Apparatus and method for mineral fibre production

Abstract

The invention is an apparatus for creating mineral fibres (10), comprising; a plasma torch (30) arranged to heat a carrier gas and supply this carrier gas to a cooling ring chamber (20); the cooling ring chamber (20), arranged to cool the carrier gas and subsequently supply the carrier gas to at least a portion of a heating region (9) into which fibres (10) are passed and a spinning chamber with the heating region (9) and a spinner (1) having perforations in a sidewall (2) and rotation of the spinner (1) causing formation of fibres (10) by passing molten material (4) through the perforations into the heating region (9). The invention further describes a method for heating a heating region (9) of the apparatus where a carrier gas is heated in a plasma torch (30) and directed into a cooling ring chamber (20) where the carrier gas is cooled, and the cooling ring chamber directs the carrier gas to the heating region (9).

Description

[0001] Apparatus and method for mineral fibre production

[0002] Field of the invention

[0003] The present invention relates to production of mineral fibres from a mineral melt through use of heat to maintain fibres in a molten state. This is typically for implementation in cup spinning for glass wool or stone wool production.

[0004] Background

[0005] Forming fibres from molten mineral material is known from e.g. WO 2008 / 116176 A1 which describes:

[0006] Fibres of glass and other thermoplastic materials are useful in a variety of applications including acoustical and thermal insulation materials. Common methods for producing glass fibres for use in insulation products involve producing glass fibres from a rotary process. In a rotary process, a glass composition is melted and forced through orifices in the outer peripheral wall of a centrifuge, commonly known as a centrifugal spinner, to produce the fibres. One commonly used spinner is generally cup-shaped and has a bottom wall with a central hole, a top opening and an outer peripheral sidewall that curves upward from the bottom wall, forming the top opening. A drive shaft is used to rotate the spinner and is typically fixed to the spinner with a quill.

[0007] In order to avoid blocking of the orifices in the outer peripheral sidewall of the spinner, the fibres have to be kept in a molten state. This is achieved by creating a flow of heated gas and directing this gas through the fibres immediately after they are generated by the spinner. The heated gas is created by combustion of gas in burners.Summary of invention

[0008] This invention provides an apparatus and a method for creating heated carrier gas using a plasma torch. The plasma torch has the advantage of heating the carrier gas by using electricity which can be created without combustion.

[0009] The heated carrier gas delivered by the plasma torch will be at a temperature which is higher than what is needed at the spinner. Therefore, the heated carrier gas delivered by the plasma torch is cooled by a cooling ring chamber before it is provided to the spinner.

[0010] Brief description of the drawing

[0011] Referring to the drawing Figure 1 illustrates one example of the invention as an apparatus for creating mineral fibres (10) comprising a spinner (1), a cooling ring chamber (20) and at least one plasma torch (30). The spinner (1 ) is positioned within a spinning chamber and comprises a sidewall (2) having perforations. Molten material melt (4) is fed into the interior of the spinner (1) from a melt gutter (6) and is moved from the base (5) of the spinner (1) towards the sidewall (2) by centrifugal force pushing the melt (4) against the sidewall (2) and through the perforations to create mineral fibres (10). The spinner (1) is rotated by a rotor shaft (7) connected to an engine (not shown).

[0012] In order to avoid blocking of the perforations and to keep the fibres (10) in a molten state, a hot gas generally moving in the direction indicated by the arrow (11) is blown into a heating region (9) surrounding the spinner (1).

[0013] The hot gas is provided from a cooling ring chamber (20) where the temperature of the hot gas is adjusted. The cooling ring chamber (20) comprises a wall with coolant passages (21) which cool the chamber (20). A number of plasma torches (30) with outlets (22) positioned in the cooling ring chamber (20) provide hot gas in the coolingring chamber (20). The cooling ring chamber (20) comprises one or more outlets (23) for directing the gas towards the heating region (9).

[0014] A carrier gas is passed through a non-transferred arc plasma torch (30) to heat the carrier gas to a temperature between 2000-5000 °C (degrees Celsius). This carrier gas enters the cooling ring chamber (20) where it is distributed and cooled to enter the heating region (9) to heat the fibres (10).

