JPH1122918A - Low nox burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the temperature of an already combusted gas, and at the same time, effectively reduce the flame temperature by increasing the circulation amount of the already combusted gas, and reduce the amount of NOx for a burner. SOLUTION: A plurality of air outlets 13 having a circular cross section are arranged in a circle, and on the inside a plurality of fuel outlets 16 are arranged on the circumferential locations which are alternate with the air outlets 13. At the central part, a combustion air outlet 11 is provided. At the tip of this burner, a guide vane 8 which circulates an already combusted gas in a manner to be a stream 14 to the burner tip part, is arranged. The already combusted gas which circulates along a furnace wall 3, and of which the temperature has decreased, flows in the guide vane 8 in parallel with a combustion air 16, and is further cooled, and thus, a flame temperature is reduced, and the generation of NOx is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx burner for generating a high-temperature gas used for a boiler for generating steam, for a high-pressure regenerator of an absorption refrigerator, or for a dryer.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional burner for generating high-temperature gas. In FIG. 2, 1 denotes a wind box, 2 denotes a refractory called a castable, and 3 denotes a furnace tube wall.

A fuel passage 5 has a plurality of fuel outlets 6 at its tip end for ejecting fuel 17. Inside the fuel passage 5 is a central air passage 1 into which primary air is led.
2 and the outside of the fuel passage 5 is secondary air,
The passage is a passage through which the tertiary air is introduced, and a plurality of air outlets 13 are formed at the end.

At the end of the central air passage 12, a disk-shaped baffle 10 for flame holding is arranged.
A central air outlet 11 is formed on the back side of the air outlet.

In the burner of FIG. 2 having the above configuration,
The air supplied to the wind box 1 is ejected from the air outlet 13 as a flow along the combustion air 16 and the back surface of the baffle 10, and the burned gas (exhaust gas) near the burner is indicated by an arrow 14 by the air jet. It is taken in as a flow or a central circulation flow indicated by an arrow 18. The circulating flow of the burned gas lowers the flame temperature of the burner.

The fuel outlet 6 is divided into a plurality of parts, and the combustion flame is sandwiched between the burned gas flows 14 and 18 to form a thin-film flame, which increases the contact area with air and burned gas, and increases the flame temperature. Lower. In this way, the flame temperature is lowered to prevent NOx generation due to the high-temperature flame.

[0007]

However, the conventional low NO NO
In a burner for generating high-temperature gas for x conversion,
The temperature of the burned gas taken in by the air jet from the blower is high, and the effect of reducing the flame temperature to achieve low NOx is not sufficient, and the pressure loss on the burned gas side is large and the circulation amount is large. There was a problem that it could not be taken.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a burner which lowers the temperature of burned gas and increases the amount of circulation of the burned gas, thereby effectively lowering the flame temperature and realizing low NOx.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an air outlet having a plurality of circular sections arranged in a circular shape, and an air outlet which is alternately provided inside the air outlet. A burner having a plurality of fuel outlets arranged in a circle at a circumferential position, and a combustion air outlet arranged at a central portion, and a burned gas is supplied to a tip portion of the burner. Provided is a burner having a guide vane circulating at the tip.

Further, in this burner, the burned gas circulating along the wall of the furnace tube is configured to flow in the guide vane in parallel with the combustion air.

Since the burner according to the present invention has the above-described structure, the burned gas is effectively circulated to the guide vanes provided at the tip of the burner. Then, the burned gas circulating in the guide vanes gives the heat of the burned gas to the furnace tube wall in the process of flowing along the furnace tube wall to lower the temperature to 200 ° C to 300 ° C.

Further, the combustion air ejected from the burner and the burned gas taken in by the flow make a U-turn and smoothly flow in the guide vanes in parallel with the combustion air, so that the burned gas is taken in with a small pressure loss. Thus, the intake amount is increased, the flame temperature is effectively reduced, and the generation of NOx by the high-temperature flame is effectively suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a low NOx burner according to the present invention will be specifically described based on the embodiment shown in FIG. In the following embodiments, the same components as those of the conventional apparatus shown in FIG. 2 are denoted by the same reference numerals for simplification of description.

In FIG. 1, reference numeral 4 denotes an air blowing pipe, and reference numeral 7 denotes a ring for adjusting the amount of burned gas mixed with fuel gas. 8 is a guide vane arranged at the tip of the burner.

The guide vanes 8 take in the burned gas from the surroundings as indicated by arrows 14 by the combustion air 16 ejected from the burner tip, and flow in the guide vanes 8 along with the combustion air 16 as a parallel flow. The fuel mixed with the fuel discharged from the fuel outlet 6 is burned. As described above, since the burned gas is taken in with a low pressure loss, the taken-in amount of the burned gas increases.

Air outlet 1 for blowing out combustion air 16
8 are arranged in a circle, and each air outlet 13
Has a circular cross-section so that the contact area between the blown combustion air and the taken-in burned gas can be increased.

The eight fuel outlets 6 are arranged in a circle inside the combustion air outlet 13 and are positioned so as to be at different circumferential positions from the combustion air outlet 13. The fuel 17 is recirculated from 200 ° C to 30 ° C.
Since the fuel is directly injected into the burned gas 15 at 0 ° C. and burned, the flame holding property is improved.

The combustion air supplied from the combustion air outlet 11 at the center of the burner further enlarges the recirculation region 18 formed at the center of the burner, thereby improving the flame holding property. The combustion air from the combustion air outlet 11 also has a function of thinning the split flame, thereby increasing the contact area of the flame with the air and reducing the heat transfer thickness of the flame, thereby contributing to a decrease in flame temperature. I do.

The burned gas 14 taken into the guide vanes 8 flows along the furnace tube wall 3 and drops in temperature from 200 ° C. to 300 ° C. due to heat exchange with the furnace tube wall. It works to lower the temperature of the burner flame in conjunction with the decrease in the flame temperature due to the concentration decrease. In addition, a central circulating flow 18 is formed on the front surface of the baffle 10 at the tip of the burner to improve flame holding properties. A region 9 is provided between the castable 2 and the guide vane 8 so that the burned gas 15 U-turned along the furnace tube wall 3 can quickly change its direction as described above.

As described above, in the burner shown in FIG. 1, the guide vanes 8 are provided to smoothly return the burned gas to the burner to lower the temperature of the flame surface. Further, since the burned gas has a low oxygen concentration, the flame temperature decreases in a portion where the burned gas is mixed with air. As described above, the generation of NOx is effectively suppressed by the decrease in the oxygen concentration and the decrease in the flame temperature.

[0021]

As described above, in the burner according to the present invention, the guide vane for circulating the burned gas is disposed at the tip, and the burned gas circulating along the furnace tube wall is guided by the guide vane. The burned gas, whose temperature has dropped due to heat exchange with the furnace tube wall, is effectively taken into the guide vanes, and flows in parallel with the combustion air. The temperature can be reduced as desired.

Further, in the burner according to the present invention, the plurality of air outlets have a circular cross section, and the contact area of the combustion air flow contacting with the taken-in burned gas is large.
The temperature of the burned gas is lowered to increase the flame temperature lowering ability.

As described above, in the burner of the present invention, NOx generated due to a high temperature can be reduced by lowering the flame temperature by the exhaust gas self-recirculation. Further, since fuel / air combustion occurs in the burned gas, the acidity concentration in the combustion area can be reduced, and NO
Since the amount of oxygen used as x is small, NOx can be further reduced.

[Brief description of the drawings]

1A and 1B are drawings showing a low NOx burner according to an embodiment of the present invention, wherein FIG. 1A is a longitudinal sectional view, and FIG.

FIGS. 2A and 2B are drawings showing a conventional low NOx burner, wherein FIG. 2A is a longitudinal sectional view, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wind box 2 Castable (refractory) 3 Furnace wall 4 Pipe for air blowing 5 Fuel passage 6 Fuel outlet 7 Ring 8 Guide vane 9 U-turn space 10 Baffle 11 Central air outlet 12 Central air passage 13 Air Outlet 15 Intaked burned gas 16 Combustion air 17 Fuel 18 Central circulation flow

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroyuki Nishida 2-1-1 Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A plurality of air outlets having a circular cross section arranged in a circle, and a plurality of circular air outlets arranged inside the air outlet at different circumferential positions from the air outlet. A burner having a fuel outlet and a combustion air outlet disposed at a center portion, wherein a guide vane for circulating burned gas to the tip portion is disposed at a tip of the burner, and a furnace tube A low NOx burner, wherein burned gas circulating along a wall flows in the guide vane in parallel with combustion air.