Experimental Study on the Wettability of Tectonic Soft Coal in Huaibei Mining Area, China
Xiaoxue Liao, Liang Wang, Jintuo Zhu, Peng Chu, Qingquan Liu, Tao Yang
Abstract
This study investigated the wettability of tectonic soft coal by analyzing the relationship between proximate analysis indexes, oxygen-containing functional groups, pore characteristics, hardness, gas adsorption capacity, and contact angles. Results show that coal was more hydrophilic with the increase of gas adsorption capacity, moisture content, ash content, and the content of Si–O–Si functional groups and was more hydrophobic with the increase of the fixed carbon content and coal hardness, while the correlation between volatile matter and wettability was not obvious. The isothermal adsorption/desorption curves of coal obtained from a low-temperature nitrogen adsorption experiment show that the greater the number of open pores and the better the connectivity of pores, the better the coal wettability. The pore fractal characteristic was analyzed with respect to two aspects: the coal surface roughness represented by the surface fractal dimension D1 and the pore irregularity and complexity represented by the structure fractal dimension D2. The relationships between D1, D2, and the contact angle show that with the increase of D1 and D2, the coal wettability becomes better, which indicates that the rougher the coal surface and the more complex the pore structure, the better the coal wettability.