Carbon dioxide electrolysis system

Abstract

The utility model discloses a carbon dioxide electrolysis system. 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] This application relates to the field of solid oxide electrolysis cell technology, and more particularly to a carbon dioxide electrolysis system. Background Technology

[0002] Faced with fossil fuel shortages 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 the fuel gas CO using renewable electricity at high temperatures (750-1000℃). SOECs have advantages such as environmental friendliness, high energy efficiency, and long-term operational stability, and have broad practical prospects.

[0003] However, for a single CO2-SOEC cell or stack operating at high temperatures, under high CO2 conversion rates, CO may be reduced to solid carbon, causing carbon buildup inside the electrolyzer, resulting in a severe decline in electrolytic performance and thus affecting the lifespan of the SOEC cell or stack. Utility Model Content

[0004] This application discloses a carbon dioxide electrolysis system that, through the series arrangement of multiple SOEC stacks, can significantly improve the CO2 conversion rate in a pure carbon dioxide electrolysis system, increase the lifespan of the stacks and the stability of long-term operation, thereby optimizing and improving system efficiency.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] This application provides a carbon dioxide electrolysis system, comprising: n SOEC stacks connected in series, wherein the n SOEC stacks are sequentially named as first SOEC stack, second SOEC stack, third SOEC stack, ..., nth SOEC stack along their series connection direction, where n is a natural number greater than or equal to 2;

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

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

[0009] The aforementioned carbon dioxide electrolysis system electrolyzes pure CO2 using at least two SOEC stacks connected in series, thereby improving the overall CO2 conversion rate. Specifically, the carbon dioxide electrolysis system of this application includes at least two SOEC stacks connected in series, and the cathode feed inlet of at least the first SOEC stack is connected to a CO2 gas source. By distributing CO2 to different SOEC stacks for electrolysis, the CO2 conversion rate of each SOEC stack can be maintained within an appropriate range, avoiding the further generation of C from CO due to excessively high CO2 conversion rates in a single stack, which would cause carbon buildup inside the SOEC stack and affect its service life. Compared to traditional single-stack electrolysis systems, the carbon dioxide electrolysis system of this 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. By connecting them in series, the overall CO2 conversion rate of the system can be increased to more than n times that of a traditional single SOEC stack system, while preventing C deposition. Therefore, the carbon dioxide electrolysis system of this application can significantly improve the overall CO2 conversion rate 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%, more preferably greater than 80%.

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

[0013] The gas separator includes a first inlet, a first outlet, and a second outlet. The first inlet is connected to the cathode product outlet of the nth SOEC stack, the first outlet is connected to the CO2 gas source, and the second 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 includes a first heat exchanger and a second heat exchanger;

[0016] The first heat exchanger includes a second air inlet, a third air inlet, a third air outlet, and a fourth air outlet. 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-assisted 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 the CO2 entering the cathode feed inlet of the first SOEC stack;

[0020] The second heater is used to heat the flow-in gas entering the anode feed 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 includes 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 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-assisted gas source, and the eighth air outlet is connected to the anode material inlet of the first SOEC stack.

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

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

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

[0027] The burner includes 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 distributor, and the eleventh air inlet is connected to the twelfth air outlet of the second distributor. The twelfth air inlet is used to introduce combustion aid.

[0028] The second heat exchanger further includes a thirteenth air inlet and a fourteenth air outlet, and the first heat exchanger further 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 for separating the liquid and gas produced by the burner;

[0030] The gas-liquid separator includes a fifteenth inlet and a sixteenth outlet. The fifteenth inlet is connected to the fifteenth outlet of the first heat exchanger, and the sixteenth 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 located between the CO2 gas source and the cathode feed inlet of the first SOEC stack connected to the CO2 gas source;

[0033] The second mass flow controller is located between the flow-aiding gas source and the anode feed inlet of the first SOEC stack connected to the flow-aiding gas source;

[0034] Preferably, the carbon dioxide electrolysis system further includes multiple temperature sensors and multiple gas concentration sensors;

[0035] The multiple temperature sensors are distributed at both ends of each SOEC stack;

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

[0037] In some embodiments, the carbon dioxide electrolysis system further includes a power generation device electrically connected to each of the SOEC stacks; the power generation device includes a photovoltaic power generation device. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a carbon dioxide electrolysis system provided in an embodiment of this application;

[0039] Figure 2 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application;

[0040] Figure 3 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application;

[0041] Figure 4This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application;

[0042] Figure 5 A schematic flowchart of a carbon dioxide electrolysis method provided in this application embodiment;

[0043] Figure 6 A schematic flowchart of a carbon dioxide electrolysis method provided in this application embodiment;

[0044] Figure 7 A schematic flowchart of a carbon dioxide electrolysis method provided in this application embodiment;

