EP2710169A2 - Cellule électrochimique et son procédé de fonctionnement - Google Patents

Cellule électrochimique et son procédé de fonctionnement

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Publication number
EP2710169A2
EP2710169A2 EP12727153.4A EP12727153A EP2710169A2 EP 2710169 A2 EP2710169 A2 EP 2710169A2 EP 12727153 A EP12727153 A EP 12727153A EP 2710169 A2 EP2710169 A2 EP 2710169A2
Authority
EP
European Patent Office
Prior art keywords
electrode
electrochemical cell
cell
electrodes
diamond
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.)
Withdrawn
Application number
EP12727153.4A
Other languages
German (de)
English (en)
Inventor
Patrick Bray
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
A Gas International Ltd
Original Assignee
A Gas International Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by A Gas International Ltd filed Critical A Gas International Ltd
Publication of EP2710169A2 publication Critical patent/EP2710169A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • 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
    • C25B15/00—Operating or servicing cells

Definitions

  • the present invention relates to an electrochemical cell and a method of operating the same.
  • the present invention concerns in particular an electrochemical cell for the production of ozone and to a method of operating the cell.
  • Electrochemical cells find use in a range of applications for conducting a variety of electrochemical processes.
  • the cells comprise an anode and a cathode, separated by a semi-permeable membrane, in particular a Cation Exchange Membrane that may also be described as a Proton Exchange Membrane.
  • a semi-permeable membrane in particular a Cation Exchange Membrane that may also be described as a Proton Exchange Membrane.
  • One particular application for electrochemical cells is the production of ozone by the electrolysis of water.
  • Ozone is one of the strongest and fastest acting oxidants and disinfectants available for water treatment. Although ozone is only partially soluble in water, it is sufficiently soluble and stable to disinfect water contaminated by pathogenic microorganisms and can be utilised for a wide range of disinfection applications including sterilisation. Microorganisms of all types are destroyed by ozone and ozonated water including bacteria, viruses, fungi and fungal spores, oocyst
  • Ozone decomposes rapidly in water into oxygen and has a relatively short half life.
  • the half life of ozone in water is dependant upon temperature, pH and other factors.
  • the short half-life of ozone is a further advantage, as once treatment has been applied, the ozone will rapidly disappear, rendering the treated water safe. Once treatment has been applied, ozone that remains in solution will rapidly decay to oxygen.
  • ozone does not form toxic halogenated intermediates and undesirable end products such as Tnhalomethanes (THMs).
  • the concentration of ozone dissolved in water determines the rate of oxidation and the degree of disinfection in any given volume of water, with the higher the concentration ozone, the faster the rate of disinfection of micro-organisms. Electrolysis of water at high electrode potential produces ozone at the anode in an electrochemical cell according to the following equations:
  • Ozone may be produced at higher current efficiencies and in higher concentrations from low conductivity water, deionised water, demineralised water, and softened water.
  • the ozone may be produced in situ in the water stream by the above-mentioned anodic reactions as water flows through the electrochemical cell past the anode.
  • Ozone dissolved in water is described as ozonated water.
  • the production of ozone and ozonated water by electrolysis using an electrochemical cell is known in the art.
  • DE 10025167 discloses an electrode assembly for use in a cell for the electrolytic production of ozone and/or oxygen.
  • the cell comprises an anode and a cathode separated by a membrane in direct contact with each of the electrodes.
  • WO 2005/058761 discloses an electrolytic cell for the treatment of contaminated water.
  • the cell comprises an anode and a cathode, with water being passed between the two electrodes.
  • the cathode is preferably formed from nickel, titanium, graphite or a conductive metal oxide.
  • the cathode is provided with a coating, preferably boron doped diamond (BDD), activated carbon or graphite.
  • BDD boron doped diamond
  • the anode is preferably formed from titanium, niobium, or a conductive non-metallic material, such as p-doped silicon.
  • the anode is preferably provided with a coating, with preferred coatings being boron doped diamond (BDD), lead oxide (Pb0 2 ), tin oxide (Sn0 2 ), platinised titanium, platinum, activated carbon and graphite.
