Inertinite Content Research Articles

石炭の粉砕によるコークス粉の粒度分布制御

Coke samples were produced by using of electrical coke test oven (300 kg charge). Packing density was varied (Series 1). And Crushing weight ratio (<3 mm) of A coal which had high inertinite content ratio was varied, and packing density of blended coal containing A coal was varied in those tests (Series 2). Produced coke samples were investigated by a drum tester according to the JIS method. Size distributions of coke breakage products smaller than 15 mm sieve size were investigated after the drum test. The results are summarized as follows.(1) There was a close correlation between weight of coke breakage products smaller than 1 mm sieve size and packing density of charged coal.(2) There was a close correlation between weight of coke breakage products (115 mm sieve size) and weight ratio (<3 mm) of crushed A coal in blended coals.These results show that the primary factor which controls the weight of coke breakage products is different in each breakage particle size fraction. Based on these results, size distribution of coke breakage products generated by mechanical impact can be controlled by the conditions of crushing operation of coals.

The petrology, organic geochemistry and palynology of Tertiary age Eureka Sound Group coals, Arctic Canada

Tertiary age lignites from Arctic Canada were analysed by petrographical, palynological and organic geochemical methods. Results from petrographic analyses indicate the predominance of wood-derived macerals (humotelinite group) in seams from the Strathcona and Stenkul Fiord areas, whereas in the Bache Peninsula area many seams are characterized by the predominance of detrital macerals (humodetrinite) and have also higher inertinite contents. Palynological assemblages are dominated by Taxodiaceae pollen, whereas Pinaceae pollen and pteridophyte spores are less common. Angiosperm derived pollen contents are quite variable. Organic geochemical results indicate that norisopimarane and pimarane are the most abundant diterpenoids. Cadalene was present in the aromatic fractions of all samples, with other components such as simonellite and retene in variable abundance. Rock-Eval data obtained from Stenkul Fiord area samples indicate low petroleum generation potential for this predominantly woody material. The depositional environment at Strathcona and Stenkul Fiords was that of a forested swamp, which formed in a lagoonal/alluvial plain setting. Palynomorph assemblages, petrographic indices and the abundance of diterpenoids suggest that the mire flora was dominated by gymnosperms, although locally angiosperms may also have been abundant as indicated by the occurrence of tetra- and pentacyclic aromatic hydrocarbons. At Bache Peninsula the mire was less forested as indicated by palynological assemblages typical for a marsh environment and petrographic characteristics such as low tissue preservation and the abundance of detrial macerals.

Petrography and geochemistry of selected lignite beds in the Gibbons Creek mine (Manning Formation, Jackson Group, Paleocene) of east-central Texas

This study examined the petrographic and geochemical characteristics of two lignite beds (3500 and 4500 beds, Manning Formation, Jackson Group, Eocene) that are mined at the Gibbons Creek mine in east-central Texas. The purpose of the study was to identify the relations among sample ash yield, coal petrography, and trace-element concentrations in lignite and adjoining rock layers of the Gibbons Creek mine. Particular interest was given to the distribution of 12 environmentally sensitive trace elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, and U) that have been identified as potentially hazardous air pollutants (HAPs) in the United States Clean Air Act Amendments of 1990. Eleven lignite, floor, and rock parting samples were collected from incremental channel samples of the 3500 and 4500 beds that were exposed in a highwall of pit A3 at the Gibbons Creek mine. Short proximate and ultimate and forms of sulfur analyses were performed on all lignite samples, and lignite and rock samples were analyzed for 60 major, minor and trace elements. Representative splits of all lignite samples were ground and cast into pellets, and polished for petrographic analyses in blue-light fluorescence and reflected white light to determine liptinite, inertinite, and huminite maceral group percentages. The following observations summarize our results and conclusions about the geochemistry, petrography, and sedimentology of the 3500 and 4500 beds of the Gibbons Creek lignite deposit: (1) Weighted average dry (db) ash yield for the two beds is 29.7%, average total sulfur content is 2.6%, and average calorific value is 7832 Btu (18.22 MJ/kg). Ash yields are greatest in the lower bench (59.33% db) of the 3500 bed and in the upper bench of the 4500 bed (74.61% db). (2) For lignite samples (on a whole-coal basis), the distributions of two of the HAPs (Pb and Sb) are positively related to ash yield, probably indicating an inorganic affinity for these elements. By using cluster analysis we found that Be and Cd were poorly associated with ash yield, indicating a possible organic affinity, and that Ni, Se, Hg, U, and Pb cluster with most of the rare-earth elements. (3) The dominance of the crypto-eugelinite maceral subgroup over the crypto-humotelinite subgroup suggests that all Gibbons Creek lignites were subjected to peat-forming conditions (either biogenic or chemical) conducive to the degradation of wood cellular material into matrix gels, or that original plant material was not very woody and was prone to formation of matrix gels. The latter idea is supported by pollen studies of Gibbons Creek lignite beds; results indicate that the peat was derived in part from marsh plants low in wood tissue. (4) The occurrence of siliceous sponge spicules in the lower benches of the 3500 bed suggests the original peat in this part of the bed was deposited in standing, fresh water. (5) The petrographic data indicate that the upper sample interval of the 3500 bed contains more inertinite (3%) than the other samples studied. Increases in inertinite content in the upper part of the 3500 bed may have been associated with alteration of the peat by acids derived from the volcanic ash or could have been caused by fire, oxidation and drying, or biologic alteration of the peat in the paleo-mire.

