Photocatalytic filters and deodorizing devices

Abstract

The invention primarily enables the creation of a photocatalytic filter that achieves a good balance between deodorization efficiency and pressure drop by using a novel filter substrate material (porous metal body). The invention relates to a photocatalytic filter 6 obtained by attaching photocatalyst 5 to filter substrate material 4. The basic material of filter substrate 4 is composed of porous metal body 11. If t (mm) is the thickness t of porous metal body 11 and C (ppi) is the average number of cells per inch of porous metal body 11, the product of thickness t and average number of cells C, namely (t×C), is between 100 and 400. Preferably, porous metal body 11 is composed of one or more materials selected from nickel, silver, copper, aluminum, nickel-chromium, nickel-tin, and nickel-iron. Preferably, porous metal body 11 containing nickel as a constituent material.

Description

Photocatalytic filters and deodorizers

[0001] This case relates to a photocatalytic filter and a deodorizing device.

[0002] Deodorizing devices using photocatalysts have already been put to practical use. These devices include a photocatalytic filter carrying (or immobilizing) a photocatalyst, and a light source that activates the photocatalyst. In these deodorizing devices, the light source is turned on to activate the photocatalyst with light from the light source, and gas is passed through the photocatalytic filter, whereby the photocatalyst in the photocatalyst filter decomposes odorous components contained in the gas (see, for example, Patent Document 1).

[0003] Existing photocatalytic filters use a porous ceramic body (porous ceramic body) as the filter substrate.

[0004] JP 2012-050979 A

[0005] In deodorizing devices that use photocatalysts, it is believed that the deodorizing efficiency is largely determined by the type of photocatalyst and light source used. Therefore, the material of the photocatalyst filter (filter substrate) that supports the photocatalyst has not been given much importance. For example, there has not been much research conducted to date on how the material of the photocatalyst filter affects the deodorizing effect of the deodorizing device. Therefore, there is still room for improvement in the filter substrate.

[0006] Therefore, this case was made in light of such issues.

[0007] In response to the above-mentioned problems, the present invention provides a photocatalytic filter in which a photocatalyst is fixed to a filter substrate, the filter substrate being a porous metal body, the thickness of the porous metal body being t (mm), and the average number of cells per inch of the porous metal body being C (ppi), wherein the product (t x C) of the thickness t and the average number of cells C is 100 or more and 400 or less.

[0008] According to the present invention, the above-mentioned configuration makes it possible to obtain a photocatalytic filter that uses a new filter substrate (porous metal body) and that has a good balance between deodorizing effect and pressure loss.

[0009] 10A is a diagram showing a state in which a deodorizing device using a photocatalytic filter according to the present embodiment is installed in a commercial facility. FIG. 10B is a perspective view of a photocatalytic filter according to the present embodiment. FIG. 10C is an overall perspective view of a decentralized deodorizing device. FIG. 10D is a longitudinal sectional view of the decentralized deodorizing device of FIG. 3. FIG. 10E is a perspective view showing a state in which the deodorizing unit of FIG. 4 is attached to and detached from a range hood. FIG. 10F is an exploded perspective view of the deodorizing unit of FIG. 5. FIG. 10G is a perspective view of the rack of the deodorizing unit of FIG. 6. FIG. 10H is an overall side view of a medium-scale decentralized deodorizing device. FIG. 10H is a longitudinal sectional view of the medium-scale decentralized deodorizing device of FIG. 8. FIG. 10H is a transverse sectional view of a centralized deodorizing device. FIG. 10H is a diagram showing the deodorizing unit of FIG. 10A. Of these, (a) is a rear view, (b) is a front view, (c) is a side view, and (d) is a bottom view.

[0010] Hereinafter, this embodiment will be described in detail with reference to the drawings.

[0011] <Configuration> The configuration of this embodiment will now be described.

[0012] As shown in Fig. 1, a deodorizing device 1 is provided in an exhaust path such as an exhaust duct 2, and deodorizes gas 3 flowing through the exhaust duct 2. Exhaust gas such as cooking gas flows through the exhaust duct 2 as the gas 3 to be deodorized.

[0013] As shown in FIG. 2, the deodorizing device 1 is provided with a photocatalytic filter 6 in which a photocatalyst 5 is supported (or fixed) on a filter substrate 4, and a light source 7 for activating the photocatalyst 5.

[0014] In the deodorizing device 1 using the photocatalyst 5, the light source 7 is turned on, and the photocatalyst 5 is activated by light 8 (mainly ultraviolet light 8a) from the light source 7. In this state, the gas 3 (untreated gas 3a) is passed through the photocatalytic filter 6. As a result, the deodorizing device 1 using the photocatalyst 5 decomposes odorous components (e.g., cooking odor) in the gas 3 (into water and carbon dioxide) using the photocatalyst 5 of the photocatalytic filter 6. The gas 3 (treated gas 3b) that has been purified by the decomposition of odorous components in the deodorizing device 1 is then released into the atmosphere.

[0015] In addition to the basic configuration described above, this embodiment can have the following configuration.

[0016] (1) In the photocatalytic filter 6 having a photocatalyst 5 fixed to a filter substrate 4, the filter substrate 4 is a porous metal body 11, the thickness of the porous metal body 11 is t (mm), and the average number of cells per inch of the porous metal body 11 is C (ppi), the product of the thickness t and the average number of cells C (t × C) is 100 or more and 400 or less.

[0017] The filter substrate 4 is a material (substrate) that constitutes the main body of the photocatalytic filter 6. The filter substrate 4 is made of a fire-resistant material.

[0018] The photocatalyst 5 is a substance that absorbs light 8 and exhibits catalytic function of causing a chemical reaction in other substances. In this case, the photocatalyst 5 used is one that can at least decompose odorous components (other substances) in the untreated gas 3a.

[0019] The photocatalytic filter 6 is a filter that performs deodorization and the like by utilizing the photocatalytic reaction of the photocatalyst 5. The photocatalytic reaction is an oxidation-reduction reaction or the like that utilizes the photocatalyst 5 and light 8. Deodorization is the decomposition of odorous components contained in the gas 3 (untreated gas 3a) to reduce or eliminate odor. In existing deodorizing devices 1, the photocatalytic filter 6 uses a ceramic porous body such as fine ceramics as the filter substrate 4. Because ceramic porous bodies are expensive, heavy, and easily broken, it is desirable to change to a different filter substrate 4.

[0020] The metal porous body 11 is a porous metal material (different from perforated plates such as punched plates) used as a filtration filter in various fields, such as industrial filters and food preparation filters. The metal porous body 11 has fine three-dimensional continuous pores inside, and therefore has a significantly higher porosity than, for example, porous materials (sintered materials) made by sintering metal fibers or metal powders. Plate-shaped (thick plate-shaped) metal porous bodies 11 are already commercially available, and in the photocatalytic filter 6 of this embodiment, commercially available plate-shaped metal porous bodies 11 are used as is or processed into the required shape. Note that the internal structure of the porous portion of the metal porous body 11 is different from that of the ceramic porous bodies previously used as the filter substrate 4, so the performance and effects of using the metal porous body 11 as the photocatalytic filter 6 are unknown.

[0021] The thickness t of the porous metal body 11 is the dimension in the direction perpendicular to the surface of the plate-shaped (rectangular plate or flat plate) porous metal body 11. The gas 3 flows through the porous metal body 11 in the direction substantially perpendicular to the surface for a distance equivalent to the thickness t of the porous metal body 11. The thickness t of the porous metal body 11 is an index mainly related to the pressure loss of the gas 3.

[0022] The average cell number C is a value indicating the density of the cells (pores) of the porous metal body 11. The average cell number C of the porous metal body 11 is an index mainly related to the contact opportunity between odorous components and the photocatalyst 5.

[0023] According to Fine Ceramics - Test Methods for Air Purification Performance of Photocatalytic Materials - Part 3: Toluene Removal Performance (JIS R 1701-3), the test conditions are: toluene flow rate: 0.500±0.025 L / min (0°C, 101.3 kPa) at the inlet of the light irradiation container; filter (fine ceramics) size: width 49.0±1.0 mm / length 99.0±1.0 mm; illuminance of ultraviolet 8a on the photocatalytic surface (surface of the metal porous body 11): 10-20 W / m2; and the filter thickness t and average cell number C (or cell density) are not specified.

[0024] Therefore, there is room for consideration of conditions such as the filter thickness t and the average cell number C (or cell density). In particular, when a metal porous body 11 is newly used as the filter substrate 4 of the photocatalytic filter 6, conditions such as the filter thickness t and the average cell number C (or cell density) become important.

[0025] Therefore, the filter size was fixed at 50 (mm) x 100 (mm), the amount of photocatalyst 5 (here, titanium oxide) was fixed at 2.0 g, and an experiment similar to JIS R 1701-3 was carried out using various existing metal porous bodies 11, and the following results were obtained.

