Fast Pyrolysis of Sewage Sludge in a Curie-Point Pyrolyzer: The Case of Sludge in the City of Shanghai, China

Two sewage sludges collected from Shanghai were pyrolyzed in a Curie-point pyrolyzer at four predetermined temperatures (315, 485, 650, and 764 degrees C). The primary objectives of this study were to characterize the two sewage sludges from Shanghai and to discuss the specialty of liquid products derived from the two sludges, as well as the effect of temperature on their compositions. The pyrolytic liquid products contained abundant oxygenated compounds and steroids, while monoaromatics and aliphatics were much less. This indicated a high contribution of lipids to the sludges. Temperature dramatically affected the liquid composition. The proportions of carboxylic acids and monoaromatics were found, to increase with increasing temperature then decrease at high temperatures. However, the decomposition of unreacted lignin increased the yields at high temperatures. The proportion of long-chain aliphatic amides and nitriles was observed to decrease at high temperatures to form nitrogen-containing heterocycles compounds. In addition, heterocyclic analogues of PAHs were detected in these liquid products, and the proportion of PAHs was particularly low because of the weakened secondary reactions.