NO and N_2 Formation Behavior during the High-Temperature O_2 Gasification of Coal Char

摘要

NO- and N_2-formation behavior during the high-temperature O_2 gasification of coal char was examined using a pulse gasification reactor, which minimizes the exothermic heat generation and the secondary reaction of NO. Coal char heat treated at 1300 ℃ was gasified with 10% O_2 in a temperature range from 1000 to 1300 ℃. Although the total nitrogen converted to NO and N_2 are independent of gasification temperature, a fraction of NO tends to increase with increasing char conversion and decrease with increasing gasification temperature. These trends can be explained by the secondary N_2-formation reaction from NO and char via nitrogen-containing surface species as an intermediate. This result is similar to that observed in the previous study at low temperatures, except that the surface nitrogen species is less stable at high temperature. In another series of experiments, the char prepared at 950 ℃ was subjected to gasification without pretreatment at 1300 ℃. The NO- and N_2-formation behavior heavily depends on whether the char was pretreated at 1300 ℃. The release of unstable char nitrogen as N_2 was observed in addition to the N_2 formation from the char―NO reaction when the char was not heat-treated at a severe condition. The relative importance of these two N_2-formation routes determines the final gas composition.