WO2012017297A1

WO2012017297A1 - Operating method of an apparatus with through-flow condensers and an apparatus with through-flow condensers for treating a fluid

Info

Publication number: WO2012017297A1
Application number: PCT/IB2011/001807
Authority: WO
Inventors: Tullio Servida
Original assignee: Idropan Dell'orto Depuratori S.R.L.
Priority date: 2010-08-06
Filing date: 2011-08-02
Publication date: 2012-02-09
Also published as: IT1401341B1; ITPD20100256A1

Abstract

Apparatus with through-flow condensers for treating a fluid, in particular for desalinating seawater, comprising one or more cells (2) each of which is provided with one or more through-flow condensers connected to a direct current power supply (36). A hydraulic system is foreseen for feeding the cell (2) with the flow of fluid to be treated through a supply duct (5) intercepted by a first valve (6), and able to receive the flow of treated fluid from the cell (2) through an extraction duct (7) intercepted by a second valve (8). The hydraulic system is also made up of a first tank (9) able to cyclically contain a first volume of fluid to be treated, immiscibly distributed inside of it with increasing concentration of charged particles going from its first access opening (9'), connected through the supply duct (5) to the cell (2) to cyclically feed it with the first volume of fluid to be treated having increasing concentration of charged particles so as to generate a flow of treated fluid with increasing concentration of charged particles. The hydraulic system is also made up of a second tank (10) able to cyclically contain a second volume of treated fluid, immiscibly distributed inside of it with decreasing concentration of charged particles going from its second access opening (10') connected through the extraction duct (7) to the cell (2) to cyclically receive from the latter the second volume of treated fluid at increasing concentration of charged particles. It is moreover foreseen for there to be a first withdrawal duct (11) intercepted by a third valve (12) shunted by the extraction duct (7) between the cell (2) and the second tank (10), through which a purified volume of treated fluid flow is extracted. Suitable return means cyclically immiscibly displace at least one part of the second volume of treated fluid in the first tank (9), from the second tank (10) through a return flow with decreasing concentration of charged particles.

Description

OPERATION METHOD OF AN APPARATUS WITH THROUGH-FLOW CONDENSERS AND AN APPARATUS WITH THROUGH-FLOW CONDENSERS FOR TREATING A FLUID

DESCRIPTION

Field of application

The present invention concerns an operation method of an apparatus with through-flow condensers and an apparatus with through-flow condensers for treating a fluid, according to the preamble of the respective independent claims.

More in detail, the apparatus according to the invention is intended to advantageously be used to remove undesired concentrations of contaminants from a fluid, for example made up of salts dissolved inside it, or rather to concentrate ionised particles inside a fluid, particularly for industrial processes, so as to facilitate their recovery or disposal.

In particular, the aforementioned apparatus is suitable for being advantageously used for the desalination of seawater, even in places in which there is little electric energy available. The aforementioned apparatus uses through-flow condensers according to operation principles which make it possible for them to obtain, in a single operation, a flow-rate of fluid that is extremely pure or rather also, according to the application, a flow-rate of fluid that is considerably concentrated in a small volume.

The apparatus according to the finding can be intended for many applications both in the industrial field and in the civil field, such as for example the desalination of seawater, the softening of particularly hard waters, the removal from the water of salts (such as chlorides and sulphates), of nitrates, of nitrites, of ammonia, of heavy metals, of organic substances or of micropoUutants in general, or rather again for the deionization of fluids for example of industrial processes or for the concentration of polluting substances that are difficult to dispose of or that are advantageous to recover for reuse.

The present invention is thus inserted in general in the field of industrial processes for the treatment of fluids having the purpose of filtering the latter or rather to concentrate some substances dissolved in them into a small volume.

State of the art

Apparatuses for purifying fluids through through-flow condensers conventionally comprise one or more cells connected to one another in series or in parallel.

Each cell is formed by one or more through-flow condensers, each of which is in turn equipped with a plurality of electrodes placed over one another, between which the fluid to be purified is made to pass with the purpose of concentrating a solute with ionised particles, or rather with the purpose of obtaining a solvent that has been purified of such particles.

The electrodes of the through-flow condensers are conventionally formed with layers of conductor materials facing one another and charged with opposite polarity by a direct current power supply so as to generate an electrostatic field between contiguous electrodes. The alternating layers of electrodes are separated from one another by spacer layers, in which the flow of fluid to be treated flows. The electrodes in the through-flow condensers electrostatically absorb and release the contaminants of ionic charges and actively participate in the process of deionization of the liquid to be treated. For such a purpose the electrodes are generally formed by porous structures of conductor materials.

More in detail, during a foreseen service step, the fluid flows between the electrodes with different polarity and the charged particles present in the fluid, for example consisting of ions of dissolved salts, are attracted by the electrodes and are held on them by the action of the electric field.

In a subsequent regeneration step, the electric field is removed and the ions, which have accumulated on the electrodes, are evacuated through the use of a washing flow.

The operation of such condensers foresees the alternation between service steps, in which there is the concentration of the ions present in the fluid at the opposite electrodes, and regeneration steps, in which the ions accumulated on the electrodes are removed through the aforementioned discharge flow.

Through-flow condensers of the known type indicated above are, for example, described in patents US 6,413,409 and US 5,360,540.

