Improvements in the Manufacture of Chlorine and Chloride of Lime and in Apparatus therefor.
Year: 1888

page_text: "
PROVISIONAL
SPECIFICATION.
Improvements in the Manufacture of Chlorine and Chloride of Lime
and in Apparatus therefor.
We, SOLVAY AND COMPANY of 19 Rue du Prince Albert, Brussels, in the Kingdom
of Belgium, Manufacturers do hereby declare the nature of this invention to be as
follows:-
-
In the Specifications of former Letters Patent viz. :
No. 77 dated 8th January 1877,
No.
91
"
9th January 1877,
No. 171
No. 838
"
.
"
No. 7258
"
12th January 1877,
6th May 1884,
25th February 1880,
No. 7259
"
6th May 1884,
No. 8724
No. 13,389
"
20th July 1885, and
A
20th October 1886,
"
there have been described processes and apparatus for producing chlorine from
chloride of calcium and for utilizing it in a commercial form. With such processes
and apparatus several difficulties and inconveniences have been met with in practice
which it is the object of the present invention to obviate by modifying the said
processes and apparatus. It has been found that mixtures of chloride of calcium with
a clayey substance can be more easily decomposed than those having a purely silicious
base but that it is not practicable to dessicate such mixture to the extent necessary
to cause it to lose the whole of its contained water without the evolution of hydro-
chloric acid; and it is advantageous to reduce the amount of hydro-chloric acid which
is simultaneously formed with the chlorine. In order to effect this reduction the clay
is according to this invention first separately calcined to drive off the water of
combination contained therein and to obtain a decomposing substance having the
advantages both of the silicious and of the clayey matters. The calcination can be
effected by introducing the clay in the form of bricks or briquettes into a heated oven
or furnace of any suitable construction, the calcined clay being afterwards reduced to
powder or the said calcination can be effected by any other suitable means.
Heretofore the retorts or furnaces used for producing chlorine have been so con-
structed as to exclude the combustible or carburetted gases from the field of the
reaction because the chlorine produced has a great tendency to unite with the carbonic
oxide and form chloride of carbonyl therewith from which it cannot be again recovered
in its active form.
The retorts or furnaces have been heated externally through considerable thicknesses
of refractory materials thereby requiring very considerable quantities of heat.
Theoretical considerations having led me to believe that the reaction of the air upon
the chloride of calcium when mixed with silica and alumina might be exothermic or
at least neutral, we have come to the conclusion that if the heating were effected

page_text: internally it might be carried out with so small a quantity of combustible
material that the formation of chloride of carbon would be reduced to insignificant
proportions.
Experiments have confirmed these conclusions. According to the present invention
therefore the decomposition is effected in a high tower of masonry that is protected
against loss of heat by radiation by very thick walls or casings of material that is a
bad conductor of heat, the combustible gases produced by a coke gasifier or gas
generator being injected into the tower simultaneously with the amount of air
necessary for combustion and for effecting the reaction which is expressed by the
following equation, CaCl2 + Si 02 + 0 = Ca O Si O2 + Cl2. The tower is charged
with the substance to be decomposed (formed as hereinbefore mentioned) so as to fill
the same from top to bottom with or without the addition according to the amount
of chloride of calcium present, of pieces of refractory material to serve as a
recuperator or regenerator of heat as described by me in the specification of former
Letters Patent.
The tower or vertical cylinder is provided at or near the middle of its height with a
ring of short branch tubes for supplying carbonic oxide, and the tower receives an
ascending current of air from below.
In such a tower there are several zones to be distinguished. There is first the zone
of combustion which begins at the level of the short branch tubes and extends upwards.
only to a very small height of the tower.
When the material to be treated arrives in this zone it should be completely
decomposed as otherwise it would meet carbonic oxide which would destroy the active
chlorine.
Immediately above the zone of combustion is the zone of decomposition.
In this zone there is no carbonic oxide, that entering the zone of combustion.
being completely burnt and converted into a small percentage of carbonic acid
which does not interfere with the reaction. The material in this zone of combustion,
which extends to a height of some metres, is red hot being continuously heated as
it descends to meet the incandescent gases. Above the zone of decomposition is
located the upper zone of recuperation. In this zone the gases which have taken
part in the reaction in the furnace would carry off a large quantity of heat if they
did not meet with an equivalent weight of material that has just been introduced in a
cold condition from above and to which they gradually yield their heat to such an
extent that they escape in a cold state. At the bottom and extending from the ring
of short branch tubes supplying the carbonic oxide is the lower zone of recuperation.
In this zone the material which enters at a bright red heat is prevented from
carrying off a great deal of heat by being caused to meet the ascending current of
cold air.
By suitably proportioning the quantities of materials treated according to their
calorific capacities, complete recuperation can be obtained and the material is
allowed to pass out in a cold condition. Instead of injecting carbonic oxide into
the tower a current of air charged with solid fuel in the form of dust may be
injected.
Solid fuel in the form of powder may be mixed with the chloride of calcium and
clay in the state of paste or in the form of pieces or lumps mixed directly with those
substances as in charging a cupola furnace. A difficulty has been experienced in
utilizing the chlorine produced by the modified process herein beforo described for the
manufacture of chloride of lime. It is known that dilute chlorine can produce very
good commercial chloride of lime so long as it does not contain any carbonic acid.
But traces of this acid prevent the formation of chloride of lime of the desired degree
of strength.
Now according to this invention several percentages of carbonic acid are introduced
into the chlorine and it has been found that the formation of liquid chloride of
lime is not at all interfered with by the carbonic acid, whilst all the chlorine is
absorbed.

page_text: Part of the carbonic acid escapes without being absorbed and the remainder
forms carbonate of lime which is not injurious since it is precipitated in an insoluble
state.
The liquid chloride of lime thus obtained is then decomposed by the hydrochloric
acid which is unavoidably produced in small quantities in the principal reaction as
herein before mentioned and which is condensed from the chlorine simultaneously
produced.
Concentrated chlorine gas is thus obtained which is then directed either upon lime
in the ordinary way or upon imperfect chloride of lime obtained with poor chlorine
and which may then be brought to the desired strength. The dilute chlorine mixed
with carbonic acid may also be employed in the manufacture of chlorates.
It is to be understood that the herein described processes and apparatus are not
limited solely to the decomposition of chloride of calcium. They are applicable to
the decomposition of chloride of magnesium, chloride of magnesium combined with
Stassfurt ores and to the decomposition of chlorides generally by the dry process.
Dated this 19th day of December 1888.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Chlorine and Ohloride of Lime
and in Apparatus therefor.
We SOLVAY AND COMPANY, of 19 Rue du Prince Albert, Brassels in the Kingdom
of Belgium, Manufacturers, 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 Specifications of former Letters Patent viz. :-
77 dated 8th January 1877,
No.
No.
91
"
No.
171
"
9th January 1877,
12th January 1877,
No.
838
"
25th February 1880,
No. 7258
"
6th May 1884,
No. 7259
"
6th May 1884,
No.
8724
"
No. 13,389
20th July 1885, and
20th October 1886,
"
there have been described processes and apparatus for producing chlorine from
chloride of calcium, and for utilizing it in a commercial form.
With such processes
and apparatus, several difficulties and inconveniences have been met with in practice
which it is the object of the present invention to obviate by modifying the said
processes and apparatus.
It has been found that mixtures of chloride of calcium with a clayey substance can
be more easily decomposed than those having a purely silicious base, but that it
is not practicable to dessicate such a mixture when proceeding in the ordinary manner
to the extent necessary to cause it to lose the whole of its contained water, without
the evolution of hydro-chloric acid, and it is advantageous to reduce the amount of
hydro-chloric acid which is simultaneously formed with the chlorine. In order to
effect this reduction, the clay is according to this invention, first separately calcined to
drive off the water of combination contained therein, and to obtain a decomposing
substance having the advantages both of the silicious and of the clayey matters.
The calcination can be effected by introducing the clay, in the form of bricks or
briquettes, into an oven or furnace of any suitable construction, the calcined clay

page_text: being afterwards reduced to powder; or the said calcination can be effected by any
other suitable means.
Heretofore the retorts or furnaces used for producing chlorine have been so .con-
structed as to exclude the combustible or carburetted gases from the field of the
reaction, because the chlorine produced has a great tendency to unite with the
carbonic oxide in the said gases and form chloride of carbonyl therewith, from which
the chlorine cannot be again recovered in its active form. The retorts or furnaces
have been heated externally through considerable thicknesses of refractory materials
and consequently have required very considerable quantities of heat.
Theoretical considerations having led us to believe that the reaction of the air upon
the chloride of calcium when mixed with silica and alumina might be exothermic or
at least neutral, we have come to the conclusion that if the heating were effected
internally it might be carried out with so small a quantity of combustible material
that the formation of chloride of carbonyl would be reduced to insignificant
proportions.
Experiments have confirmed these conclusions. According to the present invention
therefore, the decomposition is effected in a high tower of masonry somewhat similar
to a foundry cupola that is protected against loss of heat by radiation by very thick
walls or casings of material that is a bad conductor of heat, the combustible gases
produced by a coke gasifier or gas generator being injected into the tower simul-
taneously with the amount of air necessary for combustion and for effecting the
reaction which is expressed by the following equation Ca CP² + Si 02 + 0 = Ca 0 Si
OC². The tower is charged with the substance to be decomposed for example
chloride of calcium mixed with clay calcined as hereinbefore mentioned so as to fill
the same from top to bottom, with or without the addition according to the amount of
chloride of calcium present, of pieces of refractory material to serve as a recuperator
or regenerator of heat as described by me in the specification of former Letters Patent
No. 8724 of 20 July 1885.
The tower or vertical cylinder is provided at or near the middle of its height with a
ring of short branch tubes for supplying carbonic oxide, and the tower receives an
ascending current of air from below.
In such a tower there are several zones to be distinguished. There is first the zone
of combustion which begins at the level of the short branch tubes and extends
upward only to a very small height of the tower.
When the material to be treated arrives in this zone it should be completely
decomposed as otherwise it would meet carbonic oxide which would destroy the active
chlorine.
Immediately above the zone of combustion is the zone of decomposition. In this
zone there is no carbonic oxide, that entering the zone of combustion being completely
burnt and converted into a small percentage of carbonic acid which does not interfere
with the reaction. The material in this zone of combustion which extends to a height
of some metres, is red hot, being continuously heated as it descends to meet the
incandescent gases. Above the zone of decomposition is located the upper zone of
recuperation. In this zone the gases which have taken part in the reaction in the
furnace would carry off a large quantity of heat if they did not meet with an
equivalent weight of material that has just been introduced in a cold condition
from above and to which they gradually yield their heat to such an extent that they
escape in a cold state. At the bottom and extending upward to the ring of short
branch tubes supplying the carbonic oxide, is the lower zone of recuperation. In
this zone the material which enters at a bright red heat is prevented from
carrying off a great deal of heat by being caused to meet the ascending current of
cold air.
By suitably proportioning the quantities of materials treated according to their
calorific capacities complete recuperation can be obtained and the material is allowed
to pass out in a cold condition. Instead of injecting carbonic oxide into the tower,
a current of air charged with solid fuel in the form of dust may be injected

