Melting and fiberising recycled rock wool

Abstract

The invention relates to a composition of raw materials suitable for being loaded into a glass furnace, melted and then fiberised via internal centrifugation, which composition of raw materials comprises a rock wool recyclate. The invention also relates to methods for melting this composition and fiberising same via internal centrifugation, and to the mineral wool obtained by means of these methods. The invention also relates to the use of a rock wool recyclate as a source of Al2O3, CaO and MgO for the manufacture of a mineral wool.

Description

[0001] Description

[0002] Title of the invention: Melting and fiberizing recycled rock wool

[0003] The present invention relates to a raw material composition suitable for being placed in a glass furnace, melted, and then fiberized by internal centrifugation, comprising a rock wool recyclate. Also concerned are the processes for melting and fiberizing by internal centrifugation of this composition, as well as the mineral wool obtained by these processes. The invention also relates to the use of a rock wool recyclate as a source of both AI2O3, CaO and MgO for the manufacture of a mineral wool.

[0004] 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.

[0005] Mineral wool is characterized by an interweaving of discontinuous fibers, which distinguishes it from continuous fibers generally intended for the reinforcement of organic or inorganic materials (e.g. cement). Mineral wool may include one or more types of fibers resulting 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 allowing the recovery of such mineral fibers in final products, whether or not they are used. Other types of materials may be associated with mineral fibers, for example paper, aluminum-based or bituminous films, wooden pallet elements.

[0006] Such mineral fibers can be obtained from raw materials traditionally used in the glass industry or from basalt rocks. 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.

[0007] For the purposes of the invention, a mineral wool has a chemical composition comprising the following constituents:

[0008] SiO2: 30 to 75% by mass,

[0009] CaO+MgO: 5 to 45% by mass,

[0010] AI2O3: 0 to 30% by mass,

[0011] Na2O+K2O: 0 to 20% by mass,

[0012] Fe2O3: 0 to 20% by mass,

[0013] B2O3.: 0 to 14% by mass,

[0014] MnO: 0 to 4% by mass.

[0015] The term rock wool generally refers to mineral wools with fibers whose chemical composition includes the following constituents:

[0016] SiO2: 30 to 50% by mass,

[0017] AI2O3: 10 to 22% by mass,

[0018] CaO+MgO: 20 to 45% by mass,

[0019] Fe2O3: 0 to 20% by mass,

[0020] Na2O+K2O: 0 to 10% by mass,

[0021] B2O3: 0 to 1% by mass.

[0022] In contrast, the term glass wool generally refers to mineral wools with fibers whose chemical composition includes the following constituents:

[0023] - For so-called low alumina glass wools:

[0024] SiO2: 50 to 75% by mass,

[0025] AI2O3: 0 to 8% by mass,

[0026] CaO+MgO: 5 to 20% by mass,

[0027] Fe2O3: 0 to 3% by mass, Na2O+K2O: 6 to 20% by mass,

[0028] B2O3: 0 to 14% by mass,

[0029] MnO: 0 to 4% by mass;

[0030] - For so-called high alumina glass wools:

[0031] SiO2: 35 to 55% by mass,

[0032] AI2O3: 16 to 27% by mass,

[0033] CaO+MgO: 3 to 30% by mass,

[0034] Fe2O3: 0 to 15% by mass,

[0035] Na2O+K2O: 5 to 17% by mass,

[0036] B2O3: 0 to 5% by mass.

[0037] In the present application, the compositions are expressed in oxide form by convention. In particular, if the (total) iron oxide content is expressed in the form Fe2O3, this does not mean that this iron oxide is necessarily and exclusively present in the ferric form. Iron oxide can be present in both its ferric (Fe2O3) and ferrous (FeO) forms, and it is purely by convention that the total iron oxide content is designated by Fe2O3.

[0038] Preferably, the sum of the mass concentrations of SiO2, AI2O3, CaO, MgO, Fe2O3, Na2O, K2O and MnO in the composition of raw materials according to the invention and in the wool compositions described in the present application is greater than or equal to 90%, or even greater than or equal to 95%.

[0039] It is understood that the mineral wools described above may include other oxides, generally present in trace amounts, such as P2O5 or TiO2.

