JP5545776B2 - Discharge cell for ozone generator - Google Patents

Description

  The present invention relates to a plate-type discharge cell used in an ozone generator.

  The discharge cells used in the ozone generator are roughly classified into a plate type and a tube type, and the plate type is further subdivided into a disc type and a square plate type. The plate-type discharge cell generates high-concentration ozone because the discharge gap formed by using a dielectric between the high-voltage electrode and the low-voltage electrode is easy to narrow, and the discharge gap dimensions are easy to equalize in the plane. Is often used. A typical structure of the plate discharge cell will be described below.

  A plate-like dielectric made of a square ceramic plate or the like is disposed opposite to each other with a predetermined gap. The pair of dielectrics have electrode layers coated on the respective surfaces on the back side, thereby forming discharge gaps between the dielectrics. One of the pair of electrode layers is a high voltage electrode and the other is a low voltage electrode. By applying a predetermined high frequency high voltage between them, a discharge is generated in the discharge gap between the dielectrics, and the raw material passes therethrough Ozonize the gas. In some cases, the dielectric on the low voltage electrode side may be omitted, and in this case, a discharge gap is formed between the dielectric on the high voltage electrode side and the low voltage electrode.

  The discharge gap is often forcibly cooled from both sides, that is, the back sides of both electrodes, in order to increase the ozone generation efficiency. For this double-sided cooling, a refrigerant flow path is formed on each back side of the high voltage electrode and the low voltage electrode via an insulating plate. Usually, a plate-type discharge cell having such a double-sided cooling structure is used as a unit cell, and a plurality of the cells are stacked in the plate material stacking direction. One of the plate-type discharge cells having such a double-sided cooling structure is a discharge cell having a ceramic block structure described in Patent Document 1.

  Design factors in such a plate-type discharge cell include the thickness of a pair of dielectrics disposed between the high-voltage electrode and the low-voltage electrode, the gap amount of the discharge gap formed between the pair of dielectrics, the high-voltage electrode And the thicknesses of the high-voltage insulating plate and the low-voltage insulating plate arranged on the back side of the low-voltage electrode.

  The purpose of the dielectric is to increase the dielectric constant between the electrodes in order to generate silent discharge between the electrodes. In order to reduce the discharge voltage by reducing the distance between the electrodes, it is better that the thickness of the dielectric is thin. It is said that. However, if the dielectric is made too thin, the flatness is lowered, and the current state is selected to be about 0.1 to 2 mm per sheet.

  The dielectric is also often provided in contact with both the high voltage electrode and the low voltage electrode to avoid contact of the source gas and ozone gas with the electrode. That is, both electrodes are covered with a dielectric, and a discharge gap is formed between the two dielectrics. However, when the cleanliness of ozone gas is not required, it may be provided only on one electrode side (usually the high voltage electrode side) as described above.

  Regarding the gap amount of the discharge gap, it is said that the smaller is better for improving the ozone generation efficiency by cooling. From this viewpoint, the current state is reduced to 0.4 mm or less, and the case of 0.1 mm or less is not uncommon. .

  Regarding the thickness of the insulating plate, the thickness of the high voltage insulating plate is important. The high voltage insulating plate electrically insulates between the high voltage electrode on the inner side and the refrigerant (cooling water) on the outer side (back side). If the insulation between the high-voltage electrode and the cooling water on the back side is insufficient, an ineffective current flows toward the cooling water on the back side and the current to the discharge gap decreases, resulting in a decrease in ozone generation efficiency. For this reason, the thickness of the high-voltage insulating plate is sufficiently thick at several mm or more at present.

  However, a thick high-pressure insulating plate is very expensive, and when it exceeds 1 mm from the manufacturing surface, it becomes rapidly expensive. In other words, alumina plates are used for high-pressure insulating plates, but those with a thickness of 1 mm or less can be mass-produced by the doctor blade method, etc., and the manufacturing cost is also cheap, but thick plates exceeding 1 mm are cast and cut. The manufacturing method by taking out etc. is needed, and it becomes expensive rapidly.

  Note that the low-voltage insulating plate is unnecessary from the electrical aspect because the low-voltage electrode and the outside (rear side) refrigerant (cooling water) have the same potential. Is used from the viewpoint of preventing direct contact with the film and from the viewpoint of ensuring mechanical strength. For this reason, it is not necessary to use a thick material, and a thin material having a thickness of 1 mm or less is frequently used from the viewpoint of economy, and a film-like material may be used.

  Thus, in conventional discharge cells for ozone generators, the use of a high-voltage insulating plate with a large thickness is indispensable, and the increase in the insulating plate cost due to its use contributes to the increase of the discharge cell cost. is there.

JP-A-11-268902

  It is an object of the present invention to provide a high-performance and economical discharge cell for an ozone generator that can reduce the cost of an insulating plate while avoiding a decrease in ozone generation efficiency.

  The inventor has previously investigated various effects of the thickness of the dielectric and the thickness of the insulating plate on the ozone generation efficiency in the discharge cell for the ozone generator. As a result, the thickness of the insulating plate, in particular, the thickness of the high-pressure insulating plate that has contributed to the increase in the manufacturing cost of the discharge cell, is not indispensable in terms of ozone generation efficiency as conventionally considered. It has become clear.

  That is, as described above, the high voltage insulating plate electrically insulates between the inner high voltage electrode and the outer (back side) refrigerant (cooling water). It is a fact that reactive current flows to the (cooling water) side and discharge current in the discharge gap decreases, resulting in a decrease in ozone generation efficiency. However, on the other hand, the high-voltage insulating plate is between the inner high-voltage electrode and the outer cooling water, and is the largest cause of impeding cooling of the discharge gap from the high-voltage electrode side by the cooling water. For this reason, when the high-voltage insulating plate is thinned, cooling from the high-voltage electrode side is promoted, and the ozone generation efficiency is improved.

  In other words, the high-voltage insulating plate is preferably thicker from the viewpoint of high-efficiency discharge in the discharge gap, whereas it is better from the viewpoint of cooling the discharge gap. In the past, the former electrical aspect was primarily regarded as important, and from this point of view, the high voltage insulating plate has been made sufficiently thick to be several mm or more.

  However, as a result of detailed investigation by the present inventors on the relationship between the thickness of the high-pressure insulating plate and the ozone generation efficiency in the discharge cell for the ozone generator, it is better to make the high-pressure insulating plate thinner with emphasis on cooling the discharge gap. Although an electrical loss occurs in the discharge gap, the ozone generation efficiency in the discharge gap increases as a whole, and as a result, a highly concentrated ozone gas can be obtained.

  From such investigation results, the present inventor has placed a dielectric between the electrodes in contact with at least one of the electrodes so as to form a discharge gap between the high voltage electrode and the low voltage electrode to which a predetermined alternating voltage is applied. In addition, a coolant channel is formed outside both electrodes to cool the discharge gap from both sides, and a high-pressure insulating plate is disposed between the two to insulate the high-pressure side coolant channel from the high-voltage electrode. For discharge cells for ozone generators, for ozone generators, the plate thickness of the high-voltage insulating plate is 0.5 to 3.5 times the total thickness of the dielectric disposed between the high-voltage electrode and the low-voltage electrode A discharge cell was developed.

  In this discharge cell for an ozone generator, the plate thickness of the high-pressure insulating plate is made thinner than before. More specifically, because the total thickness of the dielectric disposed between the high-voltage electrode and the low-voltage electrode is made thinner than before, this increases the cooling capacity in the discharge gap and more than compensates for the current loss. Ozone generation efficiency is improved. The justification of relating the total thickness of the dielectric and the thickness of the high voltage insulating plate will be described in detail later.

  The thickness of the high voltage insulating plate is 0.5 times or more and 3.5 times or less of the total thickness of the dielectric disposed between the high voltage electrode and the low voltage electrode. Side)), the ozone generation efficiency is reduced by negating the improvement in efficiency due to the accelerated cooling in the discharge gap. Conversely, when it exceeds 3.5 times, the cooling from the high voltage electrode side is extremely insufficient. However, although the reactive current does not substantially occur, the ozone generation efficiency as a whole decreases. A particularly preferable magnification is 0.5 to 2 times, and a more preferable magnification is 1 to 1.5 times.

  The advantages of reducing the thickness of the high-voltage insulating plate are as described above. On the other hand, the mechanical strength of the high-voltage insulating plate is reduced. The conventional high-voltage insulating plate having a large plate thickness has high mechanical strength and contributes to ensuring flatness in the discharge cell, and as a result, contributes to uniform gap amount distribution in the discharge gap. For this reason, when the plate thickness of the high-voltage insulating plate is reduced, the flatness and the uniformity of the gap amount distribution in the discharge cell may be reduced.

  More specifically, in the case of a discharge cell having a block-integrated structure as shown in Patent Document 1, the mechanical strength is inherently high because of the monocoque structure that ensures the mechanical strength of the entire cell. For this reason, the problem of flatness reduction due to the reduction in the thickness of the high-voltage insulating plate hardly occurs. However, in the case of an assembly-type discharge cell in which plate materials are stacked in the plate thickness direction and fastened and fixed by tie rods, a monocoque structure is used, but a frame structure that requires a member for securing rigidity is provided. As a frame, the contribution of the high-voltage insulating plate has been large so far, and the thinness of the frame causes problems such as a decrease in flatness.

The discharge cell for an ozone generator of the present invention has been completed on the basis of such knowledge, and at least one electrode is formed to form a discharge gap between a high voltage electrode and a low voltage electrode to which a predetermined alternating voltage is applied. In order to insulate the high pressure side refrigerant flow path from the high pressure electrode while the dielectric is disposed between the electrodes and the refrigerant flow path is formed outside both electrodes to cool the discharge gap from both sides. In the discharge cell for an ozone generator in which the high-pressure insulating plate is disposed between the two, the thickness of the high-pressure electrode disposed through the high-pressure insulating plate inside the refrigerant passage on the high-pressure side is set to More than 10 times the total thickness of the dielectrics disposed between them.

In the discharge cell for an ozone generator according to the present invention, the thickness of the high-pressure electrode arranged inside the high-pressure side refrigerant flow path via the high-pressure insulating plate is changed to the dielectric material arranged between the high-voltage electrode and the low-voltage electrode. Since the thickness is 10 times or more as compared with the total thickness, the mechanical strength is improved, and high flatness and uniformity of the gap amount distribution are ensured. For this reason, the discharge cell for an ozone generator of the present invention has a thickness of the high-pressure insulating plate that insulates the high-voltage electrode from the refrigerant on the high-pressure side, and the total thickness of the dielectric disposed between the high-voltage electrode and the low-voltage electrode. This is effective when the thickness is reduced to 0.5 times or more and 3.5 times or less, especially in an assembly type discharge cell in which plate materials are stacked in the plate thickness direction and fastened and fixed by tie rods. This is effective when the thickness is reduced . The high voltage electrode is made of a metal plate such as aluminum and has good thermal conductivity. Therefore, increasing the thickness of the high voltage electrode hardly causes the cooling from the high voltage electrode side of the discharge gap.

  The dielectric may be disposed on both the high-voltage electrode side and the low-voltage electrode side, or only on one side. If cleanliness is required, it should be arranged on both sides, and if high cleanliness is not required, only one side may be used. In the case of one side, it is often provided on the high voltage electrode side.

  A low-pressure insulating plate between the low-pressure side refrigerant flow path and the low-pressure electrode is not always necessary. This is because the low-pressure side refrigerant flow path and the low-pressure electrode have the same potential (ground potential). From the viewpoint of promoting cooling from the low-pressure side and the cost of the insulating plate, the low-pressure insulating plate is unnecessary, and it is better to use it thinly. However, it should be present in terms of ensuring mechanical strength and covering low voltage electrodes. The plate thickness is preferably 0.1 mm or more and 1 mm or less, and even when the rigidity is not required, even on the order of μm (thin film level). Good. If it is too thick, the mechanical strength will increase more than necessary, and the cooling capacity and economy will deteriorate.

  One more important thing is the fact that in the case of the discharge cell of the present invention in which the high-voltage insulating plate is made thin, the ozone concentration is further increased by stacking the discharge cells in a plurality of stages. From this point of view, a laminated structure in which the discharge cell of the present invention with a thin high voltage insulating plate as a unit cell is laminated in a plurality of stages is preferable. In other words, the present invention is particularly effective in a stacked cell in which a plate-type discharge cell having a double-sided cooling structure is used as a unit cell and a plurality of the cells are stacked in the plate material stacking direction.

  Dielectrics, insulating plates, etc. are usually made of ceramics. The ceramic is preferably alumina having a purity of 80% or more, particularly preferably alumina having a purity of 90% or more, particularly 95% or more. Alumina is suitable because it is inexpensive among ceramics and has chemical resistance and sputtering resistance. Moreover, high purity is preferable in order to increase the cleanliness of ozone gas. An inorganic bonding material is suitable for bonding when the ceramic plates are laminated, and the inorganic bonding material is preferably a glass bonding material from the viewpoint of bondability and prevention of contamination.

  As for the dielectric plate among the ceramic plates, when the impurities in the dielectric plate are reduced, a decrease in ozone concentration becomes a problem. In order to solve this problem, titanium oxide is preferably contained in at least a surface layer portion of the dielectric plate in contact with the discharge gap, and titanium oxide is contained in the alumina substrate in an amount of 0.006 to 6% by weight in terms of the amount of Ti element. A sintered body is particularly preferable from the viewpoints of ozone generation characteristics and cleanliness.

The discharge cell for an ozone generator of the present invention is arranged between the high-pressure electrode and the low-pressure electrode with the thickness of the high- pressure electrode, in particular , the high-pressure electrode arranged through the high-pressure insulating plate inside the refrigerant passage on the high-pressure side . By increasing the thickness in relation to the total thickness of the dielectric, first, the mechanical strength is improved, and high flatness and uniformity of the gap amount distribution can be ensured, so that the ozone generation efficiency is favorably affected. Since the high voltage electrode is made of an aluminum plate or the like having good thermal conductivity, there is no problem of hindering cooling from the high voltage side of the discharge gap even if the thickness is increased. Second, it is possible to avoid a decrease in mechanical strength, which becomes a problem when the high-voltage insulating plate is thinned in an assembly-type discharge cell, and to ensure high flatness and uniformity of gap amount distribution. The thickness of the high-pressure insulating plate that insulates the high-pressure electrode from the refrigerant on the high-pressure side is made thinner than before in relation to the total thickness of the dielectric disposed between the high-voltage electrode and the low-pressure electrode, thereby increasing the ozone generation efficiency. Enables high concentration of ozone gas. In addition, the reduction of the plate thickness of the high voltage insulating plate reduces the insulating plate cost, and enables the discharge cell cost to be reduced. These make it possible to provide a high-performance and economical ozone generator.

It is a disassembled perspective view of the discharge cell for investigating the relationship between the plate | board thickness of a high voltage | pressure insulating board, and the total thickness of a dielectric material. It is a schematic cross section of the same discharge cell. It is an equivalent circuit of the same discharge cell. It is a schematic cross section of the discharge cell which shows embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of a discharge cell for an ozone generator for investigating the relationship between the plate thickness of a high voltage insulating plate and the total thickness of a dielectric, FIG. 2 is a schematic sectional view of the discharge cell, and FIG. It is an equivalent circuit of a cell.

  As shown in FIGS. 1 and 2, the discharge cell for an ozone generator is a plate type discharge cell having a block structure in which a plurality of square plate members are integrally laminated in the thickness direction. The plurality of plate materials are all fired plates of high-purity alumina, and are joined via a glass-based joining layer 50. Positioning through holes are provided at the four corners of each plate member, and the corners are rounded.

  The two middle plates are dielectrics 10A and 10B. The thickness is, for example, 0.3 mm. On both side edge portions of each dielectric 10 in parallel, long-hole shaped through holes 11 along the side edges are provided. The through-holes 11 and 11 are for gas distribution, and are provided continuously and linearly in almost the whole area except for both ends of both side edges. On the other parallel side edges of each dielectric 10, that is, the side edges perpendicular to the through holes 11, 11, elongated through holes 12, 12 are provided along the side edges. The through-holes 12 and 12 are for refrigerant circulation, and are provided continuously and linearly in almost the whole area except for both ends of both side edges.

  In order to form a large number of parallel gas flow paths 13, 13 extending from one of the through holes 11, 11 to the other surface of the dielectrics 10, 10 except for the gas flow paths 13, 13 ceramics. Layers 14 and 14 are laminated. The gas flow paths 13 and 13 are combined to form a discharge gap 70 between the dielectrics 10 and 10.

  The ceramic layer 14 is obtained by printing a paste made of alumina powder and glass powder on a portion other than the gas flow path on the opposite surface, repeating this to a predetermined thickness, and firing at a temperature equal to or higher than the melting point of the glass powder. Is formed. Each thickness of the ceramic layers 14, 14, that is, a rib height for forming the gas flow path 13 is, for example, 35 μm.

  Electrode layers 15 </ b> A and 15 </ b> B are coated on the back surface of the dielectrics 10 and 10. The electrode layer 15A is a high-voltage electrode, and 15B is a low-voltage electrode, both of which are, for example, a metal thin film having a thickness of 5 μm formed by printing and baking silver paste, and surrounded by the through holes 11, 11, 12, and 12. It is provided in a square area. Two adjacent corner portions of the electrode layer 15 protrude from the corner portion of the dielectric plate 10 to form circular terminal portions 16 and 16. The terminal portions 16 and 16 in one electrode layer 15A are provided at two adjacent corner portions of the dielectric plate 10A, and the terminal portions 16 and 16 in the other electrode layer 15B are terminal portions in the electrode layer 15A. 16 and 16 are provided at two adjacent corner portions of the dielectric 10B so as not to overlap with each other.

  The plate materials disposed outside the dielectrics 10A and 10B are the insulating plates 20A and 20B. One insulating plate 20A is a high-voltage insulating plate, and the other insulating plate 20B is a low-voltage insulating plate. The high-voltage insulating plate 20A is intended to insulate the inner high-voltage electrode 15A from the outer refrigerant, and the thickness thereof is conventional. It is thin, for example, 0.9 mm. The low-voltage insulating plate 20B is exclusively for the purpose of ensuring the mechanical strength, and the thickness thereof is, for example, 0.3 mm. That is, the thickness of the high voltage insulating plate 20A is 1.5 times the total thickness (0.6 mm) of the dielectrics 10A and 10B arranged between the electrode layers 15A and 15B.

  On both side edges of the insulating plates 20A and 20B, there are provided through holes 21 and 21 for gas circulation having long holes corresponding to the through holes 11 and 11, respectively. The other parallel side edges of the insulating plates 20A and 20B are provided with through-holes 22 and 22 for circulation of a long hole corresponding to the through-holes 12 and 12, respectively.

  The plate materials arranged outside the insulating plates 20A and 20B are the slit plates 30A and 30B for forming the refrigerant flow path. The thickness is 0.5 mm, for example. On the both side edges of each slit plate 30 are provided through holes 31 and 31 for gas circulation having a long hole shape corresponding to the through holes 11, 11, 21 and 21. A large number of slits 33, 33,... Are provided in parallel between the through holes 31, 31 in order to form a refrigerant flow path. Both ends of the slits 33, 33... Reach the other parallel side edges of each slit plate 30 so as to overlap with the through holes 22, 22 for circulating the refrigerant.

  The plate members disposed further outside the slit plates 30A and 30B are the cover plates 40A and 40B. The thickness of one cover plate 40A is, for example, 4 to 5 mm, and the thickness of the other cover plate 40B is, for example, 2 mm. One cover plate 40A is provided with a gas supply hole 41a and a gas discharge hole 41b communicating with the through holes 31, 31 of the inner slit plate 30A, respectively. A pair of recesses is provided on the back surface of the cover plate 40A so as to correspond to both end portions of the slits 33, 33,..., That is, the through holes 12, 12, 22, and 22. The lid plate 40A is provided with a refrigerant supply hole 42a and a refrigerant discharge hole 42b that communicate with a pair of recesses on the back surface side.

  These plate materials (sintered plates of high-purity alumina) are joined as follows.

  A glass-based bonding paste is applied to the bonding surface of each plate material to a thickness of about 30 μm, for example. The bonding paste is prepared by kneading glass powder with a binder to have a predetermined viscosity. When the application of the bonding paste is finished, the plate material is charged into a heating furnace, and the bonding paste is baked at a temperature of, for example, 850 ° C. or higher, which is the melting point of the glass powder. When the bonding paste is baked, the respective plate materials are overlapped, and the positioning pins 60 are pierced through the through holes at the four corners. The four positioning pins 60 also serve as rod-shaped leads, two of which are electrically connected to the terminal portions 16 and 16 of the high-voltage electrode layer 15A, and the remaining two are the two terminal portions 16 of the low-voltage electrode layer 15B. , 16 are conducted. Finally, the stacked plate materials are charged into a heating furnace, and the joining paste is fired at a temperature of, for example, 850 ° C. or higher, which is the melting point of the glass powder.

  By this firing, the dielectrics 10A and 10B, the outer insulating plates 20A and 20B, the outer slit plates 30A and 30B, and the outer lid plates 40A and 40B are bonded via the glass-based bonding layer 50. As a result, the discharge cell of this embodiment is completed. The characteristics of the completed discharge cell are as follows.

  By combining the gas flow paths 13 and 13 between the dielectrics 10A and 10B, a closed space for discharge, that is, a discharge gap 70 is formed between the dielectrics 10A and 10B. The thicknesses of the ceramic layers 14 and 14 forming the gas flow paths 13 and 13 are, for example, 35 μm, and the gap amount of the discharge gap 70 in this case is 70 μm. One of the ceramic layers 14 can be omitted, and the gap amount of the discharge gap 70 in this case is halved to 35 μm. The electrode layers 15A and 15B coated on the rear surface of the dielectric plates 10A and 10B are joined together with the terminal portions 16 and 16 between the dielectric plate 10 and the insulating plate 20 joined to the outside thereof. Encapsulated and insulated by layer 50.

  The terminal portions 16 and 16 of the high-voltage electrode layer 15A provided on the back side of the dielectric plate 10A are drawn out of the lid plate 40A by the two rod-shaped leads 60 and 60 and connected to the power source. On the other hand, the terminal portions 16 and 16 of the low-voltage electrode layer 15B provided on the back side of the dielectric plate 10B are drawn out to the outside of the lid plate 40A by another two rod-shaped leads 60 and 60 and grounded.

  The through holes 11, 11 of the dielectric 10, the through holes 21, 21 of the insulating plate 20, and the through holes 31, 31 of the slit plate 30 are continuous in the plate material stacking direction, so that they are vertically long and communicate with the discharge gap 70. Gas flow paths 80, 80 are formed in the laminate. Further, the through holes 12 and 12 of the dielectric 10 and the through holes 22 and 22 of the insulating plate 20 are continuous in the plate material laminating direction, so that the longitudinal direction communicates with both ends of the slits 33, 33. A horizontally long refrigerant flow path is formed in the laminate.

  In the operation of the discharge cell, a predetermined high-frequency high voltage is applied to the high-voltage electrode layer 15A via the two rod-shaped leads 60, 60. At the same time, a raw material gas is introduced into one of the two vertical gas flow paths 80, 80 formed in the stacking direction from the gas supply hole 41a of the cover plate 40A, and two vertical refrigerant flows formed in the stacking direction. Cooling water is introduced into one of the paths from the refrigerant supply hole 42a of the lid plate 40A.

  The source gas introduced into one of the gas flow paths 80, 80 travels from one end portion to the other end of the discharge gap 70 formed between the dielectrics 10 </ b> A, 10 </ b> B, and is ozonized during this time. , 80, and is discharged to the outside through the gas discharge holes 41b of the cover plate 40A. The cooling water introduced into one of the two refrigerant channels flows through the slits 33, 33,... Of the slit plates 30A, 30B in the longitudinal direction, passes through the other of the two refrigerant channels, and passes through the other of the two refrigerant channels. It is discharged from the discharge hole 42b. As a result, the discharge gap 70 formed between the dielectrics 10A and 10B between the electrode layers 15A and 15B is cooled via the insulating plates 20A and 20B from both sides.

  In this discharge cell for an ozone generator, a predetermined high frequency high voltage is applied to the high voltage electrode layer 15A, and the low voltage electrode layer 15B is grounded together with cooling water. Therefore, an equivalent circuit in the discharge cell is as shown in FIG. That is, the high voltage insulating plate 20A is inserted in parallel in the series circuit of the dielectric 10A, the discharge gap 70, and the dielectric 10B. In the figure, C10A is the capacitor capacity of the dielectric 10A, C70 is the capacitor capacity of the discharge gap 70, C10B is the capacitor capacity of the dielectric 10B, and C20A is the capacitor capacity of the high voltage insulating plate 20A. The capacitor capacity C70 of the discharge gap 70 is smaller than the capacitor capacities C10A and C10B of the dielectrics 10A and 10B, and does not greatly affect the capacitor capacity of the series circuit. The capacitor capacity of the series circuit is governed by the capacitor capacities C10A and C10B of the dielectrics 10A and 10B.

  When the high voltage insulating plate 20A is thick as in the prior art, the capacitor capacity is large, and there is almost no reactive current to the cooling water on the high voltage side. However, in this discharge cell, the high-voltage insulating plate 20A is made thinner than before. Specifically, the thickness is 0.8 mm, which corresponds to a little less than 1.5 times the total thickness (0.6 mm) of the dielectrics 10A and 10B disposed between the high-voltage electrode layer 15A and the low-voltage electrode layer 15B. . For this reason, the capacitor capacity of the high-voltage insulating plate 20A is reduced as compared with the total capacity of the dielectric 10A, the discharge gap 70, and the dielectric 10B, and generation of reactive current in the high-pressure side cooling water cannot be ignored. However, since the voltage applied to the high-voltage electrode layer 15A is alternating current, the electrical adverse effect due to the decrease in insulation is relatively small. Rather, the discharge gap 70 between the dielectrics 10A and 10B is more effectively cooled by the cooling water (high-pressure side cooling water) flowing through the slits 33 and 33 of the slit plate 30A, and loss due to reactive current is lost. By sufficiently supplementing, the ozone generation efficiency is improved, and the efficiency is not lowered unless it is improved.

  That is, the gap cooling ability is improved by thinning the high-pressure insulating plate 20A, and the advantage in ozone generation efficiency is the decrease in the discharge current in the discharge gap 70 due to the decrease in insulation, and the disadvantage in ozone generation efficiency is thereby. This offsets or surpasses, and as a result, the ozone generation efficiency is improved or maintained.

  In addition, in the discharge cell for the ozone generator, the raw material gas and the ozone gas pass through the discharge gap 70 between the dielectrics 10A and 10B from one of the vertical gas flow paths 80 and 80 and one of the vertical gas flow paths 80 and 80. To. Here, the vertical gas flow paths 80, 80 are formed in a laminate in which high-purity alumina plate materials are bonded together by the glass bonding layer 50, and neither the high-purity alumina plate material nor the glass bonding layer 50 contains a contamination source. It is an inorganic non-metallic material. Further, the discharge gap 70 is formed by the rib-structure ceramic layer 14 and the glass bonding layer 50 between the dielectrics 10 </ b> A and 10 </ b> B made of a high-purity alumina plate, and the ceramic layer 14 is as clean as the glass bonding layer 50. It is an inorganic non-metallic material. Further, the electrode layer 15 is sealed by a glass bonding layer 50 between the dielectric plate 20 and the insulating plate 20 on the back side thereof.

  For these reasons, the raw material gas and the ozone gas do not come into direct contact with the metal, but pass only through a clean distribution path formed of a clean inorganic non-metallic material that does not contain a contamination source. In other words, all gas contact parts are made of a clean material. Therefore, there is no danger of contamination of the raw material gas and ozone gas by the discharge cell, and ozone gas having a high cleanliness is generated.

  FIG. 4 is a schematic cross-sectional view of a discharge cell for an ozone generator showing an embodiment of the present invention.

  The discharge cell for an ozone generator according to the present embodiment is an assembly type discharge cell in which plate-like members are stacked in the plate thickness direction and mechanically fastened and fixed. This discharge cell includes a low voltage electrode 120 that also serves as a low pressure side cooling plate, a pair of dielectric plates 130 and 130, a high voltage electrode 140, a high voltage insulating plate 150, and a high pressure side cooling plate 160 between the bottom plate 100 and the top plate 110. It is the structure which has arrange | positioned the laminated body which piled up in order from the bottom to the top.

  The bottom plate 100 and the top plate 110 are connected by a plurality of tie rods 170 so that the separation distance does not change, and the high pressure side cooling plate 160 is pressed down by a bolt-shaped fixture 180 screwed into the top plate 110. Thus, the laminated body is pressed in the laminating direction and fixed on the bottom plate 100.

  The low voltage electrode 120 also serving as the low pressure side cooling plate and the high pressure side cooling plate 160 have substantially the same configuration, and have a configuration in which a coolant channel is formed by etching or the like between the joining surfaces of the two stainless steel plates. . The pair of dielectric plates 130 and 130 is made of a ceramic plate such as alumina, and sandwiches a plurality of spacers 190 in order to form the discharge gap 70 therebetween. The dielectric plates 130 and 130 may have an integrated structure joined via ribs similarly to the dielectric plates 10A and 10B in the first embodiment.

  The high voltage electrode 140 is made of a thick plate such as aluminum having excellent conductivity and thermal conductivity, and the high voltage insulating plate 150 thereon is made of a ceramic plate such as alumina. The plate thickness of the high voltage insulating plate 150 is reduced to 0.5 to 3.5 times the total thickness of the dielectric plates 130 and 130, while the thickness of the high voltage electrode 140 is reduced to the dielectric plates 130 and 130. It is thicker than 5 times the total thickness.

  More specifically, assuming that the thickness of each of the dielectric plates 130 and 130 is 0.3 mm and the total thickness is 0.6 mm, the thickness of the high voltage insulating plate 150 is 0.9 mm which is 1.5 times the total thickness. On the other hand, the thickness of the high voltage electrode 140 is set to 6 mm which is 10 times the total thickness of the dielectric plates 130 and 130. The plate thickness of the low voltage electrode 120 that also serves as a low pressure side cooling plate made of a metal plate such as a stainless steel plate and the high pressure side cooling plate 160 are both as thin as 2 mm.

  In the discharge cell for an ozone generator having such a configuration, the laminate is housed in the cover 200 on the end plate 100 together with the top plate 110. The cover 200 constitutes a pressure vessel together with the end plate 100, and oxygen gas which is a raw material gas is supplied into the pressure vessel. In addition, a predetermined high frequency high voltage is applied between the low voltage electrode 120 and the high voltage electrode 140 in order to generate a discharge in the discharge gap 70 between the dielectric plates 130 and 130. Further, cooling water as a refrigerant is supplied to the low voltage electrode 120 that also serves as the low pressure side cooling plate and the high pressure side cooling plate 160.

  The oxygen gas supplied into the pressure vessel passes through the discharge gap 70 between the dielectric plates 130 and 130 and is ozonized during this time to become ozone gas. The ozone gas is led out of the pressure vessel through the gas flow path 210 formed in the lower dielectric plate 130, the low voltage electrode 120 and the bottom plate 100.

  Here, the plate thickness of the high voltage insulating plate 150 is reduced to 0.9 mm, which is 1.5 times the total thickness. For this reason, the capacitor capacity of the high-voltage insulating plate 150 is reduced as compared with the total capacity of the dielectric 130, the discharge gap 70, and the dielectric 130, and generation of reactive currents in the cooling water on the high-voltage side cannot be ignored. However, since the voltage applied to the high-voltage electrode 150 is an alternating current, there are relatively few adverse electrical effects due to a decrease in insulation. Rather, by thinning the high voltage insulating plate 150, the cooling efficiency from both sides by the low voltage electrode 120 and the high voltage side cooling plate 160 is increased, and by sufficiently compensating for the loss due to reactive current, the ozone generation efficiency is improved. Even if it does not improve, the efficiency will not decrease.

  On the other hand, since the low voltage electrode 120 also serving as the low pressure side cooling plate and the high voltage side cooling plate 160 are thin metal plates, their rigidity is low. The dielectric plates 130 and 130 are small in thickness and low in rigidity. In addition, the high voltage insulating plate 150 is thinned. If this is not done, the flatness of these components decreases with fixation by the fixture 180, the uniformity of the gap in the discharge gap 70 decreases, and the ozone generation efficiency is adversely affected. However, in the discharge cell for the ozone generator of the present embodiment, since the high-voltage electrode 150 is thickened, this serves as a frame to ensure rigidity, a decrease in flatness due to fixing by the fixture 180, and a discharge gap due to this. The gap uniformity degradation at 70 is avoided. Further, since the high voltage electrode 150 is made of an aluminum plate having good thermal conductivity, there is no problem that obstructs cooling from the high voltage side of the discharge gap 70 even if the thickness is increased.

  Next, a comparative test that quantitatively shows the influence of the thickness of the high-pressure insulating plate on the ozone concentration will be described, and it will be clarified that reducing the thickness of the high-pressure insulating plate does not adversely affect the ozone concentration.

  As a comparative test 1, the thickness of the high voltage insulating plate 20A was variously changed in the discharge cells shown in FIGS. Each thickness of dielectric 10A, 10B was 0.3 mm, and the total thickness was 0.6 mm. The gap amount in the discharge gap 70 was 35 μm, the thickness of the low-pressure insulating plate 20B was 0.3 mm, and the thicknesses of the slit plates 30A and 30B were 0.5 mm. The thickness of the high voltage insulating plate 20A is 3.3 times 2 mm, 1.3 times 0.8 mm, and 0.5 times 0.3 mm with respect to the total thickness (0.6 mm) of the dielectrics 10A and 10B. Kind.

  The source gas was high purity oxygen gas (6N), the flow rate was 0.5 L / min (N), and the inlet pressure was 0.25 MPa. The amount of cooling water was 3 L / min, and the temperature was 20 ° C. The materials of the dielectrics 10A and 10B were TiO2 added alumina. The relationship between the discharge voltage and the ozone concentration shows that the ozone concentration increases as the discharge voltage is increased, and the ozone concentration tends to decrease after a certain discharge voltage reaches its peak. The discharge voltage indicating the maximum ozone concentration varies depending on the cell specifications. Here, the discharge voltage at which the ozone concentration becomes maximum when the thickness of the high-pressure insulating plate 20A is 0.8 mm is used as a reference voltage, and the ozone at this discharge voltage is set. The concentration was measured, and the relationship between the thickness of the high-pressure insulating plate 20A and the ozone concentration was investigated at this concentration.

Ozone concentration, 348 g / m ³ in the plate thickness of the high voltage insulator plate 20A is 3.3 times the 2mm total thickness dielectric (N), 357g / m ³ in the case of 1.3 times 0.8 mm ( N), and 0.5 times 0.3 mm, it was 343 g / m ³ (N). As can be seen, the thickness reduction of the high-pressure insulating plate does not cause a decrease in ozone concentration, and the thickness can be reduced by reducing the thickness.

In Comparative Test 2, the gap amount in the discharge gap 70 was set to 70 μm. Other conditions are the same. Ozone concentration, 287 g / m ³ in the plate thickness of the high voltage insulator plate 20A is 3.3 times the 2mm total thickness dielectric (N), 282g / m ³ in the case of 1.3 times 0.8 mm ( N), and 0.5 times 0.3 mm, it was 290 g / m ³ (N). Also in this case, it can be understood that the thickness reduction of the high-pressure insulating plate does not cause a decrease in the ozone concentration, and the insulating plate cost can be reduced by the thickness reduction.

  As a comparative test 3, the dielectrics 10A and 10B in Example 1, the outer insulating plates 20A and 20B, and the outer slit plates 30A and 30B are stacked in 10 steps as unit cells, and between the cover plates 40A and 40B. Sandwiched between. The slit plates 30A and 30B are shared between adjacent unit cells. The gap amount in the discharge gap 70 is 35 μm. Other conditions including the discharge voltage, the amount of gas in the discharge gap 70, and the amount of cooling water in the slit plates 30A and 30B were the same as those in Comparative Test 1.

Compared to the case where the gap amount in the discharge gap 70 is 35 μm, the ozone concentration is 348 g / m ³ (N when the plate thickness of the high pressure insulating plate 20A is 2 mm by changing the cell structure from a single layer to 10 layers. ) To 358 g / m ³ (N), 0.8 mm to 357 g / m ³ (N) to 405 g / m ³ (N), 0.3 mm to 343 g / m ³ (N) Each increased to 352 g / m ³ (N).

  As a comparative test 4, the dielectrics 10A and 10B in the second embodiment, the outer insulating plates 20A and 20B, and the outer slit plates 30A and 30B are stacked in 10 stages as unit cells, and the space between the cover plates 40A and 40B. Sandwiched between. The slit plates 30A and 30B are shared between adjacent unit cells. The gap amount in the discharge gap 70 is 70 μm. Other conditions including the discharge voltage, the gas amount in the discharge gap 70, and the cooling water amount in the slit plates 30A and 30B were the same as those in the comparative test 2.

Even when the gap amount in the discharge gap 70 is 70 μm, the ozone concentration becomes 287 g / m ³ (N when the plate thickness of the high-pressure insulating plate is 2 mm due to the change of the cell structure from a single layer to 10 layers. ) from the 297g / m ³ (N), to 325g / m ³ (N) from 282g / m ³ (N) in the case of 0.8 mm, in the case of 0.3mm from 290g / m ³ (N) Each increased to 295 g / m ³ (N).

  Thus, although the reason is not clear at present, the multilayer discharge cell structure is effective in improving the ozone concentration.

  The discharge cell for an ozone generator shown in FIGS. 1 and 2 is a square plate type discharge cell, but may be a disc type discharge cell. In this discharge cell, the dielectrics 10A and 10B are provided in contact with the electrode layers 15A and 15B between the high-voltage electrode layer 15A and the low-voltage electrode layer 15B, but one of them may be omitted. Further, if a sufficient cell strength can be obtained by design, the low-pressure insulating plate 20B can be omitted.

  Similarly, the discharge cell for the ozone generator of this embodiment shown in FIG. 4 may be either a square plate type discharge cell or a disc type discharge cell. It is also possible to stack the discharge cells back to back in such a manner that the high voltage side cooling plate 160 or the low voltage electrode 120 that also serves as the low pressure side cooling plate is shared.

DESCRIPTION OF SYMBOLS 10 Dielectric plate 11,12 Through-hole 13 Gas flow path 14 Ceramic layer 15 Electrode layer 16 Terminal part 20 Insulating plate 21,22 Through-hole 30 Slit plate 31 Through-hole 33 Slit 40 Lid plate 41 Gas hole 42 Refrigerant hole 50 Glass bonding layer 60 Rod-shaped lead 70 Discharge gap 80 Vertical gas flow path 100 End plate 110 Top plate 120 Low voltage electrode also serving as a low pressure side cooling plate 130 Dielectric plate 140 High voltage electrode 150 High pressure insulating plate 160 High pressure side cooling plate 170 Tie rod 180 Fixing tool 190 Spacer 200 cover

Claims (4)

In order to form a discharge gap between a high voltage electrode and a low voltage electrode to which a predetermined AC voltage is applied, a dielectric is disposed between the electrodes in contact with at least one electrode, and the discharge gap is cooled from both sides. In a discharge cell for an ozone generator in which a refrigerant flow path is formed outside both electrodes and a high pressure insulating plate is disposed between the two in order to insulate the high pressure side refrigerant flow path from the high pressure electrode , A discharge cell for an ozone generator in which the thickness of a high-pressure electrode disposed inside a refrigerant flow path via a high-pressure insulating plate is 10 times or more the total thickness of a dielectric disposed between the high-voltage electrode and the low-pressure electrode.   It is an assembly type in which plate materials are overlapped in the plate thickness direction and fastened and fixed by tie rods, and the plate thickness of the high voltage insulating plate is 0.5 times or more of the total thickness of the dielectric disposed between the high voltage electrode and the low voltage electrode The discharge cell for an ozone generator according to claim 1, wherein the discharge cell is 3.5 times or less.   The discharge for an ozone generator according to claim 1 or 2, wherein a pair of dielectrics are disposed between the high voltage electrode and the low voltage electrode so as to contact both electrodes, and a discharge gap is formed between the pair of dielectrics. cell.   The dielectric of 1 sheet is arrange | positioned between the high voltage electrode and the low voltage electrode in contact with only the high voltage electrode, and a discharge gap is formed between the dielectric and the low voltage electrode. Discharge cell for ozone generator.

Images