JPH08312901A - Smoke tube boiler equipped with burner in group of smoke tubes - Google Patents

Abstract

PURPOSE: To make a prior art furnace tube unnecessary and contrive the miniaturization of a boiler by a method wherein a combustion tube is connected to respective fore ends of the group of a multitude of smoke tubes provided in the water part of a boiler cylinder while a burner, provided with fuel injection nozzle in the fore ends of respective combustion tubes, is connected directly to the smoke tubes. CONSTITUTION: In an internally-fired boiler, provided with combustion gas passages or a multitude of groups of smoke tubes in the water part of a boiler cylinder and generating steam by passing combustion gas through the groups of smoke tubes by burners, respective smoke tubes 4a of a first path are provided with burning instruments or burners 5. In this case, a combustion tube 5a is secured to the fore end of the smoke tube 4a coaxially and air-tightly while a fuel injection nozzle 5b is provided at the fore end of the combustion tube 5a along the axial center C.L of the combustion tube 5a On the other hand, a plurality of combustion air injection nozzles 5c are provided on the peripheral surface of the combustion tube 5b so as to be intersected with injected fuel and an igniting means or an electric heating coil 6 is provided in the combustion tube 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smoke tube boiler equipped with a cylindrical combustor, and more specifically, it is possible to eliminate a furnace tube which occupies a large volume in a furnace tube smoke tube boiler, and to reduce a low NO during combustion. _{The present} invention relates to a smoke tube boiler equipped with a cylindrical combustor realizing _x conversion.

[0002]

2. Description of the Related Art Conventionally, as a boiler having the highest boiler efficiency among all round boilers, an internally fired fire tube boiler as shown in FIG. 4 has been widely used. This kind of thing
It has a structure in which both the furnace tube 51 and the smoke tube group 56 are provided in the boiler barrel 50, and it is common to combine one corrugated furnace tube having a large diameter with the smoke tube group.

More specifically, the combustion gas generated in the furnace tube 51 flows from the furnace tube 51 through the smoke tube group 56 and is discharged to the atmosphere from the exhaust duct 57. Then, depending on the number of times the combustion gas flows through the passage, that is, the one that flows from the front to the rear in the furnace tube and flows from the rear to the front through the smoke tube group through the rear smoke chamber is called two passes. A combustion burner 52 is provided at one end of the furnace cylinder 51, and the inside of the furnace cylinder 51 constitutes a combustion chamber 53 when the burner is ignited. In addition, the furnace barrel 51
A smoke chamber 54 is formed at the other end of the rear tube sheet 55.
The smoke tube group 56 is joined to a part of the
6 are arranged along the furnace cylinder 51 on the lateral side and the upper side near the periphery thereof. In addition, the smoke tube group 56 is the boiler barrel 50.
It is immersed in the water portion W inside to form a contact heat transfer surface, and its outlet side end communicates with the exhaust duct 57.

[0004]

The conventional furnace tube smoke tube boiler described above has a simple structure and high efficiency.
Although it is widely used for air conditioning, there is a problem that the boiler can not be downsized for space saving because the furnace cylinder occupies a large volume, and the water capacity cannot be reduced to shorten the startup time. It was Furthermore, when the boiler cylinder is downsized and high-load combustion is carried out using the current combustion system, the adverse effect that the amount of NO _x generated increases as the flame temperature rises, thus reducing NO _x . I couldn't do it either.

The present invention has been made in consideration of the above-mentioned circumstances, and by eliminating the furnace tube, it is possible to reduce the size of the boiler, reduce the water capacity, and further reduce the NO _x . An object of the present invention is to provide a smoke tube boiler equipped with a combustor for a smoke tube group.

[0006]

According to the present invention, a large number of smoke tubes that serve as passages for combustion gas are provided in the water portion of a boiler body, and combustion gas from a combustor is passed through the smoke tubes to form a heat transfer surface. In a smoke tube boiler, a combustor is provided at a front end portion of each smoke tube in a smoke tube group and a combustion tube coaxially connected to the smoke tube, and is provided at a front end portion of the combustion tube to inject fuel along an axis of the combustion tube. A plurality of fuel injection nozzles are provided on the peripheral surface of the combustion cylinder, and the fuel is focused toward the smoke tube side at a position separated from the injection port of the fuel injection nozzle by a predetermined distance, and the combustion air is injected so as to intersect the injected fuel. A smoke tube boiler having a combustor in a smoke tube group including a combustion air injection nozzle and an ignition means provided in a combustion cylinder for igniting a fuel mixed with combustion air.

In the present invention, the ignition means can be constituted by a heating wire wound in a coil shape along the inner wall of the combustion cylinder body, whereby ignition at the time of starting the combustor is performed. At the same time, it is preferable to preheat the inside of the combustion cylinder to stabilize the flame.

In the present invention, a flame stabilizer for taking in a part of the combustion air to form a vortex or swirling flow and introducing the vortex or swirling flow into the combustion cylinder can be provided around the fuel injection nozzle. Further, it is preferable that the flame stabilizer supplies the formed vortex flow or swirl flow only when the boiler is started, and stops the supply after the flame is stabilized.

In the present invention, either gas or oil can be used as the fuel, but particularly in the case of oil burning, the NO _x produced can be remarkably reduced as compared with the conventional one.

[0010]

According to the present invention, a combustor is provided in each of the smoke tubes constituting the smoke tube group, the fuel is linearly injected from the fuel injection nozzle, and the combustion air is separated from the fuel injection nozzle in the combustion tube. At a position, the fuel is injected and supplied at a predetermined angle and ignited at a portion where the fuel and the combustion air are mixed to form a flame. As a result, the fuel can burn with a blue flame, and part of the flame enters the smoke tube and is cooled there, so that NO _x can be made extremely low. The combustion cylinder is heated by the flame from the inside, but is cooled by the air from the outside, so that burning does not occur due to overheating, and the optimum temperature for maintaining the flame is maintained.

According to the structure in which the flame stabilizer is provided around the fuel injection nozzle according to the present invention, a part of the combustion air taken in becomes a vortex or a swirl flow and is introduced into the combustion cylinder, so that the fuel is ignited. And the flame becomes stable.

Further, according to the construction in which the flame stabilizer is operated only at the time of starting the boiler, it is possible to stabilize the ignition and the flame and prevent the increase of NO _x after the combustion becomes steady.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of a smoke tube boiler showing an overall configuration of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of an essential part showing a configuration of a combustor which is a characteristic part of the present invention.

In both figures, a smoke tube boiler 1 of the present embodiment is a smoke tube boiler having no furnace tube, and a large number of smoke tube groups 4 serving as passages for combustion gas are provided in a water portion 3 of a boiler body 2 to form a combustor. 5 is an internally fired boiler in which the combustion gas from No. 5 is passed through the smoke tube group to form a heat transfer surface.

The burner 5 as the combustor is provided in each smoke pipe 4a of the first pass, and as shown in FIG. 2, the smoke pipe 4a has a front end portion coaxially and airtightly with the smoke pipe 4a. 5a is fixed. At the front end portion of the combustion cylinder 5a, the axis C. A fuel injection nozzle 5b for injecting fuel along L is provided.

A plurality of, specifically, a plurality of, on the peripheral surface of the combustion tube 5b are focused toward the smoke tube 4a at a position apart from the injection port of the fuel injection nozzle 5b and intersect with the injected fuel. Two to eight combustion air injection nozzles 5c are provided. That is, the combustion air injection nozzle 5c is adapted to inject the combustion air toward the injected fuel at a predetermined angle θ. The predetermined angle θ
Is preferably about 60 ° to form a blue flame.

Inside the combustion cylinder 5a, an electric heating coil (heating wire) 6 is provided as an ignition means for igniting the fuel mixed with the combustion air. The electric heating coil 6 is spirally wound and arranged along the inner wall of the combustion cylinder 5a, and is heated to about 500 ° C. to ignite when the boiler is started and preheat the inside of the combustion cylinder 5a to generate a flame. It is designed to be stable.

Explaining the principle of the burner 5,
A fuel injection nozzle 5b for injecting fuel is provided on the front side of the inlet of the smoke pipe 4a. Combustion air is supplied from a plurality of locations on the peripheral surface of the combustion cylinder 5a to the fuel injected from the combustion injection nozzle 5b. It is supplied at a high speed with an angle.
As a result, when the fuel is gas, premixed combustion is obtained because the mixing of the fuel and combustion air is strengthened, and when the fuel is oil, re-atomization and evaporation of oil droplets are performed. Therefore, in both cases, low NO _x can be obtained.

The flame of the burner 5 is the same as that of the combustion cylinder 5a.
It is stabilized by the smoke pipe 4a communicating with it and at the same time it is stabilized.
Since it is cooled by the smoke tube 4a of
NO _x Promotion is promoted.

As described above, since the structure of the present embodiment is a simple structure without a flame stabilizer such as a diffuser or a swirler, it is conceivable that the flame becomes unstable when the boiler is started. Since the combustion cylinder 5a is heated by the electric heating coil 6, the flame upon ignition can be stabilized. As described above, if flame stability is obtained, the advantage of not having a flame stabilizer can be effectively utilized. That is, it becomes possible to strongly mix the fuel and the combustion air before the flame is generated, whereby the combustion of the premixed flame can be realized, and the NO
It is possible to significantly reduce _x .

The operation of the smoke tube boiler having the above structure will be described below. In FIG. 2, first, the combustion cylinder 5 a is heated by energizing the electric heating coil 6. Next, the fuel is linearly injected from the fuel injection nozzle 5b, and the combustion air is injected from the combustion air injection nozzle 5c toward the fuel. The fuel mixed with the combustion air is ignited inside the combustion cylinder 5a and away from the injection port of the fuel injection nozzle 5b to form a low NO _x blue flame.

The inside of the burning combustion cylinder 5a is heated by the flame, but the outside of the combustion cylinder 5a is cooled by air. Therefore, the combustion cylinder 5a is kept at a proper temperature without being burned by overheating. And, as a result, continue to maintain a stable flame.

The combustion gas flows in the smoke pipe 4a communicating with the combustion tube 5a, forms a contact heat transfer surface for the water W in the boiler barrel 2, and the exhaust gas 7 is discharged from the exhaust duct 8 to the atmosphere. It On the other hand, the required steam 9 is taken out of the boiler from the steam chamber 10.

FIG. 3 shows a structure in which the flame stabilizer 20 is provided in the burner described above. In the figure, the same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. The flame stabilizer 20 including a baffle plate, a diffuser, a swirler, or the like introduces a part of the combustion air around the fuel injection nozzle 5b provided at the front end of the combustion cylinder 5a, and swirls or swirls the air. It is given and supplied to the inside of the combustion cylinder 5a, and is fixed in the cylinder portion 5d extending from the combustion cylinder 5a. Further, an inlet port 5e for introducing a part of the combustion air, that is, the combustion stabilizing air, is provided at the front end portion of the tubular portion 5d. With this configuration, it is possible to further stabilize the ignition and the flame when the boiler is started.

Ignition using only the electric heating coil 6 described above
Although simple and inexpensive, if the capacity of the electric heating coil 6 is small, the combustion cylinder may not be sufficiently warmed at the time of starting the boiler, and ignition may take time and combustion may become unstable. However, if the flame stabilizer 20 is used, ignition and flame stability will be ensured when the boiler is started.

When the flame stabilizer 20 is used,
Flame tries to increase NO _x becomes normal red flame not blue flame, during boiler startup for the flame temperature is low, the level of the NO _x remains low. Further, the larger the amount of combustion air that passes through the flame stabilizer 20, the easier the ignition and the stabilization of the flame at the time of startup, but on the other hand, the amount of NO _x increases when the combustion reaches a steady state. . In order to eliminate this, it is preferable that a part of the combustion air passing through the flame stabilizer 20 is supplied only when the boiler is started, and the supply is stopped when the flame becomes stable.
As a means for supplying or stopping a part of the combustion air, a conventionally known manual valve or control valve can be used.

