WO2017098575A1 - オゾン発生方法 - Google Patents
オゾン発生方法 Download PDFInfo
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- WO2017098575A1 WO2017098575A1 PCT/JP2015/084361 JP2015084361W WO2017098575A1 WO 2017098575 A1 WO2017098575 A1 WO 2017098575A1 JP 2015084361 W JP2015084361 W JP 2015084361W WO 2017098575 A1 WO2017098575 A1 WO 2017098575A1
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- ozone
- metal compound
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/10—Preparation of ozone
- C01B13/11—Preparation of ozone by electric discharge
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/80—Additional processes occurring alongside the electrical discharges, e.g. catalytic processes
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/90—Control of the process
Definitions
- the present invention includes an ozone generator having first and second electrodes facing each other and a dielectric formed on the first electrode, and having a discharge space between the dielectric and the second electrode.
- the present invention relates to an ozone generation method for generating high-concentration ozone.
- ozone generation technology in the light energy of cosmic rays and sunlight that Chapman came from the universe in 1930, becomes the oxygen atom by giving energy to the oxygen molecule of the wavelength of 242nm or less, this oxygen It is said that ozone is generated by the combination of atoms and oxygen molecules, and the generated ozone absorbs light having a wavelength of 320 nm or less, and the decomposition reaction simultaneously proceeds to oxygen molecules and oxygen atoms, thereby decomposing oxygen. It has been said that ozone is generated by the balance between the reaction and the decomposition reaction of ozone.
- ozone concentration of about 2 to 8 ppm is generated by the three-body collision between oxygen atoms and oxygen molecules dissociated by these two methods.
- the ozone concentration of the ozone layer is about 2 to 8 ppm in terms of the number of ozone, it is 4 ⁇ 10 12 / cm 3 per cubic centimeter, which is 10 7 times the ionospheric plasma density (10 5 / cm 3 ).
- the gas density over the earth is 1/100 of the earth's surface (in the atmosphere), and it is said that it is a reasonable value considering that the ozone decomposition rate is very small due to collision with the wall.
- high-concentration ozone exceeding 200 (g / m 3 ) (93,333 ppm) is conventionally generated by discharge plasma density (that is, electron density).
- the discharge electron density (10 10 / cm 3 ) at the generator is much higher than that of the ionosphere (10 5 / cm 3 ), and the gas density is very high. Since there are walls on both discharge surfaces of the discharge space of the vessel, not only can ozone be generated by the collision of electrons, but the generated ozone can also generate electrons due to collisions with electrons and molecules or with the walls of the discharge surface.
- the amount of ozone generated in the process is decomposed, and the amount of ozone generated by electrons in the discharge plasma is assumed to be less than several tens (g / m 3 ) (4000 ppm). Ozone due to collisions of oxygen molecules and fast electrons Oxygen atom dissociation alone cannot fully explain the mechanism by which high-concentration ozone can be generated.
- Patent Document 1 As a conventional high-concentration ozone generation technique, there is a prior art document disclosed in Patent Document 1 as an invention related to catalyst generation of oxygen atoms by a raw material gas and discharge.
- Patent Document 2 There exist prior art documents, such as patent document 2, patent document 3, patent document 4, patent document 5, and patent document 6, as invention regarding a photocatalyst production
- Patent Document 1 As an ozone generator capable of generating high-concentration ozone having a concentration of 200 (g / m 3 ) (93,333 ppm) or more, nitrogen gas is added to oxygen gas as a source gas to be supplied. 1% (1000ppm) to several percent (tens of thousands ppm) added.
- a small amount of added nitrogen gas becomes nitrogen oxide gas by discharge, and this small amount of nitrogen oxide gas catalyzes and dissociates a large amount of oxygen molecules.
- the ability to generate high-concentration oxygen atoms enables generation and extraction of high-concentration ozone by the three-body collision reaction between the high-concentration oxygen atoms and oxygen molecules generated through this nitrogen oxide. It is described that it becomes.
- Patent Documents 2 to 6 show that high concentration ozone is generated by applying a photocatalytic substance on the discharge surface.
- Patent Documents 7 to 8 are all inventions that take out the generated ozone without being decomposed in an ozone generator, and are completely different from Patent Documents 1 to 6. Yes.
- Patent Document 7 a transition in which an alkali metal, an alkaline earth metal, or a rare earth element is contained at the A position of a transition metal oxide having a crystal structure in which no atom is present at the A position of the perovskite structure is present on the discharge surface of the ozone generator. It has been shown that high concentration ozone can be extracted without decomposing the generated ozone in the ozone generator.
- a functional substance that prevents a decrease in the ozone concentration is an ozone generator that is baked and fixed on the dielectric surface (that is, the functional substance is contained in the ceramic).
- the functional substance having the ability to generate ozone and the decrease in ozone concentration It is only a difference in the functional materials that block the production, and there is no difference in production technology, and it is determined that the described functional material is a functional material (catalyst material) that prevents a decrease in ozone concentration.
- the description only describes the empirical data on which high-concentration ozone was obtained, and the reason why high-concentration ozone is obtained is also due to the factor that prevents the ozone concentration from decreasing. Or it has become unknown description.
- a catalytic reaction is defined by accelerating a reaction for decomposing ozone and oxygen.
- it has a function of preventing a decrease in ozone concentration.
- it is not fully described in the specification of Patent Document 8.
- Patent Document 9 a functional film limited to the ozone generator surface is shown.
- Japanese Patent No. 3642572 U.S. Pat. No. 7,402,289
- Japanese Patent No. 495814 Japanese Patent No. 495814
- Japanese Patent No. 5069800 Japanese Patent No. 4825314
- Japanese Patent No. 4932037 Japanese Patent No. 7,382,087
- Japanese Patent No. 5121944 Japanese Patent No. 4948007 (U.S. Pat. No. 8,911,675)
- Japanese Patent No. 5052304 US Patent Application Publication No. 2008/01282269
- Japanese Patent No. 5369189 International Publication No. 2011-039971
- high-concentration ozone gas can be generated by gas chemical catalytic reaction during dielectric barrier discharge between oxygen gas as a main raw material gas and a small amount of nitrogen oxide gas. Since the generated ozone gas contains a small amount of nitrogen oxide gas, nitric acid vapor (HNO 3 ) gas having high chemical reactivity with the metal is also generated. This nitric oxide vapor (HNO 3 ) gas, which is a nitrogen oxide, generates metal contamination and has a problem that clean ozone gas treatment cannot be performed.
- Patent Documents 2 to 6 Although attention has been paid as an epoch-making invention, it has been shown that the metal compound material applied to the discharge surface has a photocatalytic substance effect.
- the specification of the photocatalytic substance for obtaining the concentration ozone was limited, and the range of the photocatalytic substance was not clear.
- the technical scope disclosed in Patent Documents 2 to 6 does not stipulate in detail the conditions for sufficiently exerting the effect of generating ozone in the metallic compound photocatalytic substance applied to the discharge surface.
- the method for generating high-concentration ozone is sufficiently specified.
- Patent Documents 7 to 9 although the invention shows the metal compound material applied to the discharge surface, it is not an invention for generating ozone on the discharge surface of the ozone generator. It is disclosed to suppress the decomposition of ozone, and the specification does not sufficiently show the technology related to the sufficient invention, and only the technology for suppressing the decomposition of ozone is a technology development for obtaining high-concentration ozone. Was very problematic.
- Patent Documents 8 and 9 describe baking and fixing on a dielectric surface (that is, a functional substance is contained in a ceramic).
- Patent Document 9 This technique is already disclosed in the prior art (Patent Document 9). It is pointed out as a problem. Patent Document 9 has a problem that it cannot be said that a method for generating sufficiently high-concentration ozone is disclosed only by showing a functional film limited to the surface of the ozone generator.
- an object of the present invention is to provide an ozone generation method capable of solving the above-described problems and generating ozone with a higher concentration.
- the ozone generation method includes first and second electrodes facing each other, and a dielectric formed on the first electrode, and the gap between the dielectric and the second electrode.
- the metal compound layer satisfies the following conditions (1) to (4), (1) is not a substance that promotes ozonolysis, (2) is not a conductor, (3) the metal compound (4) The hole potential of the valence band formed in the excited state of the metal compound layer is more than the binding potential of the oxygen molecule, the band gap of the layer is in the range of 2.0 to 4.0 [eV] Large, the ozone generation method is: (a) oxygen gas in the discharge space Supplying a source gas mainly comprising: (b) giving external energy, generating a dielectric barrier discharge in the discharge space, and making the metal compound layer into a photocatalytic state by the discharge light, Generating oxygen atoms from the source gas supplied in step (a), and (c) ⁇ ⁇ ⁇ ozone by collision chemical reaction between the oxygen atoms generated in step (b) and oxygen gas contained in the source gas. And (d) performing steps (a) to (c) in an environment where the ozone generator is subjected to an ozone decomposition
- the ozone generator used in the ozone generation method of the present invention has a metal compound layer that satisfies the above conditions (1) to (4), oxygen gas in the raw material gas passing through the discharge space is reduced. As a result of selectively dissociating catalytically and generating high concentration oxygen atoms, the ozone generation efficiency is increased to 0.01 mg / J (36 g / kWh) or more in the ozone generator, and high concentration Ozone can be generated.
- step (d) Furthermore, by setting the ozone generator in an environment where the ozone decomposition suppression requirement is imposed in step (d), the phenomenon in which ozone generated in step (c) is decomposed is suppressed, and a higher concentration is achieved. Fresh ozone gas can be taken out.
- FIG. 1 is a block diagram showing a configuration of a nitrogen addition-less ozone gas generator (hereinafter sometimes simply referred to as “ozone generator”) used in an ozone generation method according to an embodiment of the present invention. That is, FIG. 1 is a block diagram showing a configuration of a gas system centering on an ozone generator.
- ozone generator nitrogen addition-less ozone gas generator
- FIG. 2 is an explanatory diagram showing an element periodic table including a metal element range determined to be effective in the present invention.
- 2 also shows a metal element of a metal compound having the properties of a semiconductor that could not be obtained.
- group T1, atomic number T2, atomic element T3, metal compound material T4, and band gap T5 are shown as classification items T1 to T5 of each element.
- band gap of metal compound material T4 band gap of metal compound material T4
- manganese Mn with atomic number 25 cobalt Co with atomic number 27, nickel Ni with atomic number 28, copper Cu with atomic number 29, and silver (metal) element material with atomic number 47 are in contact with ozone. It is an element generally known as an ozonolysis catalyst substance.
- Metal compound material of zinc Zn of atomic number 30, gallium Ga of atomic number 31, germanium Ge of atomic number 32, cadmium Cd of atomic number 48, indium In of atomic number 49, tin Sn of atomic number 50 is visible light It is a conductive element that transmits light wavelengths, and it is difficult to excite the substance itself with visible light energy.
- a metal compound material of aluminum Al with atomic number 13, silicon Si with atomic number 14, scandium Sc with atomic number 21, yttrium Y with atomic number 39, zirconium Zr with atomic number 40, and howium Hf with atomic number 72 is a band.
- a metal compound material having a gap of 5 eV or more and a band gap of 5 eV or more is usually defined as an insulator material, and it is difficult to excite (activate) the material itself with discharge light energy such as dielectric barrier discharge. It is.
- a metal compound material having a band gap of 5 eV or less is usually defined as a semiconductor material having semiconductor properties. Even in the semiconductor material, if the band gap is 4 eV or less, the material itself can be excited and activated by the discharge light energy of the dielectric barrier discharge.
- FIG. 3 is an explanatory diagram schematically showing the electron coordination structure in the solid and the dissociation mechanism of oxygen molecules in the solid electron theory (band gap theory) of the photocatalyst during silent discharge.
- FIG. 4 is an explanatory view for schematically explaining the ozone generation mechanism by the three-body collision between oxygen atoms and oxygen molecules generated by the ozone generator 1.
- FIG. 3 shows an oxygen atom generation chemical reaction showing a dissociation reaction mechanism of oxygen molecules into oxygen atoms by the oxygen gas (oxygen molecules) and the excited state (photocatalytic state) of the semiconductor material in the embodiment of the present invention.
- FIG. 4 shows an ozone generation chemical reaction showing a mechanism of ozone generation by a three-body collision reaction between oxygen molecules and generated oxygen atoms in the embodiment of the present invention.
- FIG. 5 is an explanatory diagram showing the excited state of the substance with respect to the light absorption wavelength.
- 301g to 310g and 313g show the band gap and the excited state (photocatalytic state) of the metal compound material having the properties of an insulator from the semiconductor used as the discharge surface material in the metal compound layer 1d.
- chromium BG band gap
- tungsten BG 302 g vanadium BG 303 g
- molybdenum BG 304 g niobium BG 305 g
- tantalum BG 306 g nickel BG 307 g
- zinc BG 308 g yttrium BG 309 g
- vanadium BG303g shows a band gap of a metal compound (V 2 O 5 ) whose main metal element is panadium.
- the characteristic line AL-V indicates the potential of the electrons in the valence band in the excited state of each substance as an envelope
- the characteristic line BL-V indicates the + in the conduction band in the excited state of the substance.
- the potential of the hole is indicated by an envelope.
- a high-concentration ozone generation range 3001 surrounded by a broken line frame indicates a potential range of + holes and a light absorption wavelength width range in an excited state of a substance capable of generating high-concentration ozone and extracting high-concentration ozone.
- the high-concentration ozone generation range 3001 is activated by the discharge light energy of the dielectric barrier discharge generated in the discharge space, and the oxygen gas can be catalytically dissociated into oxygen atoms on the activated material surface. The range is shown.
- FIG. 6 is an explanatory view showing the ozone concentration characteristics that can be taken out with respect to the injection discharge energy due to the difference in the material of the metal compound having a semiconductor property with respect to the main metal element.
- chromium gradient characteristics 301a chromium gradient characteristics 301a, tungsten gradient characteristics 302a, vanadium gradient characteristics 303a, molybdenum gradient characteristics 304a, niobium gradient characteristics 305a, tantalum gradient characteristics 306a, nickel concentration gradient characteristics 307a, zinc gradient characteristics 308a, yttrium gradient characteristics 309a.
- a zirconium gradient characteristic 310a chromium gradient characteristics 301a, tungsten gradient characteristics 302a, vanadium gradient characteristics 303a, molybdenum gradient characteristics 304a, niobium gradient characteristics 305a, tantalum gradient characteristics 306a, nickel concentration gradient characteristics 307a, zinc gradient characteristics 308a, yttrium gradient characteristics 309a.
- the vanadium gradient characteristic 303a is a characteristic that almost overlaps with the bismuth concentration characteristic 313c
- the tantalum gradient characteristic 306a is a characteristic that overlaps with the niobium gradient characteristic 305a. Therefore, a part of the description is omitted in FIG.
- the molybdenum gradient characteristic 304a indicates the gradient characteristic of a metal compound (MoO 3 ) containing molybdenum as a main metal element.
- zirconium concentration characteristic 310b is shown.
- the molybdenum concentration characteristic 304b indicates the concentration characteristic of a metal compound (MoO 3 ) containing molybdenum as a main metal element.
- FIG. 6 also shows the high concentration ozone threshold value HCT defined in the present invention.
- HCT high concentration ozone threshold
- a high-concentration ozone generation range 2001 indicates a range in which high-concentration ozone gas can be extracted.
- the gradient characteristics 301a to 310a described above indicate tangents of ozone characteristics in the low concentration region of the ozone concentration characteristics 301b to 310b. That is, the slopes of the slope characteristics 301a to 310a indicate the amount of ozone generated per unit volume with respect to the discharge energy due to the difference in the material of the metal compound, that is, the ozone generation efficiency ⁇ .
- FIG. 7 is an explanatory diagram logarithmically representing the ozone generation amount (g) with respect to the injection discharge energy (W / Q: specific power) per unit volume of the metal compound of the specific metal element (tangential gradient characteristics 301a to 301 in FIG. 6). 301c logarithmic display is shown).
- the element concentration characteristics 301c to 310c and 313c even if the same discharge energy is injected, the amount of ozone that can be generated differs greatly depending on the material of the metal compound material. Became clear.
- the increase degree (Lc) of the ozone decomposition rate ⁇ determined depending on the ozone decomposition characteristics in the ozone generator of FIG. 10 to be described later has been found to be almost unchanged due to the difference in the material of the metal compound. It was confirmed experimentally that the degree of ozonolysis produced by the compound material did not change.
- element concentration characteristics 301c to 310c and 313c include chromium concentration characteristics 301c, tungsten concentration characteristics 302c, vanadium concentration characteristics 303c, molybdenum concentration characteristics 304c, niobium concentration characteristics 305c, tantalum concentration characteristics 306c, and nickel concentration characteristics 307c.
- a zinc concentration characteristic 308c, an yttrium concentration characteristic 309c, a zirconium concentration characteristic 310c, and a bismuth concentration characteristic 313c are shown.
- the characteristic group GA a metal compound material having the ability to generate ozone of 0.1 g or more per cubic volume of gas with respect to the specific power W / Q is shown. It was confirmed from the characteristic diagram that the ozone generator 1 capable of taking out high-concentration ozone gas can be realized by applying the metal compound layer 1d made of to the discharge surface of the ground electrode 1b and the dielectric 1c.
- the characteristic group GB shows a metal compound group having the ability to generate approximately 0.001 g of ozone, which is two orders of magnitude lower than that of the characteristic group GA. It was proved by the verification test that ozone was not generated and as a result, high concentration ozone could not be taken out.
- the characteristic group GC a metal compound group that can generate only 0.00001 g of ozone, which is four orders of magnitude lower than the characteristic group GA, is shown. Due to this low ozone generation capability, high-concentration ozone is generated. As a result, it was shown that high-concentration ozone could not be taken out, and the surprising fact that only ozone having a lower concentration than the ozone generation ability of the characteristic group GB could be generated.
- FIG. 8 shows an oxide metal in the ozone generator 1 in which a metal compound layer 1d made of a metal compound having a specific semiconductor property in this embodiment is fixed to the ground electrode 1b and the discharge surface of the dielectric 1c. It is explanatory drawing which put together the relationship between the physical-property characteristic of material, ozone production
- the characteristic numbers and product numbers of the metal compound materials shown in FIGS. 6 and 7 are associated with each other, and the material product numbers 301 to 306 (chromium, tungsten, vanadium, molybdenum, niobium, and tantalum) have high concentrations.
- An elemental metal material of a metallic compound capable of generating ozone which is a metal oxide compound corresponding to an elemental metal of group 5 or 6 in the periodic table of elements, and in each case, ozone generation efficiency ⁇ from which high-concentration ozone can be extracted and The extracted ozone concentration value is shown.
- bismuth of material number 313 is also an elemental metal material of a metal compound that can generate high-concentration ozone, and the excited state of this substance belongs to the high-concentration ozone generation range 3001 as shown in FIG. Is a metal oxide compound composed of an element that is not a metal element of Group 5 or 6 in the Periodic Table of Elements.
- ozone generation efficiency ⁇ is only 2.78E-6 (mg / J) (0.01 g / kWh), and the maximum ozone concentration Cmax that can be taken out is only 0.2 (g / m 3 ).
- Zinc 308 was a metal compound material satisfying the promising conditions for enhancing the ozone generation ability, while the band gap value and the hole potential of the metal compound material were ozone, but the ozone generation efficiency ⁇ was measured to be 9.49E. Only ⁇ 5 (mg / J) (0.34 g / kWh) can be obtained, and the maximum ozone concentration Cmax that can be taken out is only a few (g / m 3 ). It has been clarified that the zinc BG308 having the material number 308 is a substance that does not have the ability to generate high-concentration ozone.
- this metal compound material corresponds to a transparent conductive film material that particularly transmits visible light discharge light. It was found that the material escapes by reflection and transmission, does not absorb the discharge light energy effectively, and cannot excite the metal compound into the photocatalytic state. In other words, this material has physical properties corresponding to semiconductors, but is characteristically a special metal compound having the properties of an insulating material. Therefore, it is determined that the number (g / m 3 ) of ozone extracted from the generator corresponds to low-concentration ozone generated from oxygen atoms dissociated by collision of fast electrons of discharge plasma with oxygen.
- yttrium 309, zirconium 310, and aluminum 311 corresponding to the material product numbers 309 to 311 indicate metal compound materials having a band gap value of 5 eV or more, and in yttrium 309 and zirconium 310, ozone generation efficiency In the measurement, only 1.59E-4 (mg / J) (0.57 g / kWh) and 9.49E-5 (mg / J) (0.34 g / kWh) can be obtained, and the maximum ozone concentration Cmax that can be extracted is Cmax. Only a few (g / m 3 ) were obtained, and it was revealed that the substance has no ability to generate high-concentration ozone.
- the number (g / m 3 ) of ozone extracted from the generator is converted into low-concentration ozone generated from oxygen atoms dissociated by collision of fast electrons of discharge plasma with oxygen. It is judged that it corresponds.
- the band gap value of the metal compound is 7 eV or more, and even in this material, it is possible to obtain only a few (g / m 3 ) ozone concentration values extracted with high-purity oxygen gas. It is clear from Patent Document 1 and the like of the prior art.
- metal compound substances correspond to metal compound substances that cannot be absorbed at all with respect to the light wavelength emitted by the dielectric barrier discharge, and this substance corresponds to an insulator.
- FIG. 9 is an explanatory diagram showing the maximum ozone concentration value Cmax that can be taken out with respect to the ozone generation efficiency ⁇ in the apparatus in which the predetermined discharge power W is supplied to the ozone generator 1 used in the present embodiment.
- Concentration Co represents a threshold value for high-concentration ozone concentration.
- ⁇ o represents the minimum ozone generation efficiency for obtaining high-concentration ozone above the threshold.
- the maximum ozone concentration characteristics 601 to 604 indicate the maximum ozone concentration characteristics that can be taken out with respect to the ozone generation efficiency ⁇ in the ozone generator 1 shown in FIG. 1.
- the maximum ozone concentration characteristics 601, 602, 603, and 604 are the ozone concentrations. The characteristics when the temperature of the discharge surface of the generator 1 is kept constant by cooling to 40 ° C., 20 ° C., 0 ° C., and ⁇ 20 ° C. are shown.
- the surprising fact is that if the high-density discharge plasma generated by the ozone generator cannot function as an ozone-generating catalyst on the electrode surface, etc., the generated ozone has the function of decomposing ozone gas by the discharge plasma. It is a work, and is different from the ozone generation technology that has been generally accepted.
- the high-concentration ozone generation range 3001 indicates a range where high-concentration ozone can be extracted, and an ozone generation efficiency range in which high-concentration ozone can be obtained from the high-concentration ozone generation range 3001 and an ozone decomposition rate suppression range are defined. I understand that.
- the temperature setting of the electrodes 1a and 1b is largely related to the requirement for suppressing ozone decomposition.
- the structure or setting of the ozone generator 1 including the specific power amount W / Q value (W ⁇ min / L), gas pressure P value (MPa), and discharge gap length d value (mm) injected into the ozone generator 1.
- W / Q value W ⁇ min / L
- MPa gas pressure P value
- mm discharge gap length d value
- the specific power W / Q value to be injected has the property of increasing the ozone generation ability. However, if the specific power W / Q value becomes too large, it becomes a factor to increase the gas temperature. For extraction, it is necessary to set the W / Q value within the optimum range (Wm / Qm).
- the optimum specific power Wm / Qm was found to be able to extract high-concentration ozone gas by setting it to 300 (W ⁇ min / L) to 500 (W ⁇ min / L) from the actual measurement value.
- the gas pressure P value (MPa) and the discharge gap length d value (mm) depend on the discharge space volume V. If the discharge space volume V is too large, the time t (sec) (t Is proportional to V / Q), the time during which the ozone gas generated by the generator is exposed to the discharge plasma becomes longer. As a result, the ozone decomposition amount of the generated ozone amount increases, and the high concentration ozone is increased. Cannot be removed. Therefore, in order to take out high-concentration ozone, it is necessary to set the optimum gas pressure range Pm value (MPa) and the optimum gap length range dm value (mm).
- the gap length of the discharge space of the ozone generator is reduced to 0.4 mm or less, the electric field strength of the discharge plasma increases, and strong excitation light (discharge light) can be applied to the metal compound applied to the discharge surface. Since the discharge space is cooled from the discharge surface, the effect of lowering the gas temperature passing through and the effect of shortening the time t passing through the discharge space due to the reduction of the discharge space volume V described above are synergistic. By doing so, the ozone concentration that can be extracted is increased. However, if the discharge gap is lowered to less than 0.02 mm, the factor of decomposing the generated ozone is increased by the wall of the discharge surface. Therefore, in the demonstration test results, in the ozone generator of the present invention, the gap length of the discharge space is The optimal range was demonstrated to be in the 0.02-0.12 (mm) range.
- the gas pressure in the discharge space has the same effect as the effect of the gap length described above.
- the ozone generator of the present invention has an absolute pressure of 0.2 to 0.4. It is desirable to set within the range of (MPa). In the case of gas pressure, the lower the pressure, the worse the gas cooling effect and the greater the decomposition loss to the wall.
- the optimum gas pressure range Pm value (MPa) is in the range of 0.2 MPa to 0.4 MPa
- the optimum gap length range dm value (mm) is set in the range of 0.02 mm to 0.12 mm.
- FIG. 10 is an explanatory diagram showing ozone concentration characteristics (b) that can be taken out in the ozone generator 1 shown in FIG.
- FIG. 10 is a diagram logically elucidating the ozone generation phenomenon occurring in the ozone generator and the decomposition phenomenon of the generated ozone from the general ozone concentration characteristics of the ozone generator.
- the tangent line La indicates the tangent line when the specific power amount W / Q value of the ozone concentration characteristic line Lb is small.
- This tangent line La indicates that the amount of ozone generated in proportion to the specific power amount W / Q value increases, shows the ozone generation characteristic of the metal compound itself having the ozone concentration characteristic line Lb, and the tangent line La The slope indicates the ozone generation efficiency ⁇ value.
- a tangent line Lc indicates an asymptotic line (ozone decomposition characteristic) of ozone concentration attenuation with respect to the specific power amount W / Q value of the ozone concentration characteristic line Lb, and the ozone decomposition rate ⁇ ( %) Is represented by the following formula (1).
- the amount of extracted ozone TWQ indicates the amount of extracted ozone at specific power W / Q
- the amount of generated ozone GWQ indicates the amount of generated ozone at specific power W / Q.
- the slope of the tangent line Lc which is an asymptotic line, indicates the degree of decrease in the ozone concentration that can be extracted by the increase in the ozone decomposition rate ⁇ of ozone generated by the ozone generator 1 itself.
- the ozone concentration characteristic line Lb that can be taken out is determined by the synthesis of the tangent line La that defines the ozone generation efficiency ⁇ and the tangent line Lc that shows the degree of decrease in ozone concentration that can be taken out.
- the maximum ozone concentration Cmax value that can be extracted can be extracted with higher concentration ozone as the slope of the tangent line La (ozone generation efficiency ⁇ ) is larger, and conversely, the higher concentration ozone can be extracted with a smaller inclination of the tangent line Lc.
- FIG. 11 is a graph showing the relationship between the discharge gap length d and the ozone decomposition rate in the ozone generator 1 of the embodiment shown in FIG. FIG. 11 shows that ozone is generated at a specific power value (W / Q value) determined when the gas pressure in the ozone generator 1 is set to a predetermined pressure and a predetermined gas flow rate Q and a predetermined injection power W are input.
- the ozone generated in the ozone generator 1 by changing the discharge gap length d of the ozone generator 1 (distance between the opposing metal compound layers 1d and 1d) and the electrode cooling temperature T of the electrodes 1a and 1b.
- the characteristics of the ozone decomposition rate ⁇ with respect to the discharge gap length d in the ozone generator 1 itself estimated from the amount are shown.
- the characteristic curves 701 to 704 show the dependence of the ozone decomposition rate ⁇ on the discharge gap length d when the electrode cooling temperature T is constant.
- the characteristic curve 701 is when the electrode cooling temperature T is constant at 40 ° C.
- the characteristic curve 702 is when the electrode cooling temperature T is constant at 20 ° C.
- the characteristic curve 703 is when the electrode cooling temperature T is constant at 0 ° C.
- the characteristic curve 704 shows the dependence of the ozone decomposition rate ⁇ on the discharge gap length d when the electrode cooling temperature T is kept at ⁇ 20 ° C.
- the threshold (one-dot chain line) of the ozone decomposition rate ⁇ is about 80%. If the ozone decomposition rate is higher than this threshold, the ozone decomposition rate can be increased even if a large amount of ozone is generated in the ozone generator 1. This indicates the limit value at which the ozone concentration that can be taken out is too high to be high.
- the condition range in which high-concentration ozone is easily taken out in the ozone generator 1 is a high-concentration ozone extraction range 4001. That is, it is desirable that the discharge gap length d is 20 ⁇ m to 120 ⁇ m (0.02 to 0.12 (mm)), and the electrode cooling temperature T is 20 ° C. or less.
- a raw material supply system 99 for supplying oxygen (raw material gas) with a purity of 99.99 (%) or more is composed of a high-purity oxygen cylinder 991, a pressure reducing valve 992, and an on-off valve 993.
- the oxygen gas 994 is supplied to the ozone generator 1 as the source gas 995 through the MFC 3.
- the ozone generator 1 includes a high-voltage electrode 1a (first electrode), a ground electrode 1b (second electrode), a dielectric 1c, and a metal compound layer 1d.
- the pair of electrodes 1a and 1b face each other, and a dielectric 1c is provided on the facing surface (discharge surface) of the high-voltage electrode 1a.
- the metal (element) compound layer 1d is applied to the opposing surfaces (discharge surfaces) facing each other between the dielectric 1c and the ground electrode 1b. That is, the metal compound layer 1d is provided on the surfaces of the dielectric 1c and the ground electrode 1b.
- a space formed between the dielectric 1c and the ground electrode 1b through the metal compound layer 1d becomes a discharge space, and a distance between the opposing metal compound layers 1d and 1d becomes a discharge gap length d.
- FIG. 1 schematically shows the configuration of the ozone generator 1.
- the flow of gas supplied to the ozone generator is sealed from the container space of the ozone generator 1.
- the metal compound layer 1d is fixed to the opposing surface (discharge surface) between the dielectric 1c and the ground electrode 1b, and the source gas 995 flows from the left in the figure to the dielectric.
- 1c and the ground electrode 1b flow along an opposing surface (discharge surface), and can be taken out from the right outlet as an ozonized oxygen gas 996 via an APC (automatic pressure regulator) 4, and ozone gas (ozonized oxygen gas 996).
- APC automatic pressure regulator
- ozone gas ozonized oxygen gas 996
- the ozone power source 2 which is an AC high voltage power source is mainly composed of a rectifier circuit 2a, an inverter circuit 2b, and a high voltage transformer 2c.
- a rectifier circuit 2a As the output voltage of the ozone power source 2, an alternating high voltage is applied between the high voltage electrode 1a and the ground electrode 1b of the ozone generator 1 shown in FIG.
- this dielectric barrier discharge When an alternating high voltage is applied between the high-voltage electrode 1a and the ground electrode 1b, the entire surface of the dielectric 1c is charged, and when a certain amount of charge is charged, the discharge space is charged by partial dielectric breakdown. causes a dielectric barrier discharge that releases charge.
- This dielectric barrier discharge has a very short life span of about nanoseconds and is a high electric field discharge, which is a uniform and infinite number of nanosecond intermittent discharges on the entire surface of the dielectric 1c. Therefore, this dielectric barrier discharge is a discharge that uniformly gives high energy to oxygen gas, and has a discharge electron energy of about 2 eV to 4 eV, and emits light by collision of this high energy electron and gas.
- the discharge light is a discharge having about ultraviolet light (300 nm) to visible light (600 nm).
- ozone gas is generated in the ozone generator 1, and the ozone decomposition amount obtained by multiplying the generated ozone amount by the ozone decomposition rate ⁇ caused by the discharge gas temperature is The subtracted ozone amount can be taken out from the ozone generator 1 as the ozone gas extraction concentration 996 as the ozone gas extraction concentration.
- high-concentration ozone of 200 (g / m 3 (93333 ppm)) or more as the ozone concentration that can be taken out from the ozone generator 1
- 1 mol (22.4 L) Is equivalent to 0.562 ⁇ 10 23 molecules / mol (2.51 ⁇ 10 18 molecules / cm 3 ) or more
- the lifetime of oxygen atoms The number of oxygen atoms is also 0.562 ⁇ 10 23 pieces / mol (2.51 ⁇ 10 18 pieces / cm 3 ) or more considering that the amount of annihilation of oxygen atoms in the ozone generator is large due to short It is necessary to generate the number of oxygen atoms (at least several tens of times the number of ozone molecules).
- ozone In normal discharge plasma, ozone is generated by the dissociation of oxygen into atoms due to collisions of ionized fast electrons. Since the electron density of normal discharge plasma is about 10 10 atoms / cm 3 , electron collisions in the plasma Approximate the number of oxygen atoms generated only by the electron itself with the electron density in the plasma, even if the collision is repeated millions to tens of millions of times while the electrons accelerate in the plasma, It is about 10 15 to 10 16 pieces / cm 3 .
- the discharge plasma in the ozone generator is much larger than the electron density and gas density of the ozone layer on the earth, and the mean free process distance of the gas is very short, making it easy to collide with ozone and other electrons and gas particles.
- ozone generated significantly more than the ozone layer is in a state of being decomposed by collisions with electrons.
- there is no wall called discharge surface like the ozone generator there is no wall called discharge surface like the ozone generator, and it is not necessary to consider the decomposition factor caused by the collision of the generated ozone with the wall. Since the space is a short gap discharge wall, the amount of ozone decomposition due to the collision with the wall portion becomes very large.
- the number of ozone molecules generated from the obtained oxygen atoms is about 10 15 to 10 16 / cm 3 , and the ozone concentration is 1 (g / m 3 ) to 10 (g / m 3 (several). Hundred ppm to several thousand ppm)). Therefore, it is understood that the ozone concentration generated only by the electron density in the discharge plasma is a concentration that is not sufficient to obtain high-concentration ozone of 200 (g / m 3 (93333 ppm)) or more.
- Ozone when ozone is generated by supplying high-purity oxygen to the ozone generator and inducing a dielectric barrier discharge with an ozone generator with no specific metal compound attached to the discharge surface, Ozone is not generated and is at most about several tens of g / m 3 (several thousand ppm).
- the ozone concentration that can be generated by electron collision of the electron density of the discharge plasma described above, it is generated only by the electrons themselves in the discharge plasma by the ozone concentration obtained from the actual experimental results and the ozone generation mechanism by the electron collision. This is consistent with the ozone amount consideration.
- the ozone concentration described here is not an ozone concentration of several tens of g / m 3 (several thousand ppm) that can be generated by electron avalanche collision of the electron density of the discharge plasma, but high concentration ozone of 200 g / m 3 or more can be generated.
- the consideration of the ozone generation method which can be taken out as high concentration ozone which can take out the generated ozone is described.
- the ozone concentration characteristics are as shown in FIG. FIG. 10 shows the standard ozone characteristics indicating the ozone concentration characteristics that can be taken out in the ozone generator 1 of FIG. 1, and the specific power W / Q (W ⁇ min / L), which is the specific discharge power amount per unit gas flow rate Q. ) (Horizontal axis) shows the ozone concentration characteristic line Lb that can be taken out.
- the ozone concentration characteristic line Lb that can be taken out generally reaches the maximum concentration Cmax at the optimum specific power Wm / Qm, and shows the characteristic that the ozone concentration that can be taken out decreases when the optimum specific power Wm / Qm is exceeded. .
- this ozone concentration characteristic line Lb is a composite characteristic of the tangent line La and the tangent line Lc (the degree of decrease in the ozone concentration that can be extracted).
- the characteristic indicated by the tangent line La indicates an ozone generation amount proportional to the discharge power amount W / Q per unit gas flow rate, and the slope of the tangent line La indicates the ozone generation efficiency ⁇ (mg / J).
- the tangent line Lc indicates the amount by which the ozone concentration that can be extracted by decomposing ozone generated in the ozone generator 1 is attenuated. This ozone attenuation amount is determined by the structure and gas conditions of the ozone generator 1 itself, and the value of the tangent Lc indicates the degree of increase in the ozone decomposition rate ⁇ (mg / J). That is, the lower the value of the tangent Lc, the greater the amount of ozone decomposition in the ozone generator.
- the degree of increase in the ozone decomposition rate ⁇ is uniquely determined by the structure of the ozone generator 1 itself and the gas conditions.
- a characteristic value Co indicates a critical concentration value of 200 g / m 3 (93333 ppm) as an example of defining a high ozone concentration in the present embodiment.
- the first feature is to specify the metal element range of the discharge surface material having a high ozone generation efficiency ⁇ (mg / J) as the constituent material of the metal compound layer 1d.
- the second feature of the present invention is that the crystal structure of the discharge surface material applied as the metal compound layer 1d and the particle diameter range of the adhering material are specified, and at a larger flow rate, 200 g / m 3 (93333 ppm) or more. It is to be able to take out high concentration ozone gas.
- the ozone that can be extracted from the ozone generator 1 by suppressing the ozone decomposition rate ⁇ of ozone generated by the ozone generator 1 by defining the setting conditions and structure of the ozone generator 1 itself. It is to define the structure or setting means of the ozone generator 1 so that the amount can be increased and the concentration can be increased. That is, in the present invention, in addition to the first and second features that increase the ozone generation efficiency ⁇ , the third feature is that various ozone decomposition suppression requirements are imposed on the ozone generator 1 in order to suppress the ozone attenuation rate ⁇ . It is said.
- the entire surface of the discharge surface of the applied metal element material is a dielectric (an oxide compound that is a metal compound material).
- the high ozone concentration can be generated by the ozone generator 1 by the catalytic oxygen dissociation by the metal element material of the modified metal compound, and the maximum ozone concentration that can be taken out as a result was found to be able to extract high-concentration ozone of 200 g / m 3 or more.
- the modified metal compound on the entire surface of the discharge surface shows that it is a dielectric having a capacitance.
- this dielectric is examined in more detail, the metal compound having the properties of a semiconductor is found. It was found to be a dielectric.
- the ozone generator 1 can generate high-concentration ozone and generate ozone so that the ozone decomposition rate is kept as low as possible with respect to the generated ozone amount.
- An ozone generation method capable of extracting high-concentration ozone by prescribing the ozone decomposition suppression requirement by defining the structure or setting means of the vessel 1 will be described.
- FIG. 2 is an element periodic table describing a metal element and a metal oxide compound that is a metal compound thereof.
- the ozone generator 1 shown in FIG. 1 can produce a high-concentration ozone gas of 200 g / m 3 or more, and a metal compound having a semiconductor property that can be extracted can be realized. It has been confirmed from experiments that the metal element range is a metal element belonging to the first metal compound species 201.
- the first metal compound species 201 is a group 5 or group 6 metal element V (vanadium), Cr (chromium), Nb (niobium), Mo (molybdenum), Ta (tantalum), or W (tungsten). It was confirmed from the test that it is a metal compound (V 2 O 5 , CrO 3 , NbO 5 , MoO 3 , Ta 2 O 5 , WO 3 ) having the properties of a semiconductor including
- Ni element belongs to a metal compound material having catalytic decomposition action of generally known ozone, and Mn-based, Co-based, Cu-based materials other than Ni element are used as metal compound material having catalytic decomposition action. , Ag metal compound material.
- ozone-catalyzed metal compound materials are easily activated by simply receiving externally low-temperature thermal energy, and ozone is easily formed on the surface of the excited material. By contacting, it becomes an ozone catalytic decomposition substance having a very high catalytic decomposition reaction with respect to ozone gas. Therefore, when these metal compound substances that have a catalytic decomposition action on ozone react with the ozone gas, they undergo an exothermic reaction due to the ozone decomposition, and this heat generation further promotes the activated state (excited state) of the metal compound substance, and reduces the ozone gas. Decompose catalytically.
- the ozone generated in the ozone generator 1 is catalytically converted to ozone.
- most of the ozone is decomposed and returned to oxygen gas by coming into contact with the metal compound, and high-concentration ozone cannot be extracted from the ozone generator 1.
- the ozone concentration that can be actually taken out is about 5 g / m 3 (2300 ppm) or less.
- the ozone concentration of several tens of g / m 3 generated by the discharge plasma is decomposed by ozone, and the extracted ozone concentration is about 5 g / m. 3 (2300ppm) is considered to be below.
- the ozone concentration that can be taken out is about 2 g / m 3 (933 ppm). ) -20 g / m 3 or less (9333 ppm or less), and high concentration ozone gas cannot be taken out.
- Dielectric insulators such as Al 2 O 3 , SiO 2 , Y 2 O 3 , and ZrO 2 having the semiconductor properties are known for alumina (Al 2 O 3 ), quartz glass (SiO 2 ), and the like.
- These metal compound materials having the properties of semiconductors excite this material because their band gaps are very large values of about 7.8 eV, 7.0 eV, 6.0 eV and 5.0 eV, respectively.
- vacuum ultraviolet light having a light wavelength of 250 nm or less is required, but the light wavelength wavelength range by the dielectric barrier discharge is 300 nm to 600 nm. Even if the light energy of this discharge light is irradiated onto the discharge surface, It is difficult to excite the applied metal compound to the photocatalytic state.
- Examples of the metal compound having a semiconductor property having a large band gap include Sc 2 O 3 , HfO 2 , and B 2 O 3 materials, and materials such as alumina (Al 2 O 3 ) and quartz glass (SiO 2 ). However, both are said to have a band gap of 6 eV or more, and it is difficult to excite to the photocatalytic state with the light energy generated by the dielectric barrier discharge generated in the ozone generator 1. It is a substance that cannot be expected to obtain high ozone generation efficiency.
- the catalytic dissociation reaction to oxygen atoms in the photoexcited state of the present invention is hardly performed, and the discharge Since ozone is generated only by the collision of electrons with plasma, only a very low ozone concentration can be obtained.
- the metal compound material containing Zn element generally belongs to the transparent electrode material, and in the case where the metal compound material ZnO having the semiconductor properties is applied, the visible light discharge light energy is transmitted. It is difficult to excite the resulting metal compound material into a photocatalytic state. Therefore, it was found that the ozone generation efficiency is low, the ozone concentration that can be taken out is about 6 g / m 3 (2800 ppm), and high concentration ozone gas cannot be taken out.
- the metal compound material as the transparent electrode material other than the Zn element include Ga-based, Ge-based, Cd-based, In-based, and Sn-based metal compound materials. These metallic compound materials belong to the semiconductor band gap band at a band gap of 5 eV or less, but are chemically stable substances that cannot effectively activate by absorbing the discharge light energy effectively. Therefore, these metal compound materials are not semiconductors but substances that can be called insulators.
- the first metal compound species 201 indicates a metal element range of a metal compound having a semiconductor property capable of obtaining high-concentration ozone gas in the present invention. That is, high-concentration ozone can be generated by using the metal compound material having the metal element belonging to the first metal compound species 201 as the main element in the ozone generator 1 as the metal compound layer 1d.
- the second metal compound species 202 indicates a material range of a metal compound material having a semiconductor property having an ozonolysis catalyst having a greater ability to decompose the generated ozone than the ozone generation ability, and as a result. This indicates a metal element from which high-concentration ozone cannot be extracted.
- the metal compound material having a large catalytic decomposition effect of ozone is concentrated on the metal element in the vicinity of the N orbit of the electron orbit of the outermost shell, and in particular, the metal element of the first metal compound species 201 capable of obtaining high-concentration ozone.
- V and Cr elements which overlap with the second metal compound species 202 having a large ability to decompose ozone, both ozone decomposition ability and ozone generation ability (oxygen separation ability) by discharge coexist.
- the ozone concentration that can be extracted is determined depending on which capacity is greater.
- the third metal compound species 203 shows a metal compound material range in which the band gap exceeds 4 eV. Even in the metal compound of the metal element belonging to the third metal compound species 203, high-concentration ozone is present. Cannot be removed.
- the fourth metal compound species 204 indicates the material range of the metal compound material having the properties of a transparent electrode material, and even in the metal compound materials belonging to the fourth metal compound species 204, high-concentration ozone can be extracted. No metal element.
- the fifth metal compound type species 205 is specified as a platinum group substance, and these metal oxide compounds are unique in that they have a conductive property rather than a dielectric property having a semiconductor property. These substances are said to belong to metal compounds, and even if applied to the discharge surface, these substances are substances that have a low ability to activate the substance itself by receiving the discharge light energy, and the ability to generate ozone by discharge (oxygen) The range of substances with very low separation ability.
- the dielectric barrier discharge is a discharge in which an AC high voltage is applied between the discharge electrodes 1a and 1b of the ozone generator 1 through the dielectric 1c, the discharge is uniformly charged on the surface of the dielectric 1c. This is a spark discharge that discharges electric charge into the discharge space. Since this spark discharge is a discharge that releases a limited amount to the space charged in the minute portion of the dielectric 1c surface, the discharge itself becomes an intermittent discharge of a continuous discharge for a minute time with a minute discharge diameter.
- one discharge is characterized by intermittent discharge that occurs innumerably uniformly over the entire discharge surface to which a short-life discharge of nanoseconds is applied with a discharge column having a diameter of several tens of nanometers. Since it is an electric field discharge, it has a special discharge form that can emit high energy discharge light over the entire discharge surface.
- the dielectric barrier discharge can realize a high electric field discharge as the discharge surface is made low temperature or the discharge gap length d is shortened, emits high energy discharge light, and becomes discharge light shifted to the ultraviolet light side.
- the light energy of this dielectric barrier discharge is higher than that of other discharge forms, but does not have light energy of about 4 eV or more, and the wavelength range of emitted light is 600 nm to visible light. It becomes 300 nm of ultraviolet light.
- the transition metal elements, metal elements, and metalloid elements shown in the periodic rate table of FIG. 2 are converted to metal compounds having unique properties by oxidation and nitridation, and have conductivity like metal. It can be a substance, a substance having magnetism, or a dielectric substance having semiconductor properties.
- a metal compound having a dielectric property has various band gaps and is excited to an active state by absorbing light and thermal energy. Due to the behavior of excited valence electrons and holes, There are those having properties and metal compounds that function as an insulating material by blocking light and heat energy.
- FIG. 3 schematically shows a chemical reaction caused by the contact between the discharge surface in an excited state (photocatalytic state) and the oxygen gas supplied to the ozone generator 1.
- Dielectric barrier discharge is an intermittent discharge in the order of nanoseconds, so the gas temperature is low and the discharge is a high electric field discharge. Therefore, the electrons in the plasma are accelerated to high energy, and collide with the electrons to emit light.
- the discharge light wavelength of the oxygen gas to be emitted has the ability (discharge) to emit discharge light having a visible light of 600 nm to an ultraviolet light wavelength of about 300 nm.
- FIG. 3 shows an electron coordination structure and an excited state in a solid of a solid state electron theory (band gap theory) in an excited state (photocatalytic state) of a semiconductor substance in a dielectric barrier discharge.
- FIG. 3 shows a schematic diagram of the valence potential of electrons (valence electrons) pumped into the conduction band and the (+ hole) hole potential induced in the valence band.
- the potential of each valence electron and + hole and the potential difference (band gap value) between the valence electron and + hole are specific values determined by the metal compound material.
- This characteristic value indicates a dissociation reaction into oxygen atoms by a chemical reaction between the excited metal compound material and the passing oxygen gas. In particular, this dissociation reaction is closely related to the induced + hole potential in the valence band and the chemical reaction with oxygen molecules.
- FIG. 3 schematically shows a dissociation mechanism for dissociating the oxygen gas into oxygen atoms.
- a metal compound having a semiconductor property mainly composed of a metal element belonging to the first metal compound type 201 shown in FIG. 2 is formed on the wall surface (discharge surface) of an electrode or the like in the dielectric barrier discharge space.
- the band gap of the metal compound material having semiconductor properties in the metal compound layer 1d is in the range of 2 eV to 4 eV.
- the metal compound having semiconductor properties has a band gap or more.
- the dielectric barrier discharge light (discharge light energy) having the following energy is effectively absorbed.
- the metal compound material having the semiconductor property in the range of 2 eV to 4 eV by the irradiation of the discharge light becomes an excited state (photocatalytic state), and electrons jump out of the valence band and move (pump) to the conduction band.
- the valence band where electrons have moved holes are induced and a hole potential is formed.
- the lifetime of the electrons that have moved to the conduction band ends depending on whether they move around or emit electrons to the discharge region. In other words, the electrons moved to the conduction band have a very short life and several tens (psec).
- the lifetime of the holes is relatively long, 200 to 300 (nsec).
- the excited state photocatalytic state
- the outermost shared electron of the oxygen molecule is taken away, and the oxygen molecule is physically converted into an oxygen atom.
- the reaction of the dissociated and excited semiconductor material to the ground state is promoted (oxygen adsorption and dissociation phenomenon (oxidation reaction) by the photocatalyst).
- the promotion of the adsorption and dissociation phenomenon (oxidation reaction) of oxygen by this photocatalyst is greatly contributed by the relationship between the binding potential of the outermost shared electron of the oxygen molecule and the hole potential induced by excitation in the photocatalytic state of the discharge surface. Yes.
- the binding potential of the outermost shared electron of oxygen molecules is said to be about 1.25 eV. If the hole potential of the photocatalytic state exceeds 1.25 eV, the excited metallic compound hole Has the ability to deprive the outermost shared electrons of oxygen molecules and acts to easily dissociate oxygen gas.
- a metal compound having a dissociation catalytic function for dissociating oxygen gas in contact with the discharge surface into oxygen atoms a metal compound having a photocatalytic hole potential exceeding 1.25 eV generates ozone with a high concentration.
- the generator 1 works effectively. In a photocatalytic state in which oxygen gas can be easily dissociated into oxygen atoms, if this metal compound is applied directly to the discharge surface of the ozone generator 1 as a metal compound layer 1d, an infinite number of fine discharge columns in nanoseconds are obtained. The light of the dielectric barrier discharge can be effectively applied to the applied metal compound material, and the metal compound material can be effectively excited to the photocatalytic state.
- the oxygen gas in the discharge space is converted into high-concentration oxygen atoms by a dissociation reaction, and the discharge surface of the metal compound is always in an excited state by continuously irradiating the discharge surface of the metal compound with the discharge light.
- a high concentration of oxygen atoms is produced catalytically, and oxygen atoms are generated with high efficiency.
- the ozone generation efficiency in the ozone generator 1 is also increased.
- the ozone generation efficiency of the ozone generator 1 is increased, and the high-concentration ozone gas can be taken out. Acts as follows.
- the light wavelength of the discharge light emitted by the dielectric barrier discharge is about 600 nm for visible light to about 300 nm for ultraviolet light.
- a metal compound material having a band gap of 2.0 (eV) to 4.0 (eV) When a metal compound material having a band gap of 2.0 (eV) to 4.0 (eV) is fixed as the metal compound material layer 1d on the entire discharge surface (wall surface) of the ozone generator, it has a semiconductor property.
- the metal compound material absorbs discharge energy light having energy greater than or equal to the band gap, and the metal compound material having semiconductor properties is excited to enter a photocatalytic state.
- the chemical catalytic reaction at the interface where the metal compound in the photocatalytic state and oxygen gas are in contact with each other causes a chemical catalytic reaction that dissociates the oxygen gas into atoms when the metal compound returns from the photocatalytic state to the ground state.
- the discharge light is continuously irradiated, so the metal compound fixed to the entire discharge surface immediately becomes a photocatalytic state, the oxygen dissociation reaction is continued, and the dissociation into oxygen atoms is promoted. A high concentration of oxygen atoms is produced.
- a high concentration of ozone is generated by the action in which the binding action is promoted on the metal compound layer 1d (wall M) by the three-body collision between the metal and the third substance.
- the efficiency with which ozone gas can be generated per discharge power W and per unit gas amount is evaluated as ozone generation efficiency ⁇ (mg / J). The higher the ozone generation efficiency ⁇ , the higher the ozone concentration that can be extracted.
- the chemical catalytic reaction at the interface where the metal compound in a photocatalytic state and the gas are in contact with each other decomposes the ozone gas into oxygen gas and oxygen atoms by contacting with ozone gas at a relatively high temperature.
- the thermal catalytic reaction of ozonolysis is well known.
- thermal decomposition materials for ozonolysis in particular, metal compounds having metal elements of Mn, Co, Ni, Cu, and Ag, and oxides of NOx, even at lower temperatures than other metal compound substances. It is said that the following thermal catalytic reaction formulas (2) and (3) are promoted only by contact of these substances with ozone gas, and ozone is easily decomposed catalytically at low temperatures. ing.
- Q denotes a metal element or a NOx gas heat catalyst material ozonolysis
- E L represents the low temperature heat energy.
- Patent Document 1 discloses that ozone is generated by a three-body collision reaction with gas, and as a result, high-concentration ozone can be extracted.
- a dielectric barrier discharge is generated in a high-purity oxygen gas at a low temperature, and a metal compound material having semiconductor properties is applied as a metal compound layer 1d on the entire surface of the discharge surface.
- the following chemical reaction equations (4) to (6) are expressed at the interface where oxygen gas and the metal element compound in the photocatalytic state are in contact with each other. Is promoted, high concentration oxygen atoms are generated catalytically, and ozone is generated by the equation (7) which is a three-body collision reaction equation between the generated oxygen atoms and oxygen gas.
- the amount of ozone generated is larger than the amount of ozone that catalytically decomposes ozone in contact with the metal compound surface as described above, high-concentration ozone is generated in the ozone generator 1. become.
- the catalytic reaction Rather than the catalytic reaction amount that promotes the decomposition of ozone gas by the reactions of the above formulas (2) and (3), the catalytic reaction to dissociate oxygen gas into oxygen atoms in the reactions of the above formulas (4) to (6). If the selection of a metal compound material that increases the amount of reaction or the environmental condition of ozone generation that can promote the three-body collision reaction of formula (7) can be created in the ozone generator 1, the ozone generation efficiency ⁇ (g / J ) Is increased, and high-concentration ozone gas can be generated.
- the metal compound metal element satisfying the above-described conditions is selected in the periodic table, it corresponds to the element belonging to the first metal compound species 201 of FIG. 2, and V, Cr, Nb, Mo, Ta, W, etc. and Bi It corresponds to.
- the ozone concentration that can be extracted is about 2 g / m 3 (933 ppm) to 20 g / m 3 or less (9333 ppm or less).
- This metal compound having the properties of a semiconductor has a band gap of 5 eV or more, and is hardly a substance that can be excited to the above-mentioned photocatalytic state with dielectric barrier discharge light. Therefore, the reaction of formula (4), which is the excitation reaction formula of the above substance, cannot be performed, and therefore the reaction of formula (5) and formula (6), which is a reaction formula for dissociating oxygen, cannot be performed. I understand.
- FIG. 4 shows the mechanism by which ozone is generated by the binding action of oxygen atoms and oxygen molecules dissociated in a metal compound having semiconductor properties.
- a third substance (M) metal compound layer 1d
- M metal compound layer 1d
- the gas pressure in the reaction space is preferably in the range of about 0.3 (MPa) to 0.4 (MPa) absolute pressure.
- FIG. 5 is an explanatory view showing an excited state (photocatalytic state) of a metal compound having a semiconductor property used as a constituent material of the metal compound layer 1d used in the present invention.
- the horizontal axis indicates the light absorption wavelength at which the metal compound material having semiconductor properties absorbs light and becomes excited, and this light absorption wavelength is that of the metal compound material having semiconductor properties. It is correlated with the potential width of the band gap.
- the vertical axis represents the excitation potential of the valence electrons pumped to the conduction band in the excited state of the metal compound having semiconductor properties and the excitation potential of the holes induced in the valence band.
- the potential difference between the excitation potential of the valence electrons and the excitation potential of the holes corresponds to the band gap potential.
- the lower potential indicated by the characteristic line BL-V of the band gap potential width shown for each metal compound having the properties of a semiconductor indicates the hole potential formed in the valence band
- the upper potential indicated by is the electron potential of the valence electrons pumped into the conduction band.
- This band gap potential width is an important factor of the ability to excite the metal element compound by the discharge light.
- the hole potential BL-V and the electron potential AL-V in the excited material are important factors affecting the chemical reaction.
- each metal element compound is 2.2 (eV) for chromium (Cr) BG (band gap) 301g, 2.5 (eV) for tungsten (W) BG302g, and vanadium (V) as metal elements.
- a characteristic line AL-V is obtained by connecting valence electron potentials in an excited state of each metal compound, which is an excited state, with an envelope, and a characteristic line BL-V is an oxidation of each metal compound. It is connected by an envelope of the induced + Hall potential that is in an excited state of the metal compound. Each of these potentials is formed at a potential unique to the metal compound.
- the ozone generator 1 supplied with oxygen gas forms a dielectric barrier discharge with a short gap of several tens to several hundreds ⁇ m, and the discharge surface has a cooling structure such as water cooling. Therefore, the temperature of the discharge surface is devised so as to be 20 ° C. or less.
- the electric field strength of the dielectric barrier discharge generated by the ozone generator 1 is set to be higher than the electric field strength of the discharge by the normal ozone generator 1. Therefore, the discharge light energy is also increased, and the discharge light has a wavelength width from 300 nm, which is ultraviolet light, to 600 nm, which is visible light.
- the potential position indicated by the broken line of potential 1.25 V in FIG. 5 indicates the binding potential of electrons due to the outermost electrons of oxygen molecules, and external energy having energy higher than the binding potential of these electrons is the binding of oxygen molecules. This corresponds to a threshold at which oxygen gas cannot be dissociated unless it is given to electrons.
- the high-concentration ozone generation range 3001 has a light absorption wavelength width capable of absorbing the light energy of the dielectric barrier discharge and exciting the photocatalytic state in the metal compound layer 1d applied to the ozone generator 1 And in the excited state of this metal compound substance, the range which can accelerate
- this high-concentration ozone generation range 3001 corresponds to a metal compound region in which a chemical reaction that dissociates oxygen gas is promoted by a chemical reaction between the induced hole and an oxygen molecule that contacts the interface.
- the region of the light wavelength range of the high-concentration ozone generation range 3001 is a region having a light absorption wavelength of 300 (nm) to 600 (nm), and the wavelength of the discharge light emitted by a short gap dielectric barrier discharge.
- the reason why the metal compound material applied as the metal compound layer 1d on the discharge surface greatly contributes to the ozone generation action is that the oxygen atom is dissociated by the catalytically high concentration of oxygen gas by the metal compound excited by the discharge light. It can be asserted that the concentration is increased.
- zinc BG308g which is a semiconductor material containing zinc (Zn) as an element
- Zn zinc
- the metal compound material containing Zn element generally belongs to the transparent electrode material
- the discharge light of visible light is applied in the case where the metal compound material ZnO having the semiconductor property is applied. Since energy is transmitted, it is difficult to excite the applied metallic compound material into a photocatalytic state. Therefore, the ozone generation efficiency is low, the ozone concentration that can be taken out is about 6 g / m 3 (2800 ppm), and high concentration ozone gas cannot be taken out.
- the metal compound material as the transparent electrode material other than the Zn element include Ga-based, Ge-based, Cd-based, In-based, and Sn-based metal compound materials.
- Nickel (Ni) itself is one of the catalytic substances that decompose ozone gas by obtaining low-temperature thermal energy, so even if ozone gas is generated by the ozone generator 1, it is generated. Ozone is decomposed by the ozone catalysis of NiO (metallic compound) (formulas (2) and (3), which are catalytically ozonolysis reaction formulas), and as a result, the ozone concentration that can be extracted becomes very low.
- NiO metalic compound
- metal compound materials known as ozone decomposition catalyst action at low temperatures other than nickel (Ni) element include metal compound materials of Mn, Co, Cu, and Ag. Ozone generation experiments under conditions were performed and the ozone concentration that could be taken out was measured, but it was confirmed that only a few (g / m 3 ) ozone concentration was obtained.
- the metal compound itself having semiconductor properties has the ability to decompose ozone gas catalytically by the ozonolysis reaction formulas (2) and (3) by obtaining thermal energy.
- the ozone decomposition reaction action is weak, and in particular, in an ozone generator in a low temperature state, the catalytic decomposition action of ozone gas due to heat can be suppressed low.
- FIG. 6 shows the ozone concentration characteristics (301b to 310b) that can be taken out with respect to the injection discharge energy due to the difference in the material of the metal compound having a semiconductor property in the embodiment of the present invention.
- the horizontal axis represents the injection power value W / Q value (specific power amount) per unit gas flow rate from the discharge power W injected into the ozone generator 1 and the oxygen gas flow rate Q supplied to the ozone generator 1.
- the vertical axis represents the ozone concentration value.
- the ozone concentration characteristics that can be extracted by the respective metal compound materials are the ozone concentration characteristics 301b to 310b indicated by solid lines.
- the maximum ozone concentration Cmax that can be extracted from this characteristic is the maximum ozone concentration Cmax1 to Cmax6, and the results differed greatly depending on the metal compound material.
- high concentration ozone having an injected specific power value W / Q value of about 100 (W ⁇ min / L) or more and about 200 (g / m 3 ) or more can be extracted. It was found that the specific power value W / Q value for obtaining the maximum ozone concentration Cmax is in the range of 300 (W ⁇ min / L) to 500 (W ⁇ min / L). Note that the optimum range value of the specific power value W / Q value is 300 (W ⁇ min / L) to 500 (W ⁇ min / L). It was found that there was an optimum range in the discharge power W range under the condition where the flow rate Q was constant.
- the optimum range of the discharge power W is related to the discharge area S of the discharge surface of the ozone generator. Specifically, it has been found that there is an optimum range as the value of the discharge power density W / S. It has been experimentally found that the optimum discharge power density W / S is in the range of 1 to 5 (W / cm 2 ).
- the concentration characteristics 307b to 310b are about 2 g / m 3 (933 ppm) to 20 g / m 3 or less (9333 ppm or less). As a result, a high concentration could not be obtained.
- the concentration of each tangential characteristic is increased in proportion to the specific power W / Q value injected by the gradient of the tangential characteristic (gradient characteristics 301a to 311a) at low W / Q values of each ozone concentration characteristic.
- the ozone generation capacity (ozone generation amount) that can be generated with a metal compound material having the properties of a semiconductor applied to the surface is shown, and expressed as ozone generation efficiency ⁇ (mg / J).
- the ozone generation efficiency ⁇ is 0.0307 (mg / J) in the chromium gradient characteristic 301a, tungsten
- the gradient characteristic 302a is 0.05 (mg / J)
- the molybdenum gradient characteristic 304a is 0.0377 (mg / J)
- the niobium gradient characteristic 305a is 0.0406 (mg / J)
- the bismuth gradient characteristic 313a is 0.0155 ( mg / J) shows a high value
- the extracted ozone concentration is within the high-concentration ozone generation range 2001, indicating that high-concentration ozone gas of 200 g / m 3 or more can be extracted.
- the ozone generation efficiency ⁇ is 2.78E-6 (mg / J) for the nickel concentration gradient characteristic 307a, 9.49E-5 (mg / J) for the zinc gradient characteristic 308a, and yttrium gradient.
- the characteristic 309a has only 1.59E-4 (mg / J) and the zirconium gradient characteristic 310a has 9.49E-5 (mg / J), and these ozone generation efficiencies ⁇ are low. As a result, the ozone concentration that can be taken out Became very low.
- FIG. 7 is a logarithmic display of gradients of tangential characteristics (gradient characteristics 301a to 310a and 313c) at low W / Q values in the ozone generator 1 coated with each metal compound obtained from the ozone concentration characteristics of FIG. FIG. That is, the graph is a logarithm display of the ozone generation amount (g / m 3 ) with respect to the electric power (specific power W / Q (W ⁇ min / L)) injected by the dielectric barrier discharge per unit volume of the supplied oxygen gas. Is.
- element concentration characteristics 301c to 310c and 313c show characteristics that the amount of ozone that can be generated varies greatly depending on the material of the metal compound material even when the same discharge energy is injected.
- the metal compound material having the ability to generate ozone of 0.1 g or more per cubic volume of gas with respect to the specific power W / Q is shown. If the ozone generator 1 coated on the discharge surface is used as the quality layer 1d, the ozone generator 1 capable of extracting high-concentration ozone gas can be realized.
- a metal compound group having the ability to generate 0.001 g or more ozone which is two orders of magnitude lower than the characteristic group GA is shown.
- the characteristic group GC represents a metal compound group that can generate ozone only by 0.00001 g, which is four orders of magnitude lower than the characteristic group GA.
- the three-digit numeral portions 301c to 310c and 313c are metal compound materials corresponding to the three-digit numeral portion shown in FIG.
- the discharge plasma itself has an ozone generation capability of at least about less than about 20 g / m 3 due to the acceleration of electrons in the dielectric barrier discharge and the avalanche electron collision. Yes.
- the discharge surface itself is activated by the dielectric barrier discharge, so that the activated gas compound material works (force) to generate oxygen gas.
- the concentration obtained is less than about 20 g / m 3 , and the concentration that can be taken out corresponds to the ozone concentration that is obtained almost only by the collision between the electrons of the discharge plasma itself and oxygen. Therefore, it is judged that there is almost no effect by the metal compound material applied to the discharge surface.
- the metal compound material (ZnO, Y 2 O 3 , ZrO 2 ) shown in the characteristic group GB is a substance having a property of a transparent conductive metal oxide or a substance belonging to a so-called insulator having a band gap exceeding 4 eV. It is a substance that has little influence such as activation of the discharge surface itself by the discharge light energy of the dielectric barrier discharge. Therefore, oxygen may be dissociated by collision of electrons in dielectric barrier discharge and ozone may be generated, but this metal compound itself may dissociate oxygen gas and have no ability to generate ozone. Show. As other materials, transparent conductive materials include CdO, In 2 O 3 and SnO 2 in addition to ZnO.
- Substances belonging to so-called insulators whose band gap exceeds 4 eV are B 2 O 3 , alumina Al 2 O 3 and quartz SiO 2 , and it is said that any substance can extract only an ozone concentration of 20 g / m 3 or less. Yes.
- high-concentration ozone can be obtained according to Patent Document 3 of the prior art when a material such as the characteristic group GA is mixed with the above-mentioned alumina or quartz glass by a sintering means or the like.
- the concentration obtained is about several g / m 3 , and the concentration that can be taken out is reduced to about 1/10 of the concentration obtained by the discharge plasma itself.
- the applied metal compound material has no ability to generate ozone, and conversely, it is determined that the effect of decomposing ozone generated by the discharge plasma by the catalytic decomposition reaction on the surface of the metal compound material is increased.
- the metal compound material (NiO) shown in this characteristic group GC is a substance that decomposes ozone gas catalytically with low-temperature heat energy, so that the discharge surface itself is activated by the discharge light energy of the dielectric barrier discharge.
- the ozone gas itself that has generated ozone by dissociating oxygen due to the collision of electrons in the dielectric barrier discharge is also contacted with this metal compound, thereby catalytically decomposing ozone.
- the substance group which has the ability to let it be shown is shown. Therefore, as shown in FIG. 7, the ozone generation amount of the characteristic group GC is 0.00001 g / m 3 , which is two orders of magnitude lower than the ozone generation amount of the characteristic group GB.
- substances that catalytically decompose ozone gas with these low-temperature thermal energy include substances such as MnO 3 , Co 2 O 3 , Cu 2 O, and Ag 2 O.
- an ozone generator capable of extracting high-concentration ozone of 200 g / m 3 or more requires at least an ozone generation efficiency ⁇ of 0.01 (mg / J) or more, and a semiconductor coated on the discharge surface for that purpose. It has been found that the metal compound material having the following properties is required to contain V, Cr, Nb, Mo, Ta, W elements and Bi elements.
- FIG. 8 corresponds to the characteristic number and product number of the metal compound material of FIGS. 7 and 6, and the metal compound material having specific semiconductor properties in the present invention is fixed to the discharge surface as the metal compound layer 1d.
- the physical property characteristics of the oxide metal material in the ozone generator 1 and the ozone generation efficiency ⁇ and the maximum ozone generation concentration Cmax in the present invention are summarized in a tabular list.
- the material product numbers 301 to 306 and 313 indicate the first metal compound species 201 of the metal compound material from which the high-concentration ozone of the present invention can be extracted, and in the element periodic table, materials corresponding to group 5 and group 6 element metals
- the band gap is in the range of 2.0 to 4.0 (eV)
- the hole potential of the valence band formed in the excited state is greater than the binding potential (1.25 (eV)) of the oxygen molecule.
- a material having a large potential is possible.
- ozone generation efficiency ⁇ of the metal compound of vanadium 303 (V 2 O 5 ) and the metal compound of bismuth 313 (Bi 2 O 3 ) / J), 0.0155 (mg / J), the ozone compounding efficiency ⁇ of tungsten 302 metal compound (WO 3 ), molybdenum 304 metal compound (MoO 3 ), and niobium 305 metal compound (NbO 5 ) Is 0.05 (mg / J), 0.0406 (mg / J), 0.0377 (mg / J), and the maximum ozone concentration that can be taken out in the ozone generator 1 is 200 (g / m 3 ).
- the maximum ozone concentration Cmax that can be extracted corresponding to the value of the ozone generation efficiency is high, exceeding the concentration of about 500 (g / m 3 ).
- the metal compound material (NiO) of nickel 307 can only obtain an ozone generation efficiency ⁇ of 2.78E-6 (mg / J), and the maximum ozone concentration Cmax that can be taken out is only 0.2 (g / m 3 ). It is a substance that has no ozone generating ability.
- This metal compound material of nickel 307 not only has no ozone generation ability, but also catalytically decomposes and dissociates by contacting ozone gas of about several tens of g / m 3 generated by electron collision of dielectric barrier discharge. Therefore, the maximum ozone concentration Cmax that can be taken out is reduced to an ozone concentration of 0.2 (g / m 3 ), which is about 10%.
- the metal compound (ZnO) of zinc 308 has an ozone generation efficiency ⁇ of 9.49E-5 (mg / J), and this material does not have a catalytic ozone generation ability, but is a dielectric barrier discharge.
- the maximum ozone concentration Cmax that can be taken out with respect to the ozone concentration generated by electron impact of several tens of g / m 3 is about 6 (g / m 3 ), so that the generated ozone gas can be decomposed and dissociated catalytically. It is not a very large substance.
- the metal compound materials (Y 2 O 3 , ZrO 2 , Al 2 O 3 , SiO 2 ) having the material product numbers 309 to 312 generate 9.49E-5 to 1.59E-4 (mg / J) of ozone.
- the efficiency is only ⁇ , and this material has no catalytic ozone generation ability, and the maximum ozone concentration Cmax that can be extracted with respect to the ozone concentration generated by electron collision of dielectric barrier discharge is about several tens of g / m 3. Since it is 6 to 20 (g / m 3 ) or less, it can be said that the generated ozone gas is a substance that has no catalytic decomposition and dissociation ability and does not exhibit a chemical reaction.
- the metal compound materials of the material product numbers 301 to 306 and 313 have a catalytic ozone generating ability depending on the discharge surface material, and the first metal compound to which the substance capable of generating high concentration ozone of the present invention belongs.
- the metal compound material of nickel 307 corresponds to the second metal compound material species 202 which is a substance that catalytically decomposes ozone by the discharge surface material.
- the metal compound material of zinc 308 is a third metal compound that is a substance that does not transmit and absorb light with respect to the discharge light and does not have the action of catalytically generating or decomposing ozone by the discharge surface material. It corresponds to the quality species 203.
- the metal compound materials of material numbers 309 to 312 are substances whose band gap exceeds 4 eV, and have no ability to absorb light against discharge light, and ozone is generated and decomposed catalytically by the discharge surface material. It is a substance that does not have an action to be applied and corresponds to the fourth metal compound species 204. As described above, the metal compound materials having the material product numbers 301 to 313 can be classified into the four metal compound material types 201 to 204.
- the substance capable of generating high-concentration ozone of the present invention (first metal compound species 201) is not a conductor, but within a band gap range of 2.0 to 4.0 (eV), and is a dielectric barrier discharge. And the photocatalytic state can be activated by absorbing light energy, and in the photocatalytic state, the potential of the hole induced in the valence band is higher than the binding potential of oxygen molecules (1.25 (eV)). It is a metal compound having the properties of a semiconductor. Therefore, holes induced in the substance have a force to pull electrons from the outside, and the force of the holes acts to dissociate oxygen by taking away the shared electrons in the outer orbit of oxygen gas.
- chromium (Cr), vanadium (V), tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta) and bismuth (Bi) are all oxygen.
- Many atoms are generated, and as a result, high-concentration ozone gas is generated from the ozone generator 1 and high-concentration ozone gas can be taken out. It was found that the ozone generation efficiency ⁇ calculated from the ozone concentration characteristics of these substances exceeded about 0.01 (mg / J).
- the metal compound belonging to the first metal compound species 201 is not a substance that promotes ozonolysis.
- the metal compound material containing chromium (Cr), vanadium (V), tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta) and bismuth (Bi) as main metal elements is as follows. The following four conditions are satisfied.
- the band gap of the metal compound layer 1d is in the range of 2.0 to 4.0 [eV], (4) The hole potential of the valence band formed in the excited state of the metal compound layer 1d is larger than the binding potential (1.25 (eV)) of oxygen molecules.
- the elements corresponding to Group 5 and Group 6 were the highest in the metal oxide compound elemental metal from which high-concentration ozone gas was obtained.
- the metal compound material having semiconductor properties mainly composed of group 5 and group 6 metal elements has two electrons in the outermost orbital in each of the arrangement of electrons of the metal elements. Since the number is three, when the external energy such as discharge light is absorbed, the electrons in the outermost orbit can be easily pumped (excited) to the conduction band of the semiconductor material.
- the number of electrons in the outermost orbital shell is 1 or 2 in the group 3 to group 4 or group 14 to group 15 metal element or metalloid element.
- the electron in the outermost orbital is used to electronically combine two elements (for example, a metal element and an oxygen element) to form a metal compound material.
- two elements for example, a metal element and an oxygen element
- metal compounds of group 3 to group 4 and group 14 to group 15 metal elements become chemically stable insulators with a large band gap, and ozone. It tends to be a metal compound that is unsuitable for formation.
- Metal elements other than Group 3 to Group 4 or Group 14 to Group 15 are formed into electronically bonded metal compounds having surplus electrons, so that they are excited or non-excited by external energy. It tends to become a metal compound having the properties of a metal compound having the properties of a conductor that is always in an excited state.
- the ozone generator 1 that generates high-concentration ozone needs to be capable of catalytically dissociating oxygen gas
- a metal compound having semiconductor properties is particularly effective. Further, in the metal compound having the properties of a semiconductor, in particular, it can be easily activated to the photocatalytic state by the discharge light energy, and in the photocatalytic state, an oxygen electronic bond through which the induced hole potential passes. If the metal compound is larger than the potential, it can be said that the induced holes are suitable for promoting the chemical reaction of oxygen dissociation by depriving oxygen gas electrons.
- the ozone concentration characteristics of the ozone generator 1 are measured, and the ozone generation efficiency ⁇ is measured. It was confirmed that the ozone generation efficiency was increased by about 5%, and the ozone concentration that could be extracted could be increased by about 5%.
- the metal compound substance that becomes the photocatalytic substance is fixed to the discharge surface as the metal compound layer 1d, and the photocatalytic effect is increased to generate high-concentration ozone.
- Increasing the surface area of the fixed metal compound by reducing the crystal structure and particle size of the metal compound is an effective means.
- the crystal structure peculiar to the metal compound to be fixed has the effect of increasing the surface area of the discharge surface, which increases the ozone generation efficiency ⁇ and increases the concentration of ozone that can be taken out.
- the crystal structure peculiar to the metal compound is a crystal structure having a body-centered cubic structure
- the crystal of the metal compound surface grown on the discharge surface becomes the texture structure surface.
- this texture structure surface is obtained, it is said that the discharge surface irradiated with the discharge light can effectively absorb light by reducing the surface reflection loss and the light confinement effect, and is a means for increasing the ozone generation efficiency ⁇ .
- the ozone generation efficiency ⁇ in the metal compound material fixed as the metal compound layer 1d on the discharge surface is generated by dissociating oxygen gas in the photocatalytic state of the applied substance to generate ozone. It is a value determined by the difference between the ability to dissociate and the ability to dissociate and decompose ozone gas catalytically.
- the substance belonging to the first metal compound species 201 shown in the periodic table of FIG. 2 has a greater ability to generate ozone, in particular, than the ozone decomposition ability.
- Mn, Co, Ni, Cu, and Ag based metal compound materials are easily activated (thermally excited) with low-temperature thermal energy, and this thermally excited substance is more than the ability to dissociate oxygen. It can be said that the substance has a high ability to catalytically decompose ozone gas.
- an element whose outermost electron orbit is N orbital an element belonging to the second metal compound species 202 is activated (thermal excitation) by applying high-temperature thermal energy.
- thermal excitation the ability to catalytically decompose ozone gas is higher than the ability to dissociate oxygen.
- the outermost electron orbit increases from the N orbit to the O orbit and the P orbit, thermal excitation due to high-temperature thermal energy is less likely to occur, and the ability to decompose ozone gas is weakened.
- the ozone generation efficiency ⁇ is a value determined by the difference between the ability to dissociate oxygen gas and generate ozone and the ability to catalytically dissociate and decompose ozone gas in the photocatalytic state of the applied substance.
- the ozone concentration that can be taken out from the ozone generator 1 is the ozone generation efficiency ⁇ , the ozone generation amount (tangent line La) generated by the specific power W / Q injected by the discharge per unit volume, and the ozone generator.
- Ozone decomposition rate ⁇ the rate of decomposing the amount of ozone
- gas velocity flow rate
- discharge gap length d discharge gap length
- gas conditions gas temperature, gas pressure, etc. It is determined by the synthesis of the degree of decrease in density (tangent Lc).
- the first element includes selection of the material of the metal compound that increases the ozone generation efficiency ⁇ , and the surface area of the discharge surface is increased.
- the second element includes selection of the material of the metal compound that increases the ozone generation efficiency ⁇ , and the surface area of the discharge surface is increased.
- the second element includes selection of the material of the metal compound that increases the ozone generation efficiency ⁇ , and the surface area of the discharge surface is increased.
- the second element includes selection of the material of the metal compound that increases the ozone generation efficiency ⁇ , and the surface area of the discharge surface is increased.
- the second element third feature
- the structure of the ozone generator 1 itself is determined by the structural design of the ozone generator 1 and thus cannot be defined.
- the gas temperature which is a gas condition, depends on the specific power W / Q to
- a metal compound a metal that adheres to a discharge surface that generates high-concentration ozone gas and can extract high-concentration ozone in a metal oxide compound in which two kinds of elements including metal elements are electronically bonded.
- the compound material has been described, it is only necessary to satisfy the above-described four conditions, which is a metal compound in which three kinds of elements including the main metal element are electronically bonded or a metal compound material other than oxidation. That is, (1) not a substance that promotes ozonolysis, (2) is not a conductor and (3) a metal compound having a semiconductor property has a band gap of 2.0 to 4.0 (eV).
- semiconductor material (4) ⁇ ⁇ Exciting metal compound material with the above semiconductor properties (hereinafter sometimes abbreviated as “semiconductor material”) by applying energy (external energy) from outside. If the semiconducting material is in a state (photocatalytic state) and has a potential higher than the binding potential (1.25 (eV)) of the oxygen molecule, the hole potential of the valence band formed in the excited state is excited. Thus, the oxygen gas can be catalytically dissociated by the induced holes to generate high-concentration ozone gas, and high-concentration ozone can be extracted.
- reaction (1) and reaction (2) are the ozone generation reactions resulting from the activation of the metal compound material applied as the metal compound layer 1d on the discharge surface. .
- Reaction (1) is “a reaction that excites the discharge surface with discharge light + an oxygen-catalyzed dissociation reaction due to contact between the oxygen gas and the excited metal”
- reaction (2) is a “three-body collision between an oxygen atom and an oxygen molecule. The ozone generation reaction.
- the reaction time of the reaction (1) is completed in a very short time on the order of ⁇ 10 ⁇ s from the emission of the discharge light (discharge start), and the ozone of the reaction (2)
- ozone gas is generated if it takes about 100 ⁇ s at most after the oxygen atom is generated in the reaction (1). That is, ozone gas is generated in the ozone generator 1 in a series of ozone generation reactions by the reaction (1) and the reaction (2) if it is about several hundreds ⁇ s after the occurrence of discharge with the predetermined power applied.
- the generated ozone gas in order to take out the generated ozone gas, it has a gas passage time determined by the gas flow rate Q and the discharge space volume V.
- This gas passage time usually takes 10 ms to 200 ms, and this time is very long, 1000 times to 20000 times as compared with the ozone generation reaction time. Therefore, the ozone generated during this gas passage time is exposed to the gas temperature Tg heated by the discharge, and is consumed to decompose the generated ozone.
- the generated ozone has an ozone decomposition rate ⁇ determined by the gas passage time in the ozone generator 1 and the gas temperature Tg, and the generated ozone is ozone decomposed according to the ozone decomposition rate ⁇ .
- the generated ozone is ozone decomposed according to the ozone decomposition rate ⁇ .
- the gas temperature Tg in the ozone generator 1 that influences the ozone decomposition rate ⁇ at the time of ozone extraction increases as the specific power W / Q to be input increases, and the gas temperature Tg with respect to the electrodes 1a and 1b that cool the ozone generator 1 from the outside is increased.
- the lower the electrode cooling temperature T the lower the temperature. That is, if the specific power W / Q to be input is constant, the effect of suppressing the ozone decomposition rate ⁇ increases as the electrode cooling temperature T decreases, and the amount of ozone (ozone concentration) that can be extracted increases.
- the gas passage time that affects the ozone decomposition rate ⁇ at the time of another ozone extraction depends on the gas flow rate Q, the discharge space volume V, and the gas pressure P.
- the discharge space volume V increases, the gas passage time increases, the ozone decomposition rate ⁇ increases, and the ozone concentration that can be extracted tends to decrease.
- This discharge space volume V depends on the discharge gap length d of the generator, and generally, as the discharge gap length d increases, the ozone decomposition rate ⁇ increases and the ozone concentration that can be extracted tends to decrease.
- the discharge gap length d is caused by the gas temperature increase due to the specific power W / Q and the cooling ability of the electrode surface depending on the discharge volume, if the discharge gap length d is made extremely short, the ozone decomposition is reversed.
- the discharge gap length d has an optimum range because the ozone concentration that can be extracted is increased by increasing the rate ⁇ .
- FIG. 11 is a characteristic diagram in which the ozone decomposition rate with respect to the discharge gap length d and the electrode cooling temperature T in the ozone generator in one embodiment was evaluated.
- the ozone decomposition rate tends to be suppressed to the lowest at the discharge gap length d of 70 ⁇ m. If the discharge gap length d is longer than 70 ⁇ m, the time for the generated ozone gas to pass through the discharge space becomes longer, and the time for passage becomes longer, so that the ozone decomposition rate becomes higher. When the discharge gap length d is shorter than 70 ⁇ m, the time for passing through the discharge space is shortened, but the wall of the discharge space is narrowed. Therefore, the ozone gas generated tends to decompose due to contact with the wall and the ozone decomposition rate tends to increase. become.
- the lower the electrode cooling temperature T the lower the proportional ozone decomposition rate.
- the ozone generator 1 of the present embodiment when the ozone decomposition rate is evaluated by an ozone generator in order to take out high-concentration ozone gas, the ozone generator 1 can be used unless the ozone decomposition rate is suppressed to at least 80% or less. During the time in which ozone generated in the above passes through the discharge space, it is almost consumed by ozone decomposition at the gas temperature, and high-concentration ozone gas cannot be taken out.
- the electrode cooling temperature T of the electrodes 1a and 1b of the ozone generator 1 needs to be 40 ° C. or less from FIG. 11, but 20 ° C. or less in order to stably extract higher-concentration ozone gas. It is desirable to make it.
- the upper limit pressure is determined by the time for passing through the discharge space, similarly to the discharge gap length d.
- the lower limit of the gas pressure P is determined by the pressure that enhances the three-body collision reaction that contributes to ozone generation. Therefore, it is necessary to set the gas pressure in the discharge space in the range of 0.2 MPa to 0.4 MPa as an absolute pressure.
- the ozone concentration that can be taken out from the ozone generator 1 is the ozone generation efficiency ⁇ and the ozone generation amount (characteristic indicated by the tangent line La) generated by the specific power W / Q injected by the discharge per unit volume.
- the ratio (ozone decomposition rate ⁇ ) of decomposing the amount of generated ozone determined by the structure of the ozone generator 1 itself (gas velocity (flow rate Q), discharge gap length d, etc.) and gas conditions (gas temperature, gas pressure P, etc.)
- the increase is determined by the synthesis of the degree of decrease in ozone concentration that can be extracted (characteristic indicated by the tangent Lc).
- the first factor is the selection of the material of the metal compound with increased ozone generation efficiency ⁇ , the surface area of the discharge surface being increased, and the specific power W / Q to be injected.
- the second factor it is necessary to impose ozone decomposition suppression requirements on the ozone generator 1 and reduce the decomposition amount of the generated ozone amount determined by the structure and gas conditions of the ozone generator 1 itself.
- the structure of the ozone generator 1 itself is determined by the structural design of the ozone generator 1 and thus cannot be defined.
- the gas temperature which is a gas condition, depends on the specific power W / Q to be injected. The factor that decomposes the generated ozone gas with a high gas temperature is very large.
- the gas temperature in the discharge space is very high as an element that decomposes ozone gas.
- the gas temperature exceeds 20 ° C, the ozone decomposition rate becomes very high, and high-concentration ozone gas. It became clear from experiment that it became impossible to take out.
- the ozone decomposition rate can be suppressed by cooling the gas temperature through the electrodes 1a and 1b constituting the discharge surface.
- the structure allows the coolant to flow through the electrodes on the discharge surface and the discharge surfaces of the electrodes 1a and 1b can always be cooled to 20 ° C. or lower, the gas temperature in the discharge space can be kept low by heat transfer, and the ozone decomposition rate is improved.
- the ozone concentration tends to be increased.
- FIG. 9 is a characteristic diagram showing the maximum ozone concentration value Cmax that can be extracted with respect to the ozone generation efficiency ⁇ from the list of ozone generation efficiency ⁇ and the ozone concentration that can be extracted for each substance in FIG.
- concentration Co shows the threshold value of the high density
- ⁇ o indicates the minimum ozone generation efficiency ⁇ for obtaining high-concentration ozone above the threshold value, and indicates a limit value at which high concentration cannot be obtained as ozone that can be extracted unless the ozone generation efficiency ⁇ is higher than this. Yes. This value was approximately 0.01 (mg / J).
- Characteristics 601 to 604 indicate the maximum ozone concentration characteristics that can be taken out with respect to the ozone generation efficiency ⁇ by the ozone generator 1 of the present embodiment.
- Each of the maximum ozone concentration characteristics 601 to 604 represents the ozone generator 1. Shows the characteristics when the discharge surface temperature is constant by cooling to 40 ° C., 20 ° C., 0 ° C., and ⁇ 20 ° C. Even if the ozone generation efficiency ⁇ is the same, the discharge surface temperature can be extracted as the discharge surface temperature is lowered. It shows that the ozone concentration is increased. That is, this is because the gas temperature is lowered and the ozone decomposition rate is reduced by cooling the discharge surface.
- the high-concentration ozone generation possible range 3001 indicates a range where high-concentration ozone can be extracted, and the ozone generation efficiency ⁇ range in which high-concentration ozone can be obtained from the high-concentration ozone generation range 3001 and the ozone decomposition rate suppression range. Is defined.
- the maximum ozone concentration characteristic 601 even when a metal compound having a high ozone generation efficiency ⁇ is fixed to the discharge surface, if the ozone decomposition rate increases, high concentration ozone cannot be extracted. Shows that if the cooling temperature of the discharge surface (electrode cooling temperature T of the electrodes 1a and 1b) is set to a temperature exceeding 20 ° C., the amount of ozone decomposition increases and high-concentration ozone cannot be extracted.
- generation range 3002 has shown the range which high concentration ozone cannot take out.
- the oxygen purity is a high purity of 99.99 (%) or more, and 3 (L / Min)
- a raw material gas having a large flow rate is supplied to the ozone generator 1, and the ozone generator 1 has a dielectric barrier discharge space (discharge) as energy given to oxygen gas from the outside in the space through which the gas passes.
- a predetermined discharge energy W is supplied to the ozone generator 1 by forming a space.
- the discharge gap length d of the space (discharge space) through which this ozone generator 1 gas passes, and the discharge surface through which it passes should be a predetermined discharge area S or more.
- the discharge gap length d is in the range of 0.02 mm to 0.12 mm, and the gas pressure in the discharge space is an absolute pressure as ozone decomposition suppression requirements.
- the electrode cooling temperature T is 20 ° C. or lower. is there.
- electrodes 1a and 1b facing each other and a dielectric 1c formed on high-voltage electrode 1a are provided, and between dielectric 1c and ground electrode 1b.
- the ozone generator 1 further includes a metal (element) compound layer 1d on the surface (discharge surface) of each of the ground electrode 1b and the dielectric 1c.
- the metal compound substance in the metal compound substance layer 1d is the condition (1) “not a substance that promotes ozonolysis”, condition (2) “not a conductor”, condition (3) “the metal compound substance layer 1d Band gap is in the range of 2.0 to 4.0 (eV) ”and condition (4)“ The hole potential of the valence band formed in the excited state of the metal compound layer 1d is the binding potential of oxygen molecules ( Greater than 1.25 (eV)) ”.
- the ozone generation method of the present embodiment using the ozone generator 1 executes the following steps (a) to (c) ⁇ .
- Step (a) IV is a step of supplying a source gas mainly composed of oxygen gas into the discharge space.
- step (b) external energy is applied by the ozone power source 2 to generate a dielectric barrier discharge in the discharge space of the ozone generator 1, and the metal compound layer 1d is made into a photocatalytic state by the discharge light.
- step (b) external energy is applied by the ozone power source 2 to generate a dielectric barrier discharge in the discharge space of the ozone generator 1, and the metal compound layer 1d is made into a photocatalytic state by the discharge light.
- This is a step of generating oxygen atoms from the source gas supplied in step (a).
- Step (c) IV is a step in which ozone is generated by a collision chemical reaction between the oxygen atoms generated in step (b) IV and the oxygen gas contained in the raw material gas.
- step (d) IV the above steps (a) to (c) IV are executed in an environment where various ozone decomposition suppression requirements for suppressing the ozone decomposition amount are imposed on the ozone generator 1.
- the ozone generation method of the present embodiment has the effect that the ozone generation efficiency ⁇ is set to a predetermined value of 0.01 mg / J or more in the ozone generator 1 by executing steps (a) to (c) ⁇ as described above. There exists an effect which can take out high concentration ozone gas from ozone generator 1.
- the ozone generation method of the present embodiment sets the ozone generator 1 in the environment where the requirements for suppressing ozone decomposition are imposed in step (d), so that the ozone generated in step (c) By suppressing the phenomenon of decomposition, high-concentration ozone gas can be taken out.
- the metal oxide layer (Bi 2 O 3 3 ) is employed as the metal compound layer 1d using bismuth as an element, or the metal compound layer 1d in which the three elements are combined is formed, the metal compound layer 1d
- the metal compound layer 1d when the above conditions (1) to (4) are satisfied, the ozone gas having the concentration can be taken out.
- the present embodiment is characterized in that the particle diameter of the metal compound constituting the metal compound layer 1d is made a powder of 0.1 to 50 ( ⁇ m).
- the present embodiment has the above characteristics, the surface area of the metal compound excited in the metal compound layer 1d can be increased, the ozone generation efficiency ⁇ can be further increased, and the concentration of ozone that can be taken out can be easily increased. . As a result, the electric power injected into the ozone generator 1 can be further reduced, and the ozone generator 1 can be configured to be small.
- the main metal elements contained in the metal compound layer 1d include metal elements having an electron configuration belonging to Groups 5 and 6 in the periodic table.
- the metal compound includes a metal oxide layer (CrO 3 , WO 3 , V 2 O 5 , MoO 3 , NbO 5 , Ta 2 O 5 ).
- the present embodiment Since the present embodiment has the above characteristics, electrons in the outermost electron orbit of the main metal element of the metal compound layer 1d receive light energy due to the dielectric barrier discharge and easily shift to the valence band. This makes it easy to excite the metal compound layer 1d into the photocatalytic state, and has an effect of selectively and catalytically dissociating oxygen gas passing through the discharge space.
- the ozone generation method of the present embodiment is characterized in that the metal compound layer 1d has a body-centered cubic structure as its crystal structure.
- the surface of the metal compound layer 1d on the discharge space side has a regular textured structure surface, so that the metal that has been irradiated with the discharge light of the dielectric barrier discharge generated in the discharge space.
- the ozone generation efficiency ⁇ is improved.
- the metal compound layer 1d can be fixed to the fixing target portion which is the discharge surface (at least one surface) of the ground electrode 1b and the dielectric 1c by coating, spraying, baking, and surface bonding.
- the effect of increasing the ozone generation efficiency ⁇ can be brought about by fixing the metal compound layer 1d to the fixing target portion using the fixing method described above.
- the ozone generation method of the present embodiment is characterized in that the following requirements (d1) to (d3) are satisfied as the ozone decomposition suppression requirements imposed on the ozone generator 1 in the step (d). Yes.
- the requirement (d1) is “use high-purity oxygen gas with an oxygen gas purity of 99.99 (%) as the raw material gas”
- the requirement (d2) is “the gas flow rate at the time of supplying the raw material gas is 3
- the requirement (d3) is “the discharge power density in the dielectric barrier discharge is within the range of 1 to 5 (W / cm 2 ) and the specific power W / Q value”. Within the range of 300 to 500 (W ⁇ min / L) ”.
- high-concentration ozone can be generated in the ozone generator 1, and the gas temperature generated by the injection energy per unit volume by discharge can be suppressed.
- the ozone decomposition rate at 80 ° C. can be suppressed to 80% or less, and the ozone concentration that can be taken out can be generated at a concentration of 200 (g / m 3 ) or more.
- the ozone generation method of the present embodiment is the requirement (d4) “electrodes 1a and 1b in the ozone generator 1” as the ozone decomposition suppression requirement imposed on the ozone generator 1 in step (d).
- the temperature (electrode cooling temperature T) is set to 20 (° C.) or lower ”.
- the raw material gas passing through the discharge space (on the discharge surface) can be cooled to a relatively low temperature, and an effect of suppressing the thermal decomposition rate of the generated ozone is generated, and the ozone concentration that can be taken out As a result, the amount of ozone generated can be increased, the electric power injected into the ozone generator 1 can be made smaller, and the ozone generator 1 can be made smaller.
- the ozone generation method of this embodiment satisfies the following requirements (d5) and (d6) as the ozone decomposition suppression requirements imposed on the ozone generator 1 in step (d). It is said.
- the requirement (d5) is that “the discharge gap length d of the discharge space of the ozone generator 1 is set within the range of 0.02 to 0.12 (mm)”, and the requirement (d6)
- the gas pressure is set in the range of 0.2 to 0.4 (MPa) in absolute pressure.
- this embodiment Since this embodiment has the above characteristics and can shorten the extraction time of ozone gas generated in the discharge space, the effect of suppressing the thermal decomposition rate of generated ozone is generated, and the ozone concentration that can be extracted As a result, the amount of ozone generated can be increased, the electric power injected into the ozone generator 1 can be made smaller, and the ozone generator 1 can be made smaller.
- the dielectric 1c is provided on the high-voltage electrode 1a.
- the dielectric 1c may be provided on the ground electrode 1b.
- the ozone generator 1 is exemplified by a nitrogen addition-less ozone generator that supplies oxygen (raw material gas) with a purity of 99.99 (%) or more, but is not limited thereto, and includes nitrogen.
- the present invention can also be applied to an ozone generator that supplies oxygen gas as a raw material gas.
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Abstract
Description
(全体概要)
この発明による実施の形態の全体概要を図1~図11を参照して説明する。
以下、図1を参照して、(窒素添加レス・)オゾン発生器1の作用、動作、放電のエネルギー注入の説明し、オゾン発生器1内におけるオゾン生成効率とオゾン分解率の説明をし、オゾン発生器1から取り出せるオゾン濃度について理論的に説明する。
まず、3L/min以上の大流量で、純度99.99(%)以上の高純度の酸素ガス994を供給したオゾン発生器1の放電面(接地電極1b及び誘電体1cの表面)の全面に周期率表に示された数々の金属元素材料を金属化合物質層1dとして塗布し、取り出せるオゾン濃度を測定した。その結果、放電面の全面に塗布した金属化合物質層1dの材料が金属のような導電体物質の状態では、いずれの金属元素の材料においても、取り出せる最大オゾン濃度は、100g/m3以下であり、200g/m3以上の高濃度オゾンを取り出すことはできなかった。
誘電体バリア放電は、オゾン発生器1における放電電極1a,1b間に誘電体1cを介した放電空間に交流高電圧を印加させる放電であるため、放電は、誘電体1c面に均一に帯電した電荷を放電空間に放電させる火花放電である。この火花放電は、誘電体1c面の微小部に帯電電荷した空間に限定的を放出させる放電であるため、放電自身は、微小放電径で微小時間の継続放電の間欠放電となる。そのため、1つの放電は数十ナノ径の放電柱でナノ秒の短寿命放電が印加した放電面全面に均一に無数発生する間欠放電になっているのが特徴で、この放電は、非常に高電界な放電であるため、高エネルギーな放電光を放電面全面に発光できる特殊な放電形態を有するものとなっている。
つぎに、放電プラズマによって光触媒状態に励起した、金属化合物質層1dにおける放電面材料と酸素ガス解離メカニズムについて説明する。図3は、励起状態(光触媒状態)になった放電面とオゾン発生器1に供給した酸素ガスとの接触による化学反応を模式図で示している。
次に生成した高濃度の酸素原子からオゾン発生器1内で、オゾンガスの生成までのメカニズムについて説明する。
図5は、本発明に用いる金属化合物質層1dの構成材料に用いる半導体の性質を有した金属化合物質の励起状態(光触媒状態)を示す説明図である。同図において、横軸は、半導体の性質を有した金属化合物質が光を吸収して励起状態になる得る光吸収波長を示し、この光吸収波長は、半導体の性質を有した金属化合物質のバンドギャップの電位幅と相関関係になっている。また、縦軸は、半導体の性質を有した金属化合物質が励起状態での伝導帯へのポンピングした価電子の励起電位と価電子帯で誘起したホールの励起電位を示す。この価電子の励起電位とホールの励起電位の電位差がバンドギャップ電位に相当する。図5において、半導体の性質を有した各金属化合物質で示したバンドギャップ電位幅の特性線BL-Vで示す下の電位が価電子帯に形成されるホール電位を示し、特性線AL-Vで示す上の電位が伝導帯にポンピングした価電子の電子電位を示す。
(2) 導電体ではなく、
(3) 金属化合物質層1dのバンドギャップが2.0~4.0[eV]の範囲であり、
(4) 金属化合物質層1dの励起状態において形成される価電子帯部のホール電位が酸素分子の結合電位(1.25(eV))より大きい。
周期率表の第5族、第6族に属する電子配置のオゾン生成の有効性について説明する。
同時に価電子帯部にも1.25eV以上の+ホールが形成される酸化金属物質となり、光触媒状態になったバンドギャップの電位範囲とオゾン発生器1の誘電体バリア放電の光エネルギーと良く合っており、効率良く放電光を吸収することができる。このバンドギャップ範囲に加え、励起した半導体物質のホールの電位が放電空間に放電面と接触している酸素ガスの分解させる電位より高くなっていることで、化学反応が促進でき、酸素を触媒的に分解することで、高濃度の酸素原子が生成し、高濃度のオゾンガスを生成でき、結果として、高濃度のオゾンガスを取り出せることができる。
放電面に塗布する金属化合物質層1dの粒子径の優位性について説明する。
オゾン発生器1に金属化合物質層1dとして固着させる金属化合物質の表面積を高める手段としては、金属化合物質自身の粒径を小さいものにするだけでなく、放電面を微細な凹凸構造にして放電面の表面積を高めることも、オゾン発生効率ηを高めることになり、取り出せるオゾン濃度をアップさせる。
以上、放電面材料として、触媒的に酸素ガスを解離できる光触媒状態になり得る物質について述べてきたが、放電面に固着させる金属化合物質は、オゾンガスを触媒的に解離分解できる物質でもある。そのため、放電面に固着させる金属化合物質は、オゾン生成させる能力とオゾンガスを分解させる能力の2つの作用を共存している物質と言える。
オゾン生成効率ηは、塗布した物質の光触媒状態で、酸素ガスを解離してオゾンを生成する能力とオゾンガスを触媒的に解離分解させる能力との差で決まる値であると述べた。オゾン発生器1から取り出せるオゾン濃度は、図10で示すように、このオゾン生成効率ηと単位体積当たりの放電によって注入される比電力W/Qできまるオゾン生成量(接線La)とオゾン発生器1自身の構造(ガス速度(流量)、放電ギャップ長d等)やガス条件(ガス温度、ガス圧力等)によって決まる生成したオゾン量を分解する割合(オゾン分解率σ)の増加で、取り出せるオゾン濃度の低下度合(接線Lc)の合成で決まる。
オゾン発生器1から取り出せるオゾン濃度を高めるには、オゾン発生器1内で、オゾン生成効率ηを高め、生成するオゾン量を高めるとともに、生成したオゾン量に対して、オゾン分解率σを抑制するオゾン分解抑制要件をオゾン発生器1に課すべく、放電中のガス温度等のオゾン発生器1の構造もしくは設定手段を最適条件範囲にすることが必要である。
本実施の形態では、互いに対向した電極1a及び1b(第1及び第2の電極)と、高圧電極1a上に形成された誘電体1cとを有し、誘電体1cと接地電極1bとの間に放電空間を有するオゾン発生器1を用いてオゾンを発生させるオゾン発生方法を述べている。オゾン発生器1において、接地電極1b及び誘電体1cそれぞれの表面(放電面)に金属(元素)化合物質層1dをさらに有している。
なお、本実施の形態では、高圧電極1a上に誘電体1cを設けたが、接地電極1b上に誘電体1cを設けるように構成しても良い。
1a 高圧電極
1b 接地電極
1c 誘電体
1d 金属化合物質層
2 オゾン電源
99 原料供給系
Claims (10)
- 互いに対向した第1及び第2の電極(1a及び1b)と、前記第1の電極上に形成された誘電体(1c)とを有し、前記誘電体と前記第2の電極との間に放電空間を有するオゾン発生器を用いてオゾンを発生させるオゾン発生方法であって、
前記オゾン発生器は、前記第2の電極及び前記誘電体の少なくとも一つの表面に設けられる金属化合物質層(1d)をさらに有し、
前記金属化合物質層は以下の条件(1)~(4)を満足し、
(1) オゾン分解を促進させる物質ではない
(2) 導電体ではない
(3) 前記金属化合物質層のバンドギャップが2.0~4.0[eV]の範囲である
(4) 前記金属化合物質層の励起状態において形成される価電子帯部のホール電位が酸素分子の結合電位より大きい
前記オゾン発生方法は、
(a) 前記放電空間に酸素ガスを主体にした原料ガスを供給するステップと、
(b) 外部エネルギーを与え、前記放電空間において誘電体バリア放電を発生させ、その放電光によって、前記金属化合物質層を光触媒状態にすることにより、前記ステップ(a) で供給した前記原料ガスから酸素原子を生成させるステップと、
(c) 前記ステップ(b) で生成された酸素原子と前記原料ガスに含まれる酸素ガスとの衝突化学反応でオゾンを発生させるステップと、
(d) オゾンの分解量を抑制させるオゾン分解抑制要件を前記オゾン発生器に課した環境下で前記ステップ(a) ~(c) を実行させるステップとを備える、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層を構成する金属化合物の粒子径を0.1~50(μm)の粉末にしたことを特徴とする、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層に含まれる主要金属元素は、少なくとも、周期律表で第5族、第6族に属する電子配置を有した金属元素を含み、前記金属化合物質層は金属酸化層を含むことを特徴とする、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層に含まれる主要金属元素は、ビスマス元素を含み、前記金属化合物質層は金属酸化層を含むことを特徴とする、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層は、3元素が結合した金属化合物質層を含むことを特徴とする、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層は、その結晶構造として体心立方構造を有することを特徴とする、
オゾン発生方法。 - 請求項1記載のオゾン発生方法であって、
前記金属化合物質層は、塗布、吹付、焼き付け、面接合により、前記第2の電極及び前記誘電体の少なくとも一つの表面に固着されることを特徴とする、
オゾン発生方法。 - 請求項1から請求項7のうち、いずれか1項に記載のオゾン発生方法であって、
前記ステップ(d)にて前記オゾン発生器に課した前記オゾン分解抑制要件は、以下の要件(d1)~(d3)を満足することを特徴とする、
(d1) 前記原料ガスとして酸素ガス純度を99.99(%)とした高純度酸素ガスを用いる
(d2) 前記原料ガスの供給時のガス流量は3(L/min)以上とする
(d3) 前記誘電体バリア放電における放電電力密度を1~5(W/cm2)の範囲内で、かつ、比電力W/Q値を300~500(W・min/L) の範囲内にする、
オゾン発生方法。 - 請求項1から請求項8のうち、いずれか1項に記載のオゾン発生方法であって、
前記ステップ(d)にて前記オゾン発生器に課した前記オゾン分解抑制要件は、以下の要件(d4)を満足することを特徴とする、
(d4) 前記オゾン発生器における前記第1及び第2の電極の温度を20(℃)以下に設定する、
オゾン発生方法。 - 請求項1から請求項9のうち、いずれか1項に記載のオゾン発生方法であって、
前記ステップ(d)にて前記オゾン発生器に課した前記オゾン分解抑制要件は、以下の要件(d5)及び(d6)を満足することを特徴とする、
(d5) 前記オゾン発生器の放電空間のギャップ長を0.02~0.12(mm)範囲内に設定する、
(d6) 前記放電空間のガス圧力を絶対圧で、0.2~0.4(MPa)の範囲内に設定する、
オゾン発生方法。
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2015
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- 2015-12-08 EP EP15910192.2A patent/EP3388390A4/en active Pending
- 2015-12-08 WO PCT/JP2015/084361 patent/WO2017098575A1/ja active Application Filing
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- 2015-12-08 KR KR1020187015814A patent/KR102370276B1/ko active IP Right Grant
- 2015-12-08 CN CN201580085161.8A patent/CN108367919A/zh active Pending
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2016
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Publication number | Priority date | Publication date | Assignee | Title |
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WO2019225033A1 (ja) * | 2018-05-21 | 2019-11-28 | 東芝三菱電機産業システム株式会社 | オゾンガス発生システム及びオゾンガス発生方法 |
WO2019225426A1 (ja) * | 2018-05-21 | 2019-11-28 | 東芝三菱電機産業システム株式会社 | オゾンガス発生システム |
JP6657485B1 (ja) * | 2018-05-21 | 2020-03-04 | 東芝三菱電機産業システム株式会社 | オゾンガス発生システム及びオゾンガス発生方法 |
JPWO2019225426A1 (ja) * | 2018-05-21 | 2020-12-10 | 東芝三菱電機産業システム株式会社 | オゾンガス発生システム |
JP2020054954A (ja) * | 2018-10-02 | 2020-04-09 | 国立研究開発法人物質・材料研究機構 | 光触媒材料、及び、含酸素有機化合物の製造方法 |
JP7270240B2 (ja) | 2018-10-02 | 2023-05-10 | 国立研究開発法人物質・材料研究機構 | 光触媒材料、及び、含酸素有機化合物の製造方法 |
Also Published As
Publication number | Publication date |
---|---|
TW201720754A (zh) | 2017-06-16 |
EP3388390A1 (en) | 2018-10-17 |
JPWO2017098575A1 (ja) | 2018-06-07 |
US20180327264A1 (en) | 2018-11-15 |
EP3388390A4 (en) | 2019-05-01 |
KR20180078314A (ko) | 2018-07-09 |
TWI615351B (zh) | 2018-02-21 |
KR102370276B1 (ko) | 2022-03-04 |
KR20200106998A (ko) | 2020-09-15 |
CN108367919A (zh) | 2018-08-03 |
US10745277B2 (en) | 2020-08-18 |
JP6714018B2 (ja) | 2020-06-24 |
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