U.S. patent application number 09/811493 was filed with the patent office on 2001-10-18 for cryogenic air separation system with integrated mass and heat transfer.
Invention is credited to Arman, Bayram, Billingham, John Fredric, Bonaquist, Dante Patrick, Nguyen, Tu Cam, Wong, Kenneth Kai.
Application Number | 20010029751 09/811493 |
Document ID | / |
Family ID | 24193674 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029751 |
Kind Code |
A1 |
Nguyen, Tu Cam ; et
al. |
October 18, 2001 |
Cryogenic air separation system with integrated mass and heat
transfer
Abstract
A cryogenic air separation system comprising an integrated core
and typically including a double column wherein incoming feed air
is cooled in the core which also processes a stream from the double
column. A separating section of the core processes a stream from
the double column to form product.
Inventors: |
Nguyen, Tu Cam; (Falcon
Heights, MN) ; Arman, Bayram; (Grand Island, NY)
; Bonaquist, Dante Patrick; (Grand Island, NY) ;
Wong, Kenneth Kai; (Amherst, NY) ; Billingham, John
Fredric; (Getzville, NY) |
Correspondence
Address: |
PRAXAIR, INC.
LAW DEPARTMENT - M1 557
39 OLD RIDGEBURY ROAD
DANBURY
CT
06810-5113
US
|
Family ID: |
24193674 |
Appl. No.: |
09/811493 |
Filed: |
March 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09811493 |
Mar 20, 2001 |
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09549602 |
Apr 14, 2000 |
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Current U.S.
Class: |
62/643 ;
62/902 |
Current CPC
Class: |
F25J 3/04418 20130101;
F25J 3/04624 20130101; F25J 2200/38 20130101; F25J 3/04296
20130101; F25J 2270/66 20130101; F25J 2200/74 20130101; F25J
3/04284 20130101; F25J 3/044 20130101; F25J 3/04303 20130101; F25J
3/04236 20130101; F25J 2200/02 20130101; F25J 3/0463 20130101; F25J
3/04678 20130101; F25J 3/04872 20130101; F25J 2205/02 20130101;
F25J 3/0409 20130101; F25J 2200/34 20130101; F25J 2200/04 20130101;
F25J 2200/54 20130101; F25J 3/04278 20130101; Y10S 62/902 20130101;
F25J 2235/50 20130101; Y10S 62/903 20130101 |
Class at
Publication: |
62/643 ;
62/902 |
International
Class: |
F25J 003/00; F25J
005/00 |
Claims
We claim:
1. A cryogenic air separation system in flow communication with a
double column separation apparatus having a higher pressure column
and a lower pressure column, said air separation system comprising:
an integrated core comprising: (i) a first intake passage cooling a
first incoming feed air stream, and directing the cooled first
incoming feed air stream into the separation apparatus, said first
intake passage being in a heat exchange relationship with at least
one other passage of said integrated core, (ii) a first cooling
passage cooling a first bottom stream from the separation
apparatus, and directing the cooled first bottom stream back into a
separation section, said first cooling passage being in a heat
exchange relationship with at least one other passage of said
integrated core, (iii) a first warming passage warming a first
overhead stream from the separation apparatus, and discharging the
warmed first overhead stream from said integrated core, said first
warming passage being in a heat exchange relationship with at least
one other passage of said integrated core, and (iv) a vaporization
passage vaporizing a liquid phase stream and discharging the
vaporized liquid phase stream from said integrated core, said
vaporization passage being in a heat exchange relationship with at
least one other passage of said integrated core; and a separating
section separating a second bottom stream from the separation
apparatus to form an oxygen enriched stream and a nitrogen enriched
stream, wherein the nitrogen enriched stream is directed back into
the separation apparatus and the oxygen enriched stream is
separated into a vapor phase stream and the liquid phase stream,
the vapor phase stream being directed back into said separating
section.
2. The air separation system according to claim 1, wherein said
separating section is integrated within said integrated core and
wherein said integrated core further comprises a second cooling
passage cooling a condensed stream from the lower pressure column,
and directing the cooled condensed stream back into the separation
apparatus, said second cooling passage being in a heat exchange
relationship with at least one other passage of said integrated
core.
3. An integrated heat exchange core for separating gas components
in conjunction with a double column separation apparatus having a
higher pressure column and a lower pressure column, and a
separating section having a separating column, said integrated core
comprising: a first intake passage cooling a first incoming feed
air stream; a second intake passage cooling a second incoming feed
air stream, and feeding the second incoming feed air stream into
the separation apparatus; said higher pressure column of the
separation apparatus, which is integrated within said integrated
core, separating streams from at least one of the separating column
and lower pressure column into a first overhead stream enriched in
a light component and a first bottom stream enriched in a heavy
component; a first cooling passage cooling the first bottom stream,
and feeding the cooled first bottom stream into the separation
apparatus; a second cooling passage cooling a second bottom stream
from the separation apparatus, and feeding the cooled second bottom
stream back into the separation apparatus; a first warming passage
warming the first overhead stream from said higher pressure column,
and discharging the warmed first overhead stream from said
integrated core, said first warming passage being in a heat
exchange relationship with at least one of said cooling passages
and said intake passages. second bottom stream into the lower
pressure column.
4. The integrated core according to claim 3, further comprising: a
second warming passage warming a second overhead stream from the
lower pressure column, said second warming passage being in a heat
exchange relationship with at least one of said cooling passages;
and a third warming passage warming a third bottom stream from the
separating column, said third warming passage being in a heat
exchange relationship with at least one of said cooling
passages.
5. A method for separating air comprising the steps of: cooling, in
an integrated core, a first incoming feed air stream against at
least one other stream flowing through the integrated core, and
directing the cooled incoming feed air stream into a separation
apparatus; cooling, in the integrated core, a first bottom stream
from the separation apparatus against at least one other stream
flowing through the integrated core, and directing the cooled first
bottom stream back into the separation apparatus; warming, in the
integrated core, a first overhead stream from the separation
apparatus against at least one other stream flowing through the
integrated core, and discharging the warmed first overhead stream
from the integrated core; vaporizing, in the integrated core, a
liquid phase stream against at least one other stream in the
integrated core, and discharging the vaporized liquid phase stream
from the integrated core; separating a second bottom stream from
the separation apparatus to form an oxygen enriched stream and a
nitrogen enriched stream; and feeding the nitrogen enriched stream
back into the separation apparatus; and further separating the
oxygen enriched stream into a vapor phase stream and the liquid
phase stream.
6. The method according to claim 5, wherein the step of separating
the second bottom stream is performed within the integrated
core.
7. A method for separating air comprising the steps of: cooling, in
an integrated core, a first incoming feed air stream against at
least one other stream flowing through the integrated core;
cooling, in the integrated core, a second incoming feed air stream
against at least one other stream flowing through the integrated
core, and feeding the cooled incoming feed air stream into a
separation apparatus having a lower pressure column and a higher
pressure column; separating, in the higher pressure column, in the
integrated core, streams from at least one of a separating column
and the lower pressure column, into a first overhead stream
enriched in nitrogen and a first bottom stream enriched in oxygen;
cooling, in the integrated core, the first bottom stream against at
least one other stream flowing through the integrated core, and
feeding the cooled first bottom stream into the separation
apparatus; cooling, in the integrated core, a second bottom stream
from the separation apparatus against at least one other stream
flowing through the integrated core, and feeding the cooled second
bottom stream back into the separation apparatus; warming, in the
integrated core, the first overhead stream from said separating
step, against at least one other stream flowing through the
integrated core; and discharging the warmed first overhead stream
from the integrated core.
8. The method according to claim 7, further comprising the step of
feeding the second feed air stream, cooled in said step of cooling
the second incoming feed air stream, into the lower pressure
column.
9. The method according to claim 7, further comprising the steps of
warming, in the integrated core, a second overhead stream from the
lower pressure column against at least one other stream flowing
through the integrated core, and warming, in the integrated core, a
third bottom stream from the separating column against at least one
other stream flowing through the integrated core.
10. The method according to claim 7, further comprising the step of
feeding the first incoming feed air stream, cooled in said step of
cooling the first incoming feed air stream, into the higher
pressure column to be separated in said separating step.
Description
FIELD OF THE INVENTION
[0001] This invention generally relates to cryogenic air separation
and, more particularly, to the integration of various levels of
heat-transfer and mass-transfer in order to enhance thermodynamic
efficiency and to reduce capital costs.
BACKGROUND OF THE INVENTION
[0002] Cryogenic air separation systems are known in the art for
separating gas mixtures into heavy components and light components,
typically oxygen and nitrogen, respectively. Generally, the
separation process takes place in plants that cool incoming mixed
gas streams through heat exchange with other streams (either
directly or indirectly) before separating the different components
of the mixed gas through mass transfer methods such as distillation
and/or reflux condensation (dephlegmation). Once separated to
achieve desired purities, the different component streams are
warmed back to ambient temperature. Typically, the different
warming, cooling, and separating steps take place in separate
pieces of equipment, which, along with the installation and piping,
adds to the manufacturing costs for the plant.
[0003] Various air separation systems have been introduced that
combine some of the separate heat transfer components in order to
provide an integrated device that may perform a variety of
functions. In particular, systems have been proposed that partially
combine different heat exchangers for warming or cooling fluid
streams and separation devices for separating out heavy and light
components in the streams into a single heat exchange core in order
to reduce the number of pieces of equipment needed in an air
separation plant. This may reduce the overall cost of the
plant.
SUMMARY OF THE INVENTION
[0004] The present invention is directed to an air separation
system with a unique integration design that provides a single
brazed core that can combine separation networks with a host of
heat exchange functions.
[0005] Increasing the total cross section of a heat transfer core
provides a greater opportunity for heat transfer between streams,
thus increasing efficiency. This improvement may come at an
attractive cost per unit area of heat transfer.
[0006] The present invention also reduces the capital costs
associated with air separation systems (particularly the cold boxes
of cryogenic air separation systems) and increases overall
thermodynamic efficiency by utilizing designs that optimally
combine mass-transfer functions with heat-transfer functions in a
single core which results in the reduction or elimination of a
significant amount of interconnecting piping and independent
supporting structures and cold box volume thereby reducing piping
and installation costs.
[0007] Typically, the integrated core is used to (i) cool the
process feed air down to a cryogenic temperature, (ii) boil the
heavy component product (typically liquid oxygen), and (iii)
superheat/subcool various process streams. Preferably, the
integrated core is a brazed plate-fin core made of aluminum. The
integrated core may include a plurality of passages arranged so as
to effectively combine the various levels of heat-transfer, as well
as different levels and types of mass-transfer (such as
rectification and stripping).
[0008] In a preferred design of the present invention, an
integrated core is provided in flow communication with a double
column separation apparatus having a higher pressure column
(generally termed the lower column) and a lower pressure column
(generally termed the upper column). The double column separation
apparatus may be of any conventional design that provides
separation of heavy and light components from various vapor
streams.
[0009] In a preferred design, the integrated core includes a first
set of intake passages (although, it should be recognized that only
one passage for each stream in the system is required to achieve
the benefits of the present invention) in which an incoming feed
air stream is cooled and then directed into the double column
separation apparatus (typically the lower column). The cooling is
preferably accomplished by positioning the first set of intake
passages in a heat exchange relationship with at least one other
passage in the integrated core. In variations of this embodiment,
the first set of intake passages may include a section for mass
transfer, in which a condensate in the passage serves as reflux to
rectify the feed air stream. In this case, the first intake
passages will form a condensate stream that may be directed into
the upper column.
[0010] A first set of cooling passages cools a first bottom stream
from the separation apparatus (typically the lower column) and
feeds the cooled, first bottom stream back into the separation
apparatus (typically the upper column). The first set of cooling
passages may be in a heat exchange relationship with at least one
other passage (or set of passages) in the integrated core.
[0011] A first set of warming passages warms a first overhead
stream from the separation apparatus (preferably the upper column)
and discharges the warmed first overhead stream from the integrated
core. The first set of warming passages may be in a heat exchange
relationship with at least one other set of passages in the
integrated core.
[0012] A separating section (preferably a stripping column) in the
integrated heat exchanger core separates a second bottom stream
from the separation apparatus (preferably from the upper column
external to the integrated heat exchanger core) to form an oxygen
enriched stream and a nitrogen enriched stream. The nitrogen
enriched stream may be directed back into the separation apparatus
(preferably into the upper column). Preferably, the oxygen stream
is separated into a vapor phase stream and a liquid phase stream by
a phase separator. The vapor phase stream typically is directed
back into the separating section. In preferred embodiments, the
separating section is integrated within the integrated core and the
separating apparatus is external to the integrated core. In
addition, a pump may be provided to pump the liquid phase through
the integrated core.
