GB697765A - Improvements in smelting of zinciferous ore - Google Patents

Abstract

In a method of smelting zinciferous ore to produce zinc vapour capable of being condensed predominantly to massive zinc metal, a charge of the ore and solid carbonaceous reducing material is introduced into a furnace on to a body of slag which is heated to a temperature not greater than 1450 DEG C by an arc in contact with the slag and struck from an electrode terminating above the slag surface, the charge being composed of oxidized zinc ore containing (a) iron and at least one of the metals copper, silver and gold, (b) an amount of sulphur sufficient to form a matte with substantially all of the said metals and at least a portion of the iron, (c) an amount of carbonaceous reducing agent sufficient to reduce all the zinc oxide. The charge is delivered adjacent to the furnace side walls as a loose mass of discrete particles in such as way as to form a sloping bank terminating at the surface of the slag and out of direct contact with the electrode and arc. The heat necessary for smelting is imparted to the charge by radiation from the arc and through contact of the charge with the slag, the slag resulting from smelting being free from readily reducible oxides, except possibly for a proportion of iron oxide not sulphided by the sulphur constituent, before it comes into contact with the arc. The sulphur content of the charge may be provided by residual sulphur in incompletely roasted sulphidic zinc ore or by addition of extraneous iron sulphide. The amount of reducing agent used may be sufficient not only to reduce the zinc oxide but also to reduce to iron any non-sulphided iron oxide in the charge, whereby a body of molten iron is formed underlying the slag and matte. The zinc vapour evolved together with any cadmium and lead is condensed to massive zinc metal. The cadmium and lead may be separated from the zinc in a fractionating column. Specifications 601,246, 601,247, 620,644, 648,529 and 657,205 are referred to.