Prevent caking of bulk solids

Document Type

Article

Date of Original Version

4-1-2016

Abstract

Understanding the mechanisms behind caking, identifying key process variables and product specifications, and testing samples to predict the increase in cohesive strength of a powder over time are key to preventing and solving caking problems. Caking results when the magnitude of interparticle forces increases over time. The adhesive forces are primarily van der Waals forces, polar interactions, and, when moisture is present, the forces associated with liquid bridges. Van der Waals forces include all intermolecular forces that act between electrically neutral molecules. The likelihood of caking, however, generally decreases with increasing particle size. Liquid bridging occurs when moisture accumulates at the contact points between adjacent particles. The likelihood of liquid bridging can often be inferred from a powder's moisture sorption isotherm, which relates relative humidity and equilibrium moisture content. A powder's moisture sorption isotherm can indicate the likelihood of liquid bridging. This isotherm characterizes a powder prone to caking.

Publication Title, e.g., Journal

Chemical Engineering Progress

Volume

112

Issue

4

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