Zeta potential of different lithotypes in Shenfu coal

The zeta potential of different lithotypes of two coals with high content of inertinite in Shenfu Coalfield has been studied. Moreover, the effects of pH value and the addition of surfactants and inorganic salts on zeta potential have also been discussed. It has been concluded that the zero potential point (ZPP) of vitrain is between about 3.30 and 3.40 of pH value, but that of fusain is between 2.00 and 2.10 of pH value. Furthermore, it has been found that vitrain could reach its ZPP once a small amount of cationic surfactants and some inorganic salts were added to pulps. However, only when a large amount of cationic surfactants and some inorganic salts were added to pulps, could fusain reach its ZPP. The conclusions are useful in the efficient separation and preparation of single petrographic constituent.

97/01583 Oxidation properties of processed low-rank coals

The upper Eocene Hat Creek coal deposits of British Columbia, Canada, are one of the thickest lignite to subbituminous coal deposits of the world, and comprise 350–550 m of coal.Samples of sedimentary organic material were taken from a 560-m interval of interbedded shale, siltstone and carbonate that was penetrated by corehole 75–106 in the centre of the coal basin, and the reflectances of huminite (eu-ulminite) from coal and kerogen from the organic material were determined and petrographical analyses were made. The coal deposit contains many leaf- and resinite-rich horizons, and the reflectance of huminite in these horizons in lower than in corresponding horizons containing less liptinite. When compared with huminite in adjacent coal beds, the reflectance of huminite in shale is lower, that in siltstone is similar, and huminite associated with carbonate rocks has slightly higher reflectance values. The petrological variation in the coal is mainly within the huminite group of macerals. The coal at the top of the deposits is lignite (% Ro = 0.38) and becomes subbituminous C (% Ro = 0.50) at the base.The inertinite content is very low, indicating a low level of peat fire or oxidation. The early stages of transformation of gelinite to macrinite are described. The paleoenvironment appeared to be lacustrine, as determined by organic petrological analysis of coals and interbedded sediments. Four major zones, each containing many subzones, were found. Paleoenvironments were similar for the A and C zones and also for the B and D zones.

Effects of Inertinite Content in Coal on Char Structure and Combustion

This paper reports data on the combustion characteristics of seven high-volatile bituminous coals (VRr ≈ 0.65%) with increasing inertinite contents (10−68%). Structural parameters of pyrolysis chars are compared with the maceral compositions and distributions of maceral reflectances in the parent coals and with their combustion efficiencies. The microscopic study of pyrolysis chars obtained at 1000 °C reveals that inertinite-rich coal chars are much denser than those of inertinite-lean coals. The reactivity of these chars at low temperatures (500 °C) decreases with the increase of inertinite content of the parent coals, this being attributed to the highly cross-linked structure of the inertinites. However, at higher temperatures (1100 °C) the burnout levels of the inertinite-richest coals were clearly higher than those of medium-to-low inertinite coals. This cannot be explained from the assumption of a diffusional control of the combustion process. Thus, a chemical control of the process is suggested where the mechanism governing the overall reaction rate at 1100 °C would be the active site concentration in the molecular structure of pyrolysis chars, which, in turn, would depend on the aromaticity and degree of molecular ordering in the parent maceral structure.

Variation in permeability with lithotype and maceral composition of Cretaceous coals of the Canadian Cordillera

The permeability of high- and medium-volatile bituminous Cretaceous coal at the megascopic and microscopic scale is investigated utilizing a pressure-decay permeameter. The order of decreasing permeability with lithotype is: bright (average = 4.1 md), banded (0.79 md), fibrous (0.50 md), banded dull (0.14 md) and dull (0.016 md). Bright coals are the most permeable because of associated macro-fracturing (cleat). Banded dull coal permeability generally increases with increasing vitrinite content. The lowest permeabilities occur in dull coals with a high mineral and inertinite content. Fibrous coal has a higher permeability than dull coal of the same rank due to the abundance of macroporous fusinite in fibrous coal. Dull coal permeability decreases with an increase in rank, but these results are overshadowed by compositional variability between samples. Pressure-decay measurements are more reliable for dull lithotypes as these lithotypes do not fracture as easily during sample preparation. Although measured permeabilities are optimistic due to the relaxation of stress upon exposure of coal to atmospheric pressure, the results obtained are representative of the range of permeabilities of coal lithotypes and provide insight into the variability in permeability that may exist at high effective stress in the subsurface.

Bulgarian low rank coals: geology and petrology

Abstract The largest coal-forming maximum in Bulgaria took place during the Neogene. Fifteen coal deposits are located in four coal-bearing provinces. The coal deposits south of the Balkan Mountains were formed in small grabens and depressions filled with molasse. Only the coals in Northern Bulgaria were formed in a small palaeodelta. The coal measures are of varying thickness and contain a few coal seams, with compact to complex structure and a range of thickness. Three groups are defined on the basis of maceral composition, allowing a reconstruction of the coal-forming ecosystems and the genesis of the genotypes during biochemical coalification. According to Alpern’s classification the coals have middle to high ash content (ashy to coaly facies). They are of huminite type with low liptinite and inertinite content, and of low rank — lignite and mat brown coals.

Rank and Petrology of the Middle Miocene Karapinar Lignites in Southeast Turkey

The coal-bearing strata in the Basoren Formation from the Sariz-Karapinar coal region are of middle Miocene age and were deposited in a lacustrine environment. Coal in this formation is lignitic in rank (%Ro, random of eu-ulminite B is 0.37). These lignites have high inertinite content (up to 37.4%), which is higher than in any other Turkish lignites studied previously. Inertinite content in the region increases from the northeast to the southwest, possibly indicating oxidation of organic matter in the coal-forming environment due to lowering of the water level. Total sulfur content in the lignites ranges from 1.8 to 4.8%. High-rank coals present in the Upper Permian Yigiltepe Formation (%Ro, random is 0.66-0.70) contain more sulfur (Stot = 5.6-6.9%) and less inertinite (9.6-12.1%).

96/06407 Stochastic description of premixed turbulent combustion in terms of a coarse-grained flame surface density

The Carboniferous succession in the Donets Basin hosts about 130 seams, each with a thickness over 0.45 m. Nine economically important seams from the (south)western Donets Basin are studied using organic petrographical, inorganic geochemical, and organic geochemical techniques. The main aim of the study is the reconstruction of peat facies of Serpukhovian (Mississippian) and Moscovian (Middle Pennsylvanian) coals.Formation of major coal seams commenced during Serpukhovian times. Early Serpukhovian coal accumulated in a relatively narrow shore-zone and is rich in inertinite and liptinite. Very low ash yields, low to moderate sulphur contents, and upward increasing inertinite contents suggest coal deposition in raised mires.Moscovian coal has a significantly wider lateral extension and is generally rich in vitrinite. Coal properties vary widely in response to different peat facies. Low-sulphur, low-ash k7 coal was formed in a raised mire or in a low-lying mire without detrital input. l1 and l3 seams containing several fluvial partings were formed in low-lying mires. Both seams are more than 2 m thick. Seams m2 and m3 contain high-sulphur coal, a consequence of deposition in a peat with marine influence. In contrast, syngenetic sulphur content is low in the m51 upper seam, which was formed in a lacustrine setting. The late Moscovian n1 seam, up to 2.4 m thick, accumulated in a swamp with a vegetation rich in bryophytes and pteridophytes. The properties of the n1 seam are transitional between those of Serpukhovian and other Moscovian seams. Differences in maceral composition between Serpukhovian and Moscovian coals probably reflect changes in climate and vegetation type.Tuff layers are observed in the l1, l3, and m3 seams. The l3 and m3 seams contain abundant authigenic quartz. Trace element contents are high in many seams. As contents are especially high in seams c102, k7, l3 and m3. Ash in the l3 seam contains up to 8000 ppm As. Co is enriched near the base of several seams. Maxima up to 2400 ppm occur in the ash of the k7 and l3 seams. Cd contents in ash are frequently as high as 30 or 40 ppm.

Comparative petrological analysis between the Permian coals of India and Western Australia: paleoenvironments and thermal history

Abstract Permian sequences preserved in Western Australian basins (Collie, Perth and Canning) and the Gondwana basins of India (Damodar, Son-Mahanadi, Pench-Kanhan and Godavari Valley) have similar stratigraphic succession, faunal and floral assemblages, coal types and rank, and structure. As for coal types, petrographic analyses of Indian coals indicate that vitrinite, liptinite, inertinite and mineral matter content ranges from 37 to 56%, 8 to 14%, 24 to 35% and 12 to 18%, respectively. Western Australian coals show contents of vitrinite, liptinite, inertinite and mineral matter ranging from 31 to 67%, 6 to 10%, 20 to 57% and 6 to 7%, respectively. As for rank of coal, in India, high rank coals (Rvmax = 0.70–1.67%) occur in the Damodar Valley Basin. In this basin vertical rank gradients are higher, and uplift and removal of cover has occurred to a greater extent than in the other Gondwana basins of India. Some coals from Pench-Kanhan Valley Basin (Rvmax = 0.72–1.02%) and Son Valley Basin (Rvmax = 0.70–1.10%) have high reflectance values. Coals from other Gondwana basins occur at shallow depths and are of sub-bituminous rank (Rvmax = 1%) compared to other coals in the basin. Thus, the type and rank of the Permian coals indicate a similar depositional and thermal histories for the basin studied in India and Western Australia. This is consistent with the view that India and Western Australia were in close proximity before the break up of Gondwanaland.

96/04638 Report on the activities of the International Committee for Coal and Organic Petrology during the period 1991–1995

An interdisciplinary investigation of a section through the early Paleocene Ardley coal zone at Wabamun, Alberta reveals that there are distinct vertical variations in the palynological, petrographical and geochemical properties reflecting changes in the original depositional environment. Palynological assemblages are dominated by Taxodiaceaepollenites hiatus revealing that the original coal-accumulating mires were inhabited by taxodiaceous vegetation. Subordinate palynomorphs include varied gymnosperm pollen other than T. hiatus, Laevigatosporites spp (fern spores of polypodiaceous affinity), Stereisporites spp (mosses including Sphagnum) and Osmundacidites sp. (Family Osmundaceae). Coal petrography reveals that these coals are inertinite-rich. Abundant fusinite (pyrofusinite), along with semi-fusinite and inertodetrinite comprise up to 65% of the maceral assemblages. Huminite macerals are predominantly eu-ulminite B with lesser eu-ulminite A, densinite and geli-huminite (gelified huminite lacking any remnant cell structure). Liptinite macerals include resinite, sporinite and cutinite.Thinner, stratigraphically lower seams at Wabamun (seams Nos 6-3) consist predominantly of bright coal with high huminite contents. Palynofloral assemblages are comprised of T. hiatus with few abundances of other palynomorphs, suggesting that the original depositional environment was low-lying, dominated by taxodiaceous vegetation, and frequently flooded as evidenced by numerous shale partings, high ash contents and relatively high sulphur percentages. The thick No. 2 seam displays a distinct dulling-up petrographic profile resulting from increasing inertinite contents. Coupled with increased abundances of Stereisporites spp, this may be evidence of localized ombrogeny within the original Wabamun mires, and may support a genetic relationship between Stereisporites sp. and inertodetrinite. The No. 1 seam consists of abundant fibrous (fusain-rich) coal. Modes of origin of this fibrous coal include extreme oxidation due to prolonged drought and possibly forest fires. Elevated ash contents within the Nos 1 and 2 seams may be a result of this oxidation of organic matter and concentration of the inorganics, as well as airborne volcanic ash as evidenced by numerous bentonite bands within these coals. Sulphur contents are extremely low, as low as 0.05% reflecting a terrestrial depositional environment.

96/05230 The effect of inertinite content on coal combustion reactivity

Forest information over a landscape is often represented as a spatial mosaic of polygons, separated by differences in species composition, height, age, crown closure, productivity, and other variables. These polygons are commonly delineated on medium-scale photography (e.g., 1:15,000) by a photo-interpreter familiar with the inventory area, and displayed and stored in a Geographic Information System (GIS) layer as a forest cover map. Forest cover maps are used for multiple purposes including timber and habitat supply analyses, and carbon inventories, at a regional or management unit level, and for parks planning, operational planning, and selection of stands for many purposes at a local level. Attribute data for each polygon commonly include the variables used to delineate the polygon, and other variables that can be measured or estimated using these medium-scale photographs. Additional measures that can only be obtained via expensive ground measures or possibly on high resolution photographs (e.g., volume per unit area, biomass components per unit area, tree-list of species and diameters) are available only for a sample of polygons, or may have been gathered independently using a sample survey over the land area. Improved linkages over a variety of data sources may help to support landscape level analyses. This study presents an approach to combine information from a systematic (grid) ground survey, forest cover (polygon) data, and Landsat Thematic Mapper (TM) imagery using variable-space nearest neighbor methods to estimate (i) mean ground-measured attributes for each polygon, in particular, volume per ha (m3/ha), stems per ha, and quadratic mean diameter for each polygon; and (ii) variation of these ground attributes within polygons. The approach was initially evaluated using Monte Carlo simulations with known measures of these attributes. Nearest neighbor methods were then applied to an approximate 5000 ha area (about 1000 polygons) of high productivity, mountainous forests located near the Pacific Coast of British Columbia, Canada. Based on the simulation results, the use of Landsat pixel reflectances to estimate volume per ha, average tree size (i.e., quadratic mean diameter), and stems per ha did not show great promise in improving estimates for each polygon over using forest cover data alone. However, in application, the use of remotely sensed data provided estimates of within-polygon variability. At the same time, the estimated means of these three imputed variables over the entire study area were very similar to the representative sample estimates using the ground data only. Extensions to other variables such as ranges of diameters and numbers of snags may also be possible providing useful data for habitat and forest growth analysis.

Petrological, palynological and geochemical characteristics of Eureka Sound Group coals (Stenkul Fiord, southern Ellesmere Island, Arctic Canada)

Late Paleocene/Early Eocene coal-bearing strata are widespread across the Canadian Arctic Archipelago. Laterally continuous seams of substantial thickness are present in the Iceberg Bay Formation, Eureka Sound Group, at Stenkul Fiord, Ellesmere Island. Sixty-four coal seams with a cumulative thickness of 53 m of coal occur in a 450 m sequence. The investigation of the composite section is based on examination of 19 samples from seams thicker than 1 m and 7 samples from marker seams used for correlation purposes. The coals consist predominantly of wood-derived huminite macerals (79–98 vol%). Structured huminite macerals are dominant in the top part of the section whereas detrital components are abundant in the lower part. The liptinite fraction is dominated by sporinite and cutinite (1–9 vol%). Inertinite content is very low except at the base of the section (0–14 vol%). Reflectances determined on eu-ulminite (0.36–0.43% R o), geochemical parameters, and Thermal Alteration Indices indicate that the coals are of lignite to subbituminous rank. The dominance of diterpanes and the abundance of Taxodiaceae and Pinaceae pollen suggest that most of the organic matter is of gymnospermous origin. Pinaceae pollen is abundant in the lower part of the section and Taxodiaceae is abundant in the upper part. The abundance of angiosperm pollen in most of the section suggests, however, that angiospermous plants were significant members of the flora. The depositional environment for the Iceberg Bay Formation coals at Stenkul Fiord is that of forested swamps on an alluvial plain. Pollen assemblages indicate a Late Paleocene/Early Eocene age for the section, and a temperate moist climate.

Effect of changing inertinite concentration on pyrolysis yields and char reactivities of two South African coals

Pyrolysis experiments have been carried out with sets of inertinite graded samples prepared from two South African coals (Durban Navigation and Vryheid Coronation Collieries). The effects on product distributions of increasing inertinite concentration, and of different heating rates, have been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K s -1 to 700 °C with 30 s holding at peak temperature) in order to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration ; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Point of Ayr) and other Northern Hemisphere coals. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on data from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, as a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By contrast, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. It seems tempting to ascribe this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, however, many more samples need to be studied before definitive conclusions can be drawn.

Coal maceral separation using column flotation

Recent studies have found that coal macerals have properties which may allow their use as high-valued products. A conceptual approach for the production of individual maceral concentrates utilizing column flotation is presented in this publication. Before maceral separation,the coal was ground to the particle size corresponding to near complete liberation of the macerals, which was approximately 4 gmm for an Illinois No. 6 seam coal. The production of maceral concentrates using flotation was based on the differences in the flotation rates among the various macerals, which was manipulated by adjustment of the medium pH. An increase in pH from 8 to 11 resulted in an order of magnitude reduction in the flotation rate of the vptinite maceral group while the corresponding reduction for the inertinite group was about 50% . On the other hand, the kinetic rate for the vitrinite group remained unchanged. By using pH control and column flotation, the inertinite content was increased from 7.5 % to 50% . Although the upgrading of the other two maceral groups was not as significant, it was evident that the success of the maceral enrichment for a given coal is dependent on the maceral liberation characteristics and the magnitude of the flotation kinetic rate differences among the macerals.

90/01176 Beckley Smokeless brings production on-line

Megascopic, micropetrographic and scanning-electron microscopic investigations of fibrous coal indicate that paleo-wildfires were common occurrences in the mire which produced Highvale coals. At least 20 fibrous coal (fusain) horizons have been identified in corehole samples from the pit no. 3 locality at Highvale, in the central Alberta Plains. Thicknesses of individual horizons vary, and are not particular to any stratigraphic position within coal seams. The majority of these fibrous horizons is within the two thick economic seams, the Highvale Nos. 1 and 2, which are characteristically megascopically dull. The dullness of given lithotypes is largely related to inertinite content with fibrous coal containing 51% inertinite on average, and selected horizons comprised of as much as 85% inertinite. Semifusinite and inertodetrinite are the predominant inertinites, with a few horizons exhibiting highly reflecting fusinite. Macrinite is rare, and micrinite is absent. SEM investigations reveal that certain fibrous coals exhibit excellent preservation of the original gymnospermous (Taxodium) woody tissue. Features such as homogenization and swelling of the cell walls, elimination of the middle lamellae, and preservation of bordered pits are clearly indicative of charcoal formation as a product of paleo-wildfires. Depending upon the nature of the fire, temperatures obtained and the nature of the mire vegetation, a wide range of inertinite precursors can be produced.

90/01181 Geochemistry of subbituminous coals from the Highvale Mine, Alberta, Canada

