Simulations of a gasliquid stirred reactor including bubble breakage and coalescence were performed. The filtered conservation equations for the liquid phase were discretized using a lattice-Boltzmann scheme. A Lagrangian approach with a bubble parcel concept was used for the dispersed gas phase. Bubble breakage and coalescence were modeled as stochastic events. Additional assumptions for bubble breakup modeling in an EulerLagrange framework were proposed. The action of the reactor components on the liquid flow field was described using an immersed boundary condition. The predicted number-based mean diameter and long-term averaged liquid velocity components agree qualitatively and quantitatively well with experimental data for a laboratory-scale gasliquid stirred reactor with dilute dispersion. Effects of the presence of bubbles, as well as the increase in the gas flow rate, on the hydrodynamics were numerically studied. The modeling technique offers an alternative engineering tool to gain detailed insights into complex industrial-scale gasliquid stirred reactors. (c) 2011 American Institute of Chemical Engineers AIChE J, 2012