JPH07213950A - Apparatus for decarbonization of coal ash - Google Patents

Abstract

PURPOSE:To separate easily carbon content from a coal ash by providing a slurry pump taking out a liq. in a tank for floatation separation from the bottom part of the tank and circulating the liq. into the upper part of the tank, a taking-out means for a floating articles in the tank and a taking-out means for precipitation in the tank. CONSTITUTION:A slurry pump 3 is actuated to stir a boiler ash of finely powdered coal and an org. solvent with water and to disperse them into the water. After a specified time passes through, the pump 3 is stopped to keep the water under a static condition and the carbon in the boiler ash of finely powdered coal with the org. solvent is floated up and the ash part is precipitated. This floated part is recovered from an overflow pipe 8. To discharge the ash part precipitated in the tank 1 out of the tank 1, a valve 6 is closed and a valve 7 is opened and the pump 3 is actuated and it is discharged as a slurry from a pipeline 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for decarbonizing coal ash, and more particularly to an apparatus suitable for separating unburned carbon from ash of pulverized coal boiler and other ash.

[0002]

2. Description of the Related Art The following five methods are known as methods for decarbonizing coal ash.

(1) By utilizing flotation, unburned carbon is separated and removed from ash. (2) Unburned carbon and ash are separated by an oil agglomeration method, and unburned carbon is granulated and removed. (3) By dry classification, divide into fine powder part and coarse powder part,
The fine powder portion having a low unburned carbon content is separated from the coarse powder portion. (4) Pulverized coal boiler ash is crushed, unburned carbon having high grindability is collected in the fine powder portion, and the fine powder portion is removed by dry classification. (5) Separation is performed by utilizing the difference in the electrical properties of unburned carbon and ash.

[0004]

Among the above methods, (1) and (2) are excellent in removing unburned carbon. However, in the method (1), when the ash particles are small,
Separation of unburned carbon and ash is difficult. Further, when the unburned carbon content is as small as 10% or less, the method (2) also becomes difficult.

The methods (3) to (5) are suitable as a method for treating a large amount of coal ash, but the efficiency of decarbonization is low. In addition, a large classifier and crusher are required,
It is hard to become a profitable system.

[0006]

According to a first aspect of the present invention, there is provided a coal ash decarbonizing apparatus comprising: a flotation tank; and a slurry pump for extracting the liquid in the tank from the bottom of the tank and circulating it in the upper part of the tank. And a means for taking out the floating substances in the tank and a means for taking out the sediments in the tank.

According to a second aspect of the present invention, there is provided a coal ash decarbonizing apparatus according to the first aspect, further comprising a liquid cyclone into which the sediment in the tank is introduced.

[0008]

In order to decarbonize coal ash using the apparatus of the present invention, an organic solvent having a specific gravity of less than 1 and immiscible with water is added to and mixed with the coal ash. Put in the tank. By operating the slurry pump to circulate the water in the tank, the coal ash, the organic solvent and the water are mixed.

During this mixing process, the organic solvent adheres to the carbon content in the coal ash, and the carbon particles aggregate using this organic solvent as a binder. When the circulation is stopped and the liquid in the tank is allowed to stand, the aggregated carbon particles float on the water surface together with the organic solvent. Take this float to the outside of the tank. On the other hand, since the ash content settles to the bottom of the tank, this sediment is taken out of the tank.

As a result, the unburned carbon content and the ash content are separated, and the coal ash is decarbonized.

In the apparatus of claim 2, the sediment is classified and dehydrated by the hydrocyclone.

In the present invention, the coal ash is preferably pulverized coal boiler ash of a thermal power plant, but other coal ash may be used. The coal ash to be treated preferably has a carbon content of 5% by weight or more, particularly 7% by weight or more.

Organic solvents having a specific gravity of less than 1 and immiscible with water include kerosene, benzene, xylene,
Toluene, light oil, heavy oil and the like are suitable.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram for explaining an apparatus according to an embodiment of the present invention, in which a tank 1 is filled with water. At the bottom of the tank 1, a pipe 2, a slurry pump 3 and a pipe 4
A circulation mechanism consisting of is connected. A pipe 5 branches off from the middle of the pipe 4. The pipes 4 and 5 are provided with valves 6 and 7, respectively.

A mixture of coal ash and an organic solvent such as kerosene is put into the tank 1. With the valve 6 open and the valve 7 closed, the pump 3 is operated. Then, the pulverized coal boiler ash and the organic solvent are stirred with water and dispersed in water. By this stirring, the carbon content adhering to the ash particles is peeled off.

After a lapse of a predetermined time, the pump 3 is stopped and the water is kept stationary. Then, in the tank 1, the carbon in the pulverized coal boiler ash floats up together with the organic solvent, and the ash content precipitates. This floating portion is recovered by overflowing it from the overflow pipe 8. The recovered mixture of carbon and organic solvent can be used as a fuel as it is or after solid-liquid separation treatment (for example, centrifugation).

Since carbon has a greater affinity for organic solvents than for water, unburned carbon that is simply mixed in boiler ash (that is, mixed as a simple substance without adhering to ash particles) and The unburned carbon separated from the ash particles immediately has an affinity for the organic solvent, and the carbon particles adhere to each other by using the organic solvent as a binder to aggregate. In this way, the carbon particles aggregate to form large aggregate particles,
After the stirring is stopped, the surface immediately rises.

In order to discharge the ash content settled in the tank 1 to the outside of the tank 1, the valve 6 is closed, the valve 7 is opened, the pump 3 is operated, and the slurry is discharged from the pipe 5 as a slurry. The slurry containing this ash content can be used as a cement raw material or a cement admixture after dehydration treatment.

It is preferable that the slurry containing the ash content is wet classified, the coarse particles are used as a cement raw material, and the fine particles are used as a cement admixture.

In the method for decarbonizing coal ash using the apparatus shown in FIG. 1, the mixing ratio of coal ash and organic solvent is 100 parts by weight of coal ash and 5 parts of organic solvent.
-40 parts by weight, especially 5-10 parts by weight is preferable.

The amount of water in the tank 1 is preferably 3 to 10 times, especially 4 to 7 times the volume of the mixture of coal ash and organic solvent.

The tank 1 may be provided with an aeration device for floating separation.

FIG. 2 is a system diagram for explaining the method of the second embodiment. A mixture of coal ash and an organic solvent such as kerosene is put into a tank 10 filled with water. This tank 10 has a pipe 13, a slurry pump 14, a return pipe 13
A stirring mechanism consisting of a is provided. By circulating the liquid in the tank 10 by the slurry pump 14, the input material and water are mixed with stirring.

A pipe 13b communicating with the hydrocyclone 15 is branched from the pipe 13a.
The a and 13b are provided with valves (not shown) for selecting a flow path for circulating the liquid in the tank 10 and a flow path for sending the liquid to the liquid cyclone 15.

After the liquid in the tank 10 is stirred by the above circulation, it is left standing. The floating object is dehydrated by a dehydrator 1 through a pipe 11.
Sent to 2. The sediment is sent to the liquid cyclone 15 via the slurry pump 14 and the pipe 13b, and is subjected to centrifugal separation processing.

The coarse particles classified by the liquid cyclone 15 are introduced into the tank 16. The fine particles are sent to a tank 18 filled with water by a pipe 17.

The tank 16 is provided with a stirring mechanism composed of a circulation pipe and a slurry pump 21, and the introduced substance and water are stirred for a predetermined time and then left standing.

The levitated portion which has been levitated by this stationary is the pipe 1
It is sent to the dehydrator 12 via 9. The sedimented portion is sent to the liquid cyclone 22 via the slurry pump 21 and the pipe 20, and is subjected to centrifugal separation processing.

The coarse particles classified by the liquid cyclone 22 are taken out of the apparatus as coarse powder slurry through the pipe 23. The fine particles classified by the hydrocyclone 22 are pipe 2
The water is sent to the tank 18 filled with water via No. 4.

The tank 18 is also provided with a stirring mechanism composed of a circulation pipe and a slurry pump 27.
After the introduction from 7 and 24 and water were stirred for a predetermined time,
It is left to stand.

The levitation that has been levitated by this stationary is the piping 2
It is sent to the dehydrator 12 via 5. The sedimented portion is sent to the liquid cyclone 28 via the slurry pump 27 and the pipe 26 and subjected to centrifugal separation processing.

The coarse particles classified by the liquid cyclone 28 are taken out of the apparatus as intermediate powder slurry through the pipe 29. Fine particles classified by the liquid cyclone 28 are
It is sent to the tank 31 filled with water via 0.

The tank 31 is also provided with a stirring mechanism composed of a circulation pipe and a slurry pump 34.
The introduced substance from 0 and water are stirred for a predetermined time and then allowed to stand.

The levitation that has been levitated by this stationary is the piping 3
2 to the dehydrator 12. The sedimented portion is sent to the liquid cyclone 35 via the slurry pump 34 and the pipe 33, and is subjected to centrifugal separation processing.

The coarse particles classified by the liquid cyclone 35 are taken out of the apparatus as fine powder slurry through the pipe 36. Fine particles classified by the liquid cyclone 35 are
It is sent to the dehydrator 12 via 7.

The solid content dehydrated by the dehydrator 12 is mainly composed of carbon and is reused as fuel.

The coarse powder slurry and the intermediate powder slurry taken out from the pipes 23 and 29 are further dehydrated if necessary, and then used as a cement raw material in a raw material mill with other cement raw materials (limestone, clay, silica stone, etc.). Grind at the same time.

The fine powder slurry taken out from the pipe 36 is further dehydrated if necessary, and then simultaneously ground with a clinker and gypsum in a finishing mill as a cement admixture.
The solid material in this fine powder slurry is mainly composed of spherical particles, and unburned carbon is also removed, so that it fully satisfies the fly ash standard (JIS A 6201).

The slurry taken out from the pipes 23, 29, 36 contains water, but its amount is small because it is dehydrated by the liquid cyclone. Therefore, even if no dehydration treatment is carried out, the powder is dried by the heat of grinding during grinding in the finishing mill and the raw material mill.

In the decarbonization method using the apparatus of FIG. 2, the mixing ratio of coal ash and organic solvent is 5 to 40 parts by weight of organic solvent, especially 5 to 100 parts by weight of coal ash. It is preferably 10 parts by weight.

The amount of water in the tank 10 is preferably 4 to 7 times, especially about 5 times, the volume of the mixture of coal ash and organic solvent.

The tanks 10, 16, 18 and 31 are
An aeration device for floating separation may be provided. The amount of water in the tanks 16, 18, 31 is preferably 2 to 10 times, especially 2 to 4 times the volume of the slurry to be introduced.

[0043]

As described above, according to the apparatus of claim 1,
Carbon can be easily separated from coal ash. The ash content from which the carbon content has been separated has a low carbon content and thus can be used as an admixture. Therefore, even pulverized coal boiler ash having a high carbon content can be recycled.

According to the device of the present invention, the unburned carbon content is 10%.
Hereinafter, even the coal ash composed of fine particles having a maximum particle size of 50 μm or less can be efficiently decarbonized.

In the device of the present invention, since the main power is only the motor of the slurry pump, the operating cost is low.

According to the method of claim 2, since the sediment can be easily classified and dehydrated by the hydrocyclone, the size of the apparatus can be reduced. Also, because of this, the equipment cost is low.

[Brief description of drawings]

FIG. 1 is a system diagram illustrating an example device.

FIG. 2 is a system diagram illustrating an example apparatus.

[Explanation of symbols]

 1, 10, 16, 18, 31 Tanks 3, 14, 21, 27, 34 Pumps 15, 22, 28, 35 Hydrocyclone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norifumi Miota 1-1 Donan-cho, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Materials Corporation Kyushu Plant

Claims (2)

[Claims] 1. A tank for floatation separation, a slurry pump for extracting a liquid in the tank from a bottom portion of the tank and circulating the liquid in an upper portion of the tank, a means for taking out a floating material in the tank, and an inside of the tank. Coal ash decarbonizing apparatus comprising: 2. The decarburizing apparatus for coal ash according to claim 1, further comprising a liquid cyclone into which the sediment in the tank is introduced.