Slow-mode gas/liquid-induced periodic hydrodynamics in trickling packed beds derived from direct measurement of cross-sectional distributed local capacitances

Hydrodynamics of a periodically operated trickling packed bed was studied with a high-speed wire-mesh sensor technique based on direct measurement of cross-sectional distributed local capacitances. Liquid cycles in the alumina packing were generated by periodic induction of gas and/or liquid phase in distinctive slow-mode. Hydrodynamics were characterized with respect to liquid saturation and liquid saturation distribution varying period length, split and time-averaged superficial gas and liquid velocities. The sensors technique allows direct access to local phenomena during liquid pulse breakthrough, to distribution patterns and their reproducibility at different cycle positions that were studied based on transient liquid saturation distribution data of different periodicity variables. Due to simultaneous measurement at four different axial reactor positions, pulse attenuation along the reactor and pulse velocity could be analyzed. Furthermore, hydrodynamics of different modes of gas-induced periodic cycling, e.g. gas cycling only, asynchronous and synchronous cycling of gas and liquid flow rate and alternating gas–liquid cycling, were studied.