Carbon dioxide electrolysis system and electrolysis method

Abstract

The invention discloses a carbon dioxide electrolysis system and an electrolysis method. The carbon dioxide electrolysis system comprises n SOEC galvanic piles, the n SOEC galvanic piles are connected in series, the n SOEC galvanic piles are sequentially marked as the first SOEC galvanic pile, the second SOEC galvanic pile, the third SOEC galvanic pile,..., and the nth SOEC galvanic pile in the series connection direction of the n SOEC galvanic piles, and n is at least 2; at least the cathode raw material inlet of the first SOEC stack is connected with a CO2 gas source; and at least the anode raw material inlet of the first SOEC stack is connected with a flow-aiding gas source. According to the carbon dioxide electrolysis system, pure CO2 is electrolyzed through the SOEC galvanic piles connected in series, the total conversion rate of CO2 can be increased, and the service life of the SOEC galvanic piles is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of solid oxide electrolysis cells, and in particular to a carbon dioxide electrolysis system and an electrolysis method. Background Art

[0002] In the face of the shortage of fossil fuels and the global warming crisis, converting CO2 into valuable fuels is an attractive solution for sustainable development. Solid oxide electrolysis cells (SOECs) can efficiently and directly convert CO2 into fuel gas CO using renewable electricity at high temperatures (750-1000°C). SOECs have the advantages of environmental protection, high energy efficiency, and long-term operation stability, and have broad practical prospects.

[0003] However, for a single CO2-SOEC cell or stack operating at high temperature, under high CO2 conversion rates, CO may be reduced to solid carbon, causing carbon deposition inside the electrolytic cell, leading to a serious degradation of electrolysis performance, and thus affecting the life of the SOEC cell or stack. Summary of the invention

[0004] The present application discloses a carbon dioxide electrolysis system and an electrolysis method. By arranging multiple SOEC stacks in series, the CO2 conversion rate in the pure carbon dioxide electrolysis system can be greatly improved, the service life of the stack and the stability of long-term operation can be increased, thereby optimizing and improving the system efficiency.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, the present application provides a carbon dioxide electrolysis system, comprising: n SOEC stacks, the n SOEC stacks are connected in series, and the n SOEC stacks are sequentially recorded as a first SOEC stack, a second SOEC stack, a third SOEC stack, ..., an nth SOEC stack along the series direction thereof, wherein n is a natural number greater than or equal to 2;

[0007] At least the cathode raw material inlet of the first SOEC stack is connected to a CO2 gas source;

[0008] At least the anode raw material inlet of the first SOEC stack is connected to a flow-assisting gas source.

[0009] The above-mentioned carbon dioxide electrolysis system electrolyzes pure CO2 through at least two SOEC stacks connected in series, which can improve the total conversion rate of CO2. Specifically, the carbon dioxide electrolysis system of the present application includes at least two SOEC stacks connected in series, and the cathode raw material inlet of at least the first SOEC stack is connected to the CO2 gas source. By distributing CO2 to different SOEC stacks for electrolysis, the CO2 conversion rate of each SOEC stack can be kept in an appropriate range, avoiding the CO2 conversion rate of a single stack being too high, resulting in further generation of C from CO, causing carbon deposition problems inside the SOEC stack, and affecting the service life of the SOEC stack. Compared with the traditional single stack electrolysis system, the carbon dioxide electrolysis system of the present application includes at least two SOEC stacks connected in series, and the CO2 conversion rate of each SOEC stack can be controlled within its maximum conversion rate range. The CO2 conversion rate of the entire system can be increased to more than n times of the traditional single SOEC stack system by connecting in series, and C deposition can be prevented at the same time. Therefore, the carbon dioxide electrolysis system of the present application can significantly improve the total conversion rate of CO2 and extend the service life of the SOEC stack.

[0010] In some embodiments, the CO2 conversion rate of the carbon dioxide electrolysis system is greater than or equal to 60%.

[0011] In some embodiments, the CO2 conversion rate of the carbon dioxide electrolysis system is greater than or equal to 70%, and more preferably greater than 80%.

[0012] In some embodiments, the carbon dioxide electrolysis system further comprises a gas separator, a CO storage tank, and an O2 storage tank;

[0013] The gas separator comprises a first gas inlet, a first gas outlet and a second gas outlet, wherein the first gas inlet is connected to the cathode product outlet of the nth SOEC stack, the first gas outlet is connected to the CO2 gas source, and the second gas outlet is connected to the CO storage tank;

[0014] The O2 storage tank is connected to the anode product outlet of the nth SOEC stack.

[0015] In some embodiments, the carbon dioxide electrolysis system further comprises a first heat exchanger and a second heat exchanger;

[0016] The first heat exchanger comprises a second air inlet, a third air inlet, a third air outlet and a fourth air outlet, wherein the second air inlet is connected to the cathode product outlet of the nth SOEC stack, the third air inlet is connected to the CO2 gas source, the third air outlet is connected to the first air inlet of the gas separator, and the fourth air outlet is connected to the cathode raw material inlet of the first SOEC stack;

[0017] The second heat exchanger includes a fourth air inlet, a fifth air inlet, a fifth air outlet and a sixth air outlet, the fourth air inlet is connected to the anode product outlet of the nth SOEC stack, the fifth air inlet is connected to the flow-aiding gas source, the fifth air outlet is connected to the O2 storage tank, and the sixth air outlet is connected to the anode raw material inlet of the first SOEC stack.

[0018] In some embodiments, the carbon dioxide electrolysis system further includes a first heater and a second heater;

[0019] The first heater is used to heat CO2 entering the cathode raw material inlet of the first SOEC stack;

[0020] The second heater is used to heat the flow-aiding gas entering the anode raw material inlet of the first SOEC stack.

[0021] In some embodiments, both the first heater and the second heater are electric heaters;

[0022] The first heater comprises a sixth air inlet and a seventh air outlet, the sixth air inlet is connected to the CO2 gas source, and the seventh air outlet is connected to the cathode raw material inlet of the first SOEC stack;

[0023] The second heater includes a seventh air inlet and an eighth air outlet, the seventh air inlet is connected to the flow-aiding gas source, and the eighth air outlet is connected to the anode raw material inlet of the first SOEC stack.

