JPH09222500A - Electron beam irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain running cost reduction and life extension of device by providing a processing means for decomposing ozone generated during irradiation of electron beam in an atmosphere containing oxygen. SOLUTION: When electron beam is irradiated to an irradiation space 22 in an irradiation chamber, ozone and nitrogen oxide are produced. If moisture exists in the space, the nitrogen oxide is solved in water to be nitric acid. The gas in that state is sucked into an exhaust port 41 and introduced in a device 42 absorbing and processing nitrogen oxide and nitric acid. In the absorbing device 42, water as absorbing liquid 45 is filled to absorb nitrogen oxide and nitric acid. As ozone is simultaneously produced in the case of electron beam irradiation and nitrogen monoxide is oxidized to be nitrogen dioxide, and so the nitrogen oxide in the exhaust gas is absorbed in the absorption liquid 45. The exhaust gas after passing the absorption device 42 is introduced in an ozone decomposition device 43 and ozone is decomposed. It is exhausted through a fan 44 or a pump for exhausting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam irradiation apparatus equipped with an apparatus for decomposing ozone generated in an irradiation chamber by irradiation with an electron beam, and more particularly to improving the life characteristics of the ozone decomposition apparatus.

[0002]

2. Description of the Related Art As an application example of electron beam irradiation having a relatively low accelerating voltage, there are many applications utilizing a radical reaction of a polymer, for example, a method of curing a resin by a polymerization reaction or crosslinking by a crosslinking reaction. is there. In this radical reaction, when oxygen is present in the irradiation atmosphere, there is a problem in that oxygen is activated and the radicals in the polymer are bound to the oxygen, thereby inhibiting the radical reaction in the polymer. Therefore, an oxygen concentration is reduced by supplying an inert gas, for example, a high-purity nitrogen gas at a low price, to the irradiation atmosphere. Since ozone is not generated in the exhaust gas, it is not necessary to consider the decomposition process.

In recent years, in order to reduce the running cost of the apparatus, studies have been conducted on a cationic polymerization type resin in which the reaction proceeds even when electron beam irradiation is performed in an atmosphere containing oxygen.
In addition, in the case of lamination and sterilization / sterilization, irradiation in an atmosphere containing oxygen does not cause any problems, so treatment in this atmosphere can be performed, but on the other hand, ozone is generated, so nitrogen is low in purity and low in cost. Gas is supplied or ozone generated by irradiation in this atmosphere is decomposed and exhausted.

The reaction caused by electron beam irradiation in an atmosphere containing oxygen is described in detail in JP-A-7-20295, but it is known that ozone and nitrogen oxides are generated. . In addition, activated carbon or a metal catalyst is generally used for ozone treatment. Then, in the conventional device, the exhaust gas is introduced into the ozone decomposition treatment device in a state of containing ozone, nitrogen oxides and moisture in the atmosphere.

[0005]

However, the activated carbon used for the ozone treatment has a short decomposition treatment capacity,
Moreover, there is a problem that the activated carbon that is solid is pulverized to generate dust. Further, if a metal-based catalyst is used, the life is semi-permanent, but if other substances adhere to the surface of the catalyst, its decomposition ability will be lost. Then, when the electron beam is irradiated, nitrogen oxides are produced at the same time as ozone, and the nitrogen oxides dissolve in water to form nitric acid if there is water. This nitric acid has high reactivity, and reacts with a metal-based catalyst to change the surface of the catalyst to nitrification. As a result, there is a problem that the decomposition processing capability of ozone decreases. Furthermore, since ozone and nitrogen oxides are contained in the oxidant and are one of pollutants that cause air pollution, it is desirable to decompose and exhaust those substances.

[0006] The present invention has been made in view of the above, and by providing an ozone decomposing apparatus for decomposing ozone generated when an electron beam is irradiated in an atmosphere containing oxygen, the running cost of the apparatus is reduced. It is an object of the present invention to provide an electron beam irradiating device which is capable of reducing the number of times, prolonging the life of the device, and having no fear of environmental pollution. In addition, it decomposes ozone with high precision and also treats nitrogen oxides and nitric acid.
An object is to provide an electron beam irradiation device that does not cause air pollution.

