Innovative anode coating technology to reduce anode carbon consumption in aluminum electrolysis cells

Abstract

The aluminum reduction reactions in the Hall-Héroult process are responsible for approximately 85% of the net carbon consumption in the electrolysis cell by reaction of oxygen with the anode, producing carbon dioxide. Some of this reacts back with aluminum to produce carbon monoxide and this part is responsible for current efficiency loss. Some other anode reaction mechanisms: anode air oxidation, Boudouard reaction and carbon dust generation are responsible for excess carbon consumption. Studies have shown that to improve cell economics and reduce net carbon consumption in the cell, focus needs to be put on the quality of raw materials, improvement of the anode manufacturing process and finally protecting the anode from air oxidation. Air oxidation of the anode takes place on the upper part of the anode surface. In this paper, EGA is presenting an innovative approach to protect anodes in the cell by using thermal arc spray technology to coat prebaked anodes with aluminum. The EGA technology has shown improved penetration of aluminum in the porous surface area of the anode, which reinforces the adhesion of the aluminum coating layer, while preventing any impact on cell metal purity because the coating is pure aluminum.