(664d) A Molecular-Based Screening Tool for Water-Free Amine Solvents for CO2 Capture
AIChE Annual Meeting
2019 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Thermodynamics Needs of the Chemical Industry
Thursday, November 14, 2019 - 9:10am to 9:35am
In this contribution, we demonstrate the capabilities of a robust molecularâbased framework for the description of key thermophysical properties of water-free and water-lean amine-based solvents for the efficient removal of CO2 and other acid gases from industrial gas streams at relevant gas separation process conditions. The screening tool is built on the molecular-based equation of state (EoS) soft-SAFT  combined with the Free-Volume Theory for the integrated modeling of phase behavior, enthalpies, densities and viscosities. Solvents investigated in this work include mixtures of various alkanolamines with different physical solvents such as alcohols, glymes, glycols, polar aprotic solvents and ionic liquids (ILs). Molecular parameters of all the investigated substances are either taken from previous contributions or developed in this work and used here in a transferable manner for describing the solubility of CO2 in the selected solvents at conditions of relevance for industrial applications.
The description of the chemisorption of CO2 in the studied amine + physical solvent blends is done in a consistent manner with that for the chemisorption of CO2 in aqueous amine reported in our previous contributions [2,3]. A scheme of implicit reactions is used to describe the formation of carbamate and/or bicarbonate products resulting from the chemical reactions between CO2 and the examined amines. The influence of the organic solvents on the chemical reactivity of amines with CO2 in water-free solvents is investigated in detail. This procedure eliminates the need to specify the detailed equilibrium reactions and significantly reduces the number of parameters required to represent the absorption process. A maximum of two adjustable model parameters, optimized for a fixed amine concentration, suffice to represent the absorption of CO2 in the studied solvents over a broad range of conditions, with high predictive and extrapolative capabilities. The acquired results from our the developed thermodynamic framework are compared to experimental data gathered from literature and predictions from the recommended thermodynamic models implemented in the Aspen Plus® (V.10) process simulator and the model found to be capable of providing reliable solubility estimations over a broad range of pressure, temperature and compositions.
The collection of these results demonstrates that once the robust molecular model is developed and validated, it can be used as a predictive tool, combined with macroscopic thermodynamics, as a reliable platform for the screening of chemical solvents as function of key process parameters, and as a valuable tool for process modelling and optimization.
This work is partially funded by the ADNOC Gas Processing and its stakeholders through the Gas Research Center (project GRC2018-003) and Khalifa University of Science and Technology (RC2-2019-007).
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