Behavior of secondary alumina during heating

Abstract

The losses of weight and F-containing compounds by secondary alumina at various temperatures which can be reached in a bunker of automated feeding by alumina (AFA)—i.e., to 80, 100, 200, 300, and 400°C-are evaluated. The fluorine content in alumina after being held at a specified temperature was determined by the photocolorimetric method. Upon the heating of secondary alumina, noticeable losses of weight and fluorine were observed in it starting from t > 80°C, which is associated with the removal of the latter with physically adsorbed moisture. However, the larger part of fluorine remains in secondary alumina even at t = 400°C, because it consists of solid fluorides and chemisorbed particles. The desorption of fluorine from alumina even at relatively low temperatures (starting from 80°C) means that constructive and technological measures are necessary to decrease them in AFA bunkers.