Modes of Occurrence of Chromium and Their Thermal Stability in Low-Rank Coal Pyrolysis

Chromium (Cr) and the emission of its compounds into the environment have caused long-term environmental contamination. In this study, the modes of occurrence of Cr in low-rank coal and their thermal stability in pyrolysis were investigated by sequential chemical extraction (SCE), single-component samples (SCS) pyrolysis, and thermochemical equilibrium simulation. The results showed that organic matter, aluminosilicate, and carbonate were the dominant modes of occurrence of Cr in low-rank coal. The modes of occurrence and chlorine (Cl) content affected the volatilization of Cr in coal. The characteristic release temperature range of Cr bounded to aluminosilicate was >600 °C and 400–600 °C for Cr bounded to a disulfide. Cr bounded to organic matter almost released completely before 600 °C. Cl enhanced the volatility of Cr and reduced its release temperature in Cr bounded to aluminosilicate. The simulation showed the content of gas products was very low, mainly chlorides. While the content of solid products, sulfides, and oxides, was much higher than gas products, showing their high thermal stability. The sulfides and oxides in chars were closely related to the carbonate and aluminosilicate bound form of Cr. The results of the equilibrium simulation were consistent with the experimental results.

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Mercury Speciation in Various Coals Based on Sequential Chemical Extraction and Thermal Analysis Methods

Energies ◽

10.3390/en14092361 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2361

Author(s):

Yinjiao Su ◽

Xuan Liu ◽

Yang Teng ◽

Kai Zhang

Keyword(s):

Thermal Stability ◽

Coal Combustion ◽

Decomposition Methods ◽

Chemical Extraction ◽

Anthropogenic Source ◽

Coal Rank ◽

Coal Pyrolysis ◽

Mercury Emissions ◽

Sequential Chemical Extraction ◽

Removal Technology

Coal combustion is an anthropogenic source of mercury (Hg) emissions to the atmosphere. The strong toxicity and bioaccumulation potential have prompted attention to the control of mercury emissions. Pyrolysis has been regarded as an efficient Hg removal technology before coal combustion and other utilization processes. In this work, the Hg speciation in coal and its thermal stability were investigated by combined sequential chemical extraction and temperature programmed decomposition methods; the effect of coal rank on Hg speciation distribution and Hg release characteristics were clarified based on the weight loss of coal; the amount of Hg released; and the emission of sulfur-containing gases during coal pyrolysis. Five species of mercury were determined in this study: exchangeable Hg (F1), carbonate + sulfate + oxide bound Hg (F2), silicate + aluminosilicate bound Hg (F3), sulfide bound Hg (F4), and residual Hg (F5), which are quite distinct in different rank coals. Generally, Hg enriched in carbonates, sulfates, and oxides might migrate to sulfides with the transformation of minerals during the coalification process. The order of thermal stability of different Hg speciation in coal is F1 < F5 < F2 < F4 < F3. Meanwhile, the release of Hg is accompanied with sulfur gases during coal pyrolysis, which is heavily dependent on the coal rank.

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The interaction between the char solid heat carrier and the volatiles during low-rank coal pyrolysis

Journal of Analytical and Applied Pyrolysis ◽

10.1016/j.jaap.2018.10.009 ◽

2018 ◽

Vol 136 ◽

pp. 160-168 ◽

Cited By ~ 5

Author(s):

Xiao-hong Li ◽

Bao-fu Li ◽

Da-qing Fu ◽

Jie Feng ◽

Wen-ying Li

Keyword(s):

Heat Carrier ◽

Low Rank ◽

Coal Pyrolysis ◽

Low Rank Coal

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Study on the modes of occurrence of rare earth elements in coal fly ash by statistics and a sequential chemical extraction procedure

Fuel ◽

10.1016/j.fuel.2018.09.139 ◽

2019 ◽

Vol 237 ◽

pp. 555-565 ◽

Cited By ~ 27

Author(s):

Jinhe Pan ◽

Changchun Zhou ◽

Mengcheng Tang ◽

Shanshan Cao ◽

Cheng Liu ◽

...

Keyword(s):

Rare Earth ◽

Fly Ash ◽

Rare Earth Elements ◽

Coal Fly Ash ◽

Extraction Procedure ◽

Chemical Extraction ◽

Modes Of Occurrence ◽

Sequential Chemical Extraction

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Effect of Three Different Catalysts (KCl, CaO, and Fe2O3) on the Reactivity and Mechanism of Low-Rank Coal Pyrolysis

Energy & Fuels ◽

10.1021/acs.energyfuels.5b02720 ◽

2016 ◽

Vol 30 (3) ◽

pp. 2428-2433 ◽

Cited By ~ 27

Author(s):

Yu Fu ◽

YanHong Guo ◽

KeXin Zhang

Keyword(s):

Low Rank ◽

Coal Pyrolysis ◽

Low Rank Coal

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Effect of char powder on gaseous tar reaction during low-rank coal pyrolysis

Journal of Fuel Chemistry and Technology ◽

10.1016/s1872-5813(21)60056-7 ◽

2021 ◽

Vol 49 (5) ◽

pp. 626-633

Author(s):

Ting LI ◽

Tian-zhou DU ◽

Yan-feng SHEN ◽

Lun-jing YAN ◽

Jiao KONG ◽

...

Keyword(s):

Low Rank ◽

Coal Pyrolysis ◽

Low Rank Coal

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Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

Energy Exploration & Exploitation ◽

10.1177/0144598718768980 ◽

2018 ◽

Vol 36 (6) ◽

pp. 1655-1673

Author(s):

Shenjun Qin ◽

Qingfeng Lu ◽

Kang Gao ◽

Penghui Bo ◽

Shihao Wu

Keyword(s):

Trace Elements ◽

Inductively Coupled Plasma ◽

Southwest China ◽

Major And Trace Elements ◽

Chemical Extraction ◽

Late Permian ◽

Modes Of Occurrence ◽

X Ray ◽

Sequential Chemical Extraction ◽

Permian Coal

The enrichment and geochemical significance of elements associated with Late Permian coals in Southwest China have always gained widespread interest in the field of coal geology. The present study focuses on the geochemical characterization of Late Permian coal in the Zhongliangshan mine. Twenty-three samples were collected from the K1a coal seam of the Zhongliangshan mine, and the major and trace elements in the coal were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry. The composition of minerals in the Zhongliangshan coal, and the modes of occurrence of coal-associated elements, especially those with elevated contents, were studied through a combination of microscopic analyses, X-ray powder diffraction, and scanning electron microscope – energy dispersive X-ray spectrometer. The minerals in coal mainly consist of kaolinite, pyrite, calcite, and quartz, as well as small amount of gypsum and anatase. Compared with the average elemental concentrations in world coal, the Zhongliangshan coal is enriched in Cr, and slightly enriched in Li, U, Sr, V and Ag. Combining the correlation analysis and sequential chemical extraction experiments, it can be inferred that many trace elements in the Zhongliangshan coal have both inorganic and organic affinities. The elements Cr, Li, and V mainly occur in clay minerals, and also are related to organic matter in the coal. Uranium presents firstly in the organic and then silicate states. Strontium shows multiple modes of occurrence including carbonate, silicate, and exchangeable ion states, and Ag primarily occurs in sulfides followed by silicates. The terrigenous debris input from the Emeishan basalt is the major reason for the enrichment of above elements in the Zhongliangshan coal.

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Evolution Kinetics of Hydrogen Generation from Low Rank Coal Pyrolysis and Its Relation to the First Coalification Jump

Acta Physico-Chimica Sinica ◽

10.3866/pku.whxb20091218 ◽

2009 ◽

Vol 25 (12) ◽

pp. 2597-2603 ◽

Cited By ~ 6

Author(s):

LI Mei-Fen ◽

◽

ZENG Fan-Gui ◽

SUN Bei-Lei ◽

QI Fu-Hui

Keyword(s):

Hydrogen Generation ◽

Low Rank ◽

Coal Pyrolysis ◽

Low Rank Coal ◽

Kinetics Of

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Cation exchange capability and reactivity of low-rank coal and chars

Open Chemistry ◽

10.2478/s11532-013-0346-9 ◽

2014 ◽

Vol 12 (1) ◽

pp. 33-43 ◽

Cited By ~ 3

Author(s):

George Skodras ◽

Paris Kokorotsikos ◽

Maria Serafidou

Keyword(s):

Organic Matter ◽

Oxygen Content ◽

Cumulative Distribution ◽

Low Rank ◽

Low Rank Coal ◽

Solution Ph ◽

Carboxylic Groups ◽

Complete Dissociation ◽

Oxygen Conversion ◽

Maximum Weight Loss

AbstractIn this work the C.E.C. and its effect on the reactivity of low rank coal and chars were investigated. The C.E.C. was measured by potentiometric titration and was correlated with the solution pH, the carbonization extent and the oxygen content. Coal and chars presented permanent C.E.C. primarily derived from inorganic sites and was independent of solution pH, and variable C.E.C. derived from organic matter and was increased continuously, and reversibly, as the solution pH increased. The latter is due to the complete dissociation of the carboxylic groups of the organic matter of the coal and, thus, the C.E.C. is directly related with the oxygen content. The C.E.C. of chars decreased with the carbonization extents and its variation was described by a modified cumulative distribution function of the Weibull probability density function. A linear correlation was identified between the C.E.C. and the elemental oxygen conversion, justifying further the direct relation between the C.E.C. and the oxygen functional groups. Following the decrease of the C.E.C., the potassium chemisorption capacity of the chars also decreased. Chars of decreased C.E.C. were less reactive during CO2 gasification and reduced maximum weight loss and CO formation rates were obtained, also shifted at higher temperatures.

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