Impact of plenum conditions and gas-liquid distributor on bubble column hydrodynamics

In an LC-Fining (TM) hydroprocessor, the orientation of the free surface in the plenum chamber and the efficiency of the internal gas-liquid separator impact the amounts of the gas and the liquid passing through individual bubble cap risers in the grid. Various gas and liquid flowrates were thus passed through a single bubble cap riser to determine resulting bubble properties. Bubble sizes correlated well with energy dissipation rate and gas-to-liquid velocity ratio to the power of -0.4 and 0.6, respectively, in agreement with theory on the turbulent breakup of dense dispersions. Bubbles were also influenced by the gas-liquid distributor geometry, where the bubble cap produced larger bubbles than a perforated plate. Finally, the size of bubbles sparged in the plenum marginally affected overall gas holdup, suggesting that a bubble cap distributor redesign should be prioritized over upstream gas introduction equipment to optimize the performance of the hydroprocessor. (C) 2019 Elsevier Ltd. All rights reserved.