Apparatus for Separating Mixed Gases by Refrigeration, especially applicable to the Separation of Oxygen from Air.
Year: 1896

page_text: Date of Application, 9th Apr., 1896
Complete Specification Left, 8th Jan., 1897-Accepted, 6th Mar., 1897
PROVISIONAL DI ECIFICATION
Apparatus for Separating Mixed Gases by Refrigeration, especially
applicable to the Separation of Oxygen from Air.
I, WILLIAM HAMPSON, M.A. Oxford, L.S.A. London, at present lodging at
No. 334 City Road, London, of Nannerch, Mold, North Wales, do hereby declare.
the nature of this invention to be as follows:-
For the purpose of separating mixed gases I use self-intensive refrigerating
apparatus such as is described in my former Specification No. 10165, dated
23rd May, 1895, in conjunction with additional apparatus in which I effect the
separation of the mixed gases.
In the apparatus as set forth in the said specification I cause compressed gas
after passing through pipes or passages and after being in any suitable way
expanded and thereby made colder, to pass back over the surfaces of the said pipes
or passages throughout such a length as to interchange the temperatures of the
compressed gas approaching the expansion point and the expanded gas passing
away from it; thus each succeeding portion of compressed gas is cooled before
expansion and this renders colder the next portion of expanded gas-and so on;
thereby intensifying the cold. For convenience I shall hereinafter call this part
of the combined apparatus "the primary apparatus." To the primary apparatus
I add secondary apparatus. In this secondary apparatus I employ pipes which I
call "the liquefaction pipes within which the mixed gases to he separated pass
to the neighbourhood of the expansion point in the primary apparatus so as to be
exposed to the cold produced by expansion in the primary apparatus. In order
that the gases in the liquefaction pipes may liquefy and remain liquid at a higher
temperature than the expanded gas in the primary apparatus I maintain those
gases at a higher pressure than that of the said expanded gas.
If the gases to be liquefied are the same as those which circulate in the primary
apparatus as for example when both are atmospheric air, the mixed gases to be
separated are conveniently supplied from the high-pressure supply of the primary
apparatus through a reducing valve. From the neighbourhood of the expansion
point the liquefaction-pipes pass through what I call "the vaporisation-vessels "
and end in one of those vessels at a liquid-separator which allows liquid, but not
gas, to escape from the liquefaction pipes. The liquid accumulates in such
vaporization vessel under atmospheric pressure, at which pressure its more volatile
constituents begin to boil off or vaporize. The liquid becoming colder causes the
liquefaction of a further portion of gases within the liquefaction pipes whilst on
the other hand the heat withdrawn from the liquefaction pipes promotes the
vaporisation of the more volatile of the liquefied gases surrounding them. From
the first vaporization vessel the liquid passes into another or others arranged in
series; these also contain a portion of the aforesaid liquefaction pipes. By this
arrangement, the liquid, as it passes through the additional vessels, has a further
portion of its more volatile components boiled off, until in the last vessel it is
sufficiently purified. The amount of boiling-off, and therefore the extent to which
the separation is carried depends on the pressure maintained in the liquefaction
pipes which is easily regulated. The purified liquid may be drawn off by a pipe
from the bottom of the last vaporisation-vessel, or as a gas from the top thereof, in

page_text: the latter case vaporisation may be promoted by reducing the pressure below that
of the atmosphere, as for example by connecting the effluent pipe with the suction
side of a compressor-pump, with or without an intervening reservoir, in which case
the latent heat needed for vaporisation is withdrawn from the liquefaction pipes
and a further portion of gas is liquefied therein.
For the more economical working of the apparatus the vaporised gases should
pass backwards through passages surrounding the pipes by which the mixed gases
enter under pressure, thus forming a secondary exchanger; this secondary
exchanger should be disposed around or within the exchanger of the primary
apparatus, so that the same protective covering may suffice.
I employ means similar to those described in my aforesaid former specification
for protection against the ingress of heat.
When working on an industrial scale, where saving of power and increase of
effect are more important than smallness and simplicity of apparatus, a suitable
way of causing expansion is by an engine to be driven by the compressed gas and
made to perform external work, as for example to aid in the compression of gas to
be supplied to the apparatus.
Dated this 8th day of Anril 1906
Apparatus for Separating Mixed Gases by Refrigeration, especially
applicable to the Separation of Oxygen from Air.
I WILLIAM HAMPSON, M.A. Oxford, L.S.A. London, at present lodging at
No. 334 City Road, London, of Nannerch, Mould, North Wales, do hereby
declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
For the purpose of separating mixed gases I use self intensive refrigerating
apparatus such as is described in my former Specification No. 10165, dated
23rd May 1895, in conjunction with additional apparatus in which I effect the
separation of the mixed gases.
In the apparatus as set forth in the said specification I cause compressed gas
after passing through pipes or passages and after being in any suitable way
expanded and thereby made colder, to pass back over the surfaces of the said
pipes or passages throughout such a length as to interchange the temperatures of
the compressed gas approaching the expansion point and the expanded gas passing
away from it, thus each succeeding portion of compressed gas is cooled before
expansion and this renders colder the next portion of expanded gas and so on,
thereby intensifying the cold. For convenience I shall hereinafter call this part
of the combined apparatus "the primary apparatus." To the primary apparatus
add secondary apparatus. In this secondary apparatus I employ pipes which I
call "the liquefaction pipes" within which the mixed gases to be separated pass
to the neighbourhood of the expansion point in the primary apparatus so as to be
exposed to the cold produced by expansion in the primary apparatus. In order
that the gases in the liquefaction pipes may liquefy and remain liquid at a bigher
temperature than the expanded gas in the primary apparatus I maintain those
gases at a higher pressure than that of the said expanded gas.
If the gases to be liquefied are the same as those which circulate in the primary
apparatus, as for example when both are atmospheric air, the mixed gases to be
separated are conveniently supplied from the high pressure supply of the primary

page_text: apparatus through a reducing valve. From the neighbourhood of the expansion
point the liquefaction-pipes pass through what I call, the "vaporisation-vessels"
and end in one of those vessels at a liquid-separator which allows liquid, but not
gas to escape from the liquefaction pipes. The liquid accumulates in such
vaporisation vessel under atmospheric pressure, at which pressure its more volatile
constituents begin to boil off or vaporize. The liquid becoming colder causes the
liquefaction of a further portion of gases within the liquefaction pipes whilst on the
other hand the heat withdrawn from the liquefaction pipes promotes the vaporisation
of the more volatile of the liquefied gases surrounding them. From the first
vaporisation vessel the liquid passes into another or others arranged in series; these
also contain a portion of the aforesaid liquefaction pipes. By this arrangement,
the liquid, as it passes through the additional vessels, has a further portion of its
more volatile components hoiled off, until in the last vessel it is sufficiently
purified. The amount of boiling-off, and therefore the extent to which the
separation is carried depends on the pressure maintained in the liquefaction pipes
which is easily regulated. The purified liquid may be drawn off by a pipe from
the bottom of the last vaporisation-vessel or as a gas from the top thereof, in the
latter case vaporisation may be promoted by reducing the pressure below that of
the atmosphere, as for example by connecting the effluent pipe, with the suction
side of a compressor-pump, with or without an intervening reservoir, in which case
the latent heat needed for vaporisation is withdrawn from the liquefaction pipes
and a further portion of gas is liquefied therein.
For the more economical working of the apparatus the vaporised gases should
pass backwards through passages surrounding the pipes by which the mixed gases
enter under pressure, thus forming a secondary exchanger; this secondary
exchanger should be disposed around or within the exchanger of the primary
apparatus, so that the same protective covering may suffice..
I employ meaus similar to those described in my aforesaid former specification
for protection against the ingress of heat.
When working on an industrial scale, where saving of power and increase of
effect are more important than smallness and simplicity of apparatus, a suitable
way of causing expansion is by an engine to be driven by the compressed gas and
made to perform external work, as for example to aid in the compression of gas to
be supplied to the apparatus.
In the case mentioned above, where the gas which circulates in the primary
apparatus is the same mixed gas which circulates in the liquefaction coils, and the
intermediate compression is obtained from the higher compression by means of a
reducing-valve; it is desirable to place such reducing valve at the bottom of the
primary apparatus: thus the considerable expansion between the higher and the
intermediate pressure will take place at the lowest available temperature, and will
therefore produce the greatest possible cooling which it would not do if it took
place at a higher temperature. The reducing valve may then be regulated by a
rod passing to the top of the apparatus, and the pressure shewn by a gauge
attached to a pipe running from the liquefaction pipes to the top. If this
regulating rod be enclosed in a pipe, its gland and packing can then be under
observation at the top of the apparatus.
The annexed drawing shows a sectional elevation of the apparatus arranged for
separating oxygen from air A. B. C. is the heat proof jacketing, shewn in this
drawing as a vacuum. DE is the primary exchanger. This is entered at the top
by the pipe F G, which contains air freed from the vapour of water and carbonic
acid, and at high pressure. In the apparatus the pipe F G divides into branches
provided with separate regulating cocks which branches pass in successive spiral
layers from the top to near the bottom of the primary exchanger D E. Near the
bottom of the exchanger the pipes unite again and end in the orifice F* which is
controlled by a conical plug regulated by a pinion turned by the outer cylindrical
rod J. The compressed air when it escapes by the orifice F, expands; and the
expanded cooled air, flows over the pipes of the compressed air on its way back to

page_text: the top of the exchanger, from which it issues by the pipe D H, which leads it
back to the compressor. K L is a chamber enclosing D. E, and enclosed by M N,
both concentrically. K L and M N contain pipes disposed like those in D E, and
supplied with compressed air from the same pipe F G ; but when they unite at
the bottom of the concentric chambers, the compressed air from them passes to a
reducing-valve, O. The reducing valve is of a well known type in which the
pressure at the exit side of the valve causes the valve to be closed as soon as this
pressure is able to overcome an adjustable spring. The spring is regulated by a
pinion turned by the inner cylindrical rod P. The reducing valve is regulated so
that the pressure of the air in the pipe beyond it is such as to inake it liquefy near
the temperature at which oxygen vaporises under atmospheric pressure, which
temperature is hereinafter denoted by the letters tvo (signifying the temperature
of the vaporisation of oxygen) the pressure under which air liquefies at this
temperature being denoted by the letters platvo (signifying the pressure of
liquefaction of air at t vo) and the highest pressure of the compressed air by the
letters pac (signifying pressure to which air is compressed). The pressure platvo
in the pipe beyond the reducing valve is indicated by a pressure-gauge attached to
a pipe which passes through the inner cylindrical rod P; and the pressure pac
by a guage attached to the pipe F G.
The pipe beyond the reducing valve forms the liquefaction coils. These are
arranged as spirals in the lower part of the primary exchanger DE: then,
passing through the floor of this exchanger into the first nitrogen-vaporisation-
vessel L Q, they form successive spirals in the outer part of this vessel, from the
top to the bottom; whence they pass successively through further compartments
or vaporisation-vessels to R and S; thence to the top, U, and back again to the
bottom, T, of the oxygen-vaporisation vessel, UT; thence to V, and finally to W,
where they discharge into a liquid-separator, W X, so arranged as to let liquid,
but not vapour, pass out at X.
The liquid when it accumulates sufficiently lifts a float and so opens an exit
valve or cock.
When the compressor is working, the pipe F delivers to the pipes G, Y, Z, air
under the high pressure pac from which pressure some of the air, entering by G,
expands at to atmospheric pressure, being thereby cooled. But the air which
enters by Y and Z ex pands at the reducing-valve to the pressure platvo, which
then exists all along the liquefaction coils and in the liquid-separator. No more
air then passes the reducing valve. The self intensive refrigeration goes on in the
primary exchanger D E until the temperature of the expanded air at the bottom
of it reaches tvo which is about 180° C. At this temperature the air in the
liquefaction-coils at the level E, being freely exposed to it, begins to liquefy
under the pressure platvo. The latent heat which it gives out in liquefying
prevents the temperature falling further; so that the temperature for the
liquefaction of air under atmospheric pressure about 190° C., is never reached, and
therefore the expanded air from F does not liquefy. The liquefaction of air in
the liquefaction-coils reduces the pressure therein, and the reducing valve, then
allows more air to pass until the pressure is raised again to platvo. When
sufficient liquid air has collected in the liquefaction-coils to pass on to the liquid-
separator and sufficiently accumulates there, it begins to be discharged from X,
and so to pass from the pressure platvo to atmospheric pressure. This permits
a great quantity of nitrogen to boil off, and so cool the liquid which is left and
which consists largely of oxygen. But this reduction of temperature is stopped
by the liquefaction of more air at the reduced temperature in the liquefaction coils
in the neighbourhood. Thus the vaporisation of nitrogen and the liquefaction of
air promote each other. The liquid as it descends the compartments successively
from Q to S is continually freed from more nitrogen, which passes upwards so that
only very pure oxygen reaches S and begins to fill the oxygen-vaporisation-
vessel U T.
The caping nitrogen passes up through the secondary exchanger K L, and the

page_text: oxygen is withdrawn as a gas or vapour through the secondary exchanger M N,
its vaporisation under a pressure somewhat below atmospheric being promoted by
the liquefaction of more air in the outer liquefaction-coils; from which liquefaction
the latent heat for the vaporisation is obtained. The level of the liquid oxygen
in the vaporisation vessels is shewn by a gauge containing a solution of the same
density, 1-1375. This gauge is marked g. The oxygen may be drawn off as a
liquid at T, through a pipe long enough to prevent conduction of heat to the
vaporisation vessel. As a precaution against accident a safety valve is provided
upou the liquid separator.
The temperature exchangers being concentrically arranged they present only
one external surface liable to convey external heat inwards.
The newly liquified air is, it will be seen, prevented from mingling with the
liquid which has already been purified by continuous boiling, this adds greatly to
the completeness of the purification.
The nitrogen which is boiled off is not allowed to mingle with the air circulating
in the apparatus but a separate temperature interchanger is provided for it so that
it may be at once rejected.
The arrangement above described of the reducing-valve, liquefaction-coils, and
vaporisation-vessels is such that the temperatures and quantities of air, gases, and
liquids are automatically controlled without further assistance than the regulation
of the reducing-valve.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In combination with a primary system in which compressed air is allowed to
expand and produce cold which is intensified by interchange of temperature
between the compressed and the expanded air; a secondary system supplied with
mixed gases under pressure and in which the mixed gases are liquified, then drawn
off and the liquid allowed to boil thereby cooling the chamber in which liquefaction
takes place with the result that further liquefaction occurs and simultaneously a
separation is obtained by the boiling off of one of the gases from the mixture.
2. In combination with a primary system such as described a secondary system
supplied with compressed gas and having a reducing valve by which the compressed
gas is allowed to expand to a lower pressure, under which pressure the gas is
liquefied by the intensified cold generated in the apparatus.
3. Apparatus in accordance with Claim 1 and having temperature interchangers
in which the boiled off gas cools the incoming gas.
4. Apparatus in accordance with Claim 1 and having several compartments
which the liquified mixed gases traverse whilst boiling whereby a more perfect
separation is obtained.
5. Apparatus in accordance with Claim 1 and baving temperature interchangers
for the boiled off gases surrounding the temperature interchanger of the primary
system.
6. Apparatus in accordance with Claim 1 and having a separate temperature
interchanger reserved for the separate delivery of the boiled off nitrogen.
7. The combination with the primary system of my former patent of a secondary
system substantially as herein described.
Ted: co
1000
W. HAMPSON.