WO2007105335A1

WO2007105335A1 - In-furnace gas injection port

Info

Publication number: WO2007105335A1
Application number: PCT/JP2006/322040
Authority: WO
Inventors: Yusuke Ochi; Akira Baba; Kouji Kuramashi; Hirofumi Okazaki; Masayuki Taniguchi
Original assignee: Babcock-Hitachi Kabushiki Kaisha
Priority date: 2006-03-14
Filing date: 2006-10-27
Publication date: 2007-09-20
Also published as: JPWO2007105335A1; CA2645680A1; EP1995517A1; US20090087805A1

Abstract

Tertiary nozzle (3) of port (31) for gas injection into furnace (34) comprising a contracted flow producing channel provided obliquely toward central axis (C) from the upstream side of gas flow so that the gas flow has a velocity component heading from the outer circumferential side of the port (31) toward the central axis (C) and a velocity component heading along the central axis (C) toward the interior of the furnace, and comprising louver (32) disposed for guiding so that the gas flows along the surface of throat wall (26) of enlarged pipe configuration wherein the gas channel is enlarged at a furnace wall opening disposed at an outlet area of the contracted flow producing channel. Accordingly, there can be provided a gas injection port that not depending on conditions, such as the flow rate of gas injected from the port, without inviting any complication of apparatus structuring or cost increase, enables preventing of the growth in lump form of clinker caused by ash adhesion and fusion on the wall surface of throat enlarged pipe portion of the furnace.

Description

Memo book Gas injection port into the furnace 卜

Technical field - '

The present invention relates to a port for ejecting gas into a furnace such as a boiler, and more particularly to a gas ejection port into a furnace such as a boiler suitable for preventing ash adhesion at the opening of the furnace. Background technology.

Each furnace wall, such as a boiler, is provided with various types of pouches that eject gas such as air and combustion exhaust gas into the furnace. For example, a burner that ejects fuel and combustion air as a combustion device, and an after-air port for introducing two-stage combustion air (also called AAP, over-one air port, or OFA) Etc. As described above, the gas ejection port as used in the present specification is not limited to the after-air port であれば as long as the gas is ejected into the furnace. For example, a port for a burner. Further, the expanded tubular wall surface opened to the furnace provided with the port is referred to as a slot wall or a throat expanded tube portion (furnace wall surface portion where the diameter of the opening portion gradually increases toward the furnace outlet side).

In such a port, the gas jet flow reaches the center of the furnace, and the gas jet flow from the outer periphery of the port rod toward the central axis is strengthened and thrown so as to promote gas mixing near the furnace wall. Some have adopted a structure that is suitable for forming a so-called contracted flow that passes through the wall of the throat and the gas flows around the throat wall while the jet is concentrated on the central axis of the port.

Patent Documents 1 and 2 below disclose an invention of an after-apart for charging the two-stage combustion air accompanied by the contracted flow into a furnace.

In the structure of the gas ejection port suitable for forming a contracted flow of such a gas jet near the opening of the port, ash adheres and melts on the throat wall of the furnace, and the cleaning force is massive. In addition, there is a possibility that the function and performance of the port may be hindered by the fact that the massive cleansing force peels off from the wall surface.

In addition, as a technology to prevent ash from adhering and melting to the throat wall opened in the furnace and growing the clinching force into a lump, the pulverized coal panner prevents the adhesion of the clinching force to the throat wall. (Patent Document 3), Bernas' Rotor Wall (Patent Document 4), Over-Airport (Patent Document 5), etc. ,,

In addition, 'two-stage combustion technique is used as a low NO x combustion technique that keeps the nitrogen oxide (NO x) concentration in the combustion exhaust gas low. We have been developing an after-air port (AA P) that supplies a sufficient amount of combustion air for complete combustion of the combustion gas.

The conventional development of AAP has been mainly aimed at creating a structure that can prevent the unburned gas from slipping out of the Pana combustion zone in the furnace. Fig. 13 shows a drawing of a conventional swivel A A P. ,

In A A P shown in FIG. 13, the primary air 9 passes through the primary nozzle 1 and is supplied to the furnace 3 4. A secondary nozzle 2 is provided on the outer periphery of the primary nozzle 1 to supply secondary air 10. It is necessary to properly arrange the AAP with the above structure in the furnace 34, but because of the limited number of AAP installed, the combination of air and unburned gas in the vicinity of the AAP and in the center of the furnace 34 The secondary nozzle 2 is provided with a swirler 7 for the purpose of strengthening, and the swirler 7 is used for the combination of air and unburned gas in the furnace 3 4 near the AAP. Is used, and a structure in which air and unburned gas are mixed by a strong air jet reaching the center of the furnace 34 from the primary nozzle 1 is used (Patent Document 6).

In addition, the swirling secondary air flow using the swirler 7 does not sufficiently spread the swirling air flow, and in the region along the inner wall 3 4 a of the furnace 34, the mixing of unburned gas and combustion air is not sufficient There is. As a method of dealing with such problems, a tertiary having a current drift that can supply combustion air in the direction along the inner wall 3 4 a of the furnace 3 4 to the outer peripheral portion of the secondary nozzle 2 having the swirler 7. The applicant has proposed an AAP with a tertiary nozzle for air (Patent Document 7).

Patent Document 1 Japanese Patent Laid-Open No. 2 0 0 6 — 1 3 2 8 1 1 Patent Document 2 Japanese Patent Laid-Open No. 2 0 0 6-1. 3 2 7 9 8

Patent Document 3 Japanese Utility Model Publication No. 6-6 9 0 9

Patent Document 4 Japanese Patent No. 3 6 6 8 9 8 9

Patent Document 5 Japanese Patent Laid-Open No. 10-0 1 2 2 5 4 6

Patent Document 6 Japanese Patent Application Laid-Open No. 6 2-1 3 8 6 0 7

Patent Document 7 Japanese Patent Laid-Open No. 9-1 1 2 8 1 6 Disclosure of Invention

When the effect of a gas jet such as air concentrated from the outer peripheral side of the porcelain toward the central axis direction, so-called contraction, is strengthened, the constriction flow is surrounded in the furnace near the opening of the porch. In particular, in coal-fired boilers, the chance of the combustion ash accompanying the gas coming into contact with the wall surface of the throat expansion section increases. In the prior art, when the effect of the contraction of the gas jet is strengthened, the effect of preventing the growth of ash adhesion * cleaning force particularly at the furnace throat wall of the Pana pot is not sufficient.

