INSTALLATION FOR MELTING A COMPOSITION OF RAW MATERIALS AND USE OF AN INSTALLATION

Abstract

HIGH ENERGY EFFICIENCY FURNACE. The invention relates to an installation 1 for melting a composition of raw materials, adapted for obtaining glass wool, textile glass yarns and / or flat glass, comprising a melting chamber 2 equipped with at least one immersion-type burner 3, characterized in that the melting chamber 2 is defined by side walls 4 made of non-metallic refractory material and a bare metal hearth 5 to which the immersion burner is fixed, the hearth being traversed by a network of ducts adapted for the circulation of a cooling fluid, preferably water.

Description

1 / 13 “INSTALLATION FOR THE MELTING OF A COMPOSITION OF RAW MATERIALS AND USE OF AN INSTALLATION”

[0001] The present invention relates to an installation for melting a composition of raw materials adapted for obtaining glass fibers of the type mineral wool for thermal or acoustic insulation, of textile glass yarns said to be for reinforcement, and / or of flat glass.

[0002] In the present text, these “raw materials” include silica sand, but also all additives (sodium carbonate, limestone, dolomite, alumina...), the remains (which include mineral fibers) that may come from the production of said fibers or from construction sites (construction or deconstruction), all eventual liquid or solid fuels (plastic of composite or non-composite material, organic matter, coals), and any type of calcined glass.Also included are recyclable materials containing combustible (organic) elements such as, for example, coated mineral fibers with a binder (of the type used in thermal or acoustic insulation or those used in the reinforcement of plastic materials), laminated glass with polyvinyl butyral polymer sheets such as windshields, glass bottles (domestic calcined glass), or any type of "composite" material that combines glass and plastic materials such as some bottles. "Glass-metal composites" or metallic composites, such as functionalized glass with coatings containing metals, are also recyclable. These have been difficult to recycle until now because they present the risk of causing a progressive enrichment of the melting chamber with metals, generating the production of metallic silicon in the glass bath.However, the mixing achieved by fusion according to the invention prevents this sedimentation, and thus allows for the recycling of, for example, glass panes coated with layers of enamel, with layers of metal and / or with different connection system elements. In the description, the expressions "liquid glass" and "glass bath" refer to the product of the fusion of these vitrifiable materials.

[0003] The invention relates more specifically to an installation (oven) said to have “immersed burner(s)”. Such burners are fueled with gas and with Petition 870250119410, dated 12 / 24 / 2025, page 14 / 41 2 / 13 air, and generally arranged so as to emerge at the level of the melting chamber's sill, so that the flame develops within the mass of raw materials during liquefaction. These burners may be such that their gas intake ducts emerge from the wall they pass through. According to certain embodiments, it is possible to choose to inject only gases from combustion, the latter being carried out outside the melting chamber itself.

[0004] Within this context, it is known to manufacture furnaces with immersed burners in which the hearth and side walls are made of refractory materials.

[0005] In the overall description, and in accordance with ISO / R836 or AFNOR NF B 40-001 standards, "refractory" materials are defined as materials and products other than metals and alloys (including those containing a metallic constituent) whose pyroscopic resistance is equivalent to at least 1500°C. This definition means that refractory materials must withstand at least 1500°C without softening or collapsing under their own weight according to the pyroscopic resistance test standard.

[0006] Walls and sills made of refractory material have the advantage of providing very good thermal insulation, and therefore reasonable energy consumption. However, they have the disadvantage of being fragile and difficult to mold. For example, the inclusion and fixing of different elements on the sill (burners, boilers) is made difficult by the thickness of the refractory material, which is on the order of 20 to 40 centimeters.

[0007] It should also be noted that furnaces with immersion burners equipped with such walls made of refractory materials are not suitable for the production of rock wool. The melting of rock (basalt or blast furnace slag) actually requires heating the raw materials to temperatures close to 1500°C, which are significantly higher than for melting ordinary glass, and to which classic refractories can hardly withstand. Add to this a very strong agitation of the molten rock bath, due to the arrangement of the Petition 870250119410, dated 12 / 24 / 2025, page 15 / 41 3 / 13 burners below the surface of the latter, and a greater fluidity of the molten rock, compared to molten glass. These different factors contribute to accentuating the corrosion mechanisms at the level of the furnace walls.

