boiler

Abstract

To provide a boiler that can prevent malfunctions caused by overheating of water tubes, suppress NOx generation, and maintain heat exchange performance. [Solution] The boiler comprises a burner that burns hydrogen fuel and combustion air to generate combustion gas, and a rectangular boiler body in which a plurality of water tubes are arranged at predetermined intervals within the gas flow space. The water tubes are arranged so that their longitudinal direction is in the vertical direction within the gas flow space, with water supplied from the lower end and steam released from the upper end. The burner is positioned at a lower-biased position in the vertical direction of the gas flow space, and the burner ejects the combustion air or a premixed gas of combustion air and hydrogen fuel in a direction perpendicular to the longitudinal direction of the water tubes facing the burner so as to form the main flow direction of the combustion gas. Downstream from the first row of water tubes adjacent to the burner, between the water tubes, an expansion region is provided that expands the flow of the combustion gas upward within the gas flow space.

Description

Technical Field

[0005] , ,

[0004] ,

[0001] The present invention relates to a boiler that burns hydrogen fuel.

Background Art

[0002] Conventionally, boilers that use hydrogen fuel mainly composed of hydrogen as fuel are known. Boilers that burn hydrogen fuel have attracted attention because they do not generate carbon dioxide by combustion. On the other hand, since hydrogen fuel has a faster combustion rate and a higher combustion temperature than hydrocarbon gas, suppression of NOx generation accompanying combustion has become an important issue. For example, in Patent Document 1, a technique for suppressing NOx generation by adding moisture to hydrogen fuel has been devised. In addition, in boilers that use hydrocarbon gas as fuel, a NOx reduction technique for adjusting the combustion gas temperature (the temperature of the combustion flame) by a cold object near the burner is known (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the boiler having a rectangular can body structure that uses hydrocarbon gas as fuel shown in Patent Document 2, the combustion gas directly heats the water pipe group to generate steam, and the combustion gas temperature is kept low by cooling the combustion gas in the water pipe group, and it is shown that generation of harmful exhaust gases such as NOx can be suppressed. However, in a boiler having a form as shown in Patent Document 2, if hydrogen fuel is burned, since the combustion gas temperature near the burner becomes high, there is concern about overheating of the water pipe and an increase in thermal NOx generation.

[0005] The present invention aims to provide a boiler that can suppress the generation of NOx while preventing malfunctions caused by overheating of water tubes, and while maintaining heat exchange performance. [Means for solving the problem]

[0006] The present invention solves the above problem by the following means.

[0007] The boiler of the present invention comprises a burner that burns hydrogen fuel and combustion air to generate combustion gas, and a rectangular boiler body in which a plurality of water tubes are arranged at predetermined intervals within a gas flow space, wherein the water tubes are arranged so that their longitudinal direction is in the vertical direction within the gas flow space, water is supplied from the lower end and steam is released from the upper end, wherein the burner is positioned at a lower-biased position in the vertical direction within the gas flow space, and the combustion air or a premixed gas of combustion air and hydrogen fuel is ejected perpendicular to the longitudinal direction of the water tubes facing the burner so as to form the main flow direction of the combustion gas, and an expansion region is provided between the water tubes downstream of the first row of water tubes adjacent to the burner, which expands the flow of the combustion gas upward within the gas flow space.

[0008] Furthermore, it is preferable that the burner ejects at least a portion of the combustion air and at least a portion of the hydrogen fuel from one or more different nozzles, thereby causing diffusion combustion of the combustion air and the hydrogen fuel.

[0009] Furthermore, it is preferable that at least some of the water tubes are arranged in a staggered pattern, and that the enlarged region is formed by omitting one or more of the water tubes.

