Process for obtaining glass and glass obtained
The object of the invention is a continuous method for obtaining glass, comprising steps consisting of: charging raw materials upstream of a furnace, along which a plurality of burners is disposed, obtaining a mass of molten glass, and then leading said mass of molten glass to a zone of the furnace situated further downstream, at least one burner disposed in the region of this zone being fed with an over-stoichiometric quantity of oxidant, and then, forming a glass sheet, said glass sheet having a chemical composition that comprises the following constituents in an amount varying within the weight limits defined below: SiO 2 60-75% Al 2 O 3 0-10% B 2 O 3 0-5%, preferably 0 CaO 5-15% MgO 0-10% Na 2 O 5-20% K 2 O 0-10% BaO 0-5%, preferably 0, SO 3 0.1-0.4% Fe 2 O 3 (total iron) 0 to 0.015%, Redox 0.1-0.3.
1. A glass production method, comprising:
charging raw materials in an upstream part of a furnace, wherein a plurality of burners are disposed along the upstream part,
obtaining a mass of molten glass, and then
leading said mass of molten glass to a zone of the furnace situated further downstream, wherein at least one burner is disposed in the region of this zone being fed with an over-stoichiometric quantity of oxidant, and then,
forming a glass sheet, said glass sheet having a chemical composition that comprises the following constituents in an amount varying within the weight limits defined hereinafter:
SiO 2
60-75%;
Al 2 O 3
0-10%;
B 2 O 3
0-5%;
CaO
5-15%;
MgO
0-10%;
Na 2 O
5-20%;
K 2 O
0-10%;
BaO
0-5%;
SO 3
0.2-0.4%;
Fe 2 O 3 (total iron)
0 to 0.015%; and
Redox
0.2-0.3%.
2. The method as claimed in claim 1 , wherein the furnace comprises several overhead burners disposed in the region of the sidewalls of the furnace, each of said burners being able to develop a flame transversely to the axis of the furnace.
3. The method as claimed in claim 2 , wherein the overhead burners are disposed regularly upstream to downstream and are arranged in pairs of burners facing each other, the burners of each pair operating alternately so that at a given instant only burners disposed in the region of one of the sidewalls develop a flame.
4. The method as claimed in claim 3 , wherein the furnace comprises between 6 and 8 pairs of burners and only the two or three pairs of burners situated furthest downstream, or the last pair of burners situated furthest downstream, are fed with an over-stoichiometric quantity of oxidant.
5. The method as claimed in claim 1 wherein the furnace comprises, from upstream to downstream, a first chamber delimiting a glass melting zone and then a refining zone and then a second chamber delimiting a cooling zone for molten glass, all the burners being disposed in the region of the first chamber.
6. The method as claimed in claim 5 , wherein each burner fed with an over-stoichiometric quantity of oxidant is situated in the region of the glass refining zone.
7. The method as claimed in claim 1 , wherein the burners are fed with air and fuel.
8. The method as claimed in claim 7 , wherein the fuel is chosen from natural gas and fuel oil or any mixtures thereof.
9. The method as claimed in claim 1 , wherein the over-stoichiometric quantity of oxidant is such that the molar ratio of oxygen to fuel is between 1.05 and 1.5.
10. The method as claimed in claim 1 , wherein the glass sheet is formed by floating on a bath of tin.