A NEW METHOD OR PROCESS, AND A NEW COMBINATION OF PROCESSES AND APPLIANCES, FOR OBTAINING FROM SULPHIDE OF SODIUM AND SULPHIDE OF POTASSIUM CAUSTIC SODA AND CAUSTIC POTASH, AND EITHER FREK SULPHUR OR SULPHUROUS ACID
Year: 1876

page_text: LETTERS PATENT to Walter Weldon, of Abbey Lodge, Merton, in the County
of Surrey, for the Invention of "A NEW METHOD OR PROCESS, AND A NEW
COMBINATION OF PROCESSES AND APPLIANCES, FOR OBTAINING FROM SULPHIDE
OF SODIUM AND SULPHIDE OF POTASSIUM CAUSTIC SODA AND CAUSTIC
POTASH, AND EITHER FREK SULPHUR OR SULPHUROUS ACID."
Sealed the 24th November 1876, and dated the 28th August 1876.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 28th August 1876.
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey. "A NEW
METHOD OR PROCESS, AND A NEW COMBINATION OF PROCESSES AND APPLIANCES,
FOR OBTAINING FROM SULPHIDE OF SODIUM AND SULPHIDE OF POTASSIUM CAUSTIC
SODA AND CAUSTIC POTASH, AND EITHER FREE SULPHUR OR SULPHUROUS ACID "
In certain other Specifications, which will be filed at the Patent Office on the
same day as this, I have described certain Inventions relating to the manufacture
of sulphide of sodium and sulphide of potassium, whereby I believe that these
bodies can henceforth be produced so economically as to permit of their being
applied to a number of new and very important purposes. My present Invention
relates to their transformation into caustic soda and caustic potash in such wise as
to permit of their sulphur being at the same time obtained either as free sulphur
or in another form in which it can equally readily be re-utilized. In what follows
it will be convenient to speak only of sulphide of sodium and caustic soda, but all
that is said of these will be equally applicable to sulphide of potassium and caustic
potash
Sulphide of sodium manufactured in accordance with my other Inventions
aforesaid will be produced in a cylindrical furnace placed horizontally, ananged so
as to be capable of revolving on its longer axis, and having an opening at each
end to permit of the entry into it, and of the passage through it, of products of
combustion or other gases or vapours. For the purpose of my present Invention
such cylindrical or "revolving" furnace must have connected with it at one end
an apparatus for producing highly superbeated steam, which apparatus may
preferably be what is known as a Siemens-Cowper stove, and at the other end an
apparatus for treating sulphuretted hydrogen.
+

page_text: The application of my present Invention begins when the said revolving furnace
contains a charge of sulphide of sodium, which has either been produced therein,
or has been otherwise produced and afterwards charged thereinto. I now send
into the said furnace a blast of superheated steam from the aforesaid stove or other
apparatus, and while highly heated steam is thus passing into it I keep the furnace
in revolution, so that the steam shall come into contact with all parts of its
contents. Under these conditions the steam re-acts on the sulphide of sodiuin,
forming on the one hand caustic soda, and on the other hand sulphuretted
hydrogen, which goes off as gas. When the evolution of this gas has ceased, the
contents of the furnace may be drawn off directly into the "drums," or iron casks
in which caustic soda is usually sold.
The sulphuretted hydrogen produced as just described can be treated in either
of two ways: It will pass off mixed with steam, which should preferably be first
condensed out of it, leaving the sulphuretted hydrogon nearly or quite pure. The
sulphuretted hydrogen can then be either simply burnt into sulphurous acid or
treated for the obtainment of its sulphur in the free state by the Invention for
which Her Majesty's Letters Patent, numbered 2008, and bearing date the
31st July, 1871, have been granted to me. But in applying that method of
obtaining sulphur from sulphuretted hydrogen to the sulphuretted hydrogen pro-
duced in treating previously obtained sulphide of sodium by highly superhented
steam, as above described, I prefer to employ for the absorption of the sulphuretted
hydrogen either such apparatus as that which is described, and of which Drawings
are given in the Specification filed in pursuance of the conditions of the Letters
Patent dated the 16th July, 1873, and numbered 2449, or such new apparatus_as
will be described in another Specification, which will be filed at the Patent Office
on the same day as this.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Walter Weldon in the Great Seal Patent Office on the 7th February
1877.
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey.
