Enhancement of dewatering from oily sludge by addition of alcohols as cosolvents with dimethyl ether

The oil industry produces a large amount of oily sludge (OS) annually, posing a severe environmental hazard. Conventional OS treatments are limited in industrial applications owing to the high moisture content of OS. This study investigates the extraction of water from OS using alcohols as cosolvents with dimethyl ether (DME). Furthermore, the effects of the type and dosage of the cosolvent on the dehydration rate and chemical profile of the solid product were evaluated. Results revealed that the addition of alcohols significantly enhanced dew-atering from OS using DME; the maximum dewatering rate exceeded 95%, which was equivalent to saving more than half the amount of DME. The cosolvents facilitated the dissolution of resins and certain asphaltenes on the water-in-oil (W/O) emulsion interface layer, breaking the structure of the W/O emulsion and converting the mixture into an easily separated solid-liquid two-phase substance. This could reduce the amount of DME needed during the dewatering process. The thermal properties of the solid products did not change significantly, which is advantageous for their subsequent processing and utilization.