GB856425A - Improvements relating to the recovery of nickel from sulphide ores - Google Patents

Abstract

In a process for extracting nickel and iron, and cobalt if present, as carbonyls from a sulphidic nickel-bearing ore, the preparation of the feed to the volatilizer in which the carbonyls are formed includes concentration of the ore, with, or without, subsequent smelting, to produce a concentrate or matte in which the weight ratio Fe:Ni is less than 10:1, roasting to reduce the S content to 2% or less, and reducing the roasted material with reducing gas to produce a metal-containing product which on treatment with CO yields a mixture of volatilized nickel and iron carbonyls in which the ratio of Fe:Ni is 2:1 to 1:7 and the treatment in the volatilizer is effected under pressure in the presence of active sulphur. The ore is subjected to beneficiation, by froth flotation and magnetic separation, to form a concentrate in which the ratio Cu:Ni is not more than 1:10. The concentrate may be smelted to a matte containing say 10% or more Fe and dead-roasted. The roasted product is reduced at 1300-1600 DEG C. in a controlled atmosphere to convert a maximum proportion of Ni and Co and a controlled proportion of Fe to metal. The controlled atmosphere may be obtained by partial combustion of fuels, e.g. coal, oil, or natural gas, containing CO:CO2 in the volume ratio 3:2 to 1:3, which may be wholly or partially replaced by H2 and H2O in equivalent ratio, or H2 alone. The reduced product is cooled to between 60 and 32 DEG C., and treated with H2S to absorb not more than 1% S. Alternatively, active S may be introduced as in Specification 347,208 before, during, or after reduction, or during volatilization. The product is reacted with CO at between 350 and 1000 p.s.i.g. and 175 and 350 DEG F., and the mixed carbonyls of Fe, Co, and Ni are condensed and separated. Separation may be effected by cooling to crystallise cobalt carbonyl and fractionally distilling and fractionally distilling nickel and iron carbonyls, or by fractionally distilling off nickel and iron carbonyls and isolating cobalt carbonyl from the residue. The carbonyls may be decomposed to metal and the residue from the volatilization may be leached, or smelted to a matte, bessemerised, and refined to isolate copper or precious metals.