JPH0637628B2 - Method for preparing coal slurry - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preparing a coal slurry used as a fuel.

(Prior art) In recent years, pulverized coal has a small amount of water and a small amount of additives (dispersing agent, stabilizer, etc.) because it is easy to handle for transportation and storage of coal, and can be used in the same way as heavy oil during combustion. Attempts have been made to use coal / water mixed fuel (hereinafter, simply referred to as coal slurry) prepared by mixing a defoaming agent, etc.) into a slurry form.

In the above coal slurry, when the pulverized coal concentration is set to a high concentration of about 65 to 80% by weight ratio (wet amount standard, the same applies below), this is favorable in terms of fluidity, stability, etc. In order to maintain slurry characteristics, this coal slurry requires a special pulverized coal particle size composition. That is, pulverized coal is required to be distributed in a wide range in terms of particle size, and not only those having a large particle size to a minute particle size but also the type of coal to be used in order to increase the packing density. Although it depends on this, for example, an extremely large amount of 3 to 15% of ultrafine powder of less than 3 μm is required.

The pulverization method of raw coal in the case of preparing the above-mentioned coal slurry is roughly classified into a high-concentration pulverization method and a low-concentration pulverization method.

First, the high-concentration crushing method will be explained. In this method, when the raw material coal, water and additives are supplied to the pulverizer to pulverize the raw material coal, only the amount of water necessary for the product slurry is pulverized. By doing this, the product slurry is discharged directly from the crusher, and the device configuration is simple,
Further, there is an advantage that the dehydration and mixing steps are not required unlike the low-concentration grinding method described later. However, the power required for crushing per unit weight of coal is large, and since it is impossible to classify the high-concentration slurry obtained as a product of the crusher, the open circuit crushing method must be used, and therefore the fine powder in the product slurry must be used. There is a drawback in that it is difficult to adjust the particle size distribution composition of charcoal.

On the other hand, in the low-concentration pulverization method, when the raw material coal, water and the like are supplied to the pulverizer and the raw material coal is pulverized, water is supplied in an amount sufficiently larger than the amount of water required for the product slurry. In this case, the coal concentration in the slurry discharged from the crusher is, for example, about 30%, but this low-concentration slurry is dehydrated, and then adjusted water and additives are mixed to prepare a product slurry of a predetermined concentration. Is.

According to this method, the power required for the pulverizer may be relatively small, and the slurry discharged from the pulverizer may be further water-added and then classified, and the coarse powder may be returned to the pulverizer and re-pulverized. Therefore, it is easy to adjust the particle size distribution configuration of the pulverized coal in the product slurry, and there is an advantage that a deashing step can be incorporated if necessary. However, the above method has a drawback in that a dehydration and mixing step is required for adjusting the water content of the slurry and mixing the additives, and thus the equipment cost and power consumption for this step increase.

Next, the conventional structure of the low-concentration grinding method will be described in more detail with reference to FIG.

The raw coal 2 supplied to the crusher 1 is crushed by a low-concentration wet method using a sufficiently large amount of water 3 separately supplied to the crusher 1. Then, the slurry 4 obtained by this pulverization is usually further added with water for classification.

Then, the slurry 4 is continuously supplied to a wet classifier 5 such as a liquid cyclone and classified into coarse powder 6 and fine powder 7. In this case, the coarse powder 6 is returned to the crusher 1 and crushed again. On the other hand, the fine powder 7 is supplied to the dehydrator 8 and dehydrated to form a cake-like pulverized coal 9. After that, the pulverized coal 9 is supplied to a kneader 10 to which water 11 for adjusting water content and an additive 12 are added and kneaded to obtain a high-concentration slurry 13 having a predetermined water content. Then, this slurry 13 is supplied to a stirrer 14 and is made into a coal slurry 15 which is a product slurry having a predetermined fluidity and is transported to a storage step (not shown) or the like. The wastewater 16 separated from the cake-like pulverized coal 9 by the dehydrator 8 is circulated to the coal crusher 1 or the like and reused.

(Problems to be Solved by the Invention) By the way, in the method for preparing the high-concentration coal slurry 15 by the low-concentration pulverization method as described above, a vacuum type or press type filter is used as the dehydrator 8. Since the water content of the cake 9 after dehydration cannot be adjusted to a predetermined value, the water content of the dehydrator 8 is lowered to a level lower than the water content of the product slurry, and a small amount of water 11 is again added in the subsequent step. It is necessary to supply water to adjust the water content to a predetermined level. However, such work is complicated.

