Volatile Bituminous Rank Research Articles

Comparative thermal behavior, Rock-Eval signature and kinetics of distinct thermally mature vitrain, fusain lithotypes and coals from India

ABSTRACT Thermal and chemical properties of coals, and the lithotypes they contain, provide useful insight to their combustion and reaction behaviors. Analysis of thermal properties, proximate parameters, Rock-Eval signatures, and petrographic characteristics of vitrain, fusain lithotypes, and bulk coal samples of distinct ranks from Raniganj (high volatile bituminous A rank, HvbA) and Jharia (medium volatile bituminous rank, Mvb) basins (India) reveal contrasting features. The HvbA bulk coal is identified as the most reactive. HvbA and Mvb vitrains display comparable reactivities despite their distinct thermal maturities. Mvb vitrain generates spiky pyrograms, due to melt formation and bubble bursting typical of coking vitrains. Mvb fusian is more prone to self-heating, being characterized by an exothermic thermogram peak due to its greater propensity to adsorb oxygen. In contrast, HvbA fusain, with higher VM and ash, displays least reactivity. These features mean that Mvb coals require higher temperatures for ignition and consume more energy than HvbA coals. Multi-heating-rate Rock-Eval S2 pyrograms show excellent Arrhenius equation simulation fits for the HvbA and Mvb bulk coals and lithotypes, enabling determination of activation energies (E) and pre-exponential factors (A). Distinctive E and A values of the HvbA bulk coal are a consequence of its high liptinite content.

Petrology of the Parvadeh coals, Tabas Basin, Iran

The Tabas Basin is in the Tabas Block in the central part of Iran, and it contains Iran’s largest coal deposits, mostly in the Parvadeh Coalfield. The basin is structurally characterised by regional scale thrust faults and orthogonal strike-slip faults that segregate the coalfields into different areas namely Parvadeh (P) I to IV. The coals under study are in the upper Triassic Nayband Formation. Samples were collected from underground coal mines in PI, PII, PIII, and core from PIV, and prepared for petrographic analysis. The resulting vitrinite reflectance varies between 1.13% and 1.54%, which places the coals into medium volatile bituminous rank. In all samples, the vitrinite content is significantly higher than the inertinite followed by minor amounts of liptinite, mostly secondary exsudatinite. The samples also contain abundant pseudovitrinite, which can be above 40% (volume, mineral matter free basis). The maceral composition and moderate to high mineral matter with common framboidal pyrite and siderite corroborate previous interpretations of the Parvadeh coals forming in topogenous to transitional peatlands in paralic to fluvial palaeoenvironments. However, this study makes additional interpretations of the coalification history of the Parvadeh coals and the occurrence of pseudovitrinite. The coals commonly contain meta-cutinite and associated meta-exsudatinite, and fluorescing exsudatinite that permeates carbargillite lenses, lumina of inertinite macerals, and the slits of the pseudovitrinite. This suggests at least two stages of hydrocarbon generation occurred in the Parvadeh coals: the first phase during entry into the oil window and later devolatilisation to meta- exsudatinite in the early gas window; the second phase post-dates this and could be generated internally from the vitrinite else migrated from surrounding organic-rich rocks in the interburdens of the Nayband Formation. The fact that the pseudovitrinite slits are filled with exsudatinite but not meta-exsudatinite indicates that pseudovitrinite formed just before during partial devolatilisation or contemporaneous with the second generation of exsudatinite. Epigenetic mineralisation includes massive pyrite and dolomite in the fractures, indicative of potential hydrothermal circulation that may also be related to the second phase of hydrocarbon generation as exsudatinite is found trapped in the intracrystalline spaces of the carbonates.

Distribution and enrichment of Al-Li-Ga-REEs in the High-Alumina coal of the Datong Coalfield, Shanxi Province, China

