Critical Experiments on the Role of Surface Tension Driven Flow in the Kinetics of Oxygen Transfer between Gases and Liquid Silver

The kinetics of oxygen transfer between gases and liquid silver were studied at oxygen partial pressure of 0.0-1.0 atm. Three experimental systems were used. The first involved the impingement of a gas jet at the free surface of a 17 kg molten silver bath, using pure oxygen and oxygen-diluent gas mixtures at 1 atm. total pressure. The jet momentum was varied in the range 0.0-0.25 N and the lance height was 0.1 m. The second involved an unstirred 0.019 kg melt in oxygen-diluent gas mixtures at 1 atm, total pressure. The kinetics of oxygen transfer were measured by gravimetry. The third system also used gravimetry but was operated at reduced total pressure. This permitted critical experiments to elucidate the role of surface tension driven flow in absorption and desorption. For the conditions studied the kinetics were controlled by mass transfer in the liquid and/or gas phases. During desorption with oxygen-diluent gas mixtures, surface tension driven convection developed spontaneously, whereas during absorption the interface was positively stabilised. The observations were consistent with theoretical predictions which are supported by a body of experimental evidence from low temperature systems