FBD is an abbreviation for a fluidized bed dryer or fluid bed dryer. It is one of the most commonly used dryers in pharmaceutical industries for drying the granules manufactured by the wet granulation process.
If you are not familiar with the working, components and different parts of the fluid bed dryer then must read the article provided in the following link because in the current article we will only discuss the AHU of fluid bed dryer.
What is AHU?
AHU is the abbreviation of air handling unit and it is used to process the environmental air.AHU is also the most important component of the heating, ventilation and air conditioning system, where it is used to clean & process the environmental air.
Why to use AHU for FBD
We are familiar, a fluid bed dryer works on the principle of fluidization where it takes fresh air from the environment and this air comes in direct contact with our product. As the incoming air which is taken from the environment comes in direct contact with our pharmaceutical product so it must be free from contaminants including particulate and microbial contamination.
To ensure our incoming air is free from contaminants and microbes the air handling unit is installed with the fluid bed dryer which processes the air, where our environmental air after processing is passed through the HEPA filter and then this air is supplied to the fluid bed dryer for drying.
How it works
An air handling unit is installed at the start of the inlet air duct of the fluid bed dryer meaning it is present at the point from where air comes inside the fluid bed dryer.
The environmental air first of all passes through the air handling unit and then it is supplied through the inlet air duct to the fluid bed dryer.
What happens to the air when it passes through the air handling unit?
To remove the air contaminants different types of the filters are installed in the air handling unit including pre filters,bag filters and HEPA filters.
The air taken from outside is first filtered through the pre filters and after passing through the pre filters the air passes through the bag filters.
The pre-filters and bag filters remove maximum contaminants from the air & then the air passes through the cooling coil.The excessive moisture present in the air is removed due to the cooling effect and then this air passes through the heating coil.
The heating coil is used to heat the air at the temperature which is required for the drying of the product.
After filtration and heating the air, the hot air is now free from large-size particles to ensure the removal of microbes and small particles the air is passed through the HEPA filters.
After passing through the HEPA filter, now our air is clean and it is delivered to the product trolley where it comes in direct contact with the product and dry the product till required level of LOD.
The air after drying leaves the drying chamber.The air leaves the drying chamber after passing through a finger bag filter and this air is exhausted out to the environment.
Note
In some pharmaceutical industries the air handling unit is not installed along the fluid bed dryer.This practice is wrong as the air directly taken from the environment come in contact with the product which may result in contamination so always install an air handling unit for the processing of air which is supplied to the fluid bed dryer.
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