Method for preparing synthesis gas through electrochemical conversion of carbon dioxide

Abstract

The invention provides a method for preparing synthesis gas by electrochemical conversion of carbon dioxide, which comprises the following steps: feeding raw material gas containing carbon dioxide into a first absorption unit, absorbing by electrolyte to obtain a gas-liquid mixture, and sequentially separating by an electrochemical reactor and a separator to obtain gas-phase products of an anode and a cathode and electrolyte; the cathode gas-phase product is mixed with feed gas and then returns to the first absorption unit to obtain synthesis gas, and the anode gas-phase product enters the second absorption unit to obtain oxygen; and the obtained electrolyte is recycled in the reaction. The invention further provides a method for preparing synthesis gas through electrochemical conversion of carbon dioxide, raw material gas containing carbon dioxide is fed into the second absorption unit, the gas-liquid mixture reaction process is the same as that of the method, and the obtained anode gas-phase product is mixed with the raw material gas and returns to the second absorption unit to obtain oxygen. And the cathode gas-phase product enters a first absorption unit to obtain the synthesis gas. The method disclosed by the invention can effectively improve the purity of the product gas and the comprehensive conversion rate of carbon dioxide.

Description

Technical Field

[0001] The present disclosure relates to the field of electrolytic processes for producing compounds, and primarily to a method for producing synthesis gas through electrochemical conversion of carbon dioxide. Background Art

[0002] The modern chemical industry uses combustion as the main way to obtain energy. With the development of the economy, energy demand is also increasing. The emission of carbon dioxide gas in industrial production is increasing day by day. The increase of carbon dioxide in the atmosphere has caused many environmental problems such as greenhouse effect, ocean acidification, and destruction of the ozone layer. It has a great negative impact on the environment. Therefore, the capture, utilization and storage of carbon dioxide are the main ways to reduce pollution emissions, save energy and protect the environment.

[0003] Capturing carbon dioxide generated by industrial production and using it to manufacture new products with high added value, such as fertilizers, synthetic fuels, chemicals, etc., is the main direction of carbon dioxide emission reduction and energy utilization. Among them, the electrochemical conversion of carbon dioxide is the main way to recycle energy in industrial production. For example, CN112981438A discloses a carbon dioxide electrolysis synthesis gas system, which includes an electrolyte circulation device, and the electrolyte circulation device is used for the electrolyte circulation of the carbon dioxide electrolyte synthesis gas system. The system also includes a neutralization unit, and the neutralization unit receives the electrolyte discharged from the cathode chamber and the anode chamber and is used for the electrolyte circulation. The neutralization unit collects and neutralizes the electrolyte discharged from the anode chamber and the cathode chamber and incorporates it into the electrolyte circulation to form an electrolyte closed-loop circulation.

[0004] However, the existing carbon dioxide electro-conversion devices still have the problem that both the cathode product gas and the anode product gas contain some unreacted carbon dioxide, resulting in low purity of the synthesized product gas and low comprehensive carbon dioxide conversion rate. Summary of the invention

[0005] The purpose of the present disclosure is to improve the purity of product gas and the carbon dioxide conversion rate.

[0006] In order to achieve the above-mentioned object, the present disclosure provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide. In a first aspect, the present disclosure provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide, the method comprising: S1, feeding the raw gas 101 containing carbon dioxide into the first absorption unit 1 from the bottom, and countercurrently contacting with the first electrolyte 110 introduced from the top of the first absorption unit 1, to obtain a first rich solution 104; S2, mixing the first rich solution 104 and the second electrolyte 124 and sending them into the cathode chamber 31, sending the third electrolyte 125 into the anode chamber 32, and performing an electrolytic reaction in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112; S3, sending the cathode gas-liquid mixture 105 to the first separator 4 for gas-liquid separation to obtain a cathode gas phase product 106 and a cathode electrolyte 107, and sending the anode gas-liquid mixture 112 to the second separator 7 for gas-liquid separation to obtain an anode gas phase product 113 and an anode electrolyte 116; S4, returning the cathode gas phase product 106 to step S1, mixing it with the raw gas 101 containing carbon dioxide, and then sending it to the first absorption unit 1 for absorption to obtain synthesis gas 111; sending the anode gas phase product 113 to the second absorption unit 2 for absorption with the fourth electrolyte 118 to obtain oxygen 115 and a second rich solution 114; mixing the second rich solution 114 with the first rich solution 104 and the second electrolyte 124, and then sending it to the cathode chamber 31; S5. Send the cathode electrolyte 107 and the anode electrolyte 116 into the electrolyte mixing tank 6 for mixing, and then draw out the first electrolyte 110, the second electrolyte 124, the third electrolyte 125 and the fourth electrolyte 118 from the electrolyte mixing tank 6.

