Ignition and Combustion Behaviors of Coal Slime in Air

Coal slime is a byproduct of the coal preparation process. Research on coal slime combustion is of primary importance for the utilization of coal slime and energy savings. To explore applications in circulating fluidized bed boilers, the combustion characteristics of single coal slime particles in air at different furnace temperatures were studied. The temperature changes in the center of the coal slime particles, and combustion images during the combustion process were obtained. The rapid pyrolysis of the coal slime resulted in the production of small molecules of volatile gas, tar, and other pyrolysis products. Next, the pyrolysis caused an unusual change in the surface structure of the particles. The temperature changes in the different types of coal slime varied; however, those in the same coal slimes with different particle sizes at the same furnace temperature were similar. With an increasing particle size, the diffusion of internal oxygen slowed, which resulted in slower combustion processes and increases in the ignition delay and burnout times. The exothermic performance index varied for the different coal slimes and decreased with an increase in the particle diameter, which was related to the contents of volatiles and ash in the coal slime.