JPH07229608A - Multi-tube type once-through boiler - Google Patents

Abstract

PURPOSE:To provide a multi-tube type once-through boiler, permitting the reduction of NOx and miniaturization of a device, by a method wherein the generation of NOx and CO is restricted and the sudden cooling of the flame of a flaming burner is permitted. CONSTITUTION:A flaming burner 7, having a multitude of flame ports 7b on a burner plate 7a, is employed and a flame cooling unit 13, cooling flames by heat transfer tubes arranged in parallel so as to be extended vertically at positions near the flaming burner 7 and conducting combustion gas from the flaming burner 7 into a direction intersecting with the heat transfer tubes, is provided. A multi-tube type once-through boiler is provided with a convection heat transfer unit 15 consisting of a multitude of heat transfer tubes 9b, extending into a vertical direction in parallel to each other with the space of heat insulating space 14 at the downstream side of the flame cooling unit 13, while the flame cooling unit 13 is constituted of a finned heat transfer tubes 18, to which cooling promoting fins 17 are attached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tube type once-through boiler using a flammable combustion burner.

[0002]

2. Description of the Related Art FIG. 4 is a partially longitudinal front view of a multi-tube type once-through boiler using a gas fuel according to a conventional example, and FIG. 5 is a cross-sectional plan view of the same. , A fuel supply duct 2 provided on one end side of the boiler body 1 for supplying a premixed fuel 2a in which fuel gas and combustion air are sufficiently mixed in advance, and an exhaust duct 3 provided on the other end side. is doing.

The boiler body 1 has a water supply header section 4 at its lower end and a steam header section 5 parallel to the water supply header section 4 at its upper part. A large number of standing heat transfer tubes 9 are densely provided in parallel between the header portions 4 and 5 to communicate the header portions 4 and 5.

Further, the side heat transfer tubes 6 arranged on both left and right sides in the combustion gas flow direction A are connected to each other by the fins 6a, so that the heat transfer tube wall 8 is formed.
Is formed.

A burner plate 7a is attached to an end of the boiler main body 1 on the fuel supply duct 2 side.
A large number of flame holes 7b are formed in a to form a flammable combustion burner 7.

As shown in FIG. 5, the heat transfer tubes 9 arranged inside the side heat transfer tubes 6 on both sides of the heat transfer tube wall 8 are arranged at predetermined intervals up to a position close to the burner plate 7a. Closely arranged.

In such a configuration, when the premixed fuel 2a in which the fuel gas and the combustion air are sufficiently premixed is supplied from the fuel supply duct 2 to the flammable combustion burner 7 and ignited,
The flame F is formed and burned toward the inside of the boiler body 1 surrounded by the heat transfer tube wall 8.

The combustion gas produced by the flame F flows in the direction of the arrow A, but heat is absorbed by the heat transfer tube 9 and the side heat transfer tube 6 in the process, and the temperature is lowered to the exhaust duct 3 through the exhaust duct 3. Exhausted as exhaust gas.

The water supplied from the water supply header section 4 to the heat transfer tubes 9 and the side heat transfer tubes 6 rises in temperature as the heat transfer tubes 9 and the side heat transfer tubes 6 are heated, and becomes steam to become a steam header. It is taken out from the part 5.

By the way, in the above-mentioned conventional multi-tube once-through boiler using gaseous fuel, when the heat transfer tubes 9 are densely arranged from a position close to the burner plate 7a as shown in FIG. Flame F formed toward the inside
Is in contact with the heat transfer tube 9 far before the tip of the flame F and is continuously cooled, so that the flame temperature becomes low. Therefore, when the flame temperature is lowered to about 1000 ° C. or less, incomplete combustion occurs. There is a problem that CO (carbon monoxide) is increased due to this, and for this reason, a flame combustion space S having no heat transfer tube 9 at a position facing the burner plate 7a is largely formed to completely burn the structure. However, in such a configuration, even if an attempt is made to cool rapidly from the vicinity of the tip of the flame F, it is difficult to perform rapid cooling because the heat transfer area of the bare heat transfer tube 9 is small. Flame F
NOx (nitrogen oxide) generation is suppressed at the temperature of 15
There is a problem that it becomes difficult to maintain the temperature below 00 ° C. and it becomes difficult to reduce NOx.

Further, as a means for solving the above problem, it is conceivable to determine the size of the flame combustion space S so that the flame temperature becomes 1500 ° C. or less which can suppress the generation of NOx. Since the combustion gas that is not burned is continuously cooled by the downstream densely arranged heat transfer tubes 9, there is a problem that CO is discharged with incomplete combustion.