According to the applications, purification apparatuses may be required equipped with numerous cells each having one or more through-flow condensers, for treating substantial volumes of fluid or rather for lowering, in many subsequent steps, the conductivity of a flow of fluid until it is brought to desired values.

In particular, it is known for there to be apparatuses with through-flow condensers used for the desalination of seawater. Advantageously, the water is brought from seawater values of salinity, usually in the order of 50.000 μ8, to values of drinking water, usually in the order of hundreds of μ8, through the use of many apparatuses arranged in series, in which the salinity is broken down into gradually decreasing percentages in absolute terms, for example, in 5-7 stages in condensers arranged in succession.

The drawback of such a desalination method obtained through apparatuses with through-flow condensers of the conventional type, known on the market, indeed lies in having to use a high number of passages in condensers arranged in succession therefore with high system and energy consumption costs. Indeed, as it is known, each filtering stage allows the apparatus to break down, by a percentage, the salinity of the water with which the apparatus itself is supplied. Consequently, in absolute terms, the condensers of the last stages have an efficiency that is lower with respect to those of the first stages, capturing a lower amount of salts dissolved in the water, thus not reaching the complete saturation of their electrodes and consequently not exploiting their capturing possibility to their full potential.

Usually, apparatuses with through-flow condensers, to which the present invention refers to, are used for softening water and, in such a case, wash away the water used for the regeneration of the condensers.

A further example of apparatus with through-flow condensers of the known type for treating a fluid, such as in particular seawater, is described in the US patent 2003/0098266. This last apparatus of the known type comprises many cells, which are connected in inlet, through a supply duct, to a first tank containing the fluid to be treated, and are connected in outlet, through an extraction duct, to a second tank intended to receive the purified fluid coming from the cells themselves.

The supply duct and the extraction duct are respectively intercepted by a first and a second three-way valve, which can be actuated to connect the respective ducts to a washing circuit, to feed the cells with a washing fluid during a foreseen regeneration step. More in detail, the washing circuit comprises a third tank containing the washing fluid, which is connected to the supply duct through a feeding duct of the washing circuit intercepted by the first three-way valve, and is connected to the extraction duct through a return duct of the washing circuit intercepted by the second three-way valve.

Functionally, a service step is foreseen, in which the first and the second three-way valve respectively connect the supply duct to the first tank and the extraction duct to the second tank, and in which the fluid to be treated contained in the first tank is conveyed through the supply duct to the cells, from which the purified fluid comes out and is then introduced into the second tank through the extraction duct.

In the subsequent regeneration step, the first and the second three-way valve are switched to respectively connect the supply duct to the supply duct of the washing circuit and the extraction duct to the return duct of the washing circuit, and the washing fluid contained in the third tank is conveyed to the cells through the supply duct, to then return to the third tank itself through the return duct.

Also this solution of the known type, however, has the drawback of having to use a high number of passages of the fluid to be treated in the condensers of the cells to sufficiently lower the value of salinity of the purified fluid, with consequent high costs for making the apparatus and with a consequent high energy consumption.

Moreover, the purification method through the apparatus of the known type described in US 2003/0098266 necessarily requires a separate washing circuit in order to carry out the regeneration step of the cells, with the consequent use of high amounts of washing fluid and with a consequent high structural complexity of the apparatus.

A further drawback of the purification method obtained through the apparatus described in US 2003/0098266 is due to the fact that it is necessary to frequently replace the washing liquid contained in the third tank of the washing circuit in order to remove the ions trapped in the cells in an efficient manner during the regeneration step, with consequent high actuation costs of the purification method itself.

Moreover, on the market there are also known apparatuses for the desalination of water which foresee separating the salts dissolved inside it through evaporation techniques which use many evaporation chambers arranged in succession. A thermal fluid gives up heat, through an exchanger, to the supply water in a first evaporation chamber causing a fraction thereof to evaporate, which condensates in a second chamber forming a part of desalinated water and giving up heat to another fraction of supply water which in turn evaporates so as to condensate in a third chamber in turn forming a part of desalinated water and giving up heat to yet another fraction of supply water. The evaporation process is repeated in the way indicated above in many chambers arranged in sequence. The vapours separated in the last chamber are condensed through an exchanger advantageously cooled down with seawater. The main drawback of this apparatus lies in the considerable waste of energy it needs in order to bring the supply water to evaporate.

Apparatuses for the desalination of seawater are known which use semipermeable membranes (membranes with reverse osmosis) crossed through permeation so as to separate the desalinated water from the supply water.

Apparatuses are moreover known for the desalination of seawater which use electrodialysis processes, or rather, which separate a flow of desalinated water from the flow of supply water through the passage of a solute containing the salts through a membrane. The passage through the membrane is forced by the application of an electric field between two electrodes so as to make the ions migrate towards the electrode of opposite charge to its own.

The main drawback of this apparatus, as well as of its operation method, lies even in this case, in the considerable consumption of energy necessary for its operation.

There is also a known apparatus for the desalination of seawater through ion exchange principles, or rather through the removal of the Na+ and CI- ions through H⁺ and OH^" cycle resins, respectively. Through the resins, a strongly desalinated water is also obtained in a single passage. The portion of fluid to reject in this case consists of the residues of the regeneration of the resins.

