Influence of H₂–H₂O content on the reduction of acid iron ore pellets in a CO–CO₂–N₂ reducing atmosphere

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>Using hydrogen as a reducing agent for iron production has been the focus of several studies due to its environmental potential. The aim of this work is to study the influence of H₂–H₂O content in the gas phase on the reduction of acid iron ore pellets under simulated blast furnace conditions. Temperature and gas compositions for the experiments were determined with multi-point vertical probes in an industrial blast furnace. The results of the reduction tests show that higher temperatures and H₂ content increase the rate and extent of reduction. For all the gas and temperature combinations, morphological, mineralogical, and microstructure changes were observed using different characterization techniques. Microscopy images reveal that H₂–H₂O, in the gas phase, has a positive influence on reduction, with metallic iron forming at the pellet’s periphery and core at lower temperatures compared to CO–CO₂–N₂ reducing gas. Porosity and surface area changes were determined using a gas pycnometer and the BET method. The results indicate that increasing the reduction temperatures and H₂ content results in greater porosity and a larger surface area. Moreover, carbon deposition did not take place, even at lower temperatures. A rate minimum was detected for pellets reduced at 800°C, probably due to metallic iron formation, hindering the diffusion of reducing gases through the product iron layer.</p></div>