Carburization of Manganese Oxide Sources by Natural Gas

Abstract

Carburization of Comilog ore, pure MnO powder, and MnO pellet by natural gas was studied by experimental work. XRD, SEM-EDS, and thermogravimetric techniques were used for characterization and reduction behavior analysis. It was found that manganese carbide is formed through direct carburization by methane without methane cracking, and the process was governed by a diffusion-controlled reaction. Even low quantities of some phases in the manganese sources could affect the reduction process adversely. Although increase in temperature intensified the reduction severity, the formation of manganese silicate network at high temperatures hindered the reduction progress of Comilog ore; the best carburization results were achieved at 1100 °C with 24 pct manganese carbide formation. The detrimental effect of aluminates on the gaseous reduction was through lowering the melting temperature of manganese silicates. However, gaseous reduction by methane was adversely affected more by a non-reducible (Mn,Ca)O phase evolved during the pelletizing process on the pore walls rather than by sintering and formation of manganese silicate network. Although neither sintering nor non-reducible phase on the pore walls was observed in the reduction of MnO powder, no complete carburization was occurred. Soot formation and no gas access to the particle surface were recognized as the signs of blocked reduction progress.