JP2007216188A - Photocatalytic reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalytic reactor cleaning fluid such as air using a photocatalytic reaction, with which contact efficiency of a treating object with the photocatalyst can be remarkably enhanced, and treating efficiency is not lowered even when the scale of the apparatus is increased. <P>SOLUTION: A photocatalyst body formed by having the photocatalyst and a light source exciting the photocatalyst provided to the photocatalyst body, are provided in a reactor body having flow passages of the treating fluid. A means relatively moving the photocatalyst body to the fluid in order to bring the fluid into contact with the face having the photocatalyst in the photocatalyst body, is also provided to satisfy following condition (A):0.00001(W/m)≤G*δ≤1.0(W/m). In the (A), G is light irradiation density; δ is the thickness of a laminar film produced near the surface having the photocatalyst of the photocatalyst body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photocatalytic reaction device, more specifically, a photocatalytic fluid purification device such as a photocatalytic exhaust treatment device that purifies a fluid such as air using a photocatalytic reaction, a photocatalytic deodorization device that performs deodorization using a photocatalytic reaction, and the like. The present invention relates to a photocatalytic reaction apparatus that is applied to various industrial environment fields, living environment fields, and the like using a photocatalytic reaction.

  In recent years, photocatalytic technology using photocatalytic reaction has spread rapidly, and has been widely applied to various industrial environment fields, living environment fields, etc. Conventionally, in photocatalyst exhaust treatment devices and photocatalyst deodorization devices, in order to improve the contact between the photocatalyst and the material to be treated in the exhaust, the shape of the photocatalyst body provided with the photocatalyst is uneven, honeycomb, cloth, porous, etc. A material adsorbent such as activated carbon or zeolite is disposed near the photocatalyst in order to increase the surface area by increasing the shape and promoting surface adsorption. For example, the invention according to Patent Document 1 below relates to an air cleaning device, but the photocatalyst body is formed in a honeycomb shape to adsorb activated carbon.

  However, these are mainly means for promoting adsorption, and even if the surface area is increased, the irradiated light reaches only a part of the surface of the photocatalyst, so even if the contact area between the photocatalyst and air increases, the light source Only a part of the side surface functions as a photocatalyst. That is, in the photocatalytic reaction, since it is necessary to perform the catalytic reaction while performing light irradiation as described above, the catalytic reaction does not occur unless the irradiated light reaches the surface of the photocatalyst. Even if the adsorbent is arranged near the catalyst, the photocatalyst selectively adsorbs oxygen and water to the surface by photoadsorption, and donates the electrons on the photoexcited photocatalyst surface to oxygen, etc. Oxides are generated, and the material to be treated is only indirectly oxidized by these oxidizing substances, and such an adsorbent does not contribute directly to increasing the efficiency.

Moreover, although the invention which concerns on the following patent document 2 is related with the photocatalyst deodorizing apparatus which uses a xenon tube as a light source, also in this patent document 2, it is only the thing of the grade which uses activated carbon as an adsorbent. In addition, since a xenon tube is used as a light source, there is a problem that the cost is high.
Furthermore, when a condensing light source such as a xenon tube is used, the light is concentrated in a certain part, and the light density is extremely increased only in this part. Compared with black light and other light sources that can disperse the light density, the quantum efficiency There is a problem that goes down.

  Further, the invention according to Patent Document 3 below relates to a photocatalytic reaction device using a corona discharge electrode as a light source, and the invention according to Patent Document 4 below relates to a light source for a photocatalyst using an LED as a light source. No particular measures are taken to improve contact.

JP 2000-167353 A JP 2001-212216 A JP 2002-159829 A JP-A-11-309202

  The present invention has been made to solve the above-described problems, and can significantly improve the contact efficiency between the substance to be treated and the photocatalyst as compared with the conventional photocatalytic reaction apparatus, and further, the apparatus is large-sized. It is an object of the present invention to provide a photocatalytic reaction device that does not lower the processing efficiency even if it is changed.

The present invention is intended to solve such a problem. The invention according to claim 1 is a photocatalyst body 3 formed by providing a photocatalyst in an apparatus body 1 having a fluid flow path to be treated. And the light source 2 that excites the photocatalyst provided in the photocatalyst 3, and the fluid is brought into contact with the surface of the photocatalyst 3 provided with the photocatalyst so that the following condition (A) is satisfied. In order to achieve this, the photocatalyst body 3 is further provided with means for moving the photocatalyst body 3 relative to the fluid.
0.00001 (W / m) ≦ G · δ ≦ 1.0 (W / m) (A)
In (A), G represents the light irradiation density, and δ represents the thickness of the film formed in the vicinity of the surface where the photocatalyst of the photocatalyst is provided.

The invention described in claim 2 is characterized in that, in the photocatalytic reaction device described in claim 1, the light irradiation density is set so as to satisfy G ≧ 50 (W / m ² ). The invention according to claim 3 further includes a photocatalyst body 3 provided with a photocatalyst in an apparatus body 1 having a flow path of a fluid to be processed, and a light source for exciting the photocatalyst provided in the photocatalyst body 3. 2 and a means for moving the photocatalyst body 3 relative to the fluid in order to bring the fluid into contact with the surface of the photocatalyst body 3 on which the photocatalyst is provided, and the photocatalyst body. 3 is formed in a plate shape and is arranged in parallel with the fluid flow direction. According to a fourth aspect of the present invention, in the photocatalytic reaction device according to the third aspect, the surface of the plate-like photocatalyst body 3 arranged parallel to the fluid flow direction is formed with irregularities.

