JPH0452414A - Air supplier for combustion - Google Patents

Abstract

PURPOSE:To achieve reduction of NOx and drastically reduce the quantity of discharge of unburned portion by forming a central air channel in a wind box which enters an air supply port that opens in the furnace wall of a combustion device and two concentric annular air channels and installing an air flow control device at the inlet of the air channel. CONSTITUTION:A the center of an air supplier 5 a cylindrical body 31 is arranged, and to the other end of the cylindrical body 31 a sleeve 33 for adjusting air volume and an operation handle 34 are attached to form a primary air channel 32. A cylindrical body 16 is supported by the cylindrical body 31 and is arranged on the same axis as that of the cylindrical body 31 in an annular shape. Between a support plate 17 of the cylindrical body 16 and a support end plate 18 supported by the cylindrical body 31 a secondary air channel 25 is formed, and at the inlet section of this channel 25 a plurality of guide vanes 19 are arranged radially with the central axis of the cylindrical body 31 and cylindrical body 16 as its center. Between the guide vane 19 and a support plate 23 installed in the radial direction of the cylindrical body 16 a tertiary air channel 24 is formed in an annular shape. At the inlet section of this tertiary air channel 24 a plurality of guide vanes 26 area arranged and they are radially arranged with the central axis of the cylindrical bodies 31 and 16 as their center simile to the guide vanes 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a device for supplying combustion air to a combustion device, and particularly relates to a device for supplying combustion air to a combustion device, and in particular to a device for supplying combustion air to a combustion device. Regarding the supply device.

[Prior Art] Nitrogen oxides (hereinafter referred to as rNOx) are one of the air pollutants, and methods are being attempted to reduce the amount of nitrogen oxides emitted from various combustion devices as much as possible. This NOx reduction method includes a two-stage combustion method and an in-furnace denitrification combustion method based on an enhanced two-stage combustion method.

Figure 2 (a) shows the case where the two-stage combustion method is implemented in a large boiler for business use, and burners 2, 3, 4 and after air port 5 are arranged in order from the bottom of the furnace against the wall 1a of the boiler main body 1.
An air supply device called . In this boiler body 1, for example, the air ratio of the burner 2.3.4 is set to 1.0.
As follows, the combustion temperature of the fuel is lowered, thereby preventing the generation of so-called thermal NOx, and then this low NOx
The unburned components of the fuel produced by the combustion are combusted by the combustion air supplied from the after-air port 5, thereby reducing the unburned components content in the combustion exhaust gas.

FIG. 2(b) is a sectional view specifically showing the structure of this air supply device. In FIG. An air swirler 11 is installed in which a plurality of guide vanes 10 are attached radially around the centerline 9.

The combustion air A flowing into the wind box 6 at the after air port 5 is given an appropriate swirling force by the air swirler 11 by installing each guide vane 10 at a predetermined angle and turning it on. and injected into the furnace 12. Reference numeral 13 in the figure indicates an angle adjusting rod for mounting the guide vane 10;
15 is a link connecting each guide vane 10, and 15 is a handle for rotating the rod.

In the above device, in order to properly burn the unburned matter produced by low NOx combustion, it goes without saying that the combustion air supplied from the after air port 5 must be mixed well with the exhaust gas or flame resulting from low NOx combustion. It is assumed that

However, the furnace 12 of the boiler body l has a rectangular shape in plan view, and even if a large number of after air ports 5 are installed, as shown in the cross section of the furnace 12 in FIG. Alternatively, a gap 5a for air supplied from the after air port 5 is created at the corner of the furnace 12. For this reason, the combustion gas and flame pass through the gap 5a due to the strong upward force, and the mixing of unburned matter and air is significantly reduced. In other words, a gap 5a is created between adjacent after-air ports 5 in which air is not injected, resulting in a decrease in the efficiency of unburned fuel combustion.

Such a state causes a serious problem such as smoke color when a combustion burner stage with a particularly low air ratio (air excess ratio) is provided, such as in the case of in-furnace denitrification.

It should be noted that supplying a large amount of combustion air so as not to create air injection gaps 5a is effective from the viewpoint of combustion of unburned substances, but it is not preferable because a large amount of NOx is generated during this combustion.

In order to improve the drawbacks of the above-mentioned burner,
No. 9714 has an air supply device shown in FIG.

The air supply device (after air port) 5 shown in FIG. 3 consists of an air passage 26 for a straight air flow 23 and an air passage 27 for a swirling air flow 25. The air flow rate of the air passage 26 is adjusted by a damper 22. In this way, the amount of air supplied to the center and wall portions of the furnace 12 is distributed and controlled. Therefore, gaps 5a (FIG. 2(C)) of air supplied from the after air ports 5 are less likely to occur between the after air ports 5 or at the corners of the furnace 12.

[Problems to be Solved by the Invention] However, even in the invention described in JP-A-59-109714, air gaps 5a may occur in the furnace 12 when the fuel load becomes small.

For example, as the fuel load decreases, the air/fuel ratio decreases;
The air flow rate to the swirling flow 25 portion of the after air port 5 may be insufficient.

In view of the above-mentioned problems, an object of the present invention is to constantly reduce the air injection gap even if there are large fluctuations in the fuel load,
An object of the present invention is to provide an air supply device that can satisfactorily mix combustion air and unburned matter.

[Means to solve the problem] The above object of the present invention is achieved by the following configuration.

In other words, in a combustion air supply device that supplies combustion air downstream of the flame and exhaust gas flow in the combustion device and burns unburned content contained in the flame and exhaust gas, an opening in the furnace wall of the combustion device is used. A combustion air supply device in which a central air passage and two annular air passages are formed coaxially with the central air passage in a wind box facing the air supply port, and an air circulation control means is attached to the entrance of each air passage. , is.

[Function] The air supply ports, which are formed in a coaxial annular shape in at least three stages of a large-diameter portion, a medium-diameter portion, and a small-diameter portion, change the air supply port to be used in response to changes in the air supply amount, and Since a high air injection speed is always ensured regardless of the supply amount, and the amount of air supplied to each air supply port can be adjusted, air injection gaps can be eliminated.

[Example code] Examples of the present invention will be described below.

A sectional view of the air supply device 5 is shown in FIG. 1(a).

A cylindrical body 31 is arranged in the center of the air supply device 5, and its open end has a constriction structure 35 to increase the penetrating force of the air flow, and the cylinder body 31 has a cylindrical body 31 so as to be located approximately at the center of the air port 8 provided in the furnace wall 7. Deploy. The other end of this cylindrical body 31 is an air amount adjusting sleeve 3.
3 and an operating handle 34 for operating the sleeve 33, forming a primary air passage 32. The cylindrical body 16 is supported by the cylindrical body 31 and arranged in an annular shape on the same axis as the cylindrical body 31. The distal end of the cylindrical body 16 has a guide sleeve 29 which has an angle substantially equal to the opening angle of the air port 8 and expands in the same direction in order to increase the swirling force of the air flow. A support plate 17 is attached to the other end of the cylinder 16, and a secondary air passage 25 is formed between the support plate 17 and the support end plate 18 supported by the cylinder 31. A plurality of guide vanes 19 are provided at the entrance of the passage 25.
are arranged radially around the central axes of the cylinders 31 and 16. And the guide vane 19 is the rod 20
The rod 20 passes through the support plate 17 and the support end plate 18 coaxially with the cylinder 16, and is attached to the air supply device. The rod 20 is the air supply device 5
It has a handle 21 that can be operated from the outside. The mounting angle of the guide vane 19 can be adjusted using a handle 21.

