U.S. patent application number 12/257675 was filed with the patent office on 2009-05-14 for low temperature air fractionation with external fluid.
This patent application is currently assigned to LINDE AG. Invention is credited to Stefan LOCHNER.
Application Number | 20090120128 12/257675 |
Document ID | / |
Family ID | 39345197 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090120128 |
Kind Code |
A1 |
LOCHNER; Stefan |
May 14, 2009 |
Low Temperature Air Fractionation with External Fluid
Abstract
In low-temperature air fractionation, feed air (8) is cooled in
a main heat exchanger (9) and introduced into a distillation column
system for nitrogen-oxygen separation (11, 43), which system has at
least one single column (12). At least one nitrogen-enriched or
oxygen-enriched product stream (15, 16, 17; 53; 51, 56, 57; 19, 60)
is withdrawn from the distillation column system for
nitrogen-oxygen separation and warmed in the main heat exchanger
(9). A fluid from an external source is passed at least at times
into a liquid tank (70). At least at times fluid (71) is withdrawn
in the liquid state from the liquid tank (70), vaporized in the
main heat exchanger (9) and is obtained as gaseous additional
product (72, 73).
Inventors: |
LOCHNER; Stefan; (Munchen,
DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
LINDE AG
Munchen
DE
|
Family ID: |
39345197 |
Appl. No.: |
12/257675 |
Filed: |
October 24, 2008 |
Current U.S.
Class: |
62/643 |
Current CPC
Class: |
F25J 2215/50 20130101;
F25J 2220/50 20130101; F25J 2250/20 20130101; F25J 2200/90
20130101; F25J 2215/56 20130101; F25J 3/04048 20130101; F25J
3/04321 20130101; F25J 2200/94 20130101; F25J 2245/02 20130101;
F25J 3/04284 20130101; F25J 3/0426 20130101; F25J 3/0443 20130101;
F25J 2250/02 20130101; F25J 2290/62 20130101; F25J 3/0409
20130101 |
Class at
Publication: |
62/643 |
International
Class: |
F25J 3/00 20060101
F25J003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2007 |
DE |
10 2007 051 183.5 |
Claims
1. A process for low temperature air fractionation in which feed
air (8) is cooled in a main heat exchanger (9) and introduced into
a distillation column system for nitrogen-oxygen separation (11,
43), which system has at least one single column (12) for obtaining
nitrogen, at least one nitrogen-enriched or oxygen-enriched product
stream (15, 16, 17; 53; 51, 56, 57; 19, 60) is withdrawn from the
distillation column system for nitrogen-oxygen separation and
warmed in the main heat exchanger (9), the single column (12) has a
top condenser (13) in which vapor from the upper region of the
single column is at least in part condensed, a first residual
fraction (14, 19) is withdrawn in the liquid state from the lower
region of the single column (12) and at least in part vaporized in
the top condenser (13), at least a first part (20) of the first
residual fraction (19) is expanded downstream of the top condenser
(13) in an expansion machine (21) to produce work and in which a
second residual fraction (18, 29) is withdrawn from the lower or
intermediate region of the single column (12), recompressed (30)
and subsequently at least a first part is passed (32) back to the
single column (12) characterized in that a fluid from an external
source is passed at least at times into a liquid tank (70) and at
least at times fluid (71) is withdrawn in the liquid state from the
liquid tank (70), vaporized in the main heat exchanger (9) and is
obtained as gaseous additional product (72, 73), wherein neither
the fluid from the external source nor the gaseous additional
product (72, 73) is mixed with a product from the distillation
column system.
2. A process according to claim 1, characterized in that the fluid
(71) is not increased in pressure between liquid tank (70) and main
heat exchanger (9).
3. A process according to claim 1, characterized in that the fluid
(71) is introduced into the main heat exchanger (9) at a pressure
which is not higher than the operating pressure of the liquid tank
(70).
4. A process according to claim 1, characterized in that the
operating pressure of the liquid tank (70) is at least 1 bar above
atmospheric pressure.
5. A process according to claim 1, characterized in that the second
residual fraction (18, 29) is recompressed by means of a cold
compressor (30).
6. A process according to claim 1, characterized in that mechanical
energy generated in the work-producing expansion (21) is at least
in part applied to recompressing (30) the second residual
fraction.
7. A process according to claim 1, characterized in that a second
part of the first residual fraction (19) is not introduced
downstream of the top condenser (13) into the expansion machine
(21), but is taken off as gaseous impure oxygen product (60) and/or
a second part of the second residual fraction is taken off as
gaseous impure oxygen product (160) downstream of the recompression
(30).
