Experimental study on the regulation of NOX in co-pyrolysis of maize straw and woody biomass

Abstract

The NOX emissions from biomass as a carbon–neutral energy source during thermal conversion are of great concern. The research on the transformation law of NOX precursors in the thermal conversion process of biomass is an effective measure to regulate the nitrogen migration path of raw biomass and reduce the emission of NOX pollutants. In this study, maize straw was mixed with Eucalyptus wood chips and apple wood chips, respectively, and the slow pyrolysis experiment was carried out at 700 °C to control the nitrogen-containing products, the properties of char-N, tar-N and NOX precursor were studied by TGA, XPS, GC-MS and spectrophotometry, respectively.The results showed that, compared with the theoretical value of pyrolysis nitrogen products of maize straw and woody biomass alone, the addition of Eucalyptus wood chips increased the char-N yield, and the synergistic effect was the strongest under the condition of 50 wt.% addition ratio of +0.2980, the yield of char-N was 32.06 wt.%, apple wood chips was only observed to promote char-N at the addition ratio of 25 wt.%, the synergy intensity was +0.2013, the yield of char-N was 30.27 wt.%, and other experimental groups showed inhibition effect. At the same time, the co-pyrolysis system has a significant inhibitory effect on the NOX precursor nitrogen (NH3-N + HCN-N), among which the Eucalyptus wood chips addition test group has a more obvious inhibitory effect on NH3-N, the synergistic intensity reached the strongest at −0.5926 when the addition ratio was 25 wt.%; while the apple wood chips addition test group had a more obvious inhibitory effect on HCN-N, and the synergistic strength reached the strongest at −0.5798 when the addition ratio was 50 wt.%. In summary, regulating the migration path of nitrogen in the process of thermal conversion of biomass is helpful for cleaner utilization of biomass resources.