IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF CARBONATES AND BICARBONATE OF Soda AND ACCESSORY PRODUCTS THEREOF, AND ALSO IN APPARATUS USED IN SUCH MANUFACTURE
Year: 1872

page_text: LETTERS PATENT to Ernest Solvay, of Brussels, in the Kingdom of
Belgium, Manufacturer, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OR PRODUCTION OF CARBONATES AND BICARBONATE OF Soda
AND ACCESSORY PRODUCTS THEREOF, AND ALSO IN APPARATUS USED IN SUCH
MANUFACTURE."
Sealed the 19th July 1872, and dated the 18th May 1872.

page_text: MANUFACTURE," and have petitioned Her Majesty to grant unto me, my
executors, administrators, and assigns, Her Royal Letters Patent for the
same, and have made solemn Declaration that I am the true and first
Inventor thereof.
NOW KNOW YE, that I, the said Ernest Solvay, do hereby declare ||
that the following Complete Specification, under my hand and seal, fully
describes and ascertains the nature of the said Invention, and in what
manner the same is to be performed, in and by the following statement,
reference being had to the accompanying Drawings by the words,
figures and letters marked thereon and herein referred to, that is to:
say:
In the said Drawings Fig. 1 is a vertical section; Fig. 2, plan view;
Fig. 3, section; and Fig. 4, plan; Fig. 5, section of arrangements and
parts hereafter described.
The manufacture of the above named substances has hitherto been
carried out by causing carbonic acid gas to act upon a solution of
salt and ammonia in a series of horizontal cylinders, the gas and the
solution passing in opposite directions, or by an apparatus for which I
obtained Letters Patent in 1863, No. 3131, and which consisted of three
compartments superposed one above the other, each of which was
provided with horizontal shelves and with false perforated bottoms;
the gas which entered under a slight pressure passed upwards through
this apparatus and was repeatedly divided by its passage through the
perforated bottoms, while the solution entered the middle compartment
first, then passed through a pipe to the top compartment, and ultimately
through another pipe to the bottom compartment, being compelled to
make a long and circuitous route by the horizontal shelves in the
different compartments.
In all these apparatus the liquor was made to move mainly in a
horizontal direction, and was exposed to the gas in a comparatively
shallow layer, the height of which was never exceeding but generally
very much below its length or width.
Having found this mode of treatment slow and inconvenient I now
force the carbonic acid gas through a column of liquor of considerable
height, always exceeding and generally many times as large as its
greatest width, and I make the liquor pass downwards mainly in a
vertical direction, while the gas passes upward through the liquor.

page_text: In place of the apparatus divided into three compartments I now
employ a single vessel, by preference of a cylindrical shape (A, Fig. 1)
and of considerable height in proportion to its width, which vessel I
hereafter call an absorber. Into this absorber I place a number of
plates (B, Figs. 1 and 2) perforated by small holes so as to divide
the gas as much and as often as practicable, and also a number of
plates (C) provided with one or a few large holes which will just allow
the liquor and gas to pass without permitting the fresh liquor entering
the absorber to mix with the nearly saturated liquor at the bottom
of the absorber. The perforated plates I prefer to make of the shape
of a calotte or globular segment (B, Figs. 1 and 2), and to provide
them with projections or teeth = (some only marked in the Drawing)
round their circumferences, the openings between tho said teeth
allowing the liquor and gas to pass, when the small holes may bo
partially stopped up.
The above-mentioned plates may be cast as part of the apparatus,
or be separate pieces, or be supported therein by any convenient means.
This absorber is always kept nearly full of liquor, while the carbonic
acid obtained from any convenient source, but by preference from a
lime kiln, is forced, say by means of an air pump, in at the bottom of the
absorber through a pipe D. The carbonic acid should enter under a
pressure exceeding the pressure of the column of liquor which the gas
has to pass through. By these means the gas is brought into very
intimate contact with a high column of liquor moving in an opposite
direction, and is at the same time made to expand and to do a con-
siderable amount of mechanical work, in consequence whereof it absorbs
an amount of heat sufficient to prevent all heating of the liquor in the
apparatus otherwise produced by the absorption of the carbonic acid and
which I have found very difficult to effect by any other means. The
liquor is made to enter the said absorber at about half its height through
a pipe (E), and is supplied by a tank (F) in which it is always kept
at the same level, equal to about ten feet, under the top of the said
absorber. This tank is closed and connected with the top of the said
absorber by a pipe (not shewn in the Drawing) in order to equalise
the pressure in both. The same tank will supply any number of
absorbers with liquor. The liquor in the upper half of the said absorber
is thus only renewed, and descends only very slowly, and being very
soon saturated with carbonic acid it is in the proper condition to retain

page_text: height to cause at least the absorption of about one half of the carbonic
acid contained in the gas entering the said absorbers, while at the same
time all the ammonia in the liquor must be converted into bicarbonate
before leaving the absorbers.
I find that the height of 35 to 50 feet gives the best results in
practical working, which requires the gas to be forced into the said
absorbers with a pressure of from one and a half to two atmospheres.
I prefer to force the gas into the absorbers in a manner not altogether
continuous, as I thereby obtain a better agitation inside the absorbers,
which prevents the deposit of bicarbonate of soda in any part of the
apparatus and facilitates its descending with the liquor. From time
to time however the small holes in the perforated plates are partially
closed by a hard crust which forms inside the absorber. The absorber
is then emptied, subsequently filled with water and steam passed into
it until the whole of the crust is dissolved. The solution is run off and
is utilised by known means, and the absorber after cooling is filled
again with the liquor from another absorber and is set to work again
as before. The liquor after being saturated in the absorber is run
out at the bottom through pipes and taps. It may be run out con-
tinuously, but I find it preferable to draw off a quantity from time
to time, say every 30 minutes. This liquor contains a quantity of
bicarbonate of soda in suspension which may be separated by known
means, but I prefer to use for this purpose a vacuum filter. The false
bottom of this filter I cover with strong cloth or any other suitable
material. I produce the vacuum underneath it by preference by the
same pump which lifts the filtered liquor. The vacuum filter permits
the bicarbonate to be perfectly washed with a very small quantity of
water and also permits it to be obtained at once in a comparatively dry
state. In order to be fitted for the market it may be dried in the same
filter by drawing through it for some time air or any other gas or
vapour which may be heated up to about 120 degrees Fahrenheit, or
the bicarbonate may be taken out of the filter and dried in any other
convenient apparatus. If the bicarbonate is to be converted into mono-
carbonate it may be treated in the vacuum filter by drawing through it
hot air or superheated steam or the hot gases from the lime kilns or any

page_text: Other source.
But I prefer for the drying of the bicarbonate as well
as for its conversion into mono-carbonate an apparatus of the following
description :-
This apparatus (Figs. 3 and 4) consists of a vertical cylinder (G) in
which are placed a number of circular shelves (H, some only being
marked) at a convenient distance one above another. A vertical shaft
I driven by any convenient means passes from top to bottom of the
cylinder. This shaft carries arms (K) which are provided with scrapers,
(L, some only marked) and these latter are so arranged that they cause
the substance on the shelves to move alternately to the circumference
of one shelf and to the centre of the next one and so on. The shelves
themselves are double or hollow, so that steam with or without pressure
or superheated or hot air or the gases from the lime kilns or any other
source can be introduced, and they are provided alternately with suitable
openings on the circumference or in the centre which allow the sub-
stance moved by the scrapers to fall from every shelf on to the next one
beneath it until it arrives at the bottom of the cylinder. The bi-
carbonate is fed in on the top of the cylinder from a hopper (M) by means
of a shaft (N) provided with arms (O) which move slowly; the hopper
is always kept full of bicarbonate which prevents the escape of any gas
through it. The dried substance leaves the bottom of the cylinder (by
the doors P) in a finely divided state and ready for packing. By
properly regulating the temperature inside the cylinder one obtains
either bicarbonate or mono-carbonate of soda or any desired mixture
thereof. The gases driven off from the drying substance pass through
a pipe (R) in the top of the cylinder. The drying can also be effected.
in this apparatus by passing a current of air or of superheated steam,
or the gas obtained from the limekilns or any other furnace, or any
other source, through the cylinder, in which case it is not necessary
to use hollow shelves though these will be found to facilitate the drying
under all circumstances. Another drying apparatus which I have
found useful when mono-carbonate of soda is required consists in a
cast-iron pot or pan (S, shown in Fig. 5) which is tightly covered in
by a cast or wrought-iron hood (T) provided with a door (U) through
which the bicarbonate is charged into and the finished product drawn
out of the pot. A vertical shaft (V) driven by any convenient power
passes through a stuffing box in the centre of the hood and carries at
its lower end arms with scrapers (W) which continually turn over

page_text: the material to be dried. The pot is heated by a fire underneath to
the required temperature, and the gases evolved from the drying
bicarbonate pass away through an opening (X) in the hood. The gases
given off in this or the other drying apparatus are passed by means
of an air pump through any convenient cooling and absorbing apparatus
containing brine water, chloride of calcium, or an acid or other efficient
absorbent, in order to retain all the ammonia the gases contain.
When mono-carbonate of soda has been made, these gases also contain
carbonic acid, which is forced through the absorbers previously described
along with the gases obtained from the limekilns or other source. The
gases which leave the absorbers and the gases or air drawn through the
bicarbonate in the vacuum filters, and all or any gases charged with
ammonia which are obtained during any stage of the process before
being allowed to escape into the air, are passed through one or several
convenient washing vessels, by preference of a construction similar to
the absorbers and which are filled with water, brine, chloride of calcium,
an acid, or any other efficient absorbent.
In regenerating the ammonia from the liquor separated from the
bicarbonate of soda I usually employ the ordinary well-known methods,
but in places where muriatic acid is of value I evolve the ammonia
from these liquors by means of magnesia or a basic chloride of
magnesium. The solution of chloride of magnesium and chloride of
sodium thus obtained I boil down, and heat the residua in the presence
of steam until no more muriatic acid is given off, and I condense this
muriatic acid or otherwise utilize it for instance in the direct production
of chlorine by any known means. The solid residue which remains
consists mainly of magnesia and chloride of sodium. After having
dissolved the chloride of sodium by water or weak brine I employ
the remaining magnesia or basic chloride of magnesium to decompose
a new quantity of the above-mentioned liquor. By these means the
same magnesia is used over and over again to regenerate any quantity
of ammonia while at the same time all the chloride of sodium which has
not been transformed into bicarbonate of soda is recovered.
Having now particularly described and ascertained the nature of the
said Invention, and in what manner the same is to be performed or
put in practice, I would here remark that I do not limit myself to
the exact details herein-before mentioned, nor to the precise apparatus
herein-before described and illustrated by the accompanying Drawings,

page_text: nor do I claim the mere details of the said apparatus except as parts
of apparatus for carrying out the above-mentioned manufacture, neither
do I limit myself to the use of such details, but what I claim are the
herein-before described improvements in the manufacture or production
of carbonates and bicarbonate of soda and accessory products thereof, and
also the various herein-before described improvements in the apparatus
used in such manufacture.
Witness,
THOMAS MORGAN,
Secretary,
Inventors' Patent Right Association, Limited,
21, Cockspur Street,
S.W.
E. SOLVAY. (L.S.)