[0024] In some embodiments, the first heater is a burner, and the carbon dioxide electrolysis system further comprises a first flow divider and a second flow divider;

[0025] The first splitter comprises an eighth air inlet, a ninth air outlet and a tenth air outlet, the eighth air inlet is connected to the cathode product outlet of the nth SOEC stack, and the ninth air outlet is connected to the second air inlet of the first heat exchanger;

[0026] The second splitter comprises a ninth air inlet, an eleventh air outlet and a twelfth air outlet, the ninth air inlet is connected to the anode product outlet of the nth SOEC stack, and the eleventh air outlet is connected to the fourth air inlet of the second heat exchanger;

[0027] The burner comprises a tenth air inlet, an eleventh air inlet, a twelfth air inlet and a thirteenth air outlet, the tenth air inlet is connected to the tenth air outlet of the first flow divider, the eleventh air inlet is connected to the twelfth air outlet of the second flow divider, and the twelfth air inlet is used to introduce an oxidant;

[0028] The second heat exchanger also includes a thirteenth air inlet and a fourteenth air outlet, and the first heat exchanger also includes a fourteenth air inlet and a fifteenth air outlet; the thirteenth air outlet is connected to the thirteenth air inlet of the second heat exchanger, and the fourteenth air outlet is connected to the fourteenth air inlet of the first heat exchanger.

[0029] In some embodiments, the carbon dioxide electrolysis system further includes a gas-liquid separator, which is used to separate the liquid and gas generated by the burner;

[0030] The gas-liquid separator comprises a fifteenth air inlet and a sixteenth air outlet, the fifteenth air inlet is connected to the fifteenth air outlet of the first heat exchanger, and the sixteenth air outlet is connected to the CO2 gas source.

[0031] In some embodiments, the carbon dioxide electrolysis system further includes a first mass flow controller and a second mass flow controller;

[0032] The first mass flow controller is disposed between the CO2 gas source and a cathode raw material inlet of a first SOEC stack connected to the CO2 gas source;

[0033] The second mass flow controller is arranged between the flow-aiding gas source and the anode raw material inlet of the first SOEC stack connected to the flow-aiding gas source.

[0034] In some embodiments, the carbon dioxide electrolysis system further comprises a plurality of temperature sensors and a plurality of gas concentration sensors;

[0035] The plurality of temperature sensors are dispersedly disposed at both ends of each SOEC stack;

[0036] The multiple gas concentration sensors are dispersedly disposed at both ends of each SOEC stack.

[0037] In some embodiments, the carbon dioxide electrolysis system further comprises a power generation device, wherein the power generation device is electrically connected to the cathode and anode of each SOEC stack; the power generation device comprises a photovoltaic power generation device.

[0038] In a second aspect, the present application provides a method for electrolyzing carbon dioxide, comprising:

[0039] CO2 is electrolyzed using the carbon dioxide electrolysis system as described in the first aspect, and during the electrolysis process, the CO2 conversion rate of each SOEC stack is controlled to meet a preset target CO2 conversion rate.

[0040] The carbon dioxide electrolysis method of the present application utilizes multiple SOEC stacks connected in series to electrolyze pure CO2, and controls the CO2 conversion rate of each SOEC stack to meet the preset target CO2 conversion rate, thereby avoiding the problem of carbon deposition inside the SOEC stack due to the excessively high CO2 conversion rate of a single stack, thereby shortening the service life of the SOEC stack. Compared with the traditional single stack electrolysis system, the present application significantly improves the total conversion rate of CO2 and prolongs the service life of the SOEC stack.

[0041] In some embodiments, the preset target CO2 conversion rate is 10%-20%.

[0042] In some embodiments, controlling the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate includes:

[0043] The applied voltage, operating temperature and CO2 injection amount of each SOEC stack are controlled so that the CO2 conversion rate of each SOEC stack meets the preset target CO2 conversion rate.

[0044] In some embodiments, the applied voltage of each of the SOEC stacks is 1.0V-1.2V.

[0045] In some embodiments, the operating temperature of each SOEC stack is 700°C-850°C.

[0046] In some embodiments, the power generation device of the carbon dioxide electrolysis system is a photovoltaic power generation device, and the controlling of the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate includes:

[0047] Obtaining the total power generated by the power generation device, and determining the number of SOEC stacks to be started based on the total power generated and the preset target power of each SOEC stack;

[0048] Based on the preset target power and the preset target CO2 conversion rate of each SOEC stack to be started, the target CO2 flow rate and the target total CO2 flow rate of each SOEC stack to be started are obtained;

[0049] Based on the target total CO2 flow rate, adjusting the CO2 flow rate into each SOEC stack through a first mass flow controller;

[0050] Turn on the SOEC stack, and obtain the actual operating temperature, CO2 intake and CO2 output of each SOEC stack through a temperature sensor and a gas concentration sensor to obtain the actual CO2 conversion rate of each SOEC stack;

[0051] Based on the actual CO2 conversion rate of each of the SOEC stacks, the applied voltage of each of the SOEC stacks is regulated to control the CO2 conversion of each of the SOEC stacks to meet a preset target CO2 conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of the structure of a carbon dioxide electrolysis system provided in an embodiment of the present application;

[0053] Figure 2 A schematic structural diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application;

[0054] Figure 3 A schematic structural diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application;

[0055] Figure 4 A schematic structural diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application;

[0056] Figure 5 A schematic diagram of a process for electrolyzing carbon dioxide provided in an embodiment of the present application;

[0057] Figure 6 A schematic diagram of a process for electrolyzing carbon dioxide provided in an embodiment of the present application;

[0058] Figure 7 A schematic diagram of a process for electrolyzing carbon dioxide provided in an embodiment of the present application;

[0059] Figure 8 A schematic diagram of the structure of a carbon dioxide electrolysis system provided in an embodiment of the present application;

[0060] Fig. 9 A schematic structural diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application;

[0061] Fig.10 A schematic structural diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application;

[0062] Fig.11 A schematic diagram of a process for electrolyzing carbon dioxide provided in an embodiment of the present application;

[0063] Icons: 1. Gas separator; 11. First air inlet; 12. First air outlet; 13. Second air outlet; 2. First heat exchanger; 201. First sub-heat exchanger; 202. Second sub-heat exchanger; 21. Second air inlet; 22. Third air inlet; 23. Third air outlet; 24. Fourth air outlet; 25. Fourteenth air inlet; 26. Fifteenth air outlet; 27. Sixteenth air inlet; 28. Eighteenth air outlet; 3. Second heat exchanger; 301. Third sub-heat exchanger; 302. Fourth sub-heat exchanger; 31. Fourth air inlet; 32. Fifth air inlet; 33. Fifth air outlet; 34. Sixth air outlet; 35. Thirteenth air inlet; 36. Fourteenth air outlet; 37. Seventeenth air inlet; 38. Seventeenth air outlet; 4. First Heater; 41, the sixth air inlet; 42, the seventh air outlet; 5, the second heater; 51, the seventh air inlet; 52, the eighth air outlet; 6, the burner; 61, the tenth air inlet; 62, the eleventh air inlet; 63, the twelfth air inlet; 64, the thirteenth air outlet; 7, the first diverter; 71, the eighth air inlet; 72, the ninth air outlet; 73, the tenth air outlet; 8, the second diverter; 81, the ninth air inlet; 82, the eleventh air outlet; 83, the twelfth air outlet; 9, the gas-liquid separator; 91, the fifteenth air inlet; 92, the sixteenth air outlet; 01, the first mass flow controller; 02, the second mass flow controller; 03, the temperature sensor; 04, the gas concentration sensor; 05, the pressure reducing valve; 06, the gas compressor. DETAILED DESCRIPTION

[0064] The following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application. Among them, in the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" refers to two or more than two.

[0065] The terms "first" and "second" are used for descriptive purposes only and should not be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more.

[0066] For a single CO2-SOEC cell or stack operating at high temperature, CO may be reduced to solid carbon under high CO2 conversion rate, causing carbon deposition inside the electrolytic cell, resulting in a serious decrease in electrolysis performance, and thus affecting the life of the SOEC cell or stack. Therefore, there is currently a lack of an electrolysis system that can improve the CO2 conversion rate and can operate stably for a long time.

[0067] Based on the above problems, an embodiment of the present application provides a carbon dioxide electrolysis system, which may be an electrolysis system that only includes CO2 electrolysis raw materials. Figure 1 This is a schematic diagram of the structure of a carbon dioxide electrolysis system provided in an embodiment of the present application. Figure 1 As shown, the carbon dioxide electrolysis system includes n SOEC stacks, which are connected in series, and the n SOEC stacks are sequentially recorded as the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., the nth SOEC stack along the series direction, wherein n is a natural number greater than or equal to 2. For example, the number of SOEC stacks in series can be 2, 3, 4, 5, 6, 7, etc., and the actual number depends on the situation. In this application, SOEC stacks in series refer to the fuel poles of SOEC in series.

[0068] Each SOEC stack may include a cathode, an anode, and an electrolyte disposed between the cathode and the anode. Figure 1 Taking the first SOEC stack shown as an example, the upper part of the first SOEC stack is the cathode, the lower part is the anode, the upper left part is the cathode raw material inlet, the lower left part is the anode raw material inlet, the upper right part is the cathode product outlet, and the lower right part is the anode product outlet.

[0069] The specific connection method of n SOEC stacks is: the cathode product outlet of the first SOEC stack is connected to the cathode raw material inlet of the second SOEC stack, and the anode product outlet of the first SOEC stack is connected to the anode raw material inlet of the second SOEC stack; the cathode product outlet of the second SOEC stack is connected to the cathode raw material inlet of the third SOEC stack, and the anode product outlet of the second SOEC stack is connected to the anode raw material inlet of the third SOEC stack; and so on, until it is connected to the nth SOEC stack.

[0070] The total electrochemical reaction in the SOEC stack of the present application embodiment is CO2→CO+0.5O2, where the cathode reaction is CO2+2e - →CO+O 2- The anode reaction is O 2- →O2+2e - .

[0071] Among the n SOEC stacks, at least the cathode raw material inlet of the first SOEC stack is connected to a CO2 gas source. Figure 1 As shown, only the cathode raw material inlet of the first SOEC stack is connected to the CO2 gas source. Figure 1 In the case shown, the cathode raw material of the subsequent SOEC stack needs to be provided by the preceding SOEC stack, that is, the cathode product of the preceding SOEC stack includes CO2 and a portion of CO, which enter the subsequent SOEC stack together. Under preferred conditions, in order to further improve the electrolysis efficiency of the SOEC stack for CO2, the cathode material of the SOEC in each stack can be adjusted according to the CO2 partial pressure range of the stack.

[0072] Figure 2 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application. Figure 2 As shown, the cathode raw material inlets of the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., and the nth SOEC stack are all connected to the CO2 gas source. Figure 2 In the case shown, the cathode product of the preceding SOEC stack and the supplementary CO2 gas source will enter the succeeding SOEC stack at the same time. The supplementary CO2 gas source can make up for the shortage of CO2 on the one hand, and reduce the carbon deposition reaction caused by high concentration of CO on the other hand, thus extending the service life of the system.

[0073] In the n SOEC stacks, at least the anode raw material inlet of the first SOEC stack is connected to the flow-assisting gas source. Figure 1 As shown, only the anode raw material inlet of the first SOEC stack is connected to the flow-aiding gas source. The flow-aiding gas source can deliver a fluid of a specific temperature to the SOEC stack to maintain the temperature of the stack, and at the same time can drive the flow of gas inside the stack. It should be noted that the anode raw material inlets of the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., and the nth SOEC stack can also be connected to the flow-aiding gas source. The flow-aiding gas source can be air, inert gas or other gas, among which air is a more economical choice.

[0074] The above-mentioned carbon dioxide electrolysis system electrolyzes pure CO2 through at least two SOEC stacks connected in series, which can improve the total conversion rate of CO2. Specifically, the carbon dioxide electrolysis system of the present application includes at least two SOEC stacks connected in series, and the cathode raw material inlet of at least the first SOEC stack is connected to the CO2 gas source. By distributing CO2 to different SOEC stacks for electrolysis, the CO2 conversion rate of each SOEC stack can be kept in an appropriate range, avoiding the CO2 conversion rate of a single stack being too high, resulting in further generation of C from CO, causing carbon deposition problems inside the SOEC stack, and affecting the service life of the SOEC stack. Compared with the traditional single stack electrolysis system, the carbon dioxide electrolysis system of the present application includes at least two SOEC stacks connected in series, and the CO2 conversion rate of each SOEC stack can be controlled within its maximum conversion rate range. The CO2 conversion rate of the entire system can be increased to more than n times of the traditional single SOEC stack system by connecting in series, and C deposition can be prevented at the same time. Therefore, the carbon dioxide electrolysis system of the present application can significantly improve the total conversion rate of CO2 and is conducive to extending the service life of the SOEC stack.

