Physical modelling of a sidewall-blowing converter

The flow patterns of the chromium converter (CRC) during top and side-wall blowing have been studied using a physical model (1:7). The dynamic similarity between model and real system has been determined by the Froude number and specific mixing energy. This ensures reliability of model studies, although some simplifications have had to made. The model tests demonstrated clearly that mixing was not sufficient to form slag-steel emulsion by the old blowing practice. Furthermore, the mixing time was 27% shorter in the model by the new practice according to conductivity measurements. Calculations and process tests indicated that back-attack diminished and penetration of gas jets to the steel bath increased. The blowing practice of the CRC has been changed, based on the model tests and semi-empirical calculations. The portion and amount of inert gas from the sidewall tuyeres have been increased and oxygen is brought mainly with a lance to liquid steel. In the previous practice, minor penetration of gas jets and trot reactive oxide mass effected an uneven wearing profile of tuyere area. The addition of an inert gas volume rate prevented forming of 'hot spot' areas near uyeres. As a result of practice change, the lining life in the tuyere area has increased by 12%. The processing time has decreased by 13% because of a more effective mixing and increased oxygen flowrate.