Commercial operations of the Sherritt zinc pressure leach process

Abstract The use of autoclaves for the recovery of metals, using aqueous sulphate systems, has been a focus of Sherritt Inc. for more than 40 years. Following the pioneering commercialization of a pressure hydrometallurgy process in 1954 for nickel production, Sherritt Technologies have continued to develop and assist in the commercial implementation of autoclave processes for other metals, notably gold and zinc. The direct pressure oxidation of zinc sulphide concentrates to produce zinc sulphate solutions which are suitable for conventional recovery of zinc by electrowinning, while oxidizing the sulphide sulphur only as far as its elemental form, has been promoted by Sherritt for more than 30 years. Its commercial realization in 1981 by Cominco Ltd., at Trail, B.C., has been followed by Kidd Creek Division of Falconbridge Limited at Timmins, Ontario, in 1983 and Ruhr-Zink at Datteln, Germany, in 1991. In 1993, the elimination of a zinc roaster operation was achieved by Hudson Bay Mining and Smelting, through the installation of three autoclaves. This paper was prepared jointly by the operators of the pressure leach circuits at four zinc plants and focuses on the operating results and improvements achieved over the years, as well as the principal chemistry of the process.