Experimental investigation of the dewatering performance and product characteristics of oily scum at increased reaction time through hydrothermal treatment

Hydrothermal treatment (HT) is a promising thermal conversion technology that can convert wastes with high moisture content into value-added products. The effects of reaction time on the dewatering performance and product characteristics of oily scum were investigated through HT in this study. The main components in liquid and the combustion characteristics of hydrochars were also studied. Results showed that as the HT reaction time increased, the appearance of the liquid product changed from light yellow clarifying solution to yellow turbidity oil-water mixture. The liquid yield obtained from the HT process of oily scum increased with the increase of reaction time, while the moisture yield in hydrochars decreased gradually. The increase of reaction time improved the filtration performance and dewaterability of oily scum. Hydrochars presented the microscopic properties of the smooth and rough surfaces as well as the particles with different sizes. The thermogravimetric analysis showed that the devolatilization and combustion process of hydrochars was further separated into the two combustion phases of light and heavy volatiles. The combustion process of hydrochars was easier than dried oily scum due to lower activation energy and pre-exponential factor. The results obtained in this study could provide valuable references for the reasonable treatment and effective utilization of oily scum.