JPH11173507A - Combustion device and boiler having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart a strong swirl to a primary combustion air along an inner periphery, and to accelerate combustion under insufficient air at a flame center. SOLUTION: A combustion device comprises a nozzle 13 which is substantially arranged at the center thereof for injecting fuel, and a plurality of primary, secondary and third combustion air channels 1, 2, 3 which have been formed into concentric ring shapes to inject primary, secondary and third combustion airs 4, 5, 6, respectively. The secondary and the third combustion air channels 2, 3, are each formed, at least a portion of the outer periphery, such that the secondary and the third combustion airs 5, 6 are diverged outwardly of the outer periphery. The primary combustion air channel 1 at the inner periphery has a built-in flame holder 8 of a swirl vane type for imparting a swirl to the primary combustion air 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler combustion apparatus (hereinafter, referred to as a burner) using fuel, and in particular, to reduce the generation of nitrogen oxides (hereinafter, referred to as NOx).
The present invention also relates to a combustion device suitable for reducing the amount of unburned carbon and a boiler provided with the combustion device.

[0002]

2. Description of the Related Art The nitrogen content in heavy oil fuel is usually 0.3% or less, and fuel NOx generated by oxidizing the nitrogen content in fuel and oxygen in the air at high temperature become oxygen and oxygen. The amount of generation is almost equal to that of thermal NOx generated by the combination. However, recently, new types of fuels, such as asphalt and other water-emulsified fuels, and inferior oils that have high sulfur and nitrogen contents and have not been used due to their incombustibility and poor flammability have been used for their low cost. Reviewed for
Usage is increasing for the purpose of reducing power generation costs.
While these new fuels and inferior oils generally contain a large amount of nitrogen, the environmental regulation value of NOx is becoming stricter year by year.

[0003] As a method for reducing the amount of NOx generated, the following method is generally used. Normally, in a burner that injects fuel from the center, the combustion air ejected from the burner is swirled, and after being ejected from the burner throat, it is configured to flow toward the outside of the outer periphery, and the fuel and air are gradually increased. Are mixed.
This method suppresses the temperature of the combustion gas from becoming high by gradually progressing the combustion near the burner, and is called a slow combustion method. Alternatively, the amount of air supplied to the burner is set to be less than the stoichiometric amount of air necessary for complete combustion of the fuel, and the fuel is burned in an excess fuel state so that the nitrogen content is hardly oxidized due to a shortage of air, thereby reducing the amount of NOx generated. There is a two-stage combustion method. In this method, combustion air is supplied again downstream to complete combustion. But these NOx
If only new fuels and inferior oils are used, N
The reduction of Ox is becoming insufficient.

FIG. 7 shows a system diagram of a conventional boiler. The conventional boiler includes a fuel injection device 12, a combustion air blower 2
6, burner 34, two-stage combustion air supply hole 33, furnace 1
8, superheater 19, reheater 20, economizer 21, desulfurizer 2
2. It comprises a denitration device 23, a dust collector 24, a chimney 25 and the like. The fuel is injected under pressure from the nozzle 13. At this time, the fuel is usually injected together with an ejection medium such as steam passing through the spray steam regulating valve 30 or air passing through the fuel amount regulating valve 29 to promote atomization of the liquid fuel. The injected fuel is mixed with the combustion air supplied from the combustion air blower 26 and passed through the combustion air adjustment damper 31, and burned. The combustion air amount of the burner 34 is
When the two-stage combustion method is used, the theoretical air amount is 0.80 to 0.8.
It is generally operated at about 95 times. After that, the remaining combustion air is supplied from the two-stage combustion air supply hole 33 to complete combustion. This is the two-stage combustion method described above.
At this time, the total amount of combustion air supplied from the burner 34 and the two-stage combustion air supply hole 33 is equal to 1.1 of the theoretical air amount.
It is about 05 to 1.10 times. The combustion gas removes the generated sulfur oxides and nitrogen oxides from the desulfurization device 22 and the denitration device 2.
The dust is collected by a dust collector 24 and discharged from a chimney 25.

FIG. 8 shows a conventional burner. The basic burner structure is the fuel injection device 12, the primary combustion air passage 5
1. Secondary combustion air passage 52 and tertiary combustion air passage 5
The secondary combustion air 5 is swirled by the secondary vane 10, and the tertiary combustion air 6 is swirled by the tertiary register 11. Further, the fuel injector 12 is provided with a flame stabilizer 7. The combustion air sent from the combustion air blower 26 shown in FIG. 7 is divided into primary combustion air 4, secondary combustion air 5, and tertiary combustion air 6. The secondary and tertiary combustion air 5 and 6 are swirled by the secondary vane 10 and the tertiary register 11 to perform the slow combustion described above. However, it is not structured to swirl the primary combustion air 4.

