JPH0891887A - Method and device for solidifying combustion ashes of pulverized coal - Google Patents

Abstract

PURPOSE: To obtain a method of easily solidifying combustion ashes of pulverized coal by blowing the combustion ashes of pulverized coal into a lime fluidized bed and roasting the ashes, thereby including 3CaO.Al2 O3 components easily solidified by a hydration reaction in the combustion ashes of pulverized coal, kneading these ashes with water and curing the mixture. CONSTITUTION: The combustion ashes of pulverized coal stored in a hopper 28 for charging the combustion ashes of pulverized coal are pneumatically transported into the fluidized bed 16 composed of fluid media consisting of quicklime and granular coal. The combustion ashes of pulverized coal are adhered to the flow media and are stagnated in the fluidized bed 16, by which the combustion ashes of pulverized coal and the quicklime are brought into contact and reaction with each other; thereafter, reacted combustion ashes of pulverized coal entrained in exhaust gases are collected by a duct collecting cyclone 24 and the collected ashes are kneaded with the water in a kneading machine 36 and thereafter, the kneaded mixture is cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for solidifying pulverized coal combustion ash, and more specifically, to prevent leaching of harmful substances from the pulverized coal combustion ash and effectively use the pulverized coal combustion ash in a solidified form. Method and apparatus.

[0002]

2. Description of the Related Art Conventionally, as a method for solidifying fluidized bed combustion ash,
A mixed powder composed of coal ash and a used desulfurizing agent generated during fluidized bed combustion in a fluidized bed composed of coal and limestone (desulfurizing agent) has a coal ash content of 60 to 85 wt% and a lime content of 1
After adding and adjusting quick lime or slaked lime and gypsum so that the blending ratio is 0 to 25 wt% and gypsum content 8 to 25 wt%, and further adding water and kneading, the kneaded product is molded, and then this 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). Further, as a method for solidifying 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 of gypsum 7 to 25 wt% and kneaded, and then this kneaded product is molded, and then this molded product is treated with steam at normal pressure of 80 to 100 ° C. (For example, refer to Japanese Patent Publication No. 64-1418).

As described above, the fluidized bed combustion ash in which ash contains C ₃ A, that is, 3CaO.Al ₂ O _3, is easily solidified by the hydration reaction and is expressed by the following formula. ,
It produces the main strength member, ettringite. Al ₂ O ₃ (ash content of coal) + (3CaO + 3CaS
O ₄ ) (used desulfurization 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 body cannot be obtained even when kneading with water as it is, and quick lime is obtained. (CaO) and gypsum (CaSO ₄ ) must be added. Therefore, pulverized coal combustion ash has heretofore been solidified mainly as a cement raw material or mixed with cement and solidified.

[0004]

As described above, since pulverized coal combustion ash does not contain CaO or CaSO ₄ , its strength is weak even if it is kneaded and solidified with water as it is, and its range of use as a material is narrow. Further, the amount of the cement raw material is limited, and there is a problem that the cost increases when mixed with cement. Pulverized coal combustion ash, like fluidized bed combustion ash,
The only thing that does not become a high-strength solid by kneading with water is C
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 Is.

However, it has been said that pulverized coal combustion ash is a fine powder, and its particle size is too small for firing in a rotary kiln or a fluidized bed. In particular, it has been said that there is almost no retention in the fluidized bed, the particles jump out of the fluidized bed, and the solids do not react with each other. In the fluidized bed, when the particle size is certainly reduced, the residence time is shortened, but when the particle size is too small, such as pulverized coal combustion ash, of 10 μm or less, it adheres to a large fluid medium and remains in the fluidized bed. Recent studies have revealed that the residence time increases.

The present invention has been made in view of the above points, and C _{3 which is} easily solidified by a hydration reaction in the pulverized coal combustion ash by injecting the pulverized coal combustion ash into the lime fluidized bed and firing it. It is an object of the present invention to provide a method and an apparatus in which the component A is contained and the ash is kneaded with water to be cured and solidified.

[0007]

In order to achieve the above object, a method for solidifying pulverized coal combustion ash according to the present invention is a method in which pulverized coal combustion ash is flowed with a fluid medium composed of quicklime and granular coal. The pulverized coal combustion ash is carried in the bed, and the pulverized coal combustion ash is adhered to the fluidized medium and retained in the fluidized bed, and the pulverized coal combustion ash and quick lime are contacted and reacted, and then the reacted pulverized coal combustion entrained in the exhaust gas The ash is collected, and the collected ash is kneaded with water and then cured.

In another method of the present invention, pulverized coal combustion ash is charged into an exhaust gas duct of a fluidized bed furnace and solid-gas separated while being heated by exhaust gas, and the separated heated pulverized coal combustion ash is quicklime and granular coal. The air is conveyed in a fluidized bed composed of a fluidized medium consisting of, and the pulverized coal combustion ash is adhered to the fluidized medium and retained in the fluidized bed, and the pulverized coal combustion ash and quick lime are contacted and reacted, and then the exhaust gas It is characterized by collecting the reacted pulverized coal combustion ash entrained in the ash, kneading the collected ash with water, and then curing.

[0009] In the above method, it is desirable that the pulverized coal combustion ash be conveyed by an air stream. Further, it is desirable that the pulverized coal combustion ash that has been collected is kneaded with water, shaped, then cured, and then pulverized. Fluidized bed temperature is 8
Range of 00 to 1400 ° C, preferably 850 to 1310
In order to maintain and control in the range of ℃, the particle size is 0.5-10mm
The granular coal in the range of is charged into the fluidized bed. Then, the amount of limestone added to the fluidized bed is adjusted so that the quick lime concentration in the dust collecting cyclone is in the range of 5 to 20 wt%. If the temperature of the fluidized bed is less than 800 ° C, CaCO ₃ → CaO + C
The firing reaction of limestone called O ₂ does not occur, and C ₃ A (3C
The raw material of aO.Al ₂ O ₃ ) tends not to be produced, while if it exceeds 1400 ° C., it tends to melt into glass. If the particle size of the granular coal is less than 0.5 mm, the combustion ratio in the fluidized bed is low, and the amount of unburned carbon in the ash tends to increase, while 1
If it exceeds 0 mm, the fluidization tends to be poor, and it tends to precipitate at the bottom of the fluidized bed. If the concentration of quick lime in the dust collecting cyclone is less than 5 wt%, the amount of the reaction substance becomes small in quantity and C
_The amount of ₃ A produced tends to be small, while when it exceeds 20 wt%, excess CaO is added when kneading with water to solidify.
However, there is a tendency that heat is generated and crystals due to the ettringite reaction do not grow sufficiently and the strength becomes insufficient.

The pulverized coal combustion ash solidifying apparatus of the present invention has a wind box at the lower part, and a fluidized bed furnace for forming a fluidized bed on the upper side of the air box through an air dispersion plate, and this fluidized bed furnace. A connected limestone charging hopper and a granular coal charging hopper, a dust collecting cyclone connected to an exhaust gas duct of the fluidized bed furnace, and a pulverized coal combustion ash charging hopper connected to the fluidized bed via an air flow carrier pipe, It is characterized by comprising a kneader connected to the ash collection line below the dust collecting cyclone and a curing machine connected to this kneader.

Further, another apparatus of the present invention has a wind box at a lower portion thereof, and is connected to the fluidized bed furnace for forming a fluidized bed on the upper side of the wind box via an air dispersion plate. Limestone charging hopper and granular coal charging hopper, a dust collecting cyclone connected to the exhaust gas duct of this fluidized bed furnace, a suspension preheater connected to the exhaust gas duct of this dust collecting cyclone, the dust collecting cyclone and this suspension preheater And a pulverized coal combustion ash charging hopper connected to an exhaust gas duct between the suspension preheater, an air flow carrier pipe connecting the ash collection line below the suspension preheater and the fluidized bed, and an ash trap below the dust collecting 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 kneader, a molding machine, a curing machine and a crusher in series.

[0012]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications can be made as appropriate. Example 1 FIG. 1 shows an apparatus for solidifying pulverized coal combustion ash in Example 1. A fluidized bed furnace 10 has a wind box 12 in the lower part, and a fluidized bed 16 is formed on the upper side of the air box through an air dispersion plate 14. In the fluidized bed furnace 10, a limestone loading hopper 18 (hereinafter, referred to as limestone loading hopper 18) for storing limestone or dolomite and a granular coal charging hopper 2 are provided.
0 is connected.

A dust collection cyclone 24 is connected to the exhaust gas duct 22 of the fluidized bed furnace 10, and the air flow carrier pipe 2 is connected to the fluidized bed 16.
A pulverized coal combustion ash hopper 28 is connected via 6. Further, a kneading machine 36 is connected to an ash collecting line 30 below the dust collecting cyclone 24 via an ash hopper 32 and a weighing machine 34, and a kneading machine 36 is connected with a molding machine 38, a curing machine 40 and a crusher 42 in series. 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 quick lime and CO _{2 in the} furnace. Pulverized coal combustion ash is introduced into a fluidized bed 16 composed of quick lime and granular coal having a particle size of 0.5 to 10 mm while being heated by exhaust gas while being conveyed by air flow. Most of the pulverized coal combustion ash has a particle size of 10 μm or less. Then, the pulverized coal combustion ash is adhered to the fluidized medium and retained in the fluidized bed 16 to contact and react the pulverized coal combustion ash with quick lime, and then the reacted pulverized coal combustion ash entrained in the exhaust gas is collected. The cyclone 24 collects dust, and the collected ash is kneaded with water by a kneader 36, molded into a predetermined shape by a molding machine 38, then cured by a curing machine 40, and then crushed by a crusher 42. The crushed material is used for roadbed materials, building materials, etc.

As described above, the fluidized bed 16 is composed of quicklime and coal ash and has a bed temperature of 800 to 1400 ° C.
Granular coal having a particle size of 0.5 to 10 mm is charged to maintain the temperature at 850 to 1310 ° C. The quicklime is obtained by putting limestone on the fluidized bed 16 and firing and pyrolyzing it, and the amount is adjusted so that the quicklime concentration 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 a dust collecting cyclone 24, and a pulverized coal combustion ash charging 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 air flow carrier pipe 26.
By connecting the pulverized coal combustion ash to the exhaust gas duct 44 of the fluidized bed furnace 10 and heating with exhaust gas, solid-gas separation is performed by the suspension preheater 46, and the separated heated pulverized coal combustion ash is separated from quick lime and granular coal. Fluidized bed 16
It is configured so as to be introduced by air flow inside.
Other configurations and operations are similar to those of the first embodiment.

[0017]

Since the present invention is configured as described above, it has the following effects. (1) By inputting pulverized coal combustion ash into a fluidized bed 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. Since ash and quick lime contact and react with each other to generate C ₃ A, that is, 3CaO · Al ₂ O ₃ , pulverized coal combustion ash after reaction 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 and cement.

[Brief description of drawings]

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

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

[Explanation of symbols]

 10 Fluidized Bed Furnace 12 Air Box 14 Air Dispersion Plate 16 Fluidized Bed 18 Limestone Input Hopper 20 Granular Coal Input Hopper 22 Exhaust Gas Duct 24 Dust Collection Cyclone 26 Air Flow Conveying Pipe 28 Pulverized Coal Combustion Ash Input Hopper 30 Ash Collection Line 32 Ash Hopper 34 Weighing machine 36 Kneading machine 38 Molding machine 40 Curing machine 42 Crusher 44 Exhaust gas duct 46 Suspension preheater 48 Ash collecting line

Claims (10)

[Claims] 1. A pulverized coal combustion ash is conveyed by air flow in a fluidized bed composed of a fluidized medium composed of quick lime and granular coal, and the pulverized coal combustion ash is adhered to the fluidized medium and retained in the fluidized bed.
Characterized by contacting and reacting pulverized coal combustion ash with quick lime, collecting the reacted pulverized coal combustion ash entrained in the exhaust gas, kneading the collected ash with water, and then curing. Method of solidifying pulverized coal combustion ash. 2. The pulverized coal combustion ash is introduced into an exhaust gas duct of a fluidized bed furnace to be solid-gas separated while being heated by the exhaust gas, and the separated heated pulverized coal combustion ash is composed of a fluidized medium composed of quicklime and granular coal. Reacted pulverized coal entrained in the exhaust gas after being conveyed by air flow in the fluidized bed, adhering the pulverized coal combustion ash to the fluid medium and making it stay in the fluidized bed, contacting and reacting the pulverized coal combustion ash and quick lime. A method for solidifying pulverized coal combustion ash, which comprises collecting the combustion ash, kneading the collected ash with water, and curing the ash. 3. The method for solidifying pulverized coal combustion ash according to claim 1, wherein the pulverized coal combustion ash is conveyed by an air flow. 4. The pulverized coal combustion ash thus collected is kneaded with water, shaped, then cured, and then pulverized.
Alternatively, the method for solidifying pulverized coal combustion ash according to 3 above. 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 0.
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 quick lime concentration in the dust collecting cyclone 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 to be added to the fluidized bed is adjusted so as to be in the range of 0 wt%. 8. A fluidized bed furnace having a wind box at the bottom and forming a fluidized bed on the upper side of the air box through an air dispersion plate, a limestone charging hopper and granular coal charging connected to this fluidized bed furnace. A hopper, a dust collecting cyclone connected to the exhaust gas duct of the fluidized bed furnace, a pulverized coal combustion ash charging hopper connected to the fluidized bed via an air flow carrier pipe, and an ash trap at the bottom of the dust collecting cyclone. An apparatus for solidifying pulverized coal combustion ash, comprising a kneader connected to the line and a curing machine connected to the kneader. 9. A fluidized bed furnace having a wind box at the bottom and forming a fluidized bed on the upper side of the air box through an air dispersion plate, and a limestone charging hopper and granular coal charging connected to the fluidized bed furnace. A hopper, a dust collecting cyclone connected to the 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 Pulverized coal combustion ash charging hopper, an air flow carrier pipe connecting the ash collecting line below the suspension preheater and the fluidized bed, and a kneader connected to the ash collecting line below the dust collecting cyclone And a curing machine connected to the kneader, and a solidification device for pulverized coal combustion ash. 10. The apparatus for solidifying pulverized coal combustion ash according to claim 8, wherein a molding machine, a curing machine and a crusher are connected in series to the kneading machine.