JP2009264654A - Pulverized coal burner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulverized coal burner that reduces the NOx concentration in combustion gas, while maintaining ignitability using a simple structure. <P>SOLUTION: In this pulverized coal burner (20) having an oil nozzle (6), a primary air nozzle (1), a pulverized coal nozzle (4), and air nozzles (2, 3), a fixed plate (15) and a movable member (16) are arranged on the inner peripheral wall of the front end of the primary air nozzle (1); the fixed plate (15) is provided with slit holes (15a), each having a pair of opposed wall surfaces having an opening area gradually reduced from the upstream side to the downstream side; the movable member is mounted upstream of the fixed plate in the primary air nozzle (1) so as to be able to advance and retract; the movable member has grids (16a), adapted to close the slit holes (15a) and arranged in a radial pattern, at positions that correspond to the slit holes (15a); the degree of insertion for each grid (16a) into a corresponding slit hole (15a) is adjusted, to close either of a pair of gaps formed between the grid (16a) or a pair of opposed surfaces of the slit hole, and to cause primary air ejected from the other gap to swirl; and the swirl flow of the primary air is ejected into a furnace, to facilitate mixing of the primary air with atomized oil ejected from the oil nozzle (6). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pulverized coal burner used for a pulverized coal fired boiler or the like.

  In recent years, a pulverized coal burner 20 used in a furnace 21 such as a pulverized coal fired boiler as shown in FIG. 10 is intended to reduce the amount of nitrogen oxide (NOx) generated in combustion gas. Developed and put into practical use. The coal supplied from the bunker 22 to the mill 23 is pulverized and supplied from the blower 24 to the pulverized coal burner 20. Combustion air is supplied from the blower 26 to the wind box 8 around the pulverized coal burner 20 at the same time as the powder ends, and is used for burning the pulverized coal in the burner 20.

  Further, a pulverized coal burner 20 disclosed in US Pat. No. 5,697,306, which is an example of this type of pulverized coal burner 20 conventionally known, is a core air nozzle that ejects combustion air to the central axis of the burner. A pulverized coal nozzle through which a solid-gas two-phase flow of pulverized coal and conveying air flows is provided on the outer periphery thereof, and a secondary air nozzle and a tertiary air nozzle for ejecting combustion air on the outer periphery of the pulverized coal nozzle Is provided. The pulverized coal burner 20 controls the ratio of air and fuel at the burner outlet by adjusting the amount of combustion air ejected from the core air nozzle to reduce the NOx concentration in the combustion gas.

  Some pulverized coal burners 20 directly ignite a burner starting oil burner with an ignition device without having a starting torch. FIG. 11 shows an example of this type of pulverized coal burner 20 that is conventionally known. For example, a primary air nozzle that ejects combustion air around an oil spray nozzle provided in a central shaft portion like a burner described in JP-A-2002-48306, and pulverized coal is conveyed around the outer periphery of the primary air nozzle. There is disclosed a pulverized coal burner 20 provided with a pulverized coal nozzle through which a solid-gas two-phase flow with the working air flows, and a secondary air nozzle for ejecting combustion air on the outer periphery of the pulverized coal nozzle.

In the pulverized coal burner 20, the combustion air ejected from the primary air nozzle is swirled by a swirler. The primary air from the primary air nozzle is spouted from the burner into the furnace as a swirling flow, so that the primary air spreads to the outer periphery by centrifugal force and is easily mixed with pulverized coal. In addition, a low pressure portion is formed in the furnace at the central portion of the burner outlet, and a circulating flow is formed in this portion from downstream to upstream. High-temperature burned gas stays in the circulating flow, so the pulverized coal is ignited earlier. The circulation flow has an effect that a stable flame can be maintained, particularly when the oil burner is ignited by an ignition device.
US Pat. No. 5,697,306 JP 2002-48306 A

  The above-described prior art is intended to reduce the NOx concentration in the combustion gas by adjusting the mixing ratio of pulverized coal and air by providing combustion air nozzles on the outer periphery and inside of the pulverized coal nozzle. Furthermore, in the case of a configuration in which the oil burner is ignited by an ignition device without having a starting torch in the prior art, a stable flame can be maintained by forming a circulation flow on the central axis of the burner outlet. It has characteristics. However, in these pulverized coal burners 20, the solid-gas two-phase flow ejected from the pulverized coal nozzle is centrifugal force when the primary air is ejected into the furnace as a swirling flow from the primary air nozzle by a swirler during pulverized coal combustion. It spreads to the outer peripheral side and becomes easy to mix with the combustion air from the secondary air nozzle and the tertiary air nozzle. Therefore, there is a technical problem that the NOx reduction region is reduced and the NOx concentration in the combustion gas increases.

  As a solution to this problem, it is conceivable to make the structure capable of adjusting the tilt angle of the swirling blade of the swirler or the installation position of the swirler, but the structure becomes complicated and the movable part of the swirler is moved by heat radiation. There is a possibility that it will not move due to thermal expansion. Therefore, it is necessary to have a structure that can secure a gap even if the movable part of the swirler expands, but if the structure has a gap in the swivel part, there is a new problem that the strong swirling required during oil-only firing is reduced. Arise.

  An object of the present invention is to provide a pulverized coal burner that improves the above-described problems of the prior art with a simple structure and reduces the NOx concentration in combustion gas while maintaining the ignitability of pulverized coal and oil. That is.

The above-mentioned problem of the present invention is solved by the following solution means.
The present invention relates to a pulverized coal burner having a pulverized coal nozzle having an oil spray nozzle on the central axis and a primary air nozzle around the nozzle, and a solid-gas two-phase flow of pulverized coal and conveying air on the outer periphery thereof. The primary air nozzle includes a plate having a notch at the tip thereof and a structure that blocks a one-way flow path having an obstacle, and is capable of switching between a straight flow and a swirl flow depending on a combustion state. It is desirable to block the one-way flow path of the primary air nozzle and give a swirling flow to the jetting combustion air during the oil-only firing of the pulverized coal burner. By jetting into the furnace as a swirling flow, the combustion air spreads to the outer periphery by centrifugal force and becomes easy to mix with the atomized oil. Further, a low pressure portion is formed in the central portion, and a circulating flow from downstream to upstream is formed in this portion. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil.

  On the other hand, when pulverized coal is burned exclusively by the pulverized coal burner, it is desirable to give a straight flow to the combustion air ejected from the primary air nozzle. When pulverized coal is exclusively burned, the solid-gas two-phase flow spreads to the outer periphery by centrifugal force by ejecting it from the primary air nozzle as a swirling flow, making it easier to mix with the combustion air after the secondary air nozzle. Therefore, the NOx reduction region is reduced and the NOx concentration in the combustion gas increases. By giving a straight flow to the combustion air ejected from the primary air nozzle, the mixing with the combustion air after the secondary air nozzle is delayed, and the NOx concentration in the combustion gas is reduced by expanding the NOx reduction region. be able to. In addition, by having a structure in which air is ejected from two directions at the tip of the primary air nozzle, thermal expansion due to heat radiation of a structure that closes the flow path in one direction of the movable portion can be reduced.

  Further, a secondary air nozzle and a tertiary air nozzle for ejecting combustion air are provided on the outer periphery of the pulverized coal nozzle. At this time, it is desirable to have an obstacle that obstructs the flow of air ejected from the secondary air nozzle or the tertiary air nozzle at the tip of the partition wall that separates the secondary air nozzle and the tertiary air nozzle. By providing the obstacle, the pressure is reduced downstream of the obstacle, and a circulating flow is formed. High-temperature burned gas stays in the circulating flow and accelerates the ignition of pulverized coal.

  Further, it is desirable to provide a venturi inside the outer peripheral wall of the pulverized coal nozzle and a pulverized coal concentrator on the outer periphery of the primary combustion air nozzle. When a flame holder is provided on the outer peripheral portion of the fuel nozzle outlet, a recirculation region is formed in the downstream portion, and particles and gas having a light mass are entrained. When using coarse pulverized coal with a 200-mesh pass rate of around 60-70% as the fuel, the amount of pulverized coal caught in the recirculation region downstream of the flame holder decreases because there is little pulverized coal of 30 μm or less. Combustible volatile gas components released by heating the pulverized coal with the combustion air from the primary air nozzle instead of charcoal are entrained in the recirculation region, so a high-temperature gas body is also formed in the recirculation region Thus, ignition flame holding of unignited coarse pulverized coal passing in the vicinity of the flame holder is promoted. Even when high fuel specific coal is used as the fuel, if the pulverized coal is heated appropriately, a high-temperature recirculation region can be formed in the wake of the flame holder as described above, and its ignitability is improved. be able to.

  According to the present invention, during the oil-only firing at the start of the pulverized coal burner, the one-way flow path of the primary air nozzle is closed, and the swirling flow is given to the jetting combustion air, so that the combustion air is centrifugal force It spreads around the burner outlet and becomes easy to mix with the atomized oil. In addition, a low pressure portion is formed in the central portion of the burner outlet, and a circulating flow from downstream to upstream is formed in this portion. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil.

  On the other hand, when pulverized coal is burned exclusively by the pulverized coal burner, as shown in FIG. 9, a secondary air nozzle is provided by giving a straight flow to the combustion air jetted from the primary air nozzle into the furnace and further increasing the amount of combustion air. The NOx concentration in the combustion gas can be reduced by delaying the subsequent mixing with the combustion air and expanding the NOx reduction region. In addition, by having a structure in which air is ejected from two directions at the tip of the primary air nozzle, thermal expansion due to heat radiation of a structure that closes the flow path in one direction of the movable portion can be reduced.

