JPS6013890A - Production of coal-water slurry having high concentration and lowered viscosity - Google Patents

Abstract

PURPOSE:To obtain a coal-water slurry having low viscosity and high concentration, at a low cost, with improved pulverization efficiency, by supplying the coal to a wet mill dividedly in plural stages. CONSTITUTION:The coal in the bunker 1 is supplied through the feeder 2 to the mill 3, and pulverized in the presence of water and an additive to obtain a slurry having a coal concentration of usually 40-70% (preferably 50-60%). The slurry is mixed with the coal supplied from the bunker 1A through the feeder 2A at a ratio to give a coal concentration of usually 60-80%, and the mixture is further pulverized to obtain the objective coal-water slurry.

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 an active 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 prices. 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 (Coal), which is a mixture of heavy oil and coal.
and O3l Mixture) are known.

However, in this case, the weight ratio of heavy oil to coal is generally about 1:
Since it is a mixture of 1, it cannot be said to be a complete blood-free oil fuel.
There are few merifts in terms of price. Also, so-called Mekkol, which is a mixture of methanol and coal, is known.
This method is also expensive because it uses expensive methanol, and has not yet reached the practical stage.

In contrast, CWM (Co
(Al and Water Mixture) It is quite practical in terms of price and has been attracting attention recently. However, CWM has a problem in that if the proportion of water contained is high, the thermal efficiency during combustion decreases, and conversely, if the proportion of moisture contained is low, the viscosity of CWM increases and pressure loss during transportation becomes large.

Furthermore, since CWM is composed of coal particles and water, there is also a storage problem in that the coal particles settle and separate from the water over time. In order to eliminate these drawbacks, attempts have been made to produce CWM with low viscosity and good stability even at high coal concentrations by adjusting the particle size of coal particles.

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 method of pulverizing coal into such a particle size distribution is generally 60 to 80% (wt%, same hereinafter).
A high-concentration wet pulverization method is known in which coal is pulverized under a high concentration of .

However, when the coal concentration is high (the viscosity of the slurry also increases, the problem of reduced pulverization efficiency, or in other words, an increase in power consumption in the mill) becomes unavoidable.In addition, in the high-concentration wet pulverization method, the pulverization In order to promote this, it is necessary to add additives such as surfactants, but since the required amount of additives reaches approximately 1% per coal, the influence on the production cost of CWM cannot be ignored.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a method for manufacturing CWM with low viscosity and good stability even under high concentration without increasing production cost. It is about providing.

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. That is, first, the diameter is 650 mm, and the diameter is 1250 m.
hard glove index (HG) using a m-long tube mill
I, JIS-M8801) 52 bituminous coal (hereinafter referred to as A coal) is crushed and the bond at that time is
When we looked at the relationship between the work index Wi [see formula (1) below] and the coal concentration, we obtained the results shown in Figure 1, and at that time, F
go was 2830 μm, Pso = 105 am.

Wi (Kwh/1on) (where F1a is the sieve opening (μm) when 80% of the raw coal passes through, p8o is the sieve opening (μm) when 80% of the crushed material passes through) ] As is clear from Figure 1, when pulverizing coal A, the pulverizing efficiency sharply decreases (Wi increases) when the coal concentration exceeds 60%.
It can be seen that it is preferable to grind at the following concentration. 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 the above pulverization was carried out with an average residence time of 1 hour, raw coal was added separately to make the coal concentration 70%, and further pulverization was carried out (A (two-stage feeding method)). Case B when simply pulverized in 1 hour (1-stage feeding method)
When the coal particle size distribution in each of the obtained slurries was calculated, the results shown in Figure 2 were obtained. From Figure 2, we can see that the two-stage feeding method B has a wider particle size distribution (and therefore lower slurry viscosity) than the one-stage feeding method A.

Furthermore, it can be seen that the average particle size and the above-mentioned pso are smaller in the two-stage feeding method B, and the grinding efficiency is also improved. 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%. The coal-containing slurry obtained by the above pulverization is then mixed with coal supplied via bunker IA and feeder 2A to a predetermined coal concentration (generally 6
0 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) is supplied, and this is passed through the supply pipe 4.
Coal concentration 60 in the presence of water and additives supplied from
%, crushed with an average residence time of 1 hour, after which the coal concentration was 7
Coal was fed from the feeder 2A so that the amount of coal was 0%, and the powder was further crushed until particles of Pgo #105 μm were obtained. The work index Wi at this time is 41 (Kwh/t
on), and this value assumes that the coal concentration is 70% from the beginning.
Wi=50 (Kwh/1on
) was significantly lower. In addition, the slurry viscosity is 1.500 cp in the case of the former two-stage feeding method, and 1.500 cp in the latter case.
This value was lower than 1.5 oocp in the stage feeding method.

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 ash (hereinafter referred to as coal) with HGI=90.

However, in this example, the pulverization was initially performed at a coal concentration of 65%, and then coal was added until the concentration reached 75%.

The work index Wi when pulverized to Pso #105 μm is 5 B (Kwh/t o
n), whereas in two-stage supply, it is 49 (Kwh/1o
n), which was a low value. Further, the slurry viscosity at that time was 2.200 cp and 1°950 CI), respectively, and the effect of reducing the 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% per coal. The slurry viscosity at this time was 1,800 cp, and even though the amount of surfactant added was reduced,
A slurry with the same viscosity as when 0.7% surfactant was added using the stage feeding method was obtained.

Example 4 The coal used in Example 2 and bituminous coal with HGI = 36 (hereinafter referred to as
A mixture of C coal (referred to as C coal) at a weight ratio of 1:1 is supplied to the mill in one stage at a coal concentration of 70%, and this is Pso #10.
When crushed to 5 μm, the work index Wi was 58
The value was as high as (Kwh/t on). On the other hand, when a slurry was produced using the two-stage feeding method in the same manner as in Example 1 except that only coal C was initially pulverized at a coal concentration of 54% and then coal was added, the work index Wi was 45.
The value was as low as (Kwl/1on). In addition, when the two-stage feeding method was carried out in the same manner as above except for changing the feeding order of coal and C coal, the work index Wi was slightly higher than the above, but the value was as low as 50 (Kwh/t on). became.

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 characteristics even under high concentration can be produced in a small amount. It becomes possible to produce with the use of additives and with low power, which can significantly reduce the production cost of coal-water slurry.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the influence of coal concentration on coal pulverization efficiency, Figure 2 is a diagram explaining the effect of the two-stage feeding method adopted in the present invention, and Figure 3 is a diagram explaining the effect of the two-stage feeding method adopted in the present invention. FIG. 4 is a system diagram of a preferred two-stage coal supply type wet pulverization apparatus. FIG. 4 is a system diagram of another two-stage coal supply wet type pulverization apparatus suitable for carrying out the present invention. 1, IA, IB... bunker, 2.2A, 2B... feeder, 3.3B... wet mill, 4... supply pipe, 5
．． 5B...Slurry adjustment tank, 6...Pump. Figure 1 Figure 2 Grain 4 fleas (μm) Figure 3A Figure 4

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 coal supply is divided into multiple stages to produce a low-viscosity, high-concentration coal-water slurry. manufacturing method. (2. In claim 1, the coal is supplied in multiple stages so that the coal concentration in the coal-water slurry finally obtained is 60 to 80% by weight. A method for producing viscosity-enhanced highly concentrated coal-water slurry.