JP2001179207A - Method for treating waste active carbon in which dioxins are adsorbed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such social and environmental problems that dioxins are contained in flue gas generated at a refuse incineration installation or the like and are conventionally removed by a method to atomize active carbon into a flue and thereby adsorb and remove the dioxins contained in the flue gas and in order to treat waste active carbon in which the dioxins are adsorbed, the dioxins need to be decomposed by heating the waste active carbon in an oxygen shortage state under a sophisticated airtight atmosphere and further, a special installation for keeping the oxygen deficient state is required with unavoidable large investment in facilities and high maintenance cost therefor. SOLUTION: This method for treating the waste active carbon in which the dioxins are adsorbed is characterized in that at least one kind selected from the group of a phosphorus compound, an aluminum compound and a calcium compound is added to the waste active carbon in which the dioxins are adsorbed and this mixture is heated and treated at 200-600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating waste activated carbon adsorbing dioxins.

[0002]

2. Description of the Related Art Exhaust gas generated by incineration of municipal garbage, industrial waste, and the like includes:
Recently, various harmful substances such as SOx, NOx, hydrogen chloride, and heavy metals are contained. Particularly, there is a case where a large amount of toxic chlorine compounds such as dioxins is contained. .

[0003] Chlorine compounds such as dioxins (hereinafter simply referred to as dioxins) are very stable substances, do not dissolve in water, and do not lose their toxicity semipermanently. It is regarded as an important chemical for pollution control. In order to reduce the amount of dioxins that are likely to be generated when incinerating waste, especially plastic waste, at garbage incineration plants, conventional methods include spraying activated carbon powder into the flue and burning it. After the dioxin in the exhaust gas is adsorbed on the activated carbon by contacting the exhaust gas generated by the activated carbon with the activated carbon, the dioxin is removed from the exhaust gas by separating the activated carbon from the exhaust gas by passing through a bag filter. Have been.

[0004] Activated carbon that has been sprayed onto the flue of an incinerator and adsorbed dioxins in the exhaust gas may cause serious environmental problems if it is discarded as it is. A method such as dumping is adopted. Conventionally, as a method of heating and decomposing dioxins, a method of heating in a non-penetrating system in an oxygen-deficient state (Japanese Patent Publication No. 6-38863) is a method capable of efficiently decomposing dioxins. However, in this method, dioxins cannot be effectively decomposed unless they are in an oxygen-deficient state, and in order to obtain an oxygen-deficient state, work in a closed system or in an inert gas atmosphere to eliminate air intrusion, etc. It is necessary to employ the method described above, and a high airtight structure is required for the heat treatment apparatus, and thus there is a problem that high costs are required for capital investment and maintenance of the equipment. Further, in the above method, even if the chlorinated aromatic compound such as dioxins is thermally decomposed, there is a possibility that there is a substance which is decomposed only to the stage of chlorine and the aromatic compound. May be combined under heating conditions to generate dioxins and the like again.

The inventors of the present invention have been made in order to solve the above-mentioned problems, and do not require a special processing apparatus or a complicated operation such as a conventional method which requires heating in an oxygen-deficient state. An object of the present invention is to provide a method for treating waste activated carbon adsorbing dioxins, which can efficiently and thermally decompose dioxins adsorbed on activated carbon at low cost.

[0006]

That is, the method of the present invention for treating waste activated carbon having adsorbed dioxins is characterized in that at least one selected from a phosphorus compound, an aluminum compound and a calcium compound is added to the waste activated carbon having adsorbed dioxins. It is characterized in that seeds are added and heat treatment is performed at 200 to 600 ° C.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The phosphorus compounds used in the method of the present invention include, for example, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite.
Hypophosphorous acids such as ammonium hypophosphite; phosphorous acid, calcium phosphite, sodium phosphite, potassium phosphite, magnesium phosphite, ammonium phosphite, calcium hydrogen phosphite, potassium hydrogen phosphite, sodium hydrogen phosphite;
Phosphorous acids such as magnesium hydrogen phosphite; and phosphoric acids such as calcium phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate. Examples of the aluminum compound include aluminum phosphate, aluminum sulfate, aluminum hydroxide, aluminum oxide, aluminum nitrate, and alumino-silica gel. Examples of the calcium compound include calcium hydroxide, calcium oxide, and calcium carbonate. These compounds can be used as a mixture of two or more kinds. Of the above compounds, hypophosphite and aluminum compounds are preferred.

The above-mentioned phosphorus compounds, aluminum compounds,
The amount of at least one calcium compound to be added to the waste activated carbon is preferably 0.01 to 50% by weight, and particularly preferably 1 to 5% by weight of the waste activated carbon in the total amount of these compounds.

In order to heat-treat waste activated carbon to which at least one of the above compounds has been added, either a closed-type heating furnace or an open-type heating furnace in which air (air) can freely flow in and out of the furnace. Can also be used. As the heating furnace, for example, a single kiln such as a square kiln, a round kiln, and a transfer kiln, a semi-continuous kiln such as a tunnel kiln and a rotary kiln, or a continuous kiln can be used. The temperature for heating waste activated carbon is 200-600 ° C
However, 300 to 500 ° C. is more preferable. The heating time is usually about 10 to 120 minutes,
About 60 minutes is preferable.

In the method of the present invention, it is not necessary to intentionally hold the inside of the heating furnace in an oxygen-deficient state during the heat treatment, but there is no problem even if the inside of the heating furnace becomes oxygen-deficient during the heating step.

The waste activated carbon to be treated by the method of the present invention is, for example, sprayed into a flue for the purpose of adsorbing dioxins contained in exhaust gas generated when waste is incinerated in a garbage incineration plant. Examples of the activated carbon include used activated carbon and waste activated carbon adsorbing dioxins, such as activated carbon used by filling an adsorption tower through which exhaust gas after passing through a bag filter is passed.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Examples 1-5, Comparative Examples 1-2 Waste activated carbon (dioxin adsorption) used to adsorb dioxins in exhaust gas by spraying onto a flue when waste is incinerated at a garbage incineration plant Amount of 400 ng / g)
The compounds shown in Table 1 were added, and the mixture was heated in a rotary kiln at the temperature and time shown in the same table. Table 2 shows the results of measuring the concentration of dioxins remaining after being absorbed by the waste activated carbon after the treatment. The amount of dioxins adsorbed and retained in the waste activity after the heat treatment is determined by the ash sample analysis in the Dioxins Standard Measurement and Analysis Manual for Waste Treatment (February 1997, Ministry of Health and Welfare, Health and Welfare Bureau, Water Supply Environment Department, Environment Improvement Division). The extract was extracted into a solvent according to the method, and the concentration of dioxins extracted in the solvent was measured by GC-MS analysis. In addition, Examples 1 to
In No. 5, the heat treatment was performed such that oxygen was supplied from the outside into the rotary kiln during the heat treatment. Comparative Example 1,
For No. 2, before the start of the heat treatment, a nitrogen gas was supplied into the rotary kiln to replace the oxygen in the rotary kiln, and then the heat treatment was performed in an oxygen-deficient state.

[0014]

[Table 1] * 1: Weight% based on the weight of waste activated carbon

[0015]

[Table 2]

[0016]

As described above, according to the method of the present invention, waste activated carbon used for, for example, adsorbing dioxins in flue gas generated when garbage or industrial waste is incinerated can be efficiently treated. Thus, the dioxins adsorbed on the waste activated carbon can be effectively decomposed without holding the inside of the heating furnace in an oxygen-deficient state and performing heat treatment. For this reason, the method of the present invention requires less capital investment and has an effect that the treatment can be performed economically and efficiently, as compared with the conventional method that needs to maintain an oxygen-deficient state during the heat treatment.

Continued on the front page (72) Inventor Toshiharu Kuroda 4-66-1, Horikiri, Katsushika-ku, Tokyo Inside Miyoshi Yushi Corporation (72) Inventor Masatake Kawashima 4-66-1, Horikiri, Katsushika-ku, Tokyo Inside Miyoshi Yushi Corporation (72) Inventor Masafumi Moriya 4-66, Horikiri, Katsushika-ku, Tokyo Miyoshi Yushi Co., Ltd. F-term (reference) 4D002 AA21 AC04 BA04 DA41 4D004 AA47 AB07 CA22 CB09 CC11 CC12 DA03 DA06

Claims (1)

[Claims] 1. A waste activated carbon to which dioxins are adsorbed,
200-600 ° C. by adding at least one selected from a phosphorus compound, an aluminum compound, and a calcium compound
A method for treating waste activated carbon having adsorbed dioxins, wherein the activated carbon is heat-treated.