Hydrocarbon hydrodesulfurization in vertical, inclined and oscillating trickle beds - Hydrodynamics & reactor performance for offshore petroleum marine applications

Two-phase flow dynamics and hydrodesulfurization (HDS) performance were numerically analyzed for vertical, inclined, and oscillating trickle beds with a prospect of assessing the potential of implementing HDS operations on marine floating platforms. An unsteady-state three-dimensional model based on the macroscopic volume-averaged mass, momentum, energy and species balance equations coupled with simultaneous diffusion and chemical reaction within sulfide CoMo/alumina catalyst was developed for the purpose of comparative analyses using H2/dibenzothiophene/n-hexadecane model system. Angular uniform and sinusoidal oscillatory motion of the reactor between two angled symmetrical positions and between vertical and an inclined position was considered. As in the case of cold-flow passive conditions, in chemical reaction environment two-phase downflow deviates considerably from axial symmetry at higher reactor inclinations with noticeable liquid accumulation in the bottommost reactor cross-sectional area on the tilting side. Also, externally-induced reactor periodic oscillation generates complex reverse secondary flow in radial and circumferential directions and oscillatory patterns of flow field with the amplitude and propagation frequency affected by the type (uniform or sinusoidal), amplitude and period of angular motion of reactor. Inclined, symmetric and asymmetric oscillating trickle-bed reactors underperform the vertical configuration and the decline of symmetric oscillating trickle-bed reactor hydrodesulfurization performance is lower under uniform oscillatory motion conditions. Oscillating trickle-bed reactors generate an oscillatory hydrodesulfurization performance which is affected by the parameters of angular motion of reactor. The inhibiting effect induced by H2S on the hydrogenolysis is considerable at higher packed bed inclinations and in symmetric oscillating trickle-bed reactors.