JPH0315958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly concentrated coal-water slurry with low viscosity, and particularly to a method for producing a coal-water slurry suitable for reducing production costs.

Recently, there has been a growing movement to use coal in place of oil, which continues to rise in price, mainly in thermal power plants. However, coal, which is a solid fuel, is difficult to handle, and transportation costs have a large impact on coal grade. Therefore, technology development for turning coal into a slurry and handling it as a fluid is actively being carried out.

One of them is COM, which is a mixture of heavy oil and coal.
(Coal and Oil Mixture) is known. However, since this fuel is generally a mixture of heavy oil and coal in a weight ratio of about 1:1, it cannot be said to be a completely petroleum-free fuel and has little merit in terms of price. Also, so-called methanol, which is a mixture of methanol and coal, is known, but this is also expensive because it uses expensive methanol, and has not yet reached the practical stage.

In contrast, a mixture of coal and water
CWM (Coal and Water Mixture) is quite practical in terms of price and has been attracting attention recently. However, when CWM contains a high moisture content, the thermal efficiency during combustion decreases, and conversely, when the moisture content is low,
There is a problem in that the viscosity of CWM increases and the pressure loss during transportation increases. Furthermore, since CWM is composed of coal particles and water, there is a storage problem in that the coal particles settle and separate from the water over time. In order to eliminate these drawbacks,
By adjusting the particle size of coal particles, CWM with low viscosity and good stability even at high coal concentrations can be achieved.
Attempts are being made to manufacture .

In order to produce a CWM slurry with a high coal concentration, low viscosity, and good stability, it is said that it is preferable to crush the coal so that it has a particle size distribution that makes the filling rate as high as possible. One of the methods of crushing coal into such a particle size distribution is generally
A high-concentration wet pulverization method is known in which coal is pulverized at a high concentration of 60 to 80% (weight %, same hereinafter). However, as the coal concentration increases, the viscosity of the slurry also increases, which inevitably leads to a decrease in pulverization efficiency, or in other words, an increase in power consumption in the mill. In addition, in the high-concentration wet pulverization method, additives such as surfactants must be added to promote pulverization, but the required amount is 1% per coal.
The impact on the manufacturing cost of CWM cannot be ignored.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a material with low viscosity and good stability even under high concentration, without increasing production costs.
The objective is to provide a method by which CWM can be manufactured.

In order to achieve the above object, the present invention is characterized in that when coal is supplied to a wet mill and pulverized, the supply of coal is divided into multiple stages.

In the present invention, any known method may be used to divide the supply of coal into multiple stages, but in particular, the method of supplying coal in multiple stages for one mill, the method of supplying coal in multiple stages for one mill, A preferred example is a method in which coal is supplied to each mill, thereby creating a substantially multi-stage supply state.

The reason why the multi-stage pulverization method is adopted in the present invention is as follows. In other words, first, the diameter is 650mm,
A hard globe index (HGI, JIS-M8801) 52 bituminous coal (hereinafter referred to as
The relationship between the Bond work index Wi [see equation (1) below] and the coal concentration was obtained by pulverizing the A coal (referred to as A coal), and the results shown in Figure 1 were obtained.
At that time, F ₈₀ was 2830 μm and P ₈₀ = 105 μm.

[In the formula, F ₈₀ is the sieve opening (μm) when 80% of the raw coal passes through, and P ₈₀ is the sieve opening (μm) when 80% of the pulverized material passes through.] 1st As is clear from the figure, when pulverizing A coal, when the coal concentration exceeds 60%, the pulverization efficiency decreases rapidly (Wi increases), so it is found that it is preferable to pulverize at a concentration of 60% or less. However, if the coal concentration becomes too low, the required amount of pulverization (power consumption) in the second stage will increase, so about 55 to 60% can be said to be the optimum concentration.

Next, after carrying out the above pulverization with an average residence time of 1 hour, raw material coal is added separately to bring the coal concentration to 70%.
When further pulverized as A (two-stage feeding method),
When the coal particle size distribution in the resulting slurry was determined for B (one-stage feeding method), where the coal was simply pulverized with a coal concentration of 70% and an average residence time of 1 hour, the results shown in Figure 2 were obtained. It was done. From FIG. 2, it can be seen that the two-stage feeding method B has a wider particle size distribution than the one-stage feeding method A, and therefore the slurry viscosity is also lower.
Furthermore, the average particle size and the above P ₈₀ were also determined using the two-stage feeding method B.
It can be seen that the size is smaller and the crushing efficiency is also better. Note that C in FIG. 2 is a particle size distribution line of raw coal shown for reference.

As explained above, it can be seen that the pulverization efficiency can be improved by providing multiple stages of coal supply.

Hereinafter, the present invention will be explained in more detail by way of examples and drawings.