  • US 2008/156642 concerns a system for the disinfection of low-conductivity liquids, in particular water, the system comprising an electrochemical cell in which electrodes are arranged to allow the liquid to flow therearound.
  • Oxidizing agents such as ozone, are produced from the liquid by the application of an electrical current.
  • US 2007/0023273 concerns a method of sterilization and an electrolytic water ejecting apparatus.
  • Raw water is sterilized by electrolysis in a unit comprising a cell having a cathode and an anode at least having a part containing a conductive diamond material.
  • WO 2010/037391 discloses a device and process for removing microbial impurities in water.
  • the device comprises a disinfection chamber having a stack of electrodes of a least two perforated electrode plates of an electrically conductive material.
  • US 2010/0006450 discloses a diamond electrode arrangement for use in an electrochemical cell for the treatment of water and/or the production of ozone.
  • the cell comprises an anode and a cathode separated by a proton exchange membrane (PEM).
  • PEM proton exchange membrane
  • the electrode is formed with a diamond plate and is configured to have one or more slots (described as elongated apertures) therein, to provide a minimum specified apertures length per unit of working area of the electrode.
  • the metal anions in solution such as calcium, magnesium, iron and manganese
  • migrate to the cathode causing a build up of these metals and their compounds on the active surface of the cathode.
  • the deposition of these metals and their compounds individually and collectively causes passivation of the cathode and a consequential reduction in the flow of current through the electrochemical cell.
  • This process of electro-deposition of materials on the cathode passifies the electrodes in the electrochemical cell causing the current flowing through the cell to reduce over a period of time, thereby reducing the productivity of the cell over time, to the point when ozone may no longer be produced at the anode.
  • unrestricted cathodic electro-deposition of metals and their compounds in the electrochemical cell causes W
  • liquid flow channels to become restricted by the build-up of deposited substances and even, in extreme cases, to become completely blocked.
  • Chemical cleaning systems for cathodes are known in the art and have been used. Chemical cleaning systems rely on the use of agents in the catholyte to remove material deposited on the cathodes. Chemical agents that may be used in such chemical cleaning systems include acids of various types, in particular mild organic acids such as citric acid, ethylenediaminetetraactic acid (EDTA) and other mild acids. Citric acid and EDTA have a further benefit as they also act as a chelating agent, removing metal cations from solution.
  • mild organic acids such as citric acid, ethylenediaminetetraactic acid (EDTA) and other mild acids.
  • Citric acid and EDTA have a further benefit as they also act as a chelating agent, removing metal cations from solution.
  • Chemical cleaning systems for cathodes require a separate catholyte circuit.
  • the catholyte is the aqueous solution that flows past the cathodes in the electrochemical cell.
  • concentration of the chemi ' cai cleaning agent in the catholyte must be maintained at the required level in order that the performance of the electrochemical cell is maintained.
  • the use of a catholyte circuit with chemical cleaning system increases the complexity of the electrochemical cell and its operation.
  • the passivation of an electrochemical cell for use in the production of ozone or ozonated water by the electrolysis of water may be reduced or prevented entirely by the periodic reversal of the electric current flowing through the cell, provided the electrodes of the cell are provided with an active surface formed from diamond, preferably polycrystalline boron doped diamond (BDD).
  • BDD polycrystalline boron doped diamond
  • the present invention provides a method of operating an electrochemical cell for use in the electrolysis of water to produce ozone, the cell comprising a first electrode and a second electrode separated by a Cation Exchange Membrane, wherein the first and second electrodes each has an active surface formed from electrically conductive diamond, in a first mode of operation the electrochemical cell having a flow of electrical current in a first polarity, whereby the first electrode functions as an anode and the second electrode is a cathode; the method comprising:
  • the present invention provides an electrochemical cell for use in the production of ozone in normal operation, the electrochemical cell comprising:
  • first electrode and a first fluid conduit for bringing fluid into contact with the first electrode, the first electrode having an active surface formed from electrically conductive diamond;
  • the second electrode having an active surface formed from electrically conductive diamond
  • a Cation Exchange Membrane extending between the first electrode and the second electrode and separating the first fluid conduit from the second fluid conduit; an electrical supply system for providing an electric current to the first and second electrodes, the electrical supply system operable to provide the electric current to the electrodes with a first polarity during a first mode of operation and to provide an electric current to the electrodes with a second polarity opposite to the first polarity during a second mode of operation.
