WO2024045700A1 - 烟气co2电解制合成气工艺及系统 - Google Patents

烟气co2电解制合成气工艺及系统 Download PDF

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WO2024045700A1
WO2024045700A1 PCT/CN2023/095474 CN2023095474W WO2024045700A1 WO 2024045700 A1 WO2024045700 A1 WO 2024045700A1 CN 2023095474 W CN2023095474 W CN 2023095474W WO 2024045700 A1 WO2024045700 A1 WO 2024045700A1
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electrolyte
electrolysis
gas
cathode
anode
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French (fr)
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WO2024045700A9 (zh
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康鹏
张�雄
汪秀萍
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碳能科技（北京）有限公司
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/23—Carbon monoxide or syngas
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C25B9/67—Heating or cooling means

Definitions

  • This disclosure belongs to the field of resources and environmental protection, and specifically relates to CO 2 electrolysis to produce syngas processes and systems.
  • CO 2 electrolysis to syngas technology can be combined with green electricity to convert CO 2 into syngas, an important raw material for the chemical industry. At the same time, it has the environmental attributes of carbon emission reduction and the new energy attributes of energy storage. Therefore, it has many CO 2 utilization pathways and application fields. has become a research hotspot.
  • the CO2 electrolysis to synthesis gas process mainly relies on a two-chamber reaction unit with a cathode chamber and an anode chamber.
  • the more typical electrolysis process is a gas-liquid mixed electrolysis mode.
  • CO 2 gas and electrolyte are directly passed into the cathode chamber at the same time to produce syngas (composed of CO and H 2 ) through electrolysis.
  • This operation process is relatively simple and only consumes CO2 and water as raw materials, so it is highly scalable.
  • the first drawback is that the quality requirements of the gas source are relatively stringent, requiring a high-purity gas source.
  • the second flaw is that in the traditional gas-liquid mixed electrolysis process, the surface of the catalyst is covered with a large amount of electrolyte, and the mass transfer of CO 2 on its surface is limited, resulting in serious side reactions of hydrogen evolution, and a large amount of CO 2 is not involved in the conversion, allowing subsequent product gas separation. Purification operations are complex and expensive, making this technology ineffective in reducing carbon emissions and making it less economical.
  • this disclosure provides a new electrolysis process that can be applied to CO2 gas sources of different concentrations, has significant carbon emission reduction effects, and can effectively reduce the cost of CO2 electrolysis to produce syngas, so as to accelerate the engineering application process of this technology.
  • the present disclosure provides a flue gas CO2 electrolysis to produce synthesis gas process, which includes: a carbon dioxide enrichment step, using a CO2- poor electrolyte to absorb CO2 from a CO2 gas source to obtain a CO2- rich electrolyte; an electrolyte circulation step, The CO2 - rich electrolyte is transported into the cathode cavity of the electrochemical reactor, while the CO2- poor electrolyte is sent into the anode cavity of the electrochemical reactor, and the cathode discharged from the cathode cavity after electrolysis is electrolyzed The liquid is mixed with the anolyte discharged from the anode chamber and replenished with water to obtain a CO2 - lean electrolyte with a constant concentration; and an electrolysis step is to provide direct current to the electrochemical reactor, in the cathode chamber of the electrochemical reactor CO 2 and water in the CO 2 -rich electrolyte are catalytically reduced to synthesis gas, while water in the CO 2 -poor electroly
  • the absorption pressure in the carbon dioxide enrichment step is 10kPa-5MPa, and the absorption temperature is 5-90°C; the electrolysis temperature of the electrochemical reactor is 5-90°C, and the electrolysis pressure is 10kPa-5MPa .
  • the CO2 - lean electrolyte is an alkaline electrolyte, preferably a bicarbonate or carbonate electrolyte of an alkali metal; the alkali metal is lithium, sodium, potassium, rubidium, cesium One or more of them, preferably potassium and sodium, and the metal ion concentration in the electrolyte is 0.05-6mol/L.
  • the pH value of the CO2- rich electrolyte is 6-11.
  • the CO 2 volume content in the CO 2 gas source is ⁇ 3%.
  • the method before absorbing CO 2 , further includes removing impurities from the CO 2 gas source to remove powders, particles and gases harmful to the electrochemical reactor in the CO 2 gas source. .
  • the system may be in a pressure-equalizing condition, that is, the electrolysis pressure is equal to the absorption pressure of the carbon dioxide enrichment module. It can also be a non-pressure equalizing working condition, that is, the electrolysis pressure is not equal to the absorption pressure of the carbon dioxide enrichment module; the pressure equalizing working condition is preferred.
  • the present disclosure also provides a CO 2 electrolysis to produce syngas system, including: a carbon dioxide enrichment module for absorbing CO 2 from a CO 2 gas source with a CO 2 -poor electrolyte to obtain a CO 2 -rich electrolyte; an electrolysis module, including an electrolyte A chemical reactor, in the cathode cavity of the electrochemical reactor, CO 2 and water in the CO 2 rich electrolyte are catalytically reduced to synthesis gas, while in the anode cavity of the electrochemical reactor the CO 2 -poor 2.
  • Water in the electrolyte is catalytically oxidized into oxygen; and an electrolyte circulation module is used to supply the CO 2 -rich electrolyte and the CO 2 -poor electrolyte to the electrolysis module, and to conduct the cathode and anode of the electrolysis module
  • the discharged electrolyte is mixed and rehydrated to obtain a CO2 - lean electrolyte with a constant concentration.
  • the carbon dioxide enrichment module further includes an impurity removal unit, which is used to remove particulate matter and gases harmful to the electrochemical reactor in the CO 2 gas source.
  • the present disclosure provides a flue gas CO 2 enrichment electrolysis to produce syngas process and system, which relies on the CO 2 absorption function of the alkaline electrolyte in the electrolyte circulation step to realize the integration of CO 2 enrichment and electrolysis in the electrolyte.
  • the advantages of this process It has strong tolerance for CO 2 concentration in CO 2 gas source, and can be applied to high-purity gas sources as well as low-concentration CO 2 industrial gas sources, making this technology universally applicable to CO 2 gas sources in various industries. ; Compared with the traditional gas and liquid mixed electrolysis process, it is less dependent on carbon capture and relies on the electrolysis system to simultaneously achieve carbon dioxide enrichment.
  • the process operation flow is simple, effectively increasing the concentration of synthesis gas in the product gas and reducing the cost of product gas separation. and carbon utilization costs, improving CO 2 utilization efficiency and economy.
  • Figure 1 is a flow chart of the CO 2 electrolysis to synthesis gas process in Embodiment 1.
  • Figure 2 is a schematic diagram of the CO 2 electrolysis to synthesis gas system in Embodiment 1.
  • Figure 3 is a schematic diagram of the CO 2 electrolysis to synthesis gas system in Embodiment 3.
  • Figure 4 is a flow chart of the CO 2 electrolysis to synthesis gas process in Embodiment 4.
  • Figure 5 is a schematic diagram of the CO 2 electrolysis to syngas system in Embodiment 4.
  • the present disclosure provides a synthesis gas production process by electrolysis of flue gas CO2 , which uses industrial CO2 gas source and water as raw materials, and undergoes dioxygen Synthetic gas (CO+H 2 ) and oxygen (O 2 ) are obtained through the carbon enrichment step, electrolyte circulation step and electrolysis step. Furthermore, a product gas purification step can be included. The syngas and oxygen obtained through the first three steps can be further separated and purified through this step to obtain syngas products and oxygen by-products respectively. The CO 2 separated through this step can be returned to the carbon dioxide-rich gas. Set steps to recycle. The process of the present disclosure will be described in detail below.
  • the carbon dioxide enrichment step is for the CO2 - lean electrolyte to absorb CO2 from the CO2 gas source to obtain a CO2- rich electrolyte.
  • This step can pressurize the CO2 gas source so that the CO2- lean electrolyte can absorb the CO2 in the gas source to obtain a CO2- rich electrolyte.
  • the “electrolyte” includes “ CO2- poor electrolyte” and “ CO2- rich electrolyte”.
  • This step may also include an impurity removal process.
  • the CO 2 gas source Before enriching CO 2 , the CO 2 gas source may be cleaned to remove particulate matter impurities in the gas source and gases harmful to subsequent electrochemical reactors.
  • CO 2 gas sources generally come from chemical industry, thermal power, cement, steel and other industries. They can be high-purity gas sources or low-concentration gas sources. They may contain H 2 S, SO x , NO x , NH 3 , NH 2 CH 2 One or several impurities in OH, dust, etc.
  • O 2 or N 2 impurities will reduce the partial pressure of CO 2 in the gas source, thereby affecting the absorption and enrichment of CO 2
  • impurities such as H 2 S, SO x , NO x , NH 3 , NH 2 CH 2 OH, and dust It will affect the life of the catalytic electrode in the electrochemical reactor and is called a harmful impurity, so it needs to be removed before CO 2 is enriched.
  • the method for removing impurities can be any applicable method, which will be described in detail below.
  • the electrolyte circulation step includes delivering CO2 - rich electrolyte into the cathode cavity of the electrochemical reactor, while simultaneously delivering CO2 -poor electrolyte into the anode cavity of the electrochemical reactor.
  • the electrolyzed gas and liquid mixture in the cathode cavity and the gas and liquid mixture in the anode cavity are mixed with the catholyte and anolyte obtained after gas-liquid separation respectively, and at the same time, the water consumed by the reaction is replenished into the electrolyte.
  • a CO2 - lean electrolyte with constant concentration for recycling.
  • the cathode mixed gas and anode mixed gas are obtained respectively.
  • synthesis gas and oxygen are obtained respectively.
  • the cooled electrolyte of the cathode mixed gas and anode mixed gas is merged into the cathode electrolyte and the anolyte electrolyte respectively.
  • the electrolysis step provides direct current to the electrochemical reactor.
  • CO 2 and water in the CO 2 -rich electrolyte are catalytically reduced and converted into synthesis gas.
  • CO 2 -poor electrolyte is converted into synthesis gas.
  • Water is catalytically oxidized to oxygen.
  • the specific reaction principle is as follows: CO 2 and H 2 O in the CO 2 -rich electrolyte are reduced and converted into synthesis gas and OH - under the action of the cathode catalytic electrode in the cathode cavity, while H 2 O in the CO 2 -poor electrolyte is in the anode cavity It is oxidized to O 2 under the action of the anode catalytic electrode, and M + in the anode cavity migrates from the cation exchange membrane to the cathode cavity.
  • the reaction of the electrolysis process is as follows:
  • the M + concentration and pH value in the catholyte discharged after the reaction increase, while the M + concentration and pH value in the electrolyte discharged from the anode after the reaction decrease, the two solutions will be mixed to achieve pH and MHCO 3 concentration mixing. . Therefore, the electrolyte only needs to be introduced before startup. There is no electrolyte consumption during the conversion process. The water consumed during the reaction process can be added through the water replenishment unit. The entire synthesis route consumes only water and CO 2 as raw materials, and there is no need to introduce other substances. The operation is simple and low cost.
  • the present disclosure obtains a CO 2 -rich electrolyte containing dissolved CO 2 through the enrichment step, which can be directly contacted with the catalyst, effectively reducing mass transfer limitations, and improving reaction efficiency compared to the traditional gas and liquid mixed mode.
  • the product gas purification step can purify and purify the synthesis gas, obtain the synthesis gas product and separate unreacted CO 2 , and the CO 2 can be returned to the carbon dioxide enrichment step for recycling.
  • the product gas purification step can also purify and purify oxygen to obtain oxygen by-products and separate residual CO 2 , which can be returned to the carbon dioxide enrichment step for recycling.
  • the CO 2 volume content in the CO 2 gas source is ⁇ 3%, which can be a high-purity gas source, or low partial pressure CO 2 flue gas and chemical product gas.
  • the absorption pressure (gauge pressure) in the carbon dioxide enrichment step is 10kPa-5MPa
  • the absorption temperature is 5-90°C
  • the pH value of the CO2 - rich electrolyte at the outlet of the absorption tower is 6-11.
  • the electrolysis temperature of the electrochemical reactor is 5-90°C
  • the electrolysis pressure (gauge pressure) is 10kPa-5MPa.
  • the absorption pressure can be equal to the electrolysis pressure, and the electrolysis pressure is controlled through the electrolyte circulation step system.
  • the entire process system is in a pressure-equalizing condition, and the pressure control complexity can be reduced; when the absorption pressure is greater than the electrolysis pressure
  • there is a pressure difference between the enrichment module and the electrolysis module that is, non-isobaric working conditions.
  • the disadvantage is that it will increase the complexity of the pressure control of the entire process pipeline and system, and it is easy to cause CO 2 gas to escape from the liquid phase and affect the electrolysis efficiency.
  • the advantage is that the pressure difference can be used as the driving force for transporting electrolyte from the enrichment module to the electrolysis module; the purpose of the invention can also be achieved when the absorption pressure is less than the electrolysis pressure.
  • the electrolyte is an alkaline electrolyte, preferably an alkali metal bicarbonate (MHCO 3 ) or carbonate (M 2 CO 3 ) electrolyte.
  • the alkali metal (M) can be lithium, sodium, potassium, rubidium, cesium, preferably potassium and sodium, and the metal ion concentration is 0.05-6 mol/L.
  • the present disclosure also provides a CO 2 enrichment electrolysis system for producing syngas, including a carbon dioxide enrichment module, an electrolyte circulation module, and an electrolysis module.
  • a further step can include a product gas purification module.
  • the carbon dioxide enrichment module is used to absorb and enrich the CO 2 gas source. It can include a raw gas supply unit and a CO2 absorption unit. When the CO2 gas source contains harmful impurities, an impurity removal unit can also be included. When it is necessary to recycle the CO 2 tail gas, a CO 2 recycling unit is also included.
  • the raw gas supply unit includes a buffer tank and a booster. The upstream of the booster is connected to the buffer tank and the CO 2 gas source in turn, and the downstream is connected to the CO 2 absorption unit. unit or impurity removal unit.
  • the raw gas supply unit can only contain a buffer tank; the absorption unit includes an absorption tower.
  • the CO 2 gas source has no harmful impurities, Its upstream can be directly connected to the raw gas supply unit.
  • the CO2 gas source contains harmful impurities, its upstream is connected to the impurity removal unit, and its downstream is connected to the electrolyte circulation module, or it can also be connected to the CO2 circulation unit at the same time;
  • the miscellaneous unit includes an elution tower, which can be one or multiple series or parallel structures.
  • the CO 2 circulation unit includes a front buffer tank, a pressurization equipment, and a rear buffer.
  • Tank the upstream of the front buffer tank is connected to the product gas purification module, and can also be connected to the top of the absorption tower at the same time.
  • the front buffer tank, booster, and rear buffer tank are connected in sequence, and the downstream of the rear buffer tank is connected to the absorption module.
  • the boosting device can be either a fan or a compressor.
  • the CO2 tail gas is the CO2 tail gas at the top of the absorption tower and/or the CO2 tail gas of the product gas purification module.
  • the electrolysis module is used to produce syngas by electrochemical conversion of CO2 .
  • the electrochemical unit includes at least one electrochemical reactor.
  • Each electrochemical reactor contains at least one tank.
  • Each tank consists of a cathode chamber/separator/anode chamber. When multiple tanks are included, each tank can be connected in series and/or in parallel.
  • a reactor a system can contain one or more reactors.
  • the separator is a cation exchange membrane or an anion exchange membrane.
  • the upstream of the cathode cavity is connected to the absorption tower, the downstream is connected to the electrolyte circulation unit, and the upstream and downstream of the anode cavity are connected to the electrolyte circulation unit.
  • the control power supply is used to provide appropriate direct current for the electrochemical reaction unit.
  • the electrolyte circulation module is used to supply electrolyte to the electrolysis unit, separate electrolytic products and mix electrolyte. It can include an electrolyte transport unit, a gas-liquid separation unit, a mixing unit and a water replenishment unit.
  • the electrolyte transport unit includes an anode circulation pump, a relay pump and/or a cathode circulation pump.
  • the anode circulation pump is connected upstream to the mixing unit and downstream to the anode cavity. It can also be directly connected to the absorption tower to directly serve as energy supply for the relay pump.
  • the upstream and downstream of the pump are connected to the mixing unit and the absorption tower respectively, and the upstream and downstream of the cathode circulation pump are connected to the absorption tower and the cathode cavity respectively.
  • the gas-liquid separation unit includes a cathode gas-liquid separator, a cathode gas-phase cooling tower, an anode gas-liquid separator, and an anode gas-phase cooling tower.
  • the upstream of the cathode gas-phase cooler is connected to the cathode gas-liquid separator and the cathode cavity of the electrolysis unit in turn to perform gas phase processing.
  • Cold shortage the cold shortage liquid returns to the cathode gas-liquid separator, and the downstream can be connected to the product gas purification module for further purification to obtain the synthesis gas product.
  • the upstream of the anode gas phase cold shortage device is connected to the anode gas-liquid separator and the anode cavity of the electrolysis unit to obtain oxygen.
  • the downstream can also be connected to the product gas purification unit for further purification to obtain oxygen by-products.
  • the mixing unit is a mixing tank or a liquid mixer, the upstream of which is connected to the cathode gas-liquid separator and the anode gas-liquid separator respectively, and the downstream is connected to the anode circulation pump and relay pump respectively.
  • the water supply unit includes a water supply pump and a water tank. The water supply pump is connected upstream to the water tank and downstream to any one or more of the cathode gas-liquid separation tank, the anode gas-liquid separation tank or the mixing unit.
  • the product gas purification module is used to purify synthesis gas and/or oxygen and separate unreversely converted CO 2 .
  • a syngas purification unit and/or an oxygen purification unit may be included.
  • the purification unit can be any one of a membrane separation device, a pressure swing adsorption device, a temperature swing adsorption device, a chemical absorption device, etc.
  • the upstream of the syngas purification unit is connected to the cathode gas phase cold zone to produce syngas products, and the output CO 2 tail gas is connected to the front buffer tank of the CO 2 circulation unit.
  • the upstream of the oxygen purification unit is connected to the anode gas phase cold zone to produce oxygen by-products, and the output CO 2 tail gas is connected to the front buffer tank of the CO 2 circulation unit.
  • the absorption tower absorption pressure (gauge pressure) of the system is between 10kPa-5MPa, and the electrolysis module pressure (gauge pressure) is between 10kPa-5MPa.
  • the two can be equal or different.
  • the electrolysis pressure is divided into cathode side pressure and anode side pressure.
  • the cathode side pressure is controlled by the cathode gas-liquid separator or the cathode gas phase cooler outlet pressure regulating valve.