[0015] The cooling ring chamber (20) comprises chamber walls made from heat-resistant materials such as ceramics. The ring chamber (20) is cooled by coolant passages (21), surrounding the chamber walls.

[0016] The spinner (1) is fed with a stream of molten material melt (4) by the melt gutter (6) which is a trough or passage which is suitable to supply a stream of molten material melt (4) from a furnace.

[0017] Detailed description

[0018] According to an embodiment the invention is an apparatus for creating mineral fibres, comprising;

[0019] a plasma torch arranged to heat a carrier gas and supply the carrier gas to a cooling ring chamber;

[0020] the cooling ring chamber, arranged to cool the carrier gas and subsequently supply the carrier gas to at least a portion of a heating region into which fibres are passed and

[0021] a spinning chamber with the heating region and a spinner having perforations in a sidewall and rotation of the spinner causing formation of fibres by passing molten material through the perforations into the heating region.

[0022] The plasma torches used in this invention are similar to those described in WO 2022 / 106592 A1. Plasma torches generate thermal plasma using direct current (DC),alternating current (AC), radio-frequency (RF) discharge and / or other discharges. Thermal plasmas provide heat, which in DC plasma torches is produced by creating an electric arc between two electrodes. A carrier gas is passed through the arc and subsequently through a constricted opening. This elevates the temperature of the carrier gas to the point where it enters another state of matter, i.e. plasma.

[0023] The cooling ring chamber of this invention comprises cooling means for cooling the heated carrier gas supplied by the plasma torches and is arranged to direct this carrier gas to the desired position within the spinning chamber. This positioning of the flow of heated carrier gas is achieved in a manner described in US 2007 / 0261447 A1 or WO 2008 / 116176 A1.

[0024] The spinning chamber of this invention is in both form and function similar to known spinner chambers such as those described in US 2007 / 0261447 A1, WO 2016 / 022752 A1 or WO 2008 / 116176 A1. In a preferred embodiment the apparatus further comprises means for addition of attenuation gas, binder and / or coolant.

[0025] The spinner is positioned within the spinning chamber when the apparatus is used to produce mineral fibres. The spinner (1) includes a base (5), extending from a central spindle (8), and a sidewall (2). A number of perforations are positioned through the sidewall (2). Typically, the sidewall has 20,000 - 40,000 perforations.

[0026] According to a preferred embodiment the invention is the apparatus for creating mineral fibres according to the preceding embodiments where the heating region abuts the spinner.

[0027] The heating region is positioned in such a way that the fibres produced by the spinner are kept in a molten state immediately after they leave the perforation in the sidewall. The spinner itself and the mineral melt within the spinner can be heated by other means if necessary, such as the means described in US 2007 / 0261447 A1.In a preferred embodiment the cooling ring chamber has an annular outlet for the carrier gas.

[0028] The outlet of the cooling ring chamber serves to direct the carrier gas passing through the chamber to the correct position within the spinning chamber. Because the spinner creates fibres along the entire periphery of its sidewall the carrier gas preferably flows along the entire periphery. This is achieved by having an annular outlet of the cooling ring chamber allowing the carrier gas from one or more plasma torches to be distributed over the whole heating region.

[0029] According to a preferred embodiment the invention is the apparatus for creating mineral fibres according to any one of the preceding embodiments wherein the cooling ring chamber (23) comprises a wall with at least one passage (21) for circulation of coolant.

[0030] According to a further preferred embodiment the invention is the apparatus for creating mineral fibres according to the preceding preferred embodiment wherein the wall comprises a cooling jacket.

[0031] According to a further preferred embodiment the invention is the apparatus for creating mineral fibres according to any one of the preceding preferred embodiments wherein the wall comprises at least one cooling coil.

