Device and method for producing succinic acid by degrading waste and fixing carbon dioxide in situ

Abstract

The present application relates to the technical fields of bioelectrochemistry, waste resource utilization and carbon dioxide conversion and utilization, and particularly relates to a device and method for degrading waste and fixing carbon dioxide in situ to produce succinic acid. The specific technical scheme is as follows: an anode reaction tank and a cathode reaction tank in communication with the anode reaction tank are provided, a proton exchange membrane is arranged between the anode reaction tank and the cathode reaction tank, and a carbon dioxide passage is arranged in communication between the anode reaction tank and the cathode reaction tank; a gas circulation device is arranged in communication with the cathode reaction tank, the gas circulation device comprises a gas temporary storage unit, a gas inlet pipeline in communication with the gas temporary storage unit is in communication with the cathode reaction tank, and a gas outlet pipeline in communication with the gas temporary storage unit is in communication with the carbon dioxide passage in the cathode reaction tank. The present application solves the problem of insufficient coupling between the processes of anode waste degradation, electron transfer and carbon dioxide release and the process of cathode carbon dioxide fixation and synthesis in the existing bioelectrochemical system.

Description

Technical Field

[0001] This invention relates to the fields of bioelectrochemistry, waste resource utilization, and carbon dioxide conversion and utilization, specifically to an apparatus and method for in-situ fixation of carbon dioxide from waste to produce succinic acid. Background Technology

[0002] With the rapid development of urbanization, agricultural production, and the food processing industry, the amount of various organic wastes generated continues to increase. Organic waste mainly includes kitchen waste, food scraps, crop straw, livestock and poultry manure, food processing waste, residual sludge, and other wastes rich in biodegradable organic matter. This type of waste typically has characteristics such as high water content, high organic matter content, easy decomposition, easy odor production, and easy release of greenhouse gases. If not effectively treated, it can easily cause water and soil pollution, the spread of pathogenic microorganisms, the release of malodorous gases, and the emission of greenhouse gases such as methane and carbon dioxide, thus adversely affecting the ecological environment and public health safety.

[0003] Currently, the main methods for treating organic waste include landfill, incineration, composting, anaerobic digestion, and aerobic composting. These technologies have played a significant role in reducing, stabilizing, and rendering harmless waste. However, most processes still primarily focus on pollution reduction and end-of-pipe treatment, neglecting the high-value utilization of carbon, hydrogen, and oxygen resources in waste. For example, landfilling easily generates leachate and greenhouse gases; incineration faces challenges in energy recovery efficiency and flue gas control; compost products have relatively limited added value; and anaerobic digestion mainly yields biogas, making it difficult to fully realize the targeted conversion of carbon resources from waste into high-value chemicals. Therefore, promoting the transformation of organic waste treatment from reduction and harmlessness to resource recovery and high-value utilization has become an important development direction in the fields of waste resource utilization and green biomanufacturing.

[0004] Bioelectrochemical systems combine the advantages of microbial metabolic transformation and electrochemical regulation, enabling the degradation of organic matter, electron transfer, and synthesis of target products under mild conditions. This represents a crucial technological approach for the high-value utilization of organic waste. Existing bioelectrochemical technologies mainly include microbial fuel cells and microbial electrosynthesis systems. Microbial fuel cells primarily utilize anodic microorganisms to oxidize and degrade organic substrates and generate electricity, suitable for wastewater or organic waste degradation processes. However, their output power is typically low, and the carbon dioxide generated during anodic degradation is mostly directly emitted. Microbial electrosynthesis systems, on the other hand, mainly rely on cathode biocatalysis, reducing one-carbon substrates such as carbon dioxide into organic acids, alcohols, or other chemicals under the influence of applied electricity. However, existing microbial electrosynthesis systems typically focus on cathode synthesis, relying heavily on external gas sources for carbon dioxide supply. The anode side often employs inert electrode reactions or sacrificial oxidation reactions, failing to fully utilize the chemical energy and carbon resources inherent in the organic waste itself. Furthermore, the direct emission of incompletely utilized carbon dioxide from the cathode side reduces the overall carbon utilization efficiency and process economy of the system.

[0005] Succinic acid is an important C4 platform compound and bio-based chemical with wide applications in biodegradable materials, food, medicine, agriculture, and chemicals. The targeted synthesis of succinic acid using carbon dioxide and organic waste as carbon sources through a bioelectrochemical system can not only increase the added value of products from waste treatment processes but also promote the resource utilization of carbon dioxide, demonstrating significant environmental benefits and promising application prospects.

