Effects of oxygen concentrations on the coal oxidation characteristics and functional groups
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Effects of oxygen concentrations on the coal oxidation characteristics and functional groups Yang Xiao1,2 · Tao Guo1 · Chi‑Min Shu3 · Qing‑Wei Li1,2 · Da‑Jing Li1 · Long‑Gang Chen1 Received: 30 September 2019 / Accepted: 19 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract To investigate the impact of oxygen for the feature parameters of the coal oxidation process, the coal samples were selected from mines of Liuhuanggou and Ewirgol in Xinjiang Province, China. TGA/DSC–FTIR was employed to conduct the coal mass, heat, and functional groups under oxygen concentrations of 3, 6, 9, 15, and 21 vol% from 30 to 950 °C. In the entire coal–oxygen reaction, the characteristic temperatures were divided into T1 (adsorption temperature), T2 (oxygen-adsorption mass-gain starting temperature), T3 (oxygen-adsorption mass-gain maximum temperature), T4 (ignition temperature), T5 (max mass loss rate temperature), and T6 (burnout temperature). The results indicated that with the decrease in oxygen concentration, the feature temperature point gradually transferred to the high-temperature area. The coal samples maximum exothermic temperature rose, the maximum exothermic power decreased, and the net thermal release decreased along the entire reaction process of coal sample. The feature temperature excursion of the coal–oxygen composite reactive incurred the hysteresis effect, which was obvious when the oxygen concentration was 3 vol%. Furthermore, the content of main functional groups of coal microstructure was the highest at T2, and the content gradually decreased with the temperature increase continuously. As the increase in oxygen concentration, the content of main functional groups increased. Among them, there was no considerable change in the hydroxyl content in the coal microstructure on the characteristic temperatures of 75, 140, and 350 °C. As the temperature rose to 140 °C, the content of main functional groups with a varying degree grew. When the temperature reached 350 °C, the oxygen-containing functional group began to decrease. Keywords TGA/DSC–FTIR · Coal–oxygen reaction · Characteristic temperature · Thermal release · Hysteresis effect
Introduction Fossil energy has played a pivotal role in human development [1–6]. However, the process of using fossil energy has brought about numerous problems that plague humans. Coal is the key fossil fuel, but spontaneous combustion is a serious disaster associated with coal mining. Coal spontaneous combustion (CSC) not only wastes resources, but also * Yang Xiao [email protected] 1
School of Safety Science and Engineering, Xi’an University of Science and Technology (XUST), 58, Yanta Mid. Rd, Xi’an 710054, Shaanxi, People’s Republic of China
2
Shaanxi Key Laboratory of Prevention and Control of Coal Fire, XUST, Xi’an 710054, People’s Republic of China
3
Department of Safety, Health, and Environmental Engineering, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan, ROC
pollutes the atmosphere [7–11]. In coal producing countries, for
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