JPH0828821A - Radiant tube burner equipment producing little nitrogen oxide, and burning method thereof - Google Patents

Abstract

PURPOSE:To suppress production of a nitrogen oxide 6t a low level by a method wherein after a premixed gas of a high air ratio is produced in a premixing chamber, it is heated by a heat storage body and then subjected to lean combustion on the downstream side of the heat storage body. CONSTITUTION:Air for combustion is introduced into a premixing chamber 3 from an air introducing part 6 on the side A and fuel gas introduced into a gas chamber 5 is jetted into the premixing chamber 3 from a gas nozzle 4. Then the fuel gas and the air are mixed excellently in the premixing chamber 3, made to flow to a heat storage body 2 and preheated by this body 2 and lean combustion is conducted on the downstream side thereof. A combustion gas thus produced reaches the heat storage body 2 on the opposite side, i.e., on the side B, and heats the body and then it is exhausted from the air introducing part 6 on this side. In this case, an air ratio in the premixing chamber 3 is made 1.3-1.5 or more. According to this constitution, production of a nitrogen oxide can be suppressed at a low level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube burner device for low nitrogen oxide generation and a combustion method thereof.

[0002]

2. Description of the Related Art A radiant tube burner, for example, as shown in FIG. 1, is provided with burners at both ends of a radiant tube to which pipes are added, and a heat storage body is installed to open and close a valve. Alternately burned by.
By providing such a heat storage body, not only the thermal efficiency is improved, but also the temperature distribution in the longitudinal direction of the tube, the heat transfer to the treatment material are improved, and further, the life of the tube itself is extended. .

[0003]

The conventional example has a number of advantages as described above, but the greatest problem is that the amount of nitrogen oxides (NOx) generated is very high. This is for burning with high temperature air in the limited space inside the tube, and usually 200 to 1 though it depends on the operating temperature.
It can reach up to 000 ppm. In order to reduce such NOx, there are an exhaust gas recirculation system, a fuel two-stage combustion system, and the like. The former method lowers the flame temperature by mixing the exhaust gas after combustion in the tube with the combustion air to reduce NOx.
Is to lower. However, since exhaust gas is guided, the structure becomes complicated and it is difficult to adjust the balance of the amount of intake. Due to this combustion relationship, the circulation ratio between the initial combustion and stable combustion must be originally changed, but since the control system becomes complicated, it will be used at a compromise point, and the exhaust gas recirculation effect will be sufficient. There are many things that can not be demonstrated, and there is a structural cost. The latter method is a method in which fuel is supplied to combustion air in two stages to lower the flame temperature and suppress NOx generation. Since it is necessary to supply the fuel in two steps, the structure of the burner section becomes complicated, and its balance adjustment is difficult, and in some cases it is necessary to perform control to change the balance between ignition and steady state. Since the structure is complicated, the burner circumference becomes large, and the gas supply section of the second stage must be brought out of the furnace, so that it cannot be compactly set in the furnace body, and the cost rises significantly. The second-stage gas tends to generate carbon during combustion, and the complicated structure shortens the life of the burner peripheral portion. A high temperature resistant refractory lining is required inside the burner, which is heavy, complex and costly.

[0004]

In order to solve the above-mentioned problems, according to the present invention, a radiant tube is provided with a heat storage body on both sides thereof, a premixing chamber is provided upstream of the heat storage body, and a large number of the premixing chambers are provided in the premixing chamber. A gas chamber chamber having a gas nozzle is installed, and an air introduction part is provided in the premixing chamber.

Further, the present invention provides an apparatus according to claim 1, characterized in that the heat storage body is positioned inside the furnace wall so as to correspond to the thickness of the furnace wall.

The present invention also provides, in claim 1, an apparatus in which an ignition device is installed through in the burner axial direction of the heat storage body.

In order to solve the above-mentioned problems, the present invention has a heat storage body built in the burner heads on both sides of the radiant tube, and a premixing chamber is provided on the upstream side of the heat storage body. A gas chamber provided with a large number of gas nozzles is installed, and an air introduction unit is provided in the premixing chamber.
Combustion air and fuel gas are completely premixed in the premixing chamber, and the air ratio is set to a high air ratio of 1.3 to 1.5 or more, and excess air ratio combustion is performed downstream of the heat storage body. The present invention provides a combustion method characterized by:

[0008]

In the premixing chamber, after the high air ratio premixed gas is produced, it is heated through the regenerator, and the lean combustion is executed on the downstream side of the regenerator.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference numeral 1 is a radiant tube, and a heat storage body 2 is built into both sides of the radiant tube 1.
A premixing chamber 3 is provided on the upstream side of the heat storage body 2, a gas chamber 5 provided with a large number of gas nozzles 4 is provided in the premixing chamber 3, and an air introducing portion 6 is provided in the premixing chamber 3. It is a composition. Further, the heat storage body 2 may be positioned and installed in the furnace wall 7 in accordance with the thickness of the furnace wall 7, or the ignition device 8 may be installed so as to penetrate in the burner axial direction of the heat storage body 2. Further, in the premix chamber 3, the air ratio is 1.3 to 1.5.
The above-mentioned high air ratio premixed gas is produced to form a lean combustion flame on the downstream side of the heat storage body 2.

Combustion air is introduced into the premixing chamber 3 from the air introduction section 6 on the A side, and when the fuel gas introduced into the gas chamber 5 is ejected from the gas nozzle 4 into the premixing chamber 3, it is converted into fuel gas. The air is well mixed in the premix chamber 3 and the heat storage body 2
And is preheated by the heat storage body 2, and lean combustion is performed on the downstream side thereof. The combustion gas reaches the heat storage body 2 on the opposite side, that is, the B side, heats the heat storage body 2, and then is exhausted from the air introduction unit 6.

First, the air ratio in the premix chamber 3 is 1.
3 to 1.5 or more. That is, the advantages of premixed lean combustion are fully utilized, and NO generated as the air ratio is increased.
The x concentration drastically decreases, and when the air ratio is 1.5 or more, it shows an excellent low NOx value sufficiently lower than 100 ppm as shown in FIG. 4 depending on the operating temperature.

As shown in FIG. 3, the temperature gradient of the heat storage body 2 is low on the side of the premixing chamber 3 and high on the side of the radiant tube 1, so that there is no danger of flashback, and the above-mentioned air ratio By maintaining it, basically, it does not spontaneously ignite at low temperature, so that the safety is further improved. Further, at the point to be burned, that is, at the side of the tube 1 of the heat storage body 2, the temperature gradient causes the temperature of the premixed gas to become high. Therefore, ignition can be performed safely and easily even at the above air ratio. You can

By arranging the portion of the heat storage body 2 at a position corresponding to the thickness of the furnace wall 7, space is saved, and in addition, the start of combustion is executed substantially at a position in the furnace, and The life is extended, the thermal efficiency is remarkably improved, and considerable piping can be omitted.

An igniter 8 is installed on the heat storage body 2 of either the A side burner or the B side burner as indicated by a phantom line in the figure, and A
After the side burner is ignited, the heat storage body 2 in the B side burner is at a high temperature as described above, so that the B side burner can be ignited without the ignition device 8. You can Even in the A side burner and the B side burner, when the ignition device 8 is not provided, the furnace temperature is sufficiently increased by another heating source attached to the furnace body, so that the radiant tube The inside of 1 can be heated and ignited. In the present invention, no special flame holding part is required.

The ignition device 8 includes an ignition spark, a small electric heater, a pilot burner, etc., but it is considered that it is difficult to ignite in a high air ratio state at the initial stage of low temperature ignition. In this case, the air ratio is set to be slightly lower. There is a need. The means varies depending on the air ratio control method, but a slightly larger amount of gas may be output by using a bypass or the like, or the flow rate may be reduced only on the air side.

The heat storage body 2 may be a ball-shaped material, a honeycomb-shaped material, a net-shaped material, or a combination thereof, which is a commonly used heat-resistant metal, silicon carbide, or alumina ceramics, depending on the use such as temperature.

[0017]

As described above, the present invention is advantageous in that it not only provides various advantages by simplifying the apparatus but also suppresses the generation of nitrogen oxides to a low level. Is.

[Brief description of drawings]

FIG. 1 is a perspective explanatory view showing a conventional example.

FIG. 2 is a perspective explanatory view of the present invention.

FIG. 3 is an explanatory view of a main part of the present invention.

FIG. 4 is a NOx emission characteristic diagram of the premix burner according to the present invention.

[Explanation of symbols]

 1 Radiant tube 2 Heat storage body 3 Premixing chamber 4 Gas nozzle 5 Gas chamber 6 Air introduction part 7 Furnace wall 8 Ignition device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F23D 14/66 C F23L 15/02

Claims (4)

[Claims] 1. A radiant tube is provided with a heat storage body on both sides thereof, a premixing chamber is provided on the upstream side of the heat storage body, and a gas chamber provided with a number of gas nozzles is provided in the premixing chamber. A low-nitrogen oxide radiant tube burner device characterized in that an air inlet is provided in the chamber. 2. The nitrogen oxide low generation radiant tube burner apparatus according to claim 1, wherein the heat storage body is positioned inside the furnace wall so as to correspond to the thickness of the furnace wall. 3. The low-nitrogen-oxide-generating radiant tube burner device according to claim 1, wherein an igniter is installed so as to penetrate in the burner axial direction of the heat storage body. 4. A regenerator is built into the burner heads on both sides of the radiant tube, a premix chamber is provided upstream of the regenerator, and a gas chamber provided with a number of gas nozzles is provided in the premix chamber. An air inlet is provided in the premixing chamber, the combustion air and the fuel gas are completely premixed in the premixing chamber, and the air ratio is 1.3 to 1.5 or more. And a method of low-nitrogen-oxide generation radiant tube combustion, wherein excess air ratio combustion is performed in the radiant tube on the downstream side of the heat storage body.