Particle temperature and composition measurements in the ignition phase of single coal particles and particle groups under conventional and oxy-fuel atmospheres

The transition from single to group particle combustion is experimentally investigated in a laminar flow reactor. Optical techniques including two-colour pyrometry and a sampling probe provide data on surface temperature and composition of high-volatile bituminous coal particles during ignition, volatile combustion, and char burnout. Adjustable particle number densities (PND) permit studying the transition from single to group particle combustion. An optical imaging pyrometer provides simultaneously acquired data on the soot particles during the volatile combustion and the particle temperature, particle size and position in the 3D particle streak. These parameters are investigated as a function of the PND, which is used to differentiate between single and group particle combustion. Additionally, particle sampling provides particle composition data, which together with the particle temperatures extends a previously published data set from the same reactor. The results show a direct relation between the particle temperature during char burnout and the PND. As particles in group combustion absorb a significant amount of thermal energy from the surrounding atmosphere and reduce the oxygen content in the group, the measurements prove a lower temperature for particles that burn in group compared to single particle. Furthermore, sampling at several residence times indicates a notable difference in the burnout process between single particle (SP) and group particle (GP) combustion. While the effect of different atmospheres impacts the results of SP combustion, GP combustion is significantly less affected. The results of the current study are jointly discussed with previously acquired data of the same burner for a thorough interpretation.