[0007] The present disclosure also provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide, the method comprising: S1, feeding the carbon dioxide-containing raw gas 101 from the bottom into the second absorption unit 2, and countercurrently contacting with the fourth electrolyte 118 introduced from the top of the second absorption unit 2, to obtain a second rich solution 114; S2, mixing the second rich solution 114 and the second electrolyte 124 and sending them into the cathode chamber 31, sending the third electrolyte 125 into the anode chamber 32, and performing an electrolytic reaction in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112; S3, sending the cathode gas-liquid mixture 105 to the first separator 4 for gas-liquid separation to obtain a cathode gas phase product 106 and a cathode electrolyte 107, and sending the anode gas-liquid mixture 112 to the second separator 7 for gas-liquid separation to obtain an anode gas phase product 113 and an anode electrolyte 116; S4, sending the cathode gas phase product 106 to the first absorption unit 1 for absorption with the first electrolyte 110 to obtain synthesis gas 111 and the first rich solution 104; returning the anode gas phase product 113 to step S1, mixing with the carbon dioxide-containing raw gas 101, and then sending it to the second absorption unit 2 for absorption to obtain oxygen 115; mixing the first rich solution 104 with the second rich solution 114 and the second electrolyte 124, and then sending it to the cathode chamber 31; S5. Send the cathode electrolyte 107 and the anode electrolyte 116 into the electrolyte mixing tank 6 for mixing, and then draw out the first electrolyte 110, the second electrolyte 124, the third electrolyte 125 and the fourth electrolyte 118 from the electrolyte mixing tank 6.

[0008] Through the above technical scheme, the present invention realizes the separation and purification of synthesis gas and carbon dioxide in the product cathode gas by returning the gas generated by the electrochemical reaction to the absorption unit and contacting it with the electrolyte in the absorption unit again, which significantly improves the purity of the reaction generated gas, and the purity of the synthesis gas product reaches more than 98mol%. At the same time, it absorbs unreacted carbon dioxide, realizing low-cost and efficient purification of the cathode product synthesis gas and effective recovery of carbon dioxide; further, the present invention improves the separation efficiency of the gas-liquid mixture produced by the reaction by sending the anode gas-liquid mixture and the cathode gas-liquid mixture of the electrochemical reactor into different separators for separation, and promotes the gas purification rate and the circulation rate of the electrolyte in the reaction; at the same time, the parallel setting of the pipelines between the devices in the reaction allows the electrolyte in the reaction device to circulate continuously between the reaction devices. Through the method disclosed in the present invention, the comprehensive conversion rate of carbon dioxide in the raw gas is greatly improved, the low-cost purification of the product gas is achieved, and the economic benefits of the device are improved.

[0009] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is a schematic flow chart of a method for electrochemical conversion of carbon dioxide to produce synthesis gas, in which carbon dioxide raw gas enters a conversion system from a first absorption unit 1.

[0011] Figure 2 The present invention is a schematic flow chart of a method for producing synthesis gas by electrochemical conversion of carbon dioxide, in which carbon dioxide raw gas enters a conversion system from a second absorption unit.

[0012] Description of Reference Numerals 1-first absorption unit, 2-second absorption unit, 3-electrochemical reactor, 4-first separator, 5-first cooler, 6-electrolyte mixing tank, 7-second separator, 8-second cooler; 101-raw gas containing carbon dioxide, 102-first absorption unit gas, 103-second absorption unit gas, 104-first rich solution, 105-cathode gas-liquid mixture, 106-cathode gas-phase product, 107-cathode electrolyte, 108-cathode cooling electrolyte, 109-absorption unit electrolyte, 110-first electrolyte, 111-synthesis gas, 112-anode gas-liquid mixture, 113-anode gas-phase product, 114-second rich solution, 115-oxygen, 116-anode electrolyte, 117-anode cooling electrolyte, 118-fourth electrolyte, 119-deionized water, 122-mixed electrolyte, 123-electrochemical reactor electrolyte, 124-second electrolyte, 125-third electrolyte, 31-cathode chamber, 32-anode chamber. DETAILED DESCRIPTION

[0013] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0014] In the present disclosure, unless otherwise specified, directional words such as "upper, lower, top, bottom" generally refer to the upper, lower, top, bottom of the device in normal use.

