IMPROVEMENTS IN THE PURIFICATION OF BICARBONATE OF SODA AND APPARATUS THEREFOR to be as follows
Year: 1884

page_text: I HOLBROOK GASKELL the Younger of Widnes in the County of Lancaster
Chemical Manufacturer do hereby declare the nature of my said Invention for
"IMPROVEMENTS IN THE PURIFICATION OF BICARBONATE OF SODA AND APPARATUS
THEREFOR to be as follows:-
"
My Invention relates to the purification of Bicarbonate of Soda made by what
is known as the Ammonia Soda process.
In this process Ammonia and Carbonic Acid are caused to react upon Sodium,
Salts in solution in such a way as to precipitate Bicarbonate of Soda. This
precipitated Bicarbonate of Soda is contaminated with Ammonia.
According to my Invention I beat the Bicarbonate of Soda in an atmosphere of:
Carbonic Acid or I expose the Bicarbonate of Soda to an atmosphere of hot
Carbonic Acid. In either case the temperature must be high enough.to volatilize
the Ammonia which may be subsequently condensed by cooling and recovered or
used again for the Ammonia Soda process or passed into any solution capable of
absorbing and retaining Ammonia such as is now used in the Ammonia Soda.
process.
.
The Bicarbonate of Soda thus freed from Ammonia may be ground and "dressed"
as is well understood. As a convenient method of carrying into effect my.
Invention I use a chamber which may be stationary or may be caused to revolve.
and may be furnished with an agitator or scraper and is provided with suitable>
aparatus for introducing and withdrawing the Bicarbonate and with suitable
inlets for the Carbonic Acid and suitable outlets for the Carbonic Acid and .
Ammonia.
The chamber may be heated to the required temperature by means of a furnace
or by steam or the Carbonic Acid may be heated in a superheater as is well.
understood.
Dated this 0041

page_text: COMPLETE SPECIFICATION.
I, HOLBROOK GASKELL the younger of Widnes in the County of Lancaster
Chemical Manufacturer do hereby declare the nature of said invention for
"IMPROVEMENTS IN THE PURIFICATION OF BICARBONATE OF SODA AND APPARATUS
THEREFOR " and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
My Invention relates to the purification of Bicarbonate of Soda made by what
is known as the Ammonia Soda process.
In this process Ammonia and Carbonic Acid are caused to react upon Sodium
Salts in solution in such a way as to precipitate Bicarbonate of Soda.
-
This precipitated Bicarbonate of Soda is contaminated with Ammonia.
The object of my Invention is to expel by volatilization the Ammonia contained
in the precipitated Bicarbonate of Soda-without-decomposition of the Bicarbonate
of Soda. This I find can be done by maintaining-the-mixture of Bicarbonate of
Soda and Ammonia at a temperature at or above that at which Bicarbonate
of Ammonia is volatilized. This temperature varies with the pressure but at
ordinary atmospheric pressure a temperaturo not exceeding from 200 F. to 250 F.
will suffice. At this temperature- however Bicarbonate of Soda decomposes giving
off Carbonic Acid. unless an atmosphere of Carbonic Acid-is-maintained in the
apparatus.
In carrying out my invention various methods of heating the Bicarbonate-may-.
be employed. Carbonic Acid gas may-be-heated.and the hot gas be passed over or
through the Bicarbonate of Soda until all or nearly all the Ammonia is volatilised,
and the gas be afterwards deprived of the Ammonia by condensation or absorption
and if the carbonic acid gas be limited in supply, the same gas may be caused to
circulate continuously between the apparatus for heating the carbonic acid the
apparatus containing the Bicarbonate of Soda and a condenser or absorber; but the
method which I prefer is to heat the Bicarbonate of Soda directly either by steam
in a jacketed vessel or by fire applied to the outside of the vessel. I agitate in any
convenient manner by mechanical means the Bicarbonate of Soda whilst heating
it, but if the vessel containing the Bicarbonate of Soda be heated by direct fire
I prefer to cause the vessel containing it, to revolve so as to prevent over heating
of any part of the Bicarbonate. The Ammonia is volatilised and carried off by
the carbonic acid, and may be condensed by cooling or by absorbing it in water or
other liquid as is well understood.
I do not limit myself to any particular apparatus for treating such Bicarbonate
of Soda according to my Invention but I find it advantageous to, use such an
apparatus as is illustrated in side elevation end view, and plan respectively in
figures 1. 2 and 3 of tho accompanying drawings.
The iron Cylinder A is capable of being rotated upon a horizontal axis, and is
provided with hollow trunnions or axles capable of turning in bearings a carried
by a suitable framework. The hollow axle at one end of the Cylinder is used for
admitting Carbonic acid gas, and that at the other end is used for permitting the
exit of carbonic acid gas, ammonia and moisture. The hollow axles are continued
into the interior of the Cylinder and deflected upwards as shown at B in figure 1

page_text: for the purpose of avoiding the lodgment therein of solid material and the
consequent stoppage of the free passage of the gas into or from the Cylinder.
I find it advisable to have apertures as at E. E. in the Cylinder A and exit
pipe C respectively, which apertures can be closed air tight in any convenient
manner and through which when necessary the part of the exit pipe C which is
inside the Cylinder A may be cleaned easily and freed from dust, which is
sometimes deposited there. Outside the Cylinder A the exit pipe C is carried
upward to a suitable height where it passes through a trough L. containing cold
water, and is then returned downwards and connected by the branch C³ with the
pipe C by which the Carbonic acid enters at the other end of the Cylinder A.
I find that when the pipe C is carried upwards about 30 feet that the difference
of temperature and consequently the difference of specific gravity between the gas
in the upcast and that in the downcast of the pipe C³ is such that a circulation of
gas can be commenced and maintained when desired through the pipe C whereby
the ammonia and moisture which escapes from the Bicarbonate of Soda during the
process are conveyed away from the cylinder A and are condensed in the pipes and
may be collected and run off through a late X, the carbonic acid gas returning to
the cylinder by the branch C³. Figure 4 shews a lute X drawn to a larger scale.-
If at any time this circulation does not commence when desired the tap of a small
steam jet F is opened for a few moments so that steam plays upward in the upcast
branch of the pipe C-By this means circulation is at once set up in the pipe C
and when commenced continues as long as required.
The charge of impure Bicarbonate of Soda is introduced into the cylinder A
through a manhole which is then closed and the cylinder is made to revolvo
slowly, for example through the intervention of a pulley and spur gearing G.
driven by any suitable motor I find from two to six revolutions per minute are
sufficient. Carbonic acid gas is turned on or admitted into the interior of the
cylinder A by the pipe C The cylinder is then heated by means of the gas burner
shewn at H-To prevent the rapid loss of beat the cylinder is enclosed in a
casing I. The temperature of the Bicarbonate of Soda rises and the ammonia and
moisture are rapidly volatilised The circulation of the gas is then commenced by
means of the steam jet F which is only used for a few minutes, the circulation of
the gas once commenced continues until the operation is complete. In due time
the Bicarbonate of Soda will be completely free from ammonia and perfectly dry
and after discharging it by means of the moveable discharge plate K is ready for
immediate grinding and dressing-The amount of carbonic acid needed for this
operation is very small, only so much as is required to fill the cylinder and the
pipes The ammonia and moisture carried forward by the carbonic acid aro
condensed and leave the pipes by the lutes X as a solution of Bicarbonate of
Ammonia.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
First The purification of Bicarbonate of Soda contaminated with ammonia
by volatilising the ammonia in an atmosphere of carbonic acid substantially as
hereinbefore described.
Second-Tho arrangement and combination of parts constituting the apparatus
as illustrated in figure 1 of the accompanying drawings for the purpose hereinbefore
described.