Analysis of Thermal Behavior of Crystalline Minerals in Bituminous Coal Samples under Air and Argon Atmospheres

Tadanori Hashimoto; Kentaro Takai; Hung Viet Quang Nguyen; Masakatsu Nomura; Atsushi Ishihara

doi:10.1021/acsomega.0c04311

Analysis of Thermal Behavior of Crystalline Minerals in Bituminous Coal Samples under Air and Argon Atmospheres

ACS Omega. 2021 Jan 5;6(2):1197-1204. doi: 10.1021/acsomega.0c04311. eCollection 2021 Jan 19.

Authors

Tadanori Hashimoto¹, Kentaro Takai¹, Hung Viet Quang Nguyen^{1

2}, Masakatsu Nomura³, Atsushi Ishihara¹

Affiliations

¹ Division of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Kurima Machiya-Cho, Tsu-City, Mie 5148507, Japan.
² Center of Severe Materials and Environment, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cay Giay, Hanoi 10072, Vietnam.
³ Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.

Abstract

The thermal behavior of ash components in two bituminous coal samples [Upper Freeport (the "UF") and Illinois #6 (the "IL")] was investigated under air and argon atmospheres in the temperature range of 800-1200 °C using thermal gravimetric-differential thermal analysis, X-ray diffraction transmission electron microscopy (TEM), and TEM-energy dispersive X-ray spectrometry measurements. The UF treated under air formed the needle-like crystals which were assumed to be mullite-related substances formed by transformation of andalusite, because the crystals are mainly composed of SiO₂ and Al₂O₃. In contrast to the UF, the IL did not generate such crystals; however, when the IL was treated under air after carbonization under Ar, crystals appeared. The composition of the UF with an Al/Si ratio higher than that of the IL favored the formation of mullite-related substances, while the presence of lime in the IL inhibited the formation of mullite-related substances. Oldhamite was formed by the reaction of lime with sulfur at the carbonization of the IL under Ar and remained even at the successive air treatment. As lime was consumed, the formation of mullite-related substances was ceased to be inhibited under air after Ar treatment.