Numerical study of combustion characteristics for pulverized coal under oxy-MILD operation.

MILD (Moderate or Intense Low-oxygen Dilution) combustion is a novel technology to reduce NO X emission from combustion. With the development of this technology, it is expected to combine this technology with oxy-fuel combustion to jointly control the pollutants from fossil fuel combustion. The present paper investigates the combustion characteristics of coal under oxy-MILD operation with the aid of CFD simulations. A seven-step global reaction mechanism is used for modeling coal combustion involving gaseous volumetric reaction and particle surface reaction. The predicted results using the adopted models for the reference case agree well with the experimental results. It is revealed that, the combustion temperature level increases with the enhancement of initial oxygen concentration because of the reduced injection momentum and promoted heat release. The in-furnace CO formation increases but the final CO emission reduces when enhancing the oxygen concentration under oxy-MILD combustion. Moreover, oxy-MILD combustion shows a greater potential on NO X formation reduction than air-MILD combustion, and this potential is promoted at higher initial oxygen concentration. [ABSTRACT FROM AUTHOR]