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
  • C02F1/4602—Treatment of water, waste water, or sewage by electrochemical methods for prevention or elimination of deposits
• • 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
• • 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
  • C02F2001/46119—Cleaning the electrodes
• • 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
  • C02F2201/4612—Controlling or monitoring
  • C02F2201/46125—Electrical variables
  • C02F2201/4613—Inversing polarity
• • 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
  • C02F2201/4619—Supplying gas to the electrolyte

Definitions

• the present invention relates to a process for treating a fluid and especially at least decarbonation of water in a reactor, said reactor comprising at least one anode that can be connected to a positive terminal of a current generator and to the minus one cathode that can be connected to a negative terminal of said current generator. It relates more particularly to the major improvement of the performance of such a method and the associated device, both during the treatment of the fluid and during the cleaning of the electrodes used in the implementation of the electrolysis decarbonation process.
• the immediate precipitation of the calcium carbonate is carried out in the electrolytic treatment chamber: the electrolysis is carried out between an anode and a cathode within the water to be treated which constitutes the electrolyte, by first constituting the cathode a thin and porous adhesive coating comprising calcium carbonate intended for to promote the growth by nucleation and the formation of germs which support the birth of calcium carbonate crystals.
• a gas flow is produced only through the pores of the cathode (by gas blowing or by hydrogen generation in situ by electrolytic reduction of water) so that crystals that form on said porous coating are peeled off from it by the action of the gas flow.
• This method is implemented in a reactor comprising a vessel and two series of parallel plates forming anodes and cathodes, which the liquid to be treated runs upward.
• the electrochemical reaction causes the precipitation of CaCO 3 in the basic medium created in the vicinity of the cathode (s).
• This CaCO 3 falls partly in the bottom of the reactor where it is discharged regularly, but another part remains on the cathodes.
• TH Hydrophilimetric Title
• TAC Frull Alkalimetric Title
• the TAC is the content of a water in alkalis (hydroxides), in carbonates and alkali or alkaline earth bicarbonates (or hydrogen carbonates).
• pH s which is the saturation pH
• An object of the invention is to propose a major improvement of the processes of the prior art by providing a reliable decarbonation process, whose instantaneous and overall yields can be increased by at least 40%, or even 50%, or even more .
• Another object of the invention is to provide a water decarbonation process that is at least partially or completely automatic, including self-cleaning phases that require no or little human intervention.
• the present invention thus relates in its broadest sense to a process for treating a fluid and in particular at least decarbonation of water according to claim 1.
• This process is carried out in a reactor, this reactor comprising at least one anode connectable to a positive terminal of a current generator and at least one cathode connectable to a negative terminal of said current generator.
• the fluid undergoes intensive stirring inside said reactor.
• intensive stirring in the sense of the present invention is meant that the fluid is subjected to an additional mixing action, adding to the simple movement of the fluid under the action of the introduction of the fluid to be treated and the recovery of treated fluid.
• the present invention is based on a quite surprising observation: the inventors have found that additional stirring in the reactor has the consequence both of improving the instantaneous yield of the reactions, but also of facilitating the reaction. cleaning: They realized that, for a reason still unknown, the crystallization of the calcium carbonate takes place in a very particular form when the electrolyte is subjected to a mixing at the level of the
• the process according to the invention has several alternative or cumulative variants for carrying out intense stirring inside the reactor.
• said stirring is performed by injecting gas into said fluid at a flow rate at least substantially equal to that of the fluid and preferably from 2 to 10 times that of the fluid.
• the air supply flow rate is preferably:
• said stirring is performed by recirculation R carried out by suction of said fluid at at least one location in said reactor and discharge of said fluid to at least another location in said reactor.
• a recirculation R is preferably operated between a buffer tank and a treatment tank of said reactor and in that the raw water is introduced not into the treatment tank, but into the tank. buffer and distributed treated water is taken not from the treatment tank, but from the buffer tank.
• This recirculation flow R is preferably from 4 to 20 times greater, and more preferably of the order of 10 times greater, than the average flow rate of treated water delivered at the outlet of the buffer tank.
• the recirculation flow rate R in liters per hour is, preferably at least 10 times, or even at least 50 times, greater than the volume in liters of the treatment tank from which the fluid is drawn and in which the fluid is discharged.
