In-situ study on fragmentation of a single coal particle during gasification process

Researches on fragmentation of a single coal particle during gasification contribute to the establishment of a complete evolutionary system of coal particles in gasifiers. In this study, the behavior of char fragmentation and ash coalescence as well as the number and size of sub-particles are microscopically recorded to investigate the fragmentation mechanism. The proportion of small-sized sub-particles with particle sizes of 4 similar to 10 mu m are all above 50 % under different atmospheres, nevertheless the average particle size of the sub-particles decreased with the increase of the proportion of oxygen and the total number of sub-particles differed approximately by a factor of 2.5 at most. Additionally, the instantaneous production of sub-particles increases with the particle surface temperature, while the average sub-particle size follows a different pattern with the particle surface temperature under different atmospheric conditions. When the oxygen concentration is over 60 %, the subparticle size decreases as the particle surface temperature increases, while an opposite pattern is observed when the oxygen concentration is below 60 %. It is attributed to the fact that although the increase in surface temperature enhances the char fragmentation behavior, the agglomeration of ash and production large-size ash pellets would be promoted once the particle surface temperature higher than the ash flow temperature for char particles at low reaction rate. Besides, coalesced ash would attract the small-size char fragments, which may ultimately lead to an elevated ratio of large-size char fragments.