AOD/CLU process modelling: optimum mixed reductants addition

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 combin ed addition of reductants FeSi and Al is used, desulphurisation can be opti mised. A model approach to calculating the additions of FeSi, Al, and fluxe s 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 conver ter. 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 observa tion that the AOD converter appears to be close to thermodynamic equilibriu m from a sulphur point of view after the refining operations. However, a su ccessful operation requires strict control with respect to electric are fur nace slag carryover and crude steel silicon content.