The main drawback of this apparatus as well as of its operation method lies in its poor efficiency, or rather, in the possibility of production of only a small amount of desalinated water for the same energy used.

This makes it possible to use such an apparatus only for producing very limited flow rates, for example in the order of 1 m³/h, or rather, to obtain water with a very high level of purity, although indeed for only small flow rates.

Many industrial processes, for example for treating metal surfaces such as phospho- degreasing, polishing, pickling, anodisation, painting, chromatising, etc., foresee the use of water in the various productive processes, together with solutions of acids such as phosphoric acid, sulphuric acid, hydrofluoric acid, nitric acid, chromic acid or rather alkalis such as degreasing products, phosphates etc. The depuration of the wastewater from the industrial processes is one important aspect of the entire productive cycle, involving ecological, economic and legal aspects.

Usually, depuration methods of this type of industrial wastewater are based on processes of the chemical-physical type, with high consumption of reagents necessary for the precipitation and flocculation of the pollutants, considerable use of specialized labour, necessary for cleaning the probes of filtering systems, for the chemical analysis of the waters. Such depuration processes produce discharges of purified waters which must be checked to constantly verify that the parameters foreseen by the law on discharges are respected.

In order to dispose of waste fluids of industrial processes, or rather the waste water obtained from the aforementioned treatments, filtering apparatuses which exploit the treatment principles of the aforementioned fluids for the desalination of seawater can be used.

For example, the depuration of industrial wastewater can be obtained by using filtering apparatuses with ion exchange resins or rather through the use of organic compounds that are capable of removing positive or negative ions from solvents through their selective reaction towards anions or cations. Such a selective reaction is subject to bringing the resins to fix the ions in replacement of a radical thereof.

Cationic and anionic resins, however, have a predetermined number of radicals available for the exchange, which, once used, the exchange and the possibility of filtering stops. It is therefore necessary to foresee the reconstitution of the radicals through a chemical regeneration process, which usually periodically foresees washing in countercurrent with water or with solvents for removing suspended solids, as well as bringing the resins in contact with an active solution formed by an acid (such as for example hydrochloric or sulphuric acid) in the case of regeneration of a cationic resin, and with an active solution formed by a base (such as for example caustic soda, or ammonia) in the case of regeneration of an anionic resin. Moreover, evaporation and vacuum concentration methods are known through which it is possible to recycle industrial wastewater greatly limiting the production of runoff water and obtaining concentrated solutions which can advantageously be reused.

The technology used by vacuum evaporators-concentrators brings the wastewater liquids to boil at low temperature and is used in many fields of industrial application such as: galvanic, pressure die-casting, mechanical machining, painting, aluminium surface treatments, printing, jewellery, pharmaceutical, or in waste disposal sites themselves to actuate the concentration downstream of the disposal.

Such a technology requires a substantial consumption of energy and rather high costs for making disposal plants.

Presentation of the invention

In this situation the problem forming the basis of the present invention is therefore that of eliminating the problems of the prior art described above, providing a method for operating an apparatus with through-flow condensers, which makes it possible to optimise the performance of the through- flow condensers used.

Another purpose of the present invention is that of providing a method for operating an apparatus with through-flow condensers, which makes it possible to substantially reduce the concentration of ionised particles in a feed liquid.

Another purpose of the present invention is that of providing a method for operating an apparatus with through-flow condensers for treating sea water which makes it possible to obtain desalinated water in a single purification stage.

Another purpose of the present invention is that of providing a method for operating an apparatus with through-flow condensers which makes it possible to produce a purified liquid or rather to carry out the disposal of industrial wastewater in a cost-effective manner.

Another purpose of the present invention is that of providing an apparatus with through-flow condensers for treating a fluid which is simple and cost-effective to make and that is completely operatively reliable.

Another purpose of the present invention is that of providing an apparatus with through-flow condensers for treating a fluid, which makes it possible to minimise the consumption of energy.

Brief description of the drawings

The technical characteristics of the finding, according to the aforementioned purposes, are clearly described by the content of the claims below and the advantages thereof shall become clearer in the following detailed description, made with reference to the attached drawings, which represent one embodiment given purely as an example and not for limiting purposes, in which:

- figure 1 shows an operation diagram of an apparatus with through-flow condensers for treating a fluid, according to the present invention.

Detailed description of a preferred embodiment

With reference to the attached drawings an example of an apparatus for treating fluid, object of the present invention, has been indicated with reference numeral 1.

The apparatus 1 , according to the invention, is suitable for being used for the purification of fluids from ionised particles present inside them, which can be affected by the presence of an electric field, such as for example ions in solution.

In particular, the apparatus object of the present invention is suitable for being used to desalinate seawater, even in environments in which there is poor provision of electric energy. In the rest of the description the term ionised particles shall indicate generally any contaminant dissolved in the fluid to be treated that is capable of being attracted by an electrostatic field, like in particular the ions dissolved in a fluid or rather the salts in seawater. The apparatus is therefore suitable for operating both for the desalination of seawater and for the deionization of waste fluids of industrial processes since, in particular, it is capable of removing, from inside them, salts in solution (such as chlorides and sulphates), nitrates, nitrites, ammonia, and other polarised contaminants, of chemical substances, of organic substances or of micropollutants in general.

