Experimental Study of Coal MILD Combustion at a Pilot-Scale Furnace

By increasing the injection velocity to 112 m/s, the coal MILD combustion is established in both experiment and simulation without high-temperature preheating. The simulation can predict the temperature distribution and the species concentration field well, except that at the area near the burner. An experiment of swirl flame combustion is also applied as a reference. The main conclusion is that in the coal MILD combustion, the reaction zone is dispersed across the furnace like flamlete in which the reaction rate is relatively high, and an integration of dark spark appears. The combustion temperature in the MILD combustion was much lower than that in the swirl flame combustion at the centerline; the rate of temperature decrement in the MILD combustion is also slower than that in swirl flame combustion along the centerline, as the reaction is dispersed across the furnace in the MILD combustion and concentrated at a certain region in the swirl flame combustion. At the lower part of the furnace, the oxygen concentration is almost uniform and lower than 6 vol.% except that at near the axis of the high-velocity nozzle.