JP2008145006A - Burner for pulverized coal combustion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burner for pulverized coal combustion capable of securing easiness in ignition and stability in combustion while using inexpensive pulverized coal of low quality as a fuel. <P>SOLUTION: This burner for pulverized coal combustion comprises a recessed hole 3 formed on a furnace wall surface 1, a bottomed cylindrical chamber 6 disposed concentrically to the recessed hole and opened at its core-side tip, a first jetting portion 9 opened at a bottom portion 8 of the chamber, and a second jetting portion 12 of a ring-shaped space 14 formed between the chamber and the recessed hole. The core-side tip is flush with or approximately flush with the furnace wall surface, the air 17 for primary combustion is jetted with the pulverized coal 18 from the first jetting portion, and the air 21 for secondary combustion is jetted from the second jetting portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pulverized coal combustion burner used for a pulverized coal boiler, and more particularly to a pulverized coal combustion burner capable of stably burning low quality pulverized coal.

  In pulverized coal boilers using pulverized coal as fuel, bituminous coal, which has many volatile components and is easy to ignite and has excellent flame stability, has been used in recent years. It is required to use low quality pulverized coal such as semi-anthracite or oil coke as fuel.

  The pulverized coal is ignited and burned by a process in which volatile components are generated by heating the pulverized coal, first the volatile components are ignited, and then the pulverized coal main body is ignited. Therefore, pulverized coal such as anthracite, semi-anthracite, or oil coke with a small amount of volatile components is difficult to ignite and lacks stability of combustion and flame.

  For this reason, in order to ignite pulverized coal with few volatile components and to make it self-sustained stably, it is necessary to supply pulverized coal in a high temperature state where even small volatile components can ignite. Therefore, in a pulverized coal combustion burner that uses pulverized coal with less volatile components as fuel, the pulverized coal combustion burner opens directly on the inner wall surface of the furnace and receives heat from the furnace, resulting in a high temperature state. ing.

  On the other hand, when the burner for pulverized coal combustion becomes high temperature, distortion due to thermal expansion increases, and the shape of the burner is deformed. The deformation of the shape affects the flow state of pulverized coal, primary air, and secondary air, and causes combustion to become unstable.

Japanese National Patent Publication No. 10-501056

  In view of such circumstances, the present invention provides a burner for pulverized coal combustion that uses inexpensive low-quality pulverized coal as a fuel and ensures easy ignition and combustion stability.

  The present invention includes a concave hole formed in a furnace wall surface, a bottomed cylindrical chamber disposed concentrically with the concave hole and having an opening at a core-side tip, and a first ejection portion opening at the bottom of the chamber. And a second jet part of a ring-shaped space formed between the chamber and the concave hole, and the core side tip is at the same or substantially the same position as the furnace wall surface, and from the first jet part The present invention relates to a pulverized coal combustion burner configured such that primary combustion air is ejected together with pulverized coal, and secondary combustion air is ejected from the second ejection part.

  Further, the present invention relates to a pulverized coal combustion burner in which a third ejection portion is opened at the bottom, and the third ejection portion ejects temperature adjusting air into the chamber.

  The present invention also relates to a pulverized coal combustion burner in which a plurality of slits are perforated at equal intervals around the front end of the chamber, and the front end of the chamber has a skirt portion whose diameter increases toward the front end. The slit length S is related to a pulverized coal combustion burner formed so as to extend in the proximal direction from the skirt portion, and the slit length S is a chamber outer diameter D and a chamber total length L. In contrast, the present invention relates to a pulverized coal combustion burner in which S / D ≧ 0.2 and S ≦ 0.1L, and the slit length S is approximately 1/10 of the diameter of the concave hole or 100 mm. This relates to a large pulverized coal combustion burner.

  According to the present invention, a concave hole formed in the furnace wall surface, a bottomed cylindrical chamber disposed concentrically with the concave hole and having an opening at the core-side tip, and a first jet opening at the bottom of the chamber And a second jet part of a ring-shaped space formed between the chamber and the concave hole, the core-side tip is at the same or substantially the same position as the furnace wall surface, and the first jet Since the primary combustion air is ejected together with the pulverized coal from the section, and the secondary combustion air is ejected from the second ejection section, the primary combustion air is heated in the furnace and from the flame. The combustion air and the pulverized coal ejected by heating the secondary combustion air are heated, and even pulverized coal with less volatile components can be stably self-sustained.

  Further, according to the present invention, the third jetting part is opened at the bottom, and the third jetting part jets the temperature adjusting air into the chamber, so that the temperature inside the chamber can be adjusted. Enables self-sustained combustion according to quality.

  Further, according to the present invention, since a plurality of slits are formed at equal circumferential intervals at the front end of the chamber, the change in shape due to thermal expansion of the chamber is prevented, and the primary combustion air, The secondary combustion air is prevented from drifting and turbulent, and stable combustion is possible even when the chamber is at a high temperature.

  Further, according to the present invention, the distal end portion of the chamber is a skirt portion whose diameter is expanded toward the distal end, and the length S of the slit is formed so as to extend in the proximal direction from the skirt portion. The skirt portion is prevented from thermal deformation, which is liable to affect the drift and flow disturbance of the secondary combustion air, and enables stable combustion.