[0075] The CO2 conversion rate of the carbon dioxide electrolysis system of the embodiment of the present application can reach more than 60%, preferably more than 70%, and more preferably more than 80%, for example 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 82%, 85%, 90%, etc., depending on the specific circumstances.

[0076] In some embodiments, Figure 1 and Figure 2 As shown, the carbon dioxide electrolysis system of the embodiment of the present application also includes a gas separator 1, a CO storage tank and an O2 storage tank. Among them, the gas separator 1 includes a first air inlet 11, a first air outlet 12 and a second air outlet 13, and the first air inlet 11 is connected to the cathode product outlet of the nth SOEC stack, so that the cathode product flows into the gas separator 1. It can be understood that the cathode product includes CO and unreacted CO2, and the gas separator 1 can separate CO and CO2, and then CO2 flows out from the first air outlet 12, which can continue to be used as a CO2 gas source, and CO flows out from the second air outlet 13 and enters the CO storage tank for storage, ready for subsequent use. The anode product O2 of the nth SOEC stack flows out and enters the O2 storage tank for storage. It should be noted that the cathode product of the nth SOEC stack includes CO and unreacted CO2 produced by the entire system, and the anode product of the nth SOEC stack includes O2 produced by the entire system. The setting of the gas separator 1 in the present application recycles the unreacted CO2, which can further improve the utilization rate of CO2 and greatly improve the overall CO2 conversion rate and system efficiency.

[0077] In some embodiments, Figure 1 and Figure 2 As shown, the carbon dioxide electrolysis system of the embodiment of the present application also includes a first heat exchanger 2 and a second heat exchanger 3. Among them, the first heat exchanger 2 includes a second air inlet 21, a third air inlet 22, a third air outlet 23 and a fourth air outlet 24. The second air inlet 21 is connected to the cathode product outlet of the nth SOEC stack, and the third air inlet 22 is connected to the CO2 gas source, which is used to introduce the high-temperature gas product generated by the cathode into the first heat exchanger 2, and heat the CO2 flowing through the first heat exchanger 2 to play a preheating role. The third air outlet 23 is connected to the first air inlet 11 of the gas separator 1, which is used to separate and recycle the cathode product after natural cooling. The fourth air outlet 24 is connected to the cathode raw material inlet of the first SOEC stack, which is used to introduce the preheated CO2 gas into the cathode of the SOEC stack for electrolysis reaction.

[0078] The second heat exchanger 3 includes a fourth air inlet 31, a fifth air inlet 32, a fifth air outlet 33 and a sixth air outlet 34. The fourth air inlet 31 is connected to the anode product outlet of the nth SOEC stack, and the fifth air inlet 32 ​​is connected to the flow-aiding gas source, which is used to introduce the high-temperature gas product generated by the anode into the second heat exchanger 3, and heat the flow-aiding gas flowing through the second heat exchanger 3 to play a preheating role. The fifth air outlet 33 is connected to the O2 storage tank, which is used to collect and store the anode product after natural cooling. The sixth air outlet 34 is connected to the anode raw material inlet of the first SOEC stack, which is used to introduce the preheated flow-aiding gas into the anode of the SOEC stack to provide the temperature required for the electrolysis process for the SOEC stack.

[0079] In the present application, the oxygen and the flow-aiding gas generated by electrolysis flow out from the anode product outlet of the nth SOEC stack to obtain an oxygen-rich mixed gas. In some embodiments of the present application, when the flow-aiding gas is not O2, a gas separator can be further provided between the second heat exchanger 3 and the O2 storage tank to separate O2 from the flow-aiding gas, and the obtained O2 enters the O2 storage tank for storage, and the obtained flow-aiding gas is led to the flow-aiding gas source for recycling.

[0080] The present application can realize the cascade utilization of energy of the high-temperature gas products of the system by setting the first heat exchanger 2 and the second heat exchanger 3, thereby improving the energy utilization efficiency of the system, which is beneficial to improving the CO2 conversion rate.

[0081] In some embodiments, Figure 1 and Figure 2As shown, the carbon dioxide electrolysis system of the embodiment of the present application further includes a first heater 4 and a second heater 5. The first heater 4 is used to heat the CO2 entering the cathode raw material inlet of the first SOEC stack; the second heater 5 is used to heat the flow-aiding gas entering the anode raw material inlet of the first SOEC stack. The first heater 4 and the second heater 5 of the present application are used to further heat the CO2 and the flow-aiding gas to meet the temperature requirements of the cathode raw material inlet and the anode raw material inlet of the SOEC stack, thereby facilitating the subsequent electrolysis reaction and improving the CO2 conversion rate.

[0082] In the present application, the types of the first heater 4 and the second heater 5 may be known to those skilled in the art. Figure 1 and Figure 2 As shown, the first heater 4 and the second heater 5 are both electric heaters. The first heater 4 includes a sixth air inlet 41 and a seventh air outlet 42. The sixth air inlet 41 is connected to the fourth air outlet 24 of the first heat exchanger 2, and is used to continue heating the preheated CO2 to meet the temperature requirement of the cathode raw material inlet, and then flows out from the seventh air outlet 42 and enters the cathode raw material inlet of the first SOEC stack.

[0083] The second heater 5 includes a seventh air inlet 51 and an eighth air outlet 52. The seventh air inlet 51 is connected to the flow-aiding gas source and is used to continue heating the preheated flow-aiding gas to meet the temperature requirement of the anode raw material inlet, and then flows out from the eighth air outlet 52 and enters the anode raw material inlet of the first SOEC stack.

[0084] Figure 3 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application. Figure 3 As shown, in some embodiments, the first heater 4 may also be a burner 6 , and the carbon dioxide electrolysis system of the embodiment of the present application further includes a first splitter 7 and a second splitter 8 .

[0085] The first flow divider 7 includes an eighth air inlet 71, a ninth air outlet 72 and a tenth air outlet 73. The eighth air inlet 71 is connected to the cathode product outlet of the nth SOEC stack, and is used to divide the cathode products (CO and CO2), wherein most of the cathode products flow into the first heat exchanger 2 through the ninth air outlet 72 to heat CO2, and another part of the cathode products enter the burner through the tenth air outlet 73 and the tenth air inlet 61 of the burner to participate in the subsequent combustion reaction.

