Deposition of carbon from methane on manganese sources

Abstract

Carbon has been deposited on HCFeMn slag from methane-containing gas with and without CO2, creating C-MnO composites and giving a hydrogen-rich off-gas as a by-product. The maximum deposited amount corresponds to 38 ± 6% of the carbon required for reduction of all manganese in the slag to metallic Mn. This was achieved at 1100 °C with a H2-concentration in the off gas of 76%. Temperature was an important parameter. At 790 °C, no deposited carbon was detected, at temperatures ≥ 1000 °C, deposition increased with temperature. A lower gas-flow leads to more methane decomposition. Experiments with CO2 in the process gas gave less deposited carbon than other experiments. This could be caused by dilution of methane or chemical reactions involving CO2, or a combination. Investigations of fines formation indicate that the deposited carbon sticks well to the HCFeMn-slag, and would not fall off easily during transport and handling. This demonstrates that biogas can potentially be a non-fossil source of carbon in manganese production.