Method for recovering waste mineral material

Abstract

The present invention relates to a method for preparing a mineral melt in a cupola furnace comprising a plasma torch that heats mineral material and waste mineral material or recycled mineral material to form a melt wherein waste mineral material or recycled mineral 5 material is introduced into the furnace through a waste inlet located in a side wall of a hot zone of the furnace.

Description

Technical Field

[0001] The present invention relates to a method for preparing a mineral melt in a cupola furnace comprising a plasma torch for heating a mineral material and a waste mineral material or recycled mineral material to form a melt, wherein the waste mineral material or recycled mineral material is introduced into the furnace through a waste material inlet located in a side wall of the hot zone of the furnace. Background Art

[0002] Known methods for preparing mineral melts for the production of man-made mineral fibres (MMVF), such as glass fibres or stone fibres, are carried out in vertical furnaces, such as cupolas. They involve heating a mineral material to form a mineral melt. The heating may be provided by any means, but is conventionally carried out in the presence of coke and an oxygen-containing gas, or by passing an electric current between two or more electrodes, such as graphite electrodes or molybdenum electrodes. A plasma torch may also be used to melt the mineral material. Using plasma as a heat source is advantageous because it can remove harmful gases such as CO. 2 、NO x and H 2 The generation of harmful gases which would otherwise be present in the furnace exhaust gas is minimized.

[0003] The spinning process used to form MMVF inevitably produces various byproducts that form waste mineral materials. This waste mineral material can be in the form of a fine powder material, such as the material formed when cutting MMVF, or it can be fibrous in nature. In addition, MMVF products that have reached their useful life, such as MMVF insulation materials removed during building reconstruction, are also considered waste mineral materials. Waste mineral materials may contain binders used during the MMVF manufacturing process. The waste material can also be in a cured state or an uncured state.

[0004] As an alternative to its disposal in landfills, waste mineral materials can be recycled by combining them with other (conventional) mineral materials and heating them to form a mineral melt. This mineral melt can then be spun into new MMVF products.

[0005] Despite the benefits of recycling waste mineral materials, they cannot simply be combined with conventional mineral materials and added to the furnace in the usual manner. It is unacceptable to introduce waste mineral materials directly into a shaft furnace, such as placing them on top of a mineral pile. Due to the various geometries of waste mineral materials (such as fines and fibrous materials) and their insulating properties, they may block or obstruct the furnace by preventing exhaust gases from passing upward through the mineral pile, by restricting the flow of oxygen through the furnace tuyere and oxygen injection ports, or by restricting the flow of plasma from the plasma torches into the furnace. This greatly reduces the efficiency of the furnace and may also cause the melting process to fail.

[0006] Waste mineral materials can be processed to form briquettes that can be added to a shaft furnace along with conventional mineral materials. However, the briquetting process requires the addition of a binder to the waste mineral melt, which exacerbates environmental issues. The use of these briquettes is also unattractive because it increases the complexity and cost of the recycling process and is therefore unattractive on an industrial scale.

[0007] WO 90 / 07470 describes a method for preparing a melt for mineral wool production using waste cotton, wherein heat is provided by a plasma torch. The waste cotton is fed into a connecting pipe using a screw conveyor, wherein the connecting pipe transports the plasma jet to the cupola. In this method, the waste cotton is added to the plasma outside the cupola. A problem with this method is that the feed pipe accommodating the screw conveyor and the connecting pipe tend to become blocked by slag (waste cotton component), which is exacerbated when the feed pipe and the connecting pipe are water-cooled to extend the life of the equipment. A preferred embodiment attempts to reduce the effects of feed pipe blockage by gradually increasing the diameter of the feed pipe seen in the direction toward the connecting pipe, however, the connecting pipe still tends to block.

[0008] There is therefore a need for an improved method of forming a melt suitable for use in the formation of mineral fibres which uses a substantial proportion of waste mineral material. Summary of the invention

[0009] In a first aspect of the invention, there is provided a method for preparing a mineral melt in a cupola, wherein the mineral melt is used to form mineral wool, the cupola comprising:

[0010] (i) The hot zone at the base of the furnace;

[0011] (ii) melt outlet in the hot zone;

[0012] (iii) at least one plasma torch providing plasma heating to the hot zone via a plasma jet, the plasma jet being confined within the hot zone

[0013] A cavity that is substantially free of solid material; and

[0014] (iv) a waste material inlet located in a side wall of the hot zone of the furnace and configured to convey waste mineral material towards the cavity defined by the plasma jet,

[0015] Therein mineral material and waste mineral material supplied to the furnace are melted to form a mineral melt.

