Process for preparing a melt for the production of artificial mineral fibres - Patents.com

Abstract

The present invention relates to a process for preparing a mineral melt in a hot metal furnace, the furnace including a plurality of ceramic supports in a hot zone where the melt collects, together with at least one plasma torch that provides thermal energy to the furnace. The combination of the plasma torch and the ceramic support reduces or substantially eliminates the need for coke to be used in the furnace, thereby reducing the formation of environmentally harmful gases, such as CO and CO2, in the off-gas of the furnace.

Description

[Technical field]

[0001] The present invention relates to a process for preparing a mineral melt in a hot metal furnace, the furnace including a plurality of ceramic supports in a hot zone where the melt collects, together with at least one plasma torch that provides thermal energy to the furnace. The combination of the plasma torch and ceramic supports reduces or substantially eliminates the need for coke to be used in the furnace, thereby reducing the amount of environmentally harmful gases, such as CO and CO, in the off-gas of the furnace. 2 The formation of is reduced. [Background technology]

[0002] Processes for preparing a mineral melt for the production of man-made vitreous fiber (MMVF) are known to be carried out in shaft furnaces, e.g. hot metal furnaces. These processes involve heating mineral materials in the presence of coke and an oxygen-containing gas to form a mineral melt. The use of coke as a means of providing heat in the furnace and as a reducing agent results in the production of significant amounts of CO and CO 2 These have a negative impact on the environment. Considering the role that coke plays in the formation of the mineral melt, CO and CO 2 It is difficult to efficiently produce a melt in a hot metal furnace that reduces or substantially eliminates the production of .

[0003] Coke is also used to support the stack of mineral material (the raw materials used to form the melt) in hot metal furnaces: without this coke support, unmelted mineral material would be found in the melt that collected or pooled at the bottom of the hot zone and would contaminate the melt that was removed from the furnace.

[0004] Hot metal furnaces typically contain a wide range of temperature zones, including a hot zone, an oxidation zone, a reduction zone, and a preheat zone.

[0005] The lower part of the hot metal furnace constitutes the hot zone. The hot zone contains the melt formed in the hot metal furnace, which is typically located in the space between pieces of coke that rest at the bottom of the furnace and support the material upward. In a typical hot metal furnace, the melt temperature in the hot zone ranges from 1450°C to 1550°C, and it takes a relatively long time to change the temperature of the melt at this location. Furthermore, the distance between the top and bottom of the hot zone is relatively large. This is needed to ensure that the correct oxidation zone temperature is maintained in traditional hot metal furnaces.

[0006] An oxidation zone (also known as a combustion zone) typically exists above the hot zone. The lower part of the oxidation zone usually includes a gas inlet nozzle known as a tuyere, through which preheated air or another oxygen-containing gas is introduced into the furnace. Heating is usually generated by the combustion of coke. Coke combustion, together with the combustion of other forms of carbon that may be present in the mineral materials, such as oils and binders contained in the recycled materials, increases the CO2 emission in the furnace. 2 Contributes to the generation of

[0007] Combustion of coke and other carbon sources occurs as the preheated air moves up through the oxidation zone, raising the gas temperature from about 500° C. to about 2,000° C., which can heat the mineral material moving down through the oxidation zone to its melting point. This molten mineral material flows down into a hot zone at the base or bottom of the hot metal furnace. The vertical extent of the oxidation zone is determined by the amount of oxygen introduced into the furnace.

[0008] The reduction zone is located above the oxidation zone, where oxygen introduced through the tuyeres promotes the combustion of the coke. In the reduction zone, where temperatures are typically between 1,000°C and 1,500°C, coke is produced by burning off the CO formed in the oxidation zone. 2 reacts with CO on a volume basis 2 produces twice as much CO as it consumes.

[0009] The reaction is endothermic, resulting in approximately 20-25% of the energy released by combustion in the oxidation zone being lost as latent heat in the off-gas. Typically, the off-gas can be used to heat the mineral material resulting from melting in the hot metal furnace in the pre-heat zone. The pre-heat zone is above the reduction zone.

[0010] US 4,556,418 relates to a process for forming molten iron from scrap iron, scrap steel, pig iron, direct reduced iron or mixtures thereof using enriched air as the primary oxidant. The thermal energy used to form the molten iron comes from natural gas, fuel oil, or pulverized coal. A molten metal bath is generated in the lower part of the furnace. To prevent the molten bath from being cooled by the unmelted parts of the ferrous material, ceramic pieces may be located in the furnace shaft at the lower part of the furnace and above the molten metal bath, for example on a shoulder located around the inner circumference of the shaft furnace. The molten metal may be tapped from the bath via a siphon. The ceramic pieces are not located in the molten bath.

[0011] US 5,107,517 relates to a process for forming a mineral melt for mineral wool production using a melting furnace including a ceramic packing bed and a water-cooled grate above a combustion chamber in which the raw material is located. The bottom part of the combination chamber collects the melt dripping from the shaft. A problem with this design is that water must flow through the grate when the furnace is in use to prevent damage to the grate due to the high temperature environment in the furnace. Heat is applied to the combustion chamber using conventional gas (natural or liquefied) or liquid fuels such as oil. Additional electrical energy may be used to heat the furnace, but this is limited to a maximum of 20% of the total energy required. The melt may be collected via a siphon located at a certain height above the bottom of the combustion chamber and below the level of the water-cooled grate.

[0012] JPH10141629 relates to a method and an apparatus for treating waste by incinerating and pyrolyzing industrial and municipal waste using a vertical melting furnace. Such waste includes wood waste consisting of paper or wood chips, food waste, metal waste from abandoned automobiles, non-combustible waste such as glass and porcelain products, and waste plastic products. As in US5,107,517, the furnace requires the use of a water-cooled tube above the combustion chamber, where refractory material is placed. Heat is applied to the furnace using a conventional gas burner (no mention of electric or plasma heating) in the area below the water-cooled tube, and then ascends through the waste material. This arrangement is designed only to make the molten material drip through the water-cooled tube into the combustion chamber.

