Anionic Rougher-Cleaner Flotation
The Crago process has been used almost exclusively for about 50 years to recover flotation concentrate from Florida phosphate ores. Although the process has been able to produce high-grade concentrate from all manner of feeds, relatively high costs were incurred because of the need for anionic reagents, sulfuric acid, and cationic reagents. The character of current and future phosphate ores indicates that reagent costs per ton of recovered product will continue to increase. A program to evaluate alternative flotation processes that use only anionic reagents was proposed by Jacobs and approved by the Florida Institute of Phosphate Research.
Of the six process options considered, four were selected for pilot plant testing. Flotation feed from three different mines was used in the comparative testing. The majority of the tests were performed with tap water; however, plant process water was used to compare the best anionic process options to the Crago process.
One of the anionic processes tested met the goals set for an alternative process. These goals were, relative to the conventional Crago process, to improve BPL % recovery by 2 to 4% and reduce reagent costs by 33%. The disadvantage of the anionic process is production of lower grade concentrates.