Liquid air energy storage system transformation method based on retired coal-fired unit

Abstract

The invention discloses a liquid air energy storage system transformation method based on an out-of-service coal-fired unit, and the method comprises the following steps: S1, carrying out the comprehensive evaluation and planning of an out-of-service coal-fired unit system, and determining usable old equipment and equipment needing to be dismounted; s2, completing the design of the liquid air energy storage power station according to the evaluation result in the step S1; s3, integrating a liquid air energy storage system; the decommissioned coal-fired unit and the liquid air energy storage technology are combined, the technical bottleneck of adaptability of the decommissioned coal-fired unit and a novel energy storage system is broken through, efficient reuse of stock assets is achieved, the construction cost of a liquid air energy storage power station is greatly reduced, the original part of equipment of the decommissioned coal-fired unit is utilized and transformed, and the utilization rate of the decommissioned coal-fired unit is improved. The liquid air energy storage system is effectively and quickly established by integrating a newly added equipment unit, effective support service is provided for a power grid, and the problems that decommissioned coal-fired unit equipment is idle and wasted, and a newly built liquid energy storage power station is high in cost and difficult to land are solved.

Description

Technical Field

[0001] This invention relates to the field of liquid air energy storage technology, and more specifically to a method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit. Background Technology

[0002] In my country's current power system, there are nearly 900 subcritical generating units of 300MW or higher. Most of these units were put into operation relatively early and are nearing the end of their design service life. To further reduce total carbon emissions, they will gradually enter the shutdown phase. Many of these units are located in power load centers and have long played a crucial regulatory role in ensuring regional power supply and demand balance, supporting stable system operation, and responding to load fluctuations. Some units also undertake heat load tasks such as industrial heating or residential heating, playing an important role in integrated energy services. With the arrival of the decommissioning wave of coal-fired units, these decommissioned units are usually idle, and their corresponding power transmission channels cannot be effectively utilized.

[0003] Liquid air energy storage is an energy storage technology with advantages in long-term energy storage and flexible thermoelectric output. Compared with compressed air energy storage, liquid air energy storage does not require the construction of gas storage facilities. However, the construction of liquid air energy storage power plants faces problems such as high cost and difficulty in implementation.

[0004] Liquid air energy storage systems have a high degree of compatibility with the power generation cycle characteristics of coal-fired power units, and the two have a natural matching advantage. Converting retired coal-fired power units into liquid air energy storage power stations can not only provide support services for the power grid, but also effectively utilize the existing resources and power transmission advantages of coal-fired power units.

[0005] Currently, there is no existing technology for applying decommissioned coal-fired power units to liquid air energy storage systems. The usual approach is to combine in-service coal-fired power units with liquid air energy storage technology, utilizing the heat of liquid air compression and the energy recovered from the waste heat during the operation of the coal-fired power unit to provide energy for the expander. The expander then drives the generator to produce electricity. Therefore, there is a need to provide a technical solution that can retrofit and utilize decommissioned coal-fired power units, combining them with liquid air energy storage systems to provide support services for the power grid, and to provide a replicable retrofit method for similar decommissioned power units. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for retrofitting a liquid air energy storage system based on retired coal-fired power units. This method can retrofit retired coal-fired power units and apply them to the liquid air energy storage system, making full use of the existing coal-fired power unit sites, equipment resources and power transmission systems, providing effective support services for the power grid, and solving the problems of idle and wasteful retired coal-fired power unit equipment and high cost and difficulty in implementing new liquid energy storage power plants.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0008] The method for retrofitting liquid air energy storage systems based on decommissioned coal-fired power units includes the following steps: S1. Conduct a comprehensive assessment and planning of the decommissioned coal-fired power unit system to determine the equipment that can be reused and the equipment that needs to be dismantled; S2. Complete the design of the liquid air energy storage power station based on the evaluation results in step S1; Step S2 specifically includes the following steps: S21. Retrofitting design of existing equipment in coal-fired power units; S22, New system / equipment design; S3. Liquid Air Energy Storage System Integration: Integrating new equipment and existing equipment from coal-fired units into a liquid air energy storage system.

[0009] The above-mentioned method for retrofitting liquid air energy storage systems based on decommissioned coal-fired power units, specifically includes the following steps in step S1: S11. Evaluate and plan the boiler-side equipment of the coal-fired unit, including the coal conveying system, pulverizing system, desulfurization system, denitrification system, dust removal and slag removal system and flue gas system. Determine the equipment available on the boiler side according to the requirements of the liquid air energy storage system, including but not limited to pumps, fans, heat exchangers, storage tanks and boiler room space and other equipment and resources. Other equipment shall be dismantled. S12. Evaluate and plan the turbine-side equipment of the coal-fired unit, including the feedwater system, regenerative steam extraction system, circulating water system, vacuum system, DEH system, lubricating oil system, turbine shaft seal system, condensate system, and plant steam system. Determine the available equipment on the turbine side based on the requirements of the liquid air energy storage system, including but not limited to pumps, high-pressure heaters, low-pressure heaters, lubricating oil equipment, circulating cooling equipment, etc. Other equipment shall be removed. S13. Evaluate and plan the electrical side equipment of the coal-fired unit, including the excitation system, generator cooling system, load switch system, plant power system, and substation system. Determine the usable lines and equipment on the electrical side based on the dual-condition characteristics of the liquid air energy storage system for charging and discharging, including but not limited to the main transformer, high-voltage plant transformer, circuit breaker, disconnector, etc. Other equipment shall be removed.

[0010] The above-mentioned method for retrofitting liquid air energy storage systems based on decommissioned coal-fired power units, specifically includes the following steps in step S21: S21a, Low-pressure heater and high-pressure heater reuse and retrofit: The low-pressure heater of the coal-fired unit is converted into a low-pressure cooler at the compressor inlet and a low-pressure reheater between the expander stages in the liquid air energy storage system; the high-pressure heater of the coal-fired unit is converted into a high-pressure cooler between the compressor stages and a high-pressure reheater at the expander inlet in the liquid air energy storage system. S21b, Condenser Reuse and Retrofit: The original condenser of the coal-fired unit is converted into a low-temperature water storage device in the liquid air energy storage system. S21c, Boiler Reuse and Retrofit: Convert the original boiler of the coal-fired unit into a high-temperature accumulator in the liquid air energy storage system; S21d, Steam Turbine Reuse and Retrofit: Converting the original steam turbine of the coal-fired unit into an air expander in the liquid air energy storage system; S21e, Renovation and upgrading of existing electrical systems; S21f, Reuse and Upgrade of Other Auxiliary Equipment: Convert the original condensate pump into a hot water storage pump, and make adaptation modifications to other auxiliary equipment, lubrication system, turbine shaft seal system and control system.

[0011] The above-mentioned method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit, wherein the electrical system retrofitting method in step S21e is as follows: The original configuration of the coal-fired unit generator system remains unchanged, and an energy release circuit breaker is added at the generator outlet; The existing high-voltage plant transformers, plant circuit breakers, and plant busbars of the coal-fired units will remain unchanged, and the power supply for newly added auxiliary equipment will be drawn from the existing plant busbars. The existing power transmission lines, such as the booster station and high-voltage busbar of the coal-fired power unit, will remain unchanged.

[0012] The above-mentioned method for retrofitting liquid air energy storage systems based on decommissioned coal-fired power units, specifically includes the following steps in step S22: S22a. A new air compressor unit consisting of a first compressor and a second compressor is added. The rated discharge pressure and flow rate of the first compressor and the second compressor are determined according to the energy storage capacity. S22b. A new cold storage device is added. The cold storage device adopts a solid-phase cold storage method. The cold storage capacity of the cold storage device is designed to match the cold energy release of the liquefaction main heat exchanger. S22c, A new liquefaction main heat exchanger is added. The liquefaction main heat exchanger is a plate-fin heat exchanger, and the heat exchange area is determined based on the amount of air liquefaction. S22d, A new booster pump is added. The head of the booster pump is determined based on the inlet pressure of the air expander. S22e, A new evaporator is added. The evaporator is a plate-fin heat exchanger. The heat exchange area is calculated and determined based on the amount of air vaporization. S22f, additional auxiliary equipment.

[0013] A liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units, wherein the system is retrofitted using any of the retrofitting methods described above; the system includes a new equipment unit and a coal-fired power unit equipment reuse unit; the new equipment unit includes a first compressor, a second compressor, a liquefaction main heat exchanger, a cold storage device, a liquid storage tank, and an evaporator; the coal-fired power unit equipment reuse unit includes a low-temperature water storage tank, a first low-pressure cooler, a second high-pressure cooler, a high-temperature heat storage tank, a high-pressure reheater, a low-pressure reheater, an air expander, and a generator; the first compressor, the first low-pressure cooler, the second... Two compressors, a second high-pressure cooler, a liquefaction main heat exchanger, a liquid storage tank, and an evaporator are connected in series. A pressurizing pump is also installed at the liquid air outlet of the liquid storage tank. The evaporator is connected to the high-pressure reheater, and the high-pressure reheater and low-pressure reheater are respectively connected to an air expander, which is connected to a generator. The low-temperature water storage tank is connected to the first low-pressure cooler and the second high-pressure cooler, and the first low-pressure cooler and the second high-pressure cooler are respectively connected to a high-temperature heat accumulator. The output end of the high-temperature heat accumulator is connected to the water-side input end of the high-pressure reheater and the low-pressure reheater.

[0014] The above-mentioned liquid air energy storage system based on the retrofit of decommissioned coal-fired power units has the output end of the low-temperature water storage unit connected to the water-side input ends of the first low-pressure cooler and the second high-pressure cooler, respectively, and the water-side output ends of the first low-pressure cooler and the second high-pressure cooler connected to the input ends of the high-temperature heat storage unit, respectively; the outlet of the low-temperature water storage unit is equipped with a hot water storage pump.

[0015] The aforementioned liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units includes a multi-stage air expander. The output end of the evaporator is connected to the gas-side input end of the high-pressure reheater, and the gas-side output end of the high-pressure reheater is connected to the input end of the air expander. The interstage exhaust outlet of the air expander is connected to the gas-side input end of the low-pressure reheater, and the gas-side output end of the low-pressure reheater is connected to the input end of the air expander below the interstage exhaust outlet connected to the gas-side input end of the low-pressure reheater.

[0016] The aforementioned liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units includes a first compressor motor connected to a first compressor and a second compressor motor connected to a second compressor. A first energy storage circuit breaker for controlling the first compressor is installed on the power input line of the first compressor motor, and a second energy storage circuit breaker for controlling the second compressor is installed on the power input line of the second compressor motor. The first and second energy storage circuit breakers are connected in parallel and then connected to an energy storage transformer. The energy storage transformer is connected to the output of the generator.

[0017] The aforementioned liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units includes a coal-fired power unit equipment reuse unit that also includes an energy release circuit breaker, a high-voltage plant transformer, a plant power bus, a step-up substation, and a high-voltage bus of the coal-fired power unit. The energy release circuit breaker is located at the generator outlet, and the generator outlet is connected to the high-voltage plant transformer and the step-up substation, respectively. The high-voltage plant transformer and the step-up substation are connected in parallel with the energy storage transformer.

[0018] The technological advancements achieved by this invention are as follows, thanks to the adoption of the above technical solutions.

[0019] This invention provides a method for retrofitting a liquid air energy storage system based on decommissioned coal-fired power units. It combines decommissioned coal-fired power units with liquid air energy storage technology, overcoming the technical bottleneck of compatibility between decommissioned coal-fired power units and new energy storage systems, and achieving efficient reuse of existing assets. Reused equipment includes, but is not limited to, core equipment of the coal-fired power units: generators, steam turbines, booster stations, high and low pressure heaters, etc., significantly reducing the construction cost of liquid air energy storage power plants, with system investment reduced by more than 30%. By utilizing and retrofitting some of the original equipment of decommissioned coal-fired power units and integrating new equipment units, the effective and rapid establishment of a liquid air energy storage system is achieved, providing effective support services for the power grid and solving the problems of idle and wasted equipment in decommissioned coal-fired power units, as well as the high cost and difficulty in implementing new liquid air energy storage power plants.

[0020] This invention also reuses the power transmission channels of decommissioned generating units located in load centers, enhancing the long-term energy storage capacity of the region, strengthening the grid's ability to absorb new energy sources and regulate loads, improving the flexibility of grid regulation, and ensuring the balance of power supply and demand in the region.

[0021] This invention establishes a standardized retrofit process for coal-fired power units located at load centers that are about to be decommissioned or have already been decommissioned, promotes the large-scale transformation of decommissioned coal-fired power units, and provides a replicable technical path for the retrofit of similar decommissioned coal-fired power units.

[0022] The liquid air energy storage system modified by the method of this invention makes full use of existing equipment and sites, modifies existing equipment in decommissioned coal-fired units, and integrates and connects it with new equipment units to realize the charging and discharging function of liquid air energy storage.

[0023] During the energy storage and discharge process, the compressor, cooler, liquefaction main heat exchanger, cold storage device, and liquid storage tank work together to complete the entire process of air changing from a gaseous state to a liquid state. The liquefied air is stored in the liquid storage tank, and the heat of compression during the compression process is effectively recovered for use in the energy release stage.

[0024] During the energy release and charging process, liquid air is pressurized and vaporized by the cooperation of an evaporator, a reheater, a high-temperature accumulator, and an air expander. The vaporized air is then sent to the reheater for heating and then sent to the air expander to use the kinetic energy of the heated air to expand and do work, driving the generator to generate electricity. At the same time, the cold energy generated during the vaporization process is stored for use in the energy storage stage. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the specific process of the present invention; Figure 2 This is a block diagram of a liquid air energy storage system modified based on the method described in this invention.

[0026] Among them: 100. New equipment unit, 101. First compressor motor, 102. First compressor, 103. Second compressor motor, 104. Second compressor, 105. Liquefaction main heat exchanger, 106. Cold storage device, 107. Liquid storage tank, 108. Pressurization pump, 109. Evaporator, 110. First energy storage circuit breaker, 111. Second energy storage circuit breaker, 112. Energy storage transformer; 200. Coal-fired unit equipment reuse unit; 201. Low-temperature water storage tank; 202. Hot water storage pump; 203. First low-pressure cooler; 204. Second high-pressure cooler; 205. High-temperature heat accumulator; 206. High-pressure reheater; 207. Low-pressure reheater; 208. Air expander; 209. Generator; 210. Energy release circuit breaker; 211. High-voltage station service transformer; 212. Station service circuit breaker; 213. Station service busbar; 214. Substation; 215. High-voltage busbar of coal-fired unit. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] Methods for retrofitting liquid air energy storage systems based on decommissioned coal-fired power units, such as Figure 1 As shown, it includes the following steps: S1. Conduct a comprehensive assessment and planning of the decommissioned coal-fired power unit system to determine the equipment that can be reused and the equipment that needs to be dismantled.

[0029] Step S1 specifically includes the following steps: S11. Assess and plan the boiler-side equipment of the coal-fired unit, including the coal conveying system, pulverizing system, desulfurization system, denitrification system, dust removal and slag removal system, and flue gas system. Determine the equipment available on the boiler side based on the requirements of the liquid air energy storage system, including but not limited to pumps, fans, heat exchangers, storage tanks, and boiler room space and other equipment and resources. Other equipment shall be dismantled.

[0030] S12. Evaluate and plan the turbine-side equipment of the coal-fired unit, including the feedwater system, regenerative steam extraction system, circulating water system, vacuum system, DEH system, lubricating oil system, turbine shaft seal system, condensate system, and plant steam system. Determine the available equipment on the turbine side based on the requirements of the liquid air energy storage system, including but not limited to pumps, high-pressure heaters, low-pressure heaters, lubricating oil equipment, circulating cooling equipment, etc. Other equipment shall be removed.

[0031] S13. Evaluate and plan the electrical side equipment of the coal-fired unit, including the excitation system, generator cooling system, load switch system, plant power system, and substation system. Determine the usable lines and equipment on the electrical side based on the dual-condition characteristics of the liquid air energy storage system for charging and discharging, including but not limited to the main transformer, high-voltage plant transformer, circuit breaker, disconnector, etc. Other equipment shall be removed.

[0032] S2. Complete the design of the liquid air energy storage power station based on the evaluation results in step S1.

[0033] Step S2 specifically includes the following steps: S21. Design for retrofitting existing equipment in coal-fired power units.

[0034] Step S21 specifically includes the following steps: S21a, low-pressure heaters and high-pressure heaters are repurposed and upgraded.

[0035] Specifically, the modification method for the low-pressure heater is as follows: the low-pressure heater of the coal-fired unit is modified into a low-pressure cooler at the compressor inlet and a low-pressure reheater between the expander stages in the liquid air energy storage system. The modification process includes, but is not limited to, cleaning the scale on the heat exchange tubes, adjusting the flow direction of the medium in the tube side / shell side, and adapting to the requirements of compressor exhaust cooling and expander stage exhaust reheat.

[0036] The high-pressure heater is modified as follows: The high-pressure heater of the coal-fired unit is modified into a high-pressure cooler between the compressor stages and a high-pressure reheater at the inlet of the expander in the liquid air energy storage system. The modification process includes, but is not limited to, cleaning the scale on the heat exchange tubes, adjusting the flow direction of the medium in the tube side / shell side, and adapting to the cooling requirements of the compressor exhaust and the heating requirements of the expander intake.

[0037] S21b, condenser reuse and retrofit.

[0038] The condenser is modified as follows: the original condenser of the coal-fired unit is modified into a low-temperature water storage device in the liquid air energy storage system. The modification process includes, but is not limited to, removing the vacuum system connection pipe of the condenser and sealing the vacuum interface.

[0039] S21c, boiler reuse and renovation.

[0040] The original boiler of the coal-fired unit will be converted into a high-temperature heat accumulator in the liquid air energy storage system. The specific conversion process includes, but is not limited to, removing the burners in the furnace and the sealing fans on the furnace top.

[0041] S21d, steam turbine reuse and renovation.

[0042] The original steam turbine of the coal-fired unit is converted into an air expander in the liquid air energy storage system. Specific operations include, but are not limited to, adjusting the clearance between the moving blades and the stationary blades, replacing the seals with those adapted to the air medium, converting it into an air expander, upgrading the software of the DEH system, and adapting the speed control logic of the air expander.

[0043] S21e, Electrical system reuse and renovation.

[0044] The electrical system is modified as follows: the original coal-fired generator system configuration remains unchanged, and an energy release circuit breaker is added at the generator outlet; The existing high-voltage plant transformers, plant circuit breakers, and plant busbars of the coal-fired units will remain unchanged, and the power supply for newly added auxiliary equipment will be drawn from the existing plant busbars. The existing power transmission lines, such as the booster station and high-voltage busbar of the coal-fired power unit, will remain unchanged.

[0045] S21f and other auxiliary machines are reused and modified.

[0046] The existing condensate pumps were converted into hot water storage pumps, and other auxiliary equipment, lubrication systems, turbine shaft seal systems, and control systems were adapted for compatibility.

[0047] S22, Design of new system / equipment.

[0048] Step S22 specifically includes the following steps: S22a. A new air compressor unit consisting of a first compressor and a second compressor is added. The rated exhaust pressure and flow rate of the first compressor and the second compressor are determined according to the energy storage capacity.

[0049] S22b. A new cold storage device is added. The cold storage device adopts a solid-phase cold storage method. The cold storage capacity of the cold storage device is designed to match the cold energy release of the liquefaction main heat exchanger.

[0050] S22c: A new liquefaction main heat exchanger is added. The liquefaction main heat exchanger is a plate-fin heat exchanger, and the heat exchange area is calculated and determined based on the amount of air liquefaction.

[0051] S22d, A new booster pump is added. The head of the booster pump is determined based on the inlet pressure of the air expander.

[0052] S22e: A new evaporator is added. The evaporator uses a plate-fin heat exchanger, and the heat exchange area is determined based on the amount of air vaporization.

[0053] S22f, additional auxiliary equipment.

[0054] S3. Liquid Air Energy Storage System Integration: Integrating new equipment and existing equipment from coal-fired units into a liquid air energy storage system.

[0055] This invention also provides a liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units. This system is retrofitted based on the above-described method, such as... Figure 2 As shown, the liquid air energy storage system includes a new equipment unit 100 and a coal-fired power unit equipment reuse unit 200. The new equipment unit 100 and the coal-fired power unit equipment reuse unit 200 together constitute the liquid air energy storage system.

[0056] The newly added equipment unit 100 includes a first compressor 102, a second compressor 104, a liquefaction main heat exchanger 105, a cold storage device 106, a liquid storage tank 107, and an evaporator 109. The output end of the liquefaction main heat exchanger 105 is connected to the input end of the liquid storage tank 107, and the output end of the liquid storage tank 107 is connected to the input end of the evaporator 109.

[0057] A pressurizing pump 108 is also installed at the liquid air outlet of the liquid storage tank 107 to pressurize the liquid air so that it can be vaporized in the evaporator and release low-temperature cold energy.

[0058] The liquefaction main heat exchanger 105 is connected to the cold release end of the cold storage device 106, and the cold energy required for liquefaction is provided to the liquefaction main heat exchanger 105 through the cold storage device 106.

[0059] The cold storage end of the cold storage device 106 is connected to the evaporator 109. After the liquefied air enters the evaporator 109, the cold storage device 106 can absorb the low-temperature cold energy released after the liquefied air is vaporized.

[0060] Specifically, during the power generation process, the cold storage device absorbs the cold energy from the vaporization of liquid air and stores it in the cold storage device. During the charging process, the cold energy is released in the liquefaction main heat exchanger 105 to provide cooling for air liquefaction.

[0061] The newly added equipment unit 100 also includes a first compressor motor 101 connected to the first compressor 102 and a second compressor motor 103 connected to the second compressor 104. A first energy storage circuit breaker 110 for controlling the first compressor 102 is provided on the power input line of the first compressor motor 101, and a second energy storage circuit breaker 111 for controlling the second compressor 104 is provided on the power input line of the second compressor motor 103.

[0062] The first energy storage circuit breaker 110 and the second energy storage circuit breaker 111 are connected in parallel and are ultimately connected to the energy storage transformer 112 to realize the start-stop control of the first compressor 102 and the second compressor 104.

[0063] The coal-fired power unit equipment reuse unit 200 includes a low-temperature water storage tank 201, a first low-pressure cooler 203, a second high-pressure cooler 204, a high-temperature heat storage tank 205, a high-pressure reheater 206, a low-pressure reheater 207, an air expander 208, and a generator 209.

[0064] The output end of the low-temperature water storage device 201 is connected to the water-side input end of the first low-pressure cooler 203 and the second high-pressure cooler 204, respectively. The water-side output ends of the first low-pressure cooler 203 and the second high-pressure cooler 204 are connected to the input end of the high-temperature heat storage device 205, respectively.

[0065] The outlet of the low-temperature water storage tank 201 is equipped with a hot water storage pump 202, which is used to send low-temperature water into the first low-pressure cooler 203 and the second high-pressure cooler 204, and convert it into high-temperature water for storage in the high-temperature heat storage tank 205.

[0066] The gas-side input end of the first low-pressure cooler 203 is connected to the gas-side outlet end of the first compressor 102, and the gas-side output end of the first low-pressure cooler 203 is connected to the input end of the second compressor 104. It is used to cool the exhaust gas of the first compressor 102 and send it into the second compressor 104 for secondary compression.

[0067] The gas-side outlet of the second compressor 104 is connected to the gas-side input of the second high-pressure cooler 204, and the gas-side output of the second high-pressure cooler 204 is connected to the input of the liquefaction main heat exchanger 105. This is used to cool the exhaust gas of the second compressor 104 and send it into the liquefaction main heat exchanger 105, where the compressed air is liquefied.

[0068] The output end of the high-temperature heat storage device 205 is connected to the water-side input end of the high-pressure reheater 206 and the low-pressure reheater 207, respectively. The water-side output ends of the high-pressure reheater 206 and the low-pressure reheater 207 are connected to the input end of the low-temperature water storage device 201, respectively.

[0069] The gas-side input terminal of the high-pressure reheater 206 is connected to the output terminal of the evaporator 109, and the gas-side output terminal of the high-pressure reheater 206 is connected to the input terminal of the air expander 208.

[0070] The air expander 208 is a multi-stage air expander. The interstage exhaust outlet of the air expander 208 is connected to the air-side input end of the low-pressure reheater 207. The air-side output end of the low-pressure reheater 207 is connected to the input end of the air expander 208 below the interstage exhaust outlet connected to the air-side input end of the low-pressure reheater 207.

[0071] The air expander 208 is connected to the generator 209 and drives the generator to generate electricity. Specifically, after the liquid air is vaporized, it is sent into the high-pressure reheater 206 and the low-pressure reheater 207 for heating. The kinetic energy generated by the expansion of the heated air drives the generator to generate electricity.

[0072] The coal-fired power unit equipment reuse unit 200 also includes an energy release circuit breaker 210, a high-voltage plant transformer 211, a plant power busbar 213, a step-up substation 214, and a coal-fired power unit high-voltage busbar 215.

[0073] The energy release circuit breaker 210 is installed at the outlet of the generator 209 to realize grid connection control during the energy release power generation process.

[0074] The generator 209 is connected to the high-voltage plant transformer 211, the step-up substation 214, and the energy storage transformer 112 respectively. The high-voltage plant transformer 211, the step-up substation 214, and the energy storage transformer 112 are connected in parallel.

[0075] The high-voltage plant transformer 211 is connected to the plant power bus 213, and the plant power bus 213 is equipped with a plant power circuit breaker 212.

[0076] In this embodiment, the first compressor 102, the first low-pressure cooler 203, the second compressor 104, the second high-pressure cooler 204, the liquefaction main heat exchanger 105, the liquid storage tank 107, and the evaporator 109 are connected in series. During energy storage and discharge, air enters the first compressor, is compressed, and then sent to the first low-pressure cooler for low-pressure cooling. It is then compressed again by the second compressor and sent to the second high-pressure cooler for further cooling. The compressed and cooled air enters the liquefaction main heat exchanger, where it is provided with cold energy by a cold storage device to complete the air liquefaction process. At the same time, the heat from the compression process is recovered and stored by a high-temperature heat accumulator.

[0077] Evaporator 109 is connected to high-pressure reheater 206. High-pressure reheater 206 and low-pressure reheater 207 are respectively connected to air expander 208. Air expander 208 is connected to generator 209. Liquid air in the storage tank is pressurized by a pressurizing pump and sent to the evaporator for vaporization. During this process, the cold energy in the vaporization process is absorbed by a cold storage device. Then, the high-pressure air is sent to the high-pressure reheater. The waste heat recovered in the high-temperature heat storage device is used to heat the high-pressure air and send it to the multi-stage air expander. At the same time, the interstage exhaust of the air expander is also sent to the low-pressure reheater for heating. The heated air is then sent back to the air expander to expand and do work to drive the generator to generate electricity.

[0078] In this embodiment, the coal-fired power unit equipment reuse unit 200 is derived from the reuse or modification of the original equipment of the coal-fired power unit, making full use of the original equipment of the retired coal-fired power unit.

[0079] Specifically, the cryogenic water storage unit 201 is a modified condenser from a decommissioned coal-fired power unit, which enables the storage of cryogenic water and saves investment in the cryogenic water storage section of the liquid air energy storage system.

[0080] The hot water storage pump 202 is a direct reuse of the condensate pump of a decommissioned coal-fired power unit. The condensate pump of the decommissioned coal-fired power unit is located below the condenser and does not require modification. The equipment and pipelines can be used directly, saving investment in the hot water storage pump 202 and some pipelines in the liquid air energy storage system.

[0081] The first low-pressure cooler 203 and the low-pressure reheater 207 are low-pressure heaters in decommissioned coal-fired power units. Accordingly, they are selected from low-pressure heaters No. 5 to No. 8 in the regenerative system of decommissioned coal-fired power units, based on the exhaust pressure of the first compressor 102 and the interstage exhaust pressure of the air expander 208. This saves investment in energy storage process coolers and power generation process heaters in liquid air energy storage systems.

[0082] The second high-pressure cooler 204 and the high-pressure reheater 206 are high-pressure heaters in the decommissioned coal-fired power units. Accordingly, they are selected from the No. 1 to No. 3 high-pressure heaters in the regenerative system of the decommissioned coal-fired power units, based on the exhaust pressure of the second compressor 104 and the inlet pressure of the air expander 208. This also saves investment in the energy storage process cooler and the power generation process heater in the liquid air energy storage system.

[0083] The high-temperature thermal accumulator 205 was converted from the boiler of a decommissioned coal-fired unit, saving investment in the high-temperature thermal storage part of the liquid air energy storage system.

[0084] The 208 air expander was converted from a steam turbine of a decommissioned coal-fired unit, saving the investment in expanders in liquid air energy storage systems.

[0085] Generator 209 is an original generator from a decommissioned coal-fired unit, saving investment in the generator portion of the liquid air energy storage system.

[0086] The high-voltage plant transformer 211, plant circuit breaker 212, and plant busbar 213 are the original configurations of the decommissioned coal-fired power units. The power supply for the newly added auxiliary equipment in the liquid air energy storage system is all drawn from the plant busbar 213.

[0087] This invention combines retired coal-fired power units with liquid air energy storage technology. By utilizing and modifying some of the original equipment of retired coal-fired power units, and by adding new equipment units, the charging and discharging functions of the liquid air energy storage system are realized, providing effective support services for the power grid. This solves the problems of idle and wasteful retired coal-fired power unit equipment and the high cost and difficulty in implementing new liquid air energy storage power plants.

[0088] During the energy storage and discharge process, the compressor, cooler, liquefaction main heat exchanger, cold storage device, and liquid storage tank work together to complete the entire process of air changing from a gaseous state to a liquid state. The liquefied air is stored in the liquid storage tank, and the heat of compression during the compression process is effectively recovered for use in the energy release stage.

[0089] During the energy release and charging process, liquid air is pressurized and vaporized by the cooperation of an evaporator, a reheater, a high-temperature accumulator, and an air expander. The vaporized air is then sent to the reheater for heating and then sent to the air expander to use the kinetic energy of the heated air to expand and do work, driving the generator to generate electricity. At the same time, the cold energy generated during the vaporization process is stored for use in the energy storage stage.

Claims

1. A method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit, characterized in that: Includes the following steps: S1. Conduct a comprehensive assessment and planning of the decommissioned coal-fired power unit system to determine the equipment that can be reused and the equipment that needs to be dismantled; S2. Complete the design of the liquid air energy storage power station based on the evaluation results in step S1; Step S2 specifically includes the following steps: S21. Retrofitting and upgrading of existing equipment in coal-fired power units; S22, New system / equipment design; S3. Liquid Air Energy Storage System Integration: Integrating new equipment and existing equipment from coal-fired units into a liquid air energy storage system.

2. The method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit according to claim 1, characterized in that: Step S1 specifically includes the following steps: S11. Evaluate and plan the boiler-side equipment of the coal-fired unit, including the coal conveying system, pulverizing system, desulfurization system, denitrification system, dust removal and slag removal system and flue gas system. Determine the equipment available on the boiler side according to the requirements of the liquid air energy storage system, including but not limited to pumps, fans, heat exchangers, storage tanks and boiler room space and other equipment and resources. Other equipment shall be dismantled. S12. Evaluate and plan the turbine-side equipment of the coal-fired unit, including the feedwater system, regenerative steam extraction system, circulating water system, vacuum system, DEH system, lubricating oil system, turbine shaft seal system, condensate system, and plant steam system. Determine the available equipment on the turbine side based on the requirements of the liquid air energy storage system, including but not limited to pumps, high-pressure heaters, low-pressure heaters, lubricating oil equipment, circulating cooling equipment, etc. Other equipment shall be removed. S13. Evaluate and plan the electrical side equipment of the coal-fired unit, including the excitation system, generator cooling system, load switch system, plant power system, and substation system. Determine the usable lines and equipment on the electrical side based on the dual-condition characteristics of the liquid air energy storage system for charging and discharging, including but not limited to the main transformer, high-voltage plant transformer, circuit breaker, disconnector, etc. Other equipment shall be removed.

3. The method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit according to claim 1, characterized in that: Step S21 specifically includes the following steps: S21a, Low-pressure heater and high-pressure heater reuse and retrofit: The low-pressure heater of the coal-fired unit is converted into a low-pressure cooler at the compressor inlet and a low-pressure reheater between the expander stages in the liquid air energy storage system; the high-pressure heater of the coal-fired unit is converted into a high-pressure cooler between the compressor stages and a high-pressure reheater at the expander inlet in the liquid air energy storage system. S21b, Condenser Reuse and Retrofit: The original condenser of the coal-fired unit is converted into a low-temperature water storage device in the liquid air energy storage system. S21c, Boiler Reuse and Retrofit: Convert the original boiler of the coal-fired unit into a high-temperature accumulator in the liquid air energy storage system; S21d, Steam Turbine Reuse and Retrofit: Converting the original steam turbine of the coal-fired unit into an air expander in the liquid air energy storage system; S21e, renovation and upgrading of existing electrical systems; S21f, Reuse and Upgrade of Other Auxiliary Equipment: Convert the original condensate pump into a hot water storage pump, and make adaptation modifications to other auxiliary equipment, lubrication system, turbine shaft seal system and control system.

4. The method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit according to claim 3, characterized in that: The electrical system modification method in step S21e is as follows: The original configuration of the coal-fired unit generator system remains unchanged, and an energy release circuit breaker is added at the generator outlet; The existing high-voltage plant transformers, plant circuit breakers, and plant busbars of the coal-fired units will remain unchanged, and the power supply for newly added auxiliary equipment will be drawn from the existing plant busbars. The existing power transmission lines, such as the booster station and high-voltage busbar of the coal-fired power unit, will remain unchanged.

