JP6073270B2 - Combustion device, boiler, and combustion method - Google Patents

Description

The present invention relates to a combustion apparatus that reduces the amount of nitrogen oxide (hereinafter referred to as NOx) in exhaust gas after combustion (hereinafter referred to as combustion gas), a boiler using the combustion apparatus, and a combustion method .

  Conventionally, in a combustion apparatus used in a boiler or the like, the amount of NOx emissions in the combustion gas has been reduced, and the NOx in the combustion gas has been reduced to about 60 ppm in terms of 0% oxygen concentration. However, since air pollution is serious, especially in district heating and cooling facilities in urban areas, NOx emissions are required to be 40 ppm or less in terms of 0% oxygen concentration (see Patent Document 1).

  In Non-Patent Document 1, the fuel is supplied in two stages, the primary fuel is rapidly mixed and burned under a high air ratio, and the secondary gas injected from the surroundings is slowed by the combustion gas containing residual oxygen at a low concentration. It is described that NOx is reduced by burning and recirculating the combustion gas with a high-speed jet of secondary gas.

Japanese Patent Laid-Open No. 9-60811

Issued July 1, 2012 (Issued by the Energy Conservation Center, Japan) “New Theory and Practice of Gas Combustion” pp. 206-207

  In Non-Patent Document 1, as a disadvantage of fuel two-stage combustion, although NOx reduction effect is higher than air two-stage combustion, it is easy to generate unburned parts and vibration combustion is also easy, so matching with the combustion chamber is important It has been pointed out that

Further, from the burner structure introduced in Non-Patent Document 1 (FIG. 8.23) and NOx emission characteristics (FIG. 8.24), it is presumed that there are the following problems. That is,
NOx emission value is 40 ppm (O ₂ = 5%) under the combustion condition of O ₂ = 3% (air ratio 1.17), that is, 52.5 ppm when converted to an oxygen concentration of 0%. Large amount.

  ・ High air ratio of primary fuel and rapid mixed combustion using the total amount of air required for combustion, so the flow rate of the main fuel becomes higher than the flow rate of the secondary fuel, and the fuel throttle ratio (TDR: It is difficult to increase the Turn Down Ratio.

-Since all the air required for combustion is supplied to the pre-combustion port (primary fuel region), the air supply pressure loss is large.
An object of the present invention is to provide a combustion apparatus that can solve the problems of the above-described technology and can effectively achieve low NOx, a boiler using the combustion apparatus, and a combustion method .

In order to achieve the above object, in the present invention, a primary fuel nozzle provided inside a wind box, a flame holder disposed around the primary fuel nozzle, and an outer peripheral side of the flame holder A combustion apparatus comprising a plurality of secondary fuel nozzles provided inside the wind box and disposed circumferentially spaced apart on an annular region centered on the primary fuel nozzle; A plurality of air nozzles disposed on a front plate of the wind box at an outer peripheral side of the flame holder and spaced apart from each other on the annular region, wherein the plurality of secondary fuel nozzles are the front plate The plurality of air nozzles and the plurality of secondary fuel nozzles are arranged so as to be able to pass a recirculation flow of the combustion chamber alternately spaced from each other .

In the above configuration, since the air nozzle and the plurality of secondary fuel nozzles are alternately arranged on the annular region with the axis as the center at an interval, both the secondary fuel nozzle and the air nozzle are used. Due to the high-speed jet effect, the combustion gas is recirculated, resulting in a low NOx state. In addition, since the air nozzle and the plurality of secondary fuel nozzles are separated from each other, the mixing of the air and the secondary fuel gas can be delayed to maintain them in a divided state for a long period of time, and an effective slow combustion state Can be obtained. Therefore, the generation of NOx can be suppressed by this slow combustion.

  According to the present invention, there is an effect that a sufficiently low NOx can be achieved by slow combustion.

