Evolution of NOX precursors of superfine pulverized coal with a fixed bed in N2 and CO2

Superfine pulverized coal, as a novel clean coal utilization method, has been attracting more and more attention. Evolution of nitrogen oxide (NOX) precursor especially in high temperature regions (>1000 °C), plays a crucial role in further exploration of NOX formation mechanism. In this paper, the evolution of the main NOX precursors (HCN and NH3) during the rapid pyrolysis process and gasification process was investigated. Their formation mechanism at high temperature was discussed. The result indicates that experiment conditions and characteristics of parent coal have great influences on the release of HCN and NH3. Furthermore, the changes in particle size affect surface nitrogen functional groups, leading to the discrepancy in the evolution of NOX precursor. As the particle size decreases, the amounts of HCN and NH3 increase in both N2 and CO2. The ratios of nitrogen converted to HCN and NH3 are higher in low rank coals. The concentration of CO2 suppresses the formation of HCN and NH3 at high temperatures. With further increase of temperature, the ratio of nitrogen converted to HCN in CO2 reduces, and there is scarcely HCN existed when the temperature is higher than 1210 °C. However, as temperature goes up, the ratio of nitrogen converted to NH3 with HN coals in CO2 decreases and it first increases and then decreases for NMG coals. The content of NH3 is too low to be detected at 1310 °C.