[0006] Therefore, it is necessary to provide a novel, structurally sound, and tightly coupled dual-chamber bioelectrochemical device and method that enables efficient degradation of organic waste and carbon dioxide generation on the anode side, in-situ fixation of carbon dioxide and synthesis of succinic acid on the cathode side, and recycling of unused carbon dioxide from the cathode via a gas circulation device. Through the integrated coupling of anode waste degradation, electron transfer, proton migration, cross-chamber carbon dioxide transport, and cathode tail gas recycling, the synergistic effects of organic waste reduction, carbon resource recycling, and high-value synthesis of succinic acid are achieved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an apparatus and method for in-situ fixation of carbon dioxide from waste to produce succinic acid, thereby solving the problem of insufficient coupling between the anode waste degradation, electron transfer, and carbon dioxide release and the cathode carbon dioxide fixation and synthesis processes in existing bioelectrochemical systems. In particular, it addresses the issues of direct emission of carbon dioxide from the anode, reliance on external carbon dioxide for cathode synthesis, insufficient recycling of cathode tail gas, and low overall carbon utilization efficiency of the system.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention discloses an apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid, comprising an anode reaction tank and a cathode reaction tank connected thereto, wherein a proton exchange membrane is provided between the anode reaction tank and the cathode reaction tank, and a carbon dioxide passage is connected to the anode reaction tank, the carbon dioxide passage extends into the cathode reaction tank and is connected to an annular gas distribution device provided in the cathode reaction tank.

[0010] The cathode reaction cell is connected to a gas circulation device, which includes a gas storage unit. The gas inlet pipe connected to the gas storage unit is connected to the cathode reaction cell, and the gas outlet pipe connected to the gas storage unit is connected to a carbon dioxide passage located in the cathode reaction cell.

[0011] Preferably, the anode reaction cell is provided with an anode electrode brush, and the cathode reaction cell is provided with a reference electrode and a cathode working electrode. The anode electrode brush, the reference electrode, and the cathode working electrode are electrically connected to a potentiostat.

[0012] Preferably, the cathode working electrode is one or more of the following: carbon cloth, carbon felt, carbon paper, graphite plate, graphite rod, graphite felt, graphite brush, carbon brush, stainless steel mesh, or nickel foam.

[0013] Preferably, the annular air distribution device includes a first annular air distribution pipe, a second annular air distribution pipe, and a third annular air distribution pipe arranged vertically from bottom to top. The inner diameters of the first, second, and third annular air distribution pipes gradually decrease. The first, second, and third annular air distribution pipes are coaxially arranged, and an air collecting pipe is vertically arranged at the center. The air collecting pipe is connected to the first, second, and third annular air distribution pipes through branch pipes.

[0014] Preferably, the carbon dioxide passage is connected to the bottom end of the gas collecting pipe, and the first, second, and third annular gas distribution pipes are respectively provided with gas distribution holes. The holes have the same diameter, and the number of gas distribution holes on the second annular gas distribution pipe is greater than the number of gas distribution holes on the first annular gas distribution pipe, which is greater than the number of gas distribution holes on the third annular gas distribution pipe.

[0015] Preferably, one end of each branch pipe extends into the first annular air distribution pipe, the second annular air distribution pipe, and the third annular air distribution pipe, and an outlet is provided on one side of the branch pipe.

[0016] Preferably, a return pipe is provided at the top end of the gas collecting pipe, the other end of the return pipe is connected to the carbon dioxide passage, and a throttling orifice plate is provided in the middle of the return pipe.

[0017] Preferably, the throttling orifice plate is disposed inside the connecting pipe and supported by a support block disposed on the inner wall of the connecting pipe. The return pipe is disconnected at the middle position, and the two ends of the connecting pipe are respectively inserted into the two ends of the disconnected part of the return pipe and are interference fit or threaded connection.

[0018] Preferably, a diverter is inserted into the gas collecting pipe, the outer diameter of the top cover plate of the diverter is larger than the outer diameter of the gas collecting pipe, the return pipe is inserted into the cover plate and communicates with the diverter, a through hole is provided on the side wall of the diverter, the through hole corresponds to the connection of each annular gas distribution pipe and branch pipe, and a guide plate is provided above the through hole, the guide plate is inclined downward.

[0019] Accordingly, a method for producing succinic acid using the aforementioned apparatus includes the following steps:

[0020] S1. Add anodic fermentation liquid to the anodic reaction tank. The anodic fermentation liquid includes organic waste and domesticated anaerobic mixed bacteria. And install anodic electrode brushes.

[0021] S2. Add cathode fermentation liquid to the cathode reaction tank. The cathode fermentation liquid is inoculated with succinic acid-producing microorganisms, and a reference electrode, a cathode working electrode and an annular gas distribution device are set up.

[0022] S3. Connect the anode reaction cell and the cathode reaction cell through a proton exchange membrane to construct a dual-chamber bioelectrochemical reaction system;

[0023] S4. The cathode reaction potential is controlled by an external potential regulator to enable the dual-chamber bioelectrochemical reaction system to operate. The organic waste in the anode reaction tank undergoes oxidative degradation under the action of microorganisms and electrochemical action, releasing electrons, protons and carbon dioxide. The electrons participate in the cathode reduction process through the external circuit under constant potential control.

[0024] S5. Electrons generated in the anode reaction tank are transferred to the cathode reaction tank through an electronic pathway, and carbon dioxide generated in the anode reaction tank is transported to the cathode reaction tank through a carbon dioxide pathway. The carbon dioxide is then dispersed into the cathode fermentation liquid through an annular gas distribution device, serving as a cathode reaction substrate. Under the synergistic action of cathode electrochemistry and cathode microorganisms, it participates in the succinic acid synthesis process.

[0025] S6. The carbon dioxide that is not fully utilized in the cathode reaction tank is collected by the gas circulation device, then introduced back into the annular gas distribution device and returned to the cathode fermentation liquid for recycling.

