Device and method for preparing biogas and comprehensively utilizing biogas manure through anaerobic fermentation of cotton sophora japonica strips

Abstract

The invention provides a device and a method for preparing biogas and comprehensively utilizing biogas manure through anaerobic fermentation of cotton straws. A vertical plug flow type cotton straw medium-temperature anaerobic digestion (VPF) technology is mainly adopted. Cotton straw is mainly used as a raw material, after being crushed, the cotton straw is arranged and compacted by a bulldozer, the straw is conveyed to a raw material feeding system, and the materials are uniformly mixed by a spiral conveyor, fed into a hydrolysis tank for acidizing treatment and then conveyed to an anaerobic digestion system. The fermentation substrate is degraded by anaerobic microorganisms to be subjected to hydrolysis, acidification, hydrogen production and acetic acid production, hydrogen consumption and acetic acid production, methane production and other processes, organic matter is finally decomposed to generate biogas, the biogas enters a biogas utilization system, and generated biogas residues enter a biogas manure utilization system.

Description

Technical Field The invention belongs to the technical field of comprehensive utilization of renewable resources, and in particular relates to a device and method for producing biogas and comprehensive utilization of biogas fertilizer by anaerobic fermentation of cotton locust seeds. Background Art In recent years, the development of agriculture and animal husbandry in my country has been good, and a large number of cotton locust strips have been produced in the process of cotton locust planting, production and life. Although my country has vigorously promoted the resource utilization of cotton locust strips, there are still many drawbacks in the actual operation process. A large number of cotton locust strips are directly returned to the field, and the comprehensive utilization rate is low, which has an adverse impact on the rural water environment and the living environment. Cotton locust strips contain a large amount of lignin, cellulose and hemicellulose, which are stubborn materials. Their own biodegradation and digestion performance are poor. If they are digested alone without treatment, the digestion cycle will be long, and the digestion effect will be poor, leading to the problem of soil environmental pollution. Therefore, additional measures need to be taken before and during the digestion of cotton locust strips to accelerate the anaerobic digestion and fermentation process and optimize the digestion results. In addition, the direct return of crop straw to the field will affect the seed germination rate and the crop's resistance to lodging, and will also cause pests and diseases. In order to minimize the occurrence of the above problems, the present invention proposes a method of fermenting cotton locust strips under anaerobic conditions by anaerobic fermentation bacteria to produce biomass energy biogas and biogas fertilizer. The biogas produced by anaerobic digestion of cottonwood strips can be used as an important clean biorenewable energy source, with a calorific value of 39,300 KJ·m-3. 1 m3 of biogas containing 60% CH4 is equivalent to 0.6 m3 of natural gas, 1.375 m3 of coal gas, 0.76 kg of raw coal, and 6.4 kWh of electricity. Under standard conditions, 1~2.5 m3 of biogas can be produced by anaerobic microorganisms for each kilogram of volatile solid waste (dry basis). The gas contains about 50%~65% CH4, which can generate 5,400~6,000 kcal·m-3 of thermal energy. Usually, biogas is composed of 45%~85% CH4 and 15%~45% CO2, and the specific composition depends on the biogas production technology and process. In addition to CH4 and CO2, biogas often contains small amounts of hydrogen sulfide, ammonia and nitrogen. Biogas produced by anaerobic digestion is a widely used thermal energy source. Its renewable characteristics can replace traditional fossil energy and can also be used as a chemical raw material to produce related products. With the increasing maturity of anaerobic digestion technology in rural areas, biogas has become an effective substitute for traditional petrochemical energy, and the biogas slurry and biogas residue produced after digestion can be widely used in agricultural production. Anaerobic digestion has simple operating conditions and a wide range of applicable raw materials. It is the most suitable renewable energy technology for promotion in rural areas. Summary of the invention The purpose of the present invention is to solve the shortcomings of the prior art and provide a device and method for anaerobic fermentation of cotton locust seeds to produce biogas and comprehensive utilization of biogas fertilizer. To achieve the above purpose, the present invention adopts the following technical solutions: Step 1, raw material pretreatment system: After the cotton locust strips are crushed, they are compacted by a bulldozer, and the density after compaction reaches more than 0.7t / m3. The main function of the cotton locust strips yard is to store the cotton locust strips and ensure that the cotton locust strips are in an anaerobic environment for pre-acidification reaction. The cotton locust strips are broken into 1 cm fine pieces, then compacted and covered with film for storage. When the cotton locust strips fermentation raw materials are added to the system, they are transported to the feed box by a vehicle, and then transported to the next processing link-the mixed feeding system through the conveyor belt that matches the feed box.

