Unshaped product for repairing glass melting furnaces

Abstract

An unshaped product including, as weight percentages, A) particles (a) of at least one refractory material other than a glass and a glass-ceramic, and the main constituent(s) of which are alumina and/or zirconia and/or silica and/or chromium oxide: B) 2% to 15% of particles (b) of a hot binder chosen from glass-ceramic particles, particles made of a glass, and the mixtures of these particles, a glass being a noncrystalline material exhibiting a glass transition temperature of less than 1100° C., the hot binder not being in the solid state at 1500° C., C) less than 2% of particles (c) of hydraulic cement, D) less than 7% of other constituents, the particles (a) and (b) being distributed, as weight percentages in the following way: fraction<0.5 μm: ≥1%, fraction<2 μm: ≥4%, fraction<10 μm: ≥13%, fraction<40 μm: 25%-52%.

Claims

1. A wet mixture consisting of: an unshaped product comprising, as percentages by weight and for a total of 100%, A) a set of particles (a) of at least one refractory material other than a glass and a glass-ceramic, and the main constituent(s) of which are alumina (Al.sub.2O.sub.3) and/or zirconia (ZrO.sub.2) and/or silica (SiO.sub.2) and/or chromium oxide (Cr.sub.2O.sub.3), B) a set of particles (b) of a hot binder chosen from glass-ceramic particles, particles made of a glass and the mixtures of these particles: 2% to 15%, said glass being a noncrystalline material exhibiting a glass transition temperature of less than 800° C., the hot binder not being in the solid state at 1500° C., C) a set of particles (c) of hydraulic cement: less than 2%, D) less than 7% of constituents other than particles (a), (b), and (c), said particles (a) and (b) being distributed, as percentages by weight with respect to the weight of the unshaped product, in the following way: fraction<0.5 μm: ≥1%, fraction<2 μm: ≥4%, fraction<10 μm: ≥13%, fraction<40 μm: 25%-52%, the content of the set of particles (a) being the complement, to reach 100%, to the whole content of the particles (b), of the set of particles (c) and of said other constituents, and water in an amount of greater than 9%, by weight, with respect to the weight of said unshaped product.

2. The wet mixture as claimed in claim 1, wherein the amount by weight of glass-ceramic particles in the set of particles (b) is greater than 10%, on the basis of the weight of the set of particles (b), and/or, wherein said set of particles (b) comprises particles made of said glass which are particles of a glass-ceramic precursor glass, and the amount by weight of said particles of glass-ceramic precursor glass in the set of particles (b) is greater than 10%, on the basis of the weight of the set of particles (b).

3. The wet mixture as claimed in claim 1, in which the amount by weight of glass-ceramic particles in the set of particles (b) is greater than 95%, on the basis of the weight of the set of particles (b), and/or in which said set of particles (b) comprises particles made of said glass which are particles of a glass-ceramic precursor glass, and the amount by weight of said particles of glass-ceramic precursor glass in the set of particles (b) is greater than 95%, on the basis of the weight of the set of particles (b).

4. The wet mixture as claimed in claim 1, in which the amount of hydraulic cement is less than or equal to 1%.

5. The wet mixture as claimed in claim 4, in which the amount of hydraulic cement is substantially zero.

6. The wet mixture as claimed in claim 1, in which the particles of the unshaped product are distributed in the following way, as percentages by weight: fraction<0.5 m: ≤7% and/or fraction<2 μm: ≥5% and/or fraction<10 μm: ≥16% and/or fraction<40 μm: ≥27% and/or fraction of between 2 μm and 40 μm: ≥16% and/or ≤40%.

7. The wet mixture as claimed in claim 1, in which the particles of the unshaped product are distributed in the following way, as percentages by weight: fraction<0.5 μm: ≤6% and/or fraction<2 μm: ≤18% and/or fraction<10 μm: ≤40% and/or fraction<40 μm: ≥29%.

8. The wet mixture as claimed in claim 1, in which the particles of the unshaped product are distributed in the following way, as percentages by weight: fraction<2 μm: ≤14% and/or fraction<10 μm: ≤35% and/or fraction<40 μm: ≤50%.

9. The wet mixture as claimed in claim 1, in which the particles of the unshaped product are distributed in the following way, as percentages by weight: fraction<2 μm: ≤12% and/or fraction<10 μm: ≤30% and/or fraction<40 μm: ≤42%.

10. The wet mixture as claimed in claim 1, in which the maximum size of the particles of the unshaped product is less than or equal to 2.5 mm.

11. The wet mixture as claimed in claim 1, in which the maximum size of the particles of the unshaped product is less than or equal to 2 mm.

12. The wet mixture as claimed in claim 1, in which the amount of particles (a) is greater than 82% and/or less than 98% of the weight of the unshaped product.

