Method for repairing a glass melting furnace

Abstract

The invention relates to a method for hot repairing a region to be repaired (301, 302, 303) inside a glass melting furnace (10), the region to be repaired being at a temperature higher than 300°C, said method comprising the following steps: • a) installing an inner formwork (32i) in a service position, so as to produce a mold around the region to be repaired; • b) filling the mold with a repair product (41), at least part of the inner formwork being made of a ceramic matrix composite (CMC).

Description

[0001] Description

[0002] Title: METHOD FOR REPAIRING A GLASS MELTING FURNACE

[0003] Technical field

[0004] The present invention relates to a method of repairing a glass melting furnace. It also relates to a nozzle that can be used for carrying out this method.

[0005] Prior art

[0006] Figure 1 schematically represents a half-cross section of a glass melting furnace 10. In particular, a tank 12, a metal structure 14 and a superstructure 16 can be seen.

[0007] The tank 12, intended to contain the molten glass, comprises a vertical side wall 22 and a base 24. The side wall 22 is conventionally made up of lateral tank blocks which extend over the entire height of the tank, up to an upper edge 25. The base of the tank defines the substantially horizontal bottom of the tank and the side wall, substantially vertical, surrounds the bottom.

[0008] The term "superstructure" of a glass melting furnace is conventionally used to refer to the assembly consisting of the nose bricks (if present), the walls and the vault. The superstructure 16 is intended to close the furnace by covering the tank. It does not come into contact with the molten glass. It conventionally comprises, at its base, an intermediate layer 18 by which it rests on the metal structure, a side wall 26 resting on the intermediate layer and a vault 28. In a gas furnace, the burners, not shown, are arranged in the side wall 26. The intermediate layer 18 comprises, and preferably consists of, nose pieces 20 ("tuckstones" in English).

[0009] The “interior” of the oven is thus delimited by an interior surface 29 defined by an enclosure constituted by the tank and the superstructure.

[0010] Molten glass, vapors, and condensates are highly corrosive. Refractory parts are subject to significant wear.

[0011] The refractory parts used, usually in the form of blocks or slabs, are melted and cast pieces, or obtained by sintering. They are chosen according to the location where they are placed, so as to withstand local constraints and give the furnace a satisfactory lifespan. The choice is also guided by the need to avoid generating defects that would render the glass unusable, which would reduce production yields.

[0012] To increase the furnace's lifespan, the glassmaker is required to carry out repairs. A repair consists of filling a void resulting from furnace wear with a repair material, i.e., fixing a repair material in an area initially occupied by a refractory material and which has disappeared due to wear. This area is called the "area to be repaired."

[0013] As illustrated in Figure 2, a region to be repaired 30 may be “hollow”, i.e. in the form of a cavity 30i, for example in the floor. It may also be “protruding”, i.e. be a region 302 in the extension of an initially protruding block, for example a nose brick. The region to be repaired may also pass through the furnace enclosure, putting the inside and outside of the furnace into fluid communication. Such a through region to be repaired may in particular lead, in the tank, to leaks of molten glass. These leaks are dangerous and may cause the furnace to shut down. The region to be repaired 30a is an example of a through region to be repaired.

[0014] A region to be repaired is therefore an empty space (devoid of refractory material), partially delimited by one or more refractory parts of the furnace and partially by a virtual envelope, in dotted lines in figure 2, extending along the surface of the said refractory part(s) before they wear out.

[0015] To repair the furnace, as illustrated in EP0739861, a formwork is conventionally produced in order to materialize said virtual envelope and to produce, with the refractory part(s), a mold capable of retaining the repair product before it hardens. The elements of the formwork, for example in the form of plates, flat or not, are conventionally held by accessories in a service position in which they define said mold.

[0016] The formwork includes a portion inside a furnace, where wear has occurred. It may also include a portion outside the furnace when wear has led to a passage through the furnace enclosure, in order to prevent the repair material from escaping outside the furnace. The outer portion of the formwork is typically a veneer. For the sake of clarity, the portions of the formwork inside and outside the furnace are referred to as "inner formwork" and "outer formwork," respectively. A "hot" repair is one that is carried out at a temperature typically above 300°C. Repairing hot therefore requires only a limited reduction in temperature, called "de-soaking," or even no reduction in temperature, which considerably limits the duration of interruption of furnace operation. The introduction of the formwork elements into the furnace can, however, lead to their degradation, under the effect of thermal shock.

[0017] Furthermore, the interior of a furnace is difficult to access, making it difficult to create the internal formwork for certain areas requiring repair. In particular, the introduction of the internal formwork elements may require passages to be created through the furnace enclosure. Furthermore, during a hot repair, no operator can enter the furnace. The installation of the internal formwork must therefore sometimes be carried out at a distance from the area requiring repair. The size and weight of the internal formwork elements can therefore considerably slow down the creation of the formwork.

[0018] These constraints also make it very difficult to create a complex-shaped interior formwork, particularly when the area to be repaired projects towards the interior of the furnace.

[0019] The mold is then filled with repair product, typically using a pump. The repair product experiences a sudden increase in temperature as it enters the mold, resulting in a reduction in its ability to flow. This makes it difficult to fill the mold evenly.

[0020] Typically, the inner casing is made of metal and is cooled by circulating water. After the repair product has hardened, the inner casing must be removed, as the metal generates bubbles when in contact with the molten glass.

[0021] After the repair product has hardened, the formwork is removed to reveal the reconstructed refractory pieces. However, metal formwork generally does not allow for the reconstruction of the original shapes if they are complex. The temperature can then be increased to restart the furnace, in a process called "tempering."

[0022] EP 0739 861 B 1 describes an example of a method for repairing glass melting furnaces, in particular the tank.

[0023] Furthermore, there are products for repairing metalworking furnaces. However, the mechanical constraints in this application are very different from those encountered in a glassmaking furnace. In particular, the conditions for corrosion by glass or molten metal are very different. Finally, certain impurities, tolerated in metalworking furnaces, are unacceptable for glassmaking. In particular, the refractory materials used in glassmaking furnaces must not cause stone release due to fragmentation or produce bubbles. A repair product intended for a metalworking furnace is therefore not, a priori, usable for a glassmaking furnace, particularly in an area in contact with molten glass.

[0024] There is a continuing need for glass melting furnace repair solutions that address the above-mentioned issues, particularly those that enable rapid return to production of the furnace without degrading the quality of the glass produced.

[0025] The present invention aims to satisfy, at least partially, this need.

[0026] Summary of the invention

[0027] According to a first main aspect, the invention provides a method for hot repairing a region inside a glass melting furnace, called the "region to be repaired", at a temperature above 300°C, said method comprising the following steps: a) installing an internal formwork in a service position, so as to produce a mold around the region to be repaired; b) filling, preferably by pouring, the mold with a repair product, at least part of the internal formwork being made of a ceramic, preferably in the form of a Ceramic Matrix Composite (CMC).

[0028] As will be seen in more detail in the remainder of the description, the inventors have notably discovered that a ceramic, in particular in the form of a CMC, does not significantly modify the quality of the glass produced when it is brought into contact with molten glass or with the corrosive vapors present in the furnace, and therefore does not require removal of the internal formwork at the end of the repair.

[0029] Furthermore, a ceramic, particularly in the form of a CMC

[0030] - is light, which makes it easy to handle,

[0031] - is easy to conform to complex geometries, allowing precise adaptation to the configuration of the region to be repaired.

[0032] Additionally, a CMC is highly resistant to thermal shock, which allows for hot repair without damaging the formwork elements when they are introduced into the furnace. The invention thus allows for particularly rapid return to production of the furnace, without the repair affecting the quality of the glass, and in particular without affecting the quantity of defects in the glass.

[0033] A method according to the invention may also comprise one or more of the following optional and preferred features:

[0034] - the area to be repaired is located in the tank and / or in the superstructure;

[0035] - said ceramic, preferably in the form of a CMC, is sintered;

[0036] - said ceramic, preferably in the form of a CMC, consists of more than 90% of its mass of oxides;

[0037] - in said ceramic, preferably in the form of a CMC, the total content SiO +Al Oa+Z U+C Oa is preferably greater than 80%, preferably greater than 90%, preferably greater than 95%, as a percentage by mass based on the oxides;

[0038] - said CMC comprises more than 20% and less than 80% by volume of fibers, the remainder being constituted by the matrix;

[0039] - said fibers are composed of more than 90%, preferably more than 99%, preferably 100% of oxides, in mass percentage, preferably made up of an oxide;

[0040] - said fibers preferably comprise more than 50% AhCh or SiCh or Z1O2;

[0041] - said fibers are arranged in the form of a fabric;

[0042] - said matrix is ​​composed of more than 90%, preferably more than 99%, preferably 100% of oxides, in mass percentage;

[0043] - said matrix comprises AI2O3 and / or SiCh and / or Z1O2 and / or C Oa;

[0044] - in said matrix, the total content SiCh+AhCh+ZrCh+CnOa is preferably greater than 80%, preferably greater than 90%, preferably greater than 95%, as a percentage by mass based on the oxides;

[0045] - said temperature of the region to be repaired is greater than 400°C, preferably greater than 500°C, preferably greater than 600°C, preferably greater than 700°C, preferably greater than 800°C, preferably greater than 900°C;

[0046] - in step a), at least one element of said internal formwork is introduced into the furnace through a passage in a first configuration, then said formwork element is deployed from the first configuration to a second configuration incompatible with extraction of said formwork element through said passage, i.e. such that the formwork element has dimensions which, in the second configuration, prevent it from passing through the passage through the furnace enclosure;