8. A process according to claim 1, characterized in that an
oxygen-containing stream (36) is withdrawn from the single column
(12) at an intermediate point and passed (39) to a pure oxygen
column (38) and a pure oxygen product stream (41) is withdrawn in
the liquid state from the lower region of the pure oxygen column
(38), the pure oxygen product stream (41, 56), after optional
pressure elevation (55) in the liquid state, is vaporized and
warmed against feed air (8) in the main heat exchanger (9) and is
thus obtained as gaseous product (57).
9. A process according to claim 1, characterized in that the first
residual fraction (14) is taken off at the bottom of the single
column (12).
10. A process according to claim 1, characterized in that the
second residual fraction (18) is taken off from an intermediate
point arranged above the bottom of the single column (12), in
particular above the point at which the first residual fraction
(14) is withdrawn.
11. A process according to claim 1, characterized in that the main
heat exchanger (9) and the top condenser (13) are separate from one
another.
12. Apparatus for low temperature air fractionation having
distillation column system for nitrogen-oxygen separation which has
at least one single column (12) for obtaining nitrogen, a main heat
exchanger (9) for cooling feed air (8) a feed air line (11, 43) for
introducing cooled feed air into the distillation column system for
nitrogen-oxygen separation, means for feeding a nitrogen-enriched
or oxygen-enriched product stream (15, 16, 17; 53; 51, 56, 57; 19,
60) from the distillation column system for nitrogen-oxygen
separation to the main heat exchanger (9), a top condenser (13) for
the at least partial condensation of vapor from the upper region of
the single column, means for feeding a first liquid residual
fraction (14, 19) from the lower region of the single column (12)
to the top condenser (13), an expansion machine (21) for
work-producing expansion of at least a first part (20) of the first
residual fraction (19) downstream of the top condenser (13), a
recompressor (30) for recompressing a second residual fraction (18,
29) from the lower or intermediate region of the single column (12)
and having means for introducing at least a first part of the
recompressed second residual fraction into the single column (12),
characterized by a liquid tank for storage of a fluid from an
external source and means for withdrawing at least at times fluid
(71) in the liquid state from the liquid tank (70) vaporizing it in
the main heat exchanger (9) and obtaining it as gaseous additional
product (72, 73) wherein the device does not have an appliance for
mixing the fluid from the external source or the gaseous additional
product (72, 73) with a product from the distillation column
system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to concurrently filed
application "Process And Device For Low Temperature Air
Fractionation" by Stefan Lochner, Attorney Docket No. LINDE-0677,
claiming priority of DE 102007051184.3 filed Oct. 25, 2007,
incorporated by reference herein.
SPECIFICATION
[0002] Processes and devices for low temperature fractionation of
air are known, for example, from Hausen/Linde,
Tieftemperaturtechnik [Cryogenic engineering], 2nd edition 1985,
chapter 4 (pages 281 to 337). Examples of relevant air
fractionation processes are described in EP 412793 B2, EP 773417
B1, EP 780648 B1, EP 807792 B1, EP 932004 A2 and US 2007204652 A1.
It is known in such processes to withdraw a first oxygen-enriched
residual fraction from the single column, vaporize it and expand at
least a part of the vaporized residual fraction in an expansion
machine in a work-producing manner in order to generate the
refrigeration required to make up the exchange losses and, if
appropriate, for product liquefaction. The first residual fraction
is given off at the exit pressure of the expansion machine, that is
customarily at approximately atmospheric pressure, and can then
generally only be used as regeneration gas for an adsorption
appliance for purifying the feed air. In SPECTRA processes, a
second residual fraction can in this case be taken off from the
single column together with the first residual fraction and at
least in part vaporized; alternatively, the two residual fractions
can be withdrawn at different points of the single column and
vaporized separately from one another, for example in different
passages of the top condenser of the single column.
[0003] One object of this invention is to provide a particularly
economically favorable process.
[0004] Another object is to provide apparatus to perform the
process.
[0005] Upon further study of the specification and appended claims,
other objects and advantages will become apparent. The figures in
parentheses refer to drawings to facilitate an understanding of the
invention.
