JPS599413A - Combustion device - Google Patents

Abstract

PURPOSE:To reduce the concentration of NOx without increasing the amount of soot contained in exhaust gas, by forming subsidiary fuel injection ports directed toward the region between burner rows where the density of nitrogen oxides is hight in a combustion device having a plurality of burners including main fuel injection ports disposed in a plurality of stages and rows. CONSTITUTION:Although subsidiary injection ports 8 can be formed at either of an upper or lower portion between burner rows 2, 3 and 4, it is preferable to dispose them at a lower position. A mixture consisting of fuel and a small amount of air is ejected from the subsidiary injection ports 8 and produces flames 15, 16 involving reducing radicals while lowering the temperature near the ports 8. At the same time, NOx contained in the combustion gas flowing upward between the burner rows is reduced by the flames 15, 16 through contact therewith, so that the density of NOx is lowered. Although the amount of unburnt substances including reducing radicals is increased, they are burnt further by air supplied from air ports formed on the front side 5 and the rear side 6, so that the amount of soot is not increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device, and in particular to a combustion device that eliminates nitrogen oxides (
The present invention relates to a suitable boiler combustion device for reducing NOx (hereinafter referred to as NOx).

Since NOx is considered to be one of the causative substances of photochemical oxidants, there has been a demand in recent years for the development of a combustion method that effectively suppresses the generation of NOx. Combustion methods that meet these objectives include (1) exhaust gas recirculation method, (2) water injection method,
(3) Two-stage combustion method and (4) Denitrification combustion method are known, and among these, the denitrification combustion method, which is excellent in NO reduction effect, operability, etc., has been attracting particular attention in recent years.

As shown in FIGS. 1 and 2, the device applied to the conventional denitrification combustion method includes a lower burner 2 and a middle burner 3, which are provided in order from the bottom to the top on the front side wall of the combustion furnace 1.
It is mainly composed of an upper burner 4, a front air port 5 provided above the upper burner 4, and a rear air port 6 provided on the rear wall of the combustion furnace l.

The burners 2.3 and 4 are sequentially arranged in the vertical direction to form a row, and are designated by the reference numeral 9 in Fig. 4 of the edge chart.
It has a structure with a main fuel injection port in the center as shown in .

In the above configuration, the air ratio (actually supplied air amount/theoretically required air amount) set for each burner is usually 0.8 to 1.0 for the lower burner 2 and 0 for the middle burner 3. .6 to 0.8, and 0.4 to 0.6 in the upper stage burner 4. Combustion is performed under these conditions, and the combustion heat is used as a heat source for evaporating boiler feed water, while high-temperature exhaust gas 7 is discharged to the outside of the system through the upper flue of the combustion furnace 1. In this case, the NO emissions generated in the combustion areas of the lower burner 2 and middle burner 3, where there is a relatively large amount of air, come into contact with the reduced radicals generated in the combustion area of the upper burner 4, where there is an excess of fuel. will be returned to.

However, in the above combustion method, NOx is sufficiently reduced in the flame section 16 near the rear wall (hereinafter referred to as the rear flame section), but the flame section near the front wall (hereinafter referred to as the front flame section) 16 is sufficiently reduced. It was found that 15 was insufficient, and that this resulted in an increase in the overall exhaust gas concentration.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a combustion device that can reduce Not without increasing soot and dust in exhaust gas.

As a result of various studies by the present inventors regarding the reason why NO reduction is insufficient in the front flame section 15 (the NO3 concentration in the front flame section reaches 2 to 3 times that in the rear flame section), The reason for the reduction state described above is that in the rear flame section, which is far away from each burner, the flame speed is low, so the combustion region with a large amount of air and the combustion region with an excess of fuel are well mixed. In the front flame section, which is close to each burner, the flame speed is high, so the above mixing is insufficient.
We also discovered that because the burners are arranged in rows in the vertical direction, it is difficult to receive the agitation of the NO-treated metal-containing gas that rises between the nuclear rows, and therefore, the mixture with the reducing radicals is not sufficiently achieved. Ta.

The present invention has been made based on the above findings, and is aimed at a high concentration area of nitrogen oxides between the burner rows in a combustion apparatus equipped with a plurality of burners including main fuel injection ports in multiple stages and in multiple rows. It is characterized by having a sub-spout for fuel.

In the present invention, the sub-ejection port for fuels (hereinafter simply referred to as sub-ejection port) is used as long as the fuel ejected from this or its reducing combustion flame can mix with the NO and gas containing gas rising between the burner rows. , can be provided at any position toward the high concentration area of nitrogen oxides between the burner rows. The burner used in the present invention is preferably a multi-burner capable of denitrification combustion.

