Gasification performance of the hydrochar derived from co-hydrothermal carbonization of sewage sludge and sawdust.

Abstract Co-hydrothermal carbonization (co-HTC) is recognized as a promising pretreatment for upgrading fuel quality of high moisture biomass prior to further thermal conversion. The properties of the hydrochar derived from co-HTC of sewage sludge (SS) and sawdust (SD), and CO 2 gasification characteristics of the hydrochar were investigated. The results showed that the hydrochar had enhanced aromatic degree and increased metals content compared to raw sludge. The hydrochar also exhibited an enhanced gasification reactivity, resulting in high carbon monoxide content in the syngas than that from SS under identical conditions. The temperature and SD/SS mass ratio had a significant influence on the syngas composition mainly by the Boudouard reaction and water gas reaction. The gasification reactivity was strongly associated with the inorganic elements, and the KAlSi 3 O 8 inhibited while the K 2 CO 3 promoted the gasification reaction of hydrochars. Under optimal conditions, a high gasification efficiency of 77.73% was obtained, and the lower heating value of the syngas reached 8.15 MJ/Nm3. This study indicated that co-HTC of SS and SD combined with subsequent gasification had promising potential towards syngas production with high quality. Highlights • The hydrochar from co-HTC of sewage sludge and sawdust was prepared. • Hydrochar had enhanced aromatic degree, metals content and gasification reactivity. • Temperature and sawdust content had a significant influence on syngas composition. • KAlSi 3 O 8 and K 2 CO 3 had competitive effect on CO 2 gasification of the hydrochar. [ABSTRACT FROM AUTHOR]