Improvements in or relating to methods of and apparatus for treating sulphide ores

摘要

Sulphide ores such as zinc sulphide ore are dead roasted by subjecting the ore before it leaves the roasting furnace to a mixture of an oxidizing gas and sulphur dioxide produced by burning sulphur in an abundance of oxygen under conditions such that the temperature of the mixture is substantially above the temperature at which zinc sulphate dissociates, without any other extraneous heating means. A roasting furnace is provided comprising a plurality of superposed hearths over which the ore fed from a hopper 14, Fig. 1, travels progressively from top to bottom and is propelled by air cooled rabbling arms 16 driven by a gear 20. Molten sulphur heated in a steel vessel 22 by a steam coil 24 is led through steam-jacketed pipes 28 to sulphur burners 30. Instead of a gravity feed a gear pump may be used to feed the sulphur to the burners. Air is supplied from a blower 50 to the hollow shaft 18 and arms 16 and a portion of the heated air is passed down a pipe 54, Fig. 3, provided with a flow meter 156, a regulating valve 58 and branch pipes 56 leading to the several burners. Each branch pipe 56 has a gauge 60 and a regulating valve. Each burner is enclosed in a chamber 34, Fig. 4, and includes superposed pans 36 having overflow ports 40, the lowermost pan emptying into a catch basin 44 with an outlet 46. The gases from the burner should preferably contain 10-15 per cent of sulphur dioxide. The gases from the roasting operation may be treated directly for the recovery of sulphuric acid.