Direct reduction of iron oxides based on steam reforming of bio-oil: a highly efficient approach for production of DRI from bio-oil and iron ores

Abstract

Production of direct reduced iron (DRI) was performed by a novel and environmentally friendly approach through a systematic experimental process development and process integration study on bio-oil reforming and iron ores reduction. The Ni–Cu–Zn–Al₂O₃ catalyst is one of most suitable candidates for bio-oil reforming because this non-noble metal catalyst can efficiently reform the bio-oil to H₂ and CO₂ at a lower operating temperature (450–500 °C) with a longer lifetime. The catalytic activities of the Ni–Cu–Zn–Al₂O₃ catalyst for different processes, including the reforming of the oxygenated organic compounds in the bio-oil, the water–gas shift reaction and the decomposition of organic compounds, have been investigated. A hydrogen yield of 87.4% with a carbon conversion of 91.8% was obtained at T = 500 °C and S/C = 6.1. The hydrogen content reached about 94.6 vol% after simple purification by removing CO₂. Furthermore, direct reduction of iron oxides at different reduction temperatures was investigated using on-line rich-hydrogen reducing gases. The metallization for production of DRI from three ore powders (limonite, hematite and magnetite) and hematite pellets ranges from 93 to 97% at 850 °C for 1 h reduction. The reduction process from the oxidized iron to metallic iron and the intermediate phases were investigated via chemical analysis, X-ray diffraction and X-ray fluorescence analyses. The green DRI process with high reduction efficiency and real environmental benefits would, potentially, be a useful route to produce DRI from bio-oil or biomass.