Calculation of the Calorific Value of Macerals and Petrographically Inhomogeneous Coals

摘要

The measurements carried out by different authors [1-3] of the highest (with account taken of the heat of condensation of water vapor) heat of combustion (calorific value) of the organic matter Q_s~(daf) of maceral concentrates separated from coal have shown that their principal groups-vitrinite Vt, inertinite I and liptinite L differ rather substantially with respect to Q_s~(daf). Hard coals of low and medium ranks are characterized by the sequence L>Vt>I, in which the heat of combustion legitimately decreases, which is accounted for by the decrease of the hydrogen content in the structure of macerals. As the degree of metamorphism increases the difference in values of Q_s~(daf) gradually diminishes because the structural parameters of groups L, Vt and I become comparable. These specific features in the behavior of the heat of combustion of macerals are nicely illustrated by the data of Table 1 which is based on the results of a study of maceral concentrates from German coals [4]. The given values of the vitrinite reflectance index R_0, which characterizes the degree of metamorphism of coal were estimated according to the data on C~(daf) and V~(daf) on the basis of the dependence on R_0 for the carbon content in vitrinite and the volatile-matter yield from vitrinite. In the case of petrographically inhomogeneous coals their heat of combustion may be considered to be an additive function of the heats of combustion of macerals (Q_L, Q_(Vt) and Q_I) since the reaction of combustion of a mixture of organic substances is thermodynamically equivalent to the sum of such reactions for each of the substances.