LOADING, DRAINING AND HOLD-UP IN PERIODICALLY OPERATED TRICKLE-BED REACTORS

Periodic interruption of liquid flow in co-current trickle beds appears to be an attractive mode of operation. For modelling these intermittent-flow reactors, loading and draining times must be known. Experiments were undertaken using beds of activated carbon with water and air as the fluid phases. Loading time was taken as the time to water breakthrough. The gas flow was continuous while the time between the end of drainage and the start of filling was varied to simulate different periods. Drainage experiments followed the liquid flow leaving the bed as a function of time. Liquid hold-ups were determined after the filling and draining measurements. Variables considered were particle size, gas and liquid velocity. Loading closely follows the plug flow model; drainage shows tailing but does not follow literature models. Static and dynamic hold-ups at zero gas flow agree with literature correlations for the larger particle size used. A gas velocity effect on both static and dynamic hold-up was observed.