[0040] Rock melting (basalt or blast furnace slag) generally requires heating the raw materials to significantly higher temperatures than the melting of so-called glass raw materials. It is traditionally carried out in cupola furnaces, heated with large quantities of coke to temperatures around 1500°C. Refractory furnaces, traditionally used for melting glass raw materials, cannot withstand the high temperatures required for melting rock. Similarly, the fiberizing processes for these mineral wools depend directly on their respective compositions and are therefore not interchangeable.

[0041] 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 centrifugation 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 patent application EP195725.

[0042] Such a rock wool fiberization process should be distinguished from that commonly used to fiberize glass wool (low alumina glass or high alumina glass type), known as the internal centrifugal fiberization process. 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 burner, these filaments are then subjected to the action of an annular gaseous drawing current at high temperature and speed (which can reach 1000°C or even 1200°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.

[0043] 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 rock wool type composition cannot technically be fiberized by internal centrifugation, just as a glass wool type composition cannot technically be fiberized by external centrifugation.

[0044] 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.

[0045] The strict separation existing 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 or by carrying out sorting before placing in the molten bath.

[0046] 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 raw material composition suitable for being melted and fiberized by internal centrifugation to obtain a mineral wool, in particular glass wool, characterized in that said raw material composition comprises from 1% to 50% (for example from 1% to 40%, or even from 10% to 40%) by mass of rock wool recyclate.

[0047] For the purposes of the invention, a raw material composition is suitable for being fiberized by internal centrifugation when the temperature (Tlog 3) of the glass bath, for a dynamic viscosity of Log 3 Poises, is less than 1400°C, preferably less than 1300°C, more preferably less than 1250°C, better still less than 1200°C, or even less than 1100°C and the difference (Tlog3 - Tliq) between the temperature corresponding to the viscosity value Log 3 Poises and the crystallization temperature of the glass (also called liquidus temperature) is greater than 35°C, preferably greater than 70°C, more preferably greater than 100°C, better still greater than 110°C, or even greater than 120°C, for example greater than 130°C. As is known in the field of glass melting, dynamic viscosity is expressed in Log N Poises, which corresponds to 10 NPoises (and 1 Poise = 0.1 Pa.s), each viscosity value corresponding to a given temperature of the glass bath. The dynamic viscosity can be measured using a viscometer suitable for glass. The invention is based on the concept of introducing a rock wool recyclate into a raw material composition intended to be melted and then fiberized by internal centrifugation, a fiberizing process usually reserved for the production of mineral wool, in particular glass wool. The addition of rock wool recyclates which, due to their composition, are not initially suitable for fiberizing by internal 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 allows an operator to gain flexibility in the choice of raw materials to use, and thus to seize opportunities that may be temporarily offered by recycling channels organized near the melting and fiberizing facilities.

[0048] The solution proposed by this invention also has the advantage of being both economical and ecological. Indeed, glass wool is usually manufactured from natural raw materials, such as feldspar, dolomite and lime, which are expensive and / or emit CO2 and / or penalize the melting material yield of the glass composition. The use of rock wool recyclate as a rich source of AI2O3, CaO and MgO makes it possible to reduce the use of these raw materials. The lower quantities of CO2 and water emitted during the manufacture of glass wool using recycled rock wool also make it possible to improve the material yield, i.e. the ratio between the quantity of raw materials introduced and the quantity of molten glass obtained at the end of the melting of the raw material composition.The use of rock wool also helps to reduce the energy required to melt the raw material composition.

[0049] Thus, the present invention also relates to a use of a rock wool recyclate as a source of both AI2O3, CaO and MgO for the manufacture of mineral wool, in particular glass wool.

[0050] According to a particular embodiment, said composition of raw materials comprises a mass percentage of rock wool of 2% to 38%, for example of 5% to 35%, of 10% to 30%, of 15% to 25%, of 20% to 38%, or of 25% to 38%.

[0051] According to a particular embodiment, said composition of raw materials comprises a mass percentage of rock wool recyclate of 1% to 9%. According to another particular embodiment, said composition of raw materials comprises a mass percentage of rock wool recyclate of 10% to 40%.

[0052] Rock wool recyclate includes rock wool, but also derived forms such as rock wool crushed or heated to form rock glass agglomerates.

[0053] According to a particular embodiment, the rock wool recyclate used in said raw material composition is at least partly bound rock wool. For the purposes of the invention, the expression "bound rock wool" here refers to mineral wool consisting of mineral fibers carrying on their surface an organic binder, already crosslinked. Alternatively, the rock wool may be coated with a thin layer of size or lubricant.

[0054] According to a particular embodiment, the rock wool recyclate used in said raw material composition is at least partly virgin rock wool. For the purposes of the invention, the expression "virgin rock wool" designates rock wool obtained by external centrifugation, the fibers of which are not bound to each other by means of an organic binder, as opposed to bound rock wool. Such virgin rock wool is typically used as blown-in wool for attic insulation, or sprayed-in wool for under-slab insulation.

[0055] According to a particular embodiment, the rock wool recyclate has a chemical composition comprising the following constituents, in mass percentage:

[0056] SiO2: 30 to 50%,

[0057] AI2O3: 10 to 22%,

[0058] CaO+MgO: 20 to 45%,

[0059] Fe2O3: 0 to 20%, for example 3 to 20%,

[0060] Na2O+K2O: 0 to 10%, for example 0 to 8%, and

[0061] B2O3: O at 1%.

[0062] According to a more particular embodiment, the rock wool recyclate has a chemical composition comprising the following constituents, in mass percentage:

[0063] SiO2: 40 to 48%, AI2O3: 14 to 19% (for example 15 to 17%),

[0064] CaO+MgO: 24 to 33%,

[0065] Fe2O3: 3 to 20%,

[0066] Na2O+K2O: 0 to 8% (e.g. 2 to 8%), and

[0067] B2O3: O at 1%.

[0068] For example, rock wool recyclate may have a chemical composition comprising the following constituents, in mass percentage:

[0069] SiO2: 30 to 50%,

[0070] AI2O3: 10 to 22%,

[0071] CaO+MgO: 20 to 45%,

[0072] Fe2O3: 3 to 20%,

[0073] Na2O+K2O: 0 to 5%, or even 0 to 4%, and

[0074] B2O3: O at 1%.

[0075] According to an even more particular embodiment, the rock wool recyclate has a chemical composition comprising the following constituents, in mass percentage:

[0076] SiO2: 40 to 48%,

[0077] AI2O3: 14 to 19%, for example 15 to 17%,

[0078] CaO+MgO: 24 to 33%,

[0079] Fe2O3: 5 to 12%,

[0080] Na2O+K2O: 2 to 4%, and

[0081] B2O3: O at 1%.

[0082] The detailed description describes three exemplary compositions of rock wool recyclates, under the names “rock wool 1”, “rock wool 2”, and “rock wool 3” (compositions described in the examples below) which fall within these composition ranges and are commonly used in the insulation industry. Such waste can therefore be collected from many production sites and / or construction / deconstruction sites. According to a particular embodiment, the rock wool recyclate has a boron-free composition. Such a composition finds particular application in the insulation industry.

[0083] According to a particular embodiment, said composition of raw materials comprises household cullet and / or flat glass cullet. The addition of household cullet and / or flat glass allows for greater flexibility in the choice of raw materials to be used.

[0084] According to a particular embodiment, said raw material composition comprises from 0% to 20%, for example from 0% to 15% or even from 0% to 10% of Fe2O3, by mass relative to the mass of solid matter of the raw material composition. According to a particular embodiment, said raw material composition comprises at least 2%, preferably at least 5% of Fe2O3, by mass relative to the mass of solid matter of the raw material composition. An increased Fe2O3 content of the raw material composition makes it possible, after fiberizing, to increase the maximum service temperature of the fiber obtained. In other words, such a fiber has better resistance to higher temperatures.

[0085] According to a particular embodiment, said raw material composition comprises from 0% to 25%, for example from 0% to 15% or even from 0% to 10% of AI2O3, by mass relative to the mass of solid matter of the raw material composition. According to a particular embodiment, said raw material composition comprises at least 2%, more preferably at least 5%, more preferably at least 10%, more preferably at least 20% of AI2O3, by mass relative to the mass of solid matter of the raw material composition.

[0086] According to a particular embodiment, said composition of raw materials comprises from 20% to 75%, for example from 30% to 75% or from 20% to 60% of SiO2, by mass relative to the mass of solid materials of the composition of raw materials.

[0087] More particularly, the raw material composition may comprise from 37% to 75% (e.g., from 37% to 60%, or from 50% to 75%) of SiO2, from 0% to 8% (e.g., from 0% to 6%) of AI2O3, and from 0% to 3% of Fe2O3, by mass relative to the mass of solids of the raw material composition.

[0088] Alternatively, the raw material composition may comprise from 26% to 55% (e.g., from 26% to 41% or from 35 to 55%) of SiO2, from 12% to 27% (e.g., from 16% to 27% or from 12% to 24%) of AI2O3, and from 0% to 15% (e.g., from 0% to 12%) of Fe2O3, by mass relative to the mass of solids of the raw material composition.

[0089] According to a particular embodiment, the mineral wool (i.e. target mineral wool) has a chemical composition which comprises the following constituents, in mass percentages:

[0090] SiO2: 30 to 75%,

[0091] AI2O3: 0 to 30%,

[0092] CaO+MgO: 3 to 45%,

[0093] Fe2O3: 0 to 20%,

[0094] Na2O+K2O: 4 to 20%,

[0095] B2O3: 0 to 14%, and

[0096] MnO: 0 to 4%.

[0097] According to a particular embodiment, the mineral wool (i.e. target mineral wool) has a chemical composition which comprises the following constituents, in mass percentages:

[0098] SiO2: 30 to 75%, for example 39 to 70%,

[0099] AI2O3: 0 to 30%, for example 1 to 25%,

[0100] CaO+MgO: 5 to 45%, for example 9 to 22%,

[0101] Fe2O3: 0 to 20%, for example 0 to 10%,

[0102] Na2O+K2O: 0 to 20%, for example 1 to 18%,

[0103] B2O3: 0 to 14%, and

[0104] MnO: 0 to 4%.

[0105] According to a particular embodiment, the mineral wool (i.e. target mineral wool) has a chemical composition which comprises the following constituents, in mass percentages: SiO2: 30 to 75%, for example 39 to 70%,

[0106] AI2O3: 0 to 30%, for example 1 to 25%,

[0107] CaO+MgO: 5 to 45%, for example 5 to 18%,

[0108] Fe2O3: 0 to 20%, for example 0 to 10%,

[0109] Na2O+K2O: 4 to 20%, for example 5 to 18%, or even 9 to 18%,

[0110] B2O3: 0 to 14%, and

[0111] MnO: 0 to 4%.

[0112] According to a particular embodiment, the mineral wool (i.e. target mineral wool) has a chemical composition which comprises the following constituents, in mass percentages:

[0113] SiO2: 35 to 75%,

[0114] AI2O3: 0 to 27%,

[0115] CaO+MgO: 5 to 45%, for example 5 to 18%,

[0116] Fe2O3: O at 15%,

[0117] Na2O+K2O: 4 to 20%, or even 9 to 18%,

[0118] B2O3: 0 to 14%, and

[0119] MnO: 0 to 4%.

[0120] For example, mineral wool (i.e. target mineral wool) may have a chemical composition that includes the following constituents, in mass percentages:

[0121] SiO2: 30 to 75%, for example 39 to 70%,

[0122] AI2O3: 0 to 30%, for example 1 to 25%,

[0123] CaO+MgO: 5 to 18%,

[0124] Fe2O3: 0 to 20%, for example 0 to 10%,

[0125] Na2O+K2O: 4 to 20%,

[0126] B2O3: 0 to 14%, and

[0127] MnO: 0 to 4%.

[0128] More particularly, the mineral wool (i.e. target mineral wool) may have a chemical composition which comprises the following constituents, in mass percentages: SiO2: 50 to 75%, for example 60 to 70%,

[0129] AI2O3: 0 to 8%, for example 1 to 5%,

[0130] CaO+MgO: 5 to 20%, for example 9 to 14%,

[0131] Fe2O3: 0 to 3%, for example 0 to 1%,

[0132] Na2O+K2O: 6 to 20%, for example 12 to 18%,

[0133] B2O3: O at 14%, and

[0134] MnO: 0 to 4%.

[0135] Alternatively, the mineral wool (i.e. target mineral wool) may have a chemical composition that includes the following constituents, in mass percentages:

[0136] SiO2: 35 to 55% (e.g. 40 to 50%),

[0137] AI2O3: 16 to 27% (for example 17 to 25%),

[0138] CaO+MgO: 3 to 30% (for example 3 to 18%, or even 14 to 22%),

[0139] Fe2O3: 0 to 15% (e.g. 1 to 8%),

[0140] Na2O+K2O: 5 to 17% (for example 7 to 17%, or even 9 to 17% or even 10 to 14%), and

[0141] B2O3: 0 to 5% (e.g. 0 to 2%), preferably: SiO2: 35 to 55%, AI2O3: 16 to 27%, CaO+MgO: 3 to 30% (e.g. 3 to 18%), Fe2O3: 0 to 15%, Na2O+K2O: 7 to 17%, and B2O3: 0 to 5%; more preferably: SiO2: 35 to 55%, AI2O3: 16 to 27%, CaO+MgO: 3 to 30% (e.g. 3 to 18%), Fe2O3: 0 to 15%, Na2O+K2O: 9 to 17%, and B2O3: 0 to 5%.

[0142] It should be noted that a person skilled in the art has the general knowledge to, on the basis of routine tests, adapt the remainder of the raw material composition so that the latter meets the technical specifications for internal centrifugal fiberizing. The invention further relates to a method comprising a step of melting in a glass furnace a raw material composition as defined in the present application.

[0143] 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 internal centrifugation, or be cooled and transformed into cullet, to be later (subsequently) melted again and fiberized by internal centrifugation to obtain mineral wool.

[0144] 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 internal centrifugation of the melted raw material composition.

[0145] The invention further relates to a mineral wool obtained according to such a manufacturing method.

[0146] A general method that can be implemented by a furnace operator to produce a composition of raw materials according to the invention is detailed in the remainder of the description.

[0147] In a first step, a target composition that meets the viscosity criteria for being fiberized by internal centrifugation is selected. For the purposes of the invention, such a composition is suitable for being fiberized by internal centrifugation if the temperature (Tlog 3) of the glass bath, for a dynamic viscosity of Log 3 Poises, is less than 1400°C, preferably less than 1300°C, more preferably less than 1250°C, better still less than 1200°C, and the difference (Tlog3 - Tliq) between the temperature corresponding to the Log 3 Poises viscosity value and the crystallization temperature of the glass (also called liquidus temperature) is greater than 35°C, preferably greater than 70°C, more preferably greater than 100°C.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.

[0148] 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.

[0149] 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.

[0150] These raw materials may alternatively or in combination be in the form of pure oxides, salts (such as sodium carbonate, potash, or borax), natural raw materials (silicic sands, dolomite, limestone, waste rock, slag, bauxite, feldspar, anorthosite, felith, etc.) which are already combinations of oxides, glass wool and / or rock waste, which may 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 glass cullet.Also included are recyclable materials containing combustible (organic) elements such as, for example, mineral fibers (of the type used in reinforcement), 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.

[0151] 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 internal centrifugation.

[0152] Once the target composition is obtained, it is placed in a glass furnace to be melted. The melted composition is then fiberized by internal centrifugation to form mineral wool.

[0153] Examples

[0154] Other features and advantages of the invention will become apparent in light of the following examples, which are given purely for illustrative purposes and are not intended to limit the scope of the invention, defined by the appended claims.

[0155] Example 1: Low alumina glass fiberization

[0156] The four target low alumina glass wool compositions described in Table 1 below are selected by a furnace operator. [Table 1]

[0157] %m. : % mass For these four target compositions, the liquidus temperature (Tliq) can be approximated from the experimental measurements available in the literature and the temperature Tlog3 can be calculated from the Fluegel model (A. Fluegel, “Glass Viscosity Calculation Based on a Global Statistical Modeling Approach”, Glass Technol.: Europ. J. Glass Sci. Technol. A, vol. 48, 2007, no. 1, p 13-30.). The values ​​mentioned in Table 1 above show that the four target compositions are suitable for internal spin drawing.

