Process and Apparatus for the Production of Neutral Sulphate of Soda and Sulphuric Acid from Bisulphate of Soda.
Year: 1892

page_text: Date of Application, 1st June, 1892
Complete Specification Left, 8th Sept., 1892-Accepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Process and Apparatus for the Production of Neutral Sulphate of
Soda and Sulphuric Acid from Bisulphate of Soda.
I, EUGENE JEAN BARBIER of 13 Rue des Archives, Paris, France, Manu-
facturer, do hereby declare the nature of this invention to be as follows:-
This invention has reference to a process and apparatus for the production of
neutral sulphate of soda and sulphuric acid from bisulphate of soda, whereby this
compound, which is largely produced in the manufacture of nitric acid, is rendered
of greater commercial value than heretofore.
'
For this purpose I subject a solution of bisulphate of soda to a considerable
reduction of temperature by means of suitable refrigerating apparatus and then
separate the crystals of neutral sulphate of soda thus produced, from the mother
liquor containing sulphuric acid which is afterwards concentrated to a suitable
strength.
The proportion of bisulphate of soda to water will vary with the amount of free
acid contained in the bisulphate employed, but it should be such that the resulting
solution will have a strength of from about 35° to 45° Bé. to ensure efficient
working. The solution is subjected to a series of operations in apparatus the
general arrangement of which is shown in perspective in the accompanying
drawing.
The solution is first introduced into a refrigerator A. wherein it is reduced to a
low temperature. The refrigerating machine or apparatus employed to cool this
refrigerator may be of any suitable kind, and is therefore not shown in the drawing.
The refrigerator A contains a number of troughs D of suitable material as for
examples cast iron or lead or sheet metal. The number and dimensions of these
troughs will vary with the capacity of the apparatus. Thus for example, for an
apparatus capable of treating 5,000 kilogs. of bisulphate of soda per day, four
troughs of 200 litres each may advantageously be employed, or 8 troughs of
100 litres each. The use of a number of troughs enables the working operations to
be in some measure continuous, because whilst some troughs are being discharged
or charged, the contents of the others can be subjected to the cooling action of the
refrigerator. The charging of these troughs is effected by the aid of an inter-
mediate reservoir B provided with a distributing pipe C. The reservoir B is fed
by means of a suitably arranged supply pipe or liquor elevator.
In proportion as the liquid to be treated has undergone the desired refrigeration
in the troughs D, it is discharged therefrom by opening doors or valves d d provided
at the front or below the apparatus. The liquid then flows into a collecting vessel
or spout G which conducts it into a separating and drying machine. E, that may
advantageously be a hydro-extractor or centrifugal machine as shown.
The process is carried out as follows:-
The solution of bisulphate of a strength of from about 35° to 45° Be. is intro.
duced into the troughs D. Under the cooling action of the refrigerating machine,
the temperature of the solution falls quickly. The decomposition of the bisulphate
takes place in proportion to such fall of temperature, and when a thermometer
indicates about 10° C. in the solution, the decomposition is completed or nearly so.
The decomposition will be facilitated by agitating the liquid from time to time
during cooling. The contents of the trough are then discharged, by opening the
corresponding door or valved, into the drying machine E which is then put in rapid
motion.
The complete separation of the crystallized neutral sulphate of soda containing

page_text: ten equivalents of water, and the mother liquors charged with sulphuric acid, is
thus effected, the mother liquors being collected in a reservoir R.
When this separation has been effected and whilst the drying machine is still
rotating, the crystals contained therein are washed in order to remove therefrom
the small amount of acid which still adheres to them. This washing is effected
with water supplied to the drying machine by the pipe H.
The washing waters are collected separately and serve to dissolve a further
quantity of bisulphate. The washed crystals are allowed to fall through a hopper I
into a suitable receptacle arranged below for the purpose. By this means crystal-
lized sulphate of soda having ten equivalents of water, and mother liquors having a
strength from 30° to 42° Be. are separately obtained.
The crystallized sulphate of soda may be sold as such or it may be converted into
anhydrous material according to requirement.
The mother liquors of from 30° to 42° Bc. may in certain cases be utilized
without further treatment for the preparation of the various sulphates such as those
of iron, copper, magnesia etc. and they may be concentrated it may be to 50°, or
to 60° or even to 66° C.
