Decarburization coal power system coupled with reversible Brayton cycle heat pump and operation method

Abstract

The invention discloses a decarburization coal power system coupled with a reversible Brayton cycle heat pump and a method thereof. The decarburization coal power system comprises a coal-fired power generation subsystem used for converting heat into electric energy, a decarburization subsystem used for treating carbon dioxide emission and a heat pump heat storage subsystem used for improving the energy utilization efficiency. Exhausted smoke of a boiler in the coal-fired power generation subsystem passes through a smoke steam cooler in the decarburization subsystem and then enters an absorption tower; the coal-fired power generation subsystem sends high-temperature steam generated by a boiler into the heat pump heat storage subsystem through a high-pressure cylinder and an intermediate-pressure cylinder, and the heat pump heat storage subsystem stores high-temperature molten salt after heat absorption into a high-temperature storage tank. The system has the beneficial effects that the heat pump heat storage subsystem is constructed through the reversible Brayton cycle, supercritical carbon dioxide is adopted as a cycle working medium, and a phase change material and molten salt are adopted as heat storage media, so that the energy storage density is improved, and the stability and high efficiency of the heat storage and release process are guaranteed; therefore, the system can better adapt to fluctuation of the power grid load, and quick response is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power plant decarbonization energy storage and peak shaving, in particular to a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump and a method thereof. Background Art

[0002] As a major carbon dioxide emission source, the power industry urgently needs to adopt effective emission reduction measures. Post-combustion carbon capture and storage (CCS) technology is considered a key means to reduce carbon emissions from coal-fired power plants. Among them, the carbon capture technology based on monoethanolamine (MEA) solvent has been widely adopted due to its mature process, high capture efficiency and low cost.

[0003] However, the MEA carbon capture process consumes a large amount of thermal energy and releases low-grade waste heat at the same time. Usually, the heat required by the reboiler comes from the extraction steam of the intermediate and low-pressure cylinders of the steam turbine, which will lead to a significant reduction in the power generation efficiency of coal-fired power plants and have a certain impact on the safety of the low-pressure cylinders. In addition, with the rapid growth of renewable energy sources with significant time-varying characteristics such as wind energy and solar energy, the demand for the operating flexibility of coal-fired power plants is also continuously increasing. The heat pump energy storage subsystem is a large-scale power storage technology that can achieve electricity-added heating and efficient thermoelectric conversion, and is a promising high-efficiency large-scale energy storage solution. Coupling the heat pump energy storage technology with the carbon capture coal-fired power generation system can effectively recover the low-grade waste heat in carbon capture, and is expected to reduce the energy efficiency penalty while achieving CO2 emissions reduction, and realize the safe and efficient peak shaving operation of coal-fired power plants. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the specification of this application, to avoid obscuring the purpose of this part, the abstract and the title of the specification, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] In view of the problems existing in the above or prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to provide a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump and a method thereof, which can effectively reduce the carbon capture energy efficiency penalty in the coal-fired power generation system, further expand the unit peak shaving range, improve the system operation flexibility, and achieve efficient energy storage and conversion.

[0007] To solve the above technical problems, the present invention provides the following technical solution: A decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump, which includes a coal-fired power generation subsystem that converts heat into electrical energy, a decarbonization subsystem for treating carbon dioxide emissions, and a heat pump energy storage subsystem for improving energy utilization efficiency; the flue gas discharged from the boiler in the coal-fired power generation subsystem enters the absorption tower after passing through the flue gas cooler in the decarbonization subsystem; the coal-fired power generation subsystem sends the high-temperature steam generated by the boiler into the heat pump energy storage subsystem through the high-pressure cylinder and the intermediate-pressure cylinder, and the heat pump energy storage subsystem stores the heat-absorbed high-temperature molten salt in the high-temperature storage tank.

[0008] As a preferred embodiment of the decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump of the present invention, wherein: the coal-fired power generation subsystem includes that the main steam outlet of the boiler is connected to the high-pressure cylinder, and the reheated steam outlet of the boiler is connected to the intermediate-pressure cylinder; the coal-fired power generation subsystem further includes that the other end of the intermediate-pressure cylinder is provided with a low-pressure cylinder, the other end of the low-pressure cylinder is provided with a generator, a condenser connected to the exhaust port of the low-pressure cylinder, and the other end of the condenser is provided with a condensate pump.

[0009] As a preferred embodiment of the decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump of the present invention, wherein: the coal-fired power generation subsystem further includes a high-pressure heater group connected to the high-pressure extraction steam of the high-pressure cylinder and the intermediate-pressure cylinder, and a low-pressure heater group connected to the low-pressure extraction steam of the intermediate-pressure cylinder and the low-pressure cylinder.

