JP2003053146A - Method for treating gas containing volatile organic halogen compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method which effectively and reliably makes a volatile organic halogen compound included in gas to be treated harmless for a long period. SOLUTION: This method for treating gas containing volatile organic halogen compound comprises a dehumidification process of allowing the gas to be treated to contact with an adsorbent and reducing relative humidity in the gas to be treated, a decomposition process of allowing the gas to be treated to contact with a metallic catalyst in presence of hydrogen donator gas and decomposing the volatile organic halogen compound and a regeneration process of allowing the adsorbent used in the dehumidification process to contact with a treating gas which is obtained in the decomposition process and regenerating the adsorbent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating a gas containing an organic halogen compound, and more particularly to a method for treating a gas containing a volatile organic halogen compound contained in soil or groundwater.

[0002]

2. Description of the Related Art In recent years, environment caused by harmful volatile organic halogen compounds such as dichloroethylene (DCE), trichlorethylene (TCE), and tetrachloroethylene (PCE) released from electronics factories and facilities that use solvents such as cleaning. Pollution is a big social problem. Since these are suspected to be carcinogenic and reproductive toxicity and are very stable, it is not preferable that they remain in the soil or be brought into groundwater, which is a resource of drinking water, by rainwater or the like.

As a method for removing volatile organic halogen compounds, a method of decomposing organic halogen compounds in soil with microorganisms (bioremediation method), or a method of decompressing organic halogen compounds in soil by vaporization to obtain activated carbon etc. A method of adsorbing and collecting is known. However, the bioremediation method takes a very long time to process, and the method of adsorbing it on activated carbon has a problem that it is necessary to further decompose the collected matter.

Known chemical treatment methods include a method of oxidizing and decomposing ferrous iron and hydrogen peroxide, and a method of mixing soil and iron powder for reduction treatment, all of which are iron. The amount of reagents such as hydrogen peroxide and hydrogen peroxide used is large, and the effect is not always sufficient.

Under such a background, a volatile organic halogen compound is extracted from soil or groundwater and contained in air or the like to form a gas to be treated, and the gas to be treated is brought into contact with a predetermined catalyst to reduce the volatile property. Attempts have been made to convert organic halogen compounds into harmless substances. For example, JP-A-6
JP-A-142454 discloses a treatment method in which the relative humidity of a gas to be treated containing water and a volatile organic halogen compound is reduced, and then the gas to be treated is brought into contact with a reducing gas in the presence of a metal catalyst. In order to reduce the relative humidity of the gas, heating the gas to be treated, adding dry air,
It describes the use of adsorbents such as ion exchange resins.

[0006]

However, in the processing method described in JP-A-6-142454, in order to reduce the relative humidity of the gas by heating or adding dry air, a specific device or a large amount of energy is used. Is required.
Further, in the method using the adsorbent, the water adsorbing ability of the adsorbent decreases with the lapse of processing time. Therefore, a step for removing the adsorbed water by heating or a step for exchanging the adsorbent is newly provided. There is a need. As described above, a practical treatment method capable of efficiently and inexpensively detoxifying a volatile organic halogen compound has not yet been found.

The inventors of the present invention have been devised in view of the above problems of the prior art, and provide a treatment method capable of efficiently and surely detoxifying a volatile organic halogen compound contained in a gas to be treated for a long period of time. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, a method for treating a gas containing a volatile organic halogen compound according to the present invention comprises contacting a gas to be treated containing a volatile organic halogen compound and water with an adsorbent. And a dehumidifying step of reducing the relative humidity of the gas to be treated, a decomposition step of decomposing the volatile organic halogen compound by bringing the gas to be treated into contact with the metal catalyst in the presence of a hydrogen donor gas, and dehumidifying The method is characterized by including an adsorbent regeneration step of regenerating the adsorbent by bringing the adsorbent used in the step into contact with the processing gas obtained in the decomposition step.

In the present invention, after the relative humidity of the gas to be treated is reduced in the dehumidifying step, the gas to be treated and the metal-based catalyst are brought into contact with each other in the presence of a hydrogen donor gas in the decomposing step. The volatile organic halogen compound in the processing gas can be detoxified efficiently and reliably.
Further, the water adsorption capacity of the adsorbent used in the dehumidification step may be lowered by the adsorption of water, but by contacting this with the treatment gas obtained in the decomposition step, the adsorbent can be treated without heating or the like. Since the water adsorption capacity is sufficiently enhanced,
The adsorbent after the regeneration step can be subjected to the dehumidification step again. Therefore, according to the present invention, the volatile organic halogen compound contained in the gas to be treated can be efficiently and surely rendered harmless for a long period of time.

