Melting and fiberizing of recycled rock wool

Abstract

The invention relates to a raw material composition adapted for use in a glass furnace, where it is melted and then fiberized by internal centrifugation, comprising recycled rock wool. Also related are the processes for melting and internally centrifugally fiberizing this composition, as well as the mineral wool obtained by these processes. The invention further relates to the use of recycled rock wool as a source of Al₂O₃, CaO, and MgO for the manufacture of mineral wool.

Description

Title of the invention: Melting and fiberizing of recycled rock wool

[0001] The present invention relates to a raw material composition adapted for use in a glass furnace, where it is melted and then fiberized by internal centrifugation, comprising recycled rock wool. Also related are the processes for melting and fiberizing this composition by internal centrifugation, as well as the mineral wool obtained by these processes. The invention also relates to the use of recycled rock wool as a source of Al₂O₃, CaO, and MgO for the manufacture of mineral wool.

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

[0003] Mineral wool is characterized by an entanglement of discontinuous fibers, which distinguishes it from continuous fibers generally intended for reinforcing organic or inorganic materials (e.g., cement). Mineral wool may comprise one or more types of fibers from its production (factory waste), for example, during the cutting and / or disposal of mineral wool batts, or from construction sites (construction site waste or waste from demolition sites) and / or from recycling channels that allow the recovery of such mineral fibers from finished products, whether used or not. Other types of materials may be combined with the mineral fibers, for example, paper, aluminum-based, or bituminous films, or wooden pallet components.

[0004] Such mineral fibers can, in particular, be obtained from raw materials traditionally used in the glass industry or from basaltic rocks. These are then referred to respectively as glass wool and rock wool. These two types of mineral wool differ from each other in their composition, their melting process, and also in the associated fiber-making process.

[0005] For the purposes of the invention, a mineral wool has a chemical composition comprising the following constituents:

[0006] SiO2: 30 to 75% by mass,

[0007] CaO+MgO: 5 to 45% by mass,

[0008] Al2O3: 0 to 30% by mass,

[0009] Na2O+K2O: 0 to 20% by mass,

[0010] Fe2O3: 0 to 20% by mass,

[0011] B2O3: 0 to 14% by mass,

[0012] MnO: 0 to 4% by mass.

[0013] The term rock wool generally refers to mineral wools having fibers whose chemical composition includes the following constituents:

[0014] SiO2: 30 to 50% by mass,

[0015] Al2O3: 10 to 22% by mass,

[0016] CaO+MgO: 20 to 45% by mass,

[0017] Fe2O3: 0 to 20% by mass,

[0018] Na2O+K2O: 0 to 10% by mass,

[0019] B2O3: 0 to 1% by mass.

[0020] By contrast, the term glass wool generally refers to mineral wools with fibers whose chemical composition includes the following constituents: - For so-called low-alumina glass wool:

[0021] SiO2: 50 to 75% by mass,

[0022] Al2O3: 0 to 8% by mass,

[0023] CaO+MgO: 5 to 20% by mass,

[0024] Fe2O3: 0 to 3% by mass,

[0025] Na2O+K2O: 6 to 20% by mass,

[0026] B2O3: 0 to 14% by mass,

[0027] MnO: 0 to 4% by mass; - For glass wools known as high alumina:

[0028] SiO2: 35 to 55% by mass,

[0029] Al2O3: 16 to 27% by mass,

[0030] CaO+MgO: 3 to 30% by mass,

[0031] Fe2O3: 0 to 15% by mass,

[0032] Na2O+K2O: 5 to 17% by mass,

[0033] B2O3: 0 to 5% by mass.

[0034] In this application, compositions are expressed in oxide form by convention. In particular, if the (total) iron oxide content is expressed as Fe2O3, this does not mean that this iron oxide is necessarily and exclusively present in its ferric form. Iron oxide can be present in both its ferric (Fe2O3) and ferrous (FeO) forms, and it is purely by convention that Fe2O3 designates the total iron oxide content.

[0035] Preferably, the sum of the mass concentrations of SiO2, Al2O3, CaO, MgO, Fe2O3, Na2O, K2O and MnO in the composition of raw materials according to the invention and in the wool compositions described in this application is greater than or equal to 90%, or even greater than or equal to 95%.

[0036] It is understood that the mineral wools described above may include other oxides, generally present in trace amounts, such as P2O5 or TiO2.

[0037] Melting rock (basalt or blast furnace slag) generally requires heating the raw materials to significantly higher temperatures than melting so-called glassmaking raw materials. It is traditionally carried out in cupola furnaces, heated with large quantities of coke to temperatures close to 1500°C. Refractory furnaces, conventionally used for melting glassmaking raw materials, cannot withstand the high temperatures required for melting rock.

[0038] Similarly, the fiber-making processes of these mineral wools depend directly on their respective composition, and are therefore not interchangeable.

[0039] Thus, the fiber-making process commonly used to produce rock fiber is the so-called external centrifugal process. In this process, the material to be fibered is poured in a molten state onto the peripheral belt of rotating centrifugal wheels, is accelerated by these wheels, detaches from them, and is partially transformed into fibers under the effect of centrifugal force. A gas stream is emitted tangentially to the peripheral belt of the wheels so as to pick up the fiber-formed material, separating it from the non-fibrous material and conveying it to a receiving organ. For example, see EP195725 for information on external centrifugal fiber production.

[0040] Such a rock wool fiber-making process is distinct from that commonly used for fiber-making glass wool (low-alumina or high-alumina glass type), known as the internal centrifugal fiber-making process. It consists of introducing a filament of the molten, stretchable material into a centrifuge, also called a fiber-making plate, rotating at high speed. Such a fiber-making plate may or may not be equipped with a base and is perforated around 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 (up to 1000°C or even 1200°C for the temperature, and 250 m / s for the speed, depending on the desired product) running along the wall of the centrifuge which thins them and transforms them into fibers.

[0041] There are therefore significant differences between rock wool and glass wool, with regard to their composition, their melting process, the resulting physical properties of the molten material exiting the furnace (temperature, viscosity, etc.), and the associated fiber-laying process. Regarding this last aspect, it should be noted that a rock wool type composition cannot technically be fibered by internal centrifugation, just as a glass wool type composition cannot technically be fibered by external centrifugation.

[0042] In view of these technical differences, and in the context of recycling used fibers, it is therefore natural for a person in the art 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.

[0043] 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 storage locations and / or transport distances or by carrying out sorting upstream of putting into the melt bath.

[0044] 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 adapted to be melted and fiberized by internal centrifugation to obtain mineral wool, in particular glass wool, characterized in that said composition of raw materials comprises from 1% to 50% (for example from 1% to 40%, or even from 10% to 40%) by mass of recycled rock wool.

[0045] According to the invention, a raw material composition is suitable for internal centrifugal fiberization when the temperature (Tlog 3) of the glass bath, for a dynamic viscosity of Log 3 Poise, is below 1400°C, preferably below 1300°C, more preferably below 1250°C, and even better below 1200°C, and when the difference (Tlog 3 - Tliq) between the temperature corresponding to the Log 3 Poise viscosity value and the crystallization temperature of the glass (also called the liquidus temperature) is above 35°C, preferably above 70°C, and more preferably above 100°C. As is known in the field of glass melting, dynamic viscosity is expressed in Log N Poise, which corresponds to 10N Poise (and 1 Poise = 0.1 Pa·s), each viscosity value corresponding to a given temperature of the glass bath.Dynamic viscosity can be measured using a viscometer suitable for glass.

[0046] The invention is based on the concept of introducing recycled rock wool into a raw material composition intended to be melted and then spun into fibers by internal centrifugation, a spun-in process usually reserved for the production of mineral wool, particularly glass wool. The addition of recycled rock wool, which, by its composition, is not initially suitable for spun-in fibers by internal centrifugation, introduces an additional technical difficulty for a person skilled in the art. in charge of melting and fibering. 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 fibering facilities.

[0047] 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 negatively impact the material yield of the glass composition during melting. The use of recycled rock wool as a rich source of Al2O3, CaO, and MgO reduces the use of these raw materials. Furthermore, the lower quantities of CO2 and water emitted during the manufacture of glass wool using recycled rock wool improve the material yield, that is, the ratio between the quantity of raw materials used and the quantity of molten glass obtained after melting the raw material composition.The use of rock wool also reduces the energy required to melt the raw material composition.

[0048] Thus, the present invention also relates to the use of recycled rock wool as a source of both A12O3, CaO and MgO for the manufacture of mineral wool, in particular glass wool.

[0049] According to a particular embodiment, said raw material composition comprises a mass percentage of rock wool from 2% to 38%, for example from 5% to 35%, from 10% to 30%, from 15% to 25%, from 20% to 38%, or from 25% to 38%.

