Macerals (vitrinite and inertinite) were separated from a coal to understand the mechanism of int... more Macerals (vitrinite and inertinite) were separated from a coal to understand the mechanism of interaction between them during coking. Macerals were blended in various ratios and their viscoelastic properties and expansion/contraction behaviour measured using rheometry. Inertinite increases the viscosity of vitrinite exponentially. To understand why, various solid additives were also blended with vitrinite. Additionally, the solid additives were mixed with a high viscosity liquid that does not generate volatiles (silicone oil). Results show that meso-porous solids increase viscosity exponentially, however, the exponent is far greater. Interestingly, the exponent for meso-porous and non-porous solids is the same for silicone oil, showing that volatiles are playing a role in viscosity development. Thermogravimetric analysis showed that far more volatiles are being retained for mesoporous solids, providing evidence to support the hypothesis that volatile adsorption is occurring. It is proposed that adsorption increases the driving force for liquid evaporation, which causes viscosity to increase. Only a small amount of adsorption occurred for the inertinite studied here and its effect on viscosity was mild and similar to graphite. The exponents in the viscosity vs % solid relationships could be used to evaluate solid additives, and hence, their effect on expansion/adhesion behaviour and pore structure development.
International Journal of Coal Geology, Jun 1, 2017
We report the effect of rank and lithotype on the wettability of coal in microfluidic experiments... more We report the effect of rank and lithotype on the wettability of coal in microfluidic experiments in two types of artificial microchannels; (1) reactive ion etched (RIE) channels and (2) die-cast channels prepared by pressing powdered lithotype concentrates. Five coals from the Bowen Basin with ranks in the R max% range 0.98-1.91% were examined. Contact angles and entry pressures of air and water in the artificial cleats were measured in imbibition experiments performed with a Cleat Flow Cell (CFC). The relative contact angles measured in CFC imbibition experiments were in the range 110-140° in the RIE channels and 85°-115° in the pressed discs, which are larger contact angles than measured on the flat bulk surfaces of these samples by the conventional sessile drop technique (58°-85°). The CFC observations also show the surface roughness of coal in inertinite-rich dull bands effects contact angle and the entry pressure of the air-water interface differently to the vitrinite-rich bright bands. Drainage experiments in the CFC revealed a thin residual water film on the inertinite cleat wall, yet not on the smooth vitrinite channel. The experimental observations are used to present a modified Cassie Equation model to predict coal contact angles based on the fractions of dull and bright bands, mineral content, and cleat surface roughness. The results of this study provide the basis to consider an improved relative permeability model that explicitly accounts for the effect of coal lithotype.
Oxidant stimulation using Sodium Hypochlorite (NaClO) is proposed for enhancing coal seam permeab... more Oxidant stimulation using Sodium Hypochlorite (NaClO) is proposed for enhancing coal seam permeability. To understand the effect of NaClO on different coal types, a subbituminous coal (Coal S) and a bituminous coal (Coal B) collected from the Surat Basin and Bowen Basin, Australia, respectively, were studied. The molecular structures of the two coals and their oxidised residues (Coal So and Coal Bo) were examined using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and solid state 13 C Nuclear Magnetic Resonance Spectroscopy (13 C NMR). Based on the results, the molecular structure schematic models of the samples were established. Results illustrate that Coal S is less aromatic with longer aliphatic chains and more oxygen content, while Coal B has larger average aromatic clusters, as expected given its higher rank. NaClO prefers to oxidise aliphatic chains, particularly those with oxygen functional groups. NaClO tends to oxidise small aromatic rings first, evidenced by the loss of smaller clusters in coal S, leaving the larger aromatic clusters. NaClO then attacks the larger aromatic clusters, confirmed by the average cluster size decrease for Coal B. The oxidised Coal B (Coal Bo) has a similar molecular structure to raw Coal S. After oxidation, both coal residues exhibit lower aromaticity, longer aliphatic chains and more oxygen content. The decreased aromaticity suggests reaction between NaClO and benzene rings. The breakage of aromatic rings is further suggested to give rise to longer aliphatic chains. NaClO oxidation products enriches the coals in C=O and O-C=O for both coals. These findings observed fill a gap in knowledge on coal oxidation by NaClO and contribute to the decision of selecting the most suitable oxidant stimulation targets for enhancing coal permeability.
This report brings together disparate disciplines to investigate automated (machine learning) an... more This report brings together disparate disciplines to investigate automated (machine learning) analysis of hyperspectral, Xray and photogrammetric scanner data for identification of lithologies, in particular coal quality, for the prediction of coal lithotypes, breakage behaviour and washability. It was a joint project between the UQ JKMRC and School of Earth and Environmental Sciences, and the commercial company CoreScan, and DNRM's Hylogger capability. The report can be obtained from www.acarp.com.au.
The vitrinite group macerals are the most important reactive component in the coking process, but... more The vitrinite group macerals are the most important reactive component in the coking process, but reactivity can be reduced by weathering and oxidation [1]. Maceral reactivity, and its susceptibility to oxidation, is also dependent on rank. As a result, coals are not all susceptible to weathering to the same degree, suggesting that medium volatile, moderate vitrinite coals could be stockpiled for up to 8 weeks without any deterioration in coke quality. Understanding the factors affecting coking coal variability during mining can assist with producing consistent product over the life of mine. This small study was undertaken to determine variability in coking properties arising from changes in coal lithotype and rank for a single seam, and whether stockpiling would have an effect.
Calcium phosphate apatite, Ca 5 (PO 4) 3 (OH,F,Cl), is a common accessory mineral in coal seams. ... more Calcium phosphate apatite, Ca 5 (PO 4) 3 (OH,F,Cl), is a common accessory mineral in coal seams. Although minor, its role in hosting phosphorus (P) and fluorine (F) can reduce the economic viability of coking and thermal coal deposits. Apatite in coal is commonly < 50 μm and may have several modes of occurrence. The modes of occurrence investigated as part of this study include apatite infilling small (i.e. less than 30 μm) cell lumens of fusinite and semifusinite macerals (pore-apatite); apatite infilling fractures (fracture-apatite); apatite occurring as discrete crystals in organic layers or in lithic lenses or bands (detrital-apatite); and apatite nodules or encrustations on silicate minerals (encrusting-apatite). However, the small size of the apatite and its intermixed relationship with the coal and other mineral matter precludes separating the apatite from the coal for analysis and has implications for commercial beneficiation. Therefore, this study documents the trialling of different in situ techniques for evaluating the halogens, specifically F, within these different apatite micro-crystals in polished mounts. In general, standards-based, fully quantitative analysis of major and minor elements (including F, Cl) was accomplished using electron probe microanalysis (EPMA). This in conjunction with electron backscatter diffraction was used to evaluate the measured halogen contents for the different apatites and confirmed that all of the apatites are technically fluorapatite with F contents > 1 wt%. However, the small crystallite size of the encrusting-apatites and the pits on the polished surface of the detrital-apatites intermixed with the coal layers hindered determining the halogens by this method. Although, all of the apatites in the coals were able to be analysed by infrared spectroscopy, both the combined kaolinite and apatite spectra, and the noise in the spectra at the lower wavelengths hindered evaluating the F in the apatites using this method. Despite these limitations, the findings of this study show that EPMA is probably the most suitable analytical technique for determining the halogen contents of the different modes of apatites in situ in coal pellets. Future work should focus on determining whether the modes of occurrence reflect paragenesis.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Macerals (vitrinite and inertinite) were separated from a coal to understand the mechanism of int... more Macerals (vitrinite and inertinite) were separated from a coal to understand the mechanism of interaction between them during coking. Macerals were blended in various ratios and their viscoelastic properties and expansion/contraction behaviour measured using rheometry. Inertinite increases the viscosity of vitrinite exponentially. To understand why, various solid additives were also blended with vitrinite. Additionally, the solid additives were mixed with a high viscosity liquid that does not generate volatiles (silicone oil). Results show that meso-porous solids increase viscosity exponentially, however, the exponent is far greater. Interestingly, the exponent for meso-porous and non-porous solids is the same for silicone oil, showing that volatiles are playing a role in viscosity development. Thermogravimetric analysis showed that far more volatiles are being retained for mesoporous solids, providing evidence to support the hypothesis that volatile adsorption is occurring. It is proposed that adsorption increases the driving force for liquid evaporation, which causes viscosity to increase. Only a small amount of adsorption occurred for the inertinite studied here and its effect on viscosity was mild and similar to graphite. The exponents in the viscosity vs % solid relationships could be used to evaluate solid additives, and hence, their effect on expansion/adhesion behaviour and pore structure development.
International Journal of Coal Geology, Jun 1, 2017
We report the effect of rank and lithotype on the wettability of coal in microfluidic experiments... more We report the effect of rank and lithotype on the wettability of coal in microfluidic experiments in two types of artificial microchannels; (1) reactive ion etched (RIE) channels and (2) die-cast channels prepared by pressing powdered lithotype concentrates. Five coals from the Bowen Basin with ranks in the R max% range 0.98-1.91% were examined. Contact angles and entry pressures of air and water in the artificial cleats were measured in imbibition experiments performed with a Cleat Flow Cell (CFC). The relative contact angles measured in CFC imbibition experiments were in the range 110-140° in the RIE channels and 85°-115° in the pressed discs, which are larger contact angles than measured on the flat bulk surfaces of these samples by the conventional sessile drop technique (58°-85°). The CFC observations also show the surface roughness of coal in inertinite-rich dull bands effects contact angle and the entry pressure of the air-water interface differently to the vitrinite-rich bright bands. Drainage experiments in the CFC revealed a thin residual water film on the inertinite cleat wall, yet not on the smooth vitrinite channel. The experimental observations are used to present a modified Cassie Equation model to predict coal contact angles based on the fractions of dull and bright bands, mineral content, and cleat surface roughness. The results of this study provide the basis to consider an improved relative permeability model that explicitly accounts for the effect of coal lithotype.
Oxidant stimulation using Sodium Hypochlorite (NaClO) is proposed for enhancing coal seam permeab... more Oxidant stimulation using Sodium Hypochlorite (NaClO) is proposed for enhancing coal seam permeability. To understand the effect of NaClO on different coal types, a subbituminous coal (Coal S) and a bituminous coal (Coal B) collected from the Surat Basin and Bowen Basin, Australia, respectively, were studied. The molecular structures of the two coals and their oxidised residues (Coal So and Coal Bo) were examined using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and solid state 13 C Nuclear Magnetic Resonance Spectroscopy (13 C NMR). Based on the results, the molecular structure schematic models of the samples were established. Results illustrate that Coal S is less aromatic with longer aliphatic chains and more oxygen content, while Coal B has larger average aromatic clusters, as expected given its higher rank. NaClO prefers to oxidise aliphatic chains, particularly those with oxygen functional groups. NaClO tends to oxidise small aromatic rings first, evidenced by the loss of smaller clusters in coal S, leaving the larger aromatic clusters. NaClO then attacks the larger aromatic clusters, confirmed by the average cluster size decrease for Coal B. The oxidised Coal B (Coal Bo) has a similar molecular structure to raw Coal S. After oxidation, both coal residues exhibit lower aromaticity, longer aliphatic chains and more oxygen content. The decreased aromaticity suggests reaction between NaClO and benzene rings. The breakage of aromatic rings is further suggested to give rise to longer aliphatic chains. NaClO oxidation products enriches the coals in C=O and O-C=O for both coals. These findings observed fill a gap in knowledge on coal oxidation by NaClO and contribute to the decision of selecting the most suitable oxidant stimulation targets for enhancing coal permeability.
This report brings together disparate disciplines to investigate automated (machine learning) an... more This report brings together disparate disciplines to investigate automated (machine learning) analysis of hyperspectral, Xray and photogrammetric scanner data for identification of lithologies, in particular coal quality, for the prediction of coal lithotypes, breakage behaviour and washability. It was a joint project between the UQ JKMRC and School of Earth and Environmental Sciences, and the commercial company CoreScan, and DNRM's Hylogger capability. The report can be obtained from www.acarp.com.au.
The vitrinite group macerals are the most important reactive component in the coking process, but... more The vitrinite group macerals are the most important reactive component in the coking process, but reactivity can be reduced by weathering and oxidation [1]. Maceral reactivity, and its susceptibility to oxidation, is also dependent on rank. As a result, coals are not all susceptible to weathering to the same degree, suggesting that medium volatile, moderate vitrinite coals could be stockpiled for up to 8 weeks without any deterioration in coke quality. Understanding the factors affecting coking coal variability during mining can assist with producing consistent product over the life of mine. This small study was undertaken to determine variability in coking properties arising from changes in coal lithotype and rank for a single seam, and whether stockpiling would have an effect.
Calcium phosphate apatite, Ca 5 (PO 4) 3 (OH,F,Cl), is a common accessory mineral in coal seams. ... more Calcium phosphate apatite, Ca 5 (PO 4) 3 (OH,F,Cl), is a common accessory mineral in coal seams. Although minor, its role in hosting phosphorus (P) and fluorine (F) can reduce the economic viability of coking and thermal coal deposits. Apatite in coal is commonly < 50 μm and may have several modes of occurrence. The modes of occurrence investigated as part of this study include apatite infilling small (i.e. less than 30 μm) cell lumens of fusinite and semifusinite macerals (pore-apatite); apatite infilling fractures (fracture-apatite); apatite occurring as discrete crystals in organic layers or in lithic lenses or bands (detrital-apatite); and apatite nodules or encrustations on silicate minerals (encrusting-apatite). However, the small size of the apatite and its intermixed relationship with the coal and other mineral matter precludes separating the apatite from the coal for analysis and has implications for commercial beneficiation. Therefore, this study documents the trialling of different in situ techniques for evaluating the halogens, specifically F, within these different apatite micro-crystals in polished mounts. In general, standards-based, fully quantitative analysis of major and minor elements (including F, Cl) was accomplished using electron probe microanalysis (EPMA). This in conjunction with electron backscatter diffraction was used to evaluate the measured halogen contents for the different apatites and confirmed that all of the apatites are technically fluorapatite with F contents > 1 wt%. However, the small crystallite size of the encrusting-apatites and the pits on the polished surface of the detrital-apatites intermixed with the coal layers hindered determining the halogens by this method. Although, all of the apatites in the coals were able to be analysed by infrared spectroscopy, both the combined kaolinite and apatite spectra, and the noise in the spectra at the lower wavelengths hindered evaluating the F in the apatites using this method. Despite these limitations, the findings of this study show that EPMA is probably the most suitable analytical technique for determining the halogen contents of the different modes of apatites in situ in coal pellets. Future work should focus on determining whether the modes of occurrence reflect paragenesis.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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