JPH07289617A - Ultraviolet ray radiating device - Google Patents

Abstract

PURPOSE:To provide an ultraviolet ray radiating device which prevents the drop of the output of ultraviolet rays by preventing water from collecting in an outer tube jacket. CONSTITUTION:This ultraviolet rays radiating device accommodates a low- pressure mercury lamp 20, where the coldest section is made at the bottom, in an outer tube jacket 10 whose bottom is soaked in processing liquid and whose top is opened. The top opening of the outer tube jacket 10 is closed with block means 14 and 15 which check the passage of air. Since the top of the outer jacket is closed in this way, the moisture contained in the outside air ceases to be brought in the outer tube jacket, so this can prevents moisture from dewing and water from collecting inside the outer tube jacket. Accordingly, the coldest section of the low-pressure mercury lamp is prevented from contacting with water, and the mercury steam pressure an be kept properly, and the drop of the output of the ultraviolet rays can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet irradiation device used for irradiating a treatment liquid such as sewage or the like with ultraviolet rays emitted from a low-pressure mercury lamp for purification or sterilization.

[0002]

2. Description of the Related Art Recently, a method of irradiating ultraviolet rays (UV) to purify various gases and liquids or to decompose organic substances has been adopted. For example, in the field of purification and sterilization of sewage, purification and sterilization. A means for irradiating water to be watered with an ultraviolet ray irradiation lamp is used. A low-pressure mercury lamp is known as a light source for this ultraviolet irradiation.

A low-pressure mercury lamp has a structure in which filament electrodes are sealed at both ends of an arc tube bulb, and a predetermined amount of mercury and a rare gas such as argon are sealed inside. This low-pressure mercury lamp differs from fluorescent lamps for general lighting in that the bulb material forming the arc tube is made of quartz glass, which has excellent transparency to far-ultraviolet rays, and is not provided with a phosphor coating. However, in other respects, it has a structure similar to that of a fluorescent lamp for general lighting, and has the same discharge / lighting action.

In such a low-pressure mercury lamp, mercury atoms in the arc tube are ionized and excited by discharge, and at this time, ultraviolet rays of 185 nm and 254 nm, which are mercury resonance lines, are emitted, and the ultraviolet rays pass through the tube wall of the arc tube. And then released to the outside. Therefore, ultraviolet rays of 254 nm mainly kill Escherichia coli.

Usually, when irradiating various liquids with ultraviolet rays, the low-pressure mercury lamp is housed in an outer tube jacket, and the outer tube jacket is immersed in a treatment liquid. The outer tube jacket is made of quartz glass, which has excellent UV transparency. The closed lower end is immersed in the processing liquid, and the open upper end is located above the liquid surface of the processing liquid. A low-pressure mercury lamp is inserted from the open part of the. The replacement and maintenance of the lamp are performed from the open part at the upper end, and the lead wire is also led out from this open part.

By the way, recently, improvement of the sterilizing ability of water and the ability of decomposing organic substances has been desired, and an irradiation device having a large ultraviolet ray output has been required. In the past, it was a straight tube arc tube with a rating of 65W and a total length of 1000mm,
Moreover, low-pressure mercury lamps with a tube wall load of 0.1 W / cm ² dominated, but a low-pressure mercury lamp with a rating of 65 W can only be expected to have a processing capacity of 100 m ³ a day. In contrast,
A medium-scale sewage treatment plant is required to have a treatment capacity of 5000 m ³ per day, and therefore a low pressure mercury lamp rated at 65 W requires 50 lamps. When such a large amount of low pressure mercury lamp is used, maintenance becomes complicated.

Therefore, a low-pressure mercury lamp rated at 1000 W has been developed in which the tube wall load is increased to 0.2 W / cm ² or more. The low-pressure mercury lamp rated at 1000 W has a UV output of 254 nm ten times that of the low-pressure mercury lamp rated at 65 W, and the required number of lamps is about 1/10 of the conventional one.

[0008]

However, when such a high-power low-pressure mercury lamp is housed in the outer tube jacket and lit, the UV output may drastically decrease especially in winter. When the ultraviolet ray output decreases, the bactericidal ability of Escherichia coli proportionally decreases and the processing ability decreases.

