DEM study of blockage behaviour of cohesive fine particles in a packed structure of large particles
Blockage of cohesive fine particles in a packed structure of large particles may happen in many industrial processes, of particular interests to ironmaking COREX technology. In this work, blockage behaviour of cohesive fine particles in a simplified packing structure is studied by means of discrete element method. The typical phenomena about effects of sticking force on descending velocity and blockage frequency is described. Two kinds of blockage mechanisms of fine particles in a packed bed of large particles are explored: mechanical interactions between fine particles will create arches on the pore throat and stop the flow; fine particles with high interparticle stickiness will adhere to the surface near the pore throat of the orifice, thus the sectional area of the flow channel will decrease.
With the increase of sticking force, the descending velocity will decrease, while the frequency of the blockage increases. In addition, the effects of size ratio of fine particle to packing particle, mass flow rate and magnitude of the upward force (e.g. from a gas stream) on blockage behaviour are also discussed. The results show that increasing the size ratio, mass flow rate and external force will increase the frequency of the blockage. The study provides a fundamental understanding on blockage behaviour of cohesive fine particles in a packed bed, and is useful for industry processes’ understanding and optimization.
Keywords: fine particle, sticking force, blockage.