A semi-empirical model for the electro-osmotic dewatering of slurries between fixed electrodes
Force and material balance equations were developed for the electro-osmotic dewatering of slurries between two fixed electrodes. It was assumed that the resistance to flow caused by the dewatered bed could be described in terms of Darcy's law for laminar flow. Specific cake resistances were extremely low due to the formation of channels through the dewatered bed. Owing to the complex particle-fluid interactions in the system, both the cake resistance and the electro-osmotic coefficient had to be estimated from experimental dewatering data and could not be predicted accurately from fundamental equations. Any change in the temperature of the system was accounted for by a change in the conductivities of the slurry and the dewatered bed. The temperature profiles were not predicted, but merely simulated by empirical equations. Independent measurements showed that the conductivity of the slurry increased linearly with temperature. The conductivity of the dewatered cake decreased linearly with temperature owing to the enhanced conversion of water to steam. Reasonable agreement was obtained between experimental data and model predictions of the rate of dewatering as well as the potential across the electrodes. Ultra-fine kimberlite and coal slurries were used at different electrode spacings and constant currents. © 1992.