Metal heating furnace

Abstract

When ammonia, the fuel, is burned directly after being mixed entirely with air, a large amount of nitrogen oxides are produced. Lowering the air-to-aluminum ratio results in the emission of unburned ammonia. Burning the ammonia in a low-oxygen atmosphere effectively suppresses the generation of nitrogen oxides. [Solution] In a metal heating furnace 1 that uses ammonia as fuel, a combustion air nozzle 20 for supplying combustion air into the furnace body 10 is provided on a first mounting wall, which is either a side wall 13 or a ceiling wall 12, and a fuel injection nozzle 30 for supplying ammonia into the furnace body 10 is provided on a second mounting wall, which is either the ceiling wall 12 or the side wall 13, adjacent to the first mounting wall. The combustion air nozzle 20 and the fuel injection nozzle 30 are arranged so that the central axis L1 of the combustion air nozzle 20 and the central axis L2 of the fuel injection nozzle 30 do not intersect on the same plane, and the combustion air supplied from the combustion air nozzle 20 and the ammonia supplied from the fuel injection nozzle 30 do not come into direct contact.

Description

Technical Field

[0001] The present invention relates to a metal heating furnace that uses ammonia as fuel.

Background Art

[0002] Conventionally, as fuel in a metal heating furnace for heat-treating metals such as non-ferrous metals, mainly hydrocarbon-based gases such as natural gas and propane gas have been used. As shown in FIG. 5, in such a conventional metal heating furnace, a fuel nozzle 62 is attached inside an air nozzle 61 provided in a furnace body 60, fuel is injected from the fuel nozzle 62, and it is immediately directly mixed with air supplied from the air nozzle 61 and burned. An air blower 63 and an air control valve 64 are connected to the air nozzle 61, and a fuel supply unit (not shown) and a fuel control valve (not shown) are connected to the fuel nozzle 62.

[0003] However, since the conventional metal heating furnace uses a hydrocarbon-based gas as fuel, there is a problem that it generates carbon dioxide, which causes global warming.

[0004] In view of such problems, in recent years, ammonia, which does not generate carbon dioxide even when burned, has attracted attention as a new fuel. However, it is known that when ammonia is mixed with fossil fuels or burned only with ammonia, the emission amount of nitrogen oxides (NO X ) that have an adverse effect on the human body increases, and it is also known that the generation of nitrogen oxides can be suppressed when ammonia is burned at an air ratio usually used for hydrocarbon fuels (see, for example, Patent Document 1). Further, when the air ratio is lowered to reduce the generation of nitrogen oxides, unburned ammonia is discharged.

[0005] The combustion device described in Patent Document 1 has a configuration as shown in FIG. 6 in order to solve the problem of an increase in nitrogen oxides when ammonia is added to coal and burned, so as to suppress the generation of nitrogen oxides.

[0006] In other words, as shown in Figure 6, an ammonia flow path 77 is formed inside the mixed gas flow path 71 of the burner 70, and an ammonia supply means 72 is provided for supplying ammonia to the ammonia flow path 77. Furthermore, the system includes a control means 73 that controls the supply of ammonia according to operating conditions, and a distribution means 75 (and multiple distribution transport paths 76) that distributes the ammonia sent from the ammonia supply means 72 to the input section 74. The control means 73 controls the distribution of ammonia, and ammonia is also supplied from the input section 74. In other words, in this combustion apparatus, ammonia is supplied into the furnace body from both the ammonia flow path 77 and the input section 74. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 7020759 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the combustion apparatus described in Patent Document 1, ammonia from the input section 74 can be supplied to a low-oxygen atmosphere gas inside the furnace body and burned, thus suppressing the generation of nitrogen oxides. On the other hand, ammonia supplied from the ammonia flow path 77 located inside the mixed gas flow path 71 is immediately mixed directly with the air supplied from the mixed gas flow path 71 and burned, just as in the conventional technology shown in Figure 5. Therefore, it is not possible to suppress the generation of nitrogen oxides.

