8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Substantial deposits of titanomagnetite ironsand are found throughout the west coast of the North Island of New Zealand (NZ). This titaniferous iron ore contains approximately 8% TiO2 equivalent, which prevents its use as a feedstock concentrate for conventional blast furnace (BF) processes. However, at present ~1.5 Mt pa is utilized in the rotary-kiln production of direct reduced iron (DRI), and a further > 1 Mt is exported for blending as a minority component within BF sinters. However, the increased focus on reduced CO2 emissions is now promoting renewed interest in alternatives to existing carbo-thermic DRI approaches. Here, we report initial investigative work into the production of DRI from NZ ironsand via hydrogen-reduction in an experimental fluidized bed reactor. NZ ironsand exhibits a naturally-occurring particle size distribution in the range 100-250 µm, making it potentially well-suited to fluidized bed processing. Fluidized bed processing provides potential advantage for direct use of ironsand powder without pre-treatment of material such as pelletizing and sintering. In the current project, we have determined fluidization parameters for ironsand powder through theoretical calculation and experimental validation. We have then designed and commissioned a small-scale experimental reactor that enables fluidized bed reduction in Ar-H2 atmospheres at up to 1050 °C. This experimental reactor includes a novel in-situ sampling system which utilizes a micro-cyclone to extract small amount of samples (< 5 g) of partially reduced material at specific time intervals during a batch reduction. We present initial results from this reactor, and compare metallization degree measurements of partially reduced ironsand powder using both quantitive X-ray diffraction (q-XRD) and titration techniques respectively. We show that q-XRD is a useful high-throughput approach to characterize reduction kinetics in this experiment. Finally, we discuss the onset of ‘sticking’ phenomena within this fluidized bed system, and the limitations this imposes on high-temperature rapid reduction of NZ ironsand in a fluidized bed reactor.