Experimental Measurement of CO2 Solubility in Aqueous CaCl2 Solution at Temperature from 323.15 to 423.15 K and Pressure up to 20 MPa Using the Conductometric Titration
Résumé
In the framework of the efforts of the scientific community developed for the reduction of CO2 emissions, the geological storage of CO2 in deep saline aquifers is under focus. An increase of salinity decreases the potential of CO2 solubilization into the water. In salty waters, the salinity is not only due to NaCl but also to others ions and in particular Ca and Mg. Experimental solubility data of CO2 in calcium chloride solution available in the literature at conditions relevant to carbon storage are particularly scarce. In this work, a new analytical method was developed for experimental measurement of CO2 solubility in calcium chloride solutions (1, 3, and 6 mol/kg) at high pressures (5-20 MPa) and temperatures (323.15, 373.15, and 423.15 K). This method is based on conductometric titration coupled with classical pH titration. The conductimetry shows sharper curves than the pH titration allowing a higher precision. Thirty-six new experimental data are reported in this paper. These data presented an experimental average uncertainty of 2.1% with the ANOVA calculation method based on repeatability and reproducibility experiments. The CO2 solubility in CaCl2 solutions is noticeable lower than in NaCl solution increasing the salting out effect. Considering our previous work on NaCl solutions and this paper for CaCl2 solutions, estimations of the real quantity of CO2 that may be dissolved in saline aquifers can be made with a significantly better precision.