JPH0474603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device such as a boiler device that uses pulverized coal as fuel, and particularly relates to a combustion device such as a boiler device that uses pulverized coal as a fuel. This invention relates to a charcoal burner device.

BACKGROUND OF THE INVENTION As fuel systems for boiler devices and the like, there are two types depending on the arrangement of burners: a tangential fire ring system and a horizontal fire ring system, and it is well known that these are generally employed. In the tanzenshalf earring method, for example, four burners are arranged on the same horizontal plane at the four corners of a furnace, and fuel and air are injected from these burners in the tangential direction of an imaginary circle drawn at the center of the combustion chamber. Four flames come together at the center of the combustion chamber to form a spiral flame.

On the other hand, in the horizontal fire ring method, the burner is placed on the front wall of the boiler that forms part of the furnace, or on the front and rear walls, and the fuel and air are injected in the direction of the walls facing each other. It causes a flame to form immediately. The horizontal fire ring system can hold a flame even with just one burner, so ignition and extinguishing can be done quickly and easily. It is easy to adjust, and in addition, in large boilers with multiple burners, it is possible to equalize the heat load on the heat transfer surface around the furnace, and the flow rate of combustion gas at the furnace outlet is also uniform, making it possible to It is possible to obtain desirable conditions for a fuel exchanger that mainly uses convective heat transfer.

By the way, the length of the flame in the horizontal earring method mainly depends on the mixing state of fuel and air, but when the flame gets longer, it reaches the opposite wall, where it is cooled and unburned, such as soot and carbon monoxide. Not only does the amount of heat transfer increase, but also the dirt on the heat transfer surface increases, which significantly impedes heat transfer. Therefore, it is common practice to swirl the combustion air to promote mixing of the fuel and air, thereby quickly completing the combustion.

Furthermore, when using pulverized coal or the like, which has poor ignitability as fuel, unlike gas and liquid fuels, it is especially important to keep the fuel stable, that is, flame stability.

The conditions for flame holding are that the mixture of fuel and air is in the flammable range near the fuel nozzle outlet, that the supply rate is less than the flame propagation speed, and that a heat source with a temperature higher than the ignition temperature exists. be.

In commonly used burners, the heat source is high-temperature combustion gas after burning fuel. That is, it is necessary to quickly circulate the high-temperature combustion gas to the region where the combustible mixture is formed.

On the other hand, from the viewpoint of pollution prevention, it is desired to reduce nitrogen oxides in combustion exhaust gas. It is known that nitrogen oxides are generated in large quantities when combustion occurs rapidly by promoting the mixing of fuel and air, and are reduced when combustion is performed slowly by suppressing the mixing of heating material and air. Unburnt substances such as carbon monoxide have a tendency opposite to that of nitrogen oxides, and are likely to be generated in large quantities to the extent that mixing of fuel and air is suppressed.

Furthermore, since solid particles are handled in each member constituting the burner, wear-resistant structures and materials are usually required.

That is, a desirable pulverized coal burner device has a structure that has excellent flame stability and wear resistance, and can reduce nitrogen oxides without increasing unburned content.

Conventionally, a pulverized coal burner device used in the horizontal firing method has a burner port 2 provided on a furnace wall 1 and a wind box wall 3 that pass through the burner port 2 from the wind box 4 toward the burner port 2, as shown in FIG. Further, this pulverized coal burner 5 passes a pulverized coal flow 6 carried by air, which forms part of the combustion air, to the center of the burner port 2 to an auxiliary combustion burner 7. A pulverized coal nozzle 9 is supplied through a flame stabilizer 8 provided at the tip of the pulverized coal nozzle 9, and a radial flow swirler 10 swirls fuel air taken in from a wind box 4 outside of the pulverized coal nozzle 9. Air channel 12 supplying flow 11 into burner port 2
It is known that the pulverized coal flow 6 supplied into the furnace through the pulverized coal nozzle 9 and the air flow path 12 and the swirled air flow 11 are mixed and combusted.

However, in the pulverized coal burner device as described above, the flame stabilization function is ensured by the backflow of high-temperature combustion gas caused by the vortex formed in the wake of the flame stabilizer 8 provided at the spout of the pulverized coal nozzle 9. However, since the range of the backflow area created by the vortex at the wake of the flame stabilizer 8 is narrow, and a large amount of combustion air is supplied at once, the unburned matter is destroyed with a short flame. Although it has the advantage that nitrogen oxides are relatively small, it is difficult to reduce nitrogen oxides as pollutants, and there are also drawbacks such as significant wear of the flame stabilizer 8 provided at the spout of the pulverized coal nozzle 9. .

Therefore, in order to reduce nitrogen oxides, as shown in FIG. 2, the flow of the pulverized coal nozzle 9 of the pulverized coal burner device shown in FIG. Annular air flow path 12
is rotated by an axial flow swirler 13 between
Furthermore, a new annular air flow path 16 is provided to serve as a flow path for the combustion air flow 15 whose flow rate is adjusted by the damper 14, and the air flow 11,
A method of appropriately adjusting the flow rate and degree of rotation of step 15 using radial flow swirler 10, damper 14, and axial flow swirler 13 to appropriately delay the mixing of pulverized coal and combustion air jetted from pulverized coal nozzle 9. However, as mentioned above, the backflow area downstream of the flame stabilizer 8 is narrow, and flame stabilization is required to return high-temperature combustion gas to a position where the mixing ratio of pulverized coal and combustion air is within the flammable range. Not only is the position of the boiler 8 restricted, but it is also not possible to cope with large changes in the amount of fuel and air due to changes in the load of the boiler.

Further, no improvement has been made to the wear of the flame stabilizer 8.

As another conventional example, a pulverized coal burner device is already known which has a configuration as shown in FIG. 3 in order to improve the wear of the flame stabilizer. This pulverized coal burner device has two annular air passages in the burner port 2, namely, an outer air passage 18 whose air flow rate is adjusted by a damper 17, and a radial flow swirler 19 to which a swirling force is applied. An inner air flow path 20 through which fuel air flows is formed, and a pulverized coal burner body 21 is further formed inside this inner air flow path 20. This pulverized coal burner main body 21 mainly includes a central air nozzle 22 that serves as a passage for combustion air for flame stabilization, and a pulverized coal provided outside the central air nozzle 22 to form an annular pulverized coal passage. It consists of a charcoal nozzle 23 and a flame stabilizer 8 provided inside the central air nozzle 22 on the spout side.

In the pulverized coal burner device having such a configuration, wear of the flame stabilizer 8 is avoided, but the range of the backflow region downstream of the flame stabilizer 8 is still narrow, and flame stabilization is poor.

Incidentally, in the conventional pulverized coal burner devices shown in FIGS. 1 to 3, the jet flow from the burner port 2 is a straight flow in the center, and an annular swirl flow is arranged on the outside. As a general property of the swirling flow, it is known that when the degree of rotation of the swirling flow is increased, a backflow region is formed in the center, and this backflow region is located in the backflow region of the flame stabilizer 8 described above. Compared to this, the range is much wider, and the range of the backflow region can be easily changed. However, in the above-mentioned conventional pulverized coal burner device, the pulverized coal flow or straight pulverized coal flow and air flow are ejected into the reverse region formed by the swirling annular air flow. The formed backflow disappears, and the high temperature combustion gas cannot be sufficiently refluxed, resulting in a decrease in flame stability.

In this way, conventional pulverized coal burner equipment has flame stability and
In terms of operability, the range of fuel and air amounts that can be stably combusted is narrow, and therefore it is difficult to reduce nitrogen oxides by performing slow combustion without generating unburned substances. It was hot.

Furthermore, a pulverized coal combustion device as described in Japanese Patent Publication No. 57-35368 has been proposed.

The burner section of this pulverized coal combustion equipment consists of, from the center toward the outer periphery, a central supply path A for high-pressure primary air that travels straight, an intermediate supply path B for swirling high-pressure primary air, and a central supply path B for high-pressure primary air that travels straight. An outer supply path C, a straight low-pressure pulverized coal supply path D, and a straight straight outer secondary air supply path E are formed in this order.

A plurality of partition structures are provided along the circumferential direction at the tip of the pulverized coal supply path D, and primary air and secondary air are introduced into the partitioned areas, so that the pulverized coal flow is directed in the circumferential direction. It is now divided into multiple parts along the line.

This pulverized coal combustion device adjusts the spread angle of the pulverized coal flow by increasing or decreasing the air flow rate supplied to the central supply path A, intermediate supply path B, and outer supply path C.
This is an attempt to control the main combustion position.

However, in this structure, since a high-pressure straight flow is formed in the center of the burner by the central supply path A, there is no entrainment of the pulverized coal flow into the center of the burner. This reduces the flame-holding effect, and in some cases there is a risk that the flame may be blown out by the high-pressure straight flow in the center, which poses a safety problem.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, to improve the flame stabilization function, to achieve slow combustion for suppressing the generation of nitrogen oxides, and to provide a burner member such as a flame stabilizer. It is an object of the present invention to provide a pulverized coal burner device that can prevent wear of the burner member when the burner member is in use.

In order to achieve the above object, the present invention provides a first air flow path formed in the center, a pulverized coal flow path formed adjacent to the outside of this air flow path, and a first air flow path formed in the center, a pulverized coal flow path formed adjacent to the outside of this air flow path, and and a second air flow path formed on the outside of the air flow path, and is characterized by being provided with cutting means for swirling the central air flow guided to the first air flow path.

The pulverized coal burner device of the present invention will be explained below.

FIG. 4 is a longitudinal cross-sectional view of a pulverized coal burner device that is an embodiment of the present invention, and FIG. 5 is a cross-sectional view showing a modification of the means for supplying air to the first air flow path shown in FIG. 6 is a cross-sectional view taken along the line A-A in FIG. 5, FIG. 7 is a cross-sectional view showing a modification of the center airflow flow rate adjustment means shown in FIG. 5, and FIG. FIG. 9 is a sectional view taken along the line BB in FIG. 8, and FIG. 10 is a sectional view showing another embodiment of the pulverized coal burner device of the present invention.

The pulverized coal burner main body 24 shown in FIG.
The ejection port side is fitted into a burner port 2 provided in the burner port 2, and is installed in a wind box 4 surrounded by a furnace wall 1 and a wind box wall 3. This pulverized coal burner body 24 has a central air nozzle 2
5. The pulverized coal nozzle 26 and the secondary air nozzle 27 are divided into three annular flow paths, and these annular flow paths are divided into three annular flow paths in order from the center: a first air flow path 28;
A pulverized coal channel 29 and a second air channel 30 are formed.

An auxiliary combustion burner 31 is provided at the center of the first air passage 28 at the center, and an impeller 32 is attached to the tip of the auxiliary combustion burner 31 as a flame stabilizer. Furthermore, an axial flow swirler 33 as a swirling mechanism is installed in the first air flow path 28, and a damper 3 is installed on the upstream side of the first air flow path 28.
It communicates with the wind box 4 through a duct 35 provided with a windshield 4. Further, in the second air flow path 30, a damper 37 is provided on the upstream side when viewed from the flow direction of the secondary air flow 36 flowing through this air flow path 30.
An axial flow swirler 38 is provided on the downstream side.

A third air flow path 39 is further formed outside the secondary air nozzle 27 of the pulverized coal burner main body 24, and the wind box of the third air flow path 39 located at the outermost position A radial flow swirler 40 is installed on the 4th side.

The central air flow 41 flowing through the first air flow path 28 is given a swirling force by the axial swirler 33, becomes a swirling jet, and is ejected into the furnace through the burner port 2. The secondary air flow 36 and the tertiary air flow 43 flowing through the second air flow furnace 30 and the third air flow path 39 outside the pulverized coal flow furnace 29 through which the pulverized coal flow 42 to which no swirling force is applied are axially A swirling force is applied by the flow swirler 38 and the radial swirler 40, and the swirling jet is ejected into the furnace through the burner port 2.

The pulverized coal burner device in this embodiment includes a burner port 2, a pulverized coal burner body 24, and a third air flow furnace 39.

With the above configuration, the pulverized coal flow 42 conveyed by the air forming a part of the combustion air is passed from the pulverized coal flow path 29 in the pulverized coal nozzle 26 to the burner port 2 to the furnace. It is squirted inside.
At this time, the central air flow 41 to which a swirling force is applied by the axial swirler 33 in the first air flow path 28 is ejected as a swirling jet at the jet outlet of the central air nozzle 25. By the way, the central air flow 4
The flow rate and degree of rotation of the central air flow 41 are adjusted by the damper 34 and the axial swirler 33; however, if the degree of rotation is increased, the swirling jet of the central air flow 41 will flow through the central air nozzle 25.
The central part becomes negative pressure near the jet nozzle, causing a backflow, and this backflow due to the swirling jet flows into the impeller 3.
This mutually promotes the backflow generated in the wake of No. 2 and forms a stable and wide backflow region.

The pulverized coal jet, which is an extension of the straight pulverized coal flow 42 ejected from the pulverized coal nozzle 26, is influenced by the swirling jet of the central air flow 41, and a part of the pulverized coal jet is caught in the reverse flow area.

Therefore, the high-temperature combustion gas of the pulverized coal flows back to the vicinity of the spout of the pulverized coal nozzle 26, so that combustion can be maintained stably and flame stability can be greatly improved.

On the other hand, a secondary air flow 36 is generated from the second air flow path 30 adjacent to the outside of the pulverized coal flow path 29 and the third air flow path 39 outside the second air flow path 30, respectively.
and a tertiary air flow 43 are injected into the furnace through the burner port 2, but these secondary air flow 36 and tertiary air flow 43 are usually swirled in the same direction as the swirl direction of the central air flow 41. It has become like this,
Furthermore, the flow rate and degree of rotation of the secondary air flow 36 and the tertiary air flow 43 are adjusted as appropriate by a damper 37, an axial flow swirler 38, and a radial flow swirler 40.

If the degree of rotation of the secondary airflow 36 is increased, the swirling jet, which is an extension of the secondary airflow 36, will expand outward, and mixing with the pulverized coal jet will be suppressed, resulting in a reduction in nitrogen oxides. It is valid. Further, the unburned matter that has not been completely burned by the swirling jet of the secondary air flow 36 is completely combusted by the swirling jet of the tertiary air flow 43.

Further, since the impeller 32 serving as a flame stabilizer is not exposed to the pulverized coal flow 42, wear of the impeller 32 is avoided.

Further, as a modification of the duct 35 shown in FIG. 4, as shown in FIGS. An air introduction duct 45 may also be provided. By doing so, most of the burner components are accommodated within the wind box 4, so that the installation area can be reduced.

Further, as another example of the center airflow flow rate adjustment means, as shown in FIG. A notch 4 is provided on the outer peripheral surface of the pulverized coal nozzle 26 which communicates with the flow path 28 and is further provided with a central air introduction duct 46.
7a is provided, and this sleeve 47 is rotated in the circumferential direction to open the central air introduction duct 4.
The cross-sectional area of the pulverized coal nozzle 6 may be changed.As another modification, as shown in FIGS. 8 and 9, a sleeve 48 without a notch may be used instead of the sleeve 47 in FIG. The sleeve 48 may be provided on the outer peripheral surface of the central air introduction duct 46 and slid in the axial direction to change the flow passage cross-sectional area of the central air introduction duct 46.

In the above embodiment, the swirling mechanism for swirling the central air flow 41 in the first air flow path 28 is an axial flow swirler, but the present invention is not limited to this, and for example, as shown in FIG. A plurality of (two in the figure) central air introduction ducts 49 are provided between the central air nozzle 25 and the pulverized coal nozzle 26 so that the central air introduction direction touches the outer circumferential circle of the first air flow path 28. The pulverized coal nozzle 26 may be provided with a sleeve for flow rate adjustment having notches 50a at two locations on the outer circumferential surface of the pulverized coal nozzle 26. By configuring the turning mechanism in this way, the central air introduced from the central air introduction duct 49 is turned in the circumferential direction within the first air flow path 28, as shown in FIGS. 4 and 5. The axial flow swirler 33 becomes unnecessary.

Further, in the embodiment, the auxiliary combustion burner 31
If it is not necessary to install the impeller 32
It is not necessary to provide the flame stabilizing function, and even in that case, the flame holding function will not deteriorate.

Since the present invention has the above-described structure, the rotating means creates a negative pressure in the center of the burner, which causes a reverse flow of the pulverized coal flow, resulting in a reliable flame-holding effect and high safety. Furthermore, even if the amount of pulverized coal and the amount of air supplied to the pulverized coal burner device vary over a wide range, slow combustion is possible without generating unburned matter, and nitrogen oxides can be reduced. There is an effect. Furthermore, there is also the effect that wear of burner components such as a flame stabilizer due to the pulverized coal flow can be prevented.

[Brief explanation of the drawing]

1, 2, and 3 are sectional views of different conventional pulverized coal burner devices, FIG. 4 is a vertical sectional view of a pulverized coal burner device that is an embodiment of the present invention, and FIG. 5 is shown in FIG. A cross-sectional view showing a modification of the means for supplying air to the first air flow path, FIG. 6 is a cross-sectional view taken along line A-A in FIG. 5, and FIG. 7 is a flow rate adjustment of the central air flow shown in FIG. 5. 8 is a sectional view showing a modification of the means for adjusting the flow rate of the central air flow; FIG. 9 is a sectional view taken along line B-B in FIG. 8; FIG. FIG. 2 is a sectional view showing another embodiment of the pulverized coal burner device of the present invention. 28... First air flow path, 29... Pulverized coal flow path, 30... Second air flow path, 33... Axial flow swirler (swirling mechanism), 49... Center air introduction duct (swirling mechanism).

Claims (1)

[Claims] 1 A first air flow path formed in the center, a pulverized coal flow path formed adjacent to the outside of this air flow path, and a second air flow path formed outside of this pulverized coal flow path.
an air flow path, a swirling means for swirling the central air flow guided to the first air flow channel, and a swirling means disposed on the downstream side of the swirling means in the air flow direction and near the outlet of the first air flow channel. A pulverized coal burner device comprising a flame holding means in which a backflow region is formed at the rear of the pulverized coal burner device.