A Model of Attrition in the Jetting Region of Fluidised Beds

Abstract

Attrition causes material loss and environmental hazards in powder processing. In fluidised beds, the jetting region is the main contributor to attrition. The present paper reviews the recent investigations of the effects of the interaction between single particle properties and jet hydrodynamics. A model of attrition in the jetting region of fluidised beds is presented, based on the impact attrition propensity of single particles and on modelling of the particle flow patterns in the jetting region. The experimental work, carried out for the purpose of evaluation of the model, focused especially on the effects of orifice gas velocity and diameter. The experiments involve measurements of impact attrition of single particles and measurements of particle velocities and solids concentrations in fluidised bed jets. The test materials are fluid cracking catalyst and common salt, both representatives of widely used classes of composite and crystalline materials, respectively. Significant effects of orifice gas velocity and diameter were predicted, which corroborated the experimental data. Hence, the model successfully establishes a link between single particle properties and bulk behaviour in a fluidised jet.