Reflectance, mean maximum

The mean maximum reflectance of vitrinite (Ro max) is the mean of one hundred determinations. 

Figure 8 shows the effect of rank, as measured by the mean maximum reflectance of vitrinite, on the overall conversion. 

Figure 2. Noncatalytic hydrogenation—product yields vs. vitrinite + exinite content. Curve a, total conversion (X) Curve b, extract ( ) (10). (Note Lines a and b relate to coals where the mean maximum reflectance (R0 max) of the vitrinite fall in the range 0.43-0.68%. Values in parenthesis refer to R0 max for...

Figure 7. Relationship between conversion and mean maximum reflectance...

The relationship between conversion and the mean maximum reflectance is shown in Fig.7 In Yamakawa s data, a fairly good relationship is found except for abnormal coals of high inert content (Griffin, Grose valley) and low inert content (Miike). A similar good relationship is also found in P.H. Given s data. However, the characteristics of this relationship are the reverse in both cases. Thus, it seems that the mean... 

The studies carried out consist of the megascopic description of the master columns study of thin sections for maceral assessment, determination of maceral composition on polished blocks in reflected light, determination of mean maximum reflectance values on polished pellets, proximate analyses of selected petrographic zones, hot stage studies on vitrinoids to determine the thermal behavior at various temperatures, electron microprobe and spectrochemical studies of selected zones to determine the nature of ash forming elements, analyses of certain zones petrographically important to determine the variation of total carbon, and hydrogen and microhardness determinations on certain macerals. 

Figure 7. Variation of mean maximum reflectance in various zones of Seam 4 (left) and Seam 2 (right)...

The histograms in Figure 8 show the distribution of vitrinoids in both the seams. Both the histograms generally show the same type of distribution with a peak of Vc, V4, and Vs on either side of the tail. The mean maximum reflectance values for each zone are presented in Table IV. 

Quring the past several years coal petrography has gained acceptance in certain areas of coal utilization, preparation, and mining as a useful analytical tool. The rapid evolution of this analytical technique can be attributed to the development and subsequent refinement of quantitative methods for measuring the reflectance characteristics of vitrinite in coal (8, 14, 15, 16). Mean maximum reflectance has been shown to be directly related to coal rank (14, 16). Moreover, it is known that rank is important in determining certain carbonization and chemical properties. 

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. 

Louis G. Benedict We have not observed any significant changes in mean maximum reflectance in a given coal sample with increasing moisture content. We have observed, however, that significant alterations in reflectance result from oxidation. As fresh coal is progressively oxidized, mean maximum reflectance decreases, reaches a minimum, and then increases steadily with con-... 

Two general areao in Colorado exhibit extensive alteration of coalo by igneouo intrusives. The first locality it near Somerset in the west central part of the state, and the second area is the Spanish Peaks region near Trinidad and Walsenburg. Drill core samples, outcrop samples, materials from active mines, and thin sections of the intrusive rocks were studied. The results show that mean maximum reflectance of the altered coal or natural coke increases as the distance from an intrusive body decreases. Carbon and ash values increase as the distance from intrusive decreases whereas volatile matter values decrease. Sulfur data are variable. Hydrogen values increase as the distance from an intrusive increases. Hydrogen and reflectance are considered the most sensitive and reliable indicators of degree of alteration. 

Figure 12. Variation in mean maximum reflectance across xenolith of natural coke...

The refractive index of coal can be determined by comparing the reflectance in air with that in cedar oil. A standard test method (ASTM D-2798) covers the microscopic determination of both the mean maximum reflectance and the mean random reflectance measured in oil of polished surfaces of vitrinite and other macerals in coal ranging in rank from lignite to anthracite. This test method can be used to determine the reflectance of other macerals. For vitrinite (various coals), the refractive index usually falls within the range 1.68 (58% carbon coal) to 2.02 (96% carbon coal). 

The mean maximum reflectance of vitrinite was determined in oil (ca. 1.517 index of refraction) and in 546-nm wavelength green light. A photomultiplier photometer was used to measure vitrinite reflectance. Two glass standards were used to calibrate the equipment. A Leitz MPV2 microscope photometer was used. The reflectance values were determined as designated in ASTM D2798-85 (2 5). Twenty-five vitrinite reflectance values were determined for the Rasa coal. 

In a single coal, vitrinite, which is usually the commonest maceral, has a higher reflectance than the associated liptinite, but a lower reflectance than inertinite. There is, therefore, a correlation between carbon content and reflectance, and this is used to precisely determine rank. The mean maximum reflectance of vitrinite in oil (Romax) as the level of organic maturity, or rank, of a coal sample. 

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