  • the electrochemical cell is operated in a first mode, that is with a current density applied to the electrodes in a first polarity, whereby the first electrode acts as the anode and the second electrode acts as the cathode.
  • first mode that is with a current density applied to the electrodes in a first polarity
  • second electrode acts as the cathode.
  • ozone is produced at the anode, according to the electrochemical reactions described above.
  • the operation of the electrochemical cell in the first mode is continued for a first period of time. During this mode of operation, material is deposited on the second electrode acting as the cathode, as described above.
  • electrode materials notably materials with metal oxide and mixed metal oxide coatings
  • DSATM electrodes titanium electrodes that have a single or mixed metal oxide coating of ruthenium, iridium and tantalum, such as DSATM electrodes
  • the active surface oxide layer breaks down as a result of frequent polarity reversals.
  • Lead dioxide (Pb0 2 ) has been used as an anode material in electrochemical cells for the production of ozone and ozonated water.
  • this material is unstable and erodes rapidly over time under the application of high current densities.
  • polarity reversal increases the rate of erosion of the lead dioxide electrode.
  • lead, as an electrode material is unsuitable for application in drinking water processes as a result of its known toxicity.
  • ozone is produced at the first electrode acting as the anode.
  • the first electrode becomes the cathode, and the second electrode becomes the anode.
  • the conditions prevailing in the vicinity of the anode in the electrochemical cell are acidic as a result of the generation of hydrogen ions on the surface of the anode.
  • acidic conditions are quickly established in the vicinity of the second electrode. Any substance that has been deposited on the electrode by the process of electro- deposition is dissolved and removed by the acidic conditions prevailing at the electrode. In particular, calcium and magnesium compounds formed on the surfaces of the electrodes are simply removed each time the polarity of the current applied to the electrochemical cell is reversed.
  • the process of polarity reversal is an effective means of cleaning the working electrodes in the electrochemical cell.
  • the performance and current efficiency of the cell and, hence, the production of ozone is maintained in this way.
  • One significant advantage of polarity reversal of the applied electrical current is that no chemical cleaning agents are required to maintain the performance of the electrochemical cell and the production of ozone at the anodes.
  • the electrochemical cell is operated for repeated periods of time in the first mode with a first operating current polarity, separated by operation for a second period of time in the second mode with the polarity of the current reversed.
  • the length of operation of the cell in the first and second modes and the frequency at which the polarity of the applied current is reversed in the electrochemical cell can be varied to optimise the performance and efficiency of the cell, according to the prevailing operating conditions.
  • the length of operation in each of the first and second modes may be increased or decreased to optimise performance and current efficiency.
  • the time intervals between successive polarity reversals can be varied within wide limits, in particular to optimise cell performance and take account of such operating parameters as the concentration of metal cations, such as calcium, magnesium, iron and manganese, and other substances present in the feed water serving as the anolyte to the cell.
  • concentration of metal cations such as calcium, magnesium, iron and manganese, and other substances present in the feed water serving as the anolyte to the cell.
  • the length of time that the cell is operated in the first mode of operation, so as to produce ozone at the first electrode may be determined by monitoring the condition of the second electrode and the amount of substances deposited thereon. This may be achieved, for example,, by monitoring one or more operating parameters of the cell, such as the electrical current, measured in Amps, and the potential of the cell, measured in Volts.
  • the condition of the second electrode may be similarly monitored during the operation in the second mode of operation.
  • the length of time of the first period of operation in the first mode may be varied as required to maintain efficient operation of the cell. This time may be from several seconds to one or more hours, depending upon the operation conditions of the cell.
  • the /ength of time between successive polarity reversals is preferably in the range of from 5 seconds to 60 minutes, depending upon the purity of the water and, in particular, the concentration of metal cations, such as calcium, magnesium, iron and manganese, and other substances present in the water being fed to the cell, more preferably from 5 seconds to 30 minutes, still more preferably from 5 seconds to 10 minutes, still more preferably from 5 seconds to 5 minutes, still more preferably from 5 seconds to 60 seconds.