FIG. 3 is a system diagram of a two-stage coal feed type wet crushing apparatus using one mill suitable for carrying out the present invention. In this apparatus, coal stored in a bunker 1 is fed into a mill 3 via a feeder 2 and is pulverized in the presence of water and additives introduced through a feed pipe 4. The coal concentration at this time is not uniform depending on the coal type, but is generally 40 to 70%, preferably 50 to 65%.
It is. The coal-containing slurry obtained by the above-mentioned pulverization is then mixed with coal supplied via bunker 1A and feeder 2A to a predetermined coal concentration (generally 60 to 80
%) and then further crushed. After being pulverized to a predetermined particle size, it is discharged from the outlet of the mill 3 and stored in a slurry adjustment tank 5, and then transported to a combustion device or the like (not shown) by a pump 6 as required. Note that the coal supplied from the feeder 2 may be pre-mixed with water and additives, and the coal from the feeder 2A may be supplied from either or both near the entrance or exit of the mill. It is possible.

Next, FIG. 4 is a system diagram of an apparatus showing another embodiment of the present invention, which differs from the apparatus shown in FIG. The mill 3B is connected via a pump, thereby creating a substantial two-stage coal supply structure.

In this apparatus as well, coal can be suitably pulverized similarly to the case shown in FIG.

Hereinafter, the present invention will be explained in more detail with reference to specific examples.

Example 1 The above-mentioned A coal (bituminous coal with HGI = 52) was supplied from the feeder 2 into the mill 3 of the apparatus shown in FIG. 3, and in the presence of water and additives supplied from the supply pipe 4. The powder was pulverized at a coal concentration of 60% and an average residence time of 1 hour, and then further pulverized until particles of P ₈₀ ≈105 μm were obtained while feeding coal from the feeder 2A so that the coal concentration was 70%. The work index Wi at this time is 41 (Kwh/ton), and this value is the Wi when the coal concentration is maintained at 70% from the beginning.
= 50 (Kwh/ton).
In addition, the slurry viscosity is also
1500 cp, in the latter one-stage supply method.
The value was lower than 1800 cp.

In this example, it was sufficient to add only 0.7% of anionic surfactant per coal.
As described above, according to this embodiment, the amount and efficacy of additives used can be reduced, making it possible to significantly reduce manufacturing costs.

Example 2 A slurry was produced in the same manner as in Example 1 using bituminous coal of HGI=90 (hereinafter referred to as B coal).
However, in this example, the coal was initially pulverized at a coal concentration of 65%, and then coal was added until the coal concentration reached 75%.
Work index when crushed until P ₈₀ ≒ 105 μm
Wi was 58 (Kwh/ton) in the one-stage supply, while it was 49 (Kwh/ton) in the two-stage supply, which was a low value. Furthermore, the slurry viscosity at that time was 2200 cp and 1950 cp, respectively, and the effect of reducing slurry viscosity was also observed in the two-stage feeding method.

Example 3 A slurry was produced by the two-stage feeding method in the same manner as in Example 1 except that the amount of surfactant added was 0.5% based on coal. The slurry viscosity at this time was 1800 cp, and even though the amount of surfactant added was reduced, the one-stage feeding method of Example 1 was used to reduce the amount of surfactant to 0.7 cp.
A slurry of the same viscosity as when % was added was obtained.

Example 4 A mixture of B coal used in Example 2 and bituminous coal with HGI = 36 (hereinafter referred to as C coal) at a weight ratio of 1:1 was supplied to the mill in one stage at a coal concentration of 70%, and this When it was crushed to a P ₈₀ ≒ 105 μm, the work index Wi reached a high value of 58 (Kwh/ton). In contrast, Example 1 except that initially only C coal was pulverized at a coal concentration of 54%, and then B coal was added.
When slurry was produced using the two-stage feeding method in the same manner as above, the work index Wi was as low as 45 (Kwh/ton). In addition, when the two-stage feeding method was carried out in the same manner as above except for changing the feeding order of B coal and C coal, the work index Wi was slightly higher than the above, but 50
(Kwh/ton).

As described above, according to the present invention, by dividing the coal supply to the wet mill into multiple stages, a coal slurry with a wide particle size distribution width that can provide low viscosity even under high concentration can be produced. It becomes possible to produce the coal-water slurry using fewer additives and with lower power, which can significantly reduce the production cost of the coal-water slurry.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the influence of coal concentration on coal pulverization efficiency, FIG. 2 is a diagram explaining the effect of the two-stage feeding method adopted in the present invention, and FIG.
FIG. 4 is a system diagram of a two-stage coal supply wet pulverizer suitable for carrying out the present invention. FIG. 4 is a system diagram of another two-stage coal supply wet pulverizer suitable for carrying out the present invention. 1, 1A, 1B... bunker, 2, 2A, 2B... feeder, 3, 3B... wet mill, 4... supply pipe, 5,
5B...Slurry adjustment tank, 6...Pump.

Claims (1)

[Claims] 1. A method for producing a coal-water slurry by supplying coal to a wet mill and pulverizing it, characterized in that the supply of the coal is divided into multiple stages. Method for producing coal-water slurry. 2. The method of reducing viscosity according to claim 1, characterized in that the coal is fed in multiple stages so that the coal concentration in the final coal-water slurry is 60 to 80% by weight. Method for producing highly concentrated coal-water slurry.