JP2000039108A - LOW NOx BURNER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a gas jetting method which reduces NOx unburned components of a combustion gas most efficiently by maximizing penetration force within a range of a flow rate and a pressure difference of a gas supply source allowable by presently available boilers to reflect it on the development of burners. SOLUTION: In a burner which jets a gas toward a stream of pulverized coal flowing to a combustion furnace from a primary nozzle 1 at the center part of the burner from the outer circumference part of the primary nozzle 1, at least one gas jetting port 12 is provided in the circumferential direction of a flame holder 6 installed at a primary nozzle outlet. This enables the establishing of a gas jetting method to reduce NOx unburned components of a combustion gas most efficiently (including the form of a jetting hole provided for a gas jetting nozzle, the layout position of the gas jetting nozzles and the like).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus such as a furnace, a heating furnace or a hot blast generating furnace, and more particularly to a high efficiency, low NO.
It relates to a low NOx burner that burns x.

[0002]

2. Description of the Related Art In response to stricter NOx regulations year by year, it is necessary to reduce the amount of NOx generated in combustion gas as much as possible, particularly in boilers that burn coal. As a technique for reducing NOx in pulverized coal fuel, there is a two-stage combustion method. As the two-stage combustion method, there are two methods: a method of lowering NOx in the entire furnace and a method of lowering NOx by the burner alone. When reducing NOx in the entire combustion furnace, the air ratio in the burner zone of the combustion furnace (the ratio of required air to fuel, and the air ratio 1 is a stoichiometric equivalent)
Is maintained at a fuel-rich condition of 1 or less to reduce generated NOx and to reduce NOx. At this time, the unburned fuel is supplied with air from an air inlet provided on the downstream side of the burner zone, and is completely burned.

[0003] In the two-stage combustion method for reducing NOx by a burner alone, a large reduction region is formed by turning secondary air and tertiary air to delay mixing with a pulverized coal stream ignited only by primary air. And a certain type of pulverized coal low NOx burner (Japanese Patent Laid-Open No. 60-176315).
No. JP-A-62-172105).

[0004] These technologies reduce the amount of exhausted NOx to 130
ppm (fuel ratio = 2 fixed carbon / volatiles, 1.5% nitrogen in coal, 5% or less in ash). However, NOx regulation values tend to be stricter year by year, and NOx
The regulation value is 100 ppm or less.

Low NOx with NOx emission of 100 ppm or less
As a countermeasure, a burner with an internal flame stabilizer (Japanese Patent Laid-Open No. 8-135919) for further strengthening the two-stage combustion method in the burner section and an external flame stabilizer provided on the outer periphery of the primary nozzle through which the pulverized coal stream flows are provided. (Japanese Patent Application No. 9-26615) has been developed in which a flame stabilizing device is installed so as to bridge between internal flame stabilizing devices.

[0006] A burner provided with an internal flame stabilizer can realize a significant reduction in the unburned NOx content as compared with the conventional burner. However, the installation of the internal flame stabilizer slightly increases the flow rate of the pulverized coal flow at the end of the primary nozzle outlet, which is important for ignition, due to the fact that it is installed in the primary nozzle, especially for burners with a small nozzle diameter. In addition, there is a problem that the ignitability of the nozzle outlet becomes low, and as a result, the effect of reducing NOx and unburned components cannot be sufficiently obtained. Further, in addition to the problem that the pulverized coal particles in the pulverized coal stream are directly hit, it is one subject to be easily affected by the flame radiation especially when the burner is stopped, and to increase the durability against burning.

Therefore, as an alternative to the internal flame stabilizer 7 for promoting ignition and flame holding, a single or a plurality of gas injection nozzles are provided on the outer periphery of the primary nozzle to mix the oxygen-containing gas for combustion in the primary nozzle. By squirting toward the flow and supplying the high-temperature gas created near the primary nozzle outlet to the inside of the primary nozzle, the ignition and flame holding of the fuel are improved, and as with the internal flame stabilizer, the aim is to reduce NOx. Burners have also been developed (Japanese Patent Application No. 8-190575).

[0008]

A gas injection burner that injects gas toward the center of the burner reduces the unignited area in the center of the burner and improves the ignition and flame holding properties. It is very effective for reducing unburned components. However, the effect of reducing the NOx and unburned components that promotes ignition by entraining the high-temperature gas around the primary nozzle to the center of the nozzle greatly depends on the magnitude of the penetration force (force reaching the center of the burner) of the injected air. . In particular, in the future, when the capacity of the burner is increased, the unignited area becomes large, so that a penetration force is required more than the conventional size burner.

