Table of Contents
Fluidized Bed Dryer
Principle of Fluidized Bed Dryer
In fluidized bed dryer, hot air gas is passed at high pressure through a perforated bottom of the container containing granules to be dried. The granules are lifted from the bottom and suspended in the stream of air, this condition is called fluidized state. The hot gas is surrounding every granule too completely.
Construction of Fluidized Bed Dryer
Two types of bed dryer are available, vertical fluidized bed dryer, horizontal fluidized bed dryer.
- Vertical fluidized bed dryer is made up of stainless steel or plastics.
- A detachable bowl is placed at the bottom of the dryer, which is used for charging and discharging.
- The bowl has a perforated bottom with a wire mesh support for placing material to be dried.
- A fan is mounted in the upper part for circulating air.
- Bag filters are placed above the drying bowl for the recovery of fines.
Working/process of Fluidized Bed Dreyer
- The wet granules are placed in the bowl and pushed into the dryer.
- Fresh air is allowed to pass through a prefilter, which subsequently gets heated by passing through a heat exchanger.
- Simultaneously fan is allowed to rotate. The air velocity is gradually increased.
- The granules rise in the container because of high velocity gas (1.5 to 7.5 meter/minute) and later fall back in a random motion. This condition is said to be fluidized state.
- The gas surrounds every granule to completely dry them and Periodically the bag is shaken to remove the entrained particles.
Uses/Applications of Fluidized Bed Dreyer
- Fluidized bed dryer is popularly used for drying of granules in the production of tablets.
- Fluidized bed dryer can be used for three operations such as mixing, granulation and drying.
Advantage of Fluidized Bed Dreyer
- The drying containers are mobile, making handling simple and reducing labor cost.
- It require less time to complete drying that is 20 to 40 minutes compared to 24 hours of tray dryer.
- It facilitates the drying of thermolabile substances, since the contact time for drying in short.
Disadvantage of Fluidized Bed Dreyer
- Many organic powders develop electrostatic charge during drying.
- The turbulence of the fluidized state of granules may cause attrition of some materials resulting in the production of fine (overcome this problem suitable binding agent is used).