Study on characteristics of coal gasification fine slag-coal water slurry slurrying, combustion, and ash fusion

In this study, the effects and mechanisms of coal gasification fine slag-coal water slurry (CGFS-CWS) preparation, combustion and ash fusion (AF) were assessed. As the CGFS content increased, the viscosity of the slurry increased, but the stability of the slurry improved significantly. The improvement in the slurry stability is due to the negative charge on the surface of CGFS is significantly stronger than that coal particles. This stronger charge provides strong electrostatic repulsion, which facilitates particle dispersion. The slurry combustion experiments revealed that the incorporation of CGFS significantly reduced the burnout temperature of the slurry and increased the maximum combustion rate. When the mixing amount was less than 8%, the flammability index, combustion stability index, and comprehensive combustion characteristic index significantly improved. Such finding may be due to the formation of activation centers by the alkali metals in CGFS, which promote combustion reactions. The AF temperature of the CGFS-CWS ash decreased as the CGFS blending amount in the slurry increased. This result is due to the melting-assisting effect produced by the Fe2O3 and sulfate contained in the CGFS ash. Albite crystallization with a lower fusion temperature also appeared in the CGFS-CWS, which may be generated by the reaction of nepheline in coal ash and sodium-containing compounds in CGFS ash at high temperatures.