PROCESS FOR ROASTING NICKEL-CARRYING LATERITE ORE

1392825 Reduction reacting nickeliferous laterite ore SHERRITT GORDON MINES Ltd 29 March 1972 [3 May 1971] 14897/72 Heading C1A Nickel values, leachable in aqueous solution, are recovered from nickeliferous laterite ore by H 2 reduction roasting the ore in a multiple hearth furnace heated by the partial combustion of fuel in which the H 2 concentration of the gases in the lower half of the reduction zone, supplied by H 2 gas introduced through the bottom of the reduction zone, is >25% (e.g. 30-45%), and the concentration in the gases exiting from the furnace is >3% (e.g. 6-8%), the rate of ore throughput being such that depth of ore on each furnace hearth is 0À05- 0À085 inch for each minute of ore residence time within the furnace; the reduced ore then being cooled (e.g. in a non-oxidizing atmosphere), and recovered, e.g. in aqueous ammoniacal (NH 4 ) 2 CO 3 solution. The ore may be pre-heated prior to reduction in the upper part of the furnace to a temperature of 1250‹ F. at a rate of 35-80‹ F./min. when the ore is a limonite (>40% Fe) or to a temperature of 1350‹ F. at a rate of 35-70‹ F./min. when the ore is a serpentine or garnieritic ore (