GB475254A - A process for extracting metals from oxidic ores and the like - Google Patents

Abstract

Metals having a lower heat of combustion than iron, such as copper, nickel, and cobalt are <PICT:0475254/III/1> extracted from oxidic ores, including roasted sulphides and silicates, containing also iron or metals having a higher heat of combustion than iron by reducing the ore at temperatures above 400 DEG C. for at least 15 mins. with a reducing gas to which steam is added whereby only the metals having a lower heat of combustion than iron are reduced to the metallic state, then maintaining the so reduced ore in an atmosphere of reducing gas containing carbon monoxide and/or hydrocarbons for at least 15 mins. at a temperature below 400 DEG C., completing cooling of the ore in a non-oxidizing or reducing atmosphere, and, finally bringing it into contact with an extraction electrolyte in the presence of air. In one example, an ore containing 1,4 per cent nickel and 45 per cent Fe2O3 is reduced at 700 DEG C. with say illuminating gas and steam in the proportion of 60 to 74 by volume, maintained at say 300 DEG C. in the presence of the gas for the required time, further cooled, and the nickel extracted with an ammoniacal or acid solvent, which may be 0,5 per cent H2SO4. In a second example, a sulphide ore containing 5,52 per cent copper and 25,46 per cent iron is roasted, reduced at 600 DEG C. with reducing gas and steam in the proportion of 2 to 5 by volume, cooled first to 300 DEG C. and then to room temperature, and the copper extracted with 0,2 N. sulphuric acid. In a third example, an ore containing 86 per cent silica, 4 per cent copper as oxide and sulphide, and 3,86 per cent Fe2O3 is reduced at 650 DEG C. with illuminating gas and steam in the proportion of 70 to 188 by volume, cooled first to 300 DEG C. and then to room temperature, and leached with ammoniacal ammonium carbonate to extract copper. Contrasting results are given when reduction is effected in the absence of steam. The process may be carried out in a rotary furnace 1, ore being supplied at 3, steam through a pipe 5, and reducing gas through a pipe 6. The outlet 10 for the reduced ore consists of a pipe wound \ba3/4\be of a turn round the furnace, so that the ore acts as an air lock. In the zone between 7 and 8 which is heated by burners 14 enclosed in firebrick stoves 15 closed by removable heat insulator plates 16 heating and reduction is effected in the presence of reducing gas and steam, and in the zone between 8 and 9 provided with heat insulation 13 cooling takes place in the presence of reducing gas only. Air may be admitted at 11 to provide internal heating, and heat insulation 17 is provided to bear on the middle roller 2.