Coal Macerals Research Articles

Notes on the origin of inertinite macerals in coal: Evidence for fungal and arthropod transformations of degraded macerals

The role of fungus in the formation of coal macerals, both as a primary contributor in the form of a fungus fossil/maceral funginite, and in their role in degrading wood, thus producing degraded maceral forms, has been established. Fungus, in the course of breaking down the lignin and cellulose in wood, make the wood more digestible for grazers, such as arthropods. In turn, the remnants of the digested wood and anything else eaten but not completely digested are excreted and can be preserved intact; eaten by other fauna with a repeat of the cycle; or colonized by bacteria and/or coprophilous fungi with or without subsequent preservation. Ultimately, the coprolites can be preserved as a form of macrinite.

Notes on the origin of inertinite macerals in coals: Funginite associations with cutinite and suberinite

Abstract The association of fungus with plant leaves and roots is ubiquitous. While many of these occurrences are considered to be pathogenic, mycorrhizzal fungal associations with roots are essential for plant growth. Despite the common knowledge of such relationships in plant science, with a few exceptions, the fungus/leaf/root/stem association as the macerals funginite, cutinite, and suberinite in coals has not been extensively studied. In this work, examples of funginite associations with cutinite and suberinite are discussed.

Chemometric study of functional groups in Pennsylvanian gymnosperm plant organs (Sydney Coalfield, Canada): Implications for chemotaxonomy and assessment of kerogen formation

The samples comprise the foliage of four pteridosperm-medullosalean plant-fossil species of differing preservation states and one of a cordaitean species from two Canadian Maritime sub-basins of Carboniferous age (300 Ma; Sydney and Stellarton coalfields, Nova Scotia, respectively. Included in the sample set were some coal samples from Sydney Coalfield, along with published data for coal macerals for comparison. By applying Schulze’s maceration process to the fossil foliage to obtain the cuticles, five sample forms evolved, viz. compressions, cuticles and fossilized cuticles, and acidic and alkaline solutions from Schulze’s process, to which was added the Sydney coal samples as the sixth form. Area integration of the absorbance spectra from solid and liquid state Fourier transform infrared (FTIR) spectroscopy, produced functional chemical parameters which were organized into a data matrix of eight variables and 62 samples (8 x 62 matrix). Since we were interested in grouping the sample forms as a function of phytochemistry (functional groups) to assess primarily the palaeophytotaxonomic potential as a general approach to Carboniferous taxonomy, principal components were extracted from the matrix, and a subset of 4 x 33 samples in order to refine the grouping results from the initial component analysis. In either case, a two component model resulted, accounting for least 80% of the cumulative variance in either case. Overall, the results are encouraging in offering increasing support for fossil-leaf chemotaxonomy, but bearing in mind the limited sampling number (56) and restricted sampling of genera (5). Apart from this general conclusion, which supports our previous FTIR work vis-à-vis chemotaxonomy, we noted functional-group similarities in our FTIR data with types of kerogen and coal macerals. On this basis, we hypothesize that, in combination with the different preservation states of our fossil specimens, these factors have a bearing on kerogen genesis from plant material, i.e. the oil and gas prone Types I and II.

Paramagnetic Centres in Coal Macerals

Theelectronparamagneticresonance(EPR)studyofcoalmacerals: exinite,vitriniteandinertiniteseparatedfrom clarain of the Polish medium-rank coal with carbon content of 85.6 wt% C, were performed. Using thecontinuousmicrowavesaturationtechnique(measurementsat223Kand291K),asaresultofnumericalanalysisofrecordedEPRspectraofexinite,vitriniteandinertinite,theirmulti-componentstructurewasshown. TheEPRspectraofexiniteandvitriniteconsistofthreecomponentlines: oneGaussian

Micro-Raman spectroscopy of collotelinite, fusinite and macrinite

The Raman spectra and the Raman parameters have been correlated with changes in the structure of carbon materials, and most of the studies have revealed different development of the Raman spectrum. In the present study micro-Raman spectroscopy was conducted on coal bulk samples and on individual coal macerals (collotelinite, fusinite, and macrinite) from a set of Penn State Coal Bank coals of increasing rank to study the variation of their spectral parameters with rank, and considering coal heterogeneity. The spectral parameters that better correlate with the increasing coal rank, for the coals studied are the full width at half maximum of graphitic band (G: at ∼ 1580 cm − 1 ), the position of disordered band (D: at ∼ 1350 cm − 1 ), and the integrated intensity ratio of the D band to G band (ID/IG). With increasing coal rank a narrower G band, a shift of D band to lower wavenumber, and an increase of integrated intensity ratio ID/IG are observed. For each coal, the Raman parameters obtained on fusinites and macrinites are similar and differ from those obtained on coal bulk samples and collotelinites. The variation of the Raman parameters with rank is very well reflected on the analyses of collotelinites.

