U.S. patent application number 09/766279 was filed with the patent office on 2002-07-25 for method and apparatuses for the production of synthetic air products and related gases.
Invention is credited to Ha, Bao.
Application Number | 20020095951 09/766279 |
Document ID | / |
Family ID | 25075954 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020095951 |
Kind Code |
A1 |
Ha, Bao |
July 25, 2002 |
Method and apparatuses for the production of synthetic air products
and related gases
Abstract
Processes and apparatuses are disclosed for the production of a
synthetic air product with a variable oxygen content and a varying
level of impurities.
Inventors: |
Ha, Bao; (San Ramon,
CA) |
Correspondence
Address: |
William P. Ramey, III
THE MATTEWS FIRM
1900 West Loop South
Houston
TX
77027
US
|
Family ID: |
25075954 |
Appl. No.: |
09/766279 |
Filed: |
January 19, 2001 |
Current U.S.
Class: |
62/643 ;
62/625 |
Current CPC
Class: |
F25J 2210/04 20130101;
F25J 3/04636 20130101; F25J 2210/50 20130101; F25J 3/0426 20130101;
F25J 3/044 20130101; F25J 2215/50 20130101; F25J 3/04254 20130101;
F25J 2200/72 20130101; F25J 2215/40 20130101 |
Class at
Publication: |
62/643 ;
62/625 |
International
Class: |
F25J 003/00 |
Claims
What is claimed is:
1. A process for the production of a synthetic air product
comprising the steps of: supplying a feed gas; enhancing the oxygen
content of the feed gas; passing the feed gas to a cryogenic
distillation column; rectifying the feed gas in the distillation
column to remove impurities; and, extracting a synthetic air
product at least a real or theoretical tray above where the feed
gas is passed to the column.
2. The process of claim 1 further comprising compressing the feed
gas.
3. The process of claim 1 wherein the step of enhancing the oxygen
content of the feed gas comprises mixing an oxygen stream with the
feed gas.
4. The process of claim 2 wherein the oxygen content of the feed
gas is enhanced prior to fully compressing the feed gas.
5. The process of claim 1 wherein the oxygen content of the feed
gas is enhanced prior to fully rectifying the feed gas.
6. The process of claim 1 wherein the oxygen content of the feed
gas is enhanced prior to fully cooling the feed gas.
7. The process of claim 1 wherein the oxygen content of the feed
gas is enhanced at a point in the distillation column.
8. The process of claim 7 wherein the synthetic air product is
extracted at least one real or theoretical tray above the point in
the distillation column.
9. The process of claim 1 wherein the feed gas is cooled to
generally about a dew point of the feed gas.
10. The process of claim 1 the feed gas is air.
11. The process of claim 1 wherein the step of enhancing the oxygen
content further comprises mixing an oxygen supply with the feed
gas.
12. The process of claim 11 wherein the oxygen supply is greater
than 90% by volume.
13. The process of claim 1 wherein the step of rectifying the feed
gas further comprises more than one tray.
14. The process of claim 1 further comprising the step of removing
a nitrogen enriched product.
15. The process of claim 14 wherein the nitrogen enriched product
is removed along an upper portion of the column.
16. The process of claim 1 wherein the synthetic air product
extracted has an oxygen content of about 15% by volume to about 40%
by volume.
17. The process of claim 1 wherein the synthetic air product
extracted has an oxygen content of about 20% by volume to about 30%
by volume.
18. The process of claim 1 wherein the synthetic air product
extracted has an oxygen content of about 21% by volume.
19. The process of claim 1 wherein the step of supplying the feed
gas further comprises mixing an oxygen supply with an other supply
prior to rectifying.
20. The process of claim 19 wherein at least one of the oxygen
supply and the other supply is a liquid.
21. The process of claim 19 wherein the other supply is a nitrogen
supply.
22. A cryogenic process for the production of a synthetic air
product including the steps of supplying a feed gas; substantially
removing CO2 and moisture from the feed gas; mixing the feed gas
with an oxygen content enhancing stream; cooling the feed gas,
passing the feed gas into a distillation column; and, removing a
synthetic air product.
23. The process of claim 22 further comprising compressing the feed
gas.
24. The process of claim 22 wherein the step of supplying the feed
gas further comprises mixing an oxygen supply and an other
supply.
25. The process of claim 24 wherein at least one of the oxygen
supply and the other supply is a liquid.
26. The process of claim 25 wherein at least one of oxygen supply
and the other supply is a gas.
27. The process of claim 24 wherein the other supply is a nitrogen
supply.
28. An apparatus for producing a synthetic air product comprising:
a column having an upper portion, a lower portion, a top, a bottom,
and at least one tray; a feed gas supply line connected to the
column; an oxygen content enhancing line connected to the feed gas
supply line; and, a product withdraw line connected to a portion of
the column for removing a synthetic air product.
29. The apparatus of claim 29 further comprising a line connected
to the lower portion of the column to remove rich liquid.
30. The apparatus of claim 29 wherein the oxygen content enhancing
line is connected to the column.
31. The apparatus of claim 29 wherein the feed gas supply line
further comprises a connection to an oxygen supply and an other
supply.
32. The apparatus of claim 35 wherein at least one of the other
supply and the oxygen supply is a liquid.
33. The apparatus of claim 35 wherein the other supply is a
nitrogen supply.
34. The apparatus of claim 29 wherein the product withdraw line
removes a synthetic air product with an oxygen content of about 15%
by volume to about 40% by volume.
35. The apparatus of claim 29 wherein the product withdraw line
removes a synthetic air product with an oxygen content of about 20%
by volume to about 30% by volume.
36. The apparatus of claim 29 wherein the product withdraw line
removes a synthetic air product with an oxygen content of about 21%
by volume.
Description
TECHNICAL FIELD
[0001] The present invention relates to methods and apparatuses for
the production of a synthetic air product utilizing distillation.
The methods and apparatuses of the present invention capable of
producing a synthetic air product of varying purity and
content.
BACKGROUND ART
[0002] For purposes of this patent, the following terms are
defined. As used herein, the term air separating unit or air
separation unit means and refers to a facility, plant, location or
process for separating the components of a feed gas and may include
both cryogenic and non-cryogenic facilities. The term contaminant
means and refers to impurities less volatile than oxygen. The term
oxygen content means and refers to percent oxygen by volume. The
term synthetic air means and refers to a product having an oxygen
content of about 21% by volume. However, the term synthetic air
product may be a processed product having any percent by volume
oxygen content greater than about 15% by volume.
[0003] As used herein, the term feed air means and refers to
atmospheric air. The term feed gas means and refers to a feed gas
and may include feed air. The term oxygen supply means and refers
to an oxygen supply with a determinable oxygen content and is not
limited nor excluded from a pure supply, but rather, may be any
concentration of oxygen. The term oxygen stream means and refers to
a gas or gases with a determinable oxygen content. The term
nitrogen supply means and refers to a supply with a determinable
nitrogen content and is not limited nor excluded from a pure
supply, but rather, may be any concentration of nitrogen. The term
impurity and/or impurities means and refers to a component or
components heavier than oxygen, i.e. a component or components with
a higher boiling point than oxygen.
[0004] As well, the use of a particular structure, structures, or
embodiments is not meant to be limiting. For instance, the term
apparatus or apparatuses means and includes production facilities,
plants, and the like. Further, the term process or processes means
and includes methods, plans, production plans, and the like. The
term led out means and refers to allowing out, passing out,
discharging, releasing, and/or the like.
[0005] Various air separating units for accomplishing separation of
feed gas do exist in the prior art and are well known. Generally,
in air separating units, and more especially cryogenic air
separating units, feed gas is first compressed by a compressor, and
then passed through any manner of de-carbonating apparatuses known
in the art, such as, and only by way of example and not as a
limitation, an adsorber unit, a molecular sieve, and/or a
decarbonating-drying portion; to remove carbon dioxide and moisture
from the feed gas. Then the feed gas is cooled down by heat
exchange in a heat exchanger, and rectified for separation in a
rectification column so as to provide a product. Various examples
of product gases include a nitrogen-enriched gas or liquid, a
liquid rich in oxygen (also called sometimes liquid rich) at the
bottom of the column, and other gases.
[0006] In some facilities the oxygen rich liquid bottoms is
expanded to lower pressure and vaporized in the top condenser of
the column to provide the cooling of this condenser. The vaporized
rich liquid is called the waste stream. After this,
nitrogen-enriched gas and/or waste stream are warmed to ambient
temperature by heat exchanging with the feed gas in the main heat
exchanger. Further, many other columns, rectification apparatuses,
turbo expanders, valves, heat ex-changers, vents, phase separators
and/or other like parts may be assembled in varying orders and
assemblies to effect separation and/or production of gaseous
components of a feed gas. Such other modifications of the assembly
are well within the level of ordinary skill in the art.
[0007] Common examples of the separation of a feed gas into
components are disclosed in U.S. Pat. Nos. 3,210,950 to Lady (the
'950 patent), U.S. Pat. No. 5,901,577 to Pelle et al. (the '577
patent), U.S. Pat. No. 5,970,742 to Agrawal et al. (the '742
patent), U.S. Pat. No. 6,173,584 to Agrawal (the '584 patent),
5,836,174 to Billingham et al. (the '174 patent), 5,865,041 to
Agrawal et al. (the '041 patent), U.S. Pat. No. 6,050,106 to
Yamamoto et al. (the '106 patent), and others.
[0008] The '950 patent is representative of a method and apparatus
for fractionating a gaseous mixture. The '950 patent discloses and
teaches the separation of the gas by low temperature liquification
and fractionation. Specifically, the patent is drawn to the
advantages of a low temperature liquification and fractionation for
the production of lower boiling point components in substantial
purity. The patent teaches that the production of the lower boiling
point components may be obtained by withdrawing the separation of
the lower boiling point components and recycling this withdrawn
material as a portion of the feed. However, the patent does not
teach nor disclose the production of a synthetic air product of
varying purity and content.
[0009] The '577 patent discloses a cryogenic process and plant for
the production of gaseous oxygen. The patent discloses the use of a
heat exchange line to cool the air by indirect heat exchange, an
air distillation apparatus with a medium and low pressure column,
and reboiler/condenser to which brings, into indirect heat
exchange, vapor and liquid. Primarily, the vapor is a nitrogen
product and the liquid is an oxygen product. However, the patent
does not teach nor disclose the production of a synthetic air
product of varying purity and content.
[0010] In fact, there have been several processes that have been
directed toward the distillation of multi-component gaseous
mixtures for the production of product streams. Examples of such
processes are found in the '742 patent and the '584 patent. The
'742 patent teaches a process for distillation of a multi-component
stream, of three or more components, using a two-way communication
path between two distillation columns at an end and a one-way
distillation path from the other end between the two columns.
However, the '742 patent does not teach nor disclose the production
of a synthetic air product of varying purity and content. Likewise,
the '584 patent teaches distillation of a multi-component streams,
of at least three components, into at least four products from a
first and a second distillation column. The '584 patent is
different than the '742 patent because it uses a withdraw from an
intermediate point along a column to produce a mixture stream that
may be separated in a second distillation column. Therefore, two
product streams may be produced from the top and bottom of both the
first and the second distillation column and hence, four products.
However, the patent does not teach nor disclose the production of a
synthetic air product of varying purity and content.
[0011] The prior art also includes processes and apparatuses that
have been developed for the production of an ultra high purity
product from a distillation column(s). Examples of such processes
and apparatuses are illustrated in the '106 patent. The '106 patent
teaches and discloses the use of multiple rectification trays for
the separation of a feed air. A stream is withdrawn at the top, the
top defined as between a middle portion of the column and the
absolute top, of the column containing an ultra high purity
nitrogen product. A stream is withdrawn from the bottom of the
column, defined as a point between the absolute bottom and the
middle portion, containing an ultra high purity oxygen product. A
stream may be withdrawn from the middle portion of the column to
control the reflux of the column and refrigeration of the column.
However, the patent does not disclose the production of a synthetic
air product of varying purity and content.
[0012] Other patents in the art field teach and disclose the
production of multiple product streams of varying concentration.
One such example is the '174 patent. It teaches and discloses a
cryogenic rectification system with two rectification sections in
parallel for producing product oxygen at high and low impurities
through a stripping process in the parallel columns. While he '174
patent may be effective in producing two product oxygen streams
with low impuities, the patent does not teach nor disclose the
production of a synthetic air product of varying purity and
content.
[0013] As well, the '236 patent teaches and discloses a cryogenic
rectification system for producing product oxygen at both high and
low purity. Oxygen products of varying oxygen content are produced
in this patent by the addition of a stripper column connected from
a portion of the lower section of a main distillation column. The
stripper column operates at a lower liquid to vapor ratio than the
lower portion of the main column or uses more rectification trays
to produce a higher purity oxygen product than that produced by the
lower portion of the main distillation column. The higher purity
oxygen product is removed from the stripper column. However, the
patent does not teach nor disclose the production of a synthetic
air product of varying purity and content.
[0014] The '041 patent teaches and discloses a process for
cryogenic distillation of air to produce at least two oxygen rich
streams of varying oxygen content. This patent withdraws at least
two oxygen rich streams from a distillation column and injects the
streams into a mixing column where at least two streams with
different oxygen contents are removed. However, the patent does not
teach nor disclose the production of a synthetic air product of
varying purity and content.
[0015] The '174 patent, the '236 patent, and the '041 patent
addressed an industry need for oxygen products with different
levels of oxygen content. However, in various industries, instead
of high purity nitrogen, oxygen or a combination, compressed dry
air with a composition about that of atmospheric air, or about 21%
oxygen content, is needed. One such industry is the medical gas
industry, including the medical and medical supply industry, and
semi-conductor industry. As well, some of these applications
require products with varying oxygen contents that may be both
above and below about 21%. However, it is common, but not always
required, that the product is required to be free from moisture and
carbon dioxide (CO2) and at least partially free from other
contaminants. Most commonly, a level of contaminants tolerated for
application of this type is in the ppb range (parts per billion).
However, the level of contaminants tolerated can and often does
vary depending upon a use of the product.
[0016] Industries that have such a need have referred to the
product as a synthetic air or a synthetic air product. Because of
this need, various attempts have been made in the prior art to
simultaneously, with the production of nitrogen, oxygen, and/or
other gases, to produce high purity synthetic air or a high purity
synthetic air product. In one prior art attempt, a portion of the
feed gas is passed through a decarbonating-drying adsorber. This
portion of the feed gas is then taken out as a compressed dry air
product. The production of a compressed dry synthetic air product
by such method has proven effective, but does nothing- to very
little for removing any contaminants from the feed gas, such as
light hydrocarbons (methane, ethane etc.), and components with
higher boiling points than oxygen, and the like. It is useful to
note that the adsorbers utilizing molecular sieves can remove some
heavy hydrocarbons (C4 and higher) but light hydrocarbons such as
methane, ethane, propane can pass through such adsorber units.
Therefore, the art field is in search of a method of removing
contaminants from feed gas such that a higher purity synthetic air
may be recovered.
[0017] U.S. Pat. No. 6,077,488 to Jain et al. teaches and discloses
a process and apparatus for producing a clean dry air product using
the absorbent beds mentioned above. A feed air is passed through an
adsorption bed to remove moisture and carbon dioxide. Then the feed
air is catalytically reacted to convert the impurities to moisture
and carbon dioxide. Further, the feed is passed again over an
adsorption bed to remove the moisture and carbon dioxide produced
from the catalytic conversion. However, the patent does not
disclose the production of a synthetic air product of varying
purity and content.
[0018] Another prior art solution to overcome this problem is an
air separating unit which can simultaneously generate high purity
nitrogen gas and compressed dry synthetic air of high quality freed
of light hydrocarbons such as methane and ethane. Hydrocarbons and
components heavier than nitrogen and oxygen, whose boiling points
are higher than that of nitrogen or oxygen, are partially removed
from the feed gas in a lower rectifying portion of a rectification
column as is shown and described in U.S. Pat. No. 5,546,765 to
Nagamura et al. (the '765 patent). This patent discloses a
rectification portion of a column whereby hydrocarbons, krypton and
xenon are removed from feed gas before synthetic air is
removed.
[0019] The air separating unit of the '765 patent uses feed gas
taken from the atmosphere, cooled down near to its liquefying point
by a heat exchanger, after it is compressed and freed of hydrogen,
carbon monoxide, carbon dioxide, and moisture. Then, the cooled
feed gas is introduced into a rectification column. Nitrogen gas is
separated by rectification from the feed gas in the rectification
column and is liquefied by condensation in a condenser. The liquid
nitrogen liquefied by condensation in the condenser is introduced
into the top portion of the rectification column as a reflux
liquid, and a part of the reflux liquid is led out of the
rectification column, thereby producing a liquid nitrogen product.
Further, nitrogen products may be extracted at the top of the
column. The rectification column is further characterized in that
the rectifying portion of the rectification column is divided into
a lower rectifying portion and an upper rectifying portion. The
lower rectifying portion is made to have such a minimum dimension
of height as required for removing hydrocarbons such as methane and
ethane from the feed gas so that the total content of such
hydrocarbons is lowered from the initial content. The gas or gases,
essentially freed, of hydrocarbons is then taken out as a
compressed dry air product from a space between the lower
rectifying portion and the upper rectifying portion.
[0020] However, a synthetic air product produced by this process
yields a synthetic air product with an oxygen content of about 5%
to about 15% by volume because the use of rectifying trays in the
column reduces the oxygen content of the product gas extracted
above the feed tray. Accordingly, the art field is in search of a
process or processes and an apparatus or apparatuses for producing
a synthetic air product with a variable oxygen content that has a
capability of producing a synthetic air product with an oxygen
content above about 15% and varying level of impurities.
[0021] However, there have been various attempts in the art field
to make such a product. Such attempts in the art field include the
making or production of a synthetic air product from liquid
nitrogen and liquid oxygen. In processes of this type, the oxygen
and nitrogen have been directly mixed. However, the liquid supplies
often contain impurities at a level that is not acceptable for a
high purity synthetic air product. One such process is disclosed in
U.S. Pat. No. 4,181,126 to Hendry (the '126 patent). This patent
discloses a cryogenic underwater breathing apparatus where liquid
nitrogen and liquid oxygen are mixed to obtain a synthetic air
product that will have the impurity levels of the mixed liquid
supplies. Accordingly, the art field is in search of a process and
apparatus for mixing a liquid nitrogen and liquid oxygen supply
that will remove impurities during the production of the synthetic
air product.
[0022] A prior art process that is used for the production of
various gases for semiconductor production facilities is disclosed
in U.S. Pat. No. 5,656,557 to Hata et al. (the '557 patent). The
'557 patent discloses a process that allows for the production of a
high purity nitrogen product and a synthetic air product. The
patent discloses passing a feed air stream over an adsorber to
remove moisture and carbon dioxide and then catalytically removing
the hydrocarbons and hydrogen. A portion of the feed air is then
removed as a synthetic air product while the remainder of the feed
air is introduced to a column for the production of a nitrogen
product. However, the patent does not teach nor disclose the
production of a synthetic air product of varying purity and
content.
[0023] Further U.S. Pat. No. 4,848,996 (the '996 patent) discloses
a modifications to the basic nitrogen generation process. This
patent discloses distillation trays that are added in a
fractionation section above the top condenser of the column for the
purpose of stripping oxygen from the gaseous-oxygen enriched
stream. The gaseous stream removed from this fractionation section
is described to be of a composition similar to air, and the
"synthetic air is recycled for compression and mixing with main air
feed stream to the bottom of the distillation column. The purpose
of the recycling of "synthetic air" is to improve the efficiency of
the nitrogen production cycle. However, the patent does not teach
nor disclose the production of a synthetic air product of varying
purity and content.
[0024] A further modification of the '996 patent is disclosed in
U.S. Pat. No. 4,927,441 (the '441 patent). The '441 patent
discloses another modified version of the '996 to further improves
the efficiency of the nitrogen production. However, the patent does
not teach nor disclose the production of a synthetic air product of
varying purity and content.
[0025] Some prior art patents have modified the above techniques by
recycling a "synthetic air" in another column. U.S. Pat. No.
5,711,167 discloses such a technique where the vapor portion of the
partially vaporized rich liquid of the bottom of the column is
recycled back to the column to improve the distillation for
nitrogen production. However, the patent does not teach nor
disclose the production of a synthetic air product of varying
purity and content.
[0026] An attempt to improve nitrogen production is disclosed in
U.S. Pat. No. 4,966,002 (the '002 patent). The '002 patent
discloses a process where a portion of vaporized rich liquid is
recycled and the remaining portion is expanded to improve the
performance of the nitrogen production. However, the patent does
not teach nor disclose the production of a synthetic air product of
varying purity and content.
[0027] Other patents have used processes and principals similar to
the ones described above, such as U.S. Pat. Nos. 4,867,773,
4,883,519, and 5,385,024. These patents are for the improvement in
the efficiency of the production of nitrogen by cryogenic
distillation. However, these patents do not teach nor disclose the
production of a synthetic air product of varying purity and
content.
[0028] None of the prior art herein described has taught or
disclosed the production of a synthetic air product that is
selectively free of impurities. Moreover, none of the prior art
herein described has taught or described the production of a
synthetic air product capable of processes where the oxygen content
of the synthetic air product may vary. Accordingly, the art field
is in search of processes and apparatuses to enable the production
of a synthetic air of varying removed and a varying oxygen
content.
SUMMARY OF THE INVENTION
[0029] The present invention generally relates to processes and
apparatuses for the production of a synthetic air product. The
synthetic air product may be selectively produced with a varying
oxygen content and/or varying levels of impurities.
[0030] This summary is not intended to be a limitation with respect
to the features of the invention as claimed and any examples are
merely intended as embodiments, and the scope and other objects can
be more readily observed and understood in the detailed description
of the preferred embodiment and the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0031] For a further understanding of the nature and objects of the
present invention, reference should be made to the following
detailed description, taken in conjunction with the accompanying
drawings, in which like elements are given the same or analogous
reference numbers and wherein:
[0032] FIG. 1 is an illustration of an embodiment of an apparatus
of the present invention.
[0033] FIG. 2 is an illustration of an alternate embodiment of an
apparatus of the present invention.
[0034] FIG. 3 is an illustration of an alternate embodiment of an
apparatus of the present invention.
[0035] FIG. 4 is an illustration of an alternate embodiment of an
apparatus of the present invention.
[0036] FIG. 5 is an illustration of an alternate embodiment of an
apparatus of the present invention.
GENERAL DESCRIPTION AND PREFERRED MODE FOR CARRYING OUT THE
INVENTION
[0037] For purposes of the description of this invention, the terms
"upper", "lower", "right", "left", "vertical", "horizontal", "top",
"bottom", and other related terms shall be defined as to relation
of embodiments of the present invention as it is shown an
illustrated in the accompanying Figures. Further, for purposes of
the description of this invention, the terms "upper portion,"
"lower portion," "top," "bottom," and the like shall be defined to
mean an upper portion and a lower portion and not specific
sections. However, it is to be understood that the invention may
assume various alternative structures and processes and still be
within the scope and meaning of this disclosure. Further, it is to
be understood that any specific dimensions and/or physical
characteristics related to the embodiments disclosed herein are
capable of modification and alteration while still remaining within
the scope of the present invention and are, therefore, not intended
to be limiting.
[0038] Referring now to FIG. 1, an illustration of an embodiment of
an apparatus of the present invention for production of a synthetic
air product, a flow diagram showing an embodiment of an air
separation column. Generally, a compressed feed gas is supplied to
the system through feed gas supply line 1. The feed gas may be
compressed by any method common in the art, such as compressor 15
and the like.
[0039] Feed gas supply line 1, in an embodiment, is then passed
through a CO2 and Moisture Removal Unit 16. CO2 and moisture
removal unit 16 is a de-carbonating and drying unit that removes
carbon dioxide and moisture in the feed gas. CO2 and moisture
removal unit 16 may be of any method and/or apparatus common in the
art. In an embodiment, unit 16 is an alumina combined molecular
sieve portion. Other embodiments use a molecular sieve. Further
embodiments include a CO2 and moisture removal system that uses a
heat exchanger to freeze the CO2 and moisture and separate it from
the feed gas.
[0040] In an embodiment, feed gas supply line 1 then passes through
a heat exchanger 2 where the feed gas is cooled by indirect heat
exchange with a synthetic air product in line 13 and a waste
product in line 11. However, various other embodiments of the
present invention may use different streams to effect cooling of
the feed gas and/or different processes and apparatuses to cool the
feed gas. In an embodiment, the feed gas is cooled within feed gas
supply line 1 to about its dew point or about its liquefying point
before cryogenic distillation. However other embodiments of the
invention may cool the feed gas to its liquefying point within the
distillation column or may cool the feed gas to a different
temperature level.
[0041] While an indirect heat exchanger has been illustrated for an
embodiment of the invention, other embodiments may use any method
for cooling common in the art. For example, and not by way of
limitation, various embodiments incorporate a turbo expander (not
shown) or a liquid stream (liquid assist) that is vaporized in the
process to supply the cold for the process. An embodiment utilizing
a turbo expander may use a portion of a vaporized liquid bottoms
removed from column 5. However, various other embodiments may
utilize other sources for the cooling common in the art.
[0042] Referring back to FIG. 1, the oxygen content of the feed gas
is enhanced by oxygen enhancing line 22. The oxygen content of the
feed gas may be enhanced by an oxygen supply added to the feed gas.
Depending upon the location of the injection, mixing point, or
contact point, the oxygen supply may be in any form, such as a
liquid, gas, a mixture of the aforementioned, and/or the like. In
an embodiment, the oxygen content is increased to between about 21%
by volume to about 40% by volume. However, the oxygen content may
be increased to any desired level.
[0043] In an embodiment, the oxygen is added prior to drying and
de-carbonating of the feed gas. Other manners of addition of the
oxygen supply will be readily apparent to those of skill in the art
and are fully covered by this disclosure. In various embodiments
varying levels of impurities, such as, for example and not by way
of limitation, moisture, carbon dioxide, hydrogen, and
hydrocarbons, may be removed. The feed gas is then passed into a
distillation column 5. In FIG. 1 the feed gas is passed to a lower
portion of a cryogenic distillation column 5.
[0044] In column 5, there is provided at least one tray 6 for
rectification. Column 5 is equipped with at least one tray or
contacting device, such as structure packing or other rectification
trays for removing impurities from the feed gas. In another
embodiment, there are multiple trays 6 for removing impurities. As
feed gas is supplied to column 5 the feed gas will begin to
separate and rectification will occur across the at least one tray
6.
[0045] A line 8 from a lower portion of Column 5 provides a path
for oxygen-enriched liquid bottoms, or liquid bottoms, to flow. A
portion of the oxygen-enriched liquid bottoms is then vaporized and
passed out waste line 11. The vaporized bottoms serves to condense
rising gas in column 5 as will be more fully described herein
below. Other embodiments may collect a portion of the oxygen
enriched liquid as a product or for other distillation or
rectification purposes. Such other purposes are well known in the
art field and are fully included in this disclosure.
[0046] The portion of the oxygen enriched liquid extracted at the
bottom of column 5, in an embodiment, is expanded to a lower
pressure and sent to the condenser where it is vaporized against
condensing gas of the top of the column. Liquefied condensing gas
is returned to the column as liquid reflux stream. Various
embodiments utilize waste line 11 as a coolant for indirect heat
exchange in heat exchanger 2. Other embodiments may use waste line
11 in another process or for another purpose, as will be readily
apparent to those of ordinary skill in the art.
[0047] In an embodiment, the portion of feed gas rising in column 5
is brought into gas-liquid contact in a countercurrent state with a
reflux liquid flowing down from above. As a result, the downward
liquid flow is gradually enriched in components whose boiling
points are higher than that of nitrogen to become oxygen-enriched
liquid. In the same manner, upward rising vapor is gradually
enriched in nitrogen to become nitrogen-enriched gas.
[0048] Nitrogen enriched gas which has passed through column 5 may
be extracted as synthetic air product through about line 13. The
oxygen content of the synthetic air product removed about line 13
will vary dependant upon many factors, including, but not limited
to, the number of rectification trays and the amount of oxygen
supply added to the feed gas.
[0049] The synthetic air product withdrawn at about line 13 may
have any desired oxygen content. In one embodiment, the oxygen
content is about 21% by volume. In another embodiment, the oxygen
content is about 15% by volume to about 40% by volume. In another
embodiment, the oxygen content is about 20% by volume to about 30%
by volume. However, an oxygen content of varying percentage may be
withdrawn dependant upon several factors, including, but not
limited to, the number of tray(s) 6 and the oxygen enhancement of
the feed gas. In embodiments utilizing a heat exchanger, the
synthetic air product may be warmed in indirect heat exchange with
feed gas to allow the temperature of the product to approach
ambient.
[0050] Synthetic air products produced by this process and
apparatus may be used as medical gases or for other end user
requirements. While a compressed synthetic air product gas has been
disclosed, the synthetic air product can be liquefied to yield a
liquid synthetic air product.
[0051] Now referring to FIG. 2, an illustration of an alternate
embodiment of an apparatus of the present invention for production
of a synthetic air product, a different location for oxygen content
enhancement is illustrated. In this embodiment, oxygen enhancing
line 23 is connected to feed gas supply line 10 after heat
exchanger 2.
[0052] Now referring to FIG. 3, an illustration of an alternate
embodiment of an apparatus of the present invention for production
of a synthetic air product, a different location for the oxygen
content enhancement is illustrated. In this embodiment, oxygen
enhancing line 25 is connected directly to column 5. Here, in an
embodiment, oxygen enhancement occurs with the feed gas at a
portion of column 5. In an embodiment, oxygen is added to the
distillation column below at least one tray 6.
[0053] Now referring to FIG. 4, an illustration of an alternate
embodiment of an apparatus of the present invention for production
of a synthetic air product, a different location for the oxygen
content enhancement is illustrated. In this embodiment, oxygen
enhancing line 26 is connected directly to column 5 at a tray
located at least one theoretical tray or real tray above the
connection of feed gas supply line 10 to column 5. Here, oxygen
enhancement of the feed gas occurs after the feed gas has been
introduced to column 5. In various embodiments, oxygen enhancing
line 26 is connected to column 5 above at least one real or
theoretical tray. In other embodiments, oxygen enhancing line 26
may be connected to column 5 above more than one tray. As in the
prior figures, oxygen supplied to the feed gas through oxygen
enhancing line 26 may be cooled prior to introduction, but such
cooling is not required. Other embodiments may also remove various
impurities to the oxygen before introduction to the feed gas, such
as, for example and not by way of limitation, moisture, carbon
dioxide, hydrogen, and hydrocarbons.
[0054] Now referring to FIG. 5, an illustration of an alternate
embodiment of an apparatus of the present invention, a compressor
is not used. An oxygen supply 27 and an other supply 28 are
supplied for mixing. In an embodiment, at least one of the oxygen
supply and the other supply are a liquid. In such cases, the liquid
is, vaporized in a vaporizer 30 and/or 31 and mixed in feed gas
supply line 1 for the production of a mixture before rectification.
In an embodiment, the other supply 28 is a nitrogen supply. As
well, other embodiments may use other methods of vaporizing liquid
and mixing of the components, such as mixing prior to introduction
to feed gas supply line 1. As in the other embodiments herein
disclosed, varying number of at least one tray(s) 6 may be used in
column 5 depending upon the level and type of impurities sought to
be removed.
[0055] The present invention further discloses a process or method
for preparation of a synthetic air product. The process generally
includes the cryogenic rectification of a feed gas that has been
enhanced by an oxygen stream. The process yields a synthetic air
product with varying percentage of oxygen content. Other
embodiments of the present process may include additional columns,
trays and removals of other products, such as an oxygen enriched
product, a nitrogen enriched product, and others. Other embodiments
may incorporate the use of a CO2 and moisture removal unit. Other
embodiments may utilize the mixing of a vaporized liquid nitrogen
and a vaporized liquid oxygen before rectification, including the
mixing of a gaseous source. Other embodiments may utilize a mixing
of an oxygen supply and a nitrogen supply during rectification.
Varying other embodiments of the present process will be readily
apparent to those of ordinary skill in the art.
[0056] Although various embodiments of the present invention have
been shown and described, various other modifications may be made
to the present invention while keeping within the scope and content
of the claims of the present invention. For instance, the present
invention is not intended to be limited to an embodiment for the
production of a synthetic air or a synthetic air product, but
rather may be a portion of a larger air separation process or other
process.
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