[0026] The cathode reaction potential is -0.6 to -1.0 V vs Ag / AgCl, the reaction temperature is 30 to 37°C, the pH of the cathode fermentation broth is 6.0 to 7.5, and the carbon dioxide flow rate in the cathode reaction tank is 10 to 100 mL / min.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention achieves the coupling of organic waste degradation on the anode side with the directional transport and utilization of carbon dioxide produced on the anode to the cathode side, reducing the cathode side's dependence on exogenous carbon dioxide; it improves the mass transfer efficiency of carbon dioxide in the cathode fermentation liquid through an annular gas distribution device; it realizes the recycling and reuse of carbon dioxide in the cathode tail gas through a gas circulation device; by constructing an integrated system of organic waste degradation on the anode, carbon dioxide transport on the anode, in-situ fixation at the cathode, and tail gas recycling and reuse, it achieves the synergistic transfer of electron flow, proton flow, and carbon flow, thereby improving the system's carbon utilization efficiency, succinic acid generation efficiency, and overall resource utilization level.

[0029] 2. This invention utilizes the synergistic effects of gaseous carbon dioxide transport and circulation, liquid-phase microbial transformation, and electrochemical electron transfer to form a coupled reaction chain within the same dual-chamber reaction system, encompassing organic waste degradation, electron release, proton migration, carbon dioxide transport, cathode fixation, tail gas recirculation, and succinic acid generation. This system can simultaneously achieve organic waste reduction, resource utilization of carbon dioxide produced at the anode, and high-value synthesis of succinic acid. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the annular air distribution device.

[0032] Figure 3 for Figure 2 A top view (with the manifold removed);

[0033] Figure 4 This is a schematic diagram of the flow divider structure;

[0034] Figure 5 This is a schematic diagram showing the connection between the gas collecting pipe and the carbon dioxide passage.

[0035] In the diagram: 1. Anode reaction tank; 2. Anode fermentation broth; 3. Anode electrode brush; 4. Proton exchange membrane; 5. Reference electrode; 6. Cathode working electrode; 7. Annular gas distribution device; 8. Cathode fermentation broth; 9. Cathode reaction tank; 10. Gas outlet pipe; 11. Gas storage unit; 12. Potentiostat; 13. Electronic path; 14. Carbon dioxide path; 15. First annular gas distribution pipe; 16. Second annular gas distribution pipe; 17. Third annular gas distribution pipe; 18. Gas collecting pipe; 19. Branch pipe; 20. Outlet; 21. Return pipe; 22. Orifice plate; 23. Connecting pipe; 24. Support block; 25. Diverter cylinder; 26. Cover plate; 27. Through hole; 28. Guide plate. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0038] refer to Figures 1-5 This invention discloses an apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid, comprising an anode reaction tank 1 and a cathode reaction tank 9 connected thereto. The anode reaction tank 1 is configured as a waste oxidation and degradation reaction zone, and the cathode reaction tank 9 is configured as a carbon dioxide in-situ fixation and succinic acid synthesis reaction zone. A proton exchange membrane 4 is provided between the anode reaction tank 1 and the cathode reaction tank 9 to achieve proton transfer and spatial separation between them. A carbon dioxide passage 14 is connected to the anode reaction tank 1, with one end of the carbon dioxide passage 14 located above the surface of the anode fermentation liquid. The carbon dioxide passage 14 is a gas guide connecting the anode reaction tank 1 and the cathode reaction tank 9. The carbon dioxide passage 14 extends into the cathode reaction tank 9 and is connected to an annular gas distribution device 7 disposed within the cathode reaction tank 9. A gas circulation device is connected to the cathode reaction tank 9 to collect unutilized carbon dioxide in the cathode reaction tank and return the collected carbon dioxide to the annular gas distribution device 7 to achieve carbon dioxide recycling. It should be noted that one or more of the following can be installed on the carbon dioxide passage 14: a gas pump, a one-way valve, a flow meter, a gas-liquid separator, or a gas filter, to achieve directional transport of carbon dioxide produced at the anode to the cathode side and reduce the risk of gas backflow or liquid backflow.

[0039] Furthermore, the gas circulation device includes a gas storage unit 11. An inlet pipe connected to the gas storage unit 11 is connected to the cathode reaction tank 9, with one end of the inlet pipe located above the surface of the cathode fermentation liquid. An outlet pipe 10 connected to the gas storage unit 11 is connected to a carbon dioxide passage 14 located within the cathode reaction tank 9. The gas storage unit 11 can be a gas bag, gas cylinder, buffer tank, or other container suitable for temporarily storing gases, used to collect, temporarily store, and buffer unused carbon dioxide within the cathode reaction tank.

[0040] Furthermore, an anode electrode brush 3 is provided in the anode reaction tank 1. The anode electrode brush 3 is a brush-shaped conductive material electrode used to enrich the anode biofilm and enhance the electron transfer capability of the anode reaction tank. A reference electrode 5 and a cathode working electrode 6 are provided in the cathode reaction tank 9. The cathode working electrode 6 is one or more of the following: carbon cloth, carbon felt, carbon paper, graphite plate, graphite rod, graphite felt, graphite brush, carbon brush, stainless steel mesh, or nickel foam; preferably, the cathode working electrode 6 is carbon felt, carbon cloth, or graphite felt. The anode electrode brush 3, the reference electrode 5, and the cathode working electrode 6 are electrically connected to the potentiostat 12 to form a dual-cavity bioelectrochemical reaction system controlled by an applied potential. Electrons released from the oxidation of organic waste in the anode reaction tank 1 are transferred to the cathode reaction tank 9 through the electron pathway 13 under constant potential control and participate in the cathode reduction reaction. Electronic pathway 13 is an external circuit connecting the anode electrode brush 3 and the cathode working electrode 6. Carbon dioxide generated in the anode reaction tank 1 is transported to the cathode reaction tank 9 via carbon dioxide pathway 14 and dispersed into the cathode fermentation liquid 8 via the annular gas distribution device 7 for use in the carbon dioxide fixation reaction within the cathode reaction tank 9. Unutilized carbon dioxide in the cathode reaction tank 9 is collected by the gas circulation device, reintroduced into the annular gas distribution device 7, and returned to the cathode fermentation liquid 8 for recycling, reducing direct emissions of carbon dioxide from the cathode exhaust gas and improving the overall carbon utilization efficiency of the system. It should be noted that the potentiostat 12 is used to regulate the reaction potential of the cathode working electrode 6. Specifically, electrons are released from the anodic oxidation of organic waste, and these electrons are transferred to the cathode working electrode 6 under constant potential control via the external circuit and participate in the cathode reduction process, thereby promoting the coupling of the anodic organic matter oxidation and degradation with the cathode carbon dioxide fixation and succinic acid synthesis process.

[0041] Furthermore, the surface of the cathode working electrode 6 is provided with a catalytic layer that promotes carbon dioxide mass transfer and conversion. The catalytic layer is used to promote the mass transfer and fixation reaction of carbon dioxide at the cathode interface. The catalytic layer includes carbonic anhydrase and one or more of chitosan, polydopamine, and alginate for fixing the carbonic anhydrase.

[0042] Furthermore, the cathode fermentation broth 8 is inoculated with succinic acid-producing microorganisms. The carbon dioxide generated during the degradation of organic waste in the anode reaction tank can participate in the succinic acid synthesis process as a substrate for carboxylation. The succinic acid-producing microorganisms include, but are not limited to, one or more of Actinobacillus succinogenes, Mannheimia succiniciproducens, and Basfia succiniciproducens. The cathode working electrode 6 is used to receive electrons released from the oxidation of organic waste on the anode side and transferred through the external circuit under the control of a potentiostat, and to provide reduction conditions for carbon dioxide fixation and succinic acid synthesis on the cathode side.

[0043] The cathode fermentation broth may further include basal culture medium components, buffer salts, inorganic salts, nitrogen sources, vitamins, and optional auxiliary substrates required for the growth and metabolism of succinic acid-producing microorganisms. The anode fermentation broth 2 includes organic waste and an anaerobic mixed microbial community inoculated with the waste. The organic waste is one or more of the following: kitchen waste, food waste, food processing waste, crop straw hydrolysate, livestock and poultry manure, residual sludge hydrolysate, or other waste rich in degradable organic matter. The anaerobic mixed microbial community is preferably an anaerobic or facultative anaerobic mixed microorganism with the ability to degrade organic matter and transfer extracellular electrons, such as *Geobacter sulfurreducens* and *Shewanella oneidensis*.

[0044] In the anodic reaction tank of this invention, electrons, protons, and carbon dioxide are generated during the degradation of organic waste. The electrons are transferred to the cathode reaction tank through an electron pathway, the protons migrate to the cathode reaction tank through a proton exchange membrane, and the carbon dioxide is transported to the cathode reaction tank through a carbon dioxide pathway and uniformly dispersed into the cathode fermentation liquid through an annular gas distribution device. As a cathode reaction substrate, it participates in the succinic acid synthesis process under the synergistic action of cathode electrochemistry and cathode microorganisms. The carbon dioxide that is not fully utilized in the cathode reaction tank is collected through the pipelines of the gas circulation device and the gas temporary storage unit, and then fed back to the annular gas distribution device and returned to the cathode fermentation liquid for recycling.

[0045] Furthermore, the annular gas distribution device 7 is located at the bottom of the cathode reaction tank 9 or inside the cathode fermentation liquid 8, and is connected to the carbon dioxide passage 14 and the gas circulation device. The annular gas distribution device 7 has an annular body and multiple gas distribution holes, which are used to uniformly disperse carbon dioxide into the cathode fermentation liquid 8, thereby increasing the gas-liquid contact area and improving the carbon dioxide mass transfer efficiency and utilization efficiency, and providing a carbon source for cathode microorganisms to fix carbon dioxide and synthesize succinic acid.

