Industrial CO2 electroreduction system and method

Abstract

The invention relates to the technical field of mutual conversion of electric energy and chemical energy, in particular to an electroreduction system and method for industrial CO2, industrial treatment of CO2 in an electrochemical mode is achieved through reasonable system design, a selected membrane electrode reactor is easy to carry out area amplification and stacking, and the system is simple in structure and convenient to operate. And then the electrolytic galvanic pile is flushed and purged regularly in an electrolytic reaction gap, so that the problem of poor cycling stability caused by salting-out and electrowetting is solved, and the service life is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical-chemical energy mutual conversion, and in particular to an industrialized CO2 electrical reduction system and method. Background Art

[0002] As energy conservation and carbon reduction gradually deepen, the proportion of renewable energy continues to increase. Renewable energy is intermittent and volatile, and it is difficult to match it with the demand side. Therefore, the phenomenon of wind and solar power abandonment is relatively common in some places. In the context of the dual carbon goals, the use of renewable electricity for CO2 electrolysis can reduce carbon emissions while converting electricity into high-value-added chemicals for storage. It is an important way to convert and utilize renewable energy, such as patent document CN117355638A.

[0003] The membrane electrode electrolyzer can construct a gas-liquid-solid three-phase interface and improve the reaction efficiency of electrolysis. In order to improve the reaction efficiency, reduce the cost of electrolysis, and make CO2 electrolysis closer to the scale of commercial application, it is necessary to scale up the membrane electrode reactor system. However, there are many problems at the device and system level after the scale-up, such as poor stability, severe salt precipitation, and poor consistency of the stack. Summary of the invention

[0004] In order to solve the problems of poor stability, severe salting out and poor consistency of the stack caused by the scale-up of the membrane electrode reactor system mentioned in the background technology, the present invention provides an industrial CO2 electroreduction system and method, which uses a membrane electrode reactor to scale up the electrolysis reaction to an annual ton level, and then regularly flushes and purges the electrolysis stack in the intervals between the electrolysis reactions, thereby solving the problem of poor cycle stability caused by salting out and electrowetting.

[0005] The technical solution provided by the present invention is an electric reduction system for processing tons of CO2 annually, comprising: The stack structure is provided with four connected inlets and outlets, namely the cathode inlet, cathode outlet, anode inlet and outlet; a CO2 supply system connected to the cathode inlet; an anode liquid storage system connected to the anode inlet and anode outlet respectively; a gas-liquid separation system connected to the cathode outlet; and a cleaning system connected to the cathode inlet and cathode outlet respectively.

[0006] The present invention provides an electro-reduction system capable of treating tons of CO2 per year. By using a low-concentration electrolyte to regularly clean the cathode electrode and purging with an inert gas, the problem of poor long-cycle stability caused by salting out and electrowetting in the field of electro-reduction of CO2 is solved, and the system can be operated stably for a long time. At the same time, the single chip area is not less than 250cm 2The advantage of rectangular plates is that the active area of ​​a single electrolyzer is larger, and the output of a single cell will be greater. Therefore, fewer levels of cell stacking can be achieved, reducing the cost of materials and power consumption, and better realizing the assembly and water and heat management of the battery stack.

[0007] Preferably, the battery stack structure is externally connected to a renewable energy power generation device.

[0008] Preferably, the renewable energy device is one or more of a photovoltaic power generation device, a wind power generation device, and a hydropower generation device.

[0009] Preferably, the cathode inlet is provided with a flow control device.

[0010] Preferably, the anode inlet is provided with a flow control device.

[0011] Preferably, a heating rod is arranged inside the battery stack structure.

[0012] Preferably, a pressure control device and a temperature detection device are provided at the cathode outlet and the anode outlet.

[0013] Furthermore, the stack structure is provided with an end plate current collector, a gas diffusion electrode and an ion exchange membrane.

[0014] Furthermore, the stack structure is not less than 4; each stack structure contains not less than 3 gas diffusion electrodes; the area of ​​a single gas diffusion electrode is ≥ 250 cm 2 ; The gas diffusion electrodes of a single fuel cell structure are connected in series.

[0015] Preferably, the plate flow channels formed between the gas diffusion electrodes are of parallel, single serpentine, multi-serpentine, and grid types.

[0016] Furthermore, a temperature and humidity control system is provided between the CO2 supply system and the cathode inlet.

[0017] Preferably, the source of CO2 is one of waste CO2 after power generation in power plants, waste containing high concentration of CO2 and high purity CO2 gas.

[0018] Furthermore, an electro-reduction method for treating tons of CO2 per year is characterized by: a) continuously introducing CO2 gas into the cathode side of the electrolytic stack and continuously introducing electrolyte solution into the anode side to react in the electrolytic stack; b) The product at the anode outlet re-enters the anode liquid tank for circulation; c) The product at the cathode outlet enters the gas-liquid separation system for gas-liquid separation; d) During the reaction interval of step a), the power is turned off, and a flushing liquid is introduced from the cathode inlet for flushing. After the flushing is completed, an inert gas is introduced from the cathode inlet for purging. After the purging is completed, the electrolysis reaction is continued.

[0019] Preferably, the inert gas is nitrogen.

[0020] Specifically, the reactions occurring in the battery stack are as follows: cathode: CO2+2H + +2e - →HCOOH+H2O CO2+2H + +2e - →CO+H2O 2CO2+8H + +8e - →CH3COOH+H2O 2CO2+12H + +12e - →C2H5OH+3H2O 2CO2+12H + +12e - →C2H4+4H2O anode: 2H2O→O2+4H + +4e - Overall reaction formula: xCO2+nH + +ne - →product+yH2O Preferably, when the product is CO, the cathode catalyst is one or more of Ag, Au, Zn or their alloys and oxides; when the product is HCOOH, the cathode catalyst is one or more of Pb, In or their alloys and oxides; when the product is C 2+ The cathode catalyst is one or more of Cu2O / Cu and CuAg alloy.

[0021] Preferably, the anode catalyst is one or more of IrO2 and Ru / C.

[0022] Furthermore, in step a), the temperature of the CO2 gas introduced is 50-60°C, the humidity is 60-70%, and the flow rate is 500-600 sccm.

[0023] Preferably, the temperature of the CO2 gas introduced in step a) is 55°C, the humidity is 65%, and the flow rate is 500sccm.

[0024] Furthermore, in step a), the electrolyte contains K+ 、Na + , Li + , Cs + One or more soluble metal salt solutions; the concentration of the electrolyte is 10mM to 100mM; the flow rate of the electrolyte is 500-1000ml / min.

[0025] Furthermore, in step d), the flushing liquid is ethanol: water = 90-110 vol%.

[0026] Furthermore, the flow rate of the flushing liquid is 20 to 40 ml / min; and the flushing time is 3 to 5 min.

[0027] Furthermore, the flow rate of the inert gas is 1500-1800 ml / min; and the purge time is 3-5 min.

[0028] Furthermore, 250cm 2 The size of the rectangular plate is 18.6cm×13.5cm.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention realizes the electrochemical treatment of tons of CO2 per year through reasonable system design, and the selected membrane electrode reactor is easy to scale up and stack.

[0031] (2) The present invention uses a single piece with an area of ​​not less than 250cm 2 The rectangular electrode plate has the advantage that the active area of ​​a single electrolytic cell is larger and the output of a single chamber is also greater. Therefore, fewer chamber stacking levels can be achieved, reducing the cost of materials and power consumption, and better realizing the assembly and hydrothermal management of the battery stack.

[0032] (3) The present invention solves the problem of poor long-cycle stability caused by salting out and electrowetting in the field of CO2 electroreduction by using reasonable process designs such as low-concentration electrolyte, regular cleaning of cathode electrodes, and inert gas purging, thereby achieving long-term stable operation of the system.

[0033] (4) The present invention utilizes an electrochemical device driven by renewable energy to convert CO2 into reduction products without causing additional carbon emission burden on the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a process flow chart of the present invention.

[0035] Figure 2 It is a schematic diagram of the battery stack structure.

[0036] The figures are marked as follows: 1. stack structure; 11. reactor stack; 12. cathode inlet; 13. cathode outlet; 14. anode inlet; 15. anode outlet; 16. plate temperature control device; 111. ion exchange membrane; 112. gas diffusion electrode; 113. flow channel plate; 114. end plate collector; 2. CO2 supply system; 3. anode liquid storage system; 31. anode liquid tank; 32. anode liquid pump; 33. anode liquid tank heater; 35. anode outlet heat exchanger; 36. electrolyte supply Source; 37. O2 exhaust system; 4. Gas-liquid separation system; 41. Gas-liquid separation pump; 42. Gas-liquid separation tank A; 43. Heat exchange condenser; 44. Gas-liquid separation tank B; 45. Compressor; 46. Pressure storage tank; 5. Cleaning system; 51. Inert gas supply source; 52; Cleaning medium supply source; 53. Cleaning liquid storage tank; 54. Cleaning liquid pump; 6. Temperature and humidity control system; 61. Deionized water supply source; 62. Deionized water tank; 63. Deionized water pump; 64. Temperature and humidity controller. DETAILED DESCRIPTION

[0037] The invention is further described below in conjunction with specific embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, the present invention can also be modified in several ways without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0038] Overall embodiment

[0039] like Figure 1As shown, an electric reduction system for processing tons of CO2 per year includes a stack structure 1, a CO2 supply system 2, an anode liquid storage system 3, a gas-liquid separation system 4, a cleaning system 5, and a temperature and humidity control system 6. The stack structure 1 contains a reactor 11, and there are four exchange interfaces on the reactor 11, namely, a cathode inlet 12, a cathode outlet 13, an anode inlet 14, and an anode outlet 15. After the CO2 supply system 2 is connected to the temperature and humidity controller 64, it is connected to the cathode inlet 12, the electrolyte supply source 36 is connected to the anode liquid tank 31, the bottom of the anode liquid tank 31 is connected to the anode inlet 14 through the anode liquid pump 32, and the anode outlet 15 is reconnected to the anode liquid tank 31 through the anode outlet heat exchanger 35. An O2 exhaust system is installed above the anode liquid tank 31, and the anode liquid tank 31 is equipped with an anode liquid tank heater 33. The cathode outlet 13 is connected to the gas-liquid separation tank A42, and then the heat exchange condenser 43, the gas-liquid separation tank B, the compressor 45 and the pressure-resistant storage tank 46 are connected in sequence. The cleaning system 5 includes an inert gas supply source 51, a cleaning medium supply source 52, a cleaning liquid storage tank 53 and a cleaning liquid pump 54, wherein the inert gas supply source 51 is connected to the cathode inlet 12, the cleaning medium supply source 52 is connected to the cleaning liquid storage tank 53, and then connected to the cathode inlet 12 through the cleaning liquid pump 54, and at the same time, the cathode outlet 13 is connected to the cleaning liquid storage tank.

[0040] Specifically, the system contains four battery stack structures, and each battery stack structure is connected in series.

[0041] like Figure 2 As shown, the stack structure 11 includes, from the outside to the inside, an end plate current collector 114 , a flow channel plate 113 , a gas diffusion electrode 112 and an ion exchange membrane 111 .

[0042] Specifically, each stack structure contains three gas diffusion electrodes, each with an area of ​​250 cm 2 .

[0043] According to the above-mentioned electric reduction system for processing tons of CO2 per year, the specific operation method includes the following steps: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55% and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0044] Specifically, the flow rate of CO 2 is 500 sccm.

[0045] Specifically, the flow rate of the electrolyte was 500 ml / min.

[0046] Specifically, the electrolyte medium is CsHCO3 with a concentration of 20 mM, the flow rate of the electrolyte medium is 500 ml / min, and the temperature is 55°C.

[0047] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the battery stack structure, and the temperature on both sides of the plates is strictly controlled, and the temperature is maintained at 55°C during the reaction.

[0048] Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0049] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0050] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0051] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0052] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0053] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0054] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0055] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0056] Example 1

[0057] An electro-reduction method for treating tons of CO2 per year comprises the following steps: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0058] Specifically, the flow rate of CO 2 is 500 sccm.

[0059] Specifically, the flow rate of the electrolyte was 500 ml / min.

[0060] Specifically, the electrolytic medium is a CsHCO3 solution with a concentration of 20 mM and a flow rate of 500 ml / min.

[0061] Specifically, the flow channel plate area is 250cm 2 .

[0062] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm- 2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0063] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0064] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0065] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0066] Specifically, the ion membrane is an AEM.

[0067] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0068] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0069] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0070] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0071] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0072] Table 1 Changes of CO2 electrocatalytic reaction activity and selectivity stability over time in membrane electrode reactor when the product is CO Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that step 4) in Example 1 is not performed in this comparative example, and the rest of the process is the same as that in Example 1, and the specific steps are as follows: 1) Prepare high-concentration CO2 gas from the CO2 supply system and adjust the temperature to 55°C and humidity to 65% through a temperature and humidity controller before entering the stack structure; the electrolyte is heated in the anode liquid tank and then enters the stack structure from the anode inlet through the anode liquid pump.

