Hydrothermal liquefaction of municipal sludge: Coupling effects of temperature and time on nitrogen migration

Biocrude derived from hydrothermal liquefaction of municipal sludge has a high nitrogen content, which limits its direct use. This work explored coupling effects of reaction temperature and residence time on N transformation during hydrothermal liquefaction of municipal sludge. The results showed that 350. and 40 min were the optimal conditions, which led to the highest biocrude yield, HHV, energy recovery, and N removal efficiency after hydrothermal liquefaction of municipal sludge within 200-350. for 10-50 min. More than 60 wt% N in municipal sludge was distributed in the aqueous phase and NH4 + was the richest substance after hydrothermal liquefaction. Also, N transformation pathways were clarified by correlating the effects of reaction temperature and residence time on N distribution.

Automated summary

This study investigated the coupling effects of reaction temperature and residence time on nitrogen transformation during hydrothermal liquefaction of municipal sludge. The optimal conditions were determined and the distribution and transformation pathways of nitrogen were clarified.