Pilot-plant evaluation of a water insoluble hydroxamic acid collector for single stage flotation of Florida phosphate rock

Recent laboratory results have demonstrated that selective flotation of phosphate rock can be achieved in a single stage with improved separation efficiency when compared to the standard double float process. The new reagent chemistry is based on the use of a water insoluble alcoholic solution of alkyl hydroxamic acid as collector following a conditioning procedure similar to that currently used by the Florida phosphate industry. The effectiveness of the new collector chemistry has been demonstrated by the results from single stage bench scale flotation experiments for feed material from plants in Florida, North Carolina, and Utah. Now pilot plant testing at a feed rate of 700-900 lb/hr has been completed in order to evaluate the hydroxamic acid collector on a continuous basis. Results from the pilot-plant campaign confirm the findings from laboratory experiments. Single stage flotation recovery of 95% was reached with a concentrate grade of 32% P 2 0 5 for coarse feed material (16x35 mesh). Initial economic analysis of the new flotation chemistry with AERO 6493 shows a strong dependence on the reagent price. If the cost of AERO 6493 could be reduced to $1.80/lb, the single stage flotation of coarse phosphate with the alkyl hydroxamic acid/alcohol collector would be cost competitive with the traditional double float process using fatty acid and fuel oil.