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Oct. -1, 1946.
1 c. c. ‘VAN NUYS
2,408,710 v
PROCESS FOR SEPARATING THE CONSTITUENTS OF AIR
Filed Dec. 17, 1943
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BY
ATTORNEY;
2,408,710
Patented Oct. 1, 1946'
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1 e
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’
PRooEssFoa SEPARA'I‘ING THE
-
,
,
UENTS OFAIRf
Claude
Van Nuys, Greenwich,
Conn, assignor
Incorporated, New
to Air ReductionCompany,
_York, N. 'Y., a corporation of New York
Application December 1'7, 1943, Serial No. 514,593
- slolaiins.
>. This. invention relates t ‘
(01. 62-1755)
the separation of at
mosphericair'into its constituents by liquefac
tion and recti?cation, and particularly to im
provements'in the method and apparatus there
»for.
'
'
-
.
.
.
7.1
.
In commercial liquefaction methods of ‘sepa
rating oxygen fromthe atmosphere as heretofore
practised, the necessary refrigeration to attain
.low; temperatures is obtained'by compression and
subsequent expansion of the-air treated. This
necessitates initial compression of the air to rela
'
matically an apparatus suitable for the practice
.of the invention.
In accordance" with the present . invention, the
air tobe separatedis notjutilized- to produce any
refrigeration in the cycle. I employ instead a
separate-mitrogen cycle which, acts as a heat
transfer agent everywhere in the cyclerThe air
need be compressed in accordance with my in
ventiononly to pressuresnot substantially higher
10
than three atmospheres absolute. Usually a pres-‘
sure ‘of two atmospheres,v vorv suf?cient pressure
'tively high ‘pressure of the order of 15-20 atmos-.
~~pheres. Such compression can be attained ‘only
in reciprocating compressors which require oil lu
brication. The oxygen of the air under such pres
sures and at the temperatures resulting from
compression causes decomposition ‘of; the lubri
cating oil and the introduction-to the, air stream
of; substantial proportions of hydrocarbons in ad
only to ensure movement of the gas through the
apparatus‘is needed to accomplish theypurpose
Such pressures are easily at
vof the invention. types
of blowers which require
tainable in various
no internal lubrication. Hence no lubricating oil
and decomposition products thereof are mingled
with the air which is eventuallyseparated to re
cover oxyen therefrom. The-procedure as. here
inafter described effectively increases the propor
..
dition to any’ which may be present; The-use of "
vspeciallubricating oils does not avoid this source
atmosphere and thepurity of the product,
of Since‘
contamination.
the hydrocarbons are I not removed, from
.e?ect is compressed, circulated andv expanded in
tion of'oxygen which can be recovered from the
the air stream by the usual treatment intended
to separate moisture and carbon dioxide, they
‘tend to accumulate and eventually ,find. their way
.to the compartment of the apparatus where‘ liq- '
uidoxygen accumulates. The presence of such
material in contact with pure ‘oxygen, whether
liquid ‘or gaseous, is undesirable. 'Hence very
elaborate attempts have been‘ made ‘heretofore to
eliminatethe hydrocarbons at some-point inter
mediate compression of the air andthe' forma
tion of liquid or vapor rich in oxygen in which the
hydrocarbons might accumulate. Such attempts. ‘
involve operations which interfere with the 'ef?
~ciency ofv the "cycle and the» use of necessarily
complicated equipment. '
Furthermore, these at
tempts have‘ failed substantially to achieve the
desired object." It is still possible for hydrocar
Thenitrogen which affords the refrigerative
such a way as to providestrf?cient cold so that
theair can be lique?ed ati-lowpressure. ~_The
nitrogen of the refrigeration cycledoes not, min
gle .at_;any point with the air undergoing sepa
ration. Hence the presence of vhydrocarbons in
the nitrogencycle is notvinimical to the method
and a?ords no possibility of accumulation of hy
drocarbons inthe presence of oxygen or products
rich in oxygen. , The nitrogen can be compressed
lto vthe ‘ necessary pressureyfor example ,2500
pounds per square ‘inch. in starting,5 the appara
tus, ‘and from-900x170 1,009 pounds per squareinch
thereafter,~ in any available formThe
of - quantity
compressor.
