IMPROVEMENTS IN THE MANUFACTURE OF BICARBONATE OF SODA, AND IN APPARATUS FOR THAT PURPOSE
Year: 1880

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
BICARBONATE OF SODA, AND IN APPARATUS FOR THAT PURPOSE."
A com-
munication from abroad by Alfred Rangod Pechiney, Chemical Manufacturer,
of Salindres in the Republic of France.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 24th May 1880.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. "IMPROVE-
MENTS IN THE MANUFACTURE OF BICARBONATE OF SODA, AND IN APPARATUS FOR
THAT PURPOSE." A communication from abroad by Alfred Rangod Pechiney,
Chemical Manufacturer, of Salindres, in the Republic of France.
This Invention relates to the manufacture of bicarbonate of soda by what is
known as the ammonia process.
The apparatus which forms the main part of this Invention consists of an iron
cylinder, which may be called E, disposed horizontally, and arranged so as to be
capable of turning on its longer axis. A diaphragm, which may be called A, passes
from end to end of this cylinder, the line of the centre of this diaphragm being the
line of the longer axis of the cylinder. The diaphragmn A thus divides the cylinder
longitudinally into two equal compartments. The diaphragm A is pierced with
small holes throughout all its extent. The cylinder is divided into further com-
partments by a series of diaphragms, which may be called B, which diaphragms
B are all parallel with the ends of the cylinder, and perpendicular to its longer
axis, and so perpendicular to the diaphragm A. In each of the diaphragms B is
only one aperture which is placed at its centre, so that one half of the aperture in
each diaphragm B is on one side, and the other half on the other side of the
diaphragm A. The two axles on which the cylinder turns have passages through
them by which gases and liquids can enter and pass off. They are fixed to and
turn with the cylinder, and therefore work in stuffing-boxes. One of these axles,
which may be called C, has only one passage through it; this passage serving both.
for the admission into the cylinder of the solution of ammonia and common salt,

page_text: and for the exit from the cylinder of such gases as have entered it at the other end,
and have not been absorbed in it.. The other axle, which may be called D, has two
passages through it of the nature of two tubes, one placed concentrically within the
other. The inner passage is for the exit from the cylinder of the solution holding
in suspension the bicarbonate of soda which has been formed in the cylinder, and
also for the entrance into the cylinder of the pure carbonic acid gas obtained by
the calcination of bicarbonate of soda formed in a previous operation. The annular
passage outside the inner passage is for the admission into the cylinder of impure
carbonic acid from a lime kiln or other convenient source. The inner passage com-
municates with the first of the series of compartments formed by the diaphragmns B;
but the annular passage outside that inner passage is so connected with two tubes,
each of which passes through the first three of the diaphragms B, one on one side,
and the other on the other side of the diaphragm A, that the impure gas entering
by that annular passage enters the fourth of the compartments formed by the
diaphragms B. The extremity of the passage through the axle C which is farthest
from the cylinder E communicates with the lower part of a vertical cylinder, which
may be called H. The inner of the two passages through the axle D communicates
by a bend beyond the stuffing box with a horizontal cylinder, which may be called I.
This cylinder I receives the liquid holding in suspension the bicarbonate formed in
the cylinder E, and the pure carbonic acid gas resulting from the calcination of
previously-formed bicarbonate before entering the cylinder E also enters this
cylinder I.
In order to the manufacture of bicarbonate of soda by means of this apparatus, it
is necessary that the cylinder E should make suddenly and at regular intervals a
half-revolution. Many means may be used to this end, but the inventor prefers to
effect the movement of the cylinder E automatically by means of a hydraulic
accumulator. This communicates with two hydraulic cylinders placed vertically,
one on each side of the cylinder E. These hydraulic cylinders may be called
F and G.. The piston in F communicates by a chain with a pulley placed on a
wheel, to which is attached a chain attached to the cylinder E in such wise that
when water from the accumulator forces down this piston the cylinder E makes
half a revolution. The piston in G is similarly connected with another wheel
similarly connected by a chain with the cylinder E, so that by foreing down the
piston in F, not only is the cylinder E caused to make half a revolution, but the
piston in G is at the same time raised. If water from the accumulator be now
made to force down the piston in G, the cylinder E will again make half a
revolution in the direction opposite to that of its previous half-revolution, and the
piston in F will at the same time be raised. These alternate half-revolutions with
an interval of rest between are obtained automatically by the cocks on the
cylinders F and G being worked by the accumulator itself. A single pair of
hydraulic cylinders only has been spoken of; but when the cylinder E is very long,
several pairs of bydraulic cylinders will be necessary to each cylinder E.
The apparatus works as follows:-
Ammoniacal brine enters the cylinder E from the vertical cylinder I by the
passage through the axle C. It makes its way through the apertures in the centre
of each diaphragm B until the cylinder E is completely charged, which is when
each of the compartments into which it is divided by the diaphragms B is nearly
half-filled. The operation is then continuous, ammoniacal brine continually
entering by the passage through the axle C, carbonic acid gas continually entering
by the two passages through the axle D, and mixed solution holding bicarbonate
in suspension continually passing off from the cylinder E into the cylinder H by
the inner of the two concentric passages through the axle D. The ammoniacal
brine entering by the axle C and Howing towards the axle D meets a current of
gas continually richer and richer in carbonic acid, and in the four compartments
nearest to the axle D consisting of carbonic acid only, which current of gas travels
in the opposite direction. The contact of the ammoniacal brine with the gus is
promoted by the frequent sudden half-revolution of the cylinder E. When the

page_text: cylinder E is at rest its diaphragm A is parallel with the earth's surface, and the
liquid part of the charge is all in those portions of the compartments into which
the cylinder is divided by the diaphragms B which are below the diaphragm A.
When the cylinder now makes a balf-revolution, the liquid part of the charge
passes through the holes in the diaphragm A, and falls in a finely divided state
through an atmosphere of gas into those halves of the compartments formed by the
diaphragmns B which are on the other side of the diaphragın A. The frequent
repetition of these half-revolutions of the cylinder E thus enable its liquid contents
to become saturated with carbonic acid very rapidly. To carry off the heat
generated by the absorption of the carbonic acid, cold water is kept trickling over
the exterior surface of the cylinder E.
It is preferred that the carbonic acid should be sent into the cylinder E under
considerable pressure, and a part of this Invention consists in employing the gases
which pass off from the cylinder E afterwards to do mechanical work, and in then
using them as a refrigerating agent. Before being thus employed they are washed,
first, by being made to bubble through a solution of common salt, and afterwards
by being passed up coke-towers down which a solution of salt continually trickles.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Weldon in the Great Seal Patent Office on the 22nd November
1880.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. "IMPROVE-
MENTS IN THE MANUFACTURE, OF BICARBONATE OF SODA, AND IN APPARATUS FOR
THAT PURPOSE."
This Invention relates to the manufacture of soda by what is known as the
ammonia process.
The first step in that process consists in treating a solution of ammonia and
common salt by carbonic acid gas, mixed or not with other gases.
Under the present Invention that operation is performed in and by means of
an apparatus which I will now describe by the aid of the accompanying Sheet of
Drawings.
"The apparatus includes a horizontal iron cylinder A, Figures 1 and 2, so
supported as to be capable of rotation on its longer axis. This cylinder is divided
internally into compartments by the diaphragm b, b₁, passing from end to end of
the cylinder, and by the series of vertical diaphragms a, a, a. In each vertical
diaphragm is an opening marked o. The horizontal diaphragm b, 61, is pierced with
holes over all its surface.
The trunnions B and C are hollow in order to permit that by them gases and
liquid shall enter into and pass out of the cylinder A. The details of their
disposition are shown in Figures 3, 4, 5, and 6.
The trunnion C is disposed as shown in Figure 6. By it solution of salt and
ammonia, which will hereinafter be spoken of as "ammoniacal brine," enters the
cylinder A, and the gases which have not been absorbed in that cylinder pass out
of it. It works in a stuffing-box communicating with the vertical cylinder D.
The trunnion B is more complicated. The product of the treatment in the
cylinder A of ammoniacal brine by carbonic acid gas has to pass out by it, and
both pure carbonic acid gas from the calcination of the bicarbonate of soda formed
in a previous operation and impure carbonic acid gas from a lime-kiln or other
source liave to pass in by it. It consists of two concentric tubes, as shown in
Figures 3 and 4, and works in a stuffing-box communicating with the horizontal
cylinder F. The inner tube g, Figure 4, is divided internally into two equal parts
by a longitudinal partition, and there are pierced in it, at i;, two openings, by
which either half of it can communicate with the tubulure j. The annular space
between the two tubes fand g is prolonged to right and left, as shown in horizontal
section in Figure 5, in such wise as to establish communication between that annular
space and the two tubes t and t¹.
The cylinder A is required to be capable of being made to undergo from time to
time at regular intervals a sudden semi-revolution. The appliances which can be.
used to this end are very various, but those which my correspondent believes to be
best, and which constitute a part of this Invention, are appliances by which a
sudden semi-revolution is given to the cylinder A at regular intervals by water
from an "accumulator "acting alternately, firstly, on the piston of a hydraulic
cylinder or on the pistons of a number of hydraulic cylinders placed on one side of
the cylinder A, and, secondly, on the piston of a hydraulic cylinder or on the
pistons of a number of hydraulic cylinders similarly placed on the other side of the
cylinder A, the motion of the pistons being communicated to the cylinder A by
means of chains.
These appliances are indicated in Figures 1 and 2. In these Figures P and P¹
are hydraulic cylinders placed vertically on each side the cylinder A, and fixed

page_text: between the columns N, N¹. Supported on the cross-pieces binding together the
columns N, N¹, are the pullies H, H', and I, I'. The chain c is attached by its lower
extremity to the piston working in the hydraulic cylinder P, and by its upper
extremity to the pulley I; and the chain c₁ is similarly attached by its
lower extremity to the piston working in the hydraulic cylinder P', and by its
upper extremity to the pulley I. The third chain e, e, passes under the cylinder A,
as shown in Figure 1, and is attached by its extremities to the pullies H, H'.
These appliances work as follows:-The apparatus being in the position
indicated by the Drawings water from an accumulator is admitted above the
piston in the hydraulic cylinder P¹. That piston then descends, and its descent
puts in motion the pullies I', and H', thereby causing the chain e to move in the
direction indicated by the arrow. By the time the piston in the hydraulic cylinder Pl
has completely descended the consequent motion of the chain e has carried the
cylinder A half round, and has also by the motion communicated by the chain e to
the pullies H and I, and through them to the chain c, drawn up the piston in the
hydraulic cylinder P to the upper extremity of its course. The cylinder A having
thus made half a revolution, and the piston in the cylinder P' having descended to
the bottom of that cylinder, and the piston in the cylinder P having been raised
to the upper extremity of its course, the whole system remains in this new position
until water from the accumulator is admitted above the piston in the cylinder P.
The same motions as before are then reproduced, but in the opposite direction, so
that the apparatus reassumes the position shown in Figures 1 and 2.
.These intermittent sudden movements are obtained automatically, the cocks which,
admit water alternately above the piston in the cylinder P and above the piston
in the cylinder P¹ being worked by the plunger of the accumulator itself, as will
be well understood.
Only one pair of hydraulic cylinders is shown in the Drawing, but the longer the
cylinder A the greater the number of pairs of hydraulic cylinders which will require
to be used.
Bicarbonate of soda is manufactured by means of the apparatus thus described
as follows:-Ainmonaical brine enters the cylinder D by the tube K, and passes
from the cylinder D into the last compartment of the cylinder A. It then makes
its way from compartment to compartment of the cylinder A by means of the
openings o in the diaphragms a, a, a, in such wise that, at length, as fast as .
ammoniacal brine enters through C, liquid holding bicarbonate of soda in suspension
passes out of the cylinder A by the upper part of the tube g, and then into the
recipient cylinder F by the tubulure . Carbonic acid from the calcination of a:
previously formed quantity of bicarbonate of soda passes first into the cylinder F,
whence it passes into the first compartment of the cylinder A by the tubulure j
and the lower half of the tube g. Dilute carbonic acid from a lime-kiln or other
source arrives by the tube R, and passes from the tube R into the annular space
between the the tubes fand g, whence it passes into the tubes t and t', from which
it issues into the fourth compartment of the cylinder A.. The liquid which is
treated in the cylinder A thus flows through that cylinder in one direction, and
meets in so doing a gaseous current which is flowing in the opposite direction. At
the point at which the absorptive power of the ammoniacal brine is greatest the
gaseous current is least rich in carbonic acid, but as the ammoniacal brine gradually
absorbs carbonic acid during its passage from compartment to compartiment of the
cylinder A, it comes into contact with portions of the gaseous current continually
richer in carbonic acid, until at length, in the four compartments nearest to B,
liquid nearly saturated with carbonic acid comes into contact with an atmosphere
of carbonic acid nearly or quite pure. It is easy to regulate the rutes of ingress
of the ammoniacal brine and of the carbonic acid respectively, in such wise that in
passing through the cylinder A. the former shall become completely saturated with
carbonic acid.
The object of the sudden semi-revolutions given from time to time to the
cylinder A is to promote the saturation of the liquid by carbonic acid, by bringing

page_text: it into extremely intimate contact therewith. Each time that the cylinder A makes
a half-revolution, the liquid in what was the lower half of that cylinder falls
through the holes in the diaphragm b, b, into the other half of the cylinder, and
carbonic acid gas at the same time passes through the same holes, but in the
contrary direction. After having passed through the holes in the diaphragm b, b,
the liquid falls, in a finely divided state, through an atmosphere containing carbonic
acid. The constant repetition of semi-revolutions of the cylinder A thus brings
the liquid and the gas or gases into extremely intimate contact.
To still further promote the absorption of carbonic acid by the ammoniacal brine,
or by the product of its partial saturation by carbonic acid, it is preferred to send the
carbonic acid into the cylinder A under a pressure of several atmospheres. When
this is done the unabsorbed gases which pass off from the cylinder A are under
pressure, and are therefore capable of doing mechanical work, and on being allowed
to expand after having done work they will become very cold. A part of the
present Invention consists in employing these gases to do work upon the piston of
a pump or otherwise, and then employing them as a refrigerating agent, to abstract
heat from the carbonic acid and other gases before compression, or otherwise, as most
convenient in each case. Before being thus employed they must be washed, to free
them from any vapour of ammonia which they may have carried off, and their
state of compression greatly facilitates this washing. The washing may be con-
veniently performed by their being first made to bubble through a solution of
common salt, and afterwards made to pass up a tower or towers packed with coke
down which solution of salt continually trickles.
To prevent the contents of the cylinder A. becoming too hot, by reason of the
heat liberated during the reaction of carbonic acid gas upon ammoniacal brine, cold
water is kept trickling over the exterior surface of that cylinder.
The cylinder A should preferably be provided with man-holes, as shown in
Figure 2, by which each compartment of it can be entered, if necessary.
When, as will sometimes happen, the holes in the diaphragm b, b, of the
cylinder A have become partially stopped by saline incrustations, the cylinder
must be emptied, and those saline incrustations be dissolved away by water.
Having now described the nature of the said Invention, and in what manner the
same is to be performed, I claim as the Invention of my correspondent to be
secured by the hereinbefore in part recited Letters Patent,-
Firstly. The apparatus described above and shown in the accompanying Drawings.
Secondly. Treating ammoniacal brine in an apparatus substantially such as that
so described and shown; and,
Thirdly. Utilizing the unabsorbed gases substantially as described.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and seal, this Eighteenth day of November, in the year of our Lord One
thousand eight hundred and eighty.
WALTER WELDON. (L.S.)