Coal Petrography Research Articles

Coalbody structure classification method based on dual-lateral and RXO crossplot analysis

According to the positive correlation of coal ash content and natural gamma, using a new coal core reposition method, which is ordered by global and local extreme, coal samples from medium-thickness seam are reasonably located. Integrated the data of coal macrostructure characteristics, coal petrography analysis and coal gas production test, it studies the relationship between coalbody structure and amplitude variation of different well logging data, and the tectonic coal recognition method with well logging data in fresh-water mud invasion. The results show that: the anomalous response of natural gamma ray, neutron, density and apparent resistivity does not reflect the coalbody structure type. In fresh-water drilling mud invasion, using the crossplot technique of dual-lateral, RXO resistivity response and the coalbody structure can classify granulated coal accurately; the proposed method is of good practicability and high reliability.

The age, palaeoclimate, palaeovegetation, coal seam architecture/mire types, paleodepositional environments and thermal maturity of syn-collision paralic coal from Mukah, Sarawak, Malaysia

The Mukah coal accumulated in the Balingian Formation where the time-stratigraphic position is poorly defined by fauna, though a probable Late Miocene age has always been assigned to this formation. Samples collected in the present study that yielded an abundance of Casuarina pollen associated with occurrences of Dacrydium, Stenochlaena palustris, Florschuetzia levipoli and also Stenochlaena areolaris spores, compare closely to zone PR9 of the palynological zonation of the Malay Basin, and can be tied to depositional sequences of Malay Basin Seismic sequences I2000/I3000, indicating an Early Miocene age for the studied coal. The Early Miocene age shows that the Mukah coal was formed during the collision between Luconia Block–Dangerous Grounds with the Borneo that lasted from Late Eocene to late Early Miocene. The rapid increase of deposition base-level caused by the collision is clearly reflected by the architecture of the Mukah coal seams that were generally thin, and also by the reverse order of the paleo-peat bodies.The studied coal samples contained large amounts of detrohuminite without the enrichment of liptinite group macerals, usually explained by the dominance of herbaceous plants in the paleomires. However, the pollen assemblages recovered in the present study provide no support for a ‘herbaceous’ swamp, instead the peats were likely formed mainly from forest vegetation based on the recovery of dominant arboreal pollen assemblages in the present study. Palynomorph assemblages recovered in the present study, with abundance of Casuarina pollen associated with common occurrences of Dacrydium, strongly suggest Kerangas vegetation and Kerapah type peat swamps, indicating a very wet climate. The occurrence of rattan and Pandanus pollens shows that the kerapah type peat swamps were locally bordered by rattan and Pandanus swamps. This shows that the prevailing use of coal petrography to discern the type of vegetation that was present in the peat-forming mires may lead to wrong conclusions. Therefore, a multi-disciplinary approach must be applied for a more accurate and reliable spatial interpretation of the type of vegetation that was present in the peat-forming mires.Consistent with the low sulphur content, evidence from the palynomorph assemblages recovered from the coal seams shows that the coal-forming peat was deposited in freshwater mires with little or no marine influence, despite the fact that the accumulation of the Mukah coal-forming peat took place within a coastal plain setting. Moreover, the fauna present in the host rock formation also suggested a brackish-water environment of deposition.

Coal petrology and coal facies interpretations of bark liptobiolith

A detailed analytical study of Leping bark liptobiolith in Jiangxi was conducted to determine its petrographic characteristics and depositional environment based on coal petrography and geochemistry. Results indicate that barkinite mainly occurs in the middle and lower coal sea4ms, whereas less barkinite and more vitrinite occur in the middle and upper coal seams. Coal facies analysis of bark liptobiolith was performed to determine its characteristics under various depositional conditions, such as the presence of a water table and gelification during coal formation. Results indicate that the environmental evolution of bark liptobiolith begins from brackish-marine swamp facies (barkinite-rich coal seam) and ends in back barrier swamp facies (barkinite-poor coal seam).

