U.S. patent application number 12/955100 was filed with the patent office on 2011-06-09 for liquid air method and apparatus.
Invention is credited to John Fredric Billingham, Dante Patrick Bonaquist, Marco Francesco Gatti, John Henri Royal, Mathew Roy Watt.
Application Number | 20110132032 12/955100 |
Document ID | / |
Family ID | 44080642 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110132032 |
Kind Code |
A1 |
Gatti; Marco Francesco ; et
al. |
June 9, 2011 |
LIQUID AIR METHOD AND APPARATUS
Abstract
A method and apparatus in which air is liquefied and stored for
later energy recovery during which the liquid air is pumped to high
pressure, heated and then expanded to recover the energy. During
the recovery of energy, the pumped liquid air is heated within a
regenerator that stores the refrigeration within the liquid air.
During the liquefaction of the air, part of the refrigeration
required is obtained from the refrigeration stored in the
regenerator.
Inventors: |
Gatti; Marco Francesco;
(Triuggio, MB, IT) ; Billingham; John Fredric;
(Getzville, NY) ; Royal; John Henri; (Grand
Island, NY) ; Bonaquist; Dante Patrick; (Grand
Island, NY) ; Watt; Mathew Roy; (Grand Island,
NY) |
Family ID: |
44080642 |
Appl. No.: |
12/955100 |
Filed: |
November 29, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61266347 |
Dec 3, 2009 |
|
|
|
Current U.S.
Class: |
62/615 ; 165/10;
165/4 |
Current CPC
Class: |
F25J 2240/90 20130101;
F25J 1/0045 20130101; F25J 1/0284 20130101; F25J 1/0202 20130101;
F25J 2205/24 20130101; F02C 6/14 20130101; F25J 2205/66 20130101;
F25J 2245/40 20130101; F25J 2230/20 20130101; F25J 2230/22
20130101; F25J 2220/02 20130101; F25J 1/0012 20130101; F28D 20/021
20130101; Y02E 60/145 20130101; F25J 1/0251 20130101; F25J 2235/02
20130101; F25J 2210/06 20130101; F25J 1/0037 20130101; F25J 2270/06
20130101; F02C 6/10 20130101; F25J 1/004 20130101; F25J 2240/82
20130101; F25J 2240/80 20130101; Y02E 60/14 20130101; F25J 1/0228
20130101; F25J 1/0242 20130101 |
Class at
Publication: |
62/615 ; 165/4;
165/10 |
International
Class: |
F25J 1/02 20060101
F25J001/02; F28D 17/00 20060101 F28D017/00; F28D 17/02 20060101
F28D017/02 |
Claims
1. A liquid air storage and energy recovery method comprising:
during an energy recovery phase, recovering energy from liquid air
stored in a storage tank by pumping a stream of the liquid air to
produce a pumped air stream, passing the pumped air stream through
a regenerator such that refrigeration contained in the pumped air
stream is stored within the regenerator and the pumped air stream
warms within the regenerator to produce a pressurized air stream
and expanding the pressurized air stream to produce power; during a
liquid air storage phase, liquefying air to produce a liquid air
stream and introducing the liquid air stream into the storage tank
to produce the liquid air stored in the storage tank; and providing
part of a refrigeration requirement for liquefying the air with the
refrigeration stored in the regenerator, and providing another part
of refrigeration by means of a liquefier.
2. The liquid air storage and energy recovery method of claim 1,
wherein: an air stream is compressed to produce a compressed air
stream; a first subsidiary compressed stream and a second
subsidiary compressed stream are formed at least in part by
dividing the compressed air stream into two portions; the first
subsidiary stream is introduced into the liquefier to produce a
first cooled, high pressure air stream; the second subsidiary
stream is introduced into the regenerator to produce a second
cooled high cooled high pressure air stream; a vapor phase stream
indirectly exchanges heat with the second cooled high pressure air
stream to further cool the second cooled high pressure cooled high
pressure air stream; the first and second high pressure air streams
are expanded and introduced into a phase separator to produce a
liquid phase and a vapor phase; the vapor phase stream is composed
of the vapor phase and after the indirect exchange of the heat with
the second high cooled high pressure air stream, the vapor phase
stream is introduced into the liquefier and indirectly exchanges
heat with the air cooling within the liquefier that forms the first
cooled high pressure air stream; and the liquid air stream is
composed of the liquid phase and is expanded to a lower pressure
and introduced into the storage tank; whereby, the part of the
refrigeration requirement for liquefying the air is provided by
cooling the second subsidiary stream within the regenerator,
indirectly exchanging heat from the second high pressure air stream
to the vapor phase stream and the indirect heat exchange of the
vapor phase stream within the liquefier.
3. The liquid air storage and energy recovery method of claim 2,
wherein: the air stream is compressed in a feed compressor along
with a first recycle stream to form a first combined stream; the
first combined stream is compressed in a recycle compressor along
with a second recycle stream to form a second combined stream; the
second combined stream is divided into the first subsidiary stream
and the second subsidiary stream; the first subsidiary stream is
expanded at two temperature levels within the liquefier to generate
first and second exhaust streams that indirectly exchange heat with
the air cooling within the liquefier; the first exhaust stream
results from expansion at a lower of the two temperature levels and
the second exhaust stream results from expansion at a higher of the
two levels; the first exhaust stream forms the first recycle stream
after having been fully warmed within the liquefier; and the second
exhaust stream forms the second recycle stream after having been
fully warmed within the liquefier.
4. The method of claim 3, wherein the vapor phase stream after
having exchanged heat with the air cooling within the liquefier is
recycled back to the inlet of the feed compressor.
5. The liquid air storage and energy recovery method of claim 1,
wherein: the pressurized air stream is heated in a heat
recuperator; and the pressurized air stream is expanded in at least
two expanders, serially connected, with re-heat within the heat
recuperator between the at least two expanders.
6. The liquid air storage and energy recovery method of claim 5,
wherein: the pressurized air stream is heated in a heat
recuperator; and the pressurized air stream is expanded in at least
two expanders, serially connected, with re-heat within the heat
recuperator between the at least two expanders; a high temperature
exhaust stream is produced as a result of the expansion of the
pressurized air stream; the first combined stream is purified
within a pre-purification unit; and adsorbent within the
pre-purification unit is regenerated with the high temperature
exhaust stream.
7. The liquid air storage and energy recovery method of claim 1,
wherein: the pressurized air stream is heated within a recuperator
to form a heated stream; the heated stream is expanded in a first
expander to produce a first exhaust stream; the first exhaust
stream is introduced into a combustor to produce a flue gas stream;
the flue gas stream is expanded in a second expander operating at a
higher temperature than the first expander to produce a second
exhaust stream; and the second exhaust stream is introduced into
the recuperator to heat the pressurized air stream.
