KR20060119424A - A radiant tube burner equipped with a combustion tube having radial openings to vitiate air with combustion product - Google Patents

Abstract

A radiant tube burner equipped with a combustion gas circulating combustion container is provided to preclude the temperature from going up and nitrogen oxide from occurring by dropping the oxygen concentration of the second air and slow-moving the response to the second air and the main combustion gas. A radiant tube burner equipped with a combustion gas circulating combustion container is composed of a fuel supply pipe(5); a radiant tube(2) connected with the fuel supply pipe, wherein the outer air is flowed; and a combustion container(3) formed in the radiant tube and communicated with the fuel supply pipe to have a fuel nozzle(10) and a first air supply nozzle at one side. The radiant tube is comprised by forming plural auxiliary combustion gas exhaust ports(20) at the outer wall surface of the combustion container and reducing the inlet of a main combustion gas exhaust port(21) where the fuel discharged through the fuel nozzle is combusted in the combustion container and discharged.

Description

A radiant tube burner equipped with a combustion tube having radial openings to vitiate air with combustion product}

1 is a cross-sectional view showing the structure of a typical radiant tube burner.

Figure 2 is a nozzle structure view of the first radiation tube burner in the right side.

3 is a cross-sectional view of a radiant pipe burner provided with a combustion gas circulation combustion cylinder of the present invention.

4 and 5 are views showing different embodiments of the combustion gas circulation type combustion cylinder of the present invention.

<Description of the symbols for the main parts of the drawings>

1: radiant tube burner 2: radiant tube 3: combustion tube

4: pilot burner 5: fuel supply line 10: fuel nozzle

11: Primary air supply nozzle 12: Primary air supply port

20: auxiliary combustion gas outlet 21: main combustion gas outlet

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube burner having a combustion gas circulating combustion cylinder, and more particularly to a part of the primary combustion gas by providing a combustion gas circulation combustion cylinder having an auxiliary combustion gas outlet in the radial direction of the combustion cylinder. Radiation with combustion gas circulating combustion cylinder that can be mixed with secondary air to reduce the partial pressure of oxygen in secondary air to prevent rapid combustion of the radiation tube, lower the peak temperature of the radiation tube, and greatly reduce the amount of nitrogen oxides generated. It is about a tube burner.

In general, a radiant tube burner is used to heat a material by using a heat radiation tube generated by burning a fuel in a heat-resistant tube to heat a material using an external radiation phenomenon of the tube, and is widely used in heat treatment facilities such as annealing furnaces. The radiant tube burner has a small capacity per burner, but the internal volume of the radiant tube is small, resulting in about 10 times higher load combustion than the direct installation such as a heating furnace. Therefore, in the case of the radiant tube burner, a large amount of nitrogen oxides (NOx) are generated due to the high load combustion, compared to the direct burner, and the principle of low nitrogen oxides such as air two stage combustion and light combustion is applied. However, in conventional radiation tube burners, low NOx combustion of less than 150 ppm has been known to be almost impossible due to the high load combustion.

1 is a cross-sectional view showing the structure of a typical two-stage combustion radiator burner, Figure 2 shows the configuration of the fuel nozzle and the primary air supply nozzle in detail. The air supplied to the radiation tube burner (1) passes between the primary air passing through the primary air supply nozzle (11) having a primary air supply port (12) and between the combustion cylinder (3) and the radiation tube (2). It is divided into secondary air passing through the annular space. That is, the fuel injected from the fuel nozzle 10 encounters the primary air in the combustion cylinder 3 and combustion occurs in an air shortage state. The primary combustion product flows into the radiation tube (2) and complete combustion is carried out by the secondary air. Since primary combustion is performed in an air shortage state, the amount of nitrogen oxide generated is suppressed.

The primary air is supplied through the primary air supply nozzle (11), the primary air supply nozzle (11) is composed of a plurality of primary air supply port 12 to supply the primary air into the combustion cylinder (3). . The fuel nozzle 10 is installed at the end of the fuel supply pipe (5) is provided with a plurality of fuel injection port is eccentric injection is known to reduce the nitrogen oxide is a great effect. (Korean Utility Model Registration No. 90010 (Refer to Aug. 31, 1995).

However, even in the case of using the air two-stage combustion and eccentric injection fuel nozzles, the generation of nitrogen oxides exceeds 150 to 200 ppm under high load combustion conditions. As a general performance of the radiation tube burner, development of a burner for reducing nitrogen oxides is required. come.

The present invention is to reduce the amount of nitrogen oxide generated in the high-load combustion radiation tube burner as described above, and instead of the existing combustion cylinder, a plurality of openings are formed in the radial direction of the combustion cylinder so that a part of the primary combustion gas is secondary. It is characterized by being incorporated into the air. By providing an auxiliary combustion gas outlet in the radial direction of the combustion cylinder, part of the combustion gas is mixed into the secondary air passing through the annular space between the combustion cylinder and the radiation tube, and combustion of the combustion gas and the secondary air period occurs on the surface of the combustion cylinder. . Therefore, the oxygen concentration of the secondary air reacting with the main fuel through the main combustion gas outlet is diluted, and as a result, it is possible to reduce the peak temperature by preventing rapid combustion and to uniformize the temperature distribution of the radiation tube and reduce the generation of nitrogen oxides.

That is, an object of the present invention is to reduce the amount of nitrogen oxide generated by lowering the oxygen concentration of the secondary air by providing an opening in the radial direction of the combustion cylinder so that a part of the primary combustion gas is mixed into the secondary air.

In particular, the present invention relates to the Republic of Korea Utility Model Registration No. 090010, the improvement of the fuel injection nozzle for radiant tube burner, the joke combustion type fuel nozzle and air characterized in that to supply more fuel to the lower part than the upper part based on the burner axis The purpose of this study is to reduce the amount of nitrogen oxides generated in the radiation tube burner using the two stage combustion principle.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

3 shows a radiant tube burner provided with a combustion gas circulation type combustion cylinder according to the present invention, and FIGS. 4 and 5 show an embodiment of the combustion gas circulation type combustion cylinder having different radial opening shapes.

The basic burner configuration in which the combustion gas circulation type combustion cylinder of the present invention is installed is the same as the conventional configuration of FIG. 1, except that the core of the present invention is the combustion gas circulation type combustion cylinder 3, and thus the description will be made based on this. do.

The present invention is characterized in that a plurality of auxiliary combustion gas outlets are formed on the outer wall of the combustion cylinder and the inlet of the main combustion gas outlet discharged after the fuel ejected through the fuel nozzle is combusted in the combustion cylinder is characterized in that it is configured. . EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. The radiant pipe burner according to the present invention includes a fuel supply pipe (5), a housing (13a) formed at an outer side of the fuel supply pipe, and having an air inlet (13) formed therein, and an air inlet (13) of the housing (13a). A radiation tube (2) defined by a shielding wall (14) having an opening (not shown) through which air can move, and to which the fuel supply pipe (5) is connected, and formed in the radiation pipe (2), A fuel nozzle 10 and a primary air supply nozzle 11 mounted at an end of the fuel supply pipe 5 are provided at one side, and an auxiliary combustion gas ejection port 20 is formed at an outer wall thereof.

The same primary air supply nozzle 11 as in the case of FIG. 2 is installed at the left end of the combustion cylinder 3, and a fuel supply pipe 5 to which the fuel nozzle 10 is attached is inserted in the center. The combustion cylinder 3 is formed in a cylindrical tube in which the area of the main combustion gas jet port 21 is reduced, and the diameter of the main combustion gas jet port 21 portion is smaller than the diameter of the primary air supply nozzle 11. On the outer wall surface of the combustion cylinder 3, an auxiliary combustion gas ejection opening 20 composed of a plurality of circular or rectangular openings is provided.

Referring to the operation of the burner of the present invention having such a configuration as follows.

The primary air supplied into the combustion cylinder 3 through the primary air supply nozzle 11 reacts with the fuel to generate primary combustion. Since the primary combustion is air shortage combustion, incomplete combustion occurs and the unburned combustion gas is ejected through the main combustion gas outlet 21 and the auxiliary combustion gas outlet 20. The unburned gas ejected through the auxiliary combustion gas outlet 20 reacts with the secondary air, and as a result, the oxygen concentration in the secondary air is lowered. The secondary air of which the oxygen concentration is lowered is reacted with the unburned fuel injected into the radiation pipe 2 through the main combustion gas outlet 21 to combust the combustion. In the combustion process, the higher the oxygen concentration, the more the combustion reaction is accelerated and the combustion temperature is increased. Nitrogen oxides, on the other hand, generate more at higher combustion temperatures and higher oxygen concentrations. Therefore, when the secondary air and the unburned fuel react with the lower oxygen concentration, the combustion speed is slower than the reaction with the pure air (oxygen concentration 21%). In addition, since the oxygen concentration is low, the combustion temperature is lowered, and the lowering of the combustion temperature and the lowering of the oxygen concentration suppress nitrogen oxide generation rate, and as a result, the amount of nitrogen oxide generated can be reduced as compared with the conventional combustion method.

