Isotope cascade enrichment system and method based on electrolysis-oxidation coupling circulation

Abstract

The application provides an isotope cascade enrichment system and method based on electrolysis-oxidation coupling circulation, and relates to the technical field of isotope enrichment. The system comprises N cascade enrichment stages, each enrichment stage comprising an electrolysis unit and a reverse oxidation unit. The electrolysis unit is used for reducing carbon-containing raw materials to produce residues enriched in heavy carbon isotopes and reduction products enriched in light carbon isotopes. The reverse oxidation unit is used for oxidizing the reduction products enriched in light carbon isotopes to generate oxidation products. A raw material supply pipeline is used to supply carbon-containing raw materials to the electrolysis unit of the first enrichment stage. An inter-stage transmission pipeline is used to transport the residues of the electrolysis unit of the Mth enrichment stage to the electrolysis unit of the M+1th enrichment stage. A circulation pipeline is used to transport the oxidation products of the reverse oxidation unit of the nth enrichment stage to the electrolysis unit of the n-1th enrichment stage. The system reduces the number of stages required for isotope enrichment, improves enrichment efficiency, and reduces operating costs.

Description

Technical Field

[0001] This application relates to the field of isotope enrichment technology, specifically to an isotope cascade enrichment system and method based on electrolysis-oxidation coupling cycle. Background Technology

[0002] Carbon isotopes (such as) 13 C) It has significant value in medical diagnostics (such as the Helicobacter pylori breath test), scientific research (isotope labeling tracing), and industrial fields. Currently, enrichment... 13 The main methods for carbon monoxide extraction include cryogenic distillation and chemical exchange, but these methods generally suffer from huge equipment investment and extremely high energy consumption.

[0003] Electrochemical reduction of carbon dioxide (CO2) offers a potential new approach for isotope separation. This method utilizes... 13 CO2 and 13 Slight kinetic differences (kinetic isotope effect) exist in the electrochemical reduction reaction of CO2: Slighter 12 CO2 typically has a faster reaction rate. Therefore, theoretically, through multi-stage series electrolysis, the residual CO2 gas can be purified. 13 The abundance of C increases progressively.

[0004] However, this traditional multi-stage electrolytic enrichment method has a fundamental bottleneck: 12 C accumulates continuously as a byproduct, leading to 13 The enrichment efficiency of C is low. Specifically, in each stage of electrolysis, the reaction rate is faster... 12 A large amount of CO2 is consumed and converted into reduction products (such as carbon monoxide and formic acid), while the reaction rate is relatively slow. 13 CO2 is relatively concentrated in the residue. However, in traditional cascade processes, each stage produces CO2-rich residues. 12 The reduction products of C are discharged from the system as byproducts, while those rich in C are... 13 The residue of C is then sent to the next stage. This process results in lighter isotopes ( 12 C) It cannot be effectively separated from the system, and its concentration remains high in the feed of subsequent stages, severely diluting the feed concentration and weakening the separation driving force of each stage. In order to achieve high abundance (e.g., >99%), a large number of stages (dozens or even hundreds of stages) need to be connected in series. This results in an extremely long equipment process, a large footprint, complex control, and high total energy consumption, making it difficult to achieve economically feasible large-scale production. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, this application aims to provide an isotope cascade enrichment system and method based on electrolysis-oxidation coupling cycle, so as to reduce the required number of stages, improve enrichment efficiency and reduce operating costs.

[0006] In a first aspect, this application proposes an isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle, comprising: N cascaded enrichment stages, from stage 1 to stage N, where N is an integer greater than 1, each enrichment stage includes an electrolysis unit and a reverse oxidation unit; The electrolysis unit is configured to reduce carbon-containing raw materials, producing residues enriched with heavy carbon isotopes and reduction products enriched with light carbon isotopes. The reverse oxidation unit is configured to oxidize the reduction products enriched with light carbon isotopes to generate oxidation products; Raw material supply pipeline, configured to supply the carbon-containing raw material to the electrolysis unit of the enrichment stage in the first stage; Interstage transfer conduits are configured to transport the residue from the electrolysis unit of the enrichment stage M to the electrolysis unit of the enrichment stage M+1, where M is an integer from 1 to N-1. A circulation pipeline is configured to transport the oxidation products of the reverse oxidation unit of the nth enrichment stage to the electrolysis unit of the (n-1)th enrichment stage, where n is an integer from 2 to N.

[0007] According to the technical solution provided in this application, the electrolysis unit includes an electrolysis reactor, which contains an electrolyte and is provided with a pair of flat plates; the electrolysis reactor is configured to dissolve or disperse the carbon-containing raw material in the electrolyte and carry out an electrochemical reduction reaction.

[0008] According to the technical solution provided in this application, the reverse oxidation unit includes a catalytic oxidation reactor; the system also includes an online isotope analyzer that is communicatively connected to the control unit; The online isotope analyzer is configured to detect in real time the abundance of heavy carbon isotopes in the residues output from the electrolysis unit at least the Nth enrichment stage. The control unit is configured to dynamically adjust the current density of the electrolysis unit or the reaction temperature of the reverse oxidation unit in at least one of the enrichment stages based on the abundance of the heavy carbon isotopes.

[0009] According to the technical solution provided in this application, it also includes a heat recovery device; The heat recovery device is configured to use the waste heat from the process stream from at least one of the reverse oxidation units to heat the feed stream delivered to at least one of the electrolysis units.

[0010] According to the technical solution provided in this application, the heat recovery device is a heat exchanger located at the material outlet of the reverse oxidation unit or on the circulation pipeline.

[0011] Secondly, this application proposes an isotope cascade enrichment method based on an electrolysis-oxidation coupled cycle, implemented using the isotope cascade enrichment system based on the electrolysis-oxidation coupled cycle described above, including the following steps: Raw material supply step: The carbon-containing raw material is transported to the electrolysis unit of the enrichment stage in the first stage through the raw material supply pipeline; The cascaded enrichment and cyclic steps include processing sub-steps for each level from level 1 to level N-1: Electrolytic reduction step: The input carbon-containing raw material is reduced in the electrolytic unit to generate a residue enriched with heavy carbon isotopes and a reduction product enriched with light carbon isotopes. Residue transport sub-step: The residue enriched with heavy carbon isotopes is transported through the interstage transport pipeline to the electrolysis unit of the next enrichment stage as the main part of the carbon-containing raw material input thereto; Oxidation step: In the reverse oxidation unit, the reduction product of the enriched light carbon isotope produced in the enrichment stage is oxidized to generate the oxidation product; Oxidation product recycling sub-step: The oxidation product is transported through the recycling pipeline to the electrolysis unit of the previous enrichment stage as a supplement to the carbon-containing raw material input therein; Final enrichment step: The residue from the N-1th enrichment stage is reduced in the electrolysis unit of the Nth enrichment stage to generate the target product with final enrichment of heavy carbon isotopes.