  • the length of time of the first period of operation in the first mode is preferably from 10 seconds to 60 seconds. In the case of 'hard' water, the length of time of operation in the first mode is more preferably from 5 seconds to 30 seconds.
  • the polarity of the applied current is reversed and the cell is operated in the second mode with the reversed polarity for a sufficient period of time to reduce or remove the material deposited on the second electrode. Again, this may be achieved, for example, by monitoring one or more operating parameters of the cell, such as the electrical current or the potential of the cell.
  • operation of the cell may be switched to the first mode, which in this case may be considered to be normal operation.
  • the cell will require operation in the second mode with the reversed polarity of current for the same periods of time required for the periods of operation in the first mode.
  • the cell is operated in the second mode with the polarity of the current reversed for a period of time in the range of from 5 seconds to 60 minutes, more preferably from 5 seconds to 30 minutes, still more preferably from 5 seconds to 10 minutes, still more preferably from 5 seconds to 5 minutes, still more preferably from 5 seconds to 60 seconds.
  • the operating current density, measured in Amps/cm 2 , at the electrodes is a function of the electrical current applied to the cell, measured in Amps, from the power supply, divided by the active surface area of the diamond anodes.
  • the current applied to the electrochemical cell, and therefore the current density at the anodes, during each of the first and second modes of operation may be selected to optimise the performance of the cell and to optimise the production of ozone and ozonated water.
  • the electrochemical cell may be operated at current densities up to 5.0 Amps/cm 2 , depending upon the size and duty of the cell.
  • the current density is in the range of from 0.1 to 5.0 Amps/cm 2 , more preferably from 0.4 to 3.2 Amps/cm 2 , and still more preferably in the range 0.5 to 1.2 Amps/cm 2 for the production of ozonated water for most disinfection applications.
  • the current density applied during the second mode of operation is preferably the same or substantially the same as the current density applied in the first mode of operation, in particular, when the production of ozone and/or ozonated water is required in both the first and second modes of operation.
  • the electrochemical cell may be operated at applied voltages up to 50 Volts, depending upon the conductivity of the water stream being treated. According to the operating conditions the voltage is preferably at least 10 Volts, more preferably at least 12 Volts, still more preferably at least 15 Volts, still more preferably at least 20 Volts. Voltages in excess of 25 Volts may also be applied, for example a voltage up to 30 Volts or up to 40 Volts, as required. A voltage of between 12 and 24 Volts is particularly preferred.
  • the present invention requires that the electrochemical cell has both the first and the second electrodes are provided with active surfaces formed from diamond.
  • the electrically conductive diamond material may be a layer of single crystal synthetic diamond, natural diamond, in particular Type I IB diamond, or polycrystalline diamond. Polycrystalline diamond is particularly preferred.
  • the diamond may be naturally occurring diamond, high pressure high temperature (HPHT) synthesised diamond or chemical vapour deposition (CVD) diamond, with CVD diamond again being preferred.
  • the diamond material may consist essentially of carbon, but is doped with one or more elements that provide electrical conductivity. Suitable dopants to provide the diamond with electrical conductivity are known in the art. Diamond is preferably doped with boron to confer electrical conductivity and is described as boron doped diamond (BDD).
  • a particularly suitable and preferred diamond material is polycrystalline boron doped diamond (BDD).
  • BDD is a known and commercially available material.
  • the active electrodes of the cell may be of a solid diamond material or a substrate material coated with diamond.
  • the preferred electrode material is electrically conductive, solid, free standing polycrystalline Boron-doped diamond.
  • This diamond material is manufactured by way of a process of chemical vapour deposition in a microwave plasma system. This diamond material is preferably from 200 to 1000 microns in thickness, more preferably from 300 to 800 microns thick. It is particularly preferred that the solid diamond material is a layer of thickness from 400 to 700 microns, more particularly from 500 to 600 microns.
  • the active electrode material may be a substrate material coated with conductive diamond.
  • the substrate material may be any suitable material, examples of which include silicon (Si), tungsten (W), niobium (Nb), molybdenum (Mo) or tantalum (Ta).
