U.S. patent application number 17/076487 was filed with the patent office on 2021-04-29 for method and apparatus for separating air by cryogenic distillation.
This patent application is currently assigned to L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude. The applicant listed for this patent is L'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des Procedes Georges Claude. Invention is credited to Bertrand DEMOLLIENS, Patrick LE BOT.
Application Number | 20210123671 17/076487 |
Document ID | / |
Family ID | 1000005198752 |
Filed Date | 2021-04-29 |
![](/patent/app/20210123671/US20210123671A1-20210429\US20210123671A1-2021042)
United States Patent
Application |
20210123671 |
Kind Code |
A1 |
DEMOLLIENS; Bertrand ; et
al. |
April 29, 2021 |
METHOD AND APPARATUS FOR SEPARATING AIR BY CRYOGENIC
DISTILLATION
Abstract
In a method for separating air by cryogenic distillation, cooled
air purified to remove water is sent to a first column operating at
a first pressure, where it is separated into a nitrogen-enriched
gas as an oxygen-enriched liquid; a gas enriched in argon relative
to the air is withdrawn from the second column; at least a portion
of the oxygen-enriched liquid is vaporized by heat exchange with
the argon-enriched gas; and the vaporized, oxygen-enriched liquid
is sent to an intermediate level of the second column.
Inventors: |
DEMOLLIENS; Bertrand;
(Champigny-Sur-Marne, FR) ; LE BOT; Patrick;
(Jouy-En-Josas, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des
Procedes Georges Claude |
Paris |
|
FR |
|
|
Assignee: |
L'Air Liquide, Societe Anonyme pour
l'Etude et l'Exploitation des Procedes Georges Claude
Paris
FR
|
Family ID: |
1000005198752 |
Appl. No.: |
17/076487 |
Filed: |
October 21, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 2210/40 20130101;
F25J 1/002 20130101; F25J 3/04454 20130101; F25J 1/0015 20130101;
F25J 2240/10 20130101; F25J 3/04727 20130101; F25J 2200/78
20130101; F25J 2200/76 20130101; F25J 2220/02 20130101; F25J
3/04945 20130101; F25J 2220/50 20130101; F25J 2215/40 20130101;
F25J 2200/72 20130101; F25J 2200/08 20130101; F25J 1/0017
20130101 |
International
Class: |
F25J 1/00 20060101
F25J001/00; F25J 3/04 20060101 F25J003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2019 |
FR |
FR 1911900 |
Claims
1. A method for separating air by cryogenic distillation, the
method comprising the steps of: (a) sending a cooled air that has
previous been purified to remove water to a first column operating
at a first pressure, where the cooled air is separated into a
nitrogen-enriched gas and an oxygen-enriched liquid; (b)
withdrawing a liquid enriched in nitrogen relative to the air from
the first column and sending said liquid enriched in nitrogen to
the top of a second column that is connected thermally to the first
column and operates at a second pressure, wherein the second
pressure is lower than the first pressure; (c) withdrawing a liquid
enriched in oxygen relative to the air from the first column; (d)
withdrawing a gas enriched in argon relative to the air from the
second column; (e) at least partially vaporizing at least a portion
of the oxygen-enriched liquid by heat exchange with the
argon-enriched gas to form a vaporized oxygen-enriched fluid, and
then sending the vaporized oxygen-enriched fluid to an intermediate
level of the second column; (f) returning at least one condensed
portion of the argon-enriched gas to a third column, wherein the
third column is also fed with an argon-enriched gas flow
originating from the second column, wherein an argon-enriched top
gas is withdrawn at a top portion of the third column, and an
argon-depleted liquid is returned from the third column to the
second column; (g) sending a portion of the oxygen-enriched liquid
to an overhead condenser of the third column; (h) vaporizing the
oxygen-enriched liquid sent to the overhead condenser in the
overhead condenser and then sending the resulting oxygen-enriched
vapor to the second column, wherein the portion of the
oxygen-enriched liquid that is sent to the overhead condenser of
the third column has not been reheated against the argon-enriched
gas flow.
2. A method according to claim 1, wherein the vaporized
oxygen-enriched fluid is at a pressure at least 1 bar greater than
the pressure of the second column, and is expanded in a turbine and
then sent to an intermediate level of the second column.
3. A method according to claim 1, wherein at least one condensed
portion of the argon-enriched gas is returned to the second
column.
4. A method according to claim 1, wherein the vapour produced is
sent to the second column, by being mixed with the flow expanded in
the turbine.
5. A method according to claim 1, wherein the third column is
disposed inside the second column and the at least one portion of
the oxygen-enriched liquid is vaporized by heat exchange with the
argon-enriched gas inside the second column.
6. A method according to claim 1, wherein the argon-enriched gas
sent to the exchanger in which the heat exchange takes place has a
condensation temperature greater than the vaporization temperature
of the oxygen-enriched liquid in the exchanger.
7. An apparatus for separating air by cryogenic distillation, the
apparatus comprising: a first column operating at a first pressure;
a second column connected thermally to the first column and
operating at a second pressure, which is lower than the first
pressure; a heat exchanger; means for sending cooled air that has
been purified to remove water, to the first column, operating at a
first pressure, where the cooled air is separated into a
nitrogen-enriched gas and an oxygen-enriched liquid; means for
withdrawing a liquid enriched in nitrogen relative to the air from
the first column; means for sending the nitrogen-enriched liquid to
the top of the second column; means for withdrawing a liquid
enriched in oxygen relative to the air from the first column; means
for withdrawing a gas enriched in argon relative to the air from
the second column; means for sending a portion of the
oxygen-enriched liquid to the heat exchanger for at least partial
vaporization thereof by heat exchange with the argon-enriched gas;
means for sending the oxygen-enriched liquid vaporized in the heat
exchanger to an intermediate level of the second column; a third
column; means for sending at least one condensed portion of the
argon-enriched gas in the heat exchanger to the third column; and
means for sending an argon-enriched gas flow originating from the
second column to the third column; means for withdrawing an
argon-enriched flow at the top of the third column; means for
sending an argon-depleted liquid from the third column to the
second column; means for sending a portion of the oxygen-enriched
liquid to an overhead condenser of the third column; and means for
sending the vapour produced by vaporizing the oxygen-enriched
liquid in the overhead condenser to the second column; wherein the
means for sending the portion of the oxygen-enriched liquid to the
overhead condenser are connected directly to the first column
without passing via the heat exchanger.
8. The apparatus according to claim 7, further comprising a turbine
connected to an intermediate level of the second column fed with
the vaporized oxygen-enriched fluid.
9. The apparatus according to claim 7, further comprising means for
returning at least one condensed portion of the argon-enriched gas
to the second column.
10. The apparatus according to claim 7, further comprising means
for sending the vapour produced to the second column, by being
mixed with the flow expanded in the turbine.
11. The apparatus according to claim 7, wherein the third column is
disposed inside the second column, and the apparatus further
comprises means for vaporizing the at least one portion of the
oxygen-enriched liquid by heat exchange with the argon-enriched gas
inside the second column.
12. The apparatus according to claim 7, wherein the third column
contains fewer than 50 theoretical stages.
13. The apparatus according to claim 7, wherein the third column
contains fewer than 10 theoretical stages.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn. 119 (a) and (b) to French patent application No.
FR1911900, filed Oct. 24, 2019, the entire contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and an apparatus
for improving the energy performance of a cryogenic air separation
unit with or without an argon separation column.
BACKGROUND OF THE INVENTION
[0003] Double air distillation columns are well known in the art,
and it is also common to combine them with an argon separation
column.
[0004] Conventionally, in an air separation apparatus, air which
has been purified and cooled is sent to a first column, operating
at a cryogenic temperature, to be separated into a
nitrogen-enriched gas and an oxygen-enriched liquid.
[0005] The liquid is withdrawn from the first column and sent to a
second column, operating at a pressure lower than the first column,
after expansion in a valve.
[0006] Air separation apparatuses often comprise an argon
separation column in addition to the double column. This argon
separation column may obviously serve for producing argon, although
in certain cases the main purpose of its installation is to enhance
the yield of oxygen and/or to enhance the production of nitrogen at
a high pressure and/or to enable expansion of lots of air intended
for the second column in order to increase the production of
frigories and therefore the production of liquid, or to improve the
energy performance.
[0007] A method according to the prior art is known from
EP-A-0860670. In this method, the liquid feed to the overhead
condenser of the argon column does not come directly from the first
column, but has undergone partial vaporization beforehand in order
to condense the argon mixture. As the liquid becomes more
concentrated in oxygen, there is accordingly an increase in its
vaporization temperature. The temperature difference in the argon
column condenser is then excessively low and requires a very large
exchanger volume. The consequence of this is to increase the size
of the cold box.
SUMMARY OF THE INVENTION
[0008] One aim of the present invention is to improve the energy
performance of air separation units with or without the argon
separation column being present.
[0009] Where the argon separation column is present, even if argon
is not produced and/or the column contains only very few stages,
certain embodiments of the invention aim to reduce the additional
cost linked to the presence of this column. Accordingly, the gain
in energy performance provided by the invention can be garnered
totally or partially at smaller extents.
[0010] According to one subject of the invention, a method is
provided for separating air by cryogenic distillation, in which
[0011] a) cooled air purified to remove water is sent to a first
column operating at a first pressure, where it is separated into a
nitrogen-enriched gas and an oxygen-enriched liquid,
[0012] b) a liquid enriched in nitrogen relative to the air is
withdrawn from the first column and sent to the top of a second
column which is connected thermally to the first column and
operates at a second pressure, which is lower than the first
pressure,
[0013] c) a liquid enriched in oxygen relative to the air is
withdrawn from the first column, and optionally a first portion of
the oxygen-enriched liquid is sent to an intermediate level of the
second column, optionally after having undergone a partial
vaporization step in which it has been enriched in oxygen,
[0014] d) a gas enriched in argon relative to the air is withdrawn
from the second column,
[0015] e) at least a portion of the oxygen-enriched liquid is at
least partly vaporized by heat exchange with the argon-enriched gas
and the vaporized, oxygen-enriched liquid is sent to an
intermediate level of the second column, optionally following a
step of enrichment of the vaporized liquid with oxygen,
[0016] f) at least one condensed portion of the argon-enriched gas
is returned to a third column, which is also fed with an
argon-enriched gas flow originating from the second column, an
argon-enriched flow is withdrawn at the top of the third column,
and an argon-depleted liquid is returned from the third column to
the second column.
[0017] g) a portion of the oxygen-enriched liquid is sent to an
overhead condenser of the third column,
[0018] h) the oxygen-enriched liquid sent to the overhead condenser
undergoes vaporization there, and the vapour produced is sent to
the second column
[0019] wherein the portion of the oxygen-enriched liquid that is
sent to the overhead condenser of the third column has not been
reheated against the argon-enriched gas flow.
[0020] According to other aspects, which are optional and can be
combined with one another: [0021] the vaporized, oxygen-enriched
liquid is at a pressure at least 1 bar greater than the pressure of
the second column, and is expanded in a turbine and then sent to an
intermediate level of the second column; [0022] at least one
condensed portion of the argon-enriched gas is returned to the
second column; [0023] at least one condensed portion of the
argon-enriched gas is returned to a third column, which is also fed
with an argon-enriched gas flow originating from the second column,
an argon-enriched flow is withdrawn at the top of the third column
and an argon-depleted liquid is returned from the third column to
the second column; [0024] the portion of the oxygen-enriched liquid
that is sent to the overhead condenser of the third column has not
undergone enrichment with oxygen; [0025] the third column is
disposed inside the second column and the at least one portion of
the oxygen-enriched liquid is vaporized by heat exchange with the
argon-enriched gas inside the second column; [0026] the
argon-enriched gas sent to the exchanger has a condensation
temperature greater than the vaporization temperature of the
oxygen-enriched liquid in the exchanger; [0027] all of the
oxygen-enriched liquid is sent from the bottom of the first column
to the heat exchanger; only a portion of the liquid is vaporized,
and this portion is sent to the second column; [0028] in this case,
the unvaporized portion is separated in a phase separator, expanded
and sent to the second column; [0029] a portion of the
oxygen-enriched liquid is sent from the bottom of the first column
to the heat exchanger, in which it is at least partly vaporized,
and a portion of the oxygen-enriched liquid is sent from the bottom
of the first column to the second column, without passing via the
heat exchanger.
