Process and Apparatus for the Separation of Salts from their Solutions.
Year: 1894

page_text: l'ate of Application, 31st Dec., 1894
Complete Specification Left, 30th Sept., 1895-Accepted, 9th Nov., 1895
PROVISIONAL SPECIFICATION.
Process and Apparatus for the Separation of Salts from their
Solutions.
I, CARL KELLNER, of Hallein, Austria, Director of the Kellner-Partington
Paper Pulp Co. Id. do hereby declare the nature of this invention to be as
follows:-
It is found that as a rule a solid substance can be taken up by a liquid to a
greater extent in the warm state than in the cold state; that is to say, the
solubility of most salts increases with increased temperature. Some compounds
however, form an exception to this rule, there being a maximum degree of
solubility for a certain determined temperature, and the solubility decreasing again
at higher temperatures.
Now the process forming the subject of this invention has for its object to
effect in an economical manner the separation of such substances which show the
above mentioned anomalies of solubility, from solutions in which they are contained
in relatively small quantities, together with other compounds which do not show
these anomalies. In this connection the said substance to be separated need not
be contained in the solution at first in the form in which such substance shows
the anomalies that serve to effect its separation, but said substance is first
converted into said form by means of a special operation.
Now on the basis of this process of which the general characteristics have just
been set forth, it is possible from weak solutions of common salt containing
relatively small quantities of caustic soda, such as are obtained in the form of
kathode liquid in the electrolysis of common salt, to separate the caustic soda
successfully and economically without the expensive evaporating process, by
converting the caustic soda, by saturation with carbonic acid, into sodium carbonate,
that is to say, into such a substance as will show the anomalies of solubility as
above set forth, whilst the solubility of the common salt present therewith in
solution, increases with an increase in the temperature.
100 parts by weight of water at 36° C., dissolve the maximum amount, that is
59 parts by weight, of sodium carbonate, whilst the same weight of water at 100° C.
will only dissolve 45 parts by weight of sodium carbonate. Now 100 parts by
weight of water at 40° C. will dissolve 36.64 parts by weight of common salt, aud
at 100° C. will dissolve 39-61 parts by weight thereof. Thus whilst the solubility
of sodium carbonate becomes considerably diminished in hot solutions, the
solubility of common salt under the same conditions becomes still further increased
to a slight extent.
From this it will be seen that from a hot solution containing caustic soda and
common salt, the former compound can be separated for the greater part in the
form of sodium carbonate when the solution is treated with carbonic acid. The
speed of the separation of the sodium carbonate formed is also accelerated by
the fact that the volume of the solution is slightly diminished by reason of the
evaporation produced by the high temperature ruling at the time; that is to say,
in addition to saturation of the hot solution with carbonic acid, there is also
evaporation taking place simultaneously therewith.
This process in which-and this may be emphasized here-evaporation of the
solution, saturation of the latter with carbonic acid, and separation of the resulting
|so.lium carbonate, take place in one single operation, may, as will be readily

page_text: understood from the preceding description, be applied not only to kathode liquids
containing caustic soda together with common salt, but generally to all solutions
which contain, either in addition to substances of normal conditions of solubility,
or without these, salts which can be converted into products that show anomalies of
solubility of the kind set forth.
According to this process the weak solution to be crystallized is caused to flow
in extremely thin streams over large surfaces as a countercurrent to heating or
fire gases (preferably purified) which effect the crystallizing process by means of
their bigh temperature and their contained amount of carbonic acid. For this
purpose it is preferable to employ wire ropes or chains arranged in a tower-like
casing and from which the crystals separated from the solution and adhering
thereto can be detached by a mere shaking motion.
The accompanying drawing illustrates an apparatus adapted for carrying out
this process in longitudinal section, which allows of effecting the saturation and
evaporation in a single operation, and of rapidly removing the separated crystals
from the apparatus.
A is the crystallizing tower provided at the top with a vessel B for receiving
the solution to be crystallized. The bottom of this vessel is perforated, and in the
perforations there are inserted wire ropes or chains ss which hang down freely
within the tower A, so that the liquid flowing down through the spaces between
the edges of the holes and the ropes or chains suspended in the holes, flows down
along the ropes or chains in the form of thin streams. Near the, preferably
inclined, bottom of the tower (which can be connected by means of the outlet pipe a
with a collecting vessel D), and opening into the same there is an inlet pipe R
for the fire gases coming from a furnace. These fire gases travel upwards in the
opposite direction to that of the downwardly flowing liquid along the ropes or
chains, towards the outlet pipe a¹ and thus come in intimate contact with the
particles of liquid, whereby the liquid is quickly evaporated, and the substances
thus separated are caused to crystallize and adhere to the ropes or chains.
With such apparatus, as will be evident from the foregoing, saturation of the
weak solution, and the resulting separation of the salt formed, viz. sodium carbonate
for instance, are effected on the wire ropes in one and the same operation. Thus
for example if the solution to be crystallized be a solution of caustic soda, the
said solution will be evaporated in flowing down the ropes or chains by the
oppositely travelling fire gases; whilst the carbonic acid of the fire gases
combines with the sodium to form monose-, quis and bicarbonate which becomes
deposited in the form of a crust on the surface of the ropes or chains, from which
it can be readily removed by shaking. The dropping crystals are extracted through
a side opening C, whilst the spent liquid remaining flows through the outlet pipe a
into the collecting vessel D, whence it may if desired be again charged into the
vessel B.
Dated this 31st day of December 1804
F. WISE HOWORTH,
46 Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
Process and Apparatus for the Separation of Salts from their
Solutions.
I, CARL KELLNER, of Hallein, Austria, Director of the Kellner-Partington
Paper Pulp Co. Ltd. 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 :-
It is found that as a rule a solid substance can be dissolved by a liquid to a

page_text: greater extent when it is in the warm state than when it is in the cold state, that is
to say the solubility of most salts increases with an increased temperature of the
liquid. Some compounds however, form an exception to this rule, there being a
maximum degree of solubility for a certain determined temperature, and the
solubility decreasing again at higher temperatures.
Now the process forming the subject of this invention has for its object to effect
in an economical manner the separation of substances which show the above
mentioned anomalies of solubility, from solutions in which they are contained in
relatively small quantities, together with another compound or other compounds
which do not show these anomalies. In this connection the substance to be
separated need not be contained in the solution at first in the form in which
such substance shows the anomalies that serve to effect its separation, but said
substance is first converted into said form by means of a special operation.
Now on the basis of this process, of which the general characteristics have
just been set forth, it is possible from weak solutions of common salt containing
relatively small quantities of caustic soda, such as are obtained in the form of
kathode liquid in the electrolysis of common salt, to separate the caustic soda
successfully and economically without the expensive evaporating process, by
converting the caustic soda, by saturation with carbonic acid, into sodium
carbonate, that is to say, into such a substance as will show the anomalies of
solubility above set forth, whilst the solubility of the common salt present
therewith in solution, increases with an increase in the temperature.
100 parts by weight of water at 36° C., dissolve the maximum amount, that
is about 59 parts by weight, of sodium carbonate, whilst the same weight of
water at 100° C. will only dissolve about 45 parts by weight of sodium carbonate.
Now 100 parts by weight of water at 40° C. will dissolve about 36-64 parts by
weight of common salt, and at 100° C. will dissolve about 39.61 parts by weight
thereof. Thus whilst the solubility of sodium carbonate becomes considerably
diminished in hot solutions, the solubility of common salt under the same conditions
becomes still further increased to a slight extent.
From this it will be seen that from a hot solution containing caustic soda and
common salt, the former compound can be separated for the greater part in the form
of sodium carbonate, when the solution is treated with carbonic acid. The speed of
separation of the sodium carbonate formed, is also accelerated by the fact that the
volume of the solution is slightly diminished by reason of the evaporation produced
by the high temperature existing at the time; that is to say, in addition to
saturation of the hot solution with carbonic acid, there is also evaporation taking
place simultaneously therewith.
This process in which evaporation of the solution, saturation of the latter with
carbonic acid, and separation of the resulting sodium carbonate, take place in
one single operation, may, as will be readily understood from the preceding
description, be applied not only to kathode liquids containing caustic soda
together with common salt, but generally to all solutions which contain, either
in addition to substances of normal conditions of solubility, or without these, salts
which can be converted into products that show anomalies of solubility of the kind
set forth.
According to this invention, the weak solution to be treated is caused to flow
in extremely thin streams over large surfaces as a counter current to hot fire
gases i.e. products of combustion (preferably purified) which effect the crystallizing
process by means of their high temperature and the carbonic acid contained
therein. For this purpose it is preferable to employ wire ropes or chains arranged
in a tower-like casing and from which the crystals separated from the solution and
adhering thereto can be detached by a mere shaking motion.
The drawing filed with my Provisional Specification illustrates in longitudinal
section, an apparatus adapted for carrying out this process and which allows
of effecting the saturation and evaporation in a single operation, and of rapidly
removing the separated crystals.

page_text: A is the crystallizing tower provided at the top with a vessel B for receiving the
solution to be treated. The bottom of this vessel is perforated, and in the perforations
there are inserted wire ropes or chains s¹². which hang down freely within
the tower A, so that the liquid flowing down through the spaces between the edges
of the holes and the ropes or chains suspended in the holes, flows down along the
ropes or chains in the form of thin streams. Near the, preferably inclined, bottom
of the tower (which can be connected by means of the outlet pipe a with a collecting
vessel D), and opening into the same, there is an inlet pipe R for the fire gases
coming from a furnace. These fire gases travel upwardly ie. in the opposite direction
to that of the downwardly flowing liquid on the ropes or chains, towards the outlet
pipe a', and thus come into intimate contact with the particles of liquid, whereby
the liquid is quickly evaporated, and the substances thus separated are caused to
crystallize and adhere to the ropes or chains. With such apparatus, as will be
evident from the foregoing description, saturation of the weak solution to be treated,
and the resulting separation of the salt formed, viz. sodium carbonate for instance,
are effected on the wire ropes in one and the same operation. Thus for example, if
the solution to be crystallized, be a solution of caustic soda, the said solution will
be partly evaporated in flowing down the ropes or chains by the oppositely
travelling fire gases; whilst the carbonic acid of the fire gases will combine with
the sodium to form nono-sesqui- and bi-carbonate, which will become deposited in
the form of a crust on the surface of the ropes or chains from which it can be
readily removed by shaking. The dropping crystals are extracted through a side
opening C, whilst the remaining liquid Hows through the outlet pipe a into
the collecting vessel D, whence it may, if desired, be again charged into the
vessel B.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The herein described process for separating a salt from a solution thereof, by
causing the salt solution to flow along and over wire ropes or chains in an
opposite direction to hot fire gases that effect evaporation of such solution, as
set forth.
2. For carrying out the process referred to in the preceding claim, an apparatus
comprising a tower A surmounted by a liquid supply vessel B provided with inlet
and outlet pipes R and a respectively for hot fire gases and with wire ropes or
chains s², s2, sa arranged to extend through the perforated bottom of the vessel B,
and to hang freely in the tower the arrangement being such that fire gases passing
from the inlet pipe R to the outlet pipe a will flow between and around the said
wire ropes or chains, substantially as hereinbefore described with reference to the
drawings referred to.
Dated this 30th day of September 1895
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.