JPH036960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing coal-water slurry,
In particular, the present invention relates to a coal-water slurry production apparatus using a continuous wet ball mill apparatus suitable for producing highly concentrated water slurry.

Coal-water slurry, which is made by suspending coal in water with a dispersant added thereto, is being considered for use as a fuel for boilers and the like because of its ease of handling such as transportation and storage. According to the studies of the present inventors, the conditions for a stable and directly combustible slurry are such that the coal particle size is 70 to 80% by weight passing through a 200 mesh.
and the viscosity of the slurry is about 2000 cp or less. To achieve this, it is necessary to (1) adjust the wide particle size distribution and increase the packing density to achieve high concentration, and (2) add appropriate additives to wet the particle surface and charge it, thereby attracting particles from each other. It is necessary to reduce the viscosity by repulsive dispersion.

When continuously producing such a highly concentrated coal-water slurry, a wet ball mill is generally used. Figure 1 is a system diagram of a coal-water slurry production facility using such a wet ball mill. For example, coal coarsely crushed to about 5 mm or less is passed from bunker 1 to coal feeder 2, and is then fed into steel balls inside. while water 1 is supplied to a ball mill 3 having
The additive liquid containing the additive 102 diluted with 0.00 is supplied to the mill 3 after its addition amount is adjusted so that the coal concentration at the mill inlet is about 60% by weight or more. In the mill, the coal is subjected to impact, abrasion, and shear between the balls or between the balls and the inner wall of the mill.
The amount of mesh passing through is approximately 60 to 85% by weight, and the viscosity is approximately 100%.
It is ground and mixed until it reaches ~2000 cp, then mill 3
After being discharged from the outlet of the tank 4 and temporarily stored in the tank 4, it is transported to the next process by the pump 5.

As mentioned above, in order to achieve a high concentration of coal-water slurry, it is necessary to widen the particle size distribution of coal. Generally, once the crusher and crushing method are decided,
It is known that the fineness distribution produced by pulverization depends on the pulverizability of the coal. For example, the smaller the Hard Glove Grindability Index (HGI), the worse the grindability and the narrower the particle size distribution (Coal
Preparation, 4th Edition, Chapter 7, edited
by JWLeanard, published by AIME, New
York, 1979). Therefore, once the grinding method is determined, the smaller the HGI value, the more difficult it is to thicken the slurry and reduce its viscosity. By the way, in the conventional method shown in Figure 1, the maximum concentration of coal with HGI < 50 is determined by the viscosity.
2000cp, less than 70% by weight. Furthermore, the amount of additive used in the conventional method shown in FIG. 1 is as large as about 1% by weight based on dry coal, which is also an economical problem.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to produce a coal-water slurry that uses less additives, has a higher concentration, has a lower viscosity, and has less variation in particle size distribution. - To provide an apparatus for producing water slurry.

The present invention comprises a coal bunker for storing coal, a wet ball mill for pulverizing the coal supplied from the coal bunker together with water, and a slurry tank having a stirring means for temporarily storing the wet-pulverized coal-water slurry. A coal-water slurry manufacturing apparatus comprising: a distributor disposed downstream of the slurry tank to distribute a portion of the coal-water slurry to the inlet of the wet ball mill. This invention relates to manufacturing equipment.

According to the present invention, since a part of the coal-water slurry is circulated and re-pulverized, coal particles can be pulverized and a wide particle size distribution can be obtained.
Since the coal-water slurry that is once stored is stirred and a portion of it is circulated, it is possible to absorb fluctuations in the particle size distribution of coal particles due to changes in raw coal properties and supply amount, reducing fluctuations in particle size distribution. You can get stable products.

The method of the present invention will be explained in more detail based on Examples.

FIG. 2 is a system diagram of a coal-water slurry preparation apparatus showing an embodiment of the present invention. In Figure 2,
A coal feeder 7 is connected to the inlet of the mill 8, in which 35% of the mill volume is occupied by steel balls of about 50 to 20 mm, and an additive liquid supply pipe 14 opens into the mill from the mill inlet. are doing. Further, another additive liquid supply pipe 15 opens into the mill from the mill outlet. A slurry tank 9 is installed below the mill outlet, and additives are supplied into the tank 9 by a feeder 11 and mixed by a stirrer 10. The slurry adjusted in the slurry tank 9 is transported to a distributor 13 by a pump 12,
Here, a portion is distributed and returned to the mill, and the remainder is removed as product. As the distributor 13,
For example, a distribution type feeder may be used, but any type of feeder may be used as long as it can distribute the coal particles as they are without classifying them.

The coal coarsely pulverized to about 5 mm or less is supplied in a fixed amount from the bunker 6 to the mill 8 via the coal feeder 7. An additive liquid containing a dispersant and the like is supplied to the mill inlet so that the coal concentration is about 75 to 85% by weight based on the raw coal. In the mill 8 where the coal concentration is high, the coal particles are pulverized by impact, shearing and grinding effects between the balls or between the balls and the inner wall of the mill, and flow toward the mill exit. The new surfaces of the newly generated particles are now effectively wetted by the additive from the additive liquid supply pipe 15 at the mill outlet. The slurry that has been further pulverized to form a new surface is discharged from the mill 8, stored in a slurry tank 9, and fed to a feeder 11.
It is efficiently mixed with the additives supplied from the stirrer 10. The slurry transported from the tank 9 by the pump 12 is distributed by the distributor 13, a portion is circulated to the mill and re-ground, and the remainder is taken out as a product.

FIG. 3 shows the results of producing a coal-water slurry by the method of the present invention shown in FIG. 2, where A shows the case of the present invention and B shows the case of the conventional method.

In the case of the present invention, after the mill 8 with a diameter of 650 mm is used to grind the product to 70% passing through 200 meshes, twice the amount of the product is returned to the mill using the distributor 13, whereas in the conventional method, after the above-mentioned grinding, the product is returned to the mill. It is made into a product slurry as it is. In the manufacturing method according to the present invention, a part of the product slurry is circulated through the mill, so that the particles are re-pulverized and passed through 200 meshes and 70
It is clear that even if the powder is crushed to 200% or less, it contains more fine powder than 200 mesh. Comparing the viscosity and coal concentration of slurries A and B in Figure 3, the conventional slurry B has a viscosity of 68% by weight.
The slurry A produced by the method of the present invention had a coal concentration of 70% and 1800 cp. Additionally, the amount of additive used is 1.3% by weight of coal (conventional method)
to 0.6% by weight (method of the present invention). This is because the additives and particles were effectively mixed in contact with each other due to the multi-stage addition method in which the additives were added as the grinding progressed and new surfaces of the particles were generated.

In general dry-type or wet-type ball mill equipment, a closed circuit pulverization method is used in which a classifier is installed outside the mill, the classified fine powder is recovered as a product, and the coarse powder is returned to the mill (for example, Unit Operation of
Chemical Engineering, WLMccabe and JC
Smith, Chapter 26, Mcgraw-Hill, 2nd
edition, New York, 1967). FIG. 4 shows a system diagram of this closed circuit crushing system. 16 is a ball mill, and 17 is a classifier. The reason for adopting the closed circuit pulverization method is to remove the pulverized particles into fine powder from the system, avoid over-pulverization, and reduce power consumption. FIG. 5 shows the classification efficiency of a general classifier, that is, the relationship between the weight fraction classified and returned to the mill and the particle size. Furthermore, FIG. 6 compares the particle size distribution of the product in this closed circuit grinding system with the particle size distribution in an open circuit system without a classifier. As is clear from Figure 6,
In closed-circuit pulverization, the width of the particle size distribution is narrow and the amount of fine powder produced is small. Figure 5 shows the classification efficiency of an ideally desirable classifier, in which all particles larger than a certain particle size are returned to the mill, and particles smaller than that size are recovered as products, and the classification efficiency of a classifier that does not classify at all. show. That is, the latter is a distributor in the present invention, and uniformly distributes particles in the entire particle size range to two streams at a predetermined ratio. Therefore, in a system equipped with such a distributor, fine particles are returned to the mill and over-pulverized in the same way as large particles, resulting in a wide particle size distribution (see Figure 6) and poor grinding efficiency. .

As mentioned above, the present invention uses a closed circuit system equipped with a distributor that does not classify at all, which is unprecedented in conventional pulverizer systems, to create a wider particle size distribution, thereby increasing the concentration of coal-water slurry. This achieves low viscosity.

Next, FIG. 7 is a system diagram of an apparatus for a coal-water slurry production method showing another embodiment of the method of the present invention, which has the same configuration as FIG. 2 except that the structure of the mill 8 is different. . In FIG. 7, a mill 20 is divided into two chambers by installing a partition plate 21 such as a screen.
The first chamber is filled with large diameter balls of about 75 to 40 mm, and the second chamber is filled with small diameter balls of about 40 to 12 mm. Coal that has been coarsely crushed to about 10 mm or less is classified as Banca 1.
8. A fixed amount of coal is supplied to the mill 20 via the coal feeder 19. Additive liquid containing dispersant, etc. so that the coal concentration is about 75 to 85% by weight (100 parts water and 102 parts additive)
is supplied to the first chamber of the mill 20. In the first room,
Since the powder is pulverized in a more concentrated atmosphere and with larger diameter balls than in the conventional method, a wider particle size distribution including finer powder is produced. The slurry that has passed through the partition plate 21 is efficiently crushed by small-diameter balls in the second chamber, and the particle surfaces are efficiently wetted with the newly added additive 104 to reduce the viscosity. The slurry discharged from mill 20 is mixed in tank 22 with additive 106 supplied by feeder 24 to further reduce the viscosity. Slurry is pump 2
5, it is transported to the distributor 26 and distributed, a portion is recovered as a product, and the rest is circulated to the mill where it is re-pulverized and atomized to produce a wider particle size distribution, resulting in higher concentration and lower viscosity. is achieved. Additionally, since the additive is added in multiple stages as new surfaces of the particles are generated, it works efficiently and the total amount used is less than half that of conventional methods.

As described above, according to the present invention, when manufacturing a high-concentration coal-water slurry with a coal concentration of 65% or more using a wet continuous ball mill, a closed-circuit system is installed in which a classifier that does not classify particles at all, that is, a distributor is installed. After the coal-water slurry is stored in a slurry tank and stirred, a part of it is returned to the mill and over-pulverized, creating a wider particle size distribution and less fluctuation in particle size distribution. High concentration and low viscosity of the slurry can be achieved.
In addition, additives or additive liquid are added in small amounts in multiple stages inside and outside the mill as the particles are crushed and new surfaces are generated, and by effectively mixing them with the particles, there is no wastage of additives. , its usage can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional high-concentration coal-water slurry manufacturing device, Fig. 2 is an explanatory diagram showing an embodiment of the present invention, and Fig. 3 is a comparison of slurry production test results according to the conventional method and the present invention. Figure 4 is an explanatory diagram showing a closed circuit pulverization system, Figure 5 is an explanatory diagram showing classification efficiency, Figure 6 is an explanatory diagram showing differences in particle size distribution depending on the pulverization method, and Figure 7 is an explanatory diagram showing the difference in particle size distribution depending on the pulverization method. It is an explanatory view showing other examples. 6... Coal bunker, 7... Coal feeder, 8... Ball mill, 9... Slurry tank, 10... Stirrer, 11... Feeder, 12... Pump, 13...
...Distributor, 100...Water, 102,104,10
6...Additive.

Claims (1)

[Scope of Claims] 1. A coal bunker that stores coal, a wet ball mill that pulverizes the coal supplied from the coal bunker together with water, and a stirring means that temporarily stores the coal-water slurry that has been pulverized by the wet ball mill. A coal-water slurry production apparatus comprising a slurry tank having a slurry tank, characterized in that a distributor is provided downstream of the slurry tank to distribute a portion of the coal-water slurry to the wet ball mill inlet. Coal-water slurry manufacturing equipment. 2. The coal according to claim 1, wherein the wet ball mill has two chambers, and the ball diameter of the first chamber on the mill inlet side is larger than the ball diameter of the second chamber on the outlet side. Water slurry production equipment. 3. The coal-water slurry manufacturing apparatus according to claim 1 or 2, characterized in that additive supply means are provided on the inlet side and the outlet side of the wet ball mill, respectively.