FR2844783A1 - Electrolytic water treatment plant e.g. for swimming pool, has electrode cleaning unit connected to programmable clock that controls pump - Google Patents

Abstract

The water treatment plant, comprising a system of pipes (C) connecting a pump (P), a filter (F) and an electrolysis tank (V) with two electrodes (E) that are cleaned by polarity inversion, has the electrode cleaning unit (A, B) connected electrically to the programmable clock (H) that controls the operation of the pump. The electrodes are in the form of titanium plates coated with mixed conducting metal oxides; they can comprise at least two unipolar electrodes or at least one bipolar electrode, interleaved and alternating so that the first and last electrodes are unipolar. The bipolar electrodes are surrounded by a housing of a synthetic insulating material so that their height and width is greater than the height and width of the unipolar electrodes.

Description

Installation for water sanitation whose frequency and duration

  operation are adjustable by a single user Sanitation of water, especially bathing water, is a significant problem to the point that many administrative regulations impose strict standards as to

  the hygienic quality of the water, particularly in public swimming pools.

  Private pools are also affected and there are a large number of water treatment systems for them. These are practiced on the one hand to reduce the number of microorganisms, such as bacteria and viruses, to a concentration compatible with the maintenance of good hygiene for bathers, and on the other hand to avoid the deposit of microscopic algae on the walls of the basin and in the water pipes. These algae are rarely harmful to bathers, but they can be dangerous because they make the walls of the pools slippery,

and cloud the water.

  The sun and a warm water temperature for swimming pools, or hot water for hot tubs called "JACUZZI" (registered name) favor the proliferation of microorganisms, especially with small volumes of water. The sun acts by allowing photosynthesis of microscopic algae and the destruction of sanitation products. Inadequate sanitation of the water in these facilities can cause illness among bathers. Owners of such facilities must pay close attention to the safety of bathers by carefully checking the water quality (quantity

  sufficient sanitizing products, pH, total alkalinity and hardness in calcium).

  To situate the state of the art, it may be recalled that products based on chlorine or bromine are commonly used as very effective sanitizing agents.

  They are also used against the proliferation of algae. In water, chlorine-based and bromine-based products are hydrolyzed to hypochlorous acid and hypobromous acid. These two acids are the main chemicals responsible for the sanitation of swimming pool water. Chlorine and bromine are sold in chemical form in pellets, tablets or liquid. They are then brought directly into the water circulation circuit either manually by the person

  taking care of the quality of the pond water, either by an automatic distributor.

  When the sanitation products are brought in manually, the person in charge of the water quality performs an analysis beforehand to find out the concentration of sanitation product in the basin, then he calculates the need for the product. that is, it compares the concentration of product in the basin with the concentration of theoretical product to guarantee good water hygiene. Once the quantity of product required has been calculated, the person generally brings it at once into the water circuit to obtain a good dilution of the product throughout the basin. But chlorine and bromine products have a very unpleasant smell and

are dangerous to handle.

  When a dispenser is used, it is designed to deliver the product to the water according to a predetermined cycle, either in constant quantity or in suitable quantity after automatic water analysis. But in any case, it is necessary to regularly replenish the distributor with product, which does not eliminate the test of

product handling.

  There are also devices inserted in the water sanitation circuit and which generate a sanitation product in situ. Electrolysis vessels are known which are fitted with copper / silver electrodes which, thanks to electrical energy, emit copper-silver ions into the water which sterilize the water. The disadvantage is that certain pool coatings such as the "liner", if they are of poor quality, react on contact with these

  ions and cause very unsightly black spots.

  There are also salt electrolysis water treatment devices which use electrical energy to generate from simple salt (NaCl) and water, hypochlorite ions (CIO-) and hypochlorous acid (HClO).