[0047] - said formwork element is folded in the first configuration, and unfolded in the second configuration;

[0048] - the said passage

[0049] - results from wear of the oven, or

[0050] - results from the dismantling of a burner and / or an electrode, or

[0051] - is provided by an operator for the introduction of the formwork elements inside the furnace and is refilled before the furnace is put back into operation;

[0052] - in step a), at least one formwork element having a concave shape is used, preferably having the shape of a cavity which, in the service position, is oriented towards the inner surface of the oven to produce said mold, in cooperation with said inner surface;

[0053] - in step a), at least one formwork element is used having an undercut area, i.e. an area which, due to its shape, hinders the extraction of the formwork element after the repair product has hardened;

[0054] - in step a), at least one formwork element is used in the form of a plate, flat or non-flat, the thickness of the plate being greater than 3 mm, preferably greater than 8 mm and / or less than 50 mm, preferably less than 40 mm, preferably less than 30 mm, preferably less than 20 mm, preferably less than 15 mm;

[0055] - in step a), the internal formwork is shaped so that the mold fits the region to be repaired, i.e. allows the shape of the oven to be restored after step b), before wear;

[0056] - the manufacture of the part of the interior formwork from a ceramic, preferably in the form of a ceramic matrix composite, comprises taking an impression on a replica of the part of the furnace comprising the region to be repaired, before the wear of the furnace having led to the region to be repaired;

[0057] - at least one element of said inner formwork has the shape of a part of the furnace which was projecting towards the interior of the furnace before said part disappeared through wear, in particular the shape of a surface of a nose brick initially exposed inside the furnace;

[0058] - the internal formwork comprises a ceramic plate, preferably in the form of a ceramic matrix composite, having two large faces substantially parallel to each other, the ratio of the surface area of ​​a large face (in cm 2) on the thickness (in cm, measured between the two large faces) being greater than 30 cm, preferably greater than 50 cm, preferably greater than 100 cm, preferably greater than 200 cm, preferably greater than 500 cm, preferably greater than 1000 cm, preferably greater than 2000 cm, and / or less than 250000, preferably less than 200000, preferably less than 150000, preferably less than 100000, preferably less than 50000, preferably less than 10000, preferably less than 8000, preferably less than 5000, each large face of the plate preferably having a surface area greater than 1000 cm 2 , preferably greater than 1500 cm 2 , preferably greater than 2000 cm 2 , preferably greater than 2500 cm 2 , and / or less than 10000 cm 2 , preferably less than 8000 cm 2 , preferably less than 5000 cm 2 ;

[0059] - in step a), at least one formwork element having a flat shape, i.e. a panel, is used;

[0060] - in step a), at least one formwork element is used having a shape along at least 3 faces, preferably at least 4 faces, or even 5 faces of a refractory block of a glass furnace, in particular of a nose piece;

[0061] - in step a), at least one formwork element is used having a shape following a large face, for example rectangular, and two small faces arranged along opposite sides of the large face, for example along the two small sides or the two large sides of a large rectangular face;

[0062] - in step a), accessories are used for holding the elements of the internal formwork in the service position, said accessories, preferably having a tubular shape, being made of a ceramic, preferably in the form of a CMC, preferably identical to the ceramic, preferably in the form of a CMC, of ​​the formwork elements;

[0063] - in step a), one or more ceramic tubes, preferably in the form of a CMC, and / or one or more metal rods, preferably cooled using water circulation, are positioned so as to maintain the internal formwork;

[0064] - in step a), formwork elements and, preferably, accessories are used, which are all made of a ceramic, preferably in the form of a CMC, so that the inner formwork is entirely made of a ceramic, preferably in the form of a CMC;

[0065] - in step a), formwork elements and, preferably, accessories are used, which are all made of a ceramic, preferably in the form of a CMC, said formwork elements and accessories preferably not being cooled, and in particular not being cooled using water circulation;

[0066] - at least one element of the interior formwork made of a ceramic, preferably in the form of a CMC, comprises through holes and / or recesses arranged so as to be filled by the repair product during step b);

[0067] - preferably the mass of a formwork element, preferably the mass of more than 50% by number of the formwork elements, preferably the mass of each of the formwork elements is greater than 3 kg, preferably greater than 4 kg and / or preferably less than 50 kg, preferably less than 40 kg, preferably less than 30 kg, preferably less than 20 kg;

[0068] - preferably, the largest dimension of a formwork element, preferably more than 30% by number of the formwork elements, preferably more than 50% by number of the formwork elements is greater than 400 mm, preferably greater than 600 mm and preferably less than 1600 mm, preferably less than 1400 mm;

[0069] - in step b), the repair product is introduced into the region to be repaired by crossing a passage resulting from the wear of the furnace, optionally identical to the passage through which the elements of the internal formwork were introduced;

[0070] - in step b), the mold is filled by passing the repair product through at least one nozzle, preferably previously introduced into the region to be repaired;

[0071] - the nozzle is provided with radial ejection orifices through which the repair product passes, a radial direction being relative to the direction of supply of the nozzle;

[0072] - the nozzle passes through the internal formwork or a wall of the furnace, in particular delimiting the region to be repaired;

[0073] - a first end of the nozzle is supported on a surface of the inner formwork, preferably inserted into a housing of a surface of the inner formwork, a second end of the nozzle being outside the region to be repaired, inside or outside the furnace;

[0074] - a first end of the nozzle is supported on an interior surface of the furnace defining the region to be repaired, preferably inserted into a housing of a surface of the furnace defining the region to be repaired, a second end of the nozzle being outside the region to be repaired, inside or outside the furnace;

[0075] - said nozzle(s) are made of a ceramic, preferably sintered, preferably of similar chemical composition, preferably identical to that of the cured repair product, preferably sintered;

[0076] - the method comprises, after step b), a step 5) of hardening, preferably sintering, of the repair product introduced into the mold;

[0077] - in step b), the cured, preferably sintered, repair product obtained consists of a plurality of constituents, the content of a constituent of the cured, preferably sintered repair product, preferably of any constituent of the cured, preferably sintered repair product, the content of which is greater than 5%, as a percentage by mass based on the oxides

[0078] - differs by less than 20%, preferably by less than 10% from the content of said constituent in said ceramic, preferably in the form of a CMC, and / or

[0079] - differs by less than 20%, preferably by less than 10%, from the content of said constituent in a region of the furnace delimiting the region to be repaired, and / or

[0080] - differs by less than 20%, preferably by less than 10% from the content of said constituent in said nozzle;

[0081] - the internal casing and / or the nozzle are left in the area to be repaired after said repair, i.e. they are not removed before the furnace is put back into operation:

[0082] - the method comprises, before step a), the following step:

[0083] - if the region to be repaired is, at least partially, delimited by a surface of the furnace tank in contact with the bath of molten glass, emptying, at least partially, said molten glass from the tank, so as to expose said region to be repaired; and, after step b), the following step:

[0084] - introduction of a glass composition to be melted into the tank, the temperature of the furnace being maintained in the said region to be repaired during all stages of the process;

[0085] - the method includes a step of rinsing the region to be repaired after exposing the region to be repaired.

[0086] The invention also relates to a glass melting furnace comprising at least one region repaired according to a method according to the invention.

[0087] According to a second main aspect, the invention provides a nozzle for injecting a repair product, in particular for a glass furnace, the nozzle comprising

[0088] - a feed orifice through which the repair product is intended to enter the nozzle, and

[0089] - an orifice for ejecting the repair product from the nozzle, in fluid communication with the supply orifice and opening outwards from the nozzle via an ejection opening oriented in a radial ejection direction relative to the axis of the nozzle. A nozzle according to the invention may also comprise one or more of the following optional and preferred features: - the axis of the nozzle extends in the direction of the length of the nozzle;

[0090] - the axis of the nozzle is parallel, preferably coincident with the axis of the feed orifice;

[0091] - the nozzle is made of a ceramic, preferably made of oxides for more than 90% of its mass, preferably for more than 95% of its mass, preferably for more than 98% of its mass, preferably for more than 99% of its mass, preferably for more than 99.5% of its mass;

[0092] - the content of a constituent of the nozzle, preferably any constituent whose content is greater than 5%, as a percentage by mass based on the oxides:

[0093] - differs by less than 20%, preferably by less than 10%, from the content of said constituent in a region of the furnace delimiting the region to be repaired, and / or

[0094] - differs by less than 20%, preferably by less than 10% from the content of said constituent in the cured, preferably sintered, repair product;

[0095] - the nozzle comprises more than 1, preferably more than 3, preferably more than 5, preferably more than 10, preferably more than 20 and / or less than 100, preferably less than 50 ejection orifices;

[0096] - an ejection orifice, preferably each ejection orifice is a cylindrical hole, preferably of circular or oblong section, preferably circular;

[0097] - the ejection openings of the ejection orifices are regularly distributed over at least a portion of the outer surface of the nozzle, preferably over a cylindrical portion of the outer surface of the nozzle;

[0098] - the ejection opening of an ejection orifice, preferably of each ejection orifice, has an equivalent diameter greater than 8 mm, preferably greater than 10 mm and / or less than 50 mm, preferably less than 40 mm, preferably less than 30 mm, preferably less than 25 mm;

[0099] - the nozzle has the general shape of a tube, preferably closed at one end, the axis of the nozzle being the axis of said tube;

[0100] - the nozzle has a generally cylindrical shape, preferably of circular section, one end of the nozzle preferably being closed by a bottom;

[0101] - the nozzle has a wall of substantially constant thickness, preferably greater than 5 mm, preferably greater than 7 mm, preferably greater than 10 mm and preferably less than 30 mm, preferably less than 25 mm, preferably less than 20 mm; - the nozzle has an equivalent internal diameter greater than 40 mm and preferably less than 200 mm, preferably less than 150 mm, preferably less than 100 mm.

