Microstructural changes in coal during low temperature ashing

Abstract Samples of two US coals were oxidized for 72 hours in a low temperature asher. Scanning transmission electron microscopy and automated electron microprobe analysis were employed to observe the mineralogical changes produced in the coal by the ashing process. It was found that the microstructure of the low temperature ash was strongly influenced by the mineral matter which was originally chemically-bound in the organic matrix of the starting coal. The partial oxidation of pyrite during the ashing was also observed. The results reveal some of the physical mechanisms involved in the low temperature ashing process.