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Liquid phase dispersion/mixing studies have been performed for the first time on the catalyst bed of a cold flow scaled-down upflow moving bed re-actor (MBR) using residence time distribution (RTD) at various flow rates including the scaled down condition. MBR is hydrotreater and its design includes catalyst bed with conical bottom and plena. The catalyst bed is modeled using Wave Model, and its mixing parameters are estimated using a mathematical approach based on convolution and regression. A study is also shown to illustrate the limitation of Axial Dispersion Model (ADM) while modeling the flow which noticeably deviates from plug flow. In addition, a dimensionless variance is also estimated for the bed region from the RTDs. Overall liquid dispersion/mixing is seen high in MBR, with more disper-sion/mixing in the expanded bed region. Scaled down conditions are seen best when considering the overall catalyst utilization and liquid mixing for hydrotreatment.

Upflow moving‐bed hydrotreater (MBR) is used in refineries as a guard reactor to a fixed‐bed residual desulfurization reactor. Uniform local flow distribution in these reactors is critical to avoid issues like coking, catalyst agglomeration, and hotspots in the catalyst bed. Local maldistribution is investigated on a scaled‐down MBR at a scaled‐down industrial flow condition using an experimental technique called two‐tip optical probe (TTOP), which gives local phase saturations, phase velocities, backmixing, and maldistribution at voids of a two‐phase‐flow packed bed. TTOP implemented at local radial/axial locations indicates highly fluctuating phase saturations inside the catalyst bed, with zones having low‐to‐high gas or liquid saturations, indicating severe local maldistribution. The local phase backmixing and local maldistribution is more on the upper part of the bed.