Comparison of two electrolyte models for the carbon capture with aqueous ammonia

Post-combustion carbon capture is attracting much attention due to the fact that it can be retrofitted on existing coal power plants. Among the most interesting technologies is the one that employs aqueous ammonia solutions to absorb the generated carbon dioxide. The evaluation of such process requires the modeling of electrolyte solutions.

In this work two thermodynamic models for electrolyte solutions are compared against each other with respect to experimental data. They are the e-NRTL model and the Extended UNIQUAC model, both implemented in the commercial software Aspen Plus®1 (version 7.2). Subsequently, a simple absorption/regeneration layout is simulated employing both models and the process performances are compared.

In general, the Extended UNIQUAC appears to describe the experimental data for larger ranges of temperature, pressure and concentration of ammonia more satisfactorily. The energy performances computed with the Extended UNIQUAC models are less promising than with the e-NRTL model.