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Working Principle of Fluid Bed Dryer

Fluid Bed Dryers have a single stage operation useful to convert solutions, suspensions, and slurries into dry powder. This is a high-speed process in controlled temperature which ensures its efficiency. This process has many different applications in several industries. It is useful in the chemical industry, pharmaceutical industry, food industry, dyestuff and several other processes.

Working Principle

The main principle behind the working of the fluid bed dryers is explained here. Air is allowed to flow through a bed of solid powdered material in an upward direction. This made so that the velocity is higher than the setting rate of all particles. When this happens all the solid particles will get blown up and be suspended in an air stream. The solid bed is thus converted into a boiling liquid which is known as the fluidized state. It is then possible to make use of hot air to help with the process of fluidising  the bed. This increases the drying rate of the material.

This machine consists of a stainless steel chamber with a removable perforated bottom; also known as a bowl. All the material that needs to be dried has to be placed in this bowl. The way it works, the air is introduced from the bottom of a bowl and heated to a set temperature by the heaters. Once the air is filtered with the help of a filter it is passed through the bed of the material. The constant airflow is as a result of the fans fitted at the top of the equipment. All parameters of the equipment like the rate of flow, operating temperature are adjustable with the help of a control panel.

This machine is known for its high drying rate since the material is dried in quick time. The materials are allowed to remain in a free-flowing state at all times. The bags used here have a finger-like structure which helps increase the surface area of the drying bed. This type of design helps increase the drying rate and decrease the drying time during the fluid bed drying process.

Fluid Bed Dryer

This machine can have some serious issues if it is not handled in the correct manner. Here are some of the common problems:

  • Development of an electrostatic charge in the particles.
  • Burning of material in the fluid-bed-dryer equipment.
  • Outlet filter blockage can potentially increase the pressure in the vessel resulting in an accident.
Common Applications of fluid bed dryers

Several powders are useful in the pharmaceutical industry; however, they lack uniformity, flow and are loosely packed and hence do not work well with other applications. The process of granulation involves aggregating various primary powder materials to form larger granules with greater density and better flow-ability and uniformity. This is where the fluid bed dryer are useful. It is possible to combine a it with a granulation system to ensure operations like drying, mixing, finishing, granulation, and cooling are completed during the same cycle.

Thus fluid bed drying technology has become invaluable to the pharmaceutical industry and is quickly replacing traditional methods of drying products in trays. This has helped reduce the drying times and help maintain uniform drying condition. The other advantage of using a fluid bed dryer system is that the Inlet air temperature can be controlled to ensure the correct amount of moisture evaporates from the surface of the granules.



The fluid bed dryers have several applications. It is useful in drying many different types of material like granules, fertilizers, powders, tablets, plastics. It is useful in many different types of process industries and other industries as listed here:

  • Chemical
  • Pharmaceutical
  • Food
  • Dairy
  • Metallurgical
  • Dyes