IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA, AND IN THE RECOVERY OF WASTE PRODUCTS RESULTING THERE FROM, AND IN THE APPARATUS TO BE EMPLOYED FOR SUCH PURPOSES."
Year: 1869

page_text: LETTERS PATENT to Carl Friedrich
Friedrich Claus, of Middlesborough-on-
Tees, in the County of York, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF CARBONATE OF SODA, AND IN THE RECOVERY OF
WASTE PRODUCTS RESULTING THERE FROM, AND IN THE
APPARATUS TO BE EMPLOYED FOR SUCH PURPOSES."
CONSTRUCTION OF
Scaled the 4th March 1870, and dated the 6th September 1869.
PROVISIONAL SPECIFICATION left by the said. Carl Friedrich Claus
at the Office of the Commissioners of Patents, with his Petition, on.
the 6th September 1869.
I, CARL FRIEDRICH CLAUS, of Middlesborough-on-Tees, in the County
of York, do hereby declare the nature of the said Invention for "In-
PROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA, AND IN THE RECOVERY
THE CONSTRUCTION OF
OP WASTE PRODUCTS RESULTING THEREFROM, AND IN
APPARATUS TO BE EMPLOYED FOR SUCH PURPOSES," to be as follows:-
This Invention consists in certain improvements in the manufacture
of carbonate of soda whereby such carbonate is made by converting
sulphate of soda into sulphide of sodium, and by decomposing solutions
[Price 8d1

page_text: of sulphide of sodium by carbonic acid, especially when this carbonic
acid is obtained by the combustion of carbonaceous matter, such as
furnace gases. The sulphide of sodium I manufacture by heating the
ordinary mixtures of sulphate of soda, coal, coke, or other carbonaceous
material by the aid of heat generated by combustion of gaseous fuel,
such as the waste gases from blast furnaces, the gas furnaces like or
similar to Siemens' gas furnace, or the gases from coke ovens, taking
care that before, during, and after the combustion not more atmospheric
air is admitted than is necessary to produce carbonic acid with the
carbon in the said gases, so that after the heating of the sulphate and
coke or coal mixture the products of combustion may serve as a source
of carbonic acid free from oxygen to be used in the subsequent operations.
The combustion of the gases is effected in combustion chambers con-
structed on similar principles to those of the well-known Siemens',
Cowper's, or Whitwell's blast heating stoves, and the heat generated is
conveyed into the furnace which contains the charge. To insure as
perfect an exclusion of air as possible all apparatus connected with this
process and their connections are covered in an air-tight manner with
iron plates or tubes, and no air is admitted into the system of apparatus
except that which is allowed to pass along with the gas into the com-
bustion chambers and the quantity thereof is carefully regulated by
means of the usual air valves. This quantity is easily ascertained by
practice, and can also be found by observing the action of the products
of combustion in the subsequent operation of carbonating upon the
solution of sulphide of sodium. The charging of the gas producing
furnaces in the instance of the blast furnaces, will have to be done in
such a manner that no air is allowed to enter into the waste gas tubes
during the time the charge upon the ordinary bell cover is lowered or
dropped into the furnace. This is effected by having the furnaces
covered by a double bell covering such as is now used in Cockrane's
"gas catcher," with furnaces where Cowper's blast heating stoves are
used. The charging with coal of the Siemen's gas generator furnaces is
effected by means of a luted trap door or charging valve arrangement.
The heating of the sulphate of soda and coal or coke mixture, or the
reduction of the sulphate of soda to sulphide of sodium is carried out in
reverberatory furnaces which are constructed of such materials or in
such manner that the fused sulphide of sodium has little or no effect
upon them. This 1 effect either by building the same entirely or partly
of bricks made of pure or nearly pure alumina whilst the beds or

