Mean Maximum Reflectance Research Articles

Effect of coal properties on the strength of coke under simulated blast furnace conditions

Eight cokes made from coals/blend with different properties (vitrinite mean maximum reflectance = 0.90–1.66, logarithm Gieseler maximum fluidity = 4.16–1.30) were subjected to gasification and annealing simulating the conditions within an ironmaking blast furnace (BF). The specific methodology utilised included gasification of coke with BF gas-temperature profile from 900 to 1400 °C (corresponding from the thermal reserve zone to the cohesive zone) and annealing of coke up to 2000 °C (corresponding to the raceway region). The coke microstrength and macrostrength were determined using ultra-micro indentation and tensile test to understand the effect of coal precursor properties on the strength of the resulting coke and the changes when processed under the simulated BF conditions. Under the high temperatures in the simulated BF processes, the cokes from different coals showed significant differences in their properties, even though most of them had similar Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) values. Coke microtextures experienced significant reflectance loss and structure change upon simulated BF gasification and annealing conditions. The decreases in mean maximum reflectance and bireflectance were more severe for the coke produced from the high rank coal. The cokes made from coals with higher rank and lower Gieseler maximum fluidity exhibited greater change in their microstructure upon high temperatures. As a result, microstrength of cokes produced from these coals decreased more than that of coke made from the parent coals with a lower rank and higher Gieseler maximum fluidity; this tendency was more significant in the Reactive Maceral Derived Components (RMDC) than Inert Maceral Derived Components (IMDC) microtextural type. Degradation of macrostrength of cokes produced from coals with higher rank and lower maximum fluidity was also more severe due to the greater decrease in their microstrength.

Microstructure of graptolite periderm in Silurian gas shales of Northern Poland

Core samples of Silurian graptolite shales from an exploration borehole within the Baltic Basin were examined by optical microscopy, Raman spectroscopy and high resolution transmission electron microscopy. Graptolite periderm is composed of poorly ordered carbonaceous material of mainly aromatic structures. The dimension of the coherent domains is 1–2 nm. They are composed of two to three stacked layers. Raman spectral parameters of graptolite periderm are correlated with the mean random (Rr) and mean maximum (Rmax) reflectance of graptolites. The spectral ID1/IG ratio predicts thermal maturity in a mean reflectance of graptolites (Rr) range between 1.30% and 1.80% (Rmax ≈ 1.40–2.00%; Vitrinite Reflectance Equivalent VRE ≈ 1.10–1.50%). It is possible to calculate VRERaman from the ID1/IG ratio.

Graptolite-derived organic matter in the Wufeng–Longmaxi Formations (Upper Ordovician–Lower Silurian) of southeastern Chongqing, China: Implications for gas shale evaluation

The organic-rich shales of the Wufeng–Longmaxi Formations (Ordovician-Silurian) are one of the most important hydrocarbon source rocks and shale gas exploration targets in China. Graptolites are abundant in these shales, but their contribution to the dispersed organic matter (OM) has been overlooked. This lack of attention could seriously affect the evaluation of OM type, OM maturity, hydrocarbon generation potential, reservoir characteristics and gas content of these shales. Optical microscope and focused ion beam-scanning electron microscope (FIB-SEM) techniques were employed to describe the optical characteristics and micro-nanopores of the graptolites, to determine the contribution of the graptolites and to evaluate the thermal maturity of the Wufeng–Longmaxi Formations.Non-granular graptolites, which show a stronger anisotropy and higher reflectance under polarized light than the granular graptolites, were primarily observed in these sediments. Graptolites account for 20–93% of the dispersed OM in the Wufeng–Longmaxi Formations, and the level of their contribution has been attributed to the radiation of graptolites at the late Ordovician (Kaptian) and the recovery of graptolites at the early Silurian (Rhuddanian). The bireflectance values of the non-granular graptolites fall between 2.22 and 4.32%, indicating a behavior similar to biaxial anthracitic vitrinite. The equivalent vitrinite reflectance (EqVRo) values of the sediments in the Wufeng–Longmaxi Formations, calculated from the mean maximum reflectance of non-granular graptolite, fall in the range of 3.08–4.29%, and these values have a precision that is greater than in previous studies on the Wufeng–Longmaxi Formations. Abundant organic pores were observed in the non-granular graptolites, and they are aligned parallel to the fusellar layers of the graptolites. This indicates that the fusellar layers of non-granular graptolites controlled the development and distribution of organic pores. Such abundant organic pores played a significant role in the accumulation of shale gas in the Wufeng–Longmaxi Formations of the Upper Yangtze Platform.

Regional coal seam gas distribution and burial history of the Hunter Coalfield, Sydney Basin

Basin modelling has been used to improve understanding of the origin and temporal evolution of coal seam gas in the Hunter Coalfield of the Sydney Basin. Burial history models were produced based on data from seven boreholes located in the southern, eastern, central and western areas of the coalfield. Mean random vitrinite reflectance (Rv,r) data, derived from measurements of mean maximum reflectance (Rv,max), were used for calibration of the models. A qualitative sensitivity analysis of one model shows that varying the paleoheat flow has a greater influence on calculated Rv,r than varying the eroded overburden thickness.The differences between the constructed models are significant enough to provide plausible explanations for regional gas distribution in the Hunter Coalfield. Coals in the south of the coalfield appear to have the greatest potential for thermogenic gas generation. Modelling has shown that areas that have low gas contents and decreased permeability have been uplifted more, and buried less, compared with areas that have high gas contents. Burial history modelling shows noticeable variations in the extent of burial and uplift, and, consequently, in thermal maturities and potential for thermogenic gas generation; together with the assessment of other coal and gas property data, it appears that present-day gas contents may partially reflect coal ranks and adsorption capacities, with late-stage biogenic gas generation replenishing CH4 volumes that were lost following uplift during the Late Cretaceous.

Reflectance parameters of cokes in relation to their reactivity index (CRI) and the strength after reaction (CSR), from coals of the Upper Silesian Coal Basin, Poland

Abstract Coke samples made from coals and blends of the Upper Silesian Coal Basin, Poland were studied to determine relationships between their reflectance parameters ( R max , R min , R bi ) and technological indices CRI and CSR . It was found that coke reactivity with CO 2 decreased, and coke strength after reaction increased, with increasing mean maximum reflectance ( R max ) and bireflectance ( R bi ) and with decreasing mean minimum reflectance ( R min ) of cokes. It was also observed that for cokes with bireflectance below 4.0%, CRI indices are higher than the CSR , but when coke bireflectances rises above 4.0% then their CSR s surpassed the CRI values. Thus, R bi ≅ 4.0% seems to correspond with structural transformation of cokes resulting in the increase of their mechanical strength and adequate decrease of reactivity with CO 2 and, as a consequence, improving coke quality. Relationships of the CRI and CSR indices with cokes reflectance parameters turned out to be similar but distinctly stronger than those with cokes microtextures. The results obtained showed additionally, that higher inertinite content in parent coals (≥ 30 vol.%) could make poorer resultant cokes, i.e. increase of the CRI and decrease of the CSR factors. This influence varies depending on the rank of initial coals and is greater for middle rank coals than those from lower ranks. The results show that reflectance parameters of coke, especially bireflectance, make possible the prediction of CRI and CSR indices, and thus can be used for estimation of coke quality.

A Coal-Blending Model: A Tool for Better Coal Blend Preparation

A coal-blending model has been developed using relationships between coal and coke quality parameters. This coal-blending model gives a least-cost coal blend for the desired coal blend quality in terms of ash, volatile matter, mean maximum reflectance, and coke quality based on the coke strength and ash content. The model takes into account various constraints like coal availability, minimum and maximum permitted coal usage, etc. The model has been validated using actual plant data of coal drawn from different silos. The model is presently being used in plant as a process control tool. This model can also be used to evaluate a new coal or selection of a least-cost coal blend for a plant.

Abrupt changes (jumps) in reflectance values and chemical compositions of artificial charcoals and inertinite in coals

Abrupt changes (jumps) in reflectance values and chemical compositions of charcoals during heating experiments in muffle and thermal gravimetric analyzer ovens occur at mean maximum reflectance values of about 0.50–0.60%, 1.10–1.20%, 1.40–1.50%, 2.20–2.30%, 2.80–2.90% and 3.70–3.90% ( R max). These abrupt changes are similar to the so called `coalification jumps' in vitrinite or liptinite in coals. Jumps are much more notable in low temperature charcoals (formed at less than 400°C) than in high temperature charcoals (formed at greater than 400°C). Abrupt changes in chemical composition are coincident with jumps in reflectance as evident from sudden decreases or increases in functional groups as determined by FTIR-spectra. The jumps in composition of charcoals (intertinites) during charring experiments explains the multi-modal reflectance distributions commonly documented in coals. The distribution of reflectance values and FTIR spectral characteristics of inertinite in some Western Canadian coals is consistent with a model of charring that incorporates discrete compositional jumps. The `jumps' in reflectance values and chemical compositions probably reflect progressive breaking of chemical bonds in response to attainment of specific threshold activation energies.