[0074] Specifically, the flow rate of CO 2 is 500 sccm.

[0075] Specifically, the electrolyte medium is a CsHCO3 solution with a concentration of 20 mM, the flow rate of the electrolyte medium is 500 ml / min, and the temperature is 55°C.

[0076] 2) Electrolysis reaction: A potential is applied to the positive and negative ends of the stack structure, so that the current density is controlled at 120 mA*cm -2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0077] The reaction occurring at the cathode of the stack structure is: CO2+2H+ +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0078] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0079] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0080] Specifically, the ion membrane is an AEM.

[0081] Specifically, the flow channel plate area is 250cm 2 .

[0082] 3) Product treatment: The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0083] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0084] Table 2 Effect of cleaning the cathode of the battery stack on the Faraday efficiency of CO It can be concluded from the data in Table 2 that the cathode of the fuel cell stack was not cleaned during the reaction interval (Comparative Example 1), and the Faraday efficiency of CO finally detected was significantly lower than when the cathode of the fuel cell stack was cleaned when the Faraday efficiency dropped to 75% of the initial Faraday efficiency. The reason is speculated to be: the flushing liquid can wash away the soluble salt particles produced by salting out that may exist on the surface of the gas diffusion electrode, and then the inert gas blown in can blow out the liquid that may remain on the gas diffusion electrode, so that the diffusion pores are not blocked by liquid and hinder the mass transfer of the reaction gas, thereby keeping the Faraday efficiency of the system at a high level to ensure that the reaction can continue to operate stably and efficiently.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that the flow channel plate in this comparative example has an area of ​​250 cm 2 The remaining steps are the same as those in Example 1, and the specific steps are as follows: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0087] Specifically, the flow rate of CO 2 is 500 sccm.

[0088] Specifically, the electrolyte medium was a CsHCO3 solution with a concentration of 20 mM, the flow rate of the electrolyte was 500 ml / min, and the temperature was maintained at 55°C.

[0089] Specifically, the flow channel plate is 250cm 2 square plates.

[0090] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm- 2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0091] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0092] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0093] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0094] Specifically, the ion membrane is an AEM.

[0095] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0096] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0097] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0098] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0099] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0100] Table 3 Effect of flow channel plate shape on CO Faraday efficiency It can be concluded from the data in Table 3 that, under the same flow channel plate area, the Faraday efficiency is significantly lower when using a square flow channel plate (Comparative Example 2) than a rectangular flow channel plate. The reason is speculated to be: the mass transfer of the rectangular flow channel plate is better than that of the square one, and the reactants are evenly distributed. At the same time, the sealing of the square plate is poor.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 1 is that in step 2), the concentration of the electrolyte is 2 mM, and the rest of the process is the same as that of Example 1, and the specific steps are as follows: 1) Preparation High-concentration CO2 gas is adjusted to temperature and humidity from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0103] Specifically, the flow rate of CO 2 is 500 sccm.

[0104] Specifically, the electrolytic medium was a CsHCO3 solution with a concentration of 2 mM, a flow rate of 500 ml / min, and a temperature of 55°C.

[0105] Specifically, the flow channel plate area is 250cm 2 .

[0106] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm -2, strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0107] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0108] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0109] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0110] Specifically, the ion membrane is an AEM.

[0111] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0112] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0113] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0114] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0115] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0116] Comparative Example 4

[0117] The difference between this comparative example and Example 1 is that in step 1), the concentration of the electrolyte is 200 mM, and the rest of the process is the same as that of Example 1, and the specific steps are as follows: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0118] Specifically, the flow rate of CO 2 is 500 sccm.

[0119] Specifically, the electrolytic medium is a CsHCO3 solution with a concentration of 200 mM, the flow rate of the electrolytic medium is 500 ml / min, and the temperature is 55°C.

[0120] Specifically, the flow channel plate area is 250cm 2 .

[0121] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm- 2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0122] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0123] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0124] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0125] Specifically, the ion membrane is an AEM.

[0126] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0127] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0128] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0129] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0130] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0131] Table 4 Effect of electrolyte concentration on CO Faraday efficiency From the data in Table 4, we can conclude that too low an electrolyte concentration (Comparative Example 3) or too high an electrolyte concentration (Comparative Example 4) will reduce the Faraday efficiency. The reason is speculated to be that too high or too low a cutoff concentration will reduce the conductivity of the electrolyte and affect the efficiency.

