Effect of mineral matter on the formation of NOX precursors during biomass pyrolysis

Formation of NOX precursors during pyrolysis of three typical kinds of biomass (wheat straw, rice straw and corn cob) was studied using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer in argon atmosphere. Two pretreatment methods, including deionized water washing and acid washing were utilized to investigate the effect of included minerals on the distribution of nitrogen containing species during wheat straw pyrolysis. KOH and CaO were loaded onto the demineralized (dem) wheat straw to study the effect of excluded minerals on nitrogen release. The residues of the samples after pyrolysis were characterized by X-ray diffraction (XRD) analysis. The results show that different kinds of biomass have distinctive formation characteristics of N-containing species. HCN and HNCO are the main N-containing species for rice straw, while NH3 and HCN are the main N-containing species for wheat straw and corn cob.The existence of minerals influences the formation of N-containing species during biomass pyrolysis. Both the included potassium and excluded potassium promote N-conversion to NH3, HCN, NO and HNCO at lower temperature, but decrease the total yields of N-containing species. The included calcium decreases N-conversion to HCN, NH3 and HNCO at lower temperature (