U.S. patent application number 16/603959 was filed with the patent office on 2020-04-23 for apparatus for exhaust gas abatement under reduced pressure.
The applicant listed for this patent is Kanken Techno Co., Ltd.. Invention is credited to Hiroshi IMAMURA, Masashi MAEDA, Tsutomu TSUKADA, Michihiko YANAGISAWA, Akihisa YOSHIDA.
Application Number | 20200122085 16/603959 |
Document ID | / |
Family ID | 64396488 |
Filed Date | 2020-04-23 |
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United States Patent
Application |
20200122085 |
Kind Code |
A1 |
MAEDA; Masashi ; et
al. |
April 23, 2020 |
APPARATUS FOR EXHAUST GAS ABATEMENT UNDER REDUCED PRESSURE
Abstract
An apparatus for exhaust gas abatement under reduced pressure
includes a reaction tube having, in an interior thereof, an exhaust
gas treatment space in which an exhaust gas supplied from an
exhaust gas source via a vacuum pump is heated by an electric
heater or excited by a plasma for decomposition and/or reaction
treatment. The apparatus also includes a downstream vacuum pump
connected to an exhaust gas outlet located downstream of the
reaction tube to reduce a pressure in a region located downstream
of an outlet of the vacuum pump and including the interior of the
reaction tube. The downstream vacuum pump is a water-sealed pump.
The apparatus further includes a water-washing unit for washing a
downstream end of an exhaust gas flow path in the reaction tube
with washing water. The washing water supplied by the water-washing
unit is reused as seal water for the downstream vacuum pump.
Inventors: |
MAEDA; Masashi;
(Nagaokakyo-shi, Kyoto, JP) ; YOSHIDA; Akihisa;
(Nagaokakyo-shi, Kyoto, JP) ; YANAGISAWA; Michihiko;
(Nagaokakyo-shi, Kyoto, JP) ; TSUKADA; Tsutomu;
(Nagaokakyo-shi, Kyoto, JP) ; IMAMURA; Hiroshi;
(Nagaokakyo-shi, Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kanken Techno Co., Ltd. |
Nagaokakyo-shi, Kyoto |
|
JP |
|
|
Family ID: |
64396488 |
Appl. No.: |
16/603959 |
Filed: |
May 2, 2018 |
PCT Filed: |
May 2, 2018 |
PCT NO: |
PCT/JP2018/017529 |
371 Date: |
October 9, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 53/005 20130101;
B01D 2257/2066 20130101; B01D 2257/553 20130101; F23G 7/06
20130101; C23C 16/4412 20130101; B01D 2251/604 20130101; B01D
2251/306 20130101; H01L 21/02 20130101; B01D 53/68 20130101; B01D
53/76 20130101; B01D 2251/304 20130101; B01D 2259/818 20130101;
B01D 2258/0216 20130101; B01D 53/32 20130101 |
International
Class: |
B01D 53/68 20060101
B01D053/68; F23G 7/06 20060101 F23G007/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2017 |
JP |
2017-102711 |
Claims
1. An apparatus for exhaust gas abatement under reduced pressure,
comprising: a reaction tube having, in an interior thereof, an
exhaust gas treatment space in which an exhaust gas supplied from
an exhaust gas source via a vacuum pump is heated by an electric
heater or excited by a plasma for decomposition and/or reaction
treatment; and a downstream vacuum pump that is connected to an
exhaust gas outlet located downstream of the reaction tube to
reduce a pressure in a region located downstream of an outlet of
the vacuum pump and including the interior of the reaction tube,
wherein the downstream vacuum pump is a water-sealed pump, the
apparatus further comprises a water-washing unit for washing a
downstream end of an exhaust gas flow path in the reaction tube
with washing water (W), and the washing water (W) supplied by the
water-washing unit to wash the downstream end of the exhaust gas
flow path in the reaction tube is reused as seal water for the
downstream vacuum pump.
2. The apparatus for exhaust gas abatement under reduced pressure
according to claim 1, further comprising a decomposition/reaction
agent supply unit for supplying at least one selected from the
group consisting of water, air, O.sub.2, H.sub.2 , and hydrocarbon
gases, as a decomposition/reaction agent, to the interior of the
reaction tube.
3. The apparatus for exhaust gas abatement under reduced pressure
according to claim 1, further comprising a dust removal unit that
is provided in the interior of the reaction tube to remove dust
particles deposited therein.
4. The apparatus for exhaust gas abatement under reduced pressure
according to claim 1, further comprising an inlet-side scrubber
that is a wet scrubber for washing the exhaust gas with water in a
reduced pressure atmosphere before the exhaust gas is introduced
into the reaction tube.
5. The apparatus for exhaust gas abatement under reduced pressure
according to claim 4, further comprising a circulation pump for
circulating scrubber water for use in the inlet-side scrubber, a
portion of the circulating scrubber water being supplied to the
water-washing unit for use as the washing water therein.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust gas abatement
apparatus suitable for treatment of harmful exhaust gases such as
combustible gases, toxic gases, and greenhouse gases emitted in the
manufacturing processes mainly in the electronics industry.
BACKGROUND ART
[0002] In the electronics industry for manufacturing
semiconductors, liquid crystals, etc., various CVD processes are
used for producing various films such as silicon nitride films,
silicon oxide films, silicon oxynitride films, TEOS oxide films,
high dielectric constant films, low dielectric constant films, and
metal films.
[0003] Among these, for example, silicon-based thin films are
formed by a CVD method mainly using an explosive and toxic
silane-based gas. In this CVD method, after being used in a CVD
process, the used process gas as an exhaust gas containing the
above-mentioned silane-based gas is rendered harmless in an
abatement apparatus as described in Patent Literature 1 below. It
is conventional practice to dilute the silane-based gas in the
exhaust gas with a large amount of diluent nitrogen gas introduced
upstream of the abatement apparatus so as to reduce the
concentration of the silane-based gas to a level lower than the
lower explosive limit.
[0004] Here, in a typical CVD process for forming silicon
oxynitride films, SiH.sub.4/NH.sub.3/N.sub.2O=1 slm/10 slm/10 slm
(slm: standard liter per minute, i.e., a unit of flow rate of a gas
at 0.degree. C. and 1 atm expressed in terms of liters per minute)
is used. Since the explosion range of SiH.sub.4 is 1.3% to 100%,
the gas mixture emitted in this CVD process must be diluted with
about 76 parts of diluent nitrogen gas immediately after the
emission. After the dilution, a conventional pyrolysis (thermal
decomposition) apparatus, for example, a combustion type pyrolysis
apparatus or an atmospheric plasma type pyrolysis apparatus can be
used to perform abatement treatment safely and reliably.
CITATION LIST
Patent Literature
[0005] [PTL 1] Japanese Laid-Open Patent Publication No.
11-333247
SUMMARY OF INVENTION
Technical Problem
[0006] However, the above-described conventional technique has a
problem.
[0007] Specifically, the energy required for heating the exhaust
gas mixture containing a silane-based gas and nitrogen gas used to
dilute the silane-based gas as described above to the decomposition
temperature is about 76 times the energy required for heating only
the exhaust gas containing the undiluted silane-based gas. This
means that in the conventional abatement process that requires
dilution with nitrogen gas, not only the exhaust gas but also the
nitrogen gas that is not directly involved in the abatement of the
exhaust gas must be heated and thus the energy efficiency
decreases, resulting in an increase in the cost of electricity,
fuels, etc., in addition to an increase in the cost of nitrogen gas
used in large amounts.
[0008] It is therefore a primary object of the present invention to
provide an energy-efficient and economically efficient apparatus
that can achieve exhaust gas abatement with a minimum use of
diluent nitrogen gas without sacrificing safety.
Solution to Problem
[0009] In order to achieve the above object, according to the
present invention, exhaust gas abatement is performed under reduced
pressure. More specifically, the apparatus for exhaust gas
abatement under reduced pressure according to the present invention
is configured as follows, for example, as shown in FIG. 1 and FIG.
2.
[0010] The apparatus for exhaust gas abatement under reduced
pressure according to the present invention includes a reaction
tube 16 having, in an interior thereof, an exhaust gas treatment
space 16a in which an exhaust gas E supplied from an exhaust gas
source 12 via a vacuum pump 14 is heated by an electric heater 18
or excited by a plasma for decomposition and/or reaction treatment.
The apparatus also includes a downstream vacuum pump 22 that is
connected to an exhaust gas outlet 20 located downstream of the
reaction tube 16 to reduce a pressure in a region located
downstream of an outlet of the vacuum pump 14 and including the
interior of the reaction tube 16. The downstream vacuum pump 22 is
a water-sealed pump. The apparatus further includes a water-washing
unit 24 for washing a downstream end of an exhaust gas flow path in
the reaction tube 16 with washing water W. The washing water W
supplied by the water-washing unit 24 to wash the downstream end of
the exhaust gas flow path in the reaction tube 16 is reused as seal
water for the downstream vacuum pump 22.
[0011] This invention has, for example, the following advantageous
effects.
[0012] Since the exhaust gas E supplied from the exhaust gas source
12 via the vacuum pump 14 is heated by the electric heater 18 for
decomposition and/or reaction treatment under reduced pressure,
less heat is generated by the reaction and a rapid temperature rise
or explosive reaction never occurs. Therefore, there is no need for
using diluent nitrogen gas or the use of nitrogen gas can be
reduced to a minimum. Since there is no need to dilute with diluent
nitrogen gas or the use of the nitrogen gas can be reduced to a
minimum, almost all thermal energy supplied from the electric
heater 18 can be used directly for decomposition and reaction of
the exhaust gas E. In addition, since a region located downstream
of the outlet of the exhaust gas E source and including the
abatement treatment unit is under reduced pressure, even if the
exhaust gas E contains toxic substances to humans, there is no risk
that the exhaust gas E leaks from the system before being heated by
the electric heater 18 for decomposition/reaction treatment.
[0013] Furthermore, since the apparatus includes the water-washing
unit 24 for washing the downstream end of the exhaust gas flow path
in the reaction tube 16 with washing water W, dust particles
produced as a by-product of the thermal decomposition/reaction
treatment of the exhaust gas E and deposited on the downstream end
of the exhaust gas flow path in the reaction tube 16 can be washed
away with the washing water W.
[0014] Furthermore, since the downstream vacuum pump 22 is a
water-sealed pump and the washing water W supplied by the
water-washing unit 24 to wash the downstream end of the exhaust gas
flow path in the reaction tube 16 is reused as seal water for the
downstream vacuum pump 22, the unit water consumption for the
abatement of the exhaust gas E can be reduced.
[0015] Preferably, the apparatus according to the present invention
further includes a decomposition/reaction agent supply unit 26 for
supplying at least one selected from the group consisting of water,
air, O.sub.2, H.sub.2, and hydrocarbon gases, as a
decomposition/reaction agent, to the interior of the reaction tube
16.
[0016] In this case, even if the exhaust gas E mainly contains a
large amount of combustible and harmful substances such as
SiH.sub.4 and NF.sub.3, the addition of the decomposition/reaction
agent allows these substances to be easily decomposed into stable
substances or to be rendered harmless by reaction.
[0017] Preferably, the apparatus according to the present invention
further includes a dust removal unit 28 that is provided in the
interior of the reaction tube 16 to remove dust particles deposited
therein.
[0018] In this case, the dust removal unit 28, in cooperation with
the water-washing unit 24 mentioned above, can remove dust
particles produced as a by-product of the thermal
decomposition/reaction treatment of the exhaust gas E from the
reaction tube 16 more effectively.
[0019] Preferably, the apparatus according to the present invention
further includes an inlet-side scrubber 50 that is a wet scrubber
for washing the exhaust gas E with water in a reduced pressure
atmosphere before the exhaust gas E is introduced into the reaction
tube 16.
[0020] In this case, the exhaust gas E can be washed with water
before being introduced into the reaction tube 16 to remove dust
particles and water-soluble components. In addition, water
introduced with the exhaust gas E into the reaction tube 16 also
acts as a decomposition/reaction agent.
[0021] In the case where the apparatus for exhaust gas abatement
under reduced pressure according to the present invention includes
the inlet-side scrubber 50 as described above, it is preferable
that the apparatus further includes a circulation pump 54 for
circulating scrubber water SW for use in the inlet-side scrubber 50
and a portion of the circulating scrubber water SW is supplied to
the water-washing unit 24 for use as the washing water W
therein.
[0022] In this case, the water use efficiency can be maximized and
thus the unit water consumption can be reduced.
Advantageous Effects of the Invention
[0023] According to the present invention, it is possible to
provide an energy-efficient and economically efficient apparatus
that can achieve exhaust gas abatement with a minimum use of
diluent nitrogen gas without sacrificing safety.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a block diagram showing an overview of an
apparatus for exhaust gas abatement under reduced pressure
according to an embodiment (first embodiment) of the present
invention.
[0025] FIG. 2 is a partial cross-sectional front view showing an
example of a reaction tube of the apparatus for exhaust gas
abatement under reduced pressure according to the present
invention.
[0026] FIG. 3 is a configuration diagram showing an overview of an
apparatus for exhaust gas abatement under reduced pressure
according to another embodiment (second embodiment) of the present
invention.
[0027] FIG. 4 is a configuration diagram showing an overview of an
apparatus for exhaust gas abatement under reduced pressure
according to still another embodiment (third embodiment) of the
present invention.
DESCRIPTION OF EMBODIMENTS
[0028] Hereinafter, an embodiment (first embodiment) of the present
invention will be described with reference to FIG. 1 and FIG.
2.
[0029] FIG. 1 is a diagram showing an overview of an apparatus 10
for exhaust gas abatement under reduced pressure according to an
embodiment of the present invention. As shown in FIG. 1, the
apparatus 10 for exhaust gas abatement under reduced pressure
according to this embodiment is an apparatus for abatement of an
exhaust gas E supplied from an exhaust gas source 12 such as a CVD
apparatus via a vacuum pump 14, and includes a reaction tube 16 and
a downstream vacuum pump 22.
[0030] Here, the embodiment of FIG. 1 shows a silicon oxynitride
film CVD apparatus as an example of the exhaust gas source 12. In a
typical silicon oxynitride film CVD apparatus,
SiH.sub.4/NH.sub.3/N.sub.2O=1 slm/10 slm/10 slm is used as a
process gas, and NF.sub.3/Ar=15 slm/10 slm is used as a cleaning
gas. It is presumed that SiF.sub.4 as a product of the cleaning
reaction is emitted at about 10 slm. A mixture of these spent gases
is supplied as the exhaust gas E to the apparatus 10 for abatement
under reduced pressure via the vacuum pump 14. It should be noted
that in a semiconductor device manufacturing process such as a CVD
process for forming silicon oxynitride films, a dry pump is mainly
used as the vacuum pump 14. Therefore, N.sub.2 (nitrogen gas)
supplied to this vacuum pump 14 is purging N.sub.2 supplied to seal
the shaft of the vacuum pump 14.
[0031] The reaction tube 16 is a cylindrical tubular body formed
of, for example, a corrosion-resistant metallic material such as
Hastelloy (registered trademark) and mounted upright with its axis
vertical (see FIG. 2). The upper end portion of the outer wall of
this reaction tube 16 is provided with an exhaust gas inlet 32
communicating with the outlet of the vacuum pump 14 through a pipe
30. In FIG. 2, a reference numeral 42 denotes a vacuum gauge
mounted in the pipe 30 to measure the degree of vacuum in the
reaction tube 16.
[0032] An exhaust gas treatment space 16a is formed in the interior
of the reaction tube 16, and as a heat source, an electric heater
18 described below is installed therein.
[0033] Furthermore, a water-washing unit 24 is connected in series
to the downstream end of the exhaust gas flow path in the reaction
tube 16, that is, at the lower end portion of the reaction tube 16,
so as to form a single unit with the reaction tube 16.
[0034] The water-washing unit 24 is configured to wash away dust
particles produced as a by-product of thermal
decomposition/reaction treatment of the exhaust gas E in the
exhaust gas treatment space 16a and deposited on the lower end
portion of the reaction tube 16, with the washing water W. Like the
reaction tube 16, the water-washing unit 24 is also formed of, for
example, a corrosion-resistant metallic material such as Hastelloy
(registered trademark) and includes: a casing 34 having a
funnel-shaped tapered portion 34a with an inner diameter gradually
decreasing downward from the lower end portion of the reaction tube
16; and a washing water supply nozzle 36 provided at the upper end
portion of the tapered portion 34a so as to supply the washing
water W in such a manner that the water W flows spirally downward
along the inner surface of the tapered portion 34a.
[0035] A pipe 38 communicating with the exhaust gas outlet 20 is
connected to the lower end portion of the outer wall of the casing
34 of the water-washing unit 24, and an inlet of the downstream
vacuum pump 22 is connected directly to the exhaust gas outlet 20
as the downstream end of the pipe 38. Therefore, the washing water
W supplied from the water-washing unit 24, together with the
exhaust gas E that has undergone thermal decomposition treatment,
is provided to the downstream vacuum pump 22 through the exhaust
gas outlet 20.
[0036] A nozzle 40 for introducing at least one
decomposition/reaction agent selected from the group consisting of
water, air, O.sub.2, H.sub.2 and hydrocarbon gases, which are
optionally supplied from the decomposition/reaction agent supply
unit 26, into the exhaust gas treatment space 16a is provided in
the vicinity of the exhaust gas inlet 32 located on the opposite
side to the lower end of the reaction tube 16 at which the
water-washing unit 24 is connected in series, i.e., located on the
upper part of the reaction tube 16 (see FIG. 2).
[0037] Furthermore, a heater insertion hole 16c is formed in the
central portion of a top panel 16b of the reaction tube 16, and the
electric heater 18 is disposed in the reaction tube 16 through the
heater insertion hole 16c.
[0038] The electric heater 18 is configured to heat the exhaust gas
treatment space 16a to a predetermined temperature equal to or
higher than the thermal decomposition temperature (more
specifically, about 600.degree. C. to 1300.degree. C.) of the
exhaust gas E (i.e., components to be abated, in particular) so as
to thermally decompose the exhaust gas E, and includes a heating
element 18a and a protective tube 18b.
[0039] When electric power is applied, the heating element 18a
generates heat at a temperature equal to or higher than the thermal
decomposition temperature of the exhaust gas E and serves as a heat
source of the electric heater 18. Examples of the heating element
18a include a solid or hollow silicon carbide rod and a spirally
wound metallic wire rod obtained by bending a metallic wire such as
a nichrome wire or a kanthal wire into two halves approximately
parallel to each other at the center C in its longitudinal
direction and then spirally winding them. The outer surface of this
heating element 18a is protected by the protective tube 18b.
[0040] The protective tube 18b is a bottomed tubular container made
of a ceramic material such as alumina (Al.sub.2O.sub.3), silica
(SiO.sub.2) or silicon nitride (Si.sub.3N.sub.4) or a
corrosion-resistant metallic material such as Hastelloy (registered
trademark).
[0041] The downstream vacuum pump 22 is a pump for reducing the
pressure in the region located downstream of the outlet of the
vacuum pump 14 and including the interior of the reaction tube 16
to a predetermined degree of vacuum and drawing the exhaust gas E
that has undergone abatement treatment in the reaction tube 16 to
discharge it. In the present invention, a water-sealed pump is used
as the downstream vacuum pump 22. A "water-sealed pump (i.e., a
water seal type vacuum pump)" is a vacuum pump including a casing
containing an appropriate amount of seal water and an impeller. In
this pump, the phenomenon that the space surrounded by the seal
water pushed against the inner wall of the casing by centrifugal
force and the rotating impeller varies is utilized to perform
suction and discharge operations. In the present invention, the
washing water W supplied from the water-washing unit 24 is used as
the seal water for the water-sealed pump. Therefore, before passing
through the water-sealed pump, the exhaust gas E that has undergone
abatement treatment in the reaction tube 16 is brought into full
gas-liquid contact with the washing water W to be reused as the
seal water later. Thus, most of the water-soluble components in the
exhaust gas E produced as a by-product of the abatement treatment
are dissolved in the seal water and removed from the exhaust gas E.
This means that there is no need to provide a water-washing device
such as an outlet-side scrubber.
[0042] It should be noted that at the outlet of the downstream
vacuum pump 22, a separator 45 such as a gas-liquid separator
coalescer is optionally provided to separate the treated exhaust
gas E and the seal water in their mixture discharged from the
downstream vacuum pump 22 (see FIG. 1).
[0043] Here, the reduced pressure created by the downstream vacuum
pump 22 for the exhaust gas flow region located downstream of the
outlet of the vacuum pump 14 and including the interior of the
reaction tube 16 is preferably in a range of 1 Torr or more and 700
Torr or less, more preferably in a range of 15 Torr or more and 685
Torr or less, and even more preferably in a range of 100.+-.50
Torr. When the reduced pressure is lower than 1 Torr, an expensive
and elaborate system is needed to achieve a high vacuum
environment. In contrast, when the reduced pressure is higher than
700 Torr, which is close to the atmospheric pressure, the exhaust
gas E must be diluted with a large amount of nitrogen gas, which is
comparable to the amount of nitrogen gas required to dilute the
exhaust gas E under atmospheric pressure.
[0044] The apparatus 10 for exhaust gas abatement under reduce
pressure according to the present embodiment further includes a
dust removal unit 28 provided in the reaction tube 16.
[0045] This dust removal unit 28 is composed of: a motor 44
disposed directly below the reaction tube 16; a rotatable arm 46
fixed upright to the motor 44 to extend upward into the reaction
tube 16; and dust removable arms 48 branching from the upper end of
the rotatable arm 46 and extending upward along the outer surface
of the electric heater 18. Thus, the dust removal unit 28 is
configured to blow away dust particles deposited on the inner
surface of the reaction tube 16 and the outer surface of the
electric heater 18. The dust particles are very fine fluffy
particles and fall off upon brief contact with the rotating dust
removable arms 48.
[0046] It is needless to say that the apparatus 10 for exhaust gas
abatement under reduced pressure according to the present
embodiment includes various types of detectors, controllers, and
power supplies that are necessary to operate the electric heater
18, the downstream vacuum pump 22, the dust removal unit 28, and
others, although not shown in the figures.
[0047] A method for exhaust gas E abatement under reduced pressure
using the apparatus 10 for exhaust gas abatement under reduced
pressure configured as described above will be described. The
exhaust gas E discharged from the exhaust gas source 12 is
delivered to the reaction tube 16 via the vacuum pump 14. When the
downstream vacuum pump 22 is operated, the exhaust gas E is
introduced into the exhaust gas treatment space 16a of the reaction
tube 16 under a predetermined reduced pressure, and in this exhaust
gas treatment space 16a, the exhaust gas E is subjected to
decomposition/reaction treatment by the heat generated by the
electric heater 18.
[0048] According to the apparatus 10 for exhaust gas abatement
under reduced pressure of the present embodiment, the exhaust gas E
is heated by the electric heater 18 for decomposition and/or
reaction treatment under reduced pressure, and thus, less heat is
generated by the reaction and a rapid temperature rise or explosive
reaction never occurs. Therefore, there is no need to use diluent
nitrogen gas or the use of the nitrogen gas can be reduced to a
minimum. Since there is no need to dilute with diluent nitrogen gas
or the use of the nitrogen gas can be reduced to a minimum, almost
all thermal energy supplied by the electric heater 18 can be used
directly for decomposition/reaction of the exhaust gas E. A
combination of these two advantageous effects allow the exhaust gas
E abatement apparatus to be configured very compactly.
[0049] In addition, since the region located downstream of the
outlet of the exhaust gas source 12 and including the abatement
treatment unit is under reduced pressure, even if the exhaust gas E
contains toxic substances to humans, there is no risk that the
exhaust gas E leaks from the system before being heated by the
electric heater 18 for decomposition/reaction treatment.
[0050] Next, another embodiment (second embodiment) of the present
invention shown in FIG. 3 will be described. The main difference
between the above-described apparatus 10 for exhaust gas abatement
under reduced pressure according to the first embodiment and the
apparatus of the second embodiment is that the latter apparatus is
provided with an inlet-side scrubber 50 and its ancillary equipment
on the upstream side of the reaction tube 16 in the flow path of
the exhaust gas E supplied from the exhaust gas source 12 via the
vacuum pump 14. The apparatus of the second embodiment is the same
as the apparatus 10 for exhaust gas abatement under reduced
pressure according to the first embodiment except for these
scrubber and ancillary equipment. Therefore, description
overlapping the description of the first embodiment is not repeated
herein for the second embodiment.
[0051] The inlet-side scrubber 50 is a wet scrubber for washing
dust particles and water-soluble components contained in the
exhaust gas E with water in a reduced pressure atmosphere before
the exhaust gas E is introduced into the reaction tube 16, and
includes: a straight tube type scrubber main body 50a; and one or a
plurality of spray nozzles 50b disposed inside the scrubber main
body 50a so as to spray a mist of a chemical solution such as
scrubber water SW. The scrubber main body 50a is mounted upright
with its central axis extending in the vertical direction, and a
reservoir 50c for storing the scrubber water SW is formed in the
lower end portion of the scrubber main body 50a. An upstream end of
a pipe 52 for drawing the scrubber water SW from the reservoir 50c
is connected to the lower part of the outer surface of the
reservoir 50c to communicate with the reservoir 50c, and the
downstream end of the pipe 52 is connected to the inlet of a
circulation pump 54.
[0052] The circulation pump 54 is a pump for circulating the
scrubber water SW, and the upstream end of a pipe 56 is connected
to the outlet of the circulation pump 54 to supply the scrubber
water SW to various parts. The downstream end of the pipe 56 is
connected to the spray nozzle(s) 50b in the scrubber main body 50a.
This pipe 56 branches in the middle to form a branch pipe 58, and
the downstream end of the branch pipe 58 is connected to the
washing-water supply nozzle 36. Therefore, a portion of the
scrubber water SW circulated by the circulation pump 54 is used as
washing water W in the above-mentioned water-washing unit 24.
[0053] An exhaust gas inlet 50d for introducing the exhaust gas E
into the scrubber main body 50a is formed at a position higher than
the water level in the reservoir 50c located in the lower part of
the scrubber main body 50a.
[0054] Furthermore, the reservoir 50c of the scrubber main body 50a
and a trap for the washing water W in the lower part of the casing
34 of the water-washing unit 24 are configured to communicate with
each other via a pipe 60. Therefore, a portion of the washing water
W supplied to the water-washing unit 24 through the branch pipe 58
is used as seal water for the downstream vacuum pump 22 but all the
rest of the washing water W is returned to the reservoir 50c
through the pipe 60 and recirculated as the scrubber water SW or
the washing water W by the circulation pump 54.
[0055] It should be noted that the amount of the scrubber water SW
and washing water W circulated for reuse by the circulation pump 54
decreases as a portion thereof is used as the seal water for the
downstream vacuum pump 22, but the total amount of water in the
apparatus is controlled in a well-balanced manner by supplying
additional new (unused) water through a water supply pipe 62
connected to the downstream portion of the pipe 52 to compensate
the loss of the seal water.
[0056] The upper end of the scrubber main body 50a is configured to
communicate with the exhaust gas inlet 32 of the reaction tube 16
through a pipe 30.
[0057] According to the apparatus 10 for exhaust gas abatement
under reduced pressure of the present embodiment configured as
described above, the above-mentioned operational effects can be
achieved. In addition, since the reservoir 50c of the scrubber main
body 50a and the trap for the washing water W in the lower part of
the casing 34 of the water-washing unit 24 are connected to
communicate with each other via the pipe 60, the washing water W
trapped in the lower part of the casing 34 of the water-washing
unit 24 can also be circulated by the circulation pump 54. As a
result, the amount of the washing water W to be ejected from the
washing water supply nozzle 36 of the water-washing unit 24 can be
increased and thus the cleaning ability of the water-washing unit
24 can be enhanced.
[0058] Next, still another embodiment (third embodiment) of the
present invention shown in FIG. 4 will be described. In this
apparatus 10 for exhaust gas abatement under reduced pressure of
the third embodiment, the inlet-side scrubber 50 is provided on the
upstream side of the reaction tube 16 in the exhaust gas E flow
path, as in the second embodiment described above, but the third
embodiment differs from the second embodiment in the locations of
the circulation pump 54 and the water supply pipe 62. Since the
apparatus of the third embodiment is the same as the apparatus 10
for exhaust gas abatement under reduced pressure according to the
first or second embodiment except for the locations of the
circulation pump 54 and the water supply pipe 62, description
overlapping the description of the first and second embodiments is
not repeated herein for the third embodiment.
[0059] In the present embodiment, not only the downstream end of
the pipe 52 for drawing the scrubber water SW from the reservoir
50c but also the downstream end of the pipe 64 for drawing the
washing water W trapped in the lower part of the casing 34 of the
water-washing unit 24 is connected to the inlet of the circulation
pump 54. Therefore, unlike in the apparatus of the second
embodiment, the pipe 60 for communicating the reservoir 50c of the
scrubber main body 50a and the lower part of the casing 34 of the
water-washing unit 24 is not provided in the apparatus 10 for
exhaust gas abatement under reduced pressure according to the
present embodiment.
[0060] Furthermore, the water supply pipe 62 of the present
embodiment is connected directly to the reservoir 50c of the
scrubber main body 50a so as to supply additional new water
directly to the reservoir 50c.
[0061] Since the apparatus 10 for exhaust gas abatement under
reduced pressure according to the present embodiment is configured
to supply the washing water W trapped in the lower part of the
casing 34 of the water-washing unit 24 directly to the suction port
of the circulation pump 54 through the pipe 64, the amount of the
washing water W to be ejected from the washing water supply nozzle
36 of the water-washing unit 24 can be further increased and thus
the cleaning ability of the water-washing unit 24 can be further
enhanced than in the apparatus of the second embodiment described
above.
[0062] The following modifications may be made to the embodiments
described above.
[0063] In the above embodiments, the electric heater 18 is used as
the heat source for thermal decomposition of the exhaust gas E in
the reaction tube 16, but instead, a plasma such as a DC arc
plasma, an inductively coupled plasma, or a capacitively coupled
plasma (not shown) may be used.
[0064] In the above embodiments, the water-washing unit 24 is
composed of the casing 34 having a predetermined shape and the
washing water supply nozzle 36, but the water-washing unit 24 may
be configured in any suitable manner as long as the downstream end
portion of the exhaust gas flow path in the reaction tube 16 can be
washed with the washing water W, and the configuration of the
water-washing unit 24 is not limited to that described above.
[0065] In the above embodiments, at least one selected from the
group consisting of water, air, O.sub.2, H.sub.2, and hydrocarbon
gases is given as an example of the decomposition/reaction agent
supplied from the decomposition/reaction agent supply unit 26.
However, for example, when the exhaust gas E contains a large
amount of perfluorinated compounds (PFCs) such as NF.sub.3 and thus
a large amount of HF is produced as a decomposition/reaction
product, it is preferable to add an alkaline aqueous solution such
as a KOH aqueous solution or a NaOH aqueous solution as a
neutralizer (decomposition/reaction agent).
[0066] In the above embodiments, the dust removal unit 28 as an
optional component is composed of the motor 44, the rotatable arm
46, and the dust removable arms 48, but this dust removal unit 28
may be configured in any suitable manner as long as dust particles
deposited in the interior of the reaction tube 16 can be removed,
and the configuration of the dust removal unit 28 is not limited to
that described above.
[0067] In the above embodiments, the vacuum pump 14 and the exhaust
gas inlet 32 of the reaction tube 16 are connected by the pipe 30.
However, the outlet of the vacuum pump 14 and the exhaust gas inlet
32 may be connected directly to each other. Furthermore, in the
above embodiments, the exhaust gas outlet 20 of the reaction tube
16 and the inlet of the downstream vacuum pump 22 are connected
directly to each other. However, the exhaust gas outlet 20 of the
reaction tube 16 and the downstream vacuum pump 22 may be connected
by a pipe.
[0068] It will be understood that various modifications may be made
to the above embodiments within the scope of knowledge of those
skilled in the art.
REFERENCE SIGNS LIST
[0069] 10: Apparatus for exhaust gas abatement under reduced
pressure
[0070] 12: Exhaust gas source
[0071] 14: Vacuum pump
[0072] 16: Reaction tube
[0073] 16a: Exhaust gas treatment space
[0074] 18: Electric heater
[0075] 20: Exhaust gas outlet
[0076] 22: Downstream vacuum pump
[0077] 24: Water-washing unit
[0078] 26: Decomposition/reaction agent supply unit
[0079] 28: Dust removal unit
[0080] 50: Inlet-side scrubber
[0081] 54: Circulation pump
[0082] E: Exhaust gas
[0083] W: Washing water
[0084] SW: Scrubber water
* * * * *