A tray dryer or say Hot Air Oven in the Drying industry used in pharmaceutical industry, Chemical, Food is used to dry powders, granules, and other types of materials. It consists of a heated chamber with trays to place materials. The trays are usually stacked one on top of each other, and the drying process is usually done under controlled temperature and humidity conditions.
Tray Dryer machine is used on large scale in pharmaceutical, chemical, and cosmetic industries to achieve efficient material drying at low cost. Although it is an old method to dry, but it is still used in small and medium scales industries. Before installing, it must know about the tray drier principle, construction, and working.
Tray Dryer Working Principle
The Working principle of a tray dryer is based on the process of convection drying. Convection drying involves the use of hot air to remove moisture from the material being dried. The hot air is circulated throughout the Heating chamber, and as it passes over the trays and trolley, it removes moisture / humidity from the materials on the trays. The temperature and humidity inside the chamber are controlled to ensure that the materials are dried at the appropriate rate. in short; hot air is continuously calculated inside the chamber, and forced convection heating takes place to remove moisture from the solid spread in trays.
Construction of Tray Dryer
The construction of a tray dryer is consists of a rectangular chamber whose walls are insulated. Trays are placed inside the heating chamber. The number of trays may vary with the size of the dryer. Dryers of laboratory size may contain a minimum of three trays, whereas dryers of industry size may contain more than 20 trays. Each tray is rectangular or square and about 1.2 to 2.4 metres square in area. Trays are usually loaded from 10.0 to 100.0 MM deep. The distance between the bottom of the upper tray and the (upper) surface of the substance loaded in the subsequent tray must be 40.0 MM.
Alternately the trays can be placed in trucks on wheels, which can be rolled into and out of the chamber. Two such trucks can be arranged inside the dryer. The dryer is fitted with a fan for circulating air over the trays. Electrically heated elements are provided inside (rather than outside) to heat the air (steam also can be used as it is cheaper). In the corner of the chamber, direction vanes are placed to direct air in the expected path.