[0102] In a hot repair method according to the invention, comprising steps a) and b), at least one nozzle according to the invention is preferably used to inject the repair product.

[0103] In general, the invention provides a method for repairing a region inside a glass melting furnace, called the "region to be repaired", preferably at a temperature above 300°C, said method comprising the following steps: a') installing an inner formwork in a service position, so as to produce a mold around the region to be repaired; b') filling, preferably by casting, the mold with a repair product, at least part of the inner formwork preferably being made of a ceramic, preferably in the form of a CMC, a nozzle according to the invention being installed in step a') in a supply position in which at least one ejection orifice, preferably each injection orifice, opens into the region to be repaired, and at least one supply orifice, preferably each supply orifice, opens outside the region to be repaired, preferably outside the furnace.

[0104] Preferably, in the feed position, one end of the nozzle, preferably the end of the nozzle opposite the feed orifice, is supported, preferably fixed on a surface delimiting the region to be repaired, in particular on the surface of the inner casing or on the inner surface 29 of the furnace, defined by the tank and the superstructure of the furnace. The fixing preferably results from an insertion in a housing of said nozzle end in a housing provided on the surface of the inner casing or on the inner surface of the furnace, the housing preferably being of a shape complementary to said end.

[0105] Preferably, in the feed position, the nozzle passes through a wall of the furnace, for example the side wall of the furnace tank, and is preferably fixed to the inner formwork, or passes through the inner formwork and is preferably fixed to a wall of the furnace. The support, preferably the fixing of the nozzle, advantageously contributes to the rigidity of the inner formwork. The presence of the nozzle can also advantageously contribute to the strength of the repair, by anchoring the repair product after it has hardened.

[0106] Preferably, the nozzle is left in the oven after repair. This helps anchor the repair product. This also simplifies the repair process.

[0107] Preferably, a method according to the second main aspect of the invention is a repair method according to the first main aspect of the invention, and vice versa. In particular, step a') may comprise one or more features, optional or not, of a step a), and step b') may comprise one or more features, optional or not, of a step b).

[0108] The invention also relates to a method comprising the following steps:

[0109] 2) preferably, rinsing the said region to be repaired;

[0110] 3) optionally, reduction of the temperature in the oven, up to a temperature above 300°C;

[0111] 4) implementation of steps a) and b) or steps a') and b');

[0112] 5) preferably, in particular when the method comprises a step 3), increasing and maintaining the temperature of the furnace between 900°C and 1400°C in order to sinter the repair product;

[0113] 6) introduction of a glass composition to be melted into the tank and, if said method includes a step 3), increasing the temperature of the furnace to an operating temperature leading to the melting of said composition.

[0114] Preferably, the method comprises a step 2) of rinsing the region to be repaired.

[0115] In one embodiment, the method comprises a step 3) of reducing the temperature in the furnace to a temperature above 900°C and below 1500°C, and a step 5) in which the furnace is maintained at a temperature between 900°C and 1400°C.

[0116] Preferably, the method comprises a step 5) in which said temperature is maintained for a period of more than 8 hours and less than 15 hours.

[0117] In a first particular embodiment, the region to be repaired is, at least partially, delimited by a surface of the furnace tank in contact with the bath of molten glass, and the method comprises, before step 2), the following step: 1) emptying, at least partially, said molten glass from the tank, so as to fully expose said region to be repaired.

[0118] In a second particular embodiment, the region to be repaired is entirely delimited by a surface of the furnace tank which is not in contact with the molten glass bath, and the method does not include step 1).

[0119] Brief description of the figures

[0120] Other characteristics and advantages of the invention will become apparent upon examination of the description which follows and with regard to the appended drawing in which:

[0121] - figure 1 [Fig 1], described in the preamble, schematically represents a half-cross section of a glass melting furnace, before wear;

[0122] - figure 2 [Fig 2] schematically represents the furnace of figure 1 after wear;

[0123] - figure 3 [Fig 3] schematically represents a method according to the invention;

[0124] - figure 4 [Fig 4] schematically represents a partitioned region to be repaired;

[0125] - figure 5 [Fig 5] schematically represents an example of a nozzle according to the invention making it possible to bring the repair product into the region to be repaired;

[0126] - figure 6 [Fig 6] schematically represents a first step for producing formwork, in one embodiment of the invention;

[0127] - figure 7 [Fig 7] schematically represents a second step for producing formwork, in the embodiment of the invention of figure 6;

[0128] - figure 8 [Fig 8] represents an example of formwork according to the invention;

[0129] - figure 9 [fig 9] shows an example of an interior formwork element with through holes.

[0130] Definitions

[0131] A “formwork” is a part of the “mold” into which the repair product is introduced.

[0132] H results from an assembly of one or more “formwork elements” and a positioning of the assembled formwork element(s) in the “service position”. The part of the mold defined by the formwork is completed with a part of the interior surface of the furnace so as to constitute the mold.

[0133] In addition to formwork elements, a formwork includes "accessories" used to assemble and fix the formwork elements in service position, and which are not in contact with the repair material during the repair. Unlike accessories, formwork elements are parts that come into contact with the repair material during the repair.

[0134] The area to be repaired can be compartmentalized using partitions. A partition is considered a formwork element.

[0135] A "passage" is a hole that crosses the enclosure of the oven, thus connecting the inside and the outside of the oven.

[0136] The "equivalent diameter" of a surface is the diameter of a disk with the same area as that surface.

[0137] A dry particulate mixture is called an “unformed product”.

[0138] By product “in one material” or “of one material” is meant a product consisting of more than 95%, more than 98%, preferably substantially 100% of its mass of said material.

[0139] By "refractory material" is meant a material having a melting temperature above 1500°C. This definition is commonly used by those skilled in the art and cited in "Refractory materials and technical ceramics (elements of ceramurgical and technological matters)", G. Aliprandi, Septima Paris, 1979. This work also gives on pages 297 to 301 examples of refractory materials, in particular oxides, carbides and nitrides.

[0140] The term "glass transition temperature" of a glass means the temperature at which the glass changes from a solid state to a viscous state. The glass transition temperature can be determined by differential thermal analysis (DTA). The glass transition temperature is the temperature at which the glass has a viscosity substantially equal to 10 12 No. A glass is classically considered "in the solid state" at a temperature below its glass transition temperature.

[0141] The term "hot binder" means a constituent having a melting temperature above 600°C, and capable of binding together, after hardening under the effect of a drop in temperature, particles with which it has been mixed.

[0142] The maximum size is the 99.5 percentile (099.5) of a powder, this percentile corresponding to the mass percentage of 99.5%, on the cumulative particle size distribution curve of the powder particles, the particle sizes being classified in ascending order. The particle size distributions and the maximum size can be determined using a laser particle size analyzer. The laser particle size analyzer can be a Partica LA-950 from HORIBA.

[0143] By "impurities" is meant unavoidable constituents, introduced unintentionally and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated. Preferably the quantity of impurities is less than 2%, less than 1%, less than 0.5%, or even substantially zero.

[0144] By "hot self-pourable" is meant a repair product capable of spreading under its own weight and filling the mold without segregation, in a temperature range between 300°C and 1550°C. Segregation is considered to exist when the casting face of the product obtained after placement of the repair product and sintering has a surface layer of laitance extending from said casting face to a depth of 3 mm or more. This surface layer of laitance can easily be revealed after drying or sintering of the product, the sawing being carried out in a plane perpendicular to the casting face.

[0145] AZS products are products, preferably electrocast, whose main constituents are alumina (AI2O3), zirconia (ZrO2) and silica (SiO2). In other words, alumina, zirconia and silica are the constituents with the highest mass contents. These products are well suited for the manufacture of glass furnaces. In particular, current AZS products are mainly used for the regions in contact with molten glass as well as for the superstructure of glass furnaces. AZS products include products marketed by Saint-Gobain SEFPRO, such as ER-1681, ER-1685 or ER-1711.

[0146] When referring to Z1O2 or zirconia, Z1O2 and traces of HfO2 should be understood. Indeed, a little HfO2, chemically inseparable from ZrO2 in a fusion process and having similar properties, is always naturally present in zirconia sources at contents generally lower than 2%. Hafnium oxide is then not considered an impurity. The HfO2 content in AZS particles is preferably lower than 5%, lower than 3%, lower than 2%.

[0147] The term "Ceramic Matrix Composite" or "CMC" is generally used to describe a ceramic composed of a ceramic textile stiffened by a ceramic matrix. A "textile" is an assembly of fibers, possibly a yarn, particularly an assembly of yarns. The textile typically represents between 20% and 80% of the volume of a CMC, with the remainder being the matrix.

[0148] Generally speaking, when referring to a volume percentage relative to an object, for example a CMC (e.g. a percentage of fibers) or the matrix of a CMC (as in the previous sentence), the volume to be considered is that of the object defined by its external surface, that is to say it includes the empty spaces inside the object.

[0149] A "fiber" is a filament whose length is greater than 5 times its equivalent diameter. The "equivalent diameter" of a fiber is the diameter of a disk with the same area as its cross-section at mid-length.

[0150] In a textile, the fibers may be assembled in a disorderly manner, as in felt or paper, or in one or more preferred directions, preferably in the form of threads, themselves preferably in the form of one or more fabrics. A thread of a textile may be

[0151] - a “single yarn”, which is an assembly of fibers which, in cross-section, comprises more than 10 and preferably less than 500,000 fibers, and whose length is greater than 5 times the diameter, or

[0152] - an “assembled yarn”, which is an assembly of single yarns which, in cross-section, preferably comprises more than 2 and preferably less than 500 single yarns.

[0153] A textile can be in particular:

[0154] - an organized structure of fibers, and / or threads, simple or assembled, in particular a knit or a fabric, or

[0155] - a random structure of fibers, and / or threads, single or assembled, for example a veil, and / or fibers not incorporated in the form of threads, said random structure being able to be for example a paper or a felt, a random structure not being preferred.

[0156] A "fabric" is made up of a network of parallel warp threads and weft threads crossing said network transversely.

[0157] A "knit" consists of a network of threads in the form of loops, possibly reinforced by one or more sets of threads extending substantially parallel to each other, said set or sets being trapped in said loops. A "sheet" consists of a set of parallel threads.

[0158] By "ceramic" is meant a product that is neither metallic nor organic. For the purposes of the present invention, carbon is considered a ceramic product.

[0159] A "sialon", SiAlON, is an oxynitride compound of at least the elements Si, Al and N, in particular a compound conforming to one of the following formulas:

[0160] - If xAlyOuNv, in which: x is greater than or equal to 0, greater than 0.05, greater than 0.1 or greater than 0.2, and less than or equal to 1, less than or equal to 0.8 or less than or equal to 0.4, y is greater than or equal to 0, or greater than 0.1, greater than 0.3 or greater than 0.5, and less than or equal to 1, u is greater than 0, greater than 0.1 or greater than 0.2, and less than or equal to

[0161] 1 or less than or equal to 0.7, v is greater than 0, greater than 0.1, greater than 0.2 or greater than 0.5, or greater than 0.7, and less than or equal to 1,

[0162] - x+y > 0, x, y, u e. v being stoichiometric indices and normalized with respect to the one which is the highest, made equal to 1;

[0163] - Me xSii2-(m+n)Al(m+n)OnNi6-n, with 0 < x < 2, Me a cation chosen from the lanthanide cations, Fe, Y, Ca, Li and their mixtures, 0 < m < 12, 0 < n < 12 and 0 < n+m < 12, the SiAlON following this formula being generally called "oc' - SiAlON" or "SiA10N-Oc'".

[0164] Unless otherwise stated, all percentages are mass percentages based on oxides. A mass content of an element is expressed in the form of the most stable oxide.

[0165] “Behave” or “include” or “present” shall be interpreted in a non-limiting manner.

[0166] Detailed description

[0167] Figures 1 and 2 having been described in the preamble, we refer to figure 3.

[0168] Hot repair A method according to the invention is used for hot repair of a region of a glass melting furnace.

[0169] The region to be repaired 30 may in particular be located in the tank 12, preferably in the side wall 22 of the tank and / or in the superstructure 16, in particular in the intermediate layer 18 and / or in the side wall 26 of the superstructure.

[0170] The invention is particularly useful for repairing the side wall 22 of the tank or the superstructure. It is then necessary to retain the repair product to prevent it from flowing out by gravity. This problem does not generally arise for the repair of the sole. The use of ceramic formwork elements, in particular in the form of plates, and in particular in a ceramic in the form of a CMC, advantageously makes it possible to produce a formwork that does not need to be cooled. This formwork can therefore be lighter (in particular if it is produced using thin plates). Furthermore, due to the absence of cooling and the fact that it can be left in place after repair, this formwork is very quick to install and does not need to be dismantled. The downtime of the furnace for repair is advantageously reduced. Finally, the formwork can be of complex shape.

[0171] The area to be repaired may have the form of a cavity, through or not, for example a region in depression, in particular due to wear, opening towards the interior of the furnace, for example the tank.

[0172] In one embodiment, in particular for the repair of a tank initially containing a bath of molten glass in contact with the region to be repaired, the method comprises a step 1) of emptying, at least partially, the molten glass from the tank, so as to expose said region to be repaired.

[0173] The furnace tank is then emptied, at least partially, of the molten glass it contains, until the area to be repaired is exposed. Emptying can be carried out using any technique known to those skilled in the art.

[0174] For example, it is possible to evacuate the molten glass from the furnace through passages drilled in the hearth or through passages created by the dismantling of one or more electrodes or one or more burners.

[0175] Step 1) is optional for the repair of a region that is not in contact with the molten glass bath. In step 2), optional but preferred, the region to be repaired is rinsed, i.e. freed from glass residue, according to any conventional technique. Preferably, a product suitable for increasing the fluidity of the molten glass is sprayed, at least on the region to be repaired. The glass thus fluidized is more easily removed from the furnace. Preferably, the fluidizing product is chosen from sodium sulfate, sodium carbonate, soda and mixtures thereof.

[0176] In step 3), optional, the temperature in the furnace may be reduced to a temperature preferably greater than 400°C, preferably greater than 500°C, preferably greater than 600°C, preferably greater than 700°C, preferably greater than 800°C, preferably greater than 900°C, and preferably less than 1550°C, preferably less than 1500°C or even less than 1450°C or 1400°C.

[0177] In one embodiment, the repair product used in step b) contains a hot binder, and in step 3), the temperature in the furnace is reduced to a temperature at which the hot binder is not in the solid state. In particular, when the hot binder is a glass, the temperature in the furnace is reduced to a temperature which remains higher than the glass transition temperature of said glass. Said glass is preferably chosen so that its glass transition temperature is between 600°C and 1350°C, preferably between 900°C and 1350°C, preferably between 1000°C and 1300°C, preferably between 1150°C and 1250°C.

[0178] In step 4), the repair product is applied following steps a) and b).

[0179] In step a), the region to be repaired is delimited using formwork 32, so as to constitute, with the oven, a mold for the repair product.

[0180] The formwork 32 comprises an inner formwork 32i, which delimits the mold 36 inside the furnace. The inner formwork therefore extends along the dotted lines shown inside the furnace in Figure 2. The inner formwork in particular follows the opening of the regions to be repaired 30i in the form of a cavity.

[0181] When the region to be repaired passes through the furnace, in particular the tank, such as the region to be repaired 303, the formwork 32 preferably comprises an external formwork, not shown, which delimits the external opening of the region to be repaired, through which it opens to the outside of the furnace, and thus retains the repair product before it is hardened, preferably sintered. According to the invention, at least part of the internal formwork, preferably the entire internal formwork, is made of a ceramic, preferably in the form of a CMC.

[0182] In one embodiment, at least a portion of the outer formwork, or even all of the outer formwork, is made of a ceramic, preferably in the form of a CMC.

[0183] Preferably, in particular when the region to be repaired is, at least partially, delimited by a surface of the furnace tank, at least a part of the inner formwork, preferably the entire inner formwork, and optionally the outer formwork and / or the accessories, is made of a ceramic, preferably in the form of a CMC, consisting of oxides for more than 90% of its mass, preferably for more than 95% of its mass, preferably for more than 98% of its mass, preferably for more than 99% of its mass, preferably for more than 99.5% of its mass. The compatibility of the ceramic, in particular in the form of a CMC, with the molten glass during normal operation of the furnace is advantageously improved.

[0184] The outer formwork is preferably made of the same material as any existing veneer. In one embodiment, the outer formwork is made of a ceramic in the form of a CMC, preferably identical to that of the inner formwork.

[0185] The manufacture of a ceramic, especially in the form of a CMC, can be carried out by any conventional method.

[0186] In particular, ceramics can be manufactured by casting, pressing, vibrocasting, or fusion processes. Ceramic formwork elements can be obtained directly using these processes or can be machined from blocks obtained using these processes.

[0187] The person skilled in the art knows how to adjust the parameters of the process chosen for the manufacture of ceramics, and in particular how to determine the grain size of the raw materials, the water content during shaping, and the sintering temperature if the ceramic is sintered.

[0188] The manufacture of a CMC may in particular comprise the following steps: i) arrangement, on or in a textile, of a slip capable of forming a ceramic matrix after consolidation; ii) before or after step i), shaping the textile; iii) consolidation of the preform obtained after the preceding steps, preferably by drying and / or sintering, so as to form said matrix and obtain the CMC. In step i), the textile is a set of fibers, preferably assembled in the form of threads, a thread typically comprising several hundred to several thousand fibers. The fibers, preferably the threads, preferably have a length greater than 50 mm, or even greater than 100 mm. In one embodiment, the fibers, preferably the threads, are arranged in the form of at least one fabric.

[0189] The textile may in particular have the form of a felt of unordered threads or fibers, a sheet, for example a sheet made up of threads extending substantially parallel to one another (said threads being called "unidirectional threads"), a knit, a fabric (i.e. a woven textile) or a stack of one or more felts and / or sheets, and / or knits and / or fabrics.

[0190] The textile preferably has the form of a felt or a fabric or a sheet or a stack of felt(s) and / or sheet(s) and / or fabric(s). The stacking of the fabrics and / or sheets can be carried out in such a way that the threads of the different fabrics or sheets extend substantially all in the same direction, or in 2, 3, 5, 5 or 6 different directions, depending in particular on the desired mechanical properties.

[0191] Preferably, at least a portion, preferably all of said ceramic fibers of the textile, optionally assembled in the form of single and / or assembled threads, are:

[0192] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides, and / or

[0193] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of silicon carbide, and / or

[0194] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbon.

[0195] Preferably, the fibers of the textile comprise more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides.

[0196] Preferably, at least a portion, preferably all of said ceramic fibers, are:

[0197] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiCL + AI2O3 + Z1O2 > 50%, preferably SiCL + AI2O3 + Z1O2 > 60%, or even SiCL + AI2O3 + Z1O2 > 70%, or even SiCL + AI2O3 + Z1O2 > 80%, or even S1O2 + AI2O3 + Z1O2 > 90%, as a percentage by mass based on the oxides, and / or

[0198] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that SiCL > 70%, preferably SiCL > 80%, preferably SiCL > 90%, or even SiCL > 99%, as a percentage by mass based on the oxides, and / or

[0199] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that AI2O3 > 65%, preferably AI2O3 > 70%, or even AI2O3 > 80%, or even AI2O3 > 90%, or even AI2O3 > 95%, as a percentage by mass based on the oxides.

[0200] More preferably, at least a portion, preferably all of the ceramic fibers, are

[0201] - fibers composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of alumina, and / or

[0202] - fibers composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, preferably amorphous, and / or

[0203] - fibers composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of mullite and corundum, and / or

[0204] - fibers composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of glass, preferably washed, and mixtures thereof.

[0205] Preferably, all fibers have the same composition.

[0206] The arrangement of the slip on or in the textile can be for example by impregnation. Said stacking can be carried out by pressing, or under vacuum, preferably after impregnation.

[0207] The manufacture of slip is well known to those skilled in the art. Slip is typically a suspension, for example of an aqueous base or an organic solvent, containing

[0208] - ceramic particles and / or precursors of ceramic particles, i.e. compounds which transform into ceramic particles during the manufacture of the CMC, and in particular during hardening, in particular sintering, and - optionally dispersants, plasticizers, lubricants, and / or temporary binders.

[0209] The composition of the slip, the size distribution of the ceramic particles or ceramic precursors and the mineral filler of the slip are adapted to the type of fibers and the forming technique. For example, the slip can be placed on or in the textile, in particular by direct lamination, infusion, injection, infiltration or deposition, under atmospheric pressure or under higher pressure or under vacuum, at room temperature or at higher temperature.

[0210] In step ii), the textile obtained, preferably impregnated with the slip, is shaped. The desired shape is preferably the final shape of the CMC. In one embodiment, however, the shape can be modified after hardening of the matrix, for example by machining or by deformation.

[0211] Preferably, to produce the internal formwork, the textile is shaped in such a way that the shape of the CMC is adapted so that, after installation of the formwork, the repair material only replaces material that has been extracted by wear, preferably replaces all the material that has been extracted by wear. In other words, the shape is preferably determined so that, in the service position, the internal formwork elements made of CMC follow the dotted lines in Figure 2.

[0212] The shape can be given by making, with the textile (before or preferably after introduction of the slip), an imprint on a reproduction of the part of the furnace to be repaired before wear. The mold is then a "negative" of the region to be repaired. For example, if the region to be repaired is a nose piece, the CMC can be made by depositing the textile, preferably in the form of a fabric or a superposition of several fabrics, on a replica of the nose piece, before or after impregnation with the slip but before consolidation, so that this textile fits the surface of the nose piece at least in the region corresponding to the region to be repaired. The use of a ceramic, and in particular in the form of a CMC, advantageously makes it possible to easily make complex shapes, possibly non-developable. The repair thus makes it possible to precisely reconstruct the initial profile of the interior surface of the furnace.

[0213] CMC can be manufactured by arranging prepregs, each consisting of a fabric impregnated with a slip of ceramic particles, on top of each other. The prepregs are flexible, so that they can take the desired shape. In step iii), consolidation, preferably by sintering, is preferably carried out before installing the formwork, which facilitates installation.

[0214] Generally speaking, the characteristics of ceramics, particularly in the form of CMC, result from its manufacturing process.

[0215] Preferably, said ceramic, preferably in the form of a CMC, has one or more of the following optional characteristics:

[0216] - the ceramic, preferably in the form of a CMC, is preferably sintered;

[0217] - the ceramic, preferably in the form of a CMC, preferably has an open porosity, measured by imbibition, according to the principle of Archimedes' thrust, greater than 10%, preferably greater than 15% and less than 50%, preferably less than 45%, preferably less than 40%;

[0218] - the ceramic is in the form of a CMC and preferably has an open porosity, measured by imbibition, according to the principle of Archimedes' thrust, greater than 25%, preferably greater than 30%;

[0219] - the ceramic is not in the form of a CMC and preferably has an open porosity, measured by imbibition, according to the principle of Archimedes' thrust, of less than 30%, preferably less than 25%;

[0220] - the ceramic, preferably in the form of a CMC, is preferably made up of more than 90% of its mass, preferably more than 95% of its mass, preferably more than 98% of its mass, preferably more than 99% of its mass, preferably more than 99.5% of its mass of oxides;

[0221] - preferably, the CMC comprises more than 20%, preferably more than 25%, preferably more than 30%, preferably more than 40%, preferably more than 50%, preferably more than 60% and / or less than 80%, preferably less than 70% by volume of fibers;

[0222] - the CMC comprises fibers, said fibers being composed of oxides for more than 90%, preferably for more than 95%, preferably for more than 97%, preferably for more than 98%, preferably for more than 99%, preferably for more than 99.5% by mass;

[0223] - at least a portion, preferably all of said ceramic fibers, are:

[0224] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that SiCh + AI2O3 + Z1O2 > 50%, preferably SiO2 + AI2O3 + Z1O2 > 60%, or even SiC + AI2O3 + Z1O2 > 70%, or even SiCh + AI2O3 + Z1O2 > 80%, or even SiCh + AI2O3 + Z1O2 > 90%, as a percentage by mass based on the oxides, and / or

[0225] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that SiCh > 70%, preferably SiCh > 80%, preferably SiC > 90%, or even SiC > 99%, as a percentage by mass based on the oxides, and / or

[0226] - fibers comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that AI2O3 > 65%, preferably AI2O3 > 70%, or even AI2O3 > 80%, or even AI2O3 > 90%, or even AI2O3 > 95%, or even AI2O3 > 97%, or even AI2O3 > 98%, as a percentage by mass based on the oxides;

[0227] - the ceramic is in the form of a CMC and the matrix of the CMC is composed of more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides, or carbides and / or nitrides and / or sialons, in particular of the type described above;

[0228] - the ceramic is in the form of a CMC and, preferably, the matrix of said CMC is composed of more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides;

[0229] - preferably the CMC matrix is ​​composed substantially entirely of oxides;

[0230] - the CMC matrix comprises AI2O3 and / or S i O2 and / or Z1O2 and / or Cr2O3;

[0231] - preferably, the CMC matrix comprises AI2O3 and SiCh;

[0232] - in one embodiment, the AI2O3 content in the CMC matrix, as a percentage by mass based on the oxides of the matrix, is greater than 65%, preferably greater than 70%;

[0233] - in one embodiment, the content of SiO2 in the CMC matrix, as a percentage by mass based on the oxides of the matrix, is greater than 15%, preferably greater than 20% and / or less than 35%, preferably less than 30%;

[0234] - in one embodiment, the content of SiO2 in the CMC matrix, as a percentage by mass based on the oxides of the matrix, is greater than 60%, preferably greater than 70%, preferably greater than 80%;

[0235] - in one embodiment, the content of oxides other than AI2O3 and SiCh in the CMC matrix, as a percentage by mass based on the oxides of the matrix, is less than 3%, preferably less than 2%, preferably less than 1%;

[0236] - in one embodiment, the total content of AI2O3 and SiO2 in the CMC matrix is ​​greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, in mass percentage based on the oxides of the matrix;

[0237] - in one embodiment, the silica of the CMC matrix is ​​amorphous;

[0238] - preferably, the ceramic, preferably in the form of a CMC, has a total SiCh+AhCh+ZrC+CnOa content greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, preferably greater than 97%, preferably greater than 97%. More preferably, the ceramic, preferably in the form of a CMC, has a total SiCh+AhCh content greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, preferably greater than 97%, preferably greater than 97%;

[0239] - in a preferred embodiment, the ceramic, preferably in the form of a CMC, has the following chemical analysis, in mass percentage based on the oxides and for a total of 100%:

[0240] - SiO2: 47% - 67%,

[0241] - AI2O3: 32% - 52%,

[0242] - oxide species other than AI2O3 and SiO2: < 5%, preferably < 4%, preferably < 3%, preferably < 2%;

[0243] - in one embodiment, the ceramic, preferably in the form of a CMC, is preferably amorphous, and has the following chemical analysis, in mass percentage based on the oxides and for a total of 100%:

[0244] - SiC>2: > 95%, preferably > 96%, preferably > 97%, preferably > 98%, preferably > 99%;

[0245] - the ceramic is in the form of a CMC and has an apparent density greater than 1.0 g / cm 3 , preferably greater than 1.20 g / cm 3, preferably greater than 1.40 g / cm 3 , or even greater than 1.50 g / cm 3 and / or less than 2.00 g / cm 3 , preferably less than 1.90 g / cm 3 , preferably less than 1.80 g / cm 3 ;

[0246] - the ceramic is not in the form of a CMC and has an apparent density greater than 1.80 g / cm 3 , or even greater than 2.00 g / cm 3 and / or less than 3.20 g / cm 3 , preferably less than 3.00 g / cm 3 , preferably less than 2.80 g / cm 3 .

