Phase Equilibrium of CO2 and organic sulfur species in Methyldiethanolamine (MDEA) aqueous solution; Study of acid gases loading effect on the partition coefficient of n-Propylmercaptan

Abstract

For many years, alkanolamines have been used as chemical solvents for absorbing acid gases like CO₂, H₂S and other sulfur species in both petroleum refinery and natural gas processing industry. Accurate phase equilibrium data for acid gas and amine aqueous solution systems are necessary for the design and optimization of gas treatment units. Although there are plenty of phase behavior data for main alkanolamines (e.g. MEA, DEA, MDEA) and major acid gases (e.g. CO₂, H₂S), there is still a need for generating equilibrium data concerning solubility of organic sulfur species (e.g. carbonyl sulfide COS, carbon disulfide CS_2, and mercaptans RSH) in amine aqueous solutions. In this work, new experimental data on solubility of CO₂, H₂S and n-PM in (50 wt %) MDEA aqueous solution at 366 K and pressure 0.1 MPa to 1.9 MPa are reported. The effect of CH₄ partial pressure on the partial pressure of the acid gas is also studied. The data have been generated using a "static- analytic" apparatus which takes advantage of a Rolsi^TM sampler with a gas chromatograph for components analyses. A previously reported thermodynamic model developed by Deshmukh and Mather (1981) is employed to predict acid gases loading at the above mentioned temperature and pressures.