JPH09101005A - Gas nozzle for low nox burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain gas nozzles of a low NOx burner, which are capable of effecting stabilized combustion in all the area of load change of the burner, by a method wherein the injection angle of the gas nozzles, slanted so that the inner surface side of the nozzles are positioned at the base end side of the nozzles and the outer surface side of the nozzles are positioned at the tip end side of the nozzles, is specified. SOLUTION: In a fuel two-stage supplying type low NOx burner, a primary gas nozzle 2, constituting a primary burner 1, is provided with gas injection ports 5, slanted so that the inner surface 3 side of the ports are positioned at the base end side of the nozzle and the outer surface 14 side of the ports are positioned at the tip end side of the nozzle, at a plurality of places in the circumferential direction thereof. In this case, the injection angle θ deg. of these gas injection ports 5 is set so as to be 25 deg.-35 deg.. On the other hand, piloot ports 6, whose injection angle is set so as to be 90 deg., are formed on the tip end unit of the primary gas nozzle 2 at a plurality of places in the circumferential direction thereof. In this case, the primary gas nozzle 2 is arranged in an air cylinder 7. Further, the gas injection ports 5 are arranged in one row on the outer periphery with an equal space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas nozzle that constitutes, for example, a primary burner in a two-stage fuel supply type low NOx burner applied to various heating furnaces and boilers.

[0002]

2. Description of the Related Art Conventionally, a two-stage fuel type low NOx gas burner has a structure shown in FIG. That is, in the conventional type, the primary burner (main burner) 11 supplies 40 to 50% of the total fuel gas to the primary combustion region, and the wind box 12 and the air cylinder
The total combustion air (10
(0%) is supplied, a premixed mixture with an air ratio of 2.0 or more is generated in the primary combustion zone. In the primary burner 11, 40 to 50% ejected from the gas ejection port 15 of the primary gas nozzle 14.
The fuel gas flow C of is orthogonal (θ = 90 °) to the combustion air flow D flowing in the air cylinder 13, which promotes the premixing effect, and the air flow velocity and the fuel gas flow velocity are high. Ignition (flame holding) near the gas outlet 15
Not done.

The basic principle is that ignition is performed by the overflow of the air-fuel mixture generated at the tip of the primary gas nozzle 14 and the pilot flame E. This combustion mode is the normal combustion shown in the first half of the figure, and the most stable combustion and NO
It is effective in reducing x. A plurality of (four) secondary burners 16 are arranged around the primary burner 11, and secondary combustion is performed by these.

[0004]

By the way, the off gas generated from a chemical plant contains 50% of H ₂ (hydrogen).
Some of them are contained above, burning rate is 1.0 m / s
Is over. With fuel gas with a high burning rate,
When the burner load is sequentially reduced by using the primary gas nozzle 14 described above, the ignition point of the flame becomes lower than the point A outside the tip of the primary gas nozzle 14 during normal combustion (normal) shown in the upper half diagram. It is moved to the point B side near the gas ejection port 15 at the time of abnormal combustion shown in the half diagram. This is because the fuel gas having a high burning velocity is ignited immediately after being ejected from the gas ejection port 15 with a decrease in the air flow velocity. The movement of the ignition point causes factors such as vibration combustion, resonance noise, and redness F of the primary gas nozzle 14.

Therefore, the first aspect of the present invention is to provide a low NOx burner gas nozzle capable of performing stable combustion over the entire range of the load fluctuation of the burner.

[0006]

In order to achieve the above-mentioned object, a low NOx burner gas nozzle according to claim 1 of the present invention has a plurality of circumferentially-arranged gas nozzles, in which the nozzle inner surface side is the nozzle base end side. And a gas ejection port that is inclined so that the nozzle outer surface side is positioned on the nozzle tip end side,
The feature is that the ejection angles of these gas ejection ports are set to 25 ° to 35 °.

