Furnace

Abstract

A furnace 1 comprises: ammonia burners 51 that inject a fuel F including ammonia into a combustion space S; first air ports 11 that are disposed downstream of the ammonia burners 51 in the combustion space S and that inject a first gas including oxygen into the combustion space S, the first air ports 11 injecting the first gas into the combustion space S at a first air ratio with respect to unburned ammonia generated by the ammonia burners 51; and second air ports 21 that are disposed upstream of the first air ports 11 in the combustion space S and that inject a second gas including oxygen into the combustion space S, the second air ports 21 injecting the second gas into the combustion space S at a second air ratio with respect to the unburned ammonia generated by the ammonia burners 51, and the second air ratio being lower than the first air ratio.

Description

furnace

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2024-10828, filed on January 29, 2024, the contents of which are incorporated herein by reference.

[0002] Ammonia may be used as a fuel in the furnace. For example, Patent Document 1 discloses a boiler that uses ammonia and a fossil fuel. The boiler includes a burner configured to burn the fossil fuel and a port for supplying the ammonia fuel.

[0003] Japanese Patent Application Laid-Open No. 2019-178823

[0004] Ammonia is CO ２ Ammonia is known as a fuel that does not emit NOx. However, when ammonia is burned, NOx is generated. Therefore, when ammonia is used in such a furnace, NOx can be a problem.

[0005] The present disclosure aims to provide a furnace that can reduce NOx when ammonia is used as fuel.

[0006] A furnace according to one aspect of the present disclosure includes: an ammonia burner that injects fuel containing ammonia into a combustion space; a first airport that is disposed downstream of the ammonia burner in the combustion space and that injects a first gas containing oxygen into the combustion space, the first airport injecting the first gas into the combustion space at a first air ratio to the unburned ammonia generated by the ammonia burner; and a second airport that is disposed upstream of the first airport in the combustion space and that injects a second gas containing oxygen into the combustion space, the second airport injecting the second gas into the combustion space at a second air ratio to the unburned ammonia generated by the ammonia burner, the second air ratio being lower than the first air ratio.

[0007] The second air ratio may be less than 1.0.

[0008] The second air port may be located upstream of the ammonia burner in the combustion space.

[0009] A second air port located upstream of the ammonia burner may be located in the side wall of the furnace.

[0010] The furnace may include a circulation pipe connected to the second airport port for supplying exhaust gas from the combustion space to the second airport port.

[0011] The second airport port may be located at the bottom of the furnace, and the furnace may include a circulation pipe connected to the second airport port and supplying exhaust gas from the combustion space to the second airport port.

[0012] The second airport port may be disposed at a position opposite to a region of the combustion space opposite to the ammonia burner, and the furnace may include a circulation pipe connected to the second airport port and supplying exhaust gas from the combustion space to the second airport port.

[0013] The second airport port may be disposed downstream of the ammonia burner in the combustion space, and the furnace may include a circulation pipe connected to the second airport port and supplying exhaust gas from the combustion space to the second airport port.

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

[0015] Fig. 1 is a schematic cross-sectional view of a boiler equipped with a furnace according to an embodiment. Fig. 2 shows a diagram of ammonia reaction pathways. Fig. 3 is a schematic cross-sectional view of a boiler equipped with a furnace according to another embodiment. Fig. 4 is a schematic cross-sectional view of a boiler equipped with a furnace according to yet another embodiment. Fig. 5 is a schematic cross-sectional view of a boiler equipped with a furnace according to yet another 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 furnace 1 according to an embodiment. In this embodiment, the furnace 1 is applied to the boiler 100. In other embodiments, the furnace 1 may be applied to other equipment. For example, the boiler 100 includes the furnace 1 and a flue 2. The furnace 1 also includes a burner group 50, a first airport group 10, a second airport group 20, and a control device 90. The boiler 100 and the furnace 1 may further include other components.

