JPS582321B2 - NOX Teigen Sekitan Burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a NOx-reducing coal burner that reduces the amount of nitrogen oxides generated while ensuring flame stability.

BACKGROUND ART In combustion devices such as boilers that combust solids by pulverizing them, the content of nitrogen oxides contained in the exhaust gas is large, so it is desired to reduce the nitrogen oxides as much as possible.

In conventional coal burners, pulverized coal is ejected in a conical shape from an impeller and burned as a single conical flame, resulting in a high peak temperature at the center of the flame, which in turn increases NOx in the exhaust gas.

That is, in conventional coal burners, attention has been paid to increasing the combustion efficiency of pulverized coal, and the pulverized coal injection holes of the impeller are usually arranged evenly in a honeycomb shape.

On the other hand, in order to reduce NOx, (1) two-stage combustion method,
(2) recirculation gas injection method, (3) method combining two-stage combustion method and recirculation gas injection method, etc. have been proposed.
All of these methods have the disadvantage that the equipment becomes complex and bulky.

An object of the present invention is to provide a coal burner that reduces NOx while stabilizing the flame by simple and effective means.

That is, the present invention achieves the purpose of reducing NOx through an extremely simple and rational impeller structure in which at least one pair of pulverized coal injection holes symmetrically offset is arranged in a burner impeller.

To explain in more detail with reference to the attached drawings, FIG. 1 shows a cross-sectional view of an ordinary pulverized coal burner, in which pulverized coal is passed from a pulverized coal pipe 1 to a pulverized coal elbow 2, and then from a pulverized coal nozzle 3 to the nozzle tip. while the combustion air is supplied from the wind box 7 to the burner throat 5 while passing through the air register 6 and being swirled.
It is mixed with the pulverized coal conveyed to the impeller 4 and burned in the furnace 8.

Such a pulverized coal burner usually uses an impeller 4 as shown in FIG.

That is, in the conventional coal impeller, the pulverized coal injection hole 1
0 are evenly arranged in a honeycomb shape on the impeller to uniformly mix the ejected pulverized coal and the combustion air in the circumferential direction.

Therefore, during combustion, a rapid combustion reaction occurs, and the flame peak temperature rises, especially in the center of the flame, resulting in an increase in the amount of NOx generated.

FIG. 2a shows a perspective cross-sectional view of the conventional impeller of FIG. 2 in a different direction.

In other words, in conventional coal burners, the impeller disperses (diffuses) pulverized coal in a conical shape (usually at 75 degrees) and uniformly mixes it with combustion air to generate a single conical flame. The central peak temperature was the cause of the increase in NOx.

The present invention was made based on the fact that it was confirmed that NOx can be reduced by dividing the flame to increase the cooling area to lower the peak temperature, and by slowing combustion by varying the concentration of the ejected fuel.

That is, since a splash plate 11 that changes the flow direction of the pulverized coal flow and the air flow, so-called mixed flow, is arranged at the elbow part of the pulverized coal feed pipe, the mixed flow that collides with this splash plate is caused by its inertia. The outer part of the pulverized coal feed pipe shows a thick flow of pulverized coal, and the straight part also shows a thick flow in the outer part.

Furthermore, to explain using the embodiment shown in FIG. Since the pulverized coal is pressed against the inner surface of the outer passage 12 in the upper half, the concentration of the pulverized coal flow in the outer passage 12 and the inner passage 13 is higher in the outer passage 12, and the particle size of the pulverized coal in the outer passage tends to become narrower, resulting in uneven flow. distribution is obtained.

Therefore, it has been found that the objective of reducing NOx can be achieved.

Further, the impeller of the present invention has the following features.

FIG. 3 shows the left half of an impeller according to the invention, with the pulverized coal orifices 10 arranged offset to the horizontal centerline A-A' of the figure.

In other words, the jet holes 10 are provided at symmetrical positions of the circular impeller.

Since the ejection holes 10 are provided offset in this way, an imbalance occurs in the concentration of the pulverized coal ejected from the ejection holes.

In addition, since pulverized coal fuel is not supplied to the impeller wall location 9, only combustion air is supplied, and the flame is split.
The flame cooling area increases, the flame reacts slowly, and the flame peak temperature is greatly reduced.

On the other hand, the pulverized coal ejected from a location closer to the horizontal center line AA' is sufficiently mixed with the combustion air, so that the flame can be stabilized.

As described above, the present invention has the great advantage of obtaining a sufficient NOx reduction effect under a stable flame by the extremely simple and rational means of providing at least one pair of offset pulverized coal injection holes in the impeller.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional pulverized coal burner, FIG. 2 is a front view of a conventional impeller, FIG. 2a is a perspective sectional view in a different direction from FIG. 2, and FIG. 3 is a side plan view of an impeller according to the present invention. Show the diagram. Reference numbers in the figure indicate the following: 1... Pulverized coal pipe, 2... Pulverized coal elbow, 3... Pulverized coal burner nostle, 4...
・Burner impeller, 5... Burner throat, 6... Air register, 7... Wind box, 8... Furnace, 9... Impeller wall, 10...pulverized coal injection hole.

Claims (1)

[Claims] 1. A pulverized coal feeding pipe is provided, which is composed of a pulverized coal elbow and a pulverized coal burner nozzle, to uneven the concentration distribution of pulverized coal supplied to the tip of the burner, and a burner impeller is provided at the tip of this pulverized coal feeding pipe, A NOx-reducing coal burner characterized in that a burner impeller has circular arc-shaped pulverized coal injection holes arranged offset so as to divide a combustion flame.