A multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit

Abstract

The present invention discloses a multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit, comprising an ORC high-pressure evaporator, a high-pressure working fluid circulation device, an ORC low-pressure evaporator, and a low-pressure working fluid circulation device. The hot sides of the ORC high-pressure evaporator and the ORC low-pressure evaporator are connected in series, the hot side inlet of the ORC high-pressure evaporator is connected to the waste heat outlet of the gas turbine TCA / FGH system, and the hot side outlet of the ORC low-pressure evaporator is connected to the atmosphere. The working fluid of the high-pressure working fluid circulation device exchanges heat with the ORC high-pressure evaporator to increase its temperature and then performs work. The low-pressure working fluid circulation device exchanges heat with the ORC low-pressure evaporator to increase its temperature and then merges with the working fluid of the high-pressure working fluid circulation device to perform work. This multi-stage ORC system can reasonably recover low-temperature waste heat from the gas turbine TCA / FGH system and the unit's flue gas, increasing the power generation power and efficiency of the combined cycle unit. This system not only conforms to the principle of cascaded energy utilization but also improves the unit's peak-shaving performance, thus having far-reaching energy-saving and environmental protection significance and broad market promotion value.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery and utilization of energy systems, and in particular to a multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit. Background Art

[0002] Industrial energy consumption accounts for a significant portion of my country's total energy consumption. 17-67% of this energy is ultimately converted into industrial waste heat. However, the current recovery rate for industrial waste heat in my country is only approximately 35%. This indicates that improving the utilization and efficiency of industrial waste heat plays a crucial role in my country's energy utilization and sustainable economic development. Generally, based on the temperature of the heat source carrier, heat sources below 200°C are considered low-temperature waste heat, those between 200°C and 500°C are considered medium-temperature waste heat, and those above 500°C are considered high-temperature waste heat. Currently, high- and medium-temperature waste heat utilization technologies are mature and have achieved certain market applications. However, due to the low heat flux density of low-temperature heat sources, their recovery efficiency is relatively low, hindered by technical and economic factors. In accordance with the guiding principle of "energy cascade utilization," the development of corresponding high-efficiency low-temperature heat source utilization technologies is urgently needed. Compared to other high-efficiency low-temperature heat source utilization technologies, such as the Stirling Cycle and Kalina Cycle, the Organic Rankine Cycle (ORC) offers advantages such as a relatively simple structure, high safety and stability, and low operating costs. The ORC system consists of a thermodynamic cycle through four processes: adiabatic compression, isentropic expansion, isobaric heating and work release. A low-boiling-point organic working fluid is used as the system circulating working fluid. When the heat source temperature is low, organic working fluid vapor can be generated to drive the expander to do work, thereby driving the generator to output electrical energy.

[0003] Currently, the exhaust gas temperature of advanced H- and F-class gas turbine combined cycle units is generally around 90°C. Since the sulfur content in natural gas fuel is generally negligible, there is no need to consider issues such as acid corrosion in the unit's waste heat boiler (HRSG). The flue gas from the HRSG theoretically contains a large amount of low-temperature waste heat that can be recovered and utilized. Furthermore, some advanced H- and F-class gas turbines are equipped with a TCA / FGH system (i.e., a turbine rotor cooling air / fuel performance heater heat exchange system), such as Mitsubishi's M701F gas turbine. Under the unit's designed operating conditions, this system generates low-temperature waste heat of approximately 180°C, which not only wastes energy but also creates thermal pollution for the environment. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit, which can effectively improve the operating economy of the gas turbine combined cycle unit.

[0005] The present invention is achieved through the following technical solutions:

[0006] A multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit, comprising an ORC high-pressure evaporator, a high-pressure working fluid circulation device, an ORC low-pressure evaporator, and a low-pressure working fluid circulation device;

[0007] The hot sides of the ORC high-pressure evaporator and the ORC low-pressure evaporator are connected in series, the hot side inlet of the ORC high-pressure evaporator is connected to the waste heat outlet of the gas turbine TCA / FGH system, and the hot side outlet of the ORC low-pressure evaporator is connected to the atmosphere;

[0008] The low-pressure working medium circulation device is connected in parallel with the high-pressure working medium circulation device, the cold side of the ORC high-pressure evaporator is connected in series to the circulation pipeline of the high-pressure working medium circulation device, and the cold side of the ORC low-pressure evaporator is connected in series to the circulation pipeline of the low-pressure working medium circulation device;

[0009] The working fluid of the high-pressure working fluid circulation device exchanges heat with the ORC high-pressure evaporator to increase its temperature and then performs work. The low-pressure working fluid circulation device exchanges heat with the ORC low-pressure evaporator to increase its temperature and then merges with the working fluid of the high-pressure working fluid circulation device to perform work. The working fluid after performing work is divided into two paths under a pressurized state and enters the cold side of the ORC high-pressure evaporator and the ORC low-pressure evaporator respectively.

