FLUID BED DRYING

 

Fluid bed dryers are one of the most common types of dryer used for producing dried particles (powders). Their advantages are low initial capital investment, simple structure and low maintenance costs.

 

OPEARATION

Consider a bed of particles initially at rest, supported by a perforated plate. Gas is introduced through the perforated plate and as the gas flow increases, at some point the particles become freely suspended in the air stream and the bed begins to expand.

 

VIBRO-FLUIDIZED BED DRYERS

If order to overcome problems of the fluidization, especially with products that have significant amount of oversized particles, in vibro-fluidized bed dryers the distributor is vibrated. This allows keeping the gas flow velocities low, since the large particles are kept moving by the vibrations of the distributor. For this same reason, this design is often used for beds consisting entirely of large particles.

 

VIBRATING FLUID BED DRYERS

With some difficult to handle products, one option is to install a mechanical agitator to the base of the dryer. The agitator causes to break up most of lumps and mix them into the dry powder.

 

 

Fluid bed drying in both stationary and vibrating bed types is another RALLI OY (Ltd.) specialty. Plug flow, mixed flow and multi-stage designs are available. Selection is based on through test work directed to find the best design for the desired product. Many times fluid bed dryers are used in combination with spray dryers or flash dryers to form multi-staged drying systems.