(64c) Development of a New Liquid Velocity Measurement Technique in Trickle Bed Reactors (TBRs) Using Combined Digital Radiography and Particle Tracking (DRPT) Techniques

Trickle bed reactors (TBRs) are a fixed bed of particles where liquid and gas flow concurrently downward. TBRs are widely used in various industries which produce petroleum and chemical base products.  Hydrodynamics studies in TBRs are essential as it helps process optimization. Travelling liquid velocity between the solid particles is one of the key performance characteristics of TBRs. Our preliminary work introduces the usage of Digital X-Ray Radiography combined with Particle Tracking techniques (DRPT) to map and measure the liquid velocity in TBRs (single phase). Three liquid superficial flow rates (V_sl (cm/s) = 0.4191, 0.8382 and 1.0897 or Re_L = 15.7, 31.39 and 40.81) were introduced into a 2.25 cm diameter PVC tube packed with 3 mm Expanded Polystyrene (EPS) beads. While the liquid continuously moving into the bed, it was injected with 106 μm to 125 μm barium titanate glass tracing particles, monitored and digitally recorded by an X-ray detector (50 mm x 50 mm with a 48 μm active pixel resolution and maximum frame rate of 2.7 fps). An X-ray source with operating power of 50 kVp and 3 mA current (210 mm source detector distance) was used to acquire multiple digital X-ray image frames of the moving tracing particles. The movements of the particles are assumed to be equal to the movement of the liquid. Four separate experiments were replicated such that every replication contains fresh random EPS beads packing.  A particle identifier algorithm was used to register particle location in every image and codes were designed to plot the movement and calculate the velocities. From the plotted particle movement tracks, several observations were made and among them, the liquid movement in TBRs show several trends of increasing velocity (from 4 - 5 of V_sl), the flow in the packed tube is random (inhomogeneous), some of flow is stagnant and some of the flow exhibits flow reversal. This new technique offers more options in studying the hydrodynamics of TBRs. The ranges of identified velocities are in agreement with the published data.