U.S. patent application number 12/158909 was filed with the patent office on 2008-12-25 for ozone generating electrolysis cell.
Invention is credited to Ferenc Boncz, Ferenc Darvas, Lajos Godorhazy, Tamas Karancsi, Daniel Szalay, Norbert Varga.
Application Number | 20080314740 12/158909 |
Document ID | / |
Family ID | 37492180 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080314740 |
Kind Code |
A1 |
Szalay; Daniel ; et
al. |
December 25, 2008 |
Ozone Generating Electrolysis Cell
Abstract
The ozone generating electrolysis cell (10) according to the
invention has a negative electrode (13) and an ozone generating
positive electrode (16) comprising a mixture of lead dioxide and
polytetrafluoroethylene (PTFE). A proton conducting solid
electrolytic membrane (15) is arranged between the negative and
positive electrodes (13, 16). The ozone generating electrolysis
cell (10) also comprises an electrically conducting, liquid and gas
permeable first electrode support (17) in contact with a side of
the positive electrode (16) located opposite to the membrane (15),
wherein said side of the electrode support (17) has a surface
covered with a platinum-containing layer. The positive electrode
(16) is made of a mixture prepared by the high-pressure compression
of lead dioxide grains of colloid size and PTFE filaments having a
dimension of at most 1 mm. Furthermore, the negative electrode (13)
is adjoined to a side of the membrane (15) located opposite to the
positive electrode (16) by a given compressing force and is formed
on a surface of a porous second electrode support (12).
Inventors: |
Szalay; Daniel; (Budapest,
HU) ; Varga; Norbert; (Tatabanya, HU) ; Boncz;
Ferenc; (Budapest, HU) ; Darvas; Ferenc;
(Budapest, HU) ; Karancsi; Tamas; (Budapest,
HU) ; Godorhazy; Lajos; (Erd, HU) |
Correspondence
Address: |
HAHN & VOIGHT PLLC
1012 14TH STREET, NW, SUITE 620
WASHINGTON
DC
20005
US
|
Family ID: |
37492180 |
Appl. No.: |
12/158909 |
Filed: |
December 22, 2006 |
PCT Filed: |
December 22, 2006 |
PCT NO: |
PCT/HU06/00126 |
371 Date: |
July 31, 2008 |
Current U.S.
Class: |
204/252 |
Current CPC
Class: |
C25B 11/04 20130101;
C25B 1/13 20130101; C25B 9/19 20210101 |
Class at
Publication: |
204/252 |
International
Class: |
C25B 9/00 20060101
C25B009/00; C25B 1/13 20060101 C25B001/13 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2005 |
HU |
P 05 01204 |
Claims
1. An ozone generating electrolysis cell (10) comprising a negative
electrode (13); an ozone generating positive electrode (16)
comprising a mixture of lead(IV) oxide and polytetrafluoroethylene
(PTFE); a membrane (15) arranged between the negative and positive
electrodes (13, 16); and an electrically conducting, liquid and gas
permeable first electrode support (17) in contact with a side of
the positive electrode (16) located opposite to the membrane (15),
said side of the electrode support (17) having a surface covered
with a platinum-containing layer; characterized in that said
positive electrode (16) is made of a mixture prepared at ambient
temperature by high-pressure molding of lead dioxide grains of
colloid size and PTFE filaments having a dimension of at most 1 mm;
and said negative electrode (13) is adjoined to a side of the
membrane (15) located opposite to the positive electrode (16) by a
given compressing force and is formed on a surface of a porous
second electrode support (12).
2. The cell according to claim 1, characterized in that the PTFE
filaments have a thickness of at most 100 .mu.m within the
mixture.
3. The cell according to claim 1, characterized in that the
positive electrode (16) contains PTFE in an amount of at least 10%
by weight.
4. (canceled)
5. The cell according to claim 1, characterized in that the second
electrode support (12) is a frit molded from grains of an
electrically conductive material at ambient temperature and open
air.
6. The cell according to claim 5, characterized in that the second
electrode support (12) have a grain size gradient in the direction
of depth, wherein the grains of the smallest size are arranged at
the negative electrode (13).
7. The cell according to claim 5, characterized in that the
electrically conductive material of the second electrode support
(12) is titanium.
8. The cell according to claim 7, characterized in that the
negative electrode (13) comprises platinum black applied thereon in
a suspension at ambient temperature and open air.
9. The cell according to claim 1, characterized in that the
membrane (15) is a solid electrolyte membrane with proton
conductivity.
10. The cell according to claim 1, characterized in that the
positive electrode (16) and the first electrode support (17) form
together a single integrated unit.
Description
[0001] The present invention relates to an ozone generating
electrolysis cell comprising a negative electrode, an ozone
generating positive electrode comprising a mixture of lead(IV)
oxide (referred to as lead dioxide) and polytetrafluoroethylene
(PTFE), a membrane arranged between the negative electrode and the
positive electrode, and an electrically conductive, liquid and gas
permeable first electrode support in contact with a side of the
positive electrode located opposite to the membrane, said side of
the electrode support having a surface covered with a
platinum-containing layer.
[0002] Several industrial processes are known for producing ozone
from water by utilizing electrolysis cells. In these processes,
electrolysis cells having a central part for effecting the
electrolysis and thus for generating ozone are used, said central
part being composed of an anode (positive electrode) usually in the
form of a planar plate, a cathode (negative electrode) having the
same construction, and a proton exchange membrane (e.g. Nafion.TM.)
constituting a solid electrolyte in the form of a planar plate
arranged between the anode and the cathode, as it is described in
e.g. U.S. Pat. No. 6,328,862.
[0003] According to the cited document, the anode itself is a
porous member generally made of titanium and having liquid and gas
permeable capabilities. On the (inner) surface of the anode facing
the proton exchange membrane, a thin layer of platinum is applied,
typically by an electroplating process. Between this layer of
platinum and the proton exchange membrane, an electrode layer is
arranged, said electrode layer comprising metallic or semimetallic
conductors and/or oxides thereof (e.g. lead dioxide) characterized
by high overvoltage with respect to the evolution potential of the
oxygen. Adjacent to the outer surface of the anode, ie. at its
surface opposite to the proton exchange membrane, an anode side
collector plate (also referred to as an electrode support) is
arranged in contact with the anode providing on the one hand an
electrical connection between the anode and a power supply, and on
the other hand, an outlet for the gas of oxygen/ozone produced. In
addition, the anode side collector plate can also enable directing
water required for the electrolysis to the anode itself.
[0004] The cathode also comprises of a member made of a porous
material or a material having suitable channels in it, generally
stainless steel or titanium, and having liquid and gas permeable
capabilities as well. On the (inner) surface of the cathode facing
the proton exchanging membrane, an electrode layer containing metal
is applied for generating hydrogen. This metal containing electrode
layer is generally a thin layer of platinum. Adjacent to the outer
surface of the cathode, a cathode side collector plate (also
referred to as an electrode support) is arranged in contact with
the cathode, said cathode side collector plate providing an
electrical connection between the cathode and the power supply, on
the one hand, and directing the water required for the electrolysis
to the proton exchange membrane and to the anode therethrough and,
if necessary, providing an outlet for the produced gas of hydrogen,
on the other hand.
[0005] The above described multilayer electrode structure is housed
in a suitably formed cell housing. In order to make the mounting
easier, the cell housing is usually formed of two halves, which are
aligned and then fixed together in a sealed manner by means of e.g.
through-bolts. The compressive force required for the perfect
contact between the adjacent layers of the electrode structure is
also provided by the mutual screwed fixation of the two halves of
the housing.
