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Agitation is a critical aspect of many processes, such as food production, mineral processing, and water treatment, with liquid-solid agitators representing a significant portion of all agitation installations. This research is concerned with solids suspension in a liquid-solid stirred tank at one particular agitation level â just-suspended condition in which no solids rest on the tank base for longer than one to two seconds. The novelty of this work is that though there have been many studies on the just-suspended speed of uniform solid (solid particles with same shape, size, and density), there has been very little work in the industrially important area of mixtures of solids with different physical properties. The goal of this work is to investigate whether sum of the individual solids suspension powers approach can provide a reasonable estimate of mixture just-suspended speed of solids with different physical characteristics. All tested mixtures of solids with different properties (particle size, shape, and specific gravity) are categorized into three different groups based on the specific gravities of individual solids in each system: systems where the specific gravities of both solids are below 1.5 grams per cubic centimeter (i.e. low-density system), both solid densities are above 2.4 grams per cubic centimeter (i.e. high-density system), and solids of mixed densities - that is, a solid with low density plus a solid with high density. It is found that the sum of powers approach can acceptably predict the just-suspended speed of both high-density and mixed-density solids systems while the predicted speeds from summing the individual solids suspension powers are typically ten to twenty percent greater than the measured speeds of low-density solids systems.

Publication Date


Project Designation

Graduate Research

Primary Advisor

Eric E. Janz

Primary Advisor's Department

Chemical and Materials Engineering


Stander Symposium poster

Suspension of Solid Mixtures by Mechanical Agitation