[0032] One specific way of cooling the cooling ring chamber is to have one or more walls of the chamber cooled by indirect heat exchange with a coolant flowing through passages in the chamber walls to remove heat from the carrier gas passing through the chamber. Specifically, the walls may be covered in part or wholly by a cooling jacket. The advantage of using a cooling jacket is that the entire chamber can be cooled.Alternatively, the walls may comprise cooling coils. The advantage of using cooling coils is that even cooling can be achieved across the parts of the chamber in contact with the coils because the flow in the coils is easily controllable.

[0033] According to another preferred embodiment the invention is the apparatus for creating mineral fibres according to any one of the preceding embodiments wherein the spinner comprises a sidewall and a base and is mountable on a shaft of a rotor.

[0034] A variety of spinners may be applied for this invention including the ones described in US 2007 / 0261447 A1, WO 2016 / 022752 A1 or WO 2008 / 116176 A1.

[0035] According to a preferred embodiment the invention is the apparatus for creating mineral fibres according to any one of the preceding embodiments wherein the plasma torch is a DC non-transferred arc plasma torch.

[0036] Arc plasma torches may be transferred or non-transferred. In non-transferred DC plasma torches the electrodes are positioned inside a housing of the torch, whereas in transferred arc plasma torches one electrode is located outside the housing of the torch, allowing the arc to form outside of the plasma torch and over a greater distance than the arc of the non-transferred arc plasma torch. It is preferable that the plasma torch in the present invention is a non-transferred arc plasma torch.

[0037] According to a preferred embodiment the invention is the apparatus for creating mineral fibres according to any one of the preceding embodiments characterized in that the apparatus comprises at least 4 plasma torches. In some embodiments there are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 plasma torches or at least 2, at least 3 or at least 5 plasma torches, or less than 9, less than 7 or less than 5 plasma torches.

[0038] According to another preferred embodiment the invention is the apparatus for creating mineral fibres according to the any one of the previous embodiments,characterized in that the outlets of the plasma torches are equally spaced apart in the cooling ring chamber.

[0039] The cooling ring chamber is shaped to distribute the carrier gas from one or more plasma torches evenly across the heating region. By providing a number of separate plasma torches with their outlets evenly spaced apart in the cooling ring chamber the carrier gas from each plasma torch is distributed across a smaller area of the outlet of the cooling ring chamber in order to achieve an even distribution of the gas in the heating region.

[0040] According to one embodiment the invention relates to a method for heating a heating region of the apparatus according to any one of the previous embodiments where a carrier gas is heated in a plasma torch and directed into a cooling ring chamber where the carrier gas is cooled, and the cooling ring chamber directs the carrier gas to the heating region.

[0041] In this way the heating region is kept at the desired temperature in order to allow any fibres created by the spinner to persist in a molten state while they are passing through the heating region.

[0042] According to a preferred embodiment the invention is the method for heating a heating region according to the previous embodiment wherein the plasma torch (30) heats the carrier gas to a temperature of at least 2000 °C.

[0043] According to a preferred embodiment the invention is the method for heating a heating region according to one or more previous embodiments wherein the cooling ring chamber (20) cools the carrier gas to a temperature of at most 1800 °C.

[0044] The plasma torches deliver carrier gasses at higher temperatures than what is needed in the heating region and these temperatures are so high that the equipment within the spinning chamber may be damaged. Therefore, the cooling ring chamberhas to cool the carrier gas to a temperature which does not damage the equipment, but which is still high enough to ensure that the orifices of the spinner are not blocked and that the fibres are kept in a molten state within the heating region.

[0045] One example of molten material melt is molten rock. Other examples of molten material melt include molten glass, slag and basalt. The type of molten material is a determining factor in what temperature is needed in the heating region in order to keep the fibres in a molten state.

[0046] For glass the temperature of the heating region is 900-1200 °C.

[0047] For rock the temperature of the heating region is 1100-1400 °C.

[0048] For slag or basalt, the temperature of the heating region is 1000-1300 °C.

[0049] Because all of these temperatures are well below the temperature of the carrier gas delivered by the plasma torch this carrier gas needs to be cooled before it enters the heating region so as not to remelt the fibres or damage the equipment for creating the fibres.

