Quantifying Impurities in CO2 Streams: Measurements of TEG and MeOH Solubility under Pipeline Conditions

Abstract

Trace impurities in CO2 streams are of particular concern for CO2 transportation and storage applications, where compounds used in gas processing may be cotransported unintentionally. Among these, triethylene glycol (TEG) and methanol (MeOH) are especially relevant due to their widespread use in gas dehydration and hydrate inhibition. Reliable solubility data for these species in compressed CO2 remain limited and, in some cases, are inconsistent in the literature. In this work, new experimental solubility data for TEG and MeOH in CO2 are reported over temperature and pressure ranges relevant to industrial operation. TEG solubility was measured at temperatures from 30 to 90 °C and pressures up to 111 bar, yielding concentrations between 0.31 and 142.5 ppm, while MeOH solubility was measured from 20 to 55 °C and pressures up to 84 bar, with a result of 0.64 to 3.52 mol %. Measurements were performed using a novel approach that utilizes a high-pressure saturation unit for gas–liquid equilibration, combined with quantitative 1H NMR spectroscopy for effluent composition analysis. The experimental results are compared with available literature data and with predictions from the Cubic-Plus-Association (CPA) and Peng–Robinson (PR and PR78) equations of state. The comparison reveals systematic deviations between models and experiments, a tuned CPA model provides the best overall performance with an AARD of 24.9%, highlighting the need for improved thermodynamic models of CO2-TEG and CO2-MeOH systems.