[0006] During the operation of an ozone generating electrolysis
cell having the above mentioned structure, water is fed to the
cathode side of the cell and it reaches the proton exchange
membrane and the anode therethrough via the porous cathode side
collector plate and the porous cathode itself (or the channels
formed therein). While applying a voltage for the cell at the same
time, the electrolysis of the water is caused to start and hydrogen
ions with positive charge move from the anode to the cathode
through the proton exchange membrane. At the same time, oxygen and
ozone are generated at the anode due to the electrolysis. The
coefficient of efficiency of the ozone conversion, ie. the amount
of ozone in the produced gas of oxygen, is determined by the
quality of the anodic electrode layer and the operational
parameters, therefore the ozone production capacity of the cell can
be significantly affected through an appropriate manufacturing
technology of the anodic electrode layer.
[0007] According to a common manufacturing process of the lead
dioxide containing electrode layer, the lead dioxide film is formed
on the anode by electroplating. The electrode layer thus obtained
is rather uneven, which implies a change of the superficial
electrical conductivity (resistance) of the electrode layer. In
addition, the electrode layer produced by electroplating can be
formed difficulty, it is rather rigid and it can easily break,
therefore it is not suitable for mass production of ozone
generating electrolysis cells containing solid electrolyte.
[0008] In an alternative method of manufacturing the lead dioxide
containing electrode layer in the form of a separate plate, the
pores of a thin porous PTFE sheet are filled with a mixture of lead
dioxide and the material of the proton exchange membrane, as
described in Japanese Patent No. 3,504,021 and U.S. Pat. No.
6,054,230. The proton exchange membrane is placed on the member
thus obtained, and then its surface is covered with a platinum
containing material. Subsequently, this multilayer structure is
subject to a hot pressing at a temperature between 120.degree. C.
and 140.degree. C. The pressed laminated member is inserted between
the anode and the cathode, and then housed in a cell casing to
obtain the electrolysis cell. The largest drawback of this method
is that lead dioxide is an extremely unstable composition that
easily decomposes due to heat. Hence, if at relatively high
temperatures, regions with various electrical conductivities
develop on certain parts of the surface of the anodic electrode
layer produced by hot pressing due to decomposition of the lead
dioxide, the operation of an electrolysis cell with such an
electrode layer becomes unstable.
[0009] U.S. Pat. No. 6,328,862 discloses a method for producing an
anodic electrode layer containing lead dioxide, wherein a
dispersion of PTFE, pulverised lead dioxide and volatile dispersing
agent (preferably ethanol or isopropyl alcohol) are mixed and the
mixture thus obtained is shaped to a very thin sheet, preferably by
calendering, and the dispersing agent is vaporised, for example, by
heating. Each step of the production of the electrode layer is
performed at a temperature of up to 100.degree. C. in order to
avoid possible thermal decomposition of the lead dioxide. The PTFE
content of the mixture obtained by this method is about 5% by
weight, the film itself is rigid, easily breaking and less ductile.
Moreover, the cost of such an electrolysis cell used as an ozone
generating electrode/electrode layer, where the cell contains lead
dioxide/PTFE film produced from a liquid-phase raw material, is
increased by the use of the corresponding solvent(s) and dispersing
agent(s), and by the treatment performed after the evaporation
thereof from the layers.
[0010] An object of the present inventions is therefore to provide
an ozone generating electrolysis cell which allows to produce the
ozone generating electrode from solid-phase raw materials at
ambient temperature and without the use of dispersing agent.
Another object of the invention is to provide a mixed material of
lead dioxide and PTFE, for example for the anode of an ozone
generating electrolysis cell, that is resilient and ductile due to
its relatively high content of PTFE, that can be prepared at
ambient temperature and that can be produced in less technological
steps and with lower costs than the lead dioxide/PTFE films
commonly used today. A further object of the present invention is
to provide a negative electrode side (cathode side) electrode
structure that in addition to its electrical conductivity and
mechanical strength, due to its structure, inherently has liquid
and gas permeable capabilities, too.
