A method for preparing bio-natural gas by coupling intermittent aeration, ethanol type fermentation and electric field polarization enhancement

Abstract

The present application belongs to the technical field of biological natural gas preparation, and particularly relates to a method for preparing biological natural gas by coupling intermittent aeration with ethanol fermentation and electric field polarization enhancement. The present application adopts a non-biological methane production composite reflux approach, and refluxes the substrate of alcohol fermentation to a hydrolysis zone. Alcohol reacts with free radicals generated by intermittent aeration to generate methane precursors, thereby promoting methane generation. At the same time, alcohol fermentation is an effective means for constructing a new type of direct interspecies electron transfer, can bypass the thermodynamic bottleneck of traditional acetate production and hydrogenotrophic methanogenesis, and can improve mass transfer efficiency and system stability, so that the anaerobic reactor can effectively produce gas at a pH value of 3.5-8. The free radicals and redox oscillation generated by intermittent aeration can promote the decomposition of the substrate in the hydrolysis zone through free radical generation and growth of facultative bacteria. The present application enhances the activity of respiratory enzymes by coupling an electric field, enhances the yield of free radicals and alcohol, and enhances the metabolism of methanogens, thereby improving the yield of biological natural gas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biological natural gas preparation, and particularly relates to a method for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization reinforcement. BACKGROUND

[0002] Currently, the treatment of organic solid waste mainly adopts incineration, and anaerobic digestion, aerobic composting or landfill are supplementary. Among them, anaerobic digestion has low energy consumption and high energy conversion rate, and not only biological natural gas is obtained as clean energy, but also the residual slurry and residue of fermentation can be used as organic fertilizer, which is an environmentally friendly organic solid waste treatment method. However, anaerobic digestion also has some problems, such as slow decomposition rate of organic matter, low methane conversion rate and poor stability, resulting in low overall efficiency of anaerobic digestion. SUMMARY

[0003] The present application aims to provide a method for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization reinforcement, and the method provided by the present application can realize efficient anaerobic digestion for preparing biological natural gas.

[0004] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] The application provides a method for preparing bio-natural gas by intermittent aeration coupled with ethanol fermentation and electric field polarization strengthening, and a device for preparing bio-natural gas by intermittent aeration coupled with ethanol fermentation and electric field polarization strengthening, and the method comprises the following steps: intermittently aerating oxygen in an oxygen storage device through an aeration disc between a hydrolysis zone and an acidification zone in an anaerobic reactor, the intensity of the intermittent aeration being 0.25 mL / (min·L·day)~1.25 mL / (min·L·day), injecting a first raw material, anaerobic sludge and shewanella liquid into the anaerobic reactor, immersing a positive electrode plate and a negative electrode plate, stirring and mixing the first raw material, anaerobic sludge and shewanella liquid by using a first paddle, a second paddle, a sixth paddle, a seventh paddle, a third paddle, a fourth paddle and a fifth paddle, making part of the material in the acidification zone enter a methanogenic zone, and making the remaining material backflow to the hydrolysis zone, storing bio-natural gas generated by the anaerobic reactor in a gas collection warehouse, and discharging the digestion products of the first raw material into a discharge pool; the first raw material is one or more of residual sludge and organic solid waste; the device for preparing bio-natural gas by intermittent aeration coupled with ethanol fermentation and electric field polarization strengthening comprises a feed pool, an oxygen storage device, an anaerobic reactor, a gas collection warehouse and a discharge pool, wherein the feed port of the anaerobic reactor is communicated with the feed pool, the gas inlet of the anaerobic reactor is communicated with the oxygen storage device, the anaerobic reactor is provided with a hydrolysis zone, an acidification zone and a methanogenic zone, the hydrolysis zone, the acidification zone and the methanogenic zone are sequentially away from the feed port and the gas inlet of the anaerobic reactor, the acidification zone and the hydrolysis zone form a backflow system through a backflow pump, the hydrolysis zone comprises an aeration disc and a first paddle and a second paddle arranged in the aeration direction of the aeration disc, the acidification zone comprises an aeration disc and a sixth paddle and a seventh paddle arranged in the aeration direction of the aeration disc, the methanogenic zone comprises a positive electrode plate, a negative electrode plate and a third paddle, a fourth paddle and a fifth paddle arranged between the positive electrode plate and the negative electrode plate, and the positive electrode plate and the negative electrode plate are connected with a power supply.

[0006] Preferably, the mass ratio of the part of the material entering the methanogenic zone to the remaining material backflowing to the hydrolysis zone is 1:1~1:20.

[0007] Preferably, the period of the intermittent aeration is 2 hours~5 hours, the aeration time in each period is 5 minutes~30 minutes, and the volume ratio of the aeration gas to the anaerobic reactor is 2%~6%; the temperature of the intermittent aeration is 25 ℃~38 ℃.

[0008] Preferably, the internal temperature of the anaerobic reactor is 30 ℃~45 ℃, the pH value is 6.8~8, and the hydraulic retention time is 14 days~28 days.

[0009] Preferably, the volume ratio of the residual sludge and the anaerobic sludge is 1:10-1:20; the volume ratio of the organic solid waste and the anaerobic sludge is 1:10-1:30; the total volume of the first raw material and the anaerobic sludge accounts for 50%-90% of the volume of the anaerobic reactor; the OD600 of the Shewanella liquid is 0.8-1.5; and the volume ratio of the Shewanella liquid to the anaerobic reactor is 1 / 30-1 / 15.

