Effect of the Impurities on the Phosphoric Acid Process

The element phosphorus plays key role in plants metabolism. It is widely used as fertilizer. This element is usually found in insoluble forms (Ca10(PO4)6F2). The solubilization in phosphoric acid (H3PO4) is a process widely used in fertilizer industry. The impurities in the phosphate exert significant influence on recovery and productivity phosphoric process, besides affecting the quality of products. The objective of this work is to analyze the influence of some of these main impurities (iron, aluminum and magnesium) in the production process of phosphoric acid. A referential methodology (induced crystallization) of phosphoric acid production was developed. Samples of igneous phosphate concentrate contaminated with iron, aluminum and magnesium were prepared for the experiments. The reaction control parameters were similar to an industrial operation of phosphoric acid dihydrate process. Reductions in conversions, increases in viscosity and density of phosphoric acid were observed with increasing presence of these impurities. In the filtration step was found increase in resistivity of the cake with the increase of the impurities content. The iron mineral element promoted an increase in induction time of crystals nucleation.