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A tray dryer is a conductive drying equipment with enclosed insulating chambers and trays placed on top of each other on trolleys. Dryers are used in processes where drying and heating are an important part of the industrial production process such as food products, pharmaceuticals, dyestuffs and chemical manufacturing among others. Drying materials are either solid or wet and placed on trays.
Heat is transferred by circulating hot air through the trays by a radiator coil or a stream of electric heaters. Heat transfer, as well as proper circulation of heat, is facilitated by the installed blower fan. In addition, the equipment has a control panel to control the temperature as well as other parameters fixed outside the equipment and help in its functioning.
The basic working principle of this incredible machine is the continuous circulation of hot air. In tray dryers, moisture is removed from solids placed in trays by forced convection heating. Removal of moist air is carried out partially but in a simultaneous fashion.
Initially, the wet solids are loaded into trays and the trays are placed in the dryer chamber. Then there is the introduction of fresh air through the inlet, the air passes through the heater where it is heated.
The purpose of heating is to ensure that the heated air reaches the wet solids in the tray, therefore, tray dryer fans are used to circulate the hot air at speeds of two to five meters per second. Turbulent air flow reduces the atmospheric partial vapor pressure and the thickness of air boundary layers.
Hot air lifts water. During evaporation of water from the surface, water diffuses from the interior of the solid by capillary action. All the phenomena mentioned above occur in a single pass of air. There is a short contact time and a small amount of water is picked up in a single pass and as a result, 80 to 90 percent of the discharge air is recirculated through the fan and a maximum of 20 percent is fresh. Air is introduced.
Moisture discharge occurs through the outlet. Therefore, uniform air flow and constant temperature can be maintained over the solids to achieve uniform dryness. If the drying materials are wet granules such as in capsule or tablet drying, drying is continued until the desired moisture content is obtained. After the drying process is completed, the drying trucks or trays are taken out of the chamber and taken to the tray dumping station.
Overall, large work space, solid construction, controlled temperature, uniform air circulation are the key principles of tray dryer performance. It has an admirable and delicate ability to aid drying of plastic and chemical powders, electrodes, bakery, food, among other equipment.
