Method for manufacturing molten material for artificial mineral fibers

Abstract

The present invention relates to a method for producing a mineral melt in a hot metal furnace using at least one plasma torch to supply thermal energy to the furnace. The plasma torch uses nitrogen, carbon monoxide, carbon dioxide or mixtures thereof as carrier gas. The invention also relates to a hot metal furnace for the production of a mineral melt and to the use of a plasma torch in a hot metal furnace to reduce the amount of NOx and / or hydrogen in the furnace off-gas.

Description

[Technical Field]

[0001] The present invention relates to a method for producing molten minerals in a molten iron furnace 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] The method for producing mineral molten materials for manufacturing artificial mineral fibers (MMVF) is known to be carried out in shaft-type furnaces such as molten iron furnaces. This method involves heating mineral materials in the presence of coke and oxygen-containing gases to form a mineral molten material. It is difficult to produce mineral molten materials in a process that reduces harmful emissions in the off-gas of the molten iron furnace.

[0003] A molten iron furnace typically includes various temperature zones, including a hot zone, an oxidation zone, a reduction zone, and a preheating zone.

[0004] The lower part of the molten iron furnace constitutes the hot zone. The hot zone contains the molten mineral formed within the furnace, which is located at the bottom of the furnace, in the space between the coke pieces supporting the material above. In a typical molten iron furnace, the temperature of the molten material in the hot zone is in the range of 1450°C to 1550°C, and it takes a relatively long time to change the temperature of the molten mineral material at this location. Furthermore, the distance between the top and bottom of the hot zone is relatively long. This is necessary to ensure that the correct oxidation zone temperature is maintained in conventional molten iron furnaces.

[0005] The oxidation zone (also known as the combustion zone) is located above the hot zone. Below the oxidation zone are gas inlet nozzles, typically known as tuyeres, through which preheated air or another oxidizing gas is introduced into the furnace. Heating is usually achieved by the combustion of coke. This combustion occurs as the preheated air rises through the oxidation zone, raising the gas temperature to approximately 500°C to 2,000°C, thereby heating the raw materials moving downward through the oxidation zone to their melting point. This molten mineral material flows down into the hot zone at the base of the molten iron furnace. The longitudinal extent of the oxidation zone is determined by the amount of oxygen introduced into the furnace.

[0006] The reduction zone is above the oxidation zone and begins at the level where oxygen introduced through the tuyeres is consumed by the combustion of coke. In the reduction zone, the temperature is typically 1,000°C to 1,500°C, and the coke reacts with the CO2 formed in the oxidation zone to form twice the amount of CO2 consumed by volume.

[0007] This reaction is endothermic, with approximately 20-25% of the energy released by combustion in the oxidation zone being lost as latent heat of the off-gas. A typical example is the use of off-gas to preheat raw materials intended for melting in a molten iron furnace. The preheating zone is located above the reduction zone.

[0008] International Publication No. 87 / 06926 relates to a method for producing molten minerals in which part of the heating can be supplied by the use of a plasma torch. In this method, CO in the off-gas is reduced. This can be achieved by supplying at least two-thirds of the furnace heating energy using coke. The remainder can be supplied by a plasma torch, among several methods. No distinction has been made regarding carrier gases suitable for use with the plasma torch.

[0009] While there are advantages to using a plasma torch to supply some of the thermal energy to a furnace, the inventors argue that when a plasma torch using air as a carrier gas is used to form mineral molten materials, relatively high amounts of NO, such as up to 7,000-10,000 ppm, can be produced. x We have found that off-gas containing NO is formed. x It is harmful to both the environment and animals, including humans. This is usually mitigated by adding reducing agents such as hydrocarbon gases. Such off-gases from molten iron furnaces still contain over 3,100 ppm of NO. x It may contain [something], which is several times higher than the limits in many countries. Therefore, NO x It will be necessary to provide a cleaning system to minimize the release of these gases into the atmosphere. Furthermore, hydrogen can account for up to 20% of the off-gas generated from molten iron furnaces heated by plasma torches using air as a carrier gas. This poses an explosion risk to the furnace. [Overview of the project] [Problems that the invention aims to solve]

