SIMPLIFIED DUPLEX PROCESSING OF NICKEL ORES AND/OR CONCENTRATES FOR THE PRODUCTION OF FERRONICKELS, NICKEL IRONS AND STAINLESS STEELS

摘要

Traditionally, processes to produce ferronickel, nickel iron and stainless steel are excessively multistepped, energy consuming, have refining difficulties and result in the formation of a slag, which cannot be usefully exploited as an aggregate in road material or in concrete. All of these drawbacks contribute to high manufacturing costs. These disadvantages can be overcome by using a direct smelting procedure, followed by a refining step. The source material consists of a nickel bearing ore and/or concentrate, together with an iron source as make up material, which is charged into a bath smelter (50) operating in a reduction/oxidising mode, continuously or intermittently. A reducing slag (57) containing carbonaceous material is formed over molten metal alloy (55), and oxygen (60, 61) is blown through tuyeres (58, 59) into the carbonaceous slag (57) to produce reducing gas and the space above the slag (57) to oxidise any excess carbon monoxide, so that a quiescent slag layer (56) exists between the turbulent slag layer (57) and the molten metal layer (55). Reduction to metal droplets occurs in the upper slag layer (57) and these percolate down through quiescent slag layer (56) to metal layer (55), both of which are siphoned or tapped off, as they fill to capacity. Mineral feed may consist of dried and/or calcined ores and/or concentrates of nickel sulphide and/or nickel laterite with/without iron ore and optionally chromite as a source of chromium. Fluxes such as calcium oxide are added to maintain a basic slag, which is kept fluid at the elevated temperature range of 1700 °C to 2000 °C. The second refining and finishing step is carried out in an argon oxygen decarburiser and/or a converter.