8. The liquid air storage and energy recovery method of claim 1,
wherein: an air stream is compressed to produce a compressed air
stream; a first subsidiary compressed stream and a second
subsidiary compressed stream are formed at least in part by
dividing the compressed air stream into two portions; the first
subsidiary stream is introduced into the liquefier to produce a
first cooled high pressure air stream; the second subsidiary stream
is introduced into the regenerator to produce a second cooled high
pressure air stream; the first subsidiary air stream and the second
subsidiary air stream are expanded and introduced into a phase
separator to produce a liquid phase and a vapor phase; a vapor
phase stream composed of the vapor phase is introduced into the
liquefier and indirectly exchanges heat with the air cooling within
the liquefier that forms the first cooled high pressure air stream;
and the liquid air stream is composed of the liquid phase, is
expanded to a lower pressure and introduced into the storage tank;
whereby, the part of the refrigeration requirement for liquefying
the air is provided by liquefying the second subsidiary stream
within the regenerator and the indirect heat exchange of the vapor
phase stream within the liquefier.
9. The liquid air storage and energy recovery method of claim 2,
wherein the vapor phase stream indirectly exchanges heat with the
first cooled high pressure air stream and the second cooled high
pressure air stream to subcool the first high pressure air stream
and the second cooled high pressure air stream.
10. The liquid air storage and energy recovery method of claim 1,
wherein the pressurized air stream is expanded by introducing the
pressurized air stream into a combustor and expanding resulting
flue gases in an expander.
11. The liquid air storage and energy recovery method of claim 1,
wherein at least air that is introduced into the liquefier is
purified of higher boiling contaminants comprising hydrocarbons,
carbon dioxide and water vapor.
12. The method of claim 2 or claim 3, wherein the air stream is
compressed to a supercritical pressure and the stream of the liquid
air is pumped to a supercritical pressure.
13. A regenerator comprising two or more pipe bundles, said bundles
connected to each other through one or more conduits with a higher
thermal resistance than the thermal resistance of each bundle as a
whole so that heat will not be conducted through the one or more
conduits between bundles, the pipe bundles being located within a
thermal storage medium.
14. The regenerator of claim 13, wherein the thermal storage medium
is water, and the pipe bundles are submerged within a pool of the
water either in solid or liquid form.
15. The regenerator of claim 13, where each pipe bundle is embedded
in a thermal storage medium, the thermal storage medium is composed
of a mixture of substances that will change phase during the
storage and production phases.
16. The regenerator of claim 13, wherein the thermal storage medium
is cement, gravel, ceramic, or a mineral matrix.
17. A liquid air storage and energy recovery apparatus comprising:
a storage tank for storing liquid air; a pump connected to the
storage tank to pump a stream of the liquid air during an energy
recovery phase of operation, thereby to produce a pumped liquid air
stream; a regenerator connected to the pump, the regenerator
configured such that refrigeration contained in the pumped liquid
air stream is stored within the regenerator and the pumped liquid
air stream vaporizes within the regenerator to produce a
pressurized air stream; at least one expansion device connected to
the regenerator configured to expand the pressurized air stream and
thereby to produce power; a liquefier integrated with the
regenerator such that during a liquid air storage phase, an air
stream is liquefied to produce a liquid air stream through the
refrigeration stored in the regenerator during the energy recovery
phase and additional refrigeration produced by the liquefier; and
the storage tank in flow communication with the liquefier and the
regenerator such that the liquid air stream is introduced into the
storage tank to produce the liquid air stored in the storage
tank.
18. The liquid air storage and energy recovery apparatus of claim
17, wherein: at least one compressor compresses an air stream and
thereby produces a compressed air stream; the liquefier and the
regenerator are in flow communication with the at least one
compressor such that a first subsidiary compressed stream and a
second subsidiary compressed stream are formed at least in part
from the compressed air stream, the first subsidiary compressed
stream is introduced into the liquefier to produce a first cooled
high pressure air stream and the second subsidiary stream is
introduced into the regenerator to produce a second cooled high
pressure air stream; two expansion valves are positioned between
the regenerator and the liquefier and a phase separator such that
the first cooled high pressure air stream and the second cooled
high pressure air stream are expanded and introduced into the phase
separator to produce a liquid phase and a vapor phase; a heat
exchanger is positioned between the phase separator and the
liquefier and is configured such that a vapor phase stream composed
of the vapor phase indirectly exchanges heat with the second cooled
high pressure air stream to subcool the second cooled high pressure
air stream and the vapor phase stream is introduced into the
liquefier; the liquefier is configured such that the vapor phase
stream indirectly exchanges heat with the air cooling within the
liquefier that forms the first cooled high pressure air stream; and
the storage tank is in flow communication with the phase separator
and another expansion valve is positioned between the phase
separator and the storage tank such that a liquid air stream,
composed of the liquid phase, is expanded to a lower pressure and
introduced into the storage tank; whereby, the part of the
refrigeration requirement for liquefying the air is provided by
liquefying the second subsidiary stream within the regenerator,
indirectly exchanging heat from the second cooled high pressure air
stream to the vapor phase stream and the indirectly heat exchange
of the vapor phase stream within the liquefier.
19. The liquid air storage and energy recovery apparatus of claim
18, wherein: the at least one compressor comprises a feed
compressor and a recycle compressor, the feed compressor
compressing the air stream along with a first recycle stream to
form a first combined stream and the recycle compressor connected
to the feed compressor such that the first combined stream is
compressed along with a second recycle stream to form a second
combined stream; the liquefier and the regenerator are connected to
the recycle compressor so that the second combined stream is
divided into the first subsidiary stream and the second subsidiary
stream; the liquefier has two expanders positioned at two
temperatures levels within the liquefier such that the first
subsidiary stream is expanded at two temperature levels within the
liquefier to generate first and second exhaust streams, the first
exhaust stream resulting from expansion at a lower of the two
temperature levels and the second exhaust stream resulting from
expansion at a higher of the two levels and a heat exchange network
positioned within the liquefier such that the first and second
exhaust streams indirectly exchange heat with the air cooling
within the liquefier; the feed compressor is connected to the
liquefier so that the first exhaust stream forms the first recycle
stream after having been fully warmed within the liquefier; and the
recycle compressor is connected to the liquefier so that second
exhaust stream forms the second recycle stream after having been
fully warmed within the liquefier.
20. The liquid air storage and energy recovery apparatus of claim
18, wherein the liquefier is connected to the feed compressor such
that the vapor phase stream is recycled back to the inlet of the
feed compressor.
21. The liquid air storage and energy recovery apparatus of claim
17, wherein: the at least one expansion device comprises at least
two expanders, serially connected, to expand the pressurized air
stream; and a heat recuperator positioned between the at least two
expanders to reheat the pressurized air stream.
22. The liquid air storage and energy recovery method of claim 21,
wherein: the at least two expanders produce a heated exhaust
stream; a pre-purification unit having an adsorbent purifies air of
contaminants; the pre-purification is positioned between the feed
compressor and the recycle compressor so that the first combined
stream is purified within the pre-purification unit; and the
pre-purification unit is connected to the at least two expanders to
receive a part of the heated exhaust stream to regenerate adsorbent
within the pre-purification unit.
