Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : modelling of decarburisation

In a previous study by the authors (Rout et al.[1]) a dynamic model for the BOF, employing the concept of multi-zone kinetics was developed. In the present work, the kinetics of decarburisation reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburisation such as residence time of metal drops in the emulsion, interfacial area evolution, initial size and the effect of surface active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effect of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data