The solubility of magnesium chloride and calcium chloride in near-critical and supercritical water

Applications using supercritical water often encounter the presence of inorganic compounds in feed streams, most often with a minor concentration. These compounds can lead to damage of the equipment via erosion, scaling and corrosion or can influence and disturb the main reaction and processes inside the systems. In order to avoid these problems and to predict the influence of these compounds, it is vital to posses knowledge of the properties of the most common inorganic compounds in supercritical water.

In continuation of earlier works of the authors, the solubilities of MgCl(2) and CaCl(2) are investigated via a continuous flow method in the range of 660-690K and 18.5-23.5 MPa. Contrary to earlier experiments with single-valent salts, precipitates were found during the experiments with MgCl(2) after cleaning the setup. These precipitates were analyzed via EDX and ATF-IR. In the course of the experiments, a decrease in pH of the samples was investigated what was caused by a parallel hydrolysis reaction. The solubilities of both investigated salts were corrected for the hydrolysis reaction and correlated via a semi-empirical approach based on the phase equilibrium between the present phases. (C) 2010 Elsevier BM. All rights reserved.