Process for the Purification of Brine.
Year: 1899

page_text: Process for the Purification of Brine.
I, GERHARD NICOLAAS VIS, of Schweizerhalle, near Basel, Switzerland, Doctor of
Philosophy & Chemist, do hereby declare the nature of this invention to be as
follows:-
The present invention relates to the purification of brine, and consists of an
improved process for precipitating the gypsum contained therein.
The gypsum (calcium sulphate) always contained in various proportions in brine is
the cause of serious difficulties, as is well known, in the obtaining of common salt by
means of the evaporation of the said brine, and numerous processes and apparatuses
have already been proposed for its removal.
I have discovered that a large part of the gypsum can be removed from the brine
by dissolving in the latter a sufficient quantity of an easily soluble sulphate, for
instance, sodium sulphate.
The separation of the gypsum is accelerated if the brine mixed with the sulphate
is kept constantly stirred or once boiled, or heated to a lower degree while being
stirred. After the separation of the precipitate, the residue of gypsum remaining
in the brine is removed in the usual manner by the usual means for this purpose,
preferably by means of soda.
To obtain common salt the brine is evaporated. The mother liquor remaining
which contains the sodium sulphate originally added, as well as that formed by the
addition of soda, is utilized in a subsequent process.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.
Process for the Purification of Brine.
I, GERHARD NICOLAAS VIS, of Schweizerhalle, near Basel, Switzerland, Doctor
of Philosophy and Chemist, do hereby declare the nature of this invention and in
what manner the same is to be perforined to be particularly described and ascertained
in and by the following statement :-
The present invention relates to the purification of brine, and consists of an
improved process for removing the calcium sulphate or gypsum contained in the brine
in the dissolved state.
In a prior Patent No. 26777 A.D. 1898 I have described a process for purifying
brine by means of an addition of a solution of calcium chloride whereby the sulphates
077

page_text: of sodium, potassium and magnesium present in the brine are transformed into
calcium sulphate which precipitates and a large percentage of the calcium sulphate
originally present in the brine is caused to separate out.
This process is especially advantageous for places where solutions of calcium
chloride are to be bad at a low cost, as for instance in the neighbourhood of soda
works. In other places this process may be as costly as the old method of removing
the gypsum by means of soda (carbonate of sodium) or other known precipitants.
I have found that a similar effect as that produced by the addition of calcium
chloride will be brought about by dissolving in the brine a convenient quantity of
easily soluble sulphates, for instance alkaline sulphates, alum etc. This procedure
has also the effect of causing a large percentage of the gypsum to separate out, so
that a comparatively small quantity of soda or other precipitant will suffice to
complete the removal of gypsum. Of said sulphates I prefer to use sodium sulphate
or Glauber's salt.
The purifying effect of said addition of sodium sulphate may be seen from the
following table, taking the brine of Schweizerhalle near Basel as an example.
Normally this brine contains 5,368 kilogrammes of gypsum (CaSO4) per cubic meter;
to be precipitated this quantity of gypsum would require 4.573 kilogrammes of sodium
carbonate (Na,CO).
The separation of the gypsum is accelerated if the brine, after the addition of the
sulphate, is kept constantly stirred for twenty-four hours about, or once boiled up,
or heated to a lower degree for a longer period which may be shortened by
stirring.
After the separation of the brine from the precipitated gypsum, the remainder of
the dissolved gypsum is removed from the former in the usual manner by the usual
means for this purpose, preferably by means of sodium carbonate.
The quantity of sulphate to be applied in the first phase of the process must be
calculated according to the amount of gypsum known, or determined by analysis, to
be contained in the brine.

page_text: The gypsum separated from the brine is of a very fine quality, and by its industrial
use the cost of the soda or other precipitant may be largely reduced.
In carrying the process into effect, the Schweizerhalle brine for instance is treated
as follows:-
An
To every cubic meter of this brine are added about 15 kilogrammes of sodium
sulphate. When the latter is completely dissolved the compound solution may once
be boiled up, ie. heated to 107° Centigrade about if fuel is cheap; in general we
prefer to keep said compound solution constantly stirred for 24 hours about.
abundant precipitation of gypsum takes place. The precipitate is then allowed to
settle and the brine drawn off. The latter now contains only 2.276 grammes of
calcium sulphate per liter. This remainder of gypsum is then precipitated in the
usual manner by treating the brine with one or more of the well known means for
removing the gypsum from its solution. I prefer to use sodium carbonate as in
re-acting with the gypsum it is transformed into sulphate of sodium. The brine is
again allowed to settle when it is separated from the precipitate.
To obtain the chloride of sodium (cominon salt) contained in the purified brine free
from gypsum, the brine is evaporated in the usual manner. The mother liquid
remaining after the removal of the salt crystals contains the sodium sulphate
originally added, as well as that formed by the addition of soda, and is utilized in a
subsequent process.
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. The process for the purification of brine from gypsum, which consists in first
removing the greater part of the gypsum dissolved in the brine by adding a soluble
sulphate and then removing the remainder of gypsum left behind in solution in the
usual manner, substantially as described.
2. The process for the purification of brine which consists in treating the brine first
with sodium sulphate and after the separation of the precipitate, with sodium
carbonate, substantially as described.
Dated the 14th day of November 1000
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham.