A self-sourced nanobubble circulation biohydrogen production system

Abstract

The present invention discloses a self-source nanobubble circulation biohydrogen production system, comprising a biohydrogen production module and a nanobubble preparation module; the biohydrogen production module is used to ferment and produce gas I containing hydrogen and carbon dioxide; the nanobubble preparation module comprises a gas separator and a nanobubble generator; gas I is separated into hydrogen and gas II containing no hydrogen but carbon dioxide by the gas separator; gas II is prepared into nanobubbles by the nanobubble generator, and the nanobubbles are transported to the biohydrogen production module and mixed with fermentation raw materials to produce hydrogen by fermentation. This application uses the gas produced by self-source biological fermentation as the source, separates the hydrogen, and uses the gas (mainly carbon dioxide) after the hydrogen is removed to make nanobubbles, which are then added to the biohydrogen production module, achieving the effect of increasing the biohydrogen production while circulating and purifying the hydrogen, while reducing the adverse effects of carbon dioxide emissions on the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of biological hydrogen production, and in particular relates to a self-sourced nanobubble circulation biological hydrogen production system. Background Art

[0002] Hydrogen energy is becoming a hot energy topic internationally due to its cleanliness, high energy density, zero emissions, and wide availability of raw materials. As an energy carrier, hydrogen does not involve carbon in the transfer of chemical energy, significantly reducing carbon dioxide emissions and having significant environmental implications. However, as hydrogen is a secondary energy source, it cannot be directly isolated and obtained in nature. Most current hydrogen production processes are based on fossil fuels, which are not only energy-intensive but also potentially polluting. Even hydrogen production based on water electrolysis requires significant electricity input.

[0003] Biohydrogen production, as a low-cost, low-energy green energy production technology, has attracted considerable attention due to its potential to combine organic waste treatment with clean energy production. Biohydrogen production utilizes the growth and metabolic processes of microorganisms to produce hydrogen. The raw materials used can be biomass such as organic wastewater, municipal waste, or agricultural and forestry waste. These substrates are abundant and inexpensive, and the production process is clean, energy-efficient, and does not consume mineral resources. Despite this, biohydrogen production still faces challenges with substrate utilization and low hydrogen purity for complex substrates. To address these issues, researchers have proposed various methods to improve substrate utilization by microorganisms, such as pretreating the substrate, supplementing with additives, and optimizing reactor structure and operating parameters. These methods have all resulted in improvements in substrate utilization and hydrogen purity. However, traditional physical pressurization pretreatment methods often require significant energy consumption. Chemical pretreatment and the use of additives not only require additional energy input, but also complicate the subsequent processing of the fermentation tail liquor. Direct discharge inevitably leads to secondary environmental pollution.

[0004] Nanobubble water contains numerous ultrafine bubbles with diameters less than 1000nm. This nanoscale bubble structure imparts unique physical and chemical properties, such as 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, continuously producing hydroxyl radicals (OH), which are beneficial for substrate decomposition. Furthermore, nanobubbles can significantly improve the solid-liquid contact area. The hydrophobic attraction of nanobubbles 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 green and safe, causing no secondary pollution, and has been applied in a variety of fields, including food, biomedicine, and agriculture.

[0005] Recently, nanobubbles have been used in the field of biohydrogen production. In the research to date, nanobubbles containing different types of gases have been produced and used as additives in biohydrogen production systems. They can effectively promote substrate degradation in the biohydrogen production process, improve the mass transfer characteristics of the fermentation liquid and enhance microbial activity, thereby promoting hydrogen production.

[0006] Furthermore, compared to other biohydrogen production methods, photosynthetic biohydrogen production from biomass boasts high hydrogen concentrations and energy conversion rates. Light is essential for photosynthetic biohydrogen production, and the light source, intensity, and duration of illumination significantly influence the activity of photosynthetic organisms. Currently, photosynthetic biohydrogen production is still in the laboratory research and development stage, where hydrogen production is closely related to the photosynthetic microbial photoconversion efficiency. Low photoconversion efficiency is arguably the primary constraint on the development of photosynthetic biohydrogen production technology. Studies have found that nanobubbles can enhance light transmission properties, thereby increasing the photoconversion efficiency of photosynthetic biohydrogen production and promoting hydrogen generation. However, current research remains at the laboratory stage and has not yet been applied on a large scale in actual production. Furthermore, conventional shear-type nanobubble generators require both a motor to drive the rotor at high speed and a high-pressure circulation pump to operate, often resulting in high energy consumption and high manufacturing and maintenance costs. These factors limit the practical application of nanobubble technology.