[0158] In order to obtain these target compositions, the operator uses as raw materials dolomite, sand, sodium carbonate, borax, raw limestone, felith, potash, manganese, and rock wool recyclate. The compositions of three rock wools are detailed in Table 2 below.

[0159] [Table 2]

[0160] The mass proportions (%m) of each of the raw materials are adjusted, as mentioned in Table 3 below, to obtain the target compositions (maximum of 0.2% deviation from the target composition for the majority oxides (i.e. target greater than 1% by mass) and maximum of 0.8% from the target composition for the minority oxides (i.e. target less than 1% by mass)). [Table 3]

[0161] Starting from each of the rock wool compositions 1, 2 and 3, by adding suitable raw materials, the inventors were thus able to obtain target compositions of low-alumina wools which have a mass concentration of rock fibers of 1 to 20% in the vitrifiable mixture, while satisfying the criteria necessary for fiberization by internal centrifugation. The inventors also demonstrated that the use of rock wool made it possible to reduce or even eliminate certain raw materials that emit CO2 (e.g. limestone and dolomite: 0% for target composition 4 using 4% rock wool) or are expensive (e.g. feldspar). Example 2: Fiberization of high-alumina glass

[0162] The following two target high alumina glass wool compositions described in Table 4 below are selected by a furnace operator. [Table 4]

[0163] For these two target compositions, the liquidus temperature (Tliq) and the temperature Tlog3 can be determined as shown in Example 1. The values ​​mentioned in Table 4 above show that both target compositions are suitable for internal spin fiberizing.

[0164] In order to obtain these target compositions, the operator has as raw materials in particular dolomite, bauxite, limestone, potash, sand, sodium carbonate, iron oxide, and rock wool recyclate. The compositions of two rock wools are detailed in Table 2 above. The mass proportions (%m) of each of the raw materials are adjusted, as mentioned in Table 5 below, to obtain the target compositions.

[0165] [Table 5]

[0166] Starting from each of the rock wool compositions 1 and 2, by adding suitable raw materials, the inventors were thus able to obtain target compositions which have a mass concentration of rock fibers of 13 to 37%, while satisfying the criteria necessary for fiberization by internal centrifugation.

[0167] Example 3: Economic and energy gains

[0168] Table 6 below illustrates the raw material (“PM”) savings achieved by the introduction of rock wool recyclate, for one tonne of glass produced (i.e. after melting of the raw material composition, and before fiberizing) for the raw material composition used to obtain target composition 4 (see table 3).

[0169] [Table 6]

[0170] 'Percentage by mass of rock wool recyclate 3 in the composition of raw materials (see table 3)

[0171] Using rock wool in a raw material composition for the manufacture of mineral wool improves material yield. For example, to form one tonne of molten glass (which leads to mineral wool after fiberization) with the target composition 4, 1071.3 kg of raw material are required with 4% rock wool, compared to 1077.1 kg without rock wool.

[0172] Table 7 below illustrates the gains in terms of CO2 emissions (scope 1) per tonne of glass produced, for the composition of raw materials used to obtain target composition 4 (see table 3), considering the three main contributors of CO2 emissions (scope 1):

[0173] - dolomite, which has a CO2 emission factor of 0.47 t CO2 / 1 MP,

[0174] - sodium carbonate, which has a CO2 emission factor of 0.41 t CO2 / 1 MP,

[0175] - raw limestone, which has a CO2 emission factor of 0.41 t CO2 / 1 MP.

[0176] [Table 7]

[0177] 'Percentage by mass of rock wool recyclate 3 in the composition of raw materials (see table 3) The use of rock wool in a composition of raw materials for the manufacture of mineral wool makes it possible to reduce CO2 emissions (scope 1). For example, to form a molten glass (which leads to mineral wool after fiberization) having the target composition 4, the introduction of 1% to 4% of rock wool makes it possible to reduce CO2 emissions by 5% to 17%, particularly CO2 (scope 1).

Claims

Claims 1. Composition of raw materials suitable for being melted and fiberized by internal centrifugation to obtain mineral wool, characterized in that it comprises from 1% to 50% by mass of rock wool recyclate.

2. Composition of raw materials according to claim 1, characterized in that it comprises at least 2%, preferably at least 5% of Fe2O3, by mass relative to the mass of solid materials of the composition of raw materials.