[0050] According to a particular embodiment, said raw material composition comprises a mass percentage of recycled rock wool from 1% to 9%.

[0051] According to another particular embodiment, said raw material composition comprises a mass percentage of recycled rock wool of 10% to 40%.

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

[0053] According to a particular embodiment, the recycled rock wool used in said raw material composition is rock wool that is at least partially bonded. For the purposes of the invention, the term "bonded rock wool" refers to mineral wool made up of mineral fibers bearing on their surface an organic binder that is already cross-linked. Alternatively, the rock wool may be coated with a thin layer of sizing or lubricant.

[0054] According to a particular embodiment, the recycled rock wool used in said raw material composition is at least partially virgin rock wool. For the purposes of the invention, the term "virgin rock wool" refers to rock wool obtained by external centrifugation, the fibers of which are not bonded to one another by means of an organic binder, as opposed to bonded rock wool. Such virgin rock wool is typically used as blown-in insulation for attics, or spray-on insulation for under-slab insulation.

[0055] According to a particular embodiment, the recycled rock wool has the following composition, in mass percentage:

[0056] SiO2: 30 to 50%,

[0057] A12O3: 10 to 22%,

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

[0059] Fe2O3: 0 to 20%,

[0060] Na2O+K2O: 0 to 10%,

[0061] B2O3: 0 to 1%.

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

[0063] SiO2: 40 to 48%,

[0064] A12O3: 15 to 17%,

[0065] CaO+MgO: 24 to 33%,

[0066] Fe2O3: 5 to 12%

[0067] Na2O+K2O: 2 to 4%,

[0068] B2O3: 0 to 1%.

[0069] The detailed description lists three example compositions of recycled rock wool, designated "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 numerous production sites and / or construction / demolition sites.

[0070] According to a particular embodiment, the recycled rock wool has a boron-free composition. Such a composition finds particular application in the insulation industry.

[0071] According to a particular embodiment, said raw material composition 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.

[0072] 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 in 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 in the raw material composition. An increased Fe2O3 content in the raw material composition allows, after fiberization, for an increase in the maximum service temperature of the resulting fiber. In other words, such a fiber exhibits better resistance to higher temperatures.

[0073] 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 Al₂O₃, by mass relative to the mass of solid matter in 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 Al₂O₃, by mass relative to the mass of solid matter in the raw material composition.

[0074] According to a particular embodiment, said raw material composition 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 raw material composition.

[0075] More particularly, the raw material composition may include from 37% to 75% (for example from 37% to 60%, or from 50% to 75%) of SiO2, from 0% to 8% (for example from 0% to 6%) of Al2O3, and from 0% to 3% of Fe2O3, by mass relative to the mass of solids in the raw material composition.

[0076] Alternatively, the raw material composition may comprise from 26% to 55% (for example from 26% to 41% or from 35% to 55%) of SiO2, from 12% to 27% (for example from 16% to 27% or from 12% to 24%) of Al2O3, and from 0% to 15% (for example from 0% to 12%) of Fe2O3, by mass relative to the mass of solids in the raw material composition.

[0077] According to a particular embodiment, the mineral wool (i.e., the target mineral wool) comprises, in mass percentages:

[0078] SiO2: 30 to 75%, for example 39 to 70%,

[0079] A12O3: 0 to 30%, for example 1 to 25%,

[0080] CaO+MgO: 5 to 45%, for example 9 to 22%,

[0081] Fe2O3: 0 to 20%, for example 0 to 10%,

[0082] Na2O+K2O: 0 to 20%, for example 1 to 18%,

[0083] B2O3: 0 to 14%,

[0084] MnO: 0 to 4%.

[0085] More specifically, the mineral wool (i.e., the target mineral wool) may comprise, in mass percentages:

[0086] SiO2: 50 to 75%, for example 60 to 70%,

[0087] A12O3: 0 to 8%, for example 1 to 5%,

[0088] CaO+MgO: 5 to 20%, for example 9 to 14%,

[0089] Fe2O3: 0 to 3%, for example 0 to 1%

[0090] Na2O+K2O: 6 to 20%, for example 12 to 18%

[0091] B2O3: 0 to 14%,

[0092] MnO: 0 to 4%.

[0093] Alternatively, the mineral wool (i.e., target mineral wool) may comprise, in mass percentages:

[0094] SiO2: 35 to 55%, for example 40 to 50%

[0095] A12O3: 16 to 27%, for example 17 to 25%

[0096] CaO+MgO: 3 to 30%, for example 14 to 22%

[0097] Fe2O3: 0 to 15%, for example 1 to 8%

[0098] Na2O+K2O: 5 to 17%, for example 10 to 14%

[0099] B2O3: 0 to 5%, for example 0 to 2%.

[0100] 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 of raw materials so that the latter meets the technical specifications of internal centrifugal fiber production.

[0101] The invention further relates to a process comprising a melting step in a glass furnace of a composition of raw materials as defined in this application.

[0102] In a known manner, such a raw material composition can be melted in a glass furnace with submerged and / or submerged burners, in an electric furnace, and / or in a hybrid furnace employing both at least one burner and electrodes. Upon exiting the furnace, the molten composition can either be immediately fiberized by internal centrifugation or be cooled and transformed into cullet, to be subsequently melted again and fiberized by internal centrifugation to obtain mineral wool.

[0103] The invention further relates to a process for manufacturing mineral wool characterized in that it implements such a melting process and a subsequent step of fiberizing by internal centrifugation of the composition of molten raw materials.

[0104] The invention further relates to a mineral wool obtained according to such a manufacturing process.

[0105] A general method that can be implemented by a furnace operator to develop a composition of raw materials according to the invention is detailed in the rest of the description.

[0106] In a first step, a target composition that meets the viscosity criteria for being fiber-laid by internal centrifugation is selected. According to the invention, such a composition is suitable for being fiber-laid by internal centrifugation if the temperature (Tlog 3) of the glass bath, for a dynamic viscosity of Log 3 Poise, is less than 1400°C, preferably less than 1300°C, more preferably less than 1250°C, even better less than 1200°C, and that the difference (Tlog3 - Tliq) between the temperature corresponding to the Log 3 Poise viscosity value and the crystallization temperature of the glass (also called the liquidus temperature) is greater than 35°C, preferably greater than 70°C, more preferably greater than 100°C.

[0107] In order to assist in the selection of this target composition, a furnace operator uses models relating the chemical composition and the dynamic viscosity of a mixture, such as those commonly used by the glass industries.

[0108] In an industrial context and in a known manner, 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 melting the latter, and compliance with certain concentration ranges of chemical compounds.

[0109] In a second step, the operator prepares his mixture 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.

[0110] These raw materials can 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 wool 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, coal), 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 polyvinyl butyral type polymer sheets 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 metallic compounds" such as functionalized glazing with coatings containing metals.

[0111] 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, meets the viscosity criteria to be fibered by internal centrifugation.

[0112] Once the target composition is obtained, it is placed in a glass furnace to be melted. The molten composition is then fiberized by internal centrifugation to form a mineral wool.

[0113] Examples

[0114] Other features and advantages of the invention will become apparent in the light of the following examples, which are given purely for illustrative purposes and are not intended to limit the scope of the invention, as defined by the attached claims.

[0115] Example 1: Low-alumina glass fiber

[0116] The four target compositions of low alumina glass wool described in Table 1 below are selected by a furnace operator.

[0117] [Tables] Target compositions 1 (%m.) 2 (%m.) 3 (%m.) 4 (%m.) SiO2 65 65 62.3 65.1 A12O3 3.6 2.3 2.5 2.15 CaO 6.4 8.2 9.8 7.5 MgO 4.3 4.3 3.3 2.7 Fe2O3 0.74 0 0.04 0.52 Na2O 14.8 15.4 14.5 16.6 K2O 1.8 0.9 0.5 0.65 B2O3 0 3.9 6.8 4.2 MnO 3.01 0 0 0.27 Tliq exp (°C) 1020 914 947 905 Tlog3 exp (°C) 1183 1095 1053 1065 Tlog3 - Tliq (°C) 163 182 106 147

[0118] %m. : % mass

[0119] For these four target compositions, the liquidus temperature (Tliq) can be approximated from 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, pp. 13–30). The values ​​mentioned in Table 1 above show that the four target compositions are suitable for internal centrifugal fiberization.

[0120] To obtain these target compositions, the operator uses as raw materials, in particular, dolomite, sand, sodium carbonate, borax, raw limestone, felite, potash, manganese, and recycled rock wool. The compositions of three types of rock wool are detailed in Table 2 below.

