U.S. patent number RE38,815 [Application Number 10/008,676] was granted by the patent office on 2005-10-11 for method and apparatus for the destruction of volatile organic compounds.
This patent grant is currently assigned to Vericor Power Systems LLC. Invention is credited to Luis R. Maese, Ram Srinivasan, Stephen R. Thomas.
United States Patent |
RE38,815 |
Maese , et al. |
October 11, 2005 |
Method and apparatus for the destruction of volatile organic
compounds
Abstract
A system for the destruction of volatile organic compounds while
generating power. In a preferred embodiment the system comprises a
combustor and a reaction chamber connected to an exit of the
combustor. A primary inlet to the combustor supplies a primary fuel
to the combustor. A secondary fuel, comprising air and an amount of
one or more volatile organic compounds, is supplied to a
compressor, which compresses the secondary fuel and directs the
secondary fuel to the combustor and the reaction chamber. The
system is suitably configured to enable the stoichiometric reaction
of the two fuels in a manner sufficient to destroy the volatile
organic compounds contained in the secondary fuel and power a
turbine engine connected to an exit of the reaction chamber.
Inventors: |
Maese; Luis R. (Glendale,
AZ), Srinivasan; Ram (Chandler, AZ), Thomas; Stephen
R. (Phoenix, AZ) |
Assignee: |
Vericor Power Systems LLC
(Alpharetta, GA)
|
Family
ID: |
24146366 |
Appl.
No.: |
10/008,676 |
Filed: |
December 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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538308 |
Oct 3, 1995 |
5673553 |
|
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Reissue of: |
864592 |
May 28, 1997 |
05832713 |
Nov 10, 1998 |
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Current U.S.
Class: |
60/783;
60/39.463; 60/772 |
Current CPC
Class: |
F02C
3/20 (20130101); F23G 5/46 (20130101); F23G
7/065 (20130101); F23G 2209/142 (20130101); Y02E
20/12 (20130101) |
Current International
Class: |
F02C
7/00 (20060101); F02C 007/00 () |
Field of
Search: |
;60/772,39.12,39.461,39.463,39.465,39.826,746,801 ;431/5,278 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A 0 490 283 |
|
Jun 1992 |
|
EP |
|
0 298 941 |
|
Jan 1989 |
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FR |
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WO A 95 02450 |
|
Jan 1995 |
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WO |
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Primary Examiner: Casaregola; Louis J.
Attorney, Agent or Firm: Thomas, Kayden, Horstemeyer &
Risley, L.L.P.
Parent Case Text
This is a division of application Ser. No. 08/538,308, filed Oct.
3, 1995, now U.S. Pat. No. 5,673,553.
Claims
We claim:
1. A method of destroying volatile organic compounds (VOCs)
comprising the steps of: collecting air laden with VOCs;
compressing said VOC laden air in a compressor; injecting a primary
fuel into a combustor; directing said compressed VOC laden air into
said combustor to form a mixture of said primary fuel and said VOC
laden air; combusting said mixture in said combustor and directing
said combusting mixture from said combustor into a reaction
chamber; continuing to combust said mixture in said reaction
chamber to substantially destroy said VOCs and create a resulting
stream of combustion gas; directing said resulting stream of
combustion gas to drive a power generator; and recovering power
from operation of said power generator.
2. The method of claim 1 further comprising controllably bypassing
a portion of said VOC laden air around said combustor and into said
reaction chamber to mix and react with said combusting mixture.
3. The method of claim 2 further comprising the step of:
controlling the flow of said bypassed VOC laden air and said flow
of primary fuel to maintain a suitable ratio of fuel-to-air in said
combustor.
4. The method of claim 2 further comprising the step of controlling
the flow of said bypassed VOC laden air to maintain said power
generator at a suitable operating condition.
5. The method of claim 4 wherein said operating condition is the
speed of said power generator.
6. The method of claim 4 wherein said operating condition is the
power output of said power generator.
Description
TECHNICAL FIELD
This invention relates generally to a method and apparatus for the
destruction of hazardous materials, such as volatile organic
compounds, and more particularly, to the destruction of volatile
organic compounds through the use of a turbine engine in order to
produce power.
BACKGROUND OF THE INVENTION
Increasingly over the past half century, air quality has become an
issue of public concern. Over this period, the scientific community
has steadily improved its understanding of the origins of the air
pollution that is apparent over most major U.S. cities. A large
part of this air pollution is attributable to the release of
volatile organic compounds into the atmosphere. As a result, the
reduction of the releases of volatile organic compounds has become
an increasingly important part of the overall strategy to improve
air quality.
The most familiar volatile compound reduction technique is the
control of fuel vaporization by vapor recovery techniques, first on
automobiles and now on gasoline stations located in nonobtainment
areas. As a result, the steady year over year increase in U.S.
releases of these compounds has leveled off and is now even
declining.
