A mathematic model based on eDLVO and Lifshitz theory calculating interparticle interactions in coal water slurry

Abstract

The emission of CO2 can be greatly reduced by increasing the solid loading of coal water slurry (CWS) in the gasification industry. In this paper, a mathematic model based on eDLVO and Lifshitz theory is proposed to calculate the interaction between two coal particles and guide the preparation of CWS to increase the solid loading. Lifshitz theory is adopted to calculate the retardation Hamaker constant and van der Waals interaction, which has relatively wide applicability and less assumption. Equations of hydrophobic interaction and electrical double layer are properly simplified with assumptions. It is found that the low rank coal particles in dilute solution are difficult to cross the energy barrier to form aggregations, due to large electrical double layer repulsive interaction. While for bituminous coal, even in dilute solution, the particles will attract with each other. All the coal particles in high concentration CWS will naturally attract with each other to form aggregations, due to higher ion concentration that compressed the electrical double layer with lower absolute value of zeta potential. More energy is dissipated to break the aggregating structure, thus increasing the shear viscosity. Our model can be applied to explain and quantify the influence of ions and pH successfully. For SHH CWS with pH above 9.35, the viscosity of CWS is sharply reduced to 1/3 of original value, which is caused by the greatly increase of the absolute value of zeta potential, as quantified by eDLVO model.