The content, distribution, and origin of aluminum, lithium, gallium, and rare earth elements (REEs) in the Permo-Carboniferous coal of the Datong coalfield, China, were investigated using optical microscopy and field-emission scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction, and inductively coupled plasma mass spectrometry. The Permo-Carboniferous coal of the Datong coalfield had a high volatile bituminous rank (Ro,max = 0.72% on average), and low sulfur and medium ash contents (0.58% and 25.74% on average, respectively). The main minerals in the Datong coal included kaolinite, boehmite, muscovite, calcite, dolomite, siderite, aluminum phosphate, and quartz. Of these, kaolinite, boehmite, calcite, quartz, and phosphates mainly occurred as cell fillings, indicating an authigenic origin. Compared to hard coals worldwide, the Datong coal is enriched in SiO2 (49.12%; up to 89.93%), Al2O3 (38.88%; up to 71.37%), Li (67 μg/g; up to 354.1 μg/g), Ga (18.1 μg/g; up to 70.2 μg/g), Y (20.8 μg/g; up to 46.1 μg/g), La (34 μg/g; up to 158.5 μg/g), Ce (61.3 μg/g; up to 353.8 μg/g), Tb (0.7 μg/g; up to 3.0 μg/g), Er (2.3 μg/g; up to 5.7 μg/g), and Yb (2.2 μg/g; up to 5.4 μg/g). High-alumina coal (Al2O3 content in ash > 40%) occurred in the northern and southern parts of the coalfield. In the No. 3–5 coal seam, the areas of Li enrichment were located in the north and middle of the coalfield. In the Tashan and Chaigou mines, the Ga content exceeded 30 μg/g. An area of REEs enrichment (REEs content > 300 μg/g) was identified in the Tashan and Xiaoyu mines. In the No. 3–5 coal seam, the REEs distribution pattern showed a wide and gentle “V” curve with a high left and a low right limb. These seams were characterized by a marked depletion in Eu (δEu = 0.51) and a weak negative Ce anomaly (δCe = 0.95). In the No. 3–5 coal seam, Al, Li, Ga, and REEs mainly occurred in kaolinite. Boehmite and phosphate minerals were the main carriers of Ga and REEs, respectively. The enrichment in Al-Li-Ga-REEs in the No. 3–5 coal seam was mainly influenced by the sedimentary provenance and the environment of coal accumulation. The sediment sources were oxidized bauxite in the weathering crust of the Benxi Formation and the Middle Proterozoic moyite of the Yinshan Oldland to the north and west of the coalfield. Al, Li, Ga, and REEs were transported from the source region as solutes and colloids, and they became enriched in the swamp facies of the delta plain. The Li, Ga, and REEs contents gradually increased from the bottom to the top of the Permo-Carboniferous coal seam. This increase is mainly attributed to the weak influence of seawater. The marked enrichment in heavy REEs at the bottom of the No. 5 coal seam may be related to marine transgression.

A novel VRo, Tmax, and S indices conversion formulae on data from the fold-and-thrust belt of the Western Outer Carpathians (Poland)

Results are presented on the relationships between the vitrinite reflectance VRo, the Tmax temperatures determined with Rock-Eval pyrolysis, and the smectite (S) indices representing the percentage of smectite in the mixed-layer illite-smectite (I/S) from claystones. Samples locations are recovered from the Polish part of the Outer Carpathian fold-and-thrust belt. Organic indices show thermal maturities of most outcrop samples in the range of 0.47 to 1.49% Ro and 421 to 485 °C Tmax. Inorganic S indices values range from 8 to 60%. Lateral variability of the maturity measured with both organic and inorganic indices reflects mainly differences of maximum tectonic burial in the accretionary prism and subsequent exhumation and denudation. For the Western Outer Carpathians the calculated formulae for Tmax to VRo and S to VRo conversion are VRo = 0.0152 * Tmax - 5.938 (r2 = 0.87) and VRo = 1.1432–0.01295 * S (r2 = 0.65), respectively. Maximum paleotemperatures were calculated for individual samples from S indices by applying the novel formula T = ln (1.1432–0.01295 * S) + 1.68/0.0124. The proposed new conversion formulae might be useful in other regions with a similar geological setting, i.e. for claystone formations dominated by kerogen type III in fold–and-thrust belts, characterized by rapid tectonic burial accompanied by a low geothermal gradient, as well as maturities of the sub-bituminous to the medium volatile bituminous rank (0.5 to 1.50% Ro).

Petrographic and organic geochemical study of the Eocene Kosd Formation (northern Pannonian Basin): Implications for paleoenvironment and hydrocarbon source potential

The Eocene Kosd Formation forms part of the Hungarian Palaeogene Basin. The coal measure of this formation was investigated using an 18 m drill core from borehole W–1. Petrographic and organic geochemical investigations (Rock-Eval pyrolysis, biomarker analysis) were performed in order to characterize the depositional environment, to determine the source of the organic matter within, and to assess the hydrocarbon generative potential.The presence of marine fossils, high TOC/S ratios and ash yields show that the deposition of the coal measure occurred in a marine delta with individual coal layers accumulating in low-lying, rheotrophic mires. The distribution of land plant-derived biomarkers demonstrates that the peat-forming vegetation was dominated by angiosperms, but the relative contribution of gymnosperms varied through time. In addition to land plants, algae and aquatic macrophytes contributed to the biomass. This dense vegetation established a CO2-limited environment forcing aquatic plants to utilise HCO3− during photosynthesis. The marine environment, as well as the predominance of carbonate rocks in the hinterland, caused slightly alkaline conditions, which, together with reduced oxygen availability, stimulated sulphate-reducing bacterial activity and the microbial degradation of plant remains. Consequently, Kosd Formation coal is very rich in sulphur (up to 8.8%). Moreover, the coal contains vitrinite with a strong orange-brown fluorescence colour and swells strongly during pyrolysis. These features are typical for coals with marine influences.Vitrinite reflectance, Tmax, and biomarker proxies indicate that the organic matter is thermally mature and that the Kosd coal reached the high volatile bituminous rank in the deep borehole (~2.6 km depth). Rock-Eval parameters imply that the coal is gas- and oil-prone and reached the maturity threshold critical for first gas generation and the onset of oil expulsion.

New data on geology and germanium mineralization in the Hunchun Basin, northeastern China

The geochemistry and mineralogy of Palaeogene coals from the Hunchun Coalfield, Jilin Province, northeastern China, have been studied using X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, scanning electron microscopy in combination with energy-dispersive X-ray spectrometry, and X-ray diffraction analysis of the low-temperature ash. The 22A Coal from the Banshi Mine is of subbituminous A to high volatile bituminous rank (0.53–0.56% Ro, ran) and has a low sulfur content (0.74% on average). The 22A Coal consists mainly of kaolinite, quartz, illite, and, to a lesser extent, plagioclase, siderite, and pyrite. As compared with the average world low-rank coals, the 22A Coal is enriched in As, Sb, Ge, Cs, and W.Combined with the geochemical features of six other coal seams from the Hunchun Coalfield, the terrigenous materials of the Hunchun coals were dominantly from Mesozoic (mostly Lower Cretaceous) volcanic rocks and Paleozoic granites and associated metamorphic rocks surrounding the coal basin. A minor source was the Paleogene volcaniclastics including some adakitic rocks, which are characterized by higher Sr/Y and La/Yb ratios. The Ge enrichments that are detected in some individual coal benches from the Hunchun Coalfield were related to tectonic uplift of the crystalline rocks surrounding the basin and their following denudation. The oxidized meteoric waters episodically influenced by volcanic-related hot springs might extract Ge from the source rocks and then precipitate it as a result of bio-chemical reduction, forming the mineralization disseminated in the coals.

Coalbed methane reservoir characteristics of coal seams of south Karanpura coalfield, Jharkhand, India

Coalbed methane has emerged as a viable natural gas resource in India since 2007. The understanding of gas genesis kinetics, storage mechanisms and the geological controls is vital for exploration and successful recovery of gas in a cost-effective manner. In this respect, a multidisciplinary analytical approach including gas content, stable isotopes (δ13C1), hydrocarbons distribution, reconstruction of original organic matter, chemical properties, sorption kinetics and the role of petrographic constituents have been assessed. The volatile matter content varies from 20.2 to 32.1 wt%; indicating medium volatile to high volatile bituminous rank of coal with the maximum vitrinite reflectance (VRo%) ranging from 0.63 to 0.98%. The studied coals are vitrinite rich and contains vitrinite group macerals in the range of 41–65 vol%. Dendritic micro-fractures are confined to vitrite microlithotype, and secondary mineralization helps preserve fracture connectivity. The average gas content of coal seams is 2.06 cc/g. The increase in gas content values per 100 m is about 0.38 cc/g emphasizing escape and migration of hydrocarbons during restructuring and tectonic activities in the basin. The relationship of C3/C1 and C2/C1 ratios is indicating that the hydrocarbons in desorbed gas originated from the thermogenic process. The large concentration of methane in desorbed gas and its stable isotope signatures (δ13C1 < −40‰) also indicates the thermogenic origin of gases in coal seams. Few desorbed gas samples have been found in the mixed gas region, which may be due to the influx of fresh water carrying bacteria leading to the generation of biogenic gases and subsequent mixing with the sorbed thermogenic gases. The values of S1 (0.19–0.78 mg HC/g) and S2 (10.31–25.63 mg HC/g) indicate excellent source rock potentials. The positive correlation of original hydrogen index (HIO) with present-day hydrogen index (HIPD) and original organic content (TOCO) with present-day organic content (TOCPD) suggests uniform consistency in organic carbon conversion to hydrocarbons.The gas content compared with sorption capacity reveals the undersaturation of coal seams. The experimental results summarize that the low gas content is a critical issue. Similarly, the low, quality and quantity of CH4 may affect the exploration and recovery of methane in the long term into this basin. But, the low values of sorption time (0.12–6.65 days) signifies good diffusion characteristics that may support the recovery of gas. Finally, it is concluded that depth of occurrence, maturity and pore/cleats associated with microconstituents control the gas accumulation and transport in coal seam reservoirs of South Karanpura coalfield.

Modes of occurrence and origin of mineral matter in the Palaeogene coal (No. 19-2) from the Hunchun Coalfield, Jilin Province, China

Previous investigations on minerals and elements in coals from northeastern China are very scarce. This paper investigates the mineralogy and geochemistry of the Palaeogene No. 19-2 Coal, parting, and host rocks (roof and floor strata) in the Baliancheng mine, Hunchun Coalfield, Jilin Province, northeastern China. Samples collected from this coalfield were analyzed using low-temperature ashing plus X-ray diffraction analysis, scanning electron microscopy in combination with energy-dispersive X-ray spectrometry, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The investigated coal is of subbituminous A to high volatile bituminous rank (0.50–0.56% Ro,ran) and has a low sulfur content (0.25% on average). The mineral assemblage of the coal is dominated by kaolinite, illite and expandable clays, and quartz, with a trace of albite. In comparison with low-rank coals worldwide, the No. 19-2 Coal is enriched in Cs, V, and Mo.The minerals and elements in the coal and its roof and floor strata were mainly derived from the Mesozoic (Jurassic-Lower Cretaceous) intermediate-felsic volcanic rocks surrounding the coal basin. The parting within the coal seam is identified as a tonstein (bed of altered volcanic ash) based on its mineral composition, dominantly of vermicular and book-like kaolinite (plus smectite, high-temperature quartz, sanidine, apatite, and ilmenite), and its persistent distribution throughout the coal deposit. Based on these features and its chemical composition, this tonstein is deduced to have been derived from a Paleogene intermediate-felsic volcanic ash, which is characterized by some adakitic signatures of trace elements, and terrigenous materials. Normalized to the upper continental crust, the investigated samples (particularly the tonstein layer) show positive Eu anomalies inherited from the source rocks. This is in contrast to the coals, host rocks, and tonsteins with intermediate-felsic compositions in many other coal deposits, which are generally characterized by negative Eu anomalies. Geochemical and mineralogical features also indicate that the sedimentary materials of the tonstein, and, to a lesser extent, the floor horizon, were of aeolian origin, but those of most coal plies and roof strata were the result of aqueous deposition.

Neutron scattering study of vitrinite: Insights into sub-micrometer inclusions in North American Carboniferous coals of bituminous rank

Results of SANS and USANS measurements performed on a series of six vitrinite samples having vitrinite reflectance (Ro) values ranging from 0.55% (high volatile bituminous rank) to 1.28% (medium volatile bituminous rank) were analyzed. Experimental data were acquired for two sample forms: platelets cut parallel to the bedding and pellets made up of randomly oriented, nearly-monodisperse particles.Numerical analysis indicates the presence of sub-micron sized inclusions embedded in the organic matrix. For the lowest-rank vitrinites, the dominating inclusions are monodisperse are ~7–12nm in diameter, and have concentrations of the order of 1017cm−3. Their shape is anisotropic, with the surface-to-volume ratio about three times larger than for a solid sphere.The higher-rank vitrinites contain much larger monodisperse inclusions having diameters of ~50nm, concentrations of ~1014cm−3, large surface-to-volume ratios, and fuzzy interfaces with the organic matrix. Inclusions of a similar size and concentration are also present in the lowest-rank sample, but are much less frequent than the small inclusions. We provisionally interpret those objects as inclusions of mineral matter, most likely associated with original plant material. The internal specific surface area (SSA) calculated for the small mineral matter inclusions is ~100m2/cm3 and for the large inclusions ~2m2/cm3.

Effects of maturity on the pyrolytic fingerprint of coals from North Borneo

Pyrolysis-gas chromatography-mass spectrometry (Py-GC–MS) and thermally assisted hydrolysis and methylation (THM-GC–MS) were applied to 27 coal samples of lignite to high volatile bituminous rank (vitrinite reflectance %Ro=0.28–0.66) from the Malaysian states of Sabah and Sarawak on Borneo, to investigate rank effects on molecular properties. The molecular fingerprints of these coals appeared to be controlled by diagenetic and, to a smaller extent, early catagenetic transformations (%Ro 0.28–0.50). The molecular assemblages from immature coals consist mainly of lignin-derived material and long-chain (≥C24) ester-bound polymethylene chains, whereas mature coals are enriched in short (C10–C25) free and/or trapped (isoprenoid) hydrocarbons, alkylated phenols and resinite aromatic derivatives. By comparing a large suite of potential molecular proxies of maturation (indices of pristane formation, resin aromatization, lignin alteration stages, etc.) and other maturity proxies (%Ro, Tmax), rank effects on different coal constituents are illustrated, as well as the suitability of the proxies for specific rank ranges. The results highlight the importance of decarboxylation of long-chain fatty acids (%Ro 0.35–0.40) and the progressive accumulation of resistant aryl-O (probably diaryl ether) bonds at advanced stages of maturity. The coals from Pinangah in Sabah were more mature than those from Sarawak (Mukah and Balingian coalfields), whereas the molecular signature of other coals from northeastern Sabah (Sandakan area) and southeastern Sabah (Silimpopon and Maliau areas) varied across the rank range studied.

Identification and nanoporosity of macerals in coal by scanning electron microscopy

Recent applications of scanning electron microscopy (SEM) to shale resource plays at magnifications of <500–>80,000× have reported nanoporosity in organic matter with limited interpretations of organic matter type. Macerals, inclusive of kerogen and solid bitumen, are recognized and distinguished in reflected white and epifluorescent light in coal and shale samples at magnifications of 200–750×. The objectives of this study are to identify macerals by SEM and evaluate which macerals contain primary and secondary nanoporosity. Since coals are organic rich with a better chance of identifying adjacent maceral types than when dispersed in shales, broad ion beam milled samples of humic and sapropelic (boghead and cannel) coals ranging in rank from peat to semianthracite were examined in backscattered electron (BSE) mode at low magnification (≤2,500×) to identify maceral type. Once identified, macerals were examined at higher magnifications of 1200–75,000× to assess maceral nanoporosity.Manipulation of the accelerating voltage to 10kV in BSE mode of a high volatile bituminous humic coal durain lithotype sample revealed a contrast between maceral groups (vitrinite, inertinite, liptinite), with limited identification of individual maceral types. Vitrinite maceral subgroups telovitrinite and detrovitrinite are distinguished based on their relative gray scale appearance compared to other macerals and occurrence as bands or groundmass, respectively. The liptinite macerals alginite, sporinite and cutinite are distinguished based on dark relative gray level and their shape. The liptinite maceral bituminite/amorphinite was recognized by dark relative gray level and occurrence as groundmass in a boghead coal. The inertinite macerals fusinite and semifusinite are recognized by light gray level appearance compared to other macerals and bogen structure but are not distinguishable separately. Macerals dispersed in shale, lacking the subtle contrast of adjacent macerals, are much more difficult to identify.Even though porosity is revealed at high magnification in BSE mode, too high of a magnification (>15,000×) prohibits identification of maceral types. The best approach is to examine samples at a lower magnification (e.g., 650×) at 10kV accelerating voltage in BSE mode to identify the maceral type and then go to a higher magnification at 1–2kV accelerating voltage to observe nanoporosity.Primary nanoporosity is observed within coal macerals at low rank (peat and subbituminous), but decreases in amount with increasing rank. Primary microporosity occurs as woody cell lumens in semifusinite and fusinite macerals. Secondary nanoporosity develops in post-oil solid bitumen in shale beginning below the peak of the oil window with a lack of nanoporosity at lower thermal maturity. Compared to the abundant nanoporosity of post-oil solid bitumen in shale, only trace amounts of nanoporosity is observed in other macerals in coals of high volatile bituminous rank and higher under the SEM.The emphasis of this study was the identification and nanoporosity of macerals in coal by SEM. The same results may extend to the same macerals in shale. Knowledge of organic matter porosity distribution by maceral type and development by thermal maturity provides insight for coalbed methane, shale gas and tight oil production potential.

