Application of DLVO Theory on the Interaction Forces for Rheology of Coal-Water Slurries

Based on the depletion of present fuel reserves in the world, many investigations are carried out for finding alternatives. Thus, coal-water slurries (hereafter CWS) is one of these alternatives that consists of finely dispersed coal particles suspended in water. A commercial CWS includes 55-70% fine coal, 25-40% water and 1% chemical additive [2] while these values are effective on the basic characteristics like viscosity, density and fluidity of mixtures that constitute their quality and selling conditions. As well known, the flow and the stability characteristics vary upon physical and physicochemical properties of coal suspensions, regarding volume fraction of solids, particle size, size distribution, temperature, concentration of salt and thus particle-particle interactions in mixture. Therefore, modeling of these interactions is significant for determining the relevant characteristics of suspensions by means of the movement of very fine particles dominated by surface forces [3]. In this manner, DLVO theory (Derjaguin-Landau-Vier-Overbeek theory) is the most commonly used assumption consisting of attractive London van der Waals and repulsive electrostatic double layer forces for modeling the colloidal dispersion stability. Figure 1 shows a typical potential energy vs. separation distance (h) for particle-particle interaction.