Solubility of Calcium Carbonate in Aqueous Monoethylene Glycol Mixtures under a Carbon Dioxide Atmosphere Using an Analytical Method

Abstract

Hydrate formation (low temperatures and high pressures) is a major concern in natural gas production as it can block pipelines and disrupt operations. Monoethylene glycol (MEG) is used to inhibit hydrates but reduces the solubility of salts like calcium carbonate (CaCO₃), leading to precipitation and scaling in pipelines and equipment. This study experimentally determined aqueous CaCO₃ solubility under varying CO₂ pressures (101.3–214.6 kPa) at constant temperatures (278.15, 288.15, and 298.15 K). Additional experiments examined the CaCO₃ solubility in MEG–water mixtures at 298.15 K and under CO₂ pressures (101.3–214.6 kPa). Using a novel setup with jacketed glass cells and a thermostatic bath, excess CaCO₃ ensured a constant solid presence. Results showed increased solubility in the presence of CO₂ but a significant reduction with MEG. Thermodynamic modeling was performed for the H₂O + CO₂ + CaCO₃ system, using the Pitzer model and OLI simulator, yielding good prediction results. A comprehensive literature review of CaCO₃ aqueous solubility data (273.25–368.15 K, 0.03–214.6 kPa) was compiled. The database was correlated with the Pitzer model, resulting in low deviations (AADmCaCO₃ = 0.14 mmol/kg). The Redlich–Kister expansion described accurately mixed solvent solubility data. The approach demonstrated broader applicability for the temperature and CO₂ pressure ranges of interest.