Effect of Different Thermochemical Pretreatments on Fuel Quality of Sewage Sludge

Abstract

Abstract-Sewage sludge contains large amounts of energy and gasification of sewage sludge may be one of the promising sustainable approaches for hydrogen-rich syngas production from sewage sludge. However, raw sludge is unsuitable for direct gasification and thus pretreatment is necessary to improve its fuel quality prior to further thermal process. In this study, two types of the biochars, pyrochar from low temperature pyrolysis (LTP) and hydrochar from hydrothermal carbonization (HTC) were prepared, characterized and their gasification properties were experimentally evaluated. The results showed that the hydrochar was more hydrophobic than the pyrochar and its surface was rich of oxygen-containing functional groups, which enhanced the interactions between the carbon surface and hydrogen bonding as well as gasification reactivity of the hydrochar under identical conditions. Additionally, the porous structure on the surface of the hydrochar facilitated the pores better accessible for condensable hydrocarbon molecules and the hydrochar had improved gas production and gasification efficiency. This study demonstrates that the integration of HTC pretreatment and subsequent gasification has promising potential for hydrogen-rich syngas production from sewage sludge.