JPH0775766A - Method for treating dust in waste incineration treating device - Google Patents

Abstract

PURPOSE:To decrease the used quantity of a chelating agent or to lower the eluted quantity of heavy metal to a lower level by adding water, the chelating agent and a ferrite forming salt to dust separated in a dust collector of a waste incineration plant and kneading them at specified ratios to adjust pH and/or temp. CONSTITUTION:After waste gas generated when municipal waste, etc., is incinerated in an incineration furnace is cooled by a cooler 2, it is guided to a dust collector 3, where dust is removed and 20-35 pts.wt. water, >=0.1 pts.wt. chelating agent and 5 pts.wt. chelate forming salt are added to 100 pts.wt. dust and the mixture is thrown in a kneader 4. At this time, its pH and/or temp. is set in the region of ferrite formation. Thus, reduction and nonelution effect due to the addition of ferrous chloride and/or ferrous sulfate are added to the chelate treating method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating dust in a refuse incineration facility. The dust in the exhaust gas generated from the incinerator of municipal waste is collected by an electric dust collector and a tap filter. Since the collected dust is highly dispersible and contains heavy metals such as hexavalent chromium lead, it is necessary to change it to a form that is easy to handle and does not elute harmful metals. The present invention relates to an improvement in such a dust processing method.

[0002]

2. Description of the Related Art Conventionally, as a method of treating dust in the above-mentioned incineration ash melting treatment facility, a large amount of water and a chelating agent are added to the dust to make the dust into a slurry. 5-87324).
The present invention, a detoxified treated material in incineration ash melting treatment equipment, good workability, economically, the dust does not scatter, the liquid does not elute, semi-handy for handling For the purpose of providing a method for forming a solid solution, the ratio of 22 to 30 parts by weight of water and 1 to 5 parts by weight of a chelating agent to 100 parts by weight of dust separated by a dust collector in an incineration ash melting treatment facility is used. These are kneaded.

This is because the dust is originally highly soluble in water,
Both of them are not sufficiently compatible with each other by adding a small amount of water, and the dust is scattered. Therefore, a large amount of water is added to make the dust into a slurry-like substance and a detoxification treatment is performed.

A method of treating dust is also known, in which water and hydrochloric acid are added to the dust separated by a dust collector in a refuse incineration treatment facility, and a chelating agent and then ferric chloride are added and kneaded (special feature). (See Showa 63-278589).

[0005]

However, such a conventional method has a drawback in that handling of the resulting slurry-like material is extremely troublesome. At the time of disposal, the slurry is dehydrated and then dried, but this is tedious and uneconomical.

Further, when the heavy metal in the incineration ash molten exhaust gas dust is treated only with the chelating agent as in the treatment method of the above-mentioned JP-A-5-87324, the elution of heavy metals such as hexavalent chromium and lead can be prevented. Have difficulty. Attempting to reduce the elution amount of heavy metals such as hexavalent chromium and lead to a low level requires a large amount of chelating agent, resulting in high processing cost.

[0007] In December 1992, the water quality standards stipulated in the Water Supply Act were significantly revised and the regulations were strengthened. Along with this, it is expected that regulations on landfilling of wastes, disposal into the ocean, etc. will be tightened in the near future, and it is desired to develop a technology for reducing the amount of heavy metals eluted to a low level at a lower cost. .

The object of the present invention is to use an expensive chelating agent by adding the reducing and non-elution effects of the addition of ferrous chloride and / or ferrous sulfate to the conventional chelating treatment method. With the same amount of chelating agent, it is possible to reduce the elution amount of heavy metals to a lower level, and it is also possible to insolubilize heavy metals that do not require a chelating agent. To provide a treatment method.

