Hydrogen Reduction of Pre-oxidized New Zealand Titanomagnetite Ironsand in a Fluidized Bed Reactor

Hydrogen gas is a potential alternative reducing agent that could substantially decrease CO2 emissions from the ironmaking process in New Zealand (NZ). This paper investigates the reduction of pre-oxidized NZ titanomagnetite ironsand using hydrogen gas in a laboratory scale fluidized bed (FB) reactor, at temperatures ranging from 800 degrees C to 1000 degrees C. The results show that pre-oxidation can accelerate the reduction rate at temperatures <= 900 degrees C compared to unoxidized ironsand, with no sticking of particles observed at any temperature investigated. The initial reduction of titanohematite proceeds swiftly, resulting in very high initial PH2O levels (similar to 0.9 atm), which then plateau through the reaction's middle stages as the reduction of wustite to iron is thermodynamically limited. Multiple sub-micron voids are formed within each particle, which appears to enable rapid diffusion of hydrogen gas to the inner regions of the particle, thus enhancing the reduction rate in the latter stages of the reaction.