Rate-Based Modeling for Packed Absorption Column of the MEA–CO₂–Water System at High-Pressure and High-CO₂ Loading Conditions

Abstract

Pandya proposed the first steady-state rate-based model for the chemical absorption process in a packed column using the aqueous CO 2 −MEA system. Later several modeling studies are also reported based on Pandya's approach but limited to low pressure (≈1 bar) and low CO 2 loadings (<0.5 mol/mol). Recently, the interest in processing CO 2 -rich natural gas at high-pressure conditions has been increased. Therefore, in this study, the Pandya model is modified to simulate the packed absorption column using an aqueous CO 2 −MEA system for the high-pressure and high-CO 2 loading range. The sequential chemical reactions, along with the respective mass transfer resistances that occur at low (<0.5 mol/mol) and high (>0.5 mol/mol) CO 2 loadings, are added. This is achieved by theoretically segmenting the packed column into two sections. This strategy simplifies the computation of subsequent fast and slow reaction regimes that occur over a high-CO 2 loading range. The gas−liquid nonideal behavior is described using the Peng−Robinson (EOS) and Kent Eisenberg models. The developed model is effectively validated using the experimental data at low-(≈1.03 bar) and high-(50 bar) pressure conditions over a wide CO 2 loading range (≈0−1.0 mol/mol). In a parity plot between measured and simulated CO 2 concentration, R 2 is found to be 0.99 and 0.97, respectively, for the low-(≈1.03 bar) and high-(50 bar) pressure systems. This indicates that the proposed model can accurately predict the critical design parameters at the high-pressure and high-CO 2 loading conditions, with minimum computational intricacy.

A review of semi-empirical equilibrium models for CO2-alkanolamine-H2O solutions and their mixtures at high pressure

“…The equilibria in high pressure-low temperature region and relies solely on CO2-water equilibria and physical solubility of carbon dioxide. The latter effect can be corrected by dividing the model equation into two separate equations above and below the carbon dioxide loadings of 1 mole CO2/ mole solvent, as suggested for the rate based models [4]. For loadings less than 1 mole CO2/ mole solvent, the alkanolamine based equilibrium constants must be considered.…”

“…It is preferred over other technologies in low pressure applications due to its ease of operation and low capital costs and finding new applications for separation at high pressure [2]. The technique has been extended to investigate the removal of carbon dioxide from natural gas containing high amounts of carbon dioxide [3][4][5].…”

“…The solvent absorption pathway at high pressure is generally divided into chemical absorption and physical absorption regimes [4]. Hence, the thermodynamics and kinetics of the processes are quite different.…”

Rate-Based Absorption Modeling for Postcombustion CO2 Capture with Additively Manufactured Structured Packing

“…The Enhancement factor for an instantaneous reaction with partially loaded MEA may be defined from Danckwerts and from Weiland , where K eq represents the equilibrium constant for the termolecular reaction determined by the chemical equilibria of the reaction constants, K 1 –K 5 , D i is the diffusivity in aqueous MEA for components MEACOO – , MEA, and CO 2 , and CO 2 concentrations for the bulk, b , and for the interface, i . This instantaneous Enhancement factor, E ∞ , may then be used to estimate the Enhancement factor based on the expression from Wellek: Previous work has shown this Enhancement factor model to reliably predict packed bed absorber performance for reactions between CO 2 and MEA. , Use of this Enhancement factor is designated as Model 2.…”

“…Previous work has shown this Enhancement factor model to reliably predict packed bed absorber performance for reactions between CO 2 and MEA. 55,56 Use of this Enhancement factor is designated as Model 2. demonstrated the ability to incorporate coolant channels between corrugated structured packing sheets through additive manufacturing. 30−32 Both acrylonitrile butadiene styrene (ABS) plastic and aluminum materials were used for printing device-scale packing elements.…”