[0015] refer to Figure 1 In a first aspect, the present disclosure provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide. In a first aspect, the present disclosure provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide, the method comprising: S1, feeding the raw gas 101 containing carbon dioxide into the first absorption unit 1 from the bottom, and countercurrently contacting with the first electrolyte 110 introduced from the top of the first absorption unit 1, to obtain a first rich solution 104; S2, mixing the first rich solution 104 and the second electrolyte 124 and sending them into the cathode chamber 31, sending the third electrolyte 125 into the anode chamber 32, and performing an electrolytic reaction in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112; S3, sending the cathode gas-liquid mixture 105 to the first separator 4 for gas-liquid separation to obtain a cathode gas phase product 106 and a cathode electrolyte 107, and sending the anode gas-liquid mixture 112 to the second separator 7 for gas-liquid separation to obtain an anode gas phase product 113 and an anode electrolyte 116; S4, returning the cathode gas phase product 106 to step S1, mixing it with the raw gas 101 containing carbon dioxide, and then sending it to the first absorption unit 1 for absorption to obtain synthesis gas 111; sending the anode gas phase product 113 to the second absorption unit 2 for absorption with the fourth electrolyte 118 to obtain oxygen 115 and a second rich solution 114; mixing the second rich solution 114 with the first rich solution 104 and the second electrolyte 124, and then sending it to the cathode chamber 31; S5. Send the cathode electrolyte 107 and the anode electrolyte 116 into the electrolyte mixing tank 6 for mixing, and then draw out the first electrolyte 110, the second electrolyte 124, the third electrolyte 125 and the fourth electrolyte 118 from the electrolyte mixing tank 6.

[0016] Through the above technical scheme, the present invention realizes the separation and purification of synthesis gas and carbon dioxide in the product cathode gas by returning the gas generated by the electrochemical reaction to the absorption unit to contact the electrolyte in the absorption unit again, thereby significantly improving the purity of the reaction generated gas, and the purity of the synthesis gas product reaches more than 98 mol%. At the same time, it absorbs unreacted carbon dioxide, thereby realizing low-cost and efficient purification of the cathode product synthesis gas and effective recovery of carbon dioxide.

[0017] In a specific embodiment, the method further comprises: feeding the cathode electrolyte 107 and the anode electrolyte 116 into a first cooler 5 and a second cooler 8 for cooling respectively, and feeding the cathode cooling electrolyte 108 and the anode cooling electrolyte 117 into an electrolyte mixing tank 6 for mixing; An ion diaphragm is provided between the cathode chamber 31 and the anode chamber 32. The ion diaphragm has selective permeability, and preferably the ion diaphragm has a high permeability to alkali metal cations, and a low permeability to other ions or molecules, for example, a low permeability to at least one of hydrogen ions, hydroxide ions, carbonate ions, bicarbonate ions, carbon monoxide molecules and carbon dioxide molecules. The ion diaphragm allows the free movement of alkali metal cations in the circuit within the electrochemical reactor and isolates the hydrogen and oxygen generated by the electrocatalytic process. During the electrolysis process, the transmission of alkali metal cations between the anode and the cathode can only be carried out through the ion diaphragm.

[0018] Through the above-mentioned embodiments, the present disclosure effectively separates the cathode product and the anode product by setting an ion diaphragm in the electrochemical reactor, and the materials in the cathode chamber 31 and the anode chamber 32 can be continuously circulated; the present disclosure cools the cathode electrolyte and the anode electrolyte separately and then sends them to the electrolyte mixing tank for mixing, maintains the ion balance of the reaction electrolyte, adjusts the concentration of the electrolyte and adjusts the pH, ensures the instant replenishment of the electrolyte during the reaction, makes the electrolyte content in each device of the reaction meet the reaction requirements, and maintains the stable progress of the reaction.

[0019] In a preferred embodiment, the temperature of the cathode electrolyte 107 can be 40-90°C, and the temperature of the anode electrolyte 116 can be 40-90°C; the temperature of the cathode cooling electrolyte 108 can be 40-90°C, and the temperature of the anode cooling electrolyte 117 can be 40-90°C.

[0020] In this preferred embodiment, the temperature of the electrolyte after the reaction is lowered by cooling with a cooler, and after desalted water is added to the electrolyte mixing tank and evenly mixed, the obtained low-temperature electrolyte is sent to the electrochemical reactor and the absorption unit respectively. The cooled temperature effectively promotes the dissolution rate of carbon dioxide in the raw gas in the electrolyte, thereby improving the absorption efficiency of carbon dioxide.

[0021] In a preferred embodiment, the first separator 4 and the second separator 7 are vertical gas-liquid separators or horizontal gas-liquid separators; the operating pressure in the first separator 4 can be 0.05-2.0 MPa, preferably 0.12 MPa; the operating temperature can be 10-120°C, preferably 50-85°C; the operating pressure in the second separator 7 can be 0.05-2.0 MPa, preferably 0.12 MPa; the operating temperature can be 10-120°C, preferably 63°C.

[0022] The present invention improves the separation efficiency of the gas-liquid mixture produced by the reaction, accelerates the reaction process, and promotes the gas purification rate and the circulation rate of the electrolyte in the reaction by sending the anode gas-liquid mixture and the cathode gas-liquid mixture of the electrochemical reactor into different separators for separation.

[0023] In a preferred embodiment, the method further comprises feeding desalted water 119 into the electrolyte mixing tank 6 to replenish the water consumed by the electrolysis reaction; the electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration range may be 0.2-10 mol / L, preferably 3 mol / L; Preferably, the alkali metal carbonate and / or alkali metal bicarbonate may be at least one of sodium carbonate, sodium bicarbonate or potassium carbonate, potassium bicarbonate; wherein the reaction of the raw gas carbon dioxide and the electrolyte may be: K2CO3+CO2+H2O 2KHCO3, CO3 2- + H2O + CO2 ⇋ 2HCO3 - ; The potassium ions in the electrolyte are maintained constant, and the CO2 consumed during the electrolysis reaction is replenished by the decomposition of bicarbonate ions; the electrolyte used in the present invention is not consumed as the reaction proceeds, and only the water in the electrolyte is consumed. By timely replenishing the desalted water in the electrolyte, there is no need to replenish the electrolyte during the reaction production process, saving the reaction cost.

[0024] The operating temperature of the first absorption unit 1 may be 10-120°C, preferably 60°C, and the operating pressure may be 0.05-2.0MPa, preferably 0.1MPa; the operating temperature of the second absorption unit 2 may be 10-120°C, preferably 60°C, and the operating pressure may be 0.05-2.0MPa, preferably 0.1MPa; The concentration of carbon dioxide in the carbon dioxide-containing raw gas 101 may be 85% to 100% by volume, preferably above 95% by volume; The operating temperature of the electrochemical reactor 3 may be 10-120° C., preferably 60° C., and the operating pressure may be 0.05-2.0 MPa, preferably 0.15 MPa.

[0025] Through the method disclosed in the present invention, the reaction conditions can be close to normal temperature and pressure, making the operating conditions of the reaction simpler. At the same time, lower temperature can promote the dissolution of carbon dioxide gas, improve the dissolution efficiency of carbon dioxide gas and thus improve the single-pass conversion rate of carbon dioxide gas.

[0026] The present disclosure also provides a method for producing synthesis gas by electrochemical conversion of carbon dioxide, see Figure 2 , the method comprising: S1. Feeding the carbon dioxide-containing raw gas 101 from the bottom into the second absorption unit 2, and countercurrently contacting with the fourth electrolyte 118 introduced from the top of the second absorption unit 2, to obtain a second rich solution 114; optionally, the absorption unit may be a plate tower or a packed tower; S2, mixing the second rich solution 114 and the second electrolyte 124 and sending them into the cathode chamber 31, sending the third electrolyte 125 into the anode chamber 32, and performing an electrolytic reaction in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112; S3, sending the cathode gas-liquid mixture 105 to the first separator 4 for gas-liquid separation to obtain a cathode gas-phase product 106 and a cathode electrolyte 107, sending the anode gas-liquid mixture 112 to the second separator 7 for gas-liquid separation to obtain an anode gas-phase product 113 and an anode electrolyte 116; the gas-phase product is sent to the absorption unit from the gas-phase product pipeline at the top of the separator, and the electrolyte enters the cooler along the electrolyte pipeline at the bottom of the separator due to gravity; S4, sending the cathode gas phase product 106 to the first absorption unit 1 for absorption with the first electrolyte 110 to obtain synthesis gas 111 and the first rich solution 104; returning the anode gas phase product 113 to step S1, mixing with the carbon dioxide-containing raw gas 101, and then sending it to the second absorption unit 2 for absorption to obtain oxygen 115; mixing the first rich solution 104 with the second rich solution 114 and the second electrolyte 124, and then sending it to the cathode chamber 31; the synthesis gas 111 includes hydrogen and carbon monoxide; the concentrations of the synthesis gas 111 and oxygen 115 can be above 98v%, and the synthesis gas 111 and oxygen 115 are discharged from the top of the absorption unit and enter the downstream utilization device for utilization; S5. Send the cathode electrolyte 107 and the anode electrolyte 116 into the electrolyte mixing tank 6 for mixing, and then draw out the first electrolyte 110, the second electrolyte 124, the third electrolyte 125 and the fourth electrolyte 118 from the electrolyte mixing tank 6.

[0027] This method changes the feeding mode of raw gas, provides multiple working modes for the method disclosed in the present invention, and improves the flexibility of the carbon dioxide raw gas absorption mode. The electrolyte in the method disclosed in the present invention circulates continuously during the reaction, and no electrolyte needs to be supplemented, which reduces the reaction cost.

[0028] In a specific embodiment, the method further comprises: feeding the cathode electrolyte 107 and the anode electrolyte 116 into a first cooler 5 and a second cooler 8 for cooling respectively, and feeding the cathode cooling electrolyte 108 and the anode cooling electrolyte 117 into an electrolyte mixing tank 6 for mixing; An ion membrane is disposed between the cathode chamber 31 and the anode chamber 32 .

[0029] In this embodiment, a catalyst may be attached to the electrode surface of the ion membrane, and the catalyst may be a nickel-based catalyst.

[0030] In a preferred embodiment, the temperature of the cathode electrolyte 107 can be 40-90°C, and the temperature of the anode electrolyte 116 can be 40-90°C; the temperature of the cathode cooling electrolyte 108 can be 40-90°C, and the temperature of the anode cooling electrolyte 117 can be 40-90°C.

[0031] In a preferred embodiment, the first separator 4 and the second separator 7 can be vertical gas-liquid separators or horizontal gas-liquid separators, and separation internals can be provided inside the gas-liquid separators; the operating pressure in the first separator 4 can be 0.05-2.0 MPa, preferably 0.12 MPa; the operating temperature can be 10-120°C, preferably 63°C; the operating pressure in the second separator 7 can be 0.05-2.0 MPa, preferably 0.12 MPa; the operating temperature can be 10-120°C, preferably 63°C.

[0032] In this preferred embodiment, the gas-liquid separation method can be at least one of heating, reducing pressure and blowing; reducing the temperature of the separated gas phase product and electrolyte through a separator, a cooler and a gas-liquid transmission pipeline can more effectively improve the absorption efficiency of carbon dioxide in this method.

[0033] In a preferred embodiment, the method further comprises feeding desalted water 119 into the electrolyte mixing tank 6 to replenish the water consumed by the electrolysis reaction; the electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration range may be 0.2-10 mol / L, preferably 3 mol / L; The operating temperature of the first absorption unit 1 may be 10-120°C, preferably 60°C, and the operating pressure may be 0.05-2.0MPa, preferably 0.1MPa; the operating temperature of the second absorption unit 2 may be 10-120°C, preferably 60°C, and the operating pressure may be 0.05-2.0MPa, preferably 0.1MPa; The concentration of carbon dioxide in the carbon dioxide-containing raw gas 101 may be 85% to 100% by volume, preferably above 95% by volume; The operating temperature of the electrochemical reactor 3 may be 10-120° C., preferably 60° C., and the operating pressure may be 0.05-2.0 MPa, preferably 0.15 MPa.

[0034] Through the above technical scheme, the present method utilizes the electrolyte after the reaction of the electrochemical catalytic conversion reactor, partially circulates into the first absorption unit, utilizes the alkaline characteristics of the electrolyte, realizes the separation and purification of the product cathode gas from the synthesis gas and carbon dioxide in the first absorption unit, and the purity of the synthesis gas product reaches more than 98mol%, and at the same time absorbs the unreacted carbon dioxide, realizes the low-cost and efficient purification of the cathode product synthesis gas and the effective recovery of carbon dioxide. Similarly, the electrolyte after partial reaction circulates into the second absorption unit, realizes the separation and purification of the product anode gas from oxygen and carbon dioxide in the second absorption unit, the purity of the oxygen product reaches more than 98mol%, and at the same time absorbs the unreacted carbon dioxide, realizes the low-cost and efficient purification of the anode product oxygen and the effective recovery of carbon dioxide. Optionally, the raw gas containing carbon dioxide can enter the first absorption unit or the second absorption unit, and the raw gas can be fully dissolved into the electrolyte in the absorption unit to ensure the solubility of carbon dioxide in the electrolyte, effectively improve the single-pass conversion rate and comprehensive utilization rate of carbon dioxide in the cathode of the electrochemical reactor, and improve the economic benefits of the device.

[0035] Example 1 This implementation is achieved through Figure 1 The carbon dioxide processing method shown is to produce synthesis gas by electrochemical conversion of carbon dioxide; the method of this embodiment includes the following steps: S1, feeding the raw gas 101 containing carbon dioxide (carbon dioxide concentration of 98v%, flow rate of 65.8kg / h) from the bottom into the first absorption unit 1, and countercurrently contacting with the first electrolyte 110 introduced from the top of the first absorption unit 1, to obtain a first rich solution 104; S2, mixing the first rich solution 104 and the second electrolyte 124 and sending them into the cathode chamber 31, sending the third electrolyte 125 into the anode chamber 32, and performing electrolysis reaction in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112 (the reactor outlet temperature is 63° C., and the operating pressure is 0.15 MPa); S3, sending the cathode gas-liquid mixture 105 into the first separator 4 for gas-liquid separation to obtain a cathode gas phase product 106 (composed of 39.8 kg / h carbon monoxide, 5.7 kg / h hydrogen, and 37.4 kg / h carbon dioxide) and a cathode electrolyte 107, and sending the anode gas-liquid mixture 112 into the second separator 7 for gas-liquid separation to obtain an anode gas phase product 113 (oxygen flow rate is 68.5 kg / h, carbon dioxide flow rate is 18.5 kg / h) and an anode electrolyte 116; S4, returning the cathode gas phase product 106 to step S1, mixing it with the raw gas 101 containing carbon dioxide, and then sending it to the first absorption unit 1 for absorption to obtain synthesis gas 111 (purity is 98 mol%, the molar ratio of carbon monoxide to hydrogen in the synthesis gas is 0.5, and the flow rate is 46.7 kg / h); sending the anode gas phase product 113 to the second absorption unit 2 and the fourth electrolyte 118 for absorption to obtain oxygen 115 (purity is 98 mol%, flow rate is 71 kg / h) and the second rich solution 114; the second rich solution 114 (flow rate is 5713 kg / h) is mixed with the first rich solution 104 (flow rate is 27598 kg / h) and the second electrolyte 124 (flow rate is 77065 kg / h) (total flow rate is 110376 kg / h) and sent to the cathode chamber 31; S5. The cathode electrolyte 107 and the anode electrolyte 116 are sent into the electrolyte mixing tank 6 for mixing, and then the first electrolyte 110 (with a flow rate of 27561 kg / h), the second electrolyte 124 (with a flow rate of 77065 kg / h), the third electrolyte 125 (with a flow rate of 55039 kg / h) and the fourth electrolyte 118 (with a flow rate of 5695 kg / h) are drawn out from the electrolyte mixing tank 6.