3. Composition of raw materials according to one of claims 1 and 2, characterized in that it comprises at least 2%, preferably at least 5% of AI2O3, by mass relative to the mass of solid materials of the composition of raw materials.

4. Composition of raw materials according to one of claims 1 to 3, characterized in that the rock wool recyclate has a chemical composition which comprises the following constituents, in mass percentage: SiO2: 30 to 50%, AI2O3: 10 to 22%, CaO+MgO: 20 to 45%, Fe2O3: 0 to 20%, for example 3 to 20%, Na2O+K2O: 0 to 8%, B2O3: O at 1%.

5. Composition of raw materials according to one of claims 1 to 4, characterized in that the rock wool recyclate has a chemical composition which comprises the following constituents, in mass percentage: SiO2: 30 to 50%, AI2O3: 10 to 22%, CaO+MgO: 20 to 45%, Fe2O3: 3 to 20%, Na2O+K2O: 0 to 8%, or even 0 to 5%, B2O3: O at 1%.

6. Composition of raw materials according to claim 4 or 5, characterized in that the rock wool recyclate has a chemical composition which comprises the following constituents, in mass percentage: SiO2: 40 to 48%, AI2O3: 14 to 19%, CaO+MgO: 24 to 33%, Fe2O3: 5 to 12%, Na2O+K2O: 2 to 4%, B2O3: O at 1%.

7. Composition of raw materials according to one of claims 1 to 6, characterized in that it comprises from 1 to 40%, for example from 10 to 40% by mass of rock wool recyclate.

8. Composition of raw materials according to one of claims 1 to 7, characterized in that said mineral wool has a chemical composition which comprises the following constituents, in mass percentages: SiO2: 30 to 75%, for example 39 to 70%, AI2O3: 0 to 30%, for example 1 to 25%, CaO+MgO: 5 to 45%, for example 5 to 18%, Fe2O3: 0 to 20%, for example 0 to 10%, Na2O+K2O: 4 to 20%, for example 9 to 18%, B2O3: O at 14%, MnO: 0 to 4%.

9. Composition of raw materials according to one of claims 1 to 7, characterized in that said mineral wool has a chemical composition which comprises the following constituents, in mass percentages: SiO2: 30 to 75%, AI2O3: 0 to 30%, CaO+MgO: 5 to 18%, Fe2O3: 0 to 20%, Na2O+K2O: 4 to 20%, B2O3: 0 to 14%, MnO: 0 to 4%.

10. Composition of raw materials according to any one of claims 1 to 9, characterized in that said mineral wool has a chemical composition which comprises the following constituents, in mass percentages: a) SiO2: 50 to 75%, for example 60 to 70%, AI2O3: 0 to 8%, for example 1 to 5%, CaO+MgO: 5 to 20%, for example 9 to 14%, Fe2O3: 0 to 3%, for example 0 to 1%, Na2O+K2O: 6 to 20%, for example 12 to 18%, B2O3: O at 14%, MnO: 0 to 4%; or b) SiO2: 35 to 55%, for example 40 to 50%, AI2O3: 16 to 27%, for example 17 to 25%, CaO+MgO: 3 to 30%, for example 3 to 18%, Fe2O3: 0 to 15%, for example 1 to 8%, Na2O+K2O: 5 to 17%, for example 7 to 17%, or even 9 to 17%, B2O3: 0 to 5%, for example 0 to 2%.

11. Composition of raw materials according to any one of the claims 1 to 10, characterized in that said mineral wool has a chemical composition which comprises the following constituents, in mass percentages: SiO2: 35 to 55%, AI2O3: 16 to 27%, CaO+MgO: 3 to 18%, Fe2O3: O at 15%, Na2O+K2O: 9 to 17%, B2O3: 0 to 5%.

12. Method comprising a step of melting in a glass furnace a composition of raw materials according to one of claims 1 to 11.

13. Process for manufacturing mineral wool characterized in that it implements a melting process according to claim 12, and a subsequent step of fiberizing by internal centrifugation of the melted raw material composition.

14. Mineral wool obtained according to a manufacturing process according to claim 13.

15. Use of rock wool recyclate as a source of both AI2O3, CaO and MgO for the manufacture of mineral wool.

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