[0009] Therefore, the object of the present invention is to provide a product that can effectively suppress the generation of nitrogen oxides in a metal heating furnace using ammonia as fuel by burning the ammonia used as fuel in a low-oxygen atmosphere gas without bringing it into direct contact with air. [Means for solving the problem]

[0010] To achieve the above objective, the metal heating furnace (1) of the present invention has a furnace body (10) having a hearth (11), a ceiling wall (12), and side walls (13), and uses ammonia as fuel. A combustion air nozzle (20) is provided on the first mounting wall, which is either the side wall (13) or the ceiling wall (12), and supplies combustion air into the furnace body (10), A fuel injection nozzle (30) is provided on the ceiling wall (12) or side wall (13), which is a second mounting wall adjacent to the first mounting wall, and supplies ammonia into the furnace body (10). The combustion air nozzle (20) and the fuel injection nozzle (30) are arranged such that the central axis (L1) of the combustion air nozzle (20) and the central axis (L2) of the fuel injection nozzle (30) do not intersect on the same plane, and the combustion air supplied from the combustion air nozzle (20) and the ammonia supplied from the fuel injection nozzle (30) do not come into direct contact.

[0011] Furthermore, the present invention is characterized in that, within the furnace body (10), a first cylindrical body (40) having an internal space (40a) through which the combustion air supplied from the combustion air nozzle (20) passes straight is provided via a first gap (41) at a predetermined distance from the first mounting wall, and the low-oxygen concentration atmospheric gas present in the furnace body (10) is continuously passed through the first gap (41) together with the combustion air by the entrainment force of the combustion air passing through the first cylindrical body (40) and circulated within the furnace body (10).

[0012] Furthermore, the present invention is characterized in that, within the furnace body (10), a second cylindrical body (50) having an internal space (50a) through which the ammonia supplied from the fuel injection nozzle (30) passes straight is provided via a second gap (51) at a predetermined distance from the second mounting wall, and the atmospheric gas with a low oxygen concentration present in the furnace body (10) is continuously passed through the second gap (51) together with the ammonia by the entrainment force of the ammonia passing through the second cylindrical body (50) and circulated within the furnace body (10).

[0013] Furthermore, the present invention is characterized by providing a plurality of fuel injection nozzles (30).

[0014] Here, the symbols in parentheses indicate the corresponding elements or items shown in the drawings and the embodiments for carrying out the invention described later. [Effects of the Invention]

[0015] According to the metal heating furnace of the present invention, the central axes of the combustion air nozzle provided on the first mounting wall and the fuel injection nozzle provided on the second mounting wall adjacent to the first mounting wall are arranged so that the central axes of the combustion air nozzle and the central axes of the fuel injection nozzle do not intersect on the same plane. As a result, the ammonia supplied from the fuel injection nozzle can be burned entirely in an atmosphere gas with a low oxygen concentration without directly contacting the air supplied from the combustion air nozzle. Consequently, the generation of nitrogen oxides can be effectively suppressed.

[0016] Furthermore, according to the present invention, a first cylindrical body through which combustion air supplied from a combustion air nozzle passes is provided from a first mounting wall via a first gap, and a low-oxygen concentration atmospheric gas is continuously passed through the first cylindrical body together with the combustion air by the entrainment force of the combustion air passing through the first cylindrical body via the first gap, thereby circulating within the furnace body, and thus the atmospheric gas within the furnace body can be stirred. As a result, all ammonia can be reliably burned in a low-oxygen concentration atmospheric gas, and the generation of nitrogen oxides can be suppressed more effectively.

[0017] Furthermore, according to the present invention, a second cylindrical body through which ammonia supplied from a fuel injection nozzle passes is provided from a second mounting wall via a second gap portion, and an atmosphere gas with a low oxygen concentration is caused to continuously pass through the second cylindrical body together with ammonia through the second gap portion by the entrainment force of the ammonia passing through the second cylindrical body, so that the atmosphere gas in the furnace body can be stirred. As a result, all ammonia can be surely burned in an atmosphere gas with a low oxygen concentration, and thus generation of nitrogen oxides can be more effectively suppressed.

[0018] Still further, according to the present invention, since a plurality of fuel injection nozzles are provided, ammonia supplied from each fuel injection nozzle can be burned in a wide space in the atmosphere gas without directly contacting the air supplied from a combustion air nozzle. As a result, generation of nitrogen oxides can be effectively suppressed.