The present applicant has already proposed an invention of a multi-tube once-through boiler capable of simultaneously achieving the above-mentioned reduction of NOx and CO (Japanese Patent Application No. 5-286793).

The present invention, as shown in FIGS. 6 and 7,
An integrally attached box-shaped fuel distribution chamber 11 is formed at the tip of the air supply pipe 10, and the fuel distribution chamber 11 is opened so as to surround the burner plate 7a.

Further, the fuel gas is supplied into the fuel distribution chamber 11 from a fuel gas supply pipe 12 of a system different from the air supply pipe 10. That is, the head portion 12a of the fuel gas supply pipe 12 is arranged in the fuel distribution chamber 11, and the head portion 12a has a plurality of locations (two locations in FIG. 7) in a direction orthogonal to the flow direction A of the combustion gas. A fuel gas supply port 12b is formed in the.

Further, as shown in FIG. 7, the heat transfer tube 9a on the upstream side is arranged so as to form the flame combustion space S on the downstream side of the burner plate 7a, and the flame cooling section 13 is constituted. Here, the flame F is completely combusted to a temperature of about 1800 ° C. when there is no obstacle near the tip of the flame F, but when the temperature exceeds 1500 ° C., NOx generation increases. Therefore, the temperature of the flame F must be suppressed to 1500 ° C. or lower so that NOx is not generated. Therefore, the flame cooling unit 13 is configured by arranging a required number of upstream heat transfer tubes 9a at positions where this condition is satisfied.

On the other hand, the flame F whose temperature is controlled to 1500 ° C. or lower is in a state where it cannot be said that it is completely combusted, and some CO remains in the flame. In this state, when heat is continuously taken by the heat transfer tube group 9 as shown in FIG. 5, the temperature of the combustion gas is lowered to 1000 ° C. or less, and the generated CO is discharged to the outside as it is without burning (oxidizing). Will end up.

In order to prevent this, it is necessary to completely burn the unburned fuel gas and convert CO into CO _2. For this reason, as shown in FIG. 7, the flame cooling unit 13 is used.
A heat insulating space 14 is formed downstream of the heat insulating space 14
In the above, after the unburned CO is oxidized in the range of 1000 ° C. to 1500 ° C., the unburned CO is guided to the convection heat transfer section 15 composed of the heat transfer tube 9 b arranged on the downstream side of the heat insulating space section 14.

[0018]

However, the above-mentioned Japanese Patent Application No.
Also in the invention of -286793, since the heat transfer tube 9a of the flame cooling section 13 arranged downstream of the burner plate 7a is composed of a bare tube, the cooling performance is relatively low, and the temperature of the flame F rapidly increases. It may be difficult to cool so as to lower the temperature, and thus the high temperature residence time for generating NOx may become long and it may be difficult to suppress NOx. Further, since the cooling performance is low, a large number of heat transfer tubes 9a are arranged. There is a problem that the flame cooling unit 13 becomes large in size due to the necessity, and eventually the entire boiler becomes large in size.

Further, at the combustion gas introduction positions X ₁ -X ₁ of the heat transfer tube 9b facing the heat insulating space 14 of the convective heat transfer section 15,
As shown in FIG. 8, there is a problem in that a high temperature portion where the combustion gas locally reaches a high temperature T ₁ is generated at the inner position 16 in the left-right width direction, and the heat transfer tube 9b is burned due to overheating.

The present invention has been made on the basis of such a background. It is possible to suppress the generation of NOx and CO to achieve low pollution, and the NOx generation amount of the multi-tube once-through boiler is the flame temperature. Focusing on the fact that it is greatly affected by the degree of cooling that cools CO in a short time, by providing a cooling accelerating means in the flame cooling section, further reduction of NOx and downsizing of the device can be achieved. A multi-tube structure that prevents local high temperature from occurring at the inlet of the convective heat transfer section located downstream of the heat insulation space provided for reduction, and prevents burnout due to overheating of the heat transfer tube. An object is to provide a tubular flow boiler.

[0021]

SUMMARY OF THE INVENTION The present invention uses a flammable combustion burner having a large number of flame holes in a burner plate, and a plurality of them are arranged in parallel in the longitudinal direction at a position close to the flammable combustion burner. A flame cooling section is provided by a heat transfer tube that allows combustion gas from a flammable combustion burner to flow in an intersecting direction, and a large number of heat sinks are provided on the downstream side of the flame cooling section and extend in the longitudinal direction in parallel. A multi-tube once-through boiler provided with a convection heat transfer section by arranged heat transfer tubes, wherein the flame cooling section is constituted by a heat transfer tube with fins to which cooling promoting fins are attached. A boiler and a multi-tube once-through boiler characterized in that a heat transfer tube with fins is arranged so that the flame temperature of a flame cooling section is maintained at 1500 ° C or lower and the combustion gas temperature of an adiabatic space is maintained at 1000 ° C or higher. Of the convection heat transfer section Those of the multitubular boiler, characterized in that attaching the closure fin therebetween of the heat transfer tube of the left-right width direction inside position facing the thermal space.

[0022]

According to the first means of the present invention, since the flame cooling section is constituted by the finned heat transfer tube to which the cooling promoting fins are attached, the flame of the flammable combustion burner can be cooled rapidly and surely. Therefore, the high temperature residence time for generating NOx can be shortened, and the suppression of NOx generation can be further promoted. Further, since the flame can be cooled rapidly and efficiently, the flame cooling unit can be downsized, and the overall multi-tube type tubular flow boiler can be downsized.

In the second means of the present invention, the flaming combustion burner of the finned heat transfer tube is maintained so that the flame temperature of the flame cooling section is maintained at 1500 ° C. or lower and the combustion gas temperature of the heat insulating space is maintained at 1000 ° C. or higher. Since the arrangement position and the number of installations are selected for NOx, it is possible to prevent the generation of NOx and CO at the same time.

In the third means of the present invention, since the closing fins are mounted between the heat transfer tubes at the inner positions in the left-right width direction facing the heat insulating space of the convective heat transfer section, the combustion heading in the left-right width direction is combusted. The gas is bypassed by the closing fins to the left and right sides without going straight, so that the temperature distribution in the left-right width direction of the combustion gas flowing through the convection heat transfer section can be equalized.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those in the conventional example are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a cross-sectional plan view showing an example of a multi-tube type once-through boiler according to the present invention. As shown, a burner plate 7a uses a flammable combustion burner 7 having a large number of flame holes 7b. Upstream heat transfer tubes (indicated by 9a in FIG. 7) that extend in the vertical direction and are arranged in parallel at a position near the flammable combustion burner 7 so that the combustion gas from the flammable combustion burner 7 flows in the crossing direction. ), The downstream heat transfer tubes 9b arranged in parallel in the longitudinal direction with a heat insulating space 14 at the downstream side of the flame cooling section 13.
In the multi-tube once-through boiler having the convection heat transfer section 15 according to the above, the flame cooling section 13 is constituted by the finned heat transfer tube 18 to which the cooling promoting fins 17 are attached.

At this time, the temperature of the flame F from the flammable combustion burner 7 is kept at 1500 ° C. or lower, and the temperature of the combustion gas in the heat insulating space 14 is kept at 1000 ° C. or higher. The installation position (size of the flame combustion space S) of the heat transfer tube with fins 18 of the cooling unit 13 (size of the flame combustion space S) and the number of installations are appropriately selected.

Further, the blocking fins 19 are attached between the heat transfer tubes 9b 'at the inner positions 16 in the left-right width direction facing the heat insulating space 14 of the convective heat transfer section 15.

Next, the operation of the above embodiment will be described.

When the flame cooling section 13 is constituted by the finned heat transfer tube 18 to which the cooling promotion fins 17 are attached, the flame F of the flammable combustion burner 7 can be cooled rapidly and surely. Therefore, since the high temperature residence time for producing NOx can be shortened, the NOx production suppressing effect can be further promoted.

That is, as shown in FIG. 2, the flame cooling section 13
When the heat transfer tube with fins 18 is used, the generation of NOx can be remarkably reduced as compared with the case where the flame cooling section 13 is composed of the heat transfer tube 9a of the bare tube as in the invention of FIG. .

Further, the heat transfer tube 18 with fins causes the flame F
Since it can be cooled rapidly and efficiently, the flame cooling unit 13 can be downsized, and in turn, the multitubular tubular flow boiler as a whole can be downsized.

Further, as described above, fins are attached so that the temperature of the flame F of the flame cooling section 13 is maintained at 1500 ° C. or lower and the combustion gas temperature of the heat insulating space section 14 is maintained at 1000 ° C. or higher. Since the position and number of heat transfer tubes 18 to be installed with respect to the flammable combustion burner are selected, NOx and C
It is possible to prevent the generation of O at the same time and effectively reduce pollution.