[0132] Comparative Example 5

[0133] The difference between this comparative example and Example 1 is that the flushing time of the flushing liquid in this comparative example is 30s, and the rest of the process is the same as that of the example, and the specific steps are as follows: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0134] Specifically, the flow rate of CO 2 is 500 sccm.

[0135] Specifically, the flow rate of the electrolyte was 500 ml / min.

[0136] Specifically, the electrolytic medium is a CsHCO3 solution with a concentration of 20 mM and a flow rate of 500 ml / min.

[0137] Specifically, the flow channel plate area is 250cm 2 .

[0138] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm -2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0139] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0140] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0141] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0142] Specifically, the ion membrane is an AEM.

[0143] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0144] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0145] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salting out on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 30s. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0146] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0147] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0148] Comparative Example 6

[0149] The difference between this comparative example and Example 1 is that the flushing time of the flushing liquid in this comparative example is 10 minutes, and the rest of the process is the same as Example 1, and the specific steps are: An electro-reduction method for treating tons of CO2 per year comprises the following steps: 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0150] Specifically, the flow rate of CO 2 is 500 sccm.

[0151] Specifically, the flow rate of the electrolyte was 500 ml / min.

[0152] Specifically, the electrolytic medium is a CsHCO3 solution with a concentration of 20 mM and a flow rate of 500 ml / min.

[0153] Specifically, the flow channel plate area is 250cm 2 .

[0154] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm -2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0155] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e- →CO+H2O Specifically, the cathode catalyst is Ag nanoparticles supported by carbon paper and subjected to electro-oxidation treatment.

[0156] Specifically, the anode catalyst is IrO2 supported on carbon paper.

[0157] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0158] Specifically, the ion membrane is an AEM.

[0159] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0160] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0161] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 30s. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 10min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0162] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0163] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0164] Table 5 Effect of flushing time on CO Faraday efficiency From the data in Table 5, we can conclude that if the cleaning time of the battery stack cathode is too short (Comparative Example 5), the cleaning time will not be thorough, resulting in the failure to completely remove the soluble particles produced by salting out and accumulation at the battery stack cathode; if the cleaning time of the battery stack cathode is too long (Comparative Example 6), the time cost will be too high, which is not conducive to the benefits of the enterprise.

[0165] Example 2

[0166] 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0167] Specifically, the flow rate of CO 2 is 500 sccm.

[0168] Specifically, the electrolyte medium is a CsHCO3 solution with a concentration of 20 mM, and the flow rate of the electrolyte is 500 ml / min.

[0169] , the temperature is 55℃.

[0170] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm- 2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0171] The reaction occurring at the cathode of the stack structure is: CO2+2H + +2e - →HCOOH+H2O Specifically, the cathode catalyst is a compound having formic acid reduction activity such as Bi / Bi2O2CO3 / BiOI supported on carbon paper.

[0172] Specifically, the anode catalyst is NiFoam.

[0173] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0174] Specifically, the ion membrane is a PEM.

[0175] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0176] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0177] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0178] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0179] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0180] Example 3

[0181] 1) Preparation High-concentration CO2 gas is adjusted to a temperature of 55°C and a humidity of 65% from the CO2 supply system through a temperature and humidity controller, and then enters the fuel cell stack structure; the electrolyte is heated in the anode liquid tank and then enters the fuel cell stack structure from the anode inlet through the anode liquid pump.

[0182] Specifically, the flow rate of CO 2 is 500 sccm.

[0183] Specifically, the electrolyte medium is a CsHCO3 solution with a concentration of 20 mM, a flow rate of 500 ml / min, and a temperature of 55°C.

[0184] 2) Electrolysis reaction A potential is applied to the positive and negative ends of the stack structure so that the current density is controlled at 120 mA*cm -2 , strictly control the temperature on both sides of the plate, and keep the temperature at 55℃ during the reaction.

[0185] The reaction occurring at the cathode of the stack structure is: 2CO2+12H + +12e - →C2H5OH+3H2O Specifically, the cathode catalyst is a Cu-based catalyst supported by carbon paper or the like. 2+ Reducing active compounds.

[0186] Specifically, the anode catalyst is an IrO2 catalyst supported on carbon paper.

[0187] Specifically, the catalyst is directly loaded on the diffusion layer with the carbon cloth as the substrate by ultrasonic spraying.

[0188] Specifically, the ion membrane is an AEM.

[0189] 3) Product processing The O2 discharged from the anode outlet and the O2 produced after the electrolyte passes through the heat exchanger are emptied, and the electrolyte solution re-enters the battery stack through the anode liquid tank for electrolysis; The product at the cathode outlet enters the gas-liquid separation tank and undergoes gas-liquid separation. The liquid is discharged into the waste liquid tank. The gas product is separated from the gas and liquid again through heat exchange condensation and then discharged into the compressor for storage. When the product is a gas-liquid mixture, the gas product after gas-liquid separation is discharged into the compressor for storage, and the liquid product is also purified and stored.

[0190] Specifically, when the product is only gas, it also needs to be separated into gas and liquid. The electrowetting effect will bring some water vapor, which needs to be removed in advance before entering the chromatography.

[0191] 4) Reaction interval Disconnect the potential applied to both ends of the plate and flush the cathode with flushing liquid. The flushing process is mainly to flush away the soluble salt particles that may be produced by salt precipitation on the surface of the gas diffusion electrode. The flushing uses a flow rate of 30ml / min and lasts for 3min. After the flushing is completed, N2 inert gas is purged at a flow rate of 1500ml / min for 3min to blow out the liquid that may remain on the gas diffusion electrode so that the diffusion channel is not blocked by the liquid and hinders the mass transfer of the reaction gas. When performing this operation, the anode electrolyte is also replaced to prevent the by-products such as formic acid from shuttling to the anode and affecting the selectivity of the reaction.

[0192] Specifically, the flushing liquid is ethanol:water=100 vol%.

[0193] Specifically, step 4) is performed once each time the Faraday efficiency drops to 75% of the initial Faraday efficiency to ensure that the reaction can continue to operate stably and efficiently.

[0194] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0195] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An industrial CO2 electroreduction system, characterized in that: include: The stack structure is provided with four connecting inlets and outlets, namely the cathode inlet, cathode outlet, anode inlet and outlet; a CO2 supply system connected to the cathode inlet; An anode liquid storage system connected to the anode inlet and the anode outlet respectively; a gas-liquid separation system connected to the cathode outlet; A cleaning system is connected to the cathode inlet and the cathode outlet respectively.

2. An industrialized CO2 electroreduction system according to claim 1, characterized in that: The stack structure is provided with an end plate current collector, a flow channel plate, a gas diffusion electrode and an ion exchange membrane in sequence from the inside to the outside.

3. An industrialized CO2 electroreduction system according to claim 2, characterized in that: The number of the battery stack structures is no less than 4; Each stack structure contains no less than 3 gas diffusion electrodes; The area of ​​a single gas diffusion electrode is ≥ 250 cm 2 ; The gas diffusion electrodes of a single stack structure are connected in series.

4. An industrialized CO2 electroreduction system according to claim 1, characterized in that: A temperature and humidity control system is provided between the CO2 supply system and the cathode inlet.

5. An electro-reduction method for treating tons of CO2 per year, characterized in that the steps for ： a) CO2 gas is continuously introduced into the cathode side of the electrolytic stack, and electrolyte solution is continuously introduced into the anode side to react in the electrolytic stack; b) The product at the anode outlet re-enters the anode liquid tank for circulation; c) The product at the cathode outlet enters the gas-liquid separation system for gas-liquid separation; d) During the reaction interval of step a), the power is turned off, and a flushing liquid is introduced from the cathode inlet for flushing. After the flushing is completed, an inert gas is introduced from the cathode inlet for purging. After the purging is completed, the electrolysis reaction is continued.

6. An industrialized CO2 electroreduction method according to claim 5, characterized in that: The temperature of the CO2 gas introduced in step a) is 50-60 o C, humidity is 60~700%, and flow rate is 500~600sccm.

7. The electro-reduction method for treating tons of CO2 per year according to claim 5 or 6, characterized in that: In step a), The electrolyte contains K + 、Na + , Li + , Cs + One or more soluble metal salt solutions; The concentration of the electrolyte is 10mM~100mM; The flow rate of the electrolyte was 500 ml / min.

8. An industrialized CO2 electro-reduction method according to claim 5 or 6, characterized in that: In step d), the washing liquid is ethanol: water = 90-110 vol%.

9. The industrialized CO2 electroreduction method according to claim 5, characterized in that: Flushing fluid flow rate 0~40ml / min; The flushing time is 3 to 5 minutes.

10. An industrialized CO2 electroreduction method according to claim 5, characterized in that: The flow rate of inert gas is 1500~1800ml / min; The purge time is 3~5min.

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