Hydrodynamics of Two-Phase Flow in a Trickle Bed Reactor

Hydrodynamic data from large trickle bed columns are scarce. In this study, pressure drop, liquid holdup, and transition from low interaction regime to high interaction regime were investigated in a pilot-scale trickle bed column of 13 in. inner diameter and 8 ft. bed height, using air-water system at atmospheric pressure. Data were collected in the low gas superficial velocity range, which has not been covered extensively in literature. Gas flow rate was varied from 0 to 400 SLPM (standard liter per minute), i.e., 0 – 70 mm/s, and liquid flow rate was varied from 0 to 60 gpm (gallons per minute), i.e., 0 – 45 mm/s. The system was prewetted in high interaction regime before taking each measurement. Pressure and liquid load were measured using sensors, while flow regime transition was observed visually and by noting the standard deviation in pressure drop. The aim of this study is to record and analyze hydrodynamic data that can closely match that of industrial-scale reactors. The experiments showed hysteresis, indicating multiplicity of hydrodynamic states. For experiments following a consistent prewetting procedure, significant deviation was observed from the pressure drop and liquid holdup correlations in literature. At lower liquid flow rates, flow is gravity driven, while drag forces come into play as liquid flow is increased. In addition, at higher liquid flow rates, liquid holdup is overestimated by correlations from studies on lab-scale trickle bed columns. Lastly, flow regime transition agreed with existing flow maps in literature, with the observation of local pulsing in the bed