Transition to pulsing flow in trickle‐bed reactors studied using MRI

Abstract

AbstractUltrafast magnetic resonance imaging (MRI) is used to provide two‐dimensional (2‐D) images of gas‐liquid distribution within trickle‐bed reactors with data acquisition times of 20 and 40 ms. Gas‐water, cocurrent downflow through a fixed bed of cylindrical porous pellets of length and dia. 3 mm, packed within a 43 mm internal dia. column, was studied in both the trickle‐ and pulsing‐flow regimes. Superficial gas velocities in the range 50–345 mm s−1 (0.06–0.42 kg m−2 s−1), and superficial liquid velocities in the range 0.4–13.3 mm s−1 (0.4–13.3 kg m−2 s−1) were used. MRI is used to investigate the stability of the gas‐liquid distribution in the trickle‐ and pulsing‐flow regimes. At the onset of the transition to pulsing flow, local pulsing, at the length‐scale of the size of the packing elements is observed within the bed. Increasing liquid velocity causes an increase in the number of these local pulses until a velocity is reached at which the system transforms to the rapidly‐changing gas‐liquid distribution typical of pulsing flow. © 2005 American Institute of Chemical Engineers AIChE J, 51: 615–621, 2005