JPS60202204A - Pulverized coal firing burner and operating method thereof - Google Patents

Abstract

PURPOSE:To improve the combustion of pulverized coal while reducing the quantity of NOX generated by each mounting baffle plates, inner diameters thereof gradually increase in the direction of injection, to a nose section in the direction of injection of an injection nozzle for secondary air and a nose section in the direction of injection of an injection nozzle for tertiary air. CONSTITUTION:A baffle plate 5 inclining at a predetermined angle in the direction of injection (the axial direction of a secondary-air injection nozzle) of secondary air G2 is arranged to the nose of the injection nozzle 2. Mixing to a mixing flow of pulverized coal at a central section and primary air G1 is delayed in the greater part of secondary air G2 by the baffle plate 5. A baffle plate 6 inclining at a prescribed angle to the direction of injection (the axial direction of a tertiary-air injection nozzle 3) of tertiary air G3 is disposed to the nose of the injection nozzle 3. Accordingly, the combustibility of pulverized coal is improved while the quantity of NOX generated can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pulverized coal combustion burner and a method of operating the same, and more particularly to a pulverized coal burner suitable for achieving low NOx combustion and a method of operating the same.

[Background of the invention]

In pulverized coal combustion, a large amount of fuel NOx is generated due to the high N content in the coal. For this reason, environmental measures are necessary. Currently, the combustion method has been improved and N
The development of low NOx combustion technology that attempts to suppress the generation of Ox is being promoted. Specifically, studies are underway to put this into practical use through the development of low NOx burners and the combination of multistage combustion methods.

NOx generated in pulverized coal combustion is affected by the diffusion of oxygen (02) in the combustion region, combustion temperature, etc. In particular, air diffusion is an important factor, and it is necessary to advance air mixing in stages. In addition, the above-mentioned low N
Comparing the in-furnace denitrification combustion method using a combination of an Ox combustion burner and a multistage combustion method, it is advantageous to use a burner when applied to an existing boiler. However, the conventional N
Ox burners suppress the amount of NOx generated by delaying the mixing of fuel and air, and as a result tend to worsen the combustibility of pulverized coal.

At fixed emission sources of pollutants such as thermal power plants, unburned carbon and NOx generated due to incomplete combustion of pulverized coal are not subject to total volume regulations, and it is necessary to control the amount of NOx generated in emergencies. becomes.

[Purpose of the invention]

The purpose of the present invention is to enhance the combustion of pulverized coal and at the same time reduce NOx
An object of the present invention is to provide a pulverized coal combustion burner and an operating method thereof that can reduce the amount of pulverized coal generated.

[Summary of the invention]

The key point of the present invention is that it is essential to mix combustion air with fuel in stages, and in addition to primary air (which also serves as a conveyor for pulverized coal), it is divided into secondary air and tertiary air. A flame stabilizer is installed at the tip of the primary air and pulverized coal mixed flow jetting nozzle, and a part of the secondary air from the secondary air jetting nozzle installed outside the flame holder is drawn in to improve flame holding. The combustibility of most of the secondary air and tertiary air is increased, and the mixing of most of the secondary air and tertiary air with the fuel is delayed by diversion ice provided at the tip of each jet nozzle.

Furthermore, the present invention can improve the combustibility of pulverized coal and at the same time suppress the amount of NOx generated by changing the distribution ratio of secondary air and tertiary air and adjusting the mixing position of the two.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the burner of the present invention, and in this embodiment, it is a concentric cylindrical type pulverized coal combustion burner, but the present invention is not limited to the concentric cylindrical type, and other cylindrical types may be used.