  The pulverized coal burner according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a pulverized coal burner 20 of the present embodiment. The pulverized coal burner 20 has an oil spray nozzle 6 on the central axis and a primary air nozzle 1 around the oil spray nozzle 6, and a solid-gas two-phase flow 13 of pulverized coal and conveying air is formed on the outer periphery of the primary air nozzle 1. It has a flowing pulverized coal nozzle 4. A secondary air nozzle 2 that ejects combustion air 12 to the outer periphery of the pulverized coal nozzle 4 and a tertiary air nozzle 3 to the outer periphery of the secondary air nozzle 2 are provided. An oil spray nozzle 6 that penetrates the primary air nozzle 1 and is ignited by liquid fuel is provided, and the oil spray nozzle 6 is used for assisting pulverized coal when the burner is started or during low-load combustion. . A fixed plate 15 that swirls or goes straight to the air ejected from the primary air nozzle 1 is provided around the oil spray nozzle 6 at the tip of the primary air nozzle 1, and the primary air nozzle 1 upstream of the fixed plate 15. A movable member 16 provided with a grid radially is provided around the oil spray nozzle 6 inside.

A venturi 5 for narrowing the nozzle inner diameter of the pulverized coal nozzle 4 is provided on the inner wall surface of the pulverized coal nozzle 4, and the outer wall surface of the primary air nozzle 1 in the pulverized coal nozzle 4 on the downstream side of the mounting portion of the venturi 5 is provided on the inner wall surface of the pulverized coal nozzle 4. After narrowing the flow passage cross section of the pulverized coal nozzle 4 once, an expanding pulverized coal concentrator 11 is provided, and at the tip of the partition wall separating the pulverized coal nozzle 4 and the secondary air nozzle 2 (exit of the pulverized coal nozzle 4). A flame holder 9 is provided, and an obstacle (guide sleeve) 10 is provided at the tip of the partition wall that separates the secondary air nozzle 2 and the tertiary air nozzle 3, and a furnace wall 7 to which the tip of the tertiary air nozzle 3 is attached. The opening (burner throat) is an inclined wall surface. The guide sleeve 10 and the inclined wall surface of the opening of the furnace wall 7 are configured to expand the secondary air flow path and the tertiary air flow path at substantially the same inclination angle.
Note that only the secondary air nozzle 2 or the secondary air nozzle 2 and the tertiary air nozzle 3, or a multi-stage air nozzle such as a quaternary air nozzle (not shown) may be provided on the outer periphery of the pulverized coal nozzle 4.

  1 has a structure in which air is jetted from two directions at the tip of the primary air nozzle 1, and a fixed plate 15 that blocks a unidirectional flow path during oil combustion, and a movable that blocks a unidirectional flow path of the fixed plate. A schematic diagram of the member 16 is shown in FIG. 2A is a front view of the fixed plate 15 as viewed from the furnace side, FIG. 2B is a sectional view taken along the line AA in FIG. 2A, and FIG. FIG. 2D is a sectional view taken along the line BB in FIG. 2C, and FIG. 2E is a sectional view taken along the line CC in FIG. 2C. FIG.

  The fixed plate 15 shown in FIG. 2 is inserted into the tip of the primary air nozzle 1 so as to block the flow passage cross section of the primary air nozzle 1 while being supported at the center by the oil spray nozzle 6. The fixed plate 15 is disposed at the tip of the primary air nozzle 1 and has a plurality of slit holes 15a radially from the central portion, and the primary air jets into the furnace through the slit holes 15a. It is a disk-like structure that gives a right turn or a left turn. In addition, a movable member 16 is slidably disposed in the furnace direction or in the direction away from the furnace (front-rear direction) on the upstream side of the fixed plate 15 installation portion in the primary air nozzle 1 by an operation member 17 provided outside the furnace. .

As shown in FIG. 2 (b), the slit hole 15a of the fixed plate 15 is sequentially reduced from a rectangular relatively wide opening from the upstream portion of the primary air nozzle 1 toward the furnace side, and is rectangular on the furnace side. It is the structure provided with the inclined wall surface which consists of a shape provided with relatively narrow opening. That is, each slit hole 15a is formed in at least one radial opening end (opening ridge line) 15a ₁ on the upstream side of the primary air nozzle 1 and the upstream opening end (opening ridge line) 15a ₁ . An inclination angle at which a virtual plane extending a wall surface connecting the corresponding opening end (opening ridge line) 15a ₂ on the downstream side of the primary air nozzle 1 of the same slit hole 15a intersects the surface of the fixed plate 15 at an acute angle. An inclined wall surface having α is formed.