[0247] The formwork is then installed by assembling its elements. ZI

[0248] Installing the interior formwork is tricky given the difficulty of access.

[0249] When being installed, the formwork elements can be held by one face which, in the service position, is exposed inside the furnace, or by an opposite face.

[0250] At least one element of the CMC inner casing and / or a CMC accessory may be shaped to be deformable between first and second configurations, the first configuration being suitable for introduction into the furnace, the second configuration being suitable for the service position. An element of the CMC inner casing and / or a CMC accessory may be foldable, so that they can be introduced into available access passages, for example a region to be repaired through, or through access passages that are easy to create, for example by moving a burner.

[0251] Preferably, at least some of the elements of the interior formwork are made of a ceramic, preferably a CMC, shaped to be pliable. These elements of the interior formwork may, for example, comprise two rigid panels, linked together by hinges. The hinges may be parts fixed to the two panels.

[0252] A formwork element may also comprise several panels connected together by hinges made of a deformable refractory material, for example a pre-preg.

[0253] After being folded to be inserted into the oven, the formwork element is unfolded to give it the desired shape.

[0254] Figures 6 and 7 schematically illustrate the steps for installing formwork to reconstitute a nose brick 20, in one embodiment.

[0255] Figure 6 shows the nose brick in its pre-repair condition, and in particular the wear zone 33, which partially defines the interior surface of the kiln before repair. The broken line shows the nose brick in its new condition.

[0256] Two passages, shown in dotted lines, have been provided to connect the region to be repaired 302 with the outside of the furnace. The first passage 34i is cylindrical and shaped for the introduction of a nozzle 50, described in more detail below. The second passage 342 is of substantially rectangular section and shaped for the introduction of a set of formwork elements. The formwork elements comprise first and second panels 35i and 352, respectively, and a hinge 35a connecting two adjacent edges of the first and second panels 351 and 352. Unlike the panels, which are substantially non-deformable, the hinge is flexible. It is preferably made of a prepreg, that is to say a textile impregnated with a ceramic matrix precursor, so that after sintering, the hinge is made of a CMC.

[0257] In Figure 6, the first and second panels 351 and 352 are superimposed on each other, by folding by means of the hinge. This compact configuration facilitates their introduction inside the oven, illustrated by the arrow.

[0258] After the second panel 352 has been introduced, it is unfolded and positioned to follow the region to be repaired, as shown in FIG. 7. The formwork elements then constitute the formwork 32, which, in this embodiment, comprises only an inner formwork 32i. With a portion of the inner surface, the formwork defines a mold 36, the inner volume of which, shown in gray in FIG. 6B, has a shape similar to that of the region to be repaired.

[0259] The nozzle 50 is then introduced through the first passage 34i, so as to open outside the furnace and into the region to be repaired.

[0260] Preferably, the nozzle rests on the internal formwork, preferably in a manner that contributes to maintaining the formwork elements in position. Preferably, the end of the nozzle introduced into the region to be repaired is housed in a housing 37 of complementary shape provided in the formwork.

[0261] The repair product can then be introduced into the area to be repaired, via the nozzle.

[0262] Many variations are possible. In particular,

[0263] - the nozzle can be introduced into the furnace through a passage through which the formwork elements have previously been introduced into the furnace,

[0264] - the formwork elements can be introduced through a passage which opens into the furnace, but not into the area to be repaired,

[0265] - the nozzle may not be in contact with the formwork,

[0266] - the repair product can be introduced without the aid of a nozzle, for example by pouring the repair product from the top of the (open) mold in Figure 6,

[0267] - the nozzle can be introduced into the area to be repaired by passing through the formwork, and optionally anchored in a housing, preferably of complementary shape, provided on the interior surface of the furnace.

[0268] In one embodiment, as illustrated in FIG. 4, the region to be repaired is divided into at least two compartments 38, by introducing one or more partitions 40. Remarkably, partitioning makes it possible to limit the risk of stratification of the repair product, and leads to a longer lifespan of the repair.

[0269] The partitioning is preferably determined so that each compartment has a bottom whose surface area is less than or equal to 25 m 2, preferably less than 16 m 2 , and / or greater than or equal to 3 m 2 .

[0270] In one embodiment, the partitions of said compartments are made of a said ceramic, preferably in the form of a CMC.

[0271] In one embodiment, at least one element of the inner formwork made of a ceramic, preferably in the form of a CMC, comprises through holes and / or recesses. Filling these holes and recesses with the repair product during step b) advantageously allows better immobilization of the inner formwork and makes it possible to reduce the thermal gradient in the repair product during step 5). Preferably, the average equivalent diameter of the holes is greater than 8 mm and preferably less than 20 mm, preferably less than 15 mm.

[0272] In one embodiment, said formwork element made of a ceramic, preferably in the form of a CMC, is in the form of a grid, the holes preferably being distributed homogeneously, the total surface area of ​​the holes representing more than 10%, preferably more than 15% and preferably less than 50%, preferably less than 40% of the interior surface area of ​​said formwork element, i.e. the surface area participating in the definition of the mold around the region to be repaired (surface area of ​​the holes and of the material of the grid).

[0273] In one embodiment, said holes are located on the lower two-thirds of said formwork element, and preferably distributed homogeneously. More preferably in said embodiment, the total surface area of ​​the holes represents more than 1% and less than 5% of the interior surface area of ​​said formwork element (surface area of ​​the holes and of the material of said formwork element).

[0274] The through holes and / or recesses may be made by any technique known to those skilled in the art. In particular, through holes may be made by drilling or water jet cutting, for example on ceramic, preferably in the form of a CMC, obtained after sintering. In a CMC, the through holes and / or recesses may also be made on the textile, preferably a woven fabric, before coating with the slip. Accessories are then conventionally used to hold the formwork elements in the service position.

[0275] In one embodiment, the seal between the inner casing and the inner surface of the furnace is increased by placing a sheet of ceramic fibers between said inner casing and said surface.

[0276] Figure 8 illustrates an example of interior formwork according to the invention. In particular, the interior formwork 32i can be seen, and in particular 3 adjacent panels 351 and 352 and 35a held in position by means of metal clamps 39, wedging bricks 43 and cooled tubes 45.

[0277] In step b), the mold that delimits the area to be repaired is filled with a repair product, preferably by pouring.

[0278] Repair product

[0279] The repair product may be a conventional repair product and may be prepared by any known technique.

[0280] Preferably, the repair product is the result of moistening an unshaped product. Said moistening can be carried out according to any known technique, for example in a mixer. A person skilled in the art knows how to determine the quantity of solvent, preferably water, to be used to moisten the unshaped product and obtain the repair product.

[0281] The unshaped product may include:

[0282] - the Repair Hot Bottom AZS, in particular when the area to be repaired is located at the bottom of the furnace tank,

[0283] - Repair Hot Overcoat AZS, Repair Hot Overcoat Alumina or Repair Hot Overcoat Chrom50, especially when the area to be repaired is located on a wall of the furnace tank, or

[0284] - Repair Hot Overcoat Fused Silica when the area to be repaired is located at the vault level.

[0285] These unformed products are marketed by the company Saint-Gobain Sefpro.

[0286] Preferably, the maximum particle size of the repair product or, equivalently, of the unshaped product, is less than 10 mm, preferably less than 8 mm, preferably less than 6 mm. The particle size distribution of the repair product or, equivalently, of the unshaped product is preferably determined so that the repair product is self-flowing when hot.

[0287] Preferably, the repair product is chosen so as to have a chemical analysis close to that of the furnace material which delimits the region to be repaired, preferably so that the content of any constituent of the repair product differs by less than 10% from the content of said constituent in said material.

[0288] For example, if the area to be repaired is delimited by one or more refractory blocks made of an AZS (Alumina Zirconia Silica) product, the unshaped product used to manufacture the repair product is preferably the Repair Hot Bottom AZS or the Repair Hot Overcoat AZS, depending on the location of the area to be repaired in the glass melting furnace. If the area to be repaired is delimited by one or more refractory blocks made of an AZS-Chrome product, the unshaped product used to manufacture the repair product is preferably the Repair Hot Overcoat Chrom50. Finally, if the area to be repaired is delimited by one or more refractory blocks made of a silica product, the unshaped product used to manufacture the repair product is preferably the Repair Hot Overcoat Fused Silica.

[0289] The repair product may be brought to the area to be repaired using any technique known to those skilled in the art.

[0290] If access to the area to be repaired is difficult, one or more passages, for example made by drilling, can be provided from the outside to the inside of the furnace. These passages advantageously allow the introduction of means for conveying the repair product, for example a cooled rod or a nozzle, to the area to be repaired.

[0291] In one embodiment, the repair product is pumped by means of a pump producing a suction pressure preferably less than or equal to 180 bar and preferably conveyed to the region to be repaired by means of a water-cooled rod or a nozzle.

[0292] In one embodiment, the repair product is delivered ready for use, i.e. stored in an already moistened state. Advantageously, the filling speed of the region to be repaired can be increased and / or the number or capacity of the pumps reduced.

[0293] Throughout step b), the region to be repaired is preferably maintained at a temperature above 300°C, preferably above 400°C, preferably above 500°C, preferably above 600°C, preferably above 700°C, preferably above 800°C, preferably above 900°C, and / or preferably below 1550°C, preferably below 1500°C.

[0294] Nozzle

[0295] As illustrated in Figure 4, the repair product 41 is conventionally conveyed to the region to be repaired via a tubular conduit 42 or a chute, a first end of which is connected to the outlet of the pump 44 supplied by a reservoir 46 of repair product, and a second end of which is free, or connected to a nozzle 50, preferably introduced and fixed in the region to be repaired, preferably fixed to the internal formwork and / or to the internal surface of the furnace, and in particular to the part of the internal surface delimiting the region to be repaired.

[0296] The nozzle is intended for dispensing the repair product, but also, preferably, serves as an anchor in the cast repair product, and / or helps to hold the internal formwork in position. Preferably, the nozzle helps to hold the internal formwork in position after the repair product has hardened.

[0297] When the repair product exits through the second end or through the nozzle 50, it is subjected to a sudden increase in the temperature of its environment, which in particular results in a reduction in its ability to flow. To ensure that the repair product is distributed evenly, the number of nozzles can be increased.

[0298] The inventors discovered that it was advantageous if the repair product could exit radially, preferably from all sides and preferably along the entire length of the nozzle.

[0299] Figure 5 illustrates a non-limiting embodiment of a nozzle 50 in a preferred embodiment of the invention.

[0300] The nozzle 50 has the general shape of a cylindrical sleeve with a circular base, with an X axis. The nozzle has a feed orifice 54, with an X axis, through which the repair product enters the nozzle. The X axis is therefore the feed direction of the nozzle.

[0301] On the side of the feed orifice 54, there are two circumferential through housings 58, intended for fixing the nozzle.

[0302] At the end opposite the feed orifice, the nozzle preferably comprises a bottom 56. When injecting the repair product, the bottom 56 preferably extends substantially horizontally, the length direction of the nozzle therefore being vertical. The sleeve has a wall of substantially constant thickness, preferably greater than 5 mm, preferably greater than 7 mm, preferably greater than 10 mm and preferably less than 30 mm, preferably less than 25 mm, preferably less than 20 mm. Its equivalent internal diameter is preferably greater than 40 mm and preferably less than 200 mm, preferably less than 150 mm, preferably less than 100 mm.

[0303] The nozzle length is determined based on the shape of the area to be repaired. In particular, it can be between 1 and 10 times the equivalent inner diameter of the sleeve.

[0304] The side wall of the nozzle is pierced with a plurality of ejection orifices 52 each opening, on the outer surface 53 of the nozzle, by a respective ejection opening of axis Y extending radially, that is to say intersecting the axis X, perpendicular to the axis X. The nozzle preferably comprises more than 1, preferably more than 3, preferably more than 5, preferably more than 10, preferably more than 20 and / or less than 100, preferably less than 50 ejection orifices 52, identical or different.

[0305] The ejection orifices 52 are preferably regularly distributed circumferentially. Along a circle of axis X which intersects an ejection orifice 52, preferably along each circle of axis X which intersects an ejection orifice 52, ejection orifices 52 are regularly distributed. The ejection orifices intersected by the same circle of axis X form a “row” of ejection orifices 52.

[0306] The ejection orifices 52 are preferably regularly distributed in a direction parallel to the X axis, i.e. in the direction of the length of the nozzle. Along this direction, the nozzle preferably has more than 1, preferably more than 2, preferably more than 3 and / or less than 10, preferably less than 8, preferably less than 5 rows of ejection orifices 52. The nozzle of FIG. 5 has 4 such rows.

[0307] The set of ejection orifices 52 thus preferably forms a regular pattern. The homogeneity of the distribution of the repair product is further improved.

[0308] Preferably, each ejection orifice is a cylindrical hole, preferably of circular or oblong section, preferably circular. The ejection openings of the ejection orifices, on the outer surface of the sleeve, are preferably regularly distributed over this outer surface. The homogeneity of the distribution of the repair product is thereby improved. More preferably, the ejection opening of an ejection orifice, preferably of each ejection orifice, has an equivalent diameter greater than 8 mm, preferably greater than 10 mm and less than 50 mm, preferably less than 40 mm, preferably less than 30 mm, preferably less than 25 mm.

[0309] The nozzle is preferably one-piece.

[0310] Preferably, it is made of a ceramic, preferably sintered. Preferably its chemical composition is similar, preferably identical to that of the repair product. Preferably, the content of any constituent of the repair product present in an amount greater than 5% by mass, differs by less than 20%, preferably by less than 10% from the content of said constituent in the nozzle. Advantageously, the nozzle can be left in the region to be repaired after said region to be repaired has been filled with repair product, without its presence generating a heterogeneity of composition in said region to be repaired.

[0311] In step 5), optional, and in particular if the process includes a step 3), the furnace is maintained at a temperature between 900°C and 1400°C, preferably between 1250°C and 1400°C, preferably between 1300°C and 1400°C, in order to allow sintering of the repair product, preferably for a period of more than 8 hours, preferably more than 10 hours and preferably less than 15 hours.

[0312] In step 6), normal operation of the furnace is resumed: A glass composition to be melted is introduced into the furnace and, if said process includes a step 3), the temperature of the furnace is increased to put it back into operation.

[0313] Examples

[0314] The following non-limiting examples are given to illustrate the invention.

[0315] In a first particular embodiment, in particular when the region to be repaired is located in the superstructure of the glass melting furnace, the internal formwork is made of a ceramic, preferably in the form of a CMC, preferably one or more plates made of a ceramic, preferably in the form of a CMC, preferably held against the healthy superstructure part using one or more metal rods, preferably cooled using water circulation. If the region to be repaired opens out to the outside of the furnace, a veneer, constituting the external formwork, preferably made of a ceramic, preferably in the form of a CMC, is fixed so as to externally seal the region to be repaired. The region to be repaired is then filled with the repair product.The repair product is preferably conveyed, from outside the furnace, by a pipe passing through one or more passages provided through the outer wall of the furnace, then poured into the region to be repaired through at least one nozzle according to the invention, preferably arranged in the region to be repaired.

[0316] The nozzle(s) are made of a ceramic material of chemical composition preferably similar, preferably identical to that of the repair product.

[0317] Preferably, the ceramic formwork, preferably in the form of a CMC, and / or the nozzle(s) are not removed after the repair product has been placed.

[0318] In a second particular embodiment, in particular when the region to be repaired is located at the level of the nose bricks, the parts of nose bricks having disappeared during the use of the kiln are replaced by the repair product. The formwork comprises, preferably consists of plates made of a ceramic, preferably in the form of a CMC, arranged so as to recreate, at least partially, the shape of a new nose brick. The formwork element(s) are preferably introduced folded into the kiln, then unfolded and fixed so as to delimit the region to be repaired. In one embodiment, the region to be repaired, delimited by the formwork made of a ceramic, preferably in the form of a CMC, is filled with the repair product from the inside of the kiln. In one embodiment, the region to be repaired, delimited by the formwork made of a ceramic, preferably in the form of a CMC, is filled with the repair product from the outside of the kiln.

[0319] In a third particular embodiment, in particular when the region to be repaired results from wear of the furnace tank, at least partial emptying of the molten glass is carried out. The inner casing is made of a ceramic, preferably in the form of a CMC, preferably one or more plates of a ceramic, preferably in the form of a CMC, preferably held against the tank using one or more tubes of a ceramic, preferably in the form of a CMC, and / or one or more metal rods, preferably cooled using circulating water. If the region to be repaired opens out to the outside of the furnace, a plating, constituting the outer casing, preferably made of a ceramic, preferably in the form of a CMC, is fixed so as to externally seal the region to be repaired.

[0320] The region to be repaired is then filled with the repair product. The repair product is preferably conveyed from outside the furnace by a pipe passing through one or more passages provided through the furnace enclosure, then poured into the region to be repaired through at least one nozzle according to the invention, preferably arranged in the region to be repaired.

[0321] The nozzle(s) are made of a ceramic material, preferably chosen from a material of similar chemical composition, preferably identical to that of the repair product.

[0322] Preferably, the ceramic formwork, preferably in the form of a CMC, and / or the nozzle(s) are not removed after the repair product has been placed.

[0323] In a preferred embodiment, the interior formwork elements, the optional partitions disposed in the region to be repaired, and the accessories used for the assembly of these elements and these partitions are not removed after the repair product has been placed.

[0324] Two examples were made with the same repair product, these examples being distinguished by the speed of rise of the repair product in the mold.

[0325] To manufacture the repair product, the unformed product Repair Hot Overcoat AZS, marketed by the company Saint-Gobain Sefpro, was mixed for 5 minutes in a mixer with a rotating blade and fixed tank, with 10%, in mass percentage based on the unformed product, of a colloidal silica solution with a concentration equal to 20%.

[0326] The unshaped product had the following mass composition, based on the mass of the oxides in the unshaped product:

[0327] - AI2O3: 56%,

[0328] - SiO2: 8%,

[0329] - ZrO2: 35%,

[0330] - other oxides: 1%.

[0331] 250 kg of repair product was prepared. This repair product was self-flowing when hot.

[0332] For each example, a single-piece mold in a CMC was made.

[0333] This mold had a general rectangular parallelepiped shape, with a flat bottom having a length equal to 600 mm and a width equal to 150 mm, and side walls extending from the periphery of the bottom over a height equal to 450 mm, the thickness of the walls of said mold being substantially constant and equal to 10 mm. The CMC constituting the two molds had a thermal conductivity between 20°C and 500°C of less than 0.6 Wm^.K' 1 .

[0334] The CMC was made up of:

[0335] - a superposition of fabrics (or "woven fabrics" in English) made of washed glass fibers (or "leached glass" in English) with a silica content greater than 90% by mass, representing 44% of the mass of the CMC, and

[0336] - an alumina and silica matrix, representing 56% of the mass of the CMC.

[0337] The said CMC had an open porosity equal to 38%, an apparent density equal to 1.65 g / cm 3 , an AI2O3 content equal to 42%, a SiCL content equal to 57% and a content of other oxides equal to 1%, the contents of AI2O3, SiCL and other oxides being expressed as mass percentages based on the oxides of said CMC.

[0338] The two molds were placed in an oven with a gas burner.

[0339] The furnace was then started to reach a temperature of 1200°C in 2 hours and 40 minutes, simulating a hot introduction of the CMC molds into a glass furnace. Then the temperature was increased to 1500°C, the temperature rise rate between 1200°C and 1500°C being equal to 35°C / h.

[0340] The casting of the repair product into each mold, maintained at 1500°C, was carried out using a metal chute placed above an opening made in the vault of the furnace.

[0341] For example 1, according to the invention, the repair product was cast continuously, with a flow rate substantially equal to 100 kg / min and for example 2, according to the invention, the repair product was cast continuously, with a flow rate substantially equal to 300 kg / min.

[0342] When filling, it was found that the CMC molds resisted the thrust of the repair product, without breaking or opening.

[0343] After filling the molds, the temperature was maintained at 1500°C for 24 hours. The temperature was then gradually reduced to 800°C, at a rate approximately equal to 25°C / h. Then the burner was turned off and the temperature was lowered naturally, without opening the furnace.

[0344] The inventors believe that this test accurately reproduces the conditions encountered during the repair of a part of a furnace tank. The sintered repair products found in each of the molds were then recovered.

[0345] After sawing, they presented a homogeneous texture, without cracks or internal cavities which could correspond to a break in the power supply.

[0346] Similar tests can be carried out with a single-piece mold of the same dimensions as the CMC mold described above, made of a ceramic of the same composition as the CMC, but obtained by casting a slip into a mold of suitable shape, without incorporating fibers, then sintering.

[0347] The results obtained with such a cast one-piece mold (not in the form of a CMC) are similar to those obtained with the previously tested CMC one-piece mold.

[0348] As now clearly appears, the invention thus provides a method of hot repairing a glass melting furnace which uses elements made of a ceramic, preferably in the form of a CMC, to provide the internal formwork, which:

[0349] - allows rapid manufacturing that is perfectly adapted to the region to be repaired, in particular because a ceramic, preferably in the form of a CMC, can be shaped into complex forms, and in particular so as to match the profile of the region to be repaired;

[0350] - facilitates the introduction of these elements into the furnace, particularly when these elements are bent to be introduced through narrow passages through the furnace;

[0351] - facilitates their arrangement, these elements being light and able to unfold elastically;

[0352] - allows a sacrifice of the formwork element, i.e. its retention in the furnace after the repair, in particular because the composition of a ceramic, preferably in the form of a CMC, can be chosen to be similar to that of the repair product.

[0353] A nozzle according to the invention also allows:

[0354] - pouring the repair product simultaneously in several directions and at different heights, which allows rapid filling of the area to be repaired, but also makes it possible to obtain a homogeneous repair, free of layers;

[0355] - a sacrifice of the nozzle when its chemical composition is chosen to be similar to that of the repair product.

[0356] Of course, the present invention is not limited to the embodiments described or shown, provided as illustrative and non-limiting examples. In particular, the compositions of the ceramics and / or the structures of the CMCs of the different parts of the formwork and / or the nozzle and / or the accessories may be identical or different.

Claims

CLAIMS A hot repair method for a repaired area (30i, 32i, 3Ch) inside a glass melting furnace (10), the repaired area being at a temperature above 300°C, said method comprising the following steps: a) installing an inner formwork (32i) in a service position so as to form a mold (36) around the repaired area; b) filling the mold with a repair product (41), at least a portion of the inner formwork being made of a ceramic matrix composite. A method according to the preceding claim, wherein the furnace comprises - a tank (12) comprising a side wall (22), and - a superstructure (16), the area to be repaired being located in the side wall (22) of the vessel and / or in the superstructure. A method according to any one of the preceding claims, wherein, in step a), at least one element of said inner formwork is introduced into the furnace through an opening in a first configuration, and then said formwork element is deployed from the first configuration to a second configuration incompatible with extraction of said formwork element through said opening. A method according to the immediately preceding claim, wherein said formwork element is folded in the first configuration and unfolded in the second configuration. A method according to any one of the two immediately preceding claims, wherein the opening results from wear of the furnace.A method according to any one of the preceding claims, wherein at least one element of said inner casing has the shape of a part of the oven that protruded into the oven before said part disappeared through wear. A method according to the immediately preceding claim, wherein an element of said inner formwork has the shape of a brick-nose surface delimiting, before said wear, the interior of the kiln. A method according to any one of the preceding claims, wherein the manufacture of said part of the inner formwork comprises taking an impression on a replica of the part of the kiln containing the area to be repaired, before the wear of the kiln that led to the area to be repaired. A method according to any one of the preceding claims, wherein, in step b), the mold is filled by passing the repair product through a nozzle (50), provided with radial ejection orifices (52), relative to a nozzle feed direction (X). A method according to the immediately preceding claim, wherein - a first end (56) of the nozzle (50) is supported on a surface of the inner formwork, a second end of the nozzle being outside the area to be repaired, or - a first end (56) of the nozzle rests on an internal surface of the furnace defining the area to be repaired, a second end of the nozzle being outside the area to be repaired. A method according to any one of the two immediately preceding claims, wherein the nozzle is made of a ceramic, preferably sintered, preferably of a chemical composition similar to that of the hardened repair product, preferably sintered. A method according to any one of the preceding claims, comprising, after step b), a step 5) of sintering the repair product introduced into the mold in step b), the resulting sintered repair product being composed of a plurality of constituents, the content of any constituent of the sintered repair product being greater than 5%, - differing by less than 20% from the content of said constituent in said ceramic matrix composite, and / or - differing by less than 20% from the content of said constituent in a region of the furnace delimiting the area to be repaired, and / or - when one of claims 8 to 10 applies, differing by less than 20% from the content of said constituent in said nozzle, the contents being expressed as mass percentages based on the oxides. A method according to any one of the preceding claims, wherein the inner casing (32i) and / or, when one of claims 8 to 10 applies, the nozzle (50) are left in the area to be repaired after said repair. A method according to any one of the preceding claims, wherein the inner casing (32i) is made entirely of a ceramic matrix composite. A method according to any one of the preceding claims, wherein at least one element of the inner casing made of a ceramic matrix composite has through holes and / or recesses arranged to be filled by the repair product during step b).A method according to any one of the preceding claims, wherein at least one of said formwork elements has the form of a plate, flat or non-flat, the thickness of the plate being greater than 3 mm and less than 50 mm. A method according to any one of the preceding claims, wherein the inner formwork comprises. - formwork elements partially delimiting the area to be repaired, and - accessories for holding said formwork elements in a service position, said accessories being made of a ceramic matrix composite, identical or different from the ceramic matrix composite of the formwork elements. A method according to any one of the preceding claims, wherein the ceramic matrix composite is made of said formwork elements, at least one part of the inner formwork, and / or, where claim 16 applies, the ceramic matrix composite is made of at least one accessory - is (are) sintered, and / or - exhibit an open porosity greater than 25% and less than 50%, and / or - is (are) composed of more than 90% of its mass of oxides, and / or - contain more than 20% and less than 80% by volume of fibers, and / or - comprise(s) fibers in an oxide and / or arranged in the form of a fabric, and / or - comprise(s) a matrix composed of more than 90% oxides by mass percentage, and / or - comprise(s) a matrix including Al2O3 and / or SiCh and / or Z1O2 and / or C Oa, and / or - have an apparent density greater than 1.0 g / cm³ 3 and less than 2 g / cm² 3 , and / or - exhibit a total SiCh+AhCh+ZrC+CnOa content greater than 80%, by mass percentage on the basis of the oxides. A process according to any one of the preceding claims, said process comprising, before step a), the following step: - if the area to be repaired is, at least partially, delimited by a surface of the furnace tank in contact with the molten glass bath, drain, at least partially, of said molten glass from the tank, so as to expose said area to be repaired; and, after step b), the following step: - introduction of a glass composition to be melted into the tank, the furnace temperature being maintained in said area to be repaired during all stages of the process. A process according to any one of claims 1 to 17, said process comprising, before step a), the following steps: 1) if the area to be repaired is, at least partially, delimited by a surface of the furnace tank in contact with the molten glass bath, drain, at least partially, of said molten glass from the tank, so as to expose said area to be repaired; 3) reducing the temperature in the oven to a temperature above 300°C; and, after step b), the following steps: 5) increasing and maintaining the oven temperature between 900°C and 1400°C in order to sinter the repair product; 6) introduction of a glass composition to be melted into the vat and increase from the furnace temperature to an operating temperature leading to the melting of said composition. A method according to the immediately preceding claim, wherein, in step 3), the temperature in the furnace is reduced to a temperature above 900°C and below 1500°C. A method according to any one of the three immediately preceding claims, comprising a step of rinsing the area to be repaired after exposure of the area to be repaired. A method according to any one of the preceding claims, wherein the inner formwork comprises panels made of one CMC, connected to each other by at least one hinge made of one CMC. A method according to any one of the preceding claims, wherein the mass of more than 50% by number of the formwork elements is greater than 3 kg and less than 50 kg, and / or wherein the largest dimension of more than 30% by number of the formwork elements is greater than 400 mm and less than 1600 mm.Glass melting furnace comprising at least one region repaired according to a process according to any one of the preceding claims.

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