JPS6147197B2 - - Google Patents

Description

[Detailed Description of the Invention] [Prior Art] The present invention relates to a method for granulating coal for transporting slurry, and more specifically, in order to obtain a slurry that has both dewatering properties and stability when transporting coal as a slurry. This invention relates to a method for pulverizing coal and granulating and pelletizing it in a specific manner.

BACKGROUND ART Conventionally, as a method for transporting coal, a method has been known in which coal is finely pulverized, water is added thereto to form a slurry of an appropriate concentration, and the slurry is transported by pipeline.

Figure 1 is a typical process diagram of conventional coal slurry transportation. Coal 1 is pulverized in a pulverizer 2 to particles with a particle size of 1.5 mm or less and an average particle size of 0.1 mm, and then transported in a mixing tank 3 as a transportation medium. It is mixed with water to form a slurry, which is transported by pipeline 14 to the point of consumption. However, in order to prevent coal particles from settling in the pipeline and create a stable slurry, a particle size of 40
It is necessary to mix approximately 20% of pulverized coal of μ or less. However, although the stability of the slurry improves when it is included in pulverized coal, the dehydration properties of the slurry deteriorate, so it was necessary to pass it through an extremely powerful dehydration process at the place of consumption.

In the example shown in FIG. 1, the slurry sent through the pipeline 14 is separated into solid and liquid by the centrifugal separator 17.
Since pulverized coal is still suspended on the liquid side, it is passed through a thickener 18 and further purified by a wastewater treatment facility 21. The concentrated liquid leaving the thickener 18 is further concentrated in a drum filter 19, and then dried in a hot air dryer 20 together with the solids coming out of the centrifugal separator 17, and sent to the burner 16.

As described above, the method of directly turning finely pulverized coal into a slurry has poor dewatering properties, and in order to improve this, a wet granulation method at the point of consumption has been considered.

This wet granulation method aims to improve dewatering performance by producing granulated coal at the consumption site from pulverized coal slurry transported by pipeline. That is,
When a slurry of pulverized coal and a caking agent such as heavy fuel oil are supplied into a container and a propeller is stirred in the container to create turbulent motion, the caking agent selectively adheres to the pulverized coal and the caking agent This method takes advantage of the fact that wet pulverized coal comes into contact with each other and forms agglomerates (hereinafter referred to as pellets).

However, with this technology, the pulverized coal slurry must be continuously stirred until the cores of agglomerated coal are formed in the pulverized coal slurry in the container, and most of the power consumed is spent on power for stirring the slurry rather than granulation power. Ta. In addition, the nucleation of the coagulated coal was entirely coincidental, and the disadvantage was that it generally took a long time to form pellets.

Therefore, in order to reduce the dehydration power, pulverized coal is tumble-granulated at the coal producing area to produce pellets with a diameter of several mm.
It was considered that the pellets could be transported as a slurry.

However, in the conventional rolling granulation method using, for example, a disc or drum type dry granulator, pulverized coal is rolled in the presence of water and a binder to spread the binder onto the surface of the pulverized coal particles. However, since the pulverized coal particles are simply agglomerated, the resulting pellets lack strength and are likely to disintegrate during slurry transport, resulting in poor dehydration at the consumption site.

[Purpose of the invention]

Therefore, the present invention was made to solve the above-mentioned drawbacks of the conventional methods, and by forming pellets with excellent strength and water resistance in a short time at the coal producing area and transporting the pellets by pipeline, consumption can be reduced. The purpose is to facilitate the dewatering process on land.

[Structure of the invention]

That is, the method for granulating coal for slurry transportation of the present invention involves adding water and a binder selected from the group consisting of heavy oil, light oil, and kerosene to finely pulverized coal, and kneading the resulting kneaded product. Rolling granules are formed by rolling granules containing pellet cores formed from the finely pulverized coal, and water is added to the rolling granules to perform underwater granulation to remove the pellet cores. The method is characterized in that it is grown to produce pellets of the pulverized coal.

The present invention will be specifically explained below with reference to FIG.