[0010] As a preferred embodiment of the decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump of the present invention, wherein: the exhaust steam of the intermediate-pressure cylinder is divided into three paths, one path is used to heat part of the feed water of the low-pressure heater group, one path is connected to the steam inlet of the low-pressure cylinder through a throttle valve, and one path passes through a regulating valve and enters the heat pump energy storage subsystem through the exhaust port; the intermediate extraction steam of the intermediate-pressure cylinder is divided into three paths, one path is used to heat part of the feed water of the high-pressure heater group, one path is used to heat the condensate water in the deaerator, and one path enters the small steam turbine through the extraction port.

[0011] As a preferred embodiment of the decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump of the present invention, wherein: after the deaerator receives the condensate water from the outlet of the low-pressure heater group and the drain water of the high-pressure heater group, it enters the high-pressure heater group again through the feed water pump and enters the boiler through the high-pressure heater group.

[0012] As a preferred embodiment of the decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump of the present invention, wherein: the decarbonization subsystem further includes that a rich liquid pump is provided at the bottom of the absorption tower, the other end of the rich liquid pump is provided with a rich and lean liquid heat exchanger, the other end of the rich and lean liquid heat exchanger is connected to the desorption tower, a reboiler is provided at the bottom of the desorption tower, a condenser is provided at the top of the desorption tower, and a steam-water separator is provided at the other end of the condenser; the outlet of the reboiler is also connected to the inlet of the condenser.

[0013] As a preferred embodiment of the decarbonized coal-fired power system with a coupled reversible Brayton cycle heat pump according to the present invention, the decarbonization subsystem further includes a lean liquid cooler provided at the other end of the rich-lean liquid heat exchanger. The lean liquid cooler is connected to the absorption tower through a manifold valve, and an absorption tower exhaust cooling pump is also provided on the absorption tower.

[0014] As a preferred embodiment of the decarbonized coal-fired power system with a coupled reversible Brayton cycle heat pump according to the present invention, the heat pump heat storage subsystem includes a high-temperature storage tank and a low-temperature storage tank. The high-temperature storage tank is connected to the hot-side inlet of the high-temperature heat exchanger through a first valve, and the hot-side outlet of the high-temperature heat exchanger is connected to the inlet of the low-temperature storage tank. The low-temperature storage tank is connected to the cold-side inlet of the low-temperature heat exchanger through a second valve, and the cold-side outlet of the low-temperature heat exchanger is connected to the inlet of the high-temperature storage tank.

[0015] As a preferred embodiment of the decarbonized coal-fired power system with a coupled reversible Brayton cycle heat pump according to the present invention, the heat pump heat storage subsystem further includes a first compressor and a second compressor. The first compressor is connected to a first high-temperature recuperator through a low-temperature heat exchanger. The first high-temperature recuperator is connected to a low-temperature recuperator through a first turbine, and the other end of the low-temperature recuperator is connected to the first compressor. The second compressor is connected to the high-temperature heat exchanger through a second high-temperature recuperator. The high-temperature heat exchanger is connected to a cooler through a second turbine, and the other end of the cooler is connected to the second compressor. The hot-side outlet of the second high-temperature recuperator is also connected to the main inlet of an ejector. The outlet of the first high-temperature recuperator and the outlet of the ejector are also connected to the inlet of a reboiler. The inlet working fluid of the first high-temperature recuperator and the inlet working fluid of the second high-temperature recuperator both come from the exhaust steam of the intermediate pressure cylinder in the coal-fired power generation subsystem. The hot-side inlet of the low-temperature recuperator and the inlet of the ejector are also connected to the cold-side outlet of a steam separator.

[0016] To solve the above technical problems, the present invention provides the following technical solution: A decarbonized coal-fired power operation method with a coupled reversible Brayton cycle heat pump, including a decarbonized coal-fired power system with a coupled reversible Brayton cycle heat pump.

[0017] Drive a steam turbine to generate electricity through the coal-fired power generation subsystem, and extract part of the steam for carbon capture and the heat pump heat storage subsystem.

[0018] The flue gas from the coal-fired power generation subsystem enters the absorption tower after being cooled, is absorbed by the MEA solution to remove CO2, the desorption tower releases CO2 and regenerates the lean liquid, and saturated steam is generated using the waste heat.

[0019] The heat storage process of the heat pump heat storage subsystem: Use the excess power from the power grid to drive Compressor I, compress and heat up the low-temperature working fluid, heat the low-temperature molten salt and store it in the high-temperature storage tank, converting electrical energy into heat energy.

[0020] Heat release process of the heat pump energy storage subsystem: High-temperature molten salt heats the working medium, driving Turbine II to do work, and the generated mechanical energy is used for power generation, converting thermal energy into electrical energy;

[0021] During the heat storage and heat release processes, the heat from the extraction steam of the intermediate-pressure cylinder and part of the heat released by CO2 are mixed through an ejector and jointly provide heat source for the reboiler in the decarbonization subsystem for the desorption of CO2;

[0022] Couple the coal-fired power generation subsystem, the decarbonization subsystem and the heat pump energy storage subsystem, supply heat to the heat pump and the reboiler through the extraction steam of the intermediate-pressure cylinder, and preheat the working medium with the waste heat steam.

