(331f) Periodically Pulsed Fluidized Beds – Taming a Complex System

By periodically pulsing the gas flow introduced to bubbling fluidized beds, remarkably regular bubble patterns may form within a certain range of frequencies (e.g., a few Hz for Geldart B particles) and amplitudes. This is observed in both quasi-2D and 3D fluidized beds. Viewed from the top, some of the 3D patterns are reminiscent of those formed in vibrated granular systems, and the regular ripples on dunes and beaches. However, they are conveyed to greater heights, which is especially clear in quasi-2D beds.

Fundamentally, such patterns could be used as a way to characterize a gas-solid system – and we suggest them as a method to test CFD codes. From a practical standpoint, pulsing has several advantages, such as the regular structuring of the bed (within a range of frequencies and amplitudes), which facilitates scale-up, as well as (more generally) avoiding channelling and making the hydrodynamics more uniform. This is particularly relevant when drying cohesive particles and for other processes for which local overheating would be a safety concern or detrimental to product quality.

References

M.-O. Coppens, M.A. Regelink and C.M. van den Bleek, World Conference in Particle Technology (2002).

M.-O. Coppens and J.R. van Ommen, Chem. Eng. J. 96, 117-124 (2003).

A. Akhavan, J.R. van Ommen, J. Nijenhuis, X.S. Wang, M.-O. Coppens and M. Rhodes, Ind. Eng. Chem. Res. 48, 302-309 (2009).

B. Hadi, J.R. van Ommen and M.-O. Coppens, Ind. Eng. Chem. Res. 51, 1713-1721 (2012).