Numerical analysis of residence time for particle impregnation in a rotating drum

Abstract

The impregnation is a key step for handling particles in various chemical engineering processes, which requires uniform distribution of active ingredients over particles. This paper describes the effects of particle residence time in the impregnation area on the inter-particle impregnation variability in a rotating drum. The discrete element method is used to simulate the particle dynamics and the image analysis method is used to model the spray impregnation process. It is observed that the coefficient of inter-particle impregnation variability decreases over time and converges to an asymptotic value, which depends on the particle size and the width of the impregnation area. The dead zone of impregnation near the inclined side walls of the drum is identified, which can be reduced by widening the impregnation area. In addition, the relative standard deviation of residence time for particles in the impregnation area also decrease with the increase of particle size and impregnation area width. With various particle sizes and impregnation areas, it is found that the inter-particle impregnation variability is linearly related to the relative standard deviation of the residence time of the particles in the impregnation area, since the exposure of particles in the spray area controls the impregnation over particles. This study provides fundamental insights for optimizing the particle impregnation process in a rotating drum.