Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
C-6171 This invention relates to electrolytic ~ells for
the electrolysis of aqueous salt solutions. More particular-
ly this invention relates to diaphragm type electrolytic
cells for the electrolysis of aqueous alkali metal
chloride solutionsa
Diaphragm-type electrolytic cells are widely
used in industry, particularly in the production of chlorine
and caustic soda by the electrolysis of sodium chloridebrines.
Most of these commercial cells consist of a rectangular
structure having a top section and a bottom section. The
cell bodies are constructed of heavy, load-bearing materials
such as cement or concrete with the anode mo~mted vertically
in the bottom sectionO The anode is attached to metallic
conductors and secured by a layer of lead which is ln turn
covered by a layer of cement. The cathode is mounted in
the top section or on a side wall.
In diaphragm cells where the anode has been
mounted in a side wall, as for example in U.S. Patent Nos.
3~477,938 or 3J247~090, the cell body has been constructed
of a load-bearing material such as concrete.
Brine circulation in diaphragm cells of the prior
art has been restricted generally to flowing on top of or
below and between the electrode sections. Brine has not
been free to circulate completely around the electrodes.
Therefore, there is a need for a diaphragm elec~
trolytic cell which can be fabricated from light-weight
'~
-2-
C-6171 materials of construction giving significant reduction in
cost. Xn addition~ there is need for a diaphragm electro-
lytic cell having improved electrolyte circulation which
permits brine circulation completely around and ~hru the
electrode section.
It is an object of the present invention to
provide a diaphragm cell which can be readily fabrica~ed
a~ a reduced cost and having reduced weight.
Another object of the invention is to provide a
diaphragm cell having a cathode attached to a conductive
end wall and an anode attached to an opposite conducting
end wall.
A further obj ect of the invention is a diaphragm
cell having improved electrolyte circulation.
; Yet another obj ect of the present invention is to
provide a diaphragm cell wherein the cell body is supported
by the conductive end walls.
An additional obj ect of this invention is to
provide a horizontal diaphragm cell having entrie~s to the
cell body thru the ends.
A still further obj ect of the invention is to
provide a horizontal diaphragm cell having a shorter and
more direct current path through the cell and between
adjacent cells.
These and other objects of the invention are
accomplished in an electrolytic diaphragm cell comprised
~ 3 ~
C-6171 of a horizontal cell body having opposite and substantially
parallel ends, having a first opening at one end of the
cell body and a second opening at the opposite end of the
cell body. An electroconductive cathode plate is sealingly
attached to the cell body and covers the first opening.
The cathode support has at least one cathode attached to
the inner surface of the cathode plate.
An electroconductive anode plate is sealingly
attached to the cell body and covers the second opening.
The anode plate has at least one a~ode attached to the
inner surface of the anode plate. The cathode plate and
the anode plate support the cell body.
Accompanying Figures 1-6 illustrate the novel
cell of the present invention. Corresponding parts have
the same numbers in all Figures. *
Figure 1 illustrates a side view of one embodiment
of the diaphragm cell of ~he present invention.
Figure 2 shows a partially sectioned top view of
the diaphragm cell of Figure 1.
Figure 3 depicts an end view of the diaphragm
cell of Figure 1 showing the cathode plate.
Figure 4 is a top view of the cathode section of
the diaphragm cell of Figure 1.
Figure 5 illustrates a top view of the anode
section of the diaphragm cell of Figure 1.
Figure 6 is a cross sectional view of the
* Figures 4 and 5 appear on the first sheet of drawings.
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C-6171 diaphragm cell of Figure 1 taken along lines 6-60
Appatatus described in Figures 1-6 when used to
electrolyze aqueous solutions of alkali metal halides form
halogen gas~ hydrogen gas and an alkali metal hydroxide
liquor. However~ those skilled in the art will recognize
that modifications can be made for the use of other
starting materials to produce other products.
More in detail, Figure 1 is a side view of one
embodiment of the invention illustra~ing diaphragm cell A
having a horizontal generally cylindrical cell bndy
1 and having flanges 2 and 3 surrounding each opening at
the ends of cell body 1. Anode plate 4 is attached to
flange 2 at one end of cell body 1 and ca~hode plate 5 is
attached to flange 3 at the other end of cell body I.
