Clamp Down on Clumping

First understand what’s really causing the problem.

By Tom Blackwood, Healthsite Associates

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Clumping Solutions
Is it possible to predict cohesion? Probably not. No one test is appropriate but many qualitative tests can help define the potential. So, what do you do to minimize clumping?

The solution to many prospective causes of clumping centers on minimizing solvent contact with solids, controlling particle size, limiting attrition sources and avoiding putting excess energy into solids, especially prior to packaging. Table 2 gives some specific suggestions for the ten common causes of clumping. For each there’s often a first line of defense. However, many of the solutions can treat other related causes. For example, filling a drum from an excessive height can increase attrition, mechanical deformation and solvent vapor trapped (by boosting the amount of voids). Also, packaging a hot material can promote chemical reaction, phase change, recrystallization and formation of viscous films. As a last resort you can modify solids through agglomeration or addition of flow aids such as silica. But that’s another subject.

Tom Blackwood is director of technology for Healthsite Associates, St. Louis. E-mail him at

1. Blackwood, T., “Don’t let Phase Changes Faze You,” Chem. Proc., October 2005, p. 31,
2. Carr, R. L., Jr. “Evaluating Flow Properties of Solids,” Chem. Eng., p. 163 (Jan. 18, 1965).
3. Carr, R. L., Jr., “Classifying Flow Properties of Solids,” Chem. Eng., p. 69 (Feb. 1, 1965).
4. Carr, R. L., Jr., “Particle Behavior, Storage and Flow,” Publ. 68-MH-6, ASME, New York (Oct. 1968).
5. “Standard Test Method for Bulk Solids Characterization by Carr Indices,” Standard D6393-99, ASTM Intl., West Conshohocken, Pa. (1999).
6. “Comparison of Physical Property Traits of Niacin and Niacinamide,” Tech. Bulletin TPU-0402, BASF Corp., Florham Park, N. J. (2004).


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