Tray Dryer

Principle & Working Process, Construction, Application and Advantages of Tray Dryer

Principle of Tray Dryer:

  • In Tray Dryer, basically hot air is continuously circulated in the instrument.
  • Forced Convection heating proceeds to remove the moisture from the solids placed trays in pharmaceutical industry. Similarly, the moist air is removed partially by means of Vacuum tray dryer.
  • A tray dryer is the convectional drying equipment/instruments with surrounded insulated chambers and trays placed on top of each other in a trolley.
  • The driers are used in commercial manufacturing processes where drying and heating are essential steps, including the production of food products, dyes, pharmaceuticals, and chemicals, among others.
  • Trays are filled with wet solid. In the room, trays are arranged. Fresh air is brought in through the intake, where it is heated up after passing through the heaters.
  • Fans located at a pace of 2 to 5 metres per second are used to move the hot air.
  • Turbulent flow lowers the part of partial vapour pressure in the atmosphere & also decreases the thickness of the air boundary layer. The water is picked up pass of air (hot air). As water evaporation from the surface.
  • From the solid surface, the water diffuses from the interior of the main solid by capillary action. These events happen in a single pass of air.
  • The time of contact is short and the amount of water or moisture picked up in as single pass is small.
  • Discharge of air to tune of 80-90% is circulated back by means of Fan while only 10-20% fresh air is introduced. As a result, constant temperature and airflow maintained in the dryer (achieving uniform drying and c constant temperature).

Contraction of Tray Dryer:

  • It is made up of a rectangular chamber with insulated sides. The size of the industrial dryer will determine how many trays are put inside the heating chamber.
  • Dryers of the industry scale can hold more than 20 trays, whereas dryers of the laboratory size can hold no more than three trays.
  • Each plate is rectangular or square in shape, depending on the specifications. They range in size from 1.2 to 2.4 square metres.
  • Typically, trays are filled between 10.0 and 100.0 millimetres deep.
  • There must be a 40.0 millimetre gap between the bottom of the upper tray and the top of the substance loaded into the following tray.
  • As an alternative, the trays can be put in wheeled trucks that can be moved into and out of the chamber. You can set up two of these vehicles inside the dryer.
  • The dryer is equipped with a fan to move air over the pans. To purify the air, electrically heated components are placed inside rather than outside. (air steam also may be used option as it is cheaper).
  • A highly effective Air Handling Unit (AHU) at Air Inlet should be provided wherein Blower and AHU with filters, heater and dehumidifier are contained separately in the service zone to evade sound pollution as well as to avoid interference of the maintenance people in the production process.
  • Tray and Equipment mainly made from the high grade stainless steel (i.e SS 316 or SS 304).
Pharmaceutical Tray Dryer
Tray Dryer

Use in Pharmaceuticals:

  • Wet Solids, granular mass or crystalline substance, Sticky Materials, Plastic Substances, Precipitates and Pastes can be dried in it.
  • Crude drugs, chemicals, Pharmaceutical powders, tablet wet granules or parts of equipment’s can be dried.


  • Handling can be done without too much losses
  • It is operated as batch-wise. batch drying is used extensively in the manufacture of pharmaceuticals because, Batch of material can be handled as a separate entity. batch sizes in the pharmaceutical industry arc relatively small (250 kg or less per batch) compared with the other.
  • The equipment is to operate and readily adjustable.
  • The products can be handled efficiently.
  • Loading and unloading of material is too much easy
  • Can be used for extensive variety of materials.


  1. Tray dryer required more lab persons, Hence, it may increase coast.
  2. The process is time consuming.

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