Influence of Sparger Design on Local Phase Volume Fraction Distribution in a Slurry Bubble Column: ERT Measurements and Eulerian CFD Simulations

Gas-liquid-solid bubble column reactors (SBCRs) are used to perform solid-catalysed gas-liquid reactions like FT synthesis, resid-hydrocracking etc. Sparger design significantly influences gas/solid phase distribution and thus the performance of a slurry reactor. In past, though the effect of sparger design on “overall” gas hold-up was investigated, its effect on local “spatio-temporal” distribution of gas and solid volume fraction is not investigated. Thus, the main objectives of the present work are (1) to understand the influence of different sparger configurations through space- and time-resolved measurements of gas volume fraction distribution and (2) to perform corresponding Eulerian CFD simulations to understand the influence of sparger design on space- and time-resolved gas/solid phase distribution and the dynamics of dense three-phase flow in a bubble column.

The effect of sparger designs (uniform, 4/2/1 holes) is investigated by measuring local gas volume fraction distribution in a cylindrical column (d_C=0.19m, h_c=1.35m) using Electrical Resistance Tomography (ERT) for water-air-alumina system for solid loading of 0, 10 vol% and superficial gas velocity (U_G) in the range of 5-30 cm/s, under ambient conditions. Due to significant settling of solids, gas was found to rise in the near-wall region in the sparger-zone at U_G=5cm/s, while uniform gas distribution was observed at U_G=30cm/s. A CFD model is developed based on three-fluid Eulerian+ KTGF approach. We have investigated the effect of drag force with bubble swarm corrections, and currently we are investigating the effects of non-drag forces like lift and turbulent dispersion on the local gas distribution. This model will be validated against measurements and will be used for predictions of phase distribution and dynamics of three-phase flow in SBCRs for different sparger designs. The space-/time-resolved measurements performed using ERT and development of experimentally-validated CFD models will be an important step forward in predicting the performance of slurry reactors for commercial applications.