Method of refining fine grained iron oxide material, for example, roasted pyrites

摘要

Copper, zinc and other metallic sulphides are removed from fine grained ferric oxide materials such as roasted pyrites enriched by flotation and containing 1-2 per cent of sulphur by treating at 500-1000 DEG C., e.g. 600-800 DEG C., with chlorine diluted, preferably with air or a non-reducing gas to such a concentration (e.g. 1-10, preferably 2-3 per cent by volume) that copper, zinc and other metals volatilize as chlorides, together with sulphur, whilst the iron remains unaffected by the chlorine. The ferric oxide product may be reduced to magnetite in a subsequent stage, but preferably the reduction is carried out simultaneously by mixing iron sulphide with the materials in an amount such that the sulphur content of the mixture does not exceed 3.5 per cent and in practice usually is between 2.5 and 3.5 per cent, preferably at about 900 DEG C. in an atmosphere comprising CO2, or SO2 formed in the process. The Specification also refers by way of comparison to treating the ferric oxide materials at 900-1100 DEG C. with metal chlorides such as NaCl, MgCl2 and FeCl3 replacing chlorine. Suitable apparatus comprises a rotary furnace having longitudinal shelves whereby intimate contact is promoted.