[0013] One problem with the furnaces described in US 5,107,517 and JPH 10141629 is that a standard hot metal furnace for preparing the mineral melt must be modified to accommodate water-cooled tubes and a cooling system. The tubes also deteriorate over time and must be replaced, increasing maintenance costs and downtime of the furnace.

[0014] EP2284130 relates to the production of mineral wool from a mineral melt produced in a hot metal furnace. The furnace includes a grate located above a combustion chamber to prevent mineral material from entering the combustion chamber. The melt is formed using heat generated using liquid or gas fuel burners. An outlet for removing the melt from the furnace is located in the combustion chamber.

[0015] WO2019 / 201182 relates to a cast iron smelting apparatus in which heat is applied by a plasma torch. In the furnace, the mineral material is supported on high carbon spheres which are heated by the plasma. Depending on the composition of the spheres and the conditions in the heating plasma, the high carbon spheres will experience significant degradation in use, necessitating their replacement by the addition of further high carbon spheres together with further raw material. The carbon contained within the spheres also contributes to the production of CO and CO in the furnace off-gas. 2This may contribute to the formation of

[0016] Coke plays multiple roles in the formation of the mineral melt, and finding processes that reduce or substantially eliminate the reliance of the process on coke remains a challenge, despite both the environmental and economic advantages of doing so.

[0017] Therefore, there is a need for more efficient, environmentally friendly hot metal furnaces suitable for forming mineral melts, such as MMVFs, e.g., those used to manufacture glass or stone fibers. The reduction or substantial elimination of the amount of coke and / or other carbon sources present in the furnace reduces the harmful CO and CO emissions. 2 There is also a need for a more efficient method of superheating the mineral melt in a molten iron furnace.

[0018] This need is met by using a plasma torch to heat the mineral material (i.e., the raw material used to form the mineral melt) in combination with a number of ceramic supports positioned in the section of the hot zone where the mineral melt gathers before being removed from the furnace. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 shows a schematic diagram of a hot metal furnace configuration that can be used to practice the present invention. Summary of the Invention

[0020] In a first aspect of the invention there is provided a process for preparing a mineral melt in a hot metal furnace, the hot metal furnace comprising a hot zone at the base of the furnace and a melt outlet, preferably a melt siphon, in the hot zone, (i) the furnace includes at least one plasma torch that provides plasma heating in a hot zone; (ii) more than 50% of the furnace heating energy is provided by at least one plasma torch; (iii) the furnace includes a plurality of ceramic supports positioned in a section of the hot zone where the melt collects before being removed from the furnace through a melt outlet; The above process is provided in which mineral material fed into a furnace is melted to form a mineral melt that collects in voids between the ceramic supports.

[0021] In a second aspect of the invention, there is provided a process for producing MMVF, (i) forming a melt using the process defined in the first aspect of the present invention; (ii) fiberizing the melt by an inside or outside spinning process, preferably using a cascade spinner; and (iii) collecting the formed fibers. The process includes: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The advantages of the present invention are achieved by the use of a furnace including a plurality of ceramic supports positioned in a section of the hot zone where the melt collects before the melt is removed from the furnace, along with at least one plasma torch that provides plasma heating in the hot zone. This means that the amount of coke used in the process can be reduced or substantially eliminated, resulting in less CO and CO emissions. 2 This means that it can lead to the generation of

[0023] The ceramic supports are positioned in the section of the hot zone where the melt collects or pools before it is removed from the furnace through a melt outlet, which is preferably a melt siphon. Ideally, the ceramic supports are placed on the inner base of the furnace, but they may also be suspended above the inner base. What is important is that the ceramic supports should be positioned in the furnace such that the melt, once formed, collects (or pools) in the voids between the ceramic supports before its removal. This is an important difference from the furnaces in US 5,107,517 and JPH 10141629, where the melt drips past the ceramic packing / refractory and collects at the base of the furnace, i.e., the melt does not collect in the voids between the ceramic packing / refractory before removal from the furnace.

[0024] The position of the ceramic support in the furnace will also prevent a significant portion of the mineral material from coming into contact with the collected or pooled melt. In this regard, the ceramic support may be used to separate the melt from the raw materials before it is removed from the furnace, for example through a melt outlet, preferably a melt siphon. In traditional hot metal furnaces used to make the melt, this may be achieved using coke. However, in this case it has been found to be an efficient way of filtering the melt in a coke-free process.

[0025] It has also been found that the ceramic support can increase the thermal efficiency when superheating a melt, for example one suitable for the production of MMVF. It is important to deliver the melt at the correct temperature to the next process step, for example to the spinner used to form the MMVF. Once removed from the furnace, the melt will begin to cool, so the melt may be superheated before being removed from the furnace to offset such cooling. Traditional methods of superheating melts are less efficient, especially when coke is present in the pooled melt to support the stack of mineral material. The combination of plasma heating and ceramic support according to the present invention provides more efficient superheating to the pooled melt. Without wishing to be bound by theory, this may be because combining plasma heating and ceramic support means that less CO can be produced in the furnace. The reduction in the amount of CO in the off-gas may increase the thermal efficiency of the furnace, which would mean more efficient superheating of the pooled melt.

[0026] The support may be made of any suitable ceramic type material capable of withstanding the conditions experienced in the furnace. It is understood that many ceramic type materials may be suitable for use in the present invention despite deteriorating over time when used in the furnace. Deterioration may be thermal, chemical or physical. Typically, the deterioration is by melting and / or by reacting with the mineral material used to form the mineral melt. In this regard, it is preferred that the ceramic support has high resistance to high melting temperatures and / or chemical and / or physical deterioration. This increases the durability of the ceramic support, which results in less frequent replacement of such supports.

[0027] Thus, it is preferred that the ceramic support has a melting temperature of at least 1,400° C., preferably at least 1,600° C., and more preferably at least 1,800° C. It will be appreciated that a ceramic support having a higher melting temperature will degrade at a slower rate at the temperatures experienced in the hot zone of a furnace.

[0028] The ceramic support also preferably resists chemical degradation in the hot metal furnace during formation of the melt, which may occur due to reaction between the ceramic support and the mineral materials used to form the melt.

