Determining of the Influence of Reactor Parameters on the Uniformity of Mixing Substrate Components

One of the issues related to the fermentation of substrates made from biological raw materials in drum-type reactors is the difficulty of ensuring uniform mixing of their components, which adversely affects the quality of the compost produced. Uniform mixing is achieved if the components of the material are fully dispersed at the free surface of the substrate segment. It was established that in order to fully disperse the particles of the substrate by a descending flow, it is necessary that the particles, which last fall from the blade, should reach the contact point of the drum’s shell and the free surface of the substrate. To describe the established conditions, a mathematical model has been built, which links the equation of the boundary of the blockage of substrate particles in the drum and their fall along a parabolic trajectory. The equations are given to determine the kinematic parameters of the mixing process, provided that the substrate particles are dispersed in the transverse and longitude cross-sections of the drum. The result of solving the differential equations is the equation of the linear speed of particle movement on the curved surface of the drum blade at which their full dispersal at the free surface of the substrate segment is achieved. In order to conduct this research, an experimental drum reactor was designed and manufactured. It was experimentally determined at which humidity values of the substrate and the angular velocity of the reactor drum the uniformity of the distribution of components in the substrate reaches maximum values while the resulting compost meets the acting requirements in terms of microbiological indicators. The adequacy of the mathematical model to the experimental data has been confirmed. The reported results are important because knowing the physicochemical properties of the substrate makes it possible to set such parameters of the process and equipment at which the high uniformity of mixing of substrate components is ensured, which affects the compost quality