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By combining a volume of fluid (VOF) and discrete phase model (DPM) multiphase flow models, a mathematical model is established to describe the gas and liquid two phase flow in a steelmaking converter with top and bottom combined blowing. The effect of the numbers and location of the bottom tuyeres and top lance height on the gas and liquid two phase flow are investigated and the prediction is validated by the reported actual measured results. The results show that the stirring energy of the combined blowing converter is mainly from buoyancy driven bottom blowing bubbles and the bottom tuyere arrangements have a significant impact on the bubbly plume of combined converter. The mixing efficiency using three bottom tuyeres is higher than the cases with two or four bottom tuyeres and the optimum placement for the bottom tuyeres is away from the centre of the bottom on 0?3D-0?4D (D is the diameter of converter bottom). The mixing time increases with the angle h decreasing, which is between bottom tuyeres and trunnion, and 45u is suggested for the angle h. The top lance height has little influence on the mixing efficiency for the combined blowing converter.

A CFD-PBM (Computational Fluid Dynamic-Population Balance Model) coupled model has been developed to investigate the effects of different number and position of bottom tuyeres and gas flow rate on the bubbly plume flow, inclusion removal and mixing phenomena in gas-stirred ladle. It is found that the dual blowing gives a shorter mixing time and higher inclusion removal ratio in comparison with the center blowing or eccentric blowing with one tuyere. With the increasing of separation angle of two tuyeres, the inclusion removal ratio increases, while mixing time decreases first and then increases. With the increasing of radial position of two tuyeres, the inclusion removal first increases and then decreases, and the mixing time decreases until the radial position exceeds 0.7R from the bottom center, where R is the bottom radius of ladle. It is recommended to use the two tuyeres placed at radial position of 0.6R and the angle of 135 deg in ladle to improve the joint efficiency both the inclusion removal and mixing. With the gas flow rate increasing, the efficiency both mixing and inclusion removal with the optimized tuyeres arrangement increases, however when the gas flow rate exceeds 300 NL/min in 150 ton ladle, the removal ratio and mixing time change little.