Method and system for converting CO2 in regenerated flue gas

Abstract

The invention relates to a method and a system for converting CO2 in regenerated flue gas. Water is fed into a water electrolysis device to be electrolyzed, and external oxygen and external hydrogen are obtained; feeding the external oxygen as combustion-supporting gas into a gas heat exchanger to exchange heat with high-temperature and low-pressure flue gas to obtain high-temperature combustion-supporting gas and low-temperature and low-pressure flue gas, feeding the high-temperature combustion-supporting gas into a catalytic cracking regenerator to perform regeneration and coke burning, and dividing the low-temperature and low-pressure flue gas into circulating flue gas and flue gas to be converted, and feeding the flue gas to be converted into a CO2 electrochemical conversion unit for electrochemical conversion reaction to obtain synthesis gas and regenerated oxygen. According to the invention, the regeneration efficiency of the catalyst is fully improved, the emission of CO2 in treated tail gas is reduced, the reasonable configuration of the treatment device and the efficient utilization of the electrolyzed water byproduct oxygen are realized, and the purpose of environmental protection is achieved while the economic benefit is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, and more specifically, to a method and system for converting CO2 in regenerated flue gas. Background Technology

[0002] Hydrogen, as a sustainable green energy source, has advantages such as being pollution-free, having diverse sources, abundant reserves, and wide applications. Hydrogen production technology through water electrolysis, especially alkaline water electrolysis, has been widely used due to its mature technology and low cost.

[0003] However, existing water electrolysis hydrogen production processes generate a large amount of byproduct oxygen. Most companies treat this by directly releasing it into the atmosphere or by compressing and liquefying it for industrial sale, resulting in high oxygen treatment costs and resource waste. For continuous fluidized bed reactions, such as catalytic cracking (FCC) and methanol-to-olefins (MTO) units, the catalyst regeneration and coking process requires air-assisted combustion. However, due to the low oxygen concentration in the air, the coking efficiency is low. Simultaneously, the coking process generates a large amount of CO2, which, when released into the atmosphere, exacerbates the greenhouse effect. CN103055960A discloses a catalyst regeneration method to reduce emissions. Its characteristic is that the catalyst to be regenerated is in contact with oxygen-enriched gas, water vapor, and carbon dioxide gas in a dense-phase fluidized bed regenerator, undergoing coke combustion at a temperature of 550–750℃ and an average catalyst residence time of 0.5–10.0 minutes. The regenerated catalyst enters the reactor, and the flue gas is divided into two parts after passing through a cyclone separator. One part is recycled to the regenerator inlet system to mix with the oxygen-enriched gas, while the other part enters the flue gas energy recovery system to recover carbon dioxide without emission.

[0004] However, existing catalyst regeneration methods still have problems such as incomplete utilization of oxygen produced as a byproduct of water electrolysis, high treatment costs, and large CO2 emissions in the treated exhaust gas. Summary of the Invention

[0005] The purpose of this invention is to address the problems of incomplete utilization of oxygen as a byproduct of water electrolysis, high treatment costs, and large CO2 emissions in the treated exhaust gas in existing technologies. To achieve the above objective, this invention provides a method and system for converting CO2 in regenerated flue gas.

[0006] The first aspect of the present invention provides a method for converting CO2 in regenerated flue gas, the method comprising: S1, feeding water into an electrolytic water device for electrolysis to obtain external oxygen and external hydrogen; feeding the external oxygen as a combustion-supporting gas into a gas heat exchanger to exchange heat with high-temperature low-pressure flue gas to obtain high-temperature combustion-supporting gas and low-temperature low-pressure flue gas; feeding the high-temperature combustion-supporting gas into a catalytic cracking regenerator for regeneration and coking to obtain high-temperature low-pressure flue gas; S2, dividing the low-temperature low-pressure flue gas into circulating flue gas and flue gas to be converted; feeding the circulating flue gas and external oxygen as combustion-supporting gas, and returning to step S1; the CO2 content in the low-temperature low-pressure flue gas reaches a set threshold; S3, feeding the flue gas to be converted into a CO2 electrochemical conversion unit for electrochemical conversion reaction to obtain syngas and regenerated oxygen; feeding the regenerated oxygen and the external oxygen and circulating flue gas as combustion-supporting gas and returning to step S1.

[0007] Optionally, a CO2 content detector is used to detect the CO2 content in the low-temperature, low-pressure flue gas; the set threshold is any point value within the range of 20v%-90v%.

[0008] Optionally, the method further includes: sequentially feeding the low-temperature, low-pressure flue gas into a harmful gas removal device and a dust removal device for impurity removal, then dividing the impurity-removed low-temperature, low-pressure flue gas into the flue gas to be converted and the circulating flue gas; feeding the circulating flue gas into a circulating compressor for pressurization to obtain high-pressure circulating flue gas, and feeding the high-pressure circulating flue gas together with the external oxygen and the regenerated oxygen into the catalytic cracking regenerator as combustion support.

[0009] Optionally, the method further includes: feeding the flue gas to be converted from the bottom into the absorption unit of the CO2 electrochemical conversion unit to be absorbed by the first electrolyte to obtain a rich solution; feeding the rich solution into the cathode chamber of the electrochemical reactor and feeding the second electrolyte into the anode chamber to carry out an electrochemical conversion reaction in the electrochemical reactor to obtain a cathode gas-liquid mixture and an anode gas-liquid mixture; feeding the cathode gas-liquid mixture into a first gas-liquid separator for gas-liquid separation to obtain syngas and cathode electrolyte; feeding the anode gas-liquid mixture into a second gas-liquid separator for gas-liquid separation to obtain regenerated oxygen and anode electrolyte; feeding the regenerated oxygen and the external oxygen together with the circulating flue gas into an oxygen distributor for mixing; feeding the cathode electrolyte and the anode electrolyte into an electrolyte mixing tank for mixing, and then drawing out the first electrolyte and the second electrolyte from the electrolyte mixing tank.

