JP2879308B2 - Method and apparatus for solidifying pulverized coal combustion ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for solidifying pulverized coal combustion ash, and more particularly to a method for preventing pulverized coal combustion ash from elution of harmful substances and effectively utilizing the pulverized coal combustion ash. And a method and apparatus for performing the method.

[0002]

2. Description of the Related Art Conventionally, as a method of solidifying fluidized bed combustion ash,
In a mixed powder of coal ash and spent desulfurizing agent generated during fluidized bed combustion in a fluidized bed composed of coal and limestone (desulfurizing agent), a coal ash content of 60 to 85 wt% and a lime content of 1
After adding and adjusting quicklime or slaked lime and gypsum so as to have a mixing ratio of 0 to 25 wt% and a gypsum content of 8 to 25 wt%, water is further added and kneaded, the kneaded product is formed, and then the molding is performed. A method of treating a body with steam at 70 to 100 ° C. is known (for example, Japanese Patent Publication No. 64-1).
No. 420). As a method for solidifying the pulverized coal combustion ash, coal ash 60 to 85 wt%, quick lime 10 to 25 wt%,
A method is known in which water is added to a mixed powder consisting of 7 to 25% by weight of gypsum, kneaded, and the kneaded product is formed, and then the formed body is treated with normal pressure steam at 80 to 100 ° C. (See, for example, Japanese Patent Publication No. 64-1418).

[0003] As described above, as in the case of fluidized bed combustion ash, C ₃ A, that is, 3CaO.Al ₂ O _3, is present in the ash and is easily solidified by a hydration reaction. ,
Produces ettringite, the main strength member. Al ₂ O ₃ (ash content of coal) + (3CaO + 3CaS)
O ₄ ) (Spent desulfurizing agent) + 32H ₂ O → 3CaO.Al
₂ O ₃ .3CaSO ₄ .32H ₂ O (Ettringite) However, since pulverized coal combustion ash does not contain CaO or CaSO ₄ in the ash, a high-strength solidified product cannot be obtained even when kneaded with water as it is. (CaO) and gypsum (CaSO ₄ ) must be added. For this reason, pulverized coal combustion ash has conventionally been solidified mainly as a cement raw material or mixed with cement to be solidified.

[0004]

As described above, pulverized coal combustion ash does not contain CaO or CaSO _4, and therefore has a low strength even when solidified by being directly kneaded with water, and has a narrow range of use as a material. In addition, the amount is limited for use as a cement raw material, and there is a problem that the cost increases when mixed with cement. Like pulverized coal combustion ash, like fluidized bed combustion ash,
High strength solids cannot be obtained by mixing with water only.
₃ A, that is, because you're not material that 3CaO · Al ₂ O _3, because this is possible, coal ash and lime, gypsum and solid to each other contact with a few minutes should be reacted at a high temperature It is.

However, pulverized coal combustion ash is a fine powder, and it has been said that the particle size is too small to be burned in a rotary kiln or a fluidized bed. In particular, it has been said that the particles hardly stay in the fluidized bed, jump out of the fluidized bed, and no reaction occurs between the solids. In the fluidized bed, if the particle size becomes smaller, the residence time becomes shorter, but if the particle size becomes smaller than 10 μm as in the case of pulverized coal combustion ash, it will adhere to a larger fluid medium and remain in the fluidized bed. Recent studies have shown that residence times can increase.

[0006] The present invention has been made in view of the various points described above, by blowing pulverized coal combustion ash lime fluidized bed, by baking, C ₃ to easily solidified by hydration during pulverized coal combustion ash It is an object of the present invention to provide a method and an apparatus in which the component A is contained, and this ash is kneaded with water, cured and solidified.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, a method for solidifying pulverized coal combustion ash according to the present invention is a method for solidifying pulverized coal combustion ash by using a fluidized medium composed of quicklime and granular coal. After the pulverized coal combustion ash adheres to the fluidized medium and stays in the fluidized bed, causing the pulverized coal combustion ash and quick lime to contact and react, the reacted pulverized coal combustion entrained in the exhaust gas It is configured to collect ash, knead the collected ash with water, and then cure.

In another method of the present invention, pulverized coal combustion ash is introduced into an exhaust gas duct of a fluidized bed furnace, and is separated into solid and gas while being heated by the exhaust gas, and the separated heated pulverized coal combustion ash is separated into quick lime and granular coal. After the pulverized coal combustion ash adheres to the fluidized medium and stays in the fluidized bed, the pulverized coal combustion ash and the quick lime contact and react, and then the exhaust gas It is characterized in that the reacted pulverized coal combustion ash entrained in the above is collected, and the collected ash is kneaded with water and then cured.

In the above method, it is desirable that the pneumatic coal combustion ash be conveyed in an air stream by exhaust gas. Further, it is desirable that the collected pulverized coal combustion ash is kneaded with water, molded, then cured, and then pulverized. Fluidized bed temperature is 8
In the range of 00 to 1400 ° C., preferably 850 to 1310
To maintain and control in the range of ° C, the particle size is 0.5 to 10 mm
Into the fluidized bed. Then, the amount of limestone charged into the fluidized bed is adjusted so that the concentration of quicklime in the dust collecting cyclone is in the range of 5 to 20 wt%. When the temperature of the fluidized bed is lower than 800 ° C., CaCO ₃ → CaO + C
The limestone firing reaction of O ₂ does not occur, and C ₃ A (3C
aO.Al ₂ O ₃ ) raw materials tend not to be produced, while if it exceeds 1400 ° C., they tend to melt and become glassy. When the particle size of the granular coal is less than 0.5 mm, the combustion rate in the fluidized bed is low, and the amount of unburned carbon in the ash that jumps out tends to increase.
If it exceeds 0 mm, fluidization becomes poor, and the fluid tends to precipitate at the bottom of the fluidized bed. When the concentration of quicklime in the dust collecting cyclone is less than 5% by weight, the amount of the reactant decreases stoichiometrically,
_The amount of 3A formed tends to be small, while if it exceeds 20 wt%, excess CaO is added when kneading and solidifying with water.
, And heat is generated, and crystals due to the ettringite reaction do not grow sufficiently, and the strength tends to be insufficient.

[0010] The pulverized coal combustion ash solidifying apparatus of the present invention has a wind box at the bottom, and a fluidized bed furnace which forms a fluidized bed above the wind box via an air dispersion plate. A limestone input hopper and a granular coal input hopper connected thereto, a dust collection cyclone connected to an exhaust gas duct of the fluidized bed furnace, and a pulverized coal combustion ash input hopper connected to the fluidized bed via an airflow transfer pipe, It is characterized by comprising a kneader connected to an ash collection line below the dust collecting cyclone, and a curing machine connected to the kneader.

Further, another apparatus of the present invention has a wind box at a lower portion, and a fluidized bed furnace for forming a fluidized bed above the wind box via an air distribution plate, and is connected to the fluidized bed furnace. Limestone charging hopper and granular coal charging hopper, a dust collecting cyclone connected to an exhaust gas duct of the fluidized bed furnace, a suspension preheater connected to the exhaust gas duct of the dust collecting cyclone, the dust collecting cyclone and the suspension preheater A dust coal combustion ash input hopper connected to an exhaust gas duct between the ash collection line, an ash collection line below the suspension preheater, and an air flow conveying pipe connecting the fluidized bed, and an ash trap below the dust collection cyclone. It is characterized by comprising a kneader connected to the collecting line and a curing machine connected to the kneader. In the above apparatus, it is desirable to connect a molding machine, a curing machine, and a crusher to the kneader in series.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples, and can be implemented with appropriate modifications. Embodiment 1 FIG. 1 shows an apparatus for solidifying pulverized coal combustion ash in Embodiment 1. Reference numeral 10 denotes a fluidized bed furnace, which has a wind box 12 at the lower part, and a fluidized bed 16 is formed above the wind box via an air distribution plate 14. The fluidized bed furnace 10 includes a limestone charging hopper 18 (hereinafter, referred to as a limestone charging hopper 18) and a granular coal charging hopper 2 for storing limestone or dolomite.
0 is connected.

