Vitrinite Reflectance as an Indicator of Coal Metamorphism for Cokemaking
R. R. Thompson, L. G. Benedict, 1974. "Vitrinite Reflectance as an Indicator of Coal Metamorphism for Cokemaking", Carbonaceous Materials as Indicators of Metamorphism, Kussell R. Dutcher, Peter A. Haequebard, James M. Schopf, Jack A. Simon
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The measurement of vitrinite reflectance has been employed as the standard measurement of coal metamorphism for more than a decade in the application of coal microscopy to the cokemaking industry. At Bethlehem Steel, however, it was recently found that the reflectance measurement of metamorphic stage must be restricted to truly reactive vitrinite, excluding pseudovitrinite, before acceptably accurate relations can be established between coal petrographic composition and coking properties. Pseudovitrinite, which we no longer class with vitrinite, apparently has undergone an unusual geologic history, and its reflectance measurement can be misleading as an indicator of metamorphic stage.
Restriction of the measurement of metamorphic stage to reactive vitrinite not only improves our ability to work out cokemaking relations but also reveals discontinuities in the coal metamorphic series that must have accompanied fundamental changes in coal constitution. At least three such discontinuities occur within the coking coal range, and these can be documented with cokemaking data. These findings form the basis of a practical system for the prediction of coking properties from petrographic analyses.