Parametric study on the production of phosphoric acid by the dihydrate process

In this work a computer program has been developed to simulate a three-CSTR pilot plant leaching process of phosphate rock with sulfuric acid for the production of phosphoric acid and precipitation of calcium sulfate dihydrate as a byproduct. The simulation model has been examined with real experimental data obtained from the Jordan Phosphate Mines Company (JPMC), a phosphoric acid pilot plant at Rusaifa, Jordan. The predicted results are in very good agreement with the experimental data with a relative absolute error of less than 3.5%. A parametric study has been made to find the optimum operating conditions of the pilot plant for a given phosphate rock feed flow rate, chemical composition, and particle size distribution. The effect of varying reactor(s) temperature, sulfuric acid feed rate, agitator-impeller speed, ratio of slurry recycle to feed rate, and ratio of return acid to feed rate have been investigated. A reactor temperature of 80 degreesC, slurry recycle to feed ratio of 80, and return acid to feed ratio of 2.5 have been found to give best results. The optimum conditions for sulfuric acid feed rate and agitator speed are determined only from power limitations and economics of the plant itself. (C) 2001 Elsevier Science B.V. All rights reserved.