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A lab scale trickle bed reactor (TBR) has been employed to investigate the effect of particles and liquid flow rate on the phase distribution in TBR. The TBR module, made up of 100 mm inner diameter acrylic column, was randomly packed with inert porous alumina particles of different average diameters that are used in actual reactor. Water was fed from the top of the column by "point feed" and "homogenous feed" strategies and cross-sectional liquid distributions were captured at several axial positions from the top to the bottom of the column by employing electrical resistance tomography (ERT) technique. ERT is a non-invasive cross-sectional imaging technique that provides the cross-sectional conductivity distribution by injecting current and measuring voltages between the several electrodes (16 electrodes in our case) that are attached around the column. The cross-sectional conductivity thus obtained represents the liquid hold up and degree of maldistribution of the liquid. In the experiment, quicker and more homogenous distribution of liquid was obtained for the particles with smaller diameters. That is due to capillary force that cancels the randomness of packing. Electrical resistance tomography seems to be reliable non-invasive instrumentation technique to optimize the design and operations of the trickle bed reactors.

A fixed bed reactor that operates in gas-liquid co-current down flow is called Trickle Bed Reactor (TBR). It is widely used in chemical engineering. And, recently used in purification of radioactive contamination from contaminated water generated in the Fukushima Daiichi nuclear power plant. There are several flow conditions that occur in the TBR due to gas and liquid flow rate. Since mass and heat transfer rate and particles wetting depend on flow condition, it is necessary to establish the visualization techniques to understand flow condition, transition boundary and properties of gas liquid flow in TBR. In this study, authors employed the lab-scale TBR, made of 100mm inner diameter acrylic column, packed with particles of two sizes (3, 5 mm) that are used in the actual reactor. Water and air were injected from the top of the column and cross-sectional liquid distribution was captured at the bottom of the column by electrical resistance tomography (ERT). ERT is a tomographic technique that provides the cross-sectional conductivity distribution at the rate of about 50 frames per second by injecting current and measuring voltages between the 16 electrodes that are attached around the column. By analyzing the spatial and temporal characteristics of the liquid distribution obtained by ERT, it was found that particle size has only little impact on induction of pulsating flow and larger particle causes distinct pulses. Smaller particle causes blurred tiny pulses due to higher flow resistance. Larger particle (5 mm) is advantageous for pulsating flow.

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