In the dehumidifying process, the decomposing process and the regenerating process, no special equipment such as a heat source or a large amount of energy is required when the gas to be processed or the processing gas is brought into contact with the adsorbent or the catalyst. Therefore, sufficient cost reduction can be realized.

The term "gas to be treated" as used herein means a gas which has not been subjected to the detoxification treatment by the decomposition step, and the term "treatment gas" means a gas which has been detoxified by the decomposition step. In the present invention, the two are distinguished.

In the present invention, the adsorbent used in the dehumidifying step is brought into contact with a gas containing no volatile organic halogen compound to remove the volatile organic halogen compound adhering to the adsorbent, and then the adsorbent is adsorbed. The agent may be subjected to a regeneration step. Thereby, the decomposition efficiency of the volatile organic halogen compound can be further improved.

Further, the present invention may be characterized in that the adsorbent is any one of activated carbon, activated alumina and silica gel. These adsorbents have a high water adsorption capacity and are also excellent in desorption of adsorbed water, so that the efficiency in the dehumidification process and the adsorbent regeneration process is improved, or further decomposition in the decomposition process is performed. It is preferable in terms of improving efficiency.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same elements are designated by the same reference numerals, and duplicated description will be omitted.

FIG. 1 is a flow chart schematically showing a processing apparatus preferably used in the first embodiment according to the present invention. The apparatus shown in FIG. 1 includes two dehumidifying towers 1 and 1'and a catalytic reaction tower 2, which are connected by a line described later.

The dehumidifying towers 1 and 1'are fixed bed type dehumidifying towers having adsorbent layers A and A'made of activated carbon, respectively, and these are arranged in parallel to each other via lines L1 and L2 branched at predetermined positions. It is connected. A valve V is provided in the line L1a connecting the branch point of the line L1 and the dehumidification tower 1.
1. A valve V1 'is connected to the line L1b connecting the branch point of the line L1 and the dehumidifying tower 1', and a valve V2 is connected to the line L2a connecting the branch point of the dehumidifying tower 1 and the line of the dehumidifying tower 1 '. A valve V2 'is provided in each of the lines L2b connecting the branch points of L2. Further, the line L1a and the line L1b are connected by a line L1c, the line L2a and the line L2b are connected by a line L2c, and valves V4, V are connected to the line L1c.
Valves V3 and V3 ′ are provided at 4 ′ and the line L2c. Then, by opening / closing the valves V1 to V4 and V1 ′ to V4 ′, the gas to be treated from L1 can be controlled to be supplied to the line L2 through any of the dehumidifying towers 1 and 1 ′.

A catalyst reaction tower 2 is connected to the other end of the line L2, and a line L3 for supplying hydrogen as a hydrogen donor gas is connected to a predetermined position of the line L2.
The gas to be treated from the dehumidifying towers 1 and 1'is mixed with hydrogen and supplied to the catalytic reaction tower 2.

The catalytic reaction tower 2 is provided with a packed bed Y of a catalyst in which platinum is supported on an activated alumina carrier (hereinafter referred to as "platinum-supported alumina"). By passing through Y, the volatile organic halogen compound contained in the gas to be treated can be decomposed. The type of the reactor in the catalytic reaction tower 2 used in the present invention is not particularly limited, but a fixed bed type reactor is preferable from the viewpoint that there is no problem of clogging and that regeneration treatment is unnecessary.

A line L4 is connected to the catalytic reaction tower 2, and the line L4 is connected to a predetermined position between the valves V3 and V3 'of the line L2c via a line L5.
Further, a line L6 including a valve V5 is connected to a predetermined position between the valves V4 and V4 ′ of the line L1c, and the line L2 and the line L6 are connected by a line L7 including a valve V6. As a result, the processing gas from the catalytic reaction tower 2 is supplied to the lines L4, L5, L2c, L2.
a (or L2b), dehumidifying tower 1 (or 1 '), line L1a (or L1b), L1c, L6, L7, L2 in the order of circulation in the device, or released to the atmosphere from lines L4, L6. It

Next, a method of treating a gas containing a volatile organic halogen compound using the apparatus having the above structure will be described.

