PRODUCTION OF NICKEL POWDER FROM BASIC NICKEL CARBONATE

1388664 Recovering nickel SHERRITT GORDON MINES Ltd 13 June 1972 [30 June 1971] 27690/72 Heading C7D Ni powder is produced from a nickel and cobalt bearing aqueous ammoniacal (NH 4 ) 2 CO 3 liquor containing Cu and at least one of Zn, Mg, Mn by the following process. Sufficient Co is removed from the liquor to give a molar ratio of Ni : Co of 100-200, whereupon the liquor is heated to drive off NH 3 and CO 2 , leaving a basic carbonates precipitate. This precipitate is repulped with H 2 O to form a slurry which is reduced to Ni powder in a pressure vessel, e.g. an autoclave, with H 2 , which continues until the molar ratio of Ni : Co in the end solution is between 0À5 and 1À0, and the pH is between 2 and 3. The pH can be corrected by additions of NH 3 and sulphate ions. The end solution can then be stripped of Co and the other impurities, but a portion is recycled and used to repulp the slurry prior to reduction. Before reduction, the slurry is adjusted to contain between 40 and 150 g/l of nickel and sulphate ions and NH 3 . The liquor is initially obtained from leading Ni ores, e.g. laterite. The reduction is preferably carried out in the range 80‹-350‹C and 100-500 p.s.i., and a number of reductions can be carried out successively, with periodic removal of Ni powder. Any S present may be oxidized to sulphates if desired prior to reduction.