Innovative RTS technology for dry beneficiation of phosphate

Abstract

The Crago double flotation process is widely used for upgrading raw phosphate in Florida. However, it is a water-based physicochemical process and consumes a huge amount of water and chemicals and is not efficient to remove dolomite from phosphate. In addition, the final phosphate flotation concentrate often has a grade of 30-31% P2O5, which is below the BPL content of 75% (or 34.3% P2O5) required for making the animal feed grade phosphate. This study is performed to evaluate the potential and feasibility of the innovative rotary triboelectrostatic separator (RTS) as a dry phosphate beneficiation process. The RTS technology is characterized by an innovative high efficiency rotary charger, charger electrification, laminar air flow, independent control of charging and separation condition, low energy consumption, etc. Compared to conventional triboelectrostatic separators, the unique RTS technology offers multiple technical advantages: 1) increase particle charge density 4-6 times; 2) improve solids throughput by an order of magnitude; 3) enhance process efficiency by up to 70%; 4) reduce overall energy consumption by more than 80%. A laboratory scale prototype RTS unit has been used to investigate the effects of major process parameters on particle charging efficiency and phosphate separation efficiency for Florida phosphate samples. Experimental results have shown that the RTS technology upgraded a 10% P2O5 feed (16-35 mesh) to a 30% P2O5 concentrate with a P2O5 recovery of more than 85% and acid insoluble rejection of almost 90%; it also purified a flotation concentrate with 31% P2O5 to nearly 35% P2O5. RTS also significantly reduced MgO content from a pulverized high dolomite pebble sample.