Fast fluidization and dense suspension upflow

If the superficial gas velocity is increased further than required for turbulent fluidization, a point is reached where particle 

The minimum superficial velocity for fest fluidization can be predicted as 

The radial variation of voidage at any height z can then be estimated [28] by 

The downward velocity at the wall is typically of order 1-2 m/s and has been correlated [29] by the simple empirical expression 

The net upward flux of particles averaged over the column cross section is typically 20-200 kg/m s in this fast fluidization flow regime. 

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Figure 4 Transitions between dense suspension upflow, fast fluidization, and pneumatic transport with increasing solids circulation flux at a constant gas velocity.

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