Experimental and Modeling Study of Vapor Liquid Equilibrium for a Methyldiethanolamine–CO₂–H₂S–Water Quaternary System Using Activity Coefficient Models with Corrected Equilibrium Constants

Abstract

The solubilities of CO2 and H2S mixtures in methyldiethanolamine aqueous solutions were investigated in the wide temperature range from 313.15 (absorption range) to 403.15 K (stripping range) using the static method. The values of equilibrium constants for amine protonation (K 1), activity coefficients (γ i ), and fugacity coefficients (Φ i ) were regressed from the newly obtained experimental solubility data to correct nonideality. In order to obtain the equilibrium constants for amine protonation, modified Kent–Eisenberg model was applied. Then, two kinds of activity coefficient models, the Deshmukh–Mather model and the electrolyte nonrandom two-liquid model, were applied to minimize the gaps between experimental data and predicted values with newly obtained equilibrium constants. In this study, six thermodynamic models were presented by combining (1) equilibrium model and (2) activity coefficient models. Based on the best fitted solubility results, the mole fractions of all electrolytes, the pH in the liquid phase, and the heat of absorption for CO2 and H2S were evaluated.

Effect of Blending Ratio and Temperature on CO2 Solubility in Blended Aqueous Solution of Monoethanolamine and 2-Amino-2-methyl-propanol: Experimental and Modeling Study Using the Electrolyte Nonrandom Two-Liquid Model

“…In this study, 11 equations (six equilibrium equations, four mass balances, and one charge balance) for 11 variables (four molecules, three cations, and four anions) were solved simultaneously using the successive (iterative) substitution method. 43 The relative tolerance was satisfied up to 10 −7 for all variables. The CO 2 concentration in the liquid phase was calculated using the phase equilibrium formula as shown below.…”

“…A number of parameters (binary parameters of electrolyte NRTL model, τ ij ) were regressed as minimizing SMAPE. Details of the NRTL model used in this study are included in our previous paper 43 and the Supporting Information of this paper. An in-house MATLAB model was used to solve the equilibrium equation, thermodynamic model (electrolyte NRTL), and parameter regression.…”

“…The solubility was measured over a wide range of temperatures (323.15−383.15 K) with three different blending ratios of MEA and AMP (9:21, 15:15, and 21:9 wt %), balanced with 70 wt % H 2 O. The successive substitution method 43 was used for calculating the mole fractions of all electrolytes using equilibrium, material, and charge balance equations. The gamma (activity)−phi (fugacity) approach was used for predicting the CO 2 partial pressure in the gas phase.…”

“…The electrolyte NRTL model, an activity coefficient model, was used for investigating the liquid-phase nonideality. The CO 2 partial pressure, liquid-phase concentrations for all components including carbamates, pH, and heats of absorption for all amine blending ratios, absorption/desorption temperatures, and CO 2 -loading conditions were obtained by using an in-house MATLAB model . Finally, the cyclic capacities of CO 2 (Δα CO 2 ) in the blended amine solutions were also determined for evaluating the CCS process performance.…”

The Ratio of Chemical and Physical CO2 Absorption Capacity in Triethanolamine and Methyl-diethanolamine Solution Systems

“…Idem et al stated that the energy consumed for solvent regeneration in an MDEA/MEA hybrid system was less than that consumed by an MEA system . In addition, there have been many works examining CO 2 solubility and its equilibrium in TEA and MDEA systems at various temperatures and CO 2 partial pressures, − and most of them primarily focused on increasing the overall CO 2 absorption performance of the systems. However, no studies have reported the quantitative individual amount of CO 2 chemically absorbed by amine and physically absorbed by water relative to the total absorption capacity, which can be calculated in TEA and MDEA systems.…”