Improvements in and connected with the Treatment of Crude Bicarbonate of Soda to Obtain Caustic Soda, Carbonic Acid, and other Products.
Year: 1890

page_text: Date of Application, 27th Dec., 1890
Complete Specification Left, 16th Sept., 1891-Accepted, 17th Oct., 1891
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Treatment of Crude
Bicarbonate of Soda to Obtain Caustic Soda, Carbonic Acid, and
other Products.
We ARCHIBALD CAMPBELL, of 147 Glebe Street, Glasgow, in the County
of Lanark, North Britain, Technical Chemist, WILLIAM BOYD, of The Fife
Chemical Works, Thornton, in the County of Fife, North Britain, Technical
Chemist, and ANDREW JACKSON KIRKPATRICK, of 179, West George Street,
Glasgow, aforesaid Merchant, do hereby declare the nature of this invention to be
as follows, that is to say :-
This invention has for its object by improvements in and connected with the
treatment of crude bicarbonate of soda, such as is produced in the well known
ammonia-soda process, to obtain caustic soda, carbonic acid, and other products,
in an economical and profitable manner.
In carrying out the invention the soda bicarbonate after being drained and
washed is put into one of a series of vessels,. connected with each other by pipes
and stop valves, and each provided with a branch pipe and valve connected to a
main steam supply pipe. Each vessel is charged and emptied in turn, and steam is
admitted directly into that vessel of the series which will next have to be emptied,
the steam passing through the vessels in backward order and finally through the
one last charged. The soda carbonate when acted on by the steam becomes
liquefied and parts with some carbonic acid and traces of ammonia which pass on
with the steam through the several vessels. The stream of gases or vapors leaving
the last vessel passes through a scrubber or washer in which brine is by preference
used, and in which the carbonic acid gas is cooled and the ammonia absorbed. The
carbonic acid thus obtained may be used in the ammonia-soda process itself; or,
being very pure it may be used for making commercial bicarbonate of soda, or in
any other process or manufacture requiring a pure carbonic acid.
When the contents of the vessel into which the fresh steam has been passed have
been converted with sufficient completeness into monocarbonate of soda, they are
conveyed into a causticising vessel in which they are mixed with milk of lime kept
boiling and is agitated by a mechanical agitator or by jets of air or steam.
Instead of applying steam as hereinbefore described so as by its heat to drive off
carbonic acid from the crude soda bicarbonate, we may use the hot gases from a
continuously working lime kiln. The lime-kiln gases will by these means be con-
siderably enriched by the carbonic acid detached from the soda bicarbonate, and be
the better adapted for use in the ammonia soda process. The monocarbonate of
soda obtained in this way after solution in water is to be causticised in the manner
hereinbefore described.
The lime sludge formed in the causticising vessel may be washed and elutriated
to-separate-gritty pieces of unburnt lime, and can be advantageously used for dis-
tilling off ammonia as carbonate from the chloride of ammonium formed in the
ammonia-soda process. The decomposition taking place in this operation may be
rendered practically complete by prolonged boiling in a rotational series of vessels,
or it may be completed by adding some milk of lime at the bottom. of the distilling.
vessel.
According to another modification the lime sludge is made into cake in filter
presses, in which presses it is made as free as possible from soda. The pressed
cake is then by a brick machine, working with great pressure, moulded into bricks
or blocks which are burned in a lime kiln to reproduce burnt or caustic lime and
carbonic acid to be used over again.

page_text: Or the line sludge obtained as herein before described may be used for making
cement, or for any other purpose for which its state of fine division renders it
advantageously suitable.
Dated this Twenty-third day of December 1890.
EDMUND HUNT,
Applicants' Agent.
COMPLETE SPECIFICATION.
Improvements in and connected with the Treatment of Crude
Bicarbonate of Soda to Obtain Caustic Soda, Carbonic Acid, and
other Products.
We, ARCHIBALD CAMPBELL, of 147 Glebe Street, Glasgow, in the County
of Lanark, North Britain, Technical Chemist, WILLIAM BOYD, of The Fife
Chemical Works, Thornton, in the County of Fife, North Britain, Technical
Chemist, and ANDREW JACKSON KIRKPATRICK, of 179, West George Street,
Glasgow, aforesaid, Merchant do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement, that is to say :-
:-
This invention has for its object by improvements in and connected with the
treatment of crude soda, such as is produced in the well known ammonia-soda
process, to obtain caustic soda, carbonic acid, and other products, in an economical
and profitable manner.
In carrying out the invention the soda bicarbonate after being drained and
washed is put into one of a series of vessels, which may be constructed of wrought
or cast iron, connected with each other by pipes and stop valves, and each provided
with a branch pipe and valve connected to a main steam supply pipe. Each vessel
is charged and emptied in turn, and steam is admitted directly into that vessel of
the series which will next have to be emptied, the steam passing through the vessels
in backward order, and finally through the one last charged. The soda bicarbonate
when acted on by the steam becomes more or less liquefied and parts with some
carbonic acid and traces of ammonia which pass on with the steam through the
several vessels. In the last vessel through which the steam passes the complete
solution of the soda bicarbonate or carbonate should be insured by admitting into
that vessel as much water as will make the solution.of.a strength of about 40 degrees
Twaddell. The steam enters each vessel by a pipe at the bottom of each vessel,
and passes up through the materials in the vessel.
The stream of gases or vapors leaving the last vessel passes through a scrubber
or washer, in which brine is by preference used, and in which the carbonic acid gas
is cooled and the ammonia absorbed. The carbonic acid thus obtained may be used
in the ammonia-soda process itself; or, being very pure, it may be used for making
commercial bicarbonate of soda, or in any other process or manufacture requiring a
pure carbonic acid.
When the contents of the vessel into which the fresh steam has been passed have
been converted with sufficient completeness into monocarbonate of soda, they are
conveyed into a causticising vessel, in which they are mixed with milk of lime
kept boiling and agitated by a mechanical agitator or by jets of air or steam.
Instead of applying steam as herein before described so as by its heat to drive off
carbonic acid from the crude soda bicarbonate, we may use the hot gases from a
continuously working lime kiln, such gases being forced through the vessels con-
taining the soda bicarbonate by means of a blower or other suitable apparatus.
The lime-kiln gases will by these means be considerably enriched by the carbonic
acid separated from the soda bicarbonate, and be the better adapted for use in the
ammonia-soda process. The monocarbonate obtained in this way after solution in
water is to be causticised in the mauner hereinbefore described.
The lime sludge formed in the causticising vessel may. be washed and elutriated

page_text: to separate gritty pieces of unburnt lime, and can be advantageously used for dis-
tilling of ammonia as carbonate from the chloride of ammonium formed in the
ammonia-soda process. The decomposition taking place in this operation may be
rendered practically complete by prolonged boiling in a rotational series of vessels,
or it may be completed by adding some milk of lime at the bottom of the distilling
vessel, or in the last of the rotational series of vessels.
According to another modification the lime sludge is made into cakes in filter
presses, in which presses it is made as free as possible from soda. The pressed
cakes are then by a brick machine, working with great pressure, moulded into
bricks or blocks which are burned in a lime kiln to reproduce burnt or caustic lime
and carbonic acid to be used over again.
Or the lime sludge obtained as hereinbefore described may be used for making
cement, or for any other purpose for which its state of fine division renders it
advantageously suitable.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
claim, is:
1. The improved process or combination of processes for treating crude bicar-
bonate of soda to obtain caustic soda, carbonic acid, and other products, in which
an essential part is the employment of steam acting in a rotational series of vessels
substantially in the manner hereinbefore described.
2. The passing of the hot gases from a continuously working lime kiln through
crude bicarbonate of soda in a rotational series of vessels substantially as and for the
purposes herein before described,
Dated this Fifteenth day of September 1891.
EDMUND HUNT,
Applicants' Agent.