In particular, the product slurry needs to have a high concentration of about 65 to 80%, that is, a low water content of about 20 to 35% as described above. Power is consumed, and then power is further consumed even at the stage of adding water again and kneading and stirring. Therefore, the crusher 1
The power required by itself is far less than that of the high-concentration grinding method, but the overall power required to prepare the product slurry is almost the same as that of the high-concentration grinding method, and the dehydration is also required in terms of equipment costs.・ A large amount of money is required for the kneading / stirring process.

Therefore, as shown in the basic system diagram in FIG. 5, it is conceivable to combine the high-concentration pulverization method and the low-concentration pulverization method to bring out their respective characteristics.

That is, the part 2a of the raw coal 2 and the water 3 corresponding to almost the total amount of water in the product slurry are first supplied to the low-concentration pulverizer 17, and sufficient water is used to obtain much of the ultrafine powder required for the product slurry. A low-concentration slurry 18 containing is produced. Then, the low-concentration slurry 18 and the other portion 2 of the raw coal 2
b is mixed in an appropriate ratio, and after the necessary additive 12 is added, the mixture is pulverized and mixed by the high-concentration pulverizer 19 in the next step to prepare a high-concentration coal slurry 15 having a predetermined water content.

According to this method, the power required for grinding is reduced as compared with the case of using only the high-concentration grinding method, corresponding to the work of grinding in the low-concentration grinding machine 17, and the dehydration required for the low-concentration grinding method.・ The kneading / stirring process can be omitted.

However, in order to mix the low-concentration slurry 18 with the coal 2b to adjust the water content of the product slurry, a large amount of coal must be added and mixed. For example, when preparing a 70% high-concentration slurry using a normal 30% low-concentration slurry 18, even if the water content of the additional coal 2b is ignored, it is possible to obtain about 4.5% of the pulverized coal in the low-concentration slurry 18. It is necessary to mix twice as much coal 2b, and only 20% or less of the total coal can be crushed by the low-concentration crushing method. Even if the concentration of the slurry is increased to produce the low concentration slurry 18 of 40%, only 30% or less of the total coal can be pulverized by the low concentration pulverization method. Therefore, in the case of the system diagram shown in FIG. 5, even if the dehydration, kneading, and stirring steps required for the low-concentration pulverization method are unnecessary, most of the entire coal must rely on the high-concentration pulverization method. After all, there is almost no difference from the high-concentration grinding method.

(Object of the Invention) The present invention has been made by paying attention to the above circumstances, and when pulverizing coal to prepare a desired coal slurry, the power consumption required for this preparation is rationalized. The purpose is to reduce.

(Structure of the invention) The feature of the present invention for achieving the above-mentioned object is to increase the amount of coal to be pulverized by a low-concentration pulverization method that minimizes the power required for pulverization per unit weight of coal,
The high-concentration pulverization method, which requires a relatively large amount of power for pulverization, reduces the amount of coal pulverized to the required minimum, while reducing excessive work in the dehydrator in the low-concentration pulverization method, while mixing in the pulverizer in the high-concentration pulverization method. By utilizing the effect, the stirring work is eliminated or reduced, and the particle size distribution configuration of the pulverized coal in the product slurry can be easily adjusted while performing high-concentration grinding.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

The basic structure of these embodiments is the same as the conventional structure. Therefore, common configurations are simply assigned the same reference numerals in the drawings, and description thereof is omitted, and only different configurations will be described.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.

In the figure, a part 2a of the raw coal 2 is pulverized by a low-concentration wet pulverization method into a slurry state as in the conventional example, and subsequently dehydrated by a dehydrator 8 to form a cake-like pulverized coal 9. At this time, the coal concentration in the crushing step is set to a low concentration of, for example, about 30%, which is the same as in the conventional example, and therefore the power required for crushing can be reduced. In other words, in order to take advantage of the low grinding power of the low-concentration wet grinding method, the pulverized coal concentration should be 40%.
The following is preferable.

On the other hand, in the dehydration step, unlike the conventional low-concentration pulverization method, the water content of the cake-like pulverized coal 9 after dehydration is kept at a level slightly higher than the water content in the product slurry.
The water content is around%. The water content of the cake after dehydration is 30 to 30
Dehydration work up to 40% is relatively easy, depending on the particle size distribution of the pulverized coal and water absorption, so the dehydrator 8 is small and
Also, less power is required for dehydration.

The caked pulverized coal 9 after dehydration is supplied to the high-concentration pulverizer 19 together with the newly added / supplied coal 2b and the additive 12, and is pulverized to prepare a coal slurry 15 as a product. At this time, the water content of the product slurry is adjusted to a predetermined level by the amount of the added / supplied coal 2b, and at the same time as the pulverization in the high-concentration pulverizer 19, the pulverized coal cake 9, the additional coal 2b, and the additive 12 are added. Sufficient kneading and mixing are performed. Therefore, when the slurry discharged from the high-concentration pulverizer 19 is used as a product slurry, even if it is necessary to stir the product slurry with a stirrer, the stirrer process with this stirrer can be few.

Further, in the method for preparing the coal slurry 15 as described above, since the pulverized coal cake 9 from the dehydrator 8 has already been dehydrated to a water content slightly higher than the water content in the product slurry, in order to adjust to a predetermined water content. The amount of new coal 2b that needs to be added is small compared to the amount of pulverized coal in the cake 9. For example, when the cake 9 having a water content of 35% is used to prepare the coal slurry 15 having a 70% concentration, the additional coal 2
Even if the water content of b is ignored, about 1/4 of the coal in the cake 9 may be newly supplied, and if about 1/5 of the total amount of coal in the product slurry is mixed as the additional coal 2b. good. Therefore, the amount of coal required to be pulverized by the high-concentration pulverization method, which requires a large amount of pulverization power, is small, and the increase in the required pulverization power can be suppressed to a minimum.

However, when the water content of the cake 9 after dehydration exceeds 40%, the amount of the coal 2b that needs to be added / supplied sharply increases, so it is preferable to keep the water content of the cake 9 after dehydration below this value. Further, since the coal 2b added / supplied to the high-concentration crusher 19 constitutes a relatively coarse powder in the product slurry, the amount of the additional coal 2b, and hence the cake water content after dehydration, is limited in terms of suppressing the amount of coarse powder. There is a need to.

According to the above example, most of the coal is pulverized by the low concentration wet pulverization method, the amount of coal that needs to be pulverized by the high concentration pulverization method is kept to the minimum, and the work in the dehydrator 8 is compared. The power consumption required to prepare the coal slurry can be minimized because it is kept within the range of easy dewatering.

(Second Embodiment) FIG. 2 shows a second embodiment.

In the figure, the wet pulverization of the raw coal 2 by the low-concentration pulverization method is composed of a primary pulverizer 17a and a secondary pulverizer 17b which are arranged in series with each other when viewed in the flow direction of the coal,
The respective crushers 17a and 17b are discharged slurry 18
It adopts a closed circuit system with attached classifiers 5a and 5b of a and 18b.

Then, the entire amount of the raw material coal 2 as the material to be crushed in the low-concentration crushing method is supplied to the primary crusher 17a, and at least one of the coarse powders 6 obtained by classifying the discharged slurry 18a from the primary crusher 17a. Part is supplied to the secondary crusher 17b, and the rest of the coarse powder 6 is returned to the primary crusher 17a. In addition, the discharged slurry 18 from both crushers 17a and 17b
Fine powder side slurries 7a, 7 obtained by classifying a, 18b
Both b are supplied to the dehydrator 8, and the configuration after the dehydrator 8 is the same as that of the first embodiment.

According to the above-mentioned embodiment, the secondary crusher 17b is supplied with a part of the discharged slurry 6 from the primary crusher 17a, and the ultrafine powder required for the coal slurry 15 is manufactured. Since the amount can be adjusted by the coarse crushing feed amount to the secondary crusher 17b, the particle size distribution configuration of the pulverized coal in the product slurry can be easily adjusted.

(Third Embodiment) FIG. 3 shows a third embodiment.

In the figure, the low-concentration crusher 17 is composed of a primary crusher 17a and a secondary crusher 17b which are arranged in series with each other when viewed in the flow direction of coal, and the primary crusher 17a is an open circuit system. The secondary crusher 17b has a closed circuit system to which the classifier 5 for the discharged slurry 18 is attached.

Then, the raw material coal 2 as the material to be crushed and the water 3 as the medium in the low-concentration crushing device 17 are respectively crushed by the crushers 1.
7a, 17b, and the product slurry from the primary crusher 17a is supplied to the secondary crusher 17b. That is, the raw material coal 2a supplied to the primary crusher 17a passes through both the primary and secondary crushers 17a and 17b, and the coal slurry 15
It is crushed into ultrafine powder necessary for. Therefore, the primary crusher 1
The amount of coal 2a supplied to 7a is selected according to the required amount of ultrafine powder, and the balance 2a 'is directly supplied to the secondary crusher 17b. According to this example, the particle size distribution composition of the pulverized coal in the product slurry can be easily adjusted, which is
It is similar to the embodiment.

Further, the water content adjusting coal 2b ′ supplied to the high-concentration crusher 19 is crushed by the crusher 20, and coarsely mixed with the caked pulverized coal 9 and the additive 12 after dehydration by the kneader 10, It is supplied to the concentration crusher 19. Such rough mixing facilitates mixing in the high-concentration pulverizer 19. Further, in order to effectively perform the rough mixing, it is preferable that the particle size of the coal 2b ′ supplied to the high-concentration crushing step is finer than that of the coal supplied to the low-concentration crushing step, for example, 5 to 10 mm or less, By doing so, the slurry can be supplied to the high-concentration pulverizer 19 in the form of a slurry. The high-concentration crusher 19,
Alternatively, a small amount of water for final water content adjustment can be added to the kneading machine 10.

Other Examples Although the above is based on the illustrated example, the types and structures of the crusher, the classifier, the dehydrator and the kneader, the types and positions of addition of the additives,
Whether or not the deashing step is performed is optional, and coke can be used as a part of the raw material coal. Further, it is also possible to provide a storage tank at an appropriate place during the manufacturing process.

(Effect of the Invention) According to the present invention, a part of raw material coal is wet-milled by a low-concentration pulverization method, and the low-concentration slurry obtained by this pulverization is dehydrated to form cake-like pulverized coal having a higher water content than the product slurry. , Because this cake-like pulverized coal was crushed by the high-concentration crushing method together with other parts of the raw coal,
The amount of coal to be pulverized per unit weight of coal is minimized by the low-concentration pulverization method that minimizes the power required for pulverization, while the amount of coal that is pulverized by the high-concentration pulverization method, which requires a relatively large amount of power required for pulverization, is kept to the minimum required amount. It is possible to reduce excessive work in the dehydrator in the low-concentration grinding method. Also,
By utilizing the mixing effect in the pulverizer in the high-concentration pulverization method, the stirring work can be eliminated or reduced, and the particle size distribution configuration of the pulverized coal in the product slurry can be easily adjusted while performing the high-concentration pulverization.

Therefore, when coal is pulverized to prepare a desired coal slurry, the power consumption required for this preparation can be reasonably reduced.

[Brief description of drawings]

1 to 3 are process drawings showing first to third embodiments of the present invention, and FIGS. 4 and 5 are process drawings showing first and second conventional examples. 2 ... Raw coal, 2a ... Part of raw coal, 2b ...
Other parts of raw coal, 3 ... water, 8 ... dehydrator, 9 ...
Cake-like pulverized coal, 12 ... Additive, 15 ... Coal slurry, 17 ... Low concentration crusher, 17a ... Low concentration primary crusher, 17b ... Low concentration secondary crusher, 19 ... High concentration Crusher.

Claims (7)

[Claims] Claims: 1. A part of raw coal is wet-milled by a low-concentration pulverization method, and the low-concentration slurry obtained by the pulverization is dehydrated to obtain cake-like pulverized coal having a water content higher than that of the product slurry. A method for preparing a coal slurry, which comprises pulverizing slag with other parts of raw coal by a high concentration pulverization method. 2. The method for preparing a coal slurry according to claim 1, wherein the pulverized coal concentration of the low-concentration slurry is 40% or less. 3. The method for preparing a coal slurry according to claim 1 or 2, wherein the water content of the cake-like pulverized coal is 30 to 40%. 4. The raw material coal is subjected to the primary pulverization so that the wet pulverization of the raw material coal by the low-concentration pulverization method is performed by a primary pulverizer and a secondary pulverizer which are arranged in series with each other when viewed in the flow direction of the coal. Supply to the secondary crusher and at least a part of the coarse powder obtained by classifying the slurry discharged from the primary crusher to the secondary crusher, and supplying the product slurry from both crushers to the dehydrator. The method for preparing a coal slurry according to any one of claims 1 to 3, characterized in that: 5. A part of the raw material coal is subjected to wet pulverization by a low-concentration pulverization method by a primary pulverizer and a secondary pulverizer which are arranged in series with each other when viewed in the flow direction of the coal. In addition to supplying to the primary crusher, the slurry discharged from this primary crusher and another part of the raw material coal are supplied to the secondary crusher, and the product slurry from the secondary crusher is supplied to the dehydrator. The method for preparing a coal slurry according to any one of claims 1 to 3, wherein: 6. The raw material coal to be supplied to the high-concentration crushing method is crushed more finely than the raw material coal to be supplied to the low-concentration crushing method, according to any one of claims 1 to 5. The method for preparing a coal slurry according to item 1. 7. The method according to claim 6, characterized in that cake pulverized coal, finely crushed raw material coal and additives are roughly mixed to form a slurry and then pulverized by a high concentration pulverization method. Method of preparing coal slurry of.