JP2951868B2 - Fire tube boiler with a combustor in the fire tube group - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire tube boiler provided with a cylindrical combustor, and more particularly to a fire tube boiler which can eliminate a large tube in a furnace tube boiler and can reduce a low NO during combustion. _{The present} invention relates to a smoke tube boiler provided with a cylindrical combustor that realizes _x .

[0002]

2. Description of the Related Art Conventionally, as a boiler having the highest boiler efficiency among round boilers, an inner-fired furnace tube boiler as shown in FIG. 4 has been widely used. This kind of thing
The boiler body 50 has a structure in which both a furnace tube 51 and a tube group 56 are provided, and a type in which one large-diameter corrugated tube tube is combined with a tube group is generally used.

More specifically, the combustion gas generated in the furnace tube 51 flows from the furnace tube 51 through a group of smoke tubes 56 and is discharged from the exhaust duct 57 to the atmosphere. And the two-pass is defined by the number of times that the combustion gas flows through the passage, that is, from the front to the rear in the furnace tube and from the rear to the front through the rear smoke chamber. A combustion burner 52 is provided at one end of the furnace tube 51, and the inside of the furnace tube 51 forms a combustion chamber 53 when the burner is ignited. The furnace tube 51
A smoke chamber 54 is formed at the other end of the
The above-mentioned tube group 56 is joined to a part of the
Reference numeral 6 is arranged along the furnace tube 51 on the lateral side and the upper side near the periphery thereof. In addition, the fire tube group 56 includes the boiler body 50.
The contact heat transfer surface is formed by being immersed in the water portion W of the inside, and the outlet side end thereof communicates with the exhaust duct 57.

[0004]

The conventional furnace tube boiler described above has a simple structure and a high efficiency, so that it can be used for industrial and industrial purposes.
Although widely used for air conditioning, etc., the furnace tube occupies a large volume, so there is a problem that the boiler cannot be reduced in size for the purpose of saving space and the water capacity cannot be reduced to shorten the startup time. Was. Furthermore, since on an implementation of the miniaturized high load combustion boiler body with a current combustion system produces an adverse effect that the generation amount of the NO _x increases with increasing flame temperature, reducing NO _x I couldn't do that.

[0005] The present invention has been made in consideration of the circumstances described above, capable of enabling miniaturization of the boiler, reducing the water volume by eliminating the furnace tube, further to achieve low NO _x reduction It is another object of the present invention to provide a smoke tube boiler having a combustor in a group of smoke tubes.

[0006]

According to the present invention, a large number of fire tube groups are provided in a water portion of a boiler drum as a passage of combustion gas, and a combustion gas from a combustor is passed through the smoke tube group to form a heat transfer surface. In a fire tube boiler, the combustor is located outside the tube plate of the boiler body.
Provided at the front end of each smoke tube coaxially with the smoke tube.
A closely connected combustion cylinder, a fuel injection nozzle provided at the front end of the combustion cylinder and injecting fuel along the combustion cylinder axis, and a plurality of fuel injection nozzles provided on the peripheral surface of the combustion cylinder A combustion air injection nozzle that focuses toward the smoke tube side at a predetermined distance from the injection port and injects combustion air so as to intersect with the injected fuel, and is provided in the combustion cylinder and mixed with combustion air. Bei and ignition means for igniting the fuel
The flame inside the combustion cylinder is regulated by sealing the combustion cylinder.
At the same temperature, the outer wall of the fuel cylinder is air-cooled.
This is a fire tube boiler equipped with a combustor in the formed fire tube group.

In the present invention, the igniting means may be constituted by a heating wire wound in a coil shape along the inner wall of the combustion cylinder body, thereby igniting the combustor at the time of starting. It is preferable to preheat the inside of the combustion cylinder and stabilize the flame.

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

[0009] In the present invention, the fuel can be used in the oil in the gas, particularly if oil-fired, compared with the conventional, NO _x generated can be remarkably lowered.

[0010]

According to the present invention, a combustor is provided for each of the smoke tubes constituting the smoke tube group. In the combustion tube, the fuel is injected linearly from the fuel injection nozzle, and the combustion air is separated from the fuel injection nozzle. At the position, the fuel is injected and supplied at a predetermined angle to the fuel, and is ignited at a portion where the fuel and the combustion air are mixed to form a flame. Thereby, the fuel can be burning blue flame, also because some of the flame where it is cooled by entering the smoke tubes, can be very low NO _x. The combustion cylinder is heated by the flame from the inside, but is cooled by the air from the outside, so that it does not burn out due to overheating, and maintains an optimal temperature for holding the flame.

According to the structure of the present invention in which the flame stabilizer is provided around the fuel injection nozzle, a part of the taken-in combustion air is swirled or swirled and introduced into the combustion cylinder, so that the fuel is ignited. And the flame stabilizes.

Further, according to the configuration of operating the flame stabilizer only at the start of the boiler, along with stabilizing the ignition and flame, after combustion is steady, it is possible to prevent an increase in NO _x.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of a flue-tube boiler showing an entire configuration of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part showing a configuration of a combustor which is a feature of the present invention.

In both figures, a fire tube boiler 1 according to the present embodiment is a fire tube boiler having no furnace tube. A plurality of fire tube groups 4 serving as passages of combustion gas are provided in a water portion 3 of a boiler body 2 and a combustor is provided. 5 is an inner-fired boiler in which the heat transfer surface is formed by passing the combustion gas of No. 5 through the group of tubes.

The burner 5 as a combustor is provided in each of the smoke tubes 4a of the first pass. As shown in FIG. 2, a combustion tube is provided at the front end of the smoke tube 4a coaxially and airtightly with the smoke tube 4a. 5a is fixed. Each combustion cylinder 5a is a tube sheet
2a is provided inside the wind box so as to protrude outward.
Is, at the front end of the combustion cylinder 5a, the axis C. of the combustion cylinder 5a Fuel injection nozzle 5b for injecting fuel along L
Is provided.

At a position spaced a predetermined distance from the injection port of the fuel injection nozzle 5b, a plurality of beams, specifically, a plurality of beams, specifically, are formed on the peripheral surface of the combustion tube 5b so as to intersect with the injected fuel. Two to eight combustion air injection nozzles 5c are provided. That is, the combustion air injection nozzle 5c injects combustion air toward the injected fuel at a predetermined angle θ with respect to the fuel. The predetermined angle θ
Is preferably about 60 ° to form a blue flame.

An electric heating coil (electric heating wire) 6 is provided in the combustion cylinder 5a as ignition means for igniting the fuel mixed with the combustion air. The electric heating coil 6 is spirally wound along the inner wall of the combustion cylinder 5a, and is heated to about 500 ° C. to ignite when starting the boiler and to preheat the combustion cylinder 5a to generate a flame. Can be stabilized.

The principle of the burner 5 will be described.
A fuel injection nozzle 5b for injecting fuel is provided on the front side of the entrance of the smoke tube 4a. With respect to the fuel injected from the fuel injection nozzle 5b, combustion air is supplied from a plurality of locations on the peripheral surface of the combustion cylinder 5a to a predetermined position. Supplied at high speed with an angle.
Thus, when the fuel is gas, the mixture of the fuel and the combustion air is strengthened, so that premixed combustion is obtained, and when the fuel is oil, re-atomization and evaporation of oil droplets are performed. Therefore, in each case, low NOx is obtained.

The flame of the burner 5 is generated by the combustion cylinder 5a.
It is stabilized by the smoke tube 4a communicating with it and at the same time
Because it is cooled by the smoke tube 4a
NO _x Is promoted.

As described above, since the configuration of the present embodiment is a simple configuration without a flame stabilizer such as a diffuser or a swirler, it is supposed that the flame becomes unstable when the boiler is started. Since the combustion tube 5a is heated by the electric heating coil 6, the flame at the time of ignition can be stabilized. As described above, if flame stability can be obtained, the advantage of not having a flame stabilizer can be effectively used. That is, the fuel and the combustion air can be strongly mixed before the flame is generated, whereby the combustion of the premixed flaming flame can be realized, and NO
_x can be significantly reduced.

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

Although the inside of the combustion tube 5a during combustion is heated by the flame, the outside thereof is cooled by air, so that the combustion tube 5a is maintained at an appropriate temperature without being burned out by overheating. And, as a result, maintain a stable flame.

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

FIG. 3 shows a configuration in which a flame stabilizer 20 is provided in the above-described burner. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. The flame stabilizer 20 composed of a baffle, 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 it. The fuel is supplied into the combustion cylinder 5a, and is fixed in a cylinder 5d extending from the combustion cylinder 5a. In addition, an inlet 5e for introducing a part of the combustion air, that is, the combustion stabilizing air, is provided at the front end of the cylindrical portion 5d. According to this configuration, the ignition and the flame at the time of starting the boiler can be further stabilized.