[0046] Specifically: such as Figures 2-5As shown, the annular air distribution device 7 includes a first annular air distribution pipe 15, a second annular air distribution pipe 16, and a third annular air distribution pipe 17 arranged vertically from bottom to top. The inner diameter of the first annular air distribution pipe 15, the second annular air distribution pipe 16, and the third annular air distribution pipe 17 gradually decreases. The first annular air distribution pipe 15, the second annular air distribution pipe 16, and the third annular air distribution pipe 17 are arranged coaxially, and an air collecting pipe 18 is vertically arranged at the center. The air collecting pipe 18 is connected to the first annular air distribution pipe 15, the second annular air distribution pipe 16, and the third annular air distribution pipe 17 through branch pipes 19. It should be noted that, as a preferred embodiment, the diameter of the first annular gas distributor is 3 / 4 of the inner diameter of the cathode reaction tank, the diameter of the second annular gas distributor is 1 / 2 of the inner diameter of the cathode reaction tank, and the diameter of the third annular gas distributor is 1 / 4 of the inner diameter of the cathode reaction tank. The gas distribution holes on the first annular gas distributor are located near its bottom, distributed at a 60° angle to the bottom, preferably in two rings: one ring of gas distribution holes facing outwards from the first annular gas distributor, and another ring facing inwards from the first annular gas distributor. This allows gas to diffuse towards the wall of the cathode reaction tank, eliminating dead zones at the edges. Similarly, the gas distribution holes on the second annular gas distributor are arranged in the same manner as the first annular gas distributor, except that the gas distribution holes on the second annular gas distributor are distributed at a 45° angle. The gas distribution holes on the third annular gas distributor are located at its top, thereby maximizing the contact amount and contact time between carbon dioxide gas and the fermentation broth.

[0047] Furthermore, the carbon dioxide passage 14 is connected to the bottom end of the gas collecting pipe 18. The first annular gas distribution pipe 15, the second annular gas distribution pipe 16, and the third annular gas distribution pipe 17 are each provided with gas distribution holes. The holes have the same diameter, and the number of gas distribution holes on the second annular gas distribution pipe 16 is greater than the number on the first annular gas distribution pipe 15, which in turn is greater than the number on the third annular gas distribution pipe 17. It should be noted that, based on the limitations of the three annular gas distribution pipe ring dimensions and the control of the number of gas distribution holes, the resulting resistance differences enable the gas to be automatically distributed into the three annular gas distribution pipes in different proportions. The stepped height difference maximizes the gas-liquid contact time. As another implementation scheme, the diameter of the gas distribution holes can be differentiated. For example, the diameter of the gas distribution holes decreases sequentially from the first annular gas distribution pipe to the third annular gas distribution pipe, and can be set according to actual needs.

[0048] Furthermore, one end of each branch pipe 19 extends into the first annular gas distribution pipe 15, the second annular gas distribution pipe 16, and the third annular gas distribution pipe 17, respectively. An outlet 20 is provided on one side of each branch pipe 19, with the outlet facing the inside of the annular gas distribution pipe. This prevents the gas entering the annular gas distribution pipe from directly impacting the inner wall of the pipe. Instead, it allows the gas to form a swirling flow as much as possible after entering the annular gas distribution pipe, ensuring uniform circumferential gas distribution within the gas distribution pipe and minimizing the phenomenon of one side having more gas than the other.

[0049] Furthermore, a return pipe 21 is provided at the top of the gas collecting pipe 18, and the other end of the return pipe 21 is connected to the carbon dioxide passage 14. A throttling orifice plate 22 is provided in the middle of the return pipe 21. It should be noted that the return pipe prevents the gas entering the gas collecting pipe from being discharged from its top. Instead, excess gas entering the annular gas distribution pipe is discharged from the top of the gas collecting pipe through the return pipe into the carbon dioxide passage and then continues to enter the gas collecting pipe, forming a return flow, so that carbon dioxide participates in in-situ fixation as much as possible. The purpose of the throttling orifice plate is to increase the resistance of the return pipe, so that the gas first enters the annular gas distribution pipe as much as possible, while the excess gas enters the return pipe. The volume of the gas collecting pipe is preferably 2-3 times the total gas intake. Combined with the gas circulation effect of the top return pipe, it can effectively buffer the pressure changes caused by the fluctuation of the anode gas production, so that the gas intake flow fluctuation of each annular gas distribution pipe is controlled within a certain range, ensuring the stability of the cathode reaction.

[0050] Furthermore, the orifice plate 22 is disposed within the connecting pipe 23 and supported by multiple support blocks 24 disposed radially on the inner wall of the connecting pipe 23 to support the orifice plate. The number and size of the holes on the orifice plate determine the amount of resistance, which can be set according to actual needs. When installing the connecting pipe, the return pipe 21 is disconnected at the middle position, and both ends of the connecting pipe 23 are respectively inserted into the two ends of the disconnection point of the return pipe 21 with interference fit or threaded connection. At this time, orifice plates of different diameters and numbers can be replaced as needed. In this invention, in order to facilitate the installation of components, both ends of the return pipe are respectively inserted into the top of the gas collecting pipe and the carbon dioxide passage 14. Similarly, one end of the gas outlet pipe 10 is also directly inserted into the carbon dioxide passage 14. Of course, sealing rings can be set, and the pipe connection can be set into a wedge shape, etc., as needed to avoid air leakage and increase the stability of the pipe connection. The same operation can be used in other places involving pipe connection.