  The pool water is enriched with salt (sodium chloride NaCi) at a rate of two to seven grams per liter of water. This water is pumped through a filter, then passes through an electrolysis cell in which takes place, under the effect of a direct electric current, the electrochemical oxidation of chloride ions to chlorine. This compound hydrolyzes immediately to give rise to hypochlorous acid, an active product for

  water disinfection. Under the effect of this disinfection and solar radiation, hypochlorous acid is consumed and the chloride ion is regenerated. This can be reoxidized to hypochlorous acid during a next passage in the electrolysis cell.

  To be as economical as possible, the amount of salt in a swimming pool should not exceed 4 grams per liter of water. At this concentration the current yield

  is high enough and the taste of the salt is still low (important comfort factor).

  This method of treating swimming pool water gives excellent results. Indeed, the quality of the water obtained is highly appreciated: the chlorine produced by this method is very active (the contact time for the destruction of bacteria is four to five times less long than in the case of chemical chlorine) , it has no smell, it does not sting the eyes and the salinity of the water provides a certain well-being. Despite an investment of

  significant basis, the system remains very economical in the long term.

  When the treated water is hard, that is to say when it contains a large amount of soluble calcium and magnesium carbonate, certain parasitic chemical reactions take place. In particular, the calcium and magnesium carbonates precipitate, that is to say that they agglomerate on the electrodes. If these carbonates are not removed regularly, the production of hypochlorite decreases very significantly until it vanishes completely. In addition, the service life of the electrodes can be greatly reduced. To remedy this, devices known as “polarity inverters” are known which reverse the direction of the current led to the electrodes, which allows the carbonates to

detach electrodes.

  Commonly, these inverters carry out the polarity reversal automatically and with a regular frequency thanks to an electronic unit comprising, inter alia, a time counting device and electronic elements intended to control the polarity reversal automatically and cyclically, according to a program established once and for all by the manufacturer and ensuring its functions in an unchanging manner,

  not adjustable, whatever the circumstances.

  These polarity inverters are very expensive due to the electronic box and the development by the manufacturer of the polarity reversal program. In addition, the electronic boxes are fragile and sensitive to humidity, which obliges the designer 10 of the basin to provide a separate technical room well isolated from the basin.

  Such an installation is incompatible with small recreational pools such as above-ground pools which have good water sanitation equipment (pump, filter, etc.)

  market, movable and very exposed to bad weather and shocks.

  The present invention overcomes all these drawbacks and proposes a new solution according to which the entire installation, including the polarity reverser, is less fragile, less expensive, adaptable to small basins and adjustable ad libitum by the user. To this end, the invention relates to an installation for the purification of water of the type comprising:> a basin, a pipe o at least one pump, at least one filter, at least one assistant electrolysis vessel are interposed therein to an assembly which comprises at least two electrodes connected to an electrical supply and which is generally designated by "electrode", a device for controlling the operation of the pump comprising a clock 25 programmable ad libitum by a user, said "electrode" being associated to an electrolysis box provided with a polarity reversal cleaning device with a view to the elimination of any surface deposition of a substance affecting the proper functioning of the electrodes, characterized in that said cleaning device is electrically connected not to a time counting device 30 previously programmed and usually integrated into the cleaning device, but to the programmable clock of the control device

pump operation.

  The invention will be better understood from the detailed description below made with reference to the accompanying drawing. Of course, the description and the drawing are only given as

  indicative and non-limiting example.

  Figure 1 is a schematic representation of the sanitation installation of a swimming pool equipped with a known type of housing controlling electrolysis. Figure 2 is a schematic representation of the sanitation installation of a swimming pool equipped with a box controlling electrolysis, the operation of which is subject to

pump operation.

  Figure 3 is a schematic representation of the autonomous operation of the pump 10 and a known electrolysis box.

  Figure 4 is a schematic representation of the autonomous operation of the pump

  and an electrolysis box according to the invention.

  Figure 5 is a schematic view of an "electrode" composed of so-called electrodes

  "monopolar" connected in parallel.

  Figure 6 is a schematic view of an "electrode" composed of so-called electrodes

"bipolar" connected in series.

  Figure 7 is a schematic view of a "electrode" called "mixed", that is to say

  composed of monopolar and bipolar electrodes.

