Gas-fired furnace

Abstract

The invention provides an apparatus and method for operating a cyclone burner using a gaseous fuel.

Description

Technical Field

[0001] This invention belongs to the field of furnaces for melting mineral materials, and particularly to furnaces for melting mineral materials during the manufacturing of fibers. Background Technology

[0002] Cyclone furnaces were created in the field of mineral melting processes.

[0003] Existing cyclone furnaces operate solely or primarily on coal or other solid or liquid fuels. Coal offers particular advantages as the primary fuel during cyclone furnace operation because it produces a slow-burning flame. WO2014057130A1 allows for the selective injection of secondary gaseous fuel, comprising less than 40% of the total fuel energy, into the lower part of the central region of the cyclone furnace to provide a flame there. The primary fuel used for melting mineral feedstocks is pellets.

[0004] US3077094 discloses a cyclone furnace in which air, gaseous fuel, and optional feedstock are mixed together before entering the furnace. The gaseous fuel is rapidly combusted in this configuration.

[0005] WO2016 / 092100A1 uses solid or liquid primary fuels to melt mineral feedstocks. Gaseous fuel can be used as a secondary fuel, injected together with pellet fuel in a lower section of the cyclone furnace than the primary fuel. This produces a stable flame in the lower part of the cyclone furnace near the molten pool, where the gaseous fuel burns rapidly and preheats the secondary pellet fuel. This setup allows for the efficient use of cheaper fuels, such as coal, while obtaining a high-quality melt. In WO2016 / 092100A1, pellet (i.e., solid or liquid) fuel is essential as the primary fuel, and gaseous fuel is injected together with pellet fuel only in the lower part of the cyclone furnace.

[0006] EP 1 944 873 A1 discloses a cyclone furnace for melting mineral materials, wherein the primary fuel is pellets, particularly coal. Pellet fuel is injected only at the top of the combustion chamber for the melting stage. To form a flame above the molten pool, a combination of gaseous fuel and pellet fuel is introduced into the lower part of the furnace. This flame is said to be advantageous for controlling the temperature of the molten pool, and consequently, for controlling the viscosity of the molten mineral leaving the furnace. However, pellet fuel is essential as the primary fuel described in this document.

[0007] Although coal and other pellet fuels have been widely used in cyclone furnaces for economic reasons, there is a desire to use gaseous fuels as the sole or primary fuel to improve the environmental characteristics of the melting process. During the development of this invention, attempts to directly replace pellet fuels with gaseous fuels using the same furnace setup were unsuccessful. Gaseous fuels burn faster than pellet fuels, and the flame is also shorter than that of coal. Directly replacing pellet fuels with gaseous fuels would lead to fuel inlet blockage due to slag formation, making the process infeasible. The very rapid combustion rate of gaseous fuels causes the mineral feedstock to sinter almost instantaneously, resulting in undesirable inlet blockage.

[0008] The purpose of this invention is to provide an apparatus and method for producing mineral melts using gaseous fuels in a cyclone furnace, thereby improving the environmental characteristics of the process while maintaining melt quality and apparatus lifespan. Summary of the Invention

[0009] The present invention provides a method for melting mineral materials, the method comprising: providing a cyclone furnace, granular mineral raw materials, gaseous fuel, and an oxidant; injecting the gaseous fuel into the furnace at one or more first injection ports; injecting the oxidant into the furnace at one or more second injection ports; injecting the mineral raw materials into the furnace at one or more third injection ports; causing the gaseous fuel and the oxidant to burn together, thereby melting the mineral raw materials; characterized in that each of the first injection ports and one or more of the second injection ports are spaced apart by a certain angular distance, such that when measured about a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any second injection port is less than 20 degrees.

[0010] The present invention also provides a cyclone furnace for melting mineral materials using gaseous fuel as the sole or primary fuel. The furnace includes: a furnace body having a wall, a furnace cover, one or more first injection ports for injecting gaseous fuel into the furnace, one or more second injection ports for injecting oxidant into the furnace, and one or more third injection ports for injecting mineral raw materials into the furnace; wherein the furnace body includes a top portion, a central portion, and a bottom portion, characterized in that one or more first injection ports, one or more second injection ports, and one or more third injection ports respectively inject gaseous fuel, oxidant, and mineral raw materials into the top portion of the furnace, and each first injection port is spaced apart from one or more second injection ports by a certain angular distance, such that when measured about a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any second injection port is less than 20 degrees.

[0011] The primary fuel of this invention is a gaseous fuel. The gaseous fuel can be natural gas, biogas, shale gas, or other available gas types, or combinations thereof. Preferably, at least 60% of the energy in this method originates from the gaseous fuel; more preferably, at least 80% of the energy originates from the gaseous fuel. In this invention, the sole fuel can be gaseous. This has the benefit of reducing or even eliminating particulate fuels (such as coal), thereby improving the environmental characteristics of the method.

[0012] Additional burners or electrodes for Joule heating can be positioned above or submerged in the molten pool. These burners or electrodes help to homogenize the mineral melt.

[0013] The oxidant can be air, oxygen, or oxygen-enriched air. Preferably, oxygen-enriched air is used in this invention, which can be achieved by injecting oxygen into the air supply. The use of pure oxygen allows for a smaller furnace volume, but increases costs in such a process, while using air alone reduces costs but requires a larger furnace volume than oxygen-enriched air.

[0014] The mineral raw material is preferably granular. Preferably, the raw material particles have a size in the millimeter range. Preferably, at least 99% (especially all) of the particles have a diameter less than 4 mm, and preferably 50% by weight of the particles have a diameter less than 2 mm. The composition can be any glass, stone, or slag composition generally suitable for forming artificial glass fibers (MMVF). The preferred fiber composition is within the following parameters, in terms of oxides (wt%):

[0015] SiO2: at least 30, 32, 35 or 37; not exceeding 51, 48, 45 or 43

[0016] Al2O3: at least 14, 15, 16 or 18; not exceeding 35, 30, 26 or 23

[0017] CaO: at least 8 or 10; not exceeding 30, 25 or 20

[0018] MgO: at least 2 or 5; not more than 25, 20 or 15

[0019] FeO (including Fe2O3): at least 4 or 5; not exceeding 15, 12 or 10

[0020] FeO+MgO: at least 10, 12 or 15; not exceeding 30, 25 or 20

[0021] Na₂O + K₂O: 0 or at least 1; not exceeding 10

[0022] CaO + Na₂O + K₂O: at least 10 or 15; not exceeding 30 or 25

[0023] TiO2: 0 or at least 1; not exceeding 6, 4 or 2

[0024] TiO2+FeO: at least 4 or 6; not exceeding 18 or 12

[0025] B2O3: 0 or at least 1; not exceeding 5 or 3

[0026] P2O5: 0 or at least 1; not exceeding 8 or 5

[0027] Other: 0 or at least 1; not exceeding 8 or 5.

[0028] In this method, the furnace can have a known structure for cyclone furnaces. Specifically, it can have a structure comprising a top portion, preferably substantially cylindrical, a central portion, preferably substantially truncated conical, and a lower portion, preferably substantially cylindrical. This allows a molten pool to be formed in the lower portion for collecting and clarifying the mineral melt.

[0029] Preferably, gaseous fuel, oxidant and mineral raw materials are all injected into the top of the furnace or near the top of the furnace.

[0030] Preferably, the second and third injection ports are integrated into one unit, allowing the oxidant and mineral feedstock to be injected together. In this case, the gaseous fuel is separated from the oxidant and mineral feedstock during injection.

[0031] Gaseous fuel is preferably injected through the furnace lid.

[0032] It is preferable not to inject additional fuel into the top part of the furnace.

[0033] Additional gaseous fuel can be injected into the bottom portion of the furnace through other injection ports, typically just above the molten pool. The proportion of energy generated by the fuel injected through the first injection port near the top of the furnace used in this method is typically at least 40%, preferably 45% to 55%, and particularly about 50%.

[0034] The preferred method is to inject the mineral raw materials and oxidant through the side wall of the furnace.

[0035] The individual injection ports for gaseous fuel are positioned at least 20 degrees away from any inlet for oxidant. This separation ensures that combustion and the resulting heat release occur sufficiently slowly. The angular distance is measured about a vertical axis passing through the center of the furnace.

[0036] Injecting gaseous fuel through the cover further facilitates the separation of the gaseous fuel from the oxidizer upon injection into the furnace. This separation means that the gaseous fuel burns more slowly with controlled heat release, allowing the mineral feedstock to melt inside the furnace rather than sinter at the inlet (sintering at the inlet, in turn, could lead to blockage of the mineral feedstock inlet). Another advantage of injecting gaseous fuel through the cover rather than the sidewall is a significant reduction in wear on the furnace walls.

[0037] When gaseous fuel is injected through the furnace lid, the gaseous fuel inlet can be at an upward angle of 30 to 90 degrees relative to the lid. A lower angle is preferred for better mixing of the gaseous fuel with the mineral feedstock and oxidant, allowing the gaseous fuel to swirl through the airflow and burn in a controlled manner to melt the mineral feedstock. Extremely low angles below 30 degrees are undesirable because this requires a longer lance, especially when using a thicker water-cooled furnace lid.

[0038] Gaseous fuel and gaseous oxidant can be provided in stoichiometric or superstoichiometric (excess oxygen) ratios. A volume ratio of natural gas to oxygen-enriched air in the range of 1:4 to 1:15, particularly in the range of 1:5 to 1:8, may be particularly suitable for the apparatus of the present invention.

[0039] The gaseous fuel and oxidant can independently have an injection velocity in the range of 20 m / s to 100 m / s, preferably in the range of 40 m / s to 80 m / s. The particulate feedstock can have an injection velocity in the range of 20 m / s to 60 m / s, preferably in the range of 30 m / s to 40 m / s. Attached Figure Description

[0040] Figure 1 A schematic top view of the furnace according to the present invention is shown.

[0041] Figure 2 A schematic vertical cross-section of the upper portion of the furnace according to the invention is shown.

[0042] Figure 3 A schematic diagram of a furnace according to the present invention is shown. Detailed Implementation

[0043] The figure shows an exemplary furnace according to the present invention.

[0044] Figure 1 A schematic top view of furnace 1 is shown. A gaseous fuel inlet 2 passes through the furnace cover 3, which includes an exhaust outlet 4 at its center. Mineral feedstock and an oxidant (such as air or oxygen-enriched air) are injected into the furnace through an inlet 5 located at the top of the sidewall of furnace 1. The top of furnace 1 is typically cylindrical, with a single continuous sidewall.

[0045] The gaseous fuel injection ports 2 are spaced apart from each other at equal angular distances. The angular spacing between the gaseous fuel injection ports 2 is as follows: Figure 1 Angle A is shown in the diagram. In this case, angle A is 90° because there are four such inlet ports 2, equidistantly spaced around the circumference of the furnace. Inlet ports 5 for mineral feedstocks and oxidants are spaced apart from each other at equal angular distances. The angular distance between inlet ports 5 is as follows: Figure 1 Angle B is shown in the diagram. In this case, angle B is 90 degrees.

[0046] °, because there are four such inlets 5, equidistant from each other on the circumference of the furnace. It can be seen that each inlet 5 is spaced at least 20 degrees angularly from the nearest gaseous fuel inlet 2. The angular distance between each inlet and the nearest gaseous fuel inlet 2 is shown as angle C, and in this embodiment, angle C is approximately 45°. The angular distance is measured near a point at the center of this schematic top view.

[0047] Mineral feedstock, oxidant, and gaseous fuel are tangentially injected into furnace 1 and move in a circulating flow at or near the cyclone system. The position and angle of the gaseous fuel inlet 2 mean that the gaseous fuel is injected into the flow of oxidant and mineral feedstock, promoting slower mixing and energy release, causing the mineral feedstock to melt as the gaseous fuel burns.

[0048] Figure 2 A cross-sectional side view of the furnace 1 according to the invention is shown. Mineral feedstock and an oxidant (typically air, oxygen, or oxygen-enriched air) are injected together through inlet 5. Specifically, in this embodiment, the oxidant enters through inlet 5a, the mineral feedstock enters through inlet 5b, and both components enter together into the top portion 1a of the furnace 1. Alternatively (not shown), the feedstock can be injected via cover 3 at a location adjacent to the oxidant inlet. If oxygen-enriched air is used as the oxidant, this can be achieved by injecting oxygen into the airflow at inlet 5a.

[0049] The basic direction of material flow inside furnace 1 is also as follows Figure 2 As shown. The oxidant and mineral feedstock provide a flow into which gaseous fuel is injected via inlets 2 through the furnace lid. Each inlet 2 is positioned at an angle D of 30 to 90 degrees to the furnace lid. This allows for delayed mixing, enabling the energy released from the combustion of the fuel to melt the mineral feedstock, while allowing the fuel to burn before being drawn out from the exhaust outlet 4. The circulating flow continues as the mineral material melts and descends along the furnace to the central portion 1b and the bottom portion 1c. Figure 2 (Not shown in the image).

[0050] Figure 3 An external schematic diagram of furnace 1 is shown. A top portion 1a, typically cylindrical, a central portion 1b, typically truncated conical, and a bottom portion 1c, typically cylindrical, are shown. An inlet 5 for mineral feedstock and oxidant, and an inlet 2 for gaseous fuel, are located at the top of furnace 1. Specifically, the gaseous fuel inlet 2 passes through the furnace cover 3, and the inlet 5 for mineral feedstock and oxidant passes through the side wall of the top portion 1a of furnace 1.

[0051] Additional heating devices, such as additional burners or electrodes, may be installed in the central portion 1b and / or the bottom portion 1c to heat and refine the molten mineral material. However, the primary fuel source is gaseous fuel, and the energy for melting the mineral material is provided by gaseous fuel injected at or near the top of the furnace 1.

[0052] An outlet 6 for the mineral melt is provided in the bottom portion 1c. Figure 3 In the furnace, outlet 6 is in the form of a siphon. Alternatively, outlet 6 can also be located at the base of furnace 1 (not shown).

[0053] Mineral melts can be fed into fiberizing devices, such as internal centrifuges (rotating cups) or external centrifuges (cascaded rotators). In the fiberizing device, the mineral melts are converted into fibers in a conventional manner, and then mineral fiber products can also be formed in a conventional manner.

Claims

1. A method for preparing a mineral melt, the method comprising: We provide cyclone furnaces, granular mineral feedstocks, gaseous fuels, and oxidants. Gaseous fuel is injected into the furnace through one or more first injection ports. The oxidant is injected into the furnace through one or more second injection ports. The mineral raw materials are injected into the furnace through one or more third injection ports. The gaseous fuel, the oxidant, and the mineral raw materials are all injected into the top of the furnace. The gaseous fuel is burned together with the oxidant, thereby melting the mineral raw material. The feature is that each first injection port is spaced apart from one or more second injection ports by a certain angular distance, such that when measured around a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any second injection port is less than 20 degrees.

2. The method according to claim 1, wherein each of the second injection ports and the third injection port are integrated into one unit.

3. The method of claim 1, wherein each of the first injection ports is spaced apart from the one or more third injection ports by a certain angular distance, such that when measured about a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any third injection port is less than 20 degrees.

4. The method according to any one of claims 1 to 3, wherein the gaseous fuel injected through one or more first injection ports provides at least 40% of the energy in the furnace.

5. The method of claim 4, wherein the gaseous fuel injected through one or more first injection ports provides at least 50% of the energy in the furnace.

6. The method according to any one of claims 1 to 3, wherein the furnace comprises a furnace body and a furnace cover, and wherein the first injection port passes through the furnace cover.

7. The method according to any one of claims 1 to 3, wherein the furnace comprises a furnace body having side walls and a furnace cover, the furnace body comprising a top portion, a central portion and a bottom portion, wherein the second injection port and the third injection port pass through the side wall of the top portion of the furnace body.

8. The method of claim 6, wherein one or more first injection ports are each positioned at an angle of 30 to 90 degrees to the furnace cover of the furnace.

9. The method according to any one of claims 1 to 3, wherein the mineral raw material has the following composition in weight percent: SiO2: 30 to 51 Al2O3: at least 14; and not more than 35 CaO: 8 to 30 MgO: 2 to 25 FeO includes Fe2O3: 4 to 15 FeO+MgO: 10 to 30 Na₂O + K₂O: at most 10 CaO + Na₂O + K₂O: 10 to 30 TiO2: up to 6 TiO2+FeO: 4 to 18 B2O3: up to 5 P2O5: up to 8 Other: up to 8.

10. The method of claim 9, wherein Al2O3 comprises at least 15 and no more than 30% by weight of the mineral raw material composition.

11. The method of claim 9, wherein Al2O3 comprises at least 16 and no more than 26% by weight of the mineral raw material composition.

12. The method of claim 9, wherein Al2O3 comprises at least 18 and no more than 23% by weight of the mineral raw material composition.

13. The method according to any one of claims 1 to 3, wherein the oxidant is air, oxygen or oxygen-enriched air.

14. The method of claim 13, wherein the oxidant is oxygen-enriched air.

15. A cyclone furnace for melting mineral raw materials, the cyclone furnace comprising: The furnace body, furnace cover, one or more first injection ports for injecting gaseous fuel into the furnace, one or more second injection ports for injecting oxidant into the furnace, and one or more third injection ports for injecting mineral raw materials into the furnace. The furnace body includes a top section, a central section, and a bottom section. The characteristic feature is that each first injection port is spaced apart from the one or more second injection ports by a certain angular distance, such that when measured around a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any second injection port is less than 20 degrees, and The first injection port, the second injection port, and the third injection port are each configured to inject the gaseous fuel, the oxidant, and the mineral raw material into the top of the furnace, respectively.

16. The cyclone furnace according to claim 15, wherein each of the second injection ports and the third injection port are integrated into one unit.

17. The cyclone furnace of claim 15, wherein each of the first injection ports is spaced apart from the one or more third injection ports by a certain angular distance, such that when measured about a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any third injection port is less than 20 degrees.

18. The cyclone furnace of claim 16, wherein each of the first injection ports is spaced apart from the one or more third injection ports by a certain angular distance, such that when measured about a vertical axis passing through the center of the cyclone furnace, the angular distance between any first injection port and any third injection port is less than 20 degrees.

19. The cyclone furnace according to any one of claims 15 to 18, wherein the furnace includes a side wall and a furnace cover, and wherein the first inlet passes through the furnace cover.

20. The cyclone furnace according to claim 19, wherein one or more first inlets are each positioned at an angle of 30 to 90 degrees to the furnace cover.

21. The cyclone furnace according to any one of claims 15 to 18, wherein the furnace includes a side wall and a furnace cover, the side wall including a top portion, a central portion and a bottom portion, wherein the second injection port and the third injection port pass through the top portion of the side wall.

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