Analysis of the K2CO3-NH3 Solvent Properties for Carbon Capture Applications

Absorption-based systems that typically employ amines such as monoethanolamine (MEA) are in commercial use for scrubbing CO2 from industrial flue and process gases. However, many challenges must be overcome when applying amine-based technology for the treatment of pulverized coal-fired power plants such as toxicity, degradation, high energy consumption associated with regeneration of the solvent, low regeneration pressure and cost of the chemicals. Other solvents such as aqueous solutions of ammonia (NH3) (Chilled Ammonia Process) and aqueous solution of potassium carbonate (K2CO3) are mature non-amine alternatives to the state-of-the-art MEA technology. Technology based on NH3 is capable of capturing CO2 at high loadings compared with MEA-based technology. In addition, NH3-based technology can strip CO2 at high pressure, thereby reducing CO2 compression costs and it has a kinetic of absorption comparable to the amine technologies at temperatures around 25°C. However, this process requires gas washing to reduce the NH3 emissions in the scrubbed flue gas [1-2]. The K2CO3-based process has lower regeneration energy requirements and no emission issues. However, it has a low kinetic of absorption, a very low loading capacity, and low-pressure of CO2 regeneration. Both the solvents (NH3 and K2CO3) have no problems of degradation and toxicity and they have low costs compared to the amines [3]. The aim of this work is the study of the thermodynamic properties and the kinetic of absorption of the mixture between the NH3 and K2CO3 in the same solvent in order to investigate a solution with low heat duty of regeneration reducing the ammonia slip and maintaining a higher regeneration pressure [4]. The novelty is the analysis of the thermodynamic and the kinetic of absorption of the Mixed-salt Technology solvent for the carbon capture application applied on the pulverized coal-fired exhausts with 13% of CO2 concentration. The thermodynamic analysis of the properties is conducted with the Extended UNIQUAC thermodynamic model proposed by Thomsen and Rasmussen [5] in its new version calibrated with both the experimental data of the ternary systems NH3-CO2-H2O and K2CO3-CO2-H2O, while the kinetic of absorption is studied experimentially with the Wetted Wall Column.