Foaming study combined with physical characterization of aqueous MDEA gas sweetening solutions

• Presence of propionic acid decreased both the foam volume and the foam stability.
• Heavy organic acids (C5–C7) increased foaming.
• Iron(II) sulfide increased the foaming tendency but decreased the foam stability.

This study has been carried out to investigate the foaming behavior of aqueous Methyldiethanolamine (MDEA) in presence of different degradation products and other contaminants as additives. This foaming study was combined with physical characterization of the tested solution to enhance the understanding of the foaming behavior. The foaming tendency of aqueous MDEA solution was reported in terms of foam volume. Foam stability was reported on the basis of the time required for the last bubble to break. The effect of degradation products and heavy and light dissolved organics on solution physical properties i.e. density, surface tension and viscosity were studied. The addition of 2.5 wt% of propionic acid decreased the foam volume by about 4% and the foam stability by about 7.14%, while the heaver organic acids (C5–C7) increased foaming. All organic acids increased the solution viscosity and density and decreased the solution surface tension by various extents. Formaldehyde increased the foaming tendency and enhanced the stability of the foam on MDEA solution. Iron(II) sulfide increased the foaming tendency by about 39.7%, although it decreased the foam stability by about 95.6%. The addition of both pentane and heptane decreased the foaming tendency and stability of the 50 wt% MDEA solution. Finally, a mathematical model was proposed to understand the parametric effects behind the foaming problem of aqueous MDEA solutions and to facilitate the tracking of the sources of foaming and alleviate them or reduce their impact.