The effect of friction and inter-particle cohesive forces on the hydrodynamics of gas–solid flow: A comparative analysis of theoretical predictions and experiments

Electrical capacitance tomography (ECT) was used to measure the solid fraction distribution in a freely bubbling bed. A comparative analysis of the hydrodynamic features (solid distribution, bubble shape and bed expansion) extracted from the ECT measurement and the prediction of the MFIX simulation code is presented. For a fluidised bed of group B particles, the code does not provide an accurate prediction of bubble shape and bed expansion at the intermediate to high gas velocity range. For cohesive particles such as group A/B, the code shows considerable over-expansion. This deficiency was mainly attributed to the fact that the MFIX code does not take into account the realistic existence of interparticle cohesion or frictional forces at the intermediate-dense flow regime. Accordingly, proposed interparticle cohesion and frictional shear stress terms have been incorporated, and tested in a two-fluid kinetic theory model to investigate their effect on the general hydrodynamic features of fully developed vertical duct flow. The results show that incorporating both terms in the classic kinetic theory model results in an improvement of the gas–solid distribution and a lowering of the solid carryover, which implies a reduced bed expansion in the freely bubbling column.