An observation of combustion behavior of a single coal particle entrained into hot gas flow

This experimental investigation undertakes visual observation of burning coal particles in a hot flowing gas environment, focusing on the initial stages of coal combustion. Pulverized single coal particles transported by cold carrier gas are injected perpendicularly into a high-temperature environment up to 1240 K and 16.7–40.2% of O2. High-speed photography with microscopic magnification in half-shadow conditions provided improved images of the combustion behavior of moving particles and flames in time and space. Spatial location of the particle along with a known time interval allowed positioning as related with the mixing gas flows. This approach allowed the timing of the characteristic sequence of the sub-processes. Observed images of burning particles were quantified in terms of changing size, shape, and intensity of the apparent flame emission. This method enabled an interpretation regarding the progress of volatile flame formation observed by the visual appearance of the particle and its associated flame. The size measurement of the apparent volatile flames with varying particle size and oxygen concentration also allowed instructive discussions along with model descriptions of spherically concentric formation of the volatile flames. The observation results of the burning particles starting from the injection, heat-up, formation of volatile flames as well as the progression of the heterogeneous reaction are presented.