Fluidized Bed

When a known amount of solid particles behaves like fluid in the holding vessel it is referred as fluidized bed. This happens when a pressurized fluid is pumped all the way through the solid particulate medium. The normal fluids will behave in its own way and has its own and specific characteristics as a result. The fluid can flow very easily under the gravitational force or it can even be pumped with the aid of fluid technologies. This is referred as fluidization. The fluidized beds can be used for a variety of purposes for instance as a type of chemical reactors called fluidized bed reactor or fluidized bed combustion or as fluid catalytic cracking. It may be either by transfer of heat or mass or intense modification when a coating is over the solid particles. The first fluidized bed was designed by von Winkler in the ear 1922 for coal gasification process.

Properties of Fluidized Bed:

• Fluid solid can behave as fluid particles
• Fluidized bed upper end has hydrostatic behavior
• Has single bulk density because of inhomogeneous mixtures of fluid and solid in the holding vessel
• Particle with more density sinks
• Particle with less density floats
• Exhibit Archimedes principle on the aspect of fluid behavior
• Density can be altered by changing the fraction of fluid
• Has good heat transfer inside the fluidized bed
• Homogeneous temperature is maintained

Types of Fluidized Bed:

Following are types of fluidized bed.

• Bubbling bed or stationary bed
• Circulating bed
• Vibratory fluidized bed

Based on the flow behavior they are classified as follows

• Slugging bed
• Channeling bed
• Boiling bed
• Spouting bed

Applications of Fluidized Bed:

• Increase the speed of freezing in Individually Quick Frozen (IQF) tunnel freezers
• Helps in cryogenic
• Helps in vapor compression refrigeration

Questions:

• What is fluidized bed?
• What are types of fluidized bed?
• Describe designing of fluidized bed reactor?