The Experts below are selected from a list of 1011 Experts worldwide ranked by ideXlab platform
Jonathan P. Mathews - One of the best experts on this subject based on the ideXlab platform.
-
The characterisation of slow-heated inertinite- and vitrinite-rich coals from the South African coalfields
Fuel, 2015Co-Authors: Mokone J. Roberts, Raymond C. Everson, Hein W.j.p. Neomagus, Daniel Van Niekerk, Gregory N. Okolo, Jonathan P. MathewsAbstract:Abstract The development of coal char structures with pyrolysis has been extensively investigated but has traditionally been focused on the carboniferous coals in the northern Hemisphere. In this investigation, the properties of pyrolysis chars generated from inertinite- and vitrinite-rich coals (81% and 91% mmb by volume, respectively) collected from selected South African coalfields were determined. Chars were generated at 450, 700 and 1000 °C. The properties of coals and chars were examined using the chemical, physical, petrographic, solid-state 13 C NMR and X-ray diffraction analytical techniques. The objective was to generate results for further studies including molecular modelling and atomistic reaction kinetics. A good correlation was found between the total Maceral scan (rank) and aromaticity as the pyrolysis temperature increased, as well as between the aromaticity measurements with XRD and NMR techniques. The chemical structure of the intertinite-rich and vitrinite-rich chars at 700–1000 °C was remarkably similar in terms of the proximate, ultimate, total Maceral scan and aromaticity values. Greater transition occurred in the vitrinite-rich coal, implying a thermally more activated coal. Differences in the physical structure of the chars at these temperatures were observed in terms of the surface area using the Dubinin–Radushkevich (D–R), the Brunauer–Emmet–Teller (BET) and Langmuir methods as well the microporosity from the CO 2 adsorption method. The Macerals were not distinguishable at 700–1000 °C. However, the differences in Maceral Composition of the coals resulted in substantially different char forms during thermal conversion. The intertinite-rich coal formed more denser chars and higher proportions of thicker-walled networks (60–65% by volume). The vitrinite- rich coal showed higher proportions of isotropic “coke” (91–95% by volume), which contributes to a high distribution of surface area and micropores. Therefore, on a chemical level, the high temperature chars were similar. Differences existed in the physical structure at high temperatures. The physical structures, char forms and crystallite diameter ( L a ) significantly distinguished the chars at high temperatures, where L a for inertinite-rich chars was 37.6 A compared with 30.7 A for the vitrinite-rich chars. The L a property, in particular, played a significant role in investigations for the molecular structural properties of the inertinite- and vitrinite-rich chars, including their reactivity behaviour with carbon dioxide gas.
-
Solvent swelling behavior of Permian-aged South African vitrinite-rich and inertinite-rich coals
Fuel, 2010Co-Authors: Daniel Van Niekerk, Phillip M. Halleck, Jonathan P. MathewsAbstract:Abstract Two South African coals similar in rank and age, but different in Maceral Composition, were studied using solvent swelling. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were evaluated for swelling extent and swelling rate using N-methylpyrrolidone (NMP) and CS 2 /NMP. A stop-motion videography method was developed to study individual particle swelling behavior. This method allowed observation of overshoot and climbing-type swelling, as well as swelling kinetics. Single-particle swelling experiments showed that both coals exhibited overshoot-type and climbing-type swelling. The inertinite-rich coal swelled much faster (in both solvents) than the vitrinite-rich coal. The swelling in CS 2 /NMP was faster for both coals. Kinetic parameters showed that solvent swelling was governed by relaxation (super-Case II relaxation) of the coal structure. X-ray computed tomography was conducted over a 50 h swelling period in NMP for single particles of each coal. Anisotropic swelling was observed in all the particles (swelling greater perpendicular to the bedding plane than parallel to it). The subtle changes in molecular structure, fine structural and physical differences resulted in significant differences in solvent swelling behavior.
-
Petrographic and reflectance analysis of solvent-swelled and solvent-extracted South African vitrinite-rich and inertinite-rich coals
International Journal of Coal Geology, 2010Co-Authors: Daniel Van Niekerk, Gareth D. Mitchell, Jonathan P. MathewsAbstract:Maceral transitions during solvent swelling and extraction of two South African coals similar in rank and age, but different in Maceral Composition, were evaluated. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were used. Maceral-group analysis of solvent-extracted and solvent-swelled residues showed no changes in the Maceral Composition for both coals. Solvent-extracted residues exhibited significant observable changes of some particles: particle fracturing, decrease in reflectance and rounding of particle edges. Inertinite-rich coal exhibited extensive fracturing during solvent treatment. Random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite. Vitrinite reflectograms showed a shift from the dominant reflecting V-types to lower-reflecting V-types. The inertinite reflectograms exhibited an increase in the number of reflecting inertinite-types (I-types) with solvent treatment, resulting in a broadening of the reflectograms. The changes in reflectance between the original and solvent-treated coal may be attributed to a combination of structural, elemental or surface changes. Current data for these South African coals suggests a relationship between solvent extraction and mean random reflectance: the higher the extraction yields the lower the mean random reflectance.
-
Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals
International Journal of Coal Geology, 2008Co-Authors: Daniel Van Niekerk, Ronald J. Pugmire, Mark S. Solum, Paul C. Painter, Jonathan P. MathewsAbstract:Abstract Two South African coals of the same rank and age, but different in Maceral Composition were subjected to extensive structural analyses. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were studied to determine structural differences and similarities. The two coals had similar carbon content (∼ 84%, dmmf) and vitrinite reflectance (mean-maximum 0.71% for vitrinite-rich vs. 0.75% for inertinite-rich), but differed in hydrogen content (6.23% for vitrinite-rich and 4.53% for inertinite-rich). The inertinite-rich coal was more aromatic (86% for inertinite-rich and 76% for vitrinite-rich) and more polycondensed (indicated by a higher bridgehead carbon content). The inertinite-rich coal was structurally more ordered, with a higher degree of crystalline stacking. Both coals had similar average aromatic cluster sizes (16 carbons for vitrinite-rich and 18 carbons for inertinite-rich) and number of cluster attachments (6 attachments for vitrinite-rich and 5 attachments for inertinite-rich). Mass spectrometry showed that both coals consist of similar molecular weight distributions; ranging to approximately 1700 m/z with a maximum abundance of ∼ 450 m/z for the vitrinite-rich coal and ∼ 550 m/z for the inertinite-rich coal. Compared to the Argonne Premium coals the South African vitrinite-rich Waterberg coal was comparable to the coals in the high-volatile bituminous range and inertinite-rich Highveld was closer to the medium- to low-volatile bituminous range. Both coals were surprisingly similar in bulk characterization, although inertinite-rich Highveld coal was structurally more ordered, hydrogen deficient, and more aromatic.
Daniel Van Niekerk - One of the best experts on this subject based on the ideXlab platform.
-
The characterisation of slow-heated inertinite- and vitrinite-rich coals from the South African coalfields
Fuel, 2015Co-Authors: Mokone J. Roberts, Raymond C. Everson, Hein W.j.p. Neomagus, Daniel Van Niekerk, Gregory N. Okolo, Jonathan P. MathewsAbstract:Abstract The development of coal char structures with pyrolysis has been extensively investigated but has traditionally been focused on the carboniferous coals in the northern Hemisphere. In this investigation, the properties of pyrolysis chars generated from inertinite- and vitrinite-rich coals (81% and 91% mmb by volume, respectively) collected from selected South African coalfields were determined. Chars were generated at 450, 700 and 1000 °C. The properties of coals and chars were examined using the chemical, physical, petrographic, solid-state 13 C NMR and X-ray diffraction analytical techniques. The objective was to generate results for further studies including molecular modelling and atomistic reaction kinetics. A good correlation was found between the total Maceral scan (rank) and aromaticity as the pyrolysis temperature increased, as well as between the aromaticity measurements with XRD and NMR techniques. The chemical structure of the intertinite-rich and vitrinite-rich chars at 700–1000 °C was remarkably similar in terms of the proximate, ultimate, total Maceral scan and aromaticity values. Greater transition occurred in the vitrinite-rich coal, implying a thermally more activated coal. Differences in the physical structure of the chars at these temperatures were observed in terms of the surface area using the Dubinin–Radushkevich (D–R), the Brunauer–Emmet–Teller (BET) and Langmuir methods as well the microporosity from the CO 2 adsorption method. The Macerals were not distinguishable at 700–1000 °C. However, the differences in Maceral Composition of the coals resulted in substantially different char forms during thermal conversion. The intertinite-rich coal formed more denser chars and higher proportions of thicker-walled networks (60–65% by volume). The vitrinite- rich coal showed higher proportions of isotropic “coke” (91–95% by volume), which contributes to a high distribution of surface area and micropores. Therefore, on a chemical level, the high temperature chars were similar. Differences existed in the physical structure at high temperatures. The physical structures, char forms and crystallite diameter ( L a ) significantly distinguished the chars at high temperatures, where L a for inertinite-rich chars was 37.6 A compared with 30.7 A for the vitrinite-rich chars. The L a property, in particular, played a significant role in investigations for the molecular structural properties of the inertinite- and vitrinite-rich chars, including their reactivity behaviour with carbon dioxide gas.