The apparatus is also suitable for concentrating inside small volumes, ionised particles particularly of industrial processes, so as to facilitate the recovery or the disposal thereof. Of course, the apparatus can be used as a simple softener or more in general for the deionization of water.

In the embodiment illustrated in the attached diagram of figure 1 , the apparatus 1 for the purification of a fluid, comprises at least one cell 2 (and preferably at least two), equipped with a containment structure 3 with, housed inside it, one or more through-flow condensers 4 electrically connected to one another in series or in parallel. Each condenser 4 is in turn equipped with two or more electrodes placed over one another, interfacing one another, generally with a shape that is thin, flat or wound up, for example, to form a cylinder.

Between the electrodes a flow of fluid to be treated containing ionised particles is able to flow.

Each cell 2 is electrically connected to a DC direct current power supply 36 that is suitable for charging the electrodes, through special collectors, with different polarity so as to define a plurality of pairs of interfacing electrodes which form the plate of just as many condensers in series between which electric fields are formed for attracting the charged particles as shall be made clearer in the rest of the description.

The electrodes are charged at a rated voltage (for example 1.6 Volt) and are obtained with juxtaposed and interfacing layers of conductor material, separated from one another by separator layers inside which the flow of fluid to be treated, containing the ionised particles which is desired, at least in part, to be removed, flows. The direct current power supply 36 is connected to the electrodes of the cell 2 through an electric circuit equipped with a control board which, in the different operation steps of the operation cycle of the cell 2, controls the voltage applied to the electrodes.

The conductor layers that form the electrodes are made from a conductor material with a porous structure or rather with a formation of surface pores which offer a considerable exchange surface with the liquid.

The material which forms the conductor layers can be any material known to be used in electrochemical processes of flow condensers and shall conventionally comprise active carbon sponge, or rather, it can be made up of any of the materials described for example in patent US 6,413,409 attached here as a reference from line 64 of column 3 to line 41 of column 4, or rather, from flexible conductive sheets of PTFE and particles of carbon as described in US patent 7,175,783 attached here as a reference, or rather again by any material described in US patent 6,709,560, attached here as a reference, from line 26 of column 6 to line 23 of column 7.

The separator layers can in turn be made up, for example, of highly porous non conductive material, capable of isolating the electrodes allowing the flow of fluid to pass through, like for example a synthetic porous material or other non conductive spacer materials like fibre glass or a nylon fabric.

The sizes, shape and the distribution of the layers of conductor material which make up the electrodes or rather the dimensions the shape and the distribution of the layers of separating material arranged between the electrodes do not form the object of a specific claim, and shall not be described in detail since they are well known by a man skilled in the art and, purely as an example, they are described in patent US 6,413,409 or rather in patent US 6,709,560, attached here as a reference, in particular from line 1 1 to line 23 of column 7.

The apparatus 1 moreover comprises a hydraulic system, which feeds the cell 2 with a flow of fluid to be treated through a supply duct 5 intercepted by a first valve 6, and draws the flow of treated fluid from the cell 2 through an extraction duct 7 intercepted by a second valve 8. According to the idea forming the basis of the present invention, the hydraulic system comprises a first tank 9, which is able to cyclically contain a first volume of fluid to be treated, immiscibly distributed inside of it with increasing concentration of charged particles going from its first access opening 9', connected through the supply duct 5 to the cell 2, to cyclically feed the latter with the first volume of fluid to be treated through a flow with increasing concentration of charged particles, at least partially purifying it in the cell 2 and generating a flow of treated fluid with increasing concentration of charged particles.

The hydraulic system also comprises a second tank 10 able to cyclically contain a second volume of treated fluid, immiscibly distributed inside of it with a decreasing concentration of charged particles going from its second access opening 10', connected through the extraction duct 7 to the cell 2 to cyclically receive from the latter the second volume of treated fluid with increasing concentration of charged particles.

Initially operatively, the first volume of fluid to be treated reaches the concentration of charged particles with an increasing gradient starting from its first access opening 9', only after some cycles, as shall become clearer in the rest of the description.

A first withdrawal duct 1 1 is foreseen, which is intercepted by a third valve 12 and is shunted from the extraction duct 7 between the cell 2 and the second tank 10, through which a purified volume of the flow of treated fluid is extracted from the cell 2.

The flow of treated fluid from the cell 2 has a concentration of charged particles that is initially extremely low, preferably lower than a predetermined first threshold value, which once exceeded and once the aforementioned purified volume of fluid which is drawn with a very low concentration of charged particles has been reached, means that the flow of fluid treated by the cell 2 is no longer sufficiently purified and is no longer directed to the first withdrawal duct 1 1 but to the second tank 10 through the extraction duct 7, by suitably actuating the different interception valves as described in the rest of the description.

The apparatus 1 comprises a logic control unit 100 cpu master, which actuates the different operation steps of the apparatus 1 , driving a controller which is responsible for the actuation of the single electrovalves which control the hydraulic system, and in particular cyclically determines the repeating of a service step in which the fluid coming from the first tank 9, at least partially purified in the cell 2, is partially initially drawn and partially subsequently sent to the second tank 10, and a regeneration step, in which a washing fluid, advantageously consisting of the second volume of fluid stored in the second tank 10, is preferably partially initially discharged after having washed the cell 2 and thus subsequently at least partially redirected to the first tank 9 where it is accumulated with a concentration with reverse gradient before continuing the cycle with the sanification step.

