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If air is allowed to flow upward through the solids bed and has a velocity greater than the particle settling rate, the solids will be blown off and suspended in the air flow.
At this stage, this solid bed looks like a boiling liquid, so this layer is called fluidized. The use of hot air to fluidize the bed will increase the drying rate of the material.
The FBD consists of a stainless steel chamber with a removable perforated bottom known as the bowl. This container holds the material for drying. Air is introduced from the bottom of the bowl and heated to the required temperature by the heater.
This air is filtered through the filter and then passes through the material bed. This airflow is generated by a fan mounted on the top of the equipment. Flow rate and operating temperature are adjusted by control panel.
As the air flow increases, the bed known as the FBD bag expands and the powder particles begin a turbulent motion. Due to regular contact with air, the material dries. Air exiting the FBD passes through a filter to collect fine particles of material.
Fluidized bed dryers have high drying rates and dry the material 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 which helps to increase the drying rate and reduce the drying time during the fluidized bed drying process.
Sometimes particles can develop an electrostatic charge. Many pharmaceutical companies have experience with material burning in fluid bed dryers. Outlet filter blockage is a common problem with fluid bed dryer equipment. This can increase the pressure in the vessel which can cause accidents during operation. Therefore, handling the equipment should be done carefully.
