JPH0741778A - Production of highly concentrated coal-water slurry - Google Patents

Abstract

PURPOSE:To reduce the unit quantity of power of the mill required for producing a highly concentrated coal-water slurry by grinding coal in a wet ball mill and to produce a coal-water slurry having higher concentration and lower viscosity. CONSTITUTION:In a process for producing a highly concentrated coal-water slurry by feeding coal in order under conditions of a coal concentration of at least 60wt.% into two chambers of a ball mill filled with balls of a larger diameter and those of a smaller diameter respectively to effect wet grinding, the ball mill is operated at a rotational speed of 50-64% of the critical speed. A highly concentrated coal-water slurry reduced in viscosity by at least a few hundred cP can thereby be produced with high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-concentration coal-water slurry, and more particularly to a method for producing a coal-water slurry using a wet ball mill.

[0002]

2. Description of the Related Art Coal, which is a solid fuel, is difficult to handle for storage and transportation, but if it is slurried with water, it can be easily handled. According to the study of the present inventors, the condition of the slurry that is stable and can be directly burned is that the particle size is 20.
The amount of 0 mesh passing is about 70% by weight, the coal concentration is about 60% by weight or more, and the viscosity is about 2,000 cp or less. For that purpose, it is necessary to (1) prepare a wide particle size distribution, increase the packing density to achieve a high concentration, and (2) reduce the viscosity by adding an appropriate additive.

When continuously producing such high-concentration coal-water slurry, a wet ball mill is generally used. The ball mill basically consists of a horizontal rotating cylinder. The inside is filled with steel balls of 75 to 50 mm or less, and by rotating the mill, the balls are lifted along the inner wall of the mill, tumbled down, and impact crushed coal. To do. At this time, the coal particles are sandwiched between the balls or between the balls and the inner wall surface of the mill, and are crushed by the impact. If a typical typical operation example is shown, coal roughly crushed to a size of about 5 mm or less has a coal concentration of about 60 together with a surfactant solution.
It is supplied to the inlet of the mill after being adjusted to have a weight percentage of not less than, flows toward the outlet of the mill while being pulverized and mixed in the mill, and has a 200-mesh passing amount of about 60 to 85% by weight and a viscosity of about 100 to. A coal-water slurry of about 2,000 cp is produced and discharged from the overflow type outlet of the mill. At this time, the rotation speed of the mill is generally about 65 to 80% of the critical speed (the speed at which the balls rotate with the mill along the wall of the mill due to the balance of centrifugal force and gravity). Here, the critical velocity Nc is defined by the following equation.

Nc = 42.3 / √ (D−d) rpm where D is the mill inner diameter (m) and d is the ball diameter (m). Generally, the optimum rotation speed of a dry-milling or wet-milling ball mill is recognized to be 65 to 80% of the critical speed (for example, RH Perry and CH Ch.
ilton, Chemical Engineers'
Handbook, 5th Edition, p. 8-
26, McGrow-Hill Book Co. 1
973).

[0005]

However, according to the studies made by the present inventors, at the above-mentioned rotation speed, the production capacity of the coal-water slurry is low, the power consumption is high, and the viscosity is lower. I found that I could not get it. An object of the present invention is to reduce the power consumption of the mill when pulverizing coal with a wet ball mill to produce a high-concentration coal-water slurry, and obtain a high-concentration and low-viscosity high-concentration coal-water slurry. It is to provide a manufacturing method of.

[0006]

SUMMARY OF THE INVENTION The present invention uses a two-chamber ball mill filled with a large-diameter ball and a small-diameter ball, respectively. Coal is sequentially supplied to the two-chamber ball mill under conditions of a coal concentration of 60% by weight or more. In the method for producing a high-concentration coal-water slurry, the ball mill is operated at a rotational speed of 50 to 64% of a critical speed when the high-concentration coal-water slurry is supplied by wet grinding. is there.

[0007]

EXAMPLES The present invention will now be described in more detail with reference to examples. FIG. 1 shows an embodiment of an apparatus for producing a high-concentration coal-water slurry using a wet ball mill at a lower cost. In this apparatus, a raw coal feeding feeder 2 is connected to an inlet of a mill 1 having two compartments such as a screen having a partition plate 8 installed therein, and a water feeding pipe 3 and an additive liquid feeding pipe. 4 is introduced into the first chamber through the mill inlet. The first chamber of the mill 1 is filled with large diameter balls, the second chamber is filled with small diameter balls, and the additive liquid supply pipe 5 is inserted in the second chamber. A slurry tank 6 is installed immediately below the mill outlet, and the slurry is transported from the tank 6 to the next step by a pump 7.

In the apparatus having the above construction, the raw coal roughly crushed to about 10 mm or less is quantitatively supplied from the bunker 3 to the mill 1 by the feeder 2, and the coal concentration is about 75 to 85% by weight.
Water and the additive liquid are adjusted and supplied to the first chamber of the mill 1 so that the amount of the additive is 0 to 0.3% by weight. In the first chamber, since it has a higher concentration and is crushed by a large diameter ball,
A wider particle size distribution coal slurry containing finer powder is produced. The slurry that has passed through the screen 8 is efficiently pulverized in the second chamber by the small-diameter balls, and at the same time, the viscosity of the particles is lowered by efficiently wetting the surface of the particles with the newly added additive liquid. In this apparatus, in particular, by operating the ball mill at a rotation speed of 50 to 64% of the critical speed, it is possible to further achieve cost reduction, higher slurry concentration, and lower viscosity than ever before.

[0009]

As described above, according to the present invention, when a high-concentration coal-water slurry is produced by a high-concentration wet grinding method with a coal concentration of 60% by weight or more, a ball mill filled with balls having different diameters. , The critical speed of 50-6
By operating the ball mill at a rotation speed of 4%,
It is possible to reduce the viscosity of the slurry by several hundreds of cp or more and to manufacture a high-concentration coal-water slurry with high efficiency.

[Brief description of drawings]

FIG. 1 is an explanatory view of a coal-water slurry manufacturing apparatus showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ball mill, 2 ... Feeder for raw coal supply, 3 ... Raw coal bunker, 4, 5 ... Additive liquid supply pipe, 6, 7 ... Slurry tank, 8 ... Partition plate.

Claims (1)

[Claims] 1. Using a two-chamber ball mill filled with a large-diameter ball and a small-diameter ball respectively, coal is sequentially supplied to the two-chamber ball mill under conditions of a coal concentration of 60% by weight or more, and wet pulverized to obtain high A method for producing a high-concentration coal-water slurry, which comprises operating the ball mill at a rotation speed of 50 to 64% of a critical speed when producing a high-concentration coal-water slurry.