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.