Process for the preparation of a melt for the production of man-made mineral fibres

Abstract

The invention relates to a method for producing a mineral melt in a cupola furnace, which method uses at least one plasma torch to provide thermal energy to the furnace. The plasma torch uses nitrogen, carbon monoxide, carbon dioxide or a mixture thereof as a carrier gas. The invention also relates to a cupola furnace for producing a mineral melt, and to the use of a plasma torch in a cupola furnace for reducing the amount of NOx X and / or hydrogen in the off-gas of the furnace.

Description

Technical Field

[0001] This invention relates to a method for preparing mineral melts in a cupola furnace, the method using at least one plasma torch to supply thermal energy to the furnace. The plasma torch uses nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof as a carrier gas. Background Technology

[0002] Methods for preparing mineral melts for the production of man-made mineral fibers (MMVF) are known to be carried out in vertical furnaces, such as cupola furnaces. These methods involve heating mineral materials in the presence of coke and oxygen-containing gas to form a mineral melt. Reducing harmful emissions in cupola furnace exhaust gases is challenging in methods for producing mineral melts.

[0003] A cupola furnace typically comprises a series of temperature zones, including a hot zone, an oxidation zone, a reduction zone, and a preheating zone.

[0004] The lower part of the cupola furnace constitutes the hot zone. This hot zone includes the molten mineral formed within the cupola furnace, situated in the gaps between coke sheets near the bottom of the furnace, which support the material laid upon them. In a typical cupola furnace, the molten mineral in the hot zone has a temperature of 1450°C.

[0005] The temperature ranges from 1500℃ to 1550℃, and it takes a relatively long time to change the temperature of the molten mineral at that location. Additionally, the distance between the top and bottom of the hot zone is relatively large. This is necessary to ensure the correct oxidation zone temperature is maintained in a conventional cupola furnace.

[0006] The oxidation zone (also known as the combustion zone) is located above the hot zone. The lower part of the oxidation zone typically has a gas inlet nozzle, called a tuyer, through which preheated air or other oxidizing gases are introduced into the furnace. Heating is usually generated by the combustion of coke. The combustion of the coke occurs as the preheated air moves upward through the oxidation zone, and the gas temperature can rise from about 500°C to about 2,000°C, thus heating the raw material moving downward through the oxidation zone to its melting point. This molten mineral material flows downward into the hot zone at the bottom of the cupola. The vertical extension of the oxidation zone is determined by the amount of oxygen introduced into the furnace.

[0007] The reduction zone is located above the oxidation zone and begins at the level where the oxygen introduced through the tuyeres is consumed by the combustion of coke. The temperature in the reduction zone is typically between 1,000°C and 1,500°C, and the amount of CO formed by the reaction of coke with CO2 from the oxidation zone is twice the amount of CO2 consumed per volume.

[0008] This reaction is endothermic, resulting in approximately 20-25% of the energy released during combustion in the oxidation zone being lost as latent heat in the exhaust gas. Typically, the exhaust gas can be used to heat the raw materials that are melting in the cupola furnace in the preheating zone. The preheating zone is located above the reduction zone.

[0009] WO 87 / 06926 relates to a method for producing mineral melts, in which some heat energy can be provided by using a plasma torch. In this method, CO in the exhaust gas is reduced. This can be achieved by using coke to provide at least two-thirds of the furnace's heat energy. The remaining heat energy can be provided by other methods, such as a plasma torch. There is no difference in the carrier gas used with the plasma torch.

[0010] While using a plasma torch to provide some heat to the furnace has advantages, we found that when a plasma torch using air as a carrier gas is used to form mineral melts, it results in the formation of relatively high levels of NO. X (For example, exhaust gases with concentrations as high as 7,000 to 10,000 ppm). NO X It is harmful to the environment and animals (including humans). This is usually mitigated by adding reducing agents (such as hydrocarbon gases). The exhaust gas from such a cupola may still contain more than 3,100 ppm of NO. X This is many times higher than the limits set by many countries. Therefore, it is necessary to provide purification systems to minimize NO. X It is released into the atmosphere. Furthermore, hydrogen can account for up to 20% of the exhaust gases produced by a cupola furnace heated by a plasma torch that uses air as a carrier gas. This poses an explosion risk to the furnace.

