JP4088615B2 - Pulverized coal fuel supply device - Google Patents

Description

  The present invention is applied to a combustion apparatus for pulverized coal fuel such as a coal-fired boiler that burns pulverized coal, and burners for injecting and burning pulverized coal fuel into a furnace are installed in a plurality of stages in the combustion gas flow direction of the furnace. The present invention also relates to a pulverized coal fuel supply apparatus configured to send pulverized coal obtained by pulverizing raw coal into a burner.

A coal-fired boiler configured to install a plurality of burners for injecting and burning pulverized coal fuel into the furnace in the combustion gas flow direction of the furnace, and to feed the pulverized coal obtained by pulverizing the raw coal into the burner. In the pulverized coal fuel combustion apparatus, various techniques for supplying pulverized coal fuel with high fineness to each burner are provided.
In the technique of Patent Document 1 (Japanese Patent Laid-Open No. 2004-125327), which is one of such techniques, a hopper that primarily stores pulverized coal from a mill, and a cutting hopper that quantitatively cuts pulverized coal from the hopper And a classifier provided in a transport pipe that connects the cutting hopper and the furnace burner so as to stably supply pulverized coal with a small particle size to the burner without impairing the transportability of the pulverized coal. It is configured.

JP 2004-125327 A

In a combustion apparatus for pulverized coal fuel such as a coal-fired boiler, multiple stages are installed in the flow direction of the combustion gas in the furnace to eliminate unburned components and improve combustion efficiency and reduce NOx generation. Combustion of pulverized coal from the burner with a small amount of coarse particles and high fineness (the ratio of fine powder of 200 # pass (fine powder of particle size of 75μ or less) is 95% or more) is performed throughout the furnace, and is uniform in the entire combustion zone of the furnace It is necessary to maintain combustion.
In order to realize such combustion, if the pulverized coal with high fineness as described above is uniformly supplied to the burners of the plurality of stages, the power of the mill for supplying the pulverized coal to each burner is increased. This causes an increase in roller wear accompanying an increase in load.

In addition, if the design is made such that the pulverized coal having a high fineness is supplied and the capacity of the mill is sufficient to avoid wear of the roller as described above, the mill becomes larger and the equipment cost increases.
Furthermore, although a classification device is provided inside the mill, it is difficult to increase the classification accuracy due to the drift of the flow of pulverized coal inside the mill and the high concentration of pulverized coal particles blown into the classification device. Therefore, it is difficult to supply pulverized coal having a uniform particle size to each burner.

  However, in the technique of Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-125327), the pulverized charcoal fed from the mill is supplied to the classifier by compressed air after passing through a plurality of hoppers. It is configured to classify the pulverized coal into coarse powder, supply the fine powder to the furnace, and return the coarse powder to the mill for re-grinding. No means for controlling to do so is disclosed.

  In view of the problems of the prior art, the present invention realizes uniform combustion in each stage of the burner arranged in a plurality of stages in the combustion gas flow direction of the furnace to achieve uniform combustion in each stage of the burner and NOx ( An object of the present invention is to provide a pulverized coal fuel supply device that maintains a particle size capable of suppressing the generation of nitrogen oxides and that can reduce the mill device cost by setting the mill capacity to an appropriate capacity.

The present invention achieves such an object. A burner for injecting and burning pulverized coal fuel into a furnace is installed in a plurality of stages in the combustion gas flow direction of the furnace, and pulverized coal obtained by pulverizing raw coal with a mill is used as the burner. In the pulverized coal fuel supply device configured to be fed into the pulverized coal fuel supply pipe, the outlet of the furnace among the pulverized coal supply pipes that connect the mill and the burners of each stage and convey the pulverized coal from the mill to the burner. A classification device for classifying the pulverized coal from the mill into coarse coarse particles and small fine particles is installed in the pulverized coal supply pipe connected to the downstream burner close to the downstream, and the fine powder outlet of the classification device is connected to the downstream Connected to the side burner, the coarse powder outlet of the classifier is connected to the pulverized coal supply pipe to the burner on the upstream side in the combustion gas flow direction from the downstream burner, and the fine powder classified by the classifier The downstream bar And supplies to the burner, the first aspect in that the coarse powder was configured to supply to the upstream side of the burner.
The invention of claim 1, wherein, in addition to the first aspect, the mill provided for each burner of the plurality of stages configured in the same volume, the combustion gas flow direction upstream of the downstream burner The pulverized coal is directly supplied from the mill to the intermediate stage burner via the pulverized coal supply pipe, and the coarse powder outlet of the classifier is located upstream of the intermediate stage burner in the combustion gas flow direction. It is to connect to the pulverized coal supply pipe to the burner.