The gas to be treated according to the present invention contains a volatile organic halogen compound as described above. Such an organic halogen compound usually has a boiling point of 150 ° C. or lower, preferably 80 ° C. or lower. Specifically, 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, bromodichloroethane, bromodichloromethane, chlorodibromomethane, broloform, various freons and the like.

When processing such a gas to be processed,
First, with the valves V1 and V2 open and all other valves closed, the gas to be treated is supplied to the dehumidification tower 1 through the lines L1 and L1a, and the relative humidity of the gas to be treated is sufficiently reduced. (Dehumidification process). As a result, it is possible to prevent the degradation of the decomposition efficiency due to the influence of moisture in the decomposition step described later. Particularly, the relative humidity of the aerated gas to be treated exhibits a value of 100% or close to it, but even if the relative humidity of the gas to be treated having such a high humidity is set, the relative humidity is, for example, 20% by the above dehumidification step. It can be reduced to ~ 70%.

The relative humidity of the gas to be treated supplied to the dehumidifying step is preferably 40 to 100%. That is, the volatile organic halogen compound in the gas to be treated may also be adsorbed to the adsorbent layer, but by setting the relative humidity of the gas to be treated before the dehumidifying step within the above range, adsorption of water becomes dominant, Adsorption of a volatile organic halogen compound can be suppressed. The relative humidity of the gas to be treated dehumidified in this manner is preferably 20 to 70%.

Further, the processing speed (SV) in the dehumidifying process
Is not particularly limited as long as the relative humidity of the gas to be treated is sufficiently reduced, but is usually 100 to 5000 h ^-1 ,
It is preferably 200 to 2000 h ⁻¹ .

Next, the gas to be treated sent to the line L2a is mixed with hydrogen from L3 and then brought into contact with the catalyst-packed bed in the catalytic reaction column 2, whereby the volatile organic halogen in the gas to be treated is mixed. The compound is decomposed (decomposition step). The detoxified processing gas is discharged into the atmosphere through the line L4.

After the dehumidifying step and the decomposing step are performed for a predetermined time, the valves V3, V4, V6, V1 'and V2' are opened and the other valves are closed, so that the dehumidifying step is performed. It will be held in 1 '. In addition, a part of the processing gas detoxified in the catalytic reaction tower 2 is generated by the lines L4, L5, L2
It is sent to the dehumidification tower 1 through c and L2a. At this time, the processing gas sent to the dehumidification tower 1 has a sufficiently low relative humidity, and by bringing this into contact with the adsorbent layer A,
The water adsorbed on the adsorbent layer A can be efficiently and surely removed (regeneration step). The process gas after the regeneration step is returned to the line L2 via the line L7,
It may be released into the atmosphere through the line L6, or may be reused as a gas for stripping or air purging.

As described above, in the first embodiment, the volatile organic halogen compound in the gas to be treated can be rendered harmless by sequentially performing the dehumidifying step and the decomposing step. Further, in the dehumidifying step and the regenerating step, by switching the gas to be treated and the flow of the treating gas passing through the dehumidifying tower as described above, a regenerating step of activated carbon which has been used for a predetermined time and has a reduced water adsorption capacity, Since the process gas dehumidifying step is performed at the same time, the activated carbon can be regenerated without stopping the apparatus. Therefore, both the processing accuracy and the processing efficiency are sufficiently enhanced, and stable processing operation can be performed for a long period of time.

Further, in the dehumidifying step, the decomposing step and the regenerating step, no special equipment such as a heat source or a large amount of energy is required when bringing the target gas or the processing gas into contact with the activated carbon or the catalyst. It is possible to realize sufficient cost reduction.

The first embodiment is not limited to this. For example, although FIG. 1 shows a processing apparatus including two dehumidifying towers, the above effect can be achieved even when the number of dehumidifying towers is three or more. Further, even if the number of dehumidifying towers is 1, by performing the dehumidifying step and the decomposing step and the adsorbent regenerating step alternately, the volatile organic halogen compounds in the gas to be treated are efficiently and surely harmless. Can be converted.

As the adsorbent used in the dehumidifying tower,
Activated alumina, silica gel, zeolite or the like may be used instead of activated carbon. Among these, activated carbon, activated alumina and silica gel are preferable in terms of water adsorption ability and ease of desorption of moisture once adsorbed, and activated carbon and activated alumina are particularly preferable. The activated carbon mentioned here includes activated char and activated coke.