[0010] Preferably, the acidification zone further comprises a biological agent; the biological agent is an alcohol-producing microorganism; when the acidification zone comprises a biological agent, the temperature of the acidification zone is 25 ℃-40 ℃.

[0011] Preferably, the fermentation pH value of the acidification zone is 3.5-8, the temperature is 30 ℃-42 ℃, and the hydraulic retention time is 0.5 days-3 days.

[0012] Preferably, the first raw material is pretreated before use, and the target solid content of the pretreatment is 5%-20%, and the target C / N ratio is 10:1-20:1.

[0013] Preferably, the anaerobic sludge is discharged from an anaerobic fermentation tank of a sewage treatment plant; and the volatile suspended solid content of the anaerobic sludge is 15 g / L-40 g / L.

[0014] Preferably, the organic solid waste comprises one or more of municipal sludge, kitchen waste, excrement and crop straw.

[0015] The application provides a method for preparing biological natural gas by intermittent aeration coupled with ethanol fermentation and electric field polarization enhancement. The method provided by the application can realize efficient anaerobic digestion for preparing biological natural gas: the application adopts a non-biological methanogenesis composite reflux approach, and by refluxing alcohol fermentation substrate to a front-end hydrolysis zone subjected to aeration, alcohol reacts with free radicals generated by intermittent aeration to directly generate a methane precursor, thereby promoting the generation of methane in the system; meanwhile, alcohol fermentation is an effective means for constructing a new type of direct interspecies electron transfer, can bypass the thermodynamic bottleneck of traditional acetogenesis and hydrogenotrophic methanogenesis, and can improve mass transfer efficiency and system stability, so that the anaerobic reactor can maintain effective gas production at a pH value of 3.5-8; free radicals and redox oscillation generated by intermittent aeration can promote front-end substrate decomposition through free radical generation and growth of facultative bacteria; by coupling an electric field, the application can enhance the activity of respiratory enzymes through electric field polarization, improve the yield of free radicals and alcohol, and improve the metabolism of methanogens, and systematically improve the yield of biological natural gas.

[0016] First, this invention enriches the methanogenesis pathway by employing a non-biological methanogenesis compound reflux approach. By refluxing the substrate from alcohol fermentation to the front-end aeration zone, the alcohol reacts with free radicals generated by intermittent aeration (such as ·OH-induced dehydrogenation) to directly generate methane precursors, promoting methane generation in the system. At the same time, alcohol fermentation is an effective means of constructing a novel direct interspecies electron transfer mechanism, which can bypass the thermodynamic bottlenecks of traditional acetic acid production and hydrogen-nutrition-based methanogenesis, improve mass transfer efficiency and system stability, and enable the anaerobic reactor to maintain effective gas production and regulate the metabolic energy distribution of the microbial community between pH 3.5 and 8.

[0017] Secondly, this invention employs low-intensity intermittent aeration to achieve precise and controllable aeration in the reaction tank, ensuring timed, quantitative, and component-specific aeration. Furthermore, it provides redox oscillation conditions for anaerobic digestion. Extracellular respiratory bacteria generate reactive oxygen species (ROS) under aerobic conditions using O2 as the electron acceptor for respiration, and under anaerobic conditions, they transfer electrons to exogenous electron acceptors such as Fe. 3+ Reduce it to Fe 2+ The generated reactive oxygen species (such as peroxides, superoxides, hydroxyl radicals, singlet oxygen, and α-oxygen) all have strong oxidizing properties. Through free radical oxidation, they promote cell wall disruption (decomposition of lignin, cellulose, and hemicellulose, destroying cell wall and cell membrane structures) and decomposition of macromolecular recalcitrant organic matter, increasing the biodegradability of organic matter, improving the hydrolysis rate, and shortening the anaerobic digestion cycle.

[0018] Furthermore, the hydrolytic acidifying bacteria in anaerobic digestion are mostly facultative anaerobes. The abundance of hydrolytic acidifying bacteria increases under low-intensity intermittent aeration conditions, which is beneficial to improving the hydrolysis and acidification rate.

[0019] Under normal conditions, the abundance and narrow ecological niche of highly efficient extracellular electron-transferring microorganisms (such as Shewanella or Geobacterium) in anaerobic sludge are low, resulting in low energy density and poor electroactivity, thus limiting electron transfer efficiency. This invention utilizes electric field polarization to enhance the activity of Shewanella's respiratory enzymes and increase its growth and metabolic energy while ensuring suitable oxygenation for Shewanella growth through intermittent aeration. Experiments show that at 37 °C, the growth density of Shewanella under an electric field increased by 12% after 5 hours compared to without an electric field. Therefore, the intermittent aeration coupled with an electric field system optimizes the growth and reproduction conditions of Shewanella, eliminating the need for continuous addition during production and reducing capital investment.

[0020] In addition, under the polarization of the electric field, the reducibility of the amide group in the protein complex of the anaerobic microorganism is enhanced, the polarization of the amide group increases the electronegativity of the carbonyl oxygen in the amide group, and then promotes the rupture and rearrangement of the nearby X-H group (such as -OH of alcohol and phenol, -NH of amide) through hydrogen bond interaction, and the polarization can further change the secondary structure of the protein complex (such as alpha-helix, beta-fold), increase the molecular polarity of the alpha-helix, and the change of the beta-fold structure will affect the proton transfer channel in the protein complex, and have an effect on the medium effect of electron transfer, thereby promoting the proton-coupled electron transfer (PCET) of the protein complex, facilitating the electron transfer of intracellular metabolic organic matter to extracellular electron acceptor, improving the extracellular respiration efficiency, shortening the anaerobic digestion period, and increasing the production of active oxygen.

[0021] In addition, under the polarization of the electric field, the electrical activity of the anaerobic sludge is improved, and direct interspecies electron transfer (DIET) is constructed between the anaerobic microorganisms, overcoming the thermodynamic barrier of traditional anaerobic digestion with hydrogen as the electron transfer carrier, and providing a faster electron transfer pathway. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0023] Figure 1 The structure schematic diagram of the device for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization strengthening provided by the present application (taking the example of horizontal setting of the aeration disc);

[0024] Figure 2 The partial structure schematic diagram of the device for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization strengthening provided by the present application (taking the example of vertical setting of the aeration disc);

[0025] Reference: 1 is a feed tank, 2 is a first pipeline, 3 is a feed pump, 4 is a feed valve, 5 is an oxygen storage device, 6 is a second pipeline, 7 is an air inlet pump, 8 is an air inlet valve, 9 is an aeration disc, 10 is a first paddle, 11 is a second paddle, 12 is a third paddle, 13 is a fourth paddle, 14 is a fifth paddle, 15 is a power supply, 16 is a positive electrode plate, 17 is a negative electrode plate, 18 is an air outlet valve, 19 is a gas collection bin, 20 is a discharge valve, 21 is a discharge pump, 22 is a third pipeline, 23 is a discharge tank, 24 is an anaerobic reactor, 25 is an extracellular electron transfer microbial pump, 26 is an extracellular electron transfer microbial valve, 27 is an alcohol-producing microbial material bin, 28 is an alcohol-producing microbial pump, 29 is an alcohol-producing microbial valve, 30 is a reflux pump, 31 is an acidification zone material pump, 32 is a sixth paddle, 33 is a seventh paddle, 34 is an extracellular electron transfer microbial material bin. DETAILED DESCRIPTION

[0026] The present application provides a method for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization strengthening, and a device for preparing biological natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization strengthening, comprising the following steps:

[0027] The oxygen in the oxygen storage device 5 is intermittently aerated in the hydrolysis zone and acidification zone in the anaerobic reactor 24 by the aeration disc 9, the intensity of the intermittent aeration is 0.25 mL / (min·L·day)~1.25 mL / (min·L·day), the first raw material, anaerobic sludge and shewanella liquid are injected into the anaerobic reactor 24, the positive plate 16 and the negative plate 17 are immersed, the first raw material, anaerobic sludge and shewanella liquid are stirred and mixed by the first paddle 10, the second paddle 11, the sixth paddle 32, the seventh paddle 33, the third paddle 12, the fourth paddle 13 and the fifth paddle 14, part of the material in the acidification zone enters the methane production zone, and the remaining material returns to the hydrolysis zone, the biological natural gas produced by the anaerobic reactor 24 is introduced into the gas storage warehouse 19 for storage, and the digestion product of the first raw material is discharged into the discharge tank 23; the first raw material is one or more of residual sludge and organic solid waste; the device for preparing biological natural gas by intermittent aeration coupling ethanol fermentation and electric field polarization strengthening comprises a feed tank 1; an oxygen storage device 5; an anaerobic reactor 24, the feed inlet of the anaerobic reactor 24 communicates with the feed tank 1, the gas inlet of the anaerobic reactor 24 communicates with the oxygen storage device 5, the anaerobic reactor 24 is provided with a hydrolysis zone, an acidification zone (alcohol production zone) and a methane production zone, the hydrolysis zone, the acidification zone and the methane production zone are sequentially away from the feed inlet and the gas inlet of the anaerobic reactor 24, the acidification zone forms a reflux system with the hydrolysis zone through a reflux pump 30, the hydrolysis zone comprises an aeration disc 9 and first and second paddles 10 and 11 arranged in the aeration direction of the aeration disc 9, the acidification zone comprises an aeration disc 9 and sixth and seventh paddles 32 and 33 arranged in the aeration direction of the aeration disc 9, the methane production zone comprises positive and negative plates 16 and 17 and third, fourth and fifth paddles 12, 13 and 14 arranged between the positive and negative plates 16 and 17, and the positive and negative plates 16 and 17 are connected with a power supply 15; a gas storage warehouse 19, which communicates with the anaerobic reactor 24; a discharge tank 23, which communicates with the anaerobic reactor 24.

[0028] The oxygen in the oxygen storage device 5 is intermittently aerated in the hydrolysis zone and acidification zone in the anaerobic reactor 24 by the aeration disc 9, the intensity of the intermittent aeration is 0.25 mL / (min·L·day)~1.25 mL / (min·L·day).

[0029] In the present application, the intensity of the intermittent aeration is adjusted according to the concentration of the first raw material and the volume of the anaerobic reactor 24; the intensity of the intermittent aeration is 0.25 mL / (min·L·day)~1.25 mL / (min·L·day), and specifically can be 0.5 mL / (min·L·day), 0.75 mL / (min·L·day) or 1 mL / (min·L·day).

[0030] In the present application, the period of the intermittent aeration can be 2 hours~5 hours, and specifically can be 3 hours or 4 hours; each period can be aerated for 5 minutes~30 minutes, and specifically can be 10 minutes, 15 minutes, 20 minutes or 25 minutes; the proportion of the amount of gas (calculated by air or oxygen of the same concentration) for aeration to the volume of the anaerobic reactor 24 can be 2%~6%, and specifically can be 3%, 4% or 5%.

[0031] In the present application, the aeration can be intermittent by the aeration pump through the pipeline into the aeration disc; the temperature of the intermittent aeration can be 25 ℃~38 ℃, and specifically can be 35 ℃. The above intermittent aeration of the present application makes the sludge phase of the first raw material, anaerobic sludge and shewanella liquid produce an ORP value fluctuation of 50 mV or more.

[0032] In the present application, the first raw material, anaerobic sludge and shewanella liquid are injected into the anaerobic reactor 24, and the positive plate 16 and the negative plate 17 are immersed. In the present application, the first raw material is one or more of residual sludge and organic solid waste; the residual sludge can be obtained by mixing different regions of the same region; the organic solid waste can include one or more of municipal sludge, kitchen waste, excrement and crop straw; the excrement can be cow dung. In the specific embodiment of the present application, the residual sludge is obtained by mixing the residual sludge from four regions of Dalian sewage plant, including Dalian Bay area 32.5wt%, Chunliu area 25wt%, Lingshui area 25wt% and Quanshui area 17.5wt%.

[0033] In the present application, the first raw material can be pretreated before use; the target solid content of the pretreatment can be 5%~20%, and preferably 10%; the target C / N ratio (molar ratio) can be 10:1~20:1, and specifically can be 15:1.

[0034] In the present application, the anaerobic sludge can be obtained from the effluent of the anaerobic fermentation tank of the sewage treatment plant; the volatile suspended solid content (VSS) of the anaerobic sludge can be 15 g / L~40 g / L, and preferably 25 g / L.

[0035] In the present application, the volume ratio of the residual sludge and the anaerobic sludge can be 1:10-1:20, and specifically can be 1:13 or 1:16.

[0036] In the present application, the volume ratio of the organic solid waste and the anaerobic sludge can be 1:10-1:30, and specifically can be 1:14, 1:20 or 1:25.

[0037] In the present application, the total volume of the first raw material and the anaerobic sludge can account for 50%-90% of the volume of the anaerobic reactor 24, and specifically can account for 60% or 80%.

[0038] In the present application, the OD600 of the Shewanella liquid can be 0.8-1.5, and specifically can be 1 or 1.2; the volume ratio of the Shewanella liquid to the anaerobic reactor 24 can be 1 / 30-1 / 15, and specifically can be 1 / 25 or 1 / 20. The present application constructs a biological type advanced oxidation system by adding the Shewanella liquid. This facultative microorganism with extracellular respiration capacity can transfer the intracellular metabolism generated electrons to the extracellular acceptor through the electron transfer system (ETC), produce reactive oxygen species and hydroxyl radicals to destroy the cell wall in the sludge, release intracellular organic matter, and improve the yield of natural gas prepared by anaerobic digestion.

[0039] In the present application, the first paddle 10, the second paddle 11, the sixth paddle 32, the seventh paddle 33, the third paddle 12, the fourth paddle 13 and the fifth paddle 14 are used to stir and mix the first raw material, the anaerobic sludge and the Shewanella liquid.

[0040] In the present application, the fermentation pH value of the acidification zone can be 3.5-8, and specifically can be 5 or 6; the temperature can be 30 ℃-42 ℃, and preferably is 37 ℃. The present application controls the pH value to make the material in the acidification zone produce alcohol directionally.

[0041] In the present application, the acidification zone can further include a biological agent; the biological agent can be alcohol-producing microorganisms; the alcohol-producing microorganisms can include glycerol-producing Candida or Pichia fungus; when the acidification zone includes a biological agent, the temperature of the acidification zone can be 25 ℃-40 ℃, and preferably is 32 ℃. The present application also realizes directional alcohol production by adding a biological agent.

[0042] In the present application, the hydraulic retention time of the acidification zone can be 0.5 days-3 days, and specifically can be 1 day or 2 days.

[0043] In the present application, the mass ratio of the part of the material entering the methanogenic zone and the remaining material refluxing to the hydrolysis zone can be 1:1-1:20, and specifically can be 1:5, 1:10 or 1:15.

[0044] In the present application, the internal temperature of the anaerobic reactor 24 can be 30-45 DEG C, preferably 34 DEG C, 37 DEG C or 42 DEG C, and the pH value can be 6.8-8, preferably 7.8.

[0045] In the present application, the hydraulic retention time of the anaerobic reactor 24 can be 14-28 days, and can be 18 days or 24 days in particular.

[0046] The biogenic natural gas produced by the anaerobic reactor 24 is stored in the gas storage bin 19, and the digestion products of the first raw material are discharged into the discharge tank 23.

[0047] In the present application, the device for preparing biogenic natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization enhancement comprises a feed tank 1; the feed tank 1 can be communicated with the anaerobic reactor 24 through a first pipeline 2; the first pipeline 2 can be communicated with the anaerobic reactor 24 in turn through a feed pump 3 and a feed valve 4.

[0048] In the present application, the device for preparing biogenic natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization enhancement comprises an oxygen storage device 5; in the present application, the oxygen storage device 5 can be communicated with the anaerobic reactor 24 through a second pipeline 6; the second pipeline 6 can be communicated with the anaerobic reactor 24 in turn through an air inlet pump 7 and an air inlet valve 8.

[0049] In the present application, the device for preparing biogenic natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization enhancement comprises an anaerobic reactor 24; the first paddle 10, the second paddle 11, the third paddle 12, the fourth paddle 13 and the fifth paddle 14 can be independently provided with an inclined wing plate at the end and a guide plate inside; the first paddle 10 and the second paddle 11 are staggered in the vertical direction, so that they are staggered in rotation during stirring, achieving sufficient stirring; the third paddle 12, the fourth paddle 13 and the fifth paddle 14 can be staggered in rotation during stirring, achieving sufficient stirring. The first paddle 10 and the second paddle 11 are used to stir the raw materials in the hydrolysis zone uniformly, the third paddle 12, the fourth paddle 13 and the fifth paddle 14 are used to stir the raw materials in the methanogenic zone uniformly, and the sixth paddle 32 and the seventh paddle 33 are used to stir the raw materials in the acidification zone uniformly.

[0050] In the present application, the first paddle 10 and the second paddle 11 can be arranged horizontally; the third paddle 12, the fourth paddle 13 and the fifth paddle 14 can be arranged horizontally.

[0051] In the present application, the length of the aeration disc 9 can be 0.2 m~5 m, and specifically can be 0.5 m, 0.8 m, 1 m, 2 m, 3 m or 4 m; the aeration disc 9 can be horizontally arranged or vertically arranged; when the aeration disc 9 is vertically arranged, the side of the aeration disc 9 can be loaded with the positive electrode plate 16 (as shown in FIG. 1). Figure 2 The present application loads the positive electrode plate 16 on the side of the aeration disc 9, which can realize one-way aeration while polarizing the electric field in the methanogenic zone, intermittently aerate the hydrolysis zone and the acidification zone, and block the dispersion of dissolved oxygen in the methanogenic zone, thereby better avoiding the influence of dissolved oxygen on anaerobic organisms. This method can also improve the space utilization of the device, improve the treatment capacity of the hydrolysis zone and the acidification zone, accelerate the hydrolysis, and improve the anaerobic digestion capacity.

[0052] In the present application, the aeration disc 9 can be subjected to anti-blocking treatment; the coverage ratio of the aeration disc 9 to the hydrolysis zone and the acidification zone can be 50%~100%, and specifically can be 75%. In the present application, the coverage range of the aeration disc 9 should be as large as possible to ensure uniform aeration.

[0053] In the present application, the device for intermittently aerating and coupling ethanol-type fermentation and electric field polarization to prepare biological natural gas can further comprise an alcohol-producing microbial material bin 27 and an extracellular electron transfer microbial material bin 34; the alcohol-producing microbial material bin 27 can be in communication with the acidification zone of the anaerobic reactor 24 in sequence through an alcohol-producing microbial pump 28 and an alcohol-producing microbial valve 29; the extracellular electron transfer microbial material bin 34 can be in communication with the hydrolysis zone of the anaerobic reactor 24 in sequence through an extracellular electron transfer microbial pump 25 and an extracellular electron transfer microbial valve 26.

[0054] In the present application, the extracellular electron transfer microbial material bin 34 stores extracellular electron transfer microorganisms such as Shewanella, white rot fungi and Bacillus subtilis, and the alcohol-producing microbial material bin 27 stores alcohol-producing microorganisms such as yeast, which are used to construct ethanol-type fermentation.

[0055] In the present application, the acidification zone can be in communication with the methanogenic zone through an acidification zone material pump 31.

[0056] In the present application, the power supply 15 applies voltage to the positive electrode 16 and the negative electrode 17 to form an electric field; the voltage of the power supply 15 is subject to the electric field strength of the electric field; the electric field strength of the positive electrode plate 16 and the negative electrode plate 17 can be 2 V / m~200 V / m, and specifically can be 20 V / m, 70 V / m, 120 V / m or 160 V / m; the voltage variation frequency of the power supply 15 can be 0 Hz~240 Hz, and specifically can be 60 Hz, 120 Hz or 180 Hz.

[0057] In the present application, the positive electrode 16 and the negative electrode 17 can be horizontally opposite or vertically opposite; when the positive electrode 16 and the negative electrode 17 are vertically opposite, the positive electrode 16 can be located on the left side of the negative electrode 17; when the positive electrode 16 and the negative electrode 17 are horizontally opposite, the positive electrode 16 can be located above the negative electrode 17.

[0058] In the present application, the distance between the positive electrode 16 and the negative electrode 17 can be 0.04 m~2 m, specifically 0.1 m, 0.3 m, 0.5 m, 0.8 m, 1 m, 1.3 m, 1.5 m or 1.8 m; the length of the positive electrode 16 and the negative electrode 17 can be 0.5 m~3 m, specifically 0.8 m, 1 m, 1.5 m, 2 m or 2.5 m.

[0059] In the present application, the positive electrode 16 and the negative electrode 17 can be insulated and corrosion-proof to prevent the circuit from causing corrosion of the positive electrode 16 and the negative electrode 17; the insulation and corrosion-proof treatment can be plating or passivation.

[0060] In the present application, the ratio of the length of the positive electrode 16 to the length of the hydrolysis zone (the edge parallel to the aerator 9) can be 1:0.5~1:2.5, specifically 1:1 or 1:2; the ratio of the width of the positive electrode 16 to the width of the hydrolysis zone (the remaining one edge not shown) can be 1:1~1:3, specifically 1:2. Figure 1 Figure 1 In the present application, the ratio of the length of the positive electrode 16 to the length of the hydrolysis zone (the edge parallel to the aerator 9) can be 1:0.5~1:2.5, specifically 1:1 or 1:2; the ratio of the width of the positive electrode 16 to the width of the hydrolysis zone (the remaining one edge not shown) can be 1:1~1:3, specifically 1:2.

[0061] In the present application, the device for preparing bio-natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization enhancement comprises a gas collecting bin 19; the gas collecting bin 19 can be communicated with the anaerobic reactor 24 through the exhaust valve 18; the gas collecting bin 19 is used to collect bio-natural gas produced by anaerobic digestion.

[0062] In the present application, the device for preparing bio-natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization enhancement comprises a discharge tank 23; the discharge tank 23 can be communicated with the anaerobic reactor 24 through the third pipeline 22; the third pipeline 22 can be communicated with the anaerobic reactor 24 in turn through the discharge pump 21 and the discharge valve 20.

[0063] ​The device realizes high-efficiency anaerobic digestion for preparing bio-natural gas by adopting low-intensity intermittent aeration and electric field reinforcement, and provides a more reasonable and efficient way for engineering application. The device realizes partition fermentation by push-flow stirring of the first paddle to the fifth paddle, which is more sufficient and avoids adverse effects of dissolved oxygen in the front end on anaerobic methane-producing microorganisms. The positive and negative electrode plates of the electric field are arranged in the rear area, compared with the traditional device loading the whole reactor wall, the device can reduce equipment investment and maintenance cost, and is lower in cost.

[0064] In the present application, the structure of the device for preparing bio-natural gas by intermittent aeration coupling ethanol-type fermentation and electric field polarization reinforcement is as shown in Figure 1 The feed inlet of the anaerobic reactor 24 is communicated with the feed pool 1 through the first pipeline 2, the feed pump 3 and the feed valve 4, the gas inlet is communicated with the oxygen storage device 5 through the second pipeline 6, the gas pump 7 and the gas valve 8, the anaerobic reactor 24 is provided with a hydrolysis zone, an acidification zone and a methane production zone (not a mechanical structure, but only a functional area division), the hydrolysis zone comprises the aeration disc 9 and the first paddle 10 and the second paddle 11 arranged in the aeration direction of the aeration disc 9, the first paddle 10 and the second paddle 11 are used for uniformly stirring the raw materials in the hydrolysis zone, the acidification zone comprises the aeration disc 9 and the sixth paddle 32 and the seventh paddle 33 arranged in the aeration direction of the aeration disc 9, and is used for uniformly stirring the raw materials in the acidification zone, the methane production zone comprises the positive electrode plate 16, the negative electrode plate 17 and the third paddle 12, the fourth paddle 13 and the fifth paddle 14 arranged between the positive electrode plate 16 and the negative electrode plate 17, the third paddle 12, the fourth paddle 13 and the fifth paddle 14 are used for uniformly stirring the raw materials in the methane production zone, the positive electrode plate 16 and the negative electrode plate 17 are connected with the power supply 15, the power supply 15 applies voltage to the positive electrode 16 and the negative electrode 17 to form an electric field, the gas collection bin 19 is communicated with the anaerobic reactor 24 through the exhaust valve 18, and is used for collecting bio-natural gas produced by anaerobic digestion, the first raw material after anaerobic digestion is pumped out by the discharge pump 21 through the third pipeline 22 and then enters the discharge pool 23. In the aeration stage, the gas pump 7 pumps the oxygen stored in the oxygen storage device 5 out of the aeration disc 9 through the second pipeline 6 to realize low-intensity intermittent aeration, and uniformly disperses micro-oxygen in the anaerobic reactor 24, the alcohol-producing microbial material bin 27 is communicated with the acidification zone of the anaerobic reactor 24 in turn through the alcohol-producing microbial pump 28 and the alcohol-producing microbial valve 29, the extracellular electron transfer microbial material bin 34 is communicated with the hydrolysis zone of the anaerobic reactor 24 in turn through the extracellular electron transfer microbial pump 25 and the extracellular electron transfer microbial valve 26, the acidification zone forms a reflux system with the hydrolysis zone through the reflux pump 30, and the acidification zone is communicated with the methane production zone through the acidification zone material pump 31.

[0065] In order to further illustrate the present application, the schemes of the present application are described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0066] Example 1

[0067] The device used in this example is shown in Figure 1 The specific steps of the method for preparing bio-natural gas are as follows:

[0068] The cow dung and straw are mixed to obtain cow dung and straw organic solid waste, and the solid content rate of the cow dung and straw organic solid waste after pretreatment is 20%, and the C / N ratio is 15:1. The cow dung and straw organic solid waste and anaerobic sludge (the volatile suspended solid content is 25 g / L) in the feed tank 1 are mixed in a volume ratio of 1:10 and placed into the anaerobic reactor 24, and Shewanella liquid with OD600 of 0.8 is added, the volume ratio of the Shewanella liquid to the anaerobic reactor 24 is 1 / 15, and the total volume of the cow dung and straw organic solid waste and the anaerobic sludge accounts for 80% of the volume of the anaerobic reactor 24. The cow dung and straw organic solid waste, the Shewanella liquid and the anaerobic sludge are stirred and mixed by using the first paddle 10, the second paddle 11, the sixth paddle 32, the seventh paddle 33, the third paddle 12, the fourth paddle 13 and the fifth paddle 14. 80wt% of the material in the acidification zone enters the methanogenic zone. The temperature in the anaerobic reactor 24 is maintained at 37℃, the pH value is 7.8, the hydraulic retention time is 21 days, and the electric field strength of the electrode is 25 V / m. Oxygen in the oxygen storage device 5 is intermittently aerated in the anaerobic reactor 24 by the aeration disc 9. The intensity of the intermittent aeration is 0.25 mL / (min·L·day), the cycle is 2 hours, the aeration time is 30 minutes for each cycle, the gas volume accounts for 3% of the volume of the anaerobic reactor 24, and the temperature of the intermittent aeration is 25℃. The fermentation pH value in the acidification zone is 4, the temperature is 32℃, Candida glycerinogenes is added in the acidification zone, and the hydraulic retention time is 0.5 days. The internal temperature of the anaerobic reactor 24 is 32℃, the pH value is 6.8, and the hydraulic retention time is 14 days. The bio-natural gas generated by the anaerobic reactor 24 is stored in the gas collection bin 19, and the digestion products of the cow dung and straw organic solid waste are discharged into the discharge tank 23.

[0069] Example 2

[0070] The device used in this example is shown in Figure 1 The specific steps of the method for preparing bio-natural gas are as follows:

[0071] The residual sludge in different areas of the same city is mixed for pretreatment, and after pretreatment, the solid content is 10%, and the C / N ratio is 15:1. The residual sludge in the feeding tank 1 and the anaerobic sludge (volatile suspended solid content is 25 g / L) are mixed in a volume ratio of 1:10 and placed in the anaerobic reactor 24, and the Shewanella liquid with OD600 of 1.5 is added, and the volume ratio of the Shewanella liquid to the anaerobic reactor 24 is 1 / 30, and the total volume ratio of the residual sludge and the anaerobic sludge to the anaerobic reactor 24 is 80%, and the positive plate 16 and the negative plate 17 are immersed, and the first paddle 10, the second paddle 11, the sixth paddle 32, the seventh paddle 33, the third paddle 12, the fourth paddle 13 and the fifth paddle 14 are used to stir and mix the residual sludge, the Shewanella liquid and the anaerobic sludge, 95wt% of the material in the acidification zone enters the methanogenic zone, the temperature in the anaerobic reactor 24 is maintained at 37℃, the pH value is 7.8, the hydraulic retention time is 14 days, and the electric field strength of the electrode is 25 V / m. The oxygen in the oxygen storage device 5 is intermittently aerated in the anaerobic reactor 24 through the aeration disc 9, the intensity of the intermittent aeration is 1.25 mL / (min·L·day), the cycle is 5 hours, the aeration time is 5 minutes for each cycle, the gas volume accounts for 5% of the volume of the anaerobic reactor 24, and the temperature of the intermittent aeration is 38℃. The fermentation pH value of the acidification zone is 6, the temperature is 37℃, and the hydraulic retention time is 3 days; the temperature in the anaerobic reactor 24 is 37℃, the pH value is 8, and the hydraulic retention time is 28 days. The biological natural gas generated by the anaerobic reactor 24 is stored in the gas collection bin 19, and the digestion products of the residual sludge are discharged into the discharge tank 23.

[0072] Example 3

[0073] The method for preparing biological natural gas in this example is the same as that in Example 1, except that the volume ratio of the Shewanella liquid to the anaerobic reactor 24 is 1 / 20.

[0074] Comparative Example 1

[0075] The method for preparing biological natural gas in this example is the same as that in Example 1, except that there is no electric field strengthening.

[0076] Comparative Example 2

[0077] The method for preparing biological natural gas in this example is the same as that in Example 1, except that there is no intermittent aeration and electric field strengthening.

[0078] Comparative Example 3

[0079] The method for preparing biological natural gas in this example is the same as that in Example 2, except that there is no intermittent aeration and electric field strengthening.

[0080] Comparative Example 4

[0081] The method for preparing biogas of the present comparative example is the same as that of Example 3, except that there is no electric field enhancement.

[0082] Test Example 1

[0083] The biogas production of Examples 1-2 and Comparative Examples 1-2 was tested, and the results showed that the cumulative methane production of Examples 1, Comparative Example 1, and Comparative Example 2 was 6255 mL, 5881 mL, and 4533 mL, respectively, and the cumulative methane production of Examples 2 and Comparative Example 3 was 2451 mL and 1946 mL, respectively. The biogas production of Example 1 was increased by 38% compared to Comparative Example 2, and the biogas production of Comparative Example 1 was increased by 29.75% compared to Comparative Example 2. The biogas production of Example 2 was increased by 26% compared to Comparative Example 3. It can be seen that the biogas production can be increased by intermittent aeration and electric field enhancement, which proves that the present application can efficiently prepare biogas by anaerobic digestion.

[0084] Test Example 2

[0085] The growth density of Shewanella of Example 3 and Comparative Examples 3-4 was tested, and the results proved that at a temperature of 37℃, the growth density of Shewanella under the action of an electric field was increased by 12% after 5 hours compared to that without an electric field.

[0086] From the above examples, it can be seen that the method provided by the present application realizes efficient anaerobic digestion for preparing biogas by using low-intensity intermittent aeration and electric field enhancement, through the combination of backflow and ethanol-type fermentation, which provides a more reasonable and efficient way for engineering application.

[0087] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the present embodiments, which all belong to the protection scope of the present application.

Claims

1. A method for preparing bio-natural gas by coupling ethanol-type fermentation and electric field polarization enhancement with intermittent aeration, characterized in that, The device for preparing bio-natural gas by intermittent aeration coupled with ethanol-type fermentation and electric field polarization strengthening comprises the following steps: oxygen in the oxygen storage device (5) is intermittently aerated in the hydrolysis zone and the acidification zone in the anaerobic reactor (24) through the aeration disc (9), the intensity of the intermittent aeration is 0.25 mL / (min·L·day)~1.25 mL / (min·L·day), the period of the intermittent aeration is 2 hours~5 hours, the aeration time in each period is 5 minutes~30 minutes, the proportion of the aeration gas volume to the volume of the anaerobic reactor (24) is 2%~6%, the temperature of the intermittent aeration is 25 ℃~38 ℃, the fermentation pH value of the acidification zone is 3.5~8, the first raw material, anaerobic sludge and shewanella liquid are injected into the anaerobic reactor (24), the positive electrode plate (16) and the negative electrode plate (17) are immersed, the first paddle (10), the second paddle (11), the sixth paddle (32), the seventh paddle (33), the third paddle (12), the fourth paddle (13) and the fifth paddle (14) are used to stir and mix the first raw material, anaerobic sludge and shewanella liquid, part of the material in the acidification zone enters the methanogenic zone, the remaining material flows back to the hydrolysis zone, the bio-natural gas generated by the anaerobic reactor (24) is introduced into the gas collection warehouse (19) for storage, and the digestion product of the first raw material is discharged into the discharge tank (23); the first raw material is one or more of residual sludge and organic solid waste. The device for preparing bio-natural gas by intermittent aeration coupled with ethanol fermentation and electric field polarization strengthening comprises a feed tank (1), an oxygen storage device (5), an anaerobic reactor (24), a hydrolysis zone, an acidification zone and a methane production zone, a reflux pump (30), an aeration disc (9), a first paddle (10), a second paddle (11), a sixth paddle (32), a seventh paddle (33), a biological agent, a positive electrode plate (16), a negative electrode plate (17), a third paddle (12), a fourth paddle (13), a fifth paddle (14), a gas collection bin (19) and a discharge tank (23).

2. The method of claim 1, wherein, The mass ratio of the part of the material entering the methane production zone to the remaining material refluxing to the hydrolysis zone is 1:1-1:

20.

3. The method of claim 1, wherein, The internal temperature of the anaerobic reactor (24) is 30-45 ℃, the pH value is 6.8-8, and the hydraulic retention time is 14-28 days.

4. The method of claim 1, wherein, The volume ratio of the remaining sludge to the anaerobic sludge is 1:10-1:20, the volume ratio of the organic solid waste to the anaerobic sludge is 1:10-1:30, the total volume of the first raw material and the anaerobic sludge accounts for 50%-90% of the volume of the anaerobic reactor (24), the OD600 of the Shewanella liquid is 0.8-1.5, and the volume ratio of the Shewanella liquid to the anaerobic reactor (24) is 1 / 30-1 / 15.

5. The method of claim 1, wherein, The temperature of the acidification zone is 25-40 ℃.

6. The method of claim 1, wherein, The temperature of the acidification zone is 30-42 ℃, and the hydraulic retention time is 0.5-3 days.

7. The method of claim 1, wherein, The first raw material is pretreated before use, the target solid content of the pretreatment is 5%-20%, and the target C / N ratio is 10:1-20:

1.

8. The method of claim 1, wherein, The anaerobic sludge is discharged from an anaerobic fermentation tank of a sewage treatment plant, and the volatile suspended solid content of the anaerobic sludge is 15-40 g / L.

9. The method of claim 1, wherein, The organic solid waste comprises one or more of municipal sludge, kitchen waste, excrement and crop straw. The organic solid waste comprises one or more of municipal sludge, kitchen waste, excrement and crop straw.

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