Experimental Study on Supercritical Water Oxidation of Paper Mill Sludge

Paper industry produces large amounts of sludge with about 65wt% moisture content. Due to its complex composition, the charge of traditional disposal method is high and easy to bring about secondary pollution. In this paper, the influences of temperature, oxidation coefficient and residence time on the performance of supercritical water oxidation (SCWO) of paper mill sludge were investigated. The results show that SCWO can almost completely eliminate organics in sludge and obtain transparent liquid products meeting relative national standards at 550°C, 5min with an oxidation coefficient of 3.0. However, during this process, TN changes to NH₃-N, so NH₃-N in liquid products increases with operation parameters, indicating the recalcitrant nature of NH₃-N, and which needs further treatment.