  The inclination angle α of the inclined wall surface with respect to the surface of the fixed plate 15 is 90 ° or less (<90 °). In FIG. 2B, the wall surface facing the inclined wall surface also forms the same inclination angle α in the opposite direction. Further, the number of the slit holes 15a is changed depending on the required turning strength and turning angle.

  On the other hand, each lattice 16a of the movable member 16 has a shape that can be inserted into the slit hole 15a of the fixed plate 15, and the cross-sectional shape shown in FIG. It is provided radially with fixed parts. The inclination angle β of the corner portion on the bottom side of the cross section shown in FIG. 2D of the lattice 16a of the movable member 16 is the same as the inclination angle α of the inclined wall surface of the slit hole 15a of the fixed plate 15, and the fixed plate The number of 16 lattices 16a matches the number of slit holes 15a.

  Since each lattice 16a of the movable member 16 has the same number of substantially the same cross-sectional area as the slit holes 15a of the fixed plate 15, the movable member 16 is moved from the upstream side of the pulverized coal nozzle to the furnace side, and the movable member 16 is moved. When the 16 lattices 16a are inserted into the slit holes 15a of the fixed plate 15, the opening area of the fixed plate slit holes 15a becomes narrow as shown in FIG.

  Here, when one wall surface of the inclined wall surface of the slit hole 15a of the fixed plate 15 is closed by each lattice 16a of the movable member 16, the inclined surface of the lattice 16a shown in FIG. 2B is opposed to both sides of the slit hole 15a. The smaller the gap h of one of the inclined wall surfaces is, the more the swirl strength of the primary air flow passing through this gap increases. In FIG. 2 (a), the gap is provided so that the primary air jetted into the furnace through the slit hole 15a is turned rightward as indicated by an arrow toward the furnace. The gap is formed in the slit hole 15a. If it is provided on the side of the inclined wall surface opposite to the primary air, the primary air spouted into the furnace is turned leftward toward the furnace.

The movable member 16 is attached to a tubular operation member 17 that is attached to the outer periphery of the oil spray nozzle 6 for spraying heavy oil so as to be movable forward and backward. As long as the operation member 17 can drive the movable member 16 from the outer side of a furnace wall as shown in FIG. 1, a shape and a structure will not be ask | required.
The movable member 16 can be operated by the operation member 17 so as to be able to advance and retreat in the longitudinal direction of the burner 20 (the direction along the central axis C). Is pushed into the slit hole 15a of the fixed plate 15 to close the gap between one inclined wall surface of the slit hole 15a and the lattice 16a, and the combustion air 12 is swirled from the gap between the other inclined wall surface of the slit hole 15a and the lattice 16a. Erupts as a stream. The jetted combustion air 12 spreads to the outer peripheral side of the primary air nozzle 1 by centrifugal force and is easily mixed with the atomized oil. Further, a low pressure portion is formed at the central portion at the burner outlet in the furnace, and a circulating flow is formed in this portion from downstream to upstream. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil. The swirl of the swirl flow of the combustion air 12 is preferably about 0.5 to 1.0 in terms of swirl.

  On the other hand, at the time of burning pulverized coal in the burner, the movable member 16 is pulled away from the furnace, the grids 16a of the movable member 16 are separated from the slit holes 15a of the fixed plate 15, and are ejected from the primary air nozzle 1. By giving a straight flow to the primary air 12, the mixing with the combustion air after the secondary air nozzle is delayed, and the NOx concentration in the combustion gas is expanded, so that the NOx concentration can be reduced. Even if the leakage is taken into consideration, the swirl number of the combustion air 12 in the straight flow is preferably 0.1 or less.

  In addition, since the fixed plate 15 is disposed closer to the furnace side than the driving part of the movable member 16, the heat radiation from the inside of the furnace is blocked by the fixed plate 15 and hits the driving part of the movable member 16 can be reduced. , Thermal expansion can be reduced.

In addition, although the thing of the shape where the flow-path shape of the axial longitudinal direction of the slit hole 15a of the fixed plate 15 narrows was shown in FIG. 2, this invention is not limited to this.
For example, both opposing wall surfaces of the axial longitudinal flow path of the slit hole 15a of the fixed plate 15 are formed in a direction along the central axis C, and the cross-sectional shape of the lattice 16a of the movable member 16 narrows the flow path shape in the axial longitudinal direction. The same effect can be obtained by inserting and removing the thus formed one.

  FIG. 3 shows a fixed plate 15 and a movable member 16 that have a structure in which air is ejected from two directions at the tip of the primary air nozzle 1 of FIG. 1 and closes the flow path in one direction during oil combustion. 3A is a front view of the fixed plate 15 as viewed from the furnace side, FIG. 3B is a sectional view taken along the line AA in FIG. 3A, and FIG. Front view seen from the furnace side, FIG. 3 (d) is a cross-sectional view taken along the line B-B in FIG. 3 (c), and FIG. 3 (e) is a cross-sectional view taken along the line C-C in FIG. FIG.

The fixed plate 15 shown in FIG. 3 has a shape in which a plurality of triangular slit holes 15a are provided in the circumferential direction so as to widen from the center, and the movable member 16 is inserted into each of the slit holes 15a. 15a is provided with a plurality of triangular grids 16a having a triangular cross section in the circumferential direction so as to extend from the center of the burner so that the opening of the burner 15a can be closed. It is mounted on a tubular operating member 17 that is mounted on the outer periphery of the spray nozzle 6 so as to be able to advance and retract.
Since the functions of the fixed plate 15 and the movable member 16 shown in FIG. 3 are the same as those of the fixed plate 15 and the movable member 16 described in the first embodiment, detailed description thereof will be omitted.

  In the embodiment shown in FIG. 3, the shape of the flow path in the axial longitudinal direction of the opening of the slit hole 15a of the fixed plate 15 is shown to be narrow, but the present invention is not limited to this. For example, it is possible to insert / remove the slit hole 15a whose opening in the axial longitudinal direction is parallel and whose cross-sectional shape of the movable member 16 narrows the axial longitudinal flow path. Similar effects can be obtained.

  FIG. 4 is a cross-sectional view of the pulverized coal burner 20 of the embodiment having a structure in which air is ejected from two directions at the tip of the primary air nozzle 1 and having a fixed plate that closes the flow path in one direction during oil combustion. Show. Since the pulverized coal burner 20 shown in FIG. 4 has the same structure as that of the pulverized coal burner 20 shown in FIG. 1 except for the configuration of the operation member 17, detailed description thereof will be omitted.

  FIG. 5 shows the fixed plate 15 and the movable member 16 of the burner 20 of this embodiment. 5A is a front view of the fixed plate 15 viewed from the furnace side, FIG. 5B is a cross-sectional view taken along the line AA in FIG. 5A, and FIG. Front view seen from the furnace side, FIG. 5 (d) is a cross-sectional view taken along the line B-B in FIG. 5 (c), and FIG. 5 (e) is a cross-sectional view taken along the line C-C in FIG. FIG.

  The fixed plate 15 shown in FIG. 5 has a shape in which a plurality of triangular slits are provided in the circumferential direction so as to widen from the center, and the movable member 16 is inserted into the slit 15a to open the slit hole 15a. A plurality of triangular lattices 16a are provided independently in the circumferential direction so as to be divergent from the center so that each portion can be closed, and each lattice 16a is individually connected to each lattice 16a. 17 is operated so as to freely advance and retract along the burner central axis C.

  The fixed plate 15 shown in FIG. 5 has a structure that provides a right turn toward the furnace. As shown in FIG. 4, it is fixed to the tip of the primary air nozzle 1 and a movable member 16 is installed upstream thereof. The fixed plate 15 has a slit structure and has an inclined wall surface provided with a flow path that decreases toward the furnace. Here, the inclination angle α (<90 °) and the number of slits with respect to the plane on the furnace side of the fixed plate 15 of the inclined wall surface are changed depending on the required turning strength and turning angle.

  By moving the movable member 16, the gap between the inclined wall surface in one direction of the slit hole 15 a of the fixed plate 15 and the lattice 16 a of the movable member 16 can be closed. The lattice 16a of the movable member 16 has an isosceles triangular section having the same inclination angle β as the inclination angle α of the inclined wall surface of the slit hole 15a of the fixed plate 15, and is provided in the same number as the slit holes 15a. Therefore, when the lattice 16a is inserted into the slit hole 15a of the fixed plate 15 to block the flow path on the one inclined wall surface side of the slit hole 15a, the turning strength increases as the gap h shown in FIG. . Further, in FIG. 5, the cross-section of the structure that blocks the flow path on one inclined wall surface side of the slit hole 15a is triangular, but the inflow of combustion air from the flow path on one inclined wall surface side of the slit hole 15a is prevented. The shape of the slit hole 15a is not limited as long as it is a structure in which air is ejected into the furnace from the flow path on the other inclined wall surface side of the slit hole 15a.

  At the time of oil-only firing at the time of starting the burner 20 having the above-described configuration, each of the lattices 16a of the movable member 16 is inserted into each of the plurality of triangular slits 15a, and the combustion air jetted from the fixed plate 15 to the furnace side is swirled. Thus, the combustion air spreads to the outer periphery by centrifugal force and becomes easy to mix with the atomized oil. Further, the swirl flow forms a low pressure portion at the center portion of the burner outlet, and a circulating flow is formed in this portion from downstream to upstream. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil. Further, the turning strength can be changed by changing the degree of pushing the lattice 16a of the movable member 16 into the slit 15a of the fixed plate 15. The swirl of the swirl flow of the combustion air 12 is preferably about 0.5 to 1.0 in terms of swirl.