In the invention described in Patent Document 4, since the high-pressure spray air is used to suppress the ash partial addition to the wall surface of the slow throat part over time, the device configuration is complicated, It may lead to an increase in cost and weight. In addition, in the invention described in Patent Document 3, if the gas flow from the outer peripheral side of the furnace throat wall of the PANA port toward the central axis is strengthened to increase the contraction effect, The effect of preventing ash adhesion may be weakened.

Furthermore, in the invention described in Patent Document 5, if the gas flow from the outer peripheral side of the air port toward the center axis of the port is strengthened to increase the contraction effect, the effect of preventing ash adhesion on the throat wall of the furnace may be weakened. There is sex.

In addition, if the flow rate of gas such as air for preventing ash adhesion at the throat wall of the furnace must be reduced to maintain the specified air ratio, the ash adhesion preventing effect may not be obtained sufficiently. There is.

In the conventional AAP disclosed in Patent Document 6 and the like, it was difficult to entrain unburned gas around the AAP with the swirling air flow while maintaining the penetrating force with the strong air jet. In addition, the AAP having a simple structure that replaces the swivel type AAP disclosed in Patent Document 7 and the like prevents the passage of unburned gas in the region along the inner wall 3 4 a of the furnace 34 and prevents ash from adhering to the furnace wall. Although it can be prevented, the combustion air jet that reaches the center of the furnace 34 becomes inadequate, and there is a risk that rapid mixing of unburned gas and air will not occur. ,

The problem of the present invention is that the ash adheres and melts on the wall surface of the furnace throat pipe expansion section without causing an increase in cost, regardless of conditions such as the flow rate of the ejected gas. When air is used as a gas to prevent mass growth, the combustion air and unburned gas in the vicinity of the furnace wall are stably mixed, and the combustion air enters the center of the furnace. The aim is to provide a gas ejection port that can be reliably reached and reduce the NOX concentration in the combustion gas. The above section is solved by the following means. ,

The invention according to claim 1 is provided on a furnace wall of a fire, and has a velocity component flowing toward a central axis of a gas flow perpendicular to the furnace wall and a velocity component flowing along the central axis, A flow path for contraction flow formed obliquely from the upstream side of the flow toward the central axis, and a gas flow path formed in the furnace wall opening 'part on the downstream side of the flow path for contraction flow A throat expansion section that sequentially expands in the direction of gas flow, and a flow path for contraction flow generation for guiding the gas flowing through the flow path for contraction flow to flow along the wall surface of the pipe expansion section. A gas ejection port into the fire equipped with a louver (guide plate) installed in

The gas induced in the cylinder having the configuration of the invention according to claim 1 effectively flows in the vicinity of the wall surface of the throat pipe expansion portion, and the negative pressure in the vicinity of the wall surface of the pipe expansion portion can be removed. Since the gas flowing along the outer peripheral side wall surface of the flow channel (nozzle partition wall constituting the flow channel) can be effectively guided to the wall surface side of the throat expanded portion, the throat expanded portion due to ash entrainment and its vicinity Ashes are unlikely to form on the walls of the wall. Furthermore, in the past, instead of using a ruber, an outlet for ejecting a cooling body such as air was separately provided in the gas ejection port. In contrast, in the invention according to claim 1, the louver is provided. By using it, the pressure loss of the gas jet flow can be reduced, the structure is simplified, and there is no need to install an ash adhesion suppression seal air regulator. It can be reduced. .

In addition, the gas flow ejected from the flow path for contracted flow generation according to the first aspect of the invention becomes a gas flow that accelerates gas mixing reaching the center of the furnace and gas mixing in the vicinity of the furnace wall. Therefore, when the gas ejection port is used as an AAP for a two-stage combustion panner, a highly reliable fuel capable of low NO x and low CO combustion can be burned.

According to a second aspect of the present invention, the front end portion of the gas flow upstream side of the rubbing bar is a surface extending from the outer peripheral side wall surface of the contracted flow generation flow passage in the central axis direction or the extended surface. 2. The furnace interior according to claim 1, which is located on the upstream side of the gas flow, and has a pipe expansion portion that is sequentially expanded in the gas flow direction along the wall surface of the pipe expansion portion in the gas flow downstream portion of the louver. This is a gas ejection port.

By the way, when the gas jet flowing through the flow path for contracted flow generation of the present invention flows toward the center of the gas ejection port, so-called contracted flow is relatively strengthened, the port opening of the furnace in which the port is installed In the vicinity of the wall surface of the throat expansion section provided in the section, negative pressure is applied, and ash tends to adhere to the wall surface of the throat expansion section. Here, when the contracted flow of gas is strengthened, for example, when the gas flow path on the upstream side of the gas flow of the port installed on the furnace wall surface is composed only of the contracted flow generation flow path, Alternatively, if there is another flow path and the flow rate ratio of the contracted flow generation flow path is 30% or more, the radius of the furnace wall slot (length D s in Fig. 1) is If it is less than 1.1 times the radius (length D b in FIG. 10) at the downstream end (portion b in FIG. 10) of the contracted flow generation flow path, or the contracted flow generation flow path This is the case when the angle of inclination with respect to the center axis of the port is between 30 ° and 70 °. .

According to the second aspect of the present invention, the tip of the louver on the upstream side of the gas flow has a surface where the outer peripheral side wall surface of the contracted flow generation channel extends in the direction of the central axis, or the gas flow flows more than the extended surface. Since it is located on the upstream side, the gas guided to the louver effectively flows in the vicinity of the wall surface of the slot expansion section, and the negative pressure in the vicinity of the wall surface of the expansion section can be removed. Therefore, since the gas flowing along the outer peripheral side wall surface (the nozzle partition wall constituting the flow channel) of the contracted flow generation channel can be effectively guided to the wall surface side of the throat pipe expansion part, Ashes are unlikely to form on the wall surface near the expanded pipe due to the above.

Thus, according to the invention of claim 2, in addition to the effect of the invention of claim 1, Gas is induced in the louver, which can further prevent ash from adhering to the slot expansion. ■

The invention according to claim 3 includes a mechanism for changing a ratio of a velocity component flowing along the central axis direction and a velocity component flowing toward the central axis direction of the air flow flowing through the contracted flow generation flow path. A gas ejection port into the furnace according to claim 1 or 2. According to the invention of claim 3, by changing the ratio of the velocity component flowing along the central axis direction and the velocity component flowing toward the central axis direction, the gas ejection after the merging of the respective velocity components in the furnace The flow direction can be adjusted, and when the gas is air, the unburned gas region with insufficient air that is unevenly distributed in the furnace and the combustion air can be suitably mixed to reduce unburned fuel. Furthermore, the mixed state of the gas after merging can be adjusted by adjusting the swirl strength of the two velocity components.

[Claim 4] The self-contained invention is capable of adjusting an opening degree of the contraction flow generation channel that starts to open from the outer peripheral wall surface so that gas flows along the outer peripheral side wall surface of the contraction flow generation channel. This is a gas ejection port into the furnace as described in claim 3 with a damper.

According to the invention of claim 4, when adjusting the opening degree of the flow path by moving the contracted flow generation flow path from the closed state by the damper in the opening direction, the outer wall surface side of the flow path for contracted flow generation is adjusted. When the damper starts to open, the flow rate of the gas flowing through the contracted flow generation flow path is reduced (the damper is close to the closed state), but the reduced flow generation flow path is close to the portion near the slot expansion section. Since air flows, gas is induced to the louver, and ash adhesion to the throat expansion portion can be prevented. .

The invention as set forth in claim 5 is characterized in that a swirling member for swirling gas is provided between the louver and the wall surface of the slot expanding portion. Is. In order to absorb the difference in thermal expansion, the rubber bar may be divided into a plurality of parts in the circumferential direction of the gas ejection port.

According to the fifth aspect of the present invention, the gas flowing between the louver and the wall surface of the slot expansion portion can be ejected into the furnace while being swirled by the revolving member. During this time, a part of the contracted flow easily flows from the contracted flow generation flow path, and the gas flow that seals the inner wall surface of the furnace effectively flows in the vicinity of the wall surface of the slot expanding portion. Since the negative pressure in the vicinity of the wall surface can be removed, the expansion of the slot by ash entrainment Ash adhesion in the vicinity of the furnace wall surface of the pipe part can be prevented.

The invention according to claim 6 is that the length of the throat expansion portion formed at the downstream end of the louver in the gas flow direction is 1 Z 2 or less of the wall length of the throat expansion tube ^ in the gas flow direction. A gas ejection port in the furnace according to any one of claims 1 to 5.

According to the invention of claim 6, the length of the slot formed at the downstream end of the louver in the gas flow direction of the expanded pipe portion is equal to 1 Z 2 of the wall length of the expanded pipe portion in the gas flow direction. If it is as follows, ash is less likely to adhere to the exposed surface (the surface between the e and f parts in Fig. 12) of the expanded portion of the louver.

The invention according to claim 7 is characterized in that the flow path for contracted flow generation is a tertiary nozzle, a primary nozzle through which gas flows along the central axis inside the tertiary nozzle, and a secondary outside the primary and slurries. The gas ejection port into a furnace according to any one of claims 1 to 6, wherein a nozzle is provided. '

According to the invention described in claim 7, if the gas ejection port is used as an AAP installed on the furnace wall downstream of the two-stage combustion burner, there is no ash adhesion on the furnace wall, and the reliability is high. It can be used to burn fuels that can burn low NO x and low CO. Brief Description of Drawings

FIG. 1 is a schematic view of a boiler in which the after-airport or the panner of the present invention is used.

FIG. 2 is a schematic cross-sectional view of an after air bag of Example 1 of the present invention.

FIG. 3 is a perspective view in which a part of the after-apart of the first embodiment is omitted.

FIG. 4 is a view of the air port viewed from inside the furnace of the first embodiment.

FIG. 5 is a flow velocity distribution diagram of the air flow at the A A P outlet portion performed using the A A P model of FIG.

FIG. 6 is a flow velocity distribution diagram of the air flow at the A A P outlet portion performed using the A A P model of FIG.

Fig. 7 is a flow velocity distribution diagram of the air flow at the AAP outlet part, which was performed using the AAP model of Fig. 2. FIG. 8 is a schematic cross-sectional view of an after air port according to the second embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of an after air porcelain in which a rubber bar of a comparative example for comparison with the second embodiment of the present invention is arranged along the furnace slot widened portion.

FIG. 10 is a schematic cross-sectional view of an after air port in which a comparative bar for comparison with Example 2 of the present invention is arranged in a tertiary nozzle.

FIG. 11 is a schematic cross-sectional view of an after air port according to the third embodiment of the present invention.

FIG. 1'2 is a schematic cross-sectional view of a partial after-air port for explaining the dimensional relationship when the rubber bar and the throat expansion portion of the third embodiment of the present invention are arranged in the after-air port. .

FIG. 13 is a schematic cross-sectional view of an after air bag of Example 4 of the present invention.

Fig. Γ 4 is a longitudinal sectional view of the AAP structure of the prior art.

Fig. 15 is a longitudinal sectional view of a conventional AAP structure. Best Mode for Carrying Out the Invention

Hereinafter, the airport of the present invention and the method of using the same will be described with reference to the drawings. First, a two-stage combustion type boiler using the after-air port of the present invention will be described using the overall structure of the boiler in FIG.

A plurality of burners 30 are arranged opposite to a pair of opposed furnace walls of a boiler furnace 34, and an after-air port 31 is arranged above the burner installation location. An air-fuel mixture less than the stoichiometric air ratio (for example, 0.8) from the Pana 30 is injected into the flame region inside the furnace 34, and an incomplete combustion region (not shown) is formed in the furnace. The after-air port 3 1 promotes combustion by supplying insufficient air to the combustible gas in the incomplete combustion region. In this embodiment, the fuel supplied to PANA 30 is supplied to PANA 30 from the pulverized coal supply line 33 by pulverizing the coal in the ban force 29 using a mill 35. In addition, the total amount of air for coal combustion is controlled by the air supply system, and the amount of air is distributed to the Pana 30 and the After Air Port 31. Specifically, the air supplied from the prober 36 is branched into the air supply line 3 7 a on the side of the parner 30 and the air supply line 3 7 b on the side of the abuter air port 3 1, respectively. a, 3 9 b lead to PANA 30 and after air port 卜 31. Air flow to line 3 7 a and line 3 7 b The distribution is adjusted by the damper 40 0 a on the side of the PANA 30 and the damper 40 0 b on the side of the after-airport 31 1. The output of the blower 36 is controlled so that the total air flow rate becomes a value that specifies the oxygen concentration of the exhaust gas.

