GB960698A - Improvements relating to the production of nickel from sulphide ores - Google Patents

Abstract

A Ni or Ni/Cu matte substantially free of Fe is autogenously reduced to metal by blowing a stream of oxygen-rich gas on to the surface of the molten matte which is mechanically agitated, until the sulphur content is less than 4%, the blowing is then continued with hot sulphur-free non-oxidising gas the bath being agitated and the temperature being high enough for reaction to occur between the sulphides and oxygen in the melt. The process is carried out is a rotating top blown converter (Fig. 1), oxygen-rich gas being supplied by a water cooled pipe 15 and the exhaust gases passing into flue 18 via opening 17. Charging is effected through 17 or 16 and the molten metal is tapped either by tilting the furnace or through a taphole 19. Rotation of the furnace effects agitation of the molten charge and the oxygen rich gas is preferably commercially pure oxygen. With relatively pure Ni matte blowing may commence at 850 DEG C. but generally a melt temperature of 1350 DEG C. is obtained before blowing starts. The temperature of the melt may be regulated by diluting the oxygen with air or water and when the sulphur content is less than 4%, the oxygen is replaced by a neutral or slightly reducing hot sulphur free gas such as a mixture of a highly combustible <PICT:0960698/C6-C7/1> gas e.g. natural gas or propane with oxygen. With nickel matte the bath temperature in the final blowing should be 1650-1760 DEG C. and lower if copper is present. The melt is finally deoxidised with graphite, Si or Al. The two stages may be carried out in the same furnace or in different furnaces and the Ni formed contains < 0.05% S. With iron containing mattes the process is modified by first top blowing the molten matte with oxygen and the iron is slagged off with a flux. With Ni/Cu mattes the process produces a Ni/Cu alloy but if Ni free of Cu is required the Cu is extracted from the molten matte prior to blowing by treatment with a mixture of sodium sulphide and sodium chloride. Co is removed from a matte by selective oxidation of the Co in a preliminary oxygen blowing while retaining the sulphur content of the melt above 3%. The Co is then slagged off with a flux such as SiO2. Specifications 960,699 and 960,700 are referred to.