Reduction Roasting and A cid Pressure Leaching of Calcined Cobalt Concentrates

The nickel refinery of Sherritt Gordon Mines Limited, Fort Saskatchewan, Alberta, increased its cobalt metal powder production to 700,000 pounds per year by designing and installing a roast reduction and aqueous sulphunc acid pressure leaching plant for the treatment of a calcined cobalt and nickel concentrate. The feed material, which is a by-product from a lead-zinc operation, contains about 14 per cent cobalt and 20 per cent nickel. This material, in the form of refractory ferrites was found to resist direct pressure leaching. In order to convert the nickel and cobalt to an acid-soluble form, the calcined concentrate is furnace-reduced in a hydrogen atmosphere prior to pressure leaching onder oxidizing conditions in an aqueous sulphuric acid solution. The cobalt and nickel are extracted, together with small quantities of copper and iron. The bulk of the iron hydrolyzes during leaching and is removed, together with insolubles, by filtration of the final leach slurry. Copper is precipitated from the solution by hydrogen sulphide gas and is removed as copper sulphide in a second filtration step. A pure cobalt and nickel sulphate solution is obtained, and this constitutes an ideal feed for the existing cobalt recovery circuit. The paper gives a summary of the laboratory work which was conducted to develop the process, and elaborates on plant lay-out and operating practice and experience
Keywords: Acid, Ammonia, cobalt, hydrogen sulphide, nickel, sulphuric acid, Calcine, Cobalt, copper, Iron, leaching, Materials, nickel, Reduction
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