Examination of micrinite concentrates from the Cannel City coal bed of eastern Kentucky: proposed mechanism of formation

A high volatile B, micrinite-rich bituminous coal from Morgan County, Kentucky, was crushed and screened to -100 mesh, demineralized and subjected to density gradient centrifugation (DGC). In an initial density separation, micrinite concentration was increased from 52 vol% in the demineralized coal to a maximum of 67% in the 1.25-1.26 g/ml density fraction. Micrinite enriched fractions (1.21-1.29 g/ml) were combined to yield a sample containing ∼61% micrinite. This sample was crushed to -200 mesh in an attempt to enhance micrinite liberation then reprocessed by DGC. Reprocessing resulted in a slight increase in purity to 69 vol% in the 1.25-1.28 g/ml density fraction. The original -100 mesh sample was density separated a second time with the material recovered between 1.22 and 1.30 g/ml combined, crushed, screened past 325 mesh and reprocessed by DGC. Micrinite was recovered at a purity ranging up to 73% (1.27-1.28 g/ml) from the -325 mesh sample. A density of 1.26g/ml and H/C atomic ratio of 0.79 was calculated for micrinite in one of the higher purity micrinite fractions. These values are notably different than published fusinite values and are more similar to vitrinite values measured in high volatile-B coals. The results from this study suggest that the partitioning of micrinite to a density near that of vitrinite was governed by the inherent micrinite density and not particle aggregation. Transition of the micrinite precursors through a mobile liquid phase is proposed as an explanation for the discrepancy between chemical properties and reflectance as well as to account for the observed microlithological occurrences of micrinite in this sample.