JP2014153013A - Pulverized coal burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use coal as a pulverized coal fuel, and to achieve combustion only by pulverized coal even when a furnace is in a low-temperature state.SOLUTION: A pulverized coal burner 3 uses coal as a fuel and includes: a nozzle body 7; and a combustion air adjustment device 8 formed so as to surround a tip part of the nozzle body. The nozzle body includes: an inner tube nozzle 11; an outer tube nozzle 9 formed concentrically with the inner tube nozzle; and a plasma torch 12. A fuel conduction space 14 is formed between the inner tube nozzle and the outer tube nozzle, a pulverized coal mixed flow 16 is supplied to the fuel conduction space, and the pulverized coal mixed flow is jetted from the fuel conduction space like a ring. The plasma torch is formed so that its tip comes close to a tip of the fuel conduction space and plasma 39 formed by the plasma torch is configured so as to intersect with the pulverized coal mixed flow.

Description

  The present invention relates to a pulverized coal burner using coal as fuel.

  In the pulverized coal burner usually provided in the furnace, the combustion air is heated to about 250 ° C. to 300 ° C. by heat exchange with the exhaust gas, and the conveying air for conveying the pulverized coal is 60 ° C. to 60 ° C. at the mill outlet temperature. The temperature is raised to 80 ° C., and self-sustainable combustion with pulverized coal is possible.

  However, when the burner is started (that is, when the furnace is started), the furnace is cooled, and the temperature of the combustion air or the carrier air cannot be raised due to the waste heat of the exhaust gas. For this reason, the conventional pulverized coal burner is equipped with an oil burner that uses oil as fuel. When the burner starts, combustion is performed by the oil burner, and when the furnace is sufficiently warmed, the combustion shifts to pulverized coal as fuel. To do.

  For this reason, since expensive oil is used at the time of starting the burner, there is a problem that the running cost becomes high.

  Patent Document 1 discloses a pulverized coal burner that stably burns even when the pulverized coal concentration is high. Patent Document 2 discloses a plasma ignition device for directly igniting a pulverized coal boiler. It is disclosed.

JP 2011-252625 A Japanese Patent No. 3934554

  In view of such circumstances, the present invention uses pulverized coal as a fuel, and allows combustion with pulverized coal alone even in a low-temperature furnace.

  The present invention is a pulverized coal burner comprising coal as fuel and a nozzle body and a combustion air conditioner provided so as to surround the tip of the nozzle body, the nozzle body comprising an inner cylinder nozzle, An outer cylinder nozzle provided concentrically with the inner cylinder nozzle and a plasma torch, a fuel conduction space is formed between the inner cylinder nozzle and the outer cylinder nozzle, and pulverized coal is mixed in the fuel conduction space The pulverized coal mixed flow is ejected in a ring shape from the fuel conducting space, and the plasma torch is provided so that the tip is close to the tip of the fuel conducting space, and is formed by the plasma torch. Relates to a pulverized coal burner configured to intersect the pulverized coal mixed flow.

  Further, according to the present invention, the pulverized coal mixed flow uses normal temperature primary air as a carrier medium, normal temperature secondary combustion air is supplied from the combustion air conditioner, and normal temperature tertiary air is supplied from the inner cylinder nozzle. The present invention relates to a pulverized coal burner to which combustion air is supplied.

  According to the present invention, the plasma torch is provided inside the inner cylinder nozzle, the axis of the plasma torch is inclined with respect to the axis of the inner cylinder nozzle, and the plasma formed by the plasma torch is the fine powder. It relates to a pulverized coal burner configured to intersect the coal mixture flow.

  According to the present invention, the plasma torch is provided outside the nozzle body, the axis of the plasma torch is inclined with respect to the axis of the nozzle body, and the plasma formed by the plasma torch is mixed with the pulverized coal. It relates to a pulverized coal burner configured to intersect the flow.

  Further, the present invention is such that the outer cylinder nozzle and the inner cylinder nozzle are configured such that at least a part of the front end portion of the fuel conduction space faces the center of the nozzle body, and the plasma formed by the plasma torch is the fine powder. It relates to a pulverized coal burner configured to intersect the coal mixture flow.

