A thermal power generation, solar thermal and supercritical carbon dioxide coupled power generation system and method

Abstract

The present invention discloses a thermal power generation, solar thermal and supercritical carbon dioxide integrated power generation system and method. The system includes a thermal power generation system, a heat exchange system, a concentrating solar thermal system, a molten salt energy storage system, and a supercritical carbon dioxide power generation system. The heat exchange system includes a first steam - molten salt heat exchanger, a second steam - molten salt heat exchanger, and a steam generator arranged in parallel; the molten salt energy storage system includes high - temperature, medium - temperature, and low - temperature molten salt storage tanks arranged in parallel; the supercritical carbon dioxide system includes a carbon dioxide turbine, a molten salt - carbon dioxide heat exchanger, a high - temperature recuperator, a pre - cooler, and a compressor connected in sequence; by coupling the thermal power generation system, the solar concentrating thermal system, the molten salt energy storage system, and the supercritical carbon dioxide system, through reasonable operation regulation, the adaptability to solar energy resources and grid load is greatly increased, and the whole system can output according to demand under various working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation, and particularly relates to a thermal power generation, solar thermal and supercritical carbon dioxide coupled power generation system and method. Background Art

[0002] Solar energy is a renewable energy source with extremely rich reserves. It is estimated that the solar radiation reaching the earth's surface every year is equivalent to 13 trillion tons of standard coal, which is the renewable energy source with the largest exploitable amount at present. Making full use of solar energy to generate electricity and reducing the carbon dioxide generated by the combustion of fossil fuels is an effective way to reduce carbon. At the same time, solar energy has the characteristics of intermittency, periodicity and unpredictability. Large-scale solar power generation will pose a threat to the stability and security of the power grid. To solve this problem, on the one hand, energy storage devices can be added to solar power generation, and the energy storage system can be used to cut peaks and fill valleys to smooth the volatility of solar power generation. However, this method requires the configuration of a large-scale energy storage, and there are problems such as high energy storage costs and low annual utilization hours of the energy storage system. On the other hand, the peak shaving capacity of existing thermal power units can also be used to combine the two to achieve multi-energy complementarity and promote the consumption of solar energy. However, this method requires the existing thermal power to have high flexibility. In the future, with the rapid increase in the installed capacity of solar power generation, the thermal power units need to continuously increase their peak shaving load range. However, at present, the peak shaving load range of thermal power units in China is generally not high, and it will be difficult to achieve deep peak shaving in the future and cannot meet the peak shaving requirements brought by the large-scale grid connection of the system energy. On this basis, how to flexibly configure the coupling system of multiple energy power generations to achieve stable power output of the system under various working conditions is an urgent problem to be solved. Summary of the Invention

[0003] The purpose of the present invention is to provide a thermal power generation, solar thermal and supercritical carbon dioxide coupled power generation system for the above problems in the existing technology, so as to realize the complementary utilization of multiple energies and have good environmental adaptability and output stability.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: A thermal power generation, solar thermal and supercritical carbon dioxide coupled power generation system includes a thermal power generation system, a heat exchange system, a concentrating solar collector system, a molten salt energy storage system and a supercritical carbon dioxide power generation system;

[0005] Among them, the thermal power generation system includes a boiler, a steam turbine unit and a regenerative system connected in sequence, and the steam turbine does work to drive the first generator to generate electricity;

[0006] The heat exchange system includes a first steam-molten salt heat exchanger, a second steam-molten salt heat exchanger and a steam generator arranged in parallel;

[0007] The molten salt energy storage system includes a high-temperature molten salt storage tank, a medium-temperature molten salt storage tank and a low-temperature molten salt storage tank arranged in parallel, and several molten salt pumps are arranged on each molten salt storage tank;

[0008] The supercritical carbon dioxide system includes a carbon dioxide turbine, a molten salt - carbon dioxide heat exchanger, a high - temperature recuperator, a pre - cooler, and a main compressor connected in sequence. The supercritical carbon dioxide turbine does work to drive the second generator to generate electricity;

[0009] The outlet of the boiler is respectively connected to the steam inlets of the first steam - molten salt heat exchanger and the second steam - molten salt heat exchanger of the steam - molten salt heat exchange system. The steam outlets of the first steam - molten salt heat exchanger and the second steam - molten salt heat exchanger of the steam - molten salt heat exchange system are respectively connected to the steam inlet of the regenerative system;

[0010] The outlet of the low - temperature molten salt storage tank of the molten salt thermal energy storage system is respectively connected to the molten salt inlets of the concentrating solar heat collection system, the first steam - molten salt heat exchanger and the second steam - molten salt heat exchanger in the steam - molten salt heat exchange system. The molten salt outlets of the concentrating solar heat collection system and the first steam - molten salt heat exchanger are connected to the inlet of the high - temperature molten salt storage tank; The molten salt outlet of the second steam - molten salt heat exchanger is connected to the inlet of the medium - temperature molten salt storage tank; The outlet of the medium - temperature molten salt storage tank is respectively connected to the molten salt inlets of the concentrating solar heat collection system and the steam generator in the steam - molten salt heat exchange system; The molten salt outlet of the concentrating solar heat collection system is connected to the inlet of the high - temperature molten salt storage tank; The molten salt outlet of the steam generator is connected to the molten salt inlet of the low - temperature molten salt storage tank; The outlet of the high - temperature molten salt storage tank is connected to the molten salt inlet of the molten salt - carbon dioxide heat exchanger; The molten salt outlet of the molten salt - carbon dioxide heat exchanger is connected to the molten salt inlet of the medium - temperature molten salt storage tank.

