modeling aqueous electrolyte systems in CHEMCAD
Water. It's in almost every plant and system . . . if it's not in your process streams, it's likely in your utilities. If your process is defined by aqueous electrolytes, you've probably already been modeling or planning to model concentration, boiling point rises, precipitation, pH, and so forth.
CHEMCAD has both the modified NRTL and Pitzer thermodynamic systems built right in. They are available for calculation in any unit operation, including distillation columns. With mNRTL, you can run in apparent species or true species modes (we have a great discussion on the pros and cons of each in our help system, and we'd be happy to go over it with you). There are a significant number of common electrolyte species and electrolyte reaction data sets included with the program. If you don't have reaction equilibrium constants, CHEMCAD will estimate them from Gibbs free energy of formation for the electrolyte species, or you can regress from laboratory/experimental data.
Even if you don't have electrolytes in your process streams, you can still benefit from this feature: if you'll recall from a prior post on modeling utilities (here), there are economic benefits to analyzing your cooling water system. You can watch the buildup of carbonates or other salts, to determine optimal bleed/purge rates or timing for injection of cleaning chemicals.
To jump-start your next aqueous electrolyte modeling work, get in touch with us--we'd love the chance to help make your project a positive one!