[0010] Furthermore, it is preferable that the upper end of the nozzle for the combustion air or the premixed gas of the combustion air and the hydrogen fuel is positioned within 70% of the vertical dimension of the gas flow space relative to the lower end of the burner. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a boiler that can suppress the generation of NOx while preventing malfunctions caused by overheating of water tubes, and while maintaining heat exchange performance. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram illustrating a boiler according to the first embodiment. [Figure 2] This is a cross-sectional view of the can. [Figure 3] This is a diagram explaining the expanded area. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings and other figures. Note that the following figures, including Figure 1, are schematic representations, and the size and shape of each part have been exaggerated as appropriate for ease of understanding.

[0014] (First Embodiment) Figure 1 is a diagram illustrating the boiler 1 of the first embodiment. Figure 2 is a cross-sectional view of the can body 10. The boiler 1 of this embodiment is a boiler that uses hydrogen fuel F1 as fuel, and is, for example, a once-through boiler. The boiler 1 comprises a boiler body 10 and a burner 20. The boiler 1 also comprises an exhaust pipe 40, a hydrogen fuel supply line L100 and an air supply line L200. In this specification, "line" is a general term for a flow path, route, pipeline, etc.

[0015] In this specification and in the claims, hydrogen fuel F1 includes not only hydrogen gas consisting solely of hydrogen, but also mixed gases mainly composed of hydrogen and other gases. In the case of mixed gases, it is preferable that the volume concentration of hydrogen is 50% or more (hydrogen ratio of 0.5 or more). In the case of a mixed gas of hydrocarbon fuels and hydrogen, the combustion rate increases sharply when the hydrogen ratio exceeds 0.5. On the other hand, when the hydrogen ratio is small, the combustion temperature and combustion rate tend to become closer to those of hydrocarbon fuels (combustion temperature is lower and combustion rate is lower compared to the combustion of hydrogen alone) (see reference: "Ekenechukwu C. Okafor, Yukihide Nagano, Toshiaki Kitagawa, “Experimental and theoretical analysis of cellular instability in lean H2-CH4-air flames at elevated pressures”, International Journal of Hydrogen Energy 41 (2016) p6581-6592"). Therefore, when using a hydrogen-based mixed gas as hydrogen fuel F1, a hydrogen volume concentration of 50% or more is preferable, and from the viewpoint of achieving the combustion temperature and combustion rate of a hydrogen combustion boiler, a hydrogen volume concentration of 70% or more is more preferable. In this embodiment, we will explain using an example in which hydrogen gas is used as the hydrogen fuel F1.

[0016] The boiler body 10 generates steam by heating the water supplied to the water pipes 11 inside the boiler body 10. The boiler body 10 is rectangular in shape, and as shown in Figure 2, it has a rectangular cross-section, with multiple water pipes 11 arranged at predetermined intervals within a rectangular gas flow space S in plan view. The boiler body 10 also includes a lower header 12, an upper header 13, etc. The boiler body 10 may be approximately rectangular or cubic in shape, and the gas flow space S may also be approximately rectangular. The boiler body 10 has a burner 20 positioned on one side, and an exhaust pipe 40 is connected to the side opposite to the side on which the burner 20 is positioned. In FIGS. 1 and 2, the vertical direction of the gas flow space S is indicated by the arrow d1, and the direction parallel to the main flow direction of the combustion gas is indicated by the arrow d2. In the present embodiment, an example where the direction of arrow d1 and the direction of arrow d2 are orthogonal will be described. However, the angle formed by the direction of arrow d1 and the direction of arrow d2 may be approximately orthogonal (an angle that can be regarded as orthogonal), and is not limited thereto. Further, in the main flow direction of the combustion gas (the direction of arrow d2), the burner 20 side is the upstream side and the exhaust pipe 40 side is the downstream side.

[0017] The water pipe 11 is disposed between the upper header 13 and the lower header 12 such that its longitudinal direction is the vertical direction in the gas flow space S. The water pipe 11 is supplied with water from the lower end connected to the lower header 12 and discharges steam from the upper end connected to the upper header 13. The steam discharged from the water pipe 11 is supplied to steam-using equipment (not shown) via steam extraction means (not shown) connected to the upper header 13.

[0018] Also, as shown in FIG. 2, in the present embodiment, inside the can body 10, the water pipe 11 located on the outermost side in the short side direction among the water pipe group is connected in the longitudinal direction (the direction of arrow d2) by the connecting portion 14, and a water pipe wall 15 is formed. The can body 10 forms the gas flow space S by this pair of water pipe walls 15, the lower header 12, and the upper header 13.

[0019] As shown in FIG. 2, the water pipes 11 are arranged in a staggered pattern at a predetermined interval in the gas flow space S inside the can body 10. Also, in the arranged water pipe group, when the columns are numbered 1st row and 2nd row in order from the row closest to the burner 20 side toward the exhaust pipe 40 side, an enlarged region E is formed in the region downstream of the 1st row of water pipes 11 closest to the burner 20 within the water pipe group. This enlarged region E has a function of expanding the flow of the combustion gas upward in the can body 10. In FIG. 2, the enlarged region E is the region filled with oblique lines.

[0020] This expanded region E is formed, for example, by removing one or more water pipes 11 from a group of water pipes arranged in a staggered pattern. In this embodiment, the expanded region E is shown as being formed by removing water pipes 11 located in the fourth row from the burner 20 side and some water pipes 11 located in the fifth row in the main gas flow direction (direction of arrow d2). The rows and number of water pipes removed may be selected as appropriate, as long as they can adequately fulfill the function of the expanded region E.

[0021] Burner 20 burns hydrogen fuel F1 and combustion air A1 to generate combustion gas. Burner 20 is a premixed burner with a planar premixed gas ejection surface 20a, and multiple nozzles for ejecting premixed gas are arranged on this premixed gas ejection surface 20a. The hydrogen fuel F1 supplied from the hydrogen fuel supply line L100 and the combustion air A1 supplied from the air supply line L200 are supplied to the burner 20 as a premixed gas. In this embodiment, the hydrogen fuel supply line L100 is connected to the air supply line L200 near the burner 20, and the hydrogen fuel F1 and combustion air A1 are mixed in the air supply line L200 downstream of this connection point. The premixed gas ejected from the premixed gas ejection surface 20a of the burner 20 is ignited by an ignition means such as a pilot burner (not shown), and a combustion gas accompanied by a flame F is formed in the burner 20.

[0022] The burner 20 is positioned at a lower, vertically biased location within the gas flow space S of the boiler body 10. Due to the positioning of the burner 20 as described above, the flame F generated by the combustion of the hydrogen fuel F1 strikes the lower side of the water pipe 11, particularly in the vicinity of the burner 20. Furthermore, it is preferable that the burner 20 is positioned such that, in the vertical direction (direction of arrow d1) of the gas flow space S, the uppermost end of the premixed gas nozzle at the premixed gas nozzle surface 20a is within 70% of the vertical dimension of the gas flow space S from the lower end of the gas flow space S.

[0023] Furthermore, the burner 20 injects a premixed gas of hydrogen fuel F1 and combustion air A1 in a direction perpendicular to the longitudinal direction of the water tube 11 (direction of arrow d1 in Figure 1) (direction of arrow d2 in Figure 1). Note that the angle that the direction in which the burner 20 injects the premixed gas makes with the longitudinal direction of the water tube 11 may be strictly perpendicular, or it may be inclined at an angle that can be considered perpendicular. Also, when the premixed gas of hydrogen fuel F1 and combustion air A1 is injected in a direction that makes a certain angle (for example, 45 degrees or less) with respect to the longitudinal direction of the water tube 11, it is sufficient that the main flow direction of the combustion gas is formed perpendicular to the longitudinal direction of the water tube facing the burner 20 (direction of arrow d1) (direction of arrow d2).

[0024] The exhaust stack 40 has its inlet on the side of the boiler 10 facing the burner 20 and is located at the downstream end of the boiler 10. The combustion gas generated by the burner 20 comes into contact with the water tubes 11 that make up the boiler 10 to exchange heat, and is then discharged as exhaust gas to the outside of the boiler 1 through the exhaust stack 40.

