JP5708119B2 - Pulverized coal burner - Google Patents

Description

  The present invention relates to a pulverized coal burner equipped with a plasma torch for pulverized coal ignition.

  Some pulverized coal burners use a plasma torch for ignition of pulverized coal. Since the plasma torch converts air into plasma and generates high-temperature plasma, the use of the plasma torch eliminates the need for an oil supply system and a single pulverized coal supply system, simplifying the equipment. Can be achieved.

  However, since the plasma torch has a structure in which plasma is ejected only in the axial direction from the tip, there is a problem that the high temperature region is narrow and the contact range between the high temperature region and pulverized coal is limited.

  In addition, as a plasma torch ignited using plasma to pulverized coal, there are those shown in Patent Document 1 and Patent Document 2, and in Patent Document 1, the anode shape is a differential user spreading in the flow direction of the working gas, A plasma ignition torch that draws a large amount of pulverized coal into the plasma portion due to a pressure difference by disclosing the wall surface static pressure of the differential user portion below atmospheric pressure is disclosed.

  Further, in Patent Document 2, the composite anode is used to change the plasma flow in the inner gap of the anode, thereby preventing the anode from being contaminated with pulverized coal, and the arc transport coil covered on the outside of the composite anode. A plasma ignition device is disclosed in which the length of a plasma flame is increased to improve the ignition performance of pulverized coal.

JP-A-1-244216 JP-T-2004-536270

  In view of such circumstances, the present invention provides a pulverized coal burner in which the contact range between the pulverized coal flow and the high temperature region of plasma is increased and stable ignition performance is obtained.

  The present invention provides a plasma torch on the axis of the pulverized coal burner, a pulverized coal nozzle for ejecting a pulverized coal flow concentrically with the plasma torch, and a plasma tip provided at the tip of the plasma torch, The present invention relates to a pulverized coal burner configured such that a plurality of ejection holes are formed in the circumferential direction of the plasma chip and high-temperature air is ejected from the ejection holes.

  According to the present invention, the plasma torch has a double tube structure, a plasma induction tube is provided as an inner tube, and a cooling gas nozzle is provided as an outer tube, and a cooling gas flow path is formed between the cooling gas nozzle and the plasma induction tube. A cooling gas introduction hole is provided in the plasma chip on the upstream side of the ejection hole, and the cooling gas passage and the inside of the plasma chip are communicated with each other through the cooling gas introduction hole. Is.

  According to the present invention, the ejection holes are formed in the circumferential direction of the plasma chip at a predetermined pitch, and the cooling gas introduction holes are formed in the circumferential direction of the plasma chip at a predetermined pitch. The present invention relates to a pulverized coal burner configured such that cooling gas flows into the plasma induction tube from the flow path through the cooling gas introduction hole and high-temperature air is radially ejected from the ejection hole. It relates to a pulverized coal burner whose tip is inclined with respect to the meridian of the plasma chip.

  According to the present invention, the plasma torch is disposed on the axis of the pulverized coal burner, the pulverized coal nozzle for ejecting the pulverized coal flow concentrically with the plasma torch is disposed, and the plasma tip is disposed at the tip of the plasma torch. Since a plurality of ejection holes are provided in the circumferential direction of the plasma chip and high temperature air is ejected from the ejection holes, the entire pulverized coal flow ejected from the pulverized coal nozzle is uniform. High temperature air can be brought into contact with this, and an excellent effect that stable ignition performance can be obtained is exhibited.

1 is a schematic cross-sectional view of a pulverized coal burner according to a first embodiment of the present invention. (A) is a principal part expanded sectional view of the plasma torch concerning the 1st example of the present invention, and (B) is an A arrow view of (A). It is a principal part expanded sectional view of the plasma torch concerning the 2nd example of the present invention.

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

  First, a first embodiment of the present invention will be described with reference to FIGS. 1, 2A and 2B.

  In FIG. 1, 1 is a furnace and 2 is a furnace wall of the furnace.

  A throat 3 is provided on the furnace wall 2, a wind box 4 is attached to the counter-fired furnace side of the furnace wall 2, and a pulverized coal burner 5 is provided concentrically with the throat 3 inside the wind box 4.

  The pulverized coal burner 5 includes a nozzle body 6 and a secondary air adjusting device 7 provided so as to surround the tip of the nozzle body 6.