[0001] Step 2, raw material feeding system: the raw material feeding system is mainly composed of a screw pump and a screw conveyor. The main function of the screw conveyor is to mix the cotton locust slivers to form a uniform material, and send it to the hydrolysis tank for acidification treatment. The mixed material moves along the screw conveyor toward the screw pump, and the screw pump transports the mixed material to the anaerobic fermentation tank.

[0002] Step 3, anaerobic digestion system: The anaerobic digestion stage is the key link of the entire material fermentation. Here, the fermentation substrate will be degraded by anaerobic microorganisms, and hydrolysis, acidification, hydrogen production and acetic acid production, hydrogen consumption and acetic acid production, methane production and other processes will occur respectively, and the organic matter will eventually be decomposed to produce biogas. After the material enters the anaerobic reactor, the reactor mixer will achieve uniform distribution of the material and uniform temperature, so that the fermentation substrate is fully in contact with the anaerobic microorganisms. The present invention adopts a batch feeding method, and the CSTR reactor with better effect adopts two-stage fermentation. The biogas generated by the fermentation raw material after anaerobic treatment is temporarily stored in the gas storage container after desulfurization and dehydration.

[0003] Step 4, biogas utilization system: The biogas produced by the anaerobic reactor is a mixed gas containing saturated water vapor. In addition to gas fuel CH4 and inert gas CO2, it also contains H2S and suspended particulate impurities. H2S is not only toxic, but also highly corrosive. Therefore, the newly generated biogas is not suitable for direct use as fuel, and it is also necessary to undergo purification treatments such as gas-water separation and desulfurization. The present invention intends to use biological desulfurization and dry desulfurization to desulfurize the biogas, ensuring that subsequent requirements are met in an economical and environmentally friendly manner, and ultimately H2S can be removed to less than 20 mg / m3. The biological desulfurization method utilizes colorless sulfur bacteria, such as Thiobacillus thiooxidans and Thiobacillus ferrooxidans, to oxidize H2S into elemental sulfur under microaerobic conditions. This desulfurization method has been widely used in biogas desulfurization in Germany and has been adopted in some domestic projects. Its advantages are: no catalyst is required, no chemical sludge needs to be treated, very little biological sludge is generated, low energy consumption, elemental sulfur can be recovered, and removal efficiency is high. The key to this desulfurization technology is how to control the redox reaction process in the desulfurization tower according to the concentration of H2S. Therefore, it is suitable for projects with large scale and high sulfur content in the gas. After biological desulfurization and dehydration, the biogas enters the double membrane gas storage cabinet and is delivered to the user.

[0004] Step 5, biogas fertilizer utilization system: the slurry after anaerobic fermentation in the CSTR reactor is discharged, and the sludge obtained by solid-liquid separation treatment is transported to the solid organic fertilizer production line together with the sludge produced by the production of high-end liquid fertilizer from the biogas slurry to make solid organic fertilizer; 49% of the biogas slurry is refluxed, and the remaining 2 / 3 of the biogas slurry is used to produce high-end liquid fertilizer, and 1 / 3 of the biogas slurry is directly used to produce liquid fertilizer. Biogas fertilizer is the residue of biogas fermentation, which contains comprehensive nutrients and rich organic matter. It is a high-quality organic fertilizer with the effect of improving soil. Biogas slurry is rich in macronutrients such as nitrogen, phosphorus and potassium, and a variety of trace nutrients, and these nutrients are basically in the form of fast-acting nutrients. Therefore, the biogas slurry has strong fast-acting nutritional capacity, can be quickly absorbed by crops, and has a high nutrient availability. It is a multi-dimensional fast-acting composite liquid fertilizer. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a flow chart of a device and method for producing biogas and comprehensive utilization of biogas fertilizer by anaerobic fermentation of cotton locust stalks; 1. Raw material pretreatment system, 2. Raw material feeding system, 3. Anaerobic digestion system, 4. Biogas utilization system, 5. Biogas fertilizer utilization system. DETAILED DESCRIPTION