Maceral controls on porosity characteristics of lithotypes of Pennsylvanian high volatile bituminous coal: Example from the Illinois Basin

Porosity characteristics of vitrain, clarain, durain, and fusain lithotypes of the Springfield Coal Member of the Petersburg Formation and the Danville and Hymera Coal Members of the Dugger Formation from the Illinois Basin were investigated with a special emphasis on the control of coal macerals on pore-size distribution. These Pennsylvanian coals are of high volatile bituminous rank and have vitrinite reflectance ranging from 0.51 to 0.60%. The lithotypes studied show decreasing values of Brunauer-Emmett-Teller surface area, and micro- and mesopore volumes from vitrain through clarain and durain to fusain. Within the mesopore size range, vitrain and clarain are dominated by pore-size widths of 4 to 10nm, whereas durain and fusain have more volume for pores larger than 20nm. In contrast to mesopores, micropore sizes are very similar for all lithotypes, averaging 1.37 to 1.39nm. In addition to differences among lithotypes, there are significant differences in pore characteristics among the three coals studied, with largest surface areas and pore volumes documented for the Hymera, followed by the Danville and the Springfield. A strong relationship exists between surface area, mesoporosity, and microporosity and maceral composition, with vitrinite having a very strong positive correlation, liptinite having a weak positive correlation, and inertinite having a strong negative correlation. Negative correlations of total porosity with vitrinite and liptinite and positive correlations with inertinite suggest that among the maceral groups, pores in inertinite contribute most to the total porosity. The Fourier transform infrared spectrometry technique demonstrates that fusains from the three coals studied have higher aromaticity and a higher degree of aromatic ring condensation and lower hydrocarbon potential than the other lithotypes, whereas chemical differences between vitrain, clarain, and durain are less distinct. In addition, there is a relationship between aromaticity of the lithotypes and surface area and mesopore and micropore volumes.

Elements and phosphorus minerals in the middle Jurassic inertinite-rich coals of the Muli Coalfield on the Tibetan Plateau

The content, modes of occurrence, and origin of elements and phosphorus minerals in the Jurassic coals of the Muli Coalfield, on the Tibetan Plateau, were investigated using optical microscopy, field emission-scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The Muli coals (L1 and L2 Coals) are of high volatile A bituminous to medium volatile bituminous rank, characterized by low-sulfur contents, and are generally dominated by the inertinite-group macerals (predominantly semifusinite and fusinite). The L1 Coal contains abundant apatite (7.9% on average, on an organic-matter-free basis) and alumino-phosphate minerals of goyazite–gorceixite–crandallite group (4.9% on average), and, accordingly, the concentrations of elements F (253μg/g on average), P (2349μg/g), Sr (526μg/g), and Ba (790μg/g) are elevated as compared with common world hard coals. The deposition of phosphorous-bearing minerals in the Muli coals was not derived from volcanic input; penetration of Ca- and Al-rich solutions, release of phosphorus from organic matter during plant decay, and an appropriate sedimentary environment (such as low pH, low water table for peat, and oxidizing conditions) were critical factors in deposition of the phosphorus minerals.

An occurrence of coked bitumen, Raton Formation, Purgatoire River Valley, Colorado, U.S.A.

Numerous examples of coke produced by igneous intrusion into coal have been reported in the Spanish Peaks region of south central Colorado. However, in a recent study of an intruded section of the Raton Formation (Upper Cretaceous-Paleocene) along the Purgatoire River near Medina Plaza, CO, coked bitumen has been observed. This material occurs in “fingers” (hexagonally jointed bodies) in a shaley xenolith within a lamprophyre sill and in carbonaceous Type III shale directly below the sill. The coke fingers are characterized by a remarkable flow mosaic texture, high vitrinite/coke reflectance (average random reflectance between 8% and 9%, but with maximum readings around 14–15%), high anisotropy, abundant devolatilization vacuoles, and an absence of inertinite inclusions. Within the underlying shales, the coked bitumen occurs as pore, void, and fracture linings and fillings. Geochemically, the coke in the fingers has low S1 and S2 values (<0.2 and <3mg HC/g, respectively), and low HI and OI values (<6mg HC/g TOC and <3mg CO2/g TOC, respectively). Within the fingers, there is evidence for multiple stages of accumulation, including coarse-grained circular or ribbon coke frequently containing pores edged by vapor-deposited carbon (pyrolytic carbon), layers of pyrolytic carbon, clusters of spherulitic pyrolytic carbon, and layers of highly porous coke. This coked bitumen is quite different from coked coal from the same locality. The coked coal has a medium-grained circular mosaic texture that is consistent with the high volatile bituminous rank of unaltered coal in the area. The coal-derived coke has similar devolatilization vacuoles but also has numerous inclusions of inertinite macerals such as fusinite and secretinite. A previously reported coal “dike” that had flowed through a sill in the same area also showed circular mosaic texture.These observations suggest that the coke found in this study was not formed by the direct coking of coal, but from a mobile phase (bitumen or pitch) that was subsequently coked by the intrusion. This bitumen was either derived from the abundant coal within the section above the sill, or from the organic matter contained within the Type III carbonaceous shales, or both. Unaltered Type III shale sampled at this site has a HI of ~350mg HC/g TOC suggesting some, albeit limited, capacity to generate petroleum. We suggest that bitumen was generated prior to or during the time of intrusion and was subsequently coked by the high temperatures of the emplaced sill. As the bitumen pooled adjacent to the sill, rapid heating led to the development of mesophase, resulting in a highly anisotropic ribbon mosaic texture on cooling, and vaporization of gases that subsequently condensed along pores, vacuoles, and fractures as pyrolytic carbon and spherulitic pyrolytic carbon. Bitumen within the underlying silty shales was also coked, but to a lesser degree. The texture of this coked bitumen looks very much like commercially produced petroleum coke. This coked bitumen differs from other reports of coked bitumen in its mode of occurrence (coke fingers in a xenolith), ribbon mosaic structure, and extremely high anisotropy and reflectance.

Microanalysis of barkinite from Chinese coals of high volatile bituminous rank

Permian high volatile bituminous barkinite-rich coal from China has been evaluated petrographically and analyzed by electron microprobe and micro-FTIR techniques. The analyzed samples varied in vitrinite reflectance from 0.65% to 0.73%, and the corresponding reflectance of barkinite ranged from 0.19% to 0.23%. Compared to the associated vitrinite, barkinite had a higher carbon and lower oxygen content in all samples. It had stronger aliphatic CHx absorbance at 2800–3000 and 1450–1460 cm−1 and less intense both aromatic C=C ring stretching vibration at ~1600 cm−1 and aromatic CHx out-of-plane deformation at 700–900 cm−1. Micro-FTIR revealed large variations in the aliphatic group intensities within barkinite, suggesting its varying oil generation potential. Air oxidation of barkinite over a 6-month period resulted in rapid consumption of aliphatic groups and the formation of oxygenated functional groups.

Notes on the relationship between microlithotype composition and Hardgrove grindability index for rank suites of Eastern Kentucky (Central Appalachian) coals

Hardgrove grindability index (HGI) has been a standard test in the coal and coal-fired power generation industries since the 1930s. Previous studies have demonstrated the relationship between HGI and coal rank and the maceral and mineral composition. In particular, within the high volatile bituminous rank range, HGI increases with an increase in coal rank and, for any specific rank, decreases with an increase in the liptinite content. Fundamentally, the HGI test is approximately at the scale of coal microlithotypes, the microscopic assemblages of macerals. In this study, for two relatively narrow rank ranges, each spanning 0.05% Rmax, we examined the relationship between HGI and several maceral and microlithotype ratios for Pennsylvanian eastern Kentucky coals. While some relationships do show statistically significant trends, not all were as well defined as might have been expected.

Emission and Combustion Characteristics of Lafia-Obi Coal in Fluidized Bed Combustor

The technology of fluidized bed coal combustion (FBC) and its advantages over conventional coal burning systems is now well established and is extensively reported in the literature. There is also some emphasis in literature about the suitability of Lafia-Obi coal in FBC. However, there is little quantitative or qualitative information on theperformance of Lafia-Obi in FBC. This paper reports a study of the combustion of monosized coal fractions fed continuously to the bed via an overbed feeder. Using appropriate ASTM standards, proximate and ultimate analyses of samples of Lafia-Obi coal were carried out and the coal was then combusted in a fluidized bed. Results showed that Lafia-Obi coal has low moisture, high volatile matter and very high fixed carbon content. The volatile matter content places Lafia-Obi in the medium volatile bituminous rank. The data obtained is useful in application of fluidized bed combustion for energy production using Lafia-Obi Coal

Fasies dan lingkungan pengendapan Formasi Bobong berumur Jura sebagai pembawa lapisan batubara di Taliabu, Kepulauan Sanana-Sula, Maluku Utara

Http://dx.doi.org/10.17014/ijog.vol3no3.20085The Bobong Formation is a coarse clastic sedimentary rock succession. In the lower part, it consists of breccia and conglomerate facies, then followed by quartz sandstone with intercalations of claystone facies. Upwards, the rock succession is gradually changed to become alternating shale, claystone and mudstone. In the upper section the rock unit is well exposed in the western and northern parts of the Taliabu Island. The formation is Jurassic in age and it was deposited within a fluvial-transition to shallow marine environ- ment. The coal bed found within quartz sandstone and shale and claystone-mudstone facies ocupies the upper part succession of the Bobong Formation. The coal in the Taliabu Island has two seams having a thickness of 30 - 40 cm and 100 - 120 cm, respectively. The geochemical analysis result indicates that the calorific value ranges from 6,186 to 7,350 cal/g, the sulphur content is from 3% to 4.65% , fixed carbon ranges from 45.69 to 53,96%, and ash content from 7.86 - 16.37%. On the basis of those parameter, the coal within the Bobong Formation is categorized as subbituminous to high volatile bituminous rank.

Hartshorne coal rank applied to Arkoma Basin coalbed methane activity, Oklahoma, USA

Coal rank, generalized for all coal beds at or near the surface, in the eastern Oklahoma coalfield has been known since 1915. Near the surface (depths <305m, <1000ft), coal rank increases from high volatile bituminous to low volatile bituminous from west to east in the Arkoma Basin in Oklahoma. The rank of subsurface (depths >305m, >1000ft) coals in Arkoma Basin coalbed methane (CBM) prospects was previously unknown. A new Hartshorne coal (Middle Pennsylvanian) rank map is based on mean maximum vitrinite reflectance values of 0.76% to 2.41% Rmax from 70 coal samples from vertical depths of 0 (surface) to 1327m (4355ft). Hartshorne coal rank in the subsurface increases from high-volatile bituminous to semianthracite from west to east in the Arkoma Basin in Oklahoma. Bituminous rank boundaries changed considerably from earlier surface rank maps (primarily by increasing the area of medium volatile bituminous rank coal in the subsurface) and revealed a previously unknown semianthracite rank area. This discrepancy is significant because the rank of deep (>305m, >1000ft) coal resource assessments and CBM exploration projects have been based on shallow coal rank assignments.A total of 2635 Hartshorne (Hartshorne, Lower Hartshorne, and Upper Hartshorne) CBM wells have been completed in Oklahoma since 1988. Most (1610) wells are horizontal with lateral lengths ranging from 4 to 1498m (14 to 4914ft; an average of 669m [2195ft]). Coal in most Hartshorne CBM wells is medium volatile bituminous rank. Hartshorne coal is semianthracite rank in about 160 CBM wells in Le Flore County. The four Hartshorne CBM wells with the highest initial potential (IP) gas rates (48 to 65 thousand cubic meters per day, Mcmd; 1.7 to 2.3 million cubic feet per day, MMcfd) are medium volatile bituminous rank from horizontal wells in Haskell and Pittsburg counties. IP gas rates<28.3 Mcmd (<1 MMcfd) in low volatile bituminous and semianthracite rank Hartshorne horizontal CBM wells may be low due to complications in drilling into high rank coals with cleat spacing <1cm, to stimulation differences, or to gas migration into adjacent sandstone channels.

Variations in concentrations and compositions of polycyclic aromatic hydrocarbons (PAHs) in coals related to the coal rank and origin

The release of unburnt coal particles and associated polycyclic aromatic hydrocarbons (PAHs) may cause adverse impacts on the environment. This study assessed variations in the concentration and composition of PAHs in a set of fifty coal samples from eleven coal basins worldwide. The maximum PAH concentrations at high volatile bituminous rank were recorded in samples from a single basin. Considering the entire sample set, the highest PAH concentrations were in fact found outside of this rank range, suggesting that the maceral composition and thus the coal’s origin also influenced PAH concentrations. The examination of the PAH compositions revealed that alkylated 2–3 ring PAHs remain dominant compounds irrespective of coal rank or origin. Multivariate analysis based on PAH and maceral content, bulk and maturity parameters allowed the recognition of seven groups with different rank and origin within the coal sample set.