[0011] These and other objects of the present inventions are
achieved by providing an ozone generating electrolysis cell, in
which the positive electrode (ie. the anode) is made of a mixture
prepared by high-pressure moulding of lead dioxide grains of
colloid size and PTFE filaments having a dimension of at most 1 mm,
and wherein the negative electrode (ie. the cathode) is adjoined to
a side of the membrane located opposite to the positive electrode
by a given compressing force and is formed on a surface of a porous
second electrode support.
[0012] Preferred further embodiments of the ozone generating
electrolysis cell according to the invention are specified by the
dependant claims 2 to 10.
[0013] The invention will be now described in detail with
references to the accompanying drawing, in which:
[0014] FIG. 1A is the cross-sectional view of a preferred
embodiment of the electrode structure used for an ozone generating
electrolysis cell according to the invention;
[0015] FIG. 1B is a schematic enlarged view of the material
structure of a preferred embodiment of the second electrode support
for supporting the negative electrode forming a part of the
electrode structure shown in FIG. 1A; and
[0016] FIG. 2 is a longitudinal cross-sectional view of an
assembled ozone generating electrolysis cell comprising the
electrode structure schematically illustrated in FIG. 1A.
[0017] The electrode structure 10 of FIG. 1A used in the ozone
generating electrolysis cell according to the invention primarily
comprises a negative electrode (or cathode) 13, an ozone generating
positive electrode (or anode) 16, a proton exchange membrane 15
arranged between the electrodes 15, 16, and a first (positive
electrode or anode side) electrode support 17 arranged on a side of
the positive electrode 16 located opposite to the membrane 15. The
electrode support 17 is arranged on an (anode side) bearing member
18 provided with a through-hole 19 for an electrical contact. The
electrode 13 is formed on a second (cathode side) electrode support
12 arranged in a (cathode side) bearing member 11.
[0018] The electrode support 12 serves for providing electrical
contact between an external DC power supply (not shown) and the
negative electrode 13, on the one hand, and for directing the water
required for the electrolysis to the electrode 13 during the
operation of the cell, and diverting the produced gas of hydrogen
from the electrode 13, on the other hand. Accordingly, the
electrode support 12 is in the form of a member with high
electrical conductivity and porous structure, as well as with high
mechanical strength in order to tolerate the high pressures of up
to 20 bars that may develop inside the cell. In particular, the
electrode support 12 is a thin and porous titanium frit arranged in
the bearing member 11 and produced by high-pressure cold moulding
of a titan granulate. In the description, the term "frit" is
referred to as a material produced from pulverised grains by cold
moulding. The technological parameters of the moulding process are
adjusted in such a manner that the obtained titanium frit have the
desired mechanical strength, while reaching substantial porosity.
In a preferred embodiment, as shown in FIG. 1B, the titanium
granulate preferably comprises three different sizes of titanium
grains in a layered structure, in which the layers are arranged in
the order of the grain size in such a way that before moulding, a
relatively coarse-grained titanium powder 12a (preferably
comprising grains having a dimension of 600-1200 .mu.m) is put into
the bearing member 11, then a titanium powder 12b of medium sized
grains (preferably comprising grains having a dimension of 350-600
.mu.m) is applied thereon, and finally, a fine-grained titanium
powder 12c (preferably comprising grains having a dimension of
150-350 .mu.m) is applied thereon. Accordingly, the titanium frit
produced by moulding and the cathode side electrode support 12 made
therefrom will issue a grain size gradient in the direction of
depth.
[0019] The cathode side bearing member 11 is made of a special,
chemically resistant plastic shaped to e.g. an annular member. It
is obvious, however, that the bearing member 11 may be made of any
other material and may have any other shape as well.
[0020] An essential condition for the efficient cell operation is
the good electrical contact between the electrodes 13, 16 and the
membrane 15. Therefore, formation of the electrode 13 on the
electrode support 12 made from the titanium frit has key
importance. In the electrode structure 10 according to the
invention, it is preferred that for the negative electrode 13,
extra fine-grained platinum powder (so called platinum black) is
used.
[0021] The platinum black is applied to the electrode support 12 at
ambient temperature and pressure, without the use of a protective
gas (ie. at ambient air) and in the form of a suspension. The
suspension is made from the aqueous solution of 40 mg platinum
black and sodium dodecyl sulphate (SDS) of 1 ml with a
concentration of 0.001 mol/l. For homogenisation of the suspension,
an ultrasonic bath is used for a period of 5 minutes. The
suspension remains stable till its application, that is, no
deposition can be detected. The electrode support 12 is placed onto
an absorbent paper, and then the suspension is applied onto the
surface of the electrode support 12 comprising, the finest grains,
in small quantities by means of an automated pipette. While the
solution is leaking through the electrode support 12 made of the
porous titan frit, the electrode 13 in the form of a continuous
platinum layer is caused to develop on the surface of the electrode
support 12. Smoothness of the surface thus obtained may be
improved, if necessary, for example by pressing. In an alternative
method of applying the electrode 13, water may be used instead of
the SDS solution to produce the suspension, which reduces the
production costs.
[0022] The proton exchange (or proton conducting) membrane 15 is
preferably in the form of a sulphonylated, perfluorinated polymeric
resin membrane, most preferably the polymeric membrane Nafion.RTM.
of DuPont de Nemours, Co. The membrane 15 constitutes the solid
electrolyte of the ozone generating electrolysis cell according to
the invention. In addition, the membrane 15 also provides the
separation of the gases produced on the cathode side and the anode
side. The water required for the electrolysis is introduced at one
side of the membrane 15, through the second electrode support 12
provided with the electrode 13, whereas the gaseous mixture of
oxygen and ozone to be processed is produced on the other side of
the membrane 15, that is, at the ozone generating electrode 16. It
should be noted that harmful deformation/straining of the membrane
15 resulted from the pressure effected through the electrode
structure 10 may be reduced to the lowest possible extent by
providing an extremely smooth surface on the electrode 13 (formed
by the membrane 15) produced in the above mentioned manner. This
contributes to the elongation of life time of the ozone generating
cell according to the invention.
[0023] The positive electrode 16 serves for supporting the anode
side electrochemical reaction. For the positive electrode 16,
electrically conducting metals, semimetals and/or oxides thereof
are used in general. The use of the oxides of transition metals is
advantageous because those are commonly available and inexpensive.
However, the mechanical strength of these oxides is low, thus they
have to be placed on a substrate with high mechanical strength and
chemical resistance against the highly corrosive gaseous mixture of
oxygen and ozone so that said oxides could tolerate the high
pressures arising in the cell during operation without being
mechanically damaged.
[0024] For the electrode support 17 used to support the positive
electrode 16, noble metals (e.g. platinum) with good electrical
conductivity or the alloys and/or mixture thereof can be used. In
the cell according to the invention, a suitably perforated platinum
sheet provided with through-holes preferably having a diameter of
at least 0.8 mm is used as the electrode support 17.
[0025] The anode side bearing member 18 serves for removing the
gaseous mixture of oxygen and ozone produced at the electrode 16
during operation of the cell away from the electrode 16. The
bearing member 18 is additionally used to fasten the electrode
support 17 to the electrode 16 and the latter to the membrane 15 in
order to provide a perfect electrical contact, as well as to
provide a homogenous transition surface therebetween. In a
preferred embodiment of the electrode structure 10 shown in FIG.
1A, the bearing member 18 is made of a resilient, porous,
chemically resistive material, preferably PTFE frit produced from
grained PTFE by high-pressure moulding. The bearing member 18 is
provided with a through-hole 19. In the assembled ozone generating
electrolysis cell according to the invention, the through-hole 19
is adapted to receive an anode side conducting member used for
electrically connecting the anode side electrode support 17 to an
external DC power supply (see FIG. 2).