"A NEW METHOD OR PROCESS, AND A NEW COMBINATION OF PROCESSES AND
APPLIANCES, FOR OBTAINING FROM SULPHIDE OF SODIUM AND SULPHIDE OF
POTASSIUM CAUSTIC SODA AND CAUSTIC POTASH, AND EITHER FREE SULPHUR OR
SULPHUROUS ACID.”
This Invention consists in a new method or process, a combination of this
method or process with certain other methods or processes, and a combination of
appliances, whereby I transform sulphide of sodium into caustic soda, and sulphide
of potassium into caustic potash, and at the same time obtain the sulphur of the
said sulphides, either as free sulphur or as sulphurous acid.
In describing my said Invention it will be convenient to speak only of sulphide
of sodium and caustic soda; but all that is said of these will be equally applicable
to sulphide of potassium and caustic potash.
The said new method or process consists in treating sulphide of sodium by
superheated steam in a revolving furnace lined with blocks of carbon. The steam
re-acts upon the sulphide of sodium in accordance with the equation:-
Na, S+2H,O=2 Na HO+H₂S,
'-
the sulphur of the sulphide of sodium being evolved as sulphuretted hydrogen, and
"caustic soda remaining behind in the furnace.
I combine this method of producing caustic soda with one or other of two
methods of utilizing the sulphuretted hydrogen which is produced at the same time;
the said sulphuretted hydrogen passes off mixed with steam By one method of
utilizing it I simply pass the mixture of sulphuretted hydrogen and steam through
cooling pipes or other convenient apparatus, whereby I separate the steam by con-

page_text: densation and then burn the sulphuretted hydrogen directly to sulphurous acid.
I prefer, however, to treat it for the obtainment of its sulphur in the free state by
a former Invention, for which Letters Patent bearing date the Thirty-first of July,
1871, and numbered 2008, have been granted to me
To carry into effect the above stated method of transforming sulphide of sodium
into caustic soda, together with that method of treating the resulting sulphuretted
hydrogen, which I believe to be the most advantageous, I employ a combination
of appliances, the central element of which is a revolving furnace lined with blocks
of carbon, preferably, though not necessarily, such as are produced by artificially
agglomerating coke under my Invention, the Letters Patent for which are
numbered 3382, of the year 1876. As required only for the conversion of sulphide
of sodium into caustic soda, this furnace need differ from the revolving furnaces
at present in nearly general use among manufacturers of alkali only in being lined
with blocks of carbon instead of with fire-brick; but when the furnace is to be
used not only for the conversion of sulphide of sodium into caustic soda but also
for the manufacture of the sulphide itself, it may have likewise the further
peculiarities which are described for a revolving furnace for the manufacture of
alkaline sulphides in the Specification of my Patent, numbered 3380, of the year
1876. With one end of this carbon-lined revolving furnace I connect any suitable
apparatus for the production of highly superheated steam, which apparatus may
conveniently be that which is known as the Siemens-Cowper stove; and the other
end of it I connect with such apparatus for the treatment of liquids by gases, as
is described in the Specification of my Patent, numbered 3389, of the year 1876.
To these appliances must be added an "oxidizer," such as is used in any well-known
process for the regeneration of the manganese employed in the manufacture of
chlorine.
The mode of working is as follows:-When the revolving furnace contains a
charge of sulphide of sodium which has either been produced therein or having
been produced in other apparatus has been charged thereinto. the furnace is put
into revolution, and a blast of highly heated steam from the aforesaid stove or other
apparatus is passed into it until sulphuretted hydrogen ceases to be evolved, or is
evolved if at all only in insignificant quantity. The desired reaction can take
place and may be permitted to take place at a much lower temperature, but if it be
desired that the product should be obtained in the state of fusion the temperature
of the steam should not be below the fusing point of monohydrated caustic soda,
while it must of course be below that at which caustic soda volatilizes. When the
evolution of sulphuretted hydrogen has ceased, or nearly ceased, the contents of
the furnace are withdrawn therefrom, either directly into the "drums" in which
caustic soda is usually sold, or if it be not quite pure enough for sale or use into
suitable "bogies," from which it can be transferred into apparatus for its purifica-
tion, as will be well understood.
The sulphuretted hydrogen which is evolved during the operation just described
passes on leaving the furnace into the first of a series of closed vessels or "absorbers,"
each of them partially filled with a mixture with water of finely divided oxide of
iron or of manganese. Almost any oxide of either of these metals may be used, but
I prefer to employ precipitated, and therefore hydrated, sesqui-oxide of iron. Each
vessel of the said series is furnished with a mechanical agitator, consisting of a
number of arms attached at right angles to an axis or shaft placed horizontally, and
these agitators are so arranged and are kept in such rapid motion as to maintain in
the upper part of each vessel a continual rain or spray of the mixture with water of
oxide of iron or other oxide, as aforesaid. The sulphuretted hydrogen enters the
first vessel of the said series at its upper part, and there comes into contact with an
enormous surface of the said rain or spray. It comes into contact at the same time
with the continually renewed surface of mixture of metallic oxide and water in the
lower part of the vessel. Under these conditions much of the sulphuretted hydrogen
first dissolves in the water of the said mixture and then re-acts upon the metallic
oxide therein, its sulphur entering into combination with the metal of the said

page_text: oxide, and its hydrogen with the oxygen thereof. That part of the sulphuretted
hydrogen which has not time thus to react upon the mixture of oxide and water in
the said first vessel, and thus to become absorbed in that vessel, passes on into the
upper part of the second vessel of the series, wherein a further portion of it reacts
and thereby becomes absorbed as aforesaid, what is not absorbed in the second vessel
passing on into the upper part of the next vessel of the series, and so on until every
trace of the sulphuretted hydrogen has been absorbed If the size of the absorbers
be properly adapted to the size of the revolving furnace and to the rate at which sul-
phuretted hydrogen is produced therein from four to six absorbers will suffice for its
complete absorption, but much will depend in this respect upon the speed at which the
agitators are worked. When the oxide of 11on or other oxide in the mixture thereof
with water with which the first vessel was charged has been completely converted
into sulphide the contents of that vessel are withdrawn therefrom and the contents of
the second vessel are transferred to the said first vessel, those of the third vessel are
transferred to the second vessel, and so on throughout the series, the last vessel when
its contents have been transferred to the last but one being re-chaiged with fresh
mixture of oxide and water. The mixture of metallic sulphide with water which
has thus been withdrawn from the first vessel of the series is put into an "oxidizer"
or deep cylindrical vessel connected with a blowing engine by a pipe conveying air
therefrom, which pipe terminates near the bottom of the oxidizer in an arrangement
of smaller pipes or other appliance for disseminating as far as possible through
the contents of the vessel the air which may be injected into it. Therein the
said mixture of metallic sulphide with water is ticated by air until the sulphide
in such mixture is re-converted into oxide, its sulphur being at the same time set
free. The product of this operation is a mixture with water of metallic oxide and
fice sulphur. This mixture can be used again for the absorption of mole
sulphuretted hydrogen instead of fresh mixture of oxide and water, and with inter-
mediate treatment by air it can be thus re-cumployed several times successively,
becoming continually richer and richer in sulphur When it contains such pro-
portion of sulphur as may be preferred it may be treated by hydrochloric or other
suitable acid so as to dissolve the oxide out from it, leaving pure sulphur. Or the
mixture of oxide and free sulphur may be separated from the water it is mixed
with or suspended in and be drained and dried, and may then have its sulphur burnt
off from it as sulphurous acid, as will be well understood. Applied in this last-
mentioned manner the said mixture gives sulphurous acid gas as little diluted as
can be obtained by burning the best brimstone, and far less dilute than that
obtained by burning pyrites, seeing that the sulphur in the said mixture is all in
the free state and not combined, and that the metal in the mixture is already fully
oxidized and so absorbs no oxygen in the operation of burning off the sulphur.
Having thus described and particularly ascertained the nature of my said Inven-
tion, and in what manner the saine is to be performed, I claim as the Invention to
be secured to me by the herein-before in part recited Letters Patent,-
Firstly. The new method or process for transforming sulphide of sodium into
caustic soda, and sulphide of potassium into caustic potash, which is above
described.
And, Secondly. The combination of processes and appliances whereby, sub-
stantially as is above set forth, I transform sulphide of sodium into caustic soda, and
sulphide of potassium into caustic potash, and at the same time obtain the sulphur
of the said sulphides either as free sulphur or as sulphurous acid.
.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and scal, this Second day of February, in the year of our Lord Oue
thousand eight hundred and seventy-seven.