Mineral-char interaction during gasification of high-ash coals in fluidized-bed gasification

Abstract

The mineral-char interaction can occur during the gasification of high-ash coals in fluidized-bed gasifiers when the melted minerals cover the char surface by penetrating into the cracks and pores of the char. In addition to the physical effects on char reactivity, the molten ash also appeared to participate in a chemical reaction at the char-mineral interface, which seems to have involved the modification of the carbon properties. A structurally more ordered part formed at the interaction interface and less in the unaffected part. To establish this fact, the mapping of two Raman parameters ID/IG versus IV/IG was used. This study sought to evaluate the impact of melted mineral on parts of the chars generated at 960C and 30 min in oxygen-enriched conditions, while X-ray spectroscopy [and energy-dispersive spectrometry (EDS)] mapping was used to determine the distribution of elements, such as Si, Al, Mg, Ca, and K, in the same chars. The higher ordered structure of the carbon around the melted minerals penetrating or surrounding carbon suggests a higher degree of interaction and modification of the local carbon by the minerals.