; Gaskets 6 and 7 seal anode plate 4 to flange 2
and cathode plate 5 to flange 3, respectively.
An aqueous alkali metal halide solution to be
electrolyzed enters thru brine inlet 12 housed in
cell body 1. Halogen gas is removed through halogen
outlet 10, and hydrogen gas is removed through outlet 11.
Electric current is introduced to the cell through con-
ductor 13 attached to anode plate 4. Current is removed
~; from the cell at conductor 14 attached to cathode plate 5.
Cathode plate S and anode plate 4 support the
weight of cell body lo Anode plate supportS 8 bear the
--5--
~B4~
C-6171 the weight of anode plate 4 and cathode plate suppor~s
uphold cathode plate 5. Anode plate supports ~ and
cathode plate supports 9 are bolted or otherwise attached
to insulators 23 resting on platforms 24~
Drain 15 permits the contents of the cell to be
removed. Lugs ~6 and 17 aid in the removal o~ conductive
anode plate 4 and conductive cathode plate 5, respectively.
Figure 2 depicts a partially sectioned top ~iew
of diaphragm cell A of the present inven~ion. ~nodes 21
are attached to anode plate g and project across the cell
toward cathode plate 5. Cathodes 22 are attached to
cathode plate 5 and project across the cell towards anode
plate 4. Cathodes 22 support a diaphragm (not shown) of
the type described more fully below. Anodes 21 are in-
serted within the spaces between adjacent cathodes 22.
Current enters the cell thru conductor 13 and flows thru
anode plate 4, thru anodes 21 attached, thru the electrolyte
between anodes~21 and cathodes 22 and thru cathodes 22 to
cathode plate 5. Current leaves the cell thru conduc~or 14
attached to cathode plate 5. Thus~ the current passes thru
the cell in a short and direct path. Conductors 13 and 14
have a series of holes permitting these conductors to be
attached to conductors on adjacent cells, for example, with
bolts.
Figure 3 shows an end view partially sectioned
of diaphragm cell A of the present invention. Cathode
C~6171 plate 5 is attached to cell body 1 (no~ shown) by a series
of bolts 25 spaced equidistantly around the periphery.
Cathode plate supports 9 provide support for cathode plate
Cathodes 22 are attached to and spaced ap~rt from ~he
outer edges of cathode plate 5. Conductor 14 removes
current from cathode plate 5. An aqueous alkali metal
halide solution is introduced into the cell thru brine
inlet 12. Hydrogen gas produced during electrolysis is
removed thru hydrogen outlet 11 and ~he alkali me~al hydrox-
ide liquor produced is removed through outlet 20.
A top view of cathode section 28 of diaphragm
cell A is depicted in Figure 4. Cathodes 22 are comprised
of a conductive element 26 attached to and providing support
for the surrounding screen 27. Cathodes 22 are attached to
cathode plate 5, being parallel to and separated from each
other to form cathode section 28. Cathode section 28 is
spaced apart from the perimeter of cathode plate 5 to per-
mit brine to encircle the cathode section.
Figure 5 is a top view of anode section 29 of
diaphragm cell A. Anodes 21 are attached to anode plate 4
and are parallel to and separated from each other to form
anode section 29. Anode section 29 i:, spaced apart from
the perimeter of anode plate 4 to pennit brine to encircle
the anode section.
Figure 6 shows a cross sectional view taken along
lines 6-6 of Figure 1. Anode plate 4 has a plurality of
C-6171 anodes 21 attached to form anode section 29. Cathodes 22,
attached to cathode plate 5 (not shown) are arranged so
that an anode is inserted between and is substantially
equidistant from each adjacent cathode. Anode section 29
is spaced apart from the perimeter of anode plate 4 to
permit electrolyte to encircle the anode section.
The horizontal cell body of the electroly~ic
diaphragm eell of the present invention may be of any
eonvenient configuration, for example, it may be rectang-
ular, cylindrical or elliptical. Preferably, it is gen-
erally cylindrical or elliptieal. The cell body may be
eonstructed of a variety of materials, such as, ~iber rein-
foreed plastic~ hard rubber, steel, hard rubber-lined steel,
titanium~ asbestos reinforced plastic or concrete. In one
embodiment the eell body comprises a cylindrieal shell of
fiber reinforeed plastic wherein the fiber is, for example,
fiberglass and the plastie is for example a polyester or
epoxy resin. A cell body of this type can be fabricated
easily, ~or example, on a mandrel using filament winding
teehniques to form a eell body having reduced weight and
having high body strength. Additional embodiments may
eomprise a shell of steel or eonerete lined with a pro-
tective eoating such as rubber, ceramic tile composites,
plasties rein~oreed with asbestos, earbon,siliea,or glass
flakes, or polyhaloolefin plastics such as polytetrafluoro~
ethylene or polychlorotri~luoroethylene.
C-6171 The cell body may be of any convenient height.
For example, a cell body o from about ~ to about ~5, and
preferably from about 4 to about 12 feet may be employed.
To facilitate attachment of the electrode plates, the cell
body may have a flange surrounding the opening at each end.
The anode plate attached to one end of the cell
body, is wholly or partially constructed`of an electro-
conductive material such as steel~ copper, aluminum,
; titanium or combinations of these materials. ~here the
electroconductive material can be attached by the solution
or gases in the cell it can be covered, for example, with
rubber, a chemically inert plastic such as polytetrafluoro-
ethylene or fiber reinforced plastic or a metal such as
titanium or tantalum.
In a preferred embodiment) the anode plate is
; composed of steel which is lined with rubber on the inner
surface. The steel serves both as an electroconductor and
a structural material which has sufficient strength to
support the cell body without requiring an excessive mass
of material.
The anode support plate is attached at one open-
ing of the cell body by an convenient attachment means such
as bolts, tie rods or clamps.
A series of bolts are used in one embodiment of
the present invention to attach the anode plate to the cell
~f~
C-6171 body. The bolts, placed around the periphery of the plate,
facilitate the uniform allignment of anodes when the cell
is assembled. The anode plate supports at least one
anode.
Anodes suitable for use in this invention are
composed of graphite, a valve metal such as titanium or
tantalum, or a metal, for example, steel, copper or alumi-
nu~ clad with a valve metal such as tantalum or titanium.
The valve metal has a thin coating over a least part of
its surface of a platinum group metal, platinum group metal
oxide, an alloy of a platinum group metal or a mixture
thereof. The term "platinum group metal" as used in the
specification means an element of the group consisting of
~; ruthenium, rhodium, palladium, osmium, iridium and
` platinumO
Anodes can be made in various formsJ for example,
solid sheets, perforated plates and in the case of con-
ductive metalJ as expanded metal or screen. The anodes
are attached to the anode support plate by bolting, welding,
soldering,or the like.
The anodes employed may be any convenient size~
for example, from about 1 to about 12, and preferably from
about 2 to about 10 feet in height; from about 1 to about
6~ and preferably, from about 2 to about 5 feet in length;
and from about 0.05 to about 1.00, and preferably from
" -10~
3'~
C~6171 about 0.1 to about 0.8 inches thick.
A plurality of anodes are attached to the anode
plate, the exact number depending on the size of the anode
plate~ In the diaphragm cell of the present invention, for
example, from about 2 to about 100 or more, and preferably
from about 5 to about 50 anodes are at~ached to the anode
plate and constitute the anode sec~ion. The anodes are
positioned parallel to and separated from each other on
the anode plate~ The anode section is attached to the
anode plate in such a manner that it is spaced apart from
the perimeter of the anode plate, as illustrated in Figure
6. This arrangement permits brine to flow completely aro~md
the anode section as well as up through the spaces between
the anodes.
; The cathode plate is composed wholly or partly
of an electroconductive material, for example, steel or
copper or combinations of these materials. To avoid
corrosive damage the cathode plate may be covered, for
example, with hard rubber~ a plastic such as polytetra-
fluoroethylene or fiber reinforced plastic.
A preferred embodiment is a
cathode plate composed of hard rubber lined steel. The
` steel serves both as an electroconductive metal and a
structural material able to support the cell body without
requiring an excessive mass of material. The use of steel
~ 3 ~
C-6171 is economic as it can, if desired, eliminate en~irely the
requirement for more expensive conductors such as copper.
The cathode plate is sealingly attached at one opening of
the cell body in any convenient manner, for example, by
bolts, tie rods or clamps. In one embodiment, the cathode
plate is attached to the cell body by a series of bolts
spaced around the periphery of the plate. The bolts assure
an accurate and simplified alignment of the cathodes when
the cell is assembled.
A plurality of cathodes are attached to the
cathode plate, the exact number depending on the si2e of
the cathode plate. In the diaphragm cell of the present
invention, for example, from about 2 to about 100 or more
and preferably from about 5 to about 50 cathodes con-
stitute the cathode section. The cathodes are positioned
parallel to and separated from each other on the cathode
plate.
The cathodes are foraminous projections extending
across the cell body toward the anode support plate. A
single cathode comprises a conductive element surrounded
by a conductive screen or meshO The conductive element
may be, for example, in ~e form of a plate or rod with
attachment means for the screen or mesh. In one embodiment
of the diaphragm electrolytic cell of the present
invention, the conductive element is a steel plate having
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C-6171 projec~ions at spaced intervals along the plate. The pro-
jections are attached to the cathode screen to provide
support and to supply current to the cathode screen. The
projections may be made, for example, by punching or
stamping the conductive plateO Cathodes are attached to
the cathode plate by any suitable means, for example, by
welding or bolting.
The cathodes may be of any convenient size, for
example, from about 1 to about 12~ and preferably from
lo about 2 to about 10 feet in height; from about 1 to about
6 and preferably from about 2 to about 5 feet in length;
and from about 0.5 to abou~ 2.0 and preferably from about
0.8 to about 1~5 inches thick.
In the diaphragm cell of the present invention,
the anode and cathode plates support the weight of the cell
bodyO The anode and cathode plates may support the cell
body direc~ y by having a perimeter larger than that of
the cell body whereby the weight of the cell rests
directly on the anode and cathode plates. In another
embodiment, the anode and cathode plates are each attached
at the lower edge to at least one support, for example, a
bracket, brace, or strut. The anode and cathode plate
supports are suitably insulated to prevent cuFrent loss.
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C-6171 In the use of ~he presen~ apparatus as a
diaphragm cell, any conventional inert dlaphragm material
is applied or deposited on the cathodes. The diaphragm
material which can be used to cover the screen or foraminous
portion of the cathode is a fluid permeable and halogen-
resistant ma~erial. Preferably the material is asbestos
fiber deposited on the outer surfaces of the cathode
screen by the application of suction to an asbestos fiber
slurry. Other diaphragm materials such as polyvinylidene
chloride, polypropylene, or polytetrafluoroethylene may
also be used. The cathode structure is adapted ~o permit
the use of all types of diaphragms including sheet asbestos,
deposited asbestos and synthetics which can be in the form
of woven fabrics, for example, polyethylene, polypropylene
or polytetrafluoroethylene.
In the assembled diaphragm cell of the present
invention, the cathode section is posi~ioned so that the
cathodes project across the cell body in the direction of
the anode support plate. The anode section is oppositely
positioned such that the anodes project across the cell
towards the cathode plate, with the anodes being inserted
between ad;acent cathodes. The distance between an anode
and the ad~acent cathode is normally between about 1/8 to
about 3/8 of an inchO
~ -14_
:
~g4~3~
C-6171 The diaphragm cell of the present invention may
utilize anode and cathode plates of variable height. For
example, anode and cathode plates of from about 1 to about
15 and preferably from about 4 to about 12 feet high may
be employed. Increasing the height of the diaphragm cell
permits a considerable reduction in the floor space
required to produce a given quantity of product.
In the operation of the diaphragm cell of the
present invention, an aqueous salt solution, for example~
an alkali metal chloride such as sodium chloride or
~;` potassium chloride~ may be employed. The alkali metal
chloride solution is introduced into the cell as a brine
stream of any desired concentration. The brine level with-
in the cell is brought to a point above the anode and
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3~i
C-6171 cathode sections within the cell. By adjusting the level
within the cell the hydrostatic head or pressure exerted
upon the diaphragm covering the cathodes is varied, thereby
varying the flow of electrolyte through the diaphragm into
the cathode chamber. Under normal operating conditions
the height of the brine above the anode and cathode sections
is from about 3 to about 15 or more inches.
- The anode and cathode sections are spaced apar-t
from the perimeter of their respective plates ~o provide
greatly improved brine circulation within the cell. Pre-
ferably the anode and cathode sections are centered
laterally. They are positioned vertically such that an
adequate brine height and gas release space is provided
above the anode and cathode section. In addition to per-
mitting brine to flow completely around the anodes and
cathodes, the space above the electrode sections permits
a free release of gas produced in the anode. Without being
bound by theor~y, it is believed that when chlorine gas forms
at the anodes and rises, it creates a gas lift action
directed vertically along the face of the anodes. This
gas lift action draws fresh brine from below the electrode
sections, with the fresh brine then flowing upward along
the anodes into the region above the ~nodes, at which point
chlorine gas leaves the brine. The heavier brine, from
which chlorine gas has been partially exhausted, flows
-16-
.
~ ~U ~3 S
C-6171 laterally above the electrode sections and then downward
along the outside edges of the electrode sections.
Current capacities of from about l,ooo to about
3007000 and preferably from about 10,000 to abou~ ~00,000
amps., may be employed in electrolyzing aqueous salt
solutions in the diaphragm cell of this invention.
The following example is presented to illustrate
the invention more fully. All parts and percentages are
by weight unless otherwise indicated.
EXAMPLE
A diaphragm cell, as illustrated in Figures 1-6,
was comprised of a horizontal cylindrical cell body com-
posed of glass fiber reinforced polyester resin and having
an outside diameter of about 92 inches. A flange surround-
ed the openings at each end of the cell body. At one end
of the cell a c~hode plate was bolted to -the flange of the
cell body. The cathode plate, composed of mild steel and
covered with rubber on the inside face, had an outside
diameter of about 96 inches. The cathode section was com-
prised of 27 cathodes, each cathode being welded to the
cathode face. A cathode included a steel plate having a
series of projections to which a steel screen was attached.
Deposited on the screen was an asbestos fiber diaphragm.
The cathodes were about 36 inches long, 30 inches high,
` and 1.125 inches thick and were spaced at a distance of
C-6171 205 inches between centers. The cathode section was spaced
at a distance of about 33 inches from the upper and lower
perimeters and about 14 inches from the lateral perimeters
of the cathode plate.
At the opposite end of the cell body an anode
plate was bolted to the flange. The anode plate was about
96 inches in diameter and was composed of mild steel with
the inside face being covered with rubber. The anode
section had 28 anodes soldered to the anode plate. Each
anode was composed of titanium-clad steel and had a portion
of its surface coated with a ruthenium oxide. The anodes
were about 36 inches long, 30 inches high and 0.18 inch
thick and spaced apart 2.5 inches between centers. The
anode section was spaced at a distance of about 33 inches
~rom the upper and lower perimeters and about 14 inches
from the lateral perimeters of the anode plate. The
cathode plate and ~he anode plate were each externally
supported by a~steel bracket welded to the plate. The
cathode and anode plates supported the weight of the cell
body.
An aqueous solution containing 300 grams per
liter of sodium chloride at a temperature of about 60-70C.
was introduced into the cell body thru the brine inlet in
the cathode plate. The cell operated at a current o~ 76
kiloamperes and a voltage of 3.78 to electrolyze the salt
3~
C-6171 solution to produce chlorineJ hydrogen and sodium hydro~ide.
The catholyte liquor obtained had a sodium hydroxide con-
centration of about 125 grams per liter. The chlorine gas
obtained had a hydrogen ~ontent of 0.3 percent. Over a
period of 106 hours, the cell was operated at a current
efficiency of 97 percent, based on chlorine production.