The shapes of these adsorbents are spherical, cylindrical,
It may be cylindrical or crushed. The particle size of the adsorbent is 1 to several tens of mm, preferably 1 to 10 mm, from the viewpoint of ventilation resistance and contact efficiency with the gas to be treated.

The hydrogen donor gas is not particularly limited as long as it can supply hydrogen atoms, and hydrazine or the like can be used instead of the above hydrogen. Further, hydrogen does not have to be pure hydrogen gas, and hydrogen-containing mixed gas such as electrolysis gas of water, NH ₃ decomposition gas, coke oven gas, catalytic cracking gas such as hydrocarbon may be used. Among these, it is preferable to use hydrogen or a hydrogen-containing gas because the decomposition efficiency of the volatile organic halogen compound can be further increased.

As the metal-based catalyst used in the catalytic reaction tower 2, platinum, palladium, ruthenium, rhodium, iron, copper, iridium, nickel and other metals (preferably platinum, ruthenium) are used in addition to the above-mentioned platinum-supported alumina. , A noble metal such as rhodium, more preferably platinum and palladium), or these noble metals are attached to or contained in a carrier such as alumina, titania, zirconia, silica-alumina, activated carbon, zeolite, glass, plastic, pellets or ion exchange resins. There are things.

FIG. 2 is a flow chart schematically showing a processing apparatus preferably used in the second embodiment according to the present invention. The apparatus shown in FIG. 2 includes a dehumidifying tower 1 in which the activated carbon layer A is of a moving bed type, a catalytic activation tower 2, and a regeneration tower 3 for regenerating the activated carbon.

The dehumidifying tower 1 is provided with the movable activated carbon bed A as described above, and the moving bed may be of a cross flow type or a counter flow type. Further, lines L1 and L2 are connected to predetermined positions of the dehumidification tower 1. As a result, it is introduced into the dehumidifying tower 1 from the line L1, dehumidified in the activated carbon layer A, and then sent to the line L2 (dehumidifying step). Further, an activated carbon outlet (not shown) is provided in the lower portion of the dehumidification tower 1, and an activated carbon inlet (not shown) is provided in the upper portion, so that the activated carbon is provided between the dehumidification tower 1 and the regeneration tower 3. A conveyor 4 is provided to circulate between the two. As a result, the activated carbon having a reduced water adsorption capacity after the dehumidifying step is sent from the dehumidifying tower 1 to the regenerating tower 3 by the conveyor 4, is regenerated by a regenerating process described later, and is then subjected to the dehumidifying step again.

Further, at the other end of the line L2, there is provided a catalytic reaction tower 2 equipped with a catalyst-packed bed of platinum-supported alumina, and at a predetermined position of the line L2, a line L3 for supplying hydrogen as a hydrogen donor gas, respectively. It is connected. As a result, the gas to be treated from the dehumidifying tower 1 is mixed with hydrogen and supplied to the catalytic reaction tower 2, and the volatile organic halogen compound contained in the gas to be treated is brought into contact with the catalyst by contacting the gas to be treated with the catalyst. Decomposes to be harmless (decomposition process).

A line L4 for discharging the detoxified process gas is connected to the catalytic reaction tower 2, and the line L4 is connected to the line L4.
4 is connected to the regeneration tower 3 via a line L5 at a predetermined position. As a result, a part of the detoxified processing gas is sent to the regeneration tower 3 through the line L5 and used to regenerate the activated carbon after the dehumidification step (regeneration step). The regenerated activated carbon is sent to the dehumidifying tower 1 by the conveyor 4 and is again subjected to the dehumidifying step. Further, the exhaust gas generated in the regeneration step is discharged from the line 6 connected to the regeneration tower 3, but the exhaust gas may be reused for air purging of soil or for stripping groundwater or the like, and is discharged to the atmosphere. May be.