The exhaust gas duct 22 of the fluidized bed furnace 10 is connected to a dust collecting cyclone 24, and
6, a pulverized coal combustion ash hopper 28 is connected. A kneader 36 is connected to an ash collection line 30 below the dust collecting cyclone 24 via an ash hopper 32 and a weighing machine 34, and a molding machine 38, a curing machine 40, and a crusher 42 are connected in series to the kneading machine 36. Connected to.

Next, the operation of the apparatus according to the first embodiment will be described. The limestone charged into the fluidized bed furnace 10 is thermally decomposed into quicklime and CO _{2 in the} furnace. The pulverized coal combustion ash is introduced into the fluidized bed 16 composed of quicklime and a granular coal having a particle size of 0.5 to 10 mm by airflow while being heated with exhaust gas. Most of the pulverized coal combustion ash has a particle size of 10 μm or less. Then, the pulverized coal combustion ash is made to adhere to the fluidized medium and stays in the fluidized bed 16 to contact and react with the pulverized coal combustion ash and quicklime, and then the reacted pulverized coal combustion ash entrained in the exhaust gas is collected. The dust is collected by the cyclone 24, and the collected ash is kneaded with water by the kneader 36, formed into a predetermined shape by the forming machine 38, cured by the curing machine 40, and then crushed by the crusher 42. The pulverized material is used for roadbed materials, building materials, and the like.

As described above, the fluidized bed 16 is composed of quicklime and coal ash, and has a bed temperature of 800 to 1400 ° C.
Desirably, granular coal having a particle size of 0.5 to 10 mm is charged in order to maintain the temperature at 850 to 1310 ° C. Quicklime is obtained by charging limestone on the fluidized bed 16 and calcining and pyrolyzing the limestone. The amount is adjusted so that the concentration of quicklime in the dust collecting cyclone is 5 to 20 wt%.

Embodiment 2 In this embodiment, as shown in FIG. 2, a suspension preheater 46 is connected to an exhaust gas duct 44 of the dust collecting cyclone 24, and a pulverized coal combustion ash input hopper 28 is connected to the exhaust gas duct 44. The ash collecting line 48 below the suspension preheater 46 is connected to the fluidized bed 16 through the airflow pipe 26.
The pulverized coal combustion ash is supplied to the exhaust gas duct 44 of the fluidized bed furnace 10 and is solid-gas separated by the suspension preheater 46 while being heated by the exhaust gas, and the separated heated pulverized coal combustion ash is separated from quick lime and granular coal. Fluidized bed 16
It is configured to be injected into the inside by air flow.
Other configurations and operations are the same as those of the first embodiment.

[0017]

As described above, the present invention has the following effects. (1) By introducing pulverized coal combustion ash into a fluidized bed composed of a fluidized medium composed of quick lime and granular coal, the pulverized coal combustion ash adheres to the fluidized medium and stays in the fluidized bed, resulting in pulverized coal combustion. The ash and quicklime come into contact with and react with each other to produce C ₃ A, ie, 3CaO.Al ₂ O _3. Therefore, the pulverized coal combustion ash that has been reacted is kneaded with water and cured to easily form a solidified body. be able to. (2) The solidified body obtained by the method of the present invention is lower in cost than the conventional solidified body obtained by mixing pulverized coal combustion ash with cement.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an apparatus for solidifying pulverized coal combustion ash of the present invention.

FIG. 2 is a system diagram showing another embodiment of the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fluidized bed furnace 12 Wind box 14 Air dispersion plate 16 Fluidized bed 18 Limestone charging hopper 20 Granular coal charging hopper 22 Exhaust gas duct 24 Dust collection cyclone 26 Air flow conveying pipe 28 Pulverized coal combustion ash charging hopper 30 Ash collecting line 32 Ash hopper 34 Weighing machine 36 Kneader 38 Molding machine 40 Curing machine 42 Crusher 44 Exhaust gas duct 46 Suspension preheater 48 Ash collection line

Claims (10)

(57) [Claims] Claims: 1. Pulverized coal combustion ash is air-flow conveyed into a fluidized bed composed of a fluid medium composed of quicklime and granular coal, and the pulverized coal combustion ash is attached to the fluidized medium and retained in the fluidized bed,
After contacting and reacting pulverized coal combustion ash and quicklime, the reacted pulverized coal combustion ash entrained in the exhaust gas is collected, and the collected ash is kneaded with water and then cured. Solidification method of pulverized coal combustion ash. 2. The pulverized coal combustion ash is introduced into an exhaust gas duct of a fluidized bed furnace and is separated into solid and gas while being heated by the exhaust gas. The separated heated pulverized coal combustion ash is composed of a fluid medium composed of quicklime and granular coal. After the pulverized coal combustion ash adheres to the fluidized medium and stays in the fluidized bed, the pulverized coal combustion ash and the quicklime are brought into contact with and reacted with the pulverized coal combustion ash. A method for solidifying pulverized coal combustion ash, comprising collecting combustion ash, kneading the collected ash with water, and curing. 3. The method for solidifying pulverized coal combustion ash according to claim 1, wherein the pneumatic coal combustion ash is transported in an air stream by exhaust gas. 4. The pulverized coal combustion ash that has been collected is kneaded with water, molded, cured, and then pulverized.
Or the solidification method of pulverized coal combustion ash according to 3. 5. The method for solidifying pulverized coal combustion ash according to claim 1, wherein the temperature of the fluidized bed is controlled in the range of 800 to 1400 ° C. 6. The particle size of the granular coal charged into the fluidized bed is set to 0.1.
The method for solidifying pulverized coal combustion ash according to any one of claims 1 to 5, wherein the range is 5 to 10 mm. 7. The concentration of quicklime in the cyclone for dust collection is 5 to 2.
The method for solidifying pulverized coal combustion ash according to any one of claims 1 to 6, wherein the amount of limestone charged into the fluidized bed is adjusted so as to fall within the range of 0 wt%. 8. A fluidized-bed furnace having a wind box at a lower portion and forming a fluidized bed above the wind-box via an air distribution plate, a limestone input hopper and a granular coal input connected to the fluidized-bed furnace. A hopper, a dust collection cyclone connected to an exhaust gas duct of the fluidized bed furnace, a pulverized coal combustion ash input hopper connected to the fluidized bed via an airflow conveying pipe, and an ash trap at a lower portion of the dust collection cyclone A pulverized coal combustion ash solidifying apparatus, comprising: a kneader connected to a line; and a curing machine connected to the kneader. 9. A fluidized-bed furnace having a wind box at a lower portion and forming a fluidized bed above the wind-box via an air distribution plate, a limestone input hopper and a granular coal input connected to the fluidized-bed furnace. A hopper, a dust collecting cyclone connected to an exhaust gas duct of the fluidized bed furnace, a suspension preheater connected to the exhaust gas duct of the dust collecting cyclone, and an exhaust gas duct between the dust collecting cyclone and the suspension preheater A pulverized coal combustion ash input hopper, an air flow conveying pipe connecting the ash collection line below the suspension preheater and the fluidized bed, and a kneader connected to an ash collection line below the dust collection cyclone. And a curing machine connected to the kneading machine. 10. The apparatus for solidifying pulverized coal combustion ash according to claim 8, wherein a molding machine, a curing machine and a pulverizer are connected in series to the kneader.