23. The liquid air storage and energy recovery apparatus of claim
17, wherein: The at least one expansion device is a first expander
and a second expander; a recuperator heats the pressurized air
stream and thereby to form a heated stream; the first expander is
connected to the recuperator to expand the heated stream and
thereby to produce a first exhaust stream; a combustor is connected
to the first expander to expand the first exhaust stream and
thereby to produce a flue gas stream; the second expander is
connected to the combustor to expand the flue gas stream at a
higher temperature than the first expander to produce a second
exhaust stream; and the recuperator is also connected to the second
expander so that the second exhaust stream is introduced into the
recuperator to heat the pressurized air stream.
24. The liquid air storage and energy recovery apparatus of claim
17, wherein: at least one compressor compresses an air stream and
thereby produces a compressed air stream; the liquefier and the
regenerator are in flow communication with the at least one
compressor such that a first subsidiary compressed stream and a
second subsidiary compressed stream are formed at least in part
from the compressed air stream, the first subsidiary compressed
stream is introduced into the liquefier to produce a first cooled
high pressure air stream and the second subsidiary stream is
introduced into the regenerator to produce a second cooled high
pressure air stream; two expansion valves are positioned between
the regenerator and the liquefier and a phase separator such that
the first cooled high pressure air stream and the second cooled
high pressure air stream are expanded and introduced into the phase
separator to produce a liquid phase and a vapor phase; the
liquefier is connected to the phase separator and is configured
such that a vapor phase stream composed of the vapor phase
indirectly exchanges heat with the air cooling within the liquefier
that forms the first cooled high pressure air stream; and the
storage tank in flow communication with the phase separator and
another expansion valve positioned between the phase separator and
the storage tank such that a liquid air stream, composed of the
liquid phase, is expanded to a lower pressure and introduced into
the storage tank; the liquid air stream is composed of the liquid
phase, is expanded to a lower pressure and introduced into the
storage tank; whereby, the part of the refrigeration requirement
for liquefying the air is provided by liquefying the second
subsidiary stream within the regenerator and the indirect heat
exchange of the vapor phase stream within the liquefier.
25. The liquid air storage and energy recovery apparatus of claim
18, wherein the heat exchanger is also configured such that the
vapor phase stream also indirectly exchanges heat with the first
cooled high pressure air stream to subcool the first cooled high
pressure air stream.
26. The liquid air storage and energy recovery apparatus of claim
17, wherein a combustor is positioned between the at least one
expansion device and the regenerator such that the pressurized air
stream supports combustion within the combustor to generate a flue
gas stream and the flue gas stream is expanded within the at least
one expansion device.
27. The liquid air storage and energy recovery apparatus of claim
18, further comprising a pre-purification unit containing molecular
sieve adsorbent, the pre-purification unit is connected to the at
least one compressor so that at least part of the compressed air is
purified within the pre-purification unit.
Description
RELATED APPLICATIONS
[0001] This application is a utility application of provisional
application Ser. No. 61/266,347, filed Dec. 3, 2009.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and apparatus in
which air is liquefied and stored for later energy recovery during
which the liquid air is pumped to high pressure, heated and then
expanded to recover the energy, with possible multiple expansions
and reheat between expansions. More particularly, the present
invention relates to such a method and apparatus that employs an
integrated liquefier-regenerator system in which part of the
refrigeration for a liquefier, used in liquefying the air, is
provided by a regenerator that stores refrigeration imparted to the
regenerator during the heating of the pumped and pressurized
air.
BACKGROUND
[0003] The electric grid is in place to connect and balance
electric generation and consumption. Due to the instantaneous
variations in consumption and generation and the corresponding
mismatch between them, the grid needs to include means of storing
energy during periods of oversupply, and redeploy it during period
of over demand. Due to an increase of non dispatchable generation
sources, the mismatch between electricity supply and demand has
been growing in the last few years, and it is poised to reach
levels that could compromise the stability of the grid. In order to
avoid such outcome, an increased amount of energy storage is
necessary.
[0004] In the prior art, it has been proposed to store energy by
liquefying air during periods of oversupply and then recovering the
energy during periods of demand by vaporizing the liquid air and
recovering the energy by expanding the air after having been
vaporized. As will be discussed, among other advantages, the
present invention stores refrigeration within a regenerator during
the vaporization of the air that is later recovered and used to
supply part of the refrigeration requirements in liquefying the
air. This integration between the liquefier and the regenerator
reduces the energy required in the liquefaction of the air.
SUMMARY OF THE INVENTION
[0005] The present invention, in one aspect, provides a liquid air
storage and energy recovery method. In accordance with such method,
during an energy recovery phase, energy is recovered from liquid
air stored in a storage tank by pumping a stream of the liquid air
to produce a pumped air stream, passing the pumped air stream
through a regenerator such that refrigeration contained in the
pumped air stream is stored within the regenerator and the pumped
air stream warms within the regenerator to produce a pressurized
air stream. The pressurized air stream is expanded to produce
power. During a liquid air storage phase, air is liquefied to
produce a liquid air stream. The liquid air stream is introduced
into the storage tank to produce the liquid air stored in the
storage tank. Part of the refrigeration requirement for liquefying
the air is provided with the refrigeration stored in the
regenerator and another part of refrigeration is provided by means
of a liquefier.
[0006] An air stream can be compressed to produce a compressed air
stream. A first subsidiary compressed stream and a second
subsidiary compressed stream are formed at least in part by
dividing the compressed air stream into two portions. The first
subsidiary stream is introduced into the liquefier to produce a
first cooled, high pressure air stream and the second subsidiary
stream is introduced into the regenerator to produce a second
cooled, high pressure air stream. A vapor phase stream indirectly
exchanges heat with the second cooled high pressure air stream to
further cool the second cooled high pressure air stream. The first
and second high pressure air streams are expanded and introduced
into a phase separator to produce a liquid phase and a vapor phase.
The vapor phase stream is composed of the vapor phase and after the
indirect exchange of the heat with the second high cooled high
pressure air stream, the vapor phase stream is introduced into the
liquefier and indirectly exchanges heat with the air cooling within
the liquefier that forms the first cooled high pressure air stream.
The liquid air stream is composed of the liquid phase and is
expanded to a lower pressure and then introduced into the storage
tank. As a result, the part of the refrigeration requirement for
liquefying the air is provided by cooling the second subsidiary
stream within the regenerator, indirectly exchanging heat from the
second high pressure air stream to the vapor phase stream and the
indirect heat exchange of the vapor phase stream within the
liquefier.
[0007] The air stream can be compressed in a feed compressor along
with a first recycle stream to form a first combined stream. The
first combined stream is compressed in a recycle compressor along
with a second recycle stream to form a second combined stream. The
second combined stream is divided into the first subsidiary stream
and the second subsidiary stream. The first subsidiary stream is
expanded at two temperature levels within the liquefier to generate
first and second exhaust streams that indirectly exchange heat with
the air cooling within the liquefier. The first exhaust stream
results from expansion at a lower of the two temperature levels and
the second exhaust stream results from expansion at a higher of the
two levels. The first exhaust stream forms the first recycle stream
after having been fully warmed within the liquefier and the second
exhaust stream forms the second recycle stream after having been
fully warmed within the liquefier. The vapor phase stream after,
having exchanged heat with the air cooling within the liquefier,
can be recycled back to the inlet of the feed compressor.
[0008] The pressurized air stream can be heated in a heat
recuperator. In such case, the pressurized air stream is expanded
in at least two expanders, serially connected, with re-heat within
the heat recuperator between the at least two expanders. A high
temperature exhaust stream is produced as a result of the expansion
of the pressurized air stream. The first combined stream is
purified within a pre-purification unit and the adsorbent within
the pre-purification unit is regenerated with the high temperature
exhaust stream.
[0009] The pressurized air stream can be heated within a
recuperator to form a heated stream that is expanded in a first
expander to produce a first exhaust stream. The first exhaust
stream is introduced into a combustor to produce a flue gas stream
and the flue gas stream is expanded in a second expander operating
at a higher temperature than the first expander to produce a second
exhaust stream. The second exhaust stream is introduced into the
recuperator to heat the pressurized air stream.
[0010] An air stream can be compressed to produce a compressed air
stream. A first subsidiary compressed stream and a second
subsidiary compressed stream are formed at least in part by
dividing the compressed air stream into two portions. The first
subsidiary stream is introduced into the liquefier to produce a
first cooled high pressure air stream and the second subsidiary
stream is introduced into the regenerator to produce a second
cooled high pressure air stream. The first subsidiary air stream
and the second subsidiary air stream are expanded and introduced
into a phase separator to produce a liquid phase and a vapor phase.
A vapor phase stream composed of the vapor phase is introduced into
the liquefier and indirectly exchanges heat with the air cooling
within the liquefier that forms the first cooled high pressure air
stream and the liquid air stream, which is composed of the liquid
phase, is expanded to a lower pressure and introduced into the
storage tank. As a result, the part of the refrigeration
requirement for liquefying the air is provided by liquefying the
second subsidiary stream within the regenerator and the indirect
heat exchange of the vapor phase stream within the liquefier.
[0011] In any embodiment of the present invention, the vapor phase
stream can indirectly exchange heat with the first cooled high
pressure air stream and the second cooled high pressure air stream
to subcool the first and second cooled high pressure air stream.
Additionally, in any embodiment, the pressurized air stream can be
expanded by introducing the pressurized air stream into a combustor
and expanding resulting flue gases in an expander. Also, at least
air that is introduced into the liquefier is purified of higher
boiling contaminants comprising hydrocarbons, carbon dioxide and
water vapor.
[0012] The air stream can be compressed to a supercritical pressure
and the stream of the liquid air can be pumped to a supercritical
pressure.
[0013] In another aspect, the present invention provides a
regenerator comprising two or more pipe bundles. The pipe bundles
are connected to each other through one or more conduits with a
higher thermal resistance than the thermal resistance of each
bundle as a whole so that heat will not be conducted through the
one or more conduits between bundles. The pipe bundles are located
within a thermal storage medium. The thermal storage medium can be
water, and the pipe bundles are submerged within a pool of the
water either in solid or liquid form. Alternatively, each pipe
bundle can be embedded in a thermal storage medium and the thermal
storage medium is composed of a mixture of substances that will
change phase during the storage and production phases. In a further
alternative, the thermal storage medium is cement, gravel, ceramic,
or a mineral matrix.
[0014] In yet another aspect, the present invention provides a
liquid air storage and energy recovery apparatus. In such aspect of
the present invention, a storage tank is provided for storing
liquid air. A pump is connected to the storage tank to pump a
stream of the liquid air during an energy recovery phase of
operation, thereby to produce a pumped liquid air stream. A
regenerator, connected to the pump, is configured such that
refrigeration contained in the pumped liquid air stream is stored
within the regenerator and the pumped liquid air stream vaporizes
within the regenerator to produce a pressurized air stream. At
least one expansion device is connected to the regenerator and is
configured to expand the pressurized air stream and thereby to
produce power. A liquefier is integrated with the regenerator such
that during a liquid air storage phase, an air stream is liquefied
to produce a liquid air stream through the refrigeration stored in
the regenerator. During the energy recovery phase, additional
refrigeration produced by the liquefier and the storage tank is in
flow communication with the liquefier and the regenerator such that
the liquid air stream is introduced into the storage tank to
produce the liquid air stored in the storage tank.
[0015] At least one compressor can be provided to compress an air
stream and thereby to produce a compressed air stream. The
liquefier and the regenerator are in flow communication with the at
least one compressor such that a first subsidiary compressed stream
and a second subsidiary compressed stream are formed at least in
part from the compressed air stream. The first subsidiary
compressed stream is introduced into the liquefier to produce a
first cooled high pressure air stream and the second subsidiary
stream is introduced into the regenerator to produce a second
cooled high pressure air stream. A phase separator can also be
provided. Two expansion valves are positioned between the
regenerator and the liquefier and the phase separator such that the
first cooled high pressure air stream and the second cooled high
pressure air stream are expanded and introduced into the phase
separator to produce a liquid phase and a vapor phase. A heat
exchanger is positioned between the phase separator and the
liquefier such that a vapor phase stream composed of the vapor
phase indirectly exchanges heat with the second cooled high
pressure air stream to subcool the second cooled high pressure air
stream and the vapor phase stream is introduced into the liquefier.
The liquefier is configured such that the vapor phase stream
indirectly exchanges heat with the air cooling within the liquefier
that forms the first cooled high pressure air stream. The storage
tank is in flow communication with the phase separator and another
expansion valve, positioned between the phase separator and the
storage tank, such that a liquid air stream, composed of the liquid
phase, is expanded to a lower pressure and introduced into the
storage tank. As a result, the part of the refrigeration
requirement for liquefying the air is provided by liquefying the
second subsidiary stream within the regenerator, indirectly
exchanging heat from the second cooled high pressure air stream to
the vapor phase stream and the indirectly heat exchange of the
vapor phase stream within the liquefier.
[0016] The at least one compressor can comprise a feed compressor
and a recycle compressor. The feed compressor compresses the air
stream along with a first recycle stream to form a first combined
stream and the recycle compressor is connected to the feed
compressor such that the first combined stream is compressed along
with a second recycle stream to form a second combined stream. The
liquefier and the regenerator are connected to the recycle
compressor so that the second combined stream is divided into the
first subsidiary stream and the second subsidiary stream. The
liquefier has two expanders positioned at two temperatures levels
within the liquefier such that the first subsidiary stream is
expanded at two temperature levels within the liquefier to generate
first and second exhaust streams. The first exhaust stream results
from expansion at a lower of the two temperature levels and the
second exhaust stream results from expansion at a higher of the two
levels. A heat exchange network is positioned within the liquefier
such that the first and second exhaust streams indirectly exchange
heat with the air cooling within the liquefier. The feed compressor
is connected to the liquefier so that the first exhaust stream
forms the first recycle stream after having been fully warmed
within the liquefier. The recycle compressor is connected to the
liquefier so that second exhaust stream forms the second recycle
stream after having been fully warmed within the liquefier. The
liquefier can be connected to the feed compressor such that the
vapor phase stream is recycled back to the inlet of the feed
compressor.
[0017] The at least one expansion device can comprise at least two
expanders, serially connected, to expand the pressurized air stream
and a heat recuperator can be positioned between the at least two
expanders to reheat the pressurized air stream. The at least two
expanders can produce a heated exhaust stream. A pre-purification
unit having an adsorbent purifies air of contaminants and the
pre-purification unit is positioned between the feed compressor and
the recycle compressor so that the first combined stream is
purified within the pre-purification unit. The pre-purification
unit is connected to the at least two expanders to receive a part
of the heated exhaust stream to regenerate the adsorbent contained
within the pre-purification unit.
[0018] The at least one expansion device can be a first expander
and a second expander. A recuperator can be provided to heat the
pressurized air stream and thereby to form a heated stream. A first
expander is connected to the recuperator to expand the heated
stream and thereby to produce a first exhaust stream and a
combustor connected to the first expander to expand the first
exhaust stream and thereby to produce a flue gas stream. A second
expander is connected to the combustor to expand the flue gas
stream at a higher temperature than the first expander to produce a
second exhaust stream. The recuperator is also connected to the
second expander so that the second exhaust stream is introduced
into the recuperator to heat the pressurized air stream.
[0019] At least one compressor can be provided to compress an air
stream and thereby to produce a compressed air stream. The
liquefier and the regenerator are in flow communication with the at
least one compressor such that a first subsidiary compressed stream
and a second subsidiary compressed stream are formed at least in
part from the compressed air stream. The first subsidiary
compressed stream is introduced into the liquefier to produce a
first cooled high pressure air stream and the second subsidiary
stream is introduced into the regenerator to produce a second
cooled high pressure air stream. A phase separator can be provided
and two expansion valves can be positioned between the regenerator
and the liquefier such that the first cooled high pressure air
stream and the second cooled high pressure air stream are expanded
and introduced into the phase separator to produce a liquid phase
and a vapor phase. The liquefier is connected to the phase
separator and is configured such that a vapor phase stream composed
of the vapor phase indirectly exchanges heat with the air cooling
within the liquefier that forms the first cooled high pressure air
stream. The storage tank is in flow communication with the phase
separator and another expansion valve is positioned between the
phase separator and the storage tank such that a liquid air stream,
composed of the liquid phase, is expanded to a lower pressure and
introduced into the storage tank. The liquid air stream is composed
of the liquid phase and is expanded to a lower pressure and then
introduced into the storage tank. As a result, the part of the
refrigeration requirement for liquefying the air is provided by
liquefying the second subsidiary stream within the regenerator and
the indirect heat exchange of the vapor phase stream within the
liquefier.
[0020] The heat exchanger used in subcooling the second cooled high
pressure air stream can also be configured such that the vapor
phase stream also indirectly exchanges heat with the first cooled
high pressure air stream to subcool the first cooled high pressure
air stream.
[0021] A combustor can be positioned between the at least one
expansion device and the regenerator such that the pressurized air
stream supports combustion within the combustor to generate a flue
gas stream and the flue gas stream is expanded within the at least
one expansion device.
[0022] The at least one compressor can have subsequent stages of
compression and purification units containing molecular sieve
adsorbent can be located between the stages of compression to
purify the air during compression. A pre-purification unit
containing molecular sieve adsorbent can be connected to the at
least one compressor so that at least part of the compressed air is
purified within the pre-purification unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] While the specification concludes with claims distinctly
pointing out the subject matter that Applicants regard as their
invention, it is believed that the present invention will be better
understood when taken in connection with the accompanying drawings
in which:
[0024] FIG. 1 illustrates a schematic diagram of the liquid air
storage and energy generation apparatus;
[0025] FIG. 2 illustrates a liquefier 20 used in FIG. 1 operating
during the storage phase;
[0026] FIG. 3 is a fragmentary view alternative embodiment of FIG.
1;
[0027] FIG. 4 illustrates a regenerator used in connection with
FIG. 1
[0028] FIG. 5 illustrates a fragmentary view of an alternative
embodiment of the present invention illustrating an arrangement of
expanders that could be used in the apparatus shown in FIG. 1. FIG.
1; and
[0029] FIG. 6 is an alternative embodiment of FIG. 4.
DETAILED DESCRIPTION
[0030] With reference to FIG. 1, an apparatus 1 is illustrated for
liquefying air contained in a feed air stream 10 and thereafter,
extracting energy from the liquid air that can be applied for the
production of electrical power. Briefly, apparatus 1 is designed to
operate in two phases, namely, a liquid air storage phase and an
energy recovery phase.
[0031] During the liquid air storage phase, feed air stream 10 is
compressed within a feed compressor 12 and optionally, a recycle
compressor 14 and then divided into a first subsidiary compressed
stream 16 and a second subsidiary compressed stream 18. Part of the
refrigeration requirement for liquefying the air is provided by a
liquefier 20 and a regenerator 22 in which refrigeration has been
previously stored during the energy recovery phase. In the
embodiment of the present invention illustrated in FIG. 1, this is
done by passing the first subsidiary compress stream 16 into a
liquefier 20 and the second subsidiary stream into the regenerator
22 to produce a first cooled high pressure air stream 24 and a
second cooled high pressure air stream 26, respectively. The first
cooled high pressure air stream 24 and the second cooled high
pressure air stream 26 are then valve expanded in expansion valves
27 and 28, respectively, to produce two phase streams and
introduced into a phase separator 29 where resulting vapor and
liquid phases are disengaged. A liquid phase stream 30 is then
expanded to a lower pressure by an expansion valve 31 and stored
within a storage tank 32 thereby completing the liquid storage
phase.
[0032] During the energy recovery phase, a liquid air stream 34 is
extracted from the storage tank 32, is pumped within a pump 36 to
produce a pumped air stream 38. The pumped air stream 38 is then
warmed within the regenerator 22, thereby storing refrigeration for
the subsequent liquid storage phase to produce a high pressure air
stream 40 that is subsequently expanded within expanders 118 and
124 from which the energy of expansion can be extracted by a
generator.
[0033] Having briefly described an embodiment for carrying out the
present invention, a more detailed description begins with the
compression of feed air stream 10. Feed air stream 10 and
optionally, an intermediate pressure air stream 42 that has been
purified and recycle streams 44 and 45, produced in the liquefier
20, are compressed to an intermediate pressure in a compressor 12.
The resulting intermediate compressed air is withdrawn from an
intermediate state of compressor 12, cooled in an aftercooler 46
and purified in a pre-purification unit 48. Pre-purification unit
48 as known in the art can contain one or more types of molecular
sieves that adsorb such higher boiling components of the air as
carbon dioxide, water vapor and hydrocarbons such as carbon
monoxide. The resulting intermediate pressure air stream 42 that
has been purified of the higher boiling contaminants is then
recirculated back to the compressor 12 along with recycle stream
44. The pre-purification unit 48 can be of the type in which an
adsorbent bed is utilized that is not regenerated or consists of
multiple beds operating in an out-of-phase cycle, such as a
temperature or pressure swing cycle or a combination of such
cycles, that allows for regeneration of the beds.
