Effect of particle shape on prediction of velocity-voidage relationship in fluidized solid-liquid systems

This study was undertaken with an objective to provide an alternative method to predict the velocity-voidage relationship of non-spherical particles during liquid fluidization. The prediction equation was developed by plotting;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI);for the data obtained by several investigators. ((epsilon) is porosity, (pi) is fluid density, (rho)(,s) is particle density, (mu) is dynamic viscosity, S is specific surface and u is superficial velocity);Three different shape factors were used to account for the non-sphericity of the material. They were sphericity ((psi)), the dynamic shape factor (DSF) and the hydraulically equivalent diameter shape factor ((OMEGA)). The sphericity, (psi), was found to be the most suited shape parameter for this method of prediction;The prediction is as follows: log Al = 0.71162 + 1.03956 log Re(,1) + 0.16572 (log Re(,1))(\u272) + 0.9 log (psi), where;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI);This equation can be used to predict the velocity-voidage relationship when the expanded bed porosity is below 0.9 and 1 \u3c Re(,1) \u3c 3100;From the review of literature it was shown that the two shape factors, DSF and (OMEGA), do not bear any fixed relationship to the geometric shape of the particle. These two shape factors, DSF and (OMEGA), vary with particle Reynolds numbers, and reach constant values at very low and very high particle Reynolds numbers. Therefore, when these two shape factors are used this limitation has to be borne in mind;An air permeability apparatus was found to provide a simple method to obtain the sphericity of irregular shaped material. The sphericity calculation was based on the Ergun equation for fixed bed pressure drop. The sphericity values obtained were not very sensitive to the degree of packing of the fixed bed;The \u27n\u27 slope of Richardson and Zaki can be predicted by the equations proposed by Cleasby and Fan. However, the intercept velocity, u(,i), shows considerable scatter from the equation proposed by them