Vacuum Tray Dryer (VTD) is Batch Process Drying system used for drying hygroscopic substances, which are dried to very low residual moisture content level. The Vacuum Tray Dryer consists of heating shelfs mounted one above the other on which product is placed in trays. The medium of heating is hot water, steam or thermic fluid oil flowing through the shelfs. The cabinet is evacuated by vacuum pump oil ring or ejector type for high vacuum requirements. The drying time depends on product material and quantity of product in trays.The drying takes from 4-6 hours to 1 to 2 days. Vacuum Tray Dryer are used to for drying lumpy, glutinous products or products of low pomposity without decolourization.
The dimensioning of the vacuum system is an important factor in the design of drying cabinet systems. If for example vigorous foaming of product is desired and, evacuation to operational vacuum level must take place very quickly vapors produced during drying are taken out direct, or via a steam jet compressor to a surface condenser in which the vapors condensate. The non- condemnable vapors are extracted by the vacuum system. On completion of the drying, the product can be cooled by circulating of cooled water through plates.