The present inventors have made various studies on this point, and the reason why the ultraviolet ray output is lowered in this type of ultraviolet ray irradiating device is that water is accumulated inside the outer tube jacket, and this water is generated by the low pressure mercury lamp. It was found that this temperature was lowered by contacting the coldest part formed in the lower part. As a result of investigating the cause of water accumulation in the outer jacket, it was found that dew condensation occurred on the inner surface of the outer jacket and the water drops gradually increased to form a water pool.

The dew condensation occurs on the inner surface of the outer tube jacket because the air remains in the outer tube jacket. To prevent this, the air in the outer tube jacket is
Condensation can be prevented by substituting with an inert gas such as nitrogen. However, if the air inside the outer tube jacket is replaced,
Each time the lamp is inspected or replaced, the inside of the outer tube jacket must be replaced again, resulting in poor workability.

On the other hand, in the above-mentioned high-load, high-output low-pressure mercury lamp, the temperature of the wall of the arc tube is 150 to 1 during lighting.
Since the temperature reaches 80 ° C., the arc tube is provided with a protrusion called a mercury reservoir so that the protrusion becomes the coldest portion and mercury is condensed in the coldest portion. The protrusions are designed so that the mercury temperature is 40 ° C. by the balance between the heat from the arc tube and the heat released to the outside. However, when the outer tube jacket is immersed in the processing solution and irradiated with ultraviolet rays, the temperature of the outer tube jacket is affected by the temperature of the external processing solution, and the mercury temperature is always maintained at the optimum operating temperature of 40 ° C. Becomes impossible. Therefore, without providing a protrusion
It is possible to install an amalgam. In the case of a U-shaped arc tube, the part that bends in a U-shape is located on the lower side,
The added amalgam stops at the portion that bends in a U shape and comes to exist here.

However, when such a lamp is turned on, the coldest part is generated behind the electrode, and the evaporated mercury gathers in the coolest part behind the electrode, and the mercury vapor pressure is regulated smoothly at the optimum operating temperature. There are some bugs that you cannot do.

Therefore, a first object of the present invention is to provide an ultraviolet irradiating device which prevents water from accumulating in the outer tube jacket and prevents a decrease in ultraviolet light output.

A second object of the present invention is to provide an ultraviolet irradiation device which, when using amalgam, prevents the coldest part from occurring behind the electrode and maintains an optimum vapor pressure. It is the one we are trying to provide.

[0015]

According to a first aspect of the present invention, an outer tube jacket having a sealed end at a lower end immersed in a treatment liquid and an upper end opened, and an outer tube jacket housed in the outer tube jacket, are made of quartz. A low-pressure mercury lamp in which electrodes are sealed at both ends of an arc tube made of glass, mercury and a rare gas are sealed inside, and a coldest part is formed at a lower end;
In an ultraviolet irradiating device adapted to irradiate ultraviolet rays radiated from the low-pressure mercury lamp through the outer tube jacket to irradiate an external processing solution, the upper end opening portion of the outer tube jacket is closed to prevent gas from passing therethrough. It is characterized by being closed by means.

The invention of claim 2 is characterized in that the low-pressure mercury lamp is lit at a tube wall load of 0.2 to 1.5 W / cm ² . The invention according to claim 3 is characterized in that the arc tube has a U-shape with a bent portion located on the lower side.

The invention of claim 4 is characterized in that the amalgam is held in the bent portion. The invention of claim 5 is
The low-pressure mercury lamp is characterized in that it is connected to a lighting circuit.

[0018]

According to the invention of claim 1, since the upper end of the outer tube jacket is closed, the air inside the outer tube jacket and the outside air do not interchange with each other, and the moisture contained in the outside air is removed from the outer tube. Since it is not brought into the inside of the jacket, it is possible to prevent dew condensation inside the outer tube jacket and to prevent the amount of dew condensation from gradually increasing, and to prevent water from accumulating inside the outer tube jacket. Therefore, the coldest part formed in the lower part of the low-pressure mercury lamp is prevented from coming into contact with water and its temperature is lowered, the vapor pressure of mercury is appropriately maintained, and the ultraviolet ray output is prevented from lowering. Therefore, the first purpose can be achieved.

According to the invention of claim 2, dew condensation is apt to occur when the low-pressure mercury lamp is lit under the condition that the tube wall load is 0.2 to 1.5 W / cm ^2. According to this, water can be prevented from accumulating inside the outer tube jacket even under such adverse conditions.