Megascopic, micropetrographic and scanning-electron microscopic investigations of fibrous coal indicate that paleo-wildfires were common occurrences in the mire which produced Highvale coals. At least 20 fibrous coal (fusain) horizons have been identified in corehole samples from the pit no. 3 locality at Highvale, in the central Alberta Plains. Thicknesses of individual horizons vary, and are not particular to any stratigraphic position within coal seams. The majority of these fibrous horizons is within the two thick economic seams, the Highvale Nos. 1 and 2, which are characteristically megascopically dull. The dullness of given lithotypes is largely related to inertinite content with fibrous coal containing 51% inertinite on average, and selected horizons comprised of as much as 85% inertinite. Semifusinite and inertodetrinite are the predominant inertinites, with a few horizons exhibiting highly reflecting fusinite. Macrinite is rare, and micrinite is absent. SEM investigations reveal that certain fibrous coals exhibit excellent preservation of the original gymnospermous (Taxodium) woody tissue. Features such as homogenization and swelling of the cell walls, elimination of the middle lamellae, and preservation of bordered pits are clearly indicative of charcoal formation as a product of paleo-wildfires. Depending upon the nature of the fire, temperatures obtained and the nature of the mire vegetation, a wide range of inertinite precursors can be produced.

Petrographic characterization and evolution of the Permian coal deposits of the Rajmahal basin, Bihar, India

Lower Gondwana rocks are exposed as narrow bands and discontinuous patches along the western edges of the Rajmahal Hills covering a large area of the Bengal Basin, North Bengal and Pumea. Two coalfields — Hura and Chuperbhita — have productive coal mines. Pillar coal samples from the working coal seams of Hura and Chuperbhita coalfields were collected and subjected to a detailed petrographic and geochemical study using refined procedures on a large number of samples. The results of the micropetrographic study reveal that the Rajmahal coals are rich in liptinite and inertinite contents. The fluorescence microscopy indicates that a major part, identified as argillaceous mineral matter under white incident light, is composed of liptinite macerals such as bituminite fluorinite and exsudatinite. The volatile matter and reflectance suggest these coals are subbituminous to high volatile bituminous B/C in rank. The quantitative relationships among maceral and microlithotype suggest that these coals were deposited in limnic to limno-telmatic conditions under very wet conditions that resulted from undisturbed peat that developed in situ along with subaquatic (limnic) sedimentation in swampy lakes. Further, the GI and TPI values indicate that the Hura coals were formed under oxic moor conditions with sudden episodes of flooding, while the Chuperbhita coals have originated in wet moors with intermittent moderate to high flooding. In addition, G.I. values suggest the formation of these coals in an upper delta/alluvial valley with braided plains.

The Geology and Coal Petrography of Miocene Lacustrine Lignites and Permian Bituminous Coals from the Karapinar Area, Sariz-TURKEY

Coals occur in the Karapınar area mainly within fault-bounded lacustrine Middle Miocene deposits, and locally within shales in the lower part of marine Upper Permian limestones. This study presents the geological setting, proximate analyses, mineralogical and petrographical composition, maceral-based coal facies interpretation and rank of the Middle Miocene lignites, and preliminary results of the Upper Permian bituminous coals. The lignites on an air-dried basis constitute a broad variation of ash yields (11.6-47.0 wt%, av. 28.1 wt%), relatively high total sulphur contents (1.8-4.8 wt%, av. 3.1 wt%) and low calorific values (2050-4791 kcal kg-1, av. 3505 kcal kg-1 ). X-ray powder diffraction studies of the whole coals reveal that the dominant minerals are quartz, clay minerals and pyrite. In addition, calcite and aragonite, which were derived from fossil fragments, were identified in some samples. The average maceral group composition and mineral matter content are 69.4 vol% huminite, 6.2 vol% liptinite, 8.9 vol% inertinite and 15.6 vol% mineral matter. The distribution of maceral groups in the Karapinar area suggests that the inertinite content generally increases from Sarlak mine towards Salderesi mine, whereas the huminite content decreases. This indicates that there was a relatively higher state of oxidation in the peat towards the Salderesi mine. Both the range of values (0.32-0.41 %Rr ) of mean random eu-ulminite-B reflectances and calorific analyses indicate a transition zone from lignite to subbituminous rank for the lignites. Two Upper Permian bituminous coal samples yielded, on an air-dried basis, higher amounts of total sulphur (5.6-6.9 wt%), calorific values of 5561-6149 kcal kg-1, pyrite and/or marcasite, and calcite infilling fractures, and vitrinite contents of 74.5-79.3 vol%. The mean random reflectance values (0.66-0.70 %Rr) of telocollinite suggest a high volatile bituminous coal rank which is relatively lower than the Westphalian coals located in the Zonguldak basin, NW Türkiye.