Analysis of methods and means for mixing the substrate in the methane kit of biogas plants

Abstract

The paper analyzes the existing methods and means for mixing the substrate in the digesters of bio-gas plants (BSU). In the latter, it is necessary to use high-quality mixers, since they maintain the homogeneity of the substrate, evenly distribute biomass and heat, and prevent the formation of bottom sediments and a floating layer. The necessary mixing intervals are determined individu-ally for each biogas plant by sampling. After starting, it is better to mix somewhat more often than in normal mode and slow down after it is already possible to distinguish the formation of a floating crust. Bacteria grow in colonies and form lumps. Quick mixing breaks them up and prevents bacteria from developing, their slow work is optimal. Therefore, we substantiated the use of various mixing methods in digesters, advantages and disadvantages in the process of their operation, operation and construction fea-tures. The requirements for mechanical mixers are consid-ered. The traditional mixing technique, first of all, high-speed propeller submersible mixers, was borrowed from the technique for working with manure, which was adapted for biogas technology. Due to the increase in the use of renewable raw materials, substrates with a high dry matter content are used, which negatively affect the flowing prop-erties of the substrates, therefore it is necessary to reduce the number of revolutions of the blades. Since in this case the mixing will not proceed well enough, it is necessary to increase the diameter of the agitator blades or their number. Hydraulic mixing has the advantage that the mechanical blocks necessary for mixing are located outside the reactor and, as a result, their wear is negligible and maintenance is less expensive. The use of hydraulic and pneumatic sys-tems is limited only by substrates of low viscosity with a slight tendency to foam, floating crust and sediment.