[0010] A method for producing a mineral molten material suitable for use in the formation of MMV fibers such as glass fibers or stone fibers, wherein the process does not produce NO in the off-gas of the molten iron furnace, even when a plasma torch is used. x It is desirable to provide a manufacturing method that minimizes the amount of H2. It is also desirable to minimize the amount of coke used in such a process. Furthermore, it is desirable to shorten the distance between the bottom and top of the hot zone, in particular to provide a more compact shaft-type furnace. In addition, it may be beneficial to minimize the time required to change the temperature of the molten mineral. [Means for solving the problem]

[0011] Such advantages can be achieved by using a plasma torch to supply more than 50% of the heating energy to the molten iron furnace, which uses nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), or a mixture thereof as a carrier gas, and water is removed from any zone of the molten iron furnace that is above 750°C. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows a schematic diagram of the configuration of a molten iron furnace that may be used in carrying out the present invention. [Modes for carrying out the invention]

[0013] In a first aspect of the present invention, a method for producing a molten mineral in a molten iron furnace is provided, the molten iron furnace comprising at least two temperature zones, including a hot zone at the base of the furnace and an oxidation zone above the hot zone. (i) The furnace is equipped with at least one tuyeres that supply an oxygen source to the oxidation zone, (ii) The furnace comprises at least one plasma torch that supplies plasma heating to a hot zone using nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof as a carrier gas, (iii) More than 50% of the furnace heating energy is supplied by a plasma torch, (iv) The temperature in the oxidation zone is less than 1,400°C. (v) The temperature of the hot zone is higher than the temperature of the oxidation zone. (vi) Water is substantially removed from any zone of the furnace where the temperature exceeds 750°C. Mineral material is supplied to the furnace, melted, and forms a molten mineral that is recovered at the base of the furnace; this method generates off-gas.

[0014] Plasma torches generate thermal plasma using direct current (DC), alternating current (AC), radio frequency (RF), and other discharges. Thermal plasma supplies heat. In the case of a DC plasma torch, an electric arc is sent between two electrodes, and heat is generated by passing a carrier gas through the arc within a constricted opening. As a result, the temperature of the gas rises to the point where the gas becomes the fourth state of matter, i.e., plasma. The plasma torch may be a transferred type or a non-transferred type. In the case of a non-transferred DC plasma torch, the electrodes are inside the torch housing. On the other hand, in the case of a transferred plasma torch, one electrode is located outside the torch housing, whereby the arc can be formed outside the plasma torch over a longer distance. The plasma torch of the present invention is preferably a non-transferred plasma torch. Most preferably, it is a DC non-transferred plasma torch.

[0015] Plasma torches can use various carrier gases such as oxygen, nitrogen, argon, helium, air, hydrogen, or mixtures thereof. In the present 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 excluding oxygen from the zone of a hot metal furnace containing nitrogen and at a temperature of 1400 °C or higher can significantly reduce the formation of NO x . To minimize the formation of NO x , it is desirable that the carrier gas contains at most a trace amount of oxygen. That is, the carrier gas should contain less than 5% by weight, for example less than 2% by weight, preferably less than 0.8% by weight of oxygen based on the total weight of the carrier gas. Ideally, the carrier gas contains no oxygen at all. This means that there is at most a trace amount of oxygen present.

[0016] The enthalpy of the carrier gas used in the plasma torch is preferably 2.0 - 6.0 kWh / Nm 3 , preferably 3.0 - 5.0 kWh / Nm 3 .

[0017] The enthalpy is calculated by dividing the measured output by the measured carrier gas flow rate. The enthalpy is important for controlling the melting temperature and the melting capacity.

[0018] The molten iron furnace useful in the method of the present invention may comprise one plasma torch. As another option, it may comprise a plurality of plasma torches, such as two, three, four, or more plasma torches. The output of each plasma torch typically ranges from 1 to 6 MW.

[0019] As used herein, and unless otherwise specified, the terms "oxygen", "nitrogen", "carbon monoxide", "carbon dioxide", and "hydrogen" mean O2, N2, CO, CO2, and H2, respectively. "NO x " The term is known in the art and includes nitrogen oxides such as nitric oxide (NO) and nitrogen dioxide (NO2).

[0020] Despite the benefits of using a plasma torch to supply thermal energy to a molten iron furnace, the thermal energy may be supplied by other alternative means. According to the present invention, more than 50% of the furnace heating energy is supplied by the plasma torch. It may be preferable that a larger amount of the furnace heating, such as more than 60%, preferably more than 70%, more preferably more than 80%, and most preferably more than 90%, is supplied by the plasma torch. The remainder of the thermal energy may be supplied by conventional methods, for example, by burning a fuel such as natural gas or coke in air supplied from a tuyere. The tuyere is typically located at the bottom of the oxidation zone. A molten iron furnace may have one or more tuyeres, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more. It is preferable that there be 9 to 13 tuyeres, and most preferably 11. In this case, it is preferable that the tuyeres are evenly distributed along the perimeter of the furnace, except for the location of the siphon (molten metal outlet). In any case, it is preferable that the tuyeres are not located in the same zone as the plasma torch, i.e., that there are no tuyeres in the hot zone. This helps to avoid the presence of oxygen in the molten iron furnace zone where the temperature exceeds 1,400°C. It is preferable that heating is supplied to the hot zone by the plasma torch alone.

[0021] The tuyeres produce 70-250 Nm³ of fuel per ton of input. 3 Air can be supplied at this airflow rate. The openings of each tuyeres through which air flows into the molten iron furnace are typically positioned above the plasma torch by 0 to a maximum of 1 furnace diameter. The furnace diameter is the inner diameter of the internal chamber of the molten iron furnace.

[0022] Under high temperature and high pressure, nitrogen and oxygen produce NO x Because this can be induced, the temperature of the oxidation zone in a molten iron furnace should be kept below 1,400°C. xTo further reduce this, the temperature of the oxidation zone is preferably less than 1,300°C, preferably less than 1,200°C, more preferably less than 1,100°C, even more preferably less than 1,000°C, particularly less than 900°C, and especially less than 800°C. In any case, the temperature of the hot zone should be higher than the temperature of the oxidation zone. This means that the temperature of the hot zone may be greater than 800°C, preferably greater than 900°C, more preferably greater than 1,000°C, more preferably greater than 1,100°C, more preferably greater than 1,200°C, more preferably greater than 1,300°C, and more preferably greater than 1,400°C.

[0023] Based on the above, the method of the present invention is NO x This can result in an off-gas with a content of 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.

[0024] A further unexpected benefit of heating the hot zone with a plasma torch using a carrier gas such as nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof is that the height of the hot zone can be significantly reduced compared to the corresponding molten iron furnace heated by means other than a plasma torch.

[0025] The use of a plasma torch offers further advantages in that it significantly reduces the response time required to change the temperature of a specific zone in a molten iron furnace, particularly the temperature of the molten mineral. Typically, using a plasma torch, the temperature of the molten mineral can be changed within 20 minutes, preferably within 15 minutes, and more preferably within 10 minutes. This can be a faster temperature change than when other heating means are used.

[0026] It was found that water should be removed from any zone of the furnace where the temperature exceeds 750°C. This minimizes the amount of hydrogen formed and present in the off-gas of the molten iron furnace. The amount of hydrogen in the off-gas generated by the furnace is preferably 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, no detectable amount of hydrogen is present in the off-gas.

[0027] The use of a plasma torch can significantly reduce the amount of coke used in a molten iron furnace. For example, the amount of coke used may be less than 80% of the amount used in a comparable molten iron furnace without a plasma torch. Preferably, the amount of coke used is less than 70%, such as less than 60% of the amount used in a comparable molten iron furnace without a plasma torch, for example, less than 40%, more preferably less than 20%, and most preferably less than 10%. This has the advantage of reducing emissions in the off-gas, for example, reducing the generation of CO and / or CO2 in the off-gas.