[0029] The ceramic supports will also be resistant to physical degradation, meaning that they will not lose their structural integrity due to forces applied to them, for example the weight of the stack of mineral material, in the furnace at operating temperatures.

[0030] Those skilled in the art will understand the scope of the term "ceramic" within its current usage. Ceramics are often crystalline, but may contain a combination of glass and crystalline phases. Suitable ceramics that may be used to form the support typically include a metal oxide, or more preferably a combination of metal oxides. Suitable metal oxides include, but are not limited to, Al. 2 O 3 , FeO, Fe 2 O 3 , SiO 2 , Cr 2 O 3 , ZrO 2 , MgO, and combinations thereof. The properties of the ceramic can be tailored by using different metal oxide ratios. Particularly useful ceramic supports include Al 2 O 3 , Fe 2 O 3 , SiO 2 , and Cr 2 O 3 or Al 2 O 3, SiO 2 , Na 2 O and ZrO 2 In these cases, Cr 2 O 3 or ZrO 2 is preferably present in the ceramic support in an amount of at least 5 wt. %, based on the total weight of the ceramic support. 2 O 3 Suitable ceramic supports include those designated Durital, e.g. Durital RK10 and RK50 (containing 10 and 50 wt. % Cr, respectively). 2 O 3 (including ZrO 2 Suitable ceramic supports comprising include those sold under the name SCIMOS Z. Typical compositions of these materials are outlined in the table below.

[0031] [Table 1] [Table 2]

[0032] The ceramic support may be formed from materials used to make furnace linings, which are designed to withstand the conditions in the furnace. These are commonly referred to as refractory bricks or refractory bricks, and include bricks made from the ceramic materials listed above.

[0033] As mentioned, the ceramic support may degrade over time when used in the furnace. Due to such decomposition, components of the ceramic support may be present in the melt removed from the furnace. A person skilled in the art will be able to account for the presence of ceramic support components in the final composition of the melt.

[0034] The ceramic supports may be of any shape that allows them to provide the above benefits. For example, when stacked at the bottom of the furnace, such shapes will create voids between the individual ceramic supports, and preferably, these configurations do not need to be pre-determined to do so. Reducing the surface area to volume ratio of the ceramic supports is also advantageous, since degradation of the supports tends to occur at their surfaces. Ceramic It is not necessary that the shape of the supports can be expressed in geometric terms. In fact, they may have irregular shapes. However, their overall shape may be described as being cylindrical, disc, rod or ball shaped. In this regard, cylinders preferably have a length that is 0.3 to 3 times (preferably 0.5 to 2 times) their diameter. Rods generally have a length that is much longer than their diameter, while discs generally have a length that is much shorter than their diameter. These shapes impart a surface area to volume ratio suitable for reducing the rate of degradation. However, it is preferred that the ceramic supports are cylindrical or ball shaped, as this helps to reduce the surface area to volume ratio. Cylinders have the advantage that they may be easier to manufacture, while ball shaped ceramic supports have a better surface area to volume ratio, meaning that the rate of degradation in these furnaces may be slower. The ceramic supports may have a surface area to volume ratio of 0.07 to 0.21, preferably 0.08 to 0.15, more preferably 0.09 to 0.13, and most preferably 0.10 to 0.11.

[0035] The shape of the ceramic support is preferably expressed as the "equivalent sphere diameter". This diameter is the diameter of a sphere of equivalent volume and can be calculated for any three-dimensional shape, such as cylinders, rods, and oblate and prolate spheroids. This diameter may be calculated by measuring the volume of the body and using a formula to calculate the diameter of a sphere with equivalent volume.

[0036]

number

[0037] During the ceremony d = diameter (mm) V = volume (mm 3 )

[0038] The volume of a body may be measured using the water displacement method, in which the body is submerged in water and the volume of water displaced in the process is measured, for example, by using a Eureka cup or similar container.

[0039] The ceramic supports may advantageously have a spherical equivalent diameter of 60 mm to 250 mm, preferably 70 mm to 200 mm, more preferably 80 mm to 150 mm, most preferably 90 mm to 110 mm. Ceramic supports of these spherical equivalent diameters are suitable for use in a typical furnace melt bath. Ideally, the spherical equivalent diameter should be less than the depth of the melt bath, so that multiple layers of ceramic supports, for example two or more layers (preferably two or three layers), are used to prevent the stack of mineral material from being partially submerged in the melt. The depth of the melt bath may be measured from the inner base of the furnace to the surface of the melt during the process. In practice, the ceramic supports may not be present in the furnace as an organized arrangement forming a predetermined layer. Instead, the supports may be randomly arranged. So, "multiple layers" essentially means that the total height of the ceramic supports in the furnace exceeds the spherical equivalent diameter of the supports. Also, the total height of the ceramic supports will be above the level of the melt outlet. When the outlet is a siphon, the total height of the ceramic support will be above the level of the inlet to the siphon (the area where the melt leaves the bath and enters the siphon) and it may be beneficial for the total height of the ceramic support to be above the level of the siphon outlet, which may help to prevent the stack of mineral material from being partially submerged in the melt.

[0040] The use of a ceramic support as defined above will aid processability and help ensure that suitably sized voids exist between the ceramic supports, where the melt may collect or pool prior to removal through a melt outlet, e.g., a siphon. Also, if the ceramic support is too small, it may exit the furnace through the melt outlet with the melt, or may block the melt outlet. If the ceramic support is too large, it may not properly support the mineral material in the furnace.

[0041] In view of the above, the present invention provides an advantageous method of supporting mineral material in a hot metal furnace with a substantially reduced amount of coke or even without the use of coke, and can prevent unmelted mineral material from exiting the furnace in the melt stream without the need for any modifications to existing hot metal furnaces, which is a substantial advantage over the furnaces described in US 5,107,517 and JPH 10141629, which need to be modified to accommodate water cooling tubes and a cooling system.

