Bed structure and its impact on liquid distribution in a trickle bed reactor

Abstract

Trickle bed reactors, which has been a workhorse for the process and refining industry for many decades, are progressively being challenged to provide solutions to deep processing of feedstocks. It is known that the structure of the packed bed which is formed with a certain arrangement of catalyst particles in the three‐dimensional space within the reactor modulates in an unknown fashion the flow of fluids in the trickle bed, and in turn affects the conversion and selectivity in the trickle bed. Under deep processing conditions, the impact of the bed structure in modulating the overall reactor performance in a trickle bed is not as yet established. The question begets three sequential studies: estimating and quantifying the bed structure, measuring the liquid distribution, and estimating transport parameters (that are dependent on the bed structure and liquid distribution) so that the overall performance metrics as a reactor may be quantified. This contribution relates to the second of these questions, the first being already addressed to some extent by our earlier work. The current investigation aims at quantifying the effect of structure of the packed bed on hydrodynamics of the reactor. The impact of various packing techniques is discussed along with the development of correlations for two‐phase pressure drop and dynamic liquid holdup. Liquid distribution is studied in depth for various operating parameters such as gas and liquid superficial velocities and column aspect ratio for uniform and non‐uniform packing methods. The packing devices consist of various inserts attached to a hopper which can generate packing structures having void fraction in the range of 37.2%–46.4%. The maldistribution factor and flow maps for various aspect ratio of column suggest that maldistribution rises along with the increased channeling effect along the height of the column. Uniformly packed bed were measurably less prone to maldistribution along the length than the non‐uniformly packed beds.

Local and global gas–liquid mass transfer in a micro‐packed bed reactor utilizing a noninvasive colorimetric technique

“…In the traditional trickle bed with millimeter-scale particles, the liquid flow textures in the particle level consisted of several features: liquid film, rivulet, pendulum structure, liquid filament, and liquid pocket, as shown in Figure 10A. 43,44 Based on the visual study, only the large liquid films that covered many small particles and liquid pockets as flow textures were observed in the μPBR with micronscale particles, as shown in Figure 10B. The type of liquid filament was nonexistent in the μPBR since liquid filled the bulk in the whole reactor with high liquid holdup.…”