• said stirring is operated by at least one mechanical means such as an agitator or a propeller, driven by a movement inside said reactor.
• said intense stirring is permanently proportional to the fluid flow, the proportion may preferably vary, especially during a cleaning phase.
• At least one and preferably all cathodes (s) present (s) a corrugated surface.
• the depth p of a corrugation and preferably of all the corrugations (s) is at least 2 mm relative to the mean plane of said cathode.
• the distance between the mean plane of a cathode (C) and the average plane of the adjacent anode (A) is between 10 and 60 mm and preferably between 20 and 30 mm.
• said cathode at least to be cleaned is connected to a positive terminal of a current generator and is preferably subjected to a current intensity of the current. from 3 to 30 Am 2 , especially from 5 to 20 Am 2 and preferably of the order of 10 Am -2 .
• said cathode at least to be cleaned is connected to a positive terminal of a current generator and is preferably subjected to a current intensity of the order of 1 to 3 times the current intensity used to perform said treatment.
• a current is applied across said current generator which is connected to said cathode at least to clean for a period, preferably of the order of one to several minutes.
• the conductivity of the fluid can be increased, in particular to a value of between 800 and 8000 microns per centimeter.
• one solution consists in adding at least one salt, preferably neutral, of the Na 2 SO 4 type .
• said cleaning phase is preferably programmed to be performed automatically at regular intervals, for example every week to every month or every three months, or on instruction of a measuring system, that is, that is, without human intervention or with very light human intervention.
• the present invention also relates to a reactor for treating a fluid and especially at least decarbonation of water for the implementation of the method according to the invention.
• the treatment reactor comprises at least one anode that can be connected to a positive terminal of a current generator and at least one cathode that can be connected to a negative terminal of said current generator and is characterized in that it comprises means for intense stirring inside said reactor and more specifically inside the treatment tank.
• said intense stirring means are preferably constituted by at least one porous pipe or pierced with micro-holes, said pipe being fed by a pump or a pressure reducer, for formation of bubbles in the fluid, especially air bubbles or nitrogen.
• said micro-holes preferably have a diameter less than or equal to 2 mm and preferably less than or equal to 1 mm.
• said intense stirring means are preferably constituted by at least one fluid extraction mouth, at least one fluid discharge mouth and at least one a pump positioned between said extraction mouth and said discharge mouth.
• said intense stirring means are preferably constituted by at least one mechanical means such as an agitator or a propeller, as well as a drive system capable of driving said moving mechanical means within said reactor.
• At least one and preferably all cathodes (s) present (s) a corrugated surface.
• the depth (p, p ') of a corrugation and preferably of all the corrugations (s) is at least preferably 2 mm.
• the distance between the mean plane of a cathode and the mean plane of the adjacent anode is between 10 and 60 mm and preferably between 20 and 30 mm.
• the current generator used is preferably capable of generating a current density of the order of 3 to 30 Am -2 , especially 5 to 20 Am -2, and preferably of the order of 10 Am- 2 in said cathode (s)
• the reactor preferably comprises automatic control means for automatically cleaning said cathode. less to clean at regular intervals or on instruction of a measuring system.
• Said cathodes are preferably positioned on supports facilitating their extraction.
• the reactor may comprise means for guiding the electrodes, preferably positioned outside a treatment tank.
• the present invention thus makes it possible to implement a method of electrolysis treatment, and particularly of decarbonation of water, which is particularly efficient and which may comprise a phase of cleaning the electrodes and which may be at least partially or totally automated.
• these phases being very short and very effective, it is possible to achieve them in masked time, without interrupting the extraction of fluid from the reactor.
