Ammonia thermal decomposition equipment

Abstract

To provide an ammonia heating / decomposing device capable of effectively decomposing ammonia into hydrogen and nitrogen and suppressing the discharge of NOx, to use ammonia as fuel for a burner of an industrial furnace.SOLUTION: An industrial furnace 1 combusting ammonia being supplied together with combustion air and gas fuel to a burner 10 using a flame F from the burner 10, comprises a direct heating heater H1 disposed in a specified section of an ammonia supply pipe 60 through which ammonia is supplied, to directly / entirely contact and heat ammonia flowing therethrough, and an indirect heating heater H2 attached to the outer peripheral face at the specified section of the ammonia supply pipe 60 to indirectly heat ammonia.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ammonia thermal decomposition apparatus that is attached to an industrial furnace that burns ammonia as fuel. [Background technology]

[0002] In recent years, ammonia, which does not produce carbon dioxide when burned, has been attracting attention as a new fuel from the perspective of curbing global warming. However, when ammonia is mixed with fossil fuels or burned alone, nitrogen oxides (NO X It is known that the amount of emissions of ) increases (see, for example, Patent Document 1).

[0003] The combustion device described in Patent Document 1 solves the problem of increased nitrogen oxides when coal is burned with ammonia added.

[0004] Although ammonia has been attracting attention as a new fuel, there have been no industrial furnaces that effectively use ammonia as fuel, and the technology is currently in the research and development stage. In general, the combustion speed of ammonia is about 25% of that of natural gas, and when burned, nitrogen oxides (NO X This is because the amount of CO2 emissions has increased to a level higher than the regulated value (180 ppm, O2=11%), making it unusable as fuel.

[0005] It is now beginning to be discovered that when the hydrogen content of ammonia gas is around 30%, it has a burning speed similar to that of natural gas, and even at around 20%, it has a burning speed that can be used without any problems in practical applications.

[0006] To use ammonia as fuel for the burners of industrial furnaces, the ammonia must be decomposed into hydrogen and nitrogen, but such equipment does not currently exist. Therefore, industrial furnaces still have to rely on fossil fuels, and as a result, they are unable to reduce the emission of greenhouse gases (nitrogen oxides). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7020759 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide an ammonia thermal decomposition apparatus that can effectively decompose ammonia into hydrogen and nitrogen and suppress the emission of nitrogen oxides in order to use ammonia as fuel for the burners of industrial furnaces. [Means for solving the problem]

[0009] In order to achieve the above object, an ammonia thermal decomposition apparatus (50) of the present invention is an apparatus provided in an industrial furnace (1) in which ammonia supplied to a burner (10) together with combustion air and gas fuel is combusted by a flame (F) from the burner (10), the apparatus being provided at a predetermined portion of an ammonia supply pipe (60) through which the ammonia is supplied, a direct heating heater (H1) that is provided inside a predetermined portion of the ammonia supply pipe (60) and that heats the ammonia passing through the pipe by direct contact with the entire ammonia; Along with The inner surface of a predetermined portion of the ammonia supply pipe (60) is coated with a layer of a catalyst (C) that decomposes the ammonia into hydrogen and nitrogen. It is characterized by:

[0010] The present invention also provides an apparatus for an industrial furnace (1) in which ammonia supplied to a burner (10) together with combustion air and gas fuel is burned by a flame (F) from the burner (10), the apparatus being provided at a predetermined portion of an ammonia supply pipe (60) through which the ammonia is supplied, the apparatus comprising: Inside a predetermined portion of the ammonia supply pipe (60) A heater (H1) covered with a cover (K) made of a catalyst (C) that decomposes the ammonia into hydrogen and nitrogen is provided to heat the ammonia passing through the inside. It is characterized by:

[0011] The present invention also provides 1. An apparatus for an industrial furnace (1) in which ammonia supplied to a burner (10) together with combustion air and gas fuel is burned in a flame (F) from the burner (10), the apparatus being provided at a predetermined portion of an ammonia supply pipe (60) through which the ammonia is supplied, the apparatus comprising: a direct heating heater (H1) provided inside a predetermined portion of the ammonia supply pipe (60) and adapted to heat the ammonia passing through the pipe by direct contact with the ammonia; The ammonia supply pipe (60) is characterized in that a predetermined portion thereof is entirely made of a catalyst (C) that decomposes the ammonia into hydrogen and nitrogen.