  The invention according to claim 5 further includes a photocatalyst body 3 provided with a photocatalyst in the apparatus body 1 having a flow path of a fluid to be processed, and a light source for exciting the photocatalyst provided in the photocatalyst body 3. 2 and a means for moving the photocatalyst body 3 relative to the fluid in order to bring the fluid into contact with the surface of the photocatalyst body 3 on which the photocatalyst is provided, and the photocatalyst body. 3 is characterized in that the through-hole 8 through which the fluid flows is formed in parallel to the flow direction of the fluid, or is formed obliquely with respect to the flow direction of the fluid. Further, the invention described in claim 6 is the photocatalytic reaction device described in claim 5, wherein the photocatalyst body 3 having the through holes 8 is formed in a substantially cardboard type or a substantially honeycomb type. The invention according to claim 7 is the photocatalytic reaction device according to claim 5 or 6, wherein the entire photocatalyst body 3 is formed in a substantially ring shape or a substantially disk shape.

  Further, the invention according to claim 8 is the photocatalytic reaction device according to any one of claims 1 to 7, wherein the means for moving the photocatalyst body 3 relative to the fluid is a means for rotating the photocatalyst body 3. It is characterized by being. Furthermore, the invention according to claim 9 is the photocatalytic reaction device according to any one of claims 1 to 7, wherein the means for moving the photocatalyst body 3 relative to the fluid is means for vibrating the photocatalyst body 3. It is characterized by being. Furthermore, the invention according to claim 10 is the photocatalytic reaction device according to any one of claims 1 to 9, wherein the light of the light source 2 is irradiated from a direction orthogonal to the surface of the photocatalyst 3 provided with the photocatalyst. As described above, the light source 2 and the photocatalyst body 3 are arranged.

  Furthermore, the invention according to claim 11 is the photocatalytic reaction device according to any one of claims 1 to 10, wherein the light source is a light emitting diode. Furthermore, a twelfth aspect of the present invention is the photocatalytic reaction device according to any one of the first to tenth aspects, wherein the light source is a corona discharge electrode. Furthermore, the invention described in claim 13 is the photocatalyst reaction device described in claim 12, characterized in that an electrostatic generator for corona discharge of the light source is provided integrally with the photocatalyst body 3. Furthermore, the invention according to claim 14 is the photocatalytic reaction device according to any one of claims 1 to 13, wherein the plurality of device bodies 1 are arranged in series in the fluid flow direction, and arranged in series. The impurity concentration of the fluid in the apparatus body 1 on the rear stage side is configured to be stepwise lower than the impurity concentration of the fluid in the apparatus body 1 on the front stage side.

  Furthermore, the invention according to claim 15 is the photocatalytic reaction device according to any one of claims 1 to 14, wherein the contact speed between the fluid flowing in the device body 1 and the photocatalyst in the photocatalyst 3 is changed. It is configured. Furthermore, the invention according to claim 16 is the photocatalytic reaction device according to any one of claims 1 to 15, wherein the louver is provided in the photocatalyst body 3 in a direction perpendicular to the flow direction of the fluid and in the irradiation direction of the light from the light source. It is attached.

  In general, the catalytic reaction proceeds when the catalyst surface comes into contact with the object to be treated, and occurs through three processes: adsorption of the reactant, surface reaction, and desorption of the product. A simplified reaction of each process is an elementary reaction, and when the other elementary reactions are sufficiently faster, the slowest elementary reaction is the so-called rate-limiting step. In an actual catalytic reaction, the step where the reactant approaches the catalyst often becomes the rate-limiting step. If the reactants are not stirred or fluidized, there is nothing else but diffusion to approach the catalyst. Diffusion is generally a very slow process compared to the catalytic reaction, and diffusion-limited when the stage before the catalytic reaction is late.

  Even in the photocatalytic reaction, the stage where the reactant is adsorbed on the photocatalyst is originally the rate-determining stage, but actually the stage where the reactant approaches the photocatalyst before adsorbing to the photocatalyst may become the rate-limiting stage. When the reactant enters the rate-determining step before adsorbing to the photocatalyst in this way, the reaction rate of the photocatalytic reaction when the reactant adsorbs to the photocatalyst becomes slow, so the reactant must be stirred or fluidized. However, in a photocatalytic reaction, unlike a general catalytic reaction, it is necessary to perform stirring and flow while performing light irradiation.

  In an actual apparatus, exhaust gas flows while contacting the catalyst surface. If the contact speed of the target gas is set to a certain level or more, turbulent flow is generated in the space away from the surface of the photocatalyst body, and air components are mixed. However, near the surface of the photocatalyst, there is an extremely thin laminar flow area even if the contact flow velocity is increased, and this laminar flow part and the transition part to turbulent flow are called a boundary film. The mass transfer rate of this part will dominate the overall reaction rate.

Here, the concentration gradient is extremely large, and the mass transfer is close to the diffusion rate in a stationary state. Mass transfer is expressed by the following formula (1).
q _X = (D / δ) (C _X −C _S ) (1)

In the equation (1), q _X is referred to as a material flux, and is a mass transfer rate per unit area that moves perpendicular to the boundary film. D is the material diffusion coefficient, δ is the film thickness, C _X is the material concentration outside the film, and C _S is the catalyst surface and the material concentration inside the film.

D in the formula (1) is specific to the substance and is determined by the target substance and the fluid. C _X is the concentration of the substance to be treated, and C _S is determined by the substance reaching the catalyst surface and the excited state of the photocatalyst. When C _X and C _S are given, if the boundary film thickness δ is reduced, the mass transfer amount q _X is increased.

In addition, the substance treatment amount q _S per unit surface treated on the photocatalyst surface is represented by the following formula (2).
q _S = AΦG = f (C _S ) · G (2)
A is a constant, and Φ is called quantum efficiency. Here, the quantum efficiency Φ is represented by Φ = f (C _S ), and is a function that draws a line rising in the right direction in the graph.

