1997, Itoh, Eiji, Yoshikawa, Hidemi, Kawase, Yoshinori

Α new model based on the quasi-stationary approximation is developed for removal of gas bubbles from glassmelts due to buoyant rise of bubbles. The growth and rising of multicomponent gas bubbles in glassmelts are examined from the view point of interfacial mass transfer. It is shown that the models for rising bubbles in glassmelts available in the literature are based on the quasi-steady approximation which is not very reasonable. The growth of a gas bubble initially consisting of nitrogen only is studied in a glassmelt whose diffusing gases are oxygen, water, carbon dioxide, sulfide and nitrogen. The proposed model based on the unsteady-state mass transfer (the quasi-stationary approximation) is compared with the model based on the steady-state mass transfer (the quasisteady approximation). The former, which provides more rational and better descriptions of bubble behavior in refming processes compared with the latter, predicts rather shorter refming times than the latter.

1997, Yoshikawa, Hidemi, Kawase, Yoshinori

The role of the redox reactions due to refining agents in the glass refining processes was examined. Α new approximate model for shrinkage (or growth) of gas bubbles in glassmelts in which redox reactions caused by refining agents were taken into account was developed. The proposed model is a modification of the quasi-stationary model by which the redox reactions due to refining agents can not be considered. It was found that the shrinkage (or growth) of gas bubbles in melts with refining agents is quite faster than that in those without refining agents. Numerical results for single-component and multicomponent gas bubbles indicate that the mechanism of the bubble shrinkage (or growth) in the refining process is significantly controlled by the oxidation of refining agents, which decreases (or increases) the oxygen concentration in the glassmelt and as a result causes the rapid oxygen transfer across the bubble/glassmelt Interface and hence the fast shrinkage (or growth) of the gas bubble. The applicability of the proposed model was examined using the computational results and experimental measurements in the literature. It was also found that the proposed model provides better predictions compared with the quasi-stationary model.