The time, t(C), elapsed from bubble contact to the rupture of the liquid film between two bubbles in a quasi two-dimensional column was measured to investigate the effects of the particle diameter on bubble coalescence. The particle diameter ranged from 60 to 150 mu m and the particle volumetric concentration ranged from 0 to 0.50 (50%). The effects of particle diameter on bubble coalescence were evaluated through the experiments and were implemented into a bubble lcoalescence model for a multi-fluid model. Distributions of the gas holdup in a three-dimensional slurry bubble column were also measured using an electrical conductivity probe to obtain experimental data for validation of the coalescence model. The conclusions obtained are as follows: (1) t(C) decreases, in other words, bubble coalescence is enhanced with decreasing the particle diameter, which results in the reduction of the gas holdup of the slurry bubble column, (2) the particle-effect multiplier to t(C) is of great use to take into account the effects of the particle concentration and diameter in multi-fluid simulations of slurry bubble columns, and (3) the interaction between the bubble interfaces and particles in the bubble coalescence process after bubble contact is a local phenomenon and rarely depends on the macroscopic behavior of the interface, which allows us to develop a correlation for particle-induced enhancement of bubble coalescence for three-dimensional bubble columns even with a small experimental setup like a Hele-Shaw cell.