Improvements in or relating to processes of treating nickelcopper-bearing material
A process of recovering nickel, copper and other metals from copper-nickel-bearing materials of a sulphide character, particularly mattes, comprises subjecting the material to heat in the presence of a stratifying substance to melt it and to form the mass into copper-bearing "tops" and nickel-bearing "bottoms," separating the "tops" from the "bottoms" and recovering pure metallic nickel and copper therefrom in a dry way. The first smelting takes place with alkaline sulphides such as sodium sulphide or a mixture of salt cake and coke, or calcium sulphide and the product is allowed to settle. Separation of the "tops" and "bottoms" may be effected either in the molten state or after solidification. The smelting may also be carried out in two or more steps, the copper sulphide "tops" of the second step being returned to the first smelting step and the nickel "bottoms" of the first step smelted with addition of fresh flux in the second step. The copper sulphide tops of the first step are blown to blister copper. The crushed nickel sulphide "bottoms" leached, if desired, are roasted to give an impure nickel oxide which is reduced to impure nickel containing small amounts of iron, copper, cobalt, silver, gold and metals of the platinum group. The impure nickel is converted in volatilizers by carbon monoxide at 25-100 DEG C. into nickel carbonyl which is afterwards decomposed at 125-250 DEG C. in contact with metallic nickel to deposit nickel and set free carbon monoxide which is returned to an earlier stage. Cobalt may be recovered from the unconverted residues in the volatilizers by treatment with sulphuric acid. Specification 138,600, [Class 82 (i), Metals, Extracting &c.], is referred to.