Process for the Separation of the Alkali obtained by Electrolytical Decomposition of Halogen Compounds from the Electrolyte which has not been Decomposed.
Year: 1892

page_text: Date of Application, 17th May, 1892
Complete Specification Left, 23rd May, 1892-Accepted, 16th July, 1892
PROVISIONAL SPECIFICATION.
Process for the Separation of the Alkali obtained by Electrolytical
Decomposition of Halogen Compounds from the Electrolyte
which has not been Decomposed.
I, CARL KELLNER' of IX Turkenstrasse 17 Vienna, Austria, Chemist, do hereby
declare the nature of this invention to be as follows:-
a
The processes heretofore proposed for separating the alkali produced by
electrolytical decomposition of halogen compounds from the electrolyte which has
remained undecomposed, as for example when obtaining caustic soda by electro-
lytical decomposition of common salt, are not suitable for operations on
manufacturing scale, because it is very difficult to separate the product obtained
(say caustic soda), from the incompletely decomposed electrolyte in such a manner
that the said product shall be obtained in a pure state, and at the same time that
that portion of the electrolyte which has not been decomposed shall by being
returned into the cycle of the process, be again utilised. It is true that by
evaporating up to a certain degree, a portion of the undecomposed sodium chloride
will be caused to precipitate, but if the evaporation be continued, the separation of
common salt crystals takes place so quickly and so abundantly that the precipitated
crystals absorb the caustic soda lye. From this it follows that when the evapora-
tion is carried out to an incomplete extent only, the solution of caustic soda still
contains a considerable quantity of undecomposed sodium chloride, whilst if the
evaporation be complete the crystals of common salt will retain the caustic soda
solution.
This invention relates to a process designed to obviate the above mentioned
drawbacks, and the object in view is effected by separating the incompletely decom-
posed electrolyte coming from the decomposing apparatus, after having been
deprived of crystals and evaporated so far as advantageous, from the ion (alkali)
contained therein, by systematic displacement, so that the said ion is obtained in an
almost pure condition, and the entire quantity of the undecomposed residual
electrolyte which is now separated, is returned into the cycle.
For the purpose of enabling the invention to be better understood, I will now
proceed to describe the application of this process to the decomposition of a solution
of common salt.
In the accompanying drawings,
Fig. 1 illustrates a plant for carrying out the process on a manufacturing
scale.
Fig. 2 is a plan of a portion of such plant.
The liquor containing caustic soda and coming from an electrolytical decom-
posing apparatus, is conveyed through a pipe first to a crystallizing apparatus S.
This apparatus is provided with an agitating or stirring device and is connected
with a bucket ladder T, a chain pump or worm conveyor, and in it the said liquor
is crystallized.
The apparatus S is heated by separate firing or by means of the hot gases and
products of combustion passing off from the evaporating apparatus B B' hereinafter
mentioned. The salt conveyed from said apparatus by means of the conveyor T falls
through the hopper t' of the channel t into the displacing apparatus V₁V V³
each of which is provided with a perforated false bottom covered with woven
wire fabric. The space below the faise bottom of each displacing vessel is
connected by a pipe v' with the next vessel, that is to say with the space
therein situated above the false bottom. Over all the vessels is a conduit à fer
brine.

page_text: As soon as one of the displacing vessels is filled with the salty pasty mass
coming from the crystallizing apparatus S, a quantity of brine is admitted from the
pipes into the vessel that was first filled, equal to the quantity of caustic soda
solution found by experience to be retained by the crystal pasty mass in said
vessel.
The brine displaces the liquor contained in the vessel, and at the same time
becomes saturated by dissolving the common salt which is contained in the
electrolyte that is not entirely decomposed and is contained in the separated
alkali.
The liquor displaced from V₁ passes through the pipe into the vessel V2 and
forces in a similar manner the solution contained therein and which is richer in caustic
soda, into V3 from which the solution which has been retained by the common
Balt crystals and is richest in caustic soda, passes through a pipe together
with the liquor coming from the crystallizing apparatus through pipe u into the
evaporating apparatus B.
The solution is then evaporated in B to such a degree that a sample taken
therefrom will, on cooling, not solidify, but assume a syrup-like consistency,
whereupon the entire contents of the apparatus are conveyed to a second displacing
battery W1 W2 W
arranged similarly to that just described wherein they
,
are treated as previously described.
The solution of canstic soda that issues by a pipe u³, from the vessel last
charged of this battery, and which is of very considerable strength is now brought
to the desired strength in vessels or boilers B¹ such as usually employed in the
manufacture of caustic soda as heretofore, and the clear caustic soda drawn off is
poured into moulds or drums.
The last mentioned operation is naturally more simple than heretofore, since an
addition of saltpetre as also the usual and very inconvenient purifying operations
are dispensed with, because the product is quite free from sulphur and does not
contain any other admixture other than about % of common salt.
The brine saturated with common salt in the above described displacing process,
is conveyed back into the decomposing apparatus.
Dated this 17th day of May 1902
CARL KELLNER.
By L. W., per F. B.
COMPLETE SPECIFICATION.
Process for the Separation of the Alkali obtained by Electrolytical
Decomposition of Halogen Compounds from the Electrolyte
which has not been Decomposed.
I, CARL KELLNER, of IX Turkenstrasse 17 Vienna, Austria, Chemist, 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 :-
The processes heretofore proposed for separating the alkali produced by
electrolytical decomposition of halogen compounds from the electrolyte which has
remained undecomposed, as for example when obtaining caustic soda by electro-
lytical decomposition of common salt, are not suitable for operations on a
manufacturing scale, because it is very difficult to separate the product obtained
(say caustic soda), from the incompletely decomposed electrolyte in such a manner
that the said product shall be obtained in a pure state, and at the same time that
that portion of the electrolyte which has not been decomposed shall by being
returned into the cycle of the process, be again utilised. It is true that by
evaporating up to a certain degree, a portion of the undecomposed sodium chloride
will be caused to precipitate, but if the evaporation be continued, the separation of
common salt crystals takes place so quickly and so abundantly that the

page_text: the evaporation is carried out to an incomplete extent only, the solution of caustic
soda still contains a considerable quantity of undecomposed sodium chloride, whilst
if the evaporation be complete the crystals of common salt will retain the caustic
soda solution.
This invention relates to a process designed to obviate the above mentioned
drawbacks, and the object in view is effected by separating the incompletely
decomposed electrolyte coming from the decomposing apparatus, after having been
precipitated as crystals during evaporation and evaporated so far as advantageous,
from the ion (alkali) contained therein, by systematic displacement, so that the said
ion is obtained in an almost pure condition, and the entire quantity of the
undecomposed residual electrolyte which is now separated, is returned into the
cycle.
For the purpose of enabling the invention to be better understood, I will now
proceed to describe the application of this process to the decomposition of a
solution of common salt.
Referring to the drawings left with my Provisional Specification,
Fig. 1 illustrates a plant for carrying out the process on a manufacturing
scale.
Fig. 2 is a plan of a portion of such plant..
The liquor containing caustic soda and coming from an electrolytical decomposing
apparatus, is conveyed through a piper first to a precipitating apparatus S. This
apparatus is provided with an agitating or stirring device and is connected with a
bucket ladder T, a, chain pump or worm conveyor, and in it the said liquor is
precipitated as crystals.
The apparatus S is hented by separate firing or by means of the hot gases and
products of combustion passing off from the evaporating apparatus B B' herein-
after mentioned. The salt conveyed from said apparatus by means of the
conveyor T falls through the hopper t' of the channel into the displacing
apparatus VI V² y³. . .
each of which is provided with a perforated false bottom
covered with woven wire fabric. The space below the false bottom of each
displacing vessel is connected by a pipe ¹ with the next vessel, that is to say with
the space therein situated above the false bottom. Over all the vessels is a
conduits for brine.
As soon as one of the displacing vessels is filled with the salty pasty mass
coming from the precipitating apparatus S, a quantity of brine is admitted from
the pipes into the vessel that was first filled, equal to the quantity of caustic soda
solution found by experience to be retained by the crystal pasty mass in said
vessel.
The brine displaces the liquor contained in the vessel, and at the same time
becomes saturated by dissolving the common salt which is contained in the
electrolyte that is not entirely decomposed and is contained in the separated
alkali.
The liquor displaced from V₁ passes through the pipe o into the vessel V* and
forces in a similar manner the solution contained therein and which is richer in
caustic soda, into V³ from which the solution which has been retained by the
common salt crystals and is richest in caustic soda, passes through a pipe u
together with the liquor coming from the precipitating apparatus through pipe ¹
into the evaporating apparatus B.
The solution is then evaporated in B to such a degree that a sample taken
therefrom will, on cooling, not solidify but assume a syrup-like consistency,
whereupon the entire contents of the apparatus are conveyed to a second
displacing battery WW2 W*. arranged similarly to that just described wherein
they are treated as previously described.
The solution of caustic soda that issues by a pipe 2, from the vessel last charged
of this battery, and which is of very considerable strength is now brought to the
desired strength in vessels or boilers B' such as usually employed in the

page_text: manufacture of caustic soda as heretofore, and the clear caustic soda drawn off is
poured into moulds or drums.
The last mentioned operation is naturally more simple than heretofore, since an
addition of saltpetre as also the usual and very inconvenient purifying operations
are dispensed with, because the product is quite free from sulphur and does not
contain any admixture other than about 3-6% of common salt.
The brine saturated with common salt in the above described displacing process,
is conveyed back into the decomposing apparatus.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The herein described process for separating alkali obtained by electrolytical
decomposition of halogen compounds, from the undecomposed residual electrolyte,
by first precipitating as crystals during evaporation the incompletely decomposed
electrolyte coming from the electrolytical decomposing apparatus and then, after
evaporating if necessary, separating the alkali contained therein by repeated and
systematic displacement by means of brine, whereby the said alkali is obtained in
an almost pure condition, whilst the whole of the residual undecomposed electrolyte
is separated and is returned into the cycle, as set forth.
Dated this 23rd day of May 1892.
O. KELLNER,
By L. W., per F. B.