JPS59137707A - Boiler device - Google Patents

Abstract

PURPOSE:To prevent a generation of vibratory combustion, make a simple structure of wind box, make a small clearance between the bottom surface of a furnace and the lowermost burner and make a small-sized furnace by a method wherein several clearances are formed between the fins in the water-cooled wall constituting a flat hopper so as to feed recirculated discharging gas. CONSTITUTION:A wind box 18 is formed such that it covers substantially an entire surface of a flat hopper. Five feeder inlets 19 in the wind box 18 for use in feeding recirculating discharged gas into a furnace 3 are arranged in parallel in front of the furnace 3 and similarly further five feeder inlets are arranged in parallel at the rear part of the furnace, resulting in providing ten feeder inlets. Fins 17 of boiler tubes 16 are constructed to have some clearances between the adjoining boiler tubes 16. When a gas circulating fan 10 is operated to cause the recirculating discharged gas to be fed to the wind box 18, it is fed into the furnace 3 through the clearances 21 between the fins 17a and 17b. At this time, a distribution of temperature of flame in the lowermost burner shows features of distribution of temperature in the flame in which the vibratory combustion is hard to occur (i.e. a substantially flat distribution of temperature).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler system equipped with a device for recirculating exhaust gas into the furnace to control steam temperature and reduce the level of NOx emissions, and particularly to The present invention relates to a boiler device suitable for those having a furnace with a hopper.

In recent years, the use of clean natural gas as fuel for boilers and as a pollution prevention measure has been increasing. However, gaseous fuels such as natural gas tend to cause oscillatory combustion because they form short flames due to their nature.

When this oscillatory combustion occurs, resonance vibration of the air column occurs within the space of the boiler furnace, duct, etc., generating severe noise and, in some cases, causing an accident that may damage equipment. Therefore, in boilers that use gaseous fuel, prevention of oscillatory combustion has become an important issue. Conventional means for solving this problem have employed means for predicting or monitoring the occurrence of resonance vibrations. That is,
This method focuses on the fact that only the vibration intensity of a specific frequency grows and resonance vibration occurs from the state where the vibration intensity is randomly fluctuating in the combustion equipment, and the average amplitude Amplitude of resonance component ■ Ratio of 1 I l
/ I/O is monitored and the occurrence of vibration is predicted. However, this means is only a means for early prediction of resonant vibrations, and is not a means for preventing vibrational combustion itself, which is the cause of resonant vibrations. Therefore, methods of preventing oscillatory combustion by increasing the length of the burner flame are currently being considered, and a new burner element structure is being considered as a specific method.

By the way, recently, in the case of gas-fired boilers, in order to make the furnace more compact by lowering the furnace height -a+, a structure with a horizontal furnace bottom (flat hopper) has been adopted:
became. In such a flat hopper, the flame of the lowermost burner is influenced by the recirculated exhaust gas G supplied from the bottom of the furnace, resulting in oscillating combustion. This will be explained with reference to FIGS. 1 to 3.

FIG. 1 is a schematic diagram of a boiler apparatus employing a conventional flat hopper. In the figure, 1 is a header to which water to be heated is supplied, 2 is a water cooling wall consisting of a boiler tube and its fins that pass water from header 1, 3 is a furnace, 4 is the flame of each burner, 5 is indicates the combustion exhaust gas from the furnace 3. 6 is a super heater, T is a reheater, 8 is a super heater, and 9 is an economizer, all of which are provided in the flame and combustion exhaust gas passage. 10 is a gas recirculation W4 fan that sucks in part of the combustion exhaust gas and introduces it into the furnace; 12 is a wind box that introduces recirculated exhaust gas from the gas recirculation fan; 13 is a recirculation U1
A gas passage 14 is provided in the hearth of the furnace 3 and is a recirculated exhaust gas input [+] for introducing the recirculated exhaust gas from the wind box into the furnace.

15a and i5b are the lowest stage burners, 4
a and 4b indicate the flames of burners 15a and 15b, respectively.

FIG. 2 is a plan view of the flat hopper taken along arrow A--A in FIG. 1, and FIG. 3 is a sectional view of the water cooling wall shown in FIGS. 1 and 2G. As shown in FIG. 2, the input port 14
is formed in the central part of the flat hopper.As shown in FIG. The furnace 3 is sealed by the fins 17.

In such a boiler device, the water supplied from the economizer 9 to the header 1 is transferred to the boiler tube 1 of the water cooling wall 2.
During the rise in the flame 4, it becomes high-temperature steam mainly due to radiant heat from the flame 4, and then the super heater 6.8
It is heated and becomes superheated steam. On the other hand, the large flame 4 cooled by the water-cooled wall 2 is cooled by a super heater 6, a reheater 7, an economizer 9, etc., and becomes combustion exhaust gas 5 and is discharged. This combustion exhaust gas 5 is used to control the outlet steam temperature of the reheater 1 and to lower the NOx emission level.
A portion of the gas is sucked into the gas recirculation fan 10, passed through 12 wind boxes, and is then introduced into the furnace 3 through the inlet 14. In this case, the recirculated exhaust gas is introduced into the furnace 3 approximately at the center through the elongated inlet 14 provided at approximately the center of the flat hopper.

By the way, if the amount of recirculated exhaust gas injected from the bottom of the furnace is large, the flames 4a+4b formed in the bottom stage burners 15a and 15b will be affected by it, and oscillating combustion will easily occur. That is good (known. Therefore,
*As mentioned in IJ, even if you try to prevent the occurrence of oscillating combustion by using a special burner element to make the flame longer, in a combustion device that uses a flat hopper, due to its structure, the bottom stage burners 15a and 15bc : Since the distance between the flame 4a14b and the inlet port 14 that generates a zigzag is inevitably small, the flame 4a14b is easily affected by the recirculated exhaust gas (and oscillating combustion occurs due to this). .

Also, if the distance between the flames 4a, 4b and the input port 14 is small,
Since radiation from the flame reaches the inner surface of the wind box 12 through the inlet 14, there is also the problem that the inner surface of the wind box 12 must be protected with a thick refractory material. And in order to avoid these points, flame 4a
, 4b and the input port 14 must be made large,
There was a contradictory problem in that increasing this interval would be a serious constraint for making the furnace more compact.

The present invention has been made in view of these conventional problems, and its purpose is to provide a boiler device that can prevent the occurrence of oscillatory combustion and can also have a compact furnace. It is in.

In order to achieve this object, the present invention is characterized in that the charging means for charging the recirculated exhaust gas is provided in several locations distributed in the lower part of the furnace.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 4 is a schematic configuration diagram of a boiler device according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 18 is a wind box into which recirculated exhaust gas from the gas recirculation fan 10 is introduced. The wind box 18 of this embodiment is different from the wind box 12 of the conventional device in that it is configured to cover almost the entire surface of the flat hopper. Reference numeral 19 denotes an inlet for injecting the recirculated exhaust gas from the wind box 18 into the furnace 3, and the inlet is provided at 10 locations in the flat hopper. Arrow 20 indicates the path of recirculated exhaust gas. This inlet 19 is shown more clearly in FIGS. 5 and 6.

FIG. 5 is a plan view of the flat hopper seen from the arrow B--B in FIG. 4, and FIG. 6 is a sectional view of the water cooling wall constituting the seven-rat hopper. From FIG.
It can be clearly seen that the pieces are distributed and arranged M-A. FIG. 6 shows the configuration of this inlet 19, and the fins 1T of the boiler tubes 16 are configured to have gaps between adjacent boiler tubes 16.

That is, the fins 17a of one boiler tube 16 and the fins 17b of the adjacent boiler tube 16 are tilted in almost the same direction and overlap with each other with a gap 21 between them. Placed. Each of these gaps 21 constitutes the input port 19.

When the gas recirculation fan 10 is operated to supply recirculated exhaust gas to the wind box 18, this recirculated exhaust gas is
The awns are fed into the furnace 3 through the gap 21 between the fins 17a and 17b at the inlet 19 at the location. In this case, if we look at the state in which the recirculated exhaust gas is not supplied into the furnace 3, the amount of recirculated gas in the conventional device is the flame 4a of the lower burner 15a.
In contrast, in the device of this embodiment, the flow does not separate the two flames 4a, 4b, and the flame 4b of the lower burner 15b facing the lower burner 15b. First, the way the recirculated exhaust gas affects the flames 4a and 4b is greatly different between the two.

The difference in shadow 1 will be explained based on the furnace flame temperature distribution diagram shown in FIG. In FIG. 7, the horizontal axis represents the dimensionless depth of the furnace 3, where 0 represents the morning, 0.5 represents the center of the can, and 1.0 represents the afternoon. Further, the flame temperature of the flame 4as4b of the lowest stage burners 15a, 15b is plotted on the vertical axis. Curve B shown as a solid line.

is the humidity distribution curve of the flame temperature in the secondary cylinder, and the curve B1 shown by a broken line is the temperature distribution curve of the flame temperature in the apparatus of this embodiment-1. As is clear from the figure, in the conventional device (curve B), the flame temperature in the center of the furnace is low (and the flame temperature is high in the morning and afternoon. In other words, the temperature distribution is such that there are peaks at both ends. This is because the temperature of the recirculated exhaust gas is as low as 1 IJ350℃, and this is concentrated only in the center of the furnace, which lowers the temperature in the center, but the temperature at both ends is affected by the influence of the recirculated exhaust gas. (This is to avoid causing a temperature drop.) Such a humidity distribution becomes more pronounced as the distance between the flame 48.4b and the input port becomes smaller.