In order to impart a penetrating force to the gas injected from the gas injection nozzle, it is necessary that the flow rate and the differential pressure between the gas and the surrounding gas are equal to or higher than a predetermined value. At this time, the differential pressure is 100 mmAq to 150
mmAq, the flow rate is preferably 1% to 4% of the burner primary air. Therefore, an injection method (provided in a gas injection nozzle) that can effectively reduce NOx and unburned components in the combustion gas within the differential pressure and flow rate within the above-mentioned limits, that is, can provide a sufficient penetration force. It is important to establish the appropriate shape of the injection hole and the installation position of the gas injection nozzle.)

[0010] The object of the present invention is as described above,
Within the range of the flow rate and the differential pressure of the gas supply source permitted by the current boiler, establish a gas injection method that maximizes the penetration force as much as possible and most effectively reduces NOx and unburned combustion gas, and develops a burner. It is to reflect on.

[0011]

SUMMARY OF THE INVENTION The above-mentioned object of the present invention is as follows.
In the burner that injects gas from the outer periphery of the primary nozzle toward the primary flow, at least one gas injection hole is provided in the circumferential direction of the flame stabilizer installed at the outlet of the primary nozzle, so that the NOx of the combustion gas is most effectively used. -It is possible to establish a gas injection method (e.g., a shape of an ejection hole provided in the gas injection nozzle, an arrangement position of the gas injection nozzle, etc.) for reducing unburned components.

That is, the present invention provides a powdered fuel solid
A description will be given using pulverized coal as an example. ) And a primary nozzle constituting a primary flow path for introducing a solid-gas two-phase flow (for example, pulverized coal flow) composed of a carrier gas for carrying them into a combustion furnace;
In a burner having a flow path for supplying a single or a plurality of oxygen-containing gases for combustion outside the primary nozzle, a flame stabilizer is provided at the tip end of the primary nozzle outlet, and a gas flow path is provided outside the primary nozzle. A low NOx burner in which one or more gas injection holes for injecting gas from the gas flow path toward the solid-gas two-phase flow in the primary nozzle are provided in the circumferential direction of the flame stabilizer.

In the present invention, when gas is injected from the outer periphery of the primary nozzle toward the pulverized coal stream, the gas is injected from at least one circumferential position of the flame stabilizer installed at the outlet of the primary nozzle. In the burner which applied
This is to reduce the unignited region of the combustion gas in the central part of the burner and to greatly reduce NOx and unburned components.

The present inventors previously provided a flame stabilizer at the tip of the primary nozzle, provided a gas injection pipe penetrating the flame stabilizer from the outer periphery of the primary nozzle, and provided a tip of the gas injection pipe. By injecting gas toward the center of the burner from the gas injection hole provided in the above, the invention of a burner in which the NOx and unburned portion of the combustion gas are effectively reduced has been completed, and a patent application has been filed (Japanese Patent Application No. 9-1997). No. 25637).

However, in the invention of Japanese Patent Application No. 9-25637, the effect of reducing the NOx and unburned components of the combustion gas can be sufficiently exhibited, but since the tip of the gas injection pipe protrudes to the burner outlet, it is long. During the period of use, ash or the like adhered to the tip of the pipe and was sometimes fixed.

On the other hand, according to the present invention, the gas injection hole is provided directly on the flame stabilizer, and the injection hole is provided on the side of the flame stabilizer facing the center of the burner. There is no ash adhesion.

Further, a length (diameter) a of the gas injection hole in the burner axis direction and a length (diameter) b in the radial direction orthogonal to the burner axis are provided.
It is desirable to provide one or more gas injection holes in the burner axis direction such that the ratio (a / b) becomes 1 or more. Ratio (a
By setting / b) to 1 or more, the resistance to the pulverized coal flow is small, and the penetration force of the injected gas to the center of the burner is larger than that of the injection hole having a ratio (a / b) of less than 1. There are advantages.

In the case of pulverized coal as an example of a solid fuel powder, a gas injection hole is provided in a flame holder and a gas is ejected from the gas injection hole. Due to the entrainment of the gas jet jetting from the outer peripheral portion of the primary nozzle outlet tip toward the mixed fluid (pulverized coal stream), the high-temperature gas formed near the flame stabilizer at the primary nozzle outlet tip is discharged from the primary nozzle into the furnace. Into the pulverized coal stream flowing out to promote the ignition of the pulverized coal. As a result, the combustion of the fuel in the reduction region in the downstream part of the primary nozzle is promoted, which effectively works to reduce the NOx of the combustion gas, and the flame temperature near the burner is increased to promote the expansion of the flame.

By making the cross-sectional shape of the gas injection hole of the gas injection nozzle of the present invention round or elliptical, the injected gas has a substantially round cross-section, so that it is hardly affected by the flow of the mixed fluid. This is desirable because the hot gas can easily reach the center of the flame.

It is desirable that the distance between the centers of the two or more gas injection holes is set to not more than 2.5 times the diameter of the injection holes. This is because if two gas injection holes are separated by more than 2.5 times the diameter of the injection holes, two completely different jets will be formed.
When the two jets are close to each other, the jet immediately becomes one jet at the outlet of each injection hole, so that the gas flow rate for jetting can be increased, and the jet is jetted from the apparently large jetting hole. This is because a large jet can be generated.

Using two or more adjacent gas injection holes,
Increasing the apparent diameter of the injection hole without changing the outlet flow velocity from each injection hole is a very effective method for increasing the penetration force of the gas jet. In the case of using a method of increasing the number of holes while keeping the total cross-sectional area of the injection holes constant because the apparent diameter can be obtained, the number of the injection holes is not limited. In this case, the plurality of injection holes are desirably arranged vertically along the longitudinal direction of the burner (the tube axis direction of the burner) so as to reduce the resistance of the flow of the mixed fluid.

Further, by setting the flow velocity of the gas ejected from the gas injection holes to be at least three times the flow velocity of the mixed fluid, the injected gas enters the flow of the mixed fluid with a sufficient penetration force toward the center of the burner. Effectively reduces the unignited area of the flame.

Further, when high-temperature air in which the temperature of the gas injected from the gas injection holes is raised to a temperature equal to or higher than the temperature of the solid fuel transfer gas (eg, primary air) is used, a mixed fluid of the solid fuel and the primary air after the air injection is used. To increase the combustion efficiency.

Further, the flame stabilizer provided at the tip of the primary nozzle outlet comprises a flame stabilizer in which a plurality of saw-tooth-shaped projections extending toward the center of the cross section of the burner outlet are attached in the circumferential direction of the flame stabilizer. In this case, a gas injection hole is provided at a position facing the center of the burner along the front surface of the serrated protrusion, and a recirculating flow of the mixed fluid formed immediately downstream of the serrated protrusion of the flame stabilizer is provided. The high-temperature gas formed by the ignition can be easily transported toward the center of the burner by the injection gas flow from the gas injection holes, and a part of the unignited area of the flame is changed to the ignition area, and the whole is ignited. The area can be enlarged.

The gas injection hole may be provided with a projection such as a cylinder or a square tube. Further, the injection gas to be supplied to the gas injection holes may be supplied to the burner only during the burner operation. Further, it is desirable that the supply amount of the injection gas can be adjusted according to the burner load, the boiler load, the properties of the pulverized coal fuel or the burner installation stage. Depending on the properties of the fuel, the burner can be sufficiently reduced in NOx even without performing the gas injection according to the present invention. In such a case, the supply of the power can be minimized by stopping the gas injection from the gas injection nozzle by the flow rate adjusting device or suppressing the flow rate.

Further, even in a burner whose operation is stopped during the operation of the boiler, it is possible to prevent burning of the stopped burner due to radiant heat from the furnace by flowing gas from the gas injection holes. In this case, the flow rate from the gas injection holes can be adjusted so as to be a part of the amount of air used during the operation of the boiler.

As the gas to be supplied to the gas injection holes, not only preheated air but also combustion air inside a boiler wind box or other air may be used, or combustion exhaust gas may be circulated and supplied. . Further, a dedicated fan may be provided and supplied.

Further, the flow rate of the injected gas from the gas injection holes can be made variable or zero according to the conditions during the burner operation or at rest by installing the injection gas flow rate adjusting device as described above.

The present invention includes a combustion device such as a boiler, a heating furnace or a hot-air generating furnace provided with the above-mentioned low NOx burner. The solid fuel of the present invention is pulverized coal, petroleum coke, or coal coke.

[0030]

Embodiments of the present invention will be described. The structure of a pulverized coal burner using pulverized coal as a solid fuel will be described. 1 (a) and 1 (b) are a side sectional view and a front view of a gas injection type burner of the present embodiment. FIG. 2 is an enlarged view near the flame stabilizer.

A mixed fluid of pulverized coal of fuel and carrier air (primary air) is supplied to a combustion furnace through a primary nozzle 1.
A flame stabilizer 6 is arranged at the tip of the primary nozzle 1, and a boiler flame is formed from near the burner by the effect of the circulation vortex of the mixed fluid formed on the downstream side. A secondary flow path 9 and a tertiary flow path 10 which are paths for secondary air for combustion are provided on the outer periphery of the primary nozzle 1. The tertiary air flowing through the tertiary flow path 10 is spread outward in the combustion furnace by the swirl generator 3, so that a so-called excess fuel condition is formed in which there is a shortage of air at the center of the flame. Suitable conditions are set. The tertiary air is further expanded outward by the guide sleeve 8 which separates the flow of the secondary air and the tertiary air, so that a so-called excess fuel condition is created in which the center of the flame is short of air. The most suitable combustion state can be obtained.

An oil-fired burner 5 used at the time of starting the burner is provided at a central portion in the primary flow path 1, and on the outer periphery of the oil-fired burner 5, a pulverized coal stream is separated into a concentrated stream and a lean stream. Is provided. The pulverized coal flow is reduced at the front end of the concentrator 2 and flows toward the inner wall side of the primary flow path 1, and then the flow is expanded near the rear end of the concentrator 2 so that the pulverized coal particles and the gas The particles are separated to the inner wall side of the primary flow path 1 and the gas is separated to the center by the difference in inertial force. Therefore, the portion where the primary flow path 1 at the front end of the concentrator 2 containing a large amount of pulverized coal particles is reduced also serves to prevent flashback. The venturi section 4 is provided on the inner peripheral portion of the wall constituting the primary flow path 1 on the upstream side of the front end of the concentrator 2, and has a function of preventing the backflow of the flame by restricting the pulverized coal flow. It is.

As shown in FIG. 1B, the gas injection holes are desirably provided so as to overlap with the saw-toothed flame holding plate 7 of the flame stabilizer 6 as viewed from the front of the burner. The gas ejected from the gas ejection holes 12 is introduced from the ejection gas passage 11 outside the primary nozzle 1 of the burner. Further, the amount of gas injected from the gas ejection holes 12 can be changed according to fuel properties, burner load, combustion conditions, and the like.

The number of the gas injection holes 12 is not limited to four, and one or more gas injection holes 12 can be provided on the circumference of the wall surface of the primary nozzle 2. When two or more gas injection holes 12 are installed, they can be installed at equal intervals. As the installation form, a form as shown in FIG. 3 can be adopted. 3 (a) to 3 (e) are diagrams showing the installation type of the gas injection holes 12 as viewed from the furnace side, but here only the gas jet 13 is shown.

Next, a low NOx reduction mechanism by gas injection will be described. Usually, in a coal-fired burner, fine coal particles are caught in a flame holder 6 provided with a saw-shaped flame holding plate 7 having a saw-shaped protrusion directed to the inside of the primary flow path at the tip of the primary nozzle 1 to ignite. A flame is formed around the downstream side of the flame stabilizer 6, and a high-temperature gas zone A (FIG. 2) is formed in this portion by combustion. Thereafter, the flame is propagated to the center of the burner.

In order to reduce NOx and unburned components in the combustion gas, it is necessary to improve ignition and flame holding, and to reduce the unignited area at the center of the burner as much as possible. If the unignited area can be reduced, the ignition will be improved accordingly, and not only the NOx in the combustion gas but also the unburned portion will be reduced.

In particular, when the burner is increased in capacity, since it takes time for the flame to propagate to the center of the burner, the unignited area (so-called unburned core) becomes large, and some measures are taken to reduce them. Is the future N
It is very important to greatly reduce Ox and unburned components.

Therefore, if gas is injected from the gas injection holes 12 (FIG. 1) toward the pulverized coal stream at the burner outlet, it is effective to reduce the unignited area. FIGS. 4 and 5 show how the unignited area is reduced by gas injection. In FIG. 5, the unignited region after gas injection is C, and the ignition region before gas injection is C ′.
Expressed by

In order to reduce the unignited area C, heat must be forcibly supplied to the area. However, as shown in FIG. It is around the wake of the firearm 6. When the gas is injected from the gas injection holes 12 of the flame stabilizer 6 corresponding to the outside of the hot gas zone A formed downstream of the flame stabilizer 6 toward the unignited region in the center of the burner, the high temperature of the hot gas zone A The gas is entrained with the gas jet 13 into the center of the burner, which becomes a heat source,
The temperature in the center of the burner increases, and the unignited area is reduced.

In the experiment, the measurement point on the burner center axis (2)
The temperature in FIG. 4 was 600 to 800 ° C. before the gas was injected from the gas injection holes 12, but was changed to 8 by the gas injection.
It rose to 00-1000 degreeC. This means that the unignited area C 'at the center of the burner has the unignited area C as indicated by the arrow.
It has been reduced to. According to experimental values, NOx is reduced by about 20% and unburned content is reduced by about 10% after the gas is injected as compared to before the injection. In FIG. 7, the temperature at the measurement point (1) is 500 ° C. before and after the gas is injected, and the temperature at the measurement point (3) is 800 before the gas is injected.
~ 1000 ° C, but 900 ~ 12 after gas injection.
It was 00 ° C.

The mechanism for reducing NOx and unburned components in the combustion gas by gas injection depends on the penetration force of the injected gas and the size of the unignited region. Is a compromise between the two. Since the unignited area at the burner outlet increases as the burner increases in capacity, as long as the penetration force reaching the unignited area C can be obtained, the effect of reducing NOx and unburned components by gas injection increases the burner. The more the capacity, the more effective.

FIGS. 6 to 9 and 12 show the experimental results of the gas injection burner. FIG. 6 shows the temperature at the time of traversing the burner central axis along the axial direction, and the temperature on the burner central axis increases as the distance from the burner outlet increases. Here, the temperature measured on the central axis of the burner is 800 ° C
The following places are used as one guide for indicating the end of the unfired area C (FIG. 5). 80 before the gas is injected from the gas injection holes 12
While the value of the horizontal axis (burner axial distance / burner radius) in FIG. 6 that intersects 0 ° C. is 4.3, the value of the intersecting horizontal axis decreases to 3.2 when gas is injected, It can be seen that the end of the unignited region C approaches the burner outlet.
At this time, as shown in FIG. 7, the gas injected from the gas injection hole 12 has a penetrating force (the horizontal axis in FIGS.
The injection flow ratio for one minute with respect to the unit flow per book is shown. ), Hot gas can be entrained into the center of the burner, and the temperature in the center increases accordingly. As long as the injected gas has a penetrating force, the unignited area C becomes smaller,
As shown in FIG. 8, the NOx concentration in the combustion gas is also reduced.
Is the value calculated as ).

FIG. 9 shows the relationship between the number of circumferential gas injection holes 12 provided on the inner wall of the flame stabilizer 6 and NOx in the combustion gas. The result shown in FIG. 9 is a result in the case where the amount of gas ejected from one gas injection hole 12 is fixed. As the number of gas injection holes 12 increases, the amount of ejected gas increases as the number increases. At this time, due to the increase in the number of the gas injection holes 12, the amount of high-temperature gas entrained in the injection gas increases, the unignited area C decreases, and NOx decreases. FIGS. 6 to 9 show the results of experiments in which all the shapes of the gas injection holes 12 were as shown in FIG. 13C.

FIG. 10 is an example of a system diagram when the above-described burner is applied to a pulverized coal-fired boiler. Combustion air is F
After being introduced from a DF (Force Draft Fan) 14 and heated to about 350 ° C. in an air preheater 15, it enters a wind box 16, and burner secondary flow path 9 and tertiary flow path 1 as shown in FIG.
Transported to zero.

The pulverized coal pulverized by the mill 17 is PA
The air is transported to the burner section 20 by the pulverized coal transport air sent by the F (Primary Air Fan) 18 and is guided into the primary nozzle 1 shown in FIG. The injection gas from the gas injection holes 12 (FIG. 1) supplies heated air or cold air from the air preheater 15 to the injection gas flow path 11 outside the primary burner nozzle 1 through the switching valve 19.

Since the supply pressure of the primary air is higher than that of the combustion air, the primary air can be used as the gas for injection from the gas injection holes 12. Also, supplying high-temperature air at the outlet of the air preheater 15 has the effect of heating the pulverized coal and the primary air after gas injection, thereby increasing combustion efficiency.

The gas injected from the gas injection holes 12 may be supplied to the burner section 20 only during the burner operation. Therefore, in a combustion facility having a plurality of burners, gas is injected during burner operation, and a small amount of cold air flows through the heated air / cold air switching valve 19 to prevent burner burnout when the burner is stopped.

When the burner load is low, the flow rate of the primary flow (pulverized coal flow) in the primary nozzle 1 decreases, and the resistance due to the primary flow is small. Although it is low, the penetrating power to the center of the burner can be obtained. By adjusting the gas injection flow rate with a burner load or a similar boiler load, efficient operation with the required minimum injection gas power can be achieved.

Depending on the fuel properties, the gas injection holes 1
2 low N of the combustion gas without performing gas injection from
Oxification may be performed in some cases. In such a case, the supply power can be suppressed to a necessary minimum by stopping the injection gas or suppressing the flow rate. Depending on the fuel properties, the supply flow rate of the internal flame holding air can be set by the gas injected from the gas injection holes 12.

The air for gas injection may be supplied using a dedicated fan. In this case, an optimum supply pressure for gas injection can be set, so that efficient operation in terms of power is possible. Also in this case, the air may be supplied from either low-temperature air upstream of the air preheater 15 shown in FIG. 10 or high-temperature air downstream of the air preheater 15.

The burner according to the present invention (Japanese Patent Application No. 9-256)
In No. 37), ash does not adhere near the flame stabilizer 6. In the burner filed earlier by the present inventors, as shown in FIG. 11, a gas injection pipe 22 is provided by a method of penetrating the flame stabilizer 6 'at the tip of the primary nozzle 1, and the gas injection pipe at the tip is provided. Since the gas jet 13 was jetted from the hole to the center of the burner from the downstream side of the sawtooth-shaped projection 7 ', the vicinity of the flame stabilizer 6', which is likely to form a backflow area when coal with high slagging property is fired. There is a possibility that ash may adhere to the portion of the gas injection pipe 22 that protrudes toward the inside of the combustion furnace.

However, in the present invention, since the gas injection holes are provided in the circumferential direction of the flame stabilizer 6, there is no unnecessary protrusion, and there is no fear that ash adheres. The members constituting the burner shown in FIG. 11 and having the same functions as those shown in FIG.
The same reference numerals are given and the description is omitted.

FIG. 12 shows NOx when no gas is injected between the burner according to the present invention and the burner shown in FIG.
It is an experimental result showing the relationship between the concentration and the unburned matter. FIG.
Is a value calculated by assuming that 7% is 1, and NOx is a value calculated based on a concentration of 140 ppm.

A comparison of the burner performance of the present invention with that of the conventional burner shows that NOx is reduced by more than 10% at the same unburned content and unburned by more than 5% at the same NOx.

FIG. 13 shows the gas injection hole 1 of the flame stabilizer 6 of the present invention.
It is an enlarged view of two parts. The gas injection hole 12 has any shape as long as the ratio (a / b) of the length (diameter) a of the burner in the tube axis direction to the length (diameter) b of the burner in the radial direction is 1 or more. It may be something.

FIG. 13 shows a typical example.
The gas injection holes 12 are machined so that the entire cross-sectional area is equal. The injection holes 12 shown in FIGS. 13A and 13B have a round hole shape, and the injection holes 12 shown in FIGS. 13C and 13D have a slit shape. 13 (c) is better when the slit-shaped injection holes 12 shown in FIGS. 13 (c) and 13 (d) are compared. This is because the one shown in FIG. 13 (c) has a small area to collide with the pulverized coal flow flowing in the primary nozzle 1 from the right angle direction and has a low resistance, and the gas jet easily penetrates into the center of the burner.

The round injection hole 1 shown in FIGS. 13 (a) and 13 (b)
In comparison with FIG. 2, the one shown in FIG.
Oxification effect is high. This is shown in FIG.
It is considered that two adjacent jets tend to immediately become one jet at the outlet of the injection hole 12, and a penetrating force similar to that jetted from the apparently large jet hole 12 is generated.

The round injection holes 12 shown in FIGS. 13A and 13B and the rectangular injection holes 12 shown in FIGS.
In the comparison, the gas injected from the corner of the rectangular injection hole 12 is directly affected by the pulverized coal flow, is pushed to the downstream side of the gas flow, and the unignited region due to the high-temperature gas reaching the burner center. It is necessary to make the shape of the gas injection hole round or elliptical while reducing the reduction effect. Since the injected gas has a round or elliptical cross section, it is hardly affected by the flow of the mixed fluid. This is desirable because the effect of reducing the ignition region becomes relatively large.

FIG. 14 shows the relationship between two adjacent gas injection holes 12 having the same diameter R and the distance x between the centers thereof. Relational expression (x> 2.5) shown in FIG.
14B is compared with the case where the relational expression (x ≦ 2.5) shown in FIG. 14B is satisfied, the case where the relational expression shown in FIG. A penetration force similar to that ejected from 12 is produced.

Between the intersecting jets (between the jet 13 injected from the gas injection hole 12 and the pulverized coal flow), how much of the jet 13 injected from the gas injection hole 12 is in the pulverized coal flow at the center of the burner. Is reached depends on the momentum ratio between the cross jets and the diameter of the injection holes 12. The gas flow velocity at the outlet of the injection hole 12 is preferably faster in order to obtain a momentum ratio. The larger the diameter of the injection hole 12, the greater the penetration force (the force reaching the burner center). However, when the total flow rate of the injection gas is limited, increasing the diameter of the injection hole 12 and increasing the outlet flow velocity of the injection hole 12 are contradictory, and therefore, it is difficult to achieve a balance.

Therefore, in the case of two adjacent injection holes 12 shown in FIG. 13 (a), the outlet flow velocity is as shown in FIG. 13 (b).
However, the shape is such that the apparent diameter of the injection hole 12 can be increased, so that it is a very effective method for increasing the penetration force.

The number of holes is not limited in the method of increasing the number of holes while keeping the total sectional area of the injection holes 12 constant because the apparent diameter can be increased. The arrangement of the plurality of injection holes 12 at this time is desirably arranged vertically along the tube axis direction of the burner so as to reduce the resistance of the pulverized coal flow, as described above for the slit-shaped injection holes 12. .

The shape of the injection hole 12 is not particularly limited to the one shown in FIG. 13, but the slit-shaped hole and the round hole have a larger penetration force of the injected gas than the round hole. Here, the performance of the injection hole 12 having a slit shape and a round shape has been mainly described, but any shape including an ellipse or a trapezoid as long as the resistance of the pulverized coal flow is small. But it is good.

[0064]

The effects of the present invention will be described below. (1) By bringing the ignition point of the fuel closer to the vicinity of the burner outlet, a stable and large reduction region can be secured, so that an ultra-low NOx reduction can be achieved. (2) By reducing the unignited area at the center of the burner, the unburned portion can be significantly reduced. (3) It has excellent ignition and flame stabilizing properties, and can provide very stable flames. It is suitable for burning coal with a wide load range and a wide range of properties. Can cope well. (4) To significantly improve the ignitability of the burner center,
The burner can be increased in capacity, and the number of burners attached to the furnace can be reduced. Therefore, the cost of the boiler total system can be reduced. (5) Since high performance can be obtained with respect to reduction of NOx and unburned components, the furnace can be made compact and the cost of the boiler total system can be reduced. (6) Ash hardly adheres to the gas injection holes.

[Brief description of the drawings]

FIG. 1 is a side view (FIG. 1 (a)) and a front view (FIG. 1) of a pulverized coal burner provided with gas injection holes according to an embodiment of the present invention.
(B)).

FIG. 2 is an enlarged view of the vicinity of a gas injection hole of a pulverized coal burner provided with a gas injection hole of the burner of FIG.

FIG. 3 is a diagram showing an example of the arrangement of gas injection holes of the burner of FIG. 1;

FIG. 4 is a diagram showing a temperature rise in a central portion of the burner due to gas injection from a gas injection hole of the burner of FIG. 1;

FIG. 5 is a diagram showing a relationship between a reduction in an unignited region and a NOx reduction effect when gas is injected from a gas injection hole of the burner in FIG. 1;

6 is a diagram showing a relationship between a temperature rise in a burner central axis direction and a distance in a burner central axis direction before and after gas is injected from a gas injection hole of the burner in FIG. 1;

FIG. 7 is a diagram showing a relationship between a penetration force of an injection gas from a gas injection hole of the burner of FIG. 1 and a temperature of a central axis of the burner.

8 is a diagram showing a correlation between a penetration force of gas injection from a gas injection hole of the burner of FIG. 1 and NOx in combustion gas.

9 is a diagram showing a correlation between the number of gas injection holes of the burner of FIG. 1 and NOx in combustion gas.

FIG. 10 is a system diagram of a combustion device using a burner according to the present invention.

FIG. 11 is a side view of a gas-injectable pulverized coal burner according to the inventors' earlier application invention.

12 is a comparison diagram of the NOx / unburned component characteristics in the combustion gas of the burner of FIG. 1 and the burner of FIG. 11;

FIG. 13 is a diagram showing an example of the shape of the ejection hole of the gas ejection nozzle according to one embodiment of the present invention.

FIG. 14 is a diagram showing a relationship between a hole interval and a diameter of the two-hole cascade ejection holes of FIG. 13A.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary nozzle 2 Concentrator 3 Tertiary swirler 4 Venturi 5 Heavy oil nozzle 6 Flame stabilizer 7 Serrated protrusion (flame stabilizer) 8 Guide sleeve 9 Secondary flow path 10 Tertiary flow path 11 Injected gas flow path 12 Gas injection hole 13 Gas jet

Continued on the front page (72) Inventor Kenji Kiyama 6-9 Takaracho, Kure-shi, Hiroshima Pref. Inside the Babcock Hitachi Kure Factory (72) Inventor Shunichi 6-9 Takaracho Kure-shi, Hiroshima Pref. Babcock Hitachi Kure Factory (72) Koji Kuramasu, Inventor 6-9 Takara-cho, Kure-shi, Hiroshima Babcock-Hitachi Inside the Kure Plant (72) Inventor Hironobu Kobayashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi, Ltd. F term in the laboratory (reference) 3K065 QA01 QA04 QB11 QB20 QC03 TA01 TB01 TC01 TD07 TE10 TF03

Claims (10)

[Claims] 1. A primary nozzle constituting a primary flow path for introducing a solid-gas two-phase flow composed of powdered fuel solids and a carrier gas for carrying them into a combustion furnace, and a single nozzle outside the primary nozzle. In a burner having a flow path for supplying a plurality of oxygenated gases for combustion, a flame stabilizer is provided at a tip end of a primary nozzle outlet, and a gas flow path is provided outside a primary nozzle, and a primary nozzle outlet is provided from the gas flow path. A low NOx burner characterized in that one or more gas injection holes for injecting gas toward the solid-gas two-phase flow at the tip end are provided in the circumferential direction of the flame stabilizer. 2. The low NOx burner according to claim 1, wherein the cross section of the gas injection hole is round or elliptical. 3. The length (diameter) of the gas injection hole in the burner axis direction.
A gas injection hole is provided at least one in the burner axis direction such that the ratio (a / b) of a to the radial length (diameter) b perpendicular to the burner axis is 1 or more. 3. The low NOx burner according to 1 or 2. 4. The low NOx burner according to claim 3, wherein the distance between the centers of two or more gas injection holes provided in the burner axis direction is 2.5 times or less the injection hole diameter. 5. The low NOx burner according to claim 1, wherein the flow velocity of the gas injected from the gas injection holes is three times or more the flow velocity of the solid-gas two-phase flow. 6. The low-temperature air according to claim 1, wherein the temperature of the gas injected from the gas injection holes is high-temperature air whose temperature has been raised to a temperature equal to or higher than the temperature of the solid fuel carrier gas. NOx burner. 7. The flame stabilizer provided at the outlet end of the primary nozzle is a flame stabilizer in which a plurality of serrated protrusions extending toward the center of the burner outlet cross section are attached in the circumferential direction of the flame stabilizer. 7. The low-N gas as claimed in claim 1, wherein a gas injection hole is provided at a position where the gas injected from the gas injection hole faces the center of the burner along the front surface of the saw-toothed projection.
Ox burner. 8. The low NOx burner according to claim 1, wherein a gas flow control device is provided in a gas flow path for supplying gas to the gas injection holes. 9. The gas flow adjusting device according to claim 8, wherein the gas flow rate adjusting device makes the flow rate of the gas injected from the gas injection hole variable or zero according to the condition during the burner operation or during the stop. NOx burner. 10. The gas flow control device according to claim 8, wherein the flow rate of the gas injected from the gas injection holes is varied according to a burner load, a boiler load, or the properties of the solid fuel.
The low NOx burner according to any one of the above.