Molecular Dynamics Simulation Study on the Microwetting Characteristics of Surfactants in Bituminous Coal

Coal mining has gradually extended deep, and coal dust disasters occur frequently under the condition of deep mining, which makes prevention and control difficult. The dust removal mechanism and technology are still one of the difficulties and emphases in the basic research of scientific and efficient dust removal in deep mining. Taking the raw coal collected from the Baozigou 9# coal seam as the research object, coal samples were analyzed by elemental industrial analysis, FT-IR, 13 C-NMR and XPS photoelectron spectroscopy, and the lowest energy molecular configuration of the bituminous coal aggregation state was constructed by Materials Studio. Three different ionic surfactants were selected, and two reagents were selected for each ionic surfactant. A surfactant/aqueous solution/bituminous coal system with the same concentration was constructed. The influence of different ionic surfactants on coal wetting was analyzed from the adsorption interaction energy and the mean square displacement diffusion coefficient of water. The results show that aromatic compounds in bituminous coal mainly exist in the form of naphthalene, and hydroxyl or ether oxy, carbonyl and carboxyl groups are the main oxygen-containing functional groups, accounting for 56.90%, 23.94% and 19.16%, respectively. The molecular structural formula of bituminous coal was determined to be C 165 H 128 O 10 N 2 S. The results of the molecular dynamics simulation show that the surface of coal is wetted by surfactant molecules through adsorption, the adsorption energy between the surfactant and coal is negative, and the order of absolute value is L-1>Y-2>L-2>F-1>Y-1>F-2. When three surfactants with the highest adsorption energy are mixed in pairs, the absolute value between them is Y-2+L-1. The distribution range of water molecules in the L-1+Y-2 system is the best, with a distance of 31-83 Å and a diffusion coefficient of 2.428×10 -5 cm 2 /s. The combination of zwitterionic surfactant MES-30 and anionic surfactant SDBS greatly improved the wettability of coal, indicating that it has the strongest wettability modification ability on bituminous coal surfaces