• FIG. 1 illustrates an exemplary schematic diagram of a decarbonation reactor according to the invention
• FIG. 2 illustrates the diagram of the decarbonation reactor of FIG. 1 during decarbonation
• FIG. 3 illustrates a perspective view of a decarbonation reactor according to the invention
• FIG. 4 illustrates an exploded view of the decarbonation reactor of FIG. 3
• FIG. 5 illustrates the cathode extraction step of the decarbonation reactor of FIG. 3
• Table 8 illustrates the variation of abatement and voltage during a 60-day test period of a reactor such as that illustrated in Figure 7;
• FIG. 10 illustrates a first exemplary embodiment of the intense stirring means by fluid recirculation;
• FIG. 11 illustrates a second exemplary embodiment of the intense stirring means by fluid recirculation
• Table 12 illustrates the variation of abatement as a function of the average contact time in minutes for a reactor such as that illustrated in FIG. 11;
• FIG. 13 illustrates an exemplary embodiment of the intense stirring means by setting in motion a mechanical means
• FIG. 14 illustrates a vertical sectional view of a baffled reactor, the baffles being formed with cathodes and solid anodes and the fluid passing through the top and bottom of the electrodes;
• FIG. 15 illustrates a top view of a baffled reactor, the baffles being formed with cathodes and solid anodes and the fluid passing through the right and the left of the electrodes;
• FIG. 16 illustrates a vertical sectional view of a baffled reactor, the baffles being formed with cathodes and deployed anodes and the fluid passing through the top and bottom of the cathodes and through the anodes;
• FIG. 17 illustrates an exemplary schematic diagram of the decarbonation reactor of FIG. 1 during a cleaning according to a first solution, by polarity inversion;
• FIG. 18 illustrates a corrugated anode according to the invention
• FIG. 19 illustrates a partial view of an exemplary embodiment of the corrugations of the anode of FIG. 18
• FIG. 20 illustrates a partial view of another embodiment of the corrugations of the anode of FIG. 18;
• Figure 21 illustrates the evolution of the abatement with respect to the current density, firstly for a corrugated cathode and secondly for a flat cathode under identical experimental conditions.
• FIG. 1 illustrates the schematic diagram of a known type of decarbonation treatment device or reactor (1) consisting of a current generator (2), a tank (3) and at least one anode ( A) and a cathode (C) positioned inside the vessel (3) and electrically connectable to said generator (2).
• Each anode (A) and each cathode (C) consists of a plate positioned substantially vertically and illustrated here in plan view.
• the fluid to be treated in this case water, circulates inside the hollow right parallelepiped treatment vessel (3), between the anodes and the cathodes.
• the cathodes consist for example of a flat plate made of 316L stainless steel and the anodes are of the "non-consumable" type DSA (Dimensionally Stable Anode), for example made of titanium coated with noble metals (IrO 2 , Ir, Ta, Ru,. ..).
• DSA Dissionally Stable Anode
• the anodes are electrically connected to each other by means of a bus-bar (BA) and the cathodes are electrically connected to each other using a bus-bar (BC).
• BA bus-bar
• BC bus-bar
• the tank (3) is mounted on a frame (4) comprising a hopper forming the bottom of said tank (3).
• the anodes (A) are fixedly positioned inside the tank (3) but the cathodes (C) are extractable because they are all supported by longitudinal supports (5, 5 '), themselves supported by a trolley ( 6).
• guide means (10) are provided. These guide means consist, on the illustrated version, of at least one vertical cylinder, and preferably two vertical cylinders, connected (s) rigidly to the carriage (6) and each cooperating with a vertical cylindrical tube, by sliding to inside said tube or tubes. Centering devices are also provided. All these means are provided outside the tank (3), to protect them from the action of the treatment.
• the extraction of the cathodes is made easier thanks to a removable electrical connector of the socket-lug type. This system makes it possible to connect and disconnect the connections easily manually and facilitates the extraction of the electrodes.
• the fluid is introduced through the orifice (9) located in the upper part of the hopper (4) and flows overflow by an evacuation located in the upper part of the tank (3).
• the mouth (8) located at the lower end of the hopper allows the evacuation of calcium carbonate removed from the water and unhooked cathodes, this mouth also allows the emptying of the tank.
• the fluid undergoes intensive mixing inside the reactor (1) and more precisely inside the tank (3).
• FIGS. 6 to 8 illustrate different alternative or cumulative versions of the first variant embodiment of the intense stirring according to which said intense stirring means consist of at least one porous pipe (11, 11 ', 11 ", 11'") or pierced with micro-holes (illustrated by dots), said pipe being fed by a pump or a pressure reducer (not shown), for the formation of bubbles in the fluid, in particular air or nitrogen bubbles.
• said intense stirring means consist of at least one porous pipe (11, 11 ', 11 ", 11'") or pierced with micro-holes (illustrated by dots), said pipe being fed by a pump or a pressure reducer (not shown), for the formation of bubbles in the fluid, in particular air or nitrogen bubbles.
