Combined cycle unit waste heat utilization system and method

Abstract

The invention discloses a combined cycle unit waste heat utilization system and method, a TCA gas side inlet pipeline is communicated with a TCA gas side inlet, and a TCA gas side outlet is communicated with an external turbine through a TCA gas side outlet pipeline; a TCA water side inlet pipeline is communicated with a water side inlet of the TCA through a condensed water booster pump, a water side outlet of the TCA is communicated with a water side inlet of the FGH through a TCA water side outlet pipeline and an electric heater bypass valve, and a water side outlet of the FGH is communicated with an FGH water side outlet pipeline; an FGH gas side inlet pipeline is communicated with a first opening of an FGH gas side inlet temperature control valve, a second opening of the FGH gas side inlet temperature control valve is communicated with a gas side inlet of the FGH, a gas side outlet of the FGH is communicated with an FGH gas side outlet pipeline, a third opening of the FGH gas side inlet temperature control valve is communicated with the FGH gas side outlet pipeline through an FGH bypass pipeline, and the FGH bypass pipeline is communicated with the FGH gas side outlet pipeline. The system and the method can fully recover the heat of the system.

Description

Technical Field

[0001] The invention belongs to the field of combined cycle unit thermal system operation optimization, and relates to a combined cycle unit waste heat utilization system and method. Background Art

[0002] Waste heat utilization of Mitsubishi M701F3 combined cycle unit. This type of unit is equipped with an air turbine cooling device (TCA) and a gas heating module (FGH) to cool the air turbine blades and heat the natural gas, in order to ensure the safety of the unit and improve the unit's operating efficiency. However, since both TCA and FGH use open forced heat exchange with air, the air is blown by a convection fan and then passes through TCA and FGH in turn for heat exchange, and the air after heat exchange is directly discharged into the atmosphere. However, the air discharged into the atmosphere at this time still contains a large amount of heat that is not utilized, resulting in heat waste. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and to provide a system and method for utilizing waste heat of a combined cycle unit, which can fully recover the heat of the system.

[0004] To achieve the above-mentioned object, the present invention discloses a waste heat utilization system of a combined cycle unit, comprising a TCA gas side inlet pipeline, a TCA, a TCA gas side outlet pipeline, a TCA water side inlet pipeline, a condensate booster pump, a TCA water side outlet pipeline, an electric heater bypass valve, an FGH, an FGH water side outlet pipeline, an FGH gas side inlet pipeline, an FGH gas side inlet temperature control valve and an FGH gas side outlet pipeline;

[0005] The TCA gas side inlet pipe is connected to the gas side inlet of the TCA, and the TCA gas side outlet is connected to the external turbine through the TCA gas side outlet pipe;

[0006] The TCA water side inlet pipe is connected to the TCA water side inlet via the condensate booster pump, the TCA water side outlet is connected to the FGH water side inlet via the TCA water side outlet pipe and the electric heater bypass valve, and the FGH water side outlet is connected to the FGH water side outlet pipe;

[0007] The FGH gas side inlet pipeline is connected to the first opening of the FGH gas side inlet temperature control valve, the second opening of the FGH gas side inlet temperature control valve is connected to the gas side inlet of the FGH, the gas side outlet of the FGH is connected to the FGH gas side outlet pipeline, and the third opening of the FGH gas side inlet temperature control valve is connected to the FGH gas side outlet pipeline via the FGH bypass pipeline.

[0008] Further, the electric heater bypass valve is connected in parallel to the rear electric heater pipeline.

[0009] Furthermore, an electric heater inlet valve, an electric heater and an electric heater outlet valve are sequentially arranged on the electric heater pipeline.

[0010] Further, the TCA gas side inlet pipeline is connected to the gas side inlet of the TCA via the TCA gas side inlet valve.

[0011] Furthermore, it also includes an FGH water side drum outlet valve and an FGH water side condenser outlet valve, and the water side outlet of the FGH is connected to the FGH water side drum outlet valve and the FGH water side condenser outlet valve through the FGH water side outlet pipeline.

[0012] The invention discloses a combined cycle unit waste heat utilization method, which is based on a combined cycle unit waste heat utilization system and includes a unit startup phase and a load operation phase.

[0013] Furthermore, during the start-up phase of the unit, the condensate booster pump is started to deliver low-temperature condensate to the water side of the TCA for heat exchange with the compressor extraction steam. At the same time, the condensate flow is adjusted by adjusting the frequency of the condensate booster pump so that the gas side outlet temperature of the TCA meets the operating requirements. During this process, the compressor extraction air cooled by the condensate is delivered to the air turbine through the TCA gas side outlet pipeline to cool the turbine blades. At the same time, the electric heater bypass valve is closed, the electric heater inlet valve and the electric heater outlet valve are opened, and the electric heater is started. The condensate output by the TCA is heated by the electric heater and then enters the FGH to heat the natural gas. The natural gas enters the FGH through the FGH gas side inlet temperature control valve to absorb heat, and the heated natural gas is delivered to the gas turbine for combustion.

[0014] Furthermore, during the load operation stage, the frequency of the condensate booster pump is increased with the outlet temperature of TCA as the control target to increase the condensate flow rate. The cooled compressed air is transported to the air turbine through the TCA gas side outlet pipeline to cool the turbine blades. At the same time, the electric heater bypass valve is gradually opened, the electric heater is closed, and the electric heater inlet valve and the electric heater outlet valve are gradually closed. The heated condensate releases heat in the FGH, and the natural gas is divided into two paths. One path enters the FGH through the FGH gas side inlet temperature control valve to absorb heat, and then enters the FGH gas side outlet pipeline. The other path is mixed with the high-temperature natural gas in the FGH gas side outlet pipeline through the FGH bypass pipeline to make its temperature meet the unit operation requirements.

[0015] Further, the TCA gas side inlet pipeline is connected to the gas side inlet of the TCA via the TCA gas side inlet valve.

[0016] Furthermore, it also includes an FGH water side drum outlet valve and an FGH water side condenser outlet valve, and the water side outlet of the FGH is connected to the FGH water side drum outlet valve and the FGH water side condenser outlet valve through the FGH water side outlet pipeline.

[0017] The present invention has the following beneficial effects:

[0018] In specific operation, the waste heat utilization system and method of the combined cycle unit described in the present invention utilizes condensed water to absorb heat in TCA, releases heat through FGH to heat natural gas, and finally transports the heat to the condenser or condensate system according to the condensate parameters. The present invention abandons the original open air heat exchange and utilizes condensate as the intermediate heat exchange medium, which not only realizes the closed cascade utilization of heat, but also ensures the operating safety and efficiency of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 It is a structural diagram of the present invention.

[0021] Among them, 1 is the condensate booster pump, 2 is TCA, 3 is the electric heater, 4 is FGH, 5 is the TCA gas side inlet valve, 6 is the electric heater inlet valve, 7 is the electric heater outlet valve, 8 is the electric heater bypass valve, 9 is the FGH gas side inlet temperature control valve, 10 is the FGH water side drum outlet valve, 11 is the FGH water side condenser outlet valve, 12 is the TCA water side inlet pipe, 13 is the TCA water side outlet pipe, 14 is the electric heater pipe, 15 is the FGH water side outlet pipe, 16 is the TCA gas side inlet pipe, 17 is the TCA gas side outlet pipe, 18 is the FGH gas side inlet pipe, 19 is the FGH bypass pipe, and 20 is the FGH gas side outlet pipe. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0024] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0025] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0026] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0027] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0030] Embodiment 1

[0031] refer to Figure 1 The waste heat utilization system of the combined cycle unit of the present invention comprises a TCA gas side inlet pipeline 16, TCA2, a TCA gas side outlet pipeline 17, a TCA water side inlet pipeline 12, a condensate booster pump 1, a TCA water side outlet pipeline 13, an electric heater bypass valve 8, FGH4, an FGH water side outlet pipeline 15, an FGH gas side inlet pipeline 18, an FGH gas side inlet temperature control valve 9 and an FGH gas side outlet pipeline 20; the TCA gas side inlet pipeline 16 is connected to the gas side inlet of TCA2, and the gas side outlet of TCA2 is connected to the external turbine via the TCA gas side outlet pipeline 17; the TCA water side inlet pipeline 12 is connected to the external turbine via the condensate booster pump 1 Pump 1 is connected to the water side inlet of TCA2, the water side outlet of TCA2 is connected to the water side inlet of FGH4 through TCA water side outlet pipe 13 and electric heater bypass valve 8, and the water side outlet of FGH4 is connected to FGH water side outlet pipe 15; FGH gas side inlet pipe 18 is connected to the first opening of FGH gas side inlet temperature control valve 9, the second opening of FGH gas side inlet temperature control valve 9 is connected to the gas side inlet of FGH4, the gas side outlet of FGH4 is connected to FGH gas side outlet pipe 20, and the third opening of FGH gas side inlet temperature control valve 9 is connected to FGH gas side outlet pipe 20 through FGH bypass pipe 19.

[0032] Embodiment 2

[0033] refer to Figure 1 The waste heat utilization system of the combined cycle unit of the present invention comprises a condensate booster pump 1, a TCA 2, an electric heater 3, an FGH 4, a TCA gas side inlet valve 5, an electric heater inlet valve 6, an electric heater outlet valve 7, an electric heater bypass valve 8, an FGH gas side inlet temperature control valve 9, an FGH water side drum outlet valve 10, an FGH water side condenser outlet valve 11, a TCA water side inlet pipeline 12, a TCA water side outlet pipeline 13, an electric heater pipeline 14, an FGH water side outlet pipeline 15, a TCA gas side inlet pipeline 16, a TCA gas side outlet pipeline 17, an FGH gas side inlet pipeline 18, an FGH bypass pipeline 19 and an FGH gas side outlet pipeline 20;

[0034] The TCA gas side inlet pipeline 16 is connected to the gas side inlet of TCA2 through the TCA gas side inlet valve 5, and the gas side outlet of TCA2 is connected to the external turbine through the TCA gas side outlet pipeline 17.

[0035] The TCA water side inlet pipe 12 is connected to the water side inlet of TCA2 via the condensate booster pump 1, the water side outlet of TCA2 is connected to the water side inlet of FGH4 via the TCA water side outlet pipe 13 and the electric heater bypass valve 8, and the water side outlet of FGH4 is connected to the FGH water side steam drum outlet valve 10 and the FGH water side condenser outlet valve 11 via the FGH water side outlet pipe 15.

[0036] The electric heater bypass valve 8 is connected in parallel to the electric heater pipeline 14 , and the electric heater inlet valve 6 , the electric heater 3 and the electric heater outlet valve 7 are sequentially arranged on the electric heater pipeline 14 .

[0037] The FGH gas side inlet pipe 18 is connected to the first opening of the FGH gas side inlet temperature control valve 9, the second opening of the FGH gas side inlet temperature control valve 9 is connected to the gas side inlet of FGH4, the gas side outlet of FGH4 is connected to the FGH gas side outlet pipe 20, and the third opening of the FGH gas side inlet temperature control valve 9 is connected to the FGH gas side outlet pipe 20 via the FGH bypass pipe 19.

[0038] Embodiment 3

[0039] refer to Figure 1 The present embodiment discloses a method for utilizing waste heat of a combined cycle unit. The method for utilizing waste heat of a combined cycle unit is implemented based on a waste heat utilization system of the combined cycle unit. The waste heat utilization system of the combined cycle unit includes a condensate booster pump 1, a TCA 2, an electric heater 3, an FGH 4, a TCA gas side inlet valve 5, an electric heater inlet valve 6, an electric heater outlet valve 7, an electric heater bypass valve 8, an FGH gas side inlet temperature control valve 9, an FGH water side drum outlet valve 10, an FGH water side condenser outlet valve 11, a TCA water side inlet pipe 12, a TCA water side outlet pipe 13, an electric heater pipe 14, an FGH water side outlet pipe 15, a TCA gas side inlet pipe 16, a TCA gas side outlet pipe 17, an FGH gas side inlet pipe 18, an FGH bypass pipe 19 and an FGH gas side outlet pipe 20. The method for utilizing waste heat of a combined cycle unit includes a unit startup stage and a load operation stage.

[0040] 1) Unit startup phase

[0041] During the start-up phase of the unit, the high-pressure gas turbine is ignited, and the condensate booster pump 1 is started to deliver the low-temperature condensate of 30°C to the water side of TCA2 for heat exchange with the extraction steam of the compressor. This not only satisfies the start-up requirements for the inlet temperature of the water side of TCA2, but also adjusts the frequency of the condensate booster pump 1 to adjust the condensate flow rate so that the outlet temperature of the gas side of TCA2 meets the operating requirements. In this process, the compressor extraction air cooled by the condensate is delivered to the air turbine through the TCA gas side outlet pipe 17 to cool the turbine blades. In addition, since the extraction temperature of the compressor is relatively low during the start-up process, the condensate absorbs limited heat in TCA2 and the temperature rise is relatively low. In order to effectively improve the heating effect of the low-temperature natural gas in FGH4, the electric heater bypass valve 8 is closed, the electric heater inlet valve 6 and the electric heater outlet valve 7 are opened, and the electric heater 3 is started to heat the condensate. The heated condensate heats the natural gas in FGH4. The heated natural gas comes from the natural gas booster station, enters FGH4 through the FGH gas side inlet temperature control valve 9 to absorb heat, and the heated natural gas is transported to the gas engine for combustion. In this process, the full flow of natural gas enters FGH4 through the FGH gas side inlet pipeline 18. The condensed water parameters after heat release in FGH4 are low, and the FGH water side condenser outlet valve 11 can be opened to transport it to the condenser.

[0042] 2) Load operation stage

[0043] As the gas turbine is connected to the grid and loaded, the exhaust temperature of the compressor gradually increases. In order to meet the heat exchange requirements of TCA2 and the requirements of blade cooling air, the frequency of the condensate booster pump 1 is increased with the outlet temperature of TCA2 as the control target to increase the condensate flow rate. The cooled compressed air is transported to the air turbine through the TCA gas side outlet pipe 17 to cool the turbine blades. At this time, since the condensate absorbs heat in TCA2, the temperature rises to meet the heat release requirements of the gas in FGH4. The electric heater bypass valve 8 is gradually opened, the electric heater 3 is closed, and the electric heater inlet valve 6 and the electric heater outlet valve 7 are gradually closed. The heated condensate releases heat in FGH4. Similarly, the natural gas that needs to be heated enters FGH4 through the FGH gas side inlet temperature control valve 9 to absorb heat. Since the water side of FGH4 has a large amount of heat, the temperature of the natural gas after being heated in FGH4 is relatively high. In order to make the temperature of the natural gas entering the gas turbine meet the operating requirements, a part of the low-temperature natural gas is mixed with the high-temperature natural gas in the FGH gas side outlet pipeline 20 through the FGH bypass pipeline 19 before entering FGH4, so that its temperature meets the unit operation requirements. Due to the pressure increase by the condensate booster pump 1, the condensate that releases heat in FGH4 has a higher pressure and temperature. In order to make full use of the condensate parameters, the FGH water side condenser outlet valve 11 is closed, and the FGH water side drum outlet valve 10 is opened to transport it to the drum with matching parameters for the next step of thermal cycle.

[0044] Embodiment 4

[0045] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the combined cycle unit waste heat utilization method are implemented. The memory may include a memory, such as a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk memory, etc. The processor, the network interface, and the memory are interconnected through an internal bus. The internal bus may be an industrial standard architecture bus, a peripheral component interconnection standard bus, an extended industrial standard structure bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory may include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0046] Embodiment 5

[0047] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the combined cycle unit waste heat utilization method are implemented. For example, specifically, the computer-readable storage medium includes but is not limited to volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory (cache), etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0048] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0049] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0050] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0051] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0052] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0053] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0054] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A combined cycle unit waste heat utilization system, characterized in that: It comprises a TCA gas side inlet pipeline (16), TCA (2), a TCA gas side outlet pipeline (17), a TCA water side inlet pipeline (12), a condensate booster pump (1), a TCA water side outlet pipeline (13), an electric heater bypass valve (8), FGH4, an FGH water side outlet pipeline (15), an FGH gas side inlet pipeline (18), an FGH gas side inlet temperature control valve (9) and an FGH gas side outlet pipeline (20); The TCA gas side inlet pipe (16) is connected to the gas side inlet of the TCA (2), and the gas side outlet of the TCA (2) is connected to the external turbine via the TCA gas side outlet pipe (17); The TCA water side inlet pipe (12) is connected to the water side inlet of the TCA (2) via the condensate booster pump (1); the TCA (2) water side outlet is connected to the water side inlet of the FGH (4) via the TCA water side outlet pipe (13) and the electric heater bypass valve (8); the FGH4 water side outlet is connected to the FGH water side outlet pipe (15); The FGH gas inlet pipe (18) is connected to a first opening of the FGH gas inlet temperature control valve (9), the second opening of the FGH gas inlet temperature control valve (9) is connected to the gas inlet of the FGH (4), the gas outlet of the FGH (4) is connected to the FGH gas outlet pipe (20), and the third opening of the FGH gas inlet temperature control valve (9) is connected to the FGH gas outlet pipe (20) via the FGH bypass pipe (19).

2. The waste heat utilization system of a combined cycle unit according to claim 1, characterized in that: The electric heater bypass valve (8) is connected in parallel to the electric heater pipeline (14).

3. The waste heat utilization system of a combined cycle unit according to claim 2, characterized in that: An electric heater inlet valve (6), an electric heater (3) and an electric heater outlet valve (7) are sequentially arranged on the electric heater pipeline (14).

4. The waste heat utilization system of a combined cycle unit according to claim 1, characterized in that: The TCA gas side inlet pipeline (16) is connected to the gas side inlet of the TCA (2) via the TCA gas side inlet valve (5).

5. The waste heat utilization system of a combined cycle unit according to claim 1, characterized in that: It also comprises an FGH water side drum outlet valve (10) and an FGH water side condenser outlet valve (11); the water side outlet of the FGH (4) is connected to the FGH water side drum outlet valve (10) and the FGH water side condenser outlet valve (11) via an FGH water side outlet pipeline (15).

6. A method for utilizing waste heat of a combined cycle unit, characterized in that: The waste heat utilization system for the combined cycle unit according to claim 3 includes a unit startup phase and a load operation phase.

7. The method for utilizing waste heat of a combined cycle unit according to claim 6, characterized in that: During the unit startup phase, the condensate booster pump (1) is started to deliver low-temperature condensate to the water side of the TCA (2) for heat exchange with the compressor extraction steam. At the same time, the condensate flow rate is adjusted by adjusting the frequency of the condensate booster pump (1) so that the gas side outlet temperature of the TCA (2) meets the operating requirements. During this process, the compressor extraction air cooled by the condensate is delivered to the air turbine through the TCA gas side outlet pipe (17) to cool the turbine blades. At the same time, the electric heater bypass valve (8) is closed, the electric heater inlet valve (6) and the electric heater outlet valve (7) are opened, and the electric heater (3) is started. The condensate output from the TCA (2) is heated by the electric heater (3) and then enters the FGH4 to heat the natural gas. The natural gas enters the FGH (4) through the FGH gas side inlet temperature control valve (9) to absorb heat. The heated natural gas is delivered to the gas turbine for combustion.

8. The method for utilizing waste heat of a combined cycle unit according to claim 6, characterized in that: During the load operation stage, the frequency of the condensate booster pump (1) is increased with the outlet temperature of the TCA (2) as the control target to increase the condensate flow rate. The cooled compressed air is transported to the air turbine through the TCA gas side outlet pipe (17) to cool the turbine blades. At the same time, the electric heater bypass valve (8) is gradually opened, the electric heater (3) is closed, and the electric heater inlet valve (6) and the electric heater outlet valve (7) are gradually closed. The heated condensate releases heat in the FGH (4). The natural gas is divided into two paths, one of which enters the FGH (4) through the FGH gas side inlet temperature control valve (9) to absorb heat and then enters the FGH gas side outlet pipe (20). The other path is mixed with the high-temperature natural gas in the FGH gas side outlet pipe (20) through the FGH bypass pipe (19) to make its temperature meet the unit operation requirements.

9. The method for utilizing waste heat of a combined cycle unit according to claim 6, characterized in that: The TCA gas side inlet pipeline (16) is connected to the gas side inlet of the TCA (2) via the TCA gas side inlet valve (5).

10. The waste heat utilization system of a combined cycle unit according to claim 1, characterized in that: It also comprises an FGH water side drum outlet valve (10) and an FGH water side condenser outlet valve (11); the water side outlet of the FGH (4) is connected to the FGH water side drum outlet valve (10) and the FGH water side condenser outlet valve (11) via an FGH water side outlet pipeline (15).

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