Hydrothermal treatment combined with in-situ mechanical compression for floated oily sludge dewatering

Due to the high moisture content of the oily sludge, the conventional use of oily sludge treatment presents poor feasibility in industrial applications. Hence, finding an efficient and energy-saving technology is still an urgent need for the dewatering of oily sludge. In this paper, an innovative method combining hydrothermal treatment (HT) and in-situ mechanical compression (MC) for dewatering of floated oily sludge (FOS) was proposed. Series of experiments on HT&MC were conducted to verify the method. 77–96 wt% of water can directly be separated from FOS by the HT&MC treatment under the temperature of 120–240 °C and residence times of 10–60 min. The bound water content in raw and HT&MT treated FOS were measured by employing the differential scanning calorimetry (DSC) to evaluate the dewatering ability. The result of DSC illustrates the freezing peaks shifted from −11.1 °C to −21.2 °C as the diameter of water droplets reduced. Meanwhile, the comprehensive characterization analysis of products, including chemical oxygen demand (COD), NH4⁺-N, and gas chromatograph (GC) were conducted. All results indicated that HT&MC is advisable for dewatering of oily sludge.