چكيده به لاتين
In this work, at first, a valid computational fluid dynamic (CFD) model presented in order to investigate the hydrodynamic of the ultrasonic horn reactor, and a new moving boundary condition model with an oscillating parabolic-logarithmic profile was derived to simulate the wave behavior. Moreover, the modified cavitation model in order to capture the hydrodynamic of the ultrasonic horn reactor was applied. After validating the CFD model, the simulation was utilized to predict various quantities such as cavitation zone, pressure field, flow field and turbulence parameters. Then, considering the design variables and employing the idea of injection at the active zone the performance of the flow-system was scrutinized. In this regard, at the first, the effect and decision to choose of the process variables including oxidation parameters such as oxidant-to-sulfur molar ratio, (38.88), acid-to-sulfur molar ratio, (116.67), and sonication time (29.2 min) at the specified conditions, were selected. Afterwards, some experiments with objective of minimizing the residence time and aqueous phase to fuel volume ratio have been conducted in a double-stages sonoreactor. More than 90 percent sulfur removal at residence time of 5.5 min and aqueous phase to fuel volume ratio of 0.2 was obtained. Furthermore, the UAOD process with injection of the aqueous phase is compared to a conventional UAOD. Significant improvement on the sulfur removal was observed specially in lower sonication time in the case of dispersion method in comparison with the conventional contact between two phases. Ultimately, cylindrical sonoreactor in order to use for the larger scale operation was designed, and the operating parameters such as residence time, nozzle diameter and number of nuzzles were investigated. GC analysis showed that more than 98 percent sulfur removal from the diesel fuel was attained using the two injection nuzzles and in volumetric flow rate of aqueous phase and fuel phase at 48.89 and 244.44 mL/min, total residence time of 15 min and after three step of extraction. In addition, various analysis after the oxidation process revealed that more than 99 percent of aqueous phase from the oil phase has been removed. Also, a hydrodynamic parameter named as a hydrodynamic momentum ratio is introduced to evaluate the relative strength of the ultrasonic jet versus aqueous jet. Hydrodynamic CFD model incorporated by reaction kinetic to predict the sulfur removal for model fuel within a sonoreactor. The CFD results indicated that the physical and chemical effects associated with the ultrasonic field can contribute to the enhancement of reaction and sulfur removal rates. However, the physical effects such as acoustic streaming and velocity fluctuation are predominant role for the enhancement of sulfur removal.