[0006] The process comprises a low temperature air fractionation
process in which [0007] feed air (8) is cooled in a main heat
exchanger (9) and introduced into a distillation column system for
nitrogen-oxygen separation (11, 43), which system has at least one
single column (12) for obtaining nitrogen, [0008] at least one
nitrogen-enriched or oxygen-enriched product stream (15, 16, 17;
53; 51, 56, 57; 19, 60) is withdrawn from the distillation column
system for nitrogen-oxygen separation and warmed in the main heat
exchanger (9), [0009] the single column (12) has a top condenser
(13) in which vapor from the upper region of the single column is
at least in part condensed, [0010] a first residual fraction (14,
19) is withdrawn in the liquid state from the lower region of the
single column (12) and at least in part vaporized in the top
condenser (13), [0011] at least a first part (20) of the first
residual fraction (19) is expanded downstream of the top condenser
(13) in an expansion machine (21) to produce work and in which
[0012] a second residual fraction (18, 29) is withdrawn from the
lower or intermediate region of the single column (12),
recompressed (30) and subsequently at least a first part is passed
(32) back to the single column (12), and [0013] an improvement
wherein [0014] a fluid from an external source is passed at least
at times into a liquid tank (70) and [0015] at least at times fluid
(71) is withdrawn in the liquid state from the liquid tank (70),
vaporized in the main heat exchanger (9) and is obtained as gaseous
additional product (72, 73), wherein neither the fluid from the
external source nor the gaseous additional product (72, 73) is
mixed with a product from the distillation column system.
[0016] The external fluid from the liquid tank is not, as is
customary, warmed by means of an external heat exchanger (for
example a water bath evaporator or an air-heated evaporator), but
in the main heat exchanger in which the feed air for the
distillation column system is cooled. By this means, the cold which
is present in the external fluid can be recovered for the
fractionation process by transmitting it to feed air in the main
heat exchanger.
[0017] The fluid originates from an "external source", that is to
say not from one of the separation columns of the distillation
column system for nitrogen-oxygen separation, or a separation
column connected downstream of the distillation column system for
nitrogen-oxygen separation. Preferably, it is transported from
another installation for generating liquefied gas, for example by
means of a tanker. It can be in this case a fluid which has the
chemical composition of one of the product streams of the
distillation column system for nitrogen-oxygen separation.
Preferably, however, the fluid has a different composition from
these product streams and consists, for example, of argon or
hydrogen. The process according to the invention is thereby
suitable, in particular, for supplying factories of the
semiconductor industry with industrial gases. These frequently
require such a low amount of argon and/or pure oxygen that it is
not worthwhile to connect a stage for obtaining argon downstream of
the distillation column system for nitrogen-oxygen separation. In
addition, the cold of gases such as hydrogen which are not obtained
in air fractionation plants is used for air fractionation and
thereby the energy consumption of fractionation is decreased.
[0018] The "main heat exchanger" is preferably formed by a single
heat exchange block. In relatively large plants it can be expedient
to implement the heat exchanger by a plurality of trains which are
connected in parallel with respect to the temperature course, which
trains are formed by construction elements which are separate from
one another. In principle, it is possible that the heat exchanger
for each of these trains is formed of two or more blocks connected
in series.
[0019] It is expedient if the pressure of the fluid is not
increased between liquid tank and main heat exchanger.
[0020] Preferably, the fluid is introduced into the main heat
exchanger at a pressure which is not higher than the operating
pressure of the liquid tank. The operating pressure of the liquid
tank can be constant or fluctuate, for example in the context of
maintaining pressure in the tank and the gas withdrawal system. In
the event that the operating pressure of the liquid tank
fluctuates, here the momentary operating pressure is meant.
[0021] It is expedient if the operating pressure of the liquid tank
is at least 1 bar above atmospheric pressure, preferably at least 1
bar above the product pressure of the gaseous additional product at
which this additional product is given off to an application or a
recompressor unit. The operating pressure of the liquid tank is,
for example, 2 to 36 bar, preferably 5 to 16 bar. The
superatmospheric pressure can be formed by any known measure, for
example by charging with a fluid at a corresponding pressure or by
pressurizing vaporization.
[0022] Further preferred embodiments of the invention include but
are not limited to processes wherein:
(a) the second residual fraction (18, 29) is recompressed by means
of a cold compressor (30), (b) the mechanical energy generated in
the work-producing expansion (21) is at least in part used for
recompressing (30) the second residual fraction, (c) a second part
of the first residual fraction (19) is not introduced downstream of
the top condenser (13) into the expansion machine (21), but is
taken off as gaseous impure oxygen product (60) and/or a second
part of the second residual fraction is taken off as gaseous impure
oxygen product (160) downstream of the recompression (30), (d) an
oxygen-containing stream (36) is withdrawn from the single column
(12) at an intermediate point and passed (39) to a pure oxygen
column (38) and a pure oxygen product stream (41) is withdrawn in
the liquid state from the lower region of the pure oxygen column
(38), the pure oxygen product stream (41, 56)--if appropriate after
pressure elevation (55) in the liquid state is vaporized and warmed
against feed air (8) in the main heat exchanger (9) and is finally
obtained as gaseous product (57), (e) the first residual fraction
(14) is taken off at the bottom of the single column (12), (f) the
second residual fraction (18) is taken off from an intermediate
point of the single column (12) which is arranged above the bottom,
in particular above the point at which the first residual fraction
(14) is withdrawn, and (g) the main heat exchanger (9) and the top
condenser (13) are formed by apparatuses which are separate from
one another.
