Device and method for preparing methanol through electrocatalytic reduction of carbon dioxide by serially connected membrane electrode reactors

Abstract

The invention discloses a device and a method for preparing methanol through electrocatalytic reduction of carbon dioxide by serially connected membrane electrode reactors. The methanol preparation device comprises a CO2 electro-catalytic reduction membrane electrode reactor, a CO electro-catalytic reduction membrane electrode reactor, a wind-light intermittent renewable energy source and a control system, and the output end of the CO2 electro-catalytic reduction membrane electrode reactor is connected to the input end of the CO electro-catalytic reduction membrane electrode reactor; the CO2 electrocatalytic reduction membrane electrode reactor and the CO electrocatalytic reduction membrane electrode reactor are both electrically connected with the control system, and the control system is electrically connected with the wind-solar intermittent renewable energy source. According to the invention, wind and light intermittent renewable energy is used as a power source of the electro-catalytic reduction membrane electrode reactor, and the concentration of salt ions at the cathode in the electro-catalytic reduction membrane electrode reactor system is controlled through the control system by utilizing the volatility of the renewable energy, so that salting-out is slowed down, and the service life of the electro-catalytic reduction membrane electrode reactor is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanol preparation, and specifically relates to a device and method for preparing methanol by electrocatalytic reduction of carbon dioxide in a series membrane electrode reactor by utilizing the volatility of wind and solar green electricity. Background Art

[0002] The methods for converting carbon dioxide into methanol mainly include catalytic hydrogenation, electrochemical reduction, photocatalysis and biocatalysis. Among them, the electrochemical reduction method is to reduce carbon dioxide into methanol through electrochemical reaction. In the existing technology of converting carbon dioxide into methanol by electrochemical reduction, as the reaction proceeds, ions such as K in the anode liquid + Ions generated near the cathode, such as When the concentration of these ions exceeds their solubility limit, salt precipitation occurs. At the same time, during the electrolysis process, higher voltages lead to the formation of byproduct hydroxides, which combine with other ions to further promote the occurrence of salt precipitation. The salt precipitation problem seriously affects the performance of the electrolyzer, which will reduce the active area of ​​the membrane reactor, cause flooding and hinder gas transport, thereby limiting the long-term durability and industrial applicability of the electrolyzer.

[0003] The existing technology of converting carbon dioxide into methanol by electrochemical reduction does not mention a method for solving the problem of salt precipitation. Summary of the invention

[0004] The object of the present invention is to provide a device and method for producing methanol by electrocatalytic reduction of carbon dioxide in series with membrane electrode reactors by utilizing the volatility of wind and solar green electricity to mitigate the problem raised in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions.

[0006] In a first aspect, the present invention provides a device for producing methanol from carbon dioxide by electrocatalytic reduction of membrane electrode reactors in series, comprising a CO2 electrocatalytic reduction membrane electrode reactor, a CO electrocatalytic reduction membrane electrode reactor, intermittent renewable energy sources of wind and solar power, and a control system, wherein the output end of the CO2 electrocatalytic reduction membrane electrode reactor is conductively connected to the input end of the CO electrocatalytic reduction membrane electrode reactor, the CO2 electrocatalytic reduction membrane electrode reactor and the CO electrocatalytic reduction membrane electrode reactor are both electrically connected to the control system, and the control system is electrically connected to the intermittent renewable energy sources of wind and solar power.

[0007] Preferably, the control system includes an energy monitoring module, a voltage regulation module, an ion concentration monitoring module and a duty cycle control module; the energy monitoring module is used to monitor the operating status of intermittent renewable energy sources such as wind and solar power in real time, the voltage regulation module is used to regulate the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor and the CO electrocatalytic reduction membrane electrode reactor in real time, the ion concentration monitoring module is used to monitor the concentration of salt ions at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor and the CO electrocatalytic reduction membrane electrode reactor in real time, and the duty cycle control module is used to control the duty cycle of the voltage.

