IMPROVEMENTS IN THE MANUFACTURE OF CARBONATES OF SODA, AND IN THE PROCESSES AND APPARATUS USED IN SUCH MANUFACTURE, RELATIVE SPECIALLY TO THE NODE OF USING CARBONIC ACID, AND TO THE CONVERSION OF BICARBONATE OF SODA INTO COMMERCIAL CARBONATE OF SODA
Year: 1876

page_text: LETTERS PATENT to Ernest Solvay, of Brussels, in the Kingdom of Belgium,
Manufacturer, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
CARBONATES OF SODA, AND IN THE PROCESSES AND APPARATUS USED IN SUCH
MANUFACTURE, RELATIVE SPECIALLY TO THE NODE OF USING CARBONIC ACID,
AND TO THE CONVERSION OF BICARBONATE OF SODA INTO COMMERCIAL
CARBONATE OF SODA."
Sealed the 4th August 1876, and dated the 20th May 1876.
PROVISIONAL SPECIFICATION left by the said Ernest Solvay at the Office of
the Commissioners of Patents on the 20th May 1876.
ERNEST SOLVAY, of Brussels, in the Kingdom of Belgium, Manufacturer. "IM-
PROVEMENTS IN THE MANUFACTURE OF CARBONATES OF SODA, AND IN THE PRO-
CESSES AND APPARATUS USED IN SUCH MANUFACTURE, RELATIVE SPECIALLY TO THE
MODE OF USING CARBONIC ACID, AND TO THE CONVERSION OF BICARBONATE OF
SODA INTO COMMERCIAL CARBONATE OF SODA."
My Invention relates to the manufacture of carbonates of soda by the process
generally known as the ammoniacal process, for which Letters Patent were granted
to me bearing date the 11th of December 1863, No. 3131, and the 18th of May
1872, No. 1525, and which process as further improved by me is described in two
Provisional Specifications filed by me in the Great Seal Patent Office respectively
on the 8th day of March 1876, No. 999, and the 5th day of May 1876, No. 1904.
My present Invention having reference to different parts of the said manufacture
I will describe each of the improvements separately in relation to the part of the
manufacture to which it applies. The manufacture of carbonates of soda by the
ammoniacal process is now well known, having been described in the Specification
of my said Patent of 1863.
The first part of my Invention relates to the mode of using carbonic acid in the
said manufacture.
My process of manufacturing carbonates of soda owes its success to my having
been the first to bring together in the apparatus for effecting the reaction of
carbonic acid means sufficiently powerful for the said reaction to be effected
completely in a manufacturing point of view.
To mechanical pressure, to reiterated division of the gas, to the great height of
the apparatus, and to the mode of introducing the liquid at present employed in my

page_text: process, I now add a preliminary preparation of the liquid by the addition thereto
of carbonic acid. I was led to add this operation to my process by a discovery I
inade, and by seeing the utility of obviating certain peculiarities in the arrangement
of my apparatus.
I discovered that the heating effect produced by the reaction of carbonic acid
upon ammoniacal brine is not the same in all stages of the operation; at first tho
effect is intense, it then diminishes, if it does not completely disappear. So that if
the said operation be divided into two parts it will be found that the heat is
produced nearly exclusively in the first part of the operation. Now the first part
of the operation, that is to say, a very incomplete carbonatation of the ammoniacal
liquid may be effected very easily without employing any special means, whilst the
remainder of the reaction operation presents such difficulties that many persons
have already endeavoured in vain to overcome them. One of the conditions
required for the said reaction to be effected speedily and completely is to operate at
a low temperature. Now the discovery I made gives exactly the means of confining
to the easy part of the reaction process the injurious production of heat, which,
however, may be readily counteracted, and to perform the difficult part of the
operation without injurious production of heat. The importance of this discovery
will be readily understood as it enables me to bring into action my powerful means
of absorption without injurious production of heat, and in such conditions as had
never been imagined.
The numerous advantages produced by my apparatus gives still more importance
to the division of the operation, not only as regards the refrigerator from the
difficulty of cooling in a large apparatus considerable quantities of liquid, but also
as regards preventing the loss of ammonia. For though the great multiplicity
of points of contact between the gas and liquid is exceedingly favourable to reaction
and is an essential condition of success, it has the disadvantage of causing more of
the ammonia to be carried off mechanically. This disadvantage is obviated by
fixing the ammonia in a previously formed salt which is effected by preliminary
carbonatation.
The combination herein-before described is realized as follows:-Pure carbonic
acid procured as herein-after described or produced by other means which, however,
would be less advantageous, is introduced into the upper compartments of the dis-
tilling column of the apparatus used for the distillation of ammonia. In the said
compartments the carbonic acid combines with the caustic ammonia and transforms
it into carbonate of ammonia, which is then made to pass into the apparatus for
dissolving ammonia, and is there absorbed by the brine with which it passes into
the absorber.
My Invention relates, secondly, to the conversion of bicarbonate of soda into
carbonate of soda. The decomposition and calcination of bicarbonate of soda are
now effected in a single operation by various processes. According to my Invention
I divide the operation. First I decompose the bicarbonate into carbonate of soda,
and afterwards I dry and calcinate the carbonate.
First Operation Decomposition of Bicarbonate of Soda.-I effect the decom-
position of bicarbonate of soda either by the action of steam or by chemical means.
I will first describe the mode of effecting the said decomposition by the action of
steam. By the use of ordinary steam, such as is produced in a boiler, a last lixivia-
tion may be operated and the decomposition of the bicarbonate may be effected
simultaneously. The said steam is introduced either into the filter or into any
other apparatus by which bicarbonate may be extended and brought into contact
with steam. An apparatus of the kind is described in the Provisional Specification
filed by me on the 5th day of May 1876, No. 1904.
I prefer to use the apparatus therein described as though the material has to be
transported thereto, it allows of the bicarbonate being spread more lightly, and also
several apparatus may be arranged in succession so that the steam not condensed in
the first apparatus is condensed in the second, and so on. A distributor causes the

page_text: steam to enter each apparatus successively, and allows one or two of the said
apparatus to be isolated for charging and discharging.
The apparatus consists of a suitable number of decomposers in communication
with a distributor. The steam entering the distributor passes first into the upper
part of one of the said decomposers, traverses the bicarbonate of soda it contains,
and then re-enters the distributor. It then passes into another of the said decom-
posers, re-enters the distributor, and lastly passes into a pipe which conveys the
carbonic acid gas into the distilling column. The heat of the steam is sufficient to
decompose the bicarbonate of soda, and the latent heat is utilized in decomposing
the said bicarbonate, so that I thus obtain an infinitely greater effect than if I used
a non-condensible gas or even superheated steam, the condensation of which would
be but partial, and parts of which would first be condensed and then again evaporate
before the end of the operation. The water of condensation herein-before alluded
to is collected and utilized in effecting a first lixiviation of the bicarbonate of soda
in the filter.
I will now describe the process of the decomposition of bicarbonate of soda by
chemical means.
Until now the means employed in converting bicarbonate into carbonate of soda
consisted solely in expelling therefrom the excess of carbonic acid by the action of
heat. I use a different process, which consists in placing the said bicarbonate in
presence of a basic substance which takes up the excess of carbonic acid and forms
a carbonate. For this purpose I use ammonia, either causing a current of gaseous
ammonia to pass through the bicarbonate of soda upon the filter or in a suitable
apparatus such as is herein-before described, or else placing the bicarbonate of soda
in an ammoniacal liquid, such as ammoniacal brine. When the means last described
are used the liquid after the decomposition is effected should be separated from
the carbonate of soda by another filtration, and when ammoniacal brine is used a
certain lixiviation must be effected, and for these operations it is necessary that
suitable heat should be maintained in the apparatus.
The process of decomposition herein-before described has the advantage of
effecting at the same time the preliminary carbonatation of the ammoniacal brine,
or of the ammonia to be used in the preparation of the said brine.
Second Operation.-Drying and Calcination of the Carbonate of Soda.--When the
bicarbonate of soda has been previously decomposed and deprived of its ammonia
in one of the special apparatus herein-before described, it is necessary to complete
the operation by drying or calcinating the carbonate produced, but one of the
advantages of the preliminary decarbonatation herein-before described is that the
said drying or calcination may be effected in one of the furnaces already used
in soda manufactories for making soda according to the process known as Leblanc's
process, or in any other apparatus used in the open air, there being no more gas to
Le preserved.