[0018] The furnace 1 extends vertically. In this embodiment, the furnace 1 has a rectangular shape when viewed from above. In this embodiment, the furnace 1 includes four side walls, including a front wall 1F, a rear wall 1R, a right wall, and a left wall. Each of the side walls extends vertically and horizontally. The cross-sectional view of FIG. 1 shows the front wall 1F and the rear wall 1R. The right wall and the left wall are not shown. The furnace 1 defines a combustion space S. In this disclosure, the combustion space refers to a space in which fuel is combusted. An exhaust port D is provided at the bottom of the furnace 1. For example, if the furnace 1 according to this embodiment is realized by modifying an existing furnace, a hopper H may be provided at the exhaust port D. If the furnace 1 is newly constructed, the furnace 1 may not include the hopper H. The hopper H is not an essential component.

[0019] The furnace 1 burns a fuel F containing ammonia. For example, the furnace 1 may use only ammonia as the fuel F. In this case, the furnace 1 may use a small amount of fossil fuel for ignition. A flame FL is generated by the combustion. For example, the boiler 100 includes a superheater (not shown) installed on the upper part of the furnace 1. The superheater exchanges heat between the exhaust gas generated in the furnace 1 and water. This generates steam. Furthermore, for example, the boiler 100 may further include components (not shown), such as a reheater, an economizer, or an air preheater.

[0020] The flue 2 is a passage that guides exhaust 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. For example, an exhaust pipe 2c that guides the exhaust gas to the outside is connected to the second flue 2b.

[0021] The burner group 50 includes at least one burner (ammonia burner) 51. In the present embodiment, the burner group 50 includes a plurality of burners 51. The burners 51 are provided on a side wall of the furnace 1. For example, the plurality of burners 51 are arranged in a plurality of rows along the horizontal direction, three rows in the present embodiment. In another embodiment, the plurality of burners 51 may be arranged in a single row. For example, the plurality of burners 51 are arranged at equal intervals in the horizontal direction. In another embodiment, the plurality of burners 51 may be arranged at different intervals in the horizontal direction.

[0022] The burners 51 inject fuel F containing ammonia into the combustion space S. For example, the burners 51 may inject only ammonia into the combustion space S. For example, the fuel F may be gaseous ammonia or liquid ammonia. The fuel F is combusted in the combustion space S. For example, the burners 51 are in fluid communication with a tank (ammonia supply source) 3. For example, the tank 3 stores liquid ammonia. For example, a vaporizer (not shown) may be provided in the piping between the tank 3 and the plurality of burners 51, and gaseous ammonia may be supplied to the burners 51. Alternatively, liquid ammonia may be supplied to the burners 51. In another embodiment, an ammonia manufacturing machine may be used as the ammonia supply source.

[0023] Air is supplied to the burner 51. For example, ambient air A around the furnace 1 may be supplied to the burner 51. In this embodiment, the furnace 1 includes a heat exchanger 4 for heating the ambient air A supplied to the burner 51 with exhaust gas Ex from the furnace 1. For example, the heat exchanger 4 may be provided on the exhaust pipe 2c. For example, the heat exchanger 4 may exchange heat between the ambient air A and the exhaust gas Ex flowing through the exhaust pipe 2c. The burner 51 may be of a premixed combustion type or a diffusion combustion type.

[0024] For example, the burner 51 may include a valve for adjusting the flow rate of the fuel F and a valve for adjusting the flow rate of the ambient air A. These valves may be communicatively 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 may adjust the flow rates of the fuel F and air injected from the burner 51, as well as parameters such as the air ratio in the burner 51, by controlling the opening degree of the valves. Note that although the ambient air A and the fuel F are shown for only one burner 51 in FIG. 1 , the ambient air A and the fuel F are supplied to multiple burners 51.

[0025] For example, the burner 51 may be a radiant cup burner or any other type of burner, such as a gas burner.

[0026] The first airport port group 10 includes at least one first airport port 11. In this embodiment, the first airport port group 10 includes multiple first airport ports 11. In other embodiments, the first airport port group 10 may include only a single first airport port 11. The first airport port 11 is provided on the side walls of the furnace 1, in this embodiment, on the front wall 1F and the rear wall 1R. In this embodiment, the multiple first airport ports 11 are arranged in a single row along the horizontal direction. In other embodiments, the multiple first airport ports 11 may be arranged in multiple rows. For example, the multiple first airport ports 11 are arranged at equal intervals in the horizontal direction. In other embodiments, the multiple first airport ports 11 may be arranged at different intervals in the horizontal direction.

