Ferromanganese production - Process understanding

摘要

The upper part of the ferromanganese furnace is a pre-reduction zone where the higher manganese oxides are reduced to MnO by CO gas formed in the lower part of the furnace. At the same time carbon in the coke is exposed to the energy consuming Boudouard reaction. Attention is focused on the kinetics of these reactions determining the consumption of carbon and electric energy in the ferromanganese process. Pre-reduced manganese ores will go through stages as sintering and softening before reaching the incipient reduction temperature. At this temperature the various original phases in the ore are transformed into a liquid phase and a solid MnO phase. The MnO phase, being present as clouds of solid spheres in the liquid, defines the chemical activity of MnO and also influences the physical properties of the slag. The amount of solid MnO phase decreases as the reduction proceeds until the liquidus composition is reached. The main parameters, which determine the manganese and silicon distribution between metal and slag, are the process temperature and the chemistry of the slag defined by its basicity. Investigations of industrial slags have shown that the MnO content of high basicity slags will be close to its liquidus composition and relatively far from equilibrium with solid carbon and CO-gas.