Instability of uniform fluidization

- Fluidization above a multi-orifices distributor is treated as a parallel system.
- Total solids pressure loading is introduced as the independent variable.
- Boundary between uniformity and mal-distribution is detected by stability analysis.
- Criterion for N parallel paths is simplified with the help of Hessian matrix test.
- A phase diagram indicating effects of various parameters on uniformity is provided.

Uniform gas solids distribution should be ensured to gain sufficient performance of fluidized beds. The highly chaotic entropy dissipation across solids bed will trigger non-uniform fluidization, although distributor plays an important role in obtaining homogenous gas stream. Hence, total solids pressure loading (ΦT), the pressure drop ratio between solids bed and distributor, is introduced here to present their interaction. The boundary between uniform and non-uniform fluidization can be detected by stability analysis based on Prigogine's minimum of entropy production principle, and this criterion for N parallel paths can be simplified into calculating the second derivative of pressure drop through one path with respect of ΦT. Furthermore, a phase diagram, illustrating the effects from operational parameter (ΦT), geometrical characteristics of distributor (Cd) and property of solids (Ga) on instability of uniformity, is attained to draw some useful conclusions of robust uniform fluidization.

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