[0042] Typically, the process for forming the mineral melt may be a continuous process in which the mineral melt is continuously removed from the furnace through a melt outlet while feeding further mineral material into the furnace through a feed hopper. If the ceramic support deteriorates during the furnace, further ceramic support may be added to the furnace along with the further mineral material. As the mineral material melts and is removed from the furnace, the further ceramic support descends through the furnace until it precipitates at the bottom of the hot zone. The rate at which the ceramic support deteriorates, and therefore the rate at which the support will be added to the furnace along with the further mineral material, may be empirically calculated or derived by running the furnace for a period of time, allowing the furnace to cool, and examining the remaining ceramic support. The further ceramic support may be added in any suitable amount to maintain adequate function in the furnace. This is typically an amount of 1-5% by weight, more preferably 1-2% by weight, based on the total amount of the further ceramic support and the further mineral material. If the ceramic support has a higher deterioration rate, e.g. if the ceramic support has a lower quality, it will need to be added to the furnace in a higher amount along with the further mineral material. The lower the degradation rate of the ceramic support, for example the higher the quality of the ceramic support, the lower the amount that will need to be added to the furnace along with additional mineral material.

[0043] The furnace includes at least one plasma torch that provides plasma heating in the hot zone. The plasma torch uses direct current (DC), alternating current (AC), radio frequency (RF) and other discharges to generate thermal plasma. The thermal plasma provides heat by passing an electric arc between two electrodes in the plasma torch through which a carrier gas is passed into a constricted opening. This raises the temperature of the gas to a point where it enters the fourth state of matter, i.e., plasma. The plasma torch can be transferred or non-transferred. In a non-transferred plasma torch, the electrodes are inside the torch housing. On the other hand, in a transferred plasma torch, one electrode is located outside the torch housing, allowing the arc to form outside the plasma torch over a greater distance. The plasma torch in the present invention is preferably a non-transferred plasma torch. Most preferably, it is a direct current non-transferred plasma torch.

[0044] Plasma torches can be driven by a variety of carrier gases, such as oxygen (O 2 ), nitrogen (N 2 ), Argon (Ar), Helium (He), Air, Hydrogen (H 2 ), carbon monoxide (CO), carbon dioxide (CO 2 ), or a mixture thereof may be used. In the present invention, the carrier gas is N 2 , CO, CO 2 or mixtures thereof. Oxygen (O 2 ) is removed from a zone of a hot metal furnace containing nitrogen and at a temperature of 1,400°C or higher, NO x It has been found that the production of NO can be significantly reduced. x To help minimize the formation of oxygen, the carrier gas will contain, at most, only trace amounts of oxygen. This means that the carrier gas will contain less than 5% by weight, e.g., less than 100% by weight, based on the total weight of the carrier gas. For example, this means that the carrier gas contains less than 2% by weight oxygen, preferably less than 0.8% by weight oxygen. Ideally, the carrier gas is devoid of oxygen.

[0045] As used herein, unless otherwise stated, the terms "oxygen," "nitrogen," "carbon monoxide," "carbon dioxide," and "hydrogen" are each defined as O 2 , N 2 , CO, CO 2 , and H 2 The term "NO x " is known in the art and refers to nitrogen oxides, such as nitric oxide (NO) and nitrogen dioxide (NO 2 ).

[0046] The enthalpy of the carrier gas used in the plasma torch is preferably 2.0 to 6.0 kWh / Nm 3 , preferably 3.0 to 5.0 kWh / Nm 3 The enthalpy is calculated as the measured power divided by the measured carrier gas flow rate. The enthalpy is suitable for controlling the melt temperature and melt throughput.

[0047] A hot metal furnace useful in the process of the present invention may include one plasma torch. Alternatively, it may include multiple plasma torches, e.g., two, three, four or more plasma torches. As used herein, reference to "a" or "the" plasma torch means "one or more plasma torches." The power of each plasma torch is typically in the range of 1-6 MW.

[0048] Despite the benefits of applying heat energy to the hot metal furnace using a plasma torch, the heat energy may be applied using alternative means. According to the present invention, more than 50% of the furnace heating energy is applied by the plasma torch. It may be preferred that a larger amount of furnace heating is applied by the plasma torch, for example more than 60%, preferably more than 70%, more preferably more than 80%, even more preferably more than 90%. Considering the advantages of plasma heating, it is preferred that all of the heat energy is applied by the plasma torch. Heat may be applied to the furnace in many places, but it is preferred that the heat is applied solely in the hot zone by the plasma torch.

[0049] When the heating of the furnace is not provided solely by the plasma torch, the remainder of the thermal energy may be provided, for example, in a traditional manner, i.e., by burning a fuel, e.g., natural gas or coke, in an oxygen source. The oxygen is supplied to the furnace in an oxidation zone above the hot zone. The oxygen source may be provided by any suitable means, for example, using at least one tuyere and / or at least one oxygen inlet.

[0050] The "oxygen source" may be from any suitable source, including oxygen gas, air, or a combination thereof, i.e., oxygen-enriched air. The oxygen provided may oxidize any carbon present in the mineral material or coke, as described below.

[0051] The tuyere is typically located at the bottom of the oxidation zone. The hot metal furnace may contain one tuyere, or multiple tuyere, for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more. When used, it is preferred that there are 9 to 13 tuyere, most preferably 11 tuyere. In this case, it is preferred that the tuyere is equally distributed around the outer edge of the furnace, except at the melt outlet, for example at the melt siphon. In any case, it is preferred that no tuyere is located in the same zone as the plasma torch, i.e. there are no tuyere in the hot zone. This helps to avoid oxygen being present in the zone of the hot metal furnace above 1,400 ° C.

[0052] Tuyere is 70-250Nm per tonne of charge 3 Air may be applied at a rate of 0 to 100 rpm. The diameter of each tuyere through which the air flows into the hot metal furnace is typically positioned 0 to a maximum of 1 furnace diameter larger than the plasma torch. The diameter is the inside diameter of the inner chamber of the hot metal furnace.

[0053] Because tuyere are typically located around the periphery of the hot metal furnace, they may not be able to supply oxygen to the center of the furnace, which has a large diameter. In this case, at least one oxygen inlet may be present in the furnace to help introduce oxygen to the center of the furnace. As is known in the art, the oxygen inlet may be a tube or pipe that delivers oxygen to the appropriate point in the hot metal furnace.

