JPH08247410A - Gas burner for industrial furnace - Google Patents

Abstract

PURPOSE: To obtain a gas burner, producing low NOx and flame of short length, by a method wherein an ejector, throttling the outlet port unit of a preheated air supplying passage to draw exhaust gas in a furnace, being recirculated into a recessed place, and mix it in the recessed place, is formed while fuel gas injection ports are provided on furnace walls at the side of the recessed place. CONSTITUTION: A recessed place 2, whose front surface is opened in the inside wall surface 1 of a furnace, is provided in a burner tile 3 and the outlet port of preheated air supplying passage 4 is opened on the rear end surface of the recessed place 2 while the outlet port unit of the preheated air supplying passage 4 is throttled to form an ejector 5. The ejector 5 draws gas in the furnace, which is recirculated into the recessed place 2, by the momentum of the injected preheated air and mixes it into preheated air in the recessed place 2 to inject it into the furnace again. Further, fuel gas ejection ports 6, whose ejecting direction is slanted toward the center, are provided on the wall surface 1 in the furnace at both sides of the recessed place 2 and after a temperature in the furnace has arrived at a temperature higher than the igniting temperature of the fuel, low oxygen concentration combustion and low-NOx concentration combustion can be effected by fuel, ejected out of the fuel ejection port 6, air-fuel mixture, ejected out of the recessed place 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx type gas burner used in an industrial furnace such as a forging furnace.

[0002]

2. Description of the Related Art Conventionally, in this type of furnace, it has been known that the amount of NOx produced increases when the preheated air of the gas burner is at a high temperature (400 to 500 ° C. or higher). Gas burner as shown (Japanese Patent Laid-Open No. 1-
No. 300103) has been tried. This is because after the furnace temperature is raised to the fuel ignition temperature, preheated air and fuel are jetted separately into the furnace, and the exhaust gas in the furnace is preheated before the fuel and preheated air react with each other. Since the air is entrained in and mixed with the air, the combustion becomes slow and the combustion temperature can be kept low, thereby suppressing the amount of NOx generated.

[0003]

In the conventional method as described above, the preheated air and the exhaust gas are mixed in the furnace, and the fuel is brought into contact with the mixed air, so that the preheated air jet port 10 and the fuel are mixed. There is a problem that the burner becomes large in size because it is necessary to improve the mixing of the fuel and the exhaust gas by increasing the distance from the gas ejection port 6, and the flame becomes long in order to make the combustion speed as slow as possible. There was a problem that it could not be installed in a small furnace. It is an object of the present invention to solve the above-mentioned problems in the conventional method and to provide a burner with low NOx and short flame length.

[0004]

As shown in FIG. 1, a low NOx industrial furnace according to the present invention is provided with a recess 2 having a front surface opened to a furnace inner wall surface 1 in a burner tile 3 to form a recess 2. An ejector 5 for opening the outlet of the preheated air supply passage 4 on the rear end face, sucking the exhaust gas in the furnace that recirculates into the recess 2 by narrowing down the outlet portion of the preheated air supply passage 4 and mixing it in the recess 2 is provided. The burner is formed and provided with a fuel gas ejection port 6 on the furnace wall surface 1 on the side of the recess 2 and a means for separately raising the temperature of the inside of the furnace to the fuel ignition temperature. as,
As shown in the figure, a fuel supply hole 7 for supplying the rising fuel into the preheated air supply passage 4 is provided, or as shown in FIG. 2, the starting fuel and air are supplied into the recess 2. A fuel / air supply hole 8 can be provided.

[0005]

In the above-mentioned structure, after the temperature in the furnace reaches the ignition temperature of the fuel by the temperature raising means, the operation of the temperature raising means is stopped and the combustion is performed only by the fuel supply from the fuel gas jet port 6. continue. At this time, the preheated air sucks the exhaust gas from around the ejector 5 due to its momentum, so that the preheated air and the exhaust gas are well mixed in the recess 2 due to the stirring effect of the ejector 5, so that the oxygen concentration of the air-fuel mixture becomes low. The combustion temperature can be lowered. Further, in the conventional method, high temperature is partially generated where the fuel is in direct contact with the air flow, and the reduction of NOx is incomplete. However, in the present invention, the air and the exhaust are mixed well, However, there is no possibility that a high oxygen concentration will occur. Further, since the exhaust gas is sufficiently mixed with the preheated air by the ejector 5 in the recess 2, the fuel injection port 6 is placed closer to the recess 2 or the nozzle of the fuel injection port 6 is installed obliquely toward the air-fuel mixture. Therefore, the burner can be downsized and the flame can be shortened. Further, in a furnace that does not require shortening of flame, it is possible to further reduce NOx.

[0006]

FIG. 1 shows one embodiment of the present invention.
(B) and (c) show the XX cross section and the YY cross section in (a), respectively. In the figure, a recess 2 having a front surface opened to the inner wall surface 1 of the furnace is provided in the burner tile 3, and an outlet of the preheat air supply passage 4 is opened at the rear end surface of the recess 2 to form the preheat air supply passage. An ejector 5 is formed by narrowing the outlet portion of the nozzle 4. This ejector 5
Is for sucking in-furnace exhaust gas that recirculates into the recess 2 by the momentum of the preheated air that is ejected, mixes this with preheated air in the recess 2 and ejects it again into the furnace. As shown in (a) and (c) of the same drawing, a fuel gas jet port 6 whose injection direction is inclined toward the center side is provided on the furnace inner wall surface 1 on the side of, and the temperature inside the furnace is After reaching the ignition temperature or higher, the fuel injected from the fuel gas ejection port 6 and the air-fuel mixture ejected from the recess 2 perform low NOx low NOx combustion.

In FIG. 1, when the temperature in the furnace is lower than the fuel ignition temperature, the oxygen concentration and the temperature of the preheated air are insufficient in the combustion system in which the fuel is directly injected from the fuel gas ejection port 6 into the furnace. Combustion may become unstable or misfire may occur. Therefore, in the embodiment of FIG. 1, as a means for raising the temperature of the inside of the furnace to the fuel ignition temperature, a fuel supply hole 7 for supplying startup fuel into the preheated air supply passage 4 is provided as shown in FIG. It is provided near the outlet of the preheated air supply passage 4, and thus the preheated air, which is still low in temperature but still has a high oxygen concentration, and the fuel for start-up are mixed in the recess 2 so that they are reliably burned in the furnace. The temperature inside the furnace is raised until it reaches the fuel ignition temperature. When the control device senses through the temperature sensor that the furnace temperature has reached the fuel ignition temperature, the fuel supplied to the startup fuel supply hole 7 is shut off and the fuel gas is directly injected into the furnace to the fuel gas jet port 6. Can be switched to.

2A and 2B show another embodiment of the present invention, in which FIG. 2A is a vertical sectional view and FIG. 2B is its XX sectional view. In the present embodiment, the inside of the recess 2 in FIG. 1 is divided into a mixing portion and an exhaust gas suction passage to improve the exhaust gas suction efficiency. The front surface opens to the furnace inner wall surface 1 and the rear end surface has a preheated air supply passage. 4 inside the burner tile 3 on the side of the mixing recess 2 in which the ejector 5 is open, the front end opens to the furnace inner wall surface 1 and the rear end bends to the rear side of the recess 2. An exhaust gas suction passage 9 opening to the wall surface is formed, and the ejector 5 sucks the exhaust gas in the furnace through the exhaust gas suction passage 9, mixes the exhaust gas and the preheated air in the recess 2 and jets them into the furnace. It has become. Further, in the embodiment of FIG. 3, as a means for raising the temperature of the inside of the furnace to the fuel ignition temperature in the embodiment of FIG.
The air supply hole 8 is provided across the exhaust gas suction passage 9, and the figure shows the state at the time of startup combustion.

