SUBMERGED BURNER FURNACE

Abstract

A for melting batch material includes a furnace equipped with a submerged burner, a system for supplying the submerged burner with fuel gas and with oxidizer, a system for supplying the furnace with raw material including fragments of mineral wool below the surface of the molten batch materials, a system for supplying the furnace with raw material including a vertical duct for receiving raw material through its upper side and for conveying this raw material downward toward the molten batch materials. The duct receives the combustion flue gases originating from the furnace and conveys them upward through the raw material in the duct. A system supports the solid raw material in the duct and is positioned above the surface of the molten batch material and retains the solid raw material in the duct and lets descending molten raw material pass through to fall into the molten batch material.

Claims

1. A device for melting batch material comprising a furnace equipped with at least one submerged burner, a system for supplying the submerged burner with fuel gas and with oxidizer, a system for supplying the furnace with raw material comprising fragments of mineral wool below a surface of the molten batch materials, a system for supplying the furnace with raw material comprising a vertical duct capable of receiving raw material through its upper side and capable of conveying the raw material with a direction of transport comprising a vertical component downward under the effect of its own weight above the molten batch materials, said vertical duct being capable of receiving the combustion flue gases originating from the furnace and of conveying them upward through the raw material in the vertical duct, a system for supporting the solid raw material in the vertical duct, said system being positioned above the surface of the molten batch material and capable of retaining the solid raw material in the vertical duct and capable of letting descending molten raw material pass through in order to fall into the molten batch material and capable of letting the combustion flue gases originating from the furnace pass through in order to rise in the vertical duct.

2. The device as claimed in claim 1, wherein the system for supplying the furnace with raw material below the surface of the molten batch materials is capable of pushing the raw material into the molten batch materials.

3. The device as claimed in claim 1, wherein the system for supplying below the surface of the molten batch materials is capable of introducing into the furnace a raw material comprising 50% to 100% of fragments of mineral wool by mass.

4. The device as claimed in claim 1, wherein the system for supplying the furnace with raw material below the surface of the molten batch materials comprises at least one screw conveyor.

5. The device as claimed in claim 1, wherein the system for supplying the furnace with raw material below the surface of the molten batch materials comprises at least one piston.

6. The device as claimed in claim 1, wherein the oxidizer comprises at least 80% by volume of oxygen.

7. The device as claimed in claim 1, wherein the system for supporting the solid raw material in the vertical duct comprises a grate.

8. The device as claimed in claim 7, wherein the grate comprises metal tubes through which cooling water passes.

9. The device as claimed in claim 1, wherein alumina-containing refractory balls rest on the grate.

10. The device as claimed in claim 9, wherein the alumina-containing refractory balls have a size of between 5 and 30 cm.

11. The device as claimed in claim 1, wherein the alumina-containing refractory balls comprise at least 25% by weight of alumina.

12. The device as claimed in claim 1, wherein the furnace is equipped with at least one overhead burner, the flame of which is emitted above the surface of the molten batch materials and below the means for supporting the solid raw material in the vertical duct.

13. A process for preparing molten batch material comprising the melting a batch material by the device of claim 1, raw material comprising fragments of mineral wool being introduced into the furnace below the surface of the molten batch material, raw material being introduced into the vertical duct, descending in the vertical duct and being heated therein by the combustion flue gases until the raw material melts and flows onto the surface of the molten batch material, the submerged burner operating by combustion of fuel gas and of an oxidizer comprising at least 80% by volume of oxygen.

14. The process as claimed in claim 13, wherein the raw material introduced into the vertical duct is such that at least 80% of its mass consists of grains with a size of greater than 30 mm.

15. The process as claimed in claim 13, wherein the raw material comprising fragments of mineral wool introduced below the surface of the molten batch material comprises raw material different from the fragments of mineral wool, at least 80% of the mass of the different raw material consisting of grains with a size of less than 30 mm.

16. The process as claimed in claim 13, wherein the mass of raw material introduced below the surface of the molten batch material represents 5% to 70% of the sum of the masses of all the raw materials introduced into the device.

17. The process as claimed in claim 13, wherein the mass of fragments of mineral wool represents 50% to 100% of the sum of the mass of raw material introduced below the surface of the bath of batch material.

18. The process as claimed in claim 13, wherein the fragments of mineral wool are bound.

19. The process as claimed in claim 13, wherein the fragments of mineral wool comprise, excluding binding compound, 30% to 75% by weight of SiO.sub.2 and 5% to 40% by weight of (CaO+MgO).

20. The process as claimed in claim 13, wherein the combustion in the furnace is sufficiently energetic so that the combustion flue gases are hot enough to melt the raw material in the vertical duct above the system for supporting the solid raw material in the vertical duct.

21. The process as claimed in claim 13, wherein the system for supporting the solid raw material in the vertical duct comprises a grate on which alumina-containing refractory balls rest, said refractory balls enriching the molten batch material with alumina.

22. The process as claimed in claim 13, wherein the molten batch material is brought into the furnace at a temperature above 1400° C. and below 1600° C.

23. The process as claimed in claim 13, wherein the molten batch material comprises 30% to 75% by weight of SiO.sub.2 and 5% to 40% by weight of (CaO+MgO).

Description

[0051] FIG. 1 represents an example of a device according to the invention seen in side cross section. This device comprises a furnace 1 equipped with submerged burners 2 mounted in the floor. These submerged burners are supplied, by means of a supply system 3, with fuel gas and with oxidizer. The submerged burners provide flames in the mass 4 of the bath of molten batch materials. A screw conveyor type system 5 makes it possible to supply the furnace with fragments of mineral wool and if necessary with raw material different from the wool and having a small particle size below the surface 6 of the molten batch materials. A vertical duct 7 above the surface of the molten batch material 4 makes it possible to supply the tank 8 of the furnace with raw material 9 of large particle size. The raw material 9 is introduced through the upper end of the duct 7 and is retained above the surface 6 of the molten batch material by a support means comprising a grate 10 and alumina-rich balls 11 resting on the grate. The combustion flue gases generated by the burners and below the grate pass through the grate and the balls and rise into the duct 7 acting as a stack, through the raw material 9. This raw material is thus heated by these flue gases and gradually melted. The molten raw material 12 flows through the means (grate+balls) for supporting the solid raw material in the duct and falls into the mass 4 of molten batch materials. The combustion flue gases 13 that are passed through the raw material in the duct 7 are discharged via the upper end of the duct 7. The molten batch material may be discharged through an orifice 14 in a wall of the tank 8 of the furnace.