JPH04220494A - Manufacture of highly concentrated coal/water slurry - Google Patents

Abstract

PURPOSE:To produce a highly concentrated and stable coal/water slurry having a low viscosity with low power by decreasing voids between coal particles. CONSTITUTION:Raw coal 1 is crushed on a crusher 3 into particles having an average particle diameter of 300-800mum, and water 6 and a dispersant 7 are added to the crushed material. The mixture is ground on a ball mill or rod mill 8 to obtain a highly concentrated coal/water slurry having an average particle diameter of 20-60mum. A part of the slurry is supplied to a columnar attritor 11 and ground into a highly concentrated coal/water slurry having an average particle diameter of 5-10mum. 90-60wt.% former slurry is mixed 13 with 10-40wt.% latter slurry under a shearing force, thereby decreasing the voids. Also, 10-50wt.% slurry of the ball mill or rod mill 8 is preferably circulated 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly concentrated coal-water slurry.

0002

BACKGROUND OF THE INVENTION In order to improve the transportability, storability and ease of handling of coal, coal is pulverized and dispersed in water in the form of a slurry. This coal-water slurry is a fuel that can be directly combusted, but high concentration is required from the viewpoint of combustion efficiency, and transportation and
Low viscosity is required for ease of handling. Various methods have been studied to meet the contradictory demands of high concentration and low viscosity.

[0003] As a wet method for producing a high-concentration coal-water slurry, a relatively large amount of crushed coal, water, and a dispersant are placed in a ball mill and pulverized, and then coarse particles are removed to improve the coal concentration from the beginning. The so-called high-concentration pulverization method prepares a coal-water slurry with a high concentration of 60% by weight or more, and a low-concentration coal-water slurry with a coal concentration of 60% by weight or less by placing a relatively small amount of crushed coal and water in a ball mill. A so-called low-concentration pulverization method is known in which the slurry is prepared, dehydrated to form a dehydrated cake, and the dehydrated cake is dispersed in water to prepare a high-concentration coal-water slurry.

[0004] Conventionally, the low-concentration pulverization method has been widely adopted because it is easy to remove coarse particles by classification. For example, coal is supplied together with water to a first ball mill to prepare a low concentration coal-water slurry, the slurry is diluted with water, sieved, coarse particles are removed, and then passed through a dehydrator to obtain a dehydrated cake. A method of preparing a high concentration coal-water slurry by supplying the cake together with water and a dispersant to a second ball mill (Japanese Patent Laid-Open No. 15893/1983), a method of preparing a low concentration slurry obtained by processing crushed coal with water in a tube mill. The slurry is divided into two parts, one slurry is classified to remove coarse particles and dehydrated to obtain a dehydrated cake of fine components, and the other slurry is processed with a wet ultrafine mill to obtain a dehydrated cake of fine components. A method of preparing a highly concentrated coal-water slurry by mixing (Japanese Patent Application Laid-Open No. 63-51493) has been adopted.

[0005] However, all of these methods have problems in that it is difficult to obtain a product that is satisfactory in terms of high concentration and low viscosity, that the operations are complicated, and that they require a large amount of power such as the need for a dehydrator. There was a point. An object of the present invention is to provide a method for efficiently producing a highly concentrated and low viscosity coal-water slurry using low power and obtaining a stable product.

[0006]

[Means for Solving the Problems] The present inventors have discovered that high concentration and low viscosity coal-water slurry depends on the proportion of voids formed between fine coal particles in the slurry, that is, the porosity. Noting that a coal-water slurry with higher concentration and lower viscosity can be obtained as the ratio is smaller, the relationship between the particle size distribution of fine coal particles and the porosity was studied.

As a result, the porosity can be reduced by mixing a coal-water slurry containing coarse particles with a large particle size and a coal-water slurry containing fine particles with a small particle size in the presence of shear force. Moreover, the porosity at this time is affected by the particle size of the coarse particles, the particle size of the fine particles, and the mixing ratio of the two. Also, by using a tower type mill, it is possible to reduce the The inventors have discovered that a concentrated coal-water slurry can be suitably prepared, and have completed the present invention.

That is, in the present invention, raw coal is crushed into three
High-concentration coal with an average particle size of 20-60μ and a coal concentration of 60-80% by weight is obtained by crushing the crushed material to an average particle size of 00 to 800μ, adding water and a dispersant, and pulverizing it in a ball mill or rod mill. A water slurry is prepared, and then a part of this highly concentrated coal-water slurry is fed to a tower-type grinder and subjected to a grinding process, with a coal average particle size of 5 to 10μ and a coal concentration of 60 to 80% by weight. Slurry and pear, said slurry 10
40% by weight and 90 to 60% by weight of the slurry pulverized with the ball mill or rod mill in the presence of shearing force to reduce the porosity, a method for producing a highly concentrated coal-water slurry. It is.

An example of the present invention will be explained in detail using the drawings. In Figure 1, 1 is raw coal, 2 is a raw coal hopper, 3 is a crusher, 4 is a crushed coal hopper, 5 is a quantitative coal feeder,
6 is added water, 7 is an additive, 8 is a ball mill or rod mill, 9 is a collect tank, 10 is a circulating slurry, 11 is a tower type attritor, 12 is a collect tank, 13 is a mixer, 1
4 is a product. Further, F is a flow meter, and P is a pump.

First, raw coal 1 is transferred from the raw coal hopper to the crusher 3.
For example, raw coal is supplied to a hammer crusher or an impact crusher to crush the raw coal into an average particle size of 300 to 800μ. The crushed coal is fed from the crushed coal hopper 4 through the quantitative coal feeder 5 into a ball mill or rod mill 8 together with added water 6 and a dispersant such as an anionic surfactant 7. In this ball mill or rod mill 8, the coal particles are pulverized to 20 to 60 microns, and a highly concentrated coal-water slurry having a coal concentration of 60 to 80% by weight is prepared.

The slurry discharged from the ball mill or rod mill 8 is stored in a collect tank 9, and a portion 6 of it is returned to the ball mill or rod mill 8 for circulation. The amount to be circulated is preferably 10 to 50% by weight of the slurry from the ball mill or rod mill. When circulated in this way, since the slurry coming out of the ball mill or rod mill is fine particles, the fine particles are mixed with the coarse particles in the ball mill or rod mill, which lowers the porosity of the particles in the ball mill or rod mill, and reduces the viscosity. This results in better fluidization and better movement of the mill balls. Therefore, pulverization can be carried out smoothly, which in turn reduces power consumption.

A portion of the highly concentrated coal-water slurry in the collect tank 9 is supplied to the mixing device 13 as it is. Further, a part of the high concentration coal-water slurry in the collect tank 9 is supplied to the tower-type attritor 11 . This tower-type grinder 11 is, for example, a registered trademark tower mill, and is a tower-shaped mill equipped with a screw that rotates at a low speed in the center. It has a structure that can be crushed. Coal particles are ground into particles of 5 to 10 μm using this tower-type grinder 11 . This tower-type attritor is advantageous because it can efficiently mill highly concentrated coal-water slurries.

[0013] Slurry 1 treated with this tower type attritor 11
Mixing machine 13
and mix. In the mixing at this time, the average diameter of the slurry treated with the tower-type attritor 11 is 5 to 10.
In order to lower the porosity by uniformly mixing the coal particles with an average particle size of 20 to 60 μ contained in the slurry processed only by a ball mill or rod mill, a mixer with shearing force is used. Need to mix. It is preferable to install two or more mixers in series. The slurry leaving this mixer has a decreased porosity and a significantly decreased viscosity. Therefore, this slurry whose viscosity has been reduced is classified as necessary to form a product 14. In this way, a desired high concentration and low viscosity coal-water slurry can be obtained without using a dehydrator.

[0014] In the present invention, the average particle size of coal particles in the slurry treated with a ball mill or rod mill is 20 to 20.
60μ, and the average particle size of the coal particles of the slurry that is further processed in a tower-type mill is 5 to 10μ, and both of these are mixed in a predetermined ratio, that is, 90 to 60% by weight of the former and 10 to 40% by weight of the latter. % in the presence of shear force, the porosity can be reduced and the viscosity can be significantly reduced. This point will be explained in more detail based on examples.

A mixture of a coal-water slurry with an average particle size of 51μ that has been processed only by a ball mill or a rod mill, and a coal-water slurry that has an average particle size of 5.2μ that has been further ground using a tower type mill (coal concentration 68.5%), the relationship between the mixing ratio and porosity of both, and the mixing ratio and viscosity were determined in the second
As shown in the figure. As can be seen from this figure, when adding the slurry ground by the above-mentioned tower-type grinder to the slurry that has only been subjected to ball mill or rod mill processing, as the amount added increases, the porosity decreases and the viscosity also decreases; If the amount added exceeds about 20%, the porosity will increase and the viscosity will also increase rapidly. Therefore, when two types of slurry having the above average particle diameter are used, 20% of the slurry processed with the above tower type mill and 80% of the slurry processed only with the above ball mill or rod mill are mixed to produce a highly concentrated coal. Prepare a water slurry. This product had a low viscosity of 800 cp or less even at a high coal concentration of 68.5% by weight, had good stability, and was extremely excellent.

[0016] Also, a mixture of a coal-water slurry with an average particle size of 40 μm processed only by a ball mill or a rod mill and a coal-water slurry with an average particle size of 8.4 μm processed by a tower-type mill (coal concentration Figure 3 shows the relationship between the mixing ratio and porosity, and the mixing ratio and viscosity at 67.1% by weight. In this case, 75% by weight of coal-water slurry only processed by ball mill or rod mill,
Coal-water slurry 25 which was further processed in a tower type mill
The weight percent mixture had the lowest porosity and viscosity, with a viscosity of about 500 cp.

As mentioned above, in the present invention, the mixing ratio of the slurry processed only by the ball mill or rod mill and the slurry further processed by the tower type mill differs depending on the average particle size of each slurry. By appropriately adjusting the average particle size and mixing ratio of each of these, a coal-water slurry with high concentration, low viscosity, and good stability can be easily obtained.

[0018] Furthermore, when crushing coal with a crusher such as an impact crusher, the smaller the particle size, the more power is required. do not need. However, if you try to crush particles with an average particle size of about 300μ, a large amount of power will be required, and
To make the powder finer than 00μ, grinding with a ball mill or rod mill requires less power. In addition, when grinding with a ball mill or rod mill, if you try to grind the particles to an average particle size of about 20μ or less, a large amount of power is required. Grinding requires less power. In the present invention, crushing to an average particle size of 300 to 800μ is performed using a crusher such as an impact crusher, and
Since pulverization to a particle size of up to 60 μm was carried out using a ball mill or rod mill, and grinding to an average particle size of 5 to 10 μm was carried out using a tower-type mill, the power required for refining coal can be significantly reduced.

[0019]

Effects of the Invention The present invention provides a slurry containing coal particles with an average particle size of 20 to 60μ ground at a high concentration using a ball mill or a rod mill, and a slurry containing coal particles with an average particle size of 5 μm ground at a high concentration using a tower type attritor. The slurry containing ~10μ coal particles was mixed in the presence of shear force in the proper proportions, so that a slurry with the lowest porosity could be obtained, thus providing a stable coal-water solution with high concentration and low viscosity. You can get slurry. In addition, in the present invention, since the pulverization treatment and the grinding treatment are performed at a high concentration, there is no need to dehydrate the slurry.
Power can be reduced and operation is also easier. Moreover, in the present invention, since a crusher, a pulverizer, and a grinder are used in combination according to the size of coal particles, power can be reduced in this respect as well.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing one embodiment of the present invention.

FIG. 2 is a drawing showing an embodiment of the present invention.

FIG. 3 is a drawing showing another embodiment of the present invention.

[Explanation of symbols]

1...raw coal 2...raw coal hopper 3...crusher 4...
Crushed coal hopper 5...metered coal feeder 6...additive water 7...additive 8...ball mill or rod mill 9...collect tank 10...circulation slurry 11...
Tower type attritor 12...Collect tank 13...Mixer 14...Product F...Flowmeter P...Pump

Claims (2)

[Claims] [Claim 1] Raw coal is crushed to an average particle size of 300 to 800μ using a crusher, water and a dispersant are added to the crushed material, and the mixture is crushed using a ball mill or rod mill to obtain coal with an average particle size of 2
Highly concentrated coal with a coal concentration of 0 to 60μ and a coal concentration of 60 to 80% by weight.
A water slurry is prepared, and then a part of this highly concentrated coal-water slurry is fed to a tower-type grinder and subjected to a grinding process.The highly concentrated coal has a coal average particle size of 5 to 10μ and a coal concentration of 60 to 80% by weight.
Water slurry and slurry 90 pulverized with 10 to 40% by weight of the slurry using the ball mill or rod mill.
60% by weight in the presence of shearing force to reduce the porosity. 2. The production of a highly concentrated coal-water slurry according to claim 1, wherein in the pulverization process in a ball mill or rod mill, 10 to 50% by weight of the slurry discharged from the ball mill or rod mill is returned to the ball mill or rod mill and circulated. Method.