Gas steam intercooling waste heat recovery method and system

Abstract

The application provides a gas-steam intercooling waste heat recovery method and system, belongs to the technical field of gas-steam combined cycle power generation and waste heat recovery control, and can significantly alleviate or solve the problems of direct discharge of compression heat in the intercooling process of a multistage compressor, insufficient coupling with a steam cycle, and unreasonable heat distribution under a variable working condition. The application collects gas turbine operation parameters, intercooling cycle parameters, steam cycle parameters and unit load parameters, determines a current intercooling waste heat recovery reference amount, determines a target heat distribution ratio of a boiler feed water heating branch and a low-pressure steam supplement branch according to the reference amount, and adjusts the frequency of a circulating pump and the opening degree of a flow regulating valve in linkage. The intercooling waste heat is used for feed water heating and low-pressure steam supplement through a waste heat heat exchanger, and safety judgment and feedback correction are performed. The application can improve the intercooling waste heat utilization rate and the steam cycle matching property, and enhance the variable working condition adaptability and operation safety.

Description

Technical Field

[0001] This invention belongs to the field of gas-steam combined cycle power generation and waste heat recovery control technology, specifically relating to a method and system for recovering waste heat from gas-steam intercooling. Background Technology

[0002] Combined cycle gas turbine units combine the advantages of fast gas turbine response and high waste heat utilization efficiency of steam cycle, and have been widely used in power plant peak shaving, industrial park power supply, and distributed energy systems. With the increasing demands for energy conservation, flexible peak shaving, and low-carbon operation in power systems, combined cycle units not only need to improve the efficiency of the gas turbine itself, but also need to further explore the available waste heat resources in each stage of compression, combustion, exhaust, and steam cycle to improve the economic efficiency of the unit under all operating conditions. In a gas turbine, the compressor performs the air compression function, and its compression power consumption accounts for a significant portion of the gas turbine's auxiliary energy consumption. For gas turbine systems employing multi-stage compression, to reduce the inlet temperature of subsequent compressor stages and decrease compression power consumption, an intercooler is typically installed between adjacent compressor stages to cool the high-temperature air compressed in the previous stage before it enters the next compressor stage.

[0003] During intercooling, compressed air releases heat of compression at a certain temperature level. This heat typically exhibits characteristics such as strong continuity, correlation with unit load changes, and suitable temperature levels for feedwater preheating or low-pressure side heat utilization, making it valuable for further recovery and utilization. In existing gas-steam combined cycle units, intercoolers often use cooling water, air cooling, or external heat dissipation systems to discharge the heat of compression, ensuring that the inlet temperature of the subsequent compressor meets operational requirements. However, this approach primarily focuses on compressor cooling itself, failing to effectively couple the heat of compression released during intercooling with steam cycle components such as waste heat boiler feedwater heating and low-pressure steam injection. This results in a low level of waste heat utilization from the intercooler, or even direct discharge, affecting the overall energy efficiency of the combined cycle system.

[0004] In existing technologies, while some waste heat recovery schemes can utilize low-grade waste heat for domestic hot water, plant heating, or general process heating, the heat utilization targets have a low correlation with the main cycle of the gas-steam combined cycle, making it difficult to directly improve the unit's thermal cycle efficiency. Some schemes attempt to integrate waste heat into the boiler feedwater system, but these typically only employ a single-path heat exchange utilization method, lacking a dynamic allocation control mechanism based on unit load, boiler feedwater temperature, waste heat boiler heat demand, low-pressure steam injection demand, and the operating status of the steam turbine's low-pressure cylinder. When unit load or steam cycle heat demand changes, the recovered heat is prone to supply-demand mismatch, resulting in insufficient feedwater heating, insufficient low-pressure steam injection capacity, or excessive heat absorption in local branches.

[0005] Furthermore, existing intercooler waste heat recovery structures primarily focus on equipment connections, lacking real-time determination of the current intercooler waste heat recovery baseline, and also lacking a closed-loop control relationship between circulation pump frequency, branch flow regulating valve opening, and heat distribution ratio. Under abnormal operating conditions, such as intercooler circulation overheating, overpressure, increased differential pressure in the waste heat exchanger, branch blockage, or branch failure, existing solutions typically only set up routine alarms or require manual intervention, making it difficult to promptly complete bypass switching, branch isolation, and heat redistribution.

[0006] Therefore, there is an urgent need to propose a technical solution that can recover and dynamically distribute the compression heat released by the intermediate cooling of multi-stage compressors to the steam cycle, so that the waste heat of the intermediate cooling can be distributed on demand between boiler feedwater heating and low-pressure steam injection. Through parameter acquisition, waste heat calculation, pump and valve linkage, safety protection and feedback correction, a closed-loop control is formed, thereby improving the waste heat utilization efficiency and adaptability of gas-steam combined cycle units under different operating conditions. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method and system for recovering waste heat from gas-fired steam cooling.

[0008] This invention provides a method for recovering waste heat from gas-steam intercooling, applied to a gas-steam combined cycle system. The gas-steam combined cycle system includes an intercooler disposed between two adjacent compressor stages, a waste heat exchanger connected to the intercooler via a heat exchange medium circulation loop, a boiler feedwater heating branch, a low-pressure steam makeup branch, a circulating pump, a flow regulating valve, and an intelligent control unit, comprising the following steps: S1: Collect the gas turbine operating parameters, intercooler cycle parameters, steam cycle parameters, and unit load parameters for the current control cycle; S2: Determine the current intercooler waste heat recovery baseline amount based on the intercooler air-side inlet temperature, air-side outlet temperature and intercooler cycle parameters in the gas turbine operating parameters; S3: Determine the target heat distribution ratio of the boiler feedwater heating branch and the low-pressure steam replenishment branch based on the current intermediate cooling waste heat recovery benchmark, the unit load parameters, and the steam cycle parameters; S4: Based on the target heat distribution ratio, determine the target frequency of the circulating pump and the target opening degree of the flow regulating valves of the boiler feedwater heating branch and the low-pressure steam replenishment branch, and adjust the operating frequency of the circulating pump according to the target frequency of the circulating pump, and adjust the opening degree of the flow regulating valves of the boiler feedwater heating branch and the low-pressure steam replenishment branch according to the target opening degree of the flow regulating valves. S5: The heat exchange medium is circulated between the intercooler and the waste heat exchanger to transfer the heat of compression released during the intercooling process of the multi-stage compressor to the waste heat exchanger. S6: According to the target heat distribution ratio, the intermediate cooling waste heat is transferred to the boiler feedwater heating branch and the low-pressure steam replenishment branch through the waste heat exchanger to obtain the feedwater outlet temperature and low-pressure steam replenishment parameters respectively. S7: Based on the feedwater outlet temperature, the low-pressure steam injection parameters, the intercooler circulation parameters, and the waste heat exchanger differential pressure, determine whether the current waste heat distribution status meets the safe operating conditions; if the safe operating conditions are not met, trigger the corresponding protection action and adjust the flow regulating valve opening, the circulation pump operating frequency, or the waste heat distribution path. S8: Based on the actual distribution results of the intermediate cooling waste heat, feedwater heating effect, low-pressure steam replenishment effect, safe operation condition judgment results, protection action execution results, and unit load changes in the current control cycle, feedback is used to correct the target heat distribution ratio, circulating pump target frequency, and flow regulating valve target opening for the next control cycle.

[0009] Further, in step S2, the current intermediate cooling waste heat recovery benchmark quantity is determined based on the heat exchange medium mass flow rate, the heat exchange medium constant pressure specific heat capacity, and the temperature difference between the heat exchange medium inlet and outlet of the intermediate cooler, and is verified based on the temperature drop of compressed air between the air inlet and outlet of the intermediate cooler.

[0010] Specifically, in step S3, determining the target heat allocation ratio includes: determining the feedwater heating demand based on the deviation between the boiler feedwater temperature and the target feedwater temperature; determining the supplementary steam heat demand based on the low-pressure steam replenishment demand and the operating status of the steam turbine low-pressure cylinder; and determining the target heat allocation ratio based on the feedwater heating demand, the supplementary steam heat demand, and the current intermediate cooling waste heat recovery benchmark amount.

[0011] Specifically, in step S4, adjusting the operating frequency of the circulating pump and the opening of the flow regulating valve includes: determining the target heat exchange of the corresponding branch according to the target heat distribution ratio, and correcting the opening of the flow regulating valve and the operating frequency of the circulating pump of the boiler feedwater heating branch and the low-pressure steam replenishment branch according to the deviation between the target heat exchange of the corresponding branch and the actual heat exchange of the corresponding branch.

[0012] Preferably, in step S6, the boiler feedwater heating branch is connected between the feedwater pump outlet and the waste heat boiler feedwater inlet, and the feedwater before entering the waste heat boiler is preheated or reheated through the waste heat heat exchanger.

[0013] Specifically, in step S6, the low-pressure steam replenishment branch preheats, preheats or heats the low-pressure steam replenishment medium before evaporation or through the waste heat exchanger, and sends the low-pressure steam that meets the replenishment conditions into the inlet of the low-pressure cylinder of the steam turbine through the replenishment valve.

[0014] Furthermore, in step S7, the protection actions include: reducing the operating frequency of the circulating pump or opening a preset bypass channel when the intercooling circulation temperature exceeds the preset upper limit of temperature; opening the pressure relief channel when the intercooling circulation pressure exceeds the preset upper limit of pressure; issuing a blockage alarm when the differential pressure of the waste heat exchanger exceeds the preset upper limit of differential pressure; and closing the faulty branch when any branch fails, and switching the intercooling waste heat to the non-faulty branch or the preset bypass channel.

[0015] Another aspect of the present invention provides a waste heat recovery system for intercooled gas steam, comprising: A gas turbine unit includes at least two compressor stages, a combustion chamber, and a gas turbine connected sequentially along the air compression direction. An intercooler is provided between any two adjacent compressor stages. The air-side inlet of the intercooler is connected to the air outlet of the upstream compressor stage, and the air-side outlet of the intercooler is connected to the air inlet of the downstream compressor stage. The intercooler waste heat recovery unit includes a waste heat exchanger, a heat exchange medium circulation loop, and a circulation pump. The heat exchange medium circulation loop is connected between the heat exchange medium side of the intercooler and the hot side of the waste heat exchanger. The circulation pump is installed in the heat exchange medium circulation loop so that the heat exchange medium after absorbing the heat of compression is transported from the intercooler to the waste heat exchanger and returns to the intercooler after releasing heat. The steam circulation unit includes a waste heat boiler, a steam turbine, a condenser, and a feedwater pump. The outlet of the feedwater pump is connected to the feedwater inlet of the waste heat boiler via a boiler feedwater heating branch. The boiler feedwater heating branch is connected to the cold side of the waste heat exchanger for heat exchange, so that the feedwater before entering the waste heat boiler absorbs the intermediate-cooled waste heat released by the waste heat exchanger. The low-pressure steam make-up branch is connected to the cold side of the waste heat exchanger. The outlet of the low-pressure steam make-up branch is connected to the inlet of the low-pressure cylinder of the steam turbine, so that the low-pressure steam make-up working medium absorbs the intercooled waste heat released by the waste heat exchanger and is then sent into the low-pressure cylinder of the steam turbine. A heat distribution assembly includes a heat distribution pipeline and a flow regulating valve. The heat distribution pipeline includes a first heat exchange branch connected to the boiler feedwater heating branch and a second heat exchange branch connected to the low-pressure steam replenishment branch. The flow regulating valve includes a first flow regulating valve disposed on the first heat exchange branch and a second flow regulating valve disposed on the second heat exchange branch. Parameter monitoring units are respectively installed in the heat exchange medium circulation loop, the boiler feedwater heating branch, and the low-pressure steam replenishment branch, and are connected to the intelligent control unit for data transmission; and The intelligent control unit is connected to the circulating pump, the first flow regulating valve, and the second flow regulating valve respectively. Based on the intercooling circulation parameters, boiler feedwater parameters, low-pressure steam injection parameters, and unit load parameters collected by the parameter monitoring unit, it adjusts the operating frequency of the circulating pump, the opening degree of the first flow regulating valve, and the opening degree of the second flow regulating valve to change the distribution ratio of intercooling waste heat between the boiler feedwater heating branch and the low-pressure steam injection branch.

[0016] Furthermore, the heat exchange medium side outlet of the intercooler is connected to the hot side inlet of the waste heat exchanger, and the hot side outlet of the waste heat exchanger is connected to the heat exchange medium side inlet of the intercooler via the circulating pump; the cold side of the waste heat exchanger is connected to the boiler feedwater heating branch and the low-pressure steam replenishment branch for heat exchange respectively.

[0017] Specifically, the parameter monitoring unit includes a detection component for collecting parameters such as intercooler circulation temperature, pressure, flow rate, waste heat exchanger differential pressure, boiler feedwater temperature, and low-pressure steam injection. The system also includes a safety protection actuator. The intelligent control unit includes a data acquisition module, a heat distribution calculation module, and an execution control module. The execution control module is connected to the circulating pump, the first flow regulating valve, the second flow regulating valve, and the safety protection actuator.

[0018] The beneficial effects of this invention are as follows: The invention recovers the compression heat released during the intercooling process of the multi-stage compressor through a heat exchange medium circulation loop, and transfers the intercooler waste heat to the boiler feedwater heating branch and the low-pressure steam injection branch through a waste heat exchanger, realizing the cascade utilization of intercooler waste heat to steam circulation. The intelligent control unit determines the target heat distribution ratio based on the current intercooler waste heat recovery baseline, unit load parameters, and steam circulation parameters, and adjusts the operating frequency of the circulation pump and the opening of the flow regulating valves in both branches accordingly, ensuring that the intercooler waste heat is distributed as needed between feedwater heating and low-pressure steam injection. Simultaneously, the invention performs safety assessments based on intercooler circulation temperature and pressure, waste heat exchanger differential pressure, feedwater outlet temperature, and low-pressure steam injection parameters, and corrects the control quantity for the next control cycle based on the actual heat exchange effect and protection action execution results, thereby improving the intercooler waste heat utilization efficiency, steam circulation matching, adaptability to changing operating conditions, and system operational safety. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the steps of a method for recovering waste heat from gas-fired steam cooling according to a specific embodiment of the present invention. Figure 2 This is a schematic diagram showing the overall structure, module connections, and energy flow of a gas-fired steam intercooled waste heat recovery system according to a specific embodiment of the present invention. Figure 3 This is a schematic diagram of the integration of the intermediate cooling waste heat recovery unit and the steam circulation in a gas-fired steam intermediate cooling waste heat recovery system according to a specific embodiment of the present invention.

[0020] The unit includes 1 gas turbine unit, 11 compressor, and 12 intercooler. 2. Intercooled waste heat recovery unit, 21. Waste heat exchanger, 22. Circulating pump, 23. Heat distribution pipeline, 24. Flow regulating valve, 25. Temperature sensor, 26. Pressure sensor, 27. Flow meter, 28. Insulation layer. 3 Steam circulation unit, 31 Waste heat boiler, 32 Steam turbine, 33 Condenser, 34 Feed water pump, 35 Boiler feed water heating branch; 4. Intelligent control unit. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown in the figure, a method for recovering waste heat from intercooled gas and steam, provided by a specific embodiment of the present invention, is applied to a gas-steam combined cycle system. The gas-steam combined cycle system includes an intercooler 12 disposed between two adjacent compressor stages, a waste heat exchanger 21 connected to the intercooler 12 via a heat exchange medium circulation loop, a boiler feedwater heating branch 35, a low-pressure steam makeup branch, a circulating pump 22, a flow regulating valve 24, and an intelligent control unit 4, comprising the following steps: S1: Collect the gas turbine operating parameters, intercooler cycle parameters, steam cycle parameters, and unit load parameters for the current control cycle; S2: Determine the current intercooler waste heat recovery baseline amount based on the intercooler 12 air-side inlet temperature, air-side outlet temperature and intercooler cycle parameters in the gas turbine operating parameters; S3: Determine the target heat distribution ratio of boiler feedwater heating branch 35 and low-pressure steam replenishment branch based on the current intermediate cooling waste heat recovery benchmark, the unit load parameters and the steam cycle parameters; S4: Based on the target heat distribution ratio, determine the target frequency of the circulating pump 22 and the target opening degree of the flow regulating valve 24 of the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch, and adjust the operating frequency of the circulating pump 22 according to the target frequency of the circulating pump 22, and adjust the opening degree of the flow regulating valve of the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch according to the target opening degree of the flow regulating valve 24. S5: The heat exchange medium is circulated between the intercooler 12 and the waste heat exchanger 21 to transfer the heat of compression released during the intercooling process of the multi-stage compressor to the waste heat exchanger 21. S6: According to the target heat distribution ratio, the intermediate cooling waste heat is transferred to the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch through the waste heat exchanger 21 to obtain the feedwater outlet temperature and low-pressure steam replenishment parameters respectively. S7: Based on the water outlet temperature, the low-pressure steam injection parameters, the intercooler circulation parameters, and the differential pressure of the waste heat exchanger 21, determine whether the current waste heat distribution status meets the safe operating conditions; if the safe operating conditions are not met, trigger the corresponding protection action and adjust the opening of the flow regulating valve 24, the operating frequency of the circulation pump 22, or the waste heat distribution path. S8: Based on the actual distribution results of the intermediate cooling waste heat, the feedwater heating effect, the low-pressure steam replenishment effect, the judgment results of safe operation conditions, the execution results of protection actions, and the changes in unit load in the current control cycle, feedback is used to correct the target heat distribution ratio, the target frequency of circulating pump 22, and the target opening degree of flow regulating valve 24 for the next control cycle.

[0023] In one embodiment, the current control cycle is the control cycle in which the intelligent control unit 4 performs parameter acquisition, waste heat calculation, heat distribution, pump and valve adjustment, safety judgment, and feedback correction. The gas turbine operating parameters include at least one of the following: air-side inlet temperature of the intercooler 12, air-side outlet temperature, compressor outlet pressure, and compressed air flow rate; the intercooler cycle parameters include at least one of the following: heat exchange medium inlet temperature, heat exchange medium outlet temperature, heat exchange medium flow rate, heat exchange medium pressure, and differential pressure of the waste heat heat exchanger 21; the steam cycle parameters include at least one of the following: boiler feedwater temperature, feedwater flow rate, heat demand of the waste heat boiler 31, low-pressure make-up steam pressure, low-pressure make-up steam temperature, low-pressure make-up steam flow rate, and operating status of the low-pressure cylinder of the steam turbine 32.

[0024] Preferably, the intelligent control unit 4 acquires the above parameters according to a preset sampling period, and performs outlier removal and validity judgment on the data collected within the same control period; when any key parameter is missing or exceeds the preset confidence range, the intelligent control unit 4 maintains the safe operation command of the previous control period, or switches to the preset protection operation mode.

[0025] Furthermore, the method uses the current intermediate cooling waste heat recovery benchmark as the heat source-side constraint, the boiler feedwater heating demand and low-pressure supplementary steam heat demand as the steam circulation-side constraint, and the operating frequency of the circulating pump 22 and the opening degree of the two branch flow regulating valves 24 as the execution quantities, so that a closed-loop control is formed between intermediate cooling waste heat recovery, steam recycling, safety protection and correction for the next control cycle.

[0026] Based on the above basic implementation method, in step S2, the current intermediate cooling waste heat recovery benchmark quantity is determined according to the heat exchange medium mass flow rate, the heat exchange medium constant pressure specific heat capacity, and the temperature difference between the heat exchange medium inlet and outlet of the intermediate cooler 12, and is checked according to the temperature drop of compressed air between the air inlet and outlet of the intermediate cooler 12.

[0027] Furthermore, the temperature rise of the heat exchange medium is the temperature difference before and after the heat exchange medium flows through the intercooler 12; the current intercooler waste heat recovery benchmark is determined based on the mass flow rate of the heat exchange medium, the specific heat capacity of the heat exchange medium at constant pressure, and the temperature rise of the heat exchange medium. Specifically, the intelligent control unit 4 determines the mass flow rate of the heat exchange medium based on the volumetric flow rate and density of the heat exchange medium, and obtains the heat absorbed on the heat exchange medium side based on the mass flow rate of the heat exchange medium, the specific heat capacity of the heat exchange medium at constant pressure, and the temperature difference between the inlet and outlet of the heat exchange medium on the heat exchange medium side of the intercooler 12.

[0028] Furthermore, the intelligent control unit 4 also obtains the heat released on the air side based on the compressed air mass flow rate, the specific heat capacity of compressed air at constant pressure, and the temperature drop of compressed air between the air-side inlet and air-side outlet of the intercooler 12, and compares the heat released on the air side with the heat absorbed on the heat exchange medium side; when the deviation between the two is within a preset allowable range, the heat absorbed on the heat exchange medium side is used as the current intercooler waste heat recovery benchmark; when the deviation exceeds the preset allowable range, a data verification prompt is triggered, and the current intercooler waste heat recovery benchmark is determined based on the smaller heat value or the corrected heat value; in this embodiment, the current intercooler waste heat recovery benchmark... Determined according to the following formula:

[0029] in, This is the current baseline amount for waste heat recovery from intercoolers; This refers to the mass flow rate of the heat exchange medium. The specific heat capacity at constant pressure of the heat exchange medium; The temperature at which the heat exchange medium flows out of the intercooler 12; The temperature of the heat exchange medium when it enters the intercooler 12.

[0030] Air-side heat verification Determined according to the following formula:

[0031] in, Heat verification for the air side; This refers to the mass flow rate of compressed air. The specific heat capacity at constant pressure of compressed air; This refers to the air-side inlet temperature of the intercooler 12. The air-side outlet temperature of the intercooler 12; when and When the deviation is within the preset allowable range, As the current benchmark for waste heat recovery in the intercooler; when the deviation between the two exceeds the preset allowable range, the intelligent control unit 4 verifies the heat exchange medium flow rate, temperature detection value or air side parameters, and corrects the current benchmark for waste heat recovery in the intercooler based on the verification results.

[0032] In one specific embodiment, in step S3, determining the target heat allocation ratio includes: determining the feedwater heating demand based on the deviation between the boiler feedwater temperature and the target feedwater temperature; determining the supplementary steam heat demand based on the low-pressure supplementary steam demand and the operating status of the low-pressure cylinder of the steam turbine 32; and determining the target heat allocation ratio based on the feedwater heating demand, the supplementary steam heat demand, and the current intermediate cooling waste heat recovery benchmark amount. The intelligent control unit 4 first determines the feedwater heating demand based on the deviation between the boiler feedwater temperature and the target feedwater temperature, and then determines the supplementary steam heat demand based on the low-pressure supplementary steam target pressure, target temperature, target flow rate, and current low-pressure supplementary steam parameters. When the current intermediate cooling waste heat recovery benchmark amount is greater than or equal to the sum of the feedwater heating demand and the supplementary steam heat demand, the intelligent control unit 4 determines the target heat allocation ratio according to the ratio between the feedwater heating demand and the supplementary steam heat demand. When the current intermediate cooling waste heat recovery benchmark amount is less than the sum of the feedwater heating demand and the supplementary steam heat demand, the intelligent control unit 4 determines the target heat allocation ratio of the two branches based on the unit load parameters and preset priority rules.

[0033] In this embodiment, the target heat distribution ratio includes a first target ratio allocated to the boiler feedwater heating branch 35 and a second target ratio allocated to the low-pressure steam replenishment branch. The first target ratio is determined based on the deviation between the boiler feedwater temperature and the target feedwater temperature, the feedwater flow rate, and the heat demand of the waste heat boiler 31; the second target ratio is determined based on the low-pressure steam replenishment demand, the target value of the low-pressure steam replenishment parameters, and the operating status of the low-pressure cylinder of the steam turbine 32.

[0034] Furthermore, when the boiler feedwater temperature is lower than the target feedwater temperature and the low-pressure steam replenishment demand is within the preset allowable range, the intelligent control unit 4 increases the first target proportion of the boiler feedwater heating branch 35; when the unit load increases, the low-pressure steam replenishment demand increases, or the steam intake of the low-pressure cylinder of the steam turbine 32 is insufficient, the intelligent control unit 4 increases the second target proportion of the low-pressure steam replenishment branch; when the current intermediate cooling waste heat recovery benchmark is insufficient to simultaneously meet the feedwater heating demand and the steam replenishment heat demand, the intelligent control unit 4 determines the target heat allocation ratio of the two branches according to the preset priority rules or the load-heat demand mapping relationship; in specific implementation, the feedwater heating demand can be determined based on the deviation between the target feedwater temperature and the actual feedwater temperature and the feedwater flow rate, and the steam replenishment heat demand can be determined based on the low-pressure steam replenishment target flow rate, target pressure, target temperature, and current low-pressure steam replenishment parameters. Under the condition that it does not exceed the current intermediate cooling waste heat recovery benchmark, the intelligent control unit 4 determines the target heat exchange allocated to the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch, and calculates the target heat allocation ratio accordingly.

[0035] In another specific embodiment, in step S4, adjusting the operating frequency of the circulating pump 22 and the opening of the flow regulating valve 24 includes: determining the target heat exchange of the corresponding branch according to the target heat distribution ratio, and correcting the opening of the flow regulating valve 24 and the operating frequency of the circulating pump 22 of the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch according to the deviation between the target heat exchange of the corresponding branch and the actual heat exchange of the corresponding branch; the actual heat exchange of the corresponding branch is determined based on the working fluid mass flow rate, the working fluid constant pressure specific heat capacity, and the temperature difference between the inlet and outlet of the waste heat exchanger. For the boiler feedwater heating branch, the actual heat exchange is determined based on the feedwater mass flow rate, the feedwater constant pressure specific heat capacity, and the difference between the feedwater outlet temperature and the feedwater inlet temperature; for the low-pressure steam replenishment branch, the actual heat exchange is determined based on the low-pressure steam replenishment working fluid flow rate, the low-pressure steam replenishment working fluid inlet state, and the low-pressure steam replenishment outlet state.

[0036] In this embodiment, the intelligent control unit 4 determines the target heat exchange of the boiler feedwater heating branch 35 and the target heat exchange of the low-pressure steam replenishment branch according to the target heat distribution ratio, and determines the target circulation flow of the heat exchange medium circulation loop according to the sum of the target heat exchange of the two branches; the intelligent control unit 4 determines the target frequency of the circulation pump 22 according to the target circulation flow, and determines the target opening degree of the first flow regulating valve and the second flow regulating valve according to the target heat exchange of the two branches respectively.

[0037] Specifically, when the actual heat exchange of the boiler feedwater heating branch 35 is lower than the target heat exchange of the corresponding branch, the intelligent control unit 4 increases the opening of the flow regulating valve 24 of the boiler feedwater heating branch 35; when the actual heat exchange of the low-pressure steam replenishment branch is lower than the target heat exchange of the corresponding branch, the intelligent control unit 4 increases the opening of the flow regulating valve 24 of the low-pressure steam replenishment branch; when the actual heat exchange of both branches is lower than the target heat exchange of the corresponding branches and the temperature and pressure of the intercooler circulation are within the safe range, the intelligent control unit 4 increases the operating frequency of the circulation pump 22 to increase the circulation flow of the heat exchange medium; during the adjustment process, the intelligent control unit 4 performs closed-loop correction of the target frequency of the circulation pump 22 and the target opening of the flow regulating valve 24 based on the feedback opening of the flow regulating valve 24, the feedback value of the branch flow, and the feedback value of the operating frequency of the circulation pump 22; when the deviation between the feedback value of the actuator and the target value exceeds the preset allowable deviation, the intelligent control unit 4 determines that there is an adjustment abnormality in the corresponding actuator and sends the abnormal state to the safe operation condition judgment.

[0038] In another specific embodiment, in step S6, the boiler feedwater heating branch 35 is connected between the outlet of the feedwater pump 34 and the feedwater inlet of the waste heat boiler 31, and the feedwater before entering the waste heat boiler 31 is preheated or reheated through the waste heat heat exchanger 21.

[0039] Furthermore, the boiler feedwater heating branch 35 is located between the outlet of the feedwater pump 34 and the feedwater inlet of the waste heat boiler 31. The feedwater output from the feedwater pump 34 enters the cold side channel of the waste heat exchanger 21 and indirectly exchanges heat with the heat exchange medium flowing through the hot side of the waste heat exchanger 21, absorbing the intercooled waste heat before entering the waste heat boiler 31. The boiler feedwater heating branch 35 is isolated from the heat exchange medium circulation loop, and the boiler feedwater and the heat exchange medium do not mix.

[0040] Specifically, the boiler feedwater heating branch 35 is equipped with feedwater inlet temperature detection points, feedwater outlet temperature detection points, and feedwater flow rate detection points. The intelligent control unit 4 determines the feedwater heating effect based on the feedwater inlet temperature, feedwater outlet temperature, and feedwater flow rate. When the feedwater outlet temperature is lower than the target feedwater temperature, the intelligent control unit 4 increases the opening of the flow regulating valve 24 of the boiler feedwater heating branch 35 or increases the operating frequency of the circulating pump 22; when the feedwater outlet temperature reaches or approaches the target feedwater temperature, the intelligent control unit 4 maintains or reduces the opening of the flow regulating valve 24 of the boiler feedwater heating branch 35.

[0041] In another specific embodiment, in step S6, the low-pressure steam replenishment branch preheats, preheats, or heats the low-pressure replenishment working medium before evaporation or before evaporation using the waste heat exchanger 21, and then sends the low-pressure steam that meets the replenishment conditions into the inlet of the low-pressure cylinder of the steam turbine 32 through the replenishment valve. Meeting the replenishment conditions means that the low-pressure replenishment pressure, low-pressure replenishment temperature, low-pressure replenishment flow rate, and the permissible steam inlet state of the steam turbine's low-pressure cylinder are all within a preset replenishment allowable range. The preset replenishment allowable range is determined based on the steam turbine's low-pressure cylinder design inlet parameters, unit operating procedures, and on-site commissioning data. When the condenser waste heat temperature is insufficient to directly generate low-pressure steam, the low-pressure steam replenishment branch is used to preheat or preheat the low-pressure replenishment working medium before evaporation; when the condenser waste heat temperature meets the preset evaporation conditions, the low-pressure steam replenishment branch is used to generate or heat low-pressure steam.

[0042] Furthermore, the low-pressure steam makeup branch includes a low-pressure makeup working medium inlet, a low-pressure makeup heat exchange section connected to the cold side of the waste heat exchanger 21, and a makeup steam pipeline connected to the low-pressure cylinder inlet of the steam turbine 32. The low-pressure makeup working medium absorbs the intercooled waste heat released by the waste heat exchanger 21 within the low-pressure makeup heat exchange section, forming low-pressure steam that meets the makeup conditions or a heated low-pressure makeup working medium, which is then sent to the low-pressure cylinder inlet of the steam turbine 32 via the makeup steam valve.

[0043] Specifically, the low-pressure steam replenishment parameters include at least one of low-pressure steam replenishment pressure, low-pressure steam replenishment temperature, low-pressure steam replenishment flow rate, and low-pressure steam replenishment valve opening. The intelligent control unit 4 determines the low-pressure steam replenishment effect based on the deviation between the low-pressure steam replenishment parameters and the corresponding target values. When the low-pressure steam replenishment pressure, low-pressure steam replenishment temperature, or low-pressure steam replenishment flow rate does not meet the steam replenishment conditions, the intelligent control unit 4 restricts the opening of the steam replenishment valve and reduces or switches the heat distribution ratio of the low-pressure steam replenishment branch to the boiler feedwater heating branch 35. In cases where the intercooler waste heat temperature is insufficient to directly generate low-pressure steam, the low-pressure steam replenishment branch is used to preheat or preheat the low-pressure steam replenishment working fluid before evaporation. In cases where the intercooler waste heat temperature meets the preset evaporation conditions, the low-pressure steam replenishment branch is used to collaboratively generate low-pressure steam.

[0044] In another specific embodiment, in step S7, the protection actions include: reducing the operating frequency of the circulating pump 22 or opening a preset bypass channel when the intercooler circulation temperature exceeds the preset temperature upper limit; opening the pressure relief channel when the intercooler circulation pressure exceeds the preset pressure upper limit; issuing a blockage alarm when the differential pressure of the waste heat exchanger 21 exceeds the preset differential pressure upper limit; closing the faulty branch when any branch fails, and switching the intercooler waste heat to the non-faulty branch or the preset bypass channel; the preset temperature upper limit, preset pressure upper limit, preset differential pressure upper limit, preset feedwater temperature upper limit, and preset allowable steam replenishment range are determined based on the design parameters, rated operating parameters, unit operating procedures, and on-site commissioning data of the intercooler, waste heat exchanger, circulating pump, flow regulating valve, waste heat boiler, and steam turbine low-pressure cylinder. The intelligent control unit stores the above-mentioned preset safety boundaries before the unit is put into operation and corrects some safety boundaries during operation based on equipment status and historical operating data.

[0045] Furthermore, the safe operating conditions include the intercooling cycle temperature not exceeding the preset upper limit, the intercooling cycle pressure not exceeding the preset upper limit, the differential pressure of the waste heat exchanger 21 not exceeding the preset upper limit, the feedwater outlet temperature not exceeding the preset upper limit, the low-pressure steam injection pressure and low-pressure steam injection temperature being within the preset allowable range for steam injection, and the deviation between the feedback opening degree of the flow regulating valve 24 and the target opening degree not exceeding the preset deviation threshold.

[0046] Specifically, when the intermediate cooling cycle temperature exceeds the preset upper limit, the intelligent control unit 4 reduces the operating frequency of the circulating pump 22, decreases the opening of the corresponding branch flow regulating valve 24, or opens the preset bypass channel; when the intermediate cooling cycle pressure exceeds the preset upper limit, the intelligent control unit 4 opens the pressure relief channel and reduces the operating frequency of the circulating pump 22; when the differential pressure of the waste heat exchanger 21 exceeds the preset upper limit, the intelligent control unit 4 issues a blockage alarm and reduces the flow rate of the heat exchange medium through the waste heat exchanger 21; when valve jamming, abnormal flow, or abnormal temperature occurs in the boiler feedwater heating branch 35 or the low-pressure steam injection branch, the intelligent control unit 4 closes the faulty branch and switches the intermediate cooling waste heat to the non-faulty branch or the preset bypass channel; after completing the protection action, the intelligent control unit 4 records the protection action type, trigger time, trigger parameters, and execution result, and uses the execution result of the protection action as the basis for correcting the target heat distribution ratio in the next control cycle; when the same protection action is repeatedly triggered in multiple consecutive control cycles, the intelligent control unit 4 reduces the distribution priority of the corresponding branch and outputs a maintenance prompt.

[0047] In one specific implementation, such as Figure 2 , Figure 3As shown, a gas turbine unit 1 is provided, comprising: a gas turbine unit 1, including at least two compressor stages, a combustion chamber, and a gas turbine connected sequentially along the air compression direction; an intercooler 12 is provided between any two adjacent compressor stages, the air-side inlet of the intercooler 12 is connected to the air outlet of the upstream compressor stage, and the air-side outlet of the intercooler 12 is connected to the air inlet of the downstream compressor stage; and an intercooler waste heat recovery unit 2, comprising a waste heat exchanger 21, a heat exchange medium circulation loop, and a circulation pump 22, wherein the heat exchange medium circulation loop is connected between the heat exchange medium side of the intercooler 12 and the hot side of the waste heat exchanger 21, and the circulation pump 22 is located at... In the heat exchange medium circulation loop, the heat exchange medium, after absorbing the heat of compression, is transported from the intercooler 12 to the waste heat exchanger 21, and returns to the intercooler 12 after releasing heat; the steam circulation unit 3 includes a waste heat boiler 31, a steam turbine 32, a condenser 33, and a feedwater pump 34. The outlet of the feedwater pump 34 is connected to the feedwater inlet of the waste heat boiler 31 via a boiler feedwater heating branch 35. The boiler feedwater heating branch 35 is connected to the cold side of the waste heat exchanger 21 for heat exchange, so that the feedwater before entering the waste heat boiler 31 absorbs the intercooled waste heat released by the waste heat exchanger 21; the low-pressure steam replenishment branch is connected to the cold side of the waste heat exchanger 21 for heat exchange, and the low-pressure steam replenishment branch is connected to the cold side of the waste heat exchanger 21 for heat exchange. The outlet of the low-pressure steam make-up branch is connected to the inlet of the low-pressure cylinder of the steam turbine 32, so that the low-pressure make-up working medium absorbs the intercooled waste heat released by the waste heat exchanger 21 and is then sent into the low-pressure cylinder of the steam turbine 32; the heat distribution assembly includes a heat distribution pipeline 23 and a flow regulating valve 24. The heat distribution pipeline 23 includes a first heat exchange branch connected to the boiler feedwater heating branch 35 and a second heat exchange branch connected to the low-pressure steam make-up branch. The flow regulating valve 24 includes a first flow regulating valve installed on the first heat exchange branch and a second flow regulating valve installed on the second heat exchange branch; parameter monitoring units are respectively installed in the heat exchange medium circulation loop and the boiler feedwater... The heating branch 35 and the low-pressure steam replenishment branch are connected to the intelligent control unit 4 via data. The intelligent control unit 4 is connected to the circulating pump 22, the first flow regulating valve, and the second flow regulating valve via control. Based on the intercooling circulation parameters, boiler feedwater parameters, low-pressure steam replenishment parameters, and unit load parameters collected by the parameter monitoring unit, the operating frequency of the circulating pump 22, the opening of the first flow regulating valve, and the opening of the second flow regulating valve are adjusted to change the distribution ratio of the intercooling waste heat between the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch. The at least two-stage compressor is formed by at least two compressors 11 connected sequentially along the air compression direction.

[0048] In this embodiment, energy transfer is achieved between the gas turbine unit 1, the intercooled waste heat recovery unit 2, and the steam circulation unit 3 through a compressed air flow path, a heat exchange medium circulation flow path, a boiler feedwater flow path, and a low-pressure make-up steam flow path. The compressed air flow path is used to cool the compressed air discharged from the upstream first-stage compressor through the intercooler 12 before it enters the downstream first-stage compressor; the heat exchange medium circulation flow path is used to circulate the heat exchange medium between the intercooler 12 and the waste heat heat exchanger 21 and transfer the intercooled waste heat; the boiler feedwater flow path is used to allow the feedwater before entering the waste heat boiler 31 to absorb the intercooled waste heat; and the low-pressure make-up steam flow path is used to allow the low-pressure make-up steam working medium to absorb the intercooled waste heat and enter the low-pressure cylinder of the steam turbine 32.

[0049] Specifically, the waste heat exchanger 21 includes a hot-side channel connected to the heat exchange medium circulation loop, and a cold-side channel that respectively cooperates with the boiler feedwater heating branch 35 and the low-pressure steam makeup branch for heat exchange. The heat exchange medium flowing through the hot-side channel and the boiler feedwater or low-pressure steam makeup medium flowing through the cold-side channel exchange heat indirectly, so that the heat exchange medium, boiler feedwater and low-pressure steam makeup medium flow in their respective independent channels, avoiding mixing of different working media.

[0050] In one specific embodiment, the heat exchange medium side outlet of the intercooler 12 is connected to the hot side inlet of the waste heat exchanger 21, and the hot side outlet of the waste heat exchanger 21 is connected to the heat exchange medium side inlet of the intercooler 12 via the circulating pump 22; the cold side of the waste heat exchanger 21 is respectively connected to the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch for heat exchange.

[0051] Furthermore, the heat distribution pipeline 23 is located on the cold side of the waste heat exchanger 21. The first heat exchange branch is correspondingly arranged with the boiler feedwater heating branch 35, and the second heat exchange branch is correspondingly arranged with the low-pressure steam replenishment branch. The first flow regulating valve is used to regulate the feedwater flow rate entering the boiler feedwater heating branch 35 or the flow rate of the cold-side working medium that exchanges heat with the boiler feedwater. The second flow regulating valve is used to regulate the flow rate of the low-pressure steam replenishment working medium entering the low-pressure steam replenishment branch.

[0052] Furthermore, the heat exchange medium circulation loop is equipped with a circulation pump 22, temperature detection points, pressure detection points, and flow detection points; the boiler feedwater heating branch 35 is equipped with feedwater inlet temperature detection points, feedwater outlet temperature detection points, and feedwater flow detection points; and the low-pressure steam replenishment branch is equipped with replenishment steam pressure detection points, replenishment steam temperature detection points, replenishment steam flow detection points, and replenishment steam valves. All of these detection points are connected to the intelligent control unit 4, enabling the intelligent control unit 4 to acquire the operating status of the heat source side, feedwater side, and replenishment steam side.

[0053] In one specific embodiment, the parameter monitoring unit includes a detection component for collecting parameters such as intercooler circulation temperature, pressure, flow rate, waste heat exchanger differential pressure, boiler feedwater temperature, and low-pressure steam injection. The system also includes a safety protection actuator. The intelligent control unit 4 includes a data acquisition module, a heat distribution calculation module, and an execution control module. The execution control module is connected to the circulating pump 22, the first flow regulating valve, the second flow regulating valve, and the safety protection actuator.

[0054] In this embodiment, the data acquisition module is used to receive signals collected by the temperature sensor 25, pressure sensor 26, flow meter 27, and differential pressure sensor, and convert the collected signals into gas turbine operating parameters, intercooler cycle parameters, steam cycle parameters, and unit load parameters for the current control cycle; the heat distribution calculation module is used to calculate the target heat distribution ratio of the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch based on the current intercooler waste heat recovery baseline, boiler feedwater heating demand, and low-pressure steam replenishment heat demand; the execution control module is used to output the operating frequency control command of the circulating pump 22, the opening control command of the first flow regulating valve, the opening control command of the second flow regulating valve, and the safety protection execution command.

[0055] Specifically, the safety protection actuator includes at least one of a preset bypass valve, a pressure relief valve, a branch isolation valve, an alarm, and a standby circulating pump. When the intelligent control unit 4 determines that the current waste heat distribution status does not meet the safe operating conditions, it controls the safety protection actuator to perform bypass switching, pressure relief, branch isolation, alarm, or standby circulating pump start-up operations, and feeds back the safety protection execution result to the heat distribution calculation module to correct the target heat distribution ratio for the next control cycle. In this embodiment, the above-mentioned gas-fired steam intercooled waste heat recovery method is executed by the gas-fired steam intercooled waste heat recovery system. In this process, step S1 is executed by the data acquisition module of the parameter monitoring unit and the intelligent control unit 4; step S2 is executed by the intelligent control unit 4 based on the intercooler cycle parameters and the gas turbine operating parameters; step S3 is executed by the heat distribution calculation module; step S4 is jointly executed by the execution control module, the circulating pump 22, the first flow regulating valve, and the second flow regulating valve; step S5 is executed by the intercooler 12, the heat exchange medium circulation loop, the circulating pump 22, and the waste heat exchanger 21; step S6 is executed by the waste heat exchanger 21, the boiler feedwater heating branch 35, and the low-pressure steam replenishment branch; step S7 is executed by the parameter monitoring unit, the intelligent control unit 4, and the safety protection actuator; and step S8 is executed by the intelligent control unit 4 based on the operating results and safety protection results of the current control cycle. Thus, the waste heat from the intercooler is released from the compressed air side, transferred through the heat exchange medium circulation loop, and redistributed to the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch, and corrected in the next control cycle to form a continuous closed-loop control. The system also includes an insulation layer 28, which is disposed on the heat exchange medium circulation loop, the outer surface of the waste heat exchanger, and the outer periphery of the heat distribution pipeline to reduce the loss of waste heat during transmission and distribution. The insulation layer 28 covers at least the high-temperature heat exchange medium pipe section between the heat exchange medium side outlet of the intercooler and the hot side inlet of the waste heat exchanger, the return pipe section between the hot side outlet of the waste heat exchanger and the heat exchange medium side inlet of the intercooler, the first heat exchange branch corresponding to the boiler feedwater heating branch, and the second heat exchange branch corresponding to the low-pressure steam replenishment branch. The insulation layer 28 is fitted to the outer wall of each pipeline, with a protective layer on the outside to reduce heat loss of the heat exchange medium, boiler feedwater, or low-pressure steam replenishment medium during transportation. Furthermore, at the installation locations of the circulating pump, first flow regulating valve, second flow regulating valve, temperature sensor, pressure sensor, flow meter, and differential pressure sensor, the insulation layer 28 is configured as a detachable insulation structure, or maintenance openings are reserved at corresponding locations to facilitate valve maintenance, sensor calibration, and pipeline maintenance. The detachable insulation structure is fixed to the outside of the pipeline or equipment by fasteners, straps, clamps, or flange outer sleeves, and can be re-wrapped in the original installation position after disassembly. Further, the insulation layer 28 includes an insulation material layer that adheres to the outer surface of the pipeline or equipment and an outer protective layer covering the outside of the insulation material layer.The insulation material layer is made of at least one of rock wool, aluminum silicate fiber, glass wool, aerogel felt, or composite insulation material; the outer protective layer is made of at least one of aluminum plate, galvanized plate, stainless steel sheet, or waterproof and weather-resistant protective layer. This design reduces the transmission loss of residual heat in the heat exchange medium circulation loop and heat distribution pipeline, and improves the insulation stability and maintenance convenience of the system during long-term operation.

[0056] In one specific embodiment, the method of the present invention is applied to a gas-steam combined cycle unit. The gas turbine unit 1 of this unit includes two compressor stages connected sequentially along the air compression direction, with an intercooler 12 installed between adjacent compressor stages. The air-side inlet of the intercooler 12 is connected to the air outlet of the upstream compressor stage, and the air-side outlet of the intercooler 12 is connected to the air inlet of the downstream compressor stage. The heat exchange medium side of the intercooler 12 is connected to the hot side of a waste heat exchanger 21 via a heat exchange medium circulation loop. The heat exchange medium is demineralized water, and the circulation pump 22 is a variable frequency circulation pump. The cold side of the waste heat exchanger 21 is connected to the boiler feedwater heating branch 35 and the low-pressure steam makeup branch for heat exchange. A first flow regulating valve is installed on the boiler feedwater heating branch 35, and a second flow regulating valve is installed on the low-pressure steam makeup branch. In this embodiment, the control cycle of the intelligent control unit 4 is 10 seconds. During the current control cycle, the unit load is 88% of the rated load, indicating a high-load operation. The parameter monitoring unit collected the following operating parameters: the air inlet temperature of the intercooler 12 was 190℃, the air outlet temperature was 55℃, and the compressed air mass flow rate was 230 kg / s; the temperature of the heat exchange medium entering the intercooler 12 was 60℃, the temperature of the heat exchange medium exiting the intercooler 12 was 150℃, the volumetric flow rate of the heat exchange medium was 300 t / h, and the pressure of the heat exchange medium was 0.72 MPa; in the boiler feedwater heating branch 35, the feedwater flow rate was 250 t / h, the feedwater temperature before entering the waste heat exchanger 21 was 92℃, and the target feedwater temperature was 130℃; in the low-pressure steam replenishment branch, the low-pressure steam replenishment demand was 28 t / h, the target steam replenishment pressure was 0.12 MPa, and the target steam replenishment temperature was 105℃ to 112℃.

[0057] In this embodiment, in step S1, the intelligent control unit 4 collects the gas turbine operating parameters, intercooler cycle parameters, steam cycle parameters, and unit load parameters for the current control cycle. The gas turbine operating parameters include the air-side inlet temperature, air-side outlet temperature, and compressed air mass flow rate of the intercooler 12; the intercooler cycle parameters include the heat exchange medium inlet temperature, heat exchange medium outlet temperature, heat exchange medium flow rate, and heat exchange medium pressure; the steam cycle parameters include the boiler feedwater temperature, feedwater flow rate, low-pressure make-up steam demand, low-pressure make-up steam pressure, and low-pressure make-up steam temperature. In step S2, the intelligent control unit 4 determines the current intercooler waste heat recovery baseline based on the heat exchange medium mass flow rate, the heat exchange medium's constant-pressure specific heat capacity, and the temperature difference between the heat exchange medium's inlet and outlet on the heat exchange medium side of the intercooler 12. Specifically, the heat exchange medium mass flow rate is 300 t / h, or 83.33 kg / s; the heat exchange medium specific heat capacity at constant pressure is taken as 4.18 kJ / (kg·℃); and the heat exchange medium temperature rise is 90℃. Therefore, the current baseline amount for waste heat recovery from the intermediate cooling system is... for: =83.33×4.18×90=31350kW, or 31.35MW; Simultaneously, the intelligent control unit 4 performs verification based on the air-side parameters. The compressed air mass flow rate is 230kg / s, the specific heat capacity of compressed air at constant pressure is taken as 1.01kJ / (kg·℃), and the temperature drop of compressed air is 135℃. Therefore, the heat released on the air side... for: =230×1.01×135=31360.5kW, or 31.36MW; Since the deviation between the heat released on the air side and the heat absorbed on the heat exchange medium side is less than the preset allowable deviation, the intelligent control unit 4 determines 31.35MW as the current intermediate cooling waste heat recovery benchmark for the current control cycle; In step S3, the intelligent control unit 4 determines the target heat distribution ratio of the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch based on the current intermediate cooling waste heat recovery benchmark, unit load parameters and steam cycle parameters. Specifically, the boiler feedwater temperature is 92℃, the target feedwater temperature is 130℃, and the feedwater flow rate is 250t / h. Therefore, the boiler feedwater heating requirement is approximately: 250000 / 3600×4.18×(130-92)=11030kW, or 11.03MW. The low-pressure steam replenishment branch is used to heat the low-pressure replenishment working medium from 75℃ to form low-pressure steam that meets the replenishment conditions. The low-pressure replenishment steam requirement is 28t / h. Based on the initial state of the low-pressure replenishment working medium, the target replenishment steam pressure, and the target replenishment steam temperature, the intelligent control unit 4 determines the low-pressure replenishment steam heat requirement to be approximately 18.8MW. Since the current intermediate cooling waste heat recovery benchmark is 31.35MW, which can simultaneously meet the boiler feedwater heating demand and the low-pressure steam replenishment heat demand, the intelligent control unit 4 determines the target heat allocation ratio of the boiler feedwater heating branch 35 to be 36% and the target heat allocation ratio of the low-pressure steam replenishment branch to be 64%. The difference in heat between the current intermediate cooling waste heat recovery benchmark and the sum of the boiler feedwater heating demand and the low-pressure steam replenishment heat demand is used to compensate for the heat exchange loss of the waste heat exchanger, the heat loss of pipeline transmission, and to maintain the stability of the air temperature at the outlet of the intermediate cooler. When the difference in heat exceeds the preset allowable range, the intelligent control unit releases or returns this part of the heat through the preset bypass channel to avoid excessive heat absorption by the boiler feedwater heating branch or the low-pressure steam replenishment branch. In step S4, the intelligent control unit 4 determines the target frequency of the circulating pump 22, the target opening degree of the first flow regulating valve, and the target opening degree of the second flow regulating valve according to the target heat allocation ratio. In this embodiment, the intelligent control unit 4 sets the target frequency of the circulating pump 22 to 42Hz, the target opening of the first flow regulating valve to 48%, and the target opening of the second flow regulating valve to 74%. Subsequently, the intelligent control unit 4 adjusts the operating frequency of the circulating pump 22 to 42Hz and adjusts the first and second flow regulating valves to their corresponding target openings, so that the heat exchange medium circulation flow rate is maintained at approximately 300t / h, and the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch obtain heat absorption medium flow rates that match the target heat distribution ratio. In step S5, the circulating pump 22 drives the heat exchange medium to circulate between the intercooler 12 and the waste heat exchanger 21.The heat exchange medium absorbs the heat of compression released by the compressed air in the intercooler 12, causing the compressed air temperature to drop from 190°C to 55°C and the heat exchange medium temperature to rise from 60°C to 150°C. After absorbing the heat of compression, the heat exchange medium enters the hot side of the waste heat exchanger 21, transferring the intercooled waste heat to the boiler feedwater heating branch 35 and the low-pressure steam injection branch. The heat-released heat exchange medium flows back to the intercooler 12. In step S6, the intelligent control unit 4 controls the cold side heat absorption process of the waste heat exchanger 21 according to the target heat distribution ratio. The intercooled waste heat distributed to the boiler feedwater heating branch 35 is used to reheat the feedwater before it enters the waste heat boiler 31, raising the feedwater temperature from 92°C to 129.5°C, resulting in a feedwater outlet temperature of 129.5°C, corresponding to an actual feedwater heating capacity of approximately 10.88 MW. The intercooled waste heat allocated to the low-pressure steam make-up branch is used to preheat the low-pressure make-up working medium, heat it before evaporation, and form low-pressure steam, so that the low-pressure steam output from the low-pressure steam make-up branch has a pressure of 0.12 MPa, a temperature of 108℃, and a flow rate of 27.4 t / h, thus obtaining the low-pressure make-up steam parameters. Since the pressure and temperature of the low-pressure steam meet the preset make-up steam conditions, the intelligent control unit 4 opens the make-up steam valve and sends the low-pressure steam into the inlet of the low-pressure cylinder of the steam turbine 32; in step S7, the intelligent control unit 4 determines whether the current waste heat distribution status meets the safe operation conditions based on the feedwater outlet temperature, low-pressure make-up steam parameters, intercooled cycle parameters, and differential pressure of the waste heat exchanger 21. In this embodiment, the preset upper limit of temperature is 155℃, the preset upper limit of pressure is 0.90MPa, the preset upper limit of differential pressure is 0.15MPa, the upper limit of feedwater outlet temperature is 135℃, the allowable range of low-pressure steam injection pressure is 0.10MPa to 0.14MPa, and the allowable range of low-pressure steam injection temperature is 105℃ to 115℃. In the current control cycle, the highest temperature of the heat exchange medium is 150℃, the pressure of the heat exchange medium is 0.72MPa, the differential pressure of the waste heat exchanger 21 is 0.06MPa, the feedwater outlet temperature is 129.5℃, the low-pressure steam injection pressure is 0.12MPa, and the low-pressure steam injection temperature is 108℃, all within their respective allowable ranges. Therefore, the intelligent control unit 4 determines that the current waste heat distribution status meets the safe operating conditions and does not trigger any protection actions.

[0058] Specifically, in an anomaly judgment example, when the differential pressure of the waste heat exchanger 21 rises to 0.18 MPa and exceeds the preset differential pressure limit of 0.15 MPa, the intelligent control unit 4 determines that there is a risk of heat exchanger blockage, triggers a heat exchanger blockage alarm, and reduces the operating frequency of the circulating pump 22 from 42 Hz to 35 Hz. At the same time, it reduces the opening of the second flow regulating valve from 74% to 45% and opens the preset bypass channel, allowing some heat exchange medium to bypass the waste heat exchanger 21, thereby reducing the flow resistance and operating risk of the waste heat exchanger 21. In step S8, the intelligent control unit 4, based on the actual distribution results of the intercooler waste heat, the feedwater heating effect, the low-pressure steam replenishment effect, the safe operation condition judgment results, the protection action execution results, and the unit load changes in the current control cycle, feeds back and corrects the target heat distribution ratio, the target frequency of the circulating pump 22, and the target opening of the flow regulating valve 24 for the next control cycle. In this embodiment, the actual heat exchange of the boiler feedwater heating branch 35 during the current control cycle is 10.88MW, the actual heat exchange of the low-pressure steam replenishment branch is 18.2MW, and the actual total utilized waste heat from the intermediate cooling system is 29.08MW. Since the feedwater outlet temperature is 0.5℃ lower than the target feedwater temperature, and the low-pressure steam replenishment flow rate is 0.6t / h lower than the target steam replenishment demand, the intelligent control unit 4 corrects the target heat allocation ratio of the boiler feedwater heating branch 35 from 36% to 37%, the target heat allocation ratio of the low-pressure steam replenishment branch from 64% to 63%, the target frequency of the circulating pump 22 from 42Hz to 43Hz, the target opening of the first flow regulating valve from 48% to 50%, and maintains the target opening of the second flow regulating valve at 74%. This allows the distribution of intercooled waste heat in the next control cycle to more closely approximate the boiler feedwater heating demand and the low-pressure steam replenishment demand. As can be seen from the above embodiments, the method of the present invention can determine the target heat distribution ratio under high load conditions based on the current intercooled waste heat recovery benchmark, boiler feedwater heating demand, and low-pressure steam replenishment heat demand, and execute the control through the frequency of the circulating pump 22 and the opening of the two branch flow regulating valves 24. At the same time, safety judgments are made based on the feedwater outlet temperature, low-pressure steam replenishment parameters, intercooled circulation temperature, intercooled circulation pressure, and differential pressure of the waste heat exchanger 21, and feedback corrections are made for the next control cycle based on the actual heat exchange effect, thereby forming a closed-loop control of intercooled waste heat recovery, steam circulation cascade utilization, and safety protection.

[0059] In summary, this embodiment has at least the following technical effects: By setting an intercooler 12 between two adjacent compressor stages and using a heat exchange medium circulation loop to transfer the compression heat released during the compressor intercooling process to the waste heat exchanger 21, the waste heat from the intercooler is avoided from being discharged directly through the cooling system, thus improving the degree of recovery and utilization of the waste heat from the intercooler. The present invention transfers the recovered intermediate cooling waste heat to the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch respectively, so that the intermediate cooling waste heat can be used for feedwater preheating or secondary heating before entering the waste heat boiler 31, and can also be used for preheating, pre-evaporation heating or low-pressure steam heating of the low-pressure replenishment working medium, thereby improving the coupling degree between intermediate cooling waste heat and steam cycle. By heating the feedwater before it enters the waste heat boiler 31 through the boiler feedwater heating branch 35, the inlet feedwater temperature of the waste heat boiler 31 can be increased, the heat required for the waste heat boiler 31 to raise the feedwater temperature can be reduced, which is beneficial to improving the steam cycle thermodynamic process and improving the energy utilization level of the combined cycle system. The low-pressure steam supplementation branch uses the residual heat of the intercooler to heat the working medium of the low-pressure steam supplementation, and when the steam supplementation conditions are met, the low-pressure steam is sent into the inlet of the low-pressure cylinder of steam turbine 32, which can supplement the steam intake of the low-pressure side of steam turbine 32 and improve the work capacity of the low-pressure side. Based on the current benchmark amount of waste heat recovery from the intercooler, unit load parameters, boiler feedwater temperature, low-pressure steam replenishment demand, and the operating status of the low-pressure cylinder of steam turbine 32, this invention determines the target heat distribution ratio between the boiler feedwater heating branch 35 and the low-pressure steam replenishment branch, so that the waste heat from the intercooler can be dynamically distributed between the two branches according to different operating conditions, avoiding the problem of heat supply and demand mismatch in a single branch waste heat utilization method under varying operating conditions; The present invention determines the target frequency of the circulating pump 22 and the target opening of the two branch flow regulating valves 24 according to the target heat distribution ratio. By adjusting the operating frequency of the circulating pump 22 and the opening of the flow regulating valves 24, the circulating flow rate of the heat exchange medium and the flow rate of the heat absorption working fluid in the two branches are changed, so that the amount of waste heat recovery from the intermediate cooling and the actual heat exchange of the two branches can be adjusted in accordance with the target distribution ratio. This invention determines whether the current waste heat distribution status meets the safe operating conditions based on the feedwater outlet temperature, low-pressure steam injection parameters, intercooler cycle parameters, and differential pressure of waste heat exchanger 21. When over-temperature, over-pressure, heat exchanger blockage, or branch failure occurs, it performs protective actions such as reducing the frequency of circulating pump 22, opening the bypass or pressure relief channel, closing the faulty branch, and switching the waste heat distribution path to reduce the impact of abnormal operating conditions on system operation. Based on the actual distribution results of the intermediate cooling waste heat, the feedwater heating effect, the low-pressure steam replenishment effect, the judgment results of safe operation conditions, the execution results of protection actions, and the changes in unit load during the current control cycle, feedback corrections are made to the target heat distribution ratio, the target frequency of circulating pump 22, and the target opening degree of flow regulating valve 24 for the next control cycle, so that the system can adapt to changes in unit load and changes in steam cycle heat demand.

[0060] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for recovering waste heat from gas-steam intercooling, applied to a gas-steam combined cycle system, the gas-steam combined cycle system comprising an intercooler disposed between two adjacent compressor stages, a waste heat exchanger connected to the intercooler via a heat exchange medium circulation loop, a boiler feedwater heating branch, a low-pressure steam makeup branch, a circulating pump, a flow regulating valve, and an intelligent control unit, characterized in that, Includes the following steps: S1: Collect the gas turbine operating parameters, intercooler cycle parameters, steam cycle parameters, and unit load parameters for the current control cycle; S2: Determine the current intercooler waste heat recovery baseline amount based on the intercooler air-side inlet temperature, air-side outlet temperature and intercooler cycle parameters in the gas turbine operating parameters; S3: Determine the target heat distribution ratio of the boiler feedwater heating branch and the low-pressure steam replenishment branch based on the current intermediate cooling waste heat recovery benchmark, the unit load parameters, and the steam cycle parameters; S4: Based on the target heat distribution ratio, determine the target frequency of the circulating pump and the target opening degree of the flow regulating valves of the boiler feedwater heating branch and the low-pressure steam replenishment branch, and adjust the operating frequency of the circulating pump according to the target frequency of the circulating pump, and adjust the opening degree of the flow regulating valves of the boiler feedwater heating branch and the low-pressure steam replenishment branch according to the target opening degree of the flow regulating valves. S5: The heat exchange medium is circulated between the intercooler and the waste heat exchanger to transfer the heat of compression released during the intercooling process of the multi-stage compressor to the waste heat exchanger. S6: According to the target heat distribution ratio, the intermediate cooling waste heat is transferred to the boiler feedwater heating branch and the low-pressure steam replenishment branch through the waste heat exchanger to obtain the feedwater outlet temperature and low-pressure steam replenishment parameters respectively. S7: Based on the feedwater outlet temperature, the low-pressure steam injection parameters, the intercooling cycle parameters, and the waste heat exchanger differential pressure, determine whether the current waste heat distribution status meets the safe operation conditions; When the safe operating conditions are not met, the corresponding protection action is triggered, and the opening of the flow regulating valve, the operating frequency of the circulating pump, or the waste heat distribution path is adjusted. S8: Based on the actual distribution results of the intermediate cooling waste heat, feedwater heating effect, low-pressure steam replenishment effect, safe operation condition judgment results, protection action execution results, and unit load changes in the current control cycle, feedback is used to correct the target heat distribution ratio, circulating pump target frequency, and flow regulating valve target opening for the next control cycle.

2. The method for recovering waste heat from gas-fired steam cooling according to claim 1, characterized in that, In step S2, the current intermediate cooling waste heat recovery benchmark quantity is determined based on the heat exchange medium mass flow rate, the heat exchange medium constant pressure specific heat capacity, and the temperature difference between the heat exchange medium inlet and outlet of the intermediate cooler, and is verified based on the temperature drop of compressed air between the air inlet and outlet of the intermediate cooler.

3. The method for recovering waste heat from intercooled gas steam according to claim 1, characterized in that, In step S3, determining the target heat allocation ratio includes: determining the feedwater heating demand based on the deviation between the boiler feedwater temperature and the target feedwater temperature; determining the supplementary steam heat demand based on the low-pressure steam replenishment demand and the operating status of the steam turbine low-pressure cylinder; and determining the target heat allocation ratio based on the feedwater heating demand, the supplementary steam heat demand, and the current intermediate cooling waste heat recovery benchmark amount.

4. The method for recovering waste heat from gas-fired steam cooling according to claim 1, characterized in that, In step S4, adjusting the operating frequency of the circulating pump and the opening of the flow regulating valve includes: determining the target heat exchange of the corresponding branch according to the target heat distribution ratio, and correcting the opening of the flow regulating valve and the operating frequency of the circulating pump of the boiler feedwater heating branch and the low-pressure steam replenishment branch according to the deviation between the target heat exchange of the corresponding branch and the actual heat exchange of the corresponding branch.

5. The method for recovering waste heat from gas-fired steam cooling according to claim 1, characterized in that, In step S6, the boiler feedwater heating branch is connected between the feedwater pump outlet and the waste heat boiler feedwater inlet, and the feedwater before entering the waste heat boiler is preheated or reheated through the waste heat heat exchanger.

6. The method for recovering waste heat from gas-fired steam cooling according to claim 1, characterized in that, In step S6, the low-pressure steam replenishment branch preheats, preheats or heats the low-pressure steam replenishment medium before evaporation or through the waste heat exchanger, and sends the low-pressure steam that meets the replenishment conditions into the inlet of the low-pressure cylinder of the steam turbine through the replenishment valve.

7. The method for recovering residual heat from gas-fired steam according to any one of claims 1 to 6, characterized in that, In step S7, the protection actions include: reducing the operating frequency of the circulating pump or opening a preset bypass channel when the intercooling circulation temperature exceeds the preset upper limit; opening the pressure relief channel when the intercooling circulation pressure exceeds the preset upper limit; issuing a blockage alarm when the differential pressure of the waste heat exchanger exceeds the preset upper limit; and closing the faulty branch and switching the intercooling waste heat to the non-faulty branch or the preset bypass channel when a fault occurs in any branch.

8. A gas-fired steam intercooled waste heat recovery system, characterized in that, include: A gas turbine unit includes at least two compressor stages, a combustion chamber, and a gas turbine connected sequentially along the air compression direction. An intercooler is provided between any two adjacent compressor stages. The air-side inlet of the intercooler is connected to the air outlet of the upstream compressor stage, and the air-side outlet of the intercooler is connected to the air inlet of the downstream compressor stage. The intercooler waste heat recovery unit includes a waste heat exchanger, a heat exchange medium circulation loop, and a circulation pump. The heat exchange medium circulation loop is connected between the heat exchange medium side of the intercooler and the hot side of the waste heat exchanger. The circulation pump is installed in the heat exchange medium circulation loop so that the heat exchange medium after absorbing the heat of compression is transported from the intercooler to the waste heat exchanger and returns to the intercooler after releasing heat. The steam circulation unit includes a waste heat boiler, a steam turbine, a condenser, and a feedwater pump. The outlet of the feedwater pump is connected to the feedwater inlet of the waste heat boiler via a boiler feedwater heating branch. The boiler feedwater heating branch is connected to the cold side of the waste heat exchanger for heat exchange. The low-pressure steam make-up branch is connected to the cold side of the waste heat exchanger, and the outlet of the low-pressure steam make-up branch is connected to the low-pressure cylinder inlet of the steam turbine. A heat distribution assembly includes a heat distribution pipeline and a flow regulating valve. The heat distribution pipeline includes a first heat exchange branch connected to the boiler feedwater heating branch and a second heat exchange branch connected to the low-pressure steam replenishment branch. The flow regulating valve includes a first flow regulating valve disposed on the first heat exchange branch and a second flow regulating valve disposed on the second heat exchange branch. Parameter monitoring units are respectively installed in the heat exchange medium circulation loop, the boiler feedwater heating branch, and the low-pressure steam replenishment branch, and are connected to the intelligent control unit for data transmission; and The intelligent control unit is connected to the circulating pump, the first flow regulating valve, and the second flow regulating valve respectively. Based on the intercooling circulation parameters, boiler feedwater parameters, low-pressure steam injection parameters, and unit load parameters collected by the parameter monitoring unit, it adjusts the operating frequency of the circulating pump, the opening degree of the first flow regulating valve, and the opening degree of the second flow regulating valve to change the distribution ratio of intercooling waste heat between the boiler feedwater heating branch and the low-pressure steam injection branch.

9. The gas-fired steam intercooled waste heat recovery system according to claim 8, characterized in that, The heat exchange medium side outlet of the intercooler is connected to the hot side inlet of the waste heat exchanger, and the hot side outlet of the waste heat exchanger is connected to the heat exchange medium side inlet of the intercooler via the circulating pump; the cold side of the waste heat exchanger is connected to the boiler feedwater heating branch and the low-pressure steam replenishment branch for heat exchange.

10. The gas-fired steam intercooled waste heat recovery system according to claim 8, characterized in that, The parameter monitoring unit includes a detection component for collecting parameters such as intercooler circulation temperature, pressure, flow rate, waste heat exchanger differential pressure, boiler feedwater temperature, and low-pressure steam injection. The system also includes a safety protection actuator. The intelligent control unit includes a data acquisition module, a heat distribution calculation module, and an execution control module. The execution control module is connected to the circulating pump, the first flow regulating valve, the second flow regulating valve, and the safety protection actuator.

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