  • This diamond material is manufactured by known techniques, for example by way of a process of chemical vapour deposition in a hot filament system.
  • the active diamond surface of the electrode material in this case, is typically from 1 to 10 microns in thickness, more preferably from 3 to 5 microns thick.
  • Suitable techniques for manufacturing both solid free-standing electrically conductive Boron-doped diamond material and diamond coated material are known in the art. It has been found that diamond material provided as a layer formed on the substrate material is eroded under the conditions prevailing in the electrochemical cell during operation. This in turn reduces the longevity and operating life of the cell. Accordingly, it is preferred that the diamond material is provided as a layer of pre- formed solid diamond, such as the Boron-doped diamond material referred to hereinbefore.
  • the electrochemical cell comprises first and second electrodes, as noted above.
  • Each of the first and second electrodes may comprise a single electrode or, more preferably a plurality of electrodes electrically connected to act together.
  • the electrochemical cell comprises a Cation Exchange Membrane disposed between the electrodes.
  • the membrane permits the movement of cations, including hydrogen ions (protons) and positively charged metal cations, such as calcium, magnesium, iron and manganese, in the anolyte to pass through the membrane to the cathode, in either direction, depending upon the polarity of the current applied to the cell at any given time.
  • the membrane is most preferably in contact with each electrode.
  • Each electrode has a conduit for providing a fluid to contact the respective electrode, the two conduits being separated by the membrane.
  • each electrode is preferably formed to have edges to the active surface of the diamond, with the semi-permeable membrane being in contact with the edges of the diamond material.
  • ozone is produced in the water stream (ozonated water).
  • Hydrogen ions pass through the membrane to the cathode side of the cell where hydrogen gas is produced.
  • Other positively charged metal cations such as calcium, magnesium, iron and manganese also pass through the membrane and are deposited on the cathode, as noted above.
  • Suitable materials for the membrane are known in the art and are commercially available.
  • One particularly preferred class of materials for use in the membrane are sulfonated tetrafluoroethylene-based fluoropolymers. Such materials are known in the art and are commercially available, for example the NafionTM range of products available from Dow Chemical.
  • the electrochemical cell is operated under a regime of forced flow circulation. Water is supplied to the cell under pressure and is evenly distributed either side of the membrane by means of . inlet manifolds connected to the conduits adjacent to both the first and second electrodes. The electrochemical reactions that take place when the cell is operating are therefore uniformly distributed in the conduits adjacent the edges of the electrodes.
  • the water supplied to the electrochemical cell is divided equally between the anolyte and cathol te sides of the cell.
  • the water pressure either side of the membrane in the cell is equal, regardless of the rate of flow of water through the cell. Therefore, there is no hydrostatic force driving anolyte through the membrane into the catholyte side of the cell.
  • electrochemical cells that have separate catholyte circuits such as required when using chemical cleaning systems for the cathode.
  • the concentration of the anolyte and catholyte may also be maintained substantially equal. Therefore, there is no osmotic force present to drive water from the anolyte side of the cell into the catholyte side of the membrane.
  • the cell may be provided with water at any suitable flowrate.
  • the water flow through the electrochemical cell is determined several factors including the size of the cell, the number of flow channels through the cell and the dimensions of the flow channels.
  • the generation of ozone in the cell and therefore cell performance increases as the rate of mass transport increases at the interface of the anode, the membrane and the water flowing through the cell. Increasing the rate of flow of water to the optimum increases mass transport within the cell, and therefore cell efficiency, and the production of ozone.
  • the range of flow is between 0.5 and 50 litres/minute depending upon the size of the electrochemical cell and the factors described above.
  • the water flow through the cell is preferably at least 1 litre/minute, more preferably at least 5 litres/minute. Higher water flow rates may also be employed, subject to the size and capacity of the cell and particularly its flow channels, such as flow rates of at least 10 litres/minute, more preferably at least 20 litres/minute, up to 40 litres/minute.
  • the electrochemical cell can be operated at a wide range of water pressures, most conveniently at mains water pressure. Water pressures of at least 1 Bar may be employed, preferably 2 Bar, more preferably 4 Bar, still more preferably 6 Bar, and up to 8 Bar. To obtain the optimum efficiency of the electrochemical cell the water pressure should be regulated to maintain the optimum flow as described above.
  • the cell is operated with a supply of water to the conduits on both sides of the membrane within the cell, as described above. Further, the liquid outlets from each side are provided with means to divert the liquid stream leaving each side of the cell to either an anolyte system or a catholyte system.
  • anolyte produced by the cell is the required product, in particular ozonated water.
  • the catholyte is removed from the cell and is preferably passed to a degasser to remove hydrogen generated at the cathode.
  • the cell is operated for a first period of time in the first mode, with the first electrode as the anode and producing anolyte from its respective conduit to be fed to the anolyte system, while the second electrode acts as the cathode and produces catholyte from its respective conduit, to be fed to the catholyte system, such as the hydrogen degasser.
  • the polarity of the current applied to the electrodes is reversed and the cell operated in the second mode, for a second period of time.
  • the first electrode acts as the cathode and has the catholyte removed from its respective conduit directed to be processed in the catholyte system.
  • the second electrode acts as the anode in the second mode and produces anolyte within its respective conduit, which is directed to the anolyte system as product of the cell.
  • the cell may be operated in a particularly efficient manner, with each electrode of the cell operating as either the anode or the cathode, depending upon the mode of operation, and producing the required product throughout the entire operation.
  • the present invention provides a method for removing deposits from the cathode of an electrochemical cell, the cathode having an active surface formed by diamond, the method comprising reversing the polarity of the current applied to the electrodes of the cell during normal operation for a sufficient time to remove material deposited on the cathode during normal operation.
  • Figure 1 is a diagrammatical cross-sectional view of an electrochemical cell of one embodiment of the present invention
  • Figure 2 is a schematic representation of a system for producing ozonated water according to one embodiment of the present invention.
  • FIG. 1 there is shown an electrochemical cell, generally indicated as 2, for the production of ozone and/or ozonated water by the electrolysis of water.
  • the cell 2 comprises a pair of opposing cell bodies 4, 6 held together by means of a number of through bolts 12.
  • the first and second cell bodies 4, 6 may be prepared from any suitable material that is chemically resistant to strong oxidants, in particular ozone, generated within the cell.
  • Thermoplastic fluoropolymers are a preferred class of materials for forming the cell bodies, in particular polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • PMMA polymethylmethacrylate
  • Each cell body 4, 6 is provided with a plurality of cavities in a major face, with each adjacent pair of cavities as shown in Figure 1 being separated by a land.
  • the cavities and lands are arranged in the face of the cell bodies 4, 6 such that the cavities in the cell bodies are arranged in opposing pairs.
  • Each cavity forms a conduit 14 for the passage of water therethrough.
  • the conduits 14 have a generally rectangular cross-section.
  • the lands in the face of each cell body 4, 6 are arranged to form opposing pairs.
  • the surface of each land is provided with a layer of boron doped diamond (BDD) 16.
  • BDD boron doped diamond
  • the layers of BDD on the first cell body 4 form a plurality of first electrodes, while the layers of BDD on the second cell body 6 form a plurality of second electrodes.
  • a semi-permeable membrane 18 extends between the first and second cell bodies 4, 6.
  • the membrane 18 is formed from a sulfonated tetrafluoroethylene- based fluoropolymer (Nafion® N-117 membrane).
  • the membrane 18 divides the opposing conduits 14 in the faces of the cell bodies. Further, the membrane 18 extends between the opposing pairs of BDD electrodes.
  • the cell bodies 4, 6, the BDD electrodes 16 and the membrane 18 are arranged such that the surface of each of the BDD electrodes is in contact with the adjacent portion of the membrane.
  • Each cell body 4, 6 of the cell 2 is provided with a busbar 20, from which extend current feeders 22 connecting the busbar 20 with respective BDD electrodes 16.
  • the busbar 20 and current feeders 22 may be formed from any suitable conductor, for example stainless steel, aluminium, copper or brass.
  • Each busbar 20 is further provided with a current connector 24, allowing the busbar to be connected to an electrical supply system.
  • the current feeders 22 and busbars 20 are sealed within the cell bodies 4, 6 to prevent leakage from the conduits 14.
  • the electrochemical cell 2 shown in Figure 1 is connected to a system as shown in Figure 2.
  • the electrochemical cell 2 is provided with a supply of fresh water, for example mains water, via a tank 101.
  • the water is supplied to the cell through a line 102 and divided equally between lines 104 and 106, each feeding water from the supply to the conduits 14 in respective cell bodies 4, 6.
  • the conduits and electrodes on each side of the membrane are provided with water having the same composition and under the same conditions of pressure and flowrate.
  • Each solenoid valve 118, 120 is operable to direct the liquid leaving the cell 2 to either an ozonated water product line 122 or a hydrogen degassing column 124.
  • liquid may be directed from the solenoid valve 118 along either a line 134a to the hydrogen degassing column 124 or a line 34b to the product line 122.
  • liquid may be directed from the solenoid valve 120 along a line 136a to the hydrogen degassing column 24 or a line 136b to the product line 122.
  • Hydrogen gas may be recovered from the hydrogen degassing column 124, for further processing and/or use. Alternatively, the hydrogen may be safely vented to the atmosphere. Water recovered from the hydrogen degassing column may be used elsewhere, disposed of or recycled to the inlet of the system, in particular returned to the tank 101 for further use in the electrochemical cell.
  • the product line 122 returns ozonated water from the electrochemical cell to the tank 101 , where it is diluted with fresh mains water, to achieve the desired ozone concentration.
  • An ozonated and disinfected water product is removed from the tank 101.
  • a supply of direct current is provided to the electrochemical cell 2 by a DC electric supply system 150, connected by cables 152 to the current connectors 24 of each cell body 4, 6.
  • the electric supply system 150 is operable to provide current to the electrodes as required and with either of two polarities.
  • the electrochemical cell is operated in the first mode, with the water supplied to the conduits 14 in both cell bodies 4, 6.
  • Current is supplied to the cell by the electric supply system 150 with a first polarity, such that the BDD electrodes in the first cell body 4 act as the anode and the BDD electrodes in the second cell body 6 act as the cathode.
  • Anolyte produced in the conduits of the first cell body 4 leaves through the line 1 14 and is directed by the solenoid valve 1 18 to the line 134b to the product outlet line 122.
  • Catholyte produced in the conduits of the second cell body 6 leaves through the line 1 16 and is directed by the solenoid valve 20 to the line 136a, to be fed to the hydrogen degassing column 124.
  • the cell After a period of operation in the first mode, material is deposited on the electrodes in the second cell body 6, acting as the cathode. This in turn passivates the BDD electrodes, reducing the efficiency of operation of the cell.
  • the cell is switched into the second mode. In particular, the position of each of the solenoid valves 1 18 and 120 is changed and the polarity of the current supplied by the electric supply system 150. In this mode, the BDD electrodes in the second cell body 6 act as the anode and the BDD electrodes in the first cell body 4 act as the cathode.
  • Anolyte produced in the conduits of the second cell body 6 leaves through the line 1 6 and is directed by the solenoid valve 120 to the line 136b to the product outlet line 122.
  • Catholyte produced in the conduits of the first cell body 4 leaves through the line 1 14 and is directed by the soienoid valve 1 18 to the line 134a, to be fed to the hydrogen degassing column 124.
  • Operation of the system is controlled by means of a controller 180, in particular allowing the position of the solenoid valves 18, 120 to be changed and the DC power supply 150 to be controlled, in particular to change the current polarity.
  • the controller 80 further controls the concentration of ozone in the water in the tank 101, by means of an Oxidation Reduction Potential (ORP) or Redox Sensor 200, or Ozone Sensor in the base of the tank 101.
  • ORP Oxidation Reduction Potential
  • Redox Sensor 200 Ozone Sensor in the base of the tank 101.
  • the controller 180 determines the concentration of ozone in the water in the tank 101 by means of the signal received from the sensor 200.
  • the operation of the electrochemical cell is controlled to maintain the ozone concentration in the tank within the desired range, determined by the end use to be made of the ozonated water.
  • the cell may be operated in the second mode until the performance of the cell has been restored. Thereafter, operation may be switched to the first mode. Alternatively, the cell may be continued to be operated in the second mode, until the performance of the cell again deteriorates, due to the electro-deposition of material on the BDD electrodes in the first cell body 4. At this time, operation is switched to the first mode. The cell may be cycled between the first and second modes of operation in this manner. It has been found that the electrochemical cell employing the BDD electrodes may be operated in accordance with the present invention with a high overall efficiency and with substantially no attrition of the electrodes observed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)

Abstract

L'invention concerne un procédé de fonctionnement d'une cellule électrochimique destinée à être utilisée dans l'électrolyse de l'eau pour produire de l'ozone, la cellule comprenant une première électrode et une seconde électrode séparées par une membrane échangeuse de cations, les première et seconde électrodes ayant chacune une surface active formée à partir d'un diamant électro-conducteur, la cellule électrochimique ayant, dans un premier mode de fonctionnement, un flux de courant électrique dans une première polarité, moyennant quoi la première électrode fonctionne comme une anode et la seconde électrode est une cathode ; le procédé comprenant la fourniture à la cellule électrochimique dans le premier mode de fonctionnement d'une alimentation en courant vers les électrodes dans la première polarité pour produire de l'ozone au niveau de la première électrode pendant une première période de temps ; et la fourniture à la cellule électrochimique dans un second mode de fonctionnement d'une alimentation en courant vers les électrodes dans une seconde polarité, opposée à la première polarité, pendant une seconde période de temps. L'invention concerne également une cellule électrochimique destinée à être utilisée dans le procédé susmentionné.
EP12727153.4A 2011-05-17 2012-05-16 Cellule électrochimique et son procédé de fonctionnement Withdrawn EP2710169A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1108254.2A GB2490913B (en) 2011-05-17 2011-05-17 Electrochemical cell and method for operation of the same
PCT/GB2012/000441 WO2012156671A2 (fr) 2011-05-17 2012-05-16 Cellule électrochimique et son procédé de fonctionnement

Publications (1)

Publication Number Publication Date
EP2710169A2 true EP2710169A2 (fr) 2014-03-26

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EP (1) EP2710169A2 (fr)
GB (1) GB2490913B (fr)
WO (1) WO2012156671A2 (fr)
ZA (1) ZA201309362B (fr)

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GB201522500D0 (en) * 2015-12-21 2016-02-03 Element Six Technologies Ltd Electrochemical cell comprising electrically conductive diamond electrodes
WO2018075920A1 (fr) 2016-10-20 2018-04-26 Advanced Diamond Technologies, Inc. Générateurs d'ozone, procédés de fabrication de générateurs d'ozone et procédés de génération d'ozone
GB2557191B (en) * 2016-11-29 2021-02-24 Roseland Holdings Ltd Toilet assembly and method for its operation
GB2557185A (en) * 2016-11-29 2018-06-20 Roseland Holdings Ltd Electrochemical cell assembly and method for operation of the same
WO2020018983A1 (fr) * 2018-07-20 2020-01-23 Enozo Technologies, Inc. Système de production d'ozone électrolytique à haut rendement
CN110589934A (zh) * 2019-08-29 2019-12-20 浙江工商大学 一种用于水槽的嵌入式水消毒装置
US20220372637A1 (en) 2020-01-14 2022-11-24 Peter A. Barratt Process and Apparatus for Production of Ozone
AU2022421703A1 (en) * 2021-12-22 2024-05-23 Electric Hydrogen Co. Operation of an electrolytic cell or system at intermediate oxygen pressure
CN114314769B (zh) * 2022-01-20 2023-04-18 山东欣远新材料科技有限公司 一种基于bdd电极的电解模组及水处理系统

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Also Published As

Publication number Publication date
WO2012156671A2 (fr) 2012-11-22
GB2490913A (en) 2012-11-21
WO2012156671A3 (fr) 2013-04-04
GB2490913B (en) 2015-12-02
GB201108254D0 (en) 2011-06-29
ZA201309362B (en) 2020-02-26

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