Effect of column inclination and oscillation on liquid spreading in a trickle bed

Gas-liquid-solid flow in a trickle bed installed on a floating production unit is affected by oscillations imparted by sea waves. The oscillations may affect the spreading of liquid, and in turn, the performance of a reactor. The present work investigates the effect of bed inclination and two types of oscillations (roll and roll + pitch) on the spreading of liquid in a cylindrical trickle bed with a single point liquid injection by using computational fluid dynamics. In the simulations, column tilt varied in a range of 0-15 degrees and three oscillation frequencies (0.1, 0.2 and 0.5 Hz) were considered. Initially, a three-phase Eulerian model was validated using the published experimental data for a stationary column. The effect of closure models such as capillary pressure model and Ergun drag model constants on predictions was analyzed for the selection of these closures. In a tilted column, liquid was pushed to flow in the direction of tilt. Increase in tilt angle from 0 to 15 degrees resulted in increase in the flow segregation and similar to 20% reduction in pressure drop. Oscillations (both roll and roll + pitch) resulted in more uniform liquid spreading and higher liquid holdup compared to a vertical column. With decrease in oscillation frequency, the index of uniformity in the radial liquid distribution further increased. The higher uniformity and liquid holdup caused by oscillations can be attributed to higher radial velocity of liquid due to the effect of gravity in the radial direction. Compared to the roll type oscillations, the roll + pitch type resulted in higher radial velocity and radial distribution of liquid. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.