Coupled modelling of redox reactions and glass melt fining processes

The quality of glass depends upon the removal of dissolved gases and bubbles. A quantitative understanding of these processes is essential for glass production today, where quality requirements are becoming increasingly stringent. Classical fining involves adding an element or compound to the melt which will, through oxidation-reduction reactions at high temperatures, produce gases that diffuse into the bubbles present in the melt. The growth of these bubbles then enhances the rate of bubble removal from the melt. The modelling of oxidation-reduction reactions and that of fining are generally treated independently from one another. However, due to the large number of bubbles present, a significant amount of dissolved gases are consumed and the chemical equilibrium in the melt is changed. We present, in this paper, a theoretical model where redox equilibrium is coupled with bubble generation and growth, Our approach is similar to that proposed by Nemec and co-workers, but differs in the numerical method used. After a description of the model, we present the evolution of a bubble population with time and also apply the numerical method to an experimental tool where bubbling is used to equilibrate the partial pressures between the bubbles and between the melt. The model results in an equilibrium time longer than that seen experimentally. The possible origins of the disagreement are investigated and discussed.