  • the anode side pressure is regulated by the anode gas-liquid separator and the anode gas phase cooler outlet pressure. Valve control, the pressure difference between the two is less than 50kPa.
  • the CO2 -rich electrolyte in the absorption tower can be sent into the cathode chamber from the pipeline between the absorption tower and the cathode chamber relying on the pressure difference between the two. At this time, the cathode circulates The pump can be omitted or inoperable.
  • the absorption tower pressure is equal to the operating pressure of the electrolyte circulation module, the CO2 - rich electrolyte in the absorption tower needs to be transported into the cathode cavity of the electrolysis unit by a cathode circulation pump.
  • the downstream of the anode circulation pump is connected to the anode cavity and the absorption tower at the same time to transport the lean CO2 electrolyte of the mixing unit into the anode cavity and absorption tower of the electrolysis unit.
  • the relay pump can be omitted.
  • the downstream is only connected to the anode cavity to transport the CO2 - poor electrolyte of the mixing unit, such as the anode cavity of the electrolysis unit.
  • the upstream and downstream relay pumps need to be connected to the mixing unit and the absorption tower respectively to send the CO2 - poor electrolyte into the absorption tower.
  • the purity of the syngas or oxygen product output from the product gas purification device mainly depends on the downstream application requirements of the syngas or oxygen product.
  • the purification device purifies the CO 2 in the syngas to a volume content of 3%-6%, which can be used for low-pressure synthesis of methanol feed gas, and the separated CO 2 gas is returned to the absorption tower for recycling.
  • the purification device purifies the CO 2 in the syngas to ⁇ 15%, which can be used for Fischer-Tropsch synthesis oil wax needs.
  • purifying CO2 in oxygen to ⁇ 0.8% can be used in industrial production or process gases.
  • CO 2 gas sources generally come from chemical industry, thermal power, cement, steel and other industries. They can be high-purity gas sources or low-concentration gas sources. They may contain H 2 S, SO x , NO x , NH 3 , NH 2 CH 2 One or several impurities in OH, dust, etc.
  • O 2 or N 2 impurities will reduce the partial pressure of CO 2 in the gas source, thereby affecting the absorption and enrichment of CO 2 , but have no harmful effects on the electrolysis reaction, while H 2 S, SO x , NO x , NH 3 , NH 2 CH 2 OH, dust and other impurities will affect the performance of the electrolysis module when the content is high, and are called harmful impurities, so they need to be removed to a lower concentration by the elution tower at the front of the CO 2 absorption tower.
  • the elution tower can be composed of one or more series or parallel connections.
  • the elution tower can be single-pass or can have multiple repeated elutions to achieve the removal of harmful impurities.
  • the adsorption medium in the tower can be liquid, including pure water, acidic solution, or alkaline solution. It can also be a dry filter medium, such as filter cloth, filter screen, etc., or a dry adsorbent or catalytic oxidizer, including activated carbon, zeolite, quicklime, alumina, aluminosilicate, zinc oxide, nickel oxide, iron oxide, oxidation Any one or more of silicon, copper hydroxide, and copper sulfate.
  • the acidic solution includes any one or more of HCl, H 2 SO 4 and HNO 3 .
  • Alkaline solutions include KOH, NaOH, K 2 CO 3 , Na 2 CO 3 , KHCO 3 , NaHCO 3 , Na 2 SO 3 , Ca(OH) 2 , CuSO 4 , Pb(NO 3 ) 2 , methanol, monoethanolamine diamine An aqueous solution composed of any one or more of ethanolamine, triethanolamine, diisopropanolamine, and methyldiethanolamine.
  • the CO 2 gas source is a highly concentrated gas source (CO 2 concentration ⁇ 98%) or contains O 2 and N 2 impurities (CO 2 concentration ⁇ 5%), then this gas source can directly enter the CO 2. Absorption tower enrichment, no need to go through elution tower to remove impurities.
  • the CO 2 gas source contains dust particles (CO 2 concentration ⁇ 5%)
  • the medium in the elution tower can be any one of pure water, acidic solution or dry medium.
  • the CO 2 gas source contains any one or more acidic gases among NO m 3 , SO x content ⁇ 30mg/m 3 , H 2 S content ⁇ 15ppm, can enter the CO 2 absorption tower for enrichment.
  • the medium in the elution tower can be either an alkaline solution or a dry medium. kind.
  • the CO 2 gas source contains alkaline gases such as NH 3 and ethanolamine, it can pass through the elution tower to remove impurities, and then enter the CO 2 absorption tower for enrichment. At this time, in the elution tower The medium can be either acidic medium or dry medium.
  • the cathode chamber of the electrochemical reactor contains a cathode catalytic electrode, and the anode chamber contains an anode catalytic electrode, separated by an ion exchange membrane.
  • the cathode catalytic electrode can be composed of a cathode catalyst coated on an ion exchange membrane to form a catalytic membrane electrode, or it can also be composed of a carrier and a cathode catalyst coated on the surface of the carrier.
  • the carrier is titanium mesh, titanium foam, nickel mesh, nickel foam, carbon Paper
  • the cathode catalyst is any one of porous NC, Ni-NC, Zn-NC, Ag-NC, Cu-NC, Co-NC, etc., or it can be nanoscale Ni, Zn, Sn, Any metal element, oxide or any two-component alloy or mixed oxide of Ag, Cu, Co, In.
  • the catalyst can be supported or unsupported, and the carrier is selected from carbon powder, graphene, carbon Nanotubes, carbon black or carbon fibers.
  • the anode catalytic electrode can be composed of an anode catalyst coated on an ion exchange membrane to form a catalytic membrane electrode, or it can also be composed of a support body and an anode catalyst coated on the surface of the support body.
  • the support body is selected from titanium mesh, Titanium plate, nickel mesh, stainless steel mesh.
  • the anode catalyst is any one of supported or unsupported Ir, Pt, Ru, Ti, Co, Sn, Fe, Sb, Pb, Zr, Ni, Ce two-phase or multi-phase oxide solid solution, and the carrier is selected from Toner, graphene, carbon nanotubes, carbon black or carbon fiber.
  • the electrolysis reaction unit is supplied with direct current by the power source to electrolyze CO2 to produce syngas and oxygen.
  • the electrolyte only needs to be introduced before startup.
  • the water consumed during the reaction process can be added through the water replenishment unit.
  • the entire synthesis route consumes only water and CO 2 as raw materials, and does not require the introduction of other substances. The operation is simple and the cost is low.
  • FIG. 1 is a flow chart of the CO 2 electrolysis to synthesis gas process in this embodiment.
  • the specific process operation flow includes three steps: carbon dioxide enrichment, electrolysis and electrolyte circulation.
  • the CO 2 gas source of 1.89Nm 3 /h (from the desulfurization and denitrification flue gas of a gas boiler plant, with a CO 2 volume content of 12%, NO x content ⁇ 30 mg/m 3 , SO x content ⁇ 30 mg/m 3 , and dust ⁇ 5 mg /m 3 ), pressurize it to 0.6MPa through the fan and send it into the absorption tower. Control the temperature of the absorption tower to 60°C.
  • This CO2 - rich electrolyte is sent into the cathode cavity of the electrochemical reactor through the cathode circulation pump.
  • the anode circulation pump also sends the CO2 - poor electrolyte in the liquid mixer into the anode cavity of the electrochemical reactor.
  • the electrolysis current is controlled to 600A, and the electrolysis temperature is the average value of the CO2- rich electrolyte temperature at the reactor inlet and the CO2- poor electrolyte temperature at the outlet.
  • CO 2 and water in the CO 2 -rich electrolyte in the cathode cavity are reduced and converted into synthesis gas on the surface of the cathode catalytic electrode.
  • the gas-liquid mixture enters the cathode gas-liquid separator for separation, and is then cooled to 30°C by the cathode gas phase cooler to obtain synthesis gas.
  • the volume content of H2 and CO reaches 86.7%.
  • the cooled electrolyte returns to the cathode gas-liquid separator.
  • the catholyte returns to the gas-liquid mixer.
  • the water in the CO2- poor electrolyte in the anode cavity is oxidized.
  • Decomposition produces oxygen, and the mixed gas is cooled to 30°C by the anode gas phase cooler to obtain oxygen, of which the O2 volume content reaches 91%.
  • the cooling liquid returns to the anode gas-liquid separator, and the separated anolyte also returns to gas-liquid
  • the mixer mixes the catholyte with the concentration and pH value to obtain a lean CO 2 electrolyte.
  • the water supply pump replenishes the anode gas-liquid separator with a water consumption of 127.4g/h.
  • the concentration of the lean CO 2 electrolyte in the gas-liquid mixer is always constant. , can be recycled in closed circuit.
  • the electrolysis pressure is controlled to 0.5MPa through the gas outlet pressure regulating valves on the cathode gas phase cooler and anode gas phase cooler, and the absorption pressure can be controlled to 0.5MPa through the gas outlet pressure regulating valve of the absorption tower.
  • FIG. 2 is a schematic diagram of the system of this embodiment, including three modules of carbon dioxide enrichment, electrolysis and electrolyte circulation, which respectively correspond to the three steps of carbon dioxide enrichment, electrolysis and electrolyte circulation in the process flow chart.
  • the carbon dioxide enrichment module is used to absorb CO 2 gas source, including a fan, buffer tank, and absorption tower. Its upstream is connected to the CO 2 gas source and the anode circulation pump, and its downstream is connected to the cathode circulation pump and cathode chamber at the same time.
