21.3 SALTATION
The previous discussion of efficiency and pressure drop leaves the impression that
continually increasing the inlet gas velocity can give incrementally increasing effi-
ciency. However, the concept of “saltation” by Kalen and Zenz7 indicates that, more
than just diminishing return with increased velocity, collection efficiency actually
decreases with excess velocity. At velocities greater than the saltation velocity,
particles are not removed when they reach the cyclone wall, but are kept in suspension
as the high velocity causes the fluid boundary layer to be very thin. A correlation
for the saltation velocity was given by Koch and Licht:8