Fluidised Bed Dryer

A small seminar on the FBD . Drying of pharmaceutical solid is the main concept of the this presentation

1. FLUIDISED BED DRYER Presented By: Mr. Sagar Kumar Kadam Roll No. 24 First year M. Pharm. Department: Pharmaceutics

2. DRYING Drying is defined as the removal of small amounts of water or other liquid from a material by the application of heat . Mechanism of Drying Process Drying involves both heat transfer and mass transfer processes simultaneously. Heat transfer takes place from the heating medium to the solid material. Mass transfer involves the transfer of moisture to the surface of the solids and subsequently vaporisation from the surface into surrounding.

3. VERTICAL FLUIDISED BED DRYER

4. INTRODUCTION TO FBD Fluidized bed dryer (FBD) is well known and widely used equipment in granulation area of pharmaceutical manufacturing. It is used in the granulation process for drying the material to get desired moisture content in the tablet formulation granules required for perfect compression of tablet FBD work on the principle of fluidization of the materials. In fluidization process, hot air or gas flow is introduced through the bed of solid particulates. This gas or air will move upward through the spaces between the particles.

5. In fluidized bed dryer, hot air 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. The hot gas surrounding every granule to completely dry them. Thus, material or granules are uniformly dried. The hot air/gas used for drying can be generated by either steam coils or a combustion furnace. In fluid bed drying uniform conditions of temperature, composition and particle size distribution is achieved throughout the bed because of complete mixing between the solids and gas is obtained.

6. PRINCIPLE If air is allowed to flow through a bed of solid powdered material in the 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 this stage ,this solid bed looks like the boiling liquid, therefore this stage is called as fluidized. The hot gas is surrounding every solid particle to completely dry them. Thus, material or granules are uniformly dried.

7. CONSTRUCTION The dryer is made of stainless steel or plastic. 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 materials to be dried. A fan is mounted in the upper part for circulating hot air. Fresh air inlet, pre-filter and heat exchanger are connected serially to heat the air to the required temperatures. The temperature of hot air and exit are monitored. Bag filters are placed above the drying bowl for recovery of fines.

8. WORKING The wet solid to be dried are placed in the detachable bowl, the bowl is pushed into the dryer. Fresh air is allowed to pass through a prefilter, which subsequently gets heated by passing through a heat exchanger. The hot air is flow through the bottom of the bowl . Simultaneously fan is allowed to rotate. The air velocity gradually increased. When the velocity of the air is greater than the settling velocity of granules, the granules remain partially suspended in the gas stream. After some time, a point of pressure is reached at which frictional drag in the particles is equal to the force of gravity.

9. The granules rise in the container because of high velocity gas and fell back in a random boiling motion. This condition is said to be fluidized state. Drying is achieved at constant rate and falling rate period is very short.

10. PARAMETRES Process parameters Temperature As the inlet air temperature increases the rate of drying increases and vice versa. This approach to increase the rate of drying can not be used always because some materials are harmed by high temperature, e.g. Ibuprofen liquefies above 60°C temperature of inlet air should be optimized without any impact on product quality. If temperature is high, it leads to blistering. If temperature is low, soft spot can be formed.

11. Humidity Humidity in the inlet air should be as low as possible and ideally dehumidified air should be used for faster drying rate because as the humidity of inlet air decreases the rate of drying increases. Air flow rate Air flow rate should be controlled properly in order to get efficient use of drying air. Air flow rate should not be too fast or too slow but optimized to have efficient drying. Product Parameters 1)Initial moisture content of material It should not be high otherwise it increases drying time. 2)Batch size It should be small and optimized based on feasibility.

12. USES Fluidised bed dryer is popularly used for drying of granules in the production of tablets. Fluidised bed dryer can be used for three operations such as mixing, granulation and drying. It is modified for coating of granules.

13. REFERENCES C.V.S. Subrahmanyam et al, page no. 396-398,Pharmaceutical Engineering. K Sambamurthy, page no. 309-312,Pharmaceutical Engineering. en.wikipedia.org www.google.co.in