[0121] [Tables2] Rock wool 1 (%w.) Rock wool 2 (%w.) Rock wool 3 (%w.) SiO2 42.6 46.7 41.8 Al2O3 16.6 15.2 15.4 CaO 19.5 14.6 24.9 MgO 12.3 11.1 7.2 Fe2O3 5.5 7.8 5.5 Na2O 1.6 2.0 1.5 K2O 0.9 1.0 1.3 B2O3 <1 - -

[0122] 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 major oxides (i.e. target greater than 1% by mass) and maximum of 0.8% from the target composition for the minor oxides (i.e. target less than 1% by mass)).

[0123] [Tables3] 1 (%m.) 2 (%m.) 3 (%m.) 4 (%m.) Rock wool 1 20 - 14 - 15 - - - - Rock wool 2 - 15 - 10 - 10 - - - Rock wool 3 - - - - - - 1 2 4 Sand 56.5 54.2 59.2 57.9 56.1 54.5 9.2 9.3 9.3 Sodium carbonate 24.7 24.6 22.9 22.9 19.2 19.1 7.0 7.1 7.3 Borax pentahydrate - - 8 8 14 14 8.3 8.3 8.3 Raw limestone - - 3.4 4.1 8.9 9.7 0.9 0.7 - Felith - 5.8 - 3.9 - 4.9 - - - Dolomite 4.5 6.5 6.4 7.9 3.5 5.3 0.3 - - Potassium 2.3 2 1.1 0.9 0.5 0.3 - - - Manganese 3.8 3.8 - - - - 0.5 0.5 0.5 Feldspar - - - - - - 5.7 5.0 3.5 Internal cullet (glass waste) - - - - - - 5.6 5.6 5.6 Flat glass cullet - - - - - - 61.5 61.5 61.5

[0124] Starting with each of the rock wool compositions 1, 2, and 3, and adding suitable raw materials, the inventors were thus able to obtain target compositions of low-alumina rock wools with a rock fiber mass concentration of 1 to 20% in the vitrifiable mixture, while meeting the criteria necessary for internal centrifugal fiberization. The inventors also demonstrated that the use of rock wool made it possible to reduce or even eliminate the need for certain CO2-emitting raw materials (e.g., limestone and dolomite: 0% for target composition 4 using 4% rock wool) or costly raw materials (e.g., feldspar).

[0125] Example 2: High alumina glass fiber

[0126] The following two target compositions of high alumina glass wool described in Table 4 below are selected by a furnace operator.

[0127] [Tables4] Target composition 5 (%m.) Target composition 6 (%m.) SiO2 48.6 43.0 A12O3 17.8 23.3 CaO 15.5 14.2 MgO 5.2 1.75 Fe2O3 2.2 5.65 Na2O 7.2 6.6 K2O 3.0 4.0 Tliq exp (°C) 1154 1170 Tlog3 exp (°C) 1189 1215 Tlog3 - Tliq (°C) 35 45

[0128] For these two target compositions, the liquidus temperature (Tliq) and the Tlog3 temperature can be determined as shown in Example 1. The values ​​mentioned in Table 4 above show that the two target compositions are suitable for internal centrifugal fiberization.

[0129] To obtain these target compositions, the operator uses as raw materials, in particular, dolomite, bauxite, limestone, potash, sand, sodium carbonate, iron oxide, and recycled rock wool. The compositions of two types of rock wool are detailed in Table 2 above.

[0130] The mass proportions (%m) of each of the raw materials are adjusted, as mentioned in Table 5 below, to obtain the target compositions.

[0131] [Tables5] 5 (%m.) 6 (%m.) Rock wool 1 37 - 13 - Rock wool 2 - 25 - 15 Bauxite 16.5 19.8 30 29.7 Dolomite 2.2 10.3 - - Limestone 13.6 15.5 10.6 21.2 Potash 3.8 3.9 5.5 5.4 Sand 29.5 32.8 31.3 29.9 Sodium carbonate 11.5 11.6 11 10.8 Iron oxide - - 4.5 4.1

[0132] 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 internal centrifugal fibering.

[0133] Example 3: Economic and energy gains

[0134] Table 6 below illustrates the raw material gains (“RM”) achieved by the introduction of recycled rock wool, for one tonne of glass produced (i.e. after melting of the raw material composition, and before fibering) for the raw material composition used to obtain the target composition 4 (see Table 3).

[0135] [Tableauxô] Target composition 4 0%* 1%* 2%* 4%* Total incoming raw materials (kg) / tonne of glass 1077.1 1074.8 1072.7 1071.3 Raw material gain vs 0% recycled rock wool - -0.2% -0.4% -0.5% Raw material gain vs quantity of recycled rock wool - -21.3% -20.6% -13.5%

[0136] *Mass percentage of recycled rock wool 3 in the raw material composition (see table 3)

[0137] The use of 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 fiber) having target composition 4, 1071.3 kg of raw materials are required with 4% rock wool, compared to 1077.1 kg without rock wool.

[0138] 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 the target composition 4 (see Table 3), considering the three main contributors of CO2 emissions (scope 1):

[0139] - dolomite, which has a CO2 emission factor of 0.47 t CO2 / 1 MP,

[0140] - sodium carbonate, which has a CO2 emission factor of 0.41 t CO2 / 1 MP,

[0141] - raw limestone, which has a CO2 emission factor of 0.41 t CO2 / 1 MP.

[0142] [Tables7] Target composition 4 0%* 1%* 2%* 4%* kg CO2 / t molten glass 38.5 36.5 34.5 31.9 Tonne CO2 saving vs 0% - -5% -10% -17% Tonne CO2 saving vs quantity of recycled rock wool - -19% -19% -15%

[0143] *Mass percentage of recycled rock wool 3 in the composition of raw materials (see table 3)

[0144] The use of rock wool in a raw material composition for the manufacture of mineral wool makes it possible to reduce CO2 emissions (scope 1). For example, to form 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, in particular CO2 (scope 1), by 5% to 17%.

Claims

Demands

1. Composition of raw materials suitable for being melted and fibered by internal centrifugation to obtain mineral wool, characterized in that it comprises from 1% to 50% by mass of recycled rock wool, said recycled rock wool having a chemical composition comprising the following constituents, in mass percentage: SiO2: 30 to 50%, Al2O3: 10 to 22%, CaO+MgO: 20 to 45%, Fe2O3: 0 to 20%, Na2O+K2O: 0 to 10%, B2O3: 0 to 1%; and said mineral wool having a chemical composition comprising the following constituents, in mass percentage: a) SiO2: 50 to 75% A12O3: 0 to 8% CaO+MgO: 5 to 20% Fe2O3: 0 to 3%, Na2O+K2O: 6 to 20%, B2O3: 0 to 14%, MnO: 0 to 4%; or b) SiO2: 35 to 55%, A12O3: 16 to 27%, CaO+MgO: 3 to 30%, Fe2O3: 0 to 15%, Na2O+K2O: 5 to 17%, B2O3: 0 to 5%.

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 any one of claims 1 and 2, characterized in that it comprises at least 2%, preferably at least 5% of Al2O3, by mass relative to the mass of solids of the composition of raw materials.

4. 4. Composition of raw materials according to claim 1, characterized in that the recycled rock wool has the following composition, in mass percentage: SiO2: 40 to 48%, Al2O3: 15 to 17%, CaO+MgO: 24 to 33%, Fe2O3: 5 to 12%, Na2O+K2O: 2 to 4%, B2O3: 0 to 1%.

5. 5. Composition of raw materials according to any one of claims 1 to 4, characterized in that it comprises from 1 to 40%, for example from 10 to 40% by mass of recycled rock wool.

6. A process comprising a melting step in a glass furnace of a raw material composition according to any one of claims 1 to

7. J. A process for manufacturing mineral wool characterized in that it implements a melting process according to claim 6, and a subsequent step of fiberizing by internal centrifugation of the molten raw material composition.

8. Use of a recycled rock wool as a source of both A12O3, CaO and MgO for the manufacture of a mineral wool, said recycled rock wool having a chemical composition comprising the following constituents, in mass percentage: SiO2: 30 to 50%, A12O3: 10 to 22%, CaO+MgO: 20 to 45%, Fe2O3: 0 to 20%, Na2O+K2O: 0 to 10%, B2O3: 0 to 1%; and said mineral wool having a chemical composition comprising the following constituents, in mass percentage: a) SiO2: 50 to 75% A12O3: 0 to 8% CaO+MgO: 5 to 20% Fe2O3: 0 to 3%, Na2O+K2O: 6 to 20%, B2O3: 0 to 14%, MnO: 0 to 4%; Or b) SiO2: 35 to 55%, A12O3: 16 to 27%, CaO+MgO: 3 to 30%, Fe2O3: 0 to 15%, Na2O+K2O: 5 to 17%, B2O3: 0 to 5%.