Research on oil recovery of oily sludge by subcritical/supercritical hydrothermal upgrading

Abstract BACKGROUND Sub/supercritical hydrothermal treatment is a promising technology for efficient resource utilization and complete harmlessness of oily sludge, which is significant for promoting the green and sustainable development of the petroleum industry. In this paper, the effects of reaction temperature, reaction pressure, reaction time and oil content on oil recovery and oil quality (composition, desulfurization and denitrification, and heavy metal content) are studied in detail. RESULTS It was found that the temperature was the most critical parameter, and the optimal process conditions were 350°C, 20 MPa, 60 min and 12 wt% oil content, under which the oil recovery rate could reach 70.46%. The content of N and S in the recovered oil could be as low as 0.87 and 0.536 wt%, and the ratio of H/C was higher than 1.6. CONCLUSION It was found that reaction temperature had the most significant effect on oil recovery compared with other reaction parameters. Heavy metals are transferred from the oil phase to the water and solid phases, so the content of heavy metals in the oil phase is up to standard. The experiment shows that supercritical water heat treatment of oily sludge is feasible, which makes possible the commercial application of sub/supercritical water thermal oil collection technology. © 2024 Society of Chemical Industry (SCI).