At present, China's livestock and poultry manure is mainly used as biogas fermentation raw materials, fertilizers, and cultured earthworms. (a) Rural household biogas technology The technology is to use biogas fermentation device to carry out anaerobic fermentation treatment of livestock manure and human feces and part of organic wastes produced by farmers. The biogas produced is used for cooking and lighting, and biogas residue and biogas slurry are used for agricultural production. Rural household biogas digesters are generally 6 to 10 cubic meters, including biogas fermentation equipment, biogas slurry biogas slurry utilization equipment, and biogas transmission and distribution systems. 1. Technical route (process flow) At present, China's rural household biogas digesters are generally constructed using a bottom-feed hydraulic biogas digester type. On the basis of hydraulic biogas digesters, improvements and developments have been made. Strong reflux biogas digesters, separate biogas digesters (non-hydraulic pressure), and automatic circulation biogas digesters have been developed. The process flow is shown in Figure 2-1, Figure 2-2, Figure 2-3. 2. Main technical links and points (1) Characteristics of various components and equipment The main components of domestic household biogas digesters are the feed inlet, fermentation tank, and discharge chamber. The fermentation tank is the core component and must be airtight, have a certain pool capacity, compressive strength and service life, and be easy to maintain and other requirements. (2) The main performance parameters of the technology 1 When the air pressure in the airtight design tank is 8 kPa or 4 kPa, the 24-hour observation (water pressure method or gas pressure method may be acceptable) is less than 3% for the qualified leakage rate. 2 Gas production rate At present, China's rural biogas digesters are normally fermented at room temperature, and the average daily gas production capacity of the tank volume is 0.2-0.4 cubic meters. 3 Normal gas storage is 50% of daily gas production. 4 Intensity safety factor K ≥ 2.65. 5 normal service life of more than 20 years. 6 Live load 2000 kN/m2. 7 The design value of the foundation bearing capacity is greater than or equal to 50 kPa. 8 The normal working pressure in the working pressure pool is not higher than 8 kPa, and the maximum pressure limit is not more than 12 kPa. If the floating hood is used for gas storage, the working pressure may not exceed 4 kPa. 9 Biogas digester volume This parameter is determined according to the farmer's breeding scale and the maximum daily gas consumption, and is a key factor in the design. Currently, 6 to 10 cubic meters of biogas digesters are used in most rural areas in China. The amount of 10 feedings of biogas digesters should be determined according to different gas storage methods. For hydrostatic methane tanks, it is advisable to design the maximum capacity to be less than 90% of the volume of the main tank. For the methane tanks with floating cover gas and air bag gas storage, the design maximum feeding capacity can be considered as 95% of the main tank volume. (3) Matters needing attention when promoting this technology To give full play to its multiple benefits of energy, ecology, and economy, provide quality energy for farmers, and improve the sanitary environment in the courtyard, we must also pay attention to the latter stage of management and maintenance while ensuring the quality of construction. At the same time, we must guide farmers to develop biogas slurry and biogas residue. Use, promote the use of "four in one" and "pig - marsh - fruit" and other modes to develop circular agriculture. (4) Major construction model According to the geographical, climate and environmental conditions and the characteristics of agricultural development in various regions, there are “four in one†energy ecological models and technologies in the north, “Pig-biogas-fruit†energy eco-models and technologies in the north, and “five matching†energy ecological models in the northwest. Technology and so on. In the actual promotion, the “One Pool, Three Reforms†was implemented, ie, while the household biogas digesters were being constructed, they were planned in a unified way, and the biogas digesters, livestock houses, and toilets were connected, rebuilt, or newly constructed. (II) Large and medium-sized biogas engineering technology in intensive livestock and poultry farms Large and medium-sized biogas engineering technology in livestock and poultry farms is the main purpose of pollution control of livestock manure wastewater in large-scale livestock and poultry farms. Anaerobic digestion of livestock manure is the main technical link. It integrates sewage treatment, biogas production and resource utilization. Use as one of the system engineering technology. As livestock and poultry farm biogas technology integrates environmental protection, energy, and resource reuse, it is also known as livestock and poultry breeding energy environment engineering technology. 1. The technical route (process flow) is shown in Figure 2-4, Figure 2-5, and Figure 2-6. 2. Main technical links and points (1) Characteristics of various components and equipment 1 Pre-treatment devices include pre-treatment tanks, conditioning tanks, humidification devices, and solid-liquid separation equipment and equipment. These devices and equipments play an important role in ensuring the stable operation of the biogas engineering system. 2 Anaerobic digesters include anaerobic biological filter (AF), upflow sludge fixed bed (UASB) and other digestion devices. 3 Biogas collection, storage, and distribution systems include gas-liquid separation, purification and desulfurization, gas storage and biogas combustion and other equipment. 4 Biogas slurry post-treatment equipment includes fermentation liquid sedimentation tanks, aerobic anaerobic treatment facilities, and waste liquid discharge facilities, which are indispensable components for ensuring compliance with discharge standards. 5 The biogas residue treatment system includes the drying of solid residues after fermentation, solid-liquid separation, and the manufacture of granular fertilizers and feeds. It is the main technical measure to improve the economics of the entire project and to realize the comprehensive utilization of resources. (2) Matters needing attention when promoting this technology First, the design should be in line with the local master plan, closely integrated with the local objective reality, and correctly handle the relationship between concentration and dispersion, processing and utilization, and the near-term and long-term future. Targets should be reduced, harmless, and resource-resourced. Advanced technologies and processes should be applied to implement clean production and reduce the amount of waste discharged from the source. Second, raw materials should have sufficient and stable sources, and it is forbidden to mix in other toxic and harmful sewage or sludge. Third, it must be designed scientifically to save investment and reduce operating costs. The design shall be undertaken by a unit with corresponding design qualifications. Fourth, the operation management personnel must be familiar with the operation requirements and technical specifications of the biogas engineering process, facilities, and equipment, and should hold a professional qualification certificate (biogas production); the operators must understand the treatment process of this project and be familiar with the facilities and equipment of this post. Operating requirements and technical indicators. Fifth, the regulations for the operation, maintenance and safety of the project should comply with the existing standards. A routine maintenance, regular maintenance and overhaul three-level maintenance system should be established. Sixth, safety precautions must be taken in accordance with the requirements for fire protection and explosion protection to ensure safety. (3) The main technology (equipment). At present, the main process types are the first-generation anaerobic reactors: AC (full-blended contact anaerobic); the second-generation anaerobic reactors: AF (anaerobic biological filter bed), UASB (upflow sludge fixed bed), USR (upflow solids reactor), UBF (upflow anaerobic composite bed), anaerobic mixing reactor, anaerobic baffled reactor, etc.; 3rd generation anaerobic reactor: EGSB (granular sludge expanded bed) ), IC (internal circulation anaerobic reactor) and so on. (three) manure stack processing and production of organic fertilizer technology The manure stack processing and production of organic fertilizer technology is to regulate the ratio of carbon to nitrogen in the manure of livestock and poultry and manually control the conditions of moisture, temperature, pH, etc., and use microbial fermentation to treat livestock manure to produce organic fertilizer. During the stacking process, the organic matter is transformed from an unstable state into a stable humic substance with the process of organic decomposition and humus formation. Due to the decomposition and conversion of volatile components such as carbon, the raw materials for stacking have undergone significant changes in volume and weight, and the weight and volume have decreased by about 1/2. 1. The technical route (process flow) is shown in Figure 2-7. 2. Main technical links and points (1) Major equipment The livestock manure stacking and fertilizer production processes require the use of a large number of general equipment and non-standard equipment. 1 The pre-treatment equipment consists mainly of ground scales, stockyards, unloading stations and feed gates, storage ponds or ponds, loading machines and transport machinery. 2 The composting equipment mainly includes turning machines and fermentation tanks, multi-section shaft furnaces, barrel fermentation tanks, and screw-agitated fermentation tanks. 3 The granulation equipment includes drum granulator, rotary granulator, extrusion granulator and compression granulator. 4 Screening and packaging equipment include fixed screens, cylindrical screens, vibrating screens, etc. (2) Main technical parameters 1C/N (carbon-nitrogen ratio) The carbon-nitrogen balance of the compost mixture is a key factor for optimal microbial biological activity. The C/N of the compost mixture should be maintained at (25-35):1. 2 Humidity aerobic compost should generally be maintained at 40% to 70%. 3pH The pH varies with the type of compost mixture and the stage of the composting process. Normally it does not need to be adjusted. If adjustments are required, they can be adjusted by adding alkali or acidic substances to the mixture before the degradation of the compost begins. 4 other design parameters The rectangular fermenter does not need to be regularly turned to keep the temperature below 75°C. Turnover frequency is 2-10 days/time. The width and depth of rectangular strips are limited only by turning equipment. Bars are generally 1.2 to 1.8 meters deep and 1.8 to 3.0 meters wide. The heap height is usually 2.5 to 4.5 meters and the width is usually 2 times the depth value. (3) Matters needing attention when promoting this technology 1 Composting time Composting time varies with C/N, humidity, weather conditions, type of composting operation management, and wastes and additives. Well-run, well-managed, composted compost is generally composted for 14 to 30 days in summer. Complex composting in containers takes only 7 days to complete. 2 temperature should pay attention to the monitoring of the temperature of the compost. The temperature of the compost should exceed 55°C so that it will not only be beneficial to microbial fermentation but also to kill pathogens. 3 Humidity CAUTION Monitor the humidity of the compost mixture periodically. Both too high and too low will reduce or stop the rate of composting. 4 Odor Odor is a good indicator of the stage of composting. A rotten smell can mean that the compost turns from aerobic to anaerobic. (IV) Other Utilization Technologies 1. Livestock and poultry manure is used directly in the field. The direct return of livestock manure to fertilizer is a traditional, economical and effective method of manure disposal. It can fully utilize the nutrient substances in the manure and improve the nutrient content in the soil without exhaust pollution. Improve soil fertility and increase crop yields. However, if the amount of manure applied to soil exceeds its carrying capacity, it will not only affect the normal growth of the plant, resulting in a decrease in yield, but also pollute the environment. 2. Livestock and poultry manure resources recycling technology. Utilizing fermented livestock and poultry manure, earthworms can be quickly decomposed and converted into nutrients that can be easily utilized by themselves or other organisms through the digestive system of pupae, under the action of proteases, lipases, cellulase, and amylase. This technology can produce both good animal protein and fertile bio-organic fertilizers. 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