[0054] NO x NO can be derived from nitrogen and oxygen under high temperature and pressure. x To reduce the formation of NO, the temperature in the oxidation zone of the hot metal furnace should be between 600°C and 1,400°C. x To further reduce the formation of, it is preferred that the temperature in the 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, and especially 600°C to less than 850°C.

[0055] The temperature of the hot zone should be higher than that of the oxidation zone, meaning that the temperature in 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, more preferably above 1,400°C.

[0056] Based on the above, the process of the present invention is capable of emitting 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, more preferably less than 150 ppm. x As will be appreciated by those of ordinary skill in the art, ppm of off-gas is ppm by volume. Thus, references herein to ppm of gas are ppm by volume.

[0057] A further unexpected benefit of heating the hot zone with a plasma torch using a carrier gas that is, for example, nitrogen, carbon monoxide, carbon dioxide, or mixtures thereof, is that the height of the hot zone can be significantly reduced compared to a corresponding hot metal furnace heated by means other than a plasma torch.

[0058] The use of a plasma torch has yet a further advantage in that it significantly reduces the response time required to change the temperature in a particular zone of the molten iron furnace, and in particular the temperature of the melt. Typically, the melt temperature can be changed within 20 minutes, preferably within 15 minutes, more preferably within 10 minutes when using a plasma torch. This can be a faster temperature change than when other heating means are used.

[0059] It has been found that water should be removed from any zone in the furnace that is at a temperature above 750°C. This will minimise the amount of hydrogen that is formed and present in the hot metal furnace off-gas. It is preferred that the furnace produces an off-gas that contains hydrogen in an amount 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. It is most preferred that there is no detectable amount of hydrogen in the off-gas. As mentioned above, ppm in off-gas is ppm by volume.

[0060] By using at least one plasma torch, the amount of coke used in the hot metal furnace can be significantly reduced, substantially eliminated, or eliminated. To be "significantly reduced," the amount of coke used can be less than 5% by weight, preferably less than 3% by weight, and more preferably less than 2% by weight, based on the total amount of coke and mineral materials. To be "substantially eliminated," the amount of coke used can be less than 10% by weight, preferably less than 10% by weight, and more preferably less than 2% by weight, based on the total amount of coke and mineral materials. The coke content may be less than 0.5% by weight. Preferably, no coke is added or only a trace amount of coke is present. In this case, the coke is considered to be absent from the process, i.e., the coke is excluded. Most preferably, no coke is present in the process.

[0061] The use of at least one plasma torch in combination with ceramic supports as described herein means that the mineral melt can be formed in the hot metal furnace without the use of coke. This reduces or eliminates certain emissions in the off-gas, such as CO and / or CO produced in the off-gas. 2 The advantage is that

[0062] The mineral material used to form the mineral melt may contain carbon. For example, carbon may be present in recycled mineral material used to form the mineral melt. Recycled mineral material may be obtained from a wide range of sources, including waste MMVF. MMVF typically contains a binder and oil, the type of which depends on the intended use of the MMVF. Binders usually contain a significant amount of carbon (approximately 40-70% by weight). Oils may contain up to 90% or more by weight of carbon. When a higher percentage of recycled material is used as the mineral material, the CO and CO generated in the process may be reduced. 2 As a result, when recycled mineral materials are used to form the mineral melt, it is preferred that the mineral material contains less than 5 wt. % carbon, preferably less than 2 wt. % carbon, based on the total weight of the mineral material. This means that the process is 2 This means that the ion exchange reaction will produce only small amounts of

[0063] Notwithstanding the above, the mineral material not containing recycled material may still contain carbon as an impurity. In this case, the mineral material contains less than 1 wt. % carbon, preferably less than 0.5 wt. % carbon, based on the total weight of the mineral material, when not containing recycled mineral material. The object of the present invention is to reduce the CO and CO produced in the formation of the mineral melt. 2and therefore most preferably the mineral material is substantially free of carbon, i.e. there are only trace amounts of carbon present in the mineral material.

[0064] When coke is used in the furnace, or another carbon source is present in the mineral material, an oxygen source will be provided above the hot zone of the hot metal furnace to form an oxidation zone as described above.

[0065] Fe3+(Fe 2 O 3 It may be beneficial for the melt to contain a relatively high amount of Fe2+ (in the form of FeO) compared to iron (in the form of FeO) or metallic iron. Reduction of iron is typically accomplished using a carbon source, e.g., coal, coke or other carbonaceous particulate fuel. Since carbon is preferably excluded from the process, reduction of iron may be accomplished using metallic aluminium. The metallic aluminium may be in the form of aluminium, e.g., granular aluminium, or it may be aluminium dross. Aluminium dross is a particulate waste material from the aluminium processing industry, containing approximately 0.5-10 wt% metallic aluminium along with (usually 50-90 wt%) Al 2 O 3 Aluminum may be added to the mineral material in an amount sufficient to form the required Fe2+ / Fe3+ content in the melt. Typically, approximately 8-12 wt.% of the mineral material may be aluminum dross. When the amount of coke used is less than 0.5 wt.% based on the total weight of the coke and mineral material, it is preferred to use metallic aluminum in the process. An additional benefit of using aluminum to reduce iron is that aluminum is an Al 2 O 3 This is often a required component of the mineral melt.

[0066] The off-gas from a hot metal furnace heated using a plasma torch is N 2 , CO, CO 2 , NO x and H 2The off-gas may contain further components, such as water and particles, i.e. solid material particles. The off-gas may be used in whole or in part in the carrier gas for one or more of the plasma torches. In this regard, the term carrier gas may be used in the form of a carrier gas for one or more of the plasma torches. The carrier gas may comprise or consist of at least one component of the off-gas produced by the furnace. Essentially, the off-gas may be recycled and used as a carrier gas for plasma ignition. The components of the off-gas may be separated prior to use as a carrier gas. The components of the off-gas may be separated from each other or a combination of two or more components may be separated from the other components. This means that the carrier gas may comprise at least one component of the off-gas, e.g., 1, 2, 3, 4, 5 or more components of the off-gas. The ... 2 , CO, CO 2 Alternatively, the carrier gas may contain only one off-gas component, such as N 2 , CO, or CO 2 may include:

[0067] One or more components of the off-gas may undergo off-gas cleaning prior to use in the carrier gas. Off-gas cleaning preferably removes particles suspended in the off-gas and / or water. Off-gas cleaning may be performed on the off-gas as a whole or on at least one component thereof once separated from the remainder of the off-gas.