[0012] According to the technical solution provided in this application, before the oxidation product is transported through the circulation pipeline to the electrolysis unit of the previous enrichment stage, the following steps are also included: The oxidation products were subjected to gas-liquid separation to obtain carbon dioxide gas and water. The carbon dioxide gas is dried and purified to obtain purified carbon dioxide gas.

[0013] According to the technical solution provided in this application, the following steps are also included: Real-time detection of the abundance of heavy carbon isotopes in the target product output at level N; The abundance of the heavy carbon isotopes is compared with the target abundance setting value to obtain the comparison result; If the abundance of heavy carbon isotopes is less than the target abundance setting, then reverse adjustment is performed, and the reverse adjustment includes at least one of the following operations: The current density of the electrolytic reduction sub-step of at least one enrichment stage is increased sequentially in reverse order from stage N-1 to stage 1. The reaction temperature of the oxidative sub-step of at least one enrichment stage is decreased sequentially in reverse order from stage N-1 to stage 1.

[0014] According to the technical solution provided in this application, the execution of reverse adjustment includes the following steps: Based on the dynamic mathematical model of the system, taking the operating parameters of the current enrichment levels as the initial state, the curve of heavy carbon isotope abundance change of the target product within a first preset time period is predicted. With minimizing the deviation between the heavy carbon isotope abundance variation curve and the target abundance setting value as the optimization objective, the optimal variation sequence within the second preset time period from the current moment is obtained. The optimal variation sequence is the optimal current density sequence of the electrolytic reduction sub-step from level 1 to level N-1 and / or the optimal reaction temperature sequence of the oxidation sub-step. The optimization results corresponding to the current moment in the optimal change sequence are implemented, and the optimization results include the current density setpoint and / or reaction temperature setpoint calculated for each level from level 1 to level N-1.

[0015] According to the technical solution provided in this application, the optimization objectives also include minimizing the energy consumption required to increase the unit abundance of the final target product and minimizing the total energy consumption of the system. The solution obtains the optimal change sequence within a second preset time period from the current moment, including the following steps: A multi-objective optimization algorithm is used to weigh the three objectives of the deviation between the heavy carbon isotope abundance change curve and the target abundance setting value, the total energy consumption of the system, and the energy consumption per unit abundance increase, and to generate the Pareto optimal frontier. The optimal change sequence is selected from the Pareto optimal frontier according to a preset priority strategy.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: This invention introduces a circulation pipeline to enrich the subsequent stage... 12 The oxidation products of C are transported in the reverse direction to the upstream stage, creating a reverse stripping line in the material flow direction. This allows light isotopes to be transported in the reverse direction. 12 C is no longer a byproduct of accumulation, but is recycled back to the preceding stages and continuously extracted from the system. This architecture is mathematically equivalent to increasing the number of theoretical plates in the system, thus requiring only a fewer physical stages to achieve the same target isotopic abundance. This directly results in a significant reduction in equipment investment, system complexity, and floor space. Furthermore, it significantly improves isotope enrichment efficiency and raw material utilization: in traditional unidirectional processes, rich in... 12The reduction products of carbon are discharged as waste, resulting in a waste of carbon resources. This invention uses a reverse oxidation unit to convert the reduction products back into raw materials (such as CO2) and recycle them, achieving near-complete utilization of carbon atoms. This not only greatly improves the economic efficiency of raw materials and conforms to the principles of green chemistry, but also achieves near-complete utilization of carbon atoms through recycling. 12 C allows each electrolysis unit to operate at a more optimal feed concentration, thereby improving the separation efficiency of a single stage and the energy utilization efficiency of the entire system.

[0017] In summary, this invention solves the fundamental problem of excessive number of stages and low efficiency in traditional multi-stage electrolytic enrichment technology through a bidirectional circulation architecture, providing a brand-new technical path for achieving efficient, energy-saving, and economical enrichment of carbon isotopes. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of an isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle provided in an embodiment of this application; Figure 2 A flowchart illustrating the steps of an isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle provided in this application embodiment.

[0019] The text labels in the image represent: 1. Enrichment stage; 11. Electrolysis unit; 12. Reverse oxidation unit; 2. Raw material supply pipeline; 3. Interstage transfer pipeline; 4. Circulation pipeline. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Example 1 As mentioned in the background section, to address the problems in the prior art, this application proposes an isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle, such as... Figure 1 As shown, it includes: N cascaded enrichment stages 1, from stage 1 to stage N, where N is an integer greater than 1, each enrichment stage 1 includes an electrolysis unit 11 and a reverse oxidation unit 12; The electrolysis unit 11 is configured to reduce carbon-containing raw materials to produce residues enriched with heavy carbon isotopes and reduction products enriched with light carbon isotopes. The reverse oxidation unit 12 is configured to oxidize the reduction product enriched with light carbon isotopes to generate an oxidation product; Raw material supply pipeline 2 is configured to supply the carbon-containing raw material to the electrolysis unit 11 of the enrichment stage 1 in the first stage; Interstage transfer pipe 3 is configured to transport the residue of the electrolysis unit 11 of the enrichment stage 1 of the Mth stage to the electrolysis unit 11 of the enrichment stage 1 of the M+1th stage, where M is an integer from 1 to N-1; The circulation pipeline 4 is configured to transport the oxidation products of the reverse oxidation unit 12 of the nth enrichment stage 1 to the electrolysis unit 11 of the (n-1)th enrichment stage 1, where n is an integer from 2 to N.

[0023] Specifically, this is a multi-stage (N-stage) series system, where each stage comprises a combination of an electrolysis unit 11 and a reverse oxidation unit 12. The system features a bidirectional circulating material flow design. On one hand, carbonaceous feedstock (such as carbon dioxide) enters from stage 1, rich in target heavy isotopes (such as... 13 The residue from stage C) is sequentially transported through interstage transfer pipe 3 (stage 1 → stage 2 → ... → stage N), achieving gradual enrichment of heavy isotopes, ultimately yielding the target product with high abundance in stage N. On the other hand, the residues generated by each stage of electrolysis, rich in light isotopes (such as... 12 The reduction products of C) (such as carbon monoxide, formic acid, or methane) are not discharged as waste, but are re-oxidized by the reverse oxidation unit 12 of the same stage back to the original carbon-containing feedstock (such as carbon dioxide). Most importantly, these oxidation products are reverse-transported through the circulation pipe 4 (e.g., from stage n to stage n-1) and reinjected into the electrolysis unit 11 of the previous stage as part of the feed.

[0024] It should be noted that for the different forms of reduction products mentioned above, the oxidation treatment method can be selected and implemented according to chemical engineering methods known in the art. This application does not exhaustively limit this, and those skilled in the art can select a suitable oxidation process according to the specific type of product. For example, when the reduction product is a gas such as carbon monoxide or methane, it can be directly introduced into a catalytic oxidation reactor for gas-solid phase catalytic oxidation on a noble metal or transition metal oxide catalyst bed. When the reduction product is a liquid such as formic acid, methanol, or ethanol, it can be first heated and vaporized in a gasifier, and then introduced into a catalytic oxidation reactor for oxidation; alternatively, a liquid-phase oxidation method known in the art can be used, such as introducing an oxidant into the liquid phase and oxidizing it under the action of a catalyst. When the reduction product is a salt such as formate, it can be converted into formic acid through acidification treatment, and then oxidized according to the above method, or directly electrochemically oxidized in solution. Regardless of the oxidation method used, the purpose is to convert the reduction product enriched with light carbon isotopes into carbon dioxide, and this process does not change the abundance distribution of carbon isotopes, that is, the oxidation process is inert to the isotopic composition, because 12 C and 13 The difference in oxidation reaction rate of C under the oxidation temperature conditions of this application is much smaller than the separation effect of the electrolytic reduction step, and will not have a substantial impact on the overall separation performance of the cascade system. Therefore, the technical solutions described in this application, even when the reduction products cover the above-mentioned multiple types, can all be implemented by those skilled in the art based on their conventional chemical engineering knowledge.

[0025] Specifically, enrichment stage 1 is the basic functional unit of the system. One enrichment stage 1 represents a complete isotope separation and material recycling operation. In implementation, each stage can be an independent physical module, containing an electrolyzer and an oxidation reactor, connected by piping. The number of stages N depends on the target isotope abundance requirement; for example, to obtain >99%... 13 C and N may need to be in the range of 10-50 levels, with the specific quantity determined through process simulation.

[0026] Specifically, interstage transfer pipe 3 and circulation pipe 4 are the physical channels for achieving bidirectional circulation. In practice, they are piping systems equipped with pumps, valves, and flow meters. Interstage transfer pipe 3 ensures the enrichment process proceeds in the forward direction, while circulation pipe 4 enables the reverse reflux and reuse of light isotope components.

[0027] The carbon-containing raw materials include carbon dioxide, carbonates or bicarbonates and mixtures thereof; the reduction products enriched with light carbon isotopes include carbon monoxide, formic acid, formate, methane, ethane, methanol, ethanol, etc.; the oxidation product is carbon dioxide.

[0028] The technical principle is described below: This embodiment combines the electrochemical kinetic isotope separation effect with the concept of countercurrent extraction. Electrolysis unit 11 acts as a separator, while reverse oxidation unit 12 acts as a recirculator. The downstream enriched... 12 The material in step C is returned to the upstream stage, which is equivalent to diluting the light isotope components in the upstream feed. This makes it easier for the upstream electrolyzer to further purify the heavy isotopes in the residue. Mathematically, this architecture is equivalent to greatly increasing the theoretical number of separation stages.

[0029] This implementation significantly reduces the required number of stages: due to the extraction effect of the reverse circulation, to achieve the same target abundance (e.g., 99%), the number of physical stages N required in series can be reduced by 30%-50% or more, greatly reducing equipment complexity and investment costs. Extremely high raw material utilization: light isotopes ( 12 C) It is no longer a useless byproduct, but is recycled, with only a small amount ultimately discharged at the beginning and end of the system. The overall carbon atom utilization rate is close to 100%, making it green and environmentally friendly. The enrichment efficiency is greatly improved: each stage operates at a higher separation efficiency due to the purification effect of reverse reflux, thereby improving the energy utilization efficiency and separation speed of the entire system.

[0030] It should be noted that the technical effect of this solution is based on the well-known scientific principle in the field of the inherent kinetic isotope effect in the electrochemical reduction of carbon dioxide. During the electrolytic reduction of carbon dioxide, [the process involves...]. 12 Carbon dioxide molecules have a lower zero-point energy and a slightly lower activation energy barrier than those containing [C]. 13 For carbon dioxide molecules of type C, the rate constant k12 for gaining electrons at the electrode surface and undergoing reduction is greater than k13, thus making... 12 C preferentially converts to the reduction product, while 13 C is relatively enriched in the unreacted residue. The magnitude of this one-stage separation effect is usually characterized by the separation factor α, which is defined as the concentration of C in the residue. 13 C and 12 C abundance ratio divided by the product 13 C and 12 C abundance ratio. For the electrocatalytic reduction system used in this application, under suitable electrode materials, electrolytes and operating conditions, the single-stage separation factor α is typically in the range of 1.01 to 1.10.

[0031] Based on the aforementioned single-stage separation factor, those skilled in the art can use classical cascade theory to estimate the required number of stages. For a simple forward cascade without reflux, the minimum theoretical number of stages N_min required to achieve the target abundance can be calculated using the following formula: N_min equals the logarithm of the ratio of the target product abundance to the raw material abundance divided by the logarithm of the separation factor. For example, if the raw material... 13With a C abundance of 1.07%, a target abundance of 99%, and a single-stage separation factor α of 1.05, the theoretical number of stages required for the forward cascade is approximately 90 to 100. However, this application utilizes a recirculating pipeline to enrich the subsequent stages. 12 The oxidation products of C are transported in reverse to the previous stage, which is equivalent to introducing a current into each stage. 12 The carbon concentration is higher than that of the reflux mass transfer in the current stage feed, thus increasing the effective separation driving force of this stage. According to the countercurrent cascade theory, the equivalent separation effect of this design is far superior to that of a simple forward cascade with the same number of physical stages. Under the condition of the same equivalent single-stage separation factor, the number of physical stages required to achieve the same target abundance using the countercurrent circulation design of this application can be reduced by about 30% to 50% or more compared to a simple forward cascade. The theoretical basis of this conclusion lies in the mathematical relationship between the number of mass transfer units in a countercurrent cascade and the separation effect, which can be directly derived by those skilled in the art based on well-known cascade theory and mass transfer principles.

[0032] In addition, to further verify the carbon isotope separation effect of the electrolysis unit and the material conversion function of the reverse oxidation unit described in this application, an isotope separation experiment of single-stage electrolytic reduction of CO2 to formic acid was carried out under the experimental conditions listed in Table 1. The experimental results are shown in Table 1.

[0033] Table 1. Experimental conditions and results of isotope separation in single-stage electrolytic reduction of CO2.

[0034] Note: Separation factor α = residual CO2 13 C abundance / in products 13 C abundance. The product formic acid was converted to CO2 by catalytic oxidation, and its isotopic abundance was then determined. The oxidation process did not change the carbon isotope abundance distribution.

[0035] Table 1 shows that at a current density of 100 mA / cm² 2 Under the conditions of using a carbon paper-supported cobalt tetroxide cathode and a methylimidazolium tetrafluoroborate electrolyte, the natural abundance CO2 was reduced by electrolysis. 13 When the carbon abundance is 1.10%, the single-pass CO2 conversion rate reaches 60%. The remaining unreacted CO2 after electrolysis... 13 The carbon abundance was 1.15%, an increase of 0.05 percentage points compared to the raw material abundance; while the product formic acid, after catalytic oxidation to CO2, was measured to be... 13 The C abundance was 1.062%, a decrease of 0.038 percentage points compared to the raw material abundance. These results indicate that during the electrochemical reduction process, the C content... 12 CO2 molecules containing C preferentially gain electrons at the cathode surface and are reduced to formic acid, while those containing... 13The CO2 molecules of C remain relatively trapped in the unreacted residual CO2, thus achieving the directional enrichment of heavy carbon isotopes at the residue end. Based on the measurement results, the single-stage separation factor α is calculated to be 1.15% divided by 1.062%, which is approximately equal to 1.08.

[0036] After the formic acid product is catalytically oxidized to CO2, the CO2 content is measured. 13 The C abundance is consistent with that in the original product, indicating that the oxidation step is inert to the carbon isotope composition and will not interfere with the overall separation effect of the cascade system, thus verifying the feasibility of the reverse oxidation unit in this application.

[0037] Based on the above measured single-stage separation factor α=1.08, those skilled in the art can use the well-known countercurrent cascade theory to estimate the required number of stages. Using the natural abundance of CO2 ( 13 The raw material and target product are both C abundance (approximately 1.10%). 13 Assuming a carbon abundance of 99%, the electrolysis-oxidation coupled cascade system with a reflux architecture described in this application requires approximately 25 to 35 physical stages. In contrast, a simple forward cascade without reflux, using the same single-stage separation factor, requires approximately 50 to 70 physical stages to achieve the same target abundance. Therefore, the scheme in this application reduces the required number of physical stages by approximately 40% to 50% compared to conventional schemes, validating the claimed technical effect of significantly reducing the required number of stages and improving enrichment efficiency.

[0038] In a preferred embodiment, the electrolysis unit 11 includes an electrolysis reactor containing an electrolyte and having a pair of flat electrodes; the electrolysis reactor is configured to dissolve or disperse the carbon-containing raw material in the electrolyte and carry out an electrochemical reduction reaction.

[0039] Specifically, carbon-containing raw materials (such as carbon dioxide) need to be dissolved or dispersed in a liquid electrolyte before an electrochemical reduction reaction occurs between a plate electrode pair consisting of a cathode and an anode, thereby achieving the separation of carbon isotopes. Electrolytic reactor: This is used to contain the electrolyte and electrodes and provide the site for the electrochemical reaction. In practice, it can be a simple H-type electrolytic cell separated by an ion-exchange membrane, with separate cathode and anode chambers; or it can be a single-chamber electrolytic cell without a membrane. Plate electrode pair: This refers to a cathode and anode with flat surfaces. In practice, the cathode (working electrode) can be made of materials with CO2 reduction catalytic activity, such as metal sheets (tin, lead, copper, etc.), metal foil, or conductive plates loaded with catalysts (such as carbon paper / graphite plates). The anode (counter electrode) is usually made of inert materials such as platinum sheets or platinum-plated titanium mesh. The electrodes are fixed parallel and opposite to each other in the electrolytic reactor. Dissolved or dispersed in the electrolyte: This specifies the contact method between the reactants and the electrolyte. For gaseous CO2, it is necessary to dissolve it as much as possible in the electrolyte (such as KHCO3 aqueous solution, ionic liquid, etc.) through bubbling, stirring, etc. For other soluble or dispersible carbon-containing raw materials, the electrolyte is prepared directly.

[0040] The separation principle of this embodiment is based on the kinetic isotope effect. Dissolved in the electrolyte... 12 CO2 and 13 CO2 molecules diffuse to the surface of the flat cathode and gain electrons under the action of a catalyst and in a hydrolysis environment, undergoing a reduction reaction. Because 12 C- 16 O bond ratio 13 C- 16 The O bond is slightly weaker and lighter. 12 The diffusion rate and reaction rate of CO2 molecules are slightly higher than those of CO2 molecules. 13 CO2 leads to greater consumption near the cathode surface. 12 CO2 is gradually accumulated in the electrolysis residue (both in the bulk electrolyte and unreacted gases). 13 CO2.

[0041] In a preferred embodiment, the reverse oxidation unit 12 includes a catalytic oxidation reactor; the system also includes an online isotope analyzer communicatively connected to the control unit. The online isotope analyzer is configured to detect in real time the abundance of heavy carbon isotopes in the residue output from the electrolysis unit 11 of at least the Nth enrichment stage 1. The control unit is configured to dynamically adjust the current density of at least one of the electrolysis units 11 or the reaction temperature of the reverse oxidation unit 12 in the enrichment stage 1 based on the abundance of the heavy carbon isotopes.

[0042] Specifically, the online isotope analyzer is an instrument capable of analyzing the isotope abundance in gaseous or liquid streams in real time, continuously, or quasi-continuously. In practice, an infrared spectrometer, laser spectrometer (such as TDLAS, QCLAS), or mass spectrometer (such as MS) can be selected. This analyzer is installed on the residue outlet pipe of the Nth-stage electrolysis unit 11 to continuously monitor the highly enriched material to be collected as product. The control unit is typically a programmable logic controller (PLC) or a distributed control system (DCS). In practice, it is connected via data lines to the online isotope analyzer, the power supply of each stage of the electrolysis unit 11, and the temperature controller of each oxidation unit. It has pre-installed control algorithms (such as PID control or more advanced model predictive control, MPC).

[0043] This implementation uses the final product quality as the controlled variable and key operating parameters affecting separation efficiency (current density affects electrolysis rate and separation factor, temperature affects oxidation rate and equilibrium) as manipulated variables. The system automatically adjusts the manipulated variables by comparing the deviations between measured and set values ​​in real time to eliminate deviations and maintain stable product quality.

