Combined cycle unit air inlet heating system of clean energy coupling multi-stage compression heat pump and operation method of combined cycle unit air inlet heating system

Abstract

According to the combined cycle unit air inlet heating system and method for coupling clean energy with the multi-stage compression heat pump, geothermal energy, flue gas waste heat and solar energy are sequentially extracted through the three-stage compression heat pump, various clean energy is efficiently coupled, and the utilization rate of the clean energy is increased; the influence of solar energy intermittency and instability on the system is overcome, and the solar energy utilization rate is improved; the circulating heat efficiency of the system is improved, and natural gas consumption and pollutant emission are reduced; the COP of the heat pump is improved, the power consumption of the compressor is reduced, and the energy conversion efficiency is improved; a natural gas performance heater and an original high-grade steam heat source are replaced with the multiple clean energy coupled three-stage compression heat pump, the heat consumption rate of the unit is reduced, the operation cost and the emission amount of pollutants such as CO2 are reduced, the double-carbon and clean energy supply policy is responded, and the economic and environment-friendly double benefits are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of clean energy, and particularly relates to an intake air heating system and method for a combined cycle unit of a clean energy coupled multi-stage compression heat pump. Background Art

[0002] At present, gas-steam combined cycle units are widely used as the main technology in the field of clean energy supply. Gas turbines have high requirements for the superheat degree of natural gas intake, and it needs to be heated by a pre-module and then sent into the combustion chamber. Currently, the heating heat source of natural gas performance heaters mainly comes from the waste heat boiler or the extraction steam in the middle of the steam turbine. Due to the high requirements for the intake temperature of natural gas, generally 200 - 300 °C, the required steam quality is relatively high, resulting in energy waste. For combined cycle units in northern regions, in cold weather with low outdoor ambient temperatures, the compressor inlet filter may cause frosting and blockage, and at the same time, too low intake temperature will lead to hydrogen embrittlement fracture, seriously affecting the performance and operation safety of the unit.

[0003] The driving heat source of the steam turbine in the combined cycle unit comes from the waste heat of the gas turbine exhaust recovered by the waste heat boiler. The outlet temperature of the waste heat boiler is generally between 80 - 100 °C, and there is still a large amount of low-grade waste heat that can be recycled. How to apply this part of low-grade heat energy to the system cycle is the main problem currently faced. As important components of clean and renewable energy, if solar energy and geothermal energy can be utilized in the combined cycle process, it can greatly improve the cleanliness of the system, reduce the carbon emissions of the system, and at the same time can reduce the system energy supply cost, improve the overall energy utilization rate, and achieve double economic and environmental benefits. Summary of the Invention

[0004] Aiming at the above existing problems, the invention intends to establish an intake air heating system and method for a combined cycle unit of a clean energy coupled multi-stage compression heat pump, aiming to solve the problems of energy waste in natural gas performance heaters and too low compressor inlet temperature affecting the operation safety of the unit.

[0005] To solve the above technical problems, the invention provides an intake air heating system for a combined cycle unit of a clean energy coupled multi-stage compression heat pump, which is characterized by including: a three-stage compression heat pump unit, a solar heating unit, a flue gas waste heat recovery unit, an intake air heating unit, a geothermal energy extraction and closed-circuit water pipeline unit, wherein:

[0006] The three-stage compression heat pump unit extracts geothermal energy, flue gas waste heat, and solar energy in sequence to heat natural gas instead of the original heat source of the natural gas performance heater.

[0007] The flue gas waste heat recovery unit recovers the waste heat of the flue gas at the tail of the waste heat boiler as the medium-temperature heat source of the heat pump. At the same time, the flue gas waste heat recovery unit leads out a path to connect to the intake air heating unit, which is used to heat the intake air of the compressor in extreme weather to avoid the safety problems of frost blockage of the compressor inlet filter and hydrogen embrittlement cracking of the compressor blades;

[0008] The solar heating unit uses a solar collector to generate heat as the high-temperature heat source of the heat pump;

[0009] The geothermal energy extraction and closed-circuit circulating water pipeline unit extracts geothermal energy in a geothermal well using closed-circuit circulating water as the primary low-temperature heat source of the heat pump.

[0010] Further, the three-stage compression heat pump unit includes a condenser, a first expansion valve, a first intermediate heat exchanger, a first supplementary heat exchanger, a high-pressure stage compressor, a second expansion valve, a second intermediate heat exchanger, a second supplementary heat exchanger, a medium-pressure stage compressor, a third expansion valve, an evaporator, and a low-pressure stage compressor. Two supplementary heat loops and an evaporation loop are arranged at the inlet and outlet of the solution side of the condenser; the supplementary heat loops are divided into two paths. One path is sequentially connected to the solution inlet on the second side of the first intermediate heat exchanger, the first supplementary heat exchanger, and the high-pressure stage compressor. The other path is sequentially connected to the solution inlet on the second side of the second intermediate heat exchanger, the second supplementary heat exchanger, and the medium-pressure stage compressor; the evaporation loop is sequentially connected to the evaporator and the low-pressure stage compressor.

[0011] Further, the gas side inlet of the condenser is connected to the natural gas inlet pipeline, and the natural gas supply pipeline is led out from the gas side outlet of the condenser; the solution side outlet of the condenser is divided into two paths. One path is connected to the solution inlet on the first side of the first intermediate heat exchanger, and the other path is further divided into two paths and respectively connected to the solution inlets on the second sides of the first intermediate heat exchanger and the second intermediate heat exchanger. The solution outlet on the first side of the first intermediate heat exchanger is connected to the solution inlet on the first side of the second intermediate heat exchanger. The solution outlet on the first side of the second intermediate heat exchanger is connected to the solution inlet of the evaporator. The solution outlet on the second side of the first intermediate heat exchanger is connected to the solution inlet of the first supplementary heat exchanger. The solution outlet on the second side of the second intermediate heat exchanger is connected to the solution inlet of the second supplementary heat exchanger. The solution vapor side outlet of the evaporator is connected to the solution vapor side inlet of the low-pressure stage compressor. The vapor side outlet of the low-pressure stage compressor is merged with the vapor side outlet pipeline of the second supplementary heat exchanger and then connected to the vapor side inlet of the medium-pressure stage compressor. The vapor side outlet of the medium-pressure stage compressor is merged with the vapor side outlet pipeline of the first supplementary heat exchanger and then connected to the vapor side inlet of the high-pressure stage compressor. The vapor side outlet of the high-pressure stage compressor is connected to the gas side inlet of the condenser.