[0068] The carrier gas may consist of the off-gas or at least one component of the off-gas. Alternatively, it may comprise the off-gas or at least one component of the off-gas. In the latter case, further gas that does not form part of the off-gas may be added to the carrier gas before use. In this case, the carrier gas is "supplemented" with the further gas.

[0069] The mineral melt prepared via the process of the present invention may be suitable for the production of MMVF, for example glass or stone fibres. Preferably, the mineral melt formed is suitable for use to form MMVF. Thus, in a second aspect of the present invention, there is provided a process for producing MMVF, comprising: (i) forming a melt using a process as defined herein; (ii) fiberizing the melt by an inside or outside spinning process, preferably using a cascade spinner; and (iii) collecting the formed fibers. The process includes:

[0070] Fibers, particularly MMVF, may be made from the melt in conventional ways. Generally, these fibers are made by a centrifugal fiber formation process. For example, the fibers may be formed by a spinning cup process in which the fibers are thrown outward through perforations in the spinning cup, or the melt may be thrown from a rotating disk and fiber formation may be promoted by blasting a jet of gas through the melt. Fiber formation may be performed by pouring the melt onto a first rotor in a cascade spinner. In this case, the melt is preferably poured onto a first set of two, three, four or even more rotors, each rotating about a substantially horizontal axis such that the melt in the first rotor is mainly thrown onto the second (lower) rotor, but some may be thrown from the first rotor as fibers, the melt in the second rotor is thrown as fibers, but some may be thrown towards the third (lower) rotor, etc. Generally, it is preferred that the spinning process utilize a cascade spinner.

[0071] The required properties of the melt used in each spinning method are known to those skilled in the art, and the composition of the melt may be adjusted to impart these properties. For example, a person skilled in the art may select mineral materials to be added to a hot metal furnace to produce a particular melt composition, which is then spun by a particular spinning process.

[0072] During the fiberization process, a cloud of air-entrained fibers is formed from the melt and the fibers are collected as a web on a conveyor and carried away from the fiberizer. and then consolidated, which may include cross wrapping and / or longitudinal compression and / or vertical compression and / or wrapping around a mandrel to produce a cylindrical product for pipe insulation. Other consolidation processes may also be implemented.

[0073] The binder composition is conventionally applied to the fibers, preferably when the fibers are in an air entrained 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 fibers may be used.

[0074] After consolidation, the reinforced fiber web is passed through a curing device to cure the binder. Curing may be carried out at a temperature of 100-300°C, such as 170-270°C, such as 180-250°C, such as 190-230°C.

[0075] Curing is preferably carried out in a conventional curing oven for mineral wool manufacture, in which hot air is blown through the reinforced web, preferably operating at a temperature of 150-300° C., such as 170-270° C., for example 180-250° C., for example 190-230° C. Curing may be carried out for a period of 30 seconds to 20 minutes, such as 1-15 minutes, for example 2-10 minutes. Typically, curing is carried out at a temperature of 150-250° C., for a period of 30 seconds to 20 minutes.

[0076] The curing process may begin immediately after application of the binder to the fibers. Curing is defined as the process in which the binder composition undergoes physical and / or chemical reactions, which in the case of chemical reactions usually increase the molecular weight of the compounds in the binder composition, thereby usually increasing the viscosity of the binder composition until it reaches a solid state. The cured binder composition binds the fibers together to form a structurally coherent fiber matrix.

[0077] The curing of the binder in contact with the mineral fibres may alternatively be carried out in a hot press. The curing of the binder in contact with the mineral fibres in a hot press has the particular advantage of allowing the production of a dense product.

[0078] In general, the fibers, and the mineral melt from which they are formed, may have elemental analyses (measured as weight percent oxides) within various ranges defined by the following normal and preferred lower and upper values. SiO 2 35 to 50, preferably 38 to 48, more preferably 33 to 44 Al 2 O 3 12 to 30, preferably 15 to 28, more preferably 16 to 24 TiO 2 Maximum 2 Fe 2 O 3 2~12 CaO 5-30, preferably 5-18 MgO 0-15, preferably 1-8 Na 2 O 0~15 K 2 O 0~15 P 2 O 5 0~3 MnO 0-3 B 2 O 3 0~3.

[0079] In this case, when the melt is to be formed into an MMVF, the Fe(2+) fraction of the melt is preferably greater than 80% based on total Fe, and 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 made using a cascade spinner. Further details of these example melts can be found in WO2012 / 140173, which is incorporated herein by reference.

[0080] The amounts of Fe(2+) and Fe(3+) are given in "The ferric / ferrous ratio in basalt melts at different oxygen concentrations" "Pressures" can be determined using the Mössbauer method described in Helgason et al., Hyperfine Interact., 45 (1989), pp 287-294.

[0081] The total amount of iron in the entire melt or fiber composition, based on the total oxides in the melt or fiber, is Fe 2 O 3 This is the standard means of estimating the amount of iron present in such an MMVF, charge or melt. 2 O 3 The actual weight percentage may vary based on the iron oxide ratio and / or the redox state of the melt.

[0082] In the above examples of melts and resulting fibres, it is preferred that the amount of iron in the melt is between 2 and 15% by weight, preferably between 5 and 12% by weight. Hot metal furnaces tend to have a reducing atmosphere, especially when coke is used, which can result in the reduction of iron oxide and the formation of metallic iron. Preferably, metallic iron is not entrained in the melt and fibres, but is removed from the furnace. Therefore, conditions in the furnace may be carefully controlled to avoid over-reduction of iron. However, we are able to produce end product fibres with significant levels of iron oxide.

[0083] The process of the present invention may be used in the formation of fibres which may be shown to be soluble in saline. Suitable high aluminium biodegradable fibres which may be advantageously produced using the process of the present invention are described in WO 96 / 14454 and WO 96 / 14274, others in WO 97 / 29057, DE-U-2970027 and WO 97 / 30002 (incorporated by reference).

[0084] Such fibers preferably have a reasonable solubility in lung fluid as shown in in vivo or in vitro tests typically performed in saline buffered to about pH 4.5. Suitable solubilities are described in WO 96 / 14454. Typically, the dissolution rate is at least 10 or 20 nm / day in saline. The fibers preferably have a sintering temperature above 800°C, more preferably above 1,000°C. The melt preferably has a viscosity of 5-100 poise, preferably 10-70 poise, at a fiber formation temperature of 1,400°C. Further embodiments of this example can be found in WO 99 / 28252, which is incorporated herein by reference.

[0085] Preferably, the melt has a viscosity in this embodiment in the range of 10-30 poise at 1400°C, more preferably in the range of 15-25 poise. The advantage of choosing this viscosity is that the resulting MMVF will have a smaller diameter than when the melt viscosity is higher. Furthermore, it is possible to use a lower melt temperature to achieve the required operating viscosity. This saves energy since a lower melt temperature can be used. It also reduces wear on the rotors used to produce the fibers, since a cooler melt causes less wear. Further details of the melt of this example can be found in WO2015 / 055758, which is incorporated herein by reference. The viscosity of the melt may be determined according to ASTM C 965-96.

[0086] Hot metal furnaces useful in the process of the invention may include the components and zones described above, in addition to the following: Typically, the melt forms a pool in the hot zone where it flows out via a melt outlet, e.g., a melt siphon, to the fiber forming process. The melt may flow from the base of the hot metal furnace to another chamber where the melt collects as a pool and flows out to the fiber forming process.

[0087] The raw material (mineral material) may be in the form of briquettes, which are made in a known manner by forming a mixture of the desired particulate material and a binder into the desired briquette shape and allowing the binder to harden.

[0088] The binder may be a hydraulic binder, i.e., one that is activated by water, such as Portland cement. Other hydraulic binders may be used as partial or complete substitutes for cement, examples of which include lime, blast furnace slag powder, and certain other slags, as well as cement kiln dust and ground MMVF shot (JP-A-51075711, US 4,662,941, and US 4,724,295, each of which is incorporated herein by reference). Alternative binders include clays. Briquettes may also be formed with organic binders, such as molasses, as described, for example, in WO 95 / 34514, which is incorporated herein by reference. Such briquettes may be described as foam stone.

[0089] The MMVF may be formed as a bonded web comprising the MMVF as described above, or the MMVF made by the process described above, and a cured binder composition.

[0090] The melt formed by the process of the present invention, and the man-made fibers (preferably MMVF) made therefrom, may be suitable for use in a wide range of products, such as insulating elements (both thermal and / or acoustic), and fire-resistant elements, as well as plant growth substrates.

[0091] According to a third aspect of the present invention, (A) reducing the amount of coke required to support the mineral material and produce a mineral melt suitable for the production of MMVF; and / or (B) To increase the thermal efficiency when superheating a mineral melt suitable for the production of MMVF. The present invention provides the use of a ceramic support in a molten iron furnace for the purpose of

[0092] The use may be as defined in the process above.

[0093] The invention will now be explained in more detail with reference to a drawing which shows a furnace for carrying out the process according to the invention.

[0094] The diagram in FIG. 1 shows a hot metal furnace 1 with a feed hopper 2 in communication with a vessel 3 with a bottom constituted by an axially movable cone 4. Below the vessel 3 there is a melting chamber closed by a water-cooled jacket 5. The hot metal furnace 1 comprises at its lower end a flat furnace bottom 6, at a suitable distance above the bottom 6 a melt outlet, e.g. a melt siphon 7, is provided. At some distance above the level at which the melt outlet 7 is located a number of plasma torches 8 are integrated into the furnace wall. When an oxygen source is required in the furnace, at a higher level an annular oxygen inlet pipe 9 is provided which communicates with a number of tuyeres 10 and / or a number of oxygen inlets (not shown). The hot metal furnace 1 has an inner lining in the hot zone and is made of brick. The lining covers the furnace bottom 6 and the inner furnace wall at least up to the height of the tuyeres 10. A number of ceramic supports 11 are positioned in the section of the hot zone where the melt collects before it is removed from the furnace.

[0095] The mineral material, i.e. the raw material, having a composition corresponding to that of the desired melt, is fed into the melting chamber through a hopper 2 and a vessel 3, the dosing being carried out by suitable adjustment of the cone 4. Carbonaceous material, e.g. coke, may be added together with the mineral material when required.

[0096] The upper part of the melting chamber acts as a preheat zone as the material is heated by the soot gases. From the preheat zone the material descends through the furnace and, if present, through the oxidation zone. The lower limit of the oxidation zone is located at the level where oxygen is introduced through the tuyeres 10 and / or oxygen inlet(s). When a certain amount of coke is used, the CO 2 The temperature in the oxidation zone is controlled by the temperature in the portion of the preheat zone located just above the top of the oxidation zone, which is controlled by the temperature of the portion of the preheat zone located just above the top of the oxidation zone, to form CO 2 The temperature is kept at a level not exceeding 1000°C so as to eliminate or greatly reduce the reaction with carbon to form CO. The actual melting takes place in a part of the melting chamber located below the oxidation zone and where intense heat is introduced by a plasma torch 8. During the melting process, the mineral material is supported by ceramic supports 11. The melt formed descends towards the bottom of the furnace where it pools in the voids between the ceramic supports 11. The melt is discharged through a melt outlet 7. EXAMPLES

[0097] The invention is further illustrated by the following non-limiting examples.

[0098] N 2 The mineral melt was formed in a plasma fired hot metal furnace where a plasma torch was applied with CO as the carrier gas. The furnace was equipped with a ceramic body and no coke was added. The oxidation state of iron in the melt was adjusted by incorporating 10 wt. % Serox W (Alu-dros) (approximately 2 wt. % metallic aluminum) in the mineral charge. The mineral material used in the furnace was oxidized by CO and CO in the off-gas. 2 The briquettes contained recycled mineral wool waste, which was the main cause of the presence of. In the table below, the parameters and results of the furnace with ceramic support (column A) are compared against the theoretical furnace without ceramic support and where coke was added together with the mineral material (column B).

