Principle, Construction, Working, Uses, Merits and Demerits of Tray Dryer

Tray Dryer

Principle

Laboratory ovens are made up of cabinets with heaters at the bottom. These ovens have very little heat transfer and humidity control, so their values are very low. The circulation of forced hot air begins when we install a fan in an oven. Heat transfer is increased and local flour concentrations are reduced with this process. Heat is applied to the air, which is then oriented towards the object under controlled flow. Trays with tiers are used to disperse the material to be dried. Perforated screens in trays are lined with paper to allow air to circulate across the drying materials. As air passes over every shelf, a limited amount of heat is provided to induce vaporization. This type of dryer maintains both humidity and temperature properly.

Constructions

Steam or electricity can be used to heat a tray dryer. Depending on customer requirements, it comprises any number of trays. It includes a rigid frame constructed by angle iron with double-sided panels filled with the best compressed fiberglass insulation and a rigid door with strong hinges and an optimal locking system. Alternatively, hot air can be circulated with fans. An easy-to-operate control panel is located on the front of the oven. With a large functional space, it is constructed of mild steel, finished outside with synthetic enamel, and painted on the inside with heat resistant paint in order to withstand temperatures up to 300°C.

Working

In the pharmaceutical industry, tray dryers are widely used. The trays are used to dry materials. A side-by-side or base-by-side heater generates heat in the dryer. The other option is to use radiator coils that circulate heat using steam instead of hot air from the oven. The material to be dried is spread out on trays during the drying process. Heating air is circulated through the material. Flowing over the trays in controlled direction, it heats the material. There are three types of bases for trays: solid, perforated, and wire mesh. A paper lining could be used to reduce contamination risks from direct contact with trays. A dryer's efficiency depends on its ability to recirculate hot air. Furthermore, it is dependent on fresh air supply in addition to regular supply and presence of heated air. A fixed proportion of fresh air and heated air is combined for an efficient performance. In order to ensure uniform drying both at the bottom and at the top of a dryer, such regulated drying is essential. Insulation is provided by heating coils in addition to the double-walled construction.

Uses

• Chemicals and pharmaceuticals are two industries where tray dryers are used.
• Tray dryers are well suited to drying sticky materials, granular mass or crystallized materials, precipitates, and pastes.
• Agricultural drying has been made possible with its simple design and capacity to dry large quantities of products.

Merits

• Each batch is handled separately since it is operated in a batch mode.
• It is an energy-efficient dryer since it consumes less energy.
• Using and cleaning it is simple.
• The tray dryer can be customized to fit different sizes, which reduces the capital cost.
• External heating prevents condensation on chamber walls.
• It has a unique design with a single chamber or a multi chamber in which there is no leakage.
• The shelf and tray have excellent surface contact.
• Wet lumpy solids and wet cakes, for example, can be dried using this method in small-scale production.
• All connections are outside the chamber with a heavy-duty hollow shelf design.
• Controlling operating parameters is easier.
• When heat-sensitive materials need to be dried, vacuum systems can be most suitable.

Demerits

• The process is time-consuming because it runs at low to intermediate temperatures.
• Indirectly exposed solid particles make up only a fraction of the total. Neither heat nor mass is transferred efficiently.
• The dryer is not suitable for mass production.
• In the lower trays, the contents are prone to over-drying.
• As a result of the long cycle time (5 to 45 hours per batch) and high labor costs for loading and unloading, it is expensive to operate.
• It is also possible to dry plastic materials with this dryer.
• Thermolabile drugs, liquids, and slurries cannot be dried.

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