  • the fan pressurizes the CO2 gas source and sends it to the absorption tower.
  • the absorption pressure in the tower can be controlled by its outlet pressure regulating valve, and the heat exchanger in the absorption tower can control the absorption temperature.
  • Electrolysis module is used to generate The electrochemical conversion of CO 2 to synthesis gas includes an electrochemical reactor and control power supply.
  • the reactor is composed of a set of cathode chamber/cation exchange membrane/anode chamber connected in series.
  • the upstream of the cathode chamber is connected with the cathode circulation pump of the electrolyte circulation module in turn.
  • the absorption tower is connected, and the downstream is connected to the cathode gas-liquid separator and cathode gas-phase cold zone of the electrolyte circulation module.
  • the upstream of the anode cavity is connected to the anode circulation pump and liquid mixer of the electrolyte circulation module in turn, and the downstream is connected to the anode circulation pump and liquid mixer of the electrolyte circulation module.
  • the cathode and anode gas-liquid separators and anode gas-phase cold zone of the electrolyte circulation module are connected.
  • the electrolysis current is adjusted through the DC power supply, and the electrolysis temperature is adjusted through the electrolyte temperature at the entrance of the cathode cavity and anode cavity.
  • the electrolyte circulation module is used to supply electrolyte to the electrolysis unit, separate the gas and liquid mixture output from the electrolysis unit, and mix the electrolyte. It includes an electrolyte transport unit, a gas-liquid separation unit, a mixing unit and a water replenishment unit.
  • the electrolyte transport unit includes an anode circulation pump, a relay pump and a cathode circulation pump.
  • the upstream of the anode circulation pump is connected to the liquid mixer, and the downstream is connected to the anode chamber at the same time.
  • the upstream of the relay pump is connected to the gas-liquid mixer to mix lean CO2 from the liquid.
  • the reactor is sent to the absorption tower, and the upstream of the cathode circulation pump is connected to the absorption tower to send the CO2- rich electrolyte into the cathode cavity.
  • the gas-liquid separation unit includes a cathode gas-liquid separator, a cathode gas-phase cooling tower, an anode gas-liquid separator, and an anode gas-phase cooling tower.
  • the upstream of the cathode gas-liquid separator is connected to the cathode cavity, and the downstream is connected to the cathode gas-phase cooler to cool the gas phase to obtain The syngas and coolant return to the cathode gas-liquid separator.
  • the separated catholyte flows into the liquid mixer.
  • the upstream of the anode gas-liquid separator is connected to the anode cavity, and the downstream is connected to the anode gas-phase cooler to cool the gas phase to obtain oxygen.
  • the cold liquid returns to the anode gas-liquid separator for separation.
  • the discharged anolyte flows into the liquid mixer for mixing with the anolyte.
  • the mixing unit is a liquid mixer, the upstream of which is connected to the cathode gas-liquid separator and the anode gas-liquid separator respectively, and the downstream is connected to the anode circulation pump.
  • the electrolysis pressure is controlled by the pressure regulating valve at the gas outlet of the cathode gas phase cooler and the gas outlet of the anode gas phase cooler.
  • the water replenishment unit includes a water replenishment pump and a water tank. The upstream of the water replenishment pump is connected to the water tank, and the downstream is connected to the anode gas-liquid separator to supply water for reaction consumption.
  • Table 1 The operating parameters of each process are shown in Table 1 below:
  • the process flow chart and system schematic diagram of CO 2 electrolysis to syngas in this embodiment are the same as those in Embodiment 1.
  • the specific process operation flow includes: 1.89Nm 3 /h CO 2 gas source (same as the gas source in the embodiment) is pressurized to 0.6MPa through a fan and sent into the absorption tower.
  • the temperature of the absorption tower is controlled to 60°C and the absorption pressure is 0.5MPa.
  • the pressure regulating valve at the gas phase cooler outlet adjusts the pressure of the electrolyte circulation system to 0.1MPa.
  • the anode circulation pump also sends the CO2 - poor electrolyte in the liquid mixer into the anode cavity of the electrochemical reactor.
  • the CO2- rich electrolyte in the absorption tower relies on the pressure difference between the absorption tower and the cathode cavity to provide power from the absorption tower and cathode cavity.
  • the bypass pipeline is transported into the cathode chamber, and there is no need to start the cathode circulation pump. Other process operations are the same as in Example 1.
  • the process flow chart of CO 2 electrolysis to syngas in this embodiment is the same as that of Embodiment 1, and the system schematic diagram is shown in Figure 3 .
  • the specific process operation flow includes: passing 182L/h CO 2 gas source (from low-temperature methanol scrubbing product gas (CO 2 volume content 99.8%, H 2 S concentration 32 ppm, air pressure 0.22 MPa)) into the desulfurization tower, waiting for the gas
  • the H 2 S in the source is desulfurized by the Fe 2 O 3 / calcium magnesium aluminosilicate clay catalyst in the desulfurization tower until the H 2 S concentration drops to less than 10 ppm, and is then passed into the absorption tower for enrichment.
  • the temperature of the absorption tower is controlled to 60°C and passed
  • the pressure regulating valve at the outlet of the absorption tower controls the absorption pressure to 0.1MPa.
  • the unabsorbed part of the CO 2 tail gas is sent from the top of the tower to the absorption tower for circulation and absorption through the fan.
  • an anode circulation pump is used to circulate the lean CO 2 electrolyte (KHCO 3 ) in the mixing tank.
  • the concentration is 1 mol/L) and is sent to the absorption tower for enrichment to obtain a 60°C CO2 - rich electrolyte, which is sent into the cathode cavity through the cathode circulation pump.
  • the anode circulation pump also removes the 60°C CO2 - poor electrolyte in the liquid mixer. Send it into the anode cavity. Control the electrolysis current to 600A for electrolysis. Cool it to 30°C through the cathode gas-phase cooler to obtain synthesis gas, in which the volume content of H 2 and CO reaches 82.7%. The cooled electrolyte returns to the cathode gas-liquid separator, and is After separation, the catholyte returns to the mixing tank. At the same time, it is cooled to 30°C by the anode gas phase cooler to obtain oxygen, of which the O2 volume content reaches 89.3%.
  • the coolant returns to the anode gas-liquid separator, and the separated anolyte is also Return to the mixing tank and mix the catholyte with concentration and pH value to obtain lean CO2 electrolyte.
  • the water supply pump replenishes water to the mixing tank at about 139g/h.
  • the outlet pressure regulating valves on the cathode gas phase cooler and the anode gas phase cooler both control the pressure. is 0.1MPa.
  • the system of this embodiment includes three modules: carbon dioxide enrichment, electrolysis and electrolyte circulation, respectively corresponding to the three steps of carbon dioxide enrichment, electrolysis and electrolyte circulation in the process flow chart.
  • the carbon dioxide enrichment module is used to remove impurities and absorb CO 2 gas sources, including a desulfurization tower, an absorption tower, a front buffer tank, a fan and a rear buffer tank.
  • the upstream of the desulfurization tower is in contact with the CO 2 gas source.
  • the downstream of the absorption tower is connected to the absorption tower.
  • the gas outlet of the absorption tower is connected to the front buffer tank, fan, and rear buffer tank.
  • the rear buffer tank is connected to the inlet of the absorption tower to form a CO 2 tail gas cycle for absorption and energy supply.
  • the downstream of the absorption tower is also connected to the anode circulation pump. And input lean CO 2 electrolyte for absorption.
  • the absorption pressure in the tower can be controlled by its outlet pressure regulating valve, and the heat exchanger in the absorption tower can control the absorption temperature.
  • the electrolyte circulation module is used to supply electrolyte to the electrolysis unit, separate the gas and liquid mixture output from the electrolysis unit, and mix the electrolyte. It includes an electrolyte transport unit, a gas-liquid separation unit, a mixing unit and a water replenishment unit.
  • the electrolyte transport unit includes an anode circulation pump and a cathode circulation pump.
  • the anode circulation pump is also connected to the anode chamber to feed CO2- poor electrolyte.
  • the cathode circulation pump is connected upstream to the absorption tower to transfer rich CO2 2
  • the electrolyte is sent into the cathode cavity.
  • the gas-liquid separation unit includes a cathode gas-liquid separator, a cathode gas-phase cooling tower, an anode gas-liquid separator, and an anode gas-phase cooling tower.
  • the mixing unit includes a mixing tank. The upstream of the cathode gas-liquid separator is connected to the cathode cavity, and the downstream is connected to the cathode gas-phase cooler. The gas phase is cooled to obtain synthesis gas.
  • the cooling liquid returns to the cathode gas-liquid separator and the cathode electrolyte separated by the cathode gas-liquid separator flows into the mixing tank.
  • the upstream of the anode gas-liquid separator is connected to the anode cavity, and the downstream of the anode gas-liquid separator is connected to the anode gas phase for cooling.
  • the device is connected to obtain oxygen, the cold liquid returns to the anode gas-liquid separator, and the separated anolyte flows into the mixing tank for mixing.
  • the pressure of the electrolyte circulation system that is, the cathode side pressure or the anode side pressure, is controlled to 0.1MPa through the air outlets of the cathode and anode gas phase coolers.
  • the water replenishment unit includes a water replenishment pump and a water tank.
  • the upstream of the water replenishment pump is connected to the water tank, and the downstream is connected to the mixing tank to supply water for reaction consumption.
  • the composition and connection method of the electrolysis module are the same as those in the embodiment.
  • the process operating parameters are shown in Table 3 below:
  • the process flow chart and system schematic diagram of CO 2 electrolysis to syngas in this embodiment are shown in Figure 4 and Figure 5 respectively.
  • the difference between the process flow of this embodiment and Embodiment 3 is that a synthesis gas purification step is added downstream of the back end of the electrolyte circulation step, and the synthesis gas obtained after cooling by the cathode gas phase cooler in the electrolyte circulation step is further decarbonized and purified.
  • the syngas product is obtained, and the separated CO 2 is combined with the CO 2 tail gas at the top of the absorption tower in the carbon dioxide enrichment step.
  • the circulating fan in the carbon dioxide enrichment step is pumped into the absorption tower at a flow rate of 65.4L/h for recycling, absorption and reuse. This step recycles the CO2 tail gas discharged from the top of the absorption tower and the CO2 gas separated in the syngas purification and decarbonization step, which can significantly reduce the amount of CO2 gas source intake and improve the utilization rate of CO2 .
  • Embodiment 3 The difference between the system of this embodiment and Embodiment 3 is that a pressure swing adsorption device is added downstream of the cathode gas phase cooler of the electrolyte circulation module to further decarbonize the synthesis gas to obtain a synthesis gas product.
  • the separated CO 2 gas enters the CO 2 recycling unit of the carbon dioxide enrichment module, is pressurized by the circulating fan, and then sent to the absorption tower for circulation and absorption.
  • Table 4 The process operating parameters are shown in Table 4 below:

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Abstract

本公开公开一种CO2电解制合成气工艺和装置。所述工艺包括：二氧化碳富集步骤，用贫CO2电解液从CO2气源中吸收CO2获得富CO2电解液；电解液循环步骤，将所述富CO2电解液输送入电化学反应器的阴极腔，同时将所述贫CO2电解液送入所述电化学反应器的阳极腔，将电解后从所述阴极腔排出的阴极电解液和从所述阳极腔排出的阳极电解液混合并补充水获得浓度恒定的贫CO2电解液；及电解步骤，为所述电化学反应器提供直流电，在所述电化学反应器的阴极腔中所述富CO2电解液中CO2和水被催化还原为合成气，同时在所述电化学反应器的阳极腔中所述贫CO2电解液中水被催化氧化为氧气。本公开的工艺对CO2气源中CO2浓度容忍性较强，能适用高纯气源也可适用低浓度CO2工业气源。 (图1)

Description

烟气CO2电解制合成气工艺及系统 技术领域
本公开属于资源与环保领域，具体涉及CO2电解制合成气工艺及系统。
背景技术
CO2电解制合成气技术可结合绿电将CO2转化为化工重要原料合成气，同时兼具了碳减排的环保属性和能量存储的新能源属性，因此在众多CO2利用途径和应用领域中脱颖而出成为研究的热点。
CO2电解制合成气过程主要依靠具有阴极室和阳极室的两室反应单元来完成。其较为典型的电解工艺为气、液混合电解模式，该工艺将CO2气和电解液同时直接通入阴极室发生电解生产合成气(CO和H2组成)。这一操作流程较为简单，原材料仅消耗CO2和水，因此可放大性强。但仍具严重的问题：缺陷一是对气源品质要求较为苛刻，需要高纯气源。然而工业排放的CO2气源如电厂烟气、燃煤锅炉烟气、水泥窑尾气、化工烟气等均具有CO2浓度低，且含有大量N2、O2、NOx、SOx、粉尘等杂质特点，此类气源如直接使用，一方面对电解过程中安全性造成威胁，同时杂质的存在大幅降低了电催化剂和反应器的使用寿命，使得此工艺在碳排行业的应用受限。为此需要高度依赖碳捕集，将此类气源中CO2进一步提纯再利用，则必然增加了CO2综合利用成本。缺陷二是传统气、液混通电解工艺中催化剂表面被大量电解液覆盖，CO2在其表面传质受限，使得析氢副反应严重，且有大量CO2未参与转化、让后续产品气分离净化操作较为复杂且成本昂贵，使得该技术碳减排效果不显著，同时经济性较差。
发明内容
本公开为了解决上述问题，提供一种能适用不同浓度CO2气源、碳减排效果显著且能有效降低CO2电解制合成气成本的新型电解工艺，以加快该技术的工程化应用进程。
本公开提供一种烟气CO2电解制合成气工艺，包括：二氧化碳富集步骤，用贫CO2电解液从CO2气源中吸收CO2获得富CO2电解液；电解液循环步骤，将所述富CO2电解液输送入电化学反应器的阴极腔，同时将所述贫CO2电解液送入所述电化学反应器的阳极腔，将电解后从所述阴极腔排出的阴极电解液和从所述阳极腔排出的阳极电解液混合并补充水获得浓度恒定的贫CO2电解液；及电解步骤，为所述电化学反应器提供直流电，在所述电化学反应器的阴极腔中所述富CO2电解液中CO2和水被催化还原为合成气，同时在所述电化学反应器的阳极腔中所述贫CO2电解液中水被催化氧化为氧气。
根据本公开的一实施方式，所述二氧化碳富集步骤中吸收压力为10kPa-5MPa，吸收温度为5-90℃；所述电化学反应器电解温度为5-90℃，电解压力为10kPa-5MPa。
根据本公开的另一实施方式，所述贫CO2电解液为碱性电解液，优选碱金属的碳酸氢盐或碳酸盐电解液；所述碱金属为锂、钠、钾、铷、铯中的一种或多种，优选钾和钠，所述电解液中所述金属离子浓度为0.05-6mol/L。
根据本公开的另一实施方式，所述富CO2电解液pH值为6-11。
根据本公开的另一实施方式，所述CO2气源中CO2体积含量≥3％。
根据本公开的另一实施方式，在吸收CO2之前，还包括对所述CO2气源除杂，除去所述CO2气源中的粉末、颗粒以及对所述电化学反应器有害的气体。
根据本公开的另一实施方式，系统可为均压工况，即所述电解压力等于所述二氧化碳富集模块的吸收压力。也可为非均压工况，即所述电解压力不等于二氧化碳富集模块的吸收压力；优选均压工况。
本公开还提供一种CO2电解制合成气系统，包括：二氧化碳富集模块，用于用贫CO2电解液从CO2气源中吸收CO2获得富CO2电解液；电解模块，包括电化学反应器，在所述电化学反应器的阴极腔中所述富CO2电解液中CO2和水被催化还原为合成气，同时在所述电化学反应器的阳极腔中所述贫CO2电解液中水被催化氧化为氧气；和电解液循环模块，用于给所述电解模块供应所述富CO2电解液和所述贫CO2电解液，并对所述电解模块阴极和阳极排出的电解液进行混合并补水获得浓度恒定的贫CO2电解液。
根据本公开的另一实施方式，所述二氧化碳富集模块还包括除杂单元，所述除杂单元用于除去所述CO2气源中的颗粒物以及对所述电化学反应器有害的气体。
本公开提供的一种烟气CO2富集电解制合成气工艺和系统，依靠电解液循环步骤中碱性电解液吸收CO2功能实现CO2在电解液中的富集与电解一体化。此工艺的优势：对CO2气源中CO2浓度容忍性较强，能适用高纯气源也可适用低浓度CO2工业气源，使得该技术对各行业CO2气源具有普适性；与传统气、液混合电解工艺相比，对碳捕集依赖性较弱，依靠电解系统同步实现二氧化碳富集，工艺操作流程简单，有效提高了产物气中合成气浓度，减少产品气分离成本和碳利用成本，提高了CO2利用效率和经济性。
附图说明
图1是实施例1的CO2电解制合成气工艺流程图。
图2是实施例1的CO2电解制合成气系统示意图。
图3是实施例3的CO2电解制合成气系统示意图。
图4是实施例4的CO2电解制合成气工艺流程图。
图5是实施例4的CO2电解制合成气系统示意图。
具体实施方式
下面结合具体实施方式对本公开作详细说明。
本公开提供一种烟气CO2电解制合成气工艺，以工业CO2气源和水为原料，经过二氧 化碳富集步骤、电解液循环步骤和电解步骤获得合成气(CO+H2)和氧气(O2)。更进一步还可包括产品气净化步骤，经前三个步骤获得的合成气和氧气可经此步骤进一步分离提纯，分别获得合成气产品和氧气副产品，经此步骤分离出的CO2可返回二氧化碳富集步骤循环利用。以下将详细描述本公开的工艺。
二氧化碳富集步骤为贫CO2电解液从CO2气源吸收CO2获得富CO2电解液。该步骤可以通过对CO2气源增压，使得贫CO2电解液可以吸收气源中的CO2获得富CO2电解液。下文为了方便描述，所述“电解液”包括“贫CO2电解液”和“富CO2电解液”。
该步骤还可以包括除杂工序，在富集CO2之前，可以对CO2气源进行除杂，除去气源中的颗粒物杂质，以及对后续电化学反应器有害的气体。CO2气源一般来源于化工、热电、水泥、钢铁等行业，可为高纯气源，也可为低浓度气源，会含有H2S、SOx、NOx、NH3、NH2CH2OH、粉尘等中的一种或几种杂质。其中O2或N2杂质会使得气源中CO2分压有所降低从而影响CO2吸收富集，而H2S、SOx、NOx、NH3、NH2CH2OH、粉尘等杂质会影响电化学反应器中催化电极寿命，被称为有害杂质，故需要在CO2富集之前对其进行去除。除去杂质的方法可以任意适用方法，在下文中将详细描述。
电解液循环步骤包括将富CO2电解液输送入电化学反应器的阴极腔，同时将贫CO2电解液送入电化学反应器的阳极腔。被电解后的阴极腔中气、液混合物和阳极腔中气、液混合物，分别经气液分离后获得的阴极电解液和阳极电解液再进行混合，同时向电解液中补充反应消耗的水，以获得浓度恒定的贫CO2电解液再循环利用。经气液分离后分别获得阴极混合气和阳极混合气，经冷却脱水分后分别得到合成气和氧气，阴极混合气和阳极混合气冷却下来的电解液分别汇入阴极电解液和阳极电解液。
电解步骤为给电化学反应器提供直流电，在反应器阴极腔中，富CO2电解液中CO2和水被催化还原转化为合成气，同时在反应器阳极腔中，贫CO2电解液中水被催化氧化为氧气。具体反应原理如下式：富CO2电解液中CO2和H2O在阴极腔中阴极催化电极作用下被还原转化为合成气和OH-，同时贫CO2电解液中H2O在阳极腔阳极催化电极作用下被氧化为O2，阳极腔中M+则由阳离子交换膜迁移到阴极腔。电解过程反应如下：
阳极腔：H2O→0.5O2+2H++2e-
2H++2HCO3 -→2H2CO3
阴极腔：xCO2+xH2O+2xe-→xCO+2xOH-
2(1-x)H2O+2(1-x)e-→(1-x)H2+2(1-x)OH-
电解液中反应：2H2CO3+2OH-→2HCO3 -+2H2O
总反应：xCO2+(1-x)H2O→xCO+(1-x)H2+0.5O2
因此反应后排出的阴极电解液中M+浓度和pH值增加，而经反应后阳极排出的电解液中M+浓度和pH值降低，将进行两股溶液混合，实现pH值和MHCO3浓度混合。因此电解质仅需要在开机启动前引入，转化过程中无电解质消耗，反应过程中消耗的水可通过补水单元添加。整个合成路线消耗原料仅有水和CO2，同时无需引入其他物质，操作简单、 成本低。
本公开通过富集步骤得到包含溶解态CO2的富CO2电解液可直接与催化剂接触，有效降低了传质限制，相比于传统气、液混通模式，提高了反应效率。
产品气净化步骤可对合成气进行净化提纯，获得合成气产品并分离出未反应的CO2，CO2可返回二氧化碳富集步骤循环利用。产品气净化步骤也可对氧气进行净化提纯，获得氧气副产品并分离出残留的CO2，CO2可返回二氧化碳富集步骤循环利用。
在可选的实施方式中，CO2气源中CO2体积含量≥3％，可为高纯气源，也可为低分压CO2烟气和化工产品气。
在可选的实施方式中，二氧化碳富集步骤中吸收压力(表压)为10kPa-5MPa，吸收温度为5-90℃，吸收塔出口富CO2电解液pH值为6-11。电化学反应器电解温度为5-90℃，电解压力(表压)为10kPa-5MPa。在可选的实施方式中，吸收压力可等于电解压力，电解压力通过电解液循环步骤系统控制，此时整个工艺系统为均压工况条件，压力控制复杂性可降低；当吸收压力大于电解压力时，此时富集模块与电解模块存在压差，即非等压工况条件，缺点是会增加整个工艺管道和系统压力控制复杂性，同时易造成CO2气体从液相逃逸影响电解效率，优势是压差可作为富集模块电解液向电解模块输送的动力；当吸收压力小于电解压力也可以实现本公开的发明目的，此时同样存在压差使得系统装置工艺管道和系统压力控制复杂化。因此，从电解效率和工艺装置简单化上考虑，优选吸收压力等于电解压力。
电解液为碱性电解液，优选碱金属的碳酸氢盐(MHCO3)或碳酸盐(M2CO3)电解液。碱金属(M)可为锂、钠、钾、铷、铯，优选钾和钠，金属离子浓度为0.05-6mol/L。
本公开还提供一种CO2富集电解制合成气系统，包括二氧化碳富集模块、电解液循环模块、电解模块。更进一步还可以包括产品气净化模块。
二氧化碳富集模块用于对CO2气源进行吸收富集。可以包括原料气供应单元、CO2吸收单元。当CO2气源中含有害杂质时，还可包括除杂单元。当需要对CO2尾气进行循环利用时，还包括CO2循环单元。当CO2气源压力不高于吸收单元和除杂单元压力时，原料气供应单元包括缓冲罐、增压机，增压机上游依次与缓冲罐、CO2气源相连，下游与CO2吸收单元或除杂单元相连，当CO2气源压力高于吸收单元和除杂单元压力时，原料气供应单元可仅含缓冲罐；吸收单元包括吸收塔，当CO2气源无有害杂质时，其上游可直接与原料气供应单元相连，当CO2气源中含有害杂质时，其上游与除杂单元相连，其下游与电解液循环模块相连，也可同时与CO2循环单元相连；除杂单元包括洗脱塔，可为一个，也可是多个串联或并联构成，其上游与原料气供应单元相连，下游与吸收塔相连；CO2循环单元包括前缓冲罐、增压设备、后缓冲罐，前缓冲罐其上游与产品气净化模块，也可同时与吸收塔顶相连，前缓冲罐、增压机、后缓冲罐依次相连，后缓冲罐下游与吸收模块连接。增压设备可为风机或压缩机中的任一种。CO2尾气为吸收塔顶尾气和/或产品气净化模块CO2尾气。
电解模块用于发生CO2的电化学转化制合成气。可以包括至少一个电化学反应单元和 控制电源。电化学单元包括至少一台电化学反应器，每台电化学反应器至少包含1槽，每槽由1个阴极腔/隔膜/阳极腔组成，当包含多槽时，各槽可以串联和/或并联组成一台反应器，系统可以包含一台或多台反应器。隔膜为阳离子交换膜或阴离子交换膜。阴极腔上游与吸收塔相连，下游与电解液循环单元相连，阳极腔的上、下游均与电解液循环单元相连。控制电源用于为电化学反应单元提供应直流电。
电解液循环模块用于给电解单元供应电解液，并对电解产物进行分离和电解液混合。可以包括电解液输送单元、气液分离单元、混合单元和补水单元。电解液输送单元包括阳极循环泵、接力泵和/或阴极循环泵，阳极循环泵上游与混合单元相连，下游可与阳极腔相连，还可直接与吸收塔相连直接充当接力泵的供能，接力泵上下游分别与混合单元和吸收塔相连，阴极循环泵上下游分别与吸收塔和阴极腔相连。气液分离单元包括阴极气液分离器、阴极气相冷却塔、阳极气液分离器、阳极气相冷却塔，阴极气相冷缺器上游依次与阴极气液分离器和电解单元阴极腔相连，对气相进行冷缺，冷缺液返回阴极气液分离器，下游还可与产品气净化模块相连进一步提纯获得合成气产品，阳极气相冷缺器上游依次与阳极气液分离器和电解单元阳极腔相连获得氧气，对气相进行冷却，其冷却液返回阳极气液分离器，下游还可与产品气净化单元相连进一步提纯获得氧气副产品。混合单元为混合罐或液体混合器，其上游分别与阴极气液分离器和阳极气液分离器相连，下游分别与阳极循环泵和接力泵相连。补水单元包括补水泵和水箱，补水泵上游与水箱相连，下游与阴极气液分离罐、阳极气液分离罐或混合单元中的任一种或多种相连。
