The recent IMO 2020 regulations on sulfur oxides emissions increased the interest in heavy fuel oils (HFOs) desulfurization processes. Many studies proposed oxidative desulfurization (ODS) as a valid alternative to hydro-desulfurization (HDS). ODS presents several advantages over HDS as it operates at a lower temperature, lower pressure, and higher propensity to remove thiophenes. Despite the effort, the ODS process is not yet exploited on a commercial scale. Several limitations affect the process such as low yield, viscosity increase and separation issues. One possible solution could be to use Ultrasonically Induced Cavitation (UIC), which can drastically improve the oxidation process. Ultrasonically Induced Cavitation (UIC) is a physical process that involves the formation of vapour-filled cavities in a liquid medium irradiated by a high-frequency pressure wave source (a sonotrode). The pressure wave control nucleation, dynamics and collapse of the vapour bubbles. The bubble collapse results in localized high-temperature and high-pressure. The extreme conditions favour the radicals (like H* and OH*). We conducted an extensive experimental campaign devoted to demonstrating the effectiveness of UIC applied to ODS. In particular, we suggest that sulfur oxidation in the ODS depends heavily on the number and vapour cavities size. The combination of a greater volumetric density of the cavities and a smaller size increases the process efficiency drastically. An optimized UIC reactor could improve the ODS efficiency, decreasing the amount of hydrogen peroxide (reactant) and acetic acid (catalyst) employed during the process. This last aspect is crucial to make the entire process economically viable. To solve the optimization problem, we developed a new CFD model to predict high fidelity, formation, dynamics, and the collapse of the vapour cavities. We also propose a parametric study to identify the optimum shape of the reactor and reaction conditions. We identified the optimization process targets in the bubbles' surface area, temperature, and residence time.

Optimum cavitation chamber design for ultrasonically assisted oxidative desulfurization of HFO

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.