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What should be made clear here, is the key role of energy (acoustic or vibrational) supplied to the bed, without which the bed will not fluidize.

Chemical fluidized beds are usually supplied agitation energy by the upward flow of feedstock gases or liquid through the bed particles (often catalysts). Normally solid river deltas turn into fluidized beds only with energy input from earthquake vibrations. Landslides behave like liquids, not because they float on a layer of pressurized air beneath them, but because of the tremendous kinetic energy inputs from the slide. Rocks bounce off rocks with tremendous energies and the entire body of rocks acts like a fluidized bed. Beach sand turns liquid with foot tapping vibrational input.

In short a fluidized bed is an aggregate of particles in a matrix of gas or liquid, which is settled at rest, but becomes fluid as vibrational energy inputs cause particles to separate. No vibrational energy input, no fluidized bed.