JPH09133313A - Nitrogen oxide low generation combustion method and apparatus - Google Patents

Abstract

(57) [Summary] (Correction) [Solution] A central axial fuel injection hole 14 for ejecting auxiliary fuel is provided in the central axial direction at the tip of a fuel pipe 1, and a disc plate larger than the fuel pipe 1 is provided upstream thereof. -A slot 7 is provided and air is ejected from the cylindrical air flow forming air ejection portion 18, so that the excess fuel ejection portion 22 has excess fuel and the excess air ejection portion has excess air. The fuel from the side fuel jet portions 5 and 6 is jetted at a right angle to the air flow jetted from 3, and the mixed combustion is performed while performing the rich and lean combustion. From the central axial fuel jet hole 14, 10 to 10 of all fuel
20% is injected as an auxiliary fuel in the direction of the central axis to burn while combusting the combustion gas in the furnace, and the ratio of the air flow velocity in the long hole-shaped air ejection part 3 to the fuel flow velocity in the side fuel ejection parts 5, 6 Is 0.
It should be 2 or more. [Effect] By using the unique low NOx combustion method and its device, the conventional problems can be solved and the generation of NOx can be significantly suppressed as compared with the conventional burner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for low nitrogen oxide generation combustion.

[0002]

2. Description of the Related Art Emission regulations for NOx generated by combustion are becoming stricter year by year, and technological development for reducing NOx is being actively conducted. NOx generated during combustion includes fuel NOx, prompt NOx, and thermal NOx.
It is said that among these, thermal NOx is generated by the oxidation of nitrogen molecular components in combustion air in a high temperature atmosphere, and has high temperature dependence,
The production amount rapidly increases as the combustion temperature increases.
Thermal NOx is always generated when a nitrogen molecule component is present in the combustion gas, and especially when the fuel is a hydrocarbon-based gaseous fuel, most of the NOx discharged is said to be thermal NOx, and many reductions are made. A method has been devised. For the purpose of reducing thermal NOx, combustion methods such as a multi-stage combustion method, an exhaust gas recirculation method and a lean combustion method have been devised, and many combustion methods combining several methods have been devised.

[0003]

The multi-stage combustion method is characterized in that fuel or combustion air is divided into two or more stages and burned, and low NOx is caused by a decrease in flame temperature or a decrease in oxygen concentration. It realizes combustion. In such a combustion method, there is a problem that the combustor becomes complicated because the combustion is performed in multiple stages. The exhaust gas recirculation method aims to lower the flame temperature and oxygen concentration by mixing a part of the combustion gas with the combustion air or fuel.The forced exhaust gas recirculation method and the self-exhaust gas recirculation method are used. It is roughly divided into. The forced exhaust gas recirculation method is the most general method in which a part of combustion gas is forcibly mixed with combustion air or fuel by using a recirculation duct and a blower. In the self-exhaust gas recirculation method, by devising a combustor and using the phenomenon that the surrounding gas is sucked into the jet flow, it is possible to mix the combustion gas with the combustion air flow and fuel flow to have the effect of exhaust gas recirculation As a feature, there is an advantage that the effect of exhaust gas recirculation can be obtained without forcibly recirculating the combustion gas. Further, there is no complexity of dividing fuel or combustion air into a plurality of systems unlike the multi-stage combustion method. As a combustor characterized by utilizing self-exhaust gas recirculation, there is, for example, JP-A-62-17506, and many other combustors use the self-exhaust gas recirculation method, but NOx reduction Has a limit, and further technological development is needed to comply with the recent severe NOx regulations. Therefore, as a combustion method making the most of the merit of the self-exhaust gas recirculation method, Japanese Patent Laid-Open No. 1-3010
3, Japanese Patent Laid-Open No. 3-91601 and Japanese Utility Model Laid-Open No. 52-61545. In these combustion methods, in order to maximize the effect of self-exhaust gas recirculation, the burner does not have a flame holding mechanism, and the combustion air flow and the fuel flow are separated and injected into the furnace independently. It is characterized by that. As a result, the flame is lifted and formed without being fixed to the burner, and a portion of the combustion gas in the furnace is sufficiently sucked into the fuel flow and the combustion air flow before combustion starts. In such a combustion method, the flame becomes a slow diffusion flame, but since it does not have a flame holding mechanism, it may not be able to be used unless the temperature of the combustion region is high in order to obtain stable ignition, a heating furnace, It is suitable for high-temperature furnaces such as melting furnaces, but when used for boilers and low-temperature heating furnaces, the problem is that the amount of unburned components increases and the furnace body must be enlarged for complete combustion. was there. There is also a method of using a premixed flame as a method of reducing thermal NOx. In premixed combustion, burning NOx with a high air ratio can significantly reduce NOx, but in high air ratio burning, excess air increases, resulting in a large decrease in combustion and heat transfer efficiency and stability of the premixed flame. There was a problem that it was inferior to. Then, as a method of reducing the thermal NOx by giving the effect of self-exhaust gas recirculation to premixed combustion, Japanese Patent Laid-Open No. 3-17
There is 5211. In such a combustion method, by adding a device to the flame stabilizer, before the premixed gas burns,
NOx is reduced by mixing a part of the low-temperature combustion gas with a premixed gas to reduce the flame temperature or reduce the oxygen concentration. In such a combustion method and combustion apparatus, since the premixed combustion is used, a mixer for producing the premixed gas is required, and since the premixed gas within the flammability limit is used, the flame is burned in the burner or mixed. There are problems common to premixed combustors, such as the danger of so-called backing when returning to the interior of the reactor. Also, since a part of the combustion gas is mixed with the combustible premixed gas, if the combustion gas to be mixed is at a high temperature, it will ignite as soon as the premixed gas mixes with the combustion gas, and the effect of self-exhaust gas recirculation will be improved. There is a problem that the flame stabilizer needs to be specially devised in order to mix the premixed air and a part of the combustion gas so that the premixed air does not ignite. As described above, the self-exhaust gas recirculation method has a merit that the combustion device is simple and low NOx combustion is possible as compared with other low NOx combustion methods such as the multi-stage combustion method and the lean premixed combustion method. have. Thermal N using self exhaust gas recirculation
In the combustion method aiming at the reduction of Ox, the problem that the furnace temperature range that can be used is limited and the usable combustion equipment is limited in the method that makes maximum use of the self-exhaust gas recirculation for the diffusion flame. There was a point. In addition, in the case of applying self-exhaust gas recirculation to the premixed flame, there is a problem of flame stability peculiar to the premixed combustor such as back combustion, and a special device is required for the flame stabilizer. was there.
Combustion technology that uses the self-exhaust gas recirculation method more effectively is desired in order to meet the increasingly stringent NOx regulations of the combustor and realize even lower NOx combustion. The object of the present invention is made by paying attention to such a point, and while using the diffusion combustion, to advance the density combustion,
It is intended to provide a low-nitrogen-oxide generation combustion method and a combustion apparatus which effectively perform self-exhaust gas recirculation before the combustion thereof and have excellent flame stability even in a low temperature atmosphere.

[0004]

In order to solve the above-mentioned problems, the present invention provides a shield plate provided with a plurality of long hole-shaped air jetting portions on the outer periphery of the tip of a fuel tube inserted into an air tube, The plurality of long hole-shaped air jets are composed of a fuel excess jet and an air excess jet, and form a cylindrical air flow forming air jet on the edge side of the shield plate. Side fuel injection pipes communicating with the fuel pipe are installed on both sides of the air ejection portion, and side fuel ejection portions for ejecting fuel in the circumferential direction of the shielding plate are provided on the side portions of the fuel ejection pipe. A fuel injection hole is provided at the tip of the fuel pipe so as to project from the shield plate, and a fuel injection hole for ejecting auxiliary fuel in the direction of the fuel tube is provided at the tip of the fuel pipe. A disk plate larger than the fuel pipe is installed on the upstream side of the ejection hole, and the cylindrical air While ejecting air from the forming air ejector, the air flow ejected from the elongated hole air ejector is such that excess fuel is excessive in the fuel excess ejector and excessive air is excessive in the air excess ejector. On the other hand, the fuel ejected from the side fuel ejecting portion is ejected in a right angle direction to perform the mixed combustion while performing the rich and lean combustion, and 10 to 20% of the total fuel is ejected from the central axial fuel ejection hole.
As auxiliary fuel in the direction of the central axis, and the combustion energy in the furnace is combusted by the jet energy, and the air flow velocity at the elongated hole air ejection portion and the fuel flow velocity at the side fuel ejection portion are generated. The present invention provides a method for combustion with low generation of nitrogen oxides, wherein the ratio is 0.2 or more.

According to the present invention, in order to solve the above-mentioned problems, a shield plate provided with a plurality of long hole-shaped air jetting portions is provided on the outer periphery of the tip of a fuel tube inserted in an air tube, and The hole-shaped air ejection portion is composed of an excessive fuel ejection portion and an air excess ejection portion, and a cylindrical air flow forming air ejection portion is formed on the edge side of the shield plate, and both sides of the plurality of elongated hole air ejection portions are formed. Is provided with a side fuel ejection pipe communicating with the fuel pipe, and a side fuel ejection portion for ejecting fuel in the circumferential direction of the shielding plate is provided on a side portion of the fuel ejection pipe. Of the fuel tube is protruded from the shielding plate, and a central axial fuel injection hole for ejecting auxiliary fuel in the central axis direction of the fuel tube is provided at the distal end of the fuel tube, and the upstream side of the central axial fuel injection hole is formed. A nitrogen plate lower than the fuel pipe is installed in There is provided a raw combustion apparatus.

In order to solve the above-mentioned problems, the present invention configures the shape of the fuel injection hole in the central axis direction into a slit circular hole,
A low-nitrogen oxide combustion method is provided which is characterized in that a ring-shaped fuel is ejected from the fuel injection hole in the central axis direction so as to carry out mixed combustion while the gas in the furnace is accompanied. .

In order to solve the above problems, the present invention provides a low-nitrogen oxide combustion apparatus characterized in that the shape of the fuel injection hole in the central axis direction is a slit hole.

In order to solve the above-mentioned problems, the present invention provides a swirl vane in a slit circular hole, ejects a swirling ring-shaped fuel from the slit circular hole, and mixes combustion with gas in the furnace. The present invention provides a method for low-nitrogen-oxide generation combustion, which comprises:

In order to solve the above-mentioned problems, the present invention provides a low-nitrogen-oxide generation combustion apparatus characterized in that a swirl vane is installed in a slit circular hole.

According to the present invention, in order to solve the above-mentioned problems, the cylindrical air flow forming air ejecting portion is formed by providing an annular slit between the air pipe and the shield plate, and the annular slit forms a cylindrical shape. The invention provides a method for low-nitrogen oxide generation combustion, which is characterized in that the air is jetted and burned.

In order to solve the above-mentioned problems, the present invention is characterized in that the cylindrical air flow forming air jet portion is formed by providing an annular slit between the air pipe and the shield plate. A low-nitrogen oxide generation combustion device is provided.

According to the present invention, in order to solve the above-mentioned problems, the cylindrical air flow forming air jetting portion is constituted by arranging a large number of small holes in an annular shape inside the edge of the shield plate, and The present invention provides a method for low-nitrogen oxide generation combustion, which is characterized in that air is jetted from the small holes and burned.

According to the present invention, in order to solve the above-mentioned problems, the cylindrical air flow forming air jet portion is formed by arranging a large number of small holes in an annular shape inside the edge of the shield plate. A feature of the present invention is to provide a nitrogen oxide low generation combustion device.

In order to solve the above-mentioned problems, the present invention is characterized in that the area of the air jet portion for forming a cylindrical air flow is set to 20% or less of the total air introduction area for combustion. A method for low-nitrogen oxide generation combustion is provided.

In order to solve the above-mentioned problems, the present invention is characterized in that the area of the air jet portion for forming a cylindrical air flow is 20% or less of the total air introduction area. A low-nitrogen oxide generation combustion device is provided.

According to the present invention, in order to solve the above-mentioned problems, the excessive fuel jet portion and the excessive air jet portion are formed by relatively changing the areas of a plurality of elongated hole-like air jet portions. The present invention provides a low-nitrogen oxide generation combustion method, characterized in that a dark and light combustion is performed on the downstream side of the above-mentioned portion and the excessive air jet portion.

In order to solve the above-mentioned problems, the present invention is characterized in that the excessive fuel jet portion and the excessive air jet portion are formed by relatively changing the areas of a plurality of long hole-shaped air jet portions. A low-nitrogen oxide generation combustion device is provided.

According to the present invention, in order to solve the above-mentioned problems, the excessive fuel jet portion and the excessive air jet portion have the size of the hole of the side fuel jet portion relative to each corresponding long hole-like air jet portion. The present invention provides a low-nitrogen oxide generation combustion method, characterized in that rich and lean combustion is performed on the downstream side of the fuel excess jetting portion and the air excess jetting portion.

According to the present invention, in order to solve the above-mentioned problems, the excessive fuel jet portion and the excessive air jet portion have the size of the hole of the side fuel jet portion relative to each corresponding long hole-like air jet portion. The present invention provides a low-nitrogen oxide-generating combustion device, which is characterized in that

According to the present invention, in order to solve the above-mentioned problems, the excess fuel jet portion and the excess air jet portion are constructed by relatively changing the areas of a plurality of elongated hole-like air jet portions, and the side fuel It is characterized in that the size of the hole of the jet portion is relatively changed for each corresponding long-hole-shaped air jet portion, and the rich and lean combustion is executed on the downstream side of the fuel excess jet portion and the air excess jet portion. A method for low-nitrogen oxide generation combustion is provided.

According to the present invention, in order to solve the above-mentioned problems, the excess fuel jet portion and the excess air jet portion are formed by relatively changing the areas of a plurality of elongated hole-like air jet portions, and the side fuel The present invention provides a low-nitrogen-oxide-generating combustion device, characterized in that the size of the holes in the ejection part is relatively changed for each corresponding long-hole-shaped air ejection part.

In order to solve the above-mentioned problems, the present invention is characterized in that the combustion air introduced into the air pipe is oxygen enriched air having a volume concentration of oxygen of 21% or more. It provides a method.

The present invention separates a part of the fuel in a diffusion flame formed by ejecting fuel from the direction perpendicular to the air stream ejected from the elongated air ejecting portion so that the air envelops the fuel. By ejecting as auxiliary fuel and burning the diffusion flame without fixing it to the air ejection portion or the fuel ejection portion, and before forming the diffusion flame,
A part of the combustion gas is entangled in the auxiliary fuel flow, the air flow and the fuel flow to effectively realize self-exhaust gas recirculation, and by forming the above diffusion flame with different air ratios, Implement effective light and shade combustion. During such combustion, the air ejected from the cylindrical air flow forming air ejection portion forms a cylindrical air flow on the downstream side of the shielding plate, and a strong negative pressure portion is formed inside the cylindrical air flow. As a result, the internal recirculation is further promoted by the increase of the reverse flow and the recirculation flow of the combustion gas flow in the furnace. With the further promotion of this internal recirculation, a strong ignition source is created by the recirculation of high temperature combustion gas in the furnace, which provides excellent flame holding performance and combustion stability, and the self-exhaust gas recirculation combustion described above is performed. This is to promote effectively, and in addition to the above-mentioned rich and lean combustion, to significantly reduce NOx.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in FIGS. 1 and 2 and FIGS. 3 and 4, reference numeral 1 is a fuel tube inserted in an air tube 2, and the tip of the fuel tube 1 is A shield plate 4 provided with a plurality of long hole-shaped air jets 3 is installed on the outer periphery, and a cylindrical air flow forming air jet part 18 is formed on the edge side of the shield plate 4. Side fuel ejection pipes 5 communicating with the fuel pipe 1 are installed on both sides of the fuel ejection unit 3, and side fuel ejection pipes ejecting fuel in the circumferential direction are provided on the side fuel ejection pipes 5 on their sides. The part 6 is provided. The plurality of long hole-shaped air ejecting portions 3 are composed of an excessive fuel ejecting portion 22 and an excessive air ejecting portion 23, and an auxiliary fuel is provided at the tip of the fuel pipe 1 in the central axis direction of the fuel pipe 1. A central axial fuel jet hole 14 for jetting is provided, and a disc plate 7 larger than the fuel pipe 1 is provided upstream of the central axial fuel jet hole 14. The shape of the fuel injection hole 14 in the central axis direction may be a slit circular hole 15 as shown in the drawing. The cylindrical air flow forming air ejection portion 18 may be configured by providing an annular slit 19 between the air tube 2 and the shield plate 4, as shown in the drawing, or
You may comprise by arranging the small holes 20 annularly inside the edge of the shield plate 4. For convenience, the small holes 20 are shown only in FIGS. 2 and 4.

In the case of FIGS. 1 and 2, the excessive fuel jet portion 22 and the excessive air jet portion 23 are formed by relatively changing the areas of the plurality of long hole-shaped air jet portions 3. That is,
In the figure, for example, one air excess ejection portion 23 is provided with two fuel excess ejection portions 22 each having a smaller area.
Is provided. Since the amount of fuel jetted from each side fuel jetting portion 6 does not change, in this case, in the downstream of the air excess jetting portion 23 in which the long hole-shaped air jetting portion 3 has a large area, an excess air lean combustion flame is generated. Is formed, and a rich-fuel rich combustion flame with excess fuel is formed downstream of the two fuel excess injection portions 22 having a small area.

In the case of FIGS. 3 to 4, the areas of the plurality of long hole-shaped air ejecting portions 3 are configured to have the same size, and the area of the side fuel ejecting portion 6 is changed so that the excess fuel ejecting portion 22 is formed. And the excess air jetting section 23. For example, as shown in the figure, one excess air jet 23 having a size of d2
Is d1 of the side fuel jet portion 6 of the other fuel excess jet portion 22.
Since it is configured to be small, a lean combustion flame is formed downstream of one air excess jetting portion 23, and a rich-lean combustion flame is formed downstream of another fuel excess jetting portion 22. . Since the side fuel jetting portion 6 is composed of a plurality of holes, the size of the hole is changed corresponding to the long hole-shaped air jetting portion 3.

Excessive fuel jet 22 and excessive air jet 23
Is configured by relatively changing the areas of the plurality of long hole-shaped air ejecting portions 3 and relatively changing the areas of the plurality of side portion fuel ejecting portions 6 for each corresponding long hole-shaped air ejecting portion 3. It may be configured so that the rich and lean combustion is performed on the downstream side of the excessive fuel jet portion 22 and the excessive air jet portion 23. That is, by effectively changing the amount of jetted air, the amount of jetted fuel is also changed, and the ratio of both air ratios is appropriately set, so that effective lean-burn combustion can be performed.

Air is ejected from the plurality of long hole-shaped air ejecting portions 3, and the fuel gas is ejected from the side fuel ejecting portion 6 in a direction perpendicular to the air flow in the air flow. At this time, the ratio of the air flow velocity in the long hole-shaped air jet portion 3 and the fuel gas flow velocity in the side fuel jet portion 6 is set to 0.2 or more, and in actual operation, it is set to about 0.2 to 5. . When the ratio is set to 0.2 or less, the fuel gas penetrates the air flow, collides with the inner wall of the air tube 2 and diffuses to form a flame fixed on the air tube 2, so the ratio is 0. It cannot be less than or equal to 2. However, when the ratio is set as described above, not only does the diffusion flame fixed in the long hole-shaped air ejection portion 3 not occur, but the fuel gas flow 9 ejected from the right angle direction is
As shown in FIG. 5, the flow is in a state of being trapped in the air flow 10. At this time, from the fuel injection hole 14 in the central axis direction,
When the auxiliary fuel is ejected toward the fuel gas flow 9, the air flow 10, the in-furnace combustion gas flow 11, the internal recirculation region 12, etc., the auxiliary fuel 17 entrains the combustion gas before it burns, and The self-exhaust gas recirculation in the circulation region 12 is further promoted, the internal recirculation promotion region 8 is formed, and further reduction of NOx can be realized. That is, a fuel gas flow 9 is formed in the center, a donut-shaped air flow 10 is formed around it, and a wake indicated by an arrow is formed on the outer periphery thereof. Stream 17 is formed. Thus, the air flow 10 has a high-temperature furnace gas flow 11 from the outside, and at the same time from the inside,
The fuel gas stream 9 and the auxiliary fuel stream 17 are diffusively mixed.
In a normal diffusion flame, a flame is settled in the air ejection hole or the fuel gas ejection hole, so that the fuel starts burning before the air flow accompanies the gas in the surrounding furnace. Has the above-mentioned flow velocity ratio, so that the flame is not attached to the long hole-shaped air ejection portion 3 and the side fuel ejection portion 6. That is, in the present invention, the air flow 10 is the gas flow 1 in the furnace surrounding it.
As the temperature rises while mixing with 1, the fuel gas flow 9 and the auxiliary fuel flow 17 inside thereof gradually form a mixed state. Then, the four members develop a good mixed state, and combustion is started when the ignition conditions are satisfied at various points of temperature, fuel concentration, and oxygen concentration, and a diffusion flame is formed. In such a diffusion flame, a part of the combustion gas is sufficiently mixed with the combustion air, that is, the auxiliary fuel flow before the combustion starts, so that the effect of self-exhaust gas recirculation is maximized and the flame temperature NOx decreases remarkably due to the decrease in the oxygen concentration. In the above, the internal recirculation region 12 and the external recirculation region 13 are defined as the furnace gas flow 11
It greatly contributes to the large amount of wakes.

In the above combustion, according to the present invention, since the plurality of long hole-shaped air jets 3 are constituted by the fuel excess jet 22 and the air excess jet 23, the fuel excess combustion and the air excess combustion proceed at the same time. To do. That is, in the excessive fuel injection portion 22,
A rich combustion flame with excess fuel is formed, and a lean combustion flame with excess air is formed at the excess air jet portion 23.
The former rich combustion flame has a lower NOx value compared to the theoretical air amount combustion flame due to the lack of oxygen concentration and the resulting decrease in flame temperature, and the latter lean combustion flame due to the decrease in flame temperature. . Therefore, effective rich / lean combustion is performed by appropriately setting the ratio of both air ratios so that the excess air on the lean fuel combustion side can sufficiently burn the excess fuel on the excess fuel side. At this time, discharge N
As described above, the Ox value is a weighted average of the fuel flow rate ratios of both flames showing a lower value than the combustion flame in the vicinity of the theoretical air ratio, so that a low NOx value can be obtained for the entire combustion. Further, in the present invention essentially having no flame fixing portion, since the combustion gas is sufficiently accompanied by the fuel and the combustion air before the start of combustion, the oxygen concentration and the flame temperature decrease more effectively. It is possible to reduce NOx. Such rich-lean combustion can synergize with the above-mentioned unique combustion to further reduce NOx. (See FIGS. 8 and 9)

During the above combustion, the air ejected from the air ejecting portion 18 for forming a cylindrical air flow forms a cylindrical air flow 21 on the downstream side of the shielding plate 4, and the air inside the cylindrical air flow 21 is strongly compressed. Negative pressure part is formed, the back flow of combustion gas in the furnace,
Increased recirculation flow further facilitates self-exhaust gas recirculation within the internal recirculation zone 12. With the further promotion of this internal recirculation, a strong ignition source is created by the recirculation of high temperature combustion gas in the furnace, which provides excellent flame holding performance and combustion stability, and the self-exhaust gas recirculation combustion described above is performed. It effectively promotes and promotes the NOx reduction effect. The cylindrical air flow forming air ejection portion 18 has an annular slit 19 or a small hole 20.
Even if it is composed of, the same action and effect are brought about. Further, if the area of the above-mentioned cylindrical air flow forming air ejection portion 18 is 20% or less of the total front air introduction area,
It promotes the action and effect. (See Figure 10). Further, during the above combustion, the air jet portion 18 for forming a cylindrical air flow is formed.
Makes a great contribution to the expansion of the combustion range. That is, FIG. 11 shows a cylindrical air flow forming air ejection portion 1
8 shows the results of measuring the upper limit and the lower limit of the CO limit air ratio in the case where there is 8 and the case where it is not shown. From this figure, the cylindrical air flow forming air ejection portion 18 of the present invention is It can be clearly understood that the CO upper limit air ratio is significantly increased.

In the case of the present invention in which the side fuel jet pipes 5 are provided on both sides of the long hole-shaped air jet portion 3, a plurality of side fuel jet portions 6 are provided and the shield plate is divided from the plural places. Since the fuel can be jetted in the circumferential direction of 4 and in the direction perpendicular to the air flow 10 of the long hole-shaped air jetting portion 3,
Diffusion mixing with the above-described pre-combustion air stream 10, fuel gas stream 9 and part of the in-furnace combustion gas stream 11 is well performed,
Maintain low NOx combustion more effectively.

Further, since the disc plate 7 is provided, the internal recirculation promoting region 8 is formed on the downstream side of the disc plate 7 and the internal recirculation region 12 is expanded to remarkably increase the recirculation amount of exhaust gas. However, it further increases the effect of reducing NOx. That is, due to the existence of the disc plate 7, the air flow 1
The expansion of 0 to the high temperature internal recirculation region 12 side is prevented, and the amount of self exhaust gas recirculation increases. Such an increase in the accompanying flow rate remarkably promotes the NOx reduction effect.

Further, by forming the shape of the fuel injection hole 14 in the direction of the central axis into the slit circular hole 15, the ring-shaped fuel is wake-mixed while being expanded, so that the contact area with the in-reactor gas 11 is increased. It increases the amount and further contributes to the NOx reduction effect.

Further, the swirl vane 1 is provided in the slit circular hole 15.
In the case of No. 6, since the fuel is ejected in a ring shape while swirling, the gas entrainment in the furnace is increased, and the wake effect is further improved to promote the NOx reduction effect.

Further, a shield plate 4 provided in contact with the outer periphery of the tip of the fuel pipe 1 provided in the air pipe 2 and the inner wall of the air pipe 2.
Is provided with a long hole-shaped air ejecting portion 3, and the combustion air is ejected from the long hole-shaped air ejecting portion 3, so that the surface area of the jet flow can be increased and the surrounding combustion gas can be efficiently emitted. Can be waked. In addition, the long hole-shaped air ejection portion 3
Is formed in plural, the air flow 10 is divided and ejected, and each jet is accompanied by the in-furnace gas flow 11. Therefore, compared with a combustor having a single air jet, The surrounding combustion gas can be efficiently circulated, and the effect of self-exhaust gas recirculation can be enhanced. An internal recirculation region 12 is formed in a portion surrounded by a plurality of combustion air jets, and an external recirculation region 13 is formed in the periphery, so that a part of the combustion gas is recirculated in both recirculation regions. And is accompanied by the jet of combustion air. In particular, since the high temperature combustion gas circulates in the internal recirculation region 12, a diffusion flame having no fixing portion is ignited stably to form a flame.

By jetting the fuel at right angles to the air flow and adjusting the ratio of the air flow velocity to the fuel flow velocity as described above, the fuel jet can be jetted to the center of the combustion air jet. . In this case, as shown in FIGS. 6 and 7, the fuel jet forms a so-called twin vortex. As the fuel and the air are mixed, the vortices develop as they move away from the side fuel jet portion 6 and further from the long hole-shaped air jet portion 3. Not only the fuel and air are mixed in this vortex, but also a part of the combustion gas entrained in the air is gradually entrained, and a sufficient amount of combustion gas for fuel ignition is entrained. Then, the fuel starts to burn. Due to this vortex, the flame is stably ignited without being fixed to the long hole-shaped air ejection portion 3 and further to the side fuel ejection portion 6. When the fuel is jetted in a direction perpendicular to the direction of the air flow 10 passing through the long hole-shaped air jet portion 3, if the ratio of the flow velocity of the combustion air jet to the fuel jet is set to 0.2 or more, the flame As described above, is formed without fixing to the ejection holes, resulting in a significantly low NOx flame.

During the above combustion, the auxiliary fuel is ejected from the central axial fuel injection hole 14 in the central axis direction of the fuel pipe 1. Therefore, as described above, the mixing of the auxiliary fuel and the in-reactor gas does not occur before combustion. The NOx reduction effect is further promoted by synergistically promoting the above-mentioned combustion. During such self-exhaust gas recirculation combustion, the cylindrical air flow 21 formed by the above-mentioned cylindrical air flow forming air jetting portion 18 forms an effective continuous ignition source therein, and the self-exhaust gas recirculation combustion is effective. It is as described above that it is to be stabilized.

In the above combustion, if the shape of the fuel injection hole 14 in the central axis direction is formed as a slit circular hole 15,
Since the auxiliary fuel is jetted in a ring shape, the contact area with the gas in the furnace is increased and the wake effect is remarkably improved, so that N
Promotes Ox reduction effect.

Further, the swirl vane 1 is provided in the slit circular hole 15.
In the case of No. 6, since the fuel is ejected in a ring shape while swirling, the gas entrainment in the furnace is increased, and the wake effect is further improved to promote the NOx reduction effect.

In the above combustion, by using oxygen-enriched air having a volume concentration of oxygen of 21% or more as the combustion air to be introduced into the air pipe 2, the combustion of low NOx is continued and the combustion amount Can be increased.

In FIG. 8, the areas of the plurality of long hole-shaped air jetting portions 3 are changed so that the fuel excess jetting portion 22 and the air excess jetting portion 2 are changed.
3 shows the NOx reduction effect of the structure of FIG. Compared with the conventional example, the air / fuel flow rate ratio is 0.2 or more, 10 to 20% of the total fuel is ejected as an auxiliary fuel, and the area of the cylindrical air flow forming air ejecting portion 18 is introduced into the total air. It can be understood that NOx is remarkably reduced by configuring the area to be 20% or less and performing the above-described rich and lean combustion.

In FIG. 9, the areas of the side fuel jets 6 are changed without changing the areas of the plurality of long hole-shaped air jets 3 to form the excess fuel jets 22 and the air excess branch jets 23. It shows the NOx reduction effect of the constituents.
Compared with the conventional example, the flow velocity ratio of air / fuel is 0.2 or more, 10 to 20% of the total fuel is ejected as an auxiliary fuel, and the cylindrical air flow forming air ejecting portion 18 is the total air introduction amount area. It can be understood that NOx is remarkably reduced when the above-mentioned rich-lean combustion is carried out with the composition of 20% or less.

[0043]

The present invention solves the problems of the prior art all at once by using the unique low NOx combustion method and its apparatus as described above, and remarkably suppresses the generation of NOx as compared with the conventional burner. It is an excellent thing you can do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing another embodiment of the present invention.

FIG. 4 is an explanatory view showing another embodiment of the present invention.

FIG. 5 is a schematic diagram showing a fluid flow and a wake state.

FIG. 6 is a schematic diagram showing a fuel flow in an air flow.

FIG. 7 is a schematic diagram showing a fuel flow in an air flow.

FIG. 8 is a NOx performance diagram comparing the present invention with a conventional method.

FIG. 9 is another NOx comparing the present invention with the conventional method.
It is a performance diagram.

FIG. 10 is a NOx performance diagram comparing the effect of the ratio of the area of the air ejecting portion for forming a cylindrical air flow of the present invention to the total air introduction area with that of a conventional burner.

FIG. 11 is a performance comparison diagram showing the results of measurement of the upper limit and the lower limit of the CO limit air ratio with and without the cylindrical air flow forming air ejection portion.

[Explanation of symbols] [Explanation of symbols]

 1 Fuel Pipe 2 Air Pipe 3 Long Hole Air Jet 4 Shield 5 Side Fuel Jet 6 Side Fuel Jet 7 Disc Plate 8 Internal Recirculation Promotion Area 9 Fuel Gas Flow 10 Air Flow 11 Reactor Gas Flow 12 Internal recirculation region 13 External recirculation region 14 Central axial fuel injection hole 15 Slit circular hole 16 Swirl vane 17 Auxiliary fuel flow 18 Cylindrical air flow forming air injection part 19 Annular slit 20 Small hole 21 Cylindrical air flow 22 Fuel Excessive spout

Claims (19)

[Claims] 1. A shield plate provided with a plurality of elongated hole-like air ejection portions is installed on the outer periphery of a tip end portion of a fuel tube charged in an air tube, and the plurality of elongated hole-like air ejection portions are provided with excess fuel ejection. And an excess air jet portion, a cylindrical air flow forming air jet portion is formed on the edge side of the shielding plate, and a side communicating with the fuel pipe on both sides of the plurality of elongated hole air jet portions. Part fuel injection pipe is installed, a side fuel injection part for ejecting fuel in the circumferential direction of the shield plate is provided on the side part of the fuel injection pipe, and the tip end of the fuel pipe projects from the shield plate. Let
A central axial fuel injection hole for ejecting auxiliary fuel in the central axial direction of the fuel pipe is provided at the tip of the fuel pipe, and a disc plate larger than the fuel pipe is provided upstream of the central axial fuel injection hole. The long hole-shaped air is installed so that air is jetted from the cylindrical air flow forming air jetting portion while excess fuel is produced in the fuel excess jetting portion and air is excess in the air excess jetting portion. With respect to the air flow ejected from the ejection portion, the fuel ejected from the side fuel ejection portion is ejected at a right angle direction, while performing mixed combustion, performing the rich and lean combustion, and from the central axial fuel ejection hole, 10 of all fuel
Approximately 20% of the auxiliary fuel is ejected in the direction of the central axis, and the energy of the ejection is used to burn the combustion gas in the furnace while accompanying it, and the air velocity at the elongated hole air ejection portion and the side fuel ejection portion The low-nitrogen oxide generation combustion method, characterized in that the ratio of the fuel flow velocity is 0.2 or more. 2. A shield plate provided with a plurality of elongated hole-like air ejection portions is installed on the outer periphery of a fuel pipe tip portion charged in an air pipe, and the plurality of elongated hole-like air ejection portions are provided with excess fuel ejection. And an excess air jet portion, a cylindrical air flow forming air jet portion is formed on the edge side of the shielding plate, and a side communicating with the fuel pipe on both sides of the plurality of elongated hole air jet portions. Part fuel injection pipe is installed, a side fuel injection part for ejecting fuel in the circumferential direction of the shield plate is provided on the side part of the fuel injection pipe, and the tip end of the fuel pipe projects from the shield plate. Let
A central axial fuel injection hole for ejecting auxiliary fuel in the central axial direction of the fuel pipe is provided at the tip of the fuel pipe, and a disc plate larger than the fuel pipe is provided upstream of the central axial fuel injection hole. A low-nitrogen oxide generation combustion device characterized by being installed. 3. The shape of the central axial fuel injection hole is formed as a slit circular hole, and a ring-shaped fuel is ejected from the central axial fuel injection hole, and burns while wake mixing the in-reactor gas. The method for low-nitrogen oxide generation combustion according to claim 1, wherein the method is as described above. 4. The low-nitrogen oxide combustion device according to claim 2, wherein the shape of the fuel injection hole in the central axis direction is a slit circular hole. 5. A swirl vane is provided in the slit circular hole, and a swirling ring-shaped fuel is ejected from the slit circular hole to carry out mixed combustion with the gas in the furnace accompanied. 4. A method for low-nitrogen oxide combustion according to 1. 6. The low-nitrogen oxide combustion apparatus according to claim 4, wherein a swirl vane is provided in the slit circular hole. 7. The cylindrical air flow forming air jetting portion is configured by providing an annular slit between the air tube and the shield plate,
6. The low-nitrogen-oxide generation combustion method according to claim 1, wherein combustion is performed while ejecting air in a cylindrical shape from the annular slit. 8. The air jet part for forming a cylindrical air flow is formed by providing an annular slit between an air tube and a shield plate, according to claim 2, 4, or 6. Nitrogen oxide low generation combustor. 9. The cylindrical air flow forming air jetting portion is constituted by arranging a large number of small holes annularly inside the edge of a shield plate, and air is jetted and burned from the large number of small holes. 6. The low-nitrogen oxide generation combustion method according to claim 1, 3 or 5. 10. The cylindrical air flow forming air jetting portion is configured by arranging a large number of small holes annularly inside the edge of the shield plate. 6. A low-nitrogen oxide combustion device according to item 6. 11. The cylindrical air flow forming air jetting portion is configured to have an area of 20% or less with respect to the total air introduction area for combustion. 7
Alternatively, the low-nitrogen oxide generation combustion method according to the item 9. 12. The area of the cylindrical air flow forming air jetting portion is set to be 20% or less of the total air introduction area, as claimed in claim 2, 4, 6, 8 or 10. A low-nitrogen oxide generation combustion device as described. 13. The excessive fuel jet portion and the excessive air jet portion are
The plurality of elongated hole-shaped air jetting portions are configured to be relatively changed in area, and the rich and lean combustion is executed on the downstream side of the fuel excess jetting portion and the air excess jetting portion. 5, 7, 9 or 11 nitrogen oxide low generation combustion method. 14. The excess fuel jetting portion and the air excess jetting portion are formed by relatively changing the areas of a plurality of elongated hole-like air jetting portions. 1
The low-nitrogen oxide generation combustion device according to 0 or 12. 15. The fuel excess jetting portion and the air excess jetting portion are
The size of the hole of the side fuel jetting portion is relatively changed for each corresponding long hole-shaped air jetting portion, and the rich and lean combustion is executed on the downstream side of the fuel excess jetting portion and the air excess jetting portion. The low-nitrogen oxide generation combustion method according to claim 1, 3, 5, 7, 9 or 11, wherein 16. The excessive fuel jet portion and the excessive air jet portion are characterized in that the size of the hole of the side fuel jet portion is relatively changed for each corresponding long-hole air jet portion. The nitrogen oxide low generation combustion device according to claim 2, 4, 6, 8, 10 or 12. 17. The excessive fuel ejecting portion and the excessive air ejecting portion are configured by relatively changing the areas of a plurality of elongated hole-like air ejecting portions, and the size of the holes of the side fuel ejecting portion is adjusted. 2. The lean-hole air jetting section is configured to be relatively changed for each, and the rich-lean combustion is executed on the downstream side of the fuel excess jetting section and the air excess jetting section.
3. A low-nitrogen oxide generation combustion method according to 3, 5, 7, 9 or 11. 18. The excessive fuel ejecting portion and the excessive air ejecting portion are formed by relatively changing the areas of a plurality of elongated hole-like air ejecting portions, and the sizes of the holes of the side fuel ejecting portions are adjusted. It is configured such that it is relatively changed for each elongated hole-shaped air jetting part.
2. A low-nitrogen oxide combustion device according to 2. 19. The combustion air to be introduced into the air pipe is oxygen-enriched air having a volume concentration of oxygen of 21% or more.