Improvements in and Apparatus for the Treatment of Caustic Salts Obtained as a Bye-product in the Manufacture of Caustic Soda.
Year: 1894

page_text: Date of Application, 12th Feb., 1894
Complete Specification Left, 9th Nov., 1894-Accepted, 15th Dec., 1894
PROVISIONAL SPECIFICATION.
Improvements in and Apparatus for the Treatment of Caustic Salts
Obtained as a Bye-product in the Manufacture of Caustic Soda.
We JOHN BROCK of Wellfields Farnworth, Widnes, Director of The United
Alkali Company Limited, VERO CHARLES DRIFFIELD, Engineer of Appleton,
Widnes, ARTHUR CAREY, Chemist of Gateacre near Liverpool and FREDERICK
BROWN, Chemist of Hough Green near Widnes all in the County of Lancaster
do hereby declare the nature of our invention to be as follows:-
In the manufacture of caustic soda from carbonate of soda during the concentration
of the solution of caustic soda a bye-product is obtained technically known as
"caustic salts" which salts consist essentially of sodium carbonate mixed with
variable quantities of sodium hydrate (caustic soda) and of sodium sulphate,
sulphite, sulphide and chloride.
"
In consequence of the presence of sodium hydrate it is difficult to "finish
these salts in a reverberatory furnace and to oxidise thoroughly the sulphur
compounds.
Our invention consists in treating these salts with carbonic acid gas before
"finishing" in the furnace.
We prefer to first remove as far as possible the caustic soda from the salts
(which may be done by draining and steaming) and to use them in a fairly dry
condition. We place them in a chamber provided with openings for charging and
discharging, capable of being closed, and with inlet and outlet pipes for admitting
and discharging the carbonic acid gas and also with a stirrer so that fresh surfaces
of the salts may be constantly exposed to the action of the carbonic acid gas.
prefer to employ a horizontal cylindrical vessel capable of being rotated and
provided with openings which can be closed for charging the salts and with hollow
trunnions through which the carbonic acid enters and leaves the cylinder.
We
The salts absorb carbonic acid gas the sodium hydrate being converted into
carbonate of soda. We prefer to add rather more carbonic acid gas than will
convert the sodium hydrate into carbonate. A considerable amount of heat is
evolved during the reaction.
In order to remove the heat and the water vapourised in consequence we either
pass a rapid current of dilute carbonic acid gas (such for instance as can be
obtained from lime kilns) through the cylinder or vessel allowing the gas to escape
into the atmosphere or utilising it for any other purpose, or we make use of a series
of such cylinders or vessels placing a cooling and condensing apparatus between
every two cylinders or vessels of the series.
When a cheap source of pure carbonic acid gas is available we may employ a
single vessel or revolving cylinder and cause a rapid circulation of the gas between
the cylinder and a cooling apparatus propelling the gas by a fan in such a manner
that the hot gas is drawn from the vessel or cylinder forced through the cooling
apparatus and afterwards back again into the vessel or cylinder.
In either case the cooling apparatus may be simply a pipe surrounded with cold
water or may consist of several such pipes or it may consist of a chamber through
which the gas passes which chamber is traversed by a number of pipes through
which cold water flows continuously or intermittently. The cooling apparatus is
provided with an outlet for condensed water.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, Loudon, W.C., Agents.