Here, the gas nozzle is a two-stage fuel supply type low N
Various gas nozzles such as primary gas nozzles and secondary gas nozzles in Ox burners and the like. Therefore, according to the invention of claim 1, the ejection angle of the gas ejection port is 25 ° to 35 °.
By injecting the fuel gas within the angle of, the crossing angle with the flow of the combustion air can be made gentle, and the premixing effect can be suppressed as compared with the case of crossing at a right angle. By suppressing the premixing in this way, a combustion delay occurs as compared with the case of crossing at right angles, and as a result, the flow velocity of combustion air decreases when using fuel gas with a high combustion speed. Even at this time, the ignition point can be outside the tip of the gas nozzle, and stable combustion is always possible.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
A description will be given based on FIGS. 1 and 2. In FIG. 1, for example, in a primary gas nozzle 2 that constitutes the primary burner 1 in a two-stage low-NOx fuel burner, the nozzle inner surface 3 side is located at the nozzle base end side and the nozzle outer surface is provided at a plurality of locations in the circumferential direction. A gas ejection port 5 is provided so that the nozzle 4 is located on the nozzle tip side. The ejection angle θ ° of these gas ejection ports 5 is set to 25 ° to 35 °. Pilot ports 6 whose ejection angle is set to 90 ° are formed at a plurality of positions in the circumferential direction at the tip of the primary gas nozzle 2. The primary gas nozzle 2 is arranged in the air cylinder 7.

Here, in the primary gas nozzle 2, the amount of the primary fuel gas 8 ejected is divided into a gas ejection port 5 group and a pilot port 6 group, and the gas ejection port 5 groups are 90 to 95 in terms of volume ratio.
%, 6 groups of pilot mouths are divided into 10 to 5%. The gas ejection ports 5 are arranged in a line at equal intervals on the outer circumference.

The operation of the above embodiment will be described below. By making the ejection angle θ ° of the gas ejection port 5 within the set angle of 25 ° to 35 ° and ejecting the primary fuel gas 8, the crossing angle with the flow of the combustion air 9 becomes gentle and becomes a right angle. The premixing effect is suppressed as compared to the case of crossing. By suppressing the premixing in this way, a combustion delay occurs as compared with the case of crossing at right angles, and as a result, when using the primary fuel gas 8 with a high combustion speed, Even when the flow velocity of the air 9 is reduced, the ignition point is located outside the tip of the primary gas nozzle 2, and stable combustion is always possible.

The test data of the above-mentioned primary gas nozzle 2 is shown in FIG. That is, it was found that as the operating load of the primary burner 1 is reduced, the jetting angle θ ° shifts to the oscillating combustion region as the jet angle θ ° is greater than θ ° = 35 °, and nozzle red heat and resonance noise are generated. It was also found that when the jet angle θ ° is reduced, when θ ° = 25 ° or less, the flame shifts to the lift combustion region regardless of the fluctuation of the operating load, and the flame lifts (blown out). Within the range of θ ° = 25 to 35 °, vibration, red heat and lift phenomenon do not occur in the entire load fluctuation of the primary burner 1, and a stable combustion region can be secured.

[0012]

According to the first aspect of the present invention described above, the fuel gas is ejected with the ejection angle of the gas ejection port within the angle of 25 ° to 35 °, so that the intersection angle with the flow of the combustion air is gentle. Therefore, the premixing effect can be suppressed. This causes combustion delay, and as a result, the ignition point can be located outside the tip of the gas nozzle even when using a fuel gas with a high combustion rate or when the flow velocity of the combustion air decreases.
As a result, stable combustion can be always performed over the entire range of load changes of the burner, and vibration combustion, resonance noise, and red maturity of the gas nozzle can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a primary gas nozzle of a low NOx burner showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of test data in the primary gas nozzle of the low NOx burner.

FIG. 3 is a vertical sectional view of a low NOx burner showing a conventional example.

[Explanation of symbols]

 1 Primary Burner 2 Primary Gas Nozzle 3 Nozzle Inner Surface 4 Nozzle Outer Surface 5 Gas Jet Port 6 Pilot Port 8 Primary Fuel Gas 9 Combustion Air θ ° Jet Angle

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazunori Nakamura 5-3-8 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Inventor Katsuhiko Yamazaki 5-chome, Nishikujo, Osaka, Osaka City No. 28 in Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. A plurality of circumferential gas outlets are provided with inclined gas ejection ports such that the nozzle inner surface side is located at the nozzle base end side and the nozzle outer surface side is located at the nozzle tip end side, and the ejection angles of these gas ejection ports are provided. The low NOx burner gas nozzle is characterized in that the temperature is set to 25 ° to 35 °.