JPS5823054Y2 - Two-stage combustion burner for reducing nitrogen oxides - Google Patents

Description

[Detailed description of the invention] This invention utilizes the tendency of nitrogen oxide generation depending on the air-fuel ratio to reduce nitrogen oxides (hereinafter referred to as Nox), which are a factor of air pollution, while maintaining a constant heating efficiency. In order to reduce the amount generated, a single-stage combustion chamber that performs combustion with excess fuel and a second-stage combustion chamber that performs combustion by replenishing the unburned components discharged from the first-stage combustion chamber with insufficient air are arranged in the direction of the burner axis. A two-stage combustion burner for reducing nitrogen oxides, which is constructed of a single-stage combustion chamber that performs combustion in a state of excess fuel, has a truncated conical part at the bottom and a parallel cylindrical part on the downstream side connected to the one-stage combustion chamber. By forming a cylindrical body consisting of a cylindrical body, and ejecting both the fuel and combustion air parallel to the burner axis at the truncated conical bottom part to mix them in a passive manner,
A two-stage combustion chamber configured to form a columnar-secondary combustion flame with a slow combustion speed and a low combustion temperature, and which performs combustion by replenishing insufficient air to the columnar-secondary combustion flame from the first-stage combustion chamber,
The parallel cylindrical portion of the single-stage combustion chamber is formed into a truncated conical cylindrical body that expands from the downstream end, and secondary air for combustion is jetted out parallel to the burner axis at the expanding and partial peripheral wall. The present invention relates to a two-stage combustion burner for reducing nitrogen oxides, which is configured to passively mix secondary air with the columnar secondary combustion flame from the one-stage combustion chamber.

This type of two-stage combustion burner performs combustion in both the first-stage combustion chamber and the second-stage combustion chamber by passively mixing the combustion air, so the combustion speed is slow and the temperature is relatively low. Good NOx due to combustion
In addition to obtaining a reduction effect, in the two-stage combustion chamber,
Since a cylindrical negative pressure section is formed around the columnar secondary combustion flame ejected from the first stage combustion chamber, combustion exhaust gas is sucked and returned to this cylindrical negative pressure section from the downstream side of the second stage combustion chamber. Although it has an extremely simple configuration that does not require any special equipment to forcefully circulate exhaust gas,
The exhaust gas circulation combustion method has a fundamentally superior advantage in that it can also exhibit a similar NOx reduction effect.

However, precisely because such passive mixed combustion is carried out, there is a drawback that the combustion flame tends to become extremely unstable due to the effects of changes in the combustion chamber load and fuel supply pressure. Sufficient flame-holding measures are required in the single-stage combustion chamber, which has a small volume.

A tile retention method using the red heat of the burner tile is a possible measure for flame retention, but this method is useful for burners where the burner tile itself cannot be used, or even if there is a burner tile, it cannot be used. If it is used in a temperature range where it cannot become sufficiently red-hot, a sufficient flame-holding effect cannot be expected.

In addition, as a means to solve the problem of flame holding measures in the tile retention method as described above, it is possible to increase the air ratio during single-stage combustion, for example, as described in Japanese Patent Application Laid-open No. 49-130532.
As is known from the publication, the entire single-stage combustion chamber is formed into an expanding cone shape, and a plurality of nozzles are provided in multiple stages orthogonally on the cone-shaped wall surface to collect a relatively large amount of air. It is also possible to increase the overall air ratio during single-stage combustion by ejecting air, but in this case, although the flame holding effect can be improved as the air ratio increases, the air ratio increases. In addition, the combustion chamber expands into a cone shape to facilitate the flow of the supplied fuel gas and combustion air, and the combustion air agitates the fuel gas etc. sequentially from the nozzle in multiple stages during combustion. Coupled with this, the fuel gas and combustion air cannot be combusted in the first stage combustion chamber due to lack of air over a sufficient period of time, resulting in a disadvantage that the desired NOx reduction effect is reduced. This reduces the significance of the two-stage combustion burner, which was originally developed for low NOx.

In addition, as is known from, for example, Japanese Utility Model Application Publication No. 52-7436 or No. 52-22228, flame stabilizing air is ejected along the connection direction of the peripheral wall of the first stage combustion chamber to generate a vortex. Although it is conceivable to do so, in this case as well, the form of passive mixing of the fuel and combustion air would be disrupted, resulting in a decrease in the NOx reduction effect.

The present invention was devised in view of the above circumstances, and its purpose is to provide a two-stage combustion burner having the above-mentioned configuration, while sufficiently maintaining its excellent NOx reduction effect, as well as achieving good flame holding. The object of the present invention is to improve the condition so that it can be obtained, and to realize this improvement with a structure as simple as possible.

In order to achieve the above object, the two-stage combustion burner for reducing nitrogen oxides according to the present invention, in the above-mentioned one, has a peripheral wall of the parallel cylindrical portion on the downstream side of the single-stage combustion chamber perpendicular to or approximately perpendicular to the burner axis. It is characterized by a flame-holding air nozzle that supplies a small amount of air from orthogonal directions.

According to the present invention, although it has such an extremely simple characteristic configuration, the following excellent effects are exhibited.

In other words, instead of adopting an aggressive mixing mode in which flame stabilizing air is ejected along the tangential direction of the peripheral wall of the single-stage combustion chamber to generate a vortex within the combustion chamber, as in the past, a small amount of flame stabilizing air is used. By adopting a relatively passive mixing form in which the mixture is supplied to the columnar secondary combustion flame from a direction perpendicular to the burner axis direction, the NOx reduction effect of the original passive mixing form is maintained sufficiently without decreasing. This resulted in a sufficient flame-holding effect.

In addition, instead of supplying flame-holding air near the bottom of the first-stage combustion chamber, the nozzle is placed at a position where it can be supplied near the tip of the columnar-stage combustion flame, where the combustion air is consumed and there is an excessive air shortage. Since this is provided, the flame holding effect can be further ensured.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

1 is a single-stage combustion chamber that performs combustion in an excess fuel state,
It is formed of a cylindrical body consisting of a light-spreading truncated conical portion 1a at the bottom and a parallel cylindrical portion 1b on the downstream side connected thereto.

A fuel gas supply nozzle 4 fixedly arranged on the burner axis is opened at the bottom of the truncated conical portion 1a, and an air port 6 having a combustion air supply port 5 is opened at the expanded portion around the fuel gas supply nozzle 4. Numerous primary air supply ports 7...
. . , and is constructed so that the fuel and combustion air are ejected parallel to the burner axis and mixed in a negative manner at the bottom truncated conical portion 1a.

The single-stage combustion chamber 1 configured as described above is designed to form a columnar combustion flame having a slow combustion speed and a low combustion temperature.

Reference numeral 2 denotes a two-stage combustion chamber 2 in which combustion is performed by supplementing the columnar-secondary combustion flame from the single-layer combustion chamber 1 with insufficient air, and the downstream end of the parallel cylindrical portion 1b of the single-stage combustion chamber 1 is A plurality of secondary air jet ports 10 are formed in a truncated conical cylindrical body that expands from the end, and at the peripheral wall of the expanded portion, a plurality of secondary air jet ports 10 for jetting secondary air for combustion in parallel to the burner axis are provided. The combustion chamber 1 is opened in such a way that secondary air is passively mixed with the columnar-secondary combustion flame from the single-stage combustion chamber 1.

Note that secondary air is supplied from the air port 6 to the secondary air outlet 10 through the secondary air port 9 and the annular air passage 8.

In the two-stage combustion burner for NOx reduction having the above configuration, the downstream parallel cylindrical portion 1b of the single-stage combustion chamber 1 is further provided.
A flame-holding air nozzle 3 is installed on the peripheral wall of the burner to eject a small amount of air from a direction perpendicular or almost perpendicular to the burner axis, thereby maintaining a negative mixing form as much as possible while maintaining a good condition in the single-stage combustion chamber 1. This makes it possible to maintain flame stability.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the two-stage combustion burner for reducing nitrogen oxides according to the present invention, with FIG. 1 being a longitudinal side view and FIG. 2 being a partially longitudinal front view. 1... Single stage combustion chamber, 1a... Light spreading truncated conical part, 1b... Parallel cylindrical part, 2...
...Two-stage combustion chamber, 3...Minor air injection nozzle for flame stabilization.

Claims (1)

[Scope of utility model registration request] A single-stage combustion chamber 1 that performs combustion in a state of excess fuel is formed by a cylindrical body cut out from a truncated conical portion 1a that widens at the bottom and a parallel cylindrical portion 1b on the downstream side connected thereto. For fuel and combustion in the conical portion 1a
By ejecting the secondary air in parallel to the burner axis and mixing the secondary air with negative polarization, it is possible to form a columnar secondary combustion flame with a slow combustion speed and a low combustion temperature. A two-stage combustion chamber 2 that performs combustion by replenishing insufficient air to a columnar combustion flame is formed into a truncated conical cylindrical body that expands from the downstream end of the parallel cylindrical portion 1b of the first-stage combustion chamber 1. At the same time, by blowing out secondary air for combustion in parallel to the burner axis at the peripheral wall of the expanded portion, the secondary air is passively mixed with the columnar-primary combustion flame from the single-stage combustion chamber 1. In the two-stage combustion burner for reducing nitrogen oxides, a flame-holding method is provided in which a small amount of air is supplied to the peripheral wall of the downstream parallel cylindrical portion 1b of the single-stage combustion chamber 1 from a direction perpendicular or substantially perpendicular to the burner axis. A two-stage combustion burner for reducing nitrogen oxides, characterized in that an air nozzle 3 is provided.