Pilot-Scale Testing and Demonstration of Picobubble Enhanced Flotation of Phosphate for Increase Recovery and Reduced Reagent Consumption

The Florida phosphate industry generates up to 85% of the United St~tes phosphate roc~. In a typical central Florida phosphate beneficiation plant the phosphate o~e IS.was?ed ~nd classIfied into three major size fractions. The coarse + 1.18 nun (+ 16 mesh) portIOn IS pnmarIly phosph.ate pebbles and no further upgrading is needed. The fine -106 11m phosphate (-150 mesh) portIOn contains virtually all of the clay minerals and is discarded as the slimes due to lack of C?st effective beneficiation processes. The lost phosphate in the slime accounts for 20% to one thIrd of the matrix phosphate value. The intermediate -1.18 mm + 106 11m (-16 +150 mesh) portion is a mixture of quartz and phosphate minerals. Beneficiation of this size fraction is often accomplished using the "Craigo" two-stage froth flotation process. The flotation recovery of coarse flotation feed (-16 + 35 mesh) is often below 60%. The combined loss of phosphate in flotation tailings and fine phosphate slimes usually amounts to about 40% of the original phosphate value. The particle-bubble collision, attachment and detachment are the most critical steps in the flotation process. The low flotation recovery of fine particles is mainly due to the low probability of bubble-particie collision while the main reason for poor flotation recovery of coarse particles is the high probability of detachment of particles from bubble surface. The use of picobubbles in flotation can effectively increase the probability of collision and reduce the probability of detachment. In addition, the picobubbles produced on the hydrophobic particle serve as "collector", increasing its surface hydrophobicity and thus the probability of attachment. The increased probabilities of collision and attachment and the reduced probability of detachment result in enhanced flotation recovery of phosphate and reduced flotation reagent consumption. Laboratory column flotation results generated from a two-year FIPR supported project have shown that the introduction of picobubbles in flotation increased phosphate recovery by 10-30% and frother and collector dosages were reduced by one third to one half. The main goal of the proposed project is to conduct a pilot-scale investigation of the picobubble enhanced flotation technology for coarse and unsized phosphate flotation feed to achieve increased recovery and reduced reagent consumption. A flotation column with l' diameter and 5' height featured with a picobubble generator based on the hydrodynamic cavitation principle and a conventional bubble generator will be designed, fabricated, installed, tested, and evaluated for its technical and economic perfonnance. The on-site flotation tests will be conducted at the sites provided by the collaborating companies, i.e., Mosaic Phosphates and CF Industry. The results obtained from this project will be used to (1) validate at a pilot scale of about 2 t!h the technical perfonnance data obtained from the previous lab experiments; (2) ~ondu~t en~nee~ng evaluati.on of the process reliability and economic feasibility; (3) establish, IIIc~nJunc~lOn. WIth the earher lab test results, the scale-up criteria for a commercial unit; (4) pro~de g~l1delmes for operation of commercial units. A successful completion of the proposed project WIll demonstrate the technical and economic benefits and commercial viability of the picobubble flotation technology.