[0034] As can be appreciated, there are other options for purifying
the air, for example, using adsorbents to purify the air upstream
of the apparatus 1. Additionally, the air can be pre-purified after
the air has been compressed to the pressure at which the liquefier
20 or regenerator 22 are operated. Another possibility is to use a
portion or all of a recycle stream 55 (to be discussed) to
regenerate adsorbent beds containing within the pre-purification
unit 48. A further alternative to achieve satisfactory air
purification is to purify only the air that is directed toward the
liquefier 20. The moisture and carbon dioxide air directed toward
the regenerator 22 will freeze in the regenerator passages, but
since less air travels through the regenerator 22 during the
storage phase than during the power producing phase, these
contaminants will be removed during the latter phase. If there is a
lack of driving force to remove the contaminants, some dry air or
nitrogen at a temperature higher than the evaporation or
sublimation temperature of said contaminants can be passed through
the regenerator 22.
[0035] The air that is fully compressed in compressor 12 is
discharged therefrom as a compressed air stream 50 that can
constitute a combined stream given the optional recycle of recycle
streams 44 and/or 45. Compressed air stream 50, after passage
through an aftercooler 52, is then compressed further in the
recycle compressor 14 up to supercritical pressure, cooled in an
aftercooler 54 and then split into at least two portions that
consist of the first subsidiary compressed stream 16 directed
toward the liquefier 20 and the second subsidiary compressed stream
18 directed toward the regenerator 22. It is to be noted that both
compressor 12 and recycle compressor 14 can be multi-stage,
intercooled machines in which the stages are commonly driven by a
bull gear driving driven gears connected to the compression stages.
One or more adiabatic compressors can be utilized in place of
multistage inter-cooled compressors, and recuperate the heat of
compression either by storing it in a regenerator or by using it to
run one or more absorption chillers. Although not illustrated, an
air suction filter house could be provided upstream of the
compressor 12 for filtering the incoming air. The compressed air
produced by the recycle compressor 14 can be another combined
stream if an optional recycle stream 55, also produced in the
liquefier 20, is introduced into an intermediate compression stage
of recycle compressor 14 and compressed along with compressed air
stream 50.
[0036] The air exits from the cold end of the liquefier 20 as the
first cooled high pressure air stream 24 that is expanded in valve
27 to a pressure higher than atmospheric and sent to the phase
separator 29. The second subsidiary compressed stream 18 exits the
regenerator 22 as the second cooled high pressure air stream 26
that is further cooled in a subcooler 56 and expanded in valve 28
to a pressure higher than atmospheric and sent to the phase
separator 29. The phase separator 29 directs the liquid phase
stream 30, composed of the liquid phase, toward the storage tank
32, throttling it through a valve 31, while a vapor phase stream 58
composed of the gaseous phase is optionally directed back to the
subcooler 56 to recover part of the refrigeration of such stream by
subcooling the second cooled high pressure air stream 26 within the
subcooler 56 and to indirectly exchange heat with the air cooling
within the liquefier 20 that forms the first cooled high pressure
air stream 24. Thus, as briefly discussed above, part of the
refrigeration requirement for liquefying the air is provided by
cooling the second subsidiary compressed stream 18 within the
regenerator 22, indirectly exchanging heat from vapor phase stream
58 to the second cooled high pressure air stream 26 within
subcooler 56 and the indirect heat exchange of the vapor phase
stream 58 with the air being cooled within the liquefier 20. This
is of course advantageous in that the refrigeration of the vapor
phase stream 58 is recovered to decrease the power requirements
involved in the liquefaction of the air.
[0037] The phase separator 29 should be operated at a pressure as
low as possible, but high enough to drive the gaseous phase through
the liquefier passages. The vapor phase stream 58 originating in
the phase separator 29, after warming within the liquefier 20, is
optionally redirected to the inlet of the compressor 12 as the
recycle stream 45 to prevent oxygen enrichment of the liquid air in
the storage tank 32. In this regard, oxygen enrichment in the
storage tank 32 can also be prevented by monitoring the oxygen
concentration and supplying nitrogen as needed from a separate
liquid nitrogen tank. However, it is possible to vent recycle
stream 45 as shown in FIG. 3, discussed in more detail below. It is
also possible to use at least part of such stream in regenerating
adsorbents utilized in pre-purification unit 48.
[0038] A more detailed schematic of the liquefier 20 is shown in
FIG. 2. Liquefier 20 is provided with a heat exchanger 60 that can
be a system of heat exchange sections having a warm temperature
heat exchange section 62, an intermediate temperature heat exchange
section 64 and a cold end temperature heat exchange section 66.
Although the heat exchange sections are illustrated as being
separated, in fact, they could be integrated in a single heat
exchanger of brazed aluminum plate-fin construction. Also provided
is a warm expander 68 and one or more cold expanders, preferably
cold expanders 70 and 72. The warm and cold expanders 68, 70 and 72
are preferably connected by a gear box 74 to commonly drive an
electrical generator 76 that can be used to help power the
compressors 12 and 14.
[0039] As indicated above, the air coming from the aftercooler 54
is split into the first and second subsidiary compressed streams 16
and 18. The first subsidiary compressed stream 16 is in turn
further divided into streams 16a and 16b. Stream 16a directed
toward the liquefier 20 and is sent through the warm heat exchange
section 62 and intermediate temperature heat exchange section 64,
while the stream 16b is first expanded through a warm turbine 68
and then sent as exhaust stream 78 to the warm heat exchange
section 62 in counterflow with stream 16a. Exhaust stream 78 exits
the warm heat exchange section 62 as recycle stream 55. Stream 16a
after passage through the intermediate heat exchange section 64 is
divided into streams 16c and 16d. Stream 16c forms the first cooled
high pressure air stream 24 after having been discharged from the
cold heat exchange section 66. Stream 16d is expanded through the
cold turbines 70 and 72 to a pressure of roughly 100 psia to form
exhaust stream 82 that in turn, after having been fully warmed
within the heat exchanger 60, is discharged as the recycle stream
44. Vapor phase stream 58 from the phase separator 29 flows through
the heat exchanger 60 and is discharged from the warm heat exchange
section 62 as the recycle stream 45 that is sent back to the inlet
of the compressor 12. As a result, part of the refrigeration needed
to sustain the operation of the liquefier 20 is provided by the
flash-off gases as vapor phase stream 58 and thus, in such manner,
there exists a thermal integration between the liquefier 20 and the
regenerator 22.
[0040] The amount of air withdrawn to feed each of the turbines 68,
70 and 72 can be adjusted to optimize the thermal profiles in the
heat exchanger 60. The expansion pressure and expansion ratio of
each of the turbines 68, 70 and 72 can also be adjusted to reach an
optimum between thermal efficiency in the liquefier's heat
exchangers and compression efficiency in the compression
stages.
[0041] It is to be noted that there are many other possible
embodiments of the present invention involving the integration of
the liquefier into the apparatus 1 and its use with phase
separators feeding a liquid storage tank. For example, the air
exiting the liquefier 20, or the air exiting the regenerator 22, or
both could be expanded using one or more turbines, followed by one
or more valves capable of throttling the expanded air to the
pressure at which the phase separator 29 is operated. In this
regard, more than one phase separator could be used in place of
phase separator 29, allowing the air coming from the liquefier 20
and the air coming from the regenerator 22 to be expanded to two
different pressures, hence generating two vapor phase streams with
different properties. The operating pressures could be optimized to
provide the right amount of refrigeration at the right temperature
inside the liquefier 20. If more than one phase separator were
used, different vapor phase streams could enter the liquefier 20 at
different locations, in order to reach an optimal temperature
profile along the liquefier heat exchanger sections. The liquefier
20 can be designed to use one or more turbines, placed at different
points in the heat exchanger 60. Furthermore, the turbines
illustrated in liquefier 20 could be replaced by Joule-Thompson
valves. The streams leaving the liquefier 20 can be either vented
or recompressed to any suitable level. The flash-off resulting from
the pressure reduction between the phase separator 29 and the
storage tank 32 can be used to do any combination of the following:
cool the regenerator, cool any of the streams entering or exiting
the phase separator, or enter a separate passage in the liquefier
to provide additional refrigeration to one or more sections of the
heat exchanger. Any recycle stream composed of dry low pressure dry
gas exiting the liquefier 20 could be introduced into a booster
compressor to raise their pressure above the outlet pressure of the
pre-purification unit 48, and integrate them in the first stage of
compressor 12 following the pre-purification unit 48. Further, any
low pressure dry gas exiting the liquefier 20 could be introduced
into an appropriate stage of compression before the
pre-purification unit 48.
[0042] The streams leaving the liquefier 20 and being directed to a
specific stage of compression can be either compressed or expanded
prior to entering said stage of compression. The expansion can take
place either through a valve or through a turbine. In order to
enhance the operational flexibility of the system, the liquefier 20
can be sized in excess of what is needed to close the heat balance
of the system. The excess capacity of the liquefier will allow the
system to produce more air than the design quantity, so that the
expansion cycle can be run for a longer period of time when
needed.
[0043] With additional reference to FIG. 3, recycle stream 55 is
vented. In fact in any embodiment of the present invention, recycle
stream 55 could be vented. Additionally, a subcooler 56' is
employed that is used to subcool both the first cooled high
pressure air stream 16 and the second cooled high pressure air
stream 18 through indirect heat exchange with the vapor phase
stream 58. Each or both of these features could be employed in any
embodiments. Conversely, possible embodiments of the present
invention might be constructed without either subcooler 56 or
56'.
[0044] Regenerator 22 can be designed to provide from 20% to 99% of
the refrigeration necessary to complete a full storage and
deployment cycle. With reference to FIG. 4, the regenerator 22 is
preferably formed of a number of pipe bundles 100, each having a
plurality of pipes 102 connected at opposite ends to manifolds 104
in a matrix that is located within a thermal storage medium 106
that can be a pool of water. The pipe bundles 100 are connected by
connection conduits 108. The second subsidiary compressed stream 18
is introduced into an end conduit 110 and the second subsidiary
compressed stream 18 flows through the pipe bundles 100 by way of
the connection conduits 108 and is discharged from an end conduit
112 located opposite side of regenerator 22. The water will
solidify during the startup process. The water will provide the
thermal ballast for the regenerator 22, and during normal operation
a thermal profile will be established such that the warm end of the
ice block is slightly below the freezing temperature, while the
cold end is at cryogenic temperature. The thermal storage medium
could be a mixture of substances that would change phase with the
change in temperature during storage and production phases.
Optionally, the thermal storage medium could be a mixture of water
and salt, hydrocarbons and an industrial gas such as nitrogen. Also
possible is a mixture of water and sand or other substances such as
cement, gravel, ceramics or a mineral matrix. In order to
recuperate the refrigeration at a temperature higher than the
freezing point, a few pipe bundles 100 at the warm end of the
regenerator 22 could be embedded in concrete, which will act as the
thermal ballast in lieu of the water. The cold end of the
regenerator 22 and a few pipe bundles 100 thereof would be
submerged in ice. Since the connection conduits are as illustrated
single pipes, such pipes will provide a high thermal resistance to
heat transfer between the pipe bundles 100.
[0045] The proposed configuration has a number of advantages, among
which standardization (e.g. the same bundles 100 can be used for
systems of any size by adjusting their number to provide the
required thermal capacity), possibility of being produced in a shop
and shipped on-site inexpensively, and ability of providing
bottlenecks in the thermal links between zones of the regenerator
operating at different temperatures. The regenerator can be housed
either in a pit dug in the ground and properly insulated or in an
off-ground pool. The choice will depend on the specific conditions
at the site.
[0046] An alternative to the water/cement flooded regenerator is a
regenerator which employs only cement as thermal ballast. A further
alternative is a regenerator that employs only water as thermal
ballast, where the section at a temperature higher than freezing is
separated from the permanently iced one and it is allowed to
undergo phase change during every cycle.
[0047] The appropriate split between the first and second
subsidiary compressed streams 16 and 18 can be determined as
follows: design the regenerator 22 to provide a given thermal
efficiency; calculate how much liquid air could be produced flowing
high pressure air through the regenerator 22 when the latter has
been cooled by the vaporization of a full charge of liquid air;
size the liquefier 20 to make up the additional refrigeration
needed to sustain the cyclical operation of the entire system, plus
a capacity margin to allow for operational flexibility. The actual
split will depend on techno-economic considerations that are quite
site specific, since the relative importance of cycle efficiency
over capital cost is dictated by the spread in low-to-high energy
prices. It is to be noted that the capacity margin for the
liquefier 20 allows more liquid air to be produced and stored in
storage tank 32 at various times to increase the power that is
produced by the system.
[0048] During the liquid storage phase the system will be
controlled through the measurement of the flow and/or temperature
of the recycle stream 45, produced by warming vapor phase stream 58
within liquefier 20 and recycled back to the feed compressor 12,
aiming for its temperature to be close to ambient, but preventing
temperature pinch points in the liquefier core, and regulated
through the appropriate split between the first and second
subsidiary compressed streams 16 and 18.
[0049] With continued reference to FIG. 1, during the power
production phase, the high pressure air stream 40 is introduced
into a recuperator 114 to produce a heated stream 116 that is
subsequently expanded in expander 118 to produce power. The exhaust
stream 120 of expander 118 is then reheated within recuperator 114
to produce a reheated stream 122 that is subsequently expanded in
an expander 124 to produce an exhaust stream 126 that can be
vented.
[0050] There are other possible embodiments of expansion of the
high pressure air stream 40 to recover power. The embodiment shown
in FIG. 5, would be used where there exists a source of suitable
waste heat. In this embodiment, high pressure air stream 40 is
heated in a recuperator 128 by waste heat from a gas turbine 129
("GT Peaker") that is used to supply power to generate additional
electrical energy during peak demand times up to as high a
temperature as possible to produce a heated air stream 130 that is
expanded through expander 132. The exhaust 134 is reheated in
recuperator 128 that is expanded in an expander 135 to produce an
exhaust stream 136. As shown in FIG. 4, optionally, as the waste
heat duty permits, the exhaust stream 136 can subsequently be
reheated in recuperator 128 to produce a reheated stream 137 that
can in turn be expanded in expander 138 to produce an exhaust
stream 140. All of the aforesaid expanders are connected through a
gear box 142, known in the art, to a generator 144 to generate
electrical power. A part 146 of the exhaust stream 140 can be then
directed toward the pre-purification unit 48 to regenerate
adsorbents and discharge a stream 148 that would be rich in the
higher boiling contaminants within the air, namely carbon monoxide,
water vapor, carbon dioxide and other hydrocarbons. The remaining
part 149 of the exhaust stream 140 is vented. As an alternative, an
air stream could be withdrawn after entering the recuperator 128 to
regenerate the adsorbent within the pre-purification unit 48. Among
sources of waste heat the following should be noted: process heat
from industrial processes, geothermal heat, and heat carried by
solar thermal farm operating fluid; the combustion turbine flue
gases represent the most practical source of waste heat for the
application here envisioned. The exact number of reheats and
expansion stages is determined by the amount of waste heat
available and the desired conversion efficiency. For most
situations, the number of expanders will range from 2 to 4.
[0051] In another embodiment shown in FIG. 6, there is no suitable
source of waste heat present. In such embodiment, the high pressure
air stream 40 is introduced into a recuperator 150 where it is
reheated to produce a heated air stream 152 by the flue gases
exiting a hot expander 154. The heated air stream 152 is then
expanded through a warm expander 156, where it is expanded to
produce an exhaust stream 160 that is at a pressure compatible with
the operation of a combustor 162. It is to be noted that part of
the exhaust stream 160 could be used to regenerate the adsorbent
within the pre-purification unit 48. The air is mixed with a
suitable fuel (preferably natural gas) and burned in combustor 162.
The air enters the hot expander 154 with a turbine inlet
temperature as high as compatible with the technology employed in
the expander. It is here envisioned that the expander can tolerate
a turbine inlet temperature of 1000.degree. C. The air is then
directed through the hot expander and expanded to a pressure close
to atmospheric. The flue gases exiting the hot expander are
directed toward the recuperator 150. A flue gas stream 168 is
discharged from the recuperator 150 that is either vented to
atmosphere, or processed in pollutants abatement systems to comply
with emission requirements specific to the region of installation
of the system. It is to be noted that the combustor 162 and the hot
expander 154 could be used alone without the recuperator 150 or the
warm expander 158.
[0052] It is to be noted that in any embodiment of the present
invention, an atmospheric vaporizer could be used to vaporize part
of the pumped liquid air stream 38 or to conduct such vaporization
on an intermittent basis and then feed the resulting high pressure
air to one or more expanders to recover power and generate
electrical energy. Furthermore, although not illustrated, during
the energy recovery phase, part of an expanded stream can be
withdrawn and used to feed an industrial facility that can make use
of a pressurized warm air stream. Such withdrawal can take place
before, during, or after the air expansion has taken place.
[0053] Apparatus 1 can be started, when the regenerator 22 is no
longer cold, by operating the compressors 12 and 14 processing
enough air to feed the liquefier, and as little extra air as
possible while maintaining conditions compatible with the operation
of said compressors. The extra air will then be redirected toward
the expanders 118 and 124 used during the power production phase.
The air liquefied by the liquefier 20 is stored in the storage tank
32 and sent through the regenerator 22 during the power production
phase, although at first it will be able to sustain operation for a
shorter time than design. This will allow for a partial cool down
of the regenerator 22. Once the peak period has passed, the storage
phase can restart. During this second step of charging, the
compressors 12 and 14 should be operated to provide enough air to
feed the liquefier 20 and enough air to take advantage of the
refrigeration stored in the regenerator 22, and as little extra air
as possible. The extra air will be sent to the expanders 114 and
118. By operating the system in this way, more liquid air will be
produced during the second cycle than during the first. Continuing
to adopt this approach for a suitable number of cycles will allow
the system to reach steady state operation without needing
significant liquid addition from other sources.
[0054] Alternative ways of starting apparatus 1 can include
proceeding in the manner outlined above, but not deploying the air
in the regenerator 22 until enough air to supply a full day of
operation is available in the tank or not deploying the air in the
regenerator 22 until enough air to cool the entire regenerator 22
is available in the tank liquid storage tank 32. Other
possibilities involve compressing enough air to feed the liquefier
20 and vent all the extra air or starting the apparatus 1 by liquid
addition in the liquid storage tank 32.
[0055] Apparatus 1 can be operated so as to have a continuous
storage phase of a duration compatible with the low price hours in
a particular power market (typically ranging from 3 to 12 hours),
and a power production phase of a duration compatible with the high
price hours of said particular power market (typically ranging from
1 to 12 hours). In order to provide other types of services to the
market, such as frequency regulation and ancillary services,
spinning reserves, interruptible loads, and generation capacity,
the system may be operated in an intermittent fashion, where less
than a full load of air is stored before being deployed, and with
said cycle being repeated several times a day. The specific mode of
operation will be strongly influenced by the details of the power
market which the system will be serving.
[0056] The following Table 1 summarizes the conditions of the main
streams both during the storage and power producing phases in the
embodiment of the present invention shown in FIG. 1. TABLE 1A and
TABLE 1B show a summary of the conditions of the streams shown in
FIG. 5 and FIG. 6, respectively. The flows are expressed in
arbitrary units. Table 2 summarizes the power consumed and produced
during the storage and power producing phases, respectively. The
power consumption is expressed in kW per metric ton of inlet air
(1). In order to obtain actual power consumptions in kW it is
necessary to multiply said values by the flow rate of stream 1,
expressed in metric tons per hour.
TABLE-US-00001 TABLE 1 Flow Pressure Stream Arbitrary Units
Temperature K psia 10 1000 290 14.5 42 1000 302.5 101 18 747 302.5
2000 16b 505 302.5 2000 16a 111 302.5 2000 78 111 225 669 16c 252
220 1998 16d 252 220 1998 82 252 102 101 24 252 105 1997 24 after
valve 27 252 80 17 26 747 103 1997 26 after subcooler 56 747 99
1996 and before valve 28 26 after valve 28 747 80 17 58 before
subcooler 56 244 80 17 30 before valve 31 755 80 17 30 after valve
31 755 79 14.7 58 after subcooler 56 244 101 16.5 55 111 301 668 44
252 301 99 45 244 301 15 34 959 79 14.7 38 959 85 2000 40 959 280
1990
TABLE-US-00002 TABLE 1A 130 959 768 1987 134 959 517 413 134 prior
to turbine 135 959 768 411 136 959 514 82 137 959 768 81 1490 815
504 16 148 144 504 15
TABLE-US-00003 TABLE 1B 152 959 557 1987 160 959 338 300 168 959
400 15
TABLE-US-00004 TABLE 2 Power Item kW/tph Feed Air compressor 12 -59
Recycle Compressor 14 -177 Liquefier Turbines (68, 70 and 72) 8.4
Pump 36 -5.6 (FIG. 5) Expanders 132, 135 and 138 212.9 (FIG. 6)
Expander 156 55.9 (FIG. 6 Expander 154 188.9
[0057] Although the present invention has been described with
reference to preferred embodiments, as would occur to those skilled
in the art, numerous changes, additions could be made without
departing from the spirit and scope of the invention as set forth
in the appended claims.
* * * * *