JPH08200618A - Pulverized coal combustion burner - Google Patents

Abstract

(57) [Summary] [Objective] To provide a pulverized coal burner capable of stable combustion even under a low load and reducing the NOx concentration. [Structure] A swirl flow generator 120 and a separation strengthening means 11 are provided from the upstream side to the inner circumference of a nozzle 102 for conveying pulverized coal by primary air.
9, the separation space 127, and the rectifier 109 are arranged. Pulverized coal is introduced into the swirl flow generator from a plurality of inlets. [Effect] Since the pulverized coal concentration at the edge of the pulverized coal nozzle can be increased and the pulverized coal concentration in the circumferential direction in the nozzle can be made uniform,
Even if the amount of pulverized coal is small, the flame can be kept stable and N
Ox reduction can also be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulverized coal combustion burner suitable for use in a coal-fired boiler and a coal combustion furnace, and more particularly to a pulverized coal combustion burner excellent in flame stability at the time of load reduction. .

[0002]

2. Description of the Related Art Various structures of a pulverized coal combustion burner have been studied in order to reduce NOx generated from a coal-fired boiler and a coal combustion furnace. As one of the burners, a pulverized coal nozzle for ejecting a mixture of coal particles and carrier air is provided in the center, and at the outside thereof, at least one air nozzle for ejecting a combustion air in a swirling flow is concentrically provided. There is. Usually, two air nozzles are concentrically provided.

In this kind of pulverized coal combustion burner, a reducing flame region that burns due to excess fuel is formed near the ejection port of the pulverized coal nozzle, and an oxidizing flame region having a high oxygen concentration is formed so as to surround the reducing flame. Then, the denitration combustion in the flame is performed.
In the reducing flame region, nitrogen in coal is decomposed into nitrogen compounds such as hydrogen cyanide (HCN) and ammonia (NH ₃ ) at the time of thermal decomposition in the early stage of combustion and released into the gas phase. While these nitrogen compounds are oxidized to NOx, they have the effect of reducing NOx under conditions of low oxygen concentration, and reduce the generated NOx. In the oxidizing flame region, combustion with a high oxygen concentration is performed to completely burn unburned components that could not be burned in the reducing flame region.

On the other hand, nowadays when nuclear power generation is the base load for power supply, coal-fired thermal power, which has been conventionally operated with a constant load, is also required to operate with a high load fluctuation. Even in coal-fired boilers, there is a tendency to reduce the load of burning only by burning coal as much as possible. However, in burning coal particles with a burner, the flame becomes unstable when the amount of coal particles is reduced. Therefore, measures are taken to prevent the flame from becoming unstable even if the amount of coal particles is reduced. An example of such a burner is disclosed in JP-A-2-259308.
Japanese Patent Laid-Open Publication No. 3-241208 discloses that the concentration of coal particles flowing on the outer peripheral side in a pulverized coal nozzle is changed by swirling a mixture of coal particles and carrier air. It is higher than the concentration.

[0005]

Emissions N of coal-fired boiler
In order to reduce the Ox concentration, it is important to promote the NOx reduction reaction in the reducing flame region in the pulverized coal burner using the in-flame denitration system. To this end, it is effective not only to improve the supply method of combustion air, but also to improve the supply method of coal particles to achieve fuel overcombustion and enhance the ability of thermal decomposition of coal particles in the reducing flame region. Become.

In order to improve the operability of the coal-fired boiler,
It is necessary to change the load in a short time. A good method from this point of view is to extend the operating limit of pulverized coal burners to low loads.

However, in the pulverized coal burner, the flow velocity of the coal particles flowing in the carrier pipe for supplying the coal particles to the burner cannot be reduced to a certain speed or lower, and therefore the air supplied to the carrier pipe cannot be reduced. There is a limit to reducing the flow rate. If the flow velocity of the coal particles is too slow, the coal particles will settle inside the carrier pipe and block the carrier pipe, and the flame of the furnace will flow back into the carrier pipe.

For this reason, in the method of expanding the operation lower limit of the pulverized coal burner to a low load, the flow rate of the carrier air is made constant and the supply amount of the coal is reduced when the load of the coal is reduced to some extent when the flow rate of the air is reduced together with the flow rate of the coal. Must be dealt with. When only the supply amount of coal decreases, the concentration of coal contained in the carrier air decreases, flames are less likely to be formed near the outlet of the pulverized coal nozzle, and the coal particles are mixed after the mixing of the coal particles and the combustion air progresses. Will start to burn. As a result, it becomes difficult to form a NOx reduction region in the flame.

Therefore, in the prior art, by swirling a mixture of coal particles and carrier air,
A region where the concentration of coal particles is high is locally formed in the pulverized coal nozzle so that the flame is stably formed even when the load is low and the amount of coal particles is small.

However, as a practical matter, even if the mixture of coal particles and carrier air is simply swirled, the flame cannot be kept stable when the load is reduced, and misfire is likely to occur.

An object of the present invention is to provide at least one air nozzle concentrically on the outer periphery of a pulverized coal nozzle,
In a burner in which the mixture of coal particles in the pulverized coal nozzle and carrier air is swirled to locally increase the concentration of coal particles on the inner and outer peripheral sides of the nozzle, the flame stability is excellent when the load is reduced, and the NOx reduction effect is also achieved. To provide an excellent pulverized coal combustion burner.

Another object of the present invention is to provide a pulverized coal boiler power generation system capable of stably burning only coal up to a low load and increasing the load change rate.

[0013]

The present invention is achieved by the following burners (1) to (18).

(1) At least one air nozzle, which ejects a combustion air in a swirling flow, is concentrically provided on the outer periphery of a pulverized coal nozzle which ejects a mixture of coal particles and a carrier air in a straight flow. Coal particles and carrier air in the swirl flow generating means are provided with swirl flow generating means for swirling a mixture of particles and transport air, and rectifying means for converting the swirl flow formed by the swirl flow generating means into a straight flow. Pulverized coal combustion burner equipped with multiple mixture supply ports in the swirling direction.

(2) In the burner of the above (1), a pulverized coal nozzle is provided with a swirl flow generating means having a plurality of blades, and a supply port for a mixture of coal particles and carrier air in the swirl flow generating means is provided. Pulverized coal combustion burner provided between the blades and at a plurality of locations.

(3) In the burner of the above (1), supply ports for a mixture of coal particles and conveying air are provided at a plurality of tangential directions on the rear end side wall surface of the pulverized coal nozzle, and the mixture is provided in a tangential direction. A pulverized coal combustion burner in which a swirl flow is formed by being supplied.

(4) In the burner according to any one of (1) to (3), a pulverized coal combustion burner is provided with a resistor for preventing swirling of a mixture of coal particles and carrier air as a rectifying means.

(5) A pulverized coal combustion burner in which a plurality of plate-like members are radially provided in a pulverized coal nozzle as a resistor in the burner of (4).

(6) In the burner according to any one of (1) to (5), a relatively small particle of the coal particles contained in the swirl flow is nozzled between the swirl flow generating means and the rectifying means. A pulverized coal combustion burner with a space sufficient to move it by inertial force in the inner center.

(7) At least one air nozzle, which ejects a combustion air in a swirling flow, is concentrically provided on the outer periphery of a pulverized coal nozzle that ejects a mixture of coal particles and a carrier air in a straight flow. Flow generating means for swirling the mixture of air and carrier air, means for gradually weakening the strength of the swirling flow of the mixture flowing in the pulverized coal nozzle toward the outlet, and changing the swirling flow into a straight flow. A pulverized coal combustion burner provided with a rectifying means and provided with a supply port for a mixture of coal particles and conveying air in the swirling flow generating means at a plurality of positions in the swirling direction.

(8) In the burner of the above (7), as a means for weakening the strength of the swirling flow of the mixture of coal particles and carrier air, the flow passage cross-sectional area of the pulverized coal nozzle is enlarged toward the downstream side. Pulverized coal combustion burner with means.