[0007]

In order to achieve the above object, the present invention irradiates an object to be irradiated with an electron beam in an atmosphere containing oxygen and nitrogen, and performs drying for reducing the amount of water in the atmosphere. The gas passing through the apparatus is supplied to the irradiation chamber, and a device for decomposing ozone in the exhaust gas generated in the irradiation chamber is provided. Also, the amount of water in the atmosphere should be 5
g / m ³ or less, and the ozone decomposition treatment apparatus is composed of a metal catalyst. Further, the irradiation target is irradiated with an electron beam in an atmosphere containing oxygen and nitrogen to remove nitrogen oxides or nitric acid in the exhaust gas generated in the irradiation chamber, and an ozone decomposition treatment device is provided in the subsequent stage. I will do it.

[0008]

With the above structure, when the electron beam is irradiated in the atmosphere containing oxygen and the exhaust gas thereafter can maintain a low water content, the nitrogen oxides do not change to nitric acid, and the exhaust gas Since it does not attack the surface of the catalyst that decomposes ozone, the ozone decomposing ability of the catalyst can be maintained for a long time. Further, since nitric acid that reacts with the surface of the ozone decomposing catalyst is absorbed before being introduced into the decomposing catalyst, it does not attack the surface of the catalyst decomposing the exhaust gas ozone. Decomposition ability can be maintained for a long time. Further, nitrogen oxide, which is one substance of the oxidant, is exhausted in a treated state.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electron beam irradiation apparatus which is an embodiment of the present invention. The electron beam irradiation apparatus of this embodiment is used for chemical polymerization, sterilization / sterilization treatment, and the electron beam generation unit 10, irradiation chamber 20, and irradiation window unit 30.
Is provided. The electron beam generator 10 includes a terminal 12 that generates an electron beam and an accelerating tube 14 that accelerates the electron beam generated at the terminal 12 in a vacuum space (acceleration space). Further, the inside of the electron beam generator 10 is
In order to prevent electrons from colliding with gas molecules to lose energy and to prevent oxidation of the filament 12a, a vacuum of 1.3 × 10 ^{−4 to} 1.3 × 10 ⁻⁵ Pa is maintained by a pump or the like not shown. ing. The terminal 12 has a linear filament 12a that emits thermoelectrons and a filament 12a.
A gun structure 12b for supporting the above, and a grid 12c for controlling thermoelectrons generated in the filament 12a.

Further, as shown in FIG.
A heating power supply 16a for heating the filament 12a to generate thermoelectrons, and a control DC power supply 16 for applying a voltage between the filament 12a and the grid 12c.
b, and a DC power supply 16c for acceleration that applies a voltage between the grid 12c and the window foil 32 provided on the irradiation window section 30. The irradiation chamber 20 includes an irradiation space 22 for irradiating an object with an electron beam. In the case of this embodiment, the interior of the irradiation chamber 20 is set to an atmosphere containing oxygen. Further, the object to be processed 24 is moved in the irradiation chamber 20 from the left side to the right side in FIG. 1 by a conveyor (not shown) such as a conveyor. The electron beam generator 10 and the irradiation chamber 20
The periphery of is covered with lead so that X-rays that are secondarily generated during electron beam irradiation do not leak to the outside.

The irradiation window portion 30 has a window foil 32 made of metal foil.
And a window frame structure 34 that supports the window foil 32 while cooling the window foil 32. The window foil 32 separates the vacuum atmosphere in the electron beam generator 10 from the oxygen-containing atmosphere in the irradiation chamber 20, and takes out the electron beam into the irradiation chamber 20 through the window foil 32. . Titanium Ti having a thickness of about 10 μm as a metal used for the window foil 32
There is. Usually, as the window foil 32, a Ti foil having a thickness of about 13 μm is most often used because it is mechanically easy to handle.