[0010] Preferably, the hot side outlet of the ORC low-pressure evaporator is connected to the cold side of the flue gas waste heat exchanger, and is heated by heat exchange with the flue gas of the combined cycle unit. The cold side outlet of the flue gas waste heat exchanger is connected to the hot side inlet of the ORC preheater, and the hot side outlet of the ORC preheater is connected to the atmosphere.

[0011] The cold side of the ORC preheater is connected in series to the low-pressure working medium circulation device, and the cold side outlet of the ORC preheater is connected to the cold side inlet of the ORC low-pressure evaporator and the cold side inlet of the ORC high-pressure evaporator respectively.

[0012] Preferably, the high-pressure working fluid circulation device includes a high-pressure working fluid pump, an ORC high-pressure auxiliary heater and an ORC high-pressure expander;

[0013] The high-pressure working fluid pump is located at the cold side inlet of the ORC high-pressure evaporator, the cold side outlet of the ORC high-pressure evaporator is connected to the ORC high-pressure auxiliary heater, the outlet of the ORC high-pressure auxiliary heater is connected to the ORC high-pressure expander, and the exhaust port of the ORC high-pressure expander is connected to the cold side outlet of the ORC low-pressure evaporator.

[0014] Preferably, the ORC liquid storage tank, ORC low-pressure working fluid pump, ORC low-pressure auxiliary heater and ORC low-pressure expander;

[0015] The outlet of the ORC liquid storage tank is connected to the cold side of the ORC preheater through an ORC low-pressure working fluid pump, the cold side outlet of the ORC low-pressure evaporator is connected to the ORC low-pressure expander through an ORC low-pressure auxiliary heater, and the outlet of the ORC low-pressure expander is connected to the inlet of the ORC liquid storage tank.

[0016] Preferably, the exhaust port of the ORC low-pressure expander is connected to the inlet of the ORC liquid storage tank through the hot side of the ORC condenser, and the cold side of the ORC condenser is connected to cooling water.

[0017] Preferably, the waste heat outlet of the gas turbine TCA / FGH system is provided with a waste heat utilization control valve group for controlling the working state of the waste heat pipeline and the multi-stage ORC system.

[0018] Preferably, the waste heat utilization control valve group includes a first valve and a second valve;

[0019] The first valve is arranged on the waste heat pipeline of the TCA / FGH system of the combustion engine, and the second valve is arranged on the hot side inlet pipeline of the ORC high-pressure evaporator.

[0020] Preferably, the gas turbine TCA / FGH system comprises a heat exchanger housing, and a TCA heat exchanger and a FGH heat exchanger disposed therein;

[0021] An air inlet is provided at the bottom of the heat exchanger housing and is connected to the induced draft fan. The air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler through a waste heat pipeline. The hot side air inlet end of the TCA heat exchanger is connected to the gas turbine compressor exhaust. The hot side air outlet end of the TCA heat exchanger is connected to the gas turbine compressor. The cold side air outlet end of the FGH heat exchanger is connected to the combustion chamber of the gas turbine.

[0022] Preferably, the working fluid is at least one of alkanes, hydrofluorocarbons, hydrocarbons and chlorofluorocarbons.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention provides a multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit. When the multi-stage ORC system is not operating, the low-temperature waste heat from the gas turbine TCA / FGH system and the unit's flue gas are discharged normally through the chimney. When the unit's waste heat is utilized by the multi-stage ORC system, a portion of the low-temperature waste heat from the gas turbine TCA / FGH system and the unit's flue gas are recovered through a heat exchange system to heat the multi-stage ORC system's organic working fluid to generate steam, which drives the multi-stage ORC expander to generate power. The remaining portion of the waste heat is discharged normally through the chimney together with the unit's flue gas. When the multi-stage ORC system is in operation, it can reasonably recover the low-temperature waste heat from the gas turbine TCA / FGH system and the unit's flue gas, increase the power generation power and power generation efficiency of the combined cycle unit, and improve the unit's peak-shaving performance. The present invention utilizes a multi-stage ORC system to reasonably recover waste heat from the gas turbine combined cycle unit, thereby improving the unit's power generation efficiency, conforming to the principle of "energy cascade utilization," and also improving the unit's operating economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of a multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to the present invention.