• Air or nitrogen is introduced into the pipe via a bubbling orifice (12, 12 ', 12 ", 12'").
• the hose (11) is wound around the water inlet pipe located longitudinally substantially horizontally, in the top of the hopper, perpendicular to the electrodes, about 15 cm from them.
• the hose (11) is wound so that it forms at least one loop on itself per meter of water inlet hose.
• This pipe is of the type used for automatic watering of gardens.
• the pipe (H ') is rigid and positioned on the entire inner periphery of the hopper, in its upper part, by welding a pipe inside the frame.
• ⁇ TH obtained without bubbling is 12 ° F
• ⁇ TH obtained with bubbling using an air flow of 25 L / Min, 10 times higher than the water flow is 16.6 0 F
• a gain of 4.6 0 F was thus obtained, which represents nearly 40%.
• the volume of the equipment can be reduced by about 30%.
• the pH is increased by bubbling and becomes identical to the initial value.
• FIG. 8 illustrates the evolution of the voltage (V in Volts) and of the reduction (in 0 F) over a period of 60 days (on the abscissa) during which the bubbling test was carried out.
• At least one rigid pipe (H ") is positioned substantially transversely in the top of the hopper, that is to say parallel to the electrodes, and / or at least one pipe (H '") rigid is positioned substantially longitudinally in the top of the hopper, that is to say perpendicular to the electrodes.
• two rigid transverse pipes (H ") and two rigid longitudinal pipes (H ') are used. These pipes can communicate with each other at their intersection to facilitate the distribution of air or injected gas.
• the intense bubbling makes it possible to raise the pH from 0 to 2 points.
• the intense bubbling allows the degassing of free chlorine from water.
• a certain concentration of free chlorine is profitable because it makes it possible to disinfect the water.
• An excess of free chlorine is however harmful since it greatly accelerates the corrosion metals in the water
• the intense bubbling thus allows degassing and evacuating the free chlorine in the atmosphere so that the corrosivity of the water is acceptable
• the intense bubbling makes it possible to reduce the concentration of free chlorine from a factor of 5 to 20 to zero values.
• the layer of limestone formed on the cathodes is porous, friable and powdery. Its density is 1.3 and a portion of the limestone formed falls to the bottom of the treatment tank.
• the most surprising effect of gas bubbling is that the layer of limestone formed on the cathodes is very dense, very hard and very compact. Its density is 1.9. It covers the entire cathode. Beads cover the edge edges of the cathode plates. Moreover, all the limestone extracted from the water remains attached to this layer. There is no deposit of limestone to evacuate from the bottom of the treatment tank. It is therefore all the more surprising to note that the adhesion of the limestone layer formed in the presence of gas bubbling on the cathode plates is very low, or almost zero.
• the holding of the limestone layer is in fact achieved by the total recovery of the cathode plates. These are taken in a limestone shell. If the edge beads are broken by hand, the limestone layer falls into heavy plates that can make the entire surface of the cathode. It is also possible to perform this stall by exerting a bending on the cathodes so as to break in a few pieces this limestone plate. Large slabs of limestone stand out then. Calcium carbonate does not adhere to the cathode at all. Once the shell is broken the plates of the cathodes are bare, with large shiny surfaces.
• This cleaning area can be a simple waste bin; 3. Bending cathodes or breaking the edges of limescale shells by hand or with a small tool (small hammer, pliers); The limestone then falls into plates in the cleaning area where it can easily be recovered;
• the air supply flow rate is measured and adjustable (flow meter, pressure gauge, control valve).
• This compressor or booster is connected to a pipe (11, 11 ', 11 ", 11'") serving as a gas nanny and placed at the bottom of the treatment tank, under the electrodes.
• the feeding of this nurse may be flexible or rigid. It can pass through the top of the tank or through the wall of the tank.
• the nurse is located in the tank, under the electrodes at a distance of 50mm to 2000mm of the latter. It is composed of at least one flexible or preferably rigid tube. If this tube is rigid it ensures the positioning and the mechanical maintenance of the diffusers at the bottom of the tank.
• the nurse may also be composed of a network of tubes connected together.
• a single tube is positioned parallel to the length of the treatment tank. It can be positioned on a tank edge or preferably in the center to keep the symmetry of the installation.
