Comparative study of phases formed during HCFemn under CO and carbon: Prereduction

During High Carbon Ferromanganese production, the understanding of phases formation is of vital importance since they determine the quality of the overall operations in the furnace. This is also strongly dependent on the chemical composition of the feed. As opposed to other manganese ores that are acidic, South Africa has a basic manganese ore. The formation of phases during HCFeMn from still needs more investigation since it has been found that some theories do not explain what is observed in the South African manganese industry. The current work compared the phases that formed in the prereduction zone when carbon was used as opposed to carbon monoxide being blown into the furnace. Manganese ore from Nchwaning was used in the current work. Coke containing 86 % fixed carbon and a bottle containing CO with 98 % purity were used. The basicity was adjusted to 1 through addition of silica. The ore and the flux were crushed and milled together for better homogenization of the feed. XRD, XRF and SEM were used to characterize the feed and the products. The working temperatures were from 1200oC to 1300oC with 50oC increment. Graphite crucible was used for the experiments. To ensure that products analysed were not from the interaction with the crucible, only samples from the centre of the crucible were considered. Experiments were conducted in an alumina tube furnace for two hours after reaching the aimed temperature. Although carbon monoxide was blown into the furnace at a rate to ensure more reducing conditions that would presumably prevail same than when using carbon, results show similarities in the phase composition but the MnO content differed considerably.