Abstract
The present investigation is aimed at finding the reason for the anomalous increase in viscosity of coal water mixtures (CWMs) in the higher temperature range (>150°C). The ζ-potential of coal particles in the higher temperature range was measured with the addition of six kinds of surfactants. The experimental results showed that the ζ-potential of Wallarah coal with anionic surfactants still show negatively higher values in the higher temperature range; thus it was expected that no significant desorption of anionic surfactants occurs. Furthermore, from considerations based on the DLVO theory it was concluded that the temperature dependence of the dielectric constant of water affects the coagulation of coal particles.
