KR100466178B1 - A low NOx regenerative radiant tube burner equipped with multiple fuel nozzles - Google Patents

Abstract

The present invention relates to a low nitrogen oxide (NOx) regenerative radiation tube burner, and more particularly, to a fuel split injection type fuel nozzle which can reduce the amount of nitrogen oxide generated by splitting the fuel to equalize the fuel concentration in the radiation tube. It is an object of the present invention to provide a low-nitrogen oxide regenerative radiation tube burner.

The low nitrogen oxide heat storage radiation burner having the fuel split injection fuel nozzle of the present invention has a fuel supply pipe extending downward from the burner's nozzle plate, and constitutes a plurality of fuel injection holes in the longitudinal direction of the fuel supply pipe. It characterized in that the fuel is divided into injection.

The low nitrogen oxide regenerative radiation tube burner equipped with the fuel split injection fuel nozzle of the present invention can achieve the effect of delaying the mixing of air and fuel, and improve the combustion stability by the fuel injected at a position relatively close to the air. While securing flame splitting and multi-stage combustion effects, nitrogen oxides can be reduced even in regenerative radiant burners using high temperature air.

Description

A low NOx regenerative radiant tube burner equipped with multiple fuel nozzles}

The present invention relates to a low nitrogen oxide (NOx) regenerative radiation tube burner for splitting and injecting fuel, and more particularly, a portion of the fuel supply tube extends below the nozzle plate of the burner and is installed in the longitudinal direction of the fuel supply tube. The present invention relates to a low-nitrogen oxide regenerative radiation burner having a fuel split injection type fuel nozzle capable of reducing the amount of nitrogen oxide generated by uniformizing the fuel concentration in the radiation tube by constituting a plurality of fuel injection ports.

In general, radiant tube burners are used for indirect heating equipment that heats a tube using heat generated when burning fuel in a heat-resistant tube and uses the external radiation of the tube to heat the material. It is widely used for such purposes.

The radiant tube burner has a small capacity per burner, but the internal volume of the radiant tube serving as a combustion chamber is 10 times higher than that of a direct installation such as a heating furnace.

The regenerative combustion technology is an energy-saving combustion technology that preheats and burns combustion air at a high temperature of 800 ° C. or higher by a regenerator, and efforts have been actively made for its application. However, the thermal efficiency is increased by recovering the waste heat and preheating the combustion air to a high temperature during the regenerative combustion, but the generation of a large amount of nitrogen oxides due to the high temperature combustion by using the high temperature preheating air is pointed out as a big problem.

In particular, in the case of a radiant tube burner, a large amount of nitrogen oxides are generated due to the high load combustion compared to the direct burner, and there are no satisfactory low nitrogen oxide regenerative radiant tube burners worldwide.

To date, the most effective method of reducing nitrogen oxides in regenerative combustion is high-speed injection of air. When high-speed air is injected into the furnace, combustion gas in the furnace is mixed in the air classification, and the oxygen concentration in the air is lowered. It is homogenized and production | generation of nitrogen oxide is suppressed.

This method has a great effect in the case of a direct fired furnace, but in the case of a radiant tube burner, since there is a flame in the tube, it is difficult to reduce nitrogen oxides by high-speed injection alone, and thus, regenerative radiation that has satisfactory low nitrogen oxide performance to date. The tube burner is not developed.

For example, a technique for reducing nitrogen oxides by eccentric high-speed injection of air is shown in Japanese Patent Laid-Open Nos. 10-176810 and 6,027,333, but the inventors of the present invention directly experimented with these burners. According to the bar, but smaller than other types of burners, there was a problem that more than 200ppm nitrogen oxides.

Hereinafter, the operation principle of a general regenerative radiation tube burner will be described in detail.

1 is a schematic cross-sectional view showing a general heat storage radiation burner, a pair of burners (30, 30 ') are provided at both ends of the radiation pipe (1), respectively, and a fuel nozzle (3) at the center of the burners (30, 30'). 20 and 20 'are installed, and heat accumulators 22 and 22' are installed on the outer circumferences of the fuel nozzles 20 and 20 ', respectively. The air is configured to be injected through the air nozzles 21 and 21 'in the nozzle plates 25 and 25'.

When combustion occurs in one burner 30 of the regenerative radiation tube having the above-described configuration, the combustion gas passes through the heat accumulator 22 'in the opposite burner 30' to supply air to the four-side switching valve 4 and the exhaust gas outlet. Heat is stored in the heat accumulator 22 'while being discharged to the 24, and the combustion gas is discharged to a temperature below 200 ℃.

After a certain time, the combustion is switched so that the burner in the combustion mode becomes the heat storage mode, and the above process is repeatedly repeated. At this time, the supply of fuel, air and combustion gas is controlled by an appropriate switching mechanism.

In such radiant tube combustion, since the heat load in the tube is high and the flame is formed in the tube, the effect of the conventional low nitrogen oxide combustion method such as high-speed injection is small. That is, even though air is injected at high speed from the air nozzles 21 and 21 ', the amount of combustion gas in the radiant pipe is not large compared to the amount of air, so the effect of lowering the oxygen concentration by suction of the gas in the furnace is small.

In order to maximize the effect of the high-speed injection, a large amount of combustion gas in the furnace should be sucked in the vicinity of the air nozzles 21 and 21 ', but in the radiation pipe 1, a flame is formed long over the radiation pipe, and the volume of the radiation pipe is increased. Because of this small, effective suction of combustion gas is not achieved.

Therefore, in order to reduce the nitrogen oxides in the radiation tube, a method for reducing nitrogen oxides other than high-speed injection should be devised, and it is desirable to improve the burner structure and the radiation tube structure.

In addition, the inventors of the present invention, Korean Patent Application No. 2001-51771 (filed date: Aug. 27, 2001, the name of the invention) that the principle of low nitrogen oxides of the general burner burner does not apply as it is in the case of a radiation tube burner. The low nitrogen oxide regenerative radiation burner with dual fuel nozzles has been described in detail, and it has been found that it is important to design the burner to have a mixed delay structure of air and fuel in order to reduce nitrogen oxides.

FIG. 2A is a schematic cross-sectional view of an eccentric injection burner according to US Pat. No. 6,027,333, which is known to be the best in terms of nitrogen oxide generation to date, and FIG. 2B is a partial detailed view of the nozzle plate of FIG. The fuel nozzle 20 is disposed at the center of the nozzle plate 25, and the air nozzle 21 is disposed below the nozzle plate 25.

The burner 30 having the above-described configuration increases the circulation of the high temperature combustion gas in the radiant tube according to the injection of the high-speed air and eccentrically arranges the air nozzle 21, thereby delaying the initial mixing of the air and the fuel, We plan reduction.

The burner 30 has improved nitrogen oxide generation performance than the conventional regenerative radiant tube burner, but in the operating conditions of a conventional indirect heating furnace having a furnace temperature of 950 ° C and an air temperature for combustion of about 900 ° C, When combustion of natural gas, nitrogen oxide of 180 ~ 270ppm was generated, and it was shown that additional reduction is necessary for the smooth application to the actual equipment.

As described above, the application of energy-saving regenerative combustion technology to the radiant tube burner is a problem of excessive generation of nitrogen oxides, and the low-nitrogen oxide combustion technology has not been developed so far. Development is desired.

The present invention has been made to solve the above problems, the fuel supply pipe is installed to extend below the nozzle plate of the burner, by forming a plurality of fuel injection port in the longitudinal direction of the fuel supply pipe by splitting the fuel injection, It is an object of the present invention to provide a low-nitrogen oxide regenerative radiation burner having a fuel split injection fuel nozzle capable of reducing the generation of nitrogen oxides by equalizing the fuel concentration.

1 is a schematic cross-sectional view showing a typical regenerative radiant burner

Figure 2a is a schematic cross-sectional view showing a conventional eccentric injection burner

FIG. 2B is a partial detail view of the nozzle plate of FIG. 2A

Figure 3a is a cross-sectional view showing a low nitrogen oxide regenerative radiation burner having a fuel split injection fuel nozzle of the present invention.

3B and 3C are cross-sectional views showing another embodiment of the low nitrogen oxide regenerative radiation burner provided with the fuel split injection fuel nozzle of the present invention, respectively.

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

1: radiant tube 4: all four sides

20, 20 ': Fuel nozzle 21, 21': Air nozzle

22, 22 ': heat storage 25, 25': nozzle plate

30, 30 ': Burner 40, 40': Primary fuel nozzle

41, 41 ': 2nd fuel nozzle 42, 42': 2nd fuel injection port

As a means for achieving the above object, the low-nitrogen oxide regenerative radiation burner provided with the fuel split injection type fuel nozzle of the present invention is provided with a primary fuel nozzle in the center of the nozzle plate, respectively, and on the inner wall of the radiation pipe. After the internal contact, the secondary fuel nozzle is installed so that the axial position extends from the primary fuel nozzle by penetrating the outer circumference of the nozzle plate. By uniformly split injection in the longitudinal direction therein, the mixture of fuel and oxygen in the radiant tube is uniform, preventing rapid combustion and at the same time suppressing nitrogen oxides.

In addition, the low nitrogen oxide regenerative radiation burner provided with the fuel split injection type fuel nozzle of the present invention is characterized by constituting one or more secondary fuel nozzles.

Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 3A to 3C.

Figure 3a is a cross-sectional view showing a low nitrogen oxide regenerative radiation burner having a fuel split injection fuel nozzle of the present invention, Figures 3b and 3c is a low nitrogen oxide regenerative radiation burner having a fuel split injection fuel nozzle of the present invention. It is sectional drawing which shows each other form of.

First, referring to FIG. 3A, a low nitrogen oxide regenerative radiation burner having a fuel split injection fuel nozzle according to the present invention will be described.

The nozzle plates 25 and 25 'are installed at the front end of the fuel accumulator 22 and 22' in the burner 30 and 30 'installed in the radiation pipe 1, and the nozzle plates 25 and 25' are installed. ), Slit-type air nozzles 21 and 21 'are provided. In this case, the installation positions of the air nozzles 21 and 21 'may be variously changed as shown in FIGS. 3B and 3C, and the shape may also be variously changed to a slit type or a circular shape.

The fuel nozzle is composed of the primary fuel nozzles 40 and 40 'and the secondary fuel nozzles 41 and 41', wherein the primary fuel nozzles 40 and 40 'are formed of the nozzle plates 25 and 25'. The secondary fuel nozzles 41 and 41 'pass through the nozzle plates 25 and 25' and are connected to the inner wall of the radiation pipe 1 so that the secondary fuel nozzles 41 and 41 'are end faces of the nozzle plates 25 and 25'. It extends onto the pipe in the fuel flow direction and is installed in the radiant pipe 1.

At this time, the secondary fuel nozzles 41 and 41 'are provided with a plurality of secondary fuel injection holes 42 and 42' in the longitudinal direction.

The secondary fuel nozzles 41 and 41 'may be configured by one or a plurality of burners, and the primary fuel nozzles 40 and 40' may be omitted.

In addition, the axial position of the tip portion of the secondary fuel nozzles 41 and 41 'can be appropriately extended or reduced depending on the shape and length of the radiation tube.

The combustion air nozzles 21 and 21 'may be arranged in any position in the nozzle plates 25 and 25' in the form of a slit or a circle.

3b illustrates a case where only one secondary fuel nozzle 41 is installed for each burner, and FIG. 3c illustrates a case where only one primary fuel nozzle 40 is omitted and only one secondary fuel nozzle 41 is installed for each burner. will be.

In the case where only one secondary fuel nozzle 41 is installed, the air nozzles 21 are preferably provided opposite to each other in the radial direction of the secondary fuel nozzle 41 and the radiation pipe 1.

And when there are many secondary fuel nozzles 41, the air nozzle 21 may be arrange | positioned in the furthest position from the axial center of a burner or the secondary fuel nozzle 41. FIG.

The operation of the low nitrogen oxide regenerative radiation tube burner with the fuel split injection fuel nozzle of the present invention having the above-described configuration will be described below.

First, when air is jetted at high speed from the air nozzle 21 of the nozzle plate 25, combustion gas inside the radiator pipe 1 is sucked into the air, and then the primary fuel nozzle 40 and the secondary fuel nozzle 41 are discharged. When fuel is injected through a plurality of secondary fuel injection holes 42 formed in the primary fuel, the primary fuel passing through the primary fuel nozzle 40 first reacts with air to generate primary combustion in an excess of air. This will serve as an inflammation.

Since the generation of nitrogen oxides can be suppressed when the air ratio is high or the air is insufficient, the amount of nitrogen oxides generated in the combustion zone of the primary fuel is reduced.

In addition, the secondary fuel is sequentially mixed with the primary combustion product and air while being injected through the secondary fuel injection port 42 of the secondary fuel nozzle 41 installed in front of the nozzle plate 25 in the axial direction than the primary fuel. It burns while reacting.

As described above, the fuel is divided into primary fuels and secondary fuels in different axial positions and dividedly injected to obtain a fuel multistage combustion effect, and the nitrogen oxide generated in the primary combustion reacts with the secondary fuel. Part is reduced to nitrogen.

In particular, since the secondary fuel nozzles 41 are provided with a plurality of fuel injection holes 42 in the axial direction, combustion is not terminated prematurely, and the mixing of fuel and air is delayed, so that the flame length inside the radiant tube is larger than that of the conventional burner. It will be longer.

That is, compared with the case where the fuel is injected from a single nozzle, the local fuel concentration in the radiant tube can be adjusted, so that the fuel concentration in the longitudinal direction in the radiant tube can be made uniform, thereby increasing the complete mixing performance.

Therefore, the temperature distribution in the radiation tube is uniform and the combustion zone is extended, which is advantageous in reducing nitrogen oxides.

That is, by the split injection of fuel by the configuration of the low nitrogen oxide regenerative radiation tube burner having the fuel split injection type fuel nozzle of the present invention, the mixing delay with the air and the flame length are extended, and the heat generation rate per unit volume of the radiation tube is increased. Is lowered.

Therefore, the combustion temperature can be lowered, and the concentration of the fuel inside the radiant tube can be adjusted more uniformly than the conventional burner, thereby preventing the generation of local peak temperature.

In addition, since the nitrogen oxide produced in the primary combustion zone reacts with the secondary fuel and can be reduced to nitrogen, it is possible to reduce the amount of nitrogen oxide generated as a whole.

In addition, since the fuel is eccentrically injected in the configuration of FIGS. 3B and 3C, further reduction of nitrogen oxides by the function of light-burning is possible.

On the other hand, as the fuel is split into primary and secondary fuels, the flame is also split, thereby increasing the surface area of the flame, thereby facilitating heat transfer to the radiation tube, thereby further reducing nitrogen oxides by increasing the heat release rate.

Further, the low nitrogen oxide regenerative radiation tube burner having the fuel split injection type fuel nozzle of the present invention corresponds to an improvement of Korean Patent Application No. 2001-51771 to which the inventors of the present invention apply. In addition to the combustion method, it is possible to greatly reduce the amount of nitrogen oxide generated in the radiation tube even during the heat storage combustion by increasing the complete mixing performance and excluding the local high temperature portion.

Hereinafter, the effect of the low nitrogen oxide heat storage type radiation tube burner having the fuel split injection type fuel nozzle according to the present invention will be described.

(Example 1)

The conventional eccentric injection type low nitrogen oxide burner shown in FIG. 2 is a natural fuel (LNG) which is a clean fuel under the operating conditions of a conventional indirect furnace having a combustion capacity of 100,000 kcal / hr, a furnace temperature of 950 ° C, and a combustion air temperature of about 900 ° C. In the combustion of, nitrogen oxide of 180-270ppm was generated, and the oxygen concentration in the combustion gas was 5.7-8.7% of excess air.

However, the low nitrogen oxide regenerative radiation tube burner having the fuel split injection type fuel nozzle of the present invention shown in FIG. 3A is a U-type radiant tube combustion experiment using coke furnace gas, which is known to generate more nitrogen oxide than natural gas. The results of the combustion experiment in the furnace are shown in Table 1 below.

In general, the combustion air temperature was higher than that of the comparison burner and the oxygen concentration in the combustion gas was low, so it was found that the generation amount of nitrogen oxide was relatively decreased even in the combustion conditions in which nitrogen oxide was more likely to be generated. The results demonstrate the effect of inhibiting nitrogen oxide generation by mixing delay and flame length extension.

Noon (℃) Nitrogen oxide generation amount (ppm) Oxygen Concentration in Combustion Gas (%) Air temperature (℃) 935 136-173 4.1-4.6 1022-1111 948 138-170 3.5-4.8 1043-1102 960 161-212 2.3-3.0 1048-1122 975 142-206 2.6-3.2 1045-1119

Table 1 shows the amount of nitrogen oxide generated by the combustion conditions of the burner according to the present invention.

For reference, in regenerative combustion, as shown in [Table 1], as the combustion temperature changes, the air temperature and the oxygen concentration in the combustion gas change within a certain range, so that the amount of nitrogen oxides also changes within the same switching cycle. The maximum concentration of nitrogen oxides corresponds to the maximum of air temperature.

As described above, the low nitrogen oxide regenerative radiation tube burner having the fuel split injection type fuel nozzle of the present invention achieves a delay effect of mixing air and fuel, and improves combustion stability by fuel injected from a position relatively close to air. While securing the flame splitting and multi-stage combustion effects, it is possible to reduce the amount of nitrogen oxides even in the regenerative radiant burner using high temperature air because it is equipped with the effect of light-burning and nitrogen oxide reduction.

Claims (2)

The fuel nozzles 20 and 20 'for supplying fuel through the heat accumulators 22 and 22' and the air nozzles 21 and 21 'for supplying air while supporting the fuel nozzles 20 and 20' communicate with each other. The regenerative radiation pipe is installed in the radiating pipe 1 in which the combustion heat is radiated to the outside in the process of mixing and combusting the nozzle plates 25 and 25 'and the fuel through the fuel nozzle and the air through the air nozzle. In the burner, primary fuel nozzles 40 and 40 'are installed at the centers of the nozzle plates 25 and 25', respectively, and inscribed on the inner wall surface of the radiation pipe 1, and then the nozzle plate 25 and Secondary fuel nozzles 41 and 41 'are installed so as to extend through the outer circumference of 25' to the axial position than the primary fuel nozzle, and the secondary fuel nozzles 41 and 41 'are longitudinally respectively provided. The fuel split injection type fuel nozzle is characterized in that a plurality of fuel injection holes (42, 42 ') are provided. Low NOx regenerative burner tube copy. 2. The low nitrogen oxide regenerative radiation burner having a fuel split injection type fuel nozzle according to claim 1, wherein the secondary fuel nozzles (41, 41 ') are configured in one or more numbers.