13. The wet mixture as claimed in claim 1, in which the amount of particles (b) is greater than 2% and less than 13% of the weight of the unshaped product.

14. The wet mixture as claimed in the claim 13, in which the amount of particles (b) is greater than 3% and less than 12% of the weight of the unshaped product.

15. The wet mixture as claimed in claim 1, in which the particles (b) exhibit a melting point of greater than 750° C. and of less than 1650° C.

16. The wet mixture as claimed in claim 1, in which the particles (b) consist of a glass having a chemical composition, said chemical composition comprising, as percentage by weight, more than 90% of oxides.

17. The wet mixture as claimed in claim 1, in which the particles (b) consist of a glass having a chemical composition, said chemical composition comprising, as percentage by weight, more than 45% and less than 80% of silica.

18. The wet mixture as claimed in claim 1, in which the particles (b) made of a glass-ceramic precursor glass and/or the particles (b) made of glass-ceramic exhibit the following chemical composition, as percentages by weight on the basis of the oxides and for a total of more than 95%: SiO.sub.2: 45-75%, and Al.sub.2O.sub.3: 5-40%, and CaO+MgO+Li.sub.2O: 3-30%, nucleating agents, expressed in an oxide form: 0.1-20%.

19. The wet mixture as claimed in claim 18, in which the amount by weight of the nucleating agents is greater than 1% and less than 10%.

20. The wet mixture as claimed in claim 18, in which said nucleating agents are chosen from TiO.sub.2, ZrO.sub.2, P.sub.2O.sub.5 and their mixtures.

21. The wet mixture as claimed in claim 1, in which the particles (b) are distributed in the following way, as percentages by weight on the basis of the particles (b): fraction<1 mm: ≥80%, and/or fraction<0.5 mm: ≥80%, and/or fraction<0.1 mm: ≥25% and/or fraction<0.04 mm: ≤30%.

22. The wet mixture as claimed in claim 1, in which the unshaped product exhibits a chemical composition such that, in percentages by weight, the sum Al.sub.2O.sub.3+ZrO.sub.2+SiO.sub.2+Cr.sub.2O.sub.3≥85%.

23. The wet mixture as claimed in the claim 22, in which the unshaped product exhibits a chemical composition such that, in percentages by weight, the sum Al.sub.2O.sub.3+ZrO.sub.2+SiO.sub.2≥85%.

24. The wet mixture as claimed in claim 1, in which the unshaped product exhibits a following composition, in percentages by weight, for a total of more than 95%: Al.sub.2O.sub.3: 85%-97%, SiO.sub.2: ≥1% and ≤11%.

25. The wet mixture as claimed in claim 1, in which the unshaped product exhibits a composition, in percentages by weight such that: Al.sub.2O.sub.3: 43%-60%, ZrO.sub.2: 20%-43%, SiO.sub.2: 10%-26%.

26. The wet mixture as claimed in claim 1, in which the unshaped product exhibits a composition, in percentages by weight such that: Al.sub.2O.sub.3: 5%-60%, ZrO.sup.2: ≤35%, SiO.sub.2: 5%-25%, Cr.sub.2O.sub.3: 10%-90%.

27. The wet mixture as claimed in claim 1, in which the unshaped product comprises a surface-active agent in an amount of between 0.075% and 1% of the weight of said unshaped product.

28. The wet mixture as claimed in claim 1, in which the fraction of the particles with a size of less than 500 μm represents more than 50% of the weight of said unshaped product.

29. The wet mixture as claimed in claim 1, in which the fraction of the particles with a size of greater than 1 mm is between 0 and 22% of the weight of said unshaped product.

30. A glass melting furnace comprising at least one part, especially in contact with molten glass obtained from a wet mixture as claimed in claim 1.

31. A wet mixture according to claim 1, in which the amount of water is less than 13%, by weight, with respect to the weight of said unshaped product.

32. A wet mixture according to claim 1, in which the unshaped product comprises at least one antisegregation adjuvant.

33. A wet mixture according to claim 1, in which the amount of water is less than 13%, by weight, with respect to the weight of said unshaped product, and in which the unshaped product comprises an antisegregation adjuvant in an amount of between 0.05% and 0.5% of the weight of the unshaped product.

Description

SPECIFIC EMBODIMENTS

(1) In one embodiment, the unshaped product exhibits a chemical composition such that the sum Al.sub.2O.sub.3+ZrO.sub.2+SiO.sub.2≥85%, preferably ≥90%, preferably ≥92%, indeed even greater than 94%, indeed even greater than 95%.

(2) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%: Al.sub.2O.sub.3: 85%-97%, preferably ≥90%, and/or ≤94%, SiO.sub.2: ≥1%, preferably ≥2% and/or ≤10%, preferably ≤9%, preferably ≤7%.

