Nitric oxide formation during corn straw/sewage sludge co-pyrolysis/gasification

Nitric oxide formation in accompanying with biomass-derived gas during pyrolysis/gasification would contribute to around 15% of nitrogen oxide emission during subsequence combustion. In this work, in order to meet the increasingly stringent nitrogen oxide emission regulation, nitric oxide emission characteristics during co-pyrolysis/gasification of corn straw and sewage sludge were investigated in a laboratory-scale tubular furnace. Results showed that nitric oxide formation was noticeably occurring, and the synergistic effect was existed during corn straw/sewage sludge co-pyrolysis. The sewage sludge proportion of 75 wt% caused 25.3% nitric oxide reduction, double the figure for 50 wt% sewage sludge and 25 wt% sewage sludge (12.5% for 50 wt% sewage sludge and 13.2% for 25 wt% sewage sludge). During co-pyrolysis, nitric oxide emission was affected by different parameters. Heating rate could affect nitric oxide emission through a comprehensive mechanism which contented the effect on reaction time, nitric oxide reduction by carbon monoxide on char surface, and the effect on the devolatilization strength. Hydrogen/nitrogen ratio could also affect nitric oxide emission, however, the influence degree decreased as hydrogen/nitrogen increased. Furthermore, the oxygen/nitrogen ratio in fuel blends was determined as the most critical parameter on nitric oxide emission through Grey Relational Analysis. During co-gasification, Nitrogen functional groups were determined by Fourier Transform infrared spectroscopy. Char residues in 5%Oxygen/95%Argon atmosphere showed more functional groups related to N-containing matters than that in 5% Carbon dioxide/95%Argon, especially Amide group (Carbon-Nitrogen bond amide Ill, Carbon-Oxygen double bonds amide I) and Nitrogen-Hydrogen bond remained. And this result indicated that different atmospheres could affect nitric oxide emission through the pathway of the fuel-nitrogen transformation.1. (C) 2018 Elsevier Ltd. All rights reserved.