Fluidisation in a pulsed gas flow

The effect offlow pulsations on a 4 in dia air-fluidised bed of glass beads has been investigated in the frequency range 1 to 10 Hz. It was found that the beds have a natural frequency which can be calculated approximately from a model which assumes piston-like behaviour. The shape of the air bubbles rising through the bed fluctuates synchronously with the applied pulsations. Tracer studies using helium gas have shown that pulsation can increase the gas retention time by as much as 51 %.