FIG. 9 shows the operation of a conventional burner. The flame stabilizer 7 forms a stagnation point 16 by the primary combustion air 4. Since the stagnation point 16 is formed on the windward side of the flame stabilizer 7 and the flow velocity becomes extremely slow, it is configured such that a flame exists in this portion. The secondary and tertiary combustion air 5 and 6 are swirled by the secondary vane 10 and the tertiary register 11, respectively. Centrifugal force is generated by the swirling force of the combustion air, and after the burner throat 14, the combustion air spreads toward the outer periphery. Therefore, the combustion air and the fuel 15 are gradually mixed and burn slowly. In the conventional burner, by rapidly mixing the combustion air and the fuel, a rapid rise in temperature due to combustion is suppressed, and the amount of thermal NOx generated by oxidizing nitrogen in the air at a high temperature is reduced. Was the subject.

A two-stage combustion method used in a conventional boiler;
It is gradually becoming difficult to satisfy the current environmental regulation values with the conventional NOx reduction method using the slow burn method in a burner. The method for reducing the amount of NOx generated by the slow combustion method is mainly for reducing thermal NOx generated by the combination of nitrogen and oxygen in a high temperature range, and reduces fuel NOx generated from nitrogen in fuel. The effect is small. However, in the future, the use of a new fuel or a poor quality oil having a high nitrogen content will increase the proportion of the amount of fuel NOx generated due to the nitrogen content in the fuel. Moreover, it is easily expected that it becomes difficult to satisfy the environmental regulation values due to the strengthening of the environmental regulation values. In addition, increasing the load on the environmental device requires increasing the exhaust gas treatment capacity of the catalyst used in the desulfurization device. In other words, increase the catalyst loading,
Alternatively, it is necessary to increase the activity of the catalyst itself. This means that the initial cost and running cost of the desulfurizer are increased. That is, even if the aim is to promote cost reduction by using a low-cost new species fuel or inferior oil, the cost is increased by the environmental device, and the effect is reduced.

[0008] In other words, to meet the current need to reduce the operating cost by using a fuel having a high nitrogen content, it is urgently necessary to reduce the generation of fuel NOx generated by oxidizing nitrogen in the fuel. It is essential. However, in the slow combustion method used in the conventional burner, although sufficient consideration has been given to reducing thermal NOx, it is not sufficient to reduce the fuel NOx generated due to oxidation of the nitrogen itself in the fuel itself. No consideration was given.

[0009]

In the future, the use of new types of fuels or inferior oils having a high nitrogen content will increase the proportion of the amount of fuel NOx generated due to the nitrogen content in the fuel. It is necessary to increase the exhaust gas treatment capacity of the catalyst used. That is, even if the aim is to promote cost reduction by using a low-cost new-type fuel or inferior oil, the cost is increased by the environmental device, and the effect is reduced. That is, in the slow combustion method, sufficient consideration was given to reducing thermal NOx, but sufficient consideration was not given to reducing fuel NOx generated by oxidization of nitrogen itself in fuel. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion device which gives a strong swirl to combustion air such as primary combustion air in the inner periphery to promote combustion in a center portion of a flame under a shortage of air, and a boiler provided with the combustion device. To provide.

[0011]

In order to achieve the above-mentioned object, a combustion apparatus according to the present invention injects fuel substantially from the center, and uses a plurality of combustion air passages divided concentrically to form combustion air. In the combustion device that injects air, at least a part of the combustion air flow path on the outer periphery is formed so that the combustion air spreads outward from the outer circumference, and the combustion air flow path on the inner circumference is formed in the combustion air flow path. A swirl vane type flame stabilizer is provided so as to give a swivel.

[0012] At least a part of the combustion air flow path on the outer periphery is formed so as to swirl the combustion air so as to expand outward from the outer circumference, and the combustion air flow path on the inner circumference is provided with a combustion air flow path. A swirl vane type flame stabilizer may be built-in so as to give a swirl.

Further, at least a part of the outer periphery of the combustion air flow path may be formed so that after the combustion air has spread outward from the outer periphery, the downstream side of the combustion air flows backward toward the center. .

