JP2003275714A - Ash treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ash treatment method which prevents fly ash from attaching to the inner surface of a retort in a rotating drum type heater. <P>SOLUTION: This ash treatment method is a method for subjecting the fly ash (a) collected from an apparatus such as dust collector and boiler of incineration furnace of stoker type or fluidized bed type and air preheater to dechlorination treatment by means of a heating dechlorination device B. Anti- sticking material (e) such as incineration ash discharged from the bottom of the incineration furnace is mixed to the fly ash (a) in a prescribed proportion and the mixture is supplied to the heating dechlorination device B. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to dechlorination of fly ash collected from equipment such as a dust collector of an incinerator of a stoker type or a fluidized bed type, a boiler and an air preheater by a heating dechlorination treatment apparatus. The present invention relates to an ash treatment method for chemical treatment.

[0002]

2. Description of the Related Art When incinerating general waste such as municipal solid waste or industrial waste including combustible materials such as waste plastic in a stoker type or fluidized bed type incinerator, incinerator ash is discharged from the bottom of the incinerator. On the other hand, fly ash is captured from devices such as a dust collector of an incinerator, a boiler, and an air preheater.

Of these ashes, fly ash, in particular, contains a large amount of dioxins such as organic chlorine compounds harmful to the human body, for example, PCDD (polychlorinated dibenzodioxin) and PCDF (polychlorinated dibenzofuran). It is said that

Conventionally, for example, the fly ash has been dechlorinated using the heating dechlorination apparatus A shown in FIG. The thermal dechlorination treatment device A is a fixed amount supply device 2, 1 comprising a fly ash storage tank 1, a hopper 3 and a fixed amount feeder 4.
To a rotary drum type heating device 5 consisting of several heating pipes (hereinafter referred to as retort) 7 and a tubular heating part 8, an air heater 6, a discharge device 9 provided at the outlet of the rotary drum type heating device 5, a rotation The drum type cooler 10, the blower blower 11, the dust collector 12, the activated carbon adsorption tower 13, and the attracting blower 14 are formed.

The fly ash a in the fly ash storage tank 1 is supplied to the rotary drum type heating device 5 by the hopper 3 and the fixed amount feeder 4 of the constant amount supply device 2 and heated by the air heater 6. In the presence of b, while passing through one to several retorts 7 of the rotary drum heating device 5,
It is heated to a predetermined temperature by a cylindrical heating unit 8 located outside thereof.

Dioxins are dechlorinated by thermal decomposition while evaporating the contained water. The dechlorinated ash a ′ is passed through the discharging device 9 and then the rotating drum type cooler 1
It is supplied to 0 and cooled rapidly. And ash a ″ at room temperature
Becomes

On the other hand, the exhaust gas d separated by the exhaust device 9
After being diluted with the air b taken in by the blower blower 11, it is supplied to the incinerator (not shown) via the dust collector 12, the activated carbon adsorption tower 13 and the attracting blower 14. Also, the ash a ′ captured by the dust collector 12 is
Returned to hopper 3.

[0008]

However, when the fly ash a is heated by the rotary drum type heating device 5, the fly ash a adheres to the inner surface of the retort 7 and interferes with the dechlorination process. That is, the inert component in the fly ash (S that is stable even when heated)
_{iO 2, Al 2 O 3,} Fe 2 O 3 when the ratio of the like) is small (for example, if inert component in the fly ash is less than 20 wt%), when the particle size of the fly ash is extremely fine (100 [mu] m
Below), or due to low melting point salts contained in fly ash, etc., when heating to a temperature necessary for decomposing and removing organochlorine compounds (for example, dioxins) in fly ash. , (1) Fly ash adheres to the inner wall surface of the retort, heat transfer deteriorates, and electric power consumption tends to increase (2)
Fly ash clumps like balls in the retort (for example, diameter 3
0 mm or more), and the organic chlorine compound may be delivered from the heater before it is sufficiently decomposed.

When the fly ash a adheres to the inner surface of the retort 7 as described above, the heat transfer efficiency decreases and it becomes difficult to heat the fly ash a to a predetermined temperature. Therefore, if the set temperature is raised in order to heat the fly ash a to a predetermined temperature, power consumption may increase and a situation may occur in which peripheral devices are adversely affected.

The fly ash a adhering to the inner surface of the retort 7 is peeled from the inner surface of the retort 7 when the retort 7 and the cylindrical heating portion 8 on the outer side thereof are hit with a hammer or the like, but the heating device 5 Despite the low speed, it is rotating at 3 to 15 times / minute, so it is dangerous to approach while driving.

Therefore, in order to remove the fly ash a adhering to the inner wall surface of the retort 7, it is conceivable that the operation of the rotary drum type heating device 5 is temporarily interrupted, but the operation of the rotary drum type heating device 5 is temporarily stopped. If the operation is interrupted, the operation efficiency will be reduced accordingly.

The present invention has been made in order to solve such a problem, and it is a main object of the present invention to provide an ash treatment method for preventing fly ash from adhering to the inner surface of a retort of a rotary drum type heating device. It is intended.

[0013]

In order to solve such problems, the present invention is constructed as follows.

(1) When the fly ash collected from equipment such as a dust collector of an incinerator of a stoker type or a fluidized bed type, a boiler, an air preheater, etc. is dechlorinated by a heating dechlorination treatment apparatus, In the fly ash, an ash treatment method characterized in that an anti-adhesion material such as incineration ash discharged from the bottom of the incinerator is mixed at a predetermined ratio, and the mixture is supplied to the thermal dechlorination treatment apparatus. is there.

(2) A mixture of fly ash and an adhesion preventive material
It is the ash processing method of (1) characterized by heat-processing at 400-550 degreeC.

(3) A mixture of fly ash and an adhesion preventive material
The ash treatment method according to (1), characterized in that rapid cooling is performed at a cooling rate of 40 ° C./min or more.

(4) 10w of anti-adhesion material against fly ash
characterized by mixing at a ratio of t% or more (1),
It is the ash treatment method according to (2) or (1).

(5) In the ash treatment method according to (1), the anti-adhesion material such as incineration ash discharged from the bottom of the incinerator is crushed in advance to a particle size not larger than a predetermined value. is there.

Here, fly ash is a general term for ash collected from dust collectors (bug dust collectors, electric dust collectors, cyclones, etc.) of incinerators such as stoker type and fluidized bed type, boilers, and air preheaters. Is.

On the other hand, examples of the adhesion preventive material include incinerated ash discharged from the bottom of the incinerator, molten slag discharged from a melting furnace, sand, diatomaceous earth and the like.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, when incineration ash discharged from the bottom of an incinerator is applied as an adhesion preventing material. Take as an example.

FIG. 1 is a schematic diagram of a heating dechlorination treatment apparatus for carrying out the ash treatment method of the present invention. The heating dechlorination treatment apparatus B is a first storage tank 1, a hopper 3, and a fixed amount feeder 4. A constant amount supply device 2 consisting of 1 to several retorts 7 and a rotary drum heating device 5 consisting of a tubular heating part 8, an air heater 6, and a discharge device 9 provided at the outlet of the rotary drum heating device 5. Rotary drum cooler 10, blower blower 11,
It is formed of a dust collector 12, an activated carbon adsorption tower 13 and an attracting blower 14.

The thermal dechlorination apparatus B is further provided with a second storage tank 20 above the hopper 3, in which the incineration ash e discharged from the bottom of the incinerator is stored. ing. In FIG. 1, 1a and 20a are feeders.

Above the second storage tank 20, as shown in FIG. 2, the first vibrating screen 2 having a mesh size of about 100 mm.
1, a crusher 22, and a second vibrating screen 23 having a mesh size of about 15 mm are installed. The incinerator ash E discharged from an incinerator (not shown) is separated by the first vibrating screen 21 and then the crusher It is crushed by 22 and further separated by the second vibrating screen 23,
Below a predetermined particle size (for example, below 15 mm, preferably 13
The incineration ash e (mm or less) is stored in the second storage tank 20. The debris f remaining on the first vibrating screen 20 is removed to the outside of the system, and the debris f remaining on the second vibrating screen 23 is returned to the crusher 22 and crushed again.

The rotary drum type heating device 5 will be described in detail. As shown in FIG. 3, a cylindrical heating portion 8 having a heating means 16 such as a combustion burner or an electric heater,
The heating unit 8 includes one to several (four in the figure) retorts 7, a drive device (not shown) for rotating the retort group, and an ejector 9 provided at the outlet of the retort 7. The temperature of the heating means 16 and the temperature of the ash at its outlet are measured, and automatic control is performed so that the outlet temperature becomes constant. The temperature of the ash at the outlet is measured by the temperature sensor 17
Measure with. Further, a rotating drum type cooler 10 is provided below the heating unit 8. The heating unit 8, the retort 7, and the cooler 10 have a downward slope.

Next, the dechlorination treatment of this heating dechlorination treatment apparatus B will be explained.

When the heating dechlorination apparatus B is operated, the fly ash a in the first storage tank 1 is supplied to the hopper 3 by the feeder 1a, and the incinerated ash e in the second storage tank 20 is fed. It is supplied to the hopper 3 by 20a. that time,
The incineration ash e which is an adhesion preventing material is supplied to the fly ash a in a predetermined ratio (10 wt% or more, preferably 10 to 20 wt%). Ash in the hopper 3 (fly ash a and incinerated ash e) g
Is supplied to the rotary drum type heating device 5 by the constant amount feeder 4.

This ash g is heated by the air heater 6 in the presence of the air b to rotate the rotary drum type heating device 5
While passing through one to several retorts 7 (about 3 to 10)
It is stirred for about a minute) and mixed uniformly. At the same time, a predetermined temperature (for example, 400 to 550 ° C., preferably 430 to 480 ° C.) is set by the cylindrical heating unit 8 located outside thereof.
To be heated. At that time, water contained in the ash g is evaporated and dioxins are thermally decomposed and dechlorinated. The dechlorinated ash g'is discharged to the discharge device 9,
Unburned matter in ash g burns.

The ash g ′ discharged to the discharging device 9 is, for example, 40 ° C./min or more, preferably 150 ° C., in a rotating drum type cooling device 10 so that dioxins are not resynthesized.
It is rapidly cooled at a cooling rate of not less than 1 minute / minute, and becomes dechlorinated ash g ″ at, for example, 80 ° C. or less, preferably room temperature.

On the other hand, the exhaust gas d separated by the discharge device 9
Is diluted by the air b taken in by the blower blower 11 and sent to the dust collector 12. Then, the dust collector 12, the activated carbon adsorption tower 13, and the attracting blower 1
It is supplied to an incinerator (not shown) via No. 4. Further, the ash a ′ captured by the dust collector 12 is fixed in the fixed amount supply device 2
It is returned to the hopper 3.

As described above, when the fly ash a is mixed with the incineration ash b which is the adhesion preventing material at a predetermined ratio, the fly ash a does not adhere to the inner surface of the retort 7 of the rotary drum heating device 5.

[0032]

[Example] (Example 1) "Table" shows the results of adhesion prevention effect depending on the presence or absence of incinerated ash. Here, the operating conditions of the heating dechlorination apparatus are as follows.

[0033] 1) Incinerated ash particle size: 15 mm or less 2) Water content: 25% or less 3) Ash cooling rate: 40 ° C / min or more 4) Oxygen concentration: 5-15%

[0034]

[Table 1]

The concentration of dioxins was measured from this "Table 1" using the mixing ratio of fly ash and incineration ash and the heating temperature as parameters. When the incineration ash was not mixed, the heating temperature was 430 ° C. As the ash begins to adhere and heat transfer deteriorates, the heat treatment of fly ash becomes insufficient and the removal rate of dioxins is low. Further, when the heating temperature was 450 ° C., the fly ash was granulated, and the operation was impossible.

On the other hand, when the mixing ratio of the incinerated ash is 10 wt% or more, no granules are formed even if the heating temperature is 450 ° C., dioxins can be decomposed, and it is effective in preventing adhesion in the retort. There was found.

[0037]

As described above, according to the present invention, the following effects can be obtained. That is, 1) The fly ash, which easily adheres and the organic chlorine compound is difficult to remove, and the anti-adhesion material such as incineration ash are heat-treated at the same time to prevent the fly ash from adhering to the retort and to transfer heat Could be suppressed.

2) Fly ash solidifies into a dumpling in the retort (for example, a diameter of 30 mm or more), the organochlorine compound is not discharged from the heater before it is sufficiently decomposed, and the DXNs removal rate is improved. Improved.

3) Fly ash and the anti-adhesion material are mixed, but since they are uniformly stirred and mixed in the retort, no special device such as a stirrer or a mixer is required.

4) Since the heating temperature is low, there is almost no change in the physical properties of fly ash or the anti-adhesion material. Therefore, it can be reused as aggregate, sand or the like after the heat treatment.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for carrying out an ash treatment method according to the present invention.

FIG. 2 is a schematic diagram of a pretreatment means for incinerated ash.

FIG. 3 is a schematic view of a heating dechlorination treatment apparatus.

FIG. 4 is a schematic view of a conventional thermal dechlorination apparatus.

[Explanation of symbols]

a Fly ash A, B Heat dechlorination equipment e Material for preventing adhesion of incineration ash discharged from the bottom of incinerator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Maaya Itaya             Mitsui Shipbuilding No. 1 Hachiman Kaigan Dori, Ichihara City, Chiba Prefecture             Chiba office F-term (reference) 4D004 AA37 AB06 CA22 CA32 CC11                       DA03 DA06 DA10

Claims (5)

[Claims] 1. When the fly ash collected from equipment such as a dust collector of an incinerator of a stoker type or a fluidized bed type, a boiler, an air preheater, etc. is dechlorinated by a heating dechlorination treatment device, A method for treating ash, characterized in that ash is mixed with an anti-adhesion material such as incineration ash discharged from the bottom of an incinerator at a predetermined ratio, and the mixture is supplied to the thermal dechlorination treatment device. 2. A mixture of fly ash and an anti-adhesion material is added to 400
The ash treatment method according to claim 1, wherein the heat treatment is performed at 550 ° C. 3. A mixture of fly ash and an anti-adhesion material at 40 ° C.
The ash treatment method according to claim 1, wherein rapid cooling is performed at a cooling rate of not less than 1 minute. 4. The ash processing method according to claim 1, wherein the anti-adhesion material is mixed with fly ash in a proportion of 10 wt% or more. 5. The ash treatment method according to claim 1, wherein the adhesion preventing material such as incineration ash discharged from the bottom of the incinerator is crushed into particles having a predetermined particle size or less in advance.