Fluidiserte

Fluidiserte, or fluidized, describes a state or bed of solid particles that has been converted into a fluid-like condition by forcing a gas or liquid upward through the bed at a sufficient velocity. When the superficial velocity reaches the minimum fluidization velocity, the particles are suspended and the bed expands, behaving like a cohesive fluid. The process relies on gas–solid interactions that produce high interfacial area and vigorous mixing.

In a fluidised bed, the gas flows through the particle layer, promoting excellent gas–solid contact, and enabling rapid heat and mass transfer. This makes fluidised beds versatile for a range of operations, including chemical reactions, drying, granulation, and coating of powders. The technology is also central to energy and materials processing, notably in fluidised bed combustion and gasification, where solid fuels or biomass burn within a bed that is kept suspended by an upward gas stream. Two common configurations are bubbling fluidized beds, which operate at lower gas velocities and form bubbles within the bed, and circulating fluidized beds, where particles are continuously carried out of the bed and recirculated for thorough mixing and heat transfer.

Advantages of fluidised beds include uniform temperature distribution, robust mixing, high heat transfer coefficients, and the ability to handle feed variations and a range of particle sizes. They also enable scalable, compact designs for reactors and dryers. Challenges involve entrainment and erosion of particles and equipment, defluidization risks, and the need for careful distributor design and control of gas velocity to prevent channeling or dead zones. Overall, fluidiserte systems are widely used in chemical engineering, mining, pharmaceuticals, and energy industries due to their efficient contact and versatile operation.