Molecular simulation study on hydration of low-rank coal particles and formation of hydration film
Yangchao Xia 1
Zili Yang 1
Yaowen Xing 1
Xiahui Gui 1  
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China University of Mining and Technology
Xiahui Gui   

China University of Mining and Technology, No.1, Daxue Road, Nanhu Campus, China University of Mining and Technology, Xuzhou, Jiangsu Province, 221116 Xuzhou, China
Physicochem. Probl. Miner. Process. 2019;55(2):586–596
Water molecules in low-rank coal (LRC) significantly influence its upgrading and utilization. To investigate the hydration of LRC particles and the formation of a hydration film, molecular simulation techniques were innovatively used, including molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The adsorption of water molecules on LRC and various oxygen-containing groups was analyzed. The results show that water molecules adsorb close to the LRC surface and form a large overlapping layer at the LRC/water interface. The radial distribution functions (RDFs) show that the adsorption affinity of water molecules on oxygen-containing sites is stronger than that on carbon-containing sites, and the RDF peaks indicate the existence of a hydration film. Moreover, the differences in adsorption between various oxygen-containing groups depend on both the number of hydrogen bonds and the adsorption distances. The calculated binding energies indicate that the adsorption capacity follows the order carboxyl > phenolic hydroxyl > alcoholic hydroxyl > ether linkage > carbonyl. Experimental results show that a high sorption rate exists between water vapor and LRC samples at the beginning of sorption, which verified the simulation results.