Dunkard Group coal beds: Palynology, coal petrography and geochemistry

Coal beds that occur in the Dunkard Group are typically thin (avg. 0.3m), and are high in ash yield (avg. 27.8%) and total sulfur content (avg. 5.1%). Petrographically, Dunkard coals are high in vitrinite (avg. 83.1%, mmf), with correspondingly low to moderate amounts of liptinite (avg. 2.1%, mmf) and inertinite (avg. 13.8%, mmf). Palynologically, Dunkard coal beds are all dominated by tree fern spore taxa (avg. 96.3%), especially Punctatisporites minutus (avg. 82.8%). Calamite spores are the second most abundant plant group (avg. 2.4%), with others (lycopods, small ferns, Cordaites and other gymnosperms) having very minor representation. Overall, the coal palynofloras are strongly dominated by lowland plants (ferns and Calamites), with only rare occurrences of bisaccate–striate conifer pollen.Coal beds of the underlying Monongahela Group (Pittsburgh, Redstone, Sewickley and Waynesburg) are thicker (avg. 1.6m), and are lower in ash (avg. 13.4%) and sulfur (avg. 3.3%) than their Dunkard counterparts. Petrographically, Monongahela Group coals are very similar to Dunkard Group coals, when compared on a mineral matter free basis; coal beds that occur in both groups are strongly dominated by vitrinite macerals. Monongahela Group coals are also palynologically very similar to Dunkard Group coals, with tree fern spore taxa dominating. A coal bed of early Permian age from west-central Texas is also similar, petrographically and palynologically, to Dunkard and Monongahela coals, being vitrinite and tree fern spore dominant.The almost complete lack of coniferous pollen in Dunkard coals led earlier workers to conclude that the Dunkard was entirely Late Pennsylvanian, and not Permian, in age. However, it is now known that Late Pennsylvania lowland floras persisted into the Dunkard, especially during wet intervals. As earlier interpretations were based primarily on spore and pollen floras from coal beds, the lack of conifer pollen in Dunkard coals is probably the result of a sampling bias. Because of this ecological bias, coal palynology is a poor proxy for age dating Dunkard Group coals.Collectively, Dunkard swamps were all planar and topogenous, their formation being controlled by topography and moisture availability. A progressive decrease in wet intervals, both in terms of frequency and duration, during the Dunkard was the major control on peat accumulation and preservation. Collectively, moisture limitation appears to be the principle factor that controlled the formation of Dunkard Group coals.

Research on the Controlling Factors and Grate Prediction of the Output of Pulverized Coal in Hancheng Block, Eastern Ordos Gas Field

According to the 2012s workover treatment statistic in the Hancheng block, the eastern Ordos gas field, the workover caused by pulverized coal accounts for 41.8% of the total, which has seriously affected the continuous and stable drainage. This is one of the main factors which constraint coalbed methane production yield. In this paper, geological factors including the composition of coal petrography, the mechanical strength of coal petrography and coalbody structure destruction and engineering factors including drilling, fracturing and drainage were analyzed to study on the controlling factors on the output of pulverized coal. We conclude that the determinant on output of pulverized coal is the nature of coal seam, however engineering factors cause the output of pulverized coal directly. The root-mean-square amplitude attribute analysis was first used to display the mechanical strength of coal seam. Based on the result, we made the prediction about the possibility of the output of pulverized coal and divided the studying area into four grades. The research on the controlling factors and the prediction of the output of pulverized coal could provide the basis for the prevention and comprehensive treatment of pulverized coal.

The impact of particle size and maceral segregation on char formation in a packed bed combustion unit

Highveld parent coal was crushed into three size fractions, namely: 5mm–75mm, 5mm–53mm, and 5–37.5mm. The crushed samples were subjected as feed coals to heating in a packed-bed reactor to investigate the influence of particle size reduction on char formation and reactivity. Coal petrography was utilized to assess the maceral and char formation distribution of the feed coal samples and their packed-bed combustion unit’s products. The maceral distribution of the feed coal fractions differed from the typical run-of-mine Highveld coal petrographic composition; the smallest size fractions (−53mm and −37.5mm) having the highest vitrinite content. Maceral distribution was further divided into total reactive maceral particles, total inert maceral particles, and total inertinite particles. The −53mm and −37.5mm feed coal samples had the highest total reactive maceral particle content. Inert char particles dominated in the packed-bed combustion unit samples due to high inertinite maceral group content of the Highveld coals. Unexpectedly, the −53mm feed coal sample had higher content of total reactive maceral particles and lower content of total inert maceral particles; whereas the −37.5mm feed coal sample had high content of reactive maceral particles and high content of total inert maceral particles. This variation in maceral group content lead to the −53mm feed coal sample being more reactive (producing more devolatilized and porous chars and thus reacting faster with reactant gases) than the −37.5mm feed coal sample. This was due to inert maceral particles restricting the −37.5mm feed coal sample from fully softening and reacting with reactant gas. This was also this was attributed to variation in volatile propagation of the three particle sizes. This confirms that a feed coal with smaller particle sizes results in different reactivity, char formation, and better heat transfer during combustion than the feed coal with large particle size range. Another important factor that plays a role in combustion is maceral association; it was observed that maceral distribution has a great influence on the char formation and its reactivity more than coal particle size.

Evolution of an old mining district between 725 and 1630 ad at the boundary between Thüringen and Bayern, SE Germany, using mineralogical and chemical markers, radio-carbon dating, and coal petrography of slags

Joint investigations of smelting residues, using mineralogical, chemical, and coal petrographic methods as well as radio-carbon dating, are a clue to unravel the history of ancient mining and smelting districts. The data can also contribute to the history of colonization and industrialization of a particular region as well as to constrain and depict human-induced disasters in the past. In the present case, it is a mining area straddling the border between Thuringen (Thuringia) and Bayern (Bavaria), SE Germany. Thermodynamical calculations provide numerical results on the smelting process as to the temperature of formation, proper, and allow for a precise description of the dumping sites as to the redox conditions (Eh) and pH of the fluids under near-ambient conditions. The soluble components involved in these processes may be determined. During the early Middle ages, Sorbian tribes were roaming the area in search of soft iron ores being well exposed near the surface and easily to smelt. During the early modern times, the interest of the miners had shifted towards more complex ore, also containing lead. Gentries in possession of the land were granted mining licenses by the Counts of Nurnberg to exploit these ores. The ore was almost exclusively derived from vein-type deposits rich in ankerite and siderite, which altered into soft Fe ore giving rise to goethite in the gossans. Stratabound SEDEX deposits were only high up on the agenda of miners when they were looking for iron-only deposits. The small size of SEDEX deposits in this region and some difficulties the miners were confronted with during their exploitation did not render this type of ore a real competitor for Fe being mined elsewhere in Germany. Towards modern times, the miners began extracting the byproducts, Pb and Cu, from the siderite veins, and Fe became a residue within the tailings, as it was no longer of economic interest. The miners drifted steadily deeper with a jump in depth of mining at the passage from the High Middle Ages to the Late Middle Ages. Obviously, the miners managed to cope with the hydraulic problems and found more efficacious methods of working in the underground mines. Coal petrographic methods allow for a determination of the temperature of formation and also to constrain the derivation of firewood they used to poke the fire in the smelting furnace. The way the ancient miners produced their charcoal was be described. It was a very inefficient method yielding a low-quality coal with a moderate caloric output from softwood- and hardwood-based organic matter. Thermodynamical calculations based upon Fe phosphates and sulfates show that the slags were laid down always under dry conditions far above wetlands inundated periodically. A blaze at the dumping sites caused an introduction of sulfur in an otherwise sulfur-deficient slag environment after 1275 ad. Therefore, even the secondary minerals within the slags are still of value for a historical environment analysis of the human habitat.

Study on Influencing Factors of Coal Fines Produced by CBM Wells in Hancheng Block, Shaanxi Province, China

To ensure the continuous and stable exhaust process of coalbed methane wells, prevent coal fines from lowering the guidance ability of seepage channel, and solve the problem of stuck pump and submerged pump caused by gathering of coal fines, taking Hancheng block as the experimental area, this paper analyses on the source of the coal fines, and divides it into two categories of original coal fines and secondary coal fines. Based on the characteristics of coal petrography, coal structure, coal seam and engineering factors, we make analysis of their factor on the output of coal fines, and we conclude that the characteristics of coal petrography are the foundation, and the engineering is the precipitating factor, but the development of deformed coal is the primary factor. The study on the division of types of coal fines and output factors can provide a guidance for reasonable coal-fines-control measures.

