DEVELOPMENT OF A NEW THEORY FOR HINDERED SETTLING SUSPENSIONS

Above a certain concentration, the fall of any particle in a suspensio n is observed to be hinder-ed by the presence of other particles in it s path. Several theories have been presented which describe the hinder ed settling nature of suspended particles using monoexponential equati ons. These equations, however, could explain such phenomenon only with in a small range of porosities. Using an extended range of porosities reveals a break in the linear plot of the logarithm of the interface f alling rate versus the solid porosity of the medium. In this study, an attempt has been made to describe this non linearity in hindered sett ling phenomenon. A new theory, based on the classification of a concen trated suspension into a diffusion and a main compartment, has been de veloped It also determines the mean spherical radii of the settling fl ocs. Concentrated tricalcium phosphate suspensions are used and interp reted as the model,,for the behavior of such systems. A biexponential relationship is discovered between the sedimentation rate and the soli d porosity of the system. The mean values for the floc radius obtained by this new theory is several times larger than that obtained from ex isting monoexponential equations. II is believed that the higher value s obtained reflect the real situation of aggregation occurring in a co ncentrated suspension.