Abstract

The thermal decomposition of carbonate minerals as pre-treatment before smelting reduces the energy requirement for smelting. It can also make the combustion of fossil fuels for heating unnecassary. Thermal decomposition may become important in reducing greenhouse gas emissions when producing ferromanganese alloys while simultaneously reducing electrical energy demand during smelting. A kinetic reaction rate model for the thermal decomposition of manganese ores is presented, based on published reaction rate kinetics for the decomposition of manganese oxides and calcium carbonate. The model was validated against thermogravimetric data for two carbonaceous manganese ore samples and one ferruginous manganese ore sample. The reaction rate model shows that carbonate minerals in the manganese ores are decomposed at temperatures above 900 degrees C while pyrolusite is decomposed at temperatures from 450 degrees C to 500 degrees C. Mn2O3 decomposes rapidly at 550 degrees C. Braunite decomposition at temperatures below 1000 degrees C was negligible. The presence of organic carbon in the samples led to further reduction of the samples during thermal treatment.