Combustor

Abstract

The present invention reduces unburned ammonia when ammonia is used as fuel. A combustor (10) comprises: a burner (11) that injects fuel containing ammonia into a combustion space (S); and a refractory material (12) that defines at least a portion of the combustion space (S). The refractory material (12) blocks passage of combustion gas, and the refractory material (12) contains a catalyst (C), which decomposes ammonia into hydrogen and nitrogen, on a surface (1b) that defines at least a portion of the combustion space (S).

Description

Technical Field

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[0001] The present disclosure relates to a combustor. This application claims the benefit of priority based on Japanese Patent Application No. 2023-97817 filed on June 14, 2023, the content of which is incorporated herein by reference.

Background Art

[0002] In a combustor, a catalyst may be used to promote combustion. For example, Patent Document 1 discloses a catalyst cylinder used for a burner nozzle. In this burner nozzle, a fuel such as kerosene is used. The primary combustion flame from the burner nozzle is blown into the catalyst cylinder. The catalyst cylinder includes a number of outlet holes. The primary combustion flame is completely burned by the catalyst when passing through the catalyst cylinder and is ejected as a secondary combustion flame from the number of outlet holes.

[0003] Further, Patent Document 2 discloses a cylindrical catalyst layer used for a pipe burner. The catalyst layer is arranged to surround the pipe burner. The pipe burner includes a number of small holes. Also, the catalyst layer has gas permeability. A mixed gas of fuel and air is supplied to the pipe burner. The mixed gas is ignited, and flames are formed from the number of small holes of the pipe burner. Also, the combustion gas is catalytically burned when passing through the catalyst layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Ammonia is known as a fuel that does not emit CO2. However, its combustion rate is slower than that of other fuels such as natural gas. Therefore, when using ammonia in the combustor described above, unburned ammonia can become a problem.

[0006] This disclosure aims to provide a combustor that can reduce unburned ammonia when ammonia is used as fuel. [Means for solving the problem]

[0007] A combustor according to one aspect of the present disclosure comprises a burner for injecting a fuel containing ammonia into a combustion space, and a refractory material defining at least a portion of the combustion space, wherein the refractory material blocks the passage of gas, and the refractory material contains a catalyst for decomposing ammonia into hydrogen and nitrogen on a surface defining at least a portion of the combustion space.

[0008] The catalyst may also contain a transition metal.

[0009] The combustion device may be a radiant burner, and the refractory material may be burner tiles.

[0010] The radiant burner may be a radiant cup burner, and the burner tile may include a recess as at least part of the combustion space.

[0011] The depression may be defined by a smooth spherical surface.

[0012] The surface of the burner tile containing the catalyst may include at least one of protrusions and grooves.

[0013] The refractory material may also be part of the furnace wall where the burner is located. [Effects of the Invention]

[0014] According to this disclosure, unburned ammonia can be reduced when ammonia is used as fuel. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic cross-sectional view of a boiler equipped with a combustor according to the first embodiment. [Figure 2] Figure 2 is a schematic enlarged view of section A in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing a combustor according to the second embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing a combustor according to the third embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing a combustor according to the fourth embodiment. [Modes for carrying out the invention]

[0016] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The specific dimensions, materials, and numerical values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0017] Figure 1 is a schematic cross-sectional view of a boiler 100 equipped with a combustor 10 according to the first embodiment. In this embodiment, the combustor 10 is applied to the boiler 100. In other embodiments, the combustor 10 may be applied to other combustion equipment such as an industrial furnace or combustion furnace. For example, the boiler 100 comprises a furnace 1, a flue 2, and a plurality of combustors 10. The boiler 100 may further comprise other components.

[0018] The furnace 1 burns a fuel containing ammonia to generate combustion gas. For example, the furnace 1 may burn a mixed fuel of ammonia and other fuels such as pulverized coal. Also, the furnace 1 may burn only ammonia. Further, the furnace 1 may burn a fuel not containing ammonia as required.

[0019] The furnace 1 extends in the vertical direction. The lower part of the furnace 1 defines a combustion space S. In the present disclosure, the combustion space means the space where the fuel is burned. An outlet Ex is provided at the bottom of the furnace 1. The outlet Ex discharges the ash generated by combustion to the outside.

[0020] The flue 2 is a passage for guiding the combustion gas generated in the furnace 1 to the outside. The flue 2 is connected to the upper part of the furnace 1. For example, the flue 2 includes a first flue 2a and a second flue 2b. The first flue 2a extends horizontally from the upper part of the furnace 1. The second flue 2b extends downward from the end of the first flue 2a.

[0021] For example, the boiler 100 includes a superheater (not shown) installed in the upper part of the furnace 1. The superheater exchanges heat between the combustion gas generated in the furnace 1 and water. Thereby, steam is generated. Also, for example, the boiler 100 may further include components (not shown) such as a reheater, a fuel economizer or an air preheater.

[0022] The combustor 10 is provided on the lower wall of the furnace 1. A plurality of combustors 10 are arranged at intervals along the wall of the furnace 1 in the horizontal direction. FIG. 1 shows only a single row of combustors 10 in the vertical direction, but multiple rows of combustors 10 may be arranged at intervals in the vertical direction.

[0023] The combustor 10 injects fuel into the combustion space S. By igniting the fuel injected from the combustor 10, a flame F is formed in the combustion space S. The furnace 1 is provided with an ignition device (not shown) for igniting the fuel injected from the combustor 10.

[0024] Figure 2 is a schematic enlarged view of part A in Figure 1. For example, in this embodiment, the combustor 10 includes a burner 11, a refractory material 12, an oxidizer flow path 13, and a control device 90. The combustor 10 may further include other components.

[0025] For example, the burner 11 is mounted on the wall of the furnace 1 outside the furnace 1. The burner 11 faces the combustion space S. The burner 11 injects a fuel containing ammonia into the combustion space S. The burner 11 includes a nozzle (not shown) for injecting ammonia. The burner 11 may further include a nozzle (not shown) for injecting other fuels, such as pulverized coal. The burner 11 may further include a nozzle (not shown) for injecting an oxidizer (e.g., air).

[0026] For example, a valve V1 may be provided in the ammonia line L1 connected to the burner 11. The valve V1 may be connected to the control device 90 via wired or wireless communication and may be controlled by the control device 90. For example, the control device 90 adjusts the flow rate of ammonia supplied to the burner 11 by controlling the opening of the valve V1.

[0027] The burner 11 has a generally cylindrical shape. In this disclosure, the axial direction, radial direction, and circumferential direction of the burner 11 may be simply referred to as "axial direction," "radial direction," and "circumferential direction" unless otherwise specified. The same applies to the burner 22 (described later) according to the second embodiment. One end of the burner 11 in the axial direction includes an injection hole 11a and is exposed to the combustion space S. The injection hole 11a injects fuel into the combustion space S.

[0028] The refractory material 12 defines at least a portion of the combustion space S. In this embodiment, the refractory material 12 is part of the wall of the furnace 1 where the burner 11 is located. The refractory material 12 blocks the passage of gas.

[0029] At least a portion of the surface of the refractory material 12 that defines the combustion space S contains a catalyst C that decomposes ammonia into hydrogen and nitrogen. Specifically, in this embodiment, the furnace 1 includes a plurality of communication holes 1a. The communication holes 1a penetrate horizontally through the wall of the furnace 1. For example, the communication holes 1a have a cylindrical shape. A burner 11 is attached to each communication hole 1a. The burner 11 faces the interior of the furnace 1 through the communication hole 1a. The burner 11 injects fuel into the space inside the communication hole 1a. Therefore, the inner circumferential surface 1b of the communication hole 1a defines a portion of the combustion space S.

[0030] The inner circumferential surface 1b contains the catalyst C. Specifically, for example, the inner circumferential surface 1b may be formed by a layer 1c of a carrier supporting the catalyst C. For example, such a layer 1c may be provided on the surface of a through hole formed in the wall of the furnace 1.

[0031] For example, catalyst C contains a transition element (also called a transition metal). For example, catalyst C may contain a noble metal such as Ru. Alternatively, for example, catalyst C may contain non-noble metals among the transition elements, such as Fe, Co, Ni, and Cu. Non-noble metals may exhibit high activity when combined with certain supports. As a support, for example, an oxide such as Al2O3 or SiO2 may be used. If necessary, a support that can suppress sintering, such as CeO2, may also be used.

[0032] The oxidizer channel 13 supplies an oxidizer (e.g., air) Ox to the combustion space S. The oxidizer channel 13 is in fluid communication with the combustion space S. For example, the oxidizer channel 13 supplies the oxidizer Ox to the combustion space S from the radially outside of the injection hole 11a. For example, the oxidizer channel 13 is located radially outside the burner 11. For example, the oxidizer channel 13 is continuous in the circumferential direction. In this embodiment, the oxidizer channel 13 has a generally truncated cone shape. In this embodiment, the oxidizer channel 13 is located concentrically with the burner 11.

[0033] For example, a valve V2 may be provided in the oxidizer line L2 connected to the oxidizer flow path 13. The valve V2 may be connected to the control device 90 via wired or wireless communication and may be controlled by the control device 90. For example, the control device 90 adjusts the flow rate of the oxidizer Ox supplied to the combustion space S via the oxidizer flow path 13 by controlling the opening degree of the valve V2.

[0034] The control device 90 controls all or some of the multiple combustors 10. The control device 90 may also control at least some of the other components of the boiler 100. For example, the control device 90 may control the entire boiler 100. The boiler 100 may also include a main control device (not shown), and the control device 90 may communicate with the main control device. The control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, which are connected to each other via a bus. For example, the processor 90a includes a CPU (Central Processing Unit), etc. For example, the storage device 90b is a hard drive. The control device 90 includes a disk, a ROM for storing programs, and RAM as a work area. The control device 90 is connected to each component of the combustor 10 via a connector 90c so as to be able to communicate with it by wire or wirelessly. For example, the control device 90 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. For example, the operation of the control device 90 may be realized by having the processor 90a execute a program stored in the storage device 90b.

[0035] Ammonia reacts on catalyst C to produce the following reactions (1), (2), or a combination thereof. (1)NH3→1.5H2+0.5N2ΔH=45.4(kJ / mol) (2)2NH3+1.5O2→N2+3H2O ΔH=-382.6(kJ / mol)

[0036] For example, in this embodiment, catalyst C can cause both reactions (1) and (2). For example, the control device 90 may control the combustor 10 so that reaction (1) constitutes the majority of the reaction in catalyst C. For example, the control device 90 can increase the proportion of reaction (1) in catalyst C by controlling valve V2 to reduce the amount of oxidant Ox supplied to the combustion space S. Conversely, if the combustion space S requires more oxidant Ox for combustion, the control device 90 may control valve V2 to increase the amount of oxidant Ox supplied to the combustion space S.

[0037] Next, we will explain the operation of the combustor 10.

[0038] Fuel containing ammonia is injected from the injection hole 11a of the burner 11 into the combustion space S. Ox oxidizer is also injected from the oxidizer flow path 13 into the combustion space S. The mixed gas of fuel and oxidizer Ox is ignited by an ignition device (not shown) to form a flame F. The inner circumferential surface 1b of the communication hole 1a is heated by the flame F to a temperature above which catalyst C begins to activate. Therefore, some of the ammonia in the combustion space S comes into contact with the inner circumferential surface 1b and is decomposed into hydrogen and nitrogen by catalyst C. Since the refractory material 12 blocks the passage of gas, the hydrogen and nitrogen flow radially inward from the inner circumferential surface 1b and merge with the mixed gas. Hydrogen is more easily combustible than ammonia. Therefore, the combustibility of the mixed gas is improved. This reduces the amount of unburned ammonia.

