A PIV study of hydrodynamics in gas–liquid high throughput experimentation (HTE) reactors with eccentric impeller configurations

High-throughput experimentation (HTE) is used for the screening of novel catalyst formulations via miniature agitated gas–liquid reactors with vessel volumes of an order of magnitude below the laboratory scale. An investigation of the macroscopic hydrodynamic performance of a miniaturised unbaffled stirred vessel of diameter 45 mm for an air–water system has been carried out at gassing rates of 0.25 and 0.5 vvm (dispersed flow regime) using particle image velocimetry (PIV). Measurements of bubble size and gas hold-up were also made. Eccentric agitation was employed as a means of breaking solid body rotation within the vessel, using a 6-blade, up-pumping pitched blade turbine. The gas phase was introduced via sintered glass panel spargers mounted in the vessel base. Two different configurations were used: firstly where the sparger located directly below the impeller, and secondly where the sparger was located opposite the impeller on the other side of the vessel. Measured distributions of turbulent kinetic energy (TKE) for both gassed configurations were similar and showed significant differences to the ungassed case. Estimates of the gas–liquid interfacial area were at least 2–3 times higher than those found in conventional, lab-scale baffled vessels; this was attributed to the creation of very small bubbles at the sparger (d32≈100μm).