A Representation of the Thermodynamic Properties of Sulfuric Acid and Oleum

 

Paul M. Mathias,^# Chau-Chyun Chen,^# Baisheng Zou,^* David L. Randolph III^* and Frank J. Doering^*

^#AspenTech, ^*Monsanto Envirochem

 

Sulfuric acid is the highest-volume industrial chemical and is thus industrially important.  Modeling of the sulfuric acid system poses significant scientific challenges because of the complex solution chemistry and the interactions between the ionic species and the molecular species in the liquid phase.  We have developed a model for the sulfuric acid system based upon the ElectrolyteNRTL model of Chen et al. (1979, 1982, 1986).  The model covers the range from dilute sulfuric acid and concentrated oleum.  The model provides a quantitative description of the vapor-liquid equilibrium (including the azeotrope that occurs for concentrated sulfuric acid) and liquid enthalpy and thus provides the basis for accurate simulations of sulfuric acid processes.  This presentation will present the scientific basis of the model and demonstrate how it is used in industrial process design.

 

References

 

Chen, C-C. and Evans, L. B., "A Local Composition Model for the Excess Gibbs Energy of Aqueous Electrolyte Systems," AIChE J., 32, 444 (1986).

 

Chen, C-C., Britt, H. I., Boston, J. F., and Evans, L. B., "Extension and Application of the Pitzer Equation for Vapor-Liquid Equilibrium of Aqueous Electrolyte Systems with Molecular Species," AIChE J., 25, 820 (1979).

 

Chen, C-C., Britt, H. I., Boston, J. F., and Evans, L. B., "Local Composition Model for Excess Gibbs Energy of Electrolyte Systems," AIChE J., 28, 588 (1982).