(9) In the burner of the above (8), as a flow passage cross-sectional area enlarging means, a pulverized coal combustion in which a member having a conical shape at the axial center of the pulverized coal nozzle and the top of the cone is directed to the downstream side is arranged Burner.

(10) At least one air nozzle for ejecting a combustion air in a swirl flow is concentrically provided on the outer periphery of a pulverized coal nozzle for ejecting a mixture of coal particles and a carrier air in a straight flow, and coal particles are provided. Flow generating means for swirling a mixture of air and carrier air, distributing means for dividing the swirling flow of the mixture flowing in the pulverized coal nozzle toward the outlet direction into a plurality of annular flows, and the distributing means A fine powder provided with a rectifying means for converting a swirl flow divided into a plurality of flows into a straight flow, and supply ports for a mixture of coal particles and carrier air in the swirl flow generating means at a plurality of positions in the swirl direction. Charcoal burning burner.

(11) At least one air nozzle for ejecting a combustion air in a swirling flow is concentrically provided on the outer periphery of a pulverized coal nozzle for ejecting a mixture of coal particles and a carrier air in a straight flow, A swirl flow generating means for swirling a mixture of particles and carrier air, a means for gradually weakening the strength of the swirl flow of the mixture flowing in the pulverized coal nozzle toward the outlet, and an outlet of the pulverized coal nozzle A distribution means for dividing the swirling flow into a plurality of annular flows in the vicinity and a rectifying means for converting the swirling flow into a straight flow are provided, and a mixture of coal particles and carrier air in the swirling flow generating means is provided. Pulverized coal combustion burner with supply ports at multiple points in the turning direction.

(12) A pulverized coal combustion burner in which at least one cylindrical member having the same axis as the nozzle is provided in the pulverized coal nozzle as the distributing means in the burner of (10) or (11).

(13) In the burner of (12) above,
A pulverized coal combustion burner in which an inner diameter and an outer diameter of a cylinder of a tubular member are made substantially constant, and an inclination is provided on an outer surface of the tubular member located upstream of a pulverized coal nozzle.

(14) In the burner of (12) above,
Pulverized coal in which the flow velocity of the mixture of pulverized coal and carrier air at the lower end of the tubular member is made substantially equal inside and outside the tubular member by increasing the inner diameter and outer diameter of the tubular member on the upstream side and decreasing it on the downstream side. Combustion burner. (15) A pulverized coal combustion burner according to any one of the above (1) to (14), which is provided with a means for changing the strength of the swirl flow generated by the swirl flow generating means.

(16) In the burner of (15) above,
A pulverized coal combustion burner comprising a swirl flow generating means having a plurality of blades in a pulverized coal nozzle, and changing the inclination of the blades to change the strength of the swirl flow.

(17) A fine powder provided with means for changing the strength of the swirl flow generated by the swirl flow generating means in the burner of (15) or (16) so that it becomes large at low load and becomes small at high load. Charcoal burning burner.

(18) In the burner according to any one of (1) to (17) above, a pulverized coal combustion burner having an oil burner in the pulverized coal nozzle.

In the burner of the present invention, the plate member is radially arranged from the central portion of the pulverized coal nozzle as a rectifying means for converting a swirling flow of a mixture of coal particles and carrier air (hereinafter also referred to as primary air) into a straight flow. When a plurality of plate-like members are attached, it is desirable that the plate-like member is attached over the entire flow passage width of the pulverized coal nozzle, whereby the swirling flow can be converted into a straight flow without interruption.

Downstream of the swirling flow generating means in the pulverized coal nozzle, coarse particles having a relatively large particle size are collected on the outer peripheral side by the centrifugal force associated with the swirling, and fine particles having a relatively small particle size are disposed on the central side. It is desirable to provide the necessary separation space for collecting. By providing the separation space, the sorting effect based on the particle size of the coal particles is enhanced. Further, by providing means for gradually increasing the flow path step area of the pulverized coal nozzle in the separation space toward the downstream, the effect of increasing the average diameter of the coal particles on the outer peripheral side of the nozzle and decreasing the average diameter of the center side Will be higher.

The swirl flow generator is preferably connected to the driving machine via a support rod integrally attached to the axis of the swirl flow generator. If the swirl generator can be adjusted by the drive,
The swirling strength of the carrier air flowing through the pulverized coal nozzle can be adjusted. By adjusting the swirl strength, it is possible to adjust the proportion of relatively large particles moving to the inner and outer peripheral sides of the nozzle among the coal particles flowing in the central part of the nozzle, and the coal concentration in the inner and outer peripheral parts of the nozzle It can be relatively higher than the coal concentration.

Further, in the present invention, it is desirable to provide a control means for controlling the swirl strength of the swirl flow generator and the opening of the flow rate control valve of the carrier gas according to the load command, whereby the coal particles are When the load is low, the swirl strength of the swirl flow generator can be increased to increase the coal concentration at the edge of the pulverized coal nozzle.

In the present invention, a distributor capable of dividing the pulverized coal nozzle into at least two concentric flow paths can be arranged downstream of the separation space. This distributor is preferably arranged upstream of the rectifying means. A tubular member can be used as the distributor. When using a tubular member, the diameter of the tubular member in the radial direction may be changed between the upstream side and the downstream side in the flow direction of the coal particles so that the diameter becomes smaller toward the downstream side. desirable. Further, it is more desirable to provide a portion having a constant diameter downstream of the portion having a reduced radial diameter.

The rectifier that changes the swirling flow of the mixture of coal particles and the carrier air into a straight flow is preferably provided on the downstream side of the distributor, and the rectifier may be attached to a part of the downstream side of the distributor. For example, it is preferable to arrange the rectifier at a position where the diameter of the distributor in the radial direction is reduced and then becomes constant.

The swirl generator can be supplied with a mixture of coal particles and carrier air from a plurality of locations. As a result, it is possible to eliminate variations in the concentration of coal particles in the swirling direction of the mixture and to keep the concentration in the circumferential direction uniform. The number of supply ports for the mixture of coal particles and carrier air is as high as possible.

The combustion method of the present invention is to supply the coal carrier air at a constant flow rate under a low load with a small coal flow rate, and increase the swirling strength as the coal supply rate decreases. When the load is low and it is difficult to burn coal exclusively, an auxiliary combustion nozzle such as an oil burner is provided inside the pulverized coal nozzle.
It is desirable to carry out oil combustion.

In the pulverized coal boiler power generation system of the present invention, pulverized coal combustion burners are provided at a plurality of positions in the height direction of the wall of the boiler furnace for burning coal, and after air ports are provided above the burners, and after furnaces are provided in the furnace. A heat transfer tube that absorbs heat generated by the combustion of coal to generate steam is provided, and a steam turbine and a generator that generate electricity by the steam obtained by the heat transfer tube are provided. Further, when the power generation load is small, the pulverized coal combustion burner is used. Among them, a burner control device that operates only the upper burner and interrupts it as the power generation load increases and expands the operation to the lower burner is provided, and as the pulverized coal combustion burner, a mixture of coal particles and carrier air flows straight. The pulverized coal nozzle ejected by the above has at least one air nozzle which ejects the combustion air in a swirling flow around the outer periphery, and the coal particles and the carrier air are mixed. A swirling flow generating means for swirling, a rectifying means for converting the swirling flow formed by the swirling flow generating means into a straight flow, and a supply port for a mixture of coal particles and carrier air in the swirling flow generating means It is constructed by including pulverized coal combustion burners provided at multiple locations.

[0040]

In the coal-fired boiler, in order to reduce the NOx concentration, an oxidizing flame region that burns in an atmosphere with a high oxygen concentration is formed on the outer periphery of the flame, and a reducing flame region that burns with excess fuel inside the oxidizing flame region. Is effective. To this end, in the pulverized coal burner, it is effective to provide a pulverized coal nozzle for ejecting a mixture of coal particles and carrier air in the central portion of the burner which is relatively likely to be supplied to the reducing flame region.

By constructing the pulverized coal burner in this way and further increasing the concentration of the coal particles flowing in the pulverized coal nozzle locally on either the outer peripheral side or the central side, a low coal load and a low load can be achieved. Even if there is, the coal can be burned stably, and NOx emission is achieved by achieving denitration combustion in the flame.
The concentration can be reduced.

