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Open AccessArticle

Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy

School of Energy and Power Engineering, Changsha University of Science & Technology, Changsha 410114, China
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Crystals 2019, 9(10), 513; https://doi.org/10.3390/cryst9100513
Received: 23 August 2019 / Revised: 24 September 2019 / Accepted: 30 September 2019 / Published: 2 October 2019
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite bands because of the relatively high silicates content. In contrast, the Raman spectra of raw coals show strong disordered carbon bands but no mineral bands since Raman spectroscopy is highly sensitive to carbonaceous phases. The overlapping bands of mineral components (e.g., calcite, feldspar, and muscovite) were successfully resolved by the method of second-derivative infrared spectroscopy. The results of infrared spectra indicate the presence of metakaolinite in coal ashes, suggesting the thermal transformation of kaolinite during ashing. Intense quartz bands were shown in both infrared and Raman spectra of coal ashes. In addition, Raman spectra of coal ashes show a very strong characteristic band of anatase (149 cm–1), although the titanium oxides content is very low. Combined use of second-derivative infrared spectroscopy and Raman spectroscopy provides valuable insight into the analyses of mineralogical composition. The XRD results generally agree with those of FTIR and Raman spectroscopic analyses. View Full-Text
Keywords: coals; coal ashes; minerals; second-derivative infrared spectroscopy; Raman spectroscopy coals; coal ashes; minerals; second-derivative infrared spectroscopy; Raman spectroscopy
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MDPI and ACS Style

Yin, Y.; Yin, H.; Wu, Z.; Qi, C.; Tian, H.; Zhang, W.; Hu, Z.; Feng, L. Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy. Crystals 2019, 9, 513.

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