Air below the theoretical air ratio is supplied from the air supply line 3 7 a to the PANA 30, and the pulverized coal is conveyed by air from the pulverized coal supply line 33. The air-fuel mixture jetted from the Pana 30 into the furnace 3 4. is less than the amount of air required for complete combustion, resulting in incomplete combustion. At this time, NOx can be reduced. Since the fuel does not burn completely, a flow of combustible gas is formed downstream of the PANA 30.

The air that has entered the air box 3 9 b of the after-air port 3 1 through the air supply line 3 7 b is distributed to the primary nozzle 1, the secondary nozzle 2, and the tertiary nozzle 3 of the air port 3 1 described later. It is supplied to the flow of combustible gas in the furnace (incomplete combustion area). This air is mixed with the flow of combustible gas and burned completely to become combustion gas, which is converted into combustion gas in the furnace 3 4 and steamed to water in the heat exchanger 4 2 installed in the furnace 3 4 After the steam is heated and steam is generated, it flows to the outlet of the furnace 34. Also, a boiler water pipe (not shown) is arranged on the boiler furnace wall surface, and is heated by combustion of fuel in the furnace 34 to generate steam.

(Example 1)

― Next, after air port (hereinafter referred to as “port 卜” or “A A P”) applied to the upper E boiler furnace 3 4 will be described with reference to the following examples.

2 is a cross-sectional view of the port 3 1 according to the present embodiment (cross-sectional view taken along the line AA ′ of FIG. 4), FIG. 3 is a perspective view with a part thereof omitted, and FIG. 4 is a port view from the furnace 3 4 side. 3 Each figure showing 1 is shown.

The port 3 1 is arranged in the wind box 39 b, and its air nozzle mechanism has a primary nozzle 1 and a secondary nozzle that blows out swirling air along the outer periphery of the primary nozzle 1 as secondary air 1 0. It has a nozzle 2 and a tertiary nozzle 3 that blows out air flowing from the outside of the primary nozzle 1 toward the central axis C of the port 卜 3 1 as tertiary air 1 1.

The primary nozzle 1, the secondary nozzle 2, and the tertiary nozzle 3 have a coaxial nozzle structure. The primary nozzle 1 is in the center, the secondary nozzle 2 is outside, and the tertiary nozzle 3 is outside. Is arranged. The primary nozzle 1 has a straight tubular shape, has an air outlet 1A (Fig. 3) at the front end, and an air intake 1B at the rear end. The primary damper 5 adjusts the primary air flow rate by adjusting the opening area of the air intake 1B. Primary nozzle 1 ejects straight-flowing air parallel to the central axis C of port 卜 3 1 as primary air 5. The opening area of the air intake 1 B is adjusted to the primary damper 5 on the outer periphery of the primary nozzle 1 according to the adjustment lever 1 5 connected to the primary damper 5 and provided with a handle on the outside of the wind box 39 b. It can be changed by

The secondary nozzle 2 has an annular air inlet 2B (Fig. 3) on the rear end side, and has a tubular secondary air between the inner periphery of the secondary nozzle 2 and the outer periphery of the primary nozzle 1. A passage is formed

10 The secondary air 10 flowing in from the air inlet 2 B is given a swirling force by the secondary air register (deflecting plate) 7, and the secondary nozzle outlet is accompanied by a swirling flow along the outer periphery of the primary nozzle 1. (Front end) 2 Spout from A. The opening area of the air inlet 2 B of the secondary nozzle 2 is connected to the cylindrical secondary damper 6 and the secondary damper 6 is connected to the windbox 3 9 b by the adjusting lever 1 6 with a handle on the outer side. Slided in the direction of the center axis C of port 3 1

The secondary air flow rate is adjusted accordingly. The multiple secondary air registers 7 are operated by operating the register drive 1 3 and the secondary air intake 2 so that the deflection angle can be changed in the same way via the support shaft 7a by a cooperative mechanism (not shown). Attached to B, secondary air intake 2 Multiple in the circumferential direction of B

■ Be placed. By changing the deflection angle of the secondary air register 7, secondary air 1 0

The turning force applied to 20 can be changed.

The tertiary nozzle 3 has a conical front wall 3 0 1 and a conical rear wall 3 0 2 disposed opposite to the front wall 3 0 1, and the front wall 3 0 1 and the rear wall 3 0 2 A conical air flow path of the tertiary nozzle 3 is formed between them. The air inlet 3B (Fig. 3) of the tertiary nozzle 3 has a ring shape, and the opening area is connected to the cylindrical tertiary damper 8 and is outside the wind box 39b.

Adjustment lever 17 equipped with a handle 25 can be changed by sliding the third damper 8 along the central axis C direction of the rod 3 1, thereby adjusting the tertiary air flow rate. The front wall 3 0 1 and the rear wall 3 0 2 are joined via a plurality of connecting plates 4 arranged in the air intake port 3B. The outlet 3 A of the tertiary nozzle 3 is connected to the tip of the secondary nozzle 2, and the tertiary air 1 1 and the secondary air 10 join together to form an air flow 1 2. It is formed so as to be ejected into the furnace 3 4.

Here, the secondary air 10 flowing into the secondary nozzle 2 flows into the furnace 34 in a direction parallel to the central axis C of the port 3 1, and the swirl force is further generated by the secondary air register 7. Given and ejected into the furnace 3 4. On the other hand, the tertiary nozzle 3 has an inward inclination toward the central axis C direction of the port 31. Therefore, the tertiary air flowing into the tertiary nozzle 3. The air 1 1 is in the central axis C direction of the port 31. This is a structure suitable for forming a constricted flow concentrated on the surface. 'By changing the flow ratio of the secondary air 10 and the tertiary air 11, it is possible to adjust the jet direction of the air flow 12 after the merge of the secondary air 10 and the tertiary air 11. For example, if the flow rate of the tertiary air 1 1 is 0, the inward velocity component of the air flow 1 2 after the merge of the secondary air 1 0 and the tertiary air 1 1 (velocity component toward the center of the air flow 1 2) Becomes 0. If the flow rate of the secondary air 10 is 0, the air flow 1 2 is occupied by the tertiary air 1 · 1, so the inward velocity component increases and the air is ejected in the direction of inclination of the tertiary nozzle 3 (diagonally inward). . By adjusting the jet direction of the air flow 12, the unburned gas region that is unevenly distributed in the furnace 34 and the combustion air can be suitably mixed to reduce unburned fuel. In addition, the mixing state can be adjusted by the strength of the swirling of the secondary air 10.

Primary damper 5, secondary damper 6 and tertiary damper 8 are used to adjust the air flow ratio of primary air 9, secondary air Γ 0 and tertiary air 11 of port 3 1.

'' Some fuels contain ash, such as coal, heavy oil, etc., but when using such fuels, increase the flow rate of tertiary air 1 1 and 'port air flow 1 2 When concentrated in the direction of the central axis C of 3 1, so-called contracted flow, the turbulence around the contracted flow increases, and the surrounding combustion gas is easily accompanied by the contracted flow. The ash melted in the combustion gas 25 is also entrained and may adhere to the vicinity of the water pipe 23 at the outlet of the porridge 31 to produce an ash adhesion layer 18. This state is schematically shown in the cross-sectional view of the pouch 31 in FIG.

When the ash adhesion layer 18 grows and forms a clinching force, there is a possibility that the air flow may be hindered or the water pipe 23 may be damaged due to the clinker dropping. In such a case, it is necessary to reduce the ash adhesion potential at the exit of port 3 1. The ash adhesion mechanism and prevention measures are shown in Figs. Figures 5 to 7 show the flow velocity distribution (actual measurement data) at the outlet of Po 卜 31. The vertical axis shows the distance from the central axis C of the AAP, with C as the origin. The horizontal axis shows the distance from the AAP in the furnace 3 4 to 0 to 5 Shown in the range of 0 0 O mm. The color of the flow velocity distribution chart is 25 to 30 m / s for brown, 20 to 25 m / s for red, 15 to 20 m / s for pink, 10 to yellow: L 5 mZ s The dark blue color is 5 to: L 0 m / s, the blue color is 0 to 5 m / s, the dark blue color is -5 to Om / s, and the dark blue color is 10 to 5. m / s. 'Note that the minus sign of dark blue and dark blue represents the reverse flow area. The AAP model used was a full-scale machine (AAP of the size applicable to a 100 MW MW boiler), and the air flow was also tested in the same way as the actual machine. However, since the air temperature is room temperature, the absolute value of the flow velocity is decreasing. The measurement conditions were as follows: the flow rate of the swirling air of the secondary air 10 and the flow rate of the primary air 9 were changed while the contracted flow rate of the tertiary air 11 was constant. Figure 5 shows a furnace with straight primary air 9 without swirling flowing in at 14% of the total, secondary air 1 0 at 6 2%, and tertiary air 1 1 at 24 ° / _0. It can be seen that there is little formation of a backflow region at the center of the furnace 34.

Figure 6 shows the case where the primary air 9 is 0%, the secondary swirling flow of the secondary air 10 is 70%, and the tertiary air 11 is 30%. Fig. 7 shows the case where primary air 9 is 0%, secondary air 10 is 63% of the strong swirling flow, and tertiary air 11 is 37%. 6 and 7, there is little difference in the spread of the air jet in the furnace 34, and there is a difference in the flow velocity distribution in the central part of the furnace 34. The lower side of Figs. 5 to 7 corresponds to the central axis C of A A P.

Focusing on the spread of the high-speed air jet in Figs. 5 to 7, it is difficult to understand because the measurement position is slightly away from the front end of the AAP, but along the widening of the exit of the furnace throat wall 26 None of the jets are affected by contraction. In other words, since the air jet is separated from the furnace throat wall 26 shown in Fig. 2, although it is a small region, a backflow occurs, and the ash particles accompanying this flow grow on the wall. Potential.

Thus, as in the conventional AAP shown in Fig. 14, the air flow 1 2 (the confluence of secondary air 10 + tertiary air 1 1) peeled off from the furnace throw wall 2 6 and was reduced in flow. Indicates the situation. Therefore, the ash adhesion layer 18 shown in Fig. 14 is formed on the furnace throat wall 26. It is.

Therefore, in this embodiment, as shown in FIG. 2, a rubar 3 2 is installed along the furnace throat wall 26 from the outlet of the tertiary nozzle 3, and the outlet force of the rubar 3 2 and the tertiary nozzle 3 is set. The space between the furnace throat wall 2 6 and the furnace throat wall 2 6 is provided with an interval in which a partial flow 1 1 ′ of the tertiary air 1 1 flows. Because of this structure, the partial flow 1 1 ′ of the tertiary air 1 1 flows so as to seal the surface of the throat wall 2 6, so that the combustion ash accompanying the contracted flow of the tertiary air 1 1 throat wall 2 Adhering to the surface of 6 can be minimized.

FIG. 2 shows the situation where the ash 'adhesion layer 18 is formed on the inclined portion of the furnace throw wall 26, but ash removal in this region is impossible in this embodiment. However, ash adhesion in this area does not affect the performance of A A P and does not affect boiler performance, so it can be ignored. However, the ash adhesion layer 18 shown in Fig. 14 must be removed because it has an impact on the A A P performance because it peels and falls into the A A P when the boiler stops. .. '' (Example 2).

FIG. 8 shows a cross-sectional view of the port 3 1 of the second embodiment. FIGS. 9 and 10 are schematic diagrams of the port 31 of the comparative example shown for comparison with the port 31 of the embodiment 2 shown in FIG. .

― As shown in Fig. 8, the primary nozzle 1 ', the secondary nozzle 2 and the tertiary nozzle 3 are shown as concentric primary air, secondary air and tertiary air, respectively. However, at least the flow from the outer peripheral side of the tertiary nozzle 3 in the present embodiment toward the port central axis C is strengthened to pass through the port opening (slow wall 2 6) of the furnace 3 4. Jet force Any structure suitable for forming a so-called contracted flow may be used. That is, the primary nozzle 1 and the secondary nozzle 2 are not essential for forming a so-called contracted flow.

The air flowing through the primary nozzle 1 that is the central air nozzle of the port 3 1 forms a straight flow, and the secondary nozzle 2 has a secondary air register 7 having a swirling function at the inlet, and the secondary nozzle 2 furnace. 3 The main part including the end on the 4 side (secondary nozzle outlet) is a straight pipe centered on the port center axis C. Accordingly, in FIG. 8, the radius D a of the pipe inlet end of the secondary nozzle 2 is equal to the radius D b of the pipe outlet end. Further, unlike the primary nozzle 1 and the secondary nozzle 2, the tertiary nozzle 3 forms a jet flow having an inclination angle of 30 ° to 70 ° with respect to the port center axis C, thereby obtaining a contraction effect. It is said.

The contracted flow effect means that the entrained gas 20 of the surrounding gas in the furnace 34 is generated in the vicinity of the inlet wall 26 where the gas flow path formed at the opening of the furnace wall is expanded. It is an effect. ,

To adjust the air flow rate of the primary nozzle 1, adjust the damper 5 provided at the air inlet 1B of the primary nozzle 1 from the outside of the windbox 3 9b by operating the adjustment lever 1 5 from the outside of the air box 3B. Adjust the opening and adjust the air flow rate of the secondary nozzle 2 by operating the damper 6 provided at the air inlet 2B of the secondary nozzle 2 B from the outside of the windbox 3 9b. Then, adjust the opening of the air intake 2B of the secondary nozzle 2 and simultaneously rotate the register 7 provided in the air intake 2B of the secondary nozzle 2 with the secondary air register drive 13 To adjust the air swirling strength. The air flow rate of the tertiary nozzle 3 can be adjusted by operating the adjustment lever 1 7 from the outside of the wind box 3 9 b by operating the damper 8 provided at the air inlet 3 B of the tertiary nozzle 3 and removing the air from the tertiary nozzle 3. 3 Adjust the opening of B. .

The throat part 26 of the furnace wall on the outlet side of the tertiary nozzle 3 (the side going into the furnace 34) has a diameter downstream from the central axis C of the port 31 toward the downstream side of the gas flow. It is expanding. When the tertiary damper 8 is fully closed, the swirling flow from the expanded throat wall 26 and the secondary nozzle 2 forms an air flow that expands in the radial direction of the port center axis C. Also, in order to prevent ash from adhering to the expanded throat wall 2 6 on the outlet side of the tertiary nozzle 3, a part of the flow 1 1 ′ of the tertiary air 1 1 is thrown in the outer circumferential direction of the wall 2 6. A ring-shaped louver 3 2 is provided that expands as the cross-sectional area goes to the furnace 3 4 side. The upstream end of the gas bar 3 2 (the inlet side of the air nozzle 3) is on the extension line E of the outer wall of the tertiary nozzle 3 or on the upstream side of the gas flow (on the air line) It is provided so that it is located on the nozzle inlet side; the direction away from the inside of the furnace.

The features of the present embodiment will be described in comparison with FIG. 9 and FIG.

The port 図 3 1 of this embodiment shown in FIG. 8 is parallel to the furnace wall surface of the expanded wall 1 6 on the outlet side of the tertiary nozzle 3 (the side going into the furnace 3 4). The throat wall A ring-shaped bar 3 2 whose cross-sectional area increases toward the side closer to the inside of the furnace 6 of 26 is provided.

On the other hand, FIG. 9 and FIG. 10 show a cross-sectional view of the port 3 1 having the same configuration as FIG. 8, but the configuration different from the port 3 1 in FIG. Gas flow The tip on the upstream side is provided so that it is located on the downstream side of the gas flow downstream of the extension line E of the outer partition wall of the tertiary nozzle 3, and in FIG. 10 all the louvers 3 2 "are from the third nozzle 3. This pouch is provided so as to be located in a contracted flow toward the central axis C.

The upstream end of the gas flow upstream of the louver 3 2 of this embodiment shown in FIG. 8 is provided so as to block a part of the tertiary nozzle 3, so that the tertiary air 1 1 flowing through the tertiary nozzle 3 is reduced. The upstream end of the louver 3 2 becomes an obstacle to the flow, and dynamic pressure is generated by the tertiary air 1 1 on the outer periphery side (slow wall 2 6 side) of the louver 3 2. And a partial flow 1 1 ′ of tertiary air 1 1 flows between the throat wall 2 6 and the expanded throat wall 2 6. The flow 1 1 ′, which becomes the seal air flowing between the rubber bar 3 2 and the inlet wall 2 6, is induced in the furnace 3 4 by being guided by the rubber 3 2. • Flows in the vicinity of the furnace 6 • Entrained gas flow inside the furnace wall (wall seal air flow) 2 0 effectively flows along the inner wall of the furnace 3 4 near the throat wall 2 6 of the port 3 1, Slow 卜 Wall 2 6 The negative pressure near the wall surface can be removed.

• On the other hand, in the configuration shown in Fig. 9 and Fig. 10, the tertiary air generated in the vicinity of the throat wall 26, which is the opening of the furnace, due to the arrangement relationship between the rubber bar 3 2 ', 3 2 "and the tertiary nozzle 3 1 The flow of entrained gas near the side wall of furnace 3 4 under the influence of partial flow 1 1 'in 1 becomes a circulation flow, so that the ash adhesion layer on the throat wall 2 of furnace 3 4 1 8 is possible.

Thus, in the configuration of this embodiment shown in FIG. 8, the wall surface constituting the expanded throat wall 26 of the outlet of the tertiary nozzle 3 due to ash entrainment, which is a concern in the configuration shown in FIG. 9 and FIG. It is difficult for ash to adhere to the surface.

The radius (D g) of the gas flow downstream side (furnace side) of the louver 3 2 is the minimum radius (D s) of the expanded tubular throat wall 26 of the tertiary nozzle 3 (hereinafter referred to as “slow”). The diameter is sometimes referred to as “diameter.” Refer to Fig. 12), less than 1 times, particularly preferably less than 0.95 times. By making the radius of the louver 3 2 on the downstream side (furnace side) of the louver 3 2 less than 1 centimeter of the radius of the expanded tube 卜 wall 2 6, However, it is easy to install the louver 3 2 from the outside of the furnace 3 4 or to pull it out of the furnace 3 4. In addition, if the manufacturing tolerance is taken into account, the force of less than 0.95 times 5 is even easier. Note that the louver 3 2 may be divided in the circumferential direction so that the louver 3 2 can be easily taken out of the furnace 3 4 without being integrated. ,

However, the length of the plane whose diameter increases toward the downstream side of the gas flow of the louver 3 2 (the length of the line connecting the e part (circumferential direction) and the heel part (circumferential direction) in FIG. To prevent ash from adhering to the flat surface, the length of the line connecting the 10h part (circumferential direction) and the i part (circumferential direction) in Fig. 12 It is desirable that the value be 1 or 2 or less. This applies not only to the present embodiment but also to the present invention as a whole.

Also, if the spreading angle of the gas bar 3 2 in the gas flow direction is equal to or larger than the spreading angle of the expanded tubular wall 26 of the port 31, it is effective for preventing ash adhesion. It is possible to induce air volume.

15 Further, the damper 8 at the inlet of the tertiary nozzle 3 is arranged on the side away from the furnace 3 4 at the inlet of the nozzle 3, and when the air intake 3B of the tertiary nozzle 3 is closed by the damper 8. It is desirable to slide the damper 8 in a direction approaching the furnace 3 4. This is because even when the air flow rate when the inlet of the nozzle 3 is closed is reduced (the damper 8 is close to the closed state), the expanded throat wall 20 of the pipe 3 1 in the tertiary nozzle 3 20 This is because air flows in a portion close to 26, so that air is guided to louver 3 2 and ash adhesion to the expanded tubular slot wall 26 can be prevented.

The damper 8 is shown in the form of a cylindrical member that slides substantially parallel to the port center axis C. However, a plurality of butterfly-shaped valves or flaps whose rotation axis is the port 卜 3 1 It may be arranged in a line in the circumferential direction at a position parallel to the central axis C. This is not limited to the present embodiment but is a configuration example that can be applied to the following embodiments.

In this embodiment shown in FIG. 8, the port 3 1 has a triple structure. However, the port 3 1 does not have the primary nozzle 1 or the secondary nozzle 2 and is composed only of the tertiary nozzle 3 having a contracted flow structure. The above effect can be obtained even with 3 1. In other embodiments, the point 3 1 may be composed only of the tertiary nozzle 3. When an air nozzle such as the secondary nozzle 2 is provided inside the tertiary nozzle 3 shown in FIG. 8, the end of the partition wall constituting the secondary nozzle 2 on the downstream side of the gas flow (point of Fig. I? (A)) b) with respect to a line F formed by a virtual straight cylinder for gas straight travel (a line parallel to the central axis C of the port ポー including point b in Fig. 1 2 (a)) (Fig. 1 2 (a) Point b) 'and the angle 6 formed by the line G connecting the end of the louver 3 2 on the gas flow side of the soil flow (point c in Figure 12 (a)) It is desirable that the upstream end of the louver 3 2 (point c in FIG. 12 (a)) is disposed in the interior (see FIG. 12 (a)).

This is because when the damper 8 at the inlet of the tertiary nozzle 3 is fully closed and air flows from the secondary nozzle 2, the air ejected from the secondary nozzle 2 spreads inside the port 3 1. This is because the divergence angle of the jet flow is usually about 15 degrees. For this reason, by installing the upstream end of the louver 3 2 in the region sandwiched between the lines F and G, the outer side flow of the louver 3 2 can be obtained even when the secondary air is not swirled. Gas flows along the path, and the gas flow can be guided in the outer circumferential direction in the vicinity of the wall surface of the slow wall. In other words, compared to the conventional configuration in which a jet outlet for jetting a cooling body such as air is separately provided, the configuration of the present embodiment allows the throat wall 2 under any operating conditions of the port 31. As a result, it is possible to prevent ash from adhering to the wall surface in or near 6 and reduce the pressure loss when supplying the gas supplied from the port 3 1 to the furnace 3 4, simplifying the structure of the port 3 1, It is no longer necessary to install a regulator for the ash adhesion suppression seal air ', and as a whole, the weight of the furnace 34 and the steel materials can be reduced.

The louver 3 2 is supported by a fixing rib 2 7 (see FIG. 11) on the outer flow path wall of the tertiary nozzle 3 constituting the contracted flow. Normally, in the boiler furnace 3 4, the thermal expansion is different in each part of the furnace 3 4, so that the wall surface of the furnace 3 4 that forms the outer periphery of the outermost air nozzle (the tertiary nozzle 3 in the case of FIG. 8) The distance from Po 卜 center axis C varies depending on the operating load. By fixing the louver 3 2 or the like from the inside of the port 3 1, the distance between the expanded slow throat wall 2 6 of the port 3 1 and the louver 3 2 can be kept constant.

(Example 3) FIG. 11 is a schematic diagram of a port 31 showing the third embodiment. In the configuration shown in FIG. 11, the same parts as those shown in FIG. .

In this embodiment, the expanded tubular throat wall 26 of the port 31 has a parallel portion 26 a parallel to the center axis C with a constant flow path cross-sectional area. Further, the cylinder 3 2 is also provided with a cylindrical portion 3 2 a along the parallel portion 2 6 a. Also, between the louver 3 2 and the expanded tubular throat wall 2 6, a part of the contracted flow from the tertiary nozzle 3 flows in, and the tertiary that seals the surface of the furnace 3 4 spout and the first wall 2 6 Since the partial flow 1 1 'of air 1 1 flows effectively in the vicinity of the wall of the sloping wall 2 6 and the negative pressure in the vicinity of the wall surface of the throat wall 2 6 can be removed, the throat wall due to ash entrainment Ashes become less likely to occur in the vicinity of 26. Fig. 12 (a) is an enlarged view of the port 31 first outlet portion of Fig. 11. The tip of the louver 32 on the upstream side of the gas flow (point c) is the tertiary nozzle that forms the contracted flow. The outer peripheral side wall surface of 3 (front wall) is located on the extension line E of 301 and on the upstream side of the gas flow (in the direction away from the furnace) from the extension line E. In addition, the radius D g of the furnace 3 of the ruby 3 3 is less than one half of the half wall D s of the slot wall 26 so that the ruby 3 2 can be inserted from the side of the wind box 3 9 and b. And More specifically, the radius D s of the parallel portion 2 6 a of the expanded tubular throat wall 2 6 is made larger than the radius D g of the maximum diameter portion of the louver 3 2 (radius D g <radius D s). Actually, considering the manufacturing tolerances, the radius D s of the parallel part 2 6 a of the pipe 26 2 is less than 0.95 times larger than the radius D g of the largest diameter part of the bar 3 2 (D s <0.95 D. g) is desirable.

The radius D p of the parallel portion 3 2 a of the louver 3 2 is 20% or less of the radius D s of the parallel portion 2 6 a of the throat wall 26 (1.0 0 D s> D p ≥ 0.8 D s The length D p is the radius of the cylindrical portion 3 2 a of the louver 3 2 (part parallel to the port center axis C), and the divergence angle of the louver 3 2 If the angle is equal to or larger than the spreading angle of the low ridge wall 26, it is possible to induce an effective amount of air for preventing ash adhesion to the throat wall 26. However, considering the sustainability of the contraction effect caused by the gas flowing through the tertiary nozzle 3, the radius Dp with respect to the radius Ds is reduced by about 10% (1.0 D s> D p≥ 0.9 D s) I hope that. In other words, if too much air is allocated to prevent ash from adhering to the throat wall 2 6 of the furnace 3 4, the air jet for the original combustion control reaches the center of the furnace 3 4, while the vicinity of the furnace wall Facilitate gas mixing This is because the purpose of the contraction flow formation is hindered. The air jet flow from the outer periphery of port 3 1 toward the central axis C is strengthened to pass through the throat part 26, and the air jet is concentrated on the central axis C of the port 卜 31 while the throat part is concentrated. It is not desirable that the flow that entrains the gas in the furnace 3 4 around 2 6 cannot be maintained. '

Figure 12 (a) shows the port radius D a (point a; radius at the introduction of the secondary nozzle 2) and D b (point b; secondary nozzle 2) In this example, the end of the partition wall on the downstream side of the gas flow) and the radius of the slow 卜 wall 26 (the radius of the parallel portion of the throw Dwall 26) are almost the same. The same applies when the radius D s of the throat wall 2 6 is larger or smaller than the radius D a of 2 and the radius D b.

For example, as shown in FIG. 1 2 (b), when the radius D a of the secondary nozzle 2 and the radius D s of the walls 2 and 6 are larger than the radius D a and the radius D b, the partition walls constituting the secondary nozzle 2 The center line C of the port including the point b (Fig. 12 (b) b) of the virtual gas straight cylinder including the end of the gas flow downstream side (Point b in Fig. 12 (b)) The line G connecting the end (point b in Figure 12 (b)) and the upstream end of the louver 3 2 (point c in Figure 12). It is desirable to provide the gas flow upstream end of the louver 3 2 within an angle range where the absolute value of the angle Θ is smaller than 15 degrees. ·

However, the length of the plane of the louver 3 2 whose diameter increases toward the downstream side of the gas flow (the length of the line connecting e ¾ (circumferential direction) and f part (circumferential direction) in FIG. 12) is In order to prevent ash from adhering to the flat surface, the gas flow in the surface surrounded by the wall length of the slot wall 26 in the gas flow direction (Fig. 12 h part (circumferential direction) and heel part (circumferential direction ')) The length in the direction) should be 1 or 2 or less.

In Fig. 1 2 (b), the radius D s of the throat wall 26 is larger than the radius D g of the louver 3 2, so that the louver 3 2 can be easily pulled out of the furnace wall. (Example 4)

FIG. 13 is a schematic diagram of a part 31 showing the fourth embodiment. In the configuration shown in FIG. 13, the same parts as those shown in FIG.

In this embodiment, as in the configuration shown in FIG. 11, a parallel portion 2 6 a parallel to the central axis C having a constant flow path cross-sectional area is provided on the slow trough wall 26 and the cylindrical portion 3 is provided on the louver 3 2. 2 Set a Have A swirler 2 2 for inducing a flow velocity component in the circumferential direction of the throat wall 2 6 is provided between the parallel portion 2 6 a and the cylindrical portion 3 2 a of the cylinder 3 2.

As a result, a part of the contracted flow from the tertiary nozzle 3 flows between the louver 3 2 and the throat wall 2 6, and the air flow 1 1 ′ sealing the surface of the throat wall 2 6 of the furnace 3 4 is generated. Since it flows effectively near the wall surface of the expanded throat wall 26 and can remove the negative pressure near the wall surface of the throat wall 26, ash adhesion occurs in the vicinity of the throat wall 26 due to ash entrainment. It becomes

In addition, the projected area of the surface perpendicular to the port center axis C as seen from the furnace side of the rubber bar 32 can be reduced, and the amount of radiant heat received from the flame can be reduced. For this reason, the temperature of the louver 32 can be reduced, and heat loss such as thermal deformation and corrosion in a high temperature field is unlikely to occur. Also, when the ring-shaped louver 3 2 having an enlarged cross-sectional area for guiding the gas flow in the direction of the throat wall 26 6 is provided at the tip of the swirler 22 2 on the downstream side of the gas flow, ash is involved. Can prevent ash adhesion near the nozzle. '.. Industrial applicability

• The present invention is not limited to boiler furnaces, but can be applied to the furnace wall surfaces of combustion equipment where ash produced by combustion of coal or the like tends to adhere.

Claims

The scope of the claims

1. A velocity component which is provided on the furnace wall of the furnace and has a velocity component which flows toward the central axis of the gas flow perpendicular to the furnace wall and a velocity component which flows along the central axis. A flow path for contracted flow generation formed obliquely toward the axis; and

A throat pipe expanding section in which a gas flow path formed in the furnace wall opening on the downstream side of the flow path for contracted flow generation sequentially expands in the gas flow direction;

A louver provided in the contraction flow generation channel for guiding the gas flowing through the contraction flow generation channel to flow along the wall surface of the slot expansion portion;

A gas ejection port into the furnace characterized by comprising

2. The gas flow upstream side tip of the rubbing bar is located on the gas flow upstream side of the outer peripheral side wall surface of the contracted flow generation flow path extending in the direction of the central axis or the extended surface. 2. The gas jet into the furnace according to claim 1, wherein the gas flow downstream side portion of the louver has a tube expanding portion that sequentially expands in the gas flow direction so as to follow the wall surface of the throat tube expanding portion. Port.

3. It has a mechanism for changing the ratio of the velocity component flowing in the direction of the central axis and the velocity component flowing in the direction of the central axis of the air flow flowing through the flow path for self-condensed flow generation. A gas ejection port into the furnace according to claim 1 or 2.

4. Provided with a damper capable of adjusting the opening of the flow path for contraction flow that starts to open from the outer peripheral wall surface side so that gas flows along the outer peripheral wall surface of the flow path for contraction flow generation. The gas ejection port into the furnace according to claim 3, characterized in that it is a gas ejection port.

5. A gas jet into a furnace according to any one of claims 1 to 4, characterized in that a swirl member for swirling gas is provided between the louver and the wall surface of the slot expansion section. port.

6. The length in the gas flow direction of the single-tube expansion section formed at the downstream end of the louver is 12 or less of the wall length in the gas flow direction of the single-tube expansion section. The gas ejection port into the furnace according to any one of claims 1 to 5, wherein

7. The contracted flow generation flow path is a tertiary nozzle, and a primary nozzle through which gas flows along the central axis and a secondary nozzle outside the primary nozzle are provided inside the tertiary nozzle. The gas ejection port in the furnace according to any one of claims 1 to 6, wherein