I- PROVEMENTS IN THE MANUFACTURE OF SULPHUR FROM SODA RESIDUES, GYPSUM, BARYTA, SULPHATE AND SULPHUROUS ACID, AND IN THE SIMUL- TANEOUS PRODUCTION IN THE FORM OF CARBONATES OF THE EARTHS COM- BINED WITH THE SULPHUR
Year: 1878

page_text: LETTERS PATENT to Gerard Wenzeslaus von Nawrocki, of the Firm of J. Brandt
and G. W. von Nawrocki, Civil Engineers and Patent Agents, of No. 127,
Leipzigerstrasse, Berlin, in the German Empire, for the Invention of "I-
PROVEMENTS IN THE MANUFACTURE OF SULPHUR FROM SODA RESIDUES,
GYPSUM, BARYTA, SULPHATE AND SULPHUROUS ACID, AND IN THE SIMUL-
TANEOUS PRODUCTION IN THE FORM OF CARBONATES OF THE EARTHS COM-
BINED WITH THE SULPHUR." A communication from Max Schaffner and
Wilhelm Helbig, both of Aussig, in the Austrian Empire.
PROVISIONAL SPECIFICATION left by the said Gerard Wenzeslaus von
Nawrocki at the Office of the Commissioners of Patents on the 9th March
1878.
GERARD WENZESLAUS VON NAWROCKI, of the Firm of J. Brandt and G. W. von
Nawrocki, Civil Engineers and Patent Agents, of No. 127, Leipzigerstrasse, Berlin,
in the German Empire. "IMPROVEMENTS IN THE MANUFACTURE OF SULPHUR
FROM SODA RESIDUES, GYPSUM, BARYTA, SULPHATE AND SULPhurous Acid, AND
IN THE SIMULTANEOUS PRODUCTION IN THE FORM OF CARBONATES OF THE EARTHS
COMBINED WITH THE SULPHUR." [A communication from Max Schaffner and
Wilhelm Helbig, both of Aussig, in the Austrian Empire.]
The processes usually employed during the past 15 years for turning to account
soda residues consist essentially in oxidation to a certain extent by the oxygen of
the atmosphere and treatment of the resulting lye with hydrochloric acid for the
precipitation of sulphur. Thus from 50 to 60 per cent. of the sulphur is removed,
from 40 to 50 per cent. remaining in the form of calcium sulphide mixed with
calcium sulphite and sulphate, forming a residue of comparatively little use though
of inconveniently large bulk.
The fact that only about half the sulphur of soda residue has been thus recovered
and none of the lime, has led to experiments with a view of attaining the ideal

page_text: result, that is to say, the recovery of all the sulphur and lime.
After many unsuc-
cessful experiments which need not be particularised, a simple method previously
untried of completely attaining the desired result has been discovered and formns the
subject of this Invention.
The new process of treating soda residue for the recovery of the sulphur and lime
contained therein is based chiefly on the following re-actions:-
a. The hitherto practically unknown and unapplied action of magnesium chloride
on calcium sulphate according to the formula,
Ca S+Mg Cl + HO = Ca Cl + MgO + HS,
that is to say, calcium sulphide, magnesium chloride, and water become converted
into calcium chloride, magnesia, and sulphuretted hydrogen, the carbonate of lime
not being decomposed by the magnesium chloride.
b. The recovery of the applied magnesium chloride by the action of carbonic acid
on the residue after driving off the sulphuretted hydrogen, that is to say, magnesia,
calcium chloride, and other matters that existed in the soda residue, this action
being expressed by the formula,—
Mg O+ Ca Cl + CO³ = Mg Cl + Ca O + CO%,
that is to say, magnesia and calcium chloride with carbonic acid become con-
verted into magnesium chloride and carbonate of lime. The same action of magnesium
chloride takes place if instead of operating entirely with that substance a portion
only is used, and hydrochloric acid is continuously or intermittently added so as to
reconvert the separated magnesia into magnesium chloride, which acts in its turn.
This method of operating where hydrochloric acid exists in abundance affords
convenient means of utilising the same, and also for producing the necessary
· calcium chloride required for the subsequent process when this does not exist as
a by-product. The material treated being boiled down and allowed to settle a
considerable portion of the solution of calcium chloride can be drained clear.
