The geometry and operating conditions in the real converter were simulated using a water model. The mixing in this semi-continuous gas-liquid reactor equipped with top and bottom pneumatic agitation was studied. The relationship between mixing time and agitation power was studied, and a new expression for the agitation power due to top blowing is proposed. The effect of different parameters was also studied: the relative effect of top and bottom agitation, streamlines; as well as the effect of the variation of different variables: liquid volume, surface tension, addition of a second liquid phase. variation of the relative position of the lance with respect to the quiescent bath level and the change in the top and bottom gas flow rate.