Principle and Working of Fluidized Bed Dryer (FBD)

Principle and Working of Fluidized Bed Dryer (FBD)

Fluidized bed dryer (FBD) is well known and widely used equipment in granulation area of pharmaceutical manufacturing. It is used in the granulation process for drying the material to get desired moisture content in the tablet formulation granules required for perfect compression of tablets.

The Principle of Fluidized Bed Dryer:

Working of FBD

If air is allowed to flow through a bed of solid powdered material in the upward direction with the velocity greater than the settling rate of the particles, the solid particles will be blown up and become suspended in the air stream.

At this stage, this solid bed looks like the boiling liquid, therefore this stage is called as fluidized. Use of hot air to fluidizing the bed will increase the drying rate of the material.

FBD contains a stainless steel chamber having a removable perforated bottom known as the bowl. Material to be dry is placed in this bowl. Air is introduced from the bottom of the bowl and heated at required temperature by the heaters.

This air is filtered through the filter and then passes through the bed of the material. This airflow is generated by the fans fitted at the top of the equipment. The flow rate and the operating temperature are adjusted by the control panel.

As the flow of air increases, the bed known as FBD bag expands and particles of powder start a turbulent motion. Due to the regular contact with air, the material gets dry. The air leaving the FBD passes through the filter to collect the fine particles of the material.

Fluidized bed dryer has a high drying rate and the material is dried in a very short time. Material remains free-flowing and uniform. FBD bags are finger-like in structure to increase the surface area of the drying bed that helps to increase the drying rate and decrease the drying time during the fluidized bed drying process.

How does a Fluid Bed Dryer work for Drying Applications?

A fluid bed dryer is a kind of equipment which can be used for applications like drying of powders, mixing of powders and agglomeration. This is efficiently employed for applications in chemical, pharmaceutical, dyetuff, foodstuff, dairy and various other process industries. Fluid bed dryers are often employed with the spray dryers and granulation systems for effective drying, mixing, granualtion, finishing and cooling of powdered substances. These are often preferred over rotary dryers for drying and cooling a wide range of polymer materials which require precise control of residence time and temperature for effective processing.

Fluid-Bed GranulatorFG5FG15FG30FG60FG120FG200FG300FG500
Materials Bowl VolumeL224510025042067010601500
Production capacityKg/batch5153060120200300500
Compressed airPressureMpa0.45~0.6
Fan powerKw5.57.51118.518.5304555
Outline dimensionsWmm820870120014601650189020902300

Fluid bed Granulator / Fluid bed dryer / Fluid Bed Processor / combo / Multi Purpose available range from 20 kg to 1000 kegs batch size.


Machine General Layout for Fluid bed Coater/ Processor / Multipurpose


Lab Model Fluid Bed Coater / Processor / Fluid bed dryer – 2 kg to 20 kg batch sizes.


Fluid Bed Coater(Bottom Spray) 60 /120/ 250/ 500 kegs batch size.


Rapid Mixer Granulator / High Speed Mixer and Granulator / High Shear Mixer Granulator



Fluid bed dryer works on a principle of fluidization of the materials. In fluidization process, hot air or gas flow is introduced through the bed of solid particulates. This gas or air will move upwards through the spaces between the particles. As the velocity increases, upward drag forces on the particles increase and at a stage become equal to the gravitational forces beneath. Hence the bed is said to be fluidized and the particles are suspended in the fluid.

There are various advantages of fluid bed dryer in pharmaceutical industries. Some of them are as follows.

Advantages of Fluid Bed Dryer

  • High thermal efficiency is achieved when the thermal energy is supplied by internal heat exchanger
  • Low Capital Cost
  • Ease of Maintenance and Control
  • High Heat and Mass Transfer Rates

In a fluid bed dryer used for powder drying, initially the air is sucked inside from the surroundings with a fan run with electric motor inside the dryer. The air then passes through heating system within the dryer and gets heated up. This hot drying air is then made to flow through bed of the moist materials that are laid on shaking perforated steel bed. This air is introduced with required velocity and temperature that the bed gets fluidized allowing intimate contact of each particle with the air. As the bed vibrates or shakes, the particles in the bed are carried forward slowly along the length of the dryer. All the moisture present in particles get sucked by the hot air which then escapes into the dust recovery system and is recycled for the further use in process. The velocity and temperature of air can be controlled as the particles pass on the bed and hence very wet to sticky materials can also be dried with a fluid bed dryer effectively. The dried material is then fed into the cooling zone where cool air reduces the temperature of the material to the required state.

Therefore in this way product or powder drying can be efficiently achieved with the help of a fluid bed dryer.

Buying Fluid Bed Dryers for efficient Drying Processes

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