Reductive roasting process for nickel-bearing laterite ores.

摘要

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 (40% Fe) and then the ore maintained within Œ25‹ F. of this temperature in its passage down the furnace. The gas temperature across any hearth may #1450‹ F. Air may be injected through a series of nozzles around the periphery of the furnace into the preheat zone to burn the excess reductants contained in the partially combusted fuel gases and thereby control the per cent H 2 in the exit gases. The H 2 is preferably injected in at two points on opposite sides of the lowermost hearth. The hot combustion gases may be injected into the furnace through a plurality of vertically spaced conduits.