Investigation of the Phenomena Associated with Iron Ore Reduction by Raw Biomass and Charcoal Volatiles

The volatile matter is the major constituent of the biomass but its potential as a reducing agent for iron oxides is still little explored, especially for carbonized biomass. In this study, the volatile products from raw biomass and charcoal were evaluated concerning their reducing potential of iron ore. Firstly, biomass samples were heated from room temperature up to 1000 ºC with a continuous outlet gas analysis. Following, these experiments were conducted under the same conditions with iron ore placed separately over the biomass bed. The heating of raw biomass and iron ore decreased the yield of CO and H₂, while CO₂ increased. When the charcoal was heated with iron ore, an increase in the yield of CO and CO₂ was observed, whereas the final volume of H₂ decreased. These results were associated with iron ore reduction by different agents and the tar catalytic cracking. From XRD, the magnetite was formed in all iron ore particle sizes and biomass, while wüstite was significantly identified only when the charcoal volatiles reacted with medium and fine ore. Interrupted tests carried out up to 600 ºC showed the ability of the biomass volatiles to pre-reduce the iron ore and deposit carbon on the surface of the ore from the tar catalytic cracking. From the experiments carried out up to 1000 ºC, the morphology of wüstite indicated that hydrogen was the main reducing agent of the iron ore heated with charcoal, while deposited carbon was the reducing agent responsible for the ore morphology that was heated with raw biomass.