Length to diameter ratio of extrudates in catalyst technology II. Bending strength versus impulsive forces

Abstract

This article describes the reduction of the length to diameter ratio of extrudates, by breakage on collision with a surface. The approach links the rupture force of the extrudate by bending to the impulsive force the extrudate experiences due to collision. The bending or flexural strength of the extrudate is described by the Euler-Bernoulli modulus of rupture. The impulsive force the extrudate experiences is described by Newton's second law. We apply the force balance at the asymptotic length to diameter ratio which is reached after many repeated impacts. This balance yields a dimensionless group as the ratio of the rupture force by bending to the impulsive force by collision. The analysis shows that the asymptotic length to diameter ratio is directly proportional to the square root of this group. This dimensionless group also allows one to define a severity of the collision via the impact velocity and the time of contact of the collision. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2658–2669, 2016.