(485g) The Transition to the Bubbly Flow Regime in Trickle Bed Reactors

Accurate characterization of flow regime transitions in trickle bed reactors is necessary because of the impact on reactor performance [1, 2]. While a significant number of studies have been reported in the literature for the trickle-pulsing transition, none are available which thoroughly evaluate the transition from trickle to bubbly flow that occurs at low gas and high liquid superficial velocity. In this work, the trickle-bubbly flow regime transition was characterized by standard deviation of pressure drop for a range of packing media. The effects of bed variables (particle size, shape, and void fraction) on the trickle to bubbly flow regime transition were evaluated along with the effect of liquid surface tension. For all cases, the liquid superficial velocity required for the trickle-bubbly transition was observed to be relatively independent of the gas superficial velocity. Literature models, defined originally for the trickle-pulse transition, were unable to predict this trend when extrapolated to low gas superficial velocities. A correlation for the trickle-bubbly transition is therefore proposed which accounts for the effects observed in this work.

References

[1] Wilhite, B.A.; Wu, R.; Huang, X.; McCready, M.J.; Varma, A. AIChE J. 2001, 47 (11) 2548.

[2] Al-Dahhan, M.H; Larachi, F.; Dudukovic, M.P.; Laurent, A. Ind. Eng. Chem. Res. 1997, 36 (8) 3292.