[0008] Preferably, one of the input ends of the CO2 electrocatalytic reduction membrane electrode reactor is conductively connected to the first peristaltic pump, and the other input end is conductively connected to the first flow controller, and the input end of the first flow controller is conductively connected to the first valve.

[0009] Preferably, one of the output ends of the CO2 electrocatalytic reduction membrane electrode reactor is conductively connected to the first gas-liquid separator, and the output end of the first gas-liquid separator is conductively connected to the input end of the first peristaltic pump.

[0010] Preferably, the other output end of the CO2 electrocatalytic reduction membrane electrode reactor is conductively connected to a NaOH solution capture trap, and the output end of the NaOH solution capture trap is conductively connected to one of the input ends of the CO electrocatalytic reduction membrane electrode reactor.

[0011] Preferably, another input end of the CO electrocatalytic reduction membrane electrode reactor is conductively connected to a second peristaltic pump.

[0012] Preferably, one of the output ends of the CO electrocatalytic reduction membrane electrode reactor is conductively connected to the second gas-liquid separator, and the output end of the second gas-liquid separator is conductively connected to the input end of the second peristaltic pump.

[0013] Preferably, the other output end of the CO electrocatalytic reduction membrane electrode reactor is conductively connected to a second valve, and the output end of the second valve is conductively connected to a second flow control meter.

[0014] In a second aspect, the present invention provides a method for producing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors, which comprises the following steps: energy monitoring; step 2, electrocatalytic reduction of CO2 to generate CO; step 3, CO transmission and intermediate processing; step 4, electrocatalytic reduction of CO to generate CH3OH; In the above step 1, the control system is used to monitor the operating status of the intermittent renewable energy sources of wind and solar in real time, and the CO2 electrocatalytic reduction membrane electrode reactor and the CO electrocatalytic reduction membrane electrode reactor are regulated accordingly; In the above step 2, CO2 is introduced into the cathode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor, and KOH solution is introduced into the anode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor. Under the action of electricity provided by intermittent renewable energy sources of wind and solar power, an electrocatalytic reduction reaction is carried out to convert CO2 into CO. At the same time, the control system adjusts the voltage and duty cycle according to the fluctuation of intermittent renewable energy sources of wind and solar power to control the salt ion concentration at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor to prevent salt precipitation; In the above step 3, the CO generated in step 1 is passed into a NaOH solution capture trap to remove CO2 therein to obtain pure CO; In the above step 4, the pure CO obtained in step 3 is introduced into the cathode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor, and the KHCO3 solution is introduced into the anode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor. Under the action of the electric power provided by the intermittent renewable energy of wind and solar power, an electrocatalytic reduction reaction is carried out to convert CO into CH3OH. At the same time, the control system adjusts the voltage and duty cycle according to the fluctuation of the intermittent renewable energy of wind and solar power to control the salt ion concentration at the cathode of the CO electrocatalytic reduction membrane electrode reactor to prevent salt precipitation.

[0015] Preferably, in step one, step two and step four, the specific steps for preventing salt precipitation are: when the output power of intermittent renewable energy sources such as wind and solar power is higher than a threshold value, reducing the duty cycle to reduce the formation of byproduct hydroxide and reduce the ion concentration; when the output power of intermittent renewable energy sources such as wind and solar power is lower than a threshold value, increasing the duty cycle to maintain ion transport.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts intermittent renewable energy such as wind and solar power as the power source of the electrocatalytic reduction membrane electrode reactor, utilizes the volatility of renewable energy, and controls the salt ion concentration at the cathode in the electrocatalytic reduction membrane electrode reactor system through a control system, thereby slowing down salt precipitation, thereby improving the operating life of the electrocatalytic reduction membrane electrode reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a device for producing methanol by electrocatalytic reduction of carbon dioxide in series with membrane electrode reactors according to the present invention; Figure 2 for Figure 1 The structural block diagram of the control system; Figure 3 The present invention is a flow chart of the method for producing methanol by electrocatalytic reduction of carbon dioxide by connecting membrane electrode reactors in series.

[0018] In the figure: 1. CO2 electrocatalytic reduction membrane electrode reactor; 11. first peristaltic pump; 12. first flow controller; 13. first valve; 14. first gas-liquid separator; 15. NaOH solution capture trap; 2. CO electrocatalytic reduction membrane electrode reactor; 21. second peristaltic pump; 22. second gas-liquid separator; 23. second valve; 24. second flow controller; 3. wind and solar intermittent renewable energy; 4. control system; 41. energy monitoring module; 42. voltage regulation module; 43. ion concentration monitoring module; 44. duty cycle control module. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Please see attached Figure 1 -Attached Figure 2An embodiment provided by the present invention is a device for producing methanol by electrocatalytic reduction of carbon dioxide by connecting membrane electrode reactors in series, comprising a CO2 electrocatalytic reduction membrane electrode reactor 1, a CO electrocatalytic reduction membrane electrode reactor 2, a wind-solar intermittent renewable energy source 3 and a control system 4, wherein the output end of the CO2 electrocatalytic reduction membrane electrode reactor 1 is conductively connected to the input end of the CO electrocatalytic reduction membrane electrode reactor 2, the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 are both electrically connected to the control system 4, the control system 4 is electrically connected to the wind-solar intermittent renewable energy source 3, the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 are used to provide a reaction site, and the wind-solar intermittent renewable energy source 3 is used to provide a reaction site for the CO2 electrocatalytic reduction membrane electrode reactor. The control system 4 is used to power the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2, and the control system 4 is used to monitor and adjust the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2; the control system 4 includes an energy monitoring module 41, a voltage regulation module 42, an ion concentration monitoring module 43 and a duty cycle control module 44. The control system 4 uses the energy monitoring module 41 to monitor the operating status of the wind and solar intermittent renewable energy 3 in real time, uses the voltage regulation module 42 to regulate the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time, and uses the ion concentration monitoring module 43 to monitor the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time. The concentration of salt ions at the cathode is controlled by using the duty cycle control module 44 to control the duty cycle of the voltage; one of the input ends of the CO2 electrocatalytic reduction membrane electrode reactor 1 is connected to the first peristaltic pump 11, and the other input end is connected to the first flow controller 12, the input end of the first flow controller 12 is connected to the first valve 13, the first peristaltic pump 11 is used to transport KOH, the first valve 13 is used to control the on and off of the CO2 transport pipeline, and the first flow controller 12 is used to control the CO2 flow; one of the output ends of the CO2 electrocatalytic reduction membrane electrode reactor 1 is connected to the first gas-liquid separator 14, and the output end of the first gas-liquid separator 14 is connected to the input end of the first peristaltic pump 11, and the first gas-liquid separator 14 is used to conduct electrolyte Gas-liquid separation; another output end of the CO2 electrocatalytic reduction membrane electrode reactor 1 is conductively connected to the NaOH solution capture trap 15, and the output end of the NaOH solution capture trap 15 is conductively connected to one of the input ends of the CO electrocatalytic reduction membrane electrode reactor 2, and the NaOH solution capture trap 15 is used to absorb CO2 in CO; another input end of the CO electrocatalytic reduction membrane electrode reactor 2 is conductively connected to the second peristaltic pump 21, and the second peristaltic pump 21 is used to transport KHCO3; one of the output ends of the CO electrocatalytic reduction membrane electrode reactor 2 is conductively connected to the second gas-liquid separator 22, and the output end of the second gas-liquid separator 22 is conductively connected to the input end of the second peristaltic pump 21, and the second gas-liquid separator 22 is used to perform gas-liquid separation on the electrolyte;The other output end of the CO electrocatalytic reduction membrane electrode reactor 2 is connected to the second valve 23, and the output end of the second valve 23 is connected to the second flow controller 24. The second valve 23 is used to control the on-off of the CH3OH discharge pipeline, and the second flow controller 24 is used to control the CH3OH flow. ;

