Two Liquid Phases of the Plastic Mass of Coking Coals

摘要

In (1) data was presented which make it possible to conclude that within the plastic range of Donetsk coals there exist two periods of formation of liquid degradation products or two liquid phases. At a later time (2) it was presumed that this phenomenon is universal, being common to all caking coals. An analogous idea was used by Ulanovsky (3) to explain the existence of two peaks of fluidity of the plastic mass of Donetsk coals on the basis of the "two-phase" model of coals. The first period of high fluidity was tied up with the melting of natural low-molecular-mass components of coals and the second with the thermal degradation of the macromolecular phase, which forms new liquid substances. In the light of the experimental data reported by the authors cited and of the data available in the literature, the two-period character of formation of liquid substances during the coking of coals with attendant effects deserve a detailed analysis.The problem of the existence of two fluid phases, which successively appear, with an interval of 30-60 deg C, in intergrain spaces of the mass being coked, arose in connection with the work by Smutkina et al. (4), who have shown, using a Donetsk coal from the "Pioneer" mine (G6) and a Kuznetsk coal from the "Polysaevskaya" mine (G6), that upon their hot briquetting the dependence of the strength of briquettes on the briquetting temperature passes through two well-pronounced maxima. Though no conclusion was made concerning the two fluid phases, it nevertheless was "in the air" since the work (4) was preceded by the publication of the data presented at the USSR Conference of Coke Chemists in 1965 (5), which show that the dependence of the rate of liberation of tar from Donetsk coals of various stages of genesis of seam m_3 on the temperature of their heating exhibit two closely located and partially overlapping peaks (Fig. 1). Other authors (6) have shown, for the "Pioneer" coal, that the "viscosity" of its plastic mass as determined in the Kushnirevich plastometer usually has two peaks of close heights rather than one peak. It is characteristic that two peaks were not observed for the coarse-grain mass but appeared distinctly upon fine pulverization (self-leaning) of coal. This pointed to the possible cause of the previous nonobservance of this phenomenon. The petrographic homogeneity of samples served as an unambiguous indication that we are dealing in this case with the specificity of the behavior of vitrinite.