JP2005103520A - Pollutant decomposing method and apparatus used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the discharge of a chlorine gas to environment to efficiently utilize chlorine in a pollutant decomposing method for decomposing and purifying a gaseous organochlorine compound, and a pollutant decomposing apparatus used therein. <P>SOLUTION: The pollutant decomposing method has a process for bringing air after decomposition treatment into contact with an adsorbing material to adsorb chlorine by an adsorbing material and a process for desorbing chlorine from the adsorbing material to utilize the same as a chlorine producing source. The pollutant decomposing apparatus is also disclosed. Especially, the adsorption and desorption of chlorine are alternately performed in a plurality of adsorbing columns in the pollutant decomposing method and the pollutant decomposing apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for decomposing a gaseous organochlorine compound and a decomposing / purifying apparatus used therefor.

  With the development of industrial technology until recently, organochlorine compounds (for example, chlorinated ethylene, chlorinated methane, etc.) have been used enormously, and their disposal has become a serious problem. In addition, these used gases cause environmental problems such as polluting the natural environment, and great efforts are being made to solve them.

  As a method of treating these, for example, there is a method of decomposing chlorinated ethylene using an oxidizing agent or a catalyst. Specifically, a method of decomposing with chlorinated ozone (Japanese Patent Laid-Open No. 3-38297 (Patent Document 1)). In addition, a method of irradiating ultraviolet rays in the presence of hydrogen peroxide (Japanese Patent Laid-Open No. 63-218293 (Patent Document 2)) is known.

  In addition to the above, a photolysis method in which ultraviolet rays are irradiated in the gas phase without using an oxidizing agent has already been attempted. For example, exhaust gas containing an organic halogen compound is irradiated with ultraviolet rays to form an acidic decomposition gas, and then washed with alkali to render it harmless (Japanese Patent Laid-Open No. 62-191025 (Patent Document 3)), organic halogen An apparatus (Japanese Patent Laid-Open No. 62-191095 (Patent Document 4)) that aspirates a wastewater containing a compound, irradiates the exhausted gas with ultraviolet rays, and then performs alkali cleaning has been proposed. Further, it is a photodecomposition apparatus using a phenomenon in which UV-B and C ultraviolet rays decompose a part of pollutants, such as JP-A-9-299753 (Patent Document 5) and JP-A-10-180040 (Patents). There is a disclosure example of Document 6).

  In addition, the decomposition of chlorinated ethylene by iron powder is also known (Japanese Patent Laid-Open No. 8-257570 (Patent Document 7)). In this case, it is presumed that reductive decomposition is probably occurring. In addition, reductive decomposition has also been reported for the decomposition of tetrachloroethylene (hereinafter abbreviated as PCE) using silicon fine particles.

  In addition, chlorinated aliphatic hydrocarbons such as trichlorethylene (hereinafter abbreviated as TCE) and PCE are known to be decomposed aerobically or anaerobically by microorganisms. Attempts have also been made to decompose or purify.

  There has also been proposed a decomposition / purification apparatus for gaseous organic chlorine compounds in which a gas containing chlorine gas and a gaseous organic chlorine compound to be decomposed are mixed and the mixed gas is irradiated with light. This method is excellent in that it can be decomposed with relatively low light energy due to the presence of chlorine.

  Here, chlorine gas generated from a solution containing chlorine is used as a simple and safe means for obtaining a gas containing chlorine gas. Such a solution can be obtained, for example, by dissolving hypochlorite (sodium hypochlorite or potassium hypochlorite) in water. Further, when an inorganic acid or the like is included in this solution, chlorine gas can be generated efficiently.

In addition, the description of JP-A-9-234338 (Patent Document 8) is cited in the present invention.
JP-A-3-38297 JP 63-218293 A JP 62-191025 A JP 62-191095 A Japanese Unexamined Patent Publication No. 9-299753 Japanese Patent Laid-Open No. 10-180040 JP-A-8-257570 JP-A-9-234338

  However, the gaseous organochlorine compound decomposition and purification apparatus described above may have the following disadvantages. That is, in the decomposition and purification apparatus, the decomposition reaction is started by mixing chlorine gas and a gaseous organic chlorine compound as a decomposition target substance under light irradiation.

  However, depending on the conditions of the decomposition treatment, not all chlorine gas is consumed by the decomposition reaction, but rather most of it is discharged as it is, and there is a fear that it will be released into the environment. Moreover, the fact that most is released means that the amount of chlorine used for decomposition in the entire system is a small amount of the total chlorine and is inefficient.

  An object of this invention is to provide the apparatus which decomposes | disassembles the gaseous organic chlorine compound which suppresses discharge | release to an environment and utilizes chlorine efficiently.

  The present invention solves the above problems by collecting the discharged chlorine and again subjecting it to a decomposition reaction.

That is, a method for decomposing and purifying a gaseous organochlorine compound according to one embodiment of the present invention that can achieve the above-described object is as follows.
In a pollutant decomposition and purification method having a step of decomposing the pollutant by irradiating light from the light irradiation means to the gas to be treated containing chlorine and the pollutant in the air,
Contacting the adsorbent with the air after the decomposition treatment and adsorbing chlorine to the adsorbent;
Desorbing chlorine from the adsorbent and utilizing it as a generation source of chlorine for the decomposition treatment;
It is related with the pollutant decomposition purification method characterized by having.

  Furthermore, the process of desorbing chlorine from the adsorbent and using it as a generation source of chlorine for the decomposition treatment includes the step of sending a gas to the adsorbent to generate air containing chlorine. It relates to a purification method.

  The present invention also relates to the pollutant decomposition and purification method as described above, which comprises a step in which there are a plurality of adsorption towers containing adsorbents, and at least one adsorbs chlorine, and the other desorbs chlorine.

Further, in the plurality of adsorption towers,
The method for decomposing and purifying pollutants as described above, wherein the air sent into the adsorption tower for desorbing chlorine is the air after the photodecomposed air is adsorbed by the adsorbent in the other adsorption tower.

Moreover, the apparatus for decomposing and purifying a gaseous organochlorine compound according to one embodiment of the present invention capable of achieving the above-mentioned object,
In the pollutant decomposition and purification apparatus for decomposing the pollutant by irradiating light from the light irradiation means to the gas to be treated containing chlorine and the pollutant in the air,
Means for performing the light irradiation;
A decomposition treatment area for decomposing the contaminants;
Means for bringing the air after the decomposition treatment into contact with an adsorbent to form a chlorine-containing adsorbent;
Means for desorbing chlorine from the chlorine-containing adsorbent and reusing it as a chlorine source for the decomposition treatment;
It is related with the pollutant decomposition purification apparatus characterized by having.

  The present invention also relates to the pollutant decomposition and purification apparatus as described above, wherein a plurality of adsorption towers for storing the adsorbents are used to simultaneously perform a chlorine adsorption operation in at least one adsorption tower and a chlorine desorption operation in the other adsorption tower.

  By reusing chlorine after decomposition, it became possible to use chlorine efficiently.

[Embodiment 1]
A basic configuration of one embodiment of the decomposition and purification apparatus according to the present invention will be described below with reference to FIG.

  In FIG. 1, reference numeral 11 denotes a means for supplying a decomposition target substance, which is supplied to the photoreaction tank 3. A light irradiation means 4 is arranged inside the photoreaction tank 3. 6 is a means for supplying a gas containing chlorine. For example, a gas containing chlorine is generated by sending air into a solution containing chlorine (chlorine solution). First, the gas containing chlorine supplied from 6 is sent to the photoreaction tank 3 through the supply control valve 7 and mixed with the gaseous organic chlorine compound to be decomposed in the photoreaction tank 3, and the four light irradiation means. The organic chlorine compound is decomposed by light irradiation at.