[0016] In a second aspect of the present invention, there is provided a method for producing a man-made vitreous fiber (MMVF), comprising the steps of:

[0017] (i) using the method defined in the first aspect of the present invention or any embodiment thereof to form

[0018] Mineral melts;

[0019] (ii) preferably using a cascade spinning machine, the mineral is made into a fiber by an internal spinning process or an external spinning process.

[0020] melt fiberization; and

[0021] (iii) collecting the formed fibers.

[0022] In a third aspect of the present invention, there is provided a cupola for preparing a mineral melt according to the method defined in accordance with the first aspect of the present invention or any embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a cross section of a cupola furnace configuration that may be used to practice the present invention. DETAILED DESCRIPTION

[0024] The present invention is based on the surprising discovery that a waste material inlet located in the wall of the hot zone of a cupola can effectively and efficiently convey waste mineral material into a plasma jet where it is melted to form a mineral melt without the above mentioned disadvantages.

[0025] Cupola furnaces using plasma heating typically include a hot zone in the lower part of the furnace (also referred to as the base of the furnace). One or more plasma torches can provide heating to the hot zone at a level sufficient to melt the mineral material (mineral charge). Thus, the mineral melt forms a pool at the base of the hot zone, in the space between the structures supporting the mineral material pile (usually using the mineral material itself or coke in the process). After a certain volume of the mineral melt is produced, it can be removed from the furnace by some form of melt outlet, such as a siphon. After being removed from the furnace, the mineral melt can be used to form man-made vitreous fibers (MMVF) by any suitable spinning method.

[0026] Plasma torches use direct current (DC), alternating current (AC), radio frequency (RF) and other discharges to produce hot plasma. Hot plasma provides heat, which is generated in a DC plasma torch by sending an arc between two electrodes, through which a carrier gas passes in a contracted opening. This raises the temperature of the gas to the extent that it enters the fourth state of matter (i.e., plasma). Plasma torches can be transfer or non-transfer. In a non-transfer DC plasma torch, the electrode is inside the housing of the torch. In a transfer plasma torch, one electrode is located outside the housing of the torch, thereby allowing an arc to be formed outside the plasma torch and at a greater distance. Preferably, the plasma torch in the present invention is a non-transfer plasma torch. Most preferably, it is a DC non-transfer plasma torch.

[0027] The plasma torch can use a variety of carrier gases, such as oxygen, nitrogen, argon, helium, air, hydrogen, water vapor, or mixtures thereof.

[0028] One or more plasma torches are usually installed outside the furnace so that the hot plasma (commonly referred to as a plasma jet) produced penetrates the hot zone of the furnace. The plasma jet can reach a temperature of up to 7000°C, which is sufficient to melt the mineral material near it. As the solid mineral material is melted (and subsequently removed from the furnace via the melt outlet), the mineral material pile moves downward through the furnace to replace it. It is found that in practice, the plasma jet defines a cavity (three-dimensional shape) in the furnace, and the cavity is substantially free of solid materials, such as mineral materials, waste mineral materials, and coke. The temperature and environment in the plasma jet are such that the mineral material in the furnace will usually melt before entering the defined cavity, however, the cavity may contain some solid materials. For example, a portion of the mineral material pile may become detached from the bulk material and fall into the plasma jet. Alternatively, due to the melting process, the pile may suddenly and partially collapse, causing solid mineral material to enter the plasma jet. The solid material also includes waste mineral materials from the waste inlet as discussed below. In any case, any solid material in the cavity will be instantaneous because it will be quickly melted by the plasma jet.

[0029] Preferably, the plasma jet defines a cavity within the hot zone which is free of solid material. That is, no mineral material or waste mineral material enters the cavity.