[0039] The combustor 10 described above comprises a burner 11 that injects a fuel containing ammonia into a combustion space S, and a refractory material 12 that defines at least a portion of the combustion space S. The refractory material 12 contains a catalyst C on its inner circumferential surface 1b that blocks the passage of gas and decomposes ammonia into hydrogen and nitrogen, thereby blocking the passage of gas and decomposing ammonia into hydrogen and nitrogen. With this configuration, a portion of the ammonia in the combustion space S can be decomposed into hydrogen and nitrogen by the catalyst C, and the decomposed hydrogen can be returned to the mixed gas. Therefore, the combustibility of the fuel containing ammonia is improved. This makes it possible to reduce unburned ammonia.

[0040] Furthermore, in this embodiment, catalyst C includes a transition metal. With this configuration, ammonia readily interacts with the transition metal, allowing for efficient decomposition of ammonia.

[0041] Furthermore, in this embodiment, the refractory material 12 is part of the wall of the furnace 1 where the burner 11 is located. With this configuration, for example, the combustibility of ammonia-containing fuel can be improved with only minor design changes from existing combustors.

[0042] Next, other embodiments will be described.

[0043] Figure 3 is a schematic cross-sectional view showing a combustor 20 according to the second embodiment. In this embodiment, the combustor is a radiant burner 20. The radiant burner 20 heats the surface 21d of a burner tile 21 by combustion of a mixed gas containing ammonia and an oxidizer (e.g., air), and heats an object (not shown) positioned at a distance from the radiant burner 20 by radiant heat from the heated surface 21d.

[0044] For example, the radiant burner 20 comprises a burner tile (fire-resistant material) 21 and a burner 22. The radiant burner 20 may further comprise other components.

[0045] The burner tile 21 is formed from a refractory material, such as a molded product containing ceramic. The burner tile 21 blocks the passage of combustion gases. In this embodiment, the burner tile 21 has a generally rectangular parallelepiped shape. The burner tile 21 is not limited to this and may have other shapes. The burner tile 21 includes a front surface 21a that is positioned facing the object, and a back surface 21b opposite to the front surface 21a.

[0046] In this embodiment, the burner tile 21 includes a recess 21c on its front surface 21a. The recess 21c is formed from the front surface 21a toward the back surface 21b. The recess 21c is used as a combustion space S. The recess 21c is defined by a surface 21d. That is, the surface 21d defines the combustion space S. In this embodiment, the surface 21d is a smooth sphere. In other embodiments, the surface 21d may have other shapes, such as a cylindrical shape or a polygonal prism shape. In other embodiments, the burner tile 21 may not include a recess 21c.

[0047] Of the surfaces of the burner tile 21, the surface 21d that defines the combustion space S contains a catalyst C that decomposes ammonia into hydrogen and nitrogen. Similar to the first embodiment, for example, the surface 21d may be formed by a layer of a carrier supporting the catalyst C. The catalyst C may be the same as that used in the first embodiment.

[0048] In this disclosure, the burner tile 21 including the recess 21c is also referred to as a "radiant cup." In this disclosure, the radiant burner 20 including the radiant cup is also referred to as a "radiant cup burner."

[0049] The burner 22 protrudes from the burner tile 21 toward the combustion space S. The burner 22 injects a fuel containing ammonia into the combustion space S. In this embodiment, the burner 22 injects a mixed gas containing ammonia and an oxidizer (e.g., air) into the combustion space S (premixing method). The radiant burner 20 is not limited to the premixing method and may also be a diffusion method.

[0050] The burner 22 is generally cylindrical or tubular in shape. The burner 22 is located in the center of the surface 21d. The burner 22 penetrates the wall of the burner tile 21 from the back surface 21b and protrudes into the recess 21c.

[0051] The burner 22 includes a plurality of injection holes 22a. The injection holes 22a inject a gas mixture into the combustion space S. The injection holes 22a are located axially between the tip 22b of the burner 22 and the bottom of the recess 21c. The number of injection holes 22a may be two, three, four, five, or more. For example, the plurality of injection holes 22a are evenly arranged along the circumferential direction.

[0052] In this embodiment, the injection hole 22a opens generally in the radial direction. The injection hole 22a may have various shapes, such as circular, elliptical, or polygonal.

[0053] The inner wall of the burner 22 defines a flow path 22c for the mixed gas. The flow path 22c is in fluid communication with the injection hole 22a. The flow path 22c has a generally cylindrical shape.

[0054] A valve V3 may be provided in the ammonia line L3 connected to the burner 22. The valve V3 may be connected to the control device 90 via wired or wireless communication and may be controlled by the control device 90. For example, the control device 90 adjusts the flow rate of ammonia supplied to the burner 22 by controlling the opening of the valve V3.

[0055] A valve V4 may be provided in the oxidizer line L4 connected to the burner 22. The valve V4 may be connected to the control device 90 via wired or wireless communication and may be controlled by the control device 90. For example, the control device 90 adjusts the flow rate of the oxidizer supplied to the burner 22 by controlling the opening of the valve V4.

[0056] Similar to the first embodiment, the control device 90 may control the radiant burner 20 such that the above reaction (1) constitutes the majority of the reaction in catalyst C.

[0057] Next, we will explain the operation of the Radiant Burner 20.

[0058] A mixed gas containing ammonia and an oxidizer is injected from the injection port 22a of the burner 22 into the combustion space S. The mixed gas is injected from the injection port 22a generally radially outward. The mixed gas forms a flow along the surface 21d of the depression 21c. The pressure in the central region of the combustion space S, more specifically the pressure around the tip 22b, is lower than the pressure in the surrounding region. Therefore, the mixed gas changes the direction of its flow from radially outward to radially inward, and further flows along the central axis toward the tip 22b. The mixed gas ignites at the tip 22b, is sufficiently heated and burns before changing the direction of its flow. The hot combustion gas flows toward the tip 22b.

[0059] Furthermore, surface 21d is heated by the flame. Catalyst C on surface 21d promotes the combustion reaction by reducing the activation energy in the reaction between ammonia and the oxidizer in reaction (2). This allows ignition and combustion of ammonia even at lower temperatures. After the oxidizer reacts, the remaining ammonia is decomposed into hydrogen and nitrogen by reaction (1) through catalyst C. The generated hydrogen and nitrogen flow towards tip 22b via recirculation flow, as described above, and merge with the mixed gas. Hydrogen is more flammable than ammonia. Therefore, the flammability of the mixed gas is improved. Catalyst C enables ignition even at low temperatures, achieving earlier ignition, and the decomposed hydrogen improves flammability. As a result, the temperature of the vernatile 21 can be increased, and the amount of radiative heat transfer can be increased.

[0060] Such a radiant burner 20 provides generally the same effects as the combustor 10 according to the first embodiment. In this embodiment, the combustor is a radiant burner 20, and the refractory material is a burner tile 21. In the radiant burner 20, a flow of the mixed gas is formed along the surface 21d of the burner tile 21. Therefore, ammonia in the mixed gas comes into contact with the catalyst C. As a result, ammonia can be further decomposed into hydrogen and nitrogen. Consequently, the combustibility of the fuel containing ammonia is improved. This makes it possible to reduce unburned ammonia.

[0061] Furthermore, in this embodiment, the radiant burner 20 is a radiant cup burner, and the burner tile 21 includes a recess 21c as at least part of the combustion space S. With this configuration, the mixed gas can remain in the recess 21c for a longer period. This allows more ammonia to react on the catalyst C, generating more hydrogen. Thus, the combustibility of the ammonia-containing fuel is improved.

[0062] Furthermore, in this embodiment, the recess 21c is defined by a smooth spherical surface 21d. With this configuration, a circulating flow is formed in front of the burner tile, increasing the residence time and enabling efficient combustion of the fuel gas.

[0063] Figure 4 is a schematic cross-sectional view showing a radiant burner 20A according to the third embodiment. In this embodiment as well, the combustor is a radiant burner 20A. The radiant burner 20A differs from the radiant burner 20 according to the second embodiment in the shape of the surface 21d that defines the combustion space S. In other configurations, the radiant burner 20A may be the same as the radiant burner 20.

[0064] In this embodiment, the surface 21d includes a plurality of stepped portions (projections) 21e. The stepped portions 21e project axially and radially inward. For example, the stepped portions 21e may be continuous in the circumferential direction. In this case, the stepped portions 21e have an annular shape. In other embodiments, the stepped portions 21e may be divided in the circumferential direction. In other embodiments, the surface 21d may include a plurality of grooves instead of or in addition to the stepped portions 21e.

[0065] Such a radiant burner 20A has generally the same effects as the radiant burner 20 according to the second embodiment. In this embodiment, the surface 21d of the burner tile 21 includes a stepped portion 21e. With this configuration, turbulence of the mixed gas is generated on the surface 21d. Therefore, the mixed gas remains on the surface 21d for a longer period of time. In addition, the stepped portion 21e increases the surface area of ​​the surface 21d that is in contact with the combustion space S. As a result, more ammonia can react on the catalyst C, and more hydrogen is generated. Therefore, the combustibility of fuels containing ammonia is further improved.

[0066] Figure 5 is a schematic cross-sectional view showing the combustor 20B according to the fourth embodiment. In this embodiment as well, the combustor is a radiant burner 20B. The radiant burner 20B differs from the radiant burner 20A according to the third embodiment in that the burner tile 21 does not have a cup shape. In other configurations, the radiant burner 20B may be the same as the radiant burners 20 and 20A.

[0067] In this embodiment, the burner tile 21 has a generally flat shape and does not contain any recesses. In this embodiment, the front surface 21a of the burner tile 21 faces the combustion space S and defines at least a portion of the combustion space S. The burner tile 21 also includes a plurality of projections 21f. The projections 21f project axially from the front surface 21a toward the combustion space S. For example, the projections 21f may be continuous in the circumferential direction. In this case, the projections 21f have an annular shape. In other embodiments, the projections 21f may be divided in the circumferential direction. In other embodiments, the front surface 21a may include a plurality of grooves instead of or in addition to the projections 21f.

[0068] Such a radiant burner 20B provides generally the same effects as the radiant burner 20A according to the third embodiment.

[0069] While embodiments have been described above with reference to the attached drawings, this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of this disclosure.

[0070] This disclosure can promote the use of ammonia, which leads to a reduction in CO2 emissions, and thus can contribute, for example, to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy," and Goal 13, "Take urgent action to combat climate change and its impacts." [Explanation of Symbols]

[0071] 1 furnace 1b Inner surface (a surface that defines at least a portion of the combustion space) 10 Combustor 11 Burner 12 Fireproof materials 20 Radiant burner (combustion device) 20A Radiant Burner (Combustion Device) 20B Radiant Burner (Combustion Device) 21. Burner Tile (fire-resistant material) 21a Front surface (a surface that defines at least a portion of the combustion space) 21c depression 21d Surface (a surface that defines at least a portion of the combustion space) 21e Step part (protrusion) 21f protrusion 22 burners C catalyst S Combustion Space

Claims

1. A burner that injects ammonia-containing fuel into the combustion chamber, A fire-resistant material that defines at least a portion of the combustion space, This fire-resistant material blocks the passage of gas, The fire-resistant material contains a catalyst that decomposes ammonia into hydrogen and nitrogen on a surface that defines at least a portion of the combustion space. Fire-resistant material, A combustion device equipped with a combustion chamber.

2. The combustor according to claim 1, wherein the catalyst comprises a transition metal.

3. The aforementioned combustor is a radiant burner, The aforementioned fire-resistant material is a burner tile. The combustion device according to claim 1 or 2.

4. The aforementioned radiant burner is a radiant cup burner, The burner tile includes a recess as at least a part of the combustion space, The combustor according to claim 3.

5. The aforementioned depression is defined by a smooth spherical surface. The combustion device according to claim 4.

6. The surface of the vernatile containing the catalyst includes at least one of protrusions and grooves. The combustor according to claim 3.

7. The surface of the vernatile containing the catalyst includes at least one of protrusions and grooves. The combustion device according to claim 4.

8. The combustion apparatus according to claim 1 or 2, wherein the refractory material is part of the wall of the furnace in which the burner is located.

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