[0023] More detailed descriptions of the above preferred
embodiments are incorporated by reference herein from concurrently
filed application attorney docket number LINDE-0677 by the present
inventor entitled "Process And Device For Low Temperature Air
Fractionation" claiming priority of German patent application
102007051184.3 filed Oct. 25, 2007.
[0024] The invention, in addition, relates to apparatus comprising
[0025] distillation column system for nitrogen-oxygen separation
which has at least one single column (12) for obtaining nitrogen,
[0026] a main heat exchanger (9) for cooling feed air (8) [0027] a
feed air line (11, 43) for introducing cooled feed air into the
distillation column system for nitrogen-oxygen separation, [0028]
means for feeding a nitrogen-enriched or oxygen-enriched product
stream (15, 16, 17; 53; 51, 56, 57; 19, 60) from the distillation
column system for nitrogen-oxygen separation to the main heat
exchanger (9), [0029] a top condenser (13) for the at least partial
condensation of vapour from the upper region of the single column,
[0030] means for feeding a first liquid residual fraction (14, 19)
from the lower region of the single column (12) to the top
condenser (13), [0031] an expansion machine (21) for work-producing
expansion of at least a first part (20) of the first residual
fraction (19) downstream of the top condenser (13), [0032] a
recompressor (30) for recompressing a second residual fraction (18,
29) from the lower or intermediate region of the single column (12)
[0033] and having means for introducing at least a first part of
the recompressed second residual fraction into the single column
(12), and [0034] an improvement wherein: [0035] a liquid tank for
storage of a fluid from an external source and [0036] means for
withdrawing at least at times fluid (71) in the liquid state from
the liquid tank (70) vaporizing it in the main heat exchanger (9)
and obtaining it as gaseous additional product (72, 73) [0037]
wherein the device does not have an appliance for mixing the fluid
from the external source or the gaseous additional product (72, 73)
with a product from the distillation column system.
BRIEF DESCRIPTION OF DRAWING
[0038] The invention and also further details of the invention will
be described in more detail hereinafter with reference to an
exemplary embodiment shown diagrammatically in the drawing.
DETAILED DESCRIPTION OF DRAWING
[0039] The distillation column system of the exemplary embodiment
has a single column 12 and a pure oxygen column 38. (The invention
is likewise applicable to a similar process without pure oxygen
column.) Atmospheric air 1 is drawn in through a filter 2 by an air
compressor and there compressed to an absolute pressure of 6 to 20
bar, preferably about 9 bar. After it flows through an aftercooler
4 and a water separator 5, the compressed air 6 is purified in a
purification device 7 which has a pair of containers filled with
adsorption material, preferably a molecular sieve. The purified air
8 is cooled to about dew point in a main heat exchanger 9 and in
part liquefied. A first part 11 of the cooled air 10 is introduced
via a throttle valve 51 into the single column 12. Said cooled air
is fed in preferably some practical or theoretical plates above the
bottom.
[0040] The operating pressure of the single column 12 (at the top)
is 6 to 20 bar, preferably about 9 bar. Its top condenser is cooled
by a second residual fraction 18 and a first residual fraction 14.
The first residual fraction 14 is taken off from the bottom of the
single column 12, the second residual fraction 18 from an
intermediate point some practical or theoretical plates above the
air infeed or at the same height as this.
[0041] As the main product of single column 12, gaseous nitrogen
15, 16 is taken off at the top, warmed in the main heat exchanger 9
to approximately ambient temperature and finally taken off via line
17 as pressurized gaseous product (PGAN). A part 53 of the
condensate 52 from the top condenser 13 can be obtained as product
liquid nitrogen (PLIN); the remainder 54 is applied as reflux to
the top of the single column.
[0042] The second residual fraction 18 is vaporized in the top
condenser 13 at a pressure of 2 to 9 bar, preferably about 4 bar,
and flows in the gaseous state via line 29 to a cold compressor 30
in which it is recompressed to approximately the operating pressure
of the single column. The recompressed residual fraction 31 is
cooled back to column temperature in the main heat exchanger 9 and
finally fed back via line 32 to the single column 12 at the
bottom.
[0043] The first residual fraction 14 is vaporized in the top
condenser 13 at a pressure of 2 to 9 bar, preferably about 4 bar,
and flows in the gaseous state via line 19 to the cold end of the
main heat exchanger 9. A first part 20 of the first residual
fraction is withdrawn again (line 20) at an intermediate
temperature. A second part remains in the main heat exchanger 9, is
warmed there again to approximately ambient temperature and leaves
the installation via line 60 as gaseous impure oxygen product
(GOX-Imp.). The first part 20 of the first residual fraction is
expanded to about 300 mbar over atmospheric pressure so as to
produce work in an expansion machine 21 which is constructed in the
example as a turbo expander. The expansion machine is mechanically
coupled to the cold compressor 30 and a braking appliance 22 which,
in the exemplary embodiment, is formed by an oil brake. The
expanded first residual fraction 23 is warmed in the main heat
exchanger 9 to approximately ambient temperature. The warm first
residual fraction 24 is blown off to atmosphere (line 25) and/or
used as regeneration gas 26, 27 in the purification device 7, if
appropriate after heating in the heating appliance 28.
Alternatively, or in addition, an impure oxygen product can be
branched off from the recompressed second residual fraction 31 and
warmed in the main heat exchanger 9 to approximately ambient
temperature.
[0044] An oxygen-containing stream 36 which is essentially free of
low volatility impurities is taken off from an intermediate point
of the single column 12 in the liquid state, which intermediate
point is arranged 5 to 25 theoretical or practical plates above the
air infeed. The oxygen-containing stream 36 is, if appropriate,
subcooled in a bottoms evaporator 37 of the pure oxygen column 38
and applied to the top of the pure oxygen column 38 via line 39 and
throttle valve 40. The operating pressure of the pure oxygen column
38 (at the top) is 1.3 to 4 bar, preferably about 2.5 bar.
[0045] The bottoms evaporator 37 of the pure oxygen column 38 is in
addition cooled by means of a second part 42 of the cooled feed air
10. The feed air stream 42 is in this case at least in part, for
example completely, condensed and flows via line 43 to the single
column 12 where it is introduced approximately at the height of the
infeed of the remaining feed air 11.
[0046] From the bottom of the pure oxygen column 38, a pure oxygen
product stream 41 is withdrawn in the liquid state, brought by
means of a pump 55 to an elevated pressure of 2 to 100 bar,
preferably about 12 bar, passed via line 56 to the cold end of the
main heat exchanger 9, vaporized there at the elevated pressure and
warmed to about ambient temperature and finally obtained via line
57 as gaseous product (GOX-IC).
[0047] The overhead gas 58 of the pure oxygen column 38 is admixed
to the expanded first residual fraction 23. Via a bypass line 59,
if appropriate a part of the feed air is passed for pump protection
of the cold compressor 30 to the inlet thereof (anti-surge
control).
[0048] If required, a liquid oxygen can be withdrawn as liquid
product from the installation upstream and/or downstream of the
pump 55 (not shown in the drawing). In addition, an external
liquid, for example liquid argon, liquid nitrogen or liquid oxygen
from a liquid tank can be vaporized in the main heat exchanger 9 in
indirect heat exchange with the feed air (not shown in the
drawing).
[0049] A liquid tank 70 is filled with liquid argon as "fluid" from
time to time from a tanker. The fluid is introduced at about 12
bar, the operating pressure of the liquid tank. Liquid fluid is
withdrawn continuously via line 71 at about 12 bar, vaporized at
this pressure in the main heat exchanger 9 and warmed and finally
taken off as gaseous additional product via lines 72 and 73.
[0050] In addition, a further stream 74 of the liquid pressurized
fluid can be withdrawn from the liquid tank 70, vaporized in an
evaporator 75 which is heated by means of an external heat carrier
(for example atmospheric air or water) and added via line 76 to the
gaseous additional product. The evaporator 75 can, however, also be
used for emergency supply in the event of loss of the main heat
exchanger 9. The flow rates are set by means of the valves 77 and
78.
[0051] The process according to the invention and the corresponding
device can be used particularly expediently in the semiconductor
industry or in the pyrogenic silicic acid production which require
not only nitrogen but also impure oxygen and if appropriate pure
oxygen as products.
[0052] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0053] The entire disclosures of all applications, patents and
publications, cited herein and of corresponding DE application No.
102007051183.5, filed Oct. 25, 2007, as well as concurrently filed
the disclosure relating to claims 5-11 in particular, incorporated
by reference herein.
[0054] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *