JP3317643B2 - Coal ash spheroidizing method and coal ash spheroidizing apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of spheroidizing coal ash particles and an apparatus utilizing the method. More specifically, the present invention relates to a method for spheroidizing irregular-shaped particles and deposited particles of coal ash and an apparatus using the method.

[0002]

2. Description of the Related Art In recent years, the use of coal has been expanded due to the diversification of energy sources, and the development of technologies such as gasification and high-concentration coal / water mixed fuel (CWM) has been promoted. But,
Since some time is still required for its widespread use, conventional coal burning, that is, the method of directly burning pulverized coal obtained by pulverizing lump coal is the mainstream of coal utilization. The amount of coal used in the electricity business in 1990 was about 3
About 10 million tons, about 10 million tons in general industry, and about 40 million tons in total.
The general industry has reached about 120 million tons, for a total of about 44 million tons.

[0003] This coal contains several to several tens of wt% of non-flammable components, mainly mineral substances called ash.
It is left as coal ash after burning. The amount of coal ash is
In 1993, the electricity business accounted for about 4.4 million tons, and the general industry for about 2 million tons, for a total of about 6.4 million tons.
In the past, the vast amount of coal ash generated was previously landfilled as industrial waste, but it can be effectively used due to the need to cope with the increase in the amount of coal ash generated and social situations requiring environmental conservation. As a result, the effective utilization rate was slightly over 60% in 1993.

[0004] The effective use of coal ash is carried out in the fields of cement, civil engineering, construction, and other fields. In particular, the proportion of the cement field is large, and exceeds 70% of the total effective use. The reason for the high utilization rate in the cement field is that coal ash can be used as a clay substitute because it has properties similar to clay, which is a raw material for cement, and spherical particles of coal ash are used as fly ash cement as a cement admixture. This is because it can be used as a secondary material and can also be used as a concrete mixed material.

[0005] Here, when coal ash is used as a clay substitute, it has no commercial value and is treated as waste and requires disposal costs. On the other hand, when it is used as a cement admixture, a cement company etc. Has the advantage of not requiring any processing costs even though it is inexpensive. Therefore, in order to further promote the effective use of coal ash, it is desirable to expand the possibility of use as a cement admixture or other materials.

[0006]

However, in order to use coal ash as a cement admixture, JIS standard (J.
IS A 6201). This JIS standard specifies the specific gravity and fineness (specific surface area) of ash collected by a dust collector from flue gas of a pulverized coal combustion boiler with a dust collector, that is, fly ash as well as chemical properties as physical properties.
-Unit water ratio and compressive strength ratio are defined. Therefore,
The collected fly ash is tested by the method specified in the JIS standard, and if it satisfies the specified values of each item described above, it becomes a JIS standard cement admixture.

However, coal ash recovered from combustion equipment such as a boiler contains irregular shaped particles and deposited particles depending on the manner of combustion, and cannot satisfy the requirement of fineness, or does not satisfy the requirement of fineness. But the liquidity is poor,
When used as an admixture, the workability of kneading cement or gypsum may be reduced. That is, as shown in FIG. 10, even if the specific surface area of fly ash itself exceeds the value specified in the JIS standard, for example, the size of the specific surface area of fly ash fluctuates due to a temporal change in the operation state of the boiler. There is. If this variation is large, the quality of fly ash cement produced by mixing fly ash will be non-uniform even if the fineness meets the JIS standard. In this case, even fly ash satisfying the JIS standard causes difficulties in commercial transactions, so that uniformity of quality is also strongly required. Furthermore, if the variation is too large, the uniformity J
IS standards cannot be met. According to the JIS standard, the value of the specific surface area of fly ash is 4 times the value of the specific surface area of the sample.
Requires no more than 50 cm ² / g. Therefore, as shown by the solid line in FIG. 10, when the difference L1 between the maximum value and the minimum value of the specific surface area is 900 cm ² / g or more, the value of the specific surface area of the fly ash becomes smaller than the specific surface area of the sample sample. Since it differs from the value by 450 cm ² / g or more, it does not become a JIS standard product.

Accordingly, the proportion of coal ash having fluidity that can be used as an admixture for cement is small, and the amount of coal ash used as an admixture in the cement field is conventionally 1/4. It is only the following.

