Abstract
The paper presents a review of stirring device designs used in biogas plants. The efficiency of a biogas plant depends on many factors, one of which is the agitation of the substrate to increase the efficiency of the biogas plant and provides: release of the biogas produced; agitation of fresh biomass and bacteria in the metatank; preventing the formation or destruction of crusts on the surface and minimizing sludge; providing uniform temperature throughout the bioreactor; and providing uniform distribution of the bacterial population. A well-mixed feedstock can yield up to 50% more biogas. Agitators operate in difficult conditions of aggressive and fire-hazardous environment, contributing to high corrosion of its elements. The design of agitators should not promote sparks or elevated temperatures to avoid explosive situations.Advantages and disadvantages of different types of agitators are discussed, as well as the problems encountered in their operation. Special attention is paid to the promising directions of development of agitators for biogas plants.The design of agitator with float device, which allows mixing biomass throughout the entire volume of the bioreactor module, is proposed. The advantage of this design is the absence of an electric motor and electric cables (which of course increases fire safety), and the mechanical agitator is driven directly by a pneumatic motor operating from compressed air, while the compressor is located outside the bioreactor, and only compressed air supply hoses lead to the reactor.