[0011] The aim is to provide a method for producing mineral melts suitable for forming MMV fibers (e.g., glass fibers or stone fibers), which minimizes NO generation in cupola exhaust gases, even when using a plasma torch. X The amount of H2. Minimizing coke usage in this method is also desirable. Reducing the distance between the bottom and top of the hot zone is also desirable, especially to provide a more compact furnace. Furthermore, minimizing the time required to change the temperature of the molten minerals may be beneficial.

[0012] This advantage can be achieved by using a plasma torch to provide more than 50% of the heat energy to the cupola, wherein the plasma torch uses nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), or a mixture thereof as the carrier gas, and water is excluded from any area of ​​the cupola above 750°C. Attached Figure Description

[0013] Figure 1 A schematic diagram of a cupola configuration that can be used to implement the present invention is shown. Summary of the Invention

[0014] In a first aspect of the invention, a method for preparing a mineral melt in a cupola furnace is provided, wherein the cupola furnace includes at least two temperature zones, the at least two temperature zones including a hot zone at the bottom of the furnace and an oxidation zone above the hot zone.

[0015] (i) The furnace is equipped with at least one tuyer in the oxidation zone to provide an oxygen source;

[0016] (ii) The furnace includes at least one plasma torch that uses nitrogen, carbon monoxide, carbon dioxide or a mixture thereof as a carrier gas and provides plasma heating in the hot zone;

[0017] (iii) The plasma torch provides more than 50% of the thermal energy of the furnace;

[0018] (iv) The temperature of the oxidation zone is below 1,400°C;

[0019] (v) The temperature of the hot zone is greater than the temperature of the oxidation zone;

[0020] (vi) Water is essentially excluded from any area of ​​the furnace where the temperature is above 750°C; and

[0021] The mineral material is fed into the furnace and melted to form a mineral melt collected at the bottom of the furnace, and the method generates waste gas.

[0022] Plasma torches generate thermal plasma using direct current (DC), alternating current (AC), radio frequency (RF), and other discharge methods. The thermal plasma provides heat; in a DC plasma torch, this heat is generated by sending an electric arc between two electrodes through which a carrier gas passes within a narrow opening. This raises the gas temperature to the point value at which it enters the fourth state of matter (i.e., plasma). Plasma torches can be transferred or non-transferred. In a non-transferred DC plasma torch, the electrodes are located inside the torch housing. In a transferred plasma torch, one electrode is located outside the torch housing, allowing the electric arc to form on the outside of the plasma torch and at a greater distance. Preferably, the plasma torch of this invention is a non-transferred plasma torch. Most preferably, a DC non-transferred plasma torch is used.

[0023] Plasma torches can use various carrier gases, such as oxygen, nitrogen, argon, helium, air, hydrogen, or mixtures thereof. In this invention, the carrier gas is selected from the group consisting of nitrogen, carbon monoxide, carbon dioxide, and mixtures thereof. Preferably, the carrier gas is nitrogen. It has been found that removing oxygen from a cupola furnace area containing nitrogen at a temperature of 1,400°C or higher significantly reduces NO. X The generation of NO. To help reduce NO production. X The carrier gas should contain at most trace amounts of oxygen. This means that, based on the total weight of the carrier gas, it should contain less than 5% by weight of oxygen, for example, less than 2% by weight, preferably less than 0.8% by weight. Ideally, the carrier gas should contain no oxygen. This means that at most only trace amounts of oxygen are present.

[0024] The preferred enthalpy of the carrier gas used in the plasma torch is 2.0 kWh / Nm³. 3 Up to 6.0 kWh / Nm 3 The preferred value is 3.0 kWh / Nm 3 Up to 5.0 kWh / Nm 3 .

[0025] Enthalpy is calculated by dividing the measured power by the measured carrier gas flow rate. Enthalpy is related to the control of melt temperature and melt volume.

[0026] The cupola furnace used in the method of the present invention may include a plasma torch. Optionally, it may include multiple plasma torches, such as two, three, four or more plasma torches. The power of each plasma torch is typically in the range of 1MW to 6MW.

[0027] As used herein, unless otherwise stated, the terms "oxygen," "nitrogen," "carbon monoxide," "carbon dioxide," and "hydrogen" refer to O2, N2, CO, CO2, and H2, respectively. The term "NO"... X "is known in the art and includes nitrogen oxides, such as nitric oxide (NO) and nitrogen dioxide (NO2).

