Abstract
To increase the productivity of the AOD/CLU converter process in stainless steelmaking, single slag practice, i.e. simultaneous top slag reduction and desulphurisation, is an attractive alternative. Furthermore, if the combined addition of reductants FeSi and Al is used, desulphurisation can be optimised. A model approach to calculating the additions of FeSi, Al, and fluxes to recover the valuable elements of the slag and to reach the aim sulphur level is presented. The paper also describes an online verification of the model, where model calculations recommended additions to a 75 t AOD converter. Finally, some aspects of model prediction are given. It was found that it is possible to obtain a sulphur content lower than 20 ppm by utilising single slag practice based on a mixed reductant addition and on the observation that the AOD converter appears to be close to thermodynamic equilibrium from a sulphur point of view after the refining operations. However, a successful operation requires strict control with respect to electric arc furnace slag carryover and crude steel silicon content.
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