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Development and Pilot-Scale Demonstration of Deep Cone Paste Thickener for Phosphatic Clay Disposal: Phase II

02-177-244Final

Abstract

Florida’s phosphate production thus far has exceeded one billion tons, of which the principal by-product is a colloidal, high-plasticity clay occurring in similar quantities as the phosphate product. Efforts to solve the problems associated with phosphatic clay impounding have persisted for many years and include testing of mechanical, electrical, biological, and chemical processes. However, none of these disposal methods has proven cost-effective for consolidating phosphatic clays.

This project was intended to demonstrate an efficient, practical, and cost-effective process for rapid dewatering of Florida phosphate clays. This process, which employs the Eimco Deep Cone Paste Thickener, is designed specifically to thicken a mixture of phosphatic clay and tailings sand to a paste that can be used for backfilling of mined areas or for surface stacking rather than impounding the clay slurry above grade.

This project continues previous work performed by the University of Kentucky, and was conducted at CF Industries South Pasture Mine, located in Hardee County. This location was considered ideal for such a test, as the clays at the South Pasture Mine have demonstrated high plasticity, which correlates with poor settling and consolidation behavior.

Based on test results and process cost, a net present value of $15.2 MM over a 25-year mine life is expected.