A dual-chamber bioelectrochemical anaerobic fermentation system and a method of using the same

Abstract

The application discloses a double-cavity bioelectrochemical anaerobic fermentation system and a use method thereof, relates to the field of biological energy, and comprises a direct-current power supply, an anaerobic reactor and a gas collector. The anaerobic reactor has two reaction cavities, the two reaction cavities are isolated through an ion exchange membrane, the two reaction cavities are connected with two gas collectors through gas guide pipes, two electrodes connected with the direct-current power supply are respectively inserted into the two reaction cavities, the electrodes are connected with the direct-current power supply through wires, the electrodes are respectively an anode and a cathode, and fermentation substrates and anaerobic active inocula are added into the reaction cavities during use. The fermentation substrates are digested and fermented through bioelectrochemical and anaerobic digestion, and biogas is generated. The application can shorten anaerobic fermentation time in the process of anaerobic digestion and biological energy regeneration, improve raw material treatment efficiency and biogas yield, and improve biogas quality and reduce cost.

Description

Technical Field

[0001] This invention relates to the field of bioenergy, and more particularly to a dual-chamber bioelectrochemical anaerobic fermentation system and its method of use. Background Technology

[0002] Lignocellulosic biomass (such as straw, wheat straw, and rice straw) can be biorefined to produce bioenergy products (such as biogas). Utilizing straw for energy not only alleviates the shortage of petroleum resources but also reduces, recovers, and generates energy from biomass waste such as straw, thereby mitigating environmental pollution. Biogas produced from biomass resources exhibits significantly lower carbon emissions than petroleum and diesel. The carbon dioxide released during the use of bioenergy products can be fixed by plants using solar energy and water. Therefore, developing bioenergy does not cause greenhouse gas emissions.

[0003] Anaerobic digestion technology has been widely applied to the biorefining of straw in recent years. Through anaerobic digestion, the organic matter in straw can be converted into clean energy biogas. The resulting biogas slurry has a low organic matter content but is rich in nutrients such as nitrogen, phosphorus, and potassium, and can be directly discharged into farmland as liquid organic fertilizer. Therefore, anaerobic digestion has multiple advantages, including treating agricultural organic waste, recovering clean energy, and reducing overall energy consumption. While traditional anaerobic digestion of straw has advantages such as low energy consumption and high processing capacity, lignocellulosic biomass, mainly composed of cellulose, hemicellulose, and lignin, is difficult to degrade during anaerobic digestion. Its anaerobic microbial community requires a long period of acclimatization to establish a new microbial community with strong tolerance and hydrolytic capacity, which increases the hydraulic retention time and reduces the efficiency of anaerobic digestion. Furthermore, the biogas composition of conventional anaerobic digestion is typically 60%-40% methane, 40%-60% carbon dioxide, and small amounts of carbon monoxide and hydrogen sulfide. Therefore, if the biogas obtained is to be refined into biomethane, it needs to undergo further decarbonization and desulfurization, which will increase equipment investment and site area.

[0004] In recent years, bioelectrochemical systems have attracted attention as an emerging technology for treating organic waste and generating electricity. In an electrochemical reactor, additional electrical energy is supplied to assist in the degradation of organic matter; this system is called a microbial electrolysis cell. The bioelectrochemical anaerobic digestion system, formed by combining a microbial electrolysis cell with an anaerobic digester, offers numerous advantages. It can improve the degradation rate of recalcitrant organic matter, increase biogas production and quality, and shorten the time required for anaerobic digestion to reach stability, all through the synergistic effect of electroactive bacteria.

[0005] By combining a dual-chamber electrochemical system with an anaerobic digestion system, a large number of electroactive bacteria are enriched in the system. At the anode, the attached electroactive bacteria can accelerate the hydrolysis and acid production process, thereby improving the overall performance of anaerobic digestion. At the cathode, methanogens can directly transfer electrons with the electrode, thereby accelerating methane production. In addition, the electrons provided by the electrode combine with hydrogen ions to generate hydrogen gas, which, along with the carbon dioxide produced during hydrolysis, can improve biogas quality through the action of hydrotrophic methanogens in the same system. However, there are currently no studies or inventions specifically addressing the independent promoting effects of the anode or cathode on the anaerobic digestion system. Therefore, developing a dual-chamber bioelectrochemical anaerobic digestion system to study the individual and combined promoting effects of the anode and cathode on the methanogenesis performance of anaerobic digestion is of great significance.

