JP2002045820A - Method and system for decomposing dioxins in incinerated residue and/or molten fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system for decomposing incinerated residue and/or molten fly ash, by which dioxins are decomposed into the reclaimable reference value or lower while lowering the initial cost. SOLUTION: This method and system for decomposing incinerated residue and/or molten fly ash comprise adding an inexpensive phosphoric acid-based dioxin decomposing chemical to a raw material to be treated consisting of incinerated residue and/or molten fly ash, heating/agitating them at a prescribed temperature for a prescribed time to decompose the dioxins by the reduction action of the phosphoric acid-based dioxin decomposing chemical and subjecting the dioxin-decomposed material to heavy metal elution preventing treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing incineration residues discharged from an incineration facility for municipal waste and / or dioxins in molten fly ash discharged from a melting facility to a landfill standard value or less and a method for decomposing the same. About the system.

[0002]

2. Description of the Related Art Conventionally, incineration residues (main ash and fly ash) discharged from incineration facilities for municipal garbage and the like and / or molten fly ash discharged from a melting facility are subjected to a treatment for preventing heavy metal elution by a chelating chemical treatment. And disposed at the final disposal site. Recently, a device for decomposing (dechlorinating) dioxins in incineration residues and / or molten fly ash has been developed.

[0003]

However, in the apparatus for decomposing (dechlorinating) dioxins, it is necessary to heat and agitate the processing raw materials in a low oxygen state, and the sealing structure of the apparatus (mainly a rotary kiln) is required. However, there is a problem that a quenching device for preventing re-synthesis of dioxin is required, and the initial cost is high. The present invention has been made in view of the above-mentioned problems, and eliminates the need for a quenching device for preventing dioxin resynthesis and reduces the initial cost of dioxins and incineration residues that can be decomposed to a landfill standard value or lower and / or An object of the present invention is to provide a method and a system for decomposing dioxins in molten fly ash.

[0004]

In order to achieve the above-mentioned object, the method of the present invention for decomposing incineration residues and / or dioxins in molten fly ash to a landfill standard value or less is described in the following. A step of adding a phosphoric acid-based dioxin-decomposing agent as a reducing agent to a processing material composed of fly ash; In a rotary kiln at a temperature of 250-550 ° C.
Heating and stirring for up to 60 minutes to decompose dioxins contained in the processing raw material by the reducing action of the phosphoric acid-based dioxin decomposing agent.

Further, in order to achieve the above object, the system for decomposing incineration residues and / or dioxins in molten fly ash to a landfill standard value or less according to the present invention quantitatively converts the incinerated residue or molten fly ash. The incineration residue or raw material quantitative supply device 1 to be supplied, the agent quantitative supply device located downstream of the raw material constant supply device and for quantitatively supplying the phosphoric acid-based dioxin decomposing agent, and the incineration residue or the The molten fly ash and the phosphoric acid-based dioxin-decomposing agent are heated and stirred at 250 to 550 ° C. and retained inside for a predetermined period of time, and the phosphoric acid-based dioxin-decomposing agent undergoes thermal decomposition during this stay, thereby reducing hydrogen and the like. Generates a reactive gas and a strong reducing agent, creates a reducing atmosphere inside, and strongly reduces chlorine in dioxins contained in incineration residues or molten fly ash A decomposer that selectively attacks and discharges the processed material in which the content of dioxins is below the reference value by dechlorinating, and a transport device that transports the processed material to the heavy metal elution prevention device without quenching. A dust collector for removing dust containing a small amount of dust generated from the decomposition device,
And conveying means for returning the exhaust gas to the inside of the incinerator or the secondary combustion furnace.

Here, the phosphoric acid-based dioxin decomposing agent is, for example, an aluminum compound and / or a phosphoric acid and / or hypophosphorous acid-containing decomposing agent or a phosphorous acid and / or hypophosphorous acid. There are degradation agents containing titanium compounds. And as the phosphorous acid,
Phosphorous acid or phosphite is used. Examples of the phosphite include sodium phosphite, potassium phosphite, calcium phosphite, magnesium phosphite, ammonium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, calcium hydrogen phosphite, and sodium phosphite. Magnesium phosphate and the like. In addition, phosphorous acid and a phosphite can be used in mixture of 2 or more types. Further, as the hypophosphorous acid, hypophosphorous acid or hypophosphite is used.
Examples of the hypophosphite include sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, ammonium hypophosphite and the like.
In addition, hypophosphorous acid and hypophosphite can be used as a mixture of two or more. Further, as the aluminum compound, for example, aluminum sulfate, aluminum hydroxide, aluminum oxide, aluminum phosphate, aluminum nitrate, alumino-silica gel, and the like, and as the titanium compound, titanium oxide, titanium nitride, titanium sulfate, and the like can be given. Here, dioxins refer to polychlorinated dibenzoparadioxins (PCDDs), polychlorinated dibenzofurans, and coplanar-PCB (polychlorinated biphenyls).

