WO2024257430A1 - Combustor - Google Patents

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

This disclosure relates to a combustor. This application claims the benefit of priority to Japanese Patent Application No. 2023-97817, filed on June 14, 2023, the contents of which are incorporated herein by reference.

In combustors, catalysts are sometimes used to promote combustion. For example, Patent Document 1 discloses a catalyst tube used for a burner nozzle. This burner nozzle uses fuel such as kerosene. The primary combustion flame from the burner nozzle is blown into the catalyst tube. The catalyst tube includes a number of exit holes. As the primary combustion flame passes through the catalyst tube, it is completely combusted by the catalyst and is ejected from the multiple exit holes as a secondary combustion flame.

Patent Document 2 also 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 mixture of fuel and air is supplied to the pipe burner. The mixture 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.

Japanese Patent Application Publication No. 11-281006 Japanese Utility Model Application Publication No. 1-144617

Ammonia is known as a fuel that does not emit _CO2 . However, the burning rate of ammonia is slower than other fuels such as natural gas. Therefore, when using ammonia in such combustors, unburned ammonia can be a problem.

The present disclosure aims to provide a combustor that can reduce unburned ammonia when ammonia is used as fuel.

A combustor according to one embodiment of the present disclosure includes a burner that injects a 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.

The catalyst may contain a transition metal.

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

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.

The depression may be defined by a smooth spherical surface.

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

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

According to the present disclosure, it is possible to reduce unburned ammonia when ammonia is used as fuel.

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 part A in FIG. FIG. 3 is a schematic cross-sectional view showing a combustor according to the 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.

Below, an embodiment of the present disclosure will be described in detail with reference to the attached drawings. Specific dimensions, materials, values, etc. shown in such 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 duplicated explanations, and elements not directly related to the present disclosure are not illustrated.

FIG. 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.

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. The furnace 1 may also burn only ammonia. The furnace 1 may also burn a fuel that does not contain ammonia, if necessary.

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

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 top 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 top of the furnace 1. The second flue 2b extends downward from the end of the first flue 2a.

For example, the boiler 100 includes a superheater (not shown) that is installed on top of the furnace 1. The superheater exchanges heat between the combustion gas generated in the furnace 1 and water. This generates steam. For example, the boiler 100 may further include components (not shown) such as a reheater, a coal economizer, or an air preheater.

The combustors 10 are provided on the lower wall of the furnace 1. The combustors 10 are arranged horizontally and spaced apart from one another 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 and spaced apart from one another.

The combustor 10 injects fuel into the combustion space S. A flame F is formed in the combustion space S by igniting the fuel injected from the combustor 10. The furnace 1 is provided with an ignition device (not shown) that ignites the fuel injected from the combustor 10.

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 oxidizer flow path 13, and a control device 90. The combustor 10 may further include other components.

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 (for example, air).

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 so as to be capable of communicating with 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.

The burner 11 has a generally cylindrical shape. In this disclosure, the axial, radial, and circumferential directions 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 the burner 22 (described below) 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.

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 in which the burner 11 is disposed. The refractory material 12 blocks the passage of gas.

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. Thus, the inner circumferential surface 1b of the communication hole 1a defines a portion of the combustion space S.

The inner circumferential surface 1b contains a 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.

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 precious metal such as Ru. Also, for example, the catalyst C may include non-precious metals such as Fe, Co, Ni, and Cu among the transition elements. Non-precious metals may exhibit high activity when combined with a specific support. As the support, for example, an oxide such as Al ₂ O ₃ or SiO ₂ may be used. Also, if necessary, a support capable of suppressing sintering such as CeO ₂ may be used.

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

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 so as to be capable of communicating with the control device 90 via a wired or wireless connection, 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.

The control device 90 controls all or part 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 be provided with 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, and these components 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 includes a hard disk, a ROM in which programs, etc. are stored, and a RAM as a work area, etc. 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 each component 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, a button, 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.

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)

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 reactions 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. In contrast, 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.

Next, the operation of the combustor 10 will be explained.

Fuel containing ammonia is injected from the injection hole 11a of the burner 11 toward the combustion space S. In addition, 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), and a flame F is formed. The inner surface 1b of the communication hole 1a is heated by the flame F to a temperature above the temperature at which the catalyst C starts to be activated. Therefore, a part of the ammonia in the combustion space S comes into contact with the inner surface 1b and is decomposed into hydrogen and nitrogen by the catalyst C. Since the refractory material 12 blocks the passage of gas, the hydrogen and nitrogen flow radially inward from the inner surface 1b and merge with the mixed gas. Hydrogen is more combustible than ammonia. Therefore, the combustibility of the mixed gas is improved. This makes it possible to reduce unburned ammonia.

The combustor 10 as described above includes a burner 11 that injects fuel containing ammonia into the combustion space S, and a refractory material 12 that defines at least a portion of the combustion space S. The refractory material 12 includes a catalyst C that blocks the passage of gas and decomposes ammonia into hydrogen and nitrogen on the 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.

In addition, in this embodiment, catalyst C contains a transition metal. With this configuration, ammonia easily interacts with the transition metal, and ammonia can be decomposed efficiently.

In addition, in this embodiment, the refractory material 12 is part of the wall of the furnace 1 in which the burner 11 is disposed. With this configuration, for example, it is possible to improve the combustibility of fuels containing ammonia by making slight design changes to an existing combustor.