The logic control unit 100 is in communication with a first sensor 15 for detecting the concentration of the charged particles, in particular consisting of a first conductivity meter, arranged so as to intercept the extraction duct 7, and with a second sensor 150 for detecting the concentration of the charged particles, in particular consisting of a second conductivity meter, arranged so as to intercept the supply duct 5.

The electrical connections of the logic control unit 100 with the valves and with the sensors have been indicated with a broken line in figure 1.

Functionally, with reference to the diagram of figure 1 , during the service step there is the passage of the flow to be treated through the cell 2, which thus reaches, purified, into the extraction duct 7 from which it is drawn through the first withdrawal duct 1 1 , being the third valve 12 open and the second valve 8 closed. As the flow to be treated at increasing concentration passes in the cell 2, there is an increase in the percentage of charged particles, also in the treated flow. When the value measured by the first sensor 15, and relative to the percentage of charged particles in the treated flow, exceeds a first predetermined threshold value, the logic control unit 100 controls the third valve 12 to close and the second valve 8 to open starting to send the treated fluid with increasing concentration of the charged particles to the second tank 10 where there is the accumulation of fluid with concentration gradient which is reversed with respect to what occurs in the first tank 9.

Return means cyclically immiscibly displaced, into the first tank 9, at least one part of the second volume of treated fluid stored in the second tank 10 starting from the second access opening 10' of the latter and with a return flow with decreasing concentration of charged particles.

More in detail the two tanks 9 and 10 are suitable for storing the flow of fluid which they receive from the respective access opening 9', 10' with a substantially laminar flow without remixing the fluid which advances becoming stored inside them. This can be advantageously obtained through for example a winding of tube with a sufficiently small section and with a flow advancement speed that is sufficiently low with respect to the viscosity, so as to ensure conditions of laminar flow without mixing the flow-rate of fluid received.

For example, assuming that the cell 2 treats 200 litres an hour or rather just more than 3 litres a minute and that the operation cycle of service and regeneration is of about one minute, it is necessary for the two tanks 9, 10 to each have the capability of accumulating about 3 litres. Such tanks 9, 10 could, for example, be obtained with 50-100 metres of winding of tube having a section with a diameter of about 6-8 mm.

In particular, the first and the second tank 9, 10 are respectively made up of a first and a second winding of tube. Such a first and second winding of tube are equipped with a respective first end, which is connected respectively to the supply duct 5, through the first access opening 9' of the first tank 9, and to the extraction duct 7 through the second access opening 10' of the second tank 10, and of a respective second end that is opposite to the first one, which is open or rather, preferably closed with a pressure compensator, respectively indicated with 9" and 10" in the attached figures, suitable for preventing the contamination of the fluid with the environment simultaneously allowing the insertion and the flowing out of the fluid itself in the tanks 9, 10.

On the other hand, the tanks 9 and 10 define a containment chamber that is subdivided through a plurality of elements, such as septums or balls, into a multitude of pits or channels that are capable of making the flow of fluid laminar dividing it in an immiscible manner. More clearly, the first and the second tank 9 and 10 respectively store the first and the second volume of fluid with concentration of charged particles with a reverse gradient, respectively decreasing and increasing, and in outlet make it go in reverse order with respect to how it arrived and without mixing.

More in detail, in accordance with a preferred embodiment of the present invention, the return means for moving the fluid from the second tank 10 to the first tank 9 comprise the extraction duct 7, through which the second flow volume of treated fluid coming from the second tank 10 passes to a concentration of particles decreasing in countercurrent inside the cell 2 to become stored, at least in part, with a reverse concentration gradient in the first tank 9.

The hydraulic system comprises a second withdrawal duct 13, intercepted by a fourth valve 14, which is shunted by the supply duct 7 between the first tank 9 and the cell 2.

Through such a second withdrawal duct 13 a waste volume of flow of treated fluid, preferably coming from the second tank 10, is extracted with decreasing concentration of charged particles.

More clearly and preferably, the second volume of treated fluid stored in the second tank 10 with increasing concentration of charged particles is subsequently extracted from the latter with reverse concentration gradient. The first part of the flow of such a second volume of treated fluid coming from the second tank 10, or rather that contaminated the most with charged particles since it was the last to have previously left the cell 2 when the latter had become saturated, is used for washing the cell 2 so that it acquires, while passing above the electrodes, all the charged particles accumulated during the service step, or rather, during the operation of the cell 2 in purification of the fluid directed from the first tank 9 to the second one 10. The first part of such a flow of treated fluid coming from the second tank 10 generates a washing volume with a particularly high concentration and higher than that of the supply fluid.

When the concentration of charged particles in the washing flow of the cell 2, or rather in the flow of the second treated volume coming from the second tank 10, starts to decrease, the same flow is diverted towards the first tank 9, suitably actuating as specified in the rest of the description, the interception valves of the different ducts, and the first tank 9 thus begins to accumulate the treated flow coming from the second tank 10 with decreasing concentration of particles.

Functionally, with reference to the diagram of figure 1 , during a foreseen regeneration step, made clearer in the rest of the description, there is the passage of a washing flow through the cell 2, so as to take away the charged particles accumulated on the electrodes advantageously through the second withdrawal duct 13, being the fourth valve 14 open and the first valve 6 closed. The washing fluid can advantageously arrive from the second tank 10 and can advantageously be obtained with the part of treated fluid that is contaminated the most which accumulated last in the second tank 10 when by that time the electrodes of the cell 2 had become almost saturated.

The treated fluid which passes through the cell 2 is thus initially made to flow into the second withdrawal duct 13 until the second sensor 150 detects a concentration of charged particles that is lower than a second predetermined threshold value and consequently the logic control unit 100 controls the closing of the fourth valve 14 and the opening of the first valve 6, starting to send the treated fluid with decreasing concentration of charged particles coming from the second tank 10 into the first tank 9 where there is the accumulation of the fluid with decreasing concentration gradient that is reversed with respect to what occurred in the second tank 10.

Overall the waste volume of concentrated fluid which is evacuated through the second withdrawal duct 13 can be very low, and for example lower than 5% of the total of the treated fluid and can be reused many times (as indicated with a dash-dot line in figure 1 where it is foreseen for there to be the circulation in a circuit 130 intercepted by a storage tank 131 , by a pump 132 and by a sixth valve 133) obtaining ever increasing concentrations thus with increasingly less waste. Therefore, in the case of waste fluids of industrial processes, the fluid to be disposed of can be extremely small and, given the high concentration of the concentrated fluid which is extracted from the second withdrawal duct 13, it could be easily disposed of or even recovered as a new process fluid according to the foreseen industrial application.

The hydraulic system moreover comprises a supply duct 16 that is connected to a source 18 of fluid to be treated, intercepted by a fifth valve 17, to supply the first tank 9 with a volume of top up fluid to be treated that is at least equal to the purified volume of the flow of treated fluid which has been extracted from the first withdrawal duct 1 1 and, preferably, increased by the waste volume extracted from the second withdrawal duct 13 and, as mentioned, preferably received from the second tank 10 at the beginning of the return of the treated fluid, with a reverse concentration gradient, into the first tank 9.

Advantageously, the aforementioned volume of top up fluid to be treated is conveyed into the supply duct 5 towards the first tank 9 after the second volume of treated fluid with decreasing concentration of said particles which comes from the second tank 10.

A circulation pump 19 is advantageously foreseen in the supply duct 5 or in the extraction duct 7 to send the flow of fluid coming from the other tank 10, 9 to the first or to the second tank 9, 10. For this purpose, the pump 19 is preferably of the rotary blade type which can be actuated by the logic control unit 100 in both rotation directions to reverse the pumping direction of the fluid.

Also a method for operating an apparatus 1 with through-flow condensers, in particular, but not exclusively, of the type described above, the reference numerals of which shall be kept for the sake of simplicity, is object of the present invention.

In accordance with the method for operating the apparatus 1 object of the present invention, the cell 2 cyclically undergoes, in a per se completely conventional manner that is well known by a man skilled in the art: a charging step, in which the electrodes of the condensers 4 of the cell 2 are charged and taken to a foreseen rated voltage, for example equal to 1.6 V, and a service step, in which with the charged electrodes, the flow of fluid to be treated is forced to pass through the condensers of the cell 2

During the service step there is the depuration of the fluid from the polarized particles due to the fact that the ionised particles are attracted by the respective electrodes with opposite polarities to their own that have progressively accumulated on the electrodes themselves. The cycle of the cell 2 also foresees a regeneration step which begins after the saturation of the electrodes with the polarized particles present in the fluid. During this step, with the electrodes deactivated, a flow of washing fluid, as shall be made clearer in the rest of the description is forced to pass in the condensers of the cell 2 with consequent removal of the ionised particles accumulated on the electrodes.

With the term "deactivated" we mean all those conditions which the electrodes undergo before continuing the charging step. During the regeneration step it is indeed preferably foreseen for there to be a discharge step with short circuiting of the electrodes, a charging step with reverse polarity, in which the electrodes are subjected to a voltage with reversed polarity aimed at moving away the charged particles from the electrodes in which they were accumulated, and a step without voltage, before continuing the charging step.

Therefore with the term "deactivated" referred to the electrodes we mean all those possible conditions of voltage present at the electrodes in the regeneration step such as: the condition of short-circuited electrodes, the condition of electrodes charged with reverse polarity, the condition of electrodes disconnected from the power supply 36.

According to the idea forming the basis of the present invention during the service step the first volume of fluid to be treated contained in an immiscible manner in the first tank 9 runs out from the latter with increasing concentration of charged particles through the cell 2 generating a flow of treated fluid at increasing concentration of charged particles, which produces firstly, in a first stage, a purified volume of treated fluid with a lower concentration of charged particles than a first threshold value, and subsequently feeds, in a second stage, in an immiscible manner, the second tank 10 with a subsequent second volume of treated fluid. The regeneration step advantageously foresees that it is the second tank 10 that supplies the cell 2 in countercurrent with washing fluid obtained with at least one part of the aforementioned second volume of treated fluid. The aforementioned washing flow continues to flow from the second tank 10 to the cell 2 and from this to the second withdrawal duct 13, until the second sensor 150 measures a concentration value, downstream of the cell 2, that is lower than a second threshold value.

From that moment the flow of the second volume of treated fluid with decreasing concentration of charged particles is sent to the first tank 9, advantageously continuing in any case to pass through the cell 2.

On the other hand, the regeneration step is obtained with a flow of washing fluid obtained with a flow of fluid to be treated, for example consisting of seawater in the case, in fact, in which the apparatus is intended to desalinate seawater. In such a case, the source 18 of fluid to be treated is connected through a joining duct 20 (indicated with dash-dot-dot line in the attached figure) to the extraction duct 7 downstream of the cell 2 to supply it with the washing flow until the electrodes are purified from the charged particles accumulated during the service step.

In general, the invention foresees a recovery step in which the second tank 10 feeds the first tank 9 in an immiscible manner with at least one return volume of the second volume of treated fluid having decreasing concentration of charged particles. The aforementioned return volume will then again be processed in the cell 2 for a second time. Generally, it is not strictly necessary for the return volume to pass through the cell 2 in countercurrent, with it also being possible for it to be bypassed.

Preferably however, the recovery step foresees supplying the first tank 9 with the return volume of the second volume of treated fluid of the second tank 10 passing through the cell 2. The second volume of treated fluid thus advantageously comprises the washing volume which passes through the cell 2 but does not reach the first tank 9 since it is extracted from the second withdrawal duct 13 until it reaches the second threshold value, and the return volume that, preferably passing in any case through the cell 2, reaches the first tank 9 becoming stored without mixing with reverse concentration gradient to that in which it was stored in the second tank 10.

The regeneration step is therefore obtained with the passage of the part of the second volume of treated fluid corresponding to the washing volume before the recovery step with the movement of the return volume from the second tank 10 to the first tank 9.

It is also foreseen for there to be a topping up step in which at least one volume of top up fluid to be treated, equal to at least the purified volume of the flow of treated fluid, is conveyed into the first tank 9 substantially after the return volume which flows towards the first tank 9 from the second tank 10 with decreasing concentration of the charged particles. Advantageously, during such a step even the part of the second treated volume coming from the second tank 10 and that is used for washing the cell 2, will be compensated with the volume of top up fluid. Such a topping up step is made by controlling the opening of the fifth valve 17, for the time necessary to feed the first tank 9 through the supply duct 5 with the aforementioned volume of top up fluid.

Of course, when the apparatus 1 is turned on, the first volume of fluid to be treated contained in the first tank 9 will not have a differentiated concentration gradient starting from its first access opening 9'. Advantageously, it shall initially be foreseen for there to be some cycles for treating the fluid (charging step, service step and regeneration step) without being able to draw the volume of purified fluid. At the end of such initial cycles the first volume of fluid to be treated contained in the first tank 9 will have a concentration gradient inside it with the minimum amount of charged particles at the fluid arranged near to its first access opening 9', so as to ensure it to be purified and drawn after the subsequent service step of the cell 2.

Thanks to the method and to the apparatus object of the present invention the cells 2 are exploited to the maximum of their capturing capability allowing the apparatus to have greater efficiency which translates into lower plant costs and lower energy costs for it to operate. The method and the apparatus thus conceived therefore achieve the predetermined purposes. Of course, the apparatus can even take up, in its practical embodiment, shapes and configurations that are different from that illustrated above without, for this reason, departing from the present scope of protection.

Moreover, all the details can be replaced by technically equivalent elements and the sizes, shapes and the materials used can be any according to the requirement.

Claims

C L A I M S

1. Method for treating a fluid through an apparatus (1) with through-flow condensers equipped with at least one cell (2) having interfacing electrodes between which a flow of fluid to be treated containing ionised particles is able to flow,

said method cyclically comprising:

- at least one charging step, wherein a power supply (36) charges the electrodes of said cell (2) with different polarity;

- at least one service step, in which said flow of fluid to be treated is forced to pass through the charged electrodes of said cell (2) with progressive accumulation of said ionised particles on said electrodes;

- at least one regeneration step, in which, with said electrodes deactivated, a flow of washing fluid is forced to pass through said cell (2) with consequent removal of said ionised particles accumulated on said electrodes;

characterised in that

- during said service step a first volume of said flow of fluid to be treated runs out from a first tank (9), in which it is immiscibly contained, with increasing concentration of charged particles through said cell (2) generating a flow of treated fluid at increasing concentration of said charged particles, which produces, firstly in a first stage, a purified volume of treated fluid with a lower concentration of charged particles than a first threshold value, and then, in a second stage, it immiscibly feeds a second tank (10) with a subsequent second volume of treated fluid.

2. Method for treating a fluid according to claim 1, characterised in that it comprises a recovery step in which said second tank (10) immiscibly feeds said first tank (9) with at least one return volume of said second volume of treated fluid having decreasing concentration of charged particles.

3. Method for treating a fluid according to claim 2, characterised in that in said recovery step said second tank (10) feeds said first tank (9) passing through said cell (2) with at least said return volume.

