Performance comparison between different sparger plate orifice patterns: Hydrodynamic investigation using ultrafast X-ray tomography

Abstract

In this work, the effect of the sparger design on the hydrodynamic performance in a bubble column of 0.1m ID downstream a single (coarse) and multi-orifice (fine) perforated plate sparger was studied using the ultrafast X-ray tomography. The liquid was kept in semi-batch mode and the superficial gas velocity was varied between 0.011 and 0.025ms−1 to ensure non-jetting flow through the sparger holes. The effect of the orifice patterns on the hydrodynamic performance was evaluated through bubble size distribution (BSD), radial gas holdup profile and overall gas holdup as well as Sauter mean bubble diameter and magnitude of the interfacial area. To evaluate sparger and bubble column performance, respectively, also the mass transfer was investigated. Due to the high turbulence induced by the large bubbles released from the coarse sparger, the equilibrium BSD was already reached at a dimensionless height of h/D=1.0. However, average bubble characteristics, such as interfacial area and Sauter mean diameter, were similar for both sparger types at a column height of h/D⩾7.0. Based on a comprehensive hydrodynamic analysis, requirements for sparger refinement were derived depending on respective reaction rates, mixing properties, heat production and removal duty. Eventually, adapted correlations are proposed for radial holdup profile and Sauter mean diameter accounting for various plate refinements using liquids which inhibit coalesce of gas bubbles.