(3) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%: Al.sub.2O.sub.3: 43%-60%. ZrO.sub.2: 20%-43%. SiO.sub.2: 10%-26%.

(4) Preferably, Al.sub.2O.sub.3: ≥45%, preferably ≥50% and/or ≤58%, preferably ≤55%, and/or ZrO.sub.2: ≥25% and/or ≤35%, and/or SiO.sub.2: ≥12%, preferably ≥14%, preferably ≥15% and/or ≤23%, preferably ≤19%.

(5) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%: Al.sub.2O.sub.3: 5%-60%, ZrO.sub.2: ≤35%, SiO.sub.2: 5%-25%, Cr.sub.2O.sub.3: 10%-90%.

(6) Preferably, Al.sub.2O.sub.3: ≥40%, preferably ≥50% and/or ≤60%, and/or ZrO.sub.2: ≥5%, preferably ≥10% and/or ≤30%, indeed even≤20%, and/or SiO.sub.2: ≥10% and/or ≤20%, and/or Cr.sub.2O.sub.3: ≥15%, preferably ≥20% and/or ≤65%, indeed even≤60%.

(7) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 85%-97%, preferably ≥90%, and/or ≤94%, SiO.sub.2: ≥1%, preferably ≥2% and/or ≤10%, preferably ≤9%, preferably ≤7%,
and, preferably, the combined particles (a): comprise reactive alumina in an amount by weight of greater than 2%, of greater than 4%, of greater than 5%, and/or of less than 13%, of less than 10%, on the basis of the weight of the unshaped product, and/or comprise calcined alumina in an amount by weight of greater than 20%, of greater than 25%, and/or of less than 38%, of less than 35%, on the basis of the weight of the unshaped product, and/or comprise electrofused alumina in an amount by weight of greater than 50%, of greater than 55%, and/or of less than 70%, of less than 65%, on the basis of the weight of the unshaped product,
and, preferably, the combined particles (b) of the unshaped product exhibit the following chemical composition: SiO.sub.2: 70%-75%, Al.sub.2O.sub.3: ≤2%, CaO: 8%-12%. Na.sub.2O: 11%-14%. K.sub.2O: ≤4%, MgO: ≤6%, Others: ≤3%.

(8) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 43%-60%, ZrO.sub.2: 20%-43%. SiO.sub.2: 10%-26%.

(9) Preferably, Al.sub.2O.sub.3: ≥45%, preferably ≥50% and/or ≤58%, preferably ≤55%, and/or ZrO.sub.2: ≥25% and/or ≤35%, and/or SiO.sub.2: ≥12%, preferably ≥14%, preferably ≥15% and/or ≤23%, preferably ≤19%.
and, preferably, the combined particles (a): comprise AZS particles in an amount by weight of greater than 80%, preferably of greater than 85%, and/or of less than 95%, on the basis of the weight of the unshaped product, and/or comprise reactive alumina in an amount by weight of greater than 3%, of greater than 5%, and/or of less than 10%, of less than 8%, on the basis of the weight of the unshaped product,
and, preferably, the combined particles (b) exhibit the following chemical composition: SiO.sub.2: 70%-75%. Al.sub.2O.sub.3: ≤2%, CaO: 8%-12%, Na.sub.2O: 11%-14%, K.sub.2O: ≤4%, MgO: ≤6%, Others: ≤3%.

(10) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 5%-60%, ZrO.sub.2: ≤35%, SiO.sub.2: 5%-25%, Cr.sub.2O.sub.3: 10%-90%.

