JPH0321594B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a high-concentration coal-water slurry, and particularly to a method for producing a coal-water slurry having a high coal concentration, low viscosity, and good stability at a low cost. In recent years, coal has been used as an alternative fuel to oil, mainly in thermal power plants. However, since coal is a solid fuel, it is not easy to handle, which increases transportation costs, which has a large impact on the price of coal itself. Therefore, fluidization technology is actively being used to crush coal and mix it with various liquids so that it can be treated like a fluid. One of the fluidization technologies is to use a mixture of heavy oil and coal.
There is COM (Coal and Oil Mixture). However, in the case of COM, the weight ratio of heavy oil to coal is approximately 1.
The ratio is 1:1, so it cannot be said that it is a completely oil-free fuel, and the merits in terms of price are considered to be small. Also,
Methanol, which is a mixture of methanol and coal, is also expensive and has not yet reached the practical stage. From the above, it is desired to form a slurry using coal and water. When producing coal-water slurry, it is important to have low viscosity and low water content (approximately 30%) in terms of transportation and combustion efficiency. On the other hand, the particle size distribution has a large influence on the slurry properties, and a slurry having a wide particle size distribution is desired. However, the conventional method of one-stage pulverization using a tube mill has drawbacks such as a small throughput per unit time and a narrow particle size distribution for low HGI coal, and it is difficult to improve slurry properties. Therefore, a method is desired in which coal is pulverized with low power until it becomes ultrafine particles of several microns or less. The purpose of the present invention is to eliminate the drawbacks of the prior art described above, to provide a method for efficiently producing ultrafine particles (several microns or less) at low cost, and providing a wide particle size distribution to coal-water slurry. be. The present inventor focused on separately producing ultrafine coal particles of several micrometers or less, and added a slurry containing ultrafine coal particles obtained by wet pulverization using a Stard mill to the slurry produced using a tube mill, thereby producing low HGI coal. However, it has been found that a slurry having a wide particle size range can be produced at low cost. The present invention has been made based on the above findings, and is characterized in that a wet tube mill and a wet stard mill are used in combination in a method for producing a coal-water slurry. In the present invention, fine coal particles pulverized by a stard mill may be supplied from the inlet or outlet side of the tube mill, or mixed in a slurry tank or the like after the outlet of the tube mill.
Preferably, more than one treatment is performed. In order to obtain a wider coal particle size distribution, it is preferable to divide the tube mill into two or more chambers and use balls of different diameters in each chamber. Hereinafter, the present invention will be explained in detail with reference to the drawings. 1 of the manufacturing process of high concentration coal-water slurry of the present invention
An example is shown in FIG. Bunker 3 by conveyor 2
After being coarsely crushed to -7mesh in the coarse crusher 4, the coal A sent to the
Cecil, H. Chilton “Chemical
Engineers′Handbook”5th ed.p8−29～30,
New York, 1973). At this time, water and additives are supplied into each mill through pipes 7 and 8. Wet grinding with Stard Mill 9,
The manufactured slurry is supplied into the mill from the inlet side of the tube mill through a pipe line 10, wet-pulverized and mixed, and then passed through a pipe line 13 as a highly concentrated coal-water slurry.
sent from. As Stard Mill 9, US Union Process
company's Atlighter (trademark, same document) and West German
There is a tower mill (Tower Mill by Shigekatsu Kawabata, Powder to Industry Co., Ltd., 1972) as a pulverizer that can obtain the same effect as Drais' Pearl Mill (trademark) or Stard Mill 9. Mills are also included as a type of "stard mill". In addition to the above, there are two methods for producing high-concentration coal-water slurry: (1) supplying the slurry produced in a stard mill into the mill from the outlet side of the tube mill, pulverizing and mixing it, and (2) producing it in a stard mill. A method in which the slurry is mixed in a tank after exiting a tube mill. (3) A method in which a slurry obtained by wet-pulverizing low HGI coal in a stard mill is wet-pulverized and mixed with high-HGI coal in a tube mill, (4) Contrary to the above (3), a stard mill is used to produce slurry.
Slurry obtained by wet-pulverizing coal with high HGI,
Wet grinding in a tube mill with low HGI coal,
(5) A method in which a part of the slurry produced in the Stard mill is supplied to a tube mill, wet-pulverized with coal, and mixed with the remaining slurry derived from the Stard mill, ( 6) There is a method in which slurry produced in a tube mill is supplied to a stard mill, wet-pulverized and mixed with coal. FIG. 2 shows the manufacturing method described in (1) above, in which coal A supplied to the bunker 3 by the conveyor 2 is coarsely pulverized to -7 mesh by the coarse pulverizer 4, and then The raw material is supplied to a tube mill 11 and a stard mill 9 through pipes 5 and 6, respectively, and wet-pulverized. At this time, water and additives are supplied into each mill through pipes 7 and 8. Here, the slurry produced in the Stard mill 9 is supplied into the mill from the outlet side of the tube mill 11 through a pipe line 10, pulverized and mixed, and then sent out from a pipe line 13 as a highly concentrated coal-water slurry. FIG. 3 shows the production method (2) above, in which coal A supplied to the bunker 3 by the conveyor 2 is coarsely crushed to -7 mesh by the coarse crusher 4, and then The raw material is supplied to a tube mill 11 and a stard mill 9 through pipes 5 and 6, respectively, and wet-pulverized.
At this time, water and additives are supplied into the mill through pipes 7 and 8, respectively. Here, the slurry produced in Stard Mill 9 is supplied to tank 12 through pipe 10, mixed with the slurry produced in tube mill 11, and sent out from pipe 13 as a highly concentrated coal-water slurry. Figure 4 shows the manufacturing method of (3).
This is a method for producing a highly concentrated coal-water slurry using two types of coal A and coal B that have different crushability. The coal A supplied to the bunker 3' by the conveyor 2' is coarsely pulverized to -7 mesh by the coarse pulverizer 4', and then supplied to the star mill 9 from the pipe line 6. At the same time, water and additives are also piped. It is supplied from route 8 and subjected to wet pulverization. On the other hand, coal B supplied to bunker 3 by conveyor 2 is crushed by -7
After being coarsely pulverized to a mesh, it is supplied to the tube mill 1 through a conduit 5. At the same time, water and additives are supplied through conduit 7, and the slurry produced in star mill 9 is supplied through conduit 10, wet-pulverized and mixed, and a highly concentrated coal-water slurry is obtained through conduit 13. Figure 5 shows the production method in (4) above, but in the opposite case to the production method in (3), a slurry produced from coal B using Stard Mill 9 in the same manner as in (3) is used. , is introduced into the tube mill together with coal A, and a highly concentrated coal-water slurry is obtained from pipe line 13. FIG. 6 shows the manufacturing method (5) above, in which coal A sent to the bunker 3 by the conveyor 2 is coarsely crushed to -7 mesh by the coarse crusher 4, and then Tube mill 11 from pipes 5 and 6 respectively
and supplied to Stard Mill 9. Water and additives are introduced through pipe 8, and a portion of the slurry produced in Stard Mill 9 is supplied to the tube mill through pipe 10 together with water and additives sent from pipe 7, where they are wet-pulverized and mixed. Sent to tank 12. In the tank 12, it is mixed with the slurry produced in the star mill 9, and sent out through the pipe 13 as a highly concentrated coal-water slurry. FIG. 7 shows the production method (6) above, in which coal A supplied to the bunker 3 by the conveyor is coarsely pulverized to -7 mesh by the coarse pulverizer 4, and then Water and additives are supplied to the tube mill 11 and stard mill 9 through conduits 5 and 6, and water and additives are supplied into the respective mills through conduits 7 and 8. The slurry produced in the tube mill 11 is supplied to the Stard mill 9 through a pipe line 10, where it is wet-pulverized and mixed, and then passed through the pipe line 1 as a highly concentrated coal-water slurry.
Sent out from 3. In the example shown in the flow sheet above,
The coal concentration in the star mill is 20-70% (preferably 40-60%), and the coal concentration in the tube mill is 50-80% (preferably 65-75%).
Also, of the total amount of coal, the amount to be crushed by the Stard Mill is 5 to 50% (preferably 10 to 20%) of the total. Less than 5% is less effective, and more than 50% requires the entire crushing power. becomes larger. Specific examples of the present invention will be shown below. Example 1 Coal A (HGI = 36, ash content = 11.7%), which had been coarsely crushed to 7 meshes or less, was wet-pulverized by 20% using a star mill in a 650φ tube mill system based on the system diagram shown in Figure 1. (coal concentration 50%, dry coal base), then fed to a tube mill and wet-pulverized until the maximum particle size was 297 μm. However, as an additive, 0.2% of anionic surfactant is added to the coal in the tube mill, and 0.1% to the coal in the star mill.
% added. FIG. 8 shows the results of measuring the particle size distribution of the slurry thus obtained and the slurry produced by the conventional method using only a tube mill under the same conditions. In the figure, 20 indicates the case of the conventional method, and 21 indicates the case of the method of the present invention. It can be seen that for low HGI coal such as A coal, when the present invention is used (21), the particle size distribution covers a much wider range than when only the tube mill is used. In this way, because a wide particle size distribution was obtained, the coal concentration of the produced slurry could be increased from 67% to 70%, and the slurry viscosity could be reduced from 3000 cp to 1200 cp. Next, the stability of each slurry was examined.
That is, each slurry was
Its stability was investigated by placing it in a 300 mm cylinder and leaving it stationary. To test stability, a cylinder filled with slurry is filled with a length of
A glass rod of 370 mm in diameter and 5 mm in diameter was penetrated, and when the glass rod fell under its own weight and came to rest, the thickness of the hard pack that had settled at the bottom of the cylinder was measured. The results are shown in Figure 9. Regarding the slurry (22) produced only with a tube mill,
The thickness of the hard pack reached 5 cm in 100 days, whereas the thickness of the hard pack of the slurry (23) produced according to the present invention remained unchanged even after 100 days had passed.
It was found that the slurry was extremely stable, with a thickness of 0.5 cm. Obtaining such a stable slurry reduces troubles in slurry storage and transportation. Furthermore, for each slurry, the relationship between the amount of anionic surfactant added during production and the slurry viscosity was investigated. The viscosity of the slurry was measured using a rotational viscometer, and the measurement results for each addition amount are shown in FIG. For slurry produced only by tube mill (24), the amount of surfactant added was 0.5 per weight of coal to obtain a 3000 cp coal-water slurry.
% required, whereas according to the present invention (25)
At 0.3%, the slurry viscosity is 1200 cp. That is, by applying the present invention, the coal concentration can be increased by 3% and the amount of surfactant can be reduced by 40%, making it possible to reduce the manufacturing cost of a highly concentrated coal-water slurry. Table 1 shows the production volume per hour, coal concentration, and power consumption of each slurry.
As is clear from Table 1, according to the present invention, compared to the conventional method, the amount of slurry produced per hour, that is, the amount of coal crushed per hour, is increased by about 57%, and as a result, the power consumption rate is approximately decreased by 10%.

[Table] Example 2 Similar to Example 1, the present invention shown in FIG.
A method of producing coal-water slurry using only two tube mills was carried out on B coal (HGI = 72, ash content = 35.0%). As a result, it was found that the particle size distribution of the obtained slurry was wider when the present invention was used. In addition, the stability of the slurry produced was measured using the same method as in Example 1, and the result was that the thickness of the hard pack of the slurry produced according to the present invention was 0.2 cm after 100 days of standing. The resulting slurry had a hard pack thickness of 1 cm after being allowed to stand for 100 days, and when the present invention was used, a stable, highly concentrated coal-water slurry could be obtained. Table 2 shows the test results comparing the method of the present invention and the conventional method. As can be seen from Table 2, according to the method of the present invention, the amount of slurry produced per hour, that is, the amount of coal crushed per hour increased by about 56%, resulting in
Power consumption decreased by approximately 9%. In addition, the viscosity of the slurry produced was reduced by approximately 20%, even though only 60% of the surfactant was used compared to the conventional method. Thus, in the present invention, a highly concentrated coal-water slurry could be produced at low cost not only for coal with low HGI but also for coal with high HGI.

[Table] Example 3 The apparatus of the present invention shown in FIG. C coal was wet-pulverized in a star mill (coal concentration 70
%, based on dry coal), and then fed to the tube mill together with D charcoal. Table 3 shows the conventional method using only a tube mill,
The test results comparing the method of the present invention are shown. As can be seen from Table 3, according to the method of the present invention, the amount of coal crushed per hour increased by about 56%, and as a result, the power consumption rate decreased by about 20%. Also, the viscosity of the produced slurry was reduced by 60%, even though only 60% of the surfactant was used compared to conventional methods. This is a very good result compared to Example 1 and Example 2.
The manufactured slurry also had excellent stability.

[Table] As described above, according to the present invention, single-stage pulverization using only a conventional tube mill produces
It has been difficult to provide a wide particle size distribution in the production slurry, but by combining a tube mill and a stard mill, (1) it is possible to widen the particle size distribution of the production slurry, especially for HGI coal. This makes it possible to increase the proportion of ultrafine coal particles of several microns or less present in the slurry by, for example, 10 to 20%. (2)
By providing the slurry with a wide particle size distribution, the viscosity of the slurry produced can be reduced and stability improved, and (3) the amount of surfactant that has a large effect on slurry properties can be reduced by, for example, 40%. Effects such as a reduction in the manufacturing cost of highly concentrated coal-water slurry can be obtained.

[Brief explanation of the drawing]

Figures 1 to 7 are flow sheets of a method for producing a highly concentrated coal-water slurry showing examples of the present invention, Figure 8 is a diagram showing the cumulative particle size distribution, and Figure 9 is a diagram showing a highly concentrated coal-water slurry. Diagram showing the stability of water slurry, 1st
Figure 0 is a diagram showing the relationship between the amount of surfactant added and viscosity. 2... Conveyor, 3... Bunker, 4... Coarse crusher, 5
~8...Pipe line, 9...Stard mill, 10...Pipe line, 1
1...tube mill, 12...slurry tank, 13...
Slurry pipe, A, B...coal.

Claims (1)

[Claims] 1. A method for producing a highly concentrated coal-water slurry, characterized in that a wet tube mill and a wet stard mill are used in combination. 2. In claim 1, fine coal particles pulverized by a stard mill are supplied through the inlet or outlet of the tube mill, or mixed in a slurry tank or the like after the outlet of the tube mill, or one or more of the following treatments: A method for producing a highly concentrated coal-water slurry, characterized by carrying out the following steps. 3 In claim 1 or 2,
A method for producing highly concentrated coal-water slurry, characterized in that the interior of a tube mill is divided into two or more chambers, and balls of different diameters are used in each chamber.