The filament 12 is heated by the heating power source 16a.
When a current is applied to a to heat it, the filament 12a emits thermoelectrons, and the thermoelectrons are attracted in all directions by the control voltage of the control DC power supply 16b applied between the filament 12a and the grid 12c. Of these, only those that have passed through the grid 12c are effectively extracted as electron beams. The electron beam extracted from the grid 12c is accelerated in the acceleration space in the accelerating tube 14 by the acceleration voltage of the acceleration DC power supply 16c applied between the grid 12c and the window foil 32, and then the window foil. The object to be processed, which passes through 32 and is conveyed in the irradiation chamber 20 below the irradiation window 30, is irradiated. The beam current is usually adjusted by setting the heating power supply 16a and the acceleration DC power supply 16c to predetermined values and making the control DC power supply 16b variable.

FIG. 3 shows an example of the configuration of the electron beam irradiation apparatus according to the present invention. As the electron beam irradiation apparatus, CB250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd. is used and contains oxygen to be supplied into the irradiation chamber. The compressed air dehumidifier 1 is used as a device for drying the atmosphere. The dehumidifier has an atmospheric pressure dew point of −2 ° C. to −15 ° C. The dry air is supplied from the compressor 4 through the filter 3 of 5 μm, and the compressed air is supplied after the regulator 2 for adjusting the supply pressure. The dehumidification is performed by passing through the dehumidifier 1. The supply flow rate in this case is 100 l / min. It is.

Next, an experimental example will be described. It was decided to confirm the ratio of the concentration of nitrogen oxides at the inlet and outlet of the ozone decomposition catalyst by checking whether or not the supply gas passed through the dehumidifier 1 as a drying device. The ozone decomposition catalyst used was a manganese-type honeycomb type, and the concentration of nitrogen oxides was measured with a Kitagawa type detector tube. In this case, the temperature of the irradiation chamber is 25 ° C. and the humidity is 68% RH. The measurement results of the concentration of this nitrogen oxide are shown in Table 1.

[0015]

[Table 1]

In the ozone decomposition in the above experimental example, since the decomposition catalyst was the latest, the concentration of ozone at the inlet was 50 ppm and the concentration of the outlet was less than 0.1 ppm. Furthermore, after performing a life test for 500 hours with or without a dehumidifier, the ozone decomposing ability of each was measured. When the dehumidifier was not used, the ozone inlet concentration was 50 pp.
m was 3 ppm at the exit. On the other hand, with the dehumidifier, the initial characteristics were maintained and the outlet concentration was 0.1 ppm or less.

The dehumidifier of the above experimental example is in a state where the atmospheric dew point temperature is low and the saturated moisture content is almost removed. In practice, the moisture content is preferably low, but the minimum condition is that no dew condensation occurs. Therefore, a saturated moisture content of 0 ° C. or less is sufficient considering the normal irradiation atmosphere. The water content at 0 ° C. is 5 g / m ³ .

The constituent material of the electron beam irradiation device is a part made of metal, such as a clamp material for the electron beam irradiation window, which reacts with nitric acid like a catalyst and is corroded by the oxidizing power of ozone. May be promoted. Therefore, by implementing the present invention, this phenomenon can also be prevented.

FIG. 4 shows another configuration example of the electron beam irradiation apparatus according to the present invention, which uses CB250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd. as the electron beam irradiation apparatus. When the irradiation space 22 of the irradiation chamber is irradiated with an electron beam, ozone and nitrogen oxides are generated. If water is present in the space, nitrogen oxides dissolve in water to nitric acid. In such a gas state, the gas is sucked into the exhaust port 41 and introduced into the device 42 for absorbing nitrogen oxide and nitric acid. The absorbing device 42 is filled with, for example, water as the absorbing liquid 45 and absorbs nitrogen oxide and nitric acid. Of the nitrogen oxides, nitric oxide is very slightly soluble in water, but nitrogen dioxide is well soluble.

In the case of electron beam irradiation, since ozone is generated at the same time, nitric oxide is oxidized into nitrogen dioxide, so that the nitrogen oxide in the exhaust gas is absorbed by the absorbing liquid 45. In order to improve the absorption efficiency, the exhaust gas is made into a vertically long container in order to make the contact with the absorbing liquid 45 as fine bubbles with a glass filter and to keep the contact time long. As the material of the container, glass or vinyl chloride is selected because the exhaust gas has a strong oxidizing power. The exhaust gas is introduced into the ozone decomposing device 43 after the absorbing device 42, and the ozone is decomposed. Then, the gas is exhausted through the exhaust fan 44 or the pump.

Then, changes in the concentration of nitrogen oxides depending on the presence or absence of the absorber 42 and the life of the ozone decomposer 43 were confirmed. The exhaust flow rate in this case is 100 l / min. It is. Table 2 shows the measurement results of the nitrogen oxide concentration. (Hereinafter, margin)

[0022]

[Table 2]

Further, the decomposition of ozone in the above experimental example is
Since the decomposition catalyst was in the initial stage, the ozone concentration at the inlet was 50 ppm and the concentration at the outlet was 0.1 ppm or less.
Furthermore, after carrying out a life test for 500 hours with and without an absorber, the ozone decomposing ability of each was measured.
pm was 3 ppm at the exit. On the other hand, with the absorber, the initial characteristics were maintained and the outlet concentration was 0.1 ppm or less. It should be noted that during the life test, the PH of the absorbing liquid 45 is lowered (acidic) and the acid concentration is increased, so that it is desirable to replace it periodically. In this case, the absorbing solution was changed once in 250 hours.

[0024]

As is clear from the above description, the electron beam irradiation apparatus according to the present invention supplies dry air having a low water content to the irradiation chamber, and in that state, passes the catalyst for decomposing ozone, There are advantages that the processing capacity of the ozone decomposition catalyst is not deteriorated, there is no fear of environmental pollution, the life of the device is extended, and the total cost is reduced.

Further, by arranging the ozone decomposing device after the device for absorbing and removing the nitrogen oxides and nitric acid in the exhaust gas generated when the electron beam irradiation is performed in the atmosphere containing oxygen and nitrogen, the ozone is decomposed. The life of the decomposition catalyst is extended without deteriorating the treatment capacity of the decomposition catalyst. Further, the oxidant concentration of the exhaust gas is extremely low, which is advantageous in that air pollution can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an electron beam irradiation apparatus according to an embodiment of the present invention.

FIG. 2 is likewise a schematic circuit diagram of an electron beam generator.

FIG. 3 is a configuration diagram of an electron beam irradiation apparatus according to an embodiment of the present invention.

FIG. 4 is also another configuration diagram of the electron beam irradiation apparatus.

[Explanation of symbols]

1 Dehumidifier 41 Exhaust port 2 Regulator 42 Absorber 3 Filter 43 Ozone decomposing catalyst containing device 4 Compressor 44 Exhaust fan 5 Ozone decomposing catalyst containing device 45 Absorbing liquid 6 Exhaust fan 10 Electron beam generating part 12 Terminal 12a Filament 12b Gun structure 12c Grid 14 Accelerator tube 20 Irradiation chamber 22 Irradiation space 30 Irradiation window 32 Window foil 34 Window frame structure

Claims (3)

[Claims] 1. An electron beam irradiation apparatus for irradiating an irradiation object with an electron beam in an atmosphere containing oxygen and nitrogen, wherein a gas passed through a drying device for reducing the amount of water in the atmosphere is supplied to an irradiation chamber. An electron beam irradiation apparatus provided with a device for decomposing ozone in exhaust gas generated in the irradiation chamber. 2. The electron beam irradiation apparatus according to claim 1, wherein the amount of water in the atmosphere is 5 g / m ³ or less, and the ozone decomposition treatment apparatus is composed of a metal catalyst. 3. An electron beam irradiation apparatus for irradiating an irradiation object with an electron beam in an atmosphere containing oxygen and nitrogen, and an apparatus for removing nitrogen oxides or nitric acid in exhaust gas generated in an irradiation chamber, and thereafter. An electron beam irradiation device comprising an ozone decomposition treatment device in each stage.