I use in my manufacture as a calcinator a rotatory furnace similar to what is used
in other manufactories for melting and combining together certain substances, but
modified to suit its present destination by arranging it so that the salt remains in
it only long enough for it to be calcined and not melted. For this purpose the
furnace may be slightly inclined or may be made of a conical shape and is open at
both ends. The salt is poured in continuously at one end and passes out at the
other end into a suitable chamber in which it is collected. The advance of the salt
is regulated by the velocity of rotation of the furnace according to the intensity of
the fire. The apparatus used consists of a rotatory cylinder lined inside with fire-
bricks, and receiving rotatory motion from suitable gearing. The said cylinder,
which is heated internally either by means of a firegrate or a gas generator, is
supported on rollers. The bicarbonate of soda is introduced into the said cylinder
through a tube at one end and passes out into a chamber at the other end.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Ernest Solvay in the Great Seal Patent Office on the 13th November
1876.
ERNEST SOLVAY, of Brussels, in the Kingdom of Belgium, Manufacturer.
"IM-
PROVEMENTS IN THE MANUFACTURE OF CARBONATES OF SODA, AND IN THE PROCESSES
AND APPARATUS USED IN SUCH MANUFACTURE, RELATIVE SPECIALLY TO THE MODE
OF USING CARBONIC ACID, AND TO THE CONVERSION OF BICARBONATE OF SODA
INTO COMMERCIAL CARBONATE OF SODA,"
My Invention relates to the manufacture of carbonates of soda by the process
generally known as the ammoniacal process, for which Letters Patent were granted
to me bearing date the 11th of December 1863, No. 3131, and the 18th of May
1872, No. 1525, and which process as further improved by me is described in the
Specifications of Letters Patent granted to me bearing date respectively the 8th day
of March 1876, No. 999, and the 5th day of May 1876, No. 1904.
My present Invention having reference to different parts of the said manufacture
I will describe each of the improvements separately in relation to the part of the
manufacture to which it applies. The manufacture of carbonates of soda by the
ammoniacal process is now well known, having been described in the Specification
of the said Patent of 1863.
The first part of my Invention relates to the mode of using carbonic acid in the
said manufacture.
My process of manufacturing carbonates of soda owes its success to my having
been the first to bring together in the apparatus for effecting the reaction of
carbonic acid means sufficiently powerful for the said reaction to be effected
completely in a manufacturing point of view. To mechanical pressure, to reiterated
division of the gas, to the great height of the apparatus, and to the mode of intro-
ducing the liquid at present employed in my process, I now add a preliminary
preparation of the liquid by the addition thereto of carbonic acid. I was led to
add this operation to my process by a discovery I made, and by seeing the utility
of obviating certain peculiarities in the arrangement of my apparatus.
I discovered that the heating effect produced by the reaction of carbonic acid
upon ammoniacal brine is not the same in all stages of the operation; at first the
effect is intense, it then diminishes, if it does not completely disappear. So that if
the said operation be divided into two parts it will be found that the heat is
produced nearly exclusively in the first part of the operation. Now the first part
of the operation, that is to say, a very incomplete carbonatation of the ammoniacal
liquid may be effected very easily without employing any special means, whilst
the remainder of the reaction operation presents such difficulties that many persons
have already endeavoured in vain to overcome them. One of the conditions
required for the said reaction to be effected speedily and completely is to operate
at a low temperature. Now the discovery I have made gives exactly the means
of confining to the easy part of the reaction process the injurious production of
heat, which, however, may be readily counteracted, and to perform the difficult
part of the operation without injurious production of heat. The importance of
this discovery will be readily understood as it enables me to bring into action my
powerful means of absorption without injurious production of heat, and in such
conditions as had never been imagined.
