Supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak regulation cogeneration system

Abstract

The invention discloses a supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak regulation cogeneration system, which is characterized in that circulating flue gas of a pressurized oxygen-enriched circulating fluidized bed combustion mechanism for co-combustion of coal and biomass provides multiple times of heat exchange for a working medium of a supercritical carbon dioxide power generation mechanism; meanwhile, high-temperature flue gas rich in water vapor is pressurized to preheat electrolytic reactant water in the SOEC peak regulation cogeneration mechanism; one part of pure CO2 obtained by treating combustion products is used as a circulating working medium, the other part of the pure CO2 is used as another electrolytic reactant, oxygen generated by co-electrolysis can provide an oxygen source for combustion, and generated hydrocarbon substances are used as chemicals or fuels; the SOEC and the supercritical carbon dioxide power generation mechanism realize the targets of flexible start and stop and peak and frequency regulation under the background of power grid load change. According to the system, the pressurized oxygen-enriched fluidized bed, supercritical carbon dioxide circulation and SOEC peak regulation are integrated, efficient power generation, carbon emission reduction and energy storage peak regulation are considered, and the overall benefit of an energy system is improved.

Description

Technical Field

[0001] This invention relates to a fluidized bed power generation system, and more particularly to a supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving cogeneration system. Background Technology

[0002] Conventional air combustion and steam Rankine cycles are no longer sufficient to meet the power plant's demands for low carbon emissions, high efficiency, and flexible peak shaving. Oxygen-enriched combustion, with its advantages of low retrofit costs, high carbon capture efficiency, and wide fuel adaptability, is suitable for large thermal power units and is one of the most promising carbon capture technologies currently available. However, conventional oxy-fuel combustion suffers from energy losses due to mismatches between the carbon dioxide compression unit and the air separation oxygen production unit and the combustion pressure. Pressurized oxy-fuel combustion can solve this problem. Furthermore, the increased pressure helps recover the latent heat of vaporization of water vapor in boiler flue gas, effectively improving the system's cycle efficiency. It also offers better fuel adaptability, more uniform temperature distribution within the furnace, and lower SO2 and NO emissions. x Characteristics such as emissions.

[0003] Carbon dioxide readily reaches a supercritical state, possessing advantages such as high energy density, good compressibility, excellent heat transfer performance, and low corrosiveness to metals. The Brayton cycle, using carbon dioxide as the working fluid, not only boasts higher efficiency than the traditional steam Rankine cycle but also features a compact system, simple cycle, and high safety. Applying supercritical carbon dioxide cycles to coal-fired power generation can significantly improve cycle efficiency. Meanwhile, circulating fluidized bed boilers offer advantages such as wide fuel adaptability, high combustion efficiency, rapid load response, and low pollutant emissions. Coupled with S-CO2 cycles, they can further enhance the peak-shaving performance and environmental benefits of thermal power units. For example, Chinese patent 2018105681888 uses a pressurized oxygen-enriched fluidized bed for coal combustion, employing a supercritical carbon dioxide cycle for external power generation to improve the pressure matching of the combustion system and increase the power generation efficiency of the thermal cycle. However, insufficient comprehensive energy utilization still exists, making it difficult to simultaneously meet the multiple demands of high-efficiency power generation, deep carbon reduction, and flexible peak-shaving. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide a supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak shaving cogeneration system that integrates pressurized oxygen-enriched fluidized bed, supercritical carbon dioxide cycle and SOEC peak shaving, so as to take into account efficient power generation, carbon emission reduction and energy storage peak shaving, and improve the overall efficiency and competitiveness of the energy system.

[0005] Technical Solution: The present invention discloses a supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving cogeneration system, comprising a pressurized oxygen-enriched circulating fluidized bed combustion mechanism, a supercritical carbon dioxide power generation mechanism, and an SOEC peak-shaving cogeneration mechanism. The circulating flue gas from the pressurized oxygen-enriched circulating fluidized bed combustion mechanism provides cascade heat exchange for the circulating working fluid of the supercritical carbon dioxide power generation mechanism, and preheats and vaporizes the water electrolysis reactant in the SOEC peak-shaving cogeneration mechanism. Part of the CO2 obtained after processing the combustion products serves as the circulating working fluid of the supercritical carbon dioxide power generation mechanism, and the remaining CO2 serves as another electrolysis reactant in the SOEC peak-shaving cogeneration mechanism. After heat exchange in the combustion mechanism, part of the working fluid of the supercritical carbon dioxide power generation mechanism enters the SOEC peak-shaving cogeneration mechanism for electrolysis. The oxygen generated by SOEC electrolysis provides the oxygen source for the combustion mechanism. Furthermore, the supercritical carbon dioxide power generation mechanism and the SOEC peak-shaving cogeneration mechanism can be flexibly started and stopped according to different grid load levels to complete peak shaving and frequency regulation, achieving peak shaving and valley filling and ensuring stable grid operation.

[0006] Preferably, the pressurized oxygen-enriched circulating fluidized bed combustion mechanism includes a circulating fluidized bed, one or more reheaters, a cyclone separator, and a return feeder. The one or more reheaters are sequentially arranged inside the circulating fluidized bed. The inlet of the cyclone separator is connected to the circulating fluidized bed. The solid outlet below the cyclone separator is connected to the return feeder, and the gas outlet above it is connected to the exhaust gas heating surface. The high-temperature flue gas and particles generated during combustion exchange heat with the working fluid of the supercritical carbon dioxide power generation mechanism through the one or more reheaters, and then undergo gas-solid separation through the cyclone separator. The resulting particles enter the return feeder and are diverted: one part is returned to the circulating fluidized bed, and the other part enters an external heat exchanger connected to the return feeder to exchange heat with the working fluid of the supercritical carbon dioxide power generation mechanism. The cooled particles are then returned to the circulating fluidized bed, achieving the dual functions of secondary heat utilization and bed temperature regulation. The resulting high-temperature flue gas enters the exhaust gas heating surface for waste heat recovery.