[0010] Optionally, the method further includes: the dry basis oxygen content in the combustion-supporting gas is 21v%-29v; the oxygen content in the regenerated oxygen is 60v%-100v; the external oxygen is pure oxygen; and the through-hole linear velocity range of the oxygen distributor is 55 m / s-90 m / s.

[0011] Optionally, the catalyst is regenerated by coking in the catalytic cracking regenerator at a temperature of 700℃-730℃; the dry basis dust content of the low-temperature, low-pressure flue gas is less than 5 mg / Nm³. 3 The high-temperature low-pressure flue gas has a pressure of 0.1MPa-0.2MPa and a temperature of 340℃-430℃; the high-pressure circulating flue gas has a pressure of 0.23MPa-0.39MPa and a temperature of 60℃-120℃; the high-temperature combustion-supporting gas has a temperature of 180℃-240℃; and the circulating flue gas has a temperature of 45℃-61℃.

[0012] Another aspect of the present invention provides a system for the conversion of CO2 in regenerated flue gas. The system includes: a water electrolysis device, a gas heat exchanger, an oxygen distributor, a catalytic cracking regenerator, a flue gas impurity removal unit, and a CO2 electrochemical conversion unit. The gas heat exchanger includes a low-temperature combustion-supporting inlet, a high-temperature combustion-supporting outlet, a flue gas inlet, and a flue gas outlet arranged sequentially. The CO2 electrochemical conversion unit includes a flue gas inlet to be converted, a regenerated oxygen outlet, and a syngas outlet arranged sequentially. The oxygen distributor includes an external oxygen inlet, a circulating flue gas inlet, a regenerated oxygen inlet, and a combustion-supporting outlet arranged sequentially. A pure oxygen pipeline is provided between the oxygen outlet of the water electrolysis device and the external oxygen inlet of the oxygen distributor, and the combustion-supporting outlet of the oxygen distributor is connected to the gas heat exchanger. A low-temperature combustion gas pipeline is provided between the low-temperature combustion gas inlet and the high-temperature combustion gas pipeline is provided between the high-temperature combustion gas outlet of the gas heat exchanger and the combustion gas inlet of the catalytic cracking regenerator. The high-temperature, low-pressure flue gas outlet of the catalytic cracking regenerator is connected to the flue gas inlet of the gas heat exchanger. The flue gas outlet of the gas heat exchanger is connected to the flue gas inlet of the flue gas purification unit. The flue gas outlet of the flue gas purification unit is connected to the circulating flue gas inlet of the oxygen distributor. The flue gas outlet of the flue gas purification unit is also connected to the flue gas inlet to be converted of the CO2 electrochemical conversion unit. The regenerated oxygen outlet of the CO2 electrochemical conversion unit is connected to the regenerated oxygen inlet of the oxygen distributor. The syngas outlet of the CO2 electrochemical conversion unit is connected to the downstream utilization unit.

[0013] Preferably, the CO2 electrochemical conversion unit includes an absorption unit, an electrochemical reactor, a first gas-liquid separator, a second gas-liquid separator, and an electrolyte mixing tank arranged sequentially; the electrochemical reactor includes a cathode chamber and an anode chamber separated by an ion-exchange membrane; the absorption unit includes a first electrolyte inlet, a flue gas inlet to be converted, and a rich solution outlet arranged sequentially from top to bottom; the rich solution outlet of the absorption unit is connected to the rich solution inlet of the cathode chamber, the cathode gas-liquid mixture outlet of the cathode chamber is connected to the cathode gas-liquid mixture inlet of the first gas-liquid separator, and the anode gas-liquid mixture outlet of the anode chamber is connected to the anode gas-liquid mixture inlet of the second gas-liquid separator. The first gas-liquid separator further includes a syngas outlet and a cathode electrolyte outlet, the syngas outlet being connected to a downstream utilization device, and the cathode electrolyte outlet being connected to the cathode electrolyte inlet of the electrolyte mixing tank; the second gas-liquid separator further includes a regenerated oxygen outlet and an anode electrolyte outlet, the regenerated oxygen outlet being connected to the regenerated oxygen inlet of the oxygen distributor, and the anode electrolyte outlet being connected to the anode electrolyte inlet of the electrolyte mixing tank; the electrolyte mixing tank further includes a first electrolyte outlet and a second electrolyte outlet, the first electrolyte outlet being connected to the first electrolyte inlet of the absorption unit, and the second electrolyte outlet being connected to the anode electrolyte inlet of the anode chamber.

[0014] Optionally, the system further includes: the flue gas outlet of the gas heat exchanger is connected to the flue gas impurity removal unit, the flue gas impurity removal unit includes a harmful gas removal device and a dust removal device arranged in sequence; the flue gas outlet of the gas heat exchanger is connected to the harmful gas removal device, the flue gas outlet of the harmful gas removal device is connected to the flue gas inlet of the dust removal device, the flue gas outlet of the dust removal device is provided with a low-temperature, low-pressure flue gas pipeline, the low-temperature, low-pressure flue gas pipeline is divided into a flue gas pipeline to be collected and a circulating flue gas pipeline; the flue gas pipeline to be collected is connected to the flue gas inlet of the CO2 electrochemical conversion unit, and the circulating flue gas pipeline is connected to the circulating flue gas inlet of the oxygen distributor; a circulating compressor is also provided between the flue gas outlet of the dust removal device and the circulating flue gas inlet of the oxygen distributor, and a flue gas turbine is also provided between the catalytic cracking regenerator and the gas heat exchanger.

