Decarburisation of liquid Fe-C-S drops using multiple oxidants of 02, C02 and H20

Abstract

The decarburisation of liquid Fe-C-S drops was studied at 1 723 K employing the electromagnetic lévitation technique with two different types of gas mixtures, namely, mixtures of O2 and C2, and mixtures of 2 and H20. For the decarburisation with O2 and C2, the rate is limited by the 2 and C2 transport in the gas phase with additional resistance arising from the interfacial reaction kinetics of C2. Sulphur significantly reduces the surface reaction rate with C2, and the retarding effect appears to be enhanced by existence of the simultaneous oxygen decarburisation. For the simultaneous decarburisation by O2 and H20, the basic mechanism of decarburisation is similar to that of 2 and C2, but there exists evidence that the homogeneous gas phase flame reaction of 2 and CO to produce C2 occurs in the vicinity of the interface. This results in a much lower rate of decarburisation than the expected one, since portion of the incoming 2 gas is converted to C2 and the rate of decarburisation with C2 is slower to a great extent than that with O2. The conversion rate is increased as the sulphur content in the melt is increased, and this is attributed to the increase in H20 in the vicinity of the interface with increase in sulphur. Mixed control models are developed and found to adequately explain the observed results. © 1999 ISIJ.