JPS6072993A - Apparatus for producing coal/water slurry - Google Patents

Abstract

PURPOSE:To form a slurry which has a high concn. and a low viscosity, by using a ball mill having a specified form in the production of a coal/water slurry by a wet crushing process using a continuous ball mill. CONSTITUTION:Coal A having a particle size of 5mm. or below is fed from a coal bunker 1 through a feeder 2 to a ball mill 3, where the coal is mixed with water B and an additive C fed through a pipe 4 and crushed. The resulting coal/water slurry is continuously transferred through a tank 5 and a pump 6 to the subsequent stage. When a ball mill having a ratio of L/D (wherein D is diameter, L is length) of 2 or below (pref. 1<=L/D<=1.8) is used as said ball mill 3, a coal/ water slurry having a high concn. and a low viscosity (coal concn.: 65-80wt%, viscosity: 2,000cp or below) can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing coal-water slurry, and more particularly to an apparatus for producing highly concentrated coal-water slurry by wet-pulverizing coal using a continuous ball mill.

In recent years, against the background of the world energy situation, oil, LNG,
Coal, which has abundant reserves and is inexpensive, is once again being looked at as an alternative fuel to fluid fuels such as LPG. however,
Since coal is solid, it has the disadvantage of being difficult to handle during storage and transportation. As a technology to overcome this problem, the use of fluidized coal has recently been considered. One example is COM (C), which is a mixture of coal and oil.

a 1-Oi I Mixtures) and coal-water slurry CWM (Coal-Water Mixtures)
- or CWS (Co a l -Water
Slurries). COM has an oil dependence rate of 5.
There is a problem with economic efficiency between 0 and 60%, and coal-water slurry (
Currently, CWM (hereinafter referred to as CWM) is attracting attention.

The conditions for direct combustion and pump transportation of this CWM are 74 p m 11! Semi-fluid (, JISZ88
01) has a fineness that allows about 60 weight percent or more of the coal particles in the CWM to pass through, and the coal concentration in the CWM is high, about 60 weight percent or more, and the viscosity of the CWM is about 2. 06Qcp or less. To achieve this, (1) adjust the particle size distribution to a wide range, increase the packing density, and achieve high concentration of -ζ;
2) It is necessary to add additives such as appropriate dispersants and pH adjusters to adjust the surface potential of the particles, thereby repelling the particles and stably dispersing them to reduce viscosity.

When continuously manufacturing such high concentration CWM, a wet ball mill is generally used.

FIG. 1 is an explanatory diagram showing the configuration of an apparatus for manufacturing CWM using a general wet ball mill. A ball mill basically consists of a horizontally rotating cylinder filled with cast iron balls, and as the mill rotates, the balls are lifted along the inner wall and allowed to fall freely or roll down the surface of the contents. At this time, the coal particles are caught between the balls or between the balls and the inner wall of the mill, and are crushed by friction or impact. In Fig. 1, coal A, which has been coarsely crushed to about 3 to 5 yen or less, is adjusted together with an additive liquid (water B and additive C) so that the coal concentration is about 60% by weight or more, and is placed in a coal bunker. 1 to the inlet of a ball mill 3 by a feeder 2, and in the mill 3, the coal particles are crushed and mixed as described above, and the amount passing through a 74 μm standard sieve is about 60-85% by weight, the viscosity is about 100-2, 0
CWM of approximately 00 cp is produced and discharged from the outlet of mill 3. Note that 4 is a supply pipe line for the additive liquid.

Generally, once the grinding capacity of a ball mill is determined, how to determine the mill size and length becomes important. However, according to the inventors' study, the crushing capacity. The relationship between , mill diameter, length and volume is expressed by the following formula.

QCCVI)'°3～0・5 π 20. J-tr, f +1) (--D LD Therefore, when the mill diameter or length L is determined, the other is uniquely determined, so it is necessary to take this point into consideration when determining L/D.L/D 99% of the crushed material is 88μ
Cement finishing mills that require ultrafine grinding such as passing through a standard sieve use mills with an L/D of 2.5. (“On-site experience of operating a 3500kw closed circuit ball mill”, Proceedings of Symposium on Crushing, Grinding and Their Applications 1, Society of Materials Science, Japan, 1982), and CWM
L/D-2 to 3 for fine crushing when manufacturing or COM
mills are used. For CWM, (Coal-
Water 5lurry as Utility Bo
iler Fuel, EPRI-C3-2287, Ma
Technic for rch, 1982, COM
al Re5ults of EPDC's COM
R&D.

5TEPI Laboratory Te5ts.

(See M a r c h 197 B).

Furthermore, since fine coal particle size is required as a necessary condition for CWM, the conventional general idea is to increase the length of the mill (increase L/D) in order to increase the residence time. The idea was that

In fact, according to the conventional example, the coal grindability index (JIs 2
8801), using coal with HGI = 50, coal concentration 7
As equipment for manufacturing 0 weight percent CWM at 100 kg/h, 570 dragon φ x 1.710 dragon L (L/D=
If the ball mill of 3) is selected and pulverized so that the amount passing through the 74 μm standard sieve is 70% by weight, the slurry concentration is 69% by weight and the viscosity is 2-. 400cp
(See the conventional example in Table 1 below), and H
Coal with GI≦50, at a high concentration of 70 weight basis liters or more, and with a viscosity of 2. It is very difficult to produce a CWM of less than OO'Ocp, and as mentioned above, it is unsuitable for direct combustion. Generally, most of the coal used in power plant boilers has a grindability index (HGI) of around 50, so in order to put CWM into practical use, it is necessary to establish technology that can economically produce CWM with higher concentration and lower viscosity. is desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a coal-water slurry that eliminates the above-mentioned drawbacks of the prior art and provides CWM with high concentration and low viscosity.

In short, the present invention manufactures CWM with high concentration and low viscosity by adjusting a wider particle size distribution than in the prior art by selecting a ball mill with a length-to-inner-diameter ratio of less than 2. This is what makes it possible.

Embodiments of the present invention will be described below using the general device configuration shown in FIG.

In FIG. 1, the ball mill 3 has an L/D of 1
The structure is the same as the conventional one except that ≦L/D<2, preferably 1.2 to 1.99. Inside the mill,
For example, no more than about 75 to 501 poles are filled.

A slurry tank 5 is arranged at the outlet of the mill 3, and the CWM is discharged from this tank 5 by a slurry pump 6 to the next process. Coal that has been coarsely crushed to about 5 mm or less is fed from bunker 1 to mill 3 via feeder 2. Additives (surfactant and
The H adjuster) liquid is supplied to the mill 3 from the additive liquid supply pipe 4 so that the coal concentration becomes a predetermined value. The coal particles are efficiently pulverized and mixed in the ball mill 3, and the coal concentration is approximately 65%.
~80 weight percent I- with a viscosity of about 2. ．． 0OOcp
The following CWM is produced and discharged continuously from the outlet of mill 3.

Based on the above embodiment of the present invention, using a ball mill (L/D = 1.92) with an inner diameter of 650 +n and a length of 1.250 mm, coal of HGI 50 was processed using a slurry concentration of 70 M volume percent and a 74 μm standard sieve passing amount of 70 mm. The experimental results when pulverized to weight percent are shown in Table 1 as Example 1. For comparison, the table also shows the results of a conventional operation using a ball mill with an inner diameter of 55011111 and a length of 1650 va (L/D=3>).

Moreover, the viscosity distribution of the obtained slurry is shown in FIG.

In the figure, 11 indicates Example 1 of the present invention, and 10 indicates the conventional method.

Table 1 in the margin below ■ As is clear from the table, even though the coal concentration in the slurry was increased by 1% by weight, the viscosity was reduced to 65'.
It was possible to lower the OCp. This is because, as shown in Figure 2, when milling to a 14 pm standard sieve passing rate of 70% by weight, the present invention provides a wider particle size distribution than the conventional method, resulting in a particle packing density. This is because the amount increases and high concentration and low viscosity are achieved.

In order to explain the results, we conducted the following study. For the above two mills, 1-racer was dissolved in 50 cc of additive liquid, this additive liquid was introduced into the mill inlet for a short period of about 1 second, and 9 samples were taken intermittently at the mill outlet. , the tracer concentration was analyzed and the residence time distribution in the mill was determined. Figure 3 shows the residence time distribution of trays in the mill.The horizontal axis shows the dimensionless time, which is the elapsed time divided by the average residence time, and the vertical axis shows the frequency of discharge from the mill. ) 1- has been done. From Figure 3, the L/D of the conventional method
= 3, the residence time distribution 13 in the mill is close to the extrusion flow (piston flow) distribution 16, and L/D =
It was found that the mill residence time distribution 14 of 1.92· is close to the distribution 15 of complete mixing (Chemical Engineering IV, 991-9
4. Tokyo Kagaku Doujin, 1965).

In addition, when we actually measured the residence time distribution of a mill with L/D = 2.1, it was the same as 15 in the case of complete mixing in Figure 3, and L
It was found that the residence time distribution rapidly approached the extrusion flow when /D = 1.92 to 2.1. Also, a mill with L/D=1 (800111=diameter×8001IIl
When the residence time distribution of the sample (long) was measured, it almost coincided with the distribution 15 for complete mixing in FIG.

A similar test was performed with L/D = 0.82 mil (850 - Yu 1
As a result, the residence time distribution was almost complete mixing, but the proportion of coarse particles discharged increased. When CWM is used as boiler fuel, L/
In any case where D is different, it is necessary to remove coarse particles with a strainer or the like and recirculate coarse particles with a size of 500 to 840 μm or more to the mill.

When L/D=0.8, the coarse particles increased to 5-10%, which is not preferable (, s Kotokawa power 1) ko.

The number of times a particular coal particle is crushed in a mill is proportional to the residence time of the other particles. Therefore, for example, in the mill with L/D=1.92 in the embodiment of the present invention,
In order to approach a pattern of complete mixing, both the particles exit the mill earlier than the average residence time (,s) and the particles that remain in the mill longer than the average residence time and are exposed to more grinding opportunities. L/D = 3, which is close to the piston flow of the conventional method
It was found that the number of times of 15) was higher than in the case of Mill. Therefore, the particle size distribution of coal particles discharged from the mill with L/D = 1.92 in the embodiment of the present invention is different from that of the conventional method with L/D = 1.92.
The width is wider than the -3 mil. As previously mentioned,
One of the conditions necessary to produce CWM with high concentration and low viscosity is to obtain a wide particle size distribution. It has become clear that a mill with a large flea and a short length is suitable. From the above-mentioned inspection results, the range of L/D in the present invention is L/D<2, preferably 1≦L.
/D≦1.99, more preferably 1≦1. /D≦1.
It is 8.

Next, FIG. 4 shows an example of a process for producing high concentration CWM with lower viscosity and lower cost I. using a wet ball mill. In FIG. 4, the ball mill 3 is
A feeder 2 for supplying raw coal is connected to the inlet of the ball mill 3, which is 2-nitrided by installing a porous partition plate 7 and has a ratio of length L to mill inner diameter smaller than 2. A tube 4 is introduced into the first chamber of the mill 3 from the inlet of the mill 3. The first chamber of the mill 3 is filled with balls with a large diameter, and the second chamber is filled with balls with a small diameter, and a second additive liquid supply pipe 8 is introduced from the outlet side of the mill 3. has been done. A slurry tank 5 is installed below the outlet of the mill 3, and a pump 6 for transporting slurry is connected to the tank 5.

The coal, which has been coarsely ground to about 10 mm or less, is fed in a fixed amount from the feeder 2 to the mill 3. Coal concentration is approximately 70 to 85% by weight, additive amount is approximately θ to 0 relative to coal (dry coal standard)
．． Water and additive liquid are adjusted and fed to the first chamber of mill 3 at 3 weight percent. In the first chamber, the particles are crushed in a more concentrated atmosphere and by large-diameter balls, resulting in a wider particle size distribution. Naka(”su J#F
The slurry that has passed through steps i and 7 is efficiently crushed by small-diameter balls in the second chamber, and adsorbed onto the particle surface by the newly added additive liquid.
High concentration and low viscosity CWM can be produced. In this example, the additive is added as new particle surfaces are generated by pulverization, and the additive is added in two stages so that it is evenly and wastelessly adsorbed onto the particle surfaces, so the total addition The amount of drug can be significantly reduced. Implementation 912 in Table 1 and 12 in FIG.
The results of pulverizing coal in a ball mill with a diameter of 50 fi and a length of 1,250 m to produce a high-concentration CWM with a final slurry concentration of 7 Off volume percent and an appropriate amount of 70 weight percent passing through a 74 μm standard sieve are summarized in the conventional method and the first method of the present invention. This is a comparison with the example. As can be seen from these results, according to this example, the coal crushing capacity was increased by about 7% compared to the conventional method, and the amount of additive used was 40% higher than that of the conventional method.
%, it can be seen that the viscosity can be reduced by as much as 1.0 00 c p, and the particle size distribution is wider than that of the conventional method.

According to the present invention, by using a ball mill in which the ratio of the length L to the mill inner diameter is smaller than 2, in particular L/D<2, a low viscosity high concentration coal-water suitable for direct combustion is used. Slurry can be produced efficiently and with the amount of additive liquid reduced to less than half.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a high concentration coal-water slurry manufacturing apparatus according to the conventional method and the first embodiment of the present invention, and Fig. 2 is an explanatory diagram showing a comparison of CWM manufacturing test results according to the conventional method and the present invention. ,
FIG. 3 is an explanatory diagram showing the residence time distribution of particles in a ball mill, and FIG. 4 is a system diagram of an apparatus showing another embodiment of the present invention. ■... Coal bunker, 2... Feeder, 3... Ball mill, 4... Additive liquid supply pipe, 5... Slurry tank, 6... Slurry pump, 7... Porous Intermediate 9J board, 8...Additive liquid supply pipe. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] (1) In a coal-water slurry production apparatus for wet-pulverizing coal using a continuous ball mill to obtain a highly concentrated coal-water slurry, a length L) relative to a diameter (D) of the ball mill is provided. A coal-water slurry manufacturing apparatus characterized in that the ratio (L/D) is in the range of L/D<2. (2. In claim 1, the L/Dt-
A coal-water slurry manufacturing apparatus characterized in that the range is 1≦L/D≦1.99. (3) In claim 1, the L/D is 1
Coal characterized by having a range of ≦L/D≦1.8.
Water slurry production equipment. (4) The coal-water slurry manufacturing apparatus according to claim 1, wherein the mill is a multi-chamber mill divided into two or more chambers.