By the carbonization there is obtained only such a quantity of carbonate of
lime as corresponds to the magnesium chloride employed.
c. From the sulphuretted hydrogen produced, as shewn by the first formula,
sulphur is obtained by the addition of sulphurous acid according to the formula,-
2 HS + SO2 = 3S + 2 HO,
that is to say, two equivalents of sulphuretted hydrogen with sulphurous acid
become three of sulphur with two of water.
In many cases of the action of sulphuretted hydrogen on sulphurous acid there
result not only sulphur and water but also a considerable proportion of other com-
pounds, such as pentathionic acid, and consequently this re-action on the large
scale, though often tried, would fail but for the application of means for entirely
preventing the forination of these compounds, or for separating the sulphur when
they occur. These means consist in the application of solutions of calcium chloride
or magnesium chloride.
If aqueous solutions of sulphuretted hydrogen and sulphurous acid be mixed in
the proportions given in the above formula, the liquid becomes milky, and on the
addition of a solution of calcium chloride or magnesium chloride a considerable pre-
cipitation of sulphur in flakes takes place. Though the function which these chlorine
compounds perform in the re-action is unknown, it is nevertheless certain that about
one equivalent of calcium chloride or magnesium chloride is necessary to effect the
separation of all the sulphur.
The magnesium chloride obtained according to the second formula can be employed
in the treatment of a farther quantity of soda residue, and the carbonate of lime can
be used again in the soda manufacture.
The treatment of soda residue on a large scale according to this Invention consists
therefore in the following operations:-
I. Decomposition of the soda residue by magnesium chloride.
II. Separation of dross and other impurities from the residue of the first
operation.
…: .III.. Regeneration of the lime and magnesium chloride.

page_text: IV. Decomposition of the sulphuretted hydrogen resulting from the first operation
with sulphurous acid.
For the first operation are employed large iron closed vessels provided with
agitators and with pipe connections for charging and for escape of gas. In these
vessels the soda residue with solution of magnesium chloride is mixed and heated,
either the magnesium chloride or the residue being added by portions at intervals
to the full charge of the other ingredient, or both being charged together in their
equivalent proportion from time to time.
The success of the treatment and the safety of the attendants demand that the
operations should be capable of being arrested with the least possible loss of time,
which is only possible with one or other of the above methods of operating, and
particularly that there should be no escape of sulphurreted hydrogen, for which
reason care should be taken that there is no excess of pressure in the vessels, pro-
viding against its occurrence by chimney draught, or ventilators, or pumps. It is
also advisable to have an excess of sulphurous acid present, so that no excess of
sulphuretted hydrogen can ever occur.
In the second operation, since soda residue contains generally a considerable
quantity of earthy ingredients, such as sand and clay, which if they remained with
the regenerated lime would render it unfit for use in the soda manufacture, it is
necessary to provide for the removal of these impurities. This object is effected in
a simple manner, either by elutriation or by passing the residue of the decomposition
through a fine sieve, the earthy and carbonaceous portions of the residue being
coarser and heavier than the precipitated magnesia. By either method impurities
to the extent of 25 to 30 per cent. of the whole mass of dry soda residue are
separated, consisting chiefly of dross and excess of the limestone used in the soda
manufacture.
In the third operation the regeneration of the magnesium chloride and lime from
the products of decomposition freed from impurities follows simply from the addition
of carbonic acid or carbonic anhydride in products of combustion.
In the fourth operation the sulphuretted hydrogen resulting from the decom-
position is by mechanical means, as in the first operation, brought into contact with
the sulphurous acid and an aqueous solution of calcium chloride or magnesium
chloride, for which purpose vats or shower columns may be employed. When the
latter are used the sulphuretted hydrogen is admitted below and the sulphurous acid
somewhat bigher. The sulphur, which is rapidly precipitated by the peculiar action
of the calcium chloride or inagnesium chloride, is separated by decanting or filtering
from the liquid, which can be used again and again in the process, so that. the loss
of chloride is reduced to a minimum.
The gas pipes are arranged so as to be readily accessible for cleansing.
The sulphurous acid may be obtained from pyrites, or from sulphur, or sul-
phuretted hydrogen, or from any gas containing it, and may be led directly into.
the decomposing apparatus, or, after condensation in the manner of hydrochloric
acid, as an aqueous solution, or solution with calcium chloride or magnesium
chloride.
