Tray dryers are used to dry wet solid materials like pharmaceuticals and chemicals. They consist of rectangular chambers containing racks that hold shallow trays loaded with the wet material. Heated air is circulated between the trays by fans and vents out moist air while pulling in fresh air. The trays are loaded with wet material and the heated air picks up water as it passes through in a single pass. Once dried, the trays or racks are removed and the dried material unloaded. Tray dryers are useful for small batch production of valuable materials but require more labor and have longer drying cycles than other dryers.

1. TRAY DRYER

2. Content
1. About Tray Dryer
2. Construction of Tray dryer
3. Working of Tray Dryer
4. Advantages
5. Disadvantages
6. References

3. About Tray Dryer
Tray dryer is the device which is used for drying of the wet
products of the crude drugs, chemicals, powders or the granules
etc.
The material which needs to agitate, are not dried in tray dryer.

4. Construction of Tray Dryer
1. It consist of rectangular chamber of sheet
metal containing two trucks that support
racks H.
2. Each rack carries a number of shallow trays,
perhaps 750 mm2 and 50 to 150 mm deep,
that are loaded with material to be dried.
3. Heated air is circulated at 2 to 5 m/s b/w the
trays by fan C and motor D and passes over
heaters E.
4. Baffles G distribute the air uniformly over
the stack of trays.
5. Some moist air is continuously vented
through exhaust duct B; make up fresh air
enters through inlet A.
6. The racks are mounted on truck wheel I, so
that the end of the drying cycle the truck can
be pulled out of the chamber and taken to a
tray-dumping station.

5. Working Of Tray Dryer
1. Wet solid is loaded in to the trays and Trays are placed in the chamber.
2. Fresh air is introduced through inlet, which passes through the heaters and gets heated up.
3. The hot air is circulated by means of fans and then water is picked up by the air.
4. These events occur in a single pass of air. The time of contact is short and amount of water
picked up in a single pass is small.
5. At the end of the drying trays or trucks are pulled out of the chamber and taken to a tray
dumping station.

6. Advantages
1. Tray dryer are very useful when the production rate is small.
2. They find most frequent application for valuable products like dyes and pharmaceuticals.
3. In the tray dryers the handling of the materials, loading and unloading of the materials can be done
without losses.
4. Energy saving is significant.

7. Disadvantages
1. Tray dryers requires more labour to load and unload, hence increases in the cost.
2. They are expensive to operate.
3. Drying by circulation of air across stationary layer of solid is slow, and drying cycles are long : 3 to
48hour per batch.

8. Conclusion
Tray drier is used industrially in large as well as in small
operations for drying the desired feed material for
fulfilling our aspects.

9. References
1. http://www.pharmainfo.net/book/pharmaceutical-machines/tray-dryer
2. Unit operations of chemical engineering (By Warren L. McCabe ,Julian C. Smith and Peter Harriott
)/Drying of solid/Drying equipment/tray dryers