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Renin Angiotensin Mechanism.

Tray Dryers.

 

Definition

  • Drying is defined as the removal of liquid from a product usually with application of heat.

  • Equipment used for the purpose of drying are called “Dryers”.

Tray Dryers.

  • Also known as: Shelf dryers, Compartment dryers, Cabinet dryers.

  • Common example is Hot Air Oven.

Principle:

  • It's a static bed dryer where drying takes place by “Forced Convection”.

Construction:

  • It consists of a rectangular double layer stainless steel chamber whose walls are insulated. 

  • Inside layer is mirror polished. 

  • Door has a rubber lining. 

  • Dryers are fitted with a heating device, thermostat, fan and timer. 

  • Stainless steel trays are placed on the shelf of the drying chamber. 

  • Fresh air enters through an inlet, which is through a filter, a heater and a fan. 

  • In the corner of the chamber direction vanes can be placed to direct air in the expected path. 

  • The distance between the bottom of the upper tray and the upper surface of the material loaded in the subsequent tray must be 40 mm. 

  • Trays are usually loaded from 10 to 100 mm deep. 

  • Tray dryers are available in various sizes. 

  • The air with moisture absorbed from the substances leaves the dryer from an outlet as shown in the diagram below.

Working:

  • The material to be dried is placed in thin layers in trays. 

  • Trays are placed in the chamber as air is introduced through the inlet, which passes through the filters and heaters as it becomes hot. 

  • The hot air is circulated by means of fans at 2 to 5 meters per second. 

  • Air flows in the direction of the arrows over each shelf in turn as shown in the above figure. 

  • The moist air is removed through the outlet. 

  • Constant temperature and uniform airflow over the materials can be maintained for achieving uniform drying. 

  • In case of the wet granules, drying is continued until the desired moisture content is obtained. 

  • At the end of operation trays are pulled out of the chamber and the product is collected.

Uses:

  1. Used to dry variety of materials like,

    1. Sticky materials,

    2. Granules.

    3. Crystalline materials.

    4. Crude drugs.

    5. Precipitates.

    6. Some equipment and laboratory glassware.

Advantages:

  1. No loss of material while handling.

  2. Loading and unloading is easy.

  3. Easy to operate.

  4. Good for batch drying.

Disadvantages:

  1. Less efficient: only the surface of the product is exposed to heat.

  2. High labor cost.

  3. Not suitable for large scale drying.

  4. Liquids can not be dried.

  5. Time required is more.

  6. Not suitable for thermolabile substances.

Commonly Asked Questions.

  1. With a well labelled diagram describe construction and working of Tray Dryers.

  2. Write a short note on the Tray Dryer.
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