Ceramics-Silikáty 44 (4) 129-134 (2000)

THE ABSORPTION OF H₂ AND CO FROM BUBBLES IN A GLASS MELT

L. Němec, J. Kloužek 

Hydrogen and carbon monoxide bubbles in a glass melt are produced by reactions of carbon, iron and ferrous oxide impurities with oxygen or water vapour. Their modelling in melting spaces joined with defect bubble analyses could help to identify the appropriate bubble defect source, however, mechanisms of bubble interactions with melts are not yet known. The experimental examination of bubbles initially containing 95 vol. % H₂ and 5 vol. % N₂ showed a rapid absorption of hydrogen by the melt. The proposed mechanism of interaction involved the controlling role of hydrogen and oxidizing components counter-diffusion in bubble surroundings and influence of chemical reaction of hydrogen with the mentioned oxidizing melt components (O₂, sulphate ions).  The governing equations of this phenomenon were presented, as well as a simplified mechanism applying the value of hydrogen effective diffusion coefficient under given value of the redox state of glass. Using the results of experimental observations, the temperature dependencies of the product of effective diffusion coefficient and solubility of hydrogen - necessary for the modelling of bubbles containing hydrogen - were determined in soda-lime-silica glass containing 0.5 wt.% SO₃  

( = exp(0.866-7438/T) and amber glass 

( = exp(0.946-9125/T), where T is temperature in Kelvins.