Insights into the Dispersion Mechanism of Microfine Coal Particles Modified with Naphthalene Sulfonate Formaldehyde Based on EDLVO Theory

Coalwater slurry (CWS) fuel prepared using microfine coal particleswith a size distribution of 1-10 mu m is a promising wayto cleanly utilize solid resources in engines, even catering a popularapplication for clean coal technology. In an attempt to address theproblems in coal aggregation in microfine coal water slurry (MCWS),dispersants are used to improve the dispersing status of microfinecoal particles. Based on the experimental results and extended Derjaguin-Landau-Verwey-Overbeek(EDLVO) theory calculations, the role of naphthalene sulfonate formaldehyde(NSF) in MCWS performance was explored. The measurement of the slurryability of microfine coals demonstrated that the apparent viscosityand yield stress of MCWS were decreased significantly with 1.5% NSFaddition, which was consistent with the saturated adsorption valueof NSF on microfine coals. Furthermore, the zeta-potential andcontact angle of microfine coals were both decreased as a functionof the NSF dosage, indicating that a larger electrostatic repulsionforce and better wetting ability of the coal surface would be obtainedin the presence of NSF. The thickness calculation results showed thatthe thickness is increased with NSF addition, which is attributedto that the NSF molecule extends into the surrounding solution toform a hydrophilic film. The EDLVO calculations illustrated that thetotal interaction was turned from an attractive force into a repulsiveforce in the case of NSF, noting that the better dispersion of microfinecoals mainly resulted from the better hydrophilicity of the coal surfacemodified with NSF. The findings might provide guidance for MCWS preparationby revealing the interaction mechanism of microfine coals modifiedwith NSF.