| Popis: |
High speed camera is employed to capture the transient images of the burning particle in a flat-flame entrained flow reactor, some information of the burning particle, such as the optical intensity and the residence time, are obtained through analysis of transient images. The ignition and devolatilization behavior of different rank coals at 1,670, 1,770 and 1,940 K over a range of 2–30% O2 in both N2 and CO2 diluent gases are researched. The results indicate that the laws of ignition and devolatilization of pulverized coals in low oxygen O2/CO2 atmosphere are consistent with the literature, which focus on the environments of high oxygen contents (10–30%) or lower temperate (900–1,500 K). With the gas temperature and oxygen content increased, the ignition delay time and devolatilization time for the lower oxygen content cases decreased for both N2 and CO2 atmosphere. With the use CO2 in place of N2 in low oxygen content, the ignition delay was retarded and the duration of devolatilization was increased. The effect of CO2 on coal particle ignition is explained by its higher molar specific heat. And the effect of CO2 on devolatilization results from its effect on the diffusion rates of volatile fuel and oxygen. |