[0007] Nanobubbles used in biohydrogen production in the prior art are generally prepared using exogenous gases, which may affect the normal fermentation and hydrogen production. If biohydrogen (containing hydrogen, carbon dioxide and water vapor) produced in the biohydrogen production process is used as the source gas to produce nanobubbles, the following advantages will be produced: (1) The rupture of biohydrogen nanobubbles can produce hydroxyl radicals, which help to oxidize and decompose complex organic matter and improve the utilization of organic matter; (2) Biohydrogen nanobubbles can improve the fluidity of the liquid and accelerate the generation and consumption of nutrients in the biohydrogen production process; (3) Biohydrogen nanobubbles have higher gas solubility, which can stimulate microbial activity and increase hydrogen production; (4) Biohydrogen nanobubbles also have light transmission properties, which can improve the utilization rate of light for photosynthetic microorganisms. Therefore, after adding biohydrogen nanobubbles to the biohydrogen production system, the hydrogen content and production can be increased in situ during the continuous circulation process.

[0008] Based on the above technical problems, the present application intends to provide a technology for producing biohydrogen nanobubbles using the gas produced by waste biohydrogen production as a source and adding them to the biohydrogen production system. Summary of the Invention

[0009] The purpose of the present invention is to provide a self-source nanobubble circulation biological hydrogen production system to solve the shortcomings of the existing technology.

[0010] The purpose of the present invention is achieved by the following technical solutions:

[0011] A self-source nanobubble circulation biohydrogen production system, comprising a biohydrogen production module and a nanobubble preparation module;

[0012] The biohydrogen production module is used to ferment and produce gas containing hydrogen and carbon dioxide I;

[0013] The nanobubble preparation module includes a gas separator and a nanobubble generator; the gas I is separated into hydrogen and gas II containing no hydrogen but carbon dioxide by the gas separator; the gas II is prepared into nanobubbles by the nanobubble generator, and the nanobubbles are transported to the biological hydrogen production module and mixed with fermentation raw materials to produce hydrogen by fermentation.

[0014] Preferably, the biohydrogen production module comprises a feed box, a peristaltic pump, a biohydrogen production reactor and a water outlet tank connected in sequence;

[0015] The feed box is used to store fermentation raw materials, and the peristaltic pump is used to transport the fermentation raw materials to the biohydrogen production reactor; the nanobubbles generated by the nanobubble generator are also transported to the biohydrogen production reactor, and the biohydrogen production reactor is also filled with hydrogen-producing microorganisms. The hydrogen-producing microorganisms, the fermentation raw materials and the nanobubbles are fully mixed in the biohydrogen production reactor to ferment and produce the gas I and fermentation liquid; the gas I is transported to the gas separator, and the fermentation liquid is transported to the water outlet pool.

[0016] Preferably, the biohydrogen production reactor is a fully mixed photosynthetic biological anaerobic hydrogen production reactor or a fully mixed dark fermentation anaerobic hydrogen production reactor.

[0017] Preferably, the fully hybrid photosynthetic biological anaerobic hydrogen production reactor is provided with a built-in light source and photosynthetic hydrogen production microorganisms;

[0018] The fully mixed dark fermentation anaerobic hydrogen production reactor is filled with dark fermentation hydrogen production microorganisms.

[0019] Preferably, the fully mixed photosynthetic biological anaerobic hydrogen production reactor and the fully mixed dark fermentation anaerobic hydrogen production reactor are provided with a sewage outlet at the bottom.

[0020] Preferably, the nanobubble preparation module further comprises a gas collecting device, a water tank and a nanobubble pool;

[0021] The gas collecting device is connected to the gas separator and is used to collect the separated hydrogen;

[0022] The water tank is connected to the nanobubble generator and is used to provide the nanobubble generator with water required for preparing nanobubbles;

[0023] The water inlet and the water outlet of the nanobubble pool are respectively connected to the nanobubble generator and the biological hydrogen production module, and are used to store the nanobubbles generated by the nanobubble generator and provide the nanobubbles to the biological hydrogen production module;

[0024] A gas flow meter and a pressure sensor are provided between the gas separator and the nano bubble generator; and a liquid flow meter is provided between the water tank and the nano bubble generator.

[0025] Preferably, a control system is further included, and the gas flow meter, the pressure sensor, and the liquid flow meter are electrically connected to the control system.

[0026] 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;

[0027] The high-pressure water pump includes a liquid inlet, an air inlet and a liquid outlet, the air inlet is used to receive the gas II separated by the gas separator, and the liquid outlet is connected to the liquid inlet end of the sleeve;

[0028] 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;

[0029] Raw water enters the high-pressure water pump through the liquid inlet and mixes with the gas II 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.

[0030] Preferably, the porous membrane is a microfiltration membrane with a cut-off particle size of 0.1 to 10 μm.

[0031] Preferably, the pitch of the composite thread teeth is adjustable.

[0032] This application uses the gas produced by self-source biological fermentation as the source, separates the hydrogen, and uses the gas after hydrogen removal (mainly carbon dioxide) to make nanobubbles, which are added to the biological hydrogen production module, achieving the effect of increasing biohydrogen production while circulating and purifying hydrogen, while reducing the adverse effects of carbon dioxide emissions on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the self-source nanobubble circulation biological hydrogen production system provided by the present invention;

[0034] Figure 2 This is a structural diagram of a fully hybrid photosynthetic biological anaerobic hydrogen production reactor (CSTR) provided by the present invention;

[0035] Figure 3 This is a schematic structural diagram of a fully mixed dark fermentation anaerobic hydrogen production reactor (CSTR) provided by the present invention;

[0036] Figure 4 It is a structural schematic diagram of the nano bubble generator provided by the present invention;

[0037] Figure 5 yes Figure 4 Schematic diagram of the structure of the medium composite thread with four thread lines;

[0038] Figure 6 yes Figure 4 Schematic diagram of the structure of the composite thread with two thread lines;

[0039] Figure 7 yes Figure 4 Schematic diagram of the structure of a single thread tooth line of a medium composite thread tooth;

[0040] Figure 8 yes Figure 4 Schematic diagram of the structure of the intermediate shaft;

[0041] 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-built-in light source; 17-photosynthetic microorganisms; 18-dark fermentation hydrogen-producing microorganisms. DETAILED DESCRIPTION

[0042] The present invention provides a self-sourced nanobubble circulating biohydrogen production system, such as Figure 1 As shown, it includes a biohydrogen production module and a nanobubble preparation module.

[0043] The biohydrogen production module is used to ferment and produce gas containing hydrogen and carbon dioxide. I. The biohydrogen production module can use a conventional biohydrogen production reactor, as long as it can produce hydrogen through biological fermentation. The fermentation feedstock can be domestic waste, agricultural and forestry waste, urban sewage, etc.

[0044] The nanobubble preparation module includes a gas separator and a nanobubble generator; gas I is separated into hydrogen and gas II which does not contain hydrogen but contains carbon dioxide through the gas separator; gas II is prepared into nanobubbles through the nanobubble generator, and the nanobubbles are transported to the biohydrogen production module and mixed with fermentation raw materials to produce hydrogen through fermentation.

[0045] In the prior art, the gas I (i.e., biohydrogen) produced by biological fermentation mainly contains H2, CO2, and water vapor. Therefore, it is generally necessary to undergo a decarbonization process for purification. However, the present application directly uses a gas separator to separate hydrogen from other gases, thereby achieving hydrogen purification. There is no need to perform decarbonization as in the prior art, which increases the calorific value of hydrogen and reduces subsequent processing costs. At the same time, the gas II after hydrogen 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 biological hydrogen production process. On the other hand, bicarbonate ions can play a buffering role, preventing the pH of the fermentation liquid from dropping sharply during the hydrogen production process and affecting fermentation, thereby increasing hydrogen production. Moreover, the formed nanobubbles are recycled into the system, which can reduce CO2 emissions and reduce pollution.

[0046] 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.

[0047] Therefore, the present application uses the gas produced by self-source biological fermentation as the source, separates the hydrogen, uses the gas after hydrogen removal (mainly carbon dioxide) to make nanobubbles, and adds them to the biological hydrogen production module, thereby achieving the effect of increasing the biohydrogen production and circulating and purifying the hydrogen at the same time, while reducing the adverse effects of carbon dioxide emissions on the environment.

[0048] Preferably, the biohydrogen production module comprises a feed box, a peristaltic pump, a biohydrogen production reactor and a water outlet tank connected in sequence;

[0049] The feed tank stores fermentation feedstock, and a peristaltic pump delivers it to the biohydrogen 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 biohydrogen reactor, which is also filled with hydrogen-producing microorganisms. The microorganisms, fermentation feedstock, and nanobubbles are thoroughly mixed within the biohydrogen reactor, where they ferment to produce Gas I and fermentation liquid. Gas I is delivered 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.

[0050] Preferably, the biohydrogen production reactor of the present application adopts a fully hybrid photosynthetic anaerobic hydrogen production reactor or a fully hybrid dark fermentation anaerobic hydrogen production reactor. Both reactors are CSTR reactors, which have the characteristics of simple design, low cost, small footprint, and wide application range.

[0051] The specific structures of the fully mixed photosynthetic biological anaerobic hydrogen production reactor and the fully mixed dark fermentation anaerobic hydrogen production reactor are as follows: Figure 2 and 3 As shown, each includes a tank body 9, with a feed inlet 12 at the bottom, connected to a peristaltic pump for adding fermentation raw materials. The upper portion of the tank body 9 is equipped 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 fermentation gas I, and the water outlet 14 is connected to a water outlet tank for discharging the fermentation liquid. The tank body also includes an automatic stirring device 10 and hydrogen-producing microorganisms. The hydrogen-producing microorganisms in the fully hybrid photosynthetic anaerobic hydrogen production reactor are photosynthetic microorganisms 17. A built-in light source 16 is also provided within the fully hybrid dark fermentation anaerobic hydrogen production reactor to provide illumination for the photosynthetic microorganisms. The hydrogen-producing microorganisms in the fully hybrid dark fermentation anaerobic hydrogen production reactor are dark fermentation microorganisms 18.

[0052] During operation, fermentation feedstock enters the reactor tank from the bottom, while nanobubbles enter from the top. Automatic stirring device 10 mixes the feedstock, hydrogen-producing microorganisms, and nanobubbles evenly, promoting sufficient microbial contact with the substrate and increasing substrate degradation. After hydrogen production is complete, the fermentation liquid flows out of the upper outlet into the outlet tank. Gas I containing hydrogen and carbon dioxide produced by biohydrogen production is discharged through the upper outlet. A sewage outlet 15 is also provided at the bottom of the tank to facilitate regular wastewater discharge.

[0053] Further preferably, the tank body 9 is made of a stainless steel assembled tank body for easy disassembly.

[0054] Preferably, the gas separator is a gas separation membrane. Gas I generated by the biohydrogen production reactor first enters the gas separation membrane, which can selectively separate gases under different pressure conditions, separating hydrogen from other gases (primarily carbon dioxide). The gas permeation rate increases with increasing pressure. The gas separation membrane can be made of organic polymer membranes, inorganic membranes, and mixed matrix membranes. Preferably, an organic polymer material commonly used for H2 separation (due to its low cost and simple process) such as a polyimide (PI) gas separation membrane is used to separate the biohydrogen mixed gas (primarily H2 / CO2).

[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 hydrogen; 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 biological hydrogen production module to store the nanobubbles generated by the nanobubble generator and provide the nanobubbles to the biological hydrogen production 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 gas II (mainly CO2) is extracted. The water and gas II 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 biohydrogen production reactor as needed.

[0059] Preferably, the present application is provided with a control system, which is electrically connected to a gas flow meter, a pressure sensor, a liquid flow meter, etc., and can control the gas II flow rate, the water flow rate, the internal pressure of the generator, and the bubble generation time, thereby adjusting 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 4 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 gas II 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 gas II 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 four 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 8 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 5 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 densely distributed, the shear force is large, and the bubble size produced is small. Figure 6 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 the substrate utilization in the biohydrogen production process, stimulates the activity of hydrogen-producing microorganisms, and increases hydrogen production.

