JPH06201103A - Boiler having water tube group - Google Patents

Abstract

PURPOSE:To provide a boiler, provided with a small sized high performance water tube group, excellent in burning property, high in low-NOx performance and capable of matching with any burner. CONSTITUTION:A boiler is provided with a multitude of water tubes as heat transfer surfaces and is provided with the group of water tubes of D/d3=1.5-3.0, L/d3=0.2-1.0 when the water tubes are arranged in check but provided with the group of water tubes of D/d3=1.5-3.0 and L/d3=0.1-0.5 when the tubes are arranged in zigzag. On the other hand, the group of water tubes in first-second row or first-fourth row are arrayed in zigzag and the water tubes in other groups are arrayed in check. Further, the boiler is provided with groups of water tubes having a heat insulating space by omitting one part of the water tubes in a part whereat the temperature of combustion gas is reduced to 1300 deg.C or lower, or the temperature of 1300-900 deg.C.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of enhancing combustion performance by arranging a large number of water pipes in a so-called heat absorption water pipe insertion type combustion chamber and achieving NOx reduction. The present invention relates to an improvement of a boiler having a compact and high-performance water tube group.

[0002]

2. Description of the Related Art Conventionally, a large number of water pipes are arranged in a combustion chamber to form a heat absorption water pipe insertion type combustion chamber, and fuel is burned in the large number of water pipe groups to downsize the boiler and cool the flame by the water pipes. There is an invention of the present applicant who intends to reduce NOx by the effect (Japanese Patent Application No. 63-227181). However, in the case of the above-mentioned invention of the applicant of the present invention, the characteristics of the burner, the arrangement and shape of the burner and the water tube group, the arrangement of the water tube group, and the like are large, and the combustibility is reduced even if the NOx reduction is achieved. If it becomes worse, or conversely if the combustibility is good, the NOx value becomes large against expectations and there are many problems to be studied in the future, and various improvements for practical use were necessary.

In the present invention, good combustibility means that there is no oscillatory combustion of the burner, no CO or unburned substances are generated, and the combustion capacity range is wide and the air-fuel ratio range is wide. ing.

[0004]

At present, the generation mechanism of NOx has been almost clarified, and it is considered that most of the high-quality fuel is thermal NO generated in the high temperature region of the flame. Therefore, in order to suppress the generation of NOx, it is preferable to dispose the water pipe as close as possible to the tip of the burner so that the flame temperature is not raised from the upstream portion as much as possible. However, if the water pipe is too close to the burner, it will burn.
The flame holding performance at the tip of the burner is impaired, the mixing of fuel and air in the burner jet becomes poor, and in that state, cooling is effected by the water pipe, resulting in poor combustion performance.

In order to improve the above-mentioned prior invention of the applicant, the present inventors have studied in detail the factors affecting both the combustion performance and the low NOx performance, and as a result, the following problems have been clarified. . That is, (a) The ratio of the burner outlet diameter to the typical size (e.g. diameter) of the combustion chamber governs the jet flow pattern when determining the arrangement of the pipe groups, and is combined with other influencing factors. It strongly affects combustion performance and low NOx performance. (B)
The ratio of the burner jet diameter to the distance from the burner tip to the first water pipe is related to (a) above, and the combustion performance of the boiler and low NO
x Significantly affects performance. In short, if the above distance is increased, the distance that the fuel and air are mixed by the time it hits the water pipe and is cooled will improve the combustibility, but due to the above reason, the NOx value will increase. Like On the other hand, if the distance from the tip of the burner to the first water pipe is reduced, the NOx value decreases as described above, but the combustibility deteriorates because the water pipe cools the mixture of air and fuel in poor condition. If they are brought too close to each other, flame holding may be deteriorated, which may cause vibrational combustion or misfire. (C) The arrangement method of the water tubes has a strong influence on the combustion characteristics and NOx values in the combustion in the tube group. That is, the flame hits the first water pipe and affects the performance of the subsequent mixing of the entire air and fuel. In the case of the secondary arrangement, the water tube group has a rectifying effect, and the flame is divided along the flow. Originally, the flow path with a poor air-fuel ratio is
No matter how much mixing is promoted by the Karman vortices generated in the wake of each water pipe, the combustibility is eventually poor, and the combustibility is poor as a whole even if there are other suitable air-fuel ratio passages. On the other hand, the chidori array has less flow passage division along the flow, and since fluid mixing in the direction perpendicular to the flow is easy to occur, the combustibility is better than that of the granular array, but the NOx value tends to be correspondingly higher. (D) Taking advantage of the improved mixing performance of the Chidori array, bring the water pipe closer to the burner than the first eye array, and
It is possible to reduce the Ox value. In the present invention, whether to use the staggered arrangement or the fine-grained arrangement has respective heat transfer characteristics, and therefore may be determined from other design conditions and is not particularly limited. Therefore, depending on the case, even if a duster array is adopted as a part of the burner side, and thereafter, even if it is a second eye array, the combustion characteristics and the NOx value are close to those of the entire duster array. (E) Under any of the conditions, the object of the present invention is to carry out combustion and heat transfer in the water tube group at a low temperature and to perform constant temperature combustion. Since the generation in the high temperature part is dominant, it is effective to remove a part of the water pipe to provide an adiabatic space in order to promote combustion when the temperature falls below that. However, if the temperature is below 900 ° C, the combustion reaction has already become difficult to proceed, so that effect is not obtained.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a boiler having a water pipe group, and in order to solve the above problems, the first invention is a boiler having a large number of water pipe groups as heat transfer surfaces.
When the fuel and the combustion air are separately or mixed and ejected from the burner and burned, the water pipes in the combustion chamber are arranged such that the diameter or one side of the combustion chamber is arranged when the water pipes are in the first-row arrangement. Of the length D of the burner and the diameter d ₃ of the burner outlet D / d ₃ = 1.5 to 3.
0 and the distance L and d from the burner tip to the first water pipe
A boiler having a water tube _group, wherein a ₃ and the ratio L / d ₃ = 0.2 ~1.0 the second invention in the case of the water tube group is a zigzag sequence in the first aspect the D / d ₃ = 1.5 ~
3.0 and L / d ₃ = 0.1 to 0.5, and the third invention is the first to second columns or the first to fourth in the second invention.
The row of water pipes is arranged in a staggered arrangement, and the water pipes after that are arranged in a coarse arrangement, and the fourth invention is the combustion after the combustion gas temperature drops to 1300 ° C or less in the first, second or third invention. This is a boiler having a water pipe group in which a heat insulating space is provided by removing a part of the water pipe at a gas temperature of 1300 to 900 ° C.

In the first aspect of the present invention, when D / d ₃ is less than 1.5, the burner outlet diameter (d ₃ ), that is, its area becomes too large with respect to the cross section of the combustion chamber, and the burner jet speed. or summer flammability Na itself is poor, bar - - slow server Na weak recirculation of involving the combustion gases around the upstream water tube by the jet, the low NO _x resistance, flammability both deteriorated. Also D / d ₃
The larger the value, the better. However, if D / d ₃ is larger than 3.0, the ejection speed of the burner becomes too high and the burner is lifted beyond the flame holding limit or misfired. Furthermore, the wind pressure loss of the burner increases, and the pushing fan power increases. L / d ₃ = 0.2 under this condition in the first-order arrangement
It was found that the range of up to 1.0 is the best in terms of flammability and low NOx property. That is, when L / d ₃ is less than 0.2, the NOx value is low but the combustibility is poor, and when L / d ₃ exceeds 1.0, the combustibility is improved but the NOx value is high.

In the first aspect of the present invention, when the water tube group has a staggered arrangement, the above D / d ₃ = 1.5 to 3.0 and L / d ₃ =
It should be 0.1 to 0.5. Although the value of D / d ₃ is as described above, the present inventors found that in the case of the small arrangement, the combustion was better than in the first arrangement, and the NOx value tended to increase. Therefore, the optimum condition of L / d _{3 in} the case of the chidori array was found to be in the range of L / d ₃ = 0.1 to 0.5 as a result of the study by the present inventors. When L / d ₃ is less than 0.1, the water pipe comes too close to the tip of the burner, so that the flame holding performance of the burner itself deteriorates and vibration combustion or misfire occurs. Further, when L / d ₃ in the chidori array exceeds 0.5, the NOx value becomes extremely high, which is not suitable.

When the first to second rows or the first to fourth rows of water pipes are arranged in a staggered manner, even if the subsequent water pipes are arranged in a staggered arrangement, the same effect as the staggered arrangement continues as a whole, and the staggered arrangement is completed. This tube group configuration is effective for making the entire boiler more compact due to the heat transfer performance of the array. Further, when the combustion gas temperature has dropped to 1300 ° C or lower in the above, by removing a part of the water pipe where the combustion gas temperature is 1300 to 900 ° C and providing an adiabatic space, the combustion performance and low NOx performance are improved. Can be made.

The burner used in the present invention is a premixed burner.
Combustion and heat transfer are performed in the water tube group. In this case, the mixing characteristics of the burner itself are basically important, but this does not change the numerical limitation of the present invention. In the conventional burner with a long flame that does not mix well, it is necessary to roughly arrange the water pipes to weaken the heat absorption to the flame, that is, to lengthen the tube group combustion part (LL), but the present invention is a premixing burner. As long as it does not burn on the burner surface like D, d / d ₃ , L / d
The inventor has found that the numerical limitation of ₃ does not change.
It was found by the test of Na.

[0011]

EXAMPLES The present invention will be described below with reference to examples. Figure 1 shows a water pipe from a distance L from the burner (1) nozzle.
(3) is an example of a boiler having a group of water tubes in a heat collecting water pipe insertion type combustion chamber (2) in which the heat collecting water pipe is arranged, and the air supplied to the burner The fuel is flame-held in the burner head portion to start combustion, and is jetted from the burner jet diameter d ₃ . The combustion reaction starts in the burner head, and the combustion and heat transfer proceed simultaneously in the water tube group.
It ends with the length of (LL). Combustion gas temperature in LL is 90
It is necessary to keep the temperature above 0 ° C, and if it is lower than this, the combustion reaction is suppressed and unburned gas and CO
Will remain. Therefore, arrangement of water pipes (h / d, l / d)
The length of LL and LL is determined by the mixing performance and combustion performance of the burner itself, and is determined by the limitation of the present invention. As described above, FIG. 1 shows a group of water tubes in a horizontal arrangement, but the same applies to the case of a small arrangement.

In FIG. 1, D / d ₃ = 1.8 to 3.0, L
The burner and the heat collecting water pipe insertion type combustion chamber are constituted in the range of / d ₃ = 0.2 to 1.0. Therefore, as described above, it is possible to provide a boiler having an extremely small and high-performance water pipe which satisfies the combustibility and the low NOx property. Although not shown after the heat-collecting water pipe insertion type combustion chamber, the heat is absorbed up to an appropriate exhaust gas temperature as a convection heat transfer unit composed of a bare water pipe or a finned water pipe in the subsequent flow section of the boiler. It is discharged outside.

Next, when the water tubes are arranged in a small line, macro mixing in the tube group is promoted, combustion is improved, and the amount of NOx generated is increased, so L must be made smaller than in the case of the eye arrangement. The preferred range is L / d ₃ = 0.1-as described above.
It is 0.5. In this case, it has been found that substantially the same effect can be obtained even if only the first to second columns or the first to fourth columns are arranged in a staggered arrangement and the others are arranged in a coarse arrangement. Further, from the viewpoint of energy saving, the O ₂ concentration of exhaust gas should be made as low as possible to reduce the O ₂
In order to improve the performance, it is necessary to improve the combustibility while achieving low NOx. In this case, the combustion gas temperature is
Combustion gas temperature after falling below 1300 ℃ is 1300 to 900
By removing a part of the water pipe in the temperature range of ℃ to provide an adiabatic space and promoting the macro mixing in this part, the combustibility can be enhanced without increasing the amount of NOx produced.

In the present embodiment, by removing the third and fourth rows of the water pipe, the conventional O ₂ concentration can be narrowed down to about 3 to 4% without deteriorating the low NOx performance.
I was able to narrow down to about 2%.

[0015]

The effects of the present invention are summarized as follows. The present invention relates to a heat-collecting water pipe-inserting type boiler, wherein when the heat-collecting water pipe group is in a side-by-side arrangement, D / d is 1.5 to 3.0, and
By setting d ₃ to 0.2 to 1.0, the ejection speed of the burner is increased, and there is no oscillatory combustion of the burner, and there is no CO or unburned gas generation. We have completed a boiler with a small and high-performance water tube group that enhances the low NOx performance of a simple boiler and matches it to any burner.

