A fast response system and method for coal-fired power plants based on thermochemical energy storage

Abstract

This invention discloses a rapid response system and method for coal-fired power plants based on thermochemical energy storage, applicable to the field of grid energy storage, including coal-fired power generation, carbon capture, energy storage, and power generation units. The coal-fired power generation unit includes a boiler, turbine, generator, and regenerative system; the carbon capture unit includes an absorption tower, separation tower, and reboiler; the energy storage unit includes a dry air pump, an air heater, and a thermochemical energy storage reactor. Steam extraction from the intermediate-pressure cylinder is connected to the air heater, and steam extraction from the low-pressure cylinder is connected to the reactor inlet. The reactor outlet steam is supplied to the reboiler and the organic Rankine cycle power generation unit. Waste heat recovery from the carbon capture unit cooler is used for preheating the organic working fluid, achieving cascaded energy utilization and rapid peak shaving. This invention constructs a two-way "energy storage-energy release" operation mechanism through the thermochemical energy storage unit, solving the problems of reduced output and slow response during peak shaving in carbon capture power plants, enabling more steam to be used for power generation, broadening the peak shaving range, and improving the response rate.

Description

Technical Field

[0001] This invention relates to the field of power grid energy storage technology, and in particular to a rapid response system and method for coal-fired power plants based on thermochemical energy storage. Background Technology

[0002] As the energy structure shifts towards green and low-carbon development, the proportion of renewable energy generation such as wind power and photovoltaic power continues to increase. The volatility of their output poses a challenge to the stable operation of the power grid, and thermal power units therefore face more frequent and rapid peak-shaving demands.

[0003] Existing coal-fired power plants equipped with carbon capture systems have significant shortcomings when participating in peak shaving. To maintain carbon capture operation, a large amount of high-temperature, high-pressure steam needs to be extracted from the turbine, resulting in a substantial reduction in main power generation and a decrease in overall system efficiency. At the same time, there is a parameter mismatch between the extracted steam for heating and the reboiler demand, leading to a slow system response and an inability to adapt to the grid's requirements for rapid load adjustment, severely limiting the unit's operational flexibility and economy.

[0004] Therefore, how to effectively solve the problems of reduced unit efficiency and slow peak-shaving response caused by steam extraction, so as to achieve efficient and flexible operation of coal-fired power plants, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a rapid response system and method for coal-fired power plants based on thermochemical energy storage, enabling rapid and flexible peak shaving for coal-fired power plants equipped with carbon capture systems across a wide load range.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a rapid response system for coal-fired power plants based on thermochemical energy storage, comprising a carbon capture unit, a power generation unit, an energy storage unit, and a coal-fired power generation unit.

[0007] The coal-fired power generation unit includes a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a generator, and a multi-stage regenerative assembly, all connected by pipelines.

[0008] The carbon capture unit includes an absorption tower for absorbing carbon dioxide and a separation tower for rich liquid regeneration, the separation tower being equipped with a reboiler capable of absorbing external heat sources.

[0009] The energy storage unit includes a dry air pump, an air heater, and a thermochemical energy storage reactor connected in sequence via pipelines.

[0010] The outlet of the intermediate-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the air heater of the energy storage unit through a steam extraction pipe, and the steam extraction port of the low-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the thermochemical energy storage reactor of the energy storage unit through a steam extraction pipe.

[0011] The steam outlet of the thermochemical energy storage reactor of the energy storage unit is connected to the steam inlet of the reboiler of the carbon capture unit via a steam supply pipeline.

[0012] The cooler of the carbon capture unit is connected to the organic working fluid preheater of the power generation unit via a waste heat recovery pipeline.

[0013] The steam outlet of the thermochemical energy storage reactor of the energy storage unit is also connected to the organic working fluid evaporator of the power generation unit via a branch steam supply pipeline.

[0014] Furthermore, the power generation unit is an organic Rankine cycle power generation unit, including an organic working fluid evaporator, an organic working fluid turbine, a generator, a first condenser, and an organic working fluid pump connected by pipelines. The organic working fluid preheater is installed on the pipeline between the outlet of the organic working fluid pump and the inlet of the organic working fluid evaporator.

[0015] Furthermore, the multi-stage regenerative assembly includes a second condenser, several low-pressure heaters, a deaerator, and several high-pressure heaters connected in sequence via pipes and a feed water pump.

[0016] Furthermore, the system also includes a heat pump heating unit, which includes an absorption heat pump. The heat pump generator of the absorption heat pump is connected to the air outlet of the thermochemical energy storage reactor of the energy storage unit through a pipe to receive the waste heat air discharged from the reactor as a driving heat source.

[0017] Furthermore, the carbon capture unit also includes a compression and cooling subsystem, which includes a rich liquid pump, a lean and rich liquid heat exchanger, a lean liquid pump, and several compressors and several coolers for processing pure carbon dioxide, connected in sequence.

[0018] Furthermore, the waste heat recovery pipeline is connected between the cooler of the compression cooling subsystem and the organic working fluid preheater of the organic Rankine cycle power generation unit.

[0019] Furthermore, the system also includes a controller, which is signal-connected to the energy storage unit, the coal-fired power generation unit, and the carbon capture unit, and is used to adjust the extraction steam flow rate, dry air flow rate, and the operating status of the thermochemical energy storage reactor according to the grid load demand.

[0020] Furthermore, the thermochemical energy storage reactor is filled with a hygroscopic thermochemical energy storage material, which releases heat during the moisture absorption process and absorbs heat during the dehumidification process.

[0021] Furthermore, the coal-fired power generation unit also includes a waste heat recovery unit. The shell-side inlet of the waste heat recovery unit is connected to the outlet of the reboiler, the tube-side inlet of the waste heat recovery unit is connected to the outlet of the first-stage regenerator in the multi-stage regenerator assembly, and the tube-side outlet of the waste heat recovery unit is connected to the inlet of the next higher-stage regenerator. This is used to recover the heat of the working fluid at the reboiler outlet to heat the feedwater.

[0022] Another embodiment of the present invention provides a fast response method for coal-fired power plants based on thermochemical energy storage, comprising:

[0023] In response to the power grid's request to reduce the power plant's generating load, the system executes a load reduction energy storage process:

[0024] First steam is drawn from the intermediate pressure cylinder of the main steam turbine of the coal-fired power generation unit. The first steam is used to heat dry air, and the heated dry air is introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a dehydration reaction, so as to realize the storage of thermal energy.

[0025] In response to the power grid's request to increase the power plant's generating load, the system executes an energy release and load increase process:

[0026] Second steam is drawn from the low-pressure cylinder of the main turbine of the coal-fired power generation unit and introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a hydration reaction, generating high-temperature steam to release thermal energy.

[0027] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0028] By introducing thermochemical energy storage units, a flexible operating mechanism of "energy storage-release" bidirectional coupling is constructed, effectively solving the problems of reduced output and slow response faced by coal-fired power plants equipped with carbon capture systems during peak shaving. When the grid needs to reduce load, the system can convert surplus steam heat energy into chemical energy for storage; when rapid load increase is required, the stored energy can be released to replace turbine extraction steam to heat the carbon capture system, allowing more steam from the main turbine to be used for power generation, thereby significantly expanding the peak shaving range of the unit and greatly improving the load response rate. The thermochemical energy storage and release process is coupled with organic Rankine cycle power generation and absorption heat pumps to realize the recovery of various low-grade heat energy such as compression heat and reboiler waste heat in the carbon capture process for power generation or heating, turning waste into treasure. This overcomes the significant energy efficiency penalty caused by steam extraction in traditional carbon capture power plants and improves the economic efficiency and environmental compatibility of the power plant in the electricity market. Attached Figure Description

[0029] Figure 1 This is a structural block diagram of a rapid response system for a coal-fired power plant based on thermochemical energy storage, according to one embodiment of the present invention.

[0030] Figure label:

[0031] The components include: 1. Flue gas; 2. First cooler; 3. Flue gas compressor; 4. Absorber; 5. MEA absorbent replenishment; 6. Rich liquid pump; 7. MEA lean and rich liquid heat exchanger; 8. Second cooler; 9. Flue gas with CO2 removed; 10. Reboiler; 11. Separator; 12. Lean liquid pump; 13. Third cooler; 14. Separator; 15. First compressor; 16. Fourth cooler; 17. Second compressor; 18. Fifth compressor; 19. Third compressor; 20. Sixth cooler; 21. Pure CO2 storage tank; 22. Organic working fluid evaporator; 23. Organic working fluid turbine; 24. First generator; 25. First condenser; 26. Organic working fluid circulation pump; 27. Organic working fluid preheater; 28. Heat pump generator; 29. ​​Heat pump condenser; 30. Heat pump evaporator; 31. Heat pump... 32. Pump absorber; 33. Absorption heat pump; 34. Heat user; 35. Dry air; 36. Dry air pump; 37. Air heater; 38. Thermochemical energy storage reactor; 39. Boiler; 40. High-pressure cylinder; 41. Medium-pressure cylinder; 42. Low-pressure cylinder; 43. Second generator; 44. Stage 1 extraction steam; 45. Stage 2 extraction steam; 46. Stage 3 extraction steam; 47. Stage 4 extraction steam; 48. Stage 5 extraction steam; 6th stage extraction steam; 49th and 7th stage extraction steam; 50th and 8th stage extraction steam; 51st stage exhaust steam; 52nd stage condenser; 53rd stage regenerator; 54th stage regenerator; 55th stage regenerator; 56th stage regenerator; 57th stage regenerator; 58th stage regenerator; 59th stage regenerator; 60th and 8th stage regenerator; 61st stage feedwater circulation pump; 62nd stage feedwater circulation pump; 63rd stage waste heat recovery unit. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] One embodiment of the present invention provides a rapid response system for coal-fired power plants based on thermochemical energy storage. For details, please refer to [link to documentation]. Figure 1 , Figure 1 The diagram shown is a structural block diagram of a rapid response system for a coal-fired power plant based on thermochemical energy storage, according to one embodiment of the present invention. The system includes a carbon capture unit, a power generation unit, an energy storage unit, and a coal-fired power generation unit.

[0037] The coal-fired power generation unit serves as the fundamental power source for the entire system. It comprises a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a generator, and a multi-stage regenerative assembly, all connected sequentially via high-temperature, high-pressure steam pipelines. The boiler generates high-temperature, high-pressure steam; the high, intermediate, and low-pressure cylinders form the main body of the turbine, converting the steam's thermal energy into mechanical energy; the generator further converts the mechanical energy into electrical energy for output; and the multi-stage regenerative assembly extracts steam from different stages of the turbine to heat the boiler feedwater stage by stage, thereby improving the overall plant's thermal efficiency.

[0038] Multi-stage regenerative components are key thermal systems in coal-fired power generation units used to improve the thermal efficiency of the power plant cycle. They utilize the steam extracted from each stage of the steam turbine to heat the boiler feedwater step by step, reducing cold source losses. Specifically, they include a second condenser, several low-pressure heaters, a deaerator, and several high-pressure heaters connected in sequence through insulated pipes and feedwater pumps, forming a complete feedwater regenerative process.

[0039] The coal-fired power generation unit also includes a waste heat recovery unit, a highly efficient shell-and-tube heat exchanger used for the deep recovery and utilization of low-grade waste heat generated by the carbon capture unit. Its shell-side inlet is connected to the outlet of the reboiler via piping to receive the steam-water mixture (low-temperature heat source) discharged from the reboiler at a temperature of approximately 115°C. Its tube-side inlet is connected to the outlet of the seventh-stage regenerator in the multi-stage regenerator assembly via piping to receive the lower-temperature feedwater flowing from that stage regenerator. Its tube-side outlet is connected to the inlet of the fifth-stage regenerator via piping.

[0040] Its core function is to utilize the waste heat of the reboiler outlet working fluid to heat the feedwater from the seventh-stage regenerator in the waste heat recovery unit, raising its temperature from approximately 70°C to around 95°C. The heated feedwater is then sent to the inlet of the fifth-stage regenerator, which has a higher pressure rating, thereby reducing the need for sixth-stage steam extraction from the turbine and allowing more steam to expand and perform work within the turbine.

[0041] The second condenser, as the starting point of the regenerative system, mainly functions to receive and condense the exhaust steam discharged from the low-pressure cylinder of the steam turbine, turning it into condensate and providing a basic water source for the subsequent regenerative process.

[0042] The low-pressure heaters are connected in series via pipelines and are located after the second condenser and before the deaerator. These low-pressure heaters receive low-grade extraction steam (e.g., extraction steam of a lower pressure level) from the low-pressure cylinder of the turbine, and use the latent heat of vaporization of this extraction steam to gradually heat the condensate from the second condenser, thus initially raising its temperature. During the heating process, the extraction steam itself condenses into water, which is usually collected and channeled to an appropriate location within the system.

[0043] The deaerator is located between the low-pressure heater group and the high-pressure heater group. Its core function is to remove dissolved oxygen and other non-condensable gases from the feedwater, preventing oxygen corrosion in subsequent high-temperature and high-pressure equipment. The deaerator uses extracted steam (such as saturated steam at a certain pressure) from the intermediate-pressure cylinder of the steam turbine as a heat source to heat the water to its saturation temperature, thereby causing dissolved gases to precipitate and be discharged from the system, while simultaneously completing a second heating of the feedwater.

[0044] Each high-pressure heater is connected in series via pipelines and is located after the deaerator and before the boiler feedwater inlet. These high-pressure heaters receive high-grade extraction steam (e.g., high-pressure extraction steam) from the high-pressure and intermediate-pressure cylinders of the steam turbine, and use its high-grade heat energy to perform final high-temperature heating on the deaerated feedwater, bringing its temperature close to or even reaching the boiler feedwater requirements. This significantly reduces the heat load required for boiler combustion and effectively improves the thermal economy of the entire power plant.

[0045] The carbon capture unit employs a carbon dioxide capture process based on monoethanolamine (MEA) chemical absorption, primarily consisting of an absorption tower for absorbing carbon dioxide from flue gas and a separation tower for rich liquor regeneration. The bottom of the separation tower is equipped with a reboiler, designed to absorb heat from external heat sources (such as thermochemical energy storage reactors or turbine extraction steam) to provide the thermal energy required for rich liquor desorption and regeneration; this reboiler is a key component for achieving carbon dioxide desorption.

