KR100253991B1 - Method for low nox in combustion chamber of boiler - Google Patents

Abstract

PURPOSE: An attenuating method for the nitric oxide of a boiler furnace is provided to increase or reduce fuel injecting amount by replacing the fuel nozzle of an upper burner unit. CONSTITUTION: To attenuate nitric oxide from a boiler furnace(1) consisting of air injecting holes(5) and plural nitric oxide attenuating burners, fuel injecting amount is increased in an upper burner(2) or reduced in an upper burner unit(3) to be less than amount in a lower burner unit(4). Then, the air-fuel ratio of the upper burner unit is adjusted in 0.6 to 0.8. Therefore, the generation of nitric oxide and carbon monoxide are reduced in the boiler furnace in more than 20%.

Description

How to reduce nitrogen oxides in boiler furnaces

The present invention relates to a method for reducing nitrogen oxides in a boiler furnace, and in particular, by reducing the upper part of a nitrogen oxide reducing burner disposed in a plurality of stages without changing the overall shape of an existing boiler, reducing nitrogen oxides in the combustion process, It relates to a method for increasing the reduction rate of nitrogen oxides by generating a large amount of hydrocarbon components in the nitrogen oxide reduction zone as compared to the furnace.

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.

Therefore, as the operating requirements of industrial boilers, the reduction of nitrogen oxides, as well as the complete combustion of fuels, and the increase in the amount of unburned fuels, have emerged as important items for determining performance.

Nitrogen oxide reduction techniques in boilers currently in use include the adoption of nitrogen oxide reduction burners, two-stage combustion techniques in furnaces and combustion gas recirculation.

In the exhaust gas recirculation method, a part of the burned exhaust gas is mixed with combustion air and introduced into a burner to remove the trace amount of unburned dust or nitrogen oxide remaining in the exhaust gas once more by combustion.

The nitrogen oxide reduction burner is a device that divides and supplies combustion air so that the temperature of the flame is lowered, thereby suppressing generation of thermal nitrogen oxides generated by reaction with excess oxygen in a high temperature combustion atmosphere.

The split supply of the combustion air is carried out by an aerodynamic method. In the front of the burner, the primary combustion air is supplied to form a relatively low temperature combustion atmosphere to suppress the generation of nitrogen oxides, thereby maintaining the fuel surplus and the lack of air. At this time, a large amount of secondary combustion air is supplied separately to completely burn the incomplete combustion products generated.

In the two-stage combustion method in the furnace, as shown in FIG. 3, the main content of the combustion air is divided into and supplied to the nitrogen oxide reduction burner and the air injection port. The main combustion zone is formed to maintain the lack of air to suppress the generation of nitrogen oxides. The trace nitrogen oxide formed in the main combustion zone is reduced in the nitrogen oxide reduction zone formed in the burner section and the air injection port of the furnace. This is how you do it.

In addition, the unburned powder that has passed the nitrogen oxide reduction zone is completely burned because sufficient air is injected from the air injection port to the furnace outlet, which is called unburned perfect combustion zone.

The nitrogen oxide-reduced burners that make up the furnace burner part used in the two-stage combustion method in the furnace are all burners having the same injection air quantity and injection fuel amount as the performance of the theoretical air fuel ratio (= (the amount of fuel capable of theoretical complete combustion / The amount of air) / (the amount of fuel / air of actual combustion) is about 0.85 to 0.9, which is almost constant.

However, as the numerical value of the theoretical air fuel ratio as described above, since the generation of hydrocarbons for reducing nitrogen oxides in the nitrogen oxide reduction region is extremely small, there is a problem that the reduction of nitrogen oxides is hardly achieved in such a small amount. It is discharged out of the unburned complete combustion zone with little removal.

An object of the present invention devised to solve the above problems is to change the theoretical air fuel ratio of the upper burner to about 0.6 to 0.8 to create an environment of the nitrogen oxide reduction zone that generates a large amount of hydrocarbons that effectively reduce nitrogen oxides. will be.

Such an object can be achieved by the present invention configured to replace the fuel nozzle of the upper burner part with a larger capacity than the existing one so as to increase the fuel injection amount or reduce the combustion air injection amount supplied to the upper burner part. It will be described in detail with reference to the accompanying drawings.

1 is a schematic front and side cross-sectional view of a boiler furnace to which the present invention is applied.

2 is a schematic front and side cross-sectional view of a conventional boiler furnace.

3 is a schematic diagram illustrating a two-stage combustion technique applied to the furnace of the present invention.

4 is a view comparing the present invention and the conventional nitrogen oxide and carbon monoxide emissions

* Explanation of symbols for main parts of the drawings

1: brazier 2: upper burner

3: upper burner part 4: lower burner part

5: air jet

A: Main burner combustion zone B: Nitrogen oxide reduction zone

Unburned Complete Combustion Zone

1 shows a schematic front and side cross-sectional views of a boiler furnace to which the present invention is applied.

Method for reducing the nitrogen oxides generated in the boiler furnace according to the present invention is to increase the fuel injection amount of the fuel nozzle of the upper burner (2) or the upper burner portion in the boiler furnace consisting of air injection port and a plurality of stages of nitrogen oxide reduction burner The amount of air supplied to (3) is less than the amount of air of the lower burner part 4, and the theoretical air fuel ratio of the upper burner part 3 is adjusted to 0.6-0.8.

Hereinafter, the operation of the present invention will be described in detail.

3 is a schematic diagram illustrating a two-stage combustion technique applied to the furnace of the present invention.

Compared to a conventional boiler furnace employing a plurality of nitrogen oxide-reduced burners and a two-stage combustion method in a furnace, the present invention changes the structure of the upper burner portion 3 as shown in FIG. It is possible.

Existing furnaces adopting the two-stage combustion method in the furnace shown in FIG. 2 have the same size and capacity of all burners (upper burner, lower burner), and the theoretical air fuel ratio (= amount of theoretical full combustion fuel / air volume / actuality). Fuel amount / air amount of combustion) is about 0.85-0.9 and has the same value.

However, in the present invention, when the multi-stage burner is installed, the theoretical air fuel ratio is changed to be operable by about 0.6-0.8 by changing the structure of the upper burner part 3.

In the structure of the upper burner part 3, the burner having the same size as the lower burner part 4 increases the amount of fuel by changing the fuel nozzle (not shown) or uses the fuel nozzle (not shown) as it is. And to reduce the amount of air supplied to the upper burner (2) to reduce the amount of combustion air.

As described above, when the theoretical air fuel ratio of the upper burner part 3 is operated at about 0.6-0.8, a large amount of hydrocarbons are generated in the reduction zone (b), thereby easily reducing nitrogen oxides generated in the main burner combustion zone (a).

In addition, the air injection port 5 is sprayed with sufficient air to remove unburned powder such as carbon monoxide. Therefore, as shown in FIG. 3, in the nitrogen oxide reduction zone (b) between the upper burner section 3 and the air injection port 5, the theoretical air ratio is adjusted to the optimum conditions for the reduction of nitrogen oxides, thereby achieving breakthrough nitrogen oxide reduction in the furnace. can do.

The unburned powder passing through the nitrogen oxide reduction zone (b) is injected with sufficient air from the air injection port (5) to the furnace outlet, so that complete combustion is performed in the unburned complete combustion zone (C).

The present invention provides a nitrogen oxide reduction burner that forms a burner in the furnace such that the theoretical air fuel ratio is about 0.6 to 0.8 to create an environment of a nitrogen oxide reduction zone that generates a large amount of hydrocarbons for effectively reducing nitrogen oxides. By changing some of the structure, it has an excellent effect of drastically reducing the generation of nitrogen oxides.

Figure 4 shows the present invention and the conventional nitrogen oxide and carbon monoxide emissions comparison, the results of applying the present invention was found to reduce the generation of nitrogen oxides and carbon monoxide by more than 20% without a special increase in dust.

Claims (1)

In the boiler furnace consisting of an air injection port and a multi-stage nitrogen oxide-reduced burner unit, the amount of fuel injected into the fuel nozzle of the upper burner 2 is increased or the amount of air supplied to the upper burner unit 3 is changed to the amount of air in the lower burner unit 4. A method of reducing nitrogen oxides in a boiler furnace characterized by supplying less and adjusting the theoretical air fuel ratio of the upper burner section to 0.6 to 0.8.

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