Combustion Reaction of Pulverized Coal on the Deposit Formation in the Kiln for Iron Ore Pellet Production

The serious deposits on the refractory bricks are found in the grate kiln in iron ore pellet plants, which significantly influence the pellet production. The effect of the combustion reaction of pulverized coal on the deposit formation in kiln during iron ore pellet production was investigated in this work. Hematite iron ore was used as raw material to be pelletized, and the pulverized coal, in general, was used as the fuel. The chemical compositions and microstructures of the deposit samples were detected through the chemical analysis methods, scanning electron microscopy, and energy-dispersive spectroscopy. Effects of different residual carbon contents in coal ash and roasting temperature on the deposit formation were investigated by simulated experiments. Then, the results indicated that the combustion reaction of coal had a significant influence on the deposit formation, under which condition the hematite grains in the preheated pellet were reduced by surrounding residual carbon particles in unburned coal to wustite. Low-melting-point minerals were formed as wustite reacted with silicate, aluminum, and calcium oxides, which adhered on the refractory bricks, especially the brick with cracks. The deposit was generated and became thicker when time went away.