Transformation of Coke Carbon Textures and Minerals during Gasification Investigated by SEM/EDS
The carbon textures, minerals, and their interactions of a metallurgical coke during gasification reaction were investigated using scanning electron microscopy/energy dispersive spectroscopy by analyzing exactly the same sites of coke surfaces before and after reaction. The results indicate that most inert maceral-derived component (IMDC) had a greater propensity to react with CO2 than the reactive maceral-derived component (RMDC). A portion of the carbon in mineral-carrying IMDC was removed as a result of the reaction with CO2, leaving minerals, primarily alumino-silicates, more pronounced. However, the reactivity of IMDC was found to be similar to that of RMDC in some cases. The physical features of the alumino-silicates in the coke were barely altered but bound with alkalis during the reaction. The Fe-containing phases were highly active and had strong interactions with the carbon matrix. Voids were formed in the carbon matrix associated with the Fe-containing phases as a result of the catalytic carbon–gas reactions. Iron played a major role in the reactions. The Mg- and Ca-containing phases reacted with the surrounding alumino-silicates and transformed into slag globules. Metallic iron dispersed in the voids or attached on the slag globules was formed as a result of the reduction of iron sulfate or sulfide.