[0025] The boiler 1 of this embodiment is configured as described above, and based on this configuration, the following combustion state is formed inside the boiler 1. A premixed gas of hydrogen fuel F1 and combustion air A1 is ejected from the burner 20 in a direction perpendicular to the longitudinal direction of the water tubes 11 inside the boiler 10. The combustion gas accompanied by a flame F undergoes heat exchange with the multiple water tubes 11 inside the boiler 10, and after combustion is complete, the combustion gas undergoes further heat exchange with the multiple water tubes 11 before becoming exhaust gas. The exhaust gas is discharged to the outside of the boiler 1 through an exhaust pipe 40 located at the downstream end of the boiler 10. As shown in Figure 1, the flame F produced by the combustion of hydrogen fuel F1 extends downstream of the first row of water tubes 11 facing the burner 20 in the direction of gas flow (arrow d2). The flame F generated at the burner 20 simultaneously performs heat exchange with the water tubes 11 near the burner 20 during the combustion reaction. As the combustion gas G is cooled when the flame F strikes the water tubes 11, the combustion gas temperature decreases, and the generation of harmful exhaust substances such as NOx can be suppressed.

[0026] Furthermore, the burner 20 is positioned on the lower side in the vertical direction of the gas flow space S, and the flame F strikes the lower side of the water pipe 11 in the vicinity of the burner 20. Since the water pipe 11 is supplied with water from its lower end and releases steam from its upper end, the upper side tends to become hot. Because the burner 20 is positioned in a position biased towards the lower side of the gas flow space S, the flame F mainly heats the lower side of the water pipe 11 in the vicinity of the burner 20, which contains water, and less heat is applied to the upper side, which tends to become hot. This prevents the upper part of the water pipe 11, which tends to become hot, from being heated by the flame F and suffering damage due to overheating.

[0027] As mentioned above, the water tube 11 is supplied with water from its lower end and releases steam from its upper end. In such a water tube, the degree of dryness of the steam increases as it approaches the water tube outlet at the upper end, and the heat transfer coefficient from the tube wall deteriorates. Therefore, it is common practice to slightly lower the degree of dryness at the water tube outlet to prevent overheating of the tube and to separate the moisture using a steam-water separator installed downstream of the boiler. At any of the numerous water tube outlets, excessive dryness resulting in insufficient liquid to wet the inner wall and thus overheating of the water tubes should be prevented from a malfunction prevention standpoint. Furthermore, the range of water levels in the water tubes that allows for sufficient water to wet the tube walls while keeping the dryness of the water tube outlets low is narrow, and this appropriate water level changes depending on the boiler's operating conditions (boiler pressure, combustion rate, etc.).

[0028] In this embodiment, in a burner 20 that burns hydrogen fuel F1, which has a high combustion temperature and a fast combustion speed, it is necessary to form the flame F while avoiding the upper part of the water tube 11 where overheating is likely to occur, and to ensure wetting of the inner wall of the water tube 11, direct heating by the flame must be limited to near the control water level. For this reason, it is preferable that the upper end of the premixed gas ejection surface 20a of the burner 20 be positioned at a location that is 70% of the vertical dimension of the gas flow space S from the lower end of the gas flow space S, in the vertical direction (direction of arrow d1) of the gas flow space S. In this embodiment, by positioning the burner 20 at a location that satisfies this condition, damage to the water tube 11 due to overheating can be effectively suppressed.

[0029] The combustion gas, accompanied by flame F from the burning of hydrogen fuel F1, spreads within the water pipe group as it moves downstream, and in the expanding region E, it spreads further upward in the gas flow space S. The water in the water pipe 11 is heated by heat exchange with the combustion gas and turns into steam. This steam is supplied to steam-using equipment (not shown) via steam extraction means (not shown) connected to the upper header 13. The combustion gas spreads within the group of water tubes 11 arranged in a staggered pattern inside the boiler body 10, exchanges heat with the water tubes 11, and is then discharged as exhaust gas to the outside of the boiler 1 from the exhaust stack 40 located at the downstream end of the boiler body 10.

[0030] Figure 3 is a diagram illustrating the enlarged region E. Figure 3(a) schematically shows a part of the boiler body 10 of this embodiment that has the enlarged region E, and Figure 3(b) schematically shows a comparative example boiler body 10B that does not have the enlarged region. In the comparative example boiler body 10B shown in Figure 3(b), similar to the boiler body 10 shown in Figure 3(a), the burner 20 is located on the lower side in the vertical direction of the gas flow space S. In Figure 3, for ease of understanding, the shape of the burner 20, etc. are simplified, the flow of combustion gas G is indicated by arrows, and the water pipe 11 is shaded. In the comparative example boiler 10B shown in Figure 3(b), the burner 20 is located on the lower side in the vertical direction of the gas flow space S. Therefore, the combustion gas G generated by the burner 20 is located on the lower side of the gas flow space S near the burner 20 and gradually spreads upward as it moves downstream in the gas flow direction. As a result, the upper portion of the water pipes 11 does not contribute as effectively to heat exchange as the upstream water pipes 11. This tendency gradually improves as the water pipes 11 are located further downstream, but it still extends over a wide area of ​​the water pipe group.

[0031] In contrast, in the boiler body 10 of this embodiment shown in Figure 3(a), the premixed gas ejected from the burner 20 burns in the combustion region near the burner 20 and is located below the gas flow space S. The combustion gas G flows into the expanded region E where the water tubes 11 have been removed and the vertical flow resistance caused by the water tubes 11 has decreased, and spreads upward in the space of the expanded region E. Downstream of the expanded region E, the combustion gas G spreads throughout the entire gas flow space S and flows downstream. As a result, the entire surface of the water tubes 11 can be effectively used as a heat transfer surface to perform heat exchange. Therefore, in the boiler body 10, heat exchange in the water tubes 11 downstream of the expanded region E in the gas flow space S can be promoted, and the efficiency of heat exchange can be improved.

[0032] Furthermore, since the expanded region E does not have water pipes 11, the cooling effect on the combustion gas G is reduced, and the cross-sectional area of ​​the flow path for the combustion gas G becomes wider, resulting in a slower flow velocity for the combustion gas G. Consequently, in the expanded region E, in addition to the increased residence time of the combustion gas G at the temperature at which the hydrogen combustion reaction continues, the combustion gas G that has flowed through different flow paths formed by the water pipes 11 mixes with the combustion gas G. This allows for sufficient combustion of unburned hydrogen remaining upstream of the expanded region E, thereby suppressing the generation of unburned hydrogen. Normally, lowering the combustion gas temperature to suppress NOx generation results in unburned materials such as unburned hydrogen remaining in the exhaust gas. To reduce unburned hydrogen, the combustion gas temperature needs to be increased, but in that case, NOx generation increases. As in this embodiment, by providing an expanded region E downstream of the first row, which is closest to the burner 20, within the water pipe group, the remaining unburned hydrogen can be suppressed and NOx can be reduced.

[0033] Furthermore, it is preferable that the expanded region E be located downstream of the first row of water pipes, which is closest to the burner 20, in the group of water pipes arranged within the gas flow space S, at a position where the flame temperature is approximately 1000 to 1300°C. If the flame temperature exceeds 1300°C when it enters the expanded region E, the long residence time of the combustion gas G in the expanded region E will generate a large amount of NOx. Therefore, by positioning the expanded region E at a flame temperature of approximately 1000-1300°C, the generation of NOx can be suppressed. Furthermore, by positioning the expanded region E as described above, the combustion gas G spreads upward in the gas flow space S while maintaining a temperature sufficient for heat exchange, thereby improving the efficiency of heat exchange in the downstream water tube 11. Also, even when the combustion gas G spreads upward in the gas flow space S and comes into contact with the upper part of the water tube 11 downstream of the expanded region E, the temperature of the combustion gas G is sufficiently lower than the temperature of the high-temperature part of the flame, thus suppressing overheating of the upper part of the water tube 11.

[0034] As described above, this embodiment can achieve the following effects. (1) The boiler 1 comprises a burner 20 that burns hydrogen fuel F1 and combustion air A1 to generate combustion gas G, and a rectangular boiler body 10 in which a plurality of water tubes 11 are arranged at predetermined intervals within the gas flow space S. The water tubes 11 are arranged so that their longitudinal direction is in the vertical direction within the gas flow space S, with water supplied from the lower end and steam released from the upper end. The burner 20 is positioned at a lower-biased position in the vertical direction of the gas flow space S, and injects combustion air A1 or a premixed gas of combustion air A1 and hydrogen fuel F1 (in this embodiment, premixed gas) perpendicular to the longitudinal direction of the water tubes 11 facing the burner 20 so as to form the main flow direction of the combustion gas G. Downstream from the first row of water tubes 11 adjacent to the burner 20, between the water tubes 11, an expansion region is provided that expands the flow of the combustion gas G upward in the gas flow space S.

[0035] In boiler 1, burner 20 injects a premixed gas of combustion air A and hydrogen fuel F1 perpendicular to the longitudinal direction of the water tube 11, and the main flow direction of the combustion gas G is formed perpendicular to the longitudinal direction of the water tube 11 facing burner 20. As a result, the combustion gas G flows quickly to the downstream side of the gas flow space S, and the flame from burner 20 hits the water tube 11, cooling the combustion gas G, so that the temperature of the combustion gas is kept low and the generation of harmful exhaust substances such as NOx is suppressed. Furthermore, burner 20 is positioned at a lower-biased position in the vertical direction of the gas flow space S and is located facing the lower side of the water tube 11 which contains water inside. As a result, the upper part of the water tube 11 near burner 20, which tends to become hot, is not heated by the high-temperature combustion gas and is not damaged by overheating. Furthermore, since boiler 1 is equipped with an expanded region E, the flow of combustion gas G downstream of the expanded region E can be extended upward in the gas flow space S. As a result, boiler 1 can promote heat exchange in the water tubes 11 downstream of the expanded region E, and can maintain a sufficiently high efficiency of heat exchange. Furthermore, the expanded region E of boiler 1 allows for the effective combustion of hydrogen fuel F1, thereby reducing unburned hydrogen in the exhaust gas.

[0036] (2) In the boiler 1, the multiple water tubes 11 are arranged such that at least some of them are in a staggered pattern, and the enlarged region E is formed by missing one or more water tubes 11. By providing an expanded region E and arranging the water tubes 11 in a staggered pattern, the combustion gas G spreads upward in the gas flow space S, promoting heat exchange in the water tubes 11 downstream of the expanded region E. This further promotes the mixing of the combustion gas G, advancing the combustion reaction, and simultaneously facilitates heat exchange (cooling of the flame). This allows for a more efficient balance between reducing unburned hydrogen and suppressing NOx emissions.

[0037] (3) In the boiler 1, the burner 20 is positioned such that the upper end of the nozzle for combustion air A1 or a premixed gas of combustion air A1 and hydrogen fuel F1 (in this embodiment, the nozzle for the premixed gas) is located within 70% of the vertical dimension of the gas flow space S from the lower end. By positioning the burner 20 in this manner, the flame formed by the combustion air A1 and hydrogen fuel F1 ejected from the burner 20 strikes the lower part of the water tube 11 located near the burner 20 where water is present, and is less likely to strike the upper part of the water tube 11, which tends to become hot due to the presence of water vapor inside. This suppresses problems such as damage to the water tube 11 due to overheating.

[0038] (Second Embodiment) The boiler of the second embodiment is similar in form to the boiler 1 of the first embodiment, except that the burner is a diffusion combustion burner. Therefore, parts that perform the same functions as those of the first embodiment described above are given the same reference numerals or the same reference numerals at the end, and redundant explanations are omitted as appropriate. The burner of this embodiment is a diffusion combustion burner that injects at least a portion of the combustion air A1 and at least a portion of the hydrogen fuel F1 from one or more different nozzles, thereby diffusing the combustion air A1 and the hydrogen fuel F1.

[0039] In this embodiment, the burner is connected to a hydrogen fuel supply line L100, and multiple hydrogen fuel nozzles for ejecting hydrogen fuel F1 are regularly arranged on substantially the same plane. The hydrogen fuel F1 is ejected from each hydrogen fuel nozzle at substantially the same flow velocity. Furthermore, the burner in this embodiment is connected to an air supply line L200, and a plurality of air outlets for ejecting combustion air A1 are regularly arranged on substantially the same plane. The combustion air A1 is ejected from each air outlet at substantially the same flow velocity. In this embodiment, the multiple hydrogen fuel nozzles and the multiple air nozzles are arranged on different planes.

[0040] The burner of this embodiment injects combustion air A1 from multiple air nozzles perpendicular to the longitudinal direction of the water tube 11 (direction of arrow d1 in Figure 1) (direction of arrow d2 in Figure 1), and injects hydrogen fuel F1 from multiple hydrogen fuel nozzles to promote mixing with the combustion air A1. The direction of injection of combustion air A1 may be strictly perpendicular to the longitudinal direction of the water tube 11, or it may be inclined at an angle that can be considered perpendicular. Furthermore, when combustion air A1 is injected at a certain angle (for example, 45 degrees or less) to the longitudinal direction of the water tube 11, it is sufficient that the main flow direction of the combustion gas is formed perpendicular to the longitudinal direction of the water tube facing the burner 20 (direction of arrow d2). Furthermore, the injection direction of the hydrogen fuel F1 is preferably in a direction that promotes mixing with the combustion air A1, and is intersecting with the injection direction of the combustion air A1, which in this embodiment is perpendicular to it.

[0041] The boiler 2 of this embodiment is configured as described above, and based on this configuration, the following combustion state is formed inside the boiler 1. First, hydrogen fuel F1 is injected from multiple hydrogen fuel nozzles, and combustion air A1 is injected from multiple air nozzles. At least a portion of the injected hydrogen fuel F1 mixes with the injected combustion air A1 and is ignited by an ignition device (not shown), forming a combustion gas with a flame F in the burner 20.

[0042] As described above, the burner in this embodiment is a diffusion combustion burner, injecting hydrogen fuel F1 and combustion air A1 from different nozzles and burning them while mixing. Therefore, compared to a premixed burner in which hydrogen fuel F1 and combustion air A1 are mixed beforehand, flashback into the hydrogen fuel supply line L100 is less likely to occur, improving the safety of the boiler.

[0043] Furthermore, since the hydrogen fuel F1 ejected from multiple hydrogen fuel nozzles burns while mixing with combustion air A1, the flame F spreads over a wider area between the water tubes 11 arranged within the gas flow space S compared to a premixed burner. In this case, hydrogen fuel F1, which has a faster combustion rate and higher combustibility compared to general hydrocarbon fuels, continues diffusion combustion while mixing with combustion air A1. At the same time, heat exchange occurs between the combustion gas G containing unburned hydrogen and the water pipe 11 placed in the combustion space, which lowers the combustion gas temperature and suppresses the generation of harmful exhaust substances such as NOx. Furthermore, in the expanded region E, the cooling effect on the combustion gas G in the space where the water pipes 11 have been removed is reduced, resulting in a slower flow velocity of the combustion gas G. In addition, the combustion gas G that has flowed through different channels formed by the water pipes 11 mixes with the combustion gas G. As a result, the expanded region E expands the flow of combustion gas G upward in the gas flow space S, while suppressing the generation of NOx and promoting the combustion of unburned hydrogen remaining upstream of the expanded region E.

[0044] As described above, according to this embodiment, similar to the first embodiment described above, it is possible to suppress the generation of NOx while preventing malfunctions due to overheating of the water tube 11, and to maintain sufficient heat exchange performance.

[0045] According to this embodiment, in addition to the effects of (1) to (3) described above, the following effects can be achieved. (4) In the boiler, the burner ejects at least a portion of the combustion air A1 and at least a portion of the hydrogen fuel F1 from one or more different nozzles, and diffuse combustion is performed on the combustion air A1 and the hydrogen fuel F1.

[0046] The burner in this embodiment is a diffusion combustion burner, in which the ejected hydrogen fuel F1 burns while mixing with combustion air A1. Therefore, compared to a premixed burner, the burner in this embodiment has a wider flame spread, and heat exchange (cooling of the flame) can occur simultaneously with the combustion reaction, lowering the combustion temperature and suppressing the generation of NOx. Furthermore, while there is a risk of flashback when burning hydrogen fuel F1 in a premixed burner, the burner in this embodiment is a diffusion combustion burner, so flashback can be prevented, improving the safety of the boiler.

[0047] (Transformed form) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the scope of the present invention. In this embodiment, an example using hydrogen gas as the hydrogen fuel F1 is shown, but the invention is not limited to this, and a mixed gas with a hydrogen volume concentration of 50% or more may be used. Furthermore, although this embodiment shows an example in which the water pipes 11 are arranged in a staggered pattern, it is also possible for a portion of the water pipe group to be arranged in a staggered pattern and the rest in a grid pattern.

[0048] In the first embodiment, the premixed gas of hydrogen fuel F1 and combustion air A1 was described as being ejected in a direction perpendicular to the longitudinal direction of the water tube 11. However, the embodiment is not limited to this, and the gas may be ejected in a direction perpendicular to the longitudinal direction of the water tube 11 at an angle of 45 degrees or less. In the second embodiment as well, the combustion air A1 may be ejected in a direction perpendicular to the longitudinal direction of the water pipe 11, at an angle of 45 degrees or less.

[0049] In the second embodiment, the burner was described in an example in which a plurality of air outlets for ejecting combustion air A1 are regularly arranged on substantially the same plane, but the burner is not limited to this, and the combustion air A1 may be ejected from a single air outlet.

[0050] While each embodiment and its variations can be used in combination as appropriate, a detailed explanation is omitted. Furthermore, the present invention is not limited to the embodiments described above.

[0051] Furthermore, since the present invention promotes the use of hydrogen, which does not emit carbon dioxide as a fuel, it can contribute, for example, to Goal 7 of the United Nations-led Sustainable Development Goals (SDGs), "Ensure access to affordable, reliable, sustainable and modern energy." [Explanation of Symbols]

[0052] 1 Boiler 10 can body 11 Water pipe 12 Bottom Header 13 Top Header 20 burners 40 Exhaust stack S Gas Flow Space E Enlarged Area

Claims

1. A burner that burns hydrogen fuel and combustion air to generate combustion gases, It comprises a rectangular tank body in which multiple water pipes are arranged at predetermined intervals within a gas flow space, The water pipe is arranged such that its longitudinal direction is vertical in the gas flow space, and water is supplied from its lower end and steam is released from its upper end. It is a boiler, The burner is positioned at a lower, vertically biased location within the gas flow space, and injects the combustion air or a premixed gas of the combustion air and hydrogen fuel perpendicular to the longitudinal direction of the water pipe facing the burner, so as to form the main flow direction of the combustion gas. Downstream from the first row of water pipes adjacent to the burner, an expanded region is provided between the water pipes to expand the flow of the combustion gas upward in the gas flow space. Boiler.

2. The burner ejects at least a portion of the combustion air and at least a portion of the hydrogen fuel from one or more different nozzles, thereby performing diffusion combustion of the combustion air and the hydrogen fuel. The boiler according to claim 1.

3. The plurality of water tubes are arranged such that at least a portion of them are arranged in a staggered pattern. The enlarged region is formed by omitting one or more of the water pipes. The boiler according to claim 1.

4. The burner is positioned such that, in the vertical direction of the gas flow space, the upper end of the nozzle for the combustion air or the premixed gas of the combustion air and the hydrogen fuel is located within 70% of the vertical dimension of the gas flow space from the lower end. The boiler according to claim 1.

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