[0046] The carbon capture unit also includes a compression and cooling subsystem, which is a key back-end processing step responsible for purifying, pressurizing, and liquefying the crude carbon dioxide gas desorbed from the top of the separation tower. This subsystem aims to produce high-purity, high-pressure liquid carbon dioxide products that are easy to transport and store.

[0047] The compression cooling subsystem includes a rich liquor pump, a lean-rich liquor heat exchanger, a lean liquor pump, and several compressors and coolers for processing pure carbon dioxide, all connected sequentially via process piping. The rich liquor pump pressurizes the carbon dioxide-rich MEA liquor at the bottom of the absorber and transports it to subsequent stages. The lean-rich liquor heat exchanger utilizes the heat carried by the high-temperature MEA lean liquor flowing from the bottom of the separation tower and transported by the lean liquor pump to preheat the MEA rich liquor about to enter the separation tower, achieving efficient energy recovery within the system and reducing the heat load on the reboiler. The lean liquor pump's function is to transport the regenerated high-temperature MEA lean liquor back to the top of the absorber for recycling.

[0048] Several compressors and coolers used to process pure carbon dioxide are typically arranged alternately in a "stage" configuration. Specifically, ambient temperature and pressure pure carbon dioxide gas from the separator first enters the first compressor for preliminary compression, a process that significantly increases the gas temperature. Subsequently, the high-temperature, high-pressure gas enters the fourth cooler to be cooled to near ambient temperature, reducing its volume, improving subsequent compression efficiency, and removing the heat of compression. This compression-cooling process is repeated sequentially, with continuous processing by the second compressor and fifth cooler, and the third compressor and sixth cooler, ultimately pressurizing the carbon dioxide gas to approximately 8 MPa. At this pressure, carbon dioxide can be cooled to 30°C and become liquid or supercritical, allowing it to be safely injected into pure CO2 storage tanks for storage, significantly reducing the volume requirements and safety risks of storage containers.

[0049] The energy storage unit, as the core for realizing the spatiotemporal transfer of energy and rapid system response, includes a dry air pump, an air heater, and a thermochemical energy storage reactor connected sequentially via air and steam pipes. The dry air pump provides a dry airflow; the air heater uses steam extracted from a steam turbine to heat the dry air; and the thermochemical energy storage reactor is filled with hygroscopic thermochemical energy storage material, which stores and releases thermal energy through the material's dehumidification / hygroscopic reaction.

[0050] Thermochemical energy storage reactors are filled with specific hygroscopic thermochemical energy storage materials. These materials are the core medium for storing and releasing energy in the form of chemical potential. Their working principle is based on the reversible physicochemical adsorption reaction between the material and moisture.

[0051] The material releases heat during moisture absorption, a process that is exothermic. Specifically, when water vapor molecules in the environment are adsorbed onto the material's surface or pores, the kinetic energy of the water vapor molecules is converted into heat energy and released. During system operation, this process corresponds to a condition where grid demand is reduced and energy storage is required: steam drawn from the intermediate-pressure cylinder heats dry air via an air heater, and the resulting hot dry air (approximately 180°C) is sent into the reactor. The heat in the airflow raises the material's temperature and drives its dehumidification (this is the next process). The dehumidified, high-temperature material then possesses the potential to absorb moisture. Subsequently, when the reactor switches to energy storage mode and introduces humid air at room temperature or low temperature, these dry materials will strongly absorb moisture and release a large amount of adsorption heat. This heat can be promptly extracted and utilized, such as to drive an absorption heat pump.

[0052] The material absorbs heat during dehumidification, an endothermic reaction. Specifically, when heating a saturated material, external energy is required to break the adsorption bonds between water molecules and the material, causing the water molecules to desorb and turn into water vapor. This process absorbs a large amount of heat from the heat source. During system operation, this process corresponds to a condition where grid demand increases and energy needs to be released: low-temperature, low-pressure steam (approximately 80°C, 0.11 MPa) extracted from the 7th stage extraction port of the low-pressure cylinder is introduced into the reactor. The heat contained in the steam is used to heat the humidified material, driving its dehumidification and regeneration. During dehumidification, the material absorbs the latent heat of vaporization and sensible heat of the steam, causing the steam to condense and cool down, while the material itself is regenerated to a dry state, releasing high-temperature water vapor (approximately 120°C). This high-temperature steam is transported to the reboiler or organic working fluid evaporator of the carbon capture unit, thereby replacing the high-grade extraction steam and enabling the main generator set to generate more electricity.

[0053] The outlet of the intermediate-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the air heater of the energy storage unit through a steam extraction pipe. Specifically, steam with exhaust parameters of approximately 220°C and 0.3MPa is extracted from the intermediate-pressure cylinder to drive the air heater to heat dry air from the dry air pump when it is necessary to reduce the power plant output.

[0054] The extraction port of the low-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the thermochemical energy storage reactor of the energy storage unit through another extraction pipe. Specifically, low-temperature and low-pressure steam with parameters of about 80°C and 0.11MPa is extracted from the 7th stage extraction port of the low-pressure cylinder. This steam is used to trigger the exothermic reaction of the energy storage material in the thermochemical energy storage reactor when the power plant output needs to be increased.

[0055] The steam outlet of the thermochemical energy storage reactor in the energy storage unit is connected to the steam inlet of the reboiler in the carbon capture unit via a steam supply pipeline. During the energy release phase, the steam mixture of approximately 120°C generated by the reactor is directly fed to the reboiler as a heat source for the separation tower, thereby replacing or reducing the amount of steam directly extracted from the turbine, enabling the main generator unit to generate more electricity.

[0056] The power generation unit is an organic Rankine cycle power generation unit. This unit utilizes a low-grade heat source to drive an organic working fluid in a Rankine cycle for power generation. It is a key component for achieving efficient waste heat recovery and utilization, and further improving the overall power generation efficiency. The organic Rankine cycle power generation unit includes an organic working fluid evaporator, an organic working fluid turbine, a generator, a first condenser, and an organic working fluid pump, which are connected in a circulation process through dedicated pipelines resistant to organic solvent corrosion, forming a complete closed-loop power generation cycle. The organic working fluid evaporator serves as the starting point of the cycle. Its function is to absorb low-grade heat energy from other units in the system, such as waste heat from the carbon capture unit's compression cooling subsystem (introduced through a waste heat recovery pipeline) or excess steam from the branch steam supply pipeline of the thermochemical energy storage reactor, and heat and evaporate the liquid organic working fluid into superheated steam. The organic working fluid turbine is coaxially connected to the generator. The superheated organic working fluid steam expands and does work here, converting heat energy into mechanical energy, which in turn drives the generator to rotate and generate electricity. The first condenser is usually water-cooled or air-cooled and is used to condense the exhaust steam after it has done work into liquid. The organic working fluid pump is used to pressurize the condensed liquid organic working fluid and pump it back into the circulation loop to maintain the continuous operation of the cycle.

[0057] The waste heat recovery pipeline is a key energy recovery component connecting the carbon capture unit and the organic Rankine cycle power generation unit. Specifically, it is connected between the cooler of the compression cooling subsystem and the organic working fluid preheater of the organic Rankine cycle power generation unit, forming a low-temperature waste heat high-efficiency utilization loop across units.

[0058] The coolers in the compression cooling subsystem specifically refer to the equipment used for interstage cooling of the high-temperature gas after compression during the pure carbon dioxide compression and purification process, namely the fourth, fifth, and sixth coolers. These coolers continuously discharge large amounts of low-grade waste heat during normal operation, and the heat transfer medium is typically warm water or low-pressure steam.

[0059] Waste heat recovery pipelines are used to transport the waste heat medium (such as warm water) discharged from these coolers to the organic working fluid preheater of the organic Rankine cycle power generation unit. The organic working fluid preheater, as the primary heater of the organic Rankine cycle, functions to use this low-grade waste heat to preheat the low-temperature liquid organic working fluid pumped out from the organic working fluid.

[0060] An organic working fluid preheater is additionally installed on the pipeline between the outlet of the organic working fluid pump and the inlet of the organic working fluid evaporator. Its function is to preheat the pressurized, low-temperature liquid organic working fluid, with its heat source also coming from the low-grade waste heat emitted by the compression cooling subsystem of the carbon capture unit (such as the fourth, fifth, and sixth coolers). This design achieves the cascaded recovery and utilization of the compression heat generated during the carbon capture process: the organic working fluid first absorbs some heat in the preheater to raise its temperature, and then enters the evaporator to absorb higher-grade heat and evaporate, thereby significantly improving the thermal efficiency and power generation output of the organic Rankine cycle.

[0061] The cooler of the carbon capture unit is connected to the organic working fluid preheater of the power generation unit via a waste heat recovery pipeline. Here, the cooler mainly refers to the cooler in the compression and purification subsystem of the carbon capture unit (such as the interstage cooler in the CO2 compression process). The low-grade waste heat generated by it is recovered by the organic working fluid preheater and used to preheat the organic working fluid in the organic Rankine cycle power generation unit, realizing the cascade utilization of energy.

[0062] The steam outlet of the thermochemical energy storage reactor in the energy storage unit is also connected to the organic working fluid evaporator of the power generation unit via a branch steam supply pipe. This design allows excess steam of approximately 120°C to be introduced into the organic working fluid evaporator when the steam production of the thermochemical energy storage reactor exceeds the reboiler's requirements, driving the organic Rankine cycle power generation unit to generate additional electricity, further improving the overall system efficiency and peak-shaving benefits.

[0063] Preferably, this embodiment also includes a heat pump heating unit, which is an important component for realizing the cascade utilization of system energy, improving overall energy efficiency and creating additional economic benefits. Its main function is to recover and utilize the low-temperature waste heat in the system that is difficult to generate electricity directly, and convert it into higher-grade heat energy for external heating.

[0064] The core equipment of a heat pump heating unit includes an absorption heat pump. This type of heat pump is driven by heat rather than electricity, making it more suitable for power plant waste heat recovery scenarios. Its working principle is based on the thermochemical cycle of a refrigerant-absorbent working fluid pair (such as LiBr-H2O), which achieves the process of absorbing heat from a low-temperature heat source and releasing heat to a high-temperature heat source by consuming the driving heat source.

[0065] The heat pump generator of the absorption heat pump is connected to the air outlet of the thermochemical energy storage reactor of the energy storage unit through an insulated pipe. The specific operating condition of this connection is as follows: when the power grid needs to reduce the power plant output, the steam drawn from the intermediate pressure cylinder is heated to dry air by the air heater, and then enters the thermochemical energy storage reactor to heat the internal energy storage material. After the energy storage process is completed, the temperature of the waste heat air discharged from the reactor is about 110°C. This 110°C waste heat air is the driving heat source provided by the absorption heat pump.

[0066] The heat pump generator is used to receive the waste heat air discharged from the reactor as a driving heat source. Its function is to use the hot air at about 110°C to heat the dilute lithium bromide solution in the generator, causing the water in it to evaporate into refrigerant vapor. At the same time, the lithium bromide solution is concentrated. This process is the starting point of the absorption heat pump cycle.

[0067] The system also includes a controller, which serves as the intelligent control hub of the entire rapid response system. It is typically composed of a programmable logic controller (PLC) or a distributed control system (DCS). It establishes bidirectional signal connections with the main sensors and actuators of the energy storage unit, coal-fired power generation unit, and carbon capture unit through hardwiring or industrial bus. It is used to collect system operating parameters in real time and output control commands, thereby enabling automatic and rapid adjustment of the system operating status according to grid dispatch instructions or preset load demands.

[0068] The controller is connected to the energy storage unit via a signal. Specifically, the controller receives a temperature sensor signal from the outlet of the thermochemical energy storage reactor and controls the flow rate of dry air entering the reactor by adjusting the frequency of the dry air pump or the opening of the outlet valve. At the same time, the controller controls the steam extraction flow rate used for heating air by adjusting the opening of the regulating valve on the steam pipeline connected to the air heater, ensuring that the energy storage process is carried out within the optimal temperature range.

[0069] The controller is connected to the coal-fired power generation unit via a signal connection. Specifically, the controller receives load commands from the power grid and precisely controls the steam flow rate extracted to the air heater and thermochemical energy storage reactor by coordinating the opening of regulating valves on the pipelines of each steam extraction port of the steam turbine (such as the steam extraction port at the outlet of the intermediate pressure cylinder and the 7th stage steam extraction port of the low pressure cylinder), thereby achieving rapid increase and decrease in power generation.

[0070] The controller is connected to the carbon capture unit via a signal. Specifically, the controller monitors the inlet steam pressure and temperature of the reboiler and ensures a stable heat supply for the carbon capture system by adjusting the valves on the steam supply pipeline at the outlet of the thermochemical energy storage reactor or switching to a backup steam source (such as stage 7 extraction steam), thus ensuring that the carbon dioxide capture rate is not affected by the power plant's peak-shaving operation.

[0071] The controller is used to adjust the extraction steam flow, dry air flow, and operating status of the thermochemical energy storage reactor according to the grid load demand. Its core control logic is as follows: when receiving a load reduction command from the grid, the controller increases the extraction steam flow and dry air flow to the air heater from the intermediate-pressure cylinder, strengthening the energy storage process to quickly reduce power generation; when receiving a load increase command, the controller cuts off or reduces the extraction steam to the air heater and increases the low-grade extraction steam flow from the low-pressure cylinder to the thermochemical energy storage reactor, triggering its exothermic reaction to replace the high-grade extraction steam for heating the reboiler, thereby increasing the amount of steam used for power generation in the main turbine and thus achieving a rapid increase in power generation.

[0072] This invention presents a rapid response system for coal-fired power plants based on thermochemical energy storage. By introducing thermochemical energy storage units, it constructs a flexible operating mechanism with bidirectional coupling of "energy storage and release," effectively solving the problems of reduced output and slow response faced by coal-fired power plants equipped with carbon capture systems during peak shaving. When the grid needs to reduce load, the system can convert surplus steam heat energy into chemical energy for storage; when rapid load increase is required, it can release the stored energy to replace turbine extraction steam, providing heat to the carbon capture system, allowing more steam from the main turbine to be used for power generation, thereby significantly expanding the unit's peak shaving range and greatly improving the load response rate. The thermochemical energy storage and release process is coupled with organic Rankine cycle power generation and absorption heat pumps, realizing the recovery of various low-grade heat energy, such as compression heat and reboiler waste heat, from the carbon capture process for power generation or heating, turning waste into treasure. This overcomes the significant energy efficiency penalty caused by steam extraction in traditional carbon capture power plants, improving the economic efficiency and environmental compatibility of the power plant in the electricity market.

[0073] This invention also provides a rapid response method for coal-fired power plants based on thermochemical energy storage, applied to the rapid response system for coal-fired power plants based on thermochemical energy storage as described above. The method includes:

[0074] In response to the power grid's request to reduce the power plant's generating load, the system executes a load reduction energy storage process:

[0075] First steam is drawn from the intermediate pressure cylinder of the main steam turbine of the coal-fired power generation unit. The first steam is used to heat dry air, and the heated dry air is introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a dehydration reaction, so as to realize the storage of thermal energy.

[0076] In response to the power grid's request to increase the power plant's generating load, the system executes an energy release and load increase process:

[0077] Second steam is drawn from the low-pressure cylinder of the main turbine of the coal-fired power generation unit and introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a hydration reaction, generating high-temperature steam to release thermal energy.

[0078] Specifically, please refer to Figure 1 When a request to reduce power generation load is received, in response to the power grid's request to reduce the power plant's power generation load, the system executes a load reduction and energy storage process:

[0079] The controller coordinates the actions of each unit, drawing first steam (parameters approximately 220°C, 0.3 MPa) from the outlet of the intermediate-pressure cylinder (40) of the coal-fired power generation unit and transporting it through pipelines to the steam inlet of the air heater (36) of the energy storage unit. This first steam heats the dry air (34) supplied by the dry air pump (35) within the air heater (36), producing hot, dry air at approximately 180°C. This hot, dry air is then piped into the thermochemical energy storage reactor (37), driving the hygroscopic thermochemical energy storage material filled within it to undergo a dehydration (dehumidification) reaction, absorbing heat to achieve thermal energy storage. The approximately 110°C waste heat air discharged from the air outlet of the thermochemical energy storage reactor (37) is directed to the heat pump generator (28) of the absorption heat pump (32) of the heat pump heating unit as a driving heat source. The steam condensate in the air heater (36) is returned to the deaerator (56) in the multi-stage regenerative assembly for recovery. During this period, the carbon capture unit continues to operate: flue gas (1) is cooled by the first cooler (2), pressurized by the flue gas compressor (3), and enters the absorption tower (4) to react with the MEA absorbent replenishment liquid (5) and the MEA lean liquid from the lean liquid pump (12); the generated rich liquid is transported by the rich liquid pump (6), preheated by the MEA lean and rich liquid heat exchanger (7), and enters the separation tower (11) to be regenerated by the heat source provided by the reboiler (10); the desorbed CO2 gas is separated by the separator (14) and then compressed and cooled by the first compressor (15), the fourth cooler (16), the second compressor (17), the fifth cooler (18), the third compressor (19), and the sixth cooler (20) in sequence, and is finally stored in the pure CO2 storage tank (21); the flue gas (9) with CO2 removed is discharged into the air.

[0080] When a request to increase power generation load is received, in response to the power grid's request to increase the power plant's power generation load, the system executes an energy release and load increase process:

[0081] The controller switches the heat source and extracts second steam (parameters approximately 80°C, 0.11 MPa) from the 7th stage extraction port (49) of the low-pressure cylinder (41) of the coal-fired power generation unit. This second steam is then piped into the steam inlet of the thermochemical energy storage reactor (37). The second steam drives the dehydrated energy storage material in the reactor to undergo a hydration (hygroscopic) reaction, which releases heat and generates a high-temperature steam mixture of approximately 120°C to release thermal energy. The generated high-temperature steam flows out from the steam outlet of the thermochemical energy storage reactor (37) and is mainly transported to the reboiler (10) of the carbon capture unit through the steam supply pipeline to provide a regeneration heat source for the separation tower (11). Excess steam enters the organic Rankine cycle power generation system of the power generation unit through a branch steam supply pipeline, driving the organic working fluid evaporator (22), the organic working fluid turbine (23), and the first generator (24) to generate electricity. After performing work, the exhaust steam is condensed in the first condenser (25), transported by the organic working fluid circulation pump (26), and returned to the cycle after recovering the waste heat of the compression cooling subsystem (including the fourth cooler (16), the fifth cooler (18), and the sixth cooler (20)) through the organic working fluid preheater (27). The main generator set reduces steam extraction, allowing more steam to expand and perform work in the high-pressure cylinder (39), the intermediate-pressure cylinder (40), and the low-pressure cylinder (41), driving the second generator (42) to increase output. The 115°C working fluid at the outlet of the reboiler (10) enters the shell side of the waste heat recovery unit (63), heating the tube-side feedwater from the seventh stage regenerator (59) in the multi-stage regenerator assembly. After heating, the feedwater is sent to the inlet of the fifth stage regenerator (57). The feedwater is driven by the first feedwater circulation pump (61) and the second feedwater circulation pump (62), and flows through the second condenser (52), the first stage regenerator (53), the second stage regenerator (54), the third stage regenerator (55), the deaerator (56), the fifth stage regenerator (57), the sixth stage regenerator (58), the seventh stage regenerator (59) and the eighth stage regenerator (60) before returning to the boiler (38).

[0082] The technical features and effects of the method proposed in the embodiments of the present invention are the same as those of the system proposed in the embodiments of the present invention, and will not be repeated here. Each step in the above method can be implemented, in whole or in part, by the above system. The above method can also be embedded in or independent of the processor in a computer device in software or hardware form, or stored in the memory of a computer device in software form, so that the controller can call and execute the operations corresponding to the above steps.

[0083] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A fast response system for coal-fired power plants based on thermo-chemical energy storage, characterized in that, It includes carbon capture units, power generation units, energy storage units, and coal-fired power generation units; The coal-fired power generation unit includes a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a generator, and a multi-stage regenerative assembly connected by pipelines. The carbon capture unit includes an absorption tower for absorbing carbon dioxide and a separation tower for rich liquid regeneration, the separation tower being equipped with a reboiler capable of absorbing external heat sources. The energy storage unit includes a dry air pump, an air heater, and a thermochemical energy storage reactor connected in sequence by pipelines. The outlet of the intermediate-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the air heater of the energy storage unit through a steam extraction pipe, and the steam extraction port of the low-pressure cylinder of the coal-fired power generation unit is connected to the steam inlet of the thermochemical energy storage reactor of the energy storage unit through a steam extraction pipe. The steam outlet of the thermochemical energy storage reactor of the energy storage unit is connected to the steam inlet of the reboiler of the carbon capture unit via a steam supply pipeline. The cooler of the carbon capture unit is connected to the organic working fluid preheater of the power generation unit via a waste heat recovery pipeline. The steam outlet of the thermochemical energy storage reactor of the energy storage unit is also connected to the organic working fluid evaporator of the power generation unit via a branch steam supply pipeline.

2. The thermally chemically energy storage based fast response system for coal-fired power plants of claim 1, wherein, The power generation unit is an organic Rankine cycle power generation unit, which includes an organic working fluid evaporator, an organic working fluid turbine, a generator, a first condenser, and an organic working fluid pump connected by pipes. The organic working fluid preheater is installed on the pipeline between the outlet of the organic working fluid pump and the inlet of the organic working fluid evaporator.

3. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The multi-stage regenerative assembly includes a second condenser, several low-pressure heaters, a deaerator, and several high-pressure heaters, which are connected in sequence via pipes and a water pump.

4. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The system also includes a heat pump heating unit, which includes an absorption heat pump. The heat pump generator of the absorption heat pump is connected to the air outlet of the thermochemical energy storage reactor of the energy storage unit through a pipe to receive the waste heat air discharged from the reactor as a driving heat source.

5. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The carbon capture unit also includes a compression and cooling subsystem, which includes a rich liquid pump, a lean and rich liquid heat exchanger, a lean liquid pump, and several compressors and several coolers for processing pure carbon dioxide, connected in sequence.

6. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 5, characterized in that, The waste heat recovery pipeline is connected between the cooler of the compression cooling subsystem and the organic working fluid preheater of the organic Rankine cycle power generation unit.

7. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The system also includes a controller, which is signal-connected to the energy storage unit, the coal-fired power generation unit and the carbon capture unit, and is used to adjust the extraction steam flow rate, dry air flow rate and the operating status of the thermochemical energy storage reactor according to the grid load demand.

8. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The thermochemical energy storage reactor is filled with a hygroscopic thermochemical energy storage material, which releases heat during the moisture absorption process and absorbs heat during the dehumidification process.

9. The rapid response system for coal-fired power plants based on thermochemical energy storage as described in claim 1, characterized in that, The coal-fired power generation unit also includes a waste heat recovery unit. The shell-side inlet of the waste heat recovery unit is connected to the outlet of the reboiler, the tube-side inlet of the waste heat recovery unit is connected to the outlet of the first-stage regenerator in the multi-stage regenerator assembly, and the tube-side outlet of the waste heat recovery unit is connected to the inlet of the next higher-stage regenerator. This unit is used to recover heat from the working fluid at the reboiler outlet to heat the feedwater.

10. A rapid response method for coal-fired power plants based on thermochemical energy storage, applied to the system described in any one of claims 1-9, characterized in that, include: In response to the power grid's request to reduce the power plant's generating load, the system executes a load reduction energy storage process: First steam is drawn from the intermediate pressure cylinder of the main steam turbine of the coal-fired power generation unit. The first steam is used to heat dry air. The heated dry air is then introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a dehydration reaction, thereby achieving the storage of thermal energy. In response to the power grid's request to increase the power plant's generating load, the system executes an energy release and load increase process: Second steam is drawn from the low-pressure cylinder of the main turbine of the coal-fired power generation unit and introduced into the thermochemical energy storage reactor to drive the energy storage material in the thermochemical energy storage reactor to undergo a hydration reaction, generating high-temperature steam to release thermal energy.

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