[0027] The first airport port group 10 is disposed downstream of the burner group 50 in the combustion space S. Specifically, the first airport port group 10 is disposed above the burner group 50. The first airport port group 10 is disposed spaced apart from the burner group 50 in the vertical direction. For example, the distance between the first airport port group 10 and the burner group 50 in the vertical direction may be longer than the distance between adjacent burners 51 in the vertical direction.

[0028] The first airport port 11 injects a first gas containing oxygen into the combustion space S. For example, ambient air A around the furnace 1 may be supplied to the first airport port 11, and the first airport port 11 may inject the ambient air A as the first gas into the combustion space S. Furthermore, for example, the furnace 1 may be equipped with a first circulation pipe P1. The first circulation pipe P1 supplies exhaust gas Ex from the combustion space S to the first airport port 11. For example, the first circulation pipe P1 connects the first airport port 11 to the exhaust pipe 2c. In this case, for example, the first airport port 11 may inject a mixed gas of the ambient air A and the exhaust gas Ex into the combustion space S as the first gas.

[0029] For example, the first airport port 11 may include a valve for adjusting the flow rate of the ambient air A and a valve for adjusting the flow rate of the exhaust gas Ex. These valves 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 may adjust parameters such as the flow rate of the first gas injected from the first airport port 11, the ratio between the ambient air A and the exhaust gas Ex, the oxygen concentration of the first gas, and a first air ratio (described in detail below) by controlling the opening degree of these valves. Note that although FIG. 1 shows the ambient air A and the exhaust gas Ex for only one first airport port 11, the ambient air A and the exhaust gas Ex are supplied to multiple first airport ports 11.

[0030] For example, an existing furnace may be equipped with an air port for two-stage combustion (which may also be referred to as an "over-air port"). Therefore, for example, if the furnace 1 according to this embodiment is realized by modifying an existing furnace, the existing over-air port may be used as the first airport port 11.

[0031] The second airport port group 20 includes at least one second airport port 21. In this embodiment, the second airport port group 20 includes multiple second airport ports 21. In other embodiments, the second airport port group 20 may include only a single second airport port 21. In this embodiment, the second airport port 21 is provided in the lower part of the side wall of the furnace 1. Specifically, in this embodiment, the front wall 1F and the rear wall 1R include slopes SL in their lower parts. In this embodiment, the second airport port 21 is provided on the slope SL. Note that the slope SL is not an essential component. In other embodiments, the second airport port 21 may be provided in the hopper H. In this embodiment, the second airport port 21 is arranged to face upward. In other embodiments, the second airport port 21 may be arranged to face diagonally upward or horizontally. In this embodiment, the multiple second airport ports 21 are arranged in a single row along the horizontal direction. In other embodiments, the multiple second airport ports 21 may be arranged in multiple rows. For example, the second airport ports 21 are arranged at equal intervals in the horizontal direction. In other embodiments, the second airport ports 21 may be arranged at different intervals in the horizontal direction.

[0032] The second airport port group 20 is disposed upstream of the first airport port group 10 in the combustion space S. In the present embodiment, the second airport port group 20 is disposed upstream of the burner group 50. Specifically, in the present embodiment, the second airport port group 20 is disposed below the burner group 50. The second airport port group 20 is disposed spaced apart from the burner group 50 in the vertical direction. For example, the distance between the second airport port group 20 and the burner group 50 in the vertical direction may be longer than the distance between adjacent burners 51 in the vertical direction.

[0033] The second airport port 21 injects a second gas containing oxygen into the combustion space S. For example, the second airport port 21 may be supplied with ambient air A around the furnace 1, and the second airport port 21 may inject the ambient air A as the second gas into the combustion space S. Also, for example, the furnace 1 may be equipped with a second circulation pipe P2. The second circulation pipe P2 supplies exhaust gas Ex from the combustion space S to the second airport port 21. For example, the second circulation pipe P2 connects the second airport port 21 to the exhaust pipe 2c. In this case, for example, the second airport port 21 may inject a mixed gas of ambient air A and exhaust gas Ex as the second gas into the combustion space S. Also, for example, the second airport port 21 may inject only exhaust gas Ex as the second gas into the combustion space S.

