JPS62268904A - Combustion apparatus for steam generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Regarding combustion equipment.

It is well known that in a steam generator furnace, fuel is combusted from each corner of the furnace having a substantially rectangular cross section in a tangential direction to an imaginary combustion circle set at the center of the furnace. ing. In addition to the primary air carrying the pulverized coal, auxiliary air is then introduced with the fuel immediately adjacent to the fuel nozzle. A secondary air nozzle is provided between each of the plurality of fuel combustion positions in the height of the furnace, and these secondary air nozzles supply the remaining air necessary for complete combustion of the fuel within the furnace.

In such a spiral combustion device, the burner is tilted upward or downward during operation to change the position of the fireball in the furnace,
It is also known to modify the effective furnace dimensions thereby. Such methods are very useful for steam temperature control because they alter the heat distribution between the furnace and its downstream convection surface.

This upward angular combustion can thus reduce the amount of excess air required for fuel and air. This can also slow combustion and reduce the amount of nitrogen oxides produced.

However, the swirling of the gas in the furnace causes
This gives rise to some undesirable problems.

For example, if the swirl becomes too high, a downdraft core forms in the center of the furnace. The swirl also causes distribution of the gas leaving the furnace, thereby creating a temperature imbalance at the downstream heating surface across which the gas flows. Furthermore, if the spiral is too small,
Because the combustion gas lacks tangential momentum, the fireball becomes unstable.

Therefore, in crawling combustion, it is desirable to maximize the mixing of fuel and air at all of the plurality of fuel combustion locations while minimizing residual swirling of the furnace gases.

The present invention has been made in view of these circumstances.

The combustion device for a steam generator according to the invention includes a furnace with a substantially rectangular cross section. This furnace is equipped with a gas outlet at its top. The plurality of fuel nozzle devices provided at each of the plurality of fuel combustion positions in the height direction of the furnace are each oriented in a tangential direction with respect to the virtual vertical combustion cylinder within the furnace. In this case, according to the invention, the lowest fuel nozzle arrangement is oriented towards a virtual vertical combustion cylinder of relatively large diameter, and the other fuel nozzle arrangements become progressively smaller in order of their increasing position. Oriented against a virtual vertical combustion cylinder.

Thus, by significantly increasing the diameter of the virtual vertical combustion cylinder toward which the lowest fuel nozzle arrangement is directed, the mixing and tangential movement of the fuel and air within the furnace can be enhanced, respectively. The residual gas flow from this lower location then rotates through each fuel combustion location of increasing height above it, and is thus added by the newly introduced fuel at each of these higher fuel combustion locations. Mixing of fuel and air can be achieved by reducing the tangential movement caused by the fuel. At each of these high fuel combustion positions, the diameter of the virtual combustion cylinder toward which the fuel nozzle arrangement is directed is made progressively smaller, so that the necessary mixing is obtained without increasing the swirl existing in the furnace. In this way, good mixing can be obtained, reducing the amount of unburned carbon and reducing the amount of excess air required. Also, the amount of NOX and SO7 pollutants is reduced. This is because the amount of free oxygen used to form such pollutants in the combustion zone is reduced.

According to the method of introducing fuel as described above, slagging of the furnace can also be reduced.

This is because the upper fuel nozzle arrangement introduces the fuel in such a way that the fuel is less likely to be sprayed onto the furnace walls due to residual thinning in the furnace.

This will be explained in detail.

In FIG. 1, a furnace 10 having a substantially rectangular cross section is shown.
Fuel is introduced into the furnace from each corner by a plurality of fuel nozzle arrangements 50 and combusted.

Air is supplied to the furnace by a forced fan 12. That is, a portion of the air forced by the forced fan 12 flows through the mill air line 14 to the mill 16 and carries the pulverized coal produced by the mill. This fuel-air mixture is supplied to the four corners of the furnace 10 through fuel-air lines 18 and 20 and then introduced into the furnace through fuel nozzle arrangements 50 at each corner.

Air worms flowing through the aforementioned line 14 are connected to the mill 1
Sufficient pawls are provided to dry the coal in 6 and keep it suspended throughout the flow through lines [8 and 20. The remaining air needed for combustion flows through secondary air lines 22 and 24;
Then # to Burna? Most of this secondary air is introduced into the furnace through a wind box (not shown) installed in contact with the fuel nozzle devices 50, and between each of the plurality of fuel nozzle devices 50, and between the fuel nozzle devices on the uppermost stage and the fuel on the lowermost stage. The secondary air is introduced into the furnace through a plurality of secondary air nozzles each installed below the nozzle device. A portion of the secondary air flowing through line 22 is directed to the fuel-air nozzle 3 shown in FIG.
0 and introduced separately. The distribution ratio of secondary air to secondary air nozzle 60 and fuel-air nozzle 30 is adjusted by any suitable method known in the art to obtain optimum furnace performance.

The walls of the furnace 10 are formed by a number of vertical tubes 32. These vertical tubes 32 are tubes for generating steam therein. An opening 34 is also provided at the top of the furnace 10 as an outlet for combustion gases.

The fuel and air are each introduced tangentially to the imaginary circle in the center of the furnace, thereby providing a rotating motion or swirl of the combustion gases as they flow upwardly toward the outlet opening 34.

FIG. 2 shows details of a fuel nozzle arrangement 50, indicated generally by the reference numeral 50. FIG. This fuel nozzle device 5
0 is formed by two fuel-air nozzles 30 and one fuel nozzle 40. A plurality of fuel nozzle devices 50 are provided along the height direction of the furnace, and a secondary air nozzle 60 is provided between them. Each of these nozzles 30, 40, 60 is generally oriented tangentially to a virtual combustion circle (more specifically a virtual vertical combustion cylinder, since the nozzles are vertically tiltable) within the furnace. There is.

In this case, according to the invention, a plurality of fuel nozzle devices 50
are oriented tangentially to cylinders of different diameters, as will be described in detail later.

And, according to a preferred embodiment, the plurality of secondary air nozzles 60 are all oriented tangentially to a vertical cylinder of the same size. Each nozzle 30° 40, 60 is
Thus, even when tilted upwards or downwards, it remains oriented tangentially to its associated identical cylinder.

FIG. 3 shows the direction of fuel and air introduction at various positions in the height of the furnace. For simplicity of illustration, FIG. 3 shows only two diagonally opposite corners of the furnace, and only circles are shown to represent each vertical cylinder.

Thus, the plurality of fuel nozzle devices are arranged in order from the bottom in the height direction of the furnace, reference numeral 51.52°F)3.
54.56. The fuel nozzle device 51 located at the bottom injects fuel tangentially to the virtual vertical combustion cylinder 71 inside the furnace. Similarly, the fuel nozzle devices 52 to 56 inject fuel tangentially to the virtual vertical combustion cylinders 72 to 76, respectively. In this case, as clearly shown in FIG. 3, the fuel is distributed over a plurality of cylindrical shapes 71 to 76 whose diameters gradually become smaller as they move upward in the height direction of the furnace. and are ejected in tangential directions. However, although portion 76 is described as cylindrical for purposes of illustration, its diameter is actually 10.

On the other hand, the secondary air nozzles 61 to 67 are
The secondary air is ejected in a tangential direction to the virtual vertical cylinders 81 to 87. Therefore, in the following description, each virtual cylinder of the secondary air nozzles 61 to 67 is shown. ``80j'' is used as a common reference symbol.

FIGS. 4(a)-(f) are cross-sections at various positions in the height direction of the furnace, and clearly show the relationship between the various fuel-burning cylinder shapes at each height position.

Thus, at the lowest height position shown in FIG. 4(a), the diameter of the fuel combustion cylinder 7[ is larger than the diameter of the secondary air cylinder 80. Even at the height position shown in FIG. 4(b), the diameter of the fuel combustion cylinder 72 is larger than the diameter of the secondary air cylinder 80.

However, at the height shown in FIG. 4C, the diameter of the fuel combustion cylinder 73 is substantially equal to the diameter of the secondary air cylinder 80. Then, at each height position shown in FIGS. 4(cl) and (e), the root diameters of the fuel combustion cylinders 74 and 75 are each smaller than the diameter of the secondary air cylinder 80. At the highest position shown in FIG. 4(f), the fuel burning cylinder 76
The diameter of is zero, and the secondary air cylinder 'E2 Rn5n T
1. ) l"+ j, hz9', ?"+ zh
Thick L+ Again in FIGS. 4(a)-4(e), line 38 is a line extending from a particular nozzle position in the furnace corner to the centerline of the furnace. 17. The air-related deflection angle 40 and the fuel-related deflection angles 41-46 correspond to the direction of air and fuel introduction directed tangentially to the associated virtual vertical cylinder in the furnace from a particular nozzle position in the furnace corner. This is the angle that indicates how far the direction deviates from line 38. According to the prior art, these deviation angles were all about 6°.

Therefore, in order not to change the gas thin winding formed in the furnace, the air introduction deviation angle 40 should be kept at 6 degrees.
The fuel introduction bias angles 41 to 46 are each sequentially 12 degrees,
10', 8°, 4°, 2°, and 0° are in operation. However, increased mixing of fuel and air is obtained at the higher elevations due to residual swirling from the lower elevations, resulting in reduced swirling and therefore improved furnace exit gas flow distribution. This can be easily obtained without reducing the mixing capacity of the combustible furnace. Therefore, the air introduction bias angle 40 remains 6 degrees, and the fuel introduction bias angles 41 to 46 are 10 degrees, 8 degrees, and 6 degrees, respectively.
9°.

The optimum angles are 5.6°, 4°, and 2°.

These deflection angles always remain constant regardless of whether the nozzle is tilted vertically upwards or downwards. Increased mixing is then obtained as the fuel and air ejected from the upper nozzles enter the vortex in the furnace. Furthermore, since less fuel is sprayed onto the furnace wall, slagging caused by fuel introduced from the upper nozzle is also reduced.

As is clear from the above explanation, according to the present invention,
Improved furnace performance is obtained, and at the same time gas swirling within the furnace is reduced, thus making the undesirable problems of spiral combustion devices less common than in the past.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a combustion device for a steam generator according to the present invention, FIG. 2 is a view showing a part of the fuel and secondary air nozzle part, and FIG. 3 is a diagram showing various points in the height direction of the furnace. Figure 4 showing the fuel and secondary air introduction section at the position of
Figures (a) to (D) are diagrams showing cross sections at various height positions of the furnace. 10. Furnace, 12. Forced fan, 14. Mill air line, 16. Mill, 18. 20...Fuel-air line, 22.24...Secondary air line, 30...Fuel-air nozzle, 32...Vertical pipe, 34...Outlet opening, 38...
Line extending from the nozzle to the furnace center line, 40...Secondary air introduction bias angle, 41-46...Fuel introduction bias angle, 50-5
6. Fuel nozzle device, 60-67. Secondary air nozzle, 71-76. Virtual vertical combustion cylinder, 80-87.
Virtual vertical air cylinder. Fig, 2

Claims (1)

[Claims] a furnace having a substantially rectangular cross-section, a gas outlet in the top of the furnace, a number of tubes forming the walls of the furnace, and a plurality of fuel combustion locations in the height of the furnace; A plurality of secondary air introduction positions provided between these fuel combustion positions, and a plurality of secondary air introduction positions provided at each of the fuel combustion positions, the fuel being ejected in a tangential direction to a virtual vertical combustion cylinder set in the furnace. and a plurality of secondary air nozzles that eject secondary air in a tangential direction to a virtual vertical air cylinder set in the furnace, and the plurality of fuel nozzle devices include: A combustion device for a steam generator, characterized in that fuel is injected into the virtual vertical combustion cylinder which becomes smaller in order of height.