Calorific value, vitrinite

In this paper, we demonstrate how mean maximum reflectance of vitrinite in oil (hereafter referred to as R ) can be used in place of conventional chemical-rank parameters (volatile matter and fixed carbon) to estimate the relative yields of carbonization products, specific properties of gas produced by carbonization, and chemical properties of coal such as calorific value and free swelling index (FS1). Further, we illustrate that measured R can be used to detect coal oxidation, to categorize coals for certain combustion uses, and to help classify coals by rank. 

This investigation shows that the average reflectance of vitrinite in coal (Ro) can be used to estimate carbonization product yields, by-product gas properties, chemical properties, oxidation effects, and combustion behavior. Moreover, R along with calorific value and volatile matter content might be employed to classify accurately and consistently coals of all ranks. 

As unifying, underlying concepts, type and rank certainly can be employed to envision why coals have the properties that they do. However, it is time for a reevaluation of coal classification concepts. How can we measure rank when we analyze coals of different types and when there is no simple rank progression even when vitrinite or vitrinite-rich coals are compared And how can we assess type when maceral identification criteria are highly subjective, except for reflectance measurements that routinely are not even applied to the liptinite and highly variable inerti-nite macerals And, finally, how can coals be classified scientifically when empirical and derived properties like calorific value and fixed carbon yield are employed as classifying parameters ... 

Coal rank from the petrographic point of view is commonly expressed in terms of vitrinite reflectance which may act as an indicator that is independent of other factors (e.g., coal type or grade). Unlike other chemical parameters (e.g., carbon content, hydrogen content, volatile matter yield, and calorific value) it is not dependent on the overall composition of the coal. A number of coal properties progressively change with the advance in rank and the rank of a coal is therefore a major factor influencing its potential application. 

FIGURE 8.12 Variation of carbon content and calorific value with depth for vitrinites. (From Murchison, D. and Westoll, T.S., Eds., Coal and Coal bearing Strata. Elsevier, New York, 1968.)... 

---