Ash deposition of a Spanish anthracite: effects of included and excluded mineral matter

This study has been undertaken to provide an insight into the effects of mineral matter distributions in coal on the nature of boiler slags formed during the combustion of a high ash Spanish anthracite. Three density fractions were prepared, and the light and heavy fractions were combined to give a sample containing mainly excluded mineral matter. The mineral matter in the medium density fraction was predominantly included. Slag deposits were prepared in the laboratory from the whole coal, the light+heavy and medium density fractions. The coal with excluded mineral matter was found to produce a slag similar in nature and chemistry to the whole coal ash deposit. The coal with included mineral matter produced a vitreous, iron-rich deposit. The deposits were compared with slags, obtained from a Spanish power station boiler, burning a blend containing the same anthracite.