A NEW METHOD OF APPLYING THE HEAT NECESSARY TO ENABLE CARBONACEOUS MATTER TO REDUCE SULPHATE OF SODA AND SULPHATE OF POTASH TO THE STATE OF SULPHIDE, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF 'BLACK ASII
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 OF APPLYING THE HEAT
NECESSARY TO ENABLE CARBONACEOUS MATTER TO REDUCE SULPHATE OF SODA
AND SULPHATE OF POTASH TO THE STATE OF SULPHIDE, PARTLY APPLICABLE
ALSO TO THE MANUFACTURE OF 'BLACK ASII' "
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office of
the Commissoners of Patents on the 28th August 1876.
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey. "A NEW
METHOD OF APPLYING THE HEAT NECESSARY TO ENABLE CARBONACEOUS MATTER
TO REDUCE SULPHATE OF SODA AND SULPHATE OF POTASH TO THE STATE OF
SULPHIDE, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF 'BLACK ASH."
"
It has been many times proposed, and, although less frequently, it has been many
times attempted to manufacture soda by converting sulphate of soda into sulphide
of sodium, and then decomposing such sulphide of sodium by one or other of
several known means. This method of manufacturing soda would permit the
recovery and reutilization of the whole of the sulphur contained in the sulphate
of soda employed, and would avoid the production of the offensive residue known
as "alkali waste;" but all attempts to practically apply this process have hitherto
failed.
One principal cause of this failure has lain in the methods by which in all
attempts to manufacture sulphide of sodium by the reaction upon sulphate of soda
of solid carbonaceous matter the heat necessary to enable the carbonaceous matter
to react upon the sulphate of soda has been applied. Either the method of working
has been such that the sulphide of sodium has been formed in an atmosphere of the
products of combustion employed to heat the sulphate of soda and the carbonaceous
matter, these materials, either mixed together or the sulphate of soda at one end of
a furnace and the carbonaceous matter at the other end of the same furnace being
heated by direct contact with the said products of combustion, or the sulphate of
soda and the carbonaceous matter have been mixed together in the cold, and the
mixture then subjected to transmitted heat in a "blind" furnace or muffle. The
.

page_text: first-mentioned method of applying the necessary beat has two very serious dis-
advantages. Firstly, sulphide of sodiuin is an appreciably. volatile body, and a
current of hot gases passing through the apparatus in which it is being manu-
factured carries off considerable quantities of it. The sulphide of sodium thus
carried off is not merely lost, but it attacks the bricks of the flucs or other conduits 5
for the gases passing from the apparatus in such wise as to cause their rapid
destruction. Secondly, whereas sulphide of sodium, in order to be capable of being
converted into merchantable soda in the most economical manner, must be practi-
cally pure mono-sulphide unmixed or nearly so with compounds containing more
than one equivalent of sulphur per equivalent of sodium when a mixture of 1
sulphate of soda and carbonaceous matter is heated by direct contact with products
of combustion, the steam and free oxygen in such products of combustion give riso
to reactions, which result in the production of considerable quantities of poly-
sulphides, as well as of several other compounds other than mono-sulphide of
sodium. By either method of heating, when it is coal and not coke which is mixed 1
with the sulphate of soda the hydrogen in the coal tends to the same result. In
the mothod of heating by transmitted heat a similar effect is produced by the air
which is admitted when the doors of the muffle furnace are opened to permit of
the charge being stirred. For these and other reasons some better method than
any hitherto employed or proposed of applying the heat necessary to enable car- 2
bonaceous matter to deoxidize sulphate of soda is essential to the practical realization
of the first step in the process referred to in the first paragraph above.
Another cause of the insuccess of all attempts made heretofore to practically
apply the method of manufacturing soda to which reference has been made above,
has been the difficulty of obtaining a pure carbonic acid wherewith after having
produced sulphide of sodium to convert it into merchantable soda. Theoretically,
when no excess of carbon is employed, the gaseous product of the reaction of car-
bonaceous matter upon sulphate of soda is this very agent, carbonic acid; and it
has often been proposed to employ for the decomposition of sulphide of sodium the
carbonic acid thus resulting from the reaction by which the sulphide is itself formed,
but the methods of heating employed for the production of the sulphide have
rendered the realization of this method hitherto impossible.
If carbonic acid gas is much diluted by other although inert gases, its action is
so enfeebled thereby that the quantity of it required for the decomposition of sul-
phide of sodium becomes impracticably great, while the treatment of sulphide of
sodium by carbonic acid associated with comparatively small quantities of free
oxygen yields, instead of merchantablo carbonate of soda a comparatively worth-
less mixture of carbonate with hyposulphite and other salts, hence, in all attempts
mado hitherto to manufacture sulphide of sodium it has been impossible to utilize
for the decomposition of the sulphide the gaseous product of the reaction by which
it was formed. If the sulphide were formed after the manner oftenest attempted
and proposed in presence of an excess of carbon, that gaseous product was not car-
bonic acid at all, but carbonic oxide; and when the said gaseous product has been
really carbonic acid it has always been associated with free oxygen, and generally
with large quantities of products of combustion as well; and pure carbonic acid, as
obtained by any means hitherto known, has always been, and still is, much too
costly for use for the manufacture of soda by the decomposition of sulphide of
sodium.
My present Invention consists in such a method of applying the heat necessary
to enable carbonaceous matter to react upon sulphate of soda as permits that re-
action to be performed in practically a closed vessel without access either of air or
of products of combustion in such wise as to produce at once a purer sulphide of
sodium than has ever been obtained hitherto, and a gaseous product consisting
of nearly pure and undiluted carbonic acid really available for the subsequent con-
version of the sulphide into carbonate
The said Invention consists in heating the sulphate of soda and the carbonaceous
matter separately in distinct furnaces, beforo mixing them together, and in then

page_text: obtaining sulphide of sodium by bringing into intimate contact with each other
sulphate of soda and carbonaceous matter, both of which have previously been
raised to such a temperature that on their coming into mutual contact reaction
between them can take place without any further application of heat; I am thus
enabled to produce sulphide of sodium in a vessel which for the time being has no
other opening than such as is necessary for the escape of the gaseous product of
the reaction by which the sulphide of sodium is produced, and to which vessel,
during either the whole or the greater part of the time that that reaction is going
on it is not necessary to apply heat, either externally, or by the passage into or
through it of products of combustion.
For this method of working the carbonaceous matter employed must be pow-
dered coke or other form of charcoal; the furnace in which this is heated I will
call furnace "A." It should preferably be a furnace of the kind known to alkali
manufacturers as the "revolving furnace," such furnace being a long cylinder,
placed horizontally, arranged so as to be capable of revolving on its longer axis,
and having an opening at each end to permit of its contents being heated by the
passage through it of products of combustion My furnace, "A," however, must
differ from the revolving furnaces at present in use among alkali makers in two
particulars; it must be so lined and protected by carbon blocks as to render it
inattackable by sulphide of sodium, which would completely destroy in a very short
time any revolving furnace at present in use; and it must be provided with
appliances for cutting off at will the entry into it of products of combustion, and of
completely closing the opening at one of its ends so as to admit of its being con-
verted at will into a vessel having only one open aperture.
The other furnace, which I will call furnace "B," may preferably be a Siemens's
regenerative furnace. In it I beat the sulphate of soda at least to fusion. When
the powdered coke in furnace "A" has been sufficiently heated I cut off the supply to
that furnace of products of combustion; I close the opening by which those products
had entered. Upon the hot coke in that furnace I run in fused sulphate of soda
from furnace "B," and I set furnace "A" in as rapid revolution as I conveniently
can, so as to mix its contents as quickly and as thoroughly as possible. If the
sulphate of soda and the coke have been sufficiently heated before being thus brought
into contact one with the other, the heat previously communicated to them separately
will suffice for the completion of the required reaction between them; but if they
have not been sufficiently heated before being so brought together it may be
necessary, after the reaction has proceeded as far as it can, to admit for a few
moments products of combustion.
The above-described manner of carrying out my present Invention I believe to be
the best, but it may be varied in several ways. Thus furnace "A" may be other than
a revolving furnace, and furnace "B" other than a Siemens's furnace. Moreover, the
reaction between the sulphate of soda and the powdered coke may be performed
in a third furnace instead of in the furnace in which the coke was heated; and
instead of the fused sulphate of soda being added to the hot coke the hot coke
may be added to the fused sulphate of soda Moreover, if the sulphate of soda be
sufficiently heated the heating of the coke may be dispensed with
All that is said above with respect to the manufacture of sulphate of sodium is
equally applicable to the manufacture of sulphide of potassium, and such part of the
Invention above described as relates to first heating sulphate of soda to fusion in a
separate furnace, and then running it into another furnace to be there decomposed,
is applicable also to the manufacture of what is known to alkali makers as "black
ash.'
The appliances above referred to for cutting off at will the entry of products of
combustion into the revolving furnace may conveniently be as follows:-In the
revolving furnaces at present in use the products of combustion enter through an
aperture in the centre of an annular disc formed of fire-bricks bound together by
an iron hoop. This annular disc is attached neither to the revolving furnace nor
to the furnace or combustion chamber in which the products of combustion are pro-

page_text: duced, but is suspended between the two. For the purposes of this Invention the
carbon lined revolving furnace should be provided not only with this ordinary
annular disc, but also with a second and special disc, this second disc having no
aperture, and being formed of carbon blocks bound together by an iron hoop or
ing. This second disc must be adapted, as will be well understood, so that when
the annular disc has been moved out of the way it can readily be attached to the
end of the revolving furnace in such wise as to move with the revolving furnace,
keeping the opening over which it is placed completely closed.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Weldon in the Great Seal Patent Office on the 26th February
1877.
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey. "A New
METHOD OF APPLYING THE HEAT NECESSARY TO ENABLE CARBONACEOUS Matter
TO REDUCE SULPHATE OF SODA AND SULPHATE OF POTASH TO THE STATE OF
SULPHIDE, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF BLACK ASH."
This Invention relates to the manufacture of sulphide of sodium and sulphide of
potassium by the action of solid carbonaceous matter upon sulphate of soda and
sulphate of potash.
In describing tho said Invention it will be convenient to speak only of sulphate
of soda and sulphide of sodium, but all that is said of these will be equally
applicable to sulphate of potash and sulphide of potassium.
The said Invention consists in heating the sulphate of soda and the carbonaceous
matter separately, before mixing them together, so that when they are afterwards
brought into mutual contact reaction can take place between them without any
further or with but little further application of heat.
For carrying into effect this new method of applying the heat necessary to
enable sulphate of soda and carbonaceous matter to react upon each other I do not
confine myself to the use of any particular kind or kinds of furnaces, or of any
particular combination of furnaces; but I prefer that the furnace in which the
sulphate of soda is heated should be a Siemens's regenerative furnace, and that the
furnace in which the carbonaceous matter is heated should be that in which it is
afterwards to react on the sulphate of soda. In such case the latter furnace, of
whatever kind it may be, otherwise should be protected from corrosion by the
sulphide of sodium to be produced in it by being lined interiorly with blocks,
either of artificially agglomerated coke or of some other convenient form of solid
carbon. In the former furnace I heat sulphate of soda at least to fusion; in the
latter furnace I heat powdered coke or charcoal preferably to redness. If the
fused sulphate of soda from the one furnace be now run on to the red hot coke or
charcoal in the other furnace sulphide of sodium will be produced much more
advantageously than by any method hitherto employed.
As much of the Invention above described as relates to first heating sulphate of
soda to fusion in one furnace and then running it in the fused state into another
furnace to be there decomposed, is applicable also to the manufacture of what is
known to alkali makers as black ash."
Having now described the nature of my said Invention, and in what manner the
same 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 of applying the heat necessary to enable carbonaceous
matter to reduce sulphate of soda to the state of sulphide of sodium and sulphate
of potash to the state of sulphide of potassium, which consists in heating the
sulphate of soda or the sulphate of potash and the carbonaceous matter separately,
the sulphate of soda or sulphate of potash in one furnace, and at least to fusion,

page_text: and the coke or charcoal in another furnace, and preferably to redness, before
mixing them together, so that on then bringing them into mutual contact the
sulphate may be reduced to the state of sulphide without any further or with but
little further application of heat.
And, Secondly. The new method of applying a part of the heat required in the
manufacture of black ash, which consists in heating the sulphate of soda to fusion
in a distinct furnace, and then running it into the furnace in which coal and lime-
stone are to react on it.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
and seal, this Fifth day of February, in the year of our Lord One thousand
eight hundred and seventy-seven.
(L.S.) WALTER WELDON.