5. The method for retrofitting a liquid air energy storage system based on a decommissioned coal-fired power unit according to claim 1, characterized in that: Step S22 specifically includes the following steps: S22a. A new air compressor unit consisting of a first compressor and a second compressor is added. The rated discharge pressure and flow rate of the first compressor and the second compressor are determined according to the energy storage capacity. S22b. A new cold storage device is added. The cold storage device adopts a solid-phase cold storage method. The cold storage capacity of the cold storage device is designed to match the cold energy release of the liquefaction main heat exchanger. S22c, A new liquefaction main heat exchanger is added. The liquefaction main heat exchanger is a plate-fin heat exchanger, and the heat exchange area is determined based on the amount of air liquefaction. S22d, A new booster pump is added. The head of the booster pump is determined based on the inlet pressure of the air expander. S22e, A new evaporator is added. The evaporator is a plate-fin heat exchanger. The heat exchange area is calculated and determined based on the amount of air vaporization. S22f, additional auxiliary equipment.

6. A liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units, characterized in that: The system is completed by implementing the modification method according to any one of claims 1-5; the system includes a new equipment unit (100) and a coal-fired unit equipment reuse unit (200); the new equipment unit (100) includes a first compressor (102), a second compressor (104), a liquefaction main heat exchanger (105), a cold storage device (106), a liquid storage tank (107), and an evaporator (109); the coal-fired unit equipment reuse unit (200) includes a low-temperature water storage tank (201), a first low-pressure cooler (203), a second high-pressure cooler (204), a high-temperature heat storage tank (205), a high-pressure reheater (206), a low-pressure reheater (207), an air expander (208), and a generator (209); the first compressor (102), the first low-pressure cooler (203), the second compressor (104), the second high-pressure cooler (209) and the second high-pressure cooler (209) are all included in the system. The cooler (204), the liquefaction main heat exchanger (105), the liquid storage tank (107), and the evaporator (109) are connected in series. A booster pump (108) is also provided at the liquid air outlet of the liquid storage tank (107). The evaporator (109) is connected to the high-pressure reheater (206), and the high-pressure reheater (206) and the low-pressure reheater (207) are respectively connected to the air expander (208), and the air expander (208) is connected to the generator (209). The low-temperature water storage tank (201) is respectively connected to the first low-pressure cooler (203) and the second high-pressure cooler (204), and the first low-pressure cooler (203) and the second high-pressure cooler (204) are respectively connected to the high-temperature heat storage tank (205). The output end of the high-temperature heat storage tank (205) is respectively connected to the water-side input end of the high-pressure reheater (206) and the low-pressure reheater (207).

7. The liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units according to claim 6, characterized in that: The output end of the low-temperature water storage device (201) is connected to the water-side input end of the first low-pressure cooler (203) and the second high-pressure cooler (204), respectively. The water-side output end of the first low-pressure cooler (203) and the second high-pressure cooler (204) is connected to the input end of the high-temperature heat storage device (205), respectively. A hot water pump (202) is provided at the outlet of the low-temperature water storage device (201).

8. The liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units according to claim 6, characterized in that: The air expander (208) is a multi-stage air expander; the output end of the evaporator (109) is connected to the gas-side input end of the high-pressure reheater (206), and the gas-side output end of the high-pressure reheater (206) is connected to the input end of the air expander (208); the interstage exhaust outlet of the air expander (208) is connected to the gas-side input end of the low-pressure reheater (207), and the gas-side output end of the low-pressure reheater (207) is connected to the input end of the air expander (208) below the interstage exhaust outlet connected to the gas-side input end of the low-pressure reheater (207).

9. The liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units according to claim 6, characterized in that: The newly added equipment unit (100) also includes a first compressor motor (101) connected to the first compressor (102) and a second compressor motor (103) connected to the second compressor (104). A first energy storage circuit breaker (110) for controlling the first compressor (102) is provided on the power input line of the first compressor motor (101), and a second energy storage circuit breaker (111) for controlling the second compressor (104) is provided on the power input line of the second compressor motor (103). The first energy storage circuit breaker (110) and the second energy storage circuit breaker (111) are connected in parallel and then connected to the energy storage transformer (112). The energy storage transformer (112) is connected to the outlet of the generator (209).

10. The liquid air energy storage system based on the retrofitting of decommissioned coal-fired power units according to claim 9, characterized in that: The coal-fired power unit equipment reuse unit (200) also includes an energy release circuit breaker (210), a high-voltage plant transformer (211), a plant power bus (213), a booster station (214), and a coal-fired power unit high-voltage bus (215). The energy release circuit breaker (210) is located at the outlet of the generator (209). The outlet of the generator (209) is connected to the high-voltage plant transformer (211) and the booster station (214) respectively. The high-voltage plant transformer (211) and the booster station (214) are connected in parallel with the energy storage transformer (112) respectively.

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