Predicting failure modes in agglomerates: adhesive or cohesive, from a fundamental analytical model to estimate binder-induced interactions

摘要

Prior experimental work [Boyle et al, 2003] has identified the occurrence of an adhesive failure mechanism in the hydrodynamic dispersion of partially infiltrated silica agglomerates. In this case, the outer infiltrated layer detaches from the agglomerate core at the interface between the wet and dry portions of the agglomerate. In this work, we establish a theoretical basis for the phenomenon of adhesive failure by simulating the behavior of an agglomerate using established analytical models for interaction forces at dry and wet particle-particle contacts. Specifically, this work predicts the locus and hence the mechanism of failure using a DEM approach for solving the relative displacement of portions of the agglomerate as influenced by the various forces acting on within the system. Dispersion of agglomerates is rooted to interactions between two particles, which may be modified due to the presence of interstitial binder. An accurate analytical expression for the total forces of interaction between two spheres, induced by viscous binder has been previously derived [Gopalkrishnan et al, 2002]. In this work, we employ the Rumpf model [Rumpf, 1962] to estimate the tensile strength of dry contacts within the agglomerate. Integrating these in a computer simulation predicts transmission of imposed hydrodynamic forces into an agglomerate and hence the failure thresholds. To depict a partially infiltrated agglomerate, we model the agglomerate as a line of spherical particles with the outer pairs of particles bridged by liquid binder while keeping the inner contacts dry. Monitoring the individual displacements of the spheres with reference to a critical rupture criterion gives an estimate to the locus of failure and hence the mechanism of failure of the agglomerate under consideration. Good conformance between model predictions and experimentally observed results is obtained.