  The gas after the photolysis treatment is sent to the chlorine adsorption / desorption tower 2. Chlorine adsorption / desorption tower 2 is prepared with 2a and 2b, and one adsorbent removes and removes chlorine from the process gas to obtain purified gas, and the other regenerates adsorbent and desorbs adsorbed chlorine. By doing so, a gas containing chlorine is supplied. This is done alternately.

  That is, first, as shown in FIG. 2, the gas after the decomposition treatment flows into the adsorbent 1b of the chlorine adsorption / desorption tower 2b by controlling the supply control valve 8. Chlorine is adsorbed on the adsorbent 1b and the purified gas is discharged from the exhaust pipe 9 through the distribution control valve 10.

  In this state, the operation is performed for a predetermined period, and after sufficient adsorption is performed, the connection shown in FIG. 3 is switched.

  As shown in FIG. 3, the gas after the decomposition treatment controls the supply control valve 8 and then flows into the adsorbent 1a of the chlorine adsorption / desorption tower 2a. Chlorine is adsorbed and removed by the adsorbent 1a, and the purified gas is discharged from the exhaust pipe 9 through the distribution control valve 10. At this time, by adjusting the distribution control valve 10, a part of the purified gas is caused to flow into the adsorbent 1b of the adsorption / desorption tower 2b. At the same time, if the adsorbent 1b is heated by the heater 12b, chlorine already adsorbed on the adsorbent 1b is desorbed, and gas containing chlorine is supplied to the photoreaction tank 3 by controlling the supply control valves 5a, 5b, 7, and 8. And used for decomposition. Thus, supply of chlorine necessary for decomposition from the chlorine supply means 6 becomes unnecessary at this point.

  In this state, the operation is performed for a predetermined period, and after sufficient adsorption and desorption, the connection shown in FIG. 4 is switched.

  As shown in FIG. 4, the gas after the decomposition treatment controls the supply control valve 8 and then flows into the adsorbent 1b of the chlorine adsorption / desorption tower 2b. Chlorine is adsorbed and removed by the adsorbent 1b, and the purified gas is discharged from the exhaust pipe 9 through the distribution control valve 10. At this time, by adjusting the distribution control valve 10, a part of the purified gas is caused to flow into the adsorbent 1a of the adsorption / desorption tower 2a. At the same time, if the adsorbent 1a is heated by the heater 12a, chlorine already adsorbed on the adsorbent 1a is desorbed, and gas containing chlorine is supplied to the photoreaction tank 3 by controlling the supply control valves 5a, 5b, 7, and 8. And used for decomposition.

  By adjusting the distribution control valve 10, a part of the purified gas is caused to flow into the adsorbent 1 of the adsorption / desorption tower 2 to obtain a gas containing chlorine necessary for the reaction. At this time, a part of the purified gas is discharged from the discharge pipe 9. Ideally, chlorine is adsorbed and removed by the adsorbent, but 100% may not be removed. In this case, exhaust gas from the exhaust pipe may be introduced into a means for removing chlorine (not shown).

  For example, an adsorbent or a scrubber can be used as a means for removing chlorine.

  Conversely, by installing a scrubber or the like downstream of the discharge pipe 9, a design that does not remove 100% of chlorine in the adsorption / desorption tower 2 is possible.

  As described above, in one embodiment of the present invention, two containers holding an adsorbent are prepared, and one adsorbent adsorbs a treatment gas containing chlorine, while the other adsorbent regenerates and chlorine. It is set as the structure which acquires the gas which contains, and continuous operation is enabled by performing this alternately.

  The form alternately performed as described above, and a merry-go-round type in which a plurality of adsorbents are prepared and sequentially processed can be used in the present invention. The merry-go-round type is, for example, when there is an activated carbon tower of A, B, C, when A is adsorbing, B is desorbing (regenerating), and C is in a dormant state, In the next step, when the adsorption process is performed at C, A is desorbing (regenerating), B is in a resting state, and in the next step, the adsorption process is performed at B. , C refers to a type in which continuous processing is performed by repeating alternately such that desorption (regeneration) processing is performed and A is in a resting state.

