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Principle of Fluid Bed Dryer:
If air is allowed to flow through a bed of solid powdered material in upward direction with the velocity greater than the settling rate of the particles, the solid particles will be blown up and become suspended in the air stream. At the stage solid bed looks like the boiling liquid, therefore this stage is called as fluidized. Use of hot air to fluidizing the bed will increase the drying rate of the material.
FBD contains a stainless steel chamber having a removable perforated bottom known as bowl. Material to be dry is placed in this bowl. Air is introduced from the bottom of the bowl and heated at required temperature by the heaters. This air is filtered through the filtered and then passes through the bed of the material. This airflow is generated by the fans fitted at the top of the equipment. The flow rate and the operating temperature are adjusted by control panel. As the flow of air increases, the bed known as FBD bag expands and particles of powder starts a turbulent motion. Due to the regular contact with air, material gets dry. The air leaving the FBD passes through the filter to collect the fine particles of the material. Fluidized bed dryer has a high drying rate and material is dried in a very short time. Material remains free flowing and uniform. FBD bags are finger like in structure to increase the surface area of the drying bed.
Related: Challenge Test of Solid Flow Monitor in Fluid Bed Dryer
Sometimes particles may develop electrostatic charge. Burning of the material in the fluid bed dryer equipment is experienced in many cases in different pharmaceutical companies. Outlet filter blockage is a common problem of the fluidized bed dryer equipment. It can cause in increase the pressure in the vessel. Therefore, handling of the equipment should be done carefully.