Coal: Chemical, Geochemical and Petrographical Aspects

A special issue of Minerals (ISSN 2075-163X).

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 12325

Special Issue Editors


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Guest Editor
Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences, Wuhan, China
Interests: coal geochemistry; coal mineralogy; nano-mineralogy; critical elements in coal; geochemical behavior of trace elements during coalification

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Guest Editor
Scholl of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Beijing, China
Interests: underground coal gasification; microwave-assisted metal-catalyzed pyrolysis of low-rank coal; trace elements behavior during gasification

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Guest Editor
School of Earth Sciences and Surveying and Mapping Engineering, China University of Mining and Technology (Beijing), Beijing, China
Interests: mineral matter and trace elements in coal; strategically critical metals in coal-bearing sequences and coal combustion by-products; environmental impact of coal combustion by-products
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Special Issue Information

Dear Colleagues,

Coal is a heterogeneous sedimentary rock consisting of both organic and inorganic constituents. Organic constituents, or macerals, are known to behave differently during the utilization of coal. In this sense, understanding the chemical composition and structure of coal is important for the efficient utilization of coal. Inorganic fractions in coal have also attracted wide attention because of their potential effects on human health and environment, the potential economic value due to a number of critical elements, as well as the roles these fractions play as indicators of paleoenvironments and geologic evolutions. This Special Issue covers research and technological developments in: (1) the chemical composition and structure of coal, changes during coalification, and coal conversion and utilization processes; (2) petrology, mineralogy, and geochemistry of coal; (3) advanced analytical methods.

Dr. Xiaomei Wang
Prof. Dr. Shuqin Liu
Prof. Dr. Lei Zhao
Guest Editors

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Keywords

  • coal
  • petrology
  • geochemistry
  • chemical structure
  • trace elements
  • critical elements
  • mineral matter
  • macerals
  • coal conversion
  • coal gasification

Published Papers (6 papers)

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Research

16 pages, 3938 KiB  
Article
Estimation of Carbon Content in High-Ash Coal Using Mid-Infrared Fourier-Transform Infrared Spectroscopy
by Sameeksha Mishra, Anup Krishna Prasad, Anubhav Shukla, Arya Vinod, Kumari Preety and Atul Kumar Varma
Minerals 2023, 13(7), 938; https://doi.org/10.3390/min13070938 - 13 Jul 2023
Cited by 2 | Viewed by 1777
Abstract
The carbon content of different types of coal determines its utility in industries and thermal power generation. The most popular and widely used is the conventional method (ultimate analysis) to determine coal’s carbon content (C, wt.%), along with H, N, and S. In [...] Read more.
The carbon content of different types of coal determines its utility in industries and thermal power generation. The most popular and widely used is the conventional method (ultimate analysis) to determine coal’s carbon content (C, wt.%), along with H, N, and S. In the present study, the authors attempted to analyze the carbon content (C in %) in coals via data from Fourier-transform infrared (FTIR) spectroscopy, which can be a promising alternative. As a reference, the carbon content in the coal samples, referred to as CCHNS (in wt.%), was determined from the ultimate analysis. The mid-infrared FTIR spectroscopic data were used to investigate the response of functional groups associated with carbon or its compounds, which were used to model and estimate the carbon content in coal samples (referred to as CFTIR, in wt.%). FTIR spectral signatures were utilized in specific zones (between wavenumbers 4000 and 400 cm−1) from a total of 18 coal samples from the Johilla coalfield, Umaria district, Madhya Pradesh, India. These 18 coal samples were used to produce 126 Coal+KBr pellets (at seven known dilution factors for each coal sample), and the spectral response (absorbance) from each pellet was recorded. For model development and validation, the training set and test set were formed using a 17:1 split (K-fold cross validation). The carbon content in the coal samples was modeled using the training set data by applying the piecewise linear regression method employing quasi-Newton (QN) with a breakpoint and least squares loss function. The model was validated using an independent test set. A pairwise comparison of estimates of carbon in the laboratory from the CHNS analyzer (CCHNS) and modeled carbon from FTIR data (CFTIR) exhibited a good correlation, relatively low error, and bias (coefficient of determination (R2) up to 0.93, RMSE of 23.71%, and MBE of −0.52%). Further, the significance tests for the mean and variance using the two-tailed t-test and F-test showed that no significant difference occurred between the pair of observed CCHNS and the model’s estimated CFTIR. For high-ash coals from the Johilla coalfield, the model presented here using mid-infrared FTIR spectroscopy data performs well. Thus, FTIR can potentially serve as an important method for quickly determining the carbon content of high-ash coals from various basins and can potentially be extended to soil and shale samples. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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14 pages, 2534 KiB  
Article
Geochemical Characteristics of Critical Metal Elements in the No. 9 Coal Seam from the Xinyuan Mine, Northern Qinshui Coalfield, Shanxi Province, China
by Jian Li, Shaowei Zhang, Hongdong Wang and Xichao Xie
Minerals 2023, 13(2), 278; https://doi.org/10.3390/min13020278 - 16 Feb 2023
Cited by 1 | Viewed by 1723
Abstract
As one of the main fossil fuels globally, coal can be enriched with a variety of critical metal elements in specific geological conditions. This paper investigates the mineral compositions and concentrations of major and minor element oxides and trace elements in the No. [...] Read more.
As one of the main fossil fuels globally, coal can be enriched with a variety of critical metal elements in specific geological conditions. This paper investigates the mineral compositions and concentrations of major and minor element oxides and trace elements in the No. 9 coal from the Xinyuan mine of the northern Qinshui coalfield, China, and discusses the modes of occurrence and enrichment mechanisms of critical metal elements such as Li, Ga, Th and REY. The mineral compositions of the No. 9 coal are primarily represented by clay minerals and quartz, with a small amount of calcite, siderite, anatase, etc. The major element oxides in the No. 9 coal are dominated by SiO2 and Al2O3. Compared with world hard coal, the No. 9 coal of the Xinyuan mine is rich in Li (CC = 8.00) and Th, slightly enriched with Pb, Sc, Ga, Y, La, Ce, Tb, Dy, Er, Yb and Hg, and depleted in Mn, Co, Ni, Rb, Cs and Tl. The critical metal elements such as Li, Ga, Th and REY that enriched No. 9 coal mainly occur in aluminum silicates. The genetic type of the critical metal elements in the No. 9 coal from the Xinyuan mine is source rock-controlled type. The critical metal minerals and solutions from the source area were transported to the study area by the action of water. Due to the change of swamp water conditions, the critical metal elements were combined with clay minerals and enriched the coal. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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20 pages, 5176 KiB  
Article
Optimization of Operating Parameters for Coal Low-Temperature Ashing: A Suitable and Efficient Treatment Method for Mineral Analysis in Coal
by Qiuchan Han, Jingjing Liu, Niande Shang, Shumao Zhao and Rongkun Jia
Minerals 2022, 12(9), 1119; https://doi.org/10.3390/min12091119 - 2 Sep 2022
Cited by 3 | Viewed by 1717
Abstract
Low-temperature oxygen-plasma ashing plus X-ray diffraction analysis is one of the effective techniques to identify minerals in coal. However, previous publications have not provided any details of the exact low-temperature degrees and corresponding working conditions of ashers, and this could lead to two [...] Read more.
Low-temperature oxygen-plasma ashing plus X-ray diffraction analysis is one of the effective techniques to identify minerals in coal. However, previous publications have not provided any details of the exact low-temperature degrees and corresponding working conditions of ashers, and this could lead to two adverse effects without proper operating guidance: (1) a relatively high temperature (e.g., >150 °C) may cause alteration of minerals (particularly clay minerals), and (2) a relatively low temperature (e.g., <80 °C) may cause a long ashing time and incomplete ashing of organic matter. In this study, the authors introduced the most frequently used low-temperature plasma ashers (PVA TePla IoN 40 made in America and Quorum K1050X made in Britain) to reveal optional operating parameters for low-temperature ashing. The ashing effects were analyzed from the aspects of ash mass, X-ray diffraction patterns, and the qualitative and quantitative analysis of minerals. Considering all the factors above, it is concluded that the ashing is the best when the running power is 200 W for the IoN 40, at which the diffraction peaks of chlorite d(004) and kaolinite d(002) can be clearly distinguished by LTAs-XRD analysis. In addition, different low temperatures have certain influence on the crystal structure of minerals. When the power rises to above 300 W (about 150 °C), the crystal structure of minerals undergoes changes. The symmetry and integrity of the mineral peaks became worse, and destructive interference occurred between the spacing of reflection planes, resulting in significant decrease in diffraction peak intensity; thus, some trace minerals were unable to be identified. The study on the working parameters of the instrument would be helpful to ash coals more effectively and make qualitative and quantitative analysis of minerals more accurate. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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16 pages, 2283 KiB  
Article
Modes of Occurrence and Enrichment of Trace Elements in Coal from the Anjialing Mine, Pingshuo Mining District, Ningwu Coalfield, Shanxi Province, China
by Tobechukwu Justin Ikeh, Beilei Sun, Chao Liu, Yunxia Liu, Yanlei Kong and Xinyu Pan
Minerals 2022, 12(9), 1082; https://doi.org/10.3390/min12091082 - 26 Aug 2022
Cited by 4 | Viewed by 1646
Abstract
In this paper, the mineralogical composition, concentrations, distribution, and modes of occurrence of the trace elements in coal from the Anjialing coal seam 9 in the Pingshuo mining district, Ningwu coalfield, were studied using optical microscopy, X-ray powder diffraction (XRD), inductively coupled plasma [...] Read more.
In this paper, the mineralogical composition, concentrations, distribution, and modes of occurrence of the trace elements in coal from the Anjialing coal seam 9 in the Pingshuo mining district, Ningwu coalfield, were studied using optical microscopy, X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and sequential chemical extraction procedures (SCEPs). The identified minerals included mainly kaolinite, boehmite, pyrite, calcite, quartz, and muscovite. Compared to other hard coal from around the world, the coal from seam 9 was enriched with lithium (Li); slightly enriched with gallium (Ga), hafnium (Hf), zirconium (Zr), and mercury (Hg); typically enriched with lead (Pb), and depleted in arsenic (As). The results of the SCEPs analysis showed that Li, Ga, Zr, and Hf were mainly associated with clay minerals. Arsenic mainly occurred in its silicate and sulfide forms in pyrite and Pb was mainly associated with aluminosilicate, sulfide, and carbonate minerals. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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16 pages, 5089 KiB  
Article
Modes of Occurrence of Critical Metal Elements (Li, REEs and Other Critical Elements) in Low-Grade Bauxite from Southern Shanxi Province, China
by Shangqing Zhang, Fenghua Zhao, Dongna Liu, Lei Zhao, Xiaohui Zhang, Junwei Lin, Haiyu Dong, Shuang Zhao, Xuefei Liu and Minjie Zan
Minerals 2022, 12(8), 990; https://doi.org/10.3390/min12080990 - 4 Aug 2022
Cited by 10 | Viewed by 2009
Abstract
The low-grade bauxite in southern Shanxi Province, China is enriched in multiple critical metal elements, including Li, Ga, V, Se, and rare earth elements (REEs), which have reached the standard of comprehensive utilization as independent deposits or associated resources. Even more importantly, identifying [...] Read more.
The low-grade bauxite in southern Shanxi Province, China is enriched in multiple critical metal elements, including Li, Ga, V, Se, and rare earth elements (REEs), which have reached the standard of comprehensive utilization as independent deposits or associated resources. Even more importantly, identifying the modes of occurrence of these critical elements is essential for designing technologies to extract critical metals from bauxite ores. This study used a combination of direct (X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy, and micro-X-ray fluorescence spectrometer), and indirect (size sieving method, float-sink experiment, and correlation analysis) methods to effectively reveal the distribution of critical elements in the different identified mineral phases. The results regarding the low-grade bauxite are as follows: Li was mainly hosted in cookeite as an independent mineral; Ga was mainly associated with diaspore; anatase is the main carrier mineral for V; REEs were present in the low-grade bauxite in multiples modes of occurrence, the most common of which were goyazite, and to a lesser extent, florencite; Se primarily occurs in sulfides. This study contributes to the development and utilization of these essential metal resources in bauxite by providing a useful reference. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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10 pages, 670 KiB  
Article
Green Conversion of Coal Fly Ash into Soil Conditioner: Technological Principle and Process Development
by Huidong Liu, Yongfeng Xiao and Xiaolin Jiang
Minerals 2022, 12(3), 276; https://doi.org/10.3390/min12030276 - 22 Feb 2022
Cited by 5 | Viewed by 1997
Abstract
White mud is residue discharged during the acid method in the aluminum extraction process from coal fly ash, and this material is harmful to the environment. The implementation of an environmentally friendly and valuable way to use white mud is a key factor [...] Read more.
White mud is residue discharged during the acid method in the aluminum extraction process from coal fly ash, and this material is harmful to the environment. The implementation of an environmentally friendly and valuable way to use white mud is a key factor restricting the commercial application of the acid method in the fly ash alumina extraction technology. An analysis of white mud revealed the following: (1) it was highly enriched in SiO2 (70–80%) while concentrations of acid-soluble elements, such as Na, Al, and Fe, and some hazardous heavy metals, including Pb and Cr, were significantly lower than raw fly ash; (2) approximately 80% of SiO2 had relatively high reaction activity because of the foregoing Al-extraction treatment. Through an ingenious green chemical process, the complete conversion of white mud into silicon–calcium fertilizer (SCF) was achieved under very mild reaction conditions (approximately 100 °C and atmospheric pressure). Waste liquor was totally recycled, and no secondary solid waste was generated. The SCF had an available silicon content (ASC) of 35%, significantly higher than the commercial standard (20%). Converting them into soil conditioners or ecological remediation materials with the lowest possible energy consumption and secondary pollution may be the most promising approach for the future disposal of aluminosilicate industrial solid wastes. Full article
(This article belongs to the Special Issue Coal: Chemical, Geochemical and Petrographical Aspects)
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