  In addition, as a configuration for performing adsorption treatment of chlorine and, on the other hand, regeneration of the adsorbent and acquisition of gas containing chlorine, the rotor in which the adsorbent alternately passes through the adsorption region for performing the adsorption step and the desorption region for performing the regeneration step. Mold processing equipment can be used in the present invention.

  For example, the adsorbent is installed in an annular shape, and the adsorbent arranged in a rotor shape is rotated at a predetermined speed so that the adsorbent passes alternately through the adsorption region and the desorption region. That is, when chlorine is adsorbed / removed by the adsorbent in the adsorption region, and the adsorbent adsorbed with chlorine moves to the region where desorption is performed from the adsorption region, the region is heated and desorbed and the adsorbent is regenerated. In this way, processing is performed continuously.

  As described above, the structure for continuously adsorbing and desorbing chlorine has been described. However, in a batch-type process or the like, a single chlorine adsorption / desorption tower can be used.

(Chlorine adsorbent)
Although any adsorbent can be used in the system according to the present invention, it is generally in the form of a solid solid with a porous surface. For example, in addition to activated carbon and activated carbon fibers made by carbonizing cellulosic materials such as wood and chitinous materials that are commonly used for adsorption of hydrocarbon compounds, silica gel, zeolite, iron and alumina Examples thereof include porous metal obtained by firing powder, activated clay used as an oil adsorbent and deodorant.

  A material that efficiently absorbs and desorbs chlorine is desirable.

(Chlorine separation means)
The means for separating the adsorbed material from the adsorbent may be any means, but the main means is one using a heating means or one using a pressure means.

  As the adsorbent heating means, there are methods such as microwave heating, heater heating, steam pipe or water vapor desorption, and these are determined depending on the combination with the adsorbent.

  An example of the surface temperature is about 120 ° C. Depending on the material to be separated, a higher temperature may be required, but it is necessary to determine this temperature in consideration of the ignition of the mixed material.

  As a separation means from the adsorbent by pressure, a means for forming and separating a reduced pressure environment using a pump or the like at the time of separation can be used. Pressure swing desorption (PSA) equipment and techniques can be used.

  Any gas may be used for separation. In the above description, the decomposed gas is brought into contact with the adsorbent of one chlorine adsorption / desorption tower to adsorb and remove chlorine, and then a part of the purified gas is used to remove chlorine from the other adsorbed adsorbent of chlorine. To obtain a gas containing chlorine.

  A part of such purified gas may be used for separation, but the whole may be used. The ratio to be used may be variable, or a new gas may be introduced from outside the system as a gas used for separation without being used at all.

(Means for supplying gas containing chlorine)
At the time of operation for decomposition, as the means 6 for supplying the gas containing chlorine, a chlorine gas generating means having a configuration in which chlorine is filled in a container such as a chlorine gas cylinder can be used. Further, a means for generating chlorine gas by bringing water containing chlorine into contact with air may be used. In addition, a chlorine gas generating means that performs photolysis using a processing target gas containing a decomposition target substance (hereinafter also referred to as source gas) and generates chlorine from the source gas can be used. A means for separating chlorine into the gas phase from the adsorbent adsorbed with chlorine can be used.

  In any case, it is necessary to adjust the chlorine gas supply amount so that the chlorine gas concentration in the photoreaction tank 3 is 5 ppmv (meaning volume ppm; the same applies hereinafter) to 1000 ppmv, preferably 10 ppmv to 500 ppmv.

  During operation for decomposition, chlorine gas is supplied from the above-described means for supplying a gas containing chlorine to perform decomposition treatment, and thereafter, decomposition processing is performed using chlorine in the gas after decomposition treatment.

  That is, the chlorine in the gas after the decomposition treatment is adsorbed with the adsorbent, and then the chlorine adsorbed on the adsorbent is released into the gas, and the gas containing this chlorine is supplied to the reaction field.

  Chlorine is hardly consumed in the decomposition, and chlorine is generated from the chlorine compound that is the decomposition target, so the total chlorine concentration tends to increase. do not become.

  That is, if chlorine is supplied once from the means 6 for supplying a gas containing chlorine at the beginning of the decomposition operation, then the decomposition reaction can be continued without supplying chlorine from outside the system.

  As means 6 for supplying chlorine-containing gas at the initial stage of the decomposition operation, water containing chlorine is brought into contact with air, and for example, air containing chlorine necessary for the initial stage of decomposition is generated by passing air through water containing chlorine. You may let them. In this case, an air diffuser (bubbler) can be used. The air diffuser may be an ordinary device used to blow a gas into the liquid, but it is desirable that the size of the bubbles be selected so that the surface area is sufficient for the air to diffuse chlorine. Moreover, it is desirable that a material that does not react with water components containing chlorine is selected as the material of the diffuser. For example, porous diffuser plates made of sintered glass, porous ceramics, sintered SUS 316, nets woven from fibrous SUS 316, or spargers made of glass or pipes such as SUS 316 Can be used.

  Here, as water containing chlorine as a supply source of air containing chlorine, for example, an electrolyte (for example, sodium chloride or potassium chloride) is dissolved in raw water, and this water is electrolyzed in a water tank having a pair of electrodes. By doing so, the water that can be obtained in the vicinity of the anode can be used. The chlorine-containing air can also be obtained by arranging means for introducing air into water that can be obtained in the vicinity of the anode.

  The water that can be obtained in the vicinity of the anode has a hydrogen ion concentration (pH value) of 1 to 4, preferably 2 to 3, and a dissolved chlorine concentration of 5 mg / L to 200 mg / L, preferably 30 mg / L or more. Water having a property of 120 mg / L or less is preferred.

  In addition to the above-described electrolysis method, chlorine-containing water serving as a supply source of chlorine-containing air can be obtained by dissolving various reagents in raw water. For example, it can be obtained using a chlorinated water generating means comprising a water tank, means for supplying an aqueous solution of hypochlorite to the water tank, and means for supplying an aqueous solution containing at least one of an inorganic acid and an organic acid to the water tank. it can.

  The water containing chlorine by such synthesis can be obtained, for example, by setting hydrochloric acid to 0.001 mol / L to 0.1 mol / L and sodium hypochlorite 0.0001 mol / L to 0.01 mol / L. As hypochlorite, other than sodium salt, for example, potassium salt or calcium salt may be used. The water containing chlorine thus obtained preferably has a pH of 1.0 or more and 4.0 or less, more preferably 2 or more and 3 or less, and a dissolved chlorine concentration of 2 mg / L or more and 2000 mg / L or less.

  All of these waters can generate chlorine necessary for decomposition, and the substance to be processed can be decomposed by mixing this with the gas to be processed and irradiating with light.

  Further, in a configuration in which chlorine is generated from the source gas by performing photolysis using the source gas, it is necessary to select a wavelength of light that can decompose the source gas. When the pollutant of the source gas is a general organochlorine compound, it can be decomposed by using, for example, near ultraviolet rays of 254 nm or 185 nm. The light irradiation means for generating chlorine from the source gas may also serve as the light irradiation means 4 for irradiating the photoreaction tank 3.

(Disassembly target)
Here, examples of the pollutant to be decomposed include chlorinated ethylene and chlorinated methane. Specifically, examples of the chlorinated ethylene include 1 to 4 chlorine substituted products of ethylene, that is, chloroethylene, dichloroethylene (DCE), trichloroethylene (TCE), and tetrachloroethylene (PCE). Further examples of dichloroethylene include 1,1-dichloroethylene (vinylidene chloride), cis-1,2-dichloroethylene, and trans-1,2-dichloroethylene. Examples of chlorinated methane include methane substituted chlorine, such as chloromethane, dichloromethane, and trichloromethane.

