All primary combustion burner

Abstract

To suppress back fire as much as possible while suppressing pressure loss even in a case when a fuel gas is a hydrogen gas, in an all primary combustion burner which includes a burner body 1 having an air-fuel mixture chamber 11 to which the air-fuel mixture of the fuel gas and primary air is supplied, and a combustion plate portion 2 covering an opening face 12 of the burner body facing the air-fuel mixture chamber, and in which a back fire suppression plate portion 3 opposed to the combustion plate portion at an interval is disposed, and the air-fuel mixture passing through the back fire suppression plate portion is injected from the combustion plate portion to be burned.SOLUTION: A back fire suppression plate portion has a sintered compact sheet 33 obtained by sintering a laminate on which metallic fiber or metallic beads are laminated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a full primary combustion burner, and more particularly to one that uses hydrogen gas as fuel gas. [Background technology]

[0002] One example of a fully primary combustion burner of the above type, which uses a hydrocarbon gas such as natural gas as the fuel gas, is known, for example, from Patent Document 1. This burner includes a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering the open surface of the burner body facing the mixture chamber and having a number of flame holes arranged in a row. A flashback suppression plate portion is also disposed within the mixture chamber, facing the combustion plate portion with a gap therebetween, and the flashback suppression plate portion has a number of through-holes arranged in a row that penetrate through its thickness. The mixture supplied to the mixture chamber passes through the through-holes in the flashback suppression plate portion and the gap between the flashback suppression plate portion and the combustion plate portion, and is supplied to each of the flame holes, where it is ejected and combusted. In this case, the height of the gap is set to a range of 1 mm to 4 mm, the diameter of the through-holes is set to a range of 1 mm to 5 mm, and the diameter of the flame holes is set to a range of 0.5 mm to 3 mm. This reduces pressure loss when passing through the combustion plate section and the flashback suppression plate section, forming a substantially uniform flame over the entire surface of the combustion plate section while suppressing flashback, which would otherwise occur if the flame propagated into the mixture chamber.

[0003] In recent years, hydrogen, which does not emit carbon dioxide and is an alternative fuel to hydrocarbon gases, has been attracting attention as a means of preventing global warming. However, a mixture of hydrogen gas and primary air has an extremely fast combustion rate. When a mixture of hydrogen gas and primary air is burned in the above-mentioned conventional all-primary combustion burner, the combustion plate is prone to high temperatures due to the combustion of the mixture near its surface. Because the gap is relatively narrow, the flashback suppression plate is overheated by radiant heat from the combustion plate. As a result, if a flame propagates through the gap in the mixture chamber, it may not be extinguished. Furthermore, because the through-hole diameter is relatively large, the flame that propagates through the gap easily propagates further upstream of the mixture chamber through each through-hole. As a result, flashback cannot be effectively suppressed, potentially resulting in burner damage. In such cases, it is possible to set the diameter of each through-hole to the so-called flashback limit (e.g., 0.6 mm), but this increases pressure loss. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-263614 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above, an object of the present invention is to provide a full primary combustion burner that can suppress flashback as much as possible while suppressing pressure loss, even when hydrogen gas is used as the fuel gas. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a full primary combustion burner comprising a burner body having a mixture chamber into which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering the open surface of the burner body facing the mixture chamber, wherein a flashback suppression plate portion is arranged in the mixture chamber facing the combustion plate portion with a gap therebetween, and the mixture that has passed through the flashback suppression plate portion is ejected from the combustion plate portion and combusted, wherein the fuel gas is hydrogen gas, and the flashback suppression plate portion has a sintered sheet formed by sintering a laminate of metal fibers or metal beads.

