Silver catalyzed IBES process: application to a Spanish copper–zinc sulphide concentrate: Part 3. Selection of the operational parameters for a continuous pilot plant

Abstract

The selection of the operating conditions of a continuous silver catalyzed IBES (Indirect Bioleaching with Effects Separation) process for a chalcopyrite–sphalerite concentrate from Rio Tinto is presented. The data generated from the batch tests have been used to estimate the operating parameters for the continuous system. In order to obtain metal extractions of 94% Zn and 95% Cu, two ferric sulphate leaching stages are necessary: a primary leaching at 70°C with a mean residence time of 8 h divided into five stirred reactors, and a catalytic stage at 70°C and 2.5 mg Ag g −1 concentrate with a mean residence time of 10 h divided into five stirred reactors. The approach is used to develop the complete flowsheet of a pilot plant for the treatment of 50 kg h −1 of this concentrate, including stages of chemical leaching (primary and catalytic), ferrous iron biooxidation, solvent extraction and electrowinning of zinc and copper, elemental sulphur recovery, silver recovery and effluent purification. A preliminary economic evaluation of the process indicates that for an industrial plant of 100,000 t a −1, the direct operating cost would amount to US$141 per ton; the products, copper and zinc, would be worth US$450 per ton and the value of by-products (mainly elemental sulphur and silver) was estimated at US$29 per ton.