Combination of adsorption-diffusion model with CFD for study of desulfurization in fixed bed

Abstract

A 2D porous media Computational Fluid Dynamics (CFD) model is developed for a fixed bed adsorber to remove the 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel. The Ag-TiO2-SiO2 modified by CeOx adsorbent is used to remove the 4,6-DMDBT from diesel and proves that CeOx species could promote high dispersion of Ag species on adsorbent surface. The mass source term describing mass transfer of 4,6-DMDBT inside the adsorption bed column is considered. The effects of various parameters such as feed concentration, feed rate and column height on adsorption process have been investigated. Mesh independent test is performed to investigate the effect of the grid size on the simulation results. The component distribution contour and mass transfer rate are employed to analyse further the mass transfer phenomenon in fixed bed column. The higher mass transfer rate at the beginning can be observed and the lower mass transfer rate is obtained after a period of adsorption time at high feed concentration. Results also demonstrate that the porous media CFD model can successfully describe the adsorption of 4,6-DMDBT from diesel in fixed bed column. Finally, the results of Genetic algorithm search suggest that the optimal height of mass transfer zone can be got at low feed rate, high bed height and low feed concentration.