JPH10339407A - Combustion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply low pressure secondary air without the reduction of pressure and utilize energy of high pressure primary air for the promotion of mixing of two-stage combustion air. SOLUTION: The present combustion apparatus is adapted such that high pressure air 23 and low pressure air 26 are fed from a two-stage combustion air introduction hole 13 disposed on an upper part of a burner 4 into a furnace. Part combustion air with which fine powdered coal 3 is dried and entrained is fed into a furnace 5 from the two-stage combustion air introduction hole 13 as high pressure air 21, and the low pressure air 26 lower in pressure than the high pressure air 23 is introduced into the furnace 5 from the two-stage combustion air introduction hole 13 simultaneously with the high pressure air 21. Further, the combustion apparatus includes separate individual air introduction holes for high and lower pressure airs as the two-stage combustion air introduction hole 13. The air introduction holes are alternately disposed in the width direction of the furnace or are disposed into a multi-stage in the height direction of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus, and more particularly to a combustion apparatus suitable for performing low NOx combustion by two-stage combustion and reducing unburned components.

[0002]

2. Description of the Related Art Two-stage combustion systems are widely applied for low NOx combustion. FIG. 10 shows an air system of a general two-stage combustion system in a pulverized coal combustion boiler. Primary air for drying and conveying the pulverized coal is supplied by a primary air fan 1. After the primary air is heated to a predetermined temperature by the air preheater 2, it is introduced into a pulverized coal machine (mill) 3, where the pulverized coal is dried and conveyed to a furnace 5 through a burner 4.

On the other hand, combustion air (secondary air) is supplied by a forced air fan 6. Secondary air is air preheater 2
After being warmed to a predetermined temperature in the burner 4, it is supplied to the burner wind box 9 and the two-stage combustion wind box 12 through the wind path 7,
And it is introduce | transduced into a furnace from the air inlet 13 for two-stage combustion.
In the two-stage combustion system, the total amount of the primary air and the secondary air supplied from the burner 4 is generally smaller than the theoretical air flow rate, and the remaining air required for complete combustion is the two-stage combustion in addition to the excess air supply. It is supplied from the air inlet 13.

[0004] Therefore, unburned components are generated in the combustion gas due to the flow rate of the air supplied from the burner 4, and in order to promote complete combustion of the unburned components, the two-stage combustion air is sufficiently supplied in the furnace. Must be mixed. To this end, it is common practice to increase the pressure of the two-stage combustion air box 12 by making the pressure of the two-stage combustion air box 12 higher than the pressure of the burner wind box 9. As a result, in FIG. 10, low-pressure air is supplied to the burner wind box 9 by reducing the pressure of the high-pressure air supplied from the wind path 7 at a high pressure by the burner air damper 8. Such a pressure loss due to the burner air damper 8 is an energy loss.

In some cases, a boost-up fan 10 is provided in the two-stage combustion air system. FIG. 11 shows an example in which the boost-up fan 10 is used. A part of the low-pressure air supplied at a low pressure from the wind path 7 branches and flows into the wind path to the two-stage combustion wind box 12, and the boost-up fan 10
After being pressurized, the air is supplied to the two-stage combustion air box 12, becomes high-pressure air, and is introduced into the furnace 5 from the two-stage combustion air inlet 13.

In the conventional example shown in FIG. 11, the pressure of only the two-stage combustion air can be increased without giving any resistance to the secondary air system on the burner side. Can be suppressed.

However, the temperature of the two-stage combustion air is increased by the air preheater 2 because it is injected into the fireway, and the power of the boost-up fan 10 becomes excessive due to an increase in the volume flow rate.

[0008]

In the example shown in FIG. 10, the pressure loss of the air damper for the burner directly becomes an energy loss.

In the example of FIG. 11, energy loss due to pressure loss on the burner side is suppressed, but the pressure of the two-stage combustion air is increased after the temperature is increased by the air preheater 2, so that the volume flow rate is reduced. The increase in fan power accompanying the increase cannot be ignored, and as a result, there is no much difference from the energy loss in the example of FIG.

[0010]

In order to solve the above problems, the present invention mainly employs the following configuration.

A high-pressure air supply system for supplying primary air for pulverized coal to be conveyed to a burner for combustion by a burner, and a low-pressure air having a lower pressure than the high-pressure air to a burner wind box. In a combustion device provided with a low-pressure air supply system and a means for charging the two-stage combustion air downstream of the burner in the fire path, the means for charging the two-stage combustion air includes the high-pressure air supply system and A combustion device provided with a system for supplying a part of high-pressure air and low-pressure air from the low-pressure air supply system.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a configuration relating to an air system of a combustion apparatus according to an embodiment of the present invention. In FIG.
1 is a primary air fan, 2 is an air preheater, 3 is a mill, 4 is a burner, 5 is a furnace, 6 is a forced air fan, 7 is a wind path, 8
Is a burner air damper, 9 is a burner wind box, 13 is a two-stage combustion air inlet, 21 is a two-stage combustion high-pressure air supply system, 22 is a two-stage combustion high-pressure air damper, and 23 is a two-stage combustion. High-pressure side wind box, 24 is a low-pressure side air supply system for two-stage combustion,
25 denotes a low pressure air damper for two-stage combustion, and 26 denotes a low pressure side wind box for two-stage combustion. In addition, the two-stage combustion air inlets 13 are usually provided directly above the burners 4 respectively.

Although the overall configuration of the air system of the combustion apparatus shown in FIG. 1 is similar in basic configuration to the configuration of the air system of the prior art shown in FIG. 10, the embodiment of the present invention is based on the technology described below. There is a characteristic in the subject matter.

A part of the primary air from the primary air fan 1 is branched before being supplied to the mill 3 and is subjected to a two-stage combustion through a dedicated two-stage combustion high-pressure air supply system 21 as high-pressure two-stage combustion air. Is introduced into the high pressure side wind box 23.

On the other hand, part of the low-pressure secondary air from the forced air fan 6 is branched and introduced into the two-stage combustion low-pressure side wind box 26. The air flow rate of each of the high-pressure side wind box 23 and the low-pressure side wind box 26 is adjusted and controlled by the two-stage combustion high-pressure air damper 22 and the two-stage combustion low-pressure air damper 25.

FIG. 2 shows the structure around the two-stage combustion air inlet 13 unique to this embodiment. As shown in FIG. 2, the wind box includes a high-pressure side wind box 23 for two-stage combustion and a low-pressure side wind box 26 for two-stage combustion.
Is divided into The two-stage combustion high pressure side air box 23 is supplied from the two-stage combustion high pressure side air supply system 21, and the two-stage combustion low pressure side wind box 26 is supplied from the two-stage combustion low pressure side air supply system 24. Air is respectively supplied.

The high-pressure side air 21 ′ from the high-pressure side air supply system 21 for the two-stage combustion is supplied from the high-pressure side wind box 23 for the two-stage combustion through the inner-stage air intake 27 for the two-stage combustion. After being guided to the cylinder 28, it is put into the furnace 5. The low-pressure side air 24 ′ from the two-stage combustion low-pressure side air supply system 24 is supplied from the two-stage combustion low-pressure side wind box 26 to the two-stage combustion peripheral air inlet 30 provided at the two-stage combustion peripheral air inlet 30. 2
After being turned by 9, it is put into the furnace 5.

Before describing the effects of the present embodiment, the flow pattern of the ascending gas in the furnace in a combustion device performing two-stage combustion will be described with reference to FIGS. 3 (a) and 3 (b). Since the jet of the burner 4 collides with the opposing jet at the center of the furnace 5, the rising gas flow velocity becomes the highest at the center of the furnace when viewed from the side of the furnace. In particular, such a phenomenon is illustrated in FIG.
It is shown in a side view.

On the other hand, in the furnace width direction, the highest ascending flow velocity is obtained immediately above the burner. Such a phenomenon is particularly shown in the front view of FIG. As shown in FIG. 4, the two-stage combustion air is bent toward the upper part of the furnace at the downstream side of the gas flow as shown in FIG. 4 by the rising gas flow rising from the burner side. (A)
As shown in FIG. 4, the higher the flow velocity of the two-stage combustion air jet, the harder it is to bend, and as shown in FIG. 4B, the lower the flow velocity of the two-stage combustion air jet, the easier it is to bend. That is, in the vicinity of the center of the fire path where the flow velocity of the two-stage combustion air jet is the slowest, the mixing of the rising gas flow rising from the burner side and the two-stage combustion air is the worst. Therefore, it is necessary to supply the two-stage combustion air further to the center of the furnace to promote the mixing, and for this purpose, it is necessary to increase the flow velocity of the two-stage combustion air jet, and thus to increase the high-pressure two-stage combustion air. It is necessary to supply.

Therefore, according to the present embodiment, since the high-pressure air 21 'from the primary air fan 1 is supplied from the high-pressure side air supply system 21 for the two-stage combustion, the two-stage combustion air is supplied to the center of the fire path. Can be supplied up to. However, for example, the outlet pressure of the primary air fan 1 is about 1000
As high as mmAq, such a two-stage combustion air jet has no spread, and the mixing with the rising gas flow from the burner side is partially improved, but there are cases where slip-through portions occur. Therefore, in the present embodiment, the low-pressure side air 24 'is supplied together with the high-pressure side air 21' from the two-stage combustion air supply port 13.

FIG. 5 shows a flow pattern of the two-stage combustion air in the furnace in the embodiment of FIG. FIG. 5 is a side sectional view of a fireway. Since the inner peripheral high-pressure air jet 110 has a high flow velocity and does not swirl, the penetration force in the depth direction of the furnace 5 is high, and the mixing at the center of the furnace is promoted. On the other hand, the outer peripheral low-pressure air jet 111 has a spread due to swirling, and spreads around the inner peripheral high-pressure air jet 110, so that the outer peripheral low-pressure air jet 111 is mixed with the rising gas that tends to slip through without being mixed by the inner peripheral high-pressure air jet 110. Contribute. That is, it is possible to supply the two-stage combustion air suitable for the flow pattern of the rising gas in the fire path in FIG. As a result, it is possible to efficiently increase the mixing of the two-stage combustion air while minimizing the energy loss.

FIGS. 1, 2 and 6 show examples of two-stage combustion air inlets for ejecting high-pressure air and low-pressure air concentrically. High-pressure air and low-pressure air are supplied from separate inlets. FIG. 6 shows an example of ejection.

FIG. 6 shows another embodiment of the arrangement of the high-pressure side and low-pressure side two-stage combustion air inlets. Burner 4
A high-pressure side two-stage combustion air inlet 112 is provided immediately above the burner, and a low-pressure side two-stage combustion air inlet 113 is provided immediately above the burner and near the side wall 14. The reason why the low-pressure side two-stage combustion air inlet 113 is disposed near the side wall is that the high-pressure side two-stage combustion air inlet 112 is located directly above the burner.
Is disposed, but it is possible to prevent slippage from the side wall side. In addition, by disposing the high-pressure-side two-stage combustion air inlet 112 directly above the burner, the flow velocity just above the burner where the ascending speed is the highest is reduced, and the mixing is promoted.

FIG. 7 is a cross-sectional view of a fire path, and is an embodiment showing a structural example of the two-stage combustion air inlet shown in FIG.
The wind box is divided into a high pressure side wind box 23 for two-stage combustion and a low pressure side wind box 26 for two-stage combustion. The high-pressure side wind box 23 for the two-stage combustion is supplied from the high-pressure side air supply system 21 for the two-stage combustion as in FIG. 1, and the low-pressure side wind box 26 for the two-stage combustion is supplied with the low-pressure The two-stage combustion air is supplied from the side air supply system 24. The high-pressure side two-stage combustion air inlet 203 and the low-pressure side two-stage combustion air inlet 206 are arranged alternately in the width direction of the fire path.
From the high-pressure side air supply cylinder 202 for two-stage combustion, and is introduced into the furnace 5 from the high-pressure side air inlet 203 for two-stage combustion.

The low-pressure side air is swirled by the two-stage combustion low-pressure air swirler 205 from the two-stage combustion low-pressure side wind box 26, and is then injected into the furnace 5 through the two-stage combustion low-pressure air inlet 206. Is done. In this embodiment, the distance between the burners in the furnace width direction is long, and a single-type two-stage combustion air inlet in which high-pressure air and low-pressure air are concentrically ejected as shown in the embodiment of FIG. Is suitable for a case where the two-stage combustion air cannot be sufficiently mixed with the unburned gas immediately above the burner due to the low-pressure side outer air, and the two-stage combustion low-pressure air inlet 206 is connected to the burner. It is provided immediately above the burner and blows out low-pressure air so as to complement the jet from the high-pressure side air inlet 203 for two-stage combustion, thereby preventing the unburned gas from slipping through and mixing the unburned gas. Can be reduced.

FIG. 8 shows an air system of another embodiment of the combustion apparatus. The low-pressure air box 303 is provided in the upper part and the high-pressure air box 308 is provided in the lower part. The low-pressure air from the forced air fan 6 passes through the air preheater 2 to the burner box 9. After branching from the system of
r Air Port) The air is supplied to a low-pressure air box 303 via an air system 301 and an upper AAP air damper 302.

The high-pressure air from the primary air fan 1 passes through the air preheater 2, branches off from the system to the mill 3, and then passes through the lower AAP air system 306 and the lower AAP air damper 307. It is supplied from the side air wind box 308. Each air flow rate is controlled by inlet dampers 302, 307.
Adjusted by.

In the present embodiment, the rising gas containing the unburned portion and the two-stage combustion air are mixed and burned stepwise by being supplied in multiple stages. Here, if the supply is performed in one stage, combustion occurs in an oxygen-rich state, and NOx is easily generated. However, in the present embodiment, since the supply is performed in two stages, the oxygen-rich state can be suppressed, and NOx combustion can be performed.

Further, by feeding high-pressure side air which is hardly bent into the ascending gas flow in the furnace at the lower stage and low-pressure side air which is easily bent at the upper stage, the flow velocity of the rising gas flow at the center of the fire path can be suppressed. Unburnable components can be prevented from slipping through.

FIG. 9 shows an embodiment of a method for controlling two-stage combustion air. Here, the two-stage combustion air flow rate when the combustion load is 100% is set to 100%. The higher the combustion load, the higher the ascending gas flow rate in the furnace at the two-stage combustion air input position. Therefore, in order to ensure mixing performance, the higher the load, the higher the penetration force of the two-stage combustion air must be. Further, when the combustion load is reduced, the flow velocity of the ascending gas in the fire path is reduced, so that the amount of high-pressure air can be reduced.

In this embodiment, the ratio of the high-pressure side air flow rate to the total two-stage combustion air flow rate is increased as the load increases, and only the low-pressure side air is supplied at a low load of 50% or less. doing. As a result, the mixing performance of the two-stage combustion air is ensured in the entire load range, the load is reduced, and the high-pressure side air flow rate is reduced, thereby reducing energy consumption. Further, not only the flow rate ratio between the high-pressure air and the low-pressure air is changed according to the combustion load, but also the flow rate itself is increased or decreased.

As described above, according to the present invention, since the two-stage combustion air is supplied without decompression, energy loss can be minimized and mixing of the two-stage combustion air can be ensured.

[0033]

According to the present invention, since the mixing of the two-stage combustion air can be ensured while minimizing the energy loss, a highly efficient combustion apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an air system of a combustion device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a two-stage combustion air inlet relating to an air system of a combustion device according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a flow velocity distribution of ascending gas in a furnace at a two-stage combustion air charging position.

FIG. 4 is an explanatory view showing a state in which a two-stage combustion air jet is bent by an upward flow in a furnace.

FIG. 5 is a view showing a pattern of a two-stage combustion air jet from a two-stage combustion air inlet of the combustion apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram showing an example of an arrangement of a two-stage combustion air inlet according to another embodiment of the present invention.

7 is a diagram showing a structural example of a two-stage combustion air inlet in FIG.

FIG. 8 is a diagram showing a two-stage combustion air system according to another embodiment of the present invention.

FIG. 9 is a diagram showing a method for controlling a two-stage combustion air jet.

FIG. 10 is a diagram showing an example of an air system according to the related art.

FIG. 11 is a diagram showing an example in which a booster fan is provided in a two-stage combustion air system in a conventional air system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary air fan 2 Air preheater 3 Mill 4 Burner 5 Furnace 6 Push-in air fan 7 Wind path 8 Burner air damper 9 Burner wind box 13 Two-stage combustion air inlet 21 High pressure side air supply system for two-stage combustion 22 High-pressure air damper for two-stage combustion 23 High-pressure side wind box for two-stage combustion 24 Low-pressure air supply line for two-stage combustion 25 Low-pressure air damper for two-stage combustion 26 Low-pressure side wind box for two-stage combustion 27 Inner circumference for two-stage combustion Air inlet 28 Two-stage combustion inner air supply tube 29 Two-stage combustion outer air swirler 30 Two-stage combustion outer air inlet 110 Inner high pressure air jet 111 Outer low pressure air jet 112 High pressure side two stage combustion air Inlet 113 Air inlet for low pressure side two-stage combustion

Claims (6)

[Claims] 1. A high-pressure air supply system for supplying primary air to a pulverizer for drying pulverized coal to be conveyed to a burner for combustion, and a low-pressure air having a lower pressure than the high-pressure air is supplied to a burner wind box. A combustion device provided with a low-pressure air supply system to be supplied and a means for charging the two-stage combustion air downstream of the burner in the fire path; A combustion device comprising a system and a system for supplying a part of high-pressure air and low-pressure air from the low-pressure air supply system. 2. The combustion device according to claim 1, wherein an air inlet is provided as means for feeding the two-stage combustion air, and the inside of the inlet is divided into a plurality of flow paths,
A combustion device, wherein the high-pressure air and the low-pressure air are supplied to respective flow paths. 3. The combustion device according to claim 1, wherein an air inlet is provided as a means for feeding the two-stage combustion air, and the inlet is separately charged for high-pressure air and low-pressure air. A combustion device, wherein a port is provided, and high-pressure air and low-pressure air are supplied to the air input port, respectively. 4. The combustion device according to claim 3, wherein the high-pressure air inlet and the low-pressure air inlet are alternately arranged in a width direction of the furnace, and the high-pressure air inlet is connected to a burner. A combustion device having a configuration disposed directly above the combustion device. 5. The combustion apparatus according to claim 3, wherein the high-pressure air inlet and the low-pressure air inlet are arranged in multiple stages in the height direction of the furnace. apparatus. 6. The combustion device according to claim 1, wherein a ratio of a flow rate of the high-pressure air to the low-pressure air, or a flow rate of the high-pressure air and / or the low-pressure air is determined. A combustion device controlled according to a load of the combustion device.