[0099] [Table 3]

[0100] The data show that the CO and CO in the off-gas when using a ceramic support without coke 2 The amount of CO and CO in column A is significantly reduced. 2 The amount of carbon formed may be considered as a baseline when indicating the amount of carbon present in the briquettes containing recycled mineral wool waste (up to 50% crushed mineral wool waste) used in the furnace.

Claims

1. 1. A process for preparing a mineral melt in a hot metal furnace, the hot metal furnace comprising a hot zone at a base of the furnace and a melt outlet in the hot zone; (i) the furnace includes at least one plasma torch that provides plasma heating in the hot zone; (ii) greater than 50% of the furnace heating energy is provided by the at least one plasma torch; (iii) the furnace includes a plurality of ceramic supports positioned in a section of the hot zone where the melt collects before being removed from the furnace through the melt outlet; A process in which mineral material fed into the furnace is melted to form a mineral melt that collects in voids between the ceramic supports.

2. (I) more than 60%, preferably more than 70%, more preferably more than 80%, even more preferably more than 90%, and most preferably all of the furnace heating energy is provided by the at least one plasma torch; and / or (II) heat is applied solely in the hot zone by the at least one plasma torch; The process of claim 1.

3. the hot metal furnace includes an oxidation zone above the hot zone, and an oxygen source is provided in the oxidation zone, preferably using at least one tuyere and / or at least one oxygen inlet; 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, in particular from 600°C to 1,000°C, most preferably from 600°C to 900°C, in particular from 600°C to less than 850°C; 3. The process according to claim 1 or 2.

4. (a) the temperature in 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, more preferably greater than 1,400°C; and / or (b) water is substantially removed from any zone of the furnace where the temperature is above 750°C; 3. The process according to claim 1 or 2.

5. The plurality of ceramic supports (A) has a melting temperature of at least 1,400°C, preferably at least 1,600°C, and more preferably at least 1,800°C; and / or (B) resisting chemical degradation in the hot metal furnace during the process; 3. The process according to claim 1 or 2.

6. Each ceramic support comprises Cr in an amount of at least 5 wt. % based on the total weight of said ceramic support. ２ O ３ and / or ZrO in an amount of at least 5 wt.% ２ 3. The process of claim 1 or 2, comprising:

7. The plurality of ceramic supports (I) having an equivalent spherical diameter of 60 mm to 250 mm, preferably 70 mm to 200 mm, more preferably 80 mm to 150 mm, and most preferably 90 mm to 110 mm; and / or (II) The ceramic support is ball-shaped; 3. The process according to claim 1 or 2.

8. 3. The process according to claim 1 or 2, wherein the process is a continuous process and further ceramic support and further mineral material are added to the hot metal furnace, preferably the further ceramic support is added in an amount of 1 to 5 wt. %, more preferably 1 to 2 wt. %, based on the total amount of further ceramic support and further mineral material.

9. The at least one plasma torch uses nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof as a carrier gas, and preferably has a carrier gas enthalpy of 2.0 to 6.0 kWh / Nm ３ , more preferably 3.0 to 5.0 kWh / Nm ３ 3. The process according to claim 1 or 2, wherein

10. The melt has the following composition, expressed as oxides in weight percent: SiO ２ 35 to 50, preferably 38 to 48, more preferably 33 to 44 Al ２ O ３ 12 to 30, preferably 15 to 28, more preferably 16 to 24 TiO ２ Maximum 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、 and 3. The process according to claim 1 or 2, wherein the proportion of Fe(2+) in the melt is preferably more than 80% based on total Fe, preferably at least 90%, more preferably at least 95%, most preferably at least 97% based on total Fe.

11. 3. The process of claim 1 or 2, wherein the mineral material comprises metallic aluminum which reduces the oxidation state of iron.

12. (a) Oxygen (O ２ ) is removed from a zone of the hot metal furnace containing nitrogen and at a temperature of 1,400°C or higher, so that the furnace is free of NO in an amount of less than 400 ppm by volume, preferably less than 300 ppm by volume, more preferably less than 250 ppm by volume, even more preferably less than 200 ppm by volume, more preferably less than 150 ppm by volume. ｘ and / or (b) water is removed from any zone of the furnace that is at a temperature above 750°C, such that the furnace produces an off-gas containing hydrogen in an amount of less than 20,000 ppm by volume, preferably less than 10,000 ppm by volume, preferably less than 5,000 ppm by volume, preferably less than 2,000 ppm by volume, preferably less than 1,000 ppm by volume, preferably less than 500 ppm by volume, preferably less than 100 ppm by volume, preferably less than 50 ppm by volume, and most preferably no detectable amount of hydrogen in the off-gas; 3. The process according to claim 1 or 2.

13. 3. The process of claim 1 or 2, wherein the at least one plasma torch uses a carrier gas, the carrier gas comprising or consisting of at least one component of the off-gas produced by the furnace, preferably the at least one component of the off-gas undergoes off-gas cleaning before use as a carrier gas, more preferably the off-gas cleaning is to remove particles and / or water.

14. (i) when the mineral material comprises recycled mineral material, e.g., waste man-made glass fiber, it comprises less than 5% by weight of carbon, preferably less than 2% by weight of carbon, based on the total weight of the mineral material; or (ii) when the mineral material does not contain recycled mineral material, e.g., waste man-made glass fiber, it contains less than 1 wt. % carbon, preferably less than 0.5 wt. % carbon, based on the total weight of the mineral material, and most preferably the mineral material is substantially free of carbon; 3. The process according to claim 1 or 2.

15. A process for producing man-made glass fiber (MMVF) (i) forming a melt using the process defined in claim 1 or 2; (ii) fiberizing the melt by an inside or outside spinning process, preferably using a cascade spinner; and (iii) collecting the formed fibers The process includes:

Images