JPH08281066A - Treatment of waste gases containing volatile organic chlorine compound and treating device therefor - Google Patents

Abstract

PURPOSE: To efficiently treat volatile org. chlorine compds. with low energy by irradiating waste gases contg. the volatile org. chlorine compds. with UV rays to change the properties of the volatile org. chlorine compds., then passing the waste gases through a biological treating device packed with packing materials deposited with microorganisms in a wet state. CONSTITUTION: The air contg. trichloroethylene, etc., is passed through the inside of a UV irradiation device 3 having passages and is irradiated with the UV rays by a low-pressure mercury lamp 2. The gas cracked to the org. chlorine compds., such as dichloroacetic acid with higher hydrophilic nature is introduced into the lower part of the biological treating device 4. The device 4 is internally provided with a packed phase 5 packed with the packing materials in which the microorganisms are deposited. This packed phase 5 is maintained in a wet state by sprinkling makeup water 8 replenished to a water receiving tank in the bottom of the biological treating device 4 as circulating water 7 from the sprinkling section in the upper part of the packed phase 5. The org. chlorine compds. with higher hydrophilic nature introduced into the lower part of the biological treating device 4 is passed through the packed phase 5, by which the gas is biologically treated. The gas is then discharged outside the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to exhaust gas for soil pollution treatment,
Volatile organochlorine compounds such as dry cleaning exhaust gas and metal cleaning plant exhaust gas (for example, 1,1,1 trichloroethane used in dry cleaning, tetrachloroethylene and trichlorethylene used in metal cleaning plant, methylene chloride, and other general solvents 1,2 dichloroethane, 1,1,2,2 tetrachloroethane, chloroform also used as a medicine, etc.).

[0002]

2. Description of the Related Art Conventionally, a combustion method, an activated carbon adsorption method or a combination thereof is used for treating exhaust gas containing a volatile organic chlorine compound. However, these methods are not necessarily suitable for exhaust gas with low concentration and large air flow. Biological treatment is a method capable of treating exhaust gas having a relatively low concentration and a large air volume with low energy, and has been put to practical use mainly for treating malodorous gases containing hydrogen sulfide, methyl mercaptan, ammonia and the like. However, biological treatment of volatile organochlorine compounds is still in the research stage and has not been put to practical use. Further, ultraviolet rays are a method capable of efficiently oxidizing and decomposing low-concentration substances, and are expected to be applied in the field of exhaust gas treatment in the future. The inventors of the present invention are characterized by supplying a hydrogen source into a gas phase containing a volatile organochlorine compound and then exposing the gas phase to ultraviolet rays to decompose the volatile organochlorine compound in the gas phase. Patent application 5
-329605.

[0003]

The conventional biological treatment methods are generally the following techniques. That is, the biological treatment method is to ventilate the exhaust gas into a packed bed filled with a carrier of microorganisms, to oxidize and decompose the components to be treated in the exhaust gas by the organisms attached to the carrier, at that time sprinkling water in the packed tower, waste products through watering. It is a method of removing and supplementing nutrients. However, for example, when decomposing volatile organic chlorine compounds such as 1,1,1 trichloroethane, tetrachloroethylene and trichloroethylene, a substance (hereinafter referred to as "inducing substance") that induces decomposition of the organic chlorine compounds of the microorganism is supplied. There must be. Methane gas, phenol, or the like is used as the inducer.

The need for this inducer is one of the causes of impeding the practical application of biological treatment. The reason is as follows. (i) Cost is required to supply the inducer. (ii) Methane gas has a risk of explosion and should be handled with care. (iii) Phenol is a harmful substance to the environment, so care must be taken not to release it into the environment to cause secondary pollution. UV decomposition completely decomposes volatile organic chlorine compounds (carbon dioxide,
Decomposes in water and hydrogen chloride. ) Required a long irradiation time (4 to 8 minutes). Therefore, complete decomposition is not always practical. It is an object of the present invention to solve the above problems and provide an exhaust gas treatment method and an exhaust gas treatment apparatus that effectively treat a volatile organic chlorine compound.

[0005]

The present inventors have found that "a volatile organochlorine compound is not completely decomposed by irradiation of ultraviolet rays for a short time, but is transformed into a substance having a different property." Therefore, the inventors of the present invention tried to treat a volatile organochlorine compound whose physical properties were changed by irradiation with ultraviolet rays for a short time by a biological treatment method, and found that it does not require an inducer and can be treated with high efficiency. That is the present invention. That is, (1) a step of irradiating an exhaust gas containing a volatile organochlorine compound with ultraviolet rays to change the physical properties of the volatile organochlorine compound, and subsequently, an organism filled with a filler in which microorganisms are kept in a wet state. A method for treating exhaust gas containing a volatile organic chlorine compound, which comprises a step of passing through a treatment device for treatment, and (2) an irradiation device for irradiating the exhaust gas containing a volatile organic chlorine compound with ultraviolet rays. , A packed phase filled with a packing material capable of holding microorganisms is provided in the packed tower, a sprinkler section is provided above the packed phase, and a water receiving tank is provided under the packed tower to maintain the packed material in a wet state. A treatment apparatus for exhaust gas containing a volatile organochlorine compound, which is characterized in that the exhaust gas is passed through the ultraviolet treatment apparatus and the biological treatment apparatus in order to process the exhaust gas. It is a device.

The UV lamp for UV irradiation used for treating the exhaust gas containing the volatile organochlorine compound of the present invention is not particularly limited as long as it is a lamp capable of emitting a light beam containing UV rays having a wavelength of 260 nm to 1 nm. Examples of commercially available UV lamps include UV oxidation lamp QG
L25W-3 (manufactured by Iwasaki Electric Co., Ltd.), low-pressure mercury lamp GL20ZH (manufactured by Yamakyo Electric Co., Ltd.) and the like can be mentioned as preferable ones. These lamps can emit UV light, for example with a wavelength of 185 nm, as follows. The irradiation conditions include, for example, a wavelength of 185 nm per liter of a gas containing 100 ppm of trichlorethylene.
It is possible to expect a sufficient effect by irradiating the ultraviolet rays of 10 Joules (J). Also, the concentration of trichlorethylene is about 40.
Below ppm, the effect decreases as the concentration decreases. However, at about 40 ppm or more, the effect did not decrease even if the concentration increased. It is speculated that this is because the reaction form of trichlorethylene is a radical chain reaction.

[0007]

[Function] When a volatile organic chlorine compound is irradiated with ultraviolet rays,
Reacts with oxygen or water existing in the surroundings to generate oxides or hydroxides. For example, when 1,1,1 trichloroethane was irradiated with ultraviolet rays, trichloroacetic acid and the like were produced, and in the case of trichloroethylene, dichloroacetic acid was produced. These substances are more hydrophilic than 1,1,1 trichloroethane and trichloroethylene, respectively, and trichloroacetic acid and dichloroacetic acid are 1,1,1
Biodegradation is easier than trichloroethane or trichlorethylene. Therefore, by irradiating the volatile organic chlorine compound with ultraviolet rays and supplying the gas to the biological treatment apparatus, the ultraviolet-treated product is easily biodegraded.

[0008]

The present invention will be described below with reference to examples.
The present invention is not limited to this.

Example 1 The air containing 100 ppm of trichloroethylene and 30 ppm of 1,1,1-trichloroethane was treated using the apparatus shown in FIG. It processed on the processing conditions shown. That is, the air containing trichloroethylene or 1,1,1-trichloroethane is passed through an ultraviolet irradiation device 3 having a passage, and ultraviolet rays are irradiated by a low pressure mercury lamp 2 (the QGL25W-3) having a wavelength of 185 nm, A gas decomposed into a hydrophilized organic chlorine compound such as dichloroacetic acid is introduced into the lower part of the biological treatment apparatus 4. The biological treatment device 4 is provided with a filling phase 5 filled with a filler that holds microorganisms, and the makeup water 8 replenished in the water receiving tank at the bottom of the biological treatment device 4 is used as the circulating water 7. Water is sprayed from the water sprinkling part on the upper part of 5 to maintain the packed phase 5 in a wet state. Biological treatment is carried out by passing the hydrophilized organochlorine compound introduced into the lower part of the biological treatment apparatus 4 through the packed phase 5. The bioprocessed gas is discharged out of the system as an outflow gas 6 from the upper part of the bioprocessing device 4.

Comparative Example 1 Air containing 100 ppm of trichloroethylene and 30 ppm of 1,1,1-trichloroethane was subjected to ultraviolet irradiation treatment under the treatment conditions shown in Comparative Example 1 of Table 1 using the ultraviolet irradiation apparatus shown in FIG. . That is, the ultraviolet irradiation device 1 having a passage for the air (inflow gas 9) containing the trichlorethylene or 1,1,1-trichloroethane
After passing through 0, ultraviolet rays are irradiated by a plurality of low-pressure mercury lamps 11 of the same type as in Example 1, and discharged as outflow gas 126 out of the system. Comparative Example 2 Air containing 100 ppm of trichlorethylene and 30 ppm of 1,1,1-trichloroethane was biologically treated under the treatment conditions shown in Comparative Example 2 of Table 1 using the biological treatment apparatus 14 shown in FIG. That is, as in the case of the biological treatment apparatus 4 described in Example 1, the biological treatment apparatus 14 is provided with the packing phase 15 filled with the packing material holding the microorganisms, and the biological treatment apparatus 14 has a water receiving tank at the bottom thereof. The supplied makeup water 17 is sprinkled as circulating water 18 from the sprinkler section above the filling phase 15 to maintain the filling phase 15 in a wet state. Air (inflow gas 13) containing the trichloroethylene or 1,1,1-trichloroethane introduced into the lower part of the biological treatment device 14 is passed through the filling phase 15 for biological treatment. The bioprocessed gas is discharged out of the system as an outflow gas 16 from the upper part of the bioprocessing device 14.
Table 1 shows a comparison of the processing capacities of Example 1, Comparative Example 1 and Comparative Example 2.

[0011]

[Table 1]

Table 2 shows the specifications of the ultraviolet lamps used in Example 1 and Comparative Example 1, and Table 3 shows the specifications of the biological treatment apparatus used in Examples 1 and 3 respectively.

[0013]

[Table 2]

[0014]

[Table 3]

The treatment results one month after the start of operation are shown in Example 1,
Table 4 shows Comparative Example 1 and Comparative Example 2. Trichloroethylene was removed by 99% or more by the combined treatment method of ultraviolet irradiation and biological treatment (the method of Example 1).
-Trichloroethane was also removed by 78%. Total organic carbon was also removed by 92%. On the other hand, almost only trichloroethylene was removed and 77% of 1,1,1-trichloroethane was removed by the ultraviolet irradiation alone treatment method (the method of Comparative Example 1). The removal rate of all organic carbon was 70%. This indicates that trichloroethylene and 1,1,1-trichloroethane were not completely decomposed and changed into substances having different properties. Further, trichlorethylene and 1,1,1-trichloroethane were hardly removed by the treatment method of the biological treatment alone (the method of Comparative Example 2).

[0016]

[Table 4]

[0017]

The treatment method of the present invention consumes less energy as compared with the method of completely decomposing only by irradiation of ultraviolet rays. When the concentration of the organic chlorine compound is low, the energy consumption is small compared with the combustion treatment method. Also,
Since the treatment method of the present invention does not require an inducer required for biological treatment and has a high decomposition ability, the apparatus can be downsized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a processing apparatus that performs a combined processing method of ultraviolet irradiation and biological treatment.

FIG. 2 is a conceptual diagram showing an example of a processing device that performs a processing method of ultraviolet irradiation alone.

FIG. 3 is a conceptual diagram showing an example of a processing apparatus that performs biological processing alone.

[Explanation of symbols]

 1 Inflow Gas 2 Low Pressure Mercury Lamp 3 Ultraviolet Irradiation Device 4 Biological Treatment Device 5 Filling Phase 6 Outflow Gas 7 Circulating Water 8 Makeup Water 9 Inflow Gas 10 Ultraviolet Irradiation Device 11 Ultraviolet Lamp (Low Pressure Mercury Lamp) 12 Outflow Gas 13 Inflow Gas 14 Biological Treatment device 15 Filling phase 16 Outflow gas 17 Make-up water 18 Circulating water

Claims (2)

[Claims] 1. A step of irradiating an exhaust gas containing a volatile organochlorine compound with ultraviolet rays to change the physical properties of the volatile organochlorine compound, and subsequently, a living organism filled with a filler that keeps microorganisms in a wet state. A method for treating an exhaust gas containing a volatile organic chlorine compound, comprising the step of passing the treatment through a treatment device. 2. An irradiation device for irradiating an exhaust gas containing a volatile organic chlorine compound with ultraviolet rays, a packing material capable of holding microorganisms in a packed tower, and a sprinkler section provided on the packing material. A water receiving tank is provided in the lower part of the packed tower, and a biological treatment device in which the packing material is maintained in a wet state is provided, and the ultraviolet irradiation device and the biological treatment device are sequentially arranged to pass the exhaust gas for treatment. An apparatus for treating exhaust gas containing a volatile organic chlorine compound, which is characterized by: