Improvements relating to the Production of Aluminium and Compounds or Alloys Containing the same and to Apparatus therefor.
Year: 1887

page_text: Date of Application, 14th Nov., 1887
Complete Specification Left, 13th Aug., 1888
Complete Specification Accepted, 28th Sept., 1888
Improvements relating to the Production of Aluminium and
Compounds or Alloys Containing the same and to Apparatus
therefor.
I, LUDWIG GRABAU, of Hanover, Germany, Civil Engineer do hereby declare the
nature of this invention to be as follows:-
The process of preparing aluminium by reducing aluminium fluoride or cryolite
by means of an alkaline metal possesses great defects, because the aluminium fluorides
of an alkali that are formed in the reduction and highly heated very soon destroy any
known refractory material, render reduction-crucibles, furnaces and the like un-
serviceable in a short time, and thereby cause the aluminium formed to become
impure.
The chief object of the present invention is to remedy these defects and to
enable the reduction of aluminium fluoride to be performed by means of an
alkaline metal without the reducing vessels being attacked by the aluminium
fluorides of an alkali formed, or by the liquid aluminium. The quantitative
proportions of the aluminium fluoride and the alkaline metal are preferably such
that after the reaction the most liquid salt (Al, F, 6 Na F) is present. These
quantitative proportions result from the following formula illustrative of this action
With this combining proportion the aluminium fluoride must be previously
heated to about 600 degrees centigrade in order that, when it is poured upon
molten alkaline metal, the reaction occurs without further heating. As the
aluminium fluoride remains pulverulent at the temperature to which it was
preliminarily heated, it will keep the molten sodium covered, and under these
conditions the reaction will progress from below upwards, which as regards the

page_text: yield is of great advantage, in contradistinction to the known processes of pouring
molten aluminium compounds upon alkaline metal, wherein the lighter alkaline
metal is known to pass to the surface and is partly burnt. When the alkaline
metal is placed in the reducing vessel in an unmolten state, the heating of the
aluminium fluoride must be correspondingly higher, and should reach about
700 degrees centigrade.
The reducing vessel must be cooled in order to cause the aluminium fluoride
of an alkali (Al, F., 6 Na F) formed in the reduction to solidify on the interior
sides of the vessel, for the purpose of forming a solid lining which protects the
sides of the vessel from contact with the molten mass and the molten metals,
and which lining cannot in any case be destroyed either by the molten mass or
by the aluminium.
In carrying the said invention into practice the furnace with the fire place and
chimney serves for heating two iron vessels or retorts covered outside with
chamotte. The one vessel serves for heating the aluminium fluoride and is closed
below with the slide. The other vessel serves for melting the sodium and can be
emptied through a suitable cock.
A reducing vessel provided with an annular space for the circulation of the cooling
liquid, is arranged below the iron vessels. This reducing vessel is provided with
a circulating pipe on either side one being for the admission and the other for the
discharge of the cooling liquid. If desired the said reducing vessel may be provided
with a cover, for example, when molten aluminium compounds are employed.
A lower vessel or receptacle is provided into which the molten mass is poured.
This vessel is also provided with inlet and outlet pipes and is cooled in the same
manner as above described for the reducing vessel.
The retorts are heated to a dark red heat, the one is then filled with so much
aluminium fluoride as corresponds with one charge. After the aluminium fluoride
has been heated to dark red heat which is observed by white vapours commencing
to escape, the corresponding quantity of alkaline metal is put in the other retort.
This melts very rapidly, and is, immediately after it is melted, let off into the reducing
vessel by opening the cock. When all the alkaline metal has been let off, the slide
is opened, all the aluminium fluoride then falls at once upon the alkaline metal, and
the reaction commences. As the aluminium fluoride covers the alkaline metal, not
in a molten, but pulverulent state, the said alkaline metal remains covered till the
reaction is terminated, which is of great value as regards the yield.
By the reaction is produced a very high heat, and as the quantitative proportions
between the alkaline metal and aluminium fluoride are such that after the reaction
cryolite is produced which is already fusible at red heat, the entire contents become
very fluid, solidifies at the cooled sides to form a non conducting crust which crust
cannot be attacked either by the fluid cryolite or by the aluminium, and, on account
of the great fluidity of the contents, enables the collection of the aluminium to form
a regulus without the employment of fluxes. After the reaction, which with the
above stated combining proportion lasts only a few seconds, has terminated, and
after the reducing vessel has been shaken to and fro a little, for the rapid
deposition of the aluminium, the vessel is tilted, and emptied into the lower
vessel. The cryolite crust formed in the reducing vessel remains, and the apparatus
is again serviceable for a new charge.
The mass solidified in the lower vessel can be readily separated from the aluminium
regulus likewise solidified, for example by a few blows with a hammer.
The present improvements relating to the production of linings in reducing vessels
that cannot be attacked are applicable not only to the reduction of aluminium fluoride
but also to the reduction of other aluminium compounds, for example aluminium
chloride, aluminium iodide, such reduction processes being supposed to take place by
bringing together materials, that have been previously heated separately, with a
generation of heat, and therefore being capable of being carried
on in cooled
j
vessels and this improvement relates moreover to definite mixtures which are put
in cold or cooled vessels, and designed for the preparation of aluminium or ar

page_text: aluminium alloy and which allows of heat being applied in the interior of the vessel,
in order to cause the reaction. Thus the present process of preparing linings that.
cannot be attacked can also be used, for instance with the known processes of preparing
aluminium by pouring upon sodium molten cryolite containing a flux, or a molten
mixture of chloride of aluminium and chloride of sodium, to which fluor spar or
cryolite is added as a flux, or with the processes of preparing aluminium by reducing
the halogen compounds of aluminium by magnesium or other similar metals by
bringing the ingredients that have been previously heated together in the converter.
Dated this 14th day of November 1887.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
and
Improvements relating to the Production of Aluminium
Compounds or Alloys Containing the same and to Apparatus
therefor.
I, LUDWIG GRABAU, of Hanover, Germany, Civil Engineer, 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 of preparing aluminium by reducing aluminium fluoride or cryolite by
means of an alkaline metal possesses great defects, because the aluminium fluorides of
an alkali that are formed in the reduction and highly heated very soon destroy any
known refractory material, render reduction-crucibles and the like unserviceable in
a short time, and thereby cause the aluminium formed to become impure.
The object of the present invention is to remedy these defects and to enable the
reduction of aluminium fluoride to be performed by means of an alkaline metal,
without the reducing vessels being attacked by the aluminium fluorides of an alkali
formed, or by the liquid aluminium. The quantitative proportions of the aluminium
fluoride and the alkaline metal are preferably such that after the reaction the most
liquid salt (Al, F, 6 Na F) is present. These quantitative proportions result from the
following formula illustrative of this action.
2 (Al, F) +6 Na = 2 Al + Al, F, 6 Na F. With this combining proportion the
the aluminium fluoride must be previously heated to about 600 degrees Centigrade, in
order that, when it is poured upon molten alkaline metal the reaction occurs without
further heating. As the aluminium fluoride remains pulverulent at the temperature

page_text: to which it was preliminarily heated, it will keep the molten sodium covered, and
under these conditions the reaction will progress from below upwards, which as
regards the yield is of great advantage, in contradistinction to the known processes of
pouring molten aluminium compounds upon alkaline metal, wherein the lighter
alkaline metal is known to pass to the surface and is partly burnt. When the alkaline
metal is placed in the reducing vessel in an unmolten state, the heating of the
aluminium fluoride must be correspondingly higher and should reach about 700 degrees
Centigrade.
6
The reducing vessel must be cooled in order to cause the aluminium fluoride of an
alkali (Al, F, G Na F) formed in the reduction to solidify on the interior of the
vessel, for the purpose of forming a solid lining which protects the sides of the vessel
from contact with the molten mass and the molten metals, and which lining cannot in
any case be destroyed either by the molten mass or by the aluminium.
In the accompanying drawing I have shown an apparatus constructed according to
the present invention for the extraction of aluminium.
Figure 1 is a longitudinal section of the said apparatus, and
Figure 2 is a cross section on the line x, y of Figure 1.
In carrying the said invention into practice the furnace A with the fire-place B and
chimney C serves for heating two iron vessels or retorts D and E covered outside
with chamotte. The vessel D serves for heating the aluminium fluoride and is closed
below with the slide s. The vessel E serves for melting the sodium, and can be
emptied through a suitable cock h.
A reducing vessel F provided with an annular
space for the circulation of the cooling liquid is arranged below the iron vessels. This
reducing vessel is provided with circulating pipes and 21 one being for the admission
and the other for the discharge of the cooling liquid.,
A lower vessel or receptacle G is provided into which the molten mass is poured,
this vessel is also provided with inlet and outlet pipes, and and is cooled in the
same manner as the reducing vessel F.
The retorts D and E are heated to a dark red heat, the one D is then filled with so
much aluminium fluoride as corresponds with one charge. After the aluminium
fluoride has been heated to dark red heat which is observed by white vapours
commencing to escape, the corresponding quantity of alkaline metal is put in the
other retort, E. This melts very rapidly, and is immediately after it is melted. let off
into the reducing vessel F by opening the cock h. When all the alkaline metal has
been let off, the slides is opened all the aluminium fluoride then falls at once upon
the alkaline metal, and the reaction commences. As the aluminium fluoride covers
the alkaline metal, not in a molten, but pulverulent state, the said alkaline metal
remains covered till the reaction is terminated, which is of great value as regards
the yield.
By the reaction is produced a very high heat, and as the quantitative proportions
between the alkaline metal and aluminium fluoride are such that after the reaction
cryolite is produced which is already fusible at red heat, the entire contents become
very fluid, solidifies at the cooled sides to form a non-conducting crust which crust
cannot be attacked either by the fluid cryolite or by the aluminium, and on account of
the great fluidity of the contents, enables the collection of the aluminium to form a
regulus without the employment of fluxes. After the reaction which with the above
stated combining proportion lasts only a few seconds, has terminated, and after the
reducing vessel has been shaken to and fro a little for the rapid deposition of the
aluminium, the vessel is tilted, and emptied into the lower vessel G (Figure 2). The
cryolite crust formed in the reducing vessel F remains, and the apparatus is again
serviceable for a new charge.
The mass solidified in the lower vessel G can be readily separated from the aluminium
regulus likewise solidified for example by a few blows with a hammer.
If the operation in the crucible is not intended to take place too often or only
at long intervals, the vessels having double walls are not absolutely necessary. In
this case ordinary cold (that is to say not heated) vessels lined with cryolite are
sufficient.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The production of aluminium from aluminium fluoride by means of alkaline
metal without the employment of a flux by the simultaneous use of the following
operations.
(a) The employment of such quantities of aluminium fluoride and alkaline metal, that
the process can be effected say according to formula 2 Al, F +6 R = 2 Al + Al₂ F¸,
6 RF, if R designates the alkaline metal.
(b) The preliminary heating of the aluminium fluoride without fluxes to a temperature
of about 600 degrees to 700 degrees at which it still remains pulverulent, but will
when coming in contact with the alkaline metal, be converted with the latter at once
to form aluminium and aluminium fluoride of an alkali, and,
(c) The employment of non-heated vessels lined with cryolite or vessels having
cooled walls (Figures 1 and 2) in which the preliminarily heated pulverulent
aluminium fluoride is placed on the alkaline metal without the presence of fluxes for
the purpose of effecting the reaction, in order that the aluminium fluoride of an alkali
thereby produced, which is molten at the temperature at which the reaction takes
place shall wholly or partially cool on the walls of the vessel and adhere to them and
form a protecting crust, so that the vessels receive a lining that is attacked.
Dated this 14th day of August 1888
Dated this 14th day of August 1888
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.