CN1272097A - Melting furnace, in particular for glass, and use thereof - Google Patents

Abstract

The invention concerns a furnace for melting material with high melting point such as glass, comprising a hearth (2) and side walls (3) defining a bath of molten material (5). At least part of the hearth (2) surface, and optionally the side walls (3), which is in contact with the molten material consists of at least one layer (12, 13, 21, 22, 23) comprising refractory material grit (14, 16), in particular with a mineral binder based on oxides or glassy material. The invention is useful for melting glass, in particular cullet containing metal residues and for separating the metal contained in cullet.

Description

Furnace, in particular a glass furnace, and the purpose and method of use of such a furnace

The present invention relates to techniques for melting high melting point thermoplastic materials such as glass. More particularly, the present invention relates to furnaces for melting such materials and their use.

Such a furnace for melting material such as glass must be designed such that its side walls properly insulate the melt from the outside to ensure good thermal efficiency while at the same time preventing molten glass from migrating outside.

In this respect, a typical configuration of the side walls of the furnace is to have a sufficient thickness of insulating material on the outer side and a surface made of glass-resistant refractory material on the inner side.

These refractory materials are placed in the furnace in the form of plates or slabs, which are placed side by side, between which a sealed connection should be made to avoid glass penetration.

At the bottom of the furnace, slabs of refractory material with high thermal conductivity are placed on slabs of insulating material through an unformed layer, which provides a perfectly horizontal base. This is usually a cement based on a hydraulic binder, which is deposited on the insulation slab without heating.

In principle, the furnace operates with such a temperature profile that the temperature beneath the refractory is close to the crystallization temperature of the glass, or at least the temperature at which the viscosity of the glass becomes so high that if the glass penetrates the refractory, the glass will Condensation or crystallization (devitrification) occurs in the upper layer of the insulating material, so that the movement of the glass stops.

Such glass penetration can occur particularly when the refractory panels are cracked due to thermal expansion stresses, or when the interface between two panels is not sufficiently sealed. Such glass infiltration may also occur when the glass entering the furnace in the solid state contains metal scrap. This is because when there is a drop of molten metal on the interface between the refractory material and the glass, the corrosion of the refractory material will be accelerated, and cracks may be formed through which the glass penetrates rapidly into the insulating material.

In spite of all these possible precautions, accidents still sometimes occur which cause problems with the sealing of the furnace, when the glass seems to be able to reach the insulating plates, where it is hot enough not to solidify and damage the insulation. In particular, penetration of metal entrained in the glass into panels of insulating material can cause serious damage as the metal attacks the insulating material and creates cavities which the glass thereby hollows out and/or fills.

It is important to prevent glass from penetrating the surfaces constituting the inner side walls of the furnace, since penetration of glass through the side walls of the furnace can easily affect the productivity of the furnace as well as the safety of its operation.

The object of the present invention is to reduce these risks, in particular by providing furnace side walls with improved permeability to glass when metal scrap enters the glass melt.

This object, as well as others which will be given later, is achieved according to the invention by, during its construction, giving at least a part of the inner surface of the furnace a lining comprising a refractory grit.

With regard to "refractory grit", it is generally understood in this application to mean particulate or granular refractory materials, especially materials that can be obtained by grinding or crushing.

In this respect, the subject of the invention is a furnace for melting high-melting materials such as glass, the furnace comprising a bottom and side walls which delimit the molten area of the molten material, characterized in that at least A portion of the material-contacting bottom surface, and possibly a portion of the side walls, initially consists of at least one layer of gravel containing refractory material.

With respect to "initially" it should be understood that this surface or part of this surface has the specified configuration immediately after the furnace has started to operate (either before heating or immediately after heating). In this respect, the subject of the invention is a method for manufacturing a furnace, which will be described below.

It seems surprising that sidewall surfaces fabricated from particulate material such as refractory gravel exhibit improved impermeability to glass compared to surfaces formed from the juxtaposition of pre-formed members such as flat plates.

What follows is primarily concerned with molten glass, which is regarded as the mineral material molten in the furnace; unless otherwise indicated, the expression generally refers to any natural or man-made meltable mineral material, especially glass and rock.

One problem associated with the conventional method of manufacturing the interior surfaces of the sidewalls, which is the overlapping of flat plates on top of a base layer of a different nature, is cracking due to thermal expansion stresses. This is because, due to the different coefficients of thermal expansion of the layers, different movements of the layers with friction occur relative to each other, which cause stretching of the plates, cracking or even shattering of the plates. In contrast, the use of particulate material according to the invention enables the formation of a continuous surface layer, without any seams, which has an excellent resistance to the stresses of thermal expansion of the furnace. The risk of cracking is thus reduced and the impermeability to glass is improved.

In general, the refractory material can be any type of glass-resistant material (possibly higher corrosion resistance), especially based on chromia or on zirconia, silicon oxide and/or aluminum oxide type (AZS type). According to the invention, the grit used can be obtained from recycled refractory materials.

The particle size of such grit may vary, advantageously being less than 50 mm, for example about 1 mm to 50 mm. However particle sizes greater than 50mm are also useful. For clarity, "fine" here means that the particle size of the gravel is about less than 5 mm, "medium" means that the particle size of the gravel is about 5 to 30 mm, "coarse" means that the particle size of the gravel is about 30 to 50 mm, and " "Very coarse" means that the particle size of the gravel is greater than 50mm. These particle sizes are to be understood as the size of the smallest mesh of the sieve used to screen the granular material.

In a particular form of embodiment, the surface in contact with the glass consists essentially of gravel. It is beneficial that the particle size of the grit can be selected according to the properties of the glass in the molten liquid, especially its viscosity at the side wall temperature and its surface tension, so that the grit is not wetted by the glass in the molten liquid, or Just get slightly wet, thus preventing the glass from getting into the spaces between the grit particles. In general, in this embodiment, it is advantageous to include small particle size gravel since the layer so formed is denser. The gravel advantageously comprises a mixture of particles of different sizes, which is suitable to obtain a maximum or optimum density or packing of the layer to form an impermeable layer.

In another embodiment, which may be preferred in certain respects, the layer whose surface is in contact with the glass, or at least one of the layers, contains, in addition to grit, a mineral compatible with the molten glass Binders, which may be of the chemically setting or ceramic setting type, especially mineral binders consisting of one or more fused oxides or glazing materials. In this embodiment, the voids between the grit particles are at least partially filled with the binder to form a composite material. The binder is preferably initially mixed with gravel in granular form in at least one of the layers.

The composite material based on refractory grit and this binder is a rather cohesive material which allows little or no passage of molten material such as glass between the grit particles. It is also a material with a low rate of glass corrosion, so its lifespan is improved.

The grit particle size is not critical in this embodiment since the particles are held in place by the binder. However, it is still advantageous to use a finer grit, as this may produce a dense layer with a high contact area between the particles and the binder, for glass in the melt and possibly other waste In other words, this composite layer becomes an impermeable barrier layer.

In a particular embodiment, the surface of the base (or at least a part thereof), and also the surface of the side walls, comprises only a single layer comprising refractory grit. The particle size of this layer is preferably less than 50 mm, especially less than 30 mm, especially less than 20 mm. The gravel advantageously comprises a mixture of particles of different sizes, as appropriate to obtain maximum or optimized layer density or packing to form an impermeable layer.

In some applications, however, the grit is preferably not too fine in order to prevent any risk of grit entering the glass melt due to vigorous agitation at the bottom surface as well as at the side wall surfaces, which risk is detrimental to the quality of the molten glass of.

In a particularly preferred embodiment, a first layer called a "contact layer" is placed in contact with the melt, the first layer comprising a first grit, and below the contact layer there is at least one layer called a "lower layer". Another layer, which layer contains additional gravel, the grain size of the gravel in the contact layer is larger than the particle size of the gravel and the gravel mixture of the or each lower layer.

It is beneficial that the gravel in the contact layer will not be driven by the agitation of the melt, and it protects the lower layer from the agitation.

In this case, the layer in contact with the melt preferably contains gravel with a particle size greater than 10 mm, in particular about 10 to 50 mm, especially about 20 to 50 mm, and the or each lower layer preferably contains particles with a particle size smaller than 20 mm or 10mm grit, as the case may be, especially around 1 to 10mm, very advantageously less than 5mm, if necessary, a mixture of various particle sizes.

According to a particular embodiment, the lower layer or at least one lower layer comprises a mineral binder as described above, whereas the contact layer consists essentially of coarser grit.

When the inner lining of the surface contains a binder that ensures the bond between the grit particles, this binder can consist of different mineral materials, especially oxides or glassy materials such as glass, which can also be devitrified Made of glass or rock, such as basalt. This glass may or may not be the same as the glass in the melt. In particular it can advantageously be at least partially recycled glass (cullet) or a dense glass which absorbs radiation in the infrared range.

It is especially advantageous to select the binder according to the viscosity at the temperature of the sidewall and according to the surface tension, so as to be able to at least partially close (silt up) the interstices between the gravel particles.

In an advantageous embodiment, the binder can be selected so that its density (especially at the bottom temperature) is greater than the density of the glass in the furnace. This achieves an effective physical separation between the binder glass and the molten glass produced in the furnace.

It is also advantageous that the adhesive be selected to have a viscosity greater than that of the glass in the furnace. Thus the viscosity of the binder glass at the bottom temperature is high enough to properly hold the grit particles, and this difference in viscosity prevents the binder from mixing with the molten glass produced in the furnace.

It is particularly advantageous to use clear glass as the adhesive.

It is also advantageous that the binder can be selected such that its thermal conductivity is less than that of the molten glass produced in the furnace. Thus, it is possible to reduce the rate of glass corrosion of the materials of which the furnace is constructed, while keeping the temperature below the gravel layer relatively low.

In particular, depending on the nature of the refractory gravel material used, the mineral binder is more or less chemically inert with respect to the gravel.

This is because the binder (glass or other binder material) may react with the refractory gravel material, corroding this material as oxide elements pass from the refractory into the binder phase. The refractory oxide elements contained in the binder generally have the effect of modifying the devitrification characteristics of the glass and/or of modifying the viscosity of the interstitial mineral binder.

It appears that the adhesion of the layers so formed is at least partly related to a gradual change in the chemical composition of the adhesive which results in an increase in adhesive tack and/or devitrification of the glass at bottom or sidewall temperatures, preventing The molten glass enters between the particles of the refractory material.

The larger the area exchanged with the refractory material, that is, the finer the grain size of the gravel, the more obvious the enrichment of interstitial glass (or other materials).

For the so-called "contact layer" which is in direct contact with the glass in the melt, the refractory grit material is preferably glass-resistant or insensitive thereto. The refractory material is preferably resistant to both the action of the binder glass and the action of the glass in the melt. The contact layer formed in this way then does not change or barely changes throughout the operation of the furnace, thus guaranteeing in particular a high quality of the glass produced which remains constant over time.

The refractory grit used for the contact layer advantageously contains chromium oxide, preferably at least 10% by weight, especially at least 30%, for example at least 60% by weight.

Furthermore, for the so-called "lower layer", the refractory material is preferably at least partially corroded by the interstitial binder, most particularly a material comprising alumina. Therefore, it is possible to combine the two effects: first, glass (or other adhesives) containing more refractory oxides is less corrosive to the lower structural layer; secondly, glass (or other adhesives) containing refractory oxides ) is more viscous and less susceptible to convective motion.

It is an advantage that the grit used for this layer can be chosen among AZS-type materials, especially those that are recycled, or that have a limited amount of chromium oxide added to them.

The choice of binder glass for each layer can be adjusted simultaneously in order to properly interact with the grit of each layer, depending especially on its oxide composition as well as its viscosity.

The choice of particle size and binder glass type is adjusted according to the nature of the material to be melted in the furnace.

Composite layers can be made in different ways: in particular, a mixture of refractory gravel and mineral material is laid on the surface and this mixture is then heated at the start of the furnace in order to form the composite, or first a layer of gravel is placed and then A layer of mineral material is placed and the mineral material is melted to infiltrate the grit.

In this respect, a further object of the invention is a method of manufacturing a furnace, for example a furnace for glass, in which a bottom and side walls are provided for confining a molten liquid of molten material The range is characterized in that it contains the following steps:

- laying a layer of refractory grit on at least a part of the surface of the bottom, and possibly a part of the surface of the side walls, for contact with the molten liquid, and then:

Once the temperature of the furnace is raised, a material with a high melting point, such as glass, is introduced to form a melt of molten material.

In the first stage, a mineral binder can be laid, as a mixture with at least one layer of gravel, or as a layer on top of a layer of gravel. In this first stage, preferably on top of the binder-containing layer, another layer consisting essentially of gravel having a particle size larger than this underlying layer is laid.

The second stage allows the adhesive to be melted or heat activated to form at least one composite layer.

The structure of the bottom and/or side walls may be adopted as desired; in particular the layer or layers comprising gravel may be laid on a shaped or unshaped base of flat or slabs of refractory or insulating material . By "shaped" it should be understood layers made of shaped objects, which are contained in an oven, as opposed to layers made of a homogeneous material which are deposited or dispersed in an oven. In particular, one can choose among the following possible embodiments.

- the layer or layers comprising refractory grit may be laid on slabs or slabs of refractory material which are usually used to achieve surfaces in contact with the melt;

- The layer or layers comprising refractory grit can be placed on a horizontal cement layer or directly on an insulating slab instead of a conventional material in the form of a slab or slab.

It is also possible to lay the layer or layers comprising grit on well-defined areas on the inner wall of the furnace, the selection of which depends inter alia on the temperature in or above the melt in the area concerned, or on the melting temperature in the area concerned. properties of the material in the liquid.

When it is desired to lay a refractory gravel based layer on the vertical walls of the furnace, suitable means of securing the granular material in place on the vertical walls may be used, or the granular material may be deposited so that it is free to form slopes, As long as the slope angle of the material is small enough that the surface layer is not too sloped.

When the melt depth of the furnace is shallow (especially less than 800mm, especially less than 500mm), because the inclined side wall does not occupy a very large melt volume under the appropriate slope angle, the second embodiment can prove that is particularly beneficial.

In general, composite materials based on refractory grit can be used in all types of furnaces to advantageously form the entire surface of the bottom and also of the side walls of the furnace. However, its use can vary depending on the type of furnace.

On this bottom, therefore, a layer containing grit can be used over the entire surface of the bottom of the electric furnace, especially of the type with buried electrodes, whereas in a combustion furnace such a layer can only be used in the furnace entry area, in the combustion furnace Downstream can use conventional flat plates to contact the molten material.

In general, it is advantageous for the bottom to have a layer comprising refractory grit in at least one zone of the furnace into which the material to be melted is fed. Thus, when the material contains fusible residues, in particular metal scrap, which would deposit on the bottom of the melt in the feed zone of the furnace, the surface lining according to the invention is perfectly suited to contain these residues, in particular to prevent These residues travel to the lower structural levels of the side walls, such as insulation panels.

In particular, when the material to be melted contains metal scrap, the lining of the side wall surface according to the present invention has a clear advantage in the sense that it is better than conventional refractory contact materials at temperatures close to its melting point. More resistant to corrosion by molten materials.

This is because the bottom surface in a furnace for glass is composed of a flat plate of usual refractory material, the presence of liquid metal on the bottom surface of this furnace, at the triple point of molten glass/liquid metal/refractory material, will initiate Very severe corrosion of refractory materials.