[0006] Reference Figure 1 The present invention provides a device for anaerobic fermentation of cotton locust strips to produce biogas and comprehensive utilization of biogas fertilizer, including a raw material pretreatment system 1; the raw material pretreatment system 1 is mainly for crushing the cotton locust strips, sorting and compacting them by a bulldozer, and then sending them to a feed box by a conveyor belt, and transporting the cotton locust strips to the next processing link, a desanding tank and a raw material feeding system 2; The raw material feeding system 2 is mainly composed of a screw pump and a screw conveyor. The main function of the screw conveyor is to mix the cotton locust slivers to form a uniform material, and send it into the hydrolysis tank for acidification treatment. The mixed material moves along the screw conveyor toward the screw pump, and the screw pump transports the mixed material to the anaerobic digestion system 3. The preparation method of the present invention is specifically as follows: The anaerobic digestion system 3 is the key link of the whole material fermentation. Here, the fermentation substrate will be degraded by anaerobic microorganisms, and the processes of hydrolysis, acidification, hydrogen production and acetic acid production, hydrogen consumption and acetic acid production, and methanogenesis will occur respectively. The organic matter will eventually be decomposed to produce biogas and enter the biogas utilization system 4, and the generated biogas residue will enter the biogas fertilizer utilization system 5; The biogas utilization system 4 mainly produces a mixed gas containing saturated water vapor from the anaerobic reactor. In addition to the gas fuel CH4 and the inert gas CO2, it also contains H2S and suspended particulate impurities. After desulfurization and purification, it is directly delivered to users; The biogas fertilizer utilization system 5 is a feed liquid produced by the anaerobic digestion system 3. The biogas residue obtained after solid-liquid separation treatment is transported to the solid organic fertilizer production line together with the biogas residue produced by producing high-end liquid fertilizer with biogas liquid to make solid organic fertilizer; 49% of the generated biogas liquid is refluxed, and the remaining 2 / 3 of the biogas liquid is used to produce high-end liquid fertilizer, and 1 / 3 of the biogas liquid is directly used to produce liquid fertilizer.

[0007] The invention adopts a vertical plug-flow cotton locust strip mesophilic anaerobic digestion technology (VPF). Provides a method and device for producing biogas and comprehensive utilization of biogas fertilizer by anaerobic fermentation of cotton locust strips. A new medium-temperature continuous fermentation process is adopted, and the raw materials are biomass such as cotton locust strips. The reactor is characterized in that it is suitable for treating liquid with high suspended solid content or large particles, has a simple structure, and has low operating energy consumption. It has good stability and a high gas production rate.

Claims

1. A device for anaerobic fermentation of cotton locust stalks to produce biogas and comprehensive utilization of biogas fertilizer, comprising a raw material pretreatment system and a raw material feeding system, characterized in that: The raw material pretreatment system mainly crushes the cotton locust slivers, arranges and compacts them with a bulldozer, and then sends them to a feed box by a conveyor belt, and transports the cotton locust slivers to the next processing link, the sand removal tank and the raw material feeding system; The raw material feeding system is mainly composed of a screw pump and a screw conveyor. The main function of the screw conveyor is to mix the cotton locust slivers to form a uniform material, and send it to the hydrolysis tank for acidification treatment. The mixed material moves along the screw conveyor toward the screw pump, and the screw pump transports the mixed material to the anaerobic digestion system.

2. The preparation method of the present invention is as follows: The anaerobic digestion system is the key link of the whole material fermentation. Here, the fermentation substrate will be degraded by anaerobic microorganisms, and the processes of hydrolysis, acidification, hydrogen production and acetic acid production, hydrogen consumption and acetic acid production, and methanogenesis will occur respectively. The organic matter will eventually be decomposed to produce biogas and enter the biogas utilization system 4, and the generated biogas residue will enter the biogas fertilizer utilization system; The biogas utilization system mainly produces a mixed gas containing saturated water vapor from the anaerobic reactor. In addition to the gas fuel CH4 and the inert gas CO2, it also contains H2S and suspended particulate impurities. After desulfurization and purification, it is directly delivered to users; The biogas fertilizer utilization system is a feed liquid produced by the anaerobic digestion system 3. The biogas residue obtained after solid-liquid separation treatment after discharge is transported to the solid organic fertilizer production line together with the biogas residue produced by producing high-end liquid fertilizer with biogas liquid to make solid organic fertilizer; 49% of the generated biogas liquid is refluxed, and the remaining 2 / 3 of the biogas liquid is used to produce high-end liquid fertilizer, and 1 / 3 of the biogas liquid is directly used to produce liquid fertilizer.

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