GB396933A - Improvements in or relating to processes of solubilizing metal values in oxidized ores containing iron - Google Patents

Abstract

Oxidized ores containing iron are treated to provide "active" ferrous or ferroso-ferric oxide therein, contacted dry with a chlorinating gas such as chlorine, hydrochloric acid, or ferric chloride to form ferrous chloride, and the latter then decomposed, as by chlorine, air, or water vapour, to cause chloridization of other metals present and give a loose permeable product adapted for ready leaching. The chlorinating gas may be replaced by sulphur trioxide with the production of sulphates. The "active" ferrous &c. oxide may be obtained by heating the ore, say to 400-700 DEG C., in the presence of a solid or gaseous carbonaceous combustible reducing agent and cooling the ore under non-oxidizing conditions. Alternatively the "active" oxide may be separately prepared and be mixed with the ore to be treated. Chlorination of the "active" oxide is preferably effected at 150-300 DEG C., though temperatures up to 750 DEG C. may sometimes be used, and the heat of reaction may suffice to realize and maintain the necessary temperature. In treating ores containing refractory sulphides such as nickel sulphide, any ferrous sulphate formed during the process from residual sulphide is converted to chloride by adding a small amount of an alkali or alkaline-earth metal chloride. Waste gases from the chlorination step may be stripped of any ferric chloride by passage under non-oxidizing conditions through dry ore containing "active" oxide. In one group of examples a copper sulphide ore is roasted and then reduced to provide "active" oxide, and thereafter chlorinated; at 225 DEG C. treatment with chlorine or chlorine admixed with air or dry steam gives cupric chloride; at 175 DEG C. some cuprous chloride is formed; whilst at 310 DEG C. considerable formation of cuprous chloride occurs and a sticky unworkable mass results. Treatment of a refractory copper-nickel sulphide ore by roasting and reduction, followed by treatment at 225 DEG C. with chlorine or equal volumes of chlorine and air converts copper and nickel to chlorides. In a further group of examples dealing with copper and nickel ores ferrous chloride is first formed by chlorination at 200-300 DEG C. under non-oxidizing conditions and its decomposition with formation of other metallic chlorides effected as a separate step, as by roasting at 300 DEG C. with a restricted air supply. In such case the chlorinating gas may include a reducing gas, or chlorination be followed by reduction and the chlorination be repeated, temperatures of 300-500 DEG C. being employed. In a further example, a prepared ore containing gold, silver, cobalt, and copper is treated with chlorine at 225 DEG C. to form chlorides of all the metals referred to, but considerable soluble iron remains. The process may be carried out in rotary kilns and may be applied to the purification of iron ores to obtain ferric oxide and to remove therefrom small amounts of impurities such as phosphorus.