[0026] In the electrolysis cell according to the invention, the
ozone generating electrode 16 is made of a material with good
electrical conductivity, plasticity, high overvoltage with respect
to the evolution potential and chemical resistance against the
highly corrosive gaseous mixture of oxygen and ozone, preferably a
mixture of lead dioxide and PTFE comprising PTFE in an amount of at
least 10% by weight. The mixture of lead dioxide and PTFE is
produced from solid-phase raw materials at ambient temperature by a
process described below, with no use of further additives.
[0027] On the lead dioxide, which constitutes a component of the
mixture of lead dioxide and PTFE, the evolution potential of the
oxygen is very high and thus, the desired ozone can be produced
thereon with a high conversional efficiency. Said component is
advantageous because it is inexpensive, commonly available,
chemically inert (due to not having a higher oxidation state) and
insoluble in the majority of solvents and it has better electrical
conductivity than certain metals. It is well known that during the
ozone generation, the crystal modification .beta. of the two
possible crystal modifications .alpha. and .beta. of lead dioxide
can be used to perform the desired oxygen-to-ozone conversion,
wherein during the conversion, as proved by X-ray diffraction
measurements, a .beta.-type interfacial recrystallization takes
place. It means that an alteration of the applied lead dioxide (ie.
recrystallization in the course of the reaction) is needed, which
shows a constant value after a period of 2 to 12 days. Before
producing the positive electrode 16, the lead dioxide is subject to
continuous grinding, which results in the production of lead
dioxide grains of colloid size, ie. with an average grain size of
0.5-100 .mu.m, from the initial macroscopic sized lead dioxide
pieces.
[0028] For the other component of the material of the electrode 16,
PTFE elementary filaments having a fibrous (cotton wool-type)
structure, a thickness of 50-100 .mu.m and a length of up to 1 mm
are used. PTFE filaments with such dimensions can be produced by
abrasive machining or abrasion of a PTFE block. The dimension of
the initial PTFE elementary filaments has a definite effect on the
plasticity and resiliency of the final mixture of lead dioxide and
PTFE.
[0029] In order to produce the material of the positive electrode
16, lead dioxide ground into grains of colloid size in an amount
of, for example, about 1600 mg and PTFE in the form of fine
elementary filaments in an amount of, for example, about 300 mg are
put into a mixing jar. The apolar materials can easily mix with one
another. After some agitation, preferably for a period of 10
minutes, the mixture thus obtained is poured into a frit moulding
tool especially formed for this purpose and then pressed therein by
applying a pressure of at least 50 MPa, preferably 250 MPa, to
shape a sheet with a thickness of 0.25 mm. During the moulding
process, the PTFE filaments get tangled and fused, causing the lead
dioxide grains to be joined at the same time. According to a
microscopic examination of the resulted lead dioxide/PTFE sheet, it
has been established that the material thus obtained has compact
dimensions and a continuous surface, it can be easily formed
mechanically, and in addition, it is resilient and ductile.
Finally, the electrode 16 is produced by cutting to the desired
size and shaping the resulted lead dioxide/PTFE sheet.
[0030] It should be here noted that an amount of about 16% by
weight of PTFE in the above mentioned mixture of lead dioxide and
PTFE is advantageous in respect of both plasticity/resiliency and
electrical conductivity. In case of utilisation of larger amount of
PTFE, the mixture will be more plastic but electrically less
conductive. In case of addition of smaller amount of PTFE, however,
the mixture will be less plastic but electrically more
conductive.