[0034] For example, the second airport port 21 may include a valve for adjusting the flow rate of the ambient air A and a valve for adjusting the flow rate of the exhaust gas Ex. These valves 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 may adjust parameters such as the flow rate of the second gas injected from the second airport port 21, the ratio between the ambient air A and the exhaust gas Ex, the oxygen concentration of the second gas, and the second air ratio described in detail below, by controlling the opening degree of these valves. Note that although FIG. 1 shows the ambient air A and the exhaust gas Ex for only one second airport port 21, the ambient air A and the exhaust gas Ex are supplied to multiple second airport ports 21.

[0035] For example, an existing furnace (or boiler) may have an air port for recirculating a portion of the exhaust gas to the lower part of the furnace 1. Therefore, for example, when the furnace 1 according to the present embodiment is realized by modifying such an existing furnace, the existing air port may be used as the second airport port 21, and the existing piping for recirculating the exhaust gas may be used as the second circulation piping P2.

[0036] The control device 90 controls the furnace 1. 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 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 furnace 1 via the connector 90c so as to be able to communicate with them via wired or wireless communication. 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 the processor 90a executing a program stored in the storage device 90b.

[0037] Next, the operation of the furnace 1 will be described.

[0038] The burner 51 injects fuel F and air A into the combustion space S. The fuel F is combusted in the combustion space S (first stage combustion). Specifically, the burner 51 combusts the fuel F at an air ratio greater than 0 and less than 1.0. More specifically, the burner 51 may combust the fuel F at an air ratio greater than 0.6 and less than 1.0.

[0039] With this configuration, the ammonia from the burner 51 is burned at an air ratio of less than 1.0, i.e., the ammonia is burned in a rich combustion. This type of combustion suppresses the generation of NOx, but unburned ammonia remains in the region in front of the burner 51. The combustion gas containing unburned ammonia flows toward the region in front of the first airport port group 10.

[0040] The first airport port 11 injects a first gas into the combustion space S. Specifically, the first airport port 11 injects the first gas into the combustion space S at a first air ratio relative to the unburned ammonia generated by the burner 51. Specifically, the first air ratio may be 1 or greater. Note that, when the first airport port 11 injects a mixed gas of ambient air A and exhaust gas Ex into the combustion space S, the "first air ratio" refers to the ratio of the amount of oxygen in the mixed gas actually injected from the first airport port 11 to the theoretical amount of oxygen required to combust the unburned ammonia. For example, the first airport port 11 injects ambient air A as the first gas into the combustion space S. In this case, the oxygen concentration of the ambient air A injected from the first airport port 11 is approximately 21%.

[0041] As described above, the combustion gas from the burner group 50 flows to the region in front of the first airport group 10. Unburned ammonia contained in the combustion gas is completely fueled by air from the first airports 11 (second-stage combustion).

[0042] FIG. 2 shows a diagram of the reaction pathway of ammonia. For example, in a typical two-stage combustion using ammonia as fuel, in order to reduce NOx, ammonia is burned in a fuel-rich combustion in the first stage, and air is supplied to burn the unburned ammonia in the second stage. Since ammonia is burned in a fuel-rich combustion in the first stage, in a typical two-stage combustion, the region between the first and second stages is a reduction region. In the reduction region, the decomposition rate of unburned ammonia is slow, and unburned ammonia is difficult to decompose. Unburned ammonia is burned by air supplied in the second stage, generating NOx. This is because air having a high oxygen concentration is supplied relative to the unburned ammonia, and thus the N in FIG. 2 ２ This is because the reaction to NO is dominant compared to the reaction to NO. This is because the reaction between ammonia and oxygen to form NO and the reaction between ammonia and NO to form N ２ This is because, although the reaction that produces NO and the reaction that produces NO simultaneously occur, the reaction that produces NO is dominant due to the high oxygen concentration. Thus, in a typical two-stage combustion, a large amount of NOx can be produced in the second stage.

[0043] In the present disclosure, furnace 1 is configured to reduce unburned ammonia from the first stage in order to reduce NOx produced in the second stage.

[0044] Returning to FIG. 1 , specifically, in the present disclosure, the second air port 21 injects a second gas into the combustion space S. The injection of the second gas is intended to create a region Ar having a low oxygen concentration between the region in front of the burner 51 and the region in front of the first air port 11. In the present disclosure, the region Ar may also be referred to as a "low oxygen region." For example, the oxygen concentration in the region Ar is set to about 3%. With this configuration, the combustion gas from the first stage is exposed to the region Ar having a low oxygen concentration before reaching the second stage.

[0045] Referring to FIG. 2, unburned ammonia is hardly decomposed in the reduction region where there is no oxygen, but in the region Ar having a low oxygen concentration, the N ２ The main reactions are the reaction of ammonia with oxygen to form NO, and the reaction of ammonia with NO to form N ２ However, due to the low oxygen concentration, ２ Therefore, in the region Ar, the unburned ammonia reacts with N ２ and H ２ As a result, the amount of unburned ammonia in the combustion gas flowing into the first airport port group 10 can be reduced, and the amount of NOx generated in the second stage can be reduced.

[0046] Returning to FIG. 1 , specifically, the second airport port 21 injects the second gas into the combustion space S at a second air ratio relative to the unburned ammonia generated by the burner 51. The second air ratio is lower than the first air ratio. Specifically, the second air ratio may be less than 1. More specifically, the second air ratio may be greater than 0 and equal to or less than 0.5. When the second airport port 21 injects a mixed gas of ambient air A and exhaust gas Ex into the combustion space S, the "second air ratio" refers to the ratio of the amount of oxygen in the mixed gas actually injected from the second airport port 21 to the theoretical amount of oxygen required to combust the unburned ammonia. For example, the second airport port 21 injects a mixed gas of ambient air A and exhaust gas Ex as the second gas into the combustion space S. In this case, the oxygen concentration of the ambient air A is reduced by the exhaust gas Ex. Alternatively, the second airport port 21 may inject only the exhaust gas Ex as the second gas into the combustion space S. For example, the oxygen concentration of the second gas injected from the second airport port 21 may be lower than the oxygen concentration of the first gas injected from the first airport port 11. For example, the oxygen concentration of the second gas injected from the second airport port 21 may be greater than 0% and less than 10%. Alternatively, the oxygen concentration of the second gas injected from the second airport port 21 may be greater than 0% and less than 5%.

[0047] In this embodiment, the second airport port 21 is disposed upstream of the burner 51, and therefore the second airport port 21 is separated from the region Ar. Therefore, the second gas is sufficiently mixed with the combustion gas before reaching the region Ar. Therefore, in this embodiment, the second airport port 21 may inject only the ambient air A as the second gas into the combustion space S, as long as the region Ar having a low oxygen concentration is achieved.

[0048] Furthermore, in this embodiment, the air A supplied to the burner 51 is heated by the exhaust gas Ex in the heat exchanger 4. Therefore, the ammonia supplied to the burner 51 is heated by the air A. When the ammonia is heated, the combustibility of the ammonia is improved. Therefore, the combustibility of the ammonia in the burner 51 is improved.

[0049] The furnace 1 as described above includes a burner 51 that injects a fuel F containing ammonia into the combustion space S, a first airport port 11 that is disposed downstream of the burner 51 in the combustion space S and that injects a first gas containing oxygen into the combustion space S, and a second airport port 21 that is disposed upstream of the first airport port 11 in the combustion space S and that injects a second gas containing oxygen into the combustion space S. The first airport port 11 injects the first gas into the combustion space S at a first air ratio relative to the unburned ammonia generated by the burner 51. The second airport port 21 injects the second gas into the combustion space S at a second air ratio relative to the unburned ammonia generated by the burner 51. This second air ratio is lower than the first air ratio. With this configuration, injection of the second gas can create a region Ar having a low oxygen concentration between the region in front of the burner 51 and the region in front of the first airport port 11. Therefore, the unburned ammonia generated by the burner 51 can be refrigerated in the region Ar by N ２ and H ２ As a result, it is possible to reduce the amount of unburned ammonia in the combustion gas flowing into the first airport port group 10, and it is possible to reduce the amount of NOx generated in the second stage.

[0050] From another perspective, the furnace 1 comprises a burner 51 that injects a fuel F containing ammonia into the combustion space S, a first airport port 11 that is disposed downstream of the burner 51 in the combustion space S and that injects a first gas containing oxygen into the combustion space S, and a second airport port 21 that is disposed upstream of the first airport port 11 in the combustion space S and that injects a second gas containing oxygen into the combustion space S. The first airport port 11 injects the first gas into the combustion space S at a first oxygen concentration. The second airport port 21 injects the second gas into the combustion space S at a second oxygen concentration. This second oxygen concentration is lower than the first oxygen concentration. With this configuration, injection of the second gas can create a region Ar having a low oxygen concentration between the region in front of the burner 51 and the region in front of the first airport port 11. Therefore, unburned ammonia generated by the burner 51 can be burned in the region Ar by N ２ and H ２As a result, it is possible to reduce the amount of unburned ammonia in the combustion gas flowing into the first airport port group 10, and it is possible to reduce the amount of NOx generated in the second stage.

[0051] From another perspective, the furnace 1 comprises a burner 51 that injects a fuel F containing ammonia into the combustion space S, a first airport port 11 that is arranged downstream of the burner 51 in the combustion space S and that injects a first gas containing oxygen into the combustion space S, and a second airport port 21 that is arranged upstream of the first airport port 11 in the combustion space S and that injects a second gas containing oxygen into the combustion space S. The second gas contains exhaust gas Ex from the combustion space S. With this configuration, injection of the second gas makes it possible to generate a region Ar having a low oxygen concentration between the region in front of the burner 51 and the region in front of the first airport port 11. Therefore, unburned ammonia generated by the burner 51 can be burned in the region Ar by N ２ and H ２ As a result, it is possible to reduce the amount of unburned ammonia in the combustion gas flowing into the first airport port group 10, and it is possible to reduce the amount of NOx generated in the second stage.

[0052] In addition, the second air ratio in the furnace 1 is less than 1.0. With this configuration, the oxygen concentration in the region Ar can be easily maintained low.

[0053] In the furnace 1, the second air port 21 is disposed upstream of the burner 51 in the combustion space S. With this configuration, the second air port 21 is spaced apart from the region Ar. Therefore, the second gas is sufficiently mixed with the combustion gas before reaching the region Ar. As a result, the oxygen concentration in the region Ar can be easily maintained low. With this configuration, since the second gas is sufficiently mixed with the combustion gas before reaching the region Ar, for example, only the ambient air A can be used as the second gas. Note that even with this configuration, a mixture of the ambient air A and the exhaust gas Ex may be used as the second gas.

[0054] Furthermore, in the furnace 1, the second airport port 21, which is arranged upstream of the burner 51, is arranged on the side wall of the furnace 1. As described above, for example, an existing furnace may be equipped with an air port for recirculating part of the exhaust gas to the lower part of the furnace 1. Therefore, for example, when the furnace 1 according to this embodiment is realized by modifying an existing furnace, the existing air port can be used as the second airport port 21.

[0055] The furnace 1 also includes a second circulation pipe P2 connected to the second airport port 21 and supplying exhaust gas Ex from the combustion space S to the second airport port 21. With this configuration, for example, the second airport port 21 injects a mixture of ambient air A and exhaust gas Ex into the combustion space S as the second gas. In this case, the oxygen concentration of the second gas is reduced by the exhaust gas Ex. Therefore, the oxygen concentration in the region Ar can be easily maintained low. As described above, for example, existing furnaces may include an air port for recirculating a portion of the exhaust gas to the lower part of the furnace 1. Therefore, for example, if the furnace 1 according to this embodiment is realized by modifying an existing furnace, the existing pipe for recirculating the exhaust gas can be used as the second circulation pipe P2.