[0030] All of the oxygen-enriched liquid sent to the heat exchanger
undergoes vaporization there.
[0031] According to another subject of the invention, an apparatus
is provided for separating air by cryogenic distillation,
comprising a first column operating at a first pressure, a second
column connected thermally to the first column and operating at a
second pressure, which is lower than the first pressure, a heat
exchanger, means for sending cooled air, purified to remove water,
to the first column, operating at a first pressure, where it is
separated into a nitrogen-enriched gas and an oxygen-enriched
liquid, means for withdrawing a liquid enriched in nitrogen
relative to the air from the first column, means for sending the
nitrogen-enriched liquid to the top of the second column, means for
withdrawing a liquid enriched in oxygen relative to the air from
the first column, optionally means for sending a first portion of
the oxygen-enriched liquid to an intermediate level of the second
column, optionally after enrichment thereof with oxygen, means for
withdrawing a gas enriched in argon relative to the air from the
second column, means for sending a portion of the oxygen-enriched
liquid to the heat exchanger for at least partial vaporization
thereof by heat exchange with the argon-enriched gas, and means for
sending the oxygen-enriched liquid vaporized in the heat exchanger
to an intermediate level of the second column, optionally following
a step of oxygen enrichment of the vaporized liquid, a third
column, means for sending at least one condensed portion of the
argon-enriched gas in the heat exchanger to the third column, and
means for sending an argon-enriched gas flow originating from the
second column to the third column, means for withdrawing an
argon-enriched flow at the top of the third column, means for
sending an argon-depleted liquid from the third column to the
second column, means for sending a portion of the oxygen-enriched
liquid to an overhead condenser of the third column, and means for
sending the vapour produced by vaporizing the oxygen-enriched
liquid in the overhead condenser to the second column,
characterized in that the means for sending the portion of the
oxygen-enriched liquid to the overhead condenser are connected
directly to the first column without passing via the exchanger.
[0032] According to other optional aspects: [0033] the apparatus
comprises a turbine connected to an intermediate level of the
second column fed with the vaporized, oxygen-enriched liquid;
[0034] the apparatus comprises means for returning at least one
condensed portion of the argon-enriched gas to the second column;
[0035] the apparatus comprises means for sending the vapour
produced to the second column, by being mixed with the flow
expanded in the turbine; [0036] the third column is disposed inside
the second column; [0037] the apparatus comprises means for
vaporizing the at least one portion of the oxygen-enriched liquid
by heat exchange with the argon-enriched gas inside the second
column; [0038] the third column contains fewer than 50 or even
fewer than 10, theoretical stages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Further features and advantages of the invention will become
apparent from the description hereinafter of embodiments, which are
given by way of illustration but without any limitation, the
description being given in relation with the following attached
figures:
[0040] FIG. 1 which is composed of FIGS. 1a and 1b, represents
comparative methods.
[0041] FIG. 2 represents methods according to an embodiment of the
invention.
[0042] FIG. 3 represents methods according to an embodiment of the
invention.
[0043] FIG. 4 represents a variant of FIGS. 2 and 3.
[0044] FIG. 5 also represents a variant of FIGS. 2 and 3.
DETAILED DESCRIPTION OF THE INVENTION
[0045] FIG. 1a shows a double air separation column comprising a
first column K1, operating at a first pressure, and a second column
K2, operating at a second pressure, which is lower than the first
pressure. The two columns are connected to one another thermally,
for example by a condenser-reboiler C, which vaporizes the bottom
oxygen from the second column K2 by heat exchange with the gaseous
nitrogen from the first column K1.
[0046] A nitrogen-enriched liquid 11 is sent from the top of the
first column K1 to the top of the second column K2. The first
column is fed with gaseous air by a flow of cooled air 1 which has
been purified to remove water and CO2. Air may also feed the second
column K2.
[0047] An oxygen-enriched liquid is withdrawn at the bottom of the
first column K1 and divided into two. One portion 3 is sent to the
heat exchanger E, where it is vaporized totally to form a gas 5.
The gas 5 is expanded in a turbine T and sent to an intermediate
point of the first column K1. The production of cold that is
generated at very low temperature by this expansion therefore
provides a gain in the energy consumption of the unit, by
comparison with the consumption that would occur in the absence of
this expansion.
[0048] The remainder 10 of the oxygen-enriched liquid withdrawn at
the bottom is expanded in a valve and sent as a flow 12 above the
intake points of the flows 5 and 9.
[0049] The exchanger E, which is contained within a chamber B, is
also used to liquefy a flow of intermediate gas 7 from the second
column K2. This gas 7 will be withdrawn at a position such that its
condensation temperature (bubble point) will be greater than the
vaporization temperature of the oxygen-enriched liquid 3 in the
exchanger E. Its composition will typically be that of the feed gas
of an argon production column. After having undergone condensation
in E, this flow is then sent, optionally by means of a pump P, to a
point at least above its withdrawal point and below the expanded
gas intake of the turbine T.
[0050] An oxygen-rich liquid 15 is withdrawn from the bottom of the
second column K2, and a nitrogen-enriched top gas 13 is withdrawn
from the top of the same column.
[0051] As a variant, as illustrated in FIG. 1b, all of the bottom
liquid may be sent to the exchanger E, where it undergoes partial
vaporization. The partially condensed flow is separated in a phase
separator 8 to produce a gas 5 and a liquid 100 which is enriched
in oxygen relative to the liquid 3. The resulting gas 5 is expanded
in a turbine T, and the remaining liquid 10 is expanded and sent to
the column as flow 12. In this case, the liquid enters the column
K2 at a level above the gas from the turbine T, since it has been
enriched with oxygen. FIG. 1B illustrates only a modified portion
of FIG. 1a.
[0052] These diagrams do not include an argon separation column, in
contradistinction to FIGS. 2 and 3.
[0053] In FIG. 2, which is a variant of FIG. 1, the oxygen-enriched
liquid 3 is divided into three portions 3, 17 and 19.
[0054] One portion, 17, is sent directly to the second column K2,
in liquid form.
[0055] The portion 3, as for FIG. 1, undergoes heat exchange with
an argon-enriched flow 7, which is a portion of the argon-enriched
gas withdrawn from the second column; the remainder of the gas, 7A,
is sent directly to feed the argon separation column K3.
[0056] The portion 3 is vaporized to form the gaseous flow 5 at 2.1
bar, and is then expanded in the turbine T and sent to the column
K2. The flow 7 undergoes condensation in the exchanger E contained
in a chamber B, and the resulting liquid 9 feeds the column K3,
preferably several stages above the intake of gas 7A.
[0057] The chamber B is preferably disposed above the point of
intake of the liquid 9 in the column K3.
[0058] The portion 19 of the oxygen-enriched liquid feeds the
overhead condenser N of the column K3 without having been enriched
with oxygen, and undergoes vaporization to form a gas 23. The gas
23 is mixed with gas expanded in the turbine T to form a gas 25,
which feeds the second column K2.
[0059] Accordingly, the oxygen-enriched liquid feeds the exchanger
E and the overhead condenser N in parallel.
[0060] The argon yield is of the order of 80%, if argon purified to
remove oxygen (flow 21) is recovered as the product. If the flow 21
is not recovered as a pure product, the column K3 can be very
small, since it contains only a few tens of theoretical stages
(<50), or even fewer than 10 theoretical stages.
[0061] In FIG. 3, the oxygen-enriched liquid is divided into only
two portions 3 and 3A. The portion 3A feeds the column K2, and the
portion 3 is partially vaporized in the heat exchanger E. The
remaining liquid, 3B, feeds the overhead condenser N of the column
K3, and the gas 23 formed in the condenser feeds the column K2.
[0062] The gas 7A formed in the exchanger E feeds the turbine T at
an intake pressure of 2.7 bar.
[0063] The argon yield is of the order of 75 to 76%, if argon is
recovered (flow 21).
[0064] In the cases of FIGS. 2 and 3, the argon column has a liquid
feed in addition to the usual gaseous feed. Accordingly, the
diameter of the column K3 may be reduced by approximately 20%, for
the section above the intake of the liquid 9, which reduces its
cost.
[0065] Given that the argon column is the highest column of the
apparatus, it is important to be able to reduce its volume and so
to reduce the dimensions of the cold box containing it (not
illustrated).
[0066] In a variant, the column K3 of FIGS. 2 and 3 may be located
inside the column K2, which is disposed concentrically with the
shell of the column K2. The column K3 may contain structured
packing or dumped packing.
[0067] The gas ascending in the column K2 will pass either into the
column K3 or into the annular portion surrounding the column
K2.
[0068] In this case, the overhead condenser N of the column K3 will
serve to heat a liquid bath situated at mid-height in the column
K2. The gas from the top of the column K3 will pass via a conduit
into the overhead condenser N through a barrier forming a tank at
mid-height in the column K2, and the liquid condensed in the
condenser N will pass in the same way into another conduit, through
the barrier, to return to the column K2. A valve may regulate the
amount of liquid returned from the condenser N to the column
K2.
[0069] The column K3 is surrounded by an annular section of the
column K2 in which packings are located. The gas separated at the
top of the annular section is sent to the section of the column K2,
passing through the barrier, into a conduit, or will be sent to the
outside of the column, below the barrier, to return into the column
above the barrier. The bottom liquid accumulated above the barrier
will be sent to the top of the annular section either via a conduit
which passes through the barrier or via a conduit which is
connected to the outside of the column.
[0070] In this case, the exchanger E in its chamber B is still
situated outside the column K2 and outside the column K3. In this
case, the flow 7 is withdrawn directly from the column K2, without
being divided, since the flow equivalent to 7A ascends directly in
the column K2 to the column K3.
[0071] Similarly, the liquid 3B is injected in the column K2, to be
directed to the condenser N.
[0072] For a concentric column K3 inside another column K2, since
the mixtures of fluids are not identical in composition on either
side of the internal column K3, there will be heat exchanges
through the wall of the column K2 between the inside of the column
K2 and the annular portion. Distillation is promoted by heat
exchange at the top of the column K2, whereas it is not promoted by
heat exchange at the bottom of the column.
[0073] The recommendation is therefore to improve the exchange in
the upper part of the column K3 by increasing the surface area for
heat exchange, by adding fins on the shell of the upper part of the
column K3.
[0074] Alternatively, the material used for the upper part of the
shell may be a metal with better conductivity than for the lower
part (for example, aluminium at the top of the shell of the column
K3, and stainless steel at the bottom of the column). Another
possibility is to use a shell for K3 that is entirely made of
aluminium, and to apply a coating in the lower section in order to
reduce heat exchanges.
[0075] Proposals have been made in the past to dispose an argon
separation column having an overhead condenser in a second column
(low-pressure column). One possibility is to position the overhead
column such that the top gas from the argon column undergoes
partial condensation in the overhead condenser of the argon column
and partial condensation in an overhead condenser of the
low-pressure column, by heat exchange with the oxygen-rich liquid
originating from the bottom of the first column (medium-pressure
column). The liquid formed in the overhead condenser of the second
column is sent to the top of the second column, and the vaporized
liquid is sent to a level above the overhead condenser of the argon
column. The overhead condenser may be a film evaporator.
[0076] In FIGS. 2 and 3, the turbine T may be replaced by a mixing
column K4 operating for example at between 2.2 and 2.7 bar, as
illustrated in FIG. 4. This mixing column will be fed at the bottom
with the vaporized rich liquid 5 vaporized by the exchanger E. An
intake at the top of the column K4 is a flow of impure liquid
oxygen having an oxygen content of approximately 90 mol %. The
vaporized rich liquid has an oxygen content of 34% in the case of
FIGS. 2 and 20% in the case of FIG. 3. A liquid 31 is withdrawn at
the bottom of the column K4, that has an oxygen content of 65% (in
the case of FIG. 2) or 50% (in the case of FIG. 3). A gaseous flow
43 is withdrawn in the middle of the column K4.
[0077] The column K4 produces a flow 35 at the column top that has
an oxygen content of 75% (FIG. 2) or 65% (FIG. 3) at between 2.1
and 2.7 bar. This flow is condensed in a condenser C, which may be
the bottom condenser of the second column K2 or an evaporator
external to any column. It undergoes condensation by heat exchange
with the pure liquid oxygen 39, to produce the pure gaseous oxygen
41.
[0078] Accordingly, the gas 35 may replace the gaseous nitrogen
originating from the first column in the condenser C of FIG. 2 or
3. This allows the argon yield to be increased by approximately 5%,
or enables an increase in the production of gaseous nitrogen at the
top of the first column.
[0079] Conversely, the energy gain would be reduced relative to
that of FIGS. 2 and 3; however, the turbomachine T is
eliminated.
[0080] FIG. 5 also illustrates a variant of FIGS. 2 and 3, in which
the oxygen-enriched liquid 3 from the bottom of the first column is
enriched with oxygen in an Etienne column K5, the bottom reboiler E
of which corresponds to the exchanger 3 in the preceding
figures.
[0081] Accordingly, the reboiler E is reheated by an argon-enriched
gas flow 7 originating from the second argon column. The liquid
flow 9 produced is used as a second feed to the argon column K3, in
addition to the gaseous feed.
[0082] The liquid 3 expanded in a valve descends the stages of the
column K5, becoming enriched in oxygen, to produce a oxygen-rich
flow 53 (75% oxygen), a bottom flow and an overhead gas containing
only 16% oxygen. The flow 53 feeds the column K2 and allows a gain
in argon yield of 3%.
[0083] As used herein, means for sending a fluid is understood to
include one or more conduits and the like that are configured to
transfer fluids from one location to another location.
[0084] While the invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description. Accordingly, it is
intended to embrace all such alternatives, modifications, and
variations as fall within the spirit and broad scope of the
appended claims. The present invention may suitably comprise,
consist or consist essentially of the elements disclosed and may be
practiced in the absence of an element not disclosed. Furthermore,
if there is language referring to order, such as first and second,
it should be understood in an exemplary sense and not in a limiting
sense. For example, it can be recognized by those skilled in the
art that certain steps can be combined into a single step.
[0085] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0086] "Comprising" in a claim is an open transitional term which
means the subsequently identified claim elements are a nonexclusive
listing (i.e., anything else may be additionally included and
remain within the scope of "comprising"). "Comprising" as used
herein may be replaced by the more limited transitional terms
"consisting essentially of" and "consisting of" unless otherwise
indicated herein.
[0087] "Providing" in a claim is defined to mean furnishing,
supplying, making available, or preparing something. The step may
be performed by any actor in the absence of express language in the
claim to the contrary.
[0088] Optional or optionally means that the subsequently described
event or circumstances may or may not occur. The description
includes instances where the event or circumstance occurs and
instances where it does not occur.
[0089] Ranges may be expressed herein as from about one particular
value, and/or to about another particular value. When such a range
is expressed, it is to be understood that another embodiment is
from the one particular value and/or to the other particular value,
along with all combinations within said range.
* * * * *