Investigation on the OH*and CH* chemiluminescence characteristics of single coal particle flames under O2/CO2 atmosphere

Here, the OH* and CH* chemiluminescence characteristics of a single coal particle flame combustion in a visual drop-tube furnace (VDTF) for different oxygen fraction, X i,O2 , in O 2 /CO 2 atmosphere were investigated using an optical diagnostic technique. The results indicate that the combustion of single coal particles is composed of a volatile reaction stage followed by a volatile-char reaction stage. During volatile reaction stage, the single coal particle burns in an enveloped flame. The flame becomes brighter and the flame length increases gradually. In addition, the OH* and CH* intensity shows peak values with axial distance along the furnace, with that of OH* appearing earlier as the oxygen fraction increases. In the volatile-char reaction stage, the flame length fluctuates slightly, and OH* and CH* peak position are spread over a smaller range of distance. The value of X i,O2 affects the reaction rate as it promotes the diffusion of oxygen to the interior of coal particle, as the intensity of OH* and CH* increasing rapidly for X i,O2 > 0.4. This indicates that the rate of reaction is controlled by X i,O2 . Furthermore, the peak intensity ratio of OH* and CH* increases linearly with X i,O2 . • O 2 /CO 2 atmosphere of single coal particle was studied in visual drop-tube furnace (VDTF). • Single coal particle combustion characteristic was studied using optical diagnostic technique. • OH* and CH* chemiluminescece distributions at different X i,O2 were obtained. • Effects of X i,O2 on distribution characteristics of OH* and CH* were further analyzed. • Quantitative relation among the OH* and CH* peak intensity, OH*/CH* and X i,O2 were studied.