  According to the present invention, the length S of the slit is S / D ≧ 0.2 and S ≦ 0.1L with respect to the chamber outer diameter D and the chamber total length L. Therefore, even when the slit is formed, The rigidity of the burner chamber is maintained, and stable combustion is possible.

  Furthermore, according to the present invention, since the length S of the slit is approximately 1/10 of the diameter of the concave hole or 100 mm larger, it is possible to effectively prevent the occurrence of thermal distortion in a portion where thermal deformation is likely to occur. Exhibits an excellent effect.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  First, the pulverized coal combustion burner according to the present invention will be described with reference to FIGS.

  In FIG. 1, reference numeral 1 denotes a furnace wall of a pulverized coal-fired boiler, which is made of a heat-resistant material such as a refractory brick or a water-cooled wall pipe. A required number of pulverized coal burning burners 2 are provided at required locations on the furnace wall 1.

  Hereinafter, the pulverized coal combustion burner 2 will be described.

  The furnace wall 1 is provided with a concave hole 3 penetrating the furnace wall 1, and the inner peripheral edge portion of the concave hole 3 is formed with a tapered portion 4 whose diameter increases toward the core.

  A burner cover 5 is provided on the outer peripheral side of the furnace wall 1 at a required distance from the outer peripheral surface of the furnace wall 1, and a burner chamber 6 that penetrates the burner cover 5 and is supported by the burner cover 5 is provided. It is provided concentrically with the concave hole 3.

  The burner chamber 6 has a substantially cylindrical shape and is supported by the burner cover 5 in the vicinity of the base end portion (side away from the core). A tapered skirt portion 7 whose diameter increases toward the core is formed at the distal end portion of the burner chamber 6, and the base end portion is closed by a bottom portion 8.

  The bottom portion 8 is opened with a first ejection portion 9 at an eccentric position, from which the primary combustion air 17 heated to a required temperature is ejected together with the pulverized coal 18. Further, a third ejection part 11 is opened at an eccentric position in the bottom part 8, and temperature adjusting air 10 is ejected from the third ejection part 11 (see FIG. 3).

  Between the skirt portion 7 and the taper portion 4, a ring funnel-shaped second ejection portion 12 is formed. Further, a secondary air conduction path 15 is constituted by a space 13 formed between the furnace wall 1 and the burner cover 5 and a space 14 formed between the burner chamber 6 and the concave hole 3. The secondary air conduction path 15 communicates with the second ejection part 12.

  In the space 13, variable swirl vanes 16 are arranged around the concave hole 3 at a required interval. The variable swirl vane 16 has a rotation axis parallel to the center line of the concave hole 3, and the rotation axis is As a center, all the variable swirl vanes 16 rotate in synchronization.

  The operation will be described below with reference to FIG.

  When the pulverized coal 18 having a small amount of volatile components such as anthracite, semi-anthracite, or oil coke is ejected together with the primary combustion air 17 from the first ejection part 9, the primary combustion air 17, the pulverized coal, and the like. 18 is ejected from the burner chamber 6 into the furnace. Further, since the first ejection portion 9 is eccentric, an internal circulation flow 19 is generated inside the burner chamber 6.

  When the secondary combustion air 21 is introduced from the space 13, the second combustion air 21 is deflected by the variable swirl vane 16, and flows in the space 14 so as to swirl around the burner chamber 6. It spouts out as a swirling flow expanding inside. Further, since it is ejected as an expanding swirl flow, an external circulation flow 22 is generated in front of the burner chamber 6.

  The internal circulation flow 19 is formed by the primary combustion air 17, and the external circulation flow 22 is generated by the secondary combustion air 21, whereby the internal circulation flow 19 and the external circulation flow 22 are generated. Is heated by the heat in the furnace and the heat of the flame 23, resulting in a high temperature. Accordingly, the pulverized coal injected through the internal circulation flow 19 and the external circulation flow 22 is heated to generate volatile components, which are ignited and burned.

  Thus, the pulverized coal combustion burner according to the present invention can stably ignite and burn even the pulverized coal 18 having less volatile components.

  When the temperature adjusting air 10 is ejected from the third ejecting portion 11, the temperature adjusting air 10 is ejected by traveling straight through the internal circulation flow 19 and the external circulation flow 22. Therefore, the internal circulation flow 19 is extruded, or the circulation strength of the internal circulation flow 19 and the external circulation flow 22 is weakened. Therefore, the temperature inside the burner chamber 6 can be adjusted by adjusting whether the temperature adjusting air 10 is ejected or by adjusting the flow rate. Therefore, the combustion state suitable for the volatile component contained can be realized.

  As described above, in the pulverized coal combustion burner according to the present invention, the inside of the burner chamber 6 is heated to stably burn the pulverized coal 18 having a small amount of volatile components. Accordingly, the temperature of the burner chamber 6 itself is also increased. For this reason, distortion due to thermal expansion of the burner chamber 6, that is, deformation of the burner chamber 6 must be considered.