[0045] Figure 8 This is a schematic diagram of a carbon dioxide electrolysis system provided in an embodiment of this application;

[0046] Figure 9 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application;

[0047] Figure 10 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application;

[0048] Figure 11 A schematic flowchart of a carbon dioxide electrolysis method provided in this application embodiment;

[0049] Icons: 1. Gas separator; 11. First inlet; 12. First outlet; 13. Second outlet; 2. First heat exchanger; 201. First sub-heat exchanger; 202. Second sub-heat exchanger; 21. Second inlet; 22. Third inlet; 23. Third outlet; 24. Fourth outlet; 25. Fourteenth inlet; 26. Fifteenth outlet; 27. Sixteenth inlet; 28. Eighteenth outlet; 3. Second heat exchanger; 301. Third sub-heat exchanger; 302. Fourth sub-heat exchanger; 31. Fourth inlet; 32. Fifth inlet; 33. Fifth outlet; 34. Sixth outlet; 35. Thirteenth inlet; 36. Fourteenth outlet; 37. Seventeenth inlet; 38. Seventeenth outlet; 4. First Heater; 41. Sixth air inlet; 42. Seventh air outlet; 5. Second heater; 51. Seventh air inlet; 52. Eighth air outlet; 6. Burner; 61. Tenth air inlet; 62. Eleventh air inlet; 63. Twelfth air inlet; 64. Thirteenth air outlet; 7. First distributor; 71. Eighth air inlet; 72. Ninth air outlet; 73. Tenth air outlet; 8. Second distributor; 81. Ninth air inlet; 82. Eleventh air outlet; 83. Twelfth air outlet; 9. Gas-liquid separator; 91. Fifteenth air inlet; 92. Sixteenth air outlet; 01. First mass flow controller; 02. Second mass flow controller; 03. Temperature sensor; 04. Gas concentration sensor; 05. Pressure reducing valve; 06. Gas compressor. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships, for example, A and / or B can represent: A alone, A and B at the same time, and B alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0051] The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0052] For individual CO2-SOEC cells or stacks operating at high temperatures, under high CO2 conversion rates, CO may be reduced to solid carbon, causing carbon buildup inside the electrolyzer, resulting in a severe decline in electrolysis performance and consequently affecting the lifespan of the SOEC cell or stack. Therefore, there is currently a lack of an electrolysis system that can improve CO2 conversion rates and operate stably for extended periods.

[0053] Based on the above problems, this 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 a carbon dioxide electrolysis system provided in an embodiment of this application. Figure 1 As shown, the carbon dioxide electrolysis system includes n SOEC stacks connected in series. The n SOEC stacks are sequentially designated as the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., the nth SOEC stack, where n is a natural number greater than or equal to 2. For example, the number of SOEC stacks connected in series can be 2, 3, 4, 5, 6, 7, etc., depending on the specific circumstances. In this application, the series connection of SOEC stacks refers to the series connection of the fuel electrodes of the SOEC stacks.

[0054] Each SOEC stack may include a cathode, an anode, and an electrolyte disposed between the cathode and the anode. Specifically, with Figure 1 Taking the first SOEC stack 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.

[0055] The specific connection method of n SOEC stacks is as follows: the cathode product outlet of the first SOEC stack is connected to the cathode feed inlet of the second SOEC stack, and the anode product outlet of the first SOEC stack is connected to the anode feed inlet of the second SOEC stack; the cathode product outlet of the second SOEC stack is connected to the cathode feed inlet of the third SOEC stack, and the anode product outlet of the second SOEC stack is connected to the anode feed inlet of the third SOEC stack; and so on, until connected to the nth SOEC stack.

[0056] The overall electrochemical reaction occurring in the SOEC stack of this application embodiment is CO2→CO+0.5O2, wherein the cathode reaction is CO2+2e - →CO+O 2- The anode reaction is O 2- →O2+2e - .

[0057] In n SOEC fuel cell stacks, at least the cathode feed inlet of the first SOEC fuel cell stack is connected to a CO2 gas source. For example... Figure 1 As shown, only the cathode feed inlet of the first SOEC stack is connected to a CO2 gas source. Figure 1 In the scenario shown, the cathode feedstock for the subsequent SOEC stack needs to be provided by the preceding SOEC stack. That is, the cathode products of the preceding SOEC stack, including CO2 and a portion of CO, enter the subsequent SOEC stack together. Under preferred conditions, to further improve the CO2 electrolysis efficiency of the SOEC stack, the cathode material of each SOEC stack can be adjusted according to the CO2 partial voltage range of that stack.