[0026] In the figure: 1 is the gas turbine; 2 is the waste heat boiler; 3 is the gas turbine; 4 is the condenser; 5 is the cooling tower; 6 is the feed water pump; 7 is the chimney; 8 is the gas turbine TCA / FGH system; 8A is the induced draft fan; 8B is the TCA heat exchanger; 8C is the FGH heat exchanger; 9 is the waste heat utilization control valve group; 10 is the ORC high-pressure evaporator; 11 is the ORC low-pressure evaporator; 12 is the flue gas waste heat heat exchanger; 13 is the ORC preheater; 14 is the ORC liquid storage tank; 15 is the ORC low-pressure working fluid pump; 16 is the ORC high-pressure working fluid pump; 17 is the ORC high-pressure auxiliary heater; 18 is the ORC high-pressure expander; 19 is the ORC low-pressure auxiliary heater; 20 is the ORC low-pressure expander; 21 is the ORC condenser; and 22 is the circulating water control valve group. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings, which are intended to explain rather than limit the present invention.

[0028] See Figure 1 A multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit includes a combined cycle unit, a gas turbine TCA / FGH system 8, and a multi-stage ORC waste heat utilization system; the gas turbine TCA / FGH system 8 is connected to the combined cycle unit, and the multi-stage ORC waste heat utilization system is connected to the waste heat pipeline of the gas turbine TCA / FGH system.

[0029] The combined cycle unit includes a gas turbine 1, a waste heat boiler 2, a steam turbine 3, a condenser 4, a cooling tower 5, and a feedwater pump 6. The gas turbine 1 and steam turbine 3 are coaxially connected, the output end of the steam turbine 3 is connected to the generator G, the waste heat boiler 2 is connected to the air intake end of the steam turbine 3 via a steam pipeline, the exhaust end of the steam turbine 3 is connected via the hot side inlet of the condenser 4, the hot side outlet of the condenser 4 is connected to the feedwater pipeline of the waste heat boiler 2 via the feedwater pump 6, and the cold side of the condenser is connected to the cooling tower 5.

[0030] The gas turbine TCA / FGH system 8 includes a heat exchanger housing, and a TCA heat exchanger 8B and an FGH heat exchanger 8C arranged therein. An air inlet is provided at the bottom of the heat exchanger housing and is connected to the induced draft fan 8A. The air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler 2 through a waste heat pipeline. The TCA heat exchanger 8B is provided with a compressed air inlet and outlet, and the FGH heat exchanger 8C is provided with a fuel inlet and outlet. The hot side air inlet end of the TCA heat exchanger 8B is connected to the exhaust of the gas turbine compressor, the hot side air outlet end of the TCA heat exchanger 8B is connected to the compressor of the gas turbine 2, and the cold side air outlet end of the FGH heat exchanger 8C is connected to the combustion chamber of the gas turbine 2.

[0031] In the gas turbine TCA / FGH system 8, the induced draft fan 8A draws in low-temperature air, which then exchanges heat with the compressor exhaust air on the hot side of the TCA heat exchanger 8B to form high-temperature air. The high-temperature air then exchanges heat with the low-temperature fuel in the FGH heat exchanger 8C and is discharged into the atmosphere.

[0032] The multi-stage ORC waste heat utilization system includes a low-pressure waste heat utilization device and a high-pressure waste heat utilization device connected in parallel; the working fluid of the high-pressure waste heat utilization device is heated by heat exchange with the waste heat of the gas turbine TCA / FGH system and then performs work. The waste heat is cooled by heat exchange in the high-pressure waste heat utilization device and then used to heat the working fluid of the low-pressure waste heat utilization device. The cooled waste heat is then heated by heat exchange with the flue gas waste heat of the combined cycle unit and then heated to heat the working fluid of the low-pressure waste heat utilization device and then discharged. After performing work, the working fluid of the high-pressure waste heat utilization device is merged with the working fluid of the low-pressure waste heat utilization device and then performs work.

[0033] The high-pressure waste heat utilization device includes an ORC high-pressure evaporator 10 , an ORC high-pressure working fluid pump 16 , an ORC high-pressure auxiliary heater 17 and an ORC high-pressure expander 18 .