Brief Description of the Drawings

[0019] [Figure 1] It is a side cross-sectional view of a metal heating furnace according to an embodiment of the present invention. [Figure 2] It is a plan view of the metal heating furnace shown in FIG. 1. [Figure 3] It is a plan view showing a metal heating furnace according to another embodiment of the present invention. [Figure 4] It is a plan view showing a metal heating furnace according to still another embodiment of the present invention. [Figure 5] It is a side cross-sectional view showing a metal heating furnace according to a conventional example. [Figure 6] It is a side partial cross-sectional view showing a metal heating furnace according to another conventional example.

Embodiments for Carrying Out the Invention

[0020] Referring to FIGS. 1 and 2, a metal heating furnace 1 according to an embodiment of the present invention will be described.

[0021] The metal heating furnace 1 according to this embodiment has a furnace body 10 having a hearth 11, a ceiling wall 12, and four side walls 13, and burns ammonia as fuel. It has a combustion air nozzle 20 and three fuel injection nozzles 30. The combustion air nozzle 20 is connected to a blower 21 and a blower control valve 22, and the fuel injection nozzles 30 are connected to a fuel supply unit (not shown) and a fuel control valve 31.

[0022] The combustion air nozzle 20 is installed on the first mounting wall, which is one of the four side walls 13, and supplies combustion air sent from the blower 21 into the furnace body 10 via the combustion air nozzle 20. The fuel injection nozzle 30 is installed on the second mounting wall, which is the ceiling wall 12 adjacent to the first mounting wall, and supplies (injects) ammonia, which is the fuel, into the furnace body 10 via the fuel control valve 31.

[0023] In this embodiment, the side wall 13 is designated as the first mounting wall and the ceiling wall 12 as the second mounting wall, but the present invention is not limited thereto. Therefore, the ceiling wall 12 can also be designated as the first mounting wall and the side wall 13 as the second mounting wall.

[0024] The combustion air nozzle 20 and the three fuel injection nozzles 30 are arranged so that the central axis L1 of the combustion air nozzle 20 and the central axis L2 of each fuel injection nozzle 30 do not intersect on the same plane (see Figure 2). Specifically, in a plan view, one of the three fuel injection nozzles 30 is located on one side of the central axis L1 of the combustion air nozzle 20, and the remaining two are located on the other side of that central axis L1.

[0025] The central axis L1 of the combustion air nozzle 20 is a virtual axis extending parallel to the direction in which the combustion air nozzle 20 extends, from the radial center of the combustion air nozzle 20. Similarly, the central axis L2 of the fuel injection nozzle 30 is a virtual axis extending parallel to the direction in which the fuel injection nozzle 30 extends, from the radial center of the fuel injection nozzle 30.

[0026] In this way, by arranging the combustion air nozzle 20 and the fuel injection nozzle 30 so that their central axes L1 and L2 do not intersect on the same plane, the combustion air supplied from the combustion air nozzle 20 and the ammonia supplied from the fuel injection nozzle 30 are prevented from coming into direct contact.

[0027] Furthermore, this metal heating furnace 1 includes a first cylindrical body 40 and a second cylindrical body 50 within the furnace body 10. The first cylindrical body 40 is cylindrical in shape with an internal space 40a and is positioned near the first mounting wall (side wall 13) via a first gap 41, with its front shape directly facing the combustion air nozzle 20, and in a direction parallel to the direction in which the combustion air nozzle 20 extends. As a result, the combustion air supplied from the combustion air nozzle 20 passes straight through the internal space 40a of the first cylindrical body 40. The constituent material of the first cylindrical body 40 is not limited, but it can be formed from a material with excellent heat resistance, such as solid ceramics or heat-resistant metal.

[0028] The diameter of the internal space 40a of the first cylindrical body 40 is set to be larger than the diameter of the nozzle hole of the combustion air nozzle 20. This allows all the air supplied from the combustion air nozzle 20 to pass through the internal space 40a of the first cylindrical body 40. The size of the first gap 41 between the first mounting wall (side wall 13) and the first cylindrical body 40 located nearby is set to an extent that the so-called ejector effect is produced.

