Numerical study of glass fining in a pot melting space with different melt-flow patterns

Abstract

A numerical model of glass-melt flow and bubble removal was applied in a pot melting space with a different character of melt flow. The linear-temperature gradients with a higher temperature either near the space wall or in the center of the melt level were put on the melt level to simulate the melt circulations, corresponding to melt heating through the pot wall and from the top, respectively. The removal times of the small bubbles have been calculated at different intensities of evoked melt circulations and compared with the values attained in the quiescent glass melt. The results have shown that the melt circulations increased the rising time of bubbles and consequently led to higher energy consumption and lower melting performance. The impact of melt circulations became stronger with the increasing intensity of the circulations and weakened with the increasing bubble growth rate. The removal times of critical bubbles were generally lower in the case of heating from the top and the relevant values obtained in the space at very low bubble growth rates and relatively high melt circulation velocities attained even lower values than in the quiescent melt. The low values of the bubble fining times were described by the characteristic shapes of the critical bubble trajectories. The case may be utilized for the fining of special glasses without addition of fining agents.