For this purpose, at least one air nozzle for supplying combustion air is concentrically provided on the outer periphery of the pulverized coal nozzle for carrying the coal particles by air flow, and the coal particles and the carrier air flowing in the pulverized coal nozzle are swirled. When swirling, it is necessary to supply a mixture of coal particles and carrier air to the swirler from a plurality of locations and to provide a rectifying means for converting the swirling flow into a straight flow in the pulverized coal nozzle. By doing so, the concentration of coal particles in the swirling flow can be made uniform in the circumferential direction, and the coal can be stably burned even under a low load. In the case where the rectifying means is not provided, the mixture of coal particles and combustion air is jetted from the pulverized coal nozzle in a swirling flow, and after being jetted from the nozzle, it spreads radially, and the coal particles in the reducing flame region Insufficient supply.

According to the burner of the present invention, one pulverized coal inflow port is provided tangentially to the rear end of the pulverized coal nozzle as in the invention disclosed in Japanese Patent Laid-Open No. 3-241208. The pulverized coal fuel and carrier gas jets, which tend to occur in a burner, do not cause non-uniformity in the pulverized coal concentration at the nozzle outlet, and the instability of the flame is eliminated.

In the separation space located on the downstream side of the swirling flow generator, the centrifugal force generated by the swirling flow generated upstream acts more strongly on particles having a larger particle size, so that a relatively small particle size flowing through the center of the pulverized coal nozzle is obtained. Large coal particles can be moved to the outer periphery of the nozzle. As a result, the particle size of the coal particles flowing through the flow path at the center of the pulverized coal nozzle becomes relatively small. The probability that coal particles will be supplied to the reducing flame region in the center of the flame becomes higher as the coal particles are supplied from the center of the pulverized coal nozzle. The fine particles have a higher surface area ratio to the weight of the coal than the coarse particles, so they are highly reactive, and if the fine particles are collected in the center of the nozzle, the thermal decomposition reaction of the coal with carbon dioxide or water in the reducing flame region will occur. Can be promoted. As a result, the amount of NOx precursors obtained from the coal particles in the reducing flame region is increased, so the ability to reduce NOx generated in the oxidizing flame region is increased, and the NOx concentration generated by the combustion of coal by the pulverized coal burner is increased. It can be reduced.

In a preferred embodiment when the swirl flow generator is provided in the pulverized coal nozzle, a member for reducing the flow passage cross-sectional area is provided in the nozzle, and the flow passage cross-sectional area is once reduced in the nozzle ejection direction. After that, the swirl vanes are provided at a position where the flow passage cross-sectional area is minimized. This produces the following three actions and effects. The first effect is that the flow passage in the pulverized coal nozzle is reduced by the flow passage cross-sectional area reducing member. Due to the inertial force generated when the coal particles move in the outer peripheral direction, the particles move in the outer peripheral direction rather than the carrier gas, so that many coal particles gather near the outer peripheral wall of the nozzle and increase the concentration of the outer peripheral coal particles. You can The second effect is that the swirl vanes are attached to the position where the flow path in the nozzle is the smallest. Since the swirl flow generation efficiency increases as the swirl vanes are separated in the outer peripheral direction, a strong swirl flow can be generated without increasing the pressure loss of the swirl flow generator. The third effect is the effect of narrowing the flow path in the nozzle on the downstream side of the swirl vane. As a result, the carrier gas moves to the center of the nozzle, and the fine particles having small inertia follow and move to the center side. Since the coarse particles having large inertia go straight without following the gas, the amount of coal particles flowing on the outer peripheral side in the nozzle is larger. Due to the action of these three points, a large amount of coal particles are collected on the outer peripheral wall in the nozzle, so that the ignition flame holding performance can be enhanced.

The coarse particles collected in large quantity in the outer peripheral portion of the pulverized coal nozzle by the action of the swirling flow generator and the subsequent separation space are integrally mixed with the pulverized coal flowing in the outer peripheral portion of the nozzle. Is supplied to the furnace from the edge of the. Since the concentration of coal particles supplied from the nozzle edge is relatively higher than the concentration determined by the supply amount of coal and air,
The flame formed by the coal formed from the rim can be stabilized. As a result, the amount of coal particles that burn in the region near the pulverized coal nozzle can be increased, and the flame temperature can be increased.
Since the high temperature flame also raises the temperature of the reducing flame region at the same time, the thermal decomposition capability of the coal in the reducing flame region also increases at the same time.
As a result, the NOx reduction reaction in the reducing flame region is promoted, and N generated by the combustion of coal by the pulverized coal burner is promoted.
The Ox concentration can be reduced.

The rectifier serves as a resistance element for the carrier air flowing swirling in the separation space, so that the carrier air can be converted into a straight flow and the coal particles can be ejected from the pulverized coal nozzle into the furnace. As a result, it is possible to suppress the radial dispersion of the coal particles, which tends to occur due to the jetting in the swirling flow.

On the downstream side of the swirl flow generator, there can be provided a separation enhancing means for enhancing the selective separation and supply ability depending on the particle size in the separation space. Since the separation enhancing means has a function of attenuating the velocity component of the swirling in the flow direction, the centrifugal force due to the swirling flow and the inertial force of the particles act more strongly on the larger particles. Accordingly, coal particles having a smaller particle size can be moved to the wall surface of the outer periphery of the fuel nozzle in a swirling flow.

The most preferable example for enhancing the particle size separation ability by the separation enhancing means is characterized in that the flow path cross-sectional area of the pulverized coal nozzle on the downstream side of the swirl flow generator gradually increases toward the downstream side. The shape. By doing so, a swirl flow having a large velocity component in the swirling direction can be generated in a portion having a relatively small flow passage cross-sectional area. Can be supplied inside. Since the centrifugal force acting on the particles in the swirling flow is stronger for the larger particles, such particles are collected in a region near the wall surface on the outer peripheral side of the pulverized coal nozzle. Furthermore, since the inertial force acting on the coal particles is larger for the larger particles, the velocity difference between the relatively large particles and the gas is large in the region where the velocity component in the swirling direction of the gas decreases toward the downstream side. Due to this speed difference, more particles can be collected in a region near the outer peripheral wall surface of the pulverized coal nozzle.

The swirl flow generating means may have swirl strength adjusting means for changing the strength of the swirl flow. For this purpose, it is desirable that a swirl flow generator with swirl vanes is attached to a support rod, and the support rod is connected to a driving device attached to the outside of the nozzle for rotation. Another swirl strength adjusting means can be achieved by changing the angle of the swirl vanes.

A preferred example of changing the strength of the swirl flow generator arranged in the pulverized coal nozzle by the swirl strength adjusting means is to adjust the strength of the swirl flow based on the flow rate of the coal particles flowing through the nozzle. For example, when the coal flow rate becomes smaller than the set value, the swirl strength of the swirl flow generator can be increased together with the decrease in the coal flow rate. As a result, even if the amount of coal particles supplied is reduced, the coal concentration at the nozzle rim can be increased, so that a flame can be stably formed in a region near the nozzle rim even under a low load. If the flame is maintained at the nozzle rim, the coal particles can be burned before the mixing of the coal particles and the combustion air proceeds, so that a reducing flame region can be formed in the flame even when the load is low. As a result, NOx can be reduced to nitrogen in the reducing flame region, so the NOx concentration at low load can be reduced.

The distributor has a function of preserving the particle size distribution of coal particles classified in the nozzle radial direction in the separation space. The distributor can achieve its function by, for example, a tubular flow path that is arranged concentrically with the pulverized coal nozzle. This can prevent the coal particles classified in the radial direction from being homogenized again in the radial direction of the nozzle due to the action of the turbulent flow in the nozzle. If the coal concentration at the rim of the pulverized coal nozzle is increased, the flame can be formed more stably, the NOx reducing ability in the reducing flame region in the flame can be enhanced, and the NOx concentration of the burner can be reduced.

When the rectifier is provided on the downstream side of the distributor, the separation performance of coal particles can be enhanced. The rectifier eliminates the swirling component by blocking the flow and converts it into a straight flow. At this time, the coal particles collected on the outer periphery of the pulverized coal nozzle are also scattered again because the gas flow is disturbed. Therefore, in the case of the structure in which the rectifier is provided on the upstream side of the distributor, the coal particles are re-scattered, so that the particles are mixed in the radial direction and the separation effect due to the swirling flow is reduced.

The swirling flow generator applies the centrifugal force generated by the swirling flow to the particles. Centrifugal force is, for example, Japanese Patent Laid-Open No.
A force larger than the inertial force generated by changing the flow direction as described in the publication can be applied to the particles. Therefore, rather than the separation method by inertia,
The diameter of particles that can be separated, that is, the so-called separation limit particle diameter can be reduced. That is, by adopting a method of supplying coal particles in a swirling flow, the separation limit particle diameter can be made small, and even smaller particles can be supplied to the nozzle edge. As a result, first, the coal particles supplied to the reducing flame region become smaller, so that the coal particles in this region are more likely to react. The higher the reactivity, the higher the NOx reduction capacity and the lower NOx combustion can be achieved. Next, since the concentration of coal particles at the nozzle rim can be further increased, the ignition performance of coal can be increased. As a result, even under operating conditions where the coal concentration is low, the concentration of coal particles can be increased, so that the flame can be kept stable.

The velocity of the gas at the outlet of the distributor can be changed by changing the shape of the axial section of the cylindrical distributor. For example, when the flow passage cross-sectional area is changed by increasing the diameter of the distributor cylinder on the upstream side of the nozzle and decreasing it on the downstream side, the flow path on the outer peripheral side of the distributor reduces the gas velocity, The flow path on the inner peripheral side of the distributor increases the velocity of gas. As a result, the gas ejection speed at the outlet of the pulverized coal nozzle can be made uniform in the radial direction. If the velocity difference between the two concentric jets is small, it becomes difficult for the two jets to mix with each other.Therefore, the dispersed state of the coal particles in the radial direction is kept the same as the dispersed state at the nozzle outlet even if it is separated from the nozzle. be able to. As a result, the particle size of coal supplied to the reducing flame region can be reduced, so that the NOx reduction reaction in the reducing flame region is promoted and the NOx concentration can be reduced.

[0056]

EXAMPLES Examples of the pulverized coal burner of the present invention will be described below. However, the present invention is not limited to this embodiment.

Example 1 (i) Structure of Burner The pulverized coal burner shown in FIGS. 1 and 2 will be described. FIG. 1 is a sectional view including a central axis of a pulverized coal burner. FIG. 2 is a side view of the pulverized coal burner shown in FIG. 1 viewed from the furnace 100 side. The pulverized coal burner of this embodiment includes a pulverized coal nozzle 102 attached to the center of the burner and a pulverized coal nozzle 1.
The secondary air nozzle 103, which is arranged concentrically with the secondary air nozzle 02, supplies the secondary air 106, and the tertiary air nozzle 104, which is mounted on the outer circumference of the secondary air nozzle 103, supplies the tertiary air 107. The pulverized coal nozzle 102 supplies a mixture 105 of primary air (conveying air) and coal particles. Secondary air nozzle 103 and tertiary air nozzle 104
Is a flow path for supplying the combustion air supplied to the wind box 101 to the furnace 100.

The pulverized coal nozzle 102 has the primary throat 11
1 is a tubular flow path having 1 as an outer wall. In the case of the pulverized coal burner of the present embodiment, an oil gun 10 for auxiliary combustion for preheating a water pipe (not shown) attached to the inner wall of the furnace 100.
8 is attached to the center of the pulverized coal nozzle 102. The pulverized coal nozzle 102 is provided with the flame stabilizer 110, the rectifier 109, the separation space 1 as it goes from the furnace 100 toward the upstream side.
27, a separation enhancing means 119, and a swirl flow generator 120.

The flame stabilizer 110 is a disk-shaped member partially protruding toward the secondary air nozzle 103, and a cone member connected to the outer peripheral end of the disk-shaped member and having a diameter increasing toward the furnace side. And a plurality of rectangular projections 126 connected to the inner peripheral end of the disc-shaped member and arranged in the circumferential direction.

The rectifier 109 is composed of a plurality of plate-shaped members radially arranged around the oil gun 108 and having a width in the flow direction of coal particles. In the example shown in FIG. 2, the plate-shaped member and the protrusion 126 are arranged in the same projecting positional relationship.

The separation space 127 is an annular passage having the oil gun 108 as an inner peripheral wall and the primary throat 111 as an outer peripheral wall.

The separation enhancing means 119 has means for changing the swirling component of the flow velocity toward the downstream. An example of the separation enhancing means 119 for a pulverized coal burner shown in FIG. 1 has a venturi shape, and has a constricted portion where the flow passage decreases toward the downstream side, an annular portion where the flow passage is constant, and a flow passage It is composed of an enlarged portion that increases toward the downstream side.

The swirl flow generator 120 has means for injecting coal particles from at least two inlets to generate a swirl flow 121. For this purpose, it is preferable that the coal particles are made to flow into the swirl flow generator 120 from the tangential direction of the primary throat 111, and further at a plurality of points. In this case, the number of nozzles for supplying coal particles in the tangential direction is large, and the nozzle diameter is set to the primary throat 1
The length projected in the radial direction of 11 is 1 of the primary throat radius.
Under the condition of smaller than / 2, the circumferential deviation of the coal concentration distribution at the throat of the primary throat could be reduced. On the other hand, if the nozzle that supplies the coal particles in the tangential direction is narrowed, the pressure loss for supplying the coal particles increases. From this, (the length of the nozzle aperture projected in the radial direction of the primary throat) ×
It is desirable that (the number of the nozzles) be larger than the radius of the primary throat.

An example of a more desirable swirl flow generator 120 is the axial flow swirl flow generator shown in FIG. The swirl flow generator 120 has a plurality of fan-shaped blades arranged in the circumferential direction of the pulverized coal nozzle 102, and these blades are fixed to the cross-sectional reduction member (separation strengthening means 119) at the center of the flow path. Has been done. The cross-sectional reduction member is fixed to the oil gun 108.

The secondary air nozzle 103 has the primary throat 1
It is an annular flow path having 11 as an inner peripheral wall and a secondary throat 112 as an outer peripheral wall. The secondary air nozzle 103 is connected to the wind box 101 via a register vane 116.

The register vane 116 is connected to the secondary air 106.
Is supplied in a swirling flow. The register vane is a radial flow type register vane, and is composed of a plurality of plate-shaped blades arranged in the circumferential direction of the flow path, and a support rod integrally attached to the blades. The intensity of the swirling flow of the register vanes 116 is adjusted by changing the angle of the vanes by a driving device (not shown).

The tertiary air nozzle 104 is connected to the secondary throat 1
12 is an annular flow path having an inner peripheral wall and a tertiary throat 113 as an outer peripheral wall. The tertiary air nozzle 104 is connected to the wind box 101 via a register vane 114.

The register vane 114 is connected to the tertiary air 107.
Is supplied in a swirling flow. The register vane is a radial flow type register vane, and is composed of a plurality of plate-shaped blades arranged in the circumferential direction of the flow path, and a support rod integrally attached to the blades. The intensity of the swirling flow of the register vanes 114 is adjusted by changing the angle of the vanes by a driving device (not shown). Note that reference numerals 115 and 117 both indicate a support plate, and 118 indicates a side wall.

(Ii) Action Since the swirl flow generator 120 has at least two inlets, the swirl flow is uniformly formed in the circumferential direction in the pulverized coal nozzle. Since the coal particles are carried by this swirling flow, the coal particles and the carrier air can be uniformly dispersed in the circumferential direction of the pulverized coal nozzle 102.

The swirl flow generator can apply the centrifugal force generated by the swirl flow to the particles. Since the centrifugal force is larger than the inertial force generated by the change in the flow, the separation limit particle size can be reduced. When the swirl generator of this example was adopted, coal particles having a particle size of 50 μm or more could be supplied to the rim of the primary throat. This means that the separation limit particle size was reduced by 40% as compared with the separation method by inertia which simply changes the direction of the main flow.

As described above, by adopting the method of supplying the coal particles in the swirling flow, the coal particles supplied to the reducing flame region become smaller than the conventional one, so that the coal particles are more easily reacted and the low NOx is reduced. Can achieve combustion. Furthermore,
Since the coal concentration at the throat edge of the primary throat also becomes higher, the ignition ability of the coal becomes higher, and a stable flame can be formed even under the fuel-lean operating condition.

Since the separation enhancing means 119 has means for attenuating the swirling component of the flow velocity toward the downstream side, the centrifugal force and the inertial force of the particles due to the swirling flow can be more strongly applied to larger particles. Separation enhancing means 1 according to the first embodiment
Reference numeral 19 is a shape in which the flow path cross-sectional area of the pulverized coal nozzle on the downstream side of the swirl flow generator 120 gradually increases toward the downstream side. In this way, since a portion having a relatively small flow passage cross-sectional area can generate a flow having a large velocity component in the swirling direction, the coal particles are supplied to the inside of the pulverized coal nozzle by increasing the velocity component in the swirling direction. It Since the centrifugal force due to the swirling flow is stronger for larger particles, such particles are collected in a region near the outer wall surface of the pulverized coal nozzle. Furthermore, since the inertial force acting on the coal particles is larger for the larger particles, the velocity difference between the relatively large particles and the gas is large in the region where the velocity component in the swirling direction of the gas decreases toward the downstream side. Due to this speed difference, more particles can be collected in a region close to the outer peripheral wall surface of the pulverized coal nozzle.

The separation space 127 can adjust the residence time in which particles flow in a swirling flow. As a result, relatively large particles 122 in the particles 122 flowing in the central portion of the pulverized coal nozzle 102 can be supplied integrally with the particles 123 flowing in the region near the outer periphery of the pulverized coal nozzle 102. As a result, the particle size of the coal particles at the lower end of the pulverized coal nozzle 102 becomes a fine particle 125 having a relatively small particle diameter in the central portion of the pulverized coal nozzle 102 and a relatively large coarse particle 124 near the inner peripheral wall. In the case of the first embodiment, the particles 122 in the central part to the particles 12 in the outer peripheral part are
The particles that moved to 3 were particles of 60 μm or more.

The rectifier 109 acts as a resistor for the swirling component of the flow velocity in the separation space 127, attenuates the velocity component in the swirling direction and converts it into a straight flow, so that coal particles can be supplied to the furnace in a straight flow. it can. by this,
Since it is possible to suppress the mixing of the combustion air and the coal particles, which occurs when the coal particles supplied to the furnace are diffused in the radial direction, the reducing flame region can be favorably formed inside the flame.

Pulverized coal nozzle 102 in the first embodiment
Fig. 3 shows the radial distribution of coal concentration and velocity at the rim of. The concentration and speed are standardized by the average value of the entire flow path, and the standardized value of 1 means that the pulverized coal nozzle 1
02 indicates that the coal particles are uniformly supplied over the entire flow path. The radial distance is standardized by the radius of the pulverized coal nozzle 102. According to the pulverized coal burner of the first embodiment, coal particles having a relatively high concentration can be supplied at a relatively high speed in a region where the standardized radial distance is larger than 0.6.

Since the flame stabilizer entrains and ignites the coal particles supplied at a high concentration, it is possible to enhance the combustion of the coal particles in the vicinity of the pulverized coal burner.

(Iii) Effect FIGS. 4 and 5 show the coal concentration distribution at the outlet of the pulverized coal nozzle. Coal particles having a particle size distribution in which the weight of particles of 75 μm or less is 80% are used, and the concentration distribution of this embodiment having at least two inlets in a swirl flow generator (FIG. 4), The concentration distribution (Fig. 5) when a swirling flow was generated by a so-called cyclone having one inlet described in JP-A-3-241208 was compared. The coal concentration was shown as a relative value with the average concentration set to 1. For example, a density of 1.2 means 20% more than the average density.
It shows that a high concentration of coal is flowing. In the case of the pulverized coal nozzle of this example, the isoconcentration curves are concentric, and the coal concentration is supplied without deviation in the circumferential direction. On the other hand, in the case of the cyclone method, the isoconcentration curves are not formed concentrically, and the concentration is high in a part of the nozzle. For example, the density near the outer peripheral wall of the nozzle shows a difference of 80% compared with 1.8 and 1.0.

The difference between the two depends on how the swirling flow is generated. That is, coal is injected into the swirl flow generator from at least two inlets, and a swirl flow is generated thereby, so that the coal particles are uniformly dispersed in the nozzle. When a swirl flow is generated by a cyclone having one inlet, the jet of coal particles and air flows in a single line on the inner wall of the cyclone. Since this streak corresponds to a position where the coal concentration is high, non-uniformity of the coal concentration in the circumferential direction occurs at the edge of the pulverized coal nozzle. When the burner is operated with a low load, the coal concentration becomes lean, but the flame is extinguished from the leanest point at the pulverized coal nozzle rim. Therefore, in the present embodiment, the concentration deviation in the circumferential direction is small, the flame can be retained in the flame stabilizer up to a lower load.

The separation enhancing means 119 is connected to the swirling flow generator 120.
By providing the particles downstream of the fuel nozzle 102.
The ability to collect in an area close to the inner wall of the can be enhanced.

Since the separation space 127 can move relatively large particles flowing through the center of the pulverized coal nozzle 102 to a region near the inner wall of the nozzle, the average particle size of the coal particles is larger as the inner wall of the nozzle is larger. Become.

The rectifier 109 acts as a resistor for the swirling component of the flow velocity in the separation space 127 and attenuates the velocity component of the swirling flow to convert it into a straight flow, so that the coal particles are converted into a straight flow.
00 can be supplied in a straight flow. by this,
Diffusion of pulverized coal in the radial direction is suppressed, and the reducing flame region can be well formed inside the flame.
The Ox concentration can be reduced.

In the pulverized coal burner of the first embodiment, the NOx concentration was measured with and without the rectifier 109. When coal particles are supplied to the furnace 100 in a swirling flow, the NOx concentration under the condition of the excess air ratio that supplies air 10% larger than the theoretical air amount is 450 ppm without the rectifier, whereas the rectifier 109 The NOx concentration in the case of installing the same showed a performance of 300 ppm at the same excess air ratio.

Further, since the rectifier 109 converts the jet flow into a straight flow and supplies it, the flow velocity distribution at the lower end of the pulverized coal nozzle 102 does not create a reverse flow from the furnace 100 toward the pulverized coal nozzle, and It also does not create a region of flow velocity below the velocity at which the charcoal flame propagates. As a result, burning of the burner caused by the flame of the furnace 100 propagating inside the pulverized coal nozzle 102 can be avoided.

FIG. 6 shows the relationship between burner load and flame brightness. The burner load indicates the supply ratio of fuel (coal) to the rated fuel supply amount, and the flame brightness is shown as a relative value with the flame brightness at 100% burner load being 100. In the case of the conventional example in which inertia is used to supply coal to the throat rim of the primary throat, the brightness of the flame decreases because the flame becomes unstable when the burner load is reduced by reducing the coal supply amount. , A misfire occurs when the burner load is 35%. On the other hand, in the case of this embodiment, the burner load 1
A flame that is stable up to 5% can be formed.

The pulverized coal burner in the first embodiment is shown in FIG.
Since the pulverized coal can be supplied at the concentration and speed shown in (1), the concentration of the pulverized coal flowing in the vicinity of the flame stabilizer 110 becomes high, and the combustion amount of the pulverized coal in the vicinity of the burner can be increased. By raising the temperature of this region, the temperature of the reducing flame region also rises at the same time, so the reduction of NOx is promoted by the promotion of the thermal decomposition reaction in the reducing flame region.

[Second Embodiment] (iv) Structure of Burner A second embodiment will be described. FIG. 7 is a sectional view of the pulverized coal burner of the second embodiment.

The burner of the second embodiment is the pulverized coal nozzle 1
A distributor 130 is concentrically attached to the pulverized coal nozzle 102 at the position of the rectifier 02. This distributor 130
The pulverized coal nozzle 102 is divided into an inner pipe 131 flowing inside the distributor 130 and an outer pipe 132 flowing outside.

Since the rectifier is divided in the radial direction by the distributor 130, the rectifier 109a located on the inner pipe 131 is divided.
And the rectifier 109b located in the outer tube 132. In order to effectively achieve the particle size control in the separation space, it is preferable to arrange the rectifier 109 after the pulverized coal nozzle 102 is concentrically divided by the distributor 130.

(V) Action The distributor 130 operates in the separation space 127 in the pulverized coal nozzle 102.
Coarse particles 124 flowing on the inner wall side and fine particles 12 flowing in the center
The flow of the pulverized coal separated into 5 is maintained up to the lower end of the nozzle.

The rectifier 109a is the inner tube 1 of the distributor 130.
The swirling flow of the jet of the mixture of primary air and coal particles supplied to 31 is converted into a straight flow.

The rectifier 109b is the outer tube 1 of the distributor 130.
The swirling flow of the jet of the mixture of primary air and coal particles supplied to 32 is converted into a straight flow.

(Vi) Effect The distributor 130 prevents the powder separated into the coarse particles 124 and the fine particles 125 from being gradually mixed by the action of the turbulent flow. Therefore, the coal in the outer pipe 132 at the lower end of the pulverized coal nozzle 102 is prevented. The concentration can be made higher than that in the first embodiment, and the coal concentration in the inner pipe 131 can be made lower than that in the first embodiment. FIG. 9 shows the effect of the distributor.

The NOx concentration when coal is burned will be described using the second embodiment. FIG. 10 shows the NOx concentration when fine powder 125 was supplied from the inner pipe 131 and coarse powder 124 was supplied from the outer pipe 132, and the results were measured by changing the air ratio of the inner pipe 131 and the outer pipe 132. Here, the air ratio indicates the ratio of the primary air flow rate to the air flow rate required to completely burn the coal particles. The fine powder 125 when burned in FIG. 10 is a coal particle having a particle size distribution of 53 μm or less, and the coarse powder 124 is a coal particle having a particle size distribution of 100 μm or less. NOx when coal particles having a particle size distribution of 100 μm or less shown in FIG. 11 are supplied from the inner pipe 131 and the outer pipe 132.
Compared with the concentration, the NOx concentration is reduced by about 20% by supplying the fine powder 125 from the inner pipe 131, and
The condition of the air ratio of the inner pipe 131 and the outer pipe 132 capable of reducing NOx can be widened. This is because the fine powder 125 supplied from the inner pipe 131 is mainly supplied to the reducing flame region. That is, the fine powder 125 is more reactive than the coarse powder 124, and even in the reducing flame region where oxygen is consumed, the amount of the solid component thermally decomposed by carbon dioxide or water is larger than that of the fine powder 125. This is because the phenomenon of suppressing the formation of the reducing flame atmosphere due to the reducing gas can be alleviated, so that the NOx reduction reaction in the reducing flame region can be promoted.

A swirl flow generator 120 in the pulverized coal burner of the second embodiment is shown in FIG. This swirl flow generator 120
Is a radial flow type swirl flow generator located between a cone 140 in the shape of a cone and a diffuser located on the downstream side of the cone 140 and having a flow passage area expanding toward the downstream side.
The swirl flow generator 120 is composed of a plurality of plate-shaped blades arranged in the circumferential direction of the flow path, and a support rod integrally attached to the blades. The support rod is supported by the cone 140 and the diffuser, and the angle of the blade can be changed by a driving device (not shown).

In the swirl flow generator 120 of the second embodiment, after supplying coal particles to the inner peripheral surface of the primary throat 111,
Since the swirling flow can be applied to the coal particles and the primary air, the concentration of coal supplied to the inner peripheral surface of the primary throat of the separation space 127 can be increased. As a result, the outer tube 1
Since the coal concentration supplied from 32 is higher than that of the swirl flow generator 120 having the structure shown in FIG. 7, the proportion of coal burning in the flame stabilizer 110 is increased and the temperature of the reducing flame region is increased. Low NOx combustion can be achieved by promoting the reaction.

[Third Embodiment] (vii) Structure of Burner A third embodiment will be described. FIG. 12 is a sectional view showing only the pulverized coal nozzle of the pulverized coal burner of the third embodiment, and FIG. 13 is a bird's-eye view of the swirl flow generator 120 of the third embodiment.

The burner of the third embodiment is the swirl flow generator 1
20 has a means for changing the turning strength, a means for changing the crushing amount of the coal crusher 154, and a means for changing the flow rate of the air carrying the crushed coal particles, and the turning strength is based on the command of the coal supply amount. And a means for controlling the pulverization amount and the air flow rate.

An example of means for changing the swirl strength is a support rod 151 integrally mounted on the swirl flow generator 120 upstream of the swirl flow generator 120, a support 150 for supporting the support rod 151, and a support rod 151. Drive machine 152 for driving
Consists of In response to a command from the controller 153, the supporting rod 151 is rotated about the axis of the supporting rod 151 by the driving device 152. The support 150 supports the rotation of the support rod 151, and passes through the outer peripheral surface of the support rod 151, and the fuel nozzle 1
Prevents pulverized coal from flowing out of the system of No. 02.

The means for changing the amount of crushing receives the load command from the controller 153 and changes the amount of coal supplied to the crusher 154.

The means for changing the air flow rate adjusts the primary air flow rate by the opening degree of the flow rate control valve 155 provided in the pipe of the primary air supplied to the crusher 154.

The controller 153 controls the number of revolutions of the swirling flow generator 120, the amount of coal crushed by the crusher 154, and the flow rate control valve 15.
Adjust the opening of 5.

(Viii) Action and Effect The operation of the pulverized coal burner of the third embodiment will be described with reference to FIG. FIG. 14 shows a swirl flow generator 12 for a burner load.
The relationship between the rotation speed of the swirl vane of 0, the crushing amount of the crusher 154, and the operation amount of the flow rate control valve 155 is shown. The manipulated variable is indicated by the opening with the maximum value of the manipulated variable being 100%.

The load of the pulverized coal burner of the third embodiment is 10
In the range of 0% to 50%, the rotational speed of the swirl vane is kept constant, and the crushing amount and the flow control valve are decreased with the load. That is, while maintaining the swirl strength of the swirl flow generator 120, the operation is performed with the ratio between the flow rate of coal and the flow rate of primary air being constant.

In the region where the load of the pulverized coal burner is 50% or less, the opening of the flow rate control valve is kept constant due to the restriction of the minimum flow velocity that prevents the sedimentation of particles in the primary air pipe, and the primary air flow rate is maintained by the burner. It flows a certain amount regardless of the load. The opening of the crushing amount decreases with the burner load. On the other hand, the opening degree of the number of revolutions of the swirl blade increases as the burner load is reduced, and the swirl strength inside the pulverized coal nozzle 102 is strengthened.

When the rotational speed of the swirl vanes of the swirl flow generator 120 increases, the swirl strength of the primary air in the separation space 127 increases. If the swirling strength of the primary air increases, coal particles are also supplied in a swirling flow, so that the separation space 12
7, the relatively large particles among the central particles 122 are integrated with the outer peripheral particles 123 in the primary throat 111.
The coarse particles 124 are supplied from the vicinity of the inner peripheral wall of the. On the other hand, the fine particles 125 supplied from the particles 122 in the central portion are supplied from the central portion of the primary throat 111.

The amount of particles supplied from the central particles 122 to the coarse particles 125 increases as the opening degree of the rotational speed of the swirling blade increases. As a result, even under the condition that the burner load is 50% or less and the coal flow rate in the primary air is small,
The coal concentration of the coarse particles 124 can be made close to the coal concentration under the condition of a burner load of 60% or more. For this reason,
Since the load of the burner that requires fuel such as oil for supporting combustion can be moved to a lower load side than before, the range of burner load for burning coal exclusively can be widened, so the amount of oil for supporting combustion should be reduced. You can

[Fourth Embodiment] A fourth embodiment will be described. FIG. 15 is a sectional view of the distributor of the pulverized coal burner of the fourth embodiment, and the structure of the pulverized coal burner other than this is the same as the structure of the burner shown in the first to third embodiments.

The pulverized coal burner of the fourth embodiment is characterized in that the distributor 130 arranged inside the primary throat 111 is provided with a function of adjusting the velocity distribution at the lower end of the pulverized coal nozzle 102. In an example of the fourth embodiment, as shown in FIG. 15, the speed adjusting unit 160 in which the distributor 130 is located in the flow path direction is arranged.
And the axial flow portion 161 is divided into two regions.

In the case of FIG. 15, there is shown a distribution in which the velocity of the primary air on the upstream side of the distributor 130 increases as it approaches the inner peripheral wall of the primary throat 111, and this velocity distribution is made uniform on the downstream side of the distributor 130. For the purpose of
The shape of

That is, the speed adjusting section 160 has a conical shape, and is set so that the flow passage cross-sectional area of the inner pipe 131 formed by the conical speed adjusting section 160 is small.

The axial flow portion 161 has a cylindrical shape, and this cylinder is positioned concentrically with the primary throat 111. The flow passage cross-sectional area of the inner pipe 131 made of a cylinder is constant regardless of the flow passage direction.

FIG. 16 shows the radial distribution of coal concentration and velocity at the lower end of the primary throat 111. Since the cross-sectional area of the flow passage on the outer peripheral side of the speed control unit 160 increases toward the downstream side, the flow velocity of the primary air flowing through this flow passage can be reduced. Since the cross-sectional area on the inner peripheral side of the speed adjusting section 160 becomes smaller toward the downstream side, the speed of the primary air flowing through this flow path can be increased. Thereby, the ejection speed of the primary air can be made a uniform value in the radial direction of the lower end of the primary throat 111. On the other hand, since the coal concentration is determined by the ratio of the coal particles flowing into the distributor 130 and the primary air flow rate, the coal concentration of the outer pipe 132 into which the coarse particles 124 formed by the separation space 127 flow is higher than that of the inner pipe 131. You can

The distributor 130 in the fourth embodiment can independently change the coal concentration and speed by changing the shape of the axial section of the distributor 130. When the velocity difference between the two jets supplied from the outer pipe 132 and the inner pipe 131 as shown in this embodiment is made small, the mixing of the two jets is most suppressed, so the fine particles supplied from the inner pipe 131 are suppressed. 12
5 can be better preserved and supplied to the area of reducing flame. Since the fine powder 125 has a large surface area per volume, it easily reacts with carbon dioxide and water even in a reducing flame region, and NO
Low NOx combustion can be achieved because it produces precursors that reduce x. (Fifth Embodiment) A pulverized coal boiler power generation system according to a fifth embodiment will be described with reference to FIG. The power generation system of this embodiment includes a furnace 200 for burning coal, a pulverized coal burner 201 of the present invention attached to the furnace, an after air port 202, and an air supply system 209 for supplying air to the pulverized coal burner and the after air port. A coal crusher 203, a heat transfer tube 206 for absorbing heat generated by the flame of coal, a steam turbine 207 for generating electric power by steam generated in the heat transfer tube, and a generator 208.

In the case of the pulverized coal boiler power generation system capable of generating power of 5000 MW per unit time, the pulverized coal burners installed on both sides of the furnace 200 have three stages in the height direction of the furnace and four in the depth direction of the furnace. The columns are arranged. Further, the after-air port is installed further above the uppermost pulverized coal burner. The coal pulverizer 203 pulverizes the coal so that the weight ratio of the pulverized coal having a particle size of 75 μm or less is between 60% and 90%, and the coal is conveyed to the pulverized coal burner by the conveying air.

The air used for combustion of coal is supplied from the air supply system 209, and the air flow control valves 204, 20 are supplied.
The flow rate is adjusted by 5.

The steam 211 is heated by the heat transfer tubes forming the inner wall of the furnace and then converted into pressurized steam by the plurality of heat transfer tubes 206 attached inside the flow path of the furnace. The steam turbine 207 uses the pressurized steam to generate the power generator 20.
8 is driven to generate electricity.

FIG. 18 shows an example of the operating method of this embodiment. FIG. 18 shows the load characteristics of each pulverized coal burner with time when the power generation load of the pulverized coal boiler power generation system is changed from 17% to 100%. 18A shows an example using a conventional burner, and FIG. 18B shows an example using the burner of the present invention. In the case of the conventional example, pulverized coal burner 2
Operate 01a and 201d with 50% load, load 10
It is increased to 0%, and pulverized coal burners 201b and 201 are sequentially added.
e, follow the procedure for starting the pulverized coal burners 201c and 201f.

On the other hand, when the pulverized coal burner of the present invention is used, it can be burned only with coal even under a lower load than in the conventional case, so that the pulverized coal burners 201a and 201d can be burned with a power generation load of 17%. And 201b and 201e 2
It can be operated with a load of 5%. Therefore, in order to improve the power generation load of the pulverized coal boiler power generation system to 100%, it is sufficient to activate the pulverized coal burners 201c and 201f.

Therefore, if the load change rates of the coal crushers 203 are compared under the same conditions, the time required to reach a load of 100% in this embodiment is 2/3 of the conventional case. That is,
Pulverized coal boiler power generation system load change rate of 1.5
Can be doubled.

Further, when starting and stopping the pulverized coal burner,
The introduction of air or coal accompanied by the start and stop of the coal crusher 203 causes a temporary change in the emissions of carbon monoxide and nitrogen oxides. However, when the present embodiment is applied, the number of times of starting and stopping the coal crusher 203 can be reduced, so that the emission amounts of carbon monoxide and nitrogen oxides can be stably controlled.

[0121]

According to the present invention, it is possible to provide a pulverized coal burner capable of reducing the NOx concentration. In addition, by increasing the load of the burner that can burn with only pulverized coal, the amount of auxiliary combustion material such as oil used can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a pulverized coal burner according to the present invention.

FIG. 2 is a side view of the burner shown in FIG. 1 viewed from the furnace side.

FIG. 3 is a diagram showing a radial distribution of coal concentration and velocity at the rim of a pulverized coal nozzle of a burner according to an example of the present invention.

FIG. 4 is a diagram showing a coal concentration distribution at an outlet of a pulverized coal nozzle of a burner according to this example.

FIG. 5 is a diagram showing a coal concentration distribution at an outlet of a pulverized coal nozzle of a conventional burner.

FIG. 6 is a graph showing the relationship between burner load and flame brightness.

FIG. 7 is a sectional view of a pulverized coal burner according to a second embodiment.

FIG. 8 is a side view of a swirl flow generator according to a second embodiment.

FIG. 9 is a graph showing the effect of coal concentration of the distributor.

FIG. 10 is a diagram showing the NOx concentration when the pulverized coal nozzle is divided into two flow passages, the fine powder is supplied to the inner pipe, and the coarse powder is supplied to the outer pipe by changing the air ratio.

FIG. 11 is a diagram showing the NOx concentration when the coal particles having the same particle diameter are supplied to the inner pipe and the outer pipe in the pulverized coal nozzle, while changing the air ratio.

FIG. 12 is a sectional view of a pulverized coal nozzle portion in a pulverized coal burner of a third embodiment.

FIG. 13 is a bird's-eye view showing a swirl flow generator according to a third embodiment.

FIG. 14 is a graph showing the relationship between the rotation speed of the swirl vanes of the swirl flow generator, the crushing amount of the coal crusher, and the operation amount of the flow rate control valve with respect to the burner load.

FIG. 15 is a sectional view of a distributor in a pulverized coal burner of a fourth embodiment.

FIG. 16 is a diagram showing the relationship between the coal concentration and the velocity of the mixture jet of coal and carrier air when the burner of the fourth embodiment is used.

FIG. 17 is a schematic configuration diagram of a boiler power generation system including the burner of the present invention.

18 (a) and 18 (b) are graphs showing the load characteristics of each pulverized coal burner in the boiler power generation system over time.

[Explanation of symbols]

102 ... Pulverized coal nozzle, 103 ... Secondary air nozzle, 10
4 ... Tertiary air nozzle, 105 ... Mixture of primary air and pulverized coal, 106 ... Secondary air, 107 ... Tertiary air, 108 ... Oil gun, 109 ... Rectifier, 110 ... Flame stabilizer, 119 ...
Separation strengthening means, 120 ... Swirl flow generator, 121 ... Swirl flow, 127 ... Separation space, 130 ... Distributor, 131 ... Inner tube, 132 ... Outer tube, 151 ... Support rod, 152 ... Drive unit,
153 ... Controller, 154 ... Crusher, 155 ... Flow control valve, 160 ... Speed control unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Go Kono 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Oka ▲ saki ▼ Omika-machi, Hitachi-shi, Ibaraki 7-1, 1-1 Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shigeki Morita 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (19)

[Claims] 1. A pulverized coal combustion system having at least one air nozzle concentrically provided around a pulverized coal nozzle for jetting a mixture of coal particles and a carrier air in a straight flow to jet a combustion air in a swirling flow. The burner includes swirl flow generating means for swirling a mixture of the coal particles and conveying air, and rectifying means for converting the swirl flow formed by the swirl flow generating means into a straight flow, the coal in the swirl flow generating means A pulverized coal combustion burner characterized in that a supply port for a mixture of particles and a carrier air is provided at a plurality of positions in the swirling direction. 2. The swirling flow generating means having a plurality of blades in the pulverized coal nozzle according to claim 1, wherein the swirling flow generating means is provided with a blade and a blade for supplying a mixture of coal particles and carrier air. A pulverized coal combustion burner characterized by being provided between and at a plurality of locations. 3. A supply port for a mixture of coal particles and carrier air is provided at a plurality of tangential directions on a rear end side wall surface of the pulverized coal nozzle according to claim 1, and the mixture is supplied from the tangential direction. A pulverized coal combustion burner characterized in that a swirl flow is formed by the above. 4. A pulverized coal combustion burner according to any one of claims 1 to 3, wherein the rectifying means is provided with a resistor for preventing swirling of a mixture of coal particles and carrier air. 5. The pulverized coal combustion burner according to claim 4, wherein a plurality of plate-shaped members are radially provided in the pulverized coal nozzle as the resistor. 6. The nozzle according to claim 1, wherein relatively small particles of coal particles contained in the swirling flow are provided in the center of the nozzle between the swirling flow generating means and the rectifying means. A pulverized coal combustion burner characterized in that a space sufficient to move it by inertial force is provided in the section. 7. Combustion of pulverized coal provided concentrically with at least one air nozzle that ejects combustion air in a swirling flow around the outer periphery of a pulverized coal nozzle that ejects a mixture of coal particles and carrier air in a straight flow. In the burner, a swirl flow generating means for swirling the mixture of the coal particles and the carrier air, a means for gradually weakening the strength of the swirl flow of the mixture flowing in the pulverized coal nozzle toward the outlet, and the swirling A pulverized coal combustion burner, comprising: a straightening means for changing the flow into a straight flow, and supply ports for a mixture of coal particles and conveying air in the swirling flow generating means are provided at a plurality of positions in the swirling direction. 8. A means for expanding the flow passage cross-sectional area of the pulverized coal nozzle toward the downstream side as means for weakening the strength of the swirling flow of the mixture of the coal particles and the carrier air according to claim 7. A pulverized coal combustion burner characterized by being equipped. 9. The member according to claim 8, wherein, as the means for enlarging the flow passage cross-sectional area, a member having a conical shape at the axial center of the pulverized coal nozzle, and the apex of the cone is directed to the downstream side is arranged. Pulverized coal combustion burner. 10. Pulverized coal combustion provided concentrically with at least one air nozzle for ejecting a combustion air in a swirling flow around the outer periphery of a pulverized coal nozzle for ejecting a mixture of coal particles and a carrier air in a straight flow. In the burner, a swirl flow generating means for swirling the mixture of the coal particles and the carrier air, and a distribution for dividing the swirl flow of the mixture flowing in the pulverized coal nozzle toward the outlet into a plurality of annular flows Means and a rectifying means for converting a swirling flow divided into a plurality of flows by the distributing means into a straight flow, and a feed port for a mixture of coal particles and carrier air in the swirling flow generating means is provided in a swirling direction. A pulverized coal combustion burner characterized by being installed in multiple locations. 11. Pulverized coal combustion in which at least one air nozzle for concentrically ejecting a combustion air in a swirling flow is concentrically provided on the outer periphery of a pulverized coal nozzle for ejecting a mixture of coal particles and a carrier air in a straight flow. In the burner, a swirl flow generating means for swirling the mixture of the coal particles and the carrier air, a means for gradually weakening the strength of the swirl flow of the mixture flowing in the pulverized coal nozzle toward the outlet, and the fine powder. A distribution means for dividing the swirling flow into a plurality of annular flows in the vicinity of the jet port of the charcoal nozzle, and a rectifying means for converting the swirling flow into a straight flow, for transporting the coal particles and the coal particles in the swirling flow generating means. A pulverized coal combustion burner, characterized in that supply ports for a mixture with air are provided at a plurality of positions in the swirling direction. 12. The pulverized coal combustion burner according to claim 10 or 11, wherein at least one tubular member having the same axis as the nozzle is provided in the pulverized coal nozzle as the distributing means. . 13. The cylindrical member according to claim 12, wherein the inner diameter and the outer diameter of the cylinder of the cylindrical member are substantially constant, and the outer surface of the cylindrical member located upstream of the pulverized coal nozzle is provided with an inclination. Pulverized coal burning burner. 14. The mixture of pulverized coal and carrier air at the lower end of the tubular member according to claim 12, wherein the inner diameter and the outer diameter of the tubular member are increased on the upstream side and decreased on the downstream side. A pulverized coal combustion burner characterized in that the flow velocities are almost the same inside and outside the cylinder. 15. A pulverized coal combustion burner according to claim 1, further comprising means for changing the strength of the swirl flow generated by said swirl flow generation means. 16. The swirling flow generating means having a plurality of blades in the pulverized coal nozzle according to claim 15, wherein the strength of the swirling flow can be changed by changing the inclination of the blades. Pulverized coal combustion burner. 17. The fine powder according to claim 15 or 16, further comprising means for changing the strength of the swirl flow generated by the swirl flow generating means so as to increase at low load and decrease at high load. Charcoal burning burner. 18. A pulverized coal combustion burner according to claim 1, further comprising an oil burner in the pulverized coal nozzle. 19. A pulverized coal combustion burner is provided at a plurality of positions in a height direction of a wall surface of a boiler furnace for burning coal, and an after-air port is provided above the burner so that heat generated by the combustion of the coal is generated in the furnace. A heat transfer tube for absorbing and generating steam is provided, and a steam turbine and a generator for generating power by the steam obtained by the heat transfer tube are provided, and when the power generation load is small, only the upper burner of the pulverized coal combustion burner is operated. A burner control device is installed to interrupt and expand the operation to the lower burner as the power generation load increases, and as the pulverized coal combustion burner, the outer periphery of the pulverized coal nozzle that ejects a mixture of coal particles and carrier air in a straight flow. Has at least one air nozzle for jetting combustion air into a swirling flow, and swirling flow generating means for swirling a mixture of the coal particles and conveying air and the swirling flow A pulverized coal combustion burner provided with rectifying means for converting a swirl flow formed by the flow generating means into a straight flow, and supply ports for a mixture of coal particles and carrier air in the swirl flow generating means at a plurality of positions in the swirling direction. A pulverized coal boiler power generation system comprising: a pulverized coal boiler power generation system.