According to the third aspect of the present invention, since the arc tube is U-shaped, the arc tube can be doubled in length as compared with the straight tube having the same length, resulting in a large light emitting area. , The amount of UV emission increases. In this case, the bent portion is located on the lower side, and the coldest portion is formed there to condense mercury. However, there is a concern that the coldest portion may get wet with water accumulated in the outer tube jacket. Even under such conditions, the above structure prevents water from accumulating in the outer tube jacket, and thus prevents the ultraviolet intensity from decreasing.

According to the invention of claim 4, in the case of the low-pressure mercury lamp in which the amalgam is held in the bent portion, when the upper end of the outer tube jacket is opened, the arc tube is located at the rear end of the electrode. The coldest part is generated, and mercury is condensed here. On the other hand, when the open upper end portion of the outer tube jacket is closed, the temperature of the upper end portion becomes higher inside the outer tube jacket, and the temperature of the rear portion of the electrode of the low-pressure mercury lamp can be increased. Therefore, the coldest part is prevented from being generated behind the electrode, and the evaporated mercury comes to collect on the amalgam of the bent part. Therefore, the second object can be achieved. According to the invention of claim 6, since the low-pressure mercury lamp is connected to the lighting circuit, the lighting is maintained satisfactorily.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the first embodiment shown in FIGS. The drawing shows an example of an ultraviolet irradiation device used in a sewage sterilization and purification treatment facility, and FIG. 2 is a plan view of a sewage water purification tank. The water purification tank 1 has, for example, a meandering sewage passage, and a sterilizing apparatus 2 is installed in the meandering passage. The sterilization apparatus 2 is composed of a plurality of sets of ultraviolet irradiation units 3 ...
A plurality of ultraviolet irradiation devices 10 ... Are attached to each ultraviolet irradiation unit 3.

In the case of this embodiment, four sets of ultraviolet irradiation units 3 are provided in the passage of the septic tank 1, and four ultraviolet irradiation devices 10 are installed in each ultraviolet irradiation unit 3. . Therefore, 16 ultraviolet irradiation devices 10 are used in total.

The structure of the ultraviolet irradiation unit 3 is shown in FIG. 4, where 31 is a unit upper plate and 32 is a unit lower plate. These unit upper plate 31 and unit lower plate 32
Are connected by a plurality of columns 33 .... Four unit mounting holes 34 are opened in the unit upper plate 31, and pedestals 35 are mounted in the unit lower plate 32 so as to face the mounting holes 34. A recess 36 is formed in the pedestal 35 ....

The four mounting holes 34 of the unit upper plate 31
The above-mentioned ultraviolet irradiating device 10 is arranged from above.
Is designed to be detachably inserted. As will be described later, the ultraviolet irradiation device 10 has an outer tube jacket 11, the outer tube jacket 11 is inserted through the mounting holes 34, and the closing wall at the lower end is supported by the recess 36 of the pedestal 35. It is like this. In this case, outer jacket 1
The opening 12 at the upper end of 1 is located in the mounting hole 33.

Here, the structure of the ultraviolet irradiation device 10 will be described with reference to FIG. Outer tube jacket 11
Is made of quartz glass that transmits far-ultraviolet rays, and the lower end is closed and the upper end is open, and it has a shape just like a large test tube.
For example, when the rating is 1000 W, the outer shape of the outer tube jacket 11 is 85 mm and the total length is 1600 mm.

A low-pressure mercury lamp 20 is housed in this outer tube jacket 11. The low-pressure mercury lamp 20 comprises a U-shaped arc tube 21 made of synthetic quartz glass with an inner diameter of 30 mm.
And the U-shaped bend is located below.
Anodes 22, 22 and cathodes 23, 23 are sealed at both ends of the arc tube 21, respectively.
2 and the cathodes 23, 23 are connected to external lead wires 24 ....

The arc tube 21 is provided with a protruding thin tube 25 at a bent portion bent in a U shape.
Contains mercury. This thin tube 25 is the arc tube 21.
For example, about 30 mm is projected from the bent portion of the above, so that the temperature of mercury is kept around 40 ° C. which is the optimum operating temperature. Therefore, the mercury vapor pressure in the arc tube 21 is kept optimal. In addition to the mercury, the arc tube 21 is filled with a rare gas such as argon, neon, or a neon-argon Penning gas.

The low-pressure mercury lamp 20 is provided with lamp holders 26, 26 at a plurality of vertically spaced locations, and these lamp holders 26, 26 are made of leaf springs or the like and make elastic contact with the inner surface of the outer tube jacket 11. It is like this. Therefore, the low-pressure mercury lamp 20 is held at a predetermined position on the outer tube jacket 11 via these lamp holders 26, 26. As a result, the outer surface of the arc tube 21 is spaced from the inner surface of the outer tube jacket 11.

When the low-pressure mercury lamp 20 as described above is lit, the mercury atoms in the arc tube 21 are ionized and excited by the alternating discharge between the anodes 22, 22 and the cathodes 23, 23, and at this time, they are mercury resonance lines. 185nm and 254nm
Of the ultraviolet rays, and the ultraviolet rays are transmitted to the outside through the arc tube 21 and the tube wall of the outer tube jacket 11. Therefore, the wastewater outside the outer pipe jacket 11 is irradiated with ultraviolet rays, and the wastewater is purified and sterilized.

The ultraviolet irradiating device 10 having the above structure is inserted into the mounting holes 34 ... Of the unit upper plate 31 described above, the closing wall at the lower end of the outer tube jacket 11 is supported by the recess 36 of the pedestal 35, and the upper end thereof is also supported. The opening 12 is located in the mounting hole 34. The upper end opening 12 of the outer tube jacket 11 is covered with an inner lid 14 via a packing 13 made of an elastic material such as rubber, and the inner lid 14 is pressed by the outer lid 15. ing. The inner lid 14 and the outer lid 15 constitute the closing means for blocking the passage of gas of the present invention, and the outer lid 15 is the unit upper plate 31.
It is adapted to be screwed into a threaded portion 38 formed in the mounting hole 34. By screwing the outer lid 15, the outer lid 1
5 is screwed to the unit upper plate 31 and presses the inner lid 14. The inner lid 14 pushes the upper end opening 12 of the outer tube jacket 11 via the packing 13, and thus the outer tube jacket 11 includes the unit upper plate 31 and the unit lower plate 32.
Supported by.

The inner lid 14 and the outer lid 15 are provided with lead-out holes 17 and 18 of a size large enough to pull out the external lead wire 24 led out from the arc tube 21. The line 24 is led out above the unit upper plate 31 through the lead-out holes 17 and 18.

In this case, most of the lead-out holes 17 and 18 formed in the inner lid 14 and the outer lid 15 are blocked by the lead-out of the external lead wire 24, and the gas flow is substantially blocked. It has become so. In addition, this lead-out hole 1
A sealing structure may be used to seal the 7,18.

As shown in FIG. 3, a lighting circuit housing 40 is provided above the unit upper plate 31, and a lighting circuit 41 for stably lighting the low-pressure mercury lamps 20 ... Is provided in the lighting circuit housing 40. Is housed.
The external lead wires 24 led out from a total of 16 arc tubes 21 are connected to the lighting circuit 41, and are connected to a power source through the lighting circuit 41.

The ultraviolet irradiating device 10 having such a structure is
The upper end open portion 12 of the outer tube jacket 11 is closed by a closing means composed of an inner lid 14 and an outer lid 15, so that the air in the outer tube jacket 11 and the outside air are prevented from being exchanged with each other. Therefore, it is possible to prevent moisture in the air from being condensed on the inner surface of the outer tube jacket 11 and gradually increasing. Therefore, water is prevented from collecting at the bottom of the outer tube jacket 11, and the protruding thin tube 25 of the arc tube 21 does not come into contact with water. Therefore, the temperature of the thin tube 25 can be maintained at about 40 ° C., which is the optimum operating temperature of mercury, the mercury vapor pressure of the low-pressure mercury lamp 20 is appropriately maintained, and the reduction of the ultraviolet ray output is prevented.

The results of the investigation conducted by the present inventors on the phenomenon of water accumulating in the outer tube jacket 11 as described above will be described. The phenomenon that water accumulates inside the outer tube jacket 11 is
Even if the upper end of the outer tube jacket 11 is left open, the low-pressure mercury lamp 20 is rated at 65 W and the tube wall load is 0.08 W /
It does not occur in the case of cm ² . Therefore, a lamp having an inner diameter of the arc tube 21 of 25 mm, a total length of 1400 mm, and a protruding length of the thin tube 25 forming the coldest part of 30 mm was prototyped, and the lamp current was changed, so that the wall load was 0.05 to 1.5 W. The temperature was changed within the range of / cm ² , and the upper end of the outer tube jacket 11 was left open to light up, and the presence or absence of water droplets was examined. In that case, water outside the outer tube jacket 11 is 5 ° C. in the range of 5 to 35 ° C.
It changed every time. Even when the tube wall load is 1.5 W / cm ² or more, the ultraviolet intensity reaches a saturated state and does not increase further, so the upper limit is regulated to 1.5 W / cm ² .

The results of this experiment are shown in the characteristic diagram of FIG. From the results of FIG. 5, when the tube wall load is less than 0.1 W / cm ² , water does not accumulate regardless of the water temperature. Pipe wall load is 0.1 W / cm ²
If it exceeds, dew condensation will occur due to the temperature difference from the outside water temperature.
Further, it is understood that when the tube wall load is 0.2 W / cm ² or more, water accumulates even if the water temperature is low or high.

Therefore, it is presumed that water is accumulated in the outer tube jacket 11 when dew condensation occurs when the temperature of the tube wall of the arc tube and the water temperature outside the outer tube jacket 11 have a certain temperature difference. It was Then, as a result of studying the measures, it was concluded that it suffices that moisture does not exist in the outer tube jacket 11.

Therefore, as shown in the above embodiment, the upper end open portion 12 of the outer tube jacket 11 is fitted with the inner lid 14.
And if it is closed by the closing means consisting of the outer lid 15,
Since the air in the outer tube jacket 11 is not replaced with the outer air, the moisture contained in the outer air is not brought into the outer tube jacket 11, and therefore the water gradually accumulates inside the outer tube jacket 11. Is prevented. By the way, when the tube wall load is 1.0 W / cm ² and the temperature of the external water is 5 ° C., even if the lamp is lit for 8500 hours (for almost one year), only about 1 cc of water is accumulated, and it wets the thin tube 25. It has been confirmed that it does not. Therefore, the temperature of the thin tube 25 can be maintained at about 40 ° C., the vapor pressure of mercury can be properly maintained, and the decrease in ultraviolet ray output can be prevented.

As described above, by closing the upper end of the outer pipe jacket 11, even if the outer wall of the outer pipe jacket 11 is turned on by a wall load of 0.2 to 1.5 W / cm ² , the water temperature outside the outer pipe jacket 11 will not change. It is possible to prevent water from accumulating. Therefore, the temperature of the thin tube 25 can be kept around 40 ° C., which is the optimum operating temperature of mercury, and the mercury vapor pressure of the low-pressure mercury lamp 20 is appropriately maintained to prevent a decrease in ultraviolet ray output. From this,
The bactericidal capacity of E. coli is maintained at a high level, and the sewage treatment capacity is maintained at a high level.

In the case of the first embodiment, the arc tube 2
In the above description, the protruding thin tube 25 is projectingly provided at the bent portion of No. 1 and pure water silver is accommodated in this thin tube 25. However, in such a configuration, the temperature of the thin tube 25 is the temperature of the water outside the outer tube jacket 11. It may fluctuate due to changes. Therefore, the thin tube 2
The temperature of 5 makes it difficult to maintain the optimum operating temperature of mercury (40 ° C.).

Therefore, as in the second embodiment shown in FIG. 6, it is conceivable to stop providing the thin tube 25 in the bent portion and install the amalgam 60 in the bent portion. That is, U
In the case of the arc-shaped arc tube 21, the U-shaped bent portion is located on the lower side, so that the amalgam 60 fed from the end is U-shaped.
It stops at the part that bends into a letter and comes to exist here. Since this position is in the positive column, it is less susceptible to ambient temperature changes, which is advantageous for maintaining the amalgam 60 at its optimum operating temperature.

However, when such a lamp 20 is turned on, the coldest portion is generated behind the electrode, and the evaporated mercury is condensed in the coldest portion behind the electrode, and the function of the amalgam cannot be achieved.

Therefore, similarly to the first embodiment, the upper end open portion 12 of the outer tube jacket 11 is connected to the inner lid 14 and the outer lid 15.
It was closed by a closure means consisting of. Since the structure of the closing means may be the same as that in FIG. 1, the drawing of this embodiment is omitted.

In this way, since the upper end open portion 12 of the outer pipe jacket 11 is closed, the outer pipe jacket 11 is closed.
Heat convection is generated inside the air, and high-temperature air moves to the upper end portion of the outer tube jacket 11. As a result, heat is trapped in the upper end of the outer tube jacket 11, and therefore the low-pressure mercury lamp 20.
Of the arc tube, that is, the temperature of the arc tube end portion at the rear of the electrode increases. Therefore, the coldest part is prevented from being formed behind the electrode, and the evaporated mercury is prevented from collecting behind the electrode.

In this case, the coldest portion is formed in the bent portion which is an intermediate portion between the electrodes, and the surplus mercury is returned to the amalgam 60 existing there. Therefore, the mercury vapor pressure can be controlled to an optimum state, and a predetermined ultraviolet intensity can be maintained.

The present invention is not limited to the purification and sterilization of water and sewage as in the above embodiment, but can be applied to an ultraviolet irradiation device used in the fields of purification and sterilization of other liquids. .

[0048]

As described above, according to the present invention, since the upper end of the outer tube jacket is closed, moisture contained in the outside air is not brought into the outer tube jacket, and dew condensation occurs inside the outer tube jacket. And the amount of dew condensation is prevented from gradually increasing, and thus water is prevented from accumulating inside the outer tube jacket. Therefore, the coldest part formed in the lower part of the low-pressure mercury lamp is prevented from coming into contact with the accumulated water and its temperature is lowered, the vapor pressure of mercury can be properly maintained, and the decrease of the ultraviolet ray output is prevented. . As a result, the sterilizing ability can be kept high and the high treating ability can be kept.

Further, in the case of a low pressure mercury lamp in which amalgam is held in the bent portion, if the upper end of the outer tube jacket is closed, the temperature of the upper end inside the outer tube jacket becomes high and the electrode rear of the low pressure mercury lamp is The temperature of the part can be increased. Therefore, the coldest part is prevented from being generated behind the electrode, and the evaporated mercury gathers in the amalgam of the bent part, so that the mercury vapor pressure can be appropriately maintained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ultraviolet irradiation device showing a first embodiment of the present invention.

FIG. 2 is a plan view of a sewage water purification tank.

FIG. 3 is a side view of a sterilization apparatus installed in a sewage water purification tank.

FIG. 4 is an exploded perspective view of an ultraviolet irradiation unit that constitutes the sterilization processing device.

FIG. 5 is a characteristic diagram showing a tube wall load, an external water temperature of an outer tube jacket, and a water drop generation state.

FIG. 6 is a sectional view of a main part of an ultraviolet irradiation device showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water purification tank 2 ... Sterilization processing apparatus 3 ... Ultraviolet irradiation unit 10 ... Ultraviolet irradiation apparatus 11 ... Outer tube jacket 12 ... Upper open part 13 ... Packing 14 ... Inner lid 15 ... Outer lid 20 ... Low pressure mercury lamp 21 ... Arc tube 22 , 22, 23, 23 ... Electrode 24 ... Lead wire 25 ... Capillary tube 31 ... Unit upper plate 32 ... Unit lower plate 33 ... Strut 34 ... Mounting hole 35 ... Pedestal 36 ... Recess 41 ... Lighting circuit 60 ... Amalgam

Claims (5)

[Claims] 1. An outer tube jacket having a sealed end at the lower end immersed in a treatment liquid and an open upper end, and the outer tube jacket accommodated in the outer tube jacket with air present therein. A low-pressure mercury lamp, in which electrodes are sealed at both ends of an arc tube made of quartz glass, mercury and a rare gas are sealed inside, and a coldest portion is formed at the lower end, In the ultraviolet irradiating device adapted to irradiate the external treatment liquid with the ultraviolet rays transmitted through the outer tube jacket, the upper end open part of the outer tube jacket may be closed by a closing means for blocking the passage of gas. Characteristic UV irradiation device. 2. The low-pressure mercury lamp has a tube wall load of 0.2 to.
The light source is turned on at 1.5 W / cm ^2.
The ultraviolet irradiation device according to. 3. The arc tube as set forth above, wherein the bent portion is located on the lower side.
The ultraviolet irradiation device according to claim 1 or 2, wherein the ultraviolet irradiation device has a letter shape. 4. The ultraviolet irradiation device according to claim 1, wherein an amalgam is held in the bent portion. 5. The ultraviolet irradiation device according to claim 1, wherein the low-pressure mercury lamp is connected to a lighting circuit.