[0058] Figure 2 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application. Figure 2 As shown, the cathode feed inlets of the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., the nth SOEC stack are all connected to a CO2 gas source. Figure 2 In the scenario shown, the cathode products from the preceding SOEC stack and the supplementary CO2 gas source simultaneously enter the subsequent SOEC stack. The supplementary CO2 gas source can compensate for the CO2 deficiency and reduce the carbon deposition reaction caused by high concentrations of CO, thereby extending the system's lifespan.

[0059] In n SOEC fuel cell stacks, at least the anode feed inlet of the first SOEC fuel cell stack is connected to a flow-assisted gas source. For example... Figure 1 As shown, only the anode feed inlet of the first SOEC stack is connected to the flow-aid gas source. The flow-aid gas source supplies fluid at a specific temperature to the SOEC stack to maintain its temperature and simultaneously promotes gas flow within the stack. It should be noted that the anode feed inlets of the first, second, third, ..., nth SOEC stacks can also all be connected to the flow-aid gas source. The flow-aid gas source can be air, inert gas, or other gases, with air being the most economical choice.

[0060] The aforementioned carbon dioxide electrolysis system electrolyzes pure CO2 using at least two SOEC stacks connected in series, thereby improving the overall CO2 conversion rate. Specifically, the carbon dioxide electrolysis system of this application includes at least two SOEC stacks connected in series, and the cathode feed inlet of at least the first SOEC stack is connected to a CO2 gas source. By distributing CO2 to different SOEC stacks for electrolysis, the CO2 conversion rate of each SOEC stack can be maintained within an appropriate range, avoiding the further generation of C from CO due to excessively high CO2 conversion rates in a single stack, which would cause carbon buildup inside the SOEC stack and affect its service life. Compared to traditional single-stack electrolysis systems, the carbon dioxide electrolysis system of this 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. By connecting them in series, the CO2 conversion rate of the entire system can be increased to more than n times that of a traditional single SOEC stack system, while preventing C deposition. Therefore, the carbon dioxide electrolysis system of this application can significantly improve the overall CO2 conversion rate and is beneficial for extending the service life of SOEC stacks.

[0061] The CO2 conversion rate of the carbon dioxide electrolysis system in this application embodiment can reach 60% or more, preferably 70% or more, more preferably 80% or more, for example 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 82%, 85%, 90%, etc., depending on the specific circumstances.

[0062] In some embodiments, such as Figure 1 and Figure 2 As shown, the carbon dioxide electrolysis system of this application embodiment further includes a gas separator 1, a CO storage tank, and an O2 storage tank. The gas separator 1 includes a first inlet 11, a first outlet 12, and a second outlet 13. The first inlet 11 is connected to the cathode product outlet of the nth SOEC stack, allowing the cathode product to flow into the gas separator 1. It is understood that the cathode product includes CO and unreacted CO2. The gas separator 1 separates CO and CO2. CO2 then flows out from the first outlet 12 and can continue to be used as a CO2 gas source. CO flows out from the second outlet 13 and enters the CO storage tank for later 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 generated by the entire system, and the anode product of the nth SOEC stack includes O2 generated by the entire system. The gas separator 1 in this application recycles unreacted CO2, which can further improve the utilization rate of CO2 and significantly improve the overall CO2 conversion rate and system efficiency.

[0063] In some embodiments, such as Figure 1 and Figure 2 As shown, the carbon dioxide electrolysis system of this embodiment further includes a first heat exchanger 2 and a second heat exchanger 3. The first heat exchanger 2 includes a second inlet 21, a third inlet 22, a third outlet 23, and a fourth outlet 24. The second inlet 21 is connected to the cathode product outlet of the nth SOEC stack. The third inlet 22 is connected to a CO2 gas source, used to introduce the high-temperature gaseous product generated at the cathode into the first heat exchanger 2 and to heat the CO2 flowing through the first heat exchanger 2, thus preheating it. The third outlet 23 is connected to the first inlet 11 of the gas separator 1, used to separate and recycle the naturally cooled cathode product. The fourth outlet 24 is connected to the cathode raw material inlet of the first SOEC stack, used to introduce the preheated CO2 gas into the cathode of the SOEC stack for electrolysis.

[0064] The second heat exchanger 3 includes a fourth inlet 31, a fifth inlet 32, a fifth outlet 33, and a sixth outlet 34. The fourth inlet 31 is connected to the anode product outlet of the nth SOEC stack. The fifth inlet 32 ​​is connected to a flow-supporting gas source, used to introduce the high-temperature gaseous products generated at the anode into the second heat exchanger 3 and to heat the flow-supporting gas flowing through the second heat exchanger 3, thus preheating it. The fifth outlet 33 is connected to an O2 storage tank for collecting and storing the naturally cooled anode products. The sixth outlet 34 is connected to the anode feedstock inlet of the first SOEC stack, used to introduce the preheated flow-supporting gas into the anode of the SOEC stack, providing the temperature required for the electrolysis process of the SOEC stack.