[0009]

A method for treating dust in a refuse incineration treatment facility according to the present invention is devised to achieve the above-mentioned object, and the dust separated by a dust collector in the refuse incineration treatment facility is used. Water, a chelating agent, and a ferrite-forming salt are added to water 20 to 3 per 100 parts by weight of dust.
5 parts by weight, 0.1 parts by weight or more of a chelating agent, 5 parts by weight of a chelate-forming salt are added and kneaded, and pH and / or temperature is set in a ferrite forming region before and / or after kneading. It is what

The ferrite-forming salt is preferably primary chloride.
Iron and / or ferrous sulphate, in the ferrite forming region indicated by the coordinates in the range shown in the accompanying drawings.

The pH adjusting agent for pH reduction is preferably a compound which exhibits acidity by hydrolysis of ferric chloride and / or ferric sulfate.

The kneading is preferably carried out by using a vibrating kneader or a twin-screw kneading extruder, in which a plurality of rods are charged as a kneading medium.

The drug price is as follows: chelating agent (Eporba): 800-1000 yen / kg, 30% FeCl ₂ :
60 yen _{/ kg, FeSO 4 · 7H 2} O: about 40 yen / kg
Is.

[0014]

【Example】

Example 1 In the refuse incineration facility shown in FIG. 1, the exhaust gas generated when incinerating municipal solid waste in the incinerator (1) is a cooling device (2).
After cooling with, apply it to the dust collector (3).
, The dust in the exhaust gas is removed, and the purified exhaust gas is discharged to the outside of the system.

Dust 100 is added to the dust thus separated.
33 parts by weight of a chelating agent dissolved in 30 parts by weight of water (hereinafter referred to as a chelating agent aqueous solution), 5 parts by weight of ferrous sulfate, and a plurality of rods serving as a kneading medium are used for vibration. Type kneading machine (4) or twin-screw kneading extrusion molding machine, and continuously kneading, semi-solid solution kneaded product is continuously discharged from the same kneading machine (4) or two-screw kneading extrusion molding machine Let The temperature of this kneading is 60 ° C. and the pH is 5.
It was 9.

Examples 2 and 3 In the same manner as in Example 1 except that the ratio of ferrous sulfate to 100 parts by weight of dust was changed to 10 parts by weight (Example 2) and 20 parts by weight (Example 3). Processed. The temperature of this kneading was 60 ° C. and the pH was 5.7 (Example 2) and 5.5 (Example 3).

Example 4 A treatment was carried out in the same manner as in Example 2 except that the ratio of water to 100 parts by weight of dust was changed to 20 parts by weight (thus, the amount of the chelating agent aqueous solution was 23 parts by weight). The temperature of this kneading was 60 ° C. and the pH was 5.7.

Example 5 The same process as in Example 1 was carried out except that 5 parts by weight of ferrous chloride was used for 100 parts by weight of dust instead of ferrous sulfate. The temperature of this kneading is 60 ° C. and the pH is 5.
It was 9.

Examples 6 and 7 In the refuse incineration treatment in which dry dehydrochlorination (Ca (OH) ₂ blowing) is performed, the composition of Example 2 is further added, and ferric sulfate 20 is added to 100 parts by weight of dust. The procedure was the same as in Example 1 except that 20 parts by weight of ferric chloride (Example 7) were added. The temperature of this kneading is 60 ° C., and the pH is 11.3 (Example 6), 11.6.
It was (Example 7). The pH adjusting effect of ferric sulfate and ferric chloride is shown in FIG.

Example 8 The ratio of chelating agent to 100 parts by weight of dust was 0.1.
The same procedure as in Example 2 was carried out except that the amount of the chelating agent aqueous solution was changed to 30.1 parts by weight. The temperature of this kneading was 70 ° C. and the pH was 5.7.

Comparative Example 1 Treatment was carried out in the same manner as in Example 1 except that the ratio of ferrous sulfate to 100 parts by weight of dust was changed to 1 part by weight.
The temperature of this kneading was 60 ° C. and the pH was 6.3.

Comparative Examples 2 and 3 The ratio of water to 100 parts by weight of dust is 15 parts by weight in Comparative Example 2 (thus, the amount of the chelating agent aqueous solution is 33 parts by weight), and 40 parts by weight in Comparative Example 3 (and therefore the chelating agent aqueous solution). Was treated in the same manner as in Example 2 except that the amount was changed to 43 parts by weight. The temperature of this kneading is 60 ° C,
The pH was 5.6 in Comparative Example 2 and 5.7 in Comparative Example 3.

Comparative Examples 4 and 5 In Comparative Example 4, the kneading temperature was 30 ° C., and in Comparative Example 5, the same treatments as in Example 8 were carried out except that ferrous sulfate was not added. The temperature of this kneading is 6 in Comparative Example 5.
At 0 ° C., the pH was 5.7 in Comparative Example 4 and 5.
It was 8.

Comparative Examples 6 and 7 Treatment was carried out in the same manner as in Example 1 except that ferrous sulfate was not added. The temperature of this kneading was 60 ° C., and the pH was 6.2 in Comparative Example 6 and 12.4 in Comparative Example 7.

Heavy Metal Elution Test Results of Processed Products and State of Processed Products The processed products treated in Examples and Comparative Examples were subjected to a heavy metal elution test and the state of the processed products was examined.

The results are summarized in Table 1.

[0027]

[Table 1]

[0028]

Since the method for treating dust of the present invention is constructed as described above, the amount of expensive chelating agent used can be reduced, and if the amount of chelating agent is the same, elution of heavy metals to a lower level is possible. The amount can be reduced, and insolubilization treatment of heavy metals that does not require a chelating agent is possible.

Further, according to the method of the present invention, the dust in the incineration ash melting treatment facility can be handled with good workability, economically, without scattering of the dust, and with no outflow of liquid matter. It can be made into a convenient semi-solid solution, and can fix hexavalent chromium (or insolubilize) at low cost, which was a problem in the detoxification treatment of dust in incineration ash melting treatment equipment. Therefore, the externally processed product has an advantage that heavy metals are difficult to elute even when exposed to acid rain.

[Brief description of drawings]

FIG. 1 is a system diagram schematically showing an implementation state of the present invention in relation to a refuse incineration treatment facility.

FIG. 2 is a graph showing pH adjusting effects of ferric sulfate and ferric chloride.

FIG. 3 is a graph showing the influence of pH and reaction temperature on the type of product.

[Explanation of symbols]

 1: Waste incinerator 2: Cooling device 3: Dust collector 4: Vibratory kneader

Front page continuation (72) Inventor Toshio Hama 5-3-28 Nishikujo, Konohana-ku, Osaka City Hitachi Shipbuilding Co., Ltd. In the company

Claims (4)

[Claims] 1. Water, a chelating agent, and a ferrite-forming salt are added to the dust separated by a dust collector in a refuse incineration treatment facility, and 20 to 35 parts by weight of water per 100 parts by weight of dust,
Waste incineration characterized by adding 0.1 part by weight or more of a chelating agent and 5 parts by weight of a chelate-forming salt and kneading, and setting pH and / or temperature in a ferrite forming region before and / or after kneading. Dust processing method in processing equipment. 2. The ferrite-forming salt is ferrous chloride and / or
The method for treating dust in a refuse incineration facility according to claim 1, which is ferrous sulfate and is in a ferrite forming region indicated by coordinates within a range shown in the accompanying drawings. 3. The method for treating dust in a refuse incineration facility according to claim 1 or 2, wherein the pH adjusting agent for pH reduction is a compound which exhibits acidity by hydrolysis of ferric chloride and / or ferric sulfate. . 4. The dust in the refuse incineration facility according to claim 1, 2 or 3, wherein the kneading is performed by using a vibrating kneader or a twin-screw kneading extruder, in which a plurality of rods are charged as a kneading medium. Processing method.