  The cell formed by a cathode (electrode connected to the negative pole), an anode (electrode connected to the positive pole) and the liquid (electrolyte) in which they are immersed is called "cell". An assembly of several cells connected in parallel or in series is called an "electrolyser". In practice, this electrolyser is also called

  "electrode", by difference with the electrolysis vessel.

  During the operation of the electrolyser, hydroxide ions (OH-) are formed at the cathode, greatly increasing the pH at the surface thereof. When the treated water is hard, the soluble calcium and magnesium carbonates contained in

  water precipitates on the cathode due to this increase in pH.

  A known swimming pool water purification installation, represented in FIG. 1, has a circuit of pipes C connecting a pump P propelling the water in the direction of the arrows Fl and F2, a filter F, a vessel of electrolysis V in which electrodes E are fixed, and a box for monitoring the operation of the installation. This box is connected to a current generator G, and contains a ground socket T, a neutral N, a circuit breaker D, a contactor J which is electrically linked to the pump P, to a programmable clock H and to a box 1 called "electrolysis" controlling the operation of the electrodes E. The operation of the pump P is ordered by the programmable clock H which is here of the pin type 2. Each pin 2 represents a quarter of an hour and all 5 pins 2 on the programmable clock H represent twenty four hours. When a user wants the pump to run twelve hours a day in two six-hour cycles, he raises twenty four consecutive pins 2 (representing six hours), leaves twenty-four pins 2 in place and raises the next twenty four pins 2 . The raised pins 2 authorize the operation of the pump P in two times six hours separated by a stop time of six hours. In Figure 1 (and in Figure 2), the pins 2

  raised are grayed out and the pins 2 left in place appear in white.

  The electrodes E only work (in normal polarity cx or in reverse polarity [)

if the pump is running.

  The electrolysis box 1 controls on the one hand the normal operation of the electrodes E, and on the other hand polarity reversals for cleaning the electrodes E. The electrolysis box 1 has a set of electronic components A determining the frequency and duration of the alternation polarity oc (+ or -) / polarity 3 (- or), and of the components B performing the polarity reversal. Components A and B

  constitute a device for cleaning the electrodes by reverse polarity.

  The electronic components A are, inter alia, a microprocessor (or "chip") 3 and a time counting device 4. When producing the housing 1, the manufacturer must program the chip 3 with software which controls the components B according to the information sent by the time counting device 4. In general, for an operation of the pump P for six hours, the components A 25 control the reversal of the pump P at regular intervals, for example two hours of operation in polarity cx, four minutes of reversal in polarity 3 and so

  after. If the inversion is not long enough, the electrodes E wear out quickly.

  When the pump P stops, the electrolysis unit 1 also stops. Depending on the equipment used, when the operation of pump P resumes six hours later, electrolysis resumes either by continuing the interrupted cycle, or by repeating a cycle. So, if the program allows the resumption of the interrupted cycle, the box will command either an oc polarity or an inverted polarity [depending on the progress of the operating cycle during the previous stop of the P pump. Thus, when resetting pump P running, the program takes into account the progress of the cycle

  before stopping the pump P, and resumes the cycle in this state.

  Consequently, the polarity delivered to the electrodes E by the electrolysis box 1 is subject to the time counting device 4 contained in the box 1 and to a program implemented by the chip 3 and preset in the factory. But it is understood that the two cycles respectively of the operation of the pump and the inversion of

  polarity are distinct and completely independent of each other.

  The disadvantages of such a system are its fragility due to the numerous electronic components, its high cost due to the precautions to be taken during the construction of the housing, and its very high operating rigidity due to the absence of synchronism between the operating cycles, only their stops being simultaneous but their resumptions also simultaneous restore the individual functioning of each. Indeed, when the water is very hard (presence of a large concentration of soluble carbonates), frequent polarity inversions are necessary, whereas if the water is very soft (almost absence of soluble carbonates), there is no it is not necessary to have frequent polarity reversals and it is even possible to only need to reverse polarity

  only once a week, per month or per season of pool operation.

