Glass manufacturing method using electric melting
One subject of the invention is a process for manufacturing a glass, the chemical composition of which comprises at least 3% by weight of iron oxide, expressed in the form Fe 2 O 3 , comprising a step of electric melting, using electrodes submerged in the molten glass, of a vitrifiable batch material mixture containing at least one manganese carrier wherein the manganese is in an oxidation state higher than +2.
1. A process for manufacturing a glass comprising from 3-15% by weight of iron oxide, expressed in the form Fe 2 O 3 , the process comprising:
electric melting, with electrodes submerged in a molten glass, of a vitrifiable batch material mixture comprising at least one manganese carrier in which manganese is in an oxidation state higher than +2,
wherein the glass comprises, by weight percentages:
SiO 2
35-55%;
Al 2 O 3
14-27%;
CaO
12-16%;
MgO
0-6%;
Na 2 O + K 2 O
1-17%;
B 2 O 3
0-8%;
P 2 O 5
0-3%; and
TiO 2
0-2%, and
wherein the glass comprises a combined content of CaO and MgO in the range of 14 to 18% by weight.
2. The process of claim 1 , wherein the at least one manganese carrier is selected from MnO 2 , Mn 3 O 4 , Mn 2 O 3 , Mn 2 O 7 , a permanganate, or any mixture thereof.
3. The process of claim 1 , wherein a total amount of manganese carrier contained in the vitrifiable batch material mixture is such that one ton of a dry mixture thereof comprises an amount ranging from 1 to 20 kg of manganese in an oxidation state higher than +2, expressed in the form MnO 2 .
4. The process of claim 1 , wherein the at least one manganese carrier is selected from Mn 3 O 4 , Mn 2 O 3 , Mn 2 O 7 , a permanganate, or any mixture thereof.
5. The process of claim 1 , wherein the at least one manganese carrier is Mn 2 O 3 .
6. The process of claim 1 , wherein a total amount of manganese carrier contained in the vitrifiable batch material mixture is such that one ton of a dry mixture thereof comprises an amount ranging from 2 to 10 kg of manganese in an oxidation state higher than +2, expressed in the form MnO 2 .
7. The process of claim 1 , wherein a total amount of manganese carrier contained in the vitrifiable batch material mixture is such that one ton of a dry mixture thereof comprises an amount ranging from 4 to 8 kg of manganese in an oxidation state higher than +2, expressed in the form MnO 2 .
8. The process of claim 1 , wherein the glass composition comprises at least 0.3% by weight of manganese oxide, expressed in the form MnO 2 .
9. The process of claim 1 , wherein the vitrifiable mixture contains no nitrate.
10. The process of claim 1 , wherein the glass comprises a combined content of CaO and MgO in the range of 15 to 18% by weight.
11. The process of claim 1 , wherein the electrodes comprise molybdenum.
12. The process of claim 1 , wherein the electrodes comprise tin oxide.
13. The process of claim 1 , wherein during the melting the temperature of the molten glass, measured in contact with tank refractories and at a hottest point, ranges from 1400° C. to 1650° C.
14. The process of claim 1 , wherein after the melting the molten glass is formed into mineral wool during a fiberizing step.