  Further, the present invention relates to a pulverized coal burner, wherein the pulverized coal mixed flow is a high-concentration pulverized coal mixed flow in which the air flow rate of the conveying medium is set to suppress spontaneous combustion of the pulverized coal being conveyed. Is.

  Further, the present invention relates to a pulverized coal burner in which the outer cylinder nozzle, the inner cylinder nozzle, and the plasma torch can be attached and detached from the base end side, respectively.

  According to the present invention, there is provided a pulverized coal burner comprising coal as fuel and a nozzle body and a combustion air conditioner provided so as to surround the tip of the nozzle body, wherein the nozzle body is an inner cylinder nozzle. And an outer cylinder nozzle provided concentrically with the inner cylinder nozzle, and a plasma torch, a fuel conduction space is formed between the inner cylinder nozzle and the outer cylinder nozzle, and fine powder is formed in the fuel conduction space. A charcoal mixed flow is supplied, the pulverized coal mixed flow is ejected in a ring shape from the fuel conducting space, and the plasma torch is provided so that the tip is close to the tip of the fuel conducting space, and is formed by the plasma torch. The pulverized coal is surely ignited by the high-temperature plasma regardless of the furnace temperature and the temperature of the combustion air, and steady combustion is possible. Excellent effect Exhibit.

(A) is a schematic sectional view of the pulverized coal burner according to the first embodiment, and (B) is a partial view showing the relationship between the pulverized coal mixed flow and the plasma in the first embodiment. It is a schematic sectional drawing of the pulverized coal burner which concerns on a 2nd Example. It is a fragmentary figure which shows the relationship between the pulverized coal mixed flow and plasma in a 3rd Example.

  Embodiments of the present invention will be described below with reference to the drawings.

  Coal used for a present Example is lignite, for example, a block-shaped lignite is grind | pulverized, it is made pulverized coal, and is supplied to a pulverized coal burner.

  First, an example of a pulverized coal burner according to a first embodiment of the present invention will be described with reference to FIG.

  In FIG. 1, reference numeral 1 denotes a furnace, and 2 denotes a furnace wall of the furnace 1. The pulverized coal burners shown in FIG. 3 are arranged in a required number and in a plurality of stages in the horizontal direction along the wall surface of the lower part of the furnace 1 of the boiler.

  A throat 4 is provided on the furnace wall 2, a wind box 5 is attached to the counter-fire furnace 1 side of the furnace wall 2, and the pulverized coal burner 3 is provided concentrically with the throat 4 inside the wind box 5. Yes. A combustion air supply path 6 is connected to the window box 5. A secondary air adjusting device 8 that is a combustion air adjusting device is provided at the front end portion (end portion inside the furnace) of the wind box 5, and the secondary air adjusting device 8 is concentric with the throat 4. .

  The pulverized coal burner 3 includes a nozzle body 7 and the secondary air adjustment device 8, and the secondary air adjustment device 8 is provided so as to surround the tip end portion (end portion inside the furnace) of the nozzle body 7. It has been.

  The nozzle body 7 includes an outer cylinder nozzle 9 and an inner cylinder nozzle 11 provided in a concentric multiple cylinder shape, and a plasma torch 12 housed in the inner cylinder nozzle 11.

  The outer cylinder nozzle 9 and the inner cylinder nozzle 11 each have a circular cross-sectional shape, and the furnace 1 side end is opened in a hollow cylindrical space between the outer cylinder nozzle 9 and the inner cylinder nozzle 11. A conductive space 14 is formed.

  The ratio of the cross-sectional area (flow path area) of the fuel conducting space 14 to the cross-sectional area (flow path area) of the inner cylinder nozzle 11 is such that the cross-sectional area of the inner cylinder nozzle 11 is greater than the cross-sectional area of the fuel conducting space 14 An arbitrary multiple of 10 times or less, preferably 1: 5 to 1:10, and the cross-sectional area of the inner cylinder nozzle 11 is set to be significantly larger than the cross-sectional area of the fuel conduction space 14. Therefore, the fuel conduction space 14 has a thin ring shape formed around the inner cylinder nozzle 11.

  A pulverized coal supply pipe 15 communicates with the base of the outer cylinder nozzle 9 (the end on the counter-fired furnace 1 side), and the pulverized coal supply pipe 15 is connected to a pulverized coal supply machine (not shown). From the pulverized coal supply machine, pulverized coal is supplied using primary air as a carrier medium, and a pulverized coal mixed stream 16, which is a mixed flow of primary air and pulverized coal, is supplied to the fuel via the pulverized coal supply pipe 15. The fuel flows into the conduction space 14, flows through the fuel conduction space 14, and is ejected from the tip of the fuel conduction space 14.

  One end of a tertiary air introduction pipe 17 opens at the base of the inner cylinder nozzle 11, and the other end of the tertiary air introduction pipe 17 opens into the combustion air supply path 6 and is supplied to the wind box 5. A part of the secondary combustion air 13 is taken in and led to the inner nozzle 11 as auxiliary combustion air, that is, tertiary combustion air 28. A damper 18 as a tertiary air adjusting device is provided in the middle of the tertiary air introduction pipe 17 so as to adjust the flow rate of the tertiary air as combustion air. The damper 18 is unitized and can be attached to and detached from the tertiary air introduction pipe 17.

  The secondary air adjustment device 8 includes an auxiliary air adjustment mechanism 19 that houses the tip of the nozzle body 7, and a main air adjustment mechanism 20 that is provided concentrically outside the auxiliary air adjustment mechanism 19. Yes.

  A main duct 21 is provided concentrically with the nozzle body 7. The main duct 21 is reduced in diameter toward the tip and is continuous with the throat 4. A sub duct 22 is provided inside the main duct 21 concentrically with the main duct 21. The sub duct 22 is substantially similar to the main duct 21, has a shape that decreases toward the tip, and a secondary air outlet space 23 is formed between the main duct 21 and the sub duct 22. The Further, a sub secondary air outlet space 24 is formed between the sub duct 22 and the nozzle body 7.

  A partition wall plate 25 facing the main duct 21 and the sub duct 22 in common is provided concentrically with the nozzle body 7.

  A large number of outer air vanes 26 are provided between the periphery of the main duct 21 and the partition wall plate 25 so as to be rotatable at equal circumferential intervals, and the outer air vanes 26 are linked mechanisms (not shown). The tilt angle with respect to the air flow can be changed.

  A large number of inner air vanes 27 are provided between the peripheral portion of the sub duct 22 and the partition wall plate 25 so as to be rotatable at equal circumferential intervals. The inner air vanes 27 are the same as the outer air vanes 26. Synchronous rotation is possible via a link mechanism (not shown), and the inclination angle with respect to the air flow can be changed.

  The main air adjustment mechanism 20 is configured by the main duct 21, the outer air vane 26, and the like, and the auxiliary air adjustment mechanism 19 is configured by the sub duct 22 and the inner air vane 27.

  The front end of the main duct 21 is continuous with the throat 4, and the front end of the sub duct 22 is in a position retracted from the inner wall surface of the furnace wall 2, and the outer cylinder nozzle 9 and the inner cylinder nozzle 11 The tips are at the same position, and the tips of the outer cylinder nozzle 9 and the inner cylinder nozzle 11 are in the vicinity of the tip of the sub duct 22.

  The nozzle body 7 will be further described.

  The nozzle body 7 is provided in a state in which the wind box 5 penetrates from the counter-furnace 1 side and a tip portion penetrates the partition wall plate 25.

  A circular front end flange 31 is provided on the front end side of the outer cylinder nozzle 9, and the front end flange 31 comes into contact with the partition wall plate 25 from the counter-furnace 1 side. The tip of the nozzle body 7 is positioned by abutting 31 on the partition wall plate 25. Further, the front end side flange 31 closes the outer cylinder nozzle penetrating portion of the partition wall plate 25.

  A cylindrical nozzle holder 32 is provided at a portion where the nozzle body 7 passes through the wall 5 a of the window box 5. The inner diameter of the nozzle holder 32 is larger than the outer diameter of the distal end side flange 31.

  On the base end side of the nozzle body 7, a circular base end flange 33 that abuts the nozzle holder 32 is provided, and the base end flange 33 abuts the nozzle holder 32 from the reaction furnace 1 side, The base end side flange 33 is fixed to the nozzle holder 32 by a fixing tool such as a bolt. Thus, the outer cylinder nozzle 9 is fixed to the window box 5 via the proximal end flange 33 and the nozzle holder 32.

  An outer cylinder end plate 34 is fixed to the proximal end of the nozzle body 7, and the proximal end of the nozzle body 7 is closed.

  The inner cylinder nozzle 11 is inserted into the outer cylinder nozzle 9 from the reaction furnace 1 side.

  An inner cylinder nozzle fixing flange 35 is provided on the tip side of the inner cylinder nozzle 11 from the position where the tertiary air introduction pipe 17 communicates, and the inner cylinder nozzle fixing flange 35 contacts the outer cylinder end plate 34. The inner cylinder nozzle fixing flange 35 and the outer cylinder end plate 34 are fixed by a fastener such as a bolt, and the inner cylinder nozzle 11 is attached to the outer cylinder nozzle 9.

  An inner cylinder end plate 36 is fixed to the proximal end of the inner cylinder nozzle 11, and the proximal end of the inner cylinder nozzle 11 is closed by the inner cylinder end plate 36. The inner cylinder end plate 36 is provided with a cylindrical plasma torch holder 37. The axis of the plasma torch holder 37 passes through a position deviated from the center of the inner cylinder end plate 36 and is inclined with respect to the axis of the inner cylinder nozzle 11.

  In the figure, the axis of the plasma torch holder 37 passes through a position deviating downward from the center of the inner cylinder end plate 36, and the axis is inclined so as to rise toward the tip.

  The plasma torch 12 is inserted into the plasma torch holder 37 and supported by the inner cylinder end plate 36 through the plasma torch holder 37. Accordingly, the attached plasma torch 12 is inclined so that the axis rises toward the tip.

  Further, the tip of the plasma torch 12 is in a state of being substantially coincident with the tip of the inner cylinder nozzle 11, and is the tip of the plasma torch 12 in contact with the inner surface of the inner cylinder nozzle 11? , It will be in a state of close proximity so as to be substantially in contact.

  The tip position is adjusted by sliding the plasma torch 12 with respect to the plasma torch holder 37.

  The operation will be described below.

  The coal used in this example is low quality lignite and lignite. Lignite and lignite (hereinafter collectively referred to as low-grade coal) have a large amount of volatile matter and are excellent in ignitability and burn-out. On the other hand, since there is much volatile matter, it may spontaneously ignite in a dry state.

  Therefore, in this embodiment, pulverized coal used as fuel is stored in a bin (storage container), a required amount is cut out from the bin, and supplied to the pulverized coal burner with air for conveyance. As described above, low-grade coal may spontaneously ignite in a dry state, so it must be handled in a low-temperature, low-oxygen atmosphere.

  Therefore, the amount of primary air that is the carrier medium is minimized, and the primary air is at room temperature. Further, the primary air amount is set so as to suppress spontaneous combustion of the pulverized coal being conveyed. In this embodiment, the air / pulverized coal weight ratio (A / C) of the pulverized coal mixed stream 16 is a high-concentration pulverized coal mixed stream of 0.01 to 0.5.

  Next, the secondary combustion air 13 is supplied at a normal temperature, and the tertiary combustion air 28 to which the secondary combustion air 13 is diverted is also normal temperature.

  As the combustion air, the secondary combustion air 13 is jetted to the throat 4 through the window box 5 through the main air adjustment mechanism 20 and the auxiliary air adjustment mechanism 19.

  The secondary combustion air 13 passes through the main air adjustment mechanism 20 and the auxiliary air adjustment mechanism 19, and the angles of the outer air vane 26 and the inner air vane 27 are adjusted so that a strong swirl flow is obtained. Is adjusted and the air volume is adjusted.

  The tertiary combustion air 28 divided by the tertiary air introduction pipe 17 is jetted from the inner cylinder nozzle 11 toward the throat 4.

