A thermodynamic model was developed to predict the limits of distribution of phosphates between the liquid and the solid phases in a reactor used for extracting phosphoric acid from phosphate rock by the dihydrate process. A computer code based on the model was generated to carry out different simulations of the process using several inputs of temperatures and liquid phase content of sulfates and phosphates.

Experimental data of equilibrium constants were regressed and included in the model obtaining a more accurate representation of the thermodynamic equilibrium. Results for ionic strength, solution acidity, and citrate soluble loss were used to analyze temperature and solution sulfates and phosphate effects on the system. In addition, experimental data of citrate soluble loss was used to adjust the activity coefficient of phosphoric acid by running the model at conditions analogues to the data.

Decreasing temperature and increasing sulfate levels was found to raise the acidity and the ionic strength of the solution as well as minimize the citrate soluble loss.

Extended Abstract Status: Not Uploaded