[0044] This implementation method ensures stable product quality: it automatically compensates for interference caused by catalyst activity decay, raw material concentration fluctuations, and changes in ambient temperature, consistently maintaining product abundance precisely within the target range (e.g., 99% ± 0.1%), thus guaranteeing product consistency and a high yield rate. It also achieves process optimization and energy saving: the system can automatically find the operating point that minimizes total energy consumption while meeting product quality requirements. For example, it can appropriately reduce the current density when the abundance meets the target, thereby saving energy.

[0045] In a preferred embodiment, a heat recovery device is also included; The heat recovery device is configured to use the waste heat from the process stream from at least one of the reverse oxidation units 12 to heat the feed stream delivered to at least one of the electrolysis units 11.

[0046] Specifically, this implementation is based on the principle of cascaded energy utilization and process integration. The low-grade heat energy generated by the oxidation reaction, which would otherwise be consumed by water or air cooling, is effectively captured by the heat recovery device and used to increase the enthalpy of the feed stream. The preheated feed enters the electrolysis unit 11, reducing the external heating or electrical energy consumption required by the electrolyzer to maintain the reaction temperature. This reduces the overall system energy consumption: by recovering and utilizing the heat from the oxidation reaction to preheat the electrolysis feed, the power of external heaters can be significantly reduced, directly lowering operating costs. The energy utilization efficiency of the entire process is improved. It also enhances process stability: preheating the feed makes the temperature of the material entering the electrolyzer more stable, reducing the adverse effects of temperature fluctuations on the efficiency and selectivity of the electrolysis reaction, which is beneficial for steady-state operation. It reduces the cooling load: while recovering heat, it is also equivalent to cooling the high-temperature oxidation products, reducing the burden on the downstream cooling system and potentially making subsequent gas-liquid separation and other steps easier.

[0047] In a preferred embodiment, the heat recovery device is a heat exchanger located at the material outlet of the reverse oxidation unit 12 or on the circulation pipeline 4.

[0048] Specifically, different types of heat exchangers are selected based on the system size and throughput. For small to medium-sized laboratory systems or corrosive environments, compact plate heat exchangers with high heat transfer efficiency can be used. For large industrial installations or processes involving materials with particulate matter risk, robust and easy-to-clean shell-and-tube heat exchangers can be used.

[0049] Specifically, the heat exchanger can be located at the material outlet of the reverse oxidation unit 12, that is, the heat exchanger is directly connected to the outlet flange or short section of the reverse oxidation reactor. In practice, the high-temperature oxidation products (e.g., a mixture of CO2 and H2O vapors at temperatures between 300°C and 600°C) immediately enter the shell side (or tube side) of the heat exchanger upon exiting the reactor. At this location, the temperature of the hot stream is highest, and the potential for heat recovery and the driving force of temperature difference are greatest.

[0050] Specifically, it can also be installed on the circulation pipe 4: that is, the heat exchanger is installed in series as a component of the circulation pipe 4. In practice, the high-temperature material flowing out of the oxidation unit outlet enters the circulation pipe 4, flows through the heat exchanger, transfers heat to the cold fluid, and is then transported to the previous stage electrolysis unit 11. This location provides flexibility in pipe layout and may facilitate equipment installation and maintenance.

[0051] Specifically, regarding the connection between the heat recovery device and the downstream gas-liquid separation and purification steps, it should be noted that in the process flow of this application, the high-temperature oxidation product first undergoes indirect heat exchange with the feed stream requiring preheating through a heat exchanger located at the material outlet or circulation pipeline of the reverse oxidation unit. During this process, the oxidation product is initially cooled, with its temperature dropping from 300-600 degrees Celsius to approximately 100-200 degrees Celsius, while the feed stream is preheated to the required temperature. After initial cooling, the oxidation product continues to enter the subsequent cooler and gas-liquid separator for further cooling to near room temperature to complete the condensation and separation of water vapor. The heat load distribution, heat exchange area design, and temperature node control of each stream in the aforementioned heat exchanger and subsequent cooler can all be determined by those skilled in the art based on the thermodynamic properties of the process stream and engineering experience through conventional heat balance calculations and heat exchange network design. The selection of heat exchanger type, heat transfer calculation, and design methods are all common knowledge in the field, and can be performed by referring to methods described in standard reference books such as "Chemical Engineering Principles" or "Heat Exchanger Design Manual". Therefore, this specification does not provide an excessively detailed and exhaustive description. Those skilled in the art are fully capable of completing the engineering implementation of the heat recovery unit based on the overall concept disclosed in this application and the above guidance.

[0052] Example 2 Based on Example 1, this example proposes an isotope cascade enrichment method based on an electrolysis-oxidation coupled cycle, implemented using the isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle as described in Example 1. Figure 2 As shown, it includes the following steps: S1. Raw material supply step: The carbon-containing raw material is transported to the electrolysis unit 11 of the first enrichment stage 1 through the raw material supply pipeline 2; S2, Cascaded enrichment and cyclic steps, including processing sub-steps for each level from level 1 to level N-1: S21, Electrolytic reduction sub-step: The input carbon-containing raw material is reduced in the electrolytic unit 11 to generate a residue enriched with heavy carbon isotopes and a reduction product enriched with light carbon isotopes. S22, Residue Transfer Sub-step: The residue enriched with heavy carbon isotopes is transported through the interstage transfer pipe 3 to the electrolysis unit 11 of the next enrichment stage 1, as the main part of the carbon-containing raw material input therein; S23, Oxidation step: In the reverse oxidation unit 12, the reduction product of the enriched light carbon isotope produced by the enrichment stage 1 is oxidized to generate the oxidation product; S24, Oxidation product recycling sub-step: The oxidation product is transported through the recycling pipeline 4 to the electrolysis unit 11 of the previous enrichment stage 1 as a supplement to the carbon-containing raw material input therein; S3. Final enrichment step: The residue from the N-1th enrichment stage 1 is reduced in the electrolysis unit 11 of the Nth enrichment stage 1 to generate the target product with final enrichment of heavy carbon isotopes.

[0053] Specifically, those containing naturally abundant carbon isotopes (such as...) 12 C accounts for approximately 98.93%. 13 A feed gas (such as CO2) containing approximately 1.07% carbon is supplied to the cathode chamber of the first-stage electrolysis unit 11 via feed supply pipeline 2 at a precisely controlled flow rate (e.g., 1-10 SLPM, where SLPM refers to the flow rate per liter per minute under standard conditions (0°C, 1 atm)). The cascade enrichment and circulation steps are the core circulation process for achieving isotope separation and must be performed for each stage from stage 1 to stage N-1.

[0054] Electrolytic reduction step: In electrolysis unit 11, a specific current density (e.g., 20-600 mA / cm²) is applied. 2 This causes the carbon-containing molecules dissolved or diffused onto the cathode catalyst surface to undergo a reduction reaction. Due to the kinetic isotope effect, 12 C is more easily reduced, thus resulting in unreacted residues (such as unreacted CO2) 13 C is relatively enriched. Residual transport sub-step: The electrolyzed concentrate... 13 The residue of C (gas phase or liquid phase) is quantitatively transported to the next electrolysis unit 11 via interstage transfer pipe 3 using pressure differential or pumping, serving as the main feed for the next stage. Here, "main part" means it constitutes the majority (usually over 50%) of the feed for the next stage. Oxidation step: The residue rich in C produced in this stage of electrolysis... 12 The reduction products of C (such as CO, HCOOH, methane, methanol, ethane, ethylene, etc.) are introduced into the same-stage reverse oxidation unit 12. In the presence of a catalyst (such as Au / Al2O3) and at a certain temperature (e.g., 200-450 degrees Celsius), air or oxygen is introduced to completely oxidize the C into CO2 and H2O. Oxidation product recycling sub-step: The mixed gas (CO2 and H2O) generated by oxidation is transported to the previous-stage electrolysis unit 11 through circulation pipe 4. The supplementary part refers to its mixing with residues from the previous stage, serving as feed for the previous stage electrolysis, its function being to dilute the previous stage feed. 12 C content improves the separation efficiency of the preceding stages. Final enrichment step: Stage N serves as the final purification stage, receiving only the residue from stage N-1 and electrolyzing it. The resulting residue is the desired high-abundance (e.g., >99%) heavy carbon isotopes (C). 13 C) Target product.

[0055] In a preferred embodiment, before the oxidation product is conveyed through the circulation pipe 4 to the electrolysis unit 11 of the previous enrichment stage 1, the following step is further included: The oxidation products were subjected to gas-liquid separation to obtain carbon dioxide gas and water. The carbon dioxide gas is dried and purified to obtain purified carbon dioxide gas.

[0056] Specifically, the substance transported to the electrolysis unit 11 of the previous enrichment stage 1 through the circulation pipeline 4 can be untreated oxidation products. In this embodiment, the oxidation products can be treated and the treated oxidation products can be transported to the electrolysis unit 11 of the previous enrichment stage 1. That is, the purified carbon dioxide gas is used as a supplementary part and transported to the electrolysis unit 11 of the previous enrichment stage 1.

[0057] Specifically, the high-temperature oxidation products (CO2 and H2O vapors) are first introduced into a gas-liquid separator (such as a cyclone separator or a settling tank with a cooling jacket). Water vapor is condensed into liquid water by cooling (e.g., cooling to near room temperature) and / or pressure changes, thus separating it from the CO2 gas. The separated CO2 gas is then passed into a purification unit. The purification unit includes: a dryer filled with a desiccant (such as molecular sieves or silica gel) for deep removal of residual moisture from the gas; and a purifier (optional) configured with an adsorption bed (such as activated carbon) or filter to remove trace amounts of gaseous impurities (such as unreacted O2, byproducts) or particulate matter that may be introduced from the oxidation unit. After the above treatment, clean, dry CO2 gas with a purity of over 99.9% is obtained, meeting the feed gas quality requirements of electrolysis unit 11. This step is based on the unit's operating principle, removing impurities harmful to the electrolysis process through physical methods (condensation, adsorption). Moisture can compete with the electrolysis products for reaction, leading to side reactions or corrosion of the electrodes; impurities can poison the catalyst. Purification ensures the compatibility of recycled materials with system feed.

[0058] This embodiment, compared to directly feeding untreated oxidation products into the electrolysis unit 11 of the previous enrichment stage 1, can protect the electrolysis unit 11: preventing moisture and impurities from clogging, corroding, or poisoning the precision electrodes (especially gas diffusion electrodes), thus greatly extending the life and stability of the electrolyzer. It also improves electrolysis efficiency: clean and dry CO2 feed gas ensures effective diffusion of the gas within the electrode pores and effective contact with the catalyst, maintaining high current efficiency and isotope separation factor. Finally, it ensures product purity: preventing impurities from accumulating within the system and potentially contaminating the final high-abundance product, thus affecting product quality.

[0059] In a preferred embodiment, the following steps are also included: Real-time detection of the abundance of heavy carbon isotopes in the target product output at level N; The abundance of the heavy carbon isotopes is compared with the target abundance setting value to obtain the comparison result; If the abundance of heavy carbon isotopes is less than the target abundance setting, then reverse adjustment is performed, and the reverse adjustment includes at least one of the following operations: The current density of the electrolytic reduction sub-step of at least one enrichment stage 1 is increased sequentially in reverse order from stage N-1 to stage 1. The reaction temperature of the oxidizing sub-step of at least one enrichment stage 1 is decreased sequentially in reverse order from stage N-1 to stage 1.

[0060] Specifically, an online isotope analyzer (such as a tunable diode laser absorption spectrometer, TDLAS) is installed on the Nth-stage product outlet pipe. This instrument continuously measures the gas flow at a high frequency (e.g., once per second). 13 CO2 / 12 CO2 concentration ratio, and calculate the heavy carbon isotopes ( 13 C) Real-time abundance value. The detected abundance value is sent to the control unit (such as PLC or DCS), and subtracted from the preset target abundance setpoint (such as 99.5%) to obtain a deviation signal (Δ = setpoint - measured value). Reverse adjustment is then performed: the control unit has a preset control algorithm (such as if-then logic or a more advanced model predictive control MPC). When Δ > 0 (i.e., the abundance is lower than the target), the algorithm is triggered.

[0061] Specifically, the reverse order is used: adjustments begin with level N-1, which is closest to the product. If the deviation is not eliminated after adjustment, then adjust level N-2, level N-3, and so on. This "from near to far" order conforms to the law of disturbance propagation and results in the fastest response.

[0062] Specifically, increasing the current density is achieved by increasing the DC power output of the corresponding electrolysis unit 11; decreasing the reaction temperature is achieved by adjusting the power setting of the heater in the corresponding oxidation unit. These operations are all aimed at enhancing the stage's efficiency. 13 The purification ability of C.

[0063] In a preferred embodiment, performing the reverse adjustment includes the following steps: Based on the dynamic mathematical model of the system, taking the operating parameters of the enrichment stage 1 at the current level as the initial state, the curve of the heavy carbon isotope abundance of the target product is predicted within a first preset time period in the future. With minimizing the deviation between the heavy carbon isotope abundance variation curve and the target abundance setting value as the optimization objective, the optimal variation sequence within the second preset time period from the current moment is obtained. The optimal variation sequence is the optimal current density sequence of the electrolytic reduction sub-step from level 1 to level N-1 and / or the optimal reaction temperature sequence of the oxidation sub-step. The optimization results corresponding to the current moment in the optimal change sequence are implemented, and the optimization results include the current density setpoint and / or reaction temperature setpoint calculated for each level from level 1 to level N-1.

