Microwave-assisted solvent deasphalting of heavy fuel oil and process parameters optimization

As petroleum recovery has progressed historically, the portion of heavier crudes and bottom of the barrel resi-dues from the refining process has increased. These crudes are challenging to process, leaving vacuum residues with large fractions of ash and refractory sulfur due to high asphaltene content. Asphaltenes are known to form coke in catalytic upgraders and deactivate refining catalysts. Asphaltenes, which are present in significant amounts in heavy crudes, are the cause of reduction of combustion efficiency, clogging of refinery pipes, and particulate matter emissions. Asphaltenes can be removed from heavy crudes by solvent deasphalting. But the requirement of a high solvent to oil ratio limits its commercial viability. To lower the requirement of solvent, this study investigates deasphalting of heavy fuel oil (HFO) with n-heptane, n-hexane, and n-pentane by microwave -assisted, ultrasound-assisted, and supercritical solvent deasphalting methods. Among the different methods investigated, the microwave-assisted method was found to be more efficient and removed 88 and 80 wt% of asphaltenes from HFO with heptane and hexane, respectively. Microwave irradiation selectively heats asphal-tenes in microwave transparent non-polar solvents and increases the degree of collision of asphaltenes for ag-gregation and thus precipitation. Besides, resins are readily solubilized by the solvent under microwave heating and thus they are unable to act as peptizing agents of asphaltenes. The optimization of process parameters such as solvent to HFO ratio, microwave power, and holding time was investigated for microwave-assisted deas-phalting using Central Composite Design (CCD) and artificial neural network (ANN). The optimum removal of asphaltene was observed when the solvent to HFO ratio, microwave power, and holding time were kept at 3, 150 W, and 20 min, respectively. Deasphalting also significantly improved the quality of HFO by dropping the vis-cosity along with the sulfur and nitrogen contents of HFO. The outcomes of this study are significant for the petrochemical industry as potentially improved crude oil processing with lower solvent to HFO ratios can be achieved in a more effective, economical manner using microwave assistance.

Automated summary

As petroleum recovery has increased the proportion of heavier crudes and refining process residues, the challenge of processing these crudes has risen. The presence of asphaltenes in heavy crudes leads to reduction in combustion efficiency, clogging of refinery pipes, and emissions of particulate matter. This study investigates the deasphalting of heavy fuel oil using different methods, and finds that microwave-assisted deasphalting is more efficient in removing asphaltenes. The optimization of process parameters further improved the quality of the fuel oil. The outcomes of this study are important for the petrochemical industry as they enable improved crude oil processing in a more effective and economical manner.