JPS60156795A - Manufacture of highly concentrated coal-water slurry - Google Patents

Abstract

PURPOSE:To obtain the titled slurry of high combustion efficiency by classifying a low-concentration coal-water slurry prepared by wet-grinding of coal into coarse particle-contg. slurry and coarse particle-free one followed by subjecting the both slurries to each specific treatment and mixing them again while incorporating water and additive. CONSTITUTION:A low-concentration coal-water slurry is prepared by wet-grinding of coal in water. This slurry is then classified by classification device into (A) coarse particle-free slurry and (B) coarse particle-contg. one. While introducing the dehydrated cake derived from dehydration of the component (A) into a mixing agitator, (C) ultrapulverized coal slurry produced by grinding the component (B) in an ultrapulverization will, (D) water and (E) additive are fed to the above agitator to perform stirring, thus obtaining the objective slurry.

Description

[Detailed description of the invention] The present invention relates to a method for producing a highly concentrated coal water slurry.

High-concentration coal water slurry (hereinafter referred to as high-concentration slurry) is a mixture of 60-90% by weight of finely pulverized coal and 40-10% by weight of water, with some additives added, and can be left as is without dehydration. It is a fluid fuel that can be combusted in boilers, etc., and its range of use can be dramatically expanded by turning solid fuel coal into a fluid.

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 dry 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.

Further, in the high concentration wet method, coal, water and additives are simultaneously charged into a tube mill, and pulverization, mixing and stirring are performed at the same time.

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 low concentration coal water slurry, which is then dehydrated in a dehydrator to form a dehydrated cake.
This is mixed and stirred again with a small amount of water and an additive in a stirring tank to form a highly concentrated slurry.

However, the dry method had the following drawbacks.

That is, firstly, the grinding capacity in a mill of the same size is smaller than in the low-concentration wet method, and secondly, the power required for grinding is also larger than in the low-concentration wet method. Furthermore, the 31'i point is that the wet-type high concentration slurry 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; This is smaller than the wet method. 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 chart 1 related to a conventional method for producing a high-concentration wet high-concentration slurry.

Referring to 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 mill C from respective supply lines a and b, and after wet pulverization, additives are added from supply line d to obtain a high concentration slurry, and the high concentration slurry transport line e
Transport from.

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 production according to the flow shown in Figure 1, in order to obtain a highly concentrated slurry of about 70% with many ultrafine coal particles and low viscosity, the mill e must be operated for a long time to finely pulverize the coal. I had to. For this reason, the conventional high-concentration wet method has the disadvantage that the power cost is extremely high and the crushing capacity is small.

What is illustrated in FIG. 2 is a flow chart 1 related to a conventional method for producing a low-concentration wet high-concentration slurry.

In Figure 2, a is the water supply line, b is the coal supply line, C is the mill, and f is the coal content 2 obtained in mill C.
Transportation line for 0 to 50% by weight coal low concentration water slurry (hereinafter referred to as low concentration slurry), g is a dehydrator;
This method dehydrates a low concentration slurry to form a dehydrated cake. h is a dehydration circulation line for recirculating the water obtained by dehydration in the dehydrator g to the water supply line a.

Water and coal are supplied to each supply line a, b and mill C, and are pulverized at a low concentration to form a low concentration slurry of 20 to 50% by weight. 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, the dehydrated water is recirculated to the water supply line a through the dehydration circulation line 11, and the dehydrated slurry is sent as a dehydrated cake to the mixer j via the dehydrated cake transport line i. supply This mixer J mixes and stirs the supplied dehydrated cake with water and additives supplied from the water supply line 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 production according to the flow illustrated in FIG. 2, two coals are ground in water at a low concentration, so only a small amount of ultrafine coal powder is produced. Therefore, since only a small amount of ultrafine coal particles are contained in the finished high concentration slurry, the rheological properties of the high concentration 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, a large amount of ultrafine coal particles will be contained in the low concentration slurry. In this case, the dewatering performance of the dehydrator is significantly reduced, the water content in the dehydrated cake increases, and the concentration of the resulting high-concentration slurry decreases.