[0007] According to the present invention, the air-fuel mixture supplied to the mixture chamber passes through numerous minute gaps in the sintered body sheet, which are formed by randomly entangling and bonding (welding) metal fibers or metal beads during sintering. The numerous minute gaps are smaller than the flashback limit pore size and are then supplied to the combustion plate. The increased contact area with the room-temperature air-fuel mixture suppresses the temperature rise of the sintered body sheet, i.e., the flashback suppression plate itself. Furthermore, the numerous minute gaps also suppress pressure loss. The air-fuel mixture that passes through the sintered body sheet in the flashback suppression plate passes through the gap between the flashback suppression plate and the combustion plate, and is ejected from the combustion plate and combusts. Even if a flame propagates through the gap between the combustion plate and the flashback suppression plate, the temperature rise of the flashback suppression plate is suppressed, allowing it to be extinguished by the flashback suppression plate. Even if the flame that propagates through the gap remains unextinguished on the surface of the flashback suppression plate facing the gap, the limited minute gaps in the flashback suppression plate suppress its propagation upstream. In this way, in the present invention, the flashback suppression plate has a sintered body sheet, so that flashback can be suppressed as much as possible while suppressing pressure loss, even when hydrogen gas is used as the fuel gas. Note that the metal fibers and metal beads in the present invention contain a metalloid as a constituent material.

[0008] In the present invention, it is preferable that the metal fibers or the metal beads are composed of, for example, Fe and at least one selected from Al, Cr, Mn, and Si, or a carbide thereof, and in this case, the weight per unit area of ​​the sintered sheet after sintering is 1200 g / m 2~1800g / m 2 It is preferable that the weight is set in the range of 1200 g / m. 2 If it is less than this, the minute gaps may become too large and flashback may not be suppressed. 2 The greater the amount, the greater the resistance to the passage of the mixture.

[0009] In the present invention, a temperature sensor is preferably disposed in the portion of the mixture chamber located between the combustion plate and the flashback suppression plate. In this way, if a flame that has propagated into the gap is not extinguished and burns on the surface of the flashback suppression plate facing the gap, the temperature sensor can detect the resulting temperature rise and, for example, stop the supply of the mixture, thereby quickly stopping combustion that could damage the burner.

[0010] Furthermore, in the present invention, it is preferable to set the gap between the combustion plate and the flashback suppression plate in the range of 5 mm to 30 mm. If the gap is shorter than 5 mm, the radiant heat from the combustion plate becomes dominant, and there is a risk that the flashback suppression plate will be overheated, while if the gap is longer than 30 mm, the amount of air-fuel mixture remaining in the gap between the combustion plate and the flashback suppression plate will increase, resulting in a loud noise when a flame propagates through the gap.

[0011] In addition, in the present invention, it is preferable that the combustion plate portion is made of a sintered sheet obtained by sintering a laminate of metal fibers or metal beads. This, as mentioned above, increases the contact area with the air-fuel mixture, which is advantageous in that it suppresses the temperature rise of the combustion plate portion itself. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view showing the all-primary combustion burner of this embodiment installed in a combustion housing. [Figure 2] FIG. 2 is a perspective view of the all-primary combustion burner shown in FIG. 1. [Figure 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 10 is an enlarged plan view showing a portion of a sintered body sheet according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, with reference to the drawings, an embodiment of the all-primary combustion burner CB of the present invention will be described, in which the flashback suppression plate has a sintered sheet made of a sintered laminate of metal fibers. Note that the "hydrogen" referred to in this invention is not limited to pure hydrogen, but also includes, for example, the addition of a small amount of odorant to impart odor.

[0014] 1 and 2, the all-primary combustion burner CB comprises a burner body 1 having a mixture chamber 11 to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion 2 covering an open surface 12 of the burner body 1 facing the mixture chamber 11. The all-primary combustion burner CB is fastened by screws (not shown) to a flange portion Fb1 of a combustion housing Fb that houses a heat exchanger for hot water supply (not shown) at the peripheral portion of the open surface 12 of the burner body 1, i.e., the lower peripheral portion 13, and is used to heat the heat exchanger. The burner body 1 also has an inlet 14 through which the mixture is supplied by a fan (not shown).

[0015] Referring also to FIG. 3 , the combustion plate section 2 is composed of a burner frame 21 made of sheet metal and having a longitudinal frame shape; a main body 23 provided to cover a rectangular first opening 22 enclosed by the burner frame 21 from the burner body 1 side (above); and a distribution plate 24 having numerous distribution holes 24a formed therein and disposed on the rear surface (upper surface) of the main body 23, which is the upstream surface in the flow direction of the air-fuel mixture. The burner frame 21 has an opening peripheral portion 21a located on the same plane as the first opening 22, a side plate portion 21b bent from the opening peripheral portion 21a toward the burner body 1 (above), and a frame flange portion 21c extending outward from the upper end of the side plate portion 21b. The main body 23 can be composed of a metal fiber knit, for example, made by knitting metal fibers such as heat-resistant steel. The thickness of the metal fibers constituting the metal fiber knit can be, for example, in the range of 35 μm to 100 μm. Then, with the distribution plate 24 placed on the back surface of the metal fiber knit 23, the peripheral edges of these are spot-welded at regular intervals to the opening peripheral edge 21a of the burner frame 21 to assemble them, and in this state, the burner body 1 is attached to the lower peripheral edge 13 via the frame flange 21c. Also, a flashback suppression plate 3 is arranged inside the air-fuel mixture chamber 11.

[0016] 4, the flashback suppression plate 3 includes a frame-shaped support frame 31 made of sheet metal and extending in one direction, and a sintered sheet 33 provided to cover a second opening 32, which has the same contour as the first opening 22 and is surrounded by the support frame 31, from the opposite side (above) of the combustion plate 2. The support frame 31 is then fastened to a frame-shaped seat 15 formed in the air-fuel mixture chamber 11 with screws (not shown). When the flashback suppression plate 3 is fastened, the sintered sheet 33 is secured to the combustion plate 2. 2 The sintered body sheet 33 faces the metal fiber knit 23 with a gap Gp therebetween. The gap Gp between the sintered body sheet 33 and the metal fiber knit 23 is set in the range of 5 mm to 30 mm. If the gap is shorter than 5 mm, when the combustion plate 2 is heated by a flame, the radiant heat from the combustion plate 2 becomes dominant, and there is a risk that the flashback suppression plate 3 will be overheated. On the other hand, if the gap is longer than 30 mm, the amount of air-fuel mixture remaining in the gap Gp between the combustion plate 2 and the flashback suppression plate 3 will increase, and a loud noise will be generated when the flame propagates through the gap Gp.

[0017] The sintered sheet 33 is obtained by sintering a laminate in which metal fibers 33a are stacked. The metal fibers are composed of Fe and at least one selected from Al, Cr, Mn, and Si, or carbides thereof, such as stainless steel fibers containing Fe as the main component, and have a wire diameter in the range of 50 μm to 100 μm. To manufacture the sintered sheet 33, known methods such as hot pressing (hot processing method) and HIP (hot isostatic pressing), which simultaneously perform pressure molding and sintering, can be used. For example, when manufacturing by hot pressing, although not specifically illustrated or described, the metal fibers 33a are stacked in a mold cavity without being woven or knitted to form a laminate. At this time, the weight per unit area is 1200 g / m 2 ~1800g / m 2 Next, pressure is applied to the laminate in one axial direction by a punch, and in this state the laminate is heated and held at a predetermined temperature via a mold.

[0018] As shown in the partially enlarged view of Figure 4, the sintered sheet 33 manufactured as described above has numerous minute gaps 33b formed during sintering, which are complex and smaller than the flashback limit pore size, due to the metal fibers 33a randomly entangled and bonded (welded) during sintering. In this case, the sintered sheet 33 has a porosity in the range of 60% to 80% and a thickness of 0.5 mm to 3.0 mm. If the diameter of the metal fibers is smaller than 50 μm, the area where the metal fibers are entangled during sintering increases, making it easier for heat to be transferred to the back side of the sintered sheet 33. However, if the diameter is larger than 100 μm, the minute gaps 33b become too large, which may make it difficult to suppress flashback. Furthermore, if the weight per unit area is 1200 g / m 2 If it is less than 1800 g / m, each minute gap 33b may become too large and may not be able to suppress flashback. 2 If the amount is greater than this, the void ratio within the above range cannot be obtained, and the resistance to the passage of the air-fuel mixture increases.

