Paving a way toward circular economy for oil and gas industry: A conceptual modelling of re-refining process through solvent extraction and hydrofinishing pathway

The oil and gas (O&G) industry has recently faced market headwinds due to high environmental impacts generated. Therefore, this study proposes to develop a circular economy (CE) model for the O&G industry by incorporating a re-refining process. A re-refining process based on an integrated solvent extraction and hydrotreatment unit is introduced as a media to re-valorize the waste lubricating oil (WLO) generated from crude oil. The proposed re-refining process is simulated and optimized using Aspen Plus V10 with integration into the CE model. In the CE model, 80% of the WLO is recovered to replace the portion of high-cost crude oil needed in the conventional linear economy (LE) model. Sensitivity analysis shows that the optimum re-refining process uses solvent mixture of 35% n-hexane/35% n-butanol/30% MEK. The optimum specifications are solvent extraction temperature at 25 °C, solvent to oil ratio of 3:1, hydrofinishing temperature at 270 °C and hydrofinishing pressure at 30 bar. In comparison to the LE model, the CE model achieves 22.67% lower overall annualized cost (OAC), which demonstrates the financial viability of the CE model.