(77b) Modeling and Simulation of Cyclic Operations Applied to Trickle Bed Hydrotreaters

CanmetENERGY scientists in collaboration with Laval University are conducting research with the goals of improving operations and intensifying process performance of petroleum trickle bed hydroprocessing reactors, both of which complement intensive research that have been conducted over the past several decades. At CanmetENERGY the research focuses on exploration of cyclic operations by periodically alternating the flow rates of gas or liquid, or both phases to enhance mass and heat transfer, and catalyst efficiency, and to reduce/eliminate solid fines deposition on catalyst surface.

To achieve the overarching research goals, this study utilizes computational fluid dynamics (CFD) modeling and simulation of a trickle bed reactor under gas, liquid, and gas/liquid alternating cyclic operations. The commercial CFD software FLUENT was used under an unsteady multiple-Euler framework. A number of modeling and simulation factors, such as reactor geometry meshing, numerical schemes, drag forces, gas and liquid properties and catalyst particle size, were examined to investigate their effect and sensitivity on simulation results. To validate the computation results, electrical capacitance tomography (ECT) imaging was applied to a lab-scale trickle bed reactor to track the liquid holdup waves along the bed.

Researchers at CanmetENERGY and Laval University concluded that a one-dimensional multiple-Euler CFD model with first order numerical scheme was sufficient to accurately capture the non-steady state hydrodynamic behaviours of trickle bed reactors under different type of cyclic operations. Moreover, the model was able to predict accurately the morphological characteristics of a liquid wave inside the bed for all the examined cyclic operations, including base-peak and ON-OFF modes. In addition, simulation results were in excellent agreement with experimental data in terms of both value and fluctuating behaviour of overall bed pressure drop. Finally, researchers also concluded that the liquid-solid drag force is the main cause for wave attenuation along the catalyst bed.