Valorisation of steelmaking slag by microwave treatment

Abstract

In order to optimise the recovery process of Fe and P from industrial steelmaking slag by microwave irradiation, the recovery ratios of Fe and P from slag-graphite mixtures were investigated. In the reduction of industrial slag by graphite at a fixed microwave processing time of 900 s using a microwave oven, the recovery ratio of Fe increased with increasing carbon equivalent (C-eq.: the mole ratio of carbon/oxygen to reduce Fe2O3 and FeO, yielding CO gas) and reached 0.87 when C-eq. = 51.56. The recovery ratio of P also increased with C-eq. and showed 0.93 at the same condition. From the comparison between the present and previous studies by Kim and Lee employing a synthetic slag, it was found that almost similar results were obtained. From the chemical analysis of the slag and metal after experiments, it was found that the phosphorus distribution ratio (L-p) strongly depended on the total Fe content in the slag, namely, as the FeO content decreased, the L-p value decreased. Discrepancies observed between the present and previous studies are discussed in view of microwave power and thermodynamic analysis.