Chemical functionalities of high and low sulfur Australian coals: A case study using micro attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectrometry

The macerals in bituminous coals with varying organic sulfur content from the Early Permian Greta Coal Measures at three locations (Southland Colliery, Drayton Colliery and the Cranky Corner Basin), in and around the Sydney Basin (Australia), have been studied using light-element electron microprobe (EMP) analysis and micro-ATR–FTIR. Electron microprobe analysis of individual macerals reveals that the vitrinite in both the Cranky Corner Basin and Drayton Colliery (Puxtrees seam) samples have similar carbon contents (ca. 78% C in telocollinite), suggesting that they are of equivalent rank. However, the Cranky Corner coals have anomalously low vitrinite reflectance (down to 0.45%) vs. the Drayton materials (ca. 0.7%). They also have very high organic S content (3–6.5%) and lower O content (ca. 10%) than the equivalent macerals in the Drayton sample (0.7% S and 15.6% O). A study was carried out to investigate the impacts of the high organic S on the functional groups of the macerals in these two otherwise iso-rank, stratigraphically-equivalent seams. An iso-rank low-S coal from the overlying Wittingham Coal Measures near Muswellbrook and coals of slightly higher rank from the Greta Coal Measures at Southland Colliery near Cessnock were also evaluated using the same techniques to extend the data set. Although the telocollinite in the Drayton and Cranky Corner coals have very similar carbon content (ca.78% C), the ATR–FTIR spectra of the vitrinite and inertinite macerals in these respectively low S and high S coals show some distinct differences in IR absorbance from various aliphatic and aromatic functional groups. The differences in absorbance of the aliphatic stretching bands (2800–3000 cm −1) and the aromatic carbon (C C) peak at 1606 cm −1 are very obvious. Compared to that of the Drayton sample (0.7% S and 15% O), the telocollinite of the Cranky Corner coal (6% S and 10% O) clearly shows: (i) less absorbance from OH groups, represented by a broad region around 3553 cm −1, (ii) much stronger aliphatic C–H absorbance (stretching modes around 3000–2800 cm −1 and bending modes around 1442 cm −1) and (iii) less absorbance from aromatic carbon functional groups (peaking at 1606 cm −1). Evaluation of the iso-rank Drayton and Cranky Corner coals shows that: (i) the aliphatic C–H absorbances decrease with increasing oxygen content but increase with increasing organic S content and (ii) the aromatic H to aliphatic H ratio (Har/Hali) for the telocollinite increases with (organic) O%, but decreases progressively with increasing organic S. The high organic S content in the maceral appears to be accompanied by a greater proportion of aliphatic functional groups, possibly as a result of some of the O within maceral ring structures in the high S coal samples being replaced.

Prediction of macerals contents of Indian coals from proximate and ultimate analyses using artificial neural networks

Coal, a prime source of energy needs in-depth study of its various parameters, such as proximate analysis, ultimate analysis, and its biological constituents (macerals). These properties manage the rank and calorific value of various coal varieties. Determination of the macerals in coal requires sophisticated microscopic instrumentation and expertise, unlike the other two properties mentioned above. In the present paper, an attempt has been made to predict the concentration of macerals of Indian coals using artificial neural network (ANN) by incorporating the proximate and ultimate analysis of coal. To investigate the appropriateness of this approach, the predictions by ANN are also compared with conventional multi-variate regression analysis (MVRA). For the prediction of macerals concentration, data sets have been taken from different coalfields of India for training and testing of the network. Network is trained by 149 datasets with 700 epochs, and tested and validated by 18 datasets. It was found that coefficient of determination between measured and predicted macerals by ANN was quite higher as well as mean absolute percentage error was very marginal as compared to MVRA prediction.

Effect of Hydrogen Bond on Coal Extraction by In-situ Vacuum FTIR

Coal chemical formation environment might result in different properties of hydrogen bonds in coal structure. The thermo stability, amount and types of hydrogen bond in six typical Chinese coal macerals were investigated by in situ vacuum Fourier transform infrared spectroscopy (FTIR). It was found that three types of hydrogen bond were involved in coal structure, which were OH-N, OH self associated, and OH tetrapolymer hydrogen bond. There was no correlation between the amount of three types of hydrogen bonds and extraction yield. The thermo stability of hydrogen bond in inertinite was stronger than that of vitrinite, especially the thermo stability of hydrogen bond in Pingshuo inertinite.