page_text: bottoms of the furnaces are made of mixtures of ground coal, coke,
or pitch, or ground pitch coke and pitch or tar, or I construct the
furnaces wholly or in part with double iron cisterns, the space between
the two being filled up with water or weak liquor in such a way that
the heat generated inside the furnace so constructed may be used
for evaporation or generation of steam; or, further, I construct the
furnaces by means of iron tubes placed closely together, and which may
be used for the partial heating of blast. By passing liquor, water, or
air through the hollow spaces forming the body of the furnace, the sides,
arches, and bed are kept cool, so that the fused sulphide of sodium has
no effect upon them. In order that the cooling effect of the water or
air passing through the arches, sides, and bed of the furnace may not be
too great I place the arch of the furnace at a much greater distance
from the bed than is usual in ordinary reverberatory furnaces, so as to
increase the volume of heated gases operating upon the charge on the
bed as much as possible, whilst the current of gases between the inlet
I also con-
and outlet is caused to be as near as possible to the bed.
struct these furnaces_sometimes in such a manner that the bottom or
bed is moveable and placed on wheels, so that it can be withdrawn and
another one substituted for it. I also manufacture the sulphide of
sodium by allowing sulphate of soda to descend through a column of
incandescent coke, that is, in a similar manner to that proposed by
J. Wilson in his Patent, No. 1361, 1859, with the difference only that
instead of constructing the upright cupola furnace or kiln of brickwork
I form, the same by means of a double iron cylinder or cylindrical
cistern something like an upright tubular steam boiler, which may either
be open on the top or be closed, and in the latter case it may be used for
the generation of steam, or, if open, the space between the two cylinders
may be filled with weak liquor, and may be used for the evaporation of
the same; or I construct the cupola by means of cast-iron tubes, in
which latter case the heat generated inside during the conversion of
sulphate of soda into sulphide of sodium may be utilised for the partial
heating of the blast of a blast furnace. The gases emanating from the
same are utilized in a similar manner to that described with reference
The charge of
to the process when reverberatory furnaces are used.
sulphate of soda and carbonaceous matter, which is introduced into the
furnaces described through a luted trap door, is converted in this furnace
into sulphide of sodium, part of which can be tapped off, and a great
part of the the same is volatilised, the vapours thereof passing along

page_text: with the products of combustion into the carbonating tower, which is
placed alongside of or close to it, and is connected therewith by means
of an air-tight tube. I can also conduct the operation in such a way that
all the sulphide of sodium as formed is volatilised, and allowed to pass
into the tower herein-after mentioned as vapour. This tower is con-
structed and arranged and worked as described by nie in the Specifica-
tion of an Invention for "Improvements in the Manufacture of Carbonate
of Potash and the Recovery of certain Products evolved therein," for
which Provisional Protection, bearing date the 17th day of March 1869,
No. 819, was granted to me. In this tower the gases and vapours
emanating from the furnace mingle together, and come in contact with
solutions of sulphide of sodium, the latter being obtained by dissolving
in water the sulphide of sodium formed in the furnace and tapped off
in a fused state. The vapours of sulphide of sodium in coming in the
tower in contact with the solution of sulphide of sodium in a finely divided
state are absorbed or condensed therein. By the action of the carbonic
acid in the products of combustion the sulphide of potassium becomes
converted into carbonate of soda, and the solution of carbonate of soda
is treated further in the manner generally known and practised. As
there is not sufficient carbonic acid generated during the process of con-
verting sulphate into sulphide of sodium I convey also the gases which
pass out of the blast heating stoves of iron blast furnaces, especially
when Siemens', Cowper's, or Whitwell's stove has been used into the
tower, maintaining, however, all those conditions enumerated above to
insure a freedom of the gases from excess of oxygen. I employ also
for this purpose the re-ignited waste blast furnace gases after they have
been used for the generation of steam, provided they have been burnt
in a combustion chamber similar to that of Cowper's blast heating
stoves and so that they do not contain any free oxygen. If these con-
ditions of strictly excluding excess of oxygen from the gases are carefully
attended to a carbonate of soda is obtained, which only contains 3 to 4
per cent. of hyposulphite of soda, a result which all the methods hitherto
patented in the same direction have failed to accomplish. By the action
of the carbonic acid upon the sulphide of sodium solutions sulphuretted
hydrogen is evolved, and this I utilize by passing the same in towers
through solutions of persulphate of iron, containing free acid or not:
the sulphuretted hydrogen by this operation becomes converted into solid
sulphur, whilst the persulphate of iron is converted into protosulphate,
which can again be wholly or partly converted into persulphate by

page_text: exposing the same in a tower open at the bottom, and provided with
numerous holes in the sides, to the oxidising action of air in the manner
described in the Specification of my said Invention of "Improvements
in the Manufacture of Carbonate of Potash and the Recovery of certain
Products evolved therein." As the gases leaving the carbonating towers
contain large quantities of steam, and as these would condense in and
weaken the persulphate liquors it is necessary to condense the same by
cooling the pipes conveying away the gases from the carbonating tower
in a manner most convenient; for instance, by carrying them a long.
distance before they enter the sulphur recovery towers.
The process of recovering sulphur described above is also applicable
in all such processes for manufacturing carbonate of soda, not described
herein, in which sulphuretted hydrogen is a large product.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Carl Friedrich Claus in the Great Seal Patent
Office on the 5th March 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CARL
FRIEDRICH CLAUS, of Middlesborough-on-Tees, in the County of York,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixth day of September, in the year of
our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Carl Friedrich Claus, Her special
licence that I, the said Carl Friedrich Claus, my executors, adminis-
strators, and assigns, or such others as I, the said Carl Friedrich
Claus, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA, AND IN THE
RECOVERY OF WASTE PRODUCTS RESULTING THEREFROM, AND IN THE CONSTRUCTION
OF APPARATUB TO BE EMPLOYED FOR SUCH PURPOSES," upon the condition