[0056] For example, the furnace 1 described above may be realized by modifying an existing furnace that uses fossil fuel. For example, piping for supplying ammonia may be added to some or all of the burners that burn fossil fuel. In this case, the burner that receives the supply of ammonia can be used as the burner 51 described above.

[0057] Next, other embodiments will be described.

[0058] 3 is a schematic cross-sectional view of a boiler 200 including a furnace 1A according to another embodiment. The furnace 1A differs from the furnace 1 described above in the position of the second air port 21. The furnace 1A also differs from the furnace 1 described above in that the bottom of the furnace 1A is closed and no hopper H is provided. In other respects, the boiler 200 and the furnace 1A may be the same as the boiler 100 and the furnace 1, respectively. Note that although only a single second air port 21 is shown in FIG. 3, the furnace 1A may be provided with multiple second air ports 21.

[0059] In this embodiment, the second airport port 21 is provided at the bottom of the furnace 1. In this embodiment, the second airport port 21 is arranged to face upward. In other embodiments, the second airport port 21 may be arranged to face diagonally upward or horizontally.

[0060] For example, an existing furnace (or boiler) may have an air port for recirculating a portion of the exhaust gas to the bottom of the furnace 1A. Therefore, for example, if the furnace 1A according to this embodiment is realized by modifying such an existing furnace, the existing air port may be used as the second airport port 21, and the existing piping for recirculating the exhaust gas may be used as the second circulation piping P2.

[0061] Such a furnace 1A has the same effects as the furnace 1 described above.

[0062] In particular, in the furnace 1A, the second airport 21 is arranged at the bottom of the furnace 1, and the furnace 1A is equipped with a second circulation pipe P2 connected to the second airport 21 and supplying the exhaust gas Ex from the combustion space S to the second airport 21. With this configuration, for example, when the furnace 1A according to this embodiment is realized by modifying an existing furnace equipped with an airport port for recirculating part of the exhaust gas to the bottom of the furnace 1A, the existing airport can be used as the second airport 21, and the existing pipe for recirculating the exhaust gas can be used as the second circulation pipe P2.

[0063] 4 is a schematic cross-sectional view of a boiler 300 including a furnace 1B according to another embodiment. The furnace 1B differs from the furnace 1 in the position of the second air port 21. In other respects, the boiler 300 and the furnace 1B may be the same as the boiler 100 and the furnace 1, respectively.

[0064] In the present embodiment, the second airport port 21 is disposed at a position facing a region in the combustion space S where the plurality of burners 51 face each other. For example, the second airport port 21 is disposed between the plurality of burners 51 in the vertical direction. Alternatively, for example, the second airport port 21 may be disposed between the plurality of burners 51 in the horizontal direction.

[0065] For example, an existing furnace may have additional air ports between multiple burners in the vertical or horizontal direction in addition to the over-air ports for two-stage combustion. These air ports inject air into the combustion space. Therefore, for example, if the furnace 1B according to this embodiment is realized by modifying such an existing furnace, the additional air port between the burners 51 may be used as the second air port 21. In this case, a second circulation pipe P2 may be added to connect the second air port 21 to the exhaust pipe 2c.

[0066] Such a furnace 1B has the same effects as the furnace 1 described above.

[0067] In particular, in the furnace 1B, the second airport port 21 is arranged at a position facing the region in the combustion space S where the plurality of burners 51 face each other, and the furnace 1B is equipped with a second circulation pipe P2 connected to the second airport port 21 and supplying the exhaust gas Ex from the combustion space S to the second airport port 21. With this configuration, for example, when the furnace 1B according to this embodiment is realized by modifying an existing furnace that has additional airport ports between the plurality of burners, the existing airport ports between the plurality of burners can be used as the second airport port 21.

[0068] 5 is a schematic cross-sectional view of a boiler 400 including a furnace 1C according to another embodiment. The furnace 1C differs from the furnace 1 described above in the position of the second air port 21. In other respects, the boiler 400 and the furnace 1C may be the same as the boiler 100 and the furnace 1, respectively.

[0069] In this embodiment, the second airport port 21 is provided downstream of the first airport port 11 and upstream of the burner 51. That is, in this embodiment, the second airport port 21 is located between the first airport port 11 and the burner 51 in the vertical direction. For example, the second airport port 21 is provided at a position facing the region Ar.

[0070] For example, an existing furnace may have an additional air port between the burner and the over-air port in addition to the over-air port for two-stage combustion. These air ports inject air into the combustion space. Therefore, for example, if the furnace 1C according to this embodiment is realized by modifying such an existing furnace, the additional air port between the burner 51 and the over-air port (first air port 11) may be used as the second air port 21. In this case, a second circulation pipe P2 may be added to connect the second air port 21 to the exhaust pipe 2c.

[0071] Such a furnace 1C has the same effects as the furnace 1 described above.

[0072] In particular, in the furnace 1C, the second airport port 21 is disposed downstream of the burner 51 in the combustion space S, and the furnace 1C is provided with a second circulation pipe P2 connected to the second airport port 21 and supplying the exhaust gas Ex from the combustion space S to the second airport port 21. With this configuration, for example, when the furnace 1C according to this embodiment is realized by modifying an existing furnace that has an additional airport port between the burner and the over-air port, the existing airport port between the burner and the over-air port (first airport port 11) can be used as the second airport port 21.

[0073] 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.

[0074] For example, in the above-described embodiments, the furnaces 1, 1A, 1B, and 1C are provided with the first circulation pipe P1. However, the first circulation pipe P1 is not essential.

[0075] Also, for example, in the above embodiments, the furnaces 1, 1A, 1B, and 1C are provided with a second airport port 21 for injecting the second gas. In other embodiments, a part of the burner 51 may be used as the second airport port 21. For example, when realizing a furnace according to the present disclosure by modifying an existing furnace equipped with an over-air port for two-stage combustion, a part of the burner may be used as the second airport port 21. In this case, fuel injection from the burner used as the second airport port 21 is stopped. Also, for example, when an existing furnace is equipped with an over-air port for two-stage combustion and an inspection window, an air port and piping may be added to the inspection window and used as the second airport port 21.

[0076] 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".

[0077] 1 Furnace 1A Furnace 1B Furnace 1C Furnace 11 First airport 21 Second airport 51 Burner (ammonia burner) Ex Exhaust gas P2 Second circulation piping S Combustion space

Claims

1. A furnace comprising: an ammonia burner that injects fuel containing ammonia into a combustion space; a first airport that is located in the combustion space downstream of the ammonia burner and that injects a first gas containing oxygen into the combustion space, the first airport injecting the first gas into the combustion space at a first air ratio to the unburned ammonia generated by the ammonia burner; and a second airport that is located in the combustion space upstream of the first airport and that injects a second gas containing oxygen into the combustion space, the second airport injecting the second gas into the combustion space at a second air ratio to the unburned ammonia generated by the ammonia burner, the second air ratio being lower than the first air ratio.

2. The furnace of claim 1, wherein the second air ratio is less than 1.

0.

3. The furnace according to claim 1 or 2, wherein the second air port is arranged upstream of the ammonia burner in the combustion space.

4. The furnace of claim 3, wherein the second air port is located in a side wall of the furnace.

5. The furnace according to claim 4, further comprising a circulation pipe connected to said second airport port for supplying exhaust gas from said combustion space to said second airport port.

6. The furnace according to claim 3, wherein the second airport port is disposed at the bottom of the furnace, and the furnace is provided with a circulation pipe connected to the second airport port and supplying exhaust gas from the combustion space to the second airport port.

7. A furnace according to claim 1 or 2, wherein the second airport port is arranged at a position facing the area of the combustion space facing the ammonia burner, and the furnace is provided with a circulation pipe connected to the second airport port and supplying exhaust gas from the combustion space to the second airport port.

8. A furnace according to claim 1 or 2, wherein the second airport is disposed downstream of the ammonia burner in the combustion space, and the furnace is provided with a circulation pipe connected to the second airport and supplying exhaust gas from the combustion space to the second airport.

Images