Drying

Definition: is the vaporization and removal of water or liquid from a solution or suspension.

Reasons for drying solid materials are:

1.  Decrease the weight of the material.

2.  Improve the flow properties of the material.

3.  Avoid

corrosion of container by moisture.

4.  Prevent the growth of micro-organism.

5.  Prevent hydrolysis cause Decomposition.

Moisture content is made up of bound water & free water,

 This Bound water is held by:

a. Adsorption force

b. Solution

c. Capillary action

The free water is all moisture that is in excess.

Equipments

1. Tray dryer: consist of series of shallow trays placed one on the other with air gap between the trays.

   

Drying rate not constant??

Because the air more heavily laden with water vapor and its temperature not need increased at any time of drying.

2. Rotary dryer: this is used for large scale continuous drying.

The source of heat supply

              a. Directly (Hot air current)

                

                  b. In directly(Use outer shell which contains steam Tubes)