JPH04326951A - Granulating coal cinder and apparatus therefor - Google Patents

Abstract

PURPOSE:To provide a method for granulating a coal cinder and an apparatus therefor capable of efficiently removing unburned material from the coal cinder containing the unburned material. CONSTITUTION:After it is crushed by a slit nozzle 5, a coal cinder is sorted into coarse powder 19 and fine powder 18 by means of a rebounding wall 17 and gyrating wall 54. The slit nozzle 5 pulverizes an unburned material, a component of the coal cinder liable to break with ease and the pulverized unburned material is efficiently separated in the form of the fine powder 18 due to the rebounding on the wall surface and the Coanda effect. Thus, the coarse powder 19 having a minimized content of unburned material can be recovered for use as a suitable raw material of cement, etc.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to improvements in a method and apparatus for refining coal ash, which removes unburned materials such as unburned carbon from coal ash. The present invention relates to a coal ash refining method and apparatus that can improve the removal performance of coal ash.

0002

[Prior Art] The above-mentioned coal ash is currently mainly discharged from coal-fired power plants, etc., but since the combustion temperature of coal is kept low in order to prevent pollution in the surrounding environment, it is usually produced by unburned carbon such as unburned carbon. Contains some things. However, in order to effectively utilize this coal ash as a raw material for mixing cement, etc., the content of the unburned matter should be as low as possible (for example, 3.5% or less according to the JTS fly ash standard). FIG. 12 shows an example of a coal ash refining method and apparatus for classifying and refining the coal ash using the Coanda effect. This fine particle device 5
1 is a solid-gas mixed flow 52 consisting of compressed air and the above coal ash.
A supply nozzle 53 that spouts out a gas, a swirling wall 54 that swirls the solid-gas mixed flow 52 spouted from the supply nozzle 53 as a wall adhesion flow, and a speed reduction and separation of the swirling surface of the solid-gas mixed flow 52 during swirling. a discharge pipe 55 that spouts out an auxiliary flow to prevent the coal ash from collapsing, and a discharge pipe 56 that guides the coal ash, which has been separated into fine pieces by the action of centrifugal force when swirling along the swirling wall 54, to separate rooms. , 57. In this particle refining device 51, the coal ash in the solid-gas mixed flow 52 ejected from the supply nozzle 53 is subjected to a swirling force as a wall adhesion flow along the swirling wall 54, so that fine powder is produced as shown in FIG. The powder is classified into 60 and coarse powder 61 (so-called Coanda effect) and guided to the discharge pipes 56 and 57, respectively. The main component of the above coal ash is mainly alpha quartz (S
iO2 ) and mullite (2SiO2 ・3Al2 O3
), etc., and these are usually spherical large A, medium B, small C, and aggregates D, as shown in Figure 13.
It has the form of However, the remaining unburnt materials are usually in the form of irregularly shaped large E, medium F, small G, and their agglomerates H, as shown in FIG.

[0003] Therefore, if the above-mentioned coal ash with an unburned carbon content of 4.2% is sieved using a sieve or the like and classified into fine powder having a particle size of, for example, 45 μm or less, the same fine powder can be obtained. The same content of coal ash is 2.4%, for example, below 3.5%, which makes it possible to reduce the content of unburned carbon in coal ash compared to when the Coanda effect is used. You can get what is suitable for you. On the other hand, since unburned carbon tends to gather on the relatively coarse powder side, the conventional granulation device 51 uses, for example, coal ash with an unburned carbon content of 4.2% as described above. For example, the Coanda effect can be used to classify coal ash (coarse powder) with a content of 11.2% and coal ash (fine powder) with a content of 3.7%. The same content is described in 3 above.
It does not even reach 5% or less, so it cannot be said to be an effective separation method. Furthermore, in both the particle refining device 51 and the sieving method, the fragile unburned coal ash and its aggregates have been conventionally treated in a manner that prevents them from being destroyed as much as possible. By the way, the method for sifting the coal ash mentioned above is as follows:
Its throughput is smaller than that of the grain refining device 51, and it is not suitable for mass production. Furthermore, the method of vibrating the coal ash and classifying it according to shape, for example using a swinging table, has good particle refining performance, but is similarly unsuitable for mass production. On the other hand,
The flotation method, which is a wet classification method, and the flocculation method, which attaches and aggregates the unburned materials to heavy oil, have good particle performance, but they usually involve steps such as wastewater treatment and drying. , is more time-consuming and costly than the dry method such as the above-mentioned grain refining device 51.