[0051] Furthermore, to achieve diversion of carbon dioxide entering the gas collecting pipe within the pipe, a diversion cylinder 25 is inserted into the gas collecting pipe 18. The outer diameter of the top cover plate 26 of the diversion cylinder 25 is larger than the outer diameter of the gas collecting pipe 18. The return pipe 21 is inserted into the cover plate 26 and communicates with the diversion cylinder 25. Through holes 27 are provided on the side wall of the diversion cylinder 25, corresponding to the connection points of each annular gas distribution pipe and branch pipe 19. A guide plate 28 is provided above the through holes 27, and the guide plate 28 is inclined downwards. It should be noted that the diversion cylinder is directly inserted into the gas collecting pipe, with its outer wall fitting as close as possible to the inner wall of the gas collecting pipe. Through holes are provided on the diversion cylinder and at the connection points of the annular gas distribution pipe and branch pipe, allowing carbon dioxide to enter the branch pipe through the through holes. The guide plate is positioned above the through holes and inclined downwards, serving to guide and intercept the carbon dioxide. As a preferred embodiment, such as... Figure 2 , Figure 3 As shown, the branch pipe and the annular gas distributor are staggered so that the guide plates are also staggered, achieving partial gas interception. The size of the guide plates can initially determine the amount of gas interception. For example, the central angle of the throttling plate corresponding to the first annular gas distributor is preferably 180°, and the central angle of the throttling plates corresponding to the other two annular gas distributors is preferably 90°, to achieve initial gas interception. Combined with the limitations on the size of the annular gas distributor and the number of gas distribution holes, a stable diversion of carbon dioxide entering the gas collecting pipe is ultimately achieved.

[0052] The annular gas distribution device and gas circulation device designed in this invention work in conjunction to achieve uniform dispersion, stable supply, and efficient recycling of carbon dioxide in the cathode fermentation liquid. The three-layer concentric nested annular gas distribution pipe structure, arranged vertically from bottom to top, can respectively cover the edge area, core reaction area, and central area of ​​the cathode reaction tank, forming a comprehensive gas distribution effect. This avoids the problem that a single gas distribution pipe cannot cover different radial positions in the reaction tank, effectively eliminating the carbon source supply dead zone in the reaction tank.

[0053] The diverter cylinder and its inclined guide plate installed in the gas collecting pipe can initially guide and intercept the gas entering the gas collecting pipe, so that the gas flows to different annular gas distribution pipes according to a preset ratio. Combined with the resistance difference formed by the different number of gas distribution holes on each annular gas distribution pipe, the gas can be stably distributed among the three annular gas distribution pipes without any external adjustment components, which can better adapt to the microbial metabolic needs of different areas in the cathode reaction tank.

[0054] In addition, the design of the branch pipe extending into the annular gas distribution pipe and with its outlet facing the inner circumference of the pipe allows the gas entering the annular gas distribution pipe to flow along the inner wall of the annular gas distribution pipe and form a circumferential swirling flow. This ensures the uniformity of gas output from each gas distribution hole on the annular gas distribution pipe and avoids the problem of uneven local gas output caused by gas directly impacting the inner wall of the annular pipe.

[0055] The return pipe and throttling orifice plate installed at the top of the gas collecting pipe can return excess gas in the gas collecting pipe that does not enter the branch pipe to the carbon dioxide passage for redistribution. This not only avoids the accumulation of gas at the top of the gas collecting pipe, but also buffers the pressure in the gas collecting pipe, reducing the impact of anode gas production fluctuations on cathode gas distribution stability.

[0056] Carbon dioxide not fully utilized by microorganisms in the cathode reaction tank is collected through the inlet pipe of the gas circulation device and temporarily stored and buffered in the gas storage unit. It then flows back into the carbon dioxide path through the outlet pipe, mixes with fresh carbon dioxide produced in the anode reaction tank, and re-enters the annular gas distribution device to disperse into the cathode fermentation broth for further reaction. This forms a complete closed-loop carbon flow: anode degradation carbon production – uniform cathode gas distribution – tail gas recovery and storage – recirculation and re-distribution. This significantly reduces direct carbon dioxide emissions and improves the overall carbon resource utilization efficiency of the system. The gas distribution holes on each annular gas distribution pipe are set with different tilt angles, guiding bubbles to diffuse in different directions and further optimizing the spatial distribution of carbon dioxide in the fermentation broth. Simultaneously, the pluggable distribution tube design facilitates disassembly, cleaning, and maintenance of the device, improving its long-term reliability and service life.

[0057] Compared to using a single annular gas distribution pipe, the three-layer nested annular gas distribution device designed in this invention significantly improves the gas distribution effect and reaction efficiency within the cathode reaction tank. A single annular gas distribution pipe typically only covers the central area of ​​the reactor, making it difficult to reach the peripheral areas. This can easily lead to uneven carbon source distribution within the reactor, with microorganisms in the peripheral areas experiencing reduced metabolic activity due to insufficient carbon source, while the central area may suffer from carbon source overload and waste. This device, through the combination of three layers of annular gas distribution pipes with different diameters, can cover most of the reactor's cross-sectional area, allowing carbon dioxide to be evenly supplied to all parts of the reaction tank, providing a consistent carbon source environment for microbial growth and metabolism. Furthermore, the gas distribution method of a single annular gas distribution pipe is relatively simple, making it difficult to provide targeted gas supply based on the bacterial density distribution within the reactor. This device, however, through the coordinated control of the number of guide plates and gas distribution holes, can achieve on-demand gas distribution, ensuring that more carbon source is supplied to the core reaction area with the highest bacterial density, effectively improving the utilization efficiency of the carbon source. Furthermore, single-ring gas distribution pipes are prone to uneven circumferential gas distribution, leading to poor mass transfer in localized areas within the reactor. This device, through a branch-pipe inserted swirl gas distribution design, effectively improves the uniformity of circumferential gas distribution, enhances the gas-liquid mass transfer efficiency of carbon dioxide, and thus promotes the cathode carbon dioxide fixation and succinic acid synthesis processes. Simultaneously, the device's reflux design and maintainable structure also ensure better stability during long-term operation, better meeting the requirements of continuous bioelectrochemical reactions.

