Research On Form Transformation And Releasing Regulation Of Fuel-N During Pyrolysis And Gasification

The detailed information about the formation and destruction of NOX and its precursors is required for the optimum strategies for the reduction of NOX emissions from the technology based on the pyrolysis and gasification of solid fuels. The solid fuels were pyrolyzed and gasified in a fixed-bed reactor with a heating rate of 15℃/min under Ar, CO2, Ar and O2 mixture and Ar and H2O vapour mixture atmosphere, respectively. NO, NH3 and HCN in the product gases were analyzed by Fourier transform infrared spectrometer (FT-IR). The release character of NO, NH3 and HCN and the transformation regulation of nitrogen were analyzed.N-5 is the main nitrogen-bearing compound in DT coal and NM coal. After pyrolysis at 600℃, the quantity of N-6 in the char increases for DT coal, and decreases for NM coal and FS coal. After pyrolysis at 1000℃, the quantity of N-6 decreases significantly, and for FS coal considerable quantity of N-Q is detected. When the coals were pyrolyzed under Ar atmosphere, HCN and NO yields are lower than NH3 yields. Before 700℃, considerable amounts of HCN and NH3 were produced. Compared with pyrolysis under Ar atmosphere, the presence of O2 leads to the formation temperature of NO and HCN rises greatly. CO2 atmosphere enhances the formation of NO and suppresses the formation of NH3. The presence of H2O vapour enhances greatly the formation of NO, NH3 and HCN and leads to their yields increases substantially.When biomass were pyrolyzed under Ar atmosphere, majority of NO, NH3 and HCN is formed before 800℃. The formation temperature of NH3, HCN and NO of JM is apparently higher than that of DC and MG. DC releases more NH3, HCN and NO than MG and JM. The formation temperature of HCN is apparently higher than that of NH3.The NH3 formed at lower temperature at least partly related to the thermal decomposition of the amino structures. The formation of HCN is mainly from the secondary thermal decomposition of nitrogen-containing structures in chars. Compared with pyrolysis under Ar atmosphere, the presence of O2 suppresses greatly the formation of HCN and leads to its yields decreases substantially. CO2 atmosphere enhances the formation of NO and suppresses the formation of NH3 and HCN. The presence of H2O vapour enhances greatly the formation of NO, NH3 and HCN and leads to their yields increases substantially.The yields of NOX precursors is apparently related to the nitrogen content in the sewage sludge during the pyrolysis of the sewage sludge under Ar atmosphere. Most of the NO are released during temperature range 320-600℃. The formation of NH3 begins at 200℃, and its concentration reaches maximum around 330℃. The release character of HCN is similar for GZ sewage sludge and LWZ sewage sludge, and HCN produces mainly between 300℃and 800℃. Compared with pyrolysis under Ar atmosphere, the presence of O2 suppresses the formation of NO and HCN. CO2 atmosphere enhances the formation of NO, NH3 and HCN and leads to their yields increases. The presence of H2O vapour enhances the formation of NO and NH3 and leads to their yields increases.FS coal mixed with DC, JM, and MG respectively, when pyrolyzed and gasified under different atmosphere, compared with the pyrolysis and gasification of FS coal under corresponding atmosphere:when pyrolyzed under Ar atmosphere, the formation temperature of NO rises, and its yields decreases substantially; the formation temperature of NH3 descends greatly; HCN yields decreases. When gasified under Ar and O2 mixture atmosphere, the formation temperature of NO descends greatly, and its yields increases; NH3 and HCN yields decreases. When gasified under CO2 atmosphere, the formation temperature of NO rises, and its yields decreases; the formation temperature of NH3 descends greatly, and its yields increases substantially; the formation temperature of HCN rises. When gasified under H2O vapour atmosphere, the formation temperature of NO and HCN rises, and their yields decreases; the formation temperature of NH3 descends grealy, and its yields decreases.FS coal mixed with GZ sewage sludge, LWZ sewage sludge, and NTZH sewage sludge respectively, when pyrolyzed and gasified under different atmosphere, compared with the pyrolysis and gasification of FS coal under corresponding atmosphere:when pyrolyzed under Ar atmosphere, the formation temperature of NO rises greatly, and its yields decreases; the formation temperature of NH3 descends greatly, and its yields increases substantially; the formation temperature of HCN descends greatly. When gasified under Ar and O2 mixture atmosphere, the formation temperature of NO has no change, and its yields increases; the formation temperature of NH3 and HCN descends, and their yields increases substantially. When gasified under CO2 atmosphere, NO yields decreases; the formation temperature of NH3 and HCN descends grealy, and their yields increases. When gasified under H2O vapour atmosphere, NO yields decreases substantially; the formation temperature of NH3 descends grealy, and its yields increases; the formation temperature of HCN rises.