JPS604706A - Fine powdered coal burner - Google Patents

Abstract

PURPOSE:To reduce NOx in the exhaust gas by a method wherein means for varying injection direction for varying the injecting direction of air flowing in the outermost air flow passage of the air flow passages is provided in response to a fuel ratio of fine powdered coal. CONSTITUTION:A plurality of annularly arranged third air nozzles 14 which are bent in such a way as the injection ports 14a show an angle of theta of about 10 to 80 deg. in respect to the center axis of the nozzle are installed outside of the secondary air nozzle 3 and the third air flow passage acting as the outermost air passage of the fine powder coal burner is divided and formed by the plurality of third air nozzles 14. Each of these third air nozzles 14 is constructed such that it may be cooperated with the third air injection direction adjuster unit 6 of a linkage mechanism etc. and rotated by the same angle to each other. Thereby, it is possible to provide an efficient reduction of NOx contained in the exhaust gas without increasing the non-combustioned component in the ash of the fine powdered coal fuel.

Description

Detailed Description of the Invention The present invention relates to a combustion device that transports pulverized coal while floating it in a carrier medium such as air or exhaust gas, and burns the pulverized coal. This paper relates to a pulverized coal burner.

Since the oil shock at the end of 1971, energy resources for commercial boilers have been reviewed in various fields, and the development of large-capacity pulverized coal-fired boilers has become an urgent need. In this case, the issue is air pollution prevention measures, and because coal contains a large amount of nitrogen (N) in its components, the concentration of nitrogen oxides (NOx) generated by combustion is higher than other fuels. ,
This NOx suppression is necessary.

Therefore, a pulverized coal burner that has been conventionally developed for suppressing NOx will be explained with reference to FIG.

In Fig. 1, 1 is a pulverized coal nozzle for supplying pulverized coal into the furnace using primary air, which serves as suffocation for transportation. It is known to be maintained.

Furthermore, an exhaust gas nozzle 2 and a secondary air nozzle 3 are provided in this order on the outside of the pulverized coal nozzle, and a tertiary air flow path 4 is formed outside jK of the secondary air nozzle 3. Secondary air nozzle 3 and tertiary air passage 4 to secondary vanes 32 and 3
The air ejected into the furnace through the next register 42 is mainly involved in the combustion of residual coal (char) in the coal,
A pulverized coal nozzle l and a secondary air nozzle 3 are used to separate this char combustion region from the volatile matter combustion region caused by the primary air.
Exhaust gas is spouted from the exhaust gas nozzle 2 provided between the PG bay 722 and the PG bay 722 while rotating.

However, although the conventional pulverized coal burners described above are very effective in reducing NOx, combustion efficiency decreases due to slow combustion. With carbon/volatile matter), a problem arose when the amount of unburned matter in the ash increased.

Therefore, the range of thermal coal that can be applied to the burner is limited, and when high fuel ratio coal is used as fuel, it is necessary to atomize the fuel to reduce the unburned content in the ash, which is uneconomical. 8 In addition, in accordance with other conventional examples and 1-, the combustion temperature is lowered by jetting air mixed with exhaust gas into the furnace from the secondary air nozzle 3 and the tertiary air flow path 4, respectively, as shown in Fig. 1. There is also a method to reduce NOxk by lowering the oxygen partial pressure, but this method also has the same problem as the above, in that the combustion efficiency decreases and the amount of unburned matter in the ash increases. There are disadvantages such as the range of applicable fuel coals being limited and the combination using high fuel ratio coal as fuel becoming uneconomical.

The present invention eliminates such conventional drawbacks, and its purpose is to provide a pulverized coal burner that can effectively reduce NOx'i in exhaust gas without increasing the unburned content in the ash of pulverized coal fuel. Our goal is to provide the following.

The present invention achieves all of the above objects by producing pulverized coal.

In a pulverized coal burner in which one or more combustion air passages are provided on the outer periphery of a pulverized coal nozzle that spouts a mixed fluid of pulverized coal and a conveying medium into the furnace, the air passages are arranged in accordance with the fuel ratio of pulverized coal. Among them, the provision of a jetting direction variable means for changing the jetting direction of air flowing through the outermost air flow path is a special holiday.

The pulverized coal burner of the present invention will be explained below.

Fig. 2 is a sectional view showing one embodiment of the pulverized coal burner of the present invention, and Figs. 3 (a) and (1)) respectively show the pulverized coal burner shown in Fig. 2 in which the direction of the tertiary air ejection is changed. It is a front view.

Fig. 2 shows a pulverized coal nozzle 1 that supplies pulverized coal and primary air for transporting it into the furnace, an exhaust gas nozzle 2, and a secondary air nozzle 3 that supplies secondary air for combustion into the furnace. is the same as that of the conventional pulverized coal burner shown in FIG.

Further, on the outside of the secondary air nozzle 3, an ejection port portion 14a has an angle θ of about 10° to 80° with respect to the nozzle center axis.
A plurality of tertiary air nozzles 14 bent so as to
are arranged in an annular shape, and the plurality of tertiary air nozzles 14 form the outermost air flow path of the pulverized coal burner.
The second air flow path is divided into 4 parts. Each of these tertiary air nozzles 14 is linked by a tertiary air ejection direction rA adjuster 6 using a link mechanism or the like so that the tertiary air nozzles 14 ascend at the same angle.
It has been developed.

Further, the rear outer peripheral surface of each of these tertiary air nozzles 14 located inside the wind box 7 is provided with a multi-contoured hole 14b for taking in air.

Furthermore, 22 shown in FIG. 2 is a PG vane that applies swirling force to the exhaust gas flowing inside the exhaust gas nozzle 2, and 32 is a PG vane that applies swirling force to the exhaust gas flowing inside the exhaust gas nozzle 2.
This is a secondary vane that applies swirling force to the secondary air flowing inside the secondary air nozzle 3.

Then, the ejection direction ma1 circumferential adjuster 6 is constructed to form a frame for each of the three
By changing the direction of the ejection port of the secondary air nozzle 14, the ejection direction of the tertiary air can be changed. In other words, in FIG. 3(a), the jet nozzle portion 14a is oriented in the direction indicated by the arrow (the tangential direction of the circle formed by connecting the center points of each tertiary air nozzle 14).
The figure shows a state in which the tertiary air nozzle 14 is oriented at an angle of +α counterclockwise with respect to The ejection direction is a direction away from the pulverized coal jet ejected from the pulverized coal nozzle 1 at the center of the pulverized coal burner.

3) shows a state in which the jet nozzle portion 14a is configured at an angle of -α clockwise with respect to the direction of the arrow A similar to that described above9, and in this case, the jet nozzle of each tertiary air nozzle 14 are arranged inward, that is, the direction of the tertiary air ejected from each tertiary air nozzle 14 approaches the pulverized coal jet ejected from the pulverized coal nozzle 1 at the center of the pulverized coal burner.

Incidentally, the inclination angle (+α and -α) of the jet nozzle portion 11L with respect to the incoming direction of the arrow, that is, the degree of outward or inward direction of the jet nozzle can be appropriately changed by operating the jet direction adjuster 6.

With the pulverized coal bar force configured as described above, when using low A ratio coal with high volatile content and good combustibility as fuel, the jet direction adjuster 6 should be fully operated to control each tertiary air nozzle. 1
The tertiary air is ejected away from the central pulverized coal jet with the nozzle no. 4 facing outward. This results in moderately slow combustion and reduces NOx without increasing unburned content in the ash.
can be reduced.

In addition, when using high fuel ratio coal with low volatile content and poor combustibility as fuel, operate the jet direction regulator 6 to direct the jet ports of each tertiary air nozzle 14 inward. Air is ejected close to the central pulverized coal jet. This improves combustibility moderately and reduces NOx? It is possible to reduce the unburned content in the ash without increasing it.

In addition, in order to clarify the difference between the deficient conventional pulverized coal burner and the pulverized coal burner of this example, the inventors conducted an experiment using a combustion test furnace and the experimental results are shown in Figure 4. ~
This will be explained with reference to FIG.

Fig. 4 is a system diagram showing a combustion test device used for the pulverized coal burner shown in Fig. 2, and Figs. 5 and 6 are explanatory diagrams showing experimental results in the combustion test device shown in Fig. 4. be.

8 shown in FIG. 4 is a combustion test furnace, and this combustion test furnace 8
The furnace body 9 has an internal dimension of 6001 square and a length of 5 m, and is made of a fireproof and heat-resistant caster wall (thickness 200 g), and this furnace body 9.
The burner wind box 1 is attached to one side wall of the burner, and an air supply pipe 10 is connected thereto. Then, an exhaust gas supply 'i' 12a and a pulverized coal supply pipe 12b are connected to this burner wind box 11, and a test burner 11- is attached to perform a combustion test. The conventional pulverized coal burner shown in the figure and the pulverized coal burner of this embodiment shown in FIG. 2 are used.

In addition, in the case of the pulverized coal burner of this example, θ shown in FIG.
was kept constant at 45°. Furthermore, the pulverized coal fuel used in both the conventional pulverized coal burner and the pulverized coal burner of this example is brown coal (A coal) with a fuel ratio (fixed carbon/volatile content) of 0.8;
The pulverized coal (B coal) has a fuel ratio of 1.5 and the anthracite coal (C coal) has a fuel ratio of 3.3. The particle size of these pulverized coals is 200.
80% mesh pass was used. The temperature of each air supplied to the burner was 80°C for the primary air and 300°C for the other air. And the coal supply amount is 5Qkp
/h, and the experimental results were as shown in FIGS. 5 and 6 when the oxygen concentration in the exhaust gas was kept constant across four lines.

In addition, the vertical axis in each figure is the NOx value when the conventional pulverized coal burner shown in FIG. Indicates the relative value of unburned matter.

In addition, the horizontal axis in each figure is due to the fact that the jetting direction α of the tilted air at the first outlet portion 14a of the tertiary air nozzle 14 of the pulverized coal burner of this embodiment is set in the positive direction (outward).
It can be seen that NOx f can be significantly reduced without increasing the unburned content in the ash. On the other hand, high fuel ratio coal (fuel ratio = 3.
In 3), it can be seen that by setting α in the negative direction (inward), the unburned content in the ash can be significantly reduced without increasing NOx.

From the above results, it is desirable to maintain the rotation of tertiary air and direct the tertiary air outward (0°〈α〈+90°) for low fuel ratio coal, while for high fuel ratio coal, it is desirable to direct the tertiary air inward (-90'). <α<0°) is desirable. Also, contrary to the above, the same effect can be expected even if the tertiary air is swirled, so for low fuel coal, +90°〈α〈
+180c% high fuel ratio coal -180゜<it (-9
Even 0° is good.

Next, other embodiments of the pulverized coal burner of the present invention are shown in Figs.
This will be explained using figures.

In Figure 7, 1 is the pulverized coal nozzle, 2 is the exhaust gas nozzle, 3
is a secondary air nozzle, 4 is a tertiary air flow path, 22 is a PG vane, 32 is a secondary vane, 42 is a tertiary resistor,
The difference from the pulverized coal burner shown in FIG. 2 is that the tip 3a of the secondary air nozzle 3 can be tilted with respect to the center of the pulverized coal burner by means of a link mechanism 13. accomplished,
This makes it possible to vary the ejection direction of the tertiary air flowing through the tertiary air flow path at the outermost periphery of the pulverized coal burner, either inward or outward.

That is, in the case of low fuel ratio coal, the tip 3a of the secondary air nozzle 3 is expanded outward so that the direction of ejection of tertiary air is directed outward, while in the case of high fuel ratio coal, the tip 3a is directed inward. The direction of the tertiary air is directed inward.

As a result, similarly to the embodiments described above, with low fuel ratio coal, NOx'fc can be reduced without increasing the total unburned content in the ash, and with high fuel ratio coal, the unburned content in the ash can be reduced without increasing NOx k.

Since the present invention has the above-described configuration, it has the effect of greatly reducing NOx in the exhaust gas and unburned content in the ash during the combustion of pulverized coal, and is particularly effective for reducing flame-retardant high fuel ratio coal. It can be applied to burners when designing boilers and combustors because it eliminates problems such as NOx and unburned substances even if the fuel is burned with high efficiency. lr::a has the effect of greatly expanding the range of charcoal.

Furthermore, when using high fuel ratio coal as fuel, there is no need to atomize the fuel to reduce unburned content in the ash, so the mill load does not need to be increased (more economical than conventional methods). There are also some effects.

3 is a sectional view showing one embodiment of the pulverized coal burner of the present invention.
Figures (a) and ω) are front views of the pulverized coal burner shown in Figure 2 with different directions of tertiary air ejection, respectively, and Figure 4 is a system diagram showing the combustion test equipment used for the pulverized coal burner. ,
5 and 6 are explanatory diagrams showing experimental results in the combustion test apparatus shown in FIG. 4, FIG. 7 is a sectional view showing another embodiment of the present invention, and FIG. 8 is a fine powder shown in FIG. 7. A front view of the charcoal burner, and FIG. 9 is an enlarged view of the main parts of the pulverized coal burner shown in FIG. 7.

1... Pulverized coal nozzle, 2... Exhaust gas nozzle, 3... Secondary air nozzle, 3a...
・Tip of secondary air nozzle, 4... Tertiary air flow path (outermost air flow path), 6... Ejection direction moisturizer, 13... Link Kiki, 14... Tertiary air nozzle, 14a... Outlet part. ′? 1\
l Figure 2 Figure 3'! i'L 4 Figure No. 51 ￥ 71 No. 6 I ￥/! 7th same Figure 8? r♂9 mouth'

Claims (3)

[Claims] (1) In a pulverized coal burner in which one or more air passages for combustion are provided around the outer periphery of a pulverized coal nozzle that injects a mixed fluid of pulverized coal and a carrier medium into the furnace, the A pulverized coal burner characterized in that the pulverized coal burner has a jetting direction variable means for changing the jetting direction of air flowing through the outermost air passage among the air passages. (2) The pulverized coal burner according to claim (1), wherein the ejection direction variable means comprises a plurality of rotatable nozzles each having one bent ejection portion. (3) The ejection direction variable means ejects air in a direction away from the pulverized coal jet ejected from the pulverized coal nozzle when the pulverized coal fuel ratio is less than 1.5;
5, the air is ejected in a direction approaching the pulverized coal jet.
The pulverized coal burner according to any one of paragraphs 1 and 2.