Correlation of the Sub-micrometer Ash Yield from Pulverized Coal Combustion with Coal Ash Composition

The present work investigated the correlations of the particulate matter with an aerodynamic diameter of <1 mu m (PM1) yield from pulverized coal combustion with coal and ash composition. PM1 yields from burning pulverized coals under similar conditions in laboratory reactors, together with analytical contents and ash composition of the parent coals, were collected from the literature to form a large database containing results of 75 coals. On this basis, linear regression analysis was employed to examine the correlations between the PM1 yield and the coal and particularly ash composition, using the Pearson correlation coefficient to denote the degree of correlation. The indexes evaluated include the volatile matter, ash, and sulfur contents of the coal, the contents and summed contents of oxides, and the ratios of the content or summed content of basic oxides to the summed content of acidic oxides of coal ash. PM1 yields were observed to have positive correlations with the contents and summed contents of basic oxides, except K2O, and all of the ratio indexes and negative correlations with the contents and summed contents of acidic oxides. The correlations and their degrees are strongly rank-dependent, with significant differences between lower rank (lignite and sub-bituminous) and higher rank (bituminous and anthracite) coals. Fairly good correlations exist with some combined indexes of ash composition, including Na2O + MgO, (Na2O + MgO)/(SiO2 + Al2O3) ratio, content ratio of all basic oxides to all acidic oxides (B/A ratio), and the linear combination of oxide contents. They are potentially applicable for estimating PM1 formation from pulverized coal combustion for practical purposes.