产品气净化模块用于对合成气和/氧气净化提纯并分离出未反转化CO2。可以包括合成气净化单元和/或氧气净化单元。净化单元均可为膜法分离装置、变压吸附装置、变温吸附装置、化学吸收装置等中的任一种。合成气净化单元其上游与阴极气相冷区器相连产出合成气产品，输出CO2尾气与CO2循环单元前缓冲罐相连。氧气净化单元其上游与阳极气相冷区器相连产出氧气副产品，输出CO2尾气与CO2循环单元前缓冲罐相连。
系统的吸收塔吸收压力(表压)介于10kPa-5MPa，电解模块压力(表压)介于10kPa-5MPa，两者可相等或不等。电解压力分阴极侧压力和阳极侧压力，阴极侧压力通过阴极气液分离器或阴极气相冷却器出气口调压阀控制，阳极侧压力通过阳极气液分离器和阳极气相冷却器出气口调压阀控制，两者压差低于50kPa。
在可选的实施方式中，当吸收塔压力高于电解单元压力时，吸收塔中富CO2电解液可依靠两者压差从吸收塔与阴极腔之间管线送入阴极腔，此时阴极循环泵可省略或不工作。当吸收塔压力等于电解液循环模块操作压力时时，吸收塔中富CO2电解液需要阴极循环泵输送入电解单元阴极腔。
在可选的实施方式中，阳极循环泵下游同时于阳极腔和吸收塔相连将混合单元贫CO2电解液输送入电解单元阳极腔和吸收塔，此时可省去接力泵，当阳极循环泵下游仅与阳极腔连将混合单元贫CO2电解液输送如电解单元阳极腔，则此时需要接力泵上下游分别与混合单元和吸收塔相连，将贫CO2电解液送入吸收塔。
产品气净化装置出气合成气产品或氧气产品纯度主要取决于合成气或氧气产品在下游的应用要求。在可选的实施方式中，净化装置将合成气中CO2净化至体积含量占比3％-6％可用于低压合成甲醇原料气，分离出CO2气返回吸收塔循环利用。在可选的实施方式中，净化装置将合成气中CO2净化至≤15％可用于费托合成油蜡需要。在可选的实施方式中，将氧气中CO2净化至≤0.8％可用于工业生产或加工气。
CO2气源一般来源于化工、热电、水泥、钢铁等行业，可为高纯气源，也可为低浓度气源，会含有H2S、SOx、NOx、NH3、NH2CH2OH、粉尘等中的一种或几种杂质。其中O2或N2杂质会使得气源中CO2分压有所降低从而影响CO2吸收富集，但对电解反应无有害影响，而H2S、SOx、NOx、NH3、NH2CH2OH、粉尘等杂质在含量较高时会影响电解模块性能，被称为有害杂质，故需要在CO2吸收塔前段洗脱塔去除至较低浓度。洗脱塔可为一个或多个串联或并联构成，洗脱塔中可以是单通式也可是多次反复洗脱从而实现有害杂质的去除。塔内吸附介质可为液态，包括纯水、酸性溶液、碱性溶液任一种。也可是干态过滤介质，如滤布、滤网等，也可是干态吸附剂或催化氧化剂，包括活性炭、沸石、生石灰、氧化铝、硅铝酸盐、氧化锌、氧化镍、氧化铁、氧化硅、氢氧化铜、硫酸铜中的任一种或多种。酸性溶液包括HCl、H2SO4、HNO3中的任一种或多种。碱性溶液包括KOH、NaOH、K2CO3、Na2CO3、KHCO3、NaHCO3、Na2SO3、Ca(OH)2、CuSO4、Pb(NO3)2、甲醇、一乙醇胺二乙醇胺、三乙醇胺、二异丙醇胺、甲基二乙醇胺中的任一种或多种组成的水溶液。
在可选的实施方式中，CO2气源为高浓气源(CO2浓度≥98％)或含有O2、N2杂质(CO2浓度≥5％)，则此气源可直接进入CO2吸收塔富集，无需经历洗脱塔去除杂质。本可选的实施方式中，CO2气源中如含有粉尘颗粒物(CO2浓度≥5％)，则需经历洗脱塔脱尘至粉尘含量≤5mg/m3，再进入CO2吸收塔富集，此时洗脱塔内介质可为纯水、酸性溶液或干态介质中的任一种。在可选的实施方式中，CO2气源中如含NOx、SOx、H2S中的任一种或多种酸性气体，则需经洗脱塔脱杂至NOx含量≤30mg/m3、SOx含量≤30mg/m3、H2S含量≤15ppm，即可进入CO2吸收塔富集，此时洗脱塔内介质可为碱性性溶液或干态介质中的任一种。在可选的实施方式中，CO2气源中如含NH3、乙醇胺等碱性气体，则可经历洗脱塔脱去杂质，即可进入CO2吸收塔富集，此时洗脱塔内介质可为酸性介质或干态介质中的任一种。
电化学反应器的阴极腔中含有阴极催化电极，阳极室中含有阳极催化电极，中间由离子交换膜分隔。阴极催化电极可由阴极催化剂涂覆在离子交换膜上形成催化膜电极，也可由担载体和涂覆在担载体表面的阴极催化剂组成，担载体为钛网、泡沫钛、镍网、泡沫镍、碳纸中的任一种，阴极催化剂为多孔N-C、Ni-N-C、Zn-N-C、Ag-N-C、Cu-N-C、Co-N-C等中的任一种，也可为纳米级Ni、Zn、Sn、Ag、Cu、Co、In的金属单质、氧化物或任意两组分的合金或混合氧化物中的任一种，催化剂可为负载型或非负载型，载体选自碳粉、石墨烯、碳纳米管、碳黑或碳纤维。阳极催化电极可由阳极催化剂涂覆在离子交换膜上形成催化膜电极，也可由担载体和涂覆在担载体表面的阳极催化剂组成，担载体选自钛网、 钛板、镍网、不锈钢网。阳极催化剂为负载型或非负载型的Ir、Pt、Ru、Ti、Co、Sn、Fe、Sb、Pb、Zr、Ni、Ce两相或多相氧化物固溶体中的任一种，载体选自碳粉、石墨烯、碳纳米管、碳黑或碳纤维。
电解反应单元由电源提供直流电进行电解CO2生产合成气和氧气。如前所述，转化过程中无电解质消耗，电解质仅需要在开机启动前引入，反应过程中消耗的水可通过补水单元添加。整个合成路线消耗原料仅有水和CO2，同时无需引入其他物质，操作简单、成本低。
以下通过具体实例进一步描述本公开。不过这些实例仅仅是范例性的，并不对本公开的保护范围构成任何限制。
在下述实施例和对比例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得。
如无特殊说明，以下实施例中的具体压力值均指表压。
实施例1
图1为本实施例的CO2电解制合成气工艺流程图。该具体工艺操作流程包括二氧化碳富集、电解和电解液循环三个步骤。将1.89Nm3/h的CO2气源(来自某燃气锅炉厂脱硫脱硝烟气，CO2体积含量12％、NOx含量≤30mg/m3、SOx含量≤30mg/m3、粉尘≤5mg/m3)，通过风机增压到0.6MPa送入吸收塔中，控制吸收塔温度60℃、同时用接力泵将液体混合器中贫CO2电解液(KHCO3浓度为1mol/L)输送入吸收塔进行富集获得富CO2电解液，pH＝8.3。此富CO2电解液通过阴极循环泵送入电化学反应器阴极腔，同时阳极循环泵也将液体混合器中贫CO2电解液送入电化学反应器阳极腔。控制电解电流为600A，电解温度取反应器入口富CO2电解液温度和出口贫CO2电解液温度平均值。阴极腔中富CO2电解液中CO2和水在阴极催化电极表面被还原转化为合成气，气液混合物进入阴极气液分离器分离，后再经阴极气相冷却器冷却至30℃获得合成气，其中H2和CO体积含量达86.7％，冷却下的电解液返回阴极气液分离器，经分离后阴极电解液返回气液混合器，与此同时阳极腔中贫CO2电解液中水被氧化分解产生氧气，其产出混合气经阳极气相冷却器冷却至30℃后获得氧气，其中O2体积含量达91％，冷却液返回阳极气液分离器，分离出的阳极电解液也返回气液混合器与阴极电解液进行浓度和pH值混合获得贫CO2电解液，同时由补水泵向阳极气液分离器补水消耗水量127.4g/h，气液混合器中贫CO2电解液始终浓度恒定，可闭路循环利用。电解压力通过阴极气相冷却器和阳极气相冷却器上出气调压阀控制为0.5MPa，吸收压力通过吸收塔出气口调压阀可控制为0.5MPa。
图2为本实施例系统示意图，包括二氧化碳富集、电解和电解液循环三个模块，分别对应工艺流程图中二氧化碳富集、电解和电解液循环三个步骤。二氧化碳富集模块用于对CO2气源进行吸收，包括由风机、缓冲罐、吸收塔，其上游分别可CO2气源和阳极循环泵相连，下游与阴极循环泵和阴极腔同时相连，由风机对CO2气源增压送入吸收塔，塔内吸收压力由其出气口调压阀可控制，吸收塔内换热器可控制吸收温度。电解模块用于发生 CO2的电化学转化制合成气，包括一台电化学反应器和控制电源，反应器由1组阴极腔/阳离子交换膜/阳极腔串联组成，阴极腔上游依次与电解液循环模块的阴极循环泵、吸收塔相连，下游与电解液循环模块的阴极气液分离器、阴极气相冷区器相连，所述阳极腔的上游依次与电解液循环模块的阳极循环泵、液体混合器相连，下游依次与电解液循环模块的阴阳极气液分离器、阳极气相冷区器相连，通过直流电源调节电解电流，电解温度通过阴极腔和阳极腔入口电解液温度调节。电解液循环模块用于给电解单元供应电解液，并对电解单元输出的气、液混合物进行分离和电解液混合，包括电解液输送单元、气液分离单元、混合单元和补水单元。电解液输送单元包括阳极循环泵、接力泵及阴极循环泵，阳极循环泵上游与液体混合器相连，下游分别同时与阳极腔相连，接力泵上游与气液混合器相连将贫CO2从液体混合器送入吸收塔，阴极循环泵上游与吸收塔相连，将富CO2电解液送入阴极腔。气液分离单元包括阴极气液分离器、阴极气相冷却塔、阳极气液分离器、阳极气相冷却塔，阴极气液分离器上游与阴极腔相连，下游与阴极气相冷却器相连对气相进行冷却获得合成气，冷却液返回阴极气液分离器。分离出的阴极电解液汇入液体混合器，同时阳极气液分离器上游与阳极腔相连，下游与阳极气相冷却器相连对气相进行冷区获得氧气，冷缺液返回阳极气液分离器，分离出的阳极电解液汇入液体混合器与阳极电解液进行混合。混合单元为液体混合器，其上游分别与阴极气液分离器和阳极气液分离器相连，下游与阳极循环泵相连。电解压力由阴极气相冷区器出气口和阳极气相冷却器气体出口的调压阀控制。补水单元包括补水泵和水箱，补水泵上游与水箱相连，下游与阳极气液分离器相连，供给反应消耗水。各个工艺运行参数如下表1所示：