0004

[Problem to be solved by the invention] Now, in the wet method that utilizes the cohesive properties of the unburned substances mentioned above, if the unburned substances can be further refined to improve their cohesive properties, then It is thought that it will be possible to further improve grain performance. In addition, in the airflow-type particle refining device 51 that utilizes the Coanda effect, the fragile unburned carbon is collided with a wall or the like, contrary to the conventional method, and is actively atomized.
If it is possible to recover hard and hard silica etc. from the coarse powder side as well as the fine powder side, it is thought that it will be possible to dramatically improve the fine particle performance. Therefore, the present invention has been made for the purpose of providing a method and apparatus for refining coal ash, which improves the removal performance of unburned materials by refining the unburned materials in coal ash. be.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a coal ash refining method for removing unnatural matters from coal ash containing unnatural matters, in which after the coal ash is pulverized, This method is configured as a method for refining coal ash, which is characterized by classifying the coal ash into fine powder and coarse powder.

[0006]

[Operation] In this method and apparatus for refining coal ash, after the coal ash is crushed, the coal ash is classified into fine powder and coarse powder. Therefore, with this grain refining method and apparatus, the fragile unburned materials in the coal ash can be mainly refined, and the refined unburned materials can be efficiently recovered as the fine powder. Therefore, with this granulation method and apparatus, it is possible to obtain coal ash, which is suitable as a raw material for cement, etc., and has a low content of unburnt substances on the coarse powder side.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples embodying the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. still,
The following examples are examples embodying the present invention, and are not intended to limit the technical scope of the present invention. Here, FIG. 1 is a schematic explanatory diagram showing an example of a coal ash refining method and apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic explanatory diagram showing another example of the same refining method and apparatus. 3 is a cross-sectional schematic diagram showing an example of the slit nozzle of the fine grain method and apparatus, and FIG.
) and Figure 4(b) are particle size distribution diagrams showing an example of the coal ash crushing performance of the same slit nozzle, Figure 5 is an air volume characteristic diagram showing an example of the same crushing performance, and Figure 6 is a particle size distribution diagram showing an example of the coal ash crushing performance of the same slit nozzle. Fig. 7 is a particle size distribution diagram of an example of coal ash obtained by repeatedly pulverizing coal ash using the slit nozzle shown in Fig. 3. Figure 1
Fig. 9 is a grain characteristic diagram when coal ash is repeatedly refined using the coal ash refining method and apparatus shown in FIG. 10 and 11, which are schematic explanatory diagrams showing an example, are cumulative particle size distribution maps of coal ash obtained by refining coal ash using the same refining method and apparatus, respectively. This coal ash refining method and apparatus 1 crush coal ash in a solid-gas mixed flow 4 by passing a solid-gas mixed flow 4 consisting of compressed air 2 and coal ash 3 as shown in FIG. It is equipped with a slit nozzle 5 shown below, and a front cyclone 6 and a rear cyclone 7 that classify the coal ash pulverized by the slit nozzle 5 into coarse powder and fine powder, respectively. As shown in FIG. 3, the slit nozzle 5 includes a distribution nozzle 11 for uniformly distributing the solid-gas mixed flow 4 into the cavity 10, and a distribution nozzle 11 for accelerating the solid-gas mixed flow distributed within the cavity 10. , and a collision wall 15 that causes the solid-gas mixture flow 4 discharged from the slit portion 14 to collide.

In this particle refining device 1, the solid-gas mixed flow 4 is distributed and supplied into the cavity 10 by the distribution nozzle 11, and is further accelerated by the slit part 14 and collides with the collision wall 15. As a result, the fragile unburned coal ash in the solid-gas mixture flow 4 is mainly crushed and discharged from the slit nozzle 5. Figures 4(a) and 4(b) show before and after pulverization of coal ash (solid line and broken line) when the air volume of the solid-gas mixed flow 4 passing through the slit nozzle 5 is 3Νm3/h and 25Νm3/h, respectively. An example of particle size distribution is shown. Figure 5 also shows the slit nozzle 5 when the air volume is changed from 3Νm3/h to 25Νm3/h.
An example of the average particle size of coal ash in a solid-gas mixed flow discharged from From these figures, it can be seen that the larger the airflow rate, the finer the coal ash is pulverized. The slit nozzle 5 that achieves the function of crushing the coal ash described above is an example of the crushing means. Furthermore, in this grain refining device 1, the solid-gas mixed flow 4 discharged from the slit nozzle 5 is supplied to the pre-stage cyclone 6 as shown in FIG. is separated by the first stage cyclone 6. Then, the solid-gas mixed flow 4 discharged from the previous stage cyclone 6
is further supplied to the latter stage cyclone 7, and the same solid-gas mixed flow 4
The fine powder inside is separated by the latter stage cyclone 7. As described above, in this grain refiner 1, coal ash pulverized by the slit nozzle 5 is classified into coarse powder and fine powder by the front cyclone 6 and the rear cyclone 7, respectively. In addition, FIG. 6 shows the above-mentioned front-stage cyclone 6 when the air volume of the solid-gas mixed flow 4 is changed from 3Nm3/h to 25Nm3/h.
and the content of unburned carbon in the coarse powder and fine powder classified by the latter stage cyclone 7. As can be seen from this figure, in this particle refiner 1, by setting the air flow rate to 7Nm3/h or more, the unburned carbon content of the coarse powder is reduced to 3% or less, which can be used as a raw material for cement, etc. be able to. This is thought to be because the slit nozzle 5 was able to mainly crush fragile unburned materials in the coal ash, and the unburned materials could be recovered as fine powder.

Furthermore, FIG. 2 shows a grain refining device 1a constructed by replacing the cyclone for classifying the coal ash with the grain refining device 51 (see FIG. 12) that utilizes the Coanda effect described above. . In this way, the performance of removing unburned carbon from the coal ash can be improved compared to the cyclone method.
It can be further increased (see FIG. 9, etc. described later). Cyclones 6 and 7 realize the function of classifying the solid-gas mixed flow 4 discharged from the slit nozzle 5 into coarse powder and fine powder.
The particle refining device 51 and the like are examples of the classifying means. In addition, FIG. 7 shows an example of the particle size distribution of coal ash when the solid-gas mixed flow 4 at an air flow rate of 25 Nm3/h is repeatedly passed through the slit nozzle 5 (for example, once, twice, and four times as shown in this figure). It shows. In addition, Fig. 8 shows the particle refining device 1 shown in Fig. 1 above.
The coarse powder S refined by is further refined into coarse powder T by the same refining device 1, and the same procedure is repeated to convert the same coarse powder T to coarse powder U (and the same coarse powder U to coarse powder V). ) shows the fine grains. In this way, in this particle refiner 1, the content of unburned carbon in the coarse powder V can be reduced to about 2.5%, for example, as shown in this figure. Also, Figure 9 is Figure 2
The supply nozzle 53 of the grain refining device 51 shown in (see FIG. 12)
A particle refining device 1b is shown comprising a particle refining device 51a which is provided with a repulsion wall 17 that collides the solid-gas mixed flow 4 ejected from the supply nozzle 53 between the supply nozzle 53 and the swirling wall 54. There is. In this granulator 1b, the solid-gas mixed flow 4 passes through the slit nozzle 5 to crush the coal ash in the solid-gas mixed flow 4, and the solid-gas mixed flow 4 is further jetted out from the supply nozzle 53. After colliding with the repelling wall 17, the powder is swirled along the swirling wall 54 as a wall adhering flow, and is classified into fine powder 18 and coarse powder 19 by the Coanda effect. That is, in this grain refining device 1b, the fragile unburned materials in the coal ash are crushed by the slit nozzle 5, and further collide with the repulsion wall 17, and due to the small coefficient of repulsion, the unburned materials in the coal ash are crushed by the repulsion wall 17. It is recovered as fine powder 18 due to the fact that it is not strongly repulsed and the Coanda effect mentioned above.

On the other hand, hard silica, etc. in the coal ash collides with the repulsion wall 17 without being crushed by the slit nozzle 5, and is largely repelled by the repulsion wall 17 due to its large coefficient of repulsion. Due to this and the above-mentioned Coanda effect, it is recovered as coarse powder 19. For example, when the air flow rate of the solid-gas mixed flow 4 is 20 Nm3/h, in this particle refiner 1b, the content of unburned carbon in the coarse powder 19 is 1
．． We were able to reduce it to 22%. This content of 1.22% is a dramatically smaller value compared to the conventional method. The reason why the fine grain performance of coal ash could be improved in this way is that the coal ash pulverized by the slit nozzle 5 is classified into fine grains, which are equipped with the repulsion wall 17, which has a better classification performance than that of a cyclone. This is probably because the classification was performed by the device 51a. In addition, FIG. 10 shows the coarse powder 19 and fine powder 18 (fine powder 18a classified and collected by cyclones 20 and 21).
The particle size cumulative distribution of and 18b) is shown as an example. The solid-gas mixed flow 4 discharged from the slit nozzle 5 described above is transformed into coarse powder 19 and fine powder 18 by the repulsion wall 17 and the Coanda effect.
A fine particle device 51a that realizes a repulsion classification function is an example of a classification means. In addition, Fig. 11 shows that after passing a solid-gas mixed flow with an air volume of 25 Nm3/h through the slit nozzle 5 four times (for example, by connecting four of the same slit nozzles in series), the air volume was increased to 20 Nm3/h.
The particle size cumulative distribution of fine powders 18a, 18b and coarse powder 19 as an example when repulsively classified by the particle refining device 51a is shown as m3/h. In this case, the content of unburned carbon in the coarse powder 19 could be reduced to 0.9%. As described above, this grain refiner 1b can produce coarse powder with a very low unburned carbon content, which is extremely suitable as a raw material for cement and the like. In the above example, the coal ash was pulverized by the slit nozzle 5, but the same method could be used, such as colliding the coal ash with the blades of a rotating impeller or compressing the coal ash by applying pressure. Unburned materials in the coal ash may also be pulverized. In addition, in the above embodiment, the coal ash pulverized by the slit nozzle 5 was classified and refined by the cyclones 6 and 7 (Fig. 1), the refining device 51 (Fig. 2), and the refining device 51a (Fig. 9). However, it is possible to classify and refine particles by a method that effectively utilizes the cohesiveness of the unburnt material made fine by the above-mentioned crushing process (usually, fine particles have a high cohesiveness), such as a wet method such as a coagulation method. You may also do so.

[0011]

[Effects of the Invention] Since the method and apparatus for refining coal ash according to the present invention are constructed as described above, the performance of removing unburned substances from coal ash can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of a method and apparatus for refining coal ash according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram showing another example of the fine grain method and apparatus.

FIG. 3 is a schematic cross-sectional view showing an example of a slit nozzle of the fine grain method and apparatus.

[Figure 4] A particle size distribution diagram showing an example of the coal ash crushing performance of the same slit nozzle.

[Fig. 5] An air volume characteristic diagram showing an example of the same crushing performance.

FIG. 6 is a grain characteristic diagram when coal ash is refined using the coal ash refining method and apparatus shown in FIG. 1.

7 is a particle size distribution diagram of an example of coal ash obtained by repeatedly crushing the coal ash using the slit nozzle shown in FIG. 3. FIG.

FIG. 8 is a grain characteristic diagram when coal ash is repeatedly refined using the coal ash refining method and apparatus shown in FIG. 1;

FIG. 9 is a schematic explanatory diagram showing still another example of the coal ash refining method and apparatus according to one embodiment of the present invention.

FIG. 10 is a particle size cumulative distribution diagram of coal ash obtained by refining coal ash using the same refining method and apparatus.

FIG. 11 is a particle size cumulative distribution diagram of another example of coal ash when the coal ash is refined by the same refining method and apparatus.

FIG. 12 is a schematic explanatory diagram showing a state in which coal ash is classified by the Coanda effect.

FIG. 13 is a schematic diagram showing how silica and the like in coal ash are classified by the Coanda effect.

[Explanation of symbols]

1, 1a, 1b...Particle refining device
2...Compressed air 3...Coal ash
4...Solid gas mixed flow 5...Slit nozzle (pulverizing means) 6...Pre-stage cyclone (classifying means) 7...Post-stage cyclone (classifying means) 14...Slit section 15...Collision wall 17...Repulsion wall 51, 51a...Particle refining device ( classification means) 53...supply nozzle 54...swivel wall

Claims (5)

[Claims] [Claim 1] A coal ash refining method for removing unnatural materials from coal ash containing unnatural materials, characterized in that after the coal ash is crushed, the coal ash is classified into fine powder and coarse powder. A method for refining coal ash. 2. A coal ash refining device for removing unnatural materials from coal ash containing unnatural materials, comprising a crushing means for crushing the coal ash, and a fine powder and a fine powder for the crushed coal ash. A coal ash refining device characterized by comprising a classification means for classifying into coarse powder. 3. The crushing means comprises a slit portion through which the solid-gas mixed flow consisting of the coal ash and compressed air passes, and a collision wall that collides the solid-gas mixed flow discharged from the slit portion. The coal ash refining device according to claim 2, comprising: 4. The classifying means includes a supply nozzle for spouting a solid-gas mixed flow consisting of compressed air and coal ash pulverized by the pulverizing means, and a wall surface for the solid-gas mixed flow spouted from the supply nozzle. 3. The coal ash refining device according to claim 2, further comprising a swirling wall that classifies the coal ash into fine powder and coarse powder by swirling the coal ash as an attached flow. 5. The classification means is configured to collide with a supply nozzle that spouts out a solid-gas mixed flow consisting of compressed air and coal ash crushed by the crushing means, and the solid-gas mixed flow jetted from the supply nozzle. and a swirling wall that classifies the solid-gas mixed flow into fine powder and coarse powder by swirling the solid-gas mixed flow after colliding with the rebound wall as a flow adhering to the wall surface. coal ash granulation equipment.