U.S. patent application number 12/089092 was filed with the patent office on 2009-08-27 for method for evaporation and/or condensation in a heat exchanger.
Invention is credited to Jean-Pierre Tranier, Marc Wagner.
Application Number | 20090211733 12/089092 |
Document ID | / |
Family ID | 36809237 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090211733 |
Kind Code |
A1 |
Tranier; Jean-Pierre ; et
al. |
August 27, 2009 |
METHOD FOR EVAPORATION AND/OR CONDENSATION IN A HEAT EXCHANGER
Abstract
The invention concerns a method for evaporation and/or
condensation of at least one fluid in a heat exchanger consisting
of a stack of at least one tube (3) and of at least one folded
corrugation (17), the corrugation and the tube being preferably
brazed together, wherein a fluid flows inside at least one tube,
and another fluid flows around the corrugation (17). The invention
also concerns an installation for separating a mixture of fluids by
cryogenic distillation, comprising a heat exchanger operating in
accordance with such a method.
Inventors: |
Tranier; Jean-Pierre;
(L'Hay-Les-Roses, FR) ; Wagner; Marc;
(Saint-Maur-Des-Fosses, FR) |
Correspondence
Address: |
AIR LIQUIDE;Intellectual Property
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Family ID: |
36809237 |
Appl. No.: |
12/089092 |
Filed: |
September 29, 2006 |
PCT Filed: |
September 29, 2006 |
PCT NO: |
PCT/FR2006/050962 |
371 Date: |
October 6, 2008 |
Current U.S.
Class: |
165/104.21 ;
165/164 |
Current CPC
Class: |
F25J 3/04412 20130101;
F25J 2290/44 20130101; F25J 2250/04 20130101; F25J 5/007 20130101;
F25J 2200/80 20130101; F25J 2210/18 20130101; F25B 2339/041
20130101; F28F 1/126 20130101; F28F 9/02 20130101; F28D 2021/0033
20130101; F28D 7/1684 20130101; F25J 5/005 20130101; F28F 21/08
20130101; F25J 5/002 20130101; F25J 2250/02 20130101 |
Class at
Publication: |
165/104.21 ;
165/164 |
International
Class: |
F28D 7/00 20060101
F28D007/00; F28D 15/00 20060101 F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2005 |
FR |
0553028 |
Claims
1-17. (canceled)
18. A method for the vaporization and/or condensation of at least
one fluid in a heat exchanger consisting of a stack of at least one
tube and of at least one corrugated fin, the fin and the tube being
preferably brazed to each other and in which heat exchanger a first
fluid, optionally to be condensed, flows inside at least one tube
and a second fluid, optionally to be vaporized, flows around the
fin, in which a) the first fluid condenses and the second fluid
vaporizes or b) the first fluid vaporizes and the second fluid
condenses.
19. The method of claim 18, in which the corrugation of the fins is
approximately parallel to the axis (X or Z in the case of FIG. 2;
Z.sub.0) of the tubes.
20. The method of claim 18, wherein the tubes and the fins are made
of pure or alloyed aluminum.
21. The method of claim 18, wherein the tubes and the fins are made
of a copper-based alloy.
22. The method of claim 18, wherein the tubes and the fins are made
of an iron-based alloy.
23. The method of claim 18, wherein the tubes are oblong and/or
flattened.
24. The method of claim 18, wherein part of the exchange area is
inside the tubes.
25. The method of claim 18, wherein the exchange area inside the
tubes is obtained by folding, by extrusion or by preferably brazed
inserts.
26. The method of claim 18, wherein the fins are perforated,
straight, serrated (with a partial offset), herringbone
(zigzagged), and/or louvered.
27. The method of claim 18, in which the first fluid flows inside
at least one tube along a descending vertical direction.
28. The method of claim 27, in which the first fluid is a fluid
that vaporizes in the at least one tube and the second fluid,
optionally to be condensed, flows around the fin in a descending
vertical direction.
29. The method of claim 27, in which a fluid to be vaporized (the
second fluid) flows around the fin in an ascending vertical
direction.
