JPH10180037A - Ozone decomposition ceramic heater unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ozone decomposition device which surely decomposes ozone without receiving an adverse influence from moisture and is semipermanently used without being subjected to corrosion by gaseous ozone even for waste gas containing ozone and having high moisture, differing from an ozone decomposition catalyst whose decomposition capacity is remarkably decreased by moisture. SOLUTION: This device is provided with a cylindrical ceramic heater 20 with heater wiring being buried in ceramic and a case body 21 made of stainless steel installed so as to surround the outer periphery of the ceramic heater 20. A gas injection pipe 22 is inserted into the central part of the ceramic heater 20 passing through the case body 21, and the case body 21 is provided with gas discharge ports 12, 13 near a flange part 5 thereof. Waste gas containing ozone injected from the gas injection pipe 22 is passed through an annular void 23 in the central part of the ceramic heater 20 and an annular void 24 formed by the outer periphery of the ceramic heater 20 and the case body 21 and is discharged from the gas discharge ports 12, 13. During this period, the waste gas is heated by the ceramic heater 20 to thermally decompose ozone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater unit for decomposing ozone into oxygen.

[0002]

2. Description of the Related Art In recent years, ozone gas has been increasingly used in simple water purification equipment, human waste treatment equipment, and cooling water purification equipment for cooling towers. Also, ozone water is widely used for sterilizing and cleaning processed foods and medical instruments, and ozone water production apparatuses are used. Here, the ozone water shows relatively low toxicity to the human body, but the ozone gas itself may cause various problems when a large amount of the ozone gas is inhaled. Therefore, it becomes necessary to decompose and release excess ozone gas that has not been dissolved or reacted in water into oxygen.

Conventionally, an ozone decomposing catalyst in which oxides such as titanium, manganese, silicon and the like, activated carbon and the like are granulated or formed into a honeycomb structure has been used to decompose excess ozone gas. However, these ozone decomposition catalysts are susceptible to moisture and have a problem that they are immediately deactivated when used in an environment with high humidity. This is a major weak point because each of the above-mentioned devices using ozone gas emits exhaust gas having a high moisture content. Further, the ozone decomposing catalyst has a service life due to its use even if the adverse effect of moisture is removed, and the ozone decomposing ability is reduced when a large amount of ozone is decomposed. For this reason, there has been a problem that the ozone decomposition catalyst must be frequently replaced. Therefore, it is conceivable to perform thermal decomposition using a resistor heater that becomes hot without using an ozone decomposition catalyst. However, ozone gas has extremely strong oxidizing power, and a resistor heater made of ordinary nichrome wire or the like can be used within a short period of time. There was a problem that it was oxidized and corroded.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the present invention according to claims 1 to 4 of the present invention provides a method for removing ozone gas containing a large amount of moisture even if the exhausted ozone gas contains a large amount of moisture. Decomposition without being adversely affected by
An object of the present invention is to provide a ceramic heater unit for decomposing ozone gas which can be used semi-permanently without being corroded by ozone gas. It is an object of the present invention to provide a ceramic heater unit for decomposing ozone gas, in which the effects of the inventions of claims 1 to 4 are more reliably achieved.

[0005]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, there is provided a ceramic heater in which a heater wiring formed by a metallizing technique is embedded in a ceramic; A gas distribution means for preventing gas from coming into contact with the electrode terminal portion of the heater and for flowing the gas along the surface of the ceramic heater is provided. Here, the gas distribution means refers to all means for blowing a gas onto the surface of the ceramic heater and causing the gas to flow along the surface. When formed in this way, the gas flows along the surface of the ceramic heater, and the ozone gas in the gas is heated and decomposed by heating. Since the ozone gas only touches the surface of the ceramic heater made of ceramic and does not touch the embedded heater wiring, the heater wiring does not corrode.

Here, the ceramic heater is a cylindrical ceramic heater having a flange, and the gas circulating means includes means for injecting gas into the center of the cylindrical ceramic heater. And a bottomed cylindrical case body that surrounds the outer periphery of the cylindrical ceramic heater and closely contacts the flange and has a gas discharge port near the flange. The flange of the ceramic heater and the case body may be in direct contact with each other, or may be in close contact with each other via a packing. In addition, the members may be brought into close contact with each other via other members, and may have any contact structure in which gas does not leak. With this configuration, the gas injected into the center of the cylindrical ceramic heater flows through the inner peripheral portion of the ceramic heater and is heated by the ceramic heater. The gas that has passed through the inner peripheral portion of the ceramic heater abuts on the bottom of the cylindrical case body, is changed in direction, and flows in the flange direction along the outer periphery of the cylindrical ceramic heater. At this time, the ozone gas is heated and decomposed by the ceramic heater. The decomposed gas is discharged outside from a gas discharge port near the flange.

Further, the ceramic heater is a bottomed cylindrical ceramic heater having a flange and one end of which is sealed, and the gas flow means is provided at the center of the cylindrical ceramic heater. A gas injection pipe inserted into the portion and opened near the bottom of the ceramic heater, and a bottomed cylindrical case body surrounding the outer periphery of the cylindrical ceramic heater and closely contacting the flange and having a gas discharge port near the flange. It can be characterized. The flange of the ceramic heater and the case body may be in direct contact with each other, or may be in close contact with each other via a packing. In addition, the members may be brought into close contact with each other via other members, and may have any contact structure in which gas does not leak. When formed in this manner, the gas injected from the gas injection pipe abuts against the bottom of the ceramic heater and is changed in direction, so that the inner periphery of the cylindrical ceramic heater and the annular space surrounded by the gas injection pipe are filled with the ceramic heater. It flows along the inner circumference and is heated. The gas discharged from the inner peripheral portion of the ceramic heater abuts the bottom of the cylindrical case body and changes its direction, so that the annular space surrounded by the outer periphery of the cylindrical ceramic heater and the case body extends along the outer periphery of the ceramic heater. Flows in the direction of the flange. At this time, the ozone gas is heated by the ceramic heater and decomposed. The decomposed gas is discharged outside from a gas discharge port near the flange.

According to a fourth aspect of the present invention, the ceramic heater is a plate-shaped ceramic heater, and the gas distribution means extends the electrode terminal portion of the ceramic heater to the outside to form the plate-shaped ceramic heater. It can be characterized by being composed of a case body that surrounds and has a gas inlet and a gas outlet. When formed in this manner, the gas introduced from the gas inlet is blown to the plate-shaped ceramic heater, and the ozone gas is heated and decomposed. The decomposed gas is discharged from the gas discharge port to the outside.

Further, according to the present invention, the temperature of the ceramic heater is increased from 150 ° C. to 600 ° C.
Temperature control means for controlling the temperature to a predetermined temperature range within the range. More preferably, the predetermined temperature range is controlled within a range from 300 ° C to 500 ° C. If the temperature of the ceramic heater is lower than 150 ° C., the decomposition rate of the blown ozone gas becomes slow, and the gas may not be sufficiently decomposed while flowing along the ceramic heater, and the ozone gas may be discharged while remaining. . On the other hand, if the temperature of the ceramic heater is higher than 600 ° C., the heat resistance of the member holding the ceramic heater becomes a problem, causing a problem in practicality. From these points, it is preferable to control the temperature of the ceramic heater within the range of 300 ° C. to 500 ° C. For example, when the ozone gas is heated to 500 ° C., the ozone gas is decomposed in about 0.5 seconds.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a cylindrical ceramic heater 10 having a flange with a part cut away. Two ceramic layers 2 and 3 made of alumina are wound around the outer periphery of a ceramic insulator tube 1 made of hollow cylindrical alumina to be integrated. A heater wire 4 made of tungsten is embedded between the two ceramic layers 2 and 3. The flange 5 is fixed to the upper outer periphery of the ceramic heater 10. Above the flange 5, electrode terminals 6 and 7 connected to the heater wiring 4 are provided. The electrode terminals 6 and 7 are plated with nickel to facilitate brazing of the electric wires.

A method for manufacturing the cylindrical ceramic heater 10 having the flange 5 will be described. MgO 2% (weight ratio, same hereafter), CaO 2
% And SiO ₂ 4%, and wet-pulverized with a ball mill for 50 to 80 hours, followed by dehydration and drying. 3% isobutyl methacrylate, 3% butyl ester,
Nitrocellulose 1%, dioctyl phthalate 0.5%
And trichloroethylene as a solvent, n
-Add butanol and mix with a ball mill to form a free flowing slurry. After defoaming under reduced pressure, the mixture is poured into a flat plate and gradually cooled, and the solvent is diffused to form one high-purity alumina green sheet having a thickness of 0.5 mm and a thickness of 0.05 mm.

In a similar manner, the tungsten powder is made into a slurry to form a metallized ink. 0.5m thick
The heater wiring is printed on the alumina green sheet of m using a normal screen printing method, and a thickness of 0.05 m is formed thereon.
m alumina green sheets are laminated and thermocompression bonded. A through hole for forming electrode terminals 6 and 7 to be connected to the heater wiring 4 is formed at one end of the thermally pressed alumina green sheet, and the through hole is filled with metallized ink. The thus formed product is wound around a ceramic insulator tube 1 made of alumina, at 1400 ° C. to 160 ° C.
Co-firing in a non-oxidizing atmosphere at 0 ° C. A ceramic flange 10 made of ceramic is attached to the fired cylindrical ceramic heater body, and nickel plating is applied to the electrode terminals 6 and 7 to complete the ceramic heater 10.

FIG. 2 shows a first embodiment, and is a cross-sectional view showing a ceramic heater unit 9 using the above-described ceramic heater 10. A cylindrical bottomed cylindrical case body 11 is attached to a cylindrical cylindrical ceramic heater 10 having the flange 5 described in FIG. The case body 11 has an end 11A attached to the flange 5 in close contact with the flange 5, and the outer periphery of the ceramic heater 10 is surrounded by a cylindrical part 11B and a bottom part 11C. Two gas discharge ports 12 and 13 are formed near the flange 5 of the cylindrical portion 11B of the case body 11. The case body 11 is formed of a stainless steel material resistant to ozone gas. A temperature detector 14 is attached to the outer periphery of the cylindrical portion 11B of the case body 11. Temperature detector 14
Is a thermocouple or a thermistor. The temperature detector 14 is connected to a control device 15, and the control device 15 is connected to the electrode terminals 6 and 7 of the ceramic heater 10. The control device 15 adjusts the temperature of the case body 11 from 300 ° C. to 50 ° C.
On / off control of the ceramic heater 10 is performed so as to be within the range of 0 ° C.

The operation will be described based on the above configuration. As shown by an arrow in FIG. 2, an exhaust gas containing moisture and ozone gas is injected into the central portion 16 of the cylindrical ceramic heater 10 from above in the drawing. The injected exhaust gas passes through the central portion 16 while being heated by the inner periphery of the ceramic heater 10. The exhaust gas that has passed through the central portion 16 of the ceramic heater 10 contacts the bottom 11 </ b> C of the case body 11 and changes its direction, and rises in an annular space 17 surrounded by the outer periphery of the ceramic heater 10 and the case body 11. At this time, the exhaust gas is heated from 300 ° C. to 500 ° C. by the outer periphery of the ceramic heater 10.
° C, and all the ozone gas in the exhaust gas is thermally decomposed into oxygen. The thermally decomposed exhaust gas is collected in the vicinity of flange 5
The gas is discharged from the two gas discharge ports 12 and 13 into the atmosphere. In these processes, the exhaust gas comes into contact with the case body 11 made of ceramics made of alumina and stainless steel on the surface of the ceramic heater 10, and the electrode terminals above the heater wiring 4 and the flange 5 embedded in the ceramic heater 10 are formed. Since the ceramic heater 10 does not come into contact with 6, 7 there is no possibility that the ceramic heater 10 will be corroded by ozone gas. Further, since the thermal decomposition is performed, the ceramic heater 10 is not inactivated by moisture in the exhaust gas as in the case of a catalyst, and is not deteriorated by the decomposition of ozone.
Can be used semi-permanently.

FIG. 3 is a cross-sectional view showing a ceramic heater unit 19 according to a second embodiment. In this embodiment, a ceramic heater 20 having a cylindrical shape and a bottomed cylindrical shape having a flange 5 and a closed upper end is used for the ceramic heater. The point that the case body 21 made of stainless steel having a bottomed cylindrical shape, which is a bottomed cylindrical shape, is attached to the flange 5 of the ceramic heater 20 in close contact with the flange 5 is the same as in the above-described embodiment. Two gas discharge ports 1 are provided near the flange 5 of the cylindrical portion 21B of the case body 21.
2 and 13 are formed. In this embodiment, a gas injection pipe 22 made of a stainless steel pipe is attached so as to penetrate the bottom 21C of the case body 21. The gas injection pipe 22 is inserted into the center of the cylindrical ceramic heater 20 and opens near the bottom 20A of the ceramic heater 20. The temperature detector 14 is attached to the outer periphery of the cylindrical portion 21B of the case body 21. The temperature detector 14 is connected to a control device 15, which controls the ceramic heater 20.
Are connected to the electrode terminals 6, 7. The control device 15 controls the ceramic heater 20 to be on and off so that the temperature of the case body 21 falls within a range of 300 ° C. to 500 ° C.

The operation will be described. As shown by arrows in FIG. 3, an exhaust gas containing moisture and ozone gas is injected into the gas injection pipe 22 from the right side of the drawing. The injected exhaust gas is discharged from the gas injection pipe 22 near the bottom 20A at the center of the ceramic heater 20. The discharged exhaust gas comes into contact with the bottom 20 </ b> A of the ceramic heater 20 and changes its direction, and rises downward in an annular space 23 surrounded by the outer periphery of the gas injection pipe 22 and the inner periphery of the ceramic heater 20. At this time, the exhaust gas is heated by the inner periphery of the ceramic heater 20. Exhaust gas that has passed through the center of the ceramic heater 20 abuts the bottom 21 </ b> C of the case body 21 and changes its direction, so that an annular space 2 surrounded by the outer periphery of the ceramic heater 20 and the case body 21.
4 rises. At this time, the exhaust gas is discharged from the ceramic heater 20.
Is heated from 300 ° C. to 500 ° C. by the outer periphery of the exhaust gas, and all the ozone gas in the exhaust gas is thermally decomposed into oxygen. The thermally decomposed exhaust gas is supplied to two gas outlets 1 near the flange 5.
It is discharged into the atmosphere from 2 and 13. The operation in this process is the same as in the first embodiment. In the second embodiment, there is an advantage that the time in which the exhausted ozone gas contacts the ceramic heater 20 and is heated becomes longer, and ozone can be more reliably decomposed.

In the embodiment described above, the flange 5
Although the description has been given of the case where the cylindrical ceramic heaters 10 and 20 having the following are used, the ceramic heater does not need to be cylindrical, and a plate-shaped flat ceramic heater 30 as shown in FIG. 4 may be used. . In the ceramic heater 30, a heater wiring 31 made of tungsten is embedded in a flat ceramic body made of alumina, and an electrode terminal 32 connected to the heater wiring 31 is provided on an upper portion thereof.
33 are provided. A method for manufacturing the plate-shaped ceramic heater 30 shown in FIG. 4 will be described. First
In the same manner as described in the embodiment, a fluid slurry made of alumina powder is prepared, and after degassing under reduced pressure, it is poured out into a flat plate and gradually cooled, and the solvent is diverged to a thickness. Two 0.5 mm high-purity alumina green sheets are formed. In a similar manner, the tungsten powder is converted into a slurry to form a metallized ink. Heater wiring and electrode terminals are printed on one alumina green sheet using a normal screen printing method, and the other alumina green sheet is stacked thereon and thermocompression-bonded. The product thus formed is fired in a non-oxidizing atmosphere at 1400 ° C to 1600 ° C. Fired flat ceramic heater 30
The electrode terminals 32 and 33 are plated with nickel to complete the ceramic heater 30.

FIG. 5 is a perspective view showing a ceramic heater unit 35 using a plate-shaped ceramic heater 30. In this embodiment, two flat plate-shaped ceramic heaters 30 and 40 are used. The case terminals 4 that surround the two ceramic heaters 30 and 40 by exposing the electrode terminals 32 and 33 of the ceramic heaters 30 and 40 to the outside.
1 is provided. The casing 41 is made of stainless steel and has a gas inlet 4 at the left end of the front surface.
2 is provided with a gas discharge port 43 at the right end of the rear surface. The casing 41 is divided by two ceramic heaters 30 and 40 into a front chamber 44 following the gas inlet 42, an intermediate chamber 45 defined by the front and rear ceramic heaters 30 and 40, and a gas discharge port 43. The subsequent rear chamber 46 is divided. The two ceramic heaters 30 and 40 are arranged in a staggered manner, and the front ceramic heater 30 is arranged to the left side so as to form a gap 47 between the right end of the ceramic heater 30 and the right side surface of the case body 41. Have been. On the other hand, the rear ceramic heater 40 is a case body 41.
Are arranged so that a gap 48 is formed between the left end of the ceramic heater 40 and the left side surface of the case body 41. The temperature detector 14 is mounted on the left side surface of the case body 41. The temperature detector 14 is connected to a control device 15, and the control device 15 is connected to the electrode terminals 32, 33 of the ceramic heaters 30, 40.
The controller 15 sets the temperature of the case body 41 from 300 ° C to 5 ° C.
The temperature of the ceramic heaters 30 and 4 is set to fall within the range of 00 ° C.
0 is turned on / off.

The operation will be described. As shown by arrows in FIG. 5, exhaust gas containing moisture and ozone gas is injected into the gas inlet 42. The injected exhaust gas is blown onto the flat ceramic heater 30 and flows along the surface of the ceramic heater 30. The exhaust gas flowing along the surface of the front ceramic heater 30 fills the front chamber 44 and then flows into the intermediate chamber 45 from a gap 47 between the right end of the front ceramic heater 30 and the right side of the case body 41. Intermediate room 45
Exhaust gas filled in the rear chamber 4 passes through a gap 48 between the left end of the rear ceramic heater 40 and the left side surface of the case body 41.
Flow into 6. The exhaust gas filled in the rear chamber 46 is discharged from the gas discharge port 43 to the atmosphere. Exhaust gas is in gas inlet 4
Between the two ceramic heaters 30 and 40 between the time when the gas is injected from the gas discharge port 2 and the gas is discharged from the gas discharge port 43.
The ozone gas is completely decomposed into oxygen and discharged from a temperature of from 500C to 500C.

In the above-described embodiment, two plate-shaped ceramic heaters 30 and 40 are used. However, a larger number of plate-shaped ceramic heaters are arranged in a zigzag to form a ceramic heater unit. Alternatively, the ceramic heater unit may be composed of a single plate-shaped ceramic heater. Further, in the above-described embodiment, the temperature detector 14 is attached to the case bodies 11, 21, and 41, but the temperature detector 14 is directly connected to the ceramic heaters 10, 2 and 41.
You may make it attach to the main body of 0,30,40.
Further, in the above embodiment, the case body 11
Although 21 and 41 are made of stainless steel, they may be made of any material having heat resistance and ozone resistance, for example, ceramic.

[0021]

As described above, the present invention uses a ceramic heater in which a heater wiring formed by a metallization technique is embedded in a ceramic, and allows the gas to be treated containing ozone to flow along the surface of the ceramic heater. As a result, even if the exhausted ozone gas is rich in moisture, it reliably decomposes ozone without being adversely affected by moisture, and is not subject to corrosion or deterioration due to ozone gas.
There is an excellent effect that ozone can be decomposed semipermanently.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cylindrical ceramic heater having a flange with a part cut away.

FIG. 2 shows the first embodiment, and is a cross-sectional view of a ceramic heater unit.

FIG. 3 is a cross-sectional view of a ceramic heater unit according to the second embodiment.

FIG. 4 is a front view showing the ceramic heater having a plate shape with a part cut away.

FIG. 5 is a perspective view of a ceramic heater unit according to the third embodiment.

[Explanation of symbols]

 6, 7 Electrode terminal 12, 13 Gas outlet 14 Temperature detector 15 Control device 19 Ceramic heater unit 20 Ceramic heater 21 Case body 22 Gas injection tube 23 Annular gap 24 Annular gap

Claims (5)

[Claims] A ceramic heater in which a heater wiring formed by a metallization technique is embedded in a ceramic;
A ceramic heater unit for decomposing ozone, comprising: gas distribution means for preventing gas from coming into contact with an electrode terminal portion of the ceramic heater and flowing the gas along the surface of the ceramic heater. 2. The ceramic heater according to claim 1, wherein the ceramic heater is a cylindrical ceramic heater having a flange, wherein the gas flowing means includes means for injecting a gas into a central portion of the cylindrical ceramic heater, and a peripheral part of the cylindrical ceramic heater. 2. The ceramic heater unit for decomposing ozone according to claim 1, wherein said ceramic heater unit has a bottomed cylindrical case body which is in close contact with the surrounding flange and has a gas discharge port near the flange. 3. The ceramic heater is a bottomed cylindrical ceramic heater having a flange and one end sealed, wherein the gas flow means is inserted into a center of the cylindrical ceramic heater and the bottom of the ceramic heater. 2. A bottomed cylindrical case body having a gas injection pipe which is open in the vicinity and which is in close contact with a flange surrounding the outer periphery of the cylindrical ceramic heater and has a gas discharge port in the vicinity of the flange. The ceramic heater unit for ozone decomposition according to the above. 4. The ceramic heater is a plate-shaped ceramic heater, and the gas distribution means surrounds the plate-shaped ceramic heater by extending an electrode terminal portion of the ceramic heater to the outside, and has a gas introduction port and a gas discharge port. The ceramic heater unit for ozone decomposition according to claim 1, comprising a case body having: 5. The temperature of the ceramic heater is set to 150 °
2. A temperature control device for controlling a temperature within a predetermined temperature range from C to 600 ° C.
The ceramic heater unit for ozone decomposition according to 2, 3, or 4.