[0011] Adjustable valves are provided on the pipelines from the outlet of the boiler of the thermal power generation system to the first steam - molten salt heat exchanger, from the outlet of the boiler to the second steam - molten salt heat exchanger, from the low - temperature molten salt storage tank to the first steam - molten salt heat exchanger, from the low - temperature molten salt storage tank to the second steam - molten salt heat exchanger, from the low - temperature molten salt pipeline to the concentrating solar heat collection system, from the medium - temperature molten salt storage tank to the concentrating solar heat collection system, from the medium - temperature molten salt storage tank to the steam generator, from the high - temperature molten salt storage tank to the molten salt - carbon dioxide heat exchanger, and from the outlet of the steam turbine unit of the thermal power generation system to the steam generator.

[0012] By controlling the opening degree of the first valve, the steam flow rate entering the first steam - molten salt heat exchanger from the thermal power generation system can be controlled, realizing the heat exchange between the steam drawn from the thermal power generation system and the low - temperature molten salt to generate high - temperature molten salt; by controlling the opening degree of the second valve, the steam flow rate entering the second steam - molten salt heat exchanger from the thermal power generation system can be controlled, realizing the heat exchange between the steam drawn from the thermal power generation system and the low - temperature molten salt to generate medium - temperature molten salt; by controlling the opening degree of the third valve, the flow rate of the low - temperature molten salt entering the first steam - molten salt heat exchanger can be controlled, realizing the control of the temperature of the high - temperature molten salt at the outlet of the heat exchanger; by controlling the opening degree of the fourth valve, the flow rate of the low - temperature molten salt entering the second steam - molten salt heat exchanger can be controlled, realizing the control of the temperature of the medium - temperature molten salt at the outlet of the heat exchanger; by controlling the opening degree of the fifth valve, the flow rate of the low - temperature molten salt entering the concentrating solar heat collection system can be controlled, realizing the control of the temperature of the high - temperature molten salt at the outlet of the concentrating solar heat collection system; by controlling the opening degree of the sixth valve, the flow rate of the medium - temperature molten salt entering the concentrating solar heat collection system can be controlled, realizing the control of the temperature of the high - temperature molten salt at the outlet of the concentrating solar heat collection system; by controlling the opening degree of the seventh valve, the flow rate of the medium - temperature molten salt entering the concentrating solar heat collection system can be controlled, realizing the control of the temperature of the high - temperature molten salt at the outlet of the concentrating solar heat collection system; by controlling the opening degree of the eighth valve, the flow rate of the high - temperature molten salt entering the molten salt - carbon dioxide heat exchanger can be controlled, realizing the control of the temperatures of the medium - temperature molten salt and the carbon dioxide medium at the outlet of the heat exchanger; by controlling the opening degree of the ninth valve, the flow rate of the medium - temperature molten salt entering the steam generator can be controlled, realizing the control of the temperatures of the low - temperature molten salt and the steam medium at the outlet of the heat exchanger.

[0013] The concentrating solar heat collection system is of tower type, trough type or Fresnel type; when it is of tower type, it includes a heat absorption tower and a heat absorber located at the top of the tower; when it is of trough type, it includes a number of parallel trough - type collectors; when it is of Fresnel type, it includes a number of parallel Fresnel - type collectors.

[0014] The regenerative system includes multiple high - pressure heaters, a deaerator and multiple low - pressure heaters.

[0015] The first steam - molten salt heat exchanger and the second steam - molten salt heat exchanger are single - stage or multi - stage in series; the steam generator includes a pre - heater, an evaporator and a superheater.

[0016] Both the high - temperature regenerator and the pre - cooler are single - stage or multi - stage in series.

[0017] The main compressor can be a single - stage compressor or a multi - stage series compressor. When it is multi - stage in series, a cooling device is provided between each stage.

[0018] The molten salt used is a binary molten salt including sodium nitrate and potassium nitrate; electric tracing is provided for all the molten salt pipelines.

[0019] The operation method of the thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system of the present invention includes the following operation modes:

[0020] 1) When the solar resource conditions are good during the day and the system is in the low electricity load period, the thermal power generation system, the heat exchange system, the concentrating solar thermal system, and the molten salt energy storage system in the system operate, and the supercritical carbon dioxide power generation system does not operate;

[0021] 2) When the solar energy resource conditions are good during the day and the system is in the flat electricity load period, the thermal power generation system, the concentrating solar thermal system, and the molten salt energy storage system in the system operate, and the heat exchange system and the supercritical carbon dioxide power generation system do not operate;

[0022] 3) When the solar resource conditions are good during the day and the system is in the high electricity load period, the thermal power generation system, the heat exchange system, the concentrating solar thermal system, the molten salt energy storage system, and the supercritical carbon dioxide power generation system in the system operate;

[0023] 4) When the solar resource conditions are poor during the day and the system is in the low electricity load period, the thermal power generation system, the heat exchange system, the concentrating solar thermal system, and the molten salt energy storage system in the system operate, and the supercritical carbon dioxide power generation system does not operate;

[0024] 5) When the solar energy resource conditions are poor during the day and the system is in the flat electricity load period, the thermal power generation system, the concentrating solar thermal system, and the molten salt energy storage system in the system operate, and the heat exchange system and the supercritical carbon dioxide power generation system do not operate;

[0025] 6) When the solar resource conditions are poor during the day and the system is in the high electricity load period, the thermal power generation system, the heat exchange system, the concentrating solar thermal system, the molten salt energy storage system, and the supercritical carbon dioxide power generation system in the system operate;

[0026] 7) When the system is in the low electricity load period at night, the thermal power generation system, the heat exchange system, and the molten salt energy storage system in the system operate, and the concentrating solar thermal system and the supercritical carbon dioxide power generation system do not operate;

[0027] 8) When the system is in the flat electricity load period at night, the thermal power generation system and the molten salt energy storage system in the system operate, and the heat exchange system, the concentrating solar thermal system, and the supercritical carbon dioxide power generation system do not operate;

[0028] 9) When the system is in the high electricity load period at night, the thermal power generation system, the heat exchange system, the molten salt energy storage system, and the supercritical carbon dioxide power generation system in the system operate, and the concentrating solar thermal system does not operate.

