Hydrogen reduction of lumpy Nchwaning ore in a fixed-bed reactor

The application of hydrogen gas in the pre-reduction of manganese ore may replace fossil carbon consumption and reduce CO₂ emissions in manganese ferroalloy production. The pre-reduction behavior of Nchwaning manganese ore was investigated using a fixed-bed reactor. The reduction rates at different temperatures and temperature programs were investigated, and the particles were sieved after reduction to measure the decrepitation. The reduction rate was measured by adding a tracer gas to the reducing gas and quantifying the off-gas. Samples with different particle-size distributions of the input material were reduced to investigate the effect of particle size on the reduction rate. Chemical analyses and X-ray diffraction were used to characterize the raw and reduced materials. The effects of particle size distribution and temperature on the oxygen removal rate were investigated. Manganese oxides were mostly reduced to MnO in the samples, whereas some iron oxides and carbonates remained. The degree of reduction was improved by using smaller particles and increasing the temperature.