Product Description

Vacuum Tray Dryer is the most commonly used batch dryer. They are box-shaped and loaded and unloaded via a door (two doors on the larger models).

Working:
The medium flowing through the heating plates is water, steam or thermal oil. The distance between the heating plates is determined primarily by the surface loading and the foaming of the product. To void retrograde condensation the cabinet walls are indirectly preheated by the heating plates. Next, the product is introduced and heated at atmospheric pressure. Only after all individual product trays reach the same temperature the cabinet is evacuated and drying can start. The preheating phase is very important in order that the drying curve and the foaming of the product are identical throughout the cabinet. During the main drying phase, the vacuum is in the range of 40 to 80 mbar abs and in the final drying phase vacuums of only a few mbar abs are reached. Heating temperatures are normally in the range between 800C and 1100C. Depending on product and surface load, drying takes from a few hours to 1 to 2 days. For some products, the vacuum and temperature profiles are automatically controlled in order to prevent a pass over of the critical product temperature. The non-condensable vapors are extracted by the vacuum system. On completion of the drying, the product can be cooled by circulating cooling water through the heating plates.