Discrete element study of bubble behaviors in Type D particle fluidization with and without interparticle cohesive forces

The discrete element method is used to simulate bubble behaviors in a two-dimensional Type D fluidized bed. The aim of the study is to reveal the bubble formation process and bubble structure and to investigate the effects of externally imposed interparticle forces on bubble behaviors. DEM simulations show the complete bubbling process and detail bubble structure. The bubble formation is observed to be highly dependent on the fluidizing gas velocity; the formed bubble modifies gas flow through the system and causes particle movement, which generally results in particle mixing. There is a pressure gradient within the bubble, and the isobars at the top and bottom of the bubble are not symmetrical. The gas streamlines are generally normal to the isobars. The introduction of a cohesive interparticle force not only causes the onset of bubble formation at a higher fluidizing gas velocity but also decreases the bubble growth rate. The bubble size decreases with an increase in cohesive force.