JP2002022146A - Regenerative burner and combustion method of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat the part to be heated equally even in the case when the object to be heated is located in the vicinity of a burner by elevating the temperature of flame in the vicinity of the burner higher than that in a conventional one. SOLUTION: A regenerative burner comprises a burner throat 1 supplying high-temperature combustion air, a primary fuel feed opening 2 provided in the inner peripheral surface of the burner throat 1, a secondary fuel feed opening 3 provided outside the burner throat 1 approximately parallel to the burner throat and an air supply opening for holding flame 4 provided in the inner peripheral surface of the secondary fuel feed opening 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative burner mainly used for industrial heating furnaces and a method for burning a regenerative burner.

[0002]

2. Description of the Related Art A regenerative burner performs combustion using high-temperature combustion air exceeding 800 ° C. When the fuel and the combustion air are supplied to the same burner tile, there is a problem that the NOx value in the combustion exhaust gas becomes extremely high.
Therefore, conventionally, in order to perform low NOx combustion, the fuel is divided and supplied to the primary fuel and the secondary fuel, and the primary fuel and the combustion air are mixed in the burner tile to form a primary flame, and the secondary fuel is formed. A regenerative burner has been proposed in which oxygen remaining in the primary flame forms a slow-burning secondary flame in the furnace. Such a regenerative burner includes, for example, a technique disclosed in Japanese Patent Publication No. 2683545 (hereinafter referred to as Conventional Technique 1). FIG. 3 shows the outline. In the figure, 11 is a furnace body, 12 is inside the furnace, 13 is an air supply port, 1
4 is a fuel supply port, and 15 is a low temperature fuel supply port. The air supply port 13 and the fuel supply port 14 are independently opened at a certain distance from each other in the furnace 12, and the air supply port 13 has a low-temperature fuel supply port 15 built therein.

When the temperature in the furnace is lower than the self-ignition temperature of the fuel, the combustion air is ejected from the air supply port 13 and at the same time, the fuel is ejected only from the fuel supply port 15 for low temperature and burned. . When the temperature in the furnace reaches a high temperature equal to or higher than the self-ignition temperature of the fuel, the supply of fuel from the low-temperature fuel supply port 15 is stopped and the fuel supply port 1 is stopped.
This is a combustion method in which fuel is injected only from the furnace 4 and burned while forming a recirculated flow in the furnace 12. According to this method, combustion takes place in a place where the oxygen concentration is low, and a slow burning in the furnace results in a flame having no local high temperature, and NOx
It is said that a reduction effect can be obtained.

[0004] There is another technique disclosed in Japanese Patent Application Laid-Open No. 6-159613 (hereinafter referred to as prior art 2). FIG.
The outline is shown below. In the figure, 21 is a primary fuel supply port, 22 is a secondary fuel supply port, and 23 is a burner throat. Almost all of the combustion air A is supplied to the burner throat 23, and the primary fuel F1 is injected toward the combustion air from around the flow of combustion air in the burner throat 23 to form a primary fuel around the flow of combustion air. While forming the flame B1, the burner throat 23 outside the primary flame B1
, The secondary fuel F2 is directly injected into the furnace. This is a combustion method in which the mixing of high-temperature low-oxygen air in which primary combustion gas and combustion air are mixed and secondary fuel in the furnace is slow. Further, in this method, the primary combustion ratio is increased when the furnace temperature is low or when the burner is started, and the secondary fuel ratio is increased when the furnace temperature is high or after the burner is started. According to this method, after the primary fuel is burned in a super-air excess state, NOx in the primary flame is reduced by the secondary fuel, and then the high-temperature combustion air and the secondary fuel are slowly released in the furnace. To cause secondary combustion. Since the primary flame is burned in a state of excessive air excess, the generation of NOx is suppressed, and the NOx is further reduced by the reducing action of the secondary fuel. Further, it is described that the generation of NOx is suppressed because the secondary fuel stably and slowly burns with the high-temperature combustion air.

