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

Combustor

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2023-97817, filed on June 14, 2023, the contents of which are incorporated herein by reference.

[0002] In combustors, catalysts are sometimes used to promote combustion. For example, Patent Document 1 discloses a catalyst tube used in a burner nozzle. This burner nozzle uses fuel such as kerosene. A primary combustion flame from the burner nozzle is injected into the catalyst tube. The catalyst tube includes multiple outlet holes. The primary combustion flame is completely combusted by the catalyst as it passes through the catalyst tube, and is then injected as a secondary combustion flame from the multiple outlet holes.

[0003] 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 large number of small holes. The catalyst layer is gas permeable. A mixed gas of fuel and air is supplied to the pipe burner. The mixed gas is ignited, and a flame is formed from the large number of small holes in the pipe burner. The combustion gas is catalytically combusted as it passes through the catalyst layer.

[0004] Japanese Patent Laid-Open No. 11-281006 Japanese Utility Model Laid-Open No. 1-144617

[0005] Ammonia is CO ２ However, the combustion rate of ammonia is slower than that of other fuels, such as natural gas. Therefore, when ammonia is used in such combustors, unburned ammonia can be a problem.

[0006] An object of the present disclosure is to provide a combustor that can reduce unburned ammonia when ammonia is used as fuel.

[0007] A combustor according to one aspect of the present disclosure includes a burner that injects fuel containing ammonia into a combustion space, and a refractory material that defines at least a portion of the combustion space, the refractory material blocking the passage of gas, and the refractory material including a catalyst that decomposes ammonia into hydrogen and nitrogen on a surface that defines at least a portion of the combustion space.

[0008] The catalyst may comprise a transition metal.

[0009] The combustor may be a radiant burner and the refractory material may be a burner tile.

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

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

[0012] The catalyst-containing surface of the burner tile may include protrusions and / or grooves.

[0013] The refractory material may be part of the wall of the furnace in which the burner is located.

[0014] According to the present disclosure, when ammonia is used as fuel, unburned ammonia can be reduced.

[0015] Fig. 1 is a schematic cross-sectional view of a boiler including a combustor according to a first embodiment. Fig. 2 is a schematic enlarged view of a portion A in Fig. 1. Fig. 3 is a schematic cross-sectional view showing a combustor according to a second embodiment. Fig. 4 is a schematic cross-sectional view showing a combustor according to a third embodiment. Fig. 5 is a schematic cross-sectional view showing a combustor according to a fourth embodiment.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0017] 1 is a schematic cross-sectional view of a boiler 100 including a combustor 10 according to a 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 facilities such as an industrial furnace or a combustion furnace. For example, the boiler 100 includes a furnace 1, a flue 2, and a plurality of combustors 10. The boiler 100 may further include other components.

[0018] The furnace 1 burns a fuel containing ammonia to generate combustion gas. For example, the furnace 1 may burn a mixture of ammonia and other fuels such as pulverized coal. Alternatively, the furnace 1 may burn only ammonia. Alternatively, the furnace 1 may burn a fuel that does not contain ammonia, as needed.

[0019] The furnace 1 extends vertically. The lower part of the furnace 1 defines a combustion space S. In this disclosure, the combustion space means a space in which fuel is burned. An exhaust port Ex is provided at the bottom of the furnace 1. The exhaust port Ex discharges ash generated by combustion to the outside.

[0020] The flue 2 is a passage that guides 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 on the top of the furnace 1. The superheater exchanges heat between the combustion gas generated in the furnace 1 and water, thereby generating steam. Furthermore, for example, the boiler 100 may further include components (not shown) such as a reheater, a coal economizer, or an air preheater.

[0022] The combustors 10 are provided on the wall of the lower portion of the furnace 1. The combustors 10 are arranged horizontally at intervals along the wall of the furnace 1. Although Fig. 1 shows only a single row of combustors 10 in the vertical direction, multiple rows of combustors 10 may be arranged vertically at intervals.

[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) that ignites the fuel injected from the combustor 10.

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

[0025] For example, the burner 11 is attached to 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) that injects the ammonia. For example, the burner 11 may further include a nozzle (not shown) that injects another fuel such as pulverized coal. For example, the burner 11 may further include a nozzle (not shown) that injects an oxidizer (e.g., air).

[0026] For example, a valve V1 may be provided in an ammonia line L1 connected to the burner 11. The valve V1 may be communicably connected to the control device 90 via wire or wirelessly, 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 degree 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 the "axial direction," the "radial direction," and the "circumferential direction," unless otherwise specified. The same applies to a burner 22 (described later) according to a 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 part of the combustion space S. In this embodiment, the refractory material 12 is part of the wall of the furnace 1 in which the burner 11 is arranged. 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 the wall of the furnace 1 horizontally. 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 toward 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 that supports 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, the catalyst C includes a transition element (which may also be referred to as a transition metal). For example, the catalyst C may include a noble metal such as Ru. Alternatively, for example, the catalyst C may include a non-noble metal such as Fe, Co, Ni, or Cu among the transition elements. The non-noble metal may exhibit high activity when combined with a specific support. Examples of the support include Al. ２ O ３ or SiO ２ Oxides such as CeO may also be used as needed. ２ A carrier capable of suppressing sintering such as may be used.

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

[0033] For example, a valve V2 may be provided in the oxidant line L2 connected to the oxidant flow path 13. The valve V2 may be connected to the control device 90 so as to be able to communicate with it via wire or wirelessly, and may be controlled by the control device 90. For example, the control device 90 adjusts the flow rate of the oxidant Ox supplied to the combustion space S via the oxidant 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). For example, the storage device 90b includes a hard disk, a ROM for storing programs, and a RAM as a work area. The control device 90 is connected to each component of the combustor 10 via the connector 90c so as to be able to communicate with them via a wired or wireless connection. 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 causing the processor 90a to execute a program stored in the storage device 90b.

[0035] Ammonia reacts on the catalyst C, causing the following reactions (1), (2), or a combination thereof: (1) NH ３ →1.5H ２ +0.5N ２ ΔH=45.4 (kJ / mol) (2) 2NH ３ +1.5O ２ →N ２ +3H ２ O 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) is the majority of the reaction at catalyst C. For example, the control device 90 can increase the proportion of reaction (1) at catalyst C by controlling valve V2 to reduce the amount of oxidant Ox supplied to combustion space S. In contrast, if 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 combustion space S.

[0037] Next, the operation of the combustor 10 will be described.

[0038] Fuel containing ammonia is injected from the injection hole 11a of the burner 11 toward the combustion space S. Furthermore, oxidizer Ox is injected from the oxidizer flow path 13 toward the combustion space S. The mixed gas of fuel and oxidizer Ox is ignited by an ignition device (not shown), forming a flame F. The inner circumferential surface 1b of the communication hole 1a is heated by the flame F to a temperature above the temperature at which the 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 the catalyst C. Because 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 combustible than ammonia. Therefore, the combustibility of the mixed gas is improved. This reduces unburned ammonia.

[0039] The combustor 10 as described above includes 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 the passage of gas and includes a catalyst C that decomposes ammonia into hydrogen and nitrogen on an inner circumferential surface 1b that defines at least a portion of the combustion space S. 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] In this embodiment, the catalyst C contains a transition metal. With this configuration, ammonia easily interacts with the transition metal, and the ammonia can be decomposed efficiently.

[0041] In this embodiment, the refractory material 12 is a part of the wall of the furnace 1 on which the burner 11 is disposed. With such a configuration, for example, the combustibility of fuel containing ammonia can be improved by slight design changes from an existing combustor.

[0042] Next, other embodiments will be described.

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

[0044] For example, the radiant burner 20 includes a burner tile (refractory material) 21 and a burner 22. The radiant burner 20 may further include other components.

[0045] The burner tile 21 is formed of a refractory material, such as a molded product containing ceramic. The burner tile 21 blocks the passage of combustion gas. In this embodiment, the burner tile 21 has a roughly rectangular parallelepiped shape. However, the burner tile 21 is not limited to this and may have other shapes. The burner tile 21 includes a front surface 21a disposed so as to face the target object, and a back surface 21b opposite the front surface 21a.

[0046] In this embodiment, the burner tile 21 includes a depression 21c on the front surface 21a. The depression 21c is formed from the front surface 21a toward the back surface 21b. The depression 21c is used as the combustion space S. The depression 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 spherical surface. 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 the depression 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. As in the first embodiment, for example, the surface 21d may be formed by a layer of a support that supports 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." Also, 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 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 type). The radiant burner 20 is not limited to the premixing type, and may be a diffusion type.

[0050] The burner 22 has a generally cylindrical or tubular shape and is located at the center of the front 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 the mixed gas into the combustion space S. The injection holes 22a are located between the tip 22b of the burner 22 and the bottom of the recess 21c in the axial direction. 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 holes 22a open generally in the radial direction. The injection holes 22a may have various shapes, such as a circular shape, an elliptical shape, or a polygonal shape.

[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 holes 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 communicably connected to the control device 90 via wire or wirelessly, 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 degree 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 so as to be able to communicate with it via wire or wirelessly, 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 degree of the valve V4.

[0056] As in the first embodiment, the control device 90 may control the radiant burner 20 so that the reaction (1) described above becomes the majority of the reaction in the catalyst C.

[0057] Next, the operation of the radiant burner 20 will be described.

[0058] A mixed gas containing ammonia and an oxidizer is injected from the injection hole 22a of the burner 22 toward the combustion space S. The mixed gas is injected from the injection hole 22a generally radially outward. The mixed gas forms a flow along the surface 21d of the recess 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 its flow direction from the radially outer side to the radially inner side and further flows toward the tip 22b along the central axis. The mixed gas ignites from the tip 22b and is sufficiently heated and combusted before changing its flow direction. The high-temperature combustion gas flows toward the tip 22b.

[0059] Furthermore, the surface 21d is heated by the flame. The catalyst C on the surface 21d reduces the activation energy of the reaction between ammonia and the oxidizer in reaction (2), thereby promoting the combustion reaction. Ignition and combustion of ammonia can be achieved even at lower temperatures. After the oxidizer reacts, the remaining ammonia is decomposed into hydrogen and nitrogen by the catalyst C through reaction (1). As shown above, the generated hydrogen and nitrogen flow toward the tip 22b via the recirculation flow and merge with the mixed gas. Hydrogen is more combustible than ammonia. Therefore, the combustibility of the mixed gas is improved. The catalyst C enables ignition even at low temperatures, achieving earlier ignition, and the decomposed hydrogen improves combustibility. As a result, the temperature of the burner tile 21 can be increased, thereby increasing the amount of radiative heat transfer.

[0060] Such a radiant burner 20 achieves substantially the same effects as the combustor 10 according to the first embodiment. In this embodiment, the combustor is the radiant burner 20, and the refractory material is the 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, the ammonia in the mixed gas is more likely to come into contact with the catalyst C. This allows the ammonia to be more easily decomposed into hydrogen and nitrogen. This improves the combustibility of the fuel containing ammonia. This reduces unburned ammonia.

[0061] In this embodiment, the radiant burner 20 is a radiant cup burner, and the burner tile 21 includes a recess 21c as at least a part of the combustion space S. This configuration allows the mixed gas to remain in the recess 21c for a long time. This allows more ammonia to react on the catalyst C, and more hydrogen is generated. This further improves the combustibility of fuels containing ammonia.

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

[0063] 4 is a schematic cross-sectional view showing a radiant burner 20A according to the third embodiment. In this embodiment, the combustor is also the 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 respects, the radiant burner 20A may be the same as the radiant burner 20.

[0064] In this embodiment, the surface 21d includes a plurality of steps (protrusions) 21e. The steps 21e protrude inward in the axial direction and radial direction. For example, the steps 21e may be continuous in the circumferential direction. In this case, the steps 21e have an annular shape. In other embodiments, the steps 21e may be divided in the circumferential direction. Furthermore, in other embodiments, the surface 21d may include a plurality of grooves instead of or in addition to the steps 21e.

[0065] This radiant burner 20A achieves substantially 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 step 21e. This configuration generates turbulent flow of the mixed gas on the surface 21d. Therefore, the mixed gas remains on the surface 21d for a longer period of time. The step 21e also increases the surface area of ​​the surface 21d that comes into contact with the combustion space S. This allows more ammonia to react on the catalyst C, generating more hydrogen. This further improves the combustibility of fuels containing ammonia.

[0066] 5 is a schematic cross-sectional view showing a combustor 20B according to the fourth embodiment. In this embodiment, the combustor is also 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 respects, 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 include a recess. 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 protrusions 21f. The protrusions 21f protrude in the axial direction from the front surface 21a toward the combustion space S. For example, the protrusions 21f may be continuous in the circumferential direction. In this case, the protrusions 21f have an annular shape. In another embodiment, the protrusions 21f may be divided in the circumferential direction. In another embodiment, the front surface 21a may include a plurality of grooves instead of or in addition to the protrusions 21f.

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

[0069] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that such modifications also fall within the technical scope of the present disclosure.

[0070] The present disclosure provides ２ It can promote the use of ammonia, which leads to reduced emissions, thereby contributing, for example, to Sustainable Development Goal (SDG) 7 "Ensure access to affordable, reliable, sustainable and modern energy" and SDG 13 "Take urgent action to combat climate change and its impacts".

[0071] DESCRIPTION OF SYMBOLS 1 Furnace 1b Inner peripheral surface (surface defining at least a part of the combustion space) 10 Combustor 11 Burner 12 Refractory material 20 Radiant burner (combustor) 20A Radiant burner (combustor) 20B Radiant burner (combustor) 21 Burner tile (refractory material) 21a Front surface (surface defining at least a part of the combustion space) 21c Depression 21d Surface (surface defining at least a part of the combustion space) 21e Step (protrusion) 21f Protrusion 22 Burner C Catalyst S Combustion space

Claims

1. A combustor comprising: a burner for injecting a fuel including ammonia into a combustion space; and a refractory material defining at least a portion of the combustion space, the refractory material blocking the passage of gases, the refractory material including a catalyst on a surface defining the at least a portion of the combustion space that decomposes ammonia into hydrogen and nitrogen.

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

3. The combustor according to claim 1 or 2, wherein the combustor is a radiant burner, and the refractory material is a burner tile.

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

5. The combustor of claim 4, wherein said recess is defined by a smooth spherical surface.

6. The combustor of claim 3, wherein the catalyst-containing surface of the burner tile includes at least one of protrusions and grooves.

7. The combustor of claim 4, wherein the catalyst-containing surface of the burner tile includes at least one of protrusions and grooves.

8. A combustor as claimed in claim 1 or 2, wherein the refractory material is part of the wall of a furnace in which the burner is located.