Glass melting reactions

Un article de Surface du verre et interfaces.

Glass is melted from solid raw materials such as Silica sand, sodium and calcium carbonates

   

Sand, sodium carbonate (soda ash), calcium carbonate (Limestone)

Important steps determining the homogeneity of the final glass are the following :

• melting of sodium carbonate at 850°C
• reaction between sodium carbonate and silica giving sodium silicate
• integration of calcium carbonate in the process, either through the eutectic melting with sodium carbonate, through decarbonation followed by reaction with the silicate or through direct reaction with silica.

Those chemical processes do not yield exactly the same product and their combination can produce heterogeneous glass.

Industrially, this problem is solved with the addition of "fining agents" like sodium sulphate for instance : at high temperature their reduction yield gases which efficiently contribute to the mixing of the liquid. It means high temperature and fuel consumption, and sulfur oxides release and both should be reduced as much as possible for obvious environmental and economic reasons.

This difficulty is one of the phenomena we are dealing with in the Heterogeneous reactive materials group.

 

Collaborations

Michael Toplis : Observatoire Midi Pyrenées - Dynamique Terrestre et Planétaire (UMR5562)

 

Publications

• Influence of limestone grain size on glass homogeneity , MH Chopinet, E. Gouillart, M. Toplis and S. Papin, submitted to Glass Technology.