[0008] In fact, there are high-performance refractories that have the ability to withstand such physical limitations for a time. However, the very high costs associated with manufacturing such refractories prevent their use for the production of rock wool via immersion burner furnaces.

[0009] For all these reasons, furnaces with immersion burners equipped with walls made of refractory materials are not suitable for melting rock wool.

[0010] According to an alternative approach, it is possible to manufacture furnaces with immersed burners in which the side walls and hearth are made of metal plates traversed by a network of conduits adapted for the circulation of a cooling fluid (called a "water jacket" in English). Such metal plates have the advantage of being easily disassembled and replaceable and have a long lifespan in contact with hot glass and fluid.

[0011] However, such water jacket walls have several drawbacks. Primarily, they absorb a lot of energy and thus generate very high energy consumption, which, within an industrial context of energy saving, means that the use of these water jacket walls is currently strictly limited to the field of rock wool production, where the performance of walls made of traditional refractories is lacking.

[0012] Additionally, it is worth noting that these water jacket type walls have a number of additional drawbacks that are specific to a hypothetical execution for the production of glass wool. The molten raw material bath necessary for such production has the particularity of having a very light color, hence its nickname of "clear glass" bath.

[0013] Such a clear glass bath is distinguished primarily from a molten rock bath by the greater intensity of radioactive transfers it allows. Petition 870250119410, dated 12 / 24 / 2025, page 16 / 41 4 / 13 Compared to a molten rock bath, a clear glass bath thus transmits a greater amount of heat to the furnace walls through radiation. This therefore further increases the energy consumption of water jacket walls, which reinforces a drawback already identified as a disadvantage for using water jacket walls for melting clear glass.

[0014] A clear glass bath is further distinguished from a rock bath by its lower propensity to devitrify. Now, in the case of a rock bath, the formation of a devitrified layer at the interface between the water jacket walls and the glass bath allows precisely to better protect these walls, especially against corrosion induced by the rock bath. Such a devitrified layer having more difficulty forming in the case of a clear glass bath, the water jacket walls are in this case more exposed to corrosion by the glass and therefore have a reduced lifespan.

[0015] For these reasons at least, the use of such water jacket type metal plates is currently considered to be particularly unsuitable for the production of glass wool.

[0016] The invention aims to provide a technical solution to the drawbacks described above. More specifically, in at least one embodiment, the proposed technique relates to an installation for melting a composition of raw materials, adapted for obtaining glass wool, textile glass yarns and / or flat glass, comprising a melting chamber equipped with at least one immersion-type burner, characterized in that the melting chamber, preferably cylindrical in shape, is defined by side walls made of refractory material in accordance with ISO / R836 or AFNOR NF B 40-001 standards and a bare metal hearth to which said burner is fixed and which is traversed by a network of conduits adapted for the circulation of a cooling fluid, preferably water.

[0017] In the present description, the metal sill is said to be “bare” because it is not protected by refractory materials interposed between it and the molten glass.

[0018] Faced with the drawbacks identified in the state of the art, the Petition 870250119410, dated 12 / 24 / 2025, page 17 / 41 5 / 13 inventors initially launched an advanced research program to analyze, for different furnace configurations, the convection movements of molten glass inside the furnace, the heat exchanges that occur between the molten glass and each of the elements that constitute the walls, the dome, and the hearth of the furnace, the resulting wear of each of these elements, and the energy yields obtained by the furnace for each of the configurations considered. These analyses were conducted both based on empirical tests carried out in pilot furnaces and through computer simulations.

[0019] These analyses notably highlighted that in the vicinity of the burner flames, a refractory hearth wears out significantly faster than a water jacket type metal hearth due to the strong convection currents and the particularly high temperature of the molten glass. For reasons of hearth durability, and therefore of the furnace, the choice of a water jacket type metal hearth should therefore be preferred.