[0030] The term "waste mineral material" is as mentioned above and includes various by-products of the MMVF forming process, which are generally referred to as mineral wool waste. These by-products include fine powdered materials formed in connection with cutting (e.g. edge cutting) mineral wool mats in order to form mineral wool blocks of a desired size. It also includes recycled mineral materials, such as MMVF insulation removed from buildings during reconstruction, which might otherwise end up in landfills. Waste mineral materials may contain additives added during the manufacturing process, such as binders and hydrophilic or hydrophobic compounds.

[0031] The cupola furnace comprises a waste inlet in the side wall of the hot zone of the furnace. The waste inlet is essentially an opening in the furnace wall. It is configured to convey waste mineral material to the cavity defined by the plasma jet. In essence, the waste inlet is capable of supplying waste mineral wool directly into the plasma jet. It will be appreciated that due to the environment surrounding the plasma jet, the waste mineral material may melt before it enters the plasma jet. This may depend on the amount or rate at which the waste mineral material is introduced into the furnace via the waste inlet. After melting, it will form part of the mineral melt at the base of the hot zone and can be removed via the melt outlet.

[0032] Waste mineral material may be fed through the waste material inlet and into the furnace by any suitable means. Such means may be:

[0033] (a) screw conveyor; or

[0034] (b) pneumatic tube transport, preferably wherein the pneumatic tube transport uses recycled exhaust gas from a cupola, or nitrogen (N 2 ) or any other gas which does not contain oxygen.

[0035] It is preferred that the waste mineral material is fed via the waste material inlet by a screw conveyor.

[0036] The rate at which waste mineral material is added to the cupola may depend on the size of the furnace and its melt production rate, the number of plasma torches, the number of waste inlets and their size and location in the furnace.

[0037] Ideally, the amount of waste mineral material used in the process for preparing the mineral melt is from 1% to 40%, preferably from 5% to 35%, more preferably from 10% to 20% of the total weight of the (combination of) waste mineral material and mineral material added to the furnace. The formation of the mineral melt in the cupola is generally a continuous process and therefore the ratio of waste mineral material to the combination of waste mineral material and mineral material can be measured over a period of time. This is because the waste mineral material and / or mineral material can be added to the cupola in batches.

[0038] In order to ensure a suitable rate of addition of waste mineral material to the cupola, it is preferred that each waste inlet located in the furnace wall has an area of ​​3 cm 2 Up to 320cm 2 , preferably 20cm 2 Up to 180cm 2 , more preferably 50cm 2 Up to 115cm 2 This corresponds approximately to a circular opening with a diameter of 2 to 20 cm, preferably 5 to 15 cm, more preferably 5 to 12 cm.

[0039] Ideally, the waste material inlet is located in the side wall of the hot zone of the furnace above the point where the plasma jet enters the furnace. The advantage is that the waste mineral material can easily move towards the cavity defined by the plasma jet due to gravity. Therefore, this is a highly preferred feature of the present invention.

[0040] The distance between the edge of the orifice through which the plasma jet enters the furnace and the edge of the waste inlet should be sufficient to ensure that the waste mineral material can be melted and incorporated into the mineral melt. This distance may be from 1 cm to 30 cm, preferably from 5 cm to 20 cm, more preferably from 7 cm to 12 cm. Typically, this distance is limited by the size of the water cooling jackets of both the waste inlet and the plasma jet.

[0041] Since the waste inlet is close to the plasma jet, it is preferred that the waste inlet and the device through which the waste mineral material can be fed (e.g., a screw conveyor or a pneumatic tube conveying device) are formed of a heat-resistant material and / or are provided with a cooling mechanism. The hot zone of a cupola furnace typically includes a refractory brick layer. Therefore, the waste inlet can be an opening in those refractory bricks that provide suitable heat resistance. In addition, the plasma torch is typically water-cooled. The plasma torch water cooling system can be extended to also cool the device through which the waste mineral material can be fed through the waste inlet. This can extend the working life of the furnace and minimize downtime due to maintenance, both of which improve the efficiency of the process.

[0042] Due to the diameter of common cupola furnaces, it may be preferred that it include two to five plasma torches, preferably three or four plasma torches, especially if the plasma torches are the main or only means of providing heat to the furnace. The plasma torches should be positioned substantially in a horizontal plane around the perimeter of the furnace and substantially equidistant from each other. This means that the plasma jets from each plasma torch extend toward the center of the cupola. In order to maximize the rate at which waste mineral material can be added to the furnace, each plasma torch should have an associated waste inlet.

[0043] Although the waste mineral material may take a variety of forms, a more homogeneous waste may be preferred. Therefore, before the waste is introduced into the cupola through the waste inlet, it may first be ground. Preferably a rod mill is used. In this case, the waste mineral material is preferably ground to 500 kg / m 3 Up to 1500kgm 3 , for example 700kgm 3 Up to 1250kgm 3 , for example 800kgm 3 Up to 1000kgm 3 Grinding it to those densities means it can be added to the cupola more easily using a screw conveyor or pneumatic tube conveying device.

[0044] The claimed method is particularly suitable for combination with a method as described in WO 2022 / 106592 (the contents of which are incorporated herein by reference). The method is used to produce a mineral melt suitable for forming MMV fibers, such as glass fibers or stone fibers, which method allows the NO generated in the exhaust gas of the cupola to be eliminated even when a plasma torch is used. x and H 2 This advantage can be achieved by using a plasma torch to provide more than 50% of the heating energy to the cupola, where the plasma torch uses nitrogen (N 2 ), carbon monoxide (CO), carbon dioxide (CO 2 ), or a mixture thereof as the carrier gas, and exclude water from any area of ​​the cupola above 750°C.

[0045] As is known, a cupola furnace typically includes a series of temperature zones, including a hot zone, an oxidation zone, a reduction zone, and a preheat zone.

[0046] In view of the above, in a specific feature of the method of the present invention,

[0047] (i) the furnace is equipped with at least one tuyeres providing a source of oxygen in the oxidation zone of the cupola and / or

[0048] Oxygen injection port;

[0049] (ii) At least one plasma torch using N 2 ,CO,CO 2 or a mixture thereof as carrier gas, optionally wherein the enthalpy of the carrier gas is 2.0 kWh / Nm 3 Up to 6.0kWh / Nm 3 , for example 3.0kWh / Nm 3 Up to 5.0kWh / Nm 3 , and preferably wherein the carrier gas is nitrogen (N 2 );

[0050] (iii) greater than 50% of the furnace heating energy is provided by the plasma torch;

[0051] (iv) the temperature in the oxidation zone is less than 1,400°C;

[0052] (v) the temperature in the hot zone is greater than the temperature in the oxidation zone; and / or

[0053] (vi) Water is substantially excluded from any area of ​​the furnace where the temperature is above 750°C.

[0054] It is preferred that all of features (i) to (vi) are included so that the NO generated in the exhaust gas x and H 2 When this is the goal of the method,

[0055] (I) greater than 60%, preferably greater than 70%, more preferably greater than 80%, even more preferably greater than 90%, and most preferably all of the cupola heating energy is provided by at least one plasma torch; and /

[0056] or

[0057] (II) wherein heating is provided in the hot zone solely by at least one plasma torch.

[0058] In addition, NO can be significantly reduced when oxygen is removed from the region of the cupola that contains nitrogen and is at a temperature of 1,400°C or higher. x To help make NO x In order to minimize the generation of oxygen, the carrier gas should contain at most only trace amounts of oxygen. This means that the carrier gas should contain less than 5 wt. % oxygen, such as less than 2 wt. %, preferably less than 0.8 wt. %, based on the total weight of the carrier gas. Ideally, the carrier gas contains no oxygen. This means that at most only trace amounts of oxygen are present.

[0059] NO x It can be derived from nitrogen and oxygen at high temperatures. x The temperature in the oxidation zone of the cupola should be between 600°C and 1,400°C. x The temperature of the formation, preferably oxidation zone is 600°C to 1,300°C, more preferably 600°C to 1,200°C, even more preferably 600°C to 1,100°C, especially 600°C to 1,000°C, most preferably 600°C to 900°C, especially 600°C to below 850°C.

[0060] The exhaust gas from a cupola heated using a plasma torch may contain N 2 ,CO,CO 2 、NO x and H 2, each of which is a component of the exhaust gas. The exhaust gas may contain additional components, such as water and particles, i.e., particles of solid matter. In a specific feature, the exhaust gas as a whole or in part can be used as a carrier gas for one or more plasma torches. The components of the exhaust gas can be separated before it is used as a carrier gas. The components of the exhaust gas can be separated from each other, or a combination of two or more components can be separated from other components. This means that the carrier gas can contain at least one component of the exhaust gas, such as one, two, three, four, five or more components of the exhaust gas. Preferably, the carrier gas contains the exhaust gas component N 2 ,CO,CO 2 or a combination thereof. Alternatively, the carrier gas may contain an exhaust gas component, such as N 2 , CO, or CO 2 .

