Electrokinetic Dewatering System that Effectively Removes Water from Phosphatic Clay Slurries

An Applied Low Voltage Electrical Field Enhances the Rate of Clay Dewatering, Hastening Clay Settling Pond Land Reclamation

Continuous operation of this electrokinetic dewatering system removes water from phosphatic clay suspensions, thereby achieving clay cake solid contents approaching 25 percent more rapidly than other methods. In Central Florida, the quantity of clay settling ponds covers more than 150 square miles, taking up approximately 40 percent of the phosphate mining land mass. Drying these clay settling ponds requires decades, and even then the clay remains too soft to build upon. Both the need to reduce the land area required for clay suspension storage and water usage in the mining operations has spurred the search for enhancing solids-liquid separation. Researchers at the University of Florida have developed a method that applies an electric field to slurries, thereby greatly enhancing the removal of water from the phosphatic clay. This process speeds up the separation of water and clay solids without the use of chemicals. This important attribute will allow potential future technologies the ability to more effectively recover the residual phosphate entrained in the clay matrix.

Application

An electrokinetic dewatering system for extracting water from phosphatic clay suspensions more quickly than traditional gravity settling alone

Advantages

• Continuous dewatering system minimizes energy requirements and, since no flocculating agents are needed, reducing reclamation costs
• Produces denser clay in less time, increasing the probability that clay settling areas can be reduced, reused, or repurposed more rapidly
• May be applicable to other processes that generate large quantities of dilute waste suspensions, broadening its field of use

Technology

The electrokinetic dewatering system includes a continuous slurry influent flow, a region for cake formation and cake dewatering, electrodes, and conveyor belts. Subjected to a uniform electric field, the dispersed particles in the influent migrate toward the conveying belt, where they form a layer of thickened clay or cake before being transferred to the cake dewatering zone, where water is further removed via electro-osmosis. The cake continues to thicken to a solids content of more than 25 weight percent and can then be collected for further drying and/or disposal. The separated water can be clarified and recycled to the beneficiation plant.