The hydrodynamics of G - L and G - L - L' reactors with top and bottom blowing is investigated. The reactor is a cold model of a 250 ton industrial converter, the different phases present in the real converter (steel - slag - gases) were simulated employing the triphasic system water - vaseline- air; this system was selected to maintain not only the fluidynamic similarity between both reactors. The behaviour of each phase with respect to the other phases employing different top and bottom gas flow rates was analysed. Thus, the formation of gas bubbles in the bulk of the liquid phase (important in the study of G - L mass transfer and in the mixing field), emulsions and drops (important in L - L' mass transfer) and the streamlines in the reactor were studied to better understand the refining process in the real converter. We also propose flow regime maps with coupling of the different regimes for the three phases present in the reactor, when the gas flow rate is modified.