• Bubble diffusers are connected to this nurse. They can be circular or tubular. They can be pierced with slits 0.5 mm to 4 mm long or holes 0.3 mm to 3 mm in diameter.
• the "fine bubble" type diffusers used for the oxygenation of the purification basins will be used.
• These membrane diffusers will preferably be tubular so as to allow deposits to fall to the bottom of the tank without clogging the pores of the diffusers.
• the bubble diffusers are made of an EPDM elastomeric membrane pierced with slots 1.1 mm long and 0.3 to 3 mm wide. The air is blown through these diffusers and gives bubbles of 3 mm diameter on average (0.5 to 5 mm). The number of orifices per unit area is between 7 and 20 per cm 2 .
• tubular "thin bubble" diffusers will preferably be arranged perpendicularly to a rigid and central nurse, on a horizontal plane, over the entire width of the treatment tank.
• the spacing between two diffusers can be between 200 mm and 800 mm.
• FIG. 10 illustrates a first exemplary embodiment of the second intense stirring variant according to which said intense stirring means consist of two independent suction / discharge systems.
• Each system has a fluid extraction port (13), a fluid delivery port (14) and a pump (15) positioned between said exhaust port and said delivery port, pipes (16, 16 '). connecting each mouth to the pump.
• suction / discharge system comprising a single pump but several fluid extraction mouths and / or several fluid discharge mouths.
• the fluid extraction and fluid discharge mouths are located opposite, substantially at the same height in the top of the hopper, in the longitudinal end faces, about 15 cm below the electrodes.
• FIG. 11 Another intense recirculation stirring configuration R is illustrated in FIG. 11.
• the stirring is effected by recirculation on an intermediate storage tank called a buffer tank (30).
• the operation of this configuration is as follows:
• Recirculation R consists of pumping the water to be treated from this buffer tank (30) into the tank (3) and discharging into the same buffer tank (30) the treated water leaving the tank (3). ).
• the finally distributed water (32) not being taken from the tank (3), but from the buffer tank (30).
• the recirculation flow rate R is 4 to 20 times greater than the average flow rate of treated treated water (32) at the outlet of the buffer tank (30). .
• the contact time for recirculating the water in the reactor defined as the reactor volume divided by the recirculation flow rate, is then from 2s to 60s.
• FIG. 12 illustrates the reduction measured as a function of the contact time with two different recirculation flow rates R, one at 5000 1 / h and the other at 2000 1 / h and without recirculation (SR). These measurements were made with a treatment tank of 26 liters, a buffer tank of 860 liters and a flow of raw water (28) from 0 to 138 1 / h.
• the average contact time TCM is defined as the treatment volume divided by the raw water flow rate.
• the TCM without recirculation then represents the average contact time for the raw water that flows directly into the treatment tank and not into the buffer tank.
• the operation of the treatment is operated according to the quality of the water in the buffer. This quality is not constant as a function of the volume of the raw water supply and the design of the treatment tank and the buffer tank.
• This operation is particularly recommended when a buffer tank is necessary, for example in case of need of very important but very punctual treated water or on semi-open cooling towers where the water can be treated as and when it is needed. concentrates.
• the operation is safer because even in case of failure on the water treatment, there is no risk of water supply failure. If it is necessary to have a constant quality of treated water, it suffices to block the raw water supply flow at a constant value and to make sure that the water is perfectly mixed in the buffer. This operation is then indicated in all conditions.
• FIG. 13 illustrates an exemplary embodiment of the third intense stirring variant according to which said intense stirring means consist of at least one mechanical means (17), in this case a propeller, driven in rotational movement inside the reactor (1) by a drive system (18) consisting of a reduction housing, a substantially vertical drive shaft and an electric motor, this motor being positioned under the hopper, outside the reactor.
• a drive system (18) consisting of a reduction housing, a substantially vertical drive shaft and an electric motor, this motor being positioned under the hopper, outside the reactor.
• the propeller here comprises four blades and has a diameter of about 25 cm. It is also possible to provide several propellers, driven, preferably each by the same engine, to reduce costs.
• stirrer of the magnetic stirring-type consisting of a capsule of magnetic material, situated inside the tank (3), under the electrodes, and rotated by a magnetic plate loaded inversely.
• FIGS. 14 to 16 illustrate other exemplary embodiments of the third intense stirring variant according to which said intense stirring means are formed by forcing the circulation of the fluid inside the treatment tank (3) to follow a path having a plurality of baffles.