Furthermore, by installing the blocking fins 19 between the heat transfer tubes 9b 'at the inner position 16 in the left-right width direction facing the heat insulating space portion 14 of the convective heat transfer portion 15, the heat insulating space portion 1 is provided.
The combustion gas flowing from 4 to the inside of the convection heat transfer section 15 in the left-right width direction is diverted to the left and right sides by the closing fins 19 without going straight, so that the convection heat transfer section 15 flows as shown in FIG. The temperature distribution in the left-right width direction of the combustion gas at the combustion gas introduction position X ₂ -X ₂ of the heat transfer tube 9 b facing the heat insulating space 14 is equalized, and a locally high temperature portion does not occur, and the intermediate temperature It becomes T ₂ .

Therefore, as shown in FIG. 8, there is a problem that a high temperature portion where the combustion gas locally becomes high temperature T ₁ is generated at the inner position 16 in the left-right width direction, and the heat transfer tube 9b is burned by overheating. Occurrence can be prevented.

[0036]

According to the first aspect of the present invention, since the flame cooling section is composed of the heat transfer tube with fins to which the cooling promoting fins are attached, the flame of the flammable combustion burner can be cooled rapidly and surely. Therefore, the high temperature residence time for producing NOx can be shortened, and the NOx generation preventing effect can be further promoted. Further, since the flame can be cooled rapidly and efficiently, the flame cooling unit can be downsized, and the overall multi-tube type tubular flow boiler can be downsized.

According to the second aspect of the present invention, the finned heat transfer tubes are arranged with respect to the flammable combustion burner so that the flame temperature of the flame cooling section is maintained at 1500 ° C. or lower and the combustion gas temperature of the heat insulating space is maintained at 1000 ° C. or higher. Since the installation position and the number of installations are selected, the generation of NOx and CO can be effectively prevented at the same time.

According to the third aspect of the present invention, since the closing fins are mounted between the heat transfer tubes at the inner positions in the left-right width direction facing the heat insulating space of the convection heat transfer section, the combustion gas flowing inward in the left-right width direction is By the blocking fins, it does not go straight and detours to the left and right, and the temperature distribution of the combustion gas flowing in the convection heat transfer section is equalized. It is possible to prevent the occurrence of a problem in which the heat transfer tube is burnt out due to overheating due to the generation of a high temperature portion.

[Brief description of drawings]

1 is a cross-sectional plan view of a multi-tube once-through boiler according to an embodiment of the present invention.

FIG. 2 NOx by installing the heat transfer tube with fins according to claim 1.
FIG. 6 is a diagram showing the effect of reducing

FIG. 3 is a diagram showing the effect of equalizing the combustion gas temperatures in the left-right width direction in the convection heat transfer section by installing the closing fins of claim 3;

FIG. 4 is a vertical sectional front view of a multi-tube once-through boiler according to a conventional example.

5 is a cross-sectional plan view of FIG.

FIG. 6 is a vertical sectional front view showing the configuration of the already proposed invention.

7 is a cross-sectional plan view of FIG.

8 is a diagram showing that a high temperature portion of a combustion gas is generated at an inner position in a lateral width direction in a convection heat transfer portion of the apparatus of FIG.

[Explanation of symbols]

 7 Flame Combustion Burner 7a Burner Plate 7b Flame Hole 9b Downstream Heat Transfer Tube 9b 'Downstream Heat Transfer Tube 13 Flame Cooling Section 14 Insulation Space Section 15 Convection Heat Transfer Section 16 Left / Right Width Inner Position 17 Cooling Promotion Fin 18 With Fin Heat transfer tube 19 Blocking fin

Claims (3)

[Claims] 1. A flammable combustion burner having a large number of flame holes in a burner plate is used, and a plurality of combustion gases from the flammable combustion burner are arranged in parallel at a position close to the flammable combustion burner so as to extend in the longitudinal direction. Is provided in a cross-direction through a heat transfer tube, and downstream of the flame cooling section, a convection transfer is performed by a plurality of heat transfer tubes that extend in the vertical direction and have a heat insulating space between them. A multi-tube once-through boiler having a heat section, wherein the flame cooling section is constituted by a heat transfer tube with fins to which cooling promoting fins are attached. 2. The heat transfer tube with fins is arranged so that the flame temperature of the flame cooling part is maintained at 1500 ° C. or lower and the combustion gas temperature of the heat insulating space part is maintained at 1000 ° C. or higher. The described multi-tube once-through boiler. 3. The multi-tube flow-through according to claim 1 or 2, characterized in that a closing fin is attached between the heat transfer tubes located in the left and right widthwise inner positions facing the heat insulating space of the convective heat transfer section. boiler.