Effect of temperature and water vapor on the form and evolution characteristics of nitrogen in coal char

Studying the evolution and transformation of different forms of nitrogen in pyrolysis under water vapor atmosphere is conducive to control formation of nitrogen oxides. X-ray photoelectron spectroscopy (XPS) was used to examine forms of nitrogen in typical bituminous coal and its char, and effects of temperature, water vapor on evolution and conversion characteristics of coal nitrogen were investigated. The results indicate that raising temperature and concentration of water vapor are conducive to evolution of char nitrogen. When concentration of water vapor reaches 30%, the char nitrogen evolution reaches a peak. The presence of water vapor facilitates the evolution of N-5 and N-6 from coal char and suppresses that of N-Q and N-X, because the gasification effect of water vapor is beneficial to breaking aromatic structure, but the conversion of N-6 to N-Q and N-X is promoted as a result of H and OH groups brought by the high concentration of water vapor.