Effect of H₂ on the Distribution of Phosphorus in the Gaseous Reduction of Hematite Ore

Abstract

Global steel production is growing but high-grade ores have been depleted coupled with the decarbonization of the steel industry. The world has to utilize low-grade ores and to use hydrogen in the reduction process to curb CO2 emissions. The phosphorus distribution behavior in iron ore pellets reduced by CO-H-2 gas mixtures was investigated. The total porosity, pore size distribution, and surface area of the pellets were measured using a mercury pressure porosimeter. The reduction was carried out using thermogravimetric analyses (TGA). The reduction rate increased with increasing H-2 content and was highest when 100% H-2 was used. The elemental distribution in the reduced pellet was clarified using electron probe microanalysis (EPMA) and showed that phosphorus was concentrated in slag when 50% CO-50% H-2 was used, increasing the probability of dephosphorization by magnetic separation. The partitioning of phosphorus into the slag might be related to the rate of reduction. This could not be described by one mechanism: the reaction was initially controlled by a chemical reaction and then by diffusion through the product layer in the later stage of the reduction. The activation energies were evaluated to be 20.8-50.2 kJ/mol depending on the gas composition.