JP3129858B2 - Lean burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial burner, and more particularly, to a double burner having an inner tube and an outer tube. The present invention relates to a lean burn burner in which an axial end of an intermediate gas flow path surrounded by an inner pipe and an outer pipe is used as a nozzle as a pilot nozzle.

[0002]

2. Description of the Related Art Such a lean burn burner is a burner which measures a low NOx by burning a mixed gas at a high air ratio and maintaining a combustion temperature at or below a NOx generation temperature. That is, as shown in FIG. 2A, a ring-shaped pilot nozzle is formed around the periphery of the main combustion nozzle to supply the lean mixed gas to the main combustion nozzle, and the entire periphery of the lean mixed gas is formed. By supplying the pilot gas, the pilot gas is stably burned at a low air-fuel ratio, so that the main combustion flame is forcibly ignited by the heat and stable combustion is obtained. Here, in the case of the conventional configuration, the outer pipe and the inner pipe have the same axis.

[0003]

In order to stably perform combustion in the lean burn burner configured as described above, it is desirable that the pilot burner be stably burned all around the main combustion nozzle. Further, since the pilot burner itself is a source of NOx because of its small air-fuel ratio, it is necessary to reduce the gas supply amount as much as possible. However, in the lean burn burner having the above-described configuration in which the axis is set in the horizontal direction, the supply of the pilot gas to the upper portion in the intermediate gas flow path is excessive due to the buoyancy of the mixed gas as shown in FIG. And the supply of the pilot gas to the lower portion becomes insufficient. In this state, since it is necessary to obtain stable combustion of the pilot flame, the combustion amount of the pilot flame must be increased as a whole, and conventionally, it has not been possible to sufficiently reduce NOx. Therefore, an object of the present invention is to form a pilot flame in a low NOx state favorably in a lean burn burner having a double pipe configuration in which a shaft core is horizontally arranged, so that a fire transfer to a main combustion flame is performed favorably. An object of the present invention is to obtain a lean burn burner capable of achieving stable combustion.

[0004]

To achieve this object, the lean burn burner according to the first aspect of the present invention has the following features.
When the double pipe is arranged horizontally, the axis of the inner pipe is deviated from the axis of the outer pipe so that the flow rate of the pilot gas ejected from the pilot nozzle is uniform or almost uniform in each vertical direction. The feature of the lean burn burner according to the second aspect of the present invention is that, when the double pipe is arranged horizontally, the flow rate of the pilot gas ejected from the pilot nozzle is uniform or almost uniform in the vertical direction. Thus, the opening area of the pilot nozzle is set to be smaller toward the upper side in the vertical direction, and the operation and effect are as follows.

[0005]

That is, in the lean burn burner of the present invention, when the axis is arranged in the horizontal direction, the flow rate of the pilot gas ejected from the pilot nozzle is made uniform or almost uniform. That is, in the first invention, by decentering the axis of the inner pipe with respect to the axis of the outer pipe, the cross-sectional area of the intermediate gas flow path formed therebetween is adjusted, and the flow rate is adjusted. You. On the other hand, in the second invention, this is achieved by adjusting the opening area at the nozzle outlet. Therefore, it is possible to perform combustion by supplying a uniform pilot gas over the entire circumference of the inner pipe while reducing the gas supply amount.

[0006]

As a result, the amount of pilot gas, which is a NOx generation source, can be kept to a minimum, and the amount of N generated while performing the combustion of the lean burn nozzle in a stable state can be reduced.
Ox can be kept low.

[0007]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a longitudinal sectional view of a lean burn burner 1 of the present application. The burner 1 has an inner tube 2 and an outer tube 3 as shown in the figure.
The main flame 4 is provided at the end of the inner pipe 2, and the pilot flame 6 is provided at the end of the intermediate gas flow path 5 between the inner pipe 2 and the outer pipe 3. Is formed. That is, the axial end of the inner pipe 2 is used as a main combustion nozzle.
The axial end of the intermediate gas flow path 5 is configured as a ring-shaped pilot nozzle. Here, the axis of the lean burner 1 is used horizontally.

[0008] The configuration of the end of the double pipe constituting each nozzle will be described below. The axial end 30 of the outer pipe 3 is configured to extend toward the inner pipe 2 as shown in the figure, and this end 30 is used as a fastener for fixing the wire mesh 7 (specifically, for holding the wire mesh). Of the ring member 31 and the fixing screw 32). The entire end of the wire mesh 7 in the radial direction is sandwiched between the end 30 and the ring member 31,
The wire mesh 7 is fixed. On the other hand, the end portion 30 also functions as a flame holding guidance portion that directs gas flowing in the intermediate gas flow path 5 toward the inner pipe 2 (orients the gas flow toward the main flame 4). .

The configuration of the axial end 30 of the outer pipe 3 has been described above. The arrangement of the axial end face 20 of the inner pipe 2 will be described below. That is, the portion 20 is located axially inward of the wire mesh 7, but slightly (about 1 mm) protruding outward in the axial direction from the end surface position of the outer tube 3. And the wire mesh 7 is maintained in a stretched state.

The inner peripheral surface 33 of the outer tube 3, the inner peripheral end surface 34 of the axial end 30 of the outer tube 3, and the outer peripheral surface 21 of the inner tube are all formed in a cylindrical shape. The axis 22 of the pipe is eccentric to the upper side in the vertical direction with respect to the axis 35 of the outer pipe, and the fluid resistance from the pilot gas introduction part 8 to the pilot nozzle upper part 51 and the pilot gas introduction part 8
The difference in fluid resistance from the fluid to the lower part 52 of the pilot nozzle cancels the buoyancy of the pilot gas. As a result, the flow rate of the pilot gas ejected from the pilot nozzle in the vertical direction becomes uniform or substantially uniform. As shown in FIG. 1, the pilot flame formed on the pilot nozzle is uniform in the vertical direction.
Good fire transfer to the main combustion flame can be achieved. Therefore, stable combustion can be performed in a state where the flow rate of the pilot gas is as low as possible (a state in which the amount of generated NOx is small).

The actual dimensional relationship of the lean burner 1 will be described below. Outer tube 3 Inner diameter D1 140 mm Extension part inner diameter D2 130 mm Inner tube 2 Outer diameter D3 120 mm Inner diameter D4 106 mm Eccentricity of inner tube axis with respect to outer tube shaft 1 mm Axial protrusion of inner tube with respect to outer tube end surface 1 mm Wire mesh 7 24 mesh x 0.45m
m SUS 304

In the combustion of the lean burn burner 1, a lean mixed gas whose air-fuel ratio λ is adjusted to about 1.5 is supplied to the main combustion nozzle, and the air-fuel ratio λ is set to 0.1 to the pilot nozzle. The pilot gas adjusted to about 55 is supplied, and combustion is performed. In the combustion state, the pilot flame 6 formed around the main flame 4
Ignition energy is more stably supplied to the main flame, and lean combustion occurs stably. Here, the wire mesh 7 works effectively for improving mixing in the main flame, preventing blowout of the main flame, stable combustion of the pilot flame, improvement of fire transfer to the main flame, and the like.

Application example of lean burner Applicable to boiler of about 80,000 Kcal / h Air-fuel ratio λ = 1.1 to
1.5 NOx generation amount 30 ppm or less (O ₂ 0%) (allowable maximum standard 60 ppm) CO generation amount several ppm Turndown ratio 8: 1 or more

[Alternative Embodiment] In the above embodiment, the axis 22 of the inner pipe forming the pilot nozzle is eccentric to the upper side with respect to the axis 35 of the outer pipe, so that the pilot gas flow rate in the vertical direction is reduced. However, since the gas flow rate supplied to the pilot nozzle is small, it can also be achieved by adjusting the outlet opening area of the pilot nozzle in the vertical direction while keeping the pipe axes concentric. This configuration is shown in FIG. Furthermore, an appropriate fluid resistance member is interposed so that the difference between the fluid resistance from the pilot gas introduction part to the pilot nozzle upper part and the fluid resistance from the pilot gas introduction part to the pilot nozzle lower part cancels the buoyancy of the pilot gas. It may be provided in the gas flow path 5.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the accompanying drawings.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a lean burn burner of the present application.

FIG. 2 is a diagram showing a flow velocity distribution near a pilot flame in the present application and a conventional configuration.

FIG. 3 is a diagram showing a configuration of another embodiment of the present invention.

[Explanation of symbols]

 2 Inner pipe 3 Outer pipe 5 Intermediate gas flow path 7 Wire mesh 30 Axial end 31 Fastener 32 Fastener

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-28028 (JP, A) JP-A-3-294710 (JP, A) Fully open 1983-146336 (JP, U) Really open 1983 49337 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23D 14/02-14/18 F23D 14/74 F23C 11/00 329-330

Claims (4)

(57) [Claims] 1. An inner pipe (2) comprising a double pipe having an inner pipe (2) and an outer pipe (3), wherein an axial end of the inner pipe (2) is used as a main combustion nozzle. A lean burn burner that uses an axial end of an intermediate gas flow path (5) surrounded by the outer pipe (3) and the outer pipe (3) as a pilot nozzle. The axial center of the inner pipe (2) is set so that the flow rate of
2) A lean burn burner which is eccentric with respect to the axis (35) of the outer tube. 2. An inner pipe (2) comprising a double pipe having an inner pipe (2) and an outer pipe (3), wherein an axial end of the inner pipe (2) is used as a main combustion nozzle. A lean burn burner that uses an axial end of an intermediate gas flow path (5) surrounded by the outer pipe (3) and the outer pipe (3) as a pilot nozzle. A lean burn burner in which the opening area of the pilot nozzle is set to be smaller toward the upper portion in the vertical direction such that the flow rate of the pilot gas to be jetted is uniform or substantially uniform in each vertical direction. 3. A flame-holding guide portion is provided at an axial end (30) of the outer tube to project toward the inner tube and direct the gas flowing through the intermediate gas flow path (5) toward the inner tube. 3. The burner according to claim 1, wherein the burner is a burner. 4. The flame holding guide portion is configured as a fixed seat portion of a wire mesh (7) covering the entire end face of the outer tube (3) over the main combustion nozzle and the pilot nozzle. The described lean burn burner.