[0013] A set of vaporization passages vaporizes the liquid phase
stream from the phase separator and discharges the vaporized liquid
phase stream from the integrated core. The vaporization passages
may be in heat exchange relationships with at least one other set
of passages of the integrated core.
[0014] The integrated core may also include a second set of cooling
passages that cools a condensed stream from the upper column and
directs the cooled, condensed stream back into the separation
apparatus (typically into the upper column). As with the first set
of cooling passages, the second set is preferably in a heat
exchange relationship with at least one other set of passages in
the integrated core.
[0015] The integrated core may also include a second set of warming
passages that warms a second overhead stream from the stripping
apparatus (preferably from the lower pressure column) and
discharges the warmed second overhead stream from the integrated
core. The second set of warming passages may also be in a heat
exchange relationship with at least one other set of passages in
the integrated core.
[0016] A fourth set of warming passages may be provided to warm the
oxygen enriched stream from the separating section and to direct
the oxygen enriched stream into the phase separator. These passages
may also be in heat exchange relationships with any number of other
passages in the integrated core.
[0017] The integrated core may also include a second set of intake
passages that cools a second incoming feed air stream and directs
the cooled, second incoming feed air stream into the separation
apparatus (preferably into the lower column). The second set of
intake passages may be in a heat exchange relationship with at
least one other set of passages in the integrated core.
[0018] The integrated core may also include a third set of intake
passages that cools a third incoming feed air stream and directs
the cooled, third incoming feed air stream into the separation
apparatus (preferably into the lower pressure column). The third
intake passages may be in heat exchange relationships with any
number of other passages in the integrated core, but preferably
exchange heat with the first set of warming passages and/or the
second set of warming passages. In alternative embodiments, the
third set of intake passages may cool a refrigerated air stream
received from a refrigeration unit. In such an embodiment, the
integrated core may also include a fourth set of warming passages
to warm the refrigerated air stream cooled in the third set of
intake passages against other passages in the integrated core and
to discharge the refrigerated air stream from the integrated core
back into the refrigerated unit.
[0019] Although the sets of passages may be designed so as to have
various heat exchange interactions with other sets of passages
within the integrated core, it is preferred that the first set of
intake passages and the second set of intake passages share heat
exchange relationships with any of the first set of warming
passages, the second set of warming passages, the fourth set of
warming passages, and the set of vaporization passages.
Additionally, the first set of cooling passages and the second set
of cooling passages may share heat exchange relationships with, at
least, any of the first, second, and fourth sets of warming
passages.
[0020] Generally, the integrated core is divided into a warm end,
including openings in the integrated core for flow into and out of
the intake passages and the warming passages, and a cold end,
including the separation section. Typically, the warm end is the
top end of the integrated core and the cold end is the bottom end;
however, the integrated core may be designed so that the bottom end
is the warm end (including the openings for the intake and warming
passages) and the top end is the cold end (including the separation
section).
[0021] In another embodiment of the present invention, the
integrated core may stand alone, without using a double column
separation system, in order to produce light component products. In
this embodiment, the air separation system may include a
rectification section (or other separation section) that rectifies
an incoming feed air stream to form an overhead stream enriched in
nitrogen, and a bottom stream enriched in oxygen. The rectification
section may utilize any conventional design for rectifying mixed
fluid streams. In more preferred embodiments, the rectification
section is integrated within the integrated core; however, an air
separation system may be designed such that the rectification
section is outside of, but in flow communication with, the
integrated core.
[0022] The integrated core of this embodiment includes a first set
of cooling passages that cools the incoming feed air stream and
feeds the cooled, incoming feed air stream into the rectification
section. A second set of cooling passages cools the bottom stream
from the rectification section. A first set of warming passages
warms a first portion of the overhead stream and directs the warmed
portion of the overhead stream back into the rectification section.
The first set of warming passages may be in a heat exchange
relationship with at least one of the sets of cooling passages. A
second set of warming passages warms a second portion of the
overhead stream and discharges the warmed second portion of the
overhead stream from the integrated core. The second warming
passages may also be in heat exchange relationships with any of the
cooling passages. A set of vaporization passages vaporizes the
cooled bottom stream from the second cooling passages and
discharges the vaporized bottom stream from the integrated core.
The vaporization passages may be in heat exchange relationships
with any of the cooling passages. In preferred embodiments, the
cooled bottom stream is expanded by a turboexpander.
[0023] In yet another embodiment of the present invention, an air
separation system may include a double column separation apparatus,
a rectification column (or other separation column), and an
integrated core in which is included the lower column from the
double column separation apparatus.
[0024] The integrated core of this embodiment includes a first set
of intake passages that cools a first incoming feed air stream. The
first incoming air stream may be directed into the separation
apparatus of the lower column, depending on the design particulars.
The integrated core may also include a second set of intake
passages that cools a second incoming feed air stream and feeds the
cooled, second incoming feed air stream into the double column
separation apparatus (typically into the upper column). The lower
column of the separating apparatus produces a first overhead stream
enriched in nitrogen and a first bottom stream enriched in
oxygen.
[0025] The integrated core may also include a first set of cooling
passages that cools the first bottom stream from the lower column
and feeds it back into the separation apparatus, typically into the
upper column.
[0026] The upper column may separate streams it receives from the
separation apparatus and/or the integrated core to produce a second
bottom stream, which may be enriched in oxygen, and a second
overhead stream enriched in nitrogen.
[0027] Preferably, a second set of cooling passages are provided in
the integrated core to cool the second bottom stream from a
condenser in the upper column and to feed the second bottom stream
back into the double column separation apparatus (typically into
the upper column). The second cooling passages may be in heat
exchange relationships with any passages warming streams in the
integrated core.
[0028] A first set of warming passages warms the first overhead
stream from the lower column and discharges at least a portion of
the warmed first overhead stream from the integrated core. The
remainder of the warmed first overhead stream may be condensed by a
condenser in the upper column. The first set of warming passages
may be in heat exchange relationships with any passage for cooling
a stream in the integrated core.
[0029] The integrated core may also include a second set of warming
passages that warms a second overhead stream from the lower
pressure column. The second warming passages may also be in heat
exchange relationships with any of the cooling passages of the
integrated core.
[0030] A third set of warming passages may be provided to warm a
third bottom stream from the separating column (either upper column
or integrated heat exchanger column) and to discharge that stream
from the integrated core. Typically, the third warming passages are
in heat exchange relationships with any of the cooling
passages.
[0031] In another embodiment of the present invention, an air
separation system may include two integrated cores in flow
communication with each other. Preferably, the air separation
system incorporates a double column arrangement, with the lower and
upper pressure columns being integrated in the different integrated
cores.
[0032] The first integrated core may include a first set of intake
passages that cools a first feed air stream, although additional
intake passages may be provided to receive other feed air streams
as necessary. When a second set of intake passages is incorporated
into the first integrated core, those passages may cool a second
feed air stream. Typically, the second set of intake passages feeds
its air stream into a first separation section (discussed below).
In more preferred embodiments, a portion of the second feed air
stream from the second intake passages may be expanded and fed into
the first set of intake passages.
[0033] A first separation section may separate the cooled first
feed air stream into a first overhead stream enriched in nitrogen
and a first bottom stream enriched in oxygen. The first separation
section is preferably the lower column of the double column
separation system. A first set of cooling passages cools the first
bottom stream from the first separation section.
[0034] A set of vaporization passages vaporizes a liquid phase
stream from the second integrated core (discussed below) and
discharges the vaporized liquid phase stream from the integrated
core. The vaporization passages may be in heat exchange
relationships with any of the intake passages and the first cooling
passages.
[0035] A first set of warming passages warms a second overhead
stream (preferably from the upper column in the second integrated
core) and discharges the warmed second overhead stream from the
first integrated core. The first warming passages may be in a heat
exchange relationship with any of the intake passages and the first
cooling passages.
[0036] The second integrated core may include a second set of
warming passages that warms the first overhead stream from the
first separation section and feeds the warmed first overhead stream
back into the first separation section (i.e., reflux for the lower
column). A second separation section (the upper column) receives at
least one cooled stream and separates that stream into the second
overhead stream enriched in nitrogen and a second bottom stream
enriched in oxygen. A third set of warming passages warms the
second overhead stream and feeds the warmed second overhead stream
into the first warming passages. The third warming passages may be
in heat exchange relationships with any cooling (including intake)
passages of the integrated core.
[0037] A fourth set of warming passages may be provided to warm
(and partially vaporize) the second bottom stream. The warmed
second bottom stream may be separated, using a phase separator,
into a vapor phase stream and the liquid phase stream. The liquid
phase stream may be fed into the vaporization passages and the
vapor phase stream may be fed back into the second separation
section. Preferably, the liquid phase is pumped into the
vaporization passages. The fourth warming passages may be in heat
exchange relationships with any of cooling passages (including
intake passages) of the integrated core.
[0038] The second integrated core may also include a fifth set of
warming passages that warms a third overhead stream from the second
separation section and discharges the warmed third overhead stream
from the second integrated core. A sixth set of warming passages
may be provided in the first integrated core to receive and to
discharge from the first integrated core the third overhead stream
from the fifth warming passages, while warming the stream against
at least one other stream in the first integrated core.
[0039] In some embodiments, the second integrated core may also
include a second set of cooling passages for cooling the first
bottom stream from the first cooling passages. In addition, a third
set of cooling passages may cool the second feed air stream from
the second intake passages. A fourth set of cooling passages may
receive and cool a portion of the warmed first overhead stream from
the second warming passages before that portion is fed back into
the first separation section. The second separation section (i.e.,
upper column) may separate any of the streams from the second,
third, and fourth cooling passages. In addition, the second, third
and fourth sets of cooling passages may provide cooling by being in
heat exchange relationships with any of the warming passages in the
second integrated core, particularly the second warming
passages.
[0040] However, the air separation system may not necessarily
include the second cooling passages, third cooling passages, or
fourth cooling passages, at least as described above, if an
additional separation section is incorporated into the second
integrated core. For instance, the air separation system of this
embodiment (having two integrated cores) may also incorporate an
argon separation section, which preferably may be integrated into
the second integrated core. When an argon rich stream is to be
produced, the second separation section may be modified to produce
a first argon-rich stream.
[0041] The argon separation section further separates the first
argon-rich stream into a second argon-rich stream and an
argon-depleted stream. At least a portion of the second argon-rich
stream is discharged from the second integrated core as a first
argon product stream.
[0042] A reboiler/condenser section may be provided in the second
integrated core and includes a condensing passage in a heat
exchange relationship with a boiling passage. A portion of the
cooled first bottom stream may be condensed in the condensing
passage. A portion of the second argon-rich stream typically is
boiled in the boiling passage. At least a portion of the boiled
second argon-rich stream may be fed back into the argon separation
section for reflux. The remainder of the boiled second argon-rich
stream may be discharged from the second integrated core as a
second product argon stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1A shows a first embodiment of an air separation system
of the present invention that includes an integrated core with a
side stripping column.
[0044] FIG. 1B shows an air separation system similar to the one
shown in FIG. 1A, but with a reverse orientation.
[0045] FIG. 1C shows an air separation system similar to the one
shown in FIG. 1A, but with the side stripping column positioned
outside of the integrated core.
[0046] FIG. 1D shows an air separation system similar to the one
shown in FIG. 1A, but with a refrigeration unit.
[0047] FIG. 1E shows an air separation system similar to the one
shown in FIG. 1D, but without a second compensating incoming air
stream.
[0048] FIG. 2A shows another embodiment of an air separation system
of the present invention that includes an integrated core designed
for use as an air enriching/inerting grade light component
plant.
[0049] FIG. 2B shows an air separation system similar to the one
shown in FIG. 2B, but with the separation section positioned
outside of the integrated core.
[0050] FIG. 3A shows another embodiment of the present invention in
which the integrated core of the air separation system incorporates
part of a double column stripping apparatus.
[0051] FIG. 3B shows an air separation apparatus similar to the one
shown in FIG. 3A, but with the incoming feed air being directed
into the stripping column in the integrated core.
[0052] FIG. 4 shows another embodiment of an air separation system
of the present invention that utilizes two integrated cores.
[0053] FIG. 5 shows an air separation system similar to the one
shown in FIG. 4, but with an argon separation section incorporated
into the second integrated core.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] FIG. 1A depicts a preferred embodiment of the present
invention, and generally shows a cryogenic air separation system
utilizing an integrated heat exchange core with a double column
separation apparatus for producing low purity oxygen. The system is
arranged with the cold end up. An auxiliary reboiled stripping
section or side stripper 50, used in an air separation process to
produce a low purity oxygen product (preferably from about 50 to
about 95% purity), is integrated within the heat exchange core. The
double-column separation apparatus may be of any conventional type
and, in this case, includes a lower column 20 and an upper column
40, both of which are in flow communication with each other and
integrated core 1.
[0055] To facilitate heat transfer among various fluid streams in
the system, the heat transfer section of integrated core 1 may
utilize a plate-fin design, wherein passages throughout integrated
core 1 have finned passages that allow fluid streams to flow
through integrated core 1 in heat exchange relationships with fluid
streams in other passages. It is preferred that the plate-fin
system be constructed of aluminum to facilitate heat transfer and
to keep costs low. Preferably, all of the heat exchange sections of
integrated core 1 are incorporated in a single brazed aluminum
core.
[0056] Integrated core 1 receives low pressure air stream 101, high
pressure boosted air stream 103, and intermediate pressure turbine
air stream 109 through passages in integrated core 1, which are in
heat exchange relationships with passages of integrated core 1
containing exiting process streams, including waste nitrogen stream
143, gaseous oxygen stream 172, and nitrogen product stream 124 in
the section 2 (the warm end) of integrated core 1. Through the heat
exchange relationships, each of air streams 101, 103, and 109 is
cooled as they travel through integrated core 1.
[0057] Intermediate pressure air stream 109, which typically ranges
from about 125 to about 200 psia and comprises about 7 to about 15%
of the total feed air flow, exits integrated core 1 as stream 110
after reaching a temperature that is preferably in the range of
about 140 to about 160 K; however, the temperature may depend on
the amount of refrigeration required in a particular design.
Preferably, cooled air stream 110 is expanded in expander 10 to
form stream 119, which generates the refrigeration for the plant to
compensate for various sources of refrigeration loss and heat
leakage into the process. Stream 119 may also be used for
additional refrigeration required to provide any liquid products
(not shown). In this case, expanded turbine air stream 119
(typically in the range of about 19 to about 22 psia) is fed into
upper column 40 to be separated.
[0058] Air stream 103 is further cooled along its passage(s) in
integrated core 1. In intermediate heat transfer section 3 of
integrated core 1, boosted air stream 103, which is typically in
the range from about 100 to about 450 psia and comprising about 25
to about 35% of the total feed air flow, may be condensed due to a
heat exchange relationship with the passage(s) containing boiling
liquid oxygen product stream 171. In section 3, stream 103 is
preferably in a cross-flow orientation with boiling liquid oxygen
stream 171. The resulting subcooled liquid boosted air stream 104
may exit integrated core 1 at a temperature typically in the range
of about 95 to about 115 K.
[0059] In this embodiment, liquid air stream 104 is split into
streams 105 and 107 and throttled in valves 10A and 10B,
respectively. The resulting throttled liquid air streams 106 and
108 are fed into upper column 40 and lower column 20, respectively.
Stream 106 may range from 0 to 100% of the total subcooled liquid
boosted air stream 104.
[0060] Lower pressure air stream 101 (preferably in the range of
about 45 to about 60 psia, and about 94 to about 96 K) contains the
balance of the total feed air flow. Lower pressure air stream 101
is partially condensed against boiling liquid oxygen stream 152
exiting from the bottom of the separation section 50 in heat
transfer section 4 of integrated core 1. Lower pressure air stream
101 may be in a crossflow orientation with the boiling bottom
liquid oxygen stream 153. Resulting partially condensed air stream
101 exits integrated core 1 (at a temperature in the range of about
90 to about 105.degree. K) as stream 102, with its vapor fraction
typically in the range from about 0.7 to about 0.8%. Stream 102 may
be fed into higher pressure rectification column 20.
[0061] The higher pressure column 20 separates partially condensed
feed air stream 102 and throttled subcooled liquid feed air stream
108 into an almost-pure nitrogen vapor overhead stream 121, and
oxygen-rich bottom liquid stream 125. A small fraction of overhead
stream 121, typically up to about 10%, may be taken as nitrogen
product stream 123. Product stream 123 may enter the cold end of
integrated core 1 where it is then warmed to ambient temperature
against one or more of incoming streams 101, 103 and 109, before
exiting integrated core 1 as stream 124.
[0062] Although an almost pure nitrogen vapor (about 90 to about
99.6% pure) product exits the top of lower column 20, the nitrogen
product may be withdrawn from elsewhere in the process. Although
not depicted, the nitrogen product may also be drawn from upper
column 40. In that case, the high purity nitrogen product stream
could be withdrawn from the top of upper column 40, and the waste
nitrogen could be withdrawn from a point somewhat lower in upper
column 40. Both of the nitrogen streams could then pass through
integrated core 1 in separate passages.
[0063] The balance of overhead stream 121 from lower column 20, the
almost pure nitrogen, may be fed into the upper column 40 as stream
122, where it is condensed in condenser/reboiler (main condenser)
30 against the bottom oxygen-rich liquid of upper column 40. The
condensed stream exits main condenser 30 as condensed overhead
stream 131. Stream 131 may be split into streams 132 and 133.
Stream 132 (typically in the range of about 40 to about 55% of the
total condensed overhead stream 131) is returned to lower column 20
for reflux.
[0064] Stream 133, the remaining fraction of stream 132, and kettle
liquid stream 125 (typically about 35 mole percent oxygen), which
exits the bottom of lower column 20, are indirectly cooled (to a
temperature of about 80 to about 95.degree. K) against exiting
gaseous streams 142 and 123 in heat transfer section 5 along the
length of the integrated stripping separation section 50 of
integrated core 1. The corresponding subcooled streams 134
(corresponding to stream 133) and 126 (corresponding to stream 125)
may be throttled in valves 10C and 10D, respectively, to form
throttled liquid streams 135 and 127, respectively. Streams 135 and
127 may be fed into upper column 40 to be further fractionated.
Preferably, stream 135 is fed into the top of upper column 40.
[0065] Upper column 40 separates streams 119, 127 and 135, into
gaseous nitrogen stream 142 and bottom liquid oxygen stream 141.
Boilup vapor used in lower pressure column 40 may be provided by
indirectly boiling the liquid oxygen at the bottom of upper column
40 against condensing overhead stream 122 of lower column 20, as
mentioned above with respect to the main condenser 30.
[0066] Product liquid oxygen stream 141 from upper column 40 may be
fed into section 50 of integrated core 1. Section 50 preferably
serves the function of a reboiled stripping separation column.
Accordingly, a liquid fraction is further concentrated in oxygen as
it flows down the length of stripping section 50 through
crosscurrent contact with a stripping vapor. Vapor stream 151 exits
the top of stripping section 50 and is fed into the bottom of upper
column 40. In upper column 40, vapor stream 151 combines with the
vapor generated by main condenser 30 and is further separated as it
ascends the column.
[0067] The bottom liquid stream from stripping section 50 exits as
stream 152 and then may be partially vaporized against low pressure
feed air stream 102 in section 4 of integrated core 1. The
resulting two-phase (partially vaporized) bottom liquid oxygen
stream 153 may exit integrated core 1 to be fed into phase
separator 60. Vapor stream 161 from phase separator 60, typically
comprising about 40 to about 60% of stream 153, is returned to
stripping section 50 to serve as the stripping vapor. The liquid
fraction from phase separator 60 is pressurized using pump 70 to
the desired pressure. The resulting higher pressure liquid oxygen
stream 171 enters integrated core 1 at section 3. Therein, it is
vaporized primarily against the boosted air stream 103 and, along
with the other exiting streams 127 and 143, is warmed to ambient
temperature against one or more of the other air streams 101 and
109. Stream 171 exits integrated core 1 as product oxygen stream
172.
[0068] It should be noted that phase separator 60 may be eliminated
if proper process modifications are made to insure that safety
issues are addressed related to boiling oxygen-rich streams to
dryness in a plate-fin heat exchanger. If separator 60 is
eliminated, liquid stream 152 may be taken from the bottom of
stripping section 50 as the product stream, and the rest of the
bottom liquid of stripping section 50 may be completely vaporized
in heat transfer section 4 of integrated core 1 to provide
stripping vapor to stripping section 50 (not shown). Although not
depicted, liquid products can also be withdrawn from the integrated
core with minimal changes in the process and design.
[0069] FIG. 1B depicts an alternative arrangement of the integrated
core depicted in FIG. 1A in which the directional orientation of
integrated core 1 is reversed. The cold end, containing stripping
section 50, is positioned at the bottom of integrated core 1, and
the warm end is positioned at the top. In this configuration, air
streams entering sections 2 and 3 flow in a downward direction. The
various heat transfer and mass transfer sections of integrated core
1 may be spatially arranged in this configuration to achieve the
best overall thermodynamic characteristics with minimal labor and
hardware. The remainder of the system is similar to that described
with respect to the system of FIG. 1A, and will not be repeated
herein.
[0070] FIG. 1C depicts another slight modification to the
integrated core depicted in FIG. 1A. In this embodiment, stripping
section 50 is positioned outside of integrated core 1 so as to be
segregated from the heat transfer sections.
[0071] As depicted, integrated core 1 is vertically oriented, in
terms of stream flow directions, with the cold end positioned above
the warm end. However, the warm end may be situated above the cold
end, as described with respect to the system in FIG. 1B. In
addition, with proper accommodations in the design, the integrated
core 1 may be orientated with horizontal stream flow directions.
The remainder of the heat transfer network of integrated core 1 is
similar to that discussed with respect to FIG. 1A.
[0072] FIG. 1D depicts another slight modification to the air
separation system depicted in FIG. 1A. Specifically, in this
embodiment, integrated core 1 accommodates mixed gas refrigeration
system MGR10 for the plant refrigeration, instead of expanding feed
air stream 109 in turbine 10, as described with respect to the
system in FIG. 1A. Accordingly, turbine air streams 109, 110, and
119 are absent in this system.
[0073] Preferably, stream MG109, the working fluid of mixed gas
refrigeration system MGR10, which includes a mixture of gases
suitably selected for the particular application, enters the warm
end of integrated core 1. Refrigerant stream MG109 is condensed and
subcooled in section 2 of integrated core 1 against exiting process
streams 123, 142, and 171, as well as exiting throttled refrigerant
stream MG119, discussed below. The resulting subcooled liquid
refrigerant stream MG110 may be expanded in Joule-Thompson valve
JT10, preferably after reaching a temperature in the range of about
80 to about 120.degree. K. Resulting lower pressure refrigerant
stream MG119 may be returned to integrated core 1 at a point along
the length of the core which is colder than where stream MG110
exits integrated core 1. The remainder of the air separation system
is similar to the system described with respect to FIG. 1A.
[0074] FIG. 1E depicts yet another modification to the air
separation system depicted in FIG. 1A. This system incorporates a
mixed gas refrigeration system similar to that described above with
respect to FIG. 1D; however, refrigerant fluid stream MG109 also
may be used to boil the pressurized liquid oxygen product (stream
171). Accordingly, boosted feed air stream 103 and related streams
used in the system in FIG. 1A are absent in this embodiment. Aside
from the absence of boosted air streams 103-108 and the additional
function of boiling stream 171, the remainder of the system is
similar to the system depicted in FIG. 1D. It should be noted,
however, that the exact flows and process conditions of this
embodiment may differ from the other embodiments. In addition, the
MGR system used to replace turbine 10 and stream 103 may include
more than one refrigerant loop.
[0075] FIG. 2A shows the application of the integrated core concept
to an air separation system used to produce a nitrogen product and
a very low purity oxygen product. Separation section 20 (preferably
a rectification column) is used in the separation system and is
incorporated in integrated core 1. This system uses the expansion
of the low purity oxygen to provide the required plant
refrigeration; however, other process streams such as the nitrogen
product stream, may be expanded for refrigeration purposes, if
deemed optimal for the particular plant specifications.
[0076] As shown, pre-purified feed air stream 101, typically having
a pressure in the range from about 110 to about 150 psia, is cooled
to a cryogenic temperature (preferably in the range from about 80
to about 120.degree. K) against passage(s) containing exiting
nitrogen product stream 123/124 and very low purity oxygen-rich
stream 171/172 in section 2 of integrated core 1. Separation
section 20 of integrated core 1 separates cooled feed air stream
102 into an almost-pure nitrogen liquid overhead stream 121, and
oxygen-rich bottom stream 125. A fraction of overhead stream 121
(typically about 40 to about 60%) may be taken as light component
product stream 123, which is warmed to ambient temperature against
stream 101 and is discharged as stream 124.
[0077] The remaining portion of stream 121 may be condensed against
the throttled oxygen-rich stream 127 as overhead stream 122 in heat
transfer section 30 of integrated core 1. This condensation process
serves a similar function as the condenser/reboiler 30 in the
system of FIG. 1A. The resulting condensed overhead stream is fed
into separation section 20 for reflux, typically at a temperature
of about 80 to about 90.degree. K.
[0078] Bottom oxygen-rich liquid stream 125 exits separation
section 20 and then may be indirectly cooled to a temperature of
about 90 to about 120.degree. K) against exiting gas stream 151
(preferably very low purity oxygen) in heat transfer section 5.
Stream 125 then exits integrated core 1 as stream 126. Stream 126
may be throttled in valve 10D to form stream 127, which is returned
to integrated core 1 at heat transfer section 30 as stream 151.
Stream 151 may be vaporized against stream 122 and superheated (to
a temperature of about 80 to about 100.degree. K) in section 5.
Superheated stream 151 exits the integrated core 1 as stream 170,
where it may be expanded in turbine/expander 10 to provide the
required plant refrigeration. Resulting expanded stream 171 is
returned to integrated core 1 and is warmed to ambient temperature
against incoming feed air stream 101.
[0079] FIG. 2B depicts an alternative configuration of the process
depicted in FIG. 2A. In this embodiment, section 20 which is
positioned outside of integrated core 1 (equivalent to separation
section 20 of FIG. 2A) is used to separate the feed air into
almost-pure nitrogen stream 121 and oxygen-rich bottom liquid
stream 125. Except for section 20 being positioned outside of
integrated core 1, the rest of the system is similar to the system
depicted in FIG. 2A, although the placement of the various heat
transfer sections of integrated core 1 may differ slightly.
[0080] FIG. 3A depicts an alternative application of the
integration concept to a cryogenic air separation system.
Specifically, FIG. 3A shows a system in which higher pressure
column 20 is integrated with the superheater, oxygen product
boiler, and the primary heat exchanger in integrated core 1,
instead of stripping section 50 (as in the case of the system shown
in FIG. 1A). In addition, heat transfer section 4, which typically
serves as a reboiler for section 50, is not present in the
integrated core of this embodiment. Instead, auxiliary stripping
section 50 and its reboiler 80 are situated outside of integrated
core 1. However, stripping section 50 may be eliminated altogether
with some process modification. In such a modified system, the
liquid stream from the bottom of upper column 40 would meet the
oxygen product purity requirement without the need for further
enrichment, which is typically provided by stripping section 50.
Other than the rearrangement of higher pressure column 20 and
stripping section 50, the system shown in FIG. 3A is similar to the
system of FIG. 1A.
[0081] FIG. 3B depicts integrated core 1 in the case where
stripping section 50 is eliminated. Lower pressure feed air stream
102 enters higher pressure section 20 of integrated core 1 directly
from heat transfer section 3 of integrated core 1 as a slightly
superheated vapor (typically having a temperature of about 90 to
about 110.degree. K) or a close to saturated vapor. Upper column 40
is not shown in FIG. 3B for sake of convenience. As in the case
with the system depicted in FIG. 1A, integrated core 1 of FIGS. 3A
and 3B may be modified to accommodate the most suitable directional
orientation, as well as the optimal scheme to provide the plant
refrigeration requirements.
[0082] FIG. 4 depicts yet another embodiment of the present
invention. In this embodiment, lower pressure section 40 and higher
pressure section 20 are integrated into separate integrated heat
transfer cores 1B and 1A, respectively. Thus, in addition to
integrated core 1A, which is similar to integrated core 1 depicted
in FIG. 3B, integrated core 1B may also be utilized for heat and
mass transfer by performing functions similar to those of main
condenser 30 and upper column 40 of FIG. 1A.
[0083] The air separation system of this embodiment does not use a
side-stripping column or reboiler. Instead, the system operates so
that the liquid stream at the bottom of lower pressure section 40
of integrated core 1B is provided at the desired oxygen product
purity. The remainder of the system is similar to that depicted in
FIG. 1A except: (a) lower pressure separation section 40
(integrated in core 1B) and higher pressure separation section 20
(integrated in core 1A) take the place of upper column 40 and lower
column 20; (b) heat transfer section 30 of integrated core 1B
thermally links higher pressure separation section 20 and lower
pressure separation section 40, of integrated cores 1A and 1B,
respectively, instead of using a typical reboiler/condenser; (c)
kettle liquid stream 125 and condensed nitrogen stream 133 are
subcooled against exiting gas streams in heat transfer zone 5A of
integrated core 1A and in heat transfer section 5B of integrated
core 1B, as opposed to being subcooled in a single heat transfer
section; (d) phase separator 60 separates partially vaporized
stream 153, which exits from heat transfer section 30 of integrated
core 1B instead of heat transfer section 4 of integrated core 1 in
FIG. 1A.
[0084] Additionally, liquid stream 162 from phase separator 60
constitutes the liquid oxygen product and is fed to pump 70, in the
same manner as is depicted in FIG. 1A; however, vapor stream 161 is
returned as stripping vapor to lower pressure section 40, as
opposed to the separation section 50, as depicted in FIG. 1A.
[0085] FIG. 5 illustrates the application of the integration
concept of the present invention to an argon-producing cryogenic
air separation system. FIG. 5 shows a system containing three
separation sections, although more may be used. Integrated core 1B,
with lower pressure separation section 40, is similar to that
depicted in FIG. 4, but is modified to incorporate argon
rectification section 80 and its condenser. In addition, integrated
core 1A is similar to integrated core 1A of the system depicted in
FIG. 4.
[0086] Pre-purified air streams 101 and 103 enter the warm end of
heat exchanger core 1A. Main air stream 101 may be cooled against
nitrogen product stream 143a, waste nitrogen stream 142a, and
oxygen product stream 171G. Cooled air stream 110 is taken from an
intermediate location along the length of integrated core 1A and is
fed through turbine/expander 10. (The specific pressure and
temperature at which air stream 110 is removed depends at least in
part on the plant's particular refrigeration requirement.)
Resulting expanded air stream 119 enters the section 3 of
integrated core 1A where it is further cooled before being fed into
the bottom of section 20, preferably at a temperature of about 85
to about 105.degree. K. Section 20 functions as the lower column in
FIG. 1A.
[0087] Air stream 103 flows into integrated core 1A and may be
condensed mainly against boiling oxygen product stream 171G and
subcooled in heat transfer sections 3 and 5A along the length of
integrated core 1A. Resulting subcooled liquid air stream 104 exits
integrated core 1A (preferably at a temperature of about 90 to
about 110.degree. K) where it may be divided into streams 105 and
107. Stream 107, which may comprise 0 to 100% of stream 104, may be
throttled in valve 10B. Resulting throttled liquid air stream 108
is fed into section 20 at a position several stages above the feed
point of lower pressure air stream 102.
[0088] Stream 105, including the remaining portion of liquid air
stream 104, is throttled in valve 1A. Resulting throttled liquid
air stream 106 is fed into section 40 below the stage from which
waste nitrogen stream 142 is drawn. Section 40 serves as upper
column 40 as in FIG. 1A.
[0089] Feed air streams 102 and 108, which both enter separation
section 20 of integrated core 1A, are separated into nearly pure
nitrogen stream 121, and kettle liquid stream 125. Stream 121 may
be condensed in main condenser 30 against boiling oxygen stream 152
from the bottom of separation section 40 to form stream 131. Stream
131, after exiting main condenser 30, is divided into streams 132
and 133. Stream 132, which typically includes about 45 to about 60%
of stream 131, may be used as reflux for separation section 20.
Stream 133, comprising the balance of stream 131, may be subcooled
against exiting gaseous nitrogen streams 143 and 142 in heat
transfer section 5B of integrated core 1B to a temperature of about
80 to about 100.degree. K. Resulting subcooled liquid nitrogen
stream 134 may be divided into stream 134a and stream 134b.
[0090] Stream 134b, preferably the major fraction of stream 134,
may be throttled in valve 10C to form throttled stream 135. Stream
135 preferably enters the top of separation section 40 as reflux.
Stream 134a, the remainder of stream 134, may be taken as product
liquid nitrogen.
[0091] Kettle liquid stream 125 from separation section 20 may be
subcooled against exiting gaseous streams 143a and 142a in heat
transfer section 5A at the cooler end of integrated core 1A.
Resulting stream 126 may be throttled in valve 10D, outside of
integrated core 1A, and split into two streams. Preferably, stream
127a, a smaller fraction of stream 126, enters section 40 a few
stages below the feed point of stream 106. The other fraction,
stream 127b, which may include 0 to 100% of stream 126, may be fed
into heat transfer section 90 at the colder end of integrated core
1B.
[0092] Heat transfer section 90 serves as an argon condenser. In
heat transfer section 90, stream 127b may be vaporized against
condensing argon vapor overhead stream 180 from argon rectification
section 80 of integrated core 1B. Resulting, mostly-vapor stream
190 may be fed to phase separator 60C and separated into stream
190L and stream 190V. Stream 190V, which is less rich in oxygen,
may be fed into separation section 40 a few stages below the feed
position of stream 127a. Preferably, stream 190L is fed into
separation section 40 even lower than stream 190V.
[0093] In separation section 40, feed streams 106, 127a, 190L, and
190V, along with liquid stream 185 from the bottom of argon
rectification section 80, are separated into high purity nitrogen
product stream 142, high purity liquid oxygen stream 152, waste
nitrogen stream 143, and argon-rich vapor stream 145, respectively.
Argon-rich stream 145, preferably containing about 10% to about 15%
argon, feeds into argon rectification section 80 to be further
separated.
[0094] Stream 142 typically contains less than 2 ppm of oxygen, and
stream 152 typically is about 99.5% oxygen. Streams 143 and 142 may
be superheated (to a temperature of about 80 to about 100.degree.
K) against almost-pure nitrogen stream 134 in integrated core 1B,
and then may be transferred into integrated core 1A where those
streams may be warmed to near ambient temperature.
[0095] In heat transfer section 30 of integrated core 1B, stream
152 may be vaporized against stream 121 from separation section 20.
Resulting partially vaporized, almost-pure oxygen bottom stream 153
may be fed into separator 60B, in which it may be separated into
vapor stream 161 and liquid stream 162. Vapor stream 161 may be
returned as stripping vapor to the bottom of separation section 40.
Stream 162 may be pumped to the desired pressure through pump 70 to
form stream 171 (which typically has a pressure in the range of
about 60 to about 100 psia). A small fraction of the pressurized
liquid oxygen stream 171 may be withdrawn as a product stream (not
shown). The balance, stream 171G, is fed through integrated core 1A
where it may be vaporized in heat transfer section 3 against
condensing air stream 103. Preferably, stream 171G is warmed to
near ambient temperature before being discharged from integrated
cre 1A.
[0096] Argon-rich vapor stream 145, withdrawn at about 30 to about
40 stages from the bottom of the separation section 40 and
typically containing about 10 to about 15% argon and nitrogen in
ppm level, is sent to the bottom of separation section 80 of second
integrated core 1B. Argon separation section 80 further enriches
vapor feed stream 145 in argon, resulting in an argon overhead
product, typically containing about 1 to about 3% oxygen, and a
less argon-rich bottom liquid stream 185.
[0097] Bottom liquid stream 185 may be returned to separation
section 40. A portion of the overhead argon from separation section
80 may be taken as vapor argon product (stream 183) and the rest
(stream 182) may be condensed against stream 127b in
reboiler/condenser section 90. A small fraction of the resulting
condensed overhead stream may be taken as liquid crude argon
product, as stream 193. The balance of condensed overhead stream
182 preferably is returned as reflux to argon separation section
80.
[0098] If the argon product from the rectification column is
required to meet heavy component impurity specifications of a few
ppm, another column (not shown) comprising higher stages (lower
temperatures) than the single argon column featured in FIG. 5 can
be added to further rectify the argon-rich vapor. In this case,
argon-rich vapor may flow from the top of section 80 to the bottom
of the additional rectification section and then continue upward.
Liquid from the bottom of the additional section may be pumped to
the top of section 80. Liquid argon may be withdrawn as product
argon several stages from the top of the added section in order to
meet the required ppm level of oxygen and nitrogen impurities.
[0099] A small vapor stream may be removed from the top of the
added column section to prevent nitrogen buildup in the argon
rectification sections. An overhead argon stream to be condensed in
argon condenser 90 then may be taken from the top of the added
column section instead of section 80 of integrated core 1B. In any
case, integrated cores 1A and 1B may be designed for optimal
thermal interaction between the various heat transfer and mass
transfer zones of the integrated cores.
* * * * *