[0026] Thickness t Average number of cells C t × C Toluene removal rate Evaluation No. 1 10 mm 9 ppi 90 77.2% × No. 2 15 mm 9 ppi 135 88.9% ○ No. 3 10 mm 15 ppi 150 89.7% ○ No. 4 15 mm 15 ppi 225 92.6% ○ No. 5 15 mm 25 ppi 375 94.1% ○

[0027] To summarize the results of the experiment, the sample using the 10t x 9ppi porous metal body 11 (No. 1) had the lowest toluene removal rate. The sample using the 15t x 15ppi porous metal body 11 (No. 4) had a sufficiently high toluene removal rate. The sample using the 15t x 25ppi porous metal body 11 (No. 5) had the highest toluene removal rate.

[0028] As in the case of fine ceramics, each porous metal body 11 was evaluated based on a toluene removal rate of 85.0%. The filter (No. 1) using a 10t x 9ppi porous metal body 11 was evaluated as × (failed). The other filters (No. 2 to No. 5) using porous metal bodies 11 were evaluated as ○ (passed). It should be noted that the filters using these porous metal bodies 11 were also able to remove acetaldehyde. In other words, the filters (No. 1 to No. 5) using porous metal bodies 11 all achieved acetaldehyde removal rates of 90.0% or more, achieving favorable results.

[0029] The reason for this result is thought to be that by increasing the thickness t of the metal porous body 11, the odor component (toluene) comes into contact with the photocatalyst 5 more frequently, thereby improving the removal rate of toluene.

[0030] Furthermore, by increasing the average cell number C of the metal porous body 11, the density of the cells of the metal porous body 11 increases (becomes denser), which increases the opportunity for the odor component (toluene) to come into contact with the photocatalyst 5, and is therefore thought to have improved the toluene removal rate.

[0031] However, increasing the thickness t of the metal porous body 11 increases the pressure loss accordingly. Furthermore, increasing the average cell number C of the metal porous body 11 increases the pressure loss accordingly. This increases the pressure loss, which reduces exhaust performance, making it difficult to release the gas 3 (treated gas 3b) into the atmosphere. This necessitates increasing the exhaust capacity of the fan. This results in a loss of practicality in terms of exhaust performance.

[0032] Therefore, it is necessary to keep the pressure loss small. To reduce the pressure loss, the thickness t of the porous metal body 11 may be reduced, or the average cell number C of the porous metal body 11 may be reduced (thus reducing the cell density (sparseness) of the porous metal body 11). However, taking these measures reduces the opportunity for the odor component (toluene) to come into contact with the photocatalyst 5, which in turn reduces the toluene removal rate (i.e., the deodorizing effect).

[0033] That is, there is a trade-off between the deodorizing effect and the pressure loss. Therefore, when adopting the metal porous body 11 as the new filter substrate 4, it is important to optimize the balance between the deodorizing effect and the pressure loss to achieve both the exhaust performance and the toluene removal rate.

[0034] Commercially available porous metal bodies 11 are available in a variety of thicknesses with an average cell count C of, for example, 9 ppi, 15 ppi, 25 ppi, and 50 ppi. As a result of testing using some of these bodies, it was discovered that a low value of t×C results in a low pressure loss (at 1 m / s), and a high value of t×C results in a high pressure loss.

[0035] Thickness t Average number of cells C t×C Toluene removal rate Pressure loss Evaluation No.1 10mm 9ppi 90 77.2% 1Pa × No.2 15mm 9ppi 135 88.9% 3Pa ○ No.3 10mm 15ppi 150 89.7% 7Pa ○ No.4 15mm 15ppi 225 92.6% 16Pa ○ No.5 15mm 25ppi 375 94.1% 20Pa ○ No.6 10mm 50ppi 500 50Pa ×

[0036] In the case of (No. 1) using a metal porous body 11 with a t×C value of 90, the pressure loss was low at 1 Pa. However, it was confirmed that (No. 1) had a low toluene removal rate because the odor component (toluene) passed through the filter without being able to effectively contact the odor component (toluene) with the photocatalyst 5.

[0037] Conversely, when a porous metal body 11 with a t×C value of 500 was used (No. 6), the pressure loss was 50 Pa. This was much higher than the pressure loss (20 Pa) of the current ceramic filter, and it was confirmed that (No. 6) was not suitable for use. It is preferable to keep the pressure loss at approximately the same level as the current ceramic filter (approximately 20 Pa) in order to maintain and ensure the same level of exhaust performance as the current situation.

[0038] Among these, the optimum filter for achieving both exhaust performance and toluene removal rate was (No. 4), which used a 15t x 15ppi (t x C = 225) metal porous body 11. The metal porous body 11 of (No. 4) had a toluene removal rate of 92.6% and a pressure loss of 16 Pa, while the current ceramic filter had a toluene removal rate of 92-94% and a pressure loss of approximately 20 Pa. This verification confirmed that using a metal porous body 11 for the filter substrate 4 can achieve performance almost equal to or better than that of the current ceramic filter. This made it possible to realize a new photocatalytic filter 6 using a metal porous body 11 as the filter substrate 4.

[0039] In addition, (No. 5), which used a porous metal body 11 with a thickness t and an average cell number C of 15 mm x 25 ppi = 375, also achieved a toluene removal rate of 94.1% and a pressure loss of 20 Pa. Although (No. 5) had a higher pressure loss than (No. 4), it achieved performance that was quite close to that of current ceramic filters, and therefore, both (No. 4) and (No. 5) were found to be suitable within the practical range.

[0040] In contrast, in the case of using a metal porous body 11 of 10 mm x 50 ppi = 500 (No. 6), the pressure loss was 50 Pa, which was too large and was outside the practical range.

[0041] From the results of these tests, it was confirmed that a metal porous body 11 with a product (t × C) of the thickness t and the average cell number C of 135 or more and 375 or less is suitable as the filter substrate 4 of the photocatalytic filter 6. It was also confirmed that a metal porous body 11 with a t × C value in the range of 225 to 375 is even more suitable. Furthermore, although not included in the experiments and tests conducted this time, there are commercially available metal porous bodies 11 with t × C values ​​in the range of 225 to 375, and it is estimated that these also have performance substantially equivalent to that of (No. 4) and (No. 5).

[0042] Furthermore, the toluene removal rate becomes exactly the same as the reference value of 85.0% when the product (t × C) of the thickness t and the average number of cells C is lower than 135. Furthermore, the pressure loss exceeds the value of current ceramic filters (approximately 20 Pa) when the product (t × C) of the thickness t and the average number of cells C is higher than 375. Taking these factors into consideration, it is possible to determine that the product (t × C) of the thickness t and the average number of cells C is acceptable in the range of approximately 100 to 400, including a margin. In other words, as long as the value of t × C is within the range of approximately 100 to 400, both the toluene removal rate and the pressure loss are compatible.

[0043] From the above verification, it was determined that the metal porous body 11 with an appropriate pressure drop and toluene removal rate has a t×C value within the range of approximately 100 to 400. In other words, if the metal porous body 11 has a t×C value within the range of approximately 100 to 400, it can be used as the filter substrate 4 of the photocatalytic filter 6.

[0044] In addition, for the sample (No. 6) using the metal porous body 11 with a t×C value of 500, the pressure loss was too high and it was clearly not suitable for practical use, so the toluene removal rate was not measured.

[0045] Various studies were carried out on the porous metal body 11 newly used as the filter substrate 4 of the photocatalytic filter 6 below.

[0046] (2) The porous metal body 11 is preferably made of at least one material selected from the group consisting of nickel, silver, copper, aluminum, nickel chrome, nickel-tin, and nickel-iron.

[0047] Here, nickel, silver, copper, aluminum, nickel chromium, nickel-tin, and nickel-iron are preferably pure metals or have a purity of about 99% or more, but may also be alloys. Furthermore, the metal porous body 11 may be a mixture of several of these metals in an appropriate ratio, or may partially contain a mixture of these metals.

[0048] The metal porous body 11 is required to function as the filter substrate 4 of the photocatalytic filter 6 and as a carrier for supporting the photocatalyst 5. Furthermore, it is more preferable if the metal porous body 11 itself has a catalytic function.

[0049] In addition, it is also important that the metal porous body 11 is made of a material that can be produced inexpensively and stably, and that the material is suitable for commercialization and mass production of the metal porous body 11, in order to mass-produce the photocatalytic filter 6 using the metal porous body 11 inexpensively.

[0050] Therefore, we investigated various metals to find materials that meet these various requirements. As a result, we concluded that the most suitable metal porous body 11 is one formed from or containing at least one of the following materials: nickel, silver, copper, aluminum, nickel chromium, nickel-tin, and nickel-iron. By using any of these materials for the metal porous body 11, it becomes possible to stably manufacture a photocatalytic filter 6 with good performance.