FIG. 2 is a process diagram showing an embodiment of the present invention,
Coal 1 collected at a coal-producing area is finely pulverized by a pulverizer 2, and water 4 and a binder 5 such as heavy oil are added and mixed in a mixing tank 3.

The obtained mixture 6 is kneaded in a kneading machine 7, and the obtained kneaded product is tumble-granulated in a tumbling-type dry granulator 8. Then, rolling granules 9 containing pellet cores formed by coagulating several pieces of pulverized coal via a binder are produced.

Next, this rolling granulation material 9 is supplied to a wet granulator 10, and water 4 is added and stirred to perform underwater granulation. Then, the rolling granules 9 roll while being pressed against the wall of the wet granulator 10 by the centrifugal force caused by stirring, and the ungranulated pulverized coal particles agglomerate into the cores of the pellets that have already been formed. The kernels of this pellet then grow to form pulverized coal pellets.

In addition, when transporting the obtained pellets 11 as a slurry, it is mixed with water 4 in the adjustment tank 12, and water is added to adjust the concentration to a level suitable for pipeline transport.
For example, the pellets are adjusted to a concentration of 30 to 50% by weight and transported by pump 13 to the consumption area by hydraulic power. When the pellets are used for combustion at the consumption site, they are dehydrated using a screen 15. Pellets are water repellent and are easily dehydrated. When a conventional pulverized coal-fired burner 16 is used, the pulverized coal is re-pulverized to the required particle size using the pulverizer 2 and then combusted; when a fluidized bed boiler (not shown) is used, the pulverized coal is combusted in the form of pellets. can do.

The present invention includes the following aspects.

Coal can be pulverized by any known method, and the particle size is not particularly limited, but the usual range is about 5 mm to 200 mesh. The type of coal may be anthracite, bituminous coal, sub-bituminous coal, brown coal, etc., but bituminous coal is preferred. Heavy fuel oil is most commonly used as the binder, but light oil and kerosene may also be used.

The amount of water 4 and binder 5 added to coal 1 is 5-15 kg of water and 3-15 kg of binder per 100 kg of coal.
It is in the range of 10Kg.

As the dry granulator 8, a disk type or drum type dry granulator can be used as in the conventional one, and as the wet granulator 10, a propeller agitation type in a conventional container can be used. used.

The range of the amount of water 4 added in the wet granulator 10 is:
100 to 200 kg of water per 100 kg of coal.

The pellets obtained by the present invention have a particle size of several mm.
It is preferably in the range of 0.5 to 5 mm.

In addition, the composition of the pellets can be changed as appropriate depending on the amount of binder added and the operating conditions of the granulator, but when the strength of the pellets is at its highest, the apparent specific gravity is approximately 1.2 or less, and the coal particles of the same diameter (specific gravity
1.3-1.5), the sedimentation rate is slower. The slurry transport speed in the pipeline is preferably 1.5 to 2.0 m/sec.

Next, the effects of the present invention will be described.

〔Effect of the invention〕

As described above, according to the present invention, finely pulverized coal is kneaded with a binder and water, and then granulated by rolling to produce a rolling granule containing pellet cores. Pellets are produced by adding water to the granules and granulating them underwater to grow pellet cores.

That is, the core of the pellet is first produced, and then this core is grown to produce the pellet.

As a result, according to the present invention, pellets suitable for slurry transportation are produced as described below.

(1) In the method of the present invention, since the rolling granules containing pellet cores are subjected to underwater granulation, the rolling granules are pressed against the equipment of the wet granulator by centrifugal force, The core of the pellet grows as it rolls.

Therefore, the obtained pellets have excellent strength and water resistance, and do not disintegrate during slurry transportation.

Therefore, there is no deterioration in dewatering performance due to disintegration of the pellets, and good dewatering performance can be maintained at the consumption area, and wastewater pollution at the consumption area can also be prevented.

(2) In the present invention, as described above, pellets are produced by growing the pellet core by underwater granulation, so the surface of the obtained pellets is coated with a binder.

On the other hand, since the binder is water repellent, it prevents water from entering the pellets.

Therefore, the water resistance of the pellets can be increased and disintegration during transport of the slurry can be prevented.

Furthermore, due to the water-repellent nature of the pellets, they can be easily dehydrated at the consumption site using a simple dewatering process such as using a screen, so there is no need to install new wastewater treatment facilities.

(3) The time required can be significantly reduced compared to the conventional method of producing pellets only by underwater granulation.

For example, to produce pellets from 100 kg of pulverized coal by underwater granulation in the presence of a binder, it takes approximately 30 kg to produce pellets.
It took several minutes.

However, according to the method of the present invention, it takes about 4 minutes to knead the same amount of pulverized coal with a binder and water and tumble granulate it, and about 8 minutes to granulate it in water.
Pellets can be produced in 12 minutes, cutting the time required by more than half. Naturally, the power required for pellet production is also greatly reduced.

(4) In the present invention, pellet cores are produced by rolling granulation and these cores are grown by underwater granulation, so the amount of binder used is lower than when pellets are produced only by underwater granulation. can be significantly reduced.

For example, in conventional pellet production by underwater granulation, 20 to 30 kg of caking agent is used for 100 kg of pulverized coal.

However, in the method of the present invention, the amount of caking agent used is in the range of 3 to 10 kg for the same amount of pulverized coal, and by reducing the amount of caking agent used, which is relatively expensive compared to the price of coal, it is possible to produce pellets. Costs can be significantly reduced.

(5) Since the pellet surface is covered with a soft binder coating, there is less wear on the inner wall of the pipeline during transportation, extending the life of the line.

Examples of the present invention will be described below.

〔Example〕

Australian bituminous coal is finely pulverized to 5 mm to 200 mesh, and 5.5% by weight (based on coal) of C heavy oil and 10
% (by weight of coal) of water, and after kneading with a kneading machine, it is sent to a dry disc type granulator, and pulverized coal is pulverized into rolling granules containing pellet cores by rolling granulation for about 4 minutes. Granules formed.

Next, water was added to the rolling granules to form a slurry with a coal content of 30% by weight, which was fed to a horizontal cylindrical wet granulator under operating conditions of a rotation speed of 500 rpm and an average residence time of approximately 8 minutes. Underwater granulation was performed to produce pellets with an average particle size of 1.2 mm.

Using a test pipeline loop with a diameter of 1 inch and a total length of 28 m, a pellet slurry of 30% by weight was circulated 5300 times at an average flow rate of 2.4 m/sec (equivalent to a transportation distance of 150 km).

When the pellets, which had an average granulation size of 1.2 mm before being transported, were measured again after being transported through a pipeline equivalent to 150 km, the average particle size was 1.18 mm, which was within the measurement error range.

In other words, it can be said that disintegration of pellets during long-distance pipeline transportation is not observed.

In addition, a centrifugal force field of 500 G was applied to a conventional pulverized coal slurry with an average particle size of 0.18 mm and a slurry of pellets with an average particle size of 1.2 mm using a centrifuge.

After 5 minutes, the moisture adhering to the pulverized coal and pellets was measured and found to be 31% by weight for the pulverized coal and 10.5% by weight for the pellets, indicating that dehydration treatment is easier when transported by pellet slurry. It is.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of conventional coal slurry transportation, and FIG. 2 is a process diagram showing an embodiment of the present invention. 1... Coal, 2... Fine crusher, 3... Mixing tank,
4...Water, 5...Binder, 7...Kneading machine, 8...
Dry rolling type granulator, 9... Rolling granules containing pellet cores, 10... Wet type granulator, 11... Pellet, 12... Adjustment tank, 14... Transportation pipeline.

Claims (1)

[Claims] 1. Adding and kneading water and a binder selected from the group consisting of heavy oil, light oil, and kerosene to finely pulverized coal, and rolling-granulating the resulting kneaded product to form the finely pulverized coal. forming rolling granules containing the pellet cores, adding water to the rolling granules to perform underwater granulation, and growing the pellet cores to produce the finely pulverized coal pellets. A method for granulating coal for slurry transportation, characterized by: