Maceral/microlithotype analysis of the progressive grinding of a Central Appalachian high-volatile bituminous coal blend

The petrographic composition of sized coal produced through the progressive grinding of a Central Appalachian high-volatile bituminous coal blend was analyzed for multiple sets either by removing fine, -200-mesh, coal after e ach test iteration or by retaining the fine coal in progressive test fracti ons. With prolonged grinding, coarser fractions tend to become depleted in vitrinite and vitrinite-rich microlithotypes, leading to progressively hard er-to-grind coal remaining in the oversize, +200-mesh, fractions. The latte r trend is shown both by the maceral and microlithotype composition of the coal and by the increased slope and fractal dimension of size-frequency dis tribution, implying an increase in hardness and resistance to grinding of t he oversize coal.