ELECTROLYTIC CELL SYSTEM WITH FILTER PRESS STRUCTURE

BATTERIE DE CELLULES ELECTROLYTIQUES MONTEES A LA MANIERE D'UN FILTRE-PRESSE

English Abstract

Electrolytic cell system with filter press structure, comprising a plurality
of
single cells arranged in a row, each single cell having an anolyte chamber and
a
catholyte chamber as well as a diaphragm placed therebetween, and being
sealed from the adjacent cells by impermeable cell walls, so-called bipolar
plates.
The anolyte chamber and the catholyte chamber are separated from each other
by an electrode-diaphragm-electrode (EDE) composite layer, the bipolar plate
installed on the anode side forms, by means of sintering or soldering, a stiff
even
support structure together with a corrugated grid arranged in the anolyte
chamber
and with a perforated plate lying flat on the anode of the EDE
composite layer, the bipolar plate, the corrugated grid and the perforated
plate
being made of the same material, and the EDE composite layer is pressed
against the perforated plate by means of a flexible electrically conductive
element arranged on the cathode side between said EDE composite layer and the
adjacent bipolar plate.

Claims

5
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Electrolytic cell system with filter press structure, comprising a
plurality of single cells arranged in a row, each single cell having an
anolyte
chamber and a catholyte chamber as well as a diaphragm placed
therebetween, and being sealed from the adjacent cells by impermeable cell
walls, so-called bipolar plates, in which the anolyte chamber and the
catholyte
chamber are separated from each other by an electrode-diaphragm-electrode
(EDE) composite layer, the bipolar plate installed on the anode side forms, by
means of sintering or soldering, a stiff even support structure together with
a
corrugated grid arranged in the anolyte chamber and with a perforated plate
lying
flat on the anode of the EDE composite layer, the bipolar plate, the
corrugated grid
and the perforated plate being made of the same material, and
the EDE composite layer is pressed against the perforated plate by means of a
flexible electrically conductive element arranged on the cathode side between
said
EDE composite layer and the adjacent bipolar plate.
2. Electrolytic cell system with filter press structure as defined in Claim 1,
in which the bipolar plate, the corrugated grid and the perforated plate are
made of
pure nickel, and the flexible electrically conductive element consists of a
nickel
wire netting.
3. Electrolytic cell system with filter press structure as defined in Claim 1
or
Claim 2, in which the composite layer consists only of a diaphragm and a
cathode.

Description

CA 02128980 2004-07-07
TITLE: ELECTROLYTIC CELL SYSTEM WITH FILTER PRESS
STRUCTURE
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention relates to an electrolytic cell system with filter press
structure,
comprising a plurality of single cells arranged in a row, each single cell
having
an anolyte chamber and a catholyte chamber as well as a diaphragm placed
therebetween, and being sealed from the adjacent cells by impermeable cell
to walls, so-called bipolar plates.
In each case, an electrically conductive connection is to be established in
the
electrolyte chambers between the bipolar plate and the electrodes. The
electrolyte surrounding the anode is called an anolyte and the electrolyte
t 5 surrounding the cathode is called a catholyte.
Electrolysis is a procedure by means of which determined components are
electro-chemically extracted from a watery solution of their compounds. In
particular, the electrolysis of water and the connected production of hydrogen
2o constitutes an important element in the future hydrogen-power-producing
industry. Depending on the intended application, the most different types of
electrolytic cell structures are suitable. Electrolytic cells with liquid
electrodes or
rotating electrodes are known, for instance. In most cases and for commercial
reasons, a plurality of individual cells are gathered into one unit.
2s
Electrolytic cell systems with filter press structure are characterized by a
layer
like arrangement of the individual cells, with constant repetition of
individual
elements which are braced together, forming a complete arrangement.
Therefore, in spite of the tolerances dictated by the manufacturing process, a
3o perfect electrical contact must be ensured in the cell block. This
requirement
results in an alternating arrangement of rigid and flexible building elements
in
the cell. Ullmann's Encyclopaedia of Technical Chemistry, Volume 24,
"Hydrogen" Chapter: Cell Construction, Page 278, describes a construction of

