Experimental study on the evolutionary characteristics of silicified coal functional groups during oxidation/pyrolysis

ABSTRACT

In order to study the influence of silicification on coal components and the spontaneous combustion of silicified coal and its functional group change characteristics, the coal components of silicified coal and nonsilicified coal were analyzed by proximate analyzer; the oxygen absorption capacity of silicified coal and nonsilicified coal was tested by coal spontaneous combustion tendency tester, the oxygen absorption of coal at room temperature can directly reflect the degree of spontaneous combustion of coal and the generation of related gases in the reaction process of low temperature and oxygen of silicified coal and nonsilicified coal was measured by temperature programmed experimental device; In situ diffuse reflectance Fourier transform infrared spectrometer was used to test silicified coal and nonsilicified coal in nitrogen and air atmosphere. The evolution characteristics of different chemical bonds in the process of coal oxidation were studied. The surface active group changes of two different coal samples under different gas conditions were obtained, and the oxidative spontaneous combustion characteristics of silicified coal were microscopically proved. The results show that the oxygen absorption of silicified coal is higher than that of nonsilicified coal. During the reaction of silicified coal with oxygen, with the increase of coal temperature, the amount of oxidation gas and pyrolysis gas, oxygen consumption rate and exothermic intensity are higher than those of nonsilicified coal; the changes of related functional groups were mainly manifested in the hydroxyl groups at the peak positions of 3697–3625 cm⁻¹ and 3624–3610 cm⁻¹, the methyl and methylene groups at the peaks of 2975–2915 cm⁻¹ and 2870–2845 cm⁻¹, the aromatic ring C = C double bond at the position of 1604–1599 cm⁻¹, the aromatics and the oxygen-containing functional groups at the spectral segment of 3060–3032 cm⁻¹. Thus, the transformation rules of the related microstructure of silicified and nonsilicified coal under two gas atmospheres were obtained. This study has key significance for revealing the characteristics of silicified coal oxidation at lower temperature.

KEYWORDS:

• Silicified coal
• functional groups
• coal spontaneous combustion
• infrared spectrum
• chemical bonds
• microscopic reaction characteristics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Key R&D Program of China (grant number2018YFC0808201); National Natural Science Foundation of China Youth Program (grant number 52004209); National Natural Science Foundation of China (grant numbers 51974240and52174198).