CA2124318A1 - Electrochemical cell - Google Patents
Electrochemical cellInfo
- Publication number
- CA2124318A1 CA2124318A1 CA002124318A CA2124318A CA2124318A1 CA 2124318 A1 CA2124318 A1 CA 2124318A1 CA 002124318 A CA002124318 A CA 002124318A CA 2124318 A CA2124318 A CA 2124318A CA 2124318 A1 CA2124318 A1 CA 2124318A1
- Authority
- CA
- Canada
- Prior art keywords
- cell
- anode
- electrode
- surface area
- electrode structure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/13—Ozone
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
- C02F2001/46152—Electrodes characterised by the shape or form
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2201/00—Apparatus for treatment of water, waste water or sewage
- C02F2201/46—Apparatus for electrochemical processes
- C02F2201/461—Electrolysis apparatus
- C02F2201/46105—Details relating to the electrolytic devices
- C02F2201/46155—Heating or cooling
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2201/00—Apparatus for treatment of water, waste water or sewage
- C02F2201/78—Details relating to ozone treatment devices
- C02F2201/782—Ozone generators
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Primary Cells (AREA)
Abstract
An electrolytic cell having first and second electrode structures in which the first electrode structure has a surface area which is in heat transfer relation with the electrolyte and part only of said surface area is electrolytically active. The first electrode structure may be an anode structure suitable for use in the production of ozone and the remaining part of the surface area of the anode structure may be rendered electrolytically inactive by masking this part from the cathode structure. The masked surface of the anode structure is maintained in heat transfer relation with the electrolyte.
Description
W093/11281 - 1 - 21 2 ~ 31 ~ PCT/GB92/021~7 ELEcTRoc~EMIcAL CELL.
This invention relstes to sn electrolytic cell. The invention relates in psrticulsr to an electrolytic cell in which ozone i8 to be produced.
Electrolytic cells are known in which water is tlssociated into it6 respective elemental species, i.e. 2 and ~2 which are liberated at the snode and cathode respectively. Under flppropriate conditions 03 is alsc produced at the anode.
Shus in European Patent Specification No. 0 041 365 there is described an electrolytic process for the production of ozone in which an electrol~te comprising an 4ueous 601ution of a very highly electronegative snion, for esample the ~cids or salts of hesa-fluoro-anions, is electrol~sed.
~ igh current efficiencies of up to 35~ for the production of ozone have been reported. Current efficiency (-lso ~nown as production efficiency of ozone) is a measure of ctual ozone production relative to theoretical ozone production for given inputs of electrical current, i.e. 35 current efficiency means under the conditions stated, the 2-3 gases evolved at the anode comprise 35~ (of the theoretic~l 03 production) 0~ by weight and that 35~ of the supplied current is utilised in the production of ozone.
Electrolytic cells are also known for the production of ozone which comprise air cathodes ~nd in which the cathode reaction which takes place is the reduction of ambient air to water in an acidic elec~rol~te, the wster then being oxidised at ~he anode to osygen and ozone. Consequently since hydrogen is not producet at the cathode surface. the cell voltage is Eubstantially reduced. Furthermore the construction of the cell is less comples th~n cells which comprise hydrogen evolving cathodes, for es4mple a separator between the anode and cathode is not required since hydrogen is not evolved at the cathode, and control of the oversll 3~ process is simpler, namely the need for periodic additions of water is reduced.
- 2 _ Wo93/11281 2 i 2 ll 318 PCT/GB92~021~7 Thus, in US P~tent No.4 ,541, 989 there is described an electrolytic cell for the production of ozone which comprises a tubular snode F.tructure, the outer surface of which functions ss sn anode within a tubular air cathode structure, the inner surfsce of which functions ss ~
cathode. As disclosed in the aforementioned US Patent it is desirsble in electrolytic cells for the production of ozone thst the current density ~t the snode surface is grester than that at the cathode surface, in psrticular that the ~ current density at the anode surface is at least about twice that of the cathode surface in order that the power consumption due to polari6ation losses at the cathode surface may be reduced, thereby avoiding hydrogen evolutior - and increasing air cathode lifetime.
~, Furthermore, there is a requirement in the electrolyt e production of ozone thst the anode surface is cooled. Use of a cooled anode surface substantially improves the current efficienc~ of the process. It is known for example that where the temperature of the anode is reduced from 25C to 0C, a fourfold improvement in the current efficiency may be obtained. Furshermore, use of a cooled anode in electrolytic cells for the production of ozone often increases the lifetime of the anode.
The anode is typicnlly cooled by the flow of a 2S refrigerant fluid within the anode. It is therefore important that the surface area of the anode is as large as possible in order that effective heat e~change with the electrol~e may take plsce thereby ensuring e~ficient cooling of the anode. On the other hand a low anode surfsce area relative to that of the cathode is desirable in order that the anode current density may be high.
The concentric tubular arrangement as described in U5 P~tent 4, 541, 9B9 provides one way in w~ich the current density may be greater at the anode than at the cathode 3S whilst still allowing efficient heat exchange.
However, this concentric tubular arrangement does suffer from the dissdvantage tha~ the inter electrode gap, WO93/11281 2 ~ 2 3 ~ 8 PCT~GB92/021~7 that is the distsnce between the outer surface of the ~node and the inner surface of the cathode msy be disadvantageously large in order to achieve the required low surfsce area of the anode rel~tive to that of the cathode.
For e~ample, in a cell comprising an inner tubular anode having an e~ternal radius of 2 cm and an outer tubular cathode having an internal surface area twice that of the anode, the internal radius of the cathode will be 4 cm. i.e.
the inter-electrode gap w$1i be 2 cm. This large ~ $nter-electrode gap leads to a high electr$csl resist~nce t~
the flow of current through the cell and an undesirable increase in the voltage of the cell.
These sforementioned problems arise in particular with this arrangement where the cathode ls an air cathode. In addition to the aforementioned operational problems, ai:
cathodes are difficult to fabricate in 8 tubular form and they lead to mechanical problems during manufacture of the electrolytic cell, for e~ample sealing within the cell.
~ccording to a first aspect of the present invention there is provided an electrol~t$c cell comprising first and second electrode structures, at least the first electrode structure having a surface area $n heat e~change relation with the electrolyte and part only of said surface area being electrolytically active.
2~ Typically, each of the first and ~econd electrode strurtures has a surface area which is in heat transfer relation with the elec~rolyte, a part only of said surface area of the first electrode structure being electrolytically active and the active surface area of said second electrode structure being greater ~han that of the first electrode structure.
In an electrolytic cell in which ozone is produced, the first electrode structure is an anode structure and the second electrote structure is a cashode structure, the 3~ electrolytically active surface area of the cathode structure being greater than that of the anode structure.
WO~3/11281 PC~/GB92/021~7 ~ 212~3~
Although the invention is described hereafter wls~
reference to an electrolytic cell in which ozone is to be produced, we do not exclude its ~pplication tO generstior. of products other than ozone.
The active surface areas of the anode ant cathode structures will usually be of such an estent that in operation the current density established at the surf~ce of the anode structure is at lesst 20Z greater than that established at the surface of the cathode structure.
Preferably the current density established at the surface of the anode structure is at least 50~, especially at least 802 8reater than that established at the surface of the cathode structure.
The anode structure may have high surface area in heat ~ e~change relation with the electrolyte, thus faci1itatir.g efficient heat exchange, yet only a part of that surface area is electrolytically active thus ensuring re~atively high anode current densities, relative to the cathode current densit~.
By electrol~ticallr active anode sur~ace~ there is mesnt that part of the anode surface at which the electrolytic process takes plsce, that _s that part of the anode surface with which the cathode surface has substan~ial electrical interaction, i.e. current ~n the form of a flow 2S of ions through the electrol7te takes place between the active anode surface and the active cathode surface.
In one form of the invention the ~node structure may be cons~ructet from different ms~erials; for essmple one part of the anode structure ma~ be construct2d from a suitable anode material which presents said electrolytically active ansde surface, and a second part may be constructed from a material which is not capable of functioning as an electrolyticslly active anode 6urface. In this case, the ancde surface $ncludes both the surface which is constructed 3S from a suitable anode material and the surface which is not so constructet, although the surface which functions as sn WO93/11281 ~1 2 4 3 ~ ~ PCT/GB92/02157 active anode surface is only that surface which is constructed from B suitable anode material.
~ owever, for simplicity of construction, we pre.er ~ha:
at least that part of the anode structure which has 5 surfsce sres esposed for contact with the electrolyte in operation of the cell is made completely from a material which is suitable for use as an anode snd thst a portion of the esposed anode surface is prevented from functior._n6 as n active anode curface by suppressing the elect-olvtic interaction between that portion and the cathode structure, for esample b~ providing means for masking that portion of the ancde 6urface from the cathode surface.
~ ccording to a second aspect of the present invent'c..
there is provided an electrolytic cell comprising fi-s: and 1~ ,second electrode structures, part only of the surface sres of at least the first electrode structure being electrolytically active, and means for masking the remaining part of the 6urface area of the first elec~rode structure in such wa~ as to render said remaining part of the surface area substantially electrolytically inactive.
The masking mesns msy comprise for es~mple, a coating, cover, insert or any other suitable part, such tha~ therP i5 substantially no ozone producing electrol~tic interactior.
between the masked portion(s) of the anode surface and the 2S csthode surface.
