Analysis of Local Liquid Distribution in a Pilot-scale Packed Bed with Gas-Liquid Cocurrent Flow

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Four studies were carried out to provide the fundamental and useful knowledges for the rational designing and operation of the gas-liquid cocurrent packed bed, so-called 'trickle bed', of the commercial scale.1) Measurement of the radial distribution of liquid flowrate :A pilot-scale bed of 0.38 m in diameter and 3.0 m in height was packed with the trigonal catalyst particles of which cross section is the shape of clover leaf. The distribution of liquid flowrate at the bottom of the packed bed was almost uniform in the radial direction. The 'wall flow' which means the liquid flow in the region close to the wall was not observed.2) Measurement of the radial distribution of liquid holdup :Ten pairs of platinum electrode were used to detect the electric resistance varying with the local liquid holdup. In the packed bed with small particles the liquid holdup was almost same in the center of the bed and slightly higher than that in the wall region. It is suposed that the 'wall flow' does not exist in the catalitic trickle bed reactor.3) Visual observation of the liquid flow with X-ray CT technique :The X-ray computed tomography (CT) technique was applied to visualization of the liquid flow pattern inside the bed. A contrast medium injected into liquid showed the liquid flow pattern and the 'wall flow' was not observed.4) Numerical simulation of flow pattern in the packed bed with vectorial Ergun equation :Ergun equation which is commonly used to estimate the pressure drop across the packed bed was extended to simulate the flow pattern in the whole bed with the distribution of local voidage. When the viscous resistance against the flow is dominant, the flow deviates toward the region with higher voidage. On the other hand, the channelling flow is not severe when the inertia resistance controls the flow in the bed.