Effect of structural parameters of hydrocyclones on the extraction of solid suspension particles by pressurized flotation

Abstract

A mathematical model is developed for the separation of suspensions with a non-Newtonian disperse medium by pressurized flotation in a cylindrical-conical hydrocyclone. The system of motion equations for the solid-phase particles, which takes into account the forces of inertia and Coriolis acceleration, is solved simultaneously with the kinetic equation of the pressurized-flotation process.Pressurized cyclonic flotation, which is carried out in a centrifugal force field, has come into widespread industrial use for the separation of biosynthesis products, the extraction of a finely-disperse solid phase from suspensions, and the cleaning of various process fluids. Cylindrical-conical hydrocyclones are frequently used to separate suspensions and process fluids.Studies of cyclonic flotation [1, 2] have indicated that during pressurized flotation, collision between solid-phase particles and gas molecules is the predominant mechanism responsible for the formation of flotation complexes (particle-bubble), and the efficiency of the pressurized-flotation process, which depends on the number of collisions, is determined by the distance traversed by a solid-phase particle in the liquid disperse medium. Orlov [3] has established that the centrifugal field is a factor that increases the number of collisions between particles and bubbles. Intensification of separation in a hydrocyclone is ensured by a feed of disperse gas to the flow, whereupon the particle-bubble complex can be broken down with a pronounced increase in the circumferential velocity component near the axis of the hydrocyclone [4]. Kutepov et al. [5] propose a procedure for calculation of the separation indicators of a hydrocyclone flotation plant, and also the diameter of the cylindrical section of the vessel for which assigned separation indicators and minimal capital and energy outlays are provided.Many industrially separated heterogeneous liquid systems are non-Newtonian media, the effective viscosity of which depends on the strain rate; this will exert an influence on the hydrodynamics of the vessels. The rheologic state equation of a non-Newtonian fluid, which usually assumes the form of an Ostwald de Veila power law, is applicable to multiphase heterogeneous systems [6].A description of separating processes in a hydrocyclone with a freely forming non-Newtonian liquid-phase surface on the basis of solution of complete equations of rheodynamics is of considerable theoretical and applied interest.