[0086] The second flow divider 8 includes a ninth air inlet 81, an eleventh air outlet 82 and a twelfth air outlet 83. The ninth air inlet 81 is connected to the anode product outlet of the nth SOEC stack, and is used to divide the anode product O2, wherein most of the anode product flows into the second heat exchanger 3 through the eleventh air outlet 82, playing the role of heating the flow-aiding gas, and another part of the anode product enters the burner through the twelfth air outlet 83 and the eleventh air inlet 62 of the burner to participate in the subsequent combustion reaction.

[0087] Reference Figure 3 The first heat exchanger 2 of the embodiment of the present application includes two connected sub-heat exchangers (i.e., the first sub-heat exchanger 201 and the second sub-heat exchanger 202), and the second heat exchanger 3 also includes two connected sub-heat exchangers (i.e., the third sub-heat exchanger 301 and the fourth sub-heat exchanger 302). After the heat exchange in the preceding sub-heat exchanger is completed, CO2 and the flow-aiding gas will be introduced into the corresponding subsequent sub-heat exchanger along the air flow direction to continue the heat exchange.

[0088] Specifically, the heat exchange of the flow-aiding gas is divided into two steps: first, the anode product of the nth SOEC stack enters the third sub-heat exchanger 301 through the eleventh gas outlet 82 and the fourth gas inlet 31, and the first step of heat exchange is performed on the flow-aiding gas; thereafter, the flow-aiding gas after heat exchange enters the fourth sub-heat exchanger 302 through the sixth gas outlet 34 and the seventeenth gas inlet 37. Since part of the CO and O2 entering the burner 6 undergo a combustion reaction to generate high-temperature combustion gas, the high-temperature combustion gas enters the fourth sub-heat exchanger 302 through the thirteenth gas outlet 64 and the thirteenth gas inlet 35, and the second step of heat exchange is performed on the flow-aiding gas, so that the flow-aiding gas reaches the temperature requirement of the anode raw material inlet, and flows out from the seventeenth gas outlet 38 to enter the anode raw material inlet.

[0089] The heat exchange of CO2 is also divided into two steps: first, the high-temperature combustion gas in the fourth sub-heat exchanger 302 enters the first sub-heat exchanger 201 through the fourteenth gas outlet 36 and the fourteenth gas inlet 25, and is used to perform the first step of heat exchange on CO2 (the temperature of the high-temperature combustion gas is about 400-500°C at this time); thereafter, the heat-exchanged CO2 enters the second sub-heat exchanger 202 through the fourth gas outlet 24 and the sixteenth gas inlet 27. Since the cathode product of the nth SOEC stack is high-temperature gas, the high-temperature gas enters the second sub-heat exchanger 202 through the ninth gas outlet 72 and the second gas inlet 21, and performs the second step of heat exchange on CO2 (the temperature of the high-temperature gas is about 800°C), so that CO2 reaches the temperature requirement of the cathode raw material inlet, and flows out from the eighteenth gas outlet 28 to enter the cathode raw material inlet.

[0090] The burner 6 also includes a twelfth air inlet 63, which is used to introduce a combustion aid (such as a supplementary fuel such as hydrocarbon fuel) to ensure that there is sufficient fuel in the burner 6. The temperature generated by the combustion can heat the flow-aiding gas and CO2 to meet the requirements of the fuel cell stack raw material inlet, thereby facilitating the subsequent electrolysis reaction and improving the CO2 conversion rate.

[0091] In some embodiments, Figure 3 As shown, the first sub-heat exchanger 201 also includes a fifteenth gas outlet 26, and the carbon dioxide electrolysis system of the embodiment of the present application also includes a gas-liquid separator 9, which is used to separate the liquid and gas produced by the burner 6. The gas-liquid separator 9 includes a fifteenth gas inlet 91 and a sixteenth gas outlet 92. The fifteenth gas inlet 91 is connected to the fifteenth gas outlet 26 of the first sub-heat exchanger 201, and is used to separate the mixed gas discharged from the fifteenth gas outlet 26. It can be understood that after the high-temperature gas is cooled, part of the gas will be converted into liquid (such as water, etc.), and the rest will remain as gas (such as CO2, etc.). The gas-liquid separator 9 separates the liquid and the gas, and the gas flows out through the sixteenth gas outlet 92 and continues to be used as a CO2 gas source. The setting of the gas-liquid separator 9 in the present application can further improve the utilization rate of CO2.

[0092] Figure 4 A schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of the present application. In some embodiments, Figure 4 As shown, when the high-temperature gas generated by the burner 6 can heat CO2 and the flow-aiding gas, the pipelines for directly preheating CO2 and the flow-aiding gas with the cathode high-temperature products and the anode high-temperature products of the SOEC stack can be eliminated, and the high-temperature gas generated by the burner 6 can be directly used to heat the gas source, making the system structure simpler.

[0093] In some embodiments, Figure 1-Figure 3 As shown, the carbon dioxide electrolysis system of the embodiment of the present application also includes a first mass flow controller 01 and a second mass flow controller 02. Among them, the first mass flow controller 01 is arranged between the CO2 gas source and the cathode raw material inlet of the first SOEC stack connected to the CO2 gas source, and is used to regulate the CO2 intake of the entire system. The second mass flow controller 02 is arranged between the flow-aiding gas source and the anode raw material inlet of the first SOEC stack connected to the flow-aiding gas source, and is used to regulate the intake of the flow-aiding gas of the entire system. By setting the first mass flow controller 01 and the second mass flow controller 02, the total conversion rate of CO2 of the entire system can be adjusted, and it is beneficial to extend the service life of the SOEC stack.

[0094] In some embodiments, Figure 1-Figure 3As shown, the carbon dioxide electrolysis system of the embodiment of the present application also includes multiple temperature sensors 03 and multiple gas concentration sensors 04. Multiple temperature sensors 03 are dispersed at both ends of each SOEC stack; multiple gas concentration sensors 04 are dispersed at both ends of each SOEC stack. In other words, temperature sensors 03 and gas concentration sensors 04 are provided at both ends of the inlet and outlet of each SOEC stack to monitor the temperature and gas volume during the operation of the stack, and further adjust parameters such as the CO2 input amount according to the monitoring results to control the CO2 conversion rate of the entire system, which is conducive to extending the service life of the SOEC stack.