page_text: (amongst others) that I, the said Carl Friedrich Claus, my executors
or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to
be perforined, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said Carl Friedrich Claus, do hereby
declare the nature of my said 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 consists in certain improvements in the manu
facture of carbonate of soda when such carbonate is made by converting
sulphate of soda into sulphide of sodium, and by decomposing solutions
of sulphide of sodium by carbonic acid, and when this carbonic acid is
obtained by the combustion of carbonaceous matter, such as furnace
gases. The sulphide of sodium I manufacture by heating the ordinary
mixtures of sulphate of soda, coal, coke, or other carbonaceous material
by the aid of heat generated by combustion of gaseous fuel, such as the
waste gases from blast furnaces, the gas furnaces like or similar to
Siemens' gas furnace, or the gases from coke ovens, taking care that
before, during, and after the combustion not more atmospheric air is
admitted than is necessary to produce carbonic acid with the carbon in
the said gases, so that after the heating of the sulphate and coke or coal
mixture the products of combustion may serve as a source of carbonic
acid free from oxygen to be used in the subsequent operations. The
combustion of the gases is effected in combustion chambers constructed
on similar principles to those of the well-known Siemens', Cowper's, or
Whitwell's blast heating stoves, and the heat generated is conveyed into
the furnace which contains the charge. To insure as perfect an
exclusion of air as possible all apparatus connected with this process and
their connections are covered in an air-tight manner with iron plates or
tubes, and no air is admitted into the system of apparatus except that
which is allowed to pass along with the gas into the conducting
chambers, and the quantity thereof is carefully regulated by means of
the usual air valves. This quantity is easily ascertained by practice,
and can also be found by observing the action of the products of com
bustion in the subsequent operation of carbonating upon the solution o

page_text: sulphide of sodium. The charging of the gas producing furnaces in the
instance of the blast furnaces will have to be done in such a manner
that no air is allowed to enter into the waste gas tubes during the time
the charge upon the ordinary bell cover is lowered or dropped into the
furnace. This is effected by having the furnaces covered by a double
bell covering such as is now used in Cochrane's "gas catcher" with
furnaces where Cowper's blast heating stoves are used. The charging
with coal of the Siemens' gas generator furnaces is effected by means of
a luted trap-door or charging valve arrangement. The heating of the
sulphate of soda and coal or coke mixture or the reduction of the
sulphate of soda to sulphide of sodium is carried out in reverberatory
furnaces which are constructed of such materials or in such manner that
the fused sulphide of sodium has little or no effect upon them. This I
effect either by building the same entirely or partly of bricks made of
pure or nearly pure alumina whilst the bed or bottom of the furnaces
are made of mixtures of ground coal, coke, or pitch, or ground pitch,
coke, and pitch or tar, or I construct the furnaces wholly or in part with
double iron cisterns, the space between the two being filled up with
water or weak liquor in such a way that the heat generated inside the
furnace so constructed may be used for evaporation or generation of
steam; or further, I construct the furnaces by means of iron tubes
placed closely together, and which may be used for the partial heating
of blast. By passing liquor, water, or air through the hollow spaces
forming the body of the furnace the sides, arches, and bed are kept cool,
so that the fused sulphide of sodium has no effect upon them. In order
that the cooling effect of the water or air passing through the arches,
sides, and bed of the furnace may not be too great I place the arch of
the furnace at a much greater distance from the bed than is usual in
ordinary reverberatory furnaces so as to increase the volume of heated
gases operating upon the charge on the bed as much as possible whilst
the current of gases between the inlet and outlet is caused to be as near
as possible to the bed.
I also construct these furnaces sometimes in such a manner that the
bottom or bed is moveable and placed on wheels, so that it can be with-
I also manufacture the
drawn and another one substituted for it.
sulphide of sodium by allowing sulphate of soda to descend through a
column of incandescent coke, that is, in a similar manner to that pro-
posed by J. Wilson's Patent No. 1361, 1859, with the difference only

page_text: The
that instead of constructing the upright cupola furnace or kiln of brick-
work, I form the same by means of a double iron cylinder or cylindrical
cistern something like an upright tubular steam boiler, which may either
be open on the top or be closed, and in the latter case it may be used
for the generation of steam, or if open the space between the two
cylinders may be filled with weak liquor and may be used for the
evaporation of the same, or I construct the cupola by means of cast iron
tubes, in which latter case the heat generated inside during the con-
version of sulphate of soda into sulphide of sodium may be utilised for
the partial heating of the blast of a blast furnace. The gases emanating
from the same are utilised in a similar manner to that described with
reference to the process when reverberatory furnaces are used.
charge of sulphate of soda and carbonaceous matters which is introduced
into the furnaces described through a luted trap door is converted in
this furnace into sulphide of sodium, part of which can be tapped off and
a great part of the same is volatilised, the vapours thereof passing along
with the products of combustion into the carbonating tower which is
placed along side of or close to it, and is connected therewith by means
of an air-tight tube. I also conduct the operation in such a way that all
the sulphide of sodium as formed is volatilised and allowed to pass into
the tower herein-after mentioned, as vapour. This tower is constructed
and arranged and worked as described by me in the Specification of an
Invention for "Improvements in the Manufacture of Carbonate of Potash
and the Recovery of certain Products evolved therein," for which I
obtained Letters Patent bearing date the Seventeenth day of March
One thousand eight hundred and sixty-nine, No. 819. In this tower the
gases and vapours emanating from the furnace mingle together and come
in contact with solutions of sulphide of sodium, the latter being obtained
by dissolving in water the sulphide of sodium formed in the furnace and
tapped off in a fused state. The vapours of sulphide of sodium in
coming in the tower in contact with the solution of sulphide of sodium
in a finely divided state are absorbed or condensed therein.
action of the carbonic acid in the products of combustion, the sulphide
of potassium becomes converted into carbonate of soda, and the solution
of carbonate of soda is treated further in the manner generally known
and practised. As there is not sufficient carbonic acid generated during
the process of converting sulphate into sulphide of sodium, I convey also
gases which pass out of the blast heating stoves of iron blast furnaces,
especially when Siemens', Cowper's, or Whitwell's stove has been used
the
By the

page_text: into the tower, maintaining however all those conditions enumerated
above to ensure a freedom of the gases from excess of oxygen. I employ
also for this purpose the re-ignited waste blast furnace gases after they
have been used for the generation of steam, provided they have been
burnt in a combustion chamber similar to that of Cowper's blast heat-
ing stoves, and so that they do not contain any free oxygen. If these
conditions of strictly excluding excess of oxygen from the gases are care-
fully attended to, a carbonate of soda is obtained which only contains
3 to 4% of hyposulphite of soda, a result which all the methods hitherto
patented in the same direction have failed to accomplish. By the action
of the carbonic acid upon the sulphide of sodium solutions, sulphuretted
hydrogen is evolved, and this I utilize by passing the same in towers
through solutions of persulphate of iron containing free acid or not, the
sulphuretted hydrogen by this operation becomes converted into solid
sulphur, whilst the persulphate of iron is converted into protosulphate,
which can again be wholly or partly converted into persulphate by
exposing the same in a tower open at the bottom and provided with
numerous holes in the sides to the oxidising action of air in a manner
described in the Specification of my said Invention of "Improvements
in the Manufacture of Carbonate of Potash and the Recovery of Certain
Products evolved therein," or the sulphuretted hydrogen may be re-
covered by any other known method. As the gases leaving the car-
bonating towers contain large quantities of steam, and as these would
condense in and weaken the persulphate liquors, it is necessary to
condense the same by cooling the pipes conveying away the gases from
the carbonating tower in a manner most convenient, for instance, by
carrying them a long distance before they enter the sulphur recovery
towers.
The process of recovering sulphur described above is also applicable
in all such processes for manufacturing carbonate of soda, not described
herein, in which sulphuretted hydrogen is a bye product.
Having thus declared and ascertained the nature of my said Invention
and in what manner the same is to be performed, I would observe in
conclusion that what I consider novel and original, and therefore claim
as constituting the Invention secured to me by the said herein-before in
part recited Letters Patent are,-
First. The processes for the manufacture of carbonate of soda and
in the recovery of waste products resulting therefrom, substantially as

page_text: herein-before described and set forth, or any mere modifications
thereof.
And secondly. The construction of apparatus substantially as and for
the purposes herein-before described and set forth, or any mere modi-
fications thereof.
In witness whereof, I, the said Carl Friedrich Claus, have here-
unto set my hand and seal, this Third day of March, in the year
of our Lord One thousand eight hundred and seventy.
CARL FRIEDRICH CLAUS. (L.S.)