JPH0894013A - Low nox burner - Google Patents

Abstract

PURPOSE: To provide a burner of a flame which is compact and made effective for highly efficient reduction in NOx. CONSTITUTION: A nozzle 1 which jets high temperature air for combustion at a speed by far higher than that of a fuel is arranged parallel with a nozzle 2 for ejecting the fuel while being encircled by a refractory material 3 and an end face 5 on which a jetting port 7 of the fuel nozzle 2 is formed is jutted from an end face 4 where a jetting port 6 of an air nozzle 1 so that a part of a fuel gas is dragged in by a vortex 11 formed with a part of the air for combustion being reversed as flowing along the surface 10 of a step part to form a flame as pilot flame. On the other hand, the air for combustion drags in an exhaust gas before being mixed with the fuel gas so that the fuel is induced to mix into the flow of the air for combustion down from the end face 5 lowering the concentration of oxygen. Thus, intensely directional flame and flow of the fuel gas are formed causing a slow combustion stably.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to low NOx burners. More specifically, the present invention is not only in the high temperature range in the heat storage combustion using the high temperature preheated air obtained by the heat exchange between the combustion exhaust gas and the combustion air via the heat storage medium, but also in the medium temperature range which was conventionally difficult. The present invention relates to a low NOx burner which is also effective in reducing NOx.

[0002]

2. Description of the Related Art Conventionally, in order to reduce NOx in a burner, for example, a two-stage fuel combustion method as shown in FIG. 5 has been adopted. In the fuel two-stage combustion method, the fuel is supplied to the combustion air A flowing in the burner throat 101 in two stages by the primary nozzle 102 and the secondary nozzle 103, and the primary fuel and the entire amount of combustion air are supplied. In addition to forming the primary flame, the secondary flame is formed by the reaction between the secondary fuel and the high temperature combustion gas of the primary flame. Since the oxygen concentration near the secondary fuel nozzle is low, NOx of the primary flame is reduced by the reduction reaction.

[0003]

However, in the burner based on the two-stage fuel combustion method, the injection direction of the secondary fuel forming the main flame is set to be substantially parallel to the flow of combustion air, so that the two-stage combustion at low temperature is performed. The stability of the next flame is poor and 10
The flame is not stable unless the combustion air is preheated to a high temperature of about 00 ° C or higher. Therefore, if the fuel injection direction is made closer to the direction perpendicular to the flow of combustion air in order to improve the stability of the secondary flame at low temperatures, the flame stabilizes, but local combustion occurs and the temperature rises locally. NOx increases. Thus, it was difficult to achieve both flame stability and low NOx compatibility.

Therefore, when it is used as a heat source for an aluminum melting furnace which operates at a rated temperature in a relatively low temperature range of about 700 to 800 ° C., for example, a well reflection type melting and holding furnace, or when the furnace is started up. When the temperature is low, the stability of the flame becomes poor and it is difficult to carry out the conventional two-stage fuel combustion method.

Further, the piping for injecting the primary fuel and the secondary fuel in two stages separately becomes complicated, the equipment becomes complicated, the construction work becomes complicated, the equipment cost becomes high, and the location is increased. Have a problem to take.

The present invention is a compact and highly efficient low N
The purpose is to provide an Ox burner. Further, the present invention provides a low NOx burner that is effective not only in the high temperature range but also in the medium temperature range, which has been difficult in the past, in combustion using high-temperature preheated air, and that has good flame stability. With the goal.

[0007]

In order to achieve the above object, the present invention provides a heat storage system that burns by using high temperature combustion air obtained by alternately passing combustion exhaust gas and combustion air through a heat storage body. In a combustion-type burner system, a nozzle that injects combustion air at a much higher speed than fuel and a nozzle that injects fuel are arranged in parallel, and they are surrounded by a refractory material and the injection port of the fuel nozzle is formed. A step is provided between the formed end surface and the end surface on which the injection port of the air nozzle is formed so that the end surface on the fuel nozzle side protrudes from the end surface on the air nozzle side. Here, it is preferable that the fuel nozzle also serves as the pilot burner.

Further, in the low NOx burner of the present invention, the portion of the injection port of the fuel nozzle close to the air nozzle is formed by the enlarged diameter portion formed by the curved surface or the inclined surface so that a part of the injected fuel flows out to the air nozzle side. I have to.

Further, in the low NOx burner of the present invention, the surface of the step between the end surface of the refractory material in which the injection port of the fuel nozzle is formed and the end surface of the refractory material in which the injection port of the air nozzle is formed is the air nozzle. It is circumscribed or intersects with the injection port of.

[0010]

In the case of the low NOx burner according to the first aspect of the invention,
A part of the combustion air flowing along the step surface between the end surface from which the combustion air is ejected and the end surface from which the fuel is ejected flows counter to the flow of the combustion air in the vicinity of the step on the end surface from which the fuel is ejected. A stable vortex is formed and a part of the fuel gas is engulfed to form a flame that becomes a pilot fire. Further, a negative pressure is generated in the step portion to cause a strong exhaust gas recirculation, and the exhaust gas is entrained before the combustion air is mixed with the fuel gas to reduce the oxygen concentration. Then, on the downstream side of the end surface where the fuel is injected, the fuel is attracted to the flow of the combustion air and admixed with it.

Here, since the volume of the combustion air preheated to a high temperature of about 700 to 800 ° C. or higher expands as compared with that at the normal temperature, it is suitable by setting the air nozzle to be thin or at a low temperature. By adopting a thin nozzle set so as to have a high flow velocity, it is ejected at a considerably high velocity as compared with fuel and air at room temperature.
For example, the high temperature preheated air is jetted at an extremely high flow velocity of 100 m / s or more as compared with the fuel jetted at a flow velocity of 20 to 30 m / s. Therefore, the combustion exhaust gas is strongly entrained by the high-speed flow of combustion air, and the oxygen concentration (partial pressure)
On the other hand, the fuel is attracted to the flow of the combustion air to strongly mix with it. However, the combustion air is much faster than the flow of fuel, and since a large amount of exhaust gas is entrained by the time the fuel reaches the end face where it is injected, the combustion reaction does not occur rapidly and the combustion air The surface layer where the fuel and the fuel come into contact with each other burns, causing slow combustion. Moreover, even if the combustion air has a high velocity, it is possible to maintain a stable flame without misfire due to the seed flame and the primary flame caused by the vortex of the air generated between the fuel jet and the air jet. Particularly, in the case of the invention of claim 2, since a stable primary flame is formed along the fuel jet and is attracted to the air jet side together with the fuel, a more stable flame can be formed. Further, since the flow of the combustion air is fast during the combustion reaction, the combustion reaction is continued while entraining a large amount of exhaust gas, which promotes slower combustion. Therefore, high-temperature combustion air ejected at high speed and relatively low-speed fuel gas attracted thereto are mixed in the surface layers in contact with each other, causing slow combustion and forming a flame and combustion gas flow with strong directivity. To do.

Further, when the combustion air is at a low temperature such as when starting up the furnace, the flow velocity of the combustion air is slowed and the amount of exhaust gas entrained is reduced, but the temperature of the combustion air is originally low. Little NOx is generated. On the contrary, since the oxygen concentration becomes high, a stable pilot fire is not blown out between the fuel jet near the injection port of the fuel nozzle and the combustion air jet, and the flame becomes stable.

Therefore, the burner has a low NOx at a high temperature and an excellent flame stability at a low temperature.

Further, in the case of the third aspect of the invention, the fuel easily flows to the air side, the amount of the fuel gas entrained in the air flow and the fuel for the pilot fire that occurs near the fuel injection port near the step portion. Supply amount increases.

Further, in the invention according to claim 4, since the step portion is formed around or along the injection port of the combustion air, the step portion serves as a guide and the injection direction of the combustion air. Can be forced to form a highly directional combustion air flow. Therefore, the fuel and the combustion gas flow having a strong directivity can be formed by entraining the fuel further away. Further, a negative pressure is generated in the step portion, so that the strong exhaust gas recirculation in the furnace can be further strengthened.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an embodiment of the low NOx burner of the present invention. This low NOx burner is a burner that injects a gas that is fuel in parallel with the flow of combustion air that has been preheated to a high temperature by using a heat storage body and combustion exhaust gas, and burns the combustion air that has been preheated to a high temperature. An air nozzle 1 and a fuel (gas) nozzle 2 for ejecting at a much higher speed than the refractory block 3 are formed so as to penetrate the refractory block 3.
The injection ports 6 and 7 of each nozzle are bored in the two end surfaces 4 and 5 having the steps. Here, a pipe 8 forming a flow path for supplying primary air is buried around the fuel nozzle 2, and about 10% of the secondary air is flowed around the fuel nozzle 2. In addition to the main injection port 7, an injection port 9 for injecting a part of the fuel toward the surrounding primary air flow path is opened at the tip portion of the fuel nozzle 2, and the peripheral wall of the pipe 8 uses a part of the fuel as a pilot fuel. Are provided so as to collide with and spread in the flow path of the primary air to obtain a good mixed state. An igniter (not shown) is installed there, and is provided so that a stable primary flame 12 can be formed during combustion. The piping system is composed of only the main piping and air nozzle 1 for flowing most of the combustion air used as secondary air and the fuel piping (primary air piping 8 and fuel nozzle 2) for flowing fuel and primary air. It is a compact system.

Further, the fuel injection port 7 and the air injection port 6 are not formed on the same plane but are provided on different surfaces with steps and the fuel injection port 7 is arranged on the downstream side of the air injection port 6. ing. That is, the fuel injection port 7 is an end surface (hereinafter referred to as a reference surface) 4 of a block of refractory material provided with the air injection port 6.
It is installed on an end surface (hereinafter referred to as a flame holding surface) 5 which is projected from the surface. The stable primary flame 12 and the fuel F are ejected from the fuel ejection port 7 of the flame holding surface 5. Combustion air is ejected from the center of the refractory material block 3 at high speed. At this time, the vortex 11 which flows counter to the flow of the combustion air can be stably formed in the vicinity of the stepped portion of the flame holding surface 5, and is rapidly mixed with a part of the fuel / gas to form the flame holding region. Therefore, it is possible to form a stable pilot fire not to blow out at low temperature, let alone at high temperature. The refractory block 3 for holding the air nozzles 1 and the fuel nozzles 2 in parallel is constituted by a single block integrally molded in the case of the present embodiment, but in some cases, the air nozzles 1 are held. It is also possible to use a combination of a molded portion and a portion that holds the fuel nozzle 2 separately. Further, in the case of the present embodiment, the air nozzle 1 is not composed of piping,
Holes formed in the refractory material block 3 and the refractory material block 3
It is composed of a burner body for interior. Of course, the air nozzle 1 may be constructed by piping.

Further, in the case of adopting the above-mentioned structure, the refractory block 3 has an air nozzle 1 and a fuel nozzle 2 due to strength problems.
Requires some distance between and. Therefore, the fuel tends to be difficult to be attracted to the high-speed air flow in the region immediately after the injection. Therefore, it is preferable that the shape of the portion 13 of the fuel injection port 7 near the air nozzle 1 has a curved surface shape toward the air nozzle 1 side, as shown in FIG. As a result, the fuel easily flows out to the flow side of the combustion air. Therefore, the accompanying mixing capability of fuel is further enhanced, and the generation of free unburned components such as CO and HC can be prevented. Also,
The fuel is well supplied to the vortex 11 in which the combustion air flows backward, and a more stable pilot fire can be formed. This shape is not limited to a curved surface, and any structure that fulfills such a function may be used. For example, it may be a slope.

The air nozzle 1 has a flame holding surface 5 and a reference surface 4.
It is installed at the step of the boundary with. Then, the portion near the flame holding surface 5 has a function of admixing the fuel,
The portion near the reference surface 4 has a function of recirculating exhaust gas. That is, as shown in FIG. 1B, the surface 10 of the step portion between the flame holding surface 5 and the reference surface 4 crosses the center of the injection port 4 so as to divide the injection port 6 of the air nozzle 1 in half. If so arranged, both the admixture mixing function and the recirculation function can be made compatible. On the other hand, as shown in FIG. 2 (A), in the case where the surface 10 of the step portion is circumscribed to the injection port 4 of the air nozzle 1, the exhaust gas is more exhausted than in the case shown in FIG. Since the area in which the air is entrained becomes large, the function of lowering the oxygen concentration of the combustion air is excellent. Also,
As shown in FIG. 2B, when the surfaces 10 of the stepped portions are arranged so as to cross each other so as to cover most of the injection ports 4, the injected air is the flame-retardant surface of the refractory material block 3. Since there are many portions that are constrained to 5, the flow of combustion air having a stronger directivity is ejected from the flame holding surface 5, and the admixture mixing capability of the combustion gas is excellent. 2 in FIG.
Two examples are given, but not limited to.

The combustion air is preheated to a high temperature of, for example, 700 to 800 ° C. or higher by using combustion exhaust gas and is injected. For example, by direct heat exchange in which combustion exhaust gas and combustion air are alternately passed through the heat storage body, it is preheated to a temperature substantially close to that of the combustion exhaust gas.
Here, although the heat storage body is not shown, it is installed in a burner body or a duct connected to it, or is connected by a pipe.

The low NOx shown in FIG. 1 thus constructed.
According to the burner, when the combustion air is ejected at a high temperature and a high flow rate, the high-velocity and directional combustion air ejected from the flame holding surface 5 strengthens the fuel injected in parallel at a relatively low speed early. Attract and let it accompany, fly far while mixing.
However, since the combustion air flow velocity is much higher than the fuel flow velocity, for example, 100 m / s or more, which is extremely high, and because a large amount of exhaust gas is entrained before reaching the flame holding surface 5, combustion is performed. The reaction does not occur rapidly, and the combustion reaction proceeds slowly. Further, since the air velocity is high, the combustion reaction is carried out while entraining a large amount of exhaust gas during the combustion reaction, which promotes slower combustion. This is
As is clearer from the experimental results shown in FIG. 4 in which the relationship between the flow velocity of combustion air and the amount of NOx produced is obtained, the higher the injection speed of the combustion air, the lower the amount of NOx and its effect. It became more remarkable as the amount increased (higher temperature). Therefore, according to the burner of this embodiment,
A relatively uniform and long heat flux can be formed and NOx reduction can be realized. Moreover, since a part of the fuel is attracted to the backflow of the combustion air that occurs in the region near the stepped portion of the flame holding surface 5 and diffused and mixed to form a stable flame that becomes a pilot flame, it is not only at high temperature. That is, a flame is stably formed even at a low temperature.

The low NOx of the present invention configured as described above
The burner can be used as a heat source of a non-ferrous metal molten metal holding furnace, for example, a heat source of a reverberatory furnace.

In the present embodiment, the low NOx burner is composed of one burner system 20 of the heat storage combustion type, with two burners 21 and 22 that burn alternately as one set. The heat storage type burner system 20 is arranged on the furnace wall so as to form a flame / combustion gas toward a space above the liquid level of the molten aluminum in the heating chamber of the reverberatory furnace. In this embodiment, 1
The heat storage type burner system 20 of the system is provided,
You may equip two or more systems.

The heat storage combustion type burner system 20 is not particularly limited in its structure and combustion method, but in this embodiment, the heat storage body 7 is connected to the burner body 14 as shown in FIG.
In order to be able to discharge the combustion exhaust gas through the burner and the heat storage body which are not burned and are in a stopped state, two burners 21 and 22 integrated with the heat storage body 23, 23 are integrated and burned alternately. It is provided in. An air supply system 24 for supplying combustion air and an exhaust system 25 for discharging combustion gas can be selectively connected to the two burners 21, 22 by interposing a four-way valve 26, and one burner 21 ( Alternatively, 22) is provided so that combustion air is supplied through the heat storage body 23, while combustion gas is exhausted from the other burner 22 (or 21) through the heat storage body 23. Combustion air is supplied by, for example, a push-in fan or the like (not shown), and combustion exhaust gas is sucked from the furnace by exhaust means such as an induction fan (not shown) and discharged into the atmosphere. Further, a part of the combustion air is injected through the pipes 8 and 2 together with the fuel as primary air without passing through the heat storage body 23. Further, although not shown, the fuel supply system is selectively connected to either one of the burners 21 and 22 alternately via a three-way valve to supply the fuel.

Here, as the heat storage bodies 23, 23, a material having a large heat capacity and a high durability despite a relatively low pressure loss,
For example, it is preferable to use a tubular body having a large number of honeycomb-shaped cell holes formed of ceramics such as cordierite and mullite. In this case, when heat is recovered from the combustion exhaust gas, even if the exhaust gas falls below the acid dew point temperature, the sulfur content in the fuel and its chemically modified substances are captured in the ceramics, and the exhaust system ducts, etc. located downstream are subject to low-temperature corrosion. There is nothing to do.
Of course, it is not particularly limited to this, and other heat storage bodies such as ceramic balls and nuggets may be used.

According to the well-type reflection-type melting and holding furnace constructed as described above, it is operated in a medium temperature range of about 700 to 800 ° C., but the flame holding surface 5 near the step surface 10 is filled with the combustion air. A stable flame is formed as a pilot fire due to the backflow, and the exhaust gas entrained by the high-speed flow of the combustion air reduces the oxygen concentration and gradually mixes the fuel attracted to the combustion air to cause slow combustion. Wake up. Therefore, the flame is stable and NOx does not increase.

On the other hand, the combustion exhaust gas is exhausted from the stopped burner through the air nozzle 1 and the heat storage body 23 and the exhaust system 25. That is, the pair of burners 21, 22 are alternately connected to the exhaust system 25 and the air supply system 24 by switching the four-way valve 26, and are used as an exhaust passage for combustion exhaust gas when not combusting. The molten aluminum is heated by the flame and the radiant heat of the combustion gas. Here, the burners 21, 22
The combustion air to be supplied to is heated after being preheated by direct contact with the heat storage body 23 for a short time, and is thus supplied, so that it has a high temperature close to the exhaust gas temperature. Therefore, a stable combustion is performed with a small amount of fuel, and high-temperature combustion gas can be obtained. Moreover, since the temperature of the combustion air also changes immediately as the amount of combustion increases or decreases, the response of the temperature adjustment of the hot water temperature is good.

The switching between combustion and exhaust is, for example, 10 seconds-
2 minute intervals, preferably within about 1 minute, most preferably 10 minutes
It is performed at an extremely short interval of about 40 seconds. in this case,
Heat is exchanged with high temperature efficiency. The switching may be performed when the combustion gas discharged via the heat storage body 7 reaches a predetermined temperature, for example, about 200 ° C. In this case, since the flame position changes frequently, the heat pattern in the combustion chamber can be made more uniform, and uneven heating and uneven heating can be reduced. Due to the effect of the burner and the effect of the non-stationary flame, the temperature inside the furnace can be easily made uniform. Therefore,
Because it is possible to raise the temperature setting in the furnace, and the amount of radiant heat transfer is greatly improved. Therefore, the thermal efficiency is improved and the fuel consumption is also reduced.

According to the burner of this embodiment, the heat storage body 23,
23 and the refractory block 3 are integrated into the burner body 27 and integrated, and the number of pipes is small,
It is more compact than the conventional one, the degree of freedom of application is improved, and the cost merit in manufacturing and construction is increased. Therefore, not to mention large-scale new heat equipment
The problem of investment recovery can be avoided even in small-scale energy-saving remodeling of heat equipment, which has been considered difficult to recover investment.

It should be noted that the above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, although the present embodiment has mainly described the case where the low NOx burner of the present invention is applied to a reverberatory furnace, the present invention is not particularly limited to this and can be applied to general thermal equipment regardless of direct heating or indirect heating. Further, in the present embodiment, a case has been mainly described in which high temperature combustion air is obtained by alternating combustion using a heat storage body connected to or incorporated in the burner, but the present invention is not particularly limited to this, for example, a combustion air supply system. And the exhaust system by rotating the heat storage body relative to the exhaust system, or by switching the flow direction of the fluid with respect to the heat storage body by using the flow path switching means, etc. The air preheated to a high temperature may be continuously supplied to a single burner for continuous combustion. Further, in the present embodiment, the pipe 8 for flowing the primary air is provided around the fuel nozzle 2 to form the pilot burner in the vicinity of the injection port, but the invention is not particularly limited to this, and in some cases, it may be separated from the fuel nozzle. A pilot burner may be installed near the injection port of the fuel nozzle. Further, although the case where the gas fuel is used is mainly described in the present embodiment, the present invention is not particularly limited to this, and it is also possible to use liquid fuel such as oil.

[0032]

As is apparent from the above description, in the case of the low NOx burner according to the first aspect of the present invention, the combustion for flowing along the surface of the step between the end surface from which the combustion air is ejected and the end surface from which the fuel is ejected. A part of the air stably forms a vortex that flows counter to the flow of the combustion air in the vicinity of the step on the end face from which fuel is ejected, and a part of the fuel gas is entrained to form a flame that becomes a pilot fire. On the other hand, a negative pressure is generated in the step portion and strong exhaust gas recirculation occurs, and the exhaust gas is trapped before the combustion air mixes with the fuel gas to reduce the oxygen concentration, and further downstream from the end surface where the fuel is injected, Since the fuel is attracted to and mixed with the flow of the combustion air, a flame and a combustion gas flow having a strong directivity are formed while causing stable and slow combustion. Therefore, when high-temperature combustion air is used, not only the flame stability is high, but also a highly directional flame and a combustion gas flow can be formed while suppressing the generation of NOx, so that a large space can be formed. It can be burned with a uniform heat flux. Moreover, even when the combustion air is at a low temperature, such as when starting up the furnace, the flow rate of the combustion air slows down, which reduces the amount of flue gas entrained, but since the temperature of the combustion air is low, The generated NOx is small, and conversely, the oxygen concentration is high, so that a stable pilot fire is formed between the fuel jet and the combustion air jet without being extinguished, and the flame is stabilized.
Further, in the case of the invention of claim 2, a stable primary flame can be formed by a simple structure in which the pilot burner is also used as the fuel nozzle and the primary flame can be attracted to the flow side of the combustion air together with the fuel. A stable flame can be formed even when the fuel cells are separated and injected, and the amount of flue gas exhausted can be increased to further reduce NOx.

This is because low NO in the temperature rising process in an iron-based heating furnace operating at a relatively high temperature, for example, 1000 ° C. or higher.
Although it is effective for reducing x, it is particularly effective for reducing NOx and stabilizing flames in a non-ferrous metal melting furnace that operates at a relatively low temperature, which has been considered difficult in the past.

Further, in the case of the third aspect of the invention, the fuel easily flows to the air side, the amount of the fuel gas accompanying the air flow and the fuel to the pilot fire that occurs near the fuel injection port near the step portion. Supply amount increases. For this reason, it is possible to further promote complete combustion, prevent the generation of free unburned components such as CO and HC, and stabilize the pilot fire formed in the step portion to further improve flame stability.

Further, in the case of the present invention as defined in claim 4, since the step portion is formed around or along the injection port of the combustion air, the step portion serves as a guide to inject the combustion air. The direction of the combustion air can be forced by forming a strong direction, and negative pressure is generated in the step portion to cause exhaust gas recirculation. For this reason, the flame and the combustion gas flow having a strong directivity can be formed by entraining the fuel further to the farther side, and the negative pressure is generated in the step portion, so that the strong exhaust gas recirculation in the furnace can be further strengthened. When the step surface is circumscribed with respect to the air nozzle injection port, the area in which the exhaust gas is entrained is large, which is excellent in the function of lowering the oxygen concentration of the combustion air, and the step surface almost covers the air nozzle injection port. When intersecting with each other, the air nozzle is restricted by the refractory block to the tip of the flame holding surface, and an air jet with stronger directivity is ejected from the flame holding surface. Excel.

[Brief description of drawings]

FIG. 1 is a principle view illustrating a schematic structure and a combustion state of a low NOx burner of the present invention, (A) is a vertical sectional view, and (B) is a bottom view.

FIG. 2 is a bottom view showing another embodiment of the low NOx burner of the present invention.

FIG. 3 is a schematic view showing an embodiment using the low NOx burner of the present invention.

FIG. 4 is a graph showing the results of measuring the relationship between the flow rate of combustion air and NOx in the low NOx burner of the present invention.

FIG. 5 is a principle diagram of a general fuel two-stage combustion burner as a conventional low NOx burner.

[Explanation of symbols]

1 Air Nozzle 2 Fuel Nozzle 3 Block of Refractory Material 4 End Face of Refractory Block (Reference Surface) Forming Injection Port of Air Nozzle 5 End Face of Fireproof Block (Flame Retaining Surface) Forming Injection Port of Fuel Nozzle 6 Air injection port 7 Fuel injection port 10 Surface of stepped portion 11 Vortex on flame holding surface of combustion air 12 Primary flame

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Tanaka 2-53, Shitte, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industry Co., Ltd.

Claims (4)

[Claims] 1. A regenerative combustion type burner system in which high temperature combustion air obtained by alternately passing combustion exhaust gas and combustion air through a heat storage body is used to burn the combustion air rather than fuel. A nozzle for injecting fuel at a much higher speed and a nozzle for injecting fuel are arranged in parallel, and they are surrounded by a refractory material, and the end face on which the fuel nozzle injection port is formed and the air nozzle injection port are formed. A low NOx burner, characterized in that a step is provided between the end surface of the fuel nozzle side and the end surface of the fuel nozzle side so as to protrude from the end surface of the air nozzle side. 2. The low NOx burner according to claim 1, wherein the fuel nozzle also serves as a pilot burner. 3. A portion of the injection port of the fuel nozzle near the air nozzle is formed by a diameter-expanded portion having a curved surface or an inclined surface, and a part of the injected fuel flows out toward the air nozzle side. Or the low NOx burner described in 2. 4. The step surface between the end surface of the refractory material having the injection port of the fuel nozzle and the end surface of the refractory material having the injection port of the air nozzle is circumscribed with respect to the injection port of the air nozzle. Alternatively, they intersect with each other.
The low NOx burner according to any one of 1.