= of
.OiLlubrication maybe used. .
».- nitrogen necessary for the refrigeration-cycle will , '
.depend'upon the size 1 of the apparatus but ,will
nolrin any case exceed the quantity of airicon
tained in the ‘air separation
r The‘. procedure will be readily understood’ by
reference 'to' the drawing,v in which 5' indicates a ,'
liquids rich in oxygen are present. I Y' ' ‘ w
_
having the usual trays 6 and
' t‘ is' the object of the present invention to pro 45 jrecti?cation, column
The
columniis provided. at its top
I
bubble
vcaps
1.
..
. ', a simple
.
vide
"and. effectivev ‘methqd‘ cadences .with an outlet ‘8 through-‘which
‘ratus'wh'ereby the "presence‘of' hydrocarbons re- I in nitrogen escapes. Liquid oxygen accumulates
sulting from decomposition of} oil in, the compres
in the bottom ofthe column, and the‘: vaporsv rise
bons derivedfrom theiubricating oilito accumu
late at points'in-the ‘apparatus where'gases or
’
Cyc1e~
'
1
>
'
' through the trays 6' and bubble caps
sion of the air can'be eliminated and further ini 50' .therefrom‘
l in contact ‘with liquid ?owing downwardly over
atmosphere ‘can bevobtainedt:
trays-i
. ‘ other ‘Objects and advantages of the'inrcn?ob "f the
; fire
provide ‘this liquid; - as; '; previously Yeom
will‘be apparent as it is better‘understood‘by rei
i pressed " to, Lethe; , initial pressure; preferably jsnpt
provementsinthe separation of oxygen fromjthe
"erenceto the following speci?cationfand theiac
'com'panying drawingtwhich;illustrates ‘diagram- 1
" greater than threeatmospheresfabsolute in any
2,408,710
3
4
suitable apparatus such as a blower (not shown)
is introduced through a pipe 9 into an exchanger
vapor from the condenser l4 escapes through the
pipe 41 to the lique?er 46. Hence the nitrogen
circulates continuously, affording all of the nec
essary refrigeration for the system. The nitro
I 0 and travels about pipes H and I2 therein in
heat exchange relation with cold products of the
separation. The air thus cooled is delivered
through a pipe l3 to the bottom of a backward
return condenser. l4 having tubes‘ l5 and ba?leslB
therein. The air ?ows upwardly through "the
tubes, being subjected therein to backward re
turn condensation by heat exchange with nitro
gen liquid and vapors supplie'dthrough a pipe 1:1.
The liquid from the condenser I4, which is .en
riched in oxygen, is delivered by a pipe, I8 con
trolled by a valve l9 to an intermediate level of”
the column '5.
The gaseous residue from the tubes l5 consist‘
ing principally of nitrogen i'sedelivered by apipe
gen in the refrigeration cycle does not at any
point mingle With the air undergoing separa
tion or the products thereof. Nitrogen separated
from the air is withdrawn, as is also the oxygen
10
product, independently of the refrigeration cycle.
Since the nitrogen employed for refrigeration
travelsxin an independent cycle, it is immaterial
whether or not it may carry hydrocarbons. These
hydrocarbons, if present, cannot mingle with the
air‘ undergoing separation and thus arrive at a
point in thesystem where oxygen or products rich
in oxygen are present. Thus the liquid oxygen
which-accumulates in the bottom of the column 5
is free from any contaminating hydrocarbons
2!! to a condenser 2| containing tubes 22 through
which the residue flows in heat exchange relation
with liquid nitrogen supplied through a pipe 23. 20 which might have been introduced owing to the
necessity of employing'oil in the initial compres
‘The surplus liquid from the condenser 2!‘ over
sion. of the air. The use of the bloiver'to com
flows through the pipe IT. The residue is con
press the air‘ obviates that possibility.
