Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
C-7210 In the production of halogen gases and alkali metal
hydroxides, such as for example caustic soda, in "diaphragm-
type" electrolytic cells, materials having selective
ion-exchange properties are now becoming available for
use as anolyte-catholyte separator membranes which are
capable of producing solutions having a relatively high
concentration o alkali metal hydroxides as compared with
asbestos fiber diaphragm type cells now in predominant
usage. Production of these concentrated solutions in
commercial "diaphraym-type" electrolytic cells currently
available requires, however, high cell voltages and
results in increased power costs in operating the cells.
By "diaphragm-type" i5 meant an electrolytic cell having
the electrolyte separated into anolyte and catholyte by
a parmeable or semi-permeable separator material so as
to at least lessen the amount of halogen in the alkali
metal hydroxide output stream. By "membrane-type" is
meant an electrolytic cell having the electrolyte
separated into anolyte and catholyte by an ion exchange
separator material, preferably of a cation permeable
composition such as a perfluorocarbon polymer having
pendant sulfonic groups such as marketed hy DuPont
Corporation under the trademark Nafion~. -
Is is now customary to place the membra~e on the
cathode so that there is little or no space between
the membrane and the cathode, even though this arrange-
ment impedes the release of hydrogen bubbles formed at
the cathode.
C-7210 This historic trend t~ward use of cathode-surrounding
membranes is largely a result of the vacuum deposition
methods traditionally utilized to place asbestos fiber
diaphragms on cathodes and the normal flow of electrolyte
being from anolyte to catholyte. Placement on ~he anode
would require the diaphragm to withstand tensile or
ballooning forces caused by conventional flow. With
the advent of fabric-like membranes and more cohesive
diaphragms, we have found it possible to now enclose
the anode rather than the cathode.
U.S. Patent No. 3,984,303, issued to E. J. Peters
and J. E. Loeffler, Jr., describes a cell having a series
of individual units in which a hollow cylindrical cathode
is concentrically arranged around a hollow cylindrical
anode. The anode has a tubular ion permeable membrane
covering its outer surface. While removing the membrane
from the cathode, the concentric electrodes are limited
in size, expensive to fabricate and cell operation would
result in high energy costs. Furthermore, such a design
wastes space as compared with planar interleaved anodes
and cathodes since only one side of the anodes and cathodes
is utilized as opposed to both sides in an interleaved
planar electrode arrangement. There is a need for a cell
design which allows use of beneficial aspects af both
designs. Yet, the planar design seems to rPquire membranes
having a complex glove-like structure, although being
largely adaptable to cell structures previously utilizing
the vacuum deposited diaphragms.
--3--
2~
Therefore it is an object of the present invention
to provide a membrane cell having improved hydrogen
release capabilities.
Another object of the present invention is to
provide a membrane cell having reduced energy costs while
producing concentrated alkali metal hydroxide solutions.
A further object of the present invention is to
provide a membrane cell which permits an enlarged space
between the cathode and the membrane while reducing the
cell voltage.
An additional object of the present invention is a
memhrance cell in which the anode is spaced apart from
the membrane by spacing means ~hich prevent contact between
the electrochemically active portions of the anodes and the
membrane.
Another object of the present invention is a
membrane cell which employs conventional diaphragm type
cell plants.
