Enhancement of Dispersion and Stability of Coal Water Slurry via Structural Modification of Naphthalene Sulfonate Polymers

Coal water slurry (CWS) modified with traditional linear naphthalene sulfonate formaldehyde (NSF) polymers exhibited limited stability in long-haul pipeline transportation, because of low steric hindrance energy (V S ) between coal particles. To study the effect of structural modification of dispersant on the V S value, a branched multi-arm poly(sodium acryloyloxy-2-naphthalenesulfonate) (Ma-PANS) dispersant was synthesized by controlled/living radical polymerization (CRP), using vinyl monomer sodium acryloyloxy-2-naphthalenesulfonate (ANS) with triple functional groups as precursor. The making-slurry experiment results showed that the viscosity of Yulin CWS modified with Ma-PANS dropped 319 mPa·s, and its stability was remained at 100% after 30 days. The effects of the structural modification on adsorption amount, adsorption parameters and adsorption conformation were also analyzed by adsorption experiments and molecular dynamics (MD) simulations. The results showed that the specific conformation of Ma-PANS contributed to improving adsorption parameters. This reduced the diffusion rate of dispersant on coal surface, resulting in enhanced stability of slurry. Moreover, the numerical calculation results based on the extended Derjaguin-Landau-Verwey-Overbeek theory (eDLVO) showed that the enhancements on dispersion and stability were attributed to the structure of dispersant being changed from linear to multi-arm. The unique multi-arm structure brought significant increase in the V S value when impeding the approach among particles and disrupting flocculation, thus effectively enhanced dispersion and stability of CWS.