The reduction of iron oxides by volatiles in a RHF process

For reduction of iron oxides by volatiles from coal, the major reductant was found to be H₂ which can affect the overall reduction of iron oxides. To determine the possibility of reduction by volatiles, a layer of iron oxide powders was spread on top of a high volatile containing bituminous coal and heated inside a reactor using infra-red radiation. By separating the individual reactions involved for an iron oxide/coal mixture where a complex set of reactions occur simultaneously, the sole effect of volatile reduction could be determined. Depending upon the reaction times, volatiles from coals caused significant reduction of iron oxide powders placed above the devolatizing coals. To simulate a possible multi-layer RHF process, volatile reduction of multi-layer Fe₂O₃/coal composite pellets was considered. The degree of reduction for iron oxide pellets at the top layer from volatiles evolving from the bottom layers of a three-layer pellet geometry was found to be about 15%. From the morphological observations and the kinetic calculations, volatile reduction appears to be controlled by a mixed-controlled mechanism of bulk gas mass transfer and the limited-mixed control reduction kinetics.