Extractive desulfurization of diesel fuel in a novel ultrasound-assisted spiral microfluidic contactor: Separation efficiency and energy consumption

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A novel ultrasound-assisted spiral microchannel contactor was proposed to investigate the extractive desulfurization process of untreated diesel fuel with an initial sulfur content of 1690 ppmw. The experiments were divided into two sections based on the desulfurization contactors. The conventional batch experiments evaluated the mixing time (20, 40, 70, 100, and 130 min) and solvent to fuel volume ratio (0.25, 0.5, 0.75, 1, and 1.5) impacts on the desulfurization process efficiency. The continuous process was initiated by selecting a solvent, namely, methanol, acetonitrile, and dimethylformamide, in a microchannel contactor. It was shown that dimethylformamide has the best sulfur removal efficiency. The influence of volumetric flow rate (2.86, 3.5, 4.5, 6.3, 7.85, and 10.5 ml/min) on the separation efficiency and the process energy assessment at both silent and sonicated conditions were explored. It was found that the maximum value of desulfurization in the conventional batch process was about 41 % after 100 min, while the desulfurization efficiency of ultrasound-assisted microchannel contactor reached 70.3 % within 3.6 min. Depending on the fuel flow rate, it was shown that a 5–18 % increase in desulfurization rate could be obtained in sonicated mode. The energy consumption assessment illustrated that, at a 2.86 ml/min flow rate of diesel fuel (i.e., highest residence time), the addition of the sonication feature leads to an increase in sulfur removal from 59 % to 70.3 %. In contrast, the total sulfur removal per consumed electrical energy reduced from 902 mg/J to 0.0046 mg/J. It was concluded that, although with sonication mode, higher sulfur removal can be obtained, the electrical energy consumption in exchange for obtaining clean fuel energy drastically increased.