[0095] In some embodiments, Figure 1-Figure 3 As shown, the carbon dioxide electrolysis system of the embodiment of the present application also includes a power generation device, which is electrically connected to each SOEC stack to supply power to each SOEC stack. The power generation device of the present application is a renewable energy power generation device, such as a photovoltaic power generation device. The renewable energy power generation device converts CO2 into CO by supplying power to the SOEC stack, without causing additional carbon emission burden.

[0096] In addition, the carbon dioxide electrolysis system of the embodiment of the present application further includes a pressure reducing valve 05 and a gas compressor 06. The pressure reducing valve 05 is arranged between the CO2 gas source and the first mass flow controller 01, and is used to appropriately reduce the pressure of the CO2 gas source and maintain a stable pressure output. The gas compressor 06 is arranged between the flow-aiding gas source and the second mass flow controller 02, and is used to provide power for the flow-aiding gas.

[0097] The present application also provides a method for electrolyzing carbon dioxide. Figure 5 The carbon dioxide electrolysis method shown comprises the following steps:

[0098] S501. Electrolyze CO2 using a carbon dioxide electrolysis system, and during the electrolysis process, control the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate.

[0099] The carbon dioxide electrolysis method of the present application utilizes multiple SOEC stacks connected in series to electrolyze pure CO2, and controls the CO2 conversion rate of each SOEC stack to meet the preset target CO2 conversion rate, thereby avoiding the problem of carbon deposition inside the SOEC stack due to the excessively high CO2 conversion rate of a single stack, thereby shortening the service life of the SOEC stack. Compared with the traditional single stack electrolysis system, the present application significantly improves the total conversion rate of CO2 and prolongs the service life of the SOEC stack.

[0100] In some embodiments, the preset target CO2 conversion rate is 10%-20%, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and the specific value depends on the situation. The electrolysis method of the present application can make the total CO2 conversion rate reach more than 80%, which is significantly higher than the CO2 conversion rate (10%-20%) of the traditional dry electrolysis system at the same electrolysis time. The present application ensures the normal operation of the stack by controlling the CO2 conversion rate range of each SOEC stack, thereby extending the service life of the stack and enabling the stack to maintain stable operation for a long time.

[0101] In some embodiments, Figure 6 As shown, controlling the CO2 conversion rate of each SOEC stack to meet the preset target CO2 conversion rate includes the following steps:

[0102] S601, controlling the applied voltage, operating temperature, and CO2 input amount of each SOEC stack so that the CO2 conversion rate of each SOEC stack meets the preset target CO2 conversion rate.

[0103] In some embodiments, the applied voltage of each SOEC stack is 1.0V-1.2V, for example, 1.0V, 1.02V, 1.04V, 1.06V, 1.08V, 1.1V, 1.12V, 1.14V, 1.16V, 1.18V, 1.2V, etc., and the specific value depends on the situation.

[0104] In some embodiments, the operating temperature of each SOEC stack is 700°C-850°C, for example 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, etc., and the specific value depends on the situation.

[0105] In some embodiments, Figure 7 As shown, the power generation device of the carbon dioxide electrolysis system of the embodiment of the present application is a photovoltaic power generation device, and the CO2 conversion rate of each SOEC stack is controlled to meet the preset target CO2 conversion rate, including the following steps:

[0106] S701, obtaining the total power generation of the power generation device, and determining the number of SOEC stacks to be started based on the total power generation and the preset target power of each SOEC stack;

[0107] S702, based on the preset target power and preset target CO2 conversion rate of each SOEC stack to be started, obtaining the target CO2 flow rate and the target total CO2 flow rate of each SOEC stack to be started;

[0108] S703, based on the target total CO2 flow rate, adjusting the CO2 flow rate entering each SOEC stack through a first mass flow controller;

[0109] S704, start the SOEC stack, obtain the actual operating temperature, CO2 intake and CO2 output of each SOEC stack through the temperature sensor and the gas concentration sensor, and obtain the actual CO2 conversion rate of each SOEC stack;

[0110] S705. Based on the actual CO2 conversion rate of each SOEC stack, the applied voltage of each SOEC stack is adjusted to control the CO2 conversion of each SOEC stack to meet the preset target CO2 conversion rate.

[0111] In the above S701, after obtaining the total power generation of the power generation device, the first SOEC stack is started first. When the operating power of the first SOEC stack reaches its preset target power, the next SOEC stack is started, that is, the total power generation power needs to be distributed to different stacks.

[0112] In the above S704, the actual CO2 conversion rate of each SOEC stack = (CO2 consumption) / (CO2 intake)×100%=(CO2 intake-CO2 output) / (CO2 intake)×100%.

[0113] In the above S705, the applied voltage of each SOEC stack is regulated, including the following steps: when the actual CO2 conversion rate of the SOEC stack is greater than the preset target CO2 conversion rate, the applied voltage at both ends is reduced; when the actual CO2 conversion rate of the SOEC stack is less than the preset target CO2 conversion rate, the applied voltage at both ends is increased.

[0114] It should be noted that before starting the system, it is necessary to check whether the sensors installed in various places read correctly, whether the system pipeline connections are airtight, and whether the communication of the system equipment is good and the airtightness of various gas pressure gauges. In the system startup state, the SOEC stack needs to be heated by purging, and the CO2 and flow-aiding gas are heated by electric heaters or burners to reach the operating temperature. After the electrolysis is completed, in the system cooling state, first turn off the external DC power supply, then introduce nitrogen to protect the SOEC stack, and then gradually reduce the flow of CO2 and flow-aiding gas to gradually cool the system. After the system temperature drops to ambient temperature, finally cut off the power supply of the power generation device.

[0115] In order to further illustrate the present application, a carbon dioxide electrolysis system and an electrolysis method provided by the present application are described in detail below in combination with specific embodiments.