In other words, by lowering the combustion temperature and oxygen concentration, which are the main factors for the production of nitrogen oxides, there is a beneficial feature that can dramatically reduce the generation of nitrogen oxides.

Example

In the present invention, various experiments have been carried out for the case where the burner of the fuel nozzle of FIG. 2 is attached to the burner of FIG. 1 and the combustion cylinder of FIG. 4 to FIG. 5 is attached to the burner of FIG. In the present embodiment, only representative results will be described.

A burner with a combustion capacity of 80,000 kcal / h and 120,000 kcal / h was designed and tested using a radiation tube burner test furnace equipped with a W-type 7-inch radiation tube. The fuel nozzle is a conventional type and a developed type, eccentric injection type of Figure 2 using the same nozzle and only changed the shape of the combustion cylinder. The number and area of the openings were determined by setting the primary air area ratio to 20% and the area ratio of the primary and secondary combustion gas outlets to an optimal value of 6: 4. As fuel, coke furnace gas, a by-product of steel mill, was used. The temperature control of the burner test was controlled to 850 ° C. and 950 ° C. using cold air, and the oxygen concentration at the exit of the radiator tube was maintained at 3-4%. Comparative experiment results are shown in Table 1 below.

Comparison of nitrogen oxide generation amount between conventional burner and the present burner (unit: ppm)  Burner capacity       Conventional Burner     Invention Burner Noon 850 ℃ Noon 950 ℃ Noon 850 ℃ Noon 950 ℃ 80,000kcal / h 142 189 89 101 120,000kcal / h 179 237 105 133

As shown in Table 1, it can be seen that the burner of the present invention can reduce nitrogen oxides by about 40% or more compared with the conventional burner. The result of Table 1 is an average of the results of two experiments in the same state except for the combustion cylinder. The nitrogen oxide generation amount of 150 ppm or less at a temperature of 950 ° C. is a low value that cannot be achieved in a conventional burner, and this is a result demonstrating the effect of the burner of the present invention. In particular, by the combination of the light-burning nozzle and the present invention, the reduction effect of the nitrogen oxides can be maximized. Nitrogen oxide reduction performance has also been confirmed in comparative experiments in annealing furnaces.

The radiant tube burner provided with the combustion gas circulation type combustion cylinder of the present invention reduces the oxygen concentration of the secondary air by ejecting a portion of the primary combustion gas in the radial direction of the combustion cylinder and mixing with the secondary air. By slowing down the reaction between and the main combustion gas, temperature rise and nitrogen oxide generation can be suppressed. Experimental results of the present inventors have confirmed that the use of a combustion-optimized combustion cylinder can reduce the generation of more than 40% nitrogen oxides compared to the conventional two-stage burner, it can be confirmed in the above embodiment.

Claims (3)

A fuel supply pipe 5, a radiation pipe 2 connected to the fuel supply pipe 5, into which external air can be introduced, and formed in the radiation pipe 2 and in communication with the fuel supply pipe, have a fuel nozzle 10 at one side. And a primary air supply nozzle having a combustion cylinder, Combustion gas characterized in that a plurality of auxiliary combustion gas outlets are formed on the outer wall of the combustion cylinder and the inlet of the main combustion gas outlet discharged after the fuel ejected through the fuel nozzle is burned in the combustion cylinder is reduced. Radiant tube burner with a circulating combustion cylinder. The method of claim 1, Radiation tube burner having a combustion gas circulation type combustion cylinder, characterized in that the inlet diameter of the main combustion gas outlet is smaller than the diameter of the primary air supply nozzle. The method of claim 1, Radiating tube burner having a combustion gas circulation type combustion cylinder, characterized in that the shape of the secondary combustion gas blower outlet is circular or rectangular.

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