NO Emission Characteristics of Typical Coals Under O₂/CO₂/H₂O Atmosphere at Intermediate and High Temperatures

NO emission characteristics of Datong bituminous coal (DT) and Yangquan anthracite (YQ) under O₂/H₂O/CO₂ atmosphere at intermediate and high temperatures were investigated in an isothermal thermal analysis system, and the experimental results were subsequently compared with those under O₂/N₂ and O₂/CO₂ atmospheres. Results indicate that there is an obvious peak in the NO release curve of DT under O₂/N₂ and O₂/CO₂ atmospheres at 5% oxygen concentration, but the only NO peak turns into two separated ones under O₂/CO₂/H₂O atmosphere. However, when the oxygen concentration gets up to 21%, the two separated peaks turn back into one peak under O₂/CO₂/H₂O atmosphere. The NO release profiles of YQ are similar to those of DT. The NO emission of DT in O₂/CO₂ is always lower than that in O₂/N₂. At high temperatures, the NO emission of DT in O₂/CO₂/H₂O is higher than that in O₂/CO₂ due to H₂O gasification at low oxygen concentrations. But as the oxygen concentration increases, the NO emission of DT in O₂/CO₂/H₂O becomes lower compared to that in O₂/CO₂. The NO emission of YQ is higher than that of DT, but the changing trend is similar to that of DT under different atmospheres.