(11) Preferably, Al.sub.2O.sub.3: ≥40%, preferably ≥50% and/or ≤60%, and/or ZrO.sub.2: ≥5%, preferably ≥10% and/or ≤30%, indeed even≤20%, and/or SiO.sub.2: ≥10% and/or ≤20%, and/or Cr.sub.2O.sub.3: ≥15%, preferably ≥20% and/or ≤65%, indeed even≤60%,
and, preferably, the combined particles (a) of the unshaped product: comprise particles exhibiting the following chemical analysis, as percentages by weight on the basis of the oxides: Cr.sub.2O.sub.3+Al.sub.2O.sub.3+ZrO.sub.2+MgO+Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2≥90%, preferably ≥95%, and Cr.sub.2O.sub.3+Al.sub.2O.sub.3≥40%, indeed even≥50%, indeed even≥60%, indeed even≥70%, indeed even≥80%, indeed even≥90%, indeed even≥95%, and Cr.sub.2O.sub.3≥9%, indeed even≥15%, indeed even≥20%, indeed even≥29%, indeed even≥39%, indeed even≥49%, indeed even≥59%, indeed even≥70%, indeed even≥80%, indeed even≥90%, and 20%≥SiO.sub.2≥0.5%, and other oxides: ≤10%, preferably ≤5%, in an amount by weight of greater than 10%, of greater than 20%, of greater than 30% and/or of less than 95%, on the basis of the weight of the unshaped product, and/or comprise reactive alumina in an amount by weight of greater than 2%, of greater than 3%, of greater than 4%, and/or of less than 13%, of less than 10%, of less than 8%, on the basis of the weight of the unshaped product, and/or comprise calcined alumina in an amount by weight of greater than 5%, of greater than 10%, and/or of less than 38%, of less than 35%, of less than 30%, of less than 25%, of less than 20%, on the basis of the weight of the unshaped product, and/or comprise electrofused alumina in an amount by weight of greater than 10%, of greater than 20%, of greater than 25%, and/or of less than 50%, of less than 40%, on the basis of the weight of the unshaped product, and/or comprise AZS particles in an amount by weight of greater than 10%, of greater than 20% and/or of less than 50%, of less than 40%, on the basis of the weight of the unshaped product, and/or comprise pigmentary chromium oxide particles in an amount by weight of greater than 5%, of greater than 10%, and/or of less than 25%, of less than 20%, on the basis of the weight of the unshaped product,
and, preferably, the combined particles (b) exhibit the following chemical composition: SiO.sub.2: 57%-65%, Al.sub.2O.sub.3: ≤3%, CaO: 6%-8%. Na.sub.2O: 14%-18%. K.sub.2O: ≤1%, MgO: 3%-5%. B.sub.2O.sub.3: 5%-12%, Others: ≤3%.

(12) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 85%-97%, preferably ≥90%, and/or ≤94%, SiO.sub.2: ≥1%, preferably ≥2% and/or ≤10%, preferably ≤9%, preferably ≤7%,
and, preferably, the combined particles (a): comprise reactive alumina in an amount by weight of greater than 2%, of greater than 4%, of greater than 5%, and/or of less than 13%, of less than 10%, on the basis of the weight of the unshaped product, and/or comprise calcined alumina in an amount by weight of greater than 20%, of greater than 25%, and/or of less than 38%, of less than 35%, on the basis of the weight of the unshaped product, and/or comprise electrofused alumina in an amount by weight of greater than 50%, of greater than 55%, and/or of less than 70%, of less than 65%, on the basis of the weight of the unshaped product,
and preferably the combined particles (b) of the unshaped product exhibit the following chemical composition, as percentages by weight on the basis of the oxides and for a total of more than 95%, more than 98%, preferably of substantially 100%: SiO.sub.2: 45%-75%, and Al.sub.2O.sub.3: 5%-40%, and CaO+MgO+Li.sub.2O: 3%-30%, nucleating agents, preferably chosen from TiO.sub.2, ZrO.sub.2, P.sub.2O.sub.5 and their mixtures, expressed in an oxide form: 0.1%-20%, preferably 1%-10%, preferably 1%-5%.

(13) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 43%-60%, ZrO.sub.2: 20%-43%, SiO.sub.2: 10%-26%.

(14) Preferably, Al.sub.2O.sub.3: ≥45%, preferably ≥50% and/or ≤58%, preferably ≤55%, and/or ZrO.sub.2: ≥25% and/or ≤35%, and/or SiO.sub.2: ≥12%, preferably ≥14%, preferably ≥15% and/or ≤23%, preferably ≤19%,
and, preferably, the combined particles (a): comprise AZS particles in an amount by weight of greater than 80%, preferably of greater than 85%, and/or of less than 95%, on the basis of the weight of the unshaped product, and/or comprise reactive alumina in an amount by weight of greater than 3%, of greater than 5%, and/or of less than 10%, of less than 8%, on the basis of the weight of the unshaped product,
and preferably the combined particles (b) exhibit the following chemical composition, as percentages by weight on the basis of the oxides and for a total of more than 95%, more than 98%, preferably of substantially 100%: SiO.sub.2: 45%-75%, and Al.sub.2O.sub.3: 5%-40%, and CaO+MgO+Li.sub.2O: 3%-30%. nucleating agents, preferably chosen from TiO.sub.2, ZrO.sub.2, P.sub.2O.sub.5 and their mixtures, expressed in an oxide form: 0.1%-20%, preferably 1%-10%, preferably 1%-5%.

(15) In one embodiment, the unshaped product exhibits the following composition by weight, for a total of more than 95%, preferably for a total of more than 97%, preferably for more than 99%: Al.sub.2O.sub.3: 5%-60%. ZrO.sub.2: ≤35%, SiO.sub.2: 5%-25%, Cr.sub.2O.sub.3: 10%-90%.

(16) Preferably, Al.sub.2O.sub.3: ≥40%, preferably ≥50% and/or ≤60%, and/or ZrO.sub.2: ≥5%, preferably ≥10% and/or ≤30%, indeed even≤20%, and/or SiO.sub.2: ≥10% and/or ≤20%, and/or Cr.sub.2O.sub.3: ≥15%, preferably ≥20% and/or ≤65%, indeed even≤60%,
and, preferably, the combined particles (a) of the unshaped product: comprise particles exhibiting the following chemical analysis, as percentages by weight on the basis of the oxides: Cr.sub.2O.sub.3+Al.sub.2O.sub.3+ZrO.sub.2+MgO+Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2≥90%, preferably ≥95%, and Cr.sub.2O.sub.3+Al.sub.2O.sub.3≥40%, indeed even≥50%, indeed even≥60%, indeed even≥70%, indeed even≥80%, indeed even≥90%, indeed even≥95%, and Cr.sub.2O.sub.3≥9%, indeed even≥15%, indeed even≥20%, indeed even≥29%, indeed even≥39%, indeed even≥49%, indeed even≥59%, indeed even≥70%, indeed even≥80%, indeed even≥90%, and 20%≥SiO.sub.2≥0.5%, and other oxides: ≤10%, preferably ≤5%, in an amount by weight of greater than 10%, of greater than 20%, of greater than 30% and/or of less than 95%, on the basis of the weight of the unshaped product, and/or comprise reactive alumina in an amount by weight of greater than 2%, of greater than 3%, of greater than 4%, and/or of less than 13%, of less than 10%, of less than 8%, on the basis of the weight of the unshaped product, and/or comprise calcined alumina in an amount by weight of greater than 5%, of greater than 10%, and/or of less than 38%, of less than 35%, of less than 30%, of less than 25%, of less than 20%, on the basis of the weight of the unshaped product, and/or comprise electrofused alumina in an amount by weight of greater than 10%, of greater than 20%, of greater than 25%, and/or of less than 50%, of less than 40%, on the basis of the weight of the unshaped product, and/or comprise AZS particles in an amount by weight of greater than 10%, of greater than 20% and/or of less than 50%, of less than 40%, on the basis of the weight of the unshaped product, and/or comprise pigmentary chromium oxide particles in an amount by weight of greater than 5%, of greater than 10%, and/or of less than 25%, of less than 20%, on the basis of the weight of the unshaped product,
and preferably the combined particles (b) exhibit the following chemical composition, as percentages by weight on the basis of the oxides and for a total of more than 95%, more than 98%, preferably of substantially 100%: SiO.sub.2: 45%-75%, and Al.sub.2O.sub.3: 5%-40%, and CaO+MgO+Li.sub.2O: 3%-30%, nucleating agents, preferably chosen from TiO.sub.2, ZrO.sub.2, P.sub.2O.sub.5 and their mixtures, expressed in an oxide form: 0.1%-20%, preferably 1%-10%, preferably 1%-5%.
Detailed Description of the Repair Process

(17) A repair process according to the invention comprises the stages 1) to 8) described above.

(18) Preferably, in stage 1), the different starting materials are mixed in a kneader. The optional surface-active agent may be mixed at this stage or introduced in stage 5).

(19) Preferably, in stage 1), the chemical composition of the particles (b) is chosen so that their melting point is lower than the temperature of the region to be repaired. In one embodiment, the particles (b) exhibit substantially the same composition as the molten glass in the furnace to be repaired.

(20) Preferably, in stage 2), the emptying of the molten glass is carried out at a temperature close to the melting point of the glass. Said emptying can be carried out, for example, through holes made in the bottom, or through holes created by the dismantling of one or more electrodes present.

(21) In the optional stage 3), the rinsing of the bottom, in particular of the worn zones, is preferably carried out by spraying a product suitable for melting the glass residues. Preferably, said product is chosen from sodium sulfate, sodium carbonate, sodium hydroxide and their mixtures. The products make it possible to increase the fluidity of the glass, which makes it easier to discharge it out of the furnace. Preferably, the repair process according to the invention comprises a stage 3).

(22) In stage 4), the temperature in the furnace is reduced to a temperature at which the hot binder is not in the solid state. In other words, the temperature in the furnace is reduced to a temperature which remains greater than the glass transition temperature of the glassy phase of the hot binder.

(23) The glass transition temperature of the glassy phase of the hot binder depends on the nature of the hot binder. The hot binder is preferably chosen in order for the glass transition temperature of its glassy phase to be between 900° C. and 1350° C., preferably between 1000° C. and 1300° C., preferably between 1150° C. and 1250° C.

