In this study, the gas-liquid two phase flow behavior in the vacuum vessel during the Rheinstahl-Heraeus (RH) refining process was investigated to improve the refining effect. Special attention is paid to investigate double powder injection lances system which is used to improve the refining efficiency during RH refining process. The melt flow behavior, circulation flow rate and mean residence time of the tracers with different powder injection gas flow rates and different configurations of the double powder injection lances are simulated using three dimension numerical model based on Eulerian-Eulerian approach. The results show that, with the increasing gas flow rate of the power injection, the circulating flow rate and the mean residence time of tracer increases. It is also noted that the mean residence time of tracer varies with the different positions of the powder injection lances. It is found that there is an optimum location of the positions of the powder injection lances corresponding to the increasing of the residence time of powder and can improve the refining effect. (C) 2017 Elsevier B.V. All rights reserved.