[0020] In contrast, the furnace walls are less attacked by molten glass than the hearth, hence moderate wear over time of refractory walls positioned in that location. Now, these side walls represent a significant part of the total heat exchange surface of the furnace with the glass bath, also referred to as the "glass contact surface" in the following description. The use of refractories in this location, compared to water jacket type metal walls, therefore allows limiting thermal waste and increasing the furnace's energy efficiency for an acceptable lifespan.

[0021] Based on these conclusions, a furnace according to the invention constitutes a hybrid solution that presents the advantages linked to each of the technical solutions known in the state of the art, without the drawbacks inherent in them. To do this, a furnace according to the invention skillfully combines the best-performing elements of each of these solutions in order to obtain a furnace that simultaneously exhibits good energy efficiency and satisfactory durability.

[0022] It should be noted that such hybridization is by no means obvious, given Petition 870250119410, dated 12 / 24 / 2025, page 18 / 41 6 / 13 that it results from the selection and combination of elements present in technical solutions that are a priori antagonistic, based on a successful research program that aims to identify and understand the physical mechanisms that intervene within the furnace and that impact its energy efficiency and durability.

[0023] Finally, in the absence of any external stimulus, the technical complexity and cost of developing a new furnace solution constitute an additional technical bias to overcome in order to arrive at the invention.

[0024] According to a special embodiment, said metal sill is fixed in a removable manner to said side walls.

[0025] In the overall description, the term "removable" qualifies a reversible fastening, without deterioration of the parts fastened together. In contrast, welding two parts together is considered an irreversible fastening.

[0026] During furnace maintenance, it is thus possible to replace only the defective part, the other part being reusable in that respect. In general, this first defective part is the metal hearth, since it is the one most intensely subjected to corrosion caused by the liquid glass. A furnace according to the invention therefore has a significantly increased lifespan. The production of the hearth, on the one hand, and the side walls, on the other hand, is also made easier, these two elements being produced distinctly and potentially via different processes adapted to the technical specifications of each of these parts. In other words, a furnace according to the invention has improved operational efficiency.

[0027] According to a special embodiment, said sill comprises at least a central portion adapted to form the lower surface of the melting chamber and a connecting flange adapted to rest on a flat support beneath said side walls.

[0028] The central portion is therefore adapted to be in contact with the lower part of the glass bath, while the connecting flange, formed on the contour of this central part, is adapted to serve as a support surface with the lower part of the side walls, either by direct contact or preferably by Petition 870250119410, dated 12 / 24 / 2025, page 19 / 41 7 / 13 intermediate section of a circumferential portion of the threshold.

[0029] According to a special embodiment, said connecting flange forms a protrusion with said central part.

[0030] A projection designates an abrupt change in section formed at the base of the central part of the sill.

[0031] According to a special embodiment, said sill comprises a circumferential portion that has a complementarity of form with the contour of said central portion and is adapted to serve as a base for said side walls on one side, and to be in plane support with said connecting flange on the other side.

[0032] Such a circumferential portion serves as a base (or foundation) for the side walls that rest on top, and is preferably integral with an external metal structure of the furnace. It should be noted that this circumferential portion (5c) which forms part of the hearth, is itself of the water jacket type.

[0033] Such a circumferential portion has the advantage of facilitating the execution of a hermetic connection with the side walls, with which it shares a connection in a plane support, whether reversible or irreversible, on a relatively extensive surface. The risks of combustion gas leakage are therefore reduced in this place.

[0034] This circumferential portion also allows for the creation of a hermetic connection with the central part of the sill, due to the complementary shape of the two. Such a connection is notably reinforced by the connection in the divided flat support with the connecting flange, which is recessed in relation to the glass bath, and is therefore less exposed to the heat emitted by the glass bath.

[0035] According to a special embodiment, said circumferential portion is adapted to be fixed to said connecting flange in a removable manner, preferably by a screw-nut type fastening.

[0036] During furnace maintenance, it is therefore possible to replace only the defective part, the other part being reusable in that respect. The execution Petition 870250119410, dated 12 / 24 / 2025, p. 20 / 41 8 / 13 of such a removable fastening therefore allows for improved operational efficiency of the metal hearth and, more generally, that of the furnace.

[0037] According to a special embodiment, said installation comprises at least one flue gas seal disposed at the interface between said circumferential portion and said connecting flange.

[0038] Such a sealing gasket allows limiting the risk of gas leaks from the melting chamber to the outside of the furnace. Its placement between the circumferential portion and the hearth connection flange is especially advantageous because the gasket is in this case recessed relative to the melting chamber and the heat it produces. The materials used in the composition of this sealing gasket can therefore be selected as having lower thermal resistance, in order to provide better sealing properties.

[0039] According to a preferred embodiment, said sealing gasket is made of a type of silicone adapted to withstand high temperatures (several hundred degrees).

[0040] According to a special embodiment, said bare metal hearth is adapted to be traversed by at least one immersion-type burner and / or a boil kettle, which are fixed to the hearth in a removable manner.

[0041] Selecting a water jacket type hearth allows limiting the size, weight, and cost of the elements to be fixed to the hearth (burners, oxidant injector blocks). In fact, the water jacket hearth is thinner than the refractory hearth, by a factor of 2 to 4. The elements fixed under the hearth, preferably by means of screws, must pass through it to be visible at its top and are therefore less bulky, since they have a smaller thickness to pass through. They are therefore less heavy and also less expensive to manufacture, considering the reductions in material used and the simplifications in design.

[0042] According to a special embodiment, said side walls made of refractory material are at least partly covered around their perimeter by a metal sheath through which a network of conduits adapted for the Petition 870250119410, dated 12 / 24 / 2025, page 21 / 41 9 / 13 circulation of a cooling fluid, preferably water.

[0043] The addition of this water jacket-type metal cover on the exterior of the furnace allows for supplementary cooling of the side walls made of refractory materials and / or recovery of the heat emitted through them. Furthermore, in certain special embodiments, it allows for cooling of the contact zone of the sealing joint.

[0044] According to a special embodiment, said at least one immersed-type burner comprises an injector block equipped with a combustion gas distribution network and a plurality of injectors.

[0045] The invention also relates to the use of such an installation for melting a composition of vitrifiable raw materials.

[0046] The combustion of a fuel inside a furnace is achieved thanks to the presence inside the furnace of an oxidizer that includes oxygen. The use of pure oxygen at more than 99% is evidently a good solution for the drastic reduction of NOx since such an oxidizer is almost nitrogen-free. However, this high-quality oxygen is particularly expensive.

[0047] According to a special embodiment, the gaseous oxidant used comprises 90 to 96 mol% oxygen and nitrogen. A much less expensive industrial oxygen is thus used, which nevertheless contains some nitrogen, called “VPSA” oxygen (for “Vacuum Pressure Swing Adsorption”). The use of such a mixture is advantageous because it is combined with a medium that allows the combustion temperature to be reduced. In fact, due to its low concentration inside the furnace, the small amount of nitrogen introduced with the oxidant produces little or no NOx at relatively low temperatures.

[0048] Other features and advantages of the invention will become apparent from reading the following description of special embodiments, given by way of simple illustrative and non-limiting examples, and from the attached figures, for which:

[0049] [Fig. 1] Figure 1 is a schematic exploded cross-sectional view of an installation for melting a composition of raw materials, according to a special embodiment of the invention. Petition 870250119410, dated 12 / 24 / 2025, page 22 / 41 10 / 13

[0050] [Fig. 2] Figure 2 is an enlargement of the lower part of an installation such as that shown in Figure 1, in exploded view.

[0051] [Fig. 3] Figure 3 is an enlargement of the lower part of an installation such as that shown in Figure 1, when the hearth 3 is placed at the bottom of the furnace.

[0052] The different elements illustrated by the figures are not necessarily to scale, the emphasis being more on representing the general functioning of the invention. In the different figures, unless otherwise indicated, the reference numbers that are identical represent similar or identical elements.