The present invention can be applied to both a smoke tube boiler that uses gas as a fuel and a smoke tube boiler that uses oil as a fuel. However, when it is oil-fired, it can be compared with a conventional oil-fired boiler. A significant NO _x reduction is obtained. Further, in the present invention, the combustion air injection nozzle forms a blue flame, so it is desirable to dispose the combustion air injection nozzle at an appropriate distance from the fuel injection nozzle.

Further, although the ignition means of the present invention is constituted by the electric heating coil in the above-mentioned embodiment, it is not limited to this, and any means capable of generating sufficient heat for ignition, such as pilot burner, electric spark, etc. It is also possible to use various ignition devices. Further, since the igniting means attached to the combustion cylinder is cooled by air, overheating does not occur and there is no risk of burning.

[0029]

As is apparent from the above description, the present invention has a structure in which the combustor is directly connected to the smoke pipe, so that the furnace cylinder can be eliminated, the boiler can be made smaller, and the water capacity can be reduced. You can enable it. Therefore, the time required to start the boiler can be significantly shortened and the space can be saved.

Further, according to the present invention, since a combustor capable of producing a blue flame is adopted and the flame generated in this combustor is cooled by the smoke tube, extremely low NO _x can be obtained. . Further, since the combustor is cooled by air, it does not overheat and can be maintained at a temperature necessary for stabilizing the flame.

According to the present invention, since the ignition is performed by the electric heating coil provided in the combustion cylinder, the ignition can be ensured and the cost can be reduced. In addition, since the combustor is installed in all of the smoke tubes, it is possible to guide combustion gas into the smoke tubes in an orderly manner without loss.
Combustion efficiency can be improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view showing the structure of the combustor shown in FIG.

FIG. 3 is a view corresponding to FIG. 2, showing another configuration of the combustor.

FIG. 4 is a vertical cross-sectional view showing the configuration of a conventional flue tube boiler.

[Explanation of symbols]

 1 smoke tube boiler 2 boiler body 3 water part 4 smoke tube group 4a smoke tube 5 burner 5a combustion cylinder 5b combustion injection nozzle 5c combustion air injection nozzle 6 electric heating coil 7 exhaust gas 8 exhaust duct 9 steam 10 steam chamber 20 flame stabilizer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F23D 14/66 F23D 14/66

Claims (4)

[Claims] 1. A smoke tube boiler in which a plurality of smoke tube groups serving as passages for combustion gas are provided in a water portion of a boiler body, and combustion gas from a combustor is passed through the smoke tube group to form a heat transfer surface. A combustion tube connected to the front end of each smoke tube in the smoke tube group coaxially with the smoke tube; a fuel injection nozzle provided at the front end of the combustion tube to inject fuel along an axis of the combustion tube; For combustion, a plurality of which are provided on the peripheral surface of the combustion cylinder, converge toward the smoke tube side at a position apart from the injection port of the fuel injection nozzle toward the smoke tube side, and inject the combustion air so as to intersect with the injected fuel A smoke tube boiler having a combustor in a smoke tube group, comprising: an air injection nozzle; and an ignition means provided in the combustion cylinder for igniting the fuel mixed with the combustion air. 2. The smoke tube boiler according to claim 1, wherein the ignition means is composed of a heating wire wound in a coil shape along the inner wall of the combustion barrel body. 3. The flame stabilizer according to claim 1, further comprising a flame stabilizer for introducing a part of the combustion air into the combustion cylinder and forming a vortex flow or a swirl flow around the fuel injection nozzle. Smoke tube boiler. 4. The smoke tube boiler according to claim 3, wherein the flame stabilizer supplies the formed vortex flow or swirl flow only when the boiler is started, and stops the supply after the flame is stabilized.