Top-of-line corrosion (TLC) in carbon steel pipelines carrying moist gas is caused by the condensation of water in the presence of CO2 and is difficult and expensive to mitigate. Modeling TLC allows operators to plan mitigation strategies that may reduce costs and production delays. The TLC rate is proportional to the rate of condensation and is affected by the solubility of the corrosion products. When Mono-Ethylene Glycol (MEG) is present, it evaporates and condenses with the water. Depending on mass transport rates, the gas phase may get depleted of MEG. Equilibrium calculations may not necessarily predict the condensation rate and the composition of the condensing aqueous phase correctly.

In this work, in-situ refractometry was used to study the co-condensation of water and MEG. A water/MEG mixture was heated to generate a vapor-saturated gas phase which was transported by a gas stream through heated tubes over the window of a refractometer with precisely controlled temperature. The composition of the condensed liquid was monitored over time. By varying the temperature of the condensation surface, valuable data were generated, providing insight into how the composition of the co-condensed phase develops and how it relates to thermodynamic equilibrium and mass transfer.