JPS583A - Two-stage combustion device - Google Patents

Abstract

PURPOSE:To suppress the generation of NOx without the increase of unburnt fuel by providing the furnace with secondary air injection holes of different size in diameter. CONSTITUTION:The boiler furnace 1 is provided with injection holes for the secondary air for the two-stage burning which are made above the burners 2. The injection holes 3, for example, are made smaller in diameter than the injection holes 4. With secondary air being injected into the boiler furnace 1 through the injection holes 3 and 4, the secondary air 5 through the injection holes 3 is made to flow along the walls on the side of the injection holes 3, while the secondary air 6 through the injection holes 4 is made to flow along the opposing furnace walls. This causes combustion gas and secondary air to be mixed effectively as the whole to enable perfect secondary combustion, with the result that the amount of fuel remaining unburnt fuel is reduced and that uniform distribution of oxygen and unburnt fuel is maintained at the furnace outlet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention reduces NOx while suppressing unburned components in boiler waste gas.
The present invention relates to a two-stage combustion device that can effectively reduce

In thermal power generation boilers and industrial boilers, when two-stage combustion is performed using secondary air injection holes for the purpose of reducing NOx, depending on the degree of penetration of the secondary air supplied from the secondary air injection holes into the furnace. This may have the disadvantage of increasing unburned content, and the effects of two-stage combustion may not be fully demonstrated.

In conventional two-stage combustion using secondary air injection holes,
Since all the secondary air injection holes (a) shown in Figures 1 and 3 had the same dimensions, when the secondary air velocity is small,
Secondary air cannot penetrate the boiler furnace (b) in the width direction, and as shown in Figure 1, the secondary air (C) flows along the furnace wall on the side of the secondary air injection hole (a), Conversely, when the secondary air velocity is high, the degree of penetration is large, and the secondary air (C) flows along the opposing wall of the secondary air injection hole (a), as shown in FIG. This can be explained using the results of a combustion experiment using a model that is geometrically similar to an actual boiler.

That is, in the case of the flow of secondary air (C) in Fig. 1, the oxygen distribution at the furnace outlet XX position is -21 Koshi Salvation - In the case of total combustion air flow rate gm/sec, as shown in Fig. 2 (A), there is more air on the side near the secondary air injection hole -) side furnace wall and less on the side near the opposite furnace wall, as shown in Fig. 2 (A). As shown in (B), the distribution of carbon monoxide is small on the secondary air injection hole (α) side, and large on the opposite furnace wall side, and the distribution of carbon monoxide is
The distribution of oxygen and carbon oxide at the furnace outlet X-X position in the case of a flow of
The result is as shown in Figure 1, which is the opposite of the case in Figure 1. In any case, the secondary air is not evenly distributed in the furnace, resulting in poor mixing with the combustion gas (effective two-stage combustion cannot be obtained, and this leads to an increase in unburned matter. In the figure and FIG. 3, (d) is a combustion burner.

The present invention has been made for the purpose of eliminating the above-mentioned disadvantages of the conventional means, and is characterized in that a boiler furnace is provided with an appropriate number of secondary air injection holes having different penetration degrees. It is something.

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 5 shows an embodiment of the present invention, and (1) in the figure shows a boiler furnace,
(2) is the burner, (31 (4) is the secondary air injection hole for two-stage combustion provided in a staggered manner above the burner (2), and the secondary air injection hole (3) is the secondary air injection hole. Next air injection hole (
4) Smaller diameter.

In general, the degree of penetration of air from the secondary air injection holes is determined by the rising speed of the uniform flow of combustion gas being vl, the secondary air velocity being vl, and the diameter of the secondary air injection holes being S, as shown in Figure 6. If the penetration distance of the secondary air is y and the height above the center of the secondary air injection hole at the penetration distance y is X, there is an approximate relationship, and the penetration distance y is 0 of the secondary air velocity υ.
．． It is proportional to the product of the 8th power and the diameter S of the secondary air injection hole to the 0.6th power.

Therefore, when secondary air is injected into the boiler furnace (1) from the secondary air injection hole (31 (4)), as shown in Fig. 7, the secondary air (5) from the secondary air injection hole (3) is injected into the boiler furnace (1). flows along the furnace wall on the side of the secondary air injection hole (3), and the secondary air injection hole (
Since the secondary air (6) from 4) flows along the opposing furnace wall, the secondary air and combustion gas are mixed reliably as a whole, and complete secondary combustion is possible, so unburned matter is removed. In addition, the oxygen distribution at the furnace outlet and the unburned content distribution become uniform.

FIG. 8 shows another embodiment of the present invention, in which the secondary air injection holes (
3) This is an example in which (4) are arranged alternately on a - straight line, and as shown in Figure 9, the secondary air (5) (6) rises in the boiler furnace (11) as shown in the figure. As in the case shown in the figure, complete secondary combustion is obtained and unburned matter is reduced.In the figure, the same reference numerals as those shown in FIGS. 6 and 7 indicate the same thing.

FIG. 10 shows still another embodiment of the present invention, in which a speed regulator (8) is provided at the inlet of the secondary air injection hole (7), and the speed regulator (8) adjusts the secondary air velocity. It is something like this. With such a configuration, not only can a degree of penetration commensurate with the size of the furnace be obtained, but also changes in bias ratio can be coped with.

It should be noted that the present invention is not limited to the above-described embodiments, and that speed adjustment mechanisms may be provided for secondary air injection holes of different sizes arranged in a staggered or linear manner. It goes without saying that various arrangements and combinations are possible, and that various other changes can be made without departing from the gist of the invention.

According to the two-stage combustion device of the present invention, various excellent effects as described below can be achieved.

fI) Two-stage combustion can be effectively performed in existing or new boilers, and NOx can be reduced without increasing unburned content.

(II) Since two-stage combustion can be performed effectively, the bias rate can be increased and NOx can be further reduced.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the conventional example where the degree of penetration of secondary air is small, Figure 2 (A) is an explanatory diagram of the oxygen distribution state at the furnace outlet of the boiler shown in Figure 1, and Figure 2 (Ro ) is an explanatory diagram of the distribution state of the same carbon oxide, Figure 3 is an explanatory diagram of the conventional example where the degree of penetration of secondary air is large, and Figure 4 (a) is an illustration of the oxygen at the furnace outlet of the boiler shown in Figure 3. 4(b) is an explanatory diagram of the distribution state of the same carbon oxide, FIG. 5 is an explanatory diagram of an embodiment of the present invention, and FIG. 6 is an explanatory diagram of the distribution state of the same carbon oxide. Fig. 7 is an explanatory diagram of the degree of penetration of secondary air at the injection hole portion, Fig. 7 is an explanatory diagram of the flow of secondary air in the boiler furnace shown in Fig. 5, and Fig. 7 is an explanatory diagram of the flow of secondary air in the boiler furnace shown in Fig. 5. Explanatory diagram,
FIG. 9 is an explanatory diagram of the flow of secondary air in the boiler furnace shown in FIG. 8, and FIG. 10 is an explanatory diagram of still another embodiment of the present invention. In the figure, (1) is the boiler furnace, (2) is the combustion burner, and (3) is the combustion burner.
) (4) and (7) are secondary air injection holes, (5) and (6) are secondary air, and (8) is a speed regulator. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] 1) A two-stage combustion device characterized in that a boiler furnace is provided with secondary air injection holes having different penetration degrees in appropriate combinations.