JET ATTRITION OF CATALYST PARTICLES IN GAS-FLUIDIZED BEDS

The mechanism of jet attrition of catalyst particles in gas fluidized beds has been investigated both theoretically and experimentally for two different catalysts. A model is suggested which considers the efficiency of the comminution process by relating the surface energy created by this comminution process to the kinetic energy which has been spent to produce this surface area. The attrition rate, defined as the mass of attrited fines per unit time produced by a single jet, is found to be proportional to rho0d(o)2u0(3) (rho0, jet gas density; d(o), orifice diameter; u0, jet exit velocity). The attrition rate depends on whether the jet is issuing into a pre-fluidized bed or otherwise into a non-aerated bed. The attrition effect of an upward jet is equal to that of a horizontal jet, whereas the attrition effect of a downward jet is significantly higher. The model is able to predict the attrition effect of a multihole gas distributor on the basis of a single jet attrition measurement.