| 摘要 |
1359395 Ni and Co values from ores INTERNATIONAL NICKEL CO OF CANADA Ltd 11 April 1972 [14 April 1971] 16671/72 Heading C1A Ni and Co values are recovered from lateritic ores containing limonitic and silicate fractions by separating the ore into these two fractions and then, (a) reducing the silicate fraction to selectively reduce more Ni and Co than Fe, (b) pressure leaching the Ni and Co from the limonitic fraction with an aqueous solution of H 2 SO 4 at a temperature of 150-300‹ C. to yield a leach solution containing Ni and Co and then (c) mixing the reduced silicate fraction with the leach solution and passing a gascontaining free oxygen through the slurry so formed to provide a pregnant leach solution containing Ni and Co. The slurry may be made acidic either by the leach solution or by the addition of H 2 SO 4 into the slurry. The silicate fraction preferably having a particle size of minus 20 mesh (Tyler series) may be reduced at a temperature of 650-825‹ C. with an atmosphere having a Co/Co 2 volume ratio of 0À25-1. Sulphur may be added during the reduction, e.g. as iron pyrites, pyrrho tite, So 2 or H 2 S providing 0À2-1% S in the fraction. The reduction may be carried out in a rotary kiln, fluidized bed or multi-hearth furnace. The reduced fraction may be cooled without re-oxidation or quenched in the leach solution. In the pressure-leach step the H 2 SO 4 may be formed in situ, e.g. by adding H 2 O and S (elemental or combined with Fe, e.g. 10-20% FeS 2 ) to the limonite and then leaching under an O 2 partial pressure of at least 5 atmospheres. The gas containing free oxygen may be air, O 2 -enriched air or O 2 . Step (c) may be carried out at 35-95‹ C. with a solids concentration of 20-45%, the pregnant solution produced having a pH > 1. Ni and Co values may be recovered from the pregnant solution by treating the solution with a water-insoluble quaternary ammonium thiocyanate or a thiocyanate salt of tertiary, secondary or primary amine in an organic solvent and then recovering Ni values from the aqueous raffinate, e.g. pptn. with H 2 S or as hydroxide or carbonate with a base or soda ash. Alternatively the sulphides of both Ni and Co may be pptd. from the pregnant solution by treatment with H 2 S under elevated pressure. Specification also describes a comparative pressure leach without employing a reduction step. |