As described above, the second embodiment is similar to the first embodiment in that the dehumidifying step and the decomposing step are sequentially performed, whereby the volatile organic halogen compound in the gas to be treated is decomposed and harmless. It is possible to obtain a processed gas. In addition, in the second embodiment, the activated carbon that has been subjected to the dehumidification step and has a reduced water adsorption capacity is sequentially sent from the dehumidification tower 1 to the regeneration tower 3 by the conveyor 4 and regenerated by the treated gas after the decomposition step, Since it is subjected to the dehumidifying step again, the water adsorption capacity of the activated carbon in the dehumidifying tower 1 is always maintained at a high level, and the gas to be treated can be detoxified efficiently and reliably. Further, in these steps, when the gas to be treated or the treated gas and the activated carbon or the catalyst are brought into contact with each other, a special device such as a heating source or a large amount of energy is not required, so that sufficient cost reduction is realized. It

The second embodiment is not limited to this. For example, although not shown in FIG. 2, the regeneration tower 3
A line is provided for sending a part of the processing gas discharged from the catalytic reaction tower 2 to the catalytic reaction tower 2, and the processing gas is circulated between the regeneration tower 3 and the catalytic reaction tower 2. Three
May be discharged from the device to the outside of the device. Thereby, the concentration of the volatile organic halogen compound in the processing gas can be further reduced.

In the apparatus shown in FIG. 2, the dehumidifying tower 1 and the regenerating tower 3 are separately provided,
There is no problem in accommodating these in one tower. A heating source may be provided inside or outside the regeneration tower 3.

Further, in the second embodiment, activated carbon was used as the adsorbent, hydrogen was used as the hydrogen donor gas, and platinum-supported alumina was used as the catalyst. Instead of these, the adsorbent and hydrogen donor exemplified in the first embodiment were used. Body gases and catalysts may be used.

FIG. 3 is a flow chart schematically showing a processing apparatus preferably used in the third embodiment according to the present invention. In the apparatus shown in FIG. 3, the dehumidifying tower 1, the catalytic reaction tower 2, the regeneration tower 3 and the line connecting them are the same as those in the apparatus shown in FIG. 2, but the dehumidification tower 1 and the regeneration tower 3 are 2 in that a purge tank 5 is provided between them, and that the processing gas from the catalytic reaction tower 2 is supplied to both the regeneration tower 3 and the purge tank 5 through a line L5. Be different. As a result, the activated carbon having a reduced water adsorption capacity after the dehumidifying step is sequentially sent from the dehumidifying tower 1 to the purge tank 5 and the regeneration tower 3, and then returned to the dehumidifying tower 1 again. Further, in the purge tank 5, the volatile organic halogen compound adsorbed on the activated carbon can be desorbed by contacting the activated carbon after the dehumidifying step with the processing gas from the line L5. Further, the purge tank 5 and the line L2 are connected by a line L7, whereby the processing gas from the purge tank 5 is supplied to the lines L7, L.
2, the catalytic reaction tower 2, the lines L4 and L5, and the purge tank 5 can be circulated in this order.

In the apparatus shown in FIG. 3, the purge tank 5
Since the configuration other than that and the line connected to it is the same as that of the device shown in FIG. 2, in the third embodiment as well, the same effect as the second embodiment can be obtained by performing the dehumidifying step, the decomposing step and the regenerating step. To be achieved. Further, as shown in FIG. 3, by treating the activated carbon sent to the regeneration tower 3 in the purge tank 5, a trace amount of the volatile organic halogen compound adsorbed in the dehumidifying step can be desorbed from the activated carbon. Further, since the organohalogen compound desorbed from the activated carbon is sent to the catalytic reaction tower 2 together with the processing gas for the decomposition step, the organohalogen compound in the processing gas released from the catalytic reaction tower 2 and the regeneration tower 3 is discharged. The concentration can be sufficiently reduced over a long period of time.

In the present invention, as described in the description of the first embodiment, the relative humidity of the gas to be treated supplied to the dehumidifying tower is controlled so that the adsorption of water becomes dominant and the treated material is treated. Although it is possible to suppress the phenomenon that the volatile organic halogen compound contained in the gas is adsorbed on the activated carbon, in the third embodiment, even if the organic halogen compound is adsorbed on the activated carbon, desorption is performed in the purge tank 5. Therefore, no organohalogen compound is generated in the regeneration tower 3, and the organohalogen compound in the gas in the line L6 can be reduced.

The third embodiment is not limited to this. For example, in the apparatus shown in FIG. 3, the dehumidifying tower 1, the purging tank 5 and the regeneration tower 3 are provided separately, but there is no problem if they are housed in one tower. A heating source may be provided inside or outside the regeneration tower 3.

Further, in the apparatus shown in FIG. 3, the purge tank 5
Is connected to the line L5 and the processing gas from the catalytic reaction tower 2 is supplied to the purge tank 5 to desorb the organic halogen compound adsorbed on the activated carbon. However, air is supplied to the purge tank 5. A line may be connected and the activated carbon may be purged with air.

