Numerical study of pulverized coal MILD combustion coupled with oxygen staging under O2/CO2 conditions

Coupling oxygen staging with pulverized coal MILD-oxy combustion can further reduce NO x emissions, with oxygen concentration serving as a key control parameter. This study investigates the effects of the primary-stream and total oxygen concentrations ( X O2,pri and X O2,in ) on pulverized coal MILD combustion coupled with oxygen staging under O 2 /CO 2 conditions. The results show that, as the O 2 concentration in the primary stream increased from 15% to 27%, the momentum difference between the primary and secondary streams increased, causing the MILD combustion regime to develop earlier in the furnace. The proportion of the MILD combustion region varied linearly with X O2, pri - X O2, in . Heterogeneous gasification in the furnace was enhanced, and the contribution of the H 2 O gasification reaction increased as X O2, pri + X O2, in increased. Increasing X O2, pri promoted MILD combustion and reduced the average coal consumption rate. Increasing X O2,in inhibited gasification and thus decreased the carbon consumption rate. Both increasing X O2, pri and decreasing X O2, in promoted NO reduction. At X O2, pri = 27% and X O2, in = 15%, the outlet NO concentration was 89 ppm@3%O 2 , which was 28.8% lower than that in the MILD combustion case.