JPH02122103A - Burner of powder particle fuel - Google Patents

Abstract

PURPOSE:To form a large recirculation region in the neighborhood of a burner to disperse pulverized coal in a pulverized coal concentrated flow so as to prevent primary air and the pulverized coal from turning by providing a concentrator of a powder particle-like fuel, a dispersion plate for dispersing the fuel and a turn prevention plate of the fuel in a fuel supply tube and a burner. CONSTITUTION:A pulverized coal flow carried by primary air is divided into a pulverized coal diluted flow 7 and a pulverized coal concentrated flow 8. The pulverized coal concentrated flow 8 is allowed to flow toward a burner outlet while turning in a fail pipe 21. As the result, because a porous pulverized coal dispersion plate 22 is set between a pulverized coal concentrator 6 and the burner outlet, the pulverized coal is removed from a wall surface to disperse in the fail pipe 21. Further, a turn speed constituent is eliminated by a turn flow prevention plate 23. Accordingly, since fuels such as pulverized coal and oil of fire-resistance of small volatile component can be burned by sufficiently lengthening furnace retention time, unburnt components are decreased to burn completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a combustion device for granular fuel, and particularly to a combustion device for granular fuel such as pulverized coal or petroleum coke having a low volatile content.

[Conventional technology]

Pulverized coal combustion equipment conventionally used in boilers, etc. is a combustion equipment that directly supplies coal that has been pulverized using a pulverizer (hereinafter referred to as a mill) with a built-in classifier to a pulverized coal burner. has been adopted.

This device uses heated air to dry the raw coal supplied to the mill, to classify the pulverized coal inside the mill into coarse and fine particles, and to transport the pulverized coal to the burner.

Therefore, the amount of air and the air temperature are determined depending on the moisture content, crushability, and combustibility of the raw coal.

Figure 8 shows the weight ratio (hereinafter C/A) of pulverized coal (C) and air (A) supplied from the mill to the burner with respect to the mill load.
). This figure shows that C/A decreases as the mill load decreases. This is an unavoidable phenomenon because it is necessary to maintain the amount of air to a certain level for transporting and classifying the pulverized coal.

FIG. 9 shows data regarding the ignition stability of coal.

The horizontal axis of the figure indicates the fuel ratio (hereinafter referred to as FR), which is the weight ratio of fixed carbon to volatile content in coal. The FR of coal commonly used in boilers etc. is 0.8 to 2.
It is about 5. For high fuel ratio coals of 2.5 or more and coals with high FR such as anthracite or petroleum coke of 4 or more, C
/A cannot be ignited stably unless the value of A is increased. For this reason, the 8th
When a mill with the characteristics shown in the figure is used, ignition becomes unstable under conditions of high FR coal and low C/A in a low load range, which poses a problem in terms of safe operation of the boiler.

To deal with this, the low C/Δ fine powder flow from the mill can be combined with high C/A fluid (fine powder dense) and low C/A fluid using inertia, etc.
An effective method is to branch into a fluid (dilute) and use the former for stable combustion in the burner section.

FIG. 10 is a system diagram of a pulverized coal combustion apparatus using a cyclone separator according to the prior art. In the figure, coal is stored in a coal bunker 1 and sent from a coal feeder 3 to a mill 4 via a coal supply pipe 2 depending on the load of the combustion device. Coal pulverized in the mill 4 is sent as pulverized coal together with primary air through a pulverized coal supply pipe 5 to a cyclone-type pulverized coal concentrator 6, where it is converted into pulverized coal. ! The pulverized coal is divided into four condensate streams 8 and a pulverized coal lean stream 7. The concentrated pulverized coal stream 8 is conveyed to the burner 16 and blown into the furnace 15, while the lean pulverized coal stream 7 enters the furnace 1 through the dilute liquid inlet 17 installed immediately next to the burner 16.
It is blown into 5. Such a device is known, for example, from Japanese Patent Application Laid-Open No. 61
As shown in Japanese Patent No. 192113, the burner 16 in the furnace 15 is provided on a horizontal or upwardly inclined upper wall 18b located above the front wall 18 and rear wall 18a of the furnace 15. The purpose of this is to inject pulverized coal downward from the top of the furnace (5), burn it in a U-shaped trajectory, and lengthen its residence time in the furnace.

However, the above-mentioned conventional technology does not consider the influence that the dilute flow, which is introduced into the furnace through the dilute liquid input port provided near the burner input port into which the concentrated flow is input, has on the flow pattern of the burner flame. There has been a problem in that it is difficult to form a large backflow region of high-temperature combustion gas generated in the furnace near the burner inlet, which is effective in stabilizing the flame. In addition, no consideration was given to the fact that the pulverized coal concentrated flow obtained by the pulverized coal concentrator using a cyclone was given strong swirl in the burner, and unburned coal was The problem was that the losses were large.

[Problem to be solved by the invention]

It is an object of the present invention to eliminate the problems of the prior art described above, to provide a dilute method suitable for forming a large backflow region near a burner, and to provide a means for discharging fine powder in a concentrated flow of pulverized coal that is introduced from a burner into a furnace. The object of the present invention is to provide a combustion device for dispersing charcoal and further preventing swirling of primary air and pulverized coal.

(Means for Solving the Problems) The object of the present invention described above is to provide a fuel supply pipe for supplying a mixed fluid of granular fuel and primary air to a burner, and a fuel supply pipe for injecting this mixed fluid into a combustion furnace and burning it. In a combustion apparatus for granular fuel, which is equipped with a combustion furnace in which the fuel injection port of the burner is provided in the furnace wall, a concentrator for the granular fuel and a dispersion device for dispersing the fuel are provided in the fuel supply pipe or in the burner. This is achieved by a combustion apparatus for granular fuel, which is characterized by being provided with a plate and a plate for preventing rotation of the same fuel.

[Function] As shown in Figs. 11 and 12, a double cylindrical burner is installed at the center opening at the left end of the cylindrical furnace, and a mixed flow of primary air and pulverized coal flows from the central cylindrical port, and a mixed flow of primary air and pulverized coal flows from the outer annular port. This figure shows a comparison of the gas flow in the combustion furnace in which air is introduced, with and without a dilute flow provided near the burner.

Since a vane is provided at the secondary air inlet, the secondary air is blown into the furnace while being given rotational force. Both figures show the results of numerical calculations of the gas velocity field in the cylindrical furnace (velocity hector in the upper half of the figure) and the flight trajectory of pulverized coal particles (lower half of the figure). Since the secondary air is given a swirl, the pulverized coal particles fly while swirling, and the trajectory is shown by plotting the distance from the furnace center axis to the particles on a plane. FIG. 13 is a trajectory of pulverized coal particles seen from the furnace outlet in FIG. 11.

FIG. 11 shows the calculation results when the dilute liquid inlet is placed sufficiently far from the burner, and a large backflow area, that is, a gas flow area toward the burner, is formed in the furnace. FIG. 12 shows a flow pattern when the dilute solution inlet is installed outside the burner, and it can be seen that only a smaller backflow area is formed compared to FIG. 11. 11th
In both Fig. 1 and Fig. 12, pulverized coal and secondary air are fed straight in parallel to the central axis of the furnace, but the reason why the flow expands outward in the furnace is due to swirling of the secondary air. This is because it is multiplied by

The jet ejected from the burner entrains surrounding air as it flows, but if there is not enough air to entrain it, a recirculating vortex forms around the burner jet, causing a pressure drop. As a result, the burner jet has an outwardly expanding flow pattern, creating a large backflow area. However, if sufficient air for the burner jet to be drawn in is supplied from the diluted liquid inlet installed on the outside of the burner, no recirculation vortex will be formed around the burner jet, and the formed backflow area will be small. Become.

By moving the dilute liquid inlet away from the burner as described above, it is possible to form a large backflow area that is important for flame stabilization.

In order to prevent swirling of the pulverized coal concentrated flow, a pulverized coal dispersion plate and a swirling flow prevention plate are installed inside the pulverized coal injection cylinder as described later. The pulverized coal flowing in a sushi-like manner on the wall surface of the pipe is peeled off from the wall surface and dispersed within the two-well pipe, and the latter serves to eliminate the swirling velocity component of the primary air within the two-well pipe. Figures 14 and 15 are diagrams showing flow patterns near the burner and calculation results of pulverized coal particle trajectories when a pulverized coal distribution plate and a swirl flow prevention plate are installed in the pulverized coal pipe and when they are not installed, respectively. .

In addition, Fig. 14A and Fig. 15A are Fig. 14 and Fig. 15A, respectively.
16 is an enlarged view of the vicinity of the burner in FIG. 15. FIG. In the case of Fig. 14, in which a dispersion plate and a swirl flow prevention plate are installed, the pulverized coal entering the furnace from the burner first enters the backflow region, then turns around and flies toward the burner through the backflow region. However, the high speed 2
When it encounters the next air flow, it rapidly moves away from the burner. 1
In the case of Figure 15, where the air also has a swirling velocity component, centrifugal force is acting before the pulverized coal enters the furnace, so
Compared to the figure, pulverized coal is scattered outward more quickly.

Therefore, it encounters the high-speed secondary air flow quickly and moves away from the nozzle. Due to such differences in the behavior of pulverized coal particles, the residence time in the vicinity of the burner changes.

FIG. 16 shows the residence time of particles in the vicinity of the burner using the position of the pulverized coal particles at the outlet as a parameter with respect to the average swirling speed of the pulverized coal particles (the swirling speed of -primary air). From this figure, it can be seen that the weaker the swirling of the primary air is, regardless of the swirling direction, and the farther the pulverized coal inflow position is from the fuel pipe wall, the longer the residence time becomes, and the unburned content loss is reduced.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a combustion system diagram of a high fuel ratio coal combustion boiler showing one embodiment of the present invention. In the figure, coal is stored in a coal bunker 1 and sent from a coal feeder 3 to a mill 4 depending on the load of the combustion equipment.

The coal pulverized by the mill 4 is conveyed as pulverized coal to the burner 16 by primary air. In the middle of the piping, the pulverized coal concentrator 6 divides the pulverized coal into a concentrated pulverized coal stream 8 and a diluted pulverized coal stream 7, and the pulverized coal concentrated stream 8 is conveyed to a burner 16 and then transported to a furnace 1.
It is blown into 5. On the other hand, the pulverized coal dilute flow 7 is blown into the furnace 15 from the dilute liquid inlet 17 provided in the front wall 18 of the furnace 15 .

Note that the dilute liquid inlet 17 may be provided in the furnace rear wall 18a.

Fig. 2 is a side sectional view of a high fuel ratio coal combustion burner and a cyclone type pulverized coal concentrator installed above the burner showing an embodiment of the present invention, and Fig. 3 is a side sectional view in the direction of Fig. 2. It is the motherland. Here, 6 is a cyclone type pulverized coal concentrator, 7 is a pulverized coal dilute flow, 8 is a pulverized coal concentrated flow, 20 is a pulverized coal flow, and 21
2 is a two-well pipe, 22 is a pulverized coal distribution plate, and 23 is a swirl flow prevention plate.

FIG. 4 is a diagram showing the relationship between the size of a backflow region formed near the burner and the swirl number, which is an index of the swirl strength of secondary air. As the principle has been explained using FIGS. 11 and 12, it can be seen that according to the present invention, a large backflow region can be formed with a relatively small swirl number. With conventional equipment, it can be assumed that similar effects can be obtained by increasing the number of swirls, but increasing the number of swirls requires increasing the fan power, and from an economical point of view, it is possible to achieve a large It is preferable to form a reverse region. Therefore, according to the present invention, it is possible to form a large backflow area with less fan power than in the conventional method, and it is considered that a stable flame can be created.

In FIG. 2, a pulverized coal stream 20 conveyed by primary air is divided by a pulverized coal concentrator 6 into a pulverized coal lean stream 7 and a pulverized coal concentrated stream 8 . The pulverized coal concentrated stream 8 circulates within the two-well pipe 21 and then flows toward the burner outlet. In the burner of the conventional device, the pulverized coal concentrated flow flows on the wall surface of the two-well pipe while swirling and exits the burner (in contrast, in the present invention, a porous pulverized coal distribution plate 22 is provided between the pulverized coal concentrator 6 and the burner outlet. is installed, the pulverized coal is peeled off from the wall surface and dispersed within the two-well pipe 21.

Furthermore, the swirling flow prevention plate 23 eliminates the swirling velocity component.

Figure 5 shows the distribution of the pulverized coal concentration, that is, the C/A, in the two-well pipe at the outlet of the 1st burner, with the pulverized coal distribution plate and the swirl flow prevention plate installed (the present invention) and the case without (the conventional device). FIG.

From this figure, it can be seen that in the conventional method, C/A is
is thick (in contrast, according to the present invention, it is almost -
It can be seen that there are various distributions.