densedby heat exchange with the liquid nitrogen
The invention as described affords a practical
and "is d‘el'ivered'by a pipe 24 controlled by a valve
‘25 vto the top- of the column 5 and affords the 25 and simple solution of a problem which has ex
re?ux nitrogen liquid required to effectively sepa
isted for many years in the commercial produc
v'lf’h'e oxygen product may be withdrawn as a liq
'uid‘v th-rcugh a pipe 2? controlled by a valve 28
and delivered by a liquid pump 29 to a pipe 33
‘which delivers it to the pipes i 2 of the exchanger
procedure and ‘in the apparatus as described
without departing from the invention or sacri?c
ing the advantages thereof.
l0” wherein the liquid is vaporized. The oxygen
‘product is withdrawn through a pipe 3|, and
1. The method of separating the constituents
of" atmosphere air in a liquefaction apparatus by
liquefaction and» recti?cation which comprises
tion of‘v oxygen by ‘liquefaction and recti?cation.
rate substantially all of theaoxygen from the air
It also permits substantially total recovery of
treated:
the oxygen content of the air, since the nitrogen
e?luent nitrogen from the column is de
livered‘ by the pipe 8 to'the tubes H of the ex 30 re?ux which issupplied at the top of the column
prevents the escapeof oxygen in'the e?iuent.
changer l9 and is withdrawn through a pipe 26
Various changes may bev made in the details of
to any suitable receptacle or to the atmosphere.
‘ ‘delivered to any suitable storage receptacle. Al
ternat'ively, oxygen in the form of vapor may be
withdrawn through a pipe 32 controlled by a valve
33 and. delivered ‘to the pipe 3%. Liquid oxygen
may’be withdrawn throughv a pipe 34 controlled
' by‘awvalve 35 t‘o'purge the column of any impuri
ties which-may accumulate therein.
_ ,To afford-the necessary refrigeration for the
system‘, nitrogen is compressed in a compressor
36 to a suitable pressure as hereinbefore de
scribed and delivered ‘by a pipe 31 to a cooler
38'. Thence‘ the nitrogen is delivered by a pipe .
39 to‘ an ‘exchanger All and travels about tubes 41
"therein where it is further cooled by heat ex
I claim:
'
compressingin'itrogen toa relatively high pressure,
liquefying the nitrogen, compressing the air to a
pressure not‘ materially in excess of that required
to overcome the resistance to travel of the air
through the apparatus without abrupt change in
pressure, subjecting the air to indirect heat ex
change with the liquid nitrogen ‘to separate liq
uiid fractions enriched respectively in oxygen,
and nitrogen, and rectifying the two fractions
to‘ recover substantially pure liquid oxygen.
2; The method of separating the constituents
of: atmospheric air'in a liquefaction apparatus 'by
‘liquefaction and recti?cation which comprises
change with cold nitrogen vapor returning in
compressing nitrogen to a relatively high pres
the cycle. _ The cold nitrogen is delivered by a pipe
sure, liquefying the. nitrogen, compressing the
42-“to a coil‘idt which is immersed in the liquid
oxygen accumulating in the bottom of the col
air :to;a pressure notmateria'lly'in excess of that
required to overcome the resistance to travel of
the air through the apparatus without abrupt
‘
' '
‘The resulting heat exchange cools the
change; in pressure, subjecting the air to back
ward- .return condensation "with partial con
v‘of the liquidto maintain the vapor which rises
densation-thereof, ‘condensing the gaseousresidue
7‘ through-the column. The sub-cooled nitrogen is
then? delivered through a pipe ‘44 to the tubes 60 from ‘the ‘backward'return?condensation by in
direct heat exchange'wit'h, the liquid nitrogen to
45 of an exchanger ‘5'5 where it is lique?ed by
separate liquid fractionsenriched respectively in
Iheat‘exchange with cold nitrogen vapors enter
oxygen and nitrogen, and rectifying. the two frac
iin'g'the lique?er through a pipe 41. These vapors
tions to recover‘ substantially pure1 liquid» oxygen
escape 'throgh a, pipe 48 to the exchanger 46 and '
.3. The methodof separating ‘the constituents
v‘aft-"er ‘passing’ through the‘ tubes M of the ex
of atmospheric .air by liquefaction. and recti?ca
changer, are delivered by a pipe 49 to the com
pressor 3'6.
