Fluid Bed Dryers

Fluid bed dryers are quite commonly used in almost all types of industries. They have the capacity to dry relatively free-flowing particles with a reasonably narrow particle size distribution. The wet feed may be in the form of powders, granules, crystals and pre-forms and can adjust to a wide variation in the speed or feed rate in other words. There are three basic types of fluid bed dryers:

Static fluid bed dryer: Here the dryer remains stationary. They may be suitable for continuous or batch operation. They can be rectangular or round in shape.

Vibrating fluid bed dryer: Here the body of the dryer vibrates or oscillates to facilitate the movement of material through the unit. They are rectangular in shape. They are suitable for bulk densities and large size particles.

Fluidizer fluid bed dryer: This system fluidizes the material from the top by means of tubes that deflect on a solid pan lifting the material on the deflected airflow.

Principle
Fluid bed dryers operate on a through-the-bed flow pattern. The gas passes through the product. In a batch method the feed is passed to the dryer container and processed till done. For a continuous method, the wet feed passes through to the drying container and the dry feed discharged at the same time.

For direct heat dryers, the hot gas is introduced into the dryer's wind box that distributes the gas evenly across the perforated distributor or fluidizing plate. Gas here interacts with the feed Fluid bed dryers commonly are provided with both forced and induced draft fans. Most of the fluid bed dryers are based on single pass system that is the gas once passed through the wet feed is exhausted out.

Indirect fluid bed processing is required when low cost energy source (such as steam) is available. The principles remain the same. Fluid bed dryers can use almost any heat source.