JPH06226046A - Treatment of volatile organic halogen compound - Google Patents

Abstract

PURPOSE:To efficiently and cost-effectively decomposed a volatile org. halogen compd. with lessened energy without forming by-products by bringing a volatile org. halogen compd.-contg. gas and an adsorbent into contact and regenerating the satd. adsorbent with steam, then bringing the regenerated waste liquid into contact with a reducing agent in the presence of a metallic catalyst. CONSTITUTION:The volatile org. halogen compd.-contg. water in a raw water tank 1 is supplied to the upper part of a dissipation column 3 where the water comes into counter current contact with air when the air is blown from a blower 4. The volatile org. halogen compd. is thus migrated to the air side. The compd. is absorbed away by the adsorbent when the water is sent into an adsorption column 6. The removed air is released into the atm. The steam is sent from a steam generator 7 into the adsorption column 6 to regenerate the adsorbent when the adsorbent in the adsorption column 6 attains sated. adsorption. The regenerated waste gas is condensed in a condenser 8 to the regenerated waste liquid. This waste liquid is brought as it is or the aeration gas thereof is brought into contact with the reducing agent, such as gaseous hydrogen, in the presence of the metallic catalyst, by which the volatile org. halogen compd. is decomposed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for treating volatile organic halogen compounds. More specifically, the present invention relates to a method for treating a volatile organic halogen compound that efficiently decomposes a gas containing a volatile organic halogen compound such as trichlorethylene so that it is not discharged to the outside of the system.

[0002]

2. Description of the Related Art Since volatile organic halogen compounds cause environmental pollution, it is necessary to remove the compounds contained in wastewater, etc., and thus far, water containing volatile organic halogen compounds such as trichlorethylene has been used. Various treatment methods for wastewater and wastewater have been studied. Examples of methods for removing volatile organic halogen compounds existing in water or waste water include treatments such as (1) activated carbon adsorption method, (2) catalytic pyrolysis method, (3) ultraviolet oxidation method, and (4) aeration emission method. The method etc. are known. However, in the above method (1), water and wastewater usually have other organic compounds coexisting in addition to the volatile organic halogen compound, so that the adsorption capacity for the volatile organic halogen compound itself is small. However, in the methods (2) and (3), the input energy is too large for decomposing a trace amount of volatile organic halogen compounds, and a side reaction product is liable to be generated, which remains, so that the treated water is There is a concern that it is not suitable for drinking. Further, the method (4) has a problem that the air is polluted. In order to eliminate this problem, it has been attempted to treat the effluent gas by activated carbon adsorption, but the actual situation is that no effective treatment method for the exhaust gas generated by regeneration of activated carbon or the steam regeneration has been found. is there. Also,
Catalytic thermal decomposition of waste liquid and exhaust gas may be considered, but since the input energy is excessive and acids such as hydrogen chloride are generated at high temperatures, the use of corrosion resistant materials is inevitable and expensive equipment is required. It causes problems such as

[0003]

Under the circumstances described above, the present invention provides a gas containing a volatile organic halogen compound,
The object of the present invention is to provide a method for efficiently and economically decomposing and removing by using a small amount of energy, without producing a side reaction product, and without causing air pollution.

[0004]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the inventors of the present invention firstly diffused volatile organic halogen compound-containing water by using a diffusion tower or the like, After obtaining the organohalogen compound-containing gas, the gas is contacted with an adsorbent such as activated carbon to adsorb the organohalogen compound in the gas, and then steam is passed through the saturated adsorbent to regenerate the adsorbent. It was found that the objective can be achieved by contacting the regenerated waste liquid as it is or with its aeration gas in the presence of a metal catalyst with a reducing agent, and based on this finding, the present invention has been completed. That is, according to the present invention, the volatile organic halogen compound-containing gas and the adsorbent are brought into contact with each other, the saturated adsorbent is regenerated with water vapor, and then the regenerated waste liquid is used as it is or the aerated gas thereof is reduced with a reducing agent. The present invention provides a method for treating a volatile organic halogen compound, which comprises contacting with a volatile organic halogen compound.

