Patent IE-39828-L (IE)
Title: Copper and sulphur
IPC: G11B15/467
Filed: 1974-09-02
Abstract: 1483227 Recovering iron, copper, other metals and sulphur from sulphides SHERRITT GORDON MINES Ltd and COMINCO Ltd 12 Sept 1974 [28 Sept 1973] 39750/74 Heading C1A [Also in Division C7] A process for treating metal sulphides containing iron and non-ferrous metals including copper for bulk removal of the iron content therefrom and for rendering copper and other non-ferrous metal values amenable for separate recovery comprises the steps of: heating said metal sulphides in a heating zone to an elevated temperature in a substantially non-oxidizing atmosphere (i.e. containing less than 5% of oxygen by volume) for removal of labile sulphur and formation of delabilized sulphides; maintaining said sulphides in said heating zone in an essentially non-oxidized state; contacting said delabilized sulphides in a reduction zone with a reducing gas (e.g. hydrogen) capable of accepting sulphur to convert sulphuric iron in said sulphides to an acid leachable form with formation of hydrogen sulphide, said reducing gas countercurrently contacting said delabilized sulphides, controllably burning combustible products containing H 2 S from the reduction zone and labile sulphur in the heating zone with a substantially stoichiometric amount of oxygen to provide heat for said heating step and to burn said combustible products thereby converting H 2 S and labile sulphur to SO 2 for discharge from the said heating step; subjecting said sulphides to an acid leach in aqueous sulphuric acid containing from 60 to 300 g.p.l. free sulphuric acid at a temperature in the range of 30‹ to 100‹ C. at atmospheric pressure to produce a solution of ferrous sulphate and a solids residue containing copper and iron in a molar ratio of at least 1 : 1 with concurrent evolution of H 2 S gas; discharging said ferrous sulphate and solids residue for subsequent separation, for recovery of non-ferrous metal values and for production of sulphuric acid to recycle to said acid leach: combusting a portion of said H 2 S gas from the acid leach; combining the combusted H 2 S with SO 2 from said heating step for the production of sulphuric acid required in said acid leach ; combining at least a portion of remaining H 2 S from the acid leach with remaining SO 2 from said heating step for the production of elemental sulphur, and controlling said production of sulphuric acid and elemental sulphur to supply acid requirements for the acid leach step and to produce excess sulphur as elemental sulphur. The acid leach may be conducted as a two-stage countercurrent leach and ferrous iron in the filtrate from the first stage is oxidized and hydrolysed with an oxygen bearing gas at an oxygen partial pressure in the range of 50 to 200 p.s.i. and at a temperature in the range of 140‹ to 230‹ C. in the presence of ammonia or ammonium or alkali metal-compounds for the precipitation of jarosite and production of sulphuric acid, said ammonia or ammonium or alkali metal compounds being added to said filtrate in an amount of 50 to 120% of stoichiometric requirements. Procedures are also described for the recovery of S, Zn, Ni, Co, Mo, Cu, Ag and other precious metals.
[GB1483227A]