Notes on the origin of inertinite macerals in coals: Observations on the importance of fungi in the origin of macrinite

Macrinite is a, generally, rare inertinite maceral, often incorporating remnants and fragments of other macerals, including vitrinite, liptinite, and other inertinite. The associated inertinites include multiple forms of funginite. Funginite is also commonly found in association with vitrinite of slightly elevated reflectance and with degraded varieties of vitrinite. Together with the highly degraded macrinite, the latter two associations are here inferred to be part of a continuum of fungal and microbial degradation of peat. In any case, the origin of some macrinite is potentially distinct from that of inertinite generated by fire.

Calculation on the thermodynamics of air-steam gasification of coal macerals

The results of thermodynamic calculations on gasification of coal macerals with a vitrinite reflectance of R o = 0.73% in an H2O-O2-N2 medium with varying both the ratio between the components and the temperature of the process are reported. It ha been shown that in accordance with the basic characteristics of equilibrium gasification (the yield and the heating value of the product gas, its H2 and CH4 contents, and the H2/CO ratio), the macerals are arranged in the order L > Vt > I analogous to their reactivity series. It is concluded that in the case of low-rank coal processing involving density fractionation, the heaviest fractions can be a promising feedstock for the manufacture of fuel gas via the steam gasification process.

Occurrence of non-mineral inorganic elements in macerals of low-rank coals

Abstract Electron microprobe study of individual macerals in low-rank coals of Permian to Tertiary age from Australia, New Zealand, Indonesia and Thailand has shown that measurable proportions of inorganic elements are consistently found in organic components, especially the vitrinite macerals, in which no minerals or mineral inclusions are visible under the microscope. The vitrinites of such coals have been found to contain up to around 0.5% Al, 1.5% Ca, 0.1% Mg, 0.7% Fe and 0.2% Ti. The Al occurs without measurable proportions of Si, and hence does not represent sub-micron clay minerals within the maceral components. Inertinite macerals in the coals, such as fusinite, typically contain lesser proportions of these elements, and often have no more than background ( Except where soluble minerals such as carbonates are also present, the proportion of Ca, Al and Fe indicated from microprobe analysis in the macerals, especially in the vitrinites, is very close to the mobile proportion of the same elements indicated in previous studies from selective leaching techniques. This suggests that the elements occur as an inherent part of the organic structure in the macerals, possibly as a combination of exchangeable ions, carboxylates, chelates and other organometallic compounds; they may also be held by physical absorption and adsorption mechanisms, or may possibly represent inorganic nanoparticles. The proportions of Al, Ca and Fe in the vitrinites of the samples studied decrease with coal rank. Although there are exceptions, these and other non-mineral inorganic elements (Mg, Ti) are also not usually detected by the microprobe in higher rank coals (above 75% carbon in vitrinite or around 0.6% vitrinite reflectance). Their absence is probably a consequence of expulsion from the maceral structures during the progressive aromatization associated with rank advance, by processes such as dehydration, decarboxylation and dehydroxylation.

Thermochemical Reaction Representation of Shenfu Dongshen Inertinite and Vitrinite

Shenfu Dongsheng (SD) coal liquefaction is a critical part for the energy diversification strategy in China. However, because of the unique behavior of Chinese western coal macerals during the liquefaction process, no theory exists that explains the difference between Shenfu Dongsheng inertinite (SDI) and vitrinite (SDV) and Chinese eastern coal macerals. The different thermochemistry of inertinite and vitrinite cannot be explained by only considering the structure of these coals. To investigate the unique behavior of SDI and SDV in the liquefaction process a qualitative analysis of the characteristics and transformation of covalent bonds during pyrolysis of the‘average’molecular structure of a SD coal was performed using quantum chemistry, molecular mechanics and molecular dynamics. The formation of residual coal, pyrolyzed gases and tar during pyrolysis was simulated. Results showed that the activity of SDI was higher than that of SDV during cracking and initially CO2 was released without destroying the macromolecular structure. From a statistical analysis of bond order in the molecular model, the amount of broken covalent bonds in SDV was found to be far more than that found in SDI after pyrolysis. When SDI cracked further during pyrolysis, theextent of inertinite decomposition eventually reached the same level as that for vitrinite. There was a difference in pyrolysates from SDI and SDV and there were mainly aliphatic hydrocarbons and single-ring aromatic hydrocarbons for SDV while dual-ring aromatic hydrocarbons were dominant after SDI pyrolysis. Molecular fragments obtained from quantum chemical calculations were compared to thermal gravimetric analyzer-mass spectrometry (TG-MS) data and found to agree well.

