Abstract
The pre-heating and pre-reduction are increasingly considered upstream of the smelting stage in the FeMn industry, both to save energy and limit the CO2 emissions. In the present study, the effect of pre-treatment and ore type was investigated by 11 pilot experiments. The charges were based on four different ore kinds that were either left untreated, pre-heated in air at 700–900 °C in absence of carbon, or pre-reduced in air at 700–900 °C together with coal. During the subsequent smelting stage, widely different temperatures were observed in the furnace: this is of critical importance as the 800 °C isotherm is considered as a turning point in the occurrence of the Boudouard reaction. This reaction has major consequences on the extent of CO-based reduction of manganese ores and on the overall carbon consumption and CO2 emissions. In the present work, temperature field estimates generated from measurements at specific positions inside of the charge were linked to material flow and gas composition using kinetic models developed at lab-scale to predict the pre-reduction of the ores. Predicted and measured O/Mn ratios in the ores are then compared and used to discuss the overall reduction process in the FeMn pilots. The kinetic model was also fitted for the charges for which no kinetic data was available; new kinetic data thus derived from the pilot experiments.