  On the other hand, when burning the pulverized coal of the burner 20 having the above-described configuration, all the lattices 16a are moved backward to the upstream side of the burner 20, and a straight flow is applied to the combustion air ejected from the fixed plate 15 into the furnace, so The NOx concentration in the combustion gas can be reduced by delaying the mixing with the combustion air after the air nozzle and expanding the NOx reduction region in the combustion gas. The swirl number of the combustion air 12 during the straight flow is preferably 0.1 or less. Moreover, the drive part of the grating | lattice 16a can reduce the thermal radiation from the inside of a furnace with the fixed plate 15, and can reduce thermal expansion.

  The fixed plate 15 of the present embodiment is a pulverized coal burner 20 that is fixed to the tip of the primary air nozzle 1 shown in FIG. 1 and has a configuration in which a movable member 16 is installed on the upstream side. The fixed plate 15 has, for example, a configuration shown in a front view of the fixed plate in FIG. 6A viewed from the furnace side and a cross-sectional view taken along the line AA in FIG. 6A in FIG. . 6 (c) is a front view of the movable member 16 viewed from the furnace side, FIG. 6 (d) is a sectional view taken along the line BB of FIG. 6 (c), and FIG. 6 (e) is FIG. It is a CC line cut surface arrow directional view of (c).

  The flow path which gives the flow velocity of the air jet flow swirling in the circumferential direction from one slit hole 15a of the fixed plate 15 shown in FIG. 6, and gives the flow velocity of the air jet flow in the straight direction from the other slit hole 15b. Are arranged in pairs in the circumferential direction around the center of the fixed plate 15.

  Each of the flow paths of the pair of slits 15a and 15b of the fixed plate shown in FIG. 6 is moved by the movable member 16 provided with the pair of lattices 16a and 16b for closing shown in FIGS. Close. The grids 16a and 16b of the plurality of movable members 16 are operated members 17 that slide on the outer periphery of the oil ejection nozzle 6 provided on the upstream side of the fixed plate 15 (similar to the operation members 17 attached to the grids 16a shown in FIG. 5). 6 may be the operation members 17 attached to the respective lattices 16a, 16b of FIG. The movable member 16 can close the slit hole 15a or the slit hole 15b to switch between the straight combustion flow and the swirl flow of the primary combustion air into the furnace.

  At the time of oil-only firing when the burner having the structure shown in FIG. 6 is started, the slit 15b of the fixed plate 15 is closed by operating the movable member 16 which is a slit closing member, and the swirling combustion air flow from the slit 15a (FIG. 6 ( Combustion air spreads to the outer periphery by centrifugal force and becomes easy to mix with the atomized oil. Further, the swirl flow forms a low pressure portion at the center portion of the burner outlet, and a circulating flow is formed in this portion from downstream to upstream. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil. The swirl of the swirl flow of the combustion air 12 is preferably about 0.5 to 1.0 in terms of swirl.

  On the other hand, during pulverized coal combustion, the slit 15a of the fixed plate 15 is closed by the operation of the movable member 16 in FIG. 6, and a straight flow is applied to the combustion air ejected from the slit 15b so that the combustion is performed after the secondary air nozzle 2. The NOx concentration in the combustion gas can be reduced by delaying the mixing of air and pulverized coal and expanding the NOx reduction region. The swirl number of the combustion air 12 during the straight flow is preferably 0.1 or less.

  FIG. 7 shows a modification of the fixed plate 15 and the movable member 16 shown in FIG. 7A is a front view of the fixed plate as viewed from the furnace side, FIG. 7B is a sectional view taken along the line AA in FIG. 7A, and FIG. The front view seen from the side, FIG.7 (d) is a BB line cut surface arrow directional view of FIG.7 (c), FIG.7 (e) is the CC line cut surface arrow directional view of FIG.7 (c). It is.

  As shown in FIG. 7, a plurality of pairs of slits 15a and 15b each having an inclined wall surface are provided on the fixed plate 15 at opposing positions, and the pair of slits 15a pivots in the circumferential direction. In the circumferential direction around the center portion of the fixed plate 15, a pair of flow paths that give the flow velocity of the air jet flow and give the flow velocity of the air jet flow in the direction of turning in the circumferential direction also from the other slit hole 15 b A configuration may be adopted in which a plurality are arranged uniformly.

  Also in this case, the flow path of one of the pair of slits 15a and 15b of the fixed plate 15 is closed by the pair of lattices 16a and 16b of the movable member 16 for closing the slit disposed upstream and backward of the fixed plate 15. Thus, the left and right swirl flow of the primary combustion air into the furnace (a swirl flow is generated in the directions of arrows directed to opposite sides of FIG. 7A) can be switched. The grids 16a and 16b are respectively connected to the grids 16a and 16b like the operation members 17 that slide on the outer periphery of the oil jet nozzle 6 provided on the upstream side of the fixed plate 15 (the operation members 17 attached to the grids 16a shown in FIG. 5). The operation member 17 may be attached to the operation member 17, and the operation members 17 are arranged so as to freely advance and retract.