Interaction between Supercritical CO<sub>2</sub> and Coal Petrography

CO2enhanced CBM recovery(CO2-ECBM) is an important way for reducing CO2emission into atmosphere and enhancing coal-bed methane (CBM) recovery. The interaction between supercritical CO2and coal petrography has been investigated since the 1990s. Advances in the interaction between supercritical CO2and coal petrography are reviewed in light of certain aspects, such as the competitive multi-component gas adsorption, sorption-induced coal swelling/shrinkage and the fluid-solid coupling between fluids(such as gas, liquid and supercritical fluid) and coal petrography. It is suggested that a comprehensive feasibility demonstration is necessary for a successful application of the technology for CO2-ECBM. At the same time, it also indicated that there are some questions must be discussed in future, such as the influences on pore structure, coal adsorptivity and permeability of the reaction of ScCO2-H2O and rock and small organic matters are extracted by supercritical CO2.

Abnormal concentration and origin of heavy hydrocarbon in upper permian coal seams from Enhong syncline, Yunnan, China

Coalbed gas (CBG) in Enhong (恩洪) syncline, eastern Yunnan (云南), China, is characterized by high concentration of heavy hydrocarbon with the highest content of ethane, which is more than 30%. Some previous investigators paid much attention to the abnormal concentration of heavy hydrocarbon in the CBG of Enhong, but few have researched on its origin. This article describes the characteristics of abnormal high concentration of heavy hydrocarbon in Enhong syncline and analyzes its reason from the aspects of origin and evolution of heavy hydrocarbon by carbon isotope, coal petrography, and coal rank. Features of gas carbon isotope composition display that there is no inorganic gas or oil components in the CBG, which is classified to thermogenetic gas produced by humic material, with characteristic of secondary biogenic gas in shallow coal seam. The concentration of heavy hydrocarbon in Enhong syncline increases with the increase of vitrinite, vitrinite/inertinite ratio, and hydrogen/carbon ratio and decreases with the increase of inertinite, so hydrogen-rich vitrinite may be a very important factor resulting in the abnormal concentration of heavy hydrocarbon. It also increases with the increase of degree of coalification of coking to lean coals during which the peak of heavy hydrocarbon generation is reached. Therefore, we think that high concentration of heavy hydrocarbon originated from the coupling effect of higher content of the hydrogen-rich vitrinite in the coal and the coal rank of coking to lean coals.

Paleoenvironmental settings of the Sofia lignite basin: Insights from coal petrography and molecular indicators

Compositions of Balsha lignite, Sofia coal-bearing basin, Bulgaria and carbonaceous shales are studied by petrological and geochemical proxies. The macropetrographic characteristic of profiles is relatively constant. The lignite is generally composed of dull matrix coal containing significant amounts of xylite fragments. The typical microscopic constituents of the lignite are the ulminite, and less frequently textinite lenses, scattered within attrinitic groundmass. The maceral composition of the organic matter in carbonaceous shales does not differ significantly from that of the lignite samples.Biomarker assemblages of the extractable portions are determined by gas chromatography–mass spectrometry. Additional information for the compositions of residues after extractions is obtained by TMAH thermally assisted hydrolysis/methylation.Petrographic contents, lipid assemblage and TMAH thermally assisted hydrolysis/methylation data imply that the original peat bog is formed in fresh-water forest swamp preferably composed by gymnosperms. Polar diterpenoids argue for Cupressaceae s.l., Taxodiaceae as the most probable vegetation. For one of the profiles appreciable angiosperm rich herbaceous-type flora contribution is assumed. Polar oleanane triterepenoids and their aromatized derivatives argue for angiosperm input. The relevance of A-norfriedel-8-en-10-one/friedelin ratio for groundwater level appraisal is discussed. It admits long period of high water level in the paleomire.High content of vanillyl structures and subordinated presence of syringyl units in products of TMAH thermally assisted hydrolysis/methylation are hint for Gymnospermae input in the paleoswamp and Angiospermae contribution to one of the profiles. Cinnamyl phenolic units, indicating non-woody angiosperm vegetation presence, are registered as well. Flavonoids in products are considered as taxonomic markers of Cupressaceae plants in the paleoswamp.