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, a processing raw material composed of incineration residue and / or molten fly ash is quantitatively cut out from the raw material quantitative supply device 1, and a phosphoric acid-based dioxin decomposing agent is supplied from the chemical quantitative supply device 2 to the cut out processing raw material. Supply a fixed amount. At this time, the addition amount of the phosphoric acid-based dioxin decomposing agent as a reducing agent is 0.5 to 10% by weight.
The amount in the range is useful for decomposing dioxins below the landfill standard value and is economically advantageous.

Next, the processing raw material to which the phosphoric acid-based dioxin decomposing agent has been added is put into a decomposer 3 composed of a rotary kiln set at a temperature of 250 to 550 ° C., and is heated and stirred. At this time, the raw material to be treated is supplied to a decomposition device (rotary
(Kiln) 3 to stay for 5 to 60 minutes. During this stagnation, the phosphoric acid-based dioxin-decomposing agent thermally decomposes to generate a reducing gas such as hydrogen and a strong reducing agent, thereby causing the inside of the decomposer 3 to have a reducing atmosphere and at the same time being contained in incineration residues or molten fly ash. The strong reducing agent selectively attacks chlorine in dioxins, dechlorinates, and is discharged from the decomposer 3 as a processed product in which the content of dioxins is below the reference value. Exhaust gas containing a small amount of dust generated from the decomposition device 3 is removed by the dust collector 4 and the exhaust gas is returned to an incinerator (not shown) or a secondary combustion furnace. Is returned to.

At this time, the reason why the catalyst is put into the decomposition device 3 composed of a rotary kiln at a temperature of 250 to 550 ° C. is that if the temperature is lower than 250 ° C., the phosphoric acid-based dioxin decomposing agent does not decompose. .

On the other hand, if the temperature is higher than 550 ° C., the thermal durability of the decomposition apparatus 3 tends to be a problem. It is also a temperature that can be realized at relatively low cost with an electric heater.

Further, the reason for keeping the inside of the decomposition apparatus 3 for 5 to 60 minutes is that the dioxins can be sufficiently decomposed to a landfill reference value or less in this time.

Next, the discharged processed material and dust are carried into the heavy metal elution prevention equipment 6 by the transport device 5. In this way, the dioxins are decomposed to a landfill standard value or less, and the processed products are sequentially transported to a final disposal site and discarded.

[0013]

As is apparent from the above description, the present invention comprises a step of adding a phosphoric acid-based dioxin-decomposing agent as a reducing agent to a processing raw material comprising incineration residues and / or molten fly ash; The dioxin-decomposing agent is added to the raw material in an amount of 0.5 to 10% by weight, and the raw material is treated with a rotary kiln at a temperature of 250 to 550 ° C.
Heating and stirring for up to 60 minutes to decompose dioxins contained in the processing raw material by the reducing action of the phosphoric acid-based dioxin decomposing agent. Because it is a dioxin decomposition treatment method and a system that realizes this,
This eliminates the need for a quenching device for preventing re-synthesis of dioxins, has a low initial cost, and has the effect of inexpensively decomposing dioxins in incineration residues and / or molten fly ash to landfill standard values or less.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a system that implements the present invention.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 Raw material constant supply device 2 Drug constant supply device 3 Decomposition device 4 Dust collector 5 Transport device 6 Heavy metal elution prevention equipment

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D004 AA36 AB03 AB07 CA12 CA15 CA24 CA37 CB09 CB42 CB44 CC12 DA03 DA06 DA10

Claims (3)

[Claims] 1. A step of adding a phosphoric acid-based dioxin-decomposing agent as a reducing agent to a treatment material comprising incineration residues and / or molten fly ash, The raw material added in the range of 10 to 10% by weight is heated to 250 to 550 ° C by a rotary kiln.
Heating and stirring at a temperature of 5 to 60 minutes to decompose dioxins contained in the processing raw material by the reducing action of the phosphoric acid-based dioxin decomposing agent. A method for decomposing dioxins in fly ash. 2. The method for decomposing dioxins in incineration residues and / or molten fly ash according to claim 1, wherein the oxygen concentration in the rotary kiln is 1 to 21%. 3. A raw material quantitative supply device 1 for quantitatively supplying an incineration residue or molten fly ash, and a chemical quantitative supply device positioned downstream of the raw material quantitative supply device 1 for quantitatively supplying a phosphoric acid-based dioxin decomposing agent. 2, a phosphoric acid-based dioxin-decomposing agent added at a predetermined ratio to the incineration residue or molten fly ash; and the incineration residue or molten fly ash;
The mixture is heated and stirred at 50 to 550 ° C. and retained inside for a predetermined time, and during this retention, the phosphoric acid-based dioxin decomposing agent undergoes thermal decomposition to generate a reducing gas such as hydrogen and a strong reducing agent. At the same time as the reducing atmosphere, the strong reducing agent selectively attacks chlorine in dioxins contained in the incineration residue or molten fly ash, and dechlorinates the treated products whose dioxin content is below the reference value. Disassembly device 3 to discharge
A transport device 5 for transporting the treated material to the heavy metal elution prevention device 6 without quenching, a dust collector 4 for removing exhaust gas containing a small amount of dust generated from the decomposition device 3, and a dust collector 4 for removing the exhaust gas from the incinerator. Or a transporting means for returning to the secondary combustion furnace; and a system for decomposing dioxins in incineration residues and / or molten fly ash.