Vacuum tray Dryer

Sigma mixer

Vacuum tray Dryer Machine

Vacuum Tray Dryer

Vacuum Tray Dryer works under vacuum conditions on the conduction principle. Inside the dryer are several shelves having trays on which the products are placed. The top most shelf is a dummy shelf placed there to ensure proper heating and to prevent the dried powder from escaping into the solvent extraction system. The shelves are constructed hollow with baffles cum stiffeners placed in between shelves. Every shelf has an inlet and outlet nozzle and is connected to an inlet and outlet header through these nozzles.

A hot medium reaches the shelf through the inlet header and flows through the shelves in a uniformly zig-zag pattern ensuring faster heat transfer to the surface. This in tam heats up the trays on the shelves. The hot medium flows out from the shelf through the outlet header.

The inlet and outlet headers are designed in such a way that the now of the heating medium is equally distributed into each of the shelves. The dryer chamber is constructed from heavy-duty plates to prevent the plates from buckling during th vacuum operation. Additional limpet coils are provided in order to further stiffen the body and to pass on the hot medium. The chamber is provided with a heavy door and adequate locking arrangement. The dryer chamber is connected to a shell & tube by means of a vapour column to a Heat Exchanger. This in turn is connected to a condensate receiver.

Vacuum is applied to the condensate receiver. Vapour evolved during the drying process collects in the receiver after it is cooled in the heat exchanger. The vapour to be cooled is passed through the tube side of the Heat Exchanger, while cooling water is passed through the shell side. A cooling coil in the condensate receiver cools any vapours entering the receiver before it goes into the vacuum pump. The condensate receiver is connected to a vacuum trap to make sure that any uncooled vapours from the receiver get trapped thus minimising the vapour content entering the vacuum pump.

Main Technical Parameters

Model VTD -6 VTD – 12 VTD – 24
Chamber Inner Size 1100L × 620W × 1190H 1100L × 1020W × 1190H 1100L × 1420W × 1190H
External Size In Mm 1300L × 900W × 1700H 1300L × 1300W × 1700H 1300L × 1700W × 1700H
Layer Of Backing Self 6 6 6
Size Of Backing Tray In Mm 400 × 800 × 40 (H) 400 × 800 × 40 (H) 400 × 800 × 40 (H)
No. Of Backing Tray 6 12 24
No. Of Dummy Shelf 1 1 1
No. Of Tray Per Self 1 2 3
Permitted Pressure Inside Pipe & Shelf – Kg / Cm² 4 4 4
Temperature Inside Chamber – ˚C ≤ 150 ≤ 150 ≤ 150
Vacuum Level Inside Chamber Without Load – Mm Hg 710 710 710

Vacuum Tray Dryer is used mainly for drying of high grade, temperature and oxygen sensitive products. Vacuum Tray Dryer is highly suitable for drying hygroscopic substances, which are dried to very low residual moisture, content level. Frequently vacuum drying cabinets are the sole possibility for drying lumpy, glutinous products or products of low pomposity. Vacuum Tray dryer is the most commonly used batch dryer. They are box-shaped and loaded and unloaded via a door. Inside are several heating plates mounted one above the other on which the product is placed in trays. The bottoms of both heating plates and trays should be as smooth as possible to permit optimal heat transfer between plates and product. The medium flowing through the heating plates is water, steam or thermal oil. Vacuum Tray Dryer The distance between the heating plates is determined primarily by the surface loading and thefoaming of the product. To avoid 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 is 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 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 dimensioning of the vacuum system is an important factor in the design of drying cabinet systems. If for example vigorous foaming of the product is desired, evacuation to the operational vacuum level must take place very quickly. Vapours produced during drying are taken out direct, or via a steam jet compressor to a surface condenser in which the vapours condensate. The non-condensable vapours are extracted by the vacuum system. On completion of the drying, the product can be cooled by circulating of cooling water through the heating plates. Often vacuum drying cabinets are supplied to new, small production operations in newly opened markets. Following successful development of the market, it could be worthwhile to replace the cabinets through continuous vacuum belt type dryers.

*Specification can be changed as per customers requirements

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