[0015] Optionally, the catalytic cracking regenerator includes a dilute phase zone and a dense phase zone arranged vertically from top to bottom; the dilute phase zone includes a separation system, a stripping section, a regeneration riser, and a booster arranged sequentially; the dense phase zone includes a dense phase bed, a regeneration plug valve, an air distribution pipe, a regeneration riser, and a regeneration plug valve arranged sequentially; the catalytic cracking regenerator also includes two-stage cyclone separators connected in series; the diameter of the cyclone separators is 1-2 m; the bulk density of the dilute phase zone is 5-10 kg / m³. 3The height of the dilute phase space from the dense phase zone to the inlet of the first-stage cyclone separator is 10-16m; the diameter of the dense phase zone is 6-10m; and the volume is 200-500m³. 3 The density phase bed has a bed height of 4-8m and a bed temperature of 640-690℃.

[0016] Through the above technical solutions, this invention feeds oxygen, a byproduct of water electrolysis for hydrogen production, into a catalytic cracking (FCC) unit or a methanol-to-olefins (MTO) unit to participate in the catalyst regeneration process. This fully utilizes oxygen resources and avoids the loss and waste of oxygen resources and excessively high utilization costs caused by intermediate storage and transportation of oxygen. Furthermore, this invention feeds the flue gas generated from catalyst coking regeneration into a CO2 electrochemical conversion unit, converting the pollutant CO2 in the flue gas into high-value-added syngas. The circulating flue gas is used as combustion aid for catalyst coking regeneration. This fully utilizes the combustion flue gas within the unit to reduce pollutant emissions while improving the economic efficiency of the method described in this invention. It achieves efficient utilization of oxygen produced by water electrolysis and resource utilization of CO2, significantly reducing CO2 emissions and solving problems such as incomplete utilization of oxygen produced by water electrolysis, high treatment costs, and large CO2 emissions in the treated tail gas.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a CO2 conversion system in regenerated flue gas according to one embodiment of the present invention; Figure 2 This is a schematic diagram of a CO2 electrochemical conversion unit according to one embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures A-Electrolysis water unit, B-Catalytic cracking regenerator, C-Flue gas turbine, D-Gas heat exchanger, F-Harmful gas removal unit, G-Dust removal unit, H-Circulating compressor, K-Oxygen distributor, N-Pure oxygen pipeline, P-CO2 rich main duct, R-CO2 electrochemical conversion unit, R1-Absorption unit, R2-Electrochemical reactor, R21-Cathode chamber, R22-Anode chamber, R3-First gas-liquid separator, R4-Second gas-liquid separator, R5-Electrolyte mixing tank; 1-External oxygen, 2-High temperature and low pressure flue gas, 3-Flue gas exiting the flue gas turbine, 4-Low temperature and low pressure flue gas, 5-Circulating flue gas, 6-High pressure circulating flue gas, 7-Low temperature combustion-supporting gas, 8-Flue gas to be converted, 9-High temperature combustion-supporting gas, 10-Synthesis gas, 11-Regenerated oxygen, 12-First electrolyte, 13-Rich solution, 14-Cathode gas-liquid mixture, 15-Anode gas-liquid mixture, 16-Cathode electrolyte, 17-Anode electrolyte, 18-Second electrolyte, 19-Demineralized water. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the "upper" and "lower" of different components shown in the accompanying drawings, and "upstream" and "downstream" generally refer to the sequential order of gas flow directions between components within the system.

[0022] The first aspect of the present invention provides a method for converting CO2 in regenerated flue gas, the method comprising: S1, feeding water into an electrolytic water device A for electrolysis to obtain external oxygen 1 and external hydrogen; feeding the external oxygen 1 as combustion gas into a gas heat exchanger D to exchange heat with high-temperature low-pressure flue gas 2 to obtain high-temperature combustion gas 9 and low-temperature low-pressure flue gas 4; feeding the high-temperature combustion gas 9 into a catalytic cracking regenerator B for regeneration and coking to obtain high-temperature low-pressure flue gas 2; S2, dividing the low-temperature low-pressure flue gas 4 into circulating flue gas 5 and flue gas to be converted 8; feeding the circulating flue gas 5 and external oxygen 1 as combustion gas, and returning to step S1; the CO2 content in the low-temperature low-pressure flue gas reaches a set threshold; S3, feeding the flue gas to be converted into a CO2 electrochemical conversion unit R for electrochemical conversion reaction to obtain syngas 10 and regenerated oxygen 11; feeding the regenerated oxygen 11 and external oxygen 1 and circulating flue gas as combustion gas, and returning to step S1.

[0023] In the preferred embodiments described above, the present invention provides a method for conducting a catalytic continuous fluidized bed reaction. The present invention feeds oxygen, a byproduct of hydrogen production from water electrolysis, into a catalyst regenerator. This oxygen promotes the coking process, improves coking efficiency, and enhances catalyst recovery efficiency. The method described in this invention significantly improves catalyst recovery efficiency. Simultaneously, the method uses a portion of the combustion flue gas generated during coking as recirculated flue gas to continue participating in the coking process. A portion of the combustion flue gas with a high CO2 content is fed into a CO2 electrochemical conversion unit for electroconversion, absorbing and utilizing CO2 in the flue gas, thus significantly reducing the CO2 content in the exhaust gas.

[0024] In a preferred embodiment, a CO2 content detector is used to detect the CO2 content in the low-temperature, low-pressure flue gas 4; the CO2 content in the low-temperature, low-pressure flue gas 4 is 10v% to 95v; the set threshold is any point value within the range of 20v% to 90v%, preferably 52v.

[0025] In the preferred embodiment described above, the present invention uses a CO2 content detector to divert and rationally utilize the flue gas generated by combustion, thereby improving the system's processing efficiency and rationally treating the CO2 in the flue gas. The amount of circulating flue gas is determined by the oxygen concentration of the low-temperature combustion-supporting gas and the composition and total amount of external oxygen entering the oxygen distributor.

