Coal-Derived Soot Behaviors in O2/N2 and O2/CO2 Atmospheres, Studied through a 1-D Transient Coal Combustion Model

Soot plays an essential role in radiative heat transfer in pulverized coal boilers, but the controlling processes that cause different soot behaviors in O2/N2 and O2/CO2 atmospheres are not clear. In this work, a 1-D transient model of the combustion of single coal particles with soot evolution was proposed and validated in both O2/N2 and O2/CO2 atmospheres. Gasification reactions of tar and soot were included in the soot-relevant reaction pathways, and the reaction rates were compared quantitatively to reveal controlling processes affecting soot behaviors. The results show that the predicted soot volume fraction decreases apparently in O2/CO2 environments when soot gasification and tar gasification are considered. The effect of tar gasification is more important than that of soot gasification. However, in O2/N2 environments, both soot gasification and tar gasification barely affect the predicted soot volume fraction. The decrease in soot volume fraction at the late stage of volatiles combustion is predom...