page_text: through the branch tubes. We may also throw the coal brought to this place
mechanically by means of a bend or elbow with which the furnace is provided near
the middle of its height.
Solid fuel in the form of powder may be mixed with the chloride of calcium
and clay that may be in the state of paste, or the solid fuel in the form of pieces
or lumps may be mixed directly with these substances as in charging a cupola
furnace.
A difficulty has been experienced in utilizing the chlorine produced by the
modified process hereinbefore described, for the manufacture of chloride of lime.
It is known that dilute chlorine can produce very good commercial chloride of lime
so long as it does not contain any carbonic acid. But traces of this acid prevent the
formation of chloride of lime of the desired degree of strength.
Now in manufacturing chlorine according to this invention, several percentages of
carbonic acid are introduced into the chlorine. We have discovered however that the
formation of liquid chloride of lime is not at all interfered with by the carbonic acid,
whilst all the chlorine is absorbed. Part of the carbonic acid escapes without being
absorbed and the remainder forms carbonate of lime which is not injurious since it is
precipitated in an insoluble state. We therefore cause the chlorine produced
according to this invention to pass into a solution of lime, and allow the carbonate of
lime resulting from the carbonic acid mixed with the chlorine to precipitate.
The liquid chloride of lime thus obtained is then decomposed by the hydrochloric
acid which is unavoidably produced in small quantities in the principal reaction,
as hereinbefore mentioned, and which is condensed from the chlorine simultaneously
produced.
Concentrated chlorine gas is thus obtained which is then directed either upon lime
in the ordinary way or upon imperfect chloride of lime obtained with poor chlorine
and which may then be brought to the desired strength. The dilute chlorine mixed
with carbonic acid may also be employed in the manufacture of chlorates.
It is to be understood that the herein described processes and apparatus are
not limited solely to the decomposition of chloride of calcium. They are applicable
to the decomposition of chloride of magnesium, chloride of magnesium combined
with Stassfurt ores, and to the decomposition of chlorides generally by the dry
process.
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 method or process of decomposing chlorides by the dry process for the
purpose of obtaining the chlorine therefrom, consisting in heating a decomposable
mixture containing a chloride by the direct introduction into the interior of the
decomposing apparatus containing the decomposable mixture, of combustible gas or
disintegrated fuel the internal heating being employed in conjunction with the
arrangements described to avoid the formation of oxy-chloride of carbon gas and to
reduce to a minimum the amount of heat to be supplied.
2. A furnace for the decomposition of chlorides by the dry process for the purpose
of obtaining the chlorine therefrom, consisting of a high cylindrical tower of
masonry (having a bend or elbow in the middle or not) effectually protected
against radiation and adapted to receive the combustible either from tuyeres arranged
near the middle of the height of the furnace or from the top and air from below as
described.
3. In the method or process of decomposing chlorides by heat in the presence of
air and clay the calcination of such clay previous to its admixture with the chloride to
be decomposed.
4. The manufacture of chloride of lime with chlorine containing carbonic acid,
(whether produced by our hereinabove described process or otherwise) in two stages
namely the manufacture of liquid chloride of lime, and consequent separation of the

page_text: carbo ic acid in the form of carbonate of lime, the decomposition of the liquid
chloride of lime by hydro-chloric acid, and the subsequent formation of solid chloride
of lime by the rich chlorine gas obtained.
Dated this 17th day of September 1889.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.