[0029] In other words, when the combustion air supplied from the combustion air nozzle 20 enters the internal space 40a of the first cylindrical body 40, the ambient gas present in the surrounding area is set to such an extent that it can be smoothly and effectively drawn into the internal space 40a of the first cylindrical body 40 through the first gap 41, by the amount of static pressure reduced by the dynamic pressure of the combustion air.

[0030] Furthermore, the second cylinder 50 is also cylindrical in shape and has an internal space 50a. It is positioned near the second mounting wall (ceiling wall 12), with the second gap 51 in between, with its front shape directly facing the fuel injection nozzle 30, and in a direction parallel to the direction in which the fuel injection nozzle 30 extends, so that the ammonia injected from the fuel injection nozzle 30 passes straight through the internal space 50a of the second cylinder 50. The constituent material of the second cylinder 50 is not limited, similar to the first cylinder 40, but it is preferable to form it from a solid ceramic or heat-resistant metal material that has excellent heat resistance.

[0031] The diameter of the internal space 50a of the second cylinder 50 is set to be larger than the diameter of the nozzle hole of the fuel injection nozzle 30, so that all the ammonia injected from the fuel injection nozzle 30 can pass through the internal space 50a of the second cylinder 50. The size of the second gap 51 is also set to be similar to the first gap 41, so as to produce an ejector effect. In other words, when the ammonia injected from the fuel injection nozzle 30 enters the internal space 50a of the second cylinder 50, it is set so that the atmospheric gas present in the surroundings can be smoothly and effectively drawn into the internal space 50a by the amount of static pressure reduced by the dynamic pressure of the ammonia.

[0032] As described above, the metal heating furnace 1 according to this embodiment has a combustion air nozzle 20 provided on the first mounting wall (side wall 13) and a fuel injection nozzle 30 provided on the second mounting wall (ceiling wall 12) adjacent to the first mounting wall, and is arranged so that the central axis L1 of the combustion air nozzle 20 and the central axis L2 of the fuel injection nozzle 30 do not intersect on the same plane. Therefore, the ammonia supplied (injected) from the fuel injection nozzle 30 can be burned entirely in a low-oxygen atmosphere gas without directly contacting the air supplied from the combustion air nozzle 20. As a result, the generation of nitrogen oxides can be reliably suppressed.

[0033] Furthermore, in this metal heating furnace 1, the first cylindrical body 40 is provided from the first mounting wall (side wall 13) via a first gap 41, and combustion air supplied from the combustion air nozzle 20 is passed through its internal space 40a. As a result, the entrainment force of the combustion air passing through the internal space 40a of the first cylindrical body 40 causes the surrounding low-oxygen concentration atmospheric gas to pass continuously through the internal space 40a of the first cylindrical body 40 together with the combustion air through the first gap 41, circulating within the furnace body 10. This allows the atmospheric gas within the furnace body 10 to be stirred, so that all ammonia can be reliably burned in the low-oxygen concentration atmospheric gas, and as a result, the generation of nitrogen oxides can be suppressed more reliably.

[0034] Similarly, in this metal heating furnace 1, the second cylindrical body 50 is provided from the second mounting wall (ceiling wall 12) via a second gap 51, and ammonia injected from the fuel injection nozzle 30 passes through its internal space 50a. As a result, the entrainment force of the ammonia passing through the internal space 50a of the second cylindrical body 50 causes the surrounding low-oxygen concentration atmospheric gas to pass continuously through the internal space 50a of the second cylindrical body 50 together with the combustion air through the second gap 51, circulating within the furnace body 10. This allows the atmospheric gas within the furnace body 10 to be stirred, so that all ammonia can be reliably burned in the low-oxygen concentration atmospheric gas, and as a result, the generation of nitrogen oxides can be suppressed more reliably.

[0035] In this embodiment, the metal heating furnace 1 has three fuel injection nozzles 30, and all of the fuel injection nozzles 30 are arranged so that their respective central axes L1 do not intersect with the central axis L2 of the combustion air nozzle 20 on the same plane. Therefore, the ammonia injected from each fuel injection nozzle 30 can be burned in the atmospheric gas without directly contacting the air supplied from the combustion air nozzle 20. As a result, the generation of nitrogen oxides can be effectively suppressed.

[0036] Furthermore, in the metal heating furnace 1 according to the above embodiment, three fuel injection nozzles 30 are provided, one of which is located on one side of the central axis L1 of the combustion air nozzle 20, and the remaining two are located on the other side of the central axis L1. However, the present invention is not limited to this configuration. Therefore, for example, in the case where three fuel injection nozzles 30 are provided as shown in Figure 1, all of them can be located on one side of the central axis L1. Also, as shown in Figure 3, only one fuel injection nozzle 30 can be provided and located on one side of the combustion air nozzle 20.

[0037] Furthermore, as shown in Figure 4, two fuel injection nozzles 30 can be provided, with one positioned on one side of the central axis L1 of the combustion air nozzle 20 and the other on the other side of its central axis L1. Alternatively, both can be positioned on one side (or the other side) of the central axis L1 of the combustion air nozzle 20. Moreover, four or more fuel injection nozzles 30 can be provided, and their arrangement can be appropriately set within a range where the two central axes L1 and L2 do not intersect on the same plane.

[0038] Furthermore, in a metal heating furnace 1 using ammonia as fuel, a configuration in which the combustion air nozzle 20 and the fuel injection nozzle 30 are arranged so that their central axes L1 and L2 do not intersect on the same plane is not described in the aforementioned patent document. Also, a configuration in which a first cylindrical body 40 is provided near the combustion air nozzle 20 via a first gap 41, and a second cylindrical body 50 is provided near the fuel injection nozzle 30 via a second gap 51 is not described in the same patent document. [Explanation of symbols]

[0039] 1 Metal heating furnace 10 Furnace body 11 hearth 12. Ceiling wall (second mounting wall) 13. Side wall (first mounting wall) 20 Combustion air nozzles 21 Blower 22 Airflow control valve 30 Fuel Injection Nozzles 31 Fuel control valve 40 First cylinder 40a Internal space of the first cylinder 41 First gap part 50 Second cylinder 50a Internal space of the second cylinder 51 Second gap 60 Furnace body 61 Air nozzle 62 Fuel Nozzle 63 Blower 64 Airflow control valve 70 burners 71 Mixed gas flow path 72 Ammonia supply means 73 Control means 74 Insertion section 75 Means of distribution 76 Distribution transport paths 77 Ammonia flow path L1 Combustion air nozzle center axis L2 fuel injection nozzle center axis

Claims

1. A metal heating furnace having a hearth, ceiling walls and side walls, and using ammonia as fuel, A combustion air nozzle is provided on the first mounting wall, which is one of the side walls and the ceiling wall, for supplying combustion air into the furnace body, A fuel injection nozzle is provided on the ceiling wall or side wall, which is a second mounting wall adjacent to the first mounting wall, and supplies ammonia into the furnace body. A metal heating furnace characterized in that the combustion air nozzle and the fuel injection nozzle are arranged so that their central axes do not intersect on the same plane, and the combustion air supplied from the combustion air nozzle and the ammonia supplied from the fuel injection nozzle do not come into direct contact.

2. The metal heating furnace according to claim 1, wherein a first cylindrical body having an internal space through which the combustion air supplied from the combustion air nozzle passes straight is provided within the furnace body, separated from the first mounting wall by a first gap at a predetermined distance, and a low-oxygen concentration atmospheric gas present in the furnace body is circulated within the furnace body by passing through the first gap and continuously through the first cylindrical body together with the combustion air due to the entrainment force of the combustion air passing through the first cylindrical body.

3. A metal heating furnace according to claim 1 or 2, characterized in that, within the furnace body, a second cylindrical body having an internal space through which the ammonia supplied from the fuel injection nozzle passes straight is provided with a second gap portion at a predetermined distance from the second mounting wall, and an atmospheric gas with a low oxygen concentration present in the furnace body is continuously passed through the second gap portion together with the ammonia by the entrainment force of the ammonia passing through the second cylindrical body, thereby circulating within the furnace body.

4. The metal heating furnace according to claim 1 or 2, characterized in that a plurality of fuel injection nozzles are provided.

5. The metal heating furnace according to claim 3, characterized in that a plurality of fuel injection nozzles are provided.

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