DEVICE FOR MELTING GLASS COMPRISING A FURNACE, A CHANNEL AND A BARRIER

Abstract

A device for melting glass includes a furnace equipped with electrodes in contact with the mass of vitrifiable materials. The furnace includes a side opening connected to a feeder channel for the molten glass, a removable barrier dipping into the glass in or before the opening so that a vertical plane passing through the upstream face of the barrier touches the biggest horizontal circle which can be inscribed the furthest downstream in the furnace, barrier excluded, the biggest circle being at the height of the highest side of the bottom of the channel. The device delivers a glass of good quality which can feed a fiberizing device.

Claims

1. A device for melting glass comprising: a furnace equipped with electrodes in contact with a mass of vitrifiable materials, the furnace comprising a side opening connected to a feeder channel for the molten glass, a removable barrier dipping into the glass in or before the opening so that a vertical plane passing through an upstream face of the barrier touches a biggest horizontal circle which can be inscribed the furthest downstream in the furnace, barrier excluded, the biggest circle being at a height of a highest side of a bottom of the channel.

2. The device according to the claim 1, wherein the barrier is wider than the side opening of the furnace.

3. The device according to claim 1, wherein the barrier is in the furnace and is supported against side walls of the furnace on either side of the opening.

4. The device according to claim 1, wherein the barrier is removable vertically.

5. The device according to claim 1, wherein the barrier is removable laterally.

6. The device according to claim 1, wherein the barrier is in contact with side walls of the furnace or of the channel, forcing the molten glass to pass under the barrier without being able to pass through sides of the barrier.

7. The device according to claim 1, wherein, from passage of the glass under the barrier, the glass is in plug flow.

8. The device according to claim 1, wherein the electrodes are immersed in the glass via a top.

9. The device according to claim 1, wherein the barrier is wider than the side opening of the furnace and is in the furnace, supported against side walls of the furnace on either side of the opening, and is mobile laterally.

10. A process for preparing glass, comprising: melting of vitrifiable materials by the device of claim 1.

11. The process according to claim 10, wherein the channel feeds a glass wool fiberizing device.

12. The process according to claim 10, wherein the glass comprises: SiO.sub.2: 35 to 80% by weight, Al.sub.2O.sub.3: 0 to 30% by weight, CaO+MgO: 5 to 35% by weight, Na.sub.2O+K.sub.2O: 0 to 20% by weight.

13. The process according to claim 12, wherein SiO.sub.2+Al.sub.2O.sub.3 is within a range extending from 50 to 80% by weight and Na.sub.2O+K.sub.2O+B.sub.2O.sub.3 is within a range extending from 5 to 30% by weight.

14. The process according to claim 10, wherein the glass comprises the following components: SiO.sub.2: 50 to 75% by weight, Al.sub.2O.sub.3: 0 to 8% by weight, CaO+MgO: 5 to 20% by weight, Iron oxide: 0 to 3% by weight, Na.sub.2O+K.sub.2O: 12 to 20% by weight, B.sub.2O.sub.3: 2 to 10% by weight.

15. The process according to claim 10, wherein the glass comprises the following components: SiO.sub.2: 35 to 50% by weight, Al.sub.2O.sub.3: 10 to 30% by weight, CaO+MgO: 12 to 35% by weight, Iron oxide: 2 to 10% by weight, Na.sub.2O+K.sub.2O: 0 to 20% by weight.

16. The process according to claim 10, wherein a temperature of the glass is sufficiently high for a viscosity in poises of the glass at 1 cm from the upstream face of the barrier to be such that log.sub.10 <2.

17. The process according to claim 10, wherein a temperature of the glass in the furnace is between 1200 and 1700 C.

18. The process according to claim 10, wherein a highest temperature of the glass is located in the furnace, opposite the upstream face of the barrier.

19. The process according to claim 10, wherein a draw is between 5 and 100 tonnes per day.

20. The process according to claim 10, wherein a height of glass under the barrier is less than a height of the barrier in contact with the molten glass under a crust of raw materials.

Description

[0053] FIG. 1 represents a device according to the invention, top view.

[0054] FIG. 2 represents the same device as that of FIG. 1, side view.

[0055] FIG. 3 represents a comparison of the distribution of the temperatures depending on whether the barrier is in the channel in a) or in the furnace in b).

[0056] FIG. 4 represents a furnace according to WO2013/098504 in perspective.

[0057] The figures are not to scale.

[0058] FIG. 1 represents a device according to the invention, top view. It comprises a furnace 1, the side walls 2 of which form a rectangle seen from above. The furnace comprises a side opening 3. Molybdenum electrodes 4 dip into the vitrifiable materials via the top to heat the latter by the Joule effect. This opening is connected to a feeder channel 5. A barrier 6, placed in the furnace 1, dips into the glass via the top. This barrier has a greater width than that of the opening and is supported on the jambs 7 and 7 of the walls. An upward step 8 at the beginning of the channel lowers the glass height when moving from the furnace to the channel. The step is at a distance d1 behind the barrier, d1 preferably being greater than 250 mm. The biggest circle 9 the most downstream of the furnace and being inscribed in the furnace seen from above, barrier excluded, is represented in dashes. This virtual circle touches the side walls and the two jambs on either side of the opening since, for the placing of this circle, the barrier is not taken into account. The upstream face 10 of the barrier is inside the circle 9. The vertical plane V passing through the upstream face 10 of the barrier indeed touches this circle 9 since it cuts it at two places. The barrier is in the furnace and rests on the side walls of the furnace on either side of the opening 3.

[0059] FIG. 2 represents the same device as that of FIG. 1, side view. The references shared with those of FIG. 1 denote the same components or characteristics. In the furnace 1, a crust of raw materials 20 which have not yet melted floats above the level of glass 21. The barrier dips into the glass by a depth h1 from the bottom of the crust of raw materials. The height of glass under the barrier is h2. The height h3 of glass in the channel is less than the height of molten glass h1+h2 in the furnace. The circle 9 of FIG. 1 occurs at the height of the highest side of the bottom of the channel 5, that is to say in the horizontal plane H of FIG. 2.

[0060] FIG. 3 represents a comparison of the distribution of the temperatures depending on whether the barrier is in the channel in a) or in the furnace in b). In these configurations a) and b), the side opening of the furnace is located at the level of the downstream face of the barrier positioned according to FIG. 3b). It is seen in particular that the face of the barrier turned towards the centre of the furnace (towards the left in the figures) is hotter in b) than in a). For these measurements, use was made of a furnace with a glass surface area of 2.5 m.sup.2 operating with a draw of 6.2 tonnes per day. The glass comprised 65.7% of SiO.sub.2, 17.1% of Na.sub.2O+K.sub.2O, 4.5% of B.sub.2O.sub.3, 2.05% of Al.sub.2O.sub.3, 8% of CaO and 2.5% of MgO. The bottom temperature was 1350 C.

[0061] FIG. 4 represents a furnace according to WO2013/098504, in perspective. Only the general formula is represented in order to show the place of the barrier. The furnace 40 is circular and the barrier 41, which is removable vertically, is located in the channel 42 so that the biggest horizontal circle which can be inscribed the furthest downstream in the furnace cannot touch the barrier. This biggest circle furthermore corresponds to the circular internal wall of the furnace. According to this arrangement, the barrier is in a fairly cold region and the barrier is not removable laterally. Consequently, it may happen that the barrier is blocked in the channel and very difficult to extricate.