MELTING AND FIBRINGING OF RECYCLED GLASS WOOL

Description

[0001] The present invention relates to a composition of raw materials suitable for being placed in a glass furnace, melted, and then fiberized by external centrifugation. Also concerned are the processes for melting and fiberizing by external centrifugation of this composition, as well as the mineral wool obtained by these processes.

[0002] It is known to "recycle" a mineral wool mixture by melting it in a glass furnace in order to refiberize it. Among the many advantages of recycling mineral wool waste in this way are the improvement of the energy efficiency of the glass furnace, the collected mineral wool mixture being easier to melt than a "conventional" composition of raw materials including, among other things, large quantities of silica.

[0003] For the purposes of the invention, such a mineral wool mixture comprises one or more types of fibers originating from their production (factory waste), for example during the cutting and / or disposal of mineral wool mattresses, or from construction sites (construction site waste or waste from deconstruction sites) and / or from recycling channels enabling such mineral fibers to be recovered from final products, whether or not they are used. Other types of materials may be associated with the mineral fibers, for example paper, aluminum-based or bituminous films, wooden pallet elements.

[0004] Such mineral fibers can be made of glass and / or rock. These are referred to as glass wool and rock wool respectively. These two types of mineral wool differ from each other in their composition, their melting process, and also in the associated fiberizing process.

[0005] For the purposes of the invention, mineral wool comprises, excluding sizing: SiO2: 30 to 75% by mass, CaO+MgO: 5 to 40% by mass, Al2O3: 0 to 30% by mass, Na2O+K2O: 0 to 20% by mass, Iron oxide: 0 to 15% by mass.

[0006] The main components of rock wool (also called “black glass” by those skilled in the art) are, excluding gluing: SiO2: 30 to 50% by mass, Al2O3: 10 to 22% by mass, CaO+MgO: 20 to 40% by mass, Iron oxide: 0 to 15% by mass, Na2O+K2O: 1 to 10% by mass.

[0007] In contrast, the main components of glass wool are, excluding sizing: SiO2: 50 to 75% by mass, Al2O3: 0 to 8% by mass, preferably 0.5 to 6.0%, CaO+MgO: 5 to 20% by mass, Iron oxide: 0 to 3% by mass, Na2O+K2O: 12 to 20% by mass, B2O3: 0 to 10% by mass.

[0008] Rock melting (basalt or blast furnace slag) generally requires heating the raw materials to significantly higher temperatures than ordinary glass melting. It is traditionally carried out in cupola furnaces, heated with large quantities of coke to temperatures around 1500°C. Refractory furnaces, traditionally used for glass melting, cannot withstand the high temperatures required for melting rock.

[0009] Likewise, the fiberizing processes of these mineral wools depend directly on their respective composition, and are therefore not interchangeable.

[0010] Thus, the fiberizing process commonly used to produce rock fiber is the so-called external centrifugation process. For the latter, the material to be fiberized is poured in the molten state onto the peripheral band of rotating centrifuge wheels, is accelerated by these wheels, detaches from them, and is partly transformed into fibers under the effect of centrifugal force, a gas stream being emitted tangentially to the peripheral band of the wheels so as to take charge of the fiberized material by separating it from the non-fiberized material and conveying it to a receiving member. For example, for fiberizing by external centrifugation, reference may be made to documents EP 0 195 725 and US 2020 / 0062639.

[0011] Such a process for fiberizing rock wool should be distinguished from that commonly used for fiberglass, known as the internal centrifugal fiberizing process, see document FR 2 883 865. It consists of introducing a stream of the molten stretchable material into a centrifuge, also called a fiberizing plate, rotating at high speed. Such a fiberizing plate can alternatively be equipped with or without a bottom and is pierced at its periphery by a very large number of orifices through which the material is projected in the form of filaments under the effect of centrifugal force. By means of an annular-shaped burner, these filaments are then subjected to the action of an annular gaseous drawing current at high temperature and speed (up to 1000°C for the temperature, and 250 m / s for the speed, depending on the desired product) along the wall of the centrifuge which thins them and transforms them into fibers.

