KR20010037288A - Pulverized coal burner for reducing NOx - Google Patents

Abstract

PURPOSE: A pulverized coal burner restrains the generation of nitrogen oxide and enables coal to stably burn even under low load. CONSTITUTION: A pulverized coal nozzle(60) with a pulverized coal nozzle diffuser(62) formed to have a certain inclination is installed on the front end of a firebox side. A moving nozzle(70) is placed inside the pulverized coal nozzle(60) and has a moving nozzle diffusing part(74) with the same inclination as the pulverized coal nozzle diffuser(62). Under the low load, a moving nozzle transporting bar(72) is pulled toward the outside of a burner to move the moving nozzle(70) near the pulverized coal nozzle diffuser(62) to make the pulverized coal flow concentrated by the pulverized coal nozzle diffuser(62) is focused on the central part of the pulverized coal nozzle(60) by the moving nozzle(70) to maintain appropriate ratio between primary air and pulverized coal for stable combustion.

Description

Pulverized coal burner for reducing NOx}

The present invention relates to a pulverized coal burner, and more particularly, to a pulverized coal burner capable of reducing nitrogen oxides generated during combustion of fossil fuels during combustion.

The pulverized coal burner grinds coal, which is a kind of fossil fuel, into a pulverized coal of about 50 mesh, and then sends it to the brazier by the preheater with the primary air preheated and then with the secondary air. It is a device that burns in a floating state by spraying it from.

In industrial boilers using fossil fuels, nitrogen oxides formed during the combustion process are the main cause of photochemical smog, and their emissions are strictly regulated, so the reduction of nitrogen oxides plays an important role in the design of burners.

The conventional method for reducing nitrogen oxides in industrial burners is to reduce the 'thermal NOx' produced by the reaction of nitrogen in the combustion air with excess oxygen in a high temperature combustion atmosphere. In order to suppress the excess oxygen, the reaction of nitrogen is suppressed while maintaining the fuel over-air deficiency state, and the incomplete combustion product generated by the lack of air is completely burned by injecting sufficient combustion air from the downstream side of the furnace where the firebox temperature is relatively low. The method of making is mainly used.

The combustion chamber is formed at a relatively low temperature in front of the burner to supply primary combustion air to suppress the production of nitrogen oxides, thereby maintaining fuel over-air deficiency, and in order to completely burn the incomplete combustion products generated therein, secondary combustion air. To supply.

As described above, a method that is currently put into practical use as a method for forming a fuel over-air insufficiency state in front of the burner includes an exhaust gas recirculation method (a part of the burned exhaust gas is mixed with combustion air and introduced into the burner to burn. Method) and nitrogen oxide reduction by adding equipment such as two-stage combustion in the furnace (directly sending a part of the combustion air to the hole installed on the burner to completely burn the combustion gas incompletely burned in the burner area). Although the oxide reduction effect is high, there is a problem in that an economic burden and a continuous burden on equipment, maintenance, and maintenance are required because additional equipment for reducing nitrogen oxide must be installed in the existing equipment.

Therefore, in recent years, 'low nitrogen oxide burners', which reduce the production of nitrogen oxides by controlling the mixing characteristics of combustion air and fuel by using an aerodynamic method of splitting and supplying combustion air from a burner without additional equipment, are preferred. do.

7 shows a conventional low pollution type burner.

The oil burner gun 10 including the oil burner nozzle 12 into the inside of the furnace is installed in communication with a through hole formed in a part of the burner tile 42 while being included in the oil burner outer cylinder 14. At the outside of the oil burner outer cylinder 14, a cylindrical pulverized coal nozzle 16, which can mix and supply pulverized coal which is a kind of fossil fuel and primary air, is disposed.

And the outside of the pulverized coal nozzle 16 is provided with a secondary air supply cylinder 20 and a tertiary air supply cylinder 30, each of which is equipped with a secondary air swirler 22 and a tertiary air swirler 32, respectively. . An air separation tank 50 is installed between the secondary air supply cylinder and the tertiary air supply cylinder, so that the external air introduced by the secondary air and the tertiary air swirlers 22, 32 is separated from the secondary air supply cylinder. Separate with tertiary air.

The pulverized coal burner is pulverized coal and primary air supplied through the pulverized coal nozzle 16 is ignited by the oil burner nozzle 12 installed at the tip of the oil burner gun 10 to form a flame zone. The secondary and tertiary air swirlers 22 and 32 mounted on the secondary air supply cylinder 20 and the tertiary air supply cylinder 30 flow in external air and are converted into secondary and tertiary air. Together with the effect of releasing volatiles of pulverized coal, the air keeps unburned volatiles and burned char left in a sufficient oxygen state to achieve complete combustion.

In the conventional burner as described above, the combustion of the nitrogen oxide (NOx) can be suppressed at low loads by being burned close to the complete combustion by the secondary and tertiary air supply vessels 20 and 30 at high loads. There is a problem that it is impossible to suppress the production of nitrogen oxides (NOx) due to the excessive supply.

The present invention provides a nitrogen oxide reduction burner capable of suppressing the production of nitrogen oxides (NOx) by pursuing improved combustion at a low load as well as at high loads in order to solve the above problems. Has its purpose.

In the burner of the present invention for achieving the above object, in the conventional pulverized coal burner, a nozzle venturi having a inductor surface is formed in the middle of the pulverized coal nozzle provided on the outside of the oil burner outer cylinder so that the primary air for pulverized coal transfer is pulverized coal nozzle By changing the flow rate of the pulverized coal to be concentrated or distributed by internally changing the flow path, the ignition and combustion stabilization is pursued for various loads, so that the emission of pollutants formed during the combustion process for various load changes can be suppressed. will be.

In addition, the combustion air passing through the secondary air swirler optimizes the pulverized coal and the in-house recycle and mixing, thereby promoting the formation of nitrogen gas in the coal near the burner, contributing to the formation of a reducing atmosphere in the main combustion zone, and nitrogen component oxidation reaction in the downstream side. Suppresses the production of NOx in fuels. In addition, by directing the direction of blown tertiary air to the furnace wall side, the flame zone is formed short and wide in the furnace radial direction, and creates a large recycle flow in the center.

The flame formed in the above process is concentrated in the high temperature area near the burner, but the overall radiant heat transfer is smoothly progressed by the increase of the heat transfer area with the furnace wall, and the overall flame zone temperature is kept low. It will promote the reduction reaction of the formed nitrogen oxides.

Accordingly, the pulverized coal combustion of the main flame zone slows down the volatile content, and the overall oxygen concentration of the flame zone is low, so that the amount of nitrogen oxide produced by the nitrogen content in the char does not increase significantly.

In addition, the tertiary air concentrated along the furnace wall to the downstream side of the flame zone allows the combustion of pulverized pulverized coal and the amount of dust when combusting pulverized coal. It is to reduce.

By such a pulverized coal burner, by changing the position of the concentration tank at high and low loads, and controlling the flow of air in the firebox, to prevent the accumulation of pulverized coal in the tube for various operating loads, to stabilize combustion and thus nitrogen It is to reduce the oxide.

1 is a cross-sectional view schematically showing the configuration of a pulverized coal burner according to the present invention

2 is an enlarged cross-sectional view and a line A-A 'of the main part of FIG.

3a and 3b is an operating state diagram showing the concentration of pulverized coal for each load according to the present invention

Figure 4 is a graph showing the temperature distribution characteristics in the furnace according to the present invention

5 is a graph showing the nitrogen oxide emission characteristics in the furnace according to the present invention

Figure 6 is a graph showing the discharge characteristics of the oxygen demand and dust in the furnace according to the present invention.

7 is a cross-sectional view schematically showing the configuration of a conventional pulverized coal burner

Explanation of symbols on the main parts of the drawings

10: oil nozzle 12: burner tile

20: secondary air supply container 30: tertiary air supply container

50: air separation container 60: pulverized coal nozzle 62: nozzle venturi 70: pulverized coal concentration separator

72: concentration separator moving bar 74: concentration separator support bar

76: through hole

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

Also, in the present embodiment, the same parts as those of the structure of the conventional configuration with reference to FIG. 7 use the same reference numerals to avoid duplication of description.

Figure 1 shows a schematic cross-sectional view of the nitrogen oxide reduced pulverized coal burner according to the characteristics of the present invention,

2 is an enlarged cross-sectional view and a cross-sectional view taken along line AA ′ of the main portion of FIG. 1.

The oil burner gun 10 including the oil burner nozzle 12 into the inside of the furnace is installed in communication with a through hole formed in a part of the burner tile 42 while being included in the oil burner outer cylinder 14. On the outside of the oil burner outer cylinder 14, a cylindrical pulverized coal nozzle 16, which is capable of supplying a mixture of pulverized coal and primary air, which is a kind of fossil fuel, is disposed, and a secondary air swirler outside the pulverized coal nozzle 16. In the conventional pulverized coal burner, the secondary air supply cylinder 20 and the tertiary air supply cylinder 30 equipped with the 22 and the tertiary air swirler 32 are respectively mounted.

The powdered coal nozzle 60 which has the nozzle venturi part 62 of the inclined surface in the center is formed, and the density | concentration separation cylinder 70 which is movable inside the oil burner outer cylinder 14 is comprised inside.

The pulverized coal separation tank 70 supports two cylinders by a plurality of concentration separation tank support bars 74, and is configured to be able to move on the oil burner outer cylinder 14 by the concentration separation tank moving bar 72. As such, it is possible to adjust the concentration of the pulverized coal mixed in the primary air introduced into the fire chamber by the pulverized coal concentration separation tank (70).

The pulverized coal concentration separation tank 70 realizes low oxygen in the initial combustion zone at high load, and reduces excessive primary air-coal ratio at low load, thereby pursuing NOx suppression and strengthening flame stability at low load. It is configured to do so.

Looking at the operation of the nitrogen oxide reduced burner according to the present invention configured as described above are as follows.

As the burner is operated, liquid fuel is injected from the oil nozzle 10 to ignite the flame, and at the same time, the pulverized coal and the primary air are ejected into the furnace through the pulverized coal nozzle 60.

At this time, the load is adjusted by the pulverized coal concentration separator 70. When the pulverized coal concentration separator 70 is inserted near the firebox by using the concentration separator moving bar 72 at the time of high load, the pulverized coal concentration separator is separated. The cylinder 70 is spaced apart by the nozzle venturi 62 of the pulverized coal nozzle 60 so that a large amount of pulverized coal and primary air diffuse into the firebox, and the secondary air swirlers 22 and 3 By combustion by the primary air 32, complete combustion is achieved.

In addition, when the pulverized coal concentration separator 70 is separated from the fire chamber by the concentration separator moving bar 72 at low load, the nozzle venturi 62 having the inclined surface of the pulverized coal nozzle 60 is brought close to each other. Therefore, the amount of pulverized coal mixed with the primary air flowing into the firebox is reduced, thereby preventing the formation of nitrogen oxides.

Referring to this in more detail with reference to the drawings according to the position of the load of the moving nozzle as follows.

Figure 3 shows the position and flow shape of the moving nozzle for each load,

Figure 3a shows a low load, Figure 3b shows a high load.

As shown in FIG. 3A, when the concentration separator transfer bar 72 is pulled out of the burner at the bottom of the burner, the pulverized coal concentration separator 70 is positioned near the nozzle venturi 62 of the pulverized coal burner nozzle 60. In this way, the pulverized coals concentrated through the nozzle venturi part 62 are concentrated in the center of the pulverized coal nozzle 60 by the pulverized coal concentration separator 70, so that stable combustion can be realized by maintaining an appropriate primary air / pulverized coal ratio. In addition, the formation of air-poor turbulent flames surrounded by air fruit swirls through the secondary air and tertiary air swirlers (22) and (32) promotes the evaporation and thermal decomposition of fuel due to the high temperature near the burner, thereby providing nitrogen oxides. To induce a reduction reaction with nitrogen and significantly reduce the carbon monoxide generation and opacity of the flame wake side by the inflow of the swirling combustion air.