[0019] In the all-primary combustion burner CB, the air-fuel mixture supplied from the inlet 14 of the burner body 1 into the air-fuel mixture chamber 11 passes through the numerous minute gaps 33b in the sintered body sheet 33 and is then supplied to the combustion plate 2. The increased contact area with the room-temperature air-fuel mixture suppresses the temperature rise of the sintered body sheet 33, i.e., the flashback suppression plate 3 itself. Furthermore, the numerous minute gaps 33b also suppress pressure loss. The air-fuel mixture that passes through the sintered body sheet 33 of the flashback suppression plate 3 then passes through the gap Gp between the combustion plate 2 and the flashback suppression plate 3 and is ejected from the main body 23 of the combustion plate 2, resulting in all-primary combustion (combustion without secondary air). Even if a flame propagates through the gap Gp between the combustion plate 2 and the flashback suppression plate 3, the temperature rise of the flashback suppression plate 3 is suppressed, allowing the flame to be extinguished by the flashback suppression plate 3. Even if the flame that has propagated into the gap Gp remains without being extinguished, its propagation upstream is suppressed because there is only a minute gap 33b in the flashback suppression plate 3. In this way, in the all-primary combustion burner CB of this embodiment, by arranging the flashback suppression plate 3 having the sintered body sheet 33, it is possible to suppress flashback as much as possible while suppressing pressure loss, even when the fuel gas is hydrogen gas.

[0020] Furthermore, in the all-primary combustion burner CB, a temperature sensor 4 is disposed in the portion of the air-fuel mixture chamber 11 located between the combustion plate section 2 and the flashback suppression plate section 3. Known devices such as a thermocouple or a bimetal switch can be used as the temperature sensor 4. As a result, if the flame that has propagated into the gap Gp is ​​not extinguished and burns on the surface (lower surface) of the sintered body sheet 33 facing the gap Gp, the temperature sensor 4 can detect the accompanying temperature rise and, for example, stop the supply of the air-fuel mixture, thereby quickly stopping the combustion that could damage the all-primary combustion burner CB.

[0021] Although the above describes an embodiment of the present invention, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, the sintered sheet 33 is formed by sintering a laminate of metal fibers 33a. However, the present invention is not limited to this, as long as a sintered sheet having a complex structure and numerous minute gaps smaller than the flashback limit pore size can be formed after sintering. As shown in FIG. 5, for example, metal beads 5a composed of Fe and at least one selected from Al, Cr, Mn, and Si or their carbides and having a particle size in the range of 50 μm to 500 μm can be used. A laminate of the metal beads 5a can be sintered in the same manner as above to form numerous minute gaps 5b, thereby forming a sintered sheet 5. In this case, the basis weight is 1200 g / m. 2 ~1800g / m 2 is set to the range.

[0022] In the above embodiment, the main body 23 of the combustion plate 2 is made of knitted metal fibers, but the present invention is not limited to this. Instead of knitted metal fibers, the sintered sheet 33 manufactured as described above can be used as the main body 23 of the combustion plate 2. This increases the contact area with the air-fuel mixture, which is advantageous in that it suppresses the temperature rise of the combustion plate itself. [Explanation of symbols]

[0023] CB...full primary combustion burner, 1...burner body, 11...air-fuel mixture chamber, 12...open surface, 2...combustion plate section, 3...flashback suppression plate section, 33, 5...sintered sheet, 33a...metal fiber, 4...temperature sensor, 5a...metal beads.

Claims

1. A full primary combustion burner comprising a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering an open surface of the burner body facing the mixture chamber, wherein a flashback suppression plate portion is disposed in the mixture chamber facing the combustion plate portion with a gap therebetween, and the mixture passing through the flashback suppression plate portion is ejected from the combustion plate portion and combusted, wherein the fuel gas is hydrogen gas, The flashback suppression plate portion is a laminated metal fiber without weaving or knitting, and has a basis weight of 1200 g / m ２ ~1800g / m ２ A full primary combustion burner characterized by having a sintered sheet formed by sintering a laminate set in the range.

2. 2. The all-primary combustion burner according to claim 1, wherein the metal fibers are made of Fe and at least one element selected from the group consisting of Al, Cr, Mn and Si, or a carbide thereof.

3. 2. The all-primary combustion burner according to claim 1, wherein a temperature sensor is disposed in a portion of the mixture chamber located between the combustion plate portion and the flashback suppression plate portion.

4. 4. The all-primary combustion burner according to claim 1, wherein the gap between the combustion plate portion and the flashback suppression plate portion is set in the range of 5 mm to 30 mm.

5. 2. The all-primary combustion burner according to claim 1, wherein the combustion plate portion has a sintered sheet obtained by sintering a laminate of metal fibers or metal beads.

Images