[0029] By coupling and connecting the thermal power generation system, the solar concentrating thermal system, the molten salt energy storage system, and the supercritical carbon dioxide system, and through reasonable operation control, the present invention greatly increases the adaptability to solar energy resources and grid loads, and can realize the on-demand output of the entire system under various working conditions. Compared with the prior art, there are the following 4 prominent advantages:

[0030] 1) During the low-load period of the electricity consumption load, by extracting part of the steam from the boiler outlet of the thermal power generating unit and storing the heat through heat exchange, the downward peak shaving load of the thermal power generating unit is not restricted by the minimum stable combustion load of the boiler. Compared with the prior art, the peak shaving load range of the unit is significantly increased, and more capacity space can be vacated for the accommodation of new energy.

[0031] 2) By setting up high, medium, and low-temperature molten salt storage tanks, the operation flexibility is increased. When the solar resources change, the molten salt temperature entering the concentrating solar thermal collection system can be flexibly changed to ensure the stability of the molten salt temperature at the outlet of the concentrating solar thermal collection system. In addition, for the problem that the molten salt temperature range of a separate supercritical carbon dioxide coupled solar thermal power generation system cannot be fully utilized, the present invention sets up a medium-temperature molten salt storage tank to utilize the molten salt heat in sections. The high-temperature section is used to heat the carbon dioxide medium, and the low-temperature section is used to heat the feed water medium for thermal power generation, making full use of the molten salt heat and achieving efficient energy utilization compared with the prior art.

[0032] 3) The system is configured with a supercritical carbon dioxide turbine, which uses the heat stored by thermal power and solar energy to do work and generate electricity. Compared with the prior art, the supercritical carbon dioxide medium power generation has higher efficiency, smaller floor area, and better applicability to existing units. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the system of the present invention;

[0034] Figure 2 It is a schematic structural diagram of the system of the present invention with the concentrating solar thermal collection system replaced by a trough type;

[0035] Figure 3 It is a schematic structural diagram of the system of the present invention with the concentrating solar thermal collection system replaced by a Fresnel type;

[0036] Figure 4 It is a structural diagram of the system of the present invention with the single-stage compressor replaced by a multi-stage compressor;

[0037] In the accompanying drawings: 1 - thermal power generation system; 2 - steam - molten salt heat exchange system; 3 - concentrating solar heat collection system; 4 - molten salt thermal energy storage system; 5 - supercritical carbon dioxide power generation system; 11 - boiler; 12 - steam turbine unit; 13 - regenerative system; 14 - first generator; 21 - first steam - molten salt heat exchanger; 22 - second steam - molten salt heat exchanger; 23 - steam generator; 41 - high - temperature molten salt storage tank; 42 - medium - temperature molten salt storage tank; 43 - low - temperature molten salt storage tank; 51 - carbon dioxide turbine; 52 - molten salt - carbon dioxide heat exchanger; 53 - high - temperature recuperator; 54 - pre - cooler; 55 - main compressor; 56 - second generator; 57 - re - compressor; 58 - low - temperature recuperator; 59 - cooling device; 61 - first valve; 62 - second valve; 63 - third valve; 64 - fourth valve; 65 - fifth valve; 66 - sixth valve; 67 - seventh valve; 68 - eighth valve; 69 - ninth valve. Detailed implementation manners

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] Refer to Figure 1 , a thermal power generation, solar thermal and supercritical carbon dioxide coupled power generation system of the present invention includes a thermal power generation system 1, a steam - molten salt heat exchange system 2, a concentrating solar heat collection system 3, a molten salt thermal energy storage system 4 and a supercritical carbon dioxide power generation system 5; wherein, the thermal power generation system includes a boiler 11, a steam turbine unit 12 and a regenerative system 13 connected in sequence, and the steam turbine unit 12 does work to drive the first generator 14 to generate electricity externally; the steam - molten salt heat exchange system 2 includes a first steam - molten salt heat exchanger 21, a second steam - molten salt heat exchanger 22 and a steam generator 23 arranged in parallel; the molten salt thermal energy storage system includes a high - temperature molten salt storage tank 41, a medium - temperature molten salt storage tank 42 and a low - temperature molten salt storage tank arranged in parallel, and several molten salt pumps are arranged on each molten salt storage tank; the supercritical carbon dioxide system includes a carbon dioxide turbine, a molten salt - carbon dioxide heat exchanger, a high - temperature recuperator, a pre - cooler and a compressor connected in sequence, and the supercritical carbon dioxide turbine does work to drive the second generator to generate electricity externally. The concentrating solar heat collection system 3 can adopt a tower - type, trough - type or Fresnel - type.

[0040] Refer to Figure 1 , when the concentrating solar heat collection system is tower - type, it includes a heat absorption tower and a heat absorber located at the top of the tower; refer to Figure 2 , when the concentrating solar heat collection system is trough - type, it includes several trough - type collectors arranged in parallel; refer to Figure 3 , when the concentrating solar heat collection system is Fresnel - type, it includes several Fresnel - type collectors arranged in parallel;

[0041] The outlet of the boiler in the thermal power generation system is respectively connected to the steam inlets of the first steam-salt heat exchanger 21 and the second steam-salt heat exchanger 22 of the steam-salt heat exchange system 2. The steam outlets of the first steam-salt heat exchanger 21 and the second steam-salt heat exchanger 22 of the steam-salt heat exchange system 2 are respectively connected to the steam inlets of the regenerative system 13 of the thermal power generation system 1. The outlet of the low-temperature molten salt storage tank 43 in the molten salt thermal energy storage system 4 is respectively connected to the molten salt inlets of the concentrating solar heat collection system 3, the first steam-salt heat exchanger 21 and the second steam-salt heat exchanger 22 in the steam-salt heat exchange system 2. The molten salt outlets of the concentrating solar heat collection system 3 and the first steam-salt heat exchanger 21 are connected to the inlet of the high-temperature molten salt storage tank 41. The molten salt outlet of the second steam-salt heat exchanger 22 is connected to the inlet of the medium-temperature molten salt storage tank 42. The outlet of the medium-temperature molten salt storage tank 42 is respectively connected to the molten salt inlets of the concentrating solar heat collection system 3 and the steam generator 23 in the steam-salt heat exchange system 2. The molten salt outlet of the concentrating solar heat collection system 3 is connected to the inlet of the high-temperature molten salt storage tank 41. The molten salt outlet of the steam generator 23 is connected to the molten salt inlet of the low-temperature molten salt storage tank 43. The outlet of the high-temperature molten salt storage tank 41 is connected to the molten salt inlet of the molten salt-carbon dioxide heat exchanger 52 in the supercritical carbon dioxide power generation system 5. The molten salt outlet of the molten salt-carbon dioxide heat exchanger 52 is connected to the molten salt inlet of the medium-temperature molten salt storage tank 42.

[0042] A first valve 61 is provided on the pipeline from the outlet of the boiler 11 of the thermal power generation system 1 to the first steam-salt heat exchanger 21, a second valve 62 is provided on the pipeline from the boiler outlet to the second steam-salt heat exchanger 22, a third valve 63 is provided on the pipeline from the low-temperature molten salt storage tank 43 to the first steam-salt heat exchanger 21, a fourth valve 64 is provided on the pipeline from the low-temperature molten salt storage tank 43 to the second steam-salt heat exchanger 22, a fifth valve 65 is provided on the pipeline from the low-temperature molten salt pipeline to the concentrating solar heat collection system pipeline, a sixth valve 66 is provided on the pipeline from the medium-temperature molten salt storage tank 42 to the concentrating solar heat collection system 3, a seventh valve 67 is provided on the pipeline from the medium-temperature molten salt storage tank 42 to the steam generator 23, an eighth valve 68 is provided on the pipeline from the high-temperature molten salt storage tank 41 to the molten salt-carbon dioxide heat exchanger 52, and a ninth valve 69 is provided on the pipeline from the outlet of the steam turbine unit 12 of the thermal power generation system 1 to the steam generator 23.

[0043] When the tower-type concentrating solar heat collection system of the present invention is replaced as a trough-type concentrating solar heat collection system as a whole, it is the second embodiment. As Figure 2 shown, the outlets of the low-temperature molten salt storage tank 43 and the medium-temperature molten salt storage tank 42 in the molten salt thermal energy storage system 4 are connected to the molten salt inlet of the trough-type concentrating solar heat collection system, and the molten salt outlet of the trough-type concentrating solar heat collection system is connected to the inlet of the high-temperature molten salt storage tank 41. The remaining connection methods are the same as those in Embodiment 1.

[0044] When the tower-type concentrating heat collection system of the present invention is replaced as a whole by a Fresnel-type concentrating heat collection system, it is the third embodiment. As Figure 3 shown, the outlets of the low-temperature molten salt storage tank 43 and the medium-temperature molten salt storage tank 42 of the molten salt energy storage system 4 are connected to the molten salt inlet of the Fresnel-type concentrating heat collection system, and the molten salt outlet of the Fresnel-type concentrating heat collection system is connected to the inlet of the high-temperature molten salt storage tank 41. The remaining connection methods are the same as those in Embodiment 1.

[0045] When the supercritical carbon dioxide power generation system 5 of the present invention is a recompression system, it is the fourth embodiment. As Figure 4 shown, the supercritical carbon dioxide system 4 includes a carbon dioxide turbine 51, a molten salt-carbon dioxide heat exchanger 52, a high-temperature recuperator 53, and a low-temperature recuperator 58 connected in sequence. The outlets of the recuperators are respectively connected to the inlets of the main compressor 55 and the recompressor 57. Before entering the recompressor 57, it is first cooled by an inter-stage cooling device. The outlet of the recompressor 57 is connected to the inlet of the low-temperature recuperator 58, and the outlet is mixed with the medium at the outlet of the main compressor and then enters the high-temperature recuperator 53. The remaining connection methods are the same as those in Embodiment 1.

[0046] The system of the present invention can dynamically adjust the operation mode according to weather conditions and grid load requirements to meet the stable output requirements under different working conditions. The working process and principle are as follows:

[0047] 1) When the solar resource conditions are good during the day and the system is in the low load period of electricity consumption, the thermal power generation system 1, the heat exchange system 2, the concentrating heat collection system 3, and the molten salt energy storage system 4 in the system operate, and the supercritical carbon dioxide power generation system 5 does not operate. Specifically: Open the first valve 61, draw part of the steam from the outlet of the boiler 11 into the first steam-molten salt heat exchanger 21, reduce the amount of steam entering the steam turbine unit 12, and realize the reduction of the output of the thermal power generation system; at the same time, open the third valve 63, so that the low-temperature molten salt enters the first steam-molten salt heat exchanger 21 to exchange heat with the steam and becomes high-temperature molten salt and returns to the high-temperature molten salt storage tank 41, realizing the storage of part of the steam heat in the high-temperature molten salt; at the same time, open the fifth valve 65, use the low-temperature molten salt pump to pump the low-temperature molten salt into the concentrating heat collection system 3 to absorb solar heat and become high-temperature molten salt and return to the high-temperature molten salt storage tank 41, realizing the conversion of solar energy into heat energy and storing it in the high-temperature molten salt. Under this working condition, the output of the entire system is relatively low. Since the supercritical carbon dioxide system 5 does not operate and the thermal power generation system converts part of the steam into heat for storage, only thermal power is generated and exported by the entire system. By adjusting the flow rate of the steam drawn from the outlet of the boiler 11, the output of the entire system can be regulated to meet the load fluctuation requirements during the low load period of system electricity consumption. The valves not mentioned are in the closed state, the same below.

[0048] 2) When the solar energy resource conditions are good during the day and the system is in the flat peak period of the electricity load, the thermal power generation system 1, the concentrating solar heat collection system 3, and the molten salt thermal energy storage system 4 in the system operate, while the heat exchange system 2 and the supercritical carbon dioxide power generation system 5 do not operate. Specifically: Open the fifth valve 65, use the low-temperature molten salt pump to pump the low-temperature molten salt into the concentrating solar heat collection system 3, absorb the solar heat, and become high-temperature molten salt and return to the high-temperature molten salt storage tank 41, so as to realize the conversion of solar energy into thermal energy and store it in the high-temperature molten salt. Under this condition, the output of the whole system is moderate. Since the supercritical carbon dioxide system 5 does not operate, only thermal power is generated and supplied to the outside by the whole system. By adjusting the boiler combustion evaporation, the output of the whole system can be regulated to meet the load fluctuation requirements during the flat peak period of the system's electricity consumption.

[0049] 3) When the solar resource conditions are good during the day and the system is in the peak period of the electricity load, the thermal power generation system 1, the heat exchange system 2, the concentrating solar heat collection system 3, the molten salt thermal energy storage system 4, and the supercritical carbon dioxide power generation system 5 in the system operate. Specifically: Open the eighth valve 68, use the high-temperature molten salt pump to pump the high-temperature molten salt into the molten salt - carbon dioxide heat exchanger 52 of the supercritical carbon dioxide power generation system to exchange heat with the supercritical carbon dioxide medium, generate high-temperature carbon dioxide, and drive the carbon dioxide turbine 51 to do work and generate electricity. The medium-temperature molten salt after heat exchange returns to the medium-temperature molten salt storage tank 42; at the same time, open the ninth valve 69, draw part of the feed water from the inlet of the regenerative system 13 into the steam generator 23, use the molten salt heat to generate part of the steam, and replace the extraction steam of the thermal power generation system, so as to realize the reduction of the fuel consumption of the thermal power generation system under high load; at the same time, open the seventh valve 67, use the medium-temperature molten salt pump to pump the medium-temperature molten salt into the steam generator 23 to exchange heat with the feed water, become low-temperature molten salt and return to the low-temperature molten salt storage tank 43, so as to realize the release of part of the molten salt heat to the thermal power generation system. At the same time, open the fifth valve 65, use the low-temperature molten salt pump to pump the low-temperature molten salt into the concentrating solar heat collection system 3, absorb the solar heat, and become high-temperature molten salt and return to the high-temperature molten salt storage tank 41, so as to realize the conversion of solar energy into thermal energy and store it in the high-temperature molten salt. Under this condition, the output of the whole system is high. Since both the supercritical carbon dioxide system 5 and the thermal power generation system operate, the whole system can generate and supply electricity to the outside through the first generator 14 and the second generator 56. By adjusting the boiler combustion evaporation and the flow rate of the high-temperature molten salt entering the supercritical carbon dioxide power generation system 5, the output of the whole system can be regulated to meet the load fluctuation requirements during the peak period of the system's electricity consumption.

[0050] 4) When the solar resource conditions are poor during the day and the system is in the low electricity load period, the thermal power generation system 1, the heat exchange system 2, the concentrating solar collection system 3 and the molten salt thermal energy storage system 4 in the system operate, and the supercritical carbon dioxide power generation system 5 does not operate. Specifically: Open the second valve 62, draw out part of the steam from the boiler outlet and enter the second steam - molten salt heat exchanger 22 to reduce the amount of steam entering the steam turbine unit, and realize the reduction of the output of the thermal power generation system; at the same time, open the fourth valve 64 to make the low - temperature molten salt enter the second steam - molten salt heat exchanger 22 to exchange heat with the steam and become medium - temperature molten salt and return to the medium - temperature molten salt storage tank 42, realizing the storage of part of the steam heat in the medium - temperature molten salt; at the same time, open the sixth valve 66, use the medium - temperature molten salt pump to pump the medium - temperature molten salt into the concentrating solar collection system 3 to absorb solar heat and become medium - temperature molten salt and return to the medium - temperature molten salt storage tank 42, realizing the conversion of solar energy into heat energy and storing it in the medium - temperature molten salt. Under this condition, the output of the whole system is relatively low. Since the supercritical carbon dioxide system 5 does not operate and the thermal power generation system converts part of the steam into heat for storage, only thermal power is generated for external power supply in the whole system. By adjusting the flow rate of the steam drawn out from the boiler outlet, the output of the whole system can be regulated to meet the requirements of load fluctuations during the low - electricity period of the system.

[0051] 5) When the solar resource conditions are poor during the day and the system is in the flat - peak electricity load period, the thermal power generation system 1, the concentrating solar collection system 3 and the molten salt thermal energy storage system 4 in the system operate, and the heat exchange system 2 and the supercritical carbon dioxide power generation system 5 do not operate. Specifically: Open the sixth valve, use the medium - temperature molten salt pump to pump the medium - temperature molten salt into the concentrating solar collection system 3 to absorb solar heat and become medium - temperature molten salt and return to the medium - temperature molten salt storage tank 42, realizing the conversion of solar energy into heat energy and storing it in the medium - temperature molten salt. Under this condition, the output of the whole system is moderate. Since the supercritical carbon dioxide system 5 does not operate, only thermal power is generated for external power supply in the whole system. By adjusting the boiler combustion evaporation, the output of the whole system can be regulated to meet the requirements of load fluctuations during the flat - peak electricity period of the system.

[0052] 6) When the solar resource conditions are poor during the day and the system is at the peak of the electricity load, the thermal power generation system 1, the heat exchange system 2, the concentrating solar heat collection system 3, the molten salt thermal energy storage system 4, and the supercritical carbon dioxide power generation system 5 in the system operate. Specifically: Open the eighth valve 68, use the high-temperature molten salt pump to pump the high-temperature molten salt into the molten salt - carbon dioxide heat exchanger 52 of the supercritical carbon dioxide power generation system 5 to exchange heat with the supercritical carbon dioxide medium, generate high-temperature carbon dioxide, and drive the carbon dioxide turbine 51 to do work and generate electricity. The medium-temperature molten salt after heat exchange returns to the medium-temperature molten salt storage tank 42; at the same time, open the ninth valve 69, draw part of the feed water from the inlet of the regenerative system into the steam generator 23, use the heat of the molten salt to generate part of the steam, replace the extraction steam of the thermal power generation system, and realize the reduction of the fuel consumption of the thermal power generation system at high load; at the same time, open the seventh valve 67, use the medium-temperature molten salt pump to pump the medium-temperature molten salt into the steam generator 23 to exchange heat with the feed water, and become low-temperature molten salt and return to the low-temperature molten salt storage tank 43, realizing the release of part of the molten salt heat to the thermal power generation system. At the same time, open the fifth valve 65, use the low-temperature molten salt pump to pump the low-temperature molten salt into the concentrating solar heat collection system 3 to absorb solar heat and become medium-temperature molten salt and return to the medium-temperature molten salt storage tank 42, realizing the conversion of solar energy into heat energy and storing it in the medium-temperature molten salt. In this working condition, the output of the entire system is relatively high. Since both the supercritical carbon dioxide system 5 and the thermal power generation system 1 are operating, the entire system can generate electricity externally through the first generator 14 and the second generator 56. By adjusting the boiler combustion evaporation amount and the flow rate of the high-temperature molten salt entering the supercritical carbon dioxide power generation system 5, the output of the entire system is regulated to meet the requirements of the load fluctuation during the peak electricity consumption period of the system.

[0053] 7) When the system is at the low valley of the electricity load at night, the thermal power generation system 1, the heat exchange system 2, and the molten salt thermal energy storage system 4 in the system operate, while the concentrating solar heat collection system 3 and the supercritical carbon dioxide power generation system 5 do not operate. Specifically: Open the first valve 61, draw part of the steam from the outlet of the boiler 11 into the first steam - molten salt heat exchanger 21 to reduce the amount of steam entering the steam turbine unit 12, and realize the reduction of the output of the thermal power generation system 1; at the same time, open the third valve, so that the low-temperature molten salt enters the first steam - molten salt heat exchanger 21 to exchange heat with the steam and become high-temperature molten salt and return to the high-temperature molten salt storage tank 41, realizing the storage of part of the steam heat in the high-temperature molten salt. In this working condition, the output of the entire system is relatively low. Since the supercritical carbon dioxide system 5 does not operate and the thermal power generation system 1 converts part of the steam into heat for storage, only thermal power is generated externally by the entire system. By adjusting the flow rate of the steam drawn from the boiler outlet, the output of the entire system is regulated to meet the requirements of the load fluctuation during the low valley period of the system's electricity consumption.

[0054] 8) When the system is at the flat peak period of the electricity load at night, the thermal power generation system 1 and the molten salt thermal energy storage system 4 in the system operate, while the heat exchange system 2, the concentrating solar collector system 3, and the supercritical carbon dioxide power generation system 5 do not operate. In this condition, only the thermal power generation system operates. By adjusting the combustion evaporation of the boiler, the output of the whole system can be regulated to meet the requirements of the load fluctuation during the flat peak period of the system's electricity consumption.

