Abstract
In a new integrated process, HAlMan process, hydrogen and aluminum are used to produce metallic manganese, aluminum-manganese (AlMn) and ferromanganese (FeMn) alloys with low energy consumption and carbon footprint. In this process, hydrogen gas is used to pre-reduce manganese ores and obtain an intermediate Fe- and MnO-containing pre-reduced ore. The MnO content of this material is further reduced at elevated temperatures by aluminium in a smelting-aluminothermic reduction process. The main product of the process is metallic Mn, or Al-Mn alloy, or ferromanganese, depending on the process feed chemistry. In the present work the experimental results on the hydrogen reduction of a manganese ore are presented and the effect of process conditions such as reduction temperature are evaluated. It is shown that the microstrucural properties of the reduced ore is depending on the process temperature, and moreover the rate of ore reduction is higher at elevated temperatures. In addition, the smelting-aluminothermic reduction step is discussed and it is shown that the process is flexible to produce a variety of metallic products. Mass and energy balances calculations are presented and it is shown that the energy consumption for the process is lower than the state-of-the-art technology of the submerged arc furnace . It is shown that the process is sustainable regarding the valorisation of Al-dross industrial waste. It is shown that ferromanganese production by this process will prevent the emission of about 1.5 t CO2/t metal, with less practical challenges to produce low carbon ferromanganese. The impementation of the HAlMan process in pilot scale through an EU project is presented and it is shown that how the process products can be used to make commercial metal products, and also the process products can be valorized to establish a sustainable process for the future ferroalloy industry.