[0023] Advantages of the present invention: The heat pump energy storage subsystem constructed by the reversible Brayton cycle realizes efficient energy conversion and storage, and has significant environmental and economic benefits; this system is not restricted by geographical conditions, can store heat on a large scale for a long period, and because supercritical carbon dioxide is used as the circulating working medium, the round-trip efficiency and power density are improved. In addition, the present invention effectively recovers the waste heat of the MEA carbon capture system by integrating the heat pump energy storage subsystem, reduces energy waste, and at the same time replaces part of the steam for decarbonization to provide heat for the reboiler, reducing the energy consumption in the carbon capture process. More importantly, this system can store excess electric energy in molten salt during the low electricity consumption period, smooth the power grid fluctuations, absorb new energy, expand the unit peak shaving interval, increase the peak shaving depth, and enhance the stability and flexibility of the power grid. The present invention not only improves the energy utilization efficiency of coal-fired power plants as a whole, but also provides strong support for the stable operation of the power grid and the efficient utilization of new energy. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0025] Figure 1 It is a schematic diagram of the overall structure of a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump.

[0026] Figure 2 It is a schematic diagram of a partial structure of a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump.

[0027] Figure 3 It is a schematic diagram of a partial structure of a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump.

[0028] Figure 4 It is a schematic diagram of the overall flow of the operation method of a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump. Detailed Embodiments

[0029] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or selectively exclusive embodiments from other embodiments.

[0032] Embodiment 1

[0033] Referring to Figure 1 , this is the first embodiment of the present invention. This embodiment provides a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump, which includes a coal-fired power generation subsystem 100 that converts heat into electrical energy, a decarbonization subsystem 200 for treating carbon dioxide emissions, and a heat pump energy storage subsystem 300 for improving energy utilization efficiency.

[0034] Specifically, the flue gas from the boiler 101 in the coal-fired power generation subsystem 100 enters the flue gas cooler 201 in the decarbonization subsystem 200 and then enters the absorption tower 202; the coal-fired power generation subsystem 100 sends the high-temperature steam generated by the boiler 101 into the heat pump energy storage subsystem 300 through the high-pressure cylinder 102 and the intermediate-pressure cylinder 103.

[0035] It should be noted that the heat pump in the heat pump energy storage subsystem 100 adopts a reversible Brayton cycle, with a COP greater than 4.0. The working medium of the reversible Brayton heat pump cycle is supercritical carbon dioxide, which has a large power density and can achieve a high round-trip efficiency.

[0036] It should be noted that the boiler 101 in the coal-fired power generation subsystem 100 is a circulating fluidized bed boiler, with an operating temperature of 900 °C, a pressure of 25 MPa, and a combustion efficiency of over 90%.

[0037] It should be noted that the inlet steam temperature of the high-pressure cylinder is 550 °C and the pressure is 17 MPa; the inlet steam temperature of the intermediate-pressure cylinder is 450 °C and the pressure is 10 MPa.

[0038] It should be noted that the high-temperature steam generated by the boiler 101 has a temperature of 500 °C and a pressure of 12 MPa. The flue gas passes through the indirect contact flue gas cooler 201 in the decarbonization subsystem 200, and the cooling efficiency is greater than 90%. After cooling, the temperature of the flue gas drops to 150 °C and then enters the absorption tower 202.

[0039] It should be noted that the absorption tower 202 uses ceramic packing, and the CO2 absorption efficiency reaches 96%. The high-temperature steam is sent to the heat pump heat storage subsystem 300, where the COP of the heat pump is 4.2, the heat storage medium is a phase change material, and the phase change temperature is 350 °C.

[0040] It should be noted that the heat storage medium used in the heat pump heat storage subsystem 300 is molten salt, and the operating temperature range of the molten salt is 300 °C to 400 °C, effectively ensuring the high efficiency of energy storage.

[0041] In summary, the system of the present invention not only improves the energy conversion efficiency but also reduces environmental pollution through the efficient combustion of the boiler, the efficient cooling and CO2 absorption of the flue gas, the effective utilization of high-temperature steam, and the high COP and phase change heat storage of the heat pump heat storage subsystem, effectively realizing the improvement of energy utilization efficiency and the reduction of CO2 emissions. This system uses supercritical carbon dioxide as the working medium and achieves a high COP value of 4.2, which means that the system can output more heat energy with less power consumption, significantly improving the energy utilization efficiency. This system also uses phase change materials and molten salt as heat storage media, which not only improves the energy storage density but also ensures the stability and efficiency of the heat storage and release process, enabling the system to better adapt to the fluctuations of the power grid load and achieve rapid response.

[0042] Embodiment 2

[0043] Refer to Figures 1 - 2 , which is the second embodiment of the present invention. This embodiment provides a decarbonized coal-fired power generation system coupled with a reversible Brayton cycle heat pump, which includes a coal-fired power generation subsystem 100 and a decarbonization subsystem 200. Their mutual cooperation improves the energy utilization efficiency, and through the decarbonization effect of the absorption tower 202, the carbon dioxide emissions during coal-fired power generation are reduced.

[0044] Specifically, in the coal-fired power generation subsystem 100, the main steam outlet of the boiler 101 is connected to the high-pressure cylinder 102, and the reheated steam outlet of the boiler 101 is connected to the intermediate-pressure cylinder 103; the coal-fired power generation subsystem 100 also includes that the other end of the intermediate-pressure cylinder 103 is provided with a low-pressure cylinder 104, the other end of the low-pressure cylinder 104 is provided with a generator 105, a condenser 106 connected to the exhaust port of the low-pressure cylinder 104, and a condensate pump 107 is also provided at the other end of the condenser 106.

[0045] Specifically, the coal-fired power generation subsystem 100 further includes a high-pressure heater group 108 connected to the high-pressure extraction steam of the high-pressure cylinder 102 and the intermediate-pressure cylinder 103, and a low-pressure heater group 109 connected to the low-pressure extraction steam of the intermediate-pressure cylinder 103 and the low-pressure cylinder 104.

[0046] It should be noted that the feed water enters the boiler 101, generates main steam and then enters the high-pressure cylinder 102. Part of the intermediate extraction steam of the high-pressure cylinder 102 is used to heat part of the feed water of the high-pressure heater group 108. The exhaust steam of the high-pressure cylinder 102 returns to the boiler 101 for reheating, generates reheated steam and then enters the intermediate-pressure cylinder 103.

[0047] It should be noted that part of the intermediate extraction steam of the low-pressure cylinder 104 is used to heat part of the feed water of the low-pressure heater group 109.

[0048] It should be noted that the high-pressure cylinder 102, the intermediate-pressure cylinder 103, and the low-pressure cylinder 104 are coaxially connected, transfer the generated mechanical energy to the generator 105, and output the generated electric energy to the outside.

[0049] Specifically, the exhaust steam of the intermediate-pressure cylinder 103 is divided into three paths. One path is used to heat part of the feed water of the low-pressure heater group 109. One path is connected to the steam inlet of the low-pressure cylinder 104 through a throttle valve 110. One path passes through a regulating valve 111 and enters the heat pump energy storage subsystem 300 through an exhaust port Z. The intermediate extraction steam of the intermediate-pressure cylinder 103 is divided into three paths. One path is used to heat part of the feed water of the high-pressure heater group 108. One path is used to heat the condensate water in the deaerator 112. One path enters the small steam turbine 114 through an extraction port X.

[0050] Furthermore, the inlet steam of the small steam turbine 114 comes from the extraction steam of the intermediate-pressure cylinder 103, and the steam outlet of the small steam turbine 114 is also connected to the steam inlet of the condenser 106.

[0051] Specifically, after the deaerator 112 receives the condensate water from the outlet of the low-pressure heater group 109 and the drain water of the high-pressure heater group 108, it enters the high-pressure heater group 108 again through the feed water pump 113, and enters the boiler 101 through the high-pressure heater group 108.

[0052] Specifically, the decarbonization subsystem 200 further includes a rich liquid pump 203 arranged at the bottom of the absorption tower 202, a rich-lean liquid heat exchanger 204 arranged at the other end of the rich liquid pump 203, the other end of the rich-lean liquid heat exchanger 204 is connected to the desorption tower 205, a reboiler 206 is arranged at the bottom of the desorption tower 205, a condenser 207 is arranged at the top of the desorption tower 205, and a steam-water separator 208 is arranged at the other end of the condenser 207; the outlet of the reboiler 206 is also connected to the inlet of the condenser 106.

[0053] Further, the cold-side outlet of the steam-water separator 208 is connected to the hot-side inlet of the low-temperature recuperator 311 and the ejector inlet of the ejector 315 in the heat storage subsystem 300 of the heat pump.

[0054] It should be noted that the flue gas outlet temperature of the flue gas cooler 201 drops to 150 °C.

[0055] It should be noted that the MEA solvent circulation volume of the absorption tower 202 is 2000 liters per hour, and the CO2 absorption efficiency reaches 95%. The main fluid pressure is 0.35 MPa, and the mixed gas flow pressure is stabilized at 0.3 MPa by ejecting waste heat steam.

[0056] Specifically, the decarbonization subsystem 200 further includes that the other end of the rich and lean liquid heat exchanger 204 is provided with a lean liquid cooler 209, which is connected to the absorption tower 202 through a manifold valve 210; an absorption tower exhaust gas cooling pump 211 is also provided on the absorption tower 202.

[0057] It should be noted that the lean liquid cooler 209 heats an industrial water at 25 °C through carbon capture waste heat to form a saturated steam, which reduces the extraction steam of the intermediate pressure cylinder 1033 during the heat release process and effectively reduces the energy efficiency penalty.

[0058] The flue gas treatment process of the decarbonization subsystem 200 is as follows:

[0059] The flue gas generated by the boiler 101 is cooled after being treated and then enters the flue gas cooler 201, and then enters the absorption tower 202 to be absorbed by the MEA solvent to form a rich liquid, enters the rich and lean liquid heat exchanger 204 through the rich liquid pump 203, is heated and then enters the desorption tower 205, and forms a mixed gas of carbon dioxide and water vapor under the action of the reboiler 206, and successively passes through the condenser 207 and the steam-water separator 208;

[0060] The lean liquid at the bottom of the desorption tower 205 successively passes through the rich and lean liquid heat exchanger 204 and the lean liquid cooler 209, the temperature drops, and then enters the absorption tower 202 together with the supplemented MEA and water through the manifold valve 210 to complete the cycle;

[0061] Among them, the waste heat recovery process is that a feed water at 25 °C successively exchanges heat through the lean liquid cooler 209, the flue gas cooler 201, the absorption tower exhaust gas cooling pump 211 and the steam-water separator 208, and finally forms a saturated steam;

[0062] The condensate of the reboiler 206, the exhaust steam of the small steam turbine 114, the exhaust steam of the low-pressure cylinder 104, and the drain water of the low-pressure heater group 109 converge into the condenser 106 together, where condensation occurs to produce condensate. After passing through the condensate pump 107, it enters the low-pressure heater group 109. The condensate at the outlet of the low-pressure heater group 109 and the drain water from the high-pressure heater group 108 converge into the deaerator 112 together. After the deaerator 112 produces saturated feed water, a part enters the heat pump energy storage subsystem 300, and a part enters the high-pressure heater group 108 through the feed water pump 113, and then enters the boiler 101. After new steam is generated in the boiler, it enters the high-pressure cylinder 102, and this process is repeated.

[0063] In summary, through optimizing the synergy between the coal-fired power generation subsystem and the carbon capture subsystem, the present invention significantly improves the energy utilization efficiency and reduces CO2 emissions. The main steam and reheated steam generated by the boiler enter the high-pressure cylinder and the intermediate-pressure cylinder respectively, and the mechanical energy is transmitted to the generator through the coaxially connected cylinders, improving the energy conversion efficiency. The reasonable distribution of the exhaust steam of the intermediate-pressure cylinder and the utilization of the extraction steam in the middle realize the efficient thermal energy management of the heater group and the deaerator. The carbon capture subsystem absorbs CO2 in the flue gas through the MEA solvent in the absorption tower, forms rich liquid and finally releases a mixed gas of CO2 and water vapor, significantly reducing the carbon dioxide emissions during the coal-fired power generation process. The circulation rate of the MEA solvent is 2000 liters per hour, and the CO2 absorption efficiency reaches 95%. By using regulating valves and throttle valves, the system enhances the peak shaving ability. The setting of the small steam turbine allows part of the extraction steam to be directly used for power generation, improving the energy utilization flexibility of the system. Waste heat recovery equipment such as the lean liquid cooler uses the waste heat from carbon capture to heat industrial water to form saturated steam, effectively utilizing the heat energy that might otherwise be wasted, reducing the extraction steam demand of the intermediate-pressure cylinder, reducing the energy efficiency penalty, and improving the overall energy utilization efficiency. These technical steps provide an efficient and environmentally friendly coal-fired power generation solution, effectively promoting the sustainable development of the energy industry.

[0064] Embodiment 3

[0065] Referring to Figures 1 - 3 , this is the third embodiment of the present invention. This embodiment provides a decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump, which realizes the heat transfer from a low-temperature heat source to a high-temperature heat source through the heat pump energy storage subsystem 300, thereby improving the energy utilization efficiency of the entire system.

[0066] Specifically, the heat storage module of the heat pump energy storage subsystem 300 includes a high-temperature storage tank 301 and a low-temperature storage tank 302; the high-temperature storage tank 301 is connected to the hot-side inlet of the high-temperature heat exchanger 304 through a first valve 305, and the hot-side outlet of the high-temperature heat exchanger 304 is connected to the inlet of the low-temperature storage tank 302; the low-temperature storage tank 302 is connected to the cold-side inlet of the low-temperature heat exchanger 306 through a second valve 303, and the cold-side outlet of the low-temperature heat exchanger 306 is connected to the inlet of the high-temperature storage tank 301.

[0067] Further, the high-temperature storage tank 301, the low-temperature storage tank 302, the first valve 303, the high-temperature heat exchanger 304, the second valve 305, and the low-temperature heat exchanger 306 constitute a module for closed-loop heat energy storage and release in the heat pump heat storage subsystem 300.

[0068] It should be noted that the heat storage media used in the high-temperature storage tank 301 and the low-temperature storage tank 302 are molten salts.

[0069] Specifically, the heat pump heat storage subsystem 300 further includes a first compressor 307 and a second compressor 308; the first compressor 307 is connected to a first high-temperature recuperator 309 through the low-temperature heat exchanger 306, the first high-temperature recuperator 309 is connected to a low-temperature recuperator 311 through a first turbine 310, and the other end of the low-temperature recuperator 311 is connected to the first compressor 307; the second compressor 308 is connected to the high-temperature heat exchanger 304 through a second high-temperature recuperator 312, the high-temperature heat exchanger 304 is connected to a cooler 314 through a second turbine 313, and the other end of the cooler 314 is connected to the second compressor 308; the hot-side outlet of the second high-temperature recuperator 312 is also connected to the main inlet of an ejector 315; the outlet of the first high-temperature recuperator 309 and the outlet of the ejector 315 are also connected to the inlet of a reboiler 206; the inlet working fluids of the first high-temperature recuperator 309 and the second high-temperature recuperator 312 both come from the exhaust steam of the intermediate-pressure cylinder 103 in the coal-fired power generation subsystem 100; the hot-side inlet of the low-temperature recuperator 311 and the inlet of the ejector 315 are also connected to the cold-side outlet of a steam-water separator 208.

[0070] Further, the first compressor 307, the second compressor 308, the first high-temperature recuperator 309, the first turbine 310, the low-temperature recuperator 311, the second high-temperature recuperator 312, the second turbine 313, the cooler 314, and the ejector 315 constitute a heat pump module of a reversible Brayton cycle in the heat storage module heat pump heat storage subsystem 300.

[0071] It should be noted that the inlet working fluid pressures of the first compressor 307 and the second compressor 308 are 8 - 10 MPa, and the outlet working fluid pressures are 25 - 30 MPa. The inlet working fluid pressure of the main compressor is maintained above the critical point to keep the whole cycle in a supercritical state.

[0072] It should be noted that the inlet working fluid temperatures of the first high-temperature recuperator 309 and the second high-temperature recuperator 312 are 120 °C, and the outlet working fluid temperatures are 300 °C.

[0073] It should be noted that the main fluid of the ejector 315 is steam with a pressure greater than 0.3 MPa. The ejector uses waste heat steam to make the pressure of the mixed gas flow 0.3 MPa, so as to ensure the stable pressure of the heating steam entering the reboiler 206 and improve the safety and economy of the system.

[0074] Heat storage process of the heat pump heat storage subsystem 300: Open the second valve 305 and close the first valve 303. Use the excess power from the power grid to drive the first compressor 307 to compress the carbon dioxide working medium at the cold side outlet of the low-temperature recuperator 311 to a high-temperature and high-pressure state. Then, transfer the heat to the low-temperature molten salt in the low-temperature heat exchanger 306 (low-temperature heat exchanger 28). The high-temperature molten salt after absorbing heat is stored in the high-temperature storage tank 301. The carbon dioxide at the hot side outlet of the low-temperature heat exchanger 306 enters the first high-temperature recuperator 309 to absorb the heat from the extraction steam of the intermediate-pressure cylinder 103, and then enters the first turbine 310 to do work. After absorbing the heat of the waste heat steam in the low-temperature recuperator 311, it enters the first compressor 307 to complete the cycle. Therefore, the charging process is to convert the excess power into high-grade heat energy and store it in the high-temperature storage tank.

[0075] Heat release process of the heat pump heat storage subsystem 300: Open the first valve 303 and close the second valve 305. The high-temperature and high-pressure carbon dioxide working medium coming out of the high-temperature heat exchanger 304 enters the second turbine 313 to do work, and then enters the cooler 314 to release heat. After that, it enters the second compressor 308. The working medium at the outlet of the second compressor 308 sequentially enters the cold side of the second high-temperature recuperator 312 and the cold side of the high-temperature heat exchanger 304 to absorb heat and complete the cycle. Therefore, the heat release process is to convert the stored high-grade heat energy into electric energy according to the power grid demand.

[0076] In summary, the system of the present invention can convert the excess electric energy into high-grade heat energy for storage during the low electricity consumption period, and at the same time convert the stored heat energy back into electric energy during the peak period, improving the peak shaving ability and energy utilization efficiency of the system. In addition, the system effectively recovers the waste heat of the MEA carbon capture system, reduces the energy efficiency penalty in the carbon capture process, and realizes the safe and efficient peak shaving operation of the coal-fired power plant.

[0077] Embodiment 4

[0078] Referring to Figure 4 , the fourth embodiment of the present invention provides a decarbonized coal power operation method coupled with a reversible Brayton cycle heat pump, which includes.

[0079] Drive the steam turbine to generate electricity through the coal-fired power generation subsystem, and extract part of the steam for carbon capture and the heat pump heat storage subsystem;

[0080] The flue gas of the coal-fired power generation subsystem enters the absorption tower after cooling, is absorbed by the MEA solution for CO2, the desorption tower releases CO2 and regenerates the lean liquid, and uses the waste heat to generate saturated steam;

[0081] Heat storage process of the heat pump heat storage subsystem: Use the excess power from the power grid to drive the compressor I to compress and heat up the low-temperature working medium, heat the low-temperature molten salt and store it in the high-temperature storage tank, and convert the electric energy into heat energy;

[0082] Heat release process of the heat pump thermal energy storage subsystem: The high-temperature molten salt heats the working medium, drives the turbine II to do work, and the generated mechanical energy is used for power generation, converting thermal energy into electrical energy;

[0083] During the heat storage and heat release processes, the heat from the extraction steam of the intermediate pressure cylinder and part of the heat released by CO2 are mixed through an ejector and jointly provide heat source for the reboiler in the decarbonization subsystem for the desorption of CO2;

[0084] Couple the coal-fired power generation subsystem, the decarbonization subsystem and the heat pump thermal energy storage subsystem, supply heat to the heat pump and the reboiler through the extraction steam of the intermediate pressure cylinder, and use the waste heat steam to preheat the working medium.

[0085] Importantly, it should be noted that the configurations and arrangements of the present application shown in multiple different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who refer to this disclosure should easily understand that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in this application (for example, the dimensions, scales, structures, shapes and proportions of various components, as well as parameter values (such as temperature, pressure, etc.), installation arrangements, use of materials, color, orientation changes, etc.). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature, number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "means-plus-function" clause is intended to cover the structures that perform the recited function herein, and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangements of the exemplary embodiments without departing from the scope of the present invention. Therefore, the present invention is not limited to a specific embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0086] In addition, in order to provide a concise description of the exemplary embodiments, not all features of the actual embodiments may be described (i.e., those features that are not relevant to the currently considered best mode of implementing the present invention or those features that are not relevant to implementing the present invention).

[0087] It should be understood that in the development of any actual implementation, as in any engineering or design project, a large number of specific implementation decisions may be made. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, without excessive experimentation, such development efforts will be a routine work of design, manufacturing and production.

[0088] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump, characterized in that: include, A coal-fired power generation subsystem (100) for converting heat into electrical energy, a decarbonization subsystem (200) for treating carbon dioxide emissions, and a heat pump heat storage subsystem (300) for improving energy utilization efficiency; The exhaust smoke of the boiler (101) in the coal-fired power generation subsystem (100) passes through the smoke cooler (201) in the decarbonization subsystem (200) and then enters the absorption tower (202); The coal-fired power generation subsystem (100) delivers high-temperature steam generated by the boiler (101) to the heat pump heat storage subsystem (300) through the high-pressure cylinder (102) and the medium-pressure cylinder (103), and the heat pump heat storage subsystem (300) stores the high-temperature molten salt after absorbing heat in the high-temperature storage tank (301).

2. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 1, characterized in that: The coal-fired power generation subsystem (100) comprises a main steam outlet of a boiler (101) connected to a high-pressure cylinder (102), and a reheat steam outlet of the boiler (101) connected to a medium-pressure cylinder (103); The coal-fired power generation subsystem (100) further includes: a low-pressure cylinder (104) is provided at the other end of the medium-pressure cylinder (103), a generator (105) is provided at the other end of the low-pressure cylinder (104), a condenser (106) connected to the exhaust port of the low-pressure cylinder (104), and a condensate pump (107) is provided at the other end of the condenser (106).

3. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 2, characterized in that: The coal-fired power generation subsystem (100) further includes a high-pressure heater group (108) connected to the high-pressure extraction steam of the high-pressure cylinder (102) and the medium-pressure cylinder (103), and a low-pressure heater group (109) connected to the low-pressure extraction steam of the medium-pressure cylinder (103) and the low-pressure cylinder (104).

4. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 3, characterized in that: The exhaust steam of the intermediate pressure cylinder (103) is divided into three paths, one path is used to heat part of the feed water of the low pressure heater group (109), one path is connected to the steam inlet of the low pressure cylinder (104) through the throttle valve (110), and one path passes through the regulating valve (111) and enters the heat pump heat storage subsystem (300) through the exhaust port (Z); The intermediate extraction steam of the medium pressure cylinder (103) is divided into three paths, one path is used to heat part of the feed water of the high pressure heater group (108), one path is used to heat the condensate in the deaerator (112), and one path enters the small steam turbine (114) through the extraction port (X).

5. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 4, characterized in that: After the deaerator (112) receives the condensate from the outlet of the low-pressure heater group (109) and the drain from the high-pressure heater group (108), it enters the high-pressure heater group (108) again through the feed water pump (113) and enters the boiler (101) through the high-pressure heater group (108).

6. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 5, characterized in that: The decarbonization subsystem (200) further includes: a rich liquid pump (203) is provided at the bottom of the absorption tower (202); a lean-rich liquid heat exchanger (204) is provided at the other end of the rich liquid pump (203); the other end of the lean-rich liquid heat exchanger (204) is connected to a desorption tower (205); a reboiler (206) is provided at the bottom of the desorption tower (205); a condenser (207) is provided at the top of the desorption tower (205); and a steam-water separator (208) is provided at the other end of the condenser (207); The outlet of the reboiler (206) is also connected to the inlet of the condenser (106).

7. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 6, characterized in that: The decarbonization subsystem (200) further includes: a lean liquid cooler (209) is provided at the other end of the lean-rich liquid heat exchanger (204), and the lean liquid cooler (209) is connected to the absorption tower (202) via a collecting valve (210); The absorption tower (202) is also provided with an absorption tower exhaust steam cooling pump (211).

8. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 7, characterized in that: The heat pump heat storage subsystem (300) comprises a high-temperature storage tank (301) and a low-temperature storage tank (302); The high-temperature storage tank (301) is connected to the hot side inlet of the high-temperature heat exchanger (304) through a first valve (303), and the hot side outlet of the high-temperature heat exchanger (304) is connected to the inlet of the low-temperature storage tank (302); The low-temperature storage tank (302) is connected to the cold side inlet of the low-temperature heat exchanger (306) through a second valve (305), and the cold side outlet of the low-temperature heat exchanger (306) is connected to the inlet of the high-temperature storage tank (301).

9. The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in claim 8, characterized in that: The heat pump thermal storage subsystem (300) further includes a first compressor (307) and a second compressor (308); The first compressor (307) is connected to a first high-temperature regenerator (309) via a low-temperature heat exchanger (306); the first high-temperature regenerator (309) is connected to a low-temperature regenerator (311) via a first turbine (310); and the other end of the low-temperature regenerator (311) is connected to the first compressor (307); The second compressor (308) is connected to the high-temperature heat exchanger (304) via a second high-temperature regenerator (312), the high-temperature heat exchanger (304) is connected to a cooler (314) via a second turbine (313), and the other end of the cooler (314) is connected to the second compressor (308); The hot side outlet of the second high-temperature regenerator (312) is also connected to the main inlet of the ejector (315); The outlet of the first high-temperature regenerator (309) and the outlet of the ejector (315) are also connected to the inlet of the reboiler (206); The inlet working fluid of the first high-temperature regenerator (309) and the inlet working fluid of the second high-temperature regenerator (312) are both from the exhaust steam of the medium-pressure cylinder (103) in the coal-fired power generation subsystem (100); The hot side inlet of the low-temperature regenerator (311) and the inlet of the ejector (315) are also connected to the cold side outlet of the steam-water separator (208).

10. A method for operating decarbonized coal-fired power coupled with a reversible Brayton cycle heat pump, characterized in that: A decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as claimed in any one of claims 1 to 9; and The coal-fired power generation subsystem drives the steam turbine to generate electricity, and extracts part of the steam for use in the carbon capture and heat pump thermal storage subsystem; The exhaust gas from the coal-fired power generation system enters the absorption tower after cooling, where the CO2 is absorbed by the MEA solution. The desorption tower releases the CO2 and regenerates the lean liquid, using the waste heat to generate saturated steam. The heat storage process of the heat pump heat storage subsystem: using the excess power of the power grid to drive compressor I, compressing the low-temperature working fluid to increase its temperature, heating the low-temperature molten salt and storing it in a high-temperature storage tank, converting electrical energy into thermal energy; Heat release process of heat pump heat storage subsystem: high temperature molten salt heats the working fluid, drives turbine II to do work, and the generated mechanical energy is used to generate electricity, converting thermal energy into electrical energy; During the heat storage and release process, the heat from the steam extraction of the intermediate pressure cylinder and part of the heat released by CO2 are mixed through the ejector to provide a heat source for the reboiler in the decarbonization subsystem for the desorption of CO2. The coal-fired power generation subsystem, decarbonization subsystem and heat pump heat storage subsystem are coupled to provide heat for the heat pump and reboiler through steam extraction from the intermediate pressure cylinder, and the waste heat steam is used to preheat the working medium.

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