Based on the drag force of two spheres in contact and the probability density of size ratios of particles which constitute an aggregate particle, the population balance equation describing the change of the particle-size distribution due to the disruption of aggregate particles is derived and the numerical solutions of this equation are obtained.
Experiments were carried out with fly ash particles dispersed in air stream through an orifice at various flow rates. The measured size distributions can be represented by the numerical solutions of the population balance equation.