page_text: Improvements in and Apparatus for the Treatment of Caustic Salts
Obtained as a Bye-product in the Manufacture of Caustic Soda.
We JOHN BROCK of Wellfields Farnworth Widnes Director of The United
Alkali Company Limited VERO CHARLES DRIFFIELD Engineer of Appleton
Widnes ARTHUR CAREY Chemist of Gateacre near Liverpool and FREDERICK
BROWN Chemist of Hough Green near Widnes all in the County of Lancaster 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:
In the manufacture of caustic soda from carbonate of soda during the concentration
of the solution of caustic soda a bye product is obtained technically known as
"caustic salts "
which salts consist essentially of sodium carbonate mixed with
variable quantities of sodium hydrate (caustic soda) and of sodium sulphate,
sulphite, sulphide and chloride.
In consequence of the presence of sodium hydrate it is difficult to finish these
salts in a reverberatory furnace and to oxidise thoroughly the sulphur compounds
and the salts cannot be converted into a readily saleable product.
66
"
Our invention consists in treating these salts with carbonic acid gas before
finishing in the furnace. We prefer to first remove as far as possible the
caustic soda from the salts (which may be done by draining and steaming) and to
use them in a fairly dry condition.
When dilute carbonic acid gas from a lime kiln is used, we find that by making
a short connection between the lime kiln and the carbonating chamber hereinafter
described the said gas from the kiln enters the carbonating chamber at a high
temperature and very effectually dries the salts as well as carbonating them.
We place the salts in a chamber provided with openings for charging and
discharging capable of being closed and with inlet and outlet pipes for admitting
and discharging the carbonic acid gas and also with a mechanical stirrer so that
fresh surfaces of the salts may be constantly exposed to the action of the carbonic
acid gas.
We prefer to employ a horizontal cylindrical vessel capable of being rotated
and provided with openings which can be closed for charging the salts and with
hollow trunnions through which the carbonic acid gas enters and leaves the cylinder,
the material being agitated or stirred by the rotation of the said cylinder.
The salts absorb carbonic acid gas the sodium hydrate being converted into
carbonate of soda. We prefer to add rather more carbonic acid gas than will
convert the sodium hydrate into carbonate.
In consequence of the heat inside the carbonating chamber due both to the heat
evolved by the chemical reaction of carbonating and where hot gas from a lime
kiln is used to the initial temperature of the carbonating gases, large quantities of
water are vapourized.
In order to remove the water vapourized we either pass a rapid current of dilute
carbonic acid gas (such for instance as can be obtained from lime kilns) through
the cylinder or vessel allowing the gas to escape into the atmosphere or utilizing it
for any other purpose or we make use of a series of such cylinders or vessels
placing a cooling and condensing apparatus between every two cylinders or vessels
of the series. When a cheap source of pure carbonic acid gas is available we
may employ a single vessel or revolving cylinder and cause a rapid circulation of
the gas between the cylinder and a cooling apparatus propelling the gas by a fan
in such a manner that the hot gas is drawn from the vessel or cylinder forced
through the cooling apparatus, and afterwards back again into the vessel or
cylinder.

page_text: In either case the cooling apparatus may be simply a pipe surrounded with cold
water or may consist of several such pipes or it may consist of a chamber through
which the gas passes which chamber is traversed by a number of pipes through
which cold water flows continuously or intermittently. The cooling apparatus is
provided with an outlet for condensed water.
In order that our invention may be more clearly understood we will now describe
a form of apparatus we prefer to employ for the purpose of carbonating "caustic
salts" with reference to the-annexed drawings in which Figure 1 is a side elevation
of such apparatus and Figure 2 an end view. A is the cylinder which is caused to
revolve by any suitable means such as for example by the toothed wheel K on the
cylinder A gearing with the pinion L on the shaft M on which is keyed the pulley
wheel N driven by a strap from any suitable motor. B is the door fitting over an
aperture through which the salts are introduced and when carbonated withdrawn.
Cis the pipe through which the carbonic acid gas is introduced into the cylinder
and D the pipe by which it issues from the cylinder and enters the condenser E.
The carbonic acid gas then passes out by the pipe F the water collected in the
condenser being discharged by the lute or seal G. The condenser is cooled by
water entering at H which after passing upwards through the series of tubes in
the body of the condenser is discharged at J.
During the carbonating process in the cylinder the salts are well stirred and
mixed by causing the cylinder to revolve either continuously or intermittently
according to the smaller or larger amount of moisture contained in the salts.
When the salts have been treated in this manner they may be finished in an
ordinary reverberatory furnace and then form a saleable soda ash.
Having now particularly described and ascertained the nature of our inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The treatment of caustic salts with carbonic acid gas (either pure or in
admixture with inert gases) substantially as and for the purposes hereinbefore
described.
2. In the treatment of caustic salts with carbonic acid gas an apparatus consisting
of a closed vessel fitted with apertures for charging and discharging the salts with
inlet and outlet pipes for the carbonic acid gas in combination with mechanical
stirring apparatus substantially as hereinbefore described.
3. In the treatment of caustic salts by carbonic acid the apparatus for cooling
the carbonic acid gas substantially as hereinbefore described.
4. The apparatus for treating caustic salts with carbonic acid gas substantially
as and for the purposes hereinbefore described and illustrated in the accompanying
drawings.
Dated this 9th day of November 1894.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.