Natural hematite oxygen carriers for chemical-looping gasification of biomass

The feasibility of using natural hematite as an oxygen carrier in chemical-looping gasification (CLG) of biomass has been investigated. The experiments were carried out in a thermogravimetric analyzer (TGA) and in a fluidized bed reactor using argon as fluidizing gas. The reactivity of the hematite particles as a function of the reactor temperature, reaction time was discussed. TGA experiments showed that hematite can not release the lattice oxygen in inert atmosphere, however, can provide its lattice oxygen in reducing atmosphere. It was observed that the reactivity of hematite with biomass and pyrolysis intermediate products was enhanced as temperature increased. The CO and H2 concentrations increased slightly, while CO2 and CH4 concentration declined slightly with increasing temperature during biomass gasification. The reactivity of oxygen carriers was gradually decreased as the reactions proceed in the reactor due to depletion of the active oxygen in the hematite particles in a batch test. Analysis of scanning electron microscopy (SEM) shows that the hematite particles exhibited obvious agglomeration when the reaction temperature was above 850?°C. The X-ray diffraction (XRD) experiments showed that the hematite particles occurred a transformation of Fe2O3→FeO providing the oxygen element for biomass gasification reactions. The natural hematite is a promising candidate of oxygen carriers for chemical-looping gasification of biomass.