The masking means may take any suitable shape and form provided that it ~uppresses the electrolyt~c interaction between the masked portion of the snode surface and the cathode surface. The material used for effecting masking is t~pic~ therefore an electr~cally in~ulating material. The material should also be inert to the electrolyte, which may be highly corroaive. Suitable materisls include inert polymeric materials such as polyvinyl chloride or polyfluorinated polymers, for esample . 3~ pol~tetrafluoroethylene which are electrical insulators and which h-ve resistance to osidising gases and escellent resistance to highly acidic and corrosive solutions.
The e~tent of the masking should be such as tO achieve the desired current density difference between the active anode surface and the cathode surface. Thus the unmasked anode surface ares which functicns as a~ active anode surface should be less than about 80~ of the area of the cathode surface, preferably less than about 60~ of the cathode surface.
The anode structure may have any suitable form, for e~ample it may be in the form of a tube or or it may be a planar anode. The electrol~tically sctive and inactive surface areas of the anode structure may be distributed around the periphery of the anode strueture. The anod~
structure may have an elongate configuration and the active and inactive surfaces may estend longitudinally of the ,elongate anode structure.
The electrolytic cell preferably further comprises means for circulating a coolant fluid in heat transfer relation with the an~de structure in such a way that hest exchange i8 ~ecured between the coolant a~d the electroly through the active and inactive surface are~s of the anode structure. A particularly preferred form of the anode by which such coolant circulation may be achieved is a tubular anode, the lumen of which provides a path for the flow of a coolant fluid. The coolant fluid may flow through the lumen of the anode or the lumen may be provided with a member e~tending within the lumen, for esÆmple a hollow finger through which the coolsnt fluid is caused to flow. The cold finger may be constructed, for example, of copper.
The surfsce area of the tubular anode ~tructure which is exposed for contact wi~h the electrolyte may be the outer surface or periphery of the tubulsr structure, and the electrolytically active and inactive parts of this surface area may therefore be distributed peripherally around, and estending longitudinally of, the tubular struc~ure.
In order that heat eschange may take place through the inactive surfaces of the anode structure, the electrolytic cell preferably comprises means for routing the electrolyte WO93/11281 212 4 31~ PCT/GB92/021~7 along a path in which it is in he~t exchange relation Wit:.
substantially electrolytically inactive part of th~ surface area of the anode structure. Where the ~node structure is of elongate configuration, the routing means preferably - provides at least one flow path e~tendinB longitudinally of the ~node structure.
~ he active and inactive surfaces of the anode struc~ure msy extend generally co-estensively with one another longitudin~lly of the anode structure.
ln orter that ss little a6 possible electrolytic interaction should take pl~ce between the cathode s~ructu-e and the inactive anode surface~s), the cell preferably comprises mesns for preventlng the flow of electrolyte peripherally of the anode structure from a regior. where the electrolyte is in commun~cation with an active surface of ' the anode structure to a region where the inactive surface are~ is locsted.
The csthode structure may take any 6uitable form although we generally prefer to use a plsnar or tubular 2~ structure. Where the csthode structure is in the form of a tube, the inner surface of the tube may be the electrolytically acti~e cathode 6urface and the radius of the inner surface of the cathode structure may be reduced compared to that hereinbefore described with reference to US
2~ Patent 4,541,989 thus reducing the inter elec~rode gap but maintaining the differential current density between the electrolytically active anode surface and the cathode surface.
Preferabl~ however, the cathode structure is of a planar configuration since ~e prefer to employ an air c~thode (as described hereafter). Air cathodes of planar configuration are readily manufactured and are easily installed in the electrolytic cell. Furthermore, ~n elec~rolytic cell comprising st least one tubuler anode snd 3~ at least one plsnar cathode allows both si~ple scaling of the cell to much larger sizes BS hereinafter described, and fscilitstes the schievement of the current density 212 i31g difference between the active anode surface and the ca: ~de surface defined according to the first aspect of the invention.
Where the cathodic structure is of plansr configuration, we prefer that two of said cathode structu es of planar configuration are present in the cell and that the anode structure is located between, and in spaced relation with, said cathode structures and that the anode struc~ure has separste electrolytically active surfaces in confron~
l relation with the cathode structures. The anode structures may then hsve electrolytically inactive surface areas located between the said separate active surface areas. We psrticulsrly prefer to employ a plurality of said anode structures, each having electrolytically active and inac~ive anode surface areas. The anode structures may be arrange~
between the two plsnar cathode structures in a direction paralle} to said cathode structures.
~ccording to a third aspect of the present inventio&
there is provided sn electrolytic cell for the production of ozone comprising at least one tubular structure the outer surface of which functions as an anode surfsce and at least one planar cath~de structure.
A cell in accordance with this third a6pect of the invention may incorporate ~severally or collectively, or sny combination ~hereof, as the conteYt admits~ those features of said first and second aspects of the invention as discussed hereinbefore.
In ~ preferred embodiment of this third aspect of the invention, the cell comprises at lea~t two pla~ar cathotes between which nre located one or more tubular anodes, preferably at least two tubular anodes. The number of tubular anodes which are employed depends 5t least to some estent upon the desired rate of production of ozone from the cell, the dimensions, in particular the length snd diameter 3S of the tubulsr anodes and the current density at the electrolytically active anode ~urfaces during operation of the cell. Thus, the cell msy comprise up to about 12 tubular WO93/11281 212 ~ 3 l~ PCT/GB92/021~7 anodes where ozone production in the order of loo g~hour ie desired. The ease with which the cell msy be scaled up in orter to increase the rate of production of ozone, sim~lv b~
the provision of further tubular anodes between the air cathodes and increasing the length of the ~node tubes and area dimensions of the planar air cathode, is 8 substantial advantage of this third aspect of the invention.
Furthermore, the cell may comprise more than two planar cathode structures, with one or more tubular anode ~ structures arranged between each pair of cathode structures such that the cell may comprise a row of tubular anodes between each pair of opposingly faced planar cathodes.
Further, in the electrolytic cell accorting to this third aspect of the invention, preferably onlv a portion of ~the outer surface of the tubular anode which is in heat eschange relation with the electrolyte is electrolytically ctive, and advantageously the cell comprises means m~sking the remaining part of the surface area of the anode ~ structure in such a way as to render it substantially - electrolytically inactive.
Active and inactive portions of the anode surfsce area may be defined by providing in the cell a first boundary means for bounding `eogether with the csthode structure and a part only of the 6urface area of the anode structure a 2S chamber for enclosure of an electrol~te whereby said par~
only of the anode surface area constitutes an electrolytically active surface area of the anode ~truc~ure snd second boundary means for bounding together with a further part or parts of the surface area of said anode structure ae least one channel in fluid communication with said chamber to provide for flow of electrolyte over said further part(s~ of the surface area of the anode structure, said further parts constituting a substantially electrol~tically inac~ive surface area of the anode . 35 structure. The first and second boundary means may furthe.
constitute a masking means as hereinbefore described, and ma~, for e~ample be provided by an insulsting body or bodies extending between the anode surface and the cathode surf-~e.
The, or each insulating body msy be in the form of, for e~smple, a wedge-shaped member or truncated cone, wlth its narrow end in contact with and e~tending from the cathodo surface to it6 wide end in contact with the outer surface of one or more anode structures whereby to mask that portion of the surface area of the anode structure which is not in confronting relation with the cathode surfaces, from the cathode 6urfaces.
The flr6t and 6econd boundary means, for e~amp'e one or more insulating bodies may be provided as separate inserts for provision within the cell. Conveniently however, the o-e-ch insulating body is formed as part of a cell bod~
which the anode and cathode structures are supported. Thus ,,the cell body may be so configured that i~ mask~ ~he surfaces of the anode which are not ir. con~-ont ng el&~_or.
with the cathode surfaces.
The acti~e anode surface will in this case be the surface of the anode ad~acent the cathode surface and the me-n di~tance between the acti~e anode surface and the c~thode surface is preferably less than lOmm, more prefe~ably less than 5mm and especially less than 4mm.
~s hereinbefore described it is desirable that as gre&.
an area of the anode structure as possible is in contact 2S with the electrolyte in order to achieve good heat exchange efficiency between the electrolyte and the anode surface whereby efficient cooling of the sctive anode surface ie obtained. We therefore prefer that the masked portion(s) o-^
the anode surface is ne~ertheless e~posed tO the electrol~te.
Where the masking me~ns is in the form of one or more wedge-shaped in~ulating boties e~tending from the cathode surface to the anode surface, the wedge may be shaped such that the wedge onl~ comes into contact with a small area of 3S the anode surface to be masked. For e~ampie, the wedge may be cut away to form circulation channels. at the portion of the wedge which is adjacent the anode surface to be masked WO93/11281 ~ 21~ 4 31~ PCT/GB~2/02157 so that electrolyte msy circulate over the ~node surfac~
between the masking wedge member and the anode surface.
Thus, even though the masked portions of the anode structure pla7 no significant part in the electrolytic interaction, the electrolyte may flow freely over substantially 811 or a section of the masked and electrolytically inactive portion of the anode structure, providing an ~ncreased totsl surface srea for heat e~change and thus cooling of the active anode surface.
~ ~ further advantage of the provision of, for example, re-circulstion channels atjacent the masked and elec~rolytically inactive anode portionts) is that a recirculating flow of electrolyte may be achieved over the active anode surface which serves to remove bubbles of 'gaseous products which may form on the active anode surface and which may, if not removed, lead to an increase in the cell voltage. This flow of electrolyte is achieved because substa~tially no electrolysis takes place within the recirculation channel~ so th~t the electrol~te $n the channels tends to be unga6ified. whereas the formstion of gaseous products of electrolysis takes place in the electrolyte chambers thus protucing a gasified electrolyte.
A recirculating flow of electrolyte is there~y generated by the density difference between the gasified and ungas;f,ed 2S electrolyte.
Fluid-tight seals should be maintained between the electrol~te chambers and the re-circulation channelç in order to prevent current leakage from electrolyte betweeh ~he aetive anote and cathode surfaces to the electrolyte flowing within the recircula~ion ch~nnels.
~ccording to a fourth a~pect of the present invention there is provided an electrolytic cell for the production of ozone comprising an anode structure, n cathode structure and a chamber for containing electrolyte within which 3S slectrolysis occurs and which further compri~es a~ least one re-circulation channel in fluid communication with the electrolyte but within which electrolysis does not occur.
The recirculation channels may be provided wit~ .e cell itself or they may be pro~ided e~ternally of the ce.'.
As hereinbefore described we prefer to provide ~he recirculation channels within the electrolytic cell and especially adjacent the electrolytically inactive anode surfsce.
Cell heat spaces which may serve as both disentrainment areas for product gases and reservoirs for electrolyte may be provided within the cell, into and from which elec:rolyte ~ from and into both the electrolyte chambers between .he active anode and cathode surfaces, and recirculation channels may flow, and from which product gases may be collected.
~ir cathodes, which are commercially available ' components, are t~pically composed of polytetrafluoroethylene-bonded-carbon containing sma'l mounts of catalytic materials, for e~ample platinum.
The materials used as the snode surface in the electrolytic cell of the present invention m~y be conventional anode materials BS descrlbed more fully ir" for example, Et~ropean Patent 0 041 365. The anode surface may be constructed from platinum or lead dioxide, particularly leaa dioxide in the beta crystalline form. ~owever, a special form of carbon, specifically vitreous or glassy carbon is 2S particularly preferred for use as the anode surface ma~erial s~nce it has a high oxygen overpotential and thus a h gh efficiency for ozone production, it is 6table in strong acid electrolytes and is ~table to oxidising cond~tions generated in the cell. Furthermore, glass~ carbon is a material which possesses poor electrical conductivit~ so that where current is fed to the anode structure through a conducting memeber provided adjacent only the electrolytically active surfaces of the anode (as described hereafter), current tends not to lesk from the electrolytically active anode ~S surface to the electrol~tically inactive anode surfaces.
The electrolyte used in the electrolytic cell is typically a known electrolyte, for example, an aqueous W093~11281 21~ 4 3 1 ~ PCT/GB92/02157 solution of ~ highly electronegative snion (~nd associ~ted cation) such as are, for example, described in European Patent O 041 365. The electronegative anion used is preferably as electronegative as possible, ~nd more preferably is a fluoro-ani~n. The fluoro-anion may be the fluoro-anion of B Group V-B element of the Periodic Table, for esample pho6phorous and arsenic which form hexa-fluoro anions. Other related non-metallic elements such as Si and Sb also form hesa-fluoro-anions. Other su~table fluoro-anions ma~ be mentloned, inter alia P02F2-, HTiF~-, NbF72-, TaF72~, NiF62-, ZrF62~, GeF62~, FeF62-. The phosphorou6, ar6enic, boron and silicon fluoro-anions ~re the preferred anions for addition to the squeous elec~-nly~
and in particular polyhalogenated boranes. We especial!y refer to emplo~ the tetrafluoroborate in on.
The fluoro-anions may be added to the aqueous electrolyte 601ution in the form of their respective acids or as w-ter-601uble salts. Whereas the acid-form of the fluoro-anions may be preferred because of their hi8he~
solubilitles in water, the fluoro-anion salts, for esample 60dium or potas~ium, offer the sdvantage that their aqueous solutions have higher p~'s than do the solutions of their - respective acid forms, and they therefore are less corrosiv~
towards the cathodes.
2S ~or current efficiency, it is desirable to increase the fluoro-anion concentration in the electrolyte to its maximum solubility since increasing the anion concentration increases ozone current efficiency. ~owever, an increase in the snion concentration also increase6 the corrosivity of the electrolyte towards the cathodes. Suitable anion concentrations may be readily determined by routine experimentation.
The construction of the electrolytic cell may, apart from its construction according to the various aspects of 3S the invention as hereinbefore tefined, follow conven~ional tcchnolog~ taking into consiteration the corrosive nature of the fluoro-anion electrolytes and the high osidising power WO93/11281 212 4 318 PCT/GB92/021~7 of the ozone gases. Thus, the parts of the cell in conta~
with the corrosive electrolyte and o~idisin~ products of electrolysis are preferably constructed Oc materisl~ whi~
are inert both to the highly corrosive electrolyte snd the oxidising gases. The cell body may therefore be ccnstruct~d from, or coated with, an inert material, for esample an inert pol~meric material such 85 polyvinyl chloride or polyfluorinated polymers, for example polytetrafluoroethylene which have resistance to oxid$sing gases and excellent resistance to highlv ac~d and corrosive solutions.
Where the cathodic reaction taking place in the cell produces h~drogen, the anode and csthode compartments o_ -he cell should be separated such that the h~drogen evolved ~t l~ ~'the cathode is not in fluid-flow contac~ with ~he gases evolved st the snode. Such separators are well knowr. ~s the art. Conventionally they are prepared from a perfluo.inPt~r pol~meric cation exchsnge material, for example ~Nafion"
~rcgistered Trademark of E.I.Du Pont). Such a separator _ not needed in the preferred embodiments of the invention where an air cathode is used and where hydrogen is no~
generated by the cathote process.
The anode and cathode structures are disposed within the electrolytic cell with electrical leats lesding tO the 2S exterior of the cell. Electrical potential may be spplied tC
the anode by contact with part only of a surface of the anode structure which corresponds to the electrolytically active surface area of the anode structure, for example by means of a conducting member, constructed from, for example, copper, which is provided along the snode adjacent the active anode surface in order that current is fed predominantly to the active snode surface and not to tha~
anode surface which is masked from the cathode. The conducting member is preferably provided on a surface of ~h~
~S anode which is not in direct contact with the electrolyte~
for example where the anode is in the form of a hollow tube the conducting member may be provided within the lumen of WO93/11281 - l5 - 2~ ~431 ~ PCT/GB92/021~7 the tube, in order that the conducting member is protectec from the electrolyte.
The cell is sealed prior to use, and the cel' hesd space is provided with suit~ble inlet ~nd outlet passages ;~
for water mske-up, where necessary, and the withdrawal of the gases evolved from the cathode (where hydrogen is produced) ~nd from the anode. Two discrete gas removal systems ma~, where necessary, be used to keep the cathode g~se~ separ~te fro~ the ~node gases. Nitrogen and/or air maY
be sdded, for e~ample pumped through. the gas h~ndling system in order to entrain the evolved cathode ~nd anode g~ses and carry them from the cell to the esterior where they may be stored or utilised in the desired application.
The snode ~nd cathode structures sre connected by the ~-~aforementioned electrical leads, optionally through a conducting member, to a source of power external to the cell. Typically the cell is oper~ted at electrical potentials in the order of 3-7 volts. The current densit~ e~
the snode surface m~y be in the range from ~bout a tenth o' an ampere per 6quare centimetre of effective a~ode surface up to about l.0 ampere per square centimetre of effec~ive anode surface.
The invention is illustrated with reference to the 2~ sccompanying figures in which:
Figure 1 is ~ diagrammatic partly cut away view of an electrolytic cell according to the invention, Figure 2 is s view in section along the line A-A in figure 1, Figure 3 is a view in section through the cell of Figure l along the line B-B in figure 2, - 3~
Figure 4 i6 a view in section through the cell of Figure l slong the line C-C in figure 2, - 16 _ WO93/11281 2 12 ~ 3 1 8 PCT~GB92/02157 Figure 5 is a view in section along the iine D-D in ~ igure 3, and Figure 6 is a view in section along the line E-E in fi~ure 3.
Figure 7 is 8 view in section along the line F-F in figure 3.
Referring to Figures 1 to 7, an electrolytic cell suitable for tbe generation of ozone shown generally as 1 :~:
Figure 1 co~prises a main cell boty 2, havln~ top and ~ct;om portions 4, 6 and spaced columns 8 extending there~etween~
~lthough three such columns 8 are present in the illust-~ted ~,,embodiment, a pair of end columns 8A and an intermediate column 8B, there may be more or less according to the r.umbe-of anode structures employed. A pair of air cathodes 10 wi~.
associated air chambers 12, and located between but spaced from the air cathodes ~0, a psir of tubular glas~y carbon anodes 14, are supported in the cell body. The colu~ns B, which support the snodes and cathodes in spaced relatior.
~-ith one hnother, constitute means fcr bounding, togethe~
with active surfaces 16 of the air cathodes 10 and psrts only of the outer surfaces of the anodes 18 which are in 2S confronting relstion with the active surfaces of the air cathodes, electrolyte chambers 20. The electrolyte chambers 20 extend longitudinally from the top portion 4 to the bottom portion 6 and at each end open into upper and lower cell spaces, 22, 24 respectively ~see Figure 3) within the top snd bottom portions 4 and 6, the arrangement being suc~.
that each cell space is in communication with a pair of electrolyte chambers 20 on opposite 6ides of an anode 14.
The columns have a wedge-like configuration snd hsve inwardly directed surfaces 26, the surfaces of adjacent columns converging from the cathode tO the anode at an angle of convergence so as to define a longitudinally e~tending active anode surface having an area half that of the cathode W093/11281 _ 17 - 2 1 2 4 3 ~ ~ PCT/GB92/021~7 surface 16 which is bounded by the columns. The required differential in active anode and cathode surface are~
thereby achieved provides in use the required current ten6ity d~fferential between the acti~e anode and cathode surfaces but allows a mean distance between the active and cathode surfaces of less than 4mm.
The columns 8 mask the remainder of the anode surfaces 28 from the surfaces of the cathodes and are formed with grooves or channels which constitute re-circulation channels 30 of curved, e.g. semi-circular profile, adjacent at least a part 28~ of the in~ctive surfaces of the anodes 14. Each channel 30 e~tends longitudinally from the top portion 4 to the bottom port~on 6 and at each end opens into uppe- an~
lower cell ~paces 22, 24 (see figure 4) within the tcp n~
bottom portions 4, 6, the arrangement being such that eac~.
cavity 22, 24 is in communication with a pair o' channe;s 3G
a~sociated ~ith adjacent columns and a pair of elect,olyee chambers 20 as described previously. Fluid tight seals are maintained between the surface of the anodes and the columns 2~ Of the cell body by longitudinally e~tending resiliently deformable seals 32 which prevent circumferential flow of electrolyte sbout the periphery of the anodY from the electrolyte cha~bers 20 to the re-circulation channels 3C
The lumen 34 of each anode is proYided with copper 2S conductors 36 adjacent the active surfaces of the anodes 1 through which electrical connection is made between each electrolytically active surf2ce of the anodes 18 and the source of electrical power. The anodes are constructed from glass~ csrbon which posse~ses poor electrical conductivity and which therefore serves to reduce the eendency for current to leak to the inactive snode surfaces adjscent the re-circulation channels 30. The lumen 34 also provides the flow path for circulation of 8 coolant in heat transfer relation with both the active and inactive 6urfaces of the anode structures.
The sectional views of figures 3 to 7 show more clearly the electrolyte flow around a single anode between a pair of -- 18 -- `
WO 93tll281 2 I ~ '13 I 8 PCT/GB92/021S7 sir cathodes. Figure 3 shows the flow of electrolyte rro~
the cell head space 22 downwardly through the rec culati_ channels 30 which e~tend lengthwise of the anode structure to the l~wer cell space 24 and figure 4 shows the flow of electrolyte fr~m the lower cell space 24 upwardly throu~h the electrol~te chambers 20, which also extend lengthwise Oc the snode structure to the cell hesd space 22. Product gsses are collected through gas outlet 38 provided from the cell head space. Figures 5 to 7 show clearlY the provision wi~hir.
the cell of the cell head space 22 (Figure 5) and lower cel;
space 24 (figure 7), into and from which electrolyte frn~
both the recirculation cnannels snd the electrolyte chsmbers flows.
In cperation of the cell, elec~rolyte is char~ed ~e :he l~ ,cell and the electrodes lO and 14 are ccnnected tc a sour_e of electrical power (not shown). Air is pumped th-ough air chambers 12 by an air pump (not shown), and a coolant fluid, for example a refrigerant, is caused to flow through the anode lumen 34 from a refrigeration system (not shown) externally of the cell. Ga~éous products of electrolysis formed at the electrol~tically active anode surface 18 cause the electrolyte to flow upwardly through the electrolyte chambers 20 to the cell head space 22 where the gaseous products are disentrained, the electroly~e thence flowing 2~ downw~rdly through the recirculation channels 30 adjacen.
the masked and electrolytically inacti~e anade surfaces ar which no gsseous products of electrolysis are formed.
Product gases are collected ~ia the gas outlet 38.
This invention relstes to sn electrolytic cell. The invention relates in psrticulsr to an electrolytic cell in which ozone i8 to be produced.
Electrolytic cells are known in which water is tlssociated into it6 respective elemental species, i.e. 2 and ~2 which are liberated at the snode and cathode respectively. Under flppropriate conditions 03 is alsc produced at the anode.
Shus in European Patent Specification No. 0 041 365 there is described an electrolytic process for the production of ozone in which an electrol~te comprising an 4ueous 601ution of a very highly electronegative snion, for esample the ~cids or salts of hesa-fluoro-anions, is electrol~sed.
~ igh current efficiencies of up to 35~ for the production of ozone have been reported. Current efficiency (-lso ~nown as production efficiency of ozone) is a measure of ctual ozone production relative to theoretical ozone production for given inputs of electrical current, i.e. 35 current efficiency means under the conditions stated, the 2-3 gases evolved at the anode comprise 35~ (of the theoretic~l 03 production) 0~ by weight and that 35~ of the supplied current is utilised in the production of ozone.
Electrolytic cells are also known for the production of ozone which comprise air cathodes ~nd in which the cathode reaction which takes place is the reduction of ambient air to water in an acidic elec~rol~te, the wster then being oxidised at ~he anode to osygen and ozone. Consequently since hydrogen is not producet at the cathode surface. the cell voltage is Eubstantially reduced. Furthermore the construction of the cell is less comples th~n cells which comprise hydrogen evolving cathodes, for es4mple a separator between the anode and cathode is not required since hydrogen is not evolved at the cathode, and control of the oversll 3~ process is simpler, namely the need for periodic additions of water is reduced.
- 2 _ Wo93/11281 2 i 2 ll 318 PCT/GB92~021~7 Thus, in US P~tent No.4 ,541, 989 there is described an electrolytic cell for the production of ozone which comprises a tubular snode F.tructure, the outer surface of which functions ss sn anode within a tubular air cathode structure, the inner surfsce of which functions ss ~
cathode. As disclosed in the aforementioned US Patent it is desirsble in electrolytic cells for the production of ozone thst the current density ~t the snode surface is grester than that at the cathode surface, in psrticular that the ~ current density at the anode surface is at least about twice that of the cathode surface in order that the power consumption due to polari6ation losses at the cathode surface may be reduced, thereby avoiding hydrogen evolutior - and increasing air cathode lifetime.
~, Furthermore, there is a requirement in the electrolyt e production of ozone thst the anode surface is cooled. Use of a cooled anode surface substantially improves the current efficienc~ of the process. It is known for example that where the temperature of the anode is reduced from 25C to 0C, a fourfold improvement in the current efficiency may be obtained. Furshermore, use of a cooled anode in electrolytic cells for the production of ozone often increases the lifetime of the anode.
The anode is typicnlly cooled by the flow of a 2S refrigerant fluid within the anode. It is therefore important that the surface area of the anode is as large as possible in order that effective heat e~change with the electrol~e may take plsce thereby ensuring e~ficient cooling of the anode. On the other hand a low anode surfsce area relative to that of the cathode is desirable in order that the anode current density may be high.
The concentric tubular arrangement as described in U5 P~tent 4, 541, 9B9 provides one way in w~ich the current density may be greater at the anode than at the cathode 3S whilst still allowing efficient heat exchange.
However, this concentric tubular arrangement does suffer from the dissdvantage tha~ the inter electrode gap, WO93/11281 2 ~ 2 3 ~ 8 PCT~GB92/021~7 that is the distsnce between the outer surface of the ~node and the inner surface of the cathode msy be disadvantageously large in order to achieve the required low surfsce area of the anode rel~tive to that of the cathode.
For e~ample, in a cell comprising an inner tubular anode having an e~ternal radius of 2 cm and an outer tubular cathode having an internal surface area twice that of the anode, the internal radius of the cathode will be 4 cm. i.e.
the inter-electrode gap w$1i be 2 cm. This large ~ $nter-electrode gap leads to a high electr$csl resist~nce t~
the flow of current through the cell and an undesirable increase in the voltage of the cell.
These sforementioned problems arise in particular with this arrangement where the cathode ls an air cathode. In addition to the aforementioned operational problems, ai:
cathodes are difficult to fabricate in 8 tubular form and they lead to mechanical problems during manufacture of the electrolytic cell, for e~ample sealing within the cell.
~ccording to a first aspect of the present invention there is provided an electrol~t$c cell comprising first and second electrode structures, at least the first electrode structure having a surface area $n heat e~change relation with the electrolyte and part only of said surface area being electrolytically active.
2~ Typically, each of the first and ~econd electrode strurtures has a surface area which is in heat transfer relation with the elec~rolyte, a part only of said surface area of the first electrode structure being electrolytically active and the active surface area of said second electrode structure being greater ~han that of the first electrode structure.
In an electrolytic cell in which ozone is produced, the first electrode structure is an anode structure and the second electrote structure is a cashode structure, the 3~ electrolytically active surface area of the cathode structure being greater than that of the anode structure.
WO~3/11281 PC~/GB92/021~7 ~ 212~3~
Although the invention is described hereafter wls~
reference to an electrolytic cell in which ozone is to be produced, we do not exclude its ~pplication tO generstior. of products other than ozone.
The active surface areas of the anode ant cathode structures will usually be of such an estent that in operation the current density established at the surf~ce of the anode structure is at lesst 20Z greater than that established at the surface of the cathode structure.
Preferably the current density established at the surface of the anode structure is at least 50~, especially at least 802 8reater than that established at the surface of the cathode structure.
The anode structure may have high surface area in heat ~ e~change relation with the electrolyte, thus faci1itatir.g efficient heat exchange, yet only a part of that surface area is electrolytically active thus ensuring re~atively high anode current densities, relative to the cathode current densit~.
By electrol~ticallr active anode sur~ace~ there is mesnt that part of the anode surface at which the electrolytic process takes plsce, that _s that part of the anode surface with which the cathode surface has substan~ial electrical interaction, i.e. current ~n the form of a flow 2S of ions through the electrol7te takes place between the active anode surface and the active cathode surface.
In one form of the invention the ~node structure may be cons~ructet from different ms~erials; for essmple one part of the anode structure ma~ be construct2d from a suitable anode material which presents said electrolytically active ansde surface, and a second part may be constructed from a material which is not capable of functioning as an electrolyticslly active anode 6urface. In this case, the ancde surface $ncludes both the surface which is constructed 3S from a suitable anode material and the surface which is not so constructet, although the surface which functions as sn WO93/11281 ~1 2 4 3 ~ ~ PCT/GB92/02157 active anode surface is only that surface which is constructed from B suitable anode material.
~ owever, for simplicity of construction, we pre.er ~ha:
at least that part of the anode structure which has 5 surfsce sres esposed for contact with the electrolyte in operation of the cell is made completely from a material which is suitable for use as an anode snd thst a portion of the esposed anode surface is prevented from functior._n6 as n active anode curface by suppressing the elect-olvtic interaction between that portion and the cathode structure, for esample b~ providing means for masking that portion of the ancde 6urface from the cathode surface.
~ ccording to a second aspect of the present invent'c..
there is provided an electrolytic cell comprising fi-s: and 1~ ,second electrode structures, part only of the surface sres of at least the first electrode structure being electrolytically active, and means for masking the remaining part of the 6urface area of the first elec~rode structure in such wa~ as to render said remaining part of the surface area substantially electrolytically inactive.
The masking mesns msy comprise for es~mple, a coating, cover, insert or any other suitable part, such tha~ therP i5 substantially no ozone producing electrol~tic interactior.
between the masked portion(s) of the anode surface and the 2S csthode surface.
The masking means may take any suitable shape and form provided that it ~uppresses the electrolyt~c interaction between the masked portion of the snode surface and the cathode surface. The material used for effecting masking is t~pic~ therefore an electr~cally in~ulating material. The material should also be inert to the electrolyte, which may be highly corroaive. Suitable materisls include inert polymeric materials such as polyvinyl chloride or polyfluorinated polymers, for esample . 3~ pol~tetrafluoroethylene which are electrical insulators and which h-ve resistance to osidising gases and escellent resistance to highly acidic and corrosive solutions.
The e~tent of the masking should be such as tO achieve the desired current density difference between the active anode surface and the cathode surface. Thus the unmasked anode surface ares which functicns as a~ active anode surface should be less than about 80~ of the area of the cathode surface, preferably less than about 60~ of the cathode surface.
The anode structure may have any suitable form, for e~ample it may be in the form of a tube or or it may be a planar anode. The electrol~tically sctive and inactive surface areas of the anode structure may be distributed around the periphery of the anode strueture. The anod~
structure may have an elongate configuration and the active and inactive surfaces may estend longitudinally of the ,elongate anode structure.
The electrolytic cell preferably further comprises means for circulating a coolant fluid in heat transfer relation with the an~de structure in such a way that hest exchange i8 ~ecured between the coolant a~d the electroly through the active and inactive surface are~s of the anode structure. A particularly preferred form of the anode by which such coolant circulation may be achieved is a tubular anode, the lumen of which provides a path for the flow of a coolant fluid. The coolant fluid may flow through the lumen of the anode or the lumen may be provided with a member e~tending within the lumen, for esÆmple a hollow finger through which the coolsnt fluid is caused to flow. The cold finger may be constructed, for example, of copper.
The surfsce area of the tubular anode ~tructure which is exposed for contact wi~h the electrolyte may be the outer surface or periphery of the tubulsr structure, and the electrolytically active and inactive parts of this surface area may therefore be distributed peripherally around, and estending longitudinally of, the tubular struc~ure.
In order that heat eschange may take place through the inactive surfaces of the anode structure, the electrolytic cell preferably comprises means for routing the electrolyte WO93/11281 212 4 31~ PCT/GB92/021~7 along a path in which it is in he~t exchange relation Wit:.
substantially electrolytically inactive part of th~ surface area of the anode structure. Where the ~node structure is of elongate configuration, the routing means preferably - provides at least one flow path e~tendinB longitudinally of the ~node structure.
~ he active and inactive surfaces of the anode struc~ure msy extend generally co-estensively with one another longitudin~lly of the anode structure.
ln orter that ss little a6 possible electrolytic interaction should take pl~ce between the cathode s~ructu-e and the inactive anode surface~s), the cell preferably comprises mesns for preventlng the flow of electrolyte peripherally of the anode structure from a regior. where the electrolyte is in commun~cation with an active surface of ' the anode structure to a region where the inactive surface are~ is locsted.
The csthode structure may take any 6uitable form although we generally prefer to use a plsnar or tubular 2~ structure. Where the csthode structure is in the form of a tube, the inner surface of the tube may be the electrolytically acti~e cathode 6urface and the radius of the inner surface of the cathode structure may be reduced compared to that hereinbefore described with reference to US
2~ Patent 4,541,989 thus reducing the inter elec~rode gap but maintaining the differential current density between the electrolytically active anode surface and the cathode surface.
Preferabl~ however, the cathode structure is of a planar configuration since ~e prefer to employ an air c~thode (as described hereafter). Air cathodes of planar configuration are readily manufactured and are easily installed in the electrolytic cell. Furthermore, ~n elec~rolytic cell comprising st least one tubuler anode snd 3~ at least one plsnar cathode allows both si~ple scaling of the cell to much larger sizes BS hereinafter described, and fscilitstes the schievement of the current density 212 i31g difference between the active anode surface and the ca: ~de surface defined according to the first aspect of the invention.
Where the cathodic structure is of plansr configuration, we prefer that two of said cathode structu es of planar configuration are present in the cell and that the anode structure is located between, and in spaced relation with, said cathode structures and that the anode struc~ure has separste electrolytically active surfaces in confron~
l relation with the cathode structures. The anode structures may then hsve electrolytically inactive surface areas located between the said separate active surface areas. We psrticulsrly prefer to employ a plurality of said anode structures, each having electrolytically active and inac~ive anode surface areas. The anode structures may be arrange~
between the two plsnar cathode structures in a direction paralle} to said cathode structures.
~ccording to a third aspect of the present inventio&
there is provided sn electrolytic cell for the production of ozone comprising at least one tubular structure the outer surface of which functions as an anode surfsce and at least one planar cath~de structure.
A cell in accordance with this third a6pect of the invention may incorporate ~severally or collectively, or sny combination ~hereof, as the conteYt admits~ those features of said first and second aspects of the invention as discussed hereinbefore.
In ~ preferred embodiment of this third aspect of the invention, the cell comprises at lea~t two pla~ar cathotes between which nre located one or more tubular anodes, preferably at least two tubular anodes. The number of tubular anodes which are employed depends 5t least to some estent upon the desired rate of production of ozone from the cell, the dimensions, in particular the length snd diameter 3S of the tubulsr anodes and the current density at the electrolytically active anode ~urfaces during operation of the cell. Thus, the cell msy comprise up to about 12 tubular WO93/11281 212 ~ 3 l~ PCT/GB92/021~7 anodes where ozone production in the order of loo g~hour ie desired. The ease with which the cell msy be scaled up in orter to increase the rate of production of ozone, sim~lv b~
the provision of further tubular anodes between the air cathodes and increasing the length of the ~node tubes and area dimensions of the planar air cathode, is 8 substantial advantage of this third aspect of the invention.
Furthermore, the cell may comprise more than two planar cathode structures, with one or more tubular anode ~ structures arranged between each pair of cathode structures such that the cell may comprise a row of tubular anodes between each pair of opposingly faced planar cathodes.
Further, in the electrolytic cell accorting to this third aspect of the invention, preferably onlv a portion of ~the outer surface of the tubular anode which is in heat eschange relation with the electrolyte is electrolytically ctive, and advantageously the cell comprises means m~sking the remaining part of the surface area of the anode ~ structure in such a way as to render it substantially - electrolytically inactive.
Active and inactive portions of the anode surfsce area may be defined by providing in the cell a first boundary means for bounding `eogether with the csthode structure and a part only of the 6urface area of the anode structure a 2S chamber for enclosure of an electrol~te whereby said par~
only of the anode surface area constitutes an electrolytically active surface area of the anode ~truc~ure snd second boundary means for bounding together with a further part or parts of the surface area of said anode structure ae least one channel in fluid communication with said chamber to provide for flow of electrolyte over said further part(s~ of the surface area of the anode structure, said further parts constituting a substantially electrol~tically inac~ive surface area of the anode . 35 structure. The first and second boundary means may furthe.
constitute a masking means as hereinbefore described, and ma~, for e~ample be provided by an insulsting body or bodies extending between the anode surface and the cathode surf-~e.
The, or each insulating body msy be in the form of, for e~smple, a wedge-shaped member or truncated cone, wlth its narrow end in contact with and e~tending from the cathodo surface to it6 wide end in contact with the outer surface of one or more anode structures whereby to mask that portion of the surface area of the anode structure which is not in confronting relation with the cathode surfaces, from the cathode 6urfaces.
The flr6t and 6econd boundary means, for e~amp'e one or more insulating bodies may be provided as separate inserts for provision within the cell. Conveniently however, the o-e-ch insulating body is formed as part of a cell bod~
which the anode and cathode structures are supported. Thus ,,the cell body may be so configured that i~ mask~ ~he surfaces of the anode which are not ir. con~-ont ng el&~_or.
with the cathode surfaces.
The acti~e anode surface will in this case be the surface of the anode ad~acent the cathode surface and the me-n di~tance between the acti~e anode surface and the c~thode surface is preferably less than lOmm, more prefe~ably less than 5mm and especially less than 4mm.
~s hereinbefore described it is desirable that as gre&.
an area of the anode structure as possible is in contact 2S with the electrolyte in order to achieve good heat exchange efficiency between the electrolyte and the anode surface whereby efficient cooling of the sctive anode surface ie obtained. We therefore prefer that the masked portion(s) o-^
the anode surface is ne~ertheless e~posed tO the electrol~te.
Where the masking me~ns is in the form of one or more wedge-shaped in~ulating boties e~tending from the cathode surface to the anode surface, the wedge may be shaped such that the wedge onl~ comes into contact with a small area of 3S the anode surface to be masked. For e~ampie, the wedge may be cut away to form circulation channels. at the portion of the wedge which is adjacent the anode surface to be masked WO93/11281 ~ 21~ 4 31~ PCT/GB~2/02157 so that electrolyte msy circulate over the ~node surfac~
between the masking wedge member and the anode surface.
Thus, even though the masked portions of the anode structure pla7 no significant part in the electrolytic interaction, the electrolyte may flow freely over substantially 811 or a section of the masked and electrolytically inactive portion of the anode structure, providing an ~ncreased totsl surface srea for heat e~change and thus cooling of the active anode surface.
~ ~ further advantage of the provision of, for example, re-circulstion channels atjacent the masked and elec~rolytically inactive anode portionts) is that a recirculating flow of electrolyte may be achieved over the active anode surface which serves to remove bubbles of 'gaseous products which may form on the active anode surface and which may, if not removed, lead to an increase in the cell voltage. This flow of electrolyte is achieved because substa~tially no electrolysis takes place within the recirculation channel~ so th~t the electrol~te $n the channels tends to be unga6ified. whereas the formstion of gaseous products of electrolysis takes place in the electrolyte chambers thus protucing a gasified electrolyte.
A recirculating flow of electrolyte is there~y generated by the density difference between the gasified and ungas;f,ed 2S electrolyte.
Fluid-tight seals should be maintained between the electrol~te chambers and the re-circulation channelç in order to prevent current leakage from electrolyte betweeh ~he aetive anote and cathode surfaces to the electrolyte flowing within the recircula~ion ch~nnels.
~ccording to a fourth a~pect of the present invention there is provided an electrolytic cell for the production of ozone comprising an anode structure, n cathode structure and a chamber for containing electrolyte within which 3S slectrolysis occurs and which further compri~es a~ least one re-circulation channel in fluid communication with the electrolyte but within which electrolysis does not occur.
The recirculation channels may be provided wit~ .e cell itself or they may be pro~ided e~ternally of the ce.'.
As hereinbefore described we prefer to provide ~he recirculation channels within the electrolytic cell and especially adjacent the electrolytically inactive anode surfsce.
Cell heat spaces which may serve as both disentrainment areas for product gases and reservoirs for electrolyte may be provided within the cell, into and from which elec:rolyte ~ from and into both the electrolyte chambers between .he active anode and cathode surfaces, and recirculation channels may flow, and from which product gases may be collected.
~ir cathodes, which are commercially available ' components, are t~pically composed of polytetrafluoroethylene-bonded-carbon containing sma'l mounts of catalytic materials, for e~ample platinum.
The materials used as the snode surface in the electrolytic cell of the present invention m~y be conventional anode materials BS descrlbed more fully ir" for example, Et~ropean Patent 0 041 365. The anode surface may be constructed from platinum or lead dioxide, particularly leaa dioxide in the beta crystalline form. ~owever, a special form of carbon, specifically vitreous or glassy carbon is 2S particularly preferred for use as the anode surface ma~erial s~nce it has a high oxygen overpotential and thus a h gh efficiency for ozone production, it is 6table in strong acid electrolytes and is ~table to oxidising cond~tions generated in the cell. Furthermore, glass~ carbon is a material which possesses poor electrical conductivit~ so that where current is fed to the anode structure through a conducting memeber provided adjacent only the electrolytically active surfaces of the anode (as described hereafter), current tends not to lesk from the electrolytically active anode ~S surface to the electrol~tically inactive anode surfaces.
The electrolyte used in the electrolytic cell is typically a known electrolyte, for example, an aqueous W093~11281 21~ 4 3 1 ~ PCT/GB92/02157 solution of ~ highly electronegative snion (~nd associ~ted cation) such as are, for example, described in European Patent O 041 365. The electronegative anion used is preferably as electronegative as possible, ~nd more preferably is a fluoro-ani~n. The fluoro-anion may be the fluoro-anion of B Group V-B element of the Periodic Table, for esample pho6phorous and arsenic which form hexa-fluoro anions. Other related non-metallic elements such as Si and Sb also form hesa-fluoro-anions. Other su~table fluoro-anions ma~ be mentloned, inter alia P02F2-, HTiF~-, NbF72-, TaF72~, NiF62-, ZrF62~, GeF62~, FeF62-. The phosphorou6, ar6enic, boron and silicon fluoro-anions ~re the preferred anions for addition to the squeous elec~-nly~
and in particular polyhalogenated boranes. We especial!y refer to emplo~ the tetrafluoroborate in on.
The fluoro-anions may be added to the aqueous electrolyte 601ution in the form of their respective acids or as w-ter-601uble salts. Whereas the acid-form of the fluoro-anions may be preferred because of their hi8he~
solubilitles in water, the fluoro-anion salts, for esample 60dium or potas~ium, offer the sdvantage that their aqueous solutions have higher p~'s than do the solutions of their - respective acid forms, and they therefore are less corrosiv~
towards the cathodes.
2S ~or current efficiency, it is desirable to increase the fluoro-anion concentration in the electrolyte to its maximum solubility since increasing the anion concentration increases ozone current efficiency. ~owever, an increase in the snion concentration also increase6 the corrosivity of the electrolyte towards the cathodes. Suitable anion concentrations may be readily determined by routine experimentation.
The construction of the electrolytic cell may, apart from its construction according to the various aspects of 3S the invention as hereinbefore tefined, follow conven~ional tcchnolog~ taking into consiteration the corrosive nature of the fluoro-anion electrolytes and the high osidising power WO93/11281 212 4 318 PCT/GB92/021~7 of the ozone gases. Thus, the parts of the cell in conta~
with the corrosive electrolyte and o~idisin~ products of electrolysis are preferably constructed Oc materisl~ whi~
are inert both to the highly corrosive electrolyte snd the oxidising gases. The cell body may therefore be ccnstruct~d from, or coated with, an inert material, for esample an inert pol~meric material such 85 polyvinyl chloride or polyfluorinated polymers, for example polytetrafluoroethylene which have resistance to oxid$sing gases and excellent resistance to highlv ac~d and corrosive solutions.
Where the cathodic reaction taking place in the cell produces h~drogen, the anode and csthode compartments o_ -he cell should be separated such that the h~drogen evolved ~t l~ ~'the cathode is not in fluid-flow contac~ with ~he gases evolved st the snode. Such separators are well knowr. ~s the art. Conventionally they are prepared from a perfluo.inPt~r pol~meric cation exchsnge material, for example ~Nafion"
~rcgistered Trademark of E.I.Du Pont). Such a separator _ not needed in the preferred embodiments of the invention where an air cathode is used and where hydrogen is no~
generated by the cathote process.
The anode and cathode structures are disposed within the electrolytic cell with electrical leats lesding tO the 2S exterior of the cell. Electrical potential may be spplied tC
the anode by contact with part only of a surface of the anode structure which corresponds to the electrolytically active surface area of the anode structure, for example by means of a conducting member, constructed from, for example, copper, which is provided along the snode adjacent the active anode surface in order that current is fed predominantly to the active snode surface and not to tha~
anode surface which is masked from the cathode. The conducting member is preferably provided on a surface of ~h~
~S anode which is not in direct contact with the electrolyte~
for example where the anode is in the form of a hollow tube the conducting member may be provided within the lumen of WO93/11281 - l5 - 2~ ~431 ~ PCT/GB92/021~7 the tube, in order that the conducting member is protectec from the electrolyte.
The cell is sealed prior to use, and the cel' hesd space is provided with suit~ble inlet ~nd outlet passages ;~
for water mske-up, where necessary, and the withdrawal of the gases evolved from the cathode (where hydrogen is produced) ~nd from the anode. Two discrete gas removal systems ma~, where necessary, be used to keep the cathode g~se~ separ~te fro~ the ~node gases. Nitrogen and/or air maY
be sdded, for e~ample pumped through. the gas h~ndling system in order to entrain the evolved cathode ~nd anode g~ses and carry them from the cell to the esterior where they may be stored or utilised in the desired application.
The snode ~nd cathode structures sre connected by the ~-~aforementioned electrical leads, optionally through a conducting member, to a source of power external to the cell. Typically the cell is oper~ted at electrical potentials in the order of 3-7 volts. The current densit~ e~
the snode surface m~y be in the range from ~bout a tenth o' an ampere per 6quare centimetre of effective a~ode surface up to about l.0 ampere per square centimetre of effec~ive anode surface.
The invention is illustrated with reference to the 2~ sccompanying figures in which:
Figure 1 is ~ diagrammatic partly cut away view of an electrolytic cell according to the invention, Figure 2 is s view in section along the line A-A in figure 1, Figure 3 is a view in section through the cell of Figure l along the line B-B in figure 2, - 3~
Figure 4 i6 a view in section through the cell of Figure l slong the line C-C in figure 2, - 16 _ WO93/11281 2 12 ~ 3 1 8 PCT~GB92/02157 Figure 5 is a view in section along the iine D-D in ~ igure 3, and Figure 6 is a view in section along the line E-E in fi~ure 3.
Figure 7 is 8 view in section along the line F-F in figure 3.
Referring to Figures 1 to 7, an electrolytic cell suitable for tbe generation of ozone shown generally as 1 :~:
Figure 1 co~prises a main cell boty 2, havln~ top and ~ct;om portions 4, 6 and spaced columns 8 extending there~etween~
~lthough three such columns 8 are present in the illust-~ted ~,,embodiment, a pair of end columns 8A and an intermediate column 8B, there may be more or less according to the r.umbe-of anode structures employed. A pair of air cathodes 10 wi~.
associated air chambers 12, and located between but spaced from the air cathodes ~0, a psir of tubular glas~y carbon anodes 14, are supported in the cell body. The colu~ns B, which support the snodes and cathodes in spaced relatior.
~-ith one hnother, constitute means fcr bounding, togethe~
with active surfaces 16 of the air cathodes 10 and psrts only of the outer surfaces of the anodes 18 which are in 2S confronting relstion with the active surfaces of the air cathodes, electrolyte chambers 20. The electrolyte chambers 20 extend longitudinally from the top portion 4 to the bottom portion 6 and at each end open into upper and lower cell spaces, 22, 24 respectively ~see Figure 3) within the top snd bottom portions 4 and 6, the arrangement being suc~.
that each cell space is in communication with a pair of electrolyte chambers 20 on opposite 6ides of an anode 14.
The columns have a wedge-like configuration snd hsve inwardly directed surfaces 26, the surfaces of adjacent columns converging from the cathode tO the anode at an angle of convergence so as to define a longitudinally e~tending active anode surface having an area half that of the cathode W093/11281 _ 17 - 2 1 2 4 3 ~ ~ PCT/GB92/021~7 surface 16 which is bounded by the columns. The required differential in active anode and cathode surface are~
thereby achieved provides in use the required current ten6ity d~fferential between the acti~e anode and cathode surfaces but allows a mean distance between the active and cathode surfaces of less than 4mm.
The columns 8 mask the remainder of the anode surfaces 28 from the surfaces of the cathodes and are formed with grooves or channels which constitute re-circulation channels 30 of curved, e.g. semi-circular profile, adjacent at least a part 28~ of the in~ctive surfaces of the anodes 14. Each channel 30 e~tends longitudinally from the top portion 4 to the bottom port~on 6 and at each end opens into uppe- an~
lower cell ~paces 22, 24 (see figure 4) within the tcp n~
bottom portions 4, 6, the arrangement being such that eac~.
cavity 22, 24 is in communication with a pair o' channe;s 3G
a~sociated ~ith adjacent columns and a pair of elect,olyee chambers 20 as described previously. Fluid tight seals are maintained between the surface of the anodes and the columns 2~ Of the cell body by longitudinally e~tending resiliently deformable seals 32 which prevent circumferential flow of electrolyte sbout the periphery of the anodY from the electrolyte cha~bers 20 to the re-circulation channels 3C
The lumen 34 of each anode is proYided with copper 2S conductors 36 adjacent the active surfaces of the anodes 1 through which electrical connection is made between each electrolytically active surf2ce of the anodes 18 and the source of electrical power. The anodes are constructed from glass~ csrbon which posse~ses poor electrical conductivity and which therefore serves to reduce the eendency for current to leak to the inactive snode surfaces adjscent the re-circulation channels 30. The lumen 34 also provides the flow path for circulation of 8 coolant in heat transfer relation with both the active and inactive 6urfaces of the anode structures.
The sectional views of figures 3 to 7 show more clearly the electrolyte flow around a single anode between a pair of -- 18 -- `
WO 93tll281 2 I ~ '13 I 8 PCT/GB92/021S7 sir cathodes. Figure 3 shows the flow of electrolyte rro~
the cell head space 22 downwardly through the rec culati_ channels 30 which e~tend lengthwise of the anode structure to the l~wer cell space 24 and figure 4 shows the flow of electrolyte fr~m the lower cell space 24 upwardly throu~h the electrol~te chambers 20, which also extend lengthwise Oc the snode structure to the cell hesd space 22. Product gsses are collected through gas outlet 38 provided from the cell head space. Figures 5 to 7 show clearlY the provision wi~hir.
the cell of the cell head space 22 (Figure 5) and lower cel;
space 24 (figure 7), into and from which electrolyte frn~
both the recirculation cnannels snd the electrolyte chsmbers flows.
In cperation of the cell, elec~rolyte is char~ed ~e :he l~ ,cell and the electrodes lO and 14 are ccnnected tc a sour_e of electrical power (not shown). Air is pumped th-ough air chambers 12 by an air pump (not shown), and a coolant fluid, for example a refrigerant, is caused to flow through the anode lumen 34 from a refrigeration system (not shown) externally of the cell. Ga~éous products of electrolysis formed at the electrol~tically active anode surface 18 cause the electrolyte to flow upwardly through the electrolyte chambers 20 to the cell head space 22 where the gaseous products are disentrained, the electroly~e thence flowing 2~ downw~rdly through the recirculation channels 30 adjacen.
the masked and electrolytically inacti~e anade surfaces ar which no gsseous products of electrolysis are formed.
Product gases are collected ~ia the gas outlet 38.
Claims (33)
1. An electrolytic cell comprising first and second electrode structures, at least the first electrode structure having a surface area which is in heat transfer relation with the electrolyte and part only of said surface area being electrolytically active.
2. A cell as claimed in Claim 1 in which each of said first and second electrode structures has a surface area which is in heat transfer relation with the electrolyte, a part only of said surface area of the first electrode structure being electrolytically active and the active surface area of said second electrode structure being greater than that of the first electrode structure.
3. A cell as claimed in Claim 1 or 2, said active surface area(s) being of such an extent that, in operation, the current density established at said first electrode structure is at least 20% greater than that established at the surface of the second electrode structure.
4. An electrolytic cell comprising first and second electrode structures, part only of the surface area of at least the first electrode structure being electrolytically active, and means masking the remaining part of the surface area of the first electrode structure in such a way as to render the same substantially electrolytically inactive.
5. An electrolytic cell comprising:
first and second electrode structures, at least part of the surface area of the first electrode structure being exposed to interaction with the electrolyte; and means for routing the electrolyte along A path in which it is in heat exchange relation with a substantially electrolytically inactive part of the surface area of the first electrode structure.
first and second electrode structures, at least part of the surface area of the first electrode structure being exposed to interaction with the electrolyte; and means for routing the electrolyte along A path in which it is in heat exchange relation with a substantially electrolytically inactive part of the surface area of the first electrode structure.
6. A cell as claimed in any one of Claims 1 to 5 in which the active and inactive surface areas of the first electrode structure are distributed around the periphery of the first electrode structure.
7. A cell as claimed in any one of Claims i to 6 in which the first electrode structure is of elongated configuration and the active and inactive surface areas of the first electrode structure extend longitudinally of the first electrode structure.
8. A cell as claimed in any one of Claims 1 to 7 comprising means for circulating a coolant in heat transfer relation with the first electrode structure in suck a way that heat exchange is secured between the coolant and the electrolyte through the active and inactive surface areas of the first electrode structure.
9. A cell as claimed in any one of Claims 5 to 8 in which the first electrode structure is of elongated configuration and in which said routing means provides at least one flow path extending longitudinally of the first electrode structure.
10. A cell as claimed in Claim 7 or either one of Claims 8 and 9 when dependent on Claim 7 in which the active and inactive surface areas extend alongside one another longitudinally of the first electrode structure.
11. A cell as claimed in Claim 10 in which said active and inactive surface areas are generally co-extensive with one another longitudinally of the first electrode structure.
12. A cell as claimed in any one of Claims 1 to 11 including means for preventing electrolyte flow peripherally of the first electrode means from a region where the electrolyte in communication with said active surface area to a region where the inactive surface area is located.
13. A cell as claimed in any one of Claims 1 to 12 including means for applying electrical potential to said first electrode structure by contact with part only of a peripheral surface of the latter corresponding to the active surface area of the first electrode structure.
14. A cell as claimed in Claim 13 in which the first electrode structure is fabricated from a material which possesses poor electrical conductivity.
15. A cell as claimed in any one of Claims 1 to 14 in which said first electrode structure is of tubular configuration.
16. A cell as claimed in any one of Claims 1 to 15 in which said second electrode structure is of planar configuration.
17. A cell as claimed in Claim 16 in which two of said second electrode structures are present and in which the first electrode structure is located between, and in spaced relation with, said second electrode structures and has separate active surface areas in confronting relation with the second electrode structures.
18. A cell as claimed in Claim 17 in which said first electrode means has inactive surface areas located between said separate surface areas.
19. A cell as claimed in any one of the preceding claims comprising a plurality of said first electrode structures, each having active and inactive surface areas as aforesaid.
20. A cell as claimed in Claim 18 or 19 when dependent on Claim 17 in which said first electrode structures are arranged in spaced relation in a direction parallel to said second electrode structures.
21. A cell as claimed in any one of the preceding claims comprising means for supplying electrical potential to said first and second electrode structures, said means including a contact which engages said first electrode structure at a limited region thereof corresponding to said active surface area, the first electrode structure being composed of a material having poor conductivity whereby the electrical potential prevailing at the inactive surface area is reduced.
22. An electrolytic cell comprising:
an anode structure of elongate configuration;
a cathode structure;
means supporting the anode and cathode structures in spaced relation with one another;
first boundary means for bounding together with said cathode structure and part only of the surface area of said anode structure a chamber for enclosure of an electrolyte whereby said part constitutes an electrolytically active surface area of the anode structure;
second boundary means for bounding together with a further part or parts of the surface area of said anode structure at least one channel in fluid communication with said chamber to provide for flow of electrolyte over said further part(s) of the surface area of the anode structure, said further part(s) constituting a substantially electrolytically inactive surface area(s) of the anode structure; and means for providing at least one path for flow of coolant through the anode structure in such a way that heat transfer between the coolant and the electrolyte can take place through said active and substantially inactive surface areas.
an anode structure of elongate configuration;
a cathode structure;
means supporting the anode and cathode structures in spaced relation with one another;
first boundary means for bounding together with said cathode structure and part only of the surface area of said anode structure a chamber for enclosure of an electrolyte whereby said part constitutes an electrolytically active surface area of the anode structure;
second boundary means for bounding together with a further part or parts of the surface area of said anode structure at least one channel in fluid communication with said chamber to provide for flow of electrolyte over said further part(s) of the surface area of the anode structure, said further part(s) constituting a substantially electrolytically inactive surface area(s) of the anode structure; and means for providing at least one path for flow of coolant through the anode structure in such a way that heat transfer between the coolant and the electrolyte can take place through said active and substantially inactive surface areas.
23. A cell as claimed in Claim 22 in which the anode structure is of tubular configuration and in which the hollow interior of the anode structure constitutes said path for coolant flow.
24. A cell as claimed in Claim 22 or 23 in which said chamber and said channel(s) extend lengthwise of the anode structure.
25. A cell as claimed in any one of Claims 22 to 24, said first and/or said second boundary means being formed integrally with said supporting means.
26. A cell as claimed in any one of Claims 22 to 25 in which the cathode structure is constituted by a planar air cathode.
27. A cell as claimed in any one of the preceding claims containing an electrolyte suitable for the electrochemical generation of ozone.
28. An electrolytic cell for the production of ozone comprising at least one tubular electrode, the outer surface of which functions as ]an anode, and at least one planar cathode structure.
29. A cell as claimed in Claim 28 when modified in accordance with any one of Claims 1 to 27.
30. An electrolytic cell comprising first and second electrode structures and at least one chamber for containing electrolyte within which electrolysis occurs and which further comprises at least one re-circulation channel in fluid communication with the electrolyte but within which electrolysis does not occur.
31. A cell as claimed in Claim 30 when modified in accordance with any one of claims 1 to 28.
32. A method of effecting electrolysis comprising:
electrolysing a liquid by the application of a potential difference between first and second electrode structures;
suppressing electrolytic interaction between said second structure and part of the surface area of the first electrode structure so that the current density at one of said structures is greater than that at the other structure;
and collecting a product of electrolysis resulting from interaction between said second structure and the remaining surface area of said first electrode structure.
electrolysing a liquid by the application of a potential difference between first and second electrode structures;
suppressing electrolytic interaction between said second structure and part of the surface area of the first electrode structure so that the current density at one of said structures is greater than that at the other structure;
and collecting a product of electrolysis resulting from interaction between said second structure and the remaining surface area of said first electrode structure.
33. A method of effecting electrolysis comprising electrolysing a liquid by the application of a potential difference between first and second electrode structures which are contained in an electrolytic cell as defined in any one of claims 1 to 31.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB919125680A GB9125680D0 (en) | 1991-12-03 | 1991-12-03 | Electrochemical cell |
| GB9125680.0 | 1991-12-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2124318A1 true CA2124318A1 (en) | 1993-06-10 |
Family
ID=10705607
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002124318A Abandoned CA2124318A1 (en) | 1991-12-03 | 1992-11-20 | Electrochemical cell |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0611401A1 (en) |
| JP (1) | JPH07501852A (en) |
| CN (1) | CN1074954A (en) |
| AU (1) | AU665037B2 (en) |
| CA (1) | CA2124318A1 (en) |
| FI (1) | FI942600A (en) |
| GB (2) | GB9125680D0 (en) |
| NO (1) | NO942059L (en) |
| NZ (1) | NZ245265A (en) |
| TW (1) | TW288215B (en) |
| WO (1) | WO1993011281A2 (en) |
| ZA (1) | ZA929103B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102012011314A1 (en) * | 2012-06-06 | 2013-12-12 | Manfred Völker | Electrochemical ozone generator and hydrogen generator |
| FR3038456B1 (en) * | 2015-06-30 | 2019-10-18 | Jomi Leman | ELECTROCHEMICAL DEVICE FOR STORING ELECTRIC ENERGY. |
| CN110093621B (en) * | 2019-04-24 | 2020-08-25 | 浙江工业大学 | Hydrogen-free continuous electrochemical oxidation IO3-Transformation to IO4-Method (2) |
| CN111058055B (en) * | 2019-12-20 | 2021-01-15 | 江苏安凯特科技股份有限公司 | Cathode structure of ion membrane electrolytic cell |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3575839A (en) * | 1968-02-15 | 1971-04-20 | Mikhail Alexeevich Melnikov Ei | Electrolyzer with solid electrodes |
| JPS4837668B1 (en) * | 1969-05-14 | 1973-11-13 | ||
| JPH01123086A (en) * | 1987-11-05 | 1989-05-16 | Japan Storage Battery Co Ltd | Electrochemical ozone generator |
| DE4008612A1 (en) * | 1990-03-17 | 1991-09-19 | Peter Dr Faber | Rotary DC ozoniser discharges evolved gas centrifugally - for use in situ or in separate reaction vessel, absence of valves filters, pump etc. simplifies construction |
-
1991
- 1991-12-03 GB GB919125680A patent/GB9125680D0/en active Pending
-
1992
- 1992-11-19 GB GB929224261A patent/GB9224261D0/en active Pending
- 1992-11-20 EP EP92923892A patent/EP0611401A1/en not_active Withdrawn
- 1992-11-20 WO PCT/GB1992/002157 patent/WO1993011281A2/en not_active Application Discontinuation
- 1992-11-20 JP JP5509920A patent/JPH07501852A/en active Pending
- 1992-11-20 AU AU29503/92A patent/AU665037B2/en not_active Ceased
- 1992-11-20 CA CA002124318A patent/CA2124318A1/en not_active Abandoned
- 1992-11-24 ZA ZA929103A patent/ZA929103B/en unknown
- 1992-11-25 NZ NZ245265A patent/NZ245265A/en unknown
- 1992-12-03 CN CN92111844A patent/CN1074954A/en active Pending
- 1992-12-11 TW TW081109947A patent/TW288215B/zh active
-
1994
- 1994-06-02 NO NO942059A patent/NO942059L/en unknown
- 1994-06-02 FI FI942600A patent/FI942600A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07501852A (en) | 1995-02-23 |
| NZ245265A (en) | 1996-02-27 |
| TW288215B (en) | 1996-10-11 |
| NO942059D0 (en) | 1994-06-02 |
| WO1993011281A3 (en) | 1993-07-08 |
| FI942600A0 (en) | 1994-06-02 |
| CN1074954A (en) | 1993-08-04 |
| WO1993011281A2 (en) | 1993-06-10 |
| ZA929103B (en) | 1994-03-10 |
| AU665037B2 (en) | 1995-12-14 |
| NO942059L (en) | 1994-08-01 |
| FI942600A (en) | 1994-06-02 |
| EP0611401A1 (en) | 1994-08-24 |
| GB9224261D0 (en) | 1993-01-06 |
| AU2950392A (en) | 1993-06-28 |
| GB9125680D0 (en) | 1992-01-29 |
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