[0017] The symbols in parentheses above indicate corresponding elements or matters described in the drawings and in the detailed description of the invention to be described later. [Effects of the Invention]

[0018] According to the ammonia thermal decomposition apparatus of the present invention, a direct heating heater is provided inside a predetermined portion of the ammonia supply pipe, which heats the ammonia passing through the pipe by direct contact with the entire ammonia. Therefore, the heat of the direct heating heater can be directly applied to the ammonia, thereby heating it to a predetermined temperature. This heat effectively decomposes ammonia into hydrogen and nitrogen, allowing the ammonia (hydrogen) to be used efficiently as a burner fuel while simultaneously reducing nitrogen oxide emissions.

[0020] Furthermore, according to the present invention, a predetermined portion of the ammonia supply pipe is entirely made of a catalyst that decomposes ammonia into hydrogen and nitrogen, and this catalytic effect allows ammonia to be decomposed more effectively. Therefore, ammonia can be used more efficiently as fuel for the burner, and nitrogen oxide emissions can be further reduced.

[0021] Furthermore, according to the present invention, a layer of catalyst that decomposes ammonia into hydrogen and nitrogen is coated on the inner circumferential surface of a predetermined portion of the ammonia supply pipe, and the catalytic effect of this layer makes it possible to decompose ammonia more effectively. Therefore, ammonia can be used as fuel for the burner, and nitrogen oxide emissions can be reduced.

[0022] According to the present invention, the ammonia supply pipe is provided with: A heater covered with a cover made of a catalyst that decomposes the ammonia into hydrogen and nitrogen is provided, and the ammonia passing through the inside is heated, so that the catalytic effect can be further enhanced. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a vertical cross-sectional view showing a main part of an industrial furnace equipped with an ammonia thermal decomposition apparatus according to the present invention. [Figure 2]1 is an enlarged cross-sectional view showing an ammonia thermal decomposition apparatus according to a first embodiment of the present invention. [Figure 3] FIG. 4 is an enlarged cross-sectional view showing an ammonia thermal decomposition apparatus according to a second embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing an ammonia thermal decomposition apparatus according to a third embodiment of the present invention. [Figure 5] FIG. 4 is an enlarged cross-sectional view showing another aspect of the direct heating heater according to the first to third embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] An ammonia thermal decomposition apparatus 50 according to a first embodiment of the present invention will be described with reference to FIGS.

[0028] The industrial furnace 1 (here, a metal heating furnace will be described as an example) to which the ammonia thermal decomposition apparatus 50 according to the first embodiment is attached has a generally rectangular cross section as shown in FIG. 1, and is a furnace in which a burner 10 is provided on a side wall 3 of the furnace wall that constitutes the furnace body 2, and ammonia (NH3) is mixed and burned with gas fuel by flame F from the burner 10.

[0029] Ammonia (NH3) is sent from an ammonia supply device 14 to the burner 10 via a first pipe 11, which is provided with an ammonia on-off valve (solenoid valve) 17. The gas fuel, which is an existing gas such as city gas or propane gas, is sent from a gas supply device 15 to the burner 10 via a second pipe 12, which is provided with a gas on-off valve (solenoid valve) 18. As combustion air, outside air is sent by a blower 16 to the burner 10 via an air pipe 13, which is provided with an air on-off valve (solenoid valve) 19. The burner 10 extends horizontally and radiates a flame F horizontally (from right to left in FIG. 1).

[0030] Four ammonia injection nozzles (first ammonia injection nozzle, second ammonia injection nozzle, third ammonia injection nozzle, fourth ammonia injection nozzle) 21, 22, 23, 24 are provided at intervals (equally spaced here) in the direction in which flame F extends, i.e., from right to left in FIG. 1 , on the ceiling wall 5 of industrial furnace 1.

[0031] Ammonia supplied from an ammonia supply device 14 is injected from these ammonia injection nozzles 21, 22, 23, and 24 into the furnace via solenoid valves (first solenoid valve, second solenoid valve, third solenoid valve, fourth solenoid valve) 31, 32, 33, and 34, respectively, in a direction perpendicular to the direction in which the flame F extends, i.e., from top to bottom. An ammonia supply pipe 60 for sending ammonia from the ammonia supply device 14 to each of the ammonia injection nozzles 21 , 22 , 23 , and 24 branches off from the first piping 11 between the ammonia supply device 14 and the ammonia on-off valve 17 . A flue 20 for discharging exhaust gas is provided in a part of the ceiling wall 5 of the industrial furnace 1.

[0032] The ammonia thermal decomposition apparatus 50 according to the first embodiment is attached to an industrial furnace 1 that burns ammonia, which is supplied to the burner 10 together with combustion air and gas fuel, using a flame F from the burner 10, and is provided at a predetermined portion of an ammonia supply pipe 60 through which ammonia is supplied.

[0033] As shown in FIG. 1 , four ammonia thermal decomposition devices 50 according to the first embodiment are provided (first ammonia thermal decomposition device 51, second ammonia thermal decomposition device 52, third ammonia decomposition device 53, and fourth ammonia thermal decomposition device 54). The first ammonia thermal decomposition device 51 is provided on the first ammonia supply pipe 61 between the first solenoid valve 31 and the first ammonia injection nozzle 21. Similarly, the second ammonia thermal decomposition device 52 is provided on the second ammonia supply pipe 62 between the second solenoid valve 32 and the second ammonia injection nozzle 22, and the third ammonia thermal decomposition device 53 is provided on the third ammonia supply pipe 63 between the third solenoid valve 33 and the third ammonia injection nozzle 23. The fourth ammonia thermal decomposition device 54 is similarly provided on the fourth ammonia supply pipe 64 between the fourth solenoid valve 34 and the fourth ammonia injection nozzle 21.

[0034] The location where the ammonia thermal decomposition device 50 is installed is not limited to the above-mentioned predetermined portion, and for example, as shown in Fig. 1, it can be installed only between the ammonia supply device 14 and the ammonia on-off valve 17, or it can be installed between each of the electromagnetic valves 31 to 34 and each of the ammonia injection nozzles 21 to 24 without being installed between the ammonia supply device 14 and the ammonia on-off valve 17. The ammonia thermal decomposition device 50 should be installed as close to the furnace body 2 as possible.

[0035] 2, the ammonia thermal decomposition apparatus 50 according to the first embodiment includes a direct heater H1 and an indirect heater H2 as heating means. The direct heater H1 is disposed at the center of a predetermined portion of the ammonia supply pipe 60, and is disposed so that its entire surface (front surface, rear surface, and outer circumferential surface) is in direct contact with the ammonia passing through the ammonia supply pipe 60. The indirect heater H2 is disposed on the outer circumferential surface of the same predetermined portion of the ammonia supply pipe 60, and indirectly heats the ammonia via the ammonia supply pipe 60.

[0036] Furthermore, in the ammonia thermal decomposition apparatus 50 according to the first embodiment, the inner circumferential surface of the same predetermined portion of the ammonia supply pipe 60 is coated with a layer of catalyst C that decomposes the ammonia into hydrogen and nitrogen. The catalyst C is not particularly limited, but alumina is used in this embodiment. Alumina has the advantage of being less expensive than other catalysts C (e.g., ruthenium-based metals). Therefore, the ammonia thermal decomposition apparatus 50 can be manufactured at low cost.

[0037] Furthermore, by using alumina as catalyst C, it is possible to prevent the ammonia supply pipe 60 from being corroded by ammonia or oxidized by heat, thereby improving the physical stability of the ammonia thermal decomposition apparatus 50.

[0038] Instead of coating with a layer of catalyst C, the entire predetermined portion of the ammonia supply pipe 60 can be formed with catalyst C (for example, alumina) that decomposes ammonia into hydrogen and nitrogen. This also makes it possible to suppress corrosion and oxidation of the ammonia supply pipe 60, and to physically stabilize the ammonia thermal decomposition apparatus 50.

[0039] Furthermore, the ammonia thermal decomposition apparatus 50 according to the first embodiment is provided with a heat insulating member T that surrounds the indirect heater H2. The material of the heat insulating member T is not limited, but common materials such as glass wool and rock wool can be used.

[0040] According to the ammonia thermal decomposition apparatus 50 of the first embodiment, the direct heater H1 and the indirect heater H2 are provided as heating means, and the ammonia can be effectively heated by the action of both of them. This allows the ammonia to be easily decomposed into hydrogen and nitrogen, and the ammonia (hydrogen) can be effectively used as fuel for the burner 10, while at the same time reducing the emission of nitrogen oxides.

[0041] According to the findings of the inventors, the decomposition of ammonia into hydrogen and nitrogen is promoted when heated to 200°C or higher, and the ammonia spontaneously decomposes when heated to 1000°C or higher. Catalyst C such as alumina also effectively promotes the decomposition of ammonia. Therefore, the ammonia thermal decomposition apparatus 50 according to the first embodiment is set to heat ammonia to 200°C or higher and controls the temperature to effectively decompose the ammonia through the action of this heat and the action of the catalyst C (alumina). For this reason, the ammonia thermal decomposition apparatus 50 is suitable for use in an industrial furnace 1 with a heating temperature of less than 1000°C.

[0042] Furthermore, the ammonia thermal decomposition apparatus 50 according to the first embodiment is provided with the heat-retaining member T so as to surround the indirect heating heater H2, thereby preventing heat dissipation from predetermined portions of the indirect heating heater H2 and the ammonia supply pipe 60 and improving the performance of the ammonia thermal decomposition apparatus 50. Furthermore, it is possible to prevent workers from getting burned, ensuring higher safety.

[0043] An ammonia thermal decomposition apparatus 50 according to a second embodiment of the present invention will be described with reference to Figure 3. A major feature of this ammonia thermal decomposition apparatus 50 is that a catalyst C for decomposing ammonia into hydrogen and nitrogen is provided downstream of the direct heater H1 inside a predetermined portion of the ammonia supply pipe 60. There are no particular restrictions on the catalyst C, but alumina is preferred. Note that this catalyst C can also be provided upstream of the DC heater.

[0044] As in the first embodiment, the ammonia thermal decomposition apparatus 50 according to the second embodiment also includes an indirect heater H2 and a heat-retaining member T. The indirect heater H2 can enhance the heating effect, and the heat-retaining member T can enhance the heat-retaining effect.

[0045] According to the ammonia thermal decomposition apparatus 50 of the second embodiment, the ammonia can be effectively heated by the action of the direct heater H1 and the indirect heater H2, and the decomposition of ammonia can be promoted by the action of the catalyst C. As a result, the ammonia can be efficiently decomposed into hydrogen and nitrogen, and the ammonia (hydrogen) can be effectively used as fuel for the burner 10. At the same time, the emission of nitrogen oxides can be reduced.

[0046] An ammonia thermal decomposition apparatus 50 according to a third embodiment will be described with reference to Figure 4. A major feature of this ammonia thermal decomposition apparatus 50 is that a direct heating heater H1 is provided inside a predetermined portion of an ammonia supply pipe 60, and this direct heating heater H1 is configured as a plasma heating device. As in the first embodiment, the inner surface of a predetermined portion of the ammonia supply pipe 60 is coated with a layer of catalyst C that decomposes ammonia into hydrogen and nitrogen, and a heat insulating member T is provided on the outer surface of the predetermined portion. Alumina is suitable as the catalyst C, and a common material such as glass wool can be used as the heat insulating member T.

[0047] In the ammonia thermal decomposition apparatus 50 according to the third embodiment, the direct heater H1 is configured as a plasma heating device, so that ammonia can be heated efficiently in a short time and exhaust gas can be reduced. In addition, the catalyst C promotes decomposition of ammonia, and the heat-retaining member T enhances the heat-retaining effect.

[0048] The direct heater H1 in the first to third embodiments can also be covered with a cover K made of a catalyst C (for example, alumina) as shown in Fig. 5. This can further enhance the catalytic effect.

[0049] Furthermore, although the first and second embodiments are provided with an indirect heater H2 and a heat-retaining member T, these may be omitted. Furthermore, although the third embodiment is not provided with an indirect heater H2, this may be omitted. Furthermore, as the catalyst C in the first to third embodiments, in addition to alumina and the above-mentioned ruthenium-based catalysts, high-entropy alloys made of Co, Mo, Fe, Ni, and Cu, or metal amides and imides may be used.

[0050] In the industrial furnace 1 that burns ammonia supplied to the burner 10 together with combustion air and gas fuel, the direct heating heater H1 50 that is provided inside a predetermined portion of the ammonia supply pipe 60 to which the ammonia is supplied and that heats the ammonia passing through the pipe by directly contacting the ammonia in its entirety is not described at all in the above-mentioned patent documents.

[0051] The fuel cell 50 according to this embodiment can also be used in any field where ammonia is used as fuel (for example, thermal power generation). [Explanation of symbols]

[0052] 1. Industrial furnace 2 Furnace body 3 side wall 5 Ceiling Wall 10 Burner 11 First piping 12 Second piping 13 Air piping 14 Ammonia supply device 15 Gas supply equipment 16 Blower 17 Ammonia on-off valve 18 Gas on-off valve 19 Air on-off valve 20 flue 21 First ammonia injection nozzle 22 Second ammonia injection nozzle 23 Third ammonia injection nozzle 24 No. 4 ammonia injection nozzle 31 First solenoid valve 32 Second solenoid valve 33 Third solenoid valve 34 Fourth solenoid valve 50 Ammonia thermal decomposition equipment 51 First Ammonia Thermal Decomposition Device 52 Second ammonia thermal decomposition device 53 Third Ammonia Thermal Decomposition Unit 54 No. 4 Ammonia Thermal Decomposition Unit 60 Ammonia supply pipe 61 First ammonia supply pipe 62 Second ammonia supply pipe 63 Third ammonia supply pipe 64 No. 4 ammonia supply pipe C catalyst F Flame H1 Direct Heater H2 indirect heater K Cover T Thermal insulation material

Claims

1. 1. An apparatus for use in an industrial furnace in which ammonia supplied to a burner together with combustion air and gas fuel is burned with a flame from the burner, the apparatus being provided at a predetermined portion of an ammonia supply pipe through which the ammonia is supplied, a direct heating heater that is provided inside a predetermined portion of the ammonia supply pipe and that heats the ammonia passing through the pipe by direct contact with the ammonia as a whole; an ammonia thermal decomposition apparatus, wherein a predetermined portion of the inner peripheral surface of the ammonia supply pipe is coated with a catalyst layer for decomposing the ammonia into hydrogen and nitrogen.

2. 1. An apparatus for use in an industrial furnace in which ammonia supplied to a burner together with combustion air and gas fuel is burned with a flame from the burner, the apparatus being provided at a predetermined portion of an ammonia supply pipe through which the ammonia is supplied, a heater covered with a cover made of a catalyst that decomposes the ammonia into hydrogen and nitrogen is provided inside a predetermined portion of the ammonia supply pipe, and the ammonia passing through the inside of the heater is heated.

3. 1. An apparatus for use in an industrial furnace in which ammonia supplied to a burner together with combustion air and gas fuel is burned with a flame from the burner, the apparatus being provided at a predetermined portion of an ammonia supply pipe through which the ammonia is supplied, a direct heating heater that is provided inside a predetermined portion of the ammonia supply pipe and that heats the ammonia passing through the pipe by direct contact with the ammonia as a whole; 1. An ammonia thermal decomposition apparatus, wherein a predetermined portion of the ammonia supply pipe is entirely made of a catalyst that decomposes the ammonia into hydrogen and nitrogen.

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