Calculation of collision efficiency factor by trajectory analysis in dissolved air flotation

Abstract

In order to calculate the collision efficiency factor of bubble and particle (α _bp), trajectory analysis is performed. The formulation and equations are adopted from the trajectory analysis developed to calculate the collision efficiency factor in differential sedimentation (α _os). The most recently developed hydrodynamic equation and interparticle force based on DLVO theory are included. The effect of each governing parameter is calculated. Although the inclusion of electric repulsion as a function of surface charge of particle and ionic strength of suspension is possible, only hydrodynamic and attraction forces are considered in this research to simulate the case when the bubble-particle system is destabilized. The collision efficiency factor of bubble and particle (α _bp) is found to be functions of bubble diameter, particle diameter, Hamaker constant, and particle density. The result ofα _bp shows similar trend with publishedα _Ds and experimental results.α _bp increases as bubble size decreases at constant size ratio, as particle size ratio approaches unity and as Hamaker constant increases. There is only a slight effect of particle density onα _bp.