In addition, at high load, as shown in FIG. 3B, the pulverized coal concentration separator 70 is pushed toward the fire chamber side, so that the pulverized coal concentration separator 70 has an inclined surface of the non-coal coal burner nozzle 60 ( 62, the farther away from the concentration separation container 70, the smaller the effect is, and as in the conventional pulverized coal burner, the entire caliber of the pulverized coal burner nozzle 60 is distributed and ejected into the firebox, thereby the distributed pulverized coal and primary By controlling the radial mass distribution through the secondary air swirler in the air, the flame shape can be controlled, and the nitrogen component contained in the volatile matter of the pulverized coal is converted into nitrogen molecules rather than nitrogen oxides by strengthening the reducing atmosphere.

Therefore, the amount of production can be reduced by reducing the nitrogen oxides intensively generated at the beginning of the flame zone again.

In the process of inhibiting nitrogen oxides, the inevitably increased fine dust is completely combusted by actively mixing with tertiary air after the flame zone.

In the post-combustion zone, most of the Char component that started to burn from the middle of the flame zone is continuously burned, and is mixed with sufficiently heated tertiary air as it moves to the flame zone afterwards, thereby actively burning. Unburned losses in combustion can be significantly reduced compared to conventional pulverized coal burners.

4 is a temperature distribution characteristic in a firebox by the pulverized coal burner described above.

In the conventional pulverized coal burner, the temperature distribution is formed after a gentle rise at the burner inlet and a gradual falling curve after a certain depth. In the pulverized coal burner of the present invention, the pulverized coal from the nozzle of the burner is secondary and tertiary air. The temperature rises rapidly until it is mixed with, and then drops rapidly from the part where the secondary and tertiary air are mixed.

5 is a diagram illustrating nitrogen oxide emission in the pulverized coal burner described above.

In the conventional pulverized coal burner, nitrogen oxide is discharged after a gentle rise at the burner inlet, and after a predetermined depth, while the pulverized coal burner of the present invention is rapidly discharged in the primary combustion region by the pulverized coal nozzle. However, the emission of nitrogen oxides is drastically lowered through the main combustion zone and the downstream combustion zone by the secondary air and tertiary air.

Accordingly, as shown in the figure, it can be seen that the overall amount of nitrogen oxide generation is significantly reduced than the present invention.

6 is a characteristic diagram showing the oxygen demand and the dust emission amount in the firebox;

Compared with the conventional pulverized coal burner, the amount of oxygen required is not only small, but the amount of dust emitted is also reduced.

As described above, the pulverized coal burner according to the present invention can obtain improved combustion more than a conventional burner at high load as well as at low load.

In the initial stage of combustion, a large amount of nitrogen oxides are produced, but as the low oxygen atmosphere continues, nitrogen oxides are rapidly reduced to nitrogen molecules, thereby reducing the amount of nitrogen oxides generated by about 20% or more compared with the conventional design.

It is also possible to form an appropriate coal-air ratio even at low loads, which enables stable pulverized coal combustion without additional flames by oil nozzles.

The pulverized coal burner of the present invention alone satisfies the environmental regulations without the use of a separate nitrogen oxide reduction equipment, so that the additional equipment burden can be eliminated and economical efficiency can be pursued.

Claims (3)

To separate the air by the oil nozzle supplying the liquid fuel, the secondary air supply tank and the secondary air supply cylinder equipped with the secondary air swirler and the tertiary air swirler, respectively, the secondary air supply cylinder and the tertiary air supply cylinder In the pulverized coal burner consisting of a separation container and a burner tile, A pulverized coal pulverized coal burner comprising a pulverized coal nozzle having a nozzle venturi portion having a predetermined inclination angle at the center thereof, and having a pulverized coal concentration separator disposed therein. The pulverized coal concentration separator of claim 1, wherein the pulverized coal concentration separator is fixed by a plurality of concentration separator support bars 74 between two cylinders so that pulverized coal and primary air can pass between the two cylinders. Hang Mibunta burner. The pulverized coal pulverized coal burner according to claim 1, wherein the pulverized coal concentration separator can be transferred from the outside according to the load by the concentration separator transfer support bar.