In the heat collecting water tube internal type boiler, when the water tube group is arranged in a staggered manner, D / d ₃ is set to 1.5 to 3.0 and L / d _{3 is set} to 0.1 to 0.5. It is possible to obtain a boiler having a small-sized high-performance water pipe group that achieves the above effect.

The first to second rows or the first to fourth rows of the heat collecting water pipe insertion type boiler are arranged in a staggered arrangement, and thereafter the tube group arrangement of the eye-catching arrangement has the effect of making the boiler more compact. Play.

[0018] In the heat collecting water pipe insertion type boiler, the combustion gas temperature after the combustion gas temperature drops to 1300 ° C or lower is 1300 to
It was possible to promote combustion by improving the low NOx performance of the boiler by removing a part of the water pipe at 900 ℃ and providing an adiabatic space. That is, according to the present invention, it is possible to provide a boiler having a water pipe group that matches the heat collecting water pipe insertion type combustion chamber by enhancing the combustion performance and the low NOx performance in any burner boiler for the first time. .

[Brief description of drawings]

FIG. 1 shows an embodiment of a boiler having a heat-collecting water pipe-inserted combustion chamber in which the water pipe of the present invention has a linear arrangement.

[Explanation of symbols]

 1. Burner 2. Heat absorption water pipe insertion type combustion chamber 3. Water tube LL. Tube group combustion section

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The burner used in the present invention is a premixed burner, in which combustion and heat transfer are performed in the water tube group. In this case, the mixing characteristics of the burner itself are of fundamental importance, which does not change the numerical limitation of the invention. In a conventional long-flame burner with poor mixing, it is necessary to roughly arrange the water pipes to weaken the heat absorption to the flame, that is, to lengthen the tube group combustion part (LL), but the present invention is similar to the premixing burner. Water pipe
The present inventors have found through various burner tests that the numerical limits of D / d ₃ and L / d ₃ do not change unless they burn in the extremely small space up to the first row . .

[Procedure amendment]

[Submission date] April 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The burner used in the present invention is a premixed burner, in which combustion and heat transfer are performed in the water tube group. In this case, the mixing characteristics of the burner itself are of fundamental importance, which does not change the numerical limitation of the invention. In a conventional long-flame burner with poor mixing, it is necessary to roughly arrange the water pipes to weaken the heat absorption to the flame, that is, to lengthen the tube group combustion part (LL), but the present invention is similar to the premixing burner. Unless it burns on the burner surface, the above D / d ₃ , D
/ D ₃ numerical limits inventors that does not change or the like is was found connexion by the test of the various burners.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

In the present embodiment, by removing the third and fourth rows of the water pipe, the conventional O ₂ concentration can be narrowed down to about 3 to 4% without deteriorating the low NOx performance.
It can be reduced to about 2%. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 10, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoki Ishiya 8-7 Iwazono-cho, Ashiya-shi

Claims (4)

[Claims] 1. In a boiler having a large number of water tubes as heat transfer surfaces, when the fuel and the combustion air are jetted from the burner individually or mixedly and ejected, the water tubes are arranged in the combustion chamber. When the water pipes are in a tandem arrangement, the ratio D / d ₃ = 1.5 of the diameter D of the combustion chamber or the length D of one side and the burner jet diameter d ₃
~ 3.0 and the distance L from the burner tip to the first water pipe
Boiler having a water tube group, characterized in that the ratio L / d ₃ = 0.2 ~1.0 between d ₃ and. 2. The D / d ₃ when the water pipes are arranged in a line.
= 1.5 to 3.0 and L / d ₃ = 0.1 to 0.5, the boiler having the water tube group according to the first item. 3. A boiler having a water pipe group according to claim 2, wherein the first to second rows or the first to fourth rows of the water pipe group are arranged in a staggered manner and the subsequent water pipe groups are arranged in a tandem arrangement. 4. The heat insulating space is provided by removing a part of the water pipe at a portion where the combustion gas temperature is 1300 to 900 ° C. after the combustion gas temperature is lowered to 1300 ° C. or less. Boiler with water tube group.