[0116] Example 1

[0117] like Figure 8 As shown, Example 1 provides a carbon dioxide electrolysis system. The system includes three SOEC stacks connected in series. The electrolytic cell of the SOEC stack is a fuel-supported flat-plate structure. The electrolytic cell is mainly composed of three parts, a porous cathode material, a dense electrolyte layer and a porous anode material. The fuel-supported flat-plate electrolytic cell has a low ohmic impedance and good high-temperature cycle performance. The working process of the carbon dioxide electrolysis system of Example 1 is: the CO2 gas source enters the cathode raw material inlet of the first SOEC stack through the pressure reducing valve 05, and the dry flow-aiding gas source air enters the anode raw material inlet of the first SOEC stack through the gas compressor 06. The first mass flow controller 01 and the second mass flow controller 02 are used to adjust the intake of CO2 and the flow-aiding gas to 32L / min. The cathode product and the anode product of the third SOEC stack are preheated by the first heat exchanger 2 and the second heat exchanger 3 respectively. The preheated CO2 and the flow-aiding gas are further heated by the first heater 4 and the second heater 5 to reach the inlet temperature of the first SOEC stack, that is, 750°C. A plurality of temperature sensors 03 are used to detect the inlet and outlet temperatures of the three SOEC stacks in series. Furthermore, the anode product of the third SOEC stack enters the O2 storage tank after preheating the flow-aiding gas air. The cathode product of the third SOEC stack includes CO and unreacted CO2, and CO is separated by the gas separator 1 and enters the CO storage tank. The separated CO2 is circulated back to the cathode raw material inlet of the first SOEC stack to continue to participate in the electrolysis reaction. The photovoltaic power generation equipment is used to output a DC power supply to power the three SOEC stacks in series.

[0118] Example 2

[0119] like Fig. 9As shown, Example 2 provides a carbon dioxide electrolysis system. The system includes three SOEC stacks connected in series. Compared with Example 1, Example 2 adds a CO2 supplementary gas source pipeline at the cathode raw material inlet of each SOEC stack. This is because starting from the second SOEC stack in Example 1, the gas entering the cathode of the subsequent SOEC stack contains CO produced by the previous SOEC stack reaction, which will cause the CO2 concentration to gradually decrease and the CO concentration to gradually increase, which is easy to cause carbon deposition reaction and affect the life of the stack. Therefore, the CO2 in Example 2 is divided into three air flows after passing through the pressure reducing valve 05. The first air flow directly enters the cathode raw material inlet of the first SOEC stack after being preheated by the first heat exchanger 2 and heated by the first heater 4. The remaining two paths are used as supplementary gas sources, and they merge with the cathode product gas of the previous stack and directly enter the cathode raw material inlet of the subsequent SOEC stack. The three branches are all provided with a first mass flow controller 01 for adjusting the amount of CO2 gas introduced into each path. The subsequent working process is the same as that in Example 1, which will not be repeated here. Example 2 is conducive to further improving the CO2 conversion rate and the operating life of the stack.

[0120] Example 3

[0121] like Fig.10 As shown, Example 3 provides a carbon dioxide electrolysis system. The system includes three SOEC stacks connected in series. Compared with Example 1, Example 3 has a burner 6 placed after the third SOEC stack, and the cathode product of the third SOEC stack is divided into two paths, one part enters the burner 6 and the additional combustion aid is burned in the burner 6; the other part is separated from CO by the gas separator 1 and enters the CO storage tank, and the separated CO2 is circulated back to the cathode raw material inlet of the first SOEC stack to continue to participate in the electrolysis reaction. The anode product O2 of the third SOEC stack is also divided into two paths, one part enters the burner 6 and the fuel is burned in the burner 6; the other part enters the O2 storage tank. The high-temperature gas generated by the burner 6 first preheats the cold flow-aiding gas and the cold CO2 respectively, and then passes through the gas-liquid separator 9 to cool and remove water, and the CO2 in the product is separated and recycled. It should be noted that the amount of air in the system is sufficient, and the fuel in the burner 6 will almost completely burn to generate CO2 and water when there is enough O2, and the gas-liquid separator 9 can separate the two. The burner 6 of Example 3 can directly heat the cold flow-aiding gas and cold CO2 to the temperature required at the inlet of the first SOEC stack without the need for heating using an electric heater.

[0122] Example 4

[0123] like Fig.11 As shown, Example 4 provides a method for electrolyzing carbon dioxide, which specifically includes the following steps:

[0124] S1101. Before starting the system, check whether the installed sensors read correctly, check whether the system pipe connections and gas pressure gauges are airtight, and check whether the system equipment is communicating well;

[0125] S1102, in the system startup state, turning on the CO2 gas source and the flow-aiding gas source, purging the SOEC stack, and heating the CO2 and the flow-aiding gas through an electric heater or a burner to reach an operating temperature of 750°C;

[0126] S1103, connecting the power generation device, obtaining the total power generation power of the power generation device 6kW, and determining the number of SOEC stacks to be started based on the total power generation power and the preset target power of each SOEC stack 1kW;

[0127] S1104, based on the preset target power of each SOEC stack to be started and the preset target CO2 conversion rate of 20%, a target total CO2 flow rate of 63 L / min is obtained for the SOEC stack to be started;

[0128] S1105, based on the target total CO2 flow rate, adjusting the CO2 flow rate into each SOEC stack to 63 L / min through the first mass flow controller;

[0129] S1106, turning on the SOEC stack, obtaining the actual operating temperature, CO2 intake volume, and CO2 output volume of each SOEC stack through a temperature sensor and a gas concentration sensor, and obtaining the actual CO2 conversion rate of each SOEC stack;

[0130] S1107, based on the actual CO2 conversion rate of each SOEC stack, adjusting the applied voltage of each SOEC stack by 1.2V to control the CO2 conversion of each SOEC stack to meet the preset target CO2 conversion rate;

[0131] S1108. After the electrolysis is completed, turn off the external DC power supply, introduce nitrogen, reduce the flow of CO2 and flow-aiding gas, and cut off the power supply of the power generation device after the temperature of the system drops to the ambient temperature.

[0132] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A carbon dioxide electrolysis system, characterized in that: include: n SOEC stacks, the n SOEC stacks are connected in series, and the n SOEC stacks are sequentially recorded as a first SOEC stack, a second SOEC stack, a third SOEC stack, ..., an nth SOEC stack along the series connection direction, wherein n is a natural number greater than or equal to 2; At least the cathode raw material inlet of the first SOEC stack is connected to a CO2 gas source; At least the anode raw material inlet of the first SOEC stack is connected to a flow-assisting gas source.

2. The carbon dioxide electrolysis system according to claim 1, characterized in that: The CO2 conversion rate of the carbon dioxide electrolysis system is greater than or equal to 60%; Preferably, the CO2 conversion rate of the carbon dioxide electrolysis system is greater than or equal to 70%.

3. The carbon dioxide electrolysis system according to claim 1, characterized in that: The carbon dioxide electrolysis system also includes a gas separator, a CO storage tank and an O2 storage tank; The gas separator comprises a first gas inlet, a first gas outlet and a second gas outlet, wherein the first gas inlet is connected to the cathode product outlet of the nth SOEC stack, the first gas outlet is connected to the CO2 gas source, and the second gas outlet is connected to the CO storage tank; The O2 storage tank is connected to the anode product outlet of the nth SOEC stack.

4. The carbon dioxide electrolysis system according to claim 3, characterized in that: The carbon dioxide electrolysis system also includes a first heat exchanger and a second heat exchanger; The first heat exchanger comprises a second air inlet, a third air inlet, a third air outlet and a fourth air outlet, wherein the second air inlet is connected to the cathode product outlet of the nth SOEC stack, the third air inlet is connected to the CO2 gas source, the third air outlet is connected to the first air inlet of the gas separator, and the fourth air outlet is connected to the cathode raw material inlet of the first SOEC stack; The second heat exchanger includes a fourth air inlet, a fifth air inlet, a fifth air outlet and a sixth air outlet, the fourth air inlet is connected to the anode product outlet of the nth SOEC stack, the fifth air inlet is connected to the flow-aiding gas source, the fifth air outlet is connected to the O2 storage tank, and the sixth air outlet is connected to the anode raw material inlet of the first SOEC stack.

5. The carbon dioxide electrolysis system according to claim 4, characterized in that: The carbon dioxide electrolysis system also includes a first heater and a second heater; The first heater is used to heat CO2 entering the cathode raw material inlet of the first SOEC stack; The second heater is used to heat the flow-assisting gas entering the anode raw material inlet of the first SOEC stack; Preferably, both the first heater and the second heater are electric heaters; The first heater comprises a sixth air inlet and a seventh air outlet, the sixth air inlet is connected to the CO2 gas source, and the seventh air outlet is connected to the cathode raw material inlet of the first SOEC stack; The second heater comprises a seventh air inlet and an eighth air outlet, the seventh air inlet is connected to the flow-assisting gas source, and the eighth air outlet is connected to the anode raw material inlet of the first SOEC stack; Preferably, the first heater is a burner, and the carbon dioxide electrolysis system further comprises a first flow divider and a second flow divider; The first splitter comprises an eighth air inlet, a ninth air outlet and a tenth air outlet, the eighth air inlet is connected to the cathode product outlet of the nth SOEC stack, and the ninth air outlet is connected to the second air inlet of the first heat exchanger; The second splitter comprises a ninth air inlet, an eleventh air outlet and a twelfth air outlet, the ninth air inlet is connected to the anode product outlet of the nth SOEC stack, and the eleventh air outlet is connected to the fourth air inlet of the second heat exchanger; The burner comprises a tenth air inlet, an eleventh air inlet, a twelfth air inlet and a thirteenth air outlet, the tenth air inlet is connected to the tenth air outlet of the first flow divider, the eleventh air inlet is connected to the twelfth air outlet of the second flow divider, and the twelfth air inlet is used to introduce an oxidant; The second heat exchanger also includes a thirteenth air inlet and a fourteenth air outlet, and the first heat exchanger also includes a fourteenth air inlet and a fifteenth air outlet; the thirteenth air outlet is connected to the thirteenth air inlet of the second heat exchanger, and the fourteenth air outlet is connected to the fourteenth air inlet of the first heat exchanger.

6. The carbon dioxide electrolysis system according to claim 5, characterized in that: The carbon dioxide electrolysis system further comprises a gas-liquid separator, which is used to separate the liquid and gas generated by the burner; The gas-liquid separator comprises a fifteenth air inlet and a sixteenth air outlet, the fifteenth air inlet is connected to the fifteenth air outlet of the first heat exchanger, and the sixteenth air outlet is connected to the CO2 gas source.

7. The carbon dioxide electrolysis system according to any one of claims 1 to 6, characterized in that: The carbon dioxide electrolysis system also includes a first mass flow controller and a second mass flow controller; The first mass flow controller is disposed between the CO2 gas source and a cathode raw material inlet of a first SOEC stack connected to the CO2 gas source; The second mass flow controller is disposed between the flow-aiding gas source and the anode raw material inlet of the first SOEC stack connected to the flow-aiding gas source; Preferably, the carbon dioxide electrolysis system further comprises a plurality of temperature sensors and a plurality of gas concentration sensors; The plurality of temperature sensors are dispersedly disposed at both ends of each SOEC stack; The plurality of gas concentration sensors are dispersedly disposed at both ends of each SOEC stack; Preferably, the carbon dioxide electrolysis system further comprises a power generation device, which is electrically connected to each of the SOEC stacks; the power generation device comprises a photovoltaic power generation device.

8. A method for electrolyzing carbon dioxide, characterized in that: include: Using the carbon dioxide electrolysis system as described in any one of claims 1 to 7 to electrolyze CO2, and controlling the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate during the electrolysis process; Preferably, the preset target CO2 conversion rate is 10%-20%.

9. The method for electrolyzing carbon dioxide according to claim 8, characterized in that: The controlling the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate includes: Controlling the applied voltage, operating temperature, and CO2 input amount of each SOEC stack so that the CO2 conversion rate of each SOEC stack meets the preset target CO2 conversion rate; Preferably, the applied voltage of each SOEC stack is 1.0V-1.2V; the operating temperature of each SOEC stack is 700°C-850°C.

10. The method for electrolyzing carbon dioxide according to claim 9, characterized in that: The power generation device of the carbon dioxide electrolysis system is a photovoltaic power generation device, and the CO2 conversion rate of each SOEC stack is controlled to meet a preset target CO2 conversion rate, including: Obtaining the total power generated by the power generation device, and determining the number of SOEC stacks to be started based on the total power generated and the preset target power of each SOEC stack; Based on the preset target power and the preset target CO2 conversion rate of each SOEC stack to be started, the target CO2 flow rate and the target total CO2 flow rate of each SOEC stack to be started are obtained; Based on the target total CO2 flow rate, adjusting the CO2 flow rate into each SOEC stack through a first mass flow controller; Turn on the SOEC stack, and obtain the actual operating temperature, CO2 intake and CO2 output of each SOEC stack through a temperature sensor and a gas concentration sensor to obtain the actual CO2 conversion rate of each SOEC stack; Based on the actual CO2 conversion rate of each of the SOEC stacks, the applied voltage of each of the SOEC stacks is regulated to control the CO2 conversion of each of the SOEC stacks to meet a preset target CO2 conversion rate.

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