[0012] Further, the solar heating unit includes a trough solar collector, a high-temperature molten salt heat storage tank, a high-temperature molten salt pump, a molten salt heat exchanger, a low-temperature molten salt heat storage tank, a low-temperature molten salt pump, a high-temperature heat source pump, a first electric globe valve, and a second electric globe valve. The outlet of the trough solar collector is connected to the inlet of the high-temperature molten salt heat storage tank, the outlet of the high-temperature molten salt heat storage tank is connected to the inlet of the high-temperature molten salt pump, the outlet of the high-temperature molten salt pump is connected to the inlet of the molten salt side of the molten salt heat exchanger, the outlet of the molten salt heat exchanger is connected to the inlet of the low-temperature molten salt heat storage tank, the outlet of the low-temperature molten salt heat storage tank 17 is connected to the inlet of the low-temperature molten salt pump, and the outlet of the low-temperature molten salt pump is connected to the inlet of the trough solar collector.

[0013] Further, the flue gas waste heat recovery unit includes a first electric regulating valve, a flue gas spray tower, a chimney, and a spray water circulation pump. The water side outlet of the flue gas spray tower is connected to the water side inlet of the spray water circulation pump, recovering the waste heat of the flue gas at the tail of the waste heat recovery boiler to provide a medium-temperature heat source for the three-stage compression heat pump unit system; the outlet of the spray water circulation pump is divided into two paths, one path is connected to the water side inlet of the second supplementary heat exchanger, and the other path is connected to the water side inlet of the air heater. The water side outlet pipeline of the second supplementary heat exchanger and the water side outlet pipeline of the air heater are merged and then connected to the inlet of the flue gas spray tower; the flue gas pipeline is sequentially connected to the inlet and outlet of the flue gas side of the flue gas spray tower and the inlet of the chimney flue gas side.

[0014] Further, the intake air heating unit includes a third electric globe valve, a fourth electric globe valve, a second electric regulating valve, and an air heater. The air intake pipeline is connected to the air side inlet of the air heater, and the air supply pipeline is connected to the air side outlet of the air heater; the outlet of the spray water circulation pump is connected to the water side inlet of the air heater through the fourth electric globe valve and the second electric regulating valve, and the water side outlet of the air heater is connected to the water side inlet of the flue gas spray tower through the third electric globe valve.

[0015] Furthermore, the geothermal energy extraction and closed-loop circulating water pipeline unit includes a fifth motorized globe valve, a buried pipe, a sixth motorized globe valve, a geothermal circulation pump, a seventh motorized globe valve, an eighth motorized globe valve, a high-temperature heat source pump, a molten salt heat exchanger, a first motorized globe valve, and a second motorized globe valve. The outlet of the high-temperature heat source pump is connected to the water-side inlet of the molten salt heat exchanger. At the water-side outlet of the molten salt heat exchanger, it is divided into two paths. One path is connected to the inlet of the first supplementary heat exchanger through the second motorized globe valve, and the other path is divided into two branches after passing through the fifth motorized globe valve. One branch is connected to the water-side outlet of the evaporator through the seventh motorized globe valve, and the other path is connected to the inlet of the buried pipe. The closed-loop circulating water pipeline at the outlet of the buried pipe is divided into two paths. One path is connected to the inlet of the geothermal circulation pump through the sixth motorized globe valve, and the other path is merged with the pipeline of the outlet of the first supplementary heat exchanger through the eighth motorized globe valve and the first motorized globe valve and then connected to the inlet of the high-temperature heat source pump. The closed-loop circulating water pipeline at the outlet of the geothermal circulation pump is connected to the water-side inlet of the evaporator. The outlet of the buried pipe is connected to the water-side inlet of the molten salt heat exchanger, and a high-temperature molten salt pump is provided between the outlet of the buried pipe and the water-side of the molten salt heat exchanger.

[0016] This system has established a three-stage compression heat pump, which extracts geothermal energy, flue gas waste heat, and solar energy in sequence to replace the original heat source of the natural gas performance heater to heat natural gas. The closed-circuit water is used to extract geothermal energy in the geothermal well as the primary low-temperature heat source of the heat pump. The spray tower is used to spray the flue gas at the tail of the waste heat boiler to recover the flue gas waste heat as the medium-temperature heat source of the heat pump. The solar collector is used to generate heat as the high-temperature heat source of the heat pump. The heat pump adopts a staged compression method to extract heat energy from each level of heat source in a cascaded manner, realizing efficient energy utilization methods such as temperature matching and cascaded heating, so that the final heat release temperature meets the requirement of the natural gas inlet superheat. At the same time, a path is led out from the spray water of the waste heat boiler to heat the compressor inlet in extreme weather, avoiding safety problems such as frost blockage of the compressor inlet filter and hydrogen embrittlement cracking of the compressor blades. The solar heat collection loop uses a high-temperature molten salt medium and is equipped with high- and low-temperature molten salt thermal storage tanks. The molten salt heated by absorbing solar heat is stored in the high-temperature tank and enters the molten salt heat exchanger to release heat when the heat pump needs a high-temperature heat source during the operation of the unit, and then flows into the low-temperature tank. By using this method, the influence of solar intermittency and instability on the system can be overcome. When the light conditions are sufficient, the collected heat is stored in the high-temperature tank and released when needed, optimizing the heat balance between the solar heat collection loop and the heat pump loop. Long-term extraction of geothermal energy will cause the deterioration of the temperature field of the soil layer around the buried pipe, resulting in the performance degradation of the heat pump unit. The combined cycle unit is used as a peak-shaving standby unit and only operates for some periods throughout the year. During the shutdown period of the unit, the solar heat collection is used to recharge the underground soil layer with heat, so that the annual soil temperature field remains balanced or even optimized. When extracting geothermal energy, high energy efficiency can be guaranteed, and the COP of the heat pump can be further improved, saving compressor power consumption. The system and process method of the present invention efficiently couple multiple clean energies, can reduce the fuel cost and energy supply cost of the system, improve the cleanliness degree and energy utilization efficiency of the system, and reduce the emissions of CO2 and various pollutants.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention establishes a combined three-stage compression heat pump of clean energy, extracts heat from geothermal energy, flue gas waste heat, and solar energy in sequence, and efficiently couples multiple clean energies according to the principle of temperature matching and cascaded utilization, improving the utilization rate of clean energy;

[0019] (2) The high- and low-temperature molten salt thermal storage tanks are used in cooperation with the solar collector to form a solar heating unit, balancing the supply and demand relationship between the solar heat collection and the heat demand of the high-temperature heat source of the heat pump, overcoming the influence of solar intermittency and instability on the system, and improving the utilization rate of solar energy;

[0020] (3) A spray tower is set to deeply recover the flue gas at the tail of the waste heat boiler and use it as the medium-temperature heat source of the heat pump, improving the cycle thermal efficiency of the system, reducing the consumption of natural gas and pollutant emissions;

[0021] (4) Utilize the geothermal energy with stable annual temperature as the low-temperature heat source of the heat pump, improve the COP of the heat pump, reduce the power consumption of the compressor, and improve the energy conversion efficiency;

[0022] (5) When the unit is in standby shutdown, return the excess solar heat collection to the underground soil layer to maintain the balance of the annual soil temperature field, increase the working temperature of the low-temperature heat source of the heat pump, and further improve the heat performance coefficient and economy of the heat energy;

[0023] (6) In extreme weather, heat the compressor inlet with the waste heat of the tail gas to avoid the problems of frost blockage of the compressor inlet filter and hydrogen embrittlement cracking of the compressor blades, and ensure the safe and stable operation of the unit;

[0024] (7) Replace the original high-grade steam heat source of the natural gas performance heater with a multi-clean energy coupled three-stage compression heat pump to reduce the heat consumption rate of the unit, improve the cycle heat efficiency, reduce the operating cost and pollutant emissions such as CO2, respond to the "dual carbon" and clean energy supply policies, and achieve double economic and environmental benefits. Description of the Drawings

[0025] Figure 1 is the schematic connection diagram of the composition of the system of the present invention;

[0026] Figure 2 is the schematic connection diagram of the composition of the three-stage compression heat pump unit of the present invention;

[0027] Figure 3 is the schematic connection diagram of the composition of the solar heating unit of the present invention;

[0028] Figure 4 is the schematic connection diagram of the composition of the flue gas waste heat recovery unit of the present invention;

[0029] Figure 5 is the schematic connection diagram of the composition of the intake heating unit of the present invention;

[0030] Figure 6 is the schematic connection diagram of the composition of the geothermal energy extraction and closed-circuit water pipeline of the present invention;

[0031] Among them, 1 condenser; 2 first expansion valve; 3 first intermediate heat exchanger; 4 first heat addition heat exchanger; 5 high-pressure stage compressor; 6 second expansion valve; 7 second intermediate heat exchanger; 8 second heat addition heat exchanger; 9 medium-pressure stage compressor; 10 third expansion valve; 11 evaporator; 12 low-pressure stage compressor; 13 trough solar collector; 14 high-temperature molten salt heat storage tank; 15 high-temperature molten salt pump; 16 molten salt heat exchanger; 17 low-temperature molten salt heat storage tank; 18 low-temperature molten salt pump; 19 high-temperature heat source pump; 20 first electric globe valve; 22 second electric globe valve; 23 flue gas spray tower; 24 chimney; 25 spray water circulation pump; 26 first electric control valve; 27 third electric globe valve; 28 second electric control valve; 29 air heater; 30 fourth electric globe valve; 31 buried pipe; 32 fifth electric globe valve; 33 geothermal circulation pump; 34 sixth electric globe valve; 35 seventh electric globe valve; 36 eighth electric globe valve. Detailed implementation manners

[0032] Referring to the appendix Figures 1 - 6 , the present invention includes a three-stage compression heat pump unit, a solar heating unit, a flue gas waste heat recovery unit, an intake air heating unit, a geothermal energy extraction and closed-circuit water pipeline unit; the composition and connection relationship of each unit are as follows:

[0033] The three-stage compression heat pump system includes a condenser 1, a first expansion valve 2, a first intermediate heat exchanger 3, a first heat addition heat exchanger 4, a high-pressure stage compressor 5, a second expansion valve 6, a second intermediate heat exchanger 7, a second heat addition heat exchanger 8, a medium-pressure stage compressor 9, a third expansion valve 10, an evaporator 11, and a low-pressure stage compressor 12; two heat addition loops and one evaporation loop are arranged at the inlet and outlet of the solution side of the condenser 1; the heat addition loops are divided into two paths, one path is sequentially connected to the second-side solution inlet of the first intermediate heat exchanger 3, the first heat addition heat exchanger 4, and the high-pressure stage compressor 5, and the other path is sequentially connected to the second-side solution inlet of the second intermediate heat exchanger 7, the second heat addition heat exchanger 8, and the medium-pressure stage compressor 9; the evaporation loop is sequentially connected to the evaporator 11 and the low-pressure stage compressor 12; specifically as follows:

[0034] The natural gas inlet pipeline is connected to the gas-side inlet C of the condenser 1, and the natural gas supply pipeline is led out from the gas-side outlet A of the condenser 1; the solution-side outlet B of the condenser 1 is divided into two paths. One path is connected to the first-side solution inlet A of the first intermediate heat exchanger 3, and the other path is further divided into two paths and respectively connected to the second-side solution inlets B of the first intermediate heat exchanger 3 and the second intermediate heat exchanger 7. The first-side solution outlet C of the first intermediate heat exchanger 3 is connected to the first-side solution inlet A of the second intermediate heat exchanger 7. The first-side solution outlet C of the second intermediate heat exchanger 7 is connected to the solution inlet B of the evaporator 11. The second-side solution outlet D of the first intermediate heat exchanger 3 is connected to the solution inlet B of the first heat supply compensating heat exchanger 4. The second-side solution outlet D of the second intermediate heat exchanger 7 is connected to the solution inlet B of the second heat supply compensating heat exchanger 8. The solution-vapor side outlet D of the evaporator 11 is connected to the solution-vapor side inlet C of the low-pressure stage compressor 12. The vapor side outlet A of the low-pressure stage compressor 12 and the vapor side outlet D of the second heat supply compensating heat exchanger 8 are merged through a pipeline and then connected to the vapor side inlet of the medium-pressure stage compressor 9. The vapor side outlet A of the medium-pressure stage compressor 9 and the vapor side outlet D of the first heat supply compensating heat exchanger 4 are merged through a pipeline and then connected to the vapor side inlet C of the high-pressure stage compressor 5. The vapor side outlet A of the high-pressure stage compressor 5 is connected to the gas-side inlet D of the condenser 1.

[0035] The solar heating unit includes a trough solar collector 13, a high-temperature molten salt heat storage tank 14, a high-temperature molten salt pump 15, a molten salt heat exchanger 16, a low-temperature molten salt heat storage tank 17, and a low-temperature molten salt pump 18; the outlet of the trough solar collector 13 is connected to the inlet of the high-temperature molten salt heat storage tank 14, the outlet of the high-temperature molten salt heat storage tank 14 is connected to the inlet of the high-temperature molten salt pump 15, the outlet of the high-temperature molten salt pump 15 is connected to the molten salt side inlet of the molten salt heat exchanger 16, the outlet of the molten salt heat exchanger 16 is connected to the inlet of the low-temperature molten salt heat storage tank 17, the outlet of the low-temperature molten salt heat storage tank 17 is connected to the inlet of the low-temperature molten salt pump 18, and the outlet of the low-temperature molten salt pump 18 is connected to the inlet of the trough solar collector 13. The solar heat collection unit absorbs solar energy to provide a high-temperature heat source for the high-temperature heat pump 19 and provides solar energy for the ground heat exchanger 31 during the shutdown period of the unit.

[0036] The flue gas waste heat recovery unit includes a flue gas spray tower 23, a chimney 24, a spray water circulation pump 25, and a first electric control valve 26; the water-side outlet B of the flue gas spray tower 23 is connected to the water-side inlet D of the spray water circulation pump 25 to recover the waste heat of the tail gas of the heat recovery boiler and provide an intermediate-temperature heat source for the heat pump; the outlet B of the spray water circulation pump 25 is divided into two paths. One path is connected to the water-side inlet A of the second heat supply compensating heat exchanger 8, and the other path is connected to the water-side inlet B of the air heater 29. The water-side outlet C of the second heat supply compensating heat exchanger 8 and the water-side outlet D of the air heater 29 are merged through a pipeline and then connected to the inlet D of the flue gas spray tower 23; the flue gas pipeline is sequentially connected to the flue gas-side inlet and outlet of the flue gas spray tower 23 and the flue gas-side inlet and outlet of the chimney 24.

[0037] The intake air heating unit includes a third electric shut-off valve 27, a second electric regulating valve 28, an air heater 29, and a fourth electric shut-off valve 30. The air intake pipeline is connected to the air side inlet C of the air heater 29, and the air supply pipeline is connected to the air side outlet A of the air heater 29. The outlet B of the spray water circulation pump 25 is connected to the water side inlet B of the air heater 29 through the third electric shut-off valve 27 and the second electric regulating valve 28. The water side outlet D of the air heater 29 is connected to the water side inlet D of the flue gas spray tower 23 through the fourth electric shut-off valve 30, using the waste heat of the exhaust gas to heat the air at the compressor inlet.

[0038] The geothermal energy extraction and closed-circuit water pipeline unit includes a first supplementary heat exchanger, a molten salt heat exchanger 16, a high-temperature heat pump 19, a first electric shut-off valve 20, a second electric shut-off valve 22, a ground heat exchanger pipe 31, a fifth electric shut-off valve 32, a geothermal circulation pump 33, a sixth electric shut-off valve 34, a seventh electric shut-off valve 35, and an eighth electric shut-off valve 36. The closed-circuit water pipeline is connected from the outlet of the high-temperature heat pump 19 to the water side inlet A of the molten salt heat exchanger 16. At the water side outlet B of the molten salt heat exchanger 16, it is divided into two paths. One path is connected to the inlet C of the first supplementary heat exchanger 4 through the second electric shut-off valve 22. The other path is divided into two branches after passing through the fourth electric shut-off valve 30. One branch is connected to the water side outlet C of the evaporator 11 through the sixth electric shut-off valve 34, and the other path is connected to the inlet B of the ground heat exchanger pipe 31. The closed-circuit water pipeline at the outlet A of the ground heat exchanger pipe 31 is divided into two paths. One path is connected to the inlet D of the geothermal circulation pump 33 through the fifth electric shut-off valve 32, and the other path is merged with the pipeline of the first supplementary heat exchanger 4 outlet A through the first electric shut-off valve 20 and then connected to the inlet of the high-temperature heat pump 19. The outlet B of the geothermal circulation pump 33 is connected to the water side inlet A of the evaporator 11 through a closed-circuit pipeline. The water side inlet of the molten salt heat exchanger 16 is connected to the inlet of the ground heat exchanger pipe 31. A high-temperature molten salt pump 19 is provided between the outlet of the ground heat exchanger pipe 31 and the water side of the molten salt heat exchanger 16 to store excess solar energy in the underground soil during the shutdown period of the unit.

[0039] There are two different operating modes for the startup and shutdown of the unit, as follows:

[0040] When the unit is put into operation, the fifth electric stop valve 32 and the sixth electric stop valve 34 are opened. The closed-circuit circulating water in the geothermal energy extraction unit absorbs the heat of the soil layer in the buried pipe 31 and is heated up. Then it enters the evaporator 11 and the low-temperature heat energy is extracted by the working medium of the three-stage compression heat pump unit. The geothermal circulation pump 33 provides the circulating power. The flue gas at the tail of the waste heat boiler enters the spray tower 23 and is cooled by spraying by about 30 °C. The cooled flue gas is discharged to the atmosphere through the chimney 24. The spray water falling to the bottom of the tower is heated up and then sent to the second supplementary heat exchanger 8 through the spray water circulating pump 25 to boost the pressure, where it is used as a medium-temperature heat source to extract heat. The cooled spray water returns to the flue gas spray tower 23 to continue spraying and cooling the flue gas. When the ambient temperature is too low, the third electric stop valve 27 and the fourth electric stop valve 30 are opened. A branch of the heated spray water enters the air heater 29 to heat the air at the compressor inlet. The opening of the second electric control valve 28 is adjusted according to the required inlet temperature to control the flow rate of the spray water entering the air heater 29, thereby adjusting the outlet air temperature of the air heater 29. The first electric control valve 26 is used to cooperate with the adjustment of the spray water flow rate entering the second supplementary heat exchanger 8 when the intake air heating unit is opened; when the ambient temperature does not require heating of the air, the first electric control valve 26 and the third electric stop valve 27 are closed. In the solar heat collection loop, molten salt is used as an intermediate medium. The molten salt absorbs solar energy in the trough solar collector 13 and is heated to 150 - 200 °C, and then enters the high-temperature molten salt storage tank 14. When the heat pump of the unit is started during operation, the high-temperature molten salt pump 15 pumps out the molten salt in the high-temperature tank and sends it into the molten salt heat exchanger 16, where it is used as a high-temperature heat source for the heat pump to extract heat. The cooled low-temperature molten salt flows to the low-temperature molten salt tank 17. When there is sufficient sunlight, the low-temperature molten salt pump 18 pumps it out and sends it into the trough solar collector 13 to absorb solar heat and be heated up. The heated high-temperature molten salt is then stored in the high-temperature molten salt tank 14 again. The high-temperature molten salt tank 14 and the low-temperature molten salt tank 17 have a heat storage function, which is used to balance the energy relationship between the highly volatile and intermittent solar energy and the heat demand of the unit. When the sunlight intensity is high and the collected heat is greater than the heat demand of the unit, the excess high-temperature molten salt is temporarily stored in the high-temperature molten salt tank 14. When the sunlight intensity is low and the collected heat is less than the heat demand of the unit, the heat in the previously stored excess high-temperature molten salt is released to make up for the heat gap, enabling the unit to operate smoothly throughout the day. The fourth electric stop valve 30 and the seventh electric stop valve 35 are closed to cut off the loop of solar energy supplementing heat for geothermal energy. The first electric stop valve 20 and the second electric stop valve 22 are opened. The circulating water of the solar heating unit is boosted by the high-temperature heat source pump and then sent into the molten salt heat exchanger 16, where it is evaporated into superheated steam. Then it enters the first supplementary heat exchanger 4 to condense and release heat, and is used as a high-temperature heat source for the three-stage compression heat pump unit to extract heat.The heat pump working medium absorbs the low-temperature heat in the geothermal closed-circuit water in the evaporator 11 and evaporates into working medium steam. Then, it is compressed into a low-temperature and low-pressure working medium by the low-pressure stage compressor 12. After the low-temperature and low-pressure working medium at the outlet of the low-pressure stage compressor 12 is mixed with the working medium at the outlet of the second heat supplement heat exchanger 8 and cooled down, it enters the medium-pressure stage compressor 9 and is compressed into a medium-temperature and medium-pressure working medium. The working medium at the outlet of the medium-pressure stage compressor 9 is mixed with the working medium at the outlet of the first heat supplement heat exchanger 4 and then enters the high-pressure stage compressor 5 and is compressed into a high-temperature and high-pressure working medium. The high-temperature and high-pressure working medium releases heat through condensation in the condenser 1 to heat the natural gas from the pressure regulating station to the required temperature of 200 - 300 °C at the combustion chamber inlet; the condensed working medium at the outlet of the condenser 1 is divided into two paths. One path is depressurized by the first expansion valve 2 and expands and evaporates into a medium-pressure gas-water mixed state. The other path enters the first intermediate heat exchanger 3 and exchanges heat with the medium-pressure gas-water mixed state working medium. The heated medium-pressure working medium absorbs the heat of the high-temperature molten salt in the solar heating unit in the first heat supplement heat exchanger 4 and evaporates into a saturated or superheated state, mixes with the medium-temperature and medium-pressure working medium at the outlet of the medium-pressure stage compressor 9, and the working medium cooled by the first intermediate heat exchanger 3 enters the second intermediate heat exchanger 7 backward; the working medium depressurized by the first expansion valve 2 is also divided into two paths. One path enters the first intermediate heat exchanger 3 to complete the above-mentioned heating process. The other path is depressurized and expanded into a low-pressure gas-water mixed state by the second expansion valve 6, and then enters the second intermediate heat exchanger 7 to exchange heat with the working medium cooled at the outlet of the first intermediate heat exchanger 3. The heated working medium enters the second heat supplement heat exchanger 8 and absorbs the heat of the spray water in the flue gas waste heat recovery unit and evaporates into a saturated or superheated state, mixes with the working medium at the outlet of the low-pressure stage compressor 12 and enters the medium-pressure stage compressor 9 to be compressed. The cooled working medium enters the third expansion valve 10 from the outlet of the second intermediate heat exchanger 7 and is depressurized and expanded into a very low-pressure gas-water mixed state, and then enters the evaporator 11 to absorb the low-temperature heat of the circulating water in the geothermal energy extraction unit and evaporates into a saturated or superheated state, and enters the low-pressure stage compressor 12 to be compressed to complete the cycle.

[0041] When the unit is shut down, the three-stage compression heat pump unit, the flue gas waste heat recovery unit, and the intake air heating unit are all shut down, and the corresponding motorized globe valves and circulation pumps are closed. At this time, the first motorized globe valve 20 and the second motorized globe valve 22 are closed, cutting off the loop for supplying high-temperature heat source from solar energy to the heat pump; the fifth motorized globe valve 32 and the sixth motorized globe valve 34 are closed, cutting off the loop for supplying low-temperature heat source from geothermal energy to the heat pump; the seventh motorized globe valve 35 and the eighth motorized globe valve 36 are opened. When the unit is shut down for a long time and the solar heat collection heats all the molten salts to a high temperature and fills the high-temperature molten salt heat storage tank 14, the high-temperature molten salt pump 15 pumps out part of the high-temperature molten salts in the high-temperature molten salt heat storage tank 14 to the molten salt heat exchanger 16 to exchange heat with the closed-circuit circulating water on the other side. The cooled molten salts flow into the low-temperature molten salt heat storage tank 17 to continue absorbing solar energy for heating when the light is sufficient. The heated closed-circuit circulating water enters the geothermal pipe 31 to return the heat to the underground soil to ensure the soil temperature field, maintain the balance between the annual heat extraction and the heat injection, ensure the soil temperature during heat use, reduce the working temperature difference of the heat pump, so that the heat pump operates under high COP conditions throughout the year, improving the system economy, energy efficiency and environmental protection. The high-temperature heat source pump 19 overcomes the circulation resistance for the closed-circuit circulating water at this time.

Claims

1. An intake air heating system for a combined cycle unit with a clean energy coupled multi-stage compression heat pump, characterized in that Including: A three-stage compression heat pump unit, a solar heating unit, a flue gas waste heat recovery unit, an intake air heating unit, and a geothermal energy extraction and closed-circuit circulating water pipeline unit, where: The three-stage compression heat pump unit extracts geothermal energy, flue gas waste heat, and solar energy in sequence to heat natural gas by replacing the original heat source of the natural gas performance heater; The flue gas waste heat recovery unit recovers the flue gas waste heat from the tail gas of the waste heat boiler as the medium-temperature heat source of the heat pump. At the same time, the flue gas waste heat recovery unit leads out a connection to the intake air heating unit to heat the compressor intake air in extreme weather, avoiding safety problems such as frost blockage of the compressor inlet filter and hydrogen embrittlement cracking of the compressor blades; The solar heating unit uses a solar collector to generate heat as the high-temperature heat source of the heat pump; The geothermal energy extraction and closed-circuit circulating water pipeline unit extracts geothermal energy in a geothermal well using closed-circuit circulating water as the primary low-temperature heat source of the heat pump.

2. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 1, characterized in that, The three-stage compression heat pump system includes a condenser (1), a first expansion valve (2), a first intermediate heat exchanger (3), a first heat supply supplement heat exchanger (4), a high-pressure stage compressor (5), a second expansion valve (6), a second intermediate heat exchanger (7), a second heat supply supplement heat exchanger (8), a medium-pressure stage compressor (9), a third expansion valve (10), an evaporator (11), and a low-pressure stage compressor (12); two heat supply supplement loops and an evaporation loop are arranged at the inlet and outlet of the solution side of the condenser (1); the heat supply supplement loops are divided into two paths, one path is sequentially connected to the first intermediate heat exchanger (3), the first heat supply supplement heat exchanger (4), and the high-pressure stage compressor (5), and the other path is sequentially connected to the second intermediate heat exchanger (7), the second heat supply supplement heat exchanger (8), and the medium-pressure stage compressor (9); the evaporation loop is sequentially connected to the evaporator (11) and the low-pressure stage compressor (12).

3. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 2, characterized in that, The specific structure of the two heat supplement loops and one evaporation loop is as follows: The gas-side inlet C of the condenser (1) is connected to the natural gas inlet pipeline, and the natural gas supply pipeline is led out from the gas-side outlet A of the condenser; the solution-side outlet B of the condenser is divided into two paths. One path is connected to the first-side solution inlet A of the first intermediate heat exchanger (3), and the other path is further divided into two paths and respectively connected to the second-side solution inlets B of the first intermediate heat exchanger (3) and the second intermediate heat exchanger (7). The first-side solution outlet C of the first intermediate heat exchanger (3) is connected to the first-side solution inlet A of the second intermediate heat exchanger (7). The first-side solution outlet C of the second intermediate heat exchanger is connected to the solution inlet B of the evaporator (11). The second-side solution outlet D of the first intermediate heat exchanger (3) is connected to the solution inlet B of the first heat supplement heat exchanger (4). The second-side solution outlet D of the second intermediate heat exchanger (7) is connected to the solution inlet B of the second heat supplement heat exchanger (8). The solution-vapor side outlet D of the evaporator (11) is connected to the solution-vapor side inlet C of the low-pressure stage compressor (12). The vapor side outlet A of the low-pressure stage compressor is merged with the vapor side outlet D of the second heat supplement heat exchanger (8) and then connected to the vapor side inlet of the medium-pressure stage compressor (9). The vapor side outlet (A) of the medium-pressure stage compressor is merged with the vapor side outlet D of the first heat supplement heat exchanger (3) and then connected to the vapor side inlet C of the high-pressure stage compressor (5). The vapor side outlet A of the high-pressure stage compressor is connected to the gas-side inlet D of the condenser (1).

4. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 1, characterized in that The solar heating unit includes a trough solar collector (13), a high-temperature molten salt heat storage tank (14), a high-temperature molten salt pump (15), a molten salt heat exchanger (16), a low-temperature molten salt heat storage tank (17), a low-temperature molten salt pump (18), a high-temperature heat source pump (19), a first electric stop valve, and a second electric stop valve. The outlet of the trough solar collector (13) is connected to the inlet of the high-temperature molten salt heat storage tank (14). The outlet of the high-temperature molten salt heat storage tank (14) is connected to the inlet of the high-temperature molten salt pump (15). The outlet of the high-temperature molten salt pump (15) is connected to the molten salt side inlet of the molten salt heat exchanger (16). The outlet of the molten salt heat exchanger (16) is connected to the inlet of the low-temperature molten salt heat storage tank (17). The outlet of the low-temperature molten salt heat storage tank (17) is connected to the inlet of the low-temperature molten salt pump (18). The outlet of the low-temperature molten salt pump (18) is connected to the inlet of the trough solar collector (13).

5. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 1, characterized in that, The flue gas waste heat recovery unit includes a flue gas spray tower (23), a chimney (24), a spray water circulation pump (25), and a first electric control valve (26); the water side outlet B of the flue gas spray tower (23) is connected to the water side inlet of the spray water circulation pump (25) to recover the waste heat of the tail gas of the waste heat boiler and provide an intermediate heat source for the heat pump; the outlet of the spray water circulation pump (25) is divided into two paths, one path is connected to the water side inlet A of the second heat supplement heat exchanger (8), and the other path is connected to the water side inlet B of the air heater (29). The pipelines of the water side outlet C of the second heat supplement heat exchanger (8) and the water side outlet D of the air heater (29) are merged and then connected to the inlet D of the flue gas spray tower (23); the flue gas pipeline is sequentially connected to the inlet and outlet of the flue gas side of the flue gas spray tower (23) and the inlet and outlet of the flue gas side of the chimney (24).

6. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 2, characterized in that, The intake air heating unit includes a third electric stop valve (27), a second electric control valve (28), an air heater (29), and a fourth electric stop valve (30). The air intake pipeline is connected to the gas side inlet C of the air heater (29), and the air supply pipeline is connected to the gas side outlet A of the air heater (29); the outlet of the spray water circulation pump (25) is connected to the water side inlet B of the air heater (29) through the third electric stop valve (27) and the second electric control valve (28), and the water side outlet D of the air heater (29) is connected to the water side inlet D of the flue gas spray tower (23) through the fourth electric stop valve (30).

7. The intake air heating system of the combined cycle unit of the clean energy coupled multi-stage compression heat pump according to claim 1, characterized in that, The geothermal energy extraction and closed-loop circulating water pipeline unit includes a first heat supplement heat exchanger (4), a molten salt heat exchanger (16), a high-temperature heat source pump (19), a first electric stop valve (20), a second electric stop valve (22), a ground heat exchanger pipe (31), a fifth electric stop valve (32), a geothermal circulation pump (33), a sixth electric stop valve (34), a seventh electric stop valve (35), and an eighth electric stop valve (36). The closed-loop circulating water pipeline is connected from the outlet of the high-temperature heat source pump (19) to the water side inlet A of the molten salt heat exchanger (16). At the water side outlet B of the molten salt heat exchanger (16), it is divided into two paths. One path is connected to the inlet C of the first heat supplement heat exchanger (4) through the second electric stop valve (22), and the other path is divided into two branches after passing through the eighth electric stop valve (36). One branch is connected to the water side outlet C of the evaporator (11) through the sixth electric stop valve (34), and the other path is connected to the inlet of the ground heat exchanger pipe (31); the closed-loop circulating water pipeline at the outlet of the ground heat exchanger pipe (31) is divided into two paths. One path is connected to the inlet of the geothermal circulation pump (33) through the fifth electric stop valve (32), and the other path is merged with the pipeline of the outlet A of the first heat supplement heat exchanger (4) through the first electric stop valve (20) and then connected to the inlet of the high-temperature heat source pump (19); the closed-loop circulating water pipeline at the outlet of the geothermal circulation pump (33) is connected to the water side inlet A of the evaporator (11). The water side inlet A of the molten salt heat exchanger (16) is connected to the outlet of the ground heat exchanger pipe (31), and a high-temperature molten salt pump (19) is provided between the outlet of the ground heat exchanger pipe (31) and the water side of the molten salt heat exchanger (16).

8. An operating method for an intake air heating system of a combined cycle unit using a clean energy coupled multi-stage compression heat pump according to any one of claims 1-7, characterized in that, It includes two different operation modes: unit startup and shutdown. When the unit is put into operation, the fifth electric stop valve (32) and the sixth electric stop valve (34) are opened. The closed-circuit circulating water in the geothermal energy extraction unit absorbs the heat of the soil layer and heats up in the buried pipe (31), and then enters the evaporator (11) where the low-temperature heat energy is extracted by the working medium of the three-stage compression heat pump unit. The geothermal circulation pump (33) provides the circulating power. The flue gas at the tail of the waste heat boiler enters the spray tower (23) and is cooled by spraying by about 30 °C. The cooled flue gas is discharged to the atmosphere through the chimney (24). The sprayed water falling to the bottom of the tower is heated up and then sent to the second supplementary heat exchanger (8) through the spray water circulating pump (25) to be used as a medium-temperature heat source to extract heat. The cooled spray water returns to the flue gas spray tower to continue spraying and cooling the flue gas. When the ambient temperature is too low, the third electric stop valve (27) and the fourth electric stop valve (30) are opened. A branch of the heated spray water enters the air heater (29) to heat the air at the compressor inlet. The opening of the second electric control valve (28) is adjusted according to the required inlet temperature to control the flow rate of the spray water entering the air heater (29), thereby adjusting the outlet air temperature of the air heater (29). The first electric control valve (26) is used to cooperate with the adjustment of the flow rate of the spray water entering the second supplementary heat exchanger (8) when the air intake heating unit is opened. When the ambient temperature does not require heating the air, the first electric control valve (26) and the third electric stop valve (27) are closed. In the solar heat collection loop, molten salt is used as an intermediate medium. The molten salt absorbs solar energy in the trough solar collector (13) and is heated to 150 - 200 °C and then enters the high-temperature molten salt storage tank (14). When the heat pump of the unit is started during operation, the high-temperature molten salt pump (15) pumps out the molten salt in the high-temperature tank and sends it into the molten salt heat exchanger (16) to be used as the high-temperature heat source of the heat pump to extract heat. The cooled low-temperature molten salt flows to the low-temperature molten salt tank (17). When the sunlight is sufficient, the low-temperature molten salt pump (18) pumps it out and sends it into the trough solar collector (13) to absorb solar heat and heat up. The heated high-temperature molten salt is stored in the high-temperature molten salt storage tank (14) again. The high-temperature molten salt storage tank (14) and the low-temperature molten salt tank (17) have the function of heat storage, which is used to balance the energy relationship between the highly volatile and intermittent solar energy and the heat demand of the unit. When the sunlight intensity is high and the collected heat is greater than the heat demand of the unit, the excess high-temperature molten salt is temporarily stored in the high-temperature molten salt storage tank (14). When the sunlight intensity is low and the collected heat is less than the heat demand of the unit, the heat in the previously stored excess high-temperature molten salt is released to make up for the heat gap, so that the unit can operate stably throughout the day. The fourth electric stop valve (30) and the seventh electric stop valve (35) are closed to cut off the loop of solar energy supplementing heat for geothermal energy. The first electric stop valve (20) and the second electric stop valve (22) are opened. The circulating water of the solar heating unit is boosted by the high-temperature heat source pump and then sent into the molten salt heat exchanger (16) to be evaporated into superheated steam, and then enters the first supplementary heat exchanger (4) to condense and release heat, and is used as the high-temperature heat source to be extracted by the three-stage compression heat pump unit.The heat pump working medium absorbs the low-temperature heat in the geothermal closed-circuit water in the evaporator (11) and evaporates into working medium steam. Then, it is compressed into a low-temperature and low-pressure working medium by the low-pressure stage compressor (12). After the low-temperature and low-pressure working medium at the outlet of the low-pressure stage compressor (12) is mixed with the working medium at the outlet of the second heat supplement exchanger (8) and cooled down, it enters the medium-pressure stage compressor (9) and is compressed into a medium-temperature and medium-pressure working medium. The working medium at the outlet of the medium-pressure stage compressor (9) is mixed with the working medium at the outlet of the first heat supplement exchanger (4) and then enters the high-pressure stage compressor (5) and is compressed into a high-temperature and high-pressure working medium. The high-temperature and high-pressure working medium condenses and releases heat in the condenser (1) to heat the natural gas from the pressure regulating station to the required temperature of 200 - 250 °C at the combustion chamber inlet; the condensed working medium at the outlet of the condenser 1 is divided into two paths. One path is depressurized by the first expansion valve (2) and expands and evaporates into a medium-pressure gas-water mixed state. The other path enters the first intermediate heat exchanger (3) to exchange heat with the medium-pressure gas-water mixed state working medium. The medium-pressure working medium after being heated absorbs the heat of the high-temperature molten salt in the solar heating unit in the first heat supplement exchanger (4) and evaporates into a saturated or superheated state, and is mixed with the medium-temperature and medium-pressure working medium at the outlet of the medium-pressure stage compressor (9). The working medium cooled by the first intermediate heat exchanger (3) then enters the second intermediate heat exchanger (7); the working medium depressurized by the first expansion valve (2) is also divided into two paths. One path enters the first intermediate heat exchanger (3) to complete the above heating process. The other path is depressurized and expanded by the second expansion valve (6) into a low-pressure gas-water mixed state, and then enters the second intermediate heat exchanger (7) to exchange heat with the working medium cooled at the outlet of the first intermediate heat exchanger (3). The heated working medium enters the second heat supplement exchanger (8) to absorb the heat of the spray water in the flue gas waste heat recovery unit and evaporates into a saturated or superheated state, and is mixed with the working medium at the outlet of the low-pressure stage compressor (12) and enters the medium-pressure stage compressor (9) to be compressed. The cooled working medium exits from the second intermediate heat exchanger (7) and enters the third expansion valve (10) to be depressurized and expanded into a very low-pressure gas-water mixed state, and then enters the evaporator (11) to absorb the low-temperature heat of the circulating water in the geothermal energy extraction unit and evaporates into a saturated or superheated state, and enters the low-pressure stage compressor (12) to be compressed to complete the cycle; When the unit is shut down, the three-stage compression heat pump unit, the flue gas waste heat recovery unit, and the intake air heating unit are all shut down, and the corresponding motorized globe valves and circulating pumps are closed; at this time, the first motorized globe valve (20) and the second motorized globe valve (22) are closed, cutting off the loop for supplying high-temperature heat source to the heat pump by solar energy; the fifth motorized globe valve (32) and the sixth motorized globe valve (34) are closed, cutting off the loop for supplying low-temperature heat source to the heat pump by geothermal energy; the seventh motorized globe valve (35) and the eighth motorized globe valve (36) are opened. When the unit is shut down for a long time and the solar heat collection melts all the molten salt to a high temperature and fills the high-temperature molten salt heat storage tank (14), the high-temperature molten salt pump (15) pumps out part of the high-temperature molten salt in the high-temperature molten salt heat storage tank (14) to the molten salt heat exchanger (16) to exchange heat with the closed-circuit circulating water on the other side. The cooled molten salt flows into the low-temperature molten salt heat storage tank (17) and waits to continue absorbing solar heat when the sunlight is sufficient. The heated closed-circuit circulating water enters the geothermal pipe (31) to return the heat to the underground soil to ensure the soil temperature field, maintain the balance of the annual heat extraction and heat injection, ensure the soil temperature during heat use, reduce the working temperature difference of the heat pump, so that the heat pump operates under high COP conditions throughout the year, improve the system economy, energy saving and environmental protection. At this time, the high-temperature heat source pump (19) overcomes the circulating resistance for the closed-circuit circulating water.

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