A Glycol/Water Co-Condensation Model to Investigate the Influence of Monoethylene Glycol on Top-of-the-Line Corrosion

A mechanistic model was developed to predict the co-condensation of water and monoethylene glycol (MEG) at the top of a wet gas pipeline. The dropwise condensation process of water and MEG in the presence of noncondensing gas (CO₂) is modeled based on a set of equations that describe the simultaneous heat and mass transfer to the condensed droplets. The model can predict the MEG concentration in the condensing phase, and the condensation rate of water and MEG. The accuracy of the model predictions was evaluated by comparison with flow loop experimental data. The results showed a decrease in condensation rate and increase of MEG content in the condensing phase with the increase of MEG content at the bottom of line. However, this effect is not significant unless the MEG content in the bottom liquid phase is higher than 70 wt%. Long-term corrosion experimental results showed that the presence of 50 wt% and 70 wt% MEG at the bottom liquid phase has a minimal effect on the top-of-the-line corrosion (TLC) rate, while the presence of 90 wt% MEG decreases the TLC rate significantly due to a sharp change of both condensation rate and the MEG content in the condensing phase.