(24) In stage 5), the unshaped product is wetted, so as to obtain a wet mixture, by adding thereto an amount of water preferably of greater than 8%, preferably of greater than 9%, and/or of less than 13%, of less than 12%, by weight, with respect to the weight of said unshaped product.

(25) In stage 6), the wet mixture is preferably pumped by means of a pump producing a suction pressure of less than or equal to 180 bar and transported into the furnace, preferably by means of a water-cooled blowpipe. The wet mixture is poured into the furnace, over the existing bottom, the holes produced for the emptying of the glass in stage 2) being filled in again beforehand. Said pouring may be carried out so as to produce repairs in different zones of said bottom. The wet mixture is preferably poured over the entire surface of the bottom of the furnace.

(26) In stage 7), the furnace is maintained at a temperature of between 1250° C. and 1400° C., preferably between 1300° C. and 1400° C., in order to make possible the sintering of said wet mixture, preferably for a time of greater than 8 hours, preferably of greater than 10 hours, and preferably of less than 15 hours.

(27) Preferably, when the unshaped product contains particles (b) of glass-ceramic precursor glass, the furnace is maintained at a temperature which makes it possible to promote the nucleation and the growth of the microcrystallites. A person skilled in the art knows how to determine the range of temperatures which makes possible this nucleation and this growth.

(28) The unshaped product according to the invention advantageously allows a low the sintering temperature and/or a reduced time of maintenance at said temperature. During this stage, it is possible to bore the bottom in order to install electrodes.

(29) In stage 8), the composition of glass to be melted is introduced into the furnace and the temperature of the latter is increased up to its operating temperature.

EXAMPLES

(30) The nonlimiting examples which will follow are given for the purpose of illustrating the invention.

(31) The “self-flowable” nature under hot conditions, the segregation and the appearance after the temperature has gone down again are evaluated by the following test:

(32) A flat-bottomed refractory pot exhibiting an internal diameter equal to 170 mm and an internal height equal to 45 mm is fitted into a metal tank exhibiting a diameter equal to 400 mm. The space between the wall of the tank and the wall of the pot is filled in with insulating materials.

(33) A removable lid made of refractory concrete with a thickness equal to 100 mm is suspended above the pot at a height of between 20 mm and 30 mm. This lid exhibits a hole with a diameter of 100 mm at its center which makes it possible to allow the passage of the flame of a gas burner positioned above said lid and to introduce the wet mixture.

(34) The gas burner is ignited and the inside of the refractory pot is brought to 1300° C., at a rate of temperature rise of 500° C./h.

(35) The tank+pot combination is then rotated at a speed of 6 revolutions per minute.

(36) 5 kg of wet mixture are prepared in a kneader having a rotary blade and stationary tank, with a kneading time of 5 minutes.

(37) The wet mixture is subsequently tipped into a metal valley exhibiting a length of 600 mm and edges with a height of 40 mm. Said valley exhibits a slope of 45° and one of its ends is resting on the edge of the central hole of the lid, in order to make possible the introduction under hot conditions of the wet mixture into the pot. The maximum drop height, at the start of the tipping, is approximately 175 mm. Feeding with wet mixture is halted when the latter reaches the top of the refractory pot.

(38) For the tests in which the particles (b) are glass particles, the temperature is subsequently brought to 1450° C. with a rate of temperature rise equal to 100° C./h, and is maintained for a time equal to 10 hours in order to make possible the sintering of the wet mixture.

(39) For the tests in which the particles (b) are particles made of glass-ceramic precursor, the temperature is subsequently brought to 1350° C. with a rate of temperature rise equal to 50° C./h, and is maintained for a time equal to 10 hours in order to make possible the sintering of the wet mixture and the growth of the microcrystallites.

(40) The temperature is brought down gradually at a rate equal to 100° C./h and the slug of sintered product is subsequently removed from the mold.

(41) The appearance of the slug is subsequently observed.

(42) The self-flowable nature under hot conditions is acquired if the slug of sintered product exhibits a diameter substantially equal to the internal diameter of the refractory pot and if the slug does not exhibit, to the naked eye, a hole or a recess at its center.

(43) The slug is subsequently sawn, so as to look for segregation. It is considered that there is segregation when the sawn faces reveal a surface laitance layer extending, from the upper face of the slug, over a depth of 3 mm or more.

(44) The cold compressive strength is measured using an LR150K press sold by Ametek-Lloyd, on cylinders with a diameter equal to 30 mm and with a height equal to 30 mm withdrawn from the slug.

(45) The compositions of the particulate mixtures (a)+(b)+(c) are provided in table 1. The particle size distributions of the electrofused alumina particles and of the AZS particles used are also shown in table 1.

(46) The calcined alumina used is the HVA FG alumina sold by Almatis.

