Minimum pickup velocity

Abstract

The transport of nano-scale particles has become increasingly important, but the knowledge base available is limited. This study aims to bridge the knowledge gap between the nano- and micro-scales for pneumatic conveying. A key parameter is the minimum pickup velocity (U_pu), which is the minimum fluid velocity required to initiate motion in a particle originally at rest. The U_pu values of nine alumina particles with particle diameters (d_p) ranging from 5 to 110,000 nm were determined using the weight loss method, then compared against the established pickup Zones (analogous to the Geldart Groups). Results indicated that: (1) U_pu varied non-monotonically with increasing d_p, thus revealing the missing link between the nano- and micro-scales; (2) the intermediate particle diameters surprisingly did not agree with any pickup Zone; (3) Zone III (analogous to Geldart Group C) is inadequate for all the nano-scale particles, so new boundaries and a new Zone are proposed.