Manufacturing sites are responsible for approximately 8.5 million
tons of volatile organic compound emissions annually. Solvent
vaporization or in some cases, hydrocarbon byproducts, are key to
the manufacturing process of many of by items used regularly in
daily life. The manufacture of familiar consumer products results
in the release into the atmosphere of significant amounts of
organic compounds such as pentane, ethanol, methanol, ethyl
acetate, and many others. The control of volatile organic compounds
is essential to the environmentally friendly manufacture of these
products, and thus, there remains a struggle with the cost of
control versus the loss of competitiveness.
The most common control method in use today is the thermal
oxidizer. In connection with this method, the volatile solvent is
released in amounts generally less than a few thousand parts per
million into the plant air system. This air is then selectively
collected and fed into a combustion chamber where it is mixed with
enough natural gas to sustain combustion. It is then ignited in a
large chamber that incinerates the volatile solvent, as well as,
the natural gas, thereby producing carbon dioxide and water vapor
as the primary products of combustion. These oxidizers are large,
complicated devices that represent a major capital expense and
require significant amounts of electricity and gas to operate.
While heat can sometimes be recovered, generally speaking, thermal
oxidizers represent a significant economic loss to the businesses
using them. In a typical U.S. industrial plant, the cost of
operating this type of device easily adds 25%, and often much more,
to the yearly energy bill.
Another current control technology uses solvent recovery methods
that pass the air from the plant through an activated charcoal
filter. Periodically, the charcoal is heated, driving off highly
concentrated volatile compounds into a chilled condensing system.
The output is a liquid organic compound often requiring hazardous
waste treatment. The cost of operation, as well as the initial
capital costs, are significantly higher than the thermal oxidizer,
thereby making this control technology less attractive for the
majority of industrial sites.
Accordingly, an efficient and cost effective device for the
destruction of volatile organic compounds is needed.
Such a device is described and claimed in the copending application
U.S. Ser. No. 08/538,692 now U.S. Pat. No. 5,592,811, filed on Oct.
3, 1995, and owned by the assignee of record. The subject matter of
that application is hereby incorporated herein by reference.
In that application, a system for the destruction of volatile
organic compounds is disclosed which comprises a combustor and a
reaction chamber, both of which are suitably connected to the
compressor, such as the compressor of a power generator (e.g. a gas
turbine engine). The system further comprises a primary inlet to
the combustor for supplying a primary fuel and a secondary inlet to
the combustor and the reaction chamber for supplying a secondary
fuel. The secondary fuel comprises air and an amount of a volatile
organic compound. The compressor compresses the secondary fuel and
directs the compressed fuel to the combustor and reaction chamber.
The fuel mixture is reacted in the reaction chamber, and the stream
of combustion gases directed to a power generator to generate
power.
While the system so described is suitable for use in many
applications, once assembled, particularly if the combustor is
provided for direct, in line communication with the inlet of the
reaction chamber, the size of the device becomes cumbersome for
shipping and maintenance.
Moreover, in operation of the device, particularly when the VOC
laden air is drawn from environments which vary over time, i.e. the
amount of VOCs in the air varies, control of the system can become
difficult.
SUMMARY OF THE INVENTION
A system for the destruction of volatile organic compounds
according to the present invention addresses the shortcomings of
the prior art, particularly those difficulties which may be
encountered during use of a system in accordance with some aspects
of the system described in the aforementioned copending
application.
In accordance with one aspect of the present invention, a system
for the destruction of volatile organic compounds comprises a power
generator, a compressor, a combustor and a reaction chamber. A
primary inlet to the combustor is provided for supplying a primary
fuel to the combustor. A secondary fuel comprising air and at least
one volatile organic compound is provided to the compressor. An
outlet from the compressor communicates with the reaction chamber
and the combustor. The combustor is attached to the reaction
chamber such that the flow of combusted gasses is directed
tangentially into the reaction chamber, thereby enhancing the
residence time of the mixed fuels within the reaction chamber. In
addition, the size of the device is suitable for shipping. A power
generator is connected to an exit of the reaction chamber and
utilizes the exiting fuel mixture to generate power.
In accordance with a further aspect of the present invention, the
combustor and the reaction chamber are configured to create a
cyclonic flow of the primary and secondary fuels through the
reaction chamber. This allows for the fuel to remain in the
reaction chamber for a longer period of time, thereby providing for
a better stoichiometric reaction.
In accordance with a further aspect of the present invention, an
air flow system is provided to regulate the inlet air and fuel
supplies within the combustor and reaction chamber to maintain
effective operation of the device.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The present invention will hereinafter be described in conjunction
with the appended drawing figures, wherein like designations denote
like elements, and:
FIG. 1 is a simplified schematic drawing of a destruction device in
accordance with the present invention;
FIG. 2 is a schematic drawing of a device of the type shown in FIG.
1 as utilized in an exemplary plant layout;
FIG. 3 is a cross-sectional view of a combustor used in connection
with the destruction device of FIG. 2;
FIG. 4 is a partial cross-sectional view of the combustion device
and reaction chamber of the destruction device of FIG. 2;
FIG. 5 is a cross-sectional view of the compressor of the
destruction device of FIG. 2;
FIG. 6 is a schematic drawing of an alternative plant layout of a
destruction device in accordance with the present invention;
and
FIG. 7 is a further alternative embodiment of a mobile layout of a
destruction device in accordance with the present invention.
DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS
While the way in which the present invention addresses the various
disadvantages of the prior art designs will be discussed in greater
detail hereinbelow, in general, the present invention provides a
volatile organic compound (VOC) destruction device which includes a
power generator such that the effective elimination of VOC's also
results in the co-generation of power. The power so produced can be
converted into electricity, which can in part drive the destruction
device as well as produce power for other uses.
With reference to FIGS. 1 and 2, a VOC destruction device 10, in
accordance with a preferred embodiment of the present invention,
suitably includes a power generator 12 which is driven by a fuel
system 14. Fuel system 14 preferably comprises a combustor 16 and a
reaction chamber 18. As will be discussed in greater detail
hereinbelow, in operation, VOC destruction device 10 utilizes
natural gas or any other suitable fuel as a primary fuel supply in
a conventional manner. However, in accordance with the present
invention, this primary fuel is suitably mixed with a secondary
fuel comprising air and preferably VOCs. This fuel mixture of
primary and secondary fuels is burned in power generator 12.
In accordance with a preferred embodiment of the present invention,
power generator 12 preferably comprises a gas turbine engine, for
example an AlliedSignal IE-831 engine, which is produced by
AlliedSignal Aerospace, Phoenix, Ariz. has been found to be
suitable. However, it should be recognized that any suitable engine
can be used in the context of device 10, provided such engine can
be suitably employed in the generation of power.
With continued reference to FIG. 2, power generator (engine) 12 is
preferably of a conventional design. For example, engine 12
suitably includes, in spaced relation, a generator 20, a gearbox
22, a compressor 24 and a turbine 26. Turbine 26, also preferably
of a conventional design, suitably includes a power turbine (not
shown) connected to shaft 28. As will be appreciated, shaft 28 is
suitably connected to generator 20, gearbox 22 and compressor
24.
In accordance with the present invention, VOC destruction device 10
can be utilized to concurrently destroy VOC's and realize the fuel
value of the VOC's produced from a variety of different
environments. In this context, the term "VOC" is used broadly to
refer to carbon containing compounds, such as hydrocarbons,
dioxins, alcohols, ketines aldehydes, ethers, organic acids,
halogenated forms of the foregoing and the like. For example, as
used herein, the term VOC may refer to pentane, n-ethylmorphilin,
toluene, ethanol, methanol, decabromodiphenyloxide, ethyl acetate,
benzene, polystyrene and the like. Such VOC's or similar chemical
compounds are typically produced from the evaporation of chemicals
used in and generated by basic industrial processes to produce
plastics, pharmaceuticals, bakery products, printed products and
the like. A particularly preferred application of the present
invention is in the area of control VOC's produced during the
production of expandable polystyrene (i.e. the process to make
"styrofoam") where the primary emission is the VOC pentane.
Device 10 can be employed to destroy VOC's which can be collected
from the plant as whole, from special isolated or hooded areas,
from dryers or from a VOC concentrator utilized in such plants. In
the context of the present invention, air from one or more of these
environments or areas is referred to as "VOC laden air". It should
be appreciated that the amount of VOC present in such air may vary
from small amounts or none to larger amounts, over time and as
conditions in the plant change. As with typical prior art methods
of destroying VOCs or such, the present invention may be employed
even over periods of time when the VOC level is small or
nonexistent. As such, the term VOC laden air includes air that from
time to time may not include a significant quantity (or any amount)
of a VOC.
VOC laden air, such as air laden with pentane resulting from the
manufacture of expandable polystyrene, is first collected and
thereafter suitably passed into device 10. While such VOC laden air
may be collected in any conventional manner for use in connection
with the present invention, preferably, in such a process, the VOC
laden air is ducted from the plant via one or more air ducts. These
ducts are directly or indirectly connected to an inlet duct 40 (see
FIG. 1) which provides VOC laden air to destruction device 10.
In accordance with a preferred aspect of the present invention,
power generator 12 draws in such VOC laden air together with fuel,
the combustion gases of both which flow at high velocity into
turbine 26 and thereby drive turbine 26. As previously briefly
mentioned, the primary fuel utilized in accordance with the present
invention may comprise natural gas; alternatively, diesel oil, jet
fuel, methane or any other fuel material may be utilized in an
amount sufficient to sustain combustion in combustor 16.
