Pre-mixing type hydrogen gas burner

Abstract

To provide a pre-mixed type hydrogen gas burner that reduces NOx emission and is suitable for hydrogen fuel.SOLUTION: A pre-mixed type hydrogen gas burner 1 comprises a cylindrical air flow pipe 2, an annular distribution plate 3 disposed in a manner of not protruding into the air flow pipe 2, a gas nozzle 4 penetrating the distribution plate 3 and comprising a plurality of gas ports 4b disposed on the peripheral wall of cylindrical front-end unit whose front end is closed, a pilot burner 5 disposed outside the air flow pipe 2, a primary air passage 7 disposed between the outer peripheral face of the gas nozzle 4 and the distribution plate 3, a secondary air passage 8 consisting of a plurality of columns of through holes 8a radially arranged on the distribution plate 3, and an annular tertiary air passage 9 disposed between the outer peripheral edge of the distribution plate 3 and the inner peripheral face of the air flow pipe 2, with the gas port 4b disposed to face the direction between the directions of neighboring columns of the secondary air channel 8 and the ejection port 5a of the pilot burner 5 neighboring the front end 2a of the air flow pipe 2, being disposed between the neighboring columns of the secondary air passage 8, and facing the direction of the center axis 4Y of the gas nozzle 4.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a premixed hydrogen gas burner.

Background Art

[0002] Since hydrogen does not produce carbon dioxide during combustion, it has attracted attention as a fuel for combustion devices such as boilers (Patent Document 1). Hydrogen has a higher combustion speed and flame temperature compared to hydrocarbon gases such as propane, so the amount of NOx emissions tends to increase.

[0003] In boilers and the like, there is a method (Patent Document 1 etc.) of blowing steam into the combustion chamber or adding moisture during combustion to lower the flame temperature and reduce NOx, but the exhaust gas volume increases, resulting in an increase in heat loss (the boiler efficiency decreases).

[0004] Also, there is a method (Non-Patent Document 1 etc.) of mixing a part of the exhaust gas into the combustion air to lower the oxygen partial pressure, increasing the heat capacity of the combustion gas, and lowering the flame temperature to reduce NOx, but there are problems such as the blower becoming larger and the combustion becoming unstable. Therefore, methods (Patent Documents 2, 3, etc.) of improving the structure of the premixed gas burner and performing measures such as self-exhaust gas recirculation and divided flames to reduce NOx are known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] However, the improved structure of conventional pre-mixed gas burners is designed for use with fuels that burn slowly, such as city gas. Therefore, when used with hydrogen fuel, which burns quickly, combustion proceeds rapidly before the hydrogen can diffuse, resulting in high flame temperatures and increased NOx emissions. Furthermore, the high-temperature flame near the burner can damage it, making it unsuitable for use with hydrogen fuel.

[0008] Therefore, the primary objective of the present invention is to reduce NOx emissions and provide a pre-mixed hydrogen gas burner suitable for hydrogen fuel. [Means for solving the problem]

[0009] To achieve the above objective, a pre-mixed hydrogen gas burner according to one aspect of the present invention comprises a cylindrical air supply pipe, a disc-shaped rectifier plate provided inside the outlet of the air supply pipe so as not to protrude from the outlet, a gas nozzle that penetrates the rectifier plate and has a plurality of gas ports on the peripheral wall of a cylindrical tip with a closed tip, a pilot burner disposed on the outside of the air supply pipe, a primary air passage consisting of a gap provided between the outer peripheral surface of the gas nozzle and the rectifier plate, a secondary air passage consisting of a row of through holes arranged radially in the rectifier plate, and a tertiary air passage consisting of an annular gap provided between the outer peripheral edge of the rectifier plate and the inner peripheral surface of the air supply pipe, wherein the plurality of gas ports are provided so as to face the direction between adjacent rows of the through holes in the secondary air passage, and the outlet of the pilot burner is provided so as to face the central axis of the gas nozzle, adjacent to the tip of the air supply pipe and positioned between adjacent rows of through holes in the secondary air passage.

[0010] The primary air passage, the secondary air passage, and the tertiary air passage may be configured such that their passage areas increase in that order.

[0011] The distance between the outer surface of the rectifier plate and the tip of the air vent can be 0 to 15 mm.

[0012] The outer diameter of the gas nozzle can be set to 15-25% of the inner diameter of the air supply pipe, and the distance from the rectifier plate to the center of the gas port can be set to 25-35% of the inner diameter of the air supply pipe.

[0013] The ratio of the passage area of ​​the primary air passage to the total air passage area can be 15-25%, the ratio of the passage area of ​​the secondary air passage to the total air passage area can be 25-35%, and the ratio of the passage area of ​​the tertiary air passage to the total air passage area can be 45-55%.

[0014] The system further comprises a windbox through which the aforementioned air supply pipe is provided, the windbox having an air supply port for supplying combustion air, and the pilot burner may be positioned on the opposite side of the axis between the air supply port of the windbox and the air supply pipe. [Effects of the Invention]

[0015] According to the present invention, by adopting the above configuration, the primary air flowing out from the primary air passage flows around the gas nozzle and along the gas nozzle, mixing with the hydrogen gas ejected from the gas port and pushing the hydrogen gas forward. The secondary air flowing out from the secondary air passage flows in a manner that divides the radially ejected hydrogen gas. The tertiary air ejected from the tertiary air passage forms a flow that swirls in the central axis direction along the direction between adjacent rows of through-holes in the secondary air passage of the rectifier plate, and then some of the tertiary air merges with the primary air. Furthermore, the swirl-like flow of the tertiary air in the central axis direction forms a combustion gas circulation flow (Figure 5), so some of the tertiary air merges with the combustion gas. This series of primary to tertiary air flows create an optimal divided flame formation at the tip of the gas nozzle and self-exhaust gas recirculation, resulting in slow combustion without creating localized high-temperature areas, thus suppressing NOx emissions.

[0016] In addition, since the tip of the pilot burner is arranged so as not to collide with the flame of the main burner, there is no risk of burnout. If the pilot burner is arranged in this way in a conventional gas burner for fossil fuels, the flame transfer to the main burner deteriorates. However, hydrogen fuel has better ignition properties (wider combustion range) than fossil fuels, and a flow occurs in which the combustion air is drawn from the side of the tertiary air passage to the side of the primary air passage. Therefore, the flame of the pilot burner follows the flow rectifying plate and forms a flame near the gas port, resulting in better flame transfer. Thus, the arrangement configuration of the pilot burner in the present invention can be realized.

Brief Description of the Drawings

[0017] [Figure 1] It is a longitudinal side view showing an embodiment of the front - mixing type hydrogen gas burner according to the present invention. [Figure 2] It is a front view of the front - mixing type hydrogen gas burner of FIG. 1. [Figure 3] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 4] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 5] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 6] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 7] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 8] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 9] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention. [Figure 10] It is a fluid analysis image of the front - mixing type hydrogen gas burner according to the present invention.

Modes for Carrying Out the Invention

[0018] An embodiment of the pre-mixed hydrogen gas burner according to the present invention will be described with reference to the drawings. In the following description, the same or similar components are denoted by the same reference numerals throughout all the drawings and embodiments.

[0019] Referring to Figures 1 and 2, the pre-mixed hydrogen gas burner 1 comprises a blower pipe 2 for supplying combustion air A, a rectifier plate 3 provided inside the outlet 2a of the blower pipe 2 so as not to protrude from the outlet 2a, a gas nozzle 4 having multiple gas ports 4b on the peripheral wall of a cylindrical tip portion that penetrates the rectifier plate 3 and has a closed tip 4a, and a pilot burner 5 disposed on the outside of the blower pipe 2.

[0020] The blower pipe 2 is cylindrical and is connected to the windbox 6. The blower pipe 2 is also called the blast pipe. The windbox 6 is equipped with an air damper 6b at the air supply port 6a for combustion air, and the amount of combustion air A supplied can be adjusted by the air damper 6b. The gas nozzle 4, to which hydrogen gas HG is supplied, penetrates the windbox 6 and passes through the inside of the windbox 6 and the blower pipe 2. The gas nozzle 4 can be configured to penetrate the bottom surface of the windbox 6 and extend straight through the inside of the windbox 6 to penetrate the center of the rectifier plate 3, as shown in Figure 1, or it can be configured to penetrate the side of the windbox 6, bend at a right angle inside the windbox 6, and penetrate the rectifier plate 3 (see Figure 4). The central axis Y of the gas nozzle 4 passes through the center of the rectifier plate 3.

[0021] An annular gap constituting a primary air passage 7 is provided between the outer circumferential surface of the gas nozzle 4 and the inner circumferential surface of the rectifier plate 3. The rectifier plate 3 is disc-shaped and has a secondary air passage 8 made up of a row of radially arranged through holes 8a. The multiple through holes 8a are formed on concentric circles. An annular gap constituting a tertiary air passage 9 is provided between the outer circumferential surface of the disc-shaped rectifier plate 3 and the inner circumferential surface of the cylindrical air supply pipe 2. Centering projections 3a and 3b may be formed on the inner and outer circumferential surfaces of the rectifier plate 3. These centering projections 3a and 3b only need to be small enough to align the center of the rectifier plate 3 with the central axis Y.

[0022] The combustion air A supplied to the windbox 6 is ejected from the primary air passage 7, the secondary air passage 8, and the tertiary air passage 9, respectively. The rectifier plate 3 can be fixed to the gas nozzle 4 by the bracket 10.

[0023] The rectifier plate 3 is positioned so as not to protrude beyond the outlet 2a of the air supply pipe 2, either flush with the edge of the outlet 2a of the air supply pipe 2 or near the edge of the outlet 2a. If the rectifier plate 3 protrudes beyond the outlet 2a of the air supply pipe 2, the tertiary air ejected from the tertiary air passage 9 will be ejected radially outward from the air supply pipe 2, which is undesirable.

[0024] The distance H between the outer surface of the rectifier plate 3 and the tip of the air supply pipe 2 is preferably 0 to 15 mm, more preferably 0 to 5 mm. If the distance H exceeds 15 mm, flame retention will occur within the air supply pipe 2, increasing the amount of NOx discharged and making the rectifier plate 3 more susceptible to burning, which is undesirable.

[0025] The gas ports 4b are provided near the closed tip 4a of the gas nozzle 4, and the central axis 4X of each gas port 4b, i.e., the injection direction of hydrogen gas HG, is positioned to face the direction between adjacent rows of through holes 8a in the secondary air passage 8. In the illustrated example, six gas ports 4b are formed at equal angular intervals (60° intervals) around the central axis 4Y of the gas nozzle 4. Furthermore, as shown in Figure 2, the gas ports 4b are provided at intermediate positions between adjacent rows of through holes 8a, preferably at positions that bisect the central angle α of the adjacent rows of through holes 8a. The tip of the gas nozzle 4 has a simple structure, consisting only of a pipe with the tip closed. The number and spacing of the gas ports 4b can be set as appropriate.

[0026] In the illustrated example, the rectifier plate 3 has six radial rows of three through holes 8a, spaced at equal angles (60° intervals) with the center of the rectifier plate 3 as the central angle. The rows of through holes 8a in the secondary air passage 8 are provided according to the number of gas ports 4b and are arranged alternately with the injection direction of the gas ports 4b.

[0027] The outer diameter φd of the gas nozzle 4 is preferably 15-25% of the inner diameter φD of the air supply pipe 2, and more preferably 15-20%. If φd / φD is less than 15%, the hydrogen gas HG injections from adjacent gas ports 4b will be closer together, making it impossible to form an optimal split flame, and increasing the amount of NOx generated. On the other hand, if φd / φD exceeds 25%, the hydrogen gas HG injections from adjacent gas ports 4b will be further apart, resulting in poor mixing of hydrogen and combustion air, and making it easier for unburned hydrogen to be generated.

[0028] The distance h from the rectifier plate 3 to the center of the gas port 4b is preferably 25-35% of the inner diameter φD of the air supply pipe 2, and more preferably 25-30%. If the distance h is less than 25% of the inner diameter φD, the flame will be held near the rectifier plate 3, causing combustion to proceed rapidly, which increases NOx emissions and damages the rectifier plate 3. On the other hand, if the distance h is greater than 35% of the inner diameter φD, the mixing of hydrogen and combustion air will be poor, making it easier for unburned hydrogen to be generated.

[0029] The hydrogen gas sent into the nozzle of the gas nozzle 4 collides with the closed tip 4a and is ejected radially outward around the central axis 4Y of the gas nozzle 4. The primary air flowing out from the primary air passage 7 flows around the gas nozzle 4 and along the gas nozzle 4, colliding with the hydrogen gas ejected from the gas port 4b at a near-perpendicular angle and rapidly mixing, pushing the hydrogen gas forward. The secondary air flowing out from the secondary air passage 8 flows in a manner that forms an air curtain separating the radially ejected hydrogen gas HG. The tertiary air ejected from the thin, annular tertiary air passage 9 is drawn between the flow of secondary air flowing out from the secondary air passage 8 and toward the flow of primary air flowing out from the primary air passage 7, forming a flow that swirls along the rectifier plate 3 in the direction of the central axis of the gas nozzle 4, and then some of the tertiary air merges with the primary air. Furthermore, the tertiary air's swirling flow along the central axis forms a circulating flow of combustion gases (see Figure 5) inside the furnace (not shown), causing some of the tertiary air to merge with the combustion gases. This series of primary-to-tertiary air flows creates a clean, segmented flame at the tip of the gas nozzle 4 and self-exhaust gas recirculation, resulting in slow combustion without creating localized high-temperature areas, thus suppressing NOx emissions. This series of flows remains unchanged even when the combustion load decreases, eliminating the need for a special gas burner structure. Here, self-exhaust gas recirculation refers to the process of inducing combustion gases within the furnace to mix with the combustion air using the combustion air's ejection energy.

[0030] The primary air passage 7, secondary air passage 8, and tertiary air passage 9 are configured such that their passage areas increase in that order. Preferably, the ratio of the passage area S1 of the primary air passage 7 to the total air passage area S (S1 / S) is 15-25%, the ratio of the passage area S2 of the secondary air passage 8 to the total air passage area S (S2 / S) is 25-35%, and the ratio of the passage area S3 of the tertiary air passage 9 to the total air passage area S (S3 / S) is 45-55%.

[0031] The primary air passage 7, secondary air passage 8, and tertiary air passage 9 are arranged in such a way that the passage area increases in that order, preventing combustion from progressing too quickly. Furthermore, the flow ejected from the tertiary air passage 9, which occupies about half of the total passage area, and directed towards the central axis Y promotes the circulation of combustion gases formed outside the flame (exhaust gas recirculation), resulting in slow combustion. Additionally, the secondary air passage 8 is radially divided according to the number of gas ports 4b, promoting a divided flame. Moreover, the tip of the gas nozzle 4 has no obstruction to the gas flow such as a flame-holding plate and has a straight cylindrical structure that makes it difficult to hold the flame, thus preventing the generation of localized high-temperature areas and reducing NOx emissions.

[0032] The pilot burner 5 is a pre-mixed burner for ignition. It ignites a mixture of fuel gas PG and combustion air PA, which is mixed in the nozzle, using a built-in ignition device 11 to produce a flame. The fuel gas PG in the pilot burner 5 may be a fossil fuel (city gas 13A, propane gas, etc.) or hydrogen fuel.

[0033] The nozzle 5a of the pilot burner 5 is positioned adjacent to the tip of the air supply pipe 2, as shown in Figure 1, and also positioned between adjacent rows of through holes 8a in the secondary air passage 8, as shown in Figure 2, and directed toward the central axis 4Y of the gas nozzle 4. Since the nozzle 5a at the tip of the pilot burner 5 is positioned so as not to collide with the flame of the main burner, there is no risk of the pilot burner 5 burning out. In conventional gas burners for fossil fuels, positioning the pilot burner in this manner would result in poor transfer of the flame to the main burner. However, hydrogen fuel has better ignition properties (wider combustion range) than fossil fuels, and by adopting the above configuration of the pre-mixed hydrogen gas burner according to the present invention, a flow is generated in which the combustion air is drawn from the tertiary air passage 9 side to the primary air passage side. As a result, the flame of the pilot burner 5 follows the rectifier plate 3 and forms a flame near the gas port 4b, improving the transfer of the flame, thus enabling the pilot burner 5 arrangement configuration in the present invention.

[0034] The pilot burner 5 is preferably positioned on the opposite side of the air supply port 6a of the windbox 6 and the axis of the air supply pipe 2 (which coincides with the central axis 4Y of the gas nozzle 4), as shown in the illustrated example. This is because the airflow within the windbox 6 creates a strong swirling flow of the combustion air A from the tertiary air passage 9 side to the primary air passage 7 side.

[0035] Figures 3 to 8 show the results of a fluid analysis performed on the distance h from the rectifier plate 3 to the central axis 4X of the gas port 4b and the inner diameter φD of the air supply pipe 2. Figures 3 and 4 show h / φD = 25%, Figures 5 and 6 show h / φD = 30%, and Figures 7 and 8 show h / φD = 35%. Figures 3, 5, and 7 correspond to the MM cross section of Figure 2, and Figures 4, 6, and 8 correspond to the NN cross section of Figure 2. From the results in Figures 3 to 8, it can be seen that when h / φD = 25%, the entrainment of tertiary air interferes with the flow of hydrogen ejected from the gas port, improving mixing and causing flame retention near the rectifier plate, resulting in a localized high-temperature area, an increase in NOx, and increased susceptibility to damage to the rectifier plate. Therefore, h / φD ≥ 25% is preferable. Furthermore, when h / φD = 35%, the mixing deteriorates due to the entrainment of tertiary air and the separation of the hydrogen flow ejected from the gas port, making it easier for unburned hydrogen to be generated. Therefore, it is preferable to keep h / φD ≤ 35%.

[0036] Next, Figures 9 and 10 show the results of the fluid analysis performed for a main combustion load of 20%. Figure 9 corresponds to the MM cross-section in Figure 2, and Figure 10 corresponds to the NN cross-section in Figure 2. h / φD = 30%. The results in Figures 9 and 10 show that even when the combustion load is reduced to 20%, localized high-temperature areas are not generated, thus preventing damage caused by red-hot burners and suppressing NOx generation.

[0037] The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0038] 1. Pre-mixing type hydrogen gas burner 2 Air pipe 3 Rectifier plate 4 Gas nozzles 5 Pilot Burner 6 Window Box 7 Primary air passage 8. Secondary air passage 9. Tertiary air passage HG Hydrogen Gas A Combustion air

Claims

1. A cylindrical air vent, A disc-shaped rectifier plate is provided inside the nozzle of the air blower pipe so as not to protrude from the nozzle, A gas nozzle having multiple gas ports on the circumferential wall of a cylindrical tip portion that penetrates the rectifier plate and has a closed tip, A pilot burner is provided on the outside of the aforementioned air supply pipe, A primary air passage consisting of a gap provided between the outer surface of the gas nozzle and the rectifier plate, The rectifier plate comprises a secondary air passage consisting of rows of through holes arranged radially, A tertiary air passage consisting of an annular gap provided between the outer edge of the rectifier plate and the inner surface of the air duct, Equipped with, The plurality of gas ports are arranged so as to face the direction between adjacent rows of the through holes in the secondary air passage. The nozzle of the pilot burner is located adjacent to the tip of the air supply pipe, positioned between adjacent rows of through holes in the secondary air passage, and directed toward the central axis of the gas nozzle. Pre-mixing type hydrogen gas burner.

2. The pre-mixing type hydrogen gas burner according to claim 1, wherein the passage area of ​​the primary air passage, the secondary air passage, and the tertiary air passage increases in that order.

3. The pre-mixing type hydrogen gas burner according to claim 1, wherein the distance between the outer surface of the rectifier plate and the tip of the air supply pipe is 0 to 15 mm.

4. The pre-mixing gas burner for hydrogen gas according to claim 1, wherein the outer diameter of the gas nozzle is 15 to 25% of the inner diameter of the air supply pipe, and the distance from the rectifier plate to the center of the gas port is 25 to 35% of the inner diameter of the air supply pipe.

5. The pre-mixing type hydrogen gas burner according to claim 2, wherein the ratio of the passage area of ​​the primary air passage to the total air passage area is 15 to 25%, the ratio of the passage area of ​​the secondary air passage to the total air passage area is 25 to 35%, and the ratio of the passage area of ​​the tertiary air passage to the total air passage area is 45 to 55%.

6. The aforementioned air ducts are further provided in a wind box that is connected to each other, The aforementioned window box is equipped with an air supply port through which combustion air is supplied, The pilot burner is located on the opposite side of the axis between the air supply port of the windbox and the blower pipe. The pre-mixing type hydrogen gas burner according to claim 1.

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