Structural evaluation of Xiaolongtan lignite by direct characterization and pyrolytic analysis

Wang, Qianqian; Wei, Xian‐Yong; Wang, Sheng-Kang; Li, Zhan-Ku; Li, Peng; Liu, Fang-Jing; Zong, Zhi‐Min

doi:10.1016/j.fuproc.2015.12.034

Cited by 55 publications

(26 citation statements)

References 46 publications

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“…According to the direct relationship between the peak temperature of the fitted subcurves and the energies involved for cleavage of the bonds, evolution of the different functional groups involved in these six regions was illuminated. Region one at the peak temperature 95.7 °C was ascribed to removal of the absorbed water, and then region two was mainly assigned to disintegration of the weak bonds such as C al –O, but the peak temperature was shifted to 288.0 °C, a little lower than other reports and our previous research, mainly due to the different coal rank and chemical structure of YN as analyzed above. And then, the four fitting regions left were sequentially assigned to cleavage of the relatively strong C al –C al /C al –H bonds at 432.0 °C and strong C ar –C al /C ar –O bonds at 594.1 °C, decomposition of carbonates at 686.3 °C, and then slow condensation of the aromatic rings in YN coal at 787.2 °C. , And among these six fitted regions for pyrolysis of YN, cleavage of C al –C al /C al –H bonds at region three was identified as the largest contributor.…”

Section: Results and Discussioncontrasting

confidence: 61%

Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Wang

Ding

et al. 2017

Energy Fuels

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Calcium sulfate (CaSO4) has attracted a great amount of attention as a potential oxygen carrier (OC) to be applied in chemical looping combustion (CLC) due to its high oxygen transfer capacity, wide distribution, and easy accessibility, but its low reactivity and sulfur emission from side reactions of CaSO4 should be well resolved. In this research, the CaSO4–CuO mixed OC was prepared using the template method combined with the sol–gel combustion synthesis (SGCS). Its reaction characteristics with a selected lignite (designated as YN) were investigated and the greatly enhanced reactivity of this mixed OC was confirmed relative to the single CaSO4 and CuO. Meanwhile, the comprehensive heat effect showed the desired exothermic characteristics for this mixed OC reaction with YN when the mass ratio of CaSO4 to CuO was fixed as 6:4. Furthermore, morphological analysis indicated that the solid products from YN reaction with the CaSO4–CuO mixed OC were porous without discernible sintering, mainly because the CaSO4 included not only provided the lattice oxygen involved for oxidation of YN coal, but also acted as the temporary inert support to improve the resistance of the reduced Cu to sintering. Finally, the gaseous and solid products formed were systematically investigated and clearly indicated that the gaseous sulfur species formed from the side reactions of CaSO4 were effectively fixed with solid Cu2S formation; as such the potential harms incurred could be eliminated. Overall, this preliminary research revealed the greatly enhanced reactivity of this mixed OC as well as its good fixation capacity for sulfur emitted from the side reaction of CaSO4, which is much desired in the real CLC system.

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Section: Results and Discussioncontrasting

confidence: 61%

Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Wang

Ding

et al. 2017

Energy Fuels

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“…On the other hand, the values of both f a and the aromatic bridgehead carbon molar fraction, χ, of BS and TS increased, while their degree of aromatic ring substitution, σ, decreased slightly. The f a value of BS-60 was 28.68, while the χ values of BS-60 and TS-60 were 0.21 and 0.25, respectively (for reference, the χ value of naphthalene is 0.2). This indicates that there were, on average, two aromatic rings in each cluster of BS-60 and TS-60.…”

Section: Resultsmentioning

confidence: 99%

“…Solid-state 13 C-NMR spectra of the three solutes are shown in Figure a–c. The carbon types and 3 C-NMR structural parameters of the solutes were determined by curve fitting analysis. − The peak-fitted spectra for solutes-120 are shown in Figure d–f, with the percentages of various types of carbon shown in Table S2 of the Supporting Information and the solid-state 13 C-NMR structural parameters of solutes shown in Table .…”

