Mass transfer of rising O2 bubble in molten glass coupled with the oxidation-reduction reaction of iron

Franck Pigeonneau (1)

1 SVI - Surface du Verre et Interfaces

Glass melting process involves two-phase flow for which bubbles are dispersed in a high viscous fluid. Due to the quality requirement, the bubble removal is needed. This stage is achieved by the bubble rising due to the buoyancy forces. The efficiency of the last effect is improved by increasing temperature and by bubble growth. In order to increase the bubble size, few chemical species are added which release gaseous species such as O2, SO2, by chemical reactions. The modeling of mass transfer of bubble in a molten glass has been studying since many years. Nevertheless, the modifications in mass transfer due to chemical reactions between bubbles and the molten glass are seldom. Since iron is an major element present in industrial glass coming from the raw materials and also add to change the glass color as a function of its reduction state, we investigate the particular role of the iron by taking into account the oxidation-reduction reaction of iron to describe the mass transfer around of oxygen bubble. The dimensionless mass transfer coefficient, Sherwood number, is determined as a function of the Péclet number based on the terminal rising velocity of the bubble. Two different techniques are used: the first based on the boundary layer theory and the second using a finite element method. The Sherwood number, taking into account the oxidation-reduction reaction, increases with iron content as well as with reduction state of iron [1]. The behavior of an isolated rising bubble in a molten glass is investigated both experimentally and numerically. The theoretical model to describe bubble shrinkage is based on the preceding results. We show that the bubble shrinkage increases with the reduced iron content. The behavior is very well established with the new developments on Sherwood number described above [2]. [1] F. Pigeonneau. " Mass transfer of rising bubble in molten glass with instantaneous oxidation reduction reaction ". Chem. Eng. Sci., 64:3120-3129, 2009. [2] F. Pigeonneau, D. Martin and O. Mario. " Shrinkage of oxygen bubble rising in a molten glass ". Chem. Eng. Sci., 65:3158-3168, 2010.

Domaines: Génie des procédés; Matériaux

Franck Pigeonneau. Mass transfer of rising O2 bubble in molten glass coupled with the oxidation-reduction reaction of iron. 15th International IUPAC Conference on High Temperature Materials Chemistry, Mar 2016, Orléans, France. ⟨hal-01519365⟩