[0006] Therefore, those skilled in the art are dedicated to developing an anaerobic digestion and energy regeneration device and method based on a dual-chamber electrochemical anaerobic fermentation system, which can shorten anaerobic fermentation time, improve raw material processing efficiency, and increase biogas production. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to shorten the anaerobic fermentation time, improve the raw material processing efficiency and biogas production, and improve biogas quality and reduce costs in the process of anaerobic digestion and bioenergy regeneration.

[0008] To achieve the above objectives, the present invention provides a dual-chamber bioelectrochemical anaerobic fermentation system, characterized in that it includes a DC power supply, an anaerobic reactor, and a gas collector. The anaerobic reactor has two reaction chambers, which are isolated by an ion exchange membrane. The two reaction chambers are respectively connected to two gas collectors through gas delivery pipes. Two electrodes connected to the DC power supply are respectively inserted into the two reaction chambers. The electrodes are connected to the DC power supply through wires, and the electrodes are anode and cathode, respectively.

[0009] In a preferred embodiment of the present invention, the ion exchange membrane is a cation exchange membrane.

[0010] In another preferred embodiment of the present invention, the two reaction chambers are respectively sealed with sealing plugs, and the electrodes and gas guide tubes are connected to the reaction chambers through the sealing plugs.

[0011] In another preferred embodiment of the present invention, the gas collector is a gas bag, each gas bag is provided with two gas valves, and one of the gas valves on each gas bag is connected to a gas guide pipe.

[0012] In another preferred embodiment of the present invention, during use, two reaction chambers are respectively filled with anaerobic active inoculum, and two electrodes are respectively inserted into the anaerobic active inoculum in the two reaction chambers.

[0013] In another preferred embodiment of the invention, fermentation substrate is added to both reaction chambers during use.

[0014] In another preferred embodiment of the present invention, the anaerobic active inoculum is a well-acclimated anaerobic biogas slurry with methanogenic activity, and the added fermentation substrate is corn straw.

[0015] In another preferred embodiment of the present invention, the fermentation system further includes a constant temperature water bath, in which the anaerobic reactor is placed in the water bath during use.

[0016] In another preferred embodiment of the present invention, the fermentation system further includes a stirring device, specifically a magnetic stirrer and a magnetic stirring rotor. In use, the two reaction chambers of the anaerobic reactor are respectively placed on two magnetic stirrers, and the two magnetic stirring rotors are respectively placed at the bottom of the two reaction chambers.

[0017] The present invention also provides a method for using the above-mentioned dual-chamber bioelectrochemical anaerobic fermentation system, specifically including: adding anaerobic active inoculum and fermentation substrate to the two reaction chambers of the anaerobic reactor; introducing high-purity nitrogen gas into the dual-chamber anaerobic reactor for a certain period of time; sealing the anaerobic reactor and placing it in a constant temperature water bath at 35°C, stirring the mixture in the reaction chamber evenly, turning on the DC power supply, controlling the external voltage of the dual-chamber bioelectrochemical anaerobic reactor at 0.6V-1.2V, and collecting the generated biogas through a gas collector.

[0018] Based on this invention, the following technical effects can be achieved:

[0019] 1. By combining a dual-chamber electrochemical system with an anaerobic digestion system, a large number of electroactive bacteria are enriched in the system. At the anode, the attached electroactive bacteria can accelerate the hydrolysis and acid production process, thereby improving the overall performance of anaerobic digestion. At the cathode, methanogenic bacteria can directly transfer electrons with the electrodes, thereby accelerating methane production. Therefore, the entire system can shorten the anaerobic fermentation time, improve raw material processing efficiency, and increase biogas production.

[0020] 2. The electrons provided by the cathode electrode of the dual-cavity electrochemical system can combine with hydrogen ions to generate hydrogen gas. In the same system as the carbon dioxide produced during the hydrolysis process, through the action of hydrogen-nutritive methanogenic bacteria, carbon dioxide can be converted into methane in situ, thereby improving biogas quality, reducing equipment investment, and lowering economic costs.

[0021] 3. In this invention, the cathode and anode of the anaerobic electrochemical system are separated, so that the enhancing effect of the anode and cathode on the anaerobic digestion capacity and the in-situ purification capacity of biogas can be studied separately, thereby further improving the product efficiency.

