Process for Separating Gases and Vapours from Mixtures.
Year: 1899

page_text: COMPLETE SPECIFICATION.
Process for Separating Gases and Vapours from Mixtures.
I, Dr. KONRAD KUBIERSCHKY, of Aschersleben, Germany, Director do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
The present invention depends upon the solubility of gases and vapours in
liquids.
Generally the solubility depends upon the nature of the solvent the pressure
and the temperature and the solubility is greater, the higher the pressure and the
lower the temperature. By Henry Dalton's law the solubility is in proportion to
the absolute pressure and the partial pressure.
For instance if the solubility of a gas in a liquid at atmospheric pressure is
represented by L this solubility at 4 atmospheres absolute pressure becomes 4 L,
and if there is in the mixture only 20 per cent. of the gas to be dissolved the
solubility is
that is the absolute pressure is 4 and the partial pressure
4 x x 2J
100
is equal to . If the temperature alters, L alters, but the absolute pressure and
the partial pressure always more or less keep their effect.
Neglect of these physical laws and their consequences has been the cause that
many processes proposed for separating gases remain without result. The process
mentioned by Mallet (Wagner, chem. technical annual report of 1870 page 730)
for obtaining oxygen from air by dissolving air under augmented pressure in water
and afterwards releasing the latter from pressure could therefore have no result,
because if the solubility of oxygen in water is equal to 2, that of nitrogen is equal
to about 1.
With five atmospheres absolute pressure there would be dissolved from air with
20 per cent. according to the partial pressure:
Oxygen = 2 × 5 × 1
Nitrogen 1 × 5 ×
13313
SEXXCE 2
=========
t
that is to say under the best circumstances the dissolved mixture would contain
only 33 per cent. of oxygen. But on pressure release afterwards the dissolved
gas does not escape in the same percentage as was supposed but it escapes only
with about 30 per cent., whilst the gas remaining dissolved contains nearly
44 per cent. The quantity of oxygen remaining dissolved is 30 per cent.
of the introduced quantity of oxygen 80 that there is & considerable
loss of production. The same of course takes place in a similar manner if the
30 percentage gas is again treated by the same process to produce a gas with
higher percentage.
Still worse are the proportions in obtaining carbonic acid from smoke or lime
kiln gas. After the process of Fassbender, German Patent No. 36702, gas con-
taining carbonic acid is dissolved under pressure in water and the carbonic acid
is obtained by pressure release. This process consists in introducing the gas under
pressure through a short pipe from below into a cylindrically shaped absorption

page_text: apparatus arranged in the manner of the known washers and in which the gas
meets a solution liquid entering from above which escapes from the apparatus
through a short pipe on the bottom thereof. For maintaining a temperature as
low as possible cooling coils are arranged in the apparatus. The liquid saturated
with carbonic acid enters through a short tube provided with a number of fine
openings into a so called evaporator. In the latter sieve bottoms are arranged
one upon the other over which the liquid runs down whereby its gas is more or
less evaporated according to the temperature and pressure prevailing in the
apparatus. If the pressure is P-5 the percentage of gas 30, the solubility of
the carbonic acid 1000 and the solubility of the nitrogen mixed therewith 20,
then there are dissolved:
that is, from the dissolved carbonic acid only about 40 per cent. are gained. If
the carbonic acid containing liquid thus obtained is allowed to run away the
gas is lost, but if it is used again as absorption means the gain is only very slight,
because after the above mentioned physical lawa, in the absorption of 30 per cent.
gas even by counter current the gas escapes in the manner appropriate to the
saturation-point of the solution-liquid and that is 18 per cent. because
Both these disadvantages proved in the above examples,,the small gain and the
inefficient separating, are avoided by the hereinafter described process.
The gas mixture to be used is treated with a solvent liquid in counter-current
either under augmented pressure or lower temperature. The liquid resulting
after the release of pressure or after warming, is as shown above, in itself more
or less unfit for the further continuation of the process and is therefore improved
by treatment with the raw gas in counter-current with low pressure or high
temperature, the gas or vapour contents of the solution are reduced in accordance
with the low percentage of the raw gas. The technical result of this removal of
air by raw gas is the following:-
1. The raw gas and consequently the solvent liquid are enriched with easier
soluble gas.
The gas mixture escaping at low pressure or high temperature
becomes of a higher percentage in relation to the easier soluble gas, consequently
a better dissociation of the raw gas is obtained. By poor raw gas the effect of
enriching the same is that by pressure releasing or by warming the solvent liquid
the easier soluble gas segregates whilst without the enriching, it would not
segregate at all or only by improportionately extensive lowering of pressure or
increase of temperature. Although the easier soluble gas is not gained as such
but only in connection with the solvent liquid, the higher percentage contents of
the latter makes its easier use possible. In gas mixtures containing vapours
the possibility is given by the enriching of the raw gas that the vapours after being
compressed or after being cooled separate in liquid form from the gas.
2. The solvent liquid is regenerated for renewed absorption of the easier soluble

page_text: gas by delivering to the raw gas the chief mass of the gas remaining still dissolved
even under low pressure or high temperature. In consequence also the non-
absorbed gas mixture escaping from the absorber gets poorer in its contents of the
easier dissolved gas consequently also in this respect there is a sharper separation
of the original gas mixture. The use of steam or of air vacuum effecting this
result in other employed processes is, with the treatment of the solvent liquid
with raw gas at low pressure or high temperature, rendered either entirely super-
fluous or very limited. What is true in reference to the gas mixtures serves in
the same manner for vapour mixtures. The apparatus serving for this treatment
will be hereinafter called generally, "excluder.' Sometimes it may be preferable
to combine the absorber and excluder so that they form only one apparatus whose
upper part acts as absorber and the lower part as excluder. The enriched liquid
with the enriched gas is then taken from the middle part. The process is carried
out either by difference of pressure or of heat between absorber and "excluder."
1. USE OF PRESSURE.
In the
The gas mixture to be separated into its components enters the excludere at f
whence it goes through the pipe h to the compressor which brings it to higher
pressure and sends it through pipe b to the cooler k and the absorber g.
absorber g it meets in counter-current the solvent liquid which enters through
and delivers to it its easier soluble constituents. The gas freed herefrom still
under pressure passes out at i and is in the ordinary manner used for working
purposes.
The pump q sends
into the absorber g
either with coke or
The solvent liquid to be used flows through the apparatus.
the liquid required for the absorption from above through pipe
which as well as the hereinafter described excluder e is filled
any other porous material, with pipes, sieve-plates or cascade disks, but which can
also have any other form and arrangement as used hitherto for absorption. The
liquid saturated with gas goes through pipe m to the pump p and through pipe n
to the deliverer a wherein it is freed from pressure, releasing the chief mass of the
absorbed gas. The liquid must now be freed from the more or less considerable
quantity of gas which also at low pressure remains still dissolved. From the
deliverer the liquid flows therefore through pipe o to the excluder e where it
meets in counter-current the raw gas coming through pipe f and consequently
according to the lower partial pressure of the raw gas is freed from the easier
soluble gas and becomes enriched therewith the unpurified gas.
If it is a question of obtaining vapours, that is of gas which is liquid at ordinary
temperature, and consequently in the original gas mixture exists only by tension,
such solvent liquids come into consideration wherewith the liquid to be obtained
can be mixed. Then no delivery of gas takes place but the absorbed vapour in
the excluder is wholly or partially driven out by original gas and the latter enriched
thereby.
This has the consequence that again more gas is absorbed whereby the percentage
contents of original gas are augmented. This process is continued so long till
either the liquid flowing out of the absorber contains so much of the liquid to
be obtained that a further working would not pay, or till by the compression in
consequence of the relative diminished tension, the liquid to be obtained is dis-
sociated in the cooler k.
2. USE OF HEAT.
Quite the same effect caused by absorption under pressure and afterwards release
by reduction of pressure in the deliverer and excluder can be obtained with a
constant pressure, for example, atmospheric pressure by difference of heat between
the absorber on the one hand and the deliverer and excluder on the other hand,
whereby naturally the absorber has to run cold and the air emptier and deliverer
hot. Whilst in using different pressure the regaining of the employed energy is
caused by the working effect of the non-absorbed gas being under pressure, the

page_text: energy by use of difference of heat is regained by heat interchanging apparatus
for the liquid.
Special forms are possible for the working of more or less hot gases derived
from various industrial processes such as coke, and sulphur gases, sulphurous
acid, muriatic acid and similar gas. These are brought hot into the excluder
where they deprive the solvent liquid of gas by heating and the slight partial
pressure and cool and enrich themselves.
3. USE OF PRESSURE AND HEAT IN THE SAME TIME.
Of course, in special cases a combined use of heat and pressure for applying the
process is possible according to the methods severally explained above.
Having now particularly described and ascertained the nature of my
invention, and in what manner the same is to be performed, I declare that what
I claim is:―
1. A process for separating gases or vapours from mixtures, wherein the mixture
to be treated enters an absorber under augmented pressure with a solvent liquid
whereby it delivers its easier soluble constituents to the latter, the originated gas
solution being then submitted to a pressure release in a deliverer whereby it delivers
the chief mass of the absorbed gas and finally the remaining liquid for entire
abstraction of the still dissolved gas-residue is treated under lessened pressure
in an excluder in counter-current with raw gas.
2. In the process described in Claim 1 the use of low temperature instead of
augmented pressure and augmented temperature instead of lessened pressure.
3. In the process described in Claim 1 the use of low temperature and high
pressure or high temperature and low pressure at the same time.
Dated this 2nd day of September 1899.
HERBERT HADDAN & Co.,
Agents to Applicant,
18, Buckingham Street, Strand, London.