[0036] The method further comprises: sending the cathode electrolyte 107 and the anode electrolyte 116 into a first cooler 5 and a second cooler 8 for cooling respectively, and sending the cathode cooling electrolyte 108 and the anode cooling electrolyte 117 into an electrolyte mixing tank 6 for mixing; An ion membrane is disposed between the cathode chamber 31 and the anode chamber 32 .

[0037] The temperature of the cathode electrolyte 107 is 63°C, and the temperature of the anode electrolyte 116 is 63°C; the temperature of the cathode cooling electrolyte 108 is 60°C, and the temperature of the anode cooling electrolyte 117 is 60°C.

[0038] The first separator 4 and the second separator 7 are vertical gas-liquid separators or horizontal gas-liquid separators; the operating pressure in the first separator 4 is 0.12 MPa and the operating temperature is 63°C; the operating pressure in the second separator 7 is 0.12 MPa and the operating temperature is 63°C.

[0039] The method further includes sending demineralized water 119 (flow rate of 62 kg / h) into the electrolyte mixing tank 6 to replenish the water consumed by the electrolysis reaction; the electrolyte is potassium carbonate with a concentration of 3 mol / L; The operating temperature of the first absorption unit 1 is 60°C and the operating pressure is 0.1MPa; the operating temperature of the second absorption unit 2 is 60°C and the operating pressure is 0.1MPa; the concentration of carbon dioxide in the raw gas 101 containing carbon dioxide is above 95v%; the operating temperature of the electrochemical reactor 3 is 60°C and the operating pressure is 0.15MPa. The single-pass conversion rate of carbon dioxide at the cathode of the electrochemical reactor is 52%, and the comprehensive utilization rate is 96%.

[0040] Example 2 This embodiment provides a method that is different from the method described in Example 1 in that the feed gas containing carbon dioxide is introduced in a different manner. Figure 2 , the method comprising: S1. Feeding the raw gas 101 containing carbon dioxide (carbon dioxide concentration 98v%, flow rate 65.8kg / h) from the bottom into the second absorption unit 2, and countercurrently contacting with the fourth electrolyte 118 introduced from the top of the second absorption unit 2, to obtain a second rich solution 114; optionally, the absorption unit is a plate tower or a packed tower; S2, the second rich solution 114 and the second electrolyte 124 are mixed and sent to the cathode chamber 31, the third electrolyte 125 is sent to the anode chamber 32, and an electrolytic reaction is carried out in the electrochemical reactor 3 including the cathode chamber 31 and the anode chamber 32 to obtain a cathode gas-liquid mixture 105 and an anode gas-liquid mixture 112 (the reactor outlet temperature is 63° C. and the operating pressure is 0.15 MPa); S3, sending the cathode gas-liquid mixture 105 into the first separator 4 for gas-liquid separation to obtain a cathode gas-phase product 106 (composed of 39.8 kg / h carbon monoxide, 5.7 kg / h hydrogen, and 37.4 kg / h carbon dioxide) and a cathode electrolyte 107, sending the anode gas-liquid mixture 112 into the second separator 7 for gas-liquid separation to obtain an anode gas-phase product 113 (oxygen flow rate is 68.5 kg / h, carbon dioxide flow rate is 18.5 kg / h) and an anode electrolyte 116; the gas-phase product is sent to the absorption unit from the gas-phase product pipeline at the top of the separator, and the electrolyte enters the cooler along the electrolyte pipeline at the bottom of the separator due to gravity; S4, sending the cathode gas phase product 106 to the first absorption unit 1 for absorption with the first electrolyte 110 to obtain synthesis gas 111 (purity is 98 mol%, the molar ratio of carbon monoxide to hydrogen in the synthesis gas is 0.5, and the flow rate is 46.7 kg / h) and the first rich solution 104; returning the anode gas phase product 113 to step S1, mixing with the carbon dioxide-containing raw gas 101, and then sending it to the second absorption unit 2 for absorption to obtain oxygen 115 (purity is 98 mol%, and the flow rate is 71 kg / h); the first rich solution 104 (flow rate is 14801 kg / h), the second rich solution 114 (flow rate is 18575 kg / h) and the second electrolyte 124 (75328 kg / h) are mixed (total flow rate is 108704 kg / h) and sent to the cathode chamber 31; S5. The cathode electrolyte 107 and the anode electrolyte 116 are sent into the electrolyte mixing tank 6 for mixing, and then the first electrolyte 110 (with a flow rate of 14765 kg / h), the second electrolyte 124 (with a flow rate of 75328 kg / h), the third electrolyte 125 (with a flow rate of 56711 kg / h) and the fourth electrolyte 118 (with a flow rate of 18491 kg / h) are drawn out from the electrolyte mixing tank 6.