[0047]

EXAMPLES The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to the following examples.

Example 1

Using the processing apparatus shown in FIG. 2, the volatile organic halogen compound was detoxified according to the following procedure.

First, trichlorethylene 0.2 mg / l
Was sprayed from the upper part of the stripping tower at a rate of 10 m ³ / h, and 300 m ³ / h of air was supplied from the lower part of the stripping tower for deaeration. The trichlorethylene concentration in the gas at the outlet of the stripping tower was 0.33 mg / m ³ (20 ° C.), and the concentration of trichlorethylene in the treated water discharged from the bottom of the stripping tower was 0.02 mg / l.

Next, a countercurrent flow in which the entire amount (about 307 m ³ / h) of the gas at the outlet of the stripping tower (hereinafter referred to as the “gas to be treated”) was filled with activated carbon for dehumidification (particle size: about 4 mmφ × 5 mm length) The gas was supplied to the moving bed type dehumidifying tower 1 at a treatment rate (SV) of 500 h ⁻¹ to dehumidify the gas to be treated. When the relative humidity of the outlet gas of the dehumidification tower 1 was measured by a hygrometer, it was about 35%.
Met.

Next, the gas to be treated from the dehumidifying tower 1 was mixed with 0.2 vol% of hydrogen from the line L3 and then fed to the catalytic reaction tower 2 at a treating speed (SV) of 2000 h ^-1 . As a catalyst for the catalytic reaction tower 2, platinum-supported activated alumina (supported amount of platinum: 0.5 wt%) was used.

In the above steps, the residence time of the activated carbon in the dehumidifying tower 1 is set to 25 hours, the activated carbon is continuously taken out from the bottom of the dehumidifying tower 1, sent to the regeneration tower 3, and discharged from the catalytic reaction tower 2. The activated carbon was regenerated using the entire amount of the treated gas. The activated carbon after the regeneration treatment was introduced into the dehumidification tower 1 from the upper part of the dehumidification tower 1 and was again subjected to the dehumidification step.

When this treatment was continuously carried out for 500 hours, the concentration of trichlorethylene in the treatment gas discharged from the catalytic reaction tower 2 was 0.01 mg / hour even after 500 hours of operation.
It showed a low value of m ³ and was confirmed to be almost the same as at the beginning of operation. Also, the regeneration tower 3 that is finally released into the atmosphere
The concentration of trichlorethylene in the outlet gas of 0.043 mg /
It showed a low value of m ³ .

Comparative Example 1

Using the processing apparatus shown in FIG. 2, the treated gas was detoxified in the same manner as in Example 1 except that the activated carbon was not regenerated. That is, in this comparative example, the activated carbon was not sent to the regeneration tower 3 but kept in the dehumidification tower 1 and all the treated gas from the catalytic reaction tower 2 was released to the atmosphere.

When this treatment was continuously carried out for 500 hours, the concentration of trichlorethylene in the treated gas discharged from the catalytic reaction tower 2 was 0.01 mg / m ³ at the beginning of the operation, but after the operation for 500 hours, It increased to 0.30 mg / m ³ .

Example 2

Using the processing apparatus shown in FIG. 3, the volatile organic halogen compound was detoxified according to the following procedure.

First, the same process gas as in Example 1 was applied to the countercurrent type moving bed type dehumidifying tower 1 filled with dehumidifying activated carbon (particle size: about 4 mmφ × 5 mm length) at a treating speed (SV) of 500.
It was supplied at h ⁻¹ to dehumidify the gas to be treated. When the relative humidity of the outlet gas of the dehumidification tower 1 was measured using a hygrometer,
It was about 35%.

Next, the gas to be treated from the dehumidifying tower 1 was mixed with 0.2 vol% of hydrogen from the line L3 and then fed to the catalytic reaction tower 2 at a treating speed (SV) of 2000 h ^-1 . As the catalyst of the catalytic reaction tower 2, 0.5 wt% platinum-supported activated alumina was used.

