Interactions of coal pitch with amphoteric polycarboxylate dispersant in coal pitch–water slurry: Experiments and simulations

As the main by-product of coal tar processing, large amounts of coal pitch (CP) are insufficiently utilized. In this study, to realize resource utilization, CP was used to prepare coal pitch–water slurry (CPWS) fuels with the addition of three amphoteric polycarboxylate dispersants (AAD-1, AAD-2, AAD-3). The effects of dispersants on the slurry characteristics were studied. The adsorption of dispersant and the surface properties of CP were also analyzed. Results showed that the AAD-2 with a moderate side-chain length had a better ability to increase the stability and reduce the apparent viscosity of CPWS than others. When the dosage of AAD-2 was 0.5 wt%, the maximum slurry concentration was 53.7 wt%. The adsorption behaviors of three dispersants could be fitted well by the Freundlich model, and the adsorption quantity of AAD-2 was greater than that of two other dispersants. The Zeta potential and wettability of CP were improved to the greatest for AAD-1. To explore the dispersion and stabilization mechanisms, the molecular dynamics simulation and extended DLVO theory were used to discuss the interactions between CP and dispersants, the interaction energy among CP particles. Results showed that the adsorption energy of AAD-2 with CP was the most prominent (-1520.29 kJ/mol), the mobility of water molecules was reduced. Furthermore, in the CPWS with AAD-2, the total interaction energy ΔET was more significant than that of other slurries, which was due to the larger steric hindrance energy from AAD-2. In sum, this research provided an experimental and theoretical basis for preparing slurry with CP and polycarboxylate dispersant.