[0005]

In the prior art 1, during normal operation in which the furnace temperature is equal to or higher than the ignition temperature of the fuel, the fuel is introduced into the furnace from a fuel supply port 14 different from the air supply port 13. Supplied directly. Therefore, the fuel and the combustion air are mixed in the furnace, and combustion must start at a position away from the burner. At this time, the flame temperature distribution in the length direction is as shown in FIG. The temperature is low within about 1 m near the burner until the fuel and combustion air mix. The temperature after the start of combustion is almost constant. Therefore, in the prior art 1, when the object to be heated is located near the burner in the furnace, the heating temperature of the object to be heated becomes lower in the vicinity of the burner due to the effect of the low flame temperature near the burner. Therefore, there is a problem that the object to be heated cannot be heated to a uniform temperature. In the prior art 2, the furnace temperature is higher than in the prior art 1. However, the temperature near the burner is still low because the secondary fuel is injected into the furnace while keeping the temperature low. Even in the prior art 2, the problem that the object to be heated cannot be heated to a uniform temperature cannot be solved.

The present invention has been made to solve such a problem. By increasing the flame temperature in the vicinity of the burner as compared with the related art, even when the object to be heated is located in the vicinity of the burner, the uniform heating is achieved. It is an object of the present invention to provide a regenerative burner and a combustion method thereof.

[0007]

SUMMARY OF THE INVENTION A regenerative burner according to the present invention comprises a burner throat for supplying high-temperature combustion air;
A primary fuel supply port provided on the inner peripheral surface of the burner throat, a secondary fuel supply port provided substantially parallel to the burner throat outside the burner throat, and a secondary fuel supply port provided on the inner peripheral surface of the secondary fuel supply port. And a flame holding air supply port.

In the method of burning a regenerative burner according to the present invention, the fuel is divided into primary fuel and secondary fuel and supplied, and the primary fuel and combustion air are mixed in the burner tile to form a primary flame. The secondary fuel is mixed with flame holding air supplied separately from the combustion air to form a flame holding on the outer periphery of the primary flame, and then forms a slow burning secondary flame in the furnace. It is characterized by the following. In this case, the flame temperature distribution in the length direction is controlled by changing the ratio between the primary fuel and the secondary fuel.

In the present invention, the flame holding is formed by injecting the secondary fuel and the flame holding air substantially in parallel on the outer periphery of the primary flame formed by the high temperature combustion air and the primary fuel. Therefore, the flame temperature in the vicinity of the burner can be significantly increased as compared with the conventional method, and therefore, even when the object to be heated is arranged in the vicinity of the burner, it is possible to uniformly heat the object.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an outline of a regenerative burner according to the present invention. In this regenerative burner, a primary fuel supply port 2 is provided on the inner peripheral surface of a burner throat 1 for supplying high-temperature combustion air, and a secondary fuel supply port 3 is provided substantially in parallel outside the burner throat 1. A flame holding air supply port 4 is provided on the inner peripheral surface of the next fuel supply port 3. Preferably, a plurality of secondary fuel supply ports 3 are provided so as to surround the burner throat 1. In the drawing, 5 is a burner tile, 6 is a furnace body, and 7 is a furnace interior.

In this regenerative burner, fuel is supplied separately to a primary fuel F1 and a secondary fuel F2. The primary fuel F1 is injected from the primary fuel supply port 2 from around the high-temperature combustion air A1 supplied to the burner throat 1. The high-temperature combustion air A1 and the primary fuel F1 are injected from the burner throat 1 into the furnace 7 and mixed in the burner tile 5 to form a primary flame B1 around the high-temperature combustion air A1. The primary fuel F1 is injected from at least one or more nozzles, preferably a plurality of nozzles evenly arranged on the inner peripheral surface of the burner throat 1. From the outside of the primary flame B1, a secondary fuel F2 is injected from the secondary fuel supply port 3 substantially in parallel with the burner throat 1. At this time, the flame holding air A2 is injected from the flame holding air supply port 4. Secondary fuel F2
And the flame holding air A2 are mixed on the outer periphery of the primary flame B1 to form a flame holding B3. The flame keeping air A2 is a part of the theoretical air amount corresponding to the secondary fuel F2. 2-5% of theoretical air volume
If the degree is supplied, a sufficient flame can be formed. Among the secondary fuels F2, those that have not been completely burned by the flame holding B3 come into contact with the combustion air A1 that has not contributed to the combustion in the primary combustion and are mixed slowly, and the secondary flame B of the slow burning
Form 2 Here, all of the primary fuel F1 and the secondary fuel F2 are completely burned. If the combustion air A1 is equal to or higher than the self-ignition temperature of the fuel, it is possible to easily cause secondary combustion in the furnace.

