Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~l63L7~
C-8172
MET~OD FOR ASSEMBLING
MEMBRANE ELECTRCtLYTIC CELLS
Background Of The Invention
This invention relates to a method of assembling
electrolytic cells and particularly to a me~hod for
-assembling membrane-type electrolytic cells.
Electrolytic cells have been aeveloped which
S are based on the design principles used in the unit
operation of "filter presses" used to filter solids
from liquids. These~"filter press~ cells have
followe~ the practice originated with filter presses
of assembling plates or frames housing electrodes with
intermediate membranes into a "bank~' o frames supported
with the frames in a vertical plane on~a filter press
sXeleton structureO In general" this is a convenient
method of assembling since the frames may be stored
in place and may be shifted back and forth as the
cell is assembled or dismantled. In the filtration
field, presses are commercially available that shift
frames automatically according to a program. Such
presses are generally used with filter press electro-
lytic cells in order to simplify repairs by providing
easier access to individual membranes and electrodes
: in the cell bank. This techni~ue of using a long
cell bank and a shifting press has several ~isad-
vantages. In particular, it is difficult to hold
,~.
~ :18178~
a membrane which may be wet, slippery, heavy, fragile
and soaked with caustic soda; while trying to simultane-
ously hold the electrode frames in a spaced position
to provide enough space between the electrode for
fitting the membrane between the two spaced vertical
frames and between any cross-frames or other device
used to space the frames to obtain a satisfactory seal
or fit. The membranes, which are very expensive
compared to conventional diaphragms, may tear or "bag"
out of shape or even fail to seal on all gasket surfaces.
Furthermore, it is extremely awkward and difficult to
manipulate larye, high electrode frames in such a filter
press apparatus and, therefore, the height o~ the cell
is limited by practical considerations in order to allow
15- operators to observe and repair minor gasket or membrane
irregularities on many parts of the frame circumference,
e.g. top, bottom, and high sides. Although such a
height limitation has been conventionally imposed
upon filter press cell designs, it would be desirable
20` and advantageous, if possible, to develop a much
higher cell in order to increase the amount of
product which can be produced using a given amount of
floor space in the plant in which the cell is
contained.
It has also been found that treating or
conditioning the membranes is essential if the
electrolytic cell is to operate at optimal efficiency
after assembly. Generally, the membranes are received
in a nonionic state and must be converted to an-
ionic conductive form. ~dditionally, failure to
treat or condition the membrane prior to cell
assembly will cause excessive swelling or shrinkage
of the membrane after the members are emplaced within
the cell and operation of the cell begun. Excessive
swelling causes ~rinkling in the membrane after
cell assembly. This wrinkling creates a crease that
generally bears against the anode and is attacked by
~ 1~178~
chlorine. Apparently the crease from the wrinXle
becomes hardened and splits along its top.
Alternately, where excessive shrinkage occurs,
cracking or rupturing in the membrane will occur.
Either of these two situations where there is a physical
break in .the surface of the membrane causes the cell
to dramatically drop in operating efficiency because
the caustic solution within the anode is pexmitted
ko flow into the anolyte. The quantity of chlorine
gas produced also decreases while current consumption
dramatically increases. ,Addltionally, chlorate
levels increase in the anolyte and catholyte fluids.
A solution to these and other problems
is achieved with the present invention by providing
a method of assembling a monopolar filter press-type
electrolytic cell by treating or conditioning the
membranes, assembling a vertical stack o horizontal
, electrode frames with a horizontal membrane sheet
between each pair of opposed frames, applying pressure
to the opposite vertical ends of said stack to vertically
' compress the stack,,rotating the compressed vertical
stack from a vertical orientation through approximately
90 and connecting and operating the assembled cell
in an electrolytic circuit.
17~
--4--
Brief Description Of The Drawings
The advantages of this invention will become
apparent upon consideration of the following detailed
disclosure of the invention, especially when it is
taken in conjunction with the drawings wherein;
FIGURE 1 is a side, elevational view of a
partially assembled stack o electrode frames during
the practice of the method of the invention;
FIGURE 2 is a bottom, cross-sectional view
taken along line 2-2 of FIGURE 1 illustratiny the
layering of the stack of FIGIJRE l;
FIGURE 3 is a front, elevational view of the
stack of FIGURES 1 and 2 a.fter the stack has been
rotated to a horizontal position and connected in a
series cell circuit;
FIGURE 4 is a side, elevational vie~w of the
cell circuit of FIGURE 3 taken along line 4-4 of
FIGURE 3;
FIGURE 5 is a top planar view of a cell
assembly area adapted for vertical assembly according
to the invention; and
FIGURE 6 is an elevational view of the assembly
area of FIGURE 5 taken along line 6-6 of FIGURE 5.
Il :1.~17~3~
--5--
Detailed Description
FIGURE 1 ls a side, elevational view showing
a stack 10 of anode frames 12 and cathode frames 14
with a spacer 16 and membrane 18 located between each
opposite pair of anode and cathode frames 12, 14.
FIGURE 1 also shows an optional jig 11 which
can be used for purposes of guiding and holding stack 10
during assembly according to the method of the invention.
Other guiding and support structures such as, for example,
the preferred assembly area of FIGURES 5-6 could be utilized
so long as it is still possible to properly align frames 12,
14 in stack 10 during assembly. Jig 11 is shown to be
connected temporarily to an endplate 37 upon which stack 10
rests. During their assembly in stack 10, frames 12 and 14
are maintained in a horizontal or substantially horizontal
plane in order to allow their weight to assist in compressing
the stack 10 and thereby tend to hold spacers 16 and
membranes 18 in position, as well. Jig 11 comprises four
vertical columns 38, two long cross members 40 and two
short cross members 42. Cross members 40 and 42 attach
to column 38 by pairs of bolts 44 (see FIGURE 2). FIGURE
2 also shows the same stack of frames held by columns
38 and cross members 40 and 42. The same reference numbers
in FIGURES 1-4 refer to the same parts, unless o-therwise
indicated. Each frame 12 or 14 has external lifting
eyes 36 which, when the frame is assembled in stack
10, are used to lift the frame. Eyes 36 are adapted
to receive lifting hooks (not shown). Although eight
eyes 36 are shown attached to each frame in FIGURES 1
and 2, any number of eyes could be utilized if desired.
Eight eyes are preferred because this number allows
a hook to be located at the end of each side of frames
12 and 14 so as to minimize the amount of unsupported
frame during lifting and to avoid interference of the
guides with bus bars of monopolar cell frame necessary
to connect the connector rods to a current source for
electrolysis to occur.
'`18~
.
Each frame 12 also includes a pair of
spaced, planar foraminous mesh surfaces 20 and 22
between which lie a plurality of substantially
horizontal conductor rods 24. Similarly, each ~rame 14
includes a pair of spaced, planar foraminous surfaces
28 and 30 between which lies a plurali~y of substantially
horizontal conductor rods 26. As best seen in FIGU~E 2,
each frame 12 includes a sol:id outer border portion 25
and elch frame 14 includes a Erame-like outer border
0 portion 29. Border portions 25 and 29 support
and space the mesh surfaces 22, 24, 28, and 30 while
rods 24 and 26 conduct electricity from ~he outside
of the cell to mesh surfaces 20,22 and 28,30,
respectively. Each frame 12 is provided with an
i5 outlet pipe 34 while each frame 14 is provided with an
outlet pipe 32. In the case where frames 12 are
anodes and frames 1~ are cathodes, pipe 32 would serve
as a hydrogen gas outlet while pipe 34 would serve
as a chlorine gas outlet. Pipes 32 and 34 connect
respectively, to disengagers 56 and 54 (see FIGURES
3 and 4).
The stack 10 shown in FIGURFS 1 and 2 is
termed a monopolar stack since each frame has a single
polarity. If desired, stack 10 could be made in a
bipolar configuration in which each frame should have
one anode side and one cathode side electrically
connectèd to each other. If each stack 10 was made of
bipolar frames, conductor rods 24 and 26 would not be
present since bipolar electrode frames conventionally
3~ have internal conductors from anode surface to cathode
surface.
The stacking operation could be accomplished
through use of overhead cranes and slings which could
be remotely controlled to lift and move and position
the frames into and out of jig 11 during assembly
or disassembly. Membranes 18 could be conveniently
stored in a flatt plastic-lined box filled with hydrolyzing
liquid so that they could be readily moved atop the frames
during the stacking operation. Frames 12, 14 and
~ spacers 16 could be conveniently stored in a cabinet 11~.
~ 161~
A pre~erred method of assembly is to
eliminate jig 11 and to instead use a spirit level
("carpenter's level") to vertically align each frame
as it is lowered and seated on the frames below.
FIGURES 5 and 6 show an assembly area 100 designed for
use in efficiently verticall~ stacking a pack 110 of
frames preparatory to c~ompression and use in the cell
46,48 as previously described. Reference will be made
below to membranes 16 and spacers 18 and o-ther items
shown in FIGURES 1-4.
Area 110 comprises a stack support framework
112, an elevated work platform 114, a membrane storage
box 116, a frame storage cabinet 118, and a,spacer
storage cabinet 142 which is attached to box 116 and
thus placed adjacent a side of framework 112. Stack
110 of FIGURES 5-6 is similar to stack 10 of FIGURES 1-2
except that it is free-standing so as to avoid the need
to lift membranes 18 over a jig 11, since membranes 18
could be damaged during such lifting unless proper care
was taken. With a free-standing stack 110, the membranes
18 and spacers 16 (see FIGURES 1-2) can be slid la-terally
directly onto the top of stack 110 without lifting.
Framework 112 comprises a U-shaped guide
rack 119, a rack holder 120 and four or more air cylinders
122. U shaped rack 119 has a bottom portion and two
recessed vertical member 124, 126 each having recess
128 adapted to align and restrain the outer ends of
rods 24 and 26. Air cylinders 122 are connected to
a ~loor 130 upon which the assembly area is constructed
and to the bottom portion 123 and are used to raise
or lower rack 119 so as to position the top of stack
110 at the best levels for the addition of each membrane
spacer and frame. Air cylinders 122 are preferably
remotely controlled by assembly workers 132,134 as
they assemble stack 110. A conventional remote
control system could be used for this purpose.
~embrane storage box 116 is supported from
a building wall (not shown) adjacent area 100, but
could be supported in any other desired fashion which
would not interfere with the assembly procedure.
1 :1617~
.
~ox 116 comprises a conditioning tanlc 136 and a pair
of "squeegies" or wipers 138~ The conditioning
box 116 can serve multiple purposes. Where a
hydrolyzing fluid is utilized, the box will serve to
hydrolyze the membrane (i.e. converting a salt from
the ion exchange group to the active acid form) so
that the membranes are in their ion conductive form.
The conditioning box also can serve to contain a
fluid that, either separately or concurrently with
the hydrolysis, equilibratas the membranes with the
solution in the box so that the solution pressure of
the water molecules on the membrane is at the desired
level when the membranes are assembled in the cell.
This is achieved by leaving the membranes in the
conditioning solution sufficiently long so that the
water vapor pxessure of the solution is in equilibrium
with the water vapor pressure of the membranes.
The net result of this process is that the membranes,
when placed in the cell, do not absorb water in the
cell and swell or have too much water so that the water
is given off and the membrane shrinks. Should the
membranes absorb water within the cell ~uring operation,
the membranes will swell and cause the aforementioned
wrinkles to occur. Conversely, should the membranes
have excessive water, the water will be given off
during operation in the cell and the membranes will
shrink~ creating the problem of cracking or rupturing
of the membranes. The conditioning box 116 also
serves the purpose o storing the membranes in their
hydrolyzed and/or equilibrated states until they are
used during the stacking procedure.
It is preferred that the membranes be
prepositioned in box 116 prior to the actual assembly
operation so that the membranes can most rapidly be
removed from the box 116 onto the top 140 of stack 110
during assembly. In order to more easily handle
membranes 116 during the actual assembly, it is
preferable to fabricate the membranes ahead of time
1 ~17~
with a loop in one end through which a rigid rod can
be passed, the rod being used as a handle during
the sliding of the membranes from box 116 onto stack
110. The membranes could easily be transferred
directly from a shipping box into box 116 if the
membrane was ~recut into sheets o~ proper size.
rhe procedure for rnoving the membranes from
box 116 onto stack 110 will now be described. First,
the top 140 of stack 110 is adjusted by use of air
cylinders 122 so that top 140 is at the level of the
particular membrane which is to be slid from box 116
onto stack lL0. An operator then grabs the rod which
has been passed through loops in one end of the membrane
as described above, and then pulls the membrane from
box 116 laterally directly onto the top 140 of
stack 110. In this way, the stresses on the membrane
during assembly are minimized. Box 116 is elevated so
that stack 110 will not have moved a great deal and
so that box 116 is at a convenient level for the
operator 132, 134. The sq~leegies 138 are provided
to remove the hydrolyzing or conditioning liquid from
the membranes as they are withdrawn from box 116.
Cabinet 118 is also elevated at a convenient
level for operators 132, 134. Cabinet 118 is provided
with a shelf for each frame of the cell to be constructed.
The frames are stored in cabinet 118 until needed
for the assembly operation. At some time prior to the
assembly operation, cabinet 118 is inspected to see
7 1617~
-10-
that the frames are in proper position for the stacking
operation. It will be appreciated that the frames will
be inserted into and stored within cabinet 118 with
their conductor rods pointing in the appropriate
direction so that there is no need to rotate or flip
the frames during the stacking operation. For purposes
of illustration, FIGURE 5 shows operators 132 and 134
- in position for sliding frames from cabinet 118 onto
the top 140 of stack 110. Lines 144 show the position
of one of the frames as removed from cabinet 118 just
before it is placed atop stack 110.
Platform 114 i5 a conventional elevated work
floor of any suitable material. Platform 114 is
elevated in order that the stack 110 can be lowered
to a position below the level of operators 132 and 134
and so that air cylinders 122 can be provided under-
neath rack 119 without raising rack 119 to an awkwardly
high position.
Although FIGURES 5 and 6 show operators 132
and 134 manipulating frames, it is understood that the
frames could also be handled by a bridge c~ane, a
sling, a hoist, a fork lift, or some other handling
device, such as for example, slide bars extendable from
cabinet 118, if the sizes of the frames were or the
frames were heavy enough to make it undersirable to
move them manually. In this regard, it is emphasized
that this vertical stacking assembly is designed for
use with a membrane~type electrolytic cell which is
rather high in comparison with conventional "filter
press" cells. Special cell designs are under
development which should allow the construction of
frames of sufficient size that manual operation might
become undesirable.
In order to prevent wrinkling or binding of the
membranes or spacers during stacking and during
lateral alignment of the frames in stack 110, a
vibrator could be used to jiggle the membranes and
sheets sufEiciently to make them lie flat after such
alignment operations. Also, a carpenter's level (not
shown) would be used to vertically align the frames
- ~.161'~8~
during stacking and to check the top 140 of the
stack 110 to be sure that top 140 is horizontal to
confirm that the frames are properly seated on their
g~skets so that the cell will be properly sealed
when it is later compressed.
The stack 110 is preferably "preconditioned"
following completion of the stacking operation by
passing warm, moist air through the frames in order
to put the frames at operating temperature~ This
"preconditioning" is desirable so that there is a
minimum of dimensional change Erom the time stacking
is compressed to the time that tlle cell is at operating
condition during normal operation of the cell. If
the cell is not preconditioned r larger forces are
required to compress the cell, heavier frame construction
is needed and the greater forces may tend to damage
the gaskets. Preconditioning softens the gaskets.
Preferably, the tie bolts which compress stack 110
following vertical assembly would be tightened by
application of limited torque in order to put the
stack at a predetermined dimension which has been
previously calculated to provide adequate seating but
yet not compress the gaskets so much that they are
damaged.