Sectional drawing of the combustion apparatus of 1st Embodiment. The side view of the combustion apparatus of FIG. (A) is sectional drawing of a primary fuel nozzle, (b) is a left view similarly. (A) is sectional drawing of a secondary fuel nozzle, (b) is a left view similarly. Sectional drawing which shows the operation state of the combustion apparatus of embodiment. Sectional drawing which shows the operation state of the combustion apparatus of embodiment. The graph which shows the comparison with the NOx discharge value of a prior art example, and the NOx discharge value of 1st Embodiment. Sectional drawing of the combustion apparatus of 2nd Embodiment. Sectional drawing of the combustion apparatus of 3rd Embodiment. (A) Sectional drawing of combustion apparatus of 4th Embodiment, (b) Similarly left side view. (A) Partial sectional view which shows 5th Embodiment, (b) Similarly left side view. (A) Partial sectional view which shows 6th Embodiment, (b) Similarly left side view. The partial cross section figure which shows the example of change. (A) The partial sectional view which shows another modification, (b) Similarly left side view. (A) The partial sectional view which shows another example of a change, (b) Similarly left side view. The perspective view of the combustion apparatus of 1st Embodiment. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. Similarly right side view. The CC sectional view taken on the line of FIG. The perspective view of the combustion apparatus of 3rd Embodiment. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. The DD sectional view taken on the line of FIG. The perspective view of the combustion apparatus of 4th Embodiment. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. EE sectional view taken on the line of FIG. The perspective view of the combustion apparatus of 5th Embodiment. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. The FF sectional view taken on the line of FIG. The perspective view of the combustion apparatus of 6th Embodiment. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. The GG sectional view taken on the line of FIG. The perspective view of the combustion apparatus of the example of a change of FIG. Similarly front view. Similarly rear view. FIG. Similarly bottom view. Similarly left side view. FIG. 58 is a sectional view taken along line HH in FIG. 57.

Embodiments of a combustion apparatus embodying the present invention will be described below with reference to the drawings.
(First embodiment)
1st Embodiment is described based on FIGS. 1-7 and FIGS. 16-23.

As shown in FIG. 1, a horizontal combustion chamber 22 is formed in the boiler 21, and the combustion device 31 of this embodiment is attached to the combustion chamber 22.
A pipe-like combustion air supply throat (hereinafter simply referred to as a throat) 33 is disposed on a horizontal axis 100 at the center inside the wind box 32 of the combustion device 31. The throat 33 is connected to the first air blowing chamber 34 at the rear of the wind box 32, and primary air is sent from the first air blowing chamber 34 into the throat 33, and the primary air is burned from the tip opening 35 of the throat 33. It is ejected toward the front in the chamber 22. In the present embodiment, the left side of FIG.

  As shown in FIGS. 1 and 2, a central fuel supply pipe 36 having an opening at its tip is disposed through the axis 100 in the throat 33. A primary fuel nozzle 37 is attached to the tip of the central fuel supply pipe 36, and a plurality (six in this embodiment) of nozzle holes 38 are arranged at equal intervals on the outer periphery of the tip. Therefore, the throat 33 and the primary fuel nozzle 37 are arranged coaxially. As shown in FIGS. 3A and 3B, the nozzle hole 38 is disposed on a radial line centering on the axis 100 when viewed from the direction of the axis 100, and at the axis 100 when viewed from the direction orthogonal to the axis 100. On the other hand, the central angle θ1 is opened in the direction of about 30 to 80 degrees (60 degrees in the present embodiment). A fuel gas made of city gas is supplied into the primary fuel nozzle 37 via the central fuel supply pipe 36, and the fuel gas is radiated from the nozzle hole 38 into the combustion chamber 22, that is, the combustion chamber 22. It is injected toward the diagonally forward side on the outer periphery side.

An ignition pilot burner (not shown) is provided in the throat 33 on the rear side of the primary fuel nozzle 37.
As shown in FIGS. 1 and 3A and 3B, in the rear part immediately adjacent to the nozzle hole 38, the primary fuel nozzle 37 is surrounded by the outer peripheral surface of the primary fuel nozzle 37 and the inner peripheral surface of the throat 33. A flame holder 41 is attached to the outer periphery of the flame holder 41. A plurality of (in the embodiment, six places) convex portions 43 are formed at six positions on the outer peripheral portion of the flame holder 41. Yes. A concave portion between the convex portions 43 serves as a vent 42, and a narrow vent gap 44 is formed between the tip of the convex portion 43 and the inner peripheral surface of the throat 33. The convex portion 43 is located corresponding to the portion between the nozzle holes 38. The primary air in the throat 33 is jetted along the axis 100 into the combustion chamber 22 through the vent 42 and the vent gap 44. The flame holder 41 and the throat 33 constitute a primary air nozzle for ejecting primary air into the combustion chamber 22.

