Conditioning of an oil sand slurry is a critical step in the extraction of bitumen from oil sand ore. To model the conditioning process, a constant-number Monte Carlo algorithm is used to simulate the mean-field kinetics of coalescing bitumen drops and air bubbles. The coalescence rate of drops and bubbles is described by the model of Coulaloglou and Tavlarides (1977). Simulations yield results that are consistent with aerated bitumen drop sizes and conditioning times reported in the literature. The effects of turbulent energy, bitumen concentration, and initial bitumen drop size on the evolution of drop size distributions are investigated.