[0031] It is important that by means of grinding or another
treatment exerting great shearing forces, the PTFE is subject to a
structural conversion that, according to our experiences, results
in a stabilizing effect on the .beta.-type crystal modification of
lead dioxide. As the method according to the invention, unlike
prior art methods, does not include a step of heat treatment, no
harmful crystal modification changes occur due to that. It has been
experienced that the conductivity of the fibrous electrode is
significantly higher than that of a material having a grained
structure.
[0032] In the embodiment of the electrode structure 10 described
above, the positive electrode 16 and the anode side electrode
support 17 are formed as separate members. It should be noted,
however, that the ozone generating electrode 16 and the first
electrode support 17 may be formed as a combined electrode in such
a manner that a thin platinum layer is applied on a (external)
surface of the electrode 16 made from the mixture of lead dioxide
and PTFE.
[0033] When designing the construction of the cell 100 manufactured
of the electrode structure 10, as shown in FIG. 2 in its assembled
state, and when selecting the materials for the cell 100, the
chemical resistance against the gaseous mixture of oxygen and ozone
and the mechanical strength coming from the pressure of the gas
produced by the electrolysis of water are kept in view. The cell
100 in its assembled state is composed of a cathode side half cell
110 and an anode side half cell 115 that are fixed together in a
form-fitting and thereby sealed manner. The electrode structure 10
is arranged in a seat 140 formed in the half cell 110 and defined
by a bottom wall and a side wall, wherein the bearing member 11 of
said electrode structure 10 abuts on the bottom wall of the seat
140 (see FIG. 1A). The form-fitting abutment is established between
the outer surface of a compressive flange 145 of the half cell 115
and the side wall of the seat 140. The half cell 115 is provided
with a depression 148 for receiving the anode side of the electrode
structure 10, wherein said depression 148 is laterally defined by
the compressive flange 145. In the assembled cell 100, the bearing
member 18 of the electrode structure 10 (shown in FIG. 1A) is in
close contact with the half cell 115 in the depression 148, whereas
compressive flange 145 pushes the electrode structure 10 to the
bottom wall of the seat 140 with firmly fixing it thereby.
[0034] The cathode side half cell 110 is provided with
through-holes (without reference numbers in the drawing) for
sealingly receiving a water feeding connector 160, a hydrogen and
water discharging connector 162 and a cathode side electrical
connector casing 130. The anode side half cell 115 is provided with
through-holes (not marked in the drawings) for sealingly receiving
an ozone/oxygen gas discharging connector 165 and an anode side
electrical connector casing 135. The half cells 110, 115 are made
of a chemically resistant, gas-proof material, preferably some kind
of plastic, and formed preferably by injection moulding, machining
or another shaping process.
[0035] In the electric connector casing 130, there is at least one
current conducting member 150 (see FIG. 1A) arranged for providing
electrical connection between the external power supply and the
negative electrode 13. The current conductive member 150 is in the
form of a member with the capability of reversible deformation
along its longitudinal axis and thereby the exertion of a
compressing force, said member 150 preferably being in the form of
a cylindrical spring. It is also preferred that the electrical
conductive member 150 is made of titanium.
[0036] In the electrical connector casing 135, there is at least
one current conducting member 155 (see FIG. 1A) arranged for
providing electrical connection between the external power supply
and the electrode support 17. The current conductive member 155 is
in the form of a member with the capability of reversible
deformation along its longitudinal axis and thereby the exertion of
a compressing force, said member 150 preferably being in the form
of a cylindrical spring. It is also preferred that the electrical
conductive member 155 is made of platinum. The use of electrical
conductive members 150, 155 in the form of resilient parts allows
to eliminate the changes in dimension due to size deviations and
temperature fluctuations.
[0037] The external walls of the half cells 110, 115, ie. the walls
not contacting with the electrode structure 10, are provided with a
cathode side confining plate 120 and an anode side confining plate
125, respectively. The confining plates 120, 125 serve for
protecting the half cells 110, 115 against the external mechanical
influences. Accordingly, the confining plates 120, 125 are made of
a material with high mechanical strength, preferably stainless
steel. The water feeding connector 160, the hydrogen and water
discharging connector 162 and the cathode side electrical connector
casing 130 are firmly (but releasably) fixed into through-holes
(not marked in the drawings) formed in the confining plate 120.
