Determination of the capacity of a rotary type machine for processing medical waste

The article considers the rationale for the required power of rotary-type machines for the processing of medical waste. The problem statement is formulated as follows: to develop an analytical method for calculating the power of rotary devices for waste processing. An analysis of the morphological and structural composition of medical waste made it possible to identify enlarged groups of waste, for the processing of which both cutting with a blade and crushing are used. The calculation procedure was performed for a rotary system consisting of a traverse carrying four horizontal and one U-shaped vertical knives. Due to the peculiarity of the medium being processed (medical waste), it is impossible to use the theoretical and practical experience gained during processing with cutters with chip removal from the surface of the material. The value of the critical cutting force depends on the sharpness of the blade and the breaking contact stress, which can be determined through the reduced breaking contact stress for a group of materials subject to cutting failure. When determining the critical cutting force, it must be taken into account that not the entire length of the blade is involved in the cutting process, since the medical waste loaded into the sterilization chamber has a low bulk density, which changes with time. In the presented technique, the power spent on grinding by cutting is found by integrating along the length of the cutting edge and taking into account the presence of two cutting blades. In addition to the power spent on grinding, in the process of cutting with a blade, there are power losses associated with the movement of the cut material along the bevels of the blade, depending on the thickness of the cut layer, the modulus of elasticity and the Poisson’s ratio of the material being processed. The proposed method takes into account that the grinding of brittle materials that make up medical waste is carried out during processing not by cutting, but by crushing. Since the mixing process is combined with the grinding process during the processing of medical waste, the rotating rotor plays the role of a paddle mixer. In turn, the power expended on mixing depends on the resistance force acting on the elementary area of the blade, as well as on the rotation speed. Thus, in the processing of medical waste, the total power costs are defined as the sum of the power costs for grinding and mixing. The obtained analytical expressions make it possible at the design stage not only to choose the rational drive power, but also to justify the variable rotor speed.