[0058] This invention provides a method for producing succinic acid using the aforementioned apparatus, comprising the following steps:

[0059] S1. Add anodic fermentation liquid 2 to the anodic reaction tank 1. The anodic fermentation liquid 2 includes organic waste and domesticated anaerobic mixed bacteria, and anodic electrode brush 3 is provided. The concentration of organic waste in the anodic reaction tank is 1000-10000 mg / L, preferably 3000-6000 mg / L, based on chemical oxygen demand. The reaction time is 24-120 h, preferably 48-72 h.

[0060] S2. Add culture medium to the cathode reaction tank 9 and inoculate succinic acid-producing microorganisms to form cathode fermentation broth 8, and set up a reference electrode 5, a cathode working electrode 6 and an annular gas distribution device 7; wherein, the inoculation amount of the succinic acid-producing microorganisms is 5% to 20% (v / v) of the cathode fermentation broth volume, preferably 10% (v / v).

[0061] S3. Connect the anode reaction cell 1 and the cathode reaction cell 9 through the proton exchange membrane 4 to construct a dual-chamber bioelectrochemical reaction system;

[0062] S4. The cathode reaction potential is externally controlled by a potentiostat 12, causing electrons released from the anodic oxidation of organic waste to be directionally transferred to the cathode via an external circuit and participate in the cathode reduction process under constant potential control. During operation, the organic waste in the anodic reaction tank 1 undergoes hydrolysis, acidification, and oxidative degradation under the action of microorganisms, releasing electrons, protons, and carbon dioxide. The electrons enter the electron pathway 13 through the anodic electrode brush 3 and are transferred to the cathode working electrode 6; the protons migrate to the cathode reaction tank 9 through the proton exchange membrane 4; and the carbon dioxide enters the cathode reaction tank 9 through the carbon dioxide pathway 14 and is dispersed into the cathode fermentation broth 8 via the annular gas distribution device 7. Under the reducing conditions provided by the cathode working electrode 6, the cathode microorganisms utilize carbon dioxide to participate in the succinic acid synthesis process.

[0063] S5. Electrons generated in the anode reaction tank 1 are transferred to the cathode reaction tank 9 through the electron path 13, and carbon dioxide generated in the anode reaction tank 1 is transported to the cathode reaction tank 9 as a carbon source through the carbon dioxide path 14. The carbon dioxide is dispersed into the cathode fermentation liquid 8 through the annular gas distribution device 7, and serves as a cathode reaction substrate. Under the synergistic action of cathode electrochemistry and cathode microorganisms, it participates in the succinic acid synthesis process.

[0064] S6. The carbon dioxide that is not fully utilized in the cathode reaction tank 9 is collected by the gas circulation device and then introduced back into the annular gas distribution device 7 and returned to the cathode fermentation liquid 8 for recycling. Thus, the system forms an integrated coupled process of anode organic waste degradation, electron transfer, proton migration, anode carbon dioxide production and transportation, cathode carbon dioxide fixation and cathode tail gas recycling.

[0065] The cathode reaction potential is -0.6 to -1.0 V vs Ag / AgCl, preferably -0.8 V; the reaction temperature is 30 to 37°C, preferably 37°C; the pH of the cathode fermentation broth 8 is 6.0 to 7.5, preferably 6.8; and the carbon dioxide flow rate in the cathode reaction tank 9 is 10 to 100 mL / min, preferably 30 mL / min.

[0066] This invention achieves integrated coupling of waste degradation and succinic acid synthesis through the synergistic effect of generating electrons from organic waste, transferring them through electron pathway 13 to form an electron flow, protons migrating through proton exchange membrane 4 to form a proton flow, and carbon dioxide being transported through carbon dioxide pathway 14 and returned through a gas circulation device.

[0067] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0068] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for in-situ fixation of carbon dioxide from waste to produce succinic acid, characterized in that: It includes an anode reaction tank (1) and a cathode reaction tank (9) connected thereto. A proton exchange membrane (4) is provided between the anode reaction tank (1) and the cathode reaction tank (9). A carbon dioxide passage (14) is connected to the anode reaction tank (1). The carbon dioxide passage (14) extends into the cathode reaction tank (9) and is connected to an annular gas distribution device (7) provided in the cathode reaction tank (9). The cathode reaction tank (9) is connected to a gas circulation device, which includes a gas storage unit (11). The gas inlet pipe connected to the gas storage unit (11) is connected to the cathode reaction tank (9), and the gas outlet pipe (10) connected to the gas storage unit (11) is connected to the carbon dioxide passage (14) located in the cathode reaction tank (9).

2. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 1, characterized in that: An anode electrode brush (3) is provided in the anode reaction tank (1), and a reference electrode (5) and a cathode working electrode (6) are provided in the cathode reaction tank (9). The anode electrode brush (3), the reference electrode (5), and the cathode working electrode (6) are electrically connected to the potentiostat (12).

3. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 1, characterized in that: The cathode working electrode (6) is one or more of the following: carbon cloth, carbon felt, carbon paper, graphite plate, graphite rod, graphite felt, graphite brush, carbon brush, stainless steel mesh, or nickel foam.

4. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 1, characterized in that: The annular air distribution device (7) includes a first annular air distribution pipe (15), a second annular air distribution pipe (16), and a third annular air distribution pipe (17) arranged vertically from bottom to top. The inner diameter of the first annular air distribution pipe (15), the second annular air distribution pipe (16), and the third annular air distribution pipe (17) gradually decreases. The first annular air distribution pipe (15), the second annular air distribution pipe (16), and the third annular air distribution pipe (17) are arranged coaxially, and an air collecting pipe (18) is vertically arranged at the center. The air collecting pipe (18) is connected to the first annular air distribution pipe (15), the second annular air distribution pipe (16), and the third annular air distribution pipe (17) through branch pipes (19).

5. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 4, characterized in that: The carbon dioxide passage (14) is connected to the bottom end of the gas collecting pipe (18). The first annular gas distribution pipe (15), the second annular gas distribution pipe (16) and the third annular gas distribution pipe (17) are respectively provided with gas distribution holes. The holes have the same diameter. The number of gas distribution holes on the second annular gas distribution pipe (16) is greater than the number of gas distribution holes on the first annular gas distribution pipe (15) is greater than the number of gas distribution holes on the third annular gas distribution pipe (17).

6. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 5, characterized in that: One end of each of the branch pipes (19) extends into the first annular air distribution pipe (15), the second annular air distribution pipe (16) and the third annular air distribution pipe (17), and an outlet (20) is provided on one side of the branch pipe (19).

7. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 4, characterized in that: The top end of the gas collecting pipe (18) is provided with a return pipe (21), the other end of the return pipe (21) is connected to the carbon dioxide passage (14), and a throttling orifice plate (22) is provided in the middle of the return pipe (21).

8. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 7, characterized in that: The throttling orifice plate (22) is set inside the connecting pipe (23) and supported by the support block (24) set on the inner wall of the connecting pipe (23). The return pipe (21) is broken at the middle position. The two ends of the connecting pipe (23) are respectively inserted into the two ends of the break of the return pipe (21) and are interference fit or threaded connection.

9. The apparatus for in-situ fixation of carbon dioxide from waste to produce succinic acid according to claim 5, characterized in that: A flow divider (25) is inserted into the gas collecting pipe (18). The outer diameter of the top cover plate (26) of the flow divider (25) is larger than the outer diameter of the gas collecting pipe (18). The return pipe (21) is inserted into the cover plate (26) and communicates with the flow divider (25). A through hole (27) is provided on the side wall of the flow divider (25). The through hole (27) corresponds to the connection of each annular gas distribution pipe and branch pipe (19). A guide plate (28) is provided above the through hole (27). The guide plate (28) is inclined downward.

10. A method for producing succinic acid using the apparatus according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Add anodic fermentation liquid (2) to the anodic reaction tank (1). The anodic fermentation liquid (2) includes organic waste and domesticated anaerobic mixed bacteria, and set anodic electrode brush (3). S2. Add cathode fermentation liquid (8) to cathode reaction tank (9). The cathode fermentation liquid (8) is inoculated with succinic acid producing microorganisms and is equipped with a reference electrode (5), a cathode working electrode (6) and an annular gas distribution device (7). S3. Connect the anode reaction cell (1) and the cathode reaction cell (9) through the proton exchange membrane (4) to construct a dual-cavity bioelectrochemical reaction system; S4. The cathode reaction potential is controlled by an external potential regulator (12) to make the dual-cavity bioelectrochemical reaction system run. The organic waste in the anode reaction tank (1) is oxidized and degraded under the action of microorganisms and electrochemical action, and releases electrons, protons and carbon dioxide. The electrons participate in the cathode reduction process under the constant potential control condition through the external circuit. S5. Electrons generated in the anode reaction tank (1) are transferred to the cathode reaction tank (9) through the electron path (13), and carbon dioxide generated in the anode reaction tank (1) is transported to the cathode reaction tank (9) through the carbon dioxide path (14). The carbon dioxide is dispersed into the cathode fermentation liquid (8) through the annular gas distribution device (7) and serves as the cathode reaction substrate. Under the synergistic effect of cathode electrochemistry and cathode microorganisms, it participates in the succinic acid synthesis process. S6. The carbon dioxide that is not fully utilized in the cathode reaction tank (9) is collected by the gas circulation device, introduced back into the annular gas distribution device (7) and returned to the cathode fermentation liquid (8) for recycling. The cathode reaction potential is -0.6 to -1.0 V vs Ag / AgCl, the reaction temperature is 30 to 37°C, the pH of the cathode fermentation liquid (8) is 6.0 to 7.5, and the carbon dioxide flow rate in the cathode reaction tank (9) is 10 to 100 mL / min.

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