JPS602807A - Combustion device - Google Patents

Abstract

PURPOSE:To perform high-efficient combustion and to reduce production of NOX in exhaust gas, by a method wherein a pulverized coal auxiliary burner port, located on a periphery present further outer than a periphery on which a main burner port is situated, is coupled to a bypass port formed in the outer periphery part on the slipstream side of a strangulated part in a pulverized coal conveying passage. CONSTITUTION:After coarse grain 17 and particle 18, carried by a primary air, are accelerated by means of a strangulated part 2, they are spread again, and vortexes 19 are generated. The coarse grain 17 has a high inertia force, and thereby it is hard to be influenced by a primary air and flows straight. Meanwhile, the particle 18 is drawn in the vortex 19, and thereby it is deviated to the vicinity of an inner wall. A bypass port 3 is located at a portion where the particle 18 is deviated, and only the particle 18 is supplied to an auxiliary burner port 7, resulting in formation of a stable auxiliary flame 15 similar to that of gas fuel during combustion. This prevents the occurrence of a delay in combustion even in the case of low grade coal having less volatile matter and performs high-efficient combustion, and moreover, a volatile matter is discharged for a short time, resulting in production of an eminent reduction effect and in the possibility to achieve reduction of production of NOX.

Description

[Detailed description of the invention] Misfire F! A relates to a combustion device, particularly a combustion device such as a boiler device suitable for burning low-grade, low-11-stroke pulverized coal.

Traditionally, burners have been used that have a main flame port for pulverized coal transported by primary air in the center of the burner, and air ports around the outer periphery that supply combustion air to one or more stages. In burners, the pulverized coal carried by the primary air passes through a first-stage constriction section to rectify the flow, and then is ejected from the center of the burner and burned, resulting in relatively high volatile content. Only pulverized coal, which is easily combustible, can be used as fuel, and incomplete combustion tends to occur due to load fluctuations, burner turndown ratios, and slight fluctuations in fuel properties, and the burner has an extremely narrow margin. There is. For this reason, conventional burners have a tendency to cause incomplete combustion due to the particle size and particle size distribution of pulverized coal, and due to variations in pulverized coal frost in multi-burners. In particular, the above-mentioned drawbacks have become an even bigger problem in recent years, as the need for coal has increased and even hard-to-combust high-fuel-ratio coal is being used as fuel for boilers.

In addition, in the conventional pulverized coal burner, the combustion rate of pulverized coal in the vicinity of the burner is small, and as a result, the combustion in the furnace is delayed, so the furnace of the boiler has to be made thicker. Particularly for pulverized coal with low volatile content (7), it was necessary to significantly increase the size of the furnace. In addition, since pulverized coal burns slowly near the burner, the flame temperature is low.
Since the vaporization of volatile matter is delayed, a denitrification reaction occurs in the flame due to intermediate products of combustion of hydrocarbons in the volatile matter (hereinafter referred to as radicals), resulting in nitrogen oxides (hereinafter referred to as NOx). was successfully reduced. Furthermore, in conventional pulverized coal burners, only pulverized coal cannot be burned unless the furnace is sufficiently preheated, which increases the consumption of gas or oil as auxiliary fuel, leading to an increase in operating costs.

An object of the present invention is to overcome the above-mentioned drawbacks of the prior art and provide a combustion device that can perform highly efficient combustion of pulverized coal having a volatile content ranging from a high volatile content to a low volatile content, and at the same time reduce NOx in exhaust gas. It is in.

The present invention aims to achieve the above object by supplying pulverized coal of relatively small particle size around the burner mouth to form a stable auxiliary flame. That is, the present invention provides a combustion apparatus that has a main flame port for pulverized coal carried by primary air in the center of the burner, and a string vent for supplying combustion air on the outer peripheral side of the main flame port. It has a pulverized coal auxiliary flame port on the outer periphery, and the auxiliary flame port is connected to a bypass port provided on the outer periphery on the downstream side of the throttling part of the pulverized coal conveyance channel by secondary air. shall be.

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view of a pulverized coal burner according to the present invention, and FIG. 2 is a human view thereof. This device R includes a main flame port 5 through which the primary air-borne fine powder l is ejected through a first constriction section 2 and a second constriction section 4, and a bypass port 3 in the middle of the passage leading to the main flame port 5.
From there, the pulverized coal 1 is passed through a bypass pipe 8 and a manifold 6.
an auxiliary flame rim provided on the outer circumferential side of the main flame port 5 for bypassing a portion of the auxiliary flame port 5; and secondary and tertiary air ports 12 provided between the main flame port 5 and the auxiliary flame port 12. It mainly consists of 13. Note that 9 is a wind box, and 1O111 are secondary and tertiary registers, respectively.

In the above configuration, the primary air-borne fine powder is squeezed in the first squeezing section 2, expanded again, and partially bypassed through one or more bypass ports 3, and then passed through the second squeezing section 4. The flame is narrowed down, expanded again, and supplied into the furnace through the main flame port 5. The fine powder binominated at the bypass port 3 passes through the bypass pipe 8 and once enters the binosu manifold 6, where it is rectified and then supplied into the furnace through the auxiliary flame lower. Air is routed from a combustion air fan (not shown) to a duct (
(not shown), is supplied to the inside of the wind box 9, becomes a moderate swirling flow at the secondary air register 10 and the tertiary air register 11, and is supplied into the furnace from the secondary air port 12 and the tertiary air port 13, respectively. be done. In addition, in FIG. 2, the bypass or tube 8 is 4
However, the number of bypass pipes 8 can be set to one or more depending on the properties of the fuel used. In other words, when the volatile content in the fuel is small, the number of bypass pipes 8 is increased and the auxiliary flame It is preferable to increase the amount of pulverized coal to the coal lock. Instead of increasing the number of bypass pipes 8, the diameter of the pipes may be increased.

Next, FIGS. 3 and 4 illustrate the effects of the present invention. That is, in FIG. 3, coarse particles 17 and fine particles 18 transported by the primary air are accelerated in the first constriction section 2 and then expanded again, generating a vortex A19. Coarse particles 1'7ij: Because of their large inertial force, they are less affected by the primary airflow and travel straight, and are accelerated again at the second constriction section 4. On the other hand, since the fine particles 18 are caught up in the vortex A, they are unevenly distributed near the inner wall as shown in the figure. The bypass port 3 is provided in a part where the fine particles 18 are unevenly distributed, and the pulverized coal supplied to the auxiliary flame lower is composed of the fine particles 1.
There will be only 8. The same phenomenon occurs in the flow of the second constriction section 4, and the particles are classified by the vortex B20 into fine particles 1B on the outer peripheral side and coarse particles 1'7 in the center. FIG. 4 shows the shape of the flame generated by the burner according to the present invention, and as a result of only the fine particles 18 being supplied to the auxiliary flame lower as described above, combustion is performed as if it were a stable auxiliary flame similar to gas fuel. A flame 15 is formed. On the other hand, since the pulverized coal supplied from the main flame port 5 has coarse particles 17 at the center and fine particles 18 at the outer periphery, the fine particles "1B" at the outer periphery are first combusted by the flame radiation from the auxiliary flame 15. Thereafter, the coarse particles 1'7 start to burn, forming a main flame 16.

In the present invention, various modifications and applications other than the above-mentioned embodiments are considered. For example, the shape of the widening part (swaft side) of the first throttle part 2 is determined by the degree of classification performance of pulverized coal, but it may be opened at 90 degrees like the widening part of the second throttle part 4. good.

For example, when burning coals with different fuel properties, pulverized coal with a low volatile content can be supplied to the main flame port 5, and pulverized coal with a high volatile content can be supplied to the auxiliary flame port 5.

Furthermore, FIGS. 5 to 10 show various modifications of the burner bypass port 3, bypass manifold 6, and auxiliary flame lower used in the present invention.
For example, as shown in FIG. 6, the shape may also be used as a second constriction section 17, or as shown in FIG. 8, the bypass pipe, bypass manifold,
Instead of providing a separate auxiliary burner port, it is also possible to use a configuration in which pulverized coal flowing in from the bypass port is supplied to the secondary or tertiary air pipe as a substitute for these. In this case, since premixing with secondary or tertiary air progresses, combustion becomes more stable. In this case, of course, 2
The flow rate of pulverized coal flowing into the secondary air side changes depending on the degree of rotation of the secondary air register, the secondary air flow rate through the opening, etc.

As described above, according to the present invention, as long as a stable auxiliary flame is formed, combustion of low-rank coal with low volatile content is not delayed, and highly efficient combustion is possible. Furthermore, by forming a stable auxiliary flame, stable combustion can be performed even if load fluctuations or variations in the amount of coal supplied between burners occur. Furthermore, as the volatile matter in the fuel is released in a short period of time, more hydrocarbon radicals are generated, and the NO reduction effect is remarkable, making it possible to achieve low NOx reduction. It is economical because the consumption of various materials can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the pulverized coal (-) used in the present invention, Fig. 2 is a view from the direction of the person, and Fig. 3 is a pulverized coal supply pipe in the burner of Fig. 1. A diagram showing the classification situation,
Figure 4 is a diagram showing the shape of the combustion flame at the bottom (from the slot to the auxiliary flame port) of the burner used in the present invention. It is a sectional view showing an example.l--Primary air conveyed fine powder, 2--First constriction part, 3-.
...Bypass port, 4...Second constriction part, 5-...Main flame port, 6...Bypass manifold, T...Auxiliary flame port, 8
...) (Inokusu tube, 9...inside the wind box, 10...2
Next air register, 11...Third air register, 12...
...Secondary air port, 13...Third air port, 14...Burner port, 15...Auxiliary flame, 16...Main flame, l...
・Coarse particles, 1B... Fine particles, 19... Vortex A% 20
... Uzu B0 Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] (1) In a combustion device having a main flame port for pulverized coal conveyed by primary air in the center of the burner and an air port for supplying combustion air on the outer peripheral side thereof, the main flame port It has a pulverized coal auxiliary flame port on the outer periphery, and the auxiliary flame port is connected to a bypass port provided on the outer periphery on the downstream side of the constriction part of the pulverized coal conveyance flow path by secondary air. combustion equipment. (2. In claim i1, the combustion device is characterized in that a second throttle part is provided between the main flame port and the bypass port. (3) In claim 2, A combustion device characterized in that the shape has a function of a second throttle part.