Fluid Bed Dryer (FBD)

Fluid bed dryer (FBD) is a dryer in which material is maintained suspended against gravity in an upward flowing air stream creating a fluidized condition. Electrical heaters are employed to generate heat for drying the material. This hot air expands the bed of material at its terminal velocity and creating turbulence in the product (terminal velocity is the minimum velocity of the air sufficient to keep the given particle hanging in the air). This phenomenon is known as fluidization and offers more surface area for drying as the complete particle is then comes into contact of heated air. As it produces full agitation of solid particles, it results in high rate of heat transfer and uniform drying. In quest of an appropriate drying technology for bioinoculants, the idea of fluid bed drying was borrowed from food processing industry. FBD is commonly used in food industries for making instant coffee powder and other drying operations (Brahmaprakash and Sahu, 2012).

The fluid-bed method of wet granulation is very common in the pharmaceutical and other industries as a one-step, enclosed operation. It is very useful as several ingredients can

(2013) had prepared a FBD inoculant formulation of microbial consortium. The survival of all three microorganisms in consortium was observed till 180 days of storage. FBD formulated consortium maintained a more or less constant number of cells till the end of 180 days. There was no contamination observed in any dilution. This was a very specific result achieved from FBD to maintain a contamination-free inoculant as it was speculated.

1.7.3 Advantages of FBD inoculant formulation

• The decline in number of cells is very limited (Sahu et al., 2013)

• Absolutely no contamination builds up (Brahmaprakash and Sahu, 2012)

• Several ingredients can be mixed and dried (Srivastava and Mishra, 2010)

• Ambient temperature is used for drying (Sahu, 2012)

• Possibility to change the drying temperature according to need (Sahu,