Water Solubility Measurements of the CO₂-Rich Liquid Phase in Equilibrium with Gas Hydrates Using an Indirect Method

Abstract

The solubility of water in the CO2-rich phase was measured in the presence of hydrate using an indirect method at the temperatures ranging from (274 to 294) K and pressures of (6.1 and 10.1) MPa. The experimental data set of Song and Kobayashi (SPE Form. Eval. 1987, 2, 500−508) was previously reported for this system, and a large pressure dependence was observed at the pressures of (6.21 and 10.34) MPa. The present solubility data were compared with published experimental data at the hydrate-free region. A weak pressure dependence was observed compared with the data of Song and Kobayashi in the present measurements.

Experimental Determination of the Equilibrium Water Content of CO2 at High Pressure and Low Temperature

“…Instead, CO 2 -rich samples with known water contents were prepared and the temperature at which formed hydrates disappear was visually determined by raising the temperature very slowly and keeping pressure constant. To enhance the view of the cell internals, in the current measurements the diameter of the view cell was enlarged from the one used by Seo et al 7 The uncertainty analysis of the Korea University data is presented in Appendix I. The key result is of the analysis is that the uncertainties in pressure and temperature and the combined uncertainty in water mole fraction are 0.01 MPa, 0.2 K, and 5.2·10 −5 , respectively.…”

“…Figure 5 compares water solubility data to the simple model that has been fit to the data of Seo et al 7 and the new data from Wiltec and Korea University.…”

Measurement and correlation of solubility of water in carbon dioxide-rich phase

“…For this, we used a cylindrical equilibrium cell of variable volume immersed in the water bath of which temperature is adjusted by a Polyscience circulator. This apparatus is almost the same as that of Seo et al [13] applied for the measurement of solubility of water in the presence of hydrate. A vacuum pump is attached to the cell to evacuate the equilibrium cell.…”

“…A Rheodyne injection valve is also connected to the cell to introduce small amount of water in water reservoir into the cell. Compared with the size of the sampling loop employed in our previous study, we used the injection loop with the increased calibrated volume of 125.3 ± 0.45 l since the solubility of water in the region of no hydrate formation is larger than that of hydrate formation and thus the amount of water injected to the cell should be increased compared with that of previous study [13]. A detachable gas burette connected to the injection value was used to measure the amount of CO 2 introduced into the system.…”

“…However, it is still difficult to accurately determine water mole fraction in the order of 0.001. To avoid such difficulty, Wendland et al [12] and Seo et al [13] used an indirect method for determination of hydrate-containing equilibrium of water + carbon dioxide system. This method does not require the conventional analytic composition analysis.…”