[0050] This cooling of the carrier gas from a temperature of 2000-5000 °C to the temperature needed in the heating region is carried out by the cooling ring chamber. The cooling is achieved by indirect heat exchange through the wall of the ring chamber. A coolant such as water is circulated in coolant passages surrounding the walls of the ring chamber, thereby lowering the temperature of the gas until it reaches the temperature needed in the heating region. The coolant passages can take the shape of a cooling jacket, or cooling coils positioned on the outside of the ring chamber.

[0051] According to a preferred embodiment the invention is the method for heating a heating region according to one or more previous embodiments where the carriergas comprises a gas selected from the group consisting of nitrogen, oxygen, argon, helium, air, hydrogen, carbon monoxide, carbon dioxide and mixtures thereof.

[0052] According to a preferred embodiment the invention is the method for heating a heating region according to one or more previous embodiments where the carrier gas is nitrogen.

[0053] Plasma torches may use a variety of carrier gasses, such a nitrogen, oxygen, argon, helium, air, hydrogen or mixtures thereof. In the present invention, the carrier gas may be selected from the group consisting of nitrogen, carbon monoxide, carbon dioxide and mixtures thereof. Preferably the carrier gas is nitrogen. All of these gasses are well known as carrier gasses for plasma torches as described in WO 2022 / 106592 A1. It has been found that the production of NOx may be significantly reduced when oxygen is excluded from gasses comprising nitrogen which are heated to temperatures of 1,400 °C or above. To help minimize the production of NOx, the carrier gas, preferably comprises, at most, only trace amounts of oxygen. This means that the carrier gas should comprise less than 5 weight% oxygen, such as less than 2 weight%, preferably less than 0.8 weight%, based upon the total weight of the carrier gas. Ideally, the carrier gas is devoid of oxygen. This means that there are, at most, only trace amounts of oxygen present.

[0054] The enthalpy of the carrier gas used in the plasma torch is preferably 2.0-6.0 kWh / Nm3, (kilowatt-hours per normal cubic meter) preferably 3.0-5.0 kWh / Nm3.

[0055] The enthalpy is calculated as measured power divided by measured carrier gas flow and is relevant for controlling the temperature of the carrier gas leaving the plasma torch.

[0056] As used herein, and unless otherwise stated, the terms “oxygen”, “nitrogen”, “carbon monoxide”, “carbon dioxide” and “hydrogen” refer to O2, N2, CO, CO2 and H2,respectively. The term “NOx” is known in the art and includes nitrogen oxides such as nitric oxide (NO) and nitrogen dioxide (NO2).

[0057] According to a preferred embodiment the invention is the method for heating a heating region according to one or more previous embodiments where the method further comprises the steps of;

[0058] adding mineral melt to the spinner;

[0059] rotating the spinner at a speed sufficient to push the melt through the perforations positioned in the sidewall of the spinner to produce fibres and; passing the fibres through the heating region while the heating region is being heated.

[0060] These steps to produce mineral fibres from mineral melt by cup spinning are known from WO 2008 / 116176 A1 , US 2007 / 0261447 A1 and WO 2016 / 022752 A1.

[0061] One specific example of how the above-described apparatus is used is for the production of glass fibres. A composition of raw materials for glass fiber production is melted in a furnace and the melt is poured into the spinner from the melt gutter. The spinner is rotating at a speed sufficient to push the glass melt through the perforations in the sidewall of the spinner. Glass fibres are produced and passed through the heating region. In the heating region the fibres are kept in a molten state by hot airfrom the cooling ring chamber. The hot air is generated by passing nitrogen gas of a suitable purity, such as the purity set out above, through a number of nontransferred arc plasma torches equally spaced apart from each other in a circle, thereby heating the gas to a temperature of 2000 °C. This heated nitrogen gas enters the cooling ring chamber where it is cooled, by circulation of cooling water through a cooling jacket surrounding the outside of the ring chamber, to a temperature of about 1100 °C. The hot nitrogen gas with a temperature of about 1100 °C is then passed from the annular outlet of the cooling ring chamber into the heating region through which the fibres are passed. The fibres passing through theheating region are kept in a molten state and subsequently allowed to cool and then collected to produce glass wool.

[0062] Another specific example of how the apparatus is used is for the production of mineral wool. A composition of raw materials for mineral wool production is melted in a furnace and the melt is poured into the spinner from the melt gutter. The spinner is rotating at a speed sufficient to push the glass melt through the perforations in the sidewall of the spinner. Mineral fibres are produced and passed through the heating region. In the heating region the fibres are kept in a molten state by hot air from the cooling ring chamber. The hot air is generated by passing essentially pure nitrogen gas through a non-transferred arc plasma torches equally spaced apart for each other in a circle, thereby heating the gas to a temperature of 2000 °C. This heated nitrogen gas enters the cooling ring chamber where it is cooled, by circulation of cooling water through coolant passages, to a temperature of about 1600 °C. The hot nitrogen gas with a temperature of about 1600 °C is then passed from the annular outlet of the cooling ring chamber into the heating region through which the fibres are passed. The fibres passing through the heating region are kept in a molten state and are attenuated by attenuation gasses which pull on the fibres while parts of them are still within the heating region. The mineral fibres are allowed to cool and then collected to produce mineral wool.

Claims

Claims1. An apparatus for creating mineral fibres, comprising;a spinning chamber with a heating region into which fibres are passed and a spinner having perforations in a sidewall and rotation of the spinner causing formation of fibres by passing molten material through the perforations into the heating region;a cooling ring chamber, arranged to cool a carrier gas and subsequently supply the carrier gas to at least a portion of the heating region into which fibres are passed; anda plasma torch arranged to heat the carrier gas and supply the carrier gas to the cooling ring chamber.

2. The apparatus for creating mineral fibres according to claim 1 wherein the heating region abuts the spinner.

3. The apparatus for creating mineral fibres according to any one of the preceding claims wherein the cooling ring chamber has an annular outlet for the carrier gas.

4. The apparatus for creating mineral fibres according to any one of the preceding claims wherein the cooling ring chamber comprises a wall with at least one passage for circulation of coolant.

5. The apparatus for creating mineral fibres according to claim 4 wherein the cooling ring chamber wall comprises a cooling jacket.

6. The apparatus for creating mineral fibres according to any claim 4 where the cooling ring chamber wall comprises at least one cooling coil.

7. The apparatus for creating mineral fibres according to any one of the preceding claims wherein the spinner comprises a sidewall and a base and is mountable on a shaft of a rotor.

8. The apparatus for creating mineral fibres according to any one of the preceding claims wherein the plasma torch is a DC non-transferred arc plasma torch.

9. The apparatus for creating mineral fibres according to any one of the preceding claims characterized in that the apparatus comprises at least 4 plasma torches.

10. The apparatus for creating mineral fibres according to claim 9, characterized in that outlets of the plasma torches are equally spaced apart in the cooling ring chamber.

11. A method for heating a heating region of the apparatus according to any one of the previous claims where a carrier gas is heated in a plasma torch and directed into a cooling ring chamber where the carrier gas is cooled, and the cooling ring chamber directs the carrier gas to the heating region.

12. The method for heating a heating region according to claim 11 wherein the plasma torch heats the carrier gas to a temperature of at least 2000 °C.

13. The method for heating a heating region according to any one of claims 11 and 12 wherein the cooling ring chamber cools the carrier gas to a temperature of at most 1800 °C.

14. The method for heating a heating region according to any one of claim 11-13 where the carrier comprises a gas selected from the group consisting of nitrogen, oxygen, argon, helium, air, hydrogen, carbon monoxide, carbon dioxide and mixtures thereof, preferably the carrier gas is nitrogen.

15. The method for heating a heating region according to any one of claims 11-14 where the method further comprises the steps of;adding mineral melt to the spinner;pushing the melt through the perforations positioned in the sidewall by rotating the spinner to produce fibres and;passing the fibres through the heating region while the heating region is being heated by the carrier gas directed into the heating region from the cooling ring chamber.

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