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Fluidized bed dryer (FBD): Principle, Working, Troubleshooting, and Components

Fluidized bed dryer (also known as fluid bed dryers) are commonly used in the pharmaceutical industry to reduce the moisture content of pharmaceutical particles and granules.


FBD (fluidized Bed dryer) works on the fluidization principle. A high-pressure Hot air from the supply is passed through the perforated container containing a wet mass of the granules, after some time granules, particles started to suspend in the air to become dry (called (fluidized state), the process is called fluidization.

Working of Fluidized bed dryer

Hot air is injected at high pressure through a perforated bed of moist solid particles to get a velocity greater than the settling velocity of the particles in the fluidization process. The moist solids are raised from the bottom of the bucket and suspended in an air stream (fluidized state). the hot air around the solid particles reduces the moisture content of the particles to achieve the desired drying, also refer as a loss on drying (LOD). The drying vapors carry the vaporized liquid away. Leaving gas is sometimes somewhat recycled to preserve energy.

(FBD) Diagram

Fluidized bed dryer (FBD Diagram)
Diagram of Fluidized-bed dryer

Components of Fluidized-bed dryer

  1. Body Stainless steel
  2. Inlets Filters
  3. Air preparatory unit.
  4. Product container or Bowl.
  5. Expension chamber
  6. Exhaust filter.
  7. Exhaust blower.
  8. Control panel (MMI).
  9. Air distribution plate.
  10. FBD bags (Finger Bags)
  11. plenum
  12. Gaskets

Advantages of FBD

  1. Excellent gas-particle constant results in strong heat and mass transfer rates, resulting in high moisture removal rates.
  2. If part of the thermal energy for drying is supplied by the internal heat exchanger, high thermal efficiency is usually achieved.
  3. Lower initial and ongoing costs
  4. Drying contact time is reduced.
  5. Stability and easy to control.

Disadvantage of FBD

  1. Considerable pressure drops are caused by the necessity to suspend the entire bed in gas, resulting in high energy usage.
  2. Increased gas handling is required due to substantial exhaust gas recirculation for high thermal efficiency operation.
  3. Inadequate fluidization and flexibility, particularly if the feed is overly wet.
  4. When organic solvents must be eliminated during drying, this is not the best equipment to use.
  5. For certain types of fluidized bed dryers, product quality is non-uniform.
  6. Fine particle entertainment is number six.
  1. There is a high risk of attrition and, in some situations, fine particle aggregation.
  2. When processing poisonous or flammable substances, traditional hot air fluidized bed dryers are not a good solution since there is a risk of fire or explosion if flammability limitations are exceeded.

Troubleshooting In FBD and Remedies:

Accidental Blast in FBD: Sometimes FBD outlets filter may clog. so it may create high pressure inside the chamber.

Remedies: clean the filter as per the given frequency or during batch changeover cleaning. check the pressure gradient in the manometer or alarm during the process.

FBD Broken Begs: sometimes begs may break leads to flow powder outside from the duct.

Remedies: To overcome this problem Solid flow monitor (SFM) Test is to be conducted on a frequency basis.

Electrostatic charge: Sometimes electrostatic charge may develop leads to the burning of powder.

Remedies: Do the proper earthing of equipment in use.

What is the endpoint of FBD?

The endpoint in FBD is calculated by using Loss on drying (LOD) Methods

What is the full form of FBD?

The full form of FBD is (Fluid Bed Dryer)

What is the Difference Between FBD and FBP?

FBD is used for only drying and, FBP is used for Granulation, Drying, Agglomeration, and Coating Process.

What is the full form of FBP?

FBP stands for Fluid bed processor

What is the Preheating?

Preheating of granules is done before to prevent the granules from adhering to the bowl.

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