Liquid holdup in this regime can be large but the gas velocities are low.

The higher gas velocity produces waves on the liquid surface.

This method can be affected by changes in the system pressure and gas velocity.

In order to transition from a packed bed to a fluidized condition, the gas velocity is continually raised.

Due to high gas velocities, erosion of the side walls of the cyclone can also be a problem.

The lower the gas velocity, the higher the concentration (but the lower the net ozone produced).

Therefore, by reducing pressure drop, the gas velocity is decreased and the corresponding residence time is increased.

The reduction in gas velocity allows for a longer contact time between phases and better absorption.

Since the pressure drop in each stage is smaller as compared to the impulse stages, the gas velocities are relatively low.

Maintaining an optimum gas velocity by carefully chosen tube diameter.