Treatment of Impure or Waste Potassium Salts for the Manufacture therefrom of Soda, Potash, Hydrochloric Acid, Magnesia, Calcium Sulphate, and Sulphur or Sulphuric Acid.
Year: 1890

page_text: Date of Application, 13th June, 1890
Complete Soecification Left, 13th Mar., 1391-Accepted. 6th June. 1891
PROVISIONAL SPECIFICATION.
Treatment of Impure or Waste Potassium Salts for the Manufacture
therefrom of Soda, Potash, Hydrochloric Acid, Magnesia, Calcium
Sulphate, and Sulphur or Sulphuric Acid.
A communication from abroad by CHEMISCHE FABRIK BUCKAU, Actiengesell-
schaft, of Magdeburg, German Empire.
I, WILLIAM LLOYD WISE, of 46 Lincoln's Inn Fields in the County of London,
Consulting Engineer and Patent Agent, do hereby declare the nature of this
invention to be as follows:-
This invention relates to the treatment of impure or waste potassium salts (saline
deposits) such for instance as are found at Stassfurt, particularly of kainite,
carnallite, and sylvinite, for the purpose of manufacturing therefrom soda, potash,
hydrochloric acid, magnesia, gypsum and sulphur or sulphuric acid.
Of the processes hitherto known for manufacturing potash, excepting that for
the production of the same from wood ashes and raw potash from beetroot molasses
("Schlempekohle"), only the Leblanc process has, so far as I know, proved to be
of practical value. This process however entails considerable loss of potash, and
produces residual substances which cannot be utilized in a practical manner.
Also the fact that only pure chloride of potassium is employed in the Leblanc
process, is a great drawback, since the cost of manufacturing this substance is
considerable.
In the processes hitherto employed for treating waste salts, only chloride of
potassium or sulphate of potassium is produced from the impure or waste potash
salts. The remaining constituents forming about or of the salts treated, for
instance chloride of sodium and chloride of magnesium or sulphate of magnesia,
have been hitherto waste products of no value, and in the form of lyes, have been
allowed to pollute water courses.
The process hereinafter described is free from all these drawbacks and allows of
the direct manufacture from the impure or waste salts, especially of kainite,
carnallite, and sylvinite, of soda and potash, without previous treatment and
purification of these impure or waste products. By such process no waste products
are left but only products that are of considerable value and are capable of
industrial utilization, such as potash, soda, hydrochloric acid, magnesia, gypsum,
and sulphur or sulphuric acid.
This invention is not limited to the particular process hereinafter more par-
ticularly described, but, as is herein explained, is capable of many modifications,
according as it is desired to obtain the one or the other byc product at an earlier or
later stage of the process. This entails slight modifications, but the process remains
essentially the same, so that all the bye-products constitute products that are
valuable and are capable of being utilized industrially.
When impure or waste potassium salts (Stassfurt waste salts) which consist, as is
well known, of chlorides and sulphates of potassium, sodium and magnesium, are
treated with sulphuric acid, hydrochloric acid is formed, and the bases are all
obtained in the form of sulphates.
Kainite is the most suitable substance for the herein described process, because it
already consists of about one half of sulphates.
Apparatus of various kinds suitable for manufacturing sulphate of kainite are
well known, the best being those employed in the manufacture of sulphate of soda,
or sulphate of potash. The magnesia is first separated from the sulphate of kainite,
by mixing the solution thereof with caustic lime in the form of milk of lime, the
quantity used depending upon the amount of sulphate of magnesium present,
Price G

page_text: Gypsum and magnesia are thus formed which are separated by filtration from the
solution of alkaline sulphate and are then mixed with a boiling solution of sulphate of
kainite of a strength of about 20° Beaumé, by which the gypsum is at first dissolved,
but after cooling and standing for several days, it separates in great purity, and
almost completely, in well formed crystals, so that the specifically lighter magnesia
can be separated by washing from the heavy gypsum crystals.
The solution of alkaline sulphate is now mixed with sulphide of barium which
can be readily and cheaply obtained according to a known process, and the resulting
precipitate of sulphate of barium is separated by filtering, and is after washing,
again employed for the manufacture of sulphide of barium. The resulting solution
of alkaline sulphide thus obtained is evaporated to about 20° Bé., and strong carbonic
acid such as is obtained by roasting an alkaline bi-carbonate (for instance bi-carbonate
of soda as obtained by the ammonia soda process), is then passed through the
solution until sulphuretted hydrogen ceases to be evolved and the alkalies present
are converted into bi-carbonate.
Undiluted or practically pure carbonic acid gas obtained from an alkaline
bi-carbonate has not been hitherto employed on an industrial scale for the
decomposition of sulphides such as alkaline sulphides, but only carbonic acid
produced in lime kilns and which consequently contains a large amount of oxygen
and nitrogen. In consequence of the presence of these last named gases the
attempts hitherto made to convert sulphides into carbonates, have been either
unsatisfactory or have not succeeded at all, because the impure condition of the
carbonic acid, by reason of the oxygen therein, causes a re-conversion of the
sulphide into sulphate.
As is well known, bi-carbonate of potash is considerably more soluble than
bi-carbonate of soda, and the thorough separation of the two can therefore be
easily effected. The precipitated bi-carbonate of soda is separated by filtration
from the solution of bi-carbonate of potash; and is converted by calcination into
soda. The solution of bi-carbonate of potash is afterwards converted by evaporating
and roasting into potash.
The sulphuretted hydrogen obtained as hereinbefore described and which is very
pure in consequence of the employment of undiluted carbonic acid, can either be
burned for conversion into sulphuric acid, or can be treated to obtain the sulphur
therein, in a solid form.
The process hereinbefore described for the manufacture of potash or soda, enables
all the compounds present in the impure potassium salts treated, to be converted
into valuable products namely;-potash, soda, hydrochloric acid, magnesia, gypsum,
and sulphur.
The herein described process has also the advantage over other processes and
particularly over the Leblanc process, that troublesome waste products are not
formed.
The separation of the magnesia, can, if desired, be effected before the conversion
of the impure potassium salts into sulphates. For this purpose the solution of
impure salt is mixed with milk of lime and the precipitate thus obtained is removed
by filtering. The filtrate is then evaporated to dryness with sulphuric acid, hydro-
chloric acid being given off, and a residue consisting of gypsum and alkaline
sulphate being left.
The separation of the magnesia from the impure sulphates can also be effected as
follows:-
Powdered sulphate of kainite is intimately mixed with the requisite amount of
coal and then roasted, and the resulting roasted mass, consisting of sulphide of
potassium, sulphide of sodium and magnesia, is lixiviated in the well-known
"Shank" apparatus. Earlier attempts to reduce sulphate of sodium and sulphate
of potassium to sulphides by heating with coal, have been unsuccessful commercially,
because the readily fusible alkaline sulphide attacked the material of the furnace to
such an extent that the cost for repairs has been very high. Now sulphate of
kainite behaves quite differently because the percentage of magnesia contained

page_text: therein prevents fusion. The mixture of sulphate of kainite and coal need only be
roasted until it just begins to become soft. In consequence of this the wear and
tear of the furnace is small.
The residue obtained by lixiviation of the mass consists mainly of magnesia,
5 mixed to some extent with unburnt coal, and by again roasting this residue,
magnesia suitable for industrial purposes can be obtained.
Dated this 13th day of June 1890.
W. LLOYD WISE.
COMPLETE SPECIFICATION.
Treatment of Impure or Waste Potassium Salts for the Manufacture
therefrom of Soda, Potash, Hydrochloric Acid, Magnesia, Calcium
Sulphate, and Sulphur or Sulphuric Acid.
A communication from abroad by CHEMISCHE FABRIK BUCKAU, Actiengesell-
schaft, of Magdeburg, German Empire.
I, WILLIAM LLOYD WISE of 46 Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Patent Agent, 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 :---
This invention relates to a new method of treating impure or waste potassium
salts (saline deposits) such for instance as are found at Stassfurt, particularly of
kainite, carnallite, and sylvinite, for the purpose of manufacturing therefrom soda,
potash, hydrochloric acid, magnesia, calcium sulphate and sulphur or sulphuric
acid.
Also
Of the processes hitherto known for manufacturing potash, excepting those for
the production of potash from wood ashes and raw potash from beetroot molasses
("Schlempekohle "), only the Leblanc process has so far as I know, proved to be
of practical value. This process however involves considerable loss of potash, and
produces residual substances which cannot be utilised in a practical manner.
the fact that only pure chloride of potassium is employed in the Leblanc process,
is a great drawback, since the cost of manufacturing this substance is considerable.
