GB656140A - Improvements in the recovery of sulphur as hydrogen sulphide from iron-sulphide bearing material - Google Patents

Abstract

Hydrogen sulphide is recovered from iron sulphide-bearing ore by smelting the ore to form a matte containing ferrous sulphide and a large part or substantially all of the sulphur of the original ore, treating the finely divided solid matte with aqueous sulphuric acid to produce hydrogen sulphide and aqueous ferrous sulphate, collecting the hydrogen sulphide, decomposing the ferrous sulphate from the solution to produce essentially a mixture of sulphur dioxide and trioxide, and utilizing the sulphur dioxide and trioxide to regenerate the sulphuric acid used in treating the matte. The matte may be treated at above 25 DEG C., say 50-70 DEG C., countercurrent in a series of vats by continuously introducing raw matte into the first vat and acid into the last vat of the series to produce a neutral ferrous sulphate solution and a solid residue of sulphides of cobalt, copper, gold, nickel, platinum, silver or zinc. Part of the zinc may be recovered as zinc sulphate at an intermediate stage. The solid ferrous sulphate, recovered by evaporating or cooling the solution, may be dehydrated in a rotary kiln at 400-450 DEG C. in a countercurrent of hot gas passed in contact therewith. The anhydrous product may be heated in a muffle furnace out of contact with air or combustion gases at 480 DEG to 1300 DEG C. by hot combustion gases and the waste gases may be passed to the rotary kiln. The sulphur dioxide in the sulphur dioxide/trioxide mixture from the muffle furnace is oxidized to sulphur trioxide and all the sulphur trioxide is absorbed in concentrated sulphuric acid. Specifications 566,375, 656,141, 656,142, 656,143 and 656,146 are referred to.