Multiple hydrodynamic states in trickle flow reactors: towards optimising reactor performance by manipulation of the hydrodynamic state

The hydrodynamic description of trickle flow is a complex field of study. One of the main contributors to the complexity is the existence of multiple hydrodynamic states (MHS). As early as 1978, Kan & Greenfield reported different pressure drop and holdup readings for the same liquid and gas feed rates. The study revealed that the flow history experienced by the bed determined the specific hydrodynamic state. Once this was established numerous studies confirmed the effect by using different flow histories (Christensen et al., 1986, Levec et al., 1986, Lazzaroni et al., 1988). In these studies the MHS were reported as pressure drop and liquid holdup hysteresis loops.