[0028] While using a plasma torch to provide heat for a cupola furnace is advantageous, heat can also be provided in other ways. According to the invention, more than 50% of the furnace's heat energy is provided by the plasma torch. It is preferable that a larger amount of the furnace's heat energy is provided by the plasma torch, for example, greater than 60%, preferably greater than 70%, more preferably greater than 80%, and most preferably greater than 90%. The remaining heat energy can be provided, for example, in a conventional manner, i.e., by burning fuel, such as natural gas or coke, in the air supplied through tuyeres. Tuyeres are typically located at the bottom of the oxidation zone. A cupola furnace may include one or more tuyeres, such as two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, or more tuyeres. Nine to thirteen tuyeres are preferred, and eleven tuyeres are more common. In this case, the tuyeres are preferably evenly distributed around the perimeter of the furnace, except at the location of the siphon (melt outlet). In any case, it is preferable that no tuyeres are located in the same area as the plasma torch, i.e., there are no tuyeres in the hot zone. This helps to avoid the presence of oxygen in the cupola furnace area above 1,400°C. Preferably, heating is provided solely by the plasma torch in the hot zone.

[0029] The air vent can be loaded with 70 Nm of material per ton. 3 Up to 250Nm 3 Air velocity supplies air. The air inlets for the cupola are typically located at positions ranging from 0 to a maximum of 1 furnace diameter above the plasma torch. The furnace diameter refers to the inner diameter of the cupola's internal cavity.

[0030] Due to NO under high temperature and high pressure X The oxidant may originate from nitrogen and oxygen, therefore the temperature in the cupola oxidation zone should be below 1,400°C. To further reduce NO... X Preferably, the temperature of the oxidation zone is below 1,300°C, more preferably below 1,200°C, even more preferably below 1,100°C, and still more preferably below 1,000°C, particularly below 900°C, and especially below 800°C. In any case, the temperature of the hot zone should be greater than the temperature of the oxidation zone. This means that the temperature of the hot zone can be above 800°C, preferably above 900°C, more preferably above 1,000°C, more preferably above 1,100°C, more preferably above 1,200°C, more preferably above 1,300°C, and even more preferably above 1,400°C.

[0031] Based on the above, the method of the present invention may reduce the NO contained in the exhaust gas. X The amount is less than 400 ppm, preferably less than 300 ppm, more preferably less than 250 ppm, even more preferably less than 200 ppm, and even more preferably less than 150 ppm.

[0032] Another unexpected benefit of using nitrogen, carbon monoxide, carbon dioxide, or mixtures thereof as carrier gases to heat the hot zone with a plasma torch is that the height of the hot zone can be significantly reduced compared to a corresponding cupola furnace heated by means other than a plasma torch.

[0033] An additional benefit of using a plasma torch is that it significantly reduces the response time required to change the temperature of certain areas of the cupola, particularly the temperature of the molten mineral. Typically, the temperature of the molten mineral can be changed within 20 minutes, preferably within 15 minutes, and more preferably within 10 minutes when using a plasma torch. This is likely faster than temperature changes using other heating methods.

[0034] It has been found that when temperatures exceed 750°C, water should be removed from all areas of the furnace. This minimizes the amount of hydrogen formed and present in the cupola exhaust gas. Preferably, the amount of hydrogen contained in the exhaust gas produced by the furnace is less than 20,000 ppm, preferably less than 10,000 ppm, preferably less than 5,000 ppm, preferably less than 2,000 ppm, preferably less than 1,000 ppm, preferably less than 500 ppm, preferably less than 100 ppm, and preferably less than 50 ppm. Most preferably, there is an undetectable amount of hydrogen in the exhaust gas.

[0035] Because of the use of a plasma torch, the amount of coke used in the cupola can be significantly reduced. For example, the amount of coke used can be less than 80% of the amount used in an equivalent cupola without a plasma torch. Preferably, the amount of coke used is less than 70% of the amount used in an equivalent cupola without a plasma torch, for example, less than 60%, for example, less than 40%, more preferably less than 20%, and most preferably less than 10%. This has the advantage of reducing exhaust emissions, for example, producing less CO and / or CO2 in the exhaust gas.

[0036] The exhaust gases from a cupola furnace heated by a plasma torch may include N2, CO, CO2, and NO. X H2 and N2 are each components of the exhaust gas. The exhaust gas may include other components, such as water and particles, i.e., solid particles of matter. In a specific feature of the first aspect of the invention, the exhaust gas can be used as a whole or in part as a carrier gas in one or more plasma torches. The components of the exhaust gas can be separated before being 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 may include 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 includes the exhaust gas components N2, CO, CO2 or combinations thereof. Alternatively, the carrier gas may contain one exhaust gas component, such as N2, CO or CO2.

[0037] Before being used as a carrier gas, one or more components of the exhaust gas may be purified. Exhaust gas purification preferably removes particles suspended in the exhaust gas and / or water. Purification can be performed on the entire exhaust gas, or on at least one component once separated from the rest of the exhaust gas.

[0038] The carrier gas may consist of waste gas or at least one component of waste gas. Optionally, it may include waste gas or at least one component of waste gas. In the latter case, other gases that do not constitute part of the waste gas may be added to the carrier gas before its use. In this case, the carrier gas is "filled" with other gases. The mineral melt prepared by the method of the present invention is suitable for producing artificial glass fibers, such as glass fibers or stone fibers. Preferably, the formed mineral melt is suitable for forming artificial glass fibers (MMVF). Therefore, a method for producing MMVF is provided in a second aspect of the invention, comprising the following steps:

[0039] (i) Forming a melt using the methods defined herein;

[0040] (ii) fiberizing the melt by internal or external spinning; and

[0041] (iii) Collect the fibers formed.

[0042] Fibers, particularly MMVFs, can be formed from mineral melts in a conventional manner. Typically, they are produced via centrifugal fiber forming processes. For example, fibers can be formed using a rotor process, where the mineral melt is ejected through perforations in the rotor, or the mineral melt can be ejected from a turntable, and fiber forming can be facilitated by injecting gas through the mineral melt. Fiber forming can also be achieved by pouring the mineral melt onto the first rotor in a cascade spinning machine. In this case, it is preferable to pour the mineral melt onto the first rotor in a group of two, three, or four rotors, each rotating about a substantially horizontal axis, wherein the mineral melt on the first rotor is primarily thrown onto the second (lower) rotor, although some may be thrown off the first rotor as fibers; the mineral melt on the second rotor is ejected as fibers, although some may be thrown onto the third (lower) rotor, and so on.

[0043] The preferred spinning process is using a cascade spinning machine.

[0044] The desired properties of mineral melts used in various spinning processes are known in the art, and the composition of the mineral melts can be adjusted to provide these properties. For example, those skilled in the art can select the raw materials to be added to the cupola furnace to produce a specific mineral melt composition.

[0045] Therefore, the melt is formed into a cloud of fibers entrained in the air, the fibers are collected into a fiber web on a conveyor belt, and carried away from the fiberizing device. The fiber web is then consolidated, which may involve cross-laying and / or longitudinal compression and / or vertical compression and / or winding around a mandrel to produce a cylindrical article for pipe insulation. Other consolidation processes may also be implemented.

[0046] The binder composition is typically applied to the fibers, preferably when they are air-entrained clouds. Alternatively, it can be applied after they have been collected onto a conveyor belt, but this is less preferred. Conventional types of binders used with mineral wool fibers can be used.

[0047] After consolidation, the consolidated fiber web is fed into a curing device to cure the adhesive.

[0048] Curing can be carried out at temperatures ranging from 100°C to 300°C, such as 170°C to 270°C, 180°C to 250°C, or 190°C to 230°C.

[0049] Curing is preferably carried out in a conventional curing oven used for mineral wool production, wherein hot air is blown through the solidified mesh, preferably at a temperature of 150°C to 300°C, such as 170°C to 270°C, 180°C to 250°C, or 190°C to 230°C.

[0050] Curing can take anywhere from 30 seconds to 20 minutes, for example, 1 to 15 minutes, or 2 to 10 minutes.

[0051] Typically, curing is carried out at a temperature of 150°C to 250°C for 30 seconds to 20 minutes.

[0052] The curing process can begin immediately after the adhesive is applied to the fibers. Curing is defined as the process by which the adhesive composition undergoes a physical and / or chemical reaction. In the case of a chemical reaction, the molecular weight of the compounds in the adhesive composition typically increases, thereby increasing the viscosity of the adhesive composition, usually until the adhesive composition reaches a solid state. The cured adhesive composition bonds the fibers to form a structurally continuous fibrous matrix.

[0053] The adhesive in contact with the mineral fibers can also be cured in a hot press. Curing the adhesive in contact with the mineral fibers in a hot press has the specific advantage of enabling the production of high-density products.

[0054] Typically, fibers and the mineral melts that form them can have elemental analyses (measured as a weight percentage of oxides) within different ranges defined by the following criteria and preferred lower and upper limits.

[0055]

[0056] In this case, it is preferable that, when the melt is to form an MMVF, the proportion of Fe(2+) in the mineral melt is greater than 80%, preferably at least 90%, more preferably at least 95%, and most preferably at least 97%, based on total Fe. In this case, it is preferable to use a cascade spinning machine to produce the MMVF. Further details of these mineral melt examples can be found in WO 2012 / 140173 (which is incorporated herein by reference).

[0057] As is commonly known in the art, the FeO in the mineral melt or fibrous composition mentioned herein refers to the total amount of iron in the melt or composition (calculated as FeO), and is independent of the amount of various oxidation states of iron present in the composition.

[0058] In the examples of the above-described mineral melt and the resulting fibers, the amount of iron in the mineral melt is preferably 2% to 15% by weight, more preferably 5% to 12% by weight. Cupola furnaces often 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 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 it possible to produce final product fibers that include a large amount of iron oxide.

[0059] The method of the present invention can be used to form fibers that have been shown to be soluble in physiological saline. Suitable high-alumina, biosoluble fibers can be advantageously produced using the methods of the present invention as described in WO96 / 14454 and WO96 / 14274, and other methods as described in WO97 / 29057, DE-U-2970027 and WO97 / 30002 (which are incorporated herein by reference).

[0060] This fiber preferably has sufficient solubility in pulmonary fluid, as demonstrated by in vivo or in vitro tests typically performed in physiological saline buffered to approximately pH 4.5. Suitable solubility is described in WO 96 / 14454. Typically, the dissolution rate in this saline is at least 10 nm or 20 nm per day. The fiber preferably has a sintering temperature 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, more 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).

[0061] Preferably, the mineral melt in this particular example has a viscosity in the range of 10 poise to 30 poise at 1,400°C, more preferably in the range of 20 poise to 25 poise. The advantage of choosing these viscosities is that a higher melt viscosity results in a smaller diameter MMVF. Furthermore, 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 rotors used for fiber production, as a lower melt temperature results in less wear. Further details of the mineral melt in this example can be found in WO 2015 / 055758 (which is incorporated herein by reference). The viscosity of the melt can be determined according to ASTM C 965-96.

[0062] The cupola furnace useful in the method of the present invention may include the components and areas described above, and may also include the following components and areas. Typically, the mineral melt forms a melt pool in the hot zone and flows out of the pool through a siphon to the fiber forming process. The mineral melt may enter another chamber from the bottom of the cupola furnace, where it is collected to form a melt pool, and flows out of that chamber to the fiber forming process.

[0063] The raw material can be in the form of briquettes. Briquettes are made in a known manner by molding a mixture of the desired granular material and binder into the desired briquette shape and curing the binder.

[0064] 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 substitutes for cement, and examples include lime, blast furnace slag powder and certain other slags, and even cement kiln dust and ground MMVF agglomerates (J PA-51075711, US 4,662,941 and US 4,724,295, each incorporated herein by reference). Alternative binders include clay. Briquetting can also be formed using organic binders such as molasses, for example as described in WO 95 / 34514 (which is included herein by reference). Such briquetting can be described as formstones.

[0065] In a third aspect of the invention, a cupola furnace is provided for preparing a melt according to the method of the first aspect of the invention. The cupola furnace may include the features described above.

[0066] In a fourth aspect of the invention, a method is provided for reducing NO in exhaust gas using a plasma torch, compared to corresponding methods where the plasma torch carrier gas is air or oxygen. X The use of reducing the amount of NO, CO, CO2, and / or hydrogen in exhaust gases. Preferably, the use is to reduce NO in exhaust gases. X And / or the amount of hydrogen.

[0067] MMVF can be formed as an adhesive web comprising MMVF as described above, or MMVF produced according to the method described above, or MMVF produced using the equipment described above, and a cured adhesive composition.

[0068] The melt formed according to the method of the present invention, and the man-made fibers (preferably MMVF) produced therefrom, are applicable to a range of products, such as insulating elements (thermal and / or acoustic insulating elements) and fire-resistant insulating elements.

[0069] The invention will be described in further detail with reference to the accompanying drawings, which illustrate a furnace for carrying out the method according to the invention.

[0070] Figure 1 The accompanying drawings show a cupola 1 with a feed hopper 2 communicating with a container 3 having a bottom formed by an axially movable cone 4. Below the container 3 is a melting chamber, which is enclosed by a water-cooled jacket 5. The cupola 1 includes a flat furnace bottom 6 at its lower end, and a melt outlet 7 is provided at a suitable distance above the bottom 6. Multiple plasma torches 8 are constructed within the furnace wall, extending a distance above the level where the melt outlet 7 is located. An annular air inlet 9 is provided at an even higher level, communicating with multiple tuyeres 10. The cupola 1 has a brick lining in the hot zone. The lining covers the furnace bottom 6 and the inner furnace wall to at least the height of the tuyeres 10.

[0071] Solid materials (i.e., raw materials) with a composition corresponding to the desired melt composition are fed into the melting chamber through hopper 2 and container 3, and the amount is affected by adjusting cone 4 appropriately. Carbonaceous materials, such as coke, can be added together with the solid materials as needed.

[0072] Because the material is heated by the rising flue gas, the upper part of the melting chamber serves as a preheating zone. From the preheating zone, the material descends through the furnace's oxidation zone, the lower limit of which is at the level where air is introduced through tuyeres 10. Coke burns in the oxidation zone to form CO2. The temperature of the oxidation zone is maintained at a level such that the temperature of the preheating zone portion directly above the upper end of the oxidation zone does not exceed 1000°C to eliminate or significantly reduce the reaction between the CO2 formed in the oxidation zone and carbon, thereby forming CO. Actual melting takes place in the melting chamber portion located below the oxidation zone, where intense heat is introduced through a plasma torch 8. The resulting melt descends to the bottom of the furnace and is discharged through melt outlet 7. Detailed Implementation

[0073] Example

[0074] The invention is further illustrated by the following non-limiting embodiments.

[0075] A melt is formed in a cupola furnace that burns plasma, where the plasma torch is supplied with either air or N2 as the carrier gas. The table below shows the cupola conditions for various types of carrier gases, and the composition of the exhaust gas (in % or ppm by volume). When air is used as the carrier gas, it is necessary to reduce NO. X The formation of this process is most clearly achieved through the introduction of liquid propane gas (LPG) and a carrier gas via a plasma torch. This explains the differences in power and carrier gas flow at the plasma torch. The varying air volumes at the vents are caused by these different operating conditions.

[0076]

[0077]

[0078] Data shows that when N2 is used as the carrier gas, the amounts of various components in the listed exhaust gas are significantly reduced. In particular, the amount of NO present in the exhaust gas is reduced. X The amount of H2 is significantly reduced. When N2 is used as the carrier gas, the amount of H2 generated is below the detection limit of the equipment.

Claims

1. A method for preparing mineral melt in a cupola furnace, wherein: The cupola furnace includes at least two temperature zones, comprising a hot zone at the bottom of the cupola furnace and an oxidation zone above the hot zone. (i) The cupola furnace is equipped with at least one tuyeres in the oxidation zone to provide an oxygen source; (ii) The cupola includes at least one plasma torch that uses nitrogen, carbon monoxide, carbon dioxide or a mixture thereof as a carrier gas and provides plasma heating in the hot zone; (iii) The plasma torch provides more than 50% of the heat energy of the cupola; (iv) The temperature of the oxidation zone is below 1,400°C; (v) The temperature of the hot zone is greater than the temperature of the oxidation zone; (vi) Water is essentially excluded from any area of ​​the cupola furnace where the temperature is above 750°C; and The mineral material is fed into the cupola and melted to form the mineral melt collected at the bottom of the cupola, and the method generates exhaust gas.

2. The method of claim 1, wherein more than 60% of the thermal energy of the cupola is provided by the plasma torch.

3. The method of claim 2, wherein more than 70% of the thermal energy of the cupola is provided by the plasma torch.

4. The method of claim 3, wherein more than 80% of the thermal energy of the cupola is provided by the plasma torch.

5. The method of claim 4, wherein more than 90% of the heat energy of the cupola is provided by the plasma torch.

6. The method of claim 1, wherein the temperature of the oxidation zone is below 1300°C.

7. The method of claim 6, wherein the temperature of the oxidation zone is below 1200°C.

8. The method of claim 7, wherein the temperature of the oxidation zone is below 1100°C.

9. The method of claim 8, wherein the temperature of the oxidation zone is below 1000°C.

10. The method of claim 9, wherein the temperature of the oxidation zone is below 900°C.

11. The method of claim 10, wherein the temperature of the oxidation zone is below 800°C.

12. The method of any one of claims 1 to 11, wherein heating in the hot zone is provided solely by the plasma torch.

13. The method of any one of claims 1 to 11, wherein the temperature of the hot zone is above 800°C.

14. The method of claim 13, wherein the temperature of the hot zone is higher than 900°C.

15. The method of claim 14, wherein the temperature of the hot zone is higher than 1,000°C.

16. The method of claim 15, wherein the temperature of the hot zone is higher than 1,100°C.

17. The method of claim 16, wherein the temperature of the hot zone is higher than 1,200°C.

18. The method of claim 17, wherein the temperature of the hot zone is higher than 1,300°C.

19. The method of claim 18, wherein the temperature of the hot zone is above 1,400°C.

20. The method of any one of claims 1 to 11, wherein the enthalpy of the carrier gas is 2.0 kWh / Nm 3 to 6.0 kWh / Nm 3 .

21. The method of claim 20, wherein the enthalpy of the carrier gas is 3.0 kWh / Nm 3 to 5.0 kWh / Nm 3 .

22. The method of any one of claims 1 to 11, wherein the melt has a composition expressed as oxides, in weight percent, SiO2 35-50 Al2O3 12-30 TiO2 at most 2 Fe2O32-12 CaO 5-30 MgO 0-15 Na2O 0-15 K2O 0-15 P2O5 0-3 MnO 0-3 B2O3 0-3, Based on total Fe, the proportion of Fe(2+) in the melt is greater than 80%.

23. The method of claim 22, wherein the SiO2 content is 38-48% by weight.

24. The method of claim 23, wherein the SiO2 content is 33-44% by weight.

25. The method of claim 22, wherein the Al2O3 is 15-28% by weight.

26. The method of claim 25, wherein the Al2O3 is 16-24% by weight.

27. The method of claim 22, wherein the CaO content is 5-18% by weight.

28. The method of claim 27, wherein the MgO content is 1-8% by weight.

29. The method of claim 22, wherein the proportion of Fe(2+) in the melt is at least 90%.

30. The method of claim 29, wherein the proportion of Fe(2+) in the melt is at least 95%.

31. The method of claim 30, wherein the proportion of Fe(2+) in the melt is at least 97%.

32. The method of any one of claims 1 to 11, wherein the exhaust gas generated by the cupola furnace comprises: (a) NO X Its amount is less than 400 ppm; and / or (b) Hydrogen, in amounts less than 20,000 ppm.

33. The method of claim 32, wherein NO X The amount is less than 300 ppm.

34. The method of claim 33, wherein NO X The amount is less than 250 ppm.

35. The method of claim 34, wherein NO X The amount is less than 200 ppm.

36. The method of claim 35, wherein NO X The amount is less than 150 ppm.

37. The method of claim 32, wherein the amount of hydrogen is less than 10,000 ppm.

38. The method of claim 37, wherein the amount of hydrogen is less than 5,000 ppm.

39. The method of claim 38, wherein the amount of hydrogen is less than 2,000 ppm.

40. The method of claim 39, wherein the amount of hydrogen is less than 1,000 ppm.

41. The method of claim 40, wherein the amount of hydrogen is less than 500 ppm.

42. The method of claim 41, wherein the amount of hydrogen is less than 100 ppm.

43. The method of claim 42, wherein the amount of hydrogen is less than 50 ppm.

44. The method of claim 43, wherein there is no detectable amount of hydrogen in the exhaust gas.

45. The method of any one of claims 1 to 11, wherein the carrier gas is nitrogen.

46. ​​The method of any one of claims 1 to 11, wherein the carrier gas comprises at least one component of the exhaust gas.

47. The method of claim 46, wherein at least one component of the exhaust gas is purified before it is used as a carrier gas.

48. The method of claim 47, wherein the exhaust gas purification is the removal of particulate matter and / or water.

49. The method of claim 46, wherein the carrier gas comprises at least one component of the exhaust gas.

50. The method of claim 47, wherein the carrier gas comprises at least one component of the exhaust gas.

51. A method for manufacturing artificial glass fibers, comprising the following steps: (i) Forming a melt using the method defined in any one of claims 1 to 50; (ii) The melt is fiberized by internal or external spinning. and (iii) Collect the fibers formed.

52. The method of manufacturing artificial glass fibers as claimed in claim 51, wherein the melt is fiberized by using cascaded spinnerets.

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