Principle: A tray dryer is a batch-type drying equipment used for drying solids or liquids. It operates on the principle of forced convection heating, where a fan or blower circulates hot air over the material being dried. The hot air removes moisture from the material, and the moisture-laden air is exhausted from the dryer.

Construction: A tray dryer consists of a rectangular chamber made of mild steel or stainless steel. The chamber has a series of trays or shelves mounted on vertical supports. The trays are perforated to allow air to flow through them. The dryer also has a heating system, consisting of an electric heater or steam radiator, and a fan or blower to circulate the air. A control panel is used to regulate the temperature and airflow rate.

Working: The material to be dried is placed on the trays, and the trays are loaded into the dryer. The heating system is turned on, and the fan or blower circulates hot air over the material. The moisture-laden air is exhausted from the dryer, and fresh air is drawn in to replace it. The temperature and airflow rate are controlled to ensure efficient drying of the material.

Uses: Tray dryers are commonly used in the pharmaceutical, chemical, and food industries for drying powders, granules, and other materials. They can also be used for sterilizing or pasteurizing materials.

Merits:

  1. Tray dryers are easy to operate and require minimal maintenance.
  2. They are suitable for drying a wide range of materials.
  3. Tray dryers can be used for batch or continuous drying.
  4. The drying process can be controlled to achieve the desired moisture content.

Demerits:

  1. Tray dryers have a limited capacity and are not suitable for large-scale drying operations.
  2. The drying process can be slow, especially for materials with high moisture content.
  3. The use of hot air can cause thermal degradation of the material being dried.
  4. The energy consumption of tray dryers can be high.