Difference between tray dryer and vacuum tray dryer

Tray Dryer

Tray and tunnel dryers and spray, roller, and freeze dryers are all utilised in the food drying process. Drying wet chemicals, powders, and crude pharmaceuticals is a breeze using tray dryers.

A simple tray dryer is a box-shaped cabinet with shelves stacked one on top of the other with a series of trays. Unlike an oven, which may include a heater in the cabinet’s base or on the walls, a tray drier gets its heat from circulating warm air. The heated air is blown over the trays by one or more fans.

The greatest tray dryers are those that allow you to adjust the airflow to the trays. On top of the trays, which may be linked with paper, the materials to be dried are spread out. Disposable papers are used as tray liners to reduce cleaning time and avoid contamination. The trays are frequently supported by wire mesh or perforated steel tiers.

The latest tray dryers use strategically placed deflectors to drive air from one tray to pass over the tray above in the opposite direction, achieving equal temperature throughout a well-insulated cabinet.

Air flowing in opposite directions across the trays maintains flow uniformity and helps to maintain a consistent temperature. Before passing from one shelf to the next, the air can also be reheated. Each shelf loses some heat as air goes through it (the latent heat of vaporisation of the water that is expelled from the solid material).

In a tray drier, hot air circulates continually, removing moisture from the material in the trays using forced convection. Moisture-laden air is ejected from the cabinet and vented at the same time.

After wet granulation, drying is often utilised. This is the process of breaking down a tablet mix into granules by turning it into a paste with water. In the tabletting process, granulation can improve the material’s uniformity and flowability.


  • Sticky materials are dried using this.
  • Drying of crystalline or granular materials is possible.
  • Drying can be done with wet mass, paste, powders, and chemicals.
  • Tray dryers can be used to dry a variety of tiny equipment.

Vacuum Tray Dryer

A vacuum tray dryer is primarily used to dry high-quality, temperature-sensitive, and oxygen-sensitive items. It’s ideal for drying hygroscopic materials with very low residual moisture. When it comes to lumpy, sticky, or low-porosity products, vacuum drying cabinets are frequently the only option.

  • A vacuum dryer is shaped like a box into which trays are loaded and unloaded through a door with a vacuum seal around the edges, similar to a regular tray drier. The trays are placed on top of numerous heating plates that are stacked one on top of the other.
  • Because the trays are placed directly on the heating plates, their surfaces should be as smooth as possible to allow for efficient heat transfer.
  • The heat required for drying is provided by hot water, steam, or oil flowing inside the heating plates.
  • The circulating fluid may also be used to heat the cabinet walls to prevent water condensation. 
  • The heating plates heat the water indirectly. The heating plates provide indirect preheating. The dryer is pre-heated at atmospheric pressure before being loaded with materials.
  •  The cabinet is emptied and drying begins only after all individual product trays have reached the same temperature.

A vacuum dryer’s heating temperatures can be substantially greater than those of an air dryer, ranging between 800°C and 1100°C. Temperature and vacuum profiles can be programmed automatically in some systems. Promas Engineers are one of the top-rated vacuum tray dryer manufacturers in India. 

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