The membranes which are preferred for use in
stack 110 are ion exchange membranes having sulfonic
acid or carboxylic acid or moieties as the active ion
exchange group. Such membranes are commercially
available under the trademark ~afion from E. I.
duPont De Nemours and Company or alternatively are
available under the trademark Flemion from Asahi
Glass Co. Ltd. The anode frames 12 are preferably made
of titanium with the mesh surfaces 20,22 being coated
with a catalytic anode coating such as a mixed
crystal of ruthinium oxide or titanium oxide. Other
anode materials could also be used. The cathode frames
14 are preferably made of nickel with a catalytic coating
such as Raney nickel layer or some other catalytic
coating. Frames 12 and 14 could be built of non-
metallic materials so long as the mesh surfaces 20,
-12-
22, 28/ and 30 are made of conductive materials
suitable for use as electrode surfaces. Platform 114
can be built of wood, iron, or any other desired
material. Air cylinders 122 would be of conventional
design and would be provided with a conventional
remote control so that operators 132, 134 could remotely
operate air cylinders 122 during stacking. Box 116
and cabinet 118 could be made of steel, plastic or any
other suitable material; however, a chlorine resistant
material would be preferred since it is expected that
these structures will be exposed to the environment
of a chlor-alkali plant which necessarily produces
highly corrosive products.
With the above procedural description in
mind and the above described apparatus in mind, a
number of advantages are obtained which are worthy of
additional discussion. The cell which is vertically
stacked,rotated, through approximately 90 and then con-
nected can be much large~ than conventional cells and yet ~-~
can be easily inspected for integrity of gaskets
and cells because all sides of the frame are readily
visible during assembly by merely having an operator
work around the perimeter of the vertical stack 110
and check the gaskets on the top 140 of the stack 110.
The procedure is also very rapid because box 116
and cabinet 118 can be positioned at a proper height
to allow rapid sliding of the various layers of stack
110 onto one another~
The economics of this assembly operation are
significant because in a plant of a given number
"x" cells it is economical to spend x dollars on the
cell assembly area to achieve only a resultant one
dollar cost reduction in the construction of each cellO
Also, where each one of x cells is replaced y times
in a given time period it is economical to spend xy
dollars on the assembly area to achieve a one dollar
reduction in assembly operation costs during each
~ 1~17~
. -~3-
replacement operation during such time period.
Conversely, small expenditures on removing cell
assembly techniques can often result in larger
reduc~ions in the cost of operating a commercial cell
plant. Furthermore, since the cell's production is
often lost during the replacement or reconditioning
procedure (i.e. the time during which the vertical
stacXing occurs) large expenditures for assembly
equipment may be justified in order to obtain a
small reduction of cell "down time" during each
replacement or reconditioning operation. In a
large plant, these economics mi~ht well warrant
expensive automatic assembly devices to xeplace
workers 132,134 in order to speed up the procedure
and eliminate operator errors.
Once stack 10 is fully positioned, it can
be tightened by the use of long bolts such as shown
in FIGURE 4 which pass through guide holes in frames
52. Other guiding means and other~bolt means could
also be used such as, for example, flanges on each
frame 12 and 14 which cooperate to individually
interconnect each frame wi~h the adjacent frames
through suitable insulating means. Once the assembled
stack has been bolted together, it is compressed by
further tightening the bolts to some desired pressure
and then the stack 10 is manipulated by a lifting
device such as an overhead crane, fork lift, or other
similar device and rotated from a vertical stack to
a horizontal position. In this new "pack" positionl
electrodes are vertical and the stack is a horizontal
"pack" such as in FIGURES 3 and 4. Prior to actual
operation of stack 10 as an electrolytic cell, it
is necessary to connect rods 24 and 26 to terminals
or bus bars or intercell connectors, so that current
can be passed from cell to cell in an electrical
circuit of such cells. Before operation of the cell,
it is also necessary to connect stack 10 to product
supply and withdrawal conduits so that raw materials
can be fed to the cell and products can be removed
from the cell. In particular, this requires connection
~ ~Bl~
-14-
of each frame 12 and 14 to a source of raw materials
and a product withdrawal line.
FIGURE 3 shows a pair of cells 46 and 4~,
each of which includes a stac-k 10 (see FIGURES l
and 2) of electrode frames which have been vertically
stacked and then rotated 90 clegrees to become a
horizontal stack of vertical frames and which has
been connected electrically and fluidly so that it
can operate as an electrolytic cell. Each cell 46
and 48 is provided with an anode terminal on the right
and a cathode terminal on the left. Intercell
connectors 80 serve to electrically connect the cathode
terminal of cell 48 with the anode terminal of cell
46 so that cells 46 and 48 form an electrical series.
It will be understood that any number of cells similar
to cells 46 and 48 could be included within this
electrical series circuit but that only two cells are
shown for simplicit~. Each cell 46 and 48 is provided
_ with an anolyte disengager 54 and a catholyte _
disengager 56; although if frames 12 and 14 were
sufficiently thick for disengagement to occur
therewith, the disengagers could be omitted. Disengagers
54 and 56 serve to separate or "disengage" hydrogen
gas and chlorine gas from caustic catholyte and anolyte
brine, respectively. The disengaged hydrogen
passes from disengager 56 upwardly through an outlet
line 6~ to hydrogen-removal line 72 while disengaged
chlorine passes upwardly through an outlet line 66
to a chlorine-removal line 70. ~isengager 54
receives fresh anolyte through line 62 and depleted
anolyte is removed from disengager S4 through line
64. Referring to FIGURES 1-4, gas-containing anolyte
is produced within frames 12 and flows from frames 12
to disengager 54 through pipes 34 while disengaged
anolyte is recirculated, if desired, down through a
downpipe 76 to the bottom of frames 12 so as to
increase the upward flow rate of anolyte through
frames 12. Similarly, gas-containing catholyte is
produced within frames 14 during electrolysis and is
fed through pipes 32 upwardly to disengagers 56 while
1 ~ B ~
-15-
disengaged liquid catholyte is recirculated, if
desired, downwardly through a downpipe 74 to the
bottom of frames 14 so as to increase the upward
flow rate of catholyte through frames 14 during
5 - electrolysis.
During assembly of stack-10, an end frame 52
c~n be placed under stack 10 preceding vertical
stacking. If frames 52 are placed under stack 10
during assembly, then end plate 37 of FIGURES 1-2
and end frame 52 of FIGURES 3-4 are the same item.
End plates 37 could alternatively be a pan-type end
electrode frame in addition to frames 52 and would
be extra support for the cell.
If desired, a vibrator could be utilized to
assist in the vertical assembly of the stack by
causing a vibration of the frames such that the
membranes and spacers are better seated. Also, the
vibratlons tend to smooth out any wrinkles in the
membrane during stacking.
The method of the invention is particularly
useful for cells having large frames. By "large"
frames is meant frames having dimensions in the plane
of the electrode greater than about 4 feet. The
method of the invention is also particularly useful
for cells in which the thickness of the horizontal
stack does not exceed about twice the height of the
cell. The large frames and limited thickness to
height ratio are particularly desirable economically
in order to minimize the amount of conductive material
which is needed and to maximize the amount of useful
part per unit area of producer space of any cell
plant utilizing the invention. The number of frames
which may be stacked is within the range from about 2
up to about 50 and preferably within the range of from
about 5 up to about 40 and more preferably within the
range of from about 10 up to about 30 frames. The
method may be used for bipolar cells as well as for
monopolar cells. The size of the frame which may be
used depends more on the requirement of other
~0 limitations of cell design than with limitations
1 1~17~
-16- -
of the present method. Bipolar cells, through the use
of the method of th~ invention, can be designed
practicably ~or sizes from about 2 feet up to about
30 feet in the horizontal d:irection transverse to
current flow, and from about 2 feet to up to about 15
feet in the vertical direction transverse to current
flow. However, the lesser :Length is an advantage
rather than a disadvantage because it eliminates the
need for filter pr~sses to manipulate indi~idual
frames since the cell length is made sufficiently
small through use of the present invention to enable
the cells to be removed from the circuit by use of
jumper switches of economical size without disrupting
current flow through the remaining cells.
lS Monopolar cells of extremely large size would
also be practical within the same ranges with the
added limitation that one direction must be limited to
about 10 feet maximum because of the economic
limitations upon the length of current conductors
such as conductor rods 24 and 26. The size of frames
given in the Example below, approximately 5 feet by
7 feet, are convenient and comparatively large in
~omparison with current technology; however, as is
indicated above, the present invention makes larger
sizes practical.
Prior to application of pressure to the vertical
stack, the frames and membranes can be advantageously
preconditioned by passing warm moist fluid, such as
air, through the frames for a preset time so as to
stabilize the frames at operating temperatureO When
the frames are stabilized at operating temperature-
then the pressure can be applied to compress the stack
the desired amount. Also the membranes may
nee`d to be held at a controlled humidity, once
~161~
-17-
they have been hydrolyzed, in order to prevent irreparable
damage, although the vertical assembly method is
preferably fast enough that drying can be avoided.
Additionally, it should be noted that
different solutions can be employed to hydrolyze and
condition the membranes. For instance, it may be
desirable with certain permselective membranes to
utilize a dilute caustic solution in the range of
1 to 2% concentration at a predetermined temperature
for a period as long as 16 to 24 hours prior to
assembling the membranes in the cell. With other
membranes, it may be more appropriate to utilize a
more concentrated caustic solution, such as 25%
concentration and to leave the membranes in the
solution for up to 16 hours at a predetermined
temperature. For other membranes it may be desirable
to condition and hydrolyze in a 1% brine solution or
in a deionized water solution. Whichever hydrolyzing
and/or c~nditioning solut-ion is utilized to condition
the membrane, it is to be understood that the most
appropriate solution to be emplo~ed must be determined
based upon the type of membrane and the operating
characteristics of the cell. Regardless of the type
of solution employed,, if u-tilized within the method of
assembly of the instant invention, it will be insured
that swelling or shrinkage of the membranes, as
appropriate to the particular membrane, will occur
during the conditioning steps and prior to insertion
into the cell so that such swelling or shrinkage will
not occur during operation. The operation of the cell,
thus, will not be detrimentally affected.
The method of the invention will be better
understood by reference to the following Example
which is included for purposes of illustration:
-18-
EXAMPLE
A cell haviny 70 square meters of electrode
surface with a rated capacity of 150 KA was assembled
using a vertical stacking method. Electrode frames
with gaskets cemented in place were laid horizontal
and vertically stacked in a pile, in inverse order of
assembly. Each frame was approximately ~0" X 60" X 2".
There were twel~e anode frames, eleven cathode
frames, and two end cathode frames which had cathode
mesh surface on one side and a fluid tight surface
on the other. On the adjacent side oE the rectangular
space defining the work area, a flat plastic lined box
was laid containing ion exchange membranes, hydrolyzed,
and wet with hydrolyzing liquid. The box contained
twenty-four membranes approximately 80" X 60".
A structural end frame (80" X 60") constructed of -
6" steel channels having 10 projecting lugs for
anchoring tie rods was leveled on a platform at the
center of the work area. The stack was built in
the order: end cathode, membrane, anode, membrane,
cathode, membrane . . . etc. to the final end cathode
and second structural end ~rame. As each electrode
frame was placed, it was inspected and guided into
position using a 5 foot spirit level (to maintain the
stack vertical and the frame edges in line). As each
membrane was laid in position, it was smoothed flat
and adjusted to extend evenly over the gaskets.
Tie rods with threaded ends were inserted between the
end frames and nuts tightened on the rods by hand.
Four guide frames simply constructed of 2"angle iron
were fitted, two on each side of the stack, to guide
the "collars" on the current conductor rods. These
~uides permitted the stack to be compressed, but
prevented any substantial movement of any individual
frame in the horizontal plane. Nuts were then tightened,
in proper, repetitive sequence until the stack was
tightened to proper dimensions. The approximate
height of the stack including end frames is 66". By
1 1617~
--19--
the use of two hoists, the stack was lifted and
rotated into its operating position where the stack
was 80" tall, 60" wide and 66" long (including
frames). Current conductors were installed and the
cell was transferred to the cell room for start up.
Operation and subsequent inspection indicated that the
gaskets had all been sealed and that all mernbranes
had been satisfactorily placed. The time for stack
assembly was approximately two hours.
