Improved Processes for Producing the Sulphides of the Alkalies and of the Alkaline Earths from the Sulphates thereof, and for Obtain- ing from such Sulphides Free Sulphur, Sulphurous Acid, Sulphide of Hydrogen, and Carbonates of the Alkalies.
Year: 1898

page_text: Date of Application, 25th Mar., 1898
Complete Specification Left, 27th Dec., 1898-Accepted, 18th Feb., 1899
PROVISIONAL SPECIFICATION.
Improved Processes for Producing the Sulphides of the Alkalies and
of the Alkaline Earths from the Sulphates thereof, and for Obtain-
ing from such Sulphides Free Sulphur, Sulphurous Acid, Sulphide
of Hydrogen, and Carbonates of the Alkalies.
We, WLADIMIR VON BARANOFF, Doctor, of 26, Rue des Batignolles, and EUGENE
HILDT, Chemist, of 31, Avenue de Montsouris, both in Paris, in the Republic
of France, and CARL FRIEDRICHI CLAUS, Chemist, of 9, Oxford Road, Gunnersbury,
in the County of Middlesex, do hereby declare the nature of this invention to be
as follows:-
Our invention is designed to provide for the production of the sulphides of the
alkalies and of the alkaline earths from the sulphates thereof, and for obtaining
from such sulphides free sulphur, sulphurous acid and sulphide of hydrogen, and
from the sulphides of the alkalies their carbonates. And our said invention com-
prises an improved process which is carried on as follows:-
We mix, for instance, finely ground (preferably anhydrous) sulphate of lime
intimately with carbon or carbonaceous matter, and heat the mixture in closed
vessels (such as gas-retorts) to the temperature at which the sulphate becomes
reduced to sulphide. In this manner, according to the formula
CaSO, +20 = 2 CO₂ + Ca S,
we obtain one equivalent of sulphide of calcium to two equivalents of carbonic
acid, the carbonic acid being of great richness and purity.
The sulphide of calcium we decompose, by means of the carbonic acid simul-
taneously produced in the retorts as above mentioned, in the manner and in an
apparatus similar to that described in the Specification of former Letters Patent
No. 5958 of 1883 granted to C. F. Claus, in reference to the treatment of alkali
waste. We obtain thereby carbonate of lime and free and nearly pure sulphide
of hydrogen. The sulphide of hydrogen we mix (as described in the said former
specification) with an equivalent quantity of air (or atmospheric oxygen) and pass
the mixture through a closed vessel containing oxide of iron. Thus we obtain
the greatest part of the sulphur (85 to 90 per cent.) contained in the sulphide of
hydrogen, as free and solid sulphur.
In the said former specification, lime-kiln gases containing about 30 to 35
per cent. of carbonic acid are said to be employed for the decomposition of alkali
waste, which is an impure sulphide of calcium. But in our present process, we
obtain a gas containing about 90 to 95 per cent. of carbonic acid and of this there
are, as above stated, about two equivalents to one equivalent of sulphide of calcium.
Since little or no excess of carbonic acid is required, for the complete conversion
of calcium sulphide into calcium carbonate, one equivalent of this rich and pure

page_text: furnishes also the quantity of calcium sulphide necessary for the utilization of the
above mentioned second equivalent of carbonic acid.
The above described processes can be carried out most successfully when using
anhydrous calcium sulphate, but we apply the same also with the sulphates of
barium and strontium and obtain thus their respective sulphides together with
two equivalents of rich carbonic acid as well as free sulphur or sulphurous acid.
One of the most important applications of our process, however, consists in the
treatment thereby of mixtures or double compounds of calcium sulphate with
sodium sulphate, natural or artificial, such as glauberite, or of calcium sulphate
with potassium sulphate. These, on being heated in closed vessels together with
carbon, produce sulphide of sodium and sulphide of calcium or sulphide of potas-
sium and sulphide of calcium respectively, as well as carbonic acid of the same
purity and in the same quantity as above mentioned. Or we produce these
sulphides or mixtures of sulphides by acting upon the mixed sulphates by means
of sulphide of hydrogen as above described in reference to the treatment of
sulphate of calcium by means of sulphide of hydrogen.
The mixtures of sulphide of sodium with sulphide of calcium, or of sulphide of
potassium with sulphide of calcium respectively, we now decompose in the vessels
called in the aforesaid former specification "carbonators," by means of the rich
carbonic acid produced in the retorts. This operation may be carried on until
the sulphide of calcium and the sulphide of sodium (or the sulphide of calcium

page_text: and sulphide of potassium respectively) have both become converted into
carbonates.
In this case they are separated by decantation or filtration. Or we pass carbonic
acid through these sulphides (suspended in water) until the calcium sulphide alone
has been converted into calcium carbonate.
'In such case we separate by decantation or filtration the sulphide or sulphydrate
of sodium (or potassium) from the insoluble calcium carbonate. We then employ
the former either as such or for conversion into carbonates by means of further
carbonating the same with part of the pure carbonic acid from the retorts.
We can also separate the two sulphides by simple lixiviation, the calcium
sulphide being nearly insoluble while sodium sulphide and potassium sulphide
are readily soluble in water.
1
Manch 1808
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicants.
mproved Processes for Producing the Sulphides of the Alkalies and
of the Alkaline Earths from the Sulphates thereof, and for Obtain-
ing from such Sulphides Free Sulphur, Sulphurous Acid, Sulphide
of Hydrogen, and Carbonates of the Alkalies.
We, WLADIMIR VON BARANOFF, Doctor, of 26, Rue des Batignolles, and EUGENE
HILDT, Chemist, of 31, Avenue de Montsouris, both in Paris, in the Republic of
France, and CARL FRIEDRICH CLAUS, Chemist, of 9, Oxford Road, Gunnersbury,
in the County of Middlesex, 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:--
The process forming the subject of our present invention is a combination of
several steps or processes, the principles of which are more or less known, but in
the practical carrying out of which we have made certain improvements so that
by the combination and sequence of the individual processes, more economical
results are obtained than by the practice of these individual processes separately
or by a sequence of the individual processes different to the present one.
The object of this combination of steps or processes is to produce from calcium
sulphate or from mixtures of calcium sulphate with an alkaline sulphate or from
an alkali-calcium double sulphate (such as glauberite) or from a similar compound
prepared artificially, (a) the sulphides of these bases, (b) carbonic acid of com-
paratively great purity, (c) sulphide of hydrogen, (d) sulphurous acid or free
sulphur, and, as the most essential product, (e) the carbonates of the alkalies and
calcium carbonate.
For this purpose we first mix finely ground (preferably anhydrous) sulphate of
lime, or mixtures of finely ground sulphate of lime with an alkaline sulphate
or with natural or artificial double alkali-calcium sulphate, intimately with finely
ground carbon or carbonaceous matter, and heat the mixture in closed vessels
(such as gas-retorts) to the temperature at which the sulphate becomes reduced
to sulnhide.

page_text: The reduction of calcium sulphate by carbon in heated closed vessels has already
been suggested and practised, but the practice has generally been to use a quantity
of carbon largely in excess of that required theoretically, under the impression
that thereby a more complete reduction of the sulphate to sulphide would be
obtained; and in consequence of this excess of carbon, the carbonic acid resulting
from the reduction is very poor and largely diluted by carbonic oxide.
We use in our process only the theoretical quantity of carbon, and obtain as a
most surprising result, a complete or nearly complete reduction of the sulphates,
and gases containing from 90 to 95 per cent. of carbonic acid; and we obtain
one equivalent of calcium sulphide or the corresponding quantity of alkaline
sulphide mixed with calcium sulphide, to two equivalents of carbonic acid,
according to the formula:-
CaSO + 2C
==
2 CO, + CaS.
The calcium sulphide or the corresponding alkaline sulphide mixed with calcium
sulphide thus obtained, we now mix with sufficient water for the sulphide to
become suspended therein. And we decompose these sulphides so suspended in
water, by means of the carbonic acid simultaneously produced in the retorts above
mentioned in the manner and in an apparatus similar to those described in the
Specification of former Letters Patent No. 5958 of 1883 granted to C. F. Claus in
reference to the treatment of alkali-waste, and called the "carbonators," into
which they are charged; or they may be treated in any other suitable apparatus.
We may for convenience sake store the said carbonic acid in a gas-holder and
force the same by means of a gas-compressor into the contents of the "carbonators"
in the manner described in the said former specification. We obtain thereby the
alkaline carbonates and calcium carbonate or calcium carbonate alone respectively,
and free and nearly pure hydrogen sulphide (say 90 to 95 per cent. of HS).
We have said that the reduction of calcium sulphate to sulphide by means of
carbon in heated retorts has been proposed before. So also has the treatment of the
calcium sulphide in carbonators by means of the carbonic acid from the retorts.
The hydrogen sulphide obtained was, however, as poor as the carbonic acid used
to produce it and was burnt to sulphurous acid for the manufacture of sulphuric
acid in lead chambers.
In our present process, however, we produce, as above stated, nearly pure
hydrogen sulphide and we obtain therefrom free and solid sulphur of almost
chemical purity by treating, in the manner described in the second part of the
said former specification, either the whole of the hydrogen sulphide obtained from
the carbonators or only a part thereof so that another portion of the same may
be treated in the manner to be described below.
To obtain free and solid sulphur from the said rich hydrogen sulphide, we mix
the whole of it, or only a portion respectively of the same, with an equivalent
quantity of air (atmospheric oxygen) and pass the mixture through a closed. vessel
containing oxide of iron or other solid substances such as are mentioned in the
said former specification, to obtain, by condensation of the resulting vapours of
sulphur, the greater part of the sulphur (85 to 90 per cent.) contained in the
hydrogen sulphide, as free and solid sulphur.
In the said former specification, lime-kiln gases containing 30 to 35 per cent.
of carbonic acid are said to be employed for the decomposition of alkali-waste
which is an impure calcium sulphide, and consequently the hydrogen sulphide
gas obtained thereby can only contain 30 to 35 per cent. of real hydrogen sulphide.
In our present process, we obtain and use a gas containing about 90 to 95 per cent.
of carbonic acid, and consequently the hydrogen sulphide we obtain thereby contains
90 to 95 per cent. of real hydrogen sulphide. The calcium sulphide obtained by
our process contains three times the quantity of sulphur contained in the alkali-
waste. Consequently the costly apparatus which is used for the recovery of sulphur
from alkali, when employed in our process, will be able to produce a three times

page_text: greater quantity of sulphur than it can produce from alkali-waste, and at little
more than one-third the cost without taking into consideration the value of the
alkaline carbonates simultaneously produced by the process. It may here be
mentioned that reducing on a manufacturing scale alkaline sulphates alone with
carbon in heated retorts or open furnaces has been found to be impracticable owing
to the destructive action of the alkaline sulphides; but we have found that, by
mixing calcium sulphate therewith as in our process, no such destruction takes
place.
We obtain in the retorts, as above stated, two equivalents of carbonic acid to
one equivalent of the sulphides. Only one equivalent is required for the decom-
position of one equivalent of sulphide. Working the process in the way so far
described, one equivalent of the rich carbonic acid capable of decomposing another
equivalent of calcium sulphide would be lost were no other source provided of
obtaining calcium sulphide than that afforded by the process above described.
To provide for a further supply of the calcium sulphide by another process is also
an object of our present invention, which we accomplish in the following
manner:―
Instead of mixing the whole of the sulphide of hydrogen produced by the action
of the carbonic acid upon the calcium sulphide, with air and passing it through
the 2nd part of the Claus process, we pass only a portion of the sulphide of
hydrogen into the Claus apparatus to recover the sulphur therefrom direct, and
another portion we pass, under slight pressure, through a series of retorts filled
with anhydrous sulphate of lime, unmixed with carbon, after such retorts and
This series of retorts is, therefore,
their contents have been heated up to red heat.
so arranged that the gases can pass from one retort to another and so on through
the whole series. So long as, in these retorts, an excess of sulphate of lime is
offered to the sulphide of hydrogen passing through them, a reaction takes place
which may be expressed by the formula:-
:-
ސ
3CaSO. + 4H,S 3CaS+4SO, + 4H₂O.
=
When the sulphate in the first retort has become reduced to sulphide, the H₂S
is passed into the second, while the contents of the first are discharged, and when
recharged this becomes the least in the series. By this arrangement the means
are furnished to produce SO, only or SO, and HS or free S by exhibiting a larger or
smaller surface or mass of sulphates to the stream of H2S, or vice versa by
increasing or diminishing the stream of HS passing through.
If more sulphide of hydrogen should at any time pass through the calcium
sulphate in the retorts than can be easily converted by the said calcium sulphate
hide of hydrogen will be decomposed so
When the sulphate in the first retort has become reduced to sulphide, the HS
is passed into the second, while the contents of the first are discharged, and when
recharged this becomes the least in the series. By this arrangement the means
are furnished to produce SO, only or SO, and HS or free S by exhibiting a larger or
smaller surface or mass of sulphates to the stream of H2S, or vice versa by
increasing or diminishing the stream of HS passing through.
If more sulphide of hydrogen should at any time pass through the calcium
sulphate in the retorts than can be easily converted by the said calcium sulphate
into sulphurous acid, some of this sulphide of hydrogen will be decomposed so
as to form free sulphur, which will pass away from the retorts in the form of
vapour. To readily dispose of this mixture of gases, we pass the same, along
with the hydrogen sulphide gas issuing from the carbonators, for the recovery of
sulphur therefrom, through the Claus kiln, mixed with so much air as corresponds
with the sulphide of hydrogen required for the decomposition expressed by
When sulphurous acid only is formed in the retorts according to the above
formula, it is of great purity and richness and may advantageously be made use
of in other manufactures.
The aforesaid reaction:-

page_text: The above-described processes can be carried out most successfully when using
'anhydrous calcium sulphate.
One of the most important applications of our process consists, as above stated,
in the treatment thereby of mixtures or double compounds of calcium sulphate
with sodium sulphate, natural or artificial, such as glauberite, or of calcium
sulphate with potassium sulphate. These, on being heated in closed vessels
together with carbon, produce sulphide of sodium and sulphide of calcium, or
sulphide of potassium and sulphide of calcium, as well as carbonic acid of the
same purity and in the same quantity as above mentioned. Or we produce these
sulphides or mixtures of sulphides by acting upon the mixed sulphates by means
of sulphide of hydrogen as above described with reference to the treatment of
sulphate of calcium by means of sulphide of hydrogen.'
The mixtures of sulphide of sodium with sulphide of calcium, or of sulphide of
potassium with sulphide of calcium, we now decompose in " carbonators," by
means of the rich carbonic acid produced in the retorts. This operation may be
carried on until the sulphide of calcium and the sulphide of sodium (or the
sulphide of calcium and sulphide of potassium) have both become converted into
carbonates. In this case they are separated by decantation or filtration. Or we
pass carbonic acid through these sulphides (suspended in water) until the calcium
sulphide alone has been converted into calcium carbonate. In such case we
separate by decantation or filtration the sulphide or sulphydrate of sodium (or
potassium) from the insoluble calcium carbonate. We then employ the former
either as such or for conversion into carbonates by further carbonating the same
with part of the pure carbonic acid from the retorts. We thus produce simul-
taneously calcium carbonate and an alkaline carbonate.
We can also separate the two sulphides by simple lixiviation, the calcium
sulphide being nearly insoluble while sodium sulphide and potassium sulphide are
readily soluble in water.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. The herein described process of obtaining calcium carbonate and sulphur,
with or without carbonates of the alkalies, consisting in first heating in closed
vessels or retorts calcium sulphate, or mixtures of calcium sulphate with an
alkaline sulphate, or the natural or artificial alkali-calcium sulphate, together
with carbon to form practically pure carbonic acid and calcium sulphide or
mixtures of an alkaline sulphide with calcium sulphide respectively, then decom-
posing the said sulphides in carbonators by means of one equivalent of the
carbonic acid obtained in the first part of the process, thereby converting all or
any of the said sulphides into carbonates and simultaneously producing sulphide
of hydrogen, and then producing solid sulphur by passing the said sulphide of
hydrogen through a Claus apparatus together with an equivalent, of air, and
finally separating the alkaline carbonates from calcium carbonate and obtaining
them in a marketable form.
2. The simultaneous production of calcium carbonate and an alkaline carlionate
from a mixture or double compound of calcium sulphate with an alkaline sulphate
or from the natural or artificial alkali-calcium sulphate, substantially as herein-
before described.
3. The herein described process of obtaining calcium sulphide or mixtures of
calcium sulphide with alkaline sulphides, by the action of hydrogen sulphide
(derived from the decomposition of such sulphides in carbonators by carbonic
acid) upon calcium sulphate or upon mixtures or chemical compounds of calcium
sulphate with alkaline sulphates in heated retorts, and producing at the same
time, according to the quantity of hydrogen sulphide passing through the heated
retort, either sulphurous acid, free sulphur or mixtures of hydrogen sulphide
with either or both of them.
1
:

page_text: 4. Decomposing the sulphides obtained by the process claimed in the
claiming clause, by means of the surplus carbonic acid obtained in the reduction
of the sulphates, and recovering the alkaline carbonates thus produced,
substantially as described.
D. YOUNG & Co.,
11 and 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.
Dated this 27th day
D. YOUNG & Co.,
11 and 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.