The present invention will be described in detail below. FIG. 1 is a schematic view of an example of an apparatus for carrying out the method of the present invention. First, water containing a volatile organic halogen compound in a raw water tank 1 is supplied by a pump 2 to an upper part of a stripping tower 3. At the same time, air is blown into the lower part of the diffusion tower 3 from the blower 4. The stripping tower 3 is usually filled with a packing material such as Raschig ring. In this stripping tower, the volatile organic halogen compound-containing water and air come into countercurrent contact with each other, and the volatile organic halogen compound is formed according to Henry's law. It moves to the air side and is removed, while the treated water is stored in the treated water tank 5.
The gas containing the volatile organic halogen compound thus obtained is sent to the adsorption tower 6 filled with an adsorbent. Zeolite or activated carbon is usually used as the adsorbent, and the volatile organic halogen compound is absorbed and removed by the adsorbent by hydrophobic interaction, while the air from which the volatile organic halogen compound is removed is released into the atmosphere. To be done. The mode of the adsorption tower 6 is not particularly limited, and may be a fixed bed, a fluidized bed, or a honeycomb rotating type. When the adsorbent in the adsorption tower 6 reaches saturation adsorption, steam is sent from the steam generator 7 to the adsorbent 6 and regenerated. The recycled exhaust gas is condensed in the condenser 8 to be recycled waste liquid, which is then sent to the decomposition process. However, if the recycled waste liquid contains a large amount of volatile organic halogen compounds, it is a waste of resources to decompose the entire exhaust gas. Therefore, collect as much as possible. For that purpose, the regeneration waste liquid from the condenser 8 is sent to the two-phase separator 9 and left to stand for 5 to 120 minutes. As a result, the upper phase is separated into the aqueous phase and the lower phase is separated into the organic phase in the two-phase separator 9, and the organic phase is separated and recovered. On the other hand, the remaining aqueous phase is sent to the treatment liquid receiving tank 10, and after adding a reducing agent such as hydrogen gas via the pump 11, it is sent to the catalyst tower 12 for decomposition. The treated water obtained is discharged as it is.

When the content of the volatile organic halogen compound in the treated water is more than the predetermined value, the treated water is returned to the treatment liquid receiving tank 10 again, and the above treatment is repeated.
FIG. 2 is a schematic view showing another embodiment of the method of the present invention. That is, after the aqueous phase after the two-phase separation is received in the treatment liquid receiving tank 10, the treatment liquid receiving tank 10 is aerated with an inert gas such as nitrogen gas sent from the gas receiver tank 13, and the volatile organic halogen compound is vaporized again. Make a phase. Next, after adding a predetermined amount of a reducing agent such as hydrogen gas to the volatile organic halogen compound-containing gas, it is sent to the same catalyst tower 12 as described above, where the volatile organic halogen compound is decomposed by the reducing gas in the presence of a catalyst. To do. The exhaust gas discharged from the catalyst tower may be discharged as it is, but an inert gas such as nitrogen gas is added to the exhaust gas, sent to the gas receiver tank 13 by the compressor 14, and reused as an aeration gas. Good. The volatile organic halogen compound to which the method of the present invention is applicable usually has a boiling point of 1
Volatile substances at 50 ° C or lower, preferably 80 ° C or lower, such as trichloroethylene, tetrachloroethylene, trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, carbon tetrachloride, Chloroethane, methylene chloride, chloroform, vinyl chloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, dichlorobromoethylene, 1,1,1-trichloroethane, bromodichloromethane, chlorodibromomethane, bromoform, etc. Is mentioned. Further, the catalyst used in the method of the present invention is a metal supported on a carrier, and examples of the metal include palladium, platinum, ruthenium, rhodium, copper, iron, iridium, nickel, and the like. Of these, noble metals such as palladium, platinum, ruthenium, and rhodium are preferable, and palladium and platinum are particularly preferable. As this metal, a simple metal, an oxide, a hydroxide or the like is used.

The carrier may be, for example, alumina,
Titania, activated carbon, zirconia, zeolite, glass,
Examples thereof include silica, silica-alumina, ion exchange resins, and plastic pellets. Among these, alumina, zirconia and ion exchange resins are preferable. As the ion exchange resin, a weakly basic anion exchange resin having a styrene-divinylbenzene copolymer as a matrix is preferable.
The amount of the metal supported is usually about 0.1 to 10% by weight with respect to the carrier. The shape of the metal-supported catalyst is not particularly limited, and any shape such as powder, granules or pellets can be used, but granules or pellets are packed in a column or the like and continuously treated. It is advisable to let the fluid flow. Even the powder form can be packed in a column and operated in a fluidized bed state. As the reducing agent used in the method of the present invention, in addition to hydrogen gas, hydrazine, hydroxylamine, sodium hydride and the like which generate hydrogen upon contact with the catalyst are used. The form of supplying the hydrogen gas includes electrolysis, a cylinder, a hydrogen storage alloy, and the like. In the method of the present invention, a volatile organic halogen compound is reductively decomposed by using a metal catalyst and a reducing agent. As an example, when the volatile organic halogen compound is trichlorethylene, decomposition occurs according to the following reaction formula. It is considered to be a thing. CHCl = CCl ₂ + 4H ₂ → C ₂ H ₆ + 3HCl That is, trichlorethylene is dechlorinated to produce ethane and hydrogen chloride. Hydrogen chloride is stable and does not become a source of recontamination. In addition to ethane, the formation of a very small amount of methane is also recognized. In the method of the present invention, the reducing agent is usually added in an amount necessary to replace the halogen of the volatile organic halogen compound with halogen or in a range higher than that.