[0007] Preferably, the exhaust gas heating surface is equipped with a regenerator, an economizer, and a flue gas heat exchanger. The regenerator is connected to a supercritical carbon dioxide power generation unit. The economizer inlet is connected to the supercritical carbon dioxide power generation unit, and the outlet is connected to one or more reheaters in the circulating fluidized bed. The flue gas heat exchanger is connected to an SOEC peak shaving cogeneration unit.

[0008] Preferably, the supercritical carbon dioxide power generation mechanism includes a main turbine, an auxiliary turbine, a high-temperature regenerator, a low-temperature regenerator, a multi-stage compression and cooling device, and a third compressor. The outlet of the main turbine is connected to the auxiliary turbine via the regenerator and an external heat exchanger. The auxiliary turbine has two outlets. One outlet is connected to the high-temperature regenerator and the low-temperature regenerator in sequence. The outlet of the low-temperature regenerator is divided into two paths. One path is connected to the high-temperature regenerator in sequence via the multi-stage compression and cooling device and the low-temperature regenerator. The other path is connected to the high-temperature regenerator via the third compressor. The high-temperature regenerator is connected to the heat exchanger in the circulating fluidized bed via an economizer. The other outlet of the turbine is connected to the SOEC peak-shaving cogeneration mechanism.

[0009] The working fluid at the outlet of the main turbine is divided into two streams: one stream is sent to an external heat exchanger to exchange heat with high-temperature particles and waste heat flue gas, realizing secondary heating of the working fluid and utilization of waste heat; the other stream is heated by a regenerator, and then the two streams of working fluid enter the auxiliary turbine to continue to expand and do work, thereby realizing secondary energy recovery; part of the working fluid at the outlet of the auxiliary turbine is used as a reactant and merges with part of the CO2 at the outlet of the denitrification equipment, and is sent together into the synthesis hydrocarbon reactor. Another portion enters the high-temperature regenerator and the low-temperature regenerator in sequence, fully recovering the remaining heat to the working fluid flow on the compression side, forming an efficient closed regenerating link. The regenerated CO2 working fluid is divided into two paths. One part of the working fluid is cooled and pressurized in a multi-stage compression and cooling device in sequence, and then heated by the low-temperature regenerator, so that the working fluid is gradually restored to the pressure and temperature state required for the cycle. The other part of the working fluid is pressurized by the parallel third compressor and merged with the mainstream, and enters the high-temperature regenerator for preheating. Then it enters the circulating fluidized bed through the economizer, and completes the temperature rise through the first reheater and the second reheater. It then enters the main turbine to expand and do work, thereby realizing the complete operation of the closed Brayton cycle.

[0010] Preferably, the SOEC peak-shaving cogeneration mechanism includes a gas heat exchanger, an electric heater, and an electrolysis device connected in sequence. Water vapor enters the gas heat exchanger and exchanges heat with the high-temperature tail gas from the SOEC electrolysis outlet. After heat exchange, the water vapor and a portion of the CO2 obtained after treatment enter the electric heater and are heated to the optimal operating temperature range of SOEC. Subsequently, it enters the electrolysis device to undergo a co-electrolysis reaction to generate hydrogen, carbon monoxide, and oxygen, wherein the oxygen is supplied to the pressurized oxygen-enriched circulating fluidized bed combustion mechanism.

[0011] Preferably, before the water vapor enters the gas heat exchanger, the feed water absorbs the waste heat of the high-temperature flue gas rich in water vapor from the pressurized oxygen-enriched circulating fluidized bed combustion mechanism to achieve preliminary preheating and gasification, thereby obtaining water vapor.

[0012] Preferably, the SOEC peak shaving co-production unit further includes a synthetic hydrocarbon reactor and a hydrocarbon storage device. The hydrogen and carbon monoxide generated by the co-electrolysis reaction enter the synthetic hydrocarbon reactor to react and generate hydrocarbons, which are stored in the hydrocarbon storage device. The heat released by the reaction is used to preheat the CO2 electrolysis reactants entering the SOEC peak shaving co-production unit.

[0013] Preferably, the combustion product treatment includes flue gas cooling, desulfurization, and denitrification. Part of the treated CO2 is used as an electrolysis reactant in the SOEC peak shaving cogeneration unit to participate in the co-electrolysis reaction, and the other part is used for storage or other purposes after multi-stage compression and intermediate cooling.

[0014] Preferably, the pressurized oxygen-enriched circulating fluidized bed combustion mechanism further includes an air intake mechanism, which includes a low-temperature distillation oxygen generation unit that separates oxygen from the air through the principle of low-temperature distillation, serving as the main oxygen source required for oxygen-enriched combustion.

[0015] Preferably, the flexible start-up and shutdown of the supercritical carbon dioxide power generation unit and the SOEC peak-shaving cogeneration unit to achieve peak-shaving and frequency regulation, depending on the grid load level, includes:

[0016] When the grid is under low load, some of the supercritical CO2 from the auxiliary turbine of the supercritical carbon dioxide power generation unit enters the SOEC peak shaving cogeneration unit to participate in co-electrolysis. The working fluid of the cycle is reduced, and the power generation is reduced. At the same time, the CO2 reactants in the SOEC peak shaving cogeneration unit increase. The excess electrical energy is absorbed through full-power electrolysis, and the high-temperature water vapor and carbon dioxide are converted into hydrogen, carbon monoxide and hydrocarbon fuels to achieve electrical energy storage.

[0017] When the grid load is moderate, partial electrolysis is maintained to balance power generation and energy storage.

[0018] When the power grid is under high load, all working fluids of the supercritical carbon dioxide power generation mechanism do not participate in SOEC electrolysis, maintaining the flow rate of the circulating working fluid. This allows the combustion, heat exchange, and power generation systems to operate at rated power. At the same time, electrolysis is reduced or stopped to release combustion heat for supercritical carbon dioxide cycle power generation, while stored hydrogen or hydrocarbon fuels are used as backup energy sources to achieve energy output.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0020] 1. By employing a pressurized oxygen-enriched circulating fluidized bed, supercritical CO2 circulation, and SOEC electrolysis unit working in synergy, the system can not only fully recover combustion waste heat for working fluid heating and electrolysis preheating, thus effectively compensating for energy losses from air separation and carbon capture, but also reduce energy consumption in the electrolysis process, improve the efficiency of electrical energy to chemical energy conversion, and further promote the conversion of CO2 to syngas and liquid hydrocarbons, achieving deep coupling of electro-thermal-chemical energy. This multi-path synergistic effect enables the system to achieve efficient and clean power generation while possessing flexible energy storage and diversified product output capabilities, taking into account multiple objectives such as efficient power generation, energy storage and peak shaving, carbon capture, and resource utilization, thereby comprehensively improving the overall efficiency and competitiveness of the energy system.

[0021] 2. By adopting a pressurized oxygen-enriched circulating fluidized bed boiler, the co-combustion of coal and biomass is achieved. Pressurized oxygen-enriched combustion can solve the energy loss problem caused by the mismatch between the combustion pressure and the carbon dioxide compression unit and the air separation oxygen production unit in conventional oxygen-enriched combustion. At the same time, the increased pressure can help to recover the latent heat of vaporization of water vapor in the boiler flue gas, thereby effectively improving the system's circulation efficiency. It also has the characteristics of good fuel adaptability, uniform temperature distribution in the furnace, and low SO2 and NOx emissions. In addition, combined with a carbon dioxide capture unit, near-zero or even negative carbon emissions can be achieved, resulting in significant environmental benefits.

[0022] 3. In pressurized oxygen-enriched combustion, the carbon dioxide concentration in the flue gas further increases. On the working fluid side, high-purity CO2 after capture is used as the circulating working fluid in the supercritical CO2 power generation mechanism. Due to its high energy density, excellent fluid properties, and easily achievable critical parameters, the working fluid can be efficiently circulated during power generation through reheating, regeneration, and multi-stage compression cooling, significantly improving the system's power generation efficiency and flexible adjustment capability. Compared with the traditional steam Rankine cycle, the fluidized bed heat source can provide efficient energy input for the S-CO2 cycle at a lower temperature difference, achieving higher efficiency. The efficiency is improved, and the low-temperature flue gas reduces the difficulty of high-temperature waste heat recovery. In addition, the CO2 working fluid does not undergo phase change during circulation and has low corrosivity to metals, which significantly improves the safety and durability of the high-temperature heating surface. At the same time, the arrangement of the heating surface of the circulating fluidized bed boiler is more flexible and better meets the special requirements of the S-CO2 cycle for heat exchange and heat transfer characteristics, thus outperforming the steam Rankine cycle in terms of overall efficiency and operational reliability.

[0023] 4. By setting up an SOEC peak-shaving co-production mechanism, the combined use of combustion waste heat and electric heating to raise the temperature of the electrolysis process reduces electrolysis energy consumption. Through co-electrolysis, the oxygen produced by SOEC can be fed back to the fluidized bed, while hydrogen and carbon monoxide are used as syngas for hydrocarbon production via Fischer-Tropsch synthesis. This not only achieves efficient conversion of electrical energy into hydrogen energy but also enhances the system's flexibility and energy storage capacity. This invention combines supercritical CO2 and SOEC. The S-CO2 cycle has a compact equipment volume and low thermal inertia, and its heating and cooling rates are significantly faster than the steam Rankine cycle, enabling the unit to rapidly increase or decrease load in a short time, thereby reducing the energy consumption and cost associated with peak shaving. Due to the high pressure and high fluid density of the S-CO2 cycle, the system can maintain good heat transfer and power characteristics even under varying loads, contributing to improved operational stability and safety. Furthermore, the rapid start-up and shutdown characteristics and flexible load regulation of S-CO2 can be well coupled with the dynamic operation of SOEC: during grid off-peak hours, the S-CO2 cycle can flexibly adjust power output, efficiently converting excess electrical energy into the electrical energy required for SOEC electrolysis; during peak hours, the S-CO2 cycle can quickly increase load, releasing energy in synergy with hydrogen storage or downstream chemical energy utilization. Thus, this integrated system not only possesses dual peak-shaving capabilities for both electrical and hydrogen energy, but also maintains an efficient, stable, and economical operating mode under different operating conditions. Attached Figure Description

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

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] like Figure 1As shown, the supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving cogeneration system of the present invention includes a pressurized oxygen-enriched circulating fluidized bed combustion mechanism, a supercritical carbon dioxide power generation mechanism, an SOEC peak-shaving cogeneration mechanism, and a flue gas purification and carbon dioxide compression and capture mechanism. The pressurized oxygen-enriched circulating fluidized bed combustion mechanism can fully utilize combustion waste heat to improve the circulation efficiency of the supercritical CO2 power generation mechanism. A portion of the CO2 produced by the flue gas purification and carbon dioxide compression and capture mechanism serves as the circulating working fluid of the supercritical carbon dioxide power generation mechanism, while another portion enters the SOEC peak-shaving cogeneration mechanism as an electrolysis reactant. A portion of the working fluid from the supercritical CO2 power generation mechanism also enters the SOEC peak-shaving cogeneration mechanism to participate in co-electrolysis. With varying grid load levels, the supercritical carbon dioxide power generation mechanism and the SOEC peak-shaving cogeneration mechanism can be flexibly started and stopped to complete peak shaving and frequency regulation, achieving the purpose of peak shaving and valley filling and ensuring grid stability, forming a multi-path coupling and flexible scheduling of electro-thermal-chemical energy. Oxygen generated in the SOEC peak-shaving cogeneration unit can also enter the circulating fluidized bed 5 to provide an oxygen source. Simultaneously, water, one of the electrolysis reactants in the SOEC peak-shaving cogeneration unit, absorbs the waste heat from the high-temperature flue gas rich in water vapor generated during combustion in the pressurized oxygen-enriched circulating fluidized bed combustion unit, achieving preliminary preheating and gasification. The resulting water vapor then exchanges heat with the high-temperature tail gas from the SOEC electrolysis outlet, further increasing its temperature. The entire system achieves deep coupling of pressurized oxygen-enriched fluidized bed, supercritical carbon dioxide circulation, and SOEC peak shaving, fully utilizing combustion waste heat and electrolysis byproducts to achieve synergistic operation of high-efficiency power generation, carbon capture, and energy storage peak shaving, improving the system's energy utilization rate and economy, and reducing carbon dioxide emissions while optimizing the energy structure.

[0027] The pressurized oxygen-enriched circulating fluidized bed combustion mechanism includes a feeding mechanism, an air intake mechanism, a circulating fluidized bed 5, a first reheater 6, a second reheater 7, a cyclone separator 8, and a return feeder 9. The feeding mechanism 32 includes a feeding hopper and a motor-driven conveyor belt for feeding fuel into the circulating fluidized bed 5 at a controllable rate. In this embodiment, the fuel can be a coal-biomass blend, and the biomass dye can be livestock and poultry manure, etc. The pressurized oxygen-enriched circulating fluidized bed combustion mechanism achieves efficient combustion of the coal-biomass blend and efficient carbon capture. The pressurized conditions eliminate the additional energy consumption caused by energy mismatch between the air separation unit and the carbon dioxide compression unit. The use of biomass co-combustion increases the water vapor content and heat in the flue gas. The latent heat under pressurized conditions provides a heat source for the high-temperature water vapor required by SOEC. The air intake mechanism includes an air compressor 1, an air heat exchanger 2, a distillation tower 3, and an oxygen compressor 4 connected in sequence. Air is first pressurized by air compressor 1, then undergoes efficient heat exchange with low-temperature reflux gas in air heat exchanger 2, resulting in a significant temperature reduction before entering distillation column 3. Inside distillation column 3, multi-stage distillation separates the various components in the air, yielding high-purity oxygen. The separated oxygen is then extracted and further pressurized by oxygen compressor 4, serving as the primary oxygen source for oxygen-enriched combustion in circulating fluidized bed 5. In addition to obtaining oxygen through low-temperature distillation, oxygen generated by electrolysis in the SOEC peak-shaving cogeneration unit can also be pressurized by oxygen compressor 4 and then enter circulating fluidized bed 5. This combined oxygen supply method can reduce the load and energy consumption of the air separation unit while ensuring the stability of fluidized bed combustion, thereby effectively improving the overall economy and reliability of the system operation.

[0028] The circulating fluidized bed 5 operates under pressurized and oxygen-enriched conditions. A mixture of coal and biomass fuel is fed into the bed via the feeding mechanism 32, ensuring full contact with high-concentration oxygen and achieving uniform combustion. Under pressurized conditions, the fuel combustion reaction rate is significantly increased, carbon conversion is enhanced, and the increased pressure facilitates the recovery of the latent heat of vaporization of water vapor in the flue gas, thereby effectively improving combustion efficiency and the overall thermal efficiency of the system. The oxygen-enriched environment reduces nitrogen doping, avoiding energy loss due to nitrogen involvement, while significantly suppressing NOx formation and improving pollutant emission characteristics. The combustion products are mainly carbon dioxide and water vapor, simplifying subsequent carbon capture processes and facilitating efficient carbon separation and capture. The first reheater 6 and the second reheater 7 are located inside the circulating fluidized bed 5 to absorb the sensible heat carried by the flue gas and circulating particles within the bed and efficiently transfer it to the supercritical CO2 working fluid, achieving reheating and temperature rise of the working fluid. This structure can fully utilize combustion waste heat, improving the circulation efficiency of the supercritical CO2 power generation mechanism. The high-temperature flue gas and particles generated during combustion undergo efficient gas-solid separation via cyclone separator 8. The separated particles are then diverted via return feeder 9: one portion is directly returned to circulating fluidized bed 5 to maintain stable bed temperature and material circulation balance; the other portion enters external heat exchanger 10 connected to return feeder 9, where it exchanges heat with the working fluid at the outlet of the main turbine 14 of the supercritical carbon dioxide power generation unit. The heat from the particles is effectively recovered and transferred to the CO2 working fluid. The cooled particles are then returned to circulating fluidized bed 5, achieving both secondary heat utilization and bed temperature regulation. The high-temperature gas obtained after separation enters the tail gas heating surface (equipped with regenerator 11, economizer 12, and flue gas heat exchanger 13) to recover waste heat from the flue gas, and then enters the flue gas purification and carbon dioxide compression and capture mechanism.

[0029] Operating under pressurized and oxygen-enriched conditions, the circulating fluidized bed boiler, combined with the synergistic effects of its internal two-stage reheater, cyclone separator, feed returner, and external heat exchanger, not only significantly improves combustion efficiency and heat recovery level but also reduces pollutant emissions, providing favorable conditions for achieving efficient power generation and deep carbon capture.

[0030] The supercritical carbon dioxide (S-CO2) power generation mechanism includes a main turbine 14, an auxiliary turbine 15, a high-temperature regenerator 16, a low-temperature regenerator 17, a regenerator 11, a multi-stage compression and cooling device, and a third compressor 22, forming a closed Brayton cycle system. The CO2 working fluid first absorbs sensible heat carried by flue gas and particles in the first reheater 6 and the second reheater 7 inside the circulating fluidized bed 5, and is heated to a high-temperature and high-pressure state before entering the main turbine 14 to expand, perform work, and drive the generator to generate electricity. The working fluid at the outlet of the main turbine 14 is divided into two streams: one stream is sent to the external heat exchanger 10 to exchange heat with high-temperature particles and waste heat flue gas, achieving secondary heating of the working fluid and utilization of waste heat; the other stream exchanges heat in the regenerator 11 located within the exhaust gas heating surface of the pressurized oxygen-enriched circulating fluidized bed combustion mechanism, and then enters the auxiliary turbine 15 to continue expanding and performing work, thereby achieving secondary energy recovery. The working fluid at the outlet of the auxiliary turbine 15 is divided into two streams. One stream serves directly as a reactant, merging with a portion of the CO2 separated from the outlet of the denitrification unit 28 and being fed into the synthetic hydrocarbon reactor for downstream synthetic fuel reaction. The other stream enters the high-temperature regenerator 16 to maintain the basic thermal cycle. Through this diversion method, the system's circulating working fluid flow rate is actively regulated, resulting in a corresponding reduction in turbine output power and overall power generation, achieving flexible peak shaving on the power generation side. The remaining heat is fully recovered to the working fluid flow on the compression side through the high-temperature regenerator 16 and the low-temperature regenerator 17, forming a highly efficient closed-loop regenerative circuit. The regenerated CO2 working fluid is divided into two streams. A portion of the working fluid is sequentially cooled and pressurized in a multi-stage compression and cooling device, and then heated by the low-temperature regenerator 17, gradually restoring the working fluid to the pressure and temperature required for the cycle. The multi-stage compression and cooling device includes a first cooler 18, a first compressor 19, a second cooler 20, and a second compressor 21. Meanwhile, another part of the working fluid is pressurized by the third compressor 22 connected in parallel and merged with the main flow. It enters the high-temperature regenerator 16 for preheating, and then enters the circulating fluidized bed 5 through the economizer 12 located in the exhaust gas heating surface of the pressurized oxygen-enriched circulating fluidized bed combustion mechanism. It is heated by the first reheater 6 and the second reheater 7, and then enters the main turbine 14 to expand and do work, thereby realizing the complete operation of the closed Brayton cycle.

[0031] The SOEC peak-shaving and co-production unit includes a gas heat exchanger 23, an electric heater 24, an electrolysis unit 25, a hydrocarbon synthesis reactor 30, and a hydrocarbon storage device 31. During operation, feedwater first absorbs the waste heat of high-temperature flue gas rich in water vapor in the flue gas heat exchanger 13, located within the tail gas heating surface of the pressurized oxygen-enriched circulating fluidized bed combustion unit, achieving preliminary preheating and gasification. The resulting water vapor then enters the gas heat exchanger 23, where it exchanges heat with the high-temperature tail gas from the SOEC electrolysis outlet, further increasing its temperature. After heat exchange, the water vapor is heated to the optimal operating temperature range of the SOEC in the electric heater 24, ensuring that the electrolysis reaction can proceed in a high-temperature and high-efficiency environment. Meanwhile, a portion of the supercritical CO2 working fluid from the outlet of the auxiliary turbine 15, as a reactant, is combined with a portion of the CO2 from the outlet of the denitrification equipment 28 in the flue gas purification and carbon dioxide compression and capture mechanism. After being preheated at the outlet of the synthetic hydrocarbon reactor 30, it is sent to the electric heater 24 and heated to the optimal operating temperature range of SOEC. Subsequently, the water vapor and high-temperature CO2, as electrolysis reactants, enter the electrolysis equipment 25 and generate syngas through electrolysis. Depending on the adjustment of the H2 / CO ratio, different hydrocarbons can be generated, realizing the high-value utilization of carbon dioxide and the conversion of electrical energy into chemical energy, and also improving the overall emission reduction efficiency and economic value.

[0032] The supercritical carbon dioxide power generation mechanism and SOEC peak-shaving cogeneration mechanism of this invention not only perform the function of converting electrical energy into chemical energy during operation, but also can flexibly adjust the operating mode according to the grid load, achieving a unity of peak shaving and valley filling and efficient energy utilization. When the grid is under low load or the electricity price is low, the supercritical CO2 working fluid at the outlet of the auxiliary turbine 15 is divided into two streams. One part still enters the high-temperature regenerator 16 to maintain the basic thermal cycle process, while the other part is directly used as reactant, and after merging with part of the CO2 separated from the outlet of the denitrification device 28, it is sent to the synthetic hydrocarbon reactor for downstream synthetic fuel reaction process. At the same time, as the flow rate of CO2 reactants entering the SOEC electrolysis device increases, the power consumption required for SOEC electrolysis increases synchronously, enabling the system to further absorb excess power when the grid is under low load. Thus, under the dual effect of reducing power generation and increasing electrolysis energy consumption, a deeper and more flexible peak-shaving target is achieved. At the same time, the surplus power is used to electrolyze high-temperature steam and carbon dioxide to generate hydrogen and carbon monoxide, which are further synthesized into liquid hydrocarbon fuels, thereby realizing large-scale storage of electrical energy. When the grid load is at a moderate level, the SOEC can maintain partial operation to balance power generation and energy storage needs, maintaining system energy balance and cycle stability. During peak grid periods or periods of power shortage, all supercritical CO2 working fluid from the outlet of the auxiliary turbine 15 enters the high-temperature regenerator 16 for waste heat recovery and recycling. At this time, the system maintains a high circulating working fluid flow rate, ensuring that the combustion, heat exchange, and power generation devices operate at rated power. All the generated electricity is transmitted to the grid to meet external power demand. The SOEC can quickly reduce its operating load, releasing more combustion heat energy for supercritical carbon dioxide cycle power generation, while simultaneously utilizing previously stored hydrogen or hydrocarbon fuels as backup energy, achieving reverse energy output. Due to the flexible start-up and shutdown and rapid response characteristics of S-CO2 and SOEC, the system of this invention can quickly complete peak shaving and frequency regulation, forming a multi-path coupling and flexible scheduling of electro-thermal-chemical energy.

[0033] Supercritical carbon dioxide power generation and SOEC peak-shaving cogeneration have the following advantages in the coupled peak-shaving process:

[0034] (1) More efficient use of energy in cascades: The low-temperature waste heat generated during power generation can be directly supplied to the water electrolysis hydrogen production system without the need for additional consumption of high-grade energy. Compared with the "separate power generation + separate hydrogen production" model, the overall energy utilization efficiency is improved.

[0035] (2) More agile load response: During peak electricity demand, the system can prioritize full-load power generation to reduce hydrogen production load; during off-peak electricity demand, excess electrical / thermal energy can be quickly switched to the hydrogen production process. The switching time is only minutes, which is much faster than the linkage response speed of traditional thermal power and hydrogen production systems.

[0036] (3) High system integration: The supercritical CO2 cycle itself has a small equipment size and is easy to integrate with SOEC. It can realize the integrated layout of "power generation-hydrogen production", reduce land occupation and transmission loss, and is especially suitable for the demand of new energy power plants to generate and regulate peaks nearby.

[0037] The flue gas purification and carbon dioxide compression and capture mechanism includes a flue gas cooling device 26, a desulfurization device 27, a denitrification device 28, and a CO2 compressor 29. After reheating and heat exchange, the combustion products first enter the flue gas cooling device 26 for deep cooling, bringing the flue gas to a suitable purification temperature and simultaneously releasing some condensate. The cooled flue gas then sequentially enters the desulfurization device 27 and the denitrification device 28 to remove major pollutants such as SO2 and NOx. The desulfurization process can select a dry lime-gypsum system or dry-based desulfurization technology according to specific application conditions to achieve efficient SO2 removal; the denitrification stage uses selective catalytic reduction to convert NOx into nitrogen and water, thereby reducing nitrogen oxide emissions. The flue gas after pollutant control mainly consists of carbon dioxide and water vapor, with the CO2 volume fraction exceeding 90%. After purification, most of the high-concentration CO2 undergoes condensation and separation to remove residual moisture before entering CO2 compressor 29 for multi-stage compression and intermediate cooling. The pressure is progressively increased while the temperature is decreased to reduce compression power consumption and improve efficiency, ultimately yielding high-purity, high-pressure CO2. A portion of this CO2 serves as the circulating working fluid in a supercritical carbon dioxide (S-CO2) power generation system, while another portion is readily transported to geological storage sites for long-term storage or distributed to chemical, building materials, and other industrial sectors for utilization. A further portion can participate in co-electrolysis reactions as a reactant in an SOEC peak-shaving cogeneration system. This design not only ensures that pollutant emissions meet standards but also achieves efficient carbon dioxide capture and resource utilization, providing technical support for the system to achieve near-zero emissions or even negative carbon emissions.

[0038] In the entire system, the high-temperature flue gas and particles generated by the pressurized oxygen-enriched circulating fluidized bed combustion mechanism first undergo sufficient heat exchange through the first reheater 6 and the second reheater 7, raising the temperature of a portion of the carbon dioxide working fluid after the main turbine 14 of the S-CO2 mechanism has done work. The flue gas and particles are separated in the cyclone separator 8. The flue gas at the outlet of the cyclone separator 8 recovers residual heat in the tail gas heating surface: it first enters the regenerator 11, where it exchanges heat with another portion of the carbon dioxide working fluid after the main turbine 14 has done work. Then, the flue gas passes through the economizer 12 to preheat the compressed CO2 working fluid, and then passes through the flue gas heat exchanger 13 to raise the temperature of the electrolyzed water. At this time, the flue gas temperature is further reduced. The flue gas at the outlet of the flue gas heat exchanger 13 then enters the flue gas cooling device 26 for sufficient cooling, and undergoes desulfurization and denitrification reactions in the desulfurization device 27 and the denitrification device 28 to obtain carbon dioxide. Subsequently, the carbon dioxide is compressed and captured under the action of the CO2 compressor 29.

[0039] The carbon dioxide working fluid circulation process includes: the carbon dioxide working fluid exchanges heat in the circulating fluidized bed 5 through the first reheater 6 and the second reheater 7, and then generates electricity in the S-CO2 main turbine 14. The working fluid after doing work is divided into two streams: one stream is heated by the regenerator 11, and the other stream is heated by the external heat exchanger 10. The two streams are then merged and sent to the S-CO2 auxiliary turbine 15. Part of the working fluid that has done work at the outlet of the auxiliary turbine is used as reactant and is combined with part of the CO2 separated from the outlet of the denitrification equipment 28 and sent to the synthetic hydrocarbon reactor for downstream synthetic fuel reaction process. The other part is cooled twice, first by a high-temperature regenerator 16 and then by a low-temperature regenerator 17. It is then divided into two streams: one stream is cooled by a first cooler 18 and then sent to a first compressor 19 for pressurization. After compression, it is cooled again by a second cooler 20 and then pressurized again by a second compressor 21. After two cooling and pressurization cycles, it is heated by a low-temperature regenerator 17. The other stream is pressurized by a third compressor 22 connected in parallel. The two working fluids merge, are heated by a high-temperature regenerator 16, and are then sent to an economizer 12. They then re-enter the circulating fluidized bed 5 for full heat exchange and enter the main turbine 14 to expand and do work, thus realizing the complete operation of the closed Brayton cycle.

[0040] After being preheated by the flue gas heat exchanger 13, the electrolyzed water is sent to the gas heat exchanger 23 to exchange heat with the high-temperature gas obtained from electrolysis, thereby further increasing its temperature. Under the operation of the electric heater 24, it reaches the SOEC operating temperature. Subsequently, an electrolysis reaction occurs in the SOEC electrolysis equipment according to demand. In the electrolysis equipment 25, high-temperature water vapor and carbon dioxide act as reactants, generating hydrogen and carbon monoxide under electrochemical reaction, while also generating oxygen. The electrolyzed gas is sent to the gas heat exchanger 23 to reduce its temperature. The cooled hydrogen and carbon monoxide are then stored, while the cooled oxygen is sent to the oxygen compressor 4 of the air intake mechanism to be pressurized and then sent into the circulating fluidized bed 5.

[0041] The system described in this invention integrates a pressurized oxygen-enriched fluidized bed, supercritical carbon dioxide circulation, and SOEC peak shaving to achieve efficient power generation, carbon emission reduction, and energy storage peak shaving, thereby enhancing the overall efficiency and competitiveness of the energy system. Specifically, the oxygen separated by the low-temperature distillation oxygen production unit can be combined with the oxygen generated by SOEC electrolysis to supply the fluidized bed, thus meeting the oxygen-enriched atmosphere required by the circulating fluidized bed. Under the condition of co-combustion of coal and biomass, the pressurized oxygen-enriched circulating fluidized bed has the advantages of both fuel adaptability and pollutant control. By cooperating with particulate circulation and external heat exchangers, it achieves bed temperature regulation and waste heat utilization, improving combustion efficiency. The supercritical carbon dioxide power generation unit achieves efficient circulation of the working fluid through reheating, regeneration, and multi-stage compression cooling processes, significantly improving power generation efficiency and compensating for energy losses caused by air separation and carbon capture. The SOEC peak-shaving and cogeneration unit utilizes a combination of flue gas waste heat and electric heating to raise the temperature, reducing the heat energy consumption of the electrolysis process. Furthermore, it converts CO2 into chemicals as a reactant, thereby improving carbon utilization and realizing the conversion of electrical energy into chemical energy and peak-shaving energy storage. The oxygen obtained from electrolysis can also be fed back to the fluidized bed, enhancing the system's flexibility. The flue gas purification and carbon dioxide compression and capture unit can achieve flue gas desulfurization, denitrification, and efficient carbon capture, ensuring emission compliance and carbon reduction targets are met.

Claims

1. A supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system, characterized in that, The system includes a pressurized oxygen-enriched circulating fluidized bed combustion mechanism, a supercritical carbon dioxide power generation mechanism, and an SOEC peak-shaving cogeneration mechanism. The circulating flue gas from the pressurized oxygen-enriched circulating fluidized bed combustion mechanism provides cascade heat exchange for the working fluid circulation of the supercritical carbon dioxide power generation mechanism, and performs preliminary preheating and gasification of the water electrolysis reactant in the SOEC peak-shaving cogeneration mechanism. Part of the CO2 obtained after processing the combustion products serves as the circulating working fluid of the supercritical carbon dioxide power generation mechanism, and the remaining CO2 serves as another electrolysis reactant in the SOEC peak-shaving cogeneration mechanism. After heat exchange in the combustion mechanism, part of the working fluid of the supercritical carbon dioxide power generation mechanism enters the SOEC peak-shaving cogeneration mechanism for electrolysis. The oxygen generated by SOEC electrolysis provides an oxygen source for the combustion mechanism. Furthermore, the supercritical carbon dioxide power generation mechanism and the SOEC peak-shaving cogeneration mechanism can be flexibly started and stopped according to different grid load levels to complete peak shaving and frequency regulation, achieving peak shaving and valley filling, and ensuring stable grid operation.

2. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 1, characterized in that, The pressurized oxygen-enriched circulating fluidized bed combustion mechanism includes a circulating fluidized bed (5), one or more reheaters, a cyclone separator (8), and a return feeder (9). The one or more reheaters are arranged sequentially inside the circulating fluidized bed. The inlet of the cyclone separator (8) is connected to the circulating fluidized bed (5). The solid outlet below the cyclone separator (8) is connected to the return feeder (9), and the gas outlet above is connected to the tail gas heating surface. The high-temperature flue gas and particles generated during combustion exchange heat with the working fluid of the supercritical carbon dioxide power generation mechanism through the one or more reheaters and then undergo gas-solid separation through the cyclone separator (8). The resulting particles enter the return feeder (9) and are then diverted: one part is returned to the circulating fluidized bed, and the other part enters the external heat exchanger (10) connected to the return feeder (9) to exchange heat with the working fluid of the supercritical carbon dioxide power generation mechanism. The particles cooled by heat exchange are then sent back to the circulating fluidized bed. The resulting high-temperature flue gas enters the tail gas heating surface for waste heat recovery.

3. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 2, characterized in that, The exhaust gas heating surface is equipped with a regenerator (11), an economizer (12), and a flue gas heat exchanger (13). The regenerator (11) is connected to a supercritical carbon dioxide power generation unit. The inlet of the economizer (12) is connected to the supercritical carbon dioxide power generation unit, and the outlet is connected to one or more reheaters in the circulating fluidized bed. The flue gas heat exchanger (13) is connected to an SOEC peak shaving and cogeneration unit.

4. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 3, characterized in that, The supercritical carbon dioxide power generation mechanism includes a main turbine (14), a secondary turbine (15), a high-temperature regenerator (16), a low-temperature regenerator (17), a multi-stage compression and cooling device, and a third compressor (22). The outlet of the main turbine (14) is connected to the secondary turbine (15) through the regenerator (11) and the external heat exchanger (10), respectively. The secondary turbine (15) has two outlets. One outlet is connected to the high-temperature regenerator (16) and the low-temperature regenerator (17) in sequence. The outlet of the low-temperature regenerator (17) is divided into two paths. One path is connected to the high-temperature regenerator (16) in sequence through the multi-stage compression and cooling device, the low-temperature regenerator (17), and the high-temperature regenerator (16). The other path is connected to the high-temperature regenerator (16) through the third compressor (22). The high-temperature regenerator (16) is connected to the heat exchanger in the circulating fluidized bed (5) through the economizer (12). The other outlet of the turbine (15) is connected to the SOEC peak shaving and cogeneration mechanism.

5. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 1, characterized in that, The SOEC peak-shaving cogeneration unit includes a gas heat exchanger (23), an electric heater (24), and an electrolysis unit (25) connected in sequence. Water vapor enters the gas heat exchanger (23) and exchanges heat with the high-temperature tail gas from the SOEC electrolysis outlet. After heat exchange, the water vapor and some of the CO2 obtained after treatment enter the electric heater (24) and are heated to the optimal operating temperature range of SOEC. Then, it enters the electrolysis unit (25) to undergo a co-electrolysis reaction to generate hydrogen, carbon monoxide, and oxygen. The oxygen is supplied to the pressurized oxygen-enriched circulating fluidized bed combustion unit.

6. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 5, characterized in that, Before the water vapor enters the gas heat exchanger (23), the feedwater absorbs the waste heat of the high-temperature flue gas rich in water vapor from the pressurized oxygen-enriched circulating fluidized bed combustion mechanism to achieve preliminary preheating and gasification, and obtain water vapor.

7. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 5, characterized in that, The SOEC peak shaving co-production facility also includes a synthetic hydrocarbon reactor (30) and a hydrocarbon storage device (31). The hydrogen and carbon monoxide generated by the co-electrolysis reaction enter the synthetic hydrocarbon reactor (30) to react and generate hydrocarbons, which are stored in the hydrocarbon storage device (31). The heat released by the reaction is used to preheat the CO2 electrolysis reactants entering the SOEC peak shaving co-production facility.

8. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 1, characterized in that, Combustion product treatment includes flue gas cooling, desulfurization, and denitrification. Part of the treated CO2 is used as an electrolysis reactant in the SOEC peak shaving cogeneration unit to participate in the co-electrolysis reaction, while the other part is used for storage or other purposes after multi-stage compression and intermediate cooling.

9. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 1, characterized in that, The pressurized oxygen-enriched circulating fluidized bed combustion mechanism also includes an air intake mechanism, which includes a low-temperature distillation oxygen generation unit. This unit separates oxygen from the air using the principle of low-temperature distillation, serving as the main oxygen source required for oxygen-enriched combustion.

10. The supercritical carbon dioxide pressurized oxygen-enriched fluidized bed-SOEC peak-shaving co-production system according to claim 1, characterized in that, The aforementioned flexible start-up and shutdown of the supercritical carbon dioxide power generation unit and SOEC peak-shaving cogeneration unit, in response to varying grid load levels, to achieve peak shaving and frequency regulation, includes: When the grid is under low load, some of the supercritical CO2 from the supercritical carbon dioxide power generation unit enters the SOEC peak shaving cogeneration unit to participate in co-electrolysis. The working fluid of the cycle is reduced, resulting in a decrease in power generation. At the same time, the CO2 reactants in the SOEC peak shaving cogeneration unit increase. The excess electrical energy is absorbed through electrolysis, and the high-temperature water vapor and carbon dioxide are converted into hydrogen, carbon monoxide and hydrocarbon fuels to achieve electrical energy storage. Maintain power generation and partial electrolysis when the grid load is moderate to balance power generation and energy storage. When the power grid is under high load, all working fluids of the supercritical carbon dioxide power generation mechanism do not participate in SOEC electrolysis, maintaining the flow rate of the circulating working fluid. This allows the combustion, heat exchange, and power generation systems to operate at rated power. At the same time, electrolysis is reduced or stopped to release combustion heat for supercritical carbon dioxide cycle power generation, while stored hydrogen or hydrocarbon fuels are used as backup energy sources to achieve energy output.

Images