'
tion. whichcomprises compressing the air toa
relatively low pressure such that expansion from
-"_'vI’hegliquid nitrogen from the lique?er '46 is de
thatpressure will not produce refrigeration suffr
livered through a ‘pipe 50‘ and throttle valve. 5|
70 cient to effect liquefaction; thereof, subjecting
‘to the pipe Y23 and thus to the condenser 2|, af
the compressed air to coolingand liquefaction in
fording the liquid nitrogen necessary to liquefy
[two fractions enrichedrespectively in oxygenand
thenitrogen reflux for the column .5 and also to
‘ nitrogen .by indirect heat..,excha-nge with the liq
,' e‘lrect theinitial backward. return condensation
nitrogen and causes vaporization ‘of a portion
of the air entering the system.
The nitrogen 75 uid'nitrogen,rectifyingthe two fractions to re
cover substantially pure-liquid oxygen and‘main
2,408,710
taining the refrigeration necessary for the op
eration by compressing nitrogen to relatively
high pressure and liquefying the nitrogen to sup
ply continuously the liquid required to effect
liquefaction of the air.
6
taining a separate nitrogen cycle including com
pression of the nitrogen to a relatively high
pressure and liquefaction of the nitrogen by heat
exchange with cold nitrogen vapors, subjecting
the air at low pressure to indirect heat ex
change with the liquid nitrogen to separate two
4. The method of separating the constituents
of atmospheric air by liquefaction and recti?
cation which comprises compressing the air to
a relatively low pressure suoch that expansion
from that pressure will not produce refrigeration 10 '
sufficient to effect liquefaction thereof, subject
ing the compressed air to cooling and liquefac
tion in two fractions enriched respectively in
oxygen and nitrogen by indirect heat exchange
with the liquid nitrogen, rectifying the two frac 15
tions to recover substantially pure liquid oxygen
and maintaining the refrigeration necessary for
the operation by compressing nitrogen to rela
tively high pressure and liquefying the nitrogen
by heat exchange successively with the liquid 20
liquid fractions respectively enriched in oxygen
and nitrogen and rectifying'the two fractions to
recover substantially pure liquid oxygen.
7. The method of separating the constituents
of atmospheric air which comprises compressing
nitrogen to a relatively high pressure suf?cient
to afford the necessary refrigeration to liquefy
the nitrogen, liquefying the compressed nitrogen,
compressing the air to a relatively low pressure,
vaporizing the liquid nitrogen by backward re
turn condensation of the air with partial con
densation thereof, liquefying the gaseous residue
from such backward return condensation to pro
vide two liquid fractions enriched respectively in
oxygen and nitrogen, and rectifying the two frac
tions to recover substantially pure liquid oxygen.
8. The method of separating the constituents
tinuously the liquid required to effect liquefac
of atmospheric air which comprises compressing
tion of the air.
.
'
nitrogen to a relatively high pressure sufficient
5. The method of separating the constituents
of atmospheric air which comprises compressing 25 to afford the necessary refrigeration to liquefy
the nitrogen, liquefying the compressed nitrogen,
the air to a relatively low pressure without con
compressing the air to a relatively low pressure,
tamifiating the air with lubricating oil, main
taining a separate nitrogen cycle including com
vaporizing the liquid nitrogen by backward re
pression of the nitrogen to a relatively high
turn condensation of the air with partial con
pressure and liquefaction of the nitrogen, sub 30 densation thereof, liquefying the gaseous resi
'
to indirect heat
due from such backward return condensation to
exchange with the liquid nitrogen to separate
provide two liquid fractions enriched respectively
in oxygen and nitrogen, rectifying the two frac
two liquid fractions respectively enriched in,
tions to recover substantially pure liquid oxygen,
oxygen and nitrogen, and rectifying the two frac
oxygen and cold nitrogen vapors to supply con
substantially pure liquid oxygen.‘
6. The method of separating the constituents
of atmospheric air which comprises compressing
tions to recover
the air to a relatively low pressure without con
taminating the air with lubricating oil, main
and recompressing the vapor produced by vapor
izing the liquid nitrogen to maintain the cycle.
CLAUDE C. VAN NUYS.
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