[0034] The low-pressure waste heat utilization device includes an ORC low-pressure evaporator 11, a flue gas waste heat exchanger 12, an ORC preheater 13, an ORC liquid storage tank 14, an ORC low-pressure working fluid pump 15, an ORC low-pressure auxiliary heater 19, an ORC low-pressure expander 20 and an ORC condenser 21.

[0035] The outlet of the ORC liquid storage tank 14 is connected to the inlet of the ORC low-pressure working fluid pump 15, the outlet of the ORC low-pressure working fluid pump 15 is connected to the cold side inlet of the ORC preheater 13, and the cold side outlet of the ORC preheater 13 is connected to the ORC high-pressure working fluid pump 16 and the cold side inlet of the ORC low-pressure evaporator 11 respectively, dividing the working fluid into two paths, one path entering the ORC high-pressure working fluid pump and the other path entering the cold side of the ORC low-pressure evaporator 11.

[0036] The outlet of the ORC high-pressure working medium pump is connected to the cold side of the ORC high-pressure evaporator 10, and the cold side outlet of the ORC high-pressure evaporator 10 is connected to the ORC high-pressure expander 18 through the ORC high-pressure auxiliary heater 17.

[0037] The hot side inlet of the ORC high-pressure evaporator 10 is connected to the waste heat outlet of the gas turbine TCA / FGH system, the hot side outlet of the ORC high-pressure evaporator 10 is connected to the hot side inlet of the ORC low-pressure evaporator 11, the hot side outlet of the ORC low-pressure evaporator 11 is connected to the cold side of the flue gas waste heat exchanger 12, the cold side outlet of the flue gas waste heat exchanger 12 is connected to the hot side of the ORC preheater 13, and the hot side outlet of the ORC preheater is connected to the chimney.

[0038] The cold side outlet of the ORC low-pressure evaporator 11 is connected to the exhaust port of the ORC high-pressure expander 18 and then to the ORC low-pressure auxiliary heat exchanger 19. The ORC low-pressure auxiliary heat exchanger 19 is connected to the inlet of the ORC low-pressure expander 20. The outlet of the ORC low-pressure expander 20 is connected to the hot side of the ORC condenser 21. The cold side of the ORC condenser 21 is connected to the cooling tower. The hot side outlet of the ORC condenser 21 is connected to the inlet of the ORC liquid storage tank.

[0039] The waste heat outlet of the gas turbine TCA / FGH system is provided with a waste heat utilization control valve group 9, which includes a first valve and a second valve. The first valve is provided on the waste heat pipeline of the gas turbine TCA / FGH system, and the waste heat pipeline is connected to the chimney 7. The second valve is provided on the hot side inlet pipeline of the ORC high-pressure evaporator 10.

[0040] The cold-side circulation piping of the ORC condenser 21 is equipped with a circulating water control valve assembly 22, which includes a third valve and a fourth valve. The third valve is located at the cooling tower outlet, and the fourth valve is located at the cooling tower inlet. The operating state of the multi-stage ORC waste heat utilization system is controlled by the waste heat utilization control valve assembly 9 and the circulating water control valve assembly 22. The cold-end circulating water of the multi-stage ORC waste heat utilization system is used in parallel with the cold-end circulating water of the combined cycle unit and can be coordinated and controlled by the circulating water control valve assembly, which not only saves equipment investment but also reduces system footprint.

[0041] The ORC high-pressure evaporator, ORC low-pressure evaporator, ORC preheater, and other equipment in a multi-stage ORC waste heat utilization system must be designed based on detailed heat exchange calculations. Similarly, the flue gas waste heat exchanger in a multi-stage ORC system for waste heat utilization in a gas turbine combined cycle unit must also be designed based on detailed heat exchange calculations.

[0042] The organic working fluids of the multi-stage ORC waste heat utilization system are not limited to pure working fluids such as alkanes, hydrofluorocarbons, hydrocarbons, and chlorofluorocarbons. Non-azeotropic mixed working fluids can also be selected. The temperature glide phenomenon during the evaporation and condensation process is used to improve the matching degree of the cold and heat source temperatures and reduce the irreversible losses of the system.

[0043] The working principle of the multi-stage ORC waste heat utilization system is described in detail below.

[0044] When the multi-stage ORC waste heat utilization system is not needed, the multi-stage ORC waste heat utilization system is shut down by regulating the waste heat utilization control valve group 9 and the circulating water control valve group 22, and the low-temperature waste heat of the gas turbine TCA / FGH system 8 and the unit flue gas are discharged normally through the chimney.

[0045] When the multi-stage ORC waste heat utilization system is required to work, the multi-stage ORC waste heat utilization system is started by regulating the waste heat utilization control valve group 9 and the circulating water control valve group 22.

[0046] The organic working fluid in the ORC liquid storage tank 14 is pressurized by the ORC low-pressure working fluid pump 15 and enters the ORC preheater 13 for preheating, and then is divided into two streams and flows into the high-pressure waste heat utilization device and the high-pressure waste heat utilization device respectively to continue the two-stage circulation.

[0047] The organic working fluid in the high-pressure waste heat utilization device is pressurized by the ORC high-pressure working fluid pump 16 and enters the cold side of the ORC high-pressure evaporator 10, where it exchanges heat with the low-temperature waste heat of the primary recovery gas turbine TCA / FGH system 8, heating the organic working fluid to make it boil. The heated high-temperature and high-pressure working fluid is then further heated by the ORC high-pressure auxiliary heater 17 to generate high-pressure organic working fluid superheated steam, which enters the ORC high-pressure expander 18 to perform work. The organic working fluid steam after performing work is then merged into the low-pressure cycle.

[0048] The low-pressure circulating organic fluid passes through the cold side of the ORC low-pressure evaporator 11, where it exchanges heat with the secondary recovery of low-temperature waste heat from the TCA / FGH system 8 of the gas turbine. This heats the organic fluid and brings it to a boil. The high-temperature, low-pressure fluid then merges with the high-pressure fluid after work. It is then further heated by the ORC low-pressure auxiliary heater 19, generating low-pressure superheated organic steam that enters the ORC low-pressure expander 20 to perform work. This steam is cooled and condensed in the ORC condenser 21 and returned to the ORC liquid storage tank 14, completing the cycle. After two rounds of recovery of low-temperature waste heat from the TCA / FGH system 8, the waste heat is exchanged with the unit's flue gas in the flue gas waste heat exchanger 12 before entering the ORC preheater 13 to preheat the organic fluid in the multi-stage ORC system.

[0049] The multi-stage ORC system for waste heat utilization in a gas turbine combined cycle unit consists of a waste heat utilization control valve assembly, an ORC high-pressure evaporator, an ORC low-pressure evaporator, a flue gas waste heat exchanger, an ORC high-pressure auxiliary heater, an ORC high-pressure expander, an ORC low-pressure auxiliary heater, an ORC low-pressure expander, an ORC condenser, an ORC liquid storage tank, an ORC low-pressure working fluid pump, an ORC preheater, and an ORC high-pressure working fluid pump. This system, deployed near the gas turbine combined cycle unit, utilizes the principles of heat exchange to rationally recover low-temperature waste heat from the gas turbine combined cycle unit. This system heats the organic working fluid in the multi-stage ORC system to generate steam, which drives the multi-stage ORC expander to produce work and drives the generator to output additional electricity, effectively improving the unit's operating economy.

[0050] The multi-stage ORC waste heat recovery system is connected in parallel with the low-temperature waste heat pipelines of the gas turbine TCA / FGH system and is controlled by the waste heat recovery control valve group and the circulating water control valve group. When the unit waste heat recovery multi-stage ORC system is not operating, the low-temperature waste heat from the gas turbine TCA / FGH system and the unit flue gas are discharged normally through the chimney. When the unit waste heat recovery multi-stage ORC system is operating, a portion of the low-temperature waste heat from the gas turbine TCA / FGH system and the unit flue gas is recovered through the heat exchange system to heat the organic working fluid in the multi-stage ORC system to generate steam, which drives the multi-stage ORC expander to generate power. The remaining waste heat is discharged normally through the chimney along with the unit flue gas. When the multi-stage ORC waste heat recovery system is in operation, it can effectively recover the low-temperature waste heat from the gas turbine TCA / FGH system and the unit flue gas, increasing the power generation capacity and efficiency of the combined cycle unit and improving the unit's peak-shaving performance. The present invention utilizes a multi-stage ORC system to rationally recover waste heat from a gas turbine combined cycle unit, thereby improving the unit's power generation efficiency. This not only complies with the principle of "cascaded energy utilization," but also improves the unit's operating economy, thus having far-reaching energy-saving and environmental protection significance and broad market promotion value.

[0051] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit, characterized in that: It includes an ORC high-pressure evaporator (10), a high-pressure working medium circulation device, an ORC low-pressure evaporator (11) and a low-pressure working medium circulation device; The hot sides of the ORC high-pressure evaporator (10) and the ORC low-pressure evaporator (11) are connected in series, the hot side inlet of the ORC high-pressure evaporator (10) is connected to the waste heat outlet of the gas turbine TCA / FGH system (8), and the hot side outlet of the ORC low-pressure evaporator (11) is connected to the atmosphere; The low-pressure working medium circulation device is connected in parallel with the high-pressure working medium circulation device, the cold side of the ORC high-pressure evaporator (10) is connected in series to the circulation pipeline of the high-pressure working medium circulation device, and the cold side of the ORC low-pressure evaporator (11) is connected in series to the circulation pipeline of the low-pressure working medium circulation device; The working fluid of the high-pressure working fluid circulation device exchanges heat with the ORC high-pressure evaporator (10) and heats up before performing work. The low-pressure working fluid circulation device exchanges heat with the ORC low-pressure evaporator (11) and heats up before merging with the working fluid of the high-pressure working fluid circulation device and performing work. The working fluid after performing work is divided into two paths under a pressurized state and enters the cold side of the ORC high-pressure evaporator (10) and the ORC low-pressure evaporator (11), respectively. The hot side outlet of the ORC low-pressure evaporator (11) is connected to the cold side of the flue gas waste heat exchanger (12) and is heated by heat exchange with the flue gas of the combined cycle unit. The cold side outlet of the flue gas waste heat exchanger (12) is connected to the hot side inlet of the ORC preheater (13), and the hot side outlet of the ORC preheater (13) is connected to the atmosphere. The cold side of the ORC preheater (13) is connected in series to the low-pressure working medium circulation device, and the cold side outlet of the ORC preheater (13) is connected to the cold side inlet of the ORC low-pressure evaporator (11) and the cold side inlet of the ORC high-pressure evaporator (10), respectively.

2. A multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: The high-pressure working fluid circulation device includes a high-pressure working fluid pump (16), an ORC high-pressure auxiliary heater (17) and an ORC high-pressure expander (18); The high-pressure working fluid pump (16) is located at the cold side inlet of the ORC high-pressure evaporator (10), the cold side outlet of the ORC high-pressure evaporator (10) is connected to the ORC high-pressure auxiliary heater (17), the outlet of the ORC high-pressure auxiliary heater (17) is connected to the ORC high-pressure expander (18), and the exhaust port of the ORC high-pressure expander (18) is connected to the cold side outlet of the ORC low-pressure evaporator (11).

3. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: It also includes an ORC liquid storage tank (14), an ORC low-pressure working fluid pump (15), an ORC low-pressure auxiliary heater (19) and an ORC low-pressure expander (20); The outlet of the ORC liquid storage tank (14) is connected to the cold side of the ORC preheater (13) via an ORC low-pressure working fluid pump (15), the cold side outlet of the ORC low-pressure evaporator (11) is connected to the ORC low-pressure expander (20) via an ORC low-pressure auxiliary heater (19), and the outlet of the ORC low-pressure expander (20) is connected to the inlet of the ORC liquid storage tank (14).

4. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 3, characterized in that: The exhaust port of the ORC low-pressure expander (20) is connected to the inlet of the ORC liquid storage tank (14) through the hot side of the ORC condenser (21), and the cold side of the ORC condenser (21) is connected to cooling water.

5. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: The waste heat outlet of the gas turbine TCA / FGH system (8) is provided with a waste heat utilization control valve group for controlling the working state of the waste heat pipeline and the multi-stage ORC system.

6. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: The waste heat utilization control valve group (9) comprises a first valve and a second valve; The first valve is arranged on the waste heat pipeline of the TCA / FGH system (8) of the combustion engine, and the second valve is arranged on the hot side inlet pipeline of the ORC high-pressure evaporator (10).

7. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: The gas engine TCA / FGH system (8) includes a heat exchanger housing, and a TCA heat exchanger (8B) and an FGH heat exchanger (8C) arranged inside the housing; The bottom of the heat exchanger housing is provided with an air inlet and is connected to the induced draft fan (8A); the air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler (2) through a waste heat pipeline; the hot side air inlet of the TCA heat exchanger (8B) is connected to the exhaust of the gas turbine compressor; the hot side air outlet of the TCA heat exchanger (8B) is connected to the compressor of the gas turbine (1); and the cold side air outlet of the FGH heat exchanger (8C) is connected to the combustion chamber of the gas turbine (1).

8. The multi-stage ORC system for recovering waste heat from a gas turbine combined cycle unit according to claim 1, characterized in that: The working fluid is at least one of alkanes, hydrofluorocarbons and chlorofluorocarbons.

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