Section: Resultsmentioning

confidence: 99%

Structural Evolution and Formation Mechanisms of Caking Components of Modified Lignite in Subcritical H₂O–CO Systems

et al. 2019

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A new method for the alkali catalytic modification of lignite in subcritical H2O–CO systems is presented, which can greatly improve its caking properties (caking index, >90). Soxhlet extraction technology coupled with GPC (gel permeation chromatography), FTIR (Fourier transform infrared spectroscopy), and 13C-NMR (carbon-13 nuclear magnetic resonance) analysis methods were used to investigate the structural evolution and formation mechanisms of solutes of n-hexane, benzene, and tetrahydrofuran in modified coal (denoted as NS, BS, and TS, respectively), which were the main caking components in the modified lignite. The results showed that the solutes were composed of four kinds of compounds with weight-average molecular weights in the range of 1170–2900, 300–550, 190–300, and 100–150, respectively. Oxygen-containing functional groups appeared in many forms, such as phenolic OH, aliphatic OH, ether bonds, and carbonyl and carboxyl groups, but mainly existed as C–O. When the temperature was <320 °C, NS consisted of aliphatic ring compounds, while BS and TS contained some aromatics, with an average of two aromatic rings per cluster in both. The appearance of monocyclic aromatic structures in the solutes occurred in the 320–330 °C temperature range, with one to three aromatic rings in the BS clusters, while polycyclic aromatic structures with more than five rings appeared in TS. The statistical structural models of the solutes all contained polycyclic aliphatic/aromatic structures as their main bodies, connected with substituents such as monocyclic aromatic structures, aliphatic side chains, and oxygen-containing functional groups. They are consistent with the structure of caking components in caking coal. The formation of caking components in modified lignite therefore underwent four distinct stages: separation of primary solutes, formation of pyrolysis solutes, formation of hydrogenated solutes, and formation of polycondensation solutes. This study provides valuable insights into the caking transition of modified coal and a basis for the high-added value utilization of lignite.

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“…After further reaction, coal gas and tar are generated. In addition, hydrogen and CH4 are also produced in large quantities, and the weight loss rate reaches the maximum at 400-500 °C [23,24,25] 。With the increase of pyrolysis temperature, the weight loss rate of coal increases gradually. It can be seen that the higher the heating rate is, the lower the weight loss rate is.…”

Section: Active Decomposition Stagementioning

confidence: 99%

Pyrolysis Reactive Behaviors and Kinetic Characteristics of HSW Vitrinite Coal based on Coats-Redfern and DAEM Models

Wang¹,

Wang²,

Li³

et al. 2021

Preprint

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In this work, the weight loss behavior of vitrinite in hongshiwan coal at different heating rates was investigated by thermogravimetric mass spectrometry (TG-MS). Then Coats-Redfern and DAEM models were established to analyze the kinetics of coal pyrolysis. The results show that the weight loss rate of pyrolysis decreased with the increase of heating rate. When the pyrolysis temperature reaches 400–500°C, the weight loss rate reaches the maximum, which is 0.1593, 0.1539, 0.1478 and 0.1414%/°C respectively at the heating rates of 5, 10, 15 and 20°C/min, With the increase of heating rate, the corresponding temperature peaks of the five pyrolysis gases are shifted to the high temperature direction, and the amount of gas escaping is increasing. The trend of higher heating rate delayed the release of volatile compounds was consistent with TG-DTG results. Two kinetic models both prove that the activation energy of coal pyrolysis increases with the increase of temperature. The maximum activation energy occurs between 600 ℃ and 900 ℃, because the multi condensation of coal tar and the re solidification of semi coke will occur in this temperature range.

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Structural evaluation of Xiaolongtan lignite by direct characterization and pyrolytic analysis

Cited by 55 publications

References 46 publications

Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Structural Evolution and Formation Mechanisms of Caking Components of Modified Lignite in Subcritical H₂O–CO Systems

Pyrolysis Reactive Behaviors and Kinetic Characteristics of HSW Vitrinite Coal based on Coats-Redfern and DAEM Models

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Structural evaluation of Xiaolongtan lignite by direct characterization and pyrolytic analysis

Cited by 55 publications

References 46 publications

Chemical Looping Combustion of a Typical Lignite with a CaSO4–CuO Mixed Oxygen Carrier

Chemical Looping Combustion of a Typical Lignite with a CaSO4–CuO Mixed Oxygen Carrier

Structural Evolution and Formation Mechanisms of Caking Components of Modified Lignite in Subcritical H2O–CO Systems

Pyrolysis Reactive Behaviors and Kinetic Characteristics of HSW Vitrinite Coal based on Coats-Redfern and DAEM Models

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Product

Resources

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Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Chemical Looping Combustion of a Typical Lignite with a CaSO₄–CuO Mixed Oxygen Carrier

Structural Evolution and Formation Mechanisms of Caking Components of Modified Lignite in Subcritical H₂O–CO Systems