Computational investigation of impact attrition of particles

Abstract

The attrition of particles plays an important role in process engineering due to the large effects on the technical processes. In the present work, the possibility of using the Finite Element Method (FEM) for analyzing the attrition of single particles was investigated. Besides the energy based and system specific models, an experimentally verified theoretical model for calculating the attrition of semi-brittle particles was selected, which served as the reference work. Particle-plate models with a regular hexahedral particle geometry and particle edge lengths of 2, 3, 4 and 5mm were created. The target plate was assumed to be rigid, while the particle is defined within a Lagrange reference frame. After the geometries were created, a fine mesh was generated and the grid study has been carried out for each model to get the optimum computational grid. First, the particle attrition of magnesium oxide and sodium chloride was simulated by application of the geometric strain factor and the corresponding deletion of highly distorted elements from the impact region. Finding and verification of the optimum geometric strain factors were based on the experimental results of the reference work. Afterwards, both the effects of the impact velocity and particle size on the particle attrition were examined. In the theoretical model, the fractional mass loss is given as a linear function of the particle size. However, the experimental and simulation results have an almost asymptotic behavior with a trend towards a constant value. This means that the proportionality factor of the theoretical model for the particle size parameter should be further investigated and modified. Furthermore, the attrition of aluminum nitride was modeled by using the empirical material failure model of Johnson–Holmquist 2. Since this material has not been experimentally investigated, the comparison was followed by using the theoretical model results. The results of aluminum nitride attrition as a function of the impact velocity and particle size exhibited the same trend as the experimentally investigated magnesium oxide particle.