The limits of gravitational sedimentation

Abstract

A discussion is presented of some effects which limit the range of applicability of gravitational sedimentation. Finer analyses are to be expected with increasing concentration due to particle—particle interaction. Extending analyses into the sub-micron range will also tend to indicate a higher percentage of fines due to the several effects which keep particles in suspension which, theoretically, should have settled out. These premises are illustrated by analyses of three substantially sub-micron streams from a classifier using centrifugal techniques, a gravitational technique at a low concentration and a gravitational technique at a high concentration. Since the initial object of the exercise was to obtain a grade efficiency curve for the classifier, this calculation was carried out and the results are presented in an Appendix.