JP2000055319A - LOW NOx BURNER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an NOx by forming an air flow directed in the same direction as an injecting direction of fuel gas near an end of a flame tube by operations of a flame tube group projecting into the air toward obliquely outward and a conical flame holder or turning blade, thereby forming a sharp thin toroidal flame. SOLUTION: A fuel nozzle 2 is provided at a center of a combustion cylinder 1 in which combustion air is supplied, and a plurality of short tubular flame tubes 3 directed obliquely outward are arranged in an annular state near an end of the nozzle 2. An end face of the nozzle 2 is closed, a conical flame holder 4 is fixed to the end face, and an air flow directed obliquely outward can be formed by the holder 4. An oblique angle of the conical surface of the holder 4 is formed parallel to the tube group 3 forward at 30 degree from a lateral direction. The air flow is changed in its direction obliquely outward by the holder 4, and fuel gas is injected from the group 3 along the conical air flow, thereby forming a sharp thin toroidal flame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a low NOx burner using a conical thin film flame called a toroidal flame.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional low NOx burner using a conical thin-film flame. Fuel gas is ejected obliquely outward from a central fuel nozzle and ejected along a combustion cylinder. By mixing with the burning air, a conical thin film flame, that is, a toroidal flame is formed, the residence time of the nitrogen gas in the high temperature portion of the flame is shortened, and the NOx is reduced.

[0003]

However, the toroidal flame formed in FIG. 4 is ideal because the flame ejected from the flame hole is disturbed by the combustion air blown from behind, and the thickness of the conical flame increases. It is hard to say that this is a thin film flame, so that the residence time of the air or nitrogen gas in a high temperature range becomes longer correspondingly, and there is a problem that the low NOx performance is reduced. It is an object of the present invention to solve such a problem and to further reduce the NOx of a toroidal flame burner by forming an extremely thin conical thin film flame.

[0004]

As shown in FIG. 1, a low NOx burner according to the present invention comprises a flame tube (short) directed obliquely outward at a tip end of a fuel nozzle 2 provided at the center of a combustion cylinder 1. A plurality of tubular flame holes 3 are disposed in a ring shape, and the air supplied to the combustion cylinder 1 is directed obliquely outward by a conical flame holding plate 4 fixed to the tip end surface of the fuel nozzle 2. As shown in FIG. 2, a plurality of obliquely outwardly directed flame tubes 3 are arranged in a ring shape at the tip of the fuel nozzle 2, and the combustion tube is slightly upstream of the flame tube group 3. Cylinder 1
In this case, an airflow in the same direction as the flame injection direction can be formed in the vicinity of the flame tube group 3 facing obliquely outward in any case. A sharp and thin toroidal flame can be formed without the fuel gas being diffused to the side by the air flow, thereby shortening the residence time of the nitrogen gas in the high temperature region and achieving a higher NOx reduction. It can be realized.

[0005]

FIG. 1 shows an embodiment of a low NOx burner according to the present invention. A fuel nozzle 2 is provided at the center of a combustion cylinder 1 to which combustion air is supplied. A plurality of short tubular flame holes, that is, flame tubes 3 are arranged in a ring shape in the vicinity of the front end portion toward obliquely outward (30 degrees forward from the lateral direction). The front end surface of the fuel nozzle 2 is closed, and a conical flame holding plate 4 is fixed to the front end surface, and the flame holding plate 4 forms an obliquely outward air flow. The inclination angle of the conical surface of the flame holding plate 4 is also formed in parallel with the flame tube group 3 at an angle of 30 degrees forward from the lateral direction.

According to the above-described structure, the air flow is turned obliquely outward by the flame holding plate 4, and the fuel gas is ejected from the flame tube group 3 along the conical air flow. Since the air flow is previously directed in the same direction as the fuel gas ejection direction, the fuel gas is not scattered to the side by the air flow as in the conventional example of FIG. A flame can be formed, and the residence time of the nitrogen gas in a high temperature range can be shortened to realize a high performance low NOx burner. In addition, on the front surface of the combustion cylinder 1, an air distribution plate 8 for stirring the air flow and imparting a constant flow velocity is provided, and by providing the air distribution plate 8 with a ventilation groove 9 in a gear shape, In addition, low NO due to lean combustion
The x conversion technique is also used.

FIG. 2 shows another embodiment of the present invention, in which a plurality of flame tubes 3 directed obliquely outward are arranged at the tip of a fuel nozzle 2 in a ring shape. Swirl vanes 5 are provided on the inner surface of the combustion cylinder 1 slightly upstream of the group 3. Also in this case, since the air flow in the same direction as the direction of the flame tube 3 is formed near the flame tube 3, the flame is not scattered to the side by the air flow, and a thin toroidal flame is realized. be able to. In the figure, reference numeral 10 denotes a water cooling wall or a water pipe group of a boiler for reducing NOx by cooling immediately before complete combustion of the flame. The flame can be made to approach the water cooling wall 10 in a thin film state.

FIG. 3 shows still another embodiment of the present invention. An outer cylinder 6 to which air is supplied is provided outside a combustion cylinder (inner cylinder) 1 shown in FIG. 1 or FIG. A second flame tube group 7 which is also directed obliquely outward is arranged in a ring shape on the upstream side of the second flame tube row 3.
Are projected outward through the combustion cylinder 1, and the NOx reduction method using thin-film flame is used in combination with the two-stage air combustion method to further reduce NOx.

According to the present invention, as described above, the flame tube group 3 projecting obliquely outward and into the air, and the conical flame-holding plate 4 or the swirl vanes 5 act to form the flame tube 3. Because the air flow in the same direction as the fuel gas ejection direction is formed near the tip of the flame, the flame is not diffused to the side by the air flow from behind as in the past, and it is a sharp and thin toroid. A flame can be formed, thereby reducing the residence time of the nitrogen gas in the high-temperature region, thereby increasing the lower NOx
There is an advantage that realization is realized.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a longitudinal sectional view and (b) is a front view.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing still another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion cylinder 2 Fuel nozzle 3 Flame tube 4 Flame holding plate 5 Revolving blade 6 Outer cylinder 7 Second flame tube group 8 Air dispersion plate 9 Vent groove 10 Water cooling wall

Claims (3)

[Claims] A plurality of flame tubes (short tubular flame holes) directed obliquely outwardly are arranged in a ring shape at the tip of a fuel nozzle provided at the center of a combustion cylinder, and are provided on the tip surface of the fuel nozzle. A low NOx burner in which air supplied to a combustion cylinder is directed obliquely outward by a fixed conical flame holding plate. 2. A plurality of obliquely outwardly directed flame tubes are arranged in a ring shape at the tip of a fuel nozzle provided at the center of the combustion tube. Low NOx burner with swirling vanes. 3. An outer cylinder to which air is supplied is provided outside the combustion cylinder, and a second group of flame tubes which are also directed obliquely outward are arranged in a ring upstream of the flame tube row of the fuel nozzles. The low NOx burner according to claim 1 or 2, wherein the second flame tube group is formed so as to protrude outward through a combustion cylinder.