[0021] Please see attached Figure 3 Another embodiment provided by the present invention is a method for producing methanol by electrocatalytic reduction of carbon dioxide by a series of membrane electrode reactors, which adopts the device for producing methanol by electrocatalytic reduction of carbon dioxide by a series of membrane electrode reactors described in Example 1, including step one, energy monitoring; step two, CO2 electroreduction to generate CO; step three, CO transmission and intermediate processing; step four, CO electroreduction to generate CH3OH.

[0022] In the above step one, the control system 4 is used to monitor the operating status of the wind and solar intermittent renewable energy 3 in real time, and the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 are regulated accordingly. Specifically, the control system 4 uses the energy monitoring module 41 to monitor the operating status of the wind and solar intermittent renewable energy 3 in real time, uses the voltage regulation module 42 to regulate the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time, uses the ion concentration monitoring module 43 to monitor the concentration of salt ions at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time, and uses the duty cycle control module 44 to control the duty cycle of the voltage.

[0023] In the above step 2, CO2 is introduced into the cathode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor 1, and 1M KOH solution is introduced into the anode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor 1. Under the action of the electric power provided by the wind and solar intermittent renewable energy 3, an electrocatalytic reduction reaction is carried out to convert CO2 into CO. At the same time, the control system 4 adjusts the voltage and duty cycle according to the fluctuation of the wind and solar intermittent renewable energy 3 to control the salt ion concentration at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor 1 to prevent salt precipitation. Specifically, when the output power of the wind and solar intermittent renewable energy 3 is higher than the threshold, the duty cycle is reduced to reduce the formation of by-product hydroxide and reduce the ion concentration; when the output power of the wind and solar intermittent renewable energy 3 is lower than the threshold, the duty cycle is increased to maintain the transport of ions.

[0024] In the above step 3, the CO generated in step 1 is passed into the NaOH solution capture trap 15 to remove the CO2 therein and obtain pure CO.

[0025] In the above step 4, the pure CO obtained in step 3 is introduced into the cathode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor 2, and a 0.5M KHCO3 solution is introduced into the anode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor 2. Under the action of the electric power provided by the wind and solar intermittent renewable energy 3, an electrocatalytic reduction reaction is carried out to convert CO into CH3OH. At the same time, the control system 4 adjusts the voltage and duty cycle according to the fluctuation of the wind and solar intermittent renewable energy 3 to control the salt ion concentration at the cathode of the CO electrocatalytic reduction membrane electrode reactor 2 to prevent salt precipitation. Specifically, when the output power of the wind and solar intermittent renewable energy 3 is higher than the threshold, the duty cycle is reduced to reduce the formation of by-product hydroxide and reduce the ion concentration; when the output power of the wind and solar intermittent renewable energy 3 is lower than the threshold, the duty cycle is increased to maintain the transport of ions.

[0026] When the present invention is used, the first valve 13 is opened to pass CO2 into the cathode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor 1, the CO2 flow rate is controlled by the first flow controller 12, and a 1M KOH solution is passed into the anode end plate inlet of the CO2 electrocatalytic reduction membrane electrode reactor 1 through the first peristaltic pump 11. After passing through the cathode gas diffusion layer, CO2 participates in the electrochemical reaction on the cathode cobalt phthalocyanine catalyst, and the generated CO2 / CO mixed gas enters the NaOH solution capture trap 15 through the cathode outlet. The unreacted electrolyte after participating in the electrochemical reaction enters the first gas-liquid separator 14 through the anode end plate outlet, and the separated The liquid returns to the inlet of the first peristaltic pump 11 through a pipeline for recycling; the NaOH solution capture trap 15 removes CO2, outputs pure CO, and passes it into the cathode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor 2. The 0.5M KHCO3 solution is passed into the anode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor 2 through the second peristaltic pump 21. The unreacted electrolyte after participating in the electrochemical reaction enters the second gas-liquid separator 22 through the anode end plate outlet. The separated liquid returns to the inlet of the second peristaltic pump 21 through a pipeline for recycling. The second valve 23 is opened to discharge the generated CH3OH, and the second flow controller 24 controls the The control system 4 uses an energy monitoring module 41 to monitor the output power and voltage of the intermittent renewable energy source 3 in real time, and accordingly uses a voltage regulating module 42 to adjust the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time, and uses an ion concentration monitoring module 43 to monitor the concentration of salt ions at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time, and uses a temperature monitoring module 44 to monitor the concentration of salt ions at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2 in real time. The duty cycle control module 44 controls the duty cycle of the voltage. When it is detected that the output power of the wind and solar intermittent renewable energy 3 is high, the voltage regulation module 42 increases the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2. At this time, the ion concentration monitoring module 43 will detect that the salt ion concentration at the cathode has an upward trend. In order to avoid the formation of a large amount of by-product hydroxide and salt precipitation, the duty cycle control module 44 reduces the duty cycle to reduce the voltage within a predetermined duty cycle. The voltage drop will cause the working current density to decrease, which temporarily reduces the formation of by-product hydroxide. At the same time, the K migrated from the anode liquid + Reduce, while There is extra time to move to the anode; when it is detected that the output power of the intermittent renewable energy source 3 of wind and solar power is low, the voltage regulation module 42 reduces the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor 1 and the CO electrocatalytic reduction membrane electrode reactor 2, and the duty cycle control module 44 increases the duty cycle to maintain the transport of ions in the electrocatalytic reduction system, thereby avoiding an imbalance in ion concentration and preventing the occurrence of salt precipitation.

[0027] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A device for producing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors, comprising a CO2 electrocatalytic reduction membrane electrode reactor (1), a CO electrocatalytic reduction membrane electrode reactor (2), wind and solar intermittent renewable energy (3) and a control system (4), characterized in that: The output end of the CO2 electrocatalytic reduction membrane electrode reactor (1) is conductively connected to the input end of the CO electrocatalytic reduction membrane electrode reactor (2); the CO2 electrocatalytic reduction membrane electrode reactor (1) and the CO electrocatalytic reduction membrane electrode reactor (2) are both electrically connected to a control system (4); and the control system (4) is electrically connected to wind and solar intermittent renewable energy (3).

2. The device for producing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors according to claim 1, characterized in that: The control system (4) comprises an energy monitoring module (41), a voltage regulating module (42), an ion concentration monitoring module (43) and a duty cycle control module (44). The energy monitoring module (41) is used to monitor the operating status of the wind and solar intermittent renewable energy (3) in real time. The voltage regulating module (42) is used to regulate the input voltage of the CO2 electrocatalytic reduction membrane electrode reactor (1) and the CO electrocatalytic reduction membrane electrode reactor (2) in real time. The ion concentration monitoring module (43) is used to monitor the concentration of salt ions at the cathode of the CO2 electrocatalytic reduction membrane electrode reactor (1) and the CO electrocatalytic reduction membrane electrode reactor (2) in real time. The duty cycle control module (44) is used to control the duty cycle of the voltage.

3. The device for producing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors according to claim 1, characterized in that: One of the input ends of the CO2 electrocatalytic reduction membrane electrode reactor (1) is conductively connected to a first peristaltic pump (11), the other input end is conductively connected to a first flow controller (12), and the input end of the first flow controller (12) is conductively connected to a first valve (13).

4. The device for producing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors according to claim 3, characterized in that: One of the output ends of the CO2 electrocatalytic reduction membrane electrode reactor (1) is conductively connected to the first gas-liquid separator (14), and the output end of the first gas-liquid separator (14) is conductively connected to the input end of the first peristaltic pump (11).

5. The device for producing methanol by electrocatalytic reduction of carbon dioxide using series-connected membrane electrode reactors according to claim 4, characterized in that: The other output end of the CO2 electrocatalytic reduction membrane electrode reactor (1) is conductively connected to the NaOH solution capture trap (15), and the output end of the NaOH solution capture trap (15) is conductively connected to one of the input ends of the CO electrocatalytic reduction membrane electrode reactor (2).

6. The device for producing methanol by electrocatalytic reduction of carbon dioxide using series-connected membrane electrode reactors according to claim 5, characterized in that: The other input end of the CO electrocatalytic reduction membrane electrode reactor (2) is conductively connected to a second peristaltic pump (21).

7. The device for producing methanol from carbon dioxide by electrocatalytic reduction of series-connected membrane electrode reactors according to claim 6, characterized in that: One of the output ends of the CO electrocatalytic reduction membrane electrode reactor (2) is conductively connected to the second gas-liquid separator (22), and the output end of the second gas-liquid separator (22) is conductively connected to the input end of the second peristaltic pump (21).

8. The device for producing methanol by electrocatalytic reduction of carbon dioxide using series-connected membrane electrode reactors according to claim 7, characterized in that: The other output end of the CO electrocatalytic reduction membrane electrode reactor (2) is conductively connected to a second valve (23), and the output end of the second valve (23) is conductively connected to a second flow control meter (24).

9. A method for preparing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors, which adopts the device for preparing methanol by electrocatalytic reduction of carbon dioxide using a series of membrane electrode reactors according to any one of claims 1 to 8, characterized in that: include: Step 1: Energy monitoring: using a control system (4) to monitor the operating status of wind and solar intermittent renewable energy (3) in real time, and regulating the CO2 electrocatalytic reduction membrane electrode reactor (1) and the CO electrocatalytic reduction membrane electrode reactor (2) accordingly; Step 2, CO2 is electro-reduced to generate CO: CO2 is introduced into the cathode end plate inlet of the CO2 electro-catalytic reduction membrane electrode reactor (1), and KOH solution is introduced into the anode end plate inlet of the CO2 electro-catalytic reduction membrane electrode reactor (1). Under the action of the electricity provided by the wind and solar intermittent renewable energy (3), an electro-catalytic reduction reaction is carried out to convert CO2 into CO. At the same time, the control system (4) adjusts the voltage and duty cycle according to the fluctuation of the wind and solar intermittent renewable energy (3) to control the salt ion concentration at the cathode of the CO2 electro-catalytic reduction membrane electrode reactor (1) to prevent salt precipitation; Step 3, CO transmission and intermediate treatment: the CO generated in step 1 is passed into a NaOH solution capture trap (15) to remove CO2 therein to obtain pure CO; Step 4, CO electroreduction to generate CH3OH: the pure CO obtained in step 3 is introduced into the cathode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor (2), and the KHCO3 solution is introduced into the anode end plate inlet of the CO electrocatalytic reduction membrane electrode reactor (2). Under the action of the electricity provided by the wind and solar intermittent renewable energy (3), an electrocatalytic reduction reaction is carried out to convert CO into CH3OH. At the same time, the control system (4) adjusts the voltage and duty cycle according to the fluctuation of the wind and solar intermittent renewable energy (3) to control the salt ion concentration at the cathode of the CO electrocatalytic reduction membrane electrode reactor (2) to prevent salt precipitation.

10. The method for preparing methanol by electrocatalytic reduction of carbon dioxide using series-connected membrane electrode reactors according to claim 9, characterized in that: In step 2 and step 4, the specific steps for preventing salt precipitation are: when the output power of the wind-solar intermittent renewable energy (3) is higher than the threshold, the duty cycle is reduced to reduce the formation of byproduct hydroxide and reduce the ion concentration; when the output power of the wind-solar intermittent renewable energy (3) is lower than the threshold, the duty cycle is increased to maintain the transport of ions.

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