Since the amount of substance supplied through the boundary film and the amount of substance processed on the photocatalyst surface are the same, if q _X = q _S in the equations (1) and (2),
q _X = q _S = (D / δ) (C _X −C _S ) = f (C _S ) · G (3)

For the sake of simplicity, if f (C _S ) is regarded as a function that draws a straight line, an approximate expression of the following expression (4) is obtained.
f (C _S ) = F · C _S (4)
Substituting this equation (4) into the above equation (3) and transforming it yields the following equation (5).

  From the above equations (2), (4), and (5), the following equation (6) is obtained.

In the equation (6), when G is large, q = (D / δ) · C _X , meaning that even if G is increased, the flux approaches a constant value, and so-called saturation phenomenon occurs.
On the other hand, when G is small, q = FC _X · G, and the flux is proportional to the light irradiation density.
Looking at the apparent quantum efficiency of the device as Φ _X , it is the same as equation (2)

Here, B is a constant, and 1 / B = Gδ / D + 1 / F.
Returning to the original definition and rearranging, the following equation (7) is obtained.

The meaning of the equation (7) means that if the second term of the denominator is reduced, the efficiency of the apparatus is improved and the performance originally possessed by the photocatalyst is approached. This equation can also explain that the efficiency of the apparatus decreases if the light irradiation density G is increased, and that the efficiency increases when the boundary film thickness δ is decreased. In other words, it can be said that the denominator second term = Gδ / D determines the performance of the apparatus. Among these, D is determined by the substance. For example, in the case of an exhaust treatment apparatus, it is the material diffusion coefficient of the target substance with respect to air. As an apparatus, Gδ can be taken up as a design value.

For example, when the substance concentration C _X , the displacement Q and the substance name are determined, Φ _X is determined in the conventional method.
Accordingly, the total light input = the amount of substance required for processing × quantum efficiency = the displacement of the exhaust gas × the outlet concentration difference × the quantum efficiency.
When the displacement is increased while maintaining the efficiency, if the light irradiation density G is maintained, the area of the photocatalyst proportional to the displacement is required, and the area of the photocatalyst becomes enormous. However, if the G value can be increased while maintaining efficiency, the apparatus becomes smaller. For example, if the light irradiation density G can be increased 5 times while maintaining the efficiency, the device area can be reduced to 1/5. For that purpose, according to the equation (7), the boundary film thickness δ may be set to 1/5.

The film thickness δ is not known in all cases, but if the conditions are limited to turbulent flow, it is said that the logarithmic law of the following equation (8) is established for, for example, a cylinder or a flat plate. In equation (8), U is the wind speed and ν is the kinematic viscosity coefficient. L is a representative dimension, and is determined by the structure of the fluid flow path.
δ = 25L ^0.125 (U / ν) ^−0.875 (8)

When the kinematic viscosity coefficient is calculated with the equation (8) as air at 25 ° C.,
δ = 0.001534 · L ^0.125 · U ^-0.875 (9)
It becomes. That is, the film thickness is inversely proportional to the 0.875th power of the wind speed (in this case, the relative speed of the catalyst and air may be used).

These equations (8) and (9) are established under a certain condition, but if a numerical value including the representative dimension L is regarded as a constant C, and a multiplier of 0.875 is further generalized as α,
δ = CU ^- α = C / Uα (10)
That is, a more general formula (10) indicating the relationship between the film thickness and the wind speed is obtained.

The invention described in claim 1 pays attention to these points and sets Gδ within the predetermined range. As a result of diligent research by the present inventors, the maximum value of G is set to 300 W / m ² from the viewpoint of not reducing the quantum efficiency of the device assuming an exhaust flow that circulates with the catalyst in the exhaust device or the like, and δ Was set to about 3.3 mm. Therefore, the maximum value of G · δ calculated from this set value is 300 W / m ² × 3.3 mm (0.0033 m) = 1.0 W / m. On the other hand, the minimum value of G that can be assumed by the exhaust system or the like was set to 5 W / m ² , and the minimum value of δ was set to 0.002 mm. The value of G · δ calculated from this set value is 5 W / m ² × 0.002 mm (0.000002 m) = 0.00001 W / m.
In the second aspect of the invention, G ≧ 50 (W / m ² ) is set assuming a relatively large apparatus, and the third and subsequent aspects of the invention are the invention of the first aspect. Is more concrete.

The light irradiation density G is measured with a light intensity meter along the surface of the photocatalyst body with respect to the light source, but the actual light irradiation density G _S is reduced by the grain shape of the catalyst crystal and the unevenness of the catalyst body. . For example, there is a circular 1.5 times the area of the plane apparent corrugated like corrugated cardboard type, substantially G _S value becomes G / 1.5. However, when the photocatalyst body is formed in a wave shape, there is a correlation between the fluid flow direction and the separation phenomenon of the boundary film, for example, even when the photocatalyst body is formed in a corrugated circular wave shape as described above, as having a flow direction parallel to the through hole of the fluid, without affecting the release of the boundary layer, it is possible to lower the G _S value only. Accordingly, the G _S δ product is reduced, and the contact efficiency between the fluid and the photocatalyst (the processing efficiency of the apparatus) is increased. The inventions according to claims 3 to 7 are made from such a viewpoint.

  As described above, the present invention includes a photocatalyst formed with a photocatalyst in a device body having a fluid flow path to be processed, and a light source for exciting the photocatalyst provided in the photocatalyst. And a means for moving the photocatalyst relative to the fluid so that the value of Gδ is within a predetermined range as described above so that the fluid contacts the surface of the photocatalyst provided with the photocatalyst. Since it is provided, the number of times of contact between the substance to be treated in the fluid and the photocatalyst provided in the photocatalyst body can be increased, thereby making the contact efficiency between the substance to be treated and the photocatalyst remarkably higher than before. There is an effect that it can be improved.

  Further, the photocatalyst body is formed in a plate shape, and the plate-like photocatalyst body is disposed in parallel with the fluid flow direction, or the through hole through which the fluid flows is parallel to the fluid flow direction or oblique to the fluid flow direction. When the photocatalyst body is formed so that the light source is formed as follows, such a photocatalyst body can be arranged as close to the light source as possible, and accordingly, a shadow portion is not easily generated in the light, and the light from the light source is powerful. There is an effect that can be irradiated. When the photocatalyst is plate-shaped, more photocatalysts can be arranged in the apparatus body, and the apparatus can be further downsized.

  In particular, when the photocatalyst body is formed in a substantially corrugated cardboard type or a substantially honeycomb type so that the through hole through which the fluid flows is parallel to the fluid flow direction or oblique to the fluid flow direction, the photocatalyst body and the fluid The contact area between the material to be treated and the photocatalyst is further improved.

Further, when a means for rotating or vibrating the photocatalyst is adopted as means for moving the photocatalyst relative to the fluid, the number of contacts between the photocatalyst and the substance to be treated is increased by these simple means. be able to.
Further, when the rotating means is used as the relatively moving means, it is possible to eliminate the unevenness of the irradiated light and the unevenness of the wind speed, which are often found in a light source such as a fluorescent lamp. In the photocatalyst decomposition step, an intermediate product may be generated during the oxidative decomposition. For example, benzoic acid generated in the decomposition process of toluene, but if the oxidation process is uneven, benzoic acid adheres to the part where the light is weak or the wind speed is slow (thickness film is thick), and the next oxidative decomposition process It will not proceed to. When the rotating means as described above is employed, the relative speed between the photocatalyst and the fluid increases, so that the wind speed value in the above equation (10) increases, thereby reducing the film thickness in the equation (10). Thus, it is possible to suitably prevent the occurrence of a trouble that does not proceed to the oxidative decomposition process due to the fixation of the intermediate product as described above.

  In particular, as described above, after forming the photocatalyst body so that the through hole is parallel to the fluid flow direction or oblique to the fluid flow direction, the whole is formed in a substantially ring shape or a substantially disk shape, When the means for rotating the photocatalyst body as described above is adopted, a synergistic effect between the effect of increasing the contact area between the photocatalyst body and the fluid and the effect of the rotating means as described above is exhibited, and the substance to be treated The contact efficiency between the photocatalyst and the photocatalyst is remarkably improved.

  Furthermore, when the light source light is irradiated from a direction orthogonal to the surface of the photocatalyst body provided with the photocatalyst, the light is less likely to cause a shadow portion, and the light Irradiation is also more powerful.

  Furthermore, when a light emitting diode is used as the light source, more photocatalysts can be arranged in the apparatus body, thereby reducing the weight and size of the apparatus. In addition, if an electrode is attached to the photocatalyst body and corona discharge is caused between the photocatalyst bodies, near ultraviolet rays are generated and the photocatalyst can be excited, which contributes to efficient contact between the photocatalyst and the material to be treated and downsizing of the apparatus. Will be. Further, when a light emitting diode or corona discharge is used as a light source, not only the volume of the light source is reduced, but also the light density G can be further dispersed, so that the catalyst area can be increased and the quantum efficiency can be improved.

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

(Embodiment 1)
FIG. 1 is a schematic perspective view showing a photocatalyst exhaust treatment apparatus as an embodiment of the photocatalytic reaction apparatus of the present invention. As shown in FIG. 1, the photocatalyst exhaust treatment apparatus of the present embodiment includes a plurality of light sources 2, a photocatalyst body 3, and a motor 4 in an apparatus body 1 having an air flow path.

  Although the apparatus body 1 is schematically and only partially shown in FIG. 1, the air flow path is provided in the vertical direction in FIG. In the present embodiment, a fluorescent lamp type black light is used as the light source 2, and as shown in FIG. 1, a large number of light sources are arranged in the horizontal direction at the upper and lower stages so as to be parallel to each other. ing.

  In this embodiment, the photocatalyst body 3 is formed in a rotating disk shape, that is, a circular plate shape, and the photocatalyst is provided on the entire front and back surfaces of the circular plate-like photocatalyst body 3. In this embodiment, titanium oxide is used as a photocatalyst. A large number of photocatalysts 3 are disposed between the light sources 2 and the light sources 2 that are disposed in large numbers. As a result of this arrangement, the light source 2 is present on both sides of each photocatalyst 3.

  In this case, since the light source 2 is a small substantially rod-shaped black light and the photocatalyst 3 is a circular plate, a large number of light sources 2 and photocatalysts 3 can be arranged in the apparatus body 1. Even if a large number of devices are arranged, the device body 1 does not increase in size.

  As shown in FIG. 1, the motor 4 is attached to a substantially central portion of the photocatalyst body 3 on one end side among the many photocatalyst bodies 3. Although not shown in FIG. 1, the motor 4 is provided with a rotating shaft coaxially, and a large number of photocatalysts 3 arranged in the same row around the rotating shaft are driven to rotate. Has been.

  The photocatalyst exhaust treatment apparatus of the present embodiment has the above-described configuration. When the photocatalyst exhaust treatment apparatus is used, as shown by the arrow in FIG. Circulate.

  Then, the motor 4 is driven to rotate a large number of photocatalysts 3 to irradiate the photocatalysts 3 with light from the light source 2. In this case, since the photocatalyst body 3 is disposed in the vicinity of both sides of the light source 2, the light from the light source 2 is irradiated on the entire front and back surfaces of the photocatalyst body 3 rotating on both sides in the vicinity thereof. The photocatalysts provided on the entire front and back surfaces are effectively irradiated with light.

  In addition, since the photocatalyst 3 is rotating, the number of times of contact with air is extremely increased, and the light from the light source 2 is efficiently irradiated without causing a so-called shadow portion. In the apparatus of the present embodiment, if the wind speed of the air flowing in the apparatus body 1 is set to a range smaller than the contact speed between the light source 2 and the photocatalyst body 3, the contact speed is not affected by the wind speed, and the photocatalyst body. 3 is governed by the rotation speed. This point will be described in an embodiment described later.