[0012] There are therefore significant differences between rock wool and glass wool, both in terms of their composition, their melting process, the physical properties (which result from this) of the molten material leaving the furnace (temperature, viscosity, etc.), and the associated fiberizing process. Regarding this last aspect, it should be noted that a molten rock bath cannot technically be fiberized by internal centrifugation, just as a molten glass bath cannot technically be fiberized by external centrifugation.

[0013] In view of these technical differences, and in the context of recycling used fibres, it is therefore natural for a person in the trade to dedicate the recycling of rock wool to the production of rock wool exclusively, and to dedicate the recycling of glass wool to the production of glass wool exclusively, without ever considering mixing these two distinct technical fields.

[0014] The strict separation between the use of glass wool waste on the one hand, and rock wool waste on the other, however, has the disadvantage of complicating the associated supply chains, by multiplying the storage locations and / or transport distances.

[0015] The claimed invention aims to provide a technical solution to the drawbacks described above. More particularly, in at least one embodiment, the proposed technique relates to a composition of raw materials suitable for being melted and fiberized by external centrifugation to obtain a mineral wool, characterized in that it comprises between 1 and 62% by mass of glass wool, and characterized in that the glass wool has the following composition, in mass percentage: SiO2: 50 to 75%, Al2O3: 0 to 8%, CaO+MgO: 5 to 20%, Iron oxide: 0 to 3%, Na2O+K2O: 12 to 20%, B2O3: 0 to 10%.

[0016] For the purposes of the invention, a raw material composition is suitable for being fiberized by external centrifugation when the temperature (TLog1) of the glass bath, for a dynamic viscosity Log 1, is between 1390°C and 1490°C, and the difference (TLog1 - Tlog3) between the temperatures corresponding to the viscosity values ​​Log 1 and Log 3 is between 320°C and 390°C. As is known in the field of glass melting, the dynamic viscosity is expressed in N Log Poises, which corresponds to 10N Poises (0.1 Pa.s), each viscosity value corresponding to a given temperature of the glass bath.

[0017] The invention is based on the new and inventive concept of introducing glass wool into a composition of raw materials intended to be melted and then fiberized by external centrifugation, a fiberizing process usually reserved for the production of rock wool. The addition of glass fibers which, due to their composition, are not initially suitable for fiberizing by external centrifugation, introduces an additional technical difficulty for a person skilled in the art in charge of melting and fiberizing. Despite these technical difficulties, such an addition of glass wool allows an operator to gain flexibility in the choice of raw materials to be used, and thus to seize opportunities that may be temporarily offered by recycling channels organized near the melting and fiberizing facilities.It should also be noted that a person in the trade has the tools and general knowledge to, on the basis of routine tests and as detailed in the description, adapt the rest of the composition so that the latter meets the technical specifications for fiberizing by external centrifugation.

[0018] According to a particular embodiment, said composition of raw materials comprises a mass percentage of glass wool greater than or equal to 3%, preferably greater than or equal to 5%, preferably greater than or equal to 10%, preferably greater than or equal to 15%, preferably greater than or equal to 20%, preferably greater than or equal to 25%.

[0019] According to a particular embodiment, said composition of raw materials comprises a mass percentage of glass wool less than or equal to 58%, preferably less than or equal to 55%, preferably less than or equal to 50%, preferably less than or equal to 45%, preferably less than or equal to 40%, preferably less than or equal to 35%.

[0020] According to a particular embodiment, the glass wool used in said raw material composition is at least partly sized. For the purposes of the invention, the expression "sized glass wool" here designates mineral wool made up of mineral fibers carrying on their surface an insoluble and infusible organic binder, already crosslinked.

[0021] According to a particular embodiment, the glass wool used in said raw material composition is at least partly virgin. For the purposes of the invention, the expression "virgin glass wool" designates glass wool obtained by internal centrifugation, the fibers of which are not bound to each other by means of an organic binder, as opposed to a sized glass wool. Such virgin glass wool is typically used as blown-in wool for attic insulation. The virgin wool fibers may be coated with a thin layer of size or lubricant.

[0022] According to a particular embodiment, said composition of raw materials comprises at least 3% by mass of iron oxide, preferably at least 5% by mass of iron oxide.

[0023] Increasing the iron oxide content of the raw material composition allows, after fiberizing, to increase the maximum operating temperature of the resulting fiber. In other words, such a fiber has better resistance to higher temperatures.

[0024] According to a particular embodiment, said composition of raw materials comprises at least 13% by mass of alumina, preferably at least 15% by mass of alumina.

[0025] The addition of alumina (aluminum oxide) to the composition improves its bio-solubility.

[0026] According to a particular embodiment, said glass wool has the following composition, in mass percentage: SiO2: 50 to 75%, Al2O3: 0 to 8%, preferably 0.5 to 6.0%, CaO+MgO: 5 to 20%, Iron oxide: 0 to 3%, Na2O+K2O: 12 to 20%, B2O3: 2 to 10%.

[0027] According to a particular embodiment, said glass wool has the following composition, in mass percentage: SiO2: 62.5% to 66%, Al2O3: 1.5% to 3.1%, CaO+MgO: 10.3 to 11.1%, Na2O+K2O: 15.7% to 17.3%, B2O3: 4.3% to 7.4%.

[0028] The detailed description refers to three compositions, under the names "component no. 1", "component no. 2" and "component no. 3", which fall within this composition range and are commonly used in the insulation industry. Such waste can therefore be collected on many production sites and / or construction / deconstruction sites.

[0029] According to a particular embodiment, said glass wool has a boron-free composition and represents less than 48% of the total mass of said raw material composition.

[0030] Such a glass wool composition is known as "zero-bore" and finds application in the insulation industry.

[0031] According to a particular embodiment, said composition of raw materials comprises household cullet and / or flat glass.

[0032] The addition of household cullet and / or flat glass allows for greater flexibility in the choice of raw materials to be used. Once again, it should be noted that a person skilled in the art has the general knowledge to, on the basis of routine tests, adapt the rest of the composition so that it meets the technical specifications for external centrifugal fiberizing.

[0033] The invention further relates to a method comprising a step of melting such a composition of raw materials in a glass furnace.

[0034] In a known manner, such a composition of raw materials can be melted in a glass furnace with submerged and / or emerged burners, in an electric furnace, and / or in a hybrid furnace using at least one burner and electrodes. At the furnace outlet, the molten composition can either be immediately fiberized by external centrifugation, or be cooled and transformed into cullet, to be later (subsequently) melted again and fiberized by external centrifugation to obtain mineral wool.

[0035] The invention further relates to a method for manufacturing mineral wool, characterized in that it implements such a melting method and a subsequent step of fiberizing by external centrifugation of the melted raw material composition.

[0036] The invention further relates to a mineral wool obtained according to such a manufacturing method.

[0037] As detailed in the examples of the description, such mineral wool tends, by its composition, to be distinguished from wools usually fiberized by external centrifugation, which allows it to be distinguished from the latter.

[0038] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given as simple illustrative and non-limiting examples, and the appended figures, for which: [ Fig. 1 ] There figure 1 is a graphical representation of the dynamic viscosity value of a raw material composition according to a particular embodiment of the invention, as a function of temperature variations.

[0039] Several particular embodiments of the invention are presented below. It is understood that the present invention is in no way limited by these particular embodiments and that other embodiments can be perfectly implemented.

[0040] A general method that can be implemented by a furnace operator to prepare a composition according to the invention is detailed in the remainder of the description.

[0041] In a first step, a target composition that meets the viscosity criteria for being fiberized by external centrifugation is selected. For the purposes of the invention, such a composition is suitable for being fiberized by external centrifugation if the temperature (TLog1) of the glass bath for a dynamic viscosity Log 1 is between 1390 °C and 1490 °C, and if the temperature difference (TLog1 - Tlog3) between the viscosities Log 1 and Log 3 is between 320 °C and 390 °C.

[0042] To assist in the selection of this target composition, a furnace operator uses models relating the chemical composition and dynamic viscosity of a mixture, such as those commonly used by the glass industry.

[0043] In an industrial context and as is known, other considerations may also be taken into account in the selection of the target composition, such as the final cost of the composition, the energy required for its fusion, and compliance with certain concentration ranges of chemical compounds.

[0044] In a second step, the operator develops his mixture by taking into account the respective chemical composition of each of the raw materials at his disposal, and adjusts the relative proportions of each of these raw materials to obtain the target composition.