[0065] In this application, both the oxygen and the flow-supporting gas generated by electrolysis flow out from the anode product outlet of the nth SOEC stack, resulting in an oxygen-rich mixed gas. In some embodiments of this application, when the flow-supporting gas is not O2, a gas separator can be installed between the second heat exchanger 3 and the O2 storage tank to separate the O2 and the flow-supporting gas. The obtained O2 is stored in the O2 storage tank, and the obtained flow-supporting gas is led to the flow-supporting gas source for recycling.

[0066] This application enables the energy cascade utilization of the system's high-temperature gas products by setting up a first heat exchanger 2 and a second heat exchanger 3, thereby improving the system's energy utilization efficiency and thus helping to increase the CO2 conversion rate.

[0067] In some embodiments, such as Figure 1 and Figure 2As shown, the carbon dioxide electrolysis system of this application embodiment further includes a first heater 4 and a second heater 5. The first heater 4 is used to heat the CO2 entering the cathode feed inlet of the first SOEC stack; the second heater 5 is used to heat the flow-in gas entering the anode feed inlet of the first SOEC stack. The first heater 4 and the second heater 5 of this application are used to further heat the CO2 and the flow-in gas to meet the temperature requirements of the cathode feed inlet and anode feed inlet of the SOEC stack, thereby facilitating subsequent electrolysis reactions and improving CO2 conversion rate.

[0068] In this application, the types of the first heater 4 and the second heater 5 are commonly known to those skilled in the art. In some embodiments, such as Figure 1 and Figure 2 As shown, both the first heater 4 and the second heater 5 are electric heaters. The first heater 4 includes a sixth inlet 41 and a seventh outlet 42. The sixth inlet 41 is connected to the fourth outlet 24 of the first heat exchanger 2 and is used to further heat the preheated CO2 to meet the temperature requirements of the cathode feedstock inlet. The CO2 then flows out through the seventh outlet 42 and enters the cathode feedstock inlet of the first SOEC stack.

[0069] 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-supporting gas source and is used to further heat the preheated flow-supporting gas to meet the temperature requirements of the anode raw material inlet. Then it flows out from the eighth air outlet 52 and enters the anode raw material inlet of the first SOEC stack.

[0070] Figure 3 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this 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 this application embodiment also includes a first distributor 7 and a second distributor 8.

[0071] The first splitter 7 includes an eighth inlet 71, a ninth outlet 72, and a tenth outlet 73. The eighth inlet 71 is connected to the cathode product outlet of the nth SOEC stack and is used to split the cathode products (CO and CO2). Most of the cathode products flow into the first heat exchanger 2 through the ninth outlet 72 to heat the CO2, while the other part of the cathode products enters the burner through the tenth outlet 73 and the tenth inlet 61 of the burner to participate in the subsequent combustion reaction.

[0072] The second diverter 8 includes a ninth inlet 81, an eleventh outlet 82, and a twelfth outlet 83. The ninth inlet 81 is connected to the anode product outlet of the nth SOEC stack and is used to divert the anode product O2. Most of the anode product flows into the second heat exchanger 3 through the eleventh outlet 82, which heats the flow-aiding gas. The other part of the anode product enters the burner through the twelfth outlet 83 and the eleventh inlet 62 of the burner to participate in the subsequent combustion reaction.

[0073] Reference Figure 3 The first heat exchanger 2 in this embodiment 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 CO2 and the flow-supporting gas have completed heat exchange in the preceding sub-heat exchanger, they are introduced into the corresponding subsequent sub-heat exchanger along the airflow direction to continue heat exchange.

[0074] Specifically, the heat exchange of the flow-supporting gas is divided into two steps: First, the anode products of the nth SOEC stack enter the third sub-heat exchanger 301 through the eleventh outlet 82 and the fourth inlet 31 to perform the first step of heat exchange for the flow-supporting gas; then, the heat-exchanged flow-supporting gas enters the fourth sub-heat exchanger 302 through the sixth outlet 34 and the seventeenth inlet 37. Since some of the CO and O2 entering the burner 6 undergo a combustion reaction to produce high-temperature combustion gas, this high-temperature combustion gas enters the fourth sub-heat exchanger 302 through the thirteenth outlet 64 and the thirteenth inlet 35 to perform the second step of heat exchange for the flow-supporting gas, so that the flow-supporting gas reaches the temperature requirement of the anode raw material inlet, and flows out from the seventeenth outlet 38 to enter the anode raw material inlet.

