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In addition to the use of infrared biogas analyzers to monitor the composition of biogas and adjust the operating conditions of biogas plants, pumps are also one of the key devices in such plants, as they directly affect the proper functioning of the plant. The common pumps used in biogas projects include slurry lift pumps, feed pumps, circulation mixing pumps, pumps for lifting biogas sludge and liquid, as well as hot water circulation pumps. The selection of a pump should be based on process requirements such as the flow rate of the fluid to be transported, the head required by the system, the properties of the fluid, the piping layout, and the operating conditions. 1) Flow rate: When selecting a pump, the maximum flow rate should be taken as the basis, while also considering the normal flow rate. In cases where a maximum flow rate is not available, 1.1 times the normal flow rate can generally be used as the maximum flow rate. 2) Head: Generally, the head should be selected with a 5%~10% margin added. 3) Properties of the liquid material: including the physical, chemical, and other properties of the medium in question. Physical properties include temperature, density, viscosity, the diameter of solid particles in the medium, and the gas content; these are relevant to the system’s head, the calculation of the effective net positive suction head, and the selection of the appropriate pump type. Chemical properties mainly refer to the chemical corrosivity and toxicity of the liquid medium, and they serve as an important basis for selecting pump materials and the type of shaft seal to use. 4) Pipeline layout conditions: These refer to various parameters such as the liquid delivery height, distance, direction of flow, the lowest liquid level on the suction side, and the highest liquid level on the discharge side, along with related management specifications. They also include details regarding length, material, fitting specifications, and quantity, all of which are necessary for calculating the system head and verifying the net positive suction head. 5) Operating conditions: This includes a wide range of factors, such as the saturated vapor pressure of the liquid under operation, the pressure on the suction side (absolute), the pressure at the discharge side, the height of the column, the ambient temperature, whether the operation is intermittent or continuous, and whether the pump’s position is fixed or movable, etc. Screw pumps: The screw pumps that are widely used in biogas projects in China include the G-series single-screw pumps and vertical screw pumps. Both types of screw pumps are capable of transporting high-viscosity fluids, media containing hard suspended particles, or media containing fibers. The pump has a compact structure, small size, is easy to maintain, has strong adaptability to different media, provides a steady flow rate, minimal pressure fluctuations, and high self-priming capability. The operating temperature can reach 120°C. In biogas projects, screw pumps are often used as feed pumps, and it is recommended to use them when the total solid concentration of the feed is 5% to 12%. Sludge and slurry pumps: The NL series of sewage and slurry pumps are primarily used in rural areas for pumping river silt, manure, and pulp-based feed. They can also be employed in industries such as municipal services and food processing to transfer thick liquids, dirty fluids, pasty substances, flowing sand, as well as sludge from urban rivers. In biogas projects, it is recommended to use slurry pumps when the total solid concentration of the feed or the liquid being pumped is 4% to 5%. High-efficiency clog-free sewage pump The high-efficiency clog-free sewage pump features significant energy savings, resistance to entanglement, and no clogging, making it suitable for transporting media containing solids and long fibers. The medium temperature should not exceed 60°C, the specific gravity should be between 1.2 and 1.3 kg/m3, and the pH should fall within the range of 5 to 9. In biogas projects, when the total solid concentration of the feed or the liquid being pumped is less than 4%, or when pumping biogas slurry, it is recommended to use high-efficiency, clog-resistant sewage pumps. The tubular high-efficiency clog-free sewage pump can be used for the backflow mixing of the liquid in low-concentration biogas fermentation tanks. Automatic mixing sewage pump: The automatic mixing sewage pump is based on a conventional sewage pump and features an automatic mixing device that rotates along with the motor shaft, generating strong stirring force to turn the sediments in the sewage tank into suspended particles which are then drawn into the pump and discharged. This improves the pump’s ability to prevent clogging and to handle sewage effectively, allowing for simultaneous drainage, water removal, and sediment clearance, thus reducing operating costs. The medium temperature should not exceed 60°C, the specific gravity should be between 1.0 and 1.3 kg/m3, and the pH value should lie within the range of 4 to 10. In biogas projects, it can be used for dredging the bottom of tanks and vessels, as well as for pumping in and out liquid containing a large amount of sediment. Self-priming non-clogging sewage pump: The self-priming non-clogging sewage pump is a type of pump that combines self-priming capabilities with the ability to handle non-clogging conditions. It does not require a foot valve or priming water, just like ordinary self-priming pumps for clean water; at the same time, it can pump liquids containing large particles and long fibers. It is suitable for use in municipal sewage treatment projects, as well as in industries where there are mixed suspended solids, making it an ideal pump for handling such impurities. Cam rotor pumps, high-density solid pumps – When the total solid concentration of the feed in biogas plants exceeds 25%, these pumps are not effective. In Europe, for feeding high-concentration biogas fermentation feedstocks, some plants use cam rotor pumps or high-density solid pumps. The cam rotor pump is a self-priming, valveless, positive-displacement pump; its flow rate is proportional to the speed of rotation, and it can transport various viscous fluids or those containing particles. Its completely symmetrical design allows for reverse operation in any situation; simply by changing the direction of rotation of the rotor, it is possible for a single pump to carry out both feeding and sludge discharge tasks in biogas fermentation tanks. High-density solid pumps are suitable for a wide range of raw materials and can properly transport debris with a diameter of 2/3 that of the pipe ； The concentration of the material being transported is high; the total solids content in the material can reach 25% to 40% ； Long transmission distance, up to 200m ； It can operate without failure for long periods, running continuously for 24 hours; it features a fully enclosed system, has strong adaptability to different materials, and requires minimal maintenance with low wear. (Source: Biogas Circle)