Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background of the Invention;
Field of the Invention:
The present invention relates to electrolytic cells
for obtaining aluminum from aluminum chloride by electro-
lyzing a molten salt electrolytic ba~h containing molten
aluminum chloride.
Description of the Prio~ Art:
An aluminum chloride electrolyzi.ng method of obtain-
.ing al~lminum by holding and electrolyzing such halide
molten salt electrolytic bath containing mol.ten alum
inum chloride as, for example, an electrolytic bath
of AlC13 - NaCl - LiCl system or AlC13 - MgC12 - NaCl
system at a temperature akove the melting point of
aluminum has such various advantages that it can be
operated at an electrolyzing temperature near the
temperature of 700C which is about 300C lower than
in the Hall Heroult process and that, as the anode
reaction product by the electrolysis is a chlorine
gas, no reaction with graphite used an an electrode
material will take place and therefore the electrode
will not be worn, is therefore noted as an aluminum
electrolyzing method of a type of saving energy and
resources but is not yet fixed as of an industrial
electrolytic cell.
However, considered most possible up to date is
an electrolytic cell hy horizontal bi-polar electrodes
manufactured recently by ALCOA*, U.S.A. (U.S. Patent No.
3,822,195).
The feature of this electrolytic cell of ALCOA is that
many horizontal rectangular graphite electrode plates are
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set between both electrodes o~ an electrolYtiC cell filled
with a halide molten salt containing aluminum chloride so
as to produce a proper cl.earance from the inner wall of
the cell and the aluminum chloride in the bath between ~he
respective laminated electrodes is electrol.y~ed by passinc3
an electric current between both electrodes so as to pro-
duce a chlorine gas between the anodes of the respective
electrodes and molten aluminum grains on the cathode sur~
faces, the chlorine gas produced at the anodes is made to
rise through the air gap formed between the electrodes and
the inner wall of the cell as a rising passage from one
side o~ the rectangular electrodes, a unidirectional cir-
culating current of the electrolytic bath is formed by
its rising force and, on the other hand, the molten alum~
inum grains produced at the cathodes move on the cathode
surfaces due to the above mentioned circulating current,
reach the gas rising passage, are lowered countercurrently
against the circulating current through the gas rising
passage by their own weight and are accumulated in the
bottom of the cell.
However, in such AI.COA* electrolytic cell, as
mentioned above, there have been defects that, as the
chlorine gas and molten aluminum move countercurrently
through the same gas rising passage and the chlorine
gas produced at the anodes concentrates on one slde of
the rectangle, the gas content in the electrolytic bath
between the electrodes on the discharging side will be
so large and the chances of the aluminum and chlorine
gas contacting each other will be 50 many that the alum-
inum ~ill be re-chlorinated and the current efficiency
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will be reduced.
Sun~ary o the Invention:
An object of the present invention is to provide
an electrolytic cell wherein the deects of the above
mentioned conventional electrolytic cell are ellminated
and an efficient electrolysis of aluminum chloride can
be made.
According to the invention there is provided a sealed
electrolytic cell for electrolyzing a molten salt electro-
lytic ba~h containing aluminum chloride to produce moltenaluminum metal which comprises a cell housing an electrical
element in said housing comprising an array of at least
three electrode plates inclined downwardly and inwardly
towards the housing center in fixed generally parallel
spaced apart relation, substantially centrally located
apertures in all such plates in general~y vertical align-
ment to define a common passageway extending vertically
through said electrode array and outer passages defined
between the outer side edges of said electrode plates and
the inner wall o said cell housing, one outer electrode
plate acting as a cathode, the other outer plate actiny as
an anode and each intermediate plate acting as a bi-polar
electrode, raw material inlet means at the top of said
housing for introducing aluminum chloride into the elec-
trolyte bath above and in substantial alignment with the
central common passageway in said electrode plate array,
chlorine gas discharying means at the top of said housing,
and an aluminum metal collecting reservoir at the bottom
of said housing below said electrode element.
Brief Description of the Drawings:
Fig. lA is a vertically sectional view of an embodiment
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of an electrolytic cell according to the present invention.
Fig. lB is a sectional view on line ~-B in Fig. lA.
Fig. 2 is a developed view of flan~e parts and sleeves
in the respective electrodes in the embodiment in Fig. 1.
Fig. 3 is a vertically sectional view of another
embodiment of the electrolytic cell according to the
present invention.
Fig. 4 is a plan view of the embodiment in Fig. 3.
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Detailed Description of Preferred Embodiments:
In the embodiment in Figs. 1 and 2, numeral 1 indicates
a cylindrical sealed type electrolytic cell formed of an
outer plate 2 made o~ iron, an insulating glasswool layer
3, a refractory aluminum material 4 and a refractory
nitride material 5 from outside. Numeral 6 indicates a
sealing lid part provided in the top part of the electro-
lytic cell 1 and formed the same as the electrolytic cell
1. A raw material feeding port 7 for introducing a raw
material aluminum chloride vapor into a bath is provided
in the center part of the lid part 6. A plurality of gas
discharging ports 8 for discharging a chlorine gas gener-
ated by an electrolysis out of the cell are provided in
the peripheral side part of the lid part 6.
A reservoir 9 for molten aluminum obtained by the
electrolysis is formed in the bottom part of the electro-
lytic cell 1 and bricks made of graphite are used for
the inner wall 10 of this part. Numeral 11 indicates an
outlet port for collecting molten aluminum accumulated in
the molten aluminum reservoir 9. A temperature regulating
mechanism 12 is provided on the periphery of the outlet
port 11 so that, by properly controlling the temperature
of the inner wall of the outlet port 11, the thickness of
the solidified metal layer 13 deposited on the inner wall
can be adjusted and the metal delivering velocity can be
thereby adjusted. 14, 15, 15 and 16 are funnel-shaped
electrodes made of graphite, having respectively center
holes 17 and peripheral clearances and concavely inclining
toward the center holes 17. The respective electrodes 14,
15, 15 and 16 are arranged laminately at a proper distance
between them on the vertical center axis of the
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electrolytic celi l and the uppermost electrode 14 and
lowermost electrode 16 are fitted respectively with
current passing terminals 18 and 19 so as to respectively
form an anode and cathode~ A sleeve 17a made of such a
refractory material as of alumina or nitride having a
resistance to bath is fitted in each center hole 17 as a
sealing material. By the way, the electrodes 15 located
intermediately between both electrodes 14 and 16 act as a
bi-polar electrode having functions as of both electrodes
on both upper and lower surfaces. 20, 20', 20" , 20" '
and 20'''' are sleeves made of such the refractory material
as of alumina or nitride having a resistance to bath for
coating and protecting the outside surfaces of the elec-
trodes 14, 15, 15 and 16 and holding the respective
electrodes 14, 15, 15 and 16 at a fixed distance between
them. The respective electrodes 14 J 15, 15 and 16 are
supported by the above mentioned sleeves 20, 20', 20'',
20'" and 20"'' on flange parts 21, 21', 21" and 21" '
provided respectively on the peripheries of the lower ends.
Further, the above mentioned respective sleeves and flanges
are provided respectively with incisions 23J 23', 23'' and
23' " and 24, 24', 247' and 24"' communicating at proper
intervals. By the way, as seen in the developed view shown
in Fig. 2, the incisions 24, 24', 24" and 24' " formed
respectively in the above mentioned flange parts 21, 21'
22'' and 21'" had better have the openings made gradually
larger with the approach to the upper part of the cell in
which the amount of the gas is larger. 25 is a hood made
of such refractory material as of alumina or nitride having
a resistance to bath, connecting the center hole 17 of the
upper most funnel-shaped electrode 14 with the above
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mentioned raw material feeding port 7 and having on the lower
peripheral surface a plurality of passages 26 through which
the electrolytic bath flows in. By the way, the hood 25 may
be made by cylindrically stacking firebricks or the like.
The operation of the electrolytic cell formed as in this
embodiment shall be described in the following.
When the cell 1 is first filled to the bath level 27 with
a halide electrolytic bath containing aluminum chloride and
an electric current is passed between both electrodes 14 and
16, the respective funnel-shaped electrodes 15 present as
held between the electrodes 14 and 16 will become bi-polar
electrodes and their upper surfaces and lower surfaces will
function respectively as cathodes and anodes.
Therefore, by the electrolysis of aluminum chloride in
the electrolytic bath present in the spaces between the
respective electrodes 14, 15, 15 and 16, a chlorine gas will
be produced on the anode surfaces and molten aluminum will
be deposited in the form of grains on the cathode surfaces.
Now, as the respective electrodes 14, 15, 15 and 16 are
funnel-shaped, the molten aluminum grains produced on the
cathode surfaces will lower centripetally toward the center
holes 17 along the sloped upper surfaces of the funnels and
will fall into the center holes 17 to be accumulated in the
molten metal reservoir 9. On the other hand, on the anodes,
the produced chlorine gas will diffusely rise in the periph-
eral direction along the sloped lower surfaces oE the
funnels, will rise through the peripheral clearances (gas
rising passages) through the incision 23, 23', 23l' and 23'''
of the sleeves and the incisions 24, 24', 24'' and 24''' of
the flanges and will be discharged out of the cell through
the gas discharging ports ~ provided in the peripheral part
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of the lid part 6 in the cell top part.
In such case, the electrolytic bath contained in the
above mentioned gas rising passages will produce a rising
current due to the buoyant effect by the rising force of
the chlorine 9as. On the contrary, a ~alling current will
be produced in the center hole 17 of the electrode. Thus,
as shown by the arrows in Fig. 1, the electrolytic bath
will form a circulating current which will pass through
between the respective electrodes 14, 15, 15 and 16 from
the center hole 17, will reach the peripheral part of the
cell, will rise through the peripheral clearances (gas
rising passages), will be separated from the chlorine gas
in the uppermost part and then will return to the center
hole 17 again from the passages 26 of the hood 25O
By the way, in the case of laminating a plurality of
funnel-shaped electrodes 14, 15, 15 and 16 at a fixed dis-
tance between them, the electrodes having flanges which
are also supporters are used in the dra~ing but, for
example, the electrodes may be held by setting separators
of stays by a plurality of fine alumina pipes. It is
needless to say that, in such case, a proper gas rlsing
passage will have to be provided between the electrodes
and the inner wall of the cell. Also, the electrodes may
be held only by cylindrical sleeves which may be made to
communicate with the peripheral clearances ~gas rising
passages) by providing incisions.
By the way, in this embodiment, the raw material feed-
ing port 7 and the center hole 17 of the electrode are
connected with each other through the hood 25 but the raw
material aluminum chloride vapor can be bl.own directly into
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the center hole of the electrode from the raw material ~eed-
ing port without using the hood.
The embodiment in Figs. 3 and 4 shall be described in the
following. In this embodiment, the same reference numerals
are attached to the same respective parts as in Figs. 1 and
2.
The greatest difference between this embodiment and the
above described embodiment is that pairs of right and left
inclidined electrode plate groups are provided instead of
the funnel-shaped electrodes made of graphite and used in
the above described embodiment. That is to say, 14a, 15a,
--- l5a, 16a and 14'a, 15'a, --- 15'a, 16'a are pairs of
righ~ and left inclined electrode plate groups provided as
respectively opposed to each other on the right and left.
14a and 14'a are anodes. 16a and 16'a are cathodes. 15a,
15a --- 15'a, 15'a --- ~respectively four pairs in the draw-
ing) are bi-polar electrodes formed respectively between the
anodes and cathodes 14a, 16a and 14'a, 16'a. The respective
upper surfaces function as cathodes and the respective lower
surfaces function as anodes.
The respective electrode plates are kept at a fixed
distance between them respectively by spacers 28, 28, ---
28', 28' ---, the anodes 14a and 14'a and cathodes 16a and
16'a are held in an outer casing respectively by conductive
rods 18, 18' and 19, 19' and the conductive rods 19 and 19'
are positively supported by refractory materials 30. These
right and left electrode plate groups are provided as opposed
to each other with a fixed clearance between them. A falling
passage 17a for the electrolytic bath and molten metal is
formed between them. Further, rising passages 29 and 29' for
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the electrolytic bath and chlorine gas are ~ormed between
the respective electrode plate groups 14a, 15a, - - 15a. 16a
and 14'a, 15'a, --- 15'a, 16'a and the inner wall (refractory
material layer 5) of the elect~olytic cell. By the way, it
is preferrable that the above mentioned rising passages 29
and 29' are made wider with the approach to the upper part
of the cell in which the amount of the gas is larger.
Now, the operation of the electrolytic bath of this
embodiment is substantlally the same as of the above des-
cribed embodiment~ When the cell is first filled to thebath level 27 with a halide electrolytic bath containing
aluminum chloride and an electric current is passed between
both electrodes 14a, 16a and 14'a, 16'a of the right and
left electrode plate groups, the respective electrode plates
15a and 15'a present as held between both electrodes 14a and
16a' and between both electrodes 14'a and 16a' will operate
as bi-polar electrodes in which thir upper surfaces will
function as cathodes and their lower surfaces will function
as anodes. The aluminum chloride in the electrolytic bath
present in the spaces between the respective electrode 14a,
15a, --- 15a, 16a and between the respective electrodes l~a',
15a', --- 15a', 16' will be electrolvzed~ a chlorine gas will
be produced on the anode surfaces and molten aluminum will
be deposited in the form of grains on the cathode surfaces.
However, as the respective electrode plates 14a, 15a, --
lSa, 16a and 14a', 15a', --- 15a', l~a' slant to lower
inward, the molten aluminum grains produced on the cathode
surfaces will lower due to their own weight inward of the
cell along the sloped upper surfaces of the electrode plates,
will further fall into the passage 17a formed in the
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clearance between both electrode plate groups and will be
accumulated in the molten metal reservoir 9.
On the other hand, the chlorine gas produced on th~
anode surfaces will rise outward of the cell along the
sloped lower surfaces of the respective electrode plates,
will rise through the rising passages 29 and 29' formed
of the clearances between the outer ends of the electrode
plates and the inner wall of the cell and will be discharged
out of the cell thro~lgh the gas discharging ports 8 provided
in the lid part in the top part of the cell.
In such case, the electrolytic bath contained in the
above mentioned rising passayes 29 and 29' will be subjected
to the buoyancy effect by the rise of the chlorine gas and
will prodce a rising current. On the other hand, a falling
current will be produced on the contrary in the falling pas-
sage 17a formed between the right and left electrode plate
groups and, therefore, as indicated by the arrows in Fi~. 3,
the electrolytic bath in the cell will form a circulating
current which will go outward in the cell through between
the respective electrode plates 14a, 15a, --- 15a~ 16, 14'a,
15'a, --- 15'a 16'a, will rise through the gas rising pas-
sages 29 and 29', will reach the upper part of the cell and
will return again to the falling passage 17a between the
respective electrode plate groups.
As explained in the above, according to the present
invention, as the electrode part arranged in the intermediate
part of the electrolytic cell is formed to incline so as to
be lower inward, the chlorine gas produced on the anode ~ur-
faces of the electrodes will quickly rise along the sloped
lower surfaces of the electrode plates and, on the other
hand, the molten aluminum grains deposited on the cathode
surfaces of the electrodes will quickly lower due to their
own weight along the sloped upper surfaces of the electrode
plates and therefore the chances of the a]uminum being
re-chlorinated will be remarkably few. Further, as the
chlorine gas rising passage and the molten metal falling
passage are respectively independent of each other, the
chances of the aluminum and chlorine gas contacting each
other in these parts will be also few and therefore it
will be possible to substantially perfectly prevent the
loss by the re-oxidation.
By the way, from the viewpoint of the structure and
the current efficiency in the case o~ the electrolysis,
it is proper that the angle of inclination of the inclined
electrode plates set in the embodiment of the present
invention is about 10 to 50 degrees.
Further, the present invention is not limited to the
above mentioned embodiment. For example, in the case of
obtaining an electrolytic cell of a large capacity, the
above mentioned pair of electrode plate groups may be made
one set and a plurality of such sets may be arranged in
parallel.
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