-
Solvent swelling behavior of Permian-aged South African vitrinite-rich and inertinite-rich coals
Fuel, 2010Co-Authors: Daniel Van Niekerk, Phillip M. Halleck, Jonathan P. MathewsAbstract:Abstract Two South African coals similar in rank and age, but different in Maceral Composition, were studied using solvent swelling. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were evaluated for swelling extent and swelling rate using N-methylpyrrolidone (NMP) and CS 2 /NMP. A stop-motion videography method was developed to study individual particle swelling behavior. This method allowed observation of overshoot and climbing-type swelling, as well as swelling kinetics. Single-particle swelling experiments showed that both coals exhibited overshoot-type and climbing-type swelling. The inertinite-rich coal swelled much faster (in both solvents) than the vitrinite-rich coal. The swelling in CS 2 /NMP was faster for both coals. Kinetic parameters showed that solvent swelling was governed by relaxation (super-Case II relaxation) of the coal structure. X-ray computed tomography was conducted over a 50 h swelling period in NMP for single particles of each coal. Anisotropic swelling was observed in all the particles (swelling greater perpendicular to the bedding plane than parallel to it). The subtle changes in molecular structure, fine structural and physical differences resulted in significant differences in solvent swelling behavior.
-
Petrographic and reflectance analysis of solvent-swelled and solvent-extracted South African vitrinite-rich and inertinite-rich coals
International Journal of Coal Geology, 2010Co-Authors: Daniel Van Niekerk, Gareth D. Mitchell, Jonathan P. MathewsAbstract:Maceral transitions during solvent swelling and extraction of two South African coals similar in rank and age, but different in Maceral Composition, were evaluated. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were used. Maceral-group analysis of solvent-extracted and solvent-swelled residues showed no changes in the Maceral Composition for both coals. Solvent-extracted residues exhibited significant observable changes of some particles: particle fracturing, decrease in reflectance and rounding of particle edges. Inertinite-rich coal exhibited extensive fracturing during solvent treatment. Random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite. Vitrinite reflectograms showed a shift from the dominant reflecting V-types to lower-reflecting V-types. The inertinite reflectograms exhibited an increase in the number of reflecting inertinite-types (I-types) with solvent treatment, resulting in a broadening of the reflectograms. The changes in reflectance between the original and solvent-treated coal may be attributed to a combination of structural, elemental or surface changes. Current data for these South African coals suggests a relationship between solvent extraction and mean random reflectance: the higher the extraction yields the lower the mean random reflectance.
-
Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals
International Journal of Coal Geology, 2008Co-Authors: Daniel Van Niekerk, Ronald J. Pugmire, Mark S. Solum, Paul C. Painter, Jonathan P. MathewsAbstract:Abstract Two South African coals of the same rank and age, but different in Maceral Composition were subjected to extensive structural analyses. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were studied to determine structural differences and similarities. The two coals had similar carbon content (∼ 84%, dmmf) and vitrinite reflectance (mean-maximum 0.71% for vitrinite-rich vs. 0.75% for inertinite-rich), but differed in hydrogen content (6.23% for vitrinite-rich and 4.53% for inertinite-rich). The inertinite-rich coal was more aromatic (86% for inertinite-rich and 76% for vitrinite-rich) and more polycondensed (indicated by a higher bridgehead carbon content). The inertinite-rich coal was structurally more ordered, with a higher degree of crystalline stacking. Both coals had similar average aromatic cluster sizes (16 carbons for vitrinite-rich and 18 carbons for inertinite-rich) and number of cluster attachments (6 attachments for vitrinite-rich and 5 attachments for inertinite-rich). Mass spectrometry showed that both coals consist of similar molecular weight distributions; ranging to approximately 1700 m/z with a maximum abundance of ∼ 450 m/z for the vitrinite-rich coal and ∼ 550 m/z for the inertinite-rich coal. Compared to the Argonne Premium coals the South African vitrinite-rich Waterberg coal was comparable to the coals in the high-volatile bituminous range and inertinite-rich Highveld was closer to the medium- to low-volatile bituminous range. Both coals were surprisingly similar in bulk characterization, although inertinite-rich Highveld coal was structurally more ordered, hydrogen deficient, and more aromatic.