Yet another object of the present invention is
to make the separator more easily repairable and repairable
without requiring removal of the entire separator from
the cell. `
-- 4 --
A solution to these and other problems i5 the
present invention which provides an electrolytic cell
comprising:
a) cell housing means for defininy a
chamber containing an electrolyte;
b) a plurality of first electrical con-
ductors passing through said housing
and having an exterior sur~ace;
C-7210 c~ a plurality of first planar parallel
electrodes of a given polarity disposed
within said chamber, said first elec-
trodes being in planar electrical contact
with said electrolyte and in electrical
contact with at least one of said
conductors;
d) a plurality of second electrical conductors
passing through said housing and spaced
from said first plurality of electrical
conductors;
e) a plurality of.second planar parallel
electrodes of opposite polarity to said
first electrode means, disposed within
said cell body and alternatingly interleaved
in spacea parallel relationship with said
first electrodes and in planar electrical
contact with said electrolyte and in
electrical contact with at least one of said
second conductors;
f) a plurality of first separator means,
. individually encapsulating each of said
first electrodes, for dividing said
chamber into a plurality of individual
chambers within and i~ediately
surrou.nding each of said first electrodes
and a single common cha~ber within and
.. - . ; . . . _ ~
C-7210 immediately surrounding all of said
second electrodes, said separator means
being at least ion permeable, each
separator means having poxtions defining
at least one first perforation for
passage of at least one of said first
conductors through said separator means
to the first electrode means therewithin,
at least one second perforation for
passage of supply fluid into said indi-
vidual cham~er and at least one third
perforation for passage of product fluid
out of said individual chamber; and
g) seal means for preventing fluia communica-
tion through said perforations between said
individual cha~bers and said common chamber
while allowing passage of said first con-
ductors, supply fluid and product fluid
therethrough.
2~ In yet another aspect, the invention provides a
method of assembling a combination electrode-separator
unit for use in electrolytic cells having interleaved
parallel planar cathodes and anodes, which comprises
the steps of:
a~ encapsulting an electrode with a
layer of separator material to create
a first electrolyte chamber wi~hin
said layer, and
b) providing ior passage of an electrical
conductor, a supply fluid conduit and
a product fluid conduit through said
layer into said created first electrolyte
chamber.
Accompanying Figures 1-14 illustrates the present
invention. Corresponding parts have the same numbers in all
figures.
FIGURE 1 is a side elevational view of a membrane
cell embodying the present invention.
FIGURE 2 is a horizontal cross sectional partial view
of an anode assembly taken along lines 2-2 of FIGURE 1.
FIGURE 3 is a vertical cross sectional view taken
along lines 3-3 of FIGURE 2, further showing an anode assembly
of the present invention.
FIGURES 4-6 are top plan views of various stages in
the assembly of a separator of the present invention.
FIGURES 7-10 are side elvational views showing the
assembly of an anode-separator unit utilizing the separator
of FIGURE 6.
FIGURE 11 is an enlarged cross sectional view of
portion 11 of FIGURE 2 showing one preferred sealing means
of the present invention.
Z , ..
C-7210 FIGURE 12 is a 5iae perspective vie~ showing a
plurality vf anode-separator units at~ached to an anode
backplate.
FIGURE 13 is a horizontal cross sectional view
taken along lines 13-13 of FI~URE 1 showing a preferred
relationship of cathodes and anodes within ~he elec- ¦
trolytic cell of FIGURE 1.
FIGUÆ 14 is a partial horizontal sectional view
of another embodiment of an anode separator unit of the
present invention taken along lines 13-13 of FIGURE 1.
Referring now to FIGURE 1, an electrolytic cell
10 is seen which comprises support means-ll, a housing
12, an anolyte inlet 14, a catholyte inlet 16, an
anolyte outlet 18, a catholyte liquid outlet 20, a
catholyte gas outlet 22, an anode assembly 24 and a
cathode assembly 26. Housing 12 includes a body
portion 28, an anode backplate 30, an anode backplate
gasket 31, a cathode backplate 32 and a cathode
backplate gasket 33. Body 28 can be a tubular metallic
member having flanges 34 and 35 attached to its
respective ends, flanges 34 and 35 being adapted to
receive cathode backplate 32 and anode backplate 30,
respectivPly. Backplates 30 and 32 can be metal-
lic discs attached to flanges 35 and 34, respectively,
by the use of ~olts 36 or any other removable attachment
means. Gaskets 31 and 33 would be interposed between
backplate 30 and body 28 and backplate 32 and body 28,
respectively, in order to sealingly enclose and define an
electrolyte chamber within housing 12. Housing 12 is provided
with suitable openings, as described below, in ordex to
allow raw materials to enter the electrolyte chamber defined
therewithin and to allow the removal of products therefrom.
Anolyte inlet 14 comprises a brine supply header 38 and
a brine supply connector 40 for purposes described below.
Catholyte liquid outlet 20 is connected to the bottom of
body 28 in order to allow removal of catholyte as described
below. Anolyte outlet 18 comprises a chlorine gas and
spent brine header 42 and a spent brine outlet connector 44
which will be described below in more detail. Catholyte
inlet 16 is connected to an upper portion of body 28 in
order to allow supply of catholyte liquid to the interior of
cell 10. This arrangement provides downward flow of catholyte
through cell 10 to catholyte liquid outlet 20. Also provided
is a catholyte gas outlet 22 atop cell body 28 leading to a
hydrogen withdrawal pipe 46. Outlet 22 allows removal of
gases from adjacent the cathodes within cell 10 as described
below. Conductor rods 48 and 49 from anode assemblies 24
and cathodes (not shown), respectively, are connected in
conventional manner to an external DC power source (not shown)
to provide an electric current through cell 10.
Anode backplate 30 and cathode backplate 32 are provided
with lugs 37 to enable cell 10 to be lifted or otherwise
moved and to facilitate removal of backplates 30 and 32
from cell body 28. Also attached to backplates 30 and 32
are support flanges lla which rest on insulators llb which
in turn rest upon foundation llc in order to support cell 10.
Flanges lla, insulators llb and foundation means llc together
comprise s~pport means 11.
-- 10 --
~ ~ . .
C-7210 The construction and configuration of anode assembly
24 is best seen by reference to FIGURES 2 and 3 and com-
prises anode conductors 48, mesh 50, membrane 52, brine
supply tube 54 and anolyte outlet tube 56. Optionally, a
spacer 51 can be provided, separating mesh 50 from membrane
52. Mesh 50 is an electrically conductive material con-
nected to the conductors 48 in conventional manner such
as to allow current to flow there~etween. Mesh 50
can preferably be a U-shaped planar foraminous s~ructure
enclosing an anolyte chamber 72, or could be of any other
suita~le design such as, for example, a louvered electrode
and could be with or without internal gas baffling. Mesh
50 is supported by conductors 48 which are in turn attached
to anode backplate 30 by jamb nuts 58 threaded onto
conductors 48. Tube 56 can project horizontally ~rom the
upper end of mesh S0 or be otherwise oriented in order to
provide for flow of gases and liquids out of chamber 72
and into header 42. Tube 56 is welded or otherwise
attached to mesh 50 and passes through suitable openings,
described below~ in membrane 52. Surrounding mesh 50
is a membrane 52, the construction o~ which will be
described below, membrane 52 serving to contain anions
such as chlorine ions within chamber 7~ while allowing
the passage of cations into the cathodic portion of cell 10.
Header 42 comprises side wall 78, side wall lining 79,
end wall 80, ena wall lining 81, top wall 82, top wall
lining 85, bottom wall lining 83 and bottom wall 84.
.,
Header 42 lies generally horizontal and serves to connect
each of the anolyte outlet tubes 56 to the spent brine
outlet connector 44 ~not shown .in FIGURE 3). The linings
79, 81, 83, and 85 serve to protect walls 78, 80, 84 and 82
respectively, from corrosion caused by chlorine or other
products exiting from tube 56. The particular structure of
header 42 can be varied, so long as it serves to connect each
tube 56 with outlet connector 44. In similar fashion, a
brine supply header 38 is provided to connect brine supply
connector 40 with each brine supply tube 54 leading to
chamber 72. Header 38 can be lined in similar fashion to
header 42 in order to provide corrosion resistance. Brine
supply tube 54 is attached to mesh 50 and projects outwardly
therefrom and passes through anode backplate 30 and is
attached by means of jamb nut 59 and suitable threads on
the outer end of tube 54 to anode backplate 30.
Membrane 52 is sealed along edges 106, 108 and 110
by any suitable sealing means, such as heat sealing, to
pr~vide a U-shaped seal 86 and is sealed at the points whexe
con~uctors 48, tube 54 and tube 56 pass through membrane
52 by sealing means 61, described below. Sealing means 61
and seal 86 serve to close membrane 52 about mesh 50 and
chamber 72 lying within mesh 50. Membrane 52 includes two
portions 88 and 90 lying loosely and non-adherently on
opposite sides of mesh 50 and serving to separate mesh 50
from adjacent cathodes as described below.
C-7210 Referring now to ~IGURE 11, the sealing means 61
will be described in more detail. Sealing means 61
includes an inside gasket 66, an outside gasket 67
lying on the inside and outside of a cen~ral portion
70 of membrane 52, respectively, and surrounding tube 56
to seal between tube 56, central portion 70 and anode
backplate 30. Gaskets 66 and 67 can be com~ressed and
restrained by an annular flange 68 on tube 56 during
the tightening of tube 56 against anode backplate 30
in response to the tightening of a jamb nut 60. As shown
in FIGURES 7 and 10, inside gasket 62 and outsi~e sasket
63 are provided for each conductor 48 to seal between
conductors 48, membrane 52 and anode backplate 30. '
An annular flange can be provided on each conductor 48
in order to compress gaskets 62 and 63 in response to
the tightening of jam~ nuts 58. Likewise, an inside
gasket 64 and outside gasket 65, as seen in FIGURE
3, can be provided on the insi~e and outside of membrane
52 at the point where tube 54 passes through membrane 52.
An annular flange can be provided on tube 54 in order
to compress gaskets 64 and 65 in response to the
tightening of the jamb nut 59. Thus as the anode
separator unit 24 is attached to anode backplate 30 and
jamb nuts 58, 59 and 60 are tishtenedr the perforations
through which conductors 48, tube 54 .and tube 66 pass
~hrough membrane 52 are sealed to "e~velop" or "encapsulate'
mesh 50.
- 13 -
8;~ .
C-7210 Backplate 30 can include a body portion 76 with an inner
lining 74 for corrosion resistance, as in FIGURES 2 and
11, or alternatively be unlined where a cation exchange
memhrane is used as separator 52.and the conductors 48
are separated from backplate 30 by an insulating sleeve
(not shown) or other insulating means.
- 13a -
~L~ 2~
C-7210 FIGURE 12 is a side perspective view showing a
plurality of anode-separator units or anode assemblies
24 supported from the side of anode backplate 30. A
cutaway vie~ is provided showing some of ~he interior
portions of one of these assemblies 24. Specifically
a spacer 51 is seen lying immediately within membrane
52. Lying within spacer 51 coated onto the exterior
of mesh 50 is an optional catalytic coating 11~ which
can be of any electrocatalytically active material such
as a "platinum group" metal~ i.e. an element of the
group consisting of ruthenium, rhodium, palladium,
osmium, iridium and platinum. Mesh 50 is seen to
be a planar foraminous metal anode structure which
prefera~ly has two parallel planar surfaces as best
seen in FIGURES ~, 3, 13 and 14. The units or assemblies
24 are planar and are spaced in parallel so as to allow
interleaving of a plurality of conforming planar
paraIlel spaced cathodes between said anode separator
units r as seen below in FIGURE 13.
FIGURE 13 is a horizontal-cross sectional view
along lines 13-13 of FIGURE 1 showing parallel inter-
leaving of planar cathodes 114 and assemblies or units ~4.
Backplates 30 and 32 are seen lying in spaced paxallel
relationship with units 24 and cathode 114 supported
respectively therefrom. Units 24 are attached by means
of jamb nu~s 58 threadly attached to threaded ends of
conductors 48. As previously seen in FIGURES 2 and 3,
~ 14 -
~.2g~
units 24 are preferably also held by jamb n~lts 59 and
6Q. ~hile jamb nuts 58, 5g and 60 are shown, it is within
the scope of the invention to provide any other conventional
tightening means which can provide compression of sealing
means 61. The advantage of jamb nuts 58, 59 and 60 is
that rapid disassembly is made possible. It will also
be understood that jamb nuts 59 and 60 are optional and
can be deleted by use of a conventional dynamic seal means
(not shown) at the point tubes 54 and 56 pass through membrane
52 so as to allow easier removal of units 24 by avoiding
the otherwise needea removal of headers 38 and 42 in order
to get to nuts 59 and 60. Also seen in FIGURE 1~ is the
use of an unlined anode backplate which can result from
the sealing of the perforations of membrane 52 by use of
sealing means 61 and insulation of conductors 48 from
backplate 30. Sealinq means 61 can be modified for this
purpose by replacing gasket 67 with a larger gasket 118.
Conventional aiaphragm-type cells may be modified to likewise
utilize the concept of individually enclosed anode units 24,
~0 and could apply the concept to cathodes rather than anodes.
That is, the cathode could be enclosed by a synthetic
separator (not shown) in similar fashion to the enclosure
of the anode of FIGURES 1-14. In fact, the enclosed electrode
concept could be utilized on both anodes and cathodes to
produce a three compartment cell, were such desired. Suit-
able cathode headers (not shown) would be required to
connect the individual cathode-separator units in either
case.
f~
The units 24 of FIGURE 13 also include a porous
spacer 51, although this is an optional feature. Membrane
52 is thus spaced from both anode and cathode in order
to allow gas to flow upwardly through cell 10 without undue
restriction by membrane 52. This gas flow can be assisted
by addition of a "gas collecting device" within the anode
unit 24 such as baffles, collectors or sloped or arcuate
conductor shapes (not shown) in order to help collect and
carry gaseous products of electrolysis toward conduit 5h.
~ gap could be provided at the end of unit 24 closest to
backplate 30 by use of suitable spacer collars and extra
gaskets (not shown) about conductors 48, pipe 54 and
pipe 56.
While solid cathodes 114 are depicted in FIGURES
13 and 14, foraminous mesh cathodes (not shown) of
design similar to anodes mesh 50 could be utilized having
catalytic coating or overvoltage reducing platings thereon
as desired. Furthermorel either anodes or cathodes, or
both, could be made contractable by use of a biasing mechanism
~0 to urge the two planar surfaces of mesh 50 or similar
eathodie mesh surfaces apart, the advantage to such
expandability being that the electrodes could contract
during assembly and thereafter expand. Such a mechanism
is shown in our U.S. Patent No. 4,078,987 which issued
Mareh 14, 1978 and which describes a vacuum-assisted method
1 - 16 -
:. :
-7~10 of assembly utilizing a flexible electrode enclosed
by a separator capable of maintaining a pressure
gradient so as to exert compressive forces on the
flexible electrode to contract it during assembly.
Mesh 50 i5 shown in FIGURE 13 with an outside
catalytic coating 112 while FIGURE 14 shows mesh 50
with an inside catalytic coating 116. Where the
outside coating 112 is provided, gas products will
tend to be producea at the outside coating 112 and
hence it is desirable to have a porous spacer 51 to
provide a space for the gas to flow upwardly for
removal from tha cell and to minimize overvoltages.
Such a spacer can be, for example, a screen or net
suitably composed of any non-conducting material.
By use of a spacer 51, the electrocatalytically
coated portions of the foamunous metal anode structure
can be prevented from adhering to the membrane by a
spacing means. Direct contact between the membrane and
electrocatalytically coated portions results in the
loss of current efficiency and when using a platinum
group coating, can result in an increased rate in the
loss or removal of the platinum group component from
the electrode surface.
In the embodiment of FIGURE 13, the spacing means
is, for example, a screen or net suitably composed of
any non-conducting porous chlorine-resistant material.
Typical examples include glass fiber, asbestos filaments,
- 17 -
-7210 plastic materials, for example, polyfluoroolefins,
polyvinyl chloride, polypropylene and polyvinylidene
chloride, as well as materials such as glass fiber
coated with a polyfluoroolefin, such as polytetra-
fluoroethylene.
Any suitable thickness for ~he spacing means
may be used to provide the desired degree of separation
of the anode surace from the diaphragm. Fox example,
spacing means having a thickness of from about 0.003 to
about 0.125 of an inch may be suitably used with a thick-
ness of from about 0.010 to about 0.080 of an inch being
preferred. Any mesh size which provides a suitable
opening for brine flow between the anode and the membrane
may be used. Typical mesh 5izes for the spacing means
which may be employed include from about 0.5 to about 20
and preferably from about 4 to about 12 strands per lineal
inch. The spacing means may be produced from woven or
non-woven fabric and can suitably be produced, for
example, from slit sheeting or by extrusion.
While it is not required, if desired, the
spacing means may be attached to the anode surfaces,
for example, by means of clamps, cords, wires, a~hesives,
and the like.
In another embodiment, the spacing means is the
foraminous metal anode structure itself. As illustrated
in FIGURE 14, the surface of the foraminous metal
structure which is coated with the electrocatalytic
- 18 -
'-7210 material is positioned so ~hat it faces away from the
r.em~rane 52. That is, an inside coating 116 is provided
rather than coating 112. The membrane contacts the
uncoatea surface of the foraminous metal structure.
The coated portion of the foraminous metal anode is
spaced apart fxom ~he membrane ~y a distance which is
equal to the thic~ness of the foraminous metal structure.
This distance, as cited above, is from about 0.03 to
about 0. io, and preferably from about 0.05 to about
0.08 of an inch.
Enclosing the foraminous metal anode structures
and the spacing means is a membr~ne 52 composed of an
inert, flexible material having cation exchange properties
and which is impervious to the hydrodynamic flow of the
electrolyte and the passage of chlorine sas and chloride
ions~ A first preferred memDrane material is a per~
fluorosulfonic acid resin membrane composed of a copolymer
o a polyfluoroolefin with a sulfonated perfluorovinyl
ether. The equivalent weight of the perfluorosulfonic
~o acid resin is ~rom about 900 to about 1600, and preferably
from about 1100 to about 1500~ The perfluorosulfonic
acid resin may be supported by a polyfluoroolefin.fabric.
A composite membrane sold co~mercially by E. I. DuPont
deNemours and Company under the trademark "Nafion n is a
suitable example of the preferred membrane.
-- 19 --
C-7210 A second preferred membrane is a cation exchange
membrane using a car~oxyl group as ~he ion exchange
group and having an ion exchange capacity of
O.5~2.0 mEq/g of dry resîn. Such a membrane can be
produced by chemically substituting a carboxyl group
for the sulfonic group in the above-described "Nafion"
membrane to produce a perfluorocarboxylic acid resin
supported by a polyfluoroolefin fabric. A second
method of producing the above-described cation exchange
membrane having a carboxyl group as its ion exchange
group is that described in Japanese Patent Publication
No. 1976-126398 by Asahi Glass Kabushiki Gaisha issued
November 4, 1976. This method includes direct
copolymerization of fluorinated olefin monomers
and monomers containing a carboxyl group or other
polymerizable groups which can be converted to carboxyl
groups.
~.
-19a -
In the membrane enclosed anode of the cell of the
present invention, the membrane is obtained in tube or
sheet form and sealed, for example, by heat sealing, along
the appropriate edges lQ6, 108 and 110 to form a closed
casing or "envelope". ~his envelope defines a plurality
of anolyte chambe~ 72 therewithin. As illustrated in
FIGURES 2 and 3, the anodes and cathodes are of the finger-
type which are well known in commercial diaphragm-type
electrolytic cells. A preferred type cell is that in
which the finger-like electxodes are attached ~o vertically
positionèd electrode plates, as illustrated by U.S. Patent
No. 3,89~,149, issued August 5, 1975, to M.S. Kircher
and E. N. Macken, modifiea to have headers 38 and 42.
In the membrane enclosed anode of one cell of the
present invention, the gap between the foraminous metal
anode surface and the membrane is from about 0.003 to
about 0.125 of an inch, preferably.
Spaced apart from the membrane enclosed anodes are
cathodes which are positioned, as illustrated in FIGURE 13,
such that a cathode is interleaved between adjacent
anodes. The cathodes are foraminous metal structures of
metals such as steel, nickel or copper. The structures
are preferably fabricated to facilitate the release of
hydrogen gas from the catholyte liquor. It is preferab~e
that the cathodes have an open area of at least about
10 percent, preferably an open area of from about 30 to
_ 20 ~
-7210 about 7~ percent, and more preferably an open area of
from about 45 to ahout 65 percent.
As illustrated in FIGURE 13, the space between
the cathodes 114 and the membrane 52 is preferably
greater than the space between the anode surfaces and
the membrane. In addition, this cathode-membrane gap
is free of obstructing materîals such as spacers, etc.
to provide maximum release of hydrogen gas. The cathodes
are spaced apart from the membranes a distance of from
about 0.040 to about 0.750, and preferably from about
0.060 to about 0.S00 of an inch. It is surprising that,
in producing alkali metal hydroxide solutions containing
at least about 30 percent by weight of the alkali metal
hydroxide, an increase in the cathode-membrane gap
results in a decrease in cell voltage. The cathodes
are attached to a cathode plate which is positioned
so that the cathodes are interleaved with the membrane
enclosed anode compartments, as shown in FIGURE 13.
The ca~hode compartment is the entire area of the cell
body which is not occupied by the membrane enclosed
anodes, ana provides a voluminous section for hydrogen
gas release from the alkali metal hydroxide.
The cathode structures employed in the membrane
cell of the present invention may have electrocatalytically
active coatings similar to those used on the anodes.
They may also be coated with metals such as nickel or
molybdenum or alloys thereof~
- 21
C-7210 FIGURF.S 4-10 show the fabrication procedure for
assembling the anode-separator assembly or unit 24 of
FIGURES 1-3 ana 11-14. As seen in FIGURE 4, a rectangular
sheet 92 of separator material, for example, a cation
exchange membrane of perfluorosulfonic acid resin or
other heat sealable impermeable membrane or permeable
diaphragm, i5 the starting point. The sheet 92 can be
considered to have a central portion 70 and two side
portions 88 and 90. The central portion 70 can be rein-
forced b~ adding an additional layer 94 of separator or
other material to central portion 70 to produce reinforced
sheet 93 for strengthening against damage during assembly
or cell operation and because perforations 95, 96 and 97
(FIGURE 6~ are next made in central portion 70 at prede-
termined locations and of predetermined siæe so as to
later receive conductor 48 and pipes 54, 56 therethrough.
Once the perforations 9S, 96 and 97 are made, the perforated
separator sheet 98 is ready for receipt of anode body
100. Anode ~ody 100 includes mesh 50, conductors 48,
pipes 54 and 56 and gaskets 62, 64, 66 which are placed
around conductors 48 and pipes 54 and 56, respective~y.
Preerably conductors 48 and pipes 54 and 56 have annular
flanges (such as flange 68 seen in FIGURE 11 for pipe 56)
to limit the inward movement of gaskets 62~ 64 and 66
on conductors 48 and pipes 54 and 56 and to compress
gaskets 62, 64 and 66 as previously described. After
,, ' ... .
gaskets 62, 64 and 66 are in place, conductors 48 and
pipes 54 and 56 are inserted through perforations 95 and
96 and 97, respectively, of perforated separator sheet
to produce an unfolded assembly 102. Side portions 88 and
90 are then folded loosely against opposite sides of mesh
50 to form an unsealed folded assembly 104, having adjacent
edges 106, 108, 110. Edges 106, 108 and 110 are then sealed
by any suitable means such as heat sealing to "encapsulate"
mesh 50 and chamber 72 to create a loose fitting anode-
separator unit 24 having a U-shaped sealed edge 86, bordering
three sides and the perforated central portion 70 bordering
the fourth side, as seen in FIGURE 10.
The unit 24 can then ~ecome part of cell 10 by adding
additional gaskets 63, 65 and 67 outside of central portion
70 about conductor 48 and pipes 54 and 56, respectively.
If a full lining is used on backplate 30 (FIGURE 2) gaskets
63, 66 ana 67 could be deleted as gaskets 62, 64 and 66
would be able to seal against lining 74 to seal the
perforations 95, 96 and 97.
Aiso repair of the membranes 52 is simplified as
compared with conventional glove-like separator units.
The cell is electrically disconnected and is drained through
outlet 2Q ana connector 14, a lifting hook is attached to
lugs 37 and bolts 36 of backplate 30 removed, bac~plate 30
is then removed and jamb nuts 58, 59 and 60 of a single
unit 24 are removed, and conductors 48 and pipes 54, 56
pulled out of backplate 30. A new unit is then inserted
and the jamb nuts 58, 59 and 60 tightened onto
- 23
C-7210 conductors 48 and pipes 54,56 after their passage
through backplate 30. The cell is then reasse~bled
by reattaching backpl~te 30 with bolts 56 and
refilling the cell and electrically reconnecting
the cell.
- 23a -
C-7210 EXAMPLE 1
A cell of the type illustrated in Figure 1 is
equipped with a plurality of titanium mesh anodes
having portions covered by a coating having ruthenium
dioxide as the electroactive component. A fiber glass
open fabric coated with polytetrafluoroethylene and
having a thickness of .Q35 of an inch is placed over
the mesh anode. The anode mesh and surrounding fabric
is enclosed in a perfluorosulfonic acid resin membrane
having an equivalent weight of 1200. The membrane is
perforated and heat sealed to form a plurality of
individual casings which are placed over the individual
anoae structures and sealed against the anode plate
linining to provide a plurality of self-contained com-
partments. Intermeshed with the anodes are steel
screen cathodes having an open area of about 45 percent.
The cathodes are spaced apart from the membrane about 0.50
of an inch to provide an unobstructed hydrogen release
area. Sodium chloride brine having a concentration of
about 300 grams per liter of NaCl and at a temperature
of 86C. is fed to each of the anode compartments~
Sufficient electrical energy is supplied to the cell
to provide a current density of 2 KA/m~ to produce sodium
hydroxide liquox in the cathode compartment containing
- ?4 -
C-7210 about 400 grams per liter of NaOH at a cell voltage of
3.5 ~olts. Hydrogen release from the NaOH liquor is
excellent as is the release of chlorine gas from the
NaCl ~rine in ~he membrane enclosed anodes.
ExAMæLE 2
A cell of the type described in Example 1 is operated
as described in Example 1 except that a perfluoro-
carboxylic acid resin membrane having an equivalent
weight of 1200 enclosed the mesn anode and surrounding
fabric instead of the perfluorosulfonic acid resin
membrane of Example 1. Hydrogen release from the NaO~
liquor is excellent as is the release of chlorine gas
from the NaCl brine in the mem~rane enclosed anodes.
EXAMPLE 3
A cell of the type described in Example 1 is operated
at the parameters of Example l except that a potassium
chloride brine having a concentration of 400 grams KCl
per liter of brine is fed to each of the anode compart-
ments instead of the sodium chloride brine solution of
Example 1 and a potassium hydroxide liquor i5 produced
in the cathode compartment containing about 500 gra~ of
KOH per liter of liquor instead of the NaOH liquor of
Example 1. Hydrogen gas release from the KO~ liquor and
chlorine gas release from the KCl brine are both excellent.
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