[0041] The method further comprises: sending the cathode electrolyte 107 and the anode electrolyte 116 into a first cooler 5 and a second cooler 8 for cooling respectively, and sending the cathode cooling electrolyte 108 and the anode cooling electrolyte 117 into an electrolyte mixing tank 6 for mixing; An ion membrane is disposed between the cathode chamber 31 and the anode chamber 32 .

[0042] The temperature of the cathode electrolyte 107 is 63°C, and the temperature of the anode electrolyte 116 is 63°C; the temperature of the cathode cooling electrolyte 108 is 60°C, and the temperature of the anode cooling electrolyte 117 is 60°C.

[0043] The first separator 4 and the second separator 7 are vertical gas-liquid separators or horizontal gas-liquid separators; the operating pressure in the first separator 4 is 0.12 MPa and the operating temperature is 63°C; the operating pressure in the second separator 7 is 0.12 MPa and the operating temperature is 63°C.

[0044] The method also includes sending desalted water 119 (flow rate of 62kg / h) into the electrolyte mixing tank 6 to supplement the water consumed by the electrolysis reaction; the electrolyte is an aqueous solution of potassium carbonate with a concentration of 3mol / L; the operating temperature of the first absorption unit 1 is 60°C and the operating pressure is 0.1MPa; the operating temperature of the second absorption unit 2 is 60°C and the operating pressure is 0.1MPa; the concentration of carbon dioxide in the carbon dioxide-containing raw gas 101 is above 95v%; the operating temperature of the electrochemical reactor 3 is 60°C and the operating pressure is 0.15MPa. The single-pass conversion rate of carbon dioxide at the cathode of the electrochemical reactor is 53%, and the comprehensive utilization rate is 95%.

[0045] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications are made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0047] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for producing synthesis gas by electrochemical conversion of carbon dioxide, characterized in that: The method includes: S1, feeding the raw gas (101) containing carbon dioxide into the first absorption unit (1) from the bottom, and contacting it with the first electrolyte (110) introduced from the top of the first absorption unit (1) in countercurrent flow, thereby obtaining a first rich solution (104); S2, mixing the first rich solution (104) and the second electrolyte (124) and sending the mixture into the cathode chamber (31), sending the third electrolyte (125) into the anode chamber (32), and performing an electrolytic reaction in an electrochemical reactor (3) including the cathode chamber (31) and the anode chamber (32) to obtain a cathode gas-liquid mixture (105) and an anode gas-liquid mixture (112); S3, sending the cathode gas-liquid mixture (105) into a first separator (4) for gas-liquid separation to obtain a cathode gas phase product (106) and a cathode electrolyte (107), and sending the anode gas-liquid mixture (112) into a second separator (7) for gas-liquid separation to obtain an anode gas phase product (113) and an anode electrolyte (116); S4, returning the cathode gas phase product (106) to step S1, mixing it with the raw gas (101) containing carbon dioxide, and then sending it to the first absorption unit (1) for absorption to obtain synthesis gas (111); sending the anode gas phase product (113) to the second absorption unit (2) for absorption with the fourth electrolyte (118) to obtain oxygen (115) and a second rich solution (114); mixing the second rich solution (114) with the first rich solution (104) and the second electrolyte (124), and then sending it to the cathode chamber (31); S5. The cathode electrolyte (107) and the anode electrolyte (116) are fed into an electrolyte mixing tank (6) for mixing, and then the first electrolyte (110), the second electrolyte (124), the third electrolyte (125) and the fourth electrolyte (118) are drawn out from the electrolyte mixing tank (6).

2. The method according to claim 1, wherein: The method further comprises: sending the cathode electrolyte (107) and the anode electrolyte (116) into a first cooler (5) and a second cooler (8) respectively for cooling, obtaining a cathode cooling electrolyte (108) and an anode cooling electrolyte (117), and sending them into an electrolyte mixing tank (6) for mixing; An ion membrane is provided between the cathode chamber (31) and the anode chamber (32).

3. The method according to claim 2, wherein: The temperature of the cathode electrolyte (107) is 40-90°C, and the temperature of the anode electrolyte (116) is 40-90°C; the temperature of the cathode cooling electrolyte (108) is 40-90°C, and the temperature of the anode cooling electrolyte (117) is 40-90°C.

4. The method according to claim 1, wherein: The first separator (4) and the second separator (7) are vertical gas-liquid separators or horizontal gas-liquid separators; the operating pressure in the first separator (4) is 0.05-2.0 MPa, and the operating temperature is 10-120°C; the operating pressure in the second separator (7) is 0.05-2.0 MPa, and the operating temperature is 10-120°C.

5. The method according to claim 1, wherein: The method further comprises feeding desalted water (119) into the electrolyte mixing tank (6) to replenish water consumed by the electrolysis reaction; the electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration range is 0.2-10 mol / L; The operating temperature of the first absorption unit (1) is 10-120°C, and the operating pressure is 0.05-2.0 MPa; the operating temperature of the second absorption unit (2) is 10-120°C, and the operating pressure is 0.05-2.0 MPa; The concentration of carbon dioxide in the carbon dioxide-containing raw gas (101) is 85% to 100% by volume; The operating temperature of the electrochemical reactor (3) is 10-120° C., and the operating pressure is 0.05-2.0 MPa.

6. A method for producing synthesis gas by electrochemical conversion of carbon dioxide, characterized in that: The method comprises: S1, feeding the raw gas (101) containing carbon dioxide into the second absorption unit (2) from the bottom, and countercurrently contacting with the fourth electrolyte (118) introduced from the top of the second absorption unit (2), to obtain a second rich solution (114); S2, mixing the second rich solution (114) and the second electrolyte (124) and sending the mixture into the cathode chamber (31), sending the third electrolyte (125) into the anode chamber (32), and performing an electrolytic reaction in an electrochemical reactor (3) including the cathode chamber (31) and the anode chamber (32) to obtain a cathode gas-liquid mixture (105) and an anode gas-liquid mixture (112); S3, sending the cathode gas-liquid mixture (105) into a first separator (4) for gas-liquid separation to obtain a cathode gas phase product (106) and a cathode electrolyte (107), and sending the anode gas-liquid mixture (112) into a second separator (7) for gas-liquid separation to obtain an anode gas phase product (113) and an anode electrolyte (116); S4, sending the cathode gas phase product (106) into a first absorption unit (1) to be absorbed with a first electrolyte (110) to obtain synthesis gas (111) and a first rich solution (104); returning the anode gas phase product (113) to step S1, mixing it with the carbon dioxide-containing raw gas (101), and then sending it into a second absorption unit (2) for absorption to obtain oxygen (115); mixing the first rich solution (104), the second rich solution (114), and the second electrolyte (124), and then sending it into the cathode chamber (31); S5. The cathode electrolyte (107) and the anode electrolyte (116) are fed into an electrolyte mixing tank (6) for mixing, and then the first electrolyte (110), the second electrolyte (124), the third electrolyte (125) and the fourth electrolyte (118) are drawn out from the electrolyte mixing tank (6).

7. The method according to claim 6, wherein: The method further comprises: sending the cathode electrolyte (107) and the anode electrolyte (116) into a first cooler (5) and a second cooler (8) respectively for cooling, obtaining a cathode cooling electrolyte (108) and an anode cooling electrolyte (117), and sending them into an electrolyte mixing tank (6) for mixing; An ion membrane is provided between the cathode chamber (31) and the anode chamber (32).

8. The method according to claim 6, wherein: The temperature of the cathode electrolyte (107) is 40-90°C, and the temperature of the anode electrolyte (116) is 40-90°C; the temperature of the cathode cooling electrolyte (108) is 40-90°C, and the temperature of the anode cooling electrolyte (117) is 40-90°C.

9. The method according to claim 6, wherein: The first separator (4) and the second separator (7) are vertical gas-liquid separators or horizontal gas-liquid separators; the operating pressure in the first separator (4) is 0.05-2.0 MPa, and the operating temperature is 10-120°C; the operating pressure in the second separator (7) is 0.05-2.0 MPa, and the operating temperature is 10-120°C.

10. The method according to claim 6, wherein: The method further comprises feeding desalted water (119) into the electrolyte mixing tank (6) to replenish water consumed by the electrolysis reaction; the electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration range is 0.2-10 mol / L; The operating temperature of the first absorption unit (1) is 10-120°C, and the operating pressure is 0.05-2.0 MPa; the operating temperature of the second absorption unit (2) is 10-120°C, and the operating pressure is 0.05-2.0 MPa; The concentration of carbon dioxide in the carbon dioxide-containing raw gas (101) is 85% to 100% by volume; The operating temperature of the electrochemical reactor (3) is 10-120° C., and the operating pressure is 0.05-2.0 MPa.

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