In a combustion device for pulverized coal fuel such as a coal-fired boiler with multiple burners installed in the combustion gas flow direction of the furnace, the burner is jetted into the furnace from the burner upstream in the combustion gas flow direction where the distance to the furnace outlet is large. The combustion time of the pulverized coal fuel becomes longer than the combustion time of the pulverized coal fuel from the burner on the downstream side in the combustion gas flow direction where the distance to the furnace outlet is small.
For this reason, the particle size of the pulverized coal fuel from the downstream burner with a short distance to the furnace outlet and a short combustion time is eliminated as described above to improve the ignitability and reduce the amount of NOx generated. Holding at the high fineness necessary for combustion (the proportion of fine powder of 200 # pass (fine powder of particle size 75 μm or less) is 95% or more), the combustion time is longer than the pulverized coal fuel from the downstream burner. The pulverized coal fuel from the upstream burner in the combustion gas flow direction has the same level as the pulverized coal fuel from the downstream burner even if the particle size is coarser than the particle size of the pulverized coal fuel from the downstream burner. Complete combustion is possible.

  The present invention has been made based on such knowledge, and classifies the pulverized coal from the mill into coarse pulverized powder and fine pulverized powder with a small particle size in a pulverized coal supply pipe connected to a downstream burner close to the outlet of the furnace. A classifier is connected, and the fine powder outlet of the classifier is connected to the downstream burner where the distance to the furnace outlet is small and the combustion time is short, and the particle size of the pulverized coal fuel from the downstream burner is as described above While maintaining a high fineness, the coarse powder outlet of the classifier is connected to the pulverized coal supply pipe to the burner on the upstream side in the combustion gas flow direction where the distance to the furnace outlet is large and the combustion time is long. By supplying pulverized coal fuel having a coarser particle size than the pulverized coal fuel to the downstream burner to the burner, the downstream burner and the upstream burner eliminate unburned components and improve ignitability. Reduced NOx generation It is possible to perform the level of combustion.

Therefore, according to this invention, if only the mill connected to the downstream burner near the outlet of the furnace is designed to have a capacity corresponding to the high fineness pulverized coal fuel particle size, the mill connected to the upstream burner is Even if the design is smaller than that of the mill connected to the downstream burner, combustion should be performed at the same level as that of the downstream burner with no unburned content, improved ignitability, and reduced NOx generation. Is possible.
Thereby, a classification device is installed in the pulverized coal supply pipe connected to the downstream burner, fine powder from the classification device is supplied to the downstream burner, and coarse powder from the classification device is supplied to the upstream burner. The pulverized coal fuel supply device with an extremely simple structure and low cost realizes uniform combustion in each stage of the burner, eliminates unburned components, improves ignitability, and suppresses the generation of NOx. It is possible to obtain combustion.

The invention of claim 2, wherein, in addition to the first aspect, established a collecting bottle for storing the fines to the pulverized coal supply pipe which connects the fines outlet of the classification device and said downstream burner A fine powder amount detecting means for detecting the amount of fine powder accumulated in the collection bottle, and a target range in which the fine powder amount passing through the classifier is constant based on the detected value of the fine powder amount from the fine powder amount detecting means. And a controller for controlling the rotation speed of the classifier so as to be inside.
In this invention, the fine powder amount detecting means is specifically based on the following two means.
(1) The fine powder amount detecting means comprises a level meter for detecting the level of fine powder in the collection bottle, and the controller is adapted to control the classifier so that the level detection value from the level meter is within a target level range. It is configured to control the rotational speed.
(2) The fine powder amount detection means comprises a load cell that detects the weight of fine powder in the collection bin, and the controller rotates the classifier so that the fine powder weight detection value from the load cell is within a target weight range. Configured to control the number.