[0051] (3) It is preferable that the porous metal body 11 contains nickel as a material.

[0052] Here, nickel is a metal with various characteristics, such as high corrosion resistance, excellent durability, high strength at high and low temperatures, and catalytic function. Therefore, including nickel in at least a portion of the material of the metal porous body 11 is advantageous for enhancing the functionality of the filter substrate 4 and obtaining a high-performance photocatalytic filter 6. Furthermore, because nickel is an excellent metal as described above, it is suitable as a material for the metal porous body 11. Therefore, the metal porous body 11 containing nickel is currently the most widely distributed, and is the easiest to obtain and the least expensive. Therefore, when using a metal porous body 11 as the filter material for the photocatalytic filter 6, it is preferable to use a material containing nickel.

[0053] (4) The porous metal body 11 preferably has a transmittance of 8% or less for ultraviolet light 8a.

[0054] As a result of examining the photocatalytic filter 6 using the above-mentioned metal porous body 11 as the filter substrate 4 from a different perspective, it was found that the value of t×C also affects the ultraviolet transmittance.

[0055]

[0056] That is, it was discovered that a low value of t×C results in a high ultraviolet transmittance, and a high value of t×C results in a low ultraviolet transmittance.

[0057] Furthermore, when a metal porous body 11 with a t×C value of 90 was used (No. 1), the ultraviolet transmittance was too high, and the amount of ultraviolet light 8a transmitted (leaking) from the light source 7 increased, so that the ultraviolet light 8a was not used efficiently inside the metal porous body 11, resulting in a low toluene removal rate.

[0058] On the other hand, when a metal porous body 11 having a t×C value of 375 was used (No. 5), the ultraviolet transmittance was lowered, the amount of ultraviolet light 8a transmitted (leakage) from the light source 7 was reduced, and the ultraviolet light 8a was used efficiently inside the metal porous body 11, resulting in a higher toluene removal rate.

[0059] Therefore, it was actually confirmed that the ultraviolet transmittance can be an index for determining the photocatalytic filter 6 having the optimum performance.

[0060] As described above, both the pressure loss and the toluene removal rate are appropriate when the value of t×C is in the range of approximately 100 to 400, and when the value of t×C is approximately 100 to 400, the transmittance of ultraviolet light 8a is 8% or less. That is, it has been confirmed that a metal porous body 11 with a transmittance of ultraviolet light 8a of 8% or less (up to 0.0% or more) is suitable as the filter substrate 4 of the photocatalytic filter 6. Furthermore, by setting the transmittance of ultraviolet light 8a to 8% or less, it is possible to optimize the photocatalytic filter 6 using the metal porous body 11.

[0061] If the ultraviolet transmittance falls to 0.0%, ultraviolet light 8a will not reach the opposite surface of the porous metal body 11, resulting in inactivated photocatalyst 5 inside the porous metal body 11, which is thought to result in a corresponding decrease in the toluene removal rate. Therefore, the value just short of or near 0.0% is the lower limit of the ultraviolet transmittance.

[0062] (5) The photocatalyst 5 is preferably titanium oxide.

[0063] In the current ceramic filter, titanium oxide is used as the photocatalyst 5 .

[0064] Titanium oxide is a substance (photocatalyst 5) that absorbs only ultraviolet light 8a and undergoes a photocatalytic reaction without absorbing visible light. Titanium oxide is activated by irradiation with ultraviolet light 8a with a wavelength of 400 nm or less. Titanium oxide decomposes dirt (organic matter) attached to its surface through a photocatalytic reaction. The effectiveness of titanium oxide as a photocatalyst 5 is generally proportional to the amount of light 8 (ultraviolet light 8a) and the area exposed to light 8. Titanium oxide is stable and unchanging, so its lifespan as a photocatalyst 5 is semi-permanent. Because photocatalyst 5 is hydrophilic, it is possible to utilize the hydrophilicity of photocatalyst 5 for self-cleaning and other purposes. Therefore, even when a porous metal body 11 is used for the filter substrate 4, it is considered preferable to use titanium oxide or a material containing titanium oxide as the photocatalyst 5.

[0065] It has also been confirmed that titanium oxide, acting as a photocatalyst 5, has the ability to oxidatively decompose polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons are generated by incomplete combustion during food cooking and are contained in cooking gases along with odorous components, oil mist (oil smoke), and fine particles. By using titanium oxide as the photocatalyst 5, it is possible to reduce and remove polycyclic aromatic hydrocarbons along with odorous components such as toluene and acetaldehyde.

[0066] The band gap of titanium oxide (anatase type) is 3.2 eV, calculated using the formula E (energy per photon) = h (Planck's constant) × v (frequency of photon) (V = speed of photon ÷ wavelength, therefore E = h × speed of photon ÷ wavelength → E = 1240 ÷ wavelength → 1240 ÷ 387.5 nm = 3.2 eV), which converts to a wavelength of approximately 388 nm.

[0067] Therefore, the wavelength range suitable for titanium oxide is approximately 380 nm. Therefore, it is preferable to use an ultraviolet lamp or ultraviolet LED lamp that generates UV-A (ultraviolet A rays with a wavelength range of 300 to 400 nm) as the light source 7 for activating titanium oxide. In particular, it is preferable that the ultraviolet lamp or ultraviolet LED lamp used as the light source 7 has a peak wavelength range of 380 nm. The combination of titanium oxide and a light source 7 with a wavelength range of 380 nm has such excellent functionality that it can also be used as an air purifier using a photocatalytic reaction.

[0068] Titanium oxide can also be used with the addition of additives, which makes it possible to create a photocatalyst 5 that has a catalytic effect even with light 8 with a wavelength longer than 400 nm. Furthermore, by supporting Pt (platinum), WO3 (tungsten oxide), or other precious metals on the metal porous body 11 as the photocatalyst 5, in addition to titanium oxide, the photocatalyst 5 can also utilize light 8 in the visible light range contained in the light source 7 described above. In other words, a photocatalytic filter 6 that operates with visible light can also be realized.

[0069] Therefore, it was concluded that it is most preferable to use titanium oxide, which has such excellent properties, as the photocatalyst 5 in the photocatalytic filter 6 that uses the porous metal body 11 as the filter substrate 4 .

[0070] (6) The photocatalyst 5 preferably has an average particle size of 1 nm or more and 100 nm or less.

[0071] Current ceramic filters use nanomaterials (nanoparticles) as the material for the photocatalyst 5. The ISO defines nanomaterials as follows: "Nanomaterials are solid materials manufactured from elements or other raw materials, and are nanosubstances or nanostructures (including aggregates of nanosubstances) composed of nanosubstances, with at least one of the three dimensions indicating their size ranging from approximately 1 nm to 100 nm." Titanium oxide, which is used as a material for the photocatalyst 5, generally falls into the category of nanomaterials, and photocatalyst 5 materials such as titanium oxide have an average particle size of 1 nm or more, up to 100 nm.

[0072] Then, an experiment was conducted to determine whether the photocatalyst 5 having an average particle diameter of 1 nm or more and 100 nm or less could actually be supported without any problems on the porous metal body 11. The photocatalyst 5 was supported on the porous metal body 11 by, for example, adding titanium oxide powder to an aqueous peroxotitanic acid solution (PTA solution) to prepare a titanium oxide slurry, immersing the porous metal body 11 in this titanium oxide slurry to impregnate it, drying it, and then firing it.

[0073] For titanium oxide slurry, titanium oxide may be mixed and dispersed in a dispersion medium such as water or an alcohol such as methanol or ethanol. Here, to promote dispersion of titanium oxide, a surfactant, a mineral acid such as hydrochloric acid or sulfuric acid, or a carboxylic acid such as acetic acid or citric acid may be added to the dispersion medium as needed. Subsequently, a slurry containing titanium oxide particles can be produced by crushing and dispersing the titanium oxide particles in the dispersion medium using a device such as a bead mill, ball mill, sand mill, roll mill, vibration mill, or homogenizer.

[0074] Furthermore, the titanium oxide slurry may contain a silica-based or alumina-based binder in addition to a titania-based binder such as an aqueous solution of peroxotitanic acid.

[0075] The method for supporting the titanium oxide slurry on the photocatalyst 5 may be a commonly used dip coating method, spray coating method, or the like, and is not particularly limited as long as it can be applied in accordance with the purpose.

[0076] As a result of the above, it was actually confirmed that the photocatalyst 5 described above could be supported in the amount (supported amount) described below on the metal porous body 11. Therefore, it was concluded that a photocatalyst 5 having an average particle diameter of 1 nm or more and 100 nm or less is suitable for being supported on the metal porous body 11.

[0077] (7) The amount of photocatalyst 5 supported on the filter substrate 4 is preferably 1 g to 2.5 g per area of ​​50 mm×100 mm.

[0078] In current ceramic filters, the amount of photocatalyst 5 (titanium oxide) supported per 50 mm x 100 mm area is 1 g to 3 g. Using this as a standard, the amount of photocatalyst 5 (titanium oxide) supported on the metal porous body 11 that would provide deodorizing performance equivalent to that of current ceramic filters was determined through experiments.

[0079] The amount of photocatalyst 5 supported was set and adjusted by the amount of titanium oxide slurry dispersed in methanol that was sprayed. Experiments were conducted on the filter substrate 4 (metal porous body 11) thus supporting the photocatalyst 5 under conditions conforming to JIS R 1701-3 described above. The same metal porous body 11 used in the experiments (Nos. 2 to 5) was used.

[0080] If the amount of photocatalyst 5 (titanium oxide) supported is small, the toluene removal rate decreases. If the amount of photocatalyst 5 (titanium oxide) supported is large, clogging occurs in the porous metal body 11. For these reasons, the range in which the toluene removal rate is 85.0% or more and the porous metal body 11 does not become clogged was determined to be the appropriate value.

[0081] As a result, a slightly different result was obtained from the case of the current ceramic filter. That is, it was confirmed that the amount of photocatalyst 5 supported on the metal porous body 11 should be 1 g to 2.5 g, which is less than that required for the ceramic filter.

[0082] (8) The porous metal body 11 preferably has a flat plate shape.

[0083] Here, current ceramic filters are flat. Therefore, it is conceivable that the photocatalytic filter 6 having the metal porous body 11 as the filter substrate 4 could also be flat. Furthermore, by making the photocatalytic filter 6 having the metal porous body 11 as the filter substrate 4 flat, it would be possible to replace the current ceramic filter with the photocatalytic filter 6 having the metal porous body 11 as the filter substrate 4. Therefore, a flat shape is also the most advantageous shape for the photocatalytic filter 6 having the metal porous body 11 as the substrate. In fact, when the photocatalytic filter 6 having the metal porous body 11 as the substrate was used to replace the current ceramic filter, good results equivalent to those of the current ceramic filter were obtained. However, since the metal porous body 11 has a much greater degree of freedom in terms of shape than ceramic filters, it is also fully possible to use it in a completely new shape other than a flat shape. Making the metal porous body 11 into a shape other than a flat shape is expected to be useful in the development of a completely new deodorizing device 1.

[0084] (9) The deodorizing device 1 is constructed using the photocatalytic filter 6.

[0085] As shown in Fig. 1, a deodorizing device 1 using such a photocatalyst 5 can be installed at the inlet, middle or outlet of an exhaust duct 2. Untreated gas 3a that enters the exhaust duct 2 passes through the deodorizing device 1 installed at the inlet, middle or outlet of the exhaust duct 2, is deodorized by the deodorizing device 1 to become treated gas 3b, and then flows downstream and is released into the atmosphere. The treated gas 3b released into the atmosphere has been deodorized to a high level, so there is no need to worry about environmental pollution due to odor.

[0086] The deodorizing device 1 provided at the entrance of the exhaust duct 2 is installed, for example, in kitchen equipment in a restaurant 22 located in a commercial facility 21. In this case, the deodorizing device 1 is installed at the back of a range hood 24 installed above a cooking appliance 23 in the kitchen equipment, or at the connection between the range hood 24 and the exhaust duct 2 ((small-scale) distributed deodorizing device 25). This allows cooking gas from each restaurant 22 (installed in the commercial facility 21) to be individually deodorized. This allows the deodorizing device 1 to be made as compact as possible, minimizing installation space and making management easier since each device is individualized. Furthermore, the overall exhaust duct 2 becomes less dirty.

[0087] Furthermore, the deodorizing device 1 installed in the middle of the exhaust duct 2 is installed, for example, in a branch duct 2a installed on each floor of the commercial facility 21 (medium-scale decentralized deodorizing device 26). The medium-scale decentralized deodorizing device 26 is installed in one or more locations, for example, midway along the branch duct 2a or upstream of the fire damper 27 at the outlet. This allows cooking gas from each restaurant 22 (installed in the commercial facility 21) to be deodorized collectively on each floor. This allows the deodorizing device 1 to be medium-sized, reducing the installation space and facilitating management since it is installed on each floor. Furthermore, contamination of the entire exhaust duct 2 can be reduced.

[0088] The deodorizing device 1 installed at the outlet of the exhaust duct 2 is installed, for example, on the rooftop 21a of the commercial facility 21 (centralized deodorizing device 28). The centralized deodorizing device 28 is installed in the collective duct 2b that joins the branch ducts 2a from each floor and leads them to the rooftop 21a. This allows cooking gas from each restaurant 22 to be collected in one location and deodorized simultaneously. Furthermore, the deodorizing device 1 can be enlarged to enable centralized management. This eliminates the need to manage the deodorizing device 1 for each restaurant 22 or each floor. Furthermore, the treated gas 3b can be directly released into the atmosphere from a high position such as the rooftop 21a. If there are multiple exhaust ducts 2, a centralized deodorizing device 28 may be installed for each exhaust duct 2.

[0089] The deodorizing device 1 may be provided with any one of a decentralized deodorizing device 25, a medium-scale decentralized deodorizing device 26, and a centralized deodorizing device 28 for the exhaust duct 2, or may be provided with at least one or all of them.

[0090] More specifically, the distributed deodorizing device 25 is, for example, as shown in FIGS. 3 to 7 (mainly see FIG. 4).

[0091] The decentralized deodorizing device 25 can be provided, for example, integrally with the range hood 24 connected to the exhaust duct 2 (branch duct 2a). The decentralized deodorizing device 25 can be detachably installed on the range hood 24 with the main body unitized (deodorizing unit 31). The deodorizing unit 31 is installed, for example, downstream (above) of the fan 32 installed inside the range hood 24.

[0092] The decentralized deodorizing device 25 is so powerful that it can deodorize the odor components in the gas 3 to a level that is almost imperceptible to humans. Therefore, it is structurally possible to configure the device so that the gas 3 (treated gas 3b) that has passed through the decentralized deodorizing device 25 is directly discharged indoors without being discharged outdoors through the exhaust duct 2.

[0093] The deodorizing unit 31 is, for example, an integrated unit in which a photocatalytic filter 6 and a light source 7 are arranged in a rack 33 in order from the upstream side (lower side) to the downstream side (upper side).

[0094] The rack 33 is a component that constitutes the exterior of the deodorizing unit 31. The photocatalytic filters 6 and the light sources 7 can be arranged alternately in a single or multiple stages within the rack 33 along the flow direction (vertical direction) of the gas 3. In this embodiment, for example, three or more stages of photocatalytic filters 6 are arranged parallel to each other in the vertical direction, and two or more stages of light sources 7 are arranged in the gaps between them in the vertical direction. One or more light sources 7 are provided for each gap. The light sources 7 can be the above-mentioned ultraviolet lamps or ultraviolet LED lamps. It is preferable to arrange the necessary number of light sources 7 so that the light 8 is distributed almost evenly over the entire surface of the photocatalytic filters 6. A light source 7 may be provided downstream (above) of the final (top) stage photocatalytic filter 6, but this is not particularly necessary and can be omitted.

[0095] It is also preferable to attach a grease filter 34 to the upstream surface (bottom surface) of the first-stage photocatalytic filter 6 in the rack 33. The grease filter 34 is, for example, a wire mesh filter that adheres to and removes oil mist. Furthermore, it is also possible to install an additional auxiliary filter such as an activated carbon filter 35 on the downstream surface (top surface) of the final-stage photocatalytic filter 6 in the rack 33, as needed.

[0096] The rack 33 serves as a storage section in which auxiliary filters such as the grease filter 34, photocatalytic filter 6, light source 7, and activated carbon filter 35 can be individually attached and detached. The interior of the storage section is, for example, in the form of shelves. The grease filter 34, photocatalytic filter 6, and activated carbon filter 35 are installed on the shelves of the storage section so as to cross (sideways) the cross section of the flow path of the gas 3 inside the range hood 24. The grease filter 34, photocatalytic filter 6, and activated carbon filter 35 each block the flow path of the gas 3 inside the range hood 24, dividing it into an upstream side and a downstream side.

[0097] The rack 33 itself is also formed in a shape and size that can close the cross section of the flow path of the gas 3 inside the range hood 24, and is installed inside the range hood 24 so that it can be attached and detached.

[0098] As shown in Figure 5, it is preferable that the direction in which the rack 33 is attached to or detached from the range hood 24 or the exhaust duct 2 is in a substantially horizontal direction (front-to-back direction) connecting the front and back sides when facing the range hood 24.

[0099] An attachment portion 36 for the rack 33 is provided inside the range hood 24. The attachment portion 36 is a space that forms a flow path for the gas 3 that communicates between the fan 32 and the exhaust duct 2 (branch duct 2a).

[0100] The front side of the mounting section 36 is an opening 36a, and the rack 33 is mounted by inserting it sideways from the front side to the back side into the opening 36a. Guide members 37 (slide guides) that extend in the mounting / removal direction of the rack 33 and guide the mounting / removal of the rack 33 are appropriately provided on both side surfaces inside the mounting section 36.

[0101] The guide member 37 is provided at least at a position corresponding to the lower surface of the rack 33 so as to support the lower surface of the rack 33 from below. The guide member 37 may be provided at a position corresponding to the upper surface of the rack 33 so as to define the upper surface of the rack 33 from above. The guide member 37 may also be provided at a position corresponding to the middle of the side surface portion 33a of the rack 33 so as to guide a guide recess 38 provided in the middle portion of the side surface portion 33a of the rack 33.

[0102] As shown in FIG. 6, the rack 33 is a frame member that is approximately C-shaped in plan view and has left and right side portions 33a and a rear portion 33b, and is open on the front, top, and bottom.

[0103] A front surface member 41, an upper surface member 42, and a lower surface member 43 that are detachable from the rack 33 are attached to the front, upper, and lower surfaces of the rack 33. The front surface member 41, the upper surface member 42, and the lower surface member 43 are fixed to the rack 33 by screws, for example, so as to be detachable.

[0104] By removing at least the front surface member 41 and the top surface member 42 from the rack 33, the photocatalytic filter 6, the light source 7, and the activated carbon filter 35 are exposed, making it possible to attach and detach the photocatalytic filter 6, the light source 7, and the activated carbon filter 35 to and from the rack 33. As shown in Fig. 7 , inside the rack 33, shelf sections 44 (slide guides) into which the photocatalytic filters 6 can be attached and detached by inserting them sideways from the front side to the back side are provided at intervals in the vertical direction, the same number as the number of photocatalytic filters 6 (the number of stages to be installed). In addition, light source holders 45 and light source sockets that hold the light sources 7 and supply power to the light sources 7 are installed at intervals in the vertical direction between the shelf sections 44, the same number as the number of stages to be installed of the light sources 7.

[0105] Also, as shown in Figure 5, the front member 41 may be made slightly larger than the opening 36a of the mounting portion 36 to form a flange surface, so that the rack 33 closes the opening 36a of the mounting portion 36 with the flange surface of the front member 41.

[0106] 6, the upper surface member 42 may be a perforated plate having a large number of through holes 42a, and the perforated plate may hold the activated carbon filter 35 from above. The lower surface member 43 may be made of a grease filter 34, and the grease filter 34 may directly cover the lower surface of the rack 33.

[0107] When the deodorizing unit 31 is attached to the attachment portion 36 of the exhaust duct 2, the deodorizing unit 31 blocks the entire cross section of the flow path of the gas 3 inside the range hood 24, causing all of the gas 3 to pass through the rack 33 of the deodorizing unit 31. Therefore, the gas 3 is deodorized by a photocatalytic reaction of the photocatalytic filter 6 and the like provided inside the rack 33.

[0108] By configuring the decentralized deodorizing device 25 in this manner, the entire deodorizing unit 31 can be removed at once together with the rack 33 from the mounting portion 36 of the range hood 24, which is located at a high position near the ceiling. The removed deodorizing unit 31 can be exposed by removing the front member 41 and the top member 42 of the rack 33 at a low position to expose the photocatalytic filter 6, light source 7, and activated carbon filter 35 installed on the rack 33. Therefore, by removing the grease filter 34 on the bottom from the removed deodorizing unit 31, the necessary parts of the exposed photocatalytic filter 6, light source 7, and activated carbon filter 35 can be removed, allowing for easy maintenance of each of them.

[0109] After maintenance is complete, the grease filter 34, photocatalytic filter 6, light source 7, and activated carbon filter 35 are returned to their original state on the rack 33, and the front surface member 41 and top surface member 42 are attached to the rack 33. Then, the deodorizing unit 31 for which maintenance has been completed can be attached together with the rack 33 to the attachment portion 36 of the exhaust duct 2, which is located at a high position, all at once. This reduces the amount of work done at height, making the work easier.

[0110] The medium-scale decentralized deodorizing device 26 may be, for example, as shown in FIGS.

[0111] The medium-scale decentralized deodorizing device 26 has a hollow box-shaped casing 51 provided midway along the exhaust duct 2 (branch duct 2a), and a deodorizing unit 31 similar to that described above can be attached and detached to the casing 51 from the front side to the back side of the casing 51.

[0112] The direction in which the deodorizing unit 31 is attached to and detached from the casing 51 is a substantially horizontal direction that intersects with the flow direction of the gas 3 flowing through the exhaust duct 2. An opening for attaching and detaching the deodorizing unit 31 is formed on the side surface of the casing 51 that is on the near side in the attachment and detachment direction.

[0113] The casing 51 has an inlet 52 for the gas 3 on its upstream side in the flow direction of the gas 3 flowing through the exhaust duct 2, and an outlet 53 on its downstream side. The casing 51 is attached to the ceiling or wall of the commercial facility 21 in the area where the exhaust duct 2 (branch duct 2a) is located. The deodorizing unit 31 can have a configuration substantially similar to that of the decentralized deodorizing device 25 described above. A handle 54 for attaching and detaching the deodorizing unit 31 to the casing 51 may be provided on the surface (near front) of the deodorizing unit 31 that faces the front in the attachment and detachment direction.

[0114] When the flow direction of the gas 3 in the exhaust duct 2 is approximately horizontal, the photocatalytic filter 6 can be installed perpendicular to the flow direction of the gas 3 (vertical installation), but in this embodiment, the photocatalytic filter 6 is installed parallel to the flow direction of the gas 3 (horizontal installation).

[0115] To this end, the casing 51 is provided with a partition 55 inside that separates the interior of the casing 51 into an upstream section and a downstream section. The partition 55 is installed so as to reach from the bottom surface of the casing 51 to the top surface. The partition 55 has a zigzag folded shape in a side view, with one or more vertical sections 55a, 55c and horizontal sections 55b alternating. The horizontal sections 55b of the partition 55 serve as shelves, and the deodorizing unit 31 is installed horizontally relative to the horizontal sections 55b.

[0116] The horizontal portion 55b, which serves as a shelf, has a through-hole formed therein, which allows the gas 3 to pass from the upstream portion of the casing 51 to the downstream portion and also pass through the deodorizing unit 31 installed on the shelf.

[0117] The vertical portions 55a, 55c of the partition wall 55 include the vertical portion 55a located on the upstream side within the casing 51 and the vertical portion 55c located on the downstream side within the casing 51. The upstream vertical portion 55a and the downstream vertical portion 55c are installed at different heights. The horizontal portion 55b connects the upstream vertical portion 55a and the downstream vertical portion 55c approximately horizontally. As a result, the partition wall 55 extends in the vertical direction as a whole and has a serpentine shape that makes one or more detours in the horizontal direction along the flow direction of the gas 3. The partition wall 55 may be formed into a serpentine shape by connecting multiple metal plates, or by bending one (or multiple) metal plates.

[0118] On the upstream side of the casing 51, an inlet portion 52 of the casing 51 is formed at a position where there is no upstream vertical portion 55a. On the downstream side of the casing 51, an outlet portion 53 of the casing 51 is formed at a position where there is no downstream vertical portion 55c. The inlet portion 52 and the outlet portion 53 are provided at positions at different heights in the vertical direction.

[0119] In this embodiment, the partition wall 55 is made up of two vertical portions 55a, two vertical portions 55c, and three horizontal portions 55b, which form two outlet portions 53 on the top and bottom, respectively, and the deodorizing units 31 are arranged in three vertical tiers. The deodorizing units 31 may be provided independently, or the upper and lower deodorizing units 31 may be connected together by a front face member 41 to form an integrated unit. In this embodiment, the upper deodorizing unit 31 is independent, and the lower two deodorizing units 31 are connected together by a common front face member 41. However, the configuration of the medium-scale decentralized deodorizing system 26 is not limited to the above.

[0120] By configuring the medium-scale decentralized deodorizing device 26 in this way, it is possible to obtain the same effects as the decentralized deodorizing device 25. In addition, in the medium-scale decentralized deodorizing device 26, by installing the photocatalytic filter 6 parallel to the flow direction of the gas 3, it becomes possible to form the photocatalytic filter 6 in any size that is not restricted by the flow path cross section of the exhaust duct 2, and to easily install it in the exhaust duct 2.

[0121] 10A and 10B, the centralized deodorizing device 28 is installed in a large hollow housing 61 (building) attached to the outlet of the exhaust duct 2 (collective duct 2b). The centralized deodorizing device 28 is installed by providing a partition wall 62 to separate the interior of the housing 61 into an upstream space and a downstream space, and fitting a plurality of deodorizing units 31 onto the surface of the partition wall 62.

[0122] The housing 61 is, for example, a substantially rectangular parallelepiped type, and has an inlet port 52 at one end face of the housing 61 to which the exhaust duct 2 is connected, and an outlet port 53 at the opposite end face (other end face). However, the shape of the housing 61 is not limited to this.

[0123] The partition wall 62 is preferably provided so as to substantially straddle both side portions of the inlet port portion 52 and to surround a required range of the periphery of the inlet port portion 52. The partition wall 62 is formed to a height that reaches from the floor surface of the housing 61 to the ceiling.

[0124] The partition wall 62 is preferably provided in a substantially V-shape in plan view so that the portion surrounding the inlet port 52 tapers from the inlet port 52 toward the outlet port 53. The partition wall 62 has at least two inclined wall portions 62a, 62b that form the substantially V-shaped portion in plan view.

[0125] The distance between the ends of the two inclined walls 62a, 62b on the inlet portion 52 side is approximately the same as or narrower than the width of the inlet portion 52. If the distance between the ends is not equal to the width of the inlet portion 52 (for example, if it is narrower), step walls 62c may be provided between both sides of the inlet portion 52 and the ends of the two walls 62a, 62b on the inlet portion 52 side. The step walls 62c are intended to adjust the difference in width. The inlet portion 52 and the two walls 62a, 62b may be connected by the step walls 62c.

[0126] The ends of the two inclined walls 62a, 62b on the outlet port 53 side may be directly connected, or may be connected via a short connecting wall 62d.

[0127] The partition wall 62, which is substantially V-shaped in plan view, is formed to have a length that is at least approximately half the length from the inlet portion 52 to the outlet portion 53 of the housing 61. In addition, the partition wall 62, which is substantially V-shaped in plan view, is formed to have a length that is equal to or shorter than the length from the inlet portion 52 to the outlet portion 53 of the housing 61.

[0128] In this embodiment, the length of the partition wall 62 is approximately two-thirds of the length from the inlet port 52 to the outlet port 53 of the housing 61 .

[0129] By configuring the centralized deodorizing device 28 in this manner, it is possible to obtain the same effects as the above-mentioned decentralized deodorizing device 25 and the medium-scale decentralized deodorizing device 26. In addition, by making the partition wall 62 of the centralized deodorizing device 28 approximately V-shaped in plan view, it is possible to make the partition wall 62 even more compact and also to reduce the number of deodorizing units 31 installed on the partition wall 62.

[0130] The interior of the housing 61 is divided unevenly by the partition wall 62, which is substantially V-shaped in plan view, so that the upstream space is relatively narrow (small in volume) and the downstream space is relatively wide (large in volume). Also, due to the partition wall 62, which is substantially V-shaped in plan view, the flow path cross section of the upstream space gradually becomes smaller toward the outlet portion 53.

[0131] Therefore, the untreated gas 3a entering the housing 61 from the inlet 52 travels straight and directly hits the partition wall 62, which is substantially V-shaped in plan view. The untreated gas 3a is then pressurized by the partition wall 62, which is substantially V-shaped in plan view and whose flow path cross section gradually decreases toward the outlet 53. Furthermore, a pressure difference is generated between the narrow upstream space where the pressure is high and the wide downstream space where the pressure is low, forcing the untreated gas 3a to pass through the partition wall 62. Therefore, the untreated gas 3a is efficiently deodorized by the deodorizing unit 31 provided in the partition wall 62. The treated gas 3b deodorized by the deodorizing unit 31 is released into the atmosphere from the downstream space through the outlet 53.

[0132] In this embodiment, the partition wall 62 is substantially V-shaped in plan view, but the planar shape of the partition wall 62 is not limited to this.

[0133] An inspection door 63 for accessing the downstream space is provided on one or both sides of the housing 61 in an openable and closable manner. The door 63 is preferably designed to open outward.

[0134] The partition wall 62 has one or more fitting holes 64 formed therethrough to allow the deodorizing unit 31 to be attached and detached. The fitting holes 64 are formed to have substantially the same size and shape as the outer shape of the deodorizing unit 31, allowing the deodorizing unit 31 to be fitted and fixed. The deodorizing unit 31 is detachably attached to the fitting holes 64 in a vertical orientation.

[0135] The deodorizing unit 31 may be designed to be attachable and detachable from either the upstream space or the downstream space side of the fitting hole portion 64, but for maintenance purposes, it is preferable to be able to attach and detach it from the side where the inspection door portion 63 is provided (in this embodiment, the downstream space side).

[0136] It is preferable that the multiple fitting holes 64 are formed in a regular pattern on the partition wall 62, for example, lined up vertically, lined up horizontally, or lined up vertically and horizontally in a checkerboard pattern.

[0137] As shown in Figure 11, the deodorizing unit 31 used in the centralized deodorizing system 28 has basically the same configuration and function as those of the decentralized deodorizing system 25 and the medium-scale decentralized deodorizing system 26 described above. This deodorizing unit 31 is an integrated unit in which photocatalytic filters 6 and light sources 7 are alternately installed in order from the upstream side. The deodorizing unit 31 may be integrated, for example, by sandwiching the light source 7 between a pair (two) of flat photocatalytic filters 6. Alternatively, the deodorizing unit 31 may be integrated by sandwiching the light source 7 between two or more spaces formed between three or more flat photocatalytic filters 6.

[0138] The deodorizing unit 31 has a frame 65 that serves as the main body, and the photocatalytic filter 6 and light source 7 are detachably attached to the frame 65. Two or more photocatalytic filters 6 are arranged in multiple stages parallel to each other in the thickness direction of the frame 65 (the flow direction of the gas 3). In the planar direction of the frame 65, one or more photocatalytic filters 6 are arranged side by side in the same plane in each stage so as to cover the entire cross section of the frame 65. The frame 65 has the same function as the rack 33 in Figures 6 and 7, and in this case, is formed in a rectangular shape.

[0139] The frame 65 can be formed to the same size as a single photocatalytic filter 6, but it may also be larger and multiple photocatalytic filters 6 arranged vertically or horizontally on the same surface to cover the entire surface of the frame 65. In this embodiment, the frame 65 is approximately an integer multiple of the size of the sides of the photocatalytic filter 6. For example, the frame 65 is large enough to accommodate a total of four photocatalytic filters 6 arranged vertically and horizontally. Note that by replacing the filter substrate 4 with a porous metal body 11, it is possible to make the photocatalytic filter 6 larger than existing filters. Therefore, instead of arranging multiple small photocatalytic filters 6 of the same size as existing filters (a total of four filters vertically and horizontally) on the same surface of a large frame 65, a single enlarged photocatalytic filter 6 may be installed on the same surface as the frame 65. This allows the entire surface of the frame 65 to be covered by a single photocatalytic filter 6.

[0140] Furthermore, a plurality of light sources 7 are installed vertically at intervals within the frame 65. In this embodiment, four light sources 7 are installed in parallel within one frame 65. Of these, the upper two light sources 7 are installed horizontally so as to straddle the two upper photocatalytic filters 6 arranged horizontally. Furthermore, the lower two light sources 7 are installed horizontally so as to straddle the two lower photocatalytic filters 6 arranged horizontally. However, the light sources 7 may also be installed vertically.

[0141] The frame 65 may also have a grease filter 34 removably attached to its upstream surface via a press member 66. The grease filter 34 attached to the frame 65 is preferably a single piece sized and shaped to cover the entire surface of the frame 65. One or more press members 66 are preferably provided for each side of the frame 65 so as to press down on each side of the grease filter 34. The press members 66 may also be slide guides (or slide rails) that guide the attachment and detachment of the grease filter 34 along the surface of the frame 65. By configuring the slide guides to extend along each side of the frame 65, when the slide guide on one side is removed, the grease filter 34 can be slid from the removed side in a direction perpendicular to the removed side to be attached or detached.

[0142] The grease filter 34 may be provided individually for each deodorizing unit 31. Alternatively or additionally, the grease filter 34 may be provided collectively at a position upstream of the partition wall 62 of the housing 61, for example, at the entrance of the inlet portion 52, with a size that completely covers the inlet portion 52.

[0143] <Effects> According to this embodiment, the following effects can be obtained.

[0144] For example, in a large-scale commercial facility 21 (large-scale commercial facility) such as a large shopping mall shown in Fig. 1, many restaurants 22 are located. Basically, each restaurant 22 is equipped with its own kitchen facilities (cooking equipment 23).

