Fluid Bed Dryers are designed to dry products as they float on a cushion of air or gas. The process air is supplied to the bed through a special perforated distributor plate and flows through the bed of solids at a velocity sufficient to support the weight of particles in a fluidized state. Bubbles form and collapse within the fluidized bed of material, promoting intense particle movement. In this state, the solids behave like a free flowing boiling liquid. Very high heat and mass transfer values are obtained as a result of the intimate contact with the solids and the differential velocities between individual particles and the fluidized gas. Often products are required in agglomerate or granular form to achieve good instant properties and so fluid bed dryers may be combined with spray drying, agglomeration, or granulation systems.
This type of dryer can be used in a batch of continuous process. The product flows across a perforated bed in the dryer. Hot air is blown up through the perforated bed causing the product to flow in the air stream. Continuous beds vibrate to move the product through the dryer. Batch type have agitator to keep the product moving through the air stream. Found mostly in pharmaceutical and food (dairy) plants.
Unique Features.
- Enhanced heat and mass transfer through intimate contact and mixing with the fluidizing gas.
- Heat sensitive materials can be dried at temperatures lower than the boiling point due to reduced vapor pressure .
- Indirect heat transfer surfaces can be added to increase capacity or reduce bed area .
- Closed cycle Fluid Bed systems, in which inert gases can be recycled, are available to handle toxic products, oxygen sensitive products, or flammable solvent wetted materials.
Application
- Polymers and Resins.
- Inorganic and Organic Chemicals.
- Chemicals.
- Agglomerated Products.
- Fertilizers.
- Foodstuffs in powder or agglomerated form.