  The pulverized coal mixed stream 16 having a high concentration is supplied to the fuel conduction space 14, further flows toward the tip of the fuel conduction space 14, and is ejected from the tip toward the throat 4 in a thin ring shape.

  As described above, since the air conveying the pulverized coal mixed stream 16 is reduced as much as possible, it is necessary to supply sufficient combustion air to burn the pulverized coal mixed stream 16.

  The cross-sectional area of the inner cylinder nozzle 11 is sufficiently larger than the cross-sectional area of the fuel conduction space 14. Therefore, the tertiary combustion air 28 ejected from the inner cylinder nozzle 11 is supplied to the inside of the pulverized coal mixed stream 16 ejected in a ring shape, and from the outer periphery of the pulverized coal mixed stream 16, The secondary combustion air 13 from the main air adjustment mechanism 20 and the auxiliary air adjustment mechanism 19 is supplied. Accordingly, sufficient combustion air is supplied to burn the pulverized coal mixed stream 16.

  Here, the flow rate ratio between the secondary combustion air 13 and the tertiary combustion air 28 is exemplified. Secondary combustion air flow rate: tertiary combustion air flow rate = (80% to 50%): (20% ~ 50%). In the conventional pulverized coal burner, the proportion of tertiary combustion air is at most about 1%.

  Next, the pulverized coal mixed stream 16 is ignited by the plasma torch 12.

  The axis of the plasma torch 12 is inclined with respect to the axis of the nozzle body 7, and the flame (plasma) 39 emitted from the plasma torch 12 intersects the flow of the pulverized coal mixed stream 16. Is set to In particular, the tip position and inclination of the plasma torch 12 are set so that the high temperature region of the plasma 39 intersects the pulverized coal mixed flow 16.

  In this embodiment, the temperature of the combustion air is lower than the normal temperature and the temperature of the combustion air of the conventional pulverized coal burner (200 ° C. to 250 ° C.), but the volatile content of the low-grade coal is large. In addition, since the plasma of the plasma torch 12 has a high temperature (the central portion is 6000 ° C.), ignition is possible even when the temperature of the combustion air is normal temperature, and combustion can be constantly maintained.

  Next, in the above-described embodiment, the damper 18 is separated from the tertiary air introduction pipe 17, and the inner cylinder nozzle fixing flange 35 and the outer cylinder end plate 34 are released, thereby releasing the inner cylinder nozzle 11. Can be drawn out to the counter-fired furnace 1 side. Further, by releasing the fixation between the base end side flange 33 and the nozzle holder 32, the outer cylinder nozzle 9 can be pulled out to the counter-fired furnace 1 side. Further, the plasma torch 12 can also be pulled out to the reaction furnace 1 side.

  Therefore, the nozzle body 7 can be assembled, disassembled, and maintained from the outside of the window box 5 and the workability is good.

  FIG. 2 shows a second embodiment.

  In the first embodiment, the plasma torch 12 is provided inside the inner cylinder nozzle 11, but in the second embodiment, the plasma torch 12 is provided outside the nozzle body 7.

  In FIG. 2, the same components as those shown in FIG.

  The plasma torch 12 is provided through the wall holder 5a above the nozzle holder 32 and through the partition wall plate 25. The axial center of the plasma torch 12 is inclined so as to approach the axial center of the nozzle body 7 as it approaches the tip, and the tip of the plasma torch 12 coincides with or substantially the tip of the outer cylinder nozzle 9. Match. Further, the tip of the plasma torch 12 is close to the tip of the outer cylinder nozzle 9 so as to contact or substantially contact.

  The inclination of the plasma torch 12 is set to an angle at which the plasma 39 (particularly in the high temperature region) formed by the plasma torch 12 intersects the pulverized coal mixed flow 16 ejected from the fuel conduction space 14.

  Thus, the pulverized coal mixed stream 16 ejected from the fuel conduction space 14 is ignited by the plasma torch 12 and steadily combusts.

  Even in the second embodiment, the pulverized coal can be ignited even when the temperature of the combustion air is normal, and the combustion can be constantly maintained.

  In the present invention, the pulverized coal mixed flow 16 ejected from the fuel conduction space 14 may be configured so that the high temperature region of the plasma 39 intersects. It may be configured to be.

