METHOD OF RECOVERING WATER-SOLUBLE NON-FERROUS METAL SUL PHATES FROM SULPHURBEARING ORES

摘要

1326225 Non-ferrous metal sulphate recovery CYPRUS MINES CORP 8 Oct 1970 [10 Nov 1969] 48010/70 Heading C1A Soluble non-ferrous metal sulphates are recovered from sulphur-bearing pyrite ores by: providing an aqueous slurry water and finely divided sulphur-bearing pyrite and containing non-ferrous metal sulphides, the slurry containing an amount of sulphate sulphur as ferric sulphate stoichiometrically equivalent to the amount of non-ferrous metals to form sulphates of the non-ferrous metals, heating the slurry and passing gas containing free oxygen therethrough at above atmospheric pressure for a period of time to convert the insoluble non- ferrous metal sulphides into water-soluble sulphates and produce ferric sulphate and enough sulphuric acid to oxidize ferrous sulphite to ferric sulphate and controlling the amount of gas containing free oxygen passing through the slurry to keep both the sulphuric acid and ferric sulphate concentrations in the slurry to below 50 g. per litre the sulphur values content as per cent sulphur of the slurry's solids being at least 6% by weight. The feed material is processed in a slurry mill at from 25 to 50% by weight solids and is then transferred to rubber-lined pre-heat tanks at a temperature of 150‹ to 200‹ F. at atmospheric pressure. The pre-heated slurry is then pumped into rubber lined autoclaves at a pressure of 60 to 120 p.s.i.g. for the oxidative leaching which is carried out at 158‹ to 250‹ F. Air, the most pprolical oxidizing agent, can be supplied to the slurry most effectively by subsurface injection of the air with mechanical dispersion of the gases in the slurry. The air is metered into the heated pressurized slurry at a rate of more than about 100 standard cu. ft. per min. per 1000 cu. ft. of slurry. The off gas must be bled off at approximately the same rate. The leaching which lasts at least 2 hours, is preferably continued until at least 90% of the non-ferrous metal values are converted into soluble values. Finally the slurry is cooled, filtered and the solid residue washed with water.