JPH07119428B2 - High-concentration coal / water slurry manufacturing method - Google Patents

Description

Detailed Description of the Invention a. OBJECT OF THE INVENTION Industrial field of the invention The present invention relates to a method for producing a coal / water slurry having a high concentration and good stability.

Conventional technology High-concentration coal / water slurry is abbreviated as CWM (Coal Water Mxture), which is finely pulverized coal dispersed in water.
The general specifications are a maximum particle size of coal particles of 150 to 350 μm, an average particle size of 20 to 50 μm, and a coal concentration of 60 to 75% by weight. Additives are used to impart fluidity and stability to the slurry.

From the viewpoint of increasing the concentration, it is desirable that the particles of CWM have a particle size distribution as wide as possible or have a plurality of peaks.

CWM is being researched and developed as an alternative fuel to petroleum, but the basis of its manufacturing technology is the grinding method to obtain the particle size distribution that enables the selection and high concentration of additives.

Coal pulverization methods for producing high-concentration coal / water slurry are roughly classified into a dry pulverization method and a wet pulverization method, and there are a one-step method in which pulverization is performed in one step and a two-step method in which two steps are performed. Since the present invention belongs to the wet two-step method, the prior art relating to the wet two-step method will be described below.

FIG. 2 is generally called the Carbogel method, and is the method described in Published Patent Publication No. 59-500817.

The pre-crushed coal C is supplied to the first crusher 1 together with the water W and wet-crushed. The particle size after the first stage wet pulverization is approximately 850 μm or less.

The crushed material is classified by the sieve 3 into particles having a particle diameter exceeding a certain particle diameter selected from the range of 150 to 200 μm and particles having a particle diameter not exceeding a certain particle diameter. Is pulverized together with water W, returned to the sieve 3 through the line 9 and classified. Fine particles under the sieve are decalcified from line 5 2
1. After the dehydration step 22, the additive A is mixed in the mixing step 23 to obtain a product.

This method is essentially one-step pulverization in terms of making coarse particles into fine particles, and finely pulverizing the coarse particles on the sieve to control the fine particles so as to obtain a desired particle size distribution. difficult.

Figure 3 shows, for example, Fluid Carbon
This is the method adopted by the company.

The pre-crushed coal C is supplied to the first crusher 1 together with the water W and wet-crushed. The pulverized material is classified by the sieve 3, and the coarse particles on the sieve are returned to the first pulverizer 1 by the line 10 and re-pulverized. The fine particles under the sieve are supplied to the second pulverizer 2 from the line 5, further pulverized, and classified by the second sieve 11. Sieve 11
The upper coarse particles are returned to the second crusher 2 through the line 12 and crushed again. The fine particles under the sieve are mixed with the additive A in a mixing step 23 through a deashing step 21, a dehydration step 22 and a line 13 to form a product.

In this method, the total amount of coal is pulverized in two stages, so power costs are high, and the particle size distribution only shifts to the ultrafine particle side, and it is difficult to obtain a wide particle size distribution or a particle size distribution having a plurality of peaks.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a method for producing a coal / water slurry having high concentration and good stability by pulverizing coal to adjust the particle size distribution.

B. Structure of the Invention Means for Solving Problems The high concentration coal / water slurry manufacturing method according to the present invention is
Classifying the coal particles wet-milled by the pulverizer of No. 1, and the coal particles exceeding a certain particle size are circulated to the first pulverizer and re-pulverized,
A coal / water mixture obtained by further wet-milling a part of the classified coal particles having a certain size or less with a second crusher to obtain a coal / water containing the remainder of the classified coal particles having a certain size or less. It is characterized in that it is combined with the mixture, dehydrated and then mixed with the additive.

An example of using a ball mill as a crusher will be described with reference to FIG. 1. Symbol 1 is a first ball mill and symbol 2 is a second ball mill.

The maximum diameter of the balls used in the first ball mill is 60 mm, the average diameter is 30 mm, and the maximum diameter of the balls used in the second ball mill is 20.
Appropriately, it is about 30 mm and the average diameter is about 10 mm.

Preliminarily crushed coal C having a particle size of about 3 mm is supplied to the first ball mill 1 together with water W to obtain a low concentration, for example, a coal concentration of 50
Wet milling is performed at a weight percentage of less than. It is suitable that the particle size of the coal after the first stage wet pulverization is approximately 850 μm or less. The crushed material is classified with a sieve 3. This classification has a particle size of 15
It is suitable to classify into those having a certain particle diameter selected from the range of 0 to 200 μm and those having a certain particle diameter smaller than that.

Coal particles that have been classified by the sieve 3 and exceed a certain size are in line 4.
Is circulated to the first ball mill 1 for re-grinding. In this way, all the raw material coal is pulverized to have the above-mentioned certain particle size or less.

Part of coal particles with a certain size or less obtained from line 5,
Preferably, 20 to 80%, more preferably 30 to 60% is branched to the line 6 and supplied to the second ball mill 2 to obtain a low concentration,
For example, wet pulverization is performed with a coal concentration of 50% by weight or less. This second
It is appropriate that the particle size of the coal after the wet pulverization of the stage is approximately 75 μm or less.

It is easy to obtain a desired particle size distribution by adjusting the amount branched to the line 6 and supplied to the second ball mill 2 while checking the particle size distribution of the intermediate product or the final product after the line 14.

In this way, the finely pulverized coal / water mixture is introduced in line 7, and the coal containing the coal particles having a certain particle size or less obtained by classifying the wet-milled coal particles in the first ball mill from line 5 Combine with the rest of the water mixture, line 14
Then, after the deashing process is performed in the deashing process 21 as necessary, the additive A is mixed in the mixing process 23 through the dehydration process 22 to obtain a product.

In addition to the ball mill, other types of crushers such as a rod mill and a vibration mill can be used as the crusher.
If necessary, two or more first and second crushers can be used.

Additives are used to maintain the dispersed state of coal fine particles for a long period of time and reduce the viscosity to provide fluidity.

Example 1 According to the flow shown in FIG. 1, coal from China, which had been pre-ground to a particle size of about 3 mm in advance, was ground with a first ball mill filled with balls having an average diameter of 30 mm together with an equal amount of water to obtain a particle size of 850
The particles were pulverized to a particle size of less than or equal to μm (average particle size: 60 μm), classified with a 100-mesh sieve, and the coarse particles on the sieve were returned to the first ball mill and re-pulverized.

60% of the coal / water mixture that passed through the sieve was crushed with a second ball mill filled with balls with an average diameter of 10 mm to a particle size of 75μ.
m or less (average particle size 10 μm). This was combined with the rest of the coal / water mixture that passed through the sieve, deashed and dehydrated, and then anionic surfactant (0.5% by weight) was added and mixed as an additive.

The solid content concentration of the obtained coal / water slurry product was 72% by weight, and the viscosity was 1000 CP. When the particle size distribution was measured, there were two peaks near 50 μm and around 15 μm as shown in line A of FIG. 4, and the particle size distribution was broad trapezoidal.

This coal / water slurry was stable even after 6 months.

Comparative Example 1 The same first ball mill and second as used in Example 1
Using the same ball mill as in Example 1, the same amount of coking coal as used in Example 1 was used and the flow of coal shown in FIG.
A water slurry was produced. Deashing, dehydration and the use of additives were performed in exactly the same way as in Example 1.

The solid content concentration of the obtained coal / water slurry product is 68% by weight.
The viscosity was 1000 CP as in Example 1. When the particle size distribution was measured, one peak was present in the vicinity of 40 μm as shown by the line B in FIG.

The stability of this coal / water slurry was shorter than that of the coal / water slurry of Example 1 and was about 2 months.

C. EFFECTS OF THE INVENTION It is possible to industrially advantageously manufacture a coal / water slurry having a low viscosity and good stability even at a high concentration.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the process flow of the present invention,
2 and 3 are diagrams for explaining the process flow of the prior art, and FIG. 4 is the product coal of Example 1 and Comparative Example 1.
It is a figure which shows the result of having measured the particle size distribution of water slurry.

Claims (1)

[Claims] 1. Coal particles wet-milled by a first crusher are classified, and coal particles exceeding a certain particle size are circulated to the first crusher and re-crushed to obtain classified particles having a certain particle size or less. After coal-water mixture obtained by further wet-milling a part of the coal particles with a second pulverizer is combined with the coal-water mixture containing the classified remaining coal particles having a particle size of a certain size or less, and dehydration A method for producing a high-concentration coal / water slurry, which comprises mixing with an additive.