Observation of Volatile Cloud Formation during the Early Stages of Pulverized Coal Combustion

Abstract

During the early stages of combustion when bituminous coal particles are in a nearly single particle combustion environment, a surrounding mantle of volatile products is observed. Initially, the cloud is of spherical shape and almost concentric with the particle. As the reaction progresses, more material is ejected in the shape of jet-like tails, This rapid mass release was observed through in-situ high speed photographs of particles in combustion environment, and was also confirmed by examining cross sections of the quenched samples of coal particles. The inner structure became porous, while base material softened and some portion of it was ejected due to high pressure build up inside. Direct sampling of the partly burned coal particles revealed that the material in the volatile cloud contained tarry substances and small sized particle fragments in addition to gaseous volatiles. These solid and condensible substances were seen as a luminous envelope which implied that they participated in the radiative transfer process.