Gas solid fluidized bed is the most common solid-gas contractors in many processes like reactions, drying, coating and size separation. The unique heat & mass transfer capabilities between phases and robust mixing make fluidized bed a good candidate for many gas-solid processing units. In practical applications, they can operate in bubbling, turbulent, and fast fluidization. A combination of fast fludization bed with a downer bed creates a new model for solid-gas contact, named circulating fluidized bed, in which multiple operation can be integrated into one processing unit.
Fludized beds can operate as a size/density solid classifier, a heterogeneous reactor (catalytic), a polymerization reactor, a combustion reactor, a adsorber unit for hydrocarbons (VOCs), a chemical looping combustion system, a dryer, a granulator, and a coater. All these processes contain complex phenomena that occur simultaneously. Therefore, design and scale up of these beds require a deep understanding of all these phenomena. The first necessary step, is to understand the hydrodynamics of a fluidized bed; though it is not enough for a complete analysis of these units.
In this video you see an animation of a gas-solid fluidized bed operating at bubbling regime. Particles are sand (2500 kg/m3) with mean diameter of 275 micron. Superficial air velocity at atmospheric pressure and 288 K is 0.38 m/s. The simulation has been performed using OpenFOAM® 7 and visualized using Paraview®.
if you cannot see the video properly, click here.