Low-temperature pyrolysis of Texas lignite, basic extracts and some related model compounds

Roberts, Royston M.; Sweeney, Kevin M.

doi:10.1016/0016-2361(84)90307-7

Cited by 16 publications

(4 citation statements)

References 9 publications

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“…Low-temperature pyrolysis of coal is regarded as an effective way to upgrade low-rank coals, such as lignite. It is also a common way to produce volatile matter products, typically light gases and tars, and an appropriate way for low-temperature carbonization. , Chars from low-temperature pyrolysis of lignite may be used to replace thermal coals or pulverized coal injection (PCI) coals in combustion or as inert components in a blend for coking. The combustion characteristics of char can directly affect burnout and, therefore, the unburned carbon content in ash .…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

et al. 2013

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Low-temperature pyrolysis offers a potential way of upgrading lignite and producing chars to replace thermal or pulverized coal injection (PCI) coals in combustion or being used as inert components in a blend for coking. In this study, the characteristics of chars from low-temperature pyrolysis of two lignite coals have been investigated. The changes in char morphology and chemical structures were investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The combustion reactivity of chars was analyzed in a thermogravimetric analyer (TGA) using non-isothermal techniques. The results show that chars from low-temperature pyrolysis of lignite coal below 450 °C were more reactive than higher temperature chars. Higher reactivity of low-temperature chars was attributed to the higher concentration of active sites and lower degree of structural order compared to that of high-temperature chars. Indonesian (YN) lignite showed a higher weight loss rate compared to Hulunbeier (HL) coal, which was attributed to a higher concentration of liptinite and vitrinite in YN coal. FTIR analysis indicated that the aliphatic structures and oxygen-containing functional groups decreased with an increasing pyrolysis temperature. The intensity of tightly bound cyclic OH tetramers and OH−ether O hydrogen bonds were higher than other hydrogen bonds in the 3700−3600 cm −1 region of infrared (IR) spectra. The density of alkyl chains and crosslinking reactions affected the yield of tar. The aromaticity of char increased with an increasing pyrolysis temperature. The abundance of CO and COOH structures decreased drastically with increasing temperature. A lower concentration of active sites on high-temperature chars resulted in lower combustion reactivity compared to low-temperature chars. The C−O and C C groups decreased as the temperature increased possibly because of the aromatic condensation. The extent of aromatic substitution decreased up to 650 °C. At temperatures above 650 °C, the degree of aromaticity was strengthened and larger condensed aromatic nuclei were formed. Brunauer−Emmett−Teller (BET) surface area analysis revealed that high-temperature chars have significantly higher surface area compared to chars produced at low temperatures. However, the concentration of active sites was lower in high-temperature chars. Therefore, it can be concluded that diffusion was the main reaction mechanism in high-temperature chars.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

et al. 2013

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“… 9 , 10 There exists a synergistic effect for the liquefaction properties among different coal macerals. 11 − 13 However, clarifying the molecular structure of coal macerals is the basis of understanding synergistic effect correctly. Researchers have studied the coal maceral composition, coal molecular structure, and coal aggregation structure chemistry of Shendong coal; however, the results are qualitative for primary structure coals.…”

Section: Introductionmentioning

confidence: 99%

“…Tectonic-thermal events of multi-periods in the evolution of geological histories will inevitably lead to a series of physical, chemical, and structural alterations of coal organic macromolecules, which will undergo complex deformation and metamorphism. , Accordingly, the metamorphic types of coal can be divided into three types, that is, low-temperature and high-pressure type, high temperature and high pressure type, and high temperature and low pressure type. Tectonically deformed coals (TDCs) were widely distributed in north and south China where the coal matrix not only exhibits brittle or ductile deformation but also undergoes certain extent of dynamic metamorphism. , There exist distinct differences in the macromolecules of coal among different metamorphic deformation environments. , Dongsheng coalfield is an important resource for coal liquefaction demonstration project whose macerals and liquefaction performances have been studied for a long time. , There exists a synergistic effect for the liquefaction properties among different coal macerals. − However, clarifying the molecular structure of coal macerals is the basis of understanding synergistic effect correctly. Researchers have studied the coal maceral composition, coal molecular structure, and coal aggregation structure chemistry of Shendong coal; however, the results are qualitative for primary structure coals. − The molecular structure characteristics and the formation mechanism for mylonite coal, which was formed with the coupling of thermal metamorphism and dynamic metamorphism have been minimally reported compared with the primary structure coals.…”

Section: Introductionmentioning

confidence: 99%

Creation and Generation Mechanism of Macromolecular Representation for Dongsheng Coal Vitrinite

Wang¹,

Dong

2022

ACS Omega

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Insights into macromolecules of coal were critical for improving the understanding of the coal upgrading and coalification process. Here, the creation and generation of macromolecular representation for Dongsheng coal vitrinite was clarified using industry analysis, elemental analysis, and the peak fitting technology of 13 C nuclear magnetic resonance ( 13 C NMR), Fourier transform infrared spectrum, and X-ray diffraction. The structural parameters and macromolecular representation (C 167 H 148 N 2 O 27 ) were innovatively calculated and created based on these characterization results and chemical shift correction, finally obtaining the plane macromolecular models whose 13 C NMR spectrum was close to the experimental spectrum. The property parameters of basic structural units were L a (average lateral sizes) = 19.917 Å, L c (stacking heights) = 24.776 Å, d 002 (interlayer spacing) = 3.488 Å, N (number of stacking layers) = 5.6213, and L a / L c < 1. Suffering from the dynamic metamorphism effects, the length of intermolecular aromatic lamellae for Dongsheng coal vitrinite was 7–8 aromatic rings in size. The aromatic clusters were dominated by benzene, naphthalene, and anthracene, and their numbers were 2, 4, and 2 per vitrinite model, respectively. Hydrogenated aromatic rings, ether bonds, and oxygen-methylene serve as the main bridge bonds to connect the aromatic clusters, where the short aliphatic chains were distributed around the edge of aromatic rings. Oxygen atoms exist in the form of hydroxyl, ether bond, carbonyl, and carboxyl groups, and their numbers were 2, 7, 4, and 8 per vitrinite model, respectively. The nitrogen atoms exist in the form of pyridine and pyrrole. The entropy weighting method was used to estimate the rationality of the macromolecular representation of long frame coal vitrinite, providing a new mathematical evaluation method for molecular simulation. Comparison of various macromolecular models from different geological conditions indicates that tectonic stress can promote the degree of aromatization and ring condensation. The thermal history and tectonic stress have a compensation effect for promoting the aromatization process. Aliphatic carbons were the most unstable units under thermal history and tectonic stress, and they are more easily removed from the aliphatic structure, followed by methyl. This finding of this paper can provide significance for coal liquefaction engineering in Dongsheng coalfield.

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“…Low-temperature pyrolysis is regarded as an effective way to upgrade low-rank coals, such as lignite. , Chars from low-temperature pyrolysis of lignite may be used as a fuel for power generation, to substitute thermal coals or pulverized coal injection (PCI) coals in combustion or as inert components in blends for coke making . During the pyrolysis process, sulfur and nitrogen would be released as sulfur and nitrogen compounds, such as H 2 S, COS, and NO x precursors, such as NH 3 and HCN.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Oxidation Characteristics of Lignite Chars from Low-Temperature Pyrolysis

Meng

Tahmasebi

et al. 2014

Energy Fuels

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The oxidation characteristics of chars from low-temperature pyrolysis of two lignite coals have been systematically investigated using a dual fixed-bed quartz reactor and a thermogravimetric analyzer (TGA). During oxidation experiments, the temperature profiles of coal and char samples were recorded and CO 2 and CO gases evolved were analyzed using gas chromatography. The physical and chemical structures of coals and chars were analyzed using Brunauer−Emmett−Teller (BET) adsorption isotherms and Fourier transform infrared spectroscopy (FTIR). During oxidation, the temperature of the coal sample may increase noticeably, exceeding the crossing point temperature (CPT). Chars prepared at 400 °C showed the lowest CPT, indicating the highest oxidation reactivity compared to that of parent coals and chars prepared at other temperatures. During oxidation, gaseous products are released, implying that oxygen-containing functional groups and solid oxygenated complexes decomposed and the yields increased with increasing the oxidation temperature. The amount of CO 2 generation was proportional to that of CO with the molar ratio of CO 2 /CO at around 4.15 under the present experimental conditions. During non-isothermal oxidation, the concentration of OH and other oxygen-containing functional groups increased with increasing the oxidation temperature for char samples but decreased in the case of oxidized coal. During isothermal oxidation, the concentration of oxygen functional groups in coal decreased with increasing the oxidation temperature above 250 °C. Pre-oxidation of chars decreased their combustion reactivity measured on the TGA.

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Low-temperature pyrolysis of Texas lignite, basic extracts and some related model compounds

Cited by 16 publications

References 9 publications

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Creation and Generation Mechanism of Macromolecular Representation for Dongsheng Coal Vitrinite

Low-Temperature Oxidation Characteristics of Lignite Chars from Low-Temperature Pyrolysis

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