Graptolite reflectance in the prehnite-pumpellyite zone of Northern Maine, U.S.A.

Reflectance data has been collected on Ordovician-Lower Devonian graptolites from the prehnite-pumpellyite metamorphic region in northeast Aroostook County, Maine, U.S.A., at the northern end of the Appalachian Mountain Belt. The data is reported as the mean maximum reflectance which, crossplots, (maximum and minimum reflectance vs bireflectance) demonstrate, is similar for samples mounted either perpendicular or parallel to bedding, given a moderately sized data set (> 20 points). Like the prehnite-pumpellyite subfacies, graptolite reflectance increases from west (1.5%) to east (5.5%) and supports a post-Early Devonian (Acadian) age for the regional metamorphism. Reflectance contours show, however, that the area of highest metamorphism is to the east rather than the southeast where limited data suggest the level of metamorphism may actually decrease slightly, illustrating the advantage of continuously increasing organic maturation indicators for outlining thermal patterns in broad areas of low grade regional metamorphism.

Vitrinite reflectance measurement — Some technique enhancements and relationships

Coals with non-uniaxial negative reflectance indicating surfaces (RIS) are the norm rather than the exception for coals from British Columbia coalfields and have also been reported from elsewhere around the world. Unique description of the reflectance characteristics of these coals requires determination of the three principle reflectance axes. Such axes values are determined from a standard coal particle sample using a crossplot of reflectance versus bireflectance for the apparent maximum and minimum values obtained from each particle. Computer-controlled stage rotation and reflectance measurement collection allow quality control and reflectance ellipse orientations to be assessed for each coal particle measured. The eigenvectors associated with the largest eigenvalue of a symmetrical 2×2 matrix of direction cosines of stage rotation angles, weighted by the associated reflectance value, provide the orientation of R′ max (apparent maximum reflectance) on the pellet surface. The largest and smallest eigenvalues of this matrix divided by the sum of reflectance values measured during stage rotation are the R′ max and R′ min values, respectively. The quality of measurement for each particle can be quantified by the scatter of raw reflectance values about the best fit ellipse defined by R′ max and R′ min . The calculated random reflectance value, R Mc, determined from R max and R′ min with stage rotation is not affected by the problem of light pathway induced polarization of the “non-polarized” light commonly used in the R m (mean random reflectance) measurement procedure. Reflectance variations of 15% for a coal particle with a theoretical R m of 3.06 can result from partially polarized “non-polarized” light. The relationship between R m and R max (mean maximum reflectance) is non-linear and controlled by the shape of the RIS. Errors as large as 13% for coals in this study and greater for RIS reported from other tectonic settings would result from using a single linear conversion factor.

Petrology of graptolites and their utility as indices of thermal maturity in Lower Paleozoic strata in northern Yukon, Canada

The optical characteristics and utility of graptolites as a measure of thermal maturity have been evaluated by measuring maximum, minimum, and random reflectance of specimens from the Lower Paleozoic Road River Group in northern Yukon. The progressive changes in optical properties of graptolites produced by increasing depth of burial are corrected to the optical properties of other organic matter (conodonts and bitumen) in the same sample. Measurement of maximum reflectance ( R o max) is the most reliable method of assessing the level of thermal maturity of gratolites because they have biaxial optical properties. At high levels of maturation the reflectance of graptolites is greater than that of vitrinite, whereas at low levels of maturation the reflectance of vitrinite is greater. In the Road River Group, the mean maximum reflectance of graptolites varies laterally from 4.0% to 6.5% R o max· R rmo max f graptolites increasing depth of burial and the relationship between reflectance and depth fits a log (reflectance)-linear (depth) relationship. The vertical increase of maximum reflectance of graptolites through an 800-m section ranges from 4.2% R o max at the top to 6.5% R o max at the bottom yielding a maturation gradientof 0.39 log % R o max km −1. A correlation of graptolite reflectance calibrated by color changes of conodonts (CAI) indicates that Road River strata are overmature (CAI = 5,4.0–6.5% R o max, graptolite reflectance) with respect to hydrocarbon generation.

