Changes in nascent char structure during the gasification of low-rank coals in CO2

Zhang, Lei; Kajitani, Shiro; Umemoto, Susumu; Wang, Shuai; Quyn, Dimple Mody; Song, Yao; Li, Ting‐Ting; Shu, Zhang; Dong, Li; Li, Chun‐Zhu

doi:10.1016/j.fuel.2015.06.014

Cited by 38 publications

(13 citation statements)

References 40 publications

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“…These relationships explain that HVBC coal is more reactive than its respective chars, because of its middle-ranking, lessordered structure which cause their lower reactivity index under devolatilization. Additionally, the results reveal that HVBC chars obtained under N 2 atmosphere are less reactive than those from CO 2 , which is consistent with the results presented in Figure 13 (dashed lines) and obtained by Zhang et al (2015), for a similar rank coal. Those researchers attributed this difference to a high concentration of defects in the crystal structure caused by the reaction atmosphere, differences in heating rate, and to the greater energy density of CO 2 compared to N 2 , which leads to a lower value of the I G /I ALL relationship in the structure of the char obtained under CO 2 .…”

Section: Correlation Between Structural Changes and Char Reactivitysupporting

confidence: 90%

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Valdés¹,

Guerrero²,

López³

et al. 2018

Ing. Inv.

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The influence of a CO 2 or N 2 -based atmosphere on the porous structure and microstructure of the chars obtained from the nonisothermal slow devolatilization (10 °C/min), from room temperature to 900 °C, of two coals of different rank (Semi-Anthracite (SA) and High Volatile Bituminous type C (HVBC)) and different particle size distribution was studied. Physicochemical characterization (ultimate and proximate analysis), structural and morphological characterization by Raman spectroscopy, FE-SEM, BET surface area, and volume and diameter microporous by CO 2 adsorption measurements were carried out for all the chars. It was found that the kinetic parameters, the physicochemical properties, and reactivity of the chars are different, depending on the pyrolysis atmosphere. It was also determined that for the char from SA coal with particle size greater than 0.7 mm, the BET surface area increases when the atmosphere is enriched with CO 2 . This effect appears to be promoted by the interaction of different processes such as intraparticle side reactions (softening, nucleation and coalescence of bubbles, crosslinking, among others), differences in the thermal diffusivity of N 2 and CO 2 , and the reactive effects of the latter. Additionally, tests of oxidative reactivity of chars showed that the char formed in a CO 2 atmosphere is more reactive than that formed in N 2 . With the results of Raman analysis and kinetic parameters quantified, it was concluded that the reaction atmosphere determined the degree of ordering achieved by the char structure and that the thermodiffusive properties of the reaction atmosphere promoted structural differences in the char even at low heating rates.Keywords: Slow pyrolysis, Pore size distribution, large coal particles, Oxy-combustion, reactivity. RESUMENSe estudió la influencia de una atmósfera basada en CO 2 o N 2 sobre la estructura porosa y la microestructura de carbonizados de carbón obtenidos de la pirólisis lenta no isotérmica desde temperatura ambiente hasta 900 °C de dos carbones de diferente rango (Semi-Antracita (SA) y Bituminosos Alto en Volátiles tipo C (BAVC)), y de diferentes distribuciones de tamaño de partícula. Para todos los carbonizados se realizó la caracterización fisicoquímica (Análisis ultimo y próximo), la caracterización morfológica y estructural por combinación de técnicas como espectroscopia Rama, Microscopia electrónica de barrido por emisión de campo (FE-SEM), área superficial (BET -Brunauer-Emmett-Teller) y volumen y diámetro de microporos por mediciones de adsorción en CO 2 (Horvath-Kawazoe (HK) method). Se encontró que los parámetros cinéticos, las propiedades fisicoquímicas y la reactividad de los carbonizados de carbón son diferentes dependiendo de la atmósfera de pirólisis. También se determinó que para el carbonizado de carbón de SA, con un tamaño de partícula mayor de 0,7 mm, la superficie BET aumenta cuando la atmósfera se enriquece en CO 2 . Este efecto parece ser promovido por la interacción de diferentes procesos como las reacciones secund...

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Section: Correlation Between Structural Changes and Char Reactivitysupporting

confidence: 90%

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Valdés¹,

Guerrero²,

López³

et al. 2018

Ing. Inv.

View full text Add to dashboard Cite

show abstract

“…The same conclusion was reached in the study of Zhang et al. [100,101] Lievens et al [112] reported the structure of Inner Mongolia low-rank coal, concluding that its aromatic ring structures consisting of 59% amorphous structures (G L , G, G R , V L , and V R bands), 22% highly ordered structures with no less than six rings (D band), 16% aromatic structures characterized by aliphatic and/or ether substitutions (S L , S bands), and 3% substituted benzene rings (S R , R bands).…”

Section: Study Of Coal's Functional Groupssupporting

confidence: 83%

“…In recent years, some researchers [100][101][102][103][104][105][106][107][108][109][110][111][112] studied the structure of coal by using Raman spectroscopy and referring to the curve-fitting method by Li et al [53,86,87] Zhang et al [100,101] considered the structural changes of semicoke during the rapid pyrolysis of wood and low-rank coal at 600-1,200 C and got similar result of Li et al Wang et al [102] reported that the A…”

Section: Study Of Coal's Functional Groupsmentioning

confidence: 94%

Progress of Raman spectroscopic investigations on the structure and properties of coal

Xia

Wang

et al. 2020

J Raman Spectroscopy

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Raman spectroscopy is a nondestructive and in situ analytical technique that could provide information on the chemical structure and structural ordering of carbonaceous materials. Based on the E2g symmetric stretching vibration mode in the aromatic layers (G band, ~1,580 cm−1) and the defect structure in graphite (D band, ~1,350 cm−1), Raman spectroscopy has been used extensively to characterize the structural features of carbonaceous matters since 1970. Coal is a complex organic compound made up mainly by carbon showing characteristic Raman bands. This article reviews the application of Raman spectroscopy for coal structure characterization under room temperature, to determine its chemical structure, crystallite size, coal rank, and combustion reactivity. Future research for collecting Raman spectra during coal pyrolysis at high temperatures is also discussed. The combination of high‐temperature hot stage with Raman spectroscopy technology allows direct collection of Raman spectra at high temperature.

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“…Only four significant peaks were observed in ashes spectra. On the other hand, -CH 3 /-CH 2 Other authors [40] studied gasification of two low-range carbons, finding out similar spectra in the wavelength range of 1800-600 cm −1 . They suggested that during gasification process different kinds of functional groups with oxygen were formed (C = O bonds) which were mainly tied to aromatic rings such as phenolic groups, enhancing dipole moment of the vibration of aromatic rings and vibration intensity by the stretching of C = C bond in those aromatic rings.…”

Section: Ftir Analysismentioning

confidence: 85%

Thermal analysis of olive tree pruning and the by-products obtained by its gasification and pyrolysis: The effect of some heavy metals on their devolatilization behavior

Iáñez-Rodríguez

Martín-Lara

Blázquez

et al. 2019

Journal of Energy Chemistry

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Changes in nascent char structure during the gasification of low-rank coals in CO2

Abstract: 25

Cited by 38 publications

References 40 publications

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Progress of Raman spectroscopic investigations on the structure and properties of coal

Thermal analysis of olive tree pruning and the by-products obtained by its gasification and pyrolysis: The effect of some heavy metals on their devolatilization behavior

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