The numerous advantages produced by my apparatus give still more importance
to the division of the operation, not only as regards the refrigeration from the
difficulty of cooling in a large apparatus considerable quantities of liquid, but also
as regards preventing the loss of ammonia. For though the great multiplicity of
points of contact between the gas and liquid is exceedingly favourable to reaction,
and is an essential condition of success, it has the disadvantage of causing more
of the ammonia to be carried off mechanically. This disadvantage is obviated by
fixing the ammonia in a previously formed salt, which is effected by a preliminary
carbonatation.

page_text: The combination herein-before described is realized as follows:-Puro carbonic
acid procured as hereiu-after described or produced by other means, which, however,
would be less advantageous, is introduced into the upper compartment of the
distilling column of the apparatus used for the distillation of ainmonia. In the
said compartment the carbonic acid combines with the caustic ammonia and
transforms it into carbonate of ammonia, which is then made to pass into the
apparatus for dissolving ammonia, and is there absorbed by the brine with which
it passes into the absorber.
My Invention relates, secondly, to the conversion of bicarbonate of soda into
carbonate of soda. The decomposition and calcination of bicarbonate of soda are
now effected in a single operation by various processes. According to my Invention
I divide the operation. First I decompose the bicarbonate into carbonate of soda,
and afterwards I dry and calcinate the carbonate.
First Operation. Decomposition of Bicarbonate of Soda.-I effect the decom-
position of bicarbonate of soda either by the action of steam or by chemical means.
I will first describe the mode of effecting the said decomposition by the action
of steam. By the use of ordinary steam, such as is produced in a boiler, a last
lixiviation may be operated and the decomposition of the bicarbonate may be
effected simultaneously. The said steam is introduced either into the filter or into
any other apparatus by which bicarbonate may be extended and brought into contact
with steam. An apparatus of the kind is described in the Specification of my
Letters Patent of the 8th day of March 1876, No. 999.
I prefer to use the apparatus therein described as though the material has to be
transported thereto, it allows of the bicarbonate being spread more lightly, and also
several apparatus may be arranged in succession so that the steam not condensed
in the first apparatus is condensed in the second, and so on. A distributor causes
the steam to enter each apparatus successively, and allows one or two of the said
apparatus to be isolated for charging and discharging.
Fig. 1 of the accompanying Drawing represents an elevation and section of one
of the numerous arrangements of apparatus which may be used for carrying into
effect this part of my Invention.
A, B, C, D, are the decomposers, of which there may be any suitable number.
O is a distributor, into which the steam passes through a pipe T. The said
distributor O allows of one, two, or several of the apparatus to be isolated simul-
taneously for the purpose of filling and emptying it or them. Supposing that two
of the said decomposers be isolated at the same time, and that A be the decomposer
isolated to be emptied, and D the decomposer isolated to be filled, the steam
entering the distributor O passes first through the pipe t into the upper part of
the apparatus B, traverses the bicarbonate of soda it contains, and passes out
through the pipe t, and enters again into the distributor, passing out therefrom
through the pipe t¹¹, and entering it again through the pipe t, and passing out at
last therefrom through the pipe tv, which conveys the carbonic acid gas to the
distilling column. The heat of the steam is sufficient to decompose the bicarbonate
of soda, and the latent heat is utilized in decomposing the said bicarbonate, so that
I thus obtain an infinitely greater effect than if I used a non-condensible gas or even
superheated steam, the condensation of which would be but partial, and parts of
which would first be condensed and then again evaporated before the end of the
operation. The water of condensation herein-before alluded to is collected and
utilized in effecting a first lixiviation of the bicarbonate of soda in the filter.
I will now describe the process of the decomposition of bicarbonate of soda by
chemical means.
Until now the means employed in converting bicarbonate into carbonate of soda
consisted solely in expelling therefrom the excess of carbonic acid by the action of
heat. I use a different process, which consists in placing the said bicarbonate in
presence of a basic substance, which takes up the excess of carbonic acid and forins
a carbonate. For this purpose I use aminonia, cither causing a current of gaseous
ammonia to pass through the bicarbonate of soda upon the filter or in a suitable

page_text: apparatus, such as is herein-before described, or else placing the bicarbonate of soda
in an ammoniacal liquid, such as ammoniacal brine. When the means last described
are used the liquid after the decomposition is effected should be separated from
the carbonate of soda by another filtration, and when ammoniacal brine is used a
certain lixiviation must be effected. And for these operations it is necessary that a
suitable heat should be maintained in the apparatus.