}

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Gerard Wenzeslaus von Nawrocki in the Great Seal Patent Office
on the 3rd September 1878.
.
"
GERARD WENZESLAUS VON NAWROCKI, of the Firm of J. Brandt and G. W. von
Nawrocki, Civil Engineers and Patent Agents, of No. 127, Leipzigerstrasse, Berlin,
in the German Empire. IMPROVEMENTS IN THE MANUFACTURE OF SULPHUR
FROM SODA RESIDUES, GYPSUM, BARYTA, SULPHATE AND SULPHUROUS ACID, AND
IN THE SIMULTANEOUS PRODUCTION IN THE FORM OF CARBONATES OF THE EARTHS
COMBINED WITH THE SULPHUR." A communication by Max Schaffner and
Wilhelm Helbig, both of Aussig, in the Austrian Empire.
"
The process as usually employed during the past 15 years for turning to account
the residue left behind in lixiviating crude soda or "black ash," commonly called
"tank waste ог "vat waste," consists essentially in oxidation to a certain extent
by the oxygen of the atmosphere and treatment of the resulting lye with
hydrochloric acid for the precipitation of sulphur. From 50 to 60 per cent. of the
sulphur can thus be recovered, from 40 to 50 per cent. along with brine remaining in
the form of calcium sulphide mixed with calcium sulphite and sulphate as a new
lixiviated residue, which is certainly free from the obnoxious properties of the
fresh waste, but which is still a source of great inconvenience to the alkali works
owing to its large bulk, and to the extremely restricted uses it can be put to.
The fact that hitherto from the soda waste only about one-half of the sulphur
contained therein and none of the line has been recovered, has led to making a series of
experiments with the object of attaining if possible the ideal result of recovering
practically the whole of the sulphur and of the lime from the soda waste. After
many unsuccessful experiments, which need not be particularised here, a simple
process not hitherto employed anywhere has at length been discovered for attaining
the desired result in the most satisfactory way.
This new process of treating soda waste for the recovery of the sulphur and lime
contained therein is based chiefly on the following re-actions, viz. :-
a. On the applicability of magnesium chloride not hitherto employed in practice
for decomposing calcium sulphide according to the formula,
(1.) Ca S+Mg Cl + HO = Ca Cl + MgO + HS,
that is to say, calcium sulphide, magnesium chloride, and water arc converted into
calcium chloride, magnesia, and sulphuretted hydrogen, the carbonate of lime not
being decomposed by the magnesium chloride.
.
b. On the recovery of the magnesium chloride employed in the previous stage by
the action of carbonic acid on the residue left behind from the treatment of
calcium sulphide by magnesium chloride after expelling the sulphuretted hydrogen,
which residue consists of magnesia, calcium chloride, and other matters previously
existing in the soda waste. In this case carbonate of lime and magnesium chloride
are formed according to the formula,
(2.) MgO +Ca Cl + CO₂ = Mg Cl + Ca O, CO,.
The saune action of magnesium chloride takes place if, instead of operating
entirely with that substance, only a portion of the total quantity corresponding to
that of calcium sulphide is used, but at the same time hydrochloric acid is added
either continuously or intermittently, by which the magnesia already separated is
redissolved, the newly formed magnesium chloride acting in its turn like that first em -
ployed. This method of operating affords a possibility of utilizing hydrochloric acid
in such works where there is an excess of the same produced, and at the same time a
convenient means of producing the calcium chloride required in the subsequent stage
of the process, as will be seen hereafter, in such cases where such calcium chloride is
not obtained otherwise as a by-product. In this case, before the mixture obtained
in the first stage is further operated upon, it is allowed to settle, and a corresponding

page_text: portion of the clear solution of calcium choride is drawn off. Of course, by the
carbonating process just described, only as much carbonate of lime can be recovered
as corresponds to the quantity of magnesium chloride employed.
c. To the sulphuretted hydrogen produced, as shewn by the first formula,
sulphurous acid is added, and sulphur is obtained according to the formula,—
(3.) 2 H S + SO,=3S+ 2H O.
This re-action has been proposed a great many times with the object of utilizing
the sulphur contained in sulphuretted bydrogen and sulphurous acid. It is however
well known now that the re-action under ordinary circumstances does not take
place in the simple manner indicated by the formula.