The secondary fuel comprising the VOC laden air is generally much
leaner than the primary fuel. Generally speaking, the secondary
fuel has a VOC concentration in the range of 0% to 1%. This 1%
maximum corresponds to approximately 10,000 parts per million,
depending on the type of organic compound involved. Typically this
will comply with OSHA regulations as the maximum concentration
allowed within plant air in order to prevent the possibility of an
explosion within the plant, and in the event permissible limits are
exceeded, the concentration can be reduced. However, it should be
appreciated that system 10 is capable of handling higher VOC
concentrations, as may be desirable in some applications.
With reference to FIG. 1, a simplified schematic view of
destruction device 10 is shown. As shown, VOC laden air from inlet
duct 40 is suitably directed to power generator 12, and in
particular, compressor 24 thereof. Preferably, the temperature of
the inlet air A, i.e. the VOC laden air, is at a temperature of
less than about 130.degree. F. To this end, a temperature control
system 42 is suitably positioned to measure the temperature of the
inlet air and in the event the temperature exceeds about
130.degree. F., the air is cooled through a cooling system 44. As
will be appreciated by those skilled in the art, cooling system 44
may suitably comprise an air or water heat exchanger suitably
configured to cool the temperature of inlet air to a temperature in
the range of about 59.degree. to about 130.degree. F.
Once the temperature of inlet air A is within a suitable range,
such inlet air A is passed through a control valve 46 which is
suitably provided with a VOC monitor 48. As will be discussed in
greater detail below, monitor 48 measures the level of VOC within
inlet air A. This VOC level measurement, as will be described in
greater detail below, is utilized to adjust, as appropriate, the
ratio of primary and secondary fuels which are fed into combustor
16. Regulator 46 suitably regulates the flow of air which is drawn
into compressor 24.
When device 10 is placed in initial operation, generator 20 is
utilized to initially drive compressor 24 (as well as turbine 26)
to suitably draw inlet air A into compressor 24. As operation of
device 10 continues, the power drawn from generator 20, through
gearbox 22, may be suitably decreased and thereafter compressor 24
is, at least in part, and preferably entirely driven by the power
generated through operation of device 10, and in particular,
through the generation of energy effected by turbine 26.
As discussed briefly above, compressor 24 suitably comprises the
compressor of power generator 12. With momentary reference to FIG.
5, compressor 24 preferably comprises alternate respective sets of
rotating blades 56 and stationary blades 58. Rotating blades 56 are
suitably rotated through rotation of shaft 28, which .[.is.].
.Iadd.as .Iaddend.briefly noted above, is initially activated by
generator 20. In accordance with a preferred aspect of the present
invention, compressor 24 comprises a multi-stage compressor, more
preferably a two stage compressor, i.e. there are at least .[.2.].
.Iadd.two .Iaddend.rotating .Iadd.discs containing .Iaddend.blades
.[.(impellers).]. 56 within the body of compressor 24.
As will be recognized by those skilled in the art, inlet air A
drawn into compressor 24 is suitably compressed to pressures ranges
from about 4 to about 30 atmospheres, and preferably to about 9
atmosphere. This compression raises the temperature of inlet air A,
and thus the secondary fuel, to ideally about 600.degree. F., but
suitably within the range of about 550.degree. F. to about
650.degree. F. The compressed air B then exits compressor 24
through outlets 57A, 57B and preferably enters reaction chamber 18
through inlets 59A, 59B.
With continued reference to FIG. 1, compressed air B is suitably
directed to a flow valve 50 which is provided with a monitor 52.
Valve 50 suitably controls the amount of compressed air B which is
provided to reaction chamber 18 and combustor 16.
As shown best in FIG. 1, a primary fuel inlet 70 provides primary
fuel C to combustor 16 through a flow valve 72. Flow valve 72
preferably includes a monitor 74 to monitor the volume of fuel
which is provided to combustor 16. As will be described in greater
detail hereinbelow fuel C and a limited amount of compressed air B
(including the secondary VOC fuel) is suitably provided to
combustor 16, the remaining portion of the secondary fuel being
provided to reaction chamber 18. In accordance with a particularly
preferred aspect of the present invention, the combination of
combustor 16 and reaction chamber 18 is effective to substantially
destroy the VOC within compressed air B and provide a mixed
combustion gas stream D having a temperature suitable to activate
the nozzle and turbine stages of gas turbine 26. In accordance with
a preferred aspect of the present invention, the mixed-out
temperature of mixed stream D provided to turbine 26 is in the
range between about 1500.degree. F. and about 2300.degree. F.,
preferably about 1850.degree. F.
In a conventional fashion, mixed stream D is directed to turbine
26. Turbine 26 of the type generally described above, is initially
started by cranking it over with a starter (not shown) to produce
air flow through the compressor. At the appropriate speed, fuel C
is permitted to flow into combustor 16. However, once device 10 is
in operation, mixed stream D suitably powers turbine 26 in a manner
such that the output E from turbine 26 is suitably harnessed and
utilized in subsequent operation of device 10, as well as in
connection with the production of power for other applications.
With reference to FIGS. 3 and 4, the way in which reaction chamber
18 and combustor 16 cooperatively work to effectively destroy the
VOC's in the VOC laden air in a manner to suitably drive power
generator 12 will now be described in greater detail.
Reaction chamber 18 preferably comprises a double walled vessel
having a main, inner wall 60 and an outer wall 62 that envelopes
inner wall 60. The chamber 64 defined by walls 60 and 62 is
suitably configured and positioned in proximity to compressor 24 to
receive compressed air B. Preferably, and with reference to FIGS. 4
and 5, chamber 64 receives compressed air B (containing the
secondary fuel) from outlets 57A, 57B of compressor 24. Chamber 64
extends about the periphery of reaction chamber 18. Further, in
accordance with a preferred aspect of the present invention,
chamber 64 also suitably communicates with combustor 16 in the
region of respective openings 67A and 67B by way of a plurality of
inlets 69. Thus, compressed air B is, in accordance with at least
one aspect of the present invention, suitably provided to the
combustor 16 and also directly to chamber 64 by way of tubes 116,
118, as will be discussed in further detail below.
With reference to FIG. 3, combustor 16 preferably comprises a hot
wall type thermally insulated combustor. Preferably, combustor 16
comprises an outlet wall 80 within which a conventional combustion
device 82 is suitably orientated. An inlet 84 communicates with
combustion device 82 to advantageously effect combustion of fuel C.
As previously briefly mentioned, fuel inlet C is preferably
directed from fuel supply 70 through fuel control valve 74 and
compressed air B is provided to combustion device 82 through inlets
69. In accordance with preferred aspects of the present invention,
fuel supply C is suitably controlled by a control system 150 such
that a sufficient amount of primary fuel C is provided to the
combustion chamber to effectively maintain an appropriate
equivalence ratio (ER) thereby enabling stoichiometrically correct
combustion. As shown best in FIGS. 3 and 4, the outlet 86 of
combustor 16 suitably communicates with the interior of reaction
chamber 18.
Combustor 16 may be attached to reaction chamber 18 in any
convenient manner. For example, combustor 16 can be fixably
attached to chamber 18 such that outlet 86 of combustor 16 directly
communicates with an opening of reaction chamber 18 in an in-line
manner. However, in accordance with a preferred aspect of the
present invention and as shown best in FIGS. 3 and 4, combustor 16
is attached to reaction chamber 18 such that combustor 16 is
orthogonal to the central axis X of reaction chamber 18. In this
manner, as will be described in greater detail below, the
combustion gases exit outlet 86 of combustor 16 tangentially to
reaction chamber 18 thereby tending to create a substantially
cyclonic flow of the resulting fuel mixture within reaction chamber
18. While combustor 16 is shown in FIG. 4 as being attached to
reaction chamber 18 tangentially near an end of reaction chamber 18
opposite inlets 59a, 59b, it should be appreciated that combustion
chamber 16 may be attached in any convenient fashion. For example,
combustor 16 may be attached at any angle from about 0.degree. to
about 90.degree. from the central axis X of reaction chamber 18 and
at any point along a side or the top of reaction chamber 18.
Combustion within combustor 16 takes place in a generally
conventional manner, with the exception that compressed air b, i.e.
the VOC laden air introduced into the system, is permitted to mix
with the primary fuel C within the later stages of combustor 16. As
will be appreciated by those skilled in the art, near inlet 84,
primary fuel C is relatively rich such that it burns under near
stoichiometric conditions, typically at a temperature in the range
of about 2500.degree. F. to about 3200.degree. F., preferably
between about 2800.degree. F. and about 3000.degree. F. and
optimally 3000.degree. F. In this region denoted in FIGS. 3 and 4
as "P", often referred to as the "primary zone", a minor portion of
secondary fuel B is suitably mixed with primary fuel thereby
creating a fuel mixture of primary and secondary fuels. The minor
portion of secondary fuel introduced into the primary-zone P is
about 10% to about 30% of the secondary fuel. If the portion falls
much below 10%, the fuel will become too rich and thereby cause
"rich blowout." While the amount of secondary fuel introduced into
combustor 16 will vary, in general preferably from about 0 to about
70%, and more preferably from about 0 to about 50% of the fuel
necessary to drive power generator 12 is provided by the secondary
fuel.
The residence time of the gas mixture of primary fuel and secondary
fuel within reaction chamber 18 is enhanced due to the preferred
configuration of combustor 16 relative to reaction chamber 18.
Specifically, and in accordance with a preferred aspect of the
present invention, as the combustion gases exit the combustor at
outlet 86, such gases are directed toward the opposing wall of
reaction chamber 18. The flow pattern which results in the interior
of reaction chamber 18 tends to be cyclonic, i.e. creating a spiral
pattern.
In accordance with a preferred aspect of the present invention, the
fuel mixture, comprising primary fuel and secondary fuel is
retained in reaction chamber 18 for a sufficient time to
effectively burn, i.e. combust the VOC's contained within the
secondary fuel B. Typically, the residence time of the gas mixtures
within reaction chamber 18 is on the order of about 0.25 seconds or
more. In accordance with a preferred design of the present
invention, the tangential orientation of the combustor relative the
reaction chamber has been found to not only enhance residence time,
but also to cause a degree of recirculation within reaction chamber
18 thus further enabling substantially complete destruction of the
VOC's within reaction chamber 18.
In practice, the present invention generally results in an excess
of 90%, and typically from between about 95 and 99.5% of the VOC
contained within secondary fuel B being effectively broken down
into water vapor and carbon dioxide. As will be appreciated, and as
will be discussed in greater detail below, through effective
operation of device 10, substantially all of the VOCs contained
within the inlet air A, and thus compressed air B, are thus
effectively destroyed within reaction chamber 18 and/or combustor
16.
The double-walled configuration of reaction chamber 18, which
permits flow of compressed air B through the outer chamber 64
advantageously provides for a modicum of cooling of the reaction
chamber. For example, in the region of the outlet 90 of reaction
chamber 18 cooling tends to take place due to the generally lower
temperature of the compressed air B as compared to the temperature
of the combusting fuel mixture within the inner portion chamber of
reaction chamber 18.
Outlet 90 of chamber 18 suitably communicates with turbine 26 of
power generator 12. In a conventional fashion, the high velocity
flows of the combusted gas mixture flow onto turbine 26 to thereby
drive it. Turbine 26 is suitably configured, in a conventional
fashion, to produce usable power to not only continue operation of
device 10, but also to provide power for other applications. For
example, through utilization of a preferred gas turbine engine,
e.g. an AlliedSignal IE-831 engine, in connection with destruction
device 10 of the present invention, power sufficient to run
compressor 24 and up to an additional 525 kw of electricity have
been found to be obtainable.
With reference to FIG. 2, in accordance with a preferred embodiment
of the present invention, power generator 12 is suitably positioned
such that the exhaust heat E is directed to a heat recovery system
100. Heat recovery system 100 may be of conventional design and
operate in a conventional fashion. For example, system 100 may
comprise a heat recovery steam generator suitably configured and
positioned to provide usable hot water 102 and steam 104. As also
shown in FIG. 2, water 102 can be converted into power sufficient
to power gearbox 22, thereby obviating the continuing need for
generator 20, and steam 104 can be released as process heat or
recirculated into the regional combustor 16.
Alternatively, exhaust E may be directly used. Exhaust E is
generally at a temperature of about 1000.degree. F., and thus can
be used to heat the plant directly. Because as much as about 99.5%
or more of the VOCs have been effectively destroyed through
operation of device 10, exhaust E can be released directly into the
atmosphere.
In accordance with a further aspect of a preferred exemplary
embodiment of the present invention, device 10 is suitably provided
with an inlet air control system 110. With reference to FIG. 4,
system 110 may advantageously comprise a bypass flow circuit
comprising respective bypass flow channels 112, 114.
As will be appreciated by those skilled in the art, combustor 16
requires a certain primary-zone fuel-to-air ratio to operate
properly, typically 0.04 to 0.05, while power generator 12
typically requires a fuel-to-air ratio of approximately 0.008-0.01.
Accordingly, the fuel ratio within combustor 16 generally should be
richer than, e.g. about four to five times as rich as, the overall
fuel ratio required by the generator 12 at idle or with no load. If
the VOC concentration within the air inlet A is too high, the fuel
mixture within the combustor 16 will become too lean, thereby
causing the combustor to "flame out." "Flame out" occurs when the
fuel to air mixture within the combustor primary-zone P becomes too
lean to sustain a flame. In accordance with this aspect of the
present invention, air control system 110 is provided for the
purpose of enabling enrichment of the fuel burned within combustor
16. As will be discussed in greater detail below, control system
150 monitors and controls the concentration of the VOC within the
secondary fuel, as well as the overall fuel to air ratio within the
combustor, by causing a portion of the compressed air B to be
directed only within reaction chamber 18 and not into combustor
16.
Preferably, flow channels 112, 114 of system 110 each comprise
respective tubes 116 and 118. Preferably, tubes 116 and 118 are
suitably attached to reaction chamber 18 at 116A, 118A and are in
fluid communication with chamber 64 at inlets 124 and 126. Tubes
116 and 118 each preferably include respective valves 120 and 122,
which may comprise any conventional flow control valve, such as a
general poppet-type valve or the like. Tubes 116,118 are in fluid
communication with duct 65, which is in fluid communication with
chamber 64, such that when valves 120, 122 are opened, the pressure
within chamber 64 pushes a portion of the compressed air B out of
chamber 64 through duct 65 and into tubes 116, 118. This portion of
compressed air B then travels through the tubes 116, 118 and exits
through outlets 124, 126 reaction chamber 18 causing air B to
thereby bypass the combustor 16. In a preferred embodiment, when
the valves 120, 122 are closed, all of compressed air B enters
combustor 16 in the region of openings 67A and 67B via inlets
69.
Preferably, as shown, channels 112 and 114, as well as duct 65,
comprise a single tube that allow for the adequate bypass of
compressed air B from chamber 64 directly into reaction chamber 18.
However, other arrangements for accomplishing this objective easily
can be devised and employed in the context of the present
invention. Due to size considerations, generally the number of
channels 112, 114 are minimized to two or three, and preferably
even one; however, additional channels may be employed as
desired.
Inlet air control system 110 can be activated manually or through
the computer control associated with control system 150, which will
now be described.
Preferably, control system 150 is a computer based system suitably
configured and arranged to control, among other things, power
generator 12 and fuel supply C, as well as inlet and outlet air
from device 10. In general, control system 150 operates in a
conventional manner to control power generator 12 including, among
other things, compressor 24 and turbine 26. Further, in a
conventional fashion, control system 150 operates to start device
10 initially and monitor operation of device 10 as device 10 begins
to operate due to the burning of primary fuel A and secondary fuel
C.
Control system 150, however, differs from conventional gas turbine
and other industrial engine controls in that system 150 operates to
monitor and, as necessary, adjust fuel supplies A and C, as well an
air control system 110 to achieve optimum levels of efficiency and
ensure that device 10 safely and effectively remains operative. As
previously noted, and with momentary reference to FIG. 1, control
system communicates and utilizes information received from sensors
42, 48, 52, and 72. In addition, one or more sensors 152 may be
utilized which are incorporated in proximity to or within reaction
chamber 18 or combustor 16. (While sensor 152 is shown in FIG. 1 as
being outside of both chamber 18 and combustor 16, its location is
only illustrative of its position (or the positions) somewhere
within fuel control system 14). In cooperation, these sensors
provide information reflective of, among other things: VOC level in
inlet air (e.g. sensor 48); temperature and flow rate of inlet air
A, compressed air B, fuel C, mixed stream D and the like; fuel
content and volume (e.g. sensor 74); power output from device 10;
and speeds of turbine 26. With this and other information, control
system suitably controls the operation of device 10.
For example, when the power output of power generator 12 drops
below an expected level for the measured full consumption of fuel
C, thus indicating, for example, that the fuel mixture within
combustor 16 may be becoming too lean, control system 150 may
activate control system 110. In such cases, valves 120, 122 will be
opened thereby creating a pressure difference sufficient to draw
compressed air B out of the chamber 64 and into the bypass flow
channels 112, 114, which in turn, direct compressed air B into
reaction chamber 18 thus preventing its flow into combustor 16.
Operation of control system 150 in this manner prevents the fuel
mixture within combustor 16 from becoming too lean, while still
allowing for the VOC laden air to be reacted with the primary fuel
within reaction chamber 18 to thereby destroy the VOC concentration
and retain the VOC fuel value.
Stated another way, control system 150, by monitoring the varying
VOC level in inlet air A, and thus the corresponding fuel valve of
inlet air, adjusts device 10 for appropriate operation. For
example, in the case where inlet air A has a fuel value in excess
of that necessary to drive power generator 12 at idle alone,
control system 150 suitably reduces the flow of fuel C and as
necessary, activates air control system 110 to prevent generator 12
from operating at excessive speeds and/or combustor from operating
at excessively lean or such levels.
Control system 150 may also be employed to compensate for the
relatively long lag time between fuel introduction and changes in
conditions at inlet 90 to turbine 26 caused by reactions taking
place within reaction chamber 18, as well as to monitor or control
other aspects of device 10. Control system 150 may employ any
number of control processes and perform various computations known
to those skilled in the art.
In accordance with a further embodiment of the present invention,
and with reference to FIG. 6, in some cases, it may be desirable to
initially treat VOC laden air from a typical plant prior to
destroying the VOC's contained therein. In accordance with this
aspect of the present invention; an air treatment system 200 is
advantageously employed and communicates with one or more
destruction devices, for example respective destruction devices 10A
and 10B. Destruction devices 10A and 10B are in a form similar to
device 10 described above. System 200 suitably comprises an inlet
202 which cooperates with, for example, inlet air duct 40. Inlet
air A is thereafter drawn into chamber 203 where inlet air A is
both cooled and sampled to determine the level of VOCs in inlet air
A. Preferably, one or more sensors 206 are suitably carried within
chamber 203 for the purpose of determining the VOC level within
inlet air A.