  Inside the nozzle body 6, an inner cylinder nozzle 9 provided concentrically with the nozzle body 6, and a plasma torch 8 having a double tube structure concentric with the inner cylinder nozzle 9 is provided inside the inner cylinder nozzle 9. Provided. The plasma torch 8 has a cooling gas nozzle 11 as an outer tube and a plasma induction tube 12 as an inner tube, and an inner cylindrical cooling gas channel 20 is formed between the cooling gas nozzle 11 and the plasma induction tube 12. The tip of the cooling gas channel 20 is closed. The plasma induction tube 12 is formed of a heat-resistant material such as ceramic provided at the tip, and has a cylindrical plasma chip 13 concentric with the plasma induction tube 12 and closed at the tip. A part of 13 protrudes from the cooling gas nozzle 11.

  At least the cooling gas nozzle 11, the plasma induction tube 12, and the plasma chip 13 constitute a plasma torch 8, and a water-cooled type is separately provided on the outer peripheral surface of the plasma torch 8 or in the cooling gas channel 20. A cooling mechanism (not shown) is provided so that the plasma induction tube 12 is not melted by the heat of the plasma. If the plasma induction tube 12 can be sufficiently cooled only by the cooling gas 26 (described later) flowing through the cooling gas flow path 20, the cooling mechanism can be omitted.

  A required number (eight locations in FIG. 2B) of high-temperature air ejection holes 14 are formed in the circumferential surface of the plasma chip 13 at an equiangular pitch in the circumferential direction perpendicular to the axis. A required number of cooling gas introduction holes 15 are formed perpendicularly to the shaft center at an equiangular pitch in the circumferential direction on the upstream side (left side in FIG. 2A) from the air ejection holes 14. The high-temperature air ejection hole 14 is located at a portion protruding from the cooling gas nozzle 11, the cooling gas introduction hole 15 is located at a portion covered with the cooling gas nozzle 11, and the cooling gas introduction hole 15 is inserted through the cooling gas introduction hole 15. The gas flow path 20 communicates with the inside of the plasma chip 13.

  Between the nozzle body 6 and the inner cylinder nozzle 9, a fuel conduction space 10 is formed in which a side end of the furnace 1 is opened in a hollow cylindrical space. The nozzle body 6 has a reduced diameter portion 6a that gradually decreases in diameter at the tip.

  A pulverized coal mixed flow introduction pipe 16 communicates with a base portion (an end portion on the side of the counter-fired furnace) of the nozzle body 6, and primary air and pulverized coal conveyed to the primary air through the pulverized coal mixed flow introduction pipe 16. However, it flows into the fuel conduction space 10 from the tangential direction as the pulverized coal mixed flow 17. The pulverized coal mixed flow 17 flows while turning inside the fuel conduction space 10 and is ejected from the tip of the nozzle body 6.

  A tertiary air introduction pipe 18 communicates with the base of the inner cylinder nozzle 9. The tertiary air introduction pipe 18 may take in combustion air from the atmosphere side, or is opened to the inside of the wind box 4 and is one of the combustion air (secondary air 19) supplied to the wind box 4. May be introduced to the inner cylinder nozzle 9 as the tertiary air 21.

  The base end portion of the plasma torch 8 projects through the base end surface of the inner cylinder nozzle 9. Further, the base of the plasma induction tube 12 further extends from the cooling gas nozzle 11, and plasma generating air is supplied from the extended base end through a plasma air supply line 22, and the plasma induction tube 12. Is connected to a plasma power source 23, and the plasma power source 23 supplies power necessary for plasma excitation.

  A gas joint 24 is provided at the base end of the cooling gas nozzle 11, and the gas joint 24 is connected to a cooling gas supply source (not shown) via a cooling gas supply line 25, and normal temperature air is supplied from the cooling gas supply source. The cooling gas 26 is supplied to the cooling gas passage 20 through the gas joint 24.

  The secondary air conditioner 7 has an air guide duct 27 that is reduced in diameter toward the tip, and an air volume adjusting blade 28 that is provided at equal intervals around the base of the air guide duct 27. 28 is rotatable around a rotation shaft 29. The rotary shafts 29 are connected to each other by a link mechanism (not shown), the air volume adjusting blades 28 can be rotated synchronously, and the link mechanism is connected to an air volume adjusting blade driving unit (not shown) to drive the air volume adjusting blades. The angle of the air volume adjusting blade 28 is adjusted by the portion via the link mechanism.

  The fuel in the pulverized coal burner 5 will be briefly described.

  First, ignition of the pulverized coal burner 5 will be described.