[0045] These raw materials can alternatively or in combination be in the form of pure oxides, natural stones (silica sands, dolomite, limestone, waste rock, slag, white bauxite, feldspar, anorthosite etc.) which are already combinations of oxides, glass wool and / or rock waste, which can come from the production of said fibers or from construction sites (construction or deconstruction), possible liquid or solid fuels (plastic of composite material or not, organic matter, coals), and any type of cullet.Also included are recyclable materials containing combustible (organic) elements such as, for example, sized mineral fibers with binder (of the type used in thermal or acoustic insulation or those used in the reinforcement of plastic materials), laminated glazing with polymer sheets of the polyvinyl butyral type such as windshields, glass bottles (household cullet), or any type of "composite" material combining glass and plastic materials such as certain bottles. Also recyclable are "glass-metal composites or metal compounds" such as functionalized glazing with coatings containing metals.

[0046] It should be noted that according to an alternative embodiment, an operator begins by taking into account the respective composition of each of the raw materials at his disposal in order to subsequently adjust the relative proportions of the latter and, empirically, determine and obtain a target composition which, on the basis of the models at his disposal, satisfies the viscosity criteria for being fiberized by external centrifugation.

[0047] Once the target composition is obtained, it is placed in a glass furnace to be melted. The melted composition is then fiberized by external centrifugation to form mineral wool.

[0048] As a purely illustrative and non-limiting example, the following target composition is selected by a furnace operator: SiO2: 45.1% by mass, Fe2O3: 2.2% by mass, Al2O3: 7.8% by mass, CaO: 23.0% by mass, MgO: 11.0% by mass, Na2O: 8.5% by mass, K2O: 1.5% by mass.

[0049] In order to obtain this target composition, and according to this particular embodiment, the operator has as raw materials dolomite, slag and glass wool, the respective compositions of which are detailed in Table 1 below. The mass proportions (%m) of each of these raw materials are adjusted, as mentioned in Table 1 [Tables 1], to obtain the target composition. [Tables 1] Table 1: Compositions and mass concentrations of raw materials for obtaining a target composition %m SiO2 Fe2O 3 Al2O3 CaO MgO Na2O K2O Dolomite 17% 5,5 1,2 1,8 33 15 0,1 0,4 Sterile 23% 38,8 0,1 9,2 41,8 7 0,4 0,6 Glass wool 60% 53 3 8 10 10 12 2 Target composition 45,1 2,2 7,8 23,0 11,0 8,5 1,5

[0050] Based on a model commonly used by the glass industry, the operator determines the dynamic viscosity value of the target composition, based on the variation in its temperature. Note that this target composition includes 60% by mass of glass wool.

[0051] For comparison, the dynamic viscosity values ​​are also calculated, depending on the temperature variations: glass wool whose composition is given in Table 1, standard rock wool, whose mass composition is SiO2: 37%m; Fe2O 3: 5%m; Al2O3: 21%m; CaO: 20%m; MgO: 14%m; Na2O: 2%m; K2O: 1%m.

[0052] The set of dynamic viscosity values ​​(in Log V) obtained for each of these three compositions is detailed in Table 2 [Tables 2] below, and represented graphically in Figure 1 . Table 2: Dynamic viscosity values ​​(in Log V) as a function of the chemical composition of the mixture and its temperature (in °C) Temperature Glass wool Rock wool Target composition 1000°C 3,184 3,411 3,069 1100°C 2,719 2,671 2,419 1200°C 2,288 2,036 1,869 1300°C 1,891 1,506 1,419 1400°C 1,528 1,081 1,069 1500°C 1,199 0,761 0,819 1600°C 0,904 0,546 0,669

[0053] Table 3 [Tables 3] below provides information on the temperature values ​​TLog 1 and TLog 3 (in °C) corresponding respectively to dynamic viscosity values ​​of Log 1 and Log 3 obtained for these same compositions. Table 3: Temperature values ​​(in °C) as a function of the chemical composition of the mixture and its dynamic viscosity (in Log V) Glass wool Rock wool Target composition Tlog 1 1563°C 1417°C 1390°C Tlog 3 1036°C 1062°C 1000°C Tlog1 - Tlog3 528°C 355°C 390°C

[0054] Unlike the glass wool composition, both the target composition and the rock wool composition have a Tlog1 temperature between 1390 °C and 1490 °C, and a temperature difference (TLog1 - TLog3) between 320 °C and 390 °C. Both compositions therefore meet the dynamic viscosity criteria for being fiberized by external centrifugation.

