JP5471713B2 - Pulverized coal burner - Google Patents

Description

  The present invention relates to a pulverized coal burner that conveys and burns pulverized coal.

As described in Patent Document 1 to Patent Document 3, a burner that burns pulverized coal is known in which combustion air and pulverized coal are mixed and injected and burned at an outlet of the burner. However, burners that use pulverized coal as fuel are less ignitable than heavy oil and natural gas, so the ignition point is far from the burner outlet and the non-ignition area (black zone) from the burner outlet to the ignition point is eliminated. Is difficult.
By the way, when incinerating waste in a waste incinerator or the like, because the properties of the waste are not constant, there may be local combustion residue of waste with poor ignitability and flammability in the furnace. is there. Therefore, in the pulverized coal burner for auxiliary combustion used in such an incinerator, by changing the position of the frame, it is possible to promote the combustion of waste in a place where ignition and combustion are difficult and to achieve stable combustion. Desired. For example, it is required to ignite near the burner outlet and to freely adjust the frame position.

In the pulverized coal burner proposed in Patent Document 1 and Patent Document 2, a plurality of pulverized coal jets are provided, and the frame length and the pulverized coal burner are adjusted by individually adjusting the operating conditions (the amount of pulverized coal and the amount of air). The shape is more controllable.
As described above, if the control parameter is increased by providing a plurality of supply lines capable of controlling the supply amount of pulverized coal in one burner, it is possible to cope with the adjustment of the frame. The problem that the load becomes large arises.

The pulverized coal burner of Patent Document 3 is configured to collide when jetting primary air for conveying pulverized coal and auxiliary air for combustion, and further imparts dispersion force to the pulverized coal by auxiliary air generated by a swirling flow. ing. Auxiliary air for combustion is jetted outward along a cone-like structure disposed so as to spread at the tip of the burner. It is considered that the furnace side of the corn-like structure (the central part of the burner outlet) has a negative pressure, and thus an air flow toward the negative pressure part is generated to promote ignition in the vicinity of the burner outlet.
However, the dispersion of the pulverized coal by the air for conveying the pulverized coal and the auxiliary air is not sufficient, and since the straight component remains, the ignition point is far from the burner jet, and further, the function of adjusting the frame position is not provided. In addition, it is impossible to achieve stable combustion in places where it is difficult to ignite and burn waste.

JP-A-10-160131 Japanese Patent Laid-Open No. 10-300021 JP 59-195014 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a pulverized coal burner capable of reducing the black zone and adjusting the frame position by a simple control method.

Pulverized coal burner of the present invention, the primary air ejection openings in the radially inner circumferential pulverized coal spout disposed along, arranged concentrically cylindrical radially outer secondary air injection port to the center axis In the pulverized coal burner, the primary air jet outlet swirls the primary air between a pair of shield plates provided in a cone shape for jetting the primary air radially outward. A plurality of swirl blades are provided, and the secondary air outlet is provided so that secondary air is jetted straightly or inwardly, and the inclination angle of the shield plate with respect to the central axis is θ, The opening angle along the circumferential direction of the swirl blade with respect to the direction parallel to the central axis is φ, the opening distance in the radial direction perpendicular to the central axis of the pair of shield plates is a, and the central axis direction of the shield plates is the length was set to d ₁ If, and being provided so as to satisfy the following (1) to (3).
40 ° <θ <65 ° (1)
d ₁ tan θ ≧ a (2)
0.6 <(sin ² φ + sin ² θ) / (cos φ + cos θ) ² <1.5 (3)

By providing a shield plate for imparting an outward flow and a swirl vane for imparting a swirling flow to a primary air jet outlet for dispersing pulverized coal, an outward and swirling flow is simultaneously imparted to the pulverized coal. be able to. The outward and swirling flow of primary air can accelerate the contact between the pulverized coal and the surrounding hot gas and shorten the black zone. Further, the outward flow of the primary air creates a recirculation flow that entrains the surrounding high-temperature gas and travels toward the jet outlet of the burner, thereby improving the stability of combustion.
Furthermore, since the secondary air jet outlet is provided so that the secondary air is jetted straight or inward, by adjusting the jet speed of the secondary air, the residence position of the pulverized coal is adjusted, The frame position can be adjusted. Contrary to primary air, the flow of secondary air blocks the contact between pulverized coal and the surrounding hot gas, and forms a frame with a long black zone, so the flow rate balance between primary air and secondary air is balanced. Thus, the frame position can be adjusted.

If the above equation (1) is not satisfied and the inclination angle θ of the shield plate is as small as 40 ° or less, the ejected pulverized coal cannot be sufficiently diffused into the high-temperature gas near the tip of the burner, and the black zone It cannot be shortened. Further, when the angle θ is as large as 65 ° or more, the pulverized coal is scattered too much around the periphery, and a stable frame cannot be formed in front of the burner.
When the shield plate is arranged so as to satisfy the above expression (2), the shield plate is arranged so that the upstream end of the shield plate is hidden when viewed from the front of the burner outlet. For this reason, the straight air component in the direction along the central axis is eliminated from the primary air ejected from the primary air ejection port, and the entire primary air can be made to flow along the inclination angle θ of the shield plate. It can be reliably diffused.
The design of the swirl blade needs to be combined with the shield plate so as to satisfy the above expression (3). When the opening angle φ of the swirl vane is too small, the black zone cannot be shortened because the effect of entraining the hot gas near the burner tip is small and the effect of diffusing pulverized coal is small. When the angle φ is large, the pulverized coal is scattered too much around the periphery, and a stable frame cannot be formed in front of the burner.

In the pulverized coal burner of the present invention, when the radius of the inner peripheral edge of the primary air outlet is r ₁ and the radius of the outer peripheral edge of the secondary air outlet is R, the following expression (4) is satisfied. It is good to be provided.
0.3 <r ₁ /R<0.7 (4)

If the inner peripheral edge of the primary air outlet is too small with respect to the outer peripheral edge of the secondary air outlet, the recirculation flow becomes smaller and the frame becomes unstable, and misfire is likely to occur. Therefore, the ratio r ₁ / R of the radius r ₁ of the inner peripheral edge of the primary air outlet to the radius R of the outer peripheral edge of the secondary air outlet is preferably larger than 0.3. Further, when r ₁ / R is 0.7 or more, it is difficult to form each jet port.

  According to the pulverized coal burner according to the present invention, the pulverized coal and the surrounding high-temperature gas are provided by providing the shield plate and the swirl vanes that simultaneously impart outward flow and swirl flow at the primary air jet outlet for diffusing the pulverized coal. The position of the frame can be adjusted by adjusting the flow rate balance between the primary air and the secondary air that shortens the contact with the air, shortens the black zone, and blocks the contact between the pulverized coal and the surrounding hot gas. it can.

It is a front view which shows one Embodiment of the pulverized coal burner of this invention. It is a perspective view of the pulverized coal burner front-end | tip part of FIG. It is sectional drawing explaining the structure of a pulverized coal burner. It is a figure explaining the turning blade | wing seen from the arrow X direction of FIG. It is a schematic diagram which shows the state of the flame | frame by each burner. It is a figure explaining the flow of the primary air by the difference in the inclination angle of a shield board. It is a figure explaining the generation | occurrence | production state of the recirculation flow by the difference in the ratio of the radius of the outer periphery of a secondary air ejection port, and the radius of the inner periphery of a primary air ejection port.

Hereinafter, an embodiment of the pulverized coal burner of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 to 3, the pulverized coal burner 100 of the present embodiment includes a primary air ejection path 10, a pulverized coal ejection path 20, and secondary air that are provided concentrically from the center side toward the outer peripheral side. The pulverized coal burner 100 has a jet passage 30, and a pulverized coal burner 100 is provided with a primary air jet 11 on the radially inner side and a secondary air jet 31 on the radially outer side of the pulverized coal jet 21 arranged along the circumferential direction. The entire configuration is arranged concentrically with respect to (center axis O). A hollow portion 40 is provided at the center of the pulverized coal burner 100 so that an oil burner (not shown) can be inserted.

The ejection port 11 of the primary air ejection path 10 is configured such that a plurality of swirl vanes 13 are provided between a pair of cone-shaped shield plates 12 opened toward the tip of the burner 100.
As shown in FIG. 3, the shield plate 12 is provided in a state in which the generatrix of the cone is inclined radially outward at a predetermined angle with respect to the central axis O. The inclination angle is θ. The pair of shield plates 12 have the same inclination angle (the buses are parallel), and are configured to eject primary air radially outward along the inclination of the shield plate 12.

There are six pulverized coal ejection paths 20 provided at equal intervals on the circumference between the primary air ejection path 10 and the secondary air ejection path 30 in parallel with the direction of the central axis O. Is ejected forward of the burner.
The secondary air ejection path 30 is provided in parallel with the central axis O direction and on the outermost peripheral side of the pulverized coal burner 100. A plurality of spacers are provided in the secondary air ejection passage 30 in the circumferential direction of the annular passage so that the radial width of the secondary air ejection port 31 is uniform with respect to the circumferential direction.

When the inclination angle θ is too small as 40 ° or less, the shield plate 12 cannot sufficiently diffuse the ejected pulverized coal into the region near the tip of the burner, the black zone cannot be shortened, and 65 ° If it is too large, the pulverized coal will be scattered too far to the periphery and a stable frame cannot be formed in front of the burner. Therefore, the inclination angle θ of the shield plate 12 with respect to the central axis O is shown below. It is preferable to be provided so as to satisfy the condition of the formula (1).
40 ° <θ <65 ° ・ ・ (1)

Further, the pair of shield plates 12 are provided so that the upstream end of the shield plate 12 is hidden when the spout 11 is viewed from the front of the burner 100. As a result, the flow of the straight air component in the direction along the central axis O of the primary air can be eliminated, and the entire primary air can be made to flow along the inclination angle θ of the shield plate 12 to reliably diffuse the pulverized coal. To be able to. As shown in FIG. 3, this condition is that when the opening distance in the radial direction orthogonal to the central axis O of the pair of shield plates 12 is a and the length of the shield plate 12 in the central axis O direction is d ₁ , It can be expressed by the following equation (2).
d ₁ tan θ ≧ a (2)

Further, twelve swirling blades 13 are equally arranged in the circumferential direction between the pair of shield plates 12. As shown in FIG. 4, these swirl vanes 13 are provided with an opening angle φ with respect to the direction of the arrow A along the central axis O of the burner 100, and outside the primary air provided by the shield plate 12. A flow that further swirls is added to the flow in the direction.
The swirl vane 13 needs to be designed in combination with the shield plate 12. If the opening angle φ of the swirl vane 13 is too small, the effect of entrainment in the high-temperature gas near the tip of the burner is small, and pulverized coal When the opening angle φ is large and the pulverized coal is scattered too much around the periphery, it is preferable to provide the following equation (3).
0.6 <(sin ² φ + sin ² θ) / (cos φ + cos θ) ² <1.5 (3)

Further, in the space 50 located on the inner peripheral side of the primary air outlet 11 located at the outermost part of the tip of the burner, as will be described later, the negative pressure in which the pressure decreases due to the radially outward flow of the primary air. Since it becomes a pressure part, as shown in FIG. 3, the flow (recirculation flow B) of the reverse direction to the flow (direction of arrow A) of secondary air etc. is produced. By stagnating the mixed flow of pulverized coal and high-temperature gas in the negative pressure portion by the recirculation flow B, the stability of combustion can be improved.
At this time, if the area of the space portion 50 is too small, that is, if the inner peripheral edge of the primary air outlet 11 is too small with respect to the outer peripheral edge of the secondary air outlet 31, the recirculation flow B becomes smaller. Since the frame becomes unstable, the ratio (r ₁ / R) between the radius r ₁ of the inner peripheral edge of the primary air outlet 11 and the radius R of the outer peripheral edge of the secondary air outlet 31 is set to the following (4 It is preferable to be provided so as to satisfy the condition represented by the formula (1). In addition, r ₁ / R is set to be less than 0.7 in terms of disposing each jet port.
0.3 <r ₁ /R<0.7 (4)

Next, the usage method of the pulverized coal burner 100 comprised in this way is demonstrated.
First, the pulverized coal ejected from the pulverized coal ejection channel 20 is diffused by the primary air ejected from the primary air ejection channel 10 and brought into contact with the high-temperature gas.
Since the outlet 11 of the primary air ejection path 10 is provided with a shield plate 12 that imparts an outward flow and a swirl vane 13 that imparts a swirling flow, the flow swirling outward and swirling into the pulverized coal. At the same time. At this time, the outward and swirling flow of the primary air accelerates the contact between the pulverized coal and the surrounding hot gas, and can burn the pulverized coal in the region immediately after the jet outlet of the burner 100, shortening the black zone. can do. Moreover, since the outward flow of primary air produces the recirculation flow B which goes to the jet nozzle of the burner 100, the stability of combustion can be improved.
On the other hand, on the outermost peripheral side of the burner 100, a secondary air ejection passage 30 for ejecting secondary air that blocks the contact between the pulverized coal and the surrounding high-temperature gas is provided opposite to the primary air. The frame position can be adjusted by adjusting the pulverized coal staying position by adjusting the jet speed of the flow straight from the next air jet port 31. Thus, since the frame position can be adjusted by the balance of the flow rates of the primary air and the secondary air, a simple structure can be achieved as compared with the conventional burner.

(Examples and Comparative Examples)
Next, examples and comparative examples according to the pulverized coal burner of the present invention will be described with reference to FIGS. The burner of Example 1 is 101, and the burners of Comparative Examples 1 to 6 are 102 to 107.
First, the influence of the conditional expressions (1) and (3) described above was confirmed. FIG. 5 is a schematic diagram showing the frame states of the burners 101 to 105, where (a) shows the simulation results of Example 1, (b) shows Comparative Examples 1 and 3, and (c) shows the simulation results of Comparative Examples 2 and 4. Show. The conditions of Example 1 and Comparative Examples 1 to 4 are as follows.

Example 1
Inclination angle θ: 50 °
Opening angle φ: 55 °
d ₁ tan θ = a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 1.1
r ₁ /R=0.35
(Comparative Example 1)
Inclination angle θ: 35 °
Opening angle φ: 55 °
d ₁ tan θ = a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 0.5
r ₁ /R=0.35
(Comparative Example 2)
Inclination angle θ: 67 °
Opening angle φ: 55 °
d ₁ tan θ = a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 1.6
r ₁ /R=0.35
(Comparative Example 3)
Inclination angle θ: 50 °
Opening angle φ: 40 °
d ₁ tan θ = a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 0.5
r ₁ /R=0.35
(Comparative Example 4)
Inclination angle θ: 50 °
Opening angle φ: 72 °
d ₁ tan θ = a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 1.6
r ₁ /R=0.35

In the burner 101 of the first embodiment, all the conditional expressions (1) to (4) are satisfied. As shown in FIG. 5 (a), since the pulverized coal ejected from the burner 101 is diffused and the ability to accelerate ignition is high, the frame in a state where no black zone occurs as in the frame F indicated by the solid line in the figure. Can be formed. Further, the ignition is delayed by increasing the secondary air by a factor of three, and the black zone can be extended to 3 m (L1 in the figure) while maintaining a stable combustion state as shown by a frame F indicated by a broken line.
In the burner 102 of Comparative Example 1, the conditional expressions (1) and (3) are not satisfied. Since the inclination angle θ of the shield plate 12 is small, the ability to diffuse the pulverized coal ejected from the burner 102 is low. Therefore, as shown in FIG. 5B, the frame F is 2 to 3 m from the tip of the burner (see FIG. However, even if the flow rate of the primary air or the secondary air was adjusted, the black zone could not be reduced to 2 m (L3 in the figure) or less.
The burner 103 of the comparative example 2 also does not satisfy the conditional expressions (1) and (3) like the comparative example 1 described above. In the case of this comparative example 2, since the inclination angle θ of the shield plate 12 is large, the pulverized coal ejected from the burner 103 is excessively diffused, and as shown in FIG. Even if the flow rate of the secondary air was adjusted, the frame F could not be formed in front of the burner 103.
In the burner 104 of the comparative example 3, conditional expression (3) is below the lower limit value. This conditional expression (3) has the same value as in Comparative Example 1, and the same result as in Comparative Example 1 described above was obtained.
In the burner 105 of the comparative example 4, only the conditional expression (3) is not satisfied as in the comparative example 3. The value of conditional expression (3) of the burner 105 exceeds the upper limit value. This conditional expression (3) has the same value as in Comparative Example 2, and the same result as in Comparative Example 2 described above was obtained.

Next, the influence of conditional expression (2) was confirmed by simulation. 6A and 6B are diagrams for explaining the flow of primary air depending on the difference in the inclination angle θ of the shield plate 12. FIG. 6A shows the simulation result of Example 1, and FIG. The conditions of Example 1 are as described above, and the conditions of Comparative Example 5 are as follows.
(Comparative Example 5)
Inclination angle θ: 50 °
Opening angle φ: 55 °
d ₁ tan θ <a
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 1.1
r ₁ /R=0.35
In the burner 106 of the comparative example 5, since the conditional expression (2) is not satisfied, as shown in FIG. 6B, as compared with the first example of FIG. Therefore, the black zone could not be controlled to 2 m or less, as in Comparative Example 1, because the ability to diffuse pulverized coal was low.

Finally, the influence of conditional expression (4) was confirmed by simulation. Figure 7 is a diagram for explaining the occurrence of the recycle stream B due to the difference in the ratio of the radius r ₁ of the inner peripheral edge of the secondary air jet port 31 of the outer peripheral edge of the radius R and the primary air ejection port 11, (A) shows the simulation results of Example 1, and (b) shows the simulation results of Comparative Example 6. The conditions of Example 1 are as described above, and the conditions of Comparative Example 6 are as follows.
(Comparative Example 6)
Inclination angle θ: 50 °
Opening angle φ: 55 °
d ₁ tan θ = a
r ₁ /R=0.2
(Sin ² φ + sin ² θ) / (cos φ + cos θ) ² = 1.1
In the burner 107 of Comparative Example 6, the conditional expression (4) is not satisfied, and as shown in FIG. 7B, the recirculation flow B is smaller than that in Example 1 of (a). The ability to mix with the high-temperature gas inside was low, and the flame-holding effect was not fully exhibited, and it was easy to misfire.

  From the above, in Example 1 that satisfies the conditional expressions (1) to (4), the contact between the pulverized coal and the surrounding high-temperature gas can be accelerated, the black zone can be shortened, and the flow rate of the primary air with the secondary air It was confirmed that the position of the frame F can be adjusted by adjusting the balance.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the outlet 31 of the secondary air ejection passage 30 is adapted to eject the secondary air straightly traveling in the direction of the central axis O of the burner 100, but it may be ejected slightly inward.
In this embodiment, the oil burner is not inserted into the hollow portion 40. However, by arranging the oil burner and supplying fuel such as heavy oil, combustion can be easily started when the burner is activated. In addition, combustion may be maintained by supplying fuel even during low load combustion.

DESCRIPTION OF SYMBOLS 10 Primary air ejection path 11,21,31 Outlet 12 Shield plate 13 Swirling blade 20 Pulverized coal ejection path 30 Secondary air ejection path 40 Hollow part 50 Space part 100-107 Pulverized coal burner

Claims (2)

Primary air ejection openings in the radially inner circumferential pulverized coal spout disposed along the radially outer secondary air jet port is a pulverized coal burner which is arranged concentrically cylindrical with respect to the central axis The primary air outlet is provided with a plurality of swirl vanes for swirling the primary air between a pair of shield plates provided in a cone shape for ejecting the primary air radially outward. Configured, the secondary air outlet is provided so that the secondary air is jetted straight or inward ,
An inclination angle of the shield plate with respect to the central axis is θ, an opening angle along the circumferential direction of the swirl blade with respect to a direction parallel to the central axis is φ, and a radial opening perpendicular to the central axis of the pair of shield plates A pulverized coal burner provided to satisfy the following formulas (1) to (3) , where a is the interval and d ₁ is the length of the shield plate in the central axis direction .
40 ° <θ <65 ° (1)
d ₁ tan θ ≧ a (2)
0.6 <(sin ² φ + sin ² θ) / (cos φ + cos θ) ² <1.5 (3) When the radius of the inner peripheral edge of the primary air outlet is r ₁ and the radius of the outer peripheral edge of the secondary air outlet is R, the primary air outlet is provided so as to satisfy the following expression (4): The pulverized coal burner according to claim 1 .
0.3 <r ₁ /R<0.7 (4)

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