Further, at least a part of the combustion air flow path on the outer periphery is configured such that the downstream of the combustion air flows back toward the center after the combustion air spreads outward from the outer periphery by centrifugal force due to the swirling force. A configuration may be used.

The swirling force of the combustion air has a swirl ratio of 0.5 or more.
A configuration incorporating a mechanism for adjusting the combustion air flow rate may be employed.

A structure in which a combustion air flow rate is divided and supplied to each of an inner combustion air flow path and an outer combustion air flow path, and the fuel is formed of oil fuel. May be formed at an angle of 15 ° to 45 ° with the central axis.

Further, the boiler is provided with any one of the above-mentioned combustion devices, and at least a fuel injection device, a combustion air blower, a furnace, a superheater, a reheater, a economizer, a desulfurization device and a denitration device. The configuration is as follows.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, fuel is injected from a substantially central nozzle 13, and primary, secondary, and tertiary combustion is performed by a plurality of concentric annularly divided primary, secondary, and tertiary combustion air flow paths 1, 2, and 3. A combustion device for injecting the air for use 4,4,6, wherein at least a part of the outer circumference of the secondary and tertiary combustion air passages 2,3 is formed such that the secondary and tertiary combustion air 5,6 are outside the outer circumference The primary combustion air flow path 1 is formed so as to expand toward the inner periphery, and has a structure in which a swirl vane type flame stabilizer 8 is incorporated so as to give a swirl to the primary combustion air 4.

The secondary and tertiary combustion air passages 2 and 3 of at least a part of the outer periphery are provided with secondary and tertiary combustion air 5 and 6 respectively.
And the secondary and tertiary combustion air 5 and 6 are further expanded outward from the outer periphery, and then the secondary and tertiary combustion air 5 and 6 are formed. Or secondary and tertiary combustion air after the secondary and tertiary combustion air 5 and 6 are spread outward from the outer periphery by centrifugal force due to the swirling force. It may be configured to be formed so as to flow backward toward the center downstream of 5,6. The swirling force of the combustion air has a swirl ratio of 0.5 or more.

That is, the swirler 8 built in the primary combustion air flow path 1 so as to oppose the inflow direction of the primary combustion air flow path 1 can make a strong swirl on the primary combustion air 4. FIG. 2 shows an example of the swirler 8. The swirler 8 has a swirler 9 at an angle with respect to the primary combustion air flow path 1, and the primary combustion air 4 is strongly swirled by passing through the swirler 9. Furthermore, since the secondary vanes 10 and the tertiary register 11 shown in FIG. 1 are also swirled by the secondary and tertiary combustion air 5 and 6, the combustion air 4, 5 and 6 are all swirled by the burner throat 14. After flowing out, flows so as to spread outward from the outer periphery. For this reason, a reduction area 17 having a low pressure as shown in FIG.

The operation of the embodiment will be described. First,
By giving a strong swirl to the primary, secondary and tertiary combustion air,
Centrifugal force acts on each combustion air to spread outward from the outer circumference at the outlet of the burner throat. This operation reduces the combustion air in the central portion of the burner. Therefore, this part (reduction area) has low oxygen concentration,
A part with low pressure is created. Moreover, the fuel is rapidly ignited by the swirl vane type flame stabilizer provided in the primary combustion air passage. Due to the rapid ignition of the fuel, the oxygen concentration in the central part of the burner further decreases. In addition, the temperature of this portion becomes high due to rapid ignition, and the nitrogen content contained in the fuel is once oxidized by the primary combustion air to become fuel NOx. Here, very active hydrocarbon radicals are formed, which then generate nitrogen-containing radicals. Since these radicals are active, NOx generated in the fuel can be reduced, and NOx generated from the fuel can be converted to nitrogen.

Finally, the combustion air flowing toward the outer periphery by the strong swirl operates so as to flow back to the low pressure portion generated downstream of the central axis of the burner. By this operation, a portion having a high oxygen partial pressure is formed in the downstream portion of the burner, and combustion is promoted in the most downstream portion of the burner. The strength of the swirling force given to the combustion air by the burner of the present invention is strong enough to form a low-pressure portion due to the centrifugal force caused by the swirling,
Moreover, the intensity is such that the combustion air once spreading outward from the outer periphery returns to the low-pressure portion again. The reducing action in the flame is performed by setting the swirling force of the combustion air to 0.5 or more as a swirl number (swirl ratio = swirl flow rate / axial flow rate) that defines the swirl force of the fluid as a dimensionless number. Formed reliably. In the NOx reduction method using the burner, the two-stage combustion method can be used in combination with the conventional slow combustion method.
The effect of reduction is also doubled.

