Inertinite Content Research Articles

A Nuclear Magnetic Resonance study: Implications for coal formation in the Witbank Coalfield, South Africa

In this study, carbon-13 cross-polarization magic-angle-spinning solid-state nuclear magnetic resonance (13C CP-MAS SS NMR) was undertaken on a parent coal sample and its density-fractionated derivatives, an inertinite-rich and a vitrinite-rich sample, obtained from the Witbank Coalfield of South Africa (medium rank C bituminous coal). The formation of inertinite macerals has been extensively researched and the conclusions remain largely controversial. However, most research has been confined to northern hemisphere coals, which are typically dominated by vitrinite. South African coals are widely known for their high inertinite content. Earlier workers have ascribed the inertinite macerals, in their diversity, to aerial oxidation. However, this oxidation-only pathway fails to recognize that inertinite macerals can form through other processes such as charring of plant matter. Microscopically, charred matter possesses anatomical structures that closely resembles those observed in inertinite macerals, with lignin and/or cell walls largely preserved, perhaps mechanically fragmented or compressed in some instances. Based on the NMR structural parameters, the average aromatic cluster size in the inertinite-rich sample (petrographically dominated by fusinite, semifusinite of varying reflectance, and inertodetrinite) corresponds to monocyclic, 6-aromatic carbon rings. In the vitrinite-rich sample of the same coal, the cluster sizes are larger, corresponding to multi-ring aromatic hydrocarbons. The 6-carbon rings in the inertinite-rich sample are interpreted to correspond to guaiacol and syringol, the principal products of low-temperature (below 400 °C) lignin pyrolysis. Since charring depletes cellulose and moisture, fire-affected plant matter is interpreted to have a lower compaction potential than vitrinite-forming material, sustaining 6-aromatic carbon ring isolation in the former. Lignin-derived aromatic rings in compactable plant matter merge to form the multi-ring clusters present in the collotelinite- and collodetrinite-rich sample of the same coal.

Nanostructure of cokes

Twenty eight cokes made from Australian coals and prepared under a range of experimental conditions were examined using Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) to determine the size distribution of all of their pores and also pores inaccessible to deuterated toluene (closed pores) in the size range 1 to 1000 nm radius. The main findings were that in all cokes, even those made from relatively inertinite-rich coals, nearly all pores of <5 nm radius were closed and >70% of the pores of 1000 nm in radius or larger were open. At intermediate pore sizes, the fraction of open pores was highly variable, with cokes made from inertinite-rich coals having more open pores. For all cokes made from coals sourced in Queensland, Australia, the number of open pores increased linearly with increasing inertinite content of the original coal and was not strongly affected by rank over the range investigated (0.9–1.3% mean maximum vitrinite reflectance). In contrast, all of the cokes made from the coals from the Illawarra region, New South Wales, Australia, had less than half the number of total or open pores than the other cokes. The number of pores of <5 nm radius decreased with increasing rank of the starting coal and was not strongly affected by the starting maceral composition or region of origin. The ratio of number of pores in cokes made from inertinite-rich concentrates to those made from the corresponding vitrinite concentrate from the same coal varied with pore size and was greatest at around 100 nm pore radius. The number of pores in cokes at all sizes below 1000 nm was largely unaffected by the bulk density of the charge, oven size or method of quenching. The insensitivity of numbers of nanometre-sized pores in coke to coke preparation conditions can explain why increasing the bulk density of a coal charge may increase coke strength but will have much less effect on coke reactivity to carbon dioxide.

Depositional environments of the Jurassic Maghara main coal seam in north central Sinai, Egypt

Twenty-eight channel samples with a cumulative thickness of about 4 m collected from three sections of the Maghara main coal seam in the middle Jurassic Safa Formation have been studied for their lithotype and maceral compositions to reconstruct the character of peat swamp, its hydrological regime and the predominating type of vegetation. Lithotype composition is a combination of dully lithotypes with duroclarain (19% of total cumulative thickness), clarodurain (15%), black durain (15%), and shaly coal (15%) and bright lithotypes represented by clarain (23%), vitrain (12%) and a small proportion of wild fire-generated fusain (1%). Maceral analyses revealed the dominance of vitrinite (70.6% on average), followed by liptinite (25.2%) and inertinite (8.1%). Mineral matter content is ∼9% on average and consists of clay, quartz and pyrite concentrate mostly at the base and the roof of the seam. Dominantly vitrinite composition of coal and extremely low fire- and oxidation-borne inertinite content, together with high Gelification Indices imply predomination of waterlogged anoxic conditions in the precursing mire with water tables mostly above the peat surface throughout most of the time during peat swamp formation. Increases in collotelinite contents and Tissue Preservation Index up the section, followed by a reversal trend in upper third of the coal section, further accompanied by a reversal trend in collodetrinite, liptodetrinite, alginite, sporinite and clay contents records a transition from dominately limnotelmatic and limnic at the lower part to dominately limnotelmatic with increase telmatic condition achieved in the middle part of coal. At the upper part of coal seam an opposite trend marks the return to limnic and limnotelmatic conditions in the final phases of peat swamp history and its subsequent inundation. The proportion of arborescent (mostly coniferous) and herbaceous vegetation varied throughout the section of the coal with tendency of increasing density of arborescent vegetation to the middle part of the coal seam section. The intercalation of coal in shallow marine strata implies that peat swamp precursor formed in a coastal setting, probably on delta plain or lagoon. Its formation was controlled by water table changes driven by sea level fluctuations that created an accommodation space necessary for preservation of peat.

Influence of chemical properties on CH4 adsorption capacity of anthracite derived from southern Sichuan Basin, China

This study aimed to determine the effects of high-rank coal chemical properties on CH4 adsorption capacity. A total of 24 core samples of anthracite from 11 coalbed methane wells in southern Sichuan Basin (China) were examined systemically using maceral analysis, proximate and ultimate analyses, total sulfur content test, and CH4 isotherm adsorption experiment. Results show that vitrinite group macerals are the most abundant maceral group, followed by inertinite and inorganic mineral matter of these coals. Vitrinite- and inertinite-rich coals have the similar average Langmuir volume under dry ash-free basis (VLdaf), and no positive or negative correlation was found between VLdaf and vitrinite and inertinite content. In addition, there is a weakly negative relationship between inorganic mineral matter and CH4 adsorption capacity. Effects of coal elements by ultimate analysis, such as C element and the atomic ratios of H/C, O/C and N/C, on CH4 adsorption capacity were studied. CH4 adsorption capacity has positive correlation with C element content, H/C atomic ratio and N/C atomic ratio, respectively, but negative with O/C atomic ratio. Effects of four proximate analysis parameters (moisture, ash, fixed carbon and volatile matter content) on CH4 adsorption capacity were also studied. Moisture, ash and volatile matter content negatively affect CH4 adsorption, respectively, and fixed carbon content has exactly the opposite effect. Principle component regression analyses for the set of elements and proximate analysis parameters show that C, O, ash and fixed carbon content are the important influence factors on CH4 adsorption capacity.

Distribution of Trace Elements in Fractions after Micronization and Density-Gradient Centrifugation of High-Ge Coals from the Wulantuga and Lincang Ge Ore Deposits in China

The Wulantuga (Inner Mongolia) and Lincang (Yunnan Province) germanium ore deposits in China are both considered world-class, coal-hosted Ge deposits. For this paper, two bench coals (WLTG C6-2 from Wulantuga and LC S3-6 from Lincang) were selected to characterize the associations between density fractions (maceral concentrates) and trace elements using micronization, density-gradient centrifugation (DGC), and inductively coupled plasma mass spectrometry (ICP-MS), especially for the abnormally enriched trace elements (including Ge, W, As, Sb, Be, U, and Nb) and rare earth elements and yttrium (REY) in the Wulantuga and/or Lincang high-Ge coals that are widely considered to have varying degrees of organic affinity. Huminite and inertinite contents of WLTG C6-2 account for 58.4% and 40.7%, respectively, whereas LC S3-6 is dominated by huminite (98.7%). Lower peak densities for huminite/inertinite and Gaussian distributions of DGC profiles after HCl-HF demineralization suggest that some minerals still exist ...

Material composition, pore structure and adsorption capacity of low-rank coals around the first coalification jump: A case of eastern Junggar Basin, China

The first coalification jump (FCJ) has a significant impact on low-rank coal reservoir heterogeneity, and is of great importance for coalbed methane (CBM) development. Here, a series of experiments were performed for 10 coal samples collected from eastern Junggar Basin, to compare the material composition, pore structure and adsorption capacity of lignite and candle coal. Contrast with the candle coal, the lignite has a higher inertinite content, larger pore volume, better connectivity, and greater specific surface area (SSA). During the process of FCJ, the polycondensation of coal molecules and the compaction of coal matrix occur, leading to a rapid decline of moisture, porosity and permeability, and the cell wall in the candle coal is badly crushed with clay minerals filled from optical microscopy. In general, the larger total pore volume (1.7–300 nm, measured by N2 adsorption) contributes to the larger SSA. The SSA of candle coal mainly comes from the contribution of micropore (<10 nm), especially the 2–3 nm pores, while the micropore and transition pore (10–100 nm) contribute to most of SSA of lignite. However, though the SSA of the candle coal is largely lower than that of the lignite, the CH4 adsorption capacity tends to decrease from the lignite to the candle coal due to material composition difference. Low-field NMR was used to determine the pore and fracture system by analyzing the transverse relaxation time, which showed that only two obvious peaks could be identified in lignite and three peaks at about 0.25 ms, 30 ms and 200 ms are present in the candle coal. The fractal results indicate that the pore surface and complexity inside the coal increase gradually from lignite to candle coal. These observations could deepen awareness and understanding of low-rank coal reservoir heterogeneity and the influence of FCJ on reservoir property.

Water imbibition and drainage of high rank coals in Qinshui Basin, China

Water mobility in coal plays an important role in achieving the high performance of coalbed methane (CBM) recovery from coal. To better understand this phenomenon, a systematical investigation of water imbibition and drainage was conducted experimentally using high rank coals collected from Qinshui Basin of China. The results show the shapes of the T2 spectrum for water imbibition and drainage experiments generally distribute with the bimodal pattern with a higher left peak around 1ms and a lower right peak around 50–100ms. The cumulative imbibition water content ranges from 3.09 to 6.54vol% under the 0MPa saturated hydraulic pressure at vacuumed state, which is accounting for 58.30–91.07% of total imbibition water content, and grows exponentially with the increasing of saturated hydraulic pressure. The cumulative drainage water content ranges from 0.53 to 1.71vol%, and residual water content varies from 3.47 to 6.73vol%, which latter is accounting for 72.1–88.46% of the total imbibition water content. The imbibition and drainage water contents increase with the total pore volume increasing. The well-developed macropores and mesopores increase the drainage water content and rate, while the micropores mainly contribute to the residual water content. The cumulative imbibition water content is positively related to inertinite content but negatively related to ratio of vitrinite to inertinite and ash yield, whereas it is just the opposite for drainage water content and rate. As it is expected, the increasing wetting angle generally increases the drainage water content and rate.

The influence factors for gas adsorption with different ranks of coals

In this paper, scanning electron microscopy, low-temperature N2 adsorption and CH4 isothermal adsorption experiments were performed on 11 coal samples with Ro,max between 0.98 and 3.07%. The pore structure characteristics of coals (specific surface area, total volume distribution) were studied to assess the gas adsorption capacity. The results indicate that there is significant heterogeneity on coal surface, containing numerous channel-like pores, bottle-shaped pores and wedge-shaped pores. Both Langmuir volume (VL) and Langmuir pressure (PL) show a stage change trend with the increase of coalification degree. For different coalification stages, there exist different factors influencing the VL and PL values. For low-rank coals (Ro,max &lt; 1.1%), the increase of VL values and decrease of PL values are mainly due to the abundant primary pore and fracture within coal. For middle-rank coals (1.1% &lt; Ro,max &lt; 2.1%), the moisture content, vitrinite content and total pore volume are all the factors influencing VL, and the reduction of PL is mainly attributed to the decrease of moisture content and inertinite content. Meanwhile, this result is also closely related to the pore shape. For high-rank coals (Ro,max &gt; 2.1%), VL values gradually increase and reach the maximum. When the coal has evolved into anthracite, liquid hydrocarbon within pore begins pyrolysis and gradually disappears, and a large number of macropores are converted into micropores, leading to the increase of specific surface area and total pore volume, corresponding to the increase of VL. In addition, the increase of vitrinite content within coal also contributes to the increase of VL. PL, reaches the minimum, indicating that the adsorption rate reaches the largest at the low pressure stage. The result is mainly controlled by the specific surface area and total pore volume of coal samples. This research results will provide a clearer insight into the relationship between adsorption parameters and coal rank, moisture content, maceral composition and pore structure, and it is of great significance for better assessing the gas adsorption capacity.

Petrology and palynology of the Middle Pennsylvanian Leatherwood coal bed, Eastern Kentucky: Indications for depositional environments

The Eastern Kentucky Coal Field is located in the central portion of the Appalachian Basin. The Pennsylvanian Breathitt Formation in this region is characterized by numerous sequences of bituminous coal-bearing sedimentary rocks. These coals have distinct maceral compositions due to variations in depositional environments. Coal characterization is an important method for determining conditions that influenced peat accumulation and overall depositional settings of mires. This study focuses on the characterization of the maceral composition of the Middle Pennsylvanian-age Leatherwood coal bed. It utilizes petrographical, palynological, and geochemical analyses to describe specific depositional environments and associated peat accumulation conditions. Petrographic analyses indicate that these coals have relatively high liptinite and varying inertinite content, along with trace amounts of mineral matter. Vitrinite, mainly in the form of collotelinite, is the most dominant maceral group. Geochemical data reveals low ash and sulfur content. Ancillary palynological data shows the palynomorph assemblage to be dominated by tree fern and large Lycopod tree spores, with lesser amounts of small Lycopod tree, small fern, and Cordaites and Calamites spores. The petrographic, geochemical and palynological data indicate that both domed, ombrotrophic, and planar, rheotrophic mire conditions, with limited local detrital influx, contributed to the formation of the Leatherwood coal.

Coalbed methane reservoirs’ pore-structure characterization of different macrolithotypes in the southern Junggar Basin of Northwest China

Coalbed methane (CBM) development in the southern Junggar Basin of Northwest China has aroused extensive attention owing to its significant resource potential. The accurate characterization of coal pore structure is important for CBM exploration and production. In order to explore the relationship between coal pore structure and macrolithotype, which has rarely been studied in the southern Junggar Basin, a series of laboratory experiments were performed on eight samples of different macrolithotypes. The results show that the porosity exhibits regularity with macrolithotype in the order bright < semibright < semidull < dull, and also shows an increase with the rise of the inertinite content. The pore-size distribution results show that the dominating pores of bright and semibright coals are usually greater than that of dull and semidull coals in size. The pore-type analysis indicates that the bottleneck pores (Type B) are well developed in dull and semidull coals, while bright and semibright coals mainly host two sides (Type A), namely opened pores and one-side-closed pores (Type C). The pore-type and -size distribution strongly affect pore connectivity refers to the facts that: 1) the proportion of effective porosity increases with an increasing proportion of pores greater than 100 nm in size; and 2) that the mercury withdrawal efficiency is always lower when the pores are mostly of Type B. So the pore connectivity of semibright and bright coals is higher than that of semidull and dull coals. Furthermore, pores are developed mainly in the inertinite, with pore-type being dominated by Type B and C, secondly in the vitrinite, with pore-type being dominated by Type A and C, and less developed in the liptinite with pore-type of B and C. The pore connectivity of each maceral is in the order vitrinite > inertinite > liptinite. Finally, according to the research results, the reservoir fracturing improvement should be more arranged on the dull or semi-dull coals, and the producing layers should be bright or semi-bright coals as much as possible on the premise that the gas contents of coal layers are not much different from each other.

Petrological Considerations for the Demineralization of Rajmahal Coals with Pseudomonas mendocina B6-1

ABSTRACT The present study entails the results of the petrological coniderations for demineralization of Rajmahal Gondwana coals with Psudomonas mendocina B6-1. Inertinite group macerals are the dominant constituents of these coals, followed by vitrinite group, while liptinite occurs in low concentration. The amount of Mineral matter is moderately high. The concentration of major, minor and trace elements is high when compared with Clarke values. After the treatment of these coals with Pseudomonas mendocina strain B6-1, a significant reduction in the elemental content of oxygen, hydrogen and sulphur was observed. A gradual reduction of pyrite phase due to bioleaching was identified and its signatures were reflected in the XRD spectra and FTIR absorption bands. Over 5 % reduction in the ash content and decrease of major, minor and trace element to variable degrees were also noticed. Fe, As, and Ca positively correlate with the ash removal percentage indicating that the samples with high concentration of these elements were prone to demineralization with Pseudomonas mendocina strain B6-1 whereas Ni, Zn, Cr and Cu, negatively correlate with the ash removal percentage and shows that their enrichment impeded the process of demineralization. With increasing concentration of vitrinite the removal of major/minor/trace elements also increased which is attributed to the possible association of these elements with the mineral matter occurring as superficial mounting and superficial blanketing over the vitrinite macerals. This could facilitate the bacterial access to the elements to act upon and remove it to the variable extent. Some minerals occur intergrown with inertinites causing restricted bacterial action owing to the non-exposure of the mineral particles and less surface area available to the bacteria for bioleaching. Sulfur removal strongly relates with increase in inertinite content and decrease in liptinite content. This appears that sulfur associated with liptinites have shown difficult removal condition. The maximum removal of the trace elements like Cd, Cu, Co, Zn and Pb was observed from the ‘banded dull coal’ samples of the Rajmahal basin while maximum removal of major/minor elements like Fe, Ca and Mg was noticed from the ‘banded bright coal’ samples. However, maximum removal of Mn and As was also observed in the samples of ‘banded coal’.

Effect of maceral composition and coal rank on gas diffusion in Australian coals

Gas diffusion within the coal matrix plays a key role in determining the rate of natural gas depletion and enhanced coal bed methane production via CO2 sequestration (CO2-ECBM) in coal seam gas reservoirs. In this work, we investigated the influence of maceral composition and coal rank on CO2 and CH4 diffusion rates of 18 bituminous and sub-bituminous Australian coals. We obtained measures of the gas diffusion rate and the spread of diffusion times. Gas diffusion rate through coal pores was found to vary over 6 orders of magnitude depending on the coal rank and maceral composition. This diffusion rate was independent of pressure in the range 1–5bar. It increased substantially with inertinite content of the coal in the lower rank and medium rank coals examined. In the high rank coals, the diffusion rate was less sensitive to maceral composition, but alternatively, this may reflect regional variations in the dependence of diffusion rate with maceral composition. The CO2 diffusion rate was faster than the CH4 diffusion rate. The factor describing the spread of diffusion times generally increased with increasing vitrinite content but for a given coal was similar for both CH4 and CO2. This suggests the gases penetrate the same parts of the coal structure.Based on the experimental data, different synthetic coalbed simulation models were constructed to analyse the impact of CH4 and CO2 diffusion coefficients on ECBM and CO2 sequestration performance. The numerical simulation results showed that CH4 production rate is inversely proportional to the sorption time, if the bulk flow in the cleats does not create any restriction. The results also indicated that CO2 breakthrough time is a function of the CO2 sorption time - if the CO2 adsorption is not fast enough, the injected CO2 will be spread into the seam, resulting in an early breakthrough.