To concentrate them to 50° C. they are simply passed into a concentrating vessel F,
heated by a fire, on a grate below, or waste heat may be employed for this purpose.
These mother liquors concentrated to 50°, deposit on cooling, a small quantity of
undecomposed bisulphate which is collected and added to a further quantity of
bisulphate to be treated as described. The decanted acid may be used for various
purposes, as for example in the manufacture of superphosphates.
If it be desired to re-use the said mother liquors in the manufacture of nitric
acid, the concentration must be carried to 60° to 62° Be. for the manufacture of
commercial nitric acid, and to 66° Be. for the manufacture of strong nitric acid.
To render this concentration casy and practical, there is added to the mother
liquors collected in the reservoir R from the drying machine, about 35 to 40 per
cent. of sulphuric acid of 66°, or, as is more advantageous mother liquors that have
already been concentrated to this strength. This addition, by concentrating the
mother liquors, causes the deposition therefrom of a great part of the bisulphate
present therein. The clear acid is then drawn off and concentrated in the concen-
trating apparatus F, for instance, up to 60° or to 66° as desired.
The mother liquors can also be utilized by distilling them in a retort of suitable
material for example cast iron. After collecting separately the weak acids which
are distilled off at the outset of the operation, there is obtained as a final distillate,
a pure highly concentrated acid of great commercial value.
Dated this 1st day of June 1892
E. J. BARBIER,
By L. W., per F. B.
COMPLETE SPECIFICATION.
Process and Apparatus for the Production of Neutral Sulphate of
Soda and Sulphuric Acid from Bisulphate of Soda.
I, EUGENE JEAN BARBIER, of 13 Rue des Archives, Paris, France, Manu-
facturer, 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:-
This invention has reference to a process and apparatus for the production of
neutral sulphate of soda and sulphuric acid from bisulphate of soda, whereby this
latter compound, which is largely produced in the manufacture of nitric acid, is
rendered of greater commercial value than heretofore.
For this purpose I subject a solution of bisulphate of soda to a considerable
reduction of temperature by means of suitable refrigerating apparatus and then
separate the crystals of neutral sulphate of soda thus produced, from the mother

page_text: liquor containing sulphuric acid which is afterwards concentrated to a suitable
strength.
The proportion of bisulphate of soda to water will vary with the amount of free
acid contained in the bisulphate employed, but it should be such that the resulting
solution will have a strength of from about 35° to 45° Be. to ensure efficient
working. The solution is subjected to a series of operations in apparatus the
general arrangement of which is shown in perspective in the drawing filed with my
Provisional Specification.
The solution is first introduced into a refrigerator A wherein it is reduced to a
low temperature. The refrigerating machine or apparatus employed to cool this
refrigerator may be of any suitable kind, and is therefore not shown in the
drawing. The refrigerator A contains a number of troughs D of suitable
material as for examples cast iron or lead, or sheet metal. The number and
dimensions of these troughs will vary with the capacity of the apparatus. Thus
for example, for an apparatus capable of treating 5,000 kilogs. of bisulphate of soda
per day, four troughs of 200 litres each may advantageously be employed, or
8 troughs of 100 litres each. The use of a number of troughs enables the working
operations to be in some measure continuous, because whilst some troughs are being
discharged or charged, the contents of the others can be subjected to the cooling
action of the refrigerator. The charging of these troughs is effected by the aid
of an intermediate reservoir B provided with a distributing pipe C. The
reservoir B is fed by means of a suitably arranged supply pipe or liquor elevator as
shown.
When the liquid to be treated has undergone the desired refrigeration in the
troughs D, it is discharged therefrom by opening doors or valves d d provided at
the front or below the apparatus. The liquid then Hows into a collecting vessel or
spout G which conducts it into a separating and drying machine E, that may
advantageously be a hydro-extractor or centrifugal machine as shown.
The process is carried out as follows:-
The solution of bisulphate of a strength of from about 35° to 45° Be. is intro-
duced into the troughs D. Under the cooling action of the refrigerating machine,
the temperature of the solution falls quickly. The decomposition of the bisulphate
takes place in proportion to such fall of temperature, and when a thermometer
indicates about 10° C in the solution, the decomposition is completed or nearly
So. The decomposition will be facilitated by agitating the liquid from time to
time during cooling. The contents of the trough are then discharged, by opening
the corresponding door or valve d, into the drying machine E which is then put in
rapid motion.
The complete separation of the crystallized neutral sulphate of soda containing
ten equivalents of water, and the mother liquors charged with sulphuric acid, is thus
effected, the mother liquors being collected in a reservoir R.
When this separation has been effected and whilst the drying machine is still
rotating, the crystals contained therein are washed in order to remove therefrom
the small amount of acid which still adheres to them. This washing is effected
with water supplied to the drying machine by the pipe H.
The washing waters are collected separately and serve to dissolve a further
quantity of bisulphate. The washed crystals are allowed to fall through a
hopper I into a suitable receptacle arranged below for the purpose. By this
means crystallized sulphate of soda having ten equivalents of water, and mother
liquors having a strength from 30° to 42° Be. are separately obtained.
The crystallized sulphate of soda may be sold as such or it may be converted
into anhydrous material according to requirements.
The mother liquors may in certain cases be utilized without further treatment
for the preparation of the various sulphates such as those of iron, copper,
magnesia etc. and they may be concentrated it may be to 50°, or to 60° or even
to 66° Be.
To concentrate them to 50° Be. they are simply passed into a concentrating

page_text: vessel F, heated by a fire on a grate below, or waste heat may be employed
for this purpose. These mother liquors concentrated to 50°, deposit on cooling, a
small quantity of undecomposed bisulphate which is collected and added to a further
quantity of bisulphate to be treated as described. The decanted acid may be used
for various purposes, as for example in the manufacture of superphosphates.
If it be desired to re-use the said mother liquors in the manufacture of nitric
acid, the concentration must be carried to about 60° to 62° Be. for the manufacture
of cominercial nitric acid, and to 66° Be. for the manufacture of strong nitric acid.
To render this concentration easy and practical, there is added to the mother
liquors collected in the reservoir R from the drying machine, about 35 to 40 per cent.
of sulphuric acid of 66°, or, as is more advantageous mother liquors that have
already been concentrated to this strength.. This addition, by concentrating the
mother liquors, causes the deposition therefrom of a great part of the bisulphate
present therein. The clear acid is then drawn off and concentrated in the con-
centrating apparatus F, for instance, up to 60° or to 66° as desired.
1
The mother liquors can also be utilized by distilling them in a retort of suitable
material for example cast iron. After collecting separately the weak acids which
are distilled off at the outset of the operation, there is obtained as a final distillate,
a pure highly concentrated acid of great commercial value.
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 :-
1. The herein described process for the production of neutral sulphate of soda
and sulphuric acid from bisulphate of soda, by subjecting a solution of the latter
salt to reduction of temperature and discharging the cooled liquid into a separating
and drying machine whereby the separation of the crystals of neutral sulphate of
soda are separated from the mother liquors which can then be passed into a con-
centrating oven; as hereinabove set forth.
2. In the production of sulphuric acid from bisulphate of soda as referred to in
Claim 1, effecting the deposition of part of the bisulphate of soda contained in the
mother liquors directly separated from the crystals of neutral sulphate of soda, by
the addition to such mother liquors of strong sulphuric acid or of mother liquors
that have been concentrated, substantially as described.
3. For carrying out the process referred to in Claim 1, a refrigerator constructed
with a number of compartments, each having a discharging outlet whereby the
process can be effected in a practically continuous manner, as herein set forth.
4. For separating the crystals of neutral sulphate of soda from the mother
liquors and for washing the former, apparatus comprising a centrifugal machine
into which the crystals and mother liquors are supplied from a refrigerator, and a
water supply pipe arranged to discharge water directly into the centrifugal machine,
the arrangement being such that after the mother liquors have been removed from
the crystals the latter can be washed in situ substantially as described and shown.
5. In the production of neutral sulphate of soda and sulphuric acid from
bisulphate of soda, apparatus constructed arranged and operating substantially as
described and shown.
Dated him onl 1
1000
E. J. BARBIER,
By L. W., per F. B.