JPS6280409A - Combustion device with low nox of solid fuel - Google Patents

Abstract

PURPOSE:To make a sufficient stability of fine powder fuel combustion and realize a combustion of high efficiency by a method wherein an L-shaped frame cap with its end being opened is arranged at an extremity end of a fuel pipe to make an extremity end of a secondary air pipe show a funnel shape having its diameter being expanded toward an opening end, and at the same time a passage sectional area in a fuel pipe upstream side of the flame cap is expanded. CONSTITUTION:Fuel which is broken by a mill into fine powder coal is transmitted by a primary air to form a fine coal flow 4, metered at a venturi 5, thereafter flowed in a fine powder coal pipe 41 and then injected into a furnace from a fuel injection port 6. At this time, the fine powder coal flow 22 passes through a tapered part 18 of a fine powder coal pipe and an expanded part 19 of a fine powder coal pipe to generate a speed reduction flow 21 and generate a winding eddy flow 24 over a flame holding surface 120 of a flame cap 100. In turn, a secondary air eddy flow 25 is generated and both eddy flows are mixed and ignited on a flame holding surface 120. In this way, a speed reduced flow is generated at an inner surface of the fine powder coal pipe 41 upstream side of the frame cap 100, whereby an area of the downflow eddy part of the frame cap 100 is expanded an then a stable condition of the flame is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a combustion device for reducing nitrogen oxides (hereinafter referred to as NOx), and particularly relates to a combustion device for reducing nitrogen oxides (hereinafter referred to as NOx). The present invention relates to a combustion device that can achieve NOx conversion during combustion.

(Prior Art) Due to recent changes in the fuel situation, an increasing number of large boilers for business use, including large boilers for thermal power generation, are using coal as fuel. In this case, the coal is pulverized to make it easier to burn and to improve combustion controllability. This pulverized coal combustion technology itself has been established for a long time, and now it is possible to burn it as efficiently as heavy oil.

As with gas and heavy oil, various types of pulverized coal combustors have been developed and are in use. The most basic type of burner is a burner that has a pulverized coal supply pipe at its central axis and an annular air supply passage around its outer periphery.

In this burner, the coal is finely pulverized in a mill, and then transported by air flow using conveying air that accounts for about 20 to 30% of the air required for combustion, and then introduced into the furnace through the fuel pipe nozzle. The remaining combustion air is injected from around the pulverized coal jet in a heavily or double annularly separated state, usually given some degree of swirl near the fuel nozzle.

The pulverized coal is recirculated from the furnace to the burner near the burner throw 1 due to this moderate swirling flow C11, and in some cases a fuel outpost 11a, 1j) is added to the east. The flame is held at 61' by the circular impeller, and constant; weak combustion is maintained. If you simply burn pulverized coal - one color, this type of combustion equipment will reduce the
achieved in minutes.

However, as is well known, NOx, which is a by-product of fuel combustion, is often generated in high-load combustion Harleys, and this is one of the causes of popular/I:i dyeing. Combustion improvements have been made throughout the engine.

A particular problem in pulverized coal combustion is NO caused by organic nitrogen (hereinafter referred to as l?uej!N), which is contained in large amounts (usually 1 to 2 wL%) in pulverized coal.
x (hereinafter referred to as Fue7!NOx),
It accounts for most of the NOx in the combustion exhaust gas.

Here, the production reactions of NOx and N2 from Fuel N are as shown in the following equations (1) and (2), respectively, and both reactions are performed competitively.

Fueff N+02 NOx
(1) Fu e l N-1-N(
')x →N2 (2) Therefore, N2
Securing a high temperature reducing flame is an important point in order to give priority to the generation of and maintain a certain degree of high-load combustion.

In general, the combustion method called ■-two-stage combustion is an application of this combustion reaction, creating an air-deficit condition in the burner zone of the furnace to form a high-temperature reducing flame, and discharging the insufficient air into the wake of the burner zone in the furnace. By charging the fuel from a so-called after-air boat, complete combustion is achieved and the combustion is improved throughout the furnace, reducing the amount of N(]x emissions.

Incidentally, currently, in the case of a newly installed boiler that uses general coal as fuel, the NOx emission concentration can be suppressed by a variation of 200 pp rnn.

However, in the combustion of pulverized coal, it is difficult to completely burn the reducing gases generated in the air-deficient burner zone and the remaining unburnt coal particles (141 pieces of char) by the afterair. Since the combustion time is required, a large furnace space is required. Therefore, using the above combustion method, in principle, it is extremely self-effective and low N.
Although it is an Ox combustion method, it has certain limitations.

From this, instead of controlling the combustion of the entire boiler,
A so-called dual register type burner has been developed in which each burner is configured to perform low NOxfA firing based on the above-mentioned principle.

FIG. 7 shows this dual register type burner. In the figure, pulverized coal is injected into the furnace from a pulverized coal pipe 41 as a pulverized coal flow 10 together with air for transporting the pulverized coal. This pulverized coal stream is injected into a furnace and combusted at a low air ratio to produce a reducing intermediate (gas) and reduce a portion of the NOx to N2 in the gas phase. On the other hand, the secondary air 20 that has passed through the secondary air register 61 and has been given a swirling force by the air horn 71 is directed to the outer periphery of the flame 105, and the tertiary air register is directed to the outer periphery of the flame 105. Tertiary air 30 supplied via 62 is injected.

As a result, two-stage combustion is performed using the burner alone, and it has been demonstrated that NOx is reduced to about 400 ppm (reduction rate of 40%). This type of burner has low NO
In order to achieve the On the contrary, it is required that each of these air and flame (or gas) be mixed to burn the unburned components well.

However, in this type of burner, the secondary air 20 and the tertiary air 30 are usually separated from the fuel flow or each other by the pulverized coal pipe 41 and the secondary air pipe 43, but in practice the burner Pulverized coal flow near the throat exit,
The secondary air jet and the tertiary air jet mix easily, making it impossible to maintain sufficient separation of the high-temperature reducing flame in the early stages of combustion, and it is difficult to achieve a NOx reduction of -L with this type of combustion device. proved to be extremely difficult.

In view of the above points, the present invention is based on the first aspect of the present invention (Japanese Patent Application No. 58-172147). In this device, first, open the opening 9I of the pulverized coal pipe 41 facing the furnace, and open its diameter...
Expand towards 1. 1. A structured evening (orientation freight cap (hereinafter referred to as frame camp) 100
so that the flame 105 forms at the base i')6).
It's turning. Next, as shown in FIG. tJj, person υru leak-9 [shape 101.1
02 to effectively separate the fuel 1 and air as described above.

In the apparatus having the configuration shown in FIG.
) The pulverized coal made of charcoal is injected into the furnace through the pulverized coal bed 41 and burned, but in this case, the impeller 31 for flame stabilization is not installed at the tip of the pulverized coal pipe, and the pulverized coal layer 41 is injected into the furnace and burned. A small eddy flow part 103 is formed at 100, and a small amount of fine coal is attracted to this from the outer peripheral part 31 of the pulverized coal flow ejected from the pulverized coal pipe 41, and a small amount of fine coal is drawn from the outer peripheral part of the frame cap. Air (J) is also supplied for 1 minute. In this way, a small and stable flame is maintained in the furnace, ensuring reliable ignition of the pulverized coal flow injected into the furnace from the pulverized coal pipe 41. Therefore, the flame 105 is ignited near the flame cap 100, as if the flame were close to the burner.If the ignition is delayed, the flame 105 is ignited in the wake scraped from the nozzle of the pulverized coal pipe 41. 7, the flame formation shifts to the wake.In the one in Fig. 8, the flow ratio of secondary air 20 and tertiary air 30 is approximately 1:4.
By setting the pressure G of the tertiary air 30 to 120 mmAq or more on the −L flow side of the air register 62 and applying a strong swirling force, the funnel-shaped portions at the tips of the air pipes 42 and 43 are The flame 105 is temporarily separated from the primary and tertiary air due to the action of 101 and 102 and dust.

By blowing out a relatively small amount of -primary air 2o with a swirling strength and direction different from that of tertiary air, 106 in the figure
A stable vortex is formed as shown in . This vortex 10
6 and a small vortex 103 formed by the frame gear 100, the pulverized coal flow injected from the pulverized coal pipe 41 is suppressed by the external force 11 and the flame 105 at the beginning of feeding into the furnace. It has a strong high odor in its early stages! A. It becomes a reduction flame. Radical substances such as l112 and rlN in this 1lli temperature reduction flame and 00
NOx is reduced to N2 by reducing intermediates such as. Further, on the downstream side of this high-temperature reducing flame, the injection energy of secondary air and tertiary air decreases and flows toward the burnout axis, where unburned air is combusted.

(Problems to be Solved by the Invention) In the combustion device shown in FIG.
The pulverized coal attracted to the surface of the pulverized coal and the vortex section 103 behind it ignites because most of the volatile content contained in the coal is ignited, and the remaining fixed carbon content does not reach the point of combustion.
It cannot contribute to the ignition of Freight Cap I.

Since the ratio of volatile matter in pulverized coal is low in coal with a high fuel HJ (IA material ratio - fixed carbon/volatile matter), coal with a high fuel ratio has a high ratio of volatile matter to the surface -l- of the frame cap 100 and the vortex flow behind it. It becomes difficult to maintain a stable flame in the area.

- On the other hand, the pulverized coal that has been pulverized in the mill is sent to the pulverized coal pipe 41 using primary air, but the boiler load has decreased. In order to ensure the safety of The pulverized coal concentration in the mixed flow of coal and primary air will decrease.

As a result, the amount of pulverized coal supplied to the flush portion 1- of the frame cap 100 and the vortex portion 103 becomes insufficient, which poses a problem in stably maintaining the flame. In addition, if the burner flame is ignited in the downstream area after leaving the burner nozzle,
A flame detector that has a field of view near the burner nozzle will incorrectly determine that the burner is misfiring.

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to form a high-temperature reducing flame before attaching the burner opening even when the fuel ratio is high or the load is low. Low NO of solid fuel depends on supplying sufficient air.
It is necessary to install the x-combustion device.

(First Step to Solve the Problems) The present invention has been made to solve the above problems, and has a so-L--, /,-1-yanop as shown in FIG. In the combustion device, a part of the pulverized coal flowing through the pulverized coal pipe 41 is actively removed from the frame cap and the vortex section 10.
3, the cross-sectional area inside the fuel pipe of the frame cap-L flow section is enlarged. In other words,
In the present invention, a secondary air injection qt l:J is disposed almost concentrically on the outside of a fuel pipe injection 11 that injects 211 combinations of solid fuel* and primary air, and a tertiary Air injection [-1] is applied to a solid fuel combustion device with approximately 6 concentric jets.
In 几1, there is a l1-shaped opening at the tip of the fuel pipe) I/-m:
1. The tip of the secondary air pipe constituting the outer periphery of the secondary air injection port is made into a ^tl shape in which the niy is expanded toward the open end, and the flange of the tip of the fuel tube is 1/-
It is characterized by a configuration in which the cross-sectional area of the fuel pipe passage in the fuel pipe flow section is enlarged U7.

(Embodiments of the Invention) Below, the contents of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an overall side sectional view of a powdered solid fuel combustion apparatus according to the present invention, FIG. 2 is a main view thereof, and FIG. 3 is a detailed sectional view of the vicinity of the frame cap of FIG. 1. A combustion device (
One or more bars are provided. At the tip of the pulverized coal pipe 41 passing through the center of the bar, an I-shaped frame cap 100 with an open tip is provided, as described in FIG. A guide sleeve 102 is provided. The former is a configuration necessary to ignite the fuel and maintain a stable flame through fuel injection [1] with low N (this is one of the conditions for x combustion), and the latter is a configuration that requires high-temperature reduction immediately after fuel injection. This configuration is necessary to form a flame, temporarily separate it from secondary air and tertiary air, and mix the two at the end of reductive combustion to achieve complete combustion. The guy 1-sleeve I02 is installed, and the primary air 61 and tertiary air l
The direction of At output is in the direction of I with respect to the axis of the combustion device. l
2+ regulated. FIG. 2 shows the main view A of FIG. 1, in which the oil nozzle 3 is provided on the axis, and the fuel injection port 6, flame camp 100, and secondary air injection port 12 are sequentially installed.
, guide sleeve 102, tertiary air jet 1113 and bar 1114 are passed. The inner circumference lul+ of the frame cap 100 is provided with several irregularities to increase turbulence in the pulverized coal flow 4 and stabilize the flame.

The difference from the conventional device shown in FIG.
00 An enlarged cross-sectional area portion 19 of the fuel supply pipe 41 is installed on the upstream side.
That's what happened. Note that an oil nozzle 3 is provided at the core of the fuel (1) supply pipe 41. This oil nozzle 3 is for igniting the fuel, and may be provided in other parts.

In such a configuration, at startup, at low load, or when the pulverized coal mill is stopped, oil 1/All+ passes through the oil fuel pipe 2, is sprayed from the oil nozzle 3, and is combusted. On the other hand, combustion air is raised by a blower, heated to about 300° C. by an air heater, and then supplied to the wind box 7 through the duct 1-. A part of the combustion air supplied to the wind box 7 passes through a secondary air register 61, an annular air passage composed of a pulverized coal pipe 41 and a secondary air pipe 43, and then reaches a secondary air injection port 12. is supplied into the furnace. The remaining combustion air in the wind box 7 passes through the tertiary air register 62 and enters the tertiary air injection port 1.
3 is supplied to the furnace.

After the coal is weighed by a coal feeding weighing machine, it is fed to a coal mill where it is dried and pulverized (not shown). Fuel pulverized into pulverized coal in the mill is conveyed by primary air and becomes a pulverized coal flow 4, which is squeezed by a henturi 5, flows through a pulverized coal pipe 41, and is injected into the furnace from a fuel injection port 6. At this time, the pulverized coal flow 22 passes through the pulverized coal pipe taper part 18 and the inside 19 of the pulverized coal pipe 41 to generate a decelerated flow 21 as shown in FIG. 24. On the other hand, pulverized coal pipe 4
A secondary air 20 flows outside the cylinder 1, and a secondary air vortex 25 is generated as shown in the figure, and both vortices mix and burn at the flame holding surface 120). In this way, Fushi-Mukyasob 100 [
- Every time a deceleration flow is generated on the inner surface of the flow section, the area of the wake vortex section expands and the flame is stabilized.

FIG. 4 shows another embodiment of the present invention, in which a flow divider plate 1 is installed inside a pulverized coal pipe at a certain distance from the pipe wall.
5 is installed, or by providing an outward bent portion 15a at the end of this flow divider plate on the furnace side, a passage 1 between the pulverized coal pipe 41 and flow divider plate 15 is formed. The pulverized coal that has flowed into the sound will be reliably supplied to the flame-holding surface 120 of the flame cap +00'> L
, is something. The speed is reduced by the enlarged portion 19, and the flow dividing plate 1
The pulverized coal flow guided by 5 is decelerated flow 24 and (-
2 to the flame-holding surface of the frame cap 1001-. Effective against pulverized coal.

FIG. 5 shows still another embodiment of the present invention, in which the pulverized coal pipe tip 19 shown in FIG. A flame camp 100 is installed at the tip of the flame camp 100 (J. In this case, a decelerated flow 21a is also generated) P (, , 1v flame surface 120
flame stabilization at the top is enhanced.

FIG. 6 shows still another embodiment of the present invention,
1tT between the enlarged part 19 of the pulverized coal pipe 41 and the flow divider plate 15
A travel vane 26 is provided on the f path, and the pulverized coal flow passing through it is given a travel time, and then the frame cap I is used as a decelerated flow 24.
- It is designed to supply pulverized coal to. With this device, in addition to the deceleration effect due to the expansion of the fuel pipe mentioned above,
By adding a number of trips), flame stabilization can be further promoted.

Although the case in which pulverized coal is used in 1-1 fuel and 17 has been described above, the present invention is not limited to this, and can also be applied to the case where solid fuel such as petroleum coke is pulverized in a mill and used. It goes without saying that it can be done.

(Effects of the Invention) The first effect of the present invention is that the stability of the pulverized fuel flame becomes sufficient, and as a result, it is possible to achieve high efficiency combustion with a low reduction of unburned matter of 1 to 1. Second effects i, t of the present invention:
, ignition directly at the fuel pipe injection port is ensured, and a high-temperature reducing flame can be achieved, so Fue7! Since N is reduced to N2, (III) NO OX combustion can be realized. The third effect of the present invention is that the ignition f'1 at startup and low negative (WJ) is good, so the expensive It is possible to shorten the auxiliary combustion time due to bending (*), making Meriso 1 extremely economical.

[Brief explanation of drawings]

FIG. 1 is an overall side sectional view of a combustion device showing an embodiment of the present invention, FIG. 2 is a main view of A in FIG. 1, and FIG. 3 is a detailed view of part 13 in FIG. Figures 4 to 6 are detailed cross-sectional views of the middle knob of the frame, showing other embodiments of the present invention.
8 are plane views of a conventional solid fuel combustion device, respectively. 6... slightly flame tube injection port, 7... wind box, j2...
- Missing air jet. 13...Tertiary air injection port, I4...
・Burner cone, 18...Pulverized coal pipe taper part, 19・
...Pulverized coal pipe tip, 41...Pulverized coal pipe, 43...
Secondary air pipe, 100...Flame camp, 10
2...Secondary air pipe tip enlarged part. Agent Patent Attorney Takeshi Kawakita Cho B Figure 1 Figure 2 6: Fuel (pulverized coal) pipe dipping port 19: Pulverized coal pipe enlarged part 7
: Wind noise 4] ° value Powdered coal pipe 12: Secondary air injection port 43: Secondary air pipe 13: Tertiary air number port 100 Near L/-mucap 14: Burner cone 102: Double-shaped tracheal tip expansion part 18
: Pulverized coal pipe taper part Fig. 3 Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Claims] (1) A secondary air injection port is arranged approximately concentrically on the outside of the fuel pipe injection port that injects a mixed fluid of solid fuel and primary air,
Furthermore, in a solid fuel combustion device in which a tertiary air injection port is arranged almost concentrically on the outside, an L is opened at the tip of the fuel pipe.
A letter-shaped frame cap is provided, and the tip of the secondary air pipe constituting the outer circumferential surface of the secondary air injection port is shaped like a funnel whose diameter increases toward the opening end. 1. A low NO_x combustion device for solid fuel, characterized in that the cross-sectional area of the passage in the fuel pipe is enlarged.