Calculation of flotator`s aerator for separation of ground plastics

Abstract

When creating a new equipment for flotation separation of a mixture of ground secondary plastics, it is necessary to take into account the peculiarities of their properties due to the nature of polymers. So, in comparison with mineral materials, the surface of the ground plastics is less developed, and the particle size is larger. These factors reduce the strength and stability of the “bubble - particle” complex. Turbulent pulsations in the working volume of a flotator for separating a mixture of ground plastics adversely affect the flotation efficiency, since the resulting inertial forces destroy the “bubble - particle” complex. Therefore, the turbulent motion of dispersed phases in the working volume of the apparatus is not desirable. The purpose of this work was to determine the structural and technological parameters of a pneumatic aerator, which will ensure the absence of turbulent motion of bubbles and particles. For this purpose, a method of engineering calculation of the structural and technological parameters of the flotator’s pneumatic aerator was created. The pneumatic aerator’s design was chosen as an Archimedes’ spiral. The engineering calculation method includes the following stages. From the condition of the bubbles’ laminar motion, the maximum allowable relative velocity of the spherical bubble and its diameter are calculated. Knowing the optimal gas content in the column, the relative velocity of the bubbles’ constrained floating up is calculated. The maximum equivalent particle diameter that the bubble can rise into the foam layer is determined. The spiral pitch (and the perforation pitch) is determined. The aerator’s tube length is calculated. The allowable consumption is found. Based on the calculated parameters, a laboratory installation of a column flotator with pneumatic liquid aeration was created. It studied the bubbles’ dispersion formed during the liquid aeration. The values of the calculated and experimental average gas bubble diameter were compared.