Anaerobic fermentation methane production system

Abstract

The utility model discloses an anaerobic fermentation methane production system which comprises a pretreatment tank, a hydrogen and acid production reactor, a nano bubble generation device, a first methane production reactor and a second methane production reactor which are connected in sequence, wherein the second methane production reactor is connected with the hydrogen and acid production reactor; the hydrogen and acid production reactor and the second methane production reactor are provided with outer circulation pipelines and magnetic field strengthening devices. According to the invention, the two methane production reactors are used for producing methane by respectively utilizing an acidic substrate and hydrogen produced by fermentation of the acid-producing and hydrogen-producing reactors, and the magnetic field intensifying device and the nano-bubble generating device are respectively arranged according to reaction characteristics, so that the organic matter degradation effect, the hydrogen-producing and acid-producing effect and the utilization efficiency of the hydrogen and the acid-producing substrate are improved; the yield and purity of methane are improved, and the whole fermentation period is shortened.

Description

Technical Field

[0001] The utility model belongs to the technical field of biogas production, and particularly relates to an anaerobic fermentation methane production system. Background Art

[0002] Biogas is a combustible gas produced by microorganisms through fermentation under anaerobic conditions, suitable temperature and suitable pH conditions, and its main component is methane. Straw biomass materials are a commonly used fermentation raw material. The process of converting straw biomass into methane generally includes three stages: hydrolysis acidification, hydrogen production and acetic acid production, and methanation. Among them, the hydrolysis acidification stage is the hydrolysis of straw into small molecules by cellulase, and this stage takes a long time. In traditional technologies, the above three stages are all completed in the same reactor, resulting in low raw material utilization rate, low methane production and purity. In recent years, some studies have separated the stages before methanation (hydrolysis acidification and hydrogen production and acetic acid production stages) and the methanation stage in different reactors. Although it can improve the biomass conversion rate to a certain extent and shorten the fermentation cycle, the overall biomass conversion rate is still low, and the methane production and purity are not high, so further improvement is needed. Content of the Utility Model

[0003] The purpose of the utility model is to provide an anaerobic fermentation methane production system to solve the deficiencies of the prior art.

[0004] The purpose of the utility model is achieved by the following technical solutions:

[0005] An anaerobic fermentation methane production system includes a pretreatment tank, a hydrogen production and acid production reactor, a nano-bubble generating device, a first methane production reactor connected in sequence, and a second methane production reactor connected to the hydrogen production and acid production reactor;

[0006] The pretreatment tank is used for aerobic degradation of the fermentation raw material to obtain a pretreated liquid;

[0007] The hydrogen production and acid production reactor is provided with a first external circulation pipeline and a first magnetic field strengthening device, and is used for anaerobic fermentation of the pretreated liquid to produce hydrogen and acidic substrates;

[0008] The nano-bubble generating device is used for producing nano-bubbles from the hydrogen;

[0009] The first methane production reactor is also connected to the pretreatment tank, and is used for hydrogenophilic anaerobic fermentation of the nano-bubbles and the pretreated liquid to produce methane;

[0010] The second methane production reactor is provided with a second external circulation pipeline and a second magnetic field strengthening device, and is used for acidophilic anaerobic fermentation of the acidic substrates to produce methane.

[0011] Preferably, the anaerobic fermentation methane production system provided by the present application further includes a crushing device connected to the pretreatment tank;

[0012] The crushing device is used to crush the fermentation raw materials before pretreatment.

[0013] Preferably, the first magnetic field strengthening device is located on the first external circulation pipeline; the second magnetic field strengthening device is located on the second external circulation pipeline.

[0014] Preferably, the first magnetic field strengthening device includes a first electromagnetic coil wound around the first external circulation pipeline;

[0015] The second magnetic field strengthening device includes a second electromagnetic coil wound around the second external circulation pipeline.

[0016] Preferably, the anaerobic fermentation methane production system provided by the present application further includes a heat processor connected to the hydrogen-producing and acid-producing reactor;

[0017] The heat processor is used to heat-treat the sludge to inactivate the methanogens therein, and the inactivated sludge is transported to the hydrogen-producing and acid-producing reactor as fermentation microorganisms.

[0018] Preferably, the hydrogen-producing and acid-producing reactor, the first methane-producing reactor and the second methane-producing reactor are all CSTR reactors.