Preliminary evaluation of the coalbed methane production potential and its geological controls in the Weibei Coalfield, Southeastern Ordos Basin, China

article i nfo The coalbed methane (CBM) geology, resource and production potential in the Weibei Coalfield, southeastern Ordos Basin are studied based on geological surveys and laboratory measurements. The results showed that coal rank varies both laterally and vertically and changes from volatile bituminous coals in the margin to anthracites towards the basin (1.6-2.5% Ro). Coals are composed of 60-85% vitrinite, 15-40% inertinite and a trace amount of minerals. Methane isothermal adsorption measurements of 20 coal samples revealed that the maximum adsorption capacity (on a dry and ash-free basis) of coals, which are affected by coal rank, coal maceral, coal lithotype and especially to the moisture content, varies from 13.91 to 29.54 m 3 /t. Estimated gas contents range from 0 to 15 m

Palaeobotanical evidence of wildfires in the Late Palaeozoic of South America – Early Permian, Rio Bonito Formation, Paraná Basin, Rio Grande do Sul, Brazil

Fossil charcoal, as direct evidence of palaeowildfires, has repeatedly been reported from several plant-bearing deposits from the Late Palaeozoic of the Northern Hemisphere. In contrast charcoal reports from the Late Palaeozoic deposits of the Southern Hemisphere are relatively rare in comparison to the Northern Hemisphere. Although the presence of pyrogenic coal macerals has repeatedly been reported from Late Palaeozoic coals from South America, no detailed anatomical investigations of such material have been published so far. Here is presented an anatomical analysis of charcoal originating from Early Permian sediments of the Quitéria Outcrop, Rio Bonito Formation, Paraná Basin, located in the central-eastern portion of Rio Grande do Sul, Brazil. This charcoal comes from two different coaly facies, and it was possible to scrutinize between three types, based on anatomical characters of the charcoal. Two of these charcoal types can be correlated to gymnosperm woods, and the other type corresponds to strongly permineralized bark with characteristic features of lycopsids. The presence of charcoal in different facies, ranging from parautochtonous to allochtonous origin, indicates that different vegetation types, i.e. plants which grew under wet conditions in the lowland as well as in the more dry hinterland, have experienced wildfires. Taking into account previous petrographic and lithological analyses from the facies in which the charcoal occurs and from the conditions of the wood and bark fragments, it was possible to speculate that the intensity of such wildfires most probably corresponds to forest-crown fires. Moreover, it is possible to state that wildfires have been a more or less common element in distinct Late Palaeozoic terrestrial ecosystems in the South American part of Gondwana. The data support previous assumptions on the occurrence of wildfires in the Early Permian of the Paraná Basin which were based solely on coal-petrographic data.

Fine coal preparation using novel tribo-electrostatic separator

Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of tribo-electric coal/ash cleaning is carried out with a newly built cylindrical fluidised bed tribo-charger with internal baffles, made up of copper metal. The charge transfer in coal maceral and mineral particles after repeated contact with copper plate tribo-charger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge generated during tribo-electrification is discussed with respect to gas flow rate and residence time in fluidised bed tribo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with −300 μm size fraction of coal containing 43% ash showed that the ash content can be reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.

Determining Influences of the Aggregative State of Deoxidized Coal on Its Extraction by Molecular Mechanics and Molecular Dynamics Analysis

The density gradient centrifugation method (DGC) was used to purify three parent coals with obvious deoxidation degrees into two main organic macerals, inertinite and vitrinite accordingly. These coal macerals were studied by molecular mechanics and molecular dynamics. The structure of weakly deoxidized coal was found to be in the structure of sheet layers with many open holes while the strongly deoxidized coal has a stacked structure with many closed holes. The physical aromatic sheet structure of macerals has a strong influence on coal extract yields. The combination of modeling, 13C-NMR and XRD analyses reveals that to obtain higher extraction yields of coal the non- bond chemical force energy should be low. Fewer aromatic sheet layers and lower non-bond chemical force energy within structures would result in higher extraction yields of coal macerals.