Similarly, the ozone/oxygen gas discharging connector 165 and the
anode side electrical connector casing 135 are firmly (but
releasably) fixed into through-holes (without reference numbers in
the drawing) formed in the confining plate 125. Finally, in order
to hold the cell 100 in one piece, to seal the electrode structure
10 constituting the central part of the cell 100 and to provide the
required electrical and mechanical contacts between the parts of
the cell 100 (shown in detail in FIG. 1A) in the half cells 110,
115, through-bolts 185 are arranged in through-holes formed in the
half cells 110, 115 and in the confining plates 120, 125, said
through-bolts 185 being fastened by screw nuts 190.
[0038] After producing the above mentioned structural elements, the
cell 100 according to the invention is assembled in the steps
described below. First, the through-bolts 185 are inserted into the
through-holes formed in the cathode side confining plate 120, then
the cathode side half cell 110 is arranged on the confining plate
120 with its seat 140 facing upwards. Next, the cathode side
electrode support 12 and the negative electrode 13 accommodated in
the bearing member 11 are arranged in the seat 140 in a position of
contacting with the half cell 110. The electrode support is then
wetted and the proton conductive membrane 15, which has been cut to
size and shaped, is placed thereon, followed by wetting said
membrane 15 as well. Subsequently, the electrode 16 already cut to
size and shaped and the anode side electrode support 17 are
arranged on the membrane 15. Then the anode side bearing member 18
is placed onto the electrode support 17 and the anode side half
cell 115 is pushed onto the assembly thus obtained, causing thereby
the various parts of the electrode structure 10 to be securely
fixed. Next, the bearing member 18 is wetted, the confining plate
125 is placed onto the half cell 115 and the structural elements of
the cell 100 are forced to each other by screwing the screw nuts
190 to the through-bolts 185, thereby providing the electrical and
mechanical contacts between the structural elements, as well as the
sealed joints. Finally, the connectors 160, 162, 165 and the
connector casings 130, 135 with the current conducting members 150,
155 are mounted into the cell 100.
[0039] During operation of the ozone generating electrolysis cell
100 according to the invention, water is fed into the side of the
cell 100 adjacent to the negative electrode 13, and through the
porous cathode side electrode support 12 and the porous cathode,
the water flows to the proton conductive membrane 15 and further to
the positive electrode 16 through the membrane 15. While applying a
DC voltage with a proper polarity for the cell 100 at the same
time, the electrolysis of the water is caused to start at the
electrodes 13, 16, and hydrogen ions with positive charge move from
the positive electrode 16 to the negative electrode 13 through the
proton conductive membrane 15. The hydrogen ions transform into
hydrogen of neutral charge by accepting an electron from the
negative electrode 13. At the same time, oxygen and ozone is
generated at the positive electrode 16 as a result of the
electrolysis. The efficiency of the ozone conversion, ie. the
amount of ozone in the produced gaseous mixture of oxygen and
ozone, is determined by the quality of the electrode 16 and the
operational parameters. The amount of the generated gaseous mixture
of oxygen and ozone and thereby its pressure under particular
conditions may be adjusted by changing the electrolysing current.
The amount of ozone in the gaseous mixture of oxygen and ozone
generated by the cell 100 according to the invention is preferably
at most 12% by volume.
[0040] Cooling the cell is provided by means of a water flow
introduced through the connector 160 and diverted partly through
the connector 162. It should be noted that on the anode side of the
cell 100 according to the invention, there is no need to divert
water since water not taking part in the electrolysis moves away
from the anode side with exhausting from the cell 100 through the
connector 165, together with the gaseous mixture of oxygen and
ozone, in the form of steam.
* * * * *