[0028] Off-gases from molten iron furnaces heated using plasma torches include N2, CO, CO2, and NO. x It may include H2, and these are components of the off-gas. The off-gas may further include water and particles, i.e., solid particles of matter. In certain features of the first aspect of the present invention, the off-gas may be used as a carrier gas for one or more plasma torches, either as a whole or in part. The components of the off-gas used as a carrier gas They may be separated before being released. The components of the off-gas may be separated from each other, or a combination of two or more components may be separated from other components. This means that the carrier gas may contain at least one component of the off-gas, such as component 1, 2, 3, 4, 5, or more of the off-gas. Preferably, the carrier gas contains off-gas components N2, CO, CO2, or a combination thereof. Alternatively, the carrier gas may contain one off-gas component such as N2, CO, or CO2.

[0029] One or more components of the off-gas may undergo off-gas washing before being used as a carrier gas. Off-gas washing is preferably done to remove suspended particles and / or water in the off-gas. Off-gas washing may be performed on the entire off-gas, or on at least one of its components after it has been separated from the rest of the off-gas.

[0030] The carrier gas may consist of an off-gas or at least one component of the off-gas. Alternatively, it may contain an off-gas or at least one component of the off-gas. In the latter case, additional gases that did not form part of the off-gas may be added to the carrier gas before use. In this case, the carrier gas is “replenished” with the additional gas. The mineral molten product produced by the method of the present invention may be suitable for the production of artificial glassy fibers such as glass fibers or stone fibers. The mineral molten product formed is preferably suitable for use in forming artificial glassy fibers (MMVF). Therefore, in a second aspect of the present invention, a method for producing MMVF is provided, the method is: (i) A step of forming a molten material using a method specified herein, (ii) A step of converting the molten material into fibers by an internal or external spinning process, and (iii) A process for recovering the formed fibers, Includes.

[0031] Fibers, particularly MMVF, can be produced from mineral molten materials by conventional methods. Generally, they are produced by centrifugal fiber formation processes. For example, fibers may be formed by a spinning cup process, which ejects the fibers outward from the perforations of a spinning cup, or fiber formation may be accelerated by ejecting the mineral molten material from a rotating disk and injecting a gas jet through the mineral molten material. Fiber formation may also be carried out by pouring the mineral molten material onto a first rotor of a cascade spinner. In this case, it is preferable that the mineral molten material is poured onto the first rotor in a set of two, three, or four rotors, each rotating substantially horizontally, so that some of the mineral molten material on the first rotor can be ejected as fibers from the first fiber rotor, but mainly onto the second (lower) rotor, and that some of the mineral molten material on the second rotor can be ejected as fibers, but some onto the third (lower) rotor, and so on.

[0032] The spinning process preferably uses a cascade spinning machine.

[0033] The properties required of the mineral molten material used in each spinning method are known to those skilled in the art, and the composition of the mineral molten material can be adjusted to obtain those properties. For example, those skilled in the art can select the raw materials to be fed into the molten iron furnace to obtain a specific mineral molten material composition.

[0034] The molten material then forms a cloud of fibers that are absorbed into the air, and the fibers are collected as a web on a conveyor and carried out of the fiberization equipment. The fiber web is then solidified, which involves winding onto a mandrel to produce cylindrical products for cross-wrapping and / or longitudinal compression and / or vertical compression and / or pipe insulation. This may include other solidification processes.

[0035] The binder composition is conventionally applied to the fibers, preferably when the fibers are in a cloud-like state, incorporated into the air. Alternatively, the binder composition may be applied after the fibers have been collected on a conveyor, but this is less preferred. Conventional binders may be used for mineral wool fibers.

[0036] After solidification, the solidified fiber web is sent to a curing machine to harden the binder.

[0037] Curing can be carried out at temperatures ranging from 100 to 300°C, such as 170-270°C, 180-250°C, or 190-230°C.

[0038] The curing is preferably carried out in a conventional curing oven for mineral wool production, which is preferably operated at a temperature of 150-300°C, such as 170-270°C, 180-250°C, or 190-230°C, and hot air is blown through the solidified web.

[0039] Curing can take place over a period of 30 seconds to 20 minutes, such as 1 to 15 minutes or 2 to 10 minutes.

[0040] Typically, curing takes place at a temperature of 150-250°C over a period of 30 seconds to 20 minutes.