[0053] It is further understood that the present invention is in no way limited by the special embodiments described and / or represented, and that other embodiments may perfectly well be used.

[0054] Figures 1 to 3 represent all or part of an installation 1 (furnace) for melting a composition of raw materials, and are intended to illustrate its general operation. Such an installation 1 is adapted for obtaining glass wool and / or textile glass yarns. It comprises a cylindrical melting chamber 2 oriented along a vertical axis, and is delimited by side walls 4 and a dome made of refractory materials and a bare metal hearth 5, of the water jacket type, through which an immersion-type burner 3 passes.

[0055] For the sake of clarity and simplification, the oven 1 illustrated in figures 1 to 3 comprises only a single burner 3, and no boiling pot. It is evident, however, that the scope of the invention is in no way limited by the number of burners / boiling pots used within the oven.

[0056] Furnace 1 comprises at its lower part a feed opening 8 for raw materials, located below the theoretical level of the molten raw material bath, also called the glass bath in the overall description. The raw materials are generally brought into the melting chamber 2 by means of a furnace-loading machine (not shown).

[0057] Once inside the glass bath, the raw materials are melted by Petition 870250119410, dated 12 / 24 / 2025, page 23 / 41 11 / 13 middle of the immersed type burner 3, it is also arranged below the level of the glass bath. In figures 1 and 2, this burner 3 is shown in the form of an injector block equipped with a combustion gas distribution network and a plurality of injectors. The invention, however, is not limited to the use of such a type of burner, which may, according to alternative embodiments, have, for example, an annular shape and / or a single-injector type.

[0058] The gases from the combustion of the raw materials are recovered via an exhaust chimney 9 located at the top of the combustion chamber 2. The molten mixture is extracted from the furnace 1 by means of a weir 10, for a subsequent stage of forming glass wool fibers or spinning textile glass yarns. An emergency exit 11, located at the base of the melting chamber 2 or alternatively at the hearth, allows purging the furnace if necessary.

[0059] Figures 2 and 3 are an enlargement of the lower part of the installation, and in particular of the connections that exist between the different components of the sill 5 and the side walls 4 made of refractory material.

[0060] According to a special embodiment illustrated by figures 2 and 3, the hearth 5 notably comprises a central portion 5a adapted to form the lower surface of the melting chamber 2 or, in other words, to form the bottom of the glass bath tank. This central portion 5a is specifically traversed by the burner 3, fixed at its lower part by means of screws. A circumferential metallic portion 5c of the hearth 3 serves as a base for the side walls 4 which rest on top in a flat support, while at the same time being integral with an external metallic structure of the furnace 1 (not shown).This circumferential portion 5c also presents a complementarity of form with the contour of the central portion 5a of the sill 5, so that this central portion 5a, when it is inserted into the base of the basin 2, seals the central gap formed by the side walls 4, thus forming a hermetic basin bottom, at least in the passage of the molten glass, as illustrated in figure 3. A connecting flange 5b forms a projection at the base of the central portion 5a and rests on a flat support. Petition 870250119410, dated 12 / 24 / 2025, page 24 / 41 12 / 13 against the lower part of the circumferential portion 5c, thus reinforcing the gas tightness of the bottom of the hub, notably by means of a sealing gasket (not shown) disposed at the interface between these two elements. According to the special embodiment illustrated in figures 1 to 3, the connecting flange 5b is removablely fixed to the circumferential portion 5c by means of a plurality of screws.

[0061] According to an alternative embodiment, not shown in the figures, the sill 3 does not comprise a circumferential portion 3c. The sill 3 is in this case fixed directly to the underside of the side walls 4, by plane-to-plane contact of the connecting flange 5b with the base of the side walls, or with an intermediate plate that acts as the base of the latter. Such a fixing may alternatively be of a reversible or irreversible type.

[0062] According to an alternative embodiment, not shown in the figures, the sill 3 comprises a circumferential portion 3c, but the latter is fixed in a removable manner to the side walls 4, for example by means of a plate that acts as the base of these side walls 4.