[0073] (2) A gas separation membrane is used to separate and purify the gas produced by self-sourced biohydrogen production. The impurity gas (mainly CO2) after hydrogen separation is used as the gas source for preparing nanobubbles. This reduces the consumption of exogenous gas by nanobubbles, avoids the adverse effects of using exogenous gas on biofermentation hydrogen production, and reduces the pollution of carbon dioxide emissions to the environment. In addition, CO2 dissolves in water to form bicarbonate, which has the effect of buffering the pH of the anaerobic fermentation system.

[0074] (3) Nanobubbles have light transmission properties, which can improve the utilization rate of light and microorganisms.

[0075] (4) When nanobubbles burst during the process, they will only release gas and will not cause secondary pollution.

[0076] (5) Compared with the traditional nanobubble generator, the new energy-saving nanobubble generator of the present application has the advantages of simple structure, low energy consumption and cost.

[0077] 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 circulation biological hydrogen production system, characterized in that: It includes a biohydrogen production module and a nanobubble preparation module; The biohydrogen production module is used to ferment and produce gas containing hydrogen and carbon dioxide I; The nanobubble production module includes a gas separator and a nanobubble generator; the gas I is separated into hydrogen and gas II containing no hydrogen but carbon dioxide by the gas separator; the gas II is passed through the nanobubble generator to produce nanobubble water, which is then transported to the biohydrogen production module and mixed with fermentation feedstock to produce hydrogen by 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, the air inlet is used to receive the gas II 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 gas II entering through the gas 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 then by the porous membrane to form nanobubbles, which are then discharged from the liquid outlet. The pitch of the composite thread teeth is adjustable.

2. The self-source nanobubble circulation biological hydrogen production system according to claim 1, characterized in that: The biohydrogen production module comprises a feed box, a peristaltic pump, a biohydrogen production 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 biohydrogen production reactor; the nanobubble water generated by the nanobubble generator is also transported to the biohydrogen production reactor, and the biohydrogen production reactor is also filled with hydrogen-producing microorganisms. The hydrogen-producing microorganisms, the fermentation raw materials and the nanobubble water are fully mixed in the biohydrogen production reactor to ferment and produce the gas I and fermentation liquid; the gas I is transported to the gas separator, and the fermentation liquid is transported to the water outlet pool.

3. The self-source nanobubble circulation biological hydrogen production system according to claim 2, characterized in that: The biological hydrogen production reactor is a fully mixed photosynthetic biological anaerobic hydrogen production reactor or a fully mixed dark fermentation anaerobic hydrogen production reactor.

4. The self-source nanobubble circulation biological hydrogen production system according to claim 3, characterized in that: The fully mixed photosynthetic biological anaerobic hydrogen production reactor is provided with a built-in light source and photosynthetic hydrogen production microorganisms; The fully mixed dark fermentation anaerobic hydrogen production reactor is filled with dark fermentation hydrogen production microorganisms.

5. The self-source nanobubble circulation biological hydrogen production system according to claim 3, characterized in that: The bottom of the fully mixed photosynthetic biological anaerobic hydrogen production reactor and the fully mixed dark fermentation anaerobic hydrogen production reactor is provided with a sewage outlet.

6. The self-source nanobubble circulation biological hydrogen production 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 hydrogen; 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 biological hydrogen production module, and are used to store the nanobubble water generated by the nanobubble generator and provide the nanobubble water to the biological hydrogen production module; A gas flow meter and a pressure sensor are provided between the gas separator and the nano bubble generator; and a liquid flow meter is provided between the water tank and the nano bubble generator.

7. The self-source nanobubble circulation biological hydrogen production system according to claim 1, characterized in that: It also includes a control system, and the gas flow meter, the pressure sensor, and the liquid flow meter are electrically connected to the control system.

8. The self-source nanobubble circulation biological hydrogen production system according to claim 1, characterized in that: The porous membrane is a microfiltration membrane with a cut-off particle size of 0.1 to 10 μm.

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