  In addition, when the burner 20 having the configuration shown in FIG. 7 is exclusively fired at the time of start-up, the slit closing member 15 is operated to close the slit 15a or the slit 15b of the fixing plate 15 and open to open the swirling combustion air from the slit 15a or the slit 15b. By the flow, the combustion air spreads to the outer periphery by centrifugal force and becomes easy to mix with the atomized oil. Further, the swirl flow forms a low pressure portion at the center portion of the burner outlet, and a circulating flow is formed in this portion from downstream to upstream. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil. The swirl of the swirl flow of the combustion air 12 is preferably about 0.5 to 1.0 in terms of swirl.

On the other hand, during pulverized coal firing, the slit closing member in FIG. 7 is retracted to open both the slit 15a and the slit 15b of the fixed plate 15 to give a straight flow to the combustion air ejected from the slits 15a and 15b. The NOx concentration in the combustion gas can be reduced by delaying the mixing of the combustion air and the pulverized coal after the secondary air nozzle and expanding the NOx reduction region. The swirl number of the combustion air 12 during the straight flow is preferably 0.1 or less.
The lattices 16a and 16b shown in FIGS. 6 and 7 may be integrated to form a single triangular lattice.

  The pulverized coal burner 20 of the present embodiment is the same as the cross-sectional structure of the pulverized coal burner 20 shown in FIG. 1, and the fixed plate 15 disposed at the tip of the primary air nozzle 1 is viewed from the furnace side of FIG. The front view is shown in FIG. 8 (b) in FIG. 8 (c) is a front view of the movable member 16 as viewed from the furnace side, FIG. 8 (d) is a sectional view taken along the line BB in FIG. 8 (c), and FIG. 8 (e) is a diagram. It is a CC line cut surface arrow directional view of 8 (c).

The fixed plate 15 shown in FIG. 8 has the same configuration as the fixed plate 15 shown in FIG.
However, the movable member 16 of the present embodiment has the same structure as that of the movable member 16 shown in FIG. 3, but the air-permeable plate 18 having a large number of air holes 18 a is adhered to the opposite side (back surface) of the movable member 16 to the furnace. Arranged.

  The end of the movable member 16 on the burner center side is fixed to a cylindrical operation member 17 having a diameter larger than the outer diameter of the oil spray nozzle 6. The air-permeable plate 18 is provided with a plurality of ejection holes 18a so as to be positioned between the lattices 16a of the movable member 16, and a plurality of the ejection holes 18a are radially provided from the center of the burner. Yes. The fixed plate 15 is cooled by impingement cooling by the air flow ejected from the plurality of ejection holes 18a to prevent burning. The movable member 16 can be driven in the front-rear direction toward the furnace, and moves toward the furnace during oil-only firing at the time of start-up, pushing the lattice 16a into the slit holes 15a of the fixed plate 15, so that the slit holes 15a By blocking the flow path formed on the inclined wall surface in one direction, a swirling flow is given to the jetting combustion air 12, and the combustion air 12 spreads to the outer peripheral side of the primary air nozzle 1 by centrifugal force and is atomized oil Easy to mix with. In addition, a low pressure portion is formed in the central portion of the primary air nozzle 1, and a circulating flow from downstream to upstream is formed in this portion. High-temperature burned gas stays in the circulating flow, accelerating the ignition of atomized oil. The swirl of the swirl flow of the combustion air 12 is preferably about 0.5 to 1.0 in terms of swirl.

On the other hand, during the pulverized coal firing, the movable member 16 is pulled in a direction away from the furnace, and a straight flow is applied to the combustion air 12 ejected from the primary air nozzle 1 so that the combustion air after the secondary air nozzle The NOx concentration in the fuel gas can be reduced by delaying the mixing and expanding the NOx reduction region. The swirl number of the combustion air 12 during the straight flow is preferably 0.1 or less. Moreover, since the drive part of the said movable member 16 exists in the upstream of the burner 20 rather than the fixed plate 15, the thermal radiation from the inside of a furnace can be reduced and thermal expansion can be reduced.
FIG. 9 shows the effect of reducing the NOx concentration in the combustion gas with respect to the primary air flow rate according to each of the above embodiments.

  The present invention can improve the ignitability of oil and pulverized coal when starting the pulverized coal burner 20 with a simple configuration, and can reduce the NOx concentration of the combustion gas.

1 is a cross-sectional view of a pulverized coal burner according to Example 1. FIG. It is the schematic of the movable member which block | closes the fixed plate of the pulverized coal burner concerning Example 1, and the flow path of one direction of a fixed plate, Fig.2 (a) is the front view which looked at the fixed plate from the furnace side, FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A, FIG. 2C is a front view of the movable member as viewed from the furnace side, and FIG. 2D is a cross-sectional view taken along line B- in FIG. FIG. 2E is a cross-sectional view taken along the line B-C in FIG. 2C. It is the schematic of the fixed plate and movable member of the pulverized coal burner concerning Example 2, FIG.3 (a) is the front view which looked at the fixed plate from the furnace side, FIG.3 (b) is A of FIG.3 (a). FIG. 3C is a front view of the movable member as viewed from the furnace side, and FIG. 3D is a sectional view taken along the line B-B in FIG. (E) is the CC line cut surface arrow directional view of FIG.3 (c). 4 is a cross-sectional view of a pulverized coal burner according to Example 3. FIG. It is the schematic of the fixed plate and movable member of the pulverized coal burner concerning Example 3, FIG.5 (a) is the front view which looked at the fixed plate from the furnace side, FIG.5 (b) is A of FIG.5 (a). FIG. 5C is a front view of the movable member as viewed from the furnace side, and FIG. 5D is a sectional view taken along the line BB in FIG. 5C. (E) is the CC line cut surface arrow directional view of FIG.5 (c). It is the schematic of the fixed plate and movable member of the pulverized coal burner concerning Example 4, FIG. 6 (a) is the front view seen from the furnace side of the fixed plate, FIG.6 (b) is A of FIG.6 (a). FIG. 6C is a front view of the movable member viewed from the furnace side, and FIG. 6D is a cross-sectional view taken along the line BB in FIG. 6C. (E) is the CC line cut surface arrow directional view of FIG.6 (c). 6 is a modified example of the fixed plate of FIG. 6, a front view of the fixed plate of FIG. 7A viewed from the furnace side, FIG. 7B is a cross-sectional view taken along line AA of FIG. 7 (c) is a front view of the movable member 16 as viewed from the furnace side, FIG. 7 (d) is a sectional view taken along the line BB in FIG. 7 (c), and FIG. 7 (e) is FIG. It is a CC line cut surface arrow directional view of). FIG. 8A is a front view of the fixed plate viewed from the furnace side, and FIG. 8B is an AA line in FIG. 8A. FIG. 8C is a front view of the movable member viewed from the furnace side, FIG. 8D is a sectional view taken along the line BB in FIG. 8C, and FIG. These are CC line cut surface arrow directional views of FIG.8 (c). It is a figure which shows the reduction effect of the NOx density | concentration in combustion gas with respect to the primary air flow rate by the Example of this invention. It is the schematic which shows the pulverized coal boiler system by this invention. It is sectional drawing of the pulverized coal burner of a prior art example.

Explanation of symbols

1 Primary flow path (primary air nozzle)
2 Secondary flow path (secondary air nozzle)
3 Tertiary channel (tertiary air nozzle)
4 pulverized coal nozzle 5 venturi 6 oil spray nozzle 7 boiler furnace wall 8 wind box 9 flame holder 10 guide sleeve 11 pulverized coal concentrator 12 combustion air 13 solid-gas two-phase flow
DESCRIPTION OF SYMBOLS 14 Swivel 15 Fixed plate 15a, 15b Slit hole 16 Movable member 16a, 16b Lattice 17 Operation member 18 Breathable plate 18a Ejection hole 20 Pulverized coal burner 21 Furnace 22 Bunker 23 Mill 24, 26 Blower

Claims (4)

An oil spray nozzle provided on the furnace wall and provided on the central axis, a primary air nozzle through which the primary air for combustion provided on the outer periphery of the oil spray nozzle flows, and pulverized coal provided on the outer periphery of the primary air nozzle and for transportation In a pulverized coal burner having a pulverized coal nozzle through which a solid-gas two-phase flow with air flows and an air nozzle through which at least one combustion air is provided on the outer periphery of the pulverized coal nozzle,
A fixed plate that is fixed to the inner peripheral wall side of the tip in the primary air nozzle and has at least one opening for ejecting primary air;
A pulverized coal comprising a movable structure capable of adjusting a turning force around a central axis of primary air to be ejected by changing an opening state of the opening in combination with the fixed plate. Burner. Rotating the movable structure back and forth along the central axis and / or around the central axis;
The pulverized coal burner according to claim 1, wherein the flow direction around the central axis is changeable by changing the shape of the primary air flow path along the central axis. The opening is a combination of a plurality of different ejection directions,
The pulverized coal burner according to claim 1 or 2, wherein the movable structure is rotated back and forth along the central axis and / or around the central axis to change one or both of the open states. The pulverized coal burner according to any one of claims 1 to 3, wherein a plate-like member having an air hole on the upstream side of the primary air flow of the movable structure is provided integrally with the movable structure. .

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