FIG. 6 is a diagram comparing the combustion rates of the present invention and the conventional apparatus at the furnace outlet in a combustion experiment. From this figure, it can be seen that the combustion rate is improved by about 10% compared to the conventional burner, and the present invention is effective. This is shown in Figures 14, 15, and 16.
As explained using the figures, this is thought to be due to the residence time of the pulverized coal particles in the furnace becoming longer due to the present invention.

The seventh example is a combustion system diagram of a boiler showing another embodiment of the present invention, in which a pulverized coal lean flow 7 is mixed with tertiary combustion air 19 and the mixture is introduced into a furnace 15. In this case, there is no need to install a special inlet for injecting the pulverized coal dilute stream 7 into the front wall 18 of the furnace 15. In the example shown in Fig. 1, the pulverized coal dispersion plate and the swirl flow prevention plate are installed inside the burner. Even if it is installed inside the two-well pipe, the same effect can still be obtained.

〔Effect of the invention〕

According to the present invention, fuels such as flame-retardant pulverized coal and petroleum coke powder with low volatile content can be burned with a sufficiently long residence time in the furnace, thereby reducing unburned matter. can be completely combusted.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a sectional view of a burner and a fuel concentrator in an embodiment of the present invention, and FIG.
The figures are a view from direction A in Fig. 2, Fig. 4 is a relationship between the swirl number and the backflow area volume, and Fig. 5 is a comparison of the pulverized coal concentration distribution at the burner outlet between the present invention and the prior art. Figure 6 is a comparison diagram of pulverized coal combustion rate between the present invention and the conventional technology;
Figure 7 is a system diagram of another embodiment of the present invention, Figure 8 is a diagram showing the relationship between mill load and pulverized coal concentration at the burner inlet in the prior art, and Figure 9 is a diagram showing the relationship between pulverized coal concentration, fuel ratio, and ignitability. relationship diagram,
Figure 1O is a combustion system diagram of a boiler for high fuel ratio coal combustion according to the prior art, Figure 11 is a diagram of the gas flow pattern near the burner and the flight trajectory of pulverized coal particles when the present invention is implemented, and Figure 12 is a diagram of the flight trajectory of pulverized coal particles. Figure 13 shows the gas flow pattern near the burner and the flight trajectory of pulverized coal particles in the prior art.
The figures are a visual view of the flight trajectory of pulverized coal particles as shown in FIG. 11 when exiting the furnace, FIGS. 15A is a diagram of the gas flow pattern near the burner and the flight trajectory of fuel particles in the prior art,
FIG. 16 is a diagram showing the relationship between the average swirling speed of pulverized coal particles and the residence time of the pulverized coal particles at the burner outlet. ■...Coal bunker, 3...Coal feeder, 4...
Mill, 5...Pulverized coal supply pipe, 6...Pulverized coal concentrator,
7...Pulverized coal dilute flow, 8...Pulverized coal concentrated flow, 9...
Combustion air fan, 10... Primary air fan, 11
...Heat exchanger, 12...Flow rate control valve, 13...Primary air piping, 14...Combustion air piping, 15...Furnace, ]6...Burner, 17...Leaning Fuel flow inlet, 1
8... Front wall, 18a, rear wall, 19... Tertiary air for combustion, 20... Pulverized coal flow, 21... Fuel pipe,
22...Pulverized coal dispersion plate, 23...Swirl flow dispersion plate, 2
4... Wind box, 25... Secondary air register, 26... Flame holding ring, 27... Oil burner, 28
...Secondary air nozzle. Applicant Habcock Hitachi Co., Ltd. Agent Patent Attorney Kawakita Takeshi Naga C'J () oo (Q 4 N (-) Yone Seiki Sen'xB Rule (-) ■± Enna V/D Natsuhiro Sumire Narigo Figure Figure

Claims (1)

[Claims] (1) A fuel supply pipe that supplies a mixed fluid of granular fuel and primary air to a burner, a burner that injects this mixed fluid into a combustion furnace and burns it, and a fuel injection port for this burner is provided on the furnace wall. In a granular fuel combustion device equipped with a combustion furnace,
a granular fuel concentrator in the fuel supply pipe or burner;
A combustion device for granular fuel, characterized by comprising a dispersion plate for dispersing the fuel and a plate for preventing swirling of the fuel.