JPH07139702A - Multi-tube type once-through boiler - Google Patents

Abstract

PURPOSE:To provide a multi-tube type once-through boiler, restraining the generation of NOx as well as CO and capable of contriving the reduction of public pollution. CONSTITUTION:A multi-tube type once-through boiler is provided with a type wherein a flaming burner, whose burner plate 7 is provided with a multitube of flame ports 7a, is employed and combustion gas is conducted so as to flow into a direction intersecting with a multitube of heat transfer tubes 6 arranged in parallel to vertical direction. Temperature regulating heat transfer tubes 6a are arranged at positions near the burner plate 7 and a heat insulating space 12 is formed on the downstream side of the temperature regulating heat transfer tubes 6a while the arranging position and the number of installation of the temperature regulating heat transfer tubes 6a are determined so as to retain the flame temperature of 1500 deg.C or lower and the temperature of combustion gas in the heat insulating space 12 of 1000 deg.C or higher.

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. 3 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. 4 is a transverse cross-sectional 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 combustion 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 heat transfer tubes 6 in an upright state are densely provided in parallel between the header portions 4 and 5 to communicate the header portions 4 and 5.

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

Further, the heat transfer tubes 6 on both sides in the combustion gas flow direction A are formed with heat transfer tube walls 8 by connecting adjacent heat transfer tubes 6 with fins.

As shown in FIG. 4, the heat transfer tubes 6 arranged inside the heat transfer tubes 6 on both sides constituting the heat transfer tube wall 8 are closely arranged at a predetermined interval to a position close to the burner plate 7. Has been done.

In such a structure, 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 burner plate 7 and ignited, it is surrounded by the heat transfer tube wall 8. A flame F is formed toward the inside of the boiler body 1 and burns.

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

The temperature of the water supplied from the water supply header 4 to the heat transfer tube 6 rises as the heat transfer tube 6 is heated,
It becomes steam and is taken out from the steam header portion 5.

[0010]

By the way, in the multi-tube type once-through boiler using the above-mentioned conventional gaseous fuel, as shown in FIG.
As shown in FIG.
When the groups are densely arranged, the flame F formed from the burner plate 7 toward the inside immediately touches the heat transfer tube 6 (far before the tip of the flame) and is rapidly and continuously cooled. Therefore, there is a problem that the flame temperature is lowered to about 1000 ° C. or less and CO (carbon monoxide) is generated due to incomplete combustion. Therefore, the flame combustion space that does not have the heat transfer tube 6 at the position facing the burner plate 7 is present. Although the portion S is formed to have a structure for complete combustion, it becomes difficult to maintain the flame temperature at 1500 ° C. or lower, which can suppress the generation of NOx (nitrogen oxide), and to reduce NOx. There was a problem that it was difficult to achieve.

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 is 1500 ° C. or less which can suppress the generation of NOx. The combustion gas that is not completely combusted by is continuously cooled by the heat transfer tubes 6 that are densely arranged on the downstream side, so that it is discharged as incomplete combustion and CO is generated.

The present invention has been made based on such a background, and an object thereof is to provide a multi-tube once-through boiler capable of suppressing the generation of NOx and CO and achieving low pollution.

[0013]

SUMMARY OF THE INVENTION The present invention uses a flammable combustion burner having a large number of flame holes in a burner plate, and burns combustion gas in a crossing direction with respect to a large number of heat transfer tubes arranged in parallel in the longitudinal direction. In the multi-tube type once-through boiler of the type to be circulated, the temperature control heat transfer tube is arranged at a position close to the burner plate, and a heat insulating space is formed on the downstream side of the temperature control heat transfer tube. Multi-tube once-through boiler and flame temperature of 15
Keep the temperature below 00 ° C and keep the combustion gas temperature in the adiabatic space at 10
Air provided individually to the multi-tube through-flow boiler, in which a heat transfer tube for temperature control is arranged so as to maintain the temperature at 00 ° C or higher, and to the fuel distribution chamber opened toward the burner plate. The present invention relates to a multi-tube once-through boiler, characterized in that a supply pipe and a fuel gas supply pipe are communicated with each other.

[0014]

In the first and second means, the temperature adjusting heat transfer tube suppresses the flame formed from the burner plate to 1500 ° C. or less by the temperature adjusting heat transfer tube to burn the flame, thereby suppressing the generation of NOx. Further, the combustion gas containing unburned components can be completely combusted by holding the combustion gas containing unburned components at 1000 ° C. or higher in the downstream heat insulating space to suppress generation of CO.

In the third means, in addition to the above, by incompletely mixing the fuel gas supplied from another system and the combustion air in the fuel distribution chamber immediately before combustion, C
Generation of O can be further suppressed.

[0016]

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 partially longitudinal front view of a multi-tube type once-through boiler according to the present invention, and FIG. 2 is a transverse sectional view thereof.

A box-shaped fuel distribution chamber 10 is integrally formed at the tip of the air supply pipe 9, and the fuel distribution chamber 10 is formed.
Has an opening so as to surround the periphery of the burner plate 7.

Further, fuel gas is supplied into the fuel distribution chamber 10 from a fuel gas supply pipe 11 of a system different from the air supply pipe 9. That is, the head portion 11a of the fuel gas supply pipe 11 is arranged in the fuel distribution chamber 10, and the head portion 11a has a plurality of locations (two locations in FIG. 2) in a direction orthogonal to the flow direction A of the combustion gas. Fuel gas supply port 1
1b is formed.

Further, as shown in FIG. 2, in the present invention, the arrangement of the heat transfer tubes 6 is devised. That is, the heat transfer tube 6a for temperature adjustment is arranged at a position close to the burner plate 7, and the flame F
I try to cool down the temperature of.

Here, the flame F is completely burned at 1800 ° C. if there is nothing that prevents the flame formation near the tip.
However, NOx is generated at a high temperature exceeding 1500 ° C. Therefore, the temperature of the flame must be kept below 1500 ° C. so that NOx is not generated. Therefore, the temperature adjusting heat transfer tube 6a is arranged at a position where this condition is satisfied.

On the downstream side of the temperature adjusting heat transfer tube 6a,
The heat insulating space 12 is formed.

Flame F whose temperature is controlled below 1500 ° C.
Is not completely burned, and some CO remains in the flame. In this state, if heat is taken by the heat transfer tube 6 group and the temperature of the combustion gas drops to 1000 ° C. or less, the generated CO will be discharged as it is.

In order to prevent this, it is necessary to completely burn the unburned fuel gas and react CO to convert it into CO _2. For this reason, the adiabatic heat is passed through the temperature control heat transfer pipe 6a. The temperature of the combustion gas flowing into the space 12 is 1
The arrangement position and the number of the heat transfer tubes 6a for temperature adjustment are determined so as not to drop below 000 ° C.

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

The flame F formed from the burner plate 7 is heated to 150 by the temperature adjusting heat transfer tube 6a adjacent to the burner plate 7.
NOx is generated by maintaining the temperature below 0 ℃ and burning
And the combustion gas containing unburned components is slowly combusted at a temperature of 1000 ° C. or higher in the downstream adiabatic space 12 to completely combust C
Generation of O can be prevented.

As a result of a combustion test, it was found that the flame F can reduce NOx as it is cooled from a close range, and C
It was found that O can be controlled by the number of arranged heat transfer tubes 6a for temperature adjustment and the volume of the heat insulating space 12.

Therefore, by selecting the number of the heat transfer tubes 6a for temperature adjustment and the volume of the heat insulating space 12,
Flame F from the burner plate 7 to the heat insulating space 12
Also, the temperature of the combustion gas can be maintained in the range of 1000 to 1500 ° C. to prevent the generation of NOx and CO.

Further, in the fuel distribution chamber 10, the air supply pipe 9 of another system is designed to incompletely mix the fuel gas supplied from the fuel gas supply pipe 11 and the combustion air immediately before combustion. Thereby, the generation of CO can be further suppressed.

[0030]

According to the first and second aspects of the present invention, a heat insulating space is formed on the downstream side of the temperature adjusting heat transfer tube arranged so as to face the flammable combustion burner, and the flame of the flaming combustion burner is prevented. Since the arrangement position and the number of the heat transfer tubes for temperature adjustment were determined so that the combustion gas in the heat insulating space was maintained at 1500 ° C or lower and the combustion gas in the heat insulating space was maintained at 1000 ° C or higher, N
It is possible to effectively suppress the generation of Ox and CO and obtain a multi-pipe once-through boiler with low pollution.

According to the third aspect of the present invention, the production of CO can be further reduced by causing the fuel gas and the combustion air to be mixed in the fuel distribution chamber by insufficient mixing. it can.

[Brief description of drawings]

FIG. 1 is a partially longitudinal front view of a multi-tube once-through boiler according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a multi-tube once-through boiler according to an embodiment of the present invention.

FIG. 3 is a partially longitudinal front view of a multi-tube once-through boiler according to a conventional example.

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

[Explanation of symbols]

 6 Heat Transfer Tube 6a Temperature Control Heat Transfer Tube 7 Burner Plate 7a Flame Hole 9 Air Supply Pipe 10 Fuel Distribution Chamber 11 Fuel Gas Supply Pipe 12 Adiabatic Space A Combustion Gas Flow Direction

Claims (3)

[Claims] 1. A multi-tube through flow of a type in which a combustion gas burner having a large number of flame holes in a burner plate is used, and a combustion gas is circulated in a crossing direction with respect to a large number of heat transfer tubes arranged in parallel in a longitudinal direction. A multi-tube once-through boiler, wherein a heat transfer tube for temperature control is arranged at a position close to the burner plate, and a heat insulating space is formed on the downstream side of the heat transfer tube for temperature control. 2. The temperature control heat transfer tube is arranged so as to maintain the flame temperature at 1500 ° C. or lower and the combustion gas temperature in the heat insulating space portion at 1500 ° C. or higher. Multi-tube once-through boiler. 3. The air supply pipe and the fuel gas supply pipe, which are individually provided, communicate with the fuel distribution chamber opened toward the burner plate, respectively. Tube type once-through boiler.