GB715243A - Nickel process - Google Patents

Abstract

Nickel values are extracted from material containing metallic nickel in a process comprising the steps (1) digesting the nickeliferous material without dissolving any appreciable amount of nickel values with an ammonia-ammonium carbonate solution (e.g. 8 per cent. ammonia, 8 per cent. ammonium carbonate) in the ratio by weight of about one part solids to about three parts solution, feeding an oxygen-bearing oxidizing gas into the mixture during the digesting step, continuing the digesting step until any reduced iron present is converted into an insoluble hydroxide, (2) leaching the digested mixture by dispersing it in a substantially larger volume of ammonia-ammonium carbonate solution sufficient to effect the leaching operation, agitating the mixture and feeding an oxygen-bearing oxidizing gas thereinto until at least the major portion of the metallic nickel values dissolve (3) separating the solids from the leach solution and (4) recovering the nickel values from the leach solution. Sulphide ores such as pentlandite may be first roasted under oxidizing conditions commencing at 500 DEG C. and progressively heated to 700-800 DEG C., and the so-formed oxide (or an oxide ore if this is used as the starting material) roasted under reducing conditions at a temperature of 400-600 DEG C. (better 480-525 DEG C. preferably in an atmosphere of hydrogen and with the use of a solid fuel, e.g. coke. If copper is present in sufficient quantity in the ore it may be removed after the oxidation with dilute sulphuric acid, and magnesium sulphate if present should be removed at the same stage by water washing. The flow sheet (not shown) indicates an embodiment in which a copper-containing sulphide ore is used. It is preferred to agitate the mixture mildly in the digesting step so that the solids are held in suspension and their mutual contacts effect a gently abrasive action. In the digesting step a temperature of 20-70 DEG C. is preferred and in the leaching step a two-stage modification of which is described, a superatmospheric temperature and pressure and a solids concentration of 5 per cent. by weight is preferable. It is stated that cobalt if present behaves in the same way as the nickel.ALSO:A starting material containing metallic nickel may be produced from oxidic materials such as oxide ores or oxidized sulphide ores, preferably in admixture with a solid reducing agent, e.g. coke. The reduction is preferably performed in an atmosphere of hydrogen at 400-600 DEG C. (better 480-525 DEG C.). According to the invention such material is used for extraction of nickel as carbonate by means of ammonia-ammonium carbonate solutions (see Group III). Cobalt if present is said to behave in the same way as nickel.