Characteristics of oily sludge and a treatment selection framework based on cyclone deoiling

Oily sludge is a typical hazardous waste generated during petroleum extraction. Single treatment technologies often suffer from low efficiency and poor adaptability. This study investigated differences in the physicochemical properties of oily sludge across China to guide appropriate treatment selection. The five samples showed clear physicochemical differences, with oil contents of 8–25%, water contents of 3–31%, solids content of 58–90%, and mean particle sizes of 1.66 to 27.33 μm. Medium-chain hydrocarbons accounted for up to 69.75%, while heavy carbon components reached 44.48%. Significant differences were also observed in inorganic composition. Based on these characteristics, this study proposed a treatment selection framework. For sludge with high oil content and high porosity, cyclone separation followed by thermal treatment is recommended. For sludge with complex organic compositions, thermal treatment may be considered after cyclone deoiling. Chemical extraction combined with thermal treatment may be suitable for highly viscous sludge. This study provides a scientific basis for selecting treatment technologies according to the physicochemical characteristics of oily sludge.