The front end surface of the wind box 32 protrudes into the combustion chamber 22. The front surface of the flame holder 41 is located on the back side by a predetermined length d from the front end surface of the front plate 321 of the wind box 32.
As shown in FIGS. 1, 2, 4 (a) and 4 (b), a plurality (six in this embodiment) of the front plate 321 of the wind box 32 are arranged at equal intervals on the outer peripheral side of the throat 33. The outer fuel supply pipe 51 is penetrated. A secondary fuel nozzle 52 positioned on an annular region around the axis 100 is fixed to the tip of the outer fuel supply pipe 51. A single nozzle hole 53 is formed at the tip of the secondary fuel nozzle 52. The nozzle hole 53 is centered on the axis 100 and located on a radial line passing through the vent 42 of the flame holder 41. As shown in FIG. 5, the nozzle hole 53 faces inward at an angle of about 5 to 30 degrees (15 degrees in this embodiment) with respect to the axis 100 when viewed from the direction orthogonal to the axis 100. Is open. The tip of the primary fuel nozzle 37 is disposed at the same position as the tip opening of the throat 33. Then, a fuel gas made of city gas is supplied into the secondary fuel nozzle 52 via the outer fuel supply pipe 51, and the fuel gas is injected obliquely forward from the nozzle hole 53 toward the center of the combustion chamber 22. Is done.

  As shown in FIGS. 1 and 2, a plurality of locations (six locations in the present embodiment) of the front plate 321 of the wind box 32 communicate with each other between the outer fuel supply pipes 51 on the outer peripheral side of the flame holder 41. The ports 61 are formed at equal intervals, and the secondary air nozzles 62 are attached to the front plate 321 at equal intervals from each other at the respective communication ports 61. Each secondary air nozzle 62 protrudes from the front end surface of the wind box 32 toward the combustion chamber 22. The secondary air nozzle 62 is connected to the second air blowing chamber 63 of the wind box 32. The throat 33 separates the first blower chamber 34 and the second blower chamber 63 in the wind box 32, and the air from the second blower chamber 63 passes from the tip opening 621 of the secondary air nozzle 62. Secondary air is ejected into the combustion chamber 22 in the direction along the axis 100. The tip opening 621 of the secondary air nozzle 62 is formed in a rectangular slit shape. The tip opening 621 is located on a radial line centering on the axis 100 passing through the convex portion 43, and its long side extends along the radial line. The tip opening 621 of the secondary air nozzle 62 protrudes toward the combustion chamber 22 by a predetermined length with respect to the tip opening of the throat 33.

  The secondary air nozzle 62 and the tip opening 621 thereof are arranged on a concentric annular region centering on the axis 100 together with the secondary fuel nozzle 52 and are alternately spaced from the secondary fuel nozzle 52 at equal intervals. Is arranged.

  In the present embodiment, the tip opening 621 of the secondary air nozzle 62 is extended in the direction of the radial line with the axis 100 as the center, and the length in the radial line direction should be longer than the length in the direction perpendicular to the radial line. . Therefore, the shape of the tip opening 621 is not limited to a rectangular slit, and various shapes such as an oval shape, an elliptical shape, and a weight shape in which both end portions in the radial line direction swell can be realized.

Next, the operation of the embodiment configured as described above will be described.
As shown in FIGS. 5 and 6, during the combustion operation of the combustion apparatus 31 of the embodiment, the primary fuel gas is ejected obliquely toward the combustion chamber 22 from the nozzle hole 38 around the axis 100 of the primary fuel nozzle 37. As a result, the primary flame 201 is formed. At this time, around the primary fuel nozzle 37, primary air is jetted into the combustion chamber 22 from the vent 42 and the vent gap 44 of the flame holder 41 along the extension direction of the axis 100. At this time, since the flame holder 41 is located in the throat 33, a small recirculation flow 204 is formed on the front side of the convex portion 43 of the flame holder 41, so that the primary flame 201 is While holding the flame under a high air ratio, the primary flame 201 is divided, the surface area is increased, and the temperature of the primary flame 201 is lowered.

  On the other hand, the secondary fuel gas is ejected from the nozzle hole 53 of the secondary fuel nozzle 52 in an inclined direction toward the axis 100, and this secondary fuel gas is supplied toward the vicinity of the tip of the primary flame 201. For this reason, the secondary flame 202 following the front-end | tip part of the primary flame 201 is formed by making the primary flame 201 into a pilot flame. Due to the ejection of the secondary fuel gas, the combustion gas is entrapped from the upstream side of the secondary fuel nozzle 52 and recirculated, and the secondary fuel gas is mixed into the recirculation flow 203, so that the secondary flame 202 is Slow combustion occurs and NOx generation is reduced. That is, since the secondary fuel gas from the nozzle hole 53 is burned at a site away from the nozzle hole 53, the combustion becomes slow.

  At this time, secondary air is ejected from the tip opening 621 of the secondary air nozzle 62 positioned between the secondary fuel nozzles 52 toward the combustion chamber 22. For this reason, the temperature of the secondary flame 202 is lowered by the secondary air. At the same time, the recirculation flow 203 that circulates around the secondary flame 202, the outside thereof, and the vicinity of the base end portion of the secondary air nozzle 62 is formed from the front end opening of the secondary air nozzle 62. The secondary air, the secondary fuel gas, and the combustion gas attracted by the jets of both gases circulate and mix to realize slow combustion, while holding the secondary flame.

  Since the secondary fuel nozzle 52 and the secondary air nozzle 62 are alternately arranged at equal intervals around the throat 33, as shown in FIG. 2, the recirculation flow 203 has the secondary fuel nozzle 52 and the secondary air nozzle. It passes through the space between 62. For this reason, combustion gas and secondary air become a division state, and those mixing is delayed. Moreover, slow combustion is achieved by the recirculation flow through the space between the secondary fuel nozzle 52 and the secondary air nozzle 62.

  In addition, since the secondary air nozzle 62 protrudes forward from the tip of the secondary fuel nozzle 52, the secondary air is located at the front position of the recirculation flow, that is, downstream of the recirculation flow with the secondary flame 202 as the upstream. Therefore, the oxygen supply to the secondary flame 202 is delayed, which is effective in suppressing NOx.

  As described above, in the present embodiment, the secondary fuel nozzle 52 is disposed so as to protrude into the combustion chamber 22, so that the combustion gas is caught from the upstream side of the secondary fuel nozzle 52 and recirculated. Since they are mixed, the combustion becomes slow and the generation of NOx is reduced.

  In addition, the secondary air nozzles 62 are arranged between the secondary fuel nozzles 52 so as to be spaced apart from each other, whereby both the secondary fuel from the secondary fuel nozzle 52 and the secondary air from the secondary air nozzle 62 are used. Due to the high-speed jet effect, recirculation of the combustion gas in the combustion chamber 22 is promoted, and low NOx can be obtained. Further, the primary flame 201 may be strong enough to hold the flame for the secondary flame 202. For this reason, the amount of primary fuel gas and primary air can be reduced, and low NOx is possible while ensuring a high TDR (turn-down ratio).

  Further, in the conventional fuel two-stage combustion method, all the necessary combustion air is supplied to the primary flame region, but the secondary air is divided and supplied from the secondary air nozzle 62 to perform fuel two-stage combustion. As a result, air supply pressure loss can be reduced, and primary gas fuel can be reduced.

FIG. 7 shows a comparison between NOx data described in Non-Patent Document 1 and NOx data of the first embodiment. Under the combustion condition of O ₂ = 3% (air ratio 1.17), the NOx emission value of the first embodiment is 34 ppm (O ₂ = 0% conversion value), which is about 18 ppm lower than the conventional one. Moreover, it turns out that it can fully respond also to the regulation value (40 ppm or less in oxygen concentration conversion of 0%) of the NOx emission amount in the district heating and cooling equipment in the urban area.

This embodiment has the following effects.
(1) Since the secondary fuel nozzle 52 protrudes into the combustion chamber 22 from the tip of the throat 33, the combustion gas is centered from the outer periphery side on the upstream side of the throat 33 and the secondary fuel nozzle 52 as a recirculation flow. Caught on the side. For this reason, the fuel gas from the secondary fuel nozzle 52 is gradually mixed with the recirculation flow, burned slowly, and NOx is reduced. Further, recirculation by the high speed jet from the secondary fuel nozzle 52 is executed smoothly.

  (2) The fuel gas from the primary fuel nozzle 37 may be an amount that can form a primary flame that is small enough to hold the secondary flame. That is, since a part of the total amount of air necessary for combustion is supplied to the throat 33 as primary air, the amount of primary fuel gas can be reduced relative to the amount of secondary fuel gas compared to the conventional case. For example, a high TDR can be obtained by setting the ratio of (primary fuel gas amount) / (secondary fuel gas amount) to about 1/2 to 1/10 and controlling only the amount of secondary fuel gas. . Therefore, the combustion amount of the combustion apparatus can be controlled in a wide range. Further, since it is not necessary to individually control the primary fuel gas amount and the secondary fuel gas amount, the gas metering valve is only used for the secondary fuel gas, and the cost can be reduced.

  (3) By ejecting the secondary fuel gas toward the primary fuel gas region formed on the axis 100 toward the high air ratio, it becomes possible to stabilize the secondary flame, It becomes possible to prevent the emission of carbon oxide.

  (4) The nozzle hole 53 of the secondary fuel nozzle 52 is a single hole that is inclined inward in the radial direction toward the downstream side in the direction of the axis 100. Therefore, the secondary fuel gas is ejected toward the primary fuel gas region of the high air ratio, and it becomes possible to prevent the discharge of unburned components and carbon monoxide.

  (5) Since the plurality of secondary air nozzles 62 are provided on the outer peripheral side of the throat 33 and on the annular region centered on the axis 100 at a distance from each other, the low concentration formed on the axis 100 is low. The secondary fuel gas can be effectively mixed from the surroundings with the combustion gas containing residual oxygen to make it burn slowly, and the unburned portion can be burned effectively. Therefore, even if the primary fuel gas amount is reduced, the auxiliary effect of stabilizing the primary flame 201 is exhibited.

  (6) Since the plurality of secondary air nozzles 62 and the plurality of secondary fuel nozzles 52 are alternately disposed on the annular region, due to the high-speed jet effect by both the secondary fuel nozzle and the secondary air nozzle, The combustion gas is recirculated, resulting in a low NOx state. In addition, since the secondary air nozzle 62 and the plurality of secondary fuel nozzles 52 are separated from each other, the mixing of the secondary air and the secondary fuel gas can be delayed to maintain the divided state for a long time. An effective slow combustion state can be obtained.

(7) Since the opening of the secondary air nozzle 62 is a slit-shaped single hole extending in the radial direction with the axis 100 as the center, a space between the secondary fuel nozzle and the secondary air nozzle can be secured. Therefore, can more reliably form the divided state, it is possible to obtain a more effective slow combustion state, that Do is possible to lower NOx reduction.

(8) Since the front plate 321 of the wind box 32 protrudes into the combustion chamber 22, the recirculation flow 203 flows from the rear side of the secondary air nozzle 62, and the secondary air nozzle 62 is located downstream of the flow. Secondary air is entrained and mixed. Therefore, delay mixing of secondary air to the recycle stream 203, can be more slow combustion and Do Ri, that Do enables more NOx reduction is.

  (9) Since the secondary air nozzle 62 protrudes into the combustion chamber 22, the recirculation flow 203 flows from the rear of the secondary air nozzle 62, and the secondary air is caught downstream of the flow. Since mixing is performed, mixing of the secondary air to the recirculation flow 203 is delayed. For this reason, slower combustion is possible.

  (10) Since the opening of the secondary air nozzle 62 has a slit shape and is close to the throat 33, it is possible to avoid a shortage of the oxygen amount with respect to the primary flame 201 and to suppress the generation of carbon monoxide. .

  (11) Since the throat 33 that separates and supplies primary air supplied through the flame holder 41 and secondary air supplied from around the flame holder 41 is provided, Since the secondary air can be individually controlled, the TDR can be increased as compared with the conventional case.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In each of the embodiments and modifications after the second embodiment, a description will be given focusing on portions that are different from the first embodiment.

The second embodiment differs from the first embodiment in that the outer supply pipe 51 is branched from the central supply pipe 36 as shown in FIG.
Accordingly, the second embodiment has the following effects.

(12) Since the outer supply pipe 51 is branched from the central supply pipe 36, the fuel supply structure can be simplified, leading to cost reduction.
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS. 9 and 24 to 30. In each of the third and subsequent embodiments, the right side view is the same as that of the first embodiment, and thus illustration is omitted.

  In the third embodiment, in the configuration of the first embodiment, the center side of the front plate 321 is inclined toward the throat 33. Thus, the sixth embodiment has the following effects.

(13) The recirculation flow 203 of the combustion gas is likely to flow through the separated portion between the secondary fuel nozzle 52 and the secondary air nozzle 62.
(Fourth embodiment)
A fourth embodiment of the present invention will be described based on FIGS. 10A and 10B and FIGS.

  In the fourth embodiment, the rectangular opening 621 of the secondary air nozzle 62 in the configuration of the first embodiment is changed to a circular opening 621. The shape change of the opening 621 is realized by using an existing pipe.

The fourth embodiment has the following effects.
(14) Since an existing pipe is used to form the circular opening 621, the cost is reduced. Moreover, the diameter of the opening 621 can be arbitrarily changed by appropriately selecting a ready-made pipe. For this reason, the directivity and flow rate of the recirculation flow 203 can be appropriately adjusted to help reduce NOx.

(Fifth embodiment)
A fifth embodiment of the present invention will be described based on FIGS. 11A and 11B and FIGS.

  In the fifth embodiment, a plurality of circular openings 621 of the secondary air nozzle 62 are provided along the radial direction of the wind box 32 in the configuration of the fourth embodiment. The opening 621 is formed by a pre-made pipe.

Thus, the fifth embodiment has the following effects.
(15) Since the plurality of openings 621 are arranged in the radial direction, an effect close to that of the secondary air nozzle 62 having the rectangular opening 621 can be obtained, and since an existing pipe is used, the fourth embodiment The cost can be reduced in the same way.

(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIGS. 12 (a) and 12 (b) and FIGS. 45 to 51. FIG.

  In the sixth embodiment, the opening 621 of the secondary air nozzle 62 of the fourth embodiment shown in FIGS. 10A and 10B has a central angle inwardly with respect to the axis 100 toward the front of the combustion chamber 22. θ2 is provided inclined at an angle of about 10 to 50 degrees (30 degrees in the second embodiment).

Accordingly, the sixth embodiment has the following effects.
(16) The opening 621 of the secondary air nozzle 62 is a single hole arranged to be inclined inward in the radial direction, so that the jet of secondary air from the secondary air nozzle 62 is directed inward. Therefore, the secondary air is well mixed with the combustion gas generated by the secondary flame 202 formed on the axis 100. Thus, it is possible to achieve a higher air ratio in the secondary flame region while maintaining the stability of the secondary flame 202. Therefore, it is effective for suppressing the generation of NOx. In addition, the cost is reduced by using an existing pipe.

(Example of change)
The present invention is not limited to the above-described embodiments, and can be embodied in the following aspects.

  In the first embodiment, the tip opening 621 of the secondary air nozzle 62 may be formed inward as in the sixth embodiment. If it does in this way, the effect similar to the effect as described in said (15) can be acquired.

  Change the number of secondary fuel nozzles 52 and secondary air nozzles 62. For example, the number of secondary fuel nozzles 52 and secondary air nozzles 62 may be reduced. If comprised in this way, the space between the secondary air nozzle 62 and the secondary fuel nozzle 52 will become wide, and the recirculation flow 203 will flow smoothly.

-The number of the secondary fuel nozzles 52 and the secondary air nozzles 62 may not be the same number, but may differ.
The primary and secondary fuels may be atomized liquid fuel instead of gas fuel.

-Primary and secondary air may not be air containing 21% oxygen. An exhaust gas may be mixed. In this case, it becomes external exhaust gas circulation.
The secondary fuel nozzle 52 may protrude from the secondary air nozzle 62 toward the combustion chamber 22.

The flame holder 41 is not limited to the uneven baffle flame holder as in the first to sixth embodiments, and may be another baffle flame holder. The flame holder 41 may be a swirler flame holder.
The nozzle hole 38 of the secondary fuel nozzle 52 may be a slit-shaped single hole extending along a radial line with the axis 100 as the center. Thus, the space | interval between the secondary fuel nozzle 52 and the secondary air nozzle 62 can be expanded by making the nozzle hole 38 into a slit-shaped single hole. Therefore, since the combustion is performed slowly while the combustion gas is recirculated well, NOx can be further reduced.

  As shown in FIG. 13, in the first to sixth embodiments, the throat 33 can be omitted. In this case, since the throat 33 does not exist, the primary air and the secondary air cannot be separated in the wind box 32, and their amounts cannot be controlled in the wind box 32. Accordingly, the opening area of the vent 42 of the flame holder 41 through which the primary air is ejected is appropriately set so that the distribution of the primary air amount and the secondary air amount supplied into the combustion chamber 22 is appropriate. There is a need to. In the case where the throat 33 is not present, as shown in FIGS. 14A and 14B, the front plate 321 and the flame holder 41 may be joined or integrated. When the front plate 321 and the flame holder 41 are joined or integrated, the ventilation gap 44 on the tip side of the convex portion 43 of the flame holder 41 is not formed, and therefore, a two-dot chain line in FIG. As shown, an opening serving as a ventilation gap 44 may be formed at the tip of the convex portion 43.

  It is not always necessary to provide the predetermined distance d (see FIGS. 1 and 13) between the front plate 321 and the front surface of the flame holder 41. For example, the front plate 321 in FIGS. 9 and 24 to 30 is inclined. Except for the second embodiment, as shown in FIGS. 15A and 15B and FIGS. 52 to 58, the front plate 321 and the flame holder 41 may be formed flush with each other. 15 (a) and 15 (b) and FIGS. 52 to 58, the front plate 321 and the flame holder 41 are integrated in the configuration of the first embodiment shown in FIGS. 1 to 6 and FIGS. A portion corresponding to the flame holder 41 is not provided with a concavo-convex opening, and a plurality of small holes 45 are provided in the same portion. Thus, the structure which integrates the front board 321 and the flame holder 41 and provides the small hole 45 is applied in 3rd-6th embodiment except 2nd Embodiment of FIG.9 and FIG.24-30. Also good.

  DESCRIPTION OF SYMBOLS 31 ... Combustion apparatus, 32 ... Wind box, 33 ... Throat, 37 ... Primary fuel nozzle, 41 ... Flame holder, 52 ... Secondary fuel nozzle, 62 ... Secondary air nozzle, 100 ... Axis, 321 ... Front plate.

Claims (10)

A primary fuel nozzle provided inside the wind box;
A flame holder disposed around the primary fuel nozzle;
A plurality of secondary fuel nozzles provided on the outer peripheral side of the flame holder and inside the wind box, and disposed on the annular region centered on the primary fuel nozzle and circumferentially spaced from each other; In a combustion apparatus comprising:
A plurality of air nozzles arranged on the front plate of the wind box at the outer peripheral side of the flame holder and spaced apart from each other on the annular region;
The plurality of secondary fuel nozzles are disposed through the front plate,
The combustion apparatus in which the plurality of air nozzles and the plurality of secondary fuel nozzles are arranged so as to allow a recirculation flow in the combustion chamber to pass therethrough alternately.
  The combustion apparatus according to claim 1, wherein the wind box projects from the combustion chamber.   Combustion air that is formed on the same axis as the primary fuel nozzle in the wind box and separates air supplied through the flame holder and air supplied from around the flame holder. The combustion apparatus according to claim 1 or 2, wherein a supply throat is provided.   The combustion apparatus according to any one of claims 1 to 3, wherein a front plate of the wind box protrudes into the combustion chamber.   The combustion apparatus according to claim 3 or 4, wherein the opening of the air nozzle is a single hole having a shape extending along a radial line centering on the axis.   5. The combustion apparatus according to claim 3, wherein the opening of the air nozzle is a single hole that is inclined inward in the radial direction toward the downstream side in the axial direction.   The combustion apparatus according to claim 3 or 4, wherein the opening of the secondary fuel nozzle is a slit-shaped single-hole gas fuel nozzle extending in a radial direction on a virtual arrangement circle.   5. The single-hole gas fuel nozzle according to claim 3, wherein the opening of the secondary fuel nozzle is a single-hole gas fuel nozzle disposed to be inclined inward in the radial direction toward the downstream side in the axial direction. Combustion device.   The boiler which has a combustion apparatus as described in any one of Claims 1-8.   The combustion apparatus according to any one of claims 1 to 3, wherein a ratio of (primary fuel gas amount) / (secondary fuel gas amount) is set to 1/2 or less, and only the amount of secondary fuel gas. To control the combustion method.