JPH0439512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a coal-rich water slurry.

Coal high concentration water slurry (hereinafter referred to as high concentration slurry) is a mixture of 60 to 90% by weight of finely ground coal and 40% water.
A mixture of ~10% by weight and some additives,
It is a fluid fuel that can be combusted as is in a boiler or the like without dehydration, and by converting coal, which is a solid fuel, into a fluid, its range of use can be dramatically expanded.

Conventionally, methods for producing high concentration slurry can be roughly divided into three types: dry method, high concentration wet method, and low concentration wet method. The main method uses a mill to pulverize coal in the air, and then mixes and stirs this with water and additives to form a highly concentrated slurry.

In the high-concentration wet method, coal, water, and additives are placed in a tube mill, and pulverization, mixing, and stirring are performed simultaneously.

Furthermore, in the low concentration wet method, coal and water are put into a tube mill and pulverized at a low concentration to form a coal low concentration water slurry, which is then dehydrated in a dehydrator to form a dehydrated cake, which is then poured into a stirring tank. A small amount of water and additives are again mixed and stirred in the tank to form a highly concentrated slurry.

However, the stem method had the following drawbacks.

That is, firstly, the grinding capacity in a mill of the same size is smaller than that of the low-concentration wet method;
Second, the power required for pulverization is also greater than in the low-concentration wet method. Furthermore, thirdly, the high-concentration slurry produced by the stem method has a dilatant rheological property due to the small number of ultrafine coal particles in the slurry, resulting in poor stability during storage.

On the other hand, the advantage of the high-concentration wet method is that because the slurry contains many ultrafine coal particles, the rheological properties are pseudoplastic and the stability during storage is excellent.

However, the disadvantages of the high-concentration wet method are: first, the grinding capacity in a mill of the same size is smaller than that of the low-concentration wet method, and second, the power required for grinding is also greater than that of the low-concentration wet method. .

In addition, the advantages of the low-concentration wet method are: firstly, the grinding capacity in a mill of the same size is larger than that of the dry method or the high-concentration wet method, and secondly, the power required for grinding is also lower than the dry method or the low-concentration wet method. This is small compared to . However, the disadvantage of the low concentration wet method is that because there are few ultrafine coal particles in the slurry, the rheological properties become dilatant and the storage stability is poor.

What is illustrated in FIG. 1 is a flow sheet relating to a conventional method for producing a high concentration slurry using a high concentration wet method.

In FIG. 1, a is a water supply line, b is a coal supply line, c is a mill, d is an additive supply line, and e is a high concentration slurry transport line.

Water and coal are supplied to the mill c through respective supply lines a and b, and after wet grinding, additives are added through the supply line d to obtain a highly concentrated slurry, which is transported through the highly concentrated slurry transport line e.

In this case, it is necessary to contain a large amount of ultrafine coal particles in order to make the rheological properties pseudoplastic and improve storage stability. Therefore, in manufacturing according to the flow shown in Fig. 1, in order to obtain a slurry with a high concentration of about 70%, which contains many ultrafine coal particles and has low viscosity, it is necessary to operate mill c for a long time to remove coal. It had to be pulverized. For this reason, the conventional high-concentration wet method has had the disadvantage that the power cost is extremely high and the crushing capacity is small.

What is illustrated in FIG. 2 is a flow sheet relating to a conventional method for producing a high concentration slurry using a low concentration wet method.

In Figure 2, a is a water supply line, b is a coal supply line, c is a mill, and f is a low concentration coal water slurry (hereinafter referred to as low concentration slurry) with a coal content of 20 to 50% by weight obtained in mill c. ) transport line,
Dehydrator g is a dehydrator that dehydrates a low concentration slurry to form a dehydrated cake. h is dehydrator g
This is a dehydration circulation line for recirculating the water obtained by dehydration to the water supply line a.

Water and coal are supplied to mill c from each supply line a and b, and pulverized at a low concentration of 20 to 50% by weight.
Make a low concentration slurry. This low concentration slurry is supplied to the dehydrator g via a low concentration slurry transport line f. In the dehydrator g, the low concentration slurry is dehydrated, and the dehydrated water is recirculated to the water supply line a through the dehydration circulation line h, and the dehydrated slurry is transferred as a dehydrated cake to the mixing agitator via the dehydrated cake transport line i. supply to j. This mixer j mixes and stirs the supplied dehydrated cake with water and additives supplied from the water supply line k and the additive supply line l to prepare a high concentration slurry with low viscosity. The concentrated slurry is transported from the concentrated slurry transport line e to a boiler combustion means (not shown) or the like.

In the production according to the flow illustrated in FIG. 2, since coal is crushed in water at a low concentration, only a small amount of ultrafine coal particles are produced. Therefore, since the resulting highly concentrated slurry contains only a small amount of ultrafine coal particles, the rheological properties of the highly concentrated slurry are dilatant, resulting in poor storage stability. In addition, even if ultrafine coal particles are generated in the mill by some method to make the rheological properties pseudoplastic and improve storage stability, if a large amount of ultrafine coal particles are contained in the low concentration slurry. This method had the disadvantage that the dewatering performance of the dehydrator was significantly reduced, the water content in the dehydrated cake increased, and the concentration of the resulting high-concentration slurry decreased.

The present invention improves the conventional low-concentration wet method for producing high-concentration slurry, and supplies ultra-fine coal slurry obtained by pulverizing a part of the low-concentration slurry in an ultra-fine mill to a mixing and stirring tank to create a dehydrated cake. It is characterized by mixing and stirring with water and additives, and its purpose is to have pseudoplastic rheological properties and excellent storage stability, without reducing the concentration of the finished high-concentration slurry, and to avoid conventional low-concentration wet slurry. The purpose of the present invention is to provide a method for producing a highly concentrated slurry, which has the advantage of having a large grinding capacity in a mill of the same size and requiring less power for grinding.

That is, the present invention wet-pulverizes coal in water to prepare a low-concentration slurry, and then dehydrates the low-concentration slurry to introduce a dehydrated cake obtained into a mixer and agitator, and also introduces the low-concentration slurry into the mixer and agitator. This is a method for producing a highly concentrated slurry, which is characterized by supplying an ultrafine coal slurry obtained by pulverizing a part of the coal in an ultrafine mill, water and additives, and mixing and stirring the slurry.

Hereinafter, preferred embodiments of the present invention will be described based on the embodiments illustrated in FIGS. 3 and 4.

In Fig. 3, 1 is a water supply line, 2 is a coal supply line, 3 is a main mill, 4 is a transportation line for a low concentration slurry with a coal content of 20 to 50% by weight obtained in the main mill 3, and 5 is a dehydrator, which dehydrates low concentration slurry to form a dehydrated cake. 6 is a dehydration circulation line for recirculating the water obtained by dehydration in the dehydrator 5 to the water supply line 1; 7 is a transport line for the dehydrated cake obtained in the dehydrator 5; 8 is a mixer; 9 10 is a supply line for water to be added; 10 is a supply line for additives such as surfactants; 11 is a low-concentration slurry branch transport line for branching and transporting the low-concentration slurry from low-concentration slurry transport line 4; and 12 is an ultra-fine grinding mill. For example, a conventional tube mill, ball mill, or grinding type mill using high-speed shearing force may be used. 13 is a transport line for ultra-fine coal slurry, and 14 is a transport line for high-concentration slurry.

In the embodiment configured in this manner, water and coal are supplied to the main mill 3 from the water supply line 1 and the coal supply line 2 for pulverization to produce a low concentration slurry of 20 to 50% by weight. One part of this low concentration slurry is branched and transported from the low concentration slurry transport line 4 to a low concentration slurry branch transport line 11, and the rest is supplied to the dehydrator 5. In the dehydrator 5, the low concentration slurry is dehydrated, the dehydrated water is recirculated to the water supply line 1 through the dehydration circulation line 6, and the dehydrated slurry is transferred as a dehydrated cake through the dehydrated cake transport line 7 to the mixing agitator. Supply to 8.

On the other hand, a part of the low concentration slurry branched to the low concentration slurry branch transportation line 11 is transferred to the ultrafine grinding mill 1.
2. The ultra-fine grinding mill 12 grinds the supplied low-concentration slurry so that about 50% by weight or more of the slurry is 10 μm or less. That is, the particle size of the ultrafine charcoal slurry is set to a particle size necessary to make the weight ratio of particles of 10 μm or less in the finished high-concentration slurry to 25% or more.

The ultrafine coal slurry thus obtained is supplied to the mixer agitator 8 via the ultrafine coal slurry transport line 13. The mixer 8 mixes and stirs the supplied dehydrated cake and ultrafine coal slurry with the water and additives supplied from the water supply line 9 and the additive supply line 10 to form a high concentration with low viscosity. A slurry is prepared and transported from a high concentration slurry transport line 14 to a boiler combustion means (not shown) or the like.

FIG. 4 is a flow sheet of a second embodiment of the present invention, in which a part of the dewatered water obtained in the dehydrator 6 is branched in the first embodiment shown in FIG. 3 to supply water in the first embodiment. It is connected to the line 9 via a branch pipe 15 to reduce the supply of water from outside the system.

Figure 5 shows the particle size distribution of the highly concentrated slurry produced based on the first example shown in Figure 3, where the vertical axis is weight % and the horizontal axis is particle diameter (μ). It is expressed as As shown in Fig. 5, the ultrafine coal particles obtained in the ultrafine mill 12 are packed into the comparatively large coal powder obtained in the main mill 3, and the rheological properties are pseudoplastic. A highly concentrated slurry with excellent storage stability can be obtained.

As described above in detail in the embodiments of the present invention,
The present invention wet-pulverizes coal in water to prepare a low-concentration slurry, and then dehydrates the low-concentration slurry to introduce the resulting dehydrated cake into a mixer and agitator.
A highly concentrated slurry is obtained by supplying an ultrafine coal slurry obtained by pulverizing a part of the coal in an ultrafine mill, water, and additives, and mixing and stirring to obtain the following effects.

1. In the main mill, pulverization is performed at a low concentration (20 to 50% by weight of coal) where the pulverizing power is minimum, so it is possible to operate at the point where the pulverizing power is minimum.

2. High dehydration rate is possible because dehydration is performed under conditions with few ultra-fine coal particles.

3. Addition of ultrafine coal particles makes the rheological properties of highly concentrated slurry pseudoplastic, improving storage stability.

[Brief explanation of drawings]

Figure 1 is a flow sheet of a method for manufacturing high concentration slurry using a conventional high concentration wet method, Figure 2 is a flow sheet for a method for manufacturing high concentration slurry using a conventional low concentration wet method, and Figures 3 to 5 are according to the present invention. Fig. 3 is a flow sheet of the first embodiment, Fig. 4 is a flow sheet of the second embodiment, and Fig. 5 is a schematic explanatory diagram of the particle size distribution of the high concentration slurry obtained by the first embodiment. . 1...Water supply line, 2...Coal supply line,
3... Main mill, 4... Low concentration slurry transport line, 5... Dehydrator, 6... Dehydration circulation line, 7...
... Dehydrated cake transport line, 8 ... Mixing agitator, 9
...Water supply line, 10...Additive supply line,
11...Low concentration slurry branch transportation line, 12...
...Ultra-fine pulverization mill, 13...Ultra-fine coal slurry transportation line, 14...High concentration slurry transportation line, 1
5... Branch pipe.

Claims (1)

[Claims] 1 Wet-pulverize coal in water to prepare a low-concentration coal water slurry, and then introduce the dehydrated cake obtained by dehydrating the low-concentration coal water slurry into a mixer and agitator, and add the low-concentration coal water to the mixer and agitator. A method for producing a high-concentration coal water slurry, which comprises supplying an ultrafine coal slurry obtained by pulverizing a portion of the slurry in an ultrafine mill, water, and an additive, and mixing and stirring the slurry.