[0061] One or more components of the exhaust gas may be subjected to exhaust gas purification before it is used in the carrier gas. Preferably, the exhaust gas purification is to remove particles and / or water suspended in the exhaust gas. Exhaust gas purification can be performed on the exhaust gas as a whole, or on at least one of its components after separation from the remainder of the exhaust gas. The carrier gas may consist of the exhaust gas or at least one component of the exhaust gas. Alternatively, the carrier gas may contain the exhaust gas or at least one component of the exhaust gas. In the latter case, an additional gas that does not form part of the exhaust gas may be added to the carrier gas before it is used. In this case, the carrier gas is "supplemented" with the additional gas.

[0062] The method may be used to form any mineral melt suitable for forming mineral wool. In particular, the method is particularly advantageous in the formation of a mineral melt where the mineral melt or subsequently produced MMVF has a chemical analysis of the elements (measured as weight % of oxides) within the various ranges defined by the following conventional and preferred lower and upper limits.

[0063] SiO 2 35 to 50, preferably 38 to 48, more preferably 33 to 44

[0064] Al 2 O 3 12 to 30, preferably 15 to 28, more preferably 16 to 24

[0065] TiO 2 Up to 2

[0066] Fe 2 O 3 2 to 12

[0067] CaO 5 to 30, preferably 8 to 20

[0068] MgO 0 to 15, preferably 1 to 12

[0069] Na 2 O 0 to 15

[0070] K 2 O 0 to 15

[0071] P 2 O 5 0 to 3

[0072] MnO 0 to 3

[0073] B 2 O 3 0 to 3.

[0074] In this case it is preferred that when the melt is to be formed into MMVF, the proportion of Fe(2+) in the mineral melt is greater than 80% based on total Fe, preferably at least 90%, more preferably at least 95%, and most preferably at least 97% based on total Fe. In such a case, it is preferred to use a cascade spinning machine to make the MMVF. More details of these example mineral melts can be found in WO2012 / 140173 (which is incorporated herein by reference).

[0075] As is conventional in the art, reference herein to Fe in a mineral melt or fiber composition is 2 O 3 It refers to the melt or composition (according to Fe 2 O 3 The total amount of iron (calculated) is not taken into account the amount of each oxidation state of iron present in the composition.

[0076] In the above examples of mineral melts and resulting fibers, it is preferred that the amount of iron in the mineral melt is from 2% to 15% by weight, preferably from 5% to 12% by weight. Cupola furnaces tend to have a reducing atmosphere, which can lead to the reduction of iron oxides and the formation of metallic iron. Preferably, metallic iron is not incorporated into the mineral melt and the fibers and should be removed from the furnace. Therefore, the conditions in the furnace can be carefully controlled to avoid excessive reduction of iron. However, we have found that final product fibers with significant levels of iron oxides can be produced.

[0077] The method of the present invention can be used to form fibers that can be shown to be soluble in physiological saline. Suitable high-aluminum biosoluble fibers that can be advantageously made using the method of the present invention are described in WO96 / 14454 and WO96 / 14274, and others are described in WO97 / 29057, DE-U-2970027 and WO97 / 30002 (which are incorporated herein by reference).

[0078] Such fibers preferably have sufficient solubility in lung fluid, as shown in in vivo tests or in vitro tests (usually performed in physiological saline buffered to about pH 4.5). Suitable solubility is described in WO96 / 14454. Typically, the dissolution rate in this saline is at least 10 nm or 20 nm per day. The sintering temperature of the fiber is preferably above 800°C, more preferably above 1,000°C. The viscosity of the melt at the fiber forming temperature is preferably 5 poise to 100 poise, preferably 10 poise to 70 poise at 1,400°C. Additional embodiments of this example can be found in WO 99 / 28252 (which is incorporated herein by reference).

[0079] The MMVF may be formed into a bonded web comprising the MMVF as described above or the MMVF made according to the method described above and a cured binder composition.

[0080] Preferably, the viscosity of the mineral melt in this particular example at 1400°C is in the range of 10 poise to 30 poise, more preferably in the range of 20 poise to 25 poise. One advantage of selecting these viscosities is that the resulting MMVF has a smaller diameter than if the viscosity of the melt is higher. In addition, the melt can be used at a lower temperature to achieve the desired operating viscosity. This saves energy because the melt can be used at a lower temperature. It also reduces wear on the rotor used to produce the fiber because the melt at a lower temperature causes less wear. More details of this example mineral melt can be found in WO2015 / 055758 (which is incorporated herein by reference). The viscosity of the melt can be determined according to ASTM C 965-96.

[0081] Raw materials (mineral materials) can be in the form of agglomerates. In a known manner, agglomerates are manufactured by molding a mixture of desired granular material and binder into a desired agglomerate shape and curing the binder. The binder can be a hydraulic binder, i.e., a binder activated by water, such as Portland cement. Other hydraulic binders can be used as partial or complete replacements for cement, and examples include lime, blast furnace slag powder and some other slags, and even cement kiln dust and ground MMVF pellets (JP-A-51075711, US 4,662,941 and US 4,724,295, each of which is incorporated herein by reference). Alternative binders include clay. Agglomerates can also be formed with organic binders such as molasses, for example, as described in WO 95 / 34514 (which is incorporated herein by reference). Such agglomerates can be described as formed stone (formstone).

[0082] The mineral melt prepared by the method of the present invention may be suitable for producing mineral wool, or MMVF, such as glass fiber or stone fiber. Preferably, the formed mineral melt is suitable for forming MMVF. Therefore, in a second aspect of the present invention, there is provided a method for manufacturing MMVF, comprising the following steps:

[0083] (i) forming a melt using a method as defined herein;

[0084] (ii) preferably using a cascade spinning machine, the melt is spun by an internal spinning process or an external spinning process.

[0085] body fibrosis; and

[0086] (iii) collecting the formed fibers.

[0087] Fiber, particularly MMVF, can be made by mineral melt in a conventional manner.Usually, fiber is made by centrifugal fiberization process.For example, fiber can be formed by spinning cup process (spinning cup process), wherein fiber is thrown outwards by the perforation in spinning cup, or mineral melt can be thrown out of rotating disk, and fiber formation can be promoted by passing mineral melt through gas jet injection.Fiber formation can be carried out by pouring mineral melt on the first rotor in cascade spinning machine.In this case, preferably mineral melt is poured on the first of a group of two, three, four or even more rotors, each rotor rotates around the substantially horizontal axis, and the mineral melt on the first rotor is mainly thrown on the second (lower level) rotor thus, although some may be thrown out of the first rotor as fiber, and the mineral melt on the second rotor is thrown out as fiber, although some may be thrown to the third (lower level) rotor, etc.Usually, it is preferred that the spinning process uses cascade spinning machine.

[0088] Those skilled in the art know the desired properties of the mineral melt to be used in each spinning method and can adjust the composition of the mineral melt to provide these properties. For example, those skilled in the art can select the mineral materials to be added to the cupola to produce a specific mineral melt composition to be spun by a specific spinning process.

[0089] During the fiberizing process, the melt is formed in a cloud of fibers entrained in the air, and the fibers are collected as a web on a conveyor and carried away from the fiberizing equipment. The fiber web is then consolidated, which may include cross-lapping and / or longitudinal compression and / or vertical compression and / or winding around a mandrel to produce a cylindrical product for pipe insulation. Other consolidation processes may also be performed.

[0090] The binder composition is conventionally applied to the fibres, preferably when the fibres are an airborne cloud. Alternatively, it may be applied after collection on a conveyor, but this is less preferred. Conventional types of binders for use with mineral wool fibres may be used.

[0091] After consolidation, the fiber web is sent to a curing device to cure the binder. Curing can be carried out at a temperature of 100°C to 300°C, such as 170°C to 270°C, such as 180°C to 250°C, such as 190°C to 230°C.

[0092] Preferably, curing is carried out in a conventional curing oven used for mineral wool production, wherein hot air is blown through the consolidated web, preferably operating at a temperature of 150° C. to 300° C., such as 170° C. to 270° C., such as 180° C. to 250° C., such as 190° C. to 230° C. Curing may be carried out for a period of 30 seconds to 20 minutes, such as 1 minute to 15 minutes, such as 2 minutes to 10 minutes. Typically, curing is carried out at a temperature of 150° C. to 250° C. for a period of 30 seconds to 20 minutes.

[0093] The curing process may begin immediately after the binder is applied to the fibers. Curing is defined as a process whereby the binder composition undergoes a physical and / or chemical reaction, which in the case of a chemical reaction generally increases the molecular weight of the compounds in the binder composition, thereby increasing the viscosity of the binder composition, generally until the binder composition reaches a solid state. The cured binder composition bonds the fibers to form a structurally coherent fiber matrix.

[0094] Curing of the binder in contact with the mineral fibers may alternatively be performed in a hot press. Curing of the binder in contact with the mineral fibers in a hot press has the particular advantage that it enables the production of high density products.

[0095] With reference to the attached drawings ( Figure 1 ) further describes the present invention in detail, the accompanying drawing ( Figure 1 ) is a schematic diagram of a cross-section of a cupola configuration that can be used to implement the present invention.

[0096] The plasma torch 1 comprises two separate tubular electrodes 2 and 3, to which direct current is fed via conductors 4 and 5 from a voltage regulating unit, such as a rectifier and a thyristor 6 or a rectifier and an IGBT (Insulated Gate Bipolar Transistor). The current is fed to the thyristor 6 via a conductor 7 comprising a transformer 8. The tubular electrodes 2 and 3 are provided with cooling jackets, and cooling water is introduced into the cooling jackets by a pump 9 and recirculated through a heat exchanger 10. The cooling medium is introduced into the heat exchanger 10 via a feed pipe 11 and discharged via an outlet pipe 12. The plasma torch 1 also comprises a pipe 13 for introducing a carrier gas into a distribution chamber 14, from which the carrier gas flows into the space between the electrodes 2 and 3.

[0097] The plasma torch 1 is connected to the side wall 16 of the cupola via a connecting pipe 15. The end of the connecting pipe 15 is inserted into a hole in the wall of the shaft furnace. In use, the plasma jet 17 generated by the plasma torch 1 extends towards the center of the cupola and defines a cavity (dashed line 18) that is substantially free of solid material in the hot zone. The plasma jet 17 provides plasma heating to the hot zone.

[0098] The cupola also includes a waste inlet 19 located in the side wall of the hot zone of the furnace and, in this case, above the aperture through which the plasma jet enters the cupola. In use, waste mineral material can be delivered to the cavity 18 defined by the plasma jet through the waste inlet 19. This can be achieved, for example, via a screw conveyor 20 rotatably mounted in a feed conduit 21 extending through the waste inlet 19, such as Figure 1 as shown in .

[0099] The plasma jet 17 melts the waste mineral material and mineral material in the hot zone of the furnace and the resulting mineral melt is collected at the base of the cupola.The mineral melt can be removed from the furnace in the usual manner.

Claims

1. A method for preparing a mineral melt in a cupola, wherein the mineral melt is used to form mineral wool, the cupola comprising: (i) a hot zone at the base of the furnace; (ii) a melt outlet in the hot zone; (iii) at least one plasma torch providing plasma heating to the hot zone via a plasma jet defining a cavity substantially free of solid material within the hot zone; as well as (iv) a waste material inlet located in a side wall of the hot zone of the furnace and configured to deliver waste mineral material to the cavity defined by the plasma jet, Wherein mineral material and the waste mineral material supplied to the furnace are melted to form the mineral melt.

2. The method according to claim 1, wherein the amount of waste mineral material used is 1% to 40%, preferably 5% to 35%, more preferably 10% to 20% of the total weight of waste mineral material and mineral material.

3. The method according to claim 1 or claim 2, wherein the waste inlet (I) in a wall of the furnace above the point where the plasma jet enters the furnace; and / or (II) with 3cm 2 Up to 320cm 2 , preferably 20cm 2 Up to 180cm 2 , more preferably 50cm 2 Up to 115cm 2 area.

4. A method according to any preceding claim, wherein the waste mineral material is fed through the waste material inlet by: (a) screw conveyor; or (b) a pneumatic tube conveying means, preferably wherein said pneumatic tube conveying means uses recycled exhaust gas from said cupola, or nitrogen (N2) or any other oxygen-free gas, preferably wherein said waste mineral material is fed via said waste inlet by a screw conveyor.

5. A method according to any preceding claim, wherein the cupola comprises two to five plasma torches, preferably three or four plasma torches, positioned substantially in a horizontal plane around the perimeter of the furnace and substantially equidistant from each other, wherein the plasma jet from each plasma torch extends towards the centre of the cupola, wherein each plasma torch has an associated waste inlet.

6. A method according to any preceding claim, wherein the waste mineral material is ground, preferably by a rod mill, before being introduced into the cupola through the waste inlet.

7. The method according to claim 6, wherein the waste mineral material is ground to 500 kgm 3 Up to 1500kgm 3 , for example 700kgm 3 Up to 1250kgm 3 , for example 800kgm 3 Up to 1000kgm 3 density.

8. A method according to any preceding claim, wherein (i) the furnace is equipped with at least one tuyeres and / or oxygen injection ports for providing a source of oxygen in the oxidation zone of the cupola; (ii) the at least one plasma torch uses nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2) or a mixture thereof as a carrier gas, optionally wherein the enthalpy of the carrier gas is 2.0 kWh / Nm 3 Up to 6.0kWh / Nm 3 , for example 3.0kWh / Nm 3 Up to 5.0kWh / Nm 3 ,and Preferably, the carrier gas is nitrogen (N2); (iii) greater than 50% of the furnace heating energy is provided by the plasma torch; (iv) the temperature in the oxidation zone is less than 1,400°C; (v) the temperature in the thermal zone is greater than the temperature in the oxidation zone; and / or (vi) substantially exclude water from any area of ​​the furnace where the temperature is above 750°C.

9. A method according to any preceding claim, wherein (I) greater than 60%, preferably greater than 70%, more preferably greater than 80%, even more preferably greater than 90%, and most preferably all of the cupola heating energy is provided by the at least one plasma torch; and / or (II) wherein heating is provided in said hot zone solely by said at least one plasma torch.

10. A method according to any preceding claim, wherein (a) the temperature in the oxidation zone is from 600°C to 1,400°C, preferably from 600°C to 1,300°C, more preferably from 600°C to 1,200°C, even more preferably from 600°C to 1,100°C, especially from 600°C to 1,000°C, most preferably from 600°C to 900°C, especially from 600°C to less than 850°C; and / or (b) The temperature in the hot zone is higher than 800°C, preferably higher than 900°C, more preferably higher than 1,000°C, more preferably higher than 1,100°C, more preferably higher than 1,200°C, more preferably higher than 1,300°C, more preferably higher than 1,400°C.

11. A method according to any preceding claim, wherein the mineral melt has the following composition, expressed as oxides, in wt %: SiO2 35 to 50, preferably 38 to 48, more preferably 33 to 44 Al2O3 12 to 30, preferably 15 to 28, more preferably 16 to 24 TiO2 up to 2 Fe2O3 2 to 12 CaO 5 to 30, preferably 8 to 20 MgO 0 to 15, preferably 1 to 12 Na2O 0 to 15 K2O 0 to 15 P2O5 0 to 3 MnO 0 to 3 B2O3 0 to 3.

12. A method according to any preceding claim, wherein the proportion of Fe(2+) in the mineral melt is greater than 80% based on total Fe, preferably at least 90%, more preferably at least 95%, and most preferably at least 97% based on total Fe.

13. A method according to any preceding claim, wherein the carrier gas comprises or consists of at least one component of an exhaust gas produced by the furnace, preferably wherein the at least one component of the exhaust gas is subjected to exhaust gas cleaning before its use as a carrier gas, more preferably, the exhaust gas cleaning is to remove particles and / or water.

14. A method for producing a man-made vitreous fiber (MMVF), comprising the steps of: (i) forming a mineral melt using a method as defined in any one of claims 1 to 13; (ii) fiberizing the mineral melt by an internal spinning process or an external spinning process, preferably using a cascade spinning machine; as well as (iii) collecting the formed fibers.

15. A cupola for preparing a mineral melt according to the method as defined in any one of claims 1 to 13.

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