The process of decomposition herein-before described has the advantage of effect-
ing at the same time the preliminary carbonatation of the ammoniacal brine, or of
the ammonia to be used in the preparation of the said brine.
Socond Operation.-Drying and Calcination of the Carbonate of Sodu.— When
the bicarbonate of soda has been previously decomposed and deprived of its am-
monia in one of the special apparatus herein-before described, it is necessary
to complete the operation by drying or calcinating the carbonate produced; but one
of the advantages of the preliminary decarbonatation herein-before described is that
the said drying or calcination may be effected in one of the furnaces already used
in soda manufactories for making soda according to the process known as Leblanc's
process, or in any other apparatus used in the open air, there being no more gas to
be preserved.
I use in my manufacture as a calcinator a rotatory furnace similar to what is
used in other manufactories for melting and combining together certain substances,
but modified to suit its present destination, by arranging it so that the salt remains
in it only long enough for it to be calcined and not melted. For this purpose the
furnace may be slightly inclined or may be made of a conical shape, and is open at
both ends. The salt is poured in continuously at one end and passes out at the
other end into a suitable chamber in which it is collected. The rapidity with which
the salt is caused to advance is regulated by the velocity of rotation of the furnace
according to the intensity of the fire.
The said apparatus is represented in Figs. 2 and 3. Fig. 2 being a longitudinal
section, and Fig. 2 a cross section. The said apparatus consists of a rotatory
cylinder A, the inside of which is lined with fire-bricks. A slow rotatory motion
is communicated to the said cylinder A by toothed gearing E and e. The said
cylinder which works upon rollers and is heated internally either by means of
an ordinary fire-grate or a gas generator of a more or less perfect kind, such for
instance as is represented at F, in Fig. 2, and which consists of an inclined grate
charged from the hopper T. The carbonate of soda is introduced into the furnace
A through the tubo B, and passes out in a calcined state into the chamber C, from
which it may be removed through the doorway O.
Having now described the nature of iny said Invention, and in what manner the
same is to be performed, I wish it to be understood that I do not confine myself to
the precise details herein-before described and illustrated in the accompanying
Drawings as the same may be varied without departing from the nature of my said
Invention, nor do I claim the details of the said process and apparatus except as
parts of processes and apparatus for carrying out the manufacture of carbonates of
soda by the ammoniacal process.
But I claim as my Invention―
Firstly. With reference to the mode of using carbonic acid in the said manu-
facture, I do not claim per se the preliminary carbonatation of the ammoniacal
brine by means of carbonic acid, nor the use of pure carbonic acid therefor, but I
claim the improvements in the processes and means hitherto used for effecting the
reaction of carbonic acid in the said manufacture by the combination with and
the addition to such processes and means of a preliminary carbonatation of the
ammoniacal brine essentially as herein-before described and for the purposes
set forth.
Secondly. With reference to the decomposition of the bicarbonate of soda and
the drying or calcination of the carbonate of soda produced, I claim dividing
the operation into two distinct processes, so that the process for decomposing

page_text: the bicarbonate of soda into carbonate of soda precedes the calcination of the said
carbonato.
Also I claim the application of ordinary steam to the decomposition of bicarbonate
of soda, essentially as herein-before described, that is to say, in such a manner that
the said bicarbonate will have numerous points of contact with the said steam,
and that the latent heat in the said steam may be utilized, and the water of
condensation may be used for effecting a first lixiviation of the bicarbonate of soda
upon the filter.
Also the industrial application of ammonia in the form of gas or liquid to the
decomposition of bicarbonate of soda, essentially as described.
Also the application to the calcination of carbonate of soda of a rotatory furnace
heated internally by constructing the said furnace with open ends so as to form
a continuous apparatus, essentially as herein-before described and illustrated in the
accompanying Drawings.
In witness whereof, I, the said Ernest Solvay, have hereunto set my hand
and seal, this Ninth day of November, in the year of our Lord One thousand
eight hundred and seventy-six.
ERNEST SOLVAY. (L.S.)