Principle, Construction, Working of Fluidized Bed Dryer

Principle, Construction, Working of Fluidized Bed Dryer

A fluidized bed dryer (FBD) is well known and widely used equipment in pharmaceutical manufacturing. It is used in the granulation process to attain desired moisture levels in the granules or powders required for the perfect compression of tablet formulations.

Conventional FBDs include batch fluidized bed dryer, semi-continuous fluidized bed dryer, well-mixed continuous fluidized dryer, and plug flow fluidized bed dryer. The drying rate is higher and faster. Material remains free-flowing and uniform. Read in detail Principle, Construction, Working of Fluidized Bed Dryer.

Also Read: Freeze Dryer’s Principle Construction Working

Fluidized Bed Dryer Principle

The Fluidized bed dryer (FBD)  works on a principle of fluidization of the feed materials.

In this process, hot air is introduced at high pressure through a perforated bed of damp solid particulate.

However, the solid particles are blown-up and remain suspended in the air channel, If air is allowed to flow through a bed of solid material in the upward direction with a velocity higher than the settling rate of the patches.

Heat transfer is achieved by direct contact between the wet solid and hot gases.

The use of hot air to fluidize the bed increases the drying rate.

Fluidized Bed Dryer Construction

The fluidized bed dryer contains a stainless steel chamber having a removable perforated underside known as the bowl.

A typical Fluidized bed dryer (FBD) consists of the air handling unit, product vessel, exhaust filter, exhaust blower, control panel, air distribution plate, spray nozzle, and solution delivery.

The appropriate choice of distributor used during the drying process ensures even and stable fluidization.

The pressure drops across the distributor must be high enough to assure good and even fluidization.

Fluidized Bed Dryer Diagram

Fluidized Bed Dryer Working

Material to be dried is placed in the bowl-type vessel.

Air is introduced from the top and heated at the required temperature by the heaters.

The air is filtered through the filter and then passes through the bed of the material at the bottom.

The airflow is generated by the fans fitted at the top of the equipment.

The airflow rate and the operating temperature are adjusted by the control panel.

As the flow of air increases, the bed expands and particles of powder start to rise up in a turbulent motion.

Regular contact with air causes the material to dry.

The air leaving the FBD passes through the filter to collect the fine particles of the material.

FBD bags have a finger-like shape to increase the volume of the drying bed that helps to increase the drying rate and decrease the drying time.

The vaporized liquid is carried away by the drying gases. Sometimes to save energy, the exit gas is partially recycled.

Fluidized Bed Dryer Advantages

It takes a lower time to complete drying as compared to other dryers.

 Drying is achieved at a constant rate.

 Handling time is also short

 It’s available in different sizes with different drying capacities.

The equipment is simple and lesser labor costs are needed.

 More thermal effectiveness.

 Drying capacity is more than another dryer.

 It facilitates the drying of thermolabile substances since the contact time for drying is short.

It’s a batch type or continuous type process.

Fluidized Bed Dryer Disadvantages

Many organic powders develop electrostatic charges during drying. To avoid this efficient electrical grounding of the dryer is needed.

Chance of attrition of some materials resulting in the production of fines.

Fluidized Bed Dryer Applications

A fluidized bed dryer (FBD)  is used for drying and mixing powders and agglomeration of materials.

It is used in the granulation and coating of powders, granules, tablets, pellets, beads.

It is used as a fluidized bed reactor, for solids separation and for heat/mass transfer.

The modified FBDs are used in precision granulation, top spray granulation, spray drying granulation, and granulation coating. is used for drying and mixing powders and agglomeration of materials.

It is used in the granulation and coating of powders, granules, tablets, pellets, beads.

It is used as a fluidized bed reactor, for solids separation and for heat/mass transfer.

The modified FBDs are used in precision granulation, top spray granulation, spray drying granulation, and granulation coating.

Also Read: Freeze Dryer’s Principle Construction Working

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