Abstract
The nitric acid concentration/sulfuric acid concentration (NAC/SAC) process has been widely used for concentrating dilute aqueous nitric acid and recovering spent sulfuric acid. Dilute nitric acid (65 to 80 wt %) is concentrated using sulfuric acid to bind water and break the nitric acid-water azeotrope at approximately 68 wt % nitric acid. To support heat and mass balance calculations and process simulation for NAC/SAC processes, we develop a comprehensive thermodynamic model for nitric acid-sulfuric acid-water ternary system based on previously published thermodynamic models of nitric acid-water and sulfuric acid-water binary systems with eNRTL equation. The ternary system model correlates well the isobaric vapor-liquid equilibrium data at one atmosphere and the water and nitric acid activities data at 273.15 K for the ternary. Contour plots of boiling points, vapor phase composition, and specific heat capacity of the ternary system, as well as a Merkel enthalpy-concentration chart are generated for engineering use.
Original language | English |
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Pages (from-to) | 3110-3117 |
Number of pages | 8 |
Journal | AIChE Journal |
Volume | 63 |
Issue number | 7 |
DOIs | |
State | Published - Jul 2017 |
Keywords
- boiling point
- electrolyte NRTL model
- heat capacity
- nitric acid
- nitric acid concentration/sulfuric acid concentration (NAC/SAC)
- sulfuric acid
- vapor-liquid equilibrium