表1
实施例2
本实施例的CO2电解制合成气工艺流程图和系统示意图同实施例1。具体工艺操作流程包括：将1.89Nm3/h的CO2气源(同实施例气源)，通过风机增压到0.6MPa送入吸收塔中，控制吸收塔温度60℃、吸收压力0.5MPa，同时用阳极循环泵将液体混合器中贫CO2电解液(KHCO3浓度为1mol/L)送入吸收塔进行富集获得富CO2电解液，pH＝8.3。通过阴、阳极 气相冷却器出气口调压阀将电解液循环系统压力调节为0.1MPa。阳极循环泵也将液体混合器中贫CO2电解液送入电化学反应器阳极腔，同时吸收塔中富CO2电解液则依托吸收塔与阴极腔之间压差提供动力从吸收塔与阴极腔之间旁路管线输送入阴极腔，不需要启动阴极循环泵。其他工艺操作与实施例1相同，获得的合成气中H2和CO体积含量达83.3％，获得的氧气中O2体积含量达83.3％。通过补水泵给阳极气液分离器补水148L/h。工艺运行参数如下表2所示：
表2
实施例3
本实施例的CO2电解制合成气工艺流程图同实施例1，系统示意图如图3。具体工艺操作流程包括：将182L/h的CO2气源(来自低温甲醇洗产品气(CO2体积含量99.8％、H2S浓度为32ppm、气压0.22MPa)，通入脱硫塔中，待气源中H2S被脱硫塔中Fe2O3/钙镁硅铝酸盐黏土催化剂脱硫至H2S浓度降至10ppm一下后，通入吸收塔进行富集，控制吸收塔温度60℃、通过吸收塔出气口调压阀控制吸收压力为0.1MPa，未吸收的部分CO2尾气从塔顶经风机送入吸收塔循环吸收。同时用阳极循环泵将混合罐中贫CO2电解液(KHCO3浓度为1mol/L)送入吸收塔进行富集获得60℃富CO2电解液，并通过阴极循环泵送入阴极腔，同时阳极循环泵也将液体混合器中60℃的贫CO2电解液送入阳极腔。控制电解电流为600A进行电解。经阴极气相冷却器冷却至30℃获得合成气，其中H2和CO体积含量达82.7％，冷却下的电解液返回阴极气液分离器，经分离后阴极电解液返回混合罐，与此同时经阳极气相冷却器冷却至30℃后获得氧气，其中O2体积含量达89.3％，冷却液返回阳极气液分离器，分离出的阳极电解液也返回混合罐与阴极电解液进行浓度和pH值混合获得贫CO2电解液，同时由补水泵向混合罐补水约139g/h。阴极气相冷却器和阳极气相冷却器上出气调压阀均控制压力为0.1MPa。
本实施例系统包括二氧化碳富集、电解和电解液循环三个模块分别对应工艺流程图中二氧化碳富集、电解和电解液循环三个步骤。二氧化碳富集模块用于对CO2气源进行除杂和吸收，包括由脱硫塔、吸收塔、前缓冲罐、风机和后缓冲罐，脱硫塔上游与CO2气源相 连，下游与吸收塔相连，吸收塔气体出口与前缓冲罐、风机、后缓冲罐相连，后缓冲罐与吸收塔入口相连形成CO2尾气循环吸收供能，吸收塔下游还与阳极循环泵相连并输入贫CO2电解液进行吸收，塔内吸收压力由其出气口调压阀可控制，吸收塔内换热器可控制吸收温度。电解液循环模块用于给电解单元供应电解液，并对电解单元输出的气、液混合物进行分离和电解液混合，包括电解液输送单元、气液分离单元、混合单元和补水单元。电解液输送单元包括阳极循环泵和阴极循环泵，阳极循环泵除下游与吸收塔相连外，还同时与阳极腔相连送入贫CO2电解液，阴极循环泵上游与吸收塔相连，将富CO2电解液送入阴极腔。气液分离单元包括阴极气液分离器、阴极气相冷却塔、阳极气液分离器、阳极气相冷却塔，混合单元包括混合罐，阴极气液分离器上游与阴极腔相连，下游与阴极气相冷却器对气相进行冷却获得合成气，冷却液返回阴极气液分离器经阴极气液分离器分离出的阴极电解液汇入混合罐，同时阳极气液分离器上游与阳极腔相连，下游与阳极气相冷却器相连获得氧气，冷缺液返回阳极气液分离器，分离出的阳极电解液汇入混合罐进行混合。电解液循环系统压力即阴极侧压力或阳极侧压力，均通过阴、阳气相冷却器出气口控制压力为0.1MPa。补水单元包括补水泵和水箱，补水泵上游与水箱相连，下游与混合罐相连，供给反应消耗水。电解模块组成和连接方式与实施例相同。工艺运行参数如下表3所示：
表3
实施例4
本实施例的CO2电解制合成气工艺流程图和系统示意图分别如图4和图5。本实施例工艺流程与实施例3的区别是，在电解液循环步骤后端下游增加了合成气净化步骤，和将电解液循环步骤中阴极气相冷却器冷却后得到的合成气进一步脱碳净化，获得合成气产品，同时分离出的CO2与二氧化碳富集步骤中吸收塔顶CO2尾气合并由二氧化碳富集步骤中循环风机以流量65.4L/h抽入吸收塔循环吸收再利用。此步骤将吸收塔顶排出的CO2尾气和合成气净化脱碳步骤分离的CO2气循环利用，可大幅降低CO2气源进气量，提高了CO2的利用率。
本实施例系统与实施例3的区别是在电解液循环模块阴极气相冷却器下游增加了变压吸附装置，对合成气进一步脱碳获得合成气产品。分离出的CO2气进入二氧化碳富集模块CO2循环单元，经循环风机增压后送入吸收塔循环吸收。工艺运行参数如下表4所示：
表4
以上公开的本公开优选实施例只是用于帮助阐述本公开。优选实施例并没有详尽叙述所有的细节，也不限制该发明仅为所述的具体实施方式。显然，根据本说明书的内容，可作很多的修改和变化。本说明书选取并具体描述这些实施例，是为了更好地解释本公开的原理和实际应用，从而使所属技术领域技术人员能很好地理解和利用本公开。本公开仅受权利要求书及其全部范围和等效物的限制。

Claims (10)

  1. 一种CO2电解制合成气工艺，其特征在于，包括：
    二氧化碳富集步骤，用贫CO2电解液从CO2气源中吸收CO2获得富CO2电解液；
    电解液循环步骤，将所述富CO2电解液输送入电化学反应器的阴极腔，同时将所述贫CO2电解液送入所述电化学反应器的阳极腔，将电解后从所述阴极腔排出的阴极电解液和从所述阳极腔排出的阳极电解液混合并补充水获得浓度恒定的贫CO2电解液；及
    电解步骤，为所述电化学反应器提供直流电，在所述电化学反应器的阴极腔中所述富CO2电解液中CO2和水被催化还原为合成气，同时在所述电化学反应器的阳极腔中所述贫CO2电解液中水被催化氧化为氧气。
  2. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，所述二氧化碳富集步骤中吸收压力为10kPa-5MPa，吸收温度为5-90℃；所述电化学反应器电解温度为5-90℃，电解压力为10kPa-5MPa。
  3. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，所述贫CO2电解液为碱性电解液，优选碱金属碳酸氢盐或碳酸盐电解液；所述碱金属为锂、钠、钾、铷、铯中的一种或多种，优选钾和钠，所述电解液中所述金属离子浓度为0.05-6mol/L。
  4. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，所述富CO2电解液pH值为6-11。
  5. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，所述CO2气源中CO2体积含量≥3％。
  6. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，在吸收CO2之前，还包括对所述CO2气源除杂，除去所述CO2气源中的颗粒物以及对所述电化学反应器有害的气体。
  7. 根据权利要求1所述的CO2电解制合成气工艺，其特征在于，所述富集模块压力等于或不等于电解压力，优选两者相等。
  8. 一种CO2电解制合成气系统，其特征在于，包括：
    二氧化碳富集模块，用于用贫CO2电解液从CO2气源中吸收CO2获得富CO2电解液；
    电解模块，包括电化学反应器，在所述电化学反应器的阴极腔中所述富CO2电解液中CO2和水被催化还原为合成气，同时在所述电化学反应器的阳极腔中所述贫CO2电解液中水被催化氧化为氧气；和
    电解液循环模块，用于给所述电解模块供应所述富CO2电解液和所述贫CO2电解液，并对所述电解模块阴极和阳极排出的电解液进行混合并补水获得浓度恒定的贫CO2电解液。
  9. 根据权利要求8所述的CO2电解制合成气系统，其特征在于，系统可为均压工况，即所述电解压力等于所述二氧化碳富集模块的吸收压力；也可为非均压工况，即所述电解压力不等于二氧化碳富集模块的吸收压力；优选均压工况。
  10. 根据权利要求8所述的CO2电解制合成气系统，其特征在于，所述二氧化碳富集模块还包括除杂单元，所述除杂单元用于除去所述CO2气源中的颗粒物以及对所述电化学反应器有害的气体。
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CN115970448A (zh) * 2023-02-09 2023-04-18 中海石油气电集团有限责任公司 一种烟气co2捕集电解一体化负碳方法和系统

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