Simulation Of Thiophenic Compound Adsorption On Activated Carbons For Fuel Oil Desulfurization With COMSOL Multiphysics Software

Sulfur compounds in fuel oil is the main source of pollution in the city atmosphere.With the increase of environmental awareness,low sulfur and non-sulfur fuels will be inevitably needed in the world.Adsorptive desulfurization of fuel oil with activated carbons is the focus of research in recent years,but the adsorption of thiophenic compounds on activated carbons is very complex owing to the competing adsorption of aromatic and alkene compounds and also the competing adsorption among different thiophenic compounds.Thiophenic compound adsorption on activated carbons was simulated with the COMSOL Multiphysics software to reveal thiophenic compound adsorption in presence of competing components.An adsorption model was established based on the previous experimental and theoretical study on activated carbon adsorption of thiophenic compounds in fuel oil,by which numerical simulation of thiophenic compound adsorption on activated carbons was investigated for model oils containing single component thiophenic compound,multi-component thiophenic compounds and those thiophenic compounds in presence of competing components such as cyclohexene and toluene.The main conclusions are as follows:First,the break-through curves and adsorption capacities of dibenzothiophene adsorption on different activated carbons were simulated on a cylinder adsorption column with the COMSOL Multiphysics software,which were compared with experimental results.It is found that the simulated break-through curves are similar to the experimental ones and the break-through and saturated adsorption capacities are all agree well with the experimental results,which validate the model established and applicability of the software.Second,the factors,such as velocity of the fluid,the diffusion coefficient and the ratio of column height to diameter,that affect the adsorptive breakthrough curves on the cylinder column were simulated,analyzed and optimized for a model fuel oil containing dibenzothiophene.The adsorption of thiophene,benzothiophene,dibenzothiophene and 4,6-dimethyl dibenzothiophene on activated carbons were simulated to obtain adsorption capacities and break-through curves for the model fuel oils with single thiophenic solute.It is found that the adsorption capacity increases with the increase of the Langmuir equilibrium constant,the specific surface area of activated carbons and the concentration of the thiophenic compounds.The adsorption capacity is independent of the flow velocity,diffusion coefficient and the ratio of column height to diameter.Then,the multi-component thiophenic compound adsorption on activated carbons was simulated and the selectivity for different thiophenic compounds was obtained.Results show that the selectivity of different compounds is related to the Langmuir equilibrium constant,and the greater is the constants,the higher is the selectivity.Finally,competing adsorption of decane,cyclohexene and toluene with thiophenic compounds on activated carbons was simulated.It is found that adsorption capacity of thiophenic compounds decrease little when the Langmuir equilibrium constant of a competing component that was added into the model fuel oil is far less than that of the thiophenic compound,and vice versus.When the Langmuir equilibrium constant of a competing component is close to that of the thiophenic compound,the adsorption capacity decreases significantly with the addition of the competing component.