Synergetic conversion laws of biomass and iron ore for syngas and direct reduced iron co-production

Abstract

This work describes a system for the co-production of syngas and direct reduced iron (DRI) though the synergetic conversion of biomass and iron ore. Iron ore served as the oxygen carrier and catalyst for biomass gasification, while pine sawdust (biomass) served as the reducing agent for iron ore metallization during this reciprocal conversion process. The effects of conversion temperature, biomass to iron ore ratio and calcination time were investigated. A maximum syngas yield of 72.6% (valid gasification ratio for H and C were 68.8% and 72.7%, respectively) was obtained when biomass was gasified with iron ore (mol ratio C/Fe = 0.8) at 1000 °C for 30 min. DRI with a metallization ratio (MR) of 93.8% was produced concomitantly. The lattice oxygen and catalytic properties of iron ore promoted (i) the conversion of tar and char components into syngas and (ii) the cracking of hydrocarbons into CO and H2. Volatiles derived from biomass enhanced iron ore metallization by accelerating the reduction rate, and bio-char ensured a high MR of the final DRI. The conversion pathway for this was also elucidated. Volatiles and ∼35% of the char reacted with iron ore in the first 10 min to produce all of the H2 in the final syngas and some of the CO. The remaining 65% of the char was gasified in the next 20 min to generate the rest of the CO. The lattice oxygen of iron ore played the key role in early gasification, and the fresh metallic iron played a key role in the subsequent catalysis. This co-conversion approach described herein has potential applications in green fuel gasification or DRI processes.