Pore Structure Characterization of the Lower Permian Marine-Continental Transitional Black Shale in the Southern North China Basin, Central China

The Carboniferous-Permian Taiyuan-Shanxi coal-bearing formations, as the most promising shale-gas reservoir in North China, comprise a typical shale-gas system developed in a transitional environment. To investigate the pore structure of the Taiyuan-Shanxi shale in the Southern North China Basin, field-emission scanning electron microscopy (FE-SEM), low-pressure nitrogen adsorption (LNA), and high-pressure mercury intrusion (HMI) were employed to characterize the pore type, volume, and size distributions of 11 shale samples from the Mouye-1 well. Organic-matter-hosted pores, interparticle pores, intraparticle pores, and shrinkage cracks were observed in the FE-SEM images. Compared to matured marine shale, the number of organic-matter-hosted pores within the Taiyuan-Shanxi shale was much smaller, probably because of the high content of inertinite. The nitrogen total pore volume was found to range from 20.36 × 10–3 to 31.23 × 10–3 mL/g, whereas the mercury total pore volume was found to range from 2.1 × 10–...

Influence of coal petrology on methane adsorption capacity of the Middle Jurassic coal in the Yuqia Coalfield, northern Qaidam Basin, China

The lower coalbed methane (CBM) adsorption capacity of the low rank coals is not only related to its lower maturity, but also determined by the coal maceral compositions. In this study, a total of 13 samples including 10 coals and 3 carbonaceous mudstones, were collected from the Middle Jurassic Dameigou Formation in the borehole YQ-1 of the Yuqia Coalfield, northern Qaidam Basin, NW China. Coal lithotypes, maceral compositions, coal ranks, coal facies and methane adsorption characteristics of these samples were investigated using microscopic observation, proximate analysis, porosity analysis, and isothermal adsorption experiments. The results show that the maceral composition has a great influence on the methane adsorption capacity, and the influence of vitrinite on the methane adsorption is generally stronger than that of inertinite at a similar coal rank. For most samples, there is a positive correlation between the vitrinite contents and the Langmuir volume (VL), a negative correlation between the inertinite contents and the VL, and no obvious correlation between the exinite contents and the VL. Furthermore, the vitrinite/inertinite (V/I) ratio also shows a positive relationship with the VL. However, some samples containing large amounts of unfilled fusinite and/or semifusinite have more pore spaces favoring methane adsorption and can also adsorb significant quantities of methane. Consequently, coals with higher vitrinite contents, in association with some unfilled fusinites or semifusinites, should have the greatest adsorption capacity. Coal maceral compositions vary with the types of coal facies, and thus the methane adsorption capacity of coals may be closely related to coal facies. It is found that the methane adsorption capacities of the coals in a wet forest swamp (Type I) and an intergradation forest swamp (Type II) are greater than those in a drained forest swamp (Type III) and an open water peat swamp (Type IV). It is suggested that the area developed with the wet forest swamp and in the intergradation forest swamp with high porosity should be the best target areas for the CBM exploration in the Yuqia Coalfield.