[0041] The curing process may be initiated immediately after the binder is applied to the fibers. Curing is defined as the process by which the binder composition undergoes physical and / or chemical reactions, which, in the case of chemical reactions, increase the viscosity of the binder composition, usually by increasing the molecular weight of the compounds in the binder composition, and which continues, usually until the binder composition reaches a solid state. The cured binder composition binds the fibers together to form a structurally aggregated matrix of fibers.

[0042] Alternatively, the hardening of the binder in contact with the mineral fibers may be carried out by hot pressing. Hardening of the binder by hot pressing in contact with the mineral fibers has the particular advantage of enabling the production of high-density products.

[0043] Generally, fibers and the mineral molten materials in which the fibers are formed may have elemental analysis values ​​(measured as weight % of oxides) within a range of various limits defined by the following standard preferred lower and upper limits. SiO235-50, preferably 38-48, more preferably 33-44 Al2O312-30, preferably 15-28, more preferably 16-24 Up to TiO22 Fe2O32~12 CaO 5-30, preferably 5-18 MgO 0-15, preferably 1-8 Na2O 0~15 K2O 0-15 P2O50~3 MnO 0~3 B2O30~3

[0044] When MMVF is formed from the molten material, the proportion of Fe(2+) in the mineral molten material is In this case, it is preferable that the total Fe content be greater than 80%, preferably at least 90%, more preferably at least 95%, and most preferably at least 97% based on total Fe. In such cases, the MMVF is preferably produced using a cascade spinning machine. Further details of these mineral melts can be found in International Publication No. 2012 / 140173 (incorporated herein by reference).

[0045] As is customary in the Art, any reference herein to FeO in a mineral molten or fibrous composition means the total amount of iron (calculated as FeO) in the molten or composition, regardless of the amount of each oxidation state of iron present in the composition.

[0046] In the above examples of mineral molten materials and resulting fibers, the amount of iron in the mineral molten material is 2 to 15% by weight, preferably 5 to 12% by weight. Molten iron furnaces tend to have a reducing atmosphere, which can lead to the reduction of iron oxide and the formation of metallic iron. Preferably, metallic iron should not be incorporated into the mineral molten material 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, the inventors have found that it is possible to produce fibers in the final product having a significant level of iron oxide.

[0047] The method of the present invention can be used to form fibers that can be soluble in physiological saline. Suitable high-aluminum biosoluble fibers that can be advantageously produced using the method of the present invention are described in International Publication Nos. 96 / 14454 and 96 / 14274, as well as in International Publication Nos. 97 / 29057, German Utility Model No. 2970027(U), and International Publication No. 97 / 30002 (these are incorporated herein by reference).

[0048] Such fibers preferably have adequate solubility in lung fluid, as demonstrated by in vivo testing or in vitro testing, typically performed in physiological saline buffered to approximately pH 4.5. Adequate solubility is described in International Publication No. 96 / 14454. Typically, the dissolution rate is at least 10 or 20 nm per day in its physiological saline. The fibers preferably have a sintering temperature above 800°C, more preferably above 1,000°C. The molten material preferably has a viscosity of 5 to 100 poise at the fiber formation temperature, preferably 10 to 70 poise at 1,400°C. Further embodiments of this example can be found in International Publication No. 99 / 28252 (incorporated herein by reference).

[0049] Preferably, the mineral melt in this particular example has a viscosity in the range of 10 to 30 poise at 1400°C, more preferably in the range of 20 to 25 poise. The advantage of selecting these viscosities is that the resulting MMVF has a smaller diameter than when the viscosity of the melt is higher. Furthermore, it is possible to use the melt at a lower temperature to achieve the required operating viscosity. This results in energy savings because the melt can be used at a lower temperature. Also, since a melt at a lower temperature reduces the wear that occurs, wear on the rotor used in the production of fibers is reduced. Further details of the mineral melt as an example can be found in International Publication No. 2015 / 055758 (incorporated herein by reference). The viscosity of the melt may be specified according to ASTM C965-96.

[0050] A molten iron furnace useful for the method of the present invention may have the above-described components and zones in addition to the following. Typically, the molten mineral forms a pool in the hot zone, and the molten material flows out of the pool via a siphon to the fiber formation process. The molten mineral may also flow from the base of the molten iron furnace to another chamber, in which the molten material is collected as a pool and flows out of the pool to the fiber formation process.

[0051] The raw materials may be in the form of briquettes. Briquettes are manufactured by known methods, which involve molding a mixture of the desired particulate material and a binder into the desired briquette shape and curing the binder.

[0052] The binder may be a hydraulic binder, i.e., a binder activated by water, such as Portland cement. Other hydraulic binders may be used as a partial or complete substitute for cement, examples of which include lime, blast furnace slag powder, and certain other slags, as well as cement kiln dust and crushed MMVF shot (Japanese Patent Publication No. 51-075711, U.S. Patent No. 4,662,941, and U.S. Patent No. 4,724,295, respectively, incorporated herein by reference). Another binder option is clay. Briquettes may be formed using an organic binder such as molasses, as described, for example, in International Publication No. 95 / 34514 (included herein by reference). Such briquettes may be described as formstones.

[0053] A third aspect of the present invention provides a molten iron furnace for producing a molten product according to the method of the first aspect of the present invention. The molten iron furnace may have the features already described herein.

[0054] In a fourth aspect of the present invention, NO in the off-gas is compared to the corresponding process in which the carrier gas of the plasma torch is air or oxygen. x The use of a plasma torch in a molten iron furnace is provided to reduce the amount of CO, CO2, and / or hydrogen. Preferably, this use is used to reduce NO in the off-gas. x And / or to reduce the amount of hydrogen.

[0055] The MMVF may be formed as a bound web comprising the MMVF described above, or MMVF manufactured according to the method described above, or MMVF manufactured using the apparatus described above, and a cured binder composition.

[0056] The molten material formed according to the method of the present invention, and the resulting artificial fibers (preferably MMVF), can be used in a variety of products such as insulating elements (both thermal and / or soundproofing) and fire-resistant elements.

[0057] The present invention will be described in further detail with reference to drawings showing a furnace for carrying out a method according to the present invention.

[0058] Figure 1 shows a molten iron furnace 1 having a supply hopper 2, which communicates with a vessel 3 having a bottom consisting of an axially movable cone 4. Below the vessel 3 is a molten chamber surrounded by a water-cooled jacket 5. The molten iron furnace 1 has a flat furnace bottom 6 at its lower end, and a molten material outlet 7 is provided at a suitable distance above the bottom 6. Several plasma torches 8 are incorporated at a certain distance above the level where the molten material outlet 7 is located. At a higher level is an annular air inlet pipe 9 communicating with several tuyeres 10. The molten iron furnace 1 has an internal lining in the hot zone, which is made of brick. The lining covers the furnace bottom 6 and the internal furnace walls up to at least the height of the tuyeres 10.

[0059] Solid materials having a composition corresponding to the desired molten material, i.e., raw materials, are supplied to the melting chamber through hopper 2 and container 3, and the input amount is achieved by appropriately adjusting cone 4. Carbonaceous materials such as coke may be added together with the solid materials as needed.

[0060] The upper part of the melting chamber acts as a preheating zone, as the material is heated by the rising smoke gas. From the preheating zone, the material descends through the oxidation zone of the furnace, the lower limit of which is at the level where air is introduced through the tuyeres 10. In the oxidation zone, coke is burned to form CO2. The temperature of the oxidation zone is maintained at a level such that the temperature of the preheating zone located just above the upper end of the oxidation zone does not exceed 1000°C, so that the reaction between the CO2 formed in the oxidation zone and carbon to form CO is eliminated or significantly reduced. Actual melting takes place in the part of the melting chamber located below the oxidation zone, where intense heat is introduced by the plasma torch 8. The formed molten material descends towards the bottom of the furnace and is discharged through the molten material outlet 7. [Examples]

[0061] The present invention is further illustrated by the following examples, which are not limited to this invention.

[0062] The molten metal is formed in a plasma-heated molten iron furnace, in which case either air or N2 is supplied to the plasma torch as a carrier gas. The following table shows the furnace conditions for each type of carrier gas, along with the composition of the exhaust gas (volume % or ppm). When air is used as the carrier gas, it is necessary to reduce NOx formation, which is most clearly done by adding liquid propane gas (LPG) to the plasma torch along with the carrier gas. The differences in plasma torch power and carrier gas flow rate are explained here. The different amounts of air to the tuyeres are caused by these different operating conditions. [Table 1]

[0063] The data shows that the amounts of each listed component in the off-gas are significantly reduced when N2 is used as the carrier gas. In particular, NO present in the off-gas x The amount of H2 has decreased significantly. When N2 was used as the carrier gas, the amount of H2 generated was below the detection limit of the device.

Claims

1. A method for producing molten minerals in a molten iron furnace, The molten iron furnace includes at least two temperature zones, including a hot zone at the base of the furnace and an oxidation zone above the hot zone. (i) The furnace is equipped with at least one tuyeres that supply an oxygen source to the oxidation zone, (ii) The furnace comprises at least one plasma torch that supplies plasma heating to the hot zone using nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof as a carrier gas, (iii) More than 50% of the heating energy of the furnace is supplied by the plasma torch, (iv) The temperature of the oxidation zone is less than 1,400°C. (v) The temperature of the hot zone is higher than the temperature of the oxidation zone, (vi) Water is substantially removed from any zone of the furnace where the temperature exceeds 750°C. A method comprising supplying a mineral material to a furnace, melting it to form a molten mineral material which is recovered at the base of the furnace, and generating an off-gas.

2. The method according to claim 1, wherein more than 60%, preferably more than 70%, more preferably more than 80%, and most preferably more than 90% of the heating energy of the molten iron furnace is supplied by the plasma torch.

3. The method according to claim 1 or 2, wherein the temperature of the oxidation zone is less than 1,300°C, preferably less than 1,200°C, more preferably less than 1,100°C, even more preferably less than 1,000°C, particularly less than 900°C, and especially less than 800°C.

4. The method according to any one of claims 1 to 3, wherein heating is supplied to the hot zone solely by the plasma torch.

5. Any one of claims 1 to 4, wherein the temperature of the hot zone is greater than 800°C, preferably greater than 900°C, more preferably greater than 1,000°C, more preferably greater than 1,100°C, more preferably greater than 1,200°C, more preferably greater than 1,300°C, and more preferably greater than 1,400°C. The method described in item 1.

6. The enthalpy of the carrier gas is 2.0 to 6.0 kWh / Nm³ ３ Preferably 3.0 to 5.0 kWh / Nm ３ The method according to any one of claims 1 to 5.

7. The molten material has the following composition expressed as an oxide in weight percent: SiO ２ 35-50, preferably 38-48, more preferably 33-44 Al ２ O ３ 12 to 30, preferably 15 to 28, more preferably 16 to 24 TiO ２ Up to 2 Fe ２ O ３ 2~12 CaO 5 to 30, preferably 5 to 18 MgO 0 to 15, preferably 1 to 8 Na ２ O0~15 K ２ O 0~15 P ２ O ５ 0~3 MnO 0-3 B ２ O ３ 0~3、 The method according to any one of claims 1 to 6, wherein preferably, the proportion of Fe(2+) in the molten material is greater than 80%, preferably at least 90%, more preferably at least 95%, and most preferably at least 97%, based on total Fe.

8. The aforementioned furnace, (a) NO in an amount of 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. ｘ including and / or (b) containing hydrogen in an amount of 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, preferably less than 50 ppm, and most preferably no detectable amount of hydrogen in the off-gas. The method according to any one of claims 1 to 7, which generates an off-gas containing

9. The method according to any one of claims 1 to 8, wherein the carrier gas is nitrogen.

10. The method according to any one of claims 1 to 9, wherein the carrier gas comprises at least one component of the off-gas.

11. The method according to claim 10, wherein at least one component of the off-gas undergoes off-gas washing before being used as a carrier gas, preferably for the purpose of removing particles and / or water.

12. The method according to claim 10 or 11, wherein the carrier gas consists of at least one component of the off-gas.

13. A method for manufacturing MMVF, (i) A step of forming a molten material using the method described in any one of claims 1 to 12, (ii) A step of converting the molten material into fibers by an internal spinning process or an external spinning process, preferably using a cascade spinning machine, and (iii) A step of recovering the formed fibers, Methods that include...

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