Effects of carbohydrates on NOx precursor formation from proteins during sewage sludge pyrolysis

In this study, sludge component extraction was used to probe the effects of carbohydrates on the pyrolytic formation of NOx precursors from sludge protein (SP), and the volatilization behaviors of degreased sludge (DS) and SP were studied using thermogravimetry-Fourier transform infrared spectrometry. The main nitrogen containing gases produced by sludge pyrolysis were identified as NH3 and HCN, and DS showed a higher solid residue yield and lower NH3/HCN yields than those of SP, which is ascribed to the partial fixation of nitrogen in char due to the Maillard reaction between carbohydrates and proteins in DS. Calculations based on the Friedman and Flynn-Wall-Ozawa methods show that the activation energy of SP decomposition exceeded that of DS decomposition, indicating that carbohydrates can promote protein degradation. Thus, this work provides new insights into the interactions between proteins and carbohydrates during sludge pyrolysis and promotes the optimal utilization of sewage sludge. (C) 2021 Elsevier B.V. All rights reserved.