JPH08281068A - Treatment of waste gases containing volatile organic matter and treating device therefor - Google Patents

Abstract

PURPOSE: To efficiently and completely treat volatile org. matter and more particularly, hydrophobic volatile org. matter to a completely cracked form by irradiating waste gases contg. the volatile org. matter with UV rays to oxidize and/hydroxidize the volatile org. matter, then passing the waste gases through a biological treating layer in which microorganisms are held in a wet state. CONSTITUTION: The air contg. toluene or xylene is passed through the inside of a UV irradiation device 3 which has a passage and is irradiated with the UV rays by a low-pressure mercury lamp 2. The air contg. the matter cracked to the compds., such as oxide or hydroxide 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 held. The packed phase 5 is maintained in a wet state by sprinkling makeup water 8 replenished to a water receiving layer 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 air contg. the compds. with hydrophilic nature introduced into the lower part of the biological treating device 4 is passed through the packed phase 5, by which the air is biologically treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a painting factory, a foundry,
It is a method for treating exhaust gas containing volatile organic substances, particularly hydrophobic volatile substances, discharged from a printing factory, a film manufacturing factory and the like. Hydrophobic volatile substances are, for example, toluene, xylene, benzene and styrene.
However, the object of the present invention is not limited to only hydrophobic volatile substances.

[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 volatile organic substances. However, these methods consume a large amount of energy. In particular, when treating exhaust gas with a relatively low concentration and large air volume, which has recently been regulated in Europe and the United States, the energy efficiency is extremely reduced. Biological treatment is mainly used in Europe as a method of treating exhaust gas having a relatively low concentration and a large air volume with low energy. Further, ultraviolet rays are a method capable of efficiently causing reactions such as oxidation and hydroxylation even with a low-concentration substance, 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 organic substance, and then exposing the gas phase to ultraviolet rays to decompose the volatile organic substance in the gas phase. Japanese Patent Application No. 5-329605 has proposed a method for treating volatile organic substances.

[0004]

The biological treatment system operates with the packed bed kept wet. Therefore, water exists between living things and exhaust gas. Therefore, the substance to be treated in the exhaust gas is taken into the organism through water. When the substance to be treated is hydrophobic, water impedes the movement of the substance to be treated between the gas and the organisms, resulting in low treatment efficiency of the biological treatment apparatus. For the above reasons, the conventional biological treatment device requires a long residence time when treating the exhaust gas containing the hydrophobic substance. Therefore, there is a problem that the equipment becomes huge. Moreover, the components in the exhaust gas are completely decomposed by the ultraviolet decomposition alone (completely decomposed into carbon dioxide gas and water).
It takes a lot of energy to do so. Therefore, irradiation of ultraviolet rays for a long time is required, which is unrealistic. But,
If it is released into the environment as a decomposition product that is incompletely decomposed, it causes secondary pollution. The present invention solves the above problems and provides an exhaust gas treatment method and an exhaust gas treatment apparatus for treating volatile organic substances, particularly hydrophobic volatile organic substances, in an effectively and completely decomposed form. It is an issue.

[0005]

[Means for Solving the Problems] The present inventors have stated that "volatile organic substances are not completely decomposed by irradiation with ultraviolet rays for a short time.
Change to substances with different properties. I found that. Therefore, when the inventors tried to treat the volatile organic substances whose physical properties were changed by irradiation with ultraviolet rays for a short time by a biological treatment method, it was revealed that they could be treated with high efficiency and even in a completely decomposed form. That is the present invention. That is, the object of the present invention is (1) a step of irradiating an exhaust gas containing a volatile organic substance with ultraviolet rays to oxidize and / or hydroxylate the volatile organic substance, and a biological treatment apparatus in which microorganisms are retained in a wet state. A method for treating an exhaust gas containing a volatile organic substance, which comprises a step of passing and treating,
(2) An irradiation device for irradiating exhaust gas containing volatile organic substances with ultraviolet rays, and a packing material capable of holding microorganisms in the packed tower, and a sprinkler section above the packing material and at the bottom of the packed tower. A biological treatment device in which a water receiving tank is provided and the filling material is maintained in a wet state, and the ultraviolet irradiation device and the biological treatment device are sequentially arranged so as to pass the exhaust gas for treatment. It is achieved by an apparatus for treating exhaust gas containing volatile organic substances.

The UV lamp for UV irradiation used for treating the exhaust gas containing the volatile organic substance of the present invention has a wavelength of 2
The lamp is not particularly limited as long as it is a lamp that can emit light rays including ultraviolet rays of 60 nm to 1 nm, and examples of commercially available UV lamps include, for example, an ultraviolet oxidation lamp QGL25W-
3 (manufactured by Iwasaki Electric Co., Ltd.), low pressure mercury lamp GL20Z
H (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. As an irradiation condition, for example, a sufficient effect can be expected by irradiating 10 joules (J) of ultraviolet rays having a wavelength of 185 nm per liter of a gas containing 20 ppm of toluene. Further, if the toluene concentration becomes higher, it is necessary to increase the energy amount of the ultraviolet rays to be irradiated accordingly.

[0007]

[Function] A large number of hydrophobic substances are contained in volatile organic substances. For example, toluene, xylene, benzene, styrene, etc. may be mentioned. When these substances are irradiated with UV rays, the UV-irradiated substances react with oxygen or water existing in the surroundings to form oxides or hydroxides such as phenol, benzoic acid, phenylacetic acid, catechol, and benzaldehyde. To do. As a result, the hydrophobic substance becomes hydrophilic. The hydrophilized substance is easily biodegraded, and the treatment efficiency of the biological treatment device is dramatically improved. The treatment method of the present invention, even when applied to a hydrophilic or surface-active substance instead of a hydrophobic substance, is more efficient and completely decomposed than when treated by ultraviolet irradiation alone or biological treatment alone. Can be processed up to.

[0008]

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

Example 1.20 ppm toluene and 3 p
Air containing pm xylene was treated under the treatment conditions shown in Example 1 in Table 1 using the apparatus for treating UV irradiation and biological treatment shown in FIG. 1 in combination. That is, the air containing the toluene or xylene is passed through an ultraviolet irradiation device 3 having a passage, and is irradiated with ultraviolet rays by a low pressure mercury lamp 2 (QGL25W-3) having a wavelength of 185 nm to obtain an object or a hydroxide. The air containing the decomposed hydrophilized compound 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.
The make-up water 8 replenished to the water receiving tank at the bottom of the above is used as the circulating water 7 from the sprinkling portion at the upper part of the filling phase 5 to maintain the filling phase 5 in a wet state. The biological treatment is carried out by passing the air containing the hydrophilized compound introduced into the lower portion of the biological treatment apparatus 4 through the inside of 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 20 ppm of toluene and 3 ppm of xylene was treated under the treatment conditions shown in Comparative Example 1 of Table 1 using the ultraviolet irradiation apparatus shown in FIG. That is, the air containing the toluene or xylene (inflow gas 9) is passed through an ultraviolet irradiation device 10 having a passage and is irradiated with ultraviolet rays by a plurality of low-pressure mercury lamps 11 of the same type as in Example 1 as an outflow gas 12. Discharge to the outside of the system. Comparative Example 2 Air containing 20 ppm of toluene and 3 ppm of xylene was biologically treated under the treatment conditions shown in Comparative Example 2 in 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 containing the toluene or xylene introduced into the lower part of the biological treatment device 14 (inflow gas 13)
Are biologically treated by passing through the packed phase 15. 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. In the combined treatment method of ultraviolet irradiation and biological treatment (method of Example 1), toluene and xylene were removed by 99% or more, and total organic carbon was also removed by 99%. On the other hand, by the ultraviolet irradiation alone treatment method (the method of Comparative Example 1), 80% of toluene and 60% of xylene were removed, but the removal rate of all organic carbon was 59%. The removal rates of toluene and xylene did not match the removal rates of total organic carbon. This is probably because toluene and xylene were not completely decomposed and byproducts were produced.
Further, in the treatment method of the biological treatment alone (the method of Comparative Example 2), the removal rates of both toluene and xylene were about 50%.

[0016]

[Table 4]

[0017]

The treatment method of the present invention can be treated with low energy as compared with the method of completely decomposing only by irradiation of ultraviolet rays. When the concentration of the target substance is low, the energy is low compared to the combustion process. In addition, the treatment method of the present invention has a higher decomposing ability as compared with the conventional biological treatment, so that 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 organic substance with ultraviolet rays to oxidize and / or hydroxylate the volatile organic substance, and a step of treating the exhaust gas containing the volatile organic substance by passing through a biological treatment apparatus holding microorganisms in a wet state. A method for treating exhaust gas containing a volatile organic substance, which comprises: 2. An irradiation device for irradiating an exhaust gas containing a volatile organic substance with ultraviolet rays, a packing material capable of retaining microorganisms in the packed tower, and a sprinkler section is provided above the packing material, and the packed tower is also provided. A water receiving tank is provided in the lower part, and a biological treatment device in which the filling material is maintained in a wet state is provided, and the ultraviolet irradiation device and the biological treatment device are arranged so as to pass the exhaust gas for treatment. A device for treating exhaust gas containing volatile organic substances, characterized by: