A theoretical model for the contact phenomenon of coke particle accompanied by the compressive breakage at the contact plane

This study considers the mechanism of the breakage contact of coke particles. A theoretical model has been developed standing on the hypotheses as follows: (1) The breakage mode of coke particle is the surface compressive breakage. (2) The Hertzian stress distribution is induced on the contact plane of particle surface but the region with the Hertzian stress over than the compressive strength makes contact breakage and the stress on this region reduces to the value equal to the compressive strength. (3) The energy to be consumed during breakage contact is equal to the energy to be consumed for producing breakage fragments (fines) and is in proportion to the mass of fines. On the basis of these hypotheses, the relationship between contact force and contact displacement was formulated and additionally, the breakage volume, the consumed energy, the restitution coefficient or the friction coefficient at normal, rotating and slipping contact were expressed as a function of contact force and coke mechanical properties. Particle dropping tests and simple shear tests were performed to check the authenticity of the breakage contact model and the impact forces measured at the particle dropping tests, the friction coefficient as well as the mass of generated fines at the simple shear tests were confirmed well agree with the values predicted by the model.