  A reverse polarity box 1 according to the invention and shown in Figure 2, allows the user to adapt the rate of reverse polarity to the hardness of the water in

  programming itself, and very easily the electrolysis unit 1.

  The difference with the installation of figure 1 lies in the design of the housing

electrolysis 1.

  The components A constitute a device of the remote control type which detects the functioning of the pump P. Thus, each time that the pump P stops, the components A command the reversal of polarity to the components B. On resetting

  pump P running, the polarity is therefore reversed.

  The user can therefore program the polarity reversal using the programmable clock H. Instead of programming six hours of continuous pump P operation, the user programs two hours of pump P operation during which the electrodes E receive an ox polarity, a quarter of an hour off, then two hours of operation of the pump P during which the electrodes E receive a polarity ô, etc. For this, the user lifts eight pins 2 (representing two hours) for the operation of pump P, he leaves a pin 2 to control the stopping of pump P for a quarter of an hour, then he lifts eight pins 2 for the operation of pump P, etc. The operating diagram of the pump P and of the electrolysis box 1 is represented by FIG. 3 for a device according to the state of the art and by the

  Figure 4 for a device according to the invention in an easy comparison.

  We see that the device of the invention (Figure 4) is directly dependent on the operation of the pump P. In addition, the duration of the reverse polarity is adjustable by the user and can last much longer than with a known device. The quality of the inversion is much better.

  In addition, since this device does not have an electronic chip and a time counting device, it is much cheaper and more robust. The electrical elements A which compose it are very simple and inexpensive. They don't require

particular setting.

  The electrodes available on the market all suffer from reverse polarity and their lifespan is significantly reduced in commercial devices. Careful choices of the inversion frequency, the way of reversing the current and the current density make it possible to extend this service life at economically low levels.

acceptable.

  If the current density is too low, the carbonate precipitates on the cathode so that it is difficult to detach when the current is reversed. We can therefore, despite the reverse polarity, see poorly designed electrolysers scaling regularly,

  that is to say to cover itself entirely with carbonate and no longer function.

  If the current density is too large, the lifetime of the electrodes E is greatly reduced.

  There are two types of electrodes: so-called "monopolar" electrodes and electrodes

say "bipolar".

  A monopolar electrode is an electrode which induces electrochemical reactions of the same type (either anodic or cathodic) on its two faces while a bipolar electrode is an electrode which induces electrochemical reactions of opposite type on

  each of its faces (one anode side, the other cathode side).

  An installation according to the invention can be equipped with an "electrode" currently available on the market, that is to say an "electrode" composed of at least two monopolar electrodes 5 (that is to say at least one cell called "monopolar"), corresponding to the electrode arrangements according to FIG. 5, or of an "electrode" comprising at least one bipolar electrode 6 (that is to say at least one so-called "bipolar" cell 10), corresponding to the electrode arrangements according to FIG. 6. In FIGS. 5, 6 and 7, the different electrodes are connected to a current source of which only the electric poles (positive and negative) are represented . These figures necessarily represent only one polarity, for example oc. When reversing polarity, the pole

  positive becomes the negative pole and vice versa.

  In the complete installation (Figures 1 and 2), the current is delivered by the generator G and

  treated by the various electrical components of the installation to be adapted to the operation of the electrodes (direct current, low voltage, reverse polarity, etc.).

  For the sake of simplification, the current source is subsequently assimilated to the generator G. FIG. 5 shows an "electrode" composed of nine monopolar electrodes 5 20 connected alternately to the positive pole and to the negative pole. There are then eight cells

  electrolysis represented by the space e between two successive monopolar electrodes 5.

  Thus, in an "electrode" made up of monopolar cells, the cells are electrically connected in parallel. The intensity of the current of the generator G necessary for the proper functioning of the "electrode" is equal to the sum of the intensities 25 passing through each cell connected in this way. The voltage delivered by the generator

  G is then the working voltage of a cell.