(47) The silica fume is a silica fume comprising more than 90% of silica by weight, which is provided in the form of a powder whose particles have a size of between 0.1 and 5 μm and a median size of less than 0.6 μm, sold by the Société Européenne des Produits Réfractaires.

(48) The cement used is CA25R cement sold by Almatis.

(49) The particles (b) made of glass are made of a soda-lime glass exhibiting the following chemical analysis: SiO.sub.2: 72.3%, Al.sub.2O.sub.3: 0.5%, CaO: 9.5%, Na.sub.2O: 13.4%, MgO: 4%, Others: 0.3%.

(50) The glass transition temperature of this glass is equal to 580° C. The glass transition temperature is determined by differential thermal analysis (DTA) on an STA409C device sold by Netzsch. The sample holders are each equipped with a thermocouple making possible a direct measurement of the temperature of the glass positioned in a dense sintered alumina crucible having a capacity equal to 300 μl and with an identical empty crucible regarded as reference. The glass to be analyzed is ground so as to pass through a sieve with an opening equal to 160 μm. The heat cycle applied during the measurement consists of a rise at a rate equal to 10° C./min, under air, up to 1650° C.

(51) On the thermogram obtained, the glass transition appears as the first endothermic event. The glass transition temperature is equal to the temperature of the point of inflection of the curve in said first endothermic event (i.e., “Tinfl” in the program used).

(52) After grinding, the glass particles exhibit the following particle size distribution: fraction<0.5 μm: 0%, and fraction<2 μm: 0%, and fraction<10 μm: 5%, and fraction<40 μm: 16%, and fraction<100 μm: 35%, and fraction<200 μm: 58%, and maximum size of the particles: 1 mm.

(53) The particles (b) made of a glass-ceramic precursor glass are prepared in the following way:

(54) A starting charge consisting, as percentages by weight, of 60.4% of silica powder with a purity equal to 98%, 23.4% of an alumina powder with a purity greater than 98%, 12.8% of a lithium carbonate powder, 1.6% of a titanium oxide powder and 1.8% of a zirconia powder is melted in a pot placed in an electric furnace. The pot is subsequently taken out under hot conditions and its contents are poured into a water trough, making possible rapid tempering and preventing crystallization. This results in a powder of particles of glass-ceramic precursor glass. The amorphous state of these particles is confirmed by X-ray diffraction. These particles are subsequently dried at 110° C. for 48 hours.

(55) After drying, the particles of glass-ceramic precursor glass are ground in a jaw crusher and sieved so as to obtain combined particles (b) exhibiting the following particle size distribution: fraction<0.5 μm: 0%, and fraction<2 μm: 1%, and fraction<10 μm: 7%, and fraction<40 μm: 15%, and fraction<200 μm: 62%, and maximum size of the particles: 1 mm.

(56) The particles (b) of glass-ceramic precursor glass obtained exhibit the following chemical composition, as percentages by weight: SiO.sub.2: 64.2% Al.sub.2O.sub.3: 24.8% LiO.sub.2: 5.5% TiO.sub.2: 1.7% ZrO.sub.2: 1.9% others: 1.9%.

(57) The glass transition temperature of this glass-ceramic precursor glass is less than 1100° C. This composition makes it possible for the precursor glass to form ZrTiO.sub.4, beta-quartz and beta-spodumene microcrystallites during the sintering of the unshaped product Said sintering is thus a crystallization heat treatment of the glass-ceramic precursor glass.

(58) Comparative example 1, “Comp 1”, is the ramming material described in EP 0 739 861 B1, used in particular in the repair of glass melting furnaces.

(59) Comparative example 2, “Comp 2”, is a self-leveling concrete according to WO2013132442, to which glass particles (b) have been added, the particles (b) representing 5% of the total weight of the self-leveling concrete and of the added glass.

(60) The chemical compositions of the wet unshaped products tested, and also the results of the tests carried out, are provided in table 2.

(61) The examples “Comp 2” and 1 to 5 incorporate, as particles (d), 0.2% of a surface-active agent of the family of the modified polycarboxylate ethers and 0.2% of an antisegregation adjuvant of the family of the starch ethers.

(62) In table 2: for the “Comp 1” example, the remainder to 100% of Al.sub.2O.sub.3+SiO.sub.2+ZrO.sub.2 consists of P.sub.2O.sub.5 and impurities. for the “Comp 2” example, the remainder to 100% of Al.sub.2O.sub.3+SiO.sub.2+ZrO.sub.2+ surface-active agent+antisegregation adjuvant consists of CaO contributed by the hydraulic cement and the glass, and also of Na.sub.2O, of K.sub.2O and of MgO contributed by the glass, and of impurities, for examples 1 to 4, the remainder to 100% of Al.sub.2O.sub.3+SiO.sub.2+ZrO.sub.2+ surface-active agent+antisegregation adjuvant consists of CaO, of Na.sub.2O, of K.sub.2O and of MgO contributed by the glass, and also of impurities, and for example 5, the remainder to 100% of Al.sub.2O.sub.3+SiO.sub.2+ZrO.sub.2+surface-active agent+antisegregation adjuvant consists of Li.sub.2O and of TiO.sub.2 contributed by the glass, and also of impurities.

