JP2001276567A - Method for removing dioxins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of certainly removing dioxins in a fluid such as exhaust gas or wastewater in a temperature range from a low temperature to a high temperature. SOLUTION: Artificial zeolite and an acidic substance removing material are used in order to remove dioxins.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dioxins ("dioxins" defined in Article 2 of the Law on Special Measures against Dioxins No. 105 of 1999, and "polychlorinated dibenzofurans, Polychlorinated dibenzo-para-dioxin, coplanar-polychlorinated biphenyl "
Is used as a generic expression. The same shall apply hereinafter). More specifically, the present invention relates to a method for efficiently removing dioxins contained in exhaust gas from waste incineration facilities and wastewater from wastewater treatment facilities and the like.

[0002]

2. Description of the Related Art Dioxins are contained in exhaust gas generated from garbage incineration facilities for incinerating industrial waste and general household garbage. Here, as is well known, dioxins cause skin and visceral disorders, are teratogenic and carcinogenic, and are unprecedented toxic substances. In particular, 2,3,7,8-
Dibenzo-para-dioxin tetrachloride is said to be one of the most toxic substances obtained by mankind. In addition, other dioxins are harmful to the human body. Among them, the toxicity of polychlorinated biphenyl (PCB) is a problem.
It has a particularly toxic planar structure among PCBs.

[0003] In recent years, various problems of contamination by such highly toxic dioxins have been pointed out. In particular, it has been discovered that incineration of garbage may generate dioxins, which is a further problem. In other words, depending on the operating conditions of the garbage incineration plant, dioxins are generated by incineration of the garbage, and the generated dioxins are mixed with fly ash discharged from the garbage incineration plant or as exhaust gas from the garbage incineration plant through the chimney. There have been problems such as emission and pollution of the soil around the waste incineration plant. In addition, wastewater containing dioxins is discharged from a wastewater treatment facility, causing problems such as polluting rivers.

[0004]

Heretofore, as a removal method using an adsorbent for adsorbing and capturing dioxins, a removal method using activated carbon as the adsorbent has been known. However, despite the fact that dioxins in exhaust gas from garbage incineration plants are also contained in large amounts in the tar component of the exhaust gas, activated carbon, particularly in the case of exhaust gas containing a large amount of tar component, removes the tar component itself. Is not always sufficient, and the pores are blocked by the adhesion of the tar component to the surface of the activated carbon, which results in a decrease in the ability to remove dioxins. In particular, coplanar
Regarding PCB, the removal ability is significantly reduced by the tar component, and there is a need for a removal method using an adsorbent having a stable removal ability regardless of the amount of the tar component.

In order to prevent the resynthesis of dioxins, before passing through a temperature range of about 300 ° C., which is considered particularly easy to resynthesize, aromatic hydrocarbons and chlorine, Is desirably removed, and it is therefore desirable to use an adsorbent that can be used at a high temperature of 400 ° C. or higher. However, activated carbon has a risk of explosion at high temperatures and is difficult to use at high temperatures.

Accordingly, the present inventors have conducted intensive studies to develop an adsorbent capable of sufficiently removing dioxins in exhaust gas, and as a result, it has been found that zeolite contains tar components in exhaust gas and dioxin contained therein. That it can adsorb chemicals well and that dioxins in exhaust gas can be sufficiently removed even when the amount of tar components in exhaust gas is large, and that it can be used at high temperatures and that dioxins are sufficiently removed even at high temperatures I found what I could do.

[0007] In addition, HCl, SOx, NO
When a large amount of acidic gas such as x is contained, or when a large amount of acidic substances such as hydrochloric acid, sulfuric acid, and nitric acid are contained in treated wastewater, the surface structure of zeolite is gradually destroyed. The present invention has been found to have an effect on the removal performance of a kind, and completed this invention.

[0008]

Means for Solving the Problems The present invention has been made to solve the above problems, and the invention according to claim 1 is a method for removing dioxins in a fluid, comprising an artificial zeolite. And an acidic substance removing material.

