Improvements in Obtaining Chlorine.
Year: 1890

page_text: Date of Application, 11th Apr., 1890
Complete Specification Left, 23rd Aug., 1890-Accepted, 27th Sept., 1890
PROVISIONAL SPECIFICATION.
Improvements in Obtaining Chlorine.
I, WILLIAM DONALD, of 13 Eglinton Street, Saltcoats, in the County of Ayr,
North Britain, Technical Chemist, do hereby declare the nature of this invention
to be as follows, that is to say :-
My said invention has for its object the obtainment of chlorine in an improved and
economical manner; and it consists of an advantageous modification of the series of
processes described in my Patent Specification No. 62 of 1887.
I obtain the chlorine from hydrochloric acid derived from common salt or other
suitable and conveniently obtainable chloride by well known means. 1 employ the
hydrochloric acid in a dry gaseous state, and in the earlier stages of my improved
processes I operate on two separate streams of the acid gas, arranging, however to
have the two streams as nearly as possible equal in quantity.
One stream of the hydrochloric acid is led through a vessel hereinafter terined the
decomposer in which it is subjected to the combined action of strong nitric and
sulphuric acids. In the decomposer are formed, water, which is retained by the
sulphuric acid, and chlorine and nitric peroxide which pass through a pipe into a
second vessel hereinafter termed the absorber.
The second stream of hydrochloric acid is led directly into the absorber in which its
chlorine is separated and from which the chlorine from both streams of hydrochloric
acid passes off. As a further result of the reactions taking place in the absorber there
remain nitric acid and nitrous acid.
The decomposer and absorber are provided with jackets and internal pipes or
passages for water or other suitable liquid to keep the temperature within the vessels
sufficiently low.
The chlorine after leaving the absorber may be passed through a scrubber charged
with nitric acid, and afterwards through one or more scrubbers charged with
sulphuric acid with the view of separating any remaining nitrogen compounds.
The nitrous acid formed in the absorber may be oxidised into nitric acid by weans
of air either in separate apparatus or by admitting air into the decomposer or
absorber.
Dated this Tonth days of Anvil 1800
EDMUND HUNT,
Applicant's Agent.
COMPLETE SPECIFICATION.
Improvements in Obtaining Chlorine.
I, WILLIAM DONALD of 13 Eglinton Street, Saltcoats, in the County of Ayr, North
Britain, Technical Chemist, 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, that is to say :-
My said invention has for its object the obtainment of chlorine in an improved and
economical manner; and it consists of an advantageous modification of the series of
processes described in my Patent Specification No. 62 of 1887.
I obtain the chlorine from hydrochloric acid derived from common salt, or other
suitable and conveniently obtainable chloride, by well known means. 1 employ the
hydrochloric acid in a dry gaseous state; and in the earlier stages of my improved
processes, I operate on two separate streams of the acid gas, arranging, however, to
have the two streams as nearly as possible equal in quantity.
On an accompanying sheet of explanatory drawings I show by way of example an

page_text: arrangement of apparatus which may be used in carrying out my invention, and in
particularly describing the processes I will refer to these drawings in which the
apparatus is delineated in vertical section.
Apparatus for generating and drying the hydrochloric acid gas is not shown in the
drawings, but the two streams of gas are led from such apparatus through two
pipes, A, B.
One stream of hydrochloric acid gas is led by a pipe, A, through a vessel, C,
hereinafter termed the decomposer, in which it is subjected to the combined action of
strong nitric and sulphuric acids. The hydrochloric acid gas is by a pressure
blower, 1) 1, forced to the bottom of the decomposer, C, the inlet pipe, E, extending to
the bottom and terminating in a perforated coil; and the gas, which is further sub-
divided and distributed by passing through a perforated diaphragm, F, rises through
the mixture of acids. In the decomposer, C, there are formed water, which is
retained by the sulphuric acid, and a gaseous mixture of chlorine and nitric peroxide,
which gases pass from the top of the vessel by a pipe, G.
The contents of the decomposer, C are kept at a low temperature by means of cold
water or by preference brine of a temperature at or a little below the freezing point
of water, the brine being made to circulate in a tank, H 1, in which the decomposer, C,
is placed. The other vessels employed in the modification of the process now
being described are kept at a low temperature by being placed in similar tanks, H 2, etc.,
similarly supplied with a cooling agent.
From the decomposer, C, the mixture of chlorine and nitric peroxide is, by a
pressure blower, D 2, made to pass down through a vessel, J, in which it is further
cooled by brine or other suitable liquid which passes through pipes crossing the
vessel as well as circulating round it. From the cooling vessel, J, the mixture of
-gases passes on through a pipe, K, to a vessel, L, hereinafter termed an absorber.
The second stream of hydrochloric acid gas entering by a pipe, B.- may pass
directly into the absorber, L; it is however, for a purpose hereinafter explained, by
preference made by pressure blowers, D3, D4, to pass through vessels, M, N, which
are like the decomposer, C, and cooler, J, herein before referred to, but which may at
present be regarded as merely cooling the gas. From the vessel, N, the hydro-
chloric acid gas passes by the pipe, P, into the absorber, L, in which both inlet
pipes, K, P, extend to the lower part where they terminate in perforated coils under
a perforated diaphragm, Q. In the absorber, L, there is put a quantity of nitric acid
and water, which absorbs the nitric peroxide, nitric acid and nitrous acid remaining,
whilst the chlorine passes on in a nearly pure state.
In order to further purify the chlorine it is led from the absorber, L, by a pipe, R,
into a vessel, S, in which it passes up through a series of perforated plates and
encounters nitric acid which is supplied at the top and passes downwards. The
perforated plates rest upon the cross tubes in the vessel, S, through which tubes
the cooling liquid circulates. Instead of the plates being simply perforated they
may have short tubes projecting upwards and covered with inverted cups as in
apparatus for distilling or rectifying alcohol or ammonia; or any other suitable
known scrubbing apparatus for bringing gases into close contact with liquids may
be used. On leaving what may be termed the uitric-acid scrubber, S, the chlorine
is conveyed by a pipe, T, and by means of a pressure blower, D5, down to the
bottom of a vessel, U, containing sulphuric acid up through which the chlorine
passes in small streams or bubbles. The chlorine is next led from the vessel, U,
by a pipe, V, to a scrubbing vessel, W, in which it is subjected to a final scrubbing
action with sulphuric acid, this vessel being like the nitric-acid scrubber, S. The
purified chlorine is led from the sulphuric-acid scrubber, W, by a pipe, X, to lime
chambers or other apparatus in which it is to be applied.
When the mixture of nitric and sulphuric acids employed in the decomposer, C,
has become weakened or nearly exhausted, a fresh strong mixture of the acids is put
into the vessel, M, which then becomes a decomposer for operating on the hydro-
chloric acid gas supplied by the pipe, B. A stream of hydrochloric acid gas continues
to pass by the pipe, A, but it now forms what may be distinguished as the second

page_text: stream, and is acted on in the decomposer, (), only to the extent of utilising as far as
conveniently possible the remaining effective acids in that vessel, a large portion
of the gas passing on unaltered to the absorber, L. The actions in the vessels, C,
and M, are thus alternated and the acids employed are in consequence more
completely utilised.
The nitrous acid formed in the absorber, L, may be oxidised into nitric acid in any
well known manner by means of air or otherwise either in separate apparatus or by
admitting air along with the hydrochloric acid gas or along with the mixture of
chlorine and nitric peroxide at any convenient part of the apparatus. When this last
mentioned mode of reoxidising the nitrous acid is adopted it will be advantageous to
beat the gases passing through the vessels J, N and L, instead of cooling them, the
other vessels W, U, and S, being however kept cool. The action will take place at
various temperatures; but I believe a temperature of about 30 degrees Centigrade
will be found satisfactory in practice.
The various pipes and vessels used in carrying out my invention are made of or
lined with lead or other suitable material not easily or rapidly acted on by the acids
or gases passing through them.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The improved process for obtaining chlorine wherein a stream of hydrochloric
acid gas is passed through a mixture of nitric and sulphuric acids, and the gaseous
mixture of chlorine and nitric peroxide thereby obtained is passed along with a
second stream of hydrochloric acid gas, through nitric acid substantially as herein-
before described.
2. The modification of the process forming the subject matter of the first claim,
wherein air is passed through the apparatus substantially as and for the purposes
hereinbefore described.
Dated this Twenty-second day of August 1890.
EDMUND HUNT,
Applicant's Agent.