Next, other embodiments will be described.

FIG. 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 the 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.

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.

The burner tile 21 is formed of a fireproof 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. 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 arranged to face the target object, and a back surface 21b opposite the front surface 21a.

In this embodiment, the burner tile 21 includes a recess 21c on the front surface 21a. The recess 21c is formed from the front surface 21a toward the back surface 21b. The recess 21c is used as the combustion space S. The recess 21c is defined by the 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, for example, a cylindrical shape or a polygonal prism shape. In other embodiments, the burner tile 21 may not include the recess 21c.

Among the surfaces of the burner tile 21, surface 21d that defines the combustion space S includes a catalyst C that decomposes ammonia into hydrogen and nitrogen. As in the first embodiment, for example, surface 21d may be formed by a layer of a support that supports catalyst C. Catalyst C may be the same as that used in the first embodiment.

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 a radiant cup is also referred to as a "radiant cup burner."

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.

The burner 22 has a generally cylindrical or tubular shape. The burner 22 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.

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 multiple injection holes 22a are evenly arranged along the circumferential direction.

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

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.

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 so as to be capable of communicating with 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.

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 capable of communicating with 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 the oxidizer supplied to the burner 22 by controlling the opening degree of the valve V4.

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

Next, the operation of the radiant burner 20 will be explained.

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 starting from the tip 22b, and is sufficiently heated and combusted before changing the flow direction. The high-temperature combustion gas flows toward the tip 22b.

Furthermore, the surface 21d is heated by the flame. The catalyst C on the surface 21d promotes the combustion reaction by reducing the activation energy in the reaction (2) between the ammonia and the oxidizer. Ignition can be achieved even in a lower temperature field, and ammonia can be burned. After the oxidizer reacts, the remaining ammonia is decomposed into hydrogen and nitrogen by the catalyst C in reaction (1). As shown above, the generated hydrogen and nitrogen flow toward the tip 22b by 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 allows ignition even in a low temperature field, realizing earlier ignition, and improving combustibility with the decomposed hydrogen. As a result, the temperature of the burner tile 21 can be increased, and the amount of radiative heat transfer can be increased.

Such a radiant burner 20 has substantially the same effect 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 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 allows the amount of unburned ammonia to be reduced.

In addition, 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. With this configuration, the mixed gas can remain in the recess 21c for a long time. This allows more ammonia to react on the catalyst C, and more hydrogen is generated. Therefore, the combustibility of the fuel containing ammonia is further improved.

In addition, in this embodiment, the recess 21c is defined by the surface 21d, which 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 allows the fuel gas to be burned efficiently.

FIG. 4 is a schematic cross-sectional view showing a radiant burner 20A according to the third embodiment. In this embodiment, the combustor is also 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. As for other configurations, the radiant burner 20A may be the same as the radiant burner 20.

In this embodiment, the surface 21d includes a plurality of steps (protrusions) 21e. The steps 21e protrude in the axial direction and radially inward. 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. Also, in other embodiments, the surface 21d may include a plurality of grooves instead of or in addition to the steps 21e.

Such a radiant burner 20A has substantially the same effect 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. With this configuration, a turbulent flow 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. The step 21e also increases the surface area of the surface 21d that contacts the combustion space S. This allows more ammonia to react on the catalyst C, and more hydrogen is generated. Therefore, the combustibility of the fuel containing ammonia is further improved.

FIG. 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.

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 other embodiments, the protrusions 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 protrusions 21f.

Such a radiant burner 20B provides substantially the same effects as the radiant burner 20A according to the third embodiment.

　Although the embodiments have been described above with reference to the attached 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 modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

The present disclosure can facilitate the use of ammonia leading to reduced _CO2 emissions, thereby contributing, for example, to Sustainable Development Goal (SDG) Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy" and Goal 13 "Take urgent action to combat climate change and its impacts."

1 Furnace 1b Inner peripheral surface (surface defining at least a portion 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 (fireproof material)
21a front surface (surface defining at least a portion of the combustion space)
21c recess 21d surface (surface defining at least a portion of the combustion space)
21e Step (protrusion)
21f projection 22 burner C catalyst S combustion space

Claims (8)

a burner that injects fuel containing ammonia into a combustion space;
A refractory material defining at least a portion of the combustion space,
The fireproof material blocks the passage of gas,
the refractory material includes a catalyst on a surface defining at least a portion of the combustion space that decomposes ammonia into hydrogen and nitrogen;
A fireproof material;
A combustor comprising: The combustor of claim 1, wherein the catalyst includes a transition metal. The combustor is a radiant burner,
The refractory material is a burner tile.
The combustor according to claim 1 or 2. The radiant burner is a radiant cup burner,
The burner tile includes a recess as at least a portion of the combustion space.
The combustor of claim 3 . The recess is defined by a smooth spherical surface.
The combustor of claim 4 . the catalyst-containing surface of the burner tile includes at least one of protrusions and grooves;
The combustor of claim 3 . the catalyst-containing surface of the burner tile includes at least one of protrusions and grooves;
The combustor of claim 4 . The combustor according to claim 1 or 2, wherein the refractory material is part of a wall of a furnace in which the burner is disposed.

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