In the above process, the entire amount of the processing gas from the catalytic reaction tower 2 was sent to the line L5, and a part of it was supplied to the purge tank 5 to circulate between the catalytic reaction tower 2 and the purge tank 5. . Further, the remaining processing gas was supplied to the regeneration tower 3. Then, the residence time of the activated carbon in the dehumidification tower 1 is set to 25
The time was set, and activated carbon was continuously taken out from the bottom of the dehumidification tower 1 and sent to the purge tank 5, and trichlorethylene was purged with the processing gas from the catalytic reaction tower 2 (retention time of activated carbon: 1 hour). Furthermore, the activated carbon after purging is recycled to the regeneration tower 3
And the activated carbon was regenerated by the treatment gas discharged from the catalytic reaction tower 2. The activated carbon after the regeneration treatment was introduced into the dehumidification tower 1 from the upper part of the dehumidification tower 1 and again subjected to the dehumidification step.

When this treatment was continuously carried out for 500 hours, the concentration of trichlorethylene in the treatment gas discharged from the catalytic reaction tower 2 after 500 hours was 0.012 mg / m ^3, which is substantially the same as that at the beginning of the operation, which is sufficiently low. In addition, the concentration of trichlorethylene in the outlet gas of the regeneration tower 3 finally released to the atmosphere was as low as 0.019 mg / m ³ after 500 hours of operation.

[0064]

As described above, according to the present invention,
After reducing the relative humidity of the gas to be treated in the dehumidifying step, in the decomposition step, the gas to be treated and the metal-based catalyst are brought into contact with each other in the presence of a hydrogen donor gas, so that the volatile organic halogen in the gas to be treated is reduced. The compound can be efficiently and surely rendered harmless. Further, the water adsorption capacity of the adsorbent used in the dehumidification step may be lowered by the adsorption of water, but by contacting this with the treatment gas obtained in the decomposition step, the adsorbent can be treated without heating or the like. Since the water adsorption capacity is sufficiently enhanced, it can be subjected to the dehumidification step again after such regeneration treatment. Therefore, according to the present invention, the volatile organic halogen compound contained in the gas to be treated can be efficiently and surely rendered harmless for a long period of time.

Further, in the dehumidifying process, the decomposing process and the regenerating process, no special equipment such as a heat source or a large amount of energy is required when bringing the gas to be treated or the treatment gas into contact with the adsorbent or the catalyst. Therefore, sufficient cost reduction is realized.

[Brief description of drawings]

FIG. 1 is a flow chart schematically showing an example of a processing apparatus preferably used in the first embodiment.

FIG. 2 is a flow chart schematically showing an example of a processing apparatus preferably used in the second embodiment.

FIG. 3 is a flow chart schematically showing an example of a processing apparatus preferably used in the third embodiment.

[Explanation of symbols]

1, 1 '... dehumidifying tower, 2 ... catalytic reaction tower, 3 ... regeneration tower, 4 ...
Conveyor, 5 ... Purge tank, A, A '... Activated carbon layer, L1
L7 ... line, V1a to V6 ... valve, Y ... catalyst packed bed.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 20/10 B01J 23/42 A 20/34 C09K 3/00 S B01D 53/36 G 23/42 53 / 34 134E C09K 3/00 ZAB (72) Inventor Shinichi Yamada 1-15 Kuryodai 1-15, Hiratsuka City, Kanagawa Prefecture F-Term (Reference) at Sumiju Environmental Analysis Center Co., Ltd. 4D002 AA21 AB03 BA04 CA07 DA42 DA46 EA02 EA08 EA13 FA01 HA01 4D048 AA11 AB03 BA03X BA30X BA41X BC01 CA03 CD01 4G066 AA04B AA20B AA22B CA33 DA02 EA20 4G069 AA03 BA01B BC75B CA05 CA10 CA19 DA06

Claims (3)

[Claims] 1. A dehumidifying step of bringing a gas to be treated containing a volatile organic halogen compound and water into contact with an adsorbent to reduce the relative humidity in the gas to be treated, and in the presence of a hydrogen donor gas, By bringing a gas to be treated into contact with a metal-based catalyst, a decomposing step of decomposing the volatile organic halogen compound, an adsorbent used in the dehumidifying step, and a treating gas obtained in the decomposing step are brought into contact with each other. And a regeneration step of regenerating the adsorbent, the method for treating a gas containing a volatile organohalogen compound. 2. The adsorbent used in the dehumidifying step is brought into contact with a gas containing no volatile organohalogen compound to remove the volatile organohalogen compound adhering to the adsorbent, and then the adsorption. The method for treating a volatile organohalogen compound-containing gas according to claim 1, wherein the agent is subjected to the regeneration step. 3. The method for treating a volatile organohalogen compound-containing gas according to claim 1, wherein the adsorbent is any one of activated carbon, activated alumina and silica gel.