JP2006272034A - Contamination gas treatment device and method using photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently decompose/treat a contamination gas such as an odor gas and an exhaust gas containing a volatile organic compound utilizing a photocatalyst. <P>SOLUTION: A gas G to be treated containing a contaminant is introduced to a reaction part 3 arranged with a light irradiation part 35 for irradiating a filling material part 33 arranged with a filling material carried with the photocatalyst with a light. The gas G to be treated is brought into contact with scrubber water W flowing while forming a liquid film on a surface of the filling material in an atmosphere in which an oxidation auxiliary substance fed to the reaction part 3 exists and the contaminant in the gas G to be treated is decomposed by an oxidation reaction of the photocatalyst. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a contaminated gas treatment technique using a photocatalyst. More particularly, the present invention relates to an apparatus and a method processing technique. More specifically, the present invention relates to a technique for decomposing a pollutant by an oxidation reaction of a photocatalyst on the surface of the filler while contacting a pollutant gas with water that forms a liquid film on the surface of the filler in a reaction portion where an oxidation assistant exists. .

  In general, an oxidant such as ultraviolet rays and ozone, or a purification technology for polluted gases using discharge, microwave pyrolysis, or the like is widely used.

  However, each of ultraviolet rays and ozone alone has a limit in oxidizing power, and energy utilization efficiency is low in discharge and microwave pyrolysis, so that there is a problem that the running cost is high in either method. Further, when ozone is used, ozone is harmful to the human body. Therefore, an activated carbon facility for airtight treatment and waste ozone treatment must be provided, which further increases the apparatus cost and running cost.

  On the other hand, techniques for adsorbing substances to be treated in polluted gases using adsorbents such as activated carbon and silica gel have been developed. However, with this technology, once the adsorption capacity of the adsorbent reaches saturation, the purification capacity decreases rapidly, and the treatment needs to be enlarged to increase the processing capacity. I have a problem.

  Pollutant gas purification technology using scrubber water (wash water) is known. For example, Patent Document 1 discloses a technique for decomposing odorous substances by contacting odorous gas and ozone water in a scrubber device in order to efficiently deodorize odorous gas. Patent Document 2 discloses a gas processing technique using a wet gas scrubber. Patent Document 3 discloses that the exhaust gas is purified by an electrolytic scrubber system, and the scrubber water is purified by electrolysis so that the scrubber water is closed, resulting in a low running cost device.

Subsequently, a deodorization method using a photocatalyst and ultraviolet rays that can maintain the purification capability for a long time and does not require any incidental facilities such as exhaust ozone treatment is disclosed in, for example, Patent Document 4 and Patent Document 5. It is known that a photocatalyst has an action of oxidatively decomposing causative substances such as organic substances by being excited by electrons and holes when irradiated with ultraviolet rays.
Japanese Patent Application Laid-Open No. 2004-016465. JP-A-10-128041. JP 2000-271429 A. JP-A-3-157125. JP 2002-102656 A.

  In the conventional technology that uses the oxidation effect of photocatalyst for the treatment of pollutant gas, the structure of the filler does not have a structure that can fully utilize the action and function of the photocatalyst. It is hard to say that it is being demonstrated.

  Therefore, in the present invention, a pollutant gas treatment technique capable of efficiently decomposing pollutant gases such as exhaust gas containing odor gas and volatile organic compounds (VOC; benzene, toluene, xylene, etc.) using a photocatalyst. The main purpose is to provide

  The present invention provides a reaction part in which a filler such as a Raschig ring carrying a photocatalyst, in particular, a light transmissive filler, and a light irradiation part for irradiating light to the filler are arranged. On the other hand, in the atmosphere in which the gas to be treated containing contaminants is introduced and the oxidation assistant supplied to the reaction section is present, the gas to be treated and water flowing to form a liquid film on the surface of the filler, A pollutant gas processing apparatus having a configuration for decomposing the pollutant by an oxidation reaction of the photocatalyst while contacting with the photocatalyst is provided.

  The oxidation auxiliary agent supplied to the reaction section can further improve the photocatalytic activity requiring oxygen by using a gas that has been subjected to a treatment for increasing the oxygen concentration at the stage before or at the time of supply.

  In this apparatus, (1) means for mixing a gas to be treated and an oxidation aid and introducing them into the reaction part, (2) means for mixing a gas to be treated and water and introducing them into the reaction part, (3) water By adopting any of the means for mixing and introducing the oxidation assistant into the reaction section, it is possible to obtain advantages such as the ability to consolidate the gas supply means to the reaction section.

  In addition, the excess gas component of the oxidizing aid gas supplied into the apparatus is separated into recovered gas and waste gas through the gas purification membrane, and the recovered gas is reused as an oxidizing aid. By providing the utilization means, it is possible to improve the utilization efficiency of the oxidation aid, thereby realizing a reduction in running cost.

  Next, in the present invention, a reaction gas in which a filler carrying a photocatalyst is disposed and a light irradiation unit for irradiating light to the filler is disposed on a gas to be treated containing a contaminant. In the atmosphere where the oxidation assistant supplied to the reaction section exists, the step of supplying the oxidation assistant to the reaction section, the step of supplying water to the filler, and the oxidation assistant supplied to the reaction section. And a step of decomposing the pollutant by an oxidation reaction of the photocatalyst while bringing a processing gas into contact with the flowing water that forms a liquid film on the surface of the filler.

  In this method, the photocatalytic activity is improved by performing a gas treatment step for increasing the oxygen concentration of the gas acting as an oxidation aid before or simultaneously with the supply to the reaction section, and also as an oxidation aid. By separating the surplus gas of the acting gas into recovered gas and waste gas, and performing a gas recycling step of reusing the recovered gas, the utilization efficiency of the oxidizing aid is reduced and the running cost is reduced.

  The present invention is excellent in light use efficiency, photocatalytic action efficiency, gas use efficiency, and the like, when a pollutant gas purification process is performed using an oxidation action by a photocatalyst.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below shows an example of a contaminated gas treatment apparatus according to the present invention or an apparatus example that can carry out the contaminated gas treatment method according to the present invention, and according to these illustrated embodiments, The present invention is not limited narrowly.

  First, FIG. 1 is a diagram schematically showing a configuration of a first embodiment of a contaminated gas processing apparatus and method according to the present invention.

  The code | symbol 1 shown in this FIG. 1 has shown the storage tank of the scrubber water W simply. The scrubber water W temporarily stored in the storage tank 1 is sent to the reaction unit 3 by the pump 2 and is disposed below the sprinkling pipe 31 that protrudes and opens inside the reaction unit 3. Water is poured into the sprinkling distribution plate 32.

  The water distribution plate 32 supplies the scrubber water W in a uniformly dispersed state into the filler portion 33 disposed below the water distribution plate 32. The scrubber water W flows on the surface of a filler (for example, Raschig ring filler) carrying a photocatalyst while forming a liquid film.

  At this time, the gas to be treated G, which is a contaminated gas, and the gas F functioning as an oxidation assistant are mixed and supplied into the reaction unit 3 through the gas supply pipe 34. For this reason, since the filler part 33 has an atmosphere filled with these gases G and F, the gases G and F dissolve in the liquid film of the scrubber water W while maintaining a high dissolution rate.

  In addition, the photocatalyst on the surface of the filler is excited by the light irradiated through the quartz tube 36 from the light irradiation tube 35 disposed in the vicinity of the filler, and the substance to be treated (in the scrubber water W that forms a liquid film) That is, an oxidizing action is exerted on the substance to be treated contained in the gas to be treated G, and the substance to be treated is decomposed with high efficiency.

  Here, the filler disposed in the reaction section 3 can be appropriately adopted as long as it is a material that functions so that the scrubber water W flows down while forming a liquid film, and the material and form are not particularly limited. A preferred example is a filler such as a Rashig Ring-shaped structural material. The reason for this is that Raschig rings have a large unit surface area due to their hollow shape, so that the dissolution efficiency and light reflection efficiency of the gas to be processed G and gas F are high.

  FIG. 2 is an enlarged view showing an example of the configuration of the reaction section (particularly, around the filler section 33) in the contaminated gas treatment apparatus according to the present invention.

  In the configuration shown in FIG. 2, the filler portion 33 is disposed in the space between the quartz tubes 36 and 36 that enclose the light irradiation portion 35. The filler portion 33 employs a configuration in which a large number of hollow cylindrical fillers 331 formed from the Raschig ring-shaped structural material or the like are packed.

  As described above, the present invention forms the liquid film of the scrubber water W on the surface of the filler, so that the supplied gas, that is, the gas G to be processed and the gas F of the oxidation aid dissolve at high speed in the liquid film. It has the feature to do. Further, the present invention is characterized in that the liquid film makes contact with the photocatalyst on the surface of the filler with high contact efficiency by the liquid film.

  Further, the filler 331 is formed of a light-transmitting material, more specifically, a material that transmits light that excites the photocatalyst, thereby transmitting the light irradiated from the light irradiation unit 35 to the filler. Thus, the photocatalyst supported on the surface of the filler can be guided. In such a configuration, since light can be used with high efficiency, energy efficiency is good.

  Here, the light irradiation unit 35 appropriately employs a light source suitable for excitation of the photocatalytic material to be used among hydrogen discharge tubes, xenon discharge tubes, mercury lamps, laser light sources, light emitting diodes (LEDs), and the like. These are arranged inside the transparent quartz tube 36, for example. The light emitted from the light irradiator 35 passes through the quartz tube 36 and is irradiated to the filler inside.

  In the present invention, the gas F used as an oxidation aid may be any of air, oxygen, and ozone. However, in consideration of cost, either air or oxygen is adopted. desirable.

  In particular, when air A is employed, the oxygen concentration is measured using an oxygen separation device 4 typified by an oxygen-enriched membrane (gas separation membrane) or PSA before or during the supply of air A into the reaction unit 3. A nitrogen treatment is performed by performing a gas treatment process for increasing the temperature.

  As described above, it is particularly desirable that the gas F for acting as an oxidation aid is sent to the lower region 37 of the reaction unit 3 after performing a gas treatment step for increasing the oxygen concentration in advance.

  The oxygen-enriched film separates oxygen from the air based on the principle that oxygen on the other side passes through a vacuum region on one side of a thin film such as silicon faster than nitrogen, and PSA (Pressure Swing Adsorption) Adsorption) is an apparatus that can continuously separate the target gas (oxygen in the present invention) from the air by utilizing the difference in adsorption characteristics of the adsorbent to the gas.

  Here, the photocatalyst that can be employed in the present invention is not particularly limited, and metal oxides such as zinc oxide, tungsten oxide, titanium oxide, and cerium oxide, or metal sulfides such as zinc sulfide, cadmium sulfide, and mercury sulfide can be used. .

  Furthermore, by using a photocatalyst doped with impurity ions such as nitrogen ions and sulfur ions for these metals, the photocatalytic ability can be exhibited even in the visible light region of 380 nm to 650 nm. Thereby, light irradiation devices other than the ultraviolet irradiation device can be widely applied, and the advantage that sunlight can be used as excitation of the photocatalyst is born. Moreover, when what carried | supported metals, such as platinum, is employ | adopted with respect to these metals, there exists an advantage that the efficiency in photoreaction can be improved.

  In addition, the outer cylinder part 38 of the reaction part 3 is formed of a light-transmitting material such as glass or acrylic resin, and by devising so that sunlight can be taken into the reaction part 3, the excitation efficiency of the photocatalyst is increased. It may be further increased. Considering the strength, it is desirable to form the outer cylinder portion 38 with a reinforced resin such as an acrylic resin.

  Among photocatalyst materials, titanium oxide produces hydroxy radicals and superoxide ions that have a large oxidizing power on the catalyst surface and exerts the function of powerfully oxidizing and decomposing organic substances in the water to be treated. It can be suitably used also from the viewpoint of the stability and the like.

  Examples of titanium oxide include titanium oxide such as metatitanic acid, orthotitanic acid, hydrous titanium oxide, hydrated titanium oxide, titanium hydroxide, and titanium peroxide, as well as general-purpose titanium dioxide, and titanium hydroxide. Among these, titanium oxide having anatase or rutile crystal structure is relatively inexpensive and has excellent performance.

  As a method for forming the photocatalyst layer (photocatalyst film) by supporting the photocatalyst on the surface of the filler, any method that can form the photocatalyst in a thin film state can be adopted as appropriate. For example, a vacuum deposition method, a plating method, a sol-gel method, or the like can be employed. A method of immobilizing fine powder is also applicable.

Next, referring again to FIG. 1, the apparatus denoted by reference numeral 5 in FIG. 1 is an apparatus used in the gas recycling process, and is a gas purification membrane apparatus attached to the reaction unit 3. . The gas purification membrane device 5 plays a role of separating the surplus gas F ₁ in the reaction unit 3 into a reusable recovered gas F ₁₁ and a waste gas F ₁₂ that is difficult to recycle.

Collected gas F ₁₁ separated through the gas supply unit 34, or through the gas supply pipe 34 after passing through the oxygen separation device 4, by re-supplied to the inside of the reaction unit 3, acts as an oxidizing aids The utilization efficiency of the gas F to be made can be improved.

In the filler portion 33 that performs the above-described treatment, the treated water W ₁ that has been subjected to the oxidation treatment by gas-liquid contact is taken out from the discharge port 391 at the bottom portion 39 of the reaction portion 3 and installed adjacently. It is returned to the storage tank 1 and used again as scrubber water W (see FIG. 1).

  Next, FIG. 3 is a diagram simply showing the configuration of the second embodiment of the contaminated gas processing apparatus and method according to the present invention.

  In the second embodiment shown in FIG. 3, the first embodiment shown in FIG. 1 adopts a means for mixing the gas G to be processed into the scrubber water W and introducing it into the reaction unit 3. And its configuration is different.

  In this configuration, the gas G to be treated is contained in the scrubber water W and introduced into the reaction unit 3 through the water spray pipe 31. The gas F used as an oxidizing aid is sent to the gas supply unit 34 as it is, or after being processed by the oxygen separation device 4, sent to the gas supply pipe 34 and supplied into the reaction unit 3. Since the other device configuration is the same as that of the first embodiment, description thereof is omitted.

  Next, FIG. 4 is a figure which shows simply the structure of 3rd embodiment of the contaminated gas processing apparatus and method concerning this invention.

  In the third embodiment shown in FIG. 4, it is shown in FIG. 1 that the means for mixing the gas F used as an oxidation aid into the scrubber water W and introducing it into the reaction unit 3 is adopted. The configuration is different from the first embodiment. In this configuration, the gas F used as an oxidation aid is contained in the scrubber water W and introduced into the reaction unit 3 through the sprinkling pipe 31.

  The gas F used as an oxidation aid may be introduced into the scrubber water W as it is, or may be introduced into the scrubber water W after being processed by the oxygen separator 4. On the other hand, the gas G to be treated is sent alone to the gas supply pipe 34 and supplied into the reaction section 3 (see FIG. 4). Although not shown, it is possible to mix both the gas G to be treated and the gas F used as an oxidation aid into the scrubber water W and introduce them into the reaction unit 3. Since the other device configuration is the same as that of the first embodiment, description thereof is omitted.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  In this experiment, air containing methyl ethyl ketone was used as the gas to be treated (G). Tap water was used as the scrubber water (W). In the examples, ozone gas and hydrogen peroxide water were used as oxidation assistants.

  In Examples 1 to 4, the filler used was an anatase-type powdered titanium oxide supported on a quartz Raschig ring of φ6 × 10 mm using a sol-gel method. On the other hand, in Comparative Examples 1 and 2, a material in which anatase-type titanium oxide was supported on a non-light-transmitting honeycomb by the same method was used. The amount of titanium oxide in the honeycomb-shaped photocatalyst of the comparative example and the Raschig ring-supported photocatalyst of the example was adjusted to be the same amount.

  A high pressure mercury lamp having a main wavelength of 365 nm was used as the light source. Since the high-pressure mercury lamp generates heat, quartz glass was used as a double tube, and ultrapure water as cooling water was passed between them.

Air containing 50 ppm of methyl ethyl ketone (this air is used as an oxidation aid), that is, the gas G to be treated is supplied to the reaction section with an air flow rate of 1.0 m ³ / min, and ozone gas or oxygen gas as the oxidation aid is The mixture was mixed at a concentration of 0.65 g / m ³ and 0.5 m ³ / min, and hydrogen peroxide as the same oxidation aid was added to the scrubber water so as to have a concentration of 70 mg / L. The scrubber water was sprinkled into the reaction section at 5 L / min.

  The treated gas was sampled and analyzed by gas chromatography to determine the methyl ethyl ketone removal rate. The following “Table 1” summarizes the processing methods of Examples 1 to 4 and Comparative Examples 1 and 2. Table 2 summarizes the results of this experiment.

  As can be seen from the results shown in the above-mentioned “Table 2”, in the case of the comparative example 1 using the honeycomb-shaped photocatalyst, the light is transmitted to the entire surface of the photocatalyst because the honeycomb-shaped surface area is small and it is not light transmissive. The removal rate was extremely low due to reasons such as not reaching to the area. Moreover, in the comparative example 2 which supplied ozone as an oxidation adjuvant, the oxidizing power improved with the active oxygen produced | generated from ozone, and the removal rate improved twice as compared with the comparative example 1. FIG.

  On the other hand, in Example 1, since the ultraviolet light that cannot be absorbed by the quartz Raschig ring can be supplied to another titanium oxide, the utilization efficiency of light was improved and the removal rate was further improved.

  Further, as in Examples 2 to 4, in addition to the air present in the gas to be treated, in the example in which the oxidation assistant was further supplied to the reaction part, the highest removal rate was obtained compared to other examples. Indicated. This is because the scrubber water flows on the surface of the filler while forming a liquid film, and the efficiency of contact between the catalyst and the substance to be treated dissolved in the scrubber water and contact with the oxidant is improved. It is thought that efficiency was shown.

  INDUSTRIAL APPLICABILITY The present invention can be used as a purification treatment technique for polluted gases using an oxidation action by a photocatalyst. In particular, it can be used as the purification treatment technique which is excellent in light utilization efficiency, photocatalytic action efficiency, gas utilization efficiency, and the like.

It is a figure which shows simply the structure of 1st embodiment of the contaminated gas processing apparatus and method which concern on this invention. It is an enlarged view which shows an example of a structure of the reaction part (especially periphery of a filler part) in the contaminated gas processing apparatus which concerns on this invention. It is a figure which shows simply the structure of 2nd embodiment of the contaminated gas processing apparatus and method which concern on this invention. It is a figure which shows simply the structure of 3rd embodiment of the contaminated gas processing apparatus and method which concern on this invention.

Explanation of symbols

3 Reaction unit 4 Oxygen separator 5 Gas purification membrane device 33 Filler unit 34 Gas supply pipe 35 Light irradiation unit 36 Quartz tube 331 Filler G Processed gas (contaminated gas)
F Gas used as oxidation aid F ₁ Surplus gas F ₁₁ Recycled recovery gas F ₁₂ Waste gas W Scrubber water

Claims (9)

Processed gas containing pollutants
The filler carrying the photocatalyst is disposed and introduced into the reaction section where the light irradiation section for irradiating the filler with light is disposed,
The pollutant is generated by an oxidation reaction of the photocatalyst while bringing the gas to be treated into contact with the flowing water in a liquid film formed on the surface of the filler in an atmosphere where the oxidation assistant supplied to the reaction section exists. Decomposing pollutant gas treatment equipment.   The pollutant gas processing apparatus according to claim 1, wherein the filler is Raschig ring.   The contamination gas processing apparatus according to claim 1, wherein the filler is light transmissive.   The water treatment apparatus according to any one of claims 1 to 3, wherein the oxidation aid is a gas that has been subjected to a treatment for increasing oxygen concentration. The pollutant gas processing apparatus according to claim 1, wherein any one of the following (1) to (3) is employed.
(1) Means for mixing the gas to be treated and the oxidation aid and introducing them into the reaction section.
(2) Means for mixing the gas to be treated and water and introducing them into the reaction section.
(3) Means for mixing water and an oxidation aid and introducing them into the reaction section.   It has gas recycling means for separating the surplus of the oxidizing agent gas supplied into the apparatus into a recovered gas and a waste gas through a gas purification membrane, and reusing the recovered gas as an oxidizing agent. The pollutant gas processing apparatus according to claim 1, wherein Introducing a gas to be treated containing a pollutant into a reaction section in which a filler carrying a photocatalyst is disposed and a light irradiation section for irradiating the filler with light;
Supplying an oxidizing aid to the reaction section;
Supplying water to the filler;
The pollutant is generated by an oxidation reaction of the photocatalyst while bringing the gas to be treated into contact with the flowing water in a liquid film formed on the surface of the filler in an atmosphere where the oxidation assistant supplied to the reaction section exists. Disassembling, and
Performing pollutant gas processing method.   8. The contaminated gas treatment method according to claim 7, wherein a gas treatment step for increasing the oxygen concentration of a gas acting as an oxidizing aid is performed before or simultaneously with the supply to the reaction section.   8. The pollutant gas processing method according to claim 7, wherein a gas recycling step of separating surplus gas of the gas acting as an oxidizing aid into recovered gas and waste gas and reusing the recovered gas is performed.

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