Microwave assisted oxidative desulfurization in a helical coil reactor: CFD simulation and experimental validation

In the present work, the microwave assisted oxidative desulfurization (ODS) of model light fuel oil in a helical coil reactor was investigated experimentally and numerically. The main purpose of the study was to investigate the influence of the microwave irradiation power and reactor operating parameters on the sulfur removal in the ODS process. A coupled 0D-ODE and 3D-CFD model was developed to describe the two-phase flow, heat and mass transfer, and electromagnetic waves distribution inside the reactor and microwave box. Experimental tests were also conducted to validate the proposed model. In addition, a kinetic analysis was carried out by estimating the pre-exponential factors and activation energies of the reaction system using Levenberg-Marquardt algorithm. Based on the simulation results, the effects of various operating parameters including oxidant to sulfur molar ratio (nO/ns), formic acid to sulfur molar ratio (nacid/ns), microwave irradiation time, and microwave power on the sulfur removal and electromagnetic heat generation were discussed. Accordingly, more than 97% sulfur conversion was achieved under the optimal operating conditions namely no/ns = 2, nacid/ns = 30, irradiation time = 10 min, and microwave power = 800 W. The dielectric properties of different samples under the microwave irradiation were explained to show key contribution in the extent of the electromagnetic energy absorbed and the volumetric heat generated.