Nitrogen Evolution during Fast Pyrolysis of Sewage Sludge under Inert and Reductive Atmospheres

Abstract

The influence of atmospheres on the product distribution and behaviors of nitrogen evolution during fast pyrolysis of sewage sludge (SS) was investigated in a drop-tube quartz reactor. The results indicated that H 2 improved the formation of gas products and gave a relatively low tar yield in comparison to an inert atmosphere. The char N yield obtained under a H 2 atmosphere is lower than that under an Ar atmosphere. Above 500 °C, H 2 further promoted the conversion of nitrogenous compounds to NH 3 . The HCN yield was low under all conditions. The decomposition of nitrogenous substances in SS produced more amine N, nitrile N, and heterocyclic N under a H 2 atmosphere. The synergistic effect of a reductive atmosphere and high temperature promoted the thermal decomposition of more difficult-to-cleave N-containing heterocycles, such as piperidines, pyrroles, and pyridines. This study provides a better and deep understanding of the nitrogen transformations during fast pyrolysis of SS under a reductive atmosphere, which would benefit the environmental protection and sustainable clean use of SS.