Influence of Poly(ethylene oxide) 400 (PEG400) on the Absorption of CO₂in Diethanolamine (DEA)/H₂O Systems

Abstract

An experimental device coupling vaporÀliquid equilibrium (VLE) measurements and liquid phase analysis by Fourier transform infrared (FTIR) spectroscopy has been used to study the absorption of CO 2 in water/diethanolamine (DEA)/ poly(ethylene oxide) 400 (PEG400) systems. The concentration of the molecular form of absorbed CO 2 and the evolution of the carbamate species are measured with the IR spectroscopic method. The partial pressure of carbon dioxide and the liquid phase speciation have been determined at T = 298.1 K for various PEG400 concentrations (with a mass fraction ranging from 0 to 0.3), the mass fraction of DEA being 0.3. At fixed pressure, the CO 2 solubility decreases for increasing PEG400 concentrations, which expresses the decrease in solvent polarity. For a given loading and at constant concentration of DEA, the CO 2 molecular concentration increases with the PEG400 concentration increase, whereas the ion repartition is not significantly influenced by the solvent composition. ' INTRODUCTIONAcid gas absorption is an important step of the natural gas treatment process. It generally involves alkanolamine as the chemical solvent. Most of the new gas sources contain high quantities of acid gases, and the thermodynamics modeling currently used are not accurate enough for a realistic representation of these high loaded systems needed for the optimization of the industrial process. The water/amine/acid gases systems are characterized by the presence of numerous chemical species, most of them being ions. In the case of the water/diethanolamine (DEA, IUPAC name: 2,2 0 -iminoethanol) /CO 2 system, the involved equilibria are the following:Carbon dioxide hydrolysis :Hydrogen carbonate hydrolysis :Carbamate formation : ðC 2 H 5 OHÞ 2 NH þ HCO 3To adjust the parameters of the model, solubility data are generally used. The concentration of the species produced by the reactions between DEA and acid gas can only be calculated by the model, without any assurance about its accordance with real values. Nevertheless, these data are important, especially if the model is used in connection with the representation of the absorption kinetics. Therefore, a realistic model can be obtained only if the database used for the determination of parameters model includes values related to the liquid phase speciation. We wish to present herein the development of an original device that combines a Fourier transform infrared (FTIR) spectroscopy analysis of the liquid phase with a vaporÀliquid equilibrium (VLE) measurement. This kind of apparatus has been used previously for studying water/DEA/CO 2 systems. 1 The major disadvantage of traditional solvents containing water and alkanolamines is the very high energy needed for their regeneration. That is why new solvents are developed by adding a physical solvent to the chemical previous ones. The regeneration energy cost is then lowered. 2 In a previous work, we studied the influence of methanol on the absorption of CO 2 in water/DEA systems. 3 In this work, we wish to extend this type...

Inline Monitoring of CO2 Absorption Processes Using Simple Analytical Techniques and Multivariate Modeling

“…Using FTIR for the in situ analysis of aqueous alkanolamine solutions has first been applied aiming at more accurate vapor-liquid equilibrium data for such systems. So far, this technique has been applied to equilibrium measurements of aqueous solutions of DEA [10,12,13,15] and MDEA [11,14].…”

Study on the surface tensions of MDEA-methanol aqueous solutions

“…Aqueous solutions of MDEA have been widely used for the removal of CO 2 form a variety of gas streams [9,10]. Besides the amine blends, adding a physical solvent to the aqueous solutions of alkanolamines is considered to be an effective method to lower the regeneration energy cost [11,12]. For example, Archane et al [11] studied the vapor-liquid equilibria, the concentration of the molecular form of absorbed CO 2 , the partial pressure of CO 2 and the liquid phase speciation for CO 2 -poly(ethylene oxide)400 (PEG400)-diethanolamine (DEA) aqueous solutions, and demonstrated the influence of PEG400 on the absorption of CO 2 .…”

“…Besides the amine blends, adding a physical solvent to the aqueous solutions of alkanolamines is considered to be an effective method to lower the regeneration energy cost [11,12]. For example, Archane et al [11] studied the vapor-liquid equilibria, the concentration of the molecular form of absorbed CO 2 , the partial pressure of CO 2 and the liquid phase speciation for CO 2 -poly(ethylene oxide)400 (PEG400)-diethanolamine (DEA) aqueous solutions, and demonstrated the influence of PEG400 on the absorption of CO 2 . Their results showed that lower energy cost can be achieved in regeneration because at a given CO 2 loading and constant concentration of DEA, the CO 2 molecular concentration increases with the increase of PEG400 concentration, whereas the ion repartition is not significantly influenced by the solvent composition.…”

“…Aqueous solutions of MDEA have been widely used for the removal of CO 2 form a variety of gas streams [9,10]. Besides the amine blends, adding a physical solvent to the aqueous solutions of alkanolamines is considered to be an effective method to lower the regeneration energy cost [11,12]. For example, Archane et al…”

Investigation of the absorption performance and viscosity for CO2 capture process using [Bmim][Gly] promoted MDEA (N-methyldiethanolamine) aqueous solution

“…In particular, when using the popularly applied MEA (monoethanolamine)aqueous solution as absorbent, the mass fraction of MEA must be no greater than 30% in order to lower the corrosion, thus large quantities of superheated steam are needed in the regeneration tower to heat the 70% residual water. To lower the energy cost, many new absorbents have been developed in recent years [6,7], e.g., MEA promoted MDEA (N-methyldiethanolamine) aqueous solution. MDEA has the advantages of high resistance to thermal and chemical degradation, and low corrosivity [8].…”