JPS633095A - Wet production of highly concentrated coal-water slurry - Google Patents

Abstract

PURPOSE:To obtain a highly concentrated coal-water slurry free from coarse particles in high efficiency, by successively reducing the intervals between the partition walls of a plural of grinding chambers in a wet ball mill and average particle sizes of the corresponding grinding media as the grinding proceeds. CONSTITUTION:Coal, water and a dispersant are fed through one end of a wet ball mill 1 partitioned into a plural or grinding chambers C1-C5 by partition walls. Where, grinding media in the respective grinding chambers C1-C5 have been so packed that their average particle sizes one successively reduced in the direction of the exit of the ball mill according to the change in the coal particle size distribution associated with coal grinding process; in addition, intervals L1-L5 between the partition walls of said grinding chambers have been so formed that the ratio of the average particle size of the grinding media to the effective diameter of the ball mill keeps a specified value. Thus, the objective highly concentrated coal-water slurry can be produced through wet process. EFFECT:When said slurry is combusted, unburned carbon content in the resulting combustion residue can be reduced, thus enabling the emission of the NOx in combustion exhaust gas to be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wet method for producing a highly concentrated coal/water slurry that does not contain coarse particles.

[Prior Art] A highly concentrated coal/water slurry can be used not only for transportation and storage but also for direct combustion by fluidizing coal that is a solid fuel.

In general, it is an effective fuel because it can reduce ash and sulfur content.

When burning a highly concentrated coal/water slurry in a combustion device such as a power generation boiler, the combustion time is affected by the coal fuel ratio, ash content, particle size, oxygen concentration, fuel temperature, etc. If the residence time in the combustion equipment is not sufficient compared to the combustion time, unburned carbon will remain in the combustion residue such as fly ash that is discharged with the combustion gas, and the unburned This will result in a loss. Furthermore, when reducing the air ratio and lowering the combustion temperature to some extent in order to suppress NOx emissions in the combustion gas, the combustion time similarly increases.

In particular, when burning a highly concentrated coal/water slurry containing coarse particles, NO and X emissions in the combustion gas are observed due to an increase in the unburned carbon content in the combustion residue such as fly ash and an increase in the air ratio. It will be done.

Therefore, as a method for producing a highly concentrated coal/water slurry, it is a challenge to realize a wet method for producing a highly concentrated coal/water slurry made of fine particles that do not contain coarse particles. These are required to be realized economically.

Conventionally, this type of wet VAM method for a highly concentrated coal/water slurry involves adding appropriate amounts of water and a dispersant to coal from one end of a wet ball mill, as described in, for example, Japanese Patent Laid-Open No. 13887/1987. Grinding media of different diameters (steel poles) with large and small diameters
Coal is wet-pulverized to produce coal slurry by rotating multiple crushing chambers of a wet-type ball mill, each of which is filled with coal, and a high-S degree coal/water slurry is wet-manufactured.

[Problems to be Solved by the Invention] However, in the conventional wet manufacturing method of highly concentrated coal/water slurry described above, it is not possible to produce a highly concentrated coal/water slurry that does not contain coarse particles using a simple manufacturing method. The problem was that it was difficult.

That is, the first and second crushing chambers are filled with crushing media of different diameters, large diameter and small diameter, respectively of the wet ball mill, and the rotation of the wet ball mill wetly crushes the coal to form a highly concentrated coal/water slurry. However, part of the coal supplied in the wet ball mill and part of the coal that has been crushed collide with the grinding media, and flow out of the wet ball mill without sufficient grinding action, resulting in coarse particles. This results in a coal slurry containing Particularly, in the process of producing highly concentrated coal/water slurry with a coal concentration of approximately 60% by weight or more, the viscosity of the coal/water mixture tends to increase as the pulverization process progresses. If the particles are not sufficiently dispersed between the grinding media and the coal/water mixture system, collisions between the coal and the grinding media, sufficient grinding and mixing actions such as grinding are inhibited, and coarse particles are formed. This has the disadvantage that the coal/water slurry moves on the surface of the coal/water slurry, promoting the outflow of coarse particles from the wet ball mill as described above, and producing a highly concentrated coal/water slurry containing coarse coal particles. .

The present invention solves these conventional problems,
It is possible to wet-produce a highly concentrated coal/water slurry that does not contain coarse particles, and when it is fed to a combustion equipment and burned, it is an excellent high-concentration coal that has a small amount of unburned carbon in the combustion residue and can suppress the NOx emission temperature. - Provides a wet manufacturing method for water slurry.

[Means for Solving the Problems] In order to achieve the above object, the present invention supplies coal together with water and a dispersant from one end of a wet ball mill that is divided into a plurality of crushing chambers by partition walls, and crushes the coal. The average particle size of the grinding media, which has a particle size distribution that corresponds to the particle size as the process progresses, is sequentially reduced from the inlet to the outlet of the wet ball mill, and is filled into each grinding chamber, and the partition wall of the grinding chamber is The interval is formed to maintain a predetermined ratio between the average particle size of each grinding medium and the effective diameter of the wet ball mill.As the grinding progresses due to the rotation of the wet ball mill, the movement of the grinding medium due to the partition wall of the grinding chamber is controlled. The coal is wet-pulverized by adding it sequentially.

[Function] The present invention has the following effects due to the above configuration.

That is, when coal is supplied together with water and a dispersant from one end of a wet ball mill, the coal is pulverized as the wet ball mill rotates, and as the coal pulverization progresses, a particle size distribution with an average particle size corresponding to the particle size of the coal is created. Coal was packed in a state in which grinding media with different average particle sizes were filled in each grinding chamber in the longitudinal direction of the wet ball mill, with the average particle size decreasing sequentially from the inlet to the outlet of the wet ball mill. The coal is wet-pulverized while sequentially moving through each crushing chamber, and as the pulverization of the coal progresses, the viscosity of the coal/water mixture system gradually increases. A shear force is applied to the grinding media by the partition walls on both sides of the mill, causing the grinding media to move, and is roughly added to the movement of the grinding media along the mill liner as the wet ball mill rotates. is sufficiently dispersed between the crushing media and the coal/water mixture system, and active and sufficient crushing and mixing actions, including collision and grinding between the coal and the crushing media, are carried out.
Even under high viscosity conditions, coarse particles of coal are prevented from flowing out from the wet ball mill, resulting in significant improvements in crushing efficiency and performance.
A water slurry can be produced, and when it is supplied to a combustion device and combusted, it is possible to reduce the amount of unburned carbon remaining in the combustion residue, and to suppress the NOx emission concentration in the combustion exhaust gas.

[Example] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In Figures 1 and 2, 1 indicates a wet ball mill, and 2
3 is the body of a wet ball mill, and 3 is a mill liner provided on the inner wall surface of the body 2.

4 is the inlet of the wet ball mill, and 5 is the outlet of the wet ball mill. Inside the wet ball mill 1, there are a plurality of partition walls P+ and P2 in the longitudinal direction.

P3. A plurality of crushing chambers C+,
It is divided into C2, C3, C4, and C5.

The length of each grinding chamber, that is, the interval between the partition walls of the grinding chamber, is expressed by the distance between their center lines, and is L+.

L2. L3. L4. In each of the grinding chambers C1 to C5 from the inlet 4 to the outlet 5 of the wet ball mill 1, the interval is gradually reduced.

Each of the crushing chambers C1 to C5 is filled with a crushing medium 8, but the particle size distribution and average particle size of the crushing medium 8 are different in each of the crushing chambers C+ and C2.

Particle size distribution of the grinding media 8 from the inlet to the outlet of the wet ball mill 1 as C3, C4, and C5.

The average particle size is gradually reduced.

That is, the grinding chamber C1 on the inlet side 4 of the wet ball mill 1 is filled with a grinding medium having a particle size distribution with a large average particle size, and the grinding chamber C5 on the outlet side 5 has a particle size distribution with a small average particle size. Similarly, the grinding chambers C2, C3, and C4 are filled with a grinding medium 8 having a particle size distribution in which the average particle size becomes a ratio in order. Thus, the aforementioned division of the grinding chambers prevents the grinding media 8 filled in each of the grinding chambers C1 to C5 from moving from one grinding chamber to another.

In this way, each of the crushing chambers C1 to C5 can be reliably filled with the crushing media 8 having a particle size distribution in which the average particle size is successively reduced. As coal is wet-pulverized and pulverized, it is successively collided and crushed with a pulverizing medium that has a particle size distribution with an average particle size that corresponds to the particle size of the coal to be pulverized, which significantly improves the pulverizing efficiency of the coal. sell.

The wet ball mill 1 is configured to rotate around its axis m.

When coal, which is the raw material for the highly concentrated coal/water slurry, is supplied together with water and a dispersant at the required supply rates from the inlet 4 of the wet ball mill 1, the coal is subjected to a crushing action and pulverization progresses, and the coal is sequentially pulverized into the pulverizing chamber. C1, C2, C3,
While moving through C4 and C5, the coal is wet-pulverized, and as the coal pulverization progresses, the particle size becomes finer, and from the mill outlet 5, high-concentration coal with a coal concentration and coal particle size corresponding to the above-mentioned required supply rate is produced.・Water slurry is produced,
be discharged.

FIG. 2 is a sectional view taken along the knee I line shown in FIG. 1, and the wet ball mill 1 is rotated in the direction of arrow A.

8 is a grinding medium, and as the mill rotates 10 times, the grinding medium 8 is lifted upward along the liner 3 and rises.
- After reaching a certain height, it falls due to the action of gravity. When the coal falls, it exhibits a violent cloth-like appearance, and an impact action and a grinding action are performed between the grinding medium 8 and the coal, and the coal is ground. 7 is a slit provided in each partition wall, and since the width of the slit is narrower than the diameter of the grinding medium 8, the grinding medium is prevented from moving to the adjacent grinding chamber, and only the coal slurry is allowed to flow through the partition wall. It passes through the slit 7 and is discharged from the mill outlet 5. Note that D indicates the effective diameter of the wet ball mill 1.

FIGS. 3(a) and 3(b) show the relationship between the interval between the partition walls of each grinding chamber of the wet ball mill 1 and the shear force acting on the grinding medium by the partition walls.

Figure 3(a) shows the partition wall Pi on both sides of an arbitrary grinding chamber.
, Pi+1 shows a case where the interval L13 is appropriate,
FIG. 3(b) shows a case where a similar interval "+1" is not appropriate.

In either case, the horizontal axis corresponds to the body 2 of the wet ball mill, and h indicates the height of the partition walls P. and Pi+1, respectively.

In FIG. 3(a), the shear force curve Si acting on the grinding medium on the partition wall Pi is shown.
The shear force curve acting on the grinding media at +1 is Si+
It is shown as 1. Also, shear force curve S5. are the respective shear force curves Si.

This is a composite curve of Si layer 1.

The value of the shear force reaches its maximum value at the position where the grinding medium contacts and is close to the partition walls P, P1+1, and
, Pi+1. Similarly, in FIG. 3(b), the respective shear force curves are Si, Si, and 1, and the composite curve is shown as S51.

Combined shear force curves S and S5 in FIGS. 3(a) and 3(b). Looking at the shear force S acting on the grinding media, we see that in the case of Fig. 3(b), the distance Li between the partition walls Pi and Pi+1 is wider than 'is', and the distance between the partition walls P and Pi+1 is The resultant shear force at a position away from S5. has decreased significantly and has almost no effect.

The inventors have discovered that the distance between the partition walls of each grinding chamber can be formed to maintain a predetermined ratio between the average particle size of the grinding media filled in each grinding chamber and the mill diameter. - It was discovered that high grinding efficiency and grinding performance can be obtained in a water slurry production mill even under high viscosity conditions.

The above relationship can be expressed by the following equation.

Li≦di/ (aF〕+b) where, Li: Interval between partition walls (#) di: Average particle size of grinding media in each grinding chamber (m) 1
Weight-based arithmetic mean diameter D: wet ball mill effective diameter (or) a: constant, -1,092x10' b: constant, 0.01241 As mentioned above, coal is wet-pulverized while sequentially moving through each of the crushing chambers C1 to C5. As the pulverization of coal progresses, the viscosity of the coal/water mixture system gradually increases. The partition walls on both sides of the chambers C1 to C5 cause the grinding media to move due to the action of shear force, which significantly increases the movement of the grinding media.
Even under a high viscosity environment, coal is wet-pulverized at high pulverization speeds due to collision with the pulverizing media and grinding.

Generally speaking, in the wet pulverization process, the dispersion state in the coal/water mixed system shows that the local coal concentration and coal particle size are non-uniform, but the active movement of the pulverizing media takes place, and each pulverization As the coal moves sequentially through the chambers, it becomes uniform and a sufficient grinding and mixing action is performed, which significantly reduces the generation of coarse particles of coal even in a high viscosity environment and prevents it from flowing out of the wet ball mill. This makes it possible to produce a highly concentrated coal/water slurry that does not contain coarse particles.

A table comparing the data obtained from the experimental examples based on the above-mentioned embodiments with the data obtained when high-concentration coal/water slurry was produced using a wet ball mill according to the prior art and a wet ball mill according to the present invention is shown below.

As can be seen from the above data, a highly concentrated coal/water slurry that does not contain coarse coal particles is produced in the wet production of highly concentrated coal/water slurry, and its particle size is 174 Yanagi at the mill outlet. ai, o%, +150 Yanagi without requiring particularly excessive pulverization.

The generation of coarse particles is suppressed to 1.6%, and the n-value of the Rosin-Rammler equation, which indicates particle size distribution, is increased.・It has been shown that water slurry is being manufactured. Furthermore, it has been demonstrated that this wet manufacturing method can improve the grinding efficiency and grinding/mixing performance in slurry production, and can produce slurry of excellent quality with increased grinding efficiency in terms of power consumption. ing.

When the highly concentrated coal/water slurry is supplied to a combustion device such as a boiler and burned, it is possible to reduce the unburned carbon content in the combustion residue and to suppress the NOx emission concentration in the combustion exhaust gas.

In addition, the grinding chamber of the wet ball mill used in this invention,
Of course, the embodiments such as the partition wall and the type of grinding medium are not limited to those of the above-mentioned embodiments.

[Effects of the Invention] As is clear from the above-mentioned examples, the present invention enables sufficient pulverizing and mixing action to be performed by activating the movement of the pulverizing media in a wet ball mill during the wet production of highly concentrated coal/water slurry. Therefore, it is possible to produce a highly concentrated coal/water slurry that does not contain coarse particles with good pulverization efficiency and pulverization performance, and when used in a combustion device to burn it, it improves combustion efficiency and suppresses NOx emissions. It can have a great effect of improving the

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a wet ball mill used in a wet manufacturing method for highly concentrated coal/water slurry according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line 'I knee I, and FIG. FIG. 3 is an explanatory diagram of the first fixed part. 1... Wet ball mill 8... Grinding media C+
, C2, C3, C4, Cs...Crushing chamber L1. L2
, L3. L4. L5... Spacing between partition walls Fig. 1 1... Humidity vc7: - Lumir C1, C2, C3, C4, C5... Grinding chambers Ll, L2
．． L3. L4. L5...Discovery of partition costs Figure 3

Claims (1)

[Claims] Coal is supplied together with water and a dispersant from one end of a wet ball mill divided into multiple grinding chambers by partition walls, and the average particle size of the grinding media has a particle size distribution having an average particle size according to the particle size as the coal grinding progresses. is sequentially reduced from the inlet to the outlet of the wet ball mill to fill each grinding chamber, and the distance between the partition walls of the grinding chamber maintains a predetermined ratio between the average particle size of each grinding medium and the effective diameter of the wet ball mill. A highly concentrated coal/water slurry characterized in that the coal is wet-pulverized by sequentially adding movement of the crushing media by the partition wall of the crushing chamber as the crushing progresses by the rotation of the wet-type ball mill formed to Wet manufacturing method.