Innovative RTS Technology for Efficient Separation of Dolomite from Phosphate

The Crago double flotation process is widely used for upgrading raw phosphate in Florida. While this process is efficient for removing siliceous impurities from phosphate, it is not effective to reject dolomite from phosphate. Tremendous efforts have been made to enhance dolomite separation from phosphate using a variety of processes, including flotation schemes specially designed for dolomite removal, scrubbing, selective grinding, heavy medium separation, calcinations-digestion, etc. But none of these processes are capable of reducing the dolomite to less than 1% without a significant loss of phosphate. The innovative rotary triboelectrostatic separator (RTS), recently patented by the proposer, is characterized by an innovative high efficiency rotary charger, charger electrification, independent control of charging and separation condition, 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%. This technology has been demonstrated to be able to reject siliceous impurity from phosphate very effectively. For example, it upgraded a raw phosphate feed to a 30% P2O5 concentrate with about 90% P2O5 recovery and 85% acid insoluble rejection in one stage. Recent fundamental studies have strongly indicated that this technology will be more effective for separating dolomite from phosphate. The proposed project is aimed at developing and evaluating the RTS technology for effective separation of dolomite from phosphate. A systematic study of the proposed technology will be performed using a lab scale prototype RTS unit to investigate the effects of major process parameters on separation efficiency. A series of statistically designed tests will be carried out to identify optimum conditions for maximum dolomite rejection and determine interactions between different process parameters. Fundamental studies such as charge measurements with phosphate, quartz and dolomite will be conducted to better understand the RTS separation performance and expedite process optimization. In view of the fact that phosphate pebble contains highest dolomite content but if the dolomite content in flotation concentrate can be reduced to 0.5-0.6%, the pebble may be blended with the flotation concentrate to produce a final product with less than 1% dolomite, both pebble (after grinding) and flotation concentrate will be tested in the project and a better approach will be recommended after comparative data analysis. Concerns about the sample drying cost are addressed with a description of state-of-the-art technologies that reduce energy consumption by 80-90%.