[0075] The heat exchange of CO2 is also divided into two steps: First, the high-temperature combustion gas in the fourth heat exchanger 302 enters the first heat exchanger 201 through the fourteenth outlet 36 and the fourteenth inlet 25 to perform the first step of heat exchange for CO2 (at this time, the temperature of the high-temperature combustion gas is about 400-500℃); then, the heat-exchanged CO2 enters the second heat exchanger 202 through the fourth outlet 24 and the sixteenth inlet 27. Since the cathode product of the nth SOEC stack is a high-temperature gas, this high-temperature gas enters the second heat exchanger 202 through the ninth outlet 72 and the second inlet 21 to perform the second step of heat exchange for CO2 (the temperature of the high-temperature gas is about 800℃), so that CO2 reaches the temperature requirement of the cathode raw material inlet, and flows out from the eighteenth outlet 28 and enters the cathode raw material inlet.

[0076] The burner 6 also includes a twelfth air inlet 63, which is used to introduce combustion aid (such as hydrocarbon fuel or other supplementary fuel) to ensure sufficient fuel in the burner 6. The temperature generated by combustion can heat the combustion aid gas and CO2 to meet the requirements of the fuel inlet of the fuel cell stack, thereby facilitating the subsequent electrolysis reaction and improving the CO2 conversion rate.

[0077] In some embodiments, such as Figure 3 As shown, the first heat exchanger 201 also includes a fifteenth outlet 26. The carbon dioxide electrolysis system in this embodiment further includes a gas-liquid separator 9, which separates the liquid and gas produced by the burner 6. The gas-liquid separator 9 includes a fifteenth inlet 91 and a sixteenth outlet 92. The fifteenth inlet 91 is connected to the fifteenth outlet 26 of the first heat exchanger 201 and is used to separate the mixed gas discharged from the fifteenth outlet 26. It is understood that after the high-temperature gas cools, some of the gas will convert into liquid (such as water), while the remainder remains gas (such as CO2). The gas-liquid separator 9 separates the liquid and gas, and the gas flows out through the sixteenth outlet 92 and continues to be used as a CO2 gas source. The gas-liquid separator 9 in this application can further improve the utilization rate of CO2.

[0078] Figure 4 This is a schematic diagram of another carbon dioxide electrolysis system provided in an embodiment of this application. In some embodiments, such as... Figure 4 As shown, when the high-temperature gas generated by burner 6 can heat CO2 and the flow gas, the pipeline for preheating CO2 and the flow gas by the high-temperature cathode products and high-temperature anode products of SOEC stack can be eliminated, and the high-temperature gas generated by burner 6 can be used directly to heat the gas source, making the system structure simpler.

[0079] In some embodiments, such as Figures 1-3 As shown, the carbon dioxide electrolysis system of this application embodiment further includes a first mass flow controller 01 and a second mass flow controller 02. The first mass flow controller 01 is located between the CO2 gas source and the cathode feed inlet of the first SOEC stack connected to the CO2 gas source, and is used to regulate the CO2 flow rate of the entire system. The second mass flow controller 02 is located between the flow-supporting gas source and the anode feed inlet of the first SOEC stack connected to the flow-supporting gas source, and is used to regulate the flow rate of the flow-supporting gas of the entire system. By setting the first mass flow controller 01 and the second mass flow controller 02, the overall CO2 conversion rate of the entire system can be adjusted, which is beneficial to extending the service life of the SOEC stack.

[0080] In some embodiments, such as Figures 1-3As shown, the carbon dioxide electrolysis system of this embodiment also includes multiple temperature sensors 03 and multiple gas concentration sensors 04. The multiple temperature sensors 03 are distributed across both ends of each SOEC stack; the multiple gas concentration sensors 04 are also distributed across both ends of each SOEC stack. That is, each SOEC stack has temperature sensors 03 and gas concentration sensors 04 at both its inlet and outlet ends to monitor the temperature and gas volume during stack operation. Furthermore, based on the monitoring results, parameters such as the CO2 feed rate are adjusted to control the CO2 conversion rate of the entire system, which helps extend the lifespan of the SOEC stack.

[0081] In some embodiments, such as Figures 1-3 As shown, the carbon dioxide electrolysis system in this application embodiment 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 in this 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 incurring additional carbon emission burdens.

[0082] Furthermore, the carbon dioxide electrolysis system in this embodiment also includes a pressure reducing valve 05 and a gas compressor 06. The pressure reducing valve 05 is located 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 located between the flow-aiding gas source and the second mass flow controller 02, and is used to provide power for the flow-aiding gas.

[0083] This application also provides a method for the electrolysis of carbon dioxide, such as... Figure 5 The carbon dioxide electrolysis method shown includes the following steps:

[0084] S501. CO2 is electrolyzed using a carbon dioxide electrolysis system, and the CO2 conversion rate of each SOEC stack is controlled to meet the preset target CO2 conversion rate during the electrolysis process.

