Rock phosphate, the primary raw material for fertilizer and phosphoric acid, occurs as high-grade ore (+30% P2O5), medium-grade ore (20%–30% P2O5), and low-grade ore (15%–20% P2O5). The very high-grade ore blends with medium-grade ore for direct sale. The high-grade ore is mined, crushed, and sold to various fertilizer plants. The low-grade ore is beneficiated by reverse/inverse flotation techniques.

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The low-grade ore is crushed/grinded to −74 μm size for liberation of phosphate, carbonate, and silica. The fine product is subjected to flotation after conditioning with fatty acid salt as collector and reduction of silica content in an alkaline circuit at the first stage. An addition of phosphoric and sulfuric acids in the second stage acts as Ph controller for the removal of carbonate in froths. The phosphate component is depressed in an acid environment, and moved to thickeners/filters/dryers to form a final concentrate at +30% P2O5 at an ore-to-concentration ratio of ∼2.5.