Deterioration of side wall constituents due to intrusion of metal is therefore quickly observed.

This disadvantage does not occur, or is greatly reduced, when the side wall surfaces according to the invention are realized.

In this respect, the object of the invention is also the use of the furnace described above for melting recycled glass containing metal scrap.

Recycled glass can come from different sources, especially from mirrors, from heated automotive windows, especially rear windows, or from tinned or glazed glass, especially for automotive windows, or from other recycled packaging . The metals present as metal scrap in such recycled glass can be, inter alia, silver, lead, copper, tin or other metals.

It was unexpectedly observed that the liquid metal produced by melting recycled glass may or may not penetrate the surface layer or layers, depending on the particle size of the grit used (for certain mineral binders). explain). The limiting size of the grit particles depends on the properties of the metal, especially on the viscosity in the molten state at its bottom temperature, but also on the interstitial mineral binder and the molten glass in the molten liquid.

Thus, the surfaces of the side walls of the furnace are suitable for recovering metal separated from the glass by melting, to which the surfaces are permeable.

In this respect, the object of the present invention is also a method of separating metals present in recycled glass, which method comprises a step of melting the recycled glass in a furnace as described above, during which step the grit contained in the bottom surface layer In contact with the glass, the grit has a particle size suitable to make the layer permeable to the metal.

In a first embodiment, immediately below the layer there is provided a space for recovering liquid metal flowing through the layer. It is also possible to place a perforated part such as a Sanger on top of this space to serve as a support for the contact layer.

In another embodiment, immediately below the contact layer there may be placed a second layer called a "underlayer" comprising grit having a particle size suitable to impermeable the lower layer to liquid metal.

So in the end the metal is trapped between the two grit based layers and gradually builds up during the operation of the furnace. After one or several periods of operation of the furnace, all that is required is to remove the bottom surface lining, from which the recovered metal can be easily extracted.

This method makes it possible to reuse recycled glass while separately recovering metals using the same equipment.

Further features and advantages of the present invention will be seen in the following detailed description of the accompanying drawings, in which:

Fig. 1 represents the schematic diagram of the partial longitudinal section of stove of the present invention;

Figure 2 shows an enlarged detail of the bottom of the furnace in Figure 1;

Figure 3 shows a schematic diagram of a longitudinal section through another furnace according to the invention.

In Fig. 1 and Fig. 3 only the parts necessary for understanding the invention are given without regard to the scale of the device.

In FIG. 2, only the order of magnitude of the dimensions of the corresponding components is considered.

The furnace 1 shown in Figure 1 essentially consists of a bottom 2, side walls 3 and a roof 4 which delimit a molten liquid 5 of molten material such as glass. It also includes means 6 for supplying the material 7 to be melted, such as a conveyor, and a channel 8 for the flow of the molten material, the means for melting the material 7 not being shown. The material to be melted can consist of recycled glass (cullet) and/or pulverulent oxide components.

The furnace bottom 2 mainly includes from the outside to the inside: a bottom wall made of insulating plates 9 placed in one or more rows (only one row is drawn); a layer of optional refractory cement 10, which can also be placed on this layer of cement A slab of refractory material 11 ; followed by a continuous first layer 12 and a second layer 13 based on refractory material.

Details of layers 12 and 13 can be seen from the enlarged view of FIG. 2 . The first layer 12, i.e. the lower layer, consists of refractory gravel 14, in particular of the AZS or chromium oxide type, with a small particle size, in particular less than 20 mm, advantageously less than 10 mm , especially larger than 5mm, they are buried in the adhesive 15, or are surrounded by the adhesive. The binder consists of oxides or of glassy materials such as glass.

The second layer 13, or the contact layer, consists of another refractory material, grit 16 . Its composition and the composition of the gravel 14 may be the same or different, in particular its grain size is at least 10 mm, advantageously at least 20 mm, but its grain size is larger than that of the first layer of gravel 14, the grains of the gravel 16 are bound by minerals Surrounded by an agent 17, the composition of this adhesive is the same as that of the contact layer 12, or it can be different.

These two layers on the surface of the plate 11 can be produced by different methods.

In a first manufacturing method, a lower layer of smaller grit 14 is placed on the plate 11 . An upper layer of coarser gravel 16 is then placed on top of this lower layer. Next, the entire thickness is covered with a meltable slag of glassy material, especially cullet, and the furnace is put into operation: the melting of this slag makes it possible to saturate this layer of gravel and gradually encase the grains of gravel 14 and 16, so as to finally produce layers 12 and 13 in which the molten cullet acts as an adhesive and ensures the bond of this assembly.

As the molten cullet gradually flows between the grains of the gravel, it interacts with the surface of the grains of gravel, adhering to refractory oxide elements such as Al, Zr, Si in the case of AZS gravel , in the case of chrome grit glued Cr. The glass with refractory oxide elements becomes more viscous and may end up devitrifying the glass in the free interstitial spaces, the devitrified viscous material preventing the glass from flowing from the melt to the lower layers.

In a variant embodiment, separating elements such as a grid or screen made of refractory metal can be placed between the two layers of gravel, and similar elements can be placed on the second layer in order to maintain the corresponding height of these layers .

The same technique using a retaining grid can be used to lay down a similar layer or layers on the side wall 3 .

In another method of manufacture, deposited grit particles 14 and 16 are intimately mixed with binders 15 and 17, respectively, into layers 12 and 13. When the temperature of the furnace 1 is increased to start the furnace, the molten binder coats the grit particles and ensures the bonding of the assembly. The chemical exchange phenomena described above in the manufacturing process may of course occur together with these same effects.

FIG. 2 also illustrates the difference in the behavior of the two layers 12 and 13 with respect to the metal 18 present in the molten state 5 in the molten state, especially in the case of recycled glass containing metal scrap in the material 7 to be melted. .

The particle size of the grit 16 and the nature of the binder glass 17 should be such that the layer 13 is permeable to the metal 18 .

Instead, the particle size of the grit 14 and the nature of the binder glass 15 should be such that the layer 12 is impermeable to the metal 18 .

Therefore, in operation, the metal 18 present in the molten state in the molten liquid 5 flows to the furnace bottom 2 due to gravity, passes through the layer 13, opens a channel between the grit particles 16, and finally is sandwiched between the layers 13 and 12 , where it accumulates in drops, gradually increasing in size.

The thickness of the layer 13 is advantageously determined in such a way that it provides sufficient metal storage capacity in the interstitial spaces between the grit for a certain period of furnace life.

Figure 3 shows another embodiment of the invention. Where the furnace 20 in FIG. 3 contains identical or equivalent components to those of the furnace 1, these components are designated by the same reference numerals.

Important differences from the first embodiment relate to the structure of the furnace bottom and the structure of the side walls.

This bottom consists of three layers containing refractory gravel:

The lower layer 21 (similar to the lower layer 12 in the furnace 1) comprises a binder and finer grit, e.g. with a particle size of approximately 0 to 5 mm, of a type that is more susceptible to corrosion by glass-based adhesives, e.g., the AZS type , may also include limited amounts of chromium oxide.

This layer is impermeable to glass, especially since the fine grit is very densely packed and the interstitial glass is filled with refractory oxides due to the high exchange area; moreover, this layer is corrosion resistant. In particular, this layer acts as a refractory cement and is therefore an optional role for the refractory cement layer 10;

The intermediate layer 22 comprises a binding agent and coarser gravel than the gravel of the layer 21, for example, its particle size is about 10 to 30mm, and is of a type that is relatively erosive by the glass-based adhesive, and the type of gravel in the layer 21 can be compared. The same may also be different. In a particular example, the gravel may be of the AZS type, which may contain up to 30% chromium oxide.

The function of layer 22 is to enrich the interstitial glass with refractory oxides, which, on the one hand, makes corrosion less when reaching the lower layer 21, and on the other hand, makes it more viscous in order to limit the penetration of corrosive oxides. convection and diffusion;

The upper layer 23 (which may be similar to the contact layer 13 in the furnace 1) comprises coarser grit, for example with a particle size of at least 50 mm, from which fine particles have been carefully removed, of a glass-resistant type, e.g. Single-phase and chromium oxide-rich.

The basic function of the upper layer is to prevent convection on the lower layer; due to its large particle size, it cannot be carried away by the glass flow, nor can it cause defects due to its large size.

The gravel of layers 21, 22 and 23 may be a recycled material.

Each side wall consists of a lower part made of insulating panels 9 resting on an optional layer 10 of refractory cement. On this lower part is placed a roof made of panels 3 of refractory material, for example for forming the side walls of the furnace 1 .

The surface of the side wall facing the molten glass is lined with refractory gravel which is continuous with the upper layer 23 .

This liner is inclined from the vertical at an angle corresponding to the slope angle of the refractory material used to form this layer 23 . It is used to isolate plates 3 and 9 from the glass melt.

As a variant related to the first embodiment, the two gravel-based layers 21, 22 can be produced by first preparing a mixture of the relevant gravel and the corresponding glass-based binder in particulate form, especially cullet, and a continuous spread out:

- a compact horizontal layer for the mixture of the lower layer 21;

- followed by a compact horizontal layer of this mixture for the middle layer 22 .

The upper layer 23 is made by placing a horizontal layer of coarse gravel on top of the separation layer separating the refractory panels 3 from the insulating panels 9 and, finally, laying the coarse gravel in the form of a slope along the vertical side walls.

Finally, the furnace is started to heat up to melt the binder or binders to form the layers 21 and 22 respectively. Next a high-melting material, such as glass or cullet, is introduced to start the furnace; the grit in layer 23 is then wetted by the molten material, forming a binder.

The chemical exchange between the binder glass and the refractory glass may continue for a period of time while heating or starting the furnace before reaching the desired level of impermeability.

Thanks to the grit-based lining on the inner walls of the furnace, it is possible to reduce the thickness of the refractory panels 3 and to replace the lower refractory panels 3 of the furnace 1 with less expensive insulating panels 9 and to reduce the cost of the furnace considerably without compromising the insulation and corrosion resistance.

The invention has just been described in the particular case of a glass furnace with a furnace bottom of a given structure provided on its entire surface with at least two layers of gravel, the invention is by no means limited to this embodiment. The information given in the detailed description can be extended to other embodiments, especially to the following cases: there is another structure on the bottom (in particular, no insulation boards, cement and/or slabs are present); only a single gravel base is used; Spread one or more layers on only part of the bottom.

Other conventional arrangements of current glass type furnaces are also suitable for use in the present invention.

Claims (20)

1. Furnace (1; 20) for melting high melting point materials such as glass, this furnace comprises a bottom (2) and side walls (3) which limit the extent of a molten liquid (5) of molten material, characterized in that: At least a portion of the surface of the furnace floor (2) which is in contact with the molten material (5), and possibly at least a portion of the side wall (3) which is in contact with the molten material (5), is initially made of at least one grit containing refractory material Layer (12,13; 21,22,23) composition of (14,16). 2. The furnace according to claim 1, characterized in that the refractory grit material (14, 15) is a material resistant to glass corrosion, in particular this material is of the type based on chromium oxide or based on zirconia, silicon oxide and / or type of alumina. 3. Furnace according to claim 1 or 2, characterized in that the layer or at least one of the layers (12, 13; 21, 22, 23) contains, in addition to the gravel (14, 16), There are mineral binders (15, 17), which advantageously consist of oxides or of glassy materials such as glass, especially recycled glass. 4. according to the described stove of claim 3, it is characterized in that: this layer or at least one layer of these layers (12,13; 21,22) is made of gravel and binding agent, and they begin to mix in the form of particle together. 5. Furnace according to any one of the preceding claims, characterized in that the or each binder has a density greater than the density of the molten material contained in the melt (5). 6. Furnace according to any one of the preceding claims, characterized in that the viscosity of the or each binder is greater than the viscosity of the molten material contained in the molten liquid (5). 7. According to each described stove in the preceding claim, it is characterized in that: the thermal conductance of this adhesive or each adhesive is all smaller than the molten material contained in the molten liquid (5) heat conduction. 8. The furnace according to any one of the preceding claims, characterized in that the surface or a part of the surface comprises a single layer of gravel, the size of the grains of which is preferably less than 50 mm, especially less than 20mm. 9. According to each described furnace in the claim 1 to 7, it is characterized in that: this surface or the part of this surface comprises a first layer (13; 23), and this first layer comprises and molten material contacting first grit (16), under which there is at least one lower layer (12; 22, 21) comprising lower grit (14), the particle size of the first grit (16) being larger than that of the lower grit (14) Particle size. 10. The furnace according to claim 9, characterized in that the first layer (13, 23) contains gravel (16) with a grain size of at least 10 mm, in particular approximately between 20 and 50 mm, and the lower layer ( 12; 22, 21) contains grit (14) having a particle size of less than 20 mm, especially about 1 to 10 mm. 11. Furnace according to claim 9 or 10, characterized in that the grit of the first layer (23) in contact with the molten material is glass-resistant, and the or each lower layer (21, 22 ) of the grit are easier to be corroded by glass type. 12. Stove according to any one of the preceding claims, characterized in that the layer or layers (12, 13; 21, 22, 23) comprising gravel (14, 16) are laid on a profiled On a solid or shapeless base made of flat or slabs of refractory or insulating material. 13. according to any one described furnace in the preceding claim, it is characterized in that: the surface of at least one side wall (3) is made up of lining (23), and this lining contains the grit of refractory material, it It is inclined relative to the vertical line. 14. Furnace according to any one of the preceding claims, characterized in that at least on that part of the furnace where the material to be melted is supplied, the surface of the bottom comprises a layer of refractory gravel. 15. A method of manufacturing a furnace (1) such as a glass furnace, in which a bottom (2) and side walls (3) are made to limit the extent of the molten liquid (5) of the molten material, characterized in that , which includes the following steps: - laying at least one layer (12, 13; 21) comprising refractory gravel (14, 16) on at least a part of the surface of the bottom (2), optionally also on at least a part of the surface of the side walls (3) , 22, 23) for contacting with the solution (5), then - raising the temperature of the furnace (1), introducing a high melting point material, such as glass, in order to form a melt (5) of molten material. 16. The method of manufacturing a furnace according to claim 15, characterized in that in a first step a mineral binder (15, 17) is applied as a gravel (14) with at least one layer (21, 22) , 16), or as a layer placed on top of the gravel layer (14, 16), in a second step, the binder (15, 17) is melted and/or heat activated to form at least one composite Layers (12, 13; 21, 22). 17. A method of manufacturing a furnace according to claim 16, characterized in that in a first step, a further layer (23) is laid on the layer (22) comprising adhesive, this layer comprising The particle size is substantially larger than the particle size of the lower layer or layers. 18. Use of a furnace according to any one of the preceding claims for melting recycled glass containing metal scrap. 19. Method for recovering metals (18) present in recycled glass, comprising the step of melting recycled glass in a furnace according to one of claims 1 to 15, in which furnace, contained in the bottom (2) The glass-contacting grit (16) in the layer (13) has a particle size suitable to make the layer (13) permeable to the metal (18). 20. Recycling method according to claim 19, characterized in that the furnace (1) comprises a lower layer (12) just below the surface layer (13), which lower layer contains gravel (14) whose particle size is not Suitable for infiltrating the lower layer (12) with metal (18).

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