Solubility of cupric oxide in pure subcritical and supercritical water

Abstract

THE DISSOLUTION, transport, and deposition of metallic oxides is an important factor in the operation of the high-pressure water circuit of modern power station boiler units. As feedwater purity improves, the relative importance of the metallic oxide impurities, which result largely from the corrosion of the water circuit containment itself, increases. A major parameter in each of the processes quoted above is the solubility of the oxide species in the high-temperature, high-pressure aqueous environment, but there is little data available for the systems of greatest practical significance, Fe304-H20, CuO-H20, and Cu20-H20. Sweeton et al. (8, 9) have studied the subcritical solubility of magnetite, Fe3O4, as a function of chloride ion concentration, while a small area of the supercritical solubility diagram for the system Fe304-H20 has been explored by Martynova (6). The measurements made by Pocock and Stewart (7) in the systems Cu-H20, Cu20-H20, and CuO-H20 were over a restricted range of pressure and temperature, and the results showed considerable scatter. In the present work, the solubility of cupric oxide, CuO, has been measured in pure water of pH 7.5 over the temperature range 50 to 550°C. and along a series of isobars between 3500 and 6000 p.s.i.g.