30. The method for vaporization of at least one liquid derived from
air and optionally for condensation of at least one gas derived
from air, or which is air, of claim 18,
31. The method for vaporization of at least one liquid having
methane and/or carbon monoxide and/or hydrogen as main component
and optionally for condensation of at least one gas having methane
and/or carbon monoxide and/or hydrogen as main component of claim
18.
32. An installation for separating a mixture of fluids by cryogenic
distillation in at least one column having at least one heat
exchanger operating according to the method of claim 18.
33. The installation of claim 32, in which at least one of the heat
exchangers comprises: a) a reboiler/condenser for vaporization of a
liquid by heat exchange with a gas, which condenses inside or
outside a distillation column; or b) a subcooler; or c) a
regeneration gas heater for a purification unit used for purifying
the mixture to be distilled; or d) a dephlegmator; or e) a heat
exchanger having passages for cooling the mixture to be distilled
at a cryogenic temperature; or f) an exchanger for cooling an
interstage of a compressor for compressing the mixture to be
distilled or a product of the distillation.
34. The installation of claim 33, in which a reboiler/condenser
located inside the distillation column consists of several
exchangers, the exchangers being of different widths so as to fill
the entire cross section of the column.
Description
[0001] The present invention relates to a method for vaporization
and optionally condensation of a fluid in a heat exchanger and to
an installation for separating a mixture of fluids by cryogenic
distillation, which includes at least one heat exchanger operating
according to such a method. In particular, it relates to a method
for vaporization and optionally condensation of air gases in an
installation for separating air gases by cryogenic
distillation.
[0002] Air gas separation units have used brazed aluminum plate
heat exchangers for a very long time for reboiler/condenser
functions of the distillation columns, especially the
reboiler/condenser of the double column with nitrogen condensing
and oxygen vaporizing.
[0003] Two operating principles for these reboiler/condensers have
been proposed: [0004] in thermosiphon mode: this is the oldest
solution, with two variants: [0005] 1) the body of the vaporizer
may be placed vertically and completely (or partly) immersed in a
liquid oxygen bath. This liquid oxygen enters at the bottom of the
vaporizer, is warmed up to its bubble point and then partly
vaporized. The recirculation ratio (flow of excess liquid at the
outlet to the vaporized flow) is very high, possibly ranging from 5
to 100. The dimensions of the bodies may be around 1220 mm in
width.times.1200 mm in stacking direction.times.2000 mm in length.
One of the drawbacks is that even though the minimum temperature
difference in the exchanger may be low (0.3-0.4.degree. C.), the
apparent difference (the difference between the temperature of the
nitrogen entering the reboiler/condenser and the temperature of the
vaporized oxygen) remains high (1.2-1.6.degree. C.) because of the
hydrostatic head of liquid, which increases the pressure of said
liquid at the bottom of the exchanger and therefore its
vaporization temperature. It would be conceivable to reduce the
hydrostatic head by not completely immersing the vaporizer, but
then the recirculation ratio would be reduced. However, it is
dangerous to operate with zero (or low) recirculation since by
entirely vaporizing the liquid oxygen (generally or locally), the
solubility limit of certain heavy constituents (for example
hydrocarbons) is reached in the last drop of liquid to be
vaporized. These heavy constituents run the risk of being deposited
in the vaporizer and causing an explosion therein and combustion of
the aluminum; and [0006] 2) the body of the vaporizer is placed
horizontally and completely (or partly) immersed in a liquid oxygen
bath. The operation is identical to that of the vertically
installed vaporizer. By reducing the hydrostatic head, the
operation on the oxygen side is improved. However, the design of
the nitrogen passages is not obvious. Either the length of the
exchanger body (which is cubic) is limited and the same plane of
flow is used as for the vertical bodies, or the same body length
(2000 mm or more) is retained but it is then necessary to make the
nitrogen flow horizontally (otherwise the distributors would assume
the entire height of the body) with cross-flow, thereby resulting
in heating asymmetry, which may degrade the performance, and also
defects in discharging the liquid nitrogen (gravity driving it
toward the bottom of the passages), which also locally degrades the
exchange coefficient; and [0007] in film mode: a more recent
solution, described in particular in U.S. Pat. No. 4,599,097.