In the event inlet air A is determined to be laden with an
unacceptable level of VOC, an inlet bypass device 208 opens to
allow fresh air into chamber 203. Preferably, bypass device 208
comprises a shutter valve of conventional design.
In addition, inlet air A is suitably cooled to a temperature within
an acceptable range. Preferably, such cooling is effected through a
heat exchanger system 205. Preferably system 205 comprises
respective heat exchange elements 204, 218, outlet 210 and cooling
fan 222. As will be appreciated by those skilled in the art,
element 204 is suitably connected via outlet and duct elements (not
shown) to cooling pump 211 and heat exchange element 218 such that
cooling fluid is suitably recirculated between elements 204 and
218. In a conventional manner, system 205 allows for the cooling of
inlet air A. Inlet air A once cooled, is passed through a
centrifugal separator 212 separating the VOC laden air from any
large particles. Once separated, the VOC laden air is communicated
to devices 10A and 10B, preferably by respective conduits 214 and
216. As previously briefly mentioned, devices 10A and 10B operate
in a fashion similar to that of device 10 described above to
generate respective exhausts E1, E2 which are released into the
plant to provide process heat through respective outlet 230,
232.
With reference to FIG. 7, a further alternative embodiment of the
present invention is shown. With certain applications, it may be
desirable to utilize a destruction device in accordance with the
present invention in a relatively mobile fashion. As shown in FIG.
7, a mobile destruction system 300 suitably comprises a sled 302
upon which a destruction device 10C is suitably mounted.
Destruction device 10C is suitably configured in a manner similar
to that of device 10 described hereinabove. As so configured,
device 10C includes power generator 12 to which reaction chamber 18
and combustor 16 are suitably attached. The output of device 10C,
namely exhaust E3 is suitably communicated via outlet 303 into a
heat recovery air-oil cooler 304. In accordance with this
embodiment of the present invention, a voltage source 306 is
suitably provided to provide startup power to device 10C, as well
as power, at least initially, to the other aspects of system 300. A
gas compressor 308 is also suitably mounted to sled 302 for raising
gas pressure to levels required by device 10C. Respective
ventilators 310, 312 may be also suitably mounted to sled 302. In
addition, a water supply 320 with respective auxiliary units 322,
324, 326, 328 and pump 330 may also be utilized for purposes of
water injection into the combustor 16 to control emissions of
nitrous oxide.
System 300 is suitably controlled through operation of a control
system 350 which may be optionally cooled through operation of a
refrigeration device 352. Various other devices such as
ventilators, switch and other electronic devices may be also
employed, in a conventional fashion, for a effective use of device
10C in connection with mobile system 300.
Preliminary experimental tests of devices embodying the present
invention have indicated that by using the VOC laden secondary
fuel, the amount of primary fuel needed to operate the engine is
reduced without a loss of energy content in the fuel supply.
Accordingly, the use of this volatile organic compound destruction
system 10 results in substantially complete destruction of the
volatile organic compound while reducing the amount of primary fuel
required to operate an engine for the generation of
electricity.
Thus, it will be appreciated that device 10 provides significant
advantages over prior art designs for destruction of VOCs. For
example, in accordance with experiments preformed using devices
embodying preferred aspects of the present invention, substantial
destruction of VOC laden air efficiency (e.g. at rates above 99.5%)
at a level of about 6200 ft.sup.3 / min can be obtained with the
production of a nominal 525 kw of electrical power.
To illustrate the overall impact of the present invention, consider
a typical plant using 640,000 kw hours per month with a need to
consume 12,000 cubic feet per minute of air laden with 3,500 parts
per million of a VOC. Consider further that the plant consumers
97,000 therms of fossil fuel each month. Without control, over 800
metric tons per year of VOC's are released into the atmosphere.
While prior art technique (e.g. use of a thermal oxidizer) may
reduce the emission to less than 50 metric tons per year of VOC's,
use of such devices increases the plant energy consumption to about
125,000 therms per month.
In contradistinction, through use of a device embodying the present
invention, effective VOC control is enabled with less energy.
Specifically, in this example, the energy consumed and therefore,
total fossil fuels burned, falls to 81,000 therms per month. Not
only are the total operating costs for the plant reduced, but there
is also a net reduction in the emission of carbon dioxide, nitric
oxide and sulfur oxide. The sum effect of use of the present
invention to control volatile organic emissions is thus cleaner
air, less fossil fuel consumption and resulting lower costs.
It will be understood that the foregoing description is of the
preferred exemplary embodiments of the invention, and that the
invention is not limited to the specific forms shown. Various
modifications may be made in the design and arrangement of the
elements set forth herein without departing from the scope of the
invention as expressed in the appended claims.
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