A self-sourced nanobubble circulating anaerobic fermentation system

Abstract

The present invention discloses a self-source nano bubble circulation anaerobic fermentation system, comprising an anaerobic fermentation module and a nano bubble preparation module; the anaerobic fermentation module is used to ferment and produce biogas containing methane, carbon dioxide and hydrogen; the nano bubble preparation module comprises a gas separator and a nano bubble generator; the biogas is separated into methane and miscellaneous gases containing carbon dioxide and hydrogen without methane through the gas separator; the miscellaneous gases are prepared into nano bubbles through the nano bubble generator, and the nano bubbles are transported to the anaerobic fermentation module and mixed with fermentation raw materials for anaerobic fermentation. The present application uses the gas produced by self-source biological fermentation as the source, separates methane, and uses the miscellaneous gases (mainly carbon dioxide) after removing methane to make nano bubbles, which are added to the anaerobic fermentation module, thereby achieving the effect of increasing biogas production and circulating and purifying methane at the same time, while reducing the adverse effects of carbon dioxide emission on the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of anaerobic fermentation, and in particular relates to a self-sourced nano bubble circulation anaerobic fermentation system. Background Art

[0002] Biomass energy has become an important part of renewable energy due to its advantages of abundant resources, low cost and easy availability. Anaerobic fermentation to produce biogas, as a way to utilize biomass energy, has been widely used in production and life because it can reduce environmental pressure, recycle waste energy, and has significant economic and ecological benefits. Despite this, anaerobic fermentation still has disadvantages such as slow substrate hydrolysis rate, low methane yield and low purity, especially for some substrates with complex components. In response to the above problems, researchers have proposed various methods to improve the utilization rate of substrates by microorganisms, such as pretreating the substrate, supplementing additives and optimizing the reactor structure and operating conditions, etc. These have a certain degree of improvement in substrate utilization and methane yield. However, traditional physical pressurization pretreatment methods often require huge energy consumption, and the use of chemical pretreatment and additives not only requires additional energy input, but also the subsequent treatment of fermentation tail liquid is very complicated, and direct discharge will inevitably cause secondary environmental pollution problems.

[0003] Nanobubble water contains numerous ultrafine bubbles with diameters less than 1000 nm. This nanoscale bubble structure imparts unique physicochemical properties, including a large specific surface area, negative surface charge, low buoyancy, high solubility, rapid mass transfer, and enhanced stability. Studies have shown that nanobubbles can remain stable in water for over two weeks and continuously produce hydroxyl radicals (OH), which are beneficial for substrate decomposition. Furthermore, nanobubbles significantly improve the solid-liquid contact area. Their hydrophobic attraction enables them to adhere to solid surfaces. Injection of nanobubble water enhances chemical reactions at the gas-liquid interface, thereby promoting various metabolic and chemical reactions. Nanobubble water is also environmentally friendly and safe, with no secondary pollution. It has been applied in various fields, including food, biomedicine, and agriculture. Recently, nanobubbles have been applied in anaerobic fermentation. To date, studies have produced nanobubbles containing various gases and used them as additives in anaerobic digestion systems. These nanobubbles effectively promote substrate degradation, improve mass transfer characteristics of the fermentation broth, and enhance microbial activity, thereby increasing methane production. Nanobubbles offer numerous advantages for anaerobic fermentation, notably hydrogen nanobubbles, which can serve as a substrate for the hydrogen-consuming, methane-producing phase of anaerobic fermentation, consuming carbon dioxide and increasing methane content in situ. However, current research remains at the laboratory stage and has yet to be widely applied in actual production. Furthermore, conventional shear-type nanobubble generators require a motor to drive the rotor at high speeds, working in conjunction with a high-pressure circulation pump. This often results in high energy consumption and high preparation and maintenance costs, limiting the practical application of nanobubble technology.

[0004] Nanobubbles used in anaerobic fermentation systems in the prior art are generally prepared using exogenous gas, which may affect normal fermentation.

[0005] Based on the above technical problems, the present application intends to provide a technology for producing biogas nanobubbles using the gas produced by anaerobic fermentation of waste as the source and adding them to the anaerobic fermentation system. Summary of the Invention

[0006] The purpose of the present invention is to provide a self-sourced nanobubble circulating anaerobic fermentation system to address the deficiencies of the prior art.

[0007] The purpose of the present invention is achieved by the following technical solutions:

[0008] A self-sourced nanobubble circulating anaerobic fermentation system, comprising an anaerobic fermentation module and a nanobubble preparation module;

[0009] The anaerobic fermentation module is used to ferment and produce biogas containing methane, carbon dioxide and hydrogen;

[0010] The nanobubble preparation module includes a gas separator and a nanobubble generator; the biogas is separated into methane and mixed gases that do not contain methane but contain carbon dioxide and hydrogen by the gas separator; the mixed gases are produced into nanobubbles by the nanobubble generator, and the nanobubbles are transported to the anaerobic fermentation module and mixed with fermentation raw materials for anaerobic fermentation.

[0011] Preferably, the anaerobic fermentation module comprises a feed box, a peristaltic pump, an anaerobic fermentation reactor and a water outlet tank connected in sequence;

[0012] The feed box is used to store fermentation raw materials, and the peristaltic pump is used to transport the fermentation raw materials to the anaerobic fermentation reactor; the nanobubbles generated by the nanobubble generator are also transported to the anaerobic fermentation reactor, and the anaerobic fermentation reactor is also filled with anaerobic fermentation sludge. The anaerobic fermentation sludge, the fermentation raw materials and the nanobubbles are fully mixed in the anaerobic fermentation reactor to ferment and produce the biogas and fermentation liquid; the biogas is transported to the gas separator, and the fermentation liquid is transported to the effluent tank.

[0013] Preferably, the anaerobic fermentation raw materials are one or more selected from domestic garbage, agricultural and forestry waste, and urban sewage.

[0014] Preferably, the gas separator is a gas separation membrane.

[0015] Preferably, the gas separation membrane is one selected from an organic polymer membrane, an inorganic membrane or a mixed matrix membrane.

[0016] Preferably, the nanobubble preparation module further comprises a gas collecting device, a water tank and a nanobubble pool;

[0017] The gas collecting device is connected to the gas separator and is used to collect the separated methane;

[0018] The water tank is connected to the nanobubble generator and is used to provide the nanobubble generator with water required for preparing nanobubbles;

[0019] The water inlet and the water outlet of the nanobubble pool are respectively connected to the nanobubble generator and the anaerobic fermentation module, and are used to store the nanobubbles generated by the nanobubble generator and provide the nanobubbles to the anaerobic fermentation module.

[0020] Preferably, the nanobubble generator comprises a sleeve and a high-pressure water pump, wherein the two ends of the sleeve are respectively a liquid inlet end and a liquid outlet end;

[0021] The high-pressure water pump includes a liquid inlet, an air inlet, and a liquid outlet, wherein the air inlet is used to receive the impurity gas separated by the gas separator, and the liquid outlet is connected to the liquid inlet end of the sleeve;

[0022] An intermediate shaft and composite thread teeth distributed circumferentially on the intermediate shaft are provided in the sleeve along the axial direction; a porous membrane is provided at the liquid outlet end of the sleeve;

[0023] Raw water enters the high-pressure water pump through the liquid inlet and mixes with the miscellaneous air entering through the air inlet to form a high-pressure gas-liquid mixture. The high-pressure gas-liquid mixture enters the sleeve and is sequentially sheared by the composite thread teeth and the porous membrane to form nanobubbles, which are then discharged from the liquid outlet.

[0024] Preferably, the solution flow path from the end of the intermediate shaft to the porous membrane in the sleeve gradually shrinks.

[0025] Preferably, the pitch of the composite thread teeth is adjustable.

[0026] Preferably, the composite thread teeth include a plurality of detachable thread tooth lines, and when the pitch needs to be adjusted, the corresponding thread tooth lines can be removed.

[0027] This application uses the gas produced by self-sourced biological fermentation as the source, separates the methane, uses the impurity gas (mainly carbon dioxide) after methane removal to make nanobubbles, and adds them to the anaerobic fermentation module, which has the following beneficial effects:

[0028] (1) The rupture of nanobubbles can produce hydroxyl radicals, which help oxidize and decompose complex organic matter and improve the utilization of organic matter.

[0029] (2) Nanobubbles can improve the fluidity of the fermentation liquid and accelerate the production and consumption of nutrients during anaerobic fermentation.

[0030] (3) Nanobubbles also have higher gas solubility, which can stimulate microbial activity and increase methane production.

[0031] (4) The small amount of hydrogen contained in the impurity gas serves as a substrate for the hydrogen consumption and methane production stage, which can consume part of the carbon dioxide and play a role in purifying the methane concentration in situ.

[0032] (5) Using impurity gases to make nanobubbles can, on the one hand, consume some of the carbon dioxide in the biogas, thereby reducing the carbon dioxide concentration and increasing the methane concentration. On the other hand, carbon dioxide dissolves in water to form bicarbonate, which can buffer the pH and promote methane production. Therefore, when nanobubbles made from their own source are added to the anaerobic fermentation system, they can increase the methane content and yield in the biogas in situ during the continuous circulation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1This is a flow chart of the self-source nanobubble circulating anaerobic fermentation system provided by the present invention;

[0034] Figure 2 Schematic diagram of the structure of the fully mixed anaerobic fermentation reactor (CSTR) provided by the present invention;

[0035] Figure 3 Schematic diagram of the structure of the nano bubble generator provided by the present invention;

[0036] Figure 4 yes Figure 3 Schematic diagram of the structure of the medium composite thread with four thread lines;

[0037] Figure 5 yes Figure 3 Schematic diagram of the structure of the composite thread with two thread lines;

[0038] Figure 6 yes Figure 3 Schematic diagram of the structure of a single thread tooth line of a medium composite thread tooth;

[0039] Figure 7 yes Figure 3 Schematic diagram of the structure of the intermediate shaft;

[0040] Among them, 1-high-pressure water pump; 2-liquid inlet; 3-air inlet; 4-compound threaded teeth; 5-intermediate shaft; 6-sleeve; 7-porous membrane; 8-liquid outlet; 9-tank body; 10-stirring device; 11-nanobubble inlet; 12-feed inlet; 13-air outlet; 14-water outlet; 15-sewage outlet; 16-anaerobic fermentation sludge. DETAILED DESCRIPTION

[0041] The present invention provides a self-sourced nanobubble circulating anaerobic fermentation system, such as Figure 1 As shown, it includes an anaerobic fermentation module and a nanobubble preparation module.

[0042] The anaerobic fermentation module is used to ferment and produce biogas containing methane, carbon dioxide, hydrogen, etc. The anaerobic fermentation module can adopt an anaerobic fermentation reactor in the prior art, as long as it can produce methane through biological fermentation. The fermentation raw materials can be domestic garbage, agricultural and forestry waste, urban sewage, etc.

[0043] The nanobubble preparation module includes a gas separator and a nanobubble generator; biogas is separated into methane and mixed gases that do not contain methane but contain carbon dioxide and hydrogen through the gas separator; the mixed gases are prepared into nanobubbles through the nanobubble generator, and the nanobubbles are transported to the anaerobic fermentation module and mixed with the fermentation raw materials to produce hydrogen.

[0044] In the prior art, biogas produced by biological fermentation mainly contains 50% to 70% CH4, 30% to 50% CO2, and a small amount of gases such as H2 and H2S. Therefore, it generally needs to be purified through decarbonization and desulfurization processes. However, the present application directly uses a gas separator to separate methane from other gases, thereby achieving methane purification. There is no need for further decarbonization as in the prior art, which increases the calorific value of methane and reduces subsequent processing costs. At the same time, the impurity gas after methane separation is mainly carbon dioxide. After being made into nanobubbles, in addition to being able to play the role of the nanobubbles themselves, carbon dioxide dissolves in water to form bicarbonate. On the one hand, studies have found that an appropriate amount of bicarbonate ions can stimulate microbial activity and promote the anaerobic fermentation process. On the other hand, bicarbonate ions can act as a buffer to prevent the pH of the fermentation liquid from dropping sharply during the fermentation process and affecting fermentation, thereby increasing methane production. The impurity gas after methane separation also contains a small amount of hydrogen. As a substrate for the hydrogen-eating methane production stage, it can consume part of the carbon dioxide and play the role of in-situ purification of methane concentration. Fixing impurities with nanobubble technology can reduce CO2 and H2S emissions and reduce air pollution.

[0045] In addition, the production of nanobubbles in the prior art also requires an exogenous gas (usually air), which may have an adverse effect on normal fermentation. The present application uses its own source gas to produce nanobubbles, which has no effect on normal fermentation. Moreover, as mentioned above, the carbon dioxide in the nanobubbles can also promote fermentation.

[0046] Therefore, this application uses the gas produced by its own biological fermentation as the source, separates the methane, uses the impurity gas (mainly carbon dioxide) after removing the methane to make nanobubbles, and adds them to the anaerobic fermentation module, thereby achieving the effect of increasing biogas production and circulating and purifying methane at the same time, while reducing the adverse effects of carbon dioxide emissions on the environment.