In the processes hitherto employed for treating waste salts, only chloride of
potassium, or sulphate of potassium has been produced from the impure or waste
potash salts. The remaining constituents, forming about ths or ths of the salts
treated, and consisting for instance of chloride of sodium, and chloride or sulphate
or magnesium, have hitherto been waste products of no value, and in the form of
lyes, have been allowed to pollute water courses.
The process hereinafter described is free from all these drawbacks, and allows
of the direct manufacture from the impure or waste salts especially of kainite,
carnallite, and sylvinite, of soda and potash, without previous treatment and
purification of these impure or waste products. By such process no waste products
are left, but only products that are of considerable value, and are capable of
industrial utilization, such as potash, soda, hydro-chloric acid, magnesia, calcium
sulphate, and sulphur or sulphuric acid.
This invention is not limited to the particular process hereinafter more parti-
cularly described, since, as is hereinafter explained, it is capable of many
modifications, according as it is desired to obtain one or other of the bye products
at an earlier or later stage of the process. This involves slight modifications, but
the process remains essentially the same, so that all the bye-products constitute
products that are valuable and are capable of being utilized.
When impure or waste potassium salts (Stassfurt waste salts) which consist, as
is well known, of chlorides and sulphates of potassium, sodium and magnesium, are

page_text: treated with sulphuric acid, hydrochloric acid is formed, and the bases are all
obtained in the form of sulphates.
Kainite is the most suitable substance for the herein described process, because
it already consists of about one half of sulphates.
Apparatus of various kinds suitable for manufacturing sulphate of kainite are
well known, the best being those employed in the manufacture of sulphate of
soda, and sulphate of potash. In carrying out this invention impure or waste salt
for example kainite is first treated in an apparatus of the kind referred to, with
sulphuric acid in the usual manner, and the hydrochloric acid thus produced
collected. The magnesia present in the resulting solution of sulphate of kainite
is then separated by mixing the solution with caustic lime in the form of milk of
lime, the quantity thereof used depending upon the amount of sulphate of magnesium
present which can be determined by analysis. Calcium sulphate and magnesia
will thus be formed which are separated by filtration from the solution of alkaline
sulphate. It is advantageous to add the milk of lime to a boiling solution of
sulphate of kainite having a strength of about 20° Beaumé, by which the
calcium sulphate is at first dissolved, but from which solution, after cooling and
standing for several days, it separates in great purity, and almost completely, in
well formed crystals, so that the specifically lighter magnesia can be separated by
washing from the heavy calcium sulphate crystals.
The solution of alkaline sulphate is now mixed with an equivalent quantity of
sulphide of barium, which can be readily and cheaply obtained according to a
known process, and the resulting precipitate of sulphate of barium is separated by
filtering, and can, after washing, be again converted into sulphide of barium for
re-use. The solution of alkaline sulphide thus obtained is evaporated to about
20° Bé, and pure or practically pure carbonic acid, such as is obtained by roasting
an alkaline bicarbonate (for instance bicarbonate of soda as obtained by the
ammonia soda process), is then passed through the solution until sulphuretted
hydrogen ceases to be evolved, and the alkalies present are converted into
bi-carbonates.
Undiluted or practically pure carbonic acid gas obtained from an alkaline
bi-carbonate has not been hitherto employed on an industrial scale for the decom-
position of sulphides such as alkaline sulphides, but only carbonic acid containing
a large proportion of oxygen and nitrogen and such as is produced in lime kilns.
In consequence of the presence of these last named gases, the attempts heretofore
made to convert sulphides into carbonates, have been either unsatisfactory, or have
not succeeded at all, because the impure condition of the carbonic acid, by reason
of the oxygen present therewith, causes a re-conversion of the sulphide into
sulphate.
As is well known, bi-carbonate of potash is considerably more soluble than
bi-carbonate of soda, and the thorough separation of the two can therefore be easily
effected. The precipitated bi-carbonate of soda is separated by filtration from the
solution of bicarbonate of potash; and is converted by calcination into carbonate
of soda. The solution of bicarbonate of potash is afterwards converted by
evaporation and roasting into carbonate of potash.
The sulphuretted hydrogen obtained as hereinbefore described, and which is very
pure in consequence of the employment of undiluted carbonic acid, can either be
burned for conversion into sulphuric acid, or can be treated to obtain the sulphur
therein, in a solid form as in a manner well understood.
The process hereinbefore described for the manufacture of potash or soda, enables
all the compounds present in the impure potassium salts treated, to be converted
into valuable products, namely:--potash, soda, hydrochloric acid, inagnesia, calcium
sulphate, and sulphur.
The herein described process has also the advantage over other processes, and
particularly over the Leblanc process, that troublesome waste products are not
formed.

page_text: The separation of the magnesia, can if desired, be effected before the conversion
of the impure potassium salts into sulphates. For this purpose the solution of
impure salts is mixed with milk of lime and the precipitate of magnesia thus
obtained is removed by filtering. The filtrate is then evaporated to dryness with
sulphuric acid, hydrochloric acid being given off, and a residue consisting of calcium
sulphate and alkaline sulphate being left. From this residue the alkaline sulphate
is dissolved and treated in the manner hereinbefore explained.
The separation of the magnesia from the impure sulphates can also be effected as
follows: Powdered sulphate of kainite is intimately mixed with a sufficient amount
of carbon, for example coal to convert the alkaline sulphates present, into sulphides
and the sulphate of magnesium into magnesia, and the mixture is then roasted.
The resulting roasted mass, consisting of sulphide of potassium, sulphide of sodium,
and inagnesia, is then lixiviated in the well known "Shank apparatus. Earlier
attempts to reduce sulphate of sodium and sulphate of potassium to sulphides by
heating with coal, have been unsuccessful commercially, because the readily fusible
alkaline sulphide attacked the material of the furnace to such an extent that the
cost for repairs has been very great. Now sulphate of kainite behaves quite
differently, because the percentage of magnesia contained therein is such as to
prevent ready fusion. The mixture of sulphate of kainite and coal need only be
roasted until it just begins to soften. In consequence of this the wear and tear of
the furnace will be small.
The residue obtained by lixiviation of the mass consists mainly of magnesia,
mixed to some extent with unburnt coal, and by again roasting this residue,
magnesia suitable for industrial purposes can be obtained.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The herein described treatment of impure or waste potassium salt for the
manufacture therefrom of useful products, consisting in treating such a salt with
sulphuric acid, mixing the sulphates thus produced with milk of lime, filtering the
precipitate of calcium sulphate and magnesia thus obtained, from the resulting
solution of alkaline sulphate, converting this solution into solution of alkaline
sulphide by sulphide of barium, concentrating this latter solution and treating it
with carbonic acid to form alkaline bicarbonates with the evolution of sulphuretted
hydrogen, and effecting the separation of the potassium bicarbonate from the
sodium bicarbonate by reason of their different solubilities in water, these alkaline
bicarbonates being converted into carbonate of potassium, and carbonate of sodium
respectively, by calcination as set forth.
2. In the treatment of an impure or waste potassium salt as for example sulphate
of kainite, effecting the separation of calcium sulphate and magnesia from the salt
by adding concentrated milk of lime to a boiling solution of the sulphate of kainite of
about 20 Bé, so that upon cooling the calcium sulphate will be precipitated in a
crystalline and pure condition from the solution, and the specifically lighter
magnesia can be easily removed therefrom by washing as set forth.
3. The herein described treatment of impure or waste potassium salt consisting
in treating the solution of such a salt with milk of lime, filtering off the resulting
precipitate containing magnesia, and evaporating the filtrate with sulphuric acid
substantially as herein set forth.
4. The herein described treatment of impure or waste potassium salt consisting
in intimately mixing such a salt as for example ground sulphate of kainite with
powdered coal, roasting the mixture, and separating the resulting soluble sulphide
of potassium and sulphide of sodium from the insoluble magnesia by lixiviation as
set forth.
5. In the treatment of impure or waste potassium salts, the conversion of alkaline
sulphide into alkaline carbonate or alkaline bicarbonate by means of pure or

page_text: practically pure carbonic acid obtained from a suitable source as for example by
the calcination of an alkaline bicarbonate as and for the purpose set forth.
Dated this 13th day of March 1891.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C.