Graduation Year


Document Type




Degree Name

MS in Chemical Engineering (M.S.C.H.)


Chemical Engineering

Degree Granting Department

Chemical Engineering

Major Professor

J. Carlos Busot, Ph.D.

Co-Major Professor

Luis H. Garcia-Rubio, Ph.D.

Committee Member

Scott W. Campbell, Ph.D.


A thermodynamic model was developed based upon five equilibrium reactions to predict the limits of distribution of phosphates between the liquid and the solid phases in a reactor used to extract phosphoric acid from phosphate rock. A computer code was generated to carry out different simulations of the model using several inputs of temperatures and liquid phase sulfuric acid contents. Ideal Solution, Debye-Hückel, and Robinson-Guggenheim-Bates electrolyte activity coefficient models were employed alternately in each simulation to complete the thermodynamic model and the outputs were compared to one another.

Experimental data of equilibrium constants were regressed to adjust the values of ΔCp° and ΔH° used in the simulations to obtain a more accurate representation of the thermodynamic equilibrium. Results for ionic strength, liquid phase pH, and phosphate lattice loss were used to analyze temperature and liquid phase sulfuric acid content effects on the reacting system.

Completing the thermodynamic model with Ideal Solution and Debye- Hückel electrolyte activity coefficient models was found to bind all predictions of phosphate lattice loss. The model prediction of phosphate losses was found to give a lower bound to the real phosphate losses. Furthermore, decreasing temperature and increasing liquid phase sulfuric acid content was found to minimize phosphate lattice loss.