[0145] Many of these kitchen facilities use heat for cooking. Cooking using heat inevitably generates a large amount of gas 3 (cooking gas). This large amount of cooking gas contains oil smoke (oil mist) and cooking odors. Therefore, if the cooking gas is released directly into the atmosphere, there is a risk of environmental pollution due to odors, so it is necessary to remove the oil smoke and cooking odors from the cooking gas before releasing it into the atmosphere.

[0146] Therefore, a deodorizing device 1 is installed in an exhaust duct 2 that leads cooking gases generated by each kitchen facility to the outdoors. A deodorizing device 1 used in such a large-scale commercial facility must be quite powerful so that it can actually deodorize a large amount of cooking gas at a high level. Therefore, a low-level device that does not have sufficient deodorizing capacity cannot be used in a large-scale commercial facility, and therefore the target is different from the deodorizing device 1 of this embodiment.

[0147] There are various types of deodorizing devices 1 actually used in large-scale commercial facilities, such as adsorption types that use activated carbon, neutralization types that use neutralizing agents, and bio-types that use microorganisms. Each of these technologies has its advantages and disadvantages, so currently, they coexist.

[0148] In addition to the above, deodorizing devices 1 using photocatalysts 5 have also been developed and are already in practical use. Deodorizing devices 1 using photocatalysts 5 have a higher ability to remove odorous components (deodorizing efficiency) than deodorizing devices 1 of other types, so they can effectively remove cooking odors with ample margins, even from cooking gases generated in large quantities in large commercial facilities. For this reason, deodorizing devices 1 using photocatalysts 5 are advantageous over deodorizing devices 1 of other types.

[0149] Furthermore, the deodorizing device 1 using the photocatalyst 5 can be more easily simplified and miniaturized than other types of deodorizing devices 1. Moreover, the photocatalyst 5 exhibits a self-regenerating function using light 8 as an energy source. Therefore, the deodorizing device 1 using the photocatalyst 5 does not require disposal of the photocatalytic filter 6, and the photocatalytic filter 6 can be used semi-permanently, resulting in low running costs.

[0150] The deodorizing device 1 using such a photocatalyst 5 can be widely used in ventilation facilities in large-scale commercial facilities, as well as in normal-sized commercial facilities 21, office buildings, apartment complexes, and other collective housing.

[0151] The deodorizing device 1 using the photocatalyst 5 includes at least the photocatalyst filter 6 having the photocatalyst 5 supported on the filter substrate 4, and a light source 7 that activates the photocatalyst 5. In the deodorizing device 1 using the photocatalyst 5, the light source 7 is turned on to activate the photocatalyst 5 with light 8 from the light source 7, and gas 3 (untreated gas 3a) such as cooking gas is passed through the photocatalyst filter 6. In this way, the deodorizing device 1 using the photocatalyst 5 captures odor components of cooking odors in the cooking gas with the photocatalyst filter 6 and decomposes the captured odor components with the photocatalyst 5.

[0152] The light source 7 generates light 8 (mainly ultraviolet light 8a) that activates the photocatalyst 5, and may be a fluorescent tube (ultraviolet lamp) or an LED (ultraviolet LED lamp). The light source 7 is basically installed downstream of the photocatalytic filter 6. As a result, the light source 7 is protected from the untreated gas 3a by the photocatalytic filter 6.

[0153] Light 8 from the light source 7 is directly irradiated onto one side (the downstream side) of the photocatalytic filter 6, and passes through the inside of the photocatalytic filter 6 to reach the side opposite the light source 7. This activates the photocatalyst 5 throughout the entire photocatalytic filter 6 (both sides and inside).

[0154] It is preferable to install a grease filter 34 upstream of the photocatalytic filter 6 so that the majority of the oil in the oily smoke is captured in advance by the grease filter 34. The grease filter 34 may be installed anywhere upstream of the photocatalytic filter 6. This reduces the amount of oil that reaches the photocatalytic filter 6, preventing a decrease in the deodorizing effect of the photocatalytic filter 6 and improving the deodorizing effect. Note that the photocatalytic filter 6 can also decompose and remove oil that reaches it through a photocatalytic reaction.

[0155] (Effect 1) The photocatalytic filter 6 using the photocatalyst 5 has a porous metal body 11 (a porous body made of metal) as the filter substrate 4. The porous metal body 11 is a new metal material with a sponge-like internal structure made of metal or alloy that has continuous pores with a three-dimensional network structure throughout, and is relatively lightweight, has the required strength, and also has the required heat resistance and fire resistance.

[0156] In contrast to this, existing photocatalytic filters 6 use a ceramic porous body for the filter substrate 4. However, ceramic porous bodies are expensive, relatively heavy, and prone to breakage, so they require careful handling and are prone to breakage, for example, if dropped during handling.

[0157] In contrast, by changing the filter substrate 4 to a porous metal body 11, the photocatalytic filter 6 can be provided at a low price. Furthermore, because the porous metal body 11 is light and strong, it does not require careful handling like a porous ceramic body, and it is possible to prevent damage due to dropping, etc., and to maintain (preserve) the photocatalytic filter 6 in a healthy state without any defects. Therefore, it is possible to reduce the costs of the deodorizing device 1 and the photocatalytic filter 6, and to improve the handleability of the photocatalytic filter 6.

[0158] Furthermore, since the metal porous body 11 is easier to manufacture and obtain than a ceramic porous body, it can be used relatively easily and freely as the filter substrate 4 of the photocatalytic filter 6. Furthermore, as described above, the metal porous body 11 is lighter than a ceramic porous body, which not only reduces the weight of the photocatalytic filter 6 itself and the deodorizing device 1 using the photocatalyst 5, but also improves the transportability and handling of the photocatalytic filter 6 and the deodorizing device 1, which is convenient. Therefore, it becomes easy and possible to widely deploy and popularize the deodorizing device 1 using the photocatalyst 5 both domestically and overseas.

[0159] Furthermore, since the metal porous body 11 is easier to manufacture and process than a ceramic porous body, it can be formed into a relatively free shape and size. Therefore, by using the metal porous body 11, it becomes possible to create, for example, a photocatalytic filter 6 that is thinner, larger, and has a smaller average cell number C, depending on the purpose and use of deodorization, which could not be realized with conventional ceramic porous bodies.

[0160] On the other hand, in order to improve the deodorizing effect of the deodorizing device 1, it is necessary to increase the opportunities for the odorous components in the cooking gas to come into contact with the photocatalyst 5 of the photocatalytic filter 6, or to increase the opportunities for the odorous components to come into contact with the photocatalyst 5 as much as possible.

[0161] However, increasing the number of opportunities for odorous components to come into contact with the photocatalyst 5 increases the pressure loss of the photocatalyst filter 6. Therefore, it is necessary for the photocatalyst filter 6 to minimize pressure loss while increasing the number of opportunities for odorous components to come into contact with the photocatalyst 5 (i.e., improving the deodorizing effect). By optimizing the contact opportunity and pressure loss, the photocatalyst filter 6 can be made smaller and have higher performance at the same time.

[0162] Therefore, in this embodiment, the product (t × C) of the thickness t of the metal porous body 11 and the average number of cells C per inch is set to be 100 or more and 400 or less. By setting the product (t × C) of the thickness t of the metal porous body 11 and the average number of cells C to be 100 or more and 400 or less in this way, the contact opportunity and pressure loss can be optimized, and it becomes possible to put into practical use a photocatalytic filter 6 using the metal porous body 11 as the filter substrate 4.

[0163] Therefore, by using the above-mentioned metal porous body 11 as the filter substrate 4, the photocatalytic filter 6 can be optimized and pressure loss of the photocatalytic filter 6 can be reduced. Furthermore, the untreated gas 3a can be passed almost evenly throughout the entire area of ​​the metal porous body 11, thereby increasing the contact opportunity and contact area of ​​the untreated gas 3a (odor components contained therein) with the catalyst supported on the photocatalytic filter 6 (improving the deodorizing effect). Therefore, a high-performance photocatalytic filter 6 with a good balance between deodorizing effect and pressure loss (i.e., high deodorizing effect and low pressure loss) can be obtained, and it is possible to obtain a new photocatalytic filter 6 that can replace current ceramic filters.

[0164] By using the porous metal body 11 having the above-described configuration as the filter substrate 4 of the photocatalytic filter 6, it becomes possible to uniformly demonstrate the performance of the photocatalytic filter 6, which achieves a toluene removal rate of 85% or more (as per the experimental results specified in JIS R 1701-3), throughout the entire area of ​​the photocatalytic filter 6, thereby realizing efficient operation of the entire photocatalytic filter 6. As a result, the deodorizing device 1 can be made more compact and have higher performance to the extent that the entire photocatalytic filter 6 operates efficiently.

[0165] Furthermore, the product (t × C) of the thickness t of the metal porous body 11 and the average cell number C is clarified to be 100 or more and 400 or less. This makes it possible to obtain objective selection criteria for the metal porous body 11 when it is used as the filter substrate 4 of the photocatalytic filter 6.

[0166] Therefore, when designing the deodorizing device 1, it becomes possible to quickly and reliably identify or select the optimal metal porous body 11 that is suited to the specific scale and purpose of the deodorizing device 1, and easily manufacture the photocatalytic filter 6. As a result, the effort and cost required for manufacturing the photocatalytic filter 6 can be reduced.

[0167] (Effect 2) The metal porous body 11 may be formed from at least one material selected from the group consisting of nickel, silver, copper, aluminum, nickel chromium, nickel-tin, and nickel-iron. Thus, the above-described effects can be achieved by specifying the filter substrate 4 used in the photocatalytic filter 6 as a metal porous body 11 made from at least one material selected from the group consisting of nickel, silver, copper, aluminum, nickel chromium, nickel-tin, and nickel-iron. Additionally, since clear standards are established for the metal porous body 11 used to produce a photocatalytic filter 6 with stable quality and performance, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that consistently achieves the desired deodorizing effect.

[0168] In addition, for example, it becomes easy to select the metal porous body 11 made of the most suitable material from among the multiple types of metal porous bodies 11 available on the market, in accordance with the specific deodorizing purpose and use of the deodorizing device 1, and produce the photocatalytic filter 6. Furthermore, by using a metal porous body 11 made of any of the above-mentioned materials for the photocatalytic filter 6, it is expected that the metal porous body 11 itself will have the function of promoting catalytic activity.

[0169] (Effect 3) The metal porous body 11 may contain nickel. In this way, by specifying the material of the filter substrate 4 used in the photocatalytic filter 6 as the metal porous body 11 containing nickel, the above-mentioned effects can be obtained. In addition, since a clear standard for the metal porous body 11 for producing a photocatalytic filter 6 with stable quality and performance can be established, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that always provides the desired deodorizing effect.

[0170] Nickel is a metal with various characteristics, such as high corrosion resistance, excellent durability, high strength at high and low temperatures, and catalytic function, etc. Therefore, by including nickel as a material in the metal porous body 11, the filter substrate 4 can be made highly functional, and a high-performance photocatalytic filter 6 can be obtained.

[0171] (Effect 4) The metal porous body 11 may be configured so that the transmittance of ultraviolet light 8a is 8% or less. In this way, by specifying the transmittance of ultraviolet light 8a of the metal porous body 11 used in the photocatalytic filter 6 to be 8% or less, the above-mentioned effects can be obtained. In addition, since a clear standard for the metal porous body 11 for producing a photocatalytic filter 6 with stable quality and performance can be established, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that always provides the desired deodorizing effect.

[0172] Furthermore, it is specified that the metallic porous body 11 has a transmittance of 8% or less for ultraviolet light 8a. This reduces the amount of ultraviolet light 8a that passes through the photocatalytic filter 6 and leaks to the opposite side, ensuring that more ultraviolet light 8a is available for activating the photocatalyst 5 inside the photocatalytic filter 6 (using ultraviolet light 8a more efficiently).

[0173] By checking the transmittance of ultraviolet light 8a, it becomes possible to easily inspect and determine, for example, during manufacturing, whether the photocatalytic filter 6 using the metal porous body 11 has been properly finished. Also, by checking the transmittance of ultraviolet light 8a, it becomes possible to easily determine, for example, during maintenance, whether the photocatalytic filter 6 is being maintained in an appropriate state.

[0174] (Effect 5) The photocatalyst 5 may be titanium oxide. In this way, by specifying titanium oxide as the photocatalyst 5 used in the photocatalytic filter 6 using the metal porous body 11 as the filter substrate 4, the above-mentioned effects can be obtained. In addition, since a clear standard can be established for producing a photocatalytic filter 6 with stable quality and performance, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that always provides the desired deodorizing effect.

[0175] By using titanium oxide as the photocatalyst 5, a novel photocatalytic filter 6 can be obtained in which titanium oxide, which is effective for deodorization, is fixed as the photocatalyst 5 to the metal porous body 11.

[0176] (Effect 6) The photocatalyst 5 may have an average particle diameter of 1 nm or more and 100 nm or less. In this way, by specifying the average particle diameter of the photocatalyst 5 used in the photocatalytic filter 6 using the metal porous body 11 as the filter substrate 4 to be 1 nm or more and 100 nm or less, the above-mentioned effects can be obtained. In addition, since a clear standard for the photocatalyst 5 can be established to produce a photocatalytic filter 6 with stable quality and performance, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that always provides the desired deodorizing effect.

[0177] By using a photocatalyst 5 with an average particle diameter of 1 nm or more and 100 nm or less, a high-performance photocatalytic filter 6 can be obtained in which a photocatalyst 5 with an average particle diameter that functions most effectively for deodorization is fixed to a metal porous body 11.

[0178] (Effect 7) The amount of photocatalyst 5 carried on the filter substrate 4 may be 1 g to 2.5 g per 50 mm x 100 mm area. In this way, by specifying the amount of photocatalyst 5 carried on the metal porous body 11 used in the filter substrate 4 of the photocatalytic filter 6 to 1 g to 2.5 g per 50 mm x 100 mm area, the above-mentioned effects can be obtained. In addition, since a clear standard for the photocatalyst 5 can be established to produce a photocatalytic filter 6 with stable quality and performance, it becomes possible to provide a photocatalytic filter 6 that is a highly reliable product that always provides the desired deodorizing effect.

[0179] Furthermore, by setting the amount of photocatalyst 5 carried to 1 g to 2.5 g per area of ​​50 mm x 100 mm, a new photocatalytic filter 6 can be obtained in which the optimal amount of photocatalyst 5 for deodorization is fixed to the metal porous body 11.

[0180] (Effect 8) The metal porous body 11 may be flat. In this way, the above-mentioned effects can be obtained by specifying the shape of the metal porous body 11 used in the filter substrate 4 of the photocatalytic filter 6 to be flat. In addition, since a clear standard can be established for the metal porous body 11 for producing a photocatalytic filter 6 that is easy to use and has a shape that is effective for deodorization and has stable quality and performance, it becomes possible to provide a photocatalytic filter 6 that is finished into a highly reliable product that always provides the desired deodorizing effect.

[0181] The flat-plate-shaped metal porous body 11 can be processed and formed relatively easily, and the photocatalytic filter 6 using the flat-plate-shaped metal porous body 11 can be installed relatively easily in the exhaust duct 2 and can be used as is in an existing deodorizing device 1. Moreover, the flat-plate-shaped photocatalytic filter 6 has a shape that allows the untreated gas 3a to easily pass through, so that it is possible to bring a larger amount of odorous components in the untreated gas 3a into contact with the photocatalyst 5 carried on the photocatalytic filter 6.

[0182] (Function and Effect 9) According to the deodorizing device 1 of this embodiment, the same effects as those of the photocatalytic filter 6 described above can be obtained.

[0183] REFERENCE SIGNS LIST 1 deodorizing device 4 filter substrate 5 photocatalyst 6 photocatalytic filter 7 light source 8a ultraviolet light 11 metal porous body t thickness CROSS-REFERENCE TO RELATED APPLICATIONS

[0184] This application claims priority based on Japanese Patent Application No. 2020-170238, filed with the Japan Patent Office on October 8, 2020, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A photocatalyst filter in which a photocatalyst is fixed to a filter substrate, wherein the filter substrate is a metal porous body, the thickness of the metal porous body is t (mm), and when the average number of cells per inch of the metal porous body is C (ppi), the product (t × C) of the thickness t and the average number of cells C is 100 or more and 400 or less.

2. The photocatalyst filter according to claim 1, wherein the metal porous body is formed of at least one material selected from nickel, silver, copper, aluminum, nickel chromium, nickel - tin, and nickel - iron.

3. The photocatalyst filter according to claim 1, wherein the metal porous body contains nickel in the material.

4. The photocatalyst filter according to claim 1, wherein the metal porous body has an ultraviolet transmittance of 8% or less.

5. The photocatalyst filter according to claim 1, wherein the photocatalyst is titanium oxide.

6. The photocatalyst filter according to claim 1, wherein the photocatalyst has an average particle diameter of 1 nm or more and 100 nm or less.

7. The photocatalyst filter according to claim 1, wherein the loading amount of the photocatalyst on the filter substrate is 1 g to 2.5 g per area of 50 mm × 100 mm.

8. The photocatalyst filter according to claim 1, wherein the metal porous body has a flat plate shape.

9. A deodorizing device comprising the photocatalyst filter according to claim 1.

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