(3.) By the mutual action of the sulphuretted hydrogen and sulphurous acid, not
merely sulphur and water are produced, but also considerable quantities of other
compounds, especially pentathionic acid. The application of this re-action on the
large scale, which has often been tried unsuccessfully, would not be possible in this
present case either, but for a plan having been discovered of entirely preventing the
formation of pentathionic acid, etc., or, if it should have been formed, of precipitating
the sulphur out of it. This plan for preventing the formation of pentathionic acid
and other compounds, or of precipitating the sulphur out of the same, consists in
the application of solution of calcium chloride or magnesium chloride.
If aqueous solutions of sulphuretted hydrogen and sulphurous acid are brought
together in the quantities indicated by the above formula (3), a milky fluid is
produced, from which, by the addition of a solution of calcium chloride or magnesium
chloride, a considerable precipitate of sulphur rapidly settles down in flakes. The
quantity of sulphur thus separated is as nearly as possible that indicated by
theory. An excess of one gas or the other does not influence the decomposition;
such excess is found unchanged in the liquid. It has not yet been made out
which is the part played by those chlorides in the re-action, but so much is certain
that the chemical equivalent of calcium or magnesium chloride of the total sulphur
is required.
The magnesium chloride recovered, according to the formula (2), is employed
for decomposing fresh quantities of soda waste, and the carbonate of lime obtained
at the same time can be used over again in the process of soda making.
The treatment of soda waste on the large scale, according to this process, consists
in the following operations, viz. :—
I. Decomposing the soda waste by magnesium chloride.
II. Removing the cinders or slags and other impurities of the soda waste from
the residue left in I.
III. Removing the carbonate of lime and the magnesium chloride.
IV. Decomposing the sulphuretted hydrogen obtained in the first of these
operations by means of sulphurous acid.
For the first of these operations any suitable apparatus may be used. It is con-
venient to employ large iron vessels closed air-tight provided with agitators with
arrangements for charging and discharging the materials with pipes for carrying
off the gas, and so forth. In these vessels ("generators") the fresh soda waste is
mixed with a solution of magnesium chloride in suitable manner and quantity, and
exposed to heat.
This operation can be carried on in one of the following manners, viz. :—
a. Either so that the soda waste is gradually introduced into the total quantity
of magnesium chloride a requisite for filling one of the "generators."
b. Or so that inversely the solution of magnesium chloride is run upon the total
charge of soda waste.
c. Or so that at the same time both substances in equivalent portions are
gradually introduced into the generator.
'The certainty of the treatment and the safety of the attendants can only be
secured by the possibility of stopping the operation in the generator in a minimum
of time, which is only attained by one or the other of the above-described
manners of operating.

page_text: It is also necessary with the same view that in no part of the apparatus an
escape of sulphuretted hydrogen can take place, and this is effected by taking
care,-
Firstly. That no pressure of gas can occur inside the generators and decomposing
vessels, and altogether in any apparatus containing sulphuretted hydrogen, such
pressure being easily avoided by means of chimney draught, fan blasts, pumps, and
the like attached at suitable places.
Secondly. That in decomposing vessels for sulphuretted hydrogen there is always
a larger quantity of sulphurous acid present than that which corresponds to the
sulphuretted bydrogen arriving there from the generators, so that the latter gas
can never be in excess or escape as such.
°
The second of the above-mentioned operations has for its object the removal of
certain foreign matters always present in the soda waste originating from the
impurities of the raw materials, and from the substances of the furnaces employed in
making the crude soda or "black ash." These foreign matters, including cinders
or slags, contain a certain proportion of silica and alumina, which, if they were left
with the recovered carbonate of lime, would soon accumulate in the same to such
an extent as to make it totally unfit for use in soda making. These impurities
must, therefore, be removed at some stage of the process. This object is effected in
a very simple and complete manner, either by elutriation or by passing the residue
of the decomposition through a fine sieve. The slaggy or earthy and carbonaceous
portions of the soda waste are heavier and coarser than the magnesia separated by
the decomposition.
The matters separated by one or the other of these plans amount to 25 or 30
per cent. of the dry weight of the total soda waste; they contain all impurities of
the latter prejudicial to soda making, as well as a portion of the limestone used
originally in the black ash mixture.
The third operation, viz., the recovery of the magnesium chloride and of the
carbonate of lime from the residue freed from the impurities, as above described,
takes place simply by conducting into it a current of carbonic acid or of a gas
.containing that acid, such as the gas of a limekiln or the product of combustion,
or any other source of more or less pure carbonic acid used in the arts.
In the fourth operation the sulphuretted hydrogen resulting from the decom-
position is by mechanical means, as mentioned in the first operation, brought into
contact in a suitable manner with sulphurous acid, and with an aqueous solution of
calcium chloride or magnesium chloride. For this purpose either vats or towers
(shower columns) may be employed. When the latter are used the sulphuretted
hydrogen should be admitted into the tower near its base, and the sulphurous acid
somewhat higher up. The precipitated sulphur, which owing to the peculiar action
of the calcium or magnesium chloride settles down in a strikingly short time, is
separated by decantation or filtration from the liquid, and the latter is used over
and over again in the process, by which means the loss of the requisite chlorides is
reduced to a minimum.
The gas pipes are so arranged as to be readily accessible from the outside at any
time, so that they can be cleaned out very quickly.
The requisite sulphurous acid may be obtained either by burning pyrites or
brimstone or sulphuretted hydrogen, or from any gas containing it, for instance,
such as escapes in any metallurgical operations, and it may either be conveyed
directly into the decomposing apparatus or it may be condensed separately in a
manner similar to hydrochloric acid, and used as a solution in water, or in water
containing calcium or magnesium chloride.
This Invention, as described here in detail in its application of soda waste, may
also be applied to the sulphates of lime and of barytes after previously reducing
them to sulphides.
This Invention, as will be easily seen, is also applicable for utilizing and
rendering innocuous the sulphurous acid generated in many calcining processes, and
frequently amounting to a serious nuisance,

page_text: The principal advantages of this Invention are as follows:-
1. The new process is simple and easy of execution.
2. The working up of the soda waste takes much less time than in the processes
hitherto in use.
3. The cost of manual labour is considerably less than hitherto.
4. Of the sulphur contained in the soda waste from 90 to 95 per cent. are
obtained as against from 50 to 60 per cent. in the previously used processes.
5. About 80 per cent. of the lime contained in the soda waste is obtained in the
shape of carbonate of lime suitable for soda inaking.
6. The requisite magnesium chloride and calcium chloride are again recovered,
with exception of a small loss unavoidable in practical work; the waste of these
materials is therefore extremely small.
7. The cost of obtaining the sulphur by this process is smaller than in the
processes hitherto used, both with respect to the advantages enumerated above,
and because no more fuel and considerably less manual labour is required than in
the previous processes, and because the hydrochloric acid used in the latter is
mostly worth much more than the small loss of inagnesium chloride in this new
process.
8. By generating the requisite sulphurous acid from pyrites and the like the
production of sulphur can be increased by 50 per cent, over and above the sulphur
obtainable from soda waste alone, without any essential additional expenses than
that of the pyrites, etc.
9. The new waste still remaining in this process is reduced to about 20 per cent.
of the original waste, causing a large saving in the expense of removal and the land
required for a deposit.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, as communicated to me by my correspondents, I
claim,―
First. The before-described combination of processes for the treatment of soda
residues, or waste gypsum, or baryta sulphate, whereby the greater part of the
sulphur contained therein is obtained, while the earths or lime combined with the
sulphur is simultaneously obtained in the form of carbonate.
Second. In combination with the process referred to in the first claim the pro-
duction of sulphur from sulphurous acid gas by exposing such gas to the action of
sulphuretted hydrogen in the presence of a solution of calcium chloride or magnesium
chloride, substantially as herein described.
Third. In treating sulphuretted hydrogen with sulphurous acid for the pro-
duction of sulphur the use of calcium chloride or magnesium chloride to prevent
formation of pentathionic acid, substantially as described.
Fourth. The employment of magnesium chloride for decomposing the calcium
sulphide, substantially as herein set forth.
In witness whereof, I, the said Gerard Wenzeslaus von Nawrocki, have here-
unto set my hand and seal, this Twenty-seventh day of August, in the year
of our Lord One thousand eight hundred and seventy-eight.
GERARD WENZESLAUS v. NAWROCKI (L.S.)