[0064] Specifically, a dynamic mathematical model refers to a set of mathematical equations that describe the time-varying behavior of a system. In practice, this model is established based on first principles (mass conservation, energy conservation, reaction kinetics) or can be obtained through system identification methods (such as training neural networks or regression models based on a large amount of historical operational data). Model inputs include current density at various levels, temperature, feed flow rate, etc., and the output is the predicted product abundance change. Starting from the current time k, the control unit predicts the possible trajectory of the target product abundance change within the next P sampling periods (e.g., P=10, each period is 1 minute, so the prediction is for the next 10 minutes) based on the model and the current system state. When solving for the optimal change sequence, the optimization algorithm calculates a series of manipulated variable setpoints within the next M periods (M≤P, e.g., M=5) under constraints, minimizing the deviation between the predicted trajectory and the target value. The solution is a sequence of operational instructions, which can be represented as U(k) = [u(k), u(k+1), ..., u(k+M-1)]. The sequence U(k) represents a set of operational schemes planned by the control system for the next M consecutive control cycles at the current time k. Each element u in the sequence is a multi-dimensional data package containing: the current density setpoint of each electrolysis unit from stage 1 to stage N-1, and the reaction temperature setpoint of each oxidation unit from stage 1 to stage N-1, within the corresponding control cycle. In other words, each u encapsulates all the parameter values ​​that need to be adjusted for all stages at the same time. For example, assuming the system has 5 enrichment stages, the stages that need to be adjusted are stages 1 to 4, and each u contains 4 current density setpoints and 4 reaction temperature setpoints, for a total of 8 specific parameters. In the sequence, u(k) corresponds to the operation instruction for the first future control cycle, u(k+1) corresponds to the operation instruction for the second future control cycle, and so on until u(k+M-1) corresponds to the operation instruction for the Mth future control cycle.

[0065] When implementing the optimization result at the current moment, the control system does not issue the entire sequence U(k) for execution. Instead, it extracts only the first element u(k) from the sequence, which corresponds to the optimal operation command at the current moment, and issues the current density setpoint and reaction temperature setpoint to the corresponding actuators for execution. At the next sampling moment k+1, the system updates the actual state with the newly measured product abundance value. Using the updated state as a new starting point, it re-executes the entire prediction and optimization solution process to obtain a new operation command sequence U(k+1), and then executes only u(k+1). This "measurement-prediction-optimization-execution" rolling cycle is repeated in each control cycle, enabling the system to continuously use the latest measured information to correct subsequent control strategies and always approach the target abundance value in the optimal way.

[0066] In a preferred embodiment, the optimization objective further includes minimizing the energy consumption required to increase the unit abundance of the final target product and minimizing the total energy consumption of the system; The solution obtains the optimal change sequence within a second preset time period from the current moment, including the following steps: A multi-objective optimization algorithm is used to weigh the three objectives of the deviation between the heavy carbon isotope abundance change curve and the target abundance setting value, the total energy consumption of the system, and the energy consumption per unit abundance increase, and to generate the Pareto optimal frontier. The optimal change sequence is selected from the Pareto optimal frontier according to a preset priority strategy.

[0067] Specifically, when optimizing a control system, it cannot focus solely on product quality; it must also consider both total system energy consumption and energy efficiency (i.e., the energy required to increase abundance per unit). It employs an intelligent algorithm to automatically identify the optimal operating scheme that achieves the best balance among these three conflicting objectives.

[0068] Specifically, the first step is to initiate a multi-objective optimization algorithm: In each control cycle, the system initiates a multi-objective optimizer software module. This module incorporates an advanced algorithm similar to NSGA-II, tasked with finding thousands of possible combinations of operating parameters (i.e., different current and temperature settings). The second step is to generate an optimal balance set (Pareto optimal frontier): This algorithm uses the system's mathematical model to simulate and predict each parameter combination, evaluating its impact on product quality, total power consumption, and energy efficiency. Subsequently, the algorithm filters and eliminates all inferior solutions (e.g., a solution is worse than another in terms of quality, energy consumption, and efficiency). The remaining solutions constitute an "optimal balance set." Each solution in this set represents a unique trade-off: some solutions offer slightly higher quality but also higher energy consumption, while others have very low energy consumption but slightly lower quality. There is no absolute optimal solution, only optimal solutions tailored to different priorities. The third step is to automatically select the final solution based on a preset strategy: The system makes intelligent decisions based on a "priority strategy" pre-set by the operator. This strategy typically consists of several simple rules. For example, priority strategies include: Quality assurance rule: When the real-time detected product abundance is below the safety threshold, the system automatically selects the highest quality solutions, even if they consume more energy. Cost reduction rule: When product quality is stable and has a margin, the system automatically selects the most energy-efficient solution to achieve the most economical production. Balancing mode: Under normal circumstances, the system calculates the weighted total score of each solution and selects the balancing solution with the highest overall score among quality, total energy consumption, and efficiency. Step 4: Execute the selected solution: Once the final solution is selected according to the strategy, the system immediately issues the corresponding operating instructions (i.e., new current and temperature setpoints) to each level of equipment for execution.

[0069] It should be understood that the specific operating parameters given in this specification, such as current density range, oxidation temperature range, flow rate range, and catalyst type, are illustrative and intended to help those skilled in the art understand the embodiments of the present invention, rather than constituting a limitation on the scope of protection of the present invention. Those skilled in the art can adjust and optimize these parameters based on the actual type of carbon-containing raw material, target isotope abundance requirements, production scale, and the specific equipment and materials used, through limited conventional experiments. For example, the selection of current density is related to the electrode material, electrolyte composition, and desired throughput; the selection of oxidation temperature is related to the type of catalyst used and the specific composition of the reduction products. The methods for determining these parameters fall within the conventional skill scope of those skilled in the art. The core innovation of this application lies in providing a system architecture and process flow for achieving isotope cascade enrichment through an electrolysis-oxidation coupled cycle, rather than specific numerical values ​​of certain parameters. Therefore, the technical solutions of this application can be implemented by those skilled in the art within the scope taught in this specification.

