Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals

Niekerk, Daniel van; Pugmire, Ronald J.; Solum, Mark S.; Painter, Paul C.; Mathews, Jonathan P.

doi:10.1016/j.coal.2008.08.014

Cited by 155 publications

(136 citation statements)

References 39 publications

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“…Prior to deconvolution, the 13 C-NMR spectrum was adjusted using the Nuts Software. Then, the PFM module of the Origin Software was used to subtract the baseline, add peaks manually according to the spectrum shape and assignment of NMR structure The chemical shifts and assignment for the 13 C-NMR spectra of coal and its precursor have been summarized in previous studies [57][58][59][60][79][80][81][82][83][84][85], and the reported chemical shifts are mostly identical with only minor differences. The 13 C-NMR structure parameters and assignment used in the present study are given in Table 2 [84,[86][87][88].…”

Section: Samples and Analytical Methodsmentioning

confidence: 99%

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13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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Abstract:The structure evolution characteristics of high-organic-sulfur (HOS) coals with a wide range of ranks from typical Chinese areas were investigated using 13 C-CP/MAS NMR. The results indicate that the structure parameters that are relevant to coal rank include CH 3 carbon (f al *), quaternary carbon, CH/CH 2 carbon + quaternary carbon (f al H ), aliphatic carbon (f al C ), protonated aromatic carbon (f a H ), protonated aromatic carbon + aromatic bridgehead carbon (f a H+B ), aromaticity (f a CP ), and aromatic carbon (f ar C ). The coal structure changed dramatically in the first two coalification jumps, especially the first one. A large number of aromatic structures condensed, and aliphatic structures rapidly developed at the initial stage of bituminous coal accompanied by remarkable decarboxylation. Compared to ordinary coals, the structure evolution characteristics of HOS coals manifest in three ways: First, the aromatic CH 3 carbon, alkylated aromatic carbon (f a S ), aromatic bridgehead carbon (f a B ), and phenolic ether (f a P ) are barely relevant to rank, and abundant organic sulfur has an impact on the normal evolution process of coal. Second, the average aromatic cluster sizes of some super-high-organic-sulfur (SHOS) coals are not large, and the extensive development of cross bonds and/or bridged bonds form closer connections among the aromatic fringes. Moreover, sulfur-containing functional groups are probably significant components in these linkages. Third, a considerable portion of "oxygen-containing functional groups" in SHOS coals determined by 13 C-NMR are actually sulfur-containing groups, which results in the anomaly that the oxygen-containing structures increase with coal rank.

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Section: Samples and Analytical Methodsmentioning

confidence: 99%

“…Moreover, the chemical structures of coal lithotypes and macerals were also investigated by 13 C-NMR [55,56]. This technique has developed into an indispensable analytical method for coal macromolecular characterization [57][58][59][60].…”

Section: Introductionmentioning

confidence: 99%

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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“…The peak in the 1100-1200 cm -1 region for bituminous coal was assigned to either group, as well as C-O stretching and OH bonding vibrations in phenoxy structures (Niekerk et al, 2008). Low intensity aromatic -CH out-of-plane (bending) bands were observed between 900 and 700 cm -1 in all the samples (Sonibare et al, 2010).…”

Section: Ft-ir Analysismentioning

confidence: 99%

Utilization of petrographic analysis for determination of petroleum coke mixtures

Toprak¹,

Sütcü²,

Gülen³

2014

Turkish J Earth Sci

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This study was carried out on mostly imported, processed petrocokes, which are also commercially known as "petcoke" or "petroleum coke". Petrocoke is imported in great amounts and is occasionally consumed domestically without conscientious thought. It is not a well-known material, though there is an idea of its genesis. The samples, their analysis, and their images are essential to be kept in mind for further investigations, since it is not an environmentally friendly material. Petrographic and chemical analyses were conducted on all samples. Trace element and FT-IR analyses were made on a few representative samples. It is possible to distinguish petrocokes from coal samples by means of coal petrography. Even mixtures of the petrocokes with coals can be detected very well. Some trace elements such as V, U, and Ni have much higher contents in petrocokes. They may cause environmental impacts.

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“…Raw Waterberg coal is also comprised of vitrinite macerals with a concentration of up to 90% weight by volume [6,7,8]. The main difficulty with the high ash and vitrinite content is that, this coal tends to swell and cake significantly during devolatilization (thermal treatment), leaving it irreconcilable for fixed-bed gasification purposes, unless the coal is beneficiated or the gasifiers are adjusted according to caking propensities under its operating conditions, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The main difficulty with the high ash and vitrinite content is that, this coal tends to swell and cake significantly during devolatilization (thermal treatment), leaving it irreconcilable for fixed-bed gasification purposes, unless the coal is beneficiated or the gasifiers are adjusted according to caking propensities under its operating conditions, i.e. by coal blending, or mechanically stirred to break down cakes [7,8].…”

Section: Introductionmentioning

confidence: 99%

Effect of Pressure on the Caking Propensity of Waterberg Coal

2017

Nov. 27-28, 2017 South Africa ASETWM-17, RCABES-17 &Amp; EBHSSS-17

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Abstract-In this study the high-pressure caking behavior of large Waterberg coal particles (4, 8, 10 and 20mm) was investigated. This coal was density separated into the following fractions: FL1.3, FL1.5, FL1.7, FL 1.9 and SI 1.9. Small samples (10-20g) of the 4,8,10 and 20mm density separated lump coal were reacted in a high-pressure reactor at 4 different pressures (Atm, 7.5, 15, and 30bar) at fixed temperatures of 450°C and 550°C. A 7°C per minute heating rate was employed during all experiments, which was executed in an inert nitrogen atmosphere. The degree of caking was determined on a mass% basis. X-ray computed tomography scans were conducted on the high caking density fraction FL1.3 and parent coal. Conventional coal characterization (proximate and ultimate) and petrographic analysis before and after devolatilization of the 10mm density separated coal fraction was also conducted. Finally, a predictive caking model was developed based on the coal properties. The caking propensity was found to be higher under 30bar pressure than at atmospheric conditions (0.87bar) for the 10mm particles, subjected to density cuts (FL1.5 and FL1.7) and the parent coal. The FL1.3, FL1.9 and SI1.9 fractions reported the same caking propensities under both 30bar and atmospheric pressures. On the other hand, the 4 and 8mm particles reported higher caking propensities at 550°C than for 450°C at 0.87 and 30bar pressure respectively. The 20mm particles reported slightly higher caking propensities (5 % ) than for the 10mm particles at 30bar and 550°C. It was also found that the caking propensity reaches a maximum at 15bar pressure for the 10mm particles. It is concluded that as the coal fractional density increases the caking propensity decreases. From the x-ray micro focus tomography results it is clear that the porosity of the caked particles decreases and the coalescence of the particles increase as the pressure increases. From characterization analysis it was found that the lighter density cuts contain more volatile matter, a higher CV value, lower ash content and higher vitrinite maceral composition, leading to higher caking propensity.

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Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals

Cited by 155 publications

References 39 publications

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Utilization of petrographic analysis for determination of petroleum coke mixtures

Effect of Pressure on the Caking Propensity of Waterberg Coal

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