While calcining alumina trihydrate in either the rotary or the stationary kilns the flue gases have to be ultimately passed through the Electrostatic Precipitators to capture the dust and recycle it through the calciner or the precipitation circuit. Alternatively it can be redigested to extract the available alumina.
The above alternatives adversely affect either the quality or the cost of the metallurgical grade alumina and it sometimes affects the smelter efficiencies. After various studies and trials Alumina Española has now developed a process with ESP dust as a starting material to produce a highly calcined alumina of fine granulometry and low soda content. This product is in great demand in the ceramic and refractory fields.
The paper describes the process and results of various investigations.