A DSC study on the impact of low-temperature oxidation on the behavior and drying of water in lignite
- 11 Downloads
Low-rank coals may undergo low-temperature oxidation and self-heating during mining, freightage, and handling. The oxidation of coal changes its structure which will be relected in the behaviour of coal water. A differential scanning calorimetry study was conducted to investigate the impact of low-temperature oxidation on the nature of water in a Chinese lignite and its drying behavior. The lignite sample was oxidized in the air at temperatures of 30–180 °C. The results showed that the lignite samples that underwent low-temperature oxidation did not contain any freezable bound water. It was found that the amount of non-freezable water in the oxidized samples reached the highest value of 67.38 mass% after oxidation at 80 °C. The Fourier transform infrared spectroscopy and the static sessile drop analysis results suggested that the concentration of oxygen functionalities and hydrophilicity of lignite samples peaked after oxidation at 80 °C, which in turn increased the tendency for the absorption of water as non-freezable water. It was also found that the types of water in the oxidized samples had a profound impact on its drying behavior, where free water showed higher drying rates compared with freezable bound water and non-freezable water. The coal sample pre-oxidized at 80 °C required higher energy for pre-drying compared with the raw coal, which was attributed to the higher proportion of non-freezable water after oxidation.
KeywordsLignite Low-temperature oxidation Freezable water Non-freezable water DSC
This study was supported by the National Natural Science Foundation of China (21476100 and 21676132).
- 26.Gaisford S, Kett V, Haines P. Principles of thermal analysis and calorimetry. London: Royal Society of Chemistry; 2016.Google Scholar
- 28.Höhne G, Hemminger WF, Flammersheim H-J. Differential scanning calorimetry. Berlin: Springer; 2013. p. 31–63.Google Scholar
- 43.Zhou G, Xu C, Cheng W, Zhang Q, Nie W. Effects of oxygen element and oxygen-containing functional groups on surface wettability of coal dust with various metamorphic degrees based on XPS experiment. J Anal Methods Chem. 2015;2015:8.Google Scholar