[0022] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a preferred embodiment of the dual-chamber bioelectrochemical anaerobic fermentation system of the present invention;

[0024] Figure 2 This is the total methane production of a dual-chamber bioelectrochemical anaerobic fermentation system according to a preferred embodiment of the present invention;

[0025] Figure 3 This is the total methane production of the dual-chamber bioelectrochemical anaerobic fermentation system according to another preferred embodiment of the present invention.

[0026] Among them, 1-constant temperature water bath, 2-magnetic stirrer, 3-magnetic stirring rotor, 4-anaerobic active inoculum, 5-electrode, 6-wire, 7-cation exchange membrane, 8-anaerobic reactor, 9-sealing plug, 10-gas delivery tube, 11-gas bag, 12-gas valve, 13-DC power supply. Detailed Implementation

[0027] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0028] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0029] like Figure 1 The dual-chamber bioelectrochemical anaerobic fermentation system of the present invention, as shown in the figure, includes a DC power supply 13, an anaerobic reactor 8, and a gas collector. The anaerobic reactor has two reaction chambers separated by an ion exchange membrane. The two reaction chambers are connected to two gas collectors via gas delivery pipes 10. Two electrodes 5, connected to the DC power supply 13, are inserted into the two reaction chambers respectively. Each electrode 5 is connected to the DC power supply 13 via a wire 6. The two electrodes 5 are the anode and cathode, respectively. Preferably, the two electrodes 5 are made of carbon cloth, and the ion exchange membrane is a cation exchange membrane 7.

[0030] The two reaction chambers are each sealed with a sealing plug 9, and the electrode 5 and the gas guide tube 10 both pass through the sealing plug 9 and are connected to the reaction chamber.

[0031] Preferably, the gas collector is a gas bag 11, and each gas bag 11 is equipped with two gas valves 12. One of the gas valves 12 on each gas bag 11 is connected to the gas guide pipe 10. When the reactor is working, the gas valve 12 connected to the gas guide pipe 10 is always in the open state, and the other is in the closed state. The biogas produced flows into the gas bag 11 through the gas guide pipe 10 for collection. When measuring the gas composition, the gas valve 12 in the closed state is opened, and a syringe is used to take a sample for analysis.

[0032] In use, two reaction chambers are each filled with anaerobic active inoculum 4, and two electrodes 5 are inserted into the anaerobic active inoculum 4 in the two reaction chambers respectively. Fermentation substrate is also added to both reaction chambers. Preferably, the anaerobic active inoculum 4 is a well-acclimated anaerobic biogas slurry with methanogenic activity, and the added fermentation substrate is corn straw. Preferably, the total volume of anaerobic active inoculum 4 in each reaction chamber is 200 ml, and the fermentation substrate is added to the inoculum at a solids content of 3%, that is, 6 g of corn straw (dry weight) is added to 200 ml of anaerobic active inoculum.

[0033] Preferably, the fermentation system also includes a constant temperature water bath 1, in which the anaerobic reactor is placed in the water bath during use.

[0034] Preferably, the fermentation system further includes a stirring device, specifically a magnetic stirrer 2 and a magnetic stirring rotor 3. In use, the two reaction chambers of the anaerobic reactor are placed on two magnetic stirrers 2 respectively, and the two magnetic stirring rotors 3 are placed at the bottom of the two reaction chambers respectively. After the magnetic stirrers 2 are powered on, the two magnetic stirring rotors 3 can rotate at the center of the bottom of the reaction chamber at a set speed to ensure that the anaerobic active inoculum 4 is stirred evenly.

[0035] The specific usage method is as follows:

[0036] Anaerobic active inoculum and fermentation substrate are added to the two reaction chambers of the anaerobic reactor. High-purity nitrogen gas is introduced into the dual-chamber anaerobic reactor for a certain period of time. The nitrogen gas is introduced before the reaction begins. When introducing nitrogen gas, the gas delivery tube 10 and gas bag 11 are removed. The gas needle containing nitrogen gas is inserted below the liquid surface of the reaction system through the hole connected to the gas delivery tube 10. At this time, nitrogen gas can also flow out from this hole. After the gas is introduced, the gas needle is immediately removed and put into the gas delivery tube 10 connected to the gas bag 11, thus forming an anaerobic closed environment. After sealing the anaerobic reactor, it is placed in a constant temperature water bath at 35°C. The mixture in the reaction chamber is stirred evenly. The DC power supply is turned on, and the external voltage of the dual-chamber bioelectrochemical anaerobic reactor is controlled between 0.6V and 1.2V. The biogas produced is collected through a gas collector.

[0037] The following are two embodiments of the use of the fermentation system of the present invention:

[0038] Example 1 aims to evaluate the methanogenic potential of a dual-chamber bioelectrochemical anaerobic fermentation system under low applied voltage conditions. The specific method is as follows: 6g of corn stalks (dry weight) and anaerobic active inoculum were added to the dual-chamber anaerobic reactor at a solids content of 3%, with the total volume of the anaerobic active inoculum controlled at 200ml. High-purity nitrogen gas was introduced into the dual-chamber anaerobic reactor for 10 minutes. After sealing, the reactor was placed in a constant-temperature water bath at 35℃, and the magnetic stirrer was rotated at 60rpm. A DC power supply was turned on, and the external voltage of the dual-chamber bioelectrochemical anaerobic reactor was controlled at 0.6V. The generated biogas was collected via a gas bag, and its methane content was measured.

[0039] Example 2 aims to evaluate the methanogenic potential of a dual-chamber bioelectrochemical anaerobic fermentation system under relatively high applied voltage conditions. The specific method for this example is as follows: 6g of corn stalks (dry weight) and anaerobic active inoculum were added to the dual-chamber anaerobic reactor at a solids content of 3%, with the total volume of the anaerobic active inoculum controlled at 200ml. High-purity nitrogen gas was introduced into the dual-chamber anaerobic reactor for 10 minutes. After sealing, the reactor was placed in a constant-temperature water bath at 35℃, and the magnetic stirrer was rotated at 60rpm. A DC power supply was turned on, and the external voltage of the dual-chamber bioelectrochemical anaerobic reactor was controlled at 1.2V. The generated biogas was collected via a gas bag, and its methane content was measured.

[0040] like Figure 2 As shown in Example 1, the results indicate that, compared to traditional anaerobic digestion systems, the dual-chamber bioelectrochemical anaerobic fermentation system can increase the total methane production of corn straw anaerobic fermentation by 80%. In particular, the total methane production in the anode anaerobic reactor is higher than that in the cathode, indicating that the electrochemical enhancement for lignocellulosic biomass mainly enhances its hydrolysis and acidification process.

[0041] like Figure 3 As shown in Example 2, the results indicate that, compared to traditional anaerobic digestion systems, the dual-chamber bioelectrochemical anaerobic fermentation system can increase the total methane production of corn straw anaerobic fermentation by 33%. In particular, the total methane production in the anode anaerobic reactor is higher than that in the cathode, indicating that the electrochemical enhancement for lignocellulosic biomass mainly enhances its hydrolysis and acidification process.

[0042] The comparison between Examples 1 and 2 shows that a higher applied external voltage is not necessarily better. There is an optimal applied external voltage for different anaerobic activated sludge and different raw materials.

[0043] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A dual-chamber bioelectrochemical anaerobic fermentation process, characterized in that, Includes the following steps: S1. The anaerobic reactor has two anaerobic reaction chambers. Anaerobic active inoculum and corn straw as fermentation substrate are added to the two anaerobic reaction chambers. The two anaerobic reaction chambers are separated by a cation exchange membrane. The two anaerobic reaction chambers are respectively connected to two gas collectors through gas delivery pipes. The anode and cathode, which are connected to a DC power supply through wires, are respectively inserted into the two reaction chambers. The two anaerobic reaction chambers are respectively sealed with sealing plugs. The anode, cathode, and gas delivery pipe all pass through the sealing plugs and are connected to the reaction chambers. The gas collectors are gas bags. Each gas bag is equipped with two gas valves. One of the gas valves on each gas bag is connected to the gas delivery pipe. S2. High-purity nitrogen gas is introduced into the dual-chamber anaerobic reactor to form an anaerobic closed environment; S3. After sealing the anaerobic reactor, place it in a constant temperature water bath at 35℃, stir the mixture in the reaction chamber evenly, turn on the DC power supply, and control the external voltage of the dual-chamber bioelectrochemical anaerobic reactor at 0.6V. The generated biogas is collected through a gas collector.

2. The dual-chamber bioelectrochemical anaerobic fermentation method as described in claim 1, characterized in that, The anaerobic active inoculum is a well-acclimated anaerobic biogas slurry with methanogenic activity.

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