The role of coal petrography in understanding the properties of South African coal

The variations in physical and chemical properties of coal can only be explained in terms of its petrographical composition and its rank. By means of a TREND computer programme quantitative relationships (correlation coefficients > 0.97) were established between the contents of total carbon and hydrogen (daf) of South African humic coals and their volatile-matter and oxygen contents, their calorific value (all daf) and their mean maximum reflectance of vitrinite ( R max). The inherent moisture content (ash-free), the vitrinite content (mineral-matter-free), and the Hardgrove and free-swelling indices yielded only semiquantitative relationships (correlation coefficients between 0.80 and 0.93 and high standard deviations) when expressed in terms of total carbon and hydrogen contents (daf). These interrelationships are shown graphically by means of a Seyler diagram modified for South African coal. The relatively poor correlation in the case of vitrinite content is due to the presence of fairly large amounts of reactive semifusinite in most South African coals, and for this reason it is necessary to distinguish between normal, perhydrous and subhydrous coals, depending on the relative difference between determined and inferred vitrinite contents. Due to the high content of low reflecting inertinite the modal reflectance of vitrinite is also regarded to a better rank parameter than the mean reflectance, as the former is not affected by sporadic low or high values. From the modified Seyler diagram it is also possible to devise a grade/type/rank classification for South African coals, where grade is given by the ash content (moisture-free basis). This classification complements Alpern's universal classification of solid fossil fuels. The Seyler diagram can also be used to delineate fields of the most useful application of South African coals, based on the relevant coal properties.

Swelling and plastic properties of coal devolatilized at elevated pressures: an examination of the influences of coal type

Attempts have been made to correlate the measured thermoplastic properties of 24 coals (hvCb to Ivb) pyrolysed at elevated pressures (0.1 to 2.9 MPa) with some commonly reported characterization parameters. While the thermoplastic transition temperatures can be correlated somewhat with some coal properties (e.g., vitrinite mean-maximum reflectance, or carbon content), the maximum swelling parameter of these coals, especially at elevated pressures, shows little correlation with the usual coal characteristics which are measured at atmospheric pressure (e.g., ASTM FSI or vitrinite reflectance). In general, the behaviour of the coals at elevated pressures cannot be predicted from their properties obtained at atmospheric pressure. These data stress the importance and profound influence of elevated pressure on swelling and plastic properties of coals. All thermplastic properties were measured by a high-pressure microdilatometer.

Proposal for coal classification

Several critiques to the ‘International Classification of Hard Coals by Type’ (ECE, Geneva, 1956) have been made in the past and a revision of its usefulness is currently being carried out by several investigators. The principal drawback of this classification is that it is not applicable to coals of variable maceral composition, especially those displaying a high content of inertinite. Furthermore, the parameters hitherto used in the International Classification and in some other national systems to define degree of coalification (rank), i. e. volatile matter and calorific value, are dependent on variable maceral composition. On the other hand, the parameters used in the International Classification to determine the agglutinating and coking properties of coals are competing parameters, instead of following a hierarchy. The proposed classification scheme is based on two primary parameters determined with microscopic techniques: (1) mean maximum reflectance of vitrinite, which is a good single measure of rank; and (2) petrographic composition (vitrinite and exinite) as an indication of the type of coal. A third parameter is chosen to qualify the different classes of coal: volatile matter for anthracitic coals; dilatation for semianthracitic and bituminous coals; and calorific value for subbituminous coals and lignites. The scheme is expressed by mean of a code number of four digits, which refers to the rank (first digit), type (second and third digits) and qualification (fourth digit) of coal.

Gasification reactivities of optical textures of metallurgical cokes

Optical textures of ten typical cokes before and after gasification in CO 2 were quantified by point counting under a polarized microscope to quantify the reactivities of each type of optical texture. Although absolute values of gasification rate for each texture varied considerably from coke to coke, their relative values were constant regardless of the origin of the cokes. The relative reactivities of flow, mosaic, isotropic and inert textures were 1,1.8,2.8 and 3.0, respectively. The relative reactivity of a single coke calculated from a knowledge of optical textures, was monotonicly correlated with the mean maximum reflectance ( R ̄ 0 ) of the parent coal. This indicates that the high reactivity of coke from a high-rank coal ( r ̄ 0 = 1.8% ) is due to factors other than its optical texture. The crystallite height, L c(002) ' of the coke correlated with R ̄ 0 of the parent coal, although the values of L c(002) varied only from 1.5 to 2.1 nm.

Relationship between CO2 Reactivity and Structure of Metallurgical Cokes (II)

The optical texture, pore structure and ash constituents of cokes must be generally influencial factors for CO2 gasification reaction of cokes. In the present report, the influence of pore structure of the three factors on maximum gasification rate (RM) of lump cokes at 1100°C were studied with seven cokes produced from single coking coals of various ranks.The results were as follows.(1) RM showed minimum at Ro=ca. 1.5% (mean maximum reflectance).(2) Smoky River and Itmann cokes with high contents of flow type texture, the parent coals of which were 1.57% and 1.66% in Ro respectively, had larger internal surface area mostly due to micro pore (radius: 110A>) than the others.(3) Both cokes were larger in the average radius of macro pore (radius: 110-42000A) than the others.(4) Pore-diffusion resistance, which was evaluated by “effective reaction coefficient” defined as the ratio of RM to reaction rate without the influence of pore-diffusion, tended to decrease with increasing the average radius of macro pore.It was concluded that the cokes from high rank coals have the weak pore-diffusion resistance due to macro pore with large pore radius and the large internal surface area due to well-developod micro pore, and therefore CO2 reactivity of the cokes must be high in spite of high contents of flow type texture.

Rank of coal beds of the Narragansett basin, Massachusetts and Rhode Island

Coal of the Narragansett basin generally has been considered to be anthracite and/or meta-anthracite. However, no single reliable method has been used to distinguish these two ranks in this basin. Three methods — chemical, X-ray, and petrographic — have been used with some degree of success on coal of the Narragansett basin, but too often the results are in conflict. Chemical methods have been limited by inadequate sampling on a coal-bed-by-coal-bed basis and by a lack of analyses made according to (American Society for Testing and Materials, 1974) standard specifications. In addition, when corrections are made by using the Parr formulas, as required by the ASTM (1974) procedures, the generally high to very high ash content of coal from the Narragansett basin causes the fixed-carbon content to appear higher than it actually is. X-ray methods using the degree of graphitization as a measure of rank are not reliable because some of the graphite is related to shearing and brecciation associated with folding and faulting. Petrographic methods using reflectance on vitrinite give results that are generally consistent with results from chemical determinations. However, it is not clear whether the mean maximum reflectance or mean bireflectance is a better indicator of similar rank of such high-rank coals that have been structurally deformed. Coal from the Cranston Mine, RI, is probably meta-anthracite and coal from the Portsmouth Mine is probably anthracite. These ranks are based on chemical,X-ray, and petrographic data and are supported by associated metamorphic mineral assemblages that indicate that the Cranston Mine is in a higher metamorphic zone than the zone containing the Porthmouth Mine. Interpretation of the rank of Mansfield, MA, coal on the basis of extant chemical data is difficult because it is an impure coal with an ash content of 33 to 50%. Reflectance data indicate that the Mansfield, Foxborough, and Plainville coals in the northern part of the Narragansett basin are meta-anthracite but this is in disagreement with the rank suggested by the low degree of metamorphism of the associated rocks.

Influence of alginite on the reflectance of vitrinite from Joadja, NSW, and some other coals and oil shales containing alginite

Reflectance data for vitrinite occurring in torbanites indicate that the mean maximum reflectance and the range of reflectance values are significantly lowered by the presence of alginite. This is the probable cause of apparently anomalous rank gradients in some deep oil exploration wells. Intermaceral effects need to be considered in assessing rank or maturity from vitrinite reflectance, and by inference, in most other methods. The interpretation of the cause of the effect is open to further study but the findings are highly significant in relation to coal utilization, oil and gas exploration, and studies of oil shales.

Incipient metamorphism of Cambro-Silurian clastic rocks from the Jåmtland Supergroup, Central Scandinavian Caledonides, Western Sweden: illite crystallinity and 'vitrinite' reflectance

The degree of incipient metamorphism in the Cambro-Silurian of the Jåmtland Supergroup (Eastern Complex) of the Jämtland Caledonides, from the Caledonian front autochthon westwards through the parautochthon towards the thrust front of the metamorphic main ('Western Complex') nappes, has been studied using: ( a ) determination of the illite crystallinity by X-ray powder diffraction on the K- and Mg-saturated –2 μm fractions; the low-grade limits of the anchizone and the 'opizone' of Kubler correspond to peak widths of c. 0.38° and 0.21°Δ2 (illite 001 diffraction peak) under the experimental conditions used; ( b ) determination of the rank of coaly particles in the clastic rocks by measurement of the 'vitrinite' reflectance using a reflected-light microscope with photomultipliers. In the Indalsälven segment S of Iat. 63°30' N between Brunflo in the E and Undersåker in the W, and further N to Rönnöfors-Juvuln, 4 zones of illite crystallinity may be distinguished: (A) The Östersund-Krokom zone: mean 'saturated' 10 Å peak widths of ∅0.32°Δ2θ, the highest peak widths occurring in the easternmost part of the zone ('diagenetic' zone of Kubler). (B) The Norderö-Näldsjön zone: mean peak widths between 0.27° and 0.35° Δ2θ middle-anchizone of Kubler. (C) The Mattmar–Alsensjön zone: predominance of peak widths between 0.19° and 0.25° 2θ. (D) The Mörsil–Jårpen zone; predominance of peak widths of 0.21° Δ2θ characteristic of the 'epizone' of Kubler. This zone extends N to Rönnöfors–Juvuln, W of the Offerdal nappe. 'Vitrinite' reflectance values were measured on 35 samples. In illite-crystallinity zone A the predominant mean maximum reflectance ranges from 1.4-2.9% R max oil , corresponding to low-volatile bituminous coal to low-rank anthracite. In zones B, C and D the ranges of R max oil are similar, from 3.7 to 4.3%, corresponding to high-rank anthracite. Similarly high reflectances (4.2-4.5% R max oil ) were found in 3 samples from the northern continuation of zone D. The comparative uniformity of the reflectances from zones B–D contrasts with the increase in illite crystallinities, particularly from zone B to C. Anatase was found in demineralization residues from zones A and B (together with rutile); in the residues from zones C and D rutile is the only titanium oxide. The results are consistent with the hypothesis that the incipient metamorphism in the Jåmtland Supergroup was at least in part caused by the overthrust metamorphic allochthon, particularly the mainly medium- and locally medium to high-grade metamorphic Seve nappe. The association of the onset of the anchizone with semi-anthracitic to low-rank anthracitic coal ranks (c. 2.5–2.8% R max oil ) is in agreement with the relationships found in several other areas of incipient regional metamorphism.

The Influence of Some Tectonic Structures upon Vitrinite Reflectance

Data are reported for oriented coal samples taken on traverses oblique to two high angle normal faults in underground mine workings in the Southern Coalfield of the Sydney Basin, N.S.W. Apart from faulting and regional warping, relatively little tectonic deformation has occurred in this portion of the basin. Four oriented sections cut normal to bedding at known azimuth were prepared from each of twenty-one coal samples. Vitrinite mean maximum reflectance (), using oil immersion, was measured for each section and results indicate that the vitrinite in this medium volatile coal has biaxial optical properties. Using the azimuths and values of the four sections of each sample, the true maximum reflectance () and its orientation can be determined from the elliptical calculated bedding plane section of the indicating surface (CBPSIS). The biaxial nature of the vitrinite is thought to result from asymmetrical growth of its molecular structure and to be related to stress fields which developed contemporaneously with coalification. In the vicinity of the normal faults, elliptical CBPSIS's with similar orientations occur in a pattern which is consistent for the two faults. The results suggest that anisotropic stress fields may influence coalification and that it may be possible to detect some faults using vitrinite reflectance. Vitrinite reflectance may also provide information concerning stress regimes and stress regime history in proximity to some faults. Biaxial vitrinites appear to provide direct evidence of strain even in weakly deformed terrane where indicators of strain are scarce.

Statistical Evaluation of Coal Compositional Data

Statistical techniques were applied to petrographic and chemical data obtained on 35 samples of coal ranging from lignite to anthracite. Six petrographic variables were involved in the calculation and included contents of vitrinitic components, fusinoids, massive and granular micrinoids, and exinoids plus resinoids. Also included was the mean maximum reflectance determined on the vitrinitic entities. Chemical variables included contents of ultimate carbon, hydrogen, total sulfur, and oxygen which was found by difference. Statistical techniques involved calculation of a correlation matrix and factor analysis with factor rotation. In the former procedure, positive correlations at the 1% significance level were shown to exist between carbon and vitrinite reflectance, between hydrogen and micrinoids and exinoids, between oxygen and micrinoids and exinoids, and between micrinoids and exinoids. A factor analysis by the R mode showed that four factors appeared to be responsible for 94% of the variation. The cont...