(204x) Viscosity Prediction of the Carbon Dioxide Loaded Aqueous Solutions of Alkanolamines: Thermodynamic Approach

Naser S. Matin, Joseph E. Remias and Kunlei Liu

Center for Applied Energy Research, University of Kentucky, Lexington, KY 40511, United States

The aqueous solutions of alkanolamines are well known for absorption of acid gases in natural gas processing and for post-combustion CO₂ capture. In order to have proper interpretation of reaction kinetics and transport properties of the absorption process, accurate knowledge of the system physico-chemical properties such as solution surface tension and viscosity are needed for determination of heat and mass transfer in the system. In the CO₂ loaded aqueous solution of alkanolamines viscosity is a strong function of the type and concentration of amine and of CO₂ loading. Because of significant impact of the solution viscosity on process performance, having a good method for solution viscosity prediction, especially for different solution compositions and CO₂ loadings is important [1-6]. In this study a comprehensive predictive model for liquids viscosity were employed to encompass the effects of temperature, pressure, and solution composition. A method based on the absolute-rate theory has been used and tested for estimation of the dynamic viscosity of CO₂ loaded aqueous solutions of a representative amine-monoethanolamine (MEA). In the approach employed in this work, the activation free energy of the solution estimated through electrolyte NRTL model, and subsequently the dynamic viscosity of the electrolyte CO₂:MEA:H₂O system is predicted. Different concentrations of the aqueous MEA solutions at the temperature ranges from 40 to 70^oC, and the CO₂ loadings from 0.1to 0.5 mole CO₂ per mole amine were selected for model investigation. According to this methodology, having a reliable thermodynamic model for a selected solution, and using the absolute-rate theory approach the viscosity of the strong electrolyte solution such as CO₂ loaded alkanolamine solutions at different solution concentrations, temperatures, CO₂loadings, and operating pressures can be estimated.

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