[0055] According to other particular embodiments of the invention, the glass wool waste available to the operator has 3 (three) distinct chemical compositions which are detailed in table 4 [Tables 4] below, and whose references are compo n°1, compo n°2 and compo n°3: Table 4: Chemical compositions of three glass wools SiO2 Al2O3 CaO MgO Na2O K2O B2O3 P2O5 Composition No. 1 65,3 2,1 8,1 2,4 16,4 0,7 4,5 Composition No. 2 65,5 1,7 7,5 3,0 16,4 0,7 4,9 0,12 Composition No. 3 63,0 2,9 7,4 3,5 15,2 0,7 7,2

[0056] Starting from each of these glass wool compositions, by adding pure oxides and taking into account the limiting oxide combinations, the inventors were able to obtain target compositions which have a maximum mass concentration of glass fibers, while satisfying the viscosity criteria necessary for fiberizing by external centrifugation.

[0057] All of these data are detailed in Table 5 [Tables 5] below: Table 5: Maximum mass concentrations of glass wool in 3 target compositions, dynamic viscosities and corresponding temperatures Glass wool reference Composition No. 1 Composition No. 2 Composition No. 3 Maximum mass concentration of glass wool 57% 57% 61% Target composition (in mass percentage %m) SiO2 48,3 48,3 46,3 Al2O3 3,1 2,8 3,5 CaO 35,2 34,9 34,4 MgO 1,4 1,7 2,1 Na2O 9,1 9,0 8,8 K2O 0,4 0,4 0,4 B2O3 2,6 2,8 4,4 P2O5 0,1 Dynamic Viscosity vs. Temperature TLog 1 1390°C 1390°C 1390°C TLog 3 1000°C 1000°C 1000°C TLog1-TLog3 390°C 390°C 390°C

[0058] Analysis of the results obtained allows us to conclude that each of the three target compositions detailed in Table 5 has a temperature Tlog1 between 1390 °C and 1490 °C, as well as a temperature difference (TLog1 - TLog3) between 320 °C and 390 °C. These three target compositions therefore satisfy the dynamic viscosity criterion to be fiberized by external centrifugation.

Claims

1. A composition of raw materials suitable for being melted and fiberized by external centrifugation in order to obtain a mineral wool, characterized in that it comprises between 1 and 62% by weight of glass wool, characterized in that the glass wool has the following composition, in percentage by weight: SiO2: 50 to 75%, Al2O3: 0 to 8%, CaO+MgO: 5 to 20%, Iron oxide: 0 to 3%, Na2O+K2O: 12 to 20%, B2O3: 0 to 10%.

2. The composition of raw materials according to claim 1, characterized in that it comprises at least 3% by weight of iron oxide, preferably at least 5% by weight of iron oxide.

3. The composition of raw materials according to one of claims 1 and 2, characterized in that it comprises at least 13% by weight of alumina, preferably at least 15% by weight of alumina.

4. The composition of raw materials according to one of claims 1 to 3, characterized in that the glass wool has the following composition, in percentage by weight: SiO2: 50 to 75%, Al2O3: 0.5 to 6.0%, CaO+MgO: 5 to 20%, Iron oxide: 0 to 3%, Na2O+K2O: 12 to 20%, B2O3: 2 to 10%.

5. The composition of raw materials according claim 4, characterized in that the glass wool has the following composition, in percentage by weight: SiO2: 62.5% to 66%, Al2O3: 1.5% to 3.1%, CaO+MgO: 10.3 to 11.1%, Na2O+K2O: 15.7% to 17.3%, B2O3: 4.3% to 7.4%.

6. The composition of raw materials according to one of claims 1 to 3, characterized in that said glass wool has a boron-free composition and represents less than 48% of the total mass of said composition of raw materials.

7. The composition of raw materials according to one of claims 1 to 6, characterized in that it comprises household cullet and / or flat glass cullet.

8. A method comprising a step of melting, in a glass furnace, a composition of raw materials according to one of the claims 1 to 7.

9. A method for manufacturing mineral wool, characterized in that it implements a melting method according to claim 8, and a subsequent step of fiberizing by external centrifugation of the molten composition of raw materials.

10. A mineral wool obtained according to a manufacturing method according to claim 9.