[0055] 9) When the system is at the peak period of the electricity load at night, the thermal power generation system 1, the heat exchange system 2, the molten salt thermal energy storage system 4, and the supercritical carbon dioxide power generation system 5 in the system operate, while the concentrating solar collector system 3 does not operate. Specifically: Open the eighth valve 68, and use the high-temperature molten salt pump to pump the high-temperature molten salt into the molten salt - carbon dioxide heat exchanger 52 of the supercritical carbon dioxide power generation system to exchange heat with the supercritical carbon dioxide medium, generating high-temperature carbon dioxide to drive the carbon dioxide turbine 51 to do work and generate electricity. The medium-temperature molten salt after heat exchange returns to the medium-temperature molten salt storage tank 42; at the same time, open the ninth valve 69, draw a part of the feed water from the inlet of the regenerative system 13 into the steam generator 23, and use the heat of the molten salt to generate part of the steam to replace the extraction steam of the thermal power generation system, so as to reduce the fuel consumption of the thermal power generation system 1 at high load; at the same time, open the seventh valve 67, use the medium-temperature molten salt pump to pump the medium-temperature molten salt into the steam generator 23 to exchange heat with the feed water, and it becomes low-temperature molten salt and returns to the low-temperature molten salt storage tank 43, realizing the release of part of the molten salt heat to the thermal power generation system 1. In this condition, the output of the whole system is relatively high. Since both the supercritical carbon dioxide system 5 and the thermal power generation system 1 operate, the whole system can generate electricity externally through the first generator 14 and the second generator 56. By adjusting the combustion evaporation of the boiler 11 and the flow rate of the high-temperature molten salt entering the supercritical carbon dioxide power generation system, the output of the whole system can be regulated to meet the requirements of the load fluctuation during the peak period of the system's electricity consumption.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify or equivalently replace the specific implementation manners of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention is within the scope of the protection of the claims of the present invention.

Claims

1. A thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system, characterized in that: it includes a thermal power generation system (1), a heat exchange system (2), a concentrating solar collector system (3), a molten salt energy storage system (4) and a supercritical carbon dioxide power generation system (5); Among them, the thermal power generation system (1) includes a boiler (11), a steam turbine unit (12) and a regenerative system (13) connected in sequence, and the steam turbine does work to drive the first generator (14) to generate electricity; The heat exchange system (2) includes a first steam - molten salt heat exchanger (21), a second steam - molten salt heat exchanger (22) and a steam generator (23) arranged in parallel; The molten salt energy storage system (4) includes a high - temperature molten salt storage tank (41), a medium - temperature molten salt storage tank (42), and a low - temperature molten salt storage tank (43) arranged in parallel, and several molten salt pumps are arranged on each molten salt storage tank; The supercritical carbon dioxide system (5) includes a carbon dioxide turbine (51), a molten salt - carbon dioxide heat exchanger (52), a high - temperature recuperator (53), a pre - cooler (54) and a main compressor (55) connected in sequence, and the supercritical carbon dioxide turbine does work to drive the second generator (56) to generate electricity; The outlet of the boiler (11) is respectively connected to the steam inlets of the first steam - molten salt heat exchanger (21) and the second steam - molten salt heat exchanger (22) of the steam - molten salt heat exchange system (2), and the steam outlets of the first steam - molten salt heat exchanger (21) and the second steam - molten salt heat exchanger (22) of the steam - molten salt heat exchange system (2) are respectively connected to the steam inlet of the regenerative system (13); The outlet of the low - temperature molten salt storage tank (43) of the molten salt energy storage system (4) is respectively connected to the molten salt inlets of the concentrating solar collector system (3), the first steam - molten salt heat exchanger (21) and the second steam - molten salt heat exchanger (22) in the steam - molten salt heat exchange system (2), and the molten salt outlets of the concentrating solar collector system (3) and the first steam - molten salt heat exchanger (21) are connected to the inlet of the high - temperature molten salt storage tank (41); The molten salt outlet of the second steam - molten salt heat exchanger (22) is connected to the inlet of the medium - temperature molten salt storage tank (42); The outlet of the medium - temperature molten salt storage tank (42) is respectively connected to the molten salt inlets of the concentrating solar collector system (3) and the steam generator (23) in the steam - molten salt heat exchange system (2); The molten salt outlet of the concentrating solar collector system (3) is connected to the inlet of the high - temperature molten salt storage tank (41); The molten salt outlet of the steam generator (23) is connected to the inlet of the low - temperature molten salt storage tank (43); The outlet of the high - temperature molten salt storage tank (41) is connected to the molten salt inlet of the molten salt - carbon dioxide heat exchanger (52); The molten salt outlet of the molten salt - carbon dioxide heat exchanger (52) is connected to the inlet of the medium - temperature molten salt storage tank (42).

2. The thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: Adjustable valves are provided on the pipelines from the boiler outlet of the thermal power generation system (1) to the first steam-salt heat exchanger, from the boiler outlet to the second steam-salt heat exchanger, from the low-temperature molten salt storage tank to the first steam-salt heat exchanger, from the low-temperature molten salt storage tank to the second steam-salt heat exchanger, from the low-temperature molten salt storage tank to the concentrating solar collector system, from the medium-temperature molten salt storage tank to the concentrating solar collector system, from the medium-temperature molten salt storage tank to the steam generator, from the high-temperature molten salt storage tank to the molten salt-carbon dioxide heat exchanger, and from the outlet of the steam turbine unit of the thermal power generation system to the steam generator.

3. A thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system according to claim 2, characterized in that: By controlling the opening degree of the first valve, the steam flow rate entering the first steam-salt heat exchanger from the thermal power generation system can be controlled, so as to realize the heat exchange between the steam drawn from the thermal power generation system and the low-temperature molten salt to generate high-temperature molten salt; by controlling the opening degree of the second valve, the steam flow rate entering the second steam-salt heat exchanger from the thermal power generation system can be controlled, so as to realize the heat exchange between the steam drawn from the thermal power generation system and the low-temperature molten salt to generate medium-temperature molten salt; by controlling the opening degree of the third valve, the low-temperature molten salt flow rate entering the first steam-salt heat exchanger can be controlled, so as to control the temperature of the high-temperature molten salt at the outlet of the first steam-salt heat exchanger; by controlling the opening degree of the fourth valve, the low-temperature molten salt flow rate entering the second steam-salt heat exchanger can be controlled, so as to control the temperature of the medium-temperature molten salt at the outlet of the second steam-salt heat exchanger; by controlling the opening degree of the fifth valve, the low-temperature molten salt flow rate entering the concentrating solar collector system can be controlled, so as to control the temperature of the high-temperature molten salt at the outlet of the concentrating solar collector system; by controlling the opening degree of the sixth valve, the medium-temperature molten salt flow rate entering the concentrating solar collector system can be controlled, so as to control the temperature of the high-temperature molten salt at the outlet of the concentrating solar collector system; by controlling the opening degree of the seventh valve, the medium-temperature molten salt flow rate entering the steam generator (23) can be controlled; by controlling the opening degree of the eighth valve, the high-temperature molten salt flow rate entering the molten salt-carbon dioxide heat exchanger can be controlled, so as to control the temperatures of the medium-temperature molten salt and carbon dioxide medium at the outlet of the molten salt-carbon dioxide heat exchanger; by controlling the opening degree of the ninth valve, the steam flow rate entering the steam generator (23) can be controlled, so as to control the temperatures of the low-temperature molten salt and steam medium at the outlet of the steam generator (23).

4. A thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: The concentrating solar collector system (3) is of tower type, trough type or Fresnel type; when it is of tower type, it includes a heat absorption tower and a heat absorber located at the top of the tower; when it is of trough type, it includes a number of parallel trough type collectors; when it is of Fresnel type, it includes a number of parallel Fresnel type collectors.

5. A thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: The regenerative system (13) includes multiple high-pressure heaters, a deaerator and multiple low-pressure heaters.

6. A thermal power generation, solar thermal and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: The first steam-salt heat exchanger (21) and the second steam-salt heat exchanger (22) are in single-stage or multi-stage series connection; the steam generator (23) includes a preheater, an evaporator, and a superheater.

7. A thermal power generation, solar thermal, and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: Both the high-temperature recuperator (53) and the precooler (54) are in single-stage or multi-stage series connection.

8. A thermal power generation, solar thermal, and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: The main compressor (55) is a single-stage compressor or a multi-stage series compressor. When it is in multi-stage series, a cooling device is provided between each stage.

9. A thermal power generation, solar thermal, and supercritical carbon dioxide combined power generation system according to claim 1, characterized in that: The molten salt used is a binary molten salt including sodium nitrate and potassium nitrate; electric tracing is provided for the molten salt pipelines for transporting high-temperature molten salt, medium-temperature molten salt, and low-temperature molten salt.

10. An operation method for the thermal power generation, solar thermal, and supercritical carbon dioxide combined power generation system according to any one of claims 1 to 9, characterized in that, it includes the following operation modes: 1) When the solar energy resource condition is good during the day and the system is at a low electricity load period, the thermal power generation system (1), the heat exchange system (2), the concentrating solar collection system (3), and the molten salt energy storage system (4) in the system operate, and the supercritical carbon dioxide power generation system (5) does not operate; 2) When the solar energy resource condition is good during the day and the system is at a flat electricity load period, the thermal power generation system (1), the concentrating solar collection system (3), and the molten salt energy storage system (4) in the system operate, and the heat exchange system (2) and the supercritical carbon dioxide power generation system (5) do not operate; 3) When the solar energy resource condition is good during the day and the system is at a high electricity load period, the thermal power generation system (1), the heat exchange system (2), the concentrating solar collection system (3), the molten salt energy storage system (4), and the supercritical carbon dioxide power generation system (5) in the system operate; 4) When the solar energy resource condition is poor during the day and the system is at a low electricity load period, the thermal power generation system (1), the heat exchange system (2), the concentrating solar collection system (3), and the molten salt energy storage system (4) in the system operate, and the supercritical carbon dioxide power generation system (5) does not operate; 5) When the solar energy resource condition is poor during the day and the system is at a flat electricity load period, the thermal power generation system (1), the concentrating solar collection system (3), and the molten salt energy storage system (4) in the system operate, and the heat exchange system (2) and the supercritical carbon dioxide power generation system (5) do not operate; 6) When the solar energy resource condition is poor during the day and the system is at a high electricity load period, the thermal power generation system (1), the heat exchange system (2), the concentrating solar collection system (3), the molten salt energy storage system (4), and the supercritical carbon dioxide power generation system (5) in the system operate; 7) When the system is at a low electricity load period at night, the thermal power generation system (1), the heat exchange system (2), and the molten salt energy storage system (4) in the system operate, and the concentrating solar collection system (3) and the supercritical carbon dioxide power generation system (5) do not operate; 8) When the system is at the flat peak period of the electricity load at night, the thermal power generation system (1) and the molten salt energy storage system (4) in the system operate, while the heat exchange system (2), the concentrating solar collector system (3), and the supercritical carbon dioxide power generation system (5) do not operate; 9) When the system is at the peak period of the electricity load at night, the thermal power generation system (1), the heat exchange system (2), the molten salt energy storage system (4), and the supercritical carbon dioxide power generation system (5) in the system operate, while the concentrating solar collector system (3) does not operate.

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