Educ. Reso. for Part. Techn. 014Q-Rhodes
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Pneumatic Transport of Powders

by Martin Rhodes

Keywords: pneumatic transport, dense phase, dilute phase, particles, choking velocity, saltation, pressure drop, pipeline transport, flow patterns

-- Introduction --

  For many years gases have been used successfully in industry to transport a wide range of particulate solids - from wheat flour to wheat grain and plastic chips to coal. Until quite recently most pneumatic transport was done in dilute suspension using large volumes of air at high velocity. Since the mid-1960s, however, there has been increasing interest in the so-called "dense phase" mode of transport in which the solid particles are not fully suspended. The attractions of dense phase transport lie in its low air requirements. Thus, in dense phase transport, a minimum amount of air is delivered to the process with the solids (a particular attraction in feeding solids into fluidized bed reactors, for example). A low air requirement also generally means a lower energy requirement (despite the higher pressures needed). The resulting low solids velocities mean that in dense phase transport product degradation by attrition, and pipeline erosion are not the major problems they are in dilute phase pneumatic transport.

Acknowledgements

Videos and photographs are used with the kind permission of NEU Engineering, Stockport, UK.

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Martin Rhodes is Professor of Chemical Engineering at Monash University, Melbourne, Australia.

With a keen interest in particle technology education, he has directed continuing education courses on the subject and is author of the undergraduate textbook Introduction to Particle Technology (Wiley, 1998).

His research interests include fluidization, fluid-particle flows, interparticle forces and particle mixing.

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