JP3417367B2 - Low NOx combustion method and partially premixed gas low NOx burner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx combustion method and a partially premixed gas low NOx burner.

[0002]

2. Description of the Related Art Conventionally , various proposals have been made for reducing harmful combustion exhausts in combustion equipment. In recent years, however, attention has been paid to reduction of NOx among harmful combustion exhausts due to problems such as environmental pollution. Is directed. Therefore , a large number of low NOx combustion methods and low NOx burners have been proposed in which a gaseous fuel having a low nitrogen content is used as the fuel itself and thermal NOx (thermal NOx) is reduced in the combustion process. Further, in a burner which is used in a combustion space having a relatively small volume and is required to have a large output, such as a small size and simple class boiler, it is difficult to reduce NOx, and a low NOx that can be applied to such a field is provided. Combustion method and low N
The demand for Ox burners is increasing.

[0003]

[Problems that the Invention is to Solve] solved by the present invention
The problem to be solved is to achieve further low NOx in the low NOx combustion method and the low NOx burner.

[0004]

Means for Solving the Problems] The present invention has been made to solve the above problem, the invention according to claim 1, with a partial premixing gas burner, under the pre-mix Kibuki outlet basin A thin-film cylindrical premixed airflow is formed in the
Secondary air for combustion is subdivided from the outside toward the combined flow
The feature is that a large number of small flames are formed by jetting .

The invention according to claim 2 supplies fuel.
A fuel supply pipe and an outer periphery of the fuel supply pipe,
Fuel supplied from the fuel injection port provided in the fuel supply pipe
And an internal cylinder that mixes the primary air for combustion with the mixed premix
A premixed gas spout that ejects aeration and the above premixed gas spout
Thin film in the downstream region of the mouth that forms a cylindrical premixed air flow
The forming member and the outer circumference of the inner cylinder are arranged on the outer circumference of the inner cylinder.
An outer cylinder that forms an annular flow path for secondary air for combustion with the wall
And is provided in the inner cylinder, and whether the premixed airflow is outside the premixed airflow.
Secondary air for combustion that subdivides and ejects secondary air for combustion from
It is characterized by having a spout .

Further, the invention according to claim 3 is the thin film
The film forming member is placed with a predetermined gap between it and the inner cylinder.
It is characterized by having been placed .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.
explain about. The low NOx combustion method and low NOx burner according to the present invention are implemented as a so-called partially premixed gas burner. The low NOx combustion method according to the invention, the fuel and the combustion secondary air jetted subdividing the spout to partially premixed thin cylindrical premixture combustion air,
In this combustion method, a large number of small flames are formed in a portion where the premixed air and the secondary air for combustion are in contact with each other, and the surface area of the small flames is increased to lower the temperature of the small flames to reduce NOx. Further, the low NOx burner according to the present invention ejects a partially premixed airflow which is a mixture of the primary combustion air and the fuel from the center side thereof, and ejects secondary combustion air so as to surround the partially premixed airflow. It is composed. That is,
Outer low NOx burner inner cylinder for ejecting a partial premixing air flow, the outer periphery of the inner tube, forming an annular passage the combustion secondary air flows between the inner tube according to the present invention the cylinder was placed substantially coaxially, the distal end of the inner cylinder, is constructed by placing a thin film forming member for forming a thin film cylindrical premixed stream by interposing a predetermined gap between the inner cylinder It

[0008] Then, the fuel and the combustion primary air supplied from the fuel injection holes provided in the fuel supply pipe and mixed with the downstream side of the primary air diffusing member disposed upstream of the fuel injection holes, wherein An annular premixed gas portion is formed between the fuel supply pipe and the outer wall of the fuel supply pipe . The annular premixed gas premixed gas is sufficiently mixed in a portion at its distal end, the thin film forming member and the front
Through a predetermined gap formed between the serial inner tube, it becomes wide as the thin cylindrical premixing air flow having substantially the same thickness between the gap <br/>, of the distal end side of the inner tube It flows along the surrounding wall.

Secondary air for combustion is jetted from the outside to the thin-film cylindrical premixed airflow thus formed. Sanawa
Chi, subdividing the combustion secondary air from the combustion secondary air injection port provided in the inner cylinder, is jetted toward the center of the burner. It said combustion secondary air injection port is provided in the wall <br/> surface of the inner cylinder. Said combustion secondary air injection port, so as to form a plurality of ejection ports at the tip of the inner cylinder is constituted by arranging a large number of small holes on the wall of the inner cylinder. The array of small holes may be arranged in multiple rows or in a staggered array. Also,
The shape of the small holes is circular, polygonal, or the like, and is provided by punching in a steel plate or the like. Similarly, as a means for subdividing the secondary air for combustion, a punching metal plate or a wire net may be used.

When the secondary air for combustion and the premixed air are ignited by the ignition means arranged in a portion having an air ratio suitable for combustion, a small flame starts from the portion where the secondary air for combustion and the premixed air contact each other. To form. When one small flame is formed by the ignition means, the small flames are transferred one after another to form a large number of small flames. These large number of small flame, increase the flame surface area
And, the flame is cooled, since the local high-temperature portion does not occur,
It is possible to reduce thermal NOx . Large number of small flames merge to become a flame, it is flame holding at the tip of the burner, complete combustion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings. Here, FIG. 1 is a cross-sectional explanatory view showing an embodiment of the low NOx burner according to the present invention.

Now, the low NOx burner 1 shown in FIG.
An inner cylinder 2 for ejecting a partial premixed gas is provided inside thereof. This inner cylinder-peripheral side of the secondary, is arranged the outer cylinder 4 forming the annular flow path 3 is the combustion secondary air flows between the inner tube 2 substantially coaxially. The inner cylinder 2 and the outer cylinder 4
Are both connected to an air duct 5 which is an air supply means. The air duct 5 is usually provided with a blower (not shown) on the upstream side. Inside the inner cylinder 2, a fuel supply pipe 6 is arranged substantially coaxially. The fuel supply pipe 6 is provided with fuel injection ports 7, 7,
A plurality of ... Is formed. Positions of the respective fuel injection holes 7 on the downstream side of the inner cylinder 2, in the annular premixture portion 15 which has a annular space formed between said fuel supply pipe 6, for combustion with fuel It is set to ensure a length that allows uniform mixing with the primary air. Further, a primary air diffusing member 8 for diffusing the primary air for combustion is arranged upstream of each of the fuel ejection ports 7.

Further, a premixed gas injection port portion 9 is formed at the tip of the fuel supply pipe 6 with a predetermined gap between the fuel supply pipe 6 and the inner cylinder 2. The tip of the fuel supply pipe 6, is fixed a disc-shaped thin-film forming member 10 that forms a thin film cylindrical premixed stream under basin of the premixed Kibuki outlet 9. That is, the fuel supply pipe 6 holds the thin film forming member 10 at a predetermined position at the tip of the inner cylinder 2.

The thin film forming member 10 is located at the front end of the inner cylinder 2 in a state of being attached to the front end of the fuel supply pipe 6. The positional relationship between the inner cylinder 2 and the thin film forming member 10 is as follows. Is as follows. First, the inner cylinder 2
Is are substantially is positioned coaxially with the thin film forming member 10. The relationship between the inner diameter of the inner cylinder 2 and the outer diameter of the thin film forming member 10 is that the outer diameter of the thin film forming member 10 is slightly smaller than the inner diameter of the inner cylinder 2, and is formed by this difference. The gap constitutes the premixed gas ejection port portion 9. Accordingly, the thin film forming member 10, Ru have <br/> are arranged while interposing a predetermined gap between the inner cylinder 2.

Further, an ignition means 11 and a flame detection means 12 are arranged on the downstream side of the thin film forming member 10 so as to penetrate the thin film forming member 10.

In the embodiment shown in FIG. 1, the inner cylinder 2 and the outer cylinder 4 are substantially flush with each other at the tips thereof, and the shield plate 13 is provided between the tips of the two. Is provided and shielded to form the annular flow path 3 for the secondary air for combustion. A large number of secondary air jet outlets for combustion 14, 14, ... Communicating with the annular passage 3 are formed in a staggered manner at the tip of the inner cylinder 2 within a predetermined vertical interval. (See FIG. 2).

The amounts of the primary air for combustion and the secondary air for combustion are set as follows. That is,
The supply amount of combustion primary air into the inner cylinder 2 (the flow rate) the
0.4 to the total amount of combustion air supplied to the low NOx burner 1
It should be 0.8 times. Here, the total amount of the primary air for combustion and the secondary air for combustion is an amount sufficient to burn the fuel.

Next, the combustion action of the low NOx burner 1 will be described. First, it supplies the primary air for combustion from the air duct 5 into the inner tube 2, prior
Serial supplying combustion secondary air from the air duct 5 into the annular flow path 3. In this state, when supplying fuel to the fuel supply pipe 6 from the fuel supply means (not shown), fuel is injected from the fuel injection holes 7 in the fuel supply pipe 6 to the annular pre-mixture portion 15 , Is mixed with the primary air for combustion flowing in the inner cylinder 2 to form a partially premixed air flow. Then, this part premixing air flow at the leading end side of the inner cylinder 2, is ejected from the premixed Kibuki outlet 9.

At this time, since the flow direction of the partial premixed airflow is restricted by the gap between the thin film forming member 10 and the inner cylinder 2, the partial premixed airflow is discharged from the premixed gas jet port 9 to It ejects along the inner cylinder 2 in a state of being formed into a substantially cylindrical shape with a hollow thin film. Then, toward the radially outward into the thin cylindrical premixed stream ejected by subdividing the combustion secondary air from the respective combustion secondary air injection port 14 provided in the inner tube 2 .

When the ignition means 11 ignites, a small flame is formed from the portion where the secondary air for combustion and the premixed air contact each other. When one small flame is formed by the igniting means 11, the small flames are successively transferred and a large number of small flames are formed. These large number of small flame, the flame surface area is increased,
Since the small flame is cooled and no local high temperature part is generated, thermal NOx is reduced .

The number of small flames Sa Maru NOx is reduced, merge to become a flame, said the flame holding in the low NOx burner 1 of the tip portion, to complete combustion. In other words, combustion by a large number of small flames increases the surface area of the flame and prevents the formation of a local high temperature region, thereby achieving low NOx reduction.

[0022]

As described above, according to the present invention, the partial premixed air flow from the inner cylinder is jetted by the thin film forming member into a thin film cylindrical shape, and is supplied from the annular flow passage. Combining the sub-air into smaller ones and combining them causes combustion with a large number of small flames, increasing the flame surface area and improving heat dissipation from the small flames, thus preventing the occurrence of local high temperature regions .
It is possible to achieve low NOx.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view of an embodiment of a low NOx burner according to the present invention.

FIG. 2 is a development explanatory view illustrating a state in which a secondary air jet port for combustion is expanded.

[Explanation of symbols]

2 inner cylinder 3 annular flow path 4 outer cylinder 6 Fuel supply pipe 7 Fuel spout 9 Premixed gas spout part 10 Thin film forming member 14 Secondary air jet for combustion

Claims (3)

(57) [Claims] 1. A partially premixed gas burner is used to form a thin-film cylindrical premixed air flow in the downstream region of the premixed gas ejection port 9.
The secondary combustion air from outside the premixed airflow.
A low NOx combustion method characterized in that air is fragmented and ejected to form a large number of small flames . 2. A fuel supply pipe 6 for supplying fuel and the fuel
Disposed on the outer periphery of the fuel supply pipe 6 and provided on the fuel supply pipe 6.
Supplied from the fuel injection port 7 and the primary air for combustion
The inner cylinder 2 that mixes with air and the mixed premixed gas is ejected
Of the premixed gas jet portion 9 and the premixed gas jet portion 9
A thin film forming member that forms a thin film cylindrical premixed air flow in the basin
10 and the outer circumference of the inner cylinder 2 arranged on the outer periphery of the inner cylinder 2.
Outside forming an annular flow path 3 for secondary air for combustion with the wall
The cylinder 4 and the inner cylinder 2 are provided with the premixed air flow
Combustion secondary that subdivides and ejects secondary combustion air from the outside
Partial premixing characterized by having a secondary air outlet 14
Combined gas low NOx burner. 3. The thin film forming member 10 and the inner cylinder 2
It is characterized in that a predetermined gap is interposed between them.
The partially premixed gas low NOx burner according to claim 2 .