Thermal chemical heat storage and carbon capture system for thermal power plant

Abstract

The thermal chemical heat storage and carbon capture system comprises a coal-fired boiler, a calcination reactor and a carbonation reactor, the calcination reactor extracts high-temperature flue gas from the front wall of a hearth of the coal-fired boiler, the high-temperature flue gas drives CaCO3 in the calcination reactor to be decomposed into CaO and CO2, and heat storage is achieved; the reacted flue gas is pumped back into a tail flue of the coal-fired boiler, and the flue gas flow required by the reaction is controlled through a flow control valve on a pumping pipeline; caO generated by the calcination reaction can enter the carbonation reactor in the heat release stage, a heat release carbonation reaction is carried out, heat is released, CaCO3 obtained after the heat release reaction returns to the calcination reactor through a pipeline to serve as a reaction raw material, and CO2 obtained after the heat release reaction is output to a heat supply system. The integration of heat storage, heat release and carbon capture is realized by utilizing calcium-based material circulation, and the peak regulation capacity and the carbon capture economy of the coal-fired unit are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power generation and carbon capture technology, and in particular, a thermochemical thermal storage and carbon capture system for thermal power plants. Background Technology

[0002] Currently, my country's installed capacity of new energy sources is showing a continuous growth trend. Renewable energy sources such as wind and solar power typically exhibit intermittent and fluctuating characteristics. Large-scale grid connection will cause certain impacts on the power grid, posing a series of new challenges to the power system in terms of supply and demand balance, system regulation, and stability characteristics. Therefore, in-depth peak-shaving retrofitting of thermal power units is urgently needed. To maintain the stability and balance of the power grid, the role of traditional coal-fired power plants is gradually shifting from primary power generation to peak-shaving centers. They need to possess rapid start-up and shutdown, rapid load change, and deep peak-shaving capabilities to adapt to the volatility of renewable energy and achieve flexibility and stability in power supply.

[0003] Upgrading coal-fired power units to improve their flexibility and regulation capabilities, including enhancing peak-shaving capacity, ramp-up speed, and start-up / shutdown times, is crucial for ensuring the absorption of renewable energy and the safe and stable operation of the power system. Heat and power (CHP) decoupling, a key component of this flexibility upgrade, aims to resolve the conflict between electrical and thermal loads during the heating season when units operate in a "heat-driven" mode. CHP decoupling allows coal-fired power units to more flexibly adjust their power output according to grid load demands while meeting heating needs, thus avoiding energy waste and improving energy efficiency and the overall economics of coal-fired power plants. For example, some CHP decoupling technologies combine steam and electric heating to achieve thermal storage in molten salt systems, enabling cascaded utilization of steam energy and improving energy efficiency. Developing a combination of coal-fired power and thermal storage not only benefits grid dispatch but also increases the profitability of power generation companies, thus possessing significant development potential.

[0004] Furthermore, CO2 produced by coal-fired power plants exacerbates the greenhouse effect, making it crucial to achieve greenhouse gas emission reduction targets. Carbon capture technology has been identified as a key measure to reduce carbon emissions from the power sector. Mature technologies such as chemisorbents like amine scrubbing and oxy-fuel combustion suffer significant efficiency losses when integrated into power plants. While some technologies exist for waste heat recovery and CO2 capture, systems combining thermochemical heat storage of high-temperature flue gas from coal-fired boilers, CO2 capture, and thermoelectric decoupling have not yet been fully developed and applied.

[0005] CO3 / CaO thermochemical thermal storage technology has advantages such as high thermal density and low cost. If it can be applied to coal-fired boiler systems and combined with CO2 capture and thermoelectric decoupling, it will provide a new approach for efficient energy utilization and environmental protection. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a thermochemical thermal storage and CO2 capture system based on calcium-based materials (CaCO3 / CaO) for coal-fired boilers in thermal power plants. This system directly embeds a high-temperature calcium-based thermal storage system from the boiler flue gas side, realizing thermal storage of the coal-fired boiler through high-temperature flue gas drive, solving the thermoelectric coupling problem, improving the system's flexibility and comprehensive energy utilization efficiency, and synergistically increasing the CO2 concentration in the tail flue gas, effectively reducing carbon capture operation costs.

[0007] The technical solution of the present invention is as follows: A thermochemical thermal energy storage and carbon capture system for a thermal power plant mainly includes a coal-fired boiler, a calcination reactor, and a carbonation reactor, with the following connection layout: A flue gas extraction port is provided on the front wall of the coal-fired boiler furnace. The flue gas extraction port is connected to the calcination reactor through a high-temperature flue gas conveying pipeline. The CaO outlet of the calcination reactor is connected to the carbonation reactor through a CaO conveying pipeline. A CaO storage bin is provided on the CaO conveying pipeline. An exhaust fan and a mixed flue gas extraction pipeline are provided between the mixed gas outlet of the calcination reactor and the end of the coal-fired boiler furnace. The tail flue of the coal-fired boiler is connected to the flue gas dust removal and separation device through a mixed flue gas pipeline. The CO2 outlet of the flue gas dust removal and separation device is connected to a CO2 storage tank. The CO2 storage tank is connected to the carbonation reactor through a CO2 conveying pipeline. The CaCO3 outlet of the carbonation reactor is connected to the CaCO3 storage tank via a CaCO3 conveying pipeline. The CaCO3 storage tank is connected to the CaCO3 inlet of the calcination reactor via a conveying pipeline. The CO2 outlet of the carbonation reactor is connected to the heat exchange system via a conveying pipeline. The heat storage and heat release processes implemented by the system are as follows: During the heat storage stage: High-temperature flue gas (850-1000℃) is extracted from the front wall of the coal-fired boiler furnace and transported into the calcination reactor. Under normal pressure and high temperature of 850℃, the high-temperature flue gas drives the decomposition of CaCO3 in the calcination reactor into CaO and CO2 (CaCO3→CaO+CO2-ΔH), thus storing heat. The CaO produced by the calcination reaction is stored in the CaO storage silo and used to participate in the thermochemical heat storage reaction that releases heat for later use. The CO2 produced by the calcination reaction is mixed with the flue gas after heat storage and then returned to the tail flue of the coal-fired boiler by the induced draft fan. The mixed flue gas significantly increases the CO2 concentration in the flue gas, which can improve the downstream separation efficiency and reduce carbon capture costs. The mixed flue gas from the tail flue of the coal-fired boiler is drawn into the flue gas dust removal and separation device by the induced draft fan. The separated CO2 is stored in the CO2 temporary storage tank for use in the thermochemical heat storage reaction when releasing heat. The separated flue gas is discharged through the chimney. In the exothermic stage: The carbonation reactor receives CaO from the CaO storage silo and feeds it into the carbonation reactor through the CaO feeder to carry out an exothermic carbonation reaction (CaO + CO2 → CaCO3 + ΔH), releasing heat. During the reaction, an excess of 20%-50% CO2 can be introduced into the carbonation reactor. The CO2 acts as a reactant gas and motive fluid, absorbing the heat generated. The reaction temperature is regulated by the CO2 circulation flow rate. The CO2 after the exothermic reaction in the carbonation reactor is output to the heating system.

[0008] Furthermore, a CaO cooler is provided between the calcination reactor and the CaO storage silo. The CaO obtained from the decomposition of the calcination reaction is transported to the CaO storage silo for temporary storage after absorbing residual heat in the CaO cooler.

[0009] Furthermore, a flue gas heat exchanger is installed between the CO2 outlet of the calcination reactor and the exhaust fan. The flue gas mixed in the calcination reactor is drawn into the flue gas heat exchanger for waste heat recovery, and the flue gas after waste heat recovery is returned to the tail flue of the coal-fired boiler.

[0010] Furthermore, the flue gas dust removal and separation device includes a dust removal device, a CO2 separation device, and a first compressor. The dust removal device is installed on the front end pipeline of the induced draft fan. Under the suction action of the induced draft fan, the mixed flue gas from the tail flue of the coal-fired boiler enters the dust removal device for dust removal, and then enters the CO2 separation device through the induced draft fan. The separated CO2 is compressed and stored in the CO2 temporary storage tank by the first compressor.

[0011] Furthermore, the CO2 separation device employs membrane separation technology to separate CO2 from the mixed gas through a CO2 separation membrane.

[0012] Furthermore, when the exhaust fan draws high-temperature flue gas from the coal-fired boiler, the flow rate of the flue gas is controlled by a flow control valve configured on the pipeline in front of the exhaust fan, so as to dynamically adjust the heat storage / release ratio and decouple the rigid relationship between the boiler heat load and the power generation.

[0013] Furthermore, the calcination reactor can employ a fluidized bed or moving bed structure.

[0014] Furthermore, the heating system includes a first heat exchanger and a second heat exchanger. The high-temperature CO2 discharged from the carbonation reactor is divided into two paths. One path of high-temperature CO2 gas heats the feedwater in the first heat exchanger to generate high-grade steam, which is then returned to the boiler turbine. The other path of high-temperature CO2 gas heats the circulating water in the heating system in the second heat exchanger for heat supply.

[0015] Furthermore, a second compressor and a CO2 storage tank are connected sequentially to the rear end of the first heat exchanger. After the high-temperature CO2 gas is cooled by the first heat exchanger, it is compressed by the second compressor and stored in the CO2 storage tank for other uses.

[0016] Furthermore, a CaCO3 cooler is installed between the carbonation reactor and the CaCO3 storage tank. The CaCO3 produced by the carbonation reaction absorbs residual heat in the CaCO3 cooler and is then temporarily stored in the CaCO3 storage tank. When heat storage and absorption are required, it is transported to the calcination reactor to participate in the reaction.

[0017] Furthermore, the waste heat recovery from the flue gas heat exchanger and CaO cooler can be used to heat the feedwater, exchange heat with the circulating water in the heating system, and provide heat energy to the heating system. During the operation of the system, the heat storage stage and the heat release stage cycle sequentially. MgO or Al2O3 is added as an anti-sintering agent in the CaCO3 / CaO cycle to improve the material's cycle stability.

[0018] During the heat storage stage (low grid load): increase the flue gas flow rate of the calcining reactor, store heat in CaO, and reduce boiler output.

[0019] The exothermic phase (high grid load): The carbonation reactor is started to release stored heat to generate steam, thereby increasing the unit's power supply or heating capacity.

[0020] The beneficial effects of this invention are as follows: This system, through process innovation and optimization, utilizes calcium-based materials to achieve integrated "heat storage-heat release-carbon capture", significantly improving the peak-shaving capacity and carbon capture economy of coal-fired units.

[0021] This system employs calcium-based thermochemical thermal storage, using inexpensive, non-toxic, and non-corrosive limestone as raw material. The storage temperature exceeds 850℃, and the volumetric energy density is significantly higher than that of molten salt thermal storage, breaking the upper temperature limit of molten salt thermal storage (the nitrate limit is approximately 565℃). Compared to molten salt using steam for thermal storage, this system directly utilizes high-temperature flue gas, improving the efficiency of the thermal cycle.

[0022] By dynamically adjusting the heat storage / release ratio, the rigid correlation between boiler heat load and power generation is decoupled, and heat and electricity output can be flexibly adjusted according to actual needs, thereby improving the system's flexibility and overall energy utilization efficiency.

[0023] The calcination reaction increases the CO2 concentration in flue gas, reduces capture energy consumption, and contributes to the goal of carbon neutrality, making it suitable for integration into low-carbon energy systems. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the framework structure of the present invention. Detailed Implementation

[0025] like Figure 1 As shown, a thermochemical thermal energy storage and carbon capture system for a thermal power plant mainly includes a coal-fired boiler, a calcination reactor, and a carbonation reactor, with the following connection layout: A flue gas extraction port is provided on the front wall of the coal-fired boiler furnace. The flue gas extraction port is connected to the calcination reactor through a high-temperature flue gas conveying pipeline. The CaO outlet of the calcination reactor is connected to the carbonation reactor through a CaO conveying pipeline. A CaO cooler and a CaO storage bin are installed on the CaO conveying pipeline. A flue gas heat exchanger and an induced draft fan are installed sequentially on the mixed gas extraction pipeline between the mixed gas outlet of the calcination reactor and the end of the coal-fired boiler furnace. The flue gas mixed in the calcination reactor is extracted into the flue gas heat exchanger for waste heat recovery. The flue gas after waste heat recovery is then returned to the tail flue of the coal-fired boiler.

[0026] The tail flue of the coal-fired boiler is connected to the flue gas dust removal and separation device through a mixed flue gas pipeline. The CO2 outlet of the flue gas dust removal and separation device is connected to a CO2 temporary storage tank, which is connected to the carbonation reactor through a CO2 conveying pipeline.

[0027] The CaCO3 outlet of the carbonation reactor is connected to a CaCO3 storage silo via a CaCO3 delivery pipeline. The CaCO3 storage silo is connected to the CaCO3 inlet of the calcination reactor via a delivery pipeline. When heat storage and absorption are required, the CaCO3 is delivered to the calcination reactor to participate in the reaction. The CO2 outlet of the carbonation reactor is connected to a heat exchange system via a delivery pipeline. The heating system includes a first heat exchanger and a second heat exchanger. The high-temperature CO2 discharged from the carbonation reactor is divided into two paths. One path of high-temperature CO2 gas heats the feedwater in the first heat exchanger to generate high-grade steam, which is then returned to the boiler turbine. The other path of high-temperature CO2 gas heats the circulating water in the heating system in the second heat exchanger for heat supply.

[0028] In this embodiment, the flue gas dust removal and separation device includes a dust removal device, a CO2 separation device, and a first compressor. The dust removal device is installed on the front end pipeline of the induced draft fan. Under the suction of the induced draft fan, the mixed flue gas from the tail flue of the coal-fired boiler enters the dust removal device for dust removal, and then enters the CO2 separation device through the induced draft fan. The CO2 separation device adopts membrane separation technology, and separates CO2 from the mixed gas through the CO2 separation membrane. The separated CO2 is compressed and stored in the CO2 temporary storage tank by the first compressor.

[0029] In this embodiment, a second compressor and a CO2 storage tank are connected sequentially to the rear end of the first heat exchanger. After the high-temperature CO2 gas is cooled by the first heat exchanger, it is compressed by the second compressor and stored in the CO2 storage tank for other uses.

[0030] In this embodiment, the waste heat recovery from the flue gas heat exchanger and CaO cooler can be used to heat the feedwater and exchange heat with the circulating water in the heating system to provide heat energy for the heating system.

[0031] In this embodiment, the calcination reactor of this system can adopt a fluidized bed or moving bed structure.

[0032] The system mainly consists of a heat storage phase and a heat release phase during operation.

[0033] During the heat storage stage (low grid load): increase the flue gas flow rate of the calcining reactor, store heat in CaO, and reduce boiler output.

[0034] The exothermic phase (high grid load): The carbonation reactor is started to release stored heat to generate steam, thereby increasing the unit's power supply or heating capacity.