  According to this invention, the collection bin for collecting fine powder is installed in the pulverized coal supply pipe connecting the fine powder outlet of the classifier and the downstream burner, and the amount of fine powder temporarily stored in the collection bin is set. Detecting by the level of fine powder by the level meter or the fine powder weight by the load cell, and controlling the number of rotations of the classifier so that the fine powder amount to the downstream burner is within a certain target range based on the detected value of the fine powder amount. As a result, the classification accuracy in the classification device can be maintained with high accuracy, and the particle size of the pulverized coal supplied to the burners at each stage can be achieved to achieve uniform combustion and suppress the generation of unburned components and NOx. The particle size can be maintained.

The invention of claim 5, wherein, in addition to the first aspect, established a collecting bottle for storing the fines to the pulverized coal supply pipe which connects the fines outlet of the classification device and said downstream burner In addition, an air conveyance device that conveys the fine powder in the collection bin into the pulverized coal supply pipe by an air flow is provided at a connection portion of the collection bin to the pulverized coal supply pipe, and air to the air conveyance device An air amount adjusting means for adjusting the amount is provided, and the amount of fine powder conveyed from the collection bin to the pulverized coal supply pipe is controlled by adjusting the air amount of the air conveying device by the air amount adjusting means. It is characterized by comprising.
According to this invention, the collection bin for collecting fine powder is installed in the pulverized coal supply pipe that connects the fine powder outlet of the classifier and the downstream burner, and the fine powder in the collection bin is moved to the downstream burner by the air conveying device. The amount of fine powder supplied to the downstream burner is always controlled by adjusting the air amount of the air conveying device by the air amount adjusting means and controlling the amount of fine powder supplied from the collection bin to the downstream burner. Can be maintained.

In addition, the reference technology is configured such that burners for injecting and burning pulverized coal fuel into a furnace are installed in multiple stages in the combustion gas flow direction of the furnace, and pulverized coal obtained by pulverizing raw coal by a mill is sent to the burner. In the pulverized coal fuel supply apparatus, the same number of the mills as the burners are connected to the burners at each stage via the pulverized coal supply pipes, and the mills are connected to the burners on the upstream side in the combustion gas flow direction in the furnace. Was configured such that its particle size was larger than that of the downstream mill closer to the furnace outlet than the upstream burner .
In such a reference technique , preferably, the plurality of mills provided in the same number as the burner is configured such that the downstream mill close to the furnace outlet is the smallest in particle size, and the particle size increases toward the upstream in the combustion gas flow direction. Consists of a mill.

According to such a reference technique , a mill connected to a burner on the upstream side in the flow direction of the combustion gas with a long distance to the furnace outlet and a long combustion time is connected to the downstream with a small particle size and a short combustion time to the furnace outlet. By configuring so as to be larger than the mill connected to the side burner, the particle size of the pulverized coal fuel from the mill connected to the downstream burner is maintained at a high fineness and connected to the upstream burner. By making the particle size of the pulverized coal fuel from the mill coarser than that of the downstream burner, the downstream burner and the upstream burner eliminate unburned components to improve ignitability and reduce NOx generation. The same level of combustion can be performed.
Thus, even if the capacity of the mill connected to the upstream burner is designed to be smaller than the capacity of the mill connected to the downstream burner, the combustion at the same level that eliminates unburned parts and reduces the amount of NOx generated This makes it possible to reduce the size and cost of the mill.

According to the present invention, a pulverized coal fuel having a high fineness only in a mill connected to the downstream burner close to the furnace outlet is provided by installing a high-precision classification device in the pulverized coal supply pipe connected to the downstream burner. If the capacity corresponding to the particle size is designed, even if the mill connected to the upstream burner is designed to have a smaller capacity than the mill connected to the downstream burner, the unburned portion is eliminated and the amount of NOx generated is reduced. It is possible to perform combustion at the same level as the reduced downstream burner side.
Thereby, a classification device is installed in the pulverized coal supply pipe connected to the downstream burner, fine powder from the classification device is supplied to the downstream burner, and coarse powder from the classification device is supplied to the upstream burner. With the pulverized coal fuel supply device having a very simple structure and low cost, it is possible to achieve uniform combustion in each stage of the burner and to perform combustion capable of suppressing the generation of unburned components and NOx. .

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 1 is a system diagram of a pulverized coal fuel supply apparatus in a coal fired boiler according to a first embodiment of the present invention.
In FIG. 1, 1 is a furnace of a boiler, 1a is a furnace outlet which is an outlet of combustion gas from the furnace 1, 2a, 2b and 2c are burners for injecting and burning pulverized coal fuel into the furnace 1. A plurality of stages are installed in the combustion gas flow direction (Y arrow direction) of the furnace 1. The burner 2a closest to the furnace outlet 1a constitutes a downstream burner, the burner 2c farthest from the furnace outlet 1a relative to the downstream burner 2a constitutes an upstream burner, and 2b constitutes a midstream burner. Reference numeral 5 denotes an additional air nozzle for supplying additional air to the downstream side of each of the burners 2a, 2b and 2c.

3a, 3b, and 3c are mills that pulverize raw coal to generate pulverized coal (crushed coal). 3a is a downstream mill, 3c is an upstream mill, and 3b is a midstream mill. The detailed structure of each mill will be described later. Reference numerals 4a, 4b, and 4c are pulverized coal supply pipes that connect the downstream mill 3a, the midstream mill 3b, the upstream mill 3c and the downstream burner 2a, the midstream burner 2b, and the upstream burner 2c, respectively.
A classifier 10 is installed in a pulverized coal supply pipe 4a connected to a downstream burner 2a provided at a position closest to the furnace outlet 1a, and pulverized coal from the downstream mill 3a is coarsely crushed with coarse particles. And fine powder with small particle size.

The fine powder outlet of the classifier 10 is connected to the pulverized coal supply pipe 4a to supply pulverized powder to the downstream burner 2a through the pulverized coal supply pipe 4a. The coarse powder outlet of the classifier 10 is connected to the pulverized coal supply pipe 4c of the upstream burner 2c via a feeder 12 and a coarse powder pipe 11, and the coarse powder from the classifier 10 and the upstream mill The pulverized coal (pulverized coal) from 3c is mixed and supplied to the upstream burner 2c through the pulverized coal supply pipe 4c.
The pulverized coal (pulverized coal) from the intermediate flow side mill 3b is supplied directly to the intermediate flow side burner 2b through the pulverized coal supply pipe 4b.

FIG. 8 is a cross-sectional view showing details of the mill 3 (downstream mill 3a, midstream mill 3b, upstream mill 3c). In FIG. 8, 41 is a base, 40 is a body case, and 33 is a shaft end of a roller shaft. A roller 34 is fixed to the part and is driven to rotate around a shaft by a motor or the like and is loaded with a pulverizing load by a load device 36. A pulverizing table 34 is driven to rotate around a rotation center 32a by a motor or the like. The pulverized material) passes through the supply pipe 32 and falls onto the receiving surface 34a on the pulverizing table 34, and is caught between the pulverizing surface of the roller 33 and the receiving surface 34a of the pulverizing table 34.
The coking coal is pressed against the receiving surface 34a of the crushing table 34 rotating around the rotation center 32a by the roller 33 rotating while being applied with a crushing load by the load device 36, and pulverized into fine powder. Is done. Reference numeral 35 denotes a drift plate.

The fine particles thus pulverized are conveyed to the upper classifier 31 while being dried by hot air from the hot air supply port 38. The coarse particles are blown to the inner wall of the main body case 40, fall along the inner wall, and returned to the receiving surface 34a of the crushing table 34.
In the classifier 31, the pulverized charcoal is classified into fine powder and coarse powder by a rotary blade 31a rotated by a drive motor 39, the coarse powder is dropped on the receiving surface 34a of the pulverization table 34, and the fine powder is discharged to the fine powder outlet. The pulverized coal supply pipe 4 (4a, 4b, 4c) is fed through the pipe 37. 31 b is a rectifying cone of the classifier 31.

FIG. 2 is a schematic cross-sectional view of the classification device 10 in FIG.
In FIG. 2, 19 is a main body case, 14 is a rectifying cone, 13 is pulverized charcoal (from the mill 3) from a fine powder outlet pipe 37 of the mill 3 (downstream mill 3a, midstream mill 3b, upstream mill 3c). A pulverized coal inlet pipe for introducing a fine powder component), 16 is a fine powder outlet pipe, and 11 is a coarse powder pipe.
Reference numeral 15 denotes a rotating blade fixed to a rotating shaft 18 that is rotationally driven as indicated by an arrow N by a classifier drive motor 25 and rotates. The rotating blade 15 finely pulverizes the coal introduced from the pulverized coal inlet pipe 13. And coarse powder.
The fine powder classified by the rotation of the rotary blade 15 is sent to the pulverized coal supply pipe 4a through the fine powder outlet 16, and supplied to the downstream burner 2a through the pulverized coal supply pipe 4a. On the other hand, the coarse powder classified by the rotation of the rotary blade 15 is sent to the pulverized coal supply pipe 4c of the upstream burner 2c through the coarse powder pipe 11 and the feeder 12, and pulverized charcoal (from the upstream mill 3c ( Pulverized coal) is mixed and supplied to the upstream burner 2c through the pulverized coal supply pipe 4c.

  According to the first embodiment, the pulverized coal supply pipe 4a connected to the downstream burner 2a close to the furnace outlet 1a is classified into coarse pulverized powder and fine pulverized powder having a small particle size. The apparatus 10 is installed, and the fine powder outlet 16 of the classifier 10 is connected to the downstream burner 2a where the distance to the furnace outlet 1a is small and the combustion time is short, and the particle size of the pulverized coal fuel from the downstream burner 2a is increased. While maintaining the fineness (the ratio of the fine powder of 200 # pass (fine powder of particle size 75 μm or less) is 95% or more), the distance from the coarse powder outlet (coarse powder tube 11) of the classifier 10 to the furnace outlet 1a Is connected to the pulverized coal supply pipe 4c to the upstream burner 2c in the combustion gas flow direction with a long combustion time, and the upstream burner 2c has a coarser particle size than the pulverized coal fuel to the downstream burner 2a. Supply pulverized coal fuel And by, in the downstream burner 2a and the upstream burner 2c, it is possible to perform the same level of combustion with reduced improving vital NOx emissions ignitability by eliminating unburned.

That is, in a combustion apparatus for pulverized coal fuel such as a coal-fired boiler in which a plurality of burners 2a, 2b and 2c are installed in the combustion gas flow direction of the furnace 1, the upstream side of the combustion gas flow direction having a large distance to the furnace outlet 1a The combustion time of the pulverized coal fuel ejected from the burner 2c into the furnace 1 is longer than the combustion time of the pulverized coal fuel from the downstream burner 2a in the combustion gas flow direction where the distance to the furnace outlet 1a is small.
For this reason, in order to perform combustion in which the particle size of the pulverized coal fuel from the downstream burner 2a with a short distance to the furnace outlet 1a and a short combustion time is eliminated, the ignitability is improved and the NOx generation amount is reduced. If the required high fineness is maintained, the combustion time becomes longer than the pulverized coal fuel from the downstream burner 2a, and the pulverized coal fuel from the upstream burner 2c in the combustion gas flow direction has the particle size of the downstream burner. Even if it is coarser than the particle size of the pulverized coal fuel from 2a, complete combustion at the same level as the pulverized coal fuel from the downstream burner 2a can be performed.

Therefore, according to this embodiment, if only the mill 3a connected to the downstream burner 2a close to the furnace outlet 1a is designed to have a capacity corresponding to the high fineness pulverized coal fuel particle size, it is connected to the upstream burner 2c. Even if the mill 3c is designed to have a smaller capacity than the mill 3c connected to the downstream burner 2a, it performs combustion at the same level as the downstream burner side with no unburned portion and reduced NOx generation. Is possible.
Thereby, the classification apparatus 10 is installed in the pulverized coal supply pipe 4a connected to the downstream burner 2a, the fine powder from the classification apparatus 10 is supplied to the downstream burner 2a, and the coarse powder from the classification apparatus 10 is supplied. An extremely simple structure and low-cost pulverized coal fuel supply device that supplies the upstream burner 2c realizes uniform combustion in each stage of the burner, and generates unburned matter and NOx (nitrogen oxide). Combustion capable of suppressing generation can be performed.

FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.
In this embodiment, the same number of mills 3a, 3b, and 3c as burners 2a, 2b, and 2c are provided and connected to the burners 2a, 2b, and 2c of each stage through pulverized coal supply pipes 4a, 4b, and 4c, The upstream mill 3c connected to the upstream burner 2c in the combustion gas flow direction in the furnace 1 is connected to the downstream burner 2a whose particle size is closer to the furnace outlet 1a than the upstream burner 2c. The intermediate-flow-side mill 3b is configured to have a particle size larger than the particle size of 3a and is connected to the intermediate-stream-side burner 2b located between the downstream-side burner 2a and the upstream-side burner 2c. It has a medium grain size.
That is, in this embodiment, the plurality of mills 3 provided in the same number as the burners 2 are configured such that the downstream mill 3a near the furnace outlet 1a has the smallest particle size, and the particle size increases toward the upstream in the combustion gas flow direction. The large mill 3 is used.

  According to the second embodiment, the upstream mill 3c connected to the upstream burner 2c in the combustion gas flow direction having a long distance to the furnace outlet 1a and a long combustion time has a particle size of the distance to the furnace outlet 1a. By maintaining a small particle size of the pulverized coal fuel from the mill connected to the downstream burner 2a, the particle size of the pulverized coal fuel is maintained at a high fineness by being configured to be larger than the downstream mill 3a connected to the downstream burner 2a having a small combustion time. In addition, by making the particle size of the pulverized coal fuel from the upstream mill 3c connected to the upstream burner 2c coarser than that of the downstream burner 2a, unburned in the downstream burner 2a and the upstream burner 2c. It becomes possible to perform combustion at the same level with improved ignitability and reduced NOx generation by eliminating the minute.

Thereby, the capacity of the upstream mill 3c connected to the upstream burner 2c and the capacity of the middle flow mill 3b connected to the middle flow burner 2b are set to the capacity of the downstream mill 3a connected to the downstream burner 2a. Even if designed smaller than this, it becomes possible to perform combustion at the same level with no unburned content and reduced NOx generation amount, and the mills 3a, 3b, 3c can be reduced in size and cost.
Other configurations are the same as those of the first embodiment (FIG. 1), and the same members are denoted by the same reference numerals.

FIG. 4 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.
In this embodiment, a collection bin 20 for collecting the fine powder is installed in a fine coal supply pipe 4a connecting the fine powder outlet 16 (see FIG. 2) of the classifier 10 and the downstream burner 2a. A feeder 27 opens and closes the outlet of the collection bin 20.
23 is a level meter for detecting the level of fine powder 22 stored in the collection bin 20, 21 is a load cell for detecting the weight of fine powder in the collection bin, and 24 is a rotation of a classifier drive motor 25 in the classification device 10. The fine powder level detection value from the level meter 23 and the fine powder weight detection value from the load cell 21 are input to the motor controller 24.

FIG. 5 is a control block diagram in the third embodiment.
In FIG. 5, the fine powder level detection value from the level meter 23 and the fine powder weight detection value from the load cell 21 are input to the motor rotation number calculation unit 242 of the motor controller 24. A level setting unit 241 is set so as to decrease the motor rotation speed (the rotation speed of the classifier driving motor 25) as the fine powder level increases, as shown in FIG. A weight setting unit 243 is set to decrease the motor rotation speed (the rotation speed of the classifier driving motor 25) as the load cell output increases (increase in the fine powder weight) as shown in FIG. 6B.

The motor rotation number calculation unit 242 compares the fine powder level detection value with the fine powder level setting value set in the level setting unit 241, and rotates the motor so that the fine powder level detection value becomes the fine powder level setting value. The number (correction value of the motor speed) is calculated.
Further, in the motor rotation speed calculation unit 242, the fine powder weight detection value (load cell output) is compared with the fine powder weight setting value set in the weight setting unit 243, and the fine powder weight detection value is determined as the fine powder weight setting value. The motor rotation speed (the correction value of the motor rotation speed) is calculated as follows.
Reference numeral 244 denotes a motor controller, which is a motor rotation speed correction value based on one or both of the motor rotation speed correction value based on the fine powder level and the motor rotation speed correction value based on the fine powder weight. Control the number of revolutions.
Thereby, the level detection value is within the target level range set in the level setting unit 241, or the previous fine powder weight detection value is within the target weight range set in the weight setting unit 243. The number of rotations of the classifier can be controlled.

