Quantitative characterization of coal dust wettability based on ¹³C−NMR and FTIR

Improving the wettability of coal dust is commonly used for dust control in coal mines. The wettability of coal dust can be affected by various factors. This study aims to explore the quantitative relationship between coal dust molecular structure parameters and wettability at a micro level. We selected three samples with different coal ranks, which were labeled as the Shangwan nonstick coal (BN), Zhaolou gas-fast coal (QF), and Yangquan anthracite coal (WY) respectively, and were crushed to coal dust with a particle size of less than 200 mesh (74 μm). Three different types of surfactants, i.e., alkylphenol polyoxyethylene ether (OP-10), sodium diethylhexyl sulfosuccinate (rapid penetrant T), and hexadecyl trimethyl ammonium-chloride (1631), were used for wetting coal dust. Carbon-13 nuclear magnetic resonance (¹³C-NMR) and infrared spectroscopy (FTIR) tests were conducted to obtain the microscopic molecular structure parameters of the coal samples. Then the relativity between the contact angle and ¹³C-NMR structural parameters/FTIR structural parameters were analyzed via the SPSS software to determine the principal factors. Finally, quantitative characterization equations describing the relationship between the wettability and molecular structure parameters of the studied samples were established through multiple linear regressions. Results revealed that under the action of different surfactants, the main factors affecting the wettability of coal dust are different. These factors mainly include quaternary carbon (f_\textal^\text\textH), oxygen-connecting aliphatic carbon (f_\texta^\text\textP), and aromatic bridge carbon (f_\texta^\text\textB) in ¹³C−NMR experiments and the ester group (−COO−), ether group (−O−), and carbonyl group (C=O) in FTIR experiments. The quantitative characterization equations established in this study provide a micro insight to understanding the affecting mechanism of coal dust wettability, which could facilitate the selection of surfactants and improve the reduction efficiency of coal dust.