Pressure gradient and particle adhesion in the pneumatic transport of cohesive fine powders

Pneumatic transport of Group C 20 mu m glass beads was studied in a 31.7 mm vertical line, along with 66 mu m Group A glass beads for comparison. Pres sure gradients along the riser were measured and the Zenz type state diagra ms were constructed for both type of particle. For Group C particles, the r esults show that the Zenz diagram has the usual characteristic form, but th e minimum pressure gradient is much lower and is positioned at a significan tly higher gas velocity. Multiple layers of Group C particles were found to adhere to the column wall, while only a fraction of the column inner surfa ce was covered by the 66 mu m particles. The effects of the electrostatics effect during solids conveying was also examined through the addition of an ti-static particles and was shown to be less significant for the finer part icles. This is because the tube inner surface is entirely covered by the pa rticulates, which reduces the charging since only like materials are then i n contact. (C) 2000 Elsevier Science Ltd. All rights reserved.