In FIG. 1, an auxiliary fuel (for example, heavy oil for preheating or propane) injection nozzle 9 is arranged in the center of the burner, and adjacent to this is a pulverized coal injection nozzle 1 on a concentric circle.
is provided. A flame stabilizer 5 is provided along the tip of the pulverized coal injection nozzle 1. This flame stabilizer 5 has a structure that expands in a curved shape with respect to the aperture of the nozzle l, and when the pulverized coal is ejected into the furnace through the flame stabilizer 5 by the primary air G1, the flame stabilizer 5 spreads along the flame stabilizer 5. It erupts in an expanded state. Inside of flame holder 5 (
At this time, the side in contact with the mixed flow of pulverized coal and primary air G1 is not under negative pressure, and the secondary air is ejected from the nozzle 2 provided concentrically inside the pulverized coal and primary air Gl ejection nozzle 1. G
A part of the pulverized coal is caught at the tip of the flame holder 5, and the pulverized coal forms a stable flame from the flame holder 5 and is combusted. Further, at the tip of the secondary air jetting nozzle 2, a deflecting plate 5 is arranged which is inclined at a predetermined angle with respect to the jetting direction K of the secondary air G2 (the axial direction of the nozzle).

The baffle plate 5 delays the mixing of most of the secondary air G2 with the mixed flow of pulverized coal and primary air G2 in the center. Further, at the tip of the nozzle 3 for ejecting the tertiary air G3, a deflecting plate 6 is arranged which is inclined at a predetermined angle with respect to the ejecting direction of the tertiary air G3 (the axial direction of the nozzle).

Here, FIG. 2 shows the secondary air jet nozzle 2 under a constant condition that the angle θ3 of the deflector plate 6 of the tertiary air jet nozzle 3 is 10 degrees.
This is data obtained by examining the influence of the angle θ2 of the deflecting plate 5. The experimental conditions were as follows. ″ ΔPulverized coal combustion furnace dimensions; φ60 (hn++' length 500
0 ms△ Test coal: Taiheiyo coal, a fine powder pulverized to 80% under a 200 mesh sieve was used.

△ Coal supply amount, 20 kg/h △ Primary air amount G 1 ; 30 N m ” / h △
Tertiary air nozzle diameter D3iφ300 In Fig. 2,
X in the vertical axis X/D3 is the distance in the jetting direction from the burner surface, and D3 is the diameter of the tertiary air jetting nozzle 3.
Therefore, X/Ds indicates the value when tertiary air diffuses into the central portion (combustion flame). That is, θz
This shows that under the condition of =10 to 65 degrees, the diffusion of tertiary air to the center occurs at the position of X/D s* 3.2.

FIG. 3 shows the angle θ of the deflector plate 5 of the secondary air jet nozzle 2.
2 is constant at 10 degrees, and the influence of the angle θ3 of the deflection plate 6 of the tertiary air jet nozzle 3 is examined. From Figure 3, the diffusion position of tertiary air to the center of the combustion flame X/D
It can be seen that G3, where 3 is 3 or more, is 10 degrees or more.

Next, it is composed of a mixed fluid jetting nozzle 1 of primary air G1 and pulverized coal, a secondary air jetting nozzle 2 having a deflecting plate at its tip, and a tertiary air jetting nozzle 3 having a deflecting plate at its tip,
Further, the results of a combustion test of pulverized coal in a pulverized coal combustion burner in which swirlers 7 and 8 were provided in the secondary air jetting nozzle 2 and the tertiary air jetting nozzle 3 are shown in FIGS. 4 and 5.

The experimental conditions were θ2 = 20 degrees and G3 20 degrees.
The experimental conditions are the same as in FIGS. 2 and 3.

FIG. 4 shows the change in oxygen concentration in the direction of the central axis of the combustion flame in a pulverized coal combustion burner, and FIG. 5 similarly shows the change in Nox degree in the flow direction on the central axis of the flame.

In both FIGS. 4 and 5, the horizontal axes are arranged as the ratio of the distance in the flow direction X to the diameter of the tertiary air nozzle. Figure 4.

The characteristics A to C shown in FIG. 5 correspond to the results of a combustion test under the same conditions. In the diagram, A is the tertiary air amount G
The distribution ratio of 3 and 2 water air amount G is 03/4 = 2, B is G
s/G*=3, C shows the results under conditions set so that G s /G*=4.

In this combustion test, the 1-miss air volume Gl and the pulverized coal supply amount were kept constant and not varied, and only Gt and 03 were varied. In addition, the total amount of primary to tertiary air amount G T (= G 1 + G1
(100 g) was set to be Gy/Go = 1.2 with respect to the theoretical air amount Go required to burn the pulverized coal, and GT was kept constant. As a result, A(G3/G2=2
), combustion progresses from the burner surface, and as it moves away from the burner surface, 02 is consumed and a low 0, region is formed. This tendency is the same for conditions B and C. The change in NOx concentration corresponding to this G2 concentration is shown in A in Figure 4. When combustion occurs on the burner surface, N in the coal is released as NOx, and the NOx concentration tends to increase.
In the region where the G2 concentration is reduced, NOx is reduced. This is because in the low 02 region, NHs is generated from N compounds in the coal, and when it coexists with NOx, a denitrification reaction occurs that reduces NOx to N2. However, in the characteristic A in FIG. 4, the low Ox region is short and there is a region where the G2 concentration increases next. This is because secondary air G2 and tertiary air G3 are mixed, and Gl /G2 =
Condition 2 indicates that these airs are mixed quickly.

As a result, as shown in FIG. 5, the NOx concentration tends to increase as 02 increases. This is because the oxidation reaction of N Hs existing in the low 02 region to NOx progresses, and
This is because the N compounds contained in the char are converted to NOx. Therefore, under the condition of G s / G 2 = 2, the furnace outlet N Ox = 200 ppm.
The effect of reducing Ox is small.

On the other hand, the characteristic of B in FIGS. 4 and 5 is Gi/G! =
The test results under the condition of 3 are shown, and by increasing the tertiary air amount G3, the low 0 rich region can be maintained for a long time as shown in FIG.

As a result, as shown in FIG.
The reduction reaction progresses, and the NOx concentration becomes Gs/G* of A.
= 2, it decreases significantly.

Further, as shown in FIG. 4, even at a position where the G2 concentration increases due to mixing of secondary and tertiary air, the increase in NOx can be reduced. This means that N coexisting in the low 0■ region
Since Hs is consumed in the reduction of NOx, the amount of NHsO is small at the location where air is mixed, so it is oxidized and reduced to NOx.
The amount of N in the char decreases, and the longer low 02 region lengthens the combustion time of the char.The ratio of N in the char released into the gas also increases, and the N in the char increases. This is due to the fact that the amount of NOx generated also decreases. Under this condition of G3/G2=3, the furnace outlet NOx value is 110
0 pp') N to 1/2 for the condition of Gs/G2=2
It became possible to reduce Ox. Furthermore, G3/G 2 =
The curve C in Figures 4 and 5 shows the results measured under the conditions of 4 and shows changes in the 02 concentration and NOx concentration.As G3 increases, the ejection speed of G3 increases, and the momentum of G3 increases. Therefore, the low 02 region on the central axis of Q1, which is separated from the fuel in the center and is slow to mix, can be maintained for a longer period of time, promoting the NOx reduction reaction, and reducing the
Ox became 'y o p pm. That is, G s
/ G * > 2 by controlling 03 and 02 to achieve low NOx, and these operations can be easily achieved by simply changing the angles of the secondary air and tertiary air registers. can do.

Next, from the results under each of these conditions A-C, the position where secondary and tertiary air mixes (
When the positions (■ to ■ in FIG. 4) are arranged in relation to the slow draw diameter D3 of the tertiary air nozzle 3, they can be expressed as follows. First, under condition A, X/Ds=2, and under condition B, X/D
3 in s and 4 in X/D s in the C condition. Therefore, increasing G s / G 2 means X /
In order to achieve low NOx combustion, it is necessary to increase Ds, and according to the study results of the present inventors, it is necessary to make Gs/G*>3 or more and to set the conditions of X/D3>3. .

Also, from Figures 2 and 3, the conditions for X/D3 are:
The angle of the deflector plate 5 of the secondary air jet nozzle 2 is 10 to 65.
The deflection plate 6 of the tertiary air jet nozzle 3 has an angle of 10 degrees or more. Therefore, when the deflection plate has these angles, low NOx combustion can be efficiently achieved.