4. Method for treating a fluid according to claim 1, characterised in that during said regeneration step said second tank (10) feeds said cell (2) with said flow of washing fluid for a washing volume of said second volume of treated fluid, said washing volume being discharged after having crossed said cell (2) in countercurrent without reaching said first tank (9).

5. Method for treating a fluid according to claims 3 and 4, characterised in that said regeneration step precedes said recovery step.

6. Method for treating a fluid according to claim 1 , characterised in that it comprises at least one topping up step in which at least one volume of top up fluid to be treated equal to at least said purified volume of said flow of fluid to be treated is conveyed into said first tank (9) substantially after said return volume.

7. Method for treating a fluid according to claim 4, characterised in that said washing fluid flow is discharged after having passed said cell (2) while the concentration of charged particles remains above a second threshold value.

8. Method for treating a fluid according to any one of the previous claims, characterised in that said regeneration step is obtained with said fluid to be treated.

9. Apparatus (1) with through-flow condensers for treating a fluid, in particular for carrying out the method according to one or more of the previous claims, which comprises:

- at least one cell (2) provided with at least one through-flow condenser (4) equipped with two or more electrodes between which a flow of fluid to be treated containing ionised particles is able to flow;

- at least one direct current power supply (36) electrically connected to said electrodes and able to charge them interfacing with different polarity to create an electric field between them;

- a hydraulic system, able to feed said cell (2) with said flow of fluid to be treated through a supply duct (5) intercepted by a first valve (6) and able to receive the flow of fluid to be treated from said cell (2) through an extraction duct (7) intercepted by a second valve (8); characterised in that said hydraulic system comprises:

- at least one first tank (9) able to cyclically contain a first volume of fluid to be treated, immiscibly distributed inside of it with increasing concentration of charged particles going from a first access opening (9') thereof, connected through said supply duct (5) to said cell (2) to cyclically feed the latter with said first volume of fluid to be treated through a flow with increasing concentration of said charged particles at least partially purifying it and generating a flow of fluid to be treated with increasing concentration of said charged particles;

- at least one second tank (10) able to cyclically contain a second volume of treated fluid, immiscibly distributed inside of it with decreasing concentration of charged particles going from a second access opening (10') thereof, connected through said extraction duct (7) to said cell (2) to cyclically receive from the latter said second volume of treated fluid with increasing concentration of said charged particles;

- a first withdrawal duct (1 1) intercepted by a third valve (12) shunted by said extraction duct (7) between said cell (2) and said second tank (10), through which a purified volume of said flow of treated fluid is extracted;

- return means to cyclically immiscibly displace at least one part of said second volume of treated fluid from said second tank (10) from its second access opening (10') into said first tank (9) through a return flow with decreasing concentration of said charged particles.

10. Apparatus (1) for treating a fluid according to claim 9, characterised in that said return means comprise said extraction duct (7) through which said second volume of treated fluid flow with decreasing concentration of said particles coming from said second tank (10) passes in countercurrent in said cell (2) and is at least partially stored in said first tank (9).

1 1. Apparatus (1) for treating a fluid according to claim 9, characterised in that said hydraulic system comprises at least one second withdrawal duct (13), intercepted by a fourth valve (14), shunted by said supply duct (5) between said first tank (9) and said cell (2), through which second withdrawal duct (13) a waste volume of said flow of treated fluid with decreasing concentration of said particles coming initially from said second tank (10) is extracted.

12. Apparatus (1) for treating a fluid according to claim 9, characterised in that said hydraulic system comprises at least one supply duct (16), intercepted by a fifth valve (17), able to feed said first tank (9) with a volume of top up fluid to be treated at least equal to said purified volume of said flow of treated fluid.

13. Apparatus (1) for treating a fluid according to claim 12, characterised in that said volume of top up fluid to be treated is conveyed into said supply duct (5) towards said first tank (9) after said at least one part of said second volume of treated fluid with decreasing concentration of said particles coming from said second tank (10).

14. Apparatus (1) for treating a fluid according to claim 9, characterised in that it comprises:

- at least one first sensor (15) for detecting the concentration of said charged particles, in particular consisting of a first conductivity meter, arranged to intercept said extraction duct (7),

- at least one logic control unit (100) able to control the closing of said third valve (12) and the opening of said second valve (8), while said flow of treated fluid with increasing concentration of said charged particles passes through said extraction duct (7), when the value measured by said first sensor (15) exceeds a predetermined first threshold value.

15. Apparatus (1) for treating a fluid according to claim 1 1 , characterised in that it comprises:

- at least one second sensor (150) for detecting the concentration of said charged particles, in particular consisting of a second conductivity meter, arranged to intercept said supply duct (5),

- at least one logic control unit (100) able to control the closing of said fourth valve (14) and the opening of said first valve (6), while said at least one part of said second volume of treated fluid with decreasing concentration of said charged particles, coming from said second tank (10) passes through said supply duct (5), when the value measured by said second sensor (150) falls below a predetermined second threshold value.

16. Apparatus (1) for treating a fluid according to any one of claims 9 to 15, characterised in that at least one of said first or second tank (9, 10) consists of a winding of tube able to store said first volume of fluid with laminar flow.

17. Apparatus (1) for treating a fluid according to claim 16, characterised in that said winding of tube is provided with a second open or closed end with a pressure compensator (9", 10").