CFD analysis of bed textural characteristics on TBR behaviour: Kinetics, scaling‐up, multiscale analysis, and wall effects

Abstract

A simulation of a trickle bed reactor aided by computational fluid dynamics was implemented. With a Eulerian approach, geometrical characteristics were explicitly considered and two simultaneous heterogeneous reactions were included, hydrodesulphurization (HDS) and hydrodenitrogenation (HDN). This was performed in order to achieve the following: (1) attain further insight into a proper scaling‐up procedure to be able to obtain the same hydrodynamics and kinetics behaviour in two reactors of different length and diameter scales; (2) develop a multiscale analysis regarding the communication of information between scales through the construction of a porous microstructure model from which the geometrical information of the microscale is captured by the effective transport coefficients (which affect the overall reactor behaviour); (3) investigate the effect of operation condition variations on hydrodynamics and kinetics; and (4) assess the deviations and further differences observed from average to punctual conversion values and the assumptions from kinetic literature models through a preliminary multiscale analysis. The CFD results were validated against experimental pressure drop data as well as HDS and HDN conversion theoretical data. An excellent agreement was found. The model produces a significant improvement in hydrodynamic parameter prediction, achieving 5 times better accuracy in predicting pressure drops and 50 % improvement in holdup prediction. The fully coupled model predicts HDS conversion with 96 % accuracy and HDN conversion with 94 % accuracy. Results suggest that the best way to obtain similar kinetic and hydrodynamic behaviour in TBRs with different lengths and diameter length scales is by equaling the liquid holdup true(ϵγtrue) or the mass velocities (L‐G).

Development of a hybrid pressure drop and liquid holdup phenomenological model for trickle bed reactors based on two‐phase volume averaged equations

“…Over the past several decades, there have been vast contributions in the study of trickle bed reactors (TBR) hydrodynamics [ 2‐8 ] and mass transfer [ 9‐14 ] phenomena in the literature. In these contributions, it has been recognized that the hydrodynamics of TBR, and therefore the multiphase interactions, play a determining role in the mass and heat transfer phenomena, kinetics, and performance throughput of these systems.…”

CFD in Chemical Engineering: Process Design Symposium at the 10th World Congress of Chemical Engineering (WCCE10)

“…Multiphase flow was an important theme in this special section with applications for oil transport, liquid‐liquid dispersion, flashing spray jets, solid‐fluid systems in rotating drums, trickle bed, and fluidized bed reactors, and agglomeration in cyclone separators . Mixing phenomena were reported in variety of geometries and on diverse length scales: in an agitated tubular reactor, in T‐shaped micromixers, and in fluidic oscillators .…”