The present work is carried out to understand the effect of free surface on liquid velocity distribution, dynamics and liquid phase mixing in a shallow basic oxygen furnace (BOF). Three-dimensional/transient Euler-Lagrange (EL) without/with volume-of-fluid (VOF) simulations of dispersed gas-liquid flow in a scaled-down model of the BOF were performed. For lower H/D ratios, EL simulations performed with no-slip and free-slip boundary conditions led to oscillatory plume behavior and higher liquid velocity regions which in turn led to lower mixing time. In contrast, EL1VOF simulations led to reduced meandering motion of bubble plumes and lower liquid velocities resulting in higher mixing times. Interestingly, the mixing time predicted using EL1VOF approach was found to be in a good agreement with the measurements. The results presented in this work show that free surface has a significant effect on dynamics of gas-liquid flow and liquid phase mixing for shallow vessels with H/D <= 0.5. (C) 2017 American Institute of Chemical Engineers