount of fuel supplied to the combustor 8 of the gas turbine 3, it is difficult to execute control to narrow the opening of the inlet guide vane so as to increase the turbine inlet temperature. In this regard, with the above-described configuration, in the high-load section, the second heating unit 20 heats the external air using a heat source other than the compressed air, thereby increasing the turbine inlet temperature. Since the use of the compressed air discharged from the compressor 7 as a heat source is suppressed, a decrease in the flow rate of the combustion gas flowing into the turbine 30 can also be suppressed. As a result, the operating efficiency of the two-shaft gas turbine can be improved.

[0034] <Operation method of intake air heating system 5> FIG. 7 is a flowchart illustrating an operating method for an intake air heating system 5 according to an embodiment of the present disclosure. The method is executed by a control device 80, for example. For example, the control device 80 is configured by a computer and includes a processor, a memory, and an external communication interface. The processor may be a CPU, a GPU, an MPU, a DSP, or a combination thereof. The processor according to other embodiments may be implemented by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to temporarily or non-temporarily store various data and may be implemented by at least one of a RAM, a ROM, and a flash memory. In accordance with instructions from a program loaded into the memory, the processor of the control device 80 (hereinafter sometimes simply referred to as the "processor") executes a control process for operating the intake air heating system 5. During the execution of the control process, the processor transmits control signals to the first flow control valve 12 and the second flow control valve 22. In the following description, steps may be abbreviated as "S."

[0035] First, it is determined whether the gas turbine load is within the low load section (S11). For example, the processor acquires a command indicating a specific gas turbine load, thereby determining whether the gas turbine load is within the low load section. If it is determined that the gas turbine load is within the low load section (S11: YES), a first heating unit control step is executed to control the first heating unit 10 (S13). The control method for the first heating unit 10 in the low load section is as described above, and the processor sends a predetermined control signal to the first flow control valve 12. At this time, the processor also sends a control signal to cause the second flow control valve 22 to close the heating medium flow path 29. After execution of S13, the operation method for the intake air heating system 5 ends.

[0036] If it is determined that the gas turbine load is not within the low load section (S11: NO), it is determined whether the gas turbine load is within the medium load section (S15). The determination method in S15 is the same as the determination method in S11. If it is determined that the gas turbine load is within the medium load section (S15: YES), a control step is executed to control the first heating unit 10 and the second heating unit 20 (S17). The control method for the first heating unit 10 and the second heating unit 20 in the medium load section is as described above, and the processor sends predetermined signals to the first flow control valve 12 and the second flow control valve 22, respectively. After execution of S17, the operation method for the intake air heating system 5 ends.

[0037] If it is determined that the gas turbine load is not within the medium load section (S15: NO), it is determined whether the gas turbine load is within the high load section (S19). The determination method in S19 is the same as the determination method in S11. If it is determined that the gas turbine load is within the high load section (S19: YES), a second heating unit control step is executed to control the second heating unit 20 (S21). The control method for the second heating unit 20 in the high load section is as described above. At this time, the processor also sends a control signal to the first flow control valve 12 to close the return flow path 15. After executing S21, the operation method of the intake air heating system 5 ends. Note that if it is determined that the gas turbine load is not within the high load section (S19: NO), the process returns to step S11.

[0038] <Summary> The contents of the above-described embodiments can be understood, for example, as follows.

[0039] 1) The intake air heating system (5) according to at least one embodiment of the present disclosure includes: 1. An intake air heating system (5) configured to heat external air flowing through an intake air flow path (9) communicating with a compressor (7) of a gas turbine (3), comprising: a first heating unit (10) including a return flow path (15) for returning a portion of the compressed air discharged from the compressor (7) to the intake flow path (9); a second heating unit (20) including a heater (24) configured to heat the external air using a heat source different from the compressed air; a control device (80) configured to control the second heating unit (20) so that the external air is heated by the heater (24) in a high load section in which the gas turbine load is higher than a first specified load; Equipped with.

[0040] According to the configuration 1), the external air is heated by a heat source other than the compressed air in the high load section. This makes it possible to reduce the flow rate of the compressed air flowing through the return flow path (15) as a heat source for heating the external air, thereby suppressing a decrease in the flow rate of the combustion gas supplied to the turbine (30) in the high load section. This realizes an intake air heating system (5) that improves the operating efficiency of the gas turbine (3).

