Experiment investigation of coal MILD-Oxy combustion integrated with flue gas recirculation at a 0.3 MWth furnace

Abstract

This paper presents an experimental study of coal MILD-Oxy combustion at 0.3mw pilot-scaled facility in Huazhong University of Science and Technology (HUST), which contains an entirely flue gas recycle system. By increasing the jet velocity to 100m/s, the MILD combustion was achieved without high temperature preheating. Meanwhile the experiment was operated under Oxy-fuel atmosphere that was established by the flue gas recirculation. A swirl Oxy-fuel combustion was also tested as a comparison. The CO2 concentration in flue gas could sustain a high level during the combustion. The major conclusions include: The coal MILD-Oxy combustion can be achieve by high-velocity jet in some extent. But the full dilution and homogenization of heat and reactants can't be achieved under non-premixed combustion because of the separation of fuel and oxygen, which means the ideal MILD-Oxy combustion can't be achieved but only be approached. The reaction zone was enlarged to the vast area of furnace, in which the combustion temperature and reaction rate decreased. The carbon burnout rate decreased due to the reduction of residence time and reaction rate. The NOx emission decreased nearly 40% because of the lower flame temperature.