'n Ondersoek na die veredeling van laegraadse mangaanerts met besondere verwysing na die reduseerbaarheid

Abstract

The possibility of upgrading low grade manganese ore from Mamatwan was investigated . The main purpose of the ivestigation involved the removal of lime and silica from the ore (be it before or after the partial reduction of the ore ) , decreasing the iron content, studying the breakdown of the ore during reduction and calcination, as well as the reduction rates at various temperatures. The Mamatwan ore contains 38 per cent manganese , mainly in the form of silicate (braunite) and is representative of a deposit in the Kuruman area which is estimated at several hundreds of millions of tons and is considered the largest manganese ore body in the world . The major gangue constituent is calcite, which is, however, so intergrown into the ore that beneficiation is not readily accomplished. The main purpose of the investigation was intended to be to determine to what extent the ore can be beneficiated by means of heavy media separation and, secondly, whether the ore can be sufficiently upgraded by calcination and/or partial reduction, to be exported as a high grade product. Heavy media separation tests and mineralogical investigations indicate that little success will be obtained in removing lime and silica, as regards both the natural and the reduced ore. As regards the reduction of the ore by hydrogen and carbon monoxide , it was determined tbat the manganese ore breaks down to a much lesser extent than iron ore . The reduction rate for hydrogen was higher than for carbon monoxide. A kinetic investigation in connection with the course of the reduction reactions was impeded by the fact that thermal decomposition of the carbonate structures takes place in the same temperature region as the decomposition and reduction to MnO of manganese silicate. The application of three kinetic laws to the reactions confirmed the opinion that reaction control is probably mixed and not controlled by a single mechanism . Further proof was found by the petrographic analysis .