EP4073006A1

EP4073006A1 - Method for producing mineral wool

Info

Publication number: EP4073006A1
Application number: EP20842279.0A
Authority: EP
Inventors: Andrea GIOIA
Original assignee: Saint Gobain Isover SA France
Current assignee: Saint Gobain Isover SA France
Priority date: 2019-12-11
Filing date: 2020-12-09
Publication date: 2022-10-19
Also published as: US20230057024A1; BR112022010502A2; WO2021116609A1; FR3104568A1; JP2023506446A; FR3104568B1

Abstract

The present invention relates to a method for producing mineral wool having a chemical composition, expressed as a percentage by weight of oxides, comprising: SiO2 30-50%, Al2O3 15-35%, CaO 5-25%, MgO 1-25%, Fe2O3 2-15%, and Na2O+K2O >10%, the method comprising the steps of: - providing a mixture of raw materials; - melting the mixture of raw materials to produce a melt; and - fiberising the molten material; characterised in that the raw material mixture comprises at least 8.5% by weight of a recycled raw material comprising at least 3% of magnesium, expressed by weight of oxides, the recycled raw material being essentially free of carbonates, and in that the mixture of raw materials is free of dolomite and magnesia.

Description

DESCRIPTION

TITLE: MINERAL WOOL MANUFACTURING PROCESS

The present invention relates to the field of artificial mineral fibers. It relates more particularly to a process for manufacturing mineral wool, intended in particular for the manufacture of thermal and / or acoustic insulation products.

Mineral wools are traditionally obtained by melting a mixture of raw materials in a melting furnace, the molten material thus obtained then being discharged into a stringing device by which the mineral wool is formed. The raw materials, generally natural, are selected, and their proportions adapted, according to the target chemical composition desired for the mineral wool. Magnesium oxide can be used in the composition of mineral wools in order to give them certain properties or to improve their processability. Dolomite and magnesia are the main carriers of magnesium used in the manufacture of mineral wools. However, these raw materials have certain disadvantages. They can indeed cause explosive fracturing or “decrepitation” phenomena during the melting of the mixture of raw materials. This causes a layer of debris and decrepit dust to form on the roof of the furnace, which can be detrimental to both the operation of the furnace and the quality of the molten bath. Moreover, because of their chemical compositions, these raw materials contribute significantly to the release of CO2 during the melting of the mixture of raw materials.

The objective of the present invention is to obviate the aforementioned drawbacks by proposing an economical process for manufacturing mineral wool comprising magnesium oxide while ensuring good processability, maintaining, or even improving, the quality. quality of the molten bath and properties of mineral wool, especially from the point of view of resistance to high temperatures, and reducing the environmental impact.

Thus, a first aspect of the present invention relates to a process for manufacturing mineral wool having a chemical composition, expressed as a weight percentage of oxides, comprising:

Si02 30-50%

A1203 15-35%

CaO 5-25%

MgO 1-25% Fe203 2-15%

Na20 + K20> 10% said method comprising: providing a mixture of raw materials; melting said mixture of raw materials to obtain a molten material; - the stringing of the molten material; characterized in that the raw material mixture comprises at least 8.5% by weight of a recycle raw material comprising at least 3.5% of magnesium, expressed by weight of oxides, said recycle raw material being essentially free carbonates, and in that the mixture of raw materials is free from dolomite and magnesia. The process according to the invention relates to the manufacture of mineral wool, the chemical composition of which results in a high liquidus temperature and high fluidity at the stringing temperature, associated with a high glass transition temperature.

The silica (S1O2) content is within a range ranging from 30 to 50%, preferably 35 to 48%, or even 37 to 45%. The alumina (Al2O3) content is within a range ranging from 15 to 35%, preferably from 18 to 30%, or even 20% to 28%.

The lime (CaO) content is within a range ranging from 5 to 25%, preferably from 7 to 20%, or even 8% to 18%. The magnesia (MgO) content is within a range ranging from 1 to 25%, preferably from 1 to 15%, or even 1 to 10%.

Mineral wool generally does not include alkaline earth oxides other than CaO and MgO. It may nevertheless contain small amounts of BaO or SrO, at contents which may range up to 2%, or even 1%, 0.20%, or even 0.1%, these oxides possibly being present as impurities in certain raw materials.

The total content of alkali metal oxides (R2O), in particular sodium hydroxide (Na2O) and potassium hydroxide (K2O), is greater than 10%, preferably from 10.2 to 20%, or even from 10.5 to 15%. The Na2O content typically ranges from 4 to 20%, preferably 5 to 15%, or even 6 to 13%. The K2O content is for its part typically at most 20%, preferably 1 to 15%, or even 2 to 10. The mineral wool preferably does not contain any other alkali oxide than Na2O and K2O. However, it may contain small amounts of LEO, sometimes present as impurities in certain raw materials, at levels of up to 0.5%, or even 0.2%, or even 0.1%.

The iron oxide content (total iron expressed in the form of F2O3) is within a range ranging from 2 to 15%, preferably 2 to 12%, or even 2.5 to 10%. The sum of the contents of S1O2, Al2O3, CaO, MgO, R2O and Fe2C> 3 preferably represents at least 95%, in particular at least 97%, or even at least 98% by weight of the mineral wool composition.

The chemical composition of mineral wool may also contain P2O5, in particular at levels of up to 3%, or even up to 1.2%. However, it is preferably free from P2O5.

The composition of mineral wool can also include other elements present in particular as unavoidable impurities. It may include titanium (TiCh) and zirconia (ZrCh) oxide in contents within a range of up to 3%, in particular from 0.1 to 2.0%, or even 1.0%.

The chemical composition of mineral wool typically comprises less than 0.1% by weight of halogen, especially fluorine.

It goes without saying that the various preferred ranges described above can be freely combined with one another, the various combinations not all being able to be listed for the sake of brevity.

Due to its composition, mineral wool may have the advantage of being both biosoluble, namely having the capacity to dissolve rapidly in a physiological medium, in order to prevent any potential pathogenic risk linked to the possible accumulation of the finest fibers in the body by inhalation, and have good resistance to very high temperatures. The fire resistance of a construction element corresponds to the time during which the element retains its load-bearing function, guarantees flame-tightness and retains its role of thermal insulator. The standard fire test generally consists of a rise in temperature according to ISO 834, based on the temperature curve of a cellulosic fire.

Conventionally, the composition of mineral wool as described above is obtained by preparing and melting a mixture of raw materials. The method according to the invention comprises a step of supplying a mixture of raw materials comprising at least 8.5% by weight of a raw recycling material comprising at least 3.5%, preferably at least 4%, or even at least 5% of magnesium, expressed by weight of oxides. The use of such a raw material makes it possible to dispense with dolomite and magnesia and allows a better quality of fusion. The other raw materials can be chosen from the raw materials conventionally used in the manufacture of mineral wools such as limestone, phonolite, nepheline syenite, feldspar, basalt, sodium carbonate, iron oxides. Their respective proportions in the mixture of raw materials are determined by a person skilled in the art according to their chemical compositions and the target chemical composition of the mineral wool to be obtained. In particular, the mixture of raw materials preferably comprises at least 1%, more preferably at least 2%, or even at least 3%, by weight of bauxite as an alumina carrier.

The raw material for recycling can be a by-product resulting from the treatment of aluminum slag (also called sait slag, black dross, white dross or sait cake) originating from the manufacture and / or recycling of aluminum metal. In the manufacture of aluminum, the primary slag that forms on the surface of the tanks contains a high percentage of metallic aluminum. These slags are therefore generally treated, for example in rotary kilns, to recover the aluminum they contain. In particular, in certain technologies, treatment salts can be added during this second transformation. Secondary processing slag, which contains small proportions of aluminum metallic, can in turn be treated to extract the residual metallic aluminum and to recycle the treatment salts. Certain by-products of this treatment, consisting mainly of mixtures of oxides and essentially free of metallic residue, can be used as raw material for recycling in the process according to the invention. These by-products can in turn be subjected to certain treatments (granulation, drying, calcination, etc.) before their use in the process according to the invention. Besides the fact of reducing the amount of residual water and other volatile elements such as halogens and ammonia, calcination, for example in a rotary tube furnace, makes it possible to improve the particle size distribution. However, the raw material for recycling is not limited to these examples.

The recycling raw material typically has a chemical composition, expressed in weight of oxides, comprising:

A1203 50 to 80%, preferably 60 to 75%;

SiO2 2 to 25%, preferably 5 to 50%;

MgO 3 to 20%, preferably 5 to 15%;

Le203 0.5 to 10%, preferably 1 to 8%.

It typically comprises less than 0.9%, preferably less than 0.6%, by weight of halogen, in particular fluorine and chlorine. The presence of halogens indeed requires expensive flue gas treatment installations. In a particular embodiment, the raw recycling material is in particular fluorine-free, that is to say it comprises less than 0.1% by weight of fluorine.

The raw material for recycling preferably has a composition such that the AhOVMgO mass ratio is greater than 8. Such a ratio is particularly advantageous for obtaining the mineral wool according to the invention without requiring the addition of dolomite. The raw material for recycling is preferably free from metallic particles, in particular metallic aluminum. Small amounts of metallic aluminum, (typically up to 2%, preferably up to 1%, more preferably up to 0.5%, by weight) may nevertheless be present, particularly when the recycle raw material is a by-product of the processing of aluminum slag. Likewise, small amounts of aluminum nitride (typically up to 3%, preferably up to 2%, more preferably up to 1%, by weight) may also be present, particularly when the raw material of recycling is a by-product of the processing of aluminum slag. From a mineralogical point of view, the raw material for recycling is essentially free of carbonates, that is to say it comprises at most 5%, preferably at most 2%, more preferably at most 1%, see at most 0.5% by weight of carbonates. It preferably comprises at least 20%, or even at least 30%, and generally up to 80%, or even up to 60%, by weight of amorphous phase. Large proportions of amorphous phase promote fusion. It can comprise at least 10%, even at least 20%, and generally up to 50%, by weight of crystalline phase of spinel type comprising magnesium (Mgi-xMxAh-yM'yCL M and M 'being transition metals ).

The mixture of raw materials is typically in powder form. In particular, the mixture of raw materials preferably does not include briquettes. The melting step can be carried out in various known ways, in particular by melting in a flame furnace or by electrical melting. It is generally not carried out in a cupola-type oven. The mineral fiber compositions targeted by the present invention are not very compatible with this method of melting due in particular to the relatively high alkali contents. The mixtures of materials necessary to achieve these compositions have in fact, there is a tendency to change rapidly from the solid state to a low viscosity liquid which can cover the coke particles and prevent combustion. Cupola furnaces also promote the evaporation of alkalis, generating not only material losses but also environmental or safety problems due to the high reactivity of the latter with other flights such as sulfur.

The flame furnace comprises at least one burner, aerial (the flames are arranged above the bath of molten material and heat it by radiation) or submerged (the flames are created directly within the bath of molten material). The or each burner can be fed by various fuels such as natural gas or fuel oil. The term “electrical melting” is understood to mean that the vitrifiable mixture is melted by the Joule effect, by means of electrodes immersed in the bath of molten material, to the exclusion of any use of other heating means, such as flames. The batch mixture is normally distributed homogeneously over the surface of the molten material bath using a mechanical device, and thus constitutes a heat shield limiting the temperature above the molten material bath, so that the presence a superstructure is not always necessary. The electrodes can be suspended so as to immerse in the bath of molten material from above, be installed in the hearth, or even be installed in the side walls of the tank. The first two options are generally preferred for large tanks in order to best distribute the heating of the molten material bath. The electrodes are preferably made of molybdenum, or even optionally of tin oxide. The passage of the molybdenum electrode through the hearth is preferably effected by means of a water-cooled steel electrode holder. The melting step can also implement both flame melting and electrical melting, for example by using a flame furnace also provided with side wall electrodes serving to accelerate the melting of the vitrifiable mixture.

Conventionally, the type of mineral wool targeted by the process according to the invention is fiberized by so-called “external” centrifugation processes, for example of the type of those using a cascade of centrifugation wheels fed with molten material by a static distribution device. , as described in particular in patents EP 0465310 or EP 0439385. The mineral wool composition described above however also allows so-called "internal" spinning by centrifugation, that is to say using centrifuges rotating at high speed. and pierced with holes, significantly reducing the number of infants. This process is described in particular in patents EP 0189354 or EP 0519797. The stringing step is thus preferably carried out by internal centrifugation.

The present invention also relates to the use of a recycling raw material, or of a mixture of raw materials comprising at least 8.5% by weight thereof, for the manufacture of mineral wool having a chemical composition, expressed as a weight percentage of oxides, comprising:

Si02 30-50%

A1203 15-35%

CaO 5-25% MgO 1-25%

Fe203 2-15%

Na20 + K20> 10% characterized in that the raw material for recycling comprises at least 3.5% of magnesium, expressed by weight of oxides, and is essentially free of carbonates. The mixture of The raw material is moreover preferably free from dolomite and magnesia. The use of the recycling raw material as described above, and more generally of a mixture of raw materials comprising the latter, makes it possible to significantly reduce the carbon dioxide emissions originating from the smelting of the raw materials.

A subject of the present invention is also a mineral wool capable of being obtained by the process described above. Such mineral wool comprises at least 8.5% by weight of a recycling raw material comprising at least 3% of magnesium, expressed by weight of oxides, said recycling raw material being essentially free of carbonates, and exhibits a composition chemical, expressed as a percentage by weight of oxides, comprising:

Si02 30-50%

A1203 15-35%

CaO 5-25% MgO 1-25%

Fe203 2-15%

Na20 + K20> 10%.

A subject of the invention is also a thermal insulation product comprising a mineral wool as described above. Such a product is in particular in the form of rolls or panels. It can be used for example in buildings, in industry or in means of transport, in particular rail or sea. It is particularly suitable for applications in which it may be required to undergo high temperatures, either continuously (insulation of domestic or industrial ovens or ovens, of fluid transport pipes) or accidentally, in a protective role. against fire (fire doors, insulation of ships, tunnels or off-shore platforms, etc.).

More generally, the product according to the invention can be used to thermally insulate any type of building, tertiary or dwelling (collective or individual). It can for example be used in exterior insulation systems, for insulation of timber frame houses, in sandwich panels, in ventilation ducts etc ...

The characteristics described above in relation to the process according to the invention, in particular concerning the composition of mineral wool, the mixture of raw materials and the raw material for recycling, also apply to the other aspects of the invention (uses of the recycle raw material or the mixture of raw materials including the same, mineral wool or insulation product) although these are not repeated for the sake of brevity.

The examples which follow illustrate the invention in a non-limiting manner.

Examples

Mineral wool productions having a target chemical composition as presented in Table 1 have been carried out from different mixtures of materials. The mixture of raw materials of Comparative Example C1 is a conventional mixture comprising dolomite as the carrier of magnesium. In Example II according to the invention, the dolomite was completely replaced by a recycling material according to the invention. The compositions of the raw material mixtures are detailed in Table 2. Table 3 shows the chemical composition of the recycle material. [Table 1]

[Table 2]

[Table 3]

During the various production campaigns, no decrepitation was observed during the merger of the raw material mixtures of Example II. This has the effect of a significant reduction in the amount of take-off and the risk of obstruction of the regenerators compared to the use of a mixture of raw materials of example C1. The stability of the composition of the molten bath is also improved compared to example C1. Finally, a 2 to 5% reduction in CO2 emissions during the melting of mixtures of raw materials of example II compared to that of example C1 was also observed.

Claims

1. A method of manufacturing mineral wool having a chemical composition, expressed as a weight percentage of oxides, comprising:

SÎ02 30-50% A1203 15-35%

CaO 5-25%

MgO 1-25%

Fe203 2-15%

Na20 + K20> 10% said method comprising: providing a mixture of raw materials; melting said mixture of raw materials to obtain a molten material; stringing of the molten material; characterized in that the mixture of raw materials is in powder form and comprises at least 8.5% by weight of a raw material for recycling comprising at least 3% of magnesium, expressed by weight of oxides, said raw material for recycling being essentially free of carbonates, and in that the raw material mixture is free of dolomite and magnesia.

2. Method according to claim 1, characterized in that the chemical composition of the mineral wool comprises less than 0.1% by weight of halogen.

3. Method according to claim 1, characterized in that the raw material for recycling comprises less than 0.9%, preferably less than 0.6%, by weight of halogen.

4. Method according to one of claims 1 to 3, characterized in that the raw material for recycling is free of fluorine.

5. Method according to one of claims 1 to 4, characterized in that the raw material for recycling comprises up to 2% by weight of metallic aluminum.

6. Method according to one of claims 1 to 5, characterized in that the raw recycling material has a chemical composition, expressed by weight of oxides, comprising:

A1203 50-80%;

SiO2 2 to 25%;

20% MgO 3; Fe203 0.5 to 10%.

7. Method according to one of claims 1 to 6, characterized in that the raw recycling material has a chemical composition, expressed by weight of oxides, the AhCh / MgO mass ratio of which is greater than 8.

8. Method according to one of claims 1 to 7; characterized in that the mixture of raw materials does not include briquettes.

9. Method according to one of claims 1 to 8, characterized in that the mixture of raw materials comprises at least 1% by weight of bauxite.

10. Method according to one of claims 1 to 9, characterized in that the melting of the mixture of raw materials is carried out in a flame furnace, in particular a submerged burner furnace, and / or by electrical fusion.

11. Method according to one of claims 1 to 10, characterized in that the stringing is carried out by internal centrifugation.