[0047] Preferably, the anaerobic fermentation module comprises a feed box, a peristaltic pump, an anaerobic fermentation reactor and a water outlet tank connected in sequence;

[0048] The feed tank stores fermentation feedstock, and the peristaltic pump delivers it to the anaerobic fermentation reactor. The peristaltic pump flow rate is determined by the reactor's hydraulic retention period, calculated based on the reactor's effective feed volume and hydraulic retention period. Nanobubbles produced by the nanobubble generator are also delivered to the anaerobic fermentation reactor, which is also filled with anaerobic fermentation sludge. The anaerobic fermentation sludge, fermentation feedstock, and nanobubbles are thoroughly mixed within the anaerobic fermentation reactor to produce biogas and fermentation liquid. The biogas is then transported to a gas separator for separation, while the fermentation liquid is transported to a effluent tank for storage. The fermentation liquid in the effluent tank can be used as soil fertilizer.

[0049] Preferably, the anaerobic fermentation reactor of the present application adopts a commonly used CSTR reactor, which has the characteristics of simple design, low cost, small footprint, and wide application range.

[0050] The specific structure of CSTR reactor is as follows: Figure 2 As shown, the tank body 9 includes a feed inlet 12 at the bottom of the tank body 9, which is connected to a peristaltic pump for adding fermentation raw materials to the tank body. The upper portion of the tank body 9 is provided with a nanobubble inlet 11, an air outlet 13, and a water outlet 14. The nanobubble inlet 11 is connected to a nanobubble generator for adding nanobubbles to the tank body. The air outlet 13 is connected to a gas separator for discharging biogas generated by fermentation to the gas separator. The water outlet 14 is connected to a water outlet tank for discharging fermentation liquid. The tank body is also equipped with an automatic stirring device 10 and anaerobic fermentation sludge 16.

[0051] During operation, the fermentation raw materials enter the reactor tank from the bottom, facilitating full contact with the sludge. Nanobubbles enter the reactor tank from the top. The fermentation raw materials, anaerobic fermentation sludge, and nanobubbles are evenly mixed under the stirring action of the automatic stirring device 10 to promote full contact of microorganisms with the substrate and improve the degradation rate of the substrate. After fermentation is completed, the fermentation liquid flows out from the upper water outlet into the water outlet tank. The biogas produced by anaerobic fermentation is discharged from the upper gas outlet and then enters the gas collection device through the gas separator for collection and use. A sewage outlet 15 is also provided at the bottom of the tank body to facilitate regular sewage discharge.

[0052] Further preferably, the tank body 9 is made of a stainless steel assembled tank body for easy disassembly.

[0053] Preferably, the gas separator is a gas separation membrane. The biogas produced by the anaerobic fermentation reactor first enters the gas separation membrane, which can selectively separate gases under different pressure conditions, separating methane from other gases (primarily carbon dioxide). The gas permeation rate increases with increasing pressure. Because gases such as CO2 and H2S in biogas pass through the gas separation membrane faster than CH4, biogas can be purified based on this principle. The concentrated biogas can directly pass through the separation membrane into the gas collection device, and the separated impurities are subsequently used to produce nanobubbles.

[0054] Gas separation membranes can be organic polymer membranes, inorganic membranes and mixed matrix membranes, etc. It is preferred to use organic polymer materials commonly used in biogas separation (the material cost is low and the synthesis process is simple) such as polyether copolyamide (Pebax) gas separation membranes to separate gases (mainly CO2 / CH4) in biogas.

[0055] Preferably, the nanobubble preparation module further includes a gas collecting device, a water tank and a nanobubble pool.

[0056] The gas collecting device is connected to the gas separator to collect the separated methane; the water tank is connected to the nanobubble generator to provide water for preparing nanobubbles to the nanobubble generator; the water inlet and outlet of the nanobubble water pool are respectively connected to the nanobubble generator and the anaerobic fermentation module to store the nanobubbles generated by the nanobubble generator and provide the nanobubbles to the anaerobic fermentation module.

[0057] Further preferably, a gas flow meter and a pressure sensor are provided between the gas separator and the nano bubble generator to detect the gas flow and pressure; and a liquid flow meter is provided between the water tank and the nano bubble generator to detect the liquid flow.

[0058] When producing nanobubbles, water in the water tank is first pumped into the nanobubble generator. After the machine runs stably, the separated impurities (CO2, H2S, H2, etc.) are extracted. The water and impurities enter the nanobubble generator and are made into nanobubble water. The produced nanobubble water is sent to the nanobubble water pool and then quantitatively added to the anaerobic fermentation reactor as needed.

[0059] Preferably, the present application is provided with a control system that can control the miscellaneous gas flow, water flow, internal pressure of the generator and bubble generation time, thereby regulating the amount of nanobubbles generated.

[0060] Each control system is connected to a terminal controller, which can automatically adjust the size and concentration of nanobubbles.

[0061] Preferably, in order to solve the problem of high energy consumption of nano bubble generators in the prior art, the present application provides an energy-saving nano bubble generator, which uses an intermediate shaft without an external motor and a composite threaded tooth and a porous membrane to perform secondary shearing on the gas-liquid mixture. The structure of the nano bubble generator is as follows: Figure 3 As shown, the instrument produces nanobubbles based on the principle of pressurized dissolved air, and specifically includes a sleeve 6 and a high-pressure water pump 1. The two ends of the sleeve are respectively a liquid inlet end and a liquid outlet end 8.

[0062] The high-pressure water pump includes a liquid inlet 2, an air inlet 3 and a liquid outlet. The air inlet is used to receive the impurities separated by the gas separator, and the liquid outlet is connected to the liquid inlet end of the sleeve 6; an intermediate shaft 5 and composite thread teeth 4 distributed circumferentially on the intermediate shaft are axially arranged in the sleeve; a porous membrane 7 is provided at the liquid outlet end of the sleeve.

[0063] Water enters the high-pressure water pump through the liquid inlet and mixes with the miscellaneous air entering through the air inlet to form a high-pressure gas-liquid mixture. The high-pressure gas-liquid mixture enters the sleeve and is sequentially sheared by the composite thread teeth and the porous membrane, forming nanobubbles that are discharged from the liquid outlet.

[0064] This nanobubble generator combines the advantages of throttling and shearing methods. Driven by a high-pressure circulating pump, the gas-liquid mixture collides with the tip of the composite thread teeth. As the gas-liquid mixture passes through the composite thread teeth, its pressure decreases dramatically due to the accelerated flow rate. Simultaneously, the composite thread teeth, without rotating, repeatedly shear and break up bubbles, rapidly forming them. Finally, a secondary shearing process occurs through a porous membrane, further increasing the rate of bubble generation while reducing the size of the bubbles, ultimately forming nanobubbles.

[0065] Preferably, the porous membrane may be a microfiltration membrane with a cut-off particle size of 0.1 to 10 μm.

[0066] Preferably, the solution flow path from the end of the intermediate shaft to the porous membrane in the sleeve is gradually contracted, which can further increase the flow rate of the gas-liquid mixture and enhance the secondary shear force of the porous membrane.

[0067] Preferably, the pitch of the composite thread teeth of the present application is adjustable, and different pitches have different shearing effects, which can achieve the purpose of adjusting the size of nanobubbles.

[0068] The above-mentioned adjustable pitch can be achieved by controlling the number of lines of the composite thread teeth. Specifically, the composite thread teeth include multiple detachable thread lines, and when the number of lines and pitch need to be reduced, the corresponding number of thread lines can be removed.

[0069] like Figures 4 to 7 As shown in FIG. 1 , a preferred composite thread structure provided by the present application is provided. The composite thread is provided with four detachable thread lines with a fixed lead of 20 mm, two of which can be exposed or hidden in the intermediate shaft by rotating the knob. Figure 4 As shown in the figure, the surface of the intermediate shaft has 4 thread teeth with a pitch of 5mm. At this time, the thread teeth are most densely distributed, the shear force is the largest, and the bubble size produced is the smallest. Figure 5 As shown in the figure, the number of thread teeth is reduced to 2 and the pitch is increased to 10 mm. At this time, the thread teeth are sparsely distributed, the shear force is small, and the bubble size produced is larger.

[0070] Compared with traditional nano bubble generators, this application uses composite thread teeth, which has better shearing effect and simpler structure. At the same time, it does not require an external motor, and has lower energy consumption and cost.

[0071] Therefore, compared with the prior art, this application has the following technical advantages:

[0072] (1) Adding nanobubbles to the reactor improves substrate utilization during anaerobic fermentation, stimulates microbial activity, and increases methane production.

[0073] (2) A gas separation membrane is used to separate and purify the gases produced by the anaerobic fermentation process. The impurities (mainly CO2) after methane separation are used as the gas source for preparing nanobubbles. This reduces the consumption of exogenous gases by the nanobubbles, avoids the adverse effects of exogenous gases on biological fermentation, and reduces the environmental pollution caused by carbon dioxide emissions. In addition, CO2 dissolves in water to form bicarbonate, which has the effect of buffering the pH of the anaerobic fermentation system.

[0074] (3 nano bubbles will only release gas when they burst during the process, and will not cause secondary pollution.

[0075] (4) Compared with traditional nanobubble generators, the novel energy-saving nanobubble generator of the present application has the advantages of simple structure, low energy consumption and cost.

[0076] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A self-sourced nanobubble circulating anaerobic fermentation system, characterized in that: Including anaerobic fermentation module and nanobubble preparation module; The anaerobic fermentation module is used to ferment and produce biogas containing methane, carbon dioxide and hydrogen; The nanobubble production module includes a gas separator and a nanobubble generator. The biogas is separated into methane and mixed gases containing carbon dioxide and hydrogen but not methane by the gas separator. The mixed gases are then passed through the nanobubble generator to produce nanobubble water, which is then transported to the anaerobic fermentation module and mixed with fermentation materials for anaerobic fermentation. The nano bubble generator comprises a sleeve and a high-pressure water pump, wherein the two ends of the sleeve are respectively a liquid inlet end and a liquid outlet end; The high-pressure water pump includes a liquid inlet, an air inlet, and a liquid outlet, wherein the air inlet is used to receive the impurity gas separated by the gas separator, and the liquid outlet is connected to the liquid inlet end of the sleeve; An intermediate shaft and composite thread teeth distributed circumferentially on the intermediate shaft are provided in the sleeve along the axial direction; a porous membrane is provided at the liquid outlet end of the sleeve; Raw water enters the high-pressure water pump through the liquid inlet and mixes with the miscellaneous air entering through the air inlet to form a high-pressure gas-liquid mixture. The high-pressure gas-liquid mixture enters the sleeve and is sequentially sheared by the composite thread teeth and the porous membrane to form nanobubble water, which is then discharged from the liquid outlet.

2. The self-source nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: The anaerobic fermentation module includes a feed box, a peristaltic pump, an anaerobic fermentation reactor and a water outlet tank connected in sequence; The feed box is used to store fermentation raw materials, and the peristaltic pump is used to transport the fermentation raw materials to the anaerobic fermentation reactor; the nanobubbles generated by the nanobubble generator are also transported to the anaerobic fermentation reactor, and the anaerobic fermentation reactor is also filled with anaerobic fermentation sludge. The anaerobic fermentation sludge, the fermentation raw materials and the nanobubbles are fully mixed in the anaerobic fermentation reactor to ferment and produce the biogas and fermentation liquid; the biogas is transported to the gas separator, and the fermentation liquid is transported to the effluent tank.

3. The self-source nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: The anaerobic fermentation raw materials are one or more materials selected from domestic garbage, agricultural and forestry wastes, and urban sewage.

4. The self-source nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: The gas separator is a gas separation membrane.

5. The self-source nanobubble circulating anaerobic fermentation system according to claim 4, characterized in that: The gas separation membrane is one selected from an organic polymer membrane, an inorganic membrane or a mixed matrix membrane.

6. The self-sourced nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: The nanobubble preparation module also includes a gas collecting device, a water tank and a nanobubble pool; The gas collecting device is connected to the gas separator and is used to collect the separated methane; The water tank is connected to the nanobubble generator and is used to provide the nanobubble generator with water required for preparing nanobubbles; The water inlet and the water outlet of the nanobubble water pool are respectively connected to the nanobubble generator and the anaerobic fermentation module, and are used to store the nanobubble water generated by the nanobubble generator and provide the nanobubble water to the anaerobic fermentation module.

7. The self-sourced nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: A solution flow path in the sleeve from the end of the intermediate shaft to the porous membrane gradually shrinks.

8. The self-sourced nanobubble circulating anaerobic fermentation system according to claim 1, characterized in that: The pitch of the composite thread teeth is adjustable.

9. The self-sourced nanobubble circulating anaerobic fermentation system according to claim 8, characterized in that: The composite thread teeth include a plurality of detachable thread tooth lines. When the pitch needs to be adjusted, the corresponding thread tooth lines can be removed.

Images