  A parallel connection of the cells results in an electrolyser working under strong

intensity and low voltage.

  In this connection mode (FIG. 5), each anode 51 of each cell is connected to the positive pole of the generator G and each cathode 52 is connected to the negative pole of the generator G. In monopolar mode the electric current flows from the lowest electric potential

  towards the highest electrical potential, each electrode 5 receiving 1/9 of the total current.

  The main limitation of this configuration of the "electrode" is induced by the costs of the electrical components: of the generator G, of the electrical connections and of the electrodes 5 which must be designed to withstand high current intensities. FIG. 6 represents an electrolyser composed of nine bipolar electrodes 6, that is to say that the cells are electrically connected in series. Only the electrodes of the ends are monopolar 5 and are connected, for one 51 to the positive pole of the generator, and for the other 52, to the negative pole of the generator G. Going from the highest potential to the lowest, an electrode 6 has a positive potential for the next electrode 6, but at the same time has a negative potential for

the previous electrode 6.

  Thus, the anode and the cathode are merged into a single electrode 6, the face 61, facing the next electrode 6, works as an anode and the face 62 facing the previous electrode 6 works as a cathode.

  The intensity of the current passing through each cell is equal to the intensity of the current generator G. In this case the voltage delivered by the generator G is equal to the sum

voltages of each cell.

  A serial connection of the bipolar cells will result in an "electrode" working at low intensity and high voltage.

  The European standard defining the voltage of a DC generator G for domestic or public use has set the maximum authorized at 30 Volts. If we consider a cell voltage of 3 to 3.5 V, an arrangement of 9 to 10 cells in mode

bipolar is a maximum.

  In the case of a bipolar arrangement, the intensity taken into account for the calculation of the

  production capacity is equal to the total current flowing through the cell multiplied by the number of electrodes 5-6 minus one. The cell voltage is equal to the sum of the anodic overvoltage, the cathodic overvoltage and the voltage between two electrodes (voltage equal to the resistance of the electrolyte which is here water, multiplied by the intensity of 30 current), multiplied by the number of electrodes 5-6 minus one.

  On the other hand, in the case of a monopolar arrangement, the electrical intensity taken into account for the calculation of the production capacity is equal to the total current flowing through the cell. The cell's electrical voltage is equal to the sum of the anode overvoltage, the cathode overvoltage and the voltage between two electrodes (voltage equal to the resistance of water, multiplied by the intensity of the current). Consequently, with equal production capacity, a monopolar cell has a high nominal electric current and a low nominal electric voltage, while a bipolar cell has a low nominal electric current for a high

nominal electrical voltage.

  A monopolar cell requires the use of a generator G of current of high intensity but of low voltage. High intensities require expensive technology, but low voltages do not cause corrosion of the cell electrodes. The electrodes generally used in this application are made of titanium 15 coated with mixed conductive metal oxides. If these oxides disappear, for example by dissolution, a layer of titanium oxide is formed in their place which is not at all conductive. Consequently, the tension there increases considerably. Now in the presence of chloride, the electrical breakdown voltage of the titanium oxide (voltage causing the expulsion of particles of titanium oxide) is only about eight volts. As soon as this tension is reached, particles of titanium oxide are expelled, then others in their turn to arrive very quickly

  to complete corrosion of the electrode.

  A bipolar cell imposes a current of low intensity but of high voltage.

  The construction technology of the generator G and the connectors is less expensive 25 but the high voltages higher than eight volts cause the corrosion of the anodes with

  their ends on the parts not coated with the layer of mixed oxides.

  The operation of an installation according to the invention can be greatly improved by judiciously combining monopolar electrodes 5 and electrodes

bipolar 6.

  The "electrode" is said to be "mixed" because it is composed of monopolar electrodes 5 and of bipolar electrodes 6 interleaved and alternated such as the first and the last

electrode are monopolar.

  Such an arrangement of the electrodes, shown in FIG. 7, allows the use of an average electric current which does not require expensive technology, and has an electric voltage preventing corrosion of the electrodes because the number of bipolar electrodes 6 is limited to a single electrode 6 between two monopolar electrodes 5. This arrangement limits the electrolysis voltage to a value less than eight volts. So with a mixed "electrode", you increase the production while having a

  medium intensity and medium voltage avoiding the risk of breakdown.

  Electrolysers designed on this principle benefit from a low production cost and

  with a large production capacity.

  The cell thus obtained is a hybrid of the two classic arrangements shown

in Figures 5 and 6.

  FIG. 7 represents a "electrode" composed of four bipolar electrodes 6 and of

  five monopolar 5 alternating electrodes.

  In the case of an electrolysis cell whose electrodes are arranged according to FIG. 15 7, the intensity taken into account for the calculation of the production capacity is equal to the total current flowing through the cell, multiplied by the number of bipolar electrodes 6

  interposed between two monopolar electrodes 5 plus one.

  The cell voltage is equal to the sum of the anode overvoltage, the cathode overvoltage and the voltage between two electrodes (voltage equal to the resistance of water, multiplied by the intensity of the current), multiplied by two . Typically this voltage does not exceed eight volts direct current for a leisure pool containing

  four grams of sodium chloride per liter of water.

  The spacing e between an anode and a cathode should not be too small to avoid short circuits between the electrodes 5-6, not to cause too great a hydraulic pressure drop and to allow easy cleaning of the electrolysers.

  A spacing e of three to four millimeters seems to be an excellent compromise.

  In order to guarantee a constant spacing e between two neighboring electrodes, we add

  supports (not shown) made of synthetic, insulating and rigid material.

  To prevent the current from passing from a monopolar electrode 5 to the other without passing through the bipolar electrode 6 which is interposed, it is possible to add a frame 7 of insulating material around the bipolar electrodes 6 so that the height and the width of these electrodes 6 are greater than the height and the width of the monopolar electrodes 5. Thus, the frame 7 increases the distance between two monopolar electrodes 5 and the electrons which take the shortest path between two electrodes 5 of different electrical potentials cannot pass over the bipolar electrode 6 and are

  forced to supply the bipolar electrode 6.

  A difference in height d of 5 mm between the upper edge 53 of the monopolar electrodes 5 and the upper edge 71 of the frame 7 of the bipolar electrodes 6 allows

  excellent operation of the electrolyser.

Claims (6)

  1. Installation for water sanitation of the type comprising: * a basin, * a pipe (C) where at least one pump (P) is inserted, at least one filter (F), at least one electrolysis vessel (V) added to a set which comprises at least two electrodes (E) connected to a power supply (G) and which is generally designated by "electrode", * a device for controlling the operation of the pump comprising a programmable clock ( H) ad libitum by a user, said "electrode" being associated with an electrolysis box (1) provided with a cleaning device by reverse polarity (AB) with a view to the elimination of a possible deposit in 15 surface of a substance that interferes with the proper functioning of the electrodes (E), characterized in that said cleaning device (AB) is electrically connected not to a time counting device (4) previously programmed and usually integrated into the cleaning device , but on time programmable compartment (H) of the   pump operation check (P).   2. Installation according to claim 1 characterized in that "the electrode" is composed   at least two monopolar electrodes (5).   3. Installation according to claim 1 characterized in that "the electrode" comprises at minus a bipolar electrode (6).   4. Installation according to claim 1 characterized in that "the electrode" is said to be "mixed" 25 that is to say that it is composed of monopolar electrodes (5) and of bipolar electrodes (6) interposed and alternating such that the first and the last electrode are monopolar (5).   5. Installation according to claim 1 characterized in that "the electrode" (E) is composed   electrodes (E) made of titanium plates coated with mixed metallic oxides 30 conductors.   6. Installation according to claim 4 characterized in that the bipolar electrodes (6) are surrounded by a frame (7) of insulating synthetic material so that the height and the width of these electrodes (6) are greater than the height and the width of monopolar electrodes (5).