Duplex Process to Produce Ferromanganese and Direct Reduced Iron by Natural Gas

Abstract

The application of natural gas instead of solid carbon to produce ferromanganese is a way forward in sustainable development. Mass and energy balances for an integrated duplex process to produce ferromanganese and direct reduced iron (DRI) by natural gas were studied. The process consists of natural gas injection into molten ferromanganese yielding carbon and hydrogen in which the dissolved carbon into the molten metal bath reduces MnO from a coexisting molten slag that is produced from the smelting of manganese ore. Hydrogen and CO gases reduce solid manganese oxides and iron oxides in the Mn ore to MnO and Fe in the ferromanganese reactor burden. A hot gas with a significant amount of CO and H2 leaves the reactor and is upgraded to a rich CO–H2 gas mixture via methane use in a gas reformer. The obtained highly reducing gas is then used to reduce iron ore in a direct reduction reactor for DRI production, while the DRI reactor process gas is partly looped into the gas reformer and the rest is used in an energy recovery unit for electric power generation for the ferromanganese reactor. It is shown that the presented duplex process is more sustainable than the current commercial ferromanganese production process and its application is accompanied by about 50% less electric energy consumption and about 40% less CO2 emission, excluding the source of electricity.