Power-Law Analysis of the Thermodynamics of Liquid-Phase Chemical Equilibrium: Application to CO2 Capture Solvents

Abstract

Liquid-phase chemical equilibrium has been quantitatively modeled for over five decades, and these models are used to simulate industrial processes involving electrolytes, including gas purification processes like gas sweetening, acid gas removal, and CO2 capture. The models are based upon chemical equilibrium in the liquid phase and an activity-coefficient approach for the excess Gibbs energy and, when combined with rate-based models for mass transfer and chemical kinetics, facilitate the development of powerful engineering tools to analyze and design industrial processes. Chemical solvents for CO2 capture have commonly been aqueous amines, but recently, water-lean solvents have been developed. In this work, power-law analysis is introduced to understand the differences in thermodynamic properties between aqueous amines and water-lean solvents. The power-law analysis is for the purposes of insight and understanding and is complementary to the rigorous model. The power-law approach is applicable to other cases of liquid-phase chemical equilibrium.