[0019] Preferably, the pretreatment tank is connected to a first solid-liquid separation device, and the first solid-liquid separation device is connected to a solid conveying system and a liquid conveying system;

[0020] The first solid-liquid separation device is used to separate the pretreated liquid into solid materials and liquid materials;

[0021] The solid conveying system is used to convey the solid materials to the hydrogen-producing and acid-producing reactor and the first methane-producing reactor; the liquid conveying system is used to convey the liquid materials to the hydrogen-producing and acid-producing reactor and the first methane-producing reactor.

[0022] Preferably, the anaerobic fermentation methane production system provided by the present application further includes an acidic substrate storage tank provided between the hydrogen-producing and acid-producing reactor and the second methane-producing reactor, and a hydrogen-producing tail gas storage device provided between the hydrogen-producing and acid-producing reactor and the nanobubble generating device.

[0023] Preferably, the anaerobic fermentation methane production system provided by the present application further includes a biogas collection device, a fermented material collection device and a second solid-liquid separation device;

[0024] The biogas collection device is connected to the first methanogenic reactor and the second methanogenic reactor, and is used for collecting methane generated by fermentation of the first methanogenic reactor and the second methanogenic reactor;

[0025] The post-fermentation material collection device is connected to the first methanogenic reactor and the second methanogenic reactor, and is used for collecting the materials after fermentation of the first methanogenic reactor and the second methanogenic reactor;

[0026] The second solid-liquid separation device is connected to the post-fermentation material collection device, and is used for separating the post-fermentation material into biogas slurry and biogas residue by solid-liquid separation.

[0027] Preferably, the anaerobic fermentation methane production system provided by the present application further includes an aeration tank;

[0028] The aeration tank is connected to the second solid-liquid separation device and the pretreatment tank, and is used for aerating the biogas slurry and transporting the aerated biogas slurry to the pretreatment tank for use as a water source.

[0029] The present application uses two methanogenic reactors to respectively produce methane by using the acidic substrates and hydrogen generated by fermentation of an acidogenic hydrogen-producing reactor. According to the reaction characteristics, a magnetic field strengthening device and a nano-bubble generating device are respectively equipped, which improves the degradation effect of organic matter, the acidogenic hydrogen-producing effect, and the utilization efficiency of hydrogen and acidogenic substrates, increases the methane production and purity, and shortens the entire fermentation cycle. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of the anaerobic fermentation methane production system provided by the present utility model;

[0031] Figure 2 is a schematic structural diagram of the external circulation of the acidogenic hydrogen-producing reactor.

[0032] Description of the Reference Numerals:

[0033] 1 - Pretreatment tank; 2 - Acidogenic hydrogen-producing reactor; 3 - Nano-bubble generating device; 4 - First methanogenic reactor; 5 - Second methanogenic reactor; 6 - First external circulation pipeline; 7 - First magnetic field strengthening device; 8 - Methane; 9 - Second magnetic field strengthening device; 10 - Crushing device; 11 - First electromagnetic coil; 12 - Biogas residue; 13 - First solid-liquid separation device; 14 - Acidic substrate storage tank; 15 - Hydrogen-producing tail gas storage device; 16 - Biogas collection device; 17 - Post-fermentation material collection device; 18 - Second solid-liquid separation device; 19 - Aeration tank; 20 - Fermentation raw material. Detailed Embodiments

[0034] The present utility model provides an anaerobic fermentation methane production system, as Figures 1 to 2As shown in the figure, it includes a pretreatment tank 1, a hydrogen-producing and acid-producing reactor 2, a nanobubble generating device 3, a first methane-producing reactor 4 connected in sequence, and a second methane-producing reactor 5 connected to the hydrogen-producing and acid-producing reactor 2.

[0035] The pretreatment tank 1 is used to aerobically degrade the fermentation raw material 20 to obtain a pretreated liquid, and the pretreated liquid is transported to the hydrogen-producing and acid-producing reactor 2 for anaerobic fermentation. Specifically, for straw biomass raw materials such as corn, rice, and wheat straw, aerobic microorganisms are inoculated in the pretreatment tank 1, and the straw and aerobic microorganisms can fully contact. Macromolecular substances such as straw cellulose are initially aerobically degraded into small molecular substances such as glucose and organic acids, which can shorten the fermentation cycle. After the aerobic degradation, the moisture content of the straw can also be adjusted so that the mass percentage of the total solid substances in the pretreated liquid is 6% - 8%, meeting the requirements of subsequent fermentation.