• each anode / cathode pair can be considered as a mini-reactor. All these mini-tankers are assembled in the tank side by side, in parallel, which divides all the speed of the water between the plates. To ensure intense mixing, it is then possible to put the reactors in series so that the water passes successively and at high speed in the vicinity of all the cathodes. This can be achieved by circulating the water through a network of baffles preferably formed by all the electrodes. The electrode planes are preferably placed vertically to allow the deposition of limestone in the lower part.
• the fluid passes successively from above and below the electrodes during the treatment.
• the fluid passes successively through the right and left ends of the electrodes during the treatment.
• the fluid passes successively from above and below the cathodes and through the anodes during the treatment.
• the first two devices require solid anodes AP which may consist for example of a titanium plate coated with noble metal oxide (DSA type anodes).
• the third device requires an expanded metal anode AD coated with noble metal oxide to which is added a porous membrane allowing the electric current to pass but a loss of charge when the water passes sufficient to force the passage of the water through the baffles.
• FIG. 17 illustrates a cathode cleaning solution according to which electrolysis is operated for a few moments by inverting the polarities of the generator (2).
• the "cathodes” in stainless steel are connected to the positive pole of the generator (2) via the bus-bar (BC) and titanium “anodes” are connected to the negative pole of the generator (2) via the bus-bar (BA).
• Tests have shown the effectiveness of polarity reversal for a limited time and at a given current density to clean all cathodes at once.
• Another cleaning solution consists, for example, particularly for reactors without a large number of cathodes, to specifically introduce an electrode or two electrodes reported (E, E ') in stainless steel during the cleaning operation in the reactor (1), close to a cathode to clean and perform for a few moments (of the order of minutes) electrolysis between this (or these) electrode (s) reported (s) and the (or) cathode (s) to be cleaned, transforming this (or these) cathode (s) to be cleaned in anode time cleaning.
• a third cleaning solution called “cathode-cathode electrolysis cleaning” or “cathode-cathode inversion cleaning” consists of connecting one stainless cathode on two to the + pole and the other stainless cathodes to the pole - in order to clean the polarized electrodes positively; then reverse the current to clean the second half of the stainless steel electrodes.
• the iridium oxide-coated titanium grids (the decarbonation anodes) are not electrically connected during cleaning and thus are not likely to be damaged during cleaning.
• cathodes pairs anodes For the cleaning of even cathodes it is sufficient to make the cathodes pairs anodes by connecting them to a positive terminal of the generator and putting back cathodes odd cathodes, that is to say by connecting them to a negative terminal of the generator.
• the cleaning of the cathodes is possible by electrolysis between two cathodes. It was performed on a weakly scaled cathode with a current density 1 to 3 times higher than the nominal density (8 A.nf 2 ). The electrolysis between 2 cathodes requires a voltage approximately 2 times higher at current density identical to the standard conditions due to a doubled electrolyte thickness.
• the circulation of the fluid is preferably interrupted because during this phase the fluid is not effectively treated; however, during the polarity inversion the intensive stirring means are implemented to further accelerate the stall effect by inversion.
• the circulation of the fluid is not necessarily interrupted during the cleaning because there are applications for which it is essential that the flow of water used is not interrupted, but for which it accepted that for short periods the water is not effectively treated.
• corrugated (C, C ) cathodes were made.
• cathodes have longitudinal waves over their entire surface, as can be seen in Figure 18, whose depth (p, p ') is at least 2 mm the the
• the gain in cathode surface can thus be 50% to 75% and even up to 100%, even 120%.
• the corrugations may, in cross-section, be U-shaped, as shown in FIG. 19, or V-shaped, as shown in FIG. 20, these shapes being reversible with respect to the following, or all in the same direction .
• They can also be V-shaped with a cut bottom.
• FIG. 21 thus illustrates, for an identical contact time of 37 min, the evolution of the reduction ( 0 F) in ordinate with respect to the current density (in A / m 2 ) on the abscissa, on the one hand for a corrugated cathode (solid line) and secondly for a flat cathode (dotted line) under the same experimental conditions.
• using lower current densities allows for lower power consumption.

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• 2005
  • 2005-09-15 WO PCT/FR2005/050750 patent/WO2006030162A1/fr not_active Ceased
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