JPH08164322A - Method for cooling window foil on reactor side in electron-beam irradiation equipment - Google Patents

Abstract

PURPOSE: To enhance the corrosion resistance of a secondary window foil of an electron-beam irradiation equipment on the reactor side, to prevent the formation of a corrosive material on the secondary window foil clue to the condensation of the moisture in a waste gas and to prolong the service life of the secondary window foil at a low cost. CONSTITUTION: In an electron-beam irradiation equipment, an electron beam 31 is transmitted through a primary window foil 60 on the vacuum chamber side and a secondary window foil 80 on the reactor side to irradiate a waste gas contg. such harmful components as SOx, NOx and HCl added with an alkali agent in a reactor 2, hence the harmful components in the waste gas are converted to a granular material, and the granular material is then removed from the waste gas. The secondary window foil 80 is made of pure titanium or titanium alloy. A cooling chamber 70 for passing a first cooling gas current is formed between the primary window foil 60 and secondary window foil 80 to cool the primary window foil, and a second cooling gas at a temp. above the water dew point of the waste gas flows along the surface of the secondary window foil on the cooling chamber side or the surface on the reactor side to cool the secondary window foil. The second cooling gas us kept at 35-100 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling a window foil on a reactor side, that is, a secondary window foil in an electron beam irradiation facility. Specifically, the electron beam generated in the vacuum chamber passes through the primary window foil on the vacuum chamber side and the secondary window foil on the reactor side, and SOx, Nox, HC to which the alkali agent in the reactor is added.
A secondary window foil in an electron beam irradiation facility in which the exhaust gas containing harmful components such as 1 is irradiated to convert the harmful components in the exhaust gas into particulate matter, and then the particulate matter is removed from the exhaust gas in a dust collector. The present invention relates to a cooling method which improves the cooling method of (1), prevents damage and destruction of the secondary window foil due to adhesion and condensation of strongly corrosive substances and soot, and significantly improves the life of the secondary window foil.

[0002]

2. Description of the Related Art An electron beam generated by accelerating a filament in a vacuum chamber by energizing and heating it to generate thermoelectrons passes through an irradiation window device and is extracted outside the vacuum chamber to irradiate an object to be irradiated. The beam irradiation equipment is used in many fields such as promotion of chemical reaction of polymer, sterilization of medical equipment, research and development, and also purification of combustion exhaust gas of fossil fuel such as coal and petroleum. The advantage of using an electron beam compared to the use of X-rays or gamma rays is that the electron beam source can have a large capacity and a large amount of processing. It is necessary to detect scattered electrons from the irradiated object, for example, except in the case of an electron microscope, etc., because moving the irradiated object into and out of the vacuum chamber that generates an electron beam complicates the apparatus and increases the number of steps. The electron beam irradiation equipment that takes out the electron beam to the outside of the vacuum chamber and hits it on the irradiation target outside the vacuum chamber is practical.

After adding an alkaline agent such as ammonia or lime to exhaust gas containing harmful components such as SOx, Nox and HCl and then irradiating them with an electron beam, it is possible to convert these harmful components into particulate matter. , For example, JP-A-52
It is known from JP-A-140499. This publication discloses that ammonia (NH ₃ ) is added as an alkaline agent, and an electron beam is irradiated to convert SOx into ammonium sulfate particles and Nox into ammonium nitrate particles, which are recovered from exhaust gas to be used as a fertilizer. .

In order to take out the electron beam from the vacuum chamber,
The electron beam is passed through a window foil that separates the vacuum chamber from the outside, that is, a thin metal film called a primary window foil. The primary thin film needs to have a thickness that can withstand the pressure difference, but cannot be thick in order not to increase the electron beam loss. If the exhaust gas to be treated contains a relatively low concentration of pollutants, only a primary window foil is provided between the scanning tube of the electron beam generator and the reactor. However, when the exhaust gas to be treated contains a large amount of harmful components such as SOx, Nox, HCl, etc., such as boiler exhaust gas, the electron beam passes through the secondary window foil outside the primary window foil and the reactor. And a cooling chamber is formed between the primary window foil and the secondary window foil to allow the flow of the first cooling gas to cool the primary window foil and the second cooling gas to the secondary window foil. It is designed to flow along the surface of the cooling chamber side or the surface of the reactor side, and the exhaust gas does not immediately enter the inside of the scanning tube even when the reactor window foil is damaged.

[0005]

[Problems to be Solved] Since an electron beam used for purification of exhaust gas or the like needs to have a high output,
Regardless of the window foil of any material, the thin vacuum chamber side or reaction chamber side window foil through which the electron beam passes absorbs the high output energy of the electron beam and burns out in a short time. The magnitude of loss when the electron beam passes through the window foil depends on the thickness of the window foil and the material used for the window foil. This loss becomes heat and raises the temperature of the window foil. In order to reduce the transmission loss of the electron beam as much as possible, a window foil of about several tens of microns is practically used. In addition, in order to avoid burning of the electron beam, the window foil is made slender in the X direction and the electron beam is moved by the magnetic field in the X direction.
Direction, the energy absorption amount per unit area of the window foil per unit time is kept below a certain level, and cooling air of a cooling gas such as air or nitrogen gas is blown onto the outer surface of the window foil to cool the window foil. Devised Further, the following two cooling methods have been conventionally developed for the secondary window foil.

The first cooling method is to blow a cooling gas such as air or nitrogen gas at room temperature onto the secondary window foil to cool it. In this case, the portion of the secondary window foil through which the electron beam does not pass is cooled by the cooling gas and has a temperature similar to that of the cooling gas. When the temperature of the cooling gas is equal to or lower than the water dew point of the exhaust gas, moisture in the exhaust gas is condensed and dew occurs in the window foil portion where the electron beam does not pass. On the other hand, sulfur oxides (SOx) and nitrogen oxides (NOx) contained in exhaust gas
Etc. were oxidized by the electron beam, and part of them were absorbed by the moisture condensed on the secondary window foil and became corrosive substances such as sulfuric acid and nitric acid, which corroded the window foil and hindered stable operation. .

The second method is disclosed in Japanese Unexamined Patent Publication No. 52-37553, in which the temperature of the secondary window foil is set to the acid dew point of exhaust gas or higher. The acid dew point of the exhaust gas differs depending on the SO ₃ concentration, the water concentration, etc. in the exhaust gas, but
The combustion exhaust gas of coal, heavy oil, etc. has a temperature of 120 ° C. or higher, and a large amount of energy is required to set the cooling gas temperature to 120 ° C. or higher. In addition, since the high temperature gas is blown in the electron beam transmitting portion, there is a problem that the cooling capacity is significantly lowered.

The present invention provides a cooling method for solving the above-mentioned conventional problems, sufficiently cooling the secondary window foil so as not to be burned by passage of the electron beam, and at the same time making the secondary window foil opaque to the electron beam. The purpose is to prevent the part from being cooled and the moisture in the exhaust gas from condensing to cause dew condensation and corrosion damage.
Another object of the present invention is to reduce the amount of heat used to cool the secondary window foil in a corrosion-free manner to improve the cooling capacity and reduce the operating cost of the equipment. Still another object of the present invention is to enhance the corrosion resistance of the secondary window foil to prolong the service life thereof and to enable stable operation of the electron beam irradiation equipment for a long period of time. Other objects and advantages of the present invention will be clarified by the following description.

[0009]

In the cooling method of the window foil on the reactor side in the electron beam irradiation equipment of the present invention, that is, the secondary window foil, the electron beam generated in the vacuum chamber of the electron beam generator is The SO containing the alkaline agent in the reactor is transmitted through the primary window foil on the vacuum chamber side and the secondary window foil on the reactor side.
Irradiate exhaust gas containing harmful components such as x, Nox, HCl, etc. to convert the harmful components in the exhaust gas into particulate matter, and thereafter,
Particulate matter is removed from the exhaust gas. The secondary window foil is made of pure titanium or titanium alloy. In the cooling method of the present invention, the primary window foil is cooled by forming the cooling chamber for allowing the flow of the first cooling gas (first cooling air) to be formed between the primary window foil and the secondary window foil. The second cooling gas having a temperature equal to or higher than the water dew point of the exhaust gas is flowed along the surface of the secondary window foil on the cooling chamber side or the reactor side (second cooling air) to cool the secondary window foil. It Preferably, the second cooling gas is about 35 ° C. or higher 10
It is set to 0 ° C or lower. The second cooling gas that has cooled the secondary window foil may be allowed to flow out together with the exhaust gas, but is preferably recovered and recycled. Usually, the water concentration of combustion exhaust gas such as coal and petroleum is 6% or more, and the water dew point thereof is 35 ° C or more. Further, the upper limit of the temperature of the second cooling gas is appropriately 100 ° C. or lower in terms of energy for raising the temperature and cooling capacity.

[0010]

1 is an overall schematic view of an electron beam irradiation equipment in which an irradiation window device of the present invention can be used. In the equipment of FIG. 1, SOx, Nox, HC discharged from the boiler 1
Exhaust gas containing harmful components such as 1 is introduced into the reactor 2 via a heat recovery device (not shown) and the like. Ammonia (NH ₃ ) and an alkaline agent such as lime are added to the flow of the exhaust gas entering the reactor 2. An electron beam generator 3 is arranged above the reactor 2, and the generated electron beam passes through the irradiation window device,
Enter the reactor 2. In the reactor 2, N in the exhaust gas
The Ox component and the SOx component are irradiated with the electron beam to become nitric acid and sulfuric acid, which react with the alkaline agent added to the exhaust gas to form solid particles. When the alkaline agent is ammonia, it is converted into powders of ammonium nitrate (ammonium nitrate) and ammonium sulfate (ammonium sulfate).

The exhaust gas containing the solid powder in the reactor 2 is guided from the reactor 2 to the dust collector 4, where the solid particles are separated and removed. The solid particles separated in the dust collector are introduced into a not-shown by-product processor, and when ammonia is added, ammonium nitrate and ammonium sulfate as by-products are purified. The exhaust gas that has passed through the dust collector 4 is a suction fan 5
Are sucked in and discharged from the chimney 6 into the atmosphere. FIG.
In the equipment, the exhaust gas is sucked and discharged from the equipment by the suction fan 5 and the chimney 6. Therefore, in the reactor 2, the electrostatic precipitator 4, etc., the pressure of the exhaust gas is lower than the ambient atmospheric pressure, and the exhaust gas It does not leak from and pollute the surroundings.

The electron beam generator 3 is supplied with power from a power source (not shown). The electron beam output value corresponds to the product of the acceleration voltage and the electron beam output current value. The acceleration voltage is
Since it corresponds to the penetration distance of the electron beam in the exhaust gas, it is limited by the size of the reactor 2. For example, if the transmission distance is 2.
For a 6 m reactor, the acceleration voltage may be about 800 kV,
If it is higher than that, a part of the electron beam exceeds 2.6 m and collides with the wall surface of the reactor, which is useless for the reaction and is wasted.
Since the maximum value of the accelerating voltage is limited by the size of the reactor 2, the current value is changed in order to change the electron beam output value.

FIG. 2 is a layout diagram schematically showing a main part of the electron beam irradiation equipment for carrying out the present invention. In FIG. 2, the electron beam accelerated in the acceleration tube 34 of the electron beam generator 3 is scanned in the scanning tube 35 including the ion pump 32, and the primary window foil 60 of the irradiation window device 40 and the cooling chamber 7 are scanned.
0, and the secondary window foil 80 is transmitted, and the exhaust gas in the reactor 2 is irradiated. In the reactor 2, the electron beam 31 reacts harmful components such as NOx, SOx, and HCl in the exhaust gas with the added alkaline agent to generate solid particles. The irradiation window device 40 includes a primary window foil 60, a secondary window foil 80, and a cooling chamber 70 formed between the two window foils, of which the secondary window foil 80 is made of pure titanium or titanium alloy. It The primary window foil 60 and the secondary window foil 80 of the irradiation window device 40 are cooled by the flow of cooling gas. The cooling gas flows from the blower 42 in the supply pipe 44 in the direction of the arrow R, and the cooling gas inlet 41,
It is supplied to the cooling chamber 70 via 46. In the cooling chamber 70, the cooling gas forms a flow along the primary window foil 60 and a flow along the secondary window foil 80, as shown by the arrows, and these flows are opposite to each other. After that, the cooling gas flows from the cooling chamber 70 through the cooling gas outlets 43 and 47 in the discharge pipe 51 in the direction of the arrow S and is introduced into the heat exchanger 50. The cooling gas is heat-exchanged with the cooling water C, steam or the like in the heat exchanger 50 according to the temperature and then sucked and pressurized by the blower 42 to supply the supply pipe 44 and the cooling gas inlet 41,
It is circulated to the irradiation window device 40 again via 46. In this case, when the cooling gas is blown onto the surface of the secondary window foil 80, the amount of heat released from the heat exchanger 50 is adjusted so that the temperature of the cooling gas becomes equal to or higher than the water dew point of the exhaust gas in the reactor.

FIG. 3 is a schematic enlarged cross-sectional view of another type of irradiation window device using the present invention.
But the primary window foil 6 is arranged across the elongated opening 55
0, the cooling chamber 70, and the secondary window foil 80. The primary window foil 60 is held at its peripheral edge between the flange 52 and the frame 54 provided at the end portion of the scanning tube, and the vacuum chamber and the cooling chamber 70 are provided.
Airtightly partition. The peripheral edge of the secondary window foil 80 is held between the frame 54 and the pressing flange 64, and also partitions the cooling chamber 70 and the reaction chamber 2 in an airtight manner. The electron beam 31
The irradiation window device 40 transmits the exhaust gas in the reactor 2 through the primary window foil 60, the cooling chamber 70, and the secondary window foil 80. In the reactor 2, the electron beam 31 is the NO in the exhaust gas.
The harmful components such as x, SO ₂ and HCl are reacted with the added alkaline agent to form solid particles. Secondary window foil 80
Is made of pure titanium or titanium alloy.

In the irradiation window device 40 of FIG. 3, in order to cool the primary window foil 60, the first cooling gas flow, that is, the first
In order for the cooling air 74 to flow along the primary window foil 60, the first
It is supplied from the cooling air nozzle 72. The first cooling air 74 is
It is supplied from one side surface of the cooling chamber, collides against the other side surface, is inverted, and cools the secondary window foil 80 to cool the first cooling air outlet 78.
Is more exhausted. Further, in order to cool the secondary window foil 80, the flow of the second cooling gas, that is, the second cooling air 86 is supplied from the second cooling air nozzle 82 so that it flows along the surface of the secondary window foil on the reactor side. To be done. The temperature of the second cooling air 86 is adjusted to a temperature equal to or higher than the water dew point of the exhaust gas in the reactor through a heat exchanger (not shown), the blower 42, and the like. The second cooling wind 86 is made of air and is discharged together with the exhaust gas after cooling the secondary window foil 80.

Next, the experimental results of the present invention will be described.
After adding ammonia (NH ₃ ) to the coal combustion exhaust gas having a SO ₂ concentration of 800 ppm, a NOx concentration of 200 ppm and a water content of 6%, an electron beam irradiation test was conducted in the reaction chamber 2 equipped with the irradiation window device 40 of FIG. . Secondary window foil 80
Was manufactured from pure titanium. In order to cool both the primary window foil 60 and the reactor window foil 80, a cooling gas composed of nitrogen gas adjusted to a temperature of 50 ° C. was circulated through the cooling chamber 70. After operating for about 4 months, the secondary window foil 80 was not damaged at all. The water dew point of the exhaust gas in this experiment was about 40 ° C. For comparison,
A cooling gas composed of nitrogen gas adjusted to about 25 ° C. was similarly circulated through the cooling chamber 70 by the same device as the experimental device. After running for about 4 days, the secondary window foil 80 was damaged by acid corrosion.

[0017]

In the method for cooling the secondary window foil in the electron beam irradiation equipment of the present invention, the secondary window foil is made of pure titanium or titanium alloy and has high corrosion resistance. Furthermore,
In the method of the present invention, the second cooling gas having a temperature equal to or higher than the water dew point of the exhaust gas is flowed along the surface of the secondary window foil on the cooling chamber side or the reactor side. This allows the secondary window foil to absorb part of the high output energy of the electron beam passing through it and cool it sufficiently so that it does not burn out, and the moisture in the exhaust gas does not penetrate the window foil surface, especially the electron beam. Corrosion destruction of the window foil is prevented in order to prevent dew condensation on the peripheral portion of the window foil and to prevent generation of corrosive substances such as sulfuric acid and nitric acid. According to the method of the present invention, it is possible to achieve sufficient cooling of the electron beam transmitting portion of the secondary window foil and prevention of corrosion destruction of the electron beam opaque portion at the same time. It can be a long period of time, the electron beam irradiation equipment can be stably operated for a long period of time, and therefore the operating cost of the electron beam irradiation equipment can be improved.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an electron beam irradiation facility in which a cooling method of the present invention can be used.

FIG. 2 is a layout diagram schematically showing a main part of electron beam irradiation equipment for carrying out the cooling method of the present invention.

FIG. 3 is a schematic enlarged cross-sectional view of another type of irradiation window device for carrying out the cooling method of the present invention.

[Explanation of symbols]

1: Boiler, 2: Reactor, 3: Electron beam generator, 4:
Dust collector, 5: suction fan, 6: chimney, 31: electron beam, 34: accelerating tube, 35: scanning tube, 40: irradiation window device,
41, 46: cooling gas inlet, 42: blower, 44: supply pipe, 43, 47: cooling gas outlet, 50: heat exchanger, 5
1: discharge pipe, 52: flange, 54: frame, 55:
Opening, 60: primary window foil, 64: flange, 70: cooling chamber, 72: first cooling air nozzle, 74: first cooling air (first cooling air)
Coolant gas flow), 78: cooling air outlet, 80: secondary window foil, 82: second cooling air nozzle, 86: second cooling air (second)
Cooling gas flow).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B01D 53/34 ZAB 53/68 B01D 53/34 134 A (72) Inventor Hideki Nanba Takasaki City, Gunma Prefecture 1233 Watanuki-cho, Takasaki Laboratory, Japan Atomic Energy Research Institute (72) Inventor, Masa Masa Tanaka, No. 20 Kita-Sekiyama, Otaka-cho, Midori-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. Electric Power Research Laboratory (72) Inventor Yoshimi Ogura Aichi 20 Chuo Electric Power Co., Ltd., Electric Power Technology Research Institute, 20-20 Kitakousan, Otaka-cho, Midori-ku, Nagoya-shi, Japan (72) Inventor Yoshitaka Yoshii 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo (72) Invention Person Masahiro Izutsu 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION (72) Inventor Shinji Aoki 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo Shares The company Ebara Corporation

Claims (2)

[Claims] 1. An electron beam generated in the vacuum chamber of an electron beam generator passes through a primary window foil (60) on the vacuum chamber side and a secondary window foil (80) on the reactor side, Irradiating an exhaust gas containing harmful components such as SOx, Nox, and HCl to which an alkaline agent is added to convert the harmful components in the exhaust gas into particulate matter, and thereafter, the particulate matter is removed from the exhaust gas,
The secondary window foil (80) is made of pure titanium or titanium alloy. In the method for cooling the secondary window foil in the electron beam irradiation equipment, the first cooling gas flow is passed between the primary window foil and the secondary window foil. A cooling chamber (70) is formed to cool the primary window foil (60), and a second cooling gas having a temperature equal to or higher than the water dew point of the exhaust gas is passed along the cooling chamber side surface or the reactor side surface of the secondary window foil. A cooling method, characterized in that the secondary window foil (80) is cooled by flowing. 2. The temperature of the second cooling gas is 35 ° C. to 1 ° C.
The cooling method according to claim 1, wherein the temperature is 00 ° C.