Also, when fly ash is used for applications other than cement mixing, fly ash has much smaller particles than large particles.
Fly ash that does not meet the IS standard contains irregularly shaped particles and welded particles, so it has poor fluidity and small particles cannot enter sufficiently between large particles, creating a gap, resulting in higher density. Not only is difficult, but also the improvement in fluidity due to the ball bearing effect caused by the rolling of small spherical particles around large particles cannot be expected. That is, in the JIS standard admixture, as shown in FIG. 9, most of the particles are spherical, while non-JIS
The standard fly ash includes large and angular irregular shaped particles 16 as shown in FIGS. 7 and 4, and welded particles 17 in which spherical particles are welded to each other. For this reason,
Non-JIS fly ash is less fluid than JIS fly ash. For this reason, for uses other than the cement admixture, it is desired to improve the spheroidization and fineness of the coal ash.

Most of fly ash is spherical particles as shown in FIGS. 7 and 4, and irregular particles and welding particles are mixed therein. It is considered that not only the JIS standard is satisfied but also the quality is improved by selecting spherical particles having a predetermined particle size or less. However, since the selection is performed based on the particle size, the yield is low and the treatment of the residue is another problem. It will occur as.

Accordingly, an object of the present invention is to provide a method for spheroidizing coal ash which increases the fluidity of coal ash and makes the fineness uniform, and an apparatus using the method.

[0012]

In order to achieve the above object, a method for spheroidizing coal ash according to the present invention according to claim 1 is characterized in that coal ash is rubbed against each other by rubbing and pushing the coal ash together. Except for the spherical particles in the coal ash, the irregularly shaped particles and the spherical particles that are angular and almost polyhedral are welded to each other to selectively grind them. The particles are broken to make them spherical.

Accordingly, if the coal ash collected by the dust collector or the like is a coal ash containing a large amount of irregular particles and welding particles in addition to spherical particles as shown in FIGS. By rubbing, pressing and rubbing, irregular-shaped particles are rounded and spheroidized, and the welded particles are broken to separate spherical particles. At this time, the spherical particles escape from the contact position when the particles are rubbed with each other, so that they are hardly scraped. That is, the spherical particles maintain the shape as they are, and only the irregular particles and the welded particles are selectively ground to be spherical. In addition, the irregular particles are spheroidized by shaving off the corners and corners where the irregular particles are easily shave, so that the particle size of the spheroidized particles does not become extremely small, and ultrafine particles are generated. Then, the coal ash contains a large amount of small spherical particles as shown in FIG. 8, and small spherical particles enter between particles having a large specific surface area to increase fluidity, increase the density, and reduce the ball bearing effect. It is expected to happen.

Further, the coal ash spheroidizing apparatus according to the second aspect includes a first member and a second member having a slight space between their opposing surfaces, and includes irregularly shaped particles which are angular and substantially polyhedral. The first member and the second member are moved relative to each other with the distance between the opposing surfaces being substantially constant in a state where the coal ash including the welded particles in which the spherical particles are welded to each other is sandwiched between the opposing surfaces. The particles of the coal ash are rubbed against each other to rub each other, so that the irregular shaped particles are squared and spheroidized, and the welded particles are broken to form spheroids.

Therefore, the coal ash is rubbed and pressed by the opposing surfaces of the first member and the second member which move relative to each other, and are rubbed together. As a result, coal ash containing a large amount of irregularly shaped particles and deposited particles as shown in FIGS.
After passing through the coal ash spheroidizing apparatus, the coal ash containing a large amount of small spherical particles as shown in FIG. 8 is obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an embodiment shown in the drawings.

As shown in FIG. 1, a coal ash spheroidizing apparatus 1 according to the present embodiment has a rotating disk 2 as a first member and a fixed member as a second member having a slight space between opposing surfaces. The rotating disk 2 and the fixed disk 3 are moved relative to each other with the distance between the opposing surfaces being substantially constant while the coal ash 4 is interposed between the opposing surfaces.

The rotating disk 2 has a disk shape and is rotated by a driving source such as a motor (not shown). The fixed disk 3 has substantially the same size and shape as the rotating disk 2 and is fixed so as not to rotate. In the center of the fixed disk 3, through holes 3 a penetrating through both sides of the fixed disk 3 are formed. The small diameter portion of the funnel 5 is attached to the through hole 3a. The opposing surfaces of the rotating disk 2 and the fixed disk 3 are flat surfaces. However, the surface is not limited to a flat surface, and may be a surface on which uneven portions such as grooves and projections are formed.
According to such an aspect, the rubbing and pushing of the coal ash 4 are performed in a complicated manner, and the spheroidization is performed more efficiently.

When the coal ash 4 is spheroidized by the coal ash sphering apparatus 1 described above, the rotating disk 2 is rotated.
The coal ash 4 is poured into the funnel 5. Then, the coal ash 4 flows through the through holes 3 a of the fixed disk 3, and the rotating disk 2 and the fixed disk 3
Between the opposing surfaces. Further, the coal ash 4 becomes layered by the rotation of the rotating disk 2 and is moved to the outer peripheral side by centrifugal force. Here, since there is a difference in the moving speed between the rotating disk 2 side and the fixed disk 3 side in the particle layer, the particles are rubbed and pressed by contact / separation between the particles, and the irregular shaped particles shown in FIG. At the same time, the corners of 16 are shaved off to form spheres, and the welding particles 17 are broken to separate spherical particles.

Then, while the coal ash 4 moves from the center to the outer periphery of the facing surface, the particles are repeatedly rubbed and pressed against each other, so that the coal ash 4 is formed as shown in FIG.
And the irregularly shaped particles 16 and the deposited particles 17 as shown in FIG.
From a large amount to a large amount of spherical particles as shown in FIG. Further, the spherical particles that existed before the spheroidization escaped when an external force was applied due to contact and separation between the particles, so that they were hardly pulverized.

Since the fluidity of the coal ash 4 is improved by the spheroidization of the irregular shaped particles and the welding particles, the mixing operation when the coal ash 4 is used as an admixture for cement or the like is easily performed. Will be able to do it. Further, since the amount of the small particles is sufficiently larger than the amount of the large particles, the small particles fill the gaps between the large particles, so that the density of the coal ash 4 can be increased, and the ball bearing effect is reduced. Can be expected. For this reason, the fluidity of the cement or the like is enhanced, and the strength of the solidified material can be improved.

Further, as shown in FIG. 10, the distribution of specific surface area of coal ash before spheroidization (shown by a solid line in the figure) and coal ash after spheroidization (shown by a broken line in the figure) are compared. Only the portion having a small specific surface area of the coal ash before spheroidization has an increased specific surface area. This is because only the irregular shaped particles and the deposited particles are selectively ground and spheroidized. For this reason, due to the spheroidization, the minimum value is increased although the maximum value of the specific surface area of each coal ash is equal. Thereby, the difference between the maximum value and the minimum value of the specific surface area is
It is reduced from L1 to L2. Therefore, the coal ash 4 can be homogenized, and the strength when cement or the like using the coal ash 4 as an admixture is solidified can be achieved.

The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the disk on which the funnel 5 of the coal ash spheroidizing apparatus 1 is mounted is the fixed disk 3, but this may be a rotating disk and the disk without the other funnel 5 may be a fixed disk. Absent. Alternatively, both disks may be rotated. Further, the rotating disk may be rotated while being eccentric, or may be slid without rotating.

As shown in FIG. 2, the rotating disk 2 'and the fixed disk 3' of the coal ash spheroidizing apparatus 1 are installed so that the opposing surfaces thereof are substantially vertical, and the fixed disk 3 'has through holes. The screw feeder 6 may be attached to 3a '. Then, by rotating the screw of the screw feeder 6, the coal ash 4 is fed between the rotating disk 2 'and the fixed disk 3' to be spheroidized. In this embodiment, the facing surfaces of the rotating disk 2 'and the fixed disk 3' are flat surfaces. However, the surface is not limited to a flat surface, and may be a surface on which uneven portions such as grooves and projections are formed.

Further, as shown in FIG. 3, the coal ash spheroidizing apparatus 1 is provided with two flat plates 7 and 8 as a first member and a second member opposed to each other with a slight space therebetween. No problem. Then, the coal ash 4 is supplied from above the coal ash spheroidizing apparatus 1 and relatively slid with the distance between the opposing surfaces being substantially constant while being sandwiched between the flat plates 7 and 8. In this case, as the relative motion, one of the flat plates 7 can be fixed and the other flat plate 8 can be slid in a direction parallel to the facing surface, or both the flat plates 7 and 8 can be moved. Then, the spherical motion of the coal ash 4 can be achieved by the relative motion.

Concave portions or convex portions having the same direction as the longitudinal direction are formed on the opposing surfaces of the flat plates 7 and 8 so that they can be engaged with each other, or as shown in FIG.
The coal ash 4 may be rubbed by hooking the coal ash 4 with the welding particles 17. According to this, the rubbing and pushing of the coal ash 4 are performed in a complicated manner, and the spheroidization is performed more efficiently.

Further, as shown in FIG. 5, the coal ash spheroidizing apparatus 1 includes a cylindrical member 9 as a first member, and a shaft 10 as a second member penetrated through the cylindrical member 9 by a clearance fit.
May be provided. In this case, one or both of the cylindrical member 9 and the shaft 10 are moved to rotate with each other or slide in the axial direction. Then, the cylindrical member 9 and the shaft 1
By causing the coal ash 4 to move relatively with the ash 4 interposed therebetween, the spheroidization of the coal ash 4 can be achieved.

It is also possible to form a concave or convex portion along the axial or circumferential direction on the inner peripheral surface of the cylindrical member 9 and the outer peripheral surface of the shaft 10, or to form a spiral concave or convex portion. . According to this, the rubbing and pushing of the coal ash 4 are performed in a complicated manner, and the spheroidization is performed more efficiently. In order to make the coal ash 4 flow in one direction inside the cylindrical member 9, for example, the coal ash 4 is forcibly pushed through one of the gaps, or the diameter of one end of the cylindrical member 9 and the shaft 10 is made larger than the diameter of the other end. What is necessary is just to provide a taper.

In the coal ash spheroidizing apparatus 1 shown in FIGS. 1 to 5 described above, the portion where the coal ash 4 is supplied, such as the funnel 5, and the portion where the spheroidized coal ash is discharged are separately provided. Since it is formed, even if another apparatus is arranged upstream or downstream of the coal ash spheroidizing apparatus 1, the processing of the coal ash can be performed continuously.

As shown in FIG. 6, a coal ash spheroidizing apparatus 1 comprises: a shaft member 11 as a first member;
May be provided with a bearing 12 as a second member having a concave portion 12a whose distal end portion is accommodated by a clearance fit. In this case, one or both of the shaft member 11 and the bearing 12 are moved so as to rotate with each other or slide in the axial direction. Then, by relatively moving the coal ash 4 between the concave portion 12a and the shaft member 11, the spheroidization of the coal ash 4 can be performed.

In the coal ash spheroidizing apparatus 1 shown in FIGS. 3, 5 and 6, the opposing surfaces are made smooth, but may be formed in a shape having irregularities such as grooves and projections. . Further, a shape in which a plurality of protrusions scattered on a straight line at predetermined intervals may be arranged in parallel. According to these shapes, the rubbing of the coal ash 4 is performed in a complicated manner,
Sphering is performed more reliably.

[0032]

EXAMPLE Fly ash was collected from a coal-fired power plant. FIG. 11 shows the particle size distribution of the fly ash which satisfies the JIS standard (JIS standard product 14) and the non-satisfied fly ash (non-JIS standard product (before spheroidization) 13) by accumulation under a sieve. Table 1 shows the cumulative 10%, 50%, and 90% diameters under the sieve of each fly ash.

[0033]

[Table 1]

The reason why the representative particle size of the non-JIS standard product (before spheroidization) 13 is larger than the representative particle size of the JIS standard product 14 is as follows.
As shown in FIG. 9, the S standard product 14 has many spherical particles, whereas the non-JIS standard product (before spheroidization) 13 has irregular particles having voids such as lava as shown in FIG. And a large amount of deposited particles.

Then, a non-JIS standard product 13 was introduced into the above-mentioned coal ash spheroidizing apparatus 1 to perform the spheroidizing treatment of the present invention. As a result, some of the irregular shaped particles are crushed from the voids and the like and are angular and the corners are rounded. Be transformed into Also,
The rubbing and pressing of the particles not only brings about an action of shaving the irregular shaped particles into spheroids, but also brings about an action of breaking the welded particles in which the spherical particles are welded. Thereby, the spherical particles are separated from the welded particles.

FIG. 8 shows the result of spheroidizing the non-JIS standard product 13 shown in FIG. As shown in the figure, no irregular particles were present before the spheroidization, and the distribution was similar to that of the JIS standard product shown in FIG. Further, as shown in the particle size distribution of FIG.
The particle size distribution after spheroidization of fly ash, which was S standard product, was almost the same as JIS standard product 14 at a large particle size of 30 μm or more, and higher than JIS standard product 14 on the side of small particles of 30 μm or less. It has a content rate of around. Therefore, it is clear that the irregular shaped particles and the deposited particles have been ground and spheroidized. It is clear that fineness, homogeneity and fluidity equivalent to or higher than those of the JIS standard product were obtained. Furthermore, this coal ash spheroidization technology
Sometimes applied to JIS standard fly ash,
In this case, the uniformity and stabilization of the quality can be achieved by reducing the fluctuation of the Blaine value and raising it to a higher value as a whole.

[0037]

As is apparent from the above description, the method for spheroidizing coal ash according to the first aspect removes spherical particles in coal ash by rubbing the particles of coal ash by rubbing and pressing each other. As shown in FIG. 7, coalesced ash as shown in FIG. The irregular particles and the deposited particles therein are selectively ground to be spherical, and the spherical particles maintain the shape as they are. As shown in FIG. 8, the fine particles containing a large amount of small spherical particles have a fineness. Large coal ash can be obtained.

As a result, the fluidity of the coal ash is improved, so that the kneading operation can be easily performed when the coal ash is mixed with cement or the like. Also, the amount of small particles is sufficient for the amount of large particles,
A large amount of small particles enter between the large particles, and the density of the coal ash can be increased. For this reason, it is possible to improve the strength when solidified using the cement admixture or the like. Of course, the cement admixture is one of the useful applications of the spheroidized coal ash obtained in the present invention, but is not particularly limited to this application and can be used as other building materials.

Furthermore, since only irregular-shaped particles and welded particles are selectively ground and spheroidized except for small-diameter spherical particles in coal ash, fluctuations in the Blaine value are reduced and the overall value is increased. Value can be increased to achieve uniform and stable quality. That is, as shown in FIG. 10, the difference between the maximum value and the minimum value of the specific surface area is smaller in L2 after spheroidization than in L1 before spheroidization. As a result, the fineness of the coal ash can be made uniform, which completely meets the JIS standard required for cement admixtures and improves the uniformity of strength when solidified by using it as an admixture such as cement. Can be done.

Further, in the coal ash spheroidizing apparatus according to the present invention, the first member and the second member are relatively moved with the distance between the opposed surfaces being substantially constant while the coal ash is sandwiched between the opposed surfaces. Thus, the coal ash is rubbed and pressed together, and the particles of the coal ash are rubbed against each other, so that the irregular particles are rounded and spheroidized, and the welded particles are broken to form a spheroid. As shown in FIG. 8, the irregular particles and the deposited particles in the coal ash are selected and spheroidized, and the spherical particles maintain the same shape, and the fineness including a large amount of small spherical particles as shown in FIG. Can be obtained with a simple apparatus configuration.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a coal ash spheroidizing apparatus.

FIG. 2 is a perspective view showing another embodiment of the coal ash spheroidizing apparatus.

FIG. 3 is a perspective view showing still another embodiment of a coal ash spheroidizing apparatus.

FIG. 4 is an enlarged view showing a state of coal ash spheroidization in the coal spheroidizing apparatus.

FIG. 5 is a perspective view showing another embodiment of the coal ash spheroidizing apparatus.

FIG. 6 is a perspective view showing still another embodiment of the coal ash spheroidizing apparatus.

FIG. 7 is a micrograph showing the particle structure of non-JIS standard fly ash before spheroidization.

FIG. 8 is a photomicrograph showing the particle structure of spheroidized fly ash that was a non-JIS standard product.

FIG. 9 is a photomicrograph showing a particle structure of JIS standard fly ash.

FIG. 10 is a diagram showing the change over time of the specific surface area of fly ash.

FIG. 11 is a particle size distribution diagram (by mass) of various fly ash.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coal ash spheroidizing device 2 Rotating disk (1st member) 3 Fixed disk (2nd member) 4 Coal ash 7 Flat plate (1st member) 8 Flat plate (2nd member) 9 Cylindrical member (1st member) 10 axis ( 2nd member) 11 Shaft member (1st member) 12 Bearing (2nd member) 16 Irregular particles 17 Welding particles

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 18/08 B02C 1/00 B02C 7/00 B02C 19/20 B09B 3/00 301

Claims (2)

(57) [Claims] 1. Coal ash particles are rubbed against each other by rubbing and pressing the coal ash, and irregular polygonal or spherical particles that are angular and almost polyhedral except for the spherical particles in the coal ash are welded to each other. A method for spheroidizing coal ash, wherein welding particles are selectively ground, the irregular particles are rounded to be spheroidized, and the weld particles are broken and spheroidized. 2. A method according to claim 1, further comprising a first member and a second member having a small space between the opposing surfaces, wherein irregular particles which are angular and substantially polyhedral, or welding particles in which spherical particles are welded to each other are formed. The first member and the second member are relatively moved with the interval between the opposed surfaces being substantially constant in a state where the coal ash is sandwiched between the opposed surfaces, so that the coal ash is crushed and pressed to form the coal. A coal ash spheroidizing apparatus characterized in that the ash particles are rubbed together, the irregular shaped particles are rounded and spheroidized, and the welded particles are broken and spheroidized.