Furthermore, the reason why the swirler 7.8 is provided in the secondary air nozzle 2 and the tertiary air nozzle 3 mentioned above is that the pulverized coal is combusted by the primary air under low air ratio conditions, and the flame and the secondary and tertiary air nozzles are
The following elements are necessary for proper mixing of air.
When there are no swirlers 7 and 8 and the swirling flow is not ejected, secondary air is used.

Mixing of tertiary air becomes faster. Therefore, the swirler also has the effect of slowing down the mixing of the secondary and tertiary air and the pulverized coal combustion flame between the baffle plates.

〔Effect of the invention〕

According to the present invention, the ignitability of pulverized coal is improved, the flame holding effect is increased, and the N O of 100 pl) I11 or less is
It has a low NOx effect with x generation amount, and has a secondary air, 3
Since the amount of NOx generated can be controlled simply by controlling the amount of air, it is easy to respond to emergencies such as photochemical smog warnings, and this can greatly contribute to improving reliability.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a pulverized coal burner for explaining the combustion control method of the present invention, and Figs. 2 and 3 show the angle and angle of the baffle plate.
FIGS. 4 and 5 are diagrams showing the relationship between the diffusion position of secondary air to the center of combustion personnel, and diagrams showing combustion characteristics depending on the distribution of tertiary air amount and secondary air amount. 1... Primary air and pulverized coal mixed fluid ejection nozzle, 2.
. . . Secondary air jet nozzle, 3… Tertiary air jet nozzle, 4… Flame holder, 5, 6… Deflector plate, 7.8-Swirl device, 9… Auxiliary fuel nozzle. Agent Patent Attorney Tatsuyuki Unuma Ratio 1 Kasumi Ratio 2 Kasumi Ukera Suzuki (A) Souse Neuchi (Sho) Su/Me (-La Continued on Page 1 0 Inventor Norio Arashi Ichiyuki Hitachi Town: In-house @ inventor Ken Soma - Hitachi Wheels: In-house [phase] Inventor Higashiyama Partner Hitachi Wheel: In-house 0 Inventor Kaoru Otsuka Hitachi Wheel: In-house [phase] Inventor Takao Hishinuma Hitachi City Visit: In-house @ inventor government I Tadahisa 61 Tsuba, Kure City

Claims (1)

[Claims] 1. A mixed flow jetting nozzle having a flame stabilizer at the tip in the jetting direction and spouting a mixed flow of primary air and pulverized coal, and a mixed flow jetting nozzle provided around the outer periphery of the mixed flow jetting nozzle. In a pulverized coal combustion burner equipped with a secondary air jet nozzle and a tertiary air jet nozzle provided around the outer periphery of the secondary air jet nozzle, the tip of the secondary air jet nozzle in the jet direction; A pulverized coal combustion burner characterized in that K and K are provided at the tip of the tertiary air jet nozzle in the jetting direction, and a baffle plate whose inner diameter gradually increases in the jetting direction. 2. Claim 1, characterized in that the deflection plate provided on the secondary air jet nozzle is inclined outwardly at an angle of 10 to 65 degrees with respect to the axial direction of the nozzle. pulverized coal combustion burner. 3. The pulverized coal according to claim 1, wherein the deflection plate provided on the tertiary air jet nozzle is inclined at an angle of 10 degrees or more with respect to the axial direction of the nozzle. combustion burner. 4. A mixed flow jetting nozzle that has a flame stabilizer at the tip in the jetting direction and spouts a mixed flow of primary air and pulverized coal, and a secondary air jetting nozzle provided around the outer periphery of this mixed flow jetting nozzle. and a tertiary air jet nozzle provided around the outer periphery of the secondary air jet nozzle, in which the tip of the secondary air jet in the jetting direction and the tertiary air jet nozzle are A deflector plate whose inner diameter gradually increases in the direction of ejection is provided at the tip of each ejection nozzle in the ejection direction, and the distribution of the tertiary air amount G3 and the secondary air amount G2 (
G3/G2) is controlled to be 3 or more, and the diameter D3 of the tertiary air jet nozzle and the distance in the jet direction from the burner surface
A method of operating a pulverized coal burner, characterized in that tertiary air is mixed and diffused with fuel ejected from other nozzles in a region where X/D3 expressed by the relationship is 3 or more.