According to the present invention, since the flame holding is formed at the discharge position of the secondary fuel into the furnace, there is no low-temperature gas near the burner. Therefore, the flame temperature in the vicinity of the burner becomes higher than in the conventional method. Thus, even when the object to be heated is arranged near the burner in the furnace, the object to be heated can be uniformly heated.

FIG. 2 shows the flame temperature distribution in the longitudinal direction of the burner according to the method of the present invention and the conventional method. In the conventional method, the flame temperature is particularly low within a range of 1 m from the burner. On the other hand, according to the method of the present invention, it can be seen that the flame temperature within a range of 1 m from the burner is greatly increased.

Another embodiment of the present invention is to control the flame temperature distribution of the burner by using the regenerative burner configured as described above and further changing the charging ratio of the primary fuel and the secondary fuel. is there. As the ratio of the primary fuel increases, the primary flame B1 increases, and the temperature near the burner increases. Conversely, the lower the proportion of the primary fuel, the smaller the primary flame B1 and the lower the temperature near the burner. The ratio of the primary fuel necessary for sufficiently raising the flame temperature near the burner is affected by the discharge flow rate of the fuel and the combustion air, and varies depending on the case. However, the range of 2 to 30% is sufficient. According to this method, the object to be heated can be heated to a uniform temperature. In addition, it is possible to perform the inclined heating of the object to be heated by utilizing the fact that the flame temperature distribution can be arbitrarily adjusted.

[0015]

As described above, according to the present invention, it is possible to secure a sufficiently high temperature near the burner in the flame temperature distribution in the longitudinal direction of the regenerative burner. This has the effect of improving the uniformity of the flame temperature distribution in the length direction. Therefore, even when the object to be heated is arranged near the burner, the object to be heated can be heated to a uniform temperature.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an outline of a regenerative burner according to the present invention.

FIG. 2 is a diagram showing a flame temperature distribution in a longitudinal direction of a burner of the present invention.

FIG. 3 is a schematic view of a burner according to prior art 1.

FIG. 4 is a schematic view of a burner according to prior art 2.

FIG. 5 is a view showing a flame temperature distribution in a longitudinal direction of a burner according to prior art 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Burner throat 2 Primary fuel supply port 3 Secondary fuel supply port 4 Air supply port for flame holding 5 Burner tile 6 Furnace body 7 Furnace

Continued on the front page F term (reference) 3K023 QA03 SA00 3K065 TA01 TA14 TB02 TB12 TC03 TE04 TF01 TG04 3K068 FA02 FD04 HA01

Claims (3)

[Claims] 1. A burner throat for supplying high-temperature combustion air, a primary fuel supply port provided on an inner peripheral surface of the burner throat, and a secondary fuel supply provided outside the burner throat substantially in parallel with the burner throat. A regenerative burner, comprising: a fuel supply port; and a flame holding air supply port provided on an inner peripheral surface of the secondary fuel supply port. 2. A fuel is divided and supplied into a primary fuel and a secondary fuel, and the primary fuel and the combustion air are mixed in a burner tile to form a primary flame, and the secondary fuel is separated from the combustion air. A method for burning a regenerative burner, comprising: forming a flame holding on the outer periphery of a primary flame by mixing with a flame holding air supplied to a furnace; and then forming a slow burning secondary flame in a furnace. 3. The combustion method for a regenerative burner according to claim 2, wherein the flame temperature distribution in the longitudinal direction is controlled by changing the ratio between the primary fuel and the secondary fuel.