The ignition by the electric heating coil 6 alone is as follows.
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 it may take time to ignite and the combustion may become unstable. However, if the above-mentioned flame stabilizer 20 is used, ignition and flame stabilization 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. Although the flame stabilizer 20 greater the amount of combustion air through at startup ignition and flame stability becomes easier, on the other hand, so that the amount of the NO _x when the combustion is in a steady state is increased . In order to solve 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 is stabilized.
As means for supplying or stopping supply of 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 gas tube boiler using gas as fuel and a fire tube boiler using oil as fuel. Significant NO _x reduction is obtained. Further, in the present invention, the combustion air injection nozzle is desirably disposed at an appropriate distance from the fuel injection nozzle in order to form a blue flame.

Further, the ignition means of the present invention is constituted by an electric heating coil in the above embodiment. However, the invention is not limited to this. For example, a pilot burner, an electric spark or the like can be used as long as it can generate sufficient heat for ignition. Any suitable ignition device can be used. And since the ignition means attached to the combustion tube is cooled by air, there is no possibility of overheating and burning.

[0029]

As is apparent from the above description, the present invention has a configuration in which the combustor is directly connected to the smoke tube, so that the furnace tube can be eliminated, and the boiler can be reduced in size and the water volume can be reduced. Can be made possible. Therefore, the time required for starting the boiler can be greatly reduced, and the space can be saved.

Further, according to the present invention, since adopting a combustor capable of producing a blue flame, a flame that is generated in the combustor is configured to cool at smoke tubes, very low NO _x obtained . Further, since the combustor is cooled by air, the combustor 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 configuration can be made at a low cost. In addition, since the combustors are provided in all the smoke tubes, the combustion gas can be guided into the smoke tubes orderly without loss,
Combustion efficiency can be improved.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a configuration of the combustor shown in FIG.

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

FIG. 4 is a longitudinal sectional view showing a configuration of a conventional furnace tube boiler.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Smoke tube boiler 2 Boiler trunk 3 Water part 4 Smoke tube group 4a Smoke tube 5 Burner 5a Combustion cylinder 5b Fuel injection nozzle 5c Combustion air injection nozzle 6 Electric heating coil 7 Exhaust gas 8 Exhaust duct 9 Steam 10 Steam room 20 Flame stabilizer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-119903 (JP, A) JP-A-1-239306 (JP, A) JP-A 6-65707 (JP, U) JP-A 62-119 98924 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F22B 31/00 F22B 9/10 F23D 14/12

Claims (4)

(57) [Claims] 1. A fire tube boiler in which a plurality of fire tube groups serving as combustion gas passages are provided in a water portion of a boiler body, and a combustion gas from a combustor passes through the smoke tube group to form a heat transfer surface. The smoke tube provided outside the tube plate of the boiler body;
A combustion tube which is coaxially connected to the front end of each of the smoke tubes in a gas-tight manner, a fuel injection nozzle provided at the front end of the combustion tube, and injects fuel along the axis of the combustion tube; A plurality of air injection nozzles are provided on the surface, converge toward the smoke tube side at a position separated by a predetermined distance from the injection port of the fuel injection nozzle, and inject combustion air so as to intersect with the injected fuel. , Bei and ignition means for the provided combustion cylinder, igniting the fuel mixed with combustion air
By closing the combustion cylinder, the fire in the combustion cylinder
While maintaining the flame at a predetermined temperature, the outer wall of the fuel cylinder is air-cooled.
A smoke tube boiler comprising a combustor in a group of smoke tubes, characterized in that the boiler is configured to operate. 2. The smoke tube boiler according to claim 1, wherein said ignition means is constituted by a heating wire wound in a coil shape along an inner wall of said combustion tube body. 3. The flame stabilizer according to claim 1, wherein a flame stabilizer is provided around the fuel injection nozzle to form a vortex or swirl by taking a part of combustion air and introducing the swirl or swirl into the combustion cylinder. Fire tube boiler. 4. The smoke tube boiler according to claim 3, wherein the flame stabilizer supplies the formed vortex flow or swirling flow only when the boiler is started, and stops the supply after the flame is stabilized.