[0063] In order to evaluate the role played by the materials that constitute the hearth 3 and the side walls 4 respectively, on improving the energy performance of furnace 1, a test is computer-simulated via a thermal model for a furnace that has a melter of 1 m2, for 1 m of soda-lime glass bath at 1200°C the surface of walls in contact with glass is 5 m2.

[0064] For a first sample, the entire furnace walls, including the hearth, are bare metal, of the water jacket type. Energy losses in the walls in contact with glass are estimated at 500 kW in this case.

[0065] For a second sample, the entire furnace walls, including the hearth, are made of refractory materials. Energy losses in the walls in contact with glass are estimated at 50 kW in this case.

[0066] It is therefore observed that the thermal losses in the walls in contact with glass are ten times greater in the case of water jacket walls, in Petition 870250119410, dated 12 / 24 / 2025, page 25 / 41 13 / 13 comparison with walls made of refractory materials.

[0067] For a third sample, representative of a furnace according to the invention, the side walls are made of refractory materials, while the hearth is bare metal, of the water jacket type. The energy losses in the walls in contact with the glass are in this case estimated at 140 kW.

[0068] Compared to the first sample, the use of the third sample, according to the claimed invention, therefore allows limiting thermal waste and significantly increasing the energy efficiency of the furnace, for an acceptable lifespan, the hearths made of water jacket being much more resistant to corrosion by glass than hearths made of refractory material. Petition 870250119410, dated 12 / 24 / 2025, p. 26 / 41

Claims

1 / 2 CLAIMS 1. Installation (1) for melting a composition of raw materials, adapted for obtaining glass wool, textile glass yarns and / or flat glass, comprising a melting chamber (2) equipped with at least one immersion-type burner (3), characterized in that the melting chamber (2), preferably cylindrical in shape, is defined by side walls (4) made of refractory material in accordance with ISO / R836 or AFNOR NF B 40-001 standards and a bare metal hearth (5) to which said burner (3) is fixed and which is traversed by a network of conduits adapted for the circulation of a cooling fluid, preferably water.

2. Installation (1) according to claim 1, characterized in that said metal sill (5) is fixed in a removable manner to said side walls (4).

3. Installation (1) according to any one of claims 1 and 2, characterized in that said sill (5) comprises at least a central portion (5a) adapted to form the lower surface of the melting chamber (2), and a connecting flange (5b) adapted to rest on a flat support under said side walls.

4. Installation (1) according to claim 3, characterized in that said connecting sill (5b) forms a projection with said central part (5).

5. Installation (1) according to any of claims 3 and 4, characterized in that said sill (5) comprises a circumferential portion (5c) that has a complementarity of form with the contour of said central portion (5a) and is adapted to serve as a base for said side walls (4) on one side, and to be in plane support with said connecting flange (5b) on the other side.

6. Installation (1) according to claim 5, characterized in that said circumferential portion (5c) is adapted to be fixed to said connecting flange (5b) in a removable manner, preferably by a screw-nut type fastening. Petition 870220096830, dated 20 / 10 / 2022, page 28 / 32 2 / 2 7. Installation (1) according to any one of claims 5 and 6, characterized in that it comprises at least one flue gas seal disposed at the interface between said circumferential portion (5c) and said connecting flange (5b).

8. Installation (1) according to any of claims 1 to 7, characterized in that said bare metal hearth (5) is adapted to be traversed by at least one immersion type burner (3) and / or a boil kettle, which are fixed to the hearth (5) in a removable manner.

9. Installation (1) according to any one of claims 1 to 8, characterized in that said side walls (4) made of refractory material are at least partly covered around their perimeter by a metal sheath through which a network of conduits adapted for the circulation of a cooling fluid, preferably water, can pass.

10. Installation (1) according to any one of claims 1 to 9, characterized in that said at least one immersed type burner (3) comprises an injector block fitted with a flue gas distribution network and with a plurality of injectors.

11. Use of an installation (1) defined in any one of claims 1 to 10 characterized in that it is for the melting of a composition of vitrifiable raw materials. Petition 870220096830, dated 20 / 10 / 2022, pp. 29 / 32

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