[0041] 2) In some embodiments, the intake air heating system (5) described in 1) above, the first heating unit (10) further includes a first flow rate adjustment valve (12) disposed in the return flow path (15); The control device (80) is configured to control the first heating unit (10) so that the first flow control valve (12) opens the return flow path (15) in a low load section where the gas turbine load is below a second specified load that is lower than the first specified load.

[0042] According to the configuration 2), when the first flow control valve (12) is opened in the low load section, compressed air discharged from the compressor (7) is extracted, and the extracted compressed air heats the outside air. As a result, the flow rate of the compressed air flowing into the combustor (8) decreases, and the flow rate of the combustion gas driving the turbine (30) decreases. In this case, the amount of fuel supplied to the combustor (8) is increased to maintain the output of the gas turbine system (1). This increases the combustion temperature in the combustor (8), thereby reducing the amount of CO (carbon monoxide) generated. As a result, CO generation is reduced in the low load section, and the operating efficiency of the gas turbine (3) is improved in the high load section.

[0043] 3) In some embodiments, the intake air heating system (5) described in 2) above, The control device (80) is configured to control the first heating unit (10) in the high load section so that the first flow rate adjustment valve (12) closes the return flow path (15).

[0044] According to the above configuration 3), the first heating unit (10) does not operate in the high load section, so that the operating efficiency of the gas turbine (3) can be further improved.

[0045] 4) In some embodiments, the intake air heating system (5) described in 3) above, The second heating unit (20) a heating medium flow path (29) for guiding a heating medium generated by a heat recovery boiler (19) receiving exhaust gas from the gas turbine (3) and heating boiler feedwater to the intake air flow path (9); a second flow control valve (22) provided in the heating medium flow path (29); a piping section (25) disposed in the intake air flow path (9), the piping section (25) being the heater (24) configured to receive the heating medium from the heating medium flow path (29); Including, The control device (80) is configured to control the second heating unit (20) in the low load section so that the second flow rate control valve (22) closes the heating medium flow path (29).

[0046] According to the above configuration 4), in the low load section, the second heating unit (20) does not heat the outside air, and therefore the flow rate of the compressed air flowing through the return flow path (15) can be increased accordingly, thereby further suppressing the generation of CO in the low load section.

[0047] 5) In some embodiments, the intake air heating system (5) described in 4) above, The control device (80) is configured to control the first heating unit (10) and the second heating unit (20) so that, in an intermediate load section in which the gas turbine load is equal to or greater than the second specified load and equal to or less than the first specified load, the first flow control valve (12) opens the return flow path (15) and the second flow control valve (22) opens the heating medium flow path (29).

[0048] According to the configuration of 5) above, the first heating unit (10) and the second heating unit (20) are responsible for heating the outside air in the intermediate load section. This makes it possible to operate the gas turbine system (1) while achieving a balance between suppressing CO2 generation and improving the operating efficiency of the gas turbine (3).

[0049] 6) A method of operating an intake air heating system (5) according to at least one embodiment of the present disclosure includes: 1. A method of operating an intake air heating system (5) configured to heat external air flowing through an intake air flow path (9) in communication with a compressor (7) of a gas turbine (3), comprising: The intake air heating system (5) a first heating unit (10) including a return flow path (15) for returning a portion of the compressed air discharged from the compressor (7) to the intake flow path (9); a second heating unit (20) including a heater (24) configured to heat the external air using a heat source different from the compressed air; Including, The method includes a second heating unit control step (S21) of controlling the second heating unit (20) so that the external air is heated by the heater (24) in a high load section where the gas turbine load is higher than a first specified load.

[0050] According to the configuration 6) above, for the same reason as in 1), a method for operating the intake air heating system (5) that improves the operating efficiency of the gas turbine (3) is realized.

[0051] 7) A gas turbine system (1) according to at least one embodiment of the present disclosure includes: An intake air heating system (5) according to any one of 1) to 5) above; The gas turbine (3); Equipped with.

[0052] According to the configuration 7) above, for the same reason as in 1), the gas turbine system 1 with improved operating efficiency of the gas turbine 3 is realized.

[0053] 8) In some embodiments, the gas turbine system (1) described in 7) above, The gas turbine (3) The compressor (7), a high-pressure turbine (33) having a first shaft (31) connected to a rotary shaft of the compressor (7); a low-pressure turbine (34) having a second shaft (32) different from the first shaft (31) and configured to receive exhaust gas from the high-pressure turbine (33); It is a two-shaft gas turbine including

[0054] In a two-shaft gas turbine, the opening of the inlet guide vanes of the compressor (7) is controlled to balance the output of the high-pressure turbine (33) and the power of the compressor (7). Therefore, when the turbine inlet temperature decreases due to, for example, a decrease in the amount of fuel supplied to the combustor (8) of the gas turbine (3), it is difficult to control the opening of the inlet guide vanes to increase the turbine inlet temperature. In this regard, according to the configuration of 8), the second heating unit (20) heats the external air using a heat source other than the compressed air, thereby increasing the turbine inlet temperature. Since the compressed air discharged from the compressor (7) is prevented from being used as a heat source, a decrease in the flow rate of the combustion gas flowing into the turbine (30) can also be prevented. As a result, the operating efficiency of the two-shaft gas turbine can be improved. [Explanation of symbols]

[0055] 1: Gas turbine system 3: Gas turbine 5: Intake air heating system 7: Compressor 9: Intake flow path 10: First heating unit 12: First flow control valve 15: Return flow path 19: Waste heat recovery boiler 20: Second heating unit 22: Second flow control valve 24: Heater 25: Piping section 29: Heating medium flow path 30: Turbine 31: 1st axis 32: 2nd axis 33: High pressure turbine 34: Low-pressure turbine 80: Control device

Claims

1. 1. An intake air heating system configured to heat external air flowing through an intake air flowpath communicating with a compressor of a gas turbine, the system comprising: a first heating unit including a return flow path for returning a portion of the compressed air discharged from the compressor to the intake flow path; a second heating unit including a heater configured to heat the external air using a heat source different from the compressed air; a control device configured to control the second heating unit so that the external air is heated by the heater in a high load section in which the gas turbine load is higher than a first specified load; Equipped with the first heating unit further includes a first flow rate adjustment valve disposed in the return flow path; The control device the first heating unit is controlled so that the first flow rate control valve opens the return flow path in a low load section in which the gas turbine load is below a second specified load that is lower than the first specified load, the first heating unit and the second heating unit are controlled so that, in an intermediate load section in which the gas turbine load is equal to or greater than the second specified load and equal to or less than the first specified load, the heating rate of the first heating unit decreases and the heating rate of the second heating unit increases as the gas turbine load increases. Intake air heating system.

2. the control device is configured to control the first heating unit so that the first flow rate adjustment valve closes the return flow path in the high load section. The intake air heating system of claim 1 .

3. The second heating unit is a heating medium flow path for guiding a heating medium generated by a heat recovery boiler to which exhaust gas from the gas turbine is supplied, to the intake air flow path; a second flow rate control valve provided in the heating medium flow path; a piping section disposed in the intake air flow path, the piping section being the heater configured to receive the heating medium from the heating medium flow path; Including, the control device is configured to control the second heating unit so that the second flow rate adjustment valve closes the heating medium flow path in the low load section. The intake air heating system according to claim 1 or 2.

4. the control device is configured to control the first heating unit and the second heating unit so that, in the intermediate load section, the first flow rate adjustment valve opens the return flow path and the second flow rate adjustment valve opens the heating medium flow path. The intake air heating system of claim 3 .

5. 1. A method of operating an intake air heating system configured to heat external air flowing through an intake air flowpath communicating with a compressor of a gas turbine, comprising: The intake air heating system includes: a first heating unit including a return flow path for returning a portion of the compressed air discharged from the compressor to the intake flow path; a second heating unit including a heater configured to heat the external air using a heat source different from the compressed air; Including, a second heating unit control step of controlling the second heating unit so that the external air is heated by the heater in a high load section in which the gas turbine load is higher than a first specified load, the first heating unit further includes a first flow rate adjustment valve disposed in the return flow path; controlling the first heating unit so that the first flow rate control valve opens the return flow path in a low load section in which the gas turbine load is below a second specified load that is lower than the first specified load; controlling the first heating unit and the second heating unit so that, in an intermediate load section in which the gas turbine load is equal to or greater than the second specified load and equal to or less than the first specified load, the heating rate of the first heating unit decreases and the heating rate of the second heating unit increases as the gas turbine load increases; Further equipped How to operate an intake air heating system.

6. The intake air heating system according to claim 1 or 2; the gas turbine; A gas turbine system comprising:

7. The gas turbine comprises: the compressor; a high-pressure turbine having a first shaft connected to a rotary shaft of the compressor; a low-pressure turbine having a second shaft different from the first shaft and configured to receive exhaust gas from the high-pressure turbine; A two-shaft gas turbine including: The gas turbine system of claim 6 .

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