JPH07145901A - Multitubular once-through boiler - Google Patents

Abstract

PURPOSE:To provide a multitubular once-through boiler which enables suppressing the generation of NOx and CO and lowering the environmental pollution. CONSTITUTION:The space in which heating tubes 6 are placed, bounded by heating-tube walls 8 at the two lateral sides in the direction A of the flow of the combustion gases, is divided into a first region 12 upstream and a second region 13 downstream. In the first region 12, to maintain the flame inside at temperatures in the range of 1,000 to 1,500 deg.C, an open space 14 is formed at least on the side of a burner plate 7 and filled with ceramic grains 15. In the second region 13 the heating tubes 6 are arranged at specified intervals compactly.

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 sectional front view of a multi-tube type once-through boiler using a gaseous fuel according to a conventional example, and FIG. 5 is a transverse sectional view thereof.

A multi-tube once-through boiler is a boiler main body 1 and a fuel supply duct 2 which is provided at one end of the boiler main body 1 and which supplies 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.

The boiler body 1 has a water supply header portion 4 at its lower end and a steam header portion 5 parallel to the water supply header portion 4 at its upper portion. A large number of standing heat transfer tubes 6 are provided in parallel between the header portions 4 and 5.
Both header parts 4 and 5 are communicated.

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

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. 5, 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, the heat transfer tube wall 8 for igniting by supplying the premixed fuel 2a in which the fuel gas and the combustion air are sufficiently premixed from the fuel supply duct 2 to the burner plate 7
The flame F is formed and burned toward the inside of the boiler body 1 surrounded by.

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 is lowered to be exhausted from the exhaust duct 3 as exhaust gas to the outside. 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.

[0011]

By the way, as is apparent from FIG. 5, the above-mentioned conventional multi-tube type once-through boiler using the gaseous fuel has the heat transfer tube 6 from the position close to the burner plate 7.
Since the groups are densely arranged, the flame F formed from the burner plate 7 toward the inside immediately touches the heat transfer tube 6 (well before the tip of the flame) to cool rapidly and continuously. Therefore, the flame temperature is lowered to about 1000 ° C. or lower, and there is a problem that CO (carbon monoxide) is generated due to incomplete combustion.

Further, as a means for solving the above problem, it is conceivable to form a flame combustion space portion having no heat transfer tube 6 at a position facing the burner plate 7 of the boiler body 1 for complete combustion. Since the temperature rises, there is a problem that the amount of NOx (nitrogen oxide) generated increases, and because of this, the size of the flame combustion space is adjusted so that the flame temperature is 1500 ° C or less, which can suppress the generation of NOx. However, the combustion gas that is not completely combusted in the flame combustion space is rapidly and continuously cooled by the downstream heat transfer tube, which also causes the problem of CO generation due to incomplete combustion. .

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.

[0014]

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 a circulating type, an arrangement area of the heat transfer tubes inside the heat transfer tube walls on both sides in a combustion gas flow direction is defined as an upstream first area and a downstream second area. In the first region, a space is formed at least on the side of the burner plate to fill the inside with ceramic particles, and in the second region, the heat transfer tubes are closely arranged at predetermined intervals. Or a ceramic grid is provided between the heat transfer tube walls at the boundary between the first region and the second region, or the distance between the opposing tips is greater than the diameter of the ceramic particles. The fins that become narrower are installed on the heat transfer tubes at the boundary. A multi-tube through-flow boiler as a characteristic, and a space part of the first region filled with ceramic particles are formed so that the flame temperature in the first region is maintained in the range of 1000 to 1500 ° C. The present invention relates to a once-through type boiler.

[0015]

A flame is formed from the burner plate toward the first region, but the temperature of the flame is 1000 to 1500 due to the space in the first region and the ceramic particles that are non-heat absorbing members filling the space. When kept at ℃, N
The generation of Ox is suppressed, and the combustion gas slowly flows while maintaining the temperature of 1000 ° C. or higher in the narrow space defined by the ceramic particles, so that complete combustion is performed and the generation of CO can be 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 an embodiment, FIG. 2 is a cross-sectional view of the same, and FIG. 3 is a cross-sectional view of a multi-tube type once-through boiler showing a modification of a ceramic particle holding mechanism. It is a figure.

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 disposed in the fuel distribution chamber 10, and the head portion 11a has a plurality of locations (in FIGS. 1 to 3 in the direction orthogonal to the flow direction A of the combustion gas). Fuel gas supply ports 11b are formed at four locations.

Further, as shown in FIG. 2, in the present embodiment, the arrangement area of the heat transfer tubes 6 inside the pair of heat transfer tube walls 8, 8 is a first area 12 on the upstream side and a second area 13 on the downstream side. It is divided into

In the first region 12, the temperature adjusting heat transfer tube 6a is arranged so as to form at least the space portion 14 at the upstream end facing the burner plate 7. At this time, the temperature adjusting heat transfer tubes 6a are arranged in a sparser state than in the normal arrangement.

In the space within the first region 12, the ceramic particles 1 having a predetermined diameter which is a non-heat absorbing member.
Fill 5.

In the second region 13, the heat transfer tubes 6 are normally arranged conventionally, that is, closely arranged at predetermined intervals.

Between the first area 12 and the second area 13,
A ceramic grid 16 is provided between the pair of heat transfer tube walls 8 and 8 to prevent the ceramic particles 15 in the first region 12 from entering the second region 13.

The operation of the above embodiment will be described below.

When burning gaseous fuel, the combustion temperature is 10
It is known that CO is generated at a temperature of 00 ° C. or lower, and NOx is increased at a temperature of 1500 ° C. or higher. Therefore, the flame temperature in the first region 12 is 1000 ° C. to 1500 ° C.
If the temperature is controlled in the range of ° C, the generation of CO and NOx can be suppressed.

Therefore, in the first area 12, the 10
The area of the space portion 14 and the arrangement position and the number of the temperature adjusting heat transfer tubes 6a are set so as to maintain the temperature of 0 to 1500 ° C., and the ceramic particles 15 are filled.

In such a structure, the fuel distribution chamber 10
The burner plate 7 with the fuel gas and the combustion air mixed immediately before.
A flame is formed in the first region 12 when it is jetted from the flame, but the flame temperature is 1000 to 150 depending on the size of the space portion 14, the arrangement position and the number of the temperature adjusting heat transfer tubes 6a.
Hold at 0 ° C.

By keeping the flame temperature at 1500 ° C. or lower in this way, generation of NOx is suppressed and
The ceramic particles 15 are also heated to 1000 ° C. or higher by the flame F, and the combustion gas slowly flows at a temperature of 1000 ° C. or higher in a narrow space formed by the ceramic particles 15 to perform complete combustion.
Generation of CO can be prevented.

In order to retain the ceramic particles 15 in the first region 12, as shown in FIG. 3, instead of the ceramic grid 16 in FIG. 2, a heat transfer tube at the boundary between the first region 12 and the second region 13 is provided. Alternatively, the fins 17 may be formed so as to project at 6 at a right angle to the direction of the arrow A, and the distance between the facing fins 17 may be narrower than the diameter of the ceramic particles 15.

[0031]

As described above, according to the present invention,
By forming a space so that the flame temperature in the first region is 1000 ° C to 1500 ° C and filling it with ceramic particles, CO and NOx are reduced, and low pollution of the multi-tube once-through boiler is promoted. can do.

[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 cross-sectional view of a multi-tube once-through boiler showing a modification of the ceramic particle holding mechanism.

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

FIG. 5 is a cross-sectional view of a multi-tube once-through boiler according to a conventional example.

[Description of Reference Signs] 6 heat transfer tube 7 burner plate 7a flame hole 8 heat transfer tube wall 12 first area 13 second area 14 space 15 ceramic particles 16 ceramic lattice 17 fin 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. In the boiler, the arrangement area of the heat transfer tubes inside the heat transfer tube walls on both sides in the combustion gas flow direction is divided into a first area on the upstream side and a second area on the downstream side. Is a multi-tube once-through boiler, wherein a space is formed at least on the burner plate side and ceramic particles are filled in the space, and the heat transfer tubes are closely arranged at predetermined intervals in the second region. 2. A fin is provided such that a ceramic grid is provided between the walls of the heat transfer tube at the boundary between the first region and the second region, or the distance between the facing tips is smaller than the diameter of the ceramic particles. The multi-tube once-through boiler according to claim 1, wherein a heat transfer tube is provided at a boundary portion. 3. The flame temperature in the first region of the space of the first region filled with ceramic particles is 1000 to 1500 ° C.
The multi-tube once-through boiler according to claim 1, wherein the multi-tube once-through boiler is formed so as to maintain the above range.