  There is no particular limitation on the pollutant containing the organochlorine compound to be decomposed, and it can be applied to the purification of waste water, exhaust gas, soil and groundwater contaminated with the above-mentioned pollutants in painting factories and dry cleaning factories. For example, the present invention can be used to remove pollutants contained in gas generated during air stripping, vacuum extracted gas from contaminated soil, or the like.

(Light irradiation means)
As the light irradiation means that can be used in the present invention, for example, light having a wavelength of 300 to 500 nm is preferable, and light having a wavelength of 350 to 450 nm is more preferable. As the light irradiation intensity with respect to the chlorine gas and the decomposition target, for example, a light source having a peak near a wavelength of 360 nm has an intensity of several hundred μW / cm ² (measured between 300 nm and 400 nm), and decomposition is practically sufficient.

  In the present invention, when chlorine is supplied in the initial stage, it is not necessary to use ultraviolet light having a wavelength of about 250 nm or less, which has a great influence on the human body, and thus glass or plastic can be used as a reaction tank. .

  As such a light source, natural light (for example, sunlight) or artificial light (mercury lamp, black light, color fluorescent lamp, short wavelength (500 nm or less) light emitting diode, etc.) can be used.

  On the other hand, in the case of a configuration in which chlorine is not generated in the initial stage but generated by photolysis of the source gas itself, it is necessary to use 254 nm or 185 nm of near-ultraviolet rays (for example, a germicidal lamp) for the irradiation in the initial stage. A tube is required. In the case where the light irradiation means for generating chlorine from the source gas is also used as the light irradiation means 4 for irradiating the photoreaction tank 3, the light includes both light having a wavelength of 300 to 500 nm and near ultraviolet rays having a wavelength of 254 nm and 185 nm. Is more preferable.

(Decomposition mechanism)
The present inventors have already found that the decomposition of an organic chlorine compound proceeds when irradiated with light in the presence of chlorine gas, but there are many unclear portions regarding the reaction mechanism. However, it is already known that when chlorine receives light in a specific range of wavelengths, it dissociates to produce radicals. Also in the present invention, it is considered that chlorine radicals are generated by light irradiation and the bond is broken by reacting with the decomposition target substance.

  For example, Japanese Patent Laid-Open No. 9-234338 (Patent Document 8) discloses an example in which a chlorine radical decomposes an organic chlorine compound and uses it. This is characterized in that a gas containing an organic chlorine compound is guided to an ultraviolet reaction tank, and the organic chlorine compound is decomposed by irradiating the ultraviolet light, and a part of the gas after the ultraviolet irradiation is returned to the ultraviolet reaction tank. This is a photodecomposition method for organochlorine compounds. In this method, since a part of the photodecomposition gas is returned as it is, if the return rate increases, the chlorine concentration increases but the amount of gas that can be processed decreases. A part of the photolysis gas containing chlorine is discharged.

[Embodiment 2]
In the first embodiment, an example of an apparatus that adsorbs chlorine in the processing gas and uses it again for decomposition is shown. However, the decomposition product may be removed between the decomposition treatment and the adsorption of chlorine. Is possible.

  Such an example is shown in FIG. In this system, the decomposition products contained in the process gas discharged from the reaction tank are removed by the 13 decomposition product removing means.

  When the source gas is an organic chlorine compound, the main decomposition products are haloacetic acids such as trichloroacetic acid and dichloroacetic acid, and chlorine is released from the organic chlorine compound during the decomposition process.

  As a means for removing decomposition products such as haloacetic acid, a trap tank, a gas-liquid contact tower (scrubber) or the like can be used. For example, by bringing the treatment gas from the reaction tank into contact with an aqueous solution such as water, the decomposition product can be transferred from the gas phase to the liquid phase, and a gas containing no decomposition product such as haloacetic acid can be discharged. By adjusting the pH of the aqueous solution to the acidic side, for example, the pH is 0.5 or more and 5 or less, chlorine is hardly absorbed by the aqueous solution, and is absorbed in a gas that does not contain decomposition products such as haloacetic acid that is discharged. Supplied to the desorption tower.

  Since the decomposition products are often acidic, the pH of the original aqueous solution decreases with operation. Considering this, it is preferable to set the pH of the initial aqueous solution.

  Further, the decomposition product removing means may be provided with a means for decomposing decomposition products such as haloacetic acid.

  By efficiently removing the decomposition products by the decomposition product removing means, it is possible to prevent decomposition products such as haloacetic acid from inhibiting the decomposition reaction and preventing the decomposition products from adsorbing to the adsorbent. it can.

  That is, in this decomposition product removal means, it is possible to pass only chlorine necessary for decomposition and remove other decomposition products.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Example 1)
The present invention was carried out using the processing apparatus schematically shown in FIG.

  In FIG. 1, the soil gas vacuumed from the contaminated soil is supplied to the photoreaction tank 3. A light irradiation means 4 is installed in the photoreaction tank 3. Chlorine is supplied to the photoreaction tank 3 from a chlorine supply means 6 (a chlorine cylinder in this embodiment). In this embodiment, since the light irradiation means uses a black light fluorescent lamp that does not contain a wavelength of light of 300 nm or less, a means for generating air containing chlorine gas is required. For example, light having a wavelength of 254 nm is used. When the decomposition is performed, a means for generating air containing chlorine gas is not necessarily required (see later-described Example 3).

  The gas after the decomposition treatment is sent to the chlorine adsorption / desorption tower 2 as described above. Chlorine adsorption / desorption tower 2 is prepared with 2a and 2b, and one adsorbent removes and removes chlorine from the process gas to obtain purified gas, and the other regenerates adsorbent and desorbs adsorbed chlorine. By doing so, a gas containing chlorine is supplied. This is done alternately.

  Operation was continued in this state, and it was confirmed that chlorine after decomposition treatment could be reused.

  An example in which the above is confirmed experimentally will be shown.

  Suction was performed from the soil contaminated with organochlorine compound as a substance to be decomposed with a vacuum suction pump, and the polluted gas was fed into the photolysis tank at 1 m2 / min (residence time: 30 seconds). The main pollutants and their concentrations of this pollutant gas were trichlorethylene: 5 to 20 ppmv and tetrachloroethylene: 5 to 30 ppmv.

  Chlorine was supplied from a chlorine cylinder and adjusted so that the chlorine concentration in the reaction tank was 50 ppmv.

  In this example, irradiation was performed from the outside with 16 commercially available black light fluorescent lamps (Toshiba; FL40S BLB).

  The side surface of the reaction tank was formed of a fluorine resin film, and it was confirmed that a wavelength of 300 nm or more was transmitted.

  The chlorine adsorption / desorption tower 2 was filled with synthetic zeolite as an adsorbent.

  At the time when one day had passed since the start of the operation of the apparatus, the flow path to the adsorbent was switched and the adsorption of chlorine was started in another chlorine adsorption / desorption tower 2. At the same time, the chlorine adsorption / desorption tower that has been used for adsorption of chlorine until now was heated with a heater to separate the chlorine, and the gas containing chlorine thus obtained was introduced into the photoreactor 3. At this time, supply of chlorine from the chlorine cylinder 6 was stopped.

  Thereafter, the operation was performed by switching the flow path to the adsorbent once a day.

  In order to know the concentration of trichlorethylene and tetrachloroethylene in the exhaust gas discharged from the photolysis section during this period, sampling is periodically performed with a gas tight syringe and gas chromatography (GC-14B (FID detector manufactured by Shimadzu Corporation) is used. Appendices) The column was measured with DB-624) manufactured by J & W, but was not always detected.

(Example 2)
A decomposition experiment was performed using the processing apparatus shown in FIG.

  A decomposition experiment was performed using an apparatus almost the same as in Example 1 except that the decomposition product removing means 13 was installed.

  The gas after the decomposition treatment contains haloacetic acid in a mist form. Tap water was stored in the gas-liquid contact tower that absorbs the decomposition product corresponding to the means 13 for trapping the decomposition product, and this water was circulated by a pump. The circulating stored liquid comes into contact with haloacetic acid, which is a decomposition product, at the gas-liquid contact portion and absorbs haloacetic acid to the solution side.

  After 5 months of operation, the haloacetic acid concentration in this reservoir reached 0.4%.

  In addition, it can be seen that the decomposition progressed well, and the chlorine required for the decomposition was supplied to the reaction tank in the required amount even when the decomposition product removing means 13 was installed.

Example 3
In Example 1, a light source (black light) having a light wavelength of 300 nm to 500 nm was used as the light irradiation means 4, but in this example, a light source having a peak at 254 nm (for example, a germicidal lamp) was used. For this reason, in this embodiment, a quartz tube into which a germicidal lamp is inserted is required. Except for this, the decomposition experiment was performed using the same apparatus as in Example 1.

  Although it is known that light from a light source having a peak at 254 nm or a light source having a peak at 185 nm decomposes the organochlorine compound without chlorine, the decomposition efficiency is higher in the presence of chlorine. Moreover, the improvement of the decomposition rate was confirmed when the concentration was low.

  Further, even when decomposition without adding chlorine by light from a light source having a peak at 254 nm or a light source having a peak at 185 nm, chlorine is generated as a decomposition product, so that secondary treatment is necessary.

It is the schematic of the decomposition | disassembly apparatus concerning the embodiment of this invention. It is a figure explaining the effect | action of this invention. It is a figure explaining the effect | action of this invention. It is a figure explaining the effect | action of this invention. It is the schematic of the decomposition | disassembly apparatus concerning the other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, b: Adsorbent 2a, b: Chlorine adsorption / desorption tower 3: Photoreaction tank 4: Light irradiation means 5a, b: Supply control valve 6: Supply means of chlorine containing gas 7: Supply control valve 8: Supply control valve 9: Exhaust pipe
10: Distribution control valve
11: Means for supplying substances to be decomposed
12a, b: Heater
13: Means for removing decomposition products

Claims (6)

In a pollutant decomposition and purification method having a step of decomposing the pollutant by irradiating light from the light irradiation means to the gas to be treated containing chlorine and the pollutant in the air,
Contacting the adsorbent with the air after the decomposition treatment and adsorbing chlorine to the adsorbent;
Desorbing chlorine from the adsorbent and utilizing it as a generation source of chlorine for the decomposition treatment;
A method for decomposing and purifying pollutants, comprising:   2. The pollutant decomposition according to claim 1, wherein the step of desorbing chlorine from the adsorbent and using it as a generation source of chlorine for the decomposition treatment includes a step of generating gas containing chlorine by sending a gas into the adsorbent. Purification method.   The method for decomposing and purifying pollutants according to claim 2, further comprising a step of desorbing chlorine when at least one adsorbs chlorine and at least one adsorbs chlorine. In the plurality of adsorption towers,
4. The method for decomposing and purifying pollutants according to claim 3, wherein the air fed into the adsorption tower for desorbing chlorine is the air after the light-decomposed air is adsorbed by the adsorbent in the other adsorption tower. In the pollutant decomposition and purification apparatus for decomposing the pollutant by irradiating light from the light irradiation means to the gas to be treated containing chlorine and the pollutant in the air,
Means for performing the light irradiation;
A decomposition treatment area for decomposing the contaminants;
Means for bringing the air after the decomposition treatment into contact with an adsorbent to form a chlorine-containing adsorbent;
Means for desorbing chlorine from the chlorine-containing adsorbent and reusing it as a chlorine source for the decomposition treatment;
A pollutant decomposition purification apparatus characterized by comprising:   The pollutant decomposition and purification apparatus according to claim 5, wherein a plurality of adsorption towers for storing the adsorbents are used to simultaneously perform a chlorine adsorption operation in at least one adsorption tower and a chlorine desorption operation in the other adsorption tower.

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