JPH06182151A - Treatment of exhaust gas - Google Patents

Abstract

PURPOSE:To make exhaust gas containing chlorine derivatives of methane, which are hard to be decomposed, harmless by adding gaseous chlorine derivatives of ethylene to the exhaust gas containing chlorine derivatives of methane and applying ultraviolet-rays to it. CONSTITUTION:After gaseous chlorine derivatives of ethylene such as trichloroethylene, terachloroethylene, etc., are added to exhaust gas containing chlorine derivatives of methane such as tetrachlormethane, chloroform, dichloromethane, chloromethane, etc., ultraviolet-rays are applied to the gas. As a result, the chlorine derivatives of methane are quickly and highly efficiently decomposed into inorganic compounds and the gas to be discharged outside can be made harmless.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for treating exhaust gas containing a chlorine derivative of methane.

[0002]

2. Description of the Related Art Wastewater containing harmful volatile organic chlorine compounds such as trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, carbon tetrachloride, chloroform and dichloromethane discharged from a substrate cleaning line is aeration. At present, it is released into the atmosphere as untreated, which is a problem in terms of global environmental protection.

[0003]

As a means for solving the above problems, the present inventor has already proposed "exhaust gas treatment device".
Various techniques have been proposed including (Japanese Patent Application No. 2-110500). These contents are ultraviolet rays (UV) having a wavelength of 184.9 nm and nascent ozone (O ₃ ) generated by the ultraviolet rays, or a photocatalyst decomposes a volatile organic chlorine compound contained in exhaust gas into an inorganic compound, and further ozone This is a method of decomposing residual ozone into oxygen by a decomposition catalyst to make it harmless. However, there is a problem that chlorine derivatives of methane such as carbon tetrachloride, chloroform and dichloromethane are not easily decomposed under irradiation of ultraviolet rays, ozone and a photocatalyst.

In view of the above-mentioned state of the art, the present invention is to provide a treatment method for detoxifying an exhaust gas containing a chlorine derivative of methane which is not easily decomposed.

[0005]

The present invention is characterized in that a small amount of a gaseous chlorine derivative of ethylene is added to an exhaust gas containing a chlorine derivative of methane, and then the gas is irradiated with ultraviolet rays. It is a method of treating exhaust gas containing.

The chlorine derivative of methane in the present invention means carbon tetrachloride, chloroform, dichloromethane, chloromethane and the like, and the chlorine derivative of ethylene means trichloroethylene, tetrachloroethylene and the like.

[0007]

It is known that an organic chlorine compound is decomposed into carbon dioxide (CO ₂ ) and hydrogen chloride gas (HCl) by irradiating it with ultraviolet rays. {Takashi Imagawa, Chemical Industry 4
1 , (1) 24-27 '90, Teruaki Kuninaga, Kenji Harada, etc. Water treatment technology 29 , (8) 483-487 '88} Generally, methane derivatives are more difficult to decompose than ethylene derivatives and have carbon numbers. In the same case, it is well known that the larger the number of substituted chlorines, the more difficult it is to decompose. (Teraki Kuninaga, Kenji Harada, Institute of Technology Report '89)

For example, trichlorethylene (C ₂ HCl
_The decomposition reaction of ₃ ) by ultraviolet rays (UV) is as follows, and is decomposed via radicals.

[0009]

[Chemical 1]

On the other hand, the chlorine derivative of methane is hard to generate similar radicals only by irradiation with ultraviolet rays, and is therefore difficult to decompose. Therefore, a small amount of a substance that is easily decomposed by ultraviolet irradiation is added to the exhaust gas containing the hardly decomposable organochlorine compound, and the H · radical generated in the formula (1) is generated as shown in the formula (3) below. Of oxygen (O ^* ) generated during decomposition of O ₃ or H ₂ as shown in equation (4).
Reacts with O and has strong oxidizing power. By this OH radical oxidatively decomposing a chlorine derivative of methane, a chlorine derivative of methane such as dichloromethane, which is difficult to be decomposed only by UV irradiation, is easily decomposed as shown in the following formulas (5) and (6). . That is, trichlorethylene acts as an initiator of radical decomposition reaction. Once the OH radical is generated (4)
As shown in the formula, since two H · radicals are produced from one H · radical, the chain reaction instantaneously decomposes, and a high decomposition rate can be obtained in a short time.

[0011]

[Chemical 2]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a test apparatus as an embodiment of the present invention will be described in detail with reference to FIG. In FIG. 1, the exhaust gas adjusted to have a predetermined concentration in the Tedlar bag 1 is caused to flow by the pump 2 into the photolysis reactor 4 at a predetermined flow rate. Reference numeral 3 is a buffer tank for flowing a predetermined (constant) amount into the photolysis reactor 4. Ultraviolet rays are generated from the Hg lamp 5 installed in the photolysis reactor 4 to decompose the organic chlorine compound in the exhaust gas. The decomposition rate is calculated by collecting exhaust gas from sampling points 6 and 7 and analyzing the concentration with a gas chromatograph equipped with an FID detector. If ozone, which is a by-product of the generation of ultraviolet rays, remains in the exhaust gas, it reacts with the organic chlorine compound during analysis (analysis by gas chromatograph) and the concentration of the organic chlorine compound decreases, making it impossible to accurately analyze the concentration in the exhaust gas. In advance, absorb ozone with hypo solution.

(Experimental example) 100 ppm or 1000
Table 1 shows the results obtained by irradiating the exhaust gas containing the chlorine derivative of methane adjusted to ppm and the chlorine derivative of ethylene adjusted to 1 ppm or 10 ppm with an Hg lamp for generating ultraviolet rays containing ultraviolet rays of 184.9 nm. In contrast to the difficulty of decomposing only with the chlorine derivative of methane, a significant improvement in the decomposition rate can be seen by coexisting with a minute amount of the chlorine derivative of ethylene.

[0014]

[Table 1]

[0015]

The chlorine derivative of methane can be obtained by adding a trace amount of the chlorine derivative of ethylene to the exhaust gas containing the chlorine derivative of methane which is difficult to be decomposed by the action of ozone and by-product of ultraviolet irradiation and the photocatalyst. It quickly and highly efficiently decomposes into inorganic compounds and detoxifies the gas discharged to the outside, which is useful for global environment conservation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a test apparatus as an embodiment of the present invention.

Claims (1)

[Claims] 1. A method for treating an exhaust gas containing a chlorine derivative of methane, which comprises adding a small amount of a gaseous chlorine derivative of ethylene to an exhaust gas containing the chlorine derivative of methane and then irradiating the gas with ultraviolet rays.