[0036] The aerobic microorganisms can be sewage plant sludge, which contains aerobic microorganisms and anaerobic microorganisms. The aerobic microorganisms among them can grow and reproduce under aerobic conditions to degrade the straw.

[0037] Preferably, a crushing device 10 is also connected to the front end of the pretreatment tank 1. Before pretreatment, the straw-like substances can be crushed first to prevent the straw-like substances from being too long and affecting the pretreatment and fermentation effects.

[0038] Preferably, the pretreatment tank 1 is connected to a first solid-liquid separation device 13, and the first solid-liquid separation device 13 is connected to a solid conveying system and a liquid conveying system.

[0039] After pretreatment, there is a first solid-liquid separation device 13, which can separate the pretreated materials into solid materials and liquid materials, so that they can be transported separately, improving the transportation speed. The first solid-liquid separation device can adopt a vibrating screen type solid-liquid separator. The solid materials can be transported to the hydrogen-producing and acid-producing reactor 2 and the first methane-producing reactor 4 by a screw conveyor, and the liquid materials can be transported to the hydrogen-producing and acid-producing reactor and the first methane-producing reactor 4 by a liquid extraction pump.

[0040] The hydrogen-producing and acid-producing reactor 2 is provided with a first external circulation pipeline 6 and a first magnetic field strengthening device 7, which are used to anaerobically ferment the pretreated liquid to produce hydrogen and acidic substrates. The gas including hydrogen produced by fermentation is transported to the nanobubble generating device 3, and the substrates produced by fermentation are transported to the second methane-producing reactor 5.

[0041] After pretreatment, the present application performs fermentation in two stages of hydrogen and acid production and methane production to shorten the fermentation cycle and improve the biomass conversion rate. In the first-stage hydrogen and acid production fermentation, a first external circulation pipeline is used for external circulation reflux of the fermentation broth, which can fully mix microorganisms with the substrate and is beneficial to the growth and reproduction of microorganisms. By using a first magnetic field strengthening device, the growth and reproduction of hydrogen-producing and acetic acid-producing bacteria can be promoted, their abundance can be increased, and the production of acetic acid and hydrogen during the acid production process can be increased.

[0042] Preferably, the first magnetic field strengthening device 7 is located on the first external circulation pipeline 6, which can apply a magnetic field to the reactor liquid while effectively reducing the floor area and layout range of the magnetic field.

[0043] Further preferably, the first magnetic field strengthening device 7 includes a first electromagnetic coil 11 wound around the first external circulation pipeline 6. By applying an electric current to the first electromagnetic coil, a magnetic field can be applied to the liquid in the circulation pipeline.

[0044] Since this stage is mainly hydrogen and acid production fermentation and does not require methanogens, preferably, the anaerobic fermentation methane production system provided by the present application further includes a heat treatment device connected to the hydrogen and acid production reactor 2; before inoculation, the sewage plant sludge can be first subjected to high-temperature heat treatment by the heat treatment device to inactivate the methanogens in the sludge, and the inactivated sludge is then transported to the hydrogen and acid production reactor 2 as fermentation microorganisms.

[0045] The nano-bubble generating device 3 is used to make the gas including hydrogen generated by the hydrogen and acid production reactor fermentation into nano-bubble water, and then transport it to the first methane production reactor 4.

[0046] The first methane production reactor 4 is also connected to the pretreatment tank 1 and is used for hydrogenotrophic anaerobic fermentation methane production of the nano-bubble water and the pretreatment liquid. The first methane production reactor 4 is inoculated with hydrogenotrophic methanogenic microorganisms. Preferably, the hydrogenotrophic methanogenic microorganisms are sewage plant sludge with domesticated hydrogenotrophic methanogenic microorganisms as the dominant flora. The nano-bubble water and the pretreatment liquid are used for hydrogenotrophic methanogenesis. The addition of the pretreatment liquid ensures the survival of the remaining strains in the sludge, and the remaining strains can be used to further produce hydrogen and CO 2 in the pretreatment liquid, while using hydrogenotrophic methanogenic microorganisms as the dominant strain, the utilization of CO 2 in the reactor can be promoted through the reaction of CO 2 +4H 4 =CH 2 +4H 2 O, which not only increases the methane production but also improves the methane concentration. Nano-bubbles can improve the heat and mass transfer efficiency between microorganisms and raw materials, solve the problem of low gas-liquid mass transfer efficiency in the traditional hydrogenotrophic methanogenesis process, and improve the methane production and purity.

[0047] Preferably, a hydrogen production tail gas storage device 15 is provided between the hydrogen-producing and acid-producing reactor 2 and the nanobubble generating device 3, which can temporarily store the gas generated by the fermentation of the hydrogen-producing and acid-producing reactor for convenient use.

[0048] The second methanogenic reactor 5 is provided with a second external circulation pipeline and a second magnetic field strengthening device 9 for carrying out acidophilic anaerobic fermentation to produce methane from acidic substrates.

[0049] The second methanogenic reactor 5 is inoculated with acetic acid-utilizing methanogenic microorganisms in the reactor. Preferably, sewage plant sludge with acetic acid-utilizing methanogenic microorganisms as the dominant flora after domestication is used. Methane is mainly produced through the reaction of CH 3 COOH = CH 4 + CO 2 Similar to the hydrogen-producing and acid-producing reactor, the fermentation effect of producing methane is improved by means of magnetic field strengthening and external circulation reflux of the reaction liquid. No pretreatment liquid is added to this reactor to avoid introducing H 2 which leads to an increase in hydrogen partial pressure and inhibits the acetic acid-utilizing methanogenic pathway.

[0050] Preferably, the second magnetic field strengthening device 9 is located on the second external circulation pipeline.

[0051] More preferably, the second magnetic field strengthening device includes a second electromagnetic coil wound around the second external circulation pipeline.

[0052] Since there are differences in the fermentation pH during the hydrogen-producing and acid-producing and methanogenic stages, preferably, an acidic substrate storage tank 14 is provided between the hydrogen-producing and acid-producing reactor 2 and the second methanogenic reactor 5, which can temporarily store the substrate generated by the fermentation of the hydrogen-producing and acid-producing reactor and is convenient for adjusting the pH.

[0053] In the second stage, the present application separately uses the fermentation gas and fermentation substrate in the first stage for hydrogenotrophic methanogenic fermentation and acidophilic methanogenic fermentation respectively. Compared with the prior art in which the fermentation gas and fermentation substrate are fermented together, the utilization rates of hydrogen and acidic substrates are higher, and the methane yield and purity obtained are higher.

[0054] Therefore, the present application uses two methanogenic reactors to produce methane by using the acidic substrate and hydrogen generated by the fermentation of the hydrogen-producing and acid-producing reactor respectively, and according to the reaction characteristics, magnetic field strengthening devices and nanobubble generating devices are respectively equipped, which improves the organic matter degradation effect, hydrogen-producing and acid-producing effect, and the utilization efficiency of hydrogen and acid-producing substrates, increases the methane yield and purity, and shortens the entire fermentation cycle.

[0055] Preferably, the hydrogen-producing and acid-producing reactor, the first methanogenic reactor and the second methanogenic reactor are all commonly used CSTR reactors.

[0056] Preferably, the anaerobic fermentation methane production system provided by the present application further includes a biogas collection device 16, a fermented material collection device 17, and a second solid-liquid separation device 18. Further, it also includes a heat exchanger and an aeration tank 19, and the aeration tank is connected to the second solid-liquid separation device and the pretreatment tank.

[0057] The biogas collection device 16 is connected to the first methane production reactor 4 and the second methane production reactor 5, and is used for collecting the methane fermented by the first methane production reactor 4 and the second methane production reactor 5. The collected methane 8 can be used as fuel gas after treatment, or can be subjected to temperature increase treatment by a heat exchanger. The reactions in the pretreatment tank 1, the hydrogen-producing and acid-producing reactor 2, the first methane production reactor 4, and the second methane production reactor 5 generally proceed at 30°C to 37°C. When the temperature is relatively low in winter, the methane after temperature increase can be used as a heat source and respectively transported to the jacket of the shells of the pretreatment tank 1, the hydrogen-producing and acid-producing reactor 2, the first methane production reactor 4, and the second methane production reactor 5 to provide heat for the materials in the reactors and maintain their respective reaction temperatures.

[0058] The fermented material collection device 17 is connected to the first methane production reactor 4 and the second methane production reactor 5, and is used for collecting the fermented materials of the first methane production reactor and the second methane production reactor. The second solid-liquid separation device 18 is connected to the fermented material collection device 17, and is used for solid-liquid separating the fermented materials into biogas slurry and biogas residue 12. The biogas residue 12 can be used as fertilizer. After the biogas slurry is aerated in the aeration tank 19, it can be transported to the pretreatment tank 1 as a water source to realize the recycling of fermentation waste and save resources.

[0059] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. An anaerobic fermentation methane production system, characterized in that: It includes a pretreatment tank, a hydrogen-acid-generating reactor, a nano bubble generating device, a first methanogenic reactor, and a second methanogenic reactor connected to the hydrogen-acid-generating reactor in sequence; The pretreatment tank is used to aerobically degrade the fermentation raw materials to obtain a pretreated liquid; The hydrogen-acid production reactor is provided with a first external circulation pipeline and a first magnetic field strengthening device, which are used to perform anaerobic fermentation on the pretreated liquid to produce hydrogen and acidic substrate; The nanobubble generating device is used to produce the hydrogen into nanobubbles; The first methanogenic reactor is also connected to the pretreatment tank, and is used to perform hydrogenophilic anaerobic fermentation of the nanobubbles and the pretreated liquid to produce methanogen; The second methanogenic reactor is provided with a second external circulation pipeline and a second magnetic field intensification device, which are used to produce methane by acidophilic anaerobic fermentation of the acidic substrate.

2. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: Also included is a pulverizing device connected to the pretreatment tank; The pulverizing device is used to pulverize the fermentation raw material before pretreatment.

3. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: The first magnetic field enhancement device is located on the first external circulation pipeline; the second magnetic field enhancement device is located on the second external circulation pipeline.

4. The anaerobic fermentation methanogenesis system according to claim 3, characterized in that: The first magnetic field enhancement device comprises a first electromagnetic coil wound on the first external circulation pipeline; The second magnetic field strengthening device includes a second electromagnetic coil wound on the second external circulation pipeline.

5. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: Also included is a thermal treatment device connected to the hydrogen and acid generating reactor; The thermal treatment device is used to perform thermal treatment on the sludge to inactivate the methanogens therein, and the inactivated sludge is transported to the hydrogen-acid production reactor as a fermentation microorganism.

6. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: The hydrogen- and acid-producing reactor, the first methane-producing reactor and the second methane-producing reactor are all CSTR reactors.

7. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: The pretreatment tank is connected to a first solid-liquid separation device, and the first solid-liquid separation device is connected to a solid transport system and a liquid transport system; The first solid-liquid separation device is used to separate the pretreated liquid into solid material and liquid material; The solid transport system is used to transport the solid material to the hydrogen-acid-producing reactor and the first methane-producing reactor; the liquid transport system is used to transport the liquid material to the hydrogen-acid-producing reactor and the first methane-producing reactor.

8. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: It also includes an acidic substrate storage tank disposed between the hydrogen-acid-producing reactor and the second methane-producing reactor, and a hydrogen-producing tail gas storage device disposed between the hydrogen-acid-producing reactor and the nano bubble generating device.

9. The anaerobic fermentation methanogenesis system according to claim 1, characterized in that: It also includes a biogas collection device, a post-fermentation material collection device, and a second solid-liquid separation device; The biogas collection device is connected to the first methanogenic reactor and the second methanogenic reactor, and is used to collect methane produced by fermentation in the first methanogenic reactor and the second methanogenic reactor; The post-fermentation material collection device is connected to the first methanogenic reactor and the second methanogenic reactor, and is used to collect the material after fermentation in the first methanogenic reactor and the second methanogenic reactor; The second solid-liquid separation device is connected to the post-fermentation material collection device, and is used for separating the post-fermentation material into solid-liquid biogas slurry and biogas residue.

10. The anaerobic fermentation methanogenesis system according to claim 9, characterized in that: It also includes aeration ponds; The aeration tank is connected to the second solid-liquid separation device and the pretreatment tank, and is used to aerate the biogas slurry, and transport the aerated biogas slurry to the pretreatment tank for use as a water source.

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