Petrographic, mineralogy, and geochemistry of coals of Pabedana, Kerman Province, Central Iran

This paper discusses the result of the detailed investigations carried out on the coal characteristics, including coal petrography and its geochemistry of the Pabedana region. A total of 16 samples were collected from four coal seams d2, d4, d5, and d6 of the Pabedana underground mine which is located in the central part of the Central-East Iranian Microcontinent. These samples were reduced to four samples through composite sampling of each seam and were analyzed for their petrographic, mineralogical, and geochemical compositions. Proximate analysis data of the Pabedana coals indicate no major variations in the moisture, ash, volatile matter, and fixed carbon contents in the coals of different seams. Based on sulfur content, the Pabedana coals may be classified as low-sulfur coals. The low-sulfur contents in the Pabedana coal and relatively low proportion of pyritic sulfur suggest a possible fresh water environment during the deposition of the peat of the Pabedana coal. X-ray diffraction and petrographic analyses indicate the presence of pyrite in coal samples. The Pabedana coals have been classified as a high volatile, bituminous coal in accordance with the vitrinite reflectance values (58.75–74.32 %) and other rank parameters (carbon, calorific value, and volatile matter content). The maceral analysis and reflectance study suggest that the coals in all the four seams are of good quality with low maceral matter association. Mineralogical investigations indicate that the inorganic fraction in the Pabedana coal samples is dominated by carbonates; thus, constituting the major inorganic fraction of the coal samples. Illite, kaolinite, muscovite, quartz, feldspar, apatite, and hematite occur as minor or trace phases. The variation in major elements content is relatively narrow between different coal seams. Elements Sc,, Zr, Ga, Ge, La, As, W, Ce, Sb, Nb, Th, Pb, Se, Tl, Bi, Hg, Re, Li, Zn, Mo, and Ba show varying negative correlation with ash yield. These elements possibly have an organic affinity and may be present as primary biological concentrations either with tissues in living condition and/or through sorption and formation of organometallic compounds.

Coal petrography, mineralogy and geochemistry of lignite samples from the Ogwashi–Asaba Formation, Nigeria

Organic sediments picked up randomly from seven small outcrops within the Ogwashi–Asaba Formation, southern Nigeria, are examined and evaluated by means of coal petrology and chemical and mineralogical analyses in order to determine the palaeoenvironmental conditions and the factors controlling their formation. Six samples proved to be low-rank coals C to B (lignite), one carbonaceous shale. The lignite samples display low ash yield, low telohuminite and high detrohuminite and liptinite contents; they contain small amounts of clastic minerals, mainly quartz and clays, which point to the topogenous character of the depositional palaeoenvironment. The palaeomires formed in a continental basin crossed by the mid-Tertiary palaeo-Niger River; the latter, as well as the tropical rainfall supplied the mires with water. The dense vegetation cover on the mire surface and the surroundings and/or the low relief energy of the broad area restricted the inorganic influx resulting in high-grade coal formation. As the outcrops are distributed over a distance of 60km, the expected reserves of good quality lignite constitute a very promising exploration target.

The evaporite–coal transition: Chemical, mineralogical and organic composition of the Late Triassic Abu Ruweis Formation, NW Jordan—Reference type of the “Arabian Keuper”

The Abu Ruweis Formation, NW Jordan, was studied with regard to its chemical (major, minor elements, REE, S-, O-, C isotopes, organic chemistry), mineralogical compositions (rock-forming minerals), coal petrography (maceral analyses) and palynology (age determination and palaecosystem) for the evaporite–coal facies transition which is very rarely found. The palynomorphs point to a Late Triassic/Carnian age of formation. Strong evaporation in the series is demonstrated by the presence of dolomite, gypsum and celestite. Mg, Ca, F, Cl, S, Sr and Ba reflect the variation of evaporation during basin subsidence. A detrital influx is characterized by the abundance of Si, Ti, Al, Fe, Mn Ce, Co, Cr, V, Y and the (Zr+Rb)/Sr ratio. Salinity variation may be characterized by the fractionation of LREE (La) and HREE (Lu). The element triplet Zn, Cu and Pb offers a clue to the redox regime and supports the idea of mineralogical-based proximity indicators: Zn (Eh≪0)⇒Cu (Eh≤0)⇒Pb (Eh≤0). Oxygen isotope composition (δ18O −8.3 to −0.9‰) of the carbonate fraction resulted in uniform isotope formation temperatures near 50°C. Temperature data obtained during coal petrography yielded maximum paleotemperatures of 100°C for the black shale and about 70°C for the remaining coal samples that are likely to reflect hot brine activity in some parts of the basin. The carbon isotopic composition (δ13C −12.4 to −3.9‰) of the carbonate fractions indicates a biogenic 12C-enriched CO2 source, which probably was admixed to marine pore water bicarbonate (with δ13C near 0‰) during early diagenesis. The S isotope composition (sulfide fraction −28.9 to −24.0‰) is typical of sulfides formed in the course of bacterial reduction with some sulfate (sulfate fraction +7.5 to +11.6‰) resulted from later re-oxidation of the sulfides. Phosphate distribution is a measure for the aridity while high-sulfur contents in the coal-bearing sediments point to brackish or alkaline waters. The results of the organic chemistry are interpreted in terms of a bloom of algae which were preserved during dysaerobic conditions in the course of early diagenesis. Sesqui- and diterpenoids are most probably derived from precursor molecules abundant in leaf resins of conifers. Phenanthrene and its methylated analogues derived from combustion products of fossil fuels generated by wild fires. Among the maceral types, textinites A and B represent xylem features of tree trunks and the crassi-cutinite upper leaf cuticles. The data allow for a definition of a special geological setting called the “Arabian Keuper Facies”. This facies type is characterized by an evaporite–coal transition which translates into a geodynamic setting positioned between the fully marine “Alpine Triassic Facies” of the Tethyan Ocean where submarine brines were responsible for the Alpine-type MVT Pb–Zn deposits and the epicontinental “Germanic Keuper Facies” that lacks both hydrothermal activity and major marine incursions.

The petrographic determination of reactivity differences of two South African inertinite-rich lump coals

There is limited literature on the classification and characterization of chars generated from lump coals during synthesis gas production, especially from a South African perspective. Two inertinite-rich medium rank C Highveld lump coals (Coals A and B) were utilized to study their burning behaviour in a packed-bed reactor combustion unit. Seven sample increments were dissected per coal obtained from predefined zones within the reactor. Proximate analysis revealed that Coal A released 10% more of its volatile matter yield within the reactor zones when compared to Coal B. Petrographic analysis showed that Coal B had a higher content of reactive macerals when compared to Coal A. The reactive maceral content of Coal A was dominated by vitrinite and liptinite whereas for Coal B, reactive macerals were comprised of 49% vitrinite and liptinite and the other 51% is reactive semifusinite and reactive inertodetrinite. This difference leads to different reactivity behaviour when these coal samples were subjected to high temperatures. Coal B produced a greater proportion of inert chars, ran at higher temperatures in the hotter region of the reactor because of its aromatic richness thus leads to lower CO 2 reactivity. This paper highlights the need for a detailed characterization of coals to fully determine their conversion performance; detailed coal petrography is one such tool that its value is frequently underplayed.

Preliminary Evaluation on Physical Properties of Coal Reservoirs in Boli Basin, Northeastern Heilongjiang Province, China

The Boli basin has coalbed methane (CBM) resource of 57×108m3 at a coal-bearing area of about 7200km2. Although the basin has huge CBM development potential, the study on the characteristics of coal reservoirs is still deficient. In the paper, the physical properties (including coal petrography, rank, quality, porosity and permeability) of the coals were studied by: (1) measuring vitrinite reflectance, coal maceral composition and coal quality; (2) quantitatively counting microfractures; (3) porosity and permeability tests; and (4) low-temperature N2 isotherm adsorption/desorption and mercury porosimetry analyses. Results show that: (1) coal maceral composition is dominated by vitrinite (77.0-95.1 %); (2) the maximum vitrinite reflectance of coals ranges from 0.48 to 1.76 % Ro, max; (3) coal is composed of high carbon content (63.43-85.14%), low hydrogen content (3.23-4.56%), extremely low moisture content (0.18-1.18%) and widely varied ash yield (7.54 to 29.23%); (4) Coal pores are dominated by micropores (40.6-69.3%), and the pores with a diameter of 0-10nm are dominant (59.6-80.9%); (5) coal permeability values vary from 0.04 to 3.92mD with an average of 1.98mD. In addition, according to the mercury porosimetry analysis, pore-fractures size distribution was summarized as four types: Types Ⅰ and Ⅲ are favorable for developing CBM and represent good pore-fracture structures.

CO<sub>2</sub> Storage Mechanism and Coupling Effect with Minerals in Coal Seam

CO2 storage in coal seam is the important way of reducing CO2 emission into atmosphere and enhancing coal-bed methane (CBM) recovery. This paper based upon the results of CO2 storage in coal seam in theoretical research and demonstration project, analyzed the mechanism of CO2 storage in coal seam, and recognized that the process is a complex process from a single physical process to physical, chemical, and microbial effect process. The paper also summarized the fluid-solid coupling actions between H2O-CO2 and minerals in coal seam and its effect on coal reservoir characteristics. It is considered that after H2O-CO2 action, the components of coal petrography changed. At the same time, there has been marked change in coal physical properties: the porosity enhanced, mechanics property reduced, and the changed of adsorptivity and permeability need further researches. This paper can guide the prediction storage ability and assessment the safety of CO2 in coal seam.

Improving coke strength prediction using automated coal petrography

A range of Australian and overseas coals with a mean maximum vitrinite reflectance (Ro, max) range of 0.68–1.71% were carbonized in a test coke oven. Coal properties were characterized using XRF, XRD and automated imaging of polished sections of discrete coal grains. The Full Maceral Reflectance (FMR) parameter was calculated from the reflectance data and was correlated with coal as well as coke properties. The Ro, max values and the vitrinite estimates from the semi-automated microscopic technique indicated a good correlation with similar data based on manual point count analysis. The FMR parameter is shown to increase with increasing carbon content, structural ordering of carbon and decrease with increasing volatile matter. The FMR parameter of coal was related to cold coke strength DI15150 and coke strength after reaction (CSR). The FMR parameter was modified by diluting the contribution of high reflectance coal grains as well as incorporating the effect of ash contribution to propose a combined coal index (CCI). The new coal index is shown to improve the accuracy of coke strength prediction. The combined coal index provides a promising objective measurement based alternative for predicting coke strength.

Low-temperature oxidation of some Turkish coals

Low-temperature oxidation of four different-rank Turkish coals was studied in order to assess the effects of temperature, particle size, coal petrography, and coal rank by monitoring CO2 and CO formation rates and calculated CO/CO2 ratios. Coals were classified to −425+212, −212+150, and −150+106μm size groups and oxidized at 40, 60, and 90°C. Temperature has a pronounced effect on the formation rates of CO2 and CO; when the temperature increases, the formation rates of CO2 and CO also increases. Nevertheless, the formation rates of CO2 and CO were found to be independent of particle size, particularly at relatively lower temperatures. Petrographic analysis showed that the coal sample having the highest inertinite group macerals was oxidized more easily, thus, yielding more CO2 and CO. Relatively higher rank coals were oxidized more easily, but oxidation diminishes with time. On the contrary, oxidation progresses with time for lower rank samples especially at relatively higher temperatures.

Sorption of organic contaminants by Oxford Clay and Mercia Mudstone landfill liners

Abstract This study provides an evaluation of the sorption capacity of two contrasting mineral liners or barriers widely used in the UK for a range of organic contaminants of varying hydrophobicity commonly found in landfill leachate. Batch tests (involving toluene, trichlorobenzene, trichloroethene and naphthalene) showed that the sorption capacity of Oxford Clay was not only significantly greater than that of Mercia Mudstone, but was also greater than the sorption capacity of many soils or clays reported in the literature. The organic carbon normalized sorption coefficients ( K oc ) for Mercia Mudstone were comparable with both published and empirically derived K oc values, but the K oc for Oxford Clay was underestimated by literature values by several orders of magnitude. Retardation of these contaminants by Oxford Clay was also under-predicted by estimates based solely on organic carbon content. Amorphous organic matter (the main component of the organic matter in the Oxford Clay as characterized using ‘coal petrography’ methods) was believed to be responsible for the elevated sorption capacity of the Oxford Clay liner. Sorption coefficients were reduced in the presence of dissolved organic carbon in leachate, suggesting that published K oc values derived in synthetic groundwater may overestimate the sorption capacity in landfill scenarios. Sorption coefficients and K oc – K ow correlations determined in this study can be used for modelling organic contaminant sorption in Oxford Clay and Mercia Mudstone liners as part of landfill risk assessments in the absence of site-specific data, in particular for Oxford Clay, for which published correlations were shown to be too conservative. For other types of clay liner material, the cautious approach would be to determine site-specific sorption coefficients following characterization of the organic carbon. Further research is needed into the effects of leachate dissolved organic carbon and the composition of clay liner organic carbon on sorption of hydrophobic organic compounds.