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2
cell partitions in a waffle-shaped stamped form. The formerly flat cell
partition is
stamped using the appropriate procedures, the stamping producing knob-like
prominences on both sides. Seen from the side, the cell partition has
prominences and depressions at regular distances.
s
The patent EP-A 0 297 315 describes a procedure for the manufacture of a
composite part comprised of a cerium layer and a porous metal layer on one or
both sides of the cerium layer which serves as a diaphragm with electrode(s).
In the case of such a composite part comprising electrodes) and diaphragm,
t o called (E)DE composite layer for short, the base material of the diaphragm
is an
oxide ceramic material with calcium titanate, and the electrodes consist of
porous nickel, the base material in this case being nickel oxide. With these
base materials and using a solvent or a binder, a three-layered foil is
manufactured which is then sintered in a reducing atmosphere at approximately
~ s 1200°C. This produces a less than 1 mm thick membrane. Such a
membrane
has a "zero spacing" and contains a diaphragm which is stable in 40% by mass
of
KOH up to temperatures of 150°C. This EDE composite layer is not very
ductile,
it must however be electrically contacted and mechanically stabilized from
both
sides.
The object and purpose of the present invention is the construction of an
electrolytic cell which meets the above-mentioned requirements.
According to the invention, this is achieved in that the anolyte chamber and
the
2s catholyte chamber are separated from each other by an electrode-diaphragm-
electrode (EDE) composite layer, the bipolar plate installed on the anode side
forms, by means of sintering or soldering, a stiff even support structure
together with a corrugated grid arranged in the anolyte chamber and with a
perforated plate lying flat on the anode of the EDE composite layer, the
bipolar
3o plate, the corrugated grid and the perforated plate being made of the same
material, and the EDE composite layer is pressed against the perforated plate
by
means of a flexible electrically conductive element arranged on the cathode
side
between said EDE composite layer and the adjacent bipolar plate.

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The electrolytic cell according to the invention allows establishing an
electrical
contact in a relatively simple manner, as well as effecting the mechanical
stabilization of the EDE composite layer. Because of the oxidizing effect of
oxygen, the contact points on the anode side must be sintered or soldered,
since
s otherwise the contact resistance would be too high, due to the continuing
oxidation. During sintering, a "sandwich" is created, consisting of the
bipolar
plate, the corrugated grid and the perforated plate, which is very stiff. Due
to the
different expansion coefficients of ceramics and nickel, a spatial curvature
would occur after cooling-off in the case of larger cells in which the EDE
to composite layer is sintered or soldered directly to the corrugated grid,
leading to
unacceptable mechanical tensions in the cell block. In the electrolyte cell
construction according to the invention, this is prevented by means of the
perforated plate arranged between the corrugated grid and the EDE composite
layer. The perforated plate is fused or soldered only to the corrugated grid,
but
~ s not to the EDE composite layer. In this fashion, the differences in the
expansion coefficients of the EDE composite layer and of the "sandwich"
consisting of the bipolar plate, the corrugated grid and the perforated plate,
do
not cause unacceptable spatial curvatures within the cell block. The flexible
electrically conductive element arranged on the cathode side makes it possible
2o to press the EDE composite layer firmly against the perforated plate.
One embodiment of the invention is characterized in that the bipolar plate,
the
corrugated grid and the perforated plate are made of pure nickel, and the
flexible electrically conductive element consists of a nickel wire netting.
In particular the use of pure nickel for the bipolar plate, the corrugated
grid and
the perforated plate and the use of nickel wire netting for the flexible
electrically conductive element have proven to be specially advantageous,
while involving comparatively low costs.
In a further development of the invention, it is suggested that the composite
layer
consist only of the diaphragm and the cathode.

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4
In this embodiment of the invention, the perforated plate resting flat against
the
composite layer on the anode side fulfils the function of the anode.
The electrolytic cell system with filter press structure according to the
invention is explained in more detail with reference to Figure 1. Each
individual electrolytic cell is defined by two bipolar plates 1. The
perforated
plate 3 made of pure nickel is placed on the EDE composite layer 2 on the
anode
side. The mechanical stabilization of the EDE composite layer 2 is
accomplished
by means of the corrugated grid 4. The EDE composite layer 2
t o and the perforated plate 3 are pressed flat against each other by means of
the
flexible nickel wire netting 5 on the cathode side.

Representative Drawing