  Since the burner chamber 6, particularly the tip, is exposed in the furnace, it is directly heated by the heat from the furnace and the heat from the external circulation flow 22, and it is considered that deformation due to distortion cannot be ignored. When the skirt portion 7 is deformed, the gap between the second ejection portions 12 becomes uneven on the circumference, and the secondary combustion air 21 supplied to the flame 23 becomes excessive or insufficient depending on the location, or is enlarged. This causes a problem that the swirling flow that is turbulent is disturbed and the stable external circulation flow 22 cannot be formed.

  In order to solve such a problem, a plurality of slits 24, that is, at least two slits 24 are formed at the tip of the burner chamber 6. The positions to be engraved are equally spaced in the circumferential direction, preferably four.

  The slit 24 is parallel to the center line of the burner chamber 6 and has a length S extending from the distal end to the proximal end side.

  Further, when the length S of the slit 24 is at least a length extending from the skirt portion 7 to the proximal end side, the continuity in the circumferential direction at the skirt portion 7 is cut by the slit 24, thereby expanding. There is no restriction in the circumferential direction, and since the tip of the burner chamber 6 is a free end, there is no restriction in the axial direction. Therefore, thermal expansion is not constrained, generation of thermal distortion is suppressed, and deformation is prevented.

  In particular, by preventing thermal deformation of the skirt portion 7, deformation of the shape of the second ejection portion 12 can be prevented, and the drift and turbulence of the secondary combustion air 21 can be eliminated, and at a high temperature. Combustion by the burner for pulverized coal combustion is stabilized.

  In order to prevent the occurrence of thermal distortion, it is preferable that the slit 24 is long. However, if the slit 24 is made longer than necessary, the rigidity of the burner chamber 6 alone is lowered, and thermal distortion and thermal stress are reduced. Further, the shape maintenance force against pressure fluctuation, vibration, etc. is reduced. Accordingly, the slit 24 has a length S of S / D ≧ 0 in order to maintain a rigidity necessary for, for example, pressure fluctuation, vibration, etc. in a state where the burner chamber 6 is provided in the burner cover 5. .2, S ≦ 0.1L.

  The portion of the burner chamber 6 that is most affected by the heat from the furnace and the heat of the flame 23 is the tip, and the base is cooled by the secondary combustion air 21, so the slit 24 It is sufficient if it is provided in a portion having a large heat effect.

  Further, the portion where the thermal influence is large and the distortion is a problem is, as a result of experience, about 1/6 or about 100 mm from the tip of the burner chamber 6 to the diameter of the concave hole. The length S is set to be approximately 1/10 of the diameter of the concave hole, or larger than 100 mm.

  As described above, the length S of the slit 24 is at least longer than the length of the skirt portion 7, or S / D ≧ 0.2, S ≦ 0.1L, or approximately 1 with respect to the diameter of the concave hole. By satisfying at least one condition of / 10 or greater than 100 mm, an effective deformation preventing effect can be obtained.

  The number of the slits 24 is set in consideration of the diameter of the burner chamber 6 and the like, and is set so that the rigidity of the burner chamber 6 does not decrease and thermal strain does not increase. It is preferable that about 4 are provided at a position equally divided into four circumferences. Moreover, even if a large number is provided, the effect of reducing the distortion is small with respect to the increase.

It is a schematic sectional side view of the burner for pulverized coal combustion which concerns on this invention. It is a front view of this pulverized coal combustion burner. It is explanatory drawing which shows the effect | action of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace wall 2 Burner for pulverized coal 3 Concave hole 4 Tapered part 5 Burner cover 6 Burner chamber 7 Skirt part 8 Bottom part 9 First ejection part 10 Temperature control air 11 Third ejection part 12 Second ejection part 14 Space 17 First Primary combustion air 18 Pulverized coal 19 Internal circulation flow 21 Secondary combustion air 22 External circulation flow 23 Flame 24 Slit

Claims (6)

  A concave hole formed in the furnace wall surface, a bottomed cylindrical chamber disposed concentrically with the concave hole and having an opening at the core-side tip, a first ejection portion opening at the bottom of the chamber, and the chamber A second jetting part of a ring-shaped space formed between the concave hole, the core-side tip is at the same or substantially the same position as the furnace wall surface, and the second jetting part together with the pulverized coal from the first jetting part. A pulverized coal combustion burner characterized in that primary combustion air is ejected and secondary combustion air is ejected from the second ejection section.   The pulverized coal combustion burner according to claim 1, wherein a third ejection portion is opened at the bottom, and the third ejection portion ejects temperature adjusting air into the chamber.   The burner for pulverized coal combustion according to claim 1, wherein a plurality of slits are formed at equal intervals in the front end of the chamber.   The tip portion of the chamber is a skirt portion whose diameter is expanded toward the tip portion, and the length S of the slit is formed so as to extend in the proximal direction from the skirt portion. Burner.   The burner for pulverized coal combustion according to claim 3, wherein the length S of the slit is S / D ≧ 0.2 and S ≦ 0.1L with respect to the chamber outer diameter D and the chamber total length L.   The burner for pulverized coal combustion according to claim 3, wherein the length S of the slit is approximately 1/10 of the diameter of the concave hole or greater than 100 mm.

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