Studying effects of solid structure evolution on gasification reactivity of coal chars by in-situ Raman spectroscopy

Yu, Junqin; Guo, Qinghua; Ding, Lu; Gong, Yan; Yu, Guangsuo

doi:10.1016/j.fuel.2020.117603

Cited by 58 publications

(23 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The area ratio of D1 band to G band (D1/G ratio) was usually used to quantitatively characterize the order degree of carbon structure of sample. The intensity ratio D1/G decreased during CO 2 gasification indicating the increase of the graphitization in the char, possibly due to the preferential reaction of CO 2 with D1‐type carbons 28 . Meanwhile, the trend was unclear in the case of H 2 O gasification showing the different pathways for the CO 2 and H 2 O gasification reactions.…”

Section: Resultsmentioning

confidence: 99%

Kinetic and structural changes during gasification of cashew nut shell char particles

Nguyen

Khuong

et al. 2020

Env Prog and Sustain Energy

View full text Add to dashboard Cite

Cashew Nut Shell (CNS), an abundant waste from the cashew nut production, could become a promising material for gasification. Nevertheless, engineering data regarding this technology is still small and fragmented. In this study, the evolution of the char textural properties during gasification, as well as the effect of operating conditions on char gasification kinetics were extensively investigated and quantified. The textural properties of cashew nut shell char changed significantly following different pathways between CO2 and H2O gasification. Micropores and mesopores were well developed along with the conversion in the case of H2O gasification instead of only micropores in the case of CO2 gasification. Regarding char gasification kinetics, an increase of the temperature from 800 to 1000°C enhanced five times the conversion rate under an H2O atmosphere and 15 times under a CO2 atmosphere. The conversion rate increased two times when the concentration of reacting gases changed from 20 to 60 vol % for both atmospheres. Similarities in terms of gasification kinetics between CNS chars and wood chip chars were found in this range of operating conditions.

show abstract

Section: Resultsmentioning

confidence: 99%

Kinetic and structural changes during gasification of cashew nut shell char particles

Nguyen

Khuong

et al. 2020

Env Prog and Sustain Energy

View full text Add to dashboard Cite

show abstract

“…The G band corresponds to the stretching mode of the C=C alkene bond found on perfect single crystal graphite, while the D1 band indicates large sp 2 bonding of more than six aromatic carbon atoms being presented as in-plane graphite lattice flaws. Detailed analysis concerning the position and origin of the aforementioned bands is well described in literature [54,[57][58][59]. D band is ascribed to the disordered structure of carbonaceous matter, while G band is associated with the vibrations of aromatic rings (graphite lattice) presented at varying intensities in highly or less ordered carbonaceous structures [42,[51][52][53][54][55][56].…”

Section: Raman Analysismentioning

confidence: 96%

CO2 Gasification Reactivity and Syngas Production of Greek Lignite Coal and Ex-Situ Produced Chars under Non-Isothermal and Isothermal Conditions: Structure-Performance Relationships

et al. 2022

View full text Add to dashboard Cite

The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO2 gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at 500 °C (LG500), and carbonization at 800 °C (LG800). Physicochemical characterization studies, including proximate and ultimate analysis, X-ray Diffraction (XRD), and Raman spectroscopy, revealed that the thermal treatment under inert atmospheres leads to chars with increased fixed carbon content and less ordered surface structures. The CO2 gasification reactivity of pristine LG and as-produced chars was examined by thermogravimetric (TG) analysis and in batch mode gasification tests under both isothermal and non-isothermal conditions. The key parameters affecting the devolatilization and gasification steps in the overall process toward CO-rich gas mixtures were thoroughly explored. The gasification performance of the examined fuels in terms of carbon conversion, instant CO production rate, and syngas generation revealed an opposite reactivity order during each stage. TG analysis demonstrated that raw lignite (LG) was more reactive during the thermal devolatilization phase at low and intermediate temperatures (da/dtmax,devol. = 0.022 min−1). By contrast, LG800 exhibited superior gasification reactivity at high temperatures (da/dtmax,gas. = 0.1 min−1). The latter is additionally corroborated by the enhanced CO formation of LG800 samples under both non-isothermal (5.2 mmol) and isothermal (28 mmol) conditions, compared to 4.1 mmol and 13.8 mmol over the LG sample, respectively. The pronounced CO2 gasification performance of LG800 was attributed to its higher fixed carbon content and disordered surface structure compared to LG, LG300, and LG500 samples.

show abstract

“…The band area ratios of the D1, D3 and D4 to the G (denoted as ID1/IG, ID3/IG and ID4/IG) and the G band relative to the integrated area under the spectra (denoted as IG/IAll) of each sample are shown in Table 4. Compared with the RCs, the ID1/IG of the AFC chars increased, indicating that the acid pickling removed the ash is not conducive to the orderly development of RCs [31]. The ratios of ID3/IG and ID4/IG of AFC chars were less than those of the RC chars, which was due to the hydrolysis of small aromatic structures to aromatic C=C and some aliphatic groups to C-O in phenols, alcohols, ethers and esters bands, decreasing the relative contents of sp 2 and sp 2 -sp 3 bonding carbon atoms in AFC chars.…”

Section: Raman Spectra Analysismentioning

confidence: 97%

Influences of Ash-Existing Environments and Coal Structures on CO2 Gasification Characteristics of Tri-High Coal

et al. 2020

View full text Add to dashboard Cite

Two kinds of tri-high coals were selected to determine the influences of ash-existing environments and coal structures on CO2 gasification characteristics. The TGA results showed that the gasification of ash-free coal (AFC) chars was more efficient than that of corresponding raw coal (RC) chars. To uncover the reasons, the structures of RCs and AFCs, and their char samples prepared at elevated temperatures were investigated with SEM, BET, XRD, Raman and FTIR. The BET, SEM and XRD results showed that the Ash/mineral matter is associated with coal, carbon forms the main structural framework and mineral matters are found embedded in the coal structure in the low-rank tri-high coal. The Raman and FTIR results show that the ash can hinder volatile matters from exposing to the coal particles. Those results indicate that the surface of AFC chars has more free active carbon sites than raw coal chars, which are favorable for mass transfer between C and CO2, thereby improving reactivity of the AFC chars. However, the gasification reactivity was dominated by pore structure at elevated gasification temperatures, even though the microcrystalline structure, functional group structure, and increase in the disorder carbon were improved by acid pickling.

show abstract

Studying effects of solid structure evolution on gasification reactivity of coal chars by in-situ Raman spectroscopy

Cited by 58 publications

References 34 publications

Kinetic and structural changes during gasification of cashew nut shell char particles

Kinetic and structural changes during gasification of cashew nut shell char particles

CO2 Gasification Reactivity and Syngas Production of Greek Lignite Coal and Ex-Situ Produced Chars under Non-Isothermal and Isothermal Conditions: Structure-Performance Relationships

Influences of Ash-Existing Environments and Coal Structures on CO2 Gasification Characteristics of Tri-High Coal

Contact Info

Product

Resources

About