As another method of installing the sub-nozzle, the sub-nozzle may be provided on the outer periphery of the burner, but in this case, the tip of the nozzle should be arranged to face the center between the burner rows, and the nozzle will be It is necessary to allow the fuels to be mixed with the gases flowing up between the burner rows and to prevent them from being mixed with the combustion air of the burners, resulting in excessive air combustion.

The auxiliary ejection port may be provided at any position between the burner rows, above or below, but it is desirable to provide it as low as possible. Moreover, there is no particular restriction on the installation thereof as long as the effects of the present invention are achieved, and they may be provided in each burner stage as a whole (or they may be provided in a thinned-out state as appropriate).

The fuel spouted from the sub-nozzle may be only fuel, but
In order to cool the auxiliary ejection port and prevent the generation of thermal NO, and to improve the generation of reducing radicals, it is preferable to mix a small amount of air, combustion exhaust gas, or a mixture of air and combustion exhaust gas. Note that when a sub-nozzle is provided on the outer periphery of the burner, the sub-nozzle is cooled by the combustion air ejected from inside the burner's outer periphery, so there is often no need to mix air, etc. with the fuel. .

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 3 shows an apparatus according to an embodiment of the present invention, which is an enlarged view of a portion corresponding to the burner section (2) of the apparatus shown in FIG. and 5 and the parts to which their descriptions are similarly referred, and a sub-spout port 8 provided between the burner rows.

In the above configuration, a mixture consisting of fuel and a small amount of air is ejected from the sub-ejection port 8, lowers the temperature at the ejected point and generates a flame containing reducing radicals, and the flame moves upward between the burner rows. NO in combustion gas,
is contacted and reduced, thereby achieving low NOx. Although unburned substances including the above-mentioned reducing radicals increase, they are additionally combusted by the air supplied from the front and rear air ports of the wake, so soot and dust do not increase.

Next, FIGS. 4 and 5 show a burner shape suitably used in the present invention, in which the outer periphery of the burner is inclined so that the ejection tip faces the center between the burner rows. A configuration having a sub-jet port 81 is shown. Generally, the direction of the ejected fuel is preferably horizontal or slightly diagonally downward, but the effect can also be seen in an upward direction. In addition, in the figure, 9
10 is a flame holding plate; 11 is a primary air port; 12 is a secondary air port; 13 is a main fuel jet port provided in the center of the burner;
17 indicates the tertiary air port, and 17 indicates the ejected fuel.

By adopting the burner configuration as described above, it is possible to satisfactorily reduce No. 1 in the combustion gas rising between the burner rows in the same manner as in the embodiment described above. Further, in this embodiment, since the sub-ejection port 81 is naturally cooled by the combustion air flowing through the tertiary air port 13, there is normally no need to mix cooling air or the like into the fuel.

Although the above explanation mainly concerns the front (side) combustion method, the present invention is not limited to this.
For example, the present invention can be similarly applied to a case where the boiler combustion apparatus is large-sized and uses a facing combustion system in which it is desirable to provide a burner on the rear side as well. Further, regarding the fuel used, in addition to liquid fuels such as oil and gas, solid fuels such as pulverized coal fuel are also applicable.

As described above, according to the present invention, with a simple configuration in which the sub-injection port for fuel is provided toward the position of high NOx concentration between the burner rows, the high-temperature combustion exhaust gas portion rising between the burner rows is cooled, and The newly generated radicals make it possible to reduce NOx in the gas, thereby achieving the excellent effect of further reducing NOo in the combustion exhaust gas without increasing soot and dust.

[Brief explanation of the drawing]

Figure 1 is a side sectional view showing a conventional boiler combustion device, wI
Fig. J2 is an inlet view of Fig. 1, Fig. 3 is an enlarged front view of a portion of the apparatus according to the embodiment of the present invention corresponding to the burner section ■ in Fig. 2, and Fig. 4 is an enlarged front view of the device according to the embodiment of the present invention. FIG. 5, which is an enlarged front view of the burner portion of the apparatus according to the other side of the invention, is a sectional view taken along the line v-v in FIG. 4 in the direction of arrows. 2...lower burner, 3...middle burner, 4...upper burner, 5...front air port, 6...rear air port,
8, 81...Fuel sub-spout, 9...Main fuel spout, 13...Tertiary air port, 15...Front side flame part, 17
...Gushing fuel. Agent Patent Attorney Takeshi Kawakita

Claims (1)

[Claims] (1) In a combustion device equipped with a plurality of burners including main fuel jets in multiple stages and in multiple rows, a sub-spout for fuels is provided toward the high concentration area of nitrogen oxides between the burner rows. A combustion device featuring: (2. Claim 1 is characterized in that the auxiliary ejection port for the fuel is provided on the outer periphery of the burner, and its ejection tip is directed toward the center between the burner rows. boiler combustion equipment.