рагаси 101 Compounds from Bauxite and similar Materials Containing Alumina.
Year: 1887

page_text: Date of Application, 19th July, 1887
Complete Left, 14th Apr., 1888
Complete Accepted, 15th June, 1888
Process or Frocesses and аррагаси
101
Compounds from Bauxite and similar Materials Containing
Alumina.
I, Dr. CHARLES JOSEPH BAYER, Manufacturing Chemist, of 27, Moskauer Chaussée
St. Petersburg, Russia, do hereby declare the nature of my invention to be as
follows:-
In the manufacture of sulphate of alumina or other compounds of aluminium from
bauxit and similar materials by the so-called alkaline process, crude aluminate is
obtained by heating the raw material with soda, carbonate of soda, or sulphate of soda
and charcoal.
The product of this operation is lixiviated with water, and the aluminate lye thus
produced is decomposed by saturating it with carbonic acid when hot, thereby pro-
ducing a precipitate of hydrate of alumina, and a solution of carbonate of soda, which
may again be employed for the same process. The precipitated hydrato of alumina is
filtered by one of the well-known methods, washed and further utilised.
My process, which possesses important advantages over that just described, is based
on my discovery, that an aluminate solution formed in the ordinary manner begins to
decompose, if hydrate of alumina is added while constantly stirring the liquid and
that during certain periods of time this decomposition continues until the ratio
between the number of molecules of alumina and that of soda, (Al, O,: Na ₂O) is one
to six, after which the decomposition stops.
.
Supposing the ratio of molecules in the original aluminate lye to be 1 to 1.8, as is
usually the case, about of the contained alumina will be separated by heating the
aluminates with hydrate of alumina, while remains in solution.
The separated hydrate of alumina, like that which is precipitated by carbonic acid
from a hot liquid, forms a crystalline powder which can be washed very easily, and
dissolves easily in sulphuric acid owing to its uniformity and fine distribution.
Compared with the precipitation by carbonic acid, this method offers the advantage,
that any silicic acid, phosphoric acid and similar impurities, which may occur in the
solution are not also precipitated, as is the case with the older method.
For precipitating the hydrate of alumina as completely as possible, until the
stationary ratio or proportion has been reached, the liquid containing it must be cold.
This fact occasions a considerable saving of steam or fuel, because it renders

page_text: unnecessary the heating of the aluminate lye up to nearly the boiling point. Further-
more no fuel is required for generating carbonic acid gas and for supplying the power
necessary for forcing the gas through the liquids to be saturated, and the cost of
plant for the manufacture of carbonic acids such as force-pumps, coke-ovens or lime-
kilns, with the necessary washing-apparatus and pipe-conduits is avoided.
The alkaline solution resulting from the decomposition of the aluminate by my
process, is separated from the precipitated hydrate of alumina, and subsequently
concentrated as much as possible in suitable evaporating appliances, after which it is
mixed with the bauxit boiled down and calcined. The small quantity of alumina still
remaining in the lye, will not interfere with the process. This operation also occasions
important advantages, as will be seen from the following.
in calcining the bauxit with carbonate of soda, the two ingredients should be
mixed in such proportions, that the sum of the molecules of the sesqui-oxydes
(Al, OF, O₂) contained in the bauxit is to the soda of the sodic carbonate as
1 to 1 or at the most as 1 to 1.2. If more carbonate of soda be taken, its carbonic
acid will not be completely driven out, and the presence of carbonate of soda in the
aluminate-solution renders the latter more easily decomposable, and if less carbonate
of soda be taken the bauxit will be rendered incompletely assimilable.
By dissolving in water the mass produced by heating the above described mixture
of sodic carbonate and bauxit, a portion of the hydrate of alumina is precipitated, so
that under the most favorable circumstances only about 75 per cent. of the alumina
contained in the bauxit will be utilized.
On the other hand my investigations have shown, that by first adding to the water
serving to dissolve the calcined mass, a quantity of caustic soda equal to about
30 per cent. of the soda contained in the said mass, and subsequently commencing to
dissolve, no decomposition takes place, and the whole of the assimilable alumina is
obtained in solution.
The advantages of using alcaline lyes obtained by my method of dissociation, for
the manufacture of fresh quantities of crude aluminate, are apparent. It is possible
to add to the mixture from the beginning a sufficient quantity of soda, to ensure that
in dissolving, the whole of the alumina remains in solution; for owing to the absence
of carbonate of soda, no carbonic acid need be driven out, and the drawback resulting
from an excess of carbonate of soda, as indicated above, are avoided. As there is no
carbonic acid to be driven out, the mass will be ready in less than half the time
which would be required in the other case. In my new process a thorough heating
of the mass is sufficient.
The apparatus necessary or suitable for my process, consists essentially of decom-
posing cylinders or retorts.
A continuous apparatus may for instance comprise four large upright cylinders of
sheet iron which are connected with each other by tubes in such a manner, that the
liquid passes consecutively from one cylinder to the other, entering every cylinder at
the bottom and leaving it at the top. Each cylinder contains a stirrer consisting of
a vertical shaft carrying a series of helical blades of unequal sizes. A constant stream
of aluminate solution enters at one end of the battery of cylinders (at the bottom of
the first cylinder), and is discharged at the other end (at the top of the last cylinder)
after having undergone decomposition.
Only for starting the operation, some hydrate of alumina is introduced into the first
cylinder as exciting liquid, while slowly admitting the liquid to be decomposed, and
setting the stirrer in motion from the main driving shaft which passes over the top of
the cylinder.
FAIRFAX & WETTER.
433, Strand, London,
Agents for the Applicant.

page_text: Process or Processes and Apparatus for Obtaining Pure Alumina-
compounds from Bauxite and similar Materials Containing
Alumina.
I, Dr. CHARLES JOSEPH BAYER, Manufacturing Chemist, of 27, Moskauer Chaussée
St. Petersburg, Russia, do hereby declare the nature of my invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-
In the manufacture of sulphate of alumina or other compounds of alumina from
bauxite and similar materials by the so-called alkaline process, crude aluminate is
obtained by heating the raw material with soda, carbonate of sode, or sulphate of soda
and charcoal.
The product of this operation is lixiviated with water, and the aluminate lye thus
produced is decomposed by saturating it with carbonic acid when hot, thereby
producing a precipitate of hydrate of alumina, and a solution of carbonate of soda,
which may again be employed for the same process. The precipitated hydrate of
alumina is filtered by one of the well-known methods, washed and further utilised.
My process, which possesses important advantages over that just described, is based
on my discovery, that an aluminate solution formed in the ordinary manner begins to
decompose, if hydrate of alumina is added while constantly stirring the liquid, and
that during certain periods of time this decomposition continues until the ratio
between the number of molecules of alumina and that of soda, (Al, O: Na, O) is one
to six, after which the decomposition stops.
Supposing the ratio of molecules in the original aluminate lye to be 1 to 1.8, as is
usually the case, about of the contained alumina will be separated by treating the
aluminates with hydrate of alumina, while remains in solution.
The separated hydrate of alumina, like that which is precipitated by carbonic acid
from a hot liquid, forms a crystalline powder which can be washed very easily, and
dissolves easily in sulphuric acid owing to its uniformity and fine distribution.
Compared with the precipitation by carbonic acid, this method offers the advantage,
that any silicic acid, phosphoric acid and similar impurities, which may occur in the
solution are not also precipitated, as is the case with the older method.
For precipitating the hydrate of alumina as completely as possible, until the
stationary ratio or proportion has been reached, the liquid containing it must be
cold. This fact occasions a considerable saving of steam or fuel, because it renders
unnecessary the heating of the aluminate lye up to nearly the boiling point. Further-
more no fuel is required for generating carbonic acid gas and for supplying the power
necessary for forcing the gas through the liquids to be saturated, and the cost of
plant for the manufacture of carbonic acids such as force-pumps, coke-ovens or
lime-kilns, with the necessary washing-apparatus and pipe-conduits is avoided.
The alkaline solution resulting from the decomposition of the aluminate by my
process, is separated from the precipitated hydrate of alumina, and subsequently
concentrated as much as possible in suitable evaporating appliances, after which it is
mixed with the bauxit boiled down and calcined. The small quantity of alumina still
remaining in the lye, will not interfere with the process. This operation also
occasions important advantages, as will be seen from the following.
In calcining the bauxite with carbonate of soda, the two ingredients should be
mixed in such proportions, that the sum of the molecules of the sesqui-oxydes
(Al, 0, + F, O₂) contained in the bauxite is to the soda of the sodic carbonate as

page_text: 1 to 1 or at the most as 1 to 1.2. If more carbonate of soda be taken, its carbonic acid
will not be completely driven out, and the presence of carbonate of soda in the
aluminate-solution renders the latter more easily decomposable, and if less carbonate
of soda be taken, the bauxite will be rendered incompletely assimilable.
By dissolving in water the mass produced by heating the above described mixture
of sodic carbonate and bauxite, a portion of the hydrate of alumina is precipitated, so
that under the most favorable circumstances only about 75 per cent. of the alumina
contained in the bauxite will be utilized.
On the other hand my investigations have shown, that by first adding to the water
serving to dissolve the calcined mass, a quantity of caustic soda equal to about
30 per cent. of the soda contained in the said mass, and subsequently commencing to
dissolve, no decomposition takes place, and the whole of the assimilable alumina is
obtained in solution.
The advantages of using alkaline lyes obtained by my method of dissociation, for
the manufacture of fresh quantities of crude aluminate, are apparent. It is possible
to add to the mixture from the beginning a sufficient quantity of soda, to ensure that
in dissolving, the whole of the alumina remains in solution; for owing to the absence
of carbonate of soda, no carbonic acid need be driven out, and the drawbacks resulting
from an excess of carbonate of soda, as indicated above, are avoided. As there is no
carbonic acid to be driven out, the mass will be ready in less than half the time which
would be required in the other case. In my new process a thorough heating of the
mass is sufficient.
The apparatus necessary or suitable for my process, consists essentially of
decomposing cylinders or retorts.
A continuous apparatus may for instance comprise four large upright cylinders a₁,
a₁, a, a, of sheet iron which are connected with each other by tubes 1, 2, ƒ in
such a manner, that the liquid passes consecutively from one cylinder to the other,
entering every cylinder at the bottom and leaving it at the top, as illustrated by the
accompanying drawing. Each cylinder contains a stirrer consisting of a vertical
shaft b₁, b, ba, b, carrying a series of helical blades C1, C2, Car C A constant stream of
aluminate solution enters at one end of the battery of cylinders, and is discharged at
the other end through F' after having undergone decomposition.
Only for starting the operation, some hydrate of alumina is introduced into the first
cylinder as exciting liquid, while slowly admitting the liquid to be decomposed, and
setting the stirrers in motion from the main driving shaft e by means of bevel
wheels d', d, d³, d².
The size and number of the cylinders, as well as the speed of the liquid entering
the same, depends on the quantity of the aluminate lyes to be decomposed.
Having now particularly described the nature of my said invention, and in what
manner the same is to be performed, I declare that I claim:
1. The decomposition of alkali-aluminate solutions by treating them at a low
temperature with precipitated hydrate of alumina and constantly stirring.
2. The treatment of bauxite or other material containing alumina, by calcining it
with the product obtained by boiling down the decomposed aluminate solution
resulting from the process specified by the preceding claim.
3. The application of the apparatus described above for continuously decomposing
solutions of alkali-aluminate by the process specified in claim 1.
Doted this 14th day of Anil 1000
FAIRFAX & WETTER,
433, Strand, London,
Agents.