Equilibrium and Process Analysis Involving Carbon Capture and Storage

This thesis uses the Pitzer model to investigate the equilibrium of aqueous species formed after the absorption of CO2 by chemical solvents. Since the parameters in the Pitzer equations are unknown for some species involved in the equilibrium, new expressions that correlate the virial parameters in the Pitzer equations with the ionic radii and charges of the species are derived. Further, since some ionic radii are unavailable in the literature, new expressions are derived to estimate these unknown ionic radii. Furthermore, a case study involving MEA, DEA and NH3 is investigated using the expressions that correlate the parameters in the Pitzer equations with the ionic radii and charges. Finally, a mineral carbonation process involving NH3 as the chemical solvent is simulated in Aspen Plus, and this process aims to investigate the precipitation of calcium carbonate using the fly ash generated in power plants.
As a conclusion, the calculated activity and osmotic coefficients of the aqueous species obtained using the equations that correlate the virial coefficients in the Pitzer equations with the ionic radii and charges are in good agreement with the experimental data from the literature up to a temperature 150 °C. Likewise, the expressions derived to estimate the unknown ionic radii produces results that are in good agreement with the literature data. Furthermore, the case study involving MEA, DEA and NH3 shows that the correlating equations accurately predict speciation and partial pressures up to a solvent mass fraction of about 20%. Finally, a comprehensive analysis involving the conversion of the pure CO2 produced in the amine capture plants into a solid is presented, and as a result this new process is capable not only of reducing the electricity consumption of the MEA capture plant by about 18%, but also to produce a product that may be potentially reutilized in industry, namely the PCC.