A Comparison of Axial Dispersion Coefficents for Various Granular Materials

Various batch and continuous flow industrial processes employ rotary drums to facilitate radial mixing of granular materials. Such processes, including rotary kilns, impregnators, and calciners, may also be affected by axial mixing. Because residence time is important in continuous processes, quantifying the degree of axial mixing can be used to form a comprehensive understanding of the particle dynamics in continuous systems. The degree of axial dispersion in a batch system at varying time points may be comparable to the degree of axial dispersion at various positions within a continuous system.

Characterization of the axial dispersion for several classes of granular materials has been performed utilizing a spectrophotometer and bench scale rotary drum. Using Fick’s Law, the axial dispersion coefficient has been found for cohesive and well-flowing powders relevant to industries including catalytic and pharmaceutical.