Formation of metallic phase by passing gaseous reducing agent through multicomponent oxide melt. Part 1. Theoretical principles

Abstract

A model is proposed for the formation of metallic phase when gaseous reducing agent is bubbled through multicomponent oxide melt. The model includes the following stages: the formation of bubbles when gas is injected in the melt; the reduction of metal at the surface of the bubbles and its concentration in droplet form at the rear of the bubble; motion of the bubble–droplet system in a direction determined by the ratio of the uplift forces on the bubble and the gravitational forces on the droplet; entrainment of the droplets to the surface; and coalescence of the droplets and their descent on reaching a size such that the gravitational forces exceed the sum of the hydrostatic collision forces and the surface tension forces. Equations are presented for estimating the size of the gas bubble and the droplet moving in oxide melt without decrease in size; the direction of motion of the bubble–droplet system; its rate of ascent or descent; and the conditions in which the bubble–droplet system breaks down. The factors responsible for separation of the bubble and the droplet are identified: the surface properties of the oxide melt and the metallic melts and their interphase characteristics. By adjusting these parameters, the formation of metallic phase at the bottom of the vessel may be regulated.