(63) The addition of water (g) is provided as percentage by weight on the basis of the unshaped product.

(64) The particle size distributions, measured using a Horiba laser particle sizer, are also provided in table 2.—

(65) TABLE-US-00001 TABLE 1 Particulate mixture (a) + (b) + (c), as percentages by weight AZS AZS Powder of Electrofused Electrofused particles particles AZS glass-ceramic Ex. alumina alumina Calcined Reactive Silica Hydraulic 0.5 mm- 40 μm- particles < Glass precursor No. 0.5 mm-3.5 mm 10 μm-200 μm alumina alumina fume cement 2 mm 500 μm 40 μm powder glass Comp 1 — — — — — — — — — — — Comp 2 44.7 14.2 16.1 12.35 2.85 4.8 0 0 0 5 0 1 0 0 0 5 0 0 27 31 34 3 0 2 0 0 0 6 0 0 27 31 31 5 0 3 0 0 0 3 0 0 27 31 31 8 0 4 0 0 0 6 0 0 34 38 17 5 0 5 0 0 0 3 0 0 27 31 31 0 5

(66) TABLE-US-00002 TABLE 2 Distribution of the particles Appearance Cold (a) + (b) + (c) Self- after the compres- Dry unshaped product Addition (percentages by weight) flowable temperature sive (percentages by weight) Water <0.5 <2 <10 <40 <500 >1 Maximum under hot Segre- has gone strength No. Al.sub.2O.sub.3 SiO.sub.2 ZrO.sub.2 (%) μm μm μm μm μm mm size (mm) conditions gation ? down again (MPa) Comp 1 57.2 12.5 25.1 5 10.1 11.7 37.1 53.9 80.3 8 2 no no porous 45 Comp 2 91 6.3 0.1 11 7 11.7 30.2 38.2 55.5 32.8 3.5 yes no highly n.d. cracked and very low mechanical strength 1 52.4 15.8 29.7 11 2.5 9.5 24.6 41.5 76.2 11.9 2 yes no good 70 2 51.8 16.8 28.7 11 2.4 8.9 22.9 39 76.1 11.9 2 yes no good 65 3 48.9 18.9 28.7 11 1.8 7.7 21.3 37.8 75.8 11.9 2 yes no good 60 4 51.8 16.8 28.7 11 2.3 6.9 16.4 28.6 69.8 15.1 2 yes no good n.d. 5 53.1 16.4 28.8 11 3 9.3 23.5 39.2 76.5 12 2 yes no good 80 n.d.—not determined

(67) The results make it possible to make the following observations: The “Comp 1” example, which does not comprise particles (b), does not exhibit a self-flowable nature under hot conditions. The “Comp 2” example exhibits a self-flowable nature but, after the temperature has gone down again, the slug is highly cracked and exhibits a very low mechanical strength: some zones can be broken by hand. Without being committed to any one theory, the inventors attribute this phenomenon to the presence of 4.8% of hydraulic cement in the product of the “Comp 2” example. The “Comp 1” example exhibits a lower cold compressive strength than that of the unshaped products of the examples according to the invention. The “Comp 1” example requires a sintering temperature of greater than 1350° C. to develop a cold compressive strength similar to that of the products according to the invention: the reintroduction of the composition of glass to be melted of stage 8) may thus be carried out more rapidly with the products according to the invention. The return to production is thus faster than for the product of the “Comp 1” example. The unshaped products of examples 1, 2 and 5 are the preferred examples.

(68) As is now clearly apparent, the invention provides an unshaped product which makes it possible to manufacture a wet self-flow mixture, which does not result in segregation and which exhibits, after sintering, a good mechanical strength in cold compression, even after sintering at 1350° C. Furthermore, this unshaped product, after wetting, may be pumped with suction pressures of less than or equal to 180 bar.

(69) Finally, other tests have shown that an unshaped product according to the invention, after sintering, generates only a few or no defects when it is in contact with molten glass.

(70) An unshaped product according to the invention is thus perfectly capable of being used for the repair of a glass melting furnace, in particular for a repair of a bottom of such a furnace.

(71) Of course, the present invention is not limited to the embodiments described, which are provided by way of illustrative and nonlimiting examples.