The present invention improves the conventional low-concentration wet-type high-concentration slurry manufacturing method, classifies the low-concentration slurry, and produces a low-concentration slurry containing coarse particles (hereinafter referred to as coarse-grain-containing slurry) in an ultra-fine grinding mill. The ultra-fine coal slurry obtained by pulverization is supplied to a mixing stirring tank where it is mixed and stirred with a dehydrated cake, water and additives.The purpose of this is to provide pseudoplastic rheology and storage stability. However, the high-concentration slurry does not lose its concentration, has the advantage of the conventional low-concentration wet method, and has a large grinding capacity in a mill of the same size, and also requires less power for grinding. A method for producing a concentrated slurry is provided. Moreover, since the proportion of coarse coal particles contained in the highly concentrated slurry is significantly reduced, when the highly concentrated slurry obtained by this invention is combusted in a boiler etc., the unburned carbon content is significantly reduced. Combustion efficiency can be significantly increased compared to conventional high concentration slurries.

That is, the present invention wet-pulverizes coal in water to prepare a low-concentration slurry, and then uses a classifier to remove coarse particles from the low-concentration water slurry (hereinafter referred to as coarse-grain cut low-concentration slurry). The dehydrated cake obtained by dehydrating the coarse grain cut low concentration slurry described in Section 2 above and introducing it into a mixing agitator,
2. A highly concentrated slurry characterized by supplying ultrafine pulverized coal slurry obtained by pulverizing the coarse particle-containing low concentration slurry with an ultrafine mill, water and additives to a mixing agitator and mixing and stirring the mixture. This is the manufacturing method.

Seven preferred embodiments of the present invention will be described below based on the embodiment illustrated in FIG.

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
6 is a classifier that separates the coarse grains in the supplied low concentration slurry and classifies it into coarse grain cut I/low concentration slurry and low concentration slurry containing coarse grains, and 6 is the coarse grain cut classified by classifier 5. The low concentration slurry transport line 7 is a dehydrator, and the dehydrator 7 dehydrates the coarse cut low concentration slurry to form a dehydrated cake. 8 is a dehydration circulation line for recirculating the water obtained by dehydration in the dehydrator 7 to the water supply line 1;
9 is a coarsely cut dehydrated cake obtained in dehydrator 7 (
Transportation line for coarse cut dehydrated cake (hereinafter referred to as coarse cut dehydrated cake), 10
13 is a branch pipe for transporting the water obtained by dehydration in the dehydrator 7 via the water supply line 11; 14 is a transport line for the coarse grain-containing low concentration slurry classified by the classifier 5; and 15 is a coarse grain transport line. A mill that ultra-finely pulverizes the coarse coal and pulverized coal in the low-concentration slurry containing coarse particles transported from the low-concentration slurry transport line, such as a normal tube mill, ball mill, or grinding using high-speed shearing force. Use a shape mill etc. 16 is a transportation line for the ultrafine coal slurry obtained by the ultrafine grinding mill 15.

Reference numeral 17 denotes a transport line for a highly concentrated slurry obtained by mixing and stirring coarse-cut dehydrated cake, water, additives, and ultrafine coal slurry using the mixer 10.

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.

A low concentration slurry of 20-50% by weight is made. This low concentration slurry is supplied from a low concentration slurry transport line 4 to a classifier 5 and is classified into a coarse grain cut low concentration slurry and a coarse grain containing low concentration slurry. The coarse grain cut low concentration slurry is supplied from a transport line 6 to a dehydrator 7. The dehydrator 7 dehydrates the coarse grain cut low concentration slurry.

The dehydrated water is passed through the dehydration circulation line 8 to the water supply line 1.
A portion of the water is recycled to the water supply line 11 via a branch pipe. Further, the slurry dehydrated in the dehydrator 7 is supplied as a coarse cut dehydrated cake to a mixing agitator 10 via a coarse cut dehydrated cake transport line 9. The concentrated slurry is supplied from the transport line 14 to an ultrafine grinding mill 15. . In the ultra-fine grinding mill 12, the coarse coal and pulverized coal in the supplied coarse grain-containing low-concentration slurry are ground so that 50% by weight or more of particles having a particle size of 10 μm or less is contained. In other words, the particle size of the ultrafine charcoal slurry is determined by setting the weight ratio of particles of 10μ or less in the highly concentrated slurry to 25% or more.
The granularity is as necessary to achieve this.

