Applications of Fluidization to Food Processing
Chapter One
A Description of Fluidized Bed Behaviour
An introduction to fluidization
Consider a bed of particulate solids or powder, say of a size similar to
table salt. When a fluid, either a gas or a liquid, is passed upwards
through the bed, the bed particles remain stationary or packed at low
fluid velocities. This is a packed or fixed bed. If now the velocity of the
fluid is increased, the particles will begin to separate and move away
from one another; the bed is said to expand. On increasing the velocity
further, a point will be reached at which the drag force exerted by the
fluid on a particle is balanced by the net weight of the particle. The
particles are now suspended in the upward-moving stream of fluid.
This is the point of minimum fluidization, or incipient fluidization, at
and beyond which the bed is said to be fluidized.
The superficial fluid velocity in the bed at the point of incipient fluidization
is called the minimum fluidizing velocity [u.sub.mf] and is of crucial
importance in characterising the behaviour of a fluidized bed.
... read full excerpt from Applications of Fluidization to Food Processing ebook
