Altered volcanic ashes in coal and coal-bearing sequences: A review of their nature and significance

Dai, Shifeng; Ward, Colin R.; Graham, Ian T.; French, David; Hower, James C.; Zhao, Laishi; Wang, Xibo

doi:10.1016/j.earscirev.2017.10.005

Cited by 161 publications

(119 citation statements)

References 226 publications

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“…The enrichment of uranium in coal might result from the weathering of source rocks, volcanic ashes (just the felsic or intermediate volcanic ashes [51]), magmatic intrusion, marine water influence, groundwater, hydrothermal fluids, organic matter, paleoclimate, and geologic conditions of coal-accumulating basins [9]. Note that the factors listed above have different contribution for uranium enrichment.…”

Section: Uranium In Coals From Different Coalfields In Chinamentioning

confidence: 99%

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

Chen

Yao

et al. 2017

Minerals

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Due to its environmental and resource impacts, the geochemistry of uranium in coal is of both academic and practical significance. In order to give a comprehensive summary about the geochemistry of uranium in coals, the abundance, distribution, and modes of occurrence of uranium in Chinese coals were reviewed in this paper. Although some coals from southwestern and northwestern China are significantly enriched in uranium, the common Chinese coals are of a comparable uranium concentration to the world coals. The roof and floor rocks, and parting of coalbeds, or coal benches that are close to the surrounding rock are favorable hosts for uranium in one coalbed. The uranium concentrations in coals of different ages decrease in this order, e.g., Paleogene and Neogene > Late Permian > Late Triassic > Late Carboniferous and Early Permian > Late Jurassic and Early Cretaceous > Early and Middle Jurassic. Uranium in Chinese coals is mainly associated with organic matter, and is correspondingly enriched in subbituminous coal and lignite.

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Section: Uranium In Coals From Different Coalfields In Chinamentioning

confidence: 99%

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

Chen

Yao

et al. 2017

Minerals

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“…In addition, most sulfur in some SHOS coals (e.g., the Yanshan coal [13]) was likely influenced by submarine exhalation, which was carried into the peat swamp and then evenly distributed in the organic matter [13,16]. The hydrothermal fluids that have caused highly elevated S in coal are generally of epithermal origin [20] or are closely related to volcanic activities both in the marine (e.g., submarine exhalation) and in the terrestrial environments [24]. On the other hand, the SHOS coals in some cases contain highly-elevated critical elements that have a great potential for industrial extraction and utilization (e.g., rare earth elements, Y, V, Se, Mo, U) [3,25,26].…”

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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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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“…For example, when the separation density is assumed to be 1.50 g/cm 3 , the concentration of REE, Zr and Nb in the ash of cleaned coal would be up to 1248.87 µg/g, 1126.23 µg/g and 134.19 µg/g, respectively. REE, Nb, Ta, Zr, Hf and U were found to have been enriched in volcanic-ash-influenced Late Permian coal [45,46] and coal-bearing strata [47] from southwestern China, showing potential as a rare metal resource for industrial extraction [48]. Therefore, more attention should be given to the enrichment of these elements in coal from this region.…”

Section: Distribution Of Trace Elements During Gravity Separationmentioning

confidence: 99%

Washability and Distribution Behaviors of Trace Elements of a High-Sulfur Coal, SW Guizhou, China

et al. 2018

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Abstract:The float-sink test is a commonly used technology for the study of coal washability, which determines optimal separation density for coal washing based on the desired sulfur and ash yield of the cleaned coal. In this study, the float-sink test is adopted for a high-sulfur Late Permian coal from Hongfa coalmine (No.26), southwestern Guizhou, China, to investigate its washability, and to analyze the organic affinities and distribution behaviors of some toxic and valuable trace elements. Results show that the coal is difficult to separate in terms of desulfurization. A cleaned coal could theoretically be obtained with a yield of 75.50%, sulfur 2.50%, and ash yield 11.33% when the separation density is 1.57 g/cm 3 . Trace elements' distribution behaviors during the gravity separation were evaluated by correlation analysis and calculation. It was found that Cs, Ga, Ta, Th, Rb, Sb, Nb, Hf, Ba, Pb, In, Cu, and Zr are of significant inorganic affinity; while Sn, Co, Re, U, Mo, V, Cr, Ni, and Be are of relatively strong organic affinity. LREE (Light rare earth elements), however, seem to have weaker organic affinity than HREE (Heavy rare earth elements), which can probably be attributed to lanthanide contraction. When the separation density is 1.60 g/cm 3 , a large proportion of Sn, Be, Cr, U, V, Mo, Ni, Cd, Pb, and Cu migrate to the cleaned coal, but most of Mn, Sb and Th stay in the gangue. Coal preparation provides alternativity for either toxic elements removal or valuable elements preconcentration in addition to desulfurization and deashing. The enrichment of trace elements in the cleaned coal depends on the predetermined separation density which will influence the yields and ash yields of the cleaned coal.

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Altered volcanic ashes in coal and coal-bearing sequences: A review of their nature and significance

Cited by 161 publications

References 226 publications

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

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

Washability and Distribution Behaviors of Trace Elements of a High-Sulfur Coal, SW Guizhou, China

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