Decarburization and ash characteristics during melting combustion of fine ash from entrained-flow gasifier

Abstract

Disposal of gasification fine ash (GFA), a by-product of coal gasification, is still dominated by stockpiles, increasing land and environmental problems. To explore ways to reduce and reuse GFA through combustion, our research team used the circulating fluidized bed to modify the less reactive GFA through preheating and achieved the secondary use of GFA under high-oxygen and high-temperature reaction conditions. Through this experiment, we explored the effects of equivalent ratio and oxygen concentration in a melt furnace on carbon conversion and ash characteristics. The increase of oxygen concentration in the melt furnace unit benefited decarbonization of the preheated GFA. The increased oxygen concentration in the melting furnace unit was not conducive to the generation of mineral phase structures and pore structures in the products. The mineral phase structures and elemental contents of the coarse slag, fine slag and fly ash produced by the melt furnace unit differed. Reduction of the equivalent ratio did not significantly affect the morphology of the coarse slag products. However, the morphology of the fine slag and fly ash changed more significantly. Moreover, the carbon conversion capacity decreased significantly along with the drop of equivalent ratio and the change of the reaction atmosphere.