The ultrafine coal slug IJ- thus obtained is supplied to the mixer 10 via the transport line 16. The mixer 10 mixes and stirs the coarse cut dehydrated cake and the ultrafine coal slurry that have been supplied together with water and additives that are supplied from the water supply line 11 and the additive supply line 12 to reduce the viscosity. The low-concentration slurry is adjusted and transported from the high-concentration slurry transport line 17 to a boiler combustion means (not shown) or the like.

FIG. 4 shows the particle size distribution of the highly concentrated slurry produced based on the first example shown in FIG. 3, and the vertical axis is weight %.

The horizontal axis is expressed in particle diameter (μ). As shown in Fig. 4, the ultrafine coal particles obtained in the ultrafine mill 15 are packed into relatively large coal particles 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 in detail in the above two embodiments of the present invention, the present invention wet-pulverizes coal in water to prepare a low-concentration slurry, and then uses a classifier to cut coarse grains of the low-concentration water slurry into a low-concentration slurry. The coarse grain cut and low concentration slurry containing coarse grains are classified into "2", and the coarse grain cut dehydration case obtained by dehydrating the coarse grain cut low concentration slurry is introduced into a mixing agitator, and the coarse grain containing low concentration slurry is introduced into the mixing agitator. The ultrafine coal slurry obtained by pulverizing the slurry with an ultrafine mill, water, and additives are supplied and mixed and stirred to obtain a highly concentrated sludge IJ-, so that the following effects can be obtained.

1) In the main mill, low concentration (coal 2
Since pulverization is carried out at a concentration of 0 to 50% by weight, it is possible to operate at the point where the pulverizing power is minimal.

2) High dewatering efficiency is possible because dewatering is performed under conditions with few ultrafine coal particles.

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

4) Take out the coarse grains with a classifier, and crush the coarse grains and fine grains contained in the low concentration slurry containing the coarse grains with an ultra-fine grinding mill until they become ultra-fine coal particles. Since it is supplied to the slurry to create a highly concentrated slurry, the highly concentrated slurry does not contain coarse particles. Therefore, when the high-concentration slurry obtained by the present invention is combusted in a boiler or the like, the unburned carbon content is reduced, and the combustion efficiency can be significantly increased compared to conventional high-concentration slurries.

[Brief explanation of the drawing]

Figure 1 shows flow chart 1 of a conventional high concentration slurry production method using a high concentration wet method, and Figure 2 shows flow chart 1 of a high concentration slurry production method using a conventional low concentration wet method.
Fig. 3 and Fig. 4 are related to the present invention, Fig. 3 is flow chart 1 of the first embodiment, and Fig. 4 is a general explanation of the particle size distribution of the high concentration slurry obtained by the first embodiment. It is a diagram. 1...Water supply line, 2...Coal supply line, 3.
・・Main mill, 4-・・Low concentration slug IJ-transport line, 5
... Classifier, 6... Coarse particle cut low concentration slurry transportation line, 7... Dehydrator, 8... Dehydration circulation line, 9
. . . Coarse cut dehydrated cake transport line, 10 . . . Mixing agitator, 11 . . . Water supply line. 12... Additive supply line, 13... Classifying tube, 14
...Low concentration slurry transport line containing coarse particles, 15...
Ultra-fine grinding mill. 16.Q. Ultra-fine coal slurry transportation line. 17... Highly concentrated slurry transportation line agent

Claims (1)

[Claims] Coal is wet-pulverized in water to prepare a low-concentration coal water slurry, and then the low-concentration coal water slurry is divided into a low-concentration coal water slurry from which coarse particles have been removed using a classifier, and a low-concentration coal water slurry containing coarse particles. The dehydrated cake obtained by dehydrating the coal low concentration water slurry from which the coarse particles have been removed is introduced into a mixing agitator, and the coal low concentration water containing the coarse particles is introduced into the mixing agitator as described in -. A method for producing a high-concentration coal water slurry, which comprises supplying an ultrafine coal slurry obtained by pulverizing the slurry in an ultrafine mill, water, and an additive, and mixing and stirring the slurry.