Effects of ambient temperature on the combustion processes of single pulverized coal particle

In the pulverized coal combustion, coal particles cross over a steep temperature gradient formed by a diffusion flame. This temperature gradient affects the particle temperature. This study has experimentally investigated effects of field temperature and residence time in high-temperature regions on the flame structure of single coal particles, since the substances of the devolatilization process varied due to the particle heating rate. The inlet velocity and the oxygen concentration of a laminar couterflow vary to control the residence time and the temperature gradient, respectively. A magnified two-color pyrometry was carried out to understand flame structure and the time series of flame and particle temperature. The results showed that the increase of oxygen concentration raises the volatile matter combustion temperature and flame diameter, and prolongs duration of the volatile matter combustion. The char combustion temperature decreases as the flow velocity increases. The maximum effective flame diameter increases linearly with increasing volatile matter combustion temperature regardless of particle size. This suggested an increase in flame interference distance. The maximum flame diameter increases monotonically with increasing volatile matter combustion temperature.