Next, a nozzle body 22 having approximately the same diameter as the air port 8 is formed on the side wall surface of the wind box 6 of the furnace wall 7.
2 and a support plate 23 formed on the outer periphery of the cylinder 16 and attached in the radial direction of the cylinder 16.
4 is formed into a ring shape. A plurality of guide vanes 26 are arranged at the entrance of the tertiary passage 24, and like the aforementioned guide vanes 19, they are arranged radially around the central axis of the cylinder 31.16. The installation angle of these guide vanes 26 is determined by the rod 27 which is installed through the air supply device 5.
It is adjusted by the handle 28.

In the above device, when the load on the combustion device is relatively small, the installation of the guide vane 26 changes the angle to close the tertiary air passage 24 and opens the air adjustment sleeve 33 and the guide vane 26, thereby causing combustion. All of the air A reaches the guide vane 19 and the secondary air passage 25 and primary air passage 32 in the cylinder 31 and is injected at high speed from the cylinder 16.31 having a smaller diameter than the air port 8. At this time, the air from the secondary air passage 25 becomes a wide-angle air flow along the furnace wall in relation to the guide sleeve 29. This situation is shown in Fig. 1(c).For this reason, the combustion air A has a high penetrating force even though the injection amount is small, and it is blown into the intense upward flow of flame and exhaust gas and is effectively absorbed by the unburned components. Mix. At the same time, although the injection amount is small, the air from the secondary air passage 25 forms a wide-angle air flow along the furnace wall, so the air jet gap 5a (see Fig. 2 (c)
) does not occur.

Next, when the load of the combustion device is large and an air gap 5a is created, the air adjustment sleeve 33 of the primary air passage 32
is opened, and the guide vane 26 of the secondary air passage 25 is also opened,
In addition to the air with high penetration power being injected from the cylinder 16.31, combustion air is also injected from the tertiary air passage 24. In this case, the air injected from the tertiary air passage 24 is injected into the furnace from the annular injection port, and the air is injected into the furnace from the guide sleeve 29.
Due to this relationship, the diffusion force becomes high, and no air jet gap 5a is created.

At low load, when the injection amount of combustion air A is small and the air injection gap 5a is large, the guide vane 19 is closed and the air supply from the secondary air passage 25 is stopped because a high diffusion force is required. , the combustion air may be supplied from the primary air passage 32 and the tertiary air passage 24. The situation is shown in FIG. 1(b).

[Effects of the invention] By carrying out this invention, the injection force of combustion air can be maintained at a high level regardless of the load on the combustion device, and the dispersion force can be maintained strongly, so that air gaps are not created within the combustion device. , it is possible to combust unburned components satisfactorily, achieve low NOx emissions, and significantly reduce the amount of unburned components discharged.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of the air supply device according to the present invention, and FIG. 1(b) shows the state of air flow by the air supply device, with the secondary air passage being narrowed. Figure 1 (C
) shows the state in which the tertiary air passage is constricted, Figure 2 (a)
Figure 2(b) is a cross-sectional view of the boiler showing the state of two-stage combustion.
2 is a sectional view of a conventional air supply device, and FIG. 2(c) shows the flow of air into the furnace by the conventional air supply device. FIG. 3 is a sectional view of a conventional air supply device. 5... Air supply device, 6... Wind box, 7... Furnace wall,
8... Air supply port, 19.26... Guide vane, 24...
... Primary air passage (annular air passage), 25... Secondary air passage (annular air passage), 32... Tertiary air passage (center air passage), 33... Air adjustment sleeve Applicant Babcock Hitachi Co., Ltd. Agent Patent attorney Takayoshi Matsunaga Figure 2 (b,') (c) (a) (a) Figure 2 (b)

Claims (1)

[Scope of Claim] A combustion air supply device for supplying combustion air downstream of the flow of flame and exhaust gas in a combustion device to burn unburned content contained in the flame and exhaust gas, comprising: a furnace of the combustion device; A central air passage and two annular air passages coaxial with the central air passage are formed in the wind box facing the air supply opening opened in the wall, and an air flow control means is attached to the entrance of each air passage. A combustion air supply device characterized by: