Electrolyte impurity control at the Chinchpada refinery of Sterlite Industries (India) Limited

摘要

Sterlite Industries operates a copper refinery at Silvassa, India using the ISA process with a capacity of 180,000 t/y. The anodes are received from its custom smelter at Tuticorin, Southern India. The impurities in the anodes vary substantially, and this is especially true of bismuth, which has varied from 10 ppm to 150 ppm over the last few years. This paper discusses the various operating practices and technologies adopted at the Sterlite copper refinery for electrolyte impurity management. The main emphasis is given to controlling bismuth, antimony, nickel and iron in the electrolyte. The paper discusses the control of bismuth and antimony in electrolyte by progressively increasing the arsenic concentration. It was observed that at a critical arsenic level in the electrolyte, bismuth and antimony report to the anode slime. Considerable importance is given to controlling the nickel and iron concentrations in the electrolyte by adopting a modern low cost acid purification system. This novel method, coupled with an effluent treatment plant, ensures the recovery of sulfuric acid, removal of nickel and iron from the electrolyte, production of a disposable nickel sludge besides ensuring zero discharge to the environment. With a more suitable impurity management system, Sterlite is able to achieve and sustain a cathode quality superior to the ASTM standard.