Slawomir Kedzior - One of the best experts on this subject based on the ideXlab platform.
-
reservoir parameters and Maceral Composition of coal in different carboniferous lithostratigraphical series of the upper silesian coal basin poland
International Journal of Coal Geology, 2013Co-Authors: Slawomir Kedzior, Iwona JelonekAbstract:Abstract Laboratory tests were carried out on coal samples taken from mine openings of selected coal mines in the Upper Silesian Coal Basin. The analyses involved Maceral Composition (vitrinite, inertinite and liptinite group) and vitrinite reflectance on the one hand, and reservoir parameters (coal permeability and effective porosity) on the other. The results are compared. Samples with high values of coal permeability are characterized by vitrinite contents of ca 60%, and samples with the lowest permeability by vitrinite contents of 40%. The vitrinite-rich bright coals are brittle and prone to crushing caused by tectonic pressures. Moreover, coal permeability is more strongly anisotropic in the bright coals of the Cracow Sandstone and the Mudstone Series than in the dull coals of the Upper Silesian Sandstone Series. In bright coals, permeability is much along the direction parallel to vitrain layers. Good reservoir parameters such as permeability and effective porosity are crucial for fluid flow through the coal seams and, thus, successful coalbed methane exploitation. In the Upper Silesian Coal Basin, Cracow Sandstone- and Mudstone Series with vitrinite-rich coals should be a good target, though serious geological problems must first be overcome.
-
accumulation of coal bed methane in the south west part of the upper silesian coal basin southern poland
International Journal of Coal Geology, 2009Co-Authors: Slawomir KedziorAbstract:Abstract The archives of the Polish Geological Institute house a wealth of coal-bed methane (CBM) data from surface boreholes and excavations in coal from the deposits of the Upper Silesian Coal Basin (USCB). These data support a model for the origin of substantial methane accumulations in the south-west part of the basin that reflects the interplay of the factors controlling methane sorption capacity and those controlling methane content. The factors controlling the sorption capacity of coal include coal rank, temperature, pressure, moisture content and Maceral Composition. Methane-content controls include lithology, stratigraphy, tectonics, hydrogeology and mining activity. The nature of the coal-bearing Carboniferous horizons, the sorption/desorption properties of the coals, the disposition of faults and folds, the topography of the Carboniferous palaeosurface and the presence of an impermeable Miocene cover were key controls. The methane accumulated in coal seams and in their host rocks in settings comparable with those in which petroleum and gas deposits are trapped.
Monika J Fabianska - One of the best experts on this subject based on the ideXlab platform.
-
application of organic petrology and geochemistry to coal waste studies
International Journal of Coal Geology, 2011Co-Authors: Magdalena Miszkennan, Monika J FabianskaAbstract:Abstract Coal wastes produced during mining activities are commonly deposited in nearby dumps. These wastes mostly composed of minerals and variable amounts (usually 20–30%) of organic matter start to weather immediately after deposition. Oxidation of the organic matter can lead to self heating and self combustion as a result of organic and mineral matter transformations. The degree of alteration depends on the properties of the wastes, i.e., the Maceral and microlithotype Composition of the organic matter and its rank. Alteration of wastes also depends on the heating history, i.e., the rate of heating, final heating temperature, duration of heating, and the degree of air access. Although air is probably necessary to initiate and drive the heating processes, these usually take place under relatively oxygen depleted conditions. With slow heating, color of organic matter particles changes, irregular cracks and oxidation rims develop around edges and cracks, and bitumen is expelled. As a result, massive and detritic isotropic and strongly altered organic matter forms. On the other hand, higher heating rates cause the formation of devolatilization pores, oxidation rims around these pores and along cracks, vitrinite-bands-mantling particles, and bitumen expulsions. Organic compounds generated from the wastes include n -alkanes, iso -alkanes, alkylcyclohexanes, acyclic isoprenoids, mainly pristane, phytane and, in some cases, farnesane, sesquiterpanes, tri- and tetracyclic diterpanes, tri- and pentacyclic triterpanes, and steranes, polycyclic aromatic hydrocarbons (mostly with two- to five rings, rarely six rings), and phenols. The compounds formed change during the heating history. The fact that phenols are found in dumps where heating has not yet been completed, but are absent in those where heating ceased previously suggests the presence of water washing. The organic compounds formed may migrate within the dumps. However, when they migrate out of the dumps, they become a hazard to environment. This paper is a review on transformations of organic matter (both Maceral Composition and reflectance and chemical Composition) in coal wastes deposited in coal waste dumps. Immediately after deposition the wastes are exposed to weathering conditions and sometimes undergo self heating processes.
-
thermal transformation of organic matter in coal waste from rymer cones upper silesian coal basin poland
International Journal of Coal Geology, 2010Co-Authors: Magdalena Miszkennan, Monika J FabianskaAbstract:Abstract Coal wastes produced at various stages of coal mining, washing and deposition on dumps are a source of many pollutants. In some cases, the dumped coal waste undergoes self-heating and self-combustion processes that reflect the properties of the organic matter present (Maceral Composition and rank) and the history of heating (rate, time and temperature of heating). In the examination of the coal wastes from the Rymer Cones dump, petrographic- and gas chromatography-mass spectrometry (GC-MS) techniques were used to provide different sets of complementary data. Unaltered- and variably-altered Macerals (mostly vitrinite) characterise the investigated material. Vitrinite of elevated reflectance and massive coke particles indicate that the rate of heating was low and that the availability of air was very limited; heating took place under pyrolytic conditions. Irregular cracks in particles probably also resulted from slow heating. The temperature of the heating processes, dynamically changing in time and place throughout the dump, led to chemical changes in organic matter such as the formation of phenols and their derivatives, and alteration in distributions of n-alkanes, hopanes and moretanes and polycylic aromatic hydrocarbons (PAHs) occurring in pyrolysates. Some of these compounds formed as a result of the thermal destruction of liptinite and vitrinite Macerals at various temperatures and migrated from within the dump. The changes that occurred within the dump are also reflected in values of geochemical parameters based on the same compounds, such as CPI, Ts/(Ts + Tm), MNR, DNR, TNR-1, TNR-2. Lighter compounds were probably released into the atmosphere and others, especially phenols that are easily soluble in water and PAHs, were most probably leached into deeper parts of the dump and even into underground waters since they are absent in some samples or significantly decreased in concentration. These processes probably still continue — it is this fact that creates a potential hazard to the environment.
Iwona Jelonek - One of the best experts on this subject based on the ideXlab platform.
-
reservoir parameters and Maceral Composition of coal in different carboniferous lithostratigraphical series of the upper silesian coal basin poland
International Journal of Coal Geology, 2013Co-Authors: Slawomir Kedzior, Iwona JelonekAbstract:Abstract Laboratory tests were carried out on coal samples taken from mine openings of selected coal mines in the Upper Silesian Coal Basin. The analyses involved Maceral Composition (vitrinite, inertinite and liptinite group) and vitrinite reflectance on the one hand, and reservoir parameters (coal permeability and effective porosity) on the other. The results are compared. Samples with high values of coal permeability are characterized by vitrinite contents of ca 60%, and samples with the lowest permeability by vitrinite contents of 40%. The vitrinite-rich bright coals are brittle and prone to crushing caused by tectonic pressures. Moreover, coal permeability is more strongly anisotropic in the bright coals of the Cracow Sandstone and the Mudstone Series than in the dull coals of the Upper Silesian Sandstone Series. In bright coals, permeability is much along the direction parallel to vitrain layers. Good reservoir parameters such as permeability and effective porosity are crucial for fluid flow through the coal seams and, thus, successful coalbed methane exploitation. In the Upper Silesian Coal Basin, Cracow Sandstone- and Mudstone Series with vitrinite-rich coals should be a good target, though serious geological problems must first be overcome.