When the air velocity is low, the bed of solids remains still. As the air velocity increases, the particles on the upper part of the static bed begin to move and separate from one another. When the air velocity is further increased . all the particles begin to float The particulate bed is expanded and the movement of particles become an active formation of a mixture of air and particles. This gas­ solid mixture is called “Fluidised Bed”

When the air velocity is low, the bed of solids remains still. As the air velocity increases, the particles on the upper part of the static bed begin to move and separate from one another. When the air velocity is further increased . all the particles begin to float The particulate bed is expanded and the movement of particles become an active formation of a mixture of air and particles. This gas­ solid mixture is called “Fluidised Bed”