부산대학교 도서관

Strong interactive forces, namely, van der Waals forces and electrical double-layer repulsion, between the particles in a fine-particle slurry result in complex changes in their state of dispersion and aggregation that make it extremely difficult to accurately understand cake formation behavior and predict the filtration characteristics of fine-particle slurry. To investigate the effect of the particle dispersion/aggregation state on the cake filtration properties of fine particle slurry, we developed a coupled DEM-CFD simulation of cake filtration and performed filtration simulations of mono-dispersed and poly-dispersed silica slurry with a nominal particle diameter of 0.5 µm with the dispersion/aggregation state adjusted by zeta potential. From the cake formation behavior obtained from the simulation, we found that there was no reduction in the filtration rate until the porosity directly above the filter medium decreased to around 0.5–0.6. In fact, the filtration rate is believed to decrease with resistance due to the pore blockage of the filter medium. However, this suggests that even if particles covered 40–50% of the surface of the filter medium, the cake would result in hardly any resistance. We found that although the variation in flow resistivity in the cake was greater for particles in the aggregated state than in the dispersed state, the flow resistivity was smaller on average. This is thought to be because the porosity of the cake is higher when particles aggregate, and because the fluid selectively permeates the parts in the cake where resistance is low. By reducing this latter flow bias, it should be possible to reduce the cake resistance.