[0035] When the system is started, the coal-fired boiler 1 is turned on first. After the coal-fired boiler 1 is running stably, the high-temperature flue gas of about 850-1000℃ is extracted from the flue gas extraction port on the front wall of the furnace of the coal-fired boiler 1 through the exhaust fan 4 of the flue gas extraction device and the flow control valve on the high-temperature flue gas conveying pipeline, and the high-temperature flue gas is conveyed to the calcining reactor 2. Inside the calcination reactor 2, high-temperature flue gas undergoes a thermochemical reaction with the CaCO3 / CaO heat storage material, causing CaCO3 to decompose into CaO and CO2, thus storing heat. Simultaneously, the calcination reactor 2 is equipped with temperature and pressure sensors to monitor the temperature and pressure within the reactor in real time, ensuring the reaction proceeds under suitable conditions. CaO and CO2 exchange heat with the feedwater in the power generation system through waste heat recovery.

[0036] The mixed flue gas containing CO2 produced by the reaction enters the flue gas heat exchanger 3. After waste heat recovery, it is sent to the tail flue of the coal-fired boiler by the exhaust fan 4. After particulate matter is removed by the dust removal device 5, it goes to the CO2 separation device 7. CO2 is separated from the mixed gas by membrane separation technology. The separated CO2 is compressed by the first compressor 8 and stored in the CO2 temporary storage tank 9. When heat needs to be released, the stored CO2 is passed into the carbonation reactor 13, where CaO reacts with CO2 to regenerate CaCO3 and release heat. The resulting high-temperature gas enters the first heat exchanger 17 through a pipeline, heating the feedwater to generate high-grade steam, which is used to drive the steam turbine to generate electricity. Another portion of the high-temperature gas enters the second heat exchanger through a pipeline, exchanging heat with the circulating water in the heating system for heating purposes.

[0037] During the operation of the system, the heat storage stage and the heat release stage cycle sequentially. MgO or Al2O3 is added as an anti-sintering agent in the CaCO3 / CaO cycle to improve the material's cycle stability.

[0038] Based on actual heat and electricity demands, the flow rate of extracted flue gas is controlled by adjusting the flow control valve, and the operating parameters of the thermochemical thermal storage reactor are adjusted to achieve flexible adjustment of heat and electricity output and realize the purpose of thermoelectric decoupling.

Claims

1. A thermochemical thermal energy storage and carbon capture system for a thermal power plant, characterized in that, The system includes a coal-fired boiler, a calcination reactor, and a carbonation reactor, with the following connection layout: A flue gas extraction port is provided on the front wall of the coal-fired boiler furnace. The flue gas extraction port is connected to the calcination reactor through a high-temperature flue gas conveying pipeline. The CaO outlet of the calcination reactor is connected to the carbonation reactor through a CaO conveying pipeline. A CaO storage bin is provided on the CaO conveying pipeline. An exhaust fan and a mixed flue gas extraction pipeline are provided between the mixed gas outlet of the calcination reactor and the end of the coal-fired boiler furnace. The tail flue of the coal-fired boiler is connected to the flue gas dust removal and separation device through a mixed flue gas pipeline. The CO2 outlet of the flue gas dust removal and separation device is connected to a CO2 storage tank. The CO2 storage tank is connected to the carbonation reactor through a CO2 conveying pipeline. The CaCO3 outlet of the carbonation reactor is connected to the CaCO3 storage tank via a CaCO3 conveying pipeline. The CaCO3 storage tank is connected to the CaCO3 inlet of the calcination reactor via a conveying pipeline. The CO2 outlet of the carbonation reactor is connected to the heat exchange system via a conveying pipeline.

2. The thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: A CaO cooler is installed between the calcination reactor and the CaO storage tank. The CaO obtained from the decomposition of the calcination reaction is transported to the CaO storage tank for temporary storage after absorbing the residual heat in the CaO cooler.

3. The thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: A flue gas heat exchanger is installed between the CO2 outlet of the calcination reactor and the exhaust fan. The flue gas mixed in the calcination reactor is drawn into the flue gas heat exchanger for waste heat recovery. The flue gas after waste heat recovery is then returned to the tail flue of the coal-fired boiler.

