(397e) CO2 Absorption in Aqueous Alkanolamine Systems : CO2 Concentration and Henry Constant Determination

For both energy and environmental purposes, the removal of acid gases such as carbon dioxide (CO₂) is involved in numerous processes such as natural gas treatment, as well as in petroleum refining, coal gasification, and hydrogen production. For such purification, reactive absorption with aqueous solutions of alkanolamines remains the most mature and widely implemented industrial technology.

Accurate understanding and modeling of the transfer occurring during the carbon dioxide absorption in alkanolamine solutions is of vital importance for optimizing the design of absorption units and reducing the absorber size, especially when high CO₂ loading are achieved.  For the reason, knowing the concentration of molecular CO2 c_CO2, the transferring species, is crucial. Because CO2 reacts with the solvent to form HCO3-, CO32- and carbamate if a primary or secondary amine is used, c_CO2 cannot be simply deduced from VLE measurements. A thermodynamic modeling is needed, and the Henry constant of molecular CO2 is deduced from the N2O analogy. An original experimental device has been developed allowing the direct measurement of c_CO2 [1]. In this work, original measurement of c_CO2 and HCO2 are presented for the CO2 loaded following systems (water + methyldiethanolamine MDEA), (water + MDEA + diethanolamine DEA), (water + DEA + 2-Amino-2-Méthyl-1-Propanol AMP). Differences are observed with the values deduced from the N2O analogy or predicted using electrolyte NRTL.

[1] Anas Archane, Walter Fürst and Elise Provost, Influence of Poly(ethylene oxide) 400 (PEG400) on the Absorption of CO₂ in Diethanolamine (DEA)/H₂O Systems, JCED, 2011 56(5) 1852-1856