GB718769A - Purifying and desulfurizing zinc sulfide ores and concentrates - Google Patents

Abstract

Zinc sulphide ore containing volatilizable compounds of metallic impurities such as lead, tin and cadmium is treated with an oxidizing gas insufficient in amount for complete oxidation of the sulphur content while maintaining a temperature sufficient to volatilize the said compounds, and the ore is then transferred to a second zone where it is completely oxidized by blowing through it an oxidizing gas to maintain the bed in a fluidized state. At least the second stage is effected autogenously. As shown, the first stage may be effected in a multiple hearth <PICT:0718769/III/1> furnace 10 and the oxidizing gas may be exit gas from the fluidized bed reactor 11 of the second stage, supplied to the furnace by duct 16 after removal of dust in cyclone 15. The gas may be sufficient to oxidize less than half the sulphur, and the temperature may be above 850 DEG C. The partially oxidized ore is transferred by conduits 25, 29 to the fluidized bed reactor 11 to which air is admitted at 32 to complete the oxidation. The exit gases from both stages containing 14-16 per cent. sulphur dioxide pass through waste heat boilers 18, 37 and electrical precipitator 20, 39. In an alternative embodiment the first stage is also conducted in a fluidized bed reactor.