Probably the best pharmaceutical instrument, a tray dryer, is one of the most widely used equipment for tablet preparations. It is used for the best drying results in a standard process. A laboratory oven is the basic form of it that contains a cabinet with a heater at the bottom. It has a variety of applications like drying of sticky, granular, and crystalline materials. Plastic substances can also be dried in the tray dryer.
It is also helpful in wet mass preparation, pastes, and precipitation. Moreover, in the tray dyers, unrefined drugs, chemicals, powders, and tablet granules are also dried along with some types of equipment.
The Construction of a Tray Dryer System
The tray dryer consists of a chamber, which is double-walled with either a single door or two doors. The gap between the two walls is filled with a high-density fiberglass wool insulation material to elude heat transfer. Doors are furnished with a gasket and stainless steel trays are placed on movable trolleys. The distance between the bottom of the tray above and the substance in the lower tray must be 40 mm.
Electrically heated elements are present inside rather than outside to heat the air into steam. Hot air is regularly circulated and involuntary convection takes place to eliminate moisture from the substance in the tray along with removing moist air partially. The tray dryer is provided with control panel board, process timer, and digital temperature controller with an indicator.
A tray dryer is used where heating and drying are crucial steps in a manufacturing method in industries like chemical, pharmaceutical, food products, etc. The substance to be dried is either wet or solid. Heat transfer occurs by circulation of hot air generated by electric heaters or steam in radiator coils.
After wet solids are loaded onto the tray and the trays are placed in the chamber, fresh air is introduced through the inlet that passes through the heaters. This hot air is circulated by means of fans at 2 to 5 meters per second. Unstable flow reduces the partial vapour pressure in the atmosphere and eases the thickness of the air boundary layer. The water is picked up by the air and as the water evaporates from the surface, it diffuses from the interior of the solids by capillary action.
This occurs in a single pass of air and thus the time of contact is short and the amount of water picked up is small. Therefore, the discharged air is circulated back through the fans and only 10-20% of fresh air is introduced. Moist air is removed through the outlet and thus a constant temperature, and uniform airflow is maintained. In case of wet granules in capsules, drying is continued until the desired moisture content is achieved. A control panel installed outside controls the temperature and other parameters.
The tray dryer is normally available with a choice of heating modes like electrically heated, steam heated, and thermic fluid heater. Consistent airflow, regulated temperature, robust structure, and large working space are the valuables of great tray dryers exporters, which should be appropriately designed to cover wide temperature range and efficient loading and unloading.
The use of tray dryers can help in batch-wise operation, which are advantageous as each batch can be handled as a separate unit. In addition, in the tray dryers, the handling of the materials, loading, and unloading can be done without any losses. Moreover, it is readily adjusted for drying a wide variety of materials and the valuable products are handled efficiently.