JPH08266830A - Method of reducing unburned coal in coal ash - Google Patents

Abstract

PURPOSE: To reduce the unburned coal content in fine particles as a whole by introducing unburned residual coal contg. ash whose particle diameters are distributed into a louver classifier, adjusting the angles of louver blades to change a classifying point and collecting the separated fine particles in a filter. CONSTITUTION: Unburned residual coal contg. ash which is discharged from a pulverized coal firing boiler as incineration ash having particle diameters distributed in the range of from about several μm to a hundred and scores μm is subjected to reforming treatment. An air stream containing the unburned residual coal contg. ash is introduced into a louver classifier 3 through a disperser 2, and the angles of louver blades 31 are adjusted to change a classification point, and fine particles separated on the suction side are collected and recovered in a filter. When the angles of the louver blades are thus increased, the separation efficiency curve is shifted to the small diameter side to make the rise steep to improve the separation efficiency. The unburned coal content in fine particles collected by classifying the unburned residual coal contg. ash is reduced as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention classifies unburned carbon (hereinafter referred to as unburned content) residual coal ash (raw powder) having a particle size distributed in the range of approximately several μm to hundreds of tens of μm. The present invention relates to a method and an apparatus for reducing unburned content of coal ash, which is capable of generally reducing the unburned content content in the fine powder collected.

[0002]

2. Description of the Related Art Conventionally, as a dust collector including classification of powder, a sieve device is used for classification of 100 μm or more according to the applied separation particle size, and a cyclone device (centrifugal dust collection device) for classification of 10 μm or less. A louver classifier (inertial dust collector) or the like is known as a means for supplementing the applicable particle size.

The fly ash discharged from the pulverized coal combustion boiler to be handled in the present invention has a particle size distributed in the range of several μm to hundreds of tens of μm, and it depends on the raw material used. About 3 to 6% of unburned matter remains. For this reason, only a part of it is used as a JIS standard ash in cement admixtures, concrete admixtures, and the like.

That is, when the unmixed component is used in the concrete mixture with a large amount, the adsorbed amount of methylene blue which deteriorates the quality increases, and the unburned component adsorbs the air entraining agent (AE agent). Problems such as difficulty and easy cracking prevent the expansion of use.

At present, coal ash (particularly fly ash) is treated in the following modes. For landfill. Classifying with a separator to remove high unburned coal ash particles and reduce the overall unburned content to improve the quality of cement admixture. Coal with good flammability is used to prevent the generation of residual unburned matter and to reduce the unburned matter content of coal ash to reform it into a high-quality cement admixture.

[0006]

However, the conventional processing described above has the following problems (a) to (c). (B) There is a limit to the amount of landfill that can be processed, and unused coal ash becomes useless waste. (B) In order to remove high unburned coal ash particles by classifying with a separator, an expensive separator and time (man-hour) for classifying are required. (C) The use of coal with good combustibility increases the operating cost of the boiler.

Under the circumstances, it is considered that the application of the above-mentioned louver classifier (improvement of the above (b)) is effective for the present invention in view of the properties of coal ash and the equipment cost, but the physical properties of coal ash In mechanical and mechanical processing, the classification point is changed to separate coarse particles containing unburned particles in raw powder from fine particles, and fine particles (fine powder) are collected with high accuracy to reduce unburned content. There was no knowledge or attention that they could.

The inventors of the present invention have the above findings as a result of earnest studies on quality improvement (reforming) in order to effectively use a large amount of coal ash discharged from a coal-fired power plant. We have developed a method to reduce the content of unburned matter in fine powder collected by classifying coal ash (raw powder).

The present invention has been made in view of the above circumstances, and solves the above problems and contains unburned matter in fine powder collected by classifying unburned matter residual coal ash (raw powder). An object of the present invention is to provide a method and an apparatus for reducing unburned content of coal ash, which is capable of reducing the overall rate.

[0010]

In order to achieve the above object, the present invention classifies unburned residual coal ash (raw powder) having a particle size distribution in the range of several μm to hundreds of tens μm. It is a method of reducing unburned content of coal ash that reduces the unburned content content in the fine powder collected as a whole by using the stored raw powder as a dispersed powder through a disperser, and It is characterized in that it is introduced into a louver classifier together with the air flow containing it, the angle of the louver blade is adjusted to change the classification point, and the fine powder separated on the suction side is collected by a filter.

Here, the angle adjustment of the louver blade is 50
The range of degrees to 80 degrees is effective.

[0012] Further, the content of unburned matter in the fine powder collected by classifying the unburned matter residual coal ash (raw powder) whose particle size is distributed in the range of several μm to hundreds of tens of μm It is a device for reducing unburned content of coal ash that is generally reduced.It is connected to a table feeder for storing and supplying raw powder, a pushing fan and piping, and the raw powder is dispersed powder together with an air flow containing it. A disperser for introducing the device, a louver classification device, a filter for collecting finely classified powder by connecting piping to the suction side via a louver blade, and a suction device Is.

[0013]

[Function] Raw powder supply flow rate (or suction flow rate on the fine powder recovery side)
By adjusting the louver blade angle and the louver blade angle to change the classification point, the unburned amount in the collected fine powder can be generally reduced, and the reduction rate can be changed / adjusted.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an apparatus system diagram for explaining an unburned-content reduction process by fly ash classification. The configuration of the present invention is adopted based on the fact confirmed experimentally. (Not affected by scaling.)

Here, 1 is a table feeder, 2 is a disperser, 3 is a louver classifying device, 4 is a filter, 5 is a suction device, 31 is a louver blade, and X is an unburned-content reducing device (device of the present invention). .

As shown in the figure, the device (X) of the present invention is a table feeder (1) for storing and supplying raw powder.
, A disperser (2) for communicating with a pushing fan (not shown) through a pipe and introducing the raw powder as a dispersed powder together with an air flow containing the powder, a louver classifier (3), and a louver blade (31). It is equipped with a filter (4) for connecting the classified fine powder by connecting it to the suction side through a suction device (5) and collecting the raw powder stored in the disperser (2).
The powder is introduced into the louver classifier (3) together with the air flow containing it, the angle of the louver blade (31) is adjusted to change the classification point, and the fine powder separated on the suction side is filtered ( They are collected in 4) and collected.

Here, the angle adjustment of the louver blade (31) is effective within the range of 50 to 80 degrees.

FIG. 2 is a data plot (partial separation efficiency curve) of partial separation efficiency vs. particle diameter showing the partial separation efficiency at each louver blade angle.

As can be seen from the figure, the larger the louver blade angle, the more the partial separation efficiency curve shifts to the smaller diameter side and the sharper the rising edge. This is
It shows that the classification point (50% separation diameter) shifts to the smaller diameter side and the classification performance is improved. As the louver blade angle increases, the suction angle becomes a direction more counter to gravity, so unburned It is considered that the coarse particles including the separated particles became difficult to move to the filter side, and the fine powder and the coarse powder could be clearly separated.

Table 1 shows the unburned content (unburned carbon content) in the collected fine powder and the unburned content reduction rate.

[0021]

[Table 1]

As can be seen from the table, the unburned content rate is 3.5.
For 0% of coal ash (usually raw powder), it is possible to recover modified coal ash (fine powder), which is much lower than this. [Unburned matter content 2.63% (reduction rate 2
(4.9%)]

In the method and apparatus of the present invention, it is sufficient to consider only the passage time in the apparatus with respect to the powder flow rate as the processing time, and the processing can be easily and continuously executed in a shorter time than the conventional processing such as the combustion method. It is possible. In addition, if the raw powder has an unburned content of about 5 to 6%, it can be more easily reformed to JIS standard ash of 5% or less.

An experimental scale model device (not shown)
For the above, a numerical simulation on the classification performance was performed, the flow of the air flow in the louver (not shown) and each particle trajectory (not shown) were analyzed to obtain the partial separation efficiency (calculated value), and the partial separation efficiency (calculated value) was compared with the experimental value.

FIG. 3 is a data plot (partial separation efficiency curve) of partial separation efficiency vs. particle diameter, which compares the calculated partial separation efficiency and the experimental value showing this result.

As shown in the figure, since the two are almost the same, it is concluded that the effectiveness of the device of the present invention is confirmed and that the numerical simulation can be an index for operating the device.

[0027]

The present invention is constituted as described above, and has the following beneficial effects.

(1) By adjusting the angle of the louver blade, the classification point can be changed, and the content of unburned components in the collected fine powder can be reduced as a whole. Moreover, the reduction rate can be changed (controlled).

(2) In the method and apparatus of the present invention, it is sufficient to consider only the passage time in the apparatus with respect to the powder flow velocity as the processing time, which is easier and more continuous than the conventional processing such as the combustion method in a short time. Can be processed.

(3) Since no expensive separator for classifying and removing high unburned coal ash particles or expensive coal having good combustibility and a combustion furnace by a combustion system are required, the equipment cost is reduced. Can be achieved.

[Brief description of drawings]

1 is an embodiment of the present invention, FIG. 1 is a system diagram for explaining an unburned content reduction process by fly ash classification.

FIG. 2 is a data plot (partial separation efficiency curve) of partial separation efficiency vs. particle diameter showing partial separation efficiency at each louver blade angle.

FIG. 3 is a data plot (partial separation efficiency curve) of partial separation efficiency vs. particle diameter in which calculated values of partial separation efficiency and experimental values are compared.

[Explanation of symbols]

 1 table feeder 2 disperser 3 louver classifier 4 filter 5 suction device 31 louver blade X unburned matter reduction device (device of the present invention)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideto Yoshida 981-206 Otani, Takayacho, Higashihiroshima City, Hiroshima Prefecture

Claims (3)

[Claims] 1. In a method for reforming unburned residual coal ash discharged as incinerated ash from a pulverized coal combustion boiler, an unburned component having a particle size distributed in a range of approximately several μm to hundreds of tens of μm. A method for reducing unburned content of coal ash, in which the content of unburned content in fine powder collected by classifying residual coal ash (raw powder) is reduced as a whole. Dispersed powder through the louver, introduced into the louver classification device together with the air flow containing it, the angle of the louver blade is adjusted to change the classification point, and the fine powder separated on the suction side is collected by the filter. A method for reducing unburned coal ash content. 2. The method for reducing unburned coal ash according to claim 1, wherein the angle adjustment of the louver blade is in the range of 50 degrees to 80 degrees. 3. In a reforming treatment apparatus of unburned residual coal ash discharged as incinerated ash from a pulverized coal combustion boiler, unburned components having a particle size distributed in a range of approximately several μm to hundreds of tens of μm. A coal ash unburnt content reduction device that reduces the unburned content of fine powder collected by classifying residual coal ash (raw powder), and stores and supplies the raw powder. The table feeder, the pushing fan, and the disperser for piping the raw powder as a dispersed powder and introducing the equipment together with the air flow containing it, the louver classifier, and the suction side via the louver blade are connected to the pipe for separation. An apparatus for reducing unburned content of coal ash, comprising: a filter for collecting the generated fine powder and a suction device.