The sulphur distribution ratio for ladle slags at Ovako Steel AR has been determined by calculating the sulphide capacity using the Royal Institute of Technology (KTH) model and the alumina activity via an empirical expression suggested by Ohta and Suito, and by using the well established theories for sulphur refining. A parameter study was carried out based on plant data from a previous study on desulphurisation. The effect of carbon and aluminium in the steel, the temperature of the steel, and alumina and lime in the slag on the sulphur distribution ratio was investigated. It was shown that the Al_2O_3/CaO ratio had the largest influence on the conditions studied, and that when it increased the sulphur distribution ratio decreased. Based on these results, new plant trials were carried out, in which the alumina content in the slag was changed. The calculated sulphur distribution ratios for these trials were found to be in good agreement with experimentally determined sulphur distribution ratios. It is concluded that the present approach can be used to optimise multicomponent ladle slags with respect to sulphur refining.
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