According to the third embodiment, the collection bin 20 for collecting fine powder is installed in the pulverized coal supply pipe 4a that connects the fine powder outlet of the classifier 10 and the downstream burner 2a. The amount of fine powder 22 accumulated is detected by the level of fine powder by the level meter 23 or the fine powder weight by the load cell 21, and based on the detected value of the amount of fine powder, the rotation speed of the classifier 10 is fine powder to the downstream burner 2a. By controlling the amount to be within a certain target range, the classification accuracy in the classification device 10 can be maintained with high accuracy.
Thereby, the particle size of the pulverized coal supplied to the burners 2a, 2b, and 2c at each stage can be maintained at a particle size that can realize uniform combustion and suppress the generation of unburned components and NOx.
Other configurations are the same as those of the first embodiment (FIG. 1), and the same members are denoted by the same reference numerals.

FIG. 7 is a block diagram corresponding to FIG. 1, showing a fourth embodiment of the present invention.
In this embodiment, a collection bin 20 for collecting the fine powder is installed in the fine coal supply pipe 4a connecting the fine powder outlet 16 (see FIG. 2) of the classifier 10 and the downstream burner 2a, The pulverized coal in the collection bin 20 is pulverized by the ejector action of the air flow supplied from the air compressor 43 through the air pipe 44 to the connection part of the feeder 40 outlet of the bin 20 to the pulverized coal supply pipe 4a. An air conveyance device 41 that conveys into the supply pipe 4 a is provided, and an air control valve 42 that adjusts the amount of air to the air conveyance device 41 is provided.
Then, the amount of fine powder conveyed from the collection bin 20 to the pulverized coal supply pipe 4a via the feeder 40 is controlled by adjusting the air amount of the air conveying device 41 by the air control valve 42.

  According to the fourth embodiment, the collection bin 20 for collecting fine powder is installed in the fine coal supply pipe 4a connecting the fine powder outlet 16 (see FIG. 2) of the classifier 10 and the downstream burner 2a, and The fine powder 22 in the collecting bin 20 is supplied to the downstream burner 2a by the ejector action of the air conveying device 41, and the air amount of the air conveying device 41 is adjusted by the air control valve 42 from the collecting bin 20 to the downstream burner. By controlling the amount of fine powder supplied to 2a, the amount of fine powder to the downstream burner 2a can always be maintained at an appropriate amount.

  According to the present invention, the particle size of the pulverized coal to the burners installed in a plurality of stages in the flow direction of the combustion gas in the furnace is realized so that uniform combustion can be achieved in each stage of the burner, and the unburned matter and NOx (nitrogen oxide) A pulverized coal fuel supply apparatus can be provided in which the generation capacity can be maintained and the mill capacity can be set to an appropriate capacity and the mill apparatus cost can be reduced.

It is a systematic diagram of the pulverized coal fuel supply apparatus in the coal burning boiler which concerns on 1st Example of this invention. It is a schematic sectional drawing of the classification apparatus in the said 1st Example. FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. 6 is a view corresponding to FIG. 1 showing a third embodiment of the present invention. It is a control block diagram in the third embodiment. (A) and (B) are characteristic diagrams of the classifier in the third embodiment. FIG. 6 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention. It is sectional drawing of the mill in each said Example.

Explanation of symbols

1 furnace 1a furnace outlet 2a downstream burner 2b middle stream burner 2c upstream burner 3a downstream mill 3b middle stream mill 3c upstream mill 4a, 4b, 4c pulverized coal supply pipe 5 additional air nozzle 10 classifier 11 coarse powder pipe 13 grinding Charcoal inlet pipe 15 Rotary blade 16 Fine powder outlet 20 Collection bottle 21 Load cell 23 Level meter 24 Motor controller 31 Classifier (mill)
41 Air Conveying Device 42 Air Control Valve

Claims (5)

A pulverized coal fuel supply configured to inject a pulverized coal fuel into a furnace and install it in multiple stages in the combustion gas flow direction of the furnace, and to feed the pulverized coal obtained by pulverizing the raw coal into a burner. In the apparatus, the pulverized coal connected to the downstream burner near the outlet of the furnace among the pulverized coal supply pipes that connect the mill and the burners at each stage and convey the pulverized coal from the mill to the burner. In the supply pipe, a classification device for classifying the pulverized coal from the mill into coarse coarse particles and small fine particles is installed, and the fine powder outlet of the classification device is connected to the downstream burner, and the classification device The coarse powder outlet is connected to the pulverized coal supply pipe to the burner on the upstream side in the combustion gas flow direction from the downstream burner, and the fine powder classified by the classifier is supplied to the downstream burner, and Coarse powder Configured to provide a serial upstream burner,
Further, the mill provided for each of the plurality of stages of burners is configured to have the same capacity, and the pulverized coal is supplied from the mill to the intermediate stage burner disposed upstream of the downstream burner in the combustion gas flow direction. The pulverized coal is supplied directly through a pipe, and the coarse powder outlet of the classifier is connected to a pulverized coal supply pipe to the burner upstream of the intermediate stage burner in the combustion gas flow direction. the pulverized coal fuel supply system you. A pulverized coal fuel supply configured to inject a pulverized coal fuel into a furnace and install it in multiple stages in the combustion gas flow direction of the furnace, and to feed the pulverized coal obtained by pulverizing the raw coal into a burner. In the apparatus, the pulverized coal connected to the downstream burner near the outlet of the furnace among the pulverized coal supply pipes that connect the mill and the burners at each stage and convey the pulverized coal from the mill to the burner. In the supply pipe, a classification device for classifying the pulverized coal from the mill into coarse coarse particles and small fine particles is installed, and the fine powder outlet of the classification device is connected to the downstream burner, and the classification device The coarse powder outlet is connected to the pulverized coal supply pipe to the burner on the upstream side in the combustion gas flow direction from the downstream burner, and the fine powder classified by the classifier is supplied to the downstream burner, and Coarse powder Configured to provide a serial upstream burner,
Furthermore, a collection bin for storing the fine powder is installed in the pulverized coal supply pipe connecting the fine powder outlet of the classifier and the downstream burner, and the amount of fine powder for detecting the amount of fine powder stored in the collection bin And a controller that controls the number of revolutions of the classifier so that the amount of fine powder that has passed through the classification device is within a predetermined target range based on the detected value of the amount of fine powder from the fine powder amount detection means. pulverized coal fuel supply system you characterized in that it comprises. The fine powder amount detection means comprises a level meter that detects the level of fine powder in the collection bin, and the controller controls the rotation speed of the classifier so that the level detection value from the level meter is within a target level range. The pulverized coal fuel supply device according to claim 2 , wherein the pulverized coal fuel supply device is configured to be controlled. The fine powder amount detection means comprises a load cell that detects the weight of fine powder in the collection bin, and the controller controls the rotation speed of the classification device so that the fine powder weight detection value from the load cell is within a target weight range. The pulverized coal fuel supply device according to claim 2 , wherein the pulverized coal fuel supply device is configured as described above. A pulverized coal fuel supply configured to inject a pulverized coal fuel into a furnace and install it in multiple stages in the combustion gas flow direction of the furnace, and to feed the pulverized coal obtained by pulverizing the raw coal into a burner. In the apparatus, the pulverized coal connected to the downstream burner near the outlet of the furnace among the pulverized coal supply pipes that connect the mill and the burners at each stage and convey the pulverized coal from the mill to the burner. In the supply pipe, a classification device for classifying the pulverized coal from the mill into coarse coarse particles and small fine particles is installed, and the fine powder outlet of the classification device is connected to the downstream burner, and the classification device The coarse powder outlet is connected to the pulverized coal supply pipe to the burner on the upstream side in the combustion gas flow direction from the downstream burner, and the fine powder classified by the classifier is supplied to the downstream burner, and Coarse powder Configured to provide a serial upstream burner,
Furthermore, a collection bin for storing the fine powder is installed in the pulverized coal supply pipe connecting the pulverized powder outlet of the classifier and the downstream burner, and the connection portion of the collection bin to the pulverized coal supply pipe is An air conveying device that conveys the fine powder in the collection bin into the pulverized coal supply pipe by an air flow is provided, and an air amount adjusting means that adjusts the air amount to the air conveying device is provided, and the air amount adjusting means pulverized coal fuel supply system you characterized by being configured to control the amount of fines to be transported to the pulverized coal supply pipe from the collecting bottle by adjusting the amount of air in the pneumatic conveying system.

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