(36b) Suspension of Solid Mixtures by Mechanical Agitation

The suspension of solids using mechanical agitators has been widely studied, resulting in methods that permit reasonably accurate agitator design for suspending particles with uniform characteristics (size, shape, density, etc.).  However, limited work has been performed in the area of suspending mixtures of solids with different characteristics, but there has been a growing interest in this subject.  An experimental program has been undertaken to develop guidelines that can be used to design agitators for the suspension of solid mixtures.  Although this work is ongoing, the following results have been obtained. 

- The just-suspended speed of some solid mixtures is equal to the speed required to suspend the more difficult to suspend solid alone (i.e. – addition of the easier to suspend solid does not alter the just-suspended speed).

- The power required to suspend a solid mixture can be less than, equal to, or greater than the sum of the powers required for suspension of the individual solids.

Given these findings, there appears to be no simple rule to predict the just-suspended speed of a mixture of solids from the just-suspended speeds of the individual solids.  This presentation will review the experimental work that has been performed with an aim to developing agitator design rules for suspending solid mixtures.