Apparent viscosity changes of coal-oil slurry duringheating at atmosphere

The changes of apparent viscosity of coal-oil slurries with temperature during direct coal liquefaction were studied. Several factors influencing the viscosity of coal slurries were discussed, which include solvent properties, coal concentrations, moisture content, macerals of coal, shear rate, temperature, swelling behavior, etc. The apparent viscosity of coal slurries was measured using a high-temperature viscometer. The results show that the solvent property is the main influencing factor at low temperature, and the apparent viscosity decreases with increasing temperature. Solvent properties and swelling behavior work together for the viscosity of slurries at medium temperature, leaving the apparent viscosity invariable. Swelling behavior becomes the main influencing factor at high temperature, and viscosity of slurries increases with increasing temperature.

Groups of paramagnetic centres in coal samples with different carbon contents

Complex systems of paramagnetic centres existing in demineralised flame coal (71.4 wt% C), medium-rank coal (85.6 wt% C) and anthracite (94.9 wt% C) were analysed by electron paramagnetic resonance spectroscopy (EPR). Different groups of paramagnetic centres were searched in macerals (exinite, vitrinite, inertinite) of coals with carbon contents of 73.8 wt% C and 85.6 wt% C. Experimental EPR spectra were fitted by different superposition of theoretical lines. Total concentration of paramagnetic centres both in coal and macerals increases with carbon content in the sample. Total concentration of paramagnetic centres in macerals increases from exinite to inertinite. Four groups of paramagnetic centres were found in medium-rank coal, and only two groups exist in flame coal and anthracite. The EPR spectrum of medium-rank coal is a superposition of two broad and two narrow lines. Both broad and narrow, and two narrow lines were measured in EPR spectra of flame coal and anthracite, respectively. Two types of paramagnetic centres with broad lines and one group with narrow lines exist in exinite and vitrinite from medium-rank coal. Two narrow components were observed in EPR spectra of its inertinite. Two different broad electron paramagnetic resonance signals were detected for macerals from low-coalificated coal. Paramagnetic centres systems of medium-rank coal samples reveal the most complex character. Broad EPR lines were not observed for the higher coalificated samples, i.e., anthracite and inertinite from medium-rank coal. Narrow lines do not occur in EPR spectra of low-coalificated macerals. Strong dipolar interactions and fast spin-lattice relaxation processes are characteristic for paramagnetic centres with broad lines. Strong exchange interactions and short spin-lattice relaxation time were measured for paramagnetic centres with the narrowest EPR signals.

Generation and expulsion of petroleum from coal macerals visualized in-situ during DAC pyrolysis

Liptinites, vitrinites and fusinites separated from coals of different maturity were characterized using SEM, NMR, IR, XRD and DAC-fluorescence. Their oil and gas generative potentials during thermal cracking have been evaluated by visual observations in-situ in a diamond anvil cell during semi-open and closed system pyrolysis. It has been shown that liptinite generated large amounts of visible oil-like liquid along with some gas, while fusinites generated no visible liquid and gas. The liquid (oil) from liptinite appears light in color and less viscous. In contrast, some non-perhydrous vitrinite unexpectedly generated large amounts of visible liquid, although the liquid is darker and thicker than that from liptinite, indicating that the oil potential of vitrinites is not limited to its perhydrous nature. The visual observations of oil generative potential are generally consistent with those implied from IR, XRD, NMR, and fluorescence. The peak temperatures (Tpeak) of maximum rate of liquid petroleum generation for vitrinite (465 to 540 °C) are generally higher than those for liptinites (453 to 475 °C); both of which are within the range of Rock-Eval Tmax for most organic matter. The visual oil generation potential is essentially similar in closed and semi-open systems, whereas the gas generation appears more noticeable in a closed system. Since semi-open experiments are much easier to perform, the DAC pyrolysis may be routinely conducted as a semi-open system if only oil generation is considered. In addition, the DAC pyrolysis revealed that oil retention capacity of liptinite is lower than vitrinite, thus the expulsion of oil from liptinite may not be a rate limiting step for primary migration. In contrast, the expulsion of oil from vitrinite is relatively inefficient because of the lower fluidity of the liquid and probably the high retention capability of the vitrinite molecular network.

The degree of reduction problem in structural-chemical classification of coals

A parameter (B, %) that characterizes the extent of chemical reduction of the carbon skeleton of arbitrary organic entities containing C, H, N, O, and S atoms is proposed for quantitative description of coals of different genetic types in terms of the degree of reduction in the framework of the structural-chemical classification of fossil fuels. According to the values of B, the groups of coal macerals are arranged in the order: liptinite L > vitrinite Vt > inertinite I; of the Vt group macerals, the order is collinite Vtc (VtB, desmocollinite) > telinite Vtt (VtA, telocollinite). The degree of reduction of equally metamorphized coals of similar petrographic compositions is determined by the ratio between vitrinite macerals with different degrees of reduction.