(303e) Numerical Analysis on Interparticle Adhesion Reduction Mechanism By Surface Modification

Fine particles are used in a wide range of industrial fields, however, handling and processing of fine particles (smaller than ~30 μm) is a generic industrial problem because of their poor flowability. To improve the flowability of fine particles, addition of a flow agent is one of the effective countermeasures. For example, the surface modified particle in which cohesive “host” particle is coated with “guests” flow agents can improve the flowability of host particle. However, many factors such as Van der Waals attraction, Coulomb interaction, etc. affect the flowability, and the detailed mechanism of the flowability improvement by particle surface coating has not been sufficiently clarified. In addition, most studies on the analysis of cohesive force between coated particles focused on the particle static state, not on the dynamic state.

In this study, DEM simulations of coated particles with different coating conditions (number of guest particles on a single host particle, guest and host particle size ratio, different stiffness) were conducted with considering Van der Waals attraction.

Secondly, numerical simulations in which two coated particles collided at constant initial velocity were performed under various coating conditions. In these simulations, cohesive force from JKR theory and Hertzian contact force generated on the contact were calculated. It was found that the cohesive force between the coated particles strongly depended on the contact probability between guest and guest.

Finally, numerical simulation of bulk particles in a rotating drum granulator were conducted and cohesive force and Hertzian contact force between the coated particles were calculated.

It was found that an increase of the contact probability between guest and guest contributed to a decrease in particle adhesion and the improvement of the flowability of the bulk powder.

From these findings, a novel method to estimate the cohesive force between coated particles from the contact probability between guest and guest was proposed with considering the coating conditions such as number of guests, guest and host size ratio and stiffness.