[0070] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. An isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle, characterized in that, include: N cascaded enrichment stages (1), from stage 1 to stage N, where N is an integer greater than 1, each enrichment stage (1) includes an electrolysis unit (11) and a reverse oxidation unit (12). The electrolysis unit (11) is configured to reduce carbon-containing raw materials to produce residues enriched with heavy carbon isotopes and reduction products enriched with light carbon isotopes. The reverse oxidation unit (12) is configured to oxidize the reduction product enriched with light carbon isotopes to generate an oxidation product; Raw material supply pipeline (2) is configured to supply the carbon-containing raw material to the electrolysis unit (11) of the enrichment stage (1) of the first stage; Interstage transfer pipe (3) configured to transport the residue of the electrolysis unit (11) of the enrichment stage (1) of the Mth stage to the electrolysis unit (11) of the enrichment stage (1) of the M+1th stage, where M is an integer from 1 to N-1; A circulation pipeline (4) is configured to transport the oxidation products of the reverse oxidation unit (12) of the nth enrichment stage (1) to the electrolysis unit (11) of the (n-1)th enrichment stage (1), where n is an integer from 2 to N.

2. The isotope cascade enrichment system based on electrolysis-oxidation coupling cycle according to claim 1, characterized in that: The electrolysis unit (11) includes an electrolysis reactor containing an electrolyte and equipped with a pair of flat electrodes; the electrolysis reactor is configured to dissolve or disperse the carbon-containing raw material in the electrolyte and carry out an electrochemical reduction reaction.

3. The isotope cascade enrichment system based on electrolysis-oxidation coupling cycle according to claim 2, characterized in that: The reverse oxidation unit (12) includes a catalytic oxidation reactor; the system also includes an online isotope analyzer that is communicatively connected to the control unit; The online isotope analyzer is configured to detect in real time the abundance of heavy carbon isotopes in the residue output from the electrolysis unit (11) of at least the Nth enrichment stage (1). The control unit is configured to dynamically adjust the current density of the electrolysis unit (11) or the reaction temperature of the reverse oxidation unit (12) in at least one of the enrichment stages (1) based on the abundance of the heavy carbon isotopes.

4. The isotope cascade enrichment system based on electrolysis-oxidation coupling cycle according to claim 1, characterized in that: It also includes heat recovery devices; The heat recovery device is configured to use the waste heat from the process stream from at least one of the reverse oxidation units (12) to heat the feed stream delivered to at least one of the electrolysis units (11).

5. The isotope cascade enrichment system based on electrolysis-oxidation coupling cycle according to claim 4, characterized in that: The heat recovery device is a heat exchanger located at the material outlet of the reverse oxidation unit (12) or on the circulation pipeline (4).

6. An isotope cascade enrichment method based on an electrolysis-oxidation coupled cycle, implemented based on the isotope cascade enrichment system based on an electrolysis-oxidation coupled cycle as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. Raw material supply step: The carbon-containing raw material is transported to the electrolysis unit (11) of the first enrichment stage (1) through the raw material supply pipeline (2). S2, Cascaded enrichment and cyclic steps, including processing sub-steps for each level from level 1 to level N-1: S21, Electrolytic reduction sub-step: The input carbon-containing raw material is reduced in the electrolytic unit (11) to generate a residue enriched with heavy carbon isotopes and a reduction product enriched with light carbon isotopes. S22, Residue Transport Sub-step: The residue enriched with heavy carbon isotopes is transported through the interstage transport pipeline (3) to the electrolysis unit (11) of the next enrichment stage (1) as the main part of the carbon-containing raw material input therein; S23, Oxidation step: In the reverse oxidation unit (12), the reduction product of the enriched light carbon isotope produced by the enrichment stage (1) is oxidized to generate an oxidation product; S24, Oxidation product recycling sub-step: The oxidation product is transported through the recycling pipeline (4) to the electrolysis unit (11) of the previous enrichment stage (1) as a supplement to the carbon-containing raw material input therein; S3, Final enrichment step: The residue from the enrichment stage (1) of the Nth enrichment stage (1) is reduced in the electrolysis unit (11) to generate the target product with final enrichment of heavy carbon isotopes.

7. The isotope cascade enrichment method based on electrolysis-oxidation coupling cycle according to claim 6, characterized in that: Before the oxidation product is transported through the circulation pipe (4) to the electrolysis unit (11) of the previous enrichment stage (1), the following steps are also included: The oxidation products were subjected to gas-liquid separation to obtain carbon dioxide gas and water. The carbon dioxide gas is dried and purified to obtain purified carbon dioxide gas.

8. The isotope cascade enrichment method based on electrolysis-oxidation coupling cycle according to claim 6, characterized in that: It also includes the following steps: Real-time detection of the abundance of heavy carbon isotopes in the target product output at level N; The abundance of the heavy carbon isotopes is compared with the target abundance setting value to obtain the comparison result; If the abundance of heavy carbon isotopes is less than the target abundance setting, then reverse adjustment is performed, and the reverse adjustment includes at least one of the following operations: The current density of the electrolytic reduction sub-step of at least one enrichment stage (1) is increased sequentially in reverse order from stage N-1 to stage 1. The reaction temperature of the oxidizing sub-step of at least one enrichment stage (1) is decreased sequentially in reverse order from stage N-1 to stage 1.

9. The isotope cascade enrichment method based on electrolysis-oxidation coupling cycle according to claim 8, characterized in that: The execution of reverse adjustment includes the following steps: Based on the dynamic mathematical model of the system, with the operating parameters of the enrichment level (1) at the current level as the initial state, the heavy carbon isotope abundance change curve of the target product in the first preset time period in the future is predicted. With minimizing the deviation between the heavy carbon isotope abundance variation curve and the target abundance setting value as the optimization objective, the optimal variation sequence within the second preset time period from the current moment is obtained. The optimal variation sequence is the optimal current density sequence of the electrolytic reduction sub-step from level 1 to level N-1 and / or the optimal reaction temperature sequence of the oxidation sub-step. The optimization results corresponding to the current moment in the optimal change sequence are implemented, and the optimization results include the current density setpoint and / or reaction temperature setpoint calculated for each level from level 1 to level N-1.

10. The isotope cascade enrichment method based on electrolysis-oxidation coupling cycle according to claim 9, characterized in that: The optimization objectives also include minimizing the energy consumption required to increase the unit abundance of the final target product and minimizing the total energy consumption of the system. The solution obtains the optimal change sequence within a second preset time period from the current moment, including the following steps: A multi-objective optimization algorithm is used to weigh the three objectives of the deviation between the heavy carbon isotope abundance change curve and the target abundance setting value, the total energy consumption of the system, and the energy consumption per unit abundance increase, and to generate the Pareto optimal frontier. The optimal change sequence is selected from the Pareto optimal frontier according to a preset priority strategy.

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