SOLID-LIQUID-PHASE CARBOTHERMAL REDUCTION OF NICKEL FROM ORE-COAL BRIQUETTES

Abstract

Currently, there is a difficult situation in the production of ferronickel – the reserves of rich nickel ores end, and well-developed and established classical production schemes do not provide economically efficient processing of poor oxidized nickel ores. It seems promising to use for this raw material new highly efficient and economical processes for the production of primary metal using orecoal briquettes, for example, the ITmk3 process or the smelting process in an oxygen reactor. To study the applicability of the solid-liquid-phase carbothermic reduction process for ore-coal briquettes for poor oxidized nickel ore, the conditions were used most simulating industrial conditions-the discharge of a briquette of industrial size (diameter 24 mm, height 30 – 35 mm, weight 20 – 30 g) in conditions of the furnace hot zone with a temperature of 1500 °С. The briquette surface temperature was measured with the «Pyrovision M9000» thermal imager, and the gas phase analysis was performed using a «Gasochrom-3101» chromatog­ raph. It has been experimentally established that the temperature of the briquette varies according to the same logarithmic law. Under the assumed assumption – formation as a result of reduction in the gas phase of carbon monoxide alone and taking into account a logarithmic increase in the heating rate of the sample, the experimental procedure allows to determine the rate and degree of reduction as a function of time, the total reduction time, compositions of the produced metal and slag, order of the reaction, the activation energy and limiting stage of the process. Experiments with various types of reductant and different briquette compositions at a temperature of 1500 °С have been carried out. It is shown that the process proceeds in a mixed mode with simultaneous control by internal mass transfer and chemical reaction. The optimal conditions for the solid-liquid-phase carbothermic reduction of oxidized nickel ore are determined: the type of reducing agent is semi-coke, the concentration of the reducing agent in the briquette is 5 %; fractions of components are less than 1 mm; process temperature is 1500 °С; the recovery time is 12 minutes. By varying the content of reducing agent in the briquette, it is possible to obtain ferronickel with a nickel concentration of 5 % to 22 %.