  A part of the outer cylinder nozzle 9 and the inner cylinder nozzle 11 are bent toward the center, and a part of the tip of the fuel conduction space 14 is bent toward the center. The plasma torch 12 is provided in the inner cylinder nozzle 11 in parallel with the inner cylinder nozzle 11 and close to the inner wall surface of the inner cylinder nozzle 11.

  The plasma 39 emitted from the plasma torch 12 is formed in parallel with the axis of the inner cylinder nozzle 11, but is drifted so that the pulverized coal mixed stream 16 is directed toward the center. The plasma 39 intersects and the pulverized coal mixed stream 16 is ignited and burned. In order to make the crossing more sure, the plasma torch 12 may be inclined as in the first embodiment.

  In addition, the fuel conduction space 14 may be bent to the center side, and is not limited to a part.

DESCRIPTION OF SYMBOLS 1 Furnace 3 Pulverized coal burner 4 Throat 5 Wind box 6 Combustion air supply path 7 Nozzle body 8 Secondary air conditioner 9 Outer cylinder nozzle 11 Inner cylinder nozzle 12 Plasma torch 13 Air for secondary combustion 14 Fuel conduction space 15 Pulverized coal Supply pipe 16 Pulverized coal mixed flow 17 Tertiary air introduction pipe 18 Damper 19 Auxiliary air adjustment mechanism 20 Main air adjustment mechanism 25 Partition wall plate 26 Outer air vane 27 Inner air vane 28 Tertiary combustion air 31 Tip side flange 32 Nozzle holder 33 Base end flange 34 Outer cylinder end plate 35 Inner cylinder nozzle fixing flange 36 Inner cylinder end plate 37 Plasma torch holder 39 Plasma

Claims (7)

  A pulverized coal burner comprising coal as fuel and a nozzle body and a combustion air conditioner provided so as to surround a tip portion of the nozzle body, the nozzle body comprising an inner cylinder nozzle and the inner cylinder nozzle An outer cylinder nozzle provided concentrically with the plasma torch, a fuel conduction space is formed between the inner cylinder nozzle and the outer cylinder nozzle, and a pulverized coal mixed flow is supplied to the fuel conduction space. The pulverized coal mixed flow is ejected in a ring shape from the fuel conduction space, the plasma torch is provided so that the tip is close to the tip of the fuel conduction space, and the plasma formed by the plasma torch is the pulverized coal. A pulverized coal burner configured to intersect with a mixed flow.   The pulverized coal mixed flow uses normal temperature primary air as a carrier medium, normal temperature secondary combustion air is supplied from the combustion air conditioner, and normal temperature tertiary combustion air is supplied from the inner cylinder nozzle. The pulverized coal burner according to claim 1.   The plasma torch is provided inside the inner cylinder nozzle, the axis of the plasma torch is inclined with respect to the axis of the inner cylinder nozzle, and the plasma formed by the plasma torch intersects the pulverized coal mixed flow. The pulverized coal burner according to claim 1 or 2, wherein the pulverized coal burner is configured as described above.   The plasma torch is provided outside the nozzle body, the axis of the plasma torch is inclined with respect to the axis of the nozzle body, and the plasma formed by the plasma torch intersects the pulverized coal mixed flow. The pulverized coal burner of Claim 1 or Claim 2 comprised.   The outer cylinder nozzle and the inner cylinder nozzle are configured such that at least a part of the front end portion of the fuel conduction space faces the center of the nozzle body, and the plasma formed by the plasma torch intersects the pulverized coal mixed flow. The pulverized coal burner according to any one of claims 1 to 3, wherein the pulverized coal burner is configured to do so.   The pulverized coal mixed flow is a high-concentration pulverized coal mixed flow set so that the air flow rate of the conveying medium suppresses spontaneous combustion of the pulverized coal being conveyed. 2. A pulverized coal burner according to item 1.   The pulverized coal burner according to any one of claims 1 to 6, wherein the outer cylinder nozzle, the inner cylinder nozzle, and the plasma torch can be attached and detached from a base end side, respectively.

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