Study of local powder mixing in a screw reactor: Characterisation of the active layer renewal

Abstract

Screw reactors are widely used gas/solid system in the industry. Understanding the local powder mixing is important, especially at the gas/solid interface. Therefore, a method is proposed to measure the active layer renewal using dyed powder and image processing. The method is repeatable whether the powder flows below or over the shaft (overflow). The filling degree, the Hausner ratio and the pitch length greatly influence the active layer renewal. The method has shown some stagnant zone for short inclination angle (short pitch length to screw diameter ratio). Dimensionless models are proposed to estimate the time needed to reach the active layer renewal using symbolic regression. These models accurately predict our experimental data and can be useful for modelling the hydrodynamics gas/solid screw reactor.