When it comes to drying items like tablet and capsule manufacturing granules, the tray dryer is the most widely utilized dryer in the pharmaceutical business. The moisture content of granules produced by wet granulation must be regulated to a particular degree in order to render them appropriate for tablet formation.
In the pharmaceutical industries uses are there of various types of dryers such as for drying of wet granules there are fluid bed dryers and tray dryers etc. Fluid bed dryer is another type of dryer and the duration for drying in this equipment is comparatively lesser than a tray dryer. A tray dryer is one of the simplest forms of dryers one can come across and can be described as conventional.
Construction of Tray Dryer
The tray dryer is a separate chamber with fiberglass wool within that is made of two layers of stainless steel plates and is used to dry wet granules. The insolation helps to trap heat and dry and it retains heat within the tray dryer. Tray dryer is a vertical closed compartment where trays are one over the other but with some distance so as to enable hot air to pass over all the trays and dry the product.
Bowls and trays in this feeding system are made of stainless steel. In some dryer’s trays are slid in directly to the dryer while in other dryers there is a SS trolley which is used to carry all the trays loaded with product and this trolley is then placed in the tray dryer.
Principle of tray dryer
Fresh air from outside is processed and filtered and is heated by heaters which are fitted inside the dryer and a fan circulates all over the chamber and the moisture in the wet granules is absorbed by the process of capillary. Vapors in return air are exhausted through return duct to the outside environment.
10-20% of it is expelled out through exhaust to eliminate the moisture and other remaining is allowed to flow back into the room along with fresh air. The application of fans is to enable circulation of hot air evenly at a speed of 2-5 meters per second. This is done until the value of LOD that is expected by batch manufacturing record is obtained.
Types of Trays in a Tray dryer
- Plain bottom trays
- Perforated bottom trays
Plain Bottom trays
As for the bottom trays, mostly tray dryers have plain bottom trays. This type of trays allow air to pass over the product that is put inside the trays hence drying may not be the same as top side grains will dry first while the lower side granules take a longer time to dry. One of the frequently employed and normal practices is such that, the trays containing the product must be stirred after every 2 to 3 hours to ensure that it eases the drying process because the granules get shuffled.
The tray dryers are available in different sizes with reference to the number of trays like 24, 48, and 96 trays and the like.
Perforated bottom trays
Depending on the model, some tray dryers incorporate perforated bottom trays. Basically, the holes found on the bottom of the product help the hot air to pass through the product and in this process the drying is uniformly done.
Working of tray dryer
The wet granules are then transferred to trays of tray dryer after wet sieving of granules. Make sure that equal quantity of granules is filled in each trays for proper and even drying. For Tray dryer, after loading the granules in the tray, tray is placed in the trolley for the dryer or directly into the dryer. Similarly, all the trays after they have been loaded with the product are mounted as well too, this is Evenly so because; However, after that, all the trays which have the product loaded on them are put in place as well in the same manner, all the trays as after they have been loaded with the product are arranged too.
In case of separate tray carrying trolley, the trolley only is put inside the dryer. The trolley is wheeled so that its movement can be easily controlled. For continues process, some tray dryers have an extra trolley which can be fitted immediately after the removal of the first trolley if the same product is to be dried in two or three lots.
It conserves time because the second trolley can be filled with the second batch of product while the first batch is drying. Once the trays have been placed inside the dryer, close the door to the tray dryer. There are types that have one door while others have two doors for loading the trays in and out. The gas kit is situated at the door since it becomes a great source of leakage of hot air.
After exact sealing of door turn on the fan and heating system of the tray dryer located at backside. From the heaters air of outside is passed and permits to enter in the dryer by the help of fan and then moisture is removed from the product.
Once required LOD is attained then the product is taken out from trays and it is put in containers and goes to the next process of granulation which is sieving the dry granules to have granules of accurate size.
For Organic Solvents
If organic solvent like Isopropyl Alcohol or IPA is used for granulation first of all the fresh air must be circulated for 10-15 minute to remove the fumes of IPA from product to outside as IPA is flammable and direct heating can lead to an explosion. The material of construction for the tray dryer should be such that it does not cause an explosion, the tray dryer should hence be flame proof.
For Water-based Binder
In wet granulation if water is used then after placing the trays in tray dryer and closing the door, the feed temperature is maintained higher level in the beginning. The temperature that can be employed in tray dryers ranges between 0 degrees and one hundred degrees centigrade. The heat is regulated by the temperature controller which is fitted outside the structure of the dryer.
Kerone, a leading company in the field, specializes in designing and manufacturing high-quality drying solutions tailored to meet the stringent requirements of the pharmaceutical sector. With a commitment to innovation and reliability, Kerone’s Tray Dryers ensure optimal performance, helping pharmaceutical companies achieve consistent product quality and efficiency.