[0085] This application's carbon dioxide electrolysis method utilizes multiple SOEC stacks connected in series to electrolyze pure CO2, controlling the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate. This avoids excessively high CO2 conversion rates in a single stack, which could lead to further CO formation into C, causing carbon buildup inside the SOEC stack and affecting its lifespan. Compared to traditional single-stack electrolysis systems, this application significantly improves the overall CO2 conversion rate and extends the lifespan of the SOEC stack.

[0086] 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., with the specific value depending on the circumstances. The electrolysis method of this application can achieve a total CO2 conversion rate of over 80%, significantly higher than the CO2 conversion rate (10%-20%) of a traditional dry electrolysis system with the same electrolysis time. By controlling the CO2 conversion rate range of each SOEC stack, this application ensures the normal operation of the stack, thereby extending its service life and enabling it to maintain stable operation over a long period.

[0087] In some embodiments, such as 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:

[0088] S601. Control the applied voltage, operating temperature, and CO2 input of each SOEC stack to ensure that the CO2 conversion rate of each SOEC stack meets the preset target CO2 conversion rate.

[0089] In some embodiments, the applied voltage for each SOEC stack is 1.0V-1.2V, such as 1.0V, 1.02V, 1.04V, 1.06V, 1.08V, 1.1V, 1.12V, 1.14V, 1.16V, 1.18V, 1.2V, etc., depending on the circumstances.

[0090] In some embodiments, the operating temperature of each SOEC stack is 700°C-850°C, such as 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, etc., depending on the specific circumstances.

[0091] In some embodiments, such as Figure 7 As shown, the power generation device of the carbon dioxide electrolysis system in this embodiment is a photovoltaic power generation device. Controlling the CO2 conversion rate of each SOEC stack to meet a preset target CO2 conversion rate includes the following steps:

[0092] S701. Obtain the total power output of the power generation device, and determine the number of SOEC stacks to be activated based on the total power output and the preset target power of each SOEC stack.

[0093] S702. Based on the preset target power and preset target CO2 conversion rate of each SOEC stack to be opened, obtain the target CO2 flow rate and target total CO2 flow rate of each SOEC stack to be opened.

[0094] S703. Based on the target total CO2 flow rate, the CO2 flow rate supplied to each SOEC stack is adjusted by the first mass flow controller;

[0095] S704. Start the SOEC stack and obtain the actual operating temperature, CO2 intake and CO2 exhaust of each SOEC stack through temperature sensor and gas concentration sensor to obtain the actual CO2 conversion rate of each SOEC stack.

[0096] S705. Based on the actual CO2 conversion rate of each SOEC stack, adjust the applied voltage of each SOEC stack to control the CO2 conversion of each SOEC stack to meet the preset target CO2 conversion rate.

[0097] In the above S701, after obtaining the total power generation of the power generation device, the first SOEC stack is turned on first. When the operating power of the first SOEC stack reaches its preset target power, the next SOEC stack is turned on. That is, the total power generation needs to be distributed to different stacks.

[0098] In the above S704, the actual CO2 conversion rate of each SOEC stack = (CO2 consumption) / (CO2 intake) × 100% = (CO2 intake - CO2 exhaust) / (CO2 intake) × 100%.

[0099] In the above S705, adjusting the applied voltage of each SOEC stack includes 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 its two 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 its two ends is increased.

[0100] It should be noted that before system startup, it is necessary to check whether the readings of all installed sensors are correct, to check the airtightness of system pipeline connections, and to ensure good communication between system equipment and the airtightness of various gas pressure gauges. During system startup, the SOEC stack needs to be heated by purging, and the CO2 and auxiliary gases need to be heated by an electric heater or burner to reach the operating temperature. After electrolysis, during system cooling, first turn off the external DC power supply, then introduce nitrogen to protect the SOEC stack, and then gradually reduce the flow rate of CO2 and auxiliary gases to allow the system to cool down gradually. Once the system temperature drops to ambient temperature, finally disconnect the power supply to the power generation unit.

[0101] To further illustrate this application, the following detailed description of a carbon dioxide electrolysis system and electrolysis method provided in this application is provided in conjunction with specific embodiments.