(Embodiment 2)
This embodiment is also an embodiment of the photocatalyst exhaust treatment apparatus as in the first embodiment. In this embodiment, the photocatalyst 3 is formed in a rectangular plate shape as shown in FIG. Further, as means for moving the photocatalyst body 3 relative to the light source 2, a means for vibrating is employed instead of the means for rotating in the above embodiment.

That is, in this embodiment, as shown in FIG. 1, an ultrasonic transducer 5 as a vibration drive source is provided on the top of the photocatalyst 3. As this vibration drive source, an eccentric motor or the like can be used instead of the ultrasonic vibrator 5.

  In the present embodiment, the light source 2 is arranged in the vertical direction. A large number of light sources 2 and photocatalysts 3 are arranged so that the photocatalysts 3 are located on both sides of the light source 2, and this is the same as in the first embodiment. The type of the light source 2 is the same as that in the first embodiment.

  In the present embodiment, air is circulated in the lateral direction of the device body 1 as indicated by the arrows in FIG. Then, the ultrasonic vibrator 5 which is a vibration driving source is driven to vibrate a large number of photocatalyst bodies 3 and irradiate the photocatalyst body 3 with light from the light source 2. The light from the light source 2 is irradiated on the entire front and back surfaces of the photocatalyst 3 that vibrates on both sides in the vicinity thereof, and the light is effectively irradiated on the photocatalysts provided on the entire front and back surfaces of the photocatalyst 3. This is similar to the case of the rotating means of the first embodiment.

(Embodiment 3)
In the present embodiment, a light emitting diode is used as the light source 2, and this is different from the first and second embodiments in which a fluorescent lamp type black light is used. Although the type of the light emitting diode is not limited, it is desirable to use an ultraviolet light emitting diode because the wavelength region in which absorption of titanium oxide as a photocatalyst appears is an ultraviolet region, as will be described in Examples described later. In the present embodiment, as shown in FIG. 3, a large number of light source holders 6 provided with a large number of light emitting diodes as light sources 2 on a plate-like surface and a large number of photocatalysts 3 formed in a rotating disk shape are alternately arranged. It is arranged.

  The point which rotates the photocatalyst body 3 is the same as that of Embodiment 1, and the point which used the motor 4 as a rotational drive source is also the same as that of Embodiment 1.

  In the present embodiment, since the light emitting diode much smaller than the fluorescent lamp type black light of the above embodiment is used as the light source 2, the interval between the photocatalysts 3 provided in large numbers can be narrowed, thereby further increasing the entire apparatus. It can be downsized. Further, if the arrangement of the light source 2 is also matched with the disk shape of the photocatalyst body 3, the light catalyst 2 is irradiated to a place where the photocatalyst body 3 does not exist as in the fluorescent lamp type black light of the first and second embodiments. There is also an advantage that the light density becomes uniform. As a result, the life of the light source 2 becomes longer than in the first and second embodiments, and as a result, maintenance-free may be possible.

(Embodiment 4)
In the present embodiment, a discharge electrode is used as the light source 2, and the type of the light source 2 is different from those of the first to third embodiments. More specifically, as shown in FIG. 4, a light source holding body 6 provided with a large number of light sources 2 made of needle-like electrodes and a large number of photocatalyst bodies 3 formed in a rotating disk shape are alternately arranged. Has been. In the present embodiment, the light source holder 6 is also provided with a photocatalyst.

  The point that the motor 4 is used as the drive source of the photocatalyst body 3 is the same as that of the third embodiment.

  In the present embodiment, by performing corona discharge, the periphery of the light source 2 composed of needle-like discharge electrodes emits light, and so-called corona light emission occurs. The point that the photocatalyst is excited by irradiating the photocatalyst body 3 with light is the same as in the above embodiments. The discharge electrode is insulated from other parts and a high voltage is applied. The photocatalyst 3 on the side that receives the corona discharge can be maintained in safety by being disposed in parallel with the light source holder 6 on the side that generates the corona discharge.

(Embodiment 5)
In the present embodiment, two apparatus bodies 1 are arranged, which is different from the first to fourth embodiments in which only one apparatus body 1 is used. Two device bodies 1 can be provided in parallel as shown in FIG. 5 (a), and two device bodies 1 can be provided in series as shown in FIG. 5 (b). .

  The number of apparatus bodies 1 is not limited to two as in the present embodiment, and three or more apparatus bodies 1 can be provided.

  In the present embodiment, since a plurality of apparatus bodies 1 are provided, the concentration of the substance to be processed in the apparatus body 1 can be reduced. In particular, when a plurality of device bodies 1 are provided in series, the concentration of the substance to be treated can be lowered stepwise from the previous device body 1 to the subsequent device body 1.

(Embodiment 6)
In the present embodiment, as shown in FIGS. 6 to 8, the photocatalyst 3 is formed in a substantially cardboard type. That is, as shown in the figure, the photocatalyst body 3 is configured by alternately laminating a large number of corrugated sheets 7a and a large number of planar sheets 7b.

  A space between the corrugated sheet 7a and the planar sheet 7b is formed as a large number of through holes 8 that are inclined with respect to the air flow direction. The photocatalyst body 3 having such a large number of through holes 8 is formed in a substantially ring shape as shown in FIG.

 When such a substantially ring-shaped photocatalyst 3 is rotated, air flows in from one opening 9a of the through hole 8 and is discharged from the other opening 9b, as shown in FIG. The apparent wind speed of the air passing through the through-hole 8 of the substantially cardboard type photocatalyst 3, that is, the relative speed between the air and the photocatalyst is determined by the rotational speed of the photocatalyst 3.

In this case, the light irradiation density G (W / m ² ) is the same as that of the conventional honeycomb type. But,
Since the apparent wind speed U (m / s) can be freely changed by rotating the photocatalyst 3, the boundary film thickness δ = C / Uα indicated by the above equation (10) can be freely changed. . Usually, in the case of turbulent flow, α = about 0.75.

  The apparent wind speed U (m / s) can be obtained by rotating the photocatalyst body 3 having the substantially cardboard type structure as described above according to the present embodiment, which is substantially ring-shaped as a whole, and adjusting the rotational speed thereof. It is possible to make the body 5 to 20 times or more that of a device configured in a honeycomb type or the like. As a result, the film thickness δ (mm) is about 1/10 from the above equation (10). Therefore, if the efficiency is the same, the Gδ product is the same, so that G can be increased by about 10 times. When the apparatus is configured, the fact that G can be increased 10 times means that the volume of the apparatus having the same efficiency becomes 1/10.

  The shape of the photocatalyst 3 having the through-holes 8 is not limited to the corrugated cardboard type as described above, but, for example, as shown in FIG. 10, a honeycomb type having the through-holes 8 having a substantially hexagonal cross section. It may be.

  Further, the overall shape is not limited to the substantially ring shape as shown in FIG. 9 but may be a substantially disk shape.

(Other embodiments)
Although the present invention has been described with respect to the case where air is used as the fluid flowing through the apparatus main body, a gas other than air can also be used. Furthermore, in view of the concept of the film thickness in the present invention described later, the present invention is mainly intended to use a gas as a fluid, but the present invention can also be applied to a liquid.

  In each of the above embodiments, a light source such as a phosphor-type black light, a light emitting diode, or a discharge electrode is used as the light source 2, but the type of the light source 2 is not limited thereto, and other light sources are used. Is also possible.

  Furthermore, the shape of the photocatalyst body 3 is not limited to the plate shape, disk shape, rectangular shape, substantially ring shape, or the like of each of the above embodiments. Moreover, the kind of photocatalyst is not limited to the titanium oxide of this embodiment.

Further, in each of the above embodiments, the case where the photocatalytic reaction device is used for the exhaust treatment device has been described. However, the present invention can also be applied to other deodorization devices, NO _x decomposition devices, exhaust gas treatment devices, liquid treatment devices, and the like. It is.

By the way, in the present invention, the velocity film thickness ("Basics and Application of Mass Transfer" written by Koichi Asano, published by Maruzen, P49-50) is assumed as the film thickness δ. The concentration film thickness δ _C defined as a more general concept as the film thickness has the following relationship with the speed film thickness δ.
δ _C / δ = (Sc) ^−1/3 (11)

  Here, the velocity film thickness is a concept based on the velocity distribution based on the positional relationship from the wall surface, and means the thickness of the layer where the velocity due to the frictional force between the fluid (air) and the wall surface is extremely slow. In the above equation (11), Sc is a dimensionless number called a Schmidt number and is represented by the following equation.

Sc = ν / D (12)
Here, ν is a kinematic viscosity coefficient, and D is a material diffusion coefficient.

When the material diffusion rate is faster than the energy transfer of air, the concentration film thickness δ _C becomes thinner than the velocity film thickness δ, and conversely, when the material diffusion rate is slower than the air energy transfer, the concentration film thickness δ _C may be thicker than the speed boundary film thickness δ. The difference between the concentration boundary film thickness δ _C and the velocity boundary film thickness δ is generally a problem when the fluid is a liquid, and when the fluid is a gas, Sc≈1 may be considered. ("Mass Transfer Basics and Applications" by Asano Koichi, published by Maruzen, P49-50).

Further, when the fluid is air and the substance to be treated is an organic solvent, the substance diffusion coefficient D differs depending on the type of the organic solvent, and therefore, (Sc) ^−1/3 also differs based on that. range of ^-1/3 is at most about 0.8 to 1.4, be approximated with [delta] _C ≒ [delta], effects are believed little. Therefore, in any case, in the present invention focusing on the exhaust treatment device, the air purification device, etc., when considering the value of G · δ in consideration of the above equation (10), it is considered that δ _C ≈δ. There seems to be no.

  Examples of the present invention will be described below.

Example 1
In this example, exhaust processing was performed using the apparatus of the first embodiment. Specifically, 24 disk-shaped photocatalyst bodies 3 having a diameter of 350 mm are prepared, 14 light sources 2 of 40 W black light are prepared, and the 24 photocatalyst bodies 3 and 14 light sources 2 are prepared. It was arranged in the device body 1 having an outer size of 1.3 m × 0.5 m × 0.4 m.

The material to be treated was toluene, and air with an air volume of 3 m ³ / min was circulated in the apparatus body 1. The inlet / outlet concentration ratio was 0.2 to 0.3, and it was found from the graph of FIG. 14 described later that the processing efficiency was 70 to 80%.

(Example 2)
In this example, the processing efficiency of the photocatalyst was considered. FIG. 12 is a graph showing the change in efficiency when the photocatalyst and air are changed with the same light density. In this example, trimethylbenzene was used as the target substance. As shown in FIG. 12, the processing efficiency increases as the wind speed increases. However, the processing efficiency peaks when the wind speed is around 6 m / s, and the processing efficiency decreases when the wind speed exceeds 6 m / s. Therefore, in the case of trimethylbenzene, it was found that the wind speed of 6 m / s is the optimum point of the processing efficiency. This optimal point varies depending on the target substance.

Here, the processing efficiency means the quantum efficiency of light and is expressed by the following equation.
Quantum efficiency = (decomposition amount of target substance) / (light input energy)
More specifically, the denominator of this equation is the photon number, and the molecule is the number of substance molecules.

  In a catalyst-fixed type device that does not move a general photocatalyst, the target substance concentration ratio at the inlet / outlet is proportional to the efficiency divided by the flow rate, and the efficiency increases as the wind speed increases, but it exceeds a certain amount. If the air volume increases, the processing efficiency (quantum efficiency) becomes rather small. Conversely, if the wind speed is reduced, the processing efficiency will decrease.

  When the apparatus as in Embodiment 1 is used, if the wind speed of air is set to a range smaller than the contact speed between the photocatalyst body 3 and the light source 2, the contact speed is not affected by the wind speed, and the rotation speed of the photocatalyst body 3 is increased. Dominated by. Therefore, if a suitable rotation speed is selected, the contact speed becomes optimum, and the processing efficiency can maintain the optimum point in FIG. The optimum contact speed varies depending on the substance to be treated and the substance concentration.

  The phenomenon shown in FIG. 12 is that when the light density is made constant, if the number of times of contact between the photocatalyst 3 and the air containing the substance to be treated is improved, the treatment efficiency (quantum efficiency) increases, that is, the utilization of light energy. Is meant to go up. Therefore, in addition to the means for rotating the photocatalyst body 3, the same effect can be obtained by vibrating the photocatalyst body 3 as in the second embodiment.

  Even if the photocatalyst is fixedly used as in the prior art, if it is a small indoor circulation type air purifier, it is possible to achieve a contact speed suitable to some extent, but in the case of industrial exhaust, etc. There is a change in the wind speed, and it is difficult to maintain the optimum point shown in FIG. In this regard, the method of moving the photocatalyst 3 relative to the light source 2 as in the present invention can maintain the contact speed optimally, and can provide a highly efficient photocatalytic exhaust treatment device. It can also be estimated from the graph of FIG.

  Also, from FIG. 12, it can be seen that, for example, when the wind speed is 4 m / s and when it is 6 m / s, the processing efficiency is twice or more.

(Example 3)
In this example, an emission spectrum by corona discharge was examined. FIG. 13 is a chart of the emission spectrum. As is clear from FIG. 13, the emission spectrum by corona discharge has a plurality of absorption peaks in the near ultraviolet region, that is, the wavelength region of 300 to 400 nm, and substantially coincides with the absorption peak in the emission spectrum of titanium oxide. Therefore, it was confirmed that it was effective to use titanium oxide as a photocatalyst even when the corona discharge electrode as in the fourth embodiment was used as a light source.

Example 4
In this example, the quantum efficiency was examined using toluene as the target substance. FIG. 14 is a graph showing the correlation between the toluene concentration and the quantum efficiency. Using the graph of the present embodiment, when the target substance is toluene, the quantum efficiency can be obtained based on the concentration of toluene in the apparatus body 1.

  For example, in the case of purifying industrial exhaust using an apparatus in which apparatus bodies 1 are arranged in parallel as shown in FIG. 5A, if the inlet concentration of the apparatus body 1 is 300 ppm, two apparatus bodies 1 are Since they are arranged in parallel, the concentration in the apparatus is about 150 ppm, and the quantum efficiency is 22% from the graph of FIG.

  For example, when the apparatus body 1 is arranged in two stages in series as shown in FIG. 5B, the inlet concentration of the first-stage apparatus body 1 is 300 ppm, the outlet concentration is 100 ppm, and the inlet of the second-stage apparatus body 1 is used. If the concentration is 100 ppm and the outlet concentration is 10 ppm, the quantum efficiency (processing efficiency) of the first-stage apparatus body 1 is 60% from FIG. 14, and the processing efficiency of the second-stage apparatus body 1 is 10%. As a result, the quantum efficiency is 45%, which is twice as high as when the apparatus body 1 is arranged in parallel as described above. Therefore, from this, it was confirmed that when there are a plurality of apparatus bodies 1, the processing efficiency is higher when they are arranged in series as long as space restrictions allow.

(Example 5)
In this example, the correlation between the wind speed and the concentration difference was examined. FIG. 15 is the graph,
The density difference is constant until the wind speed reaches a predetermined value. However, when the wind speed exceeds the predetermined value, the density difference rapidly disappears. Therefore, in order to obtain a required density difference regardless of the air volume, a multi-stage apparatus body is used.

By the way, when considering the concentration at the entrance and exit, in a general processing apparatus as shown in FIG.
Decomposition rate (treatment efficiency) = (concentration difference between outlet and inlet) / inlet concentration = (1 / inlet concentration) x (substance decomposition amount / air volume)
= (E / inlet concentration) × (quantum yield / wind speed) × (light input / opening area) (13)
In the equation (13), the amount of substance decomposition = E × quantum yield × light input Here, E is a unit for adjusting the unit by a constant. Further, the second term on the right side of the equation (13) indicates the horizontal / vertical axis ratio of the graph of FIG. 12, and the third term on the right side indicates the light irradiation density G. As can be seen from FIG. 12, when the wind speed is constant, the second and third terms are constant, and when the condition is fixed, a value above a certain value cannot be obtained.

  On the other hand, in the present invention, since the wind speed can be changed regardless of the air volume, the second term on the right side of the above equation (11) can be set to the optimum point, and an efficient photocatalyst exhaust treatment apparatus can be obtained. Can be configured.

(Example 6)
In this example, using the apparatus of the first embodiment, a test was conducted to consider the correlation between the light irradiation density, the decomposition rate, and the wind speed. The wind speed was two types of 13 m / s and 1 m / s. The number of black lights was increased from the apparatus shown in FIG. 1, and the light density was adjusted by an inverter dimming method. The contact speed was adjusted by changing the number of rotations of the disk. Therefore, the catalyst area is constant. The inlet concentration was 100 ppm, and the air volume was 0.5 m ³ / min. Table 1 shows the measurement results of the outlet concentration. In particular, there is a large difference where the G value is high.

  As can be seen from Table 1 and FIG. 11, it was found that, when the wind speed is constant, the higher the light irradiation density, the lower the outlet concentration and the better the decomposition rate. On the other hand, if the light irradiation density is the same, it was found that the faster the wind speed, the better the decomposition rate. This means that from the above equation (10), the thinner the boundary film thickness, the better the decomposition rate.

  As a result, as discussed in the above equation (7), focusing on considering both the light irradiation density and the boundary film thickness, the decomposition rate (processing efficiency) can be increased. It was consistent with the test results. In addition, in the test results of this example, a certain degree of decomposition rate was recognized.

The schematic perspective view of the photocatalyst exhaust processing apparatus as one Embodiment. The schematic perspective view of the photocatalyst exhaust processing apparatus of other embodiment. The schematic plan view of the photocatalyst exhaust processing apparatus of other embodiment. The schematic plan view of the photocatalyst exhaust processing apparatus of other embodiment. Schematic explanatory drawing of the photocatalyst exhaust processing apparatus of other embodiment. The schematic plan view of the photocatalyst body of other embodiment. The schematic sectional drawing of the photocatalyst body. The schematic perspective view of the photocatalyst body. The schematic perspective view which shows the whole photocatalyst body. The schematic perspective view of the photocatalyst body of other embodiments. The graph which shows correlation with light irradiation density, a decomposition rate, and a wind speed. The graph which shows the correlation with the wind speed of trimethylbenzene, and quantum efficiency. The graph which shows the emission spectrum of a discharge electrode. The graph which shows correlation with the density | concentration of toluene and quantum efficiency. The graph which shows the correlation with a wind speed and a density | concentration difference. 1 is a schematic perspective view of a general photocatalyst exhaust treatment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Apparatus body 2 ... Light source 3 ... Photocatalyst body 8 ... Through-hole

Claims (16)

A photocatalyst body (3) formed with a photocatalyst in an apparatus body (1) having a fluid flow path to be processed, and a light source (2) for exciting the photocatalyst provided in the photocatalyst body (3) And the photocatalyst (3) is brought into contact with the fluid so that the fluid contacts the surface of the photocatalyst (3) provided with the photocatalyst so that the following condition (A) is satisfied. A photocatalytic reaction device further comprising a means for relatively moving.
0.00001 (W / m) ≦ G · δ ≦ 1.0 (W / m) (A)
In (A), G represents the light irradiation density, and δ represents the thickness of the film formed in the vicinity of the surface where the photocatalyst of the photocatalyst is provided. The photocatalytic reaction device according to claim 1, wherein the light irradiation density is set such that G ≧ 50 (W / m ² ). A photocatalyst body (3) formed with a photocatalyst in an apparatus body (1) having a fluid flow path to be processed, and a light source (2) for exciting the photocatalyst provided in the photocatalyst body (3) And a means for moving the photocatalyst (3) relative to the fluid to bring the fluid into contact with the surface of the photocatalyst (3) provided with the photocatalyst. A photocatalytic reaction device, wherein the photocatalyst (3) is formed in a plate shape and is arranged in parallel with a fluid flow direction.   The photocatalytic reaction device according to claim 3, wherein irregularities are formed on the surface of the plate-like photocatalyst (3) arranged in parallel with the fluid flow direction. A photocatalyst body (3) formed with a photocatalyst in an apparatus body (1) having a fluid flow path to be processed, and a light source (2) for exciting the photocatalyst provided in the photocatalyst body (3) And a means for moving the photocatalyst (3) relative to the fluid to bring the fluid into contact with the surface of the photocatalyst (3) provided with the photocatalyst. In the photocatalyst body (3), a photocatalytic reaction is characterized in that a through hole (8) through which a fluid flows is formed in parallel to the flow direction of the fluid, or formed obliquely with respect to the flow direction of the fluid. apparatus.   The photocatalytic reaction device according to claim 5, wherein the photocatalyst body (3) having the through hole (8) is formed in a substantially cardboard type or a substantially honeycomb type.   The photocatalytic reaction device according to claim 5 or 6, wherein the entire photocatalyst body (3) is formed in a substantially ring shape.   The photocatalytic reaction device according to any one of claims 1 to 7, wherein the means for moving the photocatalyst body (3) relative to the fluid is a means for rotating the photocatalyst body (3).   The photocatalytic reaction device according to any one of claims 1 to 7, wherein the means for moving the photocatalyst body (3) relative to the fluid is a means for vibrating the photocatalyst body (3).   The said light source (2) and the photocatalyst body (3) are arrange | positioned so that the light of a light source (2) may be irradiated from the direction orthogonal to the surface provided with the photocatalyst in a photocatalyst body (3). Item 10. The photocatalytic reaction device according to any one of Items 1 to 9.   The photocatalytic reaction device according to any one of claims 1 to 10, wherein the light source (2) is a light emitting diode.   The photocatalytic reaction device according to any one of claims 1 to 10, wherein the light source (2) is a corona discharge electrode.   The photocatalytic reaction device according to claim 12, wherein an electrostatic generator for corona discharge of the light source is provided integrally with the photocatalyst body (3).   A plurality of device bodies (1) are juxtaposed in series with respect to the direction of fluid flow, and the impurity concentration of the fluid in the device body (1) on the rear stage side-by-side arranged in series is determined by the device body ( The photocatalytic reaction device according to any one of claims 1 to 13, wherein the photocatalytic reaction device is configured to be stepwise lower than the impurity concentration of the fluid in 1). The contact speed between the fluid flowing through the device body (1) and the photocatalyst in the photocatalyst body (3) is:
The photocatalytic reaction device according to any one of claims 1 to 14, which is configured to change.   The photocatalytic reaction device according to any one of claims 1 to 15, wherein a louver is attached to the photocatalyst body (3) in a direction perpendicular to a fluid flow direction and in a light irradiation direction from a light source.

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