[0008]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. Example 1 It carried out using the apparatus shown in FIG. The groundwater containing 0.1 ppm of trichlorethylene is led to the diffusion tower 3 (net ring TS-1 filling height 3 m) having a diameter of 1.7 m and a height of 7.5 m,
Water is sprinkled from above at a flow rate of 9 m ³ / Hr and 300 N from below.
Air was blown at a flow rate of m ³ / Hr for countercurrent contact. The concentration of trichlorethylene in the water at the outlet of the stripping tower is 2 ppb, and the concentration of trichlorethylene in the exhaust air is 0.5 volume p.
It was pm. The discharged air was introduced into a rotor type adsorption tower 6 (fiber amount of about 2.6 kg) 6 using activated carbon fibers to adsorb trichlorethylene. The concentration of trichlorethylene in the air after the adsorption treatment was 0.05 ppm by volume or less until 10 hours later. After 10 hours, the operation of the activated carbon fiber adsorption tower was stopped, and 25 kg / hr of 4 kg / cm ² of water vapor was supplied to regenerate the activated carbon fiber. The time required for regeneration was about 1 hour. Trichloroethylene was found to be contained in the regenerated effluent obtained by cooling this regenerated exhaust gas to room temperature with a condenser.
Since it was 50 ppm, hydrogen gas was dissolved in this liquid at a hydrogen partial pressure of 3 to 4 kg / cm ² without reuse, and then Pt was added.
The catalyst column filled with 2 liters of -γ-Al ₂ O ₃ catalyst was mixed with S
Decomposition treatment was carried out by circulating with V50Hr ^-1 . After 5 hours, trichlorethylene was not detected in the regeneration effluent. Example 2 It carried out using the apparatus shown in FIG. The regenerated effluent obtained in Example 1 was sent to the treatment liquid receiving tank 10 to supply nitrogen gas of 3N.
Aeration was carried out at m ³ / hr to obtain a volatile organic halogen compound-containing gas, 2 g / hr of hydrogen gas was added thereto, and the gas was circulated in a catalyst tower filled with 1 liter of the same catalyst as in Example 1 except that The same treatment as in Example 1 was performed. As a result, trichlorethylene was not detected in the circulating gas after 30 minutes.

[0009]

EFFECTS OF THE INVENTION The method for treating a volatile organic halogen compound according to the present invention is (1) a system in which the volatile organic halogen compound in the water or waste water is diffused into a gaseous state as a matter of course in addition to the gaseous state. Can be removed and decomposed without being discharged to the outside. (2) Volatile organic halogen compounds in the effluent of adsorbent regeneration can be recovered and reused if necessary.
(3) Since the volatile organic halogen compound in the exhaust gas does not exist or almost does not exist, it is characterized by no air pollution.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example for carrying out the method of the present invention.

FIG. 2 is a schematic diagram of another example for implementing the present invention.

[Explanation of symbols]

 1 Raw water tank 2 Pump 3 Dispersion tower 4 Blower 5 Treated water tank 6 Adsorption tower 7 Steam generator 8 Condenser 9 Two-phase separator 10 Treated liquid receiving tank 11 Pump 12 Catalyst tower 13 Gas receiver tank 14 Compressor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication C02F 1/20 ZAB A 1/58 ZAB A 1/70 ZAB Z 9045-4D (72) Inventor Tsurumaru Haruka 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A volatile organic halogen compound-containing gas and an adsorbent are brought into contact with each other, and the saturated adsorbent is regenerated with steam, and then the regenerated effluent is used as it is or with the aerated gas thereof as a reducing agent in the presence of a metal catalyst. A method for treating a volatile organic halogen compound, which comprises contacting the volatile organic halogen compound.