4. The thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The flue gas dust removal and separation device includes a dust removal device, a CO2 separation device, and a first compressor. The dust removal device is installed on the front end pipeline of the induced draft fan. Under the suction of the induced draft fan, the mixed flue gas from the tail flue of the coal-fired boiler enters the dust removal device for dust removal, and then enters the CO2 separation device through the induced draft fan. The separated CO2 is compressed and stored in the CO2 temporary storage tank by the first compressor.

5. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The CO2 separation device uses membrane separation technology to separate CO2 from the mixed gas through a CO2 separation membrane.

6. The thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The calcination reactor adopts a fluidized bed or moving bed structure.

7. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The heating system includes a first heat exchanger and a second heat exchanger. The high-temperature CO2 discharged from the carbonation reactor is divided into two paths. One path of high-temperature CO2 gas heats the feedwater in the first heat exchanger to generate high-grade steam, which is then returned to the boiler turbine. The other path of high-temperature CO2 gas heats the circulating water in the heating system in the second heat exchanger for heat supply.

8. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The first heat exchanger is connected in sequence to a second compressor and a CO2 storage tank. After the high-temperature CO2 gas is cooled by the first heat exchanger, it is compressed by the second compressor and stored in the CO2 storage tank for other uses.

9. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: A CaCO3 cooler is installed between the carbonation reactor and the CaCO3 storage tank. The CaCO3 produced by the carbonation reaction is transported to the CaCO3 storage tank for temporary storage after absorbing the residual heat in the CaCO3 cooler. When heat storage and absorption are required, the heat is transported to the calcination reactor to participate in the reaction.

10. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1, characterized in that: The waste heat recovery from the flue gas heat exchanger and CaO cooler is used to heat the feedwater, which exchanges heat with the circulating water in the heating system to provide heat energy for the heating system.

11. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to any one of claims 1-10, characterized in that, The heat storage and heat release processes implemented by the system are as follows: During the heat storage stage: High-temperature flue gas at 850-1000℃ is drawn from the front wall of the furnace of the coal-fired boiler and transported into the calcination reactor. Under normal pressure and high temperature of 850℃, the high-temperature flue gas drives the CaCO3 in the calcination reactor to decompose into CaO and CO2, thereby storing heat. The CaO produced by the calcination reaction is stored in the CaO storage silo and used to participate in the thermochemical heat storage reaction that releases heat for later use. The CO2 produced by the calcination reaction is mixed with the flue gas after heat storage and then returned to the tail flue of the coal-fired boiler by the exhaust fan. The mixed flue gas from the tail flue of the coal-fired boiler is drawn into the flue gas dust removal and separation device by the induced draft fan. The separated CO2 is stored in the CO2 temporary storage tank for use in the thermochemical heat storage reaction when releasing heat. The separated flue gas is discharged through the chimney. In the exothermic stage: the carbonation reactor receives CaO from the CaO storage silo and feeds it into the carbonation reactor through the CaO feeder to carry out an exothermic carbonation reaction and release heat; during the reaction, excess CO2 is introduced into the carbonation reactor, and CO2 absorbs the heat generated as a reaction gas and driving fluid, and the reaction temperature is regulated by the CO2 circulation flow rate; the CO2 after the exothermic reaction in the carbonation reactor is continuously output to the heating system.

12. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to any one of claims 11, characterized in that: During the reaction, an excess of 20%-50% CO2 is required to be introduced as the reaction gas and driving fluid.

13. A thermochemical thermal energy storage and carbon capture system for a thermal power plant according to claim 1 or 11, characterized in that: During the operation of the system, the heat storage stage and the heat release stage cycle sequentially, and MgO or Al2O3 is added as an anti-sintering agent in the CaCO3 / CaO cycle.

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