[0026] In an optional embodiment, the method further includes: sequentially feeding the low-temperature, low-pressure flue gas 4 into a harmful gas removal device F and a dust removal device G for impurity removal; dividing the impurity-removed low-temperature, low-pressure flue gas 4 into the flue gas to be converted 8 and the circulating flue gas 5; feeding the circulating flue gas 5 into a circulating compressor H for pressurization to obtain high-pressure circulating flue gas 6; and feeding the high-pressure circulating flue gas 6 together with the external oxygen 1 and the regenerated oxygen 11 into the catalytic cracking regenerator B as combustion-supporting gas.

[0027] In the above optional embodiments, the method provided by the present invention removes harmful gases from the combustion flue gas, extends the service life of the CO2 electrochemical conversion unit, reduces the influence of impurities on the CO2 electrochemical conversion reaction, significantly improves the CO2 conversion efficiency, and removes harmful gases from the exhaust gas to avoid environmental pollution.

[0028] In a preferred embodiment, the method further includes: feeding the flue gas 8 to be converted from the bottom into the absorption unit R1 of the CO2 electrochemical conversion unit R to be absorbed by the first electrolyte 12 to obtain a rich solution 13; feeding the rich solution 13 into the cathode chamber R21 of the electrochemical reactor R2; feeding the second electrolyte 18 into the anode chamber R22; and carrying out an electrochemical conversion reaction in the electrochemical reactor R2 to obtain a cathode gas-liquid mixture 14 and an anode gas-liquid mixture 15; and feeding the cathode gas-liquid mixture 14 into the first gas-liquid separator R3 for gas-liquid separation. Synthesis gas 10 and cathode electrolyte 16 are obtained. The anode gas-liquid mixture 15 is sent to the second gas-liquid separator R4 for gas-liquid separation to obtain regenerated oxygen 11 and anode electrolyte 17. The synthesis gas 10 is sent to the downstream utilization device. The regenerated oxygen 11 and the external oxygen 1 are sent together with the circulating flue gas 5 to the oxygen distributor K for mixing. The cathode electrolyte 16 and the anode electrolyte 17 are sent to the electrolyte mixing tank R5 for mixing. Then, the first electrolyte 12 and the second electrolyte 18 are drawn out from the electrolyte mixing tank R5.

[0029] In the preferred embodiment described above, the present invention utilizes the CO2 electrochemical conversion unit R to absorb the high-CO2 content flue gas generated during the catalyst coke regeneration process, reducing the large-scale emission of CO2 gas and its greenhouse effect, while simultaneously generating high-value-added syngas, thus achieving economic rationalization of pollutant gas treatment. In this preferred embodiment, the operating temperature of the absorption unit R1 can be 10-120℃, and the operating pressure can be 0.05-2.0 MPa; the operating temperature of the electrochemical reactor R2 can be 10-120℃, and the operating pressure can be 0.05-2.0 MPa; the first gas-liquid separator R3 and the second gas-liquid separator R4 are vertical or horizontal gas-liquid separators; the operating temperature within the first gas-liquid separator R3 can be 10-120℃, and the operating pressure can be 0.05-2.0 MPa; the operating temperature within the second gas-liquid separator R4 can be 10-120℃, and the operating pressure can be 0.05-2.0 MPa. MPa; In the above optional embodiments, during the electrochemical conversion of CO2, the continuous synthesis of products will cause the loss of water and electrolyte in the electrolyte. The present invention replenishes demineralized water 19 in the electrolyte mixing tank in a timely manner to maintain the balance of electrolyte concentration in the system, ensure the stable progress of the reaction, and continuously convert CO2 and synthesize high value-added products.

[0030] In a preferred embodiment, the method further includes: the dry basis oxygen content in the combustion-supporting gas is 21v%-29v; the oxygen content in the regenerated oxygen 11 is 60v%-100v; the external oxygen 1 is pure oxygen; and the through-hole linear velocity range of the oxygen distributor K is 55 m / s-90 m / s.

[0031] In the preferred embodiment described above, the method of the present invention improves the catalyst coking and regeneration efficiency by increasing the oxygen content in the combustion gas, enabling the catalyst in the catalytic cracking regenerator B to undergo oxygen-enriched combustion and increasing the coking temperature. Furthermore, the delivery rate of the combustion gas is controlled by controlling the through-hole linear velocity of the oxygen distributor K, ensuring that the catalyst in the catalytic cracking regenerator B is fully coked.

[0032] In a preferred embodiment, the catalyst undergoes coke burn-off regeneration in the catalytic cracking regenerator B at a temperature of 700°C-730°C; the dry basis dust content of the low-temperature, low-pressure flue gas 4 is less than 5 mg / Nm³. 3 The high-temperature low-pressure flue gas 2 has a pressure of 0.1 MPa-0.2 MPa and a temperature of 340℃-430℃; the high-pressure circulating flue gas 6 has a pressure of 0.23 MPa-0.39 MPa and a temperature of 60℃-120℃; the high-temperature combustion-supporting gas 9 has a temperature of 180℃-240℃; and the circulating flue gas 5 has a temperature of 45℃-61℃.

[0033] In the preferred embodiments described above, the catalytic regeneration coking process can be any one of single-stage regeneration, two-stage regeneration, and rapid fluidized bed regeneration. Optionally, the coking process includes pre-coking tank regeneration and post-coking tank regeneration. In the method described in this invention, the through-hole linear velocity of the oxygen distributor is in the range of 55m / s-90m / s, the inter-stage temperature of the circulating flue gas is not higher than 60°C, and condensate and cooling water are provided between stages.

[0034] Another aspect of the present invention provides a system for the conversion of CO2 in regenerated flue gas. The system includes: an electrolytic water device A, a gas heat exchanger D, an oxygen distributor K, a catalytic cracking regenerator B, a flue gas impurity removal unit, and a CO2 electrochemical conversion unit R. The gas heat exchanger D includes a low-temperature combustion-supporting inlet, a high-temperature combustion-supporting outlet, a flue gas inlet, and a flue gas outlet arranged sequentially. The CO2 electrochemical conversion unit R includes a flue gas inlet to be converted, a regenerated oxygen outlet, and a syngas outlet arranged sequentially. The oxygen distributor K includes an external oxygen inlet, a circulating flue gas inlet, a regenerated oxygen inlet, and a combustion-supporting outlet arranged sequentially. A pure oxygen pipeline N is provided between the oxygen outlet of the electrolytic water device A and the external oxygen inlet of the oxygen distributor K. The combustion-supporting outlet of the oxygen distributor K is connected to the gas heat exchanger... A low-temperature combustion gas pipeline is provided between the low-temperature combustion gas inlet of gas heat exchanger D and the combustion gas inlet of catalytic cracking regenerator B; a high-temperature combustion gas pipeline is provided between the high-temperature combustion gas outlet of gas heat exchanger D and the combustion gas inlet of catalytic cracking regenerator B; the high-temperature low-pressure flue gas outlet of catalytic cracking regenerator B is connected to the flue gas inlet of gas heat exchanger D; the flue gas outlet of gas heat exchanger D is connected to the flue gas inlet of flue gas purification unit; the flue gas outlet of flue gas purification unit is connected to the circulating flue gas inlet of oxygen distributor K; the flue gas outlet of flue gas purification unit is also connected to the flue gas inlet to be converted of CO2 electrochemical conversion unit R; the regenerated oxygen outlet of CO2 electrochemical conversion unit R is connected to the regenerated oxygen inlet of oxygen distributor K; and the syngas outlet of CO2 electrochemical conversion unit R is connected to the downstream utilization device.

[0035] In the preferred embodiment described above, the water electrolysis hydrogen production device can be an alkaline water electrolysis device. An oxygen storage buffer device can be provided between the water electrolysis device and the oxygen distributor to ensure that oxygen can be continuously and stably supplied to the oxygen distributor. The structure of the oxygen distributor includes at least one of the following: butterfly distribution, planar dendritic distribution, and annular distribution. The flue gas turbine drives the fan to generate electricity through the mechanical energy generated by the flue gas, and recovers the pressure energy of the flue gas. The device provided by the present invention realizes the rationalization of the economic benefits of device configuration.

[0036] In a preferred embodiment, the CO2 electrochemical conversion unit R includes, in sequence, an absorption unit R1, an electrochemical reactor R2, a first gas-liquid separator R3, a second gas-liquid separator R4, and an electrolyte mixing tank R5; the electrochemical reactor R2 includes a cathode chamber R21 and an anode chamber R22 separated by an ion-exchange membrane; the absorption unit R1 includes, from top to bottom, a first electrolyte inlet, a flue gas inlet to be converted, and a rich solution outlet; the rich solution outlet of the absorption unit R1 is connected to the rich solution inlet of the cathode chamber R21, the cathode gas-liquid mixture outlet of the cathode chamber R21 is connected to the cathode gas-liquid mixture inlet of the first gas-liquid separator R3, and the anode gas-liquid mixture outlet of the anode chamber R22 is connected to the second gas-liquid separator R5. The first gas-liquid separator R3 further includes a syngas outlet and a cathode electrolyte outlet. The syngas outlet is connected to the downstream utilization device, and the cathode electrolyte outlet is connected to the cathode electrolyte inlet of the electrolyte mixing tank R5. The second gas-liquid separator R4 further includes a regenerated oxygen outlet and an anode electrolyte outlet. The regenerated oxygen outlet is connected to the regenerated oxygen inlet of the oxygen distributor K, and the anode electrolyte outlet is connected to the anode electrolyte inlet of the electrolyte mixing tank R5. The electrolyte mixing tank R5 further includes a first electrolyte outlet and a second electrolyte outlet. The first electrolyte outlet is connected to the first electrolyte inlet of the absorption unit R1, and the second electrolyte outlet is connected to the anode electrolyte inlet of the anode chamber R22.

[0037] In the preferred embodiments described above, the CO2 electrochemical conversion unit R of the system provided by the present invention can effectively absorb CO2 in the exhaust gas, while reducing the amount of CO2 emitted and generating high-value-added syngas and regenerated oxygen. The syngas includes hydrogen and carbon monoxide, which is stored in the syngas storage unit K and then sent to downstream utilization devices for use. The reaction conditions of the CO2 electrochemical catalytic conversion syngas production device of the present invention can be close to ambient temperature and pressure, making the reaction operation conditions simpler. At the same time, the lower temperature can promote the dissolution of CO2 gas, improve the dissolution efficiency of CO2 gas, and thus improve the single-pass conversion rate of CO2 gas.

[0038] In an optional embodiment, the system further includes: the flue gas outlet of the gas heat exchanger D is connected to the flue gas purification unit, the flue gas purification unit including a harmful gas removal device F and a dust removal device G arranged sequentially; the flue gas outlet of the gas heat exchanger D is connected to the harmful gas removal device F, the flue gas outlet of the harmful gas removal device F is connected to the flue gas inlet of the dust removal device G, the flue gas outlet of the dust removal device G is provided with a low-temperature, low-pressure flue gas pipeline, the low-temperature, low-pressure flue gas pipeline is divided into a flue gas pipeline to be collected and a circulating flue gas pipeline; the flue gas pipeline to be collected is connected to the flue gas inlet of the CO2 electrochemical conversion unit R, and the circulating flue gas pipeline is connected to the circulating flue gas inlet of the oxygen distributor K; a circulating compressor H is also provided between the flue gas outlet of the dust removal device G and the circulating flue gas inlet of the oxygen distributor K, and a flue gas turbine C is also provided between the catalytic cracking regenerator B and the gas heat exchanger D.

[0039] In the above optional embodiments, the harmful gases removed by the device of the present invention can be SO2, nitrogen oxides and water vapor. The presence of water or water vapor will affect the catalyst coking regeneration reaction and reduce the catalyst regeneration rate.

[0040] In one optional embodiment, the catalytic cracking regenerator B includes a dilute phase zone and a dense phase zone arranged vertically from top to bottom; the dilute phase zone includes a separation system, a stripping section, a regeneration riser, and a booster arranged sequentially; the dense phase zone includes a dense phase bed, a regeneration plug valve, an air distribution pipe, a regeneration riser, and a regeneration plug valve arranged sequentially; the catalytic cracking regenerator B also includes two-stage cyclone separators connected in series; the diameter of the cyclone separators is 1-2 m; the bulk density of the dilute phase zone is 5-10 kg / m³. 3 The height of the dilute phase space from the dense phase zone to the inlet of the first-stage cyclone separator is 10-16m; the diameter of the dense phase zone is 6-10m; and the volume is 200-500m³. 3 The density phase bed has a bed height of 4-8m and a bed temperature of 640-690℃.

[0041] In the above optional embodiments, the present invention provides sufficient reaction space for the coking regeneration of the catalyst by setting up the catalytic cracking regenerator B. At the same time, the setting of the dilute phase zone and the dense phase zone allows the combustion gas to fully contact the catalyst, ensuring that the catalyst and the combustion gas react fully. It can also maintain the temperature requirements for catalyst regeneration, and the setting of the space height can reduce impurities in the flue gas. The device provided by the present invention solves the problems of incomplete utilization of by-product oxygen from water electrolysis, high treatment cost, and large CO2 emissions in the treated tail gas.

[0042] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to the embodiments.

[0043] Example 1 This embodiment uses the system shown in the attached figure to perform CO2 conversion in regenerated flue gas. The method of this embodiment includes: S1. Water is fed into water electrolysis device A for electrolysis to obtain external oxygen 1 and external hydrogen. The external oxygen 1 is fed into gas heat exchanger D as combustion-supporting gas to exchange heat with high temperature and low pressure flue gas 2 to obtain high temperature combustion-supporting gas 9 and low temperature and low pressure flue gas 4. The high temperature combustion-supporting gas 9 is fed into catalytic cracking regenerator B for regeneration and coking to obtain high temperature and low pressure flue gas 2. S2. The low-temperature, low-pressure flue gas 4 (flow rate 28.93 kg / s, carbon dioxide content 54% v%) is divided into circulating flue gas 5 (flow rate 20.72 kg / s, carbon dioxide content 54% v%) and flue gas to be converted 8 (flow rate 8.2 kg / s, carbon dioxide content 54% v%). The circulating flue gas 5 and external oxygen 1 are used as combustion-supporting gas, and the process returns to step S1. The CO2 content in the low-temperature, low-pressure flue gas reaches the set threshold. S3. The flue gas 8 to be converted is sent into the CO2 electrochemical conversion unit R for conversion reaction to obtain syngas 10 and regenerated oxygen 11. The regenerated oxygen 11 and the external oxygen 1, along with the circulating flue gas, are returned to the operation of step S1 as combustion-supporting gas.

[0044] The CO2 content in the low-temperature, low-pressure flue gas 4 is detected using a CO2 content detector; the set threshold is preferably 52v.

[0045] The method further includes: the dry basis oxygen content in the combustion-supporting gas is preferably 25% vol%; the oxygen content in the regenerated oxygen 11 is preferably 98% vol%; the external oxygen 1 is pure oxygen; and the through-hole linear velocity of the oxygen distributor K is preferably 75 m / s.

[0046] The catalyst undergoes coke burn-off regeneration in the catalytic cracking regenerator B, with a preferred temperature of 725°C; the dry basis dust content of the low-temperature, low-pressure flue gas 4 is less than 5 mg / Nm³. 3 The pressure of the high-temperature low-pressure flue gas 2 is preferably 0.15 MPa; the temperature is preferably 380°C; the pressure of the high-pressure circulating flue gas 6 is preferably 0.32 MPa; the temperature is preferably 92°C; the temperature of the high-temperature combustion-supporting gas 9 is preferably 230°C; and the temperature of the circulating flue gas 5 is preferably 58°C.

[0047] The flue gas 8 to be converted (flow rate of 8.2 kg / s, carbon dioxide content of 54%) is fed from the bottom into the absorption unit R1 of the CO2 electrochemical conversion unit R and absorbed by the first electrolyte 12 to obtain a rich solution 13. The rich solution 13 is then fed into the cathode chamber R21 of the electrochemical reactor R2, and the second electrolyte 18 is fed into the anode chamber R22. An electrochemical conversion reaction is carried out in the electrochemical reactor R2 to obtain a cathode gas-liquid mixture 14 and an anode gas-liquid mixture 15 (reactor outlet temperature of 63°C, operating pressure of 0.15 MPa). The cathode gas-liquid mixture 14 is fed into the first gas-liquid separator R3 for gas-liquid separation to obtain syngas 10 (composed of 4.96 kg / s carbon monoxide, 0.7 kg / s hydrogen and 4.66 kg / s carbon dioxide) and cathode electrolyte 16. The anode gas-liquid mixture 15 is fed into the second gas-liquid separator R4 for gas-liquid separation to obtain regenerated oxygen 11 (oxygen flow rate of 8.54 kg / s and carbon dioxide flow rate of 2.31 kg / s) and anode electrolyte 17. The syngas 10 is fed into the downstream utilization device, and the regenerated oxygen 11 and the external oxygen 1 are fed together with the circulating flue gas 5 into the oxygen distributor K for mixing; the cathode electrolyte 16 and the anode electrolyte 17 are fed into the electrolyte mixing tank R5 for mixing (total flow rate of 13755 kg / s), and then the first electrolyte 12 (flow rate of 3434.65 kg / s) and the second electrolyte 18 (flow rate of 9604 kg / s) are drawn out from the electrolyte mixing tank R5. Deionized water 19 (flow rate of 8.0 kg / s) is fed into the electrolyte mixing tank R5 to replenish the water consumed in the electrolysis reaction; the electrolyte is preferably a sodium bicarbonate solution, and the concentration is preferably 3 mol / L; The preferred operating temperature of the absorption unit R1 is 60℃, and the preferred operating pressure is 0.15MPa; the preferred operating temperature of the electrochemical reactor R2 is 60℃, and the preferred operating pressure is 0.15MPa; the first gas-liquid separator R3 and the second gas-liquid separator R4 are vertical or horizontal gas-liquid separators; the preferred operating temperature of the first gas-liquid separator R3 is 63℃, and the preferred operating pressure is 0.12MPa; the preferred operating temperature of the second gas-liquid separator R4 is 63℃, and the preferred operating pressure is 0.12MPa.

[0048] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0049] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0050] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for converting CO2 in regenerated flue gas, characterized in that, The method includes: S1. Water is fed into an electrolysis water device (A) for electrolysis to obtain external oxygen (1) and external hydrogen. The external oxygen (1) is fed into a gas heat exchanger (D) as a combustion-supporting gas to exchange heat with high temperature and low pressure flue gas (2) to obtain high temperature combustion-supporting gas (9) and low temperature and low pressure flue gas (4). The high temperature combustion-supporting gas (9) is fed into a catalytic cracking regenerator (B) for regeneration and coking to obtain high temperature and low pressure flue gas (2). S2. Divide the low-temperature and low-pressure flue gas (4) into circulating flue gas (5) and flue gas to be converted (8). Use the circulating flue gas (5) and external oxygen (1) as combustion support, and return to the operation of step S1. The CO2 content in the low-temperature and low-pressure flue gas (4) reaches the set threshold. S3. The flue gas to be converted (8) is sent into the CO2 electrochemical conversion unit (R) for electrochemical conversion reaction to obtain syngas (10) and regenerated oxygen (11). The regenerated oxygen (11) and the external oxygen (1) are returned to step S1 as combustion-supporting gas along with the circulating flue gas (5).

2. The method according to claim 1, wherein, The CO2 content in the low-temperature and low-pressure flue gas (4) is detected using a CO2 content detector; the CO2 content in the low-temperature and low-pressure flue gas (4) is 10v%~95v%; the set threshold is any point value within the range of 20v%-90v%.

3. The method according to claim 1, wherein, The method further includes: The low-temperature and low-pressure flue gas (4) is sequentially fed into the harmful gas removal device (F) and the dust removal device (G) for impurity removal. The impurity-removed low-temperature and low-pressure flue gas (4) is then divided into the flue gas to be converted (8) and the circulating flue gas (5). The circulating flue gas (5) is fed into the circulating compressor (H) for pressurization to obtain high-pressure circulating flue gas (6). The high-pressure circulating flue gas (6), together with the external oxygen (1) and the regenerated oxygen (11), is fed into the catalytic cracking regenerator (B) as combustion support.

4. The method according to claim 1, wherein, The method further includes: feeding the flue gas (8) to be converted into the absorption unit (R1) of the CO2 electrochemical conversion unit (R) from the bottom and having it absorbed by the first electrolyte (12) to obtain a rich solution (13); feeding the rich solution (13) into the cathode chamber (R21) of the electrochemical reactor (R2); feeding the second electrolyte (18) into the anode chamber (R22); and carrying out an electrochemical conversion reaction in the electrochemical reactor (R2) to obtain a cathode gas-liquid mixture (14) and an anode gas-liquid mixture (15). The cathode gas-liquid mixture (14) is fed into the first gas-liquid separator (R3) for gas-liquid separation to obtain syngas (10) and cathode electrolyte (16). The anode gas-liquid mixture (15) is fed into the second gas-liquid separator (R4) for gas-liquid separation to obtain regenerated oxygen (11) and anode electrolyte (17). The regenerated oxygen (11) and the external oxygen (1) are fed together with the circulating flue gas (5) into the oxygen distributor (K) for mixing. The cathode electrolyte (16) and the anode electrolyte (17) are fed into the electrolyte mixing tank (R5) for mixing, and then the first electrolyte (12) and the second electrolyte (18) are drawn out from the electrolyte mixing tank (R5).

5. The method according to claim 4, wherein, The method further includes: The dry basis oxygen content in the combustion-supporting gas is 21%-29%; The oxygen content in the regenerated oxygen (11) is 60%-100%; The external oxygen (1) is pure oxygen; The through-hole linear velocity of the oxygen distributor (K) ranges from 55 m / s to 90 m / s.

6. The method according to claim 1 or 3, wherein, The catalyst is regenerated by coking in the catalytic cracking regenerator (B) at a temperature of 700°C-730°C. The dry basis dust content of the low-temperature, low-pressure flue gas (4) is less than 5 mg / Nm³. 3 ; The pressure of the high-temperature, low-pressure flue gas (2) is 0.1 MPa-0.2 MPa; the temperature is 340℃-430℃. The pressure of the high-pressure circulating flue gas (6) is 0.23MPa-0.39MPa; the temperature is 60℃-120℃. The temperature of the high-temperature combustion-supporting gas (9) is 180℃-240℃; The temperature of the circulating flue gas (5) is 45℃-61℃.

7. A system for converting CO2 in regenerated flue gas, characterized in that, The system includes: an electrolysis water unit (A), a gas heat exchanger (D), an oxygen distributor (K), a catalytic cracking regenerator (B), a flue gas purification unit, and a CO2 electrochemical conversion unit (R); The gas heat exchanger (D) includes a low-temperature combustion gas inlet, a high-temperature combustion gas outlet, a flue gas inlet, and a flue gas outlet arranged sequentially. The CO2 electrochemical conversion unit (R) includes a flue gas inlet to be converted, a regenerated oxygen outlet, and a syngas outlet arranged sequentially. The oxygen distributor (K) includes an external oxygen inlet, a circulating flue gas inlet, a regenerated oxygen inlet, and a combustion-supporting outlet arranged in sequence. A pure oxygen pipeline (N) is provided between the oxygen outlet of the water electrolysis device (A) and the external oxygen inlet of the oxygen distributor (K). A low-temperature combustion-supporting pipeline is provided between the combustion-supporting outlet of the oxygen distributor (K) and the low-temperature combustion-supporting inlet of the gas heat exchanger (D). A high-temperature combustion-supporting pipeline is provided between the high-temperature combustion-supporting outlet of the gas heat exchanger (D) and the combustion-supporting inlet of the catalytic cracking regenerator (B). The high-temperature, low-pressure flue gas outlet of the catalytic cracking regenerator (B) is connected to the flue gas inlet of the gas heat exchanger (D). The flue gas outlet of the gas heat exchanger (D) is connected to the flue gas inlet of the flue gas purification unit. The flue gas outlet of the flue gas purification unit is connected to the circulating flue gas inlet of the oxygen distributor (K). The flue gas outlet of the flue gas purification unit is also connected to the flue gas inlet to be converted of the CO2 electrochemical conversion unit (R). The regenerated oxygen outlet of the CO2 electrochemical conversion unit (R) is connected to the regenerated oxygen inlet of the oxygen distributor (K).

8. The system according to claim 7, wherein, The CO2 electrochemical conversion unit (R) includes an absorption unit (R1), an electrochemical reactor (R2), a first gas-liquid separator (R3), a second gas-liquid separator (R4), and an electrolyte mixing tank (R5) arranged in sequence; the electrochemical reactor (R2) includes a cathode chamber (R21) and an anode chamber (R22) separated by an ion-exchange membrane. The absorption unit (R1) includes a first electrolyte inlet, a flue gas inlet to be converted, and a rich solution outlet arranged sequentially from top to bottom; The rich solution outlet of the absorption unit (R1) is connected to the rich solution inlet of the cathode chamber (R21), the cathode gas-liquid mixture outlet of the cathode chamber (R21) is connected to the cathode gas-liquid mixture inlet of the first gas-liquid separator (R3), the anode gas-liquid mixture outlet of the anode chamber (R22) is connected to the anode gas-liquid mixture inlet of the second gas-liquid separator (R4), the first gas-liquid separator (R3) also includes a syngas outlet and a cathode electrolyte outlet, the syngas outlet is connected to the downstream utilization device, and the cathode electrolyte outlet is connected to the cathode electrolyte inlet of the electrolyte mixing tank (R5); The second gas-liquid separator (R4) further includes a regenerated oxygen outlet and an anolyte outlet. The regenerated oxygen outlet is connected to the regenerated oxygen inlet of the oxygen distributor (K), and the anolyte outlet is connected to the anolyte inlet of the electrolyte mixing tank (R5). The electrolyte mixing tank (R5) also includes a first electrolyte outlet and a second electrolyte outlet. The first electrolyte outlet is connected to the first electrolyte inlet of the absorption unit (R1), and the second electrolyte outlet is connected to the anolyte inlet of the anode chamber (R22).

9. The system according to claim 7, wherein, The system also includes: The flue gas outlet of the gas heat exchanger (D) is connected to the flue gas purification unit, which includes a harmful gas removal device (F) and a dust removal device (G) arranged in sequence. The flue gas outlet of the gas heat exchanger (D) is connected to the harmful gas removal device (F), and the flue gas outlet of the harmful gas removal device (F) is connected to the flue gas inlet of the dust removal device (G). The flue gas outlet of the dust removal device (G) is provided with a low-temperature and low-pressure flue gas pipeline, which is divided into a flue gas pipeline to be collected and a circulating flue gas pipeline. The flue gas pipeline is connected to the flue gas inlet to be collected of the CO2 electrochemical conversion unit (R), and the circulating flue gas pipeline is connected to the circulating flue gas inlet of the oxygen distributor (K). A circulating compressor (H) is provided between the flue gas outlet of the dust removal device (G) and the circulating flue gas inlet of the oxygen distributor (K), and a flue gas turbine (C) is provided between the catalytic cracking regenerator (B) and the gas heat exchanger (D).

10. The system according to claim 7, wherein, The catalytic cracking regenerator (B) includes a dilute phase zone and a dense phase zone arranged vertically from top to bottom; The dilute phase region includes a separation system, a stripping section, a riser for steam generation, and a booster arranged in sequence. The dense phase zone includes a dense phase bed, a waiting plug valve, an air distribution pipe, a regeneration riser, and a regeneration plug valve arranged in sequence. The catalytic cracking regenerator (B) is also equipped with two-stage cyclone separators connected in series. The diameter of the cyclone separator is 1-2m; The bulk density of the rare phase region is 5-10 kg / m³. 3 ; The height of the dilute phase space between the dense phase zone and the inlet of the first-stage cyclone separator is 10-16m. The diameter of the dense phase region is 6-10 m; the volume is 200-500 m³. 3 ; The density phase bed has a bed height of 4-8m and a bed temperature of 640-690℃.

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