Decarburisation of liquid Fe-C-S drops using multiple oxidants of O-2, CO2 and H2O

Abstract

The decarburisation of liquid Fe-C-S drops was studied at 1 723 K employing the electromagnetic levitation technique with two different types of gas mixtures, namely, mixtures of O-2 and CO2, and mixtures of O-2 and H2O. For the decarburisation with O-2 and CO2, the rate is limited by the O-2 and CO2 transport in the gas phase with additional resistance arising from the interfacial reaction kinetics of CO2. Sulphur significantly reduces the surface reaction rate with CO2, and the retarding effect appears to be enhanced by existence of the simultaneous oxygen decarburisation. For the simultaneous decarburisation by O-2 and H2O, the basic mechanism of decarburisation is similar to that of O-2 and CO2, but there exists evidence that the homogeneous gas phase flame reaction of O-2 and CO to produce CO2 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 O-2 gas is converted to CO2 and the rate of decarburisation with CO2 is slower to a great extent than that with O-2 The conversion rate is increased as the sulphur content in the melt is increased, and this is attributed to the increase in H2O in the vicinity of the interface with increase in sulphur. Mixed control models are developed and found to adequately explain the observed results.