FIG. 4 shows the actual effect of reducing NOx according to the present invention as measured data.
mm (diameter) x 3100 mm (length), combustion amount 350,000 K
In a forging furnace having a cal / h and an air ratio of 1.08 to 1.10, the conventional burner (curve A) of FIG. 5 and the burner of the present invention (curve B) shown in the embodiment of FIG. The NOx value was measured with respect to the furnace temperature after the termination of the boost combustion. The NOx generation rate (oxygen concentration 0% conversion) was improved by about 6 to 8 ppm by the present invention, and the flame length was 1/2 to 1/3.
Could be shortened to

[0010]

According to the present invention, as described above, after the temperature in the furnace reaches the fuel ignition temperature, the exhaust gas is effectively sucked by the preheated air having a large momentum and mixed by the stirring effect of the ejector 5. Since a mixture of preheated air having a low oxygen concentration, exhaust gas, and fuel is brought into contact with each other and burned, even if the temperature of the mixture is high, the combustion temperature should be suppressed sufficiently low to reduce the NOx generation amount. In addition, since the air-fuel mixture is sufficiently mixed by the ejector 5 in the recess 2, there is no need to provide a distance between the fuel gas ejection port 6 and the recess 2 as in the conventional case, and the fuel injection is performed. There is an advantage that the flame can be shortened by inclining the direction to the mixed air flow side, thereby making it possible to downsize the burner and the furnace.

[Brief description of drawings]

1 shows a low NOx type gas burner according to the present invention, wherein (a) is a top view, (b) is a vertical cross-sectional view of its XX portion, and (c) is a vertical cross-sectional view of its YY portion. Fig.

2A and 2B show another embodiment of the present invention, in which FIG. 2A is a longitudinal sectional view, and FIG. 2B is a transverse sectional view taken along the line XX.

FIG. 3 is a vertical sectional view showing still another embodiment of the present invention.

FIG. 4 is a graph comparing the effects of the present invention and the conventional example.

FIG. 5 is a vertical sectional view of a conventional example.

[Explanation of symbols]

 1 Inner Wall Surface 2 Recess 3 Burner Tile 4 Preheated Air Supply Channel 5 Ejector 6 Fuel Gas Jet 7 Fuel Supply Hole 8 Fuel / Air Supply Hole 9 Exhaust Gas Suction Passage 10 Preheated Air Jet

Claims (4)

[Claims] 1. A recess is formed in the burner tile, the front surface of which is open to the inner wall surface of the furnace, the outlet of the preheating air supply passage is opened at the rear end surface of the recess, and the outlet portion of the preheating air supply passage is narrowed. A burner that forms an ejector that sucks the exhaust gas in the furnace that recirculates into the recess and mixes it in the recess, and a fuel gas jet outlet on the furnace wall on the side of the recess, and a separate furnace up to the fuel ignition temperature A gas burner for an industrial furnace, comprising: a means for raising the temperature. 2. A recess is formed in the burner tile, the front surface of which is open to the inner wall surface of the furnace, the outlet of the preheating air supply passage is opened to the rear end surface of the recess, and the front end of the recess is lateral to the furnace wall surface. An exhaust gas suction passage is formed that is open and the rear end is bent and opened on the rear side wall surface of the recess, and the outlet part of the preheat air supply passage is narrowed to suck the exhaust gas in the furnace through the exhaust gas suction passage and mix it in the recess. A gas burner for an industrial furnace, which is provided with a burner which forms an ejector and is provided with a fuel gas ejection port on a furnace wall surface on the side of the recess, and a means for separately raising the temperature of the inside of the furnace to a fuel ignition temperature. 3. The gas burner for an industrial furnace according to claim 1, wherein a fuel supply hole for supplying fuel into the preheated air supply passage is provided near the outlet of the preheated air supply passage as the temperature raising means. 4. The fuel / air supply hole for supplying fuel and air into the recess is provided as the temperature raising means.
Or the gas burner for an industrial furnace according to 2.