Supercritical water gasification of oily sludge and its life cycle assessment

Abstract

A supercritical water gasification strategy was employed to investigate the effects of different conditions on hydrogen-rich gas production from oily sludge, based on the Aspen Plus platform. Meanwhile, the entire process was assessed with a life cycle assessment (LCA) method. The results indicated that the gas yield was decreased by increasing the sludge concentration. The yield of hydrogen-rich gas (H2 and CH4) was improved with increasing temperature. Higher temperatures were more favorable to gas production. Excessive addition of oxidants could reduce the CH4 yield, thereby lowering the energy efficiency of the process. The LCA analysis found that, in comparison to the stages of raw material transportation, heat recovery, and wastewater treatment, the effect of more CO2 produced in cooling and separation stage on global warming potential (GWP) was more obvious. The corresponding process can be improved to mitigate the environmental effect of the whole gasification.