  First, the cooling gas 26 is supplied from the cooling gas supply source (not shown) to the cooling gas passage 20 through the cooling gas supply line 25. Next, air for generating plasma is supplied from the plasma air supply line 22, and power for excitation is supplied to the plasma power source 23 to generate a plasma 31 at the tip of the plasma induction tube 12.

  The plasma 31 generated at the tip of the plasma induction tube 12 is about 6000 ° C., and the plasma 31 is mixed with the cooling gas 26 introduced from the cooling gas channel 20 through the cooling gas introduction hole 15. And is ejected from the high-temperature air ejection hole 14 as high-temperature air 32 of about 1000 ° C.

  Since the high-temperature air ejection holes 14 are formed in a plurality of radial directions at equal angular pitches on the peripheral surface of the plasma chip 13, the high-temperature air 32 diffuses in the radial direction with respect to the axis of the nozzle body 6. The high temperature region 33 is formed. The high temperature region 33 preferably extends over the entire pulverized coal outlet of the nozzle body 6. Therefore, the supply amount of plasma generation air to the plasma induction tube 12 and the supply amount of the cooling gas 26 are adjusted so that the high temperature region 33 extends over the entire pulverized coal outlet of the nozzle body 6.

  The pulverized coal mixed stream 17 is supplied from the pulverized coal mixed stream introduction pipe 16 and flows while swirling in the fuel conduction space 10, and is compressed in the process of passing through the fuel conduction space 10, and the nozzle body 6 It is ejected from the tip of. The wind box 4 is supplied with secondary air 19 as combustion air, and the secondary air 19 is adjusted in turning force or turning force and air volume by the air volume adjusting blade 28. And then ejected into the furnace 1.

  The pulverized coal flow ejected from the tip of the nozzle body 6 crosses the formed high temperature region 33. The pulverized coal comes into contact with the hot air 32 diffused in the process of crossing, and is mixed with the secondary air 19 to ignite. Since the temperature of the high temperature region 33 is sufficient to ignite pulverized coal, it can be reliably ignited. Further, since the high temperature region 33 extends over the entire pulverized coal outlet, the pulverized coal flow is ignited uniformly throughout.

  The ignition by the plasma torch 8 is continued until the temperature of the furnace 1 rises to a predetermined temperature, and when the self-sustained combustion (steady combustion) with the pulverized coal burner 5 alone becomes possible, the plasma 31 Occurrence is stopped. When the steady combustion state is reached, the plasma torch 8 may be moved backward so as not to receive radiant heat from the furnace.

  Further, the combustion state of the fuel is adjusted by the tertiary air 21 ejected from the inner cylinder nozzle 9 to the throat 3.

  Thus, in the above embodiment, since it is not necessary to use oil for igniting the pulverized coal, one fuel supply system may be used, and stable ignition performance can be obtained.

  In the first embodiment, the ceramic plasma chip 13 is screwed to the tip of the metal plasma induction tube 12, and the plasma induction tube 12 is concentrically multiplexed to communicate with the plasma chip 13. Since it can be implemented by providing the cooling gas nozzle 11, the amount of processing applied to the plasma induction tube 12 itself is small, and the present invention can be easily applied to a conventional plasma torch.

  Furthermore, in the first embodiment, since the cooling gas 26 is mixed with the high temperature plasma 31 and cooled to about 1000 ° C., the plasma chip 13 formed of ceramic or the like is melted by heat. The durability of the plasma torch 8 can be improved.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIGS. 2A and 2B are denoted by the same reference numerals, and description thereof is omitted.

  In the first embodiment, the high-temperature air ejection hole 14 is formed perpendicular to the axis of the plasma chip 13, but in the second embodiment, the high-temperature air ejection hole 14 has a tip on the downstream side. It is drilled so as to face away. That is, the tip of the high-temperature air ejection hole 14 is drilled away from a meridian that is a radius in a plane perpendicular to the axis of the plasma chip 13.

  The plasma 31 ejected from the tip of the plasma induction tube 12 is mixed with the cooling gas 26 introduced from the cooling gas flow path 20 in the plasma chip 13, and as the hot air 32 of about 1000 ° C., the high temperature air ejection hole 14. It ejects radially from the peripheral surface of the plasma chip 13 toward the downstream side.

  Similarly to the first embodiment, in the second embodiment, the required number of the high-temperature air ejection holes 14 are formed in the peripheral surface of the plasma chip 13 at an equiangular pitch. It diffuses in the radial direction with respect to the 13 axial centers and toward the downstream side. The high-temperature air 32 diffused in the radial direction crosses the pulverized coal mixed flow 17 (see FIG. 1) ejected from the tip of the nozzle body 6 (see FIG. 1), and the pulverized coal comes into contact with the high-temperature air 32. Mix with air 19 (see FIG. 1) and ignite.

