U.S. patent application number 14/961916 was filed with the patent office on 2016-08-11 for process gas abatement.
The applicant listed for this patent is EDWARDS LIMITED. Invention is credited to Andrew James SEELEY.
Application Number | 20160230989 14/961916 |
Document ID | / |
Family ID | 48875984 |
Filed Date | 2016-08-11 |
United States Patent
Application |
20160230989 |
Kind Code |
A1 |
SEELEY; Andrew James |
August 11, 2016 |
PROCESS GAS ABATEMENT
Abstract
A process gas abatement apparatus and method are disclosed. The
process gas abatement apparatus comprises: a burner comprising: a
combustion chamber operable to receive an effluent gas stream from
a manufacturing process tool to be treated within the combustion
chamber at a sub-atmospheric pressure, the combustion chamber being
further operable to receive a fuel, oxidant and diluent, the fuel,
oxidant and diluent controlling combustion within the combustion
chamber to treat the effluent gas stream to produce a treated
exhaust stream, the diluent being condensable in the treated
exhaust stream. By providing a diluent in the form of, for example,
an inert condensable, the volume gain within the combustion chamber
is reduced, which reduces the volume of the exhaust stream and
reduces the volumetric load on the second pump. The volume gain
reduces because the diluent shifts phase in the exhaust stream,
thereby effectively removing the contribution of the diluent to the
volume of the exhaust stream. This leads to considerable power
saving since a lower volume of gas is output from the combustion
chamber which would need to be brought up to the second pressure,
for example atmospheric pressure, by means of the second pump.
Inventors: |
SEELEY; Andrew James;
(Bristol, Somerset, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EDWARDS LIMITED |
Manor Royal, Crawley Sussex |
|
GB |
|
|
Family ID: |
48875984 |
Appl. No.: |
14/961916 |
Filed: |
May 29, 2014 |
PCT Filed: |
May 29, 2014 |
PCT NO: |
PCT/GB2014/051631 |
371 Date: |
December 8, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23L 7/00 20130101; F23L
2900/07002 20130101; F23G 7/065 20130101 |
International
Class: |
F23G 7/06 20060101
F23G007/06; F23L 7/00 20060101 F23L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2013 |
GB |
1310252.0 |
Claims
1. A process gas abatement apparatus comprising: a burner, and a
combustion chamber operable to receive an effluent gas stream from
a manufacturing process tool to be treated within the combustion
chamber at a sub-atmospheric pressure, the combustion chamber being
further operable to receive a fuel, oxidant and diluent, the fuel,
oxidant and diluent controlling combustion within the combustion
chamber to treat the effluent gas stream to produce a treated
exhaust stream, the diluent being condensable in the treated
exhaust stream.
2. The process gas abatement apparatus of claim 1, wherein the
diluent, when introduced to the combustion chamber, comprises a
vapor.
3. The process gas abatement apparatus of claim 1, wherein the
diluent comprises a liquid prior to being vaporised for
introduction to the combustion chamber.
4. The process gas abatement apparatus of claim 1, wherein the
diluent condenses to a liquid in the treated exhaust stream.
5. The process gas abatement apparatus of claim 1 wherein the
diluent is introduced into the combustion chamber with a first
volumetric rate and occupies the treated exhaust stream with a
second volumetric rate, the second volumetric rate being lower than
the first volumetric rate.
6. The process gas abatement apparatus of claim 1, wherein the
diluent is combined with at least one of the fuel and oxidant prior
to being introduced into the combustion chamber.
7. The process gas abatement apparatus of claim 1, wherein at least
one of the fuel and the oxidant is dissolved by the diluent prior
to being introduced into the combustion chamber.
8. The process gas abatement apparatus of claim 1, wherein both the
fuel and the oxidant are dissolved by the diluent prior to being
introduced into the combustion chamber.
9. The process gas abatement apparatus of claim 1, wherein at least
one of the fuel and the oxidant dissolved by the diluent is
vaporised prior to being introduced into the combustion
chamber.
10. The process gas abatement apparatus of claim 1, wherein at
least one of the fuel and the oxidant dissolved by the diluent are
co-vaporised prior to being introduced into the combustion
chamber.
11. The process gas abatement apparatus of claim 1, wherein the
diluent comprises at least one of water, a perfluorocarbon and a
hydrocarbon.
12. The process gas abatement apparatus of claim 1, wherein the
treated exhaust stream is provided to a liquid ring pump for
compression to atmospheric pressure.
13. The process gas abatement apparatus of claim 12, wherein the
diluent condenses in the liquid ring pump.
14. The process gas abatement apparatus of claim 12, wherein the
liquid ring pump is operable to scrub the treated exhaust
stream.
15. A process gas abatement method, comprising: receiving an
effluent gas stream to be treated from a manufacturing process tool
within a combustion chamber at a sub-atmospheric pressure;
receiving a fuel, oxidant and diluent within the combustion
chamber, the fuel, oxidant and diluent controlling combustion
within the combustion chamber to treat the effluent gas stream to
produce a treated exhaust stream; and condensing the diluent in the
treated exhaust stream.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process gas abatement
apparatus and method.
BACKGROUND OF THE INVENTION
[0002] Apparatus for treating an effluent gas stream from a
manufacturing process tool operating at a sub-atmospheric pressure
used in, for example, the semiconductor or flat panel display
manufacturing industry are known. During such manufacturing,
residual perfluorinated compounds (PFCs) and other compounds exist
in the effluent gas stream pumped from the process tool. PFCs are
difficult to abate or remove from the effluent gas and their
release into the environment is undesirable because they are known
to have relatively high greenhouse activity.
[0003] One way of performing effluent gas abatement is to pump the
effluent gas from the process tool to a higher sub-atmospheric
pressure before being fed to a radiant burner. The radiant burner
uses combustion to remove the PFCs and other compounds from the
process gas stream. Typically, the effluent gas stream is a
nitrogen stream containing PFCs and other compounds. A fuel gas is
mixed with the effluent gas stream and that gas stream mixture is
conveyed into a combustion chamber that is laterally surrounded by
the exit surface of a foraminous gas burner. Fuel gas and air are
simultaneously supplied to the foraminous burner to affect
flameless combustion at the exit surface, with the amount of air
passing through the foraminous burner being sufficient to consume
not only the fuel gas supplied to the burner, but also ail the
combustibles in the gas stream mixture injected into the combustion
chamber. The resultant treated gas stream is exhausted from the
radiant burner. Thereafter, the treated gas stream is pumped to
atmospheric pressure before being vented.
[0004] Although techniques exist for processing the effluent gas
stream, they each have their own shortcomings. Accordingly, it is
desired to provide an improved technique for processing an effluent
gas stream.
SUMMARY
[0005] According to a first aspect, there is provided a process gas
abatement apparatus, comprising: a burner comprising: a combustion
chamber operable to receive an effluent gas stream from a
manufacturing process tool to be treated within the combustion
chamber at a sub-atmospheric pressure, the combustion chamber being
further operable to receive a fuel, oxidant and diluent, the fuel,
oxidant and diluent controlling combustion within the combustion
chamber to treat the effluent gas stream to produce a treated
exhaust stream, the diluent being condensable in the treated
exhaust stream.
[0006] The first aspect recognises that with existing approaches,
as mentioned above, the burner will be operated at a pressure
between that of the process tool, but below atmospheric pressure.
For example, the burner is typically operated at approximately 200
mbar, with process gases being brought up to this pressure by means
of a multi-stage dry pumping mechanism, with the combustion
by-products being brought up to a second pressure, for example
atmospheric pressure by means of second pump such as, for example,
a liquid ring pump.
[0007] Typically, a hydrocarbon fuel provides the energy source for
the combustive abatement within the combustion chamber and often
this fuel is methane. This burns with the process gas `P` to
produce a treated process gas P' according to reaction (1)
below:
10P+CH.sub.4+2O.sub.2=CO.sub.2+2H.sub.2O+10P' (1)
[0008] If it is assumed that atmospheric pressure combustion
properties also occur for sub-atmospheric combustion, then each
standard litre per minute (slm) of methane can abate around 10
standard litres per minute of process exhaust. So with CH.sub.4 and
pure oxygen, the volumetric gain between the volume of gas being
input to the combustion chamber and the volume of gas being output
by the combustion chamber is only 10% (i.e. 10 slm of process
exhaust is input into the combustion chamber and 11 slm is output
from the combustion chamber).
[0009] However, ordinarily, the O.sub.2 would be delivered as 20.9%
by volume in air and hence would be accompanied by a substantial
volume of N.sub.2. Using air is both a convenient source of O.sub.2
and also is helpful within the combustion chamber as the N.sub.2
helps to moderate the flame speed and temperature within the
combustion chamber.
[0010] With air, burning as equation (2) below:
10P+CH.sub.4+2O.sub.2+8N.sub.2=CO.sub.2+8N.sub.2+2H.sub.2O+10P'
(2)
[0011] However, the first aspect recognises that the volumetric
gain between the volume of gas being input to the combustion
chamber and the volume of gas being output by the combustion
chamber almost doubles (i.e. 10 slm of process gas input into the
combustion chamber and 19 slm output from the combustion
chamber).
[0012] Accordingly a process gas abatement apparatus may be
provided. The apparatus may comprise a burner. The burner may
comprise a combustion chamber which receives a process or effluent
gas stream from a manufacturing process tool. The effluent gas
stream may be treated within the combustion chamber at a
sub-atmospheric pressure. The combustion chamber may receive a
fuel, oxidant and diluent. The fuel, oxidant and diluent may
control combustion within the combustion chamber to treat the
effluent gas stream and produce a treated exhaust stream. The
diluent may be condensable in the treated exhaust stream.
[0013] The first aspect recognises that since the purpose of the
N.sub.2 provided in existing approaches is to moderate the flame
speed and temperature within the combustion chamber, it is only by
convenience that N.sub.2 is used as it is ordinarily present in
air. If this N.sub.2 could be replaced with a diluent in the form
of, for example, an inert condensable, the volume gain within the
combustion chamber will be reduced, which reduces the volume of the
exhaust stream and reduces the volumetric load on the second pump.
The volume gain reduces because the diluent shifts phase in the
exhaust stream, thereby effectively removing the contribution of
the diluent to the volume of the exhaust stream. This leads to
considerable power saving since a lower volume of gas is output
from the combustion chamber which would need to be brought up to
the second pressure, for example atmospheric pressure, by means of
the second pump.
[0014] In one embodiment, the diluent, when introduced to the
combustion chamber, comprises a vapour. Accordingly, the diluent
may be mixed in vapour form with the fuel and oxidant to effect
combustion with the required characteristics in order to treat the
effluent gas stream. The transition from, for example, an inert
condensable vapour to a liquid within the exhaust stream enables
the diluent to both contribute to the characteristics of the
combustion whilst also reducing the volume gain because the diluent
shifts phase in the exhaust stream, thereby effectively removing
the contribution of the diluent to the volume of the exhaust
stream.
[0015] In one embodiment, the diluent comprises a liquid prior to
being vaporised for introduction to the combustion chamber. It will
be appreciated that this significantly simplifies storage of the
diluent.
[0016] In one embodiment, the diluent condenses to a liquid in the
treated exhaust stream. It will be appreciated that the phase from
a vapour to a liquid causes a significant reduction in volume.
[0017] In one embodiment, the diluent is introduced into the
combustion chamber with a first volumetric rate and occupies the
treated exhaust stream with a second volumetric rate, the second
volumetric rate being lower than the first volumetric rate.
[0018] In one embodiment, the diluent is provided at specified
volumetric rate to control combustion conditions within the
combustion chamber to treat the effluent gas stream.
[0019] In one embodiment, the diluent is combined with at least one
of the fuel and oxidant prior to being introduced into the
combustion chamber. It will be appreciated that this significantly
simplifies storage of the diluent and/or the fuel and oxidant.
[0020] In one embodiment, at least one of the fuel and the oxidant
is dissolved by the diluent prior to being introduced into the
combustion chamber.
[0021] In one embodiment, both the fuel and the oxidant are
dissolved by the diluent prior to being introduced into the
combustion chamber.
[0022] In one embodiment, at least one of the fuel and the oxidant
dissolved by the diluent is vaporised prior to being introduced
into the combustion chamber.
[0023] In one embodiment, at least one of the fuel and the oxidant
dissolved by the diluent and the diluent are co-vaporised prior to
being introduced into the combustion chamber.
[0024] In one embodiment, the diluent comprises at least one of
water, a perfluorocarbon and a hydrocarbon.
[0025] In one embodiment, the burner comprises a radiant burner and
the combustion chamber has a porous sleeve through which the fuel,
oxidant and diluent pass for combustion proximate to a combustion
surface of the porous sleeve.
[0026] In one embodiment, the treated exhaust stream is provided to
a liquid ring pump for compression to atmospheric pressure.
[0027] In one embodiment, the diluent condenses in the liquid ring
pump. Hence, the liquid ring pump may also act as an efficient
condenser.
[0028] In one embodiment, the liquid ring pump is operable to scrub
the treated exhaust stream. Hence, the liquid ring pump may also
act as an efficient scrubber.
[0029] According to a second aspect, there is provided a process
gas abatement method, comprising: receiving an effluent gas stream
to be treated from a manufacturing process tool within a combustion
chamber at a sub-atmospheric pressure, receiving a fuel, oxidant
and diluent within the combustion chamber, the fuel, oxidant and
diluent controlling combustion within the combustion chamber to
treat the effluent gas stream to produce a treated exhaust stream;
and condensing the diluent in the treated exhaust stream.
[0030] In one embodiment, the step of receiving comprises
introducing the diluent to the combustion chamber as a vapour.
[0031] In one embodiment, the diluent comprises a liquid prior to
being vaporised for introduction to the combustion chamber.
[0032] In one embodiment, step of condensing comprises condensing
the diluent to a liquid in the treated exhaust stream.
[0033] In one embodiment, the step of receiving comprises
introducing the diluent into the combustion chamber with a first
volumetric rate and the step of condensing comprises occupying the
treated exhaust stream with a second volumetric rate, the second
volumetric rate being lower than the first volumetric rate.
[0034] In one embodiment, the step of receiving comprises providing
the diluent at specified volumetric rate to control combustion
conditions within the combustion chamber to treat the effluent gas
stream.
[0035] In one embodiment, the method comprises the step of
combining the diluent with at least one of the fuel and oxidant
prior to being introduced into the combustion chamber.
[0036] In one embodiment, the method comprises the step of
dissolving at least one of the fuel and the oxidant by the diluent
prior to being introduced into the combustion.
[0037] In one embodiment, the method comprises the step of
dissolving both the fuel and the oxidant by the diluent prior to
being introduced into the combustion.
[0038] In one embodiment, the step of receiving comprises
vaporising at least one of the fuel and the oxidant dissolved by
the diluent prior to being introduced into the combustion
chamber.
[0039] In one embodiment, the step of receiving comprises
co-vaporising at least one of the fuel and the oxidant dissolved by
the diluent and the diluent prior to being introduced into the
combusion chamber.
[0040] In one embodiment, the diluent comprises at least one of
water, a perfluorocarbon and a hydrocarbon.
[0041] In one embodiment, the burner comprises a radiant burner and
the combustion chamber has a porous sleeve through which the fuel,
oxidant and diluent pass for combustion proximate to a combustion
surface of the porous sleeve.
[0042] In one embodiment, the method comprises providing the
treated exhaust stream to a liquid ring pump for compression to
atmospheric pressure.
[0043] In one embodiment, the step of condensing comprises
condensing the diluent in the liquid ring pump.
[0044] In one embodiment, the method comprises the step of
scrubbing the treated exhaust stream using the liquid ring
pump.
[0045] Further particular and preferred aspects are set out in the
accompanying independent and dependent claims. Features of the
dependent claims may be combined with features of the independent
claims as appropriate, and in combinations other than those
explicity set out in the claims.
[0046] Where an apparatus feature is described as being operable to
provide a function, it will be appreciated that this includes an
apparatus feature which provides that function or which is adapted
or configured to provide that function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] Embodiments of the present invention will now be described
further, with reference to the accompanying drawings, in which:
[0048] FIG. 1 illustrates a process gas abatement apparatus
according to one embodiment.
DESCRIPTION OF THE EMBODIMENTS
Overview
[0049] Before discussing the embodiments in any more detail, first
an overview will be provided. In embodiments, a sub-atmospheric
combustion system is operated with a diluent which condenses in its
exhaust stream in order to reduce the volume of exhaust emitted.
This reduces the volume of exhaust which needs to be compressed to
atmospheric pressure prior to be vented to atmosphere.
Process Gas Abatement
[0050] FIG. 1 illustrates a process gas abatement apparatus,
generally 100, according to one embodiment. A first pump stage 10
evacuates a process chamber, such as a semiconductor process
chamber, and takes a process or effluent gas stream P provided at a
first pressure, such as 1 mbar and compresses the effluent gas
stream P to an intermediate pressure, such as 100-200 mbar. The
first pump stage 10 typically comprises a dry pump.
[0051] A radiant burner 20 or other combustion apparatus receives
the effluent gas stream P at the intermediate pressure. In
addition, the radiant burner 20 receives a fuel/oxidant mixture, in
addition to a diluent D. The effluent gas stream P is provided into
a combustion chamber that is laterally surrounded by the exit
surface of a foraminous gas burner. The fuel/oxidant mixture is
simultaneously supplied with the diluent D to the foraminous burner
to affect flameless combustion at the exit surface. The amount of
oxidant passing through the foraminous burner is sufficient to
consume not only the fuel supplied to the burner, but also all the
combustibles in the effluent gas stream injected into the
combustion chamber. The diluent D is provided with an amount
sufficient to control the flame speed at the exit surface of the
foraminous burner and to control the temperature and other
combustion characteristics within the combustion chamber. The
treated effluent gas stream P' is exhausted from the radiant
burner, together with the other by-products of the combustion
within the combustion chamber. The diluent D condenses within the
treated effluent gas stream.
[0052] The treated effluent gas stream P' is provided to a
secondary pump stage 30, such as a liquid ring pump, which
compresses the treated effluent gas stream P', together with the
other by-products of the combustion within the combustion chamber
to a second pressure, such as atmospheric pressure, prior to being
vented to atmosphere.
EXAMPLE OPERATION
[0053] In this example, the effluent gas stream P is provided at a
rate of 10 slm (standard litres per minute) from the first pump
stage 10 to the radiant burner 20. In order to treat the effluent
gas stream P, the fuel/oxidant mixture is provided at a rate of 3
slm, together with the diluent D at a rate of 8 slm in order to
adequately control the flame speed, temperature and other
combustion characteristics within the combustion chamber in
accordance with the reaction (3) to correctly treat the effluent
gas stream P:
10P+CH.sub.4+2O.sub.2+8D(g)=CO.sub.2+8D(I)+2H.sub.2O+10P' (3)
[0054] For example, such a radiant burner 20, operating at
approximately 200 mbar is fuelled with a hydrocarbon, for example
methane, and oxygen. This is diluted to suitable concentration of
diluent D.
[0055] Since the diluent D condenses in the effluent gas stream P',
it is typically a liquid under ambient conditions and so is heated
in order to be vaporised prior to being provided to the combustion
chamber. The liquid diluent D can therefore be mixed with the fuel
and/or with the oxidant in order to store these in a convenient
manner prior to being introduced into the combustion chamber.
Diluent
[0056] In one example, the diluent D is conveniently water. An
added advantage of the provision of substantial quantities of water
vapour at flame temperature in the combustion chamber is that this
provides additional reagent for F.sub.2 abatement in the effluent
gas stream P according to equation (4) below:
F.sub.2+H.sub.2O=2HF+1/2O.sub.2 (4)
The excess O.sub.2 generated also helps since it reacts with
deposition gases such as, for example, SiH.sub.4.
[0057] The fuel may be dissolved within the water for convenient
storage. For example, an alcohol may be dissolved within the water
to provide an aqueous solution, which is then vaporised prior to
being introduced into the combustion chamber. Likewise, the oxidant
may be dissolved within the water for convenient storage. For
example, hydrogen peroxide may be dissolved within the water to
provide an aqueous solution, which is then vaporised prior to being
introduced into the combustion chamber. Similarly, both the fuel
and oxidant may be dissolved within the water for convenient
storage, if this is derived from a 70.degree. C./300 mbar source,
this would require approximately 2600 J/g to produce. The power to
do this would be around:
(8/22.4).times.18.times.2600/60=280 Watts.
[0058] This power may be derived from waste heat generated in the
vacuum pump. In an integrated system, the water (and the pump) may
be pre-heated electrically and the temperature maintained by the
balance between evaporation and heat generation.
[0059] Considering the example above where there is around 10 slm
of process gas P to be treated, typically, around 1 slm of CH.sub.4
and 2 slm of O.sub.2 will be required. To dilute this and provide
similar combustion characteristics as would be achieved with air,
around 8 slm of H.sub.2O as the diluent D will also be needed.
[0060] The water condenses within the treated effluent gas stream
and so around 10 slm of processed effluent gas stream P', together
with 1 slm of CO.sub.2 is provided. This means that rather than 19
slm being provided to the secondary pump stage 30, only around 11
slm is provided, which considerably reduces the amount to be
compressed and reduces the power consumption to achieve this.
[0061] The secondary pump stage 30 may be a liquid ring pump.
Providing a liquid ring pump is particularly advantageous as this
assists both the condensation of the diluent and can be used to
scrub the gas stream provided.
[0062] Although the above example utilised water as the diluent, it
will be appreciated that the diluent may be any suitable compound
which condenses in the effluent gas stream such as, for example, a
perfluorocarbon or a hydrocarbon.
[0063] Although illustrative embodiments of the invention have been
disclosed in detail herein, with reference to the accompanying
drawings, it is understood that the invention is not limited to the
precise embodiment and that various changes and modifications can
be effected therein by one skilled in the art without departing
from the scope of the invention as defined by the appended claims
and their equivalents.
* * * * *