Radiant energy – Irradiation of objects or material – Ion or electron beam irradiation
Reexamination Certificate
2001-02-06
2003-09-02
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Ion or electron beam irradiation
C250S42300F, C250S492100, C250S492240, C250S493100, C250S503100, C250S505100, C250S515100, C250S496100, C250S498100, C250S455110, C313S359100, C313S360100, C313S363100, C313S420000
Reexamination Certificate
active
06614037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron beam irradiating apparatus for processing, for example, waste gas discharged from a thermal power plant. The present invention especially relates to a window foil for ejecting electrons from a vacuum vessel into a gas environment, and particularly to a crosspiece fixed to the vacuum vessel for supporting the window foil against atmospheric pressure.
2. Description of the Related Art
Some of today global problems, such as global warming and acid rain, are thought to be caused by air pollution and specifically by SOx, NOx, and other toxic components in waste combustion gases that are discharged from thermal power plants and the like. One method for removing such toxic components, as SOx and NOx, has been to conduct desulfurization and denitration by irradiating waste combustion gases with an electron beam.
FIG. 1
shows an example of an electron beam irradiating apparatus for use in such applications. An apparatus for processing waste combustion gas includes a power source
10
for generating a high DC voltage, an electron beam irradiating apparatus
11
for irradiating an electron beam onto waste combustion gas, a window foil
15
serving as an irradiating outlet for the electron beam of the electron beam irradiating apparatus
11
, and a channel
19
disposed along the window foil
15
through which the waste combustion gas flows. The window foil
15
is composed of a thin plate formed of titanium or the like.
The electron beam ejected externally via the window foil
15
irradiates such molecules in the waste combustion gas as oxygen (O
2
) and water vapor (H
2
O) to form radicals that are extremely strong oxidizers, including OH, O, and HO
2
. These radicals oxidize the toxic components SOx and NOx to generate intermediate products of sulfuric acid and nitric acid. The intermediate products react with ammonium gas (NH
3
) that has already been introduced to form ammonium sulfate and ammonium nitrate, which can be recovered for use as a fertilizer. Accordingly, this type of waste gas processing system can remove such toxic components as SOx and NOx from waste combustion gas and can recover useful by-products of ammonium sulfate and ammonium nitrate for use as a fertilizer.
In this example, the electron beam irradiating apparatus
11
includes as main components a thermoelectron generator
12
such as a thermionic filament; an accelerating tube
13
for accelerating electrons emitted from the thermoelectron generator
12
; a focusing electromagnet
16
for controlling a diameter of an electron beam by applying a magnetic field to a highly energized electron beam formed by the accelerating tube
13
; and a scanning electromagnet
17
for deflecting the electron beam by applying a magnetic field to the electron beam after it has been focused to a specific diameter. These components are accommodated in vacuum vessels
18
a
and
18
b
, which maintain a high vacuum atmosphere of approximately 10
−6
Pa. By applying a magnetic field using the scanning electromagnet
17
, the highly energized electron beam is deflected in a scanning motion through the window foil
15
and ejected onto the waste combustion gas within a prescribed range of the channel
19
.
As described above, this type of electron beam irradiating apparatus must eject an electron beam into the atmosphere after electrons have been accelerated in a vacuum environment. The window foil used in this electron beam irradiating apparatus is generally a film formed of pure titanium or a titanium alloy having a thickness of several tens of micrometers (for example, 40 &mgr;m) in order to attain a high electron transmission efficiency for ejecting the electron beam. The window foil
15
is mounted on an end of the vacuum vessel
18
a
via a mounting flange (not shown). The size of the window foil
15
is as large as 3 m×0.6 m. Here, an atmospheric pressure of approximately 1000 hPa is applied to a surface of the window foil, against an internal pressure of approximately 10
−6
Pa in the vacuum vessel. Accordingly, a large force is applied to the window foil via a relationship of area and pressure differential. Therefore, a crosspiece is affixed to a portion of the window foil surface, thereby dividing the window foil into a plurality of sections.
FIG. 2
shows an example of a construction for dividing the window foil
15
with a crosspiece, and a scanning path for an electron beam. As described above, the window foil
15
is relatively large, i.e. 3 m by 0.6 m. A central crosspiece
21
is disposed lengthwisely across a center of the window foil
15
and adhered thereon for supporting the same. Accordingly, the crosspiece
21
supports a central portion of the window foil
15
and divides the surface of the window foil
15
into two sections. This configuration prevents the window foil
15
from deforming, even while incurring a large pressure from an atmospheric side toward an evacuated side of the window foil.
Since the electron beam is emitted over a large range through the window foil
15
, which has a relatively large area, it is possible to avoid heat damage to the window foil
15
. Therefore, the electron beam scans the window foil
15
in lengthwise direction thereof along a path P in the direction shown by the arrow in
FIG. 2
in order to avoid heat damage to the window foil
15
. At this time, the electron
20
beam scans along a path that does not traverse the crosspiece in the lengthwise direction. The electron beam is accelerated by a voltage of approximately 800 kV. Even with a large electric current of approximately 500 mA, energy loss occurs when the electron beam passes through the window foil, thereby generating a large amount of heat therein. For this reason, a cooling pipe is provided in the crosspiece
21
and cooling water is flowed through the pipe to prevent damage to the window foil
15
due to excess heat.
However, in order to scan the window foil
15
along the path P shown in
FIG. 2
, the electron beam inevitably must cross end portions
21
a
and
21
b
. When the electron beam E crosses these portions and irradiates the end portions
21
a
and
21
b
, a large amount of heat is generated on these portions of the crosspiece
21
. Over extended use, this excess heat can cause thermal fatigue in portions of the cooling water pipe provided in the crosspiece
21
, leading to such accidents as water leaking into the evacuated section. If the vacuum vessel becomes contaminated, it is necessary to disassemble the electron beam irradiating apparatus to repair the damage and then reassemble the apparatus. This process requires much time and labor. Further, once the damage has been repaired, more time is required to evacuate the vacuum vessel again, thereby requiring that operations be suspended for a considerably long time, in addition to difficult repair work.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide an electron beam irradiating apparatus for scanning an electron beam across an entire surface of a window foil, wherein the window foil is reinforced by a crosspiece capable of preventing excess heat from being generated due to electron beam irradiation, thereby enabling the apparatus to perform stable operations for an extended time. It is another object of the present invention to provide such an electron beam irradiating apparatus that is easy to maintain.
These objects and others will be attained by an electron beam irradiating apparatus comprising an electron beam source for emitting electrons; an accelerating unit for accelerating electrons emitted from the electron beam source to generate a highly energized electron beam; a deflecting unit for deflecting the highly energized electron beam generated by the accelerating unit in a scanning direction; a vacuum vessel accommodating the electron beam source, the accelerating unit, and the deflecting unit in a vacuum environment; a window foil for ejecting the electron beam from the va
Ebara Corporation
El-Shammaa Mary
Lee John R.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Electron beam irradiating apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron beam irradiating apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron beam irradiating apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3109624