  At this time, the tip of the high-temperature air ejection hole 14 is inclined downstream in the plasma 31 ejection direction, so that the pressure loss when the high-temperature air 32 collides with the tip of the plasma chip 13 can be reduced. The hot air 32 ejected from the hot air ejection holes 14 can be diffused over a wide range.

  Also in the second embodiment, since it is not necessary to use oil for ignition, one fuel supply system may be used, and the high-temperature air 32 is uniformly distributed over the entire pulverized coal mixed stream 17. It can be contacted, and stable ignition performance can be obtained.

  In the second embodiment, the tip of the hot air ejection hole 14 is inclined downstream in the ejection direction of the plasma 31, but the tip of the hot air ejection hole 14 is in the ejection direction of the plasma 31. It may be inclined upstream.

  In both the first and second embodiments, the cooling gas introduction hole 15 is formed perpendicularly to the axis of the plasma chip 13, but the cooling gas introduction hole 15 has a tip. The plasma 31 may be inclined to the downstream side in the ejection direction, and the tip may be inclined to the upstream side in the plasma 31 ejection direction.

  Further, in both the first embodiment and the second embodiment, the high-temperature air ejection holes 14 and the cooling gas introduction holes 15 are formed in the peripheral surface of the plasma chip 13 at an equal angular pitch. The high-temperature air ejection holes 14 and the cooling gas introduction holes 15 may be formed at different angular pitches instead of being equiangular.

  Further, the high-temperature air ejection hole 14 and the cooling gas introduction hole 15 are not only inclined in a direction away from the plane orthogonal to the axis of the plasma chip 13 but also inclined with respect to the meridian in the plane of the plane. The high-temperature air injection hole 14 and the cooling gas introduction hole 15 are decentered with respect to the axial center, and the high-temperature air 32 is moved to the axis of the plasma chip 13. It may be diffused while swirling with respect to the mind.

  That is, the high-temperature air ejection hole 14 and the cooling gas introduction hole 15 may be inclined with respect to the meridian in a plane orthogonal to the axis of the plasma chip 13 or separated from the plane. The high temperature air injection hole 14 and the cooling gas introduction hole 15 may be inclined at different angles, and the high temperature air injection hole 14 and the cooling gas introduction hole may be different from each other. Different inclination angles may be used for each of the 15 holes.

DESCRIPTION OF SYMBOLS 1 Furnace 2 Furnace wall 3 Throat 5 Pulverized coal burner 6 Nozzle body 7 Secondary air conditioner 8 Plasma torch 9 Inner cylinder nozzle 10 Fuel conduction space 11 Cooling gas nozzle 12 Plasma induction tube 13 Plasma chip 14 Hot air ejection hole 15 Cooling gas introduction Hole 16 Pulverized coal mixed flow introduction pipe 17 Pulverized coal mixed flow 19 Secondary air 20 Cooling gas flow path 23 Power source for plasma 26 Cooling gas 31 Plasma 32 High temperature air 33 High temperature region

Claims (3)

A plasma torch is disposed on the axis of the pulverized coal burner, a pulverized coal nozzle for ejecting a pulverized coal flow concentrically with the plasma torch is disposed, a plasma chip is provided at the tip of the plasma torch, and the plasma chip A plurality of ejection holes are formed in a circumferential direction, and high temperature air is ejected from the ejection holes , and the plasma torch has a double tube structure, a plasma induction tube as an inner tube, and a cooling gas nozzle as an outer tube A cooling gas flow path is formed between the cooling gas nozzle and the plasma induction tube, a cooling gas introduction hole is provided in the plasma chip upstream of the ejection hole, and the cooling gas introduction hole is formed in the plasma chip. A pulverized coal burner characterized in that the cooling gas flow path and the inside of the plasma chip communicate with each other . The ejection holes are drilled in the circumferential direction of the plasma chip at a predetermined pitch, and the cooling gas introduction holes are drilled in the circumferential direction of the plasma chip at a predetermined pitch. the cooling gas into the plasma-induced tube through the gas introducing hole flows, pulverized coal burner of claim 1, wherein from vents hot air configured as ejected radially. The pulverized coal burner according to claim 1 or 2 , wherein a tip of the ejection hole is inclined with respect to a meridian of the plasma chip.

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