Fines deposition dynamics in gas–liquid trickle‐flow reactors

Abstract

AbstractNonfilterable fines, such as incipient coke particles or fines naturally occurring in oil sands bitumen, are known to be responsible for the severe plugging during the flow of (fine) solid–liquid suspensions in cocurrent gas–liquid trickle‐bed hydrotreating reactors. Accumulating fines in the porous medium causes pressure buildup, and thus the dropoff in hydrogen partial pressure in the bed, overutilizing recycling compressors and shortening the reactor operating cycles. In this work, a 1‐D transient two‐fluid hydrodynamic model based on the macroscopic volume‐average form of the multiphase system transport equations is developed, analyzed, and validated experimentally. The model hypothesizes that plugging occurs via deep‐bed filtration mechanisms. It incorporates physical effects of porosity and effective specific surface‐area changes due to the capture of fines, inertial effects of phases, and coupling effects between the fines filter rate equation and interfacial momentum exchange force terms. It is tested in the trickle‐flow regime for conditions mimicking a hydrotreating trickle‐bed process with spherical and trilobe catalysts. To rationalize deep‐bed filtration phenomena in trickle‐flow reactors, parametric studies are carried out on the effects of liquid velocity and viscosity, gas density and velocity, and fines feed concentration, on the plugging dynamics.