As it settles, the supernatant water is recycled for use in the beneficiation plant. A top crust is formed after a few years, but the clay beneath the crust has a large water content and a pseudo-plastic character that limits the amount of weight the settling area can support. As much as 25 -50 years are needed to reach a solids content greater than 25 wt.%. Clay settling areas cover about 30-40% of the mined land. Uses for the land are limited by the properties of the clay that leave the settling areas unstable.
Methods that employ electrokinetic phenomena have been the subject of significant research as a possible means of accelerating the dewatering process. Previous research to develop batch electrokinetic dewatering processes resulted in the determination that the electrokinetic dewatering was not economically feasible. The objective of our work was to overcome the economic hurdle through the development of continuous electrokinetic dewatering (EKD).
The previous continuous design was a single unit in which a cake was formed in the horizontal section and the cake was dewatered in the slanted section. Separation of the single-unit process into two units yielded greater throughput, but the projected cost per metric ton of dry clay was not substantially lower than that of the previous prototype. The latest prototype consists of a single unit which accepts a 10 wt.% suspension as a feed and produces up to a 38 wt.% cake. As compared to our previous prototype, the new unit has improved the viability of industrial EKD by reducing both capital and operational cost through increased throughput, reduced materials cost, and improved clay-water separation efficiency.