fluidised bed process

The fluidised bed process is a fundamental process engineering technique for the treatment of solids. In this process, particles are fluidised by a gas stream flowing from the bottom upwards, causing them to enter a suspended, fluid-like state. The particles move freely and exhibit intensive mixing behaviour.

The term ‘fluidised bed process’ does not describe a single process, but rather a whole class of process technologies. It encompasses all processes that can take place within a fluidised bed. These include thermal, chemical and physical treatment processes. Fluidisation begins when the gas flow counterbalances the weight of the particle bed. From this point onwards, the solid bed behaves similarly to a boiling liquid. Heat and mass transfer are then particularly intense and uniform. The fluidised bed process is used in many industries. Typical applications include drying, cooling, heating, coating, agglomeration and chemical reactions. Furthermore, the process plays an important role in high-temperature processes. These include high-efficiency heat generation through combustion, fluidised bed combustion, and waste incineration.

A key advantage of the fluidised bed process is that all particles are treated uniformly. Differences in temperature and concentration are minimised. At the same time, large amounts of heat can be generated or transferred efficiently. When designing a fluidised bed process, particle properties, gas velocity, bed height and flow regime must be taken into account. Depending on the operating conditions, a distinction is made between 

• Feast-bed 
• Minimum fluidisation
• bubble-forming fluidised bed
• turbulent fluidised bed