[0102] Example 1

[0103] like Figure 8 As shown, Example 1 provides a carbon dioxide electrolysis system. This system includes three SOEC stacks connected in series. The electrolysis cell of the SOEC stack is a fuel-supported flat plate structure, mainly composed of three parts: porous cathode material, a dense electrolyte layer, and porous anode material. The fuel-supported flat plate electrolysis cell has low ohmic impedance and good high-temperature cycling performance. The working process of the carbon dioxide electrolysis system in Example 1 is as follows: CO2 gas enters the cathode feed inlet of the first SOEC stack through pressure reducing valve 05, and dry flow-aiding gas enters the anode feed inlet of the first SOEC stack through gas compressor 06. A first mass flow controller 01 and a second mass flow controller 02 are used to regulate the flow rate of CO2 and flow-aiding gas. The cathode and anode products of the third SOEC stack are preheated by the first heat exchanger 2 and the second heat exchanger 3, respectively, to cool the cold CO2 and the cold flow-aiding gas. The preheated CO2 and flow-aiding gas are further heated by the first heater 4 and the second heater 5 to reach the inlet temperature requirement of the first SOEC stack. Multiple temperature sensors 03 are used to detect the inlet and outlet temperatures of the three SOEC stacks connected in series. Further, the anode products of the third SOEC stack, after preheating the flow-supporting gas, enter the O2 storage tank. The cathode products of the third SOEC stack include CO and unreacted CO2. CO is separated by gas separator 1 and enters the CO storage tank. The separated CO2 is recycled back to the cathode feed inlet of the first SOEC stack to continue participating in the electrolysis reaction. Renewable energy generation equipment is used to output DC power to supply the three SOEC stacks connected in series.

[0104] Example 2

[0105] like Figure 9 As shown, Example 2 provides a carbon dioxide electrolysis system. This system includes three SOEC stacks connected in series. Compared to Example 1, Example 2 adds a CO2 supplementary gas source pipeline to the cathode feed inlet of each SOEC stack. This is because, starting from the second SOEC stack in Example 1, the gas entering the cathode of subsequent SOEC stacks contains CO produced by the reaction in the preceding SOEC stack, leading to a gradual decrease in CO2 concentration and a gradual increase in CO concentration, which easily causes carbon deposition and affects the stack's lifespan. Therefore, in Example 2, the CO2 is divided into three gas streams after passing through the pressure reducing valve 05. The first gas stream, after preheating by the first heat exchanger 2 and heating by the first heater 4, directly enters the cathode feed inlet of the first SOEC stack. The other two streams serve as supplementary gas sources, merging with the cathode product gas from the previous stack and directly entering the cathode feed inlet of the subsequent SOEC stack. Each of the three streams is equipped with a first mass flow controller 01 to regulate the CO2 gas flow rate of each stream. The subsequent operating process is the same as in Example 1 and will not be repeated here. Example 2 is beneficial for further improving CO2 conversion rate and stack operating life.

[0106] Example 3

[0107] like Figure 10 As shown, Example 3 provides a carbon dioxide electrolysis system. This system includes three SOEC stacks connected in series. Compared to Example 1, Example 3 adds a burner 6 after the third SOEC stack. The cathode products of the third SOEC stack are divided into two paths: one part enters the burner 6 and reacts with additional combustion aid; the other part passes through a gas separator 1 to separate CO, which enters a CO storage tank. The separated CO2 is recycled back to the cathode feed inlet of the first SOEC stack to continue participating in the electrolysis reaction. The anode products O2 of the third SOEC stack are also divided into two paths: one part enters the burner 6 and reacts with fuel; the other part enters an O2 storage tank. The high-temperature gas generated by the burner 6 preheats the cold auxiliary gas and cold CO2 separately, and then passes through a gas-liquid separator 9 to cool and remove water, separating the CO2 from the products for continued recycling. It should be noted that with sufficient air in the system, the fuel in the burner 6 will almost completely burn to produce CO2 and water when there is sufficient O2; the gas-liquid separator 9 can separate these two components. The burner 6 in Example 3 can directly heat the cold booster gas and cold CO2 to the temperature required at the inlet of the first SOEC stack, without the need for an electric heater.

[0108] Example 4

[0109] like Figure 11 As shown, Example 4 provides a method for electrolyzing carbon dioxide, which specifically includes the following steps:

[0110] S1101. Before starting the system, check whether the readings of the sensors installed at each location are correct, check whether the airtightness of the system pipeline connections and gas pressure gauge is good, and check whether the system equipment communicates well.

[0111] S1102. In the system startup state, turn on the CO2 gas source and the flow-assisted gas source to purge the SOEC stack, and heat the CO2 and flow-assisted gas through the electric heater or burner to reach the operating temperature.

[0112] S1103. Connect the power generation device, obtain the total power generation of the power generation device, and determine the number of SOEC stacks to be activated based on the total power generation and the preset target power of each SOEC stack.

[0113] S1104. Based on the preset target power and preset target CO2 conversion rate of each SOEC stack to be opened, obtain the target CO2 flow rate and target total CO2 flow rate of each SOEC stack to be opened.

[0114] S1105. Based on the target total CO2 flow rate, the CO2 flow rate supplied to each SOEC stack is adjusted by the first mass flow controller;

[0115] S1106. Start the SOEC stack and obtain the actual operating temperature, CO2 intake and CO2 output of each SOEC stack through temperature sensor and gas concentration sensor to obtain the actual CO2 conversion rate of each SOEC stack.

[0116] S1107. Based on the actual CO2 conversion rate of each SOEC stack, adjust the applied voltage of each SOEC stack to control the CO2 conversion of each SOEC stack to meet the preset target CO2 conversion rate.

[0117] S1108. After electrolysis is completed, turn off the external DC power supply, introduce nitrogen gas, reduce the flow rate of CO2 and flow-aiding gas, and after the system temperature drops to the ambient temperature, disconnect the power supply of the power generation device.

[0118] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A carbon dioxide electrolysis system, characterized in that, include: There are n SOEC stacks connected in series. The n SOEC stacks are sequentially named as the first SOEC stack, the second SOEC stack, the third SOEC stack, ..., the nth SOEC stack along the series connection direction, where n is a natural number greater than or equal to 2. At least the cathode feed inlet of the first SOEC stack is connected to a CO2 gas source; At least the anode feed inlet of the first SOEC stack is connected to a flow-assisted 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%.

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

4. 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 includes a first inlet, a first outlet, and a second outlet. The first inlet is connected to the cathode product outlet of the nth SOEC stack, the first outlet is connected to the CO2 gas source, and the second outlet is connected to the CO storage tank. The O2 storage tank is connected to the anode product outlet of the nth SOEC stack.

5. The carbon dioxide electrolysis system according to claim 4, characterized in that, The carbon dioxide electrolysis system also includes a first heat exchanger and a second heat exchanger. The first heat exchanger includes a second air inlet, a third air inlet, a third air outlet, and a fourth air outlet. 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-assisted 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.

6. The carbon dioxide electrolysis system according to claim 5, characterized in that, The carbon dioxide electrolysis system also includes a first heater and a second heater; The first heater is used to heat the CO2 entering the cathode feed inlet of the first SOEC stack; The second heater is used to heat the flow-in gas entering the anode feed inlet of the first SOEC stack.

7. The carbon dioxide electrolysis system according to claim 6, characterized in that, Both the first heater and the second heater are electric heaters; The first heater includes 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 material inlet of the first SOEC stack. The second heater includes a seventh air inlet and an eighth air outlet. The seventh air inlet is connected to the flow-assisted gas source, and the eighth air outlet is connected to the anode material inlet of the first SOEC stack.

8. The carbon dioxide electrolysis system according to claim 6, characterized in that, The first heater is a burner, and the carbon dioxide electrolysis system further includes a first distributor and a second distributor; The first splitter includes an eighth inlet, a ninth outlet, and a tenth outlet. The eighth inlet is connected to the cathode product outlet of the nth SOEC stack, and the ninth outlet is connected to the second inlet of the first heat exchanger. The second splitter includes a ninth inlet, an eleventh outlet, and a twelfth outlet. The ninth inlet is connected to the anode product outlet of the nth SOEC stack, and the eleventh outlet is connected to the fourth inlet of the second heat exchanger. The burner includes 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 distributor, and the eleventh air inlet is connected to the twelfth air outlet of the second distributor. The twelfth air inlet is used to introduce combustion aid. The second heat exchanger further includes a thirteenth air inlet and a fourteenth air outlet, and the first heat exchanger further 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.

9. The carbon dioxide electrolysis system according to claim 8, characterized in that, The carbon dioxide electrolysis system also includes a gas-liquid separator, which is used to separate the liquid and gas produced by the burner; The gas-liquid separator includes a fifteenth inlet and a sixteenth outlet. The fifteenth inlet is connected to the fifteenth outlet of the first heat exchanger, and the sixteenth outlet is connected to the CO2 gas source.

10. The carbon dioxide electrolysis system according to any one of claims 1-9, 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 located between the CO2 gas source and the cathode feed inlet of the first SOEC stack connected to the CO2 gas source; The second mass flow controller is located between the flow-aiding gas source and the anode feed inlet of the first SOEC stack connected to the flow-aiding gas source.

11. The carbon dioxide electrolysis system according to claim 10, characterized in that, The carbon dioxide electrolysis system also includes multiple temperature sensors and multiple gas concentration sensors; The multiple temperature sensors are distributed at both ends of each SOEC stack; The multiple gas concentration sensors are distributed at both ends of each SOEC stack.

12. The carbon dioxide electrolysis system according to claim 10, characterized in that, The carbon dioxide electrolysis system also includes a power generation device, which is electrically connected to each of the SOEC stacks; the power generation device includes a photovoltaic power generation device.

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