Impact Properties of Two-Stage Sewage Sludge Hydrothermal Liquefaction on Nitrogen in Biocrude
Sewage sludge(SS)is an important organic solid waste from conventional municipal wastewater treatment and a potential feedstock for the preparation of bio-liquid fuels.Two-stage hydrothermal liquefaction(i.e.,the combination of low-temperature and high-temperature stages)treatment can effectively reduce the nitrogen content in biocrude derived from nitrogen-rich biomass hydrothermal liquefaction,improving its fuel grade.Comparative experiments on two-stage hydrothermal liquefaction and direct hydrothermal liquefaction of SS were carried out to investigate the nitrogen content,component and elemental mass flow characteristics of biocrude under different conditions of temperature(300,325,and 350℃),residence time(10,30,and 50 min)and solid content rate(5%,10%,15%,and 20%).The results showed that under a temperature of 325 ℃,a residence time of 10 min,and a solid content rate of 10%,the nitrogen content of the two-stage hydrothermal biocrude was significantly reduced(from 3.60%to 1.37%).Through comparative analysis,the nitrogen removal of biocrude from sewage sludge two-stage hydrothermal is mainly done by inhibiting the Maillard reactions.
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