The invention according to claim 2 is characterized in that acidic substances in the fluid are removed in advance by the acidic substance removing material, and then dioxins in the fluid are removed by the artificial zeolite.

The invention according to claim 3 is characterized in that the artificial zeolite and the acidic substance removing material are each in the form of powder,
It is characterized in that these are blown into a fluid and then both are collected.

[0011] The invention according to claim 4 is characterized in that a granular mixture of the artificial zeolite and the acidic substance removing material is formed, filled in a removing container, and a fluid is circulated in the removing container. I have.

Further, the invention according to claim 5 is characterized in that the acidic substance removing material is an alkali agent.

[0013]

Next, an embodiment of the present invention will be described. A typical example of the fluid containing dioxins removed by the removal method of the present invention is an exhaust gas from a garbage incineration plant. In addition, gases containing dioxins, liquids containing dioxins,
For example, the removal method of the present invention can be used for removing dioxins in wastewater from a wastewater facility. In particular,
The effect of the present invention is more exhibited when the exhaust gas contains a large amount of an acidic gas or a tar component, the exhaust gas contains an acidic gas and the amount of the tar component fluctuates, or the exhaust gas has a high temperature.

First, according to the first aspect of the present invention,
The present invention can be suitably carried out for removing dioxins in a fluid such as exhaust gas and wastewater. In the present invention, the artificial zeolite and the acidic substance removing material are used for removing dioxins in the fluid. By using the artificial zeolite and the acidic substance removing material, destruction of the surface structure of the artificial zeolite is prevented, and the performance of removing dioxins by the artificial zeolite is maintained. Here, it is preferable that the artificial zeolite and the acidic substance removing material are formed into a powder or a granule.

Next, in the invention according to the second aspect, the destruction factor of the surface structure of the artificial zeolite is removed in advance by removing the acidic substance in the fluid with the acidic substance removing material in advance. Thereafter, dioxins in the fluid are removed while maintaining the performance of removing the artificial zeolite. Specifically, in the case of an incinerator having a structure capable of easily removing an acidic gas, the acidic substance in the exhaust gas is removed with the acidic substance removing material, for example, an alkali agent, and then the powdery artificial zeolite is removed. Blowing into the exhaust gas, and can be a method of collecting the artificial zeolite,
Further, depending on the implementation, a method may be adopted in which the granular artificial zeolite is charged into an appropriate removal container, for example, a column, and the exhaust gas is circulated through the column.

Here, regarding the invention of claim 2,
A modification of the embodiment will be further described. First, the column is filled with the alkaline agent (hereinafter, referred to as “first packed column”), and the artificial zeolite is packed into the column (hereinafter, referred to as “second packed column”). Channel, for example, the first packed column is arranged on the upstream side of the chimney, and the second packed column is arranged on the downstream side thereof. After the exhaust gas flows through the first packed column, the second packed column is caused to flow. It can be configured.
Furthermore, the downstream side of the first column may be configured to blow the powdered artificial zeolite into exhaust gas and collect the artificial zeolite.

Next, in the invention according to the third aspect, for example, in the case of a large incinerator, the artificial zeolite and the alkaline agent in the form of powder are blown into exhaust gas, and then both are collected. This removes dioxins in the exhaust gas. As for the blowing, there are a method of blowing both at the same time toward the same spot, and a method of blowing the alkaline agent on the upstream side and blowing the artificial zeolite on the downstream side. In addition, the artificial zeolite and the alkaline agent are mixed, and a powder of this mixture is blown into exhaust gas, and then collected to remove dioxins in the exhaust gas.

Further, in the invention according to the fourth aspect, the artificial zeolite and the alkaline agent in a granular form are filled in the column, and the exhaust gas is circulated through the column to be collected. Remove dioxins in it. In addition, the artificial zeolite and the alkaline agent are mixed, the mixture is granulated, and the mixture is packed in the column, and the exhaust gas is circulated and collected in the column to remove dioxins in the exhaust gas. Remove. For example, when treating exhaust gas from an incinerator whose combustion is unstable, such as a small batch type plastic furnace, a mixture of the granulated artificial zeolite and the alkaline agent (that is, a granular mixture) or the artificial zeolite is used. And a mixture of the alkaline agent and a granulated mixture (that is,
The particulate mixture is packed in the column, and the exhaust gas is passed through the column to remove dioxins in the exhaust gas.

The artificial zeolite in the present invention is a zeolite synthesized from coal ash or the like, and is distinguished from a synthetic zeolite that requires a somewhat pure raw material (silicic acid, aluminum hydroxide, etc.). is there. And this artificial zeolite contains intermediate products and unburned carbon components that are not completely zeolite, and the purity of zeolite (content ratio of zeolite crystals) is between synthetic zeolite and natural zeolite. positioned. Therefore, this artificial zeolite, due to the impurities (intermediate products, unburned carbon components) contained,
It has specific characteristics different from synthetic zeolites and natural zeolites, for example, useful properties such as adsorption performance and ion exchange performance similar to activated carbon. The cation exchange capacity is equal to or about three times that of natural zeolite.

The method for producing the artificial zeolite is not particularly limited, and may be any one obtained by a so-called dry method or wet method. This artificial zeolite can also be manufactured from fly ash. For example, a fly ash having a small particle diameter and an aqueous sodium hydroxide solution having a concentration of about 2.5 to 3.5 N are reacted at about 90 ° C. for 12 to 28 hours, and then washed with water and dried to obtain a sodium-type artificial zeolite. Can be obtained. Further, in an aqueous solution of iron compounds (iron nitrate, iron chloride, etc.), calcium salts, aluminum salts, and potassium salts, sodium ions, iron ions, calcium ions, aluminum ions,
By replacing the potassium ions by ion exchange, artificial zeolites of iron type, calcium type, aluminum type and potassium type can be obtained. Here, as the fly ash, those derived from incineration of coal, pulp and the like are preferable, but those derived from incineration of general waste and industrial waste can also be used.

Next, an alkaline agent is suitably used as the acidic substance removing material in the present invention. This alkaline agent is used as a neutralizing agent, and examples thereof include slaked lime and sodium hydroxide. The type and the like of these alkali agents are not particularly limited, and those which are usually commercially available can be used.

The acidic component is generally discharged at a high concentration when waste contains a large amount of vinyl chloride or the like.
In particular, when the vinyl chloride content exceeds 1%, a large amount of hydrogen chloride (HCl) is generated, and in such a case, the artificial zeolite has a reduced removal ability over a long period of use,
By using the removal method of the present invention, dioxins can be sufficiently removed even when the vinyl chloride content exceeds 1%. In addition, since dioxins can be sufficiently removed regardless of the amount of acidic components, the removal rate of dioxins is stabilized with respect to changes in the amount of acidic components in exhaust gas. Therefore, it can also be used for treating exhaust gas from an incinerator where the amount of vinyl chloride in the waste varies, such as a small batch type plastic furnace.

Furthermore, the removal method of the present invention can prevent the deterioration of the removal ability due to long-term use by removing the acidic components. As a result, when the column is packed and the exhaust gas is allowed to pass, the service life until breakthrough is reached. Becomes longer.

[0024]

Next, the present invention will be described with reference to examples, but these are only examples and do not limit the scope of the present invention.

Example 1 An exhaust gas at a temperature of 160 ° C. was passed through a column filled with granular slaked lime from a batch small incinerator to reduce the hydrogen chloride concentration to 5 ppm or less in advance, and then the space velocity (so-called SV value, which is obtained by the general formula: SV = gas flow rate m ³ / h ÷ filling capacity m ³ .
At 0000 h ⁻¹ , the mixture was passed through a column filled with a granular calcium-type artificial zeolite alone, and the flow was measured according to “JIS K-03”.
11 “Dioxins and coplanar PCB in exhaust gas
Measurement method ”(hereinafter referred to as“ JIS measurement method ”), and the removal rate of dioxins was determined. When the amount of hydrogen chloride in the exhaust gas is 100 to 150 ppm, the removal rate in the initial operation is 99%, and the removal rate after 3 months is 9%.
6%.

Example 2 When passing exhaust gas from a large stoker-type incinerator containing 80 to 100 ppm of hydrogen chloride through a bag filter, 5% of powdered slaked lime was added before the bag filter.
Added powdered iron-type artificial zeolite blowing at a rate of 0.2g per exhaust gas 1 m ^3, was collected powdered iron-type artificial zeolite by the bag filter. The amount of dioxins before and after the bag filter was measured,
The removal rate of dioxins was determined according to the S measurement method. When the temperature of the exhaust gas is 160 ° C., the removal rate is 96%, and when the temperature of the exhaust gas is 450 ° C., the removal rate is 9%.
1%.

Comparative Example 1 Dioxin removal rates were determined in the same manner as in Example 2 except that slaked lime in powder form was not added. When the temperature of the exhaust gas was 160 ° C., the removal rate was 91%, and when the temperature of the exhaust gas was 450 ° C., the removal rate was 85%.

EXAMPLE 3 A powdery calcium-type artificial zeolite and a powdered slaked lime were mixed and formed into a granule having an average particle size of 10 mm, and the mixture was packed in a column. Exhaust gas having a temperature of 160 ° C. was discharged from a small batch incinerator. After passing through the column at the space velocity of 10,000 h ^-1 , dioxins before and after the treatment were measured according to the JIS measurement method, and the dioxin removal rate was determined. When the amount of hydrogen chloride in the exhaust gas was 100 to 150 ppm, the removal rate at the beginning of the operation was 98%, and the removal rate after three months was 97%.

Example 4 A column was filled with granular calcium-type artificial zeolite having an average particle diameter of 10 mm and granular slaked lime at a weight ratio of 9: 1. Exhaust gas at a temperature of 160 ° C. was discharged from a batch type small incinerator into the space. After passing through the column at a speed of 10,000 h ^-1 , the removal rate of dioxins was determined according to the JIS measurement method. When the amount of hydrogen chloride in the exhaust gas was 100 to 150 ppm, the removal rate at the beginning of the operation was 97%, and the removal rate after three months was 95%.

Comparative Example 2 The removal rate of dioxins was determined in the same manner as in Example 4 except that the granular calcium-type artificial zeolite was filled alone. When the amount of hydrogen chloride in the exhaust gas was 100 to 150 ppm, the removal rate at the beginning of the operation was 98%, and the removal rate after three months was 91%.

[0031]

As described above, according to the removal method of the present invention, since the performance degradation due to the acidic component can be prevented, dioxins in the fluid such as exhaust gas and wastewater in the temperature range from low to high can be reliably detected. Can be removed. Also, stable removal performance can be obtained even when the amount of hydrogen chloride in the fluid is large, that is, when the amount of acidic components is large.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Nakamura 7 Horie-cho, Matsuyama-shi, Ehime Miura Kogyo Co., Ltd. F-term (reference) 4D002 AA02 AA12 AA19 AA21 AC04 BA03 BA04 CA07 CA11 DA02 DA05 DA45 EA02 4D024 AA04 AB11 BA07 BB01 BB05 DB01 DB20

Claims (5)

[Claims] 1. A method for removing dioxins in a fluid, the method comprising using an artificial zeolite and an acidic substance removing material. 2. The method for removing dioxins according to claim 1, wherein the acidic substance in the fluid is removed in advance by the acidic substance removing material, and then dioxins in the fluid are removed by the artificial zeolite. . 3. The method for removing dioxins according to claim 1, wherein the artificial zeolite and the acidic substance removing material are each made into a powder, and these are blown into a fluid, and then both are collected. 4. Forming a granular mixture of the artificial zeolite and the acidic substance removing material, filling the mixture into a removing container,
2. The method for removing dioxins according to claim 1, wherein a fluid is circulated in the removal container. 5. The method for removing dioxins according to claim 1, wherein the acidic substance removing material is an alkaline agent.