Pharmaceutical Drying Process

Tray Dryer, FBD

1. Drying process Drying is the process of removal of water or other liquids from a material with the help of heat. The final product after drying is dry solid or powder. Pharmaceutical application of drying: To prepare granules for tablets & capsules. To prepare dried aluminum hydroxide, lactose & powder extracts. To reduce the bulk density & weight. For easy transport & storage. To facilitate grinding of crude drugs. To improve the stability & prevent deterioration of the drugs.

2. Types of Dryers: 1. Dryers for damp solids Tray Dryer FBD (Fluidized Bed Dryer) Tunnel Dryer Rotatory Dryer Vacuum Dryer Specialized drying Method Freeze drying 2. Dryers for slurries or solutions Drum Dryer Spray Dryer

3. Tray Dryer Tray dryer consists of a cabinet filled with trays & heaters are placed on the wall of dryer. Tray dryers are made up of stainless steel & heated air is circulated throughout the trays by fans. Number of trays are present in the dryer where substance to be dried are placed over large area. It is very effective & popular method of drying.

4. Tray Dryer

5. Tray

6. Advantages Number of tray increases the area for drying through circulation of hot air. Useful for drying of wet granules, powders, crude drugs, etc. Disadvantages Tray dryers requires more labour to load and unload. The process is time consuming.

7. FBD (Fluidized Bed Dryer) Fluidized bed dryer consists of removable bowl at the bottom of the dryer for loading & unloading of the wet granules or other material to be dried. Hot air is passed at high pressure through bottom of the bowl which suspends granules in the air (fluidized state) & dries them. The temperature of the hot air and exit air are monitored & filter bags are placed above the drying bowl for the recovery of the fines. It is made up of stainless steel since it directly comes in contact with the product. There are vertical fluidized bed dryers and horizontal fluidized bed dryers.

8. Fluidized Bed Dryer Filter Bag Removable Bowl PHARMACEUTICAL APPLICATIONS: It is used for the drying of the granules in the production of the tablets. Useful for mixing, granulation and drying.

9. ADVANTAGES 1) It takes less time to complete drying (20-40 mins ) 2) Handling time is also short. 3) Drying capacity ranges from 5 to 200 kg per hour. 4) The drying containers are mobile, easy to handle and low labour costs. 5) The thermal efficiency is higher than the tray dryer. 6) It is also used for mixing & its mixing efficiency is high. 8) Higher drying temperatures can be used that are not possible in tray dryer. 9) It facilitates the drying of thermolabile substances since the contact time for the drying is short.

10. DISADVANTAGES 1) Many organic powders develops electrostatic charges during drying. 2) The turbulence of the fluidised state of granules may causes attrition of some materials resulting in the production of fine powders.