Fires in the mire: repeated fire events in Early Permian ‘peat forming’ vegetation of India

Macro‐charcoal, as direct evidence of palaeo‐wildfires, is a common constituent throughout an Early Permian (Cisuralian) inertinite‐rich coal seam from the Dhanpuri Coal Mine (Barakar Formation, Sohagpur Coalfield, Madhya Pradesh, India). The continuous presence of macro‐charcoal within this particular seam demonstrates that fires occurred repeatedly in the source vegetation of the seam. Based on these macro‐charcoal remains, an anatomical assessment of the diversity and taxonomic composition of the vegetation, which experienced wildfires and contributed to the formation of peat/coal, is provided. The vegetation that experienced regular fires was dominated by gymnosperms, with a minor component of pteridophytes. The results also support previous studies, which suggest a pyrogenic origin for the high inertinite contents of many Permian coals within Gondwana. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Geochemical and Preliminary Reservoir Characteristics of the Carboniferous–Permian Coal-Bearing Strata in the Junger Area, Northeastern Ordos Basin, China: Source Implications for Unconventional Gas

Unconventional natural gas development, including coalbed methane, shale gas, and tight sand gas, has received extensive attention recently in coal-bearing basins. This study provides a case study of the hydrocarbon generation potential (coal and shale) and reservoir characterization (coal, shale, and sandstone) of samples from Carboniferous–Permian coal-bearing strata in the Junger area, northeastern Ordos Basin, China. Results show that the coal is dominated by vitrinite (9.3–84.1%) and inertinite (14.0–82.5%) with an average total vitrinite and inertinite content higher than 90% and maximum vitrinite reflectance (Ro,max) values from 0.44% to 0.81%. The shales contain mainly type II kerogen with high total organic carbon content (0.36–31.58%) and relatively low Ro,max (0.45–0.72%). The hydrocarbon generation potential of all the shale samples ranges from 3.25 to 82.82 mg/g rock, and the hydrogen index values range from 100.31 to 768.06 mg HC/g. Three types of fluid inclusions were detected in the microf...

On the reduction behavior, structural and mechanical features of iron ore-carbon briquettes

The utilization of Ferro-coke briquettes is increasingly being considered as a process to reduce CO2 emissions and energy consumption in blast furnace. The briquettes were prepared using iron ore, charcoal, lime, a binder and three different coals of poor coking properties. The coals have Gieseler maximum fluidity below 100ddpm and are vitrinite-rich with inertinite content close to 30%. The briquettes were carbonized up to 1000°C in a laboratory-scale oven and in a thermogravimetric analyzer which permitted a detailed evaluation of the weight loss at each stage of carbonization. Iron reduction, strength (both compression and drum tests) and optical properties of the carbon matrix were evaluated in the carbonized briquettes.The carbonization process caused significant differences in the optical textures of the carbonized materials, in particular in higher rank coals, where there was a greater range of optical texture sizes compared to the cokes from single coals. The best resistance to compression was observed in the briquettes with the larger optical texture, whereas the best resistance in a drum was that of the briquettes having larger proportion of mosaics. Furthermore, the Fe-coke briquettes produced by cold briquetting and carbonization show self-reducing properties of iron oxides.

Methane Adsorption Characteristics and Adsorbed Gas Content of Low-Rank Coal in China

Coalbed methane (CBM) reserve of low-rank coal (Ro,max < 0.65), occupying a proportion of more than 40% of the total CBM reserve of China, is 14.7 × 1012 m3. The exploration degree, particularly in situ gas content estimation of low-rank CBM reservoirs in China, is extremely low. Meanwhile, adsorption characteristics of low-rank coal reservoirs have not been revealed comprehensively. In this study, methane isothermal adsorption experiments of 30 low-rank coal samples collected from typical low-rank coal-bearing basins and coalfields in China were performed under different temperatures and moisture-equilibrated conditions. The results showed that the Langmuir volume, which was found to be relatively low when the inertinite content was above 50% and relatively high when the vitrinite content was above 50%, was positively correlated with the maximum vitrinite reflectance and generally decreased with the increase of the equilibrium moisture content. The adsorbed gas content decreased as the temperature increa...

Compositional variation and palaeoenvironment of the volcanolithic Fort Cooper Coal Measures, Bowen Basin, Australia

An integrated analysis of megascopic lithotype, microscopic maceral and mineral composition, stable carbon isotope and interburden sedimentology from a single well was used to interpret the response of the Late Permian Fort Cooper Coal Measures (FCCM) to regional and global environmental influences. The FCCM are differentiated from underlying, relatively high vitrinite Moranbah Coal Measures, and overlying higher inertinite Rangal Coal Measures in the Bowen Basin by their intercalation with abundant tuff and siliciclastic partings and interbeds. Besides this, there is little described about the variation in the organic composition of the FCCM and its causes. The FCCM can be subdivided into a lower aggradational Fair Hill Formation, transgressed by the shallow marine-derived Black Alley Shale that interfinger with/is overlain by the progradational Middle Main Seams and Burngrove Formation coal measures. The coals are dominantly dull with minor bright bands that are more abundant in the Burngrove Formation representing a change in plant composition. The maceral analysis shows that the coals in the Fair Hill Formation and Middle Main Seams are vitrinite-rich (80–90% mmf) albeit with high mineral matter suggesting the formation of precursory peat under rising water levels and with high sediment (tuff) influx and preservation. The coals in the Burngrove Formation have an increased inertinite content (30% mmf) but are also high in mineral matter suggesting a shift to increased decomposition arising from a fluctuating water table, possibly increased aridity and/or microbial activity. Tuffs occur throughout, and although their frequency is higher in the lower Fair Hill Formation, the preservation of thicker tuffs in the upper Burngrove Formation indicates increased intensity of volcanism that could have modified the environment. Variation in carbon isotope compositions show a parabolic trend, from around −24.1‰ in the Fair Hill Formation to more variable values in the Middle Main Seams with an overall 13C-enrichment upwards in the Burngrove Formation, prior to the δ13C values becoming negative (depleted between −1 to −4% from the average −24.1‰) in the top seams and into the overlying Rangal Coal Measures. The 13C-depletion trend in the upper part of the section is unexpected in view of corresponding increase in inertinite content of the coals indicating that the δ13C values/plant composition and inertinite content are decoupled, unless the inertinite origin is from intense microbial decay. Similar stable carbon isotope depletion trends have been observed elsewhere in an equivalent stratigraphic interval of the Bowen Basin suggesting that the carbon isotope values are responding to global conditions that cause negative excursions in carbon isotopes before the P-T boundary. Overall, the basin was continuously subsiding and peats accumulated with constant interruptions from excessive sedimentation and volcanic eruptions. The low proportion of visible thick bright bands coupled with high telovitrinite (mmf) content suggests a marsh to fen environment, with an open canopy and ponding able to preserve volcanic ash falls.

Coal quality characterization and its relationship with geological process of the Early Permian Huainan coal deposits, southern North China

The Huainan coalfield situated in the southern margin of North China Plate contains coal deposits of Carboniferous–Permian age. The 1 and 3 seams of the Early Permian Shanxi Formation and seams 4-1, 4-2, 5-1, 7-2 and 8 of the Late Early Permian Lower Shihezi Formation were analyzed for coal petrography, mineralogy and geochemical parameters. Collected data were designed to offer basic information on the assessment of coal quality and further to reveal possible factors controlling on coal quality. The shift of basin subsidence center from Huaibei coal-bearing basin to Huainan coal accumulation region caused the change of coal-forming environment (groundwater table, detrital matters and swamp style) which may further cause the differences in coal quality. The average vitrinite contents, ash yields and mineral matters are higher in the Lower Shihezi Formation coals than in the Shanxi Formation coals. The contents of vitrinite sharply decrease upward within coal seam 4, whereas the inertinite contents, ash yields and mineral matters show opposite trend which may be attributed to the relatively high-accommodation settings produce coals usually in the form of an upward high-to-low vitrinite succession. Two groups of elements are classified among coal seams. According to the vertical variation of elements contents among coal seams, most of elements in Group 1 are depleted in coal seam 4-2 except for Be, B, Sc, Fe, Mg, Ca, Li, Sn while almost all the elements in Group 2 are enriched in coal seam 4-2.