FIG. 3 shows another embodiment of the present invention. In another embodiment, the swirler 58 is connected to the primary combustion air passage 1.
The flame stabilizer 7 is installed at the back (inflow side) and the tip part (center), and a swirler 58 that swirls the primary combustion air 4 is provided with a flame stabilizer 7 that performs flame holding. And a divided configuration. With this configuration, the swirler 58 having a complicated shape can be installed at the back so as to be hardly corroded by corrosion or burning, and the frequency of replacing the swirler 58 can be reduced, and the swirler 58 having a complicated shape and high manufacturing cost can be provided. Can be changed to an inexpensive material, and the cost can be reduced.

FIG. 4 shows another embodiment of the present invention. In this other embodiment, the inner partition 40 of the wind box is installed in the wind box 32, and the wind box damper 4 for primary combustion air is provided at the entrance of the wind box 32.
A wind box damper 41 for the secondary combustion air is provided, and a damper (adjustment mechanism) 36 for adjusting the amount of primary combustion air and a damper (adjustment mechanism) 38 for adjusting the secondary combustion air are provided downstream of each damper. The combustion air flow rate is divided and supplied to the primary combustion air flow path 1 on the inner circumference and the secondary and tertiary combustion air flow paths 2 and 3 on the outer circumference. The flow rates of the secondary combustion air 5, the tertiary combustion air 6, and the primary combustion air 4 can be adjusted by the respective dampers. Further, the primary-combustion-air-adjustment damper 36 and the secondary-combustion-air-adjustment damper 38 are opened and closed or finely opened and closed by a primary-combustion-air-adjustment damper lever 35 and a secondary-combustion-air-adjustment damper lever 37, respectively. The adjustment can be performed, and the adjustment range of the primary combustion air 4 can be increased.
By reducing the amount of primary combustion air by this action, the reduction region becomes larger, and conversely, by increasing the amount of primary combustion air, the reduction region becomes smaller. That is, by operating the size of the reduction region, the effect of reducing NOx can be adjusted. That is, by weakening the NOx reduction effect,
It is possible to enhance the effect of reducing the amount of unburned carbon generated, and to adjust the combustion performance of the burner.

FIG. 5 schematically shows the flow of the flame and the combustion air of the burner according to the present invention. FIG. 5 is a schematic diagram of estimating the reduction region formed by the burner according to the present invention from the flow pattern based on the measurement results obtained by performing a cold test using the experimental apparatus used in the development of the burner of the present invention. It is. Due to the swirling force of the secondary and tertiary combustion air 5, 6, 15 ° to 4 ° with respect to the central axis at the center in front of the burner.
A reduction region 17 is formed in an angle range of 5 °. Further, since the primary combustion air 4 can be strongly swirled by the swirler 8,
The stagnation point 16 is formed, and the mixing performance of the oil fuel 15 and the combustion air 4, 5, 6 in the reduction region 17 is improved.

FIG. 6 shows another embodiment of the present invention. The burner shown in FIG. 6 has a cone 39 or bell mouth attached to the tip of the secondary or tertiary combustion air flow path. According to this other embodiment, the combustion air can flow outside the outer periphery, and a strong reduction region can be formed downstream on the burner center axis. By this reduction region, NOx generated from nitrogen contained in the inferior oil or the new-type fuel, that is, fuel NOx, can be converted into nitrogen in this reduction region, and the NOx generation amount can be reduced.

As another embodiment of the present invention, a boiler includes any one of the above-described combustion devices, and includes at least the fuel injection device 12, the combustion air blower 26, the furnace 18, and the like shown in FIG.
Superheater 19, reheater 20, economizer 21, desulfurizer 22,
It is configured to include a denitration device 23, a dust collector 24, and the like.

According to the present invention, fuel NOx can be reduced. For this reason, NOx in the exhaust gas can be reduced even when a fuel having a high nitrogen content is used. In addition, stable energy can be supplied at low cost, and it is particularly effective in reducing the amount of nitrogen oxides that are environmental pollutants. Another feature of the burner according to the present invention, which is excellent in ignition and flame holding properties, is that it can be operated with the oxygen concentration at the furnace outlet kept low and has low unburned matter, so that the combustion efficiency and boiler efficiency can be kept high. it can. In addition, because of its high ignition and flame holding properties, the amount of dust generated is small, and the burden on the dust collector can be reduced.

