Nitrogen transformation during coal decoulping combustion I: release behavior of coal-nitrogen during pyrolysis stage

Effect of temperature and residence time on coal-nitrogen transformation during pyrolysis of 3 coals from west China was studied in a fixed bed reactor. The results show that the duration time of HCN releasing is about 3 min at 1 073 K for pyrolysis of coal A. The start release time of HCN is earlier than that of NH3, and the released amount of HCN quickly drops to zero as NH3 starts to release. The accumulated release amounts of HCN and NH3 first reach the maximum value at different pyrolysis time and then decrease sharply. The yield of char-nitrogen increases with increasing temperature. At 973~1 123 K, about 50~60 mass percentage of the coal-nitrogen exits in char as char-nitrogen and the rest is released as volatiles, in which about 20~50 mass percentage of the volatile-nitrogen is NH3 and HCN. The mass percentage of NH3 accounts for 40%~50% and that of HCN about 50%~60% in the volatile-nitrogen.