[0008] The liquid is distributed over vertical plates. The
hydrostatic pressure therefore no longer adversely affects the
exchange and small temperature differences (of less than 1.degree.
C.) may be obtained. However, if it is desired to provide excess
liquid at the outlet of the exchanger, to avoid dry vaporization
and deposition of heavy constituents, a pump is needed. Put another
way, the operation is potentially dangerous for the same reasons as
for reboilers/condensers.
[0009] EP-A-1 008 826 proposes a falling-film evaporator in which
the exchanger comprises passages defined by parallel plates. The
liquid vaporization passages contain auxiliary passages that have
only curved surfaces, for example cylindrical tubes.
[0010] Moreover, two design types exist: reboiler/condenser inside
a column or a shell, or an external vaporizer, for example
described in U.S. Pat. No. 5,333,683.
[0011] One object of the invention is to provide a condensation
and/or vaporization method using a heat exchanger that alleviates
the drawbacks of the prior art and more generally an alternative
heat exchange method to that carried out in a brazed aluminum plate
exchanger, derived from the technology currently used in automobile
radiators.
[0012] For this purpose, one subject of the invention is a method
for the vaporization and/or condensation of at least one fluid in a
heat exchanger consisting of a stack of at least one tube and of at
least one corrugated fin, the fin and the tube being preferably
brazed to each other and in which heat exchanger a first fluid,
optionally to be condensed, flows inside at least one tube and a
second fluid, optionally to be vaporized, flows around the fin, in
which a) the first fluid condenses and the second fluid vaporizes
or b) the first fluid vaporizes and the second fluid condenses.
[0013] The method according to the invention may furthermore
comprise one or more of the following features: [0014] the
corrugation of the fins is approximately parallel to the axis of
the tubes; [0015] the tubes and the fins are made of pure or
alloyed aluminum; [0016] the tubes and the fins are made of a
copper-based alloy; [0017] the tubes and the fins are made of an
iron-based alloy; [0018] the tubes are oblong and/or flattened;
[0019] part of the exchange area is inside the tubes; [0020] the
tube has parallel channels on the inside, comprising two parallel
flat walls and internal walls which are connected to the two flat
walls and define the parallel channels; [0021] the exchange area
inside the tubes is obtained by folding, by extrusion or by
preferably brazed inserts, for example fins; and [0022] the fins
are perforated, straight, serrated and/or louvered.
[0023] Alternatively, it would be conceivable for the vaporization
to take place in the tubes, and the subject of the invention would
then be a method for vaporization and optionally condensation of at
least one fluid in a heat exchanger consisting of a stack of at
least one tube and at least one corrugated fin, the fin and the
tube preferably being brazed to each other, and in which a fluid to
be vaporized flows inside at least one tube and another fluid,
optionally to be vaporized, flows in channels generated by
fins.
[0024] The invention aims more particularly to provide a method for
vaporization of at least one liquid derived from air and optionally
for condensation of at least one gas derived from air, or which is
air, as described above.
[0025] The aim of the invention is also to provide a method for
vaporization of at least one liquid having methane and/or carbon
monoxide and/or hydrogen as main component and optionally for
condensation of at least one gas having methane and/or carbon
monoxide and/or hydrogen as main component, as described above.
[0026] Finally, the object of the invention is to provide an
installation for separating a mixture of fluids by cryogenic
distillation in at least one column having at least one heat
exchanger operating according to a heat exchange method in a heat
exchanger consisting of a stack of at least one tube and of at
least one corrugated fin, the fin and the tube preferably being
brazed to each other, and in which a fluid flows inside at least
one tube and another fluid flows around the fin, one is heated
while the other is cooled.
[0027] Preferably, at least one of the heat exchangers of such an
installation is one of the types below: [0028] i) a
reboiler/condenser for vaporization of a liquid by heat exchange
with a gas, which condenses inside or outside a distillation
column; or [0029] ii) a subcooler; or [0030] iii) a regeneration
gas heater for a purification unit used for purifying the mixture
to be distilled; or [0031] iv) a dephlegmator; or [0032] v) a heat
exchanger having passages for cooling the mixture to be distilled
at a cryogenic temperature; or [0033] vi) an exchanger for cooling
an interstage of a compressor for compressing the mixture to be
distilled or a product of the distillation.
[0034] There are many advantages of such a solution: [0035] 1) the
manufacture of the exchangers may benefit from the infrastructures
available for manufacturing automobile radiators, allowing a very
substantial reduction in the cost and lead times in manufacturing
these exchangers. At the present time, it takes several months to
design and manufacture brazed aluminum bodies. Using the technology
of automobile radiators, once standard sizes have been defined,
their manufacture will require only a few days; [0036] 2) this
technology will also allow other alternatives as regards materials.
Admittedly, aluminum will remain one option, but it will be
possible to produce copper/bronze or stainless steel exchangers. At
the same time, by obviating the risk of aluminum catching fire (for
example by using copper-based alloys), the use of reboilers and
falling-film condensers is made safer; [0037] 3) using the
conventional technology of brazed aluminum plate exchangers, when
it is desired to place them in the circular shell of a distillation
column, the useful cross section (exchange area) occupies only
about 50% of the cross section of the column. Using this "radiator"
technology, there is no longer a need to place the boxes and
headers at the same height as the exchange bodies. They may be
advantageously placed above and below the exchangers; and [0038] 4)
by no longer brazing large bodies and using copper-based alloys,
there is no longer the risk of the fins collapsing or the risk of
aluminum catching fire, since the material is much stronger and
does not release energy in the event of combustion, and the
thickness of the fins on the vaporization side may therefore be
considerably reduced (down to 50 .mu.m).
[0039] However, even though the automobile radiator technology may
be used, certain adaptations are necessary in order to make it even
more beneficial for use in a reboiler/condenser: [0040] 1)
replacement of the cross-flow with countercurrent flow in the case
of vaporization in thermosiphon mode: the headers are placed
vertically in an automobile radiator. In a thermosiphon
reboiler/condenser, in which the direction of the fluid undergoing
condensation in the tubes is countercurrent to the direction of the
vaporizing fluid in the channels generated by the fins, owing to
condensation in the tubes, the gas header wilt be placed at the top
and the liquid header at the bottom, so as to make gravity flow of
the liquid easier; [0041] 2) replacement of the cross-flow with
cocurrent flow in the case of falling-film vaporization: in this
case, the direction of the fluid undergoing condensation in the
tubes is cocurrent with the direction of the fluid vaporizing in
the channels generated by the fins, and a device for feeding the
liquid to be vaporized must be added at the top of the fins; [0042]
3) in a radiator, water is often cooled in the tubes against the
air in the fins. Since the exchange coefficient on the air side is
appreciably lower than on the water side (by a factor of at least
10), the exchange area is increased on the air side thanks to the
fins. In the case of vaporization/condensation, the exchange
coefficients on the two sides are of the same order of magnitude.
It is therefore beneficial to have similar exchange areas, hence
the solution consisting in having additional surface inside the
tubes: inserts, fins (brazed or not), corrugations, extrusion, etc.
(U.S. Pat. No. 6,241,012); and [0043] 4) such a structure could
also operate as a dephlegmator.
[0044] Finally, the use of exchangers derived from automobile
radiator technology in gas separation by cryogenic distillation is
not limited to reboiler/condensers, which vaporize a fluid by heat
exchange with another fluid, which condenses, but may also be used
for: [0045] regeneration gas heaters for purification units; [0046]
subcoolers; [0047] principal exchangers, especially for vaporizing
under pressure gaseous oxygen in tubes made of a copper-based alloy
with respect to air, which condenses; and [0048] compressor
interstage cooling exchangers.
[0049] Particular embodiments of the invention will now be
described with reference to the appended drawings, in which:
[0050] FIG. 1 is a front elevation view of a heat exchanger of a
first type according to the invention;
[0051] FIG. 2 is a schematic perspective view of a heat exchanger
for implementing the method according to the invention;
[0052] FIG. 3 is a perspective view, on a larger scale and along
the same direction, of part of the exchanger shown in FIG. 1
according to a first embodiment;
[0053] FIG. 4 is a perspective view showing a tube portion of the
exchanger of FIG. 2 according to a second embodiment;
[0054] FIG. 5 is a sectional view, in a vertical plane, of a stack
of tubes and fins of a heat exchanger according to a third
embodiment; and
[0055] FIGS. 6 and 7 are schematic views, of the top and front
respectively, of a reboiler/condenser of an installation according
to the invention, which contains exchangers of a second type,
similar to the first shown in FIGS. 1 and 2.
[0056] FIG. 1 shows schematically a heat exchanger 1 having a
structure similar to that of the exchangers used in motor vehicle
cooling circuits.
[0057] For convenience in the following description, FIGS. 1 to 5
will be oriented with respect to the orthogonal reference frame X,
Y, Z, in which: [0058] the X and Z axes define the vertical plane
of FIG. 1 and the principal directions along which the exchanger 1
lies, the X axis being supposed to be horizontal and the Z axis
supposed to be vertical; and [0059] the Y axis is the transverse
horizontal axis.
[0060] The exchanger shown in FIG. 1 essentially comprises, on the
one hand, a stack of elongate tubes 3 spaced apart and mutually
parallel, which extend horizontally along the X axis and, on the
other hand, corrugated oblong fins (not visible in FIG. 1) placed
in the gaps between two consecutive tubes 3.
[0061] The tubes 3 are connected at one of their ends to a
distribution column 5 and at their other end to a collecting column
7. The two columns 5, 7 are formed from vertical tubular pipes in
fluid communication with each of the tubes 3. Preferably, the tubes
3 are brazed to the columns 5, 7, said columns being formed
beforehand so as to allow the tubes 3 to be fitted into them. These
columns are not necessarily of cylindrical shape. Each may be a
tubular plate recessed so as to allow the tubes to be fitted into
it, onto which plate the tubes will preferably have been brazed and
to which a box, typically of semicylindrical shape, will be
attached, for example by welding after the brazing operation.
[0062] The distribution column 5 is equipped in an upper part with
a fluid inlet coupler 9 allowing the exchanger 1 to be supplied
with a first fluid.
[0063] The collecting column 7 is correspondingly provided, in a
lower part, with an outlet coupler 11 for evacuating the first
fluid from the exchanger 1.
[0064] The couplers 9, 11 are shown schematically in FIG. 2.
[0065] The exchanger shown in FIG. 2, like that in FIG. 1,
essentially comprises, on the one hand, a stack of elongate tubes
3, spaced apart and mutually parallel, and, on the other hand,
corrugated oblong fins (not visible in FIG. 2) placed in the gaps
lying between two consecutive tubes 3. Now, in the case of the
invention, the elongate tubes 3 extend vertically along the Z axis
and the corrugation or folding direction of the fins 17 in FIG. 2
is parallel to the longitudinal axis of the tubes 3, that is to say
parallel to the Y axis.
[0066] The tubes 3 are connected at their upper end to a
distribution column 5 and at their other end to a collecting column
7. The two columns 5, 7 are formed from vertical tubular pipes
placed horizontally and in fluid communication with each of the
tubes 3. Preferably, the tubes 3 are brazed to the columns 5, 7,
said columns being formed beforehand so as to allow the tubes 3 to
be fitted into them. These columns are not necessarily of
cylindrical shape. Each may be a tubular plate recessed so as to
allow the tubes to be fitted into it, onto which plate the tubes
will preferably have been brazed and to which a box, typically of
semicylindrical shape, will be attached, for example by welding
after the brazing operation.
[0067] The distribution column 7 is equipped on the left with an
inlet coupler 11, allowing the exchanger 1 to be supplied with a
first fluid in gaseous form. The coupler extends perpendicularly to
the axis of the distribution column and to the axis of the tubes.
This coupler may nevertheless extend along another direction, for
example along the Z axis or possibly the Y axis.
[0068] The collecting column 5 is correspondingly provided, in a
lower part, with an outlet coupler 9 for evacuating the first fluid
from the exchanger 1. The coupler extends perpendicularly to the
axis of the distribution column and to the axis of the tubes.
However, this coupler could extend in another direction, for
example along the Z axis or possibly the Y axis.
[0069] The couplers 9, 11 have been shown schematically in FIG.
2.