On the other hand, in the device of this embodiment (curve Bt), the temperature distribution is flat in the depth direction, and the flames 4a, 4
No temperature drop area was observed in the center of the furnace regardless of the distance between b and the inlet.

Looking at the temperature distribution of the flame in the bottom burner, we can see that the temperature distribution of the conventional device that supplies recirculated gas to the center of the furnace is similar to the temperature distribution of short flames that are likely to cause oscillating combustion Y. In contrast, the temperature distribution of this embodiment, in which recirculated exhaust gas is distributed in a distributed manner, generates oscillatory combustion and has a temperature distribution with peaks at both ends. It has a characteristic (a fairly flat temperature distribution). Therefore, it is clear that the device of this embodiment is highly effective in preventing vibrational combustion.

On the other hand, the flame 40 radiation tries to pass through each inlet 19 to the wind box 18, but as shown in FIG. I can't.

Boiler tube 1 can pass through gap 21
Only the radiation reflected from the fins 6 or fins 17 has a reflectance of about 0.2, and the transmission of radiation due to reflection is minimal. Therefore, the wind box 18 does not reach a high temperature (thick refractory material, etc. is not required).

As shown in ('), in this embodiment, a gap is formed between the fins of the water-cooled wall constituting the flat hopper to form an inlet for injecting recirculated exhaust gas, and this inlet is
Since they are installed in 0 locations, it is possible to prevent the occurrence of oscillating combustion, and since the wind box does not require thick refractory material, its construction can be simplified. Since the distance between the burner and the burner can be reduced, the furnace can be made smaller.

FIG. 8 is a schematic configuration diagram of a boiler device according to another embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 4 are given the same reference numerals, and description thereof will be omitted.

22 is each input port 19 in the wind box 18
The partition 23 provided corresponding to the partition 22 is a damper provided in the passage to the input port 19 formed by the partition 22.

The recirculated exhaust gas supplied into the wind box 18 by the gas recirculation fan 10 enters each input port 190 passage formed by the partition 22 as shown by the arrow 24, and is input into the furnace from the input port 19. Ru. In this case, damper 2
3, the flow rate of recirculated exhaust gas at each input port 19 can be controlled. For this reason, the lowest stage burners 15a, 15b a) flame 4a
, 4b can control the temperature distribution in the depth direction of the furnace, control the heat absorption characteristics of the water-cooled wall in the furnace, and suppress NOx generation by concentrating recirculated exhaust gas in the area with the highest flame temperature. You can also.

In this way, in this example, a partition and a damper corresponding to the input slot are added to the structure of the example of the rabbit, so it not only has the same effect as the example of the example of the rabbit (,
It is possible to control the heat absorption characteristics of the water-cooled wall in the furnace, and
The generation of NOx can be effectively reduced.

In addition, in the description of each of the above embodiments, a boiler device having a flat hopper has been described, but the present invention is not limited to this (and can also be applied to a boiler device having a gently sloped bottom surface of the furnace). Also, the number of input ports is not limited to 10, and it is natural that a plurality of input ports may be used.

As described above, in the present invention, since a plurality of inlets for injecting recirculated exhaust gas are distributed in the lower part of the furnace, it is possible to prevent the occurrence of oscillatory combustion, and moreover, it is possible to prevent the occurrence of oscillating combustion. O

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional boiler equipment, and Figure 2 is a diagram of a conventional boiler system.
FIG. 3 is a plan view of the flat hopper as seen from arrow A-A in the figure, FIG. 3 is a ~f side view of the water cooling wall shown in FIGS. Schematic configuration diagram, Figure 5 is a plan view of the flat hopper laminated from arrow B-B in Figure 4, Figure 6 is a sectional view of the water cooling wall that constitutes the flat hopper shown in Figure 5, and Figure 7 is the furnace. The internal flame temperature distribution diagram, FIG. 8, is a schematic configuration diagram of a boiler apparatus according to another embodiment of the present invention. 2...Water cooling wall, 3...Furnace, 414a
14b...Flame, 10...Gas recirculation fan, 16...Boiler tube, 17117
a117b---Fin, 1B---Wind box, 19---Inlet, 21---
...Gap agent Patent attorney Tsugube Takeken (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1□ (□ 1fflshi224 -

Claims (1)

[Claims] 1. A boiler device equipped with a furnace and means for recirculating exhaust gas from the furnace from a lower part of the furnace into the furnace, wherein the exhaust gas is distributed from a plurality of locations in the lower part of the furnace. A boiler device characterized in that it is provided with means for injecting exhaust gas. 2. The boiler device according to claim 1, wherein the exhaust gas input means is a gap formed in a fin between tubes in a water-cooled wall at the lower part of the furnace. 6. The boiler apparatus according to claim 1, wherein the exhaust gas input means includes a damper that adjusts the amount of input of the exhaust gas.