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Патент USA US3071542

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Jan. 1, 1963
A. KOEHL ETAL
3,071,532
CELLS FOR THE ELECTROLYSIS OF FUSED SALTS
Filed March 8, 1960
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INVENTORS
Go?fr/Zed HJeI/emann
‘Ernst Kaegi
by
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AT TORNFYS
States
tent
flies
3,dll,532
Patented Jan. 1, 1%63
2
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The anode plates may be mutually spaced apart and
may be arranged to form an annular or polygonal ring
around the column. Conveniently, the column may have
3,ll71,532
CELM; FUR THE ELEQCTRQLYSES
radially extending arms to which the plates are attached.
Preferably, the anode structure is so dimensioned and
Montltey, Switzerland, assignors to Ciba Limited, Basel,
constructed, and together with the cathode structure so
§witzerland, a Swiss ?rm
arranged within the container, that the electrolyte can
‘Filed Mar. 3, H60, Ser. No. 13,586
freely circulate within the container. Further it is ad
Claims priority, application Switzerland Dec. 7, 1959 '
vantageous that the effective opposing surfaces of the
3 Claims. (Cl. 204-443)
10 cathode and anode are not separated by any intermedi
ate surface, such as, for example, a diaphragm.
This invention relates to cells for the electrolysis of
By way of example, a cell embodying the invention,
fused electrolytes, and particularly to cells used in the
and suitable for the production of sodium by the elec
manufacture of sodium by electrolysis of common salt.
trolysis of common salt, will be described in greater
In large scale manufacturing processes, electrolysis of
molten metal salts, and particularly of alkali halides, has 15 detail and with reference to the accompanying drawings,
in which:
been carried out for many years. The manufacture of
till FUSED SALTS
_
Anton Koehl, Gattfried Fuellemann, and Ernst Kaegi,
metallic sodium from common salt or mixtures thereof
with other salts, such as calcium chloride, barium chlo
FIGURE 1 is a sectional side view of a cell embodying
the invention, and
FIGURE 2 is a section on the line A-A of FIG
ride and the like, has become of especial importance and
has resulted in the development of many types of cell. 20 URE 1.
FIGURE 1 shows a cell comprising a container in
The majority of these cells consist essentially of a cylin
which is mounted an anode structure including a cen
drical steel container, lined with a ceramic material,
trally disposed column 142, made of graphite, and a
through the bottom of which enters a central graphite
number of plates 12. forming the working anode and
anode surrounded by an annular cathode. The space
between the anode and the cathode is divided by an an
nular diaphragm which supports suitable apparatus for
25 which are renewable and attached to the central column
llll by separate support arms 14.
The anode plates 12
and support arms 14 are also made of graphite. Oppo
site and facing anode plates 12 there is an annular cathode
16, made of iron. The column 16 is mounted in the
scribed in US. Patent No. 1,501,756 to James Cloyd '
30 bottom 18 of the container and is also used to supply
Downs (patented luly 15, 1924).
current to the anode plates 12, the positive side of a
Although such cells generally have been fairly success
power supply being connected to a terminal 20 located
ful, they still have certain disadvantages, since the opera
on column llll on the underside of the container.
tion of a fused salt electrolytic cell involves technical
collection of the deposited materials, such as, for ex
ample, chlorine and sodium. A cell of this type is de
problems, due to high working temperatures, corrosive
As shown in FIGURE 1, the bottom of the container
ness of salts employed in the processes and the nature 35 consists of a shell 22 lined with a corrosion resistant
of the ?nal products, the solution of which presents di?i
material; this lining also forming the lower floor 24 of
the cell. A drainpipe 25 is provided in the floor 24
through which the cell can be emptied.
One of these problems arises in the ceramic lining of
A side wall 28, made of iron and forming the inner
such electrolytic cells. It is di?icult indeed to ?nd any
ceramic material which, for prolonged periods, can resist 40 wall of the cell, is inserted into a groove 26 in the bottom
of the container. To provide thermal insulation the side
attack due to the effects of molten salts used in the
wall 28 is enclosed in a thermally insulating layer 30.
process and due also to the products of electrolysis.
The cathode 16 is supported by four circumferentially
Apart from the fact that the ceramic materials used are
spaced bars 32 which pass, electrically insulated, through
expensive, the fabrication of the lining itself tends to be
a complicated and costly operation. Further, during re 45 a collector channel 34. The bars 32 also act as current
supply leads for the cathode 16.
newal of the lining, these cells cannot be operated making
The channel 313, which is of annular form and open
economical utilisation of the plant di?icult.
on its underside, is located above the cathode l6 and is
The use of a diaphragm also gives rise to di?’iculties
immersed in the electrolyte 46. in operation of the cell,
in that materials used in manufacturing these diaphragms
channel 34 collects sodium deposited at the cathode 16.
do not stand up to the demands made of them during
As shown on the right hand side of FlGURE 1, this
operation of cells. The metal screens used as diaphragms
channel supports at one point on its periphery a collector
have to be replaced at relatively frequent intervals during
chamber 38 within which sodium collects above the elec
which replacement operation of the cells must cease, the
trolyte, the latter having a higher density, so that the so~
latter must be partly dismantled and may even have to
culties.
be emptied, thereby further complicating the operation 55 (hum can be discharged through passage 40. At another
point on the channel 34 there is an inlet opening through
of the plant.
which the cell can be replenished with electrolyte. The
collector channel 34- is made, as is the wall of the cell,
of iron.
cient use of supply energy and current as does a cell
A collector dome for chlorine released at the anode
using a diaphragm.
Conventional cells for the electrolysis of fused salts 60 surfaces rests upon the collector annulus 34. The lower
edge 44 of the dome is immersed in the electrolyte 46
thus tend to have constructional complications and to be
thereby sealing oil": the gas space from the exterior of
relatively expensive to maintain and operate; it is an
the cell. At the highest point of the dome 42 there is
object of this invention to provide an improved cell.
an aperture 48 through which the collected chlorine can
According to the present invention, a cell for the elec
be discharged; if desired other apertures may be provided
trolysis of fused salts includes a container within which
in the dome 42 through which electrolyte also may be ad
a cathode structure surrounds an anode structure, the
mitted to the cell. The dome 42 preferably is made of
anode structure comprising a supporting column and a
a corrosion resistant ceramic material.
plurality of anode plates removably and electrically con
However, no cell is at present known which can be
operated without a diaphragm and which makes as effi
nected thereto, the plates being spaced apart from the
column and each having a face directed toward the
cathode structure.
The anode plates are so attached to the column 10
that they may be renewed. For this purpose, as is shown
in FIGURE 1, the support arms 14 have pins 13 and
3,071,532
3
15, of which pins 13 ?t into corresponding holes in the
column 19 and pins 15 into the anode plates 12. It is
to be understood that other methods of attachment may
also be used, for example, the pins of arms 14 may be
screw threaded and holes tapped in plates 12. The anode
plates are arranged to form a circular or polygonal ring,
located within the annular cathode, in general with the
tion, the ceramic lining is limited to the bottom of the
cell, and thus the surface exposed to attack by the melt
is greatly reduced. The formation of decomposition
products is also reduced, resulting in a long operating
life at a substantially constant rate of yield of the cell.
Another advantage having a similarly favorable effect
is the fact that both the working anodes and the cathode
anode plates 12 being mutually spaced apart. The sup
are arranged at some distance above the bottom of the
porting arms 14 are of adequate length to ensure that
cell, since some amount of deposit can form on the
an area of su?icient section is available at the rear side of 10 floor without being in the actual neighbourhood of the
the anode plates in ‘order to allow circulation ‘of the elec
electrodes. This features helps to diminish dangers of a
trolyte around the anode plates, as indicated by arrows
short circuit.
50, to take place. The cathode is likewise spaced from
The thermal insulation layer is provided on the out
the walls of the container. Further, the anode plates
the cathode are displaced from the bottom of the
ce
side of the cell thus not coming in ‘contact with the elec~
trolyte. Hence any desired type of insulating material
can be used since it is not subject to any particular
.
Such a design allows a free ?ow of a melt within the
posited at the cathode can rise up without any turbulence
chemical requirement. It is possible also to vary the heat
insulation of a cell during operation as required, there
by ensuring optimum, or near optimum temperature con
ditions for any particular cell.
Another advantage resulting from the elimination of
the inside lining of the cell is the very simple and ef
causing mixing of these two substances.
?cacious construction of the cell.
cell, as indicated by arrows 5t) and 52, which is well
de?ned and which particularly in the space between the
anode plates and the cathode is free from turbulence.
Chlorine forming at the anode plates and sodium de
The thermal
The sidewall is not
convection taking place between the anode and cathode
aids a comparatively rapid flow of the electrolyte in an
attached rigidly to the bottom but rests in a sealing
groove so that it can be lifted up, together with the chlo
upwards direction which is of importance in so far as
rine dome, cathode and sodium collector without di?i
culty from the ?oor of the cell, without involving the
dismantling of the thermal insulation. This provides
it prevents overheating of the electrolyte in the vicinity
of the electrodes and thereby increases the eii‘iicency
of the cell. The rising melt thus circulates between the
anode column and ‘the anode plates and also between the
cathode and the side walls of the cell Where it becomes
cooled. The favorable ?ow pattern thus achieved also
makes it possible to arrange the cathode and anode work
ing surfaces directly opposite each other without sepa
ration by a diaphragm or other intervening surface. The 35
ready access to the floor portion of the cell, so that both
inspection and maintenance of the cell are greatly facili
tated. Thus, for example, it is possible within a very
short time to lift up the upper portion of the cell, remove
any sediment collected on the bottom, replace the upper
portion, re?ll the cell and put it into operation again.
What is claimed is:
1. A cell for the electrolysis of fused salts, comprising
e?iicency of the cell, as regards consumption of supply
current and energy, however, is comparable with that
a container having a bottom to hold electrolyte, a central
obtained by use of a conventional diaphragm equipped
support column in said container, a plurality of anode
cell.
plates in said container having their active faces disposed
Apart from the fact that the design or" anodes described 40 vertically and being spaced apartfrom each other and
above results in a favorable ?ow pattern, it also leads
from said container bottom and forming together a ring
to a substantial saving in material and labor in the oper
shaped structure concentrically arranged with respect to
ation of the cells. In actual fact only the anode plates
said central support column, said anode plates being re
are subject to substantial wear during operation of the
movably attached to said central column by means of ra
cell, the supporting arms and anode column being sub
dial arms extending from said column in spoke-like con
ject to much less wear. After a given period of operation
it is su?icient, therefore, to renew only the worn anode
?guration, said radial arms located substantially equidis
tantly between the top and bottom of said container, a
plates, whereupon the cell can be re?lled and operated
ring-shaped cathode inside said container concentrically
again. This substantially simpli?es maintenance opera
surrounding said anode plates to provide a free space be
tions and reduces the time during which the cell need
be out of operation during such maintenance.
tween said oathode and anode plates, said anode plates
being spaced with respect to each other and said cathode
plate whereby ?uid ?ow mutually therebetween is pos
sible, said central column piercing said container bottom
and providing electrical connection means with said anode
Elimination of the need for a diaphragm also results
in a simpli?cation of construction and reduction ‘of cost
in the operation of the cell.
Another advantage is that the side walls are not lined 55 plates and a current supply.
.
‘and that lining is restricted to the floor of the cell. This
2. A cell as described in claim 1, wherein said con
is important as the ceramic lining of a fused salt elec
tainer comprises a base portion forming the bottom of the
trolytic cell is a difficult operation. No known material
container, an upstanding cylindrical iron side wall, a ther
will resist for a prolonged period the chemical attack by
mal insulation provided only on the exterior surface of
the contents of the cell. The lining must therefore be 60 said side wall, and a covering dome for the gases liber
renewed at comparatively short intervals of time, thereby
ated at said anode plates, each of the three parts repre
increasing the cost of operation of the cell. In the present
senting a self supporting unit easily detachable from the
case, normal maintenance work is limited to the replace
other container parts; said cell further comprising an an
ment ofthe top layer of the ?oor lining which may con
.nular collecting channel for gathering the material de
sist of ceramic slabs or a compressed material.
posited on the cathode, said channel located above said
The elimination of the ceramic lining is also advan 65 cathode and extending downward below the electrolyte
tageous from the point of view of operation of the cell.
?uid level maintained during normal cell operation.
In fact, the attack by the melt and the sodium on the
3. A cell for the electrolysis of fused salts comprising
ceramic material forms decomposition products in lined
a container, a plurality of anode plates in said container
cells which collect on the floor of the cell forming there 70 having vertically-oriented active faces, a support column
a viscous mass which in time reduces the circulation of
the melt, become electrically conductive and hence causes
for said anode plates, said column piercing the bottom
of said container and providing electrical connection be
short circuits which gradually reduce the 'e?’iciency of
tween said anode plates and an electrical current source,
the cell, necessitating its drainage and cleaning. In the
saidanode plates being removably connected with said
case of a cell constructed in accordance with this inven 75 support column by means of radial arms extending from
3,071,532
6
said column in spoke-like con?guration, said radial arms
being of substantially equal length and located substan
tially equidistantly between the top and bottom of said
container, said anode plates forming a concentric ring
with respect to said support column, and a ring-shaped 5
cathode concentrically and exteriorly arranged with re
spect to said column and said anode plates to provide a
free space between said anode plates and said cathode.
References Cited in the ?le of this patent
UNITED STATES PATENTS
452,030
568,231
1,851,789
2,194,443
2,390,114
1891
1896
1932
Hardy et a1. _________ __ Mar. 19, 1940
McNitt ______________ __ ‘Dec. 4, 1945
Castner _____________ __ May 12,
Blackrnan __________ __ Sept. 22,
Ward et al. _________ __ Mar. 29,
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