[0070] In the case of vaporization in thermosiphon mode, a fluid to
be vaporized (a second fluid) flows over the fins 17, in an
ascending vertical direction (i.e. the fluid to be vaporized is
made to flow in the channels generated by the corrugations), and a
fluid at higher temperature (first fluid) is made to flow inside
the tubes 3 along a descending vertical direction.
[0071] In the case of falling-film vaporization, a fluid optionally
to be condensed flows over the fins 17 in a descending vertical
direction (i.e. the fluid optionally to be condensed is made to
flow in the channels generated by the fins) and a lower temperature
fluid to be vaporized is made to flow inside the tubes 3 along a
descending vertical direction.
[0072] FIG. 3 shows a portion of part of the exchanger 1 of FIG. 1,
consisting of two consecutive tubes 3 and a corrugated fin 17
provided between these two tubes.
[0073] As may be seen in this figure, the tubes 3 have a running
section, in the XY vertical plane, of transversely elongate shape
along the X axis, so that they each have two approximately plane
and parallel opposed faces. In other words, the tubes 3 have an
oblong cross section on the transverse axis X that is of flattened
shape.
[0074] The fin 17 is corrugated along a corrugation or folding
direction Y perpendicular to the longitudinal axis of the tubes 3.
The fin 17 is fixed to the tubes 3, preferably by brazing, at its
peaks 19. This brazing operation may be concomitant with the
brazing of the tubes 3 to the columns 5, 7.
[0075] The fins 17 may be of any suitable type, for example one of
the following types commonly used in plate heat exchangers, namely:
perforated fins, straight fins, serrated (partially offset) fins,
herringbone (zig-zag) fins and louvered fins.
[0076] The fins 17 may have, in cross section in the YZ plane, a
sinusoidal, rectangular or triangular shape, or may have any other
suitable type of geometric pattern.
[0077] The hydraulic diameter of the channels formed by the fins 17
is typically between 100 .mu.m and 10 mm.
[0078] These fins may be made of solid sheet metal, perforated
sheet metal, sintered metal or any other metal structure (foam,
etc.).
[0079] The tubes 3 and the fins 17 may be made of pure or alloyed
aluminum.
[0080] As a variant, the tubes 3 and the fins 17 may be made of a
copper-based alloy.
[0081] As another variant, the tubes 3 and the fins 17 may be made
of an iron-based alloy.
[0082] The exchanger 1 in FIG. 2 has fins 17 no longer oriented
along the X axis but along the Z axis.
[0083] In the example shown in FIG. 4, the internal volume bounded
by each tube is divided longitudinally into two. To do this, the
tube 103 has its upper face cut along a longitudinal mid-line, the
two edges 21, 22 separated by this line being turned down toward
the interior of the tube and welded to the lower wall. The strips
thus turned down are contiguous and form a double wall separating
the two longitudinal compartments 103A, 103B thus defined. These
compartments are called channels.
[0084] The edges 21, 22 may for example be welded to the lower wall
by laser welding.
[0085] A heat exchanger made up from tubes of this type is better
able to withstand the pressure of the fluid flowing in the channels
103A, 103B since they are smaller than the tube 3. Such a design
may be used to generate a number of channels greater than 2.
[0086] Incidentally, a heat exchanger made up from tubes of this
type is capable of operating with three different fluids, one
flowing over the fins, another flowing in the channel 103A and the
third flowing in the other channel 103B.
[0087] Thus, it is possible to make two different fluids flow in
the two channels 103A, 103B, between which fluids a heat exchange
takes place so that part of the exchange area, obtained by folding
the edges 21, 22, is inside the tube 103.
[0088] FIG. 5 illustrates another embodiment of a stack of tubes
and fins suitable for implementing the method according to the
invention.
[0089] In this stack, the tubes 203 are again tubes of transversely
elongate cross section having plane and parallel opposed faces.
However, their internal volume is divided into a plurality of
parallel longitudinal channels 203A separated by mutually parallel
plane walls 23, which here are vertical. The hydraulic diameter of
these channels is typically between 100 .mu.m and 10 mm.
[0090] The walls 23 can be made as a single entity with the
external walls of the tube 203, for example by extrusion, or else
they may consist of inserts, preferably brazed inserts. These
inserts may be very similar to the fins 17.
[0091] In the example shown, each layer of tubes consists of two
adjacent parallel tubes lying in the same plane.
[0092] Thus, part of the exchange area lies inside the tubes
203.
[0093] Optionally, a wall 204 surrounds the tubes 203 and the fins
17 so as to seal the exchanger from its environment. This wall may
be brazed to the tubes 203 or simply enclosed around the tubes
203.
[0094] In the embodiment shown in FIG. 5, and unlike the embodiment
shown in FIG. 3, the fluid to be vaporized that flows over the fins
17, flows parallel to the fluids to be condensed that flow in the
tubes 203. Preferably, the fluids to be condensed on the one hand
and the fluid to be vaporized on the other will flow in opposite
directions.
[0095] FIGS. 6 and 7 show schematically part of the installation
according to the invention, which comprises, inside a shell 31 of
cylindrical general shape, a series of exchangers 301a-301n of the
same type, similar to that shown in FIGS. 1 and 2.
[0096] In these figures, the orthogonal reference frame X.sub.0,
Y.sub.0, Z.sub.0 shown is defined as follows: [0097] the
Z.sub.0axis is the upwardly oriented vertical axis; [0098] the
X.sub.0 axis is the horizontal axis defining, with the Z.sub.0axis,
the principal planes in which the exchangers 301 lie; and [0099]
the Y.sub.0axis is the horizontal axis orthogonal to the
X.sub.0axis.
[0100] The exchangers 301a-301n are all parallel to one another and
centered with respect to a diametral plane of the cylindrical shell
31, as may be seen in FIG. 6. The length of each exchanger 301a-n
is adjusted to the length, along the X.sub.0 axis, of the vertical
cross section of the shell 31 on the Y.sub.0 axis. Thus, the length
along the X.sub.0 axis of the exchangers 301a-301n increases toward
the central axis Z.sub.0 of the cylindrical shell 31.
[0101] Unlike the orientation of the exchanger 1 shown in FIG. 1,
the orientation of the exchangers 301a-n is such that the
distribution columns 305a-n extend horizontally from the upper side
of the shell 31, whereas the collecting columms 307a-n extend from
the lower side of the shell 31, again horizontally. Thus, the
stacks of tubes 303 extend between the columns 305a-n, 307a-n,
along the vertical axis Z.
[0102] Placed above the distribution columns 305a-n there is a gas
header 41 designed for supplying the group of exchangers 301a-n
with gas.
[0103] The installation shown also includes a liquid header 43
placed beneath the collecting columns 307a-n and designed to
collect the liquid phase coming from the group of exchangers
301a-n.
[0104] The fins stop before the columns 307a-n and 305a-n so as to
allow the fluid to enter and leave. The external wall shown in FIG.
5 (204) stops substantially at the same levels as the fins, again
to allow the fluids to enter and leave.
[0105] The vaporization/condensation method that has been described
above and the installation described with reference to FIGS. 6 and
7 applies to the vaporization of at least one liquid derived from
air or a liquid which is liquefied air, and to the condensation of
at least one gas derived from air, this gas possibly also being air
itself.
[0106] The method and the installation also apply to the
vaporization of at least one liquid having methane and/or carbon
monoxide and/or hydrogen as principal component and to the
condensation of at least one gas having methane and/or carbon
monoxide and/or hydrogen as principal component.
[0107] Such a method may apply to many types of installations for
separating mixtures of fluids, operating by cryogenic distillation,
in at least one column having one or more heat exchangers such as
those described above.
[0108] The installation may in particular be: [0109] a
reboiler/condenser for vaporization of a liquid by heat exchange
with a gas, which condenses inside or outside a distillation
column; or [0110] a subcooler; or [0111] a regeneration gas heater
for a purification unit used for purifying the mixture to be
distilled; or [0112] a dephlegmator; or [0113] a heat exchanger
having passages for cooling the mixture to be distilled at a
cryogenic temperature; or [0114] an exchanger for cooling an
interstage of a compressor for compressing the mixture to be
distilled or a product of the distillation.
* * * * *