Experimental Study on the Wettability of Coal with Different Metamorphism Treated by Surfactants for Coal Dust Control

Abstract

Wet dedusting is the main coal dust suppression technique in coal mines, and coal wettability is the main factor affecting dust suppression efficiency. To investigate the main factors affecting the coal wettability and improve it, the coal–water contact angle was used as an index to characterize the coal wettability, and the wettability of six coal samples with different metamorphic degree was studied by analyzing the relationship between the physicochemical properties and the contact angle. To improve the coal wettability, the nonionic surfactant alkyl polyglycoside (APG), anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and polymer surfactant polyacrylamide (PAM) were applied to the coal samples. The results show that SDBS is the most effective surfactant to improve the coal wettability, followed by APG, while the application of PAM would lead to more hydrophobic coal. It is also found that the coal wettability shows a high–low–high trend with the increase in the metamorphic degree. The wettability of long flame coal is the strongest and that of gas coal is the weakest. Moisture is the main hydrophilic factor of coal, while 1,4-dimethylbenzene is the main hydrophobic factor. The main factors affecting the treatment effect of APG, SDBS, and PAM on wettability are the aromatic methylbenzene, hydroxyl, and hydroxyl content of coal, respectively. Therefore, according to the content of hydroxyl in different coals, an SDBS solution can be prepared to improve the coal wettability. For coal with a low hydroxyl content, a higher concentration SDBS solution could be needed.

Experimental and Molecular Dynamics Simulation Study for Preferring Coal Dust Wetting Agents

“… 10 , 11 To lower the surface tension and enhance the wettability of coal, wetting agents can be incorporated into water. 12 − 14 …”

“…During manufacturing and transportation of coal from mines, massive coal dust is produced, which causes pneumoconiosis in coal miners. − Pneumoconiosis is a preventable but incurable lung disease, which not only causes chest pain but also causes significant complications such as chronic cor pulmonale and respiratory failure. − Nowadays, the main dust removal method used in coal mines is spray dust removal. − Water is ineffective in wetting coal dust since its surface tension reaches 72.8 mN/m, while for coal, it is 45 mN/m at critical wetting. , To lower the surface tension and enhance the wettability of coal, wetting agents can be incorporated into water. − …”

Spreading Behavior and Wetting Characteristics of Anionic Surfactant Droplets Impacting Bituminous Coal

“…Due to the high surface tension of water (72 mN/m), it is often ineffective in the process of wetting the coal surface. To reduce the surface tension of water and improve its wetting efficiency, surfactants are often added to water …”

“…To reduce the surface tension of water and improve its wetting efficiency, surfactants are often added to water. 19 Most of the early studies showed that the wetting ability of water was significantly improved after the use of surfactants, which was conducive to improving the dust suppression effect. Fan et al 20 and Xu et al 21 found that the addition of a surfactant to water can promote the solution properties, reduce surface tension and the contact angle of the solution, increase the wettability of the solution to coal dust, and thus improve the dust removal efficiency.…”

“…To reduce the surface tension of water and improve its wetting efficiency, surfactants are often added to water. 19 …”