Study On The Solubility And Crystallizing Metastable Zone Of Inorganic Salt In Sub-and Supercritical Water

The solubility of inorganic salts showed significant changes in high temperature and pressure water. SCWO, a potential and green technology for organic wastes treatment, was limited by salt-plugging and corrosion during the industrial application. The solubility of chloride and sulfate became a required data for the design of SCWO reactor in the world. The data were deficient because of the limitation of experiment.The solubility and metastable zone of calcium sulfate and magnesium sulfate in subcritical water were described in thesis, using a novel static method which combined capillary technology with polarizing microscope by capturing the point of crystallization and dissolution. The results indicated the influence of heating/cooling rate, pH and additives on the metastability and the growth of crystal. In the range of 79.5~157.8℃, the solubility of calcium sulfate were from 0.180 to 0.051g/100g(water), and in the range of 117.9~202.2℃, the solubility of magnesium sulfate were from 32.854 to 1.372g/100g(water), under the condition of no adjustment of pH, no addition and r =1℃/min. A negative correlation was found between the solubility/ super-solubility and temperature. The MSRK equation and Raoul's Law were employed for the calculation of pressure with matched experimental results. The S-T-P curves of brine system derived from solubility data also fit the correlation with the Hydration Reaction Model.The phase behavior of chloride in aqueous solutions in the condition of temperature (25~400℃) was observed qualitatively. The results indicated that the solubility was increased, and the critical point was deferred with the increase of the salinity. No crystals turned up in NaCl of 1.0g/100g(water) during heating to critical state, which disagreed with the common views. It was necessary to understand again for the subject.The solubility data of inorganic salt was enriched, as well as an intuitive and operable novel measurement for solubility determination was proposed, which is safe, low energy consumption, and can be used in reverse analysis. It also provided a new method and laid a foundation for further research.