The steel converter is one of the major multiphase industrial reactors in which mixing plays an important role. The molten steel in the converter is mixed with the slag by introducing a gas that is blown over the liquid phases (called top blowing), under the liquid phases (bottom blowing) or using top and bottom blowing at the same time (combined blowing). Many chemical reactions that are controlled by the mixing and temperature magnitudes take place inside the converter. All the processes take about 14 min, the first 3 min being for the addition of materials. A 1/10 length scale down of a cold model of a 250-ton capacity industrial converter was employed to carry out the present study. A conductivimetric method was used to carry out the study of the mixing in the reactor. In this study, the mixing in the bath was determined for the three blowing types by conductimetry and the behaviour of the system was modelized. (c) 2005 Elsevier Ltd. All rights reserved.