[0029]

According to the present invention, since a flame stabilizer for swirling combustion air is built in the combustion air flow path on the inner periphery, the amount of NOx generated in the exhaust gas even when a fuel having a high nitrogen content is used. The combustion efficiency and the boiler efficiency can be kept high because the combustion efficiency and boiler efficiency are low. The high ignition and flame holding properties also have the effect of reducing the amount of dust generated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the present invention.

FIG. 5 is a diagram illustrating a flow of combustion air and a fuel injection direction according to the present embodiment.

FIG. 6 is a cross-sectional view showing another embodiment of the present invention.

FIG. 7 is a view showing a conventional boiler.

FIG. 8 is a view showing a conventional combustion device.

FIG. 9 is a diagram illustrating a flow of combustion air and a fuel injection direction according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Primary combustion air flow path 22 Desulfurization device 2 Secondary combustion air flow path 23 Denitrification apparatus 3 Tertiary combustion air flow path 24 Dust collector 4 Primary combustion air 25 Chimney 5 Secondary combustion air 26 Combustion air blower Reference Signs List 6 tertiary combustion air 27 steam header 7 flame stabilizer 28 fuel tank 8,58 swirler 29 fuel amount adjustment valve 9 swirl vane 30 spray vapor adjustment valve 10 secondary vane 31 combustion air adjustment damper 11 tertiary register 32 wind box 12 Fuel injection device 33 Two-stage combustion air ejection hole 13 Nozzle 34 Burner 14 Burner throat 35 Primary combustion air amount adjustment damper lever 15 Fuel 36 Primary combustion air amount adjustment damper 16 Stagnation point 37 Secondary combustion air amount adjustment damper lever 17 Reduction Area 38 Damper for adjusting air amount for secondary combustion 18 Furnace 39 Cone 19 Superheater 40 Partition wall in wind box 20 Heat 41 secondary, tertiary combustion air windbox damper 21 economiser 42 primary combustion air windbox damper

Claims (9)

[Claims] In a combustion apparatus for injecting fuel from substantially the center and ejecting combustion air from a plurality of concentric annularly divided combustion air flow paths, at least a part of the outer circumference of the combustion air flow path includes: The combustion air is formed so as to spread outward from the outer circumference, and the combustion air flow path on the inner circumference is
A combustion device comprising a swirl-blade-type flame stabilizer for imparting a swirl to the combustion air. 2. A combustion apparatus for injecting fuel substantially from the center and ejecting combustion air from a plurality of concentrically divided combustion air flow paths, wherein at least a part of the outer circumference combustion air flow path includes: The combustion air is formed so as to swirl and expand outward from the outer circumference, and the combustion air flow path on the inner circumference is provided with a swirling vane type flame stabilizer so as to swirl the combustion air. A combustion device characterized by being built-in. 3. The combustion apparatus according to claim 1, wherein at least a part of the combustion air flow path on the outer periphery is such that after the combustion air has spread outward from the outer periphery, the downstream of the combustion air is on the center side. A combustion device formed so as to flow backward. 4. The combustion apparatus according to claim 2, wherein at least a part of the combustion air flow path on the outer periphery is formed by the combustion air that is spread outward from the outer periphery by centrifugal force generated by the swirling force. A combustion device, wherein the downstream of the air is formed so as to flow backward to the center side. 5. The combustion apparatus according to claim 1, wherein the swirling force of the combustion air has a swirl ratio of 0.5.
Combustion device characterized by being 5 or more. 6. The combustion apparatus according to claim 1, wherein the combustion air flow path on the inner periphery has a built-in mechanism for adjusting the flow rate of combustion air. . 7. The combustion apparatus according to claim 1, wherein a combustion air flow rate is divided and supplied to each of an inner combustion air flow path and an outer combustion air flow path. A combustion device